Wikipedia:Reference desk/Archives/Science/2008 May 25

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May 25

Genetics: Linked genes

I would like to know if there are any linked characteristics with a particular gene, is ther a good resource for this? In particular I would like to know if there are any traits associated with curly hair and pointed canines in humans. Bastard Soap (talk) 00:11, 25 May 2008 (UTC)

Well first you have to find out whether there are known genes that have a phenotype resulting in curly hair or pointed canines. Then you can you find the other traits associated with those genes. A good way to do this is is via OMIM. A search for "curly hair" reveals a number of genes that have alleles associated with curly hair, these include the plakoglobin gene which is responsible for Naxos disease. In these people, curly hair is associated with palmoplantar keratoderma and cardiac abnormalities. However, these alleles tend to be rare, extreme examples. Genetic association with "regular" curly hair is unknown, See: Online Mendelian Inheritance in Man (OMIM): 139450 Rockpocket 07:37, 25 May 2008 (UTC)

Transformers

Do the actual number of turns have any effect on the general system, or is it only the ratio that counts? 2000:1000 is equivalent to 2:1 in all respects? Bastard Soap (talk) 00:44, 25 May 2008 (UTC)

The greater the number of turns in the winding (other things being equal) the greater the inductance (and resistance). If you took a transformer designed to be connected to a 120 volt source in the primary winding which had 2000 turns and connected a 1 or 2 turn winding across the same 120 volt source, with no load on any other winding, I would expect extremely high current to flow due to the low inductance, causing a fuse to blow or the winding to burn out. The higher number of turns in the original transformer would have limited the no-load current to a safe value due to the higher no-load inductance. Tinkerers have sometimes taken a transformer and left the 120 volt (240 volt in other countries than the US) primary winding alone, since it has enough turns to work properly, then changed the number of turns in a the secondary wound over it to produce a high current-low voltage secondary, or a high voltage low current secondary, as desired. In summmary, a transformer with too few primary turns would draw excessive current even when there was no load on the secondary, but the no-load voltages would still vary pretty much as the turns ratio. Edison (talk) 03:49, 25 May 2008 (UTC)

The actual number of turns does have an effect. The number of primary turns must be sufficient to avoid saturation of the core or keep down the magnetising current. This is one reason that, generally, one cannot use a step down transformer backwards as a step up transformer.

Also, increased turns will, of course, put up the winding resistances. This is important when you consider losses and heat generation etc. —Preceding unsigned comment added by 79.76.141.94 (talk) 03:39, 25 May 2008 (UTC)

I've seen lots of utility power transformers and instrument transformers which worked fine to step up or to step down voltage. Step-up, step down, or unity isolation transformers. Edison (talk) 03:51, 25 May 2008 (UTC)

Isn't that the point though? You can design a transformer so it's suitable for stepping upping a voltage say 22kV to 44kV. This will work fine for other things like 44kV to 22kV, 22kV to 11kV, 440V to 220V etc. But you wouldn't want to use it for 44kV to 88kV or 88kV for 44kV Nil Einne (talk) 15:41, 25 May 2008 (UTC)

For one thing the strength of the magnetic field in the core will be different between those cases, and I think it might be possible to saturate the material in the transformer's core if the magnetic field strength is too high. But I'm not sure. I don't see any allusion to it in the articles I've looked through so far. I might have to go digging through electrodynamics textbooks at some point. --Prestidigitator (talk) 04:09, 25 May 2008 (UTC)

Therefore assuming that there are enough turns to limit the current and prevent saturation of the core, there would be no advantage what so ever in addind more turns? 88.203.106.28 (talk) 07:00, 25 May 2008 (UTC)

First, in response to Nil Einne, I agree that the 44kV to 22kV transformer can step down 44kV or step up 22 kV equally well. The problem with applying, say, 44 kV to the 22 kV winding is that the voltage stress would exceed the insulation level and could cause a short between turns or to the core or a flashover of the insulators or bushings. I would also expect the exciting current (with one winding energized and no load on the other windings) would increase with a higher than rated voltage applied. With a utility transformer, there is quite a bump when the voltage is applied, with the mechanical shock to thr transformer causing dust to fly off, and sometimes causing protective relays to trip because the harmonics or inrush current seem like there is a fault, with normal voltage applied. If it did not fail instantly from higher than rated voltage, it would at least have a greatly decreased service life. In response to 88.203.106.28, remember that each turn takes up space. If the conductor has to be of a certain diameter to carry the rated current, and the insulation has to be of a certain thickness to withstand the turn to turn and winding to winding potential differences, then having more turns per winding (while keeping the turns ratio constant) would mean a physically larger, heavier and more expensive transformer. Edison (talk) 18:56, 25 May 2008 (UTC)

