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April 24

How should antibacterial news be added to Wikipedia?

Is Antibacterial the right article to add these news items?

• http://www.scientificamerican.com/article.cfm?id=our-big-pig-problem
  • "Since 1995 Denmark has enforced progressively tighter rules on the use of antibiotics in the raising of pigs, poultry and other livestock. In the process, it has shown that it is possible to protect human health without hurting farmers."
• http://www.latimes.com/health/la-he-antibiotics-agriculture-20110425,0,7598829.story
• http://www.businessweek.com/lifestyle/content/healthday/651982.html

If so, what should the article say and in which section? Are there other article(s) where this would be (more) appropriate? Is this sort of thing appropriate for the article introduction?

Sorry for asking a help desk question on the reference desk, but I'm much more confused about the science component here than the how-to-edit component. If you figure out a good way to put this, please do go ahead and add it to the appropriate article(s). 99.39.5.103 (talk) 00:23, 24 April 2011 (UTC)

Looks like a place for it at Antibiotic_resistance#Role_of_other_animals. More so at Factory farming. I'd encourage you to consider adding your own references though - I'm just answering your question, not promising to do your editing for you. ;) Wnt (talk) 00:50, 24 April 2011 (UTC)

Also, please note that WP is not a news outlet - for that, Wikinews may be more appropriate. -- Scray (talk) 04:55, 24 April 2011 (UTC)

Not true. The policy cited above says "Wikipedia should not offer first-hand news reports on breaking stories." ... which should not discourage you from adding these or other recent sources. Wnt (talk) 06:42, 24 April 2011 (UTC)

human as a mammal

how did "Adam" created first time ?why he created as a mammal ?and for DNA , was it first program for DNA, to produce such mammal? I have not religion proposes of this question , there is scientific ideas in my mind for this filed , such as coming to be alive again based on DNA program for human and remaining that in nature for next time for our coming to be alive after death

.akbar mohammadzade--78.38.28.3 (talk) 05:54, 24 April 2011 (UTC)

Um, I'm not sure I can parse that. Humans are mammals because we all share a common ancestor. Broadly speaking, all mammals bear hair and give milk to their young, which humans do as well. Adam was the first man created by God, according to the Bible. I seriously cannot make heads or tails of anything else you say here. --Jayron32 06:01, 24 April 2011 (UTC)

By "Adam" I'll assume you mean "the first human man". The truth is that species rarely if ever start with one single individual. ("Hopeful monsters" were a popular idea in the early 1900s after X-ray mutations caused radical changes in flies, but eventually people realized those were caused by major damage to chromosomes and aren't representative of real evolution ... though nothing is impossible in biology) The way species actually start is that populations slowly change over time. You can point at one individual and say that he was the last common ancestor of all humans, but he lived in a group with many other individuals who were common ancestors of most humans. Wnt (talk) 06:39, 24 April 2011 (UTC)

Adam is just part of a religious story; he's not somebody who actually existed. There was a man who is known scientifically as Y-chromosomal Adam, but he wasn't the first human male. And although I don't really understand your question pertaining to life after death, life after death in any of its various proposed forms is purely a religious notion, that has nothing to do with science. Red Act (talk) 07:17, 24 April 2011 (UTC)

both of the wayes in thinking about "Adam" from accepting to dont accepting come to same result of which we said about the rule of DNA , I said that "DNA" as it contain our celles formula can product us again , and it is genetic discussion ,for that , I said that Ihave not religen propose .

My discuss for coming to be alive after death is so relagion based "life after death " but only give your reply according to our chemical complex . The water and carbon nitrates and other elements in our body is equal for me and you ,and other natural complexes and for air and soil , the combination and way of lying them together changes for the formula of DNA .if we replay to this question :

was it possible for breeds and fishes or crocodils to have our ability and mined ? then we will be able to imagin the creation of "ADAM" akbar mohammadzade--78.38.28.3 (talk) 05:54, 24 April 2011 (UTC)

I don't understand your question clearly, but DNA is only a minor factor of personality. Look at monozygotic twins. They have exactly the same DNA and so are some kind of natural clones, but they are different persons with different personality. 93.132.153.177 (talk) 11:22, 24 April 2011 (UTC)

Perhaps it would be easier for the questioner to write in their original language, so that the question can then be translated. As it is, it cannot be understood. Ghmyrtle (talk) 11:31, 24 April 2011 (UTC)

A good way to check if a word is correct is to look it up in wikipedia, in different languages. For example, I am quite sure that the above word "breeds" should really be "birds". What makes the OPs questions unintelligible is mostly the syntax, especially the order of the words. Then, Farsi and English have a different set of vowels. That the English vowels are not always represented by the same letters makes it even more difficult. 93.132.153.177 (talk) 11:48, 24 April 2011 (UTC)

I think the questioner is asking whether an individual's DNA could be used to restore that person to life after their death, in a process like cloning. This is a common misperception about what DNA actually does -- it is a framework for a living being, nothing more. The "environment" (in this case the sum total of all life experiences) is what shapes the "person" you become, and aside from epigenetic marks that accumulate in different cells of the body, this life experience is not written into the DNA. Thus, while it would be theoretically possible to use an individual's DNA to generate a living being with a nearly identical genetic make-up, this individual would have none of the unique experiences that contributed to the original and would for all practical purposes be his or her own unique person (like the example of identical twins given above). --- Medical geneticist (talk) 12:55, 24 April 2011 (UTC)

I think this question goes beyond what is scientifically known. "The Mind's I" is a good book to define some of the mysteries. Which neurons are part of the "self", and how many can be replaced with new neurons, or mechanical prostheses? Some of these things are unknown, and perhaps some are unknowable. Wnt (talk) 23:12, 24 April 2011 (UTC)

I agree that cloning generally creates a physical copy of an individual, but does not replicate that person's memories or most of their personality. Those are created as synapses in the brain, based on life experiences. DNA, which doesn't change much from birth, doesn't contain that info. StuRat (talk) 16:56, 25 April 2011 (UTC)

What kind of engineering will be required to make sphere wheels possible?

It has already been imagined. Now, what barriers will need to be torn down in order to make them usable on new cars? --70.179.169.115 (talk) 06:16, 24 April 2011 (UTC)

What advantage would spherical wheels give us to make it worth it to put them into production? --Jayron32 06:19, 24 April 2011 (UTC)

If you get to watch I, Robot, then you'll see how the RSQ maneuvers in ways impossible for today's vehicles. --70.179.169.115 (talk) 08:03, 24 April 2011 (UTC)

That thing looks like it has zero clearance. I'm skeptical it would clear paved roads in Pennsylvania... Wnt (talk) 06:33, 24 April 2011 (UTC)

I am confident that by '35, cars will have variable clearance mechanisms that will raise or lower the body based on what the road sensors detect up ahead. --70.179.169.115 (talk) 08:03, 24 April 2011 (UTC)

Dyson vacuum cleaners already have something similar. --TammyMoet (talk) 08:14, 24 April 2011 (UTC)

I wouldn't say a Dyson ball vacuum has a spherical wheel. The wheel is fixed and won't rotate in every possible direction, only backward and forward like a normal wheel. It is simply shaped differently from a normal wheel and looks more like a ball than it actually acts like one. – Kerαunoςcopia^◁_galaxies 16:47, 25 April 2011 (UTC)

To take advantage of a spherical wheel shape you'd have to get rid of the axle/hub design (axle/hub arrangements only allow rotation in one plane, making a sphere meaningless). This would mean that you'd need to develop entirely new types of suspension systems to allow the wheel to rotate freely while supporting the weight of the car, and entirely new power transmission systems since there would be no axle to apply torque to. Simplest, I imagine, would be to have some sort of friction system (e.g. a small, conventional axle/hub system that pressed down on the top of the spherical tire, supporting the weight of the car and applying torque to the wheel in a wide range of directions). for something more science fictionish, I imagine you could invent a mag-lev system (maybe a spherical hub inside the spherical tire that contained a superconducting magnet?). propulsion in this case would be trickier - I can visualize a system for rotating the wheels based on things like maglev trains or rail guns, but it would basically involve turning the entire wheel-well into a complex electromagnetic control system, and I can't imagine it would be practical or efficient.

Of course, in either of these scenarios you risk your wheels falling off if you hit a bad bump. --Ludwigs2 08:35, 24 April 2011 (UTC)

Spherical wheels shouldn't be too hard. Anyone who has ever looked inside a mechanical computer mouse ought to be able to toss off a quick design for drive system and mounting. DuncanHill (talk) 11:55, 24 April 2011 (UTC)

A mouse is used in a relative pristine environment, yet still eventually gets hair and such caught up inside it. If something similar was used on the street, it would suck up bits of sand, mud, etc. into the works. It might work better underwater, though, for use on a vehicle that rolls on the bottom, since the friction between the sphere and housing could be reduced by the water, and the water could also be used to clean out that area and keep it cool. I visualize a 4 wheeled vehicle with 2 conventional wheels used for drive and steering, with the other two being spherical wheels. StuRat (talk) 16:38, 25 April 2011 (UTC)

I don't believe that's a sensible design for a vehicle wheel. A ball mouse has two planetary sensor wheels (and usually one more sprung planetary wheel, to keep the ball in place). Let's just talk about the two sensor ones. They're mounted at 90 degrees to one another: call them "top" and "left". When the mouse is moved left-right, the left wheel rolls smoothly. In the same motion, the top wheel is still forced against the ball (against what is the pole of rotation of the ball). It doesn't roll, it just scrapes over the surface. Because of the forces involved in a mouse (which are pretty trivial) this isn't an issue. But for an automotive wheel you'd incur significant friction, and wear, all the time (as at least one one wheel would be dragging like this). You could probably design a more complex system where the planets are themselves balls, and their motion is restricted by some interlink that adapts to the vehicle's directions, but by this point it's a very complex design. -- Finlay McWalter ☻ Talk 13:31, 24 April 2011 (UTC)

Of relevance: Mecanum wheel, omni wheel. 94.172.116.125 (talk) 13:41, 24 April 2011 (UTC)

Besides, the goal is to create a holonomic vehicle (one that can freely navigate in the X-Y plane). There are easier ways to do this instead of using spheres: the caster wheel, as you see on office chairs, allows the chair to "glide" in X and Y directions, by offsetting the vertical rotating mount from the horizontal axis of the wheel. It's not very good for propulsion, and has some stability concerns, but it does simplify artificial intelligence path planning quite a bit. Here's an IEEE paper on robot automobiles with holonomic locomotion using conventional tires: Holonomic and omnidirectional vehicle with conventional tires. Nimur (talk) 14:40, 24 April 2011 (UTC)

Great links 94, I knew those wheels, but not those terms :) SemanticMantis (talk) 23:18, 24 April 2011 (UTC)

I had the nagging feeling we've discussed this before and seeing those links confirms it since I distinctly remember giving them before so there may be something in the archives. Nil Einne (talk) 05:43, 25 April 2011 (UTC)

window

vinyl window top sash falling? I have a sash that won't quite stay up the whole way when you open it. how do i fix it — Preceding unsigned comment added by Kci357 (talk • contribs) 07:57, 24 April 2011 (UTC)

We can't fix a sash window over the internet. You'll have to find somebody to come and look at it. Perhaps a friend, relative or neighbour that is good with that kind of thing? --Tango (talk) 13:18, 24 April 2011 (UTC)

This is a very common problem on old sash windows. I don't have any experience with "vinyl" ones. (Do you mean uPVC?) Anyway, the most likely cause is that dirt or debris has got into the sash box, so that the counterweight doesn't go all the way to the bottom, which means it won't pull the window all the way to the top. Pry open the sash box and clean it out. The other possibility is that the rope has stretched, so it needs to be untied and shortened. If it runs on a spring or chain rather than a counterweight I'm not sure how to fix it.--Shantavira|^{feed me} 15:57, 24 April 2011 (UTC)

Chemicals in the body to counteract other chemicals in mood change- e.g., caffeine

I've noticed that frequently, if there is a drug for one thing, there is not a drug to cancel it out. Sometimes this is obvious, like in the case of alcohol: alcohol simply contains too many poisons, which have to be removed from the body.

