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Early jet fighters had the air intake for the engines in the nose of the aircraft, while later aircraft had paired intakes on the sides of the fusilage. Why the difference? --67.185.172.15800:32, 29 July 2006 (UTC)[reply]
Not all early jet fighters had intakes in the nose. The world's first jet fighter – the Messerschmitt Me 262, flown by the Luftwaffe near the end of World War II – had a pair of engines, one under each wing. The United States' first jet fighter (the P-59 Airacomet) had a pair of intakes along the fuselage. Meanwhile, the British Gloster E.28/39 (Pioneer) had a single nose intake.
Anyway, the reason is pretty prosaic. Both the Me-262 and the P-59 had two jet engines, and one air intake per engine. The Gloster Pioneer, on the other hand, had only a single engine mounted in the middle of the fuselage, dictating the placement of its air intake directly forward in the nose of the aircraft. TenOfAllTrades(talk) 01:59, 29 July 2006 (UTC)[reply]
There are many ways to design an airplane- including how many engines and where they are placed. And around the same time as the jet engine was developed, airborne radar equipment was being developed. The best place for the radar antenna was the nose, which caused the air intakes to move to the sides of the fuselage. Some US fighters used different arrangements. The Republic XF-103 had the intake below the fuselage, similar to the F-16 Fighting Falcon. And the North American F-107 had the intake placed on the top of the fuselage, behind the cockpit.
The nose is useful space for istrumentation and it is also very difficult to arrange the airchannels around the cockpit without interfereing with it, so to simplify it when these problems had been realised, the air intakes were placed behind the cockpit. PhilcTECI13:52, 29 July 2006 (UTC)[reply]
What is the chemical structure and properties of...
N, N'-Methylene-bis-acrylamide
FW= 154.2
C7H10N2O2
This chemical is used in Polyacrylamide gels for SDS page with acrylamide.
Refrence: Laemmli, U.K. Cleavage of structural proteins during the assembly og the head of bacteriophage T4. Nature. 277:680-5, 1970.
In Gray's Anatomy, what is the meaning of "viz." throughout the book? One instance is, "the remaining constituents of the ovum, viz. it's limiting membrane and the solid spot..." Thanks for any help, Newnam(talk)01:25, 29 July 2006 (UTC)[reply]
In electricity, is the amp being pushed from the power supply; or is it pulled from the devise requiring power?
I guess it would be more accurate to say it is being "pushed" from the power supply, but the wording is odd - I would recommend a good read of electricity. --Bmk04:35, 29 July 2006 (UTC)[reply]
But "current" isn't a substance which can be pulled or pushed. In home plumbing, what thing is flowing inside of the pipes, is it current or is it water? Water flows in pipes, and it is charge which flows in wires. Charge gets pumped through power supplies and through any loads. A current-source is not a source of current, but instead is a source of constant current; it's a producer of constant unchanging charge-flow.
Back to the original question. A power supply pumps a little charge out of one wire and into the other. The two wires act as the two plates of a capacitor. This pumping of charge produces a voltage difference across the wires, and when this voltage rises to the same value as the power supply's output voltage, the power supply stops pumping. If we then connect a load across the two wires, this allows charge to flow back where it started, and therefore the voltage across the wires will begin falling towards zero. The power supply sees this and again starts pumping charge from one wire to the other. When things settle down, the load device is constantly discharging the imbalance of charge in the wires, and the power supply is constantly pumping the imbalance back up again. So... does the power supply push the charges, or does the load pull them? The answer is yes! :) Both things happen: the load device draws a certain amount of charge per second from one wire to the other, and this causes the power supply to pump charges at the same rate in the opposite direction so the voltage-difference is maintained. --Wjbeaty08:36, 30 July 2006 (UTC)[reply]
I suppose by 'amp' you don't mean 'amplifier' but 'ampere', ie 'current'. A current is caused by a potential difference. Whether one end is pushing or the other pulling depends on what you call 'normal'. If that is 'earth' and you've got a positive charge connected to earth then the electrical current flowing from the charge to earth might be said to push it. But I believe in household electricity there's a negative and a positive side, so you get a push an a pull at the same time. However, which way does the current flow? The electrical current goes in the opposite direction of the electron current, so which side pushes and which side pulls depends on what you are looking at - the flow of electrons or the flow of 'lack of them'. DirkvdM07:53, 29 July 2006 (UTC)[reply]
QED
2 electrons repel each other because one electron emits a virtual photon (recoils) and the other electron absorbs the photon (more energy, different momentum, changes direction) But WHEN does the electron WHEN to emit the photon? Are they conscious?
AFAIK, electrons are not conscious! My understanding is that electrons repel each other because they have similar charges - not anything to do with photons. -- SGBailey06:39, 29 July 2006 (UTC)[reply]
Similar charges repel? No, you're talking about distant action theory, an obsolete theory from before the time of Faraday. Since Faraday we know that electrons repel each other because electrons are surrounded by EM fields, and these fields interact with particles to produce attraction or repulsion force. More recently we know that electron repulsion is based on photon exchange, and that EM fields are actually composed of huge numbers of virtual photons.
Regarding the original question: we could also ask whether electrons have some sort of hidden "clockwork" which tells them when to emit a photon. This is called hidden variable theory and is disproved by experiments involving Bell's theorem. So how do electrons do what they do? They just do: it's a law of physics with no deeper mechanism allowed. Also, why do electrons persist, rather than winking out of existence? Why do they have constant charge rather than random variation? Why do they experience a particular force at a particular distance from other charges? They just do. But perhaps you'd want to look at Many Worlds Theory which assumes that during any interaction, the entire universe splits into an infinite number of copies, where the interaction happens slightly differently in each universe. Rather than one electron having to decide when to emit, instead there are many separate universes, and the electron emits a photon at a different time in each universe. --Wjbeaty08:24, 30 July 2006 (UTC)[reply]
Actually, hidden variables were not disproven, just local ones. Then again, there is nonlocality in the standard QM interpretation too. I think your other explanations aren't quite right either. (Cj6703:19, 2 August 2006 (UTC))[reply]
Well, the leading Feynman diagram that causes electrons to scatter off each other does involve exchanging a single virtual photon. But that doesn't mean that what physically happens is that one electron emits a single photon, which is absorbed by the other. Instead, the quantum fields at work in some sense figure out the combined result of all possible ways for a photon to be exchanged. Does that make any sense? Melchoir07:08, 29 July 2006 (UTC)[reply]
And all possible ways result in a repel for this case? Very perplexing!
Can anyone explain in layman's terms how electrical signals sent to the brain are converted into mechanical reflexes, resulting in movement? Thanks!
The neuron article should be a good one to read. It's pretty complicated, and very interesting, but i'll give a very general overview. Basically neurons have a cell body, the location of the nucleus and where the regular cellular processes take place, they have dendrites, and axons. Signals come in from the axons of other neurons through the dendrites, crossing the synapse, which is just the tiny gap between an axon terminal and a dendrite. If the total stimulus from the dendrites is high enough, the neuron fires, and sends a signal out to connecting neurons through the axon, propagating the signal along. Once it gets to the brain, the brain does its mysterious thing (brains are basically giant conglomerations of billions of neurons connected in complicated ways), figures out what to do about the stimulus, then sends a signal out through motor neurons, which are similar to regular neurons, except they connect to muscle cells at the axon. This connection between motor neurons and muscles is called the neuromuscular junction. Basically, the signal crosses the junction (see acetylcholine, the neurotransmitter which actually crosses), and causes the muscle cell membrane to depolarize, which in turn triggers the muscle cell to release sodium ions into the muscle, causing the muscle to contract. It's really quite complicated... to give you some clues where to look to find more details, the signal which is transmitted is actually an action potential, which is caused by the movement of ions through ion pumps and ion channels in the neuron membrane - the ions act like people doing "the wave" at a baseball game in the stands. Goodness, this is a huge topic. I'd better stop. I hope that was helpful --Bmk04:52, 29 July 2006 (UTC)[reply]
1.Tell me if the following cities snow (at least one day) in winter or not:
*Chongqing *Tokyo *Oklahoma City *Barcelona
*Shanghai *Seattle *Raleigh *Marseilles
*Seoul *San Francisco *Washington, DC *Rome
*Osaka *Dallas *Madrid *Athens
2.IF most of those cities above do snow in winter, then why?I mean, I live in Sydney in Australia where it never snows in winter.Many of those cities above are on roughly the same latitude and side of a continent as Sydney.So, if snowing is such a normal and common thing in the world and Sydney is not a very warm or hot city, then why doesn't Sydney snow in winter?
There's a section in snow about occurrence. It doesn't explain outright why, but it appears that snow only falls in extreme latitutes or on high mountains. Since Sydney is at or near sea level, it doesn't get snow. There's a great image (image:Earth-satellite-seasons.gif) that gives a n example of where it commonly snows in the world. There's a noticeable change in winter, but in Summer, the only snow I notice is in South America. But according to this list, it does snow in Australia and other places not usually associated with snowy weather. Hyenaste(tell)06:38, 29 July 2006 (UTC)[reply]
Latitude is only one of several factors which affect temperature. I live in the far south of New Zealand, and I'm as far from the equator as the Mediterranean coast of France, yet my climate is more like central England's. Ocean and air currents are as important as Latitude, as is the difference between a maritime climate and a continental climate - it is for this latter reason that Chicago - at 42°N gets more snow in one year than Barcelona (also 42°N) would in a couple of decades. Grutness...wha?07:30, 29 July 2006 (UTC)[reply]
Well it is true that a land mass like a continent causes more severe temperature differences, but the difference between the two sides of the north Atlantic is at least in part also caused by the northern branch of the Gulf Stream that takes warm water to Europe, making it much warmer than it should be. I don't know if this affects snowfall too. Nor do I know if something similar happens in other oceans. DirkvdM07:59, 29 July 2006 (UTC)[reply]
Seattle gets more than one day of snow per winter. We don't get much accumulation of snow compared to other north american cities that get snow. Typically winters here are mild, because most of the airmass is warmer tropical air from the mid Pacific: This warm, moisture-laden air keeps the winter temperature here mild, but brings lots of rain. However, if the jetstream dips far enough south, then we get a lot of very cold, dry air with corresponding low temperatures but no precipitation (either rain or snow). But if conditions are right, and we get a combination of a very cold airmass that also contains moisture then we can get snow. Typically though, the clouds that bring snow also hold in the heat, making the temperature hover right around freezing, and so we get all these "will-it-or-won't-it" forecasts for snow and often when it snows, it immediately warms up and the snow melts away.
Eastern washington is far different though. The same warm moisture-laden airmass from the pacific ocean that gives us rain cools off when it crosses the Cascade mountain range, and dumps tons of snow on Eastern washington.
- In regards to the American cities listed above in your first question, approximate average yearly snowfall is: San Francisco - trace amount, Dallas - 4 inches, Raleigh - 8 inches, Oklahoma city - 10 inches, Seattle - 10 inches, Washington D.C. - 18.5 inches. I can also say from experience that I have seen snow flurries in Rome.
topic suggestion
Can somebody suggest me a good topic related to electronics? I have to conduct a seminar in my college. The topic must be related to electronics and can also combine electronics with various other fields such as biology, astronomy, geography, military warfare science, communication or anything else but it MUST be related to electrical or electronics. the topic must be interesting. also if u dont mind can u please say in which website I can find manuals or papers related to that topic. PLEASE SOMEBODY HELP ME. I WILL BE VERY GRATEFUL TO YOU. THANK YOU VERY MUCH.
With something like this, it is really best if it is something you already know about and care about, but howabout "the history of computing" from babbage's mechanical devices through relay logic to early valve computers and then transistor and finally IC devices? -- SGBailey06:35, 29 July 2006 (UTC)[reply]
Definitely, I agree with you SGBailey, you might also talk briefly about Quantum computing as the future of Computing!--219.78.205.15506:45, 29 July 2006 (UTC)Just Love Science[reply]
my friend and i once playing table tennis and when we became exhausted i opened the bottle near me and start drinking water.. my friend stopped me from drinking..he said drinking water literally after exercise creates kidney pain...is it true?
Certainly not, this is only for COLD water. If you drink warm water it should be fine. This is because after intensive excercises, your body is still "running" and "agitated". A sudden dose of cold water would contract your organs (only for organs that has contact with the dose of water, wind pipe, throat, stomach etcetera, but the effect compiles on after another, not a sudden phenomenon) based on the fact that "cold contracts, hot expands". So your friend is correct.
I've never experienced this and I find that answer pretty suspect (your internal body temperature does not change that much during exercise, you can raise it a degree or so on a very hot day if you overdo it). If he is talking about developing cramps, that can certainly happen if you mix high water intake with exercise. In my experience though that is only really a problem if you drink a lot of water before exercising (after doesn't seem to affect it). --Fastfission10:59, 29 July 2006 (UTC)[reply]
And that's really cold water, you know, the kind with ice floating in it and condensation around the bottle.
Canada 1930's - History of Fish Oil
Hope you can help.
I am seeking any information you may have of Canadian doctors using Fish Oil for health related matters (cardiovascular or other ailments) in the 1930's.
Time travelers stranded at the beginning of human civilization. How to recreate civilization/infrastructure quickly?
Consider this sci-fi scenario:
A group of time travelers from the future (say the 2400s) go back in time to the beginning of human civilization on an expedition and get stranded there. They have a craft that is still usable for some time (for shelter and transportation) but they lost the ability to travel in time. There is no realistic hope of a rescue. They have advanced scientific knowledge and have encyclopedic information about the Earth and the history of technology. What they don't have is the advanced infrastructure of their time that would allow them to repair/re-supply their craft, or to maintain their 25th century lifestyle. These time travelers want to recreate a technology infrastructure from scratch, at a greatly accelerated pace, both for themselves and for their children.
What can they do?
(To make the exercise more interesting, consider this: these time travelers know where the natural resources are, and can fool the humans of the time into believing that they are gods and thereby obtain their cooperation.) --71.246.1.2511:54, 29 July 2006 (UTC)[reply]
This theme has been dealt with many times by science fiction writers. I seem to remember one in which the protagonist made a fortune by devising a paper clip or something like that. These scenarios tend to skip over several big problems. First, you don't jump from primitive to advanced technology in a single leap just because you have the knowledge. Advanced technological products require both social and industrial infrastructure, which develops over centures or can be transferred in decades. So what if they settle for only slightly advanced technology? The problem then is the farther ahead you are, the less you are likely to understand primitive forms of your own technology. I'll bet more people can use a GPS system than a sextant-- so as soon as the batteries on the time travellers' GPS system wears out, they are worse off than the locals at exploring and finding things. Just because you can drive a car or use a computer doesn't mean you can build one. So the ideal time traveller might be a historian of technology who has studied the evolution of technology and take whatever exists a few steps ahead faster. Third, the business of being perceived as a god has some inherent flaws. If you think about human history, what happens to "gods" and great prophets? They get co-opted or swept up or crushed by local political forces, or they become a successful political movement, all within a few years. The story of a time traveller successfully leading the local people would be the story of a time traveller converting them into a militarily aggressive and successful society by providing one or two slightly advanced weapons and tactics (i.e., an iron knife instead of a flint one), not someone who pushes them from the stone age to the industrial age in a generation. If successful, he would transformed from an astronaut/explorer/engineer type into an emperor or god/king type for a few years before he met his violent death. Maybe that's the more interesting story. alteripse12:15, 29 July 2006 (UTC)[reply]
Yeah, they'd have a very hard time if they are really at the beginning of civilization. They have no real way to generate electricity, most likely, and without that modern technology is totally screwed. Without the ability to set up extensive mines, you're not going to have the raw metals needed to build even the most rudimentary technologies. Infrastructure takes a long time to build from scratch, especially if you are doing it to build something that nobody else understands the purpose for (and unless you have a lot of barterable currency you're going to have a hard time convincing anyone to do anything for you). --Fastfission12:27, 29 July 2006 (UTC)[reply]
Without electrical generators they'd be pushed all the way back to the 1910 era. Don't forget that the industrial revolution happened before electric energy systems and was based on cast iron. --Wjbeaty07:59, 30 July 2006 (UTC)[reply]
Conceptually similar, albeit less dramatic, scenarios have enfolded time and time again throughout history. European's travelled through technologically evolved "time" when colonising Africa, South America and the Pacific Rim. More often than not, especially when the numbers are small, a significant number of the the technologically advanced colonising party meet a violent death. The indigenous parties usually suffer greatly as they are exposed to technology - and the vices and dangers that accompany them - far too quickly, eventually a strange equilibrium emerges between so-called advanced culture and tribal customs. This type of culture-clash be seen even today in regions of Africa and South America. In other words, empirical evidence would suggest that your time travellers would most likely settle into a lifestyle somewhere between theirs and their hosts. Rockpocket19:04, 29 July 2006 (UTC)[reply]
This was a plot point in A Fire Upon the Deep and A Deepness in the Sky. Planetary civilizations would crash for various reasons, and traders who'd spent a lot of time and resources getting there, and who planned to stay for a decade or two. They had a variety of discovery trees, showing how to get from the Iron Age up to the local limit of technology. Pretty much the sort of thing you're describing. grendel|khan23:55, 29 July 2006 (UTC)[reply]
Their time machine was set for 'a three hour tour'...
Don't forget to read "A Connecticut Yankee in King Arthur's Court" wherein the hero did not go back quite so far, but encountered some problems our fearless crew would doubtless have. The King thought the hero was a fine fellow, but the religious establishment resented change. Also Andre Norton wrote about "time traders." Heinlein wrote "Farnum's Freehold" (sp?) No need to worry about time travel paradoxes, because there are an infinite number of alternative universes. "Civilization" might be a term applied to the earliest time when some people appointed themselves the bosses of others, the warrior/cheiftain/priesthood, on religious/military grounds. Before that the people weren't well enough organized for mass warfare and exploitation. So our chrononauts would find rulers who wanted to retain and increase their power, and workers who perhaps wanted to be left alone or to rule in their stead. So one avenue of prosperity is trade: to offer either or both sides slightly better weapons. Hope they have everything from Wikipedia, project Gutenberg, and a lot of industrial handbooks along with some programmable robotic machine tools. Perhaps hire workers extract copper (acheived by 8700 BCE) from the ores whose location you already know, and introduce copper knives, arrows, and plows. Now you can make copper wire, and you're part way to modern industrialization. Extract tin (achieved by 3500 BC) and your customers will want the new improved bronze tools and weapons. Now they are used to mining and metallurgy, so get them extracting zinc (achieved by 1300 BCE). You are all set to make miles of copper wire, and to get power from copper-zinc galvanic batteries. Your workers should be able to make iron, so you can build steam engines, generators and motors, not to mention pistols, rifles and artillery. Those new steel drillbits will help your guys drill for petroleum and refine it in stills. Electronics and computers should be doable, so why not space travel and time travel? How many years would it take to advance technology by say 8000 years? What happens when technology develops in advance of religious and moral philosophy? Vicious amoral tribal chieftains with weapons of mass destruction? Oh wait: that is today's world situation. Never mind!Edison20:55, 5 August 2006 (UTC)[reply]
how do alterations of the CNS account for psychiatric disorders like clinical depression
hi would it be possile for you to tell explain to me the way in which alterstions of the CNS neurotransmission may account for psychiatric disorders using the xample of clinical depression. I have looked at your information about clinical depression but it appears that you do not discuss this aspect, thanks for you time and i eagerly wait for you reply. from laura
Short answer: the cause of depression isn't really known at the neuronal level. But since you asked about neurotransmission, I'd suggest taking a look at serotonin (a neuromodulator, not a neurotransmitter), which is implicated in depression. Dopamine too, to some degree, although it's most associated with Parkinson's disease. Digfarenough12:49, 29 July 2006 (UTC)[reply]
We have indirect evidence that in severe depression there are lower levels of at least one neurotransmitter, serotonin, and perhaps others such as norepinephrine. The strongest evidence is that the most effective antidepressant drugs (SSRIs) seem to work by increasing the amounts of serotonin in the neuronalsynapses. That is the short answer. A full answer is more complex and beyond my power to make something complicated intelligibly simple. There is some additional detail in our clinical depression article, which looks like a reasonably good overview, and if it hasn't changed recently, I recall we have a detailed article on psychopharmacology. alteripse12:54, 29 July 2006 (UTC)[reply]
i need a new trend in electronic field because i need to take a seminar
Can somebody suggest me a good topic related to electronics? I have to conduct a seminar in my college. The topic must be related to electronics and can also combine electronics with various other fields such as biology, astronomy, geography, military warfare science, communication or anything else but it MUST be related to electrical or electronics. the topic must be interesting. also if u dont mind can u please say in which website I can find manuals or papers related to that topic. PLEASE REMEBER THAT IT HAS GOT TO BE SOMETHING NEW AND INTERESTING. TOPICS SUCH AS "THE HISTORY OF ELECTRONICS" WON'T DO. I NEED TO EXPLAIN IN SCIENTIFIC AND MATHEMATICAL TERMS ABOUT SOME NEW INVENTION OR TECHNOLOGY OR CONCEPT OR ANYTHING INTERESTING. MUST BE RELATED TO ELECTRICAL OR ELECTRONICS.PLEASE SOMEBODY HELP ME. I WILL BE VERY GRATEFUL TO YOU. THANK YOU VERY MUCH.
You got 5 interesting topic suggestions above. Now you need someone to write it for you? You can YELL at us all you want but you are in the wrong field if nothing yet has interested you enough to be able to teach people about it. Drop your course, learn to repair computers or something and stop bothering us. Harsh, I know, but there are limits to the "do my homework" pleas. Next week someone will ask us for a PhD thesis suggestion, and then the website where they can find the already-done research. alteripse15:06, 29 July 2006 (UTC)[reply]
Does anyone know if the following levels of the following vitamins are dangerous? Their respective articles don't tell. I do heavy lifting 4-5 times a week if that has any impact... I'll leave that for ye wise to determine...
You see all, I'm considering a new multivitamin and this new one contains significantly higher levels of the above vitamins than my current one does. Don't wanna poison myself, or waste my money for that matter. Jack Daw15:17, 29 July 2006 (UTC)[reply]
Nothing you've listed is even close to toxic levels (I'm assuming a once-a-day dose). Toxicity is mostly a problem with fat soluble vitamins, not water soluble ones. - Nunh-huh15:56, 29 July 2006 (UTC)[reply]
If Americans invented the Hovercraft, did the British invent aircraft?
Over the months I've noticed that the Hovercraft article has been gradually edited to make it appear that the role of Christopher Cockerell in inventing the hovercraft was only that of doing some minor tinkering to produce a working hovercraft (that travelled across the english channel in the 1950's).
By this logic, couldnt it be equally claimed that the British invented powered flight and that the Wright Brothers only did a bit of tinkering?
Oooh, after writing the above I re-read the Hovercraft article, and saw the article has now been re-written to give CC more credit. There has also been a considerable battle on the discussion page http://en.wikipedia.org/wiki/Talk:Hovercraft about this which I had not seen.—Preceding unsigned comment added by 81.104.12.22 (talk • contribs)
I was not being sarcastic - it is a serious question. Thanks.
No, no, some German guy was the first to fly. He just didn't get the media attention, so he has almost been forgotten. Can't remember his name, though. I'll look into that tomorrow. DirkvdM19:11, 29 July 2006 (UTC)[reply]
These article illustrate how silly the question really is. Times were right for human flight to take off (pun :) ). So it happened all over the world in a very short time span. I suppose the ones who were most into publicity won the popular title. It's like with evolution. The theory was well known. Charles Darwin, however, wrote it down in a book, so he got the title. Lilienthal didn't use a motorised plane, Jatho's may not have been a controlled flight, Cockerell didn't fly very high and Pearse forgot to photograph his achievement (the publicity bit). What is flight? How high and how far do you have to fly (does a hovercraft count?) Are you allowed to crash-land? And does it have to be repeatable, to the extent that almost every flight is successful? (When was that achieved anyway? A more important issue, I'd say.) So who was first? They all were. The Wright brothers included. DirkvdM09:48, 30 July 2006 (UTC)[reply]
Sound of explosions
Watching TV footage from Beirut (and in most other similar cases where an explosion is filmed from afar) the sound recording of the explosion is superimposed onto the video footage such that there appears to be no delay - as if the cameraman was actually at the scene of the explosion. Who are they fooling? Is it just to make "better" TV, or is it done so that we, the viewers, cannot work out how far the cameraman is from the explosion?--G N Frykman18:10, 29 July 2006 (UTC)[reply]
I have always assumed the audio and video was recorded independently in such situations. Thus, in the editing suite, the are combined, and the editor simply cues up the sound precisely with the explosion, rather than try and gauge the delay. Can any foreign correspondents shed light on this? Rockpocket18:32, 29 July 2006 (UTC)[reply]
scientific question!
How many roads must a man walk down Before you call him a man?