Ooops you're right, I got somewhat confused while writing that, too tired or something perhaps. I'd intended to say you could design a transformer to step down 44kV to 22kV and you could use it for 22kV to 11kV, 11kV to 22kV etc, but you wouldn't want to use it for 22kV to 44kV (unless it was designed for that as well). Similarly you could design a transformer to 22kV to 44kV and use it for 22kV to 11kV or 11kV to 22kV etc etc but not 44kV to 22kV. Nil Einne (talk) 20:50, 26 May 2008 (UTC)

So turns are always kept at a minimum which doesn't saturate and limits the current? Bastard Soap (talk) 09:06, 27 May 2008 (UTC)

That's pretty much true. But it's also worth noting, especially for high-frequency transformers (that aren't so limited by the need for a large inductance) that transformers are basically "whole number" devices where each winding is counted in full turns around the core. This may keep you from using a transformer with a two-turn primary if the voltage ratio you need is a step-down of 50 volts to 40 volts. Fractional turns can be hard to realize in practice, especially when you consider that the external wiring may also act as part of a "turn" of the coil. So you tend not to see too many transformers with really low numbers of turns, even though they are theoretically possible. (Interestingly enough, really high frequency DC to DC converters now use transformers where the windings are a very few "turns" formed by circuit traces on the printed circuit board.)

Atlant (talk) 15:34, 27 May 2008 (UTC)

Signal fade

How far away from the Earth would you have to go before TV signals etc become indistinguishable from natural background noise? (Assuming that we are waiting long enough for the signals to actually arrive.) --Fangz (talk) 01:02, 25 May 2008 (UTC)

I wouldn't imagine it to be very far. Giving the signal such a boost for space travel would be wasted energy after all, a useless added cost for the company (assuming E.T. doesn't pay for satellite). Bastard Soap (talk) 01:28, 25 May 2008 (UTC)

I'm no electrical engineer, but I believe that the ability of an antenna to pick out a point signal source from evenly distributed background radiation is in some proportion to the antenna's size or dish diameter. Theoretically, given a sufficiently large (and perfectly constructed) parabolic dish antenna, the TV signals could be resolved at any distance. Other factors might come into play though, such as the effects of interstellar gas and dust or gravitational distortion. -- Tcncv (talk) 02:16, 25 May 2008 (UTC)

TV signals are Electromagnetic radiation, i.e. light but at radio frequency (see: Radio propagation). As light propagates through free space, its intensity spreads out, according to the Inverse square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from the source. So, "doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value." Consider the radiation from the sun. The intensity of the radiation from the sun is 9 times greater than that at Earth. At Pluto, which is approximately 39 times further away from the sun than the earth, the intensity is reduced to next to nothing, the sun just appears like a star. However, there is still some solar intensity getting to Pluto. Since radio waves are the same as light waves, the same applies. So on Pluto, you would get a very weak TV signal from the Earth (which would also be delayed since light travels at a finite speed, however if Plutonians have a decent receiver and amplifier, they will be able to watch their favourite programs. In the same way that we can see distant stars and galaxies using powerful telescopes, E.T. will be able to pick up radio transmissions from the earth using a radio telescope. The cosmic background radiation is incoherent noise, whereas the TV radio waves will contain a coherent signal, which theoretically, could always be extractable from the background noise, using a specialised Low-noise amplifier for example. Astronomers are able to detect and extract radio signals from stars, galaxies or other cosmic bodies, that are billions of light years away. I hope this helps, Jdrewitt (talk) 08:53, 25 May 2008 (UTC)