But in other cases, the drug in question is not a poison, and common sense tells me another drug should be able to nullify its effects. Specifically, I can't think of any drug that will necessarily cancel out the effect of caffeine. Caffeine's side-effects:

• Caffeine will make the individual hyper.
• Caffeine may put an individual in a good mood at first, and kind of a lousy one later. At least it does that with me (I've been a chronic drinker at times in my life... no more)
• Caffeine can make it impossible for some individuals to sleep for long periods of time. Again, it does this for me, at least.

Now I can think of several depressants, but they all have problems:

• Alcohol will make the individual mellow, and while the individual might fall asleep immediately, he will experience a rebound a few hours later. For example, after a night of heavy drinking, he may have trouble getting a normal amount of sleep that night. This rebound effect doesn't exist with caffeine.
• Marijuana - I know nothing about how this drug works, only that it makes people goofy and stupider than normal. So maybe it could effectively counter caffeine, although I doubt it from what I've seen.
• Sleeping pills - in general, I think these might be a good candidate for reversing a caffeine effect, or vice versa. However, I've had at least one occasion where I took a sleeping pill together with caffeine, and instead it just left me in a zombified state - unable to sleep deeply, but tired to the point that I still didn't want to move.
• Xanax - an anti-anxielitic, I have used this drug before. At first, it helped me sleep, but after a while, this effect disappeared for me. I never combined it with caffeine like above (I'm not stupid).

So my question is - is there a drug, illegal or legal, over the counter or prescription, which exists that could exactly reverse the effect of caffeine, and for which caffeine could exactly reverse its effect? If not, is it theoretically possible for such a drug to exist? And could such an anti-drug exist for most non-poisonous drugs (e.g., Xanax, anti-depressants, sleeping pills).

You'll note my question is theoretical only and general. I don't want this discussion to involve specifics like last time I asked about medication, where my thread ended up getting shut down. So if we have to, we can avoid the subject of caffeine and talk about other drugs.

</textwall> Magog the Ogre (talk) 08:28, 24 April 2011 (UTC)

Adenosine is probably the closest candidate. Axl ¤ [Talk] 09:27, 24 April 2011 (UTC)

Adenosine apparently doesn't cross the blood-brain barrier very effectively, so it wouldn't function as an anti-caffeine unless administered directly into the brain. (Caffeine goes right through the barrier as though it didn't exist.) There are a number of known non-selective adenosine agonists, some of which are apparently better at crossing the BBB, but the literature on this topic is too scattered for me to grasp without doing more work than I want to. Let me by the way note a glaring omission: our article on adenosine says absolutely nothing about how it is synthesized within the body. Looie496 (talk) 16:14, 24 April 2011 (UTC)

I think Looie is on the right track; see adenosine receptor for lists of agonists. In general there is no guarantee that a drug has an antidote; however agonists and antagonists often work in opposite ways at one particular receptor. Common small molecules like caffeine probably affect many receptors to some extent, but very likely hitting the adenosine receptors will affect the main effects. In general though, this is a research question: you don't really know what will happen when you mix agonists and antagonists until you try. There could be more than one type of receptor; the drug might have mixed agonist and antagonist activity; the drug might even be causing two subunits from two different related signalling pathways to come together in a way that doesn't happen in normal biology! I wouldn't rule out the possibility that a BBB-crossing drug isn't actually needed - I think that increased heart rate by itself has many subjective effects, and it seems conceivable that if you cancel that out, the other effects aren't so much of a problem. Oh, and I'll look at linking adenosine to purine biosynthesis. P.S. Be careful you don't catch the gout screwing around with experimental purines. Wnt (talk) 18:19, 24 April 2011 (UTC)

Warm salted milk may counteract many drugs if you take it immediately after so you vomit the drug. – b_jonas 20:29, 27 April 2011 (UTC)

control valves in aircrafts.

hi. what are the different types of Flow control valves used in Aircrafts. — Preceding unsigned comment added by Venkata chaitanya (talk • contribs) 10:01, 24 April 2011 (UTC)

Fuel or Air? Dismas|^(talk) 10:40, 24 April 2011 (UTC)

also hydraulic 173.58.233.95 (talk) 11:03, 24 April 2011 (UTC)

The passenger compartment, especially in a pressurized cabin aircraft, will also have a totally independent set of air flow systems and valves. Nimur (talk) 14:44, 24 April 2011 (UTC)

can cerebral palsy lead to...

1) speech impairment? 2) adverse reactions to excessive noise? —Preceding unsigned comment added by 59.189.217.21 (talk) 10:43, 24 April 2011 (UTC)

I don't know about #2, but #1 is truth. Sometimes, palsy can leave the victim's nerves so impaired that they'll need diapers due to not being able to control it. --70.179.169.115 (talk) 10:51, 24 April 2011 (UTC)

You may wish to read the article "Cerebral palsy". The article states "Speech and language disorders are common in people with Cerebral Palsy." Axl ¤ [Talk] 10:52, 24 April 2011 (UTC)

It's quite common for people with cerebral palsy to have an exaggerated startle reflex, meaning that sudden loud noises can be a significant problem. I'm not aware that steady loud noise is usually any more of an issue than it is for others. HiLo48 (talk) 12:00, 24 April 2011 (UTC)

The Primitive reflexes article says that in people with cerebral palsy, reflexes such as the startle reflex aren't as attenuated during childhood development as they are in normal children. The more pronounced startle reflex in children with cerebral palsy is also discussed in this article. Red Act (talk) 20:12, 24 April 2011 (UTC)

If there are call queues, why aren't there fax queues?

When I tried to fax an item, the fax lines were busy so I could not get it through. Why hasn't anybody ever prototyped a fax queuing system? If anyone else has even thought of putting faxes in a queue for a busy line, why hasn't it been done? What's the difficulty? What kind of invisible barrier would we need to blast down in order to make this happen? --70.179.169.115 (talk) 10:49, 24 April 2011 (UTC)

Check out the page on fax servers 173.58.233.95 (talk) 11:06, 24 April 2011 (UTC)

Even for traditional faxes, many professional fax machines have had fax queuing at the sending machine for decades, where they store faxes and repeatedly redial the sender's number until they are able to transmit the fax. The problem with a queue on the receiving end is that it usually relies on a single slow telephone line, so queuing would have to be implemented at the exchange. The actual printing was done as data was received, so there was no advantage in a print queue at the receiving end (though this was also an option on many machines). Telephone companies probably didn't have the technology decades ago to implement a queue at the exchange, and by the time they were installing sophisticated electronics in their exchanges, they would be able to foresee the end of traditional faxes, so why waste money on a technology that was being superseded by the internet? Dbfirs 08:14, 25 April 2011 (UTC)

Is there a service to send a text at a preset time?

If I send a text at 5:45, but only want the recipient to receive it at 7:45, is there an app or anything like it that will opt me to only get it to the recipient at a preset time? I'd hate to wake a recipient up to a text chime, but something spur of the moment wants me to send it before I forget it. --70.179.169.115 (talk) 10:49, 24 April 2011 (UTC)

ohdontforget.com 173.58.233.95 (talk) 10:56, 24 April 2011 (UTC)

Origin of Potential Energy

Given two massive particales seperated by a distance in a vacuum, they will accellerate towards eachother due to gravity (ignoring other forces: magnetic, Casmir, etc.).

The fist law of thermodynamics explains that energy can be transformed but not created or destroyed. Where does the kinetic energy to move the particles come from?

Do the partiles loose a small amount of mass? Or is it truly the loss of some innate "potential energy" that the particles inherited from nucleosynthesis?

~TrickSpoon0 173.58.233.95 (talk) 10:52, 24 April 2011 (UTC)

The kinetic energy does come from the potential energy and, yes, that potential energy contributes to the mass of the particles. The particles get lighter as they move together, although by a pretty insignificant amount. Two particles each of mass m a distance r apart have potential energy (relative to being zero distance apart) of ${\frac {Gm^{2}}{r}}$. If you plug that into E=mc² you find that the extra mass is ${\frac {Gm^{2}}{rc^{2}}}$. Since c is such a large number and G is such a small number, that extra mass is tiny. --Tango (talk) 13:24, 24 April 2011 (UTC)

That's not the right way of looking at it. The potential energy is actually in the gravitational field. For visualisation, picture the magnetic field between two magnets, traced by iron filings. As you move the magnets towards or away from each other, the magnetic field pattern changes. With that, the energy stored in the magnetic field changes. The same thing happens with the gravitational field. As the two masses (which determine the gravitational field) fall towards each other, the field changes and its energy decreases. That gravitational energy is converted to the kinetic energy of the particles. Saying "a particle has potential energy" is actually sloppy (although of course everybody does it). --Wrongfilter (talk) 15:11, 24 April 2011 (UTC)

Ok, technically I should say that is the mass of the field, rather than the extra mass of the particles. It's the extra mass of the system as a whole (neglecting kinetic energy, of course - we know the total is always going to be the same as long as it is a closed system), which is what I was thinking about. It's not what I wrote, though, so I apologise for that! --Tango (talk) 15:25, 24 April 2011 (UTC)

Sorry Tango, but what you said above seems wrong to me. Since energy is conserved, the relativistic mass of the system as a whole is also conserved, and the rest mass of each individual particle is also conserved, so I don't know in which sense do you claim that their masses have changed. Also, the potential energy is measured relative to an infinite distance apart, not a zero distance apart as you claimed. Dauto (talk) 15:13, 24 April 2011 (UTC)

Potential energy can be measured relative to whatever zero point you like. It often most convenient to define zero to be infinite separation and have potential energies that are always negative, but you don't have to define it that way. That said, I still did it wrong. You can't actually use zero separation, since you get problems with infinities. I should have used two finite separations, in which case you get the extra mass to be ${\frac {Gm^{2}}{c^{2}}}\left({\frac {1}{r_{1}}}-{\frac {1}{r_{2}}}\right)$. The principle is sound, though, I just messed up the maths. --Tango (talk) 15:25, 24 April 2011 (UTC)