Ah, you mean because the average trip from the bedroom to the kitchen is insufficient training for walking down an entire road? Tsk tsk, what a terrible thing to say. Melchoir04:56, 30 July 2006 (UTC)[reply]
If you estimate an average walking speed of about 4 mph and estimate that most children can walk around the time of their first birthday, then you can say that after walking down around 37,000 miles worth of roads you should legally be an adult in the United States. In reality the number would be far less than that, since you'd have to take breaks to eat, rest, attend school, etc. If you divided this by the average road length, though, you'd have an idea of how many roads you'd have to walk down, if you were continuously walking from around age 1, to become 18 years old, as a factor of time. --Fastfission02:54, 30 July 2006 (UTC)[reply]
White doves can no doubt be convinced to sleep in the sand if there are no other options, so you can probably get them to do that without sailing any seas. --Fastfission02:54, 30 July 2006 (UTC)[reply]
White doves don't sail, afaik. so this is sort of like dividing by zero. So there is no answer. In other words, it's still blowing in the wind (ha! I'm the first one this time). DirkvdM08:55, 30 July 2006 (UTC)[reply]
Ah, and (assuming the correctness of the story for the sake of the argument) if all land were covered by water then there was just one sea, so the answer is one. Which leaves the question why the dove was so stupid to return to the boat after it found some sand to sleep in after its long flight. DirkvdM09:03, 31 July 2006 (UTC)[reply]
i m required 2 submit a science project innovative in nature....i have an idea
AN ELECTROMAGNETIC GUN..using an copper coil and a iron bullet ...indeed high voltage is required...that can b taken from ny T.V set...(circuit that powers the picture tube).range and firing force could b elecronically adjusted...could b upgraded by connecting with a computer..plz comment and lemme kno about its various features that i must not have came into my mind..
Note, it is highly dangerous to experiment with high voltages and ampereages, you really need to know what you're doing if you want to try to make a coilgun. And if you do, please add pictures to the coilgun page--we don't have any Thanks,
AFAIK, you'd have to make it pretty long in order to accelerate the bullet to a decent speed (i.e. enough to kill your hypothetical target). It would require a rather large amount of electricity too (fancy lugging around a large battery pack strapped to your back?). Abandon all thoughts of your own gauss pistol... ;) --Kurt Shaped Box01:03, 30 July 2006 (UTC)[reply]
It's a school project. I don't suppose the goal is to kill any targets (hypothetical or not). It'll more likely be measuring speeds against voltages and such. But apart from the high voltages, bullets flying around is indeed a safety concern. DirkvdM09:02, 30 July 2006 (UTC)[reply]
Not only that, but if you bring any form of a gun anywhere near a school you will likely be expelled, no matter what the reason, at least in the US. Time to pick another project. StuRat04:55, 31 July 2006 (UTC)[reply]
Good. Now if only they can apply that exclusion zone to all other humans, all buildings and other structures, all animals, all forms of transportation, all geographical features, water, air, any form of matter whatsoever .... JackofOz06:29, 31 July 2006 (UTC)[reply]
What species is a seagull with a gray band around its beak?
What kind of gull has is mostly white with gray on the wings, black tail feathers and a grayish-black band around its beak? I saw it at Misquamicut State Beach in Rhode Island. Is it a normal variation on the other gulls in the area (they had a reddish spot on the lower part of the beak; I don't know what kind they were), or a different species? If so, which species? grendel|khan00:14, 30 July 2006 (UTC)[reply]
Most probably. The adults of many species of gulls have dark feathers (streaks/spots) on their heads in winter. The all-white head is the breeding plumage. --Kurt Shaped Box01:51, 30 July 2006 (UTC)[reply]
Hello, and thanks in advance. I know that Einstein worked on a theory of everything, and worked with Rosen on it, and postulated that particles were small worm holes. My question is, what was this theory called? I tried searching, but i wasn't able to find it. Any help will be apreciated. --AmateurThinker00:17, 30 July 2006 (UTC)[reply]
Einstein and Rosen's activity together was not concerning a theory of everything, however what you are looking for is probably at Einstein-Rosen bridge or their work regarding the EPR Paradox.
what are the fitness components for diving inorder of importance
Please do your own homework. The answer you are looking for probably came from your teacher or textbook. The question is too vague if otherwise. Also, try our diving article! Thanks,
Gulls - carnivores or omnivores?
I've just been reading a few of the gull articles on Wikipedia (swatting up on my specialist subject - heh). I notice that in some places gulls are described as omnivores, in others carnivores. Anyone know which one is technically correct? I'd personally lean more towards 'carnivore' as gulls are, by nature meat eaters. They were 'designed' to scavenge from carcasses and prey on small mammals/birds/fish - one look at the beak shape and the observation of a gull's aggressive demenour should tell you that. The fact that they have learned to feast on whatever we throw out, be it animal, vegetable or mineral is neither here nor there IMO. Any thoughts? I think the definition needs to be standardized across the articles... --Kurt Shaped Box00:23, 30 July 2006 (UTC)[reply]
No expert here, but I'd say if an animal will eat both meat and non-meat foods (and can actually digest them) it is an omnivore. So you could turn this around and say that the fact that some gulls only eat meat doesn't necessarily mean they aren't omnivorous. DirkvdM09:07, 30 July 2006 (UTC)[reply]
(after edit conflict) The fact that some gulls have learned to eat other stuff does seem relevant, because those that come and finish off a pizza are omnivores, while those who spend their life at sea and eat only fish are carnivores (or ichthyophagists, if you prefer). --Shantavira09:11, 30 July 2006 (UTC)[reply]
Are they really? I think of them more as exo-skeletons full of mucous. Is there really any meat in them? Maybe in grubs. Mmmmmm, all this talk has made me hungry!--Anchoress20:07, 31 July 2006 (UTC)[reply]
Evolutionary relationship between skuas and gulls?
I'm aware that both the skua and gull family are members of order Charadriiformes - but how closely are they related? Did both have a common ancestor or did one family evolve from the other? I see great black-backed gulls on a daily basis and I have had the opportunity to observe the great skua and aside from the colouration, the similarities in size, shape and behaviour are uncanny. To a non-scientist, they seem like very closely-related birds indeed. Then again, compare the skua to the small, timid black-headed gull and they seem worlds apart. --Kurt Shaped Box00:39, 30 July 2006 (UTC)[reply]
According to the tables in p.9 of the first reference in Charadriiformes, gulls are more closely related to skimmers and terns than to skuas. Skuas, for their part, might be more closely related to auks than gulls, but it's not clear. You might want to also check the refs in Lari. Melchoir01:26, 30 July 2006 (UTC)[reply]
Just find the two families you want to compare. Start at one and just sort of walk back along the line until you get to a level from which you can reach the other family. When comparing how close family A is to families B and C, see how far out you have to go to get from A to B, then from A to C. The farther you have to go, the less closely related the two families are (well, the less similar they are in whatever measure is being shown). I'm not sure I explained that totally well... :) digfarenough (talk) 15:10, 30 July 2006 (UTC)[reply]
Yes, but .........
You release a toy balloon and it flies around frantically. It will do so even in a vacuum (deep space for instance), because the pressure inside the balloon moves it away from the escaping air. If I have that right, then I think the Thrust article needs to make this clear, because unless you read it carefully it seems to infer/suggest that it is the expelling air that is pushing (on something outside the balloon). Pedants go away please, but would appreciate comment from others. Rense00:42, 30 July 2006 (UTC)[reply]
This should go on Talk:Thrust. Yes, you're right. Newton was the one who declared this.Nathan Rosen
I would have thought that a toy balloon would immediately explode in deep space, and the air would ignore the fact that the neck was open. But if any air did manage to come out of the neck, the balloon would move away so that the centre of mass of all the air was preserved. G N Frykman08:55, 30 July 2006 (UTC)[reply]
You're forgetting the mass of the balloon itself. So the centre of mass of the shreds of the balloon and of the air will move in opposite directions. DirkvdM09:19, 30 July 2006 (UTC)[reply]
A balloon in space would be able to hold the same internal/external pressure differential that it does at ground level without exploding. The center of mass of the balloon and the gas in it would stay in the same place it started if you released it in space, except for gravity effects. A newspaper editor derided Robert Goddard, physics PhD, as "not having even a high school knowledge of physics" because Goddard thought rockets would work in space "where there was no air to push against." The space program proved Goddard right. Some things never change.Edison17:30, 1 August 2006 (UTC). tjis is very true .best article[reply]
Just trying to refresh my knowledge here. IIRC (correct me if I'm wrong here), a man-portable minigun would *just* be within the realms of possibility, right? Assuming that the gun itself weighs approx 100lbs and the ammo pack and batteries to spin the thing up were located in a backpack weighing approx 150lbs (I seem to remember those figures from an article on this subject I read years ago) and the soldier in question was selected specifically for his size, strength and endurance, then a minigun could potentially be used as an (albeit impractical in the majority of situations) infantry weapon, right? --Kurt Shaped Box01:14, 30 July 2006 (UTC)[reply]
Yup, great movies - I've seen Predator too. :) I was thinking of the feasability of using a man-portable minigun for suppressive fire - a couple of 180-degree arcs of fire from a 2000RPM minigun towards a hidden foe (e.g. hiding in the undergrowth) would pretty much clear out everything, wouldn't it? Or at least cause them to retreat. Your own position would of course, have to be well-stocked. --Kurt Shaped Box01:29, 30 July 2006 (UTC)[reply]
Indeed. I have never really thought about why miniguns are not in more wide deployment. Seems like a good thing to throw in the back of a hummer and get out when you have to hold a position. --mboverload@04:00, 30 July 2006 (UTC)[reply]
the logistics of resupplying the soldier in the field would be difficult, as well as the amount of ammunition the soldier would need to carry to make it an effective weapon, given a regular light machine gun firing at around 800 rpm carries upward of 1200 rounds, scaling that up would give an enormous weight. and you have to wonder whether there is any advantage over existing weapons, which i'd doubt. Xcomradex09:23, 30 July 2006 (UTC)[reply]
I suppose. To take down an enemy soldier, you'd probably need to hit him with a quick burst from an assault rifle, just to make sure (unless you were a very good shot) - maybe four or five rounds. A direct hit from minigun fire would turn him into a pile of meat, which I guess is overkill and a waste of ammo. Going back to the Terminator movies (thinking of the future scenes), the use of miniguns against advanced robotic/cyborg infantry actually does make a lot of sense, considering the amount of damage that the endoskeletons can take and still function. In this case, tearing the enemy to shreds with a solid wall of fire would not only be advantageous - but entirely necessary. --Kurt Shaped Box11:28, 30 July 2006 (UTC)[reply]
I believe I read under trivia in the Terminator 2 article that Arnold was the only one on the set that could lift the weapon--he had to move it everywhere.
Really? You'd think that they could have afforded to hire a couple strong college kids to haul it around the set. And think how cool it'd be to list your last job as "Mini-gun wrangler" on your resume.
hello pk how r y
Hookes Law?!?!?!!
Helllooo. Can someone tell me the simple idea of what Hookes Law is please. I'v already searched it but I just cannot get the bloody gist of it lol. - Thanks Joel
You've read Hooke's law, then. Where are you getting stuck? Can you be more specific? If you can't be, I'm afraid you'll probably just get the first paragraph of the article quoted at you. If we had a better way of explaining it, we'd put it there. grendel|khan01:44, 30 July 2006 (UTC)[reply]
Yup, to be even more exact, the force you exert of a body is proportional to the extension of the body. Think of a spring. The harder you pull (greater force), the longer the spring becomes (extension from 0). And the relation between the force you exert and the extension is proportional! Ask for any help =]
Hello. I'm not an expert in the field, bit i had the pleasure of meeting a certain Professor Robin Ali, of the Institute of Ophthalmology, London, not so long ago and discussed his very impressive work. He is very much leading the way in gene therapy for retinal disorders. An overview of his work can be read here, some of his scholarly papers on animal models [2][3][4]. This source [5] (pdf) suggests that human trials are underway or planned for retinal diseases, but not RP specifically. This source [6] seems to suggest that human gene therapy for RP will be (or has been) tested. There is also more impressive work in dog models of Leber congenital amaurosis, according to these sources [7][8] human clinical trials for RPE65 gene therapy were targeted to begin in 2006. It is probably a bit early to know how successful these have been. Rockpocket03:40, 30 July 2006 (UTC)[reply]
How many calories??
Ive been reading the Calorie page and also reading up on Atwater system to calculate food energy values. But im wondering, is there a way or a formula to see how much a certain body mass (a person) is burning calories just by its normal functions, sleeping, breathing, pumping blood, other. So a person that weighs x kilos and its height is y cm, burns z calories during a 24 hour period. - Avalean - 30th July
There are things like that on the net, but they're not very accurate, because basal metabolism (resting metabolism) has many other variables besides body size. For instance, men and women of the same mass usually differ; people with higher fat percentages or higher muscle percentages; hormonal imbalances can change a person's metabolism. I've seen charts on the net but I hesitate to find them for you because I don't think they'd really be accurate. That having been said, we have an article on Basal metabolism that probably answers your question, although the article is tagged for needing cleanup, and the main formula mentioned says something about surface area of the body (sq m.) when I'd think it should be cubic metres, but what do I know? I just skimmed it anyway. But I noticed the article has some external links. Happy reading.--Anchoress03:15, 30 July 2006 (UTC)[reply]
Anchoress is correct in stating that any simple height/weight/sex/age formula is going to have poor accuracy (I'd guess +/- 20% for people in the "normal" ranges of activity, size, etc.). You could try the Harris-Benedict Equation, it's a classic. -- Scientizzle21:47, 30 July 2006 (UTC)[reply]
The reclusive lady is right, I think. Mass (which is related more to volume than BSA) matters more than body surface area. The BSA theory stuck as gospel following some heavy abstract theorising in the 19th century, and Harris-Benedict sort of preached on, without questioning the basic tenets. It seems as if general biologists these days don't even consider BSA as a real factor, but doctors and dieticians and bodybuilding product sellers carry on regardless. I see on the Basal metabolic rate article talk that it gets 5th place on Google searches at times, but to me it is pretty dense and confusing - not comparable to what I see in academic literature on the subject. I suggest Avalean should look to one of the recent mass related formulas, ignore height, and remember that an individual is not a statistic, so that just a table of values by age and weight is probably as good/bad as any formula. --Seejyb02:26, 31 July 2006 (UTC)[reply]
I seem to recall a method of calculating calories burnt by measuring the exact amount of heat given off by a person at rest, which should be directly proportional to the number of calories burnt. This test, of course, requires a laboratory and the proper equipment. StuRat04:32, 31 July 2006 (UTC)[reply]
Not just to some degree (gastric bypass) but also entirely (prevention of stomach cancer). The surgeons fashion a small pouch out of the esophagus and intestine. People without stomachs have to eat many small meals throughout the day, and avoid foods that the intestine can't digest by itself. --Allen06:01, 30 July 2006 (UTC)[reply]
I recall reading a piece online (probably here at Wikipedia, actually, but not sure) about a very unusual sound that was recorded somewhere off the southern coast of South America. IIRC, it was called a burp or a belch or something of that nature. The article mentioned that some people think it may be the vocalization of some enormous creature. Can someone provide more info? I've searched Google and Wikipedia, but I don't recall a lot of specifics, which makes searching pretty difficult. ISTR that there was a site online that provided a .WAV of the sound as well. TIA. Matt Deres04:19, 30 July 2006 (UTC)[reply]
but its not gettin compiled.
can u plzz suggest another statement.
thnk u!!
A few possible problems (I assume this is java):
You have not declared the string V1
"input" doesn't exist - that line should be
V1 = buf.readLine();
you may need to handle the IO exception from the readline statement
java is case sensitive, so v1 is not the same as V1
fix one or more of those and you may be good to go. Here's what I think it should look like instead:
Add the phrase "throws IOException" after the argument parenthesis in the method head
InputStreamReader reader = new InputStreamReader(System.in);
BufferedReader buf = new BufferedReader(reader);
String V1 = buf.readLine();
int a = Integer.parseInt(V1);
I mean it acts like a vulture (circles, eats caracsses and carrion). If the vulture had been discovered before the seagull, do you think that explorers would've named the various breeds of seagull 'sea vultures' or something? New world vultures are not real vultures either but they're called that because they act like vultures and the name stuck over the years. What do you think?
Eh - seagulls do a fair amount of hunting and foraging - they kill and eat crabs and shellfish (see seagull). I don't think they eat enough carrion to qualify them as a vulture-type bird. Whoa - I'm surprised there are any gull species links that don't exist given the number of gull fanatics on the desks! --Bmk12:53, 30 July 2006 (UTC)[reply]
Vulture is a whole seperate few families. I think I'll move this to Science.
The point I was (badly) trying to make is that the biggest seagulls fill the same niche in Northern Europe as 'vultures' do in Africa and 'vultures' do in N.America. The 'vultures' in N.America are only called 'vultures' because the first western people to see them thought they looked like the vultures they already knew about. If we define a 'vulture' as a "scavenging bird, feeding mostly on the carcasses of dead animals." as the vulture article does, then why are seagulls not classified as 'vultures' when they clearly fit the critera (in their natural habitat)? I reckon it's only because seagulls were discovered before vultures - if they didn't already have a name, they'd have been devined as 'vultures', I think. --84.67.154.5117:19, 30 July 2006 (UTC)[reply]
By that rationale, on discovery vultures could, or should, have been named as a type of gull! Historically animals would be named by their lay-discoverers after animals they already knew about, usually based on single, or groups of, defining characteristics. This may have been because they actually thought they were closely related to these animals, or simply as a way of identifying them with some meaning. These days were know that convergent evolution can lead to highly divergent animal species (in terms of evolutionary relationship) appearing very much alike as they fulfil a similar niche. Since we continue to refer to most animals by their traditional names, it can get confusing. However scholarly studies use scientific names for animals, which better reflect their phylogeny. Old and new world vultures are a good example of this. Old World vultures (Accipitridae) are of the genera: Gypaetus, Gyps, Torgos, Aegypius, Neophron, Gypohierax and Necrosyrtes while new world vultures (Cathartidae) are of Cathartes, Coragyps and Sarcorhamphus. Seagulls are from a completely different order (Charadriiformes) Thus, scientifically, there is no confusion between them. Consider also the aardvark (earthpig) and Killer Whale. Rockpocket18:46, 30 July 2006 (UTC)[reply]
It seems like we get a lot of seagull and masturbation questions on here. Anybody else notice this, or is it some illusion I have fallen for?
If 15% ("72% of statistics are made up on the spot") of article edits are vandalism why wouldn't 15% of questions be from kids who think, "let's see if we can make grown-ups talk about flying rats and wanking". Don't mind it, just answer; even if the person asking doesn't learn anything from the answer the rest of us will. Weregerbil18:33, 30 July 2006 (UTC)[reply]
I've noticed it as well, but why seagulls? If a kid wants to ask a silly question then giggle at the serious answers, why would he choose seagulls? Spanking the monkey, sure, but seagulls? Hyenaste(tell)18:42, 30 July 2006 (UTC)[reply]
Particularly funny is when there are a spate of very similar questions, often utilitising the word 'discuss', and you just know that some teacher has set a Wikipedia-savvy (well, savvy enough to know about it, but not enough to disguise homeword) class a particular problem. --Sam Pointon21:16, 30 July 2006 (UTC)[reply]
In answer to all the above, what can I say? I'm a gull fanatic. :) I spend a lot of time observing my locals birds and I've decided that I want to know as much as it's humanly possible to know about them (much of the literature tells me about what gulls *look like* or where gulls can *be found*, but very little about the lives of the actual birds themselves). I've raised baby gulls almost from the egg to re-release into the wild - I think that they're amazing birds, with a strange charm that I don't think anyone else could possibly understand unless they'd done the same thing themselves. I know a fair bit about gulls already but my head is filled with questions, which some of the guys here seem able to answer for me (it's much appreciated - this desk seems to be one of the more knowledgable gatherings of human beings on the internet). I assure you that I'm not asking silly questions for the sake of asking silly questions, or for kicks and giggles. I have no idea who keeps bringing up masturbation - I can't say that I've noticed that many threads about it recently. --Kurt Shaped Box21:19, 30 July 2006 (UTC)[reply]
You need to go to Wikibooks and write a book on seagulls to get them out of your system, since the elctroshock therapy has failed to do so. :-) StuRat01:21, 31 July 2006 (UTC)[reply]
Your gull questions aren't silly though. Hmm... did you ask the unsigned gull question just above this one? If not, gull-mania must be catching on. Hyenaste(tell)23:02, 30 July 2006 (UTC)[reply]
Maybe we can kill two birds with one stone (or at least make them go blind) by posting questions on the masturbation practices of seagulls ? :-) StuRat01:21, 31 July 2006 (UTC)[reply]
In small arms ballistics, how is "effective range" defined?
What does it mean for a rifle to have an effective range of 400m? Obviously a rifle bullet carries a dangerous amount of kinetic energy way beyond its effective range. And the probability that a target at a given range is hit in a single shot depends on many factors (e.g. marksmanship of the shooter, power of the scope, weather, size of the target). So, is there a standard definition for "effective range"?
in military terms, the effective range couples both the stopping power of the round, the velocity at that distance and the chance of hitting a target at that range. for example, in the NZDF, the effective range of the Steyr AUG was quoted as 300m, while that of the c9 lsw (a version of the FN Minimi) was quoted as much further, off the top of my head at least 600m. yet both fire the same round (5.56mm ss-109), but the c9 in normal use pumps out more rounds. Xcomradex11:12, 31 July 2006 (UTC)[reply]
Railroads: Where are the breaks on a freight car?
In the past the breaking force and break shoes on a railroad freight car were applied to the wheel rim to slow or stop the car. I don't see that on today's (USA)rail freight cars. Where is the breaking force applied and what's the mechanism that stops the wheel from rotating?
The, um, BRAKES on a railroad freight car are part of the truck assembly. This document has a really nice exploded diagram of a railcar truck on the third page. The brake shoe contacts the tread of the steel wheel. There is one shoe per wheel, four per truck.
Yes, technically the shiny part of a railroad car's wheel is the tread. If you look at this picture the shiny part of the wheel that contacts the track, that part is the tread. The raised rim on the inner edge of the wheel is the 'flange'.
Hall Effect
cant we use hall effect in producing electricity ? high voltage supply cables on their way could b made 2 pass through
tubes containing magnetic field.hence by hall effect potential difference would exist.
but i doubt the high voltage cable would get weaker in voltage after passing through the tube.
plz if anyone can explain it relating to conservation of energy and other phenomenons involved
Legend:
1. Electrons (not conventional current!)
2. Hall element, or Hall sensor
3. Magnets
4. Magnetic field
5. Power source
In drawing "A", the Hall element takes on a negative charge at the top edge (symbolised by the blue color) and positive at the lower edge (red color). In "B" and "C", either the electric current or the magnetic field is reversed, causing the polarization to reverse. Reversing both current and magnetic field (drawing "D") causes the Hall element to again assume a negative charge at the upper edge.
I would suggest checking the article too. Hall effect
Since a violation of the law of conservation of energy isn't possible (unless mass was converted into energy, which doesn't happen here), the energy passing thru the tube must be reduced to a level to match any increase outside the tube. StuRat01:12, 31 July 2006 (UTC)[reply]
I didn't read the entire post, but I saw this in it "but i doubt the high voltage cable would get weaker in voltage...." don't be so doubting. If that cable transfered any energy (via hall effect, or any other way) then yes, it would become weaker. By EXACTLY the amount that was transfered. 71.199.123.2401:05, 1 August 2006 (UTC)[reply]
Nope... the energy supplied to the electric potential comes from a change in the magnetic field. The wire loop must be moved through the field, and because of magnetic drag, this requires energy.
Fear of losing possessions?
What is a correct -phobia term for fear of losing possessions (assuming that one is NOT afraid forgetting, meaning it's not Athazagoraphobia). Bayerischermann19:43, 30 July 2006 (UTC)[reply]
When did the state of New Jersey started regulating psychotherapy? I found this online:1945 "The state of Connecticut passed licensure legislation for psychologists, becoming the first state to recognize psychology as a protected practice oriented profession." (source). --JWSchmidt04:40, 31 July 2006 (UTC)[reply]
I don't think the Board of Medical Examiners played any role, as the practice of psychotherapy seems to have been unregulated before that time. The NJBME would have (still does) regulated psychiatrists, of course, but that was the practice of medicine. - Nunh-huh05:25, 31 July 2006 (UTC)[reply]
The NJSBME certainly brings charges against those who practice medicine without a license. They list the names of those deemed guilty monthly. "Filed" wouldn't be my verb choice, but it's pretty much synonymous. - Nunh-huh06:28, 31 July 2006 (UTC)[reply]
Thanks for all of your help. This is starting to make sense. I found this which suggests that the attorney general brought the case to court. --JWSchmidt06:41, 31 July 2006 (UTC)[reply]
No problem. Perhaps the board only handles civil penalties, and the attorney general handles cases referred from the Board for criminal prosecution. - Nunh-huh06:44, 31 July 2006 (UTC)[reply]
Name for a class of chemical reactions
Is there a general name for a reaction in which a large molecule is split by the addition of a small molecule? It's the reverse of condensation, and hydrolysis is a special case. Solvolysis isn't it because the small molecule that's added isn't necessarily the solvent. Any ideas? —Keenan Pepper07:01, 31 July 2006 (UTC)[reply]
"cleavage" is used a bit in the literature, i can't think of anything more scientific, but i might be forgetting something obvious. Xcomradex11:14, 31 July 2006 (UTC)[reply]
In nuclear reactions, a large nucleus is split into two smaller atoms by collision with a small nucleus (or neutron). This is called nuclear fission but I doubt it is what you are looking for. Perhaps, decomposition? Nimur16:37, 31 July 2006 (UTC)[reply]
I'm pretty sure it's called "cleavage"... It's used all over the place in reports, specifically I recall, my old chemistry teacher's PhD work on "Rapid syntheses of difluorinated polyols using cleavable carbamates". Other stuff I've come across using 'cleavage' is "Base-catalyzed cleavage and homologation of polyhedral oligosilsesquioxanes". ≈Eh-Steve 04:26, 2 August 2006 (UTC)
Bah... What an awful article to have red-linked... Someone should sort that out... :D ≈Eh-Steve 04:30, 2 August 2006 (UTC)
No. A blackbody (usually written as one word) is an object which reflects absolutely no electromagnetic radiation that falls on it. A black hole is a perfect blackbody.