But the sun emits a much stronger signal (by many orders of magnitude) than a man-made source, so your analogy fails. We cannot detect individual stars as far away as the furthest detectable galaxy. Another example: when the sun enters the field of view of a VSAT antenna, the VSAT cannot detect the signals from the geosynchronous satellite because the sun is so much more powerful than the (much closer) satellite. This occurs for brief periods once a day near the equinoxes. -Arch dude (talk) 22:33, 26 May 2008 (UTC)

My point was that the inverse square law means that the intensity of the light reduces very quickly, yet we are still able to detect individual stars from very, very large distances. The signal emitted from radio transmissions might be small but it is still there, it doesn't disappear, it continues to propagate through space and theoretically is still detectable! The radio signal from the voyager spacecraft is extremely small indeed but it is still detectable on Earth from what is now pretty far beyond the extent of the solar system. Detection of weak signals relies on having an extremely powerful and sensitive detector to receive them but theoretically, the signal can be extracted from the background noise. The point about not being able to detect individual stars from the most distant galaxies is simply a resolution problem. When Gallileo built his telescope and looked at Jupiter, he was able to resolve four of the planets moons from what was previously just visible as a signal blob of light. As technology advances, more sensitive telescopes, photodetectors, spectrometers etc. are developed and ever more distant radio, x-ray and other manifestations of light signals are being detected on Earth. If ET is sufficiently advanced and has sufficiently sensitive instruments and data analysis techniques, they they too will be able to detect signals from very large distances. Jdrewitt (talk) 21:27, 28 May 2008 (UTC)

Don't the companies transmit the signal at the minimum power possible which allows clear reception over their area of operation? 88.203.106.28 (talk) 09:48, 25 May 2008 (UTC)

They probably do, but the signal will propagate in all directions, including into space. Electromagnetic radiation will continue to propagate indefinitely through free space, and with powerful enough receivers will be detected from any distance. Jdrewitt (talk) 11:54, 25 May 2008 (UTC)

"Free space" is only a theoretical idea, though. This paper from NASA about SETI estimates that beyond about 1000 light years, signals outside the range 10^-3 Hz to 10⁶ Hz would be lost to space dust, free electrons, and stray fields. Beyond a certain distance, the signals will lose their coherence and no amount of signal processing will be able to recover them. --Heron (talk) 14:58, 25 May 2008 (UTC)

Our Fermi paradox claims :

SETI estimates, for instance, that with a radio telescope as sensitive as the Arecibo Observatory, Earth's television and radio broadcasts would only be detectable at distances up to 0.3 light years.[44] Clearly detecting an Earth type civilization at great distances is difficult.

No idea how accurate that is. 200.127.59.151 (talk) 19:00, 26 May 2008 (UTC)

There's yet another fly in the ointment, of course. Let's consider American TV channel 7. There isn't just one transmitter (on the entire half of the planet facing ET) that is transmitting on Channel 7; there are probably a dozen or more. And at great distances, your antenna needs to not only be able to catch enough signal to distinguish the signal from the universe's noise, it also needs to have enough angular resolution to be able to separate Boston's Channel 7 (WHDH-TV) from New York City's Channel 7 (WABC-TV). Otherwise, about all you'll be able to decipher from the signal is that there are a bunch of different signals sharing the same frequency allocation and modulation methods, but you'll have a very hard time demodulating them.

Atlant (talk) 15:14, 27 May 2008 (UTC)

Chemistry.

If one takes a thin layer of water (say 3-5 mm thick) and pours a bit of isopropyl alcohol in it, the line of the water recedes as the alcohol spreads out and at the boundary there is vibration in some spots. What causes this? Also, what allows some things to evoporate (water, alcohol, gasoline, etc.), while others can't (oil)? Thanks in anticipation, Ζρς ι'β' ^¡hábleme! 01:18, 25 May 2008 (UTC)

Surface tension, Evaporation--Lisa4edit (talk) 10:30, 25 May 2008 (UTC)

Ok, would anyone like to explain? From the surface tension article: "Its cause is a complex interaction between the differing surface tensions of water and ethanol." Please explain this complex interaction. I knew it had something to do with the surface tension; I just don't know what. I couldn't find anything pertaining to my question in evaporation. Well, except it does say that if the interactions of the molecules are strong enough, the substance will not evaporate. Is this the case with oil. Please explain, Ζρς ι'β' ^¡hábleme! 00:15, 26 May 2008 (UTC)

Your quote from the article relates to "tears" in alcoholic drinks. I think that description is missing a bit about capillary action, which draws the water-alcohol azeotrope up the walls of the glass. The higher vapour pressure of the alcohol causes it to deplete more rapidly, and then the surface tension of the remaining water causes it to form droplets or "tears".