Ultimately, the potential energy came from the big bang, which scattered matter through the universe, and, thus, we now have particles at a distance from each other. StuRat (talk) 17:38, 25 April 2011 (UTC)

Typical discharge current

Bearing in mind that it is a glow discharge (which normally has an upper limit of about 1A before transitioning to arc), what is the typical current in the discharge between the electrodes of a TEA nitrogen laser? --92.28.77.227 (talk) 11:21, 24 April 2011 (UTC)

Continuously tunable multi- atmosphere small size CO2 TEA laser - "In this work we report the operational characteristics and the spectral properties ... " - as I've said before, your best bet is to refer to experts in this field. Nimur (talk) 14:46, 24 April 2011 (UTC)

Thanks but i cant get acess to that paper. I just like to know some ball park figures for current and voltage reqired to initiate lasing in atmoshpheric nitrogen. I dont have any facilities to make one. Im just interested in the theory.--92.28.77.227 (talk) 20:06, 24 April 2011 (UTC)

Here's a pretty good text book, Fundamentals of Light Sources and Lasers; and the author's accompanying webpage. I'm pretty sure there's coverage of power sources. The magnitude of your discharge or light pump current will depend entirely on your desired output; since you are particularly interested in atmospheric pressure lasers, certain domains will be off limits to you (in terms of peak power, average power, and duty cycle). In general, your average pump power must be greater than the average LASER light output power; and because an atmospheric pressure discharge will only LASE sporadically, you should consider the effect of low efficiency. The exact value of the current you need will depend on your atmosphere, and the Q factor of your optical resonator. If, as you say, you are interested in the theory, you should start with our article on LASERs; you can progress to population inversion, and optical pumping (and other types of Laser pumping), then solve the necessary equations for your specific conditions to estimate a ball-park figure for your pump current. Nimur (talk) 20:15, 24 April 2011 (UTC)

Also, Principles of Lasers, (Svelto), has an entire chapter on electrical pumping. Nimur (talk) 20:25, 24 April 2011 (UTC)

Time travel

Time travel into the past would violate causality, but time travel into the future well possible, we do it at a rate of 60 minutes per hour. In science fiction, you step inside a time machine, pull a lever and after some minutes of your time, centuries have passed on the outside. During that process interaction between the outside and the inside is limited. What real world things come closest to that? Moving near the speed of light would do the trick. Cryostasis works very well, only that nobody has been successfully revived yet. Taking a nap, hoping that at least biologically you don't age quite as fast is quite limited in effect. What other ways are there? 93.132.153.177 (talk) 13:29, 24 April 2011 (UTC)

See here. Count Iblis (talk) 14:43, 24 April 2011 (UTC)

So what they did was breed mice who suffered from the lack of a specific enzyme. They injected the missing enzyme, and, what a big surprise, the condition improved. The most interesting thing about this is that it made its way to a newspaper article. 93.132.153.177 (talk) 14:54, 24 April 2011 (UTC)

Such experiments are common. Often, the only way to work out what an enzyme does (or what the effects are of what it does) is to see what happens when it isn't there any more. It isn't really relevant to this question, though. --Tango (talk) 15:04, 24 April 2011 (UTC)

Well, it looks a bit like this: imagine they had a dog breed that can't produce ascorbic acid. They discover the dogs develop scorbut and lose their teeth. They feed ascorbic acid to other dogs, and these dogs keep their teeth. Now the scientists propose to feed huge amounts of ascorbic acid to old age toothless people in the hope they will grow new teeth. 93.132.153.177 (talk) 15:47, 24 April 2011 (UTC)

. The non-trivial effect that was observed was that the damage done by the increased rate of aging was reversed. It was not just that the mice kept aging at the normal age, their effective biological age became less. So, in the dog analogy, the observation was that the dogs that had already lost their teeth grew new teeth. Count Iblis (talk) 16:26, 24 April 2011 (UTC)

I would appreciate the result very much if it worked on mice without that specific genetic defect that were simply "ill with old age". 93.132.153.177 (talk) 17:06, 24 April 2011 (UTC)

Using mice with that defect just makes the effects more dramatic so they are easier to study. Basically, the study shows that telomerase plays a very important role in ageing. The exact details of that role and how (and if) it can be used to reduce the effects of ageing in humans will be the purpose of other studies, which will now get funding because it's been shown that they are onto something with telomerase. --Tango (talk) 17:45, 24 April 2011 (UTC)

I don't see why they didn't do the tests with a control group of simply old mice already. This could have been done easily, without much need for extra funding. That telomerase plays some role in ageing is neither surprising nor new. The key question is if working telomerase is sufficient or only necessary to slow down (or possibly stop) ageing. To me, this smells like the main purpose is to get perpetual funding. 93.132.153.177 (talk) 18:10, 24 April 2011 (UTC)

I read here that you can actually try this out yourself. Count Iblis (talk) 18:38, 24 April 2011 (UTC)

And you did? I actually would be willing to try telomerase on myself. But as an enzyme it would be very,very difficult to develop a pill that goes through your stomac and delivers the protein intact into your bloodstream, not to mention the problems to get it into your cells. The first article you mentioned could very probably give hints on how to administer telomerase. BTW, you know the joke about the man who was sentenced to prison because of deception for selling pills to prolong life? The judge was especially enraged when he found out that the culprit was a repeated offender who was previously sentenced for the same crime already in 1923, 1878 and 1492. 93.132.153.177 (talk) 19:02, 24 April 2011 (UTC)

One things you didn't mention is spending time near a massive body. Gravity causes time dilation in the same way motion does. If you rode a spacecraft on a trajectory that went near, but not past, the event horizon of a black hole you would, from your perspective, seem to have travelled into the future. --Tango (talk) 15:04, 24 April 2011 (UTC)

Of course, since there aren't any black holes nearby, we'd need another means of "time travel" (such as suspended animation or relativistic travel) to allow our "time traveller" to actually get to a black hole within his or her lifetime. ;) --Link ^(t•c•m) 16:27, 24 April 2011 (UTC)

I think that causality is more of a myth than a scientific phenomenon. If our four-dimensional spacetime includes a trip into the past at some point, then the solution for the events occurring within it simply adjusts itself to that situation. That requires the recognition that in some cases "free will" or "luck" may be distorted - you may not choose to kill your grandfather, or you may not succeed - but the universe moves on, oblivious to your dismay. Wnt (talk) 18:05, 24 April 2011 (UTC)

If you read my question again you will notice that I carefully left out the words "is impossible because it" between the "Time travel into the past" and the "would violate causality" 93.132.153.177 (talk) 18:46, 24 April 2011 (UTC)

chemistry

law of constant proportion 117.206.3.136 (talk) 14:22, 24 April 2011 (UTC)

This is a wiki, and not a search box; you will get better answers if you ask complete questions in English. Are you looking for our article on the law of definite proportions? Nimur (talk) 14:32, 24 April 2011 (UTC)

I created a redirect. Graeme Bartlett (talk) 09:00, 25 April 2011 (UTC)

Potential pollution in sea salt

Since sea salt seems to be growing in prominence as a kind of "exotic" salt, I read the sea salt article looking for an answer to one thing that has been bothering me: the potential for contamination from various sources of pollution. Our article shows that sea salt is produced worldwide, not just the Mediterranean. My worry would stem more with production in Hawaii, or anywhere along the US west coast. The Pacific Ocean has the wonderful Great Pacific Ocean Garbage Patch. Also, I'm curious about run-off from inland that may be polluted. And maybe now (this is an ignorant guess at the moment) there will be an increase, however negligible, in radiation in sea water from Japan. Finally, oceans around certain coastlines are popular for humans to boat around and surf and swim in. I haven't read anywhere that sea salt is free from any potential contaminants from these and other sources. Is it anything to be concerned about? – Kerαunoςcopia^◁_galaxies 16:22, 24 April 2011 (UTC)

Crystallisation, as happens naturally when gaining salt from sea water, is used as a method of purifying chemicals. So I think you shouldn't worry too much. Any garbage like that from Great Pacific Ocean Garbage Patch is highly unlikely to show up in your salt shaker. And if you are not anywhere near Fukushima any radioactive waste will be diluted below the amount of naturally occuring radioactive potassium. 93.132.153.177 (talk) 17:23, 24 April 2011 (UTC)

I'd always assumed that it was the unique combination of dead fish, agricultural run-off and human sewage that gave sea-salt its distinctive flavour. DuncanHill (talk) 17:27, 24 April 2011 (UTC)

I think the contaminants to look for might be other salts rather than plastic, since plastic floats but maybe salt co-crystallizes. It seems more plausible to look for lead, mercury, cadmium and such (especially near rivers that have seen extensive mining in their watersheds). And of course radioactive iodine and cesium near Fukushima... Wnt (talk) 17:44, 24 April 2011 (UTC)

Top hit off the pile:

"Our laboratory also tests for these elements that are sometimes referred to as "heavy metals" and that are present in many things we come into contact with every day in our environment. The Codex Alimentarius Commission -- formed by the FAO (Food and Agriculture Organization) and the WHO (World Health Organization) -- has established the maximum safe levels acceptable in food grade salt for some of these elements. In our most recent analysis all these elements were either non detectable (Arsenic, Cadmium, Mercury) or were well under the published safe limits specified by Codex (Lead - present at levels no higher than .000076% while the Codex limit is .000200%). There are no limits specified for Nickel (present at levels no higher than .000004%)."^[1]

While that manufacturer gives a reassuring message, no doubt there will be some who are not so responsible. Wnt (talk) 17:48, 24 April 2011 (UTC)

Here's the manufacturer of a kit for testing sea salt that claims one of their customers found 5 ppm of mercury in sea salt.^[2] (OTOH I don't know if the customer broke a thermometer the same day, and it makes for good marketing, doesn't it?) Wnt (talk) 17:52, 24 April 2011 (UTC)

Was this the customer who uses exclusively those morally and ecologically favourable Compact fluorescent lamps one of which he accidentally broke just before measuring? 93.132.153.177 (talk) 18:21, 24 April 2011 (UTC)

I didn't have much luck with NCBI just now - here's one paper about copper in sea salt for aquaria, but I don't know if it's relevant: [3] Wnt (talk) 17:58, 24 April 2011 (UTC)

What about Methylmercury, could this be a part of sea salt in some way? – Kerαunoςcopia^◁_galaxies 18:43, 24 April 2011 (UTC)

I doubt that it can be integrated into the crystal lattice of NaCl in any relevant quantity. So it will remain in the not crystallised brine. If the producer of the sea salt washes that away, as he should, instead of waiting until all liquid has evaporated (and thus every solid has crystallised) you won't find any of this in your salt. 93.132.153.177 (talk) 19:24, 24 April 2011 (UTC)