Hawking radiation is emitted from (as opposed to reflected by) black holes. Blackbodies may emit radiation (stars are almost perfect blackbodies) they just don't reflect any.
Physics - alfoil
Why doesn't aluminium foil get hot in the oven? I know it is an insulator and effective in reflecting heat, but why? Would other metals (say copper) have a similar effect? BenC709:51, 31 July 2006 (UTC)[reply]
It does get hot, but because it is so thin and has a large surface area compared to its mass, it loses most of its heat almost as soon as it comes out of the oven.--Shantavira09:58, 31 July 2006 (UTC)[reply]
It is important to note the difference between Temperature and Heat. Though the temperature may rise, there is not much heat energy stored in the foil because it is so low-mass. Also, although it reflects heat, I believe Aluminum would usually be classified as a conductor. This has a double-effect: the heat is easily conducted away whether it is warming up or cooling off! Nimur16:35, 31 July 2006 (UTC)[reply]
I'll note in response to Nimur's comment that while aluminum is a pretty good conductor of heat, it does an excellent job of blocking radiant heat (infrared radiation). Also, since the foil traps the air around the wrapped-up food, it reduces the convective cooling. TenOfAllTrades(talk) 17:48, 31 July 2006 (UTC)[reply]
Yes, I understand why food gets hot in an oven... So why are metals good at reflecting radiant heat? I assume it has something to do with the delocalization of electrons, which makes it hard for them to be pushed into an excited state...? BenC701:06, 1 August 2006 (UTC)[reply]
See plasma frequency. Basically, if the EM wave is "slow" enough (has a frequency below the plasma frequency of the metal), the electrons in the metal (which are delocalized, as you said, and mostly unbound) can match its pace perfectly. Then all the incident energy goes into moving the electrons, which then (because they are accelerating) re-radiate the energy immediately. At higher frequencies, the wave "sloshes" the electrons instead and is absorbed within the metal. Many common metals have plasma frequencies in the UV, which makes them excellent reflectors of visible light and IR. --Tardis16:49, 1 August 2006 (UTC)[reply]
I began thinking about this while driving down the road one day. Say I'm accelerating at a rate of 5 mph/sec and I come to a hill which drops my rate of acceleration to 2 mph/sec. While my rate of acceleration is decreasing, am I decelerating or still accelerating? Or both?
I suppose that you mean to say that you are travelling at a velocity of 5 mph and when you encouner a hill, your velocity drops to 2 mph. That means that you have decelerated. If your velocity is still decreasing while you are climbing uphill, then you are still decelerating. We can say that the deceleration is constant if the rate of decrease in velocity is constant (say the velocity drops by 1 mph every second).
You are still accelerating because your acceleration is still greater than 0. You just accelerate more slowly when you are on the hill. --Yanwen13:56, 31 July 2006 (UTC)[reply]
Yanwen is right. Your rate of acceleration is decreasing, but your velocity is still increasing. As an aside, as you get to the hill, and your rate of acceleration drops, your jerk is decreasing - jerk is another word for "rate of acceleration". All these quantities should become blissfully clear if you take a basic calculus course - all these quantities are different derivatives of your position. Your position is the "zeroth" derivative of position, your velocity is the first derivative of position, acceleration is the second derivative of position, jerk is the third, etc. And consequently acceleration is the first derivative of velocity, and jerk is the second, etc etc. --Bmk14:39, 31 July 2006 (UTC)[reply]
That's close, but not perfect. If the hill is ideal and encountering it is instantaneous, the acceleration drops instantly to 2 mph/s, so there is infinite jerk for 0 time at that point and no jerk elsewhere (the jerk has the form of a Dirac delta function). Part of what's confusing is the phrase "rate of acceleration" which can be interpreted as "rate of velocity change (a.k.a. acceleration)" or "rate of [change of] acceleration, a.k.a. jerk". The second interpretation is a bit odd, but there's confusion nonetheless (with "rate of speed" and such too). I'd recommend using "amount" or "rate of change of" (as appropriate) instead of "rate" where there are already speed-like variables and time-derivatives everywhere. --Tardis23:12, 31 July 2006 (UTC)[reply]
Other possibility: if the 2 mph/s value is at the top of the hill, to the entirety of which the reduction in acceleration is attributed, then there has been a negative jerk during the trip up the hill (although we can't say anything about the precise nature or distribution of the jerk without more detailed information). But this isn't what a hill would really do (given constant driving power); it would be closer to the instant change I suggested a minute ago, where when on the hill the acceleration had one constant value and when off the hill it had another, also constant, value. In other words, with a different (odd) interpretation, we can have a negative jerk, but nothing has indicated a decreasing jerk as Bmk suggested. --Tardis23:17, 31 July 2006 (UTC)[reply]
Good point - that wasn't what I meant to say - I meant to say the jerk is negative, not decreasing. Thanks --Bmk03:22, 1 August 2006 (UTC)[reply]
mph/s? Is that unit actually used? If so, it might deserve a mention (and conversion) in the acceleration article. It isn't as weird as kWh/yr, though, because that mixes up three units of time, second, hour and year (the second is in the watt, which is J/s). DirkvdM10:02, 1 August 2006 (UTC)[reply]
sun
What is the most visible part of the sun? a)Corona, b)Chromosphere, c)photosphere, d) prominence
If you read our article on the sun (<== click on the link), you will quickly find out that the most visible part of the sun is the....aack! (*#&$#@$#( Gasp.... the gods of the reference desk are smiting me for almost answering a homework question! I'm sure you'll find the answer pretty quickly. (PS: I would suggest using your browser's text search function and search for "visible" once you get to the sun article) --Bmk14:49, 31 July 2006 (UTC)[reply]
This does sound rather like a homework question. The answer should be pretty obvious if you paid attention to the different layers of the Sun.
Nope. Polaris is 44 minutes (0.74 degrees) away from the celestial north pole, so it can't be used to pinpoint exactly where the celestial north pole is. The "first point of Aries" is the reference point for right ascension: it's the point in the sky (relative to the stars) where the Sun appears to be, at the March equinox. (To be more specific: at some point during March, the Sun will appear to be directly overhead at some point along Earth's equator. The position of the Sun at this moment, relative to the stars, is right ascension 0.) As for declination, the declination of a star is simply the latitude at which the star appears to be at a 90-degree altitude. (Of course the star can't be directly overhead along the entire line of latitude, but it will appear overhead at some location along the latitude line.) --Bowlhover22:59, 31 July 2006 (UTC)[reply]
I'm confused. You say that both Jabir ibn Hayya and al-Razi discovered sulfuric acid. Which one was it?
I'm not sure who "you" is, but the wikipedia article on Sulfuric Acid states that Jabir ibn Hayyan is credited with the discovery, but al-Razi studied its properties and production. I don't see a contradiction - hope that clears things up. And btw, it's usually helpful to link to articles that you are referring to so everyone knows what you mean - do this by enclosing an article name in double square brackets. --Bmk15:41, 31 July 2006 (UTC)[reply]
Ah - thanks. That seems like a difficult contradiction to resolve - probably will take someone more familiar with the topic and the sources. There may be no good answer, but the articles should at least agree with each other. --Bmk17:38, 31 July 2006 (UTC)[reply]
What is the correct term for a person who is neither male nor female? One one hand, Wikipedia's articles state that "hermaphrodite" and "pseudo-hermaphrodite" are antiquated and offensive, and have been replaced by "intersexual." On the other hand, I have seen numerous uses of these words in the media. Including the article by Jared Diamond in Discover magazine. JianLi16:13, 31 July 2006 (UTC)[reply]
Hermaphrodite would mean both male and female, neither would be asexual. Hermaphrodite is only somewhat offensive to humans, but the term is used in biology all the time. I have never heard intersexual. Is that like transexual?
According to the relevant articles, asexuality refers to the condition of having no sexual interests or desires, while intersexuality describes the condition of having ambiguous genitalia. The latter sounds like what the questioner was asking. Intersexuality notes that advocates for intersexual people do not like the terms hermaphrodite and pseudohermaphrodite, which suggests they should be restricted to describing non-human animals. --Ginkgo100talk · contribs · e@21:25, 31 July 2006 (UTC)[reply]
Of course asexuals have no sexual desire! They can't have sex! Asexually reproducing biota include bacteria, sponges, and cnidarians.
There are two meanings of the word; one refers to organisms that reproduce asexually, the other to humans who don't feel sexual desire (see Asexuality). --Allen04:00, 1 August 2006 (UTC)[reply]
I think it's "transgender"
Transgender refers to individuals who practice behaviors usually associated with the opposite gender or who identify with the opposite gender. Asexual, in the context I was using it, also refers to a human sexual identity. Of course asexual also refers to a type of reproduction not involving the exchange of genetic material used by many non-human organisms. I apologize if I was not explicit enough with context. --Ginkgo100talk · contribs · e@19:49, 2 August 2006 (UTC)[reply]
Digital cameras and battery life?
I'm considering buying myself a new digital camera, as my old one seems to have finally died on me. Quick question - are the newer ones still as battery-hungry? My previous camera (bought about seven years ago) would go through 4xAA batteries in a couple of hours, less with rechargables - I hardly ever used it because it was so damn impractical. --Kurt Shaped Box18:40, 31 July 2006 (UTC)[reply]
I don't know about cameras being less power hungry, but in my experience modern NiMH rechargeables should easily outlast ordinary disposable AA cells. Mind you, the highest-capacity ones tend to be costly, and the capacity ratings are usually "ideal" ones: a "2400 mAh" battery does not usually last 1.5 times as long as a "1600 mAh" one in practice, and will usually cost more than 1.5 times as much. Still, even the low-end ones often outperform disposable cells in camera use, since they deliver a more stable voltage over time. A good battery charger is also important — it doesn't have to be an expensive brand-name one, but it should be ΔV-controlled ("intelligent") and should have independent charging circuits for each cell. I've had good personal experiences with the cheap store-branded "Rapid Charger" and cells from Biltema; similar products, or possibly even the exact same ones modulo branding, can probably be found in local stores elsewhere. —Ilmari Karonen (talk) 19:36, 31 July 2006 (UTC)[reply]
I have a German brand, Concord 5345z (5 Megapixels), which comes with a recharger for it's two rechargeable AA Nickel-Metal Hydride batteries. I would call it a battery hog, yes, as the two batteries only last about a day if you are taking pics constantly. However, as long as I remember to recharge them every night, a one day charge seems workable. One bad side, though, is that uploading the pics to my laptop also depletes the charge. I've learned not to dawdle when doing so. I used to upload one pic, then edit it, then do the next, etc., which ran my batteries down. If I just upload them all at once, then turn off my camera and recharge the batteries while I edit the pics, it works out much better. StuRat22:37, 31 July 2006 (UTC)[reply]
I don't know if power consumption has changed, but the major factor here is the display. A bigger one will (I assume) consume more power, but more important is how much you leave it on. If you are likely to run out of juice, turn it off when you don't need it. That way you'll still have the camera standing by without having to worry too much about the battery running down. Make sure the camera has a separate and handy button for this.
Also, whatever the power consumption might be, it is always good to have two batteries, so you can use one while the other one is being charged. Or better still, you don't need to worry about when to charge because if you take two batteries and the one in the camera runs down you can use the other. You're unlikely to go through more than one battery in one day, so in the evening you can charge the one that ran down.
So in the price of the camera you should include the price of two batteries - they differ quite a bit in price, especially if there are (decent) alternatives by other manufacturers (such as Hama (if you buy two of those you'll have Hamas :) )) DirkvdM11:59, 1 August 2006 (UTC)[reply]
Reflection and Radiation mutually exclusive?
Lets say I take a shiny metal object, one that is polished and reflects light well, and heat it until it glows red-hot. Does the object continue to reflect light while it is glowing, (I assume the intensity of the radiated light would be many times greater than that of the reflected light, obscuring the latter), or are radiation and reflection mutually exclusive behaviors? Assume that the shiny metal is heated in an oxygen-poor environtment to avoid tarnishing oxidation. I was unable to find the answer in blackbody or associated articles.Tuckerekcut19:03, 31 July 2006 (UTC)[reply]
Yes, it will continue to reflect light. And if you could build a precise-enough instrument to measure the intensity of light, (or any other part of the EM spectrum), you would be able to see that the two processes add linearly. Nimur20:47, 31 July 2006 (UTC)[reply]
Actually, this isn't really correct. If the object is hot enough to be visibly glowing, then the spectrum of excitations responsible for that glow will also make it receptive to absorbing visible light, at which point the light shined on to it would be partially contributing to heating the object. Since energy must be conserved, the total emitted light would still be expected to vary linearly with the light shined on it (neglecting other modes of energy dissipation), but the spectrum would be changed and not have the wavelength preserving qualities normally associated with reflections. Dragons flight21:43, 31 July 2006 (UTC)[reply]
in the same vein as the previous post, if the light being reflected is of a high enough frequency to be out of the blackbody radiation for the objects temperature, then it will reflect. think about a regular mirror at 298K, it is still pumping out black body radiation, yet it still reflects light, because visible light is of a much higher frequency than the blackbody radiation at room temperature. Xcomradex08:34, 1 August 2006 (UTC)[reply]
Note also that when you heat a metal until it grows red-hot, its chemical characteristics might also change in some cases, which could affect how it reflects light. – b_jonas13:07, 1 August 2006 (UTC)[reply]
Thanks, all. I'll try it in a glovebag ( [nearly] oxygen-free) when I get back to school. I'll see if I can get the palladium catalysts red hot then try to bounce a laser off the surface. I'll post my findings around here somewhere...Tuckerekcut21:07, 1 August 2006 (UTC)[reply]
String Theory as a T.O.E.
Hello. How does string theory solve the renormalization problem of gravity? And if it doesn't, why is it considered a possible T.O.E?AmateurThinker22:48, 31 July 2006 (UTC)[reply]
At a guess I would suggest that it solves the problem by saying gravitons are massless. If not (assuming it does solve it) perhaps gravitons having a non-zero spatial extent would help. I have heard a suggestion that spacetime itself is effectively comprised of gravitions, rather like a sheet of chainmail. I cannot remember where I heard this (I may even have just dreamt it up) so I cannot comment on the credibility of this theory. If it were so then gravity could be treated as a field and the problem would be almost solved.
Sleep deprivation induced cogntive impairments
Several articles I've read have mentioned such impairments, but did not mention whether they were reversible upon receiving an adequate amount of sleep, or whether such impairments were residual. Anyone?
of course this depends on how serious a situation you are talking about. Several days without any sleep at all can result in permanent madness and is actually a form of torture (a 'mild' form of which is used in Guantanamo Bay by continually leaving the lights on). Mind you, I'm talking about no sleep at all. Normally, one will have at least some microsleep (dozing off for a sec), which makes a big difference. DirkvdM12:14, 1 August 2006 (UTC)[reply]
Long-term health effects of sleep deprivation are unknown, however the cognitive function impairments all reverse after a few hours of sleep no matter how long the deprivation.
What disorder?
What is the name of the disorder/allergy where red skin is induced by scratching?
Hives and/or contact dermatitis. It's not mentioned in wikipedia, but there is a form when rubbing/scratching the skin rasies red welts (bump). I saw a picture where someone wrote the word hello on someones back, just by lightly scratching them! Also see Eczema, and maybe general Dermatitis. 71.199.123.2400:59, 1 August 2006 (UTC)[reply]
Human beings evolved to survive, but why did we evolve the ability to do calculus?
I do not understand why humans can do so many clever things that are quite unnecessary for survival. Surely evolution is parsimonious and abilities that are of no value to surviving in the savannah environment should never have been developed? --62.253.44.3400:18, 1 August 2006 (UTC)[reply]
There isn't a gene for being able to calculus. Rather, doing calculus comes naturally (with some training) to any human with a firm grasp on symbols, the concept of reducing complex problems to tiny steps, and a few other basic skills that definitely have evolutionary value. StuRat00:40, 1 August 2006 (UTC)[reply]
Intelligence is a major advantage! It allows humans to solve difficult problems, use tools (as noted by Melchoir), comunicate effectively, resolve conflicts nonviolently, waste time on the computer :), and many other things. The ability to do calculus is just an extension of the ability to do arithmetic and count, albeit a pretty big extension. Emmett504:01, 1 August 2006 (UTC)[reply]
(Warning: this opinion is very biased and discriminating. Don't take it entirely seriously.) I don't think humans have ability to do calculus genetically coded in them. Humans have evolved such that they could comprehend more and more abstract thoughts and plans (symbols, as StuRat says), and as they also learnt how to count, the ability to do algebra came naturally. Caluclus, on the other hand, is not like that. Most people don't understand calculus instinctively but have to be thought rules of calculus written in the language of algebra. The basis of calculus were invented by a few brilliant mathematical geniuses who did have a calculus instinct by fluke, e.g. Newton and Leibniz (real calculus), Euler (complex analysis). Once they wrote the foundations of a theory in the language of pure mathematical formulas, others could derive new results in calculus by manipulating the prior results using the rules of algebra. – b_jonas12:58, 1 August 2006 (UTC)[reply]
FYI Norbert Weiner as a child prodigy and after learning algebra, invented the calculus only to discover it had already been invented. (He entered college at age eleven.) This implies something; I'm not sure what. -Wfaxon23:57, 8 August 2006 (UTC)[reply]
It implies that it's a real thing, not just something silly somebody made up (like most of psychology, for example). It also implies he should have spent a bit more time studying existing theory before developing his own. StuRat01:39, 9 August 2006 (UTC)[reply]
I was thinking more along the lines that at the turn of the 18th century you needed mature world-class geniuses to invent the calculus; at the beginning of the 20th century all you needed was genius. Either that or the way that algebra was taught in 1900 itself implied the calculus since the authors of the algebra texts Weiner learned from certainly knew it. BTW one really shouldn't be too critical of a nine-year-old's lack of research back then: No internet! -Wfaxon04:21, 9 August 2006 (UTC)[reply]
The nice thing about general intelligence is that it is very flexible—you're not locked into one adaptionary box. That makes it a tremendous evolutionary advantage when you are a species that is not terribly fast, strong, or with acute senses relative to the sorts of predators around you. It also means that you can migrate with relative ease and don't have to wait hundreds of generations to develop (or lose) a shaggy coat. ;-) --Fastfission12:50, 1 August 2006 (UTC)[reply]
I used calculus as an example of intelligence. Although we take our intelligence and the man-made world for granted, I think it is very odd that it evolved at all and we can do all these things. Its as if an earthworm had somehow evolved the ability to run at 60mph - it doesnt need it to survive in its environment, so the ability to run at 60mph should never have evolved. Yet in humans this is what has happened - you dont need much intellect to survive (other animals get along without it) yet somehow we have developed this intellect and ability to do things such as eg calculus which natural selection has played no part in. How? Why?
I've heard a couple of differing opinions on what the evolutionairy advantage of our intelligence is. Some propose that our ancestors required enhanced cognitive abbilities so they could better use the tools they had. One particulair example I liked was how ancient humans might have had to use their brain to figure out the trajectories the rocks they threw would take. It could also be a result of the tight social groups we form. Being able to accurately communicate with your fellow man would be a big advantage (and this would require some decent brain power).
Whatever the basis of our smarts may be, you should remember that we haven't stopped evolving. Things like calculus, rocket science, chemistry, sudoku puzzles and Barney the dinosaur all fill a niche in our society and thus are not without purpose. So our ancestors did not do calculus because it didn't have any use to them, being able to hit a gazelle at 50-100 yards away did and from these humble beginnings the rest followed. -Pascal
The answer is that we did not evolve the ability to do calculus, or mathematics in general — that's why we are so incredibly bad at it. Consider the fact that even quite simple computers, like the one on your desk, can outperform humans in basic arithmetic by a factor of about a U.S. billion (that's 109), but have enormous trouble with tasks like, say, speech recognition, or catching a thrown object, which we did evolve for. Our ability to do any mathematics at all is basically a side effect of us having evolved, for other reasons, enough abilities for abstract thought to — barely — allow universal computation. That means we can, in principle, do anything a computer can do; it doesn't mean we can do so in any reasonably efficient manner. To use a programming analogy, all our conscious thought processes happen at an extremely high level, far from the hardware — indeed, the fact that they are subject to conscious monitoring implies that. We have efficient low level primitives for all sorts things that are useful for survival in nature, but for things we didn't evolve such primitives for, we need to rely on high-level processes that are extremely inefficient, since they are built upon systems that weren't designed for such use at all. —Ilmari Karonen (talk) 22:19, 1 August 2006 (UTC)[reply]
Consider, for example, our skills at language. Noam Chomsky's famous hypothesis is that there is a kind of language gizmo in the human brain that can learn any language, because it carries some sort of pre-prepared algorithm for verbal communication. But extensive research seems to suggest that their is no such thing as a central language processor in the human brain. Rather, language processing is distributed all over the brain: when a illiterate child looks at words, activitiy is seen in several regions in the rear part of the brain; when they listen to words, their brain shows activity in an area in its center; when they speak nouns, activity occurs in a different area of the central brain, nearer the top; when they speak verbs, activity occurs in two separate areas, one nearer the front, the other nearer the back.
In 1861, when Paul Broca discovered significant damage to an area of the brain (now called Broca's area) while doing an autopsy on a patient with a verbal disability, observers worldwide thought he might have discovered something very significant. Broca's area is on the left side of the brain, near the front; damage there will cause sufferers to speak haltingly, and mostly in nouns; they generally understand others who speak to them, and realise that they are unable to speak. Broca's patient, Leborge, was nicknamed 'Tan', because it was one of a handful of words he could say. Carl Wernicke made a similar discovery, in an area now called Wernicke's area. Wernicke's area is also on the left side of the brain, but further back. Sufferers of damage in Wernicke's area can speak fluently, but their speech is essentially a randomly assorted jumble of words.
What this shows is that our linguistic skills are not a discrete brain function. Rather, they are an aggregate of dozens, possibly hundreds of more basic skills that may have been evolved for very different reasons, such as hunting, scavenging, or tool making. Math is probably the same way. One of the most remarkable features of the human brain is its 'plasticity', or ability to rewire itself to perform completely new tasks. The most remarkable example of this is a woman who had a stroke that caused massive damage to the left hemisphere of her brain. For some time, she was unable to read, until she was coached into using her right brain to interpret symbols. She completely rewired her brain to have a totally different approach to symbols; she went from a scientific, logical approach to the interpretation of the alphabet to seeing them as an artist. Likewise, people who are talented with math have brains that have assembled basic, simple functions into a more complex skill. It is like a computer rewriting its own software to use its basic functions in a totally new way.