To your first question, adding alcohol to the water changes the surface tension, and as the shape of the meniscus changes, the area occupied by the given volume will change.

To your second question, pretty much everything evaporates, some things much faster than others, vapour pressure is what makes it happen, you can also look at partial pressure. Franamax (talk) 11:14, 26 May 2008 (UTC)

Leaky o-ring

Why is is that steatorrhea is so often associated with fecal incontinence, while diarrhea is not (or is less-so)? Tuckerekcut (talk) 02:12, 25 May 2008 (UTC)

It's because of the oily nature of steatorrhea as it contains undigested fats and oils by definition. It acts as its own lubricant.Fribbler (talk) 14:03, 25 May 2008 (UTC)

How can I change reality?

I'll be honest with you. My life is miserable and sometimes I get tired of scientific laws.- i.e. "the way things are". Facts, nature, atomic structure, etc. Science says that one day we'll be able to create a universe in the labratory, so is there hope for dreamers like me? —Preceding unsigned comment added by Dr. Carefree (talk • contribs) 03:34, 25 May 2008 (UTC)

You cant change reality, but you can change your mind! —Preceding unsigned comment added by 79.76.141.94 (talk) 03:41, 25 May 2008 (UTC)

Yeah. There's always mind altering drugs. --Fangz (talk) 11:27, 25 May 2008 (UTC)

You can change a lot about how you as a human interact with reality. You can't change reality at the physical level. Sorry. It would not be a good idea if you could—lots of problems would result. (Imagine if you weakened the strong nuclear force and all the atoms fell apart. Total bummer. No dreams, no nuthin'.)

Here's a wild idea, though: have you read any somewhat radical philosophy of science? Give Paul Feyerabend a whirl—especially Against Method. You might feel comforted to know that there are some compelling arguments out there (not compelling to scientists, of course, but who asked them?) that reality ain't all that it's cracked up to be, that facts are less concrete than they appear in textbooks, that the way of making something into a "fact" is a bit more complicated and fraught than the scientists let on. --98.217.8.46 (talk) 04:04, 25 May 2008 (UTC)

You mentioned that you were a dreamer. Well, you could try Lucid Dreaming. That way, instead of having to obey scientific laws, scientific laws have to obey you. Digger3000 (talk) 15:47, 25 May 2008 (UTC)

Reality is that which, when you stop believing in it, doesn't go away.

- Philip K. Dick

It was always my hope, in writing novels and stories which asked the question "What is reality?", to someday get an answer. This was the hope of most of my readers, too. Years passed. I wrote over thirty novels and over a hundred stories, and still I could not figure out what was real. One day a girl college student in Canada asked me to define reality for her, for a paper she was writing for her philosophy class. She wanted a one-sentence answer. I thought about it and finally said, "Reality is that which, when you stop believing in it, doesn't go away." That's all I could come up with. That was back in 1972. Since then I haven't been able to define reality any more lucidly. - Philip K. Dick 1978

202.168.50.40 (talk) 23:42, 25 May 2008 (UTC)

I just posted to your question in the 'Miscellaneous' section about 'Change'. Then I saw this one. Anyway, read Peter Berger/Luckmann's 'The Social Construction of Reality' just to get your pump primed. --Ckdavis (talk) 15:09, 30 May 2008 (UTC)

Stephens aldehyde synthesis

In the Stephens aldehyde synthesis, we have a nitrile. Nitrogen is more electronegative tha Carbon. So it will develop a partial negative charge and the Carbon will have a partial positive charge. So when H⁺Cl^-reacts with it, Cl^-must attach to the carbon. But the hydrogen(H⁺)only attaches? How does this happen?