Well, methylmercury is a salt. And remember that sea salt's main claim to fame, as marketed in the U.S. is the wide variety of micronutrients it is supposed to bring - bits of potassium, magnesium, calcium, iron etc. But methylmercury is best known for bioconcentration, leading to high doses in fish eaten, which shouldn't happen in sea salt. Wnt (talk) 19:55, 24 April 2011 (UTC)

Methylmercury a salt? I'm not a chemist, but that doesn't fit the nomenclature I'm aware of. I'd have called it an organometallic. If you'd said mercury chloride, you'd be right, of course. --Trovatore (talk) 05:16, 25 April 2011 (UTC)

CH3Hg+ X-, as per the article. Wnt (talk) 06:25, 25 April 2011 (UTC)

What's the X-? I thought methylmercury was (CH3)2 Hg, with the C-Hg bonds being a covalent-ionic mix, but more to the covalent side. --Trovatore (talk) 20:56, 25 April 2011 (UTC)

My mistake — I guess that's dimethyl mercury. So methylmercury would show up in crystalline form as a salt, although strictly speaking it's not a salt itself, but rather a cation. Methylmercury chloride, for example, would be a salt. --Trovatore (talk) 23:36, 25 April 2011 (UTC)

Potassium? Really? PANIC!!!! You know that it is radioactive!?! And BTW, not every salt has affinity to the same structure of crystal lattice, otherwise recrystallization would not work. 93.132.153.177 (talk) 20:03, 24 April 2011 (UTC)

Oh, I know that - but this isn't a chemistry lab. Who knows how many kinds of crystals they're starting with, or how far the crystallization progresses? Wnt (talk) 20:20, 24 April 2011 (UTC)

I guess the first things to form crystals are those with the highest concentration, that is, NaCl. But analogous with distillation, you should discard the first and the last part. If you don't trust the producers, you might as well assume that they mix in sand or other things. 93.132.153.177 (talk) 20:41, 24 April 2011 (UTC)

It's not that I don't trust them - it's just that they're not being paid to produce pure NaCl, but impure NaCl. If they're making pure NaCl they might as well open a salt mine. As the case I gave demonstrated, the levels of impurities in sea salt are not orders of magnitude below the defined permissible limits. If a sea salt operation is abruptly subjected to pollution (say by illegal dumping at sea, or a shift of the current from a polluted watershed) then someone has to be awake at the switch or they could indeed have impermissible levels. Not saying that's a meaningful danger, just that there is valid reason to watch. Wnt (talk) 23:03, 24 April 2011 (UTC)

There are radioactive isotopes of potassium (just as there are for most, if not all, elements), but the two most abundant abundant isotopes aren't radioactive (see the infobox on the potassium article). You don't really get abundant radioactive isotopes except where they are being produced by human activity, since radioactive means they decay, so they don't last long. There are some abundant long half-life radioactive isotopes (such as those of uranium), but long half-life means they aren't very radioactive. --Tango (talk) 21:52, 24 April 2011 (UTC)

There are naturally occuring radioactive isotopes potassium in quite large quantities. Otherwise the earth's core would not be molten any more. And no one has to feel guilty for that. But OK, for those who like it: The END is coming! Save your souls! Repent of your sins to me, do what I tell you and send me all your money.95.112.225.249 (talk) 09:33, 25 April 2011 (UTC)

The radiation from potassium in the body actually is the largest part of background radiation. See Background_radiation#Radiation_inside_the_human_body. Wnt (talk) 06:28, 25 April 2011 (UTC)

And yet here we are, alive and well. I think that is evidence supporting my point that the abundance of radioactive potassium is not sufficient to cause any problems. --Tango (talk) 10:58, 25 April 2011 (UTC)

I didn't say otherwise. Background is background - people have been surviving it since there were people. Wnt (talk) 19:57, 25 April 2011 (UTC)

Actually, on consideration, I can think of one time when it could be worth purifying potassium free of radioactivity: supplies for a manned Mars mission. If you lower the natural background of humans and plants, it might be easier to spot small leaks early in a nuclear reactor or external radiation shielding. Wnt (talk) 17:27, 27 April 2011 (UTC)

Kevlar Production

It's about the production of Kevlar by the reaction between 1,4-phenylene-diamine (para-phenylenediamine) and terephthaloyl chloride. http://en.wikipedia.org/wiki/Kevlar. By analyzing the given chemical equation, I got confused in the product of the equation. Shouldn't it be -Cl on the outside of the bracket and not -OH? Jaypril27 (talk) 16:55, 24 April 2011 (UTC)

At some point the terminal -Cl group will hydrolyze very easily with even the smallest amount of water. See Acyl_chloride#Reactions. So, I'm not sure when the terminal -Cl becomes hydrolyzed, but I am pretty confident that it is correctly converted to an -OH in the final product. --Jayron32 19:57, 24 April 2011 (UTC)

Water splitting on a worldwide scale

I'm to understand that splitting water into hydrogen and oxygen is something considered for powering hydrogen fuel vehicles. My question is...on an industrial scale what impact would this have on the world's water supply? If, say, 1 tonne of water is split into hydrogen and oxygen does that mean that the world now has 1 tonne less water? I ask this purely because I thought the earth is a 'closed' system of water and that the volume of water doesn't change, just the 'state' the water is in (e.g. solid, liquid, gas) but if we split it apart does that mean we 'lose' the water or will it recombine later? Sorry if completely daft question! ny156uk (talk) 20:49, 24 April 2011 (UTC)

Yes, there would be one ton less water; that one ton of water would have been converted into a few hundred pounds of oxygen and a few pounds of hydrogen. Later, the hydrogen would be burned, and would recombine back with oxygen to form the same amount of water. Nimur (talk) 20:53, 24 April 2011 (UTC)

Hydrogen isn't an energy source. It's just a way of storing energy. You split the water into oxygen and hydrogen, using energy that you have got from somewhere else, and then store the hydrogen until you need the energy. You then react it with oxygen (ie. burn it) and the energy is released again. The water isn't used up in this process, just temporarily transformed. --Tango (talk) 21:55, 24 April 2011 (UTC)

I suppose some leaked hydrogen might rise to the top of the atmosphere and get blown away on the solar wind - no idea if that is even a hypothetically detectable amount, though. Wnt (talk) 22:59, 24 April 2011 (UTC)

Let me just note that by a back-of-the-envelope calculation I just did, if we derived all of our energy from splitting water, and lost all of the byproducts, it would take a few hundred million years for us to run out of water. There's a lot of it out there. Looie496 (talk) 05:47, 25 April 2011 (UTC)

We don't have to run out of water to have problem. A reduction in sea level by a few feet could cause a problem, although rising sea levels from melting glaciers may cancel this out. However, if lake water was used, then we could have falling lake levels at the same time as rising oceans. StuRat (talk) 14:15, 25 April 2011 (UTC)

Yes, there's no shortage of water, so there would be negligible impact on the world's water supply, especially since most of it will be recovered (as mentioned above). There might be a slight modification in rainfall patterns as a result of moving water around the planet (either as liquid or as its constituent gases). The real problem is where will you get the energy from to split the water? Dbfirs 07:56, 25 April 2011 (UTC)

Plants do that all the time. Only they are intelligent enough not to produce hard to handle elementary hydrogen gas but to bind it to carbon. H₂O + CO₂ → O₂ + "sugar", where "sugar" is anything built from HCOH fragments. 95.112.225.249 (talk) 09:13, 25 April 2011 (UTC)

... so a genetically modified plant that has its intelligence reduced so that it produces raw hydrogen and oxygen from sunlight would be a cheap alternative to solar panels. The problem would be in safely collecting the hydrogen. Perhaps it could be modified to excrete the gases from separate ducts, or perhaps our current system of biofuels is safer? Dbfirs 11:30, 25 April 2011 (UTC)

I just imagine a hollow dandelion stem swollen to ball size with hydrogen and oxygen, waiting for someone to come along and then to go booooom 95.112.225.249 (talk) 12:01, 25 April 2011 (UTC)

Amazingly, we actually have an article on biological hydrogen production! Looie496 (talk) 04:51, 26 April 2011 (UTC)

April 25

PBS series about a family using 1980's computer

I saw a few minutes yesterday of a US Public Broadcasting System program (likely originally BBC) in which a British family was forced to use old electronics. They had to choose a 1982 computer, and chose a "BBC computer" over a Sinclair or Commodore. Later, they acquired a VHS player and huge camcorder. What was the series? It seemed almost like a Twilight Zone episode, when they went to the "Computer Museum" (rather than my living room or attic) to get electronics of the 1980's. Edison (talk) 00:53, 25 April 2011 (UTC)

It was probably Electric Dreams (TV series). I still have a BBC computer and a VHS recorder from the 1980s, and I remember using a shoulder-size video camera, though they were too expensive for me to own one. Dbfirs 07:47, 25 April 2011 (UTC) (Apologies for edit conflict with Ny156uk whose apparently earlier reply has mysteriously appeared below mine.) Dbfirs 07:59, 25 April 2011 (UTC)

Is it the series 'Electric dreams' by the BBC? (http://www.bbc.co.uk/electricdreams/) The family spend some time in the 70s, the 80s and then the 90s. We've an article on it Electric Dreams (TV series) ny156uk (talk) 07:43, 25 April 2011 (UTC)

Thanks! Edison (talk) 18:55, 25 April 2011 (UTC)

Do avocados contain cholesterol?