By the way, this is precisely the debate between Darwin and Wallace. Wallace argued that natural selection would have only had to make humans a little smarter than other big apes currently are in order to have an unbelievable evolutionary advantage, and didn't believe there was any reason for a "savage" to develop a conscience or complicated moral sensibility, much less high intelligence. Darwin countered with his theory of sexual selection, arguing that bigger brainpower might have been related to impressing females, in the same way that a peacock's feathers serve no functional purpose outside of being attractive to the ladies. Wallace never bought into that, though (it probably didn't help that he was left at the alter—he never could accept the idea that female mates were in charge of choosing attractive mates), and instead went the direction of thinking that a conscious spiritual force had guided human evolution into its present position. Darwin was understandably horrified and wondered if Wallace hadn't "murdered" their "child". --Fastfission04:39, 2 August 2006 (UTC)[reply]
As the Donna Nook fire range has been used by A-10 Thunderbolts for cannon practice and the A-10s have a GAU-8/A Avenger Gatling gun, which indeed fires depleted uranium armor-piercing shells, is there any publicly available information on the health risks associated with the place? Does anyone know whether the Freedom of Information Act could be used to request information from the MoD or is it not applicable? Thanks, E Asterionu talking to me?00:35, 1 August 2006 (UTC)[reply]
Basic Burn Question
I looked on web md, but they skirted the question. I just got a minor burn by grabbing a hot pan. It's been two or three days and the small burn has turned into a small raised blister that doesn't hurt at all unless put under particularly hot water. The raised blister's really irritating me, and i was wondering if after three days, the skin has formed underneath the scab sufficiently for me to pop it, let the liquid out, and peel off the scab to let the new skin heal over. If not, when, if ever, is this a good idea? Should I never pull the scab off, because it seems to me that that scab is not what's going to become my new top skin layer. Thanks. Sashafklein05:57, 1 August 2006 (UTC)[reply]
My understanding is that as long as there's fluid in the blister, the flesh beneath is vulnerable. All the literature I've read says never to pop blisters, so I ice them, which decreases the fluid pressure and makes them less irritating. Technically you're not supposed to apply ice directly to burns, but you're not actually applying it to the burn, you're applying it to the blister. Also, even after several days the application of cool can have anti-inflammatory benefits. Also, cover the blister with a bandaid or a loose dressing to keep it from bursting or being bumped.--Anchoress07:01, 1 August 2006 (UTC)[reply]
Actually, when you burn your skin the best thing to do is to cool it down with warm water (not hot of course, but about body temperature). This makes it hurt more at that moment, but it will prevent a blister from forming and thus reduces pain later on. At least, I heard this once and tested it on one occasion, and in my case it worked. DirkvdM12:24, 1 August 2006 (UTC)[reply]
I hadn't heard that warm water is better than cold, I'd just heard that ice isn't good for burns. But we're talking about a 3 day old burn here, IMO ice is better.--Anchoress18:24, 1 August 2006 (UTC)[reply]
Yeah, it'll either deflate or end up getting punctured on its own. If the latter happens you should wash it very carefully and put some antiseptic (e.g. Neosporin) on if you have it, and probably a bandage, to prevent infection. I've done this an embarrassingly high number of times (something about the way my toaster is made seems to encourage me to burn my fingers trying to get things out of it). --Fastfission12:48, 1 August 2006 (UTC)[reply]
I've been a burn surgeon for many years and this is my advice:
The fluid in a burn blister is clean, but not sterile and eventually will get infected. As long as the blister is intact, the burn wound is protected and relatively painless. If these blisters are small and do not interfere with function (e.g. not over a joint, or so large that they compress the circulation to a body part) then I leave them alone for 1 - 2 days. If it starts to get red, indicating infection, they need to be removed and topical antibiotics applied. If there is suspicion that the burn is fairly deep, then I remove the blister so that it can be inspected on a frequent basis. If there is any doubt, you should see a burn specialist ASAP.
BTW, cold water applied within seconds of a superficial burn will tend to lessen the degree of injury - but it must be done RIGHT AWAY. Best of luck. --Ronbarton21:35, 6 August 2006 (UTC)[reply]
Diff. b/w university and college
my question is wat is the difference b/w university/college..and university/ institute or college/institute??
If you tell us which country you are from, we might be able to be more specific regarding the use of the words college and university. However, academic institutes tend to be research orientated, while colleges and universities will offer teaching as well as research. Rockpocket07:53, 1 August 2006 (UTC)[reply]
Ever been to a university? They have many colleges.
Maybe in your country. In Australia, a college is either a tertiary learning institution of lower status than a university, or the last 2 years of high school. Universities here don't have colleges within them, as far as I know. JackofOz14:12, 1 August 2006 (UTC)[reply]
In the UK, "college" is used sometimes to mean a further education institution of lower status than a university; sometimes as a synonym for university, and for some universities, including the most prestigious, a university is divided into semi-autonomous colleges (see e.g. King's College, Cambridge). Some colleges are called schools (see e.g. London School of Hygiene & Tropical Medicine) but nobody ever uses the term "going to school" to refer to further education (this is a significant difference of usage with the US). Notinasnaid15:05, 1 August 2006 (UTC)[reply]
Want more confusion, see the article about the University named the College of Charleston. It can't even decide what it is! Well, it was a college that gained university status and decided to keep the old name for the undergrad and only change to University of Charleston for graduate courses. --Kainaw(talk)14:57, 1 August 2006 (UTC)[reply]
(edit conflict) In the UK there are plenty of schools called colleges (though then are often private schools - and to confuse matters further, they call them public schools - e.g. Fettes College). There are also sixth form colleges, which are further educational establishments, as well as higher educational establishments, called colleges. I have never heard of an UK academic institution that teaches though, and neither have i heard of a British university be anything other than a higher educational establishment. I await correction on this. So the bottom line, i think, is that college is a term that can cover a lot of different educational establishments, but university and institution are more precise (though there are possible exceptions). Rockpocket17:28, 1 August 2006 (UTC)[reply]
The Institute Of Education is part of London University, and teaches teachers.
In the U.S., generally a stand-alone college is more narrow in scope than a university, which includes several divisions usually called "colleges." For example, I graduated from the College of Arts and Sciences at the University of Oklahoma, although I took courses in other colleges (e.g. a course in the College of Business). A stand-alone college may be as rigorous as a university, or it may be less so, as is the case for community colleges, junior colleges, and (at least some) for-profit colleges. --Ginkgo100talk · contribs · e@19:58, 2 August 2006 (UTC)[reply]
ADHESIVES
WHAT IS THE BEST ADHESIVE TO BE USED BETWEEN RUBBER AND POLYURETHANE, TO PREVENT PRESSURIZED WATER TO COME BETWEEN. WALEED KHAMIS
You want something like an acrylic resin that will turn into a hard polymer in the presence of water. Luckily, that is what Super Glue is. How stiff do you want it to be? Super Glue gets very hard, so the rubber won't be flexible. (Oh - and don't shout!) --Kainaw(talk)14:54, 1 August 2006 (UTC)[reply]
Whether S-S overlapping takes place only in the formation of Hydrogen molecule? Are there any examples for such type of molecules in which S-S overlap takes place? —The preceding unsigned comment was added by Vamsi mahathian (talk • contribs) .
Does anybody know why on the label of US made True-Spec BDU trousers it is written that you should not starch them? I have heard a military urban myth that starching your battledress makes it easier to see you using night-vision equipment. Can anybody deny or confirm this claim? Thank you for your time. Mieciu K13:46, 1 August 2006 (UTC)[reply]
Standard military issue night-vision equipment works in either of two ways
By taking in the low amount of photons and magnifying the light so you can see on a little screen
Infrared radiation intensity is mapped, with different colors denoting different temperatures.
I don't know what the starch is that you use for washing is made of (perhaps starch?). If it is starch, I would think that the infrared radiation nor the visible light intensity would be had a more than negligible effect on.
Unfortunatly the label on the bottle of liquid (laundry?) starch dosen't specify what is the content of the starch that I have used, but I presume it was vegetable starch. Mieciu K14:21, 1 August 2006 (UTC)[reply]
My experience with night-vision in the Marines is that a moonlight scope (which amplifies the visible light available) gets a bit of a reflection off smooth surfaces. If you overly starched your uniform, it is possible to get a reflection off the smooth surface. But, that is not likely. Infrared, on the other hand, did pick up on guys in newly starched uniforms better then those with unstarched ones. At the time, it was DI's and recruits. The DI's have heavily starched uniforms. I could see them much better than the recruits who were in wrinkled and dirty uniforms. Just to throw a wrench into the works - this was with the old uniforms. The Marines use a different material and pattern now. --Kainaw(talk)14:47, 1 August 2006 (UTC)[reply]
Of course, it's also a bad idea to starch battle clothes for other reasons; stiff clothing is more likely to make noise, giving away your position, and cause abrasions, which may then become infected. Quite a stupid way to be injured on the battle field, isn't it ? StuRat02:10, 2 August 2006 (UTC)[reply]
Yes, that is how starch used to be made. However, I believe potato starch turns black as it oxidizes. So, you will want to experiment with the starch from other vegetables. --Kainaw(talk)14:50, 1 August 2006 (UTC)[reply]
Try drying the goop from atop a pot of boiling rice. I vaguely remember doing this in elementary school to make starch. Nrets15:32, 1 August 2006 (UTC)[reply]
Just Google "make your own starch" (use quote marks), e.g. "You can make your own starch by mixing 2 teaspoons of cornstarch with 1 litre of water." Other hits do include potato receipes.--Shantavira18:23, 1 August 2006 (UTC)[reply]
My bike has hub gears but I have to stop pedalling in order to change gear - is this a common feature of all hub gears or are mind just dodgy? Would I damage the bike if I changed the gear but carried on pedalling forward? And why is the hub physically unable to change gear unless I stop pedalling? --130.161.135.3114:35, 1 August 2006 (UTC)[reply]
You should only have to stop pedalling for a split second (not at all if you're lucky). Yes, it is perfectly normal.
Have you looked up Sturmey-Archer? With such gears it is normal to stop pedalling while changing. At traffic lights, you might even have to back-pedal in order to change gear before setting off.--G N Frykman17:12, 1 August 2006 (UTC)[reply]
If you just slow the pedals down a bit you should be able to change gear without actually stopping the "flow". Even with the other type of gears (which I can never spell) it's not a good idea to apply much force to the pedals while you change gear as this puts unnecessary strain on the mechanism.--Shantavira18:27, 1 August 2006 (UTC)[reply]
I love hub gears and hate derailler (sp?) ones. I would be interested to know if there is now another company making hub gears since Sturmley Archer went out of business, as you cannot buy new hub geared bikes in the UK (except for a very heavy dutch town bike I think). The only hub geared bikes here are very very old ones. --81.104.12.13820:50, 1 August 2006 (UTC)[reply]
Back-pedalling to change gears before traffic lights? I haven't used a gear bike in years, but I don't remember having to do that. Then again, maybe I anticipated the lights and changed gear before coming to a standstill. However, the hub gear article says "The other main advantage is that the gear can be changed when the bike is stationary, which makes them suitable for riding in city traffic with lots of stops and starts." DirkvdM07:50, 2 August 2006 (UTC)[reply]
A geared bike is like a manual transmission car. On a car to change gears you use the clutch to disengage the engine from the transmission and then change which gears are engaged. On a bike, since the pedals only work one way (forward) and freewheel the other direction, you can effectively disengage the gears from the rear wheel by pedaling slower than the gears are turning. This allows you to switch without placing major stress on various components (as would be the case if you tried to slam a car in gear without using the clutch). Since derailleur type depend on the chain to ride itself to a new sprocket it needs be moving a little.72.1.70.5813:14, 8 August 2006 (UTC)[reply]
Homework Questions
Q1) You are running a fermentation using anaerobic bacterium 'Megasphaera elsdenii' for the production of hexanoic acid using glucose as a carbon source.
(a) Assuming the hexanoic acid is a growth-associated product, draw a sketch graph of the relative concentrations of glucose, hexanoic acid and biomass with time for a batch culture. Explain what is happening at each stage of the fermentation.
(b) What calculations would you use to determine the efficiency of this fermentation in regard to the conversion of substrate to product, and the speed of production of the product?
(c) You need to increase the efficience and speed of the production of hexanoic acid. What environmental factors would you consider changing to achieve this?
i'm guessing that the answer for this is temperature and possibly pH
Q2) You have been given the task of removing the particulates from a fermentation broth, prior to extraction of the product from the liquid.
(a) i) Describe the structure and principle of operation of one type of filter you could use at production scale.
(ii) If you found that you were unable to achieve a suitable filteration rate, what other methods of particulate separation would you test?
(b) Describe one method for the drying of fermentation products, and state whether it is suitable for a heat-labile product or not.
–--81.154.224.13315:04, 1 August 2006 (UTC)[reply]
Since you failed to see the big link for posting a question at the top of this page, you probably missed the note telling you to do your own homework. --Kainaw(talk)15:36, 1 August 2006 (UTC)[reply]
Try reading the relevant articles, then come back here if you have an actual question, in your own words, about something you don't understand.--Shantavira18:31, 1 August 2006 (UTC)[reply]
Black hole A partial balck body
As far as i have read ,it says that a perfect black body is somthing that can absorb as well as EMIT every possible radiation?????
in that case why is black hole not a partial black body?????????--59.178.2.24315:14, 1 August 2006 (UTC)Harshita Gupta[reply]
I have never encountered this term "partial black body". I take it to mean anything that isn't a perfect blackbody or a perfect mirror! In theory a blackbody can emit radiation of any frequency. The frequency of radiation emitted depends on the temperature of the blackbody (there is a nice graph of this in the black body article. As the temperature of a black hole is determined by the black body radiation temperature of the radiation that comes from it, it is possible to determine that the temperature of any observable black holes (as opposed to theorised sub-atomic ones) would be extremely close to absolute zero (~.00000001-.00000000000000000001K). This is why they don't emit every possible radiation.
Ummmm.... no. See the black hole article, the temperature of black holes is roughly 2.73 K, the same as the background temperature of space. Dan15:02, 10 August 2006 (UTC)[reply]
Chronic wounds and maggot therapy
Good day,
I wish to know:
1. what are the sickness/dieases/injures would cause chronic wounds / necrotic(dead) tissue?
2. what are the sickness/dieases/injures would cause chronic wounds / necrotic(dead) tissue, but not recommend to apply Maggot Dbridement Therapy(MDT) treatment?
3. Are there any reports stated that MDT treatment fail to deliver successsful wounds healing？
4。 Are there any reports stated that MDT treatment tansforms chronic wounds worse?
Thank you very much.
Please take a short amount of time to familiarize yourself with the instructions at the top of the page. We're pleased to help out with most questions, but I'm afraid that we have to ask you to Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. TenOfAllTrades(talk) 16:16, 1 August 2006 (UTC)[reply]
Now that you mention it, I guess it did. We had zero elephants in Charleston before last month. Now, there are three times as many elephants in Charleston. --Kainaw(talk)16:26, 1 August 2006 (UTC)[reply]
Lets see.... The elephant gestation period is about 22 months. Lets assume about 50% of the elephant population is female. Even if every female was pregnant at once and gave birth in the last month (and assuming there was no elephant deaths) then the population would simply have increased by a factor of 0.5. For the population to have tripled, every female would have had to have had quadruplets in the last month. According to this source [10] "Twins are very rare in elephants" and the ones in captivity in Bangkok "may have been unique". Therefore the chances that there has ever been elephant quadruplets seems highly unlikely. Given this, the answer to your question should be obvious. Rockpocket17:44, 1 August 2006 (UTC)[reply]
For those who don't get it, last night Stephen Colbert did a segment on Wikipedia for The Colbert Report. He urged viewers to rewrite truth by editing a few Wikipedia pages, and Elephant was one of them. Melchoir19:30, 1 August 2006 (UTC)[reply]
The media are calling for mass vandalism on Wikipedia? Are they getting scared? Afraid of the competition? (in which case they should have picked Wikinews, but let's not give them any ideas). Maybe we need an article on information terrorism. DirkvdM08:00, 2 August 2006 (UTC)[reply]
Well, Colbert -- or at least his character on TV -- is a great believer in the democratic relativity of truth. He thinks that if something is repeated enough, it becomes true, and that Wikipedia is an ideal tool for exploiting this phenomenon. Of course, this is just the show's way of lampooning conservative American thinking. On the "The Word" segment, while he was talking about Wikipedia, at one point the caption read "The future will not be verified"; I take this as evidence that he's actually aware of WP:V in real life. Melchoir18:25, 2 August 2006 (UTC)[reply]
Can I use an online brokerage to invest in any stock exchange? I'm thinking specifically of the Toronto Stock Exchange (I am an American). How to specify the symbols used on each, since a three-letter symbol in one exchange might stand for a different company in another?
Silage is a functional definition for something you feed to animals while stover is just described as everything but the grain. As for earlage...
Solubility vs. Temperature Curves for Glycine-Sodium Sulfate Solutions
How do I find Solubility vs. Temperature Curves for different concentrations of Glycine and Sodium Sulfate Solutions? Glycine is the simplest amino acid (NH2CH2COOH) and Sodium Sulfate is an inorganic salt, often called saltcake (Na2SO4). Thanks for your help.
M.D.S.—
I'd like to make clear from the start that I have a lot of respect for women, that I'm a very gentle person, and that I abhor violence or aggression. To continue -
The average size of human males is greater than that of human females. I am not sure to what extent that this is true of other primate or mammalian species.
Some time ago I heard on the radio someone saying that this size difference evolved due to males fighting among themselves for female mates. I think the speaker was taking care to be P.C., as wouldnt it be more likely to be due to larger males raping less powerful smaller females, and thus evolution would select for both larger males and smaller females?
And, on a more minor point, perhaps human IQ evolved because of the machiavellian tactics required to get a mate and avoid deadly violence in a primitive society that was brutish and violent and without any ideas of gentlemanly behaviour?
Humans are social animals, meaning not that they (necessarily) behave more socially, but that they live in groups. Any aggression within the group would make it less stable and more vulnerable, giving offspring a smaller chance of surviving. Humans also form couples. A female without a mate might get less meat, which would stint the child's growth and such, giving it an evolutionary disadvantage.
However, if, like you do, you view humans as individuals fending for themselves, bigger and stronger women would have a better chance of protecting themselves and their offspring, both against rapists and other threats. I'd say that the fact that females are smaller supports the notion that they are social animals. Is this true for other animals as well? DirkvdM08:21, 2 August 2006 (UTC)[reply]
People tend to leave out the possibility that we may have been created. Intelegent design may help you to understand not only our physical atributes but also our social structure.ĆÁĎ
I have no technical info, but I can tell you it's not so bad with the earplugs. And I'm sure they're perfectly safe. Melchoir01:32, 2 August 2006 (UTC)[reply]
When I went they gave me head phones to listen to any radio station I wanted. I couldn't really hear any noises, and I could also hear the mri tech through the head phones asking me how I was doing and how long each scan was going to take.
Now that I don't know about. I seem to recall that the reason for the earplugs was more that the sound is annoyingly loud rather than dangerously loud... but my memory is terrible. Anyone else? Melchoir02:59, 2 August 2006 (UTC)[reply]
The only thing potentially dangerous about MRI scanners are freak accidents relating to the magnets—i.e. if something metallic is brought into too close of a range with an active scanner it can be pulled into the machine (when that "something" is a gun or an oxygen tank, it can easily be fatal), or if the patient has some metal in their body they don't know about (which is why people who have worked in autoshops or other places where you can get filings embedded into you without your knowledge are generally prohibited from being in MRIs). Other than that there is no known damage to be suffered from MRI scanners, to my knowledge. It's a danger worth taking seriously but it is a side effect of the way the scanner works, not a direct product of being scanned. Statistically it is very safe (I have had it done to me personally, and there was no problem at all. In the end I got a neat picture of my brain out of it by asking the people to send me the raw datafiles). --Fastfission03:14, 2 August 2006 (UTC)[reply]
The gun incident happened because there was a police officer in the room, just a bit too close to the magnet, if I recall... --Fastfission12:41, 2 August 2006 (UTC)[reply]
As stated in the article, it does indeed use RF energy. If you go to the NMRI article, and scroll down to the safety section, you can read all about the health concerns. --198.125.178.20713:35, 2 August 2006 (UTC)[reply]
MRI's can generate sound pressure levels up to about 130 dB during certain scans. There is the potential for hearing loss at these levels, so earplugs (or muffs) are necessary to protect the patient / subject's hearing.
MRI's do use RF energy. The energy can create focal heating, particularly on electrically conductive materials that can act as antennae. Make sure that there is space and / or padding between your body and the walls of the MRI and any wires used to monitor your vital signs during the exam. The RF energy is believed to be of no health concern.
Magnetic energy (and RF energy, for that matter) is non-ionizing. This means that the cancer risks that are present in conventional X-ray imaging are not present in MRI imaging. The magnetic fields used in MRI, even though they are dramatically more powerful than most people would otherwise come into contact with, are not shown to have any adverse biological effects. The magnetic fields can interfere with implants and devices, so it's critical to provide your full medical history to the MRI provider.
The primary risk in MRI is the magnetic attraction of ferromagnetic materials. These sorts of accidents make up the majority of injuries in the MRI environment. Focal heating is second. These accidents are largely avoidable and, despite recent dramatic increases in MRI accidents, are fortunately not terribly common.Tgilk (talk) 16:17, 14 December 2008 (UTC)[reply]
Speed of the Space Shuttle
Hi,
Does anyone know what the speed of the space shuttle is from T-0 to SRB separation? I was watching the launch the other week and just got around to asking the question. Deltacom151502:03, 2 August 2006 (UTC)[reply]
Sorry 'bout that. I meant the acceleration of the Shuttle from 0 to SRB separation and the velocity is is traveling when it clears the tower. Deltacom151520:51, 2 August 2006 (UTC)[reply]
What is the difference between electrostatic and electromagnetic levitation and another question
What is the difference between electrostatic and electromagnetic levitation? i have heard that electrostatic levitation can also lift non-conductive materials. is this true? secondly could electromagnetic waves or electrostatic waves be used to push an object instead of levitate it? [ by directing the force at the side rather than the bottom for example]
thanks
curious marve
The diff is that magnetic repulsion lifts in the one case and electrical repulsion in the other. Yes, only certain materials, like metal alloys containing iron, may be magnetized, while all materials can hold an electrical charge. And yes, either force could be used to fire a projectile, see coil gun, rail gun, linear accelerator, and cyclotron. StuRat03:59, 2 August 2006 (UTC)[reply]
A copper bowl can be made to levitate by coils placed below it which produce an ac magnetic field. May be related to work by Faraday with a copper disc in a magnetic field, or by Tesla with a copper egg in a rotating magnetic field. I'm told the bwol heats up so the demo is usually for a few seconds. I've seen a demo with a magnet and liquid nitrogen in which the magnet levitates, or maybe a condictor levitates over the magnet. Maglev is used for some high speed trains. A charged object should levitate above a plane conductor with the same charge, if the magnetic repulsion is greater than the object's weight. It should similarly be lifted by a plane or point of the same charge above it, but this would tend to be unstable if the charges were constant. Edison23:22, 3 August 2006 (UTC)[reply]
Thank you all, but can i crarify this please. So any material can be moved or levitated by elecrostatic fields, even stone,plastic or wood?
Curiousmarve
U.V- Effect
Hello! Very recently, one of my friends was working in the Laminar-chamber , he was busy streaking... and accidentally, the UV was switched on. Engaged in his work, he didn't realise it for about a minute , ie. he withdrew his hands from the laminar after about a min. Later, he consulted a general physician, and a radiologist too. All the tests indicated that he had no internal or external damage whatsoever. I want to know was he too lucky? Or may be the intensity of UV was too low? Is a minute's duration enough, to cause damage to human tissues(keeping in mind, the UV used here) ? --Pupunwiki02:52, 2 August 2006 (UTC)[reply]
What's a "Laminar-chamber"? You don't say what the wavelength and intensity were, so I'm thinking the dose was so low it was harmless. —Keenan Pepper03:58, 2 August 2006 (UTC)[reply]
A laminar flow cabinet is a type of biology safety cabinet for culture and/or for filtering potentially biohazards. Often they have UV sources for sterilisation purposes. Obviously UV exposure is not ideal, but i have seen quite a few scientists expose themselves to UV (usually in a electrophoresis gel transilluminator, which one might imagine to have higher UV intensity) for many minutes. Generally they suffer the equivalent of a bad sunburn on the exposed area. Of course, the long term effect of such an exposure on the skin and eyes is unknown, but there is no reason it should do any more damage than spending too long at the beach one summers day.
If your friend didn't even have superficial skin burns, then i expect the dose was low enough, the intensity was low enough and/or his skin tone was dark enough for no serious damage to be done. Or more likely a combination of all three. Either way, if the doctors have given him the all clear, it is most likely not something to worry about. Rockpocket04:38, 2 August 2006 (UTC)[reply]
Pretty much what I was going to say. Laminar flow cabinets use UVC (the shortest wavelength of UV and the most harmful) to kill germs, but one minute isn't long enough to do significant damage (unless you stare at it and it hurts your eyes). The reason for all the warnings is that if you make a habit of working with the UV on, the damage will build up over time and you'll get skin cancer. —Keenan Pepper04:46, 2 August 2006 (UTC)[reply]
I have to say, I'm a bit skeptical. When the UV is switched on in one of these hoods, there is no doubt that it has been turned on. In every model that I've ever seen, the lighting switches are configured as "on/off/UV", where "on" is working lighting, "off" is no lighting, and UV is a brilliant radiant purple or blue. I can't imagine that anybody would be so engrossed in their work that they wouldn't notice such an abrupt change in lighting, or somebody making such a mistake in the first place. That being said, such exposure for less than a minute is unlikely to have any problems. – ClockworkSoul16:35, 2 August 2006 (UTC)[reply]
At current erosion rates, how long would it take for the present continents to erode to sea level if there were not any new land mass created from volcanic activity or any other process? The reason for this question is that I heard it said that it would take only 14 million years. If this is true, then how are there any fossils found dating back any further?
Just 14 million years is indeed an impressively short time span. And in the 80's erosion was considered the biggest threat to human food production (that place is now probably taken by climate change), although that is in part due to the wrong ploughing techniques.