Can you kindly explain the mechanism? —Preceding unsigned comment added by 59.92.106.218 (talk) 03:34, 25 May 2008 (UTC)

Have you looked at the Stephen aldehyde synthesis page and Tin(II) chloride? It seems that the Cl^- does bond to the carbon atom, and then the tin(II) chloride reduces it (I don't know how exactly the reduction occurs though). --Mark PEA (talk) 15:05, 25 May 2008 (UTC)

Pronunciation of Name

How is L'Hospital (the mathemetician)'s name pronounced? Does it go like "L-apital"?? 117.194.226.87 (talk) 05:38, 25 May 2008 (UTC)

I've always heard it pronounced Low-pi-taal. Clarityfiend (talk) 06:50, 25 May 2008 (UTC)

I don't know how it was pronounced in his day, but I've always heard (an English mangling of) the usual pronunciation of the word. Algebraist 09:11, 25 May 2008 (UTC)

The modern French pronunciation of the name is "Loh-pee-tahl" — almost exactly as given by Clarityfiend, but note that the first syllable has no diphthong (as "low" might suggest). --Tardis (talk) 21:52, 28 May 2008 (UTC)

I generally hear people say either "Le-hop-it-al" or "Lop-it-al" - which, as Algebraist says, are probably English manglings of the correct pronunciation. --Tango (talk) 13:02, 25 May 2008 (UTC)

First off: Its much easier to pronounce when spelled non-anglicanized. L'Hopital is pronounced, to my knowledge, Lahoh-pee-tal (thats 3 syllables, not 4). Its tricky because its French 63.172.27.2 (talk) 14:44, 30 May 2008 (UTC)

Education & Career

What are the prospects of the animation industry in the next ten years? 117.194.226.87 (talk) 05:40, 25 May 2008 (UTC)

You might have more luck with this question at the Entertainment desk unless you'd be looking for Forensic animation maybe. --Lisa4edit (talk) 08:57, 25 May 2008 (UTC)

I copied your question over there. You can click this link Wikipedia:Reference desk/Entertainment to look for answers. —Preceding unsigned comment added by Lisa4edit (talk • contribs) 11:44, 25 May 2008 (UTC)

Wonder bar

How is it that bacteria(?) can develop immunities to various medicines like penicillin, but not against the lowly bar of soap? Clarityfiend (talk) 06:59, 25 May 2008 (UTC)

Penicilin and other medicines work on bacteria that have already infected your body. Soap reduces the number of bacteria on your skin [1]. That reduces the number of invaders your immune system has to deal with. --Lisa4edit (talk) 07:21, 25 May 2008 (UTC)

Up to my knowledge it is because the soap doesn't fragmentate, it remains of a certain concentration. While medicines, anti-bacterial soap and other stuff fall to concentrations low enough that don't finish off all bacteria. The bacteria which remain have a higher resistance to the agent (otherwise they wouldn't have survived it). These bacteria then reproduce and you have a population which is more resistant than before. Soap on the other hand just kills all the mos before they can do anything. 88.203.106.28 (talk) 07:31, 25 May 2008 (UTC)

As Lisa4edit says, it is because of a different mechanism of action. Regular soap is a physical weapon of hygiene - it is a surfactant that helps wash bacteria away. Its very difficult for anything to evolve immunity to that (beyond getting better at attachment, I suppose). In contrast, antibiotics are like chemical weapons. Because bacteria can evolve quickly as a population, they are pretty good at adapting their biology so that our chemical weapons are no longer effective. Rockpocket 07:48, 25 May 2008 (UTC)

Doesn't soap lyse open their cell wall as well? In that sense isn't it a weapon as well? Frankly I don't see any difference with regards to evolution in inside the body and outside. 88.203.106.28 (talk) 08:55, 25 May 2008 (UTC)

With antibiotics you create Evolutionary pressure. Only resistant bacteria survive and multiply. And they are already in the body. With soap everything gets flushed down the same drain, no matter what variation evolved. Even if bacteria somehow developed a superior attachment and thicker cell wall, they'd still have to get into the body and battle the body's defenses. The intent of soap is to prevent infection, antibiotics are used to fight it. Lisa4edit (talk) 10:10, 25 May 2008 (UTC)