Do Avocados contain cholesterol? Also, why does the label on the bottle of vegatable oil at my local supermarket read "No cholesterol" if vegatable oil doesn't normally contain cholesterol anyways? Which foods DO contain cholesterol? Thank you. 161.165.196.84 (talk) 03:39, 25 April 2011 (UTC)

The short answer is "no". Cholesterol is only present in any reasonable amount in animal tissue. Cholesterol is a molecule that forms part of the cellular membrane in animals. Plants have a different architecture in their cell walls that does not require cholesterol to regulate fluidity, therefore only animal derived foods contain it. Vegetables and vegetable-derived products, such as avocados and vegetable oil do not contain cholesterol. The statement on your vegetable oil bottle may be obvious to an informed consumer like yourself, but nevertheless is put on for marketing to make the product more desirable for buyers. —Preceding unsigned comment added by 160.79.139.10 (talk) 05:01, 25 April 2011 (UTC)

It should also be noted that choloesterol intake does not directly corrolate to blood cholesterol levels. Your body manufactures cholesterol and cholesterol derivatives from all sorts of sources, so its quite possible to subsist on a fully vegetarian diet and have a high cholesterol. People still have that silly "you are what you eat" mentality, so when the doctor says "You need to get your cholesterol down" they think they can simply cut cholesterol out of their diet and that will help. Its way more complex than that. --Jayron32 05:11, 25 April 2011 (UTC)

Understood; It has always been my understanding that the purpose of cholesterol is to act as a sort of temperature buffer (regulating fluidity) in the phospholipid bi-layers of animal cell membranes; so it makes sense that plant products would not contain cholesterol. thank you for the responses and helping me put this debate to rest. Sorry Roberto / Charissa —Preceding unsigned comment added by 161.165.196.84 (talk) 05:30, 25 April 2011 (UTC)

I always thought the main purpose of cholesterol was to serve as a reservoir of raw material for the manufacture of steroids. Hadn't heard of the temperature thing; sounds interesting though. --Trovatore (talk) 05:41, 25 April 2011 (UTC)

Plants have no substantial reservoirs of cholesterol, but do produce lots of steroids, see Phytosterol. I'm pretty sure that the steroids, being terpenes, can all be synthesized from first principles without going through cholesterol directly. --Jayron32 05:56, 25 April 2011 (UTC)

See also Lanosterol, which IS the starting material for steroids. I think cholesterol, being a steroid, is actually synthesized from Lanosterol like the rest of them. --Jayron32 05:58, 25 April 2011 (UTC)

As per Cholesterol#Dietary sources, fat intake, particularly of saturated fat and trans fat, actually plays a larger role in blood cholesterol than consumption of cholesterol itself. Saturated fat is mainly found in animal fats, but there are also a few plant foods containing large amounts of saturated fat, in particular palm oil and its relatives. However, palm oil might not be as bad for you as animal sources of saturated fat; see Palm oil#Comparison with animal saturated fat. Animal fats used to be the only source of dietary trans fats, but they are now also in partially hydrogenated vegetable oils. (Regular liquid vegetable oil hasn't been hydrogenated.) Red Act (talk) 06:13, 25 April 2011 (UTC)

You are aware that hydrogenating removes a double bond? That is you saturate the fat. 95.112.225.249 (talk) 09:07, 25 April 2011 (UTC)

Not if it has more than one double bond, hence partially hydrogenated. --Jayron32 12:59, 25 April 2011 (UTC)

blood type

If the mother is type B and the father is Type AB is it possible to have a type A baby? If both parents are type B is it possible to have a type A baby? — Preceding unsigned comment added by Everlalin (talk • contribs) 09:51, 25 April 2011 (UTC)

Yes for the first question, no for the second. See ABO blood group system. As with everything that has to do with biology, there might be very rare exceptions to the rules. Type B has either double genes for B or one for B, one for O. AB always has both A and B genes. Type A has either double A or A and O. So if the mother has genes B and O and the father A and B there is a 1 in 4 chance that the child will have A and O genes and as the O genes don't express anything that is measured by the tests the resulting blood type will be A. If both parents lack the A gene it is impossible for the child to have one. 95.112.225.249 (talk) 10:24, 25 April 2011 (UTC)

Before anyone makes any conclusions such as diagnosing a "nonpaternity event," he should also note that occasionally the blood type for an individual is reported incorrectly. In a case where both parents are reported to be or or thought to be type B, one might be in fact something else. Even if someone with incorrectly reported blood type received a transfusion in an operation, there are variations in which it would not have caused a serious reaction (like 60% of the time, on average), so the incorrect report would not have been caught (for other mismatches there would be fatal results). Edison (talk) 18:53, 25 April 2011 (UTC)

Some other weird aberrations include the Bombay phenotype and random deletions.^[4] Though admittedly it is far-fetched, though not quite impossible, to picture a way to witch an A out of a BxB mating. I think genetic mosaicism is the most likely example. I remember a news story about a woman genetically "proven" not to have given birth to her baby, and taken into custody, but I can't find the link now. Wnt (talk) 00:29, 27 April 2011 (UTC)

Does Diet Coke cause cancer?

People have told me not to drink Diet Coke or any diet sodas because they contain aspartame which causes cancer, is there any truth to this? --112.213.139.29 (talk) 10:47, 25 April 2011 (UTC)

We have an article about aspartame, where you can read all about this ingredient, and follow further to the Aspartame controversy article about health concerns. Both of these appear to be well-referenced from many reliable sources (rather than just "I heard...") to explain the concerns and currently available research and conclusions. Also, there are diet sodas that use other artificial sweeteners instead, so you can easily avoid this ingredient rather than the broader category of products that might contain it. DMacks (talk) 10:50, 25 April 2011 (UTC)

Pretty much everything you can imagine has been reported to cause cancer in one study or another. There is no way you can avoid them all. See Carcinogen for some details. --Tango (talk) 11:02, 25 April 2011 (UTC)

You may be interested in the Daily Mail Oncological Ontology Project.--Shantavira|^{feed me} 11:31, 25 April 2011 (UTC)

But some chemicals have stronger correlations than others, obviously. (Or put more precisely, all cancer-causing agents are probabilistic — some increase your risk factor more than others.) That's what the OP is most likely concerned about. There are quite a lot of studies on aspartame in particular, which are discussed in the article. --Mr.98 (talk) 11:35, 25 April 2011 (UTC)

I think that when looking into chemical controversies, the first thing to put into context is the patent expiration date. In the case of aspartame that was December 14, 1992, at which time the price fell from $70 per pound to $20-$35 per pound.^[5] When the same or other companies have new patented products to compete on the market, such a cheap competitor is clearly a major problem.

Now by comparison to other chemicals, the situation with aspartame was adjudicated with great integrity. By contrast, the FDA had just made up a new power to ban the herb stevia in 1991, requiring congressional action (DSHEA) four years afterward.

Also consider Accutane, which upon its patent expiration in 2002 was found to be so teratogenic that special restrictions had to be placed on it. Then the FDA, finding that the original manufacturer had abused its first program, decreed that once generics would become available, it was necessary to impose iPLEDGE, a program so draconian and lunatic that, for example, men had to promise not to become pregnant.

For a similar example, consider Oxycontin, which in slow-release form was patented as a "less addictive opiate". This turned out to be bogus advertising, and the manufacturer was hit up with an unprecedented $600 million fine (for its $1.2 billion annual profit on the drug). After that they introduced a new "safer" form and have ten more years on that patent.

I don't think it is unreasonable to conclude that proving a compound unsafe at the end of its patent term is as important to the pharmaceutical company as proving it safe when it is introduced. (And often not so difficult for those who know all the little details glossed over in the original studies) Wnt (talk) 19:52, 25 April 2011 (UTC)

Laser pump design

In electrically pumped TEA lasers, what consideration is given to the efficient matching of the source and load impedances? I mean, do designers of this type of laser ever think about efficiently matching, or is this not possible? What is the effictive load impedance of the discharge etc? Also, why do the designs waste half of the energy by shorting out one of the capacitor plates with a spark gap and therby losing half the stored energy? This seems most inefficient.--79.66.81.54 (talk) 10:56, 25 April 2011 (UTC)

If you're referring to the circuit designs linked from Professor Csele's webpage above, that was a "homemade TEA laser," (albeit, made by a professional laser physicist). An industrially designed LASER from one of the major vendors will probably have a team of power electronics engineers specifically dedicated to optimizing the power supply. A major problem in lasers, particularly of the sort you've been investigating, is thermal loss in the gain medium due to poor quantum efficiency; the power supply should be tuned to deliver a pulse duration and intensity that is suitable for the statistics of the gain medium. The chemical and physical properties of the gain medium will determine its electrical impedance, and cannot be easily summarized, even as a complex impedance. See active laser medium for details. It's not unlike asking for the impedance of a transistor or a vacuum tube; the device is active and has multiple ports, so the system as a whole requires a more elaborate treatment. Other common power supply efficiency can be analyzed as well, such as power factor correction, albeit that the load impedance is very very very nonlinear/non-uniform/non-ideal. In an ordinary experimental setup, it's up to the physicist to determine if that thermal energy loss interferes with his/her measurement, or affects his electric bill in any meaningful way. Nimur (talk) 14:31, 25 April 2011 (UTC)

Can a dish washer dissolve rubber compeletely?

I had a rubber band for home canning the like of which you can see here in my dish washer and can't find the least trace of it now, not even tiny bits spread around in an ugly way and sticking to everything else, as sometimes happens with other things. Is it possible that it has been completely dissolved? 95.112.225.249 (talk) 14:33, 25 April 2011 (UTC)

It's unlikely that the temperatures of the dishwasher could melt the rubber; nor that any chemical in the detergents would dissolve rubber completely. However, the combination of heat and detergent sounds like a great scenario to denature the rubber - it probably loses its elasticity, becomes crumbly, and the pieces easily flow down the drain. We have discussion of the chemistry behind natural rubber elasticity at our article. Nimur (talk) 14:38, 25 April 2011 (UTC)

I am astonished. So you could make a kind of fridge that uses rubber instead of a gas? My late rubber band would be originally designed to withstand boiling temperatures whereas the dish washer nominally gets only up to 70C°. 95.112.225.249 (talk) 14:49, 25 April 2011 (UTC)

It's true that rubber has interesting thermoelastic properties, and the thermodynamics of elasticity has been heavily studied by physicists and material scientists. I don't think you could make a practical refrigerator out of it; we have several articles related to refrigerator thermodynamics, start with heat pump and refrigeration cycle for an overview. Numerous lab demos exist to show the effect of temperature on elasticity; it's harder (but not impossible) to show the effect of elastic expansion on temperature. Nimur (talk) 16:27, 25 April 2011 (UTC)

From the section natural rubber elasticity you gave I can see that you can "wring out" the heat energy from rubber by stretching it like water from a sponge. This is what normally happens in the condenser step of the refrigerator cycle. So I imagine it is easy to put up a cycle where rubber is stretched and, loosing degrees of freedom, gains temperature and looses heat energy by exchange with the environment. When relaxed again, it gains degrees of freedom, the heat capacity goes up and it takes heat energy from the environment. I cannot believe I'm the first one to think of it. Either there is some flaw in my reasoning or there must be some rubber-fridge already. 95.112.225.249 (talk) 22:10, 25 April 2011 (UTC)

You may be interested in thermoplastic. Also, some descriptions of kevlar attribute the armor's "bullet-stopping" capability to the thermal properties of the fibers. While it is possible to transform bulk kinetic energy into thermal energy, and therefore transfer heat, a practical refrigerator needs a medium with a high heat capacity; the quantity of thermal energy you can transfer using only elastic deformation of a polymer is very small, compared to a conventional refrigerant. Nimur (talk) 22:57, 25 April 2011 (UTC)

Do you have any figures at hand? (I admit I'm too tired and lazy right now to search for myself9. The key figures would be the heat capacity of the rubber when stretched compared to when relaxed. I don't see how any melting points or glass temperatures would come in. 95.112.225.249 (talk) 23:11, 25 April 2011 (UTC)

No, I don't have any hard numbers; but if you don't have the physical intuition to see why a rubber band stores very little heat as it expands, compared to a refrigerant, what makes you think you've got the physical intuition to interpret a numeric measure of heat capacity? At the end of the day, the universe does what it should, irrespective of any equation we wrote to model it numerically. Nimur (talk) 03:23, 26 April 2011 (UTC)

Nimur's words with Voltaire's Pangloss express the Leibnizian optimism of Pangloss about the Universe. The OP may inspect the door seal on their dishwasher that I wager is made of Neoprene, a synthetic rubber that hopefully has not perished as unvulcanized caoutchouc is prone to do. Cuddlyable3 (talk) 08:54, 26 April 2011 (UTC)

Pharmacology - Dose Effect Curves

A standard pharmacology experiment is to place a piece of smooth muscle into an organ bath, that contains a concentration of drug and to measure the contraction / relaxation of the drug.