Anyway, erosion is not just the removal of material - the material also gets deposited elsewehere. Also, it doesn't take all land above sea level to erode to below the present sea level. As more material gets deposited into the seas, sea levels will rise, speeding up the process. So the mountain tops will erode away, depositing their material on the lower ground, where most life resides. In time, this will get flooded, life will move further up, get covered in turn, etc, until it is all gone. And buried. In real life, apart from volcanic activity, there's also the rising (and falling) of landmasses. So many bones buried beneath the sea will eventually 'surface' (literally). Some have even made it to the highest peaks (sea shells on Mount Everest).
You ask " If this is true, then how are there any fossils found dating back any further?" That's an easy one, because there is volcanic activity and other processes. Personally, though, I doubt it can be true. Would Mount Everest erode to nothing in 14 million years? Let's see now, it is 8,850 m high. To go away in 14 million years it would have to erode 8850 / 14000000 m per year, which is about 0.6 mm per year. That's quite a lot for solid rock. Notinasnaid09:36, 2 August 2006 (UTC)[reply]
That rate sounds believable to me. The missing element is that the mountains are being pushed up as fast or faster than they are being worn down, however. StuRat06:31, 3 August 2006 (UTC)[reply]
Do fossils get buried by volcanic activity? Of course some will, but are they preserved for us to find? Sediments (from erosion) sound more probable to me. DirkvdM10:36, 3 August 2006 (UTC)[reply]
Ok, I visited the suggested web pages. Thank you for the advise. However the web page said that 200 million years ago the mouth of the Miss. was as far back as Illinoise. My question has changed direction. How is it that Florida formed? If you receed all rivers back proportionately the same amount Florida becomes disconnected. Florida also has the St. John river, which is pretty large, that would split it. Florida seems to be to flat to be formed from plate uplift or volcanic activity. both of these actions make me think of mountains, Florida does not have any. I hope ya'll like to answer questions because I have a lot. Thank you for your patience.ĆÁḌ
I believe most of Florida, the Gulf coast, and central US were underwater at that time. I'm not sure if the water level was higher or the land lower or some combo of the two. Do we have a map of this in Wikipedia ? StuRat06:17, 5 August 2006 (UTC)[reply]
I geus nobody has a good answer?
Sure we do. Your assumption that erosion happens by itself is wrong. At the same time some surfaces are being eroded, many others are being buried in sediment. Surfaces so buried, and any fossils they contain, are completely protected from erosion. StuRat06:30, 7 August 2006 (UTC)[reply]
MRI accident on House
In an episode of House ("Euphoria" part 1), Dr. House wants to find out whether it's safe to do an MRI on a patient with ferromagnetic bullet fragments in his head, so he goes down to the morgue, shoots a corpse with the same kind of gun, and puts the corpse in the MRI. The bullet fragments jump out of the corpse and destroy the MRI machine.
Two questions:
How large does a ferromagnetic object have to be to cause harm to the MRI machine or the patient? I mean, many breakfast cereals contain "reduced iron" which is basically iron filings. Is it safe to undergo MRI after eating a lot of Cheerios?
Why did Dr. House think it would work? He's a brilliant doctor, he speaks many languages and he knows random facts about everything... why is he so clueless about basic physics? Did the show's writers just make a mistake? —Keenan Pepper04:25, 2 August 2006 (UTC)[reply]
I would suggest the primary explanation is that it makes better tv to have him destroy a MRI after shooting a corpse to demonstrate the point, than explain the same thing in dry scientific language. And anyway, House isn't really that smart. Rockpocket04:49, 2 August 2006 (UTC)[reply]
What about ear/eyebrow rings? I have a few. I wonder if they'd be torn from my flesh and fly around like shrapnel inside the machine? --Kurt Shaped Box08:36, 2 August 2006 (UTC)[reply]
Yep, if you google 'mri accidents' you'll see there was a case where someones hairpin was dragged inside their head... Xcomradex10:07, 2 August 2006 (UTC)[reply]
If you walk by an MRI machine with metal earrings you can feel them start to tug (or so said my girlfriend at the time), much less a bullet in a gun. My guess is that it made more sense for the writers to have eclectic Dr. House do something like that than it did to have him say, "Well, obviously the better way to test if a bullet is ferromagnetic (if we need to test this at all) is to, I don't know, just put it near a smaller magnet, or maybe even just very slowly introduce it into contact with the MRI machine?" Anyway... when you sign up for an MRI they make you answer a million questions about ways you might have accidentally got metal filing into your body (people who have worked in machine shops for a living are not allowed to take them because of the chance they might have a metal sliver in them somewhere that they don't know about), so I imagine it doesn't have to be too big of a piece. I am sure the iron content of your blood is not a problem though, X-Men 2 not withstanding. --Fastfission12:47, 2 August 2006 (UTC)[reply]
I had to get my permanent retainer temporarily removed to have an MRI awhile ago, but oddly enough, the reason they gave is that it would ruin the image(distort the field around my head), not that it might rip my teeth out. Black Carrot22:03, 2 August 2006 (UTC)[reply]
The retainer may have been made out of a metal that is not ferromagnetic, which would not pull your teeth out but could cause distortion. 48v18:37, 4 August 2006 (UTC)[reply]
Based on my experience, people who have worked in machine shops are not prevented from having an MRI scan performed on them. Depending on the risk exposure, they may be x-rayed a few times to see if any fragments of metal are actually still in them (in the eyeball, in my case); and if none are found the MRI scan will proceed. Anecdotally, I heard that one can hold something metal, like, say, a spoon up to the wall outside an MRI suite and it will be magnetically stuck to the wall. Depends on the building, of course, and how close the MRI scanner is to a wall...
Didn't that whole episode turn out to be a hallucination? House might be allowed a little rhythm under those circumstances.... --Trovatore04:02, 3 August 2006 (UTC)[reply]
How large does a ferromagnetic object need to be? A patient was blinded by a tiny sliver of ferromagnetic material in the eye some years back. An aneurysm clip of a couple centimeters twisted and tore, killing a patient, and a nail clipper put out an eye of yet another patient. So, depending on where it is, a very small mass of material can be very dangerous to a patient. Damage to the MRI machine typically requires something a bit more massive (i.e. chairs, gurneys, gas cylinders, etc...). However, MRI service personnel are sometimes called to take care of a machine that isn't producing quality images, a problem that is often triggered by a collection of small ferromagnetic materials (barrettes, jewelry, paperclips, etc...) that wind up getting collected inside the MRI machine.
Would his corpse experiment work? NO, it wouldn't, at least not the way it was shown on TV. There are two forces that act on ferromagnetic materials in the presence of a magnetic field. One is torque where the object tries to line-up with the magnetic polarity of the field. The other is the translational (or 'missile') effect which draws ferromagnetic materials to the strongest part of the MRI field (in the center, where the patient lies). The torque forces keep getting larger and larger as you move to the center of the MRI. The 'missile' effect forces, however, are greatest near the entrance to the 'mouth' of the MRI and actually drop to zero where the patient would be for imaging.
So, when House put the corpse into the MRI and 'turned it on' and the bullet came flying out, there are a number of things wrong. First, there is no turning the MRI's magnetic field on and off for most systems. So, the attractive 'missile' effect would have been present and increasing as they brought the corpse towards the MRI, but would have dropped to zero once they had the corpse's head in the middle of the MRI. The torque, which would have wanted the bullet to align with the polar orientation of the MRI's magnetic field, would have grown and grown, but having the bullet simply twist wouldn't have been nearly as good 'TV drama' as having it blow through the skull and 'shoot' the MRI machine.
Now the recent ER episode of the patient being pinned to the MRI by the gurney that they were brought into the room on... that's another story... see
http://mrimetaldetector.com/blog/?p=217
How about when I put 5 amps through a nail-and-copper-coil solenoid I made in high school? That thing made some noise! — [Mac Davis] (talk)
If you stop a fan from going round, then the coils in the motor will be pulling on each other, or on the permanent magnets if there are any, with a force that's proportional to the current. Assuming the fan is mains-powered, then that current is alternating at 50 or 60 hertz (cycles per second). This makes the force pulsate at 100 or 120 hertz (because each cycle of current has two peaks, one positive and one negative). The pulsating force makes a buzzing noise because the parts of the fan are periodically distorted by the force. The same thing applies to the solenoid. The distortion is partly due to electrostrictionmagnetostriction and partly just to mechanical forces. --Heron21:02, 2 August 2006 (UTC)[reply]
light speed
What if light were travelling in a striaght tunnel,and the tunnel happened to be the radii of a fast moving object.Since the end of the rod would be moving faster,would not that light be moving faster than light?
I'm not sure I really understand the question; but the answer is no.
Light moving faster than light, so something moving faster than itself? I suppose you mean a specific beam of light moving faster than 'the speed of light'. In other words, you're asking why there is such a thing as 'the speed of light', ie why light has a fixed speed. I could try an answer, but I'll leave that to someone more knowledgeable. I just tried to help you make your question clearer. DirkvdM09:47, 2 August 2006 (UTC)[reply]
I'm going to guess that you are imagining a long tube being spun round and then light shone down the tube, and then you are imagining that the light would move at the sum of it's own velocity and the velocity of the tube it is shining down. The answer is still no, because a) relativistic effects would ensure that the light always moved at constant speed and b) if the tube were spinning at any noticable speed the light would hit the walls, not follow the changing path of the tube. Light doesn't change direction to follow the walls it is 'contained' in. DJ Clayworth17:43, 2 August 2006 (UTC)[reply]
There are several different recorded light speeds. I just heard on NPR radio that scientist claim to have stopped light and held it in place for a few seconds.
The speed of light depends on the medium it's travelling in. Air reduces it by a percentage point or two, diamond by about 60%, and certain exotic materials by a great amount indeed. This doesn't affect the fact that the speed of light in vacuum is a constant, and the highest possible speed. --Pyroclastic14:03, 10 August 2006 (UTC)[reply]
Quanta UNIVERSE
We know that the theory of everything comprises strings.So does that not make it possible only for integral values of particles or strings to exist,so therby only intergral values of force and other quantity to be transmitted and recieved?
Please don't say "just a theory." However string theory fulfills only half of the scientific method. The theoretical part, not the experimental. — [Mac Davis] (talk)
I will say whatever I please. :) You're right that something being 'just a theory' doesn't mean it doesn't have value (the general theory of relativity being one example). Everything starts off as a theory anyway. But my point was that you shouldnb't confuse theory with knowledge. Strictly speaking, we don't know anything and everything is theory. Which again boosts the status of theories, of course. DirkvdM10:41, 3 August 2006 (UTC)[reply]
Electron
An charged particle under acceleration should emit radiation.Then why would not a charged particle undergoing acceleration around the nucleus of the atom or in the cyclotron emit radiation,as it is tracing a circular path and objects tracing a circular path undergo constant acceleration?
The image of electrons as orbiting nuclei in a similar way to planets orbiting stars is a simplification. See Quantum Mechanics.
whats the advantage of air brakes over their hydraulic counterparts. i see that heavy trucks and trains tend to prefer air brakes over hydraulic,why?why not have these air brakes on passenger cars if they are that effective?
An obvious answer is that passenger cars aren't quite as heavy as trucks. The other part of the answer would then be that hydraulic brakes are in some ways more expensive (the brakes themselves, their operation, maintenance, whatever). DirkvdM09:57, 2 August 2006 (UTC)[reply]
There is no advantage - the two types of brakes do different jobs. Air brakes are used only as a failsafe backup system. In an emergency, the air is vented to the outside to apply the brakes. This is simple and reliable, but too cumbersome and not controllable enough for normal braking. Trucks, like cars, use hydraulic brakes for normal braking, because hydraulic brakes are quicker, smaller, easier to control and more powerful. --Heron20:53, 2 August 2006 (UTC)[reply]
Many heavy vehicles do use pneumatic brakes for normal braking—haven't you ever heard them at a stop light? In order to stop a heavy vehicle quickly you need to exert much more force than for a passenger car. One could design a hydraulic system with enough mechanical advantage to provide this force from a foot pedal, but then you would have much less control over braking. Air brakes are controled by a valve which feeds air from a reservoir to the pistons—giving much more control over the range of forces which can be applied. Air brakes are also more tolerant of leaks and water in the system.
Pneumatic brakes are not used in passenger vechicles because the are not necessay, are more expensive and bulky, and require more maintenance.EricR02:10, 3 August 2006 (UTC)[reply]
Well, what do you know, a subject I know next to nothing about and my answer was spot-on. Long live educated guesses. :) DirkvdM10:45, 3 August 2006 (UTC)[reply]
In the event of a major catastrophe, that sent mankind back centuries or approached (near-)existinction levels, could the internet data (such as the information from wikipedia) theoretically be retrieved then at a much later date? (such as the case of the Rosetta Stone being "translated" in the 19th Century)
Also, could theoretically the internet be received or "read" by other distant civilizations? (as in the way that extraterrestial communication/signals are hoped for possibly through radio waves I think)
Thanks for info. ==Joel==
Something similar was asked before here at the ref desk. Apart from that, the rosetta stone wasn't translated, it was itself a translation, helping with other translations. And if humans were almost extinct, the information on the Internet would not survive (it needs electricity). So the info would have to be stored in a different way. DirkvdM10:10, 2 August 2006 (UTC)[reply]
The information does not need active electricity in order to survive as just data on a million computers. There is a lot of worried discussion among computer scientists about how long current data storage mediums last — not too long. The Rosetta Stone, being carved in a rock, is much more durable than magnetic storage media, much less affected by the elements, much easier to use if part of it became damaged. Still, I imagine the sheer volume of data which goes into the internet means that quite a bit could be recovered even if nobody was tending to it for a few centuries. I imagine that many servers are in places that would be relatively protected from the elements (such as those buried deep within large facilities).
As for the second questions, the only way that the internet would be read by someone off of Earth is whether it is broadcast (like television or radio). I don't know enough about tramission protocols, but I do think that some internet connectivity is done via satellite? If that's true then those connections may be potentially interceptable, decrypted, etc., I suppose (I don't imagine WiFi signals to be strong enough to make it that far, but I know little about this sort of thing). Let's hope that the people with connections like that don't just use it to surf for porn. ;-) --Fastfission12:59, 2 August 2006 (UTC)[reply]
I've read a description of a wished-for radio telescope talked of by a radio astronomer: You take a star as your lens and sit back where the stuff you're interested in is focused by the gravity. The radio astronomer described it as potentially able to hear a walkie talkie (hand held radio) being used on a planet 10 light years distant. The latancy would suck though.
In my opinion, if it were some space beings coming to Earth long after humans were gone, it wouldn't be by chance. They would be attracted by the radio and television waves shooting out into space. Surely, they would decipher it before arriving on Earth and will have prejudged humans based on what they've seen and heard - pretty much how humans prejudge other cultures based on mass media. Youth in Asia15:01, 2 August 2006 (UTC)[reply]
The beauty of the Internet is that it is designed to work over just about anything - TCP/IP consists of many ayers and you just need to adjust the bottom layer (I think). And it does work over anything. I one route doesn't work, another one is used. So I suppose that everyone will at least once in a while receive some data that have gone through satellites. DirkvdM10:50, 3 August 2006 (UTC)[reply]
Thanks to all above for the info., Joel
how do we know if its been tried?
hi my names ben, ive been thinking about this perpetual motion thing a bit, since i noticed what seems like a working example, i dont expect to hold the key, but im curious to see other failed attempts based on this illusion of free energy. is there a list i can go through?
because regardless of weather or not it does create free energy, i think it may still be useful.
i think we'll figure it out one day, we'll follow a trail that will lead us to the very beginning, and there we'll find the supernatural, proof of thats not hard to find, also seems someone have allready nailed it,i like the way joal thinks, out side the box,i consider the physical universe as we know it a box.theres alot more if if you know how to open your eyes. search psychic witnesses, and ufo evidence.
thanks heaps for any help
Beno
You want us to check if something you will not describe has been tried before? Thanks for the confidence, but we're not gods. :) DirkvdM10:13, 2 August 2006 (UTC)[reply]
There's "a lot more" out there than "psychic witnesses" and "ufo evidence", indeed. But the latter two strike me as not very interesting, frankly: examples of a human willingness to believe, age-old desires to know that someone is in control, somewhere -- a hope that there is still mystery in the world. But there's much more mystery in the natural world than there are in dreams of the supernatural. How much more interesting the mantis shrimp is than the "greys" that the UFO nuts like to talk about! How much more bizarre the human mind is, with its strange wiring and odd sense of the world, than ramblings of New Age "psychics"! Oh, if only we could really appreciate how fascinating and bizarre the natural world is, we wouldn't have to take refuge in the relative banality of fantasies, which only reflect the limits of the human imagination! --Fastfission13:06, 2 August 2006 (UTC)[reply]
Very well said. I'm keeping that. — [Mac Davis] (talk)
Truth is indeed, in many ways, stranger than fiction. Sadly, though, the curious appearance of a shrimp doesn't help me make things levitate. Black Carrot21:51, 2 August 2006 (UTC)[reply]
I wouldn't view an apparently successful perpetual motion machine as proof of the supernatural, but rather as evidence of a natural, although currently unknown, form of energy. Radio wave energy, for example, was unknown for most of human existence StuRat06:08, 3 August 2006 (UTC)[reply]
You can fill in pretty much what you like for 'radio wave energy' because most of what we know now was unknown for most of human existence. DirkvdM18:52, 3 August 2006 (UTC)[reply]
When you talk about tings supernatural you are only talking about things observed that we can not yet understand. Things such as religion. There is ample amounts of imformation to support the thought of intelligent desighn. One day ,if man ever does find a way to understand these things in a way that would go further than religion, these things will be facts & not religion. Something that is truth from the begining is not less true simply because we do not understand. If nothing else, Science has taught us that. So, indeed there is an answer to prpetual motion and energy.ĆÁĎ
Consumption
I was looking for disseases/afflictios that greatly eat up/damage the inside of the body. Necrosis and consumption, but i'm looking for other, and perferabbly stronger examples.
Consumption doesn't eat up the body any more than many other diseases (see tuberculosis), though it was once thought so. The classic diseasse that eats up the inside of the body is cancer. For nasty and well known diseases try leprosy and ebola. Notinasnaid11:38, 2 August 2006 (UTC)[reply]
As well as 'eating up' the inside, im looking for things that make them go black-like when you see those anti-smoking adds, and they show you those black lungs.
That doesn't 'eat up' the lungs either, nor is it a disease, and anyway, working in a coalmine (or living next to a highway) is much more effective in blackening your lungs. DirkvdM10:53, 3 August 2006 (UTC)[reply]
These are all very good, and thanks to all the contriubtors. What woudl be great though are things that are very astheticaly profound, like more with an urg factor.
Did you read the article on ebola? Hollywood has embraced it because it considers (perhaps wrongly) that it has more urg factor than any other condition in history. Notinasnaid12:28, 3 August 2006 (UTC)[reply]
sexual thought freqency
Is there a real study on the freqency of sexual thoughts in men and women? All I find is contradictory and annecdotal.
I saw an article once (I forget where) about an interesting experiment which tackles (one element of) this question. They kitted out subjects with special spectacles which recorded where they were directing their attention. If I remember correctly, it was found that the average woman does look at the "interesting bits" of men, but proportionately less than men do for women.
I don't the experiment analysing gay men and women's behaviour.
Clearly, looking at bums is just one aspect of sexual thought, but it was a usefully revealing methodology, even if the specs themselves weren't all that revealing. --Dweller15:04, 2 August 2006 (UTC)[reply]
I've never understood the concept of "sexual thought frequency". To think about it repeatedly, wouldn't you actually have to stop thinking about sex at some point ? Who can do that ? :-) StuRat04:07, 9 August 2006 (UTC)[reply]
Geologic time scale terminology: Paleo- vs Eo-
In the Archean eon, why does the Eoarchean era precede the Paleoarchean era, when in the Paleogene period (early Cenozoic) the Paleocene epoch precedes the Eocene epoch? (Yes, I realize that the Precambrian time divisions were only recently established and assigning names to them is somewhat arbitrary; but even so, why would the International Commission on Stratigraphy have chosen to go along with a usage of prefixes which is inconsistent with the already long-established Cenozoic sequence of epochs? Were they catering to previous publications, or lazy geologists, or what?) Lots of searching on this seemingly trivial point has revealed absolutely nothing, which makes it all the more annoying (to me, anyway). --DWIII15:08, 2 August 2006 (UTC)[reply]
Megawatt_hour
How to compute the cumulative power output (in MWh) of a power plant generating 100MW?
What do you mean by 'at least for a day'? In case you're confused, the unit Wh is confusing and converting from power to energy is sort of 'the wrong way around'. One watt is one joule per second. So the Wh first divides by one unit of time (the second) and then multiplies by another (the hour). 100 MW means 100 MJ/s (one Joule of energy every second). There are 60x60x24 = 86400 seconds in one day, so the power plant produces 86400 Joule (or 86.4 GJ) per day. Which is equal to 2400 MWh, but that is not an SI unit (because of the 'hour' in it), so preferably use J. DirkvdM11:03, 3 August 2006 (UTC)[reply]
I think the picture is fake. The plausible types of 'invisibility' I've come across either require you to look through a specific viewpoint (and so would be handy to make your car look transparent from the rear view mirror) or only work at specific wavelengths, currently very small, meaning they could cloak against some detection systems, but not the human eye. I'm trying to work out which this is, or if it's new. Skittle17:44, 2 August 2006 (UTC)[reply]
Mmmm...yeah, the hand picture looks fake to me. The article is kind of vague about what exactly the research finding or engineering breakthrough is. It sounds kind of like they're talking about a metamaterial, but it's hard to say. And the appications they talk about don't make any sense, at least under that interpretation. If they've invented a specialized material that is invisible, how would that help you look through earthquake rubble? Or see through a hand? In any case, materials that are invisible (i.e. allow visible light to pass through them) are nothing new!! See glass and water and diamond, etc, etc. I really don't know what this article is talking about. But i'm also confused, because I thought the Royal Society was a reputable organization... someone want to clarify, or confirm, or explain why this is legitimate after all? --198.125.178.20718:08, 2 August 2006 (UTC)[reply]
The alt text for the hand image says "This is what you'd see if the system worked with the atoms in your hand". It doesn't work with the atoms in your hand, so the picture is a fake. There's a slightly less dumbed-down version of the story at hero.ac.uk. --Heron20:39, 2 August 2006 (UTC)[reply]
Ah. That makes much more sense. The other article did a good job making it sound like a crackpot fraud. None of that silly "seeing through earthquate rubble" stuff. --198.125.178.20721:10, 2 August 2006 (UTC)[reply]
It did sound awesome though, thanks.
The picture isn't supposed to be a picture of the experiment (it is still all hypothesized anyway), just as a nice looking thing that goes with the article. If you want to learn more, what the articles talk about are nanotechnology's quantum dots used as artificial atoms. — [Mac Davis] (talk)
I should also point out that there are other, far more likely causes, such as dry air, mold spores in the air, dust mites, pet dander, chemicals (like formaldehyde) released from new furniture, carpets, paint, and cleaning compounds, etc. StuRat05:58, 3 August 2006 (UTC)[reply]
Candles are supposed to produce ozone and I thought that was a good thing, or is that just new age mumbo jumbo? DirkvdM11:08, 3 August 2006 (UTC)[reply]
Ozone indoors (and outdoors, at ground level) is generally a bad thing, although it can kill bacteria and viruses in the air. As for candles, I'd be more concerned with the soot they produce than any small amounts of ozone. StuRat21:01, 3 August 2006 (UTC)[reply]
You haven't been breathing in air out of your microwave after you put lots of metal in it have you? That might be the cause. It could be inhalation of bug zapper fumes. — [Mac Davis] (talk)
unit question about article : List of countries by electricity consumption
Hello,
I am quite interested in the total number of Watts countries around the world use for industry/civilian purposes/others...
But : List of countries by electricity consumption gives consumption in numbers of kWh, and consumption per capita in kWh as well. Call me crazy, but I thought people use Watts/kilowatts , and they use kilowatthours during a day or year or whatever.
So in short : what is up with the units? Are they for a full year or what?
The unit "kilowatt hour" is a unit of energy - it is the amount of energy transferred in one hour by one thousand watts (a watt is a unit of power). The list you cited is describing how much electrical energy each country consumes in a year. I agree that it is confusing - the article should say that the time period is one year (i'm fairly sure it is).
I'm not sure what you would use "watts/kilowatts" - for. The per-capita figure is simply the total figure divided by the population of the country. If you want to know the power usage, you can find the average power usage of the country by dividing by the number of hours in a year (8760); then you will have the average power consumption of the country in kilowatts. --198.125.178.20719:19, 2 August 2006 (UTC)[reply]
I think it can be assumed that the figures are kWh/year, since there's a column in the table that states which year the figure is for. I added "/year" anyway, just to make it clearer. --Heron20:30, 2 August 2006 (UTC)[reply]
Thanks, I discussed this with my dad (he works with industrial energy) and he agreed there is almost no doubt they mean :per year. But I wanted to check with you.