There's another reason for this, that you seem to be overlooking. Inside the body, there are lots of delicate things, so any antibacterial weapons we feed into our systems have to be very selective, or they'll kill us as well. Our cells are based on similar principles to those of the bad guys. It's easy enough to get resistant to something that targets, say, DNA transcriptase, or some other wacky enzyme that might be found, in a particular form, in just a handful of species. It's a whole different ball game trying to build up a resistance to acid, heat, cold, or just plain washing stuff down the sink. 203.221.126.247 (talk) 11:08, 25 May 2008 (UTC)

In other words (and I don't think this goes quite so far as to be medical advice, as it falls pretty well under the category of common sense), don't eat soap. ;-) --Prestidigitator (talk) 18:53, 25 May 2008 (UTC)

Striking out medical advice. ;-) --Tango (talk) 19:24, 25 May 2008 (UTC)

'Lest you go blind from Lifebuoy Poisoning!

Atlant (talk) 14:58, 27 May 2008 (UTC)

Some very good points and I'd also like to say who said bacteria aren't 'resistant' to soap (in as much as this has any meaning which is not much). If I get a resonably deep wound from a dirty sharp object, I'd take the antibiotics over the soap/soapy water any day you force me to choose Nil Einne (talk) 15:26, 25 May 2008 (UTC)

NE, I think you'd be fighting against every tenet of medical practice - first, you cleanse the wound from the outside. Antibiotics are the last line, not the first line of defence, for reasons of evolution of antibiotic resistance given above. In your deep-wound case, you might do both, but surely you'd wash yourself off first? Franamax (talk) 10:58, 26 May 2008 (UTC)

Well as I said, if you FORCE mt to choose I would choose the antibiotics. You're right that antibiotics are supposed to be the last line of defence, but if you're force me to choose only one option, most people who know abit about bacteria, antibiotics and soap (I think even most doctors) would choose the antibiotics (particularly if it's one with a low level of resistance in the environment) at least for a deep wound from a dirty object. My point was that antibiotics are far better at killing bacteria then soap (since of course soap primarily washes away the bacteria, as has already been discussed) so it's even more meaningless to say bacteria has no 'resistance' soap then it seems from the discussion. (Of course bacteria are not likely to develop greater 'resistance' to soap, for the reasons already highlighted.) This doesn't mean you should go around using antibiotics willy nilly, as you said, it's a bad idea because your going to help the development of resistance. (In fact I personally very rarely apply topical antibiotics and I seem to cut myself a lot. I don't even disinfect a lot of the time which probably isn't good practice but anyway...) N.B. Obviously it's still far better to wash first whatever the case since beyond the resistance, even if you do feel the need for antibiotics, it's far better to wash away (and perhaps then kill with a disinfectant) 95%-99% of bacteria first rather then hope to kill them all/stop an infection with the antibiotics. Nil Einne (talk) 20:40, 26 May 2008 (UTC)

Very interesting. And there I was, thinking soap killed bacteria. Thanks. Clarityfiend (talk) 23:07, 25 May 2008 (UTC)

You might find this article interesting [2]--Lisa4edit (talk) 08:01, 26 May 2008 (UTC)

Evolutionary Anthropology and Psychology

Are evolutionary anthropology and evolutionary psychology legitimate sciences? If not what is the scientific rationale for ethology and evolutionary biology applying to animals but not to humans? 71.231.121.77 (talk) 13:22, 25 May 2008 (UTC)

evolutionary anthropology Evolutionary psychology Evolutionary psychology controversy may help.--Lisa4edit (talk) 13:46, 25 May 2008 (UTC)

Of course they are legitimate sciences - they both have peer-reviewed journals, which is one of the defining traits of "good science" (i.e. a lot of people who are educated about the field have come to a consensus about most of the basic facts, and these provide the foundation for published work on the topic). This does not mean that every theory, hypothesis, or publication about evolutionary anthropology or psychology is guaranteed to be accurate or correct; but it has probably passed a review process. Nimur (talk) 15:04, 27 May 2008 (UTC)

There is actually debate in contemporary philosophy of science as to whether or not social sciences such as anthropology, sociology, and psychology in general should be labeled "sciences" at all. Just putting that out there, not stating an opinion. --Shaggorama (talk) 19:16, 27 May 2008 (UTC)

"For shaver only"