Can then plot a dose effect curve for the results at different concentrations and use this to work out the maximum response that a drug can produce and the EC50 value.

My question is... Since the concentration of the drug in the organ bath is completely different from the concentration of drug at the receptors, what is the point of this experiment? Is not the drug concentration at which a 50% maximal response obtained then completely arbitrary? Or can the results of this experiment only be used to compare other drugs in exact some situations?

Hope that makes sense!

Thanks :) — Preceding unsigned comment added by 138.38.187.77 (talk • contribs)

Trees and/or plants affected by white-tailed deer and invasive species in Maryland

I'm looking to research a plant or tree whose future is potentially compromised by both overgrazing of the white-tailed deer population and the presence of invasive species, specifically in the state of Maryland. Any suggestions, links or reading recommendations would be greatly appreciated. — Preceding unsigned comment added by Marie Poling 03 (talk • contribs) 19:05, 25 April 2011 (UTC)

Have you tried using Google Scholar to start your research? --Jayron32 19:08, 25 April 2011 (UTC)

Also try the invasive species listing for Maryland. ~AH1 ^(discuss!) 21:16, 25 April 2011 (UTC)

motional electric field

http://www.rexresearch.com/hooper/horizon.htm#intro 'During World War II the writer, working on an invention for a "drift and ground speed meter for aircraft", arrived at a plan for utilizing the vertical component of the earth's magnetic field. If the voltage induced between the ends of two oriented linear conductors traveling horizontally across the vertical component could be measured within an aircraft, a self-contained meter, independent of ground instrumentalities, would be forthcoming. The plan was reviewed by the U.S. Bureau of Standards, and its workability confirmed under a certain restriction. It was stated that the device would be inoperable within a conducting cavity such as a metal-clad aircraft. Our textbbooks have taught us that when a linear conductor moves with a velocity V across a magnetic flux of intensity B, an electric field of vector intensity VxB is induced within the wire and gives rise to a voltage at its terminals. This electromagnetically induced electric field, often called a motional electric field, we have been taught, would be electrostatic in character, that is, identical and indistinguishable from an electric field arising from charges of electricity. We know that radio tubes, silvered on the inside, shield the interior from stray electrostatic fields. In the same way, it was explained, such a drift and ground speed meter within a metal-clad aircraft would be shielded from the electric field induced in a conductor by motion across the vertical component of the earth's magnetic field. This explanation was a jolt to the writer. How could we know, without experimental evidence, that such would be the case? This presented a great challenge! Some of the foremost thinkers in physics were consulted. It was discovered that there was no experimental evidence to support the popular belief held by physicists that the motionally induced V x B field was electrostatic in its fundamental character and therefore subject to shielding. It will be shown how, step by step, the writer has been guided over a period of 20 years to experimental means which at last reveal experimentally, beyond all doubt, the beautiful unique properties of the motional electric field. It is not electrostatic! Its immunity to shielding, magnetic or electrostatic, is the exciting property which it shares with the gravitational field and thereby indicates their kinship. By a general theorem in electric field theory we know that a non-uniform B x V field must also act attractively on matter! Thus the motional electric field has acquired a status which makes it quite unique.'

What are your thoughts on the article how the electric field should be shielded? and the fact that we do not know that the the motionally induced V X B field was electrostatic in its nature and the fact that the non uniform B x V field must attractively on matter is this true from the article? How has not modern traditional science not seen this? — Preceding unsigned comment added by Lufc88 (talk • contribs) 20:38, 25 April 2011 (UTC)

Bluntly, you've stumbled on the self-published work of a crank who thinks he's discovered some sort of new fundamental theory of electromagnetism, and wants to use it to build gravity-cancelling devices. TenOfAllTrades(talk) 22:02, 25 April 2011 (UTC)

The Earth's magnetic field indeed penetrates an aluminium-clad aircraft but you will find it does not penetrate a thick iron-walled sphere. I don't know why you wish to shield an electric field but a Faraday cage is a means. The linked article notes that Faraday cages cannot block static and slowly varying magnetic fields, such as Earth's magnetic field (a compass will still work inside), and they are only partially effective in blocking electromagnetic radiation. I apologise that the OP's initial link was TLDR for me and I still need convincing that a "non-uniform B x V field must [act?] attractively on matter". Does that cause radio transmitter antennas to collect dust? Cuddlyable3 (talk) 08:37, 26 April 2011 (UTC)

The linked article really isn't worth reading all of. I only read a bit of it myself, but in what I did read, the author was racking up points on crackpot index items 11, 17, and 18, at least, which just isn't a good sign. Red Act (talk) 13:07, 26 April 2011 (UTC)

oh right any one else got any thoughts on this Lufc88 (talk) 16:13, 26 April 2011 (UTC) Lufc 88

NNRTIs and Hep B

Are any NNRTIs used to treat Hepatitis B infection? The drugs used to prevent Hep B replication only appear to be of the NRTI class. I've had a look on each NNRTI page but they all seem to be used to treat HIV. Trying to search for it on Google only seems to bring up a side-effect of NNRTI usage as hepatitis... So even judging from that, it does seem unlikely they would be used but maybe someone knows better than I do. Thanks! 86.185.188.62 (talk) 21:13, 25 April 2011 (UTC)

I never bothered to learn about HBV, so I started with Hepatitis B and Hepatitis B virus. The latter article describes only four genes, of which three don't sound like they have known enzymatic activity. So I focused on Hepatitis B virus DNA polymerase. Specifically, I typed into Google "Hepatitis B virus DNA polymerase inhibitor". Unfortunately, no direct hits. The non-quoted phrase hits cover all sorts of nucleotide inhibitors - I looked at one page of hits. Among these I ran across description of IFN alfa-2b as a treatment, but not curative.^[6] That isn't what I'd call NNRTI though. So I tried the phrase without quotes and added quoted term "non-nucleoside". This gave some 34 hits, including [7]: this includes foscarnet as a "non-nucleotide inhibitor", but it's a product analogue (pyrophosphate). In my mind that doesn't count either. To quote (Google serves up pages from this $439.95 book, written 2007):

"As described above, nucleoside analogues can inhibit cellular as well as viral enzymes, and viruses can mutate to resist to these drugs. As a result, efforts have been made to discover compounds that might inhibit viral polymerases by other mechanisms. The first of these to be approved for clinical use was foscarnet (phosphonoformic acid [PFA]), whose structure is shown in Figure 14.6. Although it is not orally available and intravenous administration is required, it is nephrotoxic; it is approved for treatment of severe HSV, VZV, and HCMV infections that are resistant to front-line drugs.

Foscarnet is an analogue of pyrophosphate, which is a product of polymerization of nucleic acids. Unlike the nucleoside analogues described above, it does not require activation by either cell or viral enzymes but rather inhibits Pol directly. Inhibition is not competitive with deoxynucleoside triphosphates. Rather, it appears that foscarnet acts as a product analogue, evidently by binding to the site normally occupied by pyrophosphate and preventing normal pyrophosphate release so the polymerase cannot complete the catalytic cycle (97,248). Selectivity arises from the viral Pol being more sensitive than cellular enzymes, which is confirmed by the existence of foscarnet-resistant pol mutants (82,96,114). Resistance is caused by an altered polymerase that is less susceptible to foscarnet inhibition.

Because foscarnet is not a nucleoside analogue HSV tk mutants and HCMV UL97 mutants are not resistant to it. Although foscarnet inhibits DNA polymerase by a mechanism that differs substantially from the nucleoside analogs, many pol mutants that are resistant to nucleoside analogs are resistant to foscarnet. Moreover, most foscarnet-resistant mutants are resistant to one or more nucleoside analogs (116). Thus, for some patients with serious herpesvirus infections, no viable treatment options are available. This should be an impetus to further drug development."^[8]

Now searching "foscarnet hepatitis B" on PubMed,^[9] I don't find any recent papers mentioning it, which I would think would happen if someone were testing a new non-nucleoside inhibitor for the viral polymerase. But I haven't searched those other funny proteins with other functions yet. At the most fundamental level, HBV doesn't look like it has a protease, so it doesn't have HIV protease inhibitor like drugs as an option. I hope that by tracing my steps here, I've shown those interested how to continue researching these things over time as drug development progresses. Wnt (talk) 23:35, 25 April 2011 (UTC)

Hmmm, taking another look, it seems like HBx now has a known function as a transcriptional activator (It's not a transcription factor that binds DNA directly^[10] - it just changes the effect of something like E2F).^[11] It sounds like it makes the liver cell more vulnerable to apoptosis from other causes (such as transient ischemia).^[12] But according to PMID 21468663 the bastard little protein actually protects expressing cells from death by etoposide, reducing the effectiveness of this as an anti-cancer treatment. (But not cisplatin) And if that's not enough, it interferes with DNA repair.^{[ PMID 21375739]} According to PMID 21490166, it predisposes the liver to hepatocellular carcinoma more when a particular mutation, HBx5, is present. It is actually essential to the HBV life cycle.^{PMID 21376091}

Now transcriptional factor activity is conceptually a sort of vast neural network of cellular decision-making, and there are many ways to try to counteract an effect. One I found in the search was PMID 19172229 (2010), concerning a Phase II clinical trial to test PXD101 (belinostat), a histone deacetylase inhibitor, in inoperable hepatitis B hepatocellular carcinoma. As you can see this has been a really quick and dirty search; hopefully there is more I missed, and more on the way. Wnt (talk) 00:02, 26 April 2011 (UTC)

(response to OP, further indented to avoid confusion with post above) For NRTIs (which are nucleoside/nucleotide RT substrate analogs), there are shared binding determinants because both HIV RT and HBV Pol have reverse transcriptase activity, resulting in substantial active site homology. NNRTIs bind at sites removed from the active site; therefore, there's little reason to expect that NNRTIs developed for HIV would be active against HBV - here is an example: PMID 10377169. With over a billion people infected with HBV, and many of those infected with both HIV and HBV, you can be assured that the pharma companies are looking for such activity for two reasons: (i) market, and (ii) safety issues of inadvertent HBV treatment when treating HIV - due to issues of resistance and HBV flares when HIV treatment is stopped PMID 18447614. -- Scray (talk) 00:40, 26 April 2011 (UTC)

the kinetics of 3H + 2H ---> 4He + n

How do I calculate the final kinetic energies of each particle, if Q is 17.7 MeV and final momentum is zero? This apparently should be a really really easy two-body problem, but all the google guides on collisions out there assume your masses don't change mass and release energy. John Riemann Soong (talk) 22:22, 25 April 2011 (UTC)

The equations are simple: E₁+E₂=E₃+E₄ with E_i= (c₀²+1/2 v_i²)m_i and v₁m₁ + v₂m₂=0. When I said the equations are simple I didn't mean to say it is easy to resolve them, not at my given local time of day. But I don't see any higher maths involved either.95.112.225.249 (talk) 22:51, 25 April 2011 (UTC)

The solution given above assumes non-relativistic speeds which may or may not be the case. If that's indeed the case, than the solution is really trivial. use the second equation to express one of the final velocities in terms of the other and substitute it on the first equation, which will then have only one unknown and will be easy to solve. Dauto (talk) 23:20, 25 April 2011 (UTC)

I'm afraid that with neutrons of that energy we are on the brink of leaving the range of Newtonian mechanics. Neutron temperature#Fast neutrons. 93.132.131.100 (talk) 23:41, 25 April 2011 (UTC)

Nah... The neutron mass is about 50 times larger than that energy. Newtonian mechanics should still give a reasonable approximation. Dauto (talk) 04:33, 26 April 2011 (UTC)

April 26

Application of brain lateralization to UI design?