Now forgive my insolence, but I like to think in Watts (megawatts) too. For instance the power generated by windmills is given in megawatts. So... wouldn't it be nice to have a separate column converting it to Watt too? I mean, it would also be nice to compare then with [12]
I am willing to take care of that conversion.
Evilbu22:23, 2 August 2006 (UTC)[reply]
It's generally assumed that readers will be able to convert between units. Otherwise we'd have to include horsepower, ergs/second, etc. Composite units like kWh/year actually make sense, because giving consumption in watts would give a false impression of continuous consumption when actually electricity consumption is highly diurnal and seasonal. 1 kWh/yr = 0.114 W. EdC03:35, 3 August 2006 (UTC)[reply]
Wow, that is even more important. Are you saying that the Orders of magnitude article uses Watt as unit while the numbers are incorrect?? Evilbu11:25, 3 August 2006 (UTC)[reply]
That would indeed be a rather serious error., Especially if it isn't done consistently. What makes you say that?
Btw, Watt and Megawatt aren't different units. It's the same unit with an SI prefix. 'Mega' means million, so 1 MW is 1,000,000 W, The conversion is so easy it doesn't need to be given, but then of course you do need to know about prefixes, but you should learn that pretty soon at school. However, kWh/yr doesn't make sense because it mixes up three units of time: second, hour and year. I keepon trying to add this info to Watt-hour#Explanation, but it keeps on being removed because it wouldn't be interresting info. I think this discussion disproves that.
If you're from the US it may take some getting used to that there is just one unit per quantity in the SI system, but ultimately it's a much easier (because simpler) system. DirkvdM13:04, 3 August 2006 (UTC)[reply]
Yes, thanks ... also, it should say "red on yellow, kill a fellow," as a milk snake can certainly bite. Its bite is not venomous, but it could be painful. --Ginkgo100talk · contribs · e@03:26, 3 August 2006 (UTC)[reply]
I always thought the "friend of Jack" part was a really lousy rhyme in comparison to the "kill a fellow" part. Jack? Jack who? In any case, this little rule does take the fun out of movies when one can easily see that a "deadly snake" is a relatively harmless milk snake. --Fastfission05:00, 3 August 2006 (UTC)[reply]
I agree. When I heard 'friend of Jack', I thought 'friend of the devil', either meaning the snake was really bad or that the person who came in contact with the snake would be dispatched to the afterlife. Combined with the 'bite a fellow' mistype, I thought the rhyme was backwards.--Anchoress06:11, 3 August 2006 (UTC)[reply]
Don't ask me, I've never heard that rhyme before, and I know next to nothing about snakes (which is very surprising, given that I am the Devil incarnate). :--) JackofOz03:22, 4 August 2006 (UTC)[reply]
While playing around with some alcohol gel, I sprinkled some common table salt into it, and found that it causes the gel to seperate into a thinner liquid (just the alcohol and alcohol soluable substances?) and a whitish, flaky solid. Has anyone else see this phenomenon? What causes it? Any ideas? Brian Schlosser4220:50, 2 August 2006 (UTC)[reply]
Might be interesting to read the ingredients of the alcohol gel to see what ions or other dissolved solids might be present. DMacks22:57, 2 August 2006 (UTC)[reply]
Here are the ingredients from the Purell website- Active: Ethyl Alcohol Inactive: water, isopropyl alcohol, glycerin, carbomer, fragrance, aminomethyl propanol, propylene glycol, isopropyl myristate, and tocopheryl acetate. Brian Schlosser4212:17, 3 August 2006 (UTC)[reply]
I don't have an answer, but intuitively, it doesn't seem illogical that the salt could de-emulsify the substance, causing the liquid to separate from the gelling agent.--Anchoress06:09, 3 August 2006 (UTC)[reply]
Molecular orbitals and symmetry
I was going to ask this question about benzene, but then it occurred to me that acetylene is a simpler molecule with the same basic problem. Acetylene has two pairs of electrons in two perpendicular pi bonds, but its electrostatic potential map has full cylindrical () symmetry. How is this possible if neither of the pi orbitals has cylindrical symmetry? —Keenan Pepper21:05, 2 August 2006 (UTC)[reply]
Now I'm curious to know the answer too. Also, the second paragraph of acetylene says, "As the molecule cannot twist around the triple bond, all four atoms lie in the same straight line, with bond angles of 180°." Now, the first part of that sentence makes sense with the two pi bonds, and would go agaist the cylindrical symmetry. But the second part of that sentence seems to be a non-sequitur. The bond angles would be 180 degrees either way, right? --Allen22:32, 2 August 2006 (UTC)[reply]
"Not twisting around a pi bond" is how we normally explain the existence of cis and transisomers in substituted ethenes to our pupils. The phrase is meaningless with ethyne - twisting of this linear molecule would mean bending, and I am sure that there is an IR absorption for triple bonds doing this! The cylindrical symmetry in ethyne (lengthwise) implies indistinguishable overlap between the two perpendicular pi bonds.--G N Frykman22:48, 2 August 2006 (UTC)[reply]
The "twisting" phrase is a bit odd for a triple bond. There presumably is no twisting in the olefin sense (rotation of the orbitals on one atom in a way that breaks and then reforms a different π system), but that would have no effect on the geometry. I'd be interested to see an electrostatic map that includes orbital information and is cylindrical. For most purposes, treating the triple bond as a "fat bond", a cylinder of π cloud, gives good enough results. DMacks23:11, 2 August 2006 (UTC)[reply]
There is a fundamentally simpler answer to this question. Recall that the px, py, and pzorbitals are actually probability maps for where electrons will be in space at a given time. Combined, all three p orbitals map to a perfect sphere. The usual drawings of the orbitals are actually drawings of the area in space in which there is a 60% probability that an electron occupying the orbital will reside at a given instant in time. There is, however, a 40% probability that one or more electrons will be outside of this area at a given instant. Thus, in acetylene, the py and pz orbitals that hybridize to form the pi bonds seem to be asymmetric when drawn, but this is because you are only considering 60% of the probability density for each electron. If you instead consider the volume of space for which there is a probability density that one or more of the four pi electrons will reside at any given instant, you will actually see a perfectly symmetric tube surrounding the x-axis of the molecule. Hence, if there is a lower probability that a py electron will reside in a specific area, this is compensated by the fact that there is a higher probability that a pz electron will be in this area. As such, it is correct to say that acetylene has symmetry.
As for rotation around pi-bonds, there is actually some computational evidence to suggest that it requires less energy to rotate around a triple bond than a double bond. While this may seem counter-intuitive because two pi bonds must be broken to rotate around a triple bond (versus one for a double bond), it actually makes sense because the overlapping p orbitals must only rotate 45 degrees out of phase before they come into phase with a new set of p orbitals and begin to re-form a pair of pi bonds. Since energy varies non-linearly as the orbitals come out of phase, the net energy barrier to rotation around a triple bond is lower than around a double bond. However, since the four atoms in the triple bond lie along a single axis (this is due to electron repulsion, NOT molecular orbitals: electrostatic repulsion leads to molecular geometry which, in turn, leads to the mathematical construct of molecular orbitals - probability densities determined by specific molecular conditions unique to each molecular environment), this cannot be tested experimentally and is therefore basically irrelevant. -- C. S. Joiner (talk) 01:02, 10 August 2006 (UTC)[reply]
Brushing your teeth
Everyone in the know seems to recommend brushing your teeth for 2.5 minutes, twice or three times a day. But what I wonder is, after the first 30 seconds or so, what is being cleaned off my teeth? And is it better to brush my teeth twice a day for 2.5 minutes, or five times a day for a minute?--Anchoress21:41, 2 August 2006 (UTC)[reply]
My Sonicare manual says that you should brush for two minutes. As for what is cleaned off, it is probably like scrubbing a wall. If you scrub for too long, you will through the paint and into the drywall. I don't think it is a matter of how many times you brush. It is when. You do not want food - especially sugar - sitting on your teeth. So, brushing every time you eat and then not drinking sugar-water between meals will not only help your teeth but also help your breath. --Kainaw(talk)23:09, 2 August 2006 (UTC)[reply]
Its really something that is more qualitative than quantitative: How well you brush, not how long. — [Mac Davis] (talk)
But brushing straight after you eat can cause slight erosion of the enamel on your teeth, which can build up over time if you do it regularly. So wait a while after eating. Or brush before eating to remove the plaque so there's nothing for the sugar to stick to. Sugar doesn't just stick to enamel. At least, that's what I was taught. Skittle12:49, 3 August 2006 (UTC)[reply]
I thought that brushing after or before eating was a bad idea, which is why just before going to bed is the best time to brush. Also, it depends on the food. Sugar rots your teeth, so you should avoid eating that, and especially around brushing time. Acids are also bad. One of the worst combinations is yoghurt with sugar. Or cola, which also contains loads of acid and sugar. When I was a kid I drank loads of cola (almost a litre per day!) and almost all my fillings are from around that time. I got accustomed to getting new filings every time I went to the dentist. From my twenties that stopped and until a few years ago (I'm now in my fourties) I almost never had any problems at the dentist. Also, when I was a teenager I brushed my teeth more often than later on in life, so that should give the previous explanation extra credibility, unless brushing your teeth (the way I did it?) is actually bad for your teeth. DirkvdM13:22, 3 August 2006 (UTC)[reply]
My Sonicare says to spend 2 seconds on each tooth, on the front surface and then the rear. Given the standard human allotment of 32 teeth, that's 128 seconds. --LarryMac14:59, 3 August 2006 (UTC)[reply]
I don't know what 'my first sony-care' is, but does it do one tooth at a time. My toothbrush is several teeth wide. Still, I spend more than 2 minutes brushing my teeth, but I do it only once a day - the quality vs quantity thing that MacDavis mentioned, just a different interpretation of the principle. :) DirkvdM19:13, 3 August 2006 (UTC)[reply]
Having been to the dentist this morning, I'm in a good position to chime in here! Apparently, the number 1 cause of adult tooth loss in the UK is not tooth decay, but gum disease. The time spent brushing your teeth (and, as importantly, flossing), is to improve the health of your gums; preventing your otherwise healthy, decay-free teeth from falling out! --Dweller14:10, 4 August 2006 (UTC)[reply]
Considering my background, perhaps I should say something as well. Though there may be some technical result found in research saying that it is harmful to brush after eating, in reality this is not seen as a problem. Brushing your teeth after you eat is generally not seen as causing detectable levels of damage. However, how you brush is important, and not necessarily how often. If you brush 26 times a day but not in a manner to remove all the plaque, then those 26 times really do no good. Since the point of brushing is to remove all the plaque, you probably will not remove all the plaque off a tooth on your first stroke--- which is why you will have to spend some time on it. And a bit unrelated, sugar helps form tooth decay, but the frequency of your sugar intake is more important than the amount. So, eating a bag of candy in 30 minutes will be less harmful for you teeth than eating the same bag of candy slowly throughout the day. - Dozenisttalk23:05, 8 August 2006 (UTC)[reply]
Valium + Alcohol = ?
I'm currently taking valium, prescribed by my doctor (5mg, every 3 hours). Is it safe to drink *any* alcohol at all? What happens when you mix the two? Is it a case of just getting drunk quicker or could it kill me?
Valium + Alcohol = Death. They are both depressants. Its best to stay away, the combination of the effects can cause your heart to stop if the right amounts are taken. Don't be stupid. pschemp | talk22:20, 2 August 2006 (UTC)[reply]
a) I agree with pschemp; they're both nervous system depressants. b) talk to your doctor or pharmacist. This is definitely near the top as far as questions that should not be settled on the advice of anonymous posters.--Anchoress22:24, 2 August 2006 (UTC)[reply]
I think it was answered quite well here, by saying they should NEVER be taken together. You can't go wrong by taking that advice. StuRat05:50, 3 August 2006 (UTC)[reply]
It's always a good idea to not be stupid. That should, however, not be confused with ignorant. If there is any danger in combining valium with alcohol, there should be a warning on the valium bottle (or whatever that comes in). If there isn't then that would be stupid (and if you're in the US you might think of sueing them). DirkvdM13:25, 3 August 2006 (UTC)[reply]
There is a warning: "Drunk, pregnant children operating heavy machinery while driving should not take this product". Or something like that. :-) StuRat21:09, 3 August 2006 (UTC)[reply]
Value and alchohol can make your brain work like its never worked before. that can either kill you or make you a super human. you choose the red pill and your free.
I dunno, but don't eat it no matter what anyone here says! :) ok, now more knowledgeable people can take over and identify it. --18.239.5.6102:09, 3 August 2006 (UTC)[reply]
It looks a lot like the death caps I see in the forests where I go mushrooming (and they are not portobellos as those are rare in this climate). All white, pronounced collar, and a sock (is that what it is called in English). Given the deadly nastiness of death caps I certainly don't mind scaring people away from all white mushrooms that can't be positively identified. Like for all mushrooms: I love picking and eating them, but not enough to die for a meal. Weregerbil20:44, 3 August 2006 (UTC)[reply]
Yeah. You can see from the protruding spots on top that it's almost certainly a death cap, and absolutely not a portobello. Do not eat this, if you were considering it. If you have a mouse problem, cut it up, soak the pieces in milk, and wait a couple days. All the mice in your house will die fairly quickly, because the milk attracts them. Sashafklein22:40, 3 August 2006 (UTC)[reply]
Thanks for all the imput. I certainly will not eat it. I was just wondering, as this mushroom was by itself, and the first I ever noticed in my yard. Thanks again, Newnam(talk)03:43, 4 August 2006 (UTC)[reply]
Might be a destroying angel too, or some other similar Amanita species. If the photo was a bit sharper it'd make the identification easier, as would seeing the gills and, most important, knowing where the photo was taken. I could be wrong, of course — I'm certainly no mushroom expert — but something about the general shape does scream Amanita to me, at least enough that I'd leave the thing well enough alone. —Ilmari Karonen (talk) 23:51, 10 August 2006 (UTC)[reply]
August 3
Human-raised birds
Say if I was to hatch a bird (e.g. a crow) from the egg myself and raise him from chick to adulthood without him ever seeing another bird, would he still be able to fly? Or would he not know how and walk around like a human instead?
It would depend largely on if it fledged properly. Actually, the article uses the term a little differently from how I use it; I use fledge to mean "to learn to fly as a chick at the right developmental stage." In wild birds this seems to happen when the flight feathers are significantly (but not necessarily completely) grown out, which incidentally is right now in the temperate northern hemisphere, and it's a time of high mortality for chicks. With many pet birds such as parrots, if they don't learn to fly at the right time during their "chickhood," often they never really do. I had a yellow-collared macaw who never fledged and who absolutely refused to fly voluntarily, even though I let his flight feathers grow out and tried to teach him with gentle tosses to the bed. I also have a ringneck parakeet who didn't fledge as a chick either, but he has done better at learning as an adult. Neither of these birds was raised by other birds; what matters with a human-raised bird is whether it is taught to fly. --Ginkgo100talk · contribs · e@03:35, 3 August 2006 (UTC)[reply]
It's really hot in here...
and the airconditioner isn't working. how hot does it have to be before a computer goes from sluggish to not working at all? it's already over 100 (oF) in here, how much more can it take?--152.163.100.7401:48, 3 August 2006 (UTC)[reply]
It depends on how efficient your computer's cooling system is. Generally consumer CPUs are rated at anything between 65° and 95°, so the ambient temperature isn't going to cause problems per se, but it will obviously make cooling less efficient. You can monitor the internal temperature sensors with free tools e.g. Gnome Sensors Applet. EdC03:04, 3 August 2006 (UTC)[reply]
Hello all -
I have a general question about using munitions to disrupt hurricanes. Is something like this possible? I read over the hurricane page (specifically the section on Artificial dissipation) and Googled this topic, but I really did not find anything that really answered the question.
Here is the scenario: If a Rita/Katrina-type hurricane should brew in the Atlantic Ocean, is it possible to drop several powerful cluster bombs throughout the eye (and exterior) of the hurricane and disrupt or eliminate the hurricane, or at the very least lessen the force of the hurricane. I would imagine that thousands of explosions within the center of the hurricane, at the waters surface, and beneath the waters surface would severely disrupt the strength of the hurricane. I think this might be akin to using explosion to put out fires: the vacuum created by the explosion might disrupt the wall and eye of the hurricane, thus decreasing the force of the hurricane.
Thanks for the comment. I just would imagine that if there were thousands of powerful cluster bombs being detonated at all altitude levels, at the waters surface, and under water, this would have the potential to disrupt the hurricane. -Rangermike03:52, 3 August 2006 (UTC)[reply]
I would think many nuclear weapons would be needed to disrupt a hurricane. A new hurricane would spawn almost immediately, in the same area, however, as the water temp cooling would stop once the old hurricane was disrupted. This hot water would then generate a new hurricane in the same area. Another method of disrupting hurricanes would be to dump millions of tons of a special gel (which absorbs a million times it's weight in water) from cargo planes, into the hurricane. This particular gel (I can't recall the name) dissolves in sea water, and is nontoxic. Unfortunately, the hurricane would also respawn after this method was used. The real cure for hurricanes, then, is to prevent to water from overheating in the first place. I propose partially covering the tropical oceans with solar collectors to generate electricity and prevent a heat buildup. Perhaps in a century of two we can manage it. StuRat05:41, 3 August 2006 (UTC)[reply]
You're somewhat correct that a tropical cyclone would probably remain in the same place, but I doubt it'd be a new hurricane because of high SSTs. Hurricanes don't just "spawn" in hot water, else New Orleans would be hit every other month when the Loop Current sheds an eddy. The larger-scale structure takes too long to develop and they're fairly fragile while developing. If you could really just get rid of the hurricane entirely or put it back to its "random mess of convection" stage, it would take a long time for it to return to its prior strength.
But using bombs (i.e. randomly blowing up the hurricane's structure) would probably only degenerate it back to a tropical storm's structure at most if you're lucky and get the right bits. Tropical storms already aren't that organized and you probably won't find any structures to bomb on a small-enough size scale. Also, bombs probably wouldn't be able to stop the winds and low-level convergence and upper-level divergence already spun up. The same things that were favorable to the intensity of the 'cane before would probably act to re-strengthen the same storm. —AySz88\^-^06:58, 3 August 2006 (UTC)[reply]
Given that hurricanes are a phenomena that is hundreds of km wide, I doubt very much that any munition could have any significant effect, but seeding the clouds to make rains at appropriate location(s) and time(s) could shift the path of an hurricane enough to avoid populated areas.
Not if it's stored in an airtight container. If it's left out in the open, though, it will quickly evaporate, forming dangerously flammable vapor. —Keenan Pepper04:03, 3 August 2006 (UTC)[reply]
Sorry I left that all without context ... my professor's point was that the mechanics of the cheetah's spine contributes something like 10% to its speed.
List of countries by electricity consumption - part 2
In the List of countries by electricity consumption someone seems to have gone through the trouble of filling in the per capita values for scandinavian countries, where these values are very high. Same for Canada (even higher than the US). For other western countries (excluding the US) it's much lower. I can understand a higher energy consumption due to heating, but why do they consume two to four (!) times as much electricity? DirkvdM13:37, 3 August 2006 (UTC)[reply]
I looked at that and I thought that it isn't accurate to claim that each person is consuming 2-4 times the electricity. The figure is dividing the country-wide consumption by the population. So, a completely robotic factory with only a handful of workers will consume a lot of electricity. That is being added to each person's average usage on that specific table. Therefore, I expect industrialized nations to have a much higher per-capita usage due to business/factory/government use and not really due to personal use. --Kainaw(talk)13:47, 3 August 2006 (UTC)[reply]
Norway, for instance, produces a lot of cheap hydroelectric power, and has the lowest population density in Europe. Despite having no bauxite, they are one of the leading producers of aluminium.EricR14:13, 3 August 2006 (UTC)[reply]
The situation in Canada is similar. There are a number of sites that produce a lot of hydroelectricity, and Canada imports enough bauxite to refine nearly 3 million tons [14] of aluminum each year; at 15 kWh per kilogram of aluminum produced, that comes about 40 GWh of electricity consumption per year. In other words, a single resource industry accounts for about 8% of Canada's total electricity consumption. Most of that aluminum is exported to other countries – Canada is the second-largest aluminum exporter in the world, after Russia[15] so counting that electricity use as 'Canadian' gives a somewhat skewed picture of that country's consumption. TenOfAllTrades(talk) 14:33, 3 August 2006 (UTC)[reply]
I guess industry could account for some of it - I also assumed it's because it's so cold all the time that heating costs were higher. But I don't know. --198.125.178.20717:39, 3 August 2006 (UTC)[reply]
There ought to be a correlation between per capita wealth and consumption. For energy, think of heating houses, cooling houses ; and this, mostly in countries located where temperatures vary : wealth is related to temp variation (personal research). --DLL18:32, 3 August 2006 (UTC)[reply]
Like I said, I assume heating is not done with electricity, so that couldn't cover it then. And bauxite represents 'only' 8% of the electricity consumption of Canada, but the total consumption is more than double that of other western countries, so that can't explain it. And for Norway and Iceland it's even three resp four times as high. Those are huge differences. But Norway does have a lot of water power, so maybe they use more electricity and less fossil fuels. Hold on, don't they have a lot of cars running on electricity? That might explain it. And then Iceland. That has a lot of geoithermal power. But I can't think of how that could explain it. Is it just a coincidence that countries close to the North Pole use more elctricity? DirkvdM19:24, 3 August 2006 (UTC)[reply]
Aaaaw c'mon, let's just come out and say it! Canadians are the energy hogs of the entire world! :-) Oh sorry, can't talk any more, I have to take my recycling out of the dishwasher, and the dryer's finished heating up the bathroom for my shower. ;-)--Anchoress19:32, 3 August 2006 (UTC)[reply]
Oops, sorry. Well what if I said it's the US's fault that we're such energy hogs?
From a soon-to-be-aired episode of Oprah
[Canada] (sobbing) He doesn't respect me! He never listens to me! I wouldn't have a problem with reckless consumption if I got the acknowledgement I deserve! I mean, how big do I have to be before I get some recognition?
[Oprah] There there, little Canada. When he runs out of steam I'm sure he'll notice you.
They don't have to. If gravity didn't pull down on it, making the bottom thick and heavy while the top becomes thin and fragile, it would just go on being a happy little bubble. But, gravity is evil and hates soap bubbles, so it pushes down and down and eventually the top is so thin that the surface tension cannot hold. The little soap molecules cry as their fingers slip and pop - no more soap bubble. --Kainaw(talk)14:02, 3 August 2006 (UTC)[reply]
I disagree. Even without gravity the bubble solution would quickly evaporate and burst the bubble. Perhaps in a zero g, 100% humidity environment they might last until they hit something. StuRat20:44, 3 August 2006 (UTC)[reply]
My answer was limited in scope to Earth-bound bubbles. Gravity gets to them faster than the environment. I learned about it in a strange place - watching a documentary on making colored bubbles. Turns out that making bubbles with a solid color is very hard. Gravity pushes the dye to the bottom and then POP, you get a stain on the floor. --Kainaw(talk)13:34, 4 August 2006 (UTC)[reply]
"Soap bubbles in space" - interesting question. Of course the Earth itself is in space and it is possible to make soap bubbles here. In zero gravity (or microgravity really) we find soap bubbles on the International Space Stationhere. For bubbles in vacuum: possible, but the liquid will evaporate quickly and thus the bubble has only a short lifetime[16]. Weregerbil15:06, 3 August 2006 (UTC)[reply]
In Yakov Perelman's Physics for entertainment, he mentions that the bubbles made of right solution are not as short lived as we presume them to be. He cites examples where bubbles were stored for (I think) about a month --Wikicheng04:48, 4 August 2006 (UTC)[reply]
My bike has brakes that occur at the hub of the wheel, instead of at the top (pressing against the wheel rim) like I'm used to. What kind of brakes are these? --130.161.182.7714:01, 3 August 2006 (UTC)[reply]
last week I experienced the not so frequent pleasure of finding a hedgehog in my garden. I had heard that you should always check the little guys for ticks (care for sick/wounded hedgehogs can be done for free in bird centers here), but as usual he ran off almost immediately.
When I went to Wikipedia, to my amazement I discovered that hedgehogs are not to be found in the USA at all! Does the average US'er even know what a hedgehog looks like?
Anyway, are there any other surprisingly non present animals ( in parts of the world with about the same climate and flora, I am not surprised there are no elephants here).