I have here a NiMH AA batter charger with an ungrounded unpolarized US plug. It says "Input: 100-240 VAC, 50/60 Hz, 0.16 A". I also have a US-to-UK plug adapter which says "250V, 1A fuse, for shaver only". Is there any reason I can't use this adapter to plug this non-shaving device into a UK outlet? And what are the specs of those "shavers only" outlets in airplane lavatories and hotel bathrooms and the like? Thanks. 81.98.253.215 (talk) 17:37, 25 May 2008 (UTC)

I would guess that the "shaver only" thing is there because it's only rated at 1 amp, which is quite a lot lower than other devices expect (13 amps is the standard for a UK plug, I think). If the charger only draws 0.16A, though, it should be fine. The other problem is that 250V is more than 240V, although it's not far off, so you might get away with it, but if it blows up and burns your house down, don't blame me! When in doubt, follow the instructions! --Tango (talk) 18:11, 25 May 2008 (UTC)

You should be OK. The "shavers only" plugs are indeed current-limited (on planes due to limited power supply, in bathrooms due to risk of electrocution due to proximity to water), since your charger only draws 0.16A you ought to be fine. Your UK-to-US adapter is probably limited to 1A due to the internal transformer which can't handle higher currents (it would melt if it didn't have a fuse). Bottom line - you should be able to plug your charger into a "shavers only" outlet. — QuantumEleven 21:27, 25 May 2008 (UTC)

And a typical 240 V "shavers only" wall outlet is limited to 200 mA [3], so you will just about get away with plugging your battery charger into it. --Heron (talk) 11:04, 26 May 2008 (UTC)

I would have no qualms about plugging a "universal voltage" (100-240 VAC, 50/60 Hz) batery charger into a "shaver only" outlet, but I must relate a cautionary tale to you: While travelling in the UK, I plugged my transformer-equipped 120 VAC-only NiMH battery charger into an outlet that was labeled "115 VAC shaver only" and the transformer in the charger overheated overnight, opening its internal thermal fuse and killing this charger. This was early in the NiMH days so we ended up scrambling through a lot of UK electrics shops before we found another charger. Oddly enough, it was the same model family as our American charger, but equipped with a BS 1363 plug instead. I concluded after the fact that the "115 VAC" shaver outlet probably just had a rectifier diode in series with the line; this would have worked with the motor of an electric razor but was death to the transformer in my charger. Nowadays, in Europe, I carry a universal-voltage charger and plug adapters but for the UK, I'd bring my souvenir BS 1363 charger ;-).

Atlant (talk) 14:53, 27 May 2008 (UTC)

Glass & Acid

Why is glass resistant to acid? I assume it's due to some element or compound not present in other materials. And is this property unique to glass or are there other substances that are not affected by acid? 92.2.194.36 (talk) 19:46, 25 May 2008 (UTC)

If I remember my chemistry correctly glass does not react with acid because the electrons of the silicone dioxide that glass is composed of are too strongly attracted to its own molecule. That is they are not available to react with the relatively free protons of an acid. This property is not unique to glass but is the same for any highly non-polar molecule. For instance wax or plastic. 71.231.121.77 (talk) 20:00, 25 May 2008 (UTC)

Hydrofluoric acid can dissolve glass however, due to the presence of fluoride than can react with silicone dioxide. Graeme Bartlett (talk) 22:12, 25 May 2008 (UTC)

So why does dishwasher detergent etch glass? Does it contain hydrofluoric acid? Or is some other process? —Preceding unsigned comment added by 71.236.23.111 (talk) 23:31, 25 May 2008 (UTC) oops darn bot Lisa4edit

Abrasives in the detergent. My mom got paid for ruined glassware because they had a shipment of scratchy detergent. But HF does dissolve glass - I worked for an engineering company where we quoted equipment for a confidential process, which turned out to be HF: boom goes all the fiberglass insulation, now let's look at the expensive stuff. Franamax (talk) 23:57, 25 May 2008 (UTC)

The expensive stuff was Grafoil, in case anyone asks :) Franamax (talk) 00:04, 26 May 2008 (UTC)

Should we have a page on "flexible graphite"? It seems to have unique properties that I can't find covered in any of our articles I looked at. --Lisa4edit (talk) 05:56, 26 May 2008 (UTC)

I've been out of the refining biz for 10 years, but at least at the time, Grafoil was the go-to gasket, and wildly expensive. Seems notable to me... Franamax (talk) 10:42, 26 May 2008 (UTC)

If dishwasher tablets contained Hydroflouric acid (HF) then they would be extremely dangerous, not only does it dissolve glass but also very small quantities of HF will attack human tissue and bone leading to extreme pain and even death. HF won't dissolve all forms of glass though, only glass that contains SiO2, which is one of the most common forms of glass but there are many other compositions, e.g. chalcogenide glass. Many other materials are resistant to acid, for example most plastics, many chemicals are stored in plastic containers.