The article Lateralization of brain function doesn't discuss the phenomenon's applications. This article claims that gamers should place UI elements that they respond to with the right hand on the right side of the screen, and those that they respond to with the left hand on the left side, to shorten reaction time. Do any ergonomic studies support this claim? Is it possible that a gamer might be able to process some elements of the game state faster in one lobe than the other? NeonMerlin 00:43, 26 April 2011 (UTC)

A lot of "left-brain" and "right-brain" theory was never founded on scientific experiment, and most of it has been pretty thoroughly discredited. What we're left with is a much more vague, but much more believable, theory of functional specialization (brain). It may take decades for "pop psychology" to let the numerous invalid ideas go to rest, though. There is very little actual evidence to suggest, for example, that the "left side" of the brain is more suited to (or more active during) quantitative or numeric cognitive activity. Nimur (talk) 00:50, 26 April 2011 (UTC)

That's all true, but there is some pretty solid evidence that simple visuomotor reactions are faster when they use the hand on the same side as the stimulus (for example PMID 7128169). It is much less clear what happens when the stimuli are more complex or require sophisticated decision-making. From an anatomical point of view, the brain is wired such that the visual input from the right side of the world goes to the hemisphere that controls the right hand, and the left side matches with the left hand, so the basis for such an effect is certainly there. Looie496 (talk) 01:28, 26 April 2011 (UTC)

How to save generic annotated DNA sequences?

There is a sequence here in a generic form with annotations. How do I save it so that I can open it in a capable program which will feature the described annotations? Thanks. --129.215.47.59 (talk) 14:24, 26 April 2011 (UTC)

Can you be more specific about what you want to ultimately be able to do with the sequence? The "capable program" you choose (and there are lots of options) is going to depend on your application, and each program probably has a different input format. If you already have a program you want to use, then there should be some kind of FAQ or user guide that describes the required input. If you haven't already selected a program, then the question you really want to ask is "what program should I use to accomplish X". --- Medical geneticist (talk) 15:01, 26 April 2011 (UTC)

Hi. Thanks for your response. The program is called SeqBuilder; it's a miserable excuse for a cloning tool which we use because our Institute cannot afford Vector NTI. However, the page that I link to presents the genetic and annotation information in a way which I have seen time and time again in my short scientific life and this leads me to believe that it is some sort of generic format, capable of being understood by a number of different programs. If I save it as an .sbd file, SeqBuilder will open the sequence but ignore the annotations. I hope that by appending the correct file extension, I'll achieve an annotated sequence. --129.215.47.59 (talk) 19:33, 26 April 2011 (UTC)

You say, "the page that I link to" - which page is that? If you have an example of the layout you desire it will be easier to guide you. The options are remarkably diverse. Examples of free programs: Artemis, CLC sequence viewer. Geneious is not free, but has great features & students can get a 1-month license for $39. If these aren't what you want, please be more specific. -- Scray (talk) 02:54, 27 April 2011 (UTC)

The file format you link appears to be a variant of the EMBL or Swiss-Prot file formats (see [13] and [14]). If it doesn't autodetect the format, you would have to see what extension your program expects files with such a format to have. (Besides looking in the manual, one way to do so would be to try *saving* as EMBL format, and see what extension the program give it.) -- 140.142.20.229 (talk) 00:40, 27 April 2011 (UTC)

Fermi Paradox and data encryption

Our article on the Fermi paradox says that compressed data streams would be almost indistinguishable from white noise. Would not the same apply if the data was encrypted? A Quest For Knowledge (talk) 17:06, 26 April 2011 (UTC)

If it's good encryption, then absolutely. See page 13 of this book. So you're hypothesizing that the galaxy is teeming with life that communicates by radio, but it's encrypted, so we have no idea? Comet Tuttle (talk) 17:13, 26 April 2011 (UTC)

Both for compressed and encrypted streams, this assumes the data is sent with no kind of framing. You can communicate over an unreliable medium with a self-synchronising code, but why would you bother (unless you were trying to conceal the transmission)? Note that the assertion about compressed streams in that article is unsourced. -- Finlay McWalter ☻ Talk 17:23, 26 April 2011 (UTC)

I think concealment must be the whole point; see Prime Directive. Comet Tuttle (talk) 22:41, 26 April 2011 (UTC)

I'm also not convinced, absent a decent reference, either that a) a compressed stream resembles white noise as opposed to another colour (particularly for schemes which periodically flush their dictionaries) or b) that the cosmic or galactic noise you'd typically see is white either. -- Finlay McWalter ☻ Talk 17:36, 26 April 2011 (UTC)

It also depends on what your definition of a "resemblance" is. A wide band signal will fill the fourier-domain spectrum, but not with random data. So, if you define a signal to "resemble" white noise, solely on the basis of whether it occupies a wide frequency band, then a lot of things "resemble" white noise. Ultimately, if you use a deterministic compression methodology, each compressed input stream will have a unique spectral signature; so the characteristics of the output stream will depend entirely on what data is being transmitted. If you use a lossy compression scheme, any particular source stream will map to one of a finite set of possible compressed stream spectral signatures. I'm not very happy about our "color of noise" article, which seems to blur the terminology. I like our noise shaping article much better; and will toss in that digital signal quantization has unique spectral properties that are easily detectable as "band limiting;" the modulation scheme for any particular signal will dictate whether the band limitation exists as a fourier frequency band, or as some other more abstract vector-space spectrum (such as phase-space, or generalized wavelet spectrum, etc). Nimur (talk) 18:13, 26 April 2011 (UTC)

Toasted bread

why does the toasted bread tastes sweeter than the normal bread? —Preceding unsigned comment added by 122.162.128.226 (talk) 17:29, 26 April 2011 (UTC)

See Maillard reaction. --Jayron32 17:38, 26 April 2011 (UTC)

The sugar components of starch (amylose, glucose, etc) are relatively tastless in starch form. But when subjected to dry heat it produces pyrodextrins through process called pydrodextrinization (strange as it may seem). More like the sugars we use for sweetening. Wiki article (starch)scroll to pyrodextrinization.Phalcor (talk) 18:48, 26 April 2011 (UTC)

Without reading the article, I will tell you that you can link to the 'starch' article on this wiki by typing [[starch]], which gives you a blue link like this: starch. If there is a header 'pyrodextrinization' in the article, you can link to it by typing [[starch#pyrodextrinization]] which produces starch#pyrodextrinization. 82.24.248.137 (talk) 20:43, 26 April 2011 (UTC)

Oh, and I see that you probably meant people to read the bit under Starch#Dextrinization. 82.24.248.137 (talk) 20:44, 26 April 2011 (UTC)

perennial

Resolved

The Taraxacum officinale article says that they are perennial, but I can't see any mention of exactly how long they usually live. I know perennial means more than 2 years, I would like to know more specifically how long they can live for. 82.43.89.63 (talk) 18:56, 26 April 2011 (UTC)

The thing is, 'death by old age' doesn't really apply here. Dandelions exhibit indeterminate growth. So, death of a mature plant will usually be due to Plant_pathogens, herbivory, roundup, etc. In this light, the average life-span of a dandelion in a given population will depend on how prevalent these sources of mortality are. In principle, I know of no reason why a well-cared for specimen couldn't live 100 years or more. SemanticMantis (talk) 19:23, 26 April 2011 (UTC)

Thanks! 82.43.89.63 (talk) 20:33, 26 April 2011 (UTC)

Higgs boson

How does the Higgs boson explain the difference between the massless photon, which mediates electromagnetism, and the massive W and Z bosons — Preceding unsigned comment added by Lufc88 (talk • contribs) 20:04, 26 April 2011 (UTC)

Assuming you understand the contents of these articles (I certainly don't), you may find your answer at Higgs mechanism or 1964 PRL symmetry breaking papers or Higgs_boson#Theoretical_overview. Presumably, the information therin could be summarized in a way that someone who isn't familiar with the mathematics involved can still understand, which I will leave to someone else to do. --Jayron32 20:14, 26 April 2011 (UTC)

Perhaps that editor could also write such a summary in the appropriate articles. Like, as line #1 of each article. Comet Tuttle (talk) 22:39, 26 April 2011 (UTC)

How about starting with an explanation of this...:

"In the standard model, at temperatures high enough so that electroweak symmetry is unbroken, all elementary particles are massless. At a critical temperature, the symmetry is spontaneously broken, and the W and Z bosons acquire masses.

Fermions, such as the leptons and quarks in the Standard Model, can also acquire mass as a result of their interaction with the Higgs field, but not in the same way as the gauge bosons."

Now to be clear - at some very high temperature, does this mean that electron, quark, W, and Z (and photon?) all zip around at the speed of light, as massless particles, and can't go any slower than the speed of light? Are they all actually the same at that point, or just have the same apparent properties?

And at some point, they gain masses by interacting with the non-zero vacuum expectation Higgs field. Is there anything about the massless particle that says ahead of time whether it will become an electron, quark, W, or Z when it interacts with the Higgs?