Yes, there are many. Australia is a great place to find unique animals that could survive elsewhere, but haven't really ventured out into the world. As for Americans and hedgehogs, there is a small group of people in the U.S. that own domesticated hedgehogs as pets. However, most couldn't tell the difference between a hedgehog and a porcupine. Finally, the trick to picking up hedgehogs is to scoop them from both sides. I face them as I do so, I think it is less traumatic (though it has to be frightening to get picked up) if they see it coming. They will roll into a ball and make a lot of huffing and popping noises. After a long time (I've had it take over 10 minutes), they will relax. Of course, it is actually easier to inspect them as they are rolled up in a ball than it is to inspect them when they are relaxed and the quills are laying flat. --Kainaw(talk)14:30, 3 August 2006 (UTC)[reply]
I was extremely surprised to find out recently that there are no Skunks in Africa, Europe and most of Asia. You don't know what you're missing.--Anchoress19:27, 3 August 2006 (UTC)[reply]
Anybody want to trade hedgehogs for skunks? I'd take a hedgehog infestation any day over the tyranny that skunks have. As Darwin wrote of them: "Conscious of its power, it roams by day about the open plain, and fears neither dog nor man. If a dog is urged to the attack, its courage is instantly checked by a few drops of the fetid oil, which brings on violent sickness and running at the nose. Whatever is once polluted by it, is for ever useless." --Fastfission19:32, 3 August 2006 (UTC)[reply]
One obvious animal present, just, in the UK but not in similar habitats in the U.S.A. or, as far as I know, elsewhere outside Europe is the Red Squirrel. That though is because the, more aggressive & less attractive, Grey Squirrels outcompete them. AllanHainey15:03, 4 August 2006 (UTC)[reply]
What kind of Praying mantis is this?
Can anyone help me find the latin name for this particularly beautiful Praying mantis? It was uploaded to Wikicommons by a French speaking user, who labelled it a Sudanese mantis. But I haven't been able to find any other pictures of Sudanese mantises, I'm not sure whether that is the actual vernacular name or just a description (a mantis found in Soudan). Help would be appreciated. Do you think it could be Blepharopsis mendica? --woggly15:48, 3 August 2006 (UTC)[reply]
Hmm. Yes and no. The eyes are angled differently from the head, but that might just be a difference in the angle of the photograph... I'd really like to know, because I want to nominate this for a featured picture, and for that it needs to be illustrating the proper article (not just Praying mantis - there are too many other good pictures there). Anyway, it wouldn't be a larva, but a nymph. Thanks for finding that picture, which is the closest I've seen so far! --woggly19:59, 3 August 2006 (UTC)[reply]
I've loooked at more Blepharosis mendica pictures, and I don't think this is it. The Blephs all seem to have mottled eyes and long antennae, whereas this guy has distinct "pupils" and short or no antennae. Still looking... more ideas would be appreciated. --woggly05:42, 4 August 2006 (UTC)[reply]
Logo or symbol or abbreviation for engineers
Is there any internationally recognized logo or symbol for engineers? e.g. red cross for doctors.What is the short title for an engineer(Er or Ir or Ing) e.g. Dr for doctor.
I've only seen "Eng." used. It is rarely used alone. For example, I am a CSciEng, not an EEng. Then, some drop the "ng". EEng is often just EE. --Kainaw(talk)17:27, 3 August 2006 (UTC)[reply]
For an international title there would have to be an interntionally accepted exam, at least that would make sense. Then again, dr is indeed rather international, without there being international exams (afaik). Btw, Ir and Ing are Dutch. Are you? Or are these titles used elsewhere too? DirkvdM19:33, 3 August 2006 (UTC)[reply]
I don't know of any internationally recognized logo but in context something like a gear would probably be recognized by most people. --Fastfission21:31, 3 August 2006 (UTC)[reply]
The closest thing to an 'official abbreviation' will be a variant of P.E., which at least in the US stands for Professional Engineer. It is used after one's name, as in John Doe, P.E. But it wouldn't be used in typical day-to-day correspondence, only in situations where the title would be familiar to the audience. If our John Doe wrote a letter to the editor of the newspaper, he wouldn't include the P.E. after his name; but if he was authoring a report commissioned by a client of his engineering firm, then he would.
In Canada, the common abbreviation for a professional engineer is P.Eng. in English and, I believe, Ing. in French. I think that Ing. is also used in Germany. As far as logos or symbols, there's no clearly accepted symbol, particularly since engineers do so many different types of work. I've seen a cogwheel, chains, the beaver and the Vitruvian Man used, but not universally. In Canada, the Iron ring is understood as an engineering symbol. --ByeByeBaby06:53, 5 August 2006 (UTC)[reply]
Hepatitus c and Vitiligo
i am looking for advice how to treat a Vitiligo (1 year) if have a Hipatitus c (5 years).
Vitiligo and Hepatitis C may have some useful information about each condition, but for a real answer, you should see a doctor. (Note the statement at the top of this page: "If requesting medical...advice, please consider asking a doctor...instead.") -- Scientizzle19:59, 3 August 2006 (UTC)[reply]
cat with neurological problem - stroke?
He had a temperature of 104 F at the beginning, now gets around slowly and shakily, barely responsive to stimuli, licks soft food, doesn't drink without bottle help, wants to put his head into corners, has forgotten how to use litter box. Does anyone have ideas for rehabilitating a cat who's had a stroke, or something like it? --Halcatalyst
That doesn't sound like a stroke. That sounds like sickness. He should go to a vet. After a stroke, cats have trouble moving, usually the back legs. They don't curl up and wait to die. --Kainaw(talk)19:27, 3 August 2006 (UTC)[reply]
Was that a useful addition? What's this tendency to point out the blatantly obvious, even when that was already done by the previous poster? DirkvdM19:38, 3 August 2006 (UTC)[reply]
It was added before I noticed Kainaw had already added his veterinarian comment. Note the similar edit times. And the obviousness of the comment isn't really relevant. It is the best possible advice. --198.125.178.20719:46, 3 August 2006 (UTC)[reply]
We did take him to a vet and he was in the hospital for several days. They eventually diagnosed a neurological disorder and released him to our care. They said they had never seen anything like this and also suggested it might be time for euthanasia. We're hoping there might be something to be done to help him recover. --Halcatalyst19:40, 3 August 2006 (UTC)[reply]
(As I've mentioned many times, I work in a hospital, so I can ask random doctors for advice - but do not consider it binding advice as I'm just a comptuer programmer)...
According to a doctor here, if it was a human he would first send it to MRI to test for pressure on the brain. Then, he would send it to GI to have the intestines checked. Because of the fever, he suspects a viral infection. --Kainaw(talk)19:44, 3 August 2006 (UTC)[reply]
The vet at first thought it was a gastro-intestinal infection, but the tests came back normal. And he hasn't improved on the antibiotic (which we're still giving him. He's also on prednizone. --Halcatalyst20:08, 3 August 2006 (UTC)[reply]
I know how it feels to see your pet going through suffering. I can't help you with the treatment, but I wish you the best of luck. --mboverload@23:22, 3 August 2006 (UTC)[reply]
I agree. My last hedgehog had very similar symptoms. On Monday he didn't eat much, but kept running around like normal. On Tuesday, he didn't want to run. He just curled up by me and kept sleeping, so I made an appointment for the vet on Wednesday. On Wednesday morning, I got him up to check on him and he was the same. I got dressed and went back in and he had passed away. Later, I found out he had multiple cancerous tumors in his intestines. I was frustrated because I had taken him to the vet a month earlier and he got a clean bill of health. I felt like the vets didn't take it seriously because it was a hedgehog and not a dog. There is a lot of emotion involved - pain, sorrow, anger. I now feel that I should have listened to my doubts about the first vet and gone to a different one. Keep finding a different one until you find one that isn't just going through the motions to cash a check. I'm sure there are a few vets out there that take the job seriously. They are just hard to find. --Kainaw(talk)13:26, 4 August 2006 (UTC)[reply]
I'm not sure that was a redundant addition. In some parts of the world vet is not commonly the abbreviation for veterinarian; but for combat veteran. Many of them are hungry, but that doesn't mean they will want your cat. Notinasnaid13:55, 4 August 2006 (UTC)[reply]
My mentor is an immunologist (PhD) and vet (DVM), and he agrees that given the information supplied that the source of the cat's neurological symptoms is most likely suffering an infection. He also highly recommends that you look around for possible sources of the infection: other animals contacts (wild or otherwise), and the like. Possible contagion to or from other animals is a very serious consideration (though it is highly unlikely that the pathogen is infectious to humans). – ClockworkSoul19:02, 4 August 2006 (UTC)[reply]
Because of the high temperature, the vet[erinarian] ran a full set of tests, which were negative. Nevertheless, the cat has been on antibiotics for ten days now. In a week, he has urinated a couple of times and only one very liquid bowel movement.
Thank you all for your interest. Poor Ozzie is worse these last two days; he can't get around at all anymore, but he is eating soft food ravenously. He can't drink by himself (it's as if he doesn't know what water is), and I hope I'm getting him enough hydration. He doesn't appear to be in any pain. --Halcatalyst01:44, 6 August 2006 (UTC)[reply]
Ref Desk Archive Problem
I keep on ending up on an archived page accidentally. It seems when I edit certain questions on an active Ref Desk page I end up in an archived page, after I finish. Does anybody know what's going on here ? It has been happening for quite some time, but only happens, say, 10% of the time. StuRat20:50, 3 August 2006 (UTC)[reply]
Weird, I thought I answered this earlier.It's because you are editing a section from an archive that is transcluded onto this page. When you edit the section and save, it sends you to the page that you actually edited. Actually, if you hit 'edit this page' at the top instead of just a section, you'll easily see that the first few days displayed on this page are transclusions of archives. Hyenaste(tell)01:37, 4 August 2006 (UTC)[reply]
So why do we do that ("transclude" archived pages that appear to be on the active ref page) ? I would think they should either be on the active page or the archived page, not somewhere in limbo between the two states. StuRat05:34, 4 August 2006 (UTC)[reply]
Ready to learn easy maintenance tricks ? OK, listen : never listen to complaining customers (I admit this only occurs in sci-fi stories about horrid old admins with tentacles). --DLL15:29, 4 August 2006 (UTC)[reply]
Physical basis of the Mendelian ratios?
What's the physical basis of some genes being dominant and recessive? Is this well understood at the moment? I poked around the pages which looked most relevant here (recessive gene, dominant gene, Mendelian inheritance, classical genetics, molecular genetics) but saw nothing about this. I'm just curious, that's all. Is this a universal function of all DNA-carrying organisms? I can see the evolutionary advantage of recessive genes but it surprises me that all organisms have them—one could hypothetically imagine DNA that dealt with only dominant genes. Which would lead me to think that either the ability to have recessives is so basic and advantageous (in a way I don't understand) that it would have outpaced a dominant-only arrangement early on, or it is closely related to the basic functioning of DNA in a way I don't understand. Anybody have a clue? --Fastfission21:22, 3 August 2006 (UTC)[reply]
What they taught me in college is that there's actually a spectrum of dominance, from completely recessive to completely dominant and everything in between. The physical basis is simply the body's reaction to different amounts of protein. If you have two copies of an allele, you'll have about twice the resulting protein as if you have one copy. If the body needs the full amount for whatever function, then having only one copy will mess you up, and the disease-causing allele will be dominant. But if the body only needs a little bit, so that 1X or 2X the amount makes no difference, then the disease-causing allele will be recessive (you only need one copy of the good allele, meaning to be sick you need both copies of the bad allele). There are examples, though I can't quote them off my head, of diseases where having one good copy and one bad copy will cause a disease, but having two bad copies will cause a more serious disease or even prevent the fetus from developing at all. The article you need is Dominance relationship, but I just now found that after writing this, so I hope I'm on-base. --Allen21:40, 3 August 2006 (UTC)[reply]
An example would be sickle cell anemia, where one sickle cell gene causes mild symptoms, but also provides partial immunity to malaria. Two sickle cell genes, on the other hand, cause a serious and often fatal version of the disease. StuRat05:30, 4 August 2006 (UTC)[reply]
I assume you understand that for most human genes, every person normally has two copies of each type of gene, one copy from each parent (see: diploid). Here is an analogy for a recessive disease: think about human vision. If you have damage to one eye, you can still see fairly well with just one functioning eye. For many genes, if the copy from one parent is defective, the biological function that is normally accomplished by that type of gene can be accomplished using just the one good copy from the other parent. In order to seriously disrupt the function of that type of gene, you need to have inherited mutated versions of the gene from each parent. For many dominant gene mutations, having one normal copy of the gene from one parent cannot compensate for the problem caused by having one copy of the mutant gene. Some proteins coded for by mutant genes have been shown to function at the molecular level as "dominant negative" regulators of cell processes. In some cases, even a very small amount of altered protein from a mutant gene can have dominate effects over the normal protein. Often this is the case because many proteins normally exist in an "inactive" conformation. Such proteins normally do nothing inside cells until something special happens to activate them and as soon as the special condition is over, the protein goes back to being inactive. In many cases, dominant mutations in the genes for such proteins result in a version of the protein that is always on. This over-activity can cause a disease condition, even if half of the proteins of this type are normal (produced by the non-mutated copy of the gene. Analogy: think of fire sprinklers. If 50% of the sprinkler heads in a building had a defect that made them activate at room temperature, that building would have a problem. Even if only 1% of the sprinkler heads had this defect, most building owners would object. Dominant mutations are often of this type....the mutant gene codes for a protein that causes trouble. --JWSchmidt22:18, 3 August 2006 (UTC)[reply]
Those are interesting and good descriptions, thanks. It's a bit more complicated than the classical genetics approach usually makes it out to be. --Fastfission15:19, 4 August 2006 (UTC)[reply]
Bromine and its effect on swimsuits....
Hello....I swim several times a week for fitness and have noticed that I need a new swimsuit about every three to four months...sometimes I swim in a pool with bromine instead of chlorine...is bromine more caustic to swimsuit material than chlorine??? Just curious...thank you for your time...Jane----
According to this site bromine is less caustic than chlorine and "will not fade bathing suits or yellow blonde hair". It would appear chlorine is used for economic reasons rather than functional ones. Perhaps you should swim more regularly in the bromine treated pool and see if your swimsuit degrades at the same rate. Rockpocket00:07, 4 August 2006 (UTC)[reply]
(after edit conflict) As an isolated element, Bromine is actually less chemically active than Chlorine and, based on a little research, the bromine compounds commonly used in swimming pools appear to be less damaging to hair, skin, and bathing suits than chlorine. Bromine is often the sanitizer of choice in spas and hot tubs as it is more resistant to very hot water. --Nebular11000:15, 4 August 2006 (UTC)[reply]
hormones
Please explain the origin and function of gherin, i.e. what stimulates its release, what tissues make it, and what tissues are targets.
First, please explain the function of homework (this sounds like homework to me). Next, try searching for gherin and hormone in your favorite search engine. If you have questions needing to clarify anything you find, feel free to come back and ask them. digfarenough (talk) 23:06, 3 August 2006 (UTC)[reply]
what is gastro enteritis??
i hav tried looking it up heaps of times but there isnt anything.
i know that it is something that can happen if you are poisoned but i want to know wat it acctually is. for ex.
vomitting, dizzynous, etc.
any help would be greatly appresiated
--Sammie hero23:08, 3 August 2006 (UTC)[reply]
A question to Doctors.regarding my strainge chest pain.
All respected concerned health exeperts, would you please guide me the course of action I should take to takle my strainge pain which I am feeling for the last 4 to 5 days .I call it strainge as I AM QUITE NORMAL though at 66 of age my day to day activities are normal and Iam not experincing any kind of simptums other than this pain on the chest at right breast region.Pain is not consistant all through the day,I feel it when I sneege and or when I cough occasionally.If I sqeese the muscle on the breast Idont feel the pain but when I PRESS the right brest with my paw I feel the pain.Is it a impending heart problem ? Please adise me whether to ignore it as it might subside after few days or should I consult compintant Doctor.Iam male quite healthy at 66 of age except for slight hiper tension with reading 155 -86. I am vegitarian non smoker and active all through the day. Thank you yours loving s.k.pujar
There are many causes of chest pain. You should definitely see a doctor so that they can diagnose it. No one is going to be able to diagnose such a complicated thing well based on an online description, except to say, "It might be serious, go get it checked out." --Fastfission03:11, 4 August 2006 (UTC)[reply]
You ask us Reference Desk editors to advise you whether to ignore your pain. Well, I advise you NOT TO IGNORE IT because we cannot give appropriate medical advice. A physician examining you can. Please do not hesitate to visit a doctor -- immediately if possible. --Ginkgo100talk · contribs · e@03:22, 4 August 2006 (UTC)[reply]
Of all of the chest pains that are seen, chest pain which is on the right side and you can reproduce by pressing the chest wall is least likely to be related to your heart. Especially after five days of constant pain without other symptoms. However, just because it might not be cardiac doesn't mean that it can't be something else just as bad. Please, go get it checked out as soon as possible! InvictaHOG03:26, 4 August 2006 (UTC)[reply]
All cell phones charge on DC. The wall adapters convert AC to DC; the car adapters convert DC to a lower voltage DC (the car voltage is ~28VDC, while most phones charge at less than 5VDC). However, the DC to DC converter can do it by first converting to a high-frequency AC and then back to DC (and, in the same way, the wall adapters can convert AC to DC to high-frequency AC to DC; this is usually done in the smaller wall adapters, while the big heavy ones use a large transformer and a direct AC to DC conversion). So, your car cell phone charger might be in fact converting to AC (but only as an intermediate step). --cesarb16:46, 4 August 2006 (UTC)[reply]
A friend of mine bought one of these, plugged it on one end into the car and on the other end into his regular wall cell phone charger. Is this wasteful/silly?
Hearing pianos over the phone
Why can't you hear pianos clearly over cellphones? This problem doesn't appear to exist with other instruments, the guitar for example. Any ideas? Please answer on my talk page. Thanks for your help! MarkBuckles (talk)04:49, 4 August 2006 (UTC)[reply]
I would guess it's the small frequency range on each piano note. They may fall into "frequency holes", which are omitted to fit more conversations into a given bandwidth in a highly compressed cell phone transmission. StuRat05:14, 4 August 2006 (UTC)[reply]
Piano notes have a small frequency range? Most keys hit more than one string and they're in an encasing that gives them ample opportunity to give off all possible vibrations, resulting in many overtones. On top of that, the piano is the instrument with the widest tone-range. A telephone line is, however, restricted to the frequencies that are important for speech. Piano key frequencies range from 27 to over 4000 Hz. The range of the guitar is from 82 to less than 1000 Hz (way up on the neck). I can't find what frequencies are transmitted over a telephone (searching for 'telephone frequencies' only leads to radio frequencies the connections use, which is something different). But it may be in the hundreds of Hz (althogh I thought it was around 1000 Hz), which would explain why you can't hear notes above that. You could still hear lower notes, though, through the overtones. So same answer, just the other way around. :) DirkvdM07:59, 4 August 2006 (UTC).[reply]
The standard sampling rate for telephony is 8000Hz, which due to the Nyquist–Shannon theorem means the highest frequency transmitted is 4000Hz (see Nyquist rate). If you use 8 bits per sample, you have a bitrate of exactly 64000 bit/s, which uses too much radio bandwidth (on POTS, however, you have almost the full 64000bps rate). To reduce the bandwidth, the sound is compressed using special speech codecs (which can vary from 13kbit/s to as low as 4.75 kbit/s). Of course, to reduce the data rate that much, some information is lost; these codecs are optimized to retain more information related to the human voice (and, sometimes out-of-band, DTMF tones), and less information related to everything else (including background noise and music; comfort noise can also be generated at the receiver). It's not a specific frequency being dropped (i.e. there are no "frequency holes"); these codecs actually try to predict the waveform using mathematical models (tuned to the human voice), and encode the resulting coefficients and residuals. --cesarb16:22, 4 August 2006 (UTC)[reply]
So the explanation would be that (somehow) a guitar behaves more like a human voice? Might be interresting to test how different instruments and different notes on those instruments come across on a telephone. i just don't know who I might call who would be equally interrested in such an experiment. Ah come on, do I really have no interresting friends? Is that why I spend so much time here? Or is that the other way around? ... I will now just go and sit in a corner and feel sorry for myself. DirkvdM19:04, 4 August 2006 (UTC)[reply]
You could try to find implementations of these codecs which run on a normal PC, convert a small sample of music (losslessly compressed if possible) to the codec and back to a normal wave file, and then do a blind a/b test (we seem to be missing either an article or a redirect here; any takers?). --cesarb23:43, 4 August 2006 (UTC)[reply]
Part of the characterist sound of a piano is not the sustained tone alone, composed of a fundamental plus harmonics, but the initial attack as the key is struck. The 300 or 400 Hz high frequency cutoff in modern phones may allow the fundamental tones to pass, but block some of the harmonics. It may also cut off some of the envelope of the initial attack, which is somewhat percussive and may include more high frequencies. Edison18:24, 5 August 2006 (UTC)[reply]
exhausting a portable air conditioner through the chimney flue
Is it possible to exhaust a portable air conditioner's exhaust through the chimney flue instead of the window? Would I be able to force the air out with a fan (after closing a furnace exhust vent) if the atmospheric pressure is too great?
Maybe. As you seem to already know, the exhaust from the A/C unit won't be sufficient in volume or heat to create a proper draft up the chimney. A fan at the chimney alone probably wouldn't be sufficient, either, as this would create a negative pressure in the house sucking the exhaust back down the chimney. If a second fan were added to force air into the house, this would probably do the trick. However, this would be blowing in hot air from outside which is going to fight the A/C unit. I suppose it still might cool the room containing the A/C unit, but the room in which the air enters the house would get hot. So, I recommend against this approach. Now, if you could rig up a long tube and route it up the chimney, and force the exhaust up the tube, that might work a lot better. A dryer vent hose might work. StuRat05:08, 4 August 2006 (UTC)[reply]
Our toilet has such a ventilation shaft with a fan, so it should work. Air will easily get sucked in through all sorts of holes and chinks (is that the right word?) in the house. If it's hot and you create a lot of current that would be like having a fan for the whole house, so you can leave the ac off. It would have to be pretty strong, though. But then you wouldn't need the ac, which is begging the question. I suppose you'd better ignore this advise. DirkvdM08:11, 4 August 2006 (UTC)[reply]
Every portable AC that I've had also drips water out the back. If you try to put it in a chimney opening, you'll end up with a puddle in your chimney. --Kainaw(talk)14:48, 4 August 2006 (UTC)[reply]
The air conditioner doesn't really exhaust air; it exhausts heat. The fan on the hot side of an air conditioner is only there to increase the heat transfer not get rid of air. So, a single fan in the chimney would do very little as you need to be pulling cooler air into the condensing coils of the air conditioner. StuRat's idea of a tube within the chimney (a tube within a tube, effectively) to pull down cooler air and push out hotter air would be best. Modern wood-burning stoves do this. They pull the combustion air down the outside of a double-walled stack, burn the wood, and the combustion gases are vented up the middle of the stack. This prevents the stove from stealing your warm air in the house for combustion and pushing it out the chimney. In this case, you don't want the air conditioner stealing your cooled air to cool the condensor coil and push it out the chimney. —Bradley17:16, 4 August 2006 (UTC)[reply]
Meteorite
Is it possible that a meteorite could hit the earth at an angle that would forever increase the speed at which our planet rotates on its axis. Thanks.
Sure, but not by a lot. Something the size of what killed the dinosaurs could change the angular velocity of the Earth by up to about a few milliseconds per day. Dragons flight05:29, 4 August 2006 (UTC)[reply]
Just consider classical physics questions of momentum--the metorite would have to have a combination of mass*velocity (useful to visualize as a vector) that was non-negligable to the mass*velocity vector of the earth in order to detectably alter the earth's vector. I'd be more worried about massive global extinctions over resetting my Timex if something that large were to come our way... -- Scientizzle07:45, 4 August 2006 (UTC)[reply]
Let's fill this in. Earth's volume is 1012 km3. A really really big meteorite could be 10x10x10 km = 103 km3. Assuming the same mass per volume, that would mean the meteorite's mass is only one billionth of Earth's. Earth has a rotational velocity of 465 m/s at the equator. Compensating for the fact that not all mass is at the surface, let's say 100 m/s. If the meteorite had 1000 times that speed (100,000 m/s or 360,000 km/hr - an enormous speed) then that would only constitute 1 millionth of Earth's rotational momentum. Also, just a tiny fraction would go into a rotational change - most of the energy would be absorbed (on this scale the Earth is quite elastic) and of the remaining energy, most will change the Earth's direction (and thus its orbit), not it's rotation, depending on the angle at which it hits. And that change would also be minute. DirkvdM08:26, 4 August 2006 (UTC)[reply]
Let's just make some assumptions to simplify things here. a) Assume all the momentum transfered from the meteorite to the Earth is transfered to the Earth's angular momentum about the centre of mass (it hits a cliff). b) Assume the collision is perfectly elastic. The angular momentum of a sphere is given by (the moment of inertia) multiplied by the angular velocity. For the Earth this works (I think) at about 2.5x1057. I'll leave you to come up with momenta for meteorites. As DirkvdM says, in reality most of the momentum would be affecting the angular momentum of Earth's centre of mass (it's orbit), but as this is so much higher than the angular momentum about the centre of mass I would guess that (depending on the angle of collision) there would be a greater effect on the Earth's rotation (about its axis) than on its orbit.