I'm not certain of this, but it has always been my impression that ordinary cheap soda-lime glass degrades in a dishwasher because it isn't pure fused silicon dioxide (silica). As a result, some of the other constituents of the glass can eventually be dissolved out of the glass by repeated washings in the harsh chemicals found in automatic dishwashing detergents. I'm disappointed by our article on soda-lime glass to find that even Pyrex is now made of this stuff rather than the tougher borosilicate glass it used to be made of.

Atlant (talk) 14:43, 27 May 2008 (UTC)

Thanks for that tip on Pyrex! I share your disappointment, I'm from the "only use Pyrex" school, or I was until today. Another totem toppled :( Franamax (talk) 17:15, 27 May 2008 (UTC)

I believe detergents and soaps are also often basic rather than acidic. If I recall correctly, bases are always kept in plastic containers rather than glass in the lab. Is that right? Why? --Prestidigitator (talk) 00:49, 29 May 2008 (UTC)

Thats not quite true. Bases are sometimes kept in plastic over glass. Its mostly an issue of the concentration of the base. The reason is because is that if, for example, you have ground glass the base can fuse ground glass joints together in as little as 30 seconds because of the extremely high surface area they have. Basically, the hydroxide ions are dropping their hydrogen atoms and becoming part of the glass network. In standard glass, the effect is much slower, but if you're using the glass bottle for storage, I could see it happening eventually. 63.172.27.2 (talk) 14:53, 30 May 2008 (UTC)

Same protein with two names?

This question is a little involved: Here is a paper. It talks about PIG2 and says that due to similarity between it and GREM1, that what they found for PIG2 must apply to GREM1. I think that's awful reasoning, but when I follow the given accession numbers I get this and this. Are they actually the same protein? If so, why were they thought to be two "similar" proteins and not one ["exactly the same"] protein? ----Seans Potato Business 21:41, 25 May 2008 (UTC)

Are you linking the right paper? I couldn't find either of PIG or GREM. In any case, the accessions you give show different genetic loci, different lengths and different sequences. A case of convergent genes/convergent structures? They have different sequences, what is the resulting amino sequence? Franamax (talk) 22:46, 25 May 2008 (UTC)

Sorry, I'd linked to the wrong paper (fixed now). There is a string of characters, the translation, which is the same for both proteins, but it's exactly the same (not similar). Could they have been thought to be different but now they're known to be exactly the same? Are you sure that they are different genetic loci? I cannot interpret 'AY232290' as a locus. These databases are very user-unfriendly. Wont someone think of the children? ----Seans Potato Business 23:10, 25 May 2008 (UTC)

That's more clear now (or less clear lol). It looks to me like two separate loci with different DNA/mRNA sequences producing apparently identical amino-acid sequences. That would be an example of gene duplication with accumulated null mutations? The essence here is that the CATG sequences are different, but the amino-sequences are identical. Interesting. You're right that we should think of the children, children are our future - "unless we stop them now-w-w" :) Franamax (talk) 23:50, 25 May 2008 (UTC)

Electroelution

In Electroelution, wont the DNA be daamged when it gets free from the gel and encounters the anode? ----Seans Potato Business 23:19, 25 May 2008 (UTC)

I'm not sure, and this is based on a quick scan of the document, but this may provide a bit of info on the effects of electricity on DNA. Fribbler (talk) 23:53, 25 May 2008 (UTC)

After reading it fully, I think the only useful sentance is And biologists have agonised about how conductivity might affect its function. Fribbler (talk) 00:01, 26 May 2008 (UTC)

In practice, electroelutors "catch" the DNA with dialysis tubing or DEAE paper or a salt bridge before it contacts the anode. Woodlore (talk) 03:29, 26 May 2008 (UTC)