One possible explanation for how the moon formed is as a result of a giant meteor collision with Earth. A meteor this size would likely have affected the rotation rate of the Earth by a significant amount. StuRat07:45, 5 August 2006 (UTC)[reply]
Bullet
If I fired a bullet stright up into the air would it (technically) hit the ground at the same speed that it left the gun from. Assuming there is no wind etc.
If fired in a vacuum, however, it would. When dealing with speeds that don't approach the terminal velocity of the object in question, it's safe to say that upward release velocity will be essentially equal to downward falling velocity at the same height (with variations due to chaotic perturbations of the air and object, etc.). The nature of an atmosphere that provides non-negligable friction makes things slightly more complicated at higher velocities... -- Scientizzle07:38, 4 August 2006 (UTC)[reply]
They also pointed out that the bullet would retain spin if it had any arc in the path. To keep it from spinning, you have to fire it straight up - which is nearly impossible to do. The gun, wind, spin of the Earth, and all will contribute to causing the bullet to go up at an angle, arc over (still spinning), and come back down.
Answering the question, though - no. It will not be at the same speed. Bullets do slow down as they pass through the air. Even though it will still be a lethal speed, it will be slower than the muzzle velocity. --Kainaw(talk)13:30, 4 August 2006 (UTC)[reply]
The only real factor that would cause the bullet to have a different speed would be air resistance. Firing the gun from the surface of the Earth, it would be nearly impossible to get it to move in anything other than an arc due to the coriolis force caused by the Earth's rotation (which wouldn't be very much unless it was a very very powerful gun). This shouldn't effect its speed when it lands though as it wont travel any further coming down than it would going up. It's all about conservation of energy. Mathematically, the velocity with which it would hit the ground would look something like:½ where v is the final velocity, u is the initial velocity and Du and Dd are the energy losses on the ascent and decent respectively.
If he stood on the equator of the moon, facing in the direction of the moon's rotation and fired his pistol straight up (so no air resistance) at 300 m/s, would it go straight up and come straight down and (theoretically) land in the barrel of the pistol? The gun rotates with the moon surface at 4.63 m/s in a slightly curved path. The bullet along with its decelerating vertical velocity has an initial horizontal velocity of 4.63 m/s. At the moon's gravity of 1.622 m/sec squared, the bullet would rise for 185 seconds to its highest point. It would fall for another 185 seconds. If the shooter could see it, it would appear to move along the equator retrograde to the direction of rotation, and would land to the retrograde side of the gun. Not good enough at orbital mechanics to say exactly how far behind, but I am curious. Then assume he stood on the north pole of the moon and repeated the experiment. The coriolis effect due to the moon's rotation should be absent, but what effect would the orbital velocity of the moon about the earth and about the sun have?Edison19:35, 5 August 2006 (UTC)[reply]
Energy consumption per country
We've got lists on just about anything, but I can't find a list showing the energy consumption per capita per country. All I can find is Image:Energyconsumption.jpg and Image:Energy per capita.png, but those don't show what I am looking for and only give vague indications. The latter has a list it's based on plus a source, but before I make that into an article I want to be sure there isn't already such a list (in a less obvious place perhaps) and also that I can use (and re-arrage) the data (no copyright violation). DirkvdM08:50, 4 August 2006 (UTC)[reply]
When I worked in energy conservation 30 years ago, we we able to find figures for the "quads" of total energy used by the US and other countries. It should be easier now with the internet, but maybe you should visit a good sized library and have the librarian direct you to reference books on energy. We had a very small proportion of the earth's population and used a very large portion of the energy. Have things changed much? I don't think so, except that there are decreasing reserves of oil and increasing demand in developing nations. Don't forget to combine all sources of energy, and to allocate electricity to end users.Edison19:40, 5 August 2006 (UTC)[reply]
Birds in Slovenia
Why are apparently very few birds in Slovenia. On a holiday in the region of Lake Bohinj, it was noticed that there was no dawn chorus, and few visible birds. Why is this? Thanks, --217.42.132.20709:38, 4 August 2006 (UTC)[reply]
I believe this is because people take pot-shots at them for sport. It's much the same in many parts of eastern and southern Europe. One side effect is that butterflies etc flourish in places like this.--Shantavira11:53, 4 August 2006 (UTC)[reply]
The same thing happens in Italy, people shoot them for food & sport when they migrate over & large numbers don't make it. There was a BBC Radio 4 programme on several months ago about this and the steps being taken to try to preserve the birds, such as legislation & bird reserves. I don't think that there has been a great deal of success in stopping the hunters. AllanHainey14:28, 4 August 2006 (UTC)[reply]
HD-DVD or Blu-Ray
At this point, which standard seems more likely to be adopted as the primary for consumers and studios?
I can't remember which way round it is, but one is supported by Apple and the other by Microsoft. I'd plumb for the one supported by Apple.
Really, we don't know. It is whatever hits The Tipping Point first. They both have their pros and cons. Sony is supporting Blu-Ray all the way, they already are putting out movies in DVD and Blu-Ray. If you just looked at the names, and they were the same thing, you would pick Blu-Ray. I've found I personally, and most people, like technology names to be less abstract. They prefer Mac OS Tiger, or Lisa over AOL version 10.2.3, or Microsoft XP SP3. — [Mac Davis] (talk)
I am holding out until Blu-Ray 2.0, then, just to be contrary!
Weird really. The whole point of the free market system and competing companies and technologies is that the consumers pick the ones they like so those manufacturers get an impulse to make more such products. Sounds good in theory, but in this case consumers just sit around waiting for which one will become the standard and only then go out and buy it. Which is the wrong way around. The central problem here is that the determining factor is the standard. So that should really be set by others, after which the manufacturers can then all use this open (!) standard and start competing with actual products. The openness of the standard is essential for this (the free market really works on the wrong level here). So who should set that then? The old answer would have been governments. But the new answer is the Open Source community. Any ideas how this could be brought about? Is it just a matter of some people deciding to come up with a standard and then presenting that to manufacturers? Or do the consumers need to be convinced to go for that one? DirkvdM19:24, 4 August 2006 (UTC)[reply]
I don't know much about blu-ray/hddvd, but isn't it a fundamental hardware difference? How can open-source communities handle this? If it were up to open-source folks, there would be 10 different versions of the new DVD instead of two.
As a consumer, I don't really care about blu-ray or hddvd, I just want to consume video at a reasonable quality and reasonable availableness for the cheapest price possible. I don't want to invest and put in some mighty dollar votes for the newest gadgets. It's a means to an end and that's all.
The link you want is dollar voting. Make sure to also check out the talk page.
The open source community would converge on one standard. If you're thinking about the many Linux distros, that's exactly what I mean. There are many distros, but they all use the same Linux core. That's the standard. Commercial companies (and others) can then use that for their own version, thus putting the competition where it should be, but leaving the standard alone. DirkvdM09:09, 5 August 2006 (UTC)[reply]
All the latest talk is about how HD-DVD is better in quality, and the players are 1/2 the price of a bluray. Given Sony's hysterical failings of making new standards I seriously don't see how they will ever succeed --mboverload@00:45, 5 August 2006 (UTC)[reply]
It's possible - perhaps likely - that the true successor to DVDs will be neither Blu-Ray nor HD-DVD, but instead will be online file-transfer, scrapping physical media altogether. The current competition between Blu-Ray and HD will hold everything up a long time, where as digital files have many more benefits to producers (there's essentially no cost to creating a new file, and if they use something like BitTorrent to distribute it, bandwith costs fall on consumers). In short - the average person shouldn't bother getting either Blu-Ray and HD-DVD for a long time, if ever. zafiroblue05 | Talk01:13, 5 August 2006 (UTC)[reply]
The dirty truth is that we might not even need a new format. A movie encoded with H.264 or similar advanced codec can fit an HD movie on a standard DVD. In fact I have The Transporter in 720p HD in only 4 gigs, while standard movie dvds are 8. --mboverload@07:08, 5 August 2006 (UTC)[reply]
I'd like a new format, I will always think it's a good idea to back up my hard-drive on a read-only disc. And my hard-drive can only get bigger in the future.
priming fuel pumps
i wonder why internal combustion engines use centrifugal pumps for the fuel delivery system.this gives us the headaches of priming the pumps.isnt it possible just to use a positive displacement pump for fuel delivery since it needs no priming?why prefering the centrifugal ones.moreover i understand centrifugal pumps do not develop good pressure heads. --Chiwaye13:48, 4 August 2006 (UTC)Chiwaye,04/08/06[reply]
Rabbit Internal Organs
Hello,
Can someone tell me what the, relatively, large white organ rabbits have, I've ruled out the heart, stomach & I think kidneys but I've no idea what it is. It's white with a few red flecks or thin veins & its ovalish. Any ideas? AllanHainey14:22, 4 August 2006 (UTC)[reply]
Can lichen, growing on the bark of trees, damage the trees? I have a Wigelia (tree form)that is covered with lichen and one branch has become so soft that it has twisted and flopped to the ground.
Thanks to everyone for any help you can give me.
Antcathy
Oldest surviving sound recordings
Dear Wikipedia, I have tried searching on wikipedia for the oldest surviving sound recordings. Wikipedia provides a video file of the 'Roundhay Garden Scene' (1888); supposedly the oldest motion picture and also provides the oldest surviving photograph; 'View from the study window' (1826/27) by Niepce (I think that's how you spell his name). Wikipedia doesn't, however, seem to provide the world's oldest surviving sound recordings. I wrote to the British Library a while ago to find out more. Here is a copy of my question and their answer...
'Hello, my name's Russell and I may have an FAQ for you. I am interested in finding the world's oldest surviving sound recording.
I've heard that the first thing ever recored was Edison's 'Mary had a little lamb' from Decemeber 1877 but presumably this does not still exist.
I've tried searching on the Internet but can't seem to find out. If you could help I'd be grateful.
Reference Specialist (Sound Archive)
Humanities Reference Service
The British Library
96 Euston Road
London NW1 2DB
UK
Email: <e-mail removed to prevent spam>
Tel: +44 (0)20 7412 7676
I am no expert so I'm a little dubious about writing an article.
Thanks for doing the research! Sometimes on Wikipedia, in order to avoid knighting a thing as "the oldest X" where there is uncertainty or disagreement, we'll have a list of candidates. Then, if a candidate has an article, its claim to the title is linked to the list. Examples can be found in Category:World records. Perhaps it's time for an Oldest sound recording article, with a section for surviving recordings? Melchoir20:08, 4 August 2006 (UTC)[reply]
Edison's first phonograph was demonstrated to Scientific American editors in their offices and featured in the December 22, 1877 issue. IIRC, they included an illustration supposed to be an exact representation of a photo of the pattern of indentation in a tinfoil recording. That photograph or to a less accurate degree the illistration published would theoretically be one of the oldest "surviving" recordings. Actual foils are supposed to be too fragile to play, but a laser scan of one might produce reproducible sounds. A month or so later, tin the multi-volume collected papers of Edison, one of his assistants wrote he had made a plaster impression of a tinfoil recording which accurately reproduced all the indentations, and that he thought copies could be made from it. There is no sign this was done at the time, but maybe it is in a file somewhere. The phonautograph was pre-Edison and made accurate sound tracings on smoked glass cylinders. In fiction, they have been copied and played and perhaps could be in reality. There are urban legends of ancient pottery turned on a wheel and decorated with a wooden stylus having accidentally recorded sounds in the pottery shop, but the potter's hand would be far less effective than Edison's diaphragm connected to a recording stylus as a sound collector. Edison19:59, 5 August 2006 (UTC)[reply]
about macbook (screen size 13.3 inches)
Have anyone seen the new mac book from apple which has a screen size of 13.3 inches? Is it big enough for anyone? Or is it just for students aged under 18? Is it good enough for adults?
One more thing I would like to know
What is the ideal distance between this monitor and our eyes while reading?
Thanks
I personally find that the bigger the screen, the better, because quality is not an issue with MacBook screens. I think if you're not a college kid without any money, you should get a bigger screen. I just checked the site, [18], and it says 13.3 is the only size for MacBooks!! I guess if you want a bigger screen you'll have to get a Pro. As for ideal monitor-eye distance, it is like the whole "don't sit too close to the tv Timmy, you'll hurt your eyes." You put your eyes where ever it is easiest for you to read. — [Mac Davis] (talk)
I think one good thing to check about a screen/computer combination is the refresh rate - try opening a window, then dragging it around the screen very quickly - if the motion looks choppy, you might want to look elsewhere. --Bmk18:14, 4 August 2006 (UTC)[reply]
Just to get all pedantic on you, it's an LCD screen, so it doesn't have a refresh rate: it has a pixel response time. - Nunh-huh04:32, 5 August 2006 (UTC)[reply]
Screen size in laptops is usually directly correlated with weight. If you plan to carry this around with you a lot, a smaller size can make a lot of difference (I use a 12" iBook for this reason, it is large enough for everything I use it for). But if you have doubts you should go to an Apple retail store, where they will no doubt have many display units out that you can play with and see.--Fastfission18:26, 4 August 2006 (UTC)[reply]
It really depends on what you're doing. When I'm programming, I find the 17-inch display on my laptop to be too small, but for reading ebooks, the 2.5-inch screen on my PDA is just fine. --67.185.172.15804:23, 5 August 2006 (UTC)[reply]
Resolution is most of it for me, I had been using a 19xx by 16xx resolution for a while I think, I came back home, got on my old iMac, with a 1280x800 resolution, and everything seemed so fat. lol — [Mac Davis] (talk)
Freaky Plant Situation
Is it possible for two plants to get fused together or exchange genetic material just by being planted very close together? Because I have two plants, a green one and a purple one, and recently the greeen one's been getting streaks of purple in the leaves. The purple plant has vine-like stems and now the green plant is growing vines and it never did before. I have no idea what type of plants they are. It's sort of freaky, but I swear it's absolutely true. Is it possible the purple plant's a parasite or something?
--Anakata22:05, 4 August 2006 (UTC)[reply]
Also, another thing is that one of the abnormal vines on the green plant is actually growing through one of its own leaves, i.e. it poked a hole through it.--Anakata22:14, 4 August 2006 (UTC)[reply]
The Chimera thing could be the cause, but these strange purple streaks only started appearing very recently, like one month ago. Before that the plant was perfectly fine and green throughout. If it was a chimera, wouldn't it be like this from the start?--Anakata23:02, 4 August 2006 (UTC)[reply]
Are the two plants of the same species, and do the reproduce sexually (via stamen, pistols, and pollen) ? If so you may get a cross pollination between the two color phases. I've seen this in alyssum myself. StuRat07:24, 5 August 2006 (UTC)[reply]
If the colouring is caused by some chemical, there need not be an exchange of genetic material, just picking up some of the other's juices. Just a guess DirkvdM09:16, 5 August 2006 (UTC)[reply]
Reproductivity of results
What is meant by reproducibility of results in science? Why is this important in science?
Some time ago, I heard about a group of researchers at a university extracting a substance strongly resembling silk from pigs' ears, and using it to make a purse. However, I can't find anything about this besides retellings of the story, with various embellishments. Is there any truth to this, or is it another urban legend? --67.185.172.15804:20, 5 August 2006 (UTC)[reply]
Tails of shrimp, stems of peperoncini, and peels of oranges and banannas
People often think I am some kind of weirdo because I eat the tails of shrimp, stems of peperoncini, and the peels of oranges.
I sortof understand from a taste/texture point of view - shrip tails are really crunchy and hard to eat, peperoncini stems are stringy, and orange/bananna peels are just bitter.
Are any of them bad for you, though? Is it really that weird to eat these things? It just comes from a family where, if you have food, you EAT it. --69.138.61.16805:12, 5 August 2006 (UTC)[reply]
Nope. I've visited parts of the word where these things are considered delicacies - of course, they are prepared differently than what I imagine a typical Wikipedian would. --HappyCamper05:15, 5 August 2006 (UTC)[reply]
One thing to watch out for is that orange peels may have pesticides and dyes in them that are not intended for human consumption. So, you'd better stick with organic oranges if you intend to eat the peels. StuRat07:19, 5 August 2006 (UTC)[reply]
And in the tropics it is often advised to only eat peeled fruit (and to peel it yourself) to avoid diseases. Don't know which ones, though. DirkvdM09:20, 5 August 2006 (UTC)[reply]
i ned an urgent info
dear sir, i need an urgent info how to separate UREA and CREATININ from a water solution?
please get me the details in this regards as soon as poissible. thanks..
with regards,
budhaditya chattopadhyay,
bangalore, india
BE(medical electronics)
<email address removed>
depends on what purpose they need to be seperated for. if you just want to seperate them analytically, i'm sure RP-HPLC will do the trick. If you want to seperate them preperatively, it becomes more tricky. perhaps cation exchange chromatography? you could exploit the charge differences, i imagine creatinine picks up a positive charge at a higher pH than urea. from a quick look, it seems creatinine forms a complex with zinc chloride, you could have a go at that. Xcomradex07:44, 5 August 2006 (UTC)[reply]
possible infant diarrhea epidemic in Detroit's Harper Hospital in 1943
My infant brother died of diarrhea that year and the family story was that many babies died of it at Harper Hospital during the time of the 1943 race riots because they could not separate the well babies from the sick babies during the riot. I recall at one time years ago reading a newspaper clipping about it but cannot find any now. I am a retired reference librarian so I've looked pretty hard under subject headings pertaining to the (1)riots,(2)Harper's history and(3)medicine, but I know the databases are very different today.
Thank you.
--209.112.212.4006:12, 5 August 2006 (UTC)[reply]
I don't have an answer, but would like to point out that diarrhea isn't a disease, but rather a symptom of many diseases, quite a few of which result from poor sanitation, especially drinking dirty water. It would be important to know the actual disease which caused the fatal diarrhea if you wanted to research it more thoroughly. Also note that simple rehydration therapy (drinking fluids somewhat similar in composition to Gatorade) can prevent death from diarrhea, so I would research whether this was done at that hospital at that time. StuRat07:10, 5 August 2006 (UTC)[reply]
Chromatography
SIR,
I am not able to understand the basic concept of chromatography hence i am fasing problem to learn and understand it.
1) For, eg. " In chromatography , the sample is applied at one end of the porous support which holds the stationary phase and the mobile phase is made to flow over it". The various constituents in the sample gets seperated due to difference in their distribution behaviour.
Now, the stationary phase is the porous support or the sample which is applied? What it is ment by distribution behaviour?
2) The various chromatographic techniques can be classified depanding upon the forces of interacting phenomenon between the solute molecules and the stationary phase.
Now which is the solute molecule and whice is stationary phase, Can you give me any example.
3) Can you explain me the principle of gel- filtration chromatography in simple english.
Fusion generally releases more energy. This is what you should write down. — [Mac Davis] (talk)
...that is, fusion of a given mass generally releases more energy than fission of an identical mass. Fusion also requires much more energy to initiate. StuRat20:32, 5 August 2006 (UTC)[reply]
After the Big Bang, why is it that the Universe is expanding in one general direction? If this is not the case, then what is on the other side of the initial point of the Big Bang?
In one general direction? It expands forward in time. If it expands backward in time from its starting point, I don't think we'd know. In most (all?) big bang scenarios, time started at the initial point and so nothing was before it because there was no time before it. digfarenough (talk) 16:53, 5 August 2006 (UTC)[reply]
In some branches of String Theory it is possible that there was a 'before the big bang'.
I think that Dparisi is under the impression that the universe is moving out into the left (or right). In reality, because the universe itself is expanding (not a bunch of things moving away into the universe), it makes no sense to say that it is expanding in a direction. Space is just getting bigger. —Daniel(‽)17:39, 5 August 2006 (UTC)[reply]
One way to visualise this is as a balloon with dots on it. When you blow up the balloon, all the dots move away from each other. We observe (almost) all stars around us moving away from us, so the conclusion was that we must be part of an 'expanding balloon', ie the universe is expanding. Of course one flaw here is that you can see that the balloon is expanding in relation to its surroundings (the other option would be that everything else is getting smaller, which would be silly). But the universe is everything, so what do you measure its size against? Don't we have to assume that the size of the universe is fixed? (if it indeed is everything) DirkvdM17:48, 5 August 2006 (UTC)[reply]
It is usual to say that all the galaxies in the Universe are moving away from us as opposed to most stars (although as all the stars in the Universe apart from the ones in our galaxy are moving away from us). The balloon analogy can be better expressed by affixing coins to the balloon (top represent galaxies) as these wont expand with the expansion of the balloon. The only real problem with the balloon analogy is that the curvature of a balloon is positive and the curvature of the Universe is zero. This analogy is useful for demonstrating that the big bang happened both everywhere and nowhere. We measure the size of the Universe from the inside by using standard candles to determine the rate of expansion (the Hubble Constant). Once we know this value the age of the Universe can be established then, by association, the size of the visible Universe. We do not know how big the Universe it is, but it is a fair bet that the visible Universe is not the whole Universe. I'm not sure why one would assume the size of the Universe is fixed. The Universe is expanding in either 4, 10, 11 or 26 dimensions; depending on which theory you take to be true.
Since at least one of those dimensions is time, what exactly does "expanding in the temporal direction" mean ? Getting older ? I guess I'm "expanding in a temporal direction", too, then (not to mention a couple of spatial dimensions). :-) StuRat20:24, 5 August 2006 (UTC)[reply]
I'm a senior high school student doing (or will start doing) a kinetic study of the permanganate/oxalate reaction for my final grade 12 year. I have an idea of what I'm going to do and how I'm going about it, but I have a few questions about the experiment. The equation for the reaction is the following:
2 MnO4-(aq) + 5 C2O42-(aq) + 16 H+(aq) --> 2Mn2+(aq) + 10 CO2(aq) + 8 H2O (l)
1. The reaction is very often mentioned as autocatalytic, which I have no reason to doubt. The problem is that most sources do not explain why this is so. The closest to an answer I've seen is something to do with the manganous ion produced collides with manganese complexes and this speeds up the reaction, but even then I could be wrong since I saw this in one source that tried to explain it. Then that doesn't really help me either, even if its correct. Some clarity on that would be appreciated.
2. The reaction procedes in an acidic solution. Would the rate law look like this: rate = k[MnO4-]x[C2O42-]y or do I have to add the proton (like [H+]z) to the equation?
3. I've read some experiment writeups where sulfuric acid was added to the reaction. Does it have to do with the reaction needing to be acidified? Would it be required if I used say oxalic acid instead of sodium oxalate (although oxalic acid isn't very strong)? Another explanation I've found is that it destroys the permanganate and speeds up the reaction and otherwise this reaction would take too long. Any ideas?
If you look at the basic equation you have written, you will see that it requires, at least theoretically, for two negative ions to react together. This would indicate that the reaction has high activation energy. You must look at the way the two manganese-containing ions react together. Secondly, you cannot predict the rate equation by looking at the balanced chemical equation. Rate equations can only be worked out by a series of experiments, for example, varying the concentration of H+ ions. Thirdly, the reaction is a very heavy consumer of H+ ions. These can only be provided by a strong acid. The original ethanedioic acid is far to weak to do this.--G N Frykman21:01, 5 August 2006 (UTC)[reply]
electromagnetic fields and radiation pressure
What is the difference between the lorentz force exerted by electrostatic and electromagnetic fields and the raditation pressure of electromagnetic radiation pressure. Secondly I saw an article in the 70s where small glass balls were levitated by electromagnetic radiation pressure, what is the largest and heaviest object moved by radiation pressure to date?
Curiosgeorge
Vinegar reacts with hairspray to form a solid
A strange elastic white porous soild formed when I poured vinegar into a hairspary formula (40% alcohol) at room temperature and standard pressure. I smell the ethyl acetate, but that doesn't explain the solid. Can someone tell me what happened?
I'm a labworker and during my work I get into contact with many nasty substances like ethidium bromide and DAPI. I tend to handle these substances (even in heavily diluted form) as if they were death incarnate. Sadly I'm also an incredible clutz and did get some DAPI on me and possibly in me. Of course I freaked out like no tomorrow especially because there is so very little known about the substance at hand. There are however quite a few other substances like this like Benzopyrene and Alfatoxin both of which, if I can believe the wikipedia articles, occur in my toast with peanutbutter (all be it in small doses).
Yet both these substances are flagged as highly carcinogenic (just like ethidium bromide and DAPI). So why aren't we dying of cancer left and right. Given the world we live in, with it's smoke, bbq's and crispy brown baked bacon, we should be accumalating this crud in our system at a staggering rate. So what gives? Am I missing something here? Can the body " deal " with these molecules shunting themselves between our precious base pairs thus causing happy frame shift mutations and the like? - Pascal
First, are you sure they accumulate instead of passing through the system ? Second, perhaps the dosage is insufficient to cause a problem. Third, perhaps it's not in a harmful form (for example, elemental mercury is far less dangerous than methyl mercury). StuRat21:43, 5 August 2006 (UTC)[reply]
how a snowboarder turns around while on the air
As far as I am concerned, things need stable things to move. (Car-Road, Boat-sea). So how a snowboarder turns around in the air an astronout in space without touching anything else. if so which musles are more likely to be used while in the action?
Any relevant answer would be much appreciated...