If you cool down a photon enough, so that it has a really really really tiny energy and a huge wavelength, could it interact with a Higgs and become some new particle we don't yet know about? Wnt (talk) 00:41, 27 April 2011 (UTC)

The short version is that the symmetry breaking mechanism leaves some symmetry behind, and names like "photon" and "electron" are assigned after the fact in accordance with the remaining symmetry. Start with a featureless sphere. There are three independent continuous symmetries of the sphere: rotation around any three mutually perpendicular axes. Now break the symmetry by drawing a dot somewhere on the sphere. Probably, rotation around any of your original axes will move the dot. But there was never any reason to choose those particular axes, so throw them away and choose a new axis through the dot and two other axes perpendicular to that one. Now you have one rotational direction that preserves the remaining symmetry of the sphere-with dot, and two that don't. This is not the greatest of analogies, but it sort of resembles the origin of the photon and the W^± bosons. Keeping in mind that the choice of axes depends on the location of the dot, and the dot can be anywhere, do those axes "exist" before the dot is drawn? In one sense yes, in another sense no. -- BenRG (talk) 10:51, 27 April 2011 (UTC)

I think thye sphere with a dot is a good analogy. Dauto (talk) 13:46, 27 April 2011 (UTC)

April 27

quarks

how do they know that the quarks in a proton maintain their color? in other words do we know that the "red" up quark stays "red"? since we can only take still shots could the red up change to a blue up quark in different still shots without detection? —Preceding unsigned comment added by 98.221.254.154 (talk) 03:58, 27 April 2011 (UTC)

Quarks are constantly exchanging colors with their neighbors. That's part of how the strong interaction works. Dragons flight (talk) 04:04, 27 April 2011 (UTC)

Couldn't that be explained more simply as at the time of the observation one quark was moving toward the observer and another was moving away, or more complexly spinning right and moving toward or spinning left and away? Color seems awfully similar to length width and height, why not use those instead? —Preceding unsigned comment added by 98.221.254.154 (talk) 04:30, 27 April 2011 (UTC)

Because calling it a form of motion would be wrong. The Color charge of quarks was specifically called a color because it is a fundemental property which is quite unlike other properties such as "spin" and "electric charge" and stuff like that. Since the tripartite existance of quarks within nucleons required 6 values to capture all possible combinations, the 6 color charges (red, antired, blue, antiblue, green, antigreen) allow that to work. Electric charge only requires 2 values (+ and -) to work out. The goal is to pick an analogy which won't be confused with other properties, like length, volume, or spin. --Jayron32 04:41, 27 April 2011 (UTC)

(edit conflict) Color charge has nothing at all to do with visible color. Quarks don't "look" red or blue, and their color charge has nothing to do with how they are moving. The "red", "blue", and "green" quark charges are simply labels used to refer to different kinds of charge. This is analogous to how objects can have an "electrical" charge, except that in this case "red", "blue", and "green" refer to other kinds charge that only encountered in the hearts of nucleons. These are simply labels that physicists adopted. Admittedly, using the familiar terms and calling it "color" can be confusing to outsiders since the whole process has nothing at all to do with the normal experience of color. Dragons flight (talk) 04:46, 27 April 2011 (UTC)

No, I mean like the "height" position of the quark in the nutron at the time of the photo or single observation, as in one of the three dimensions of space that that particular quark is occupying at that particular time. —Preceding unsigned comment added by 98.221.254.154 (talk) 04:48, 27 April 2011 (UTC)

Except you can't take a photo of a quark in an observation. Their position exists only as a statistical average of their location taken over an arbitrarily long period of time, exactly as electrons do. The three quarks in a nucleon exist in a small sphere whose volume is defined by the distance over which the strong interaction operates. They don't actually exist in any specific place within that sphere, and it is completely meaningless to speak of a quark as a little ball which can be "frozen in time" by a photograph. Fundemental particles don't work that way. Your presumption that you could define it as such is flawed at the most basic level. --Jayron32 04:56, 27 April 2011 (UTC)

Ok, the height "quality" of the nutron the length quality of the nutron and the width quality of the nutron gives the nutron the ability to be in all three dimensions, but each quark takes turns as each of those qualities equally. —Preceding unsigned comment added by 98.221.254.154 (talk) 05:02, 27 April 2011 (UTC)

(edit conflict) with below. This response is to the above.I guess so. We can "call" the three quark charges anything we like. You could say that the three quark charges are called "Tom, Dick and Harry" if you wanted to, then describe gluon interactions as "A tom quark emits an tom-antidick gluon, which converts the neighboring dick quark to a tom quark, which itself then emits a dick-antiharry gluon, converting the harry quark to a dick quark" The choice of the three names for the three quark charges is completely arbitrary, and any set of three names would work. Height-Width-Length is a nice three-part set, the problem with using it is that those three words already apply to a part of physical reality which is already "coded for" in the x-y-z axis system inherent in the particle spin quantum number. Since the particle spin axis is defined as the z (height) axis, it doesn't make any sense to define both spin and quark charge using the same set of terms. Since the height-width-length (z-y-x if you prefer) is already fundemental to how spin is defined, it would be beyond confusing to use the same terms to define quark charge. Even the Tom-Dick-Harry system would be better. The advantage of the color system is that quark-quark interactions through gluon exchange can be directly modeled by how colors interact. Just as combining red with its complementary color (cyan or "antired") results in colorless (white) light, combining a red quark with an antired gluon will "cancel" the red color. --Jayron32 05:20, 27 April 2011 (UTC)

Quarks already have positions. Color charge refers to an entirely different set of properties that are in addition to the position characteristics. Dragons flight (talk) 05:12, 27 April 2011 (UTC)

That's not what Jayron just said. —Preceding unsigned comment added by 98.221.254.154 (talk) 05:13, 27 April 2011 (UTC)

(post EC response). A quarks spin defines the three dimensions (the axis of the spin fixes the "z" axis of the coordinate system). However, quarks, like other fundemental particles such as electrons, can't be localized to a specific point within their defined probability distribution. As far as I know, there's no way to specifically define a position within the nucleon for each quark to occupy. We draw pictures of quarks as three little circles within a bigger circle because this allows us to visualize them, but this is no more an accurate model of the quark than the lewis structure is an accurate model of the electron. --Jayron32 05:20, 27 April 2011 (UTC)

I get that the "three little colored circles" are not representative of the dynamics of a nutron. I don't believe that simply identifying the xyz coordinates is equivalent to explaining how a nutron exists in those dimensions. Would you agree that just as two electrons cannot occupy the same state two quarks in a nutron cannot occupy the same dimension. that in order to have a nutron it must occupy three dimensions. To have a nutron with two height qualities and a length quality would leave out the width quality —Preceding unsigned comment added by 98.221.254.154 (talk) 05:35, 27 April 2011 (UTC)

Then we're just debating semantics here. You can literally use any three words to define quark charge that you want (see my Tom-Dick-Harry explanation above), so long as you don't mistake the three words you choose as representing any real property except for the quark charge. The disadvantage of using the positional terms is that it implies a connection to reality which does not exist and may confuse. The advantage of the color system is twofold. First, it is less likely to confuse since it uses terms and concepts which are not encountered elsewhere in the model. Secondly, the way in which colors interact (see my red-cyan colormixing example above) makes a nice analog for how color-charge works. So, yes, you are technically correct that you could choose any set of three words to represent the quark-charge concept. However, don't overextend the words you use to take on meanings that do not correlate to behavior. Using words like "height, width, and length" to describe the three aspects of quark charge has no connection to any other definition of those terms. It would be just as arbitrary of a system as the color system would, so why upset the applecart. Instead, just stick with the system that exists which, while equally arbitrary as your proposed system would be, has the distinct advantage that everyone is already using it. --Jayron32 05:48, 27 April 2011 (UTC)

The animation of gluons in color charge shows a neutron transiently having two red down quarks. But the article says "...introduced the notion of color charge to explain how quarks could coexist inside some hadrons in otherwise identical quantum states without violating the Pauli exclusion principle." Is either of these things wrong or misleading? Wnt (talk) 05:52, 27 April 2011 (UTC)

The picture is attempting to show the gluon exchanges happening in isolation. It is my understanding that, in reality, all three gluon exchanges would happen simultaneously, so all three gluons would change color at the same time. If the gluon exchanges happened sequentially (as shown in the animations) rather than simultaneously, it would lead to some rather impossible situations. The animations are showing isolated gluon exchanges probably because it makes it easier to show how the two-color gluons (say red-antigreen) can change the color of the target proton. In reality, these exchanges are happening simultaneously, and at the speed of light, over a distance of a few femtometers, which is about as instantaneous as the universe will allow. --Jayron32 06:02, 27 April 2011 (UTC)

The animation is accurate and consistent with the exclusion principle. Dauto (talk) 13:40, 27 April 2011 (UTC)

So noone knows what physical properties the colors represent? I figured that the colors were to make it easier to understand, not that no one knows how else to interpret it. wow. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:44, 27 April 2011 (UTC)

Sure, we know what physical property the colors represent. They represent the 6-fold "quark charge" which is fundemental to how the strong nuclear force works. This is exactly analogous to the 2-fold electric charge which is fundemental to how the electromagnetic force works. If you understand what physical property + and - mean with regards to the electromagnetic force, then you also exactly understand what the 6 colors of color charge mean with regard to the strong nuclear force. Its the exact same sort of thing. --Jayron32 18:48, 27 April 2011 (UTC)

Think carefully about it. What do you mean by a physical property? For instance, what physical property does the mass of a particle represent? Dauto (talk) 18:57, 27 April 2011 (UTC)

Why couldn't it be the H-W-L qualities? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:56, 27 April 2011 (UTC)

H-W-L are spacial properties. color charge are not spacial properties the same way that electric charges are not spacial properties. Dauto (talk) 18:59, 27 April 2011 (UTC)

How do you know: Photon 1 dimension = no charge; Electron 2 dimensions +,-; Quark 3 dimensions HWL? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:02, 27 April 2011 (UTC)

Do you mean 0, 1 and 2 dimensions respectively? – b_jonas 19:34, 27 April 2011 (UTC)

I don't think so? How do you mean? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:46, 27 April 2011 (UTC)

Again, I need to ask the question: Why are you so tied to the words used to describe the property? You seem to be having a problem conceptualizing that the word is not the thing itself. This is purely a linguistic problem. We've already conceded that the words you use to describe the quark charge thing are completely arbitrary, there's nothing inherently wrong with your system, excepting that it isn't any improvement on the current system, which has the advantage that its already used. Why is height-width-length any better to describe the system than red-green-blue is? The fact that HWL is coincidentally a 3-dimensional system? So isn't red-green-blue (see color space). What makes your three-dimensional system better than the existing three dimensional system already in use? --Jayron32 21:01, 27 April 2011 (UTC)

I guess its better to me only because it helps me understand.

That's cool. If you've got a model that works for you, then stick with it I guess; but you also need to be able to work with the existing model and understand it as well. --Jayron32 01:01, 28 April 2011 (UTC)

Why does coldness hasten the browning of a banana peel?

I took two nearly identical bananas and put one inside the cold refrigerator and one on the room temperature counter and after a couple of hours the one in the fridge was significantly more browned. I assume the chemical content of the air (%O2, %N2, etc...) is the same since the fridge door opens and closes frequently enough and there's nothing else in the fridge I think is giving off or absorbing gases much. The physical difference between the different temperature airs is then pressure. I don't have a bell jar with vacuum pump, though. Will a banana peel brown at an accelerated rate in a vacuum? Thanks. 20.137.18.50 (talk) 14:43, 27 April 2011 (UTC)

Surveying the Web, it's apparent that cold injury sets in below about 10 C. What happens is that the plant senses damage, and (perhaps via ethylene) activates enzymes such as phenylalanine ammonia lyase and polyphenol oxidase. It is possible to slow this down with a modified atmosphere with less oxygen and more carbon dioxide.[15] I saw claims on non-reliable sites that you could slow down the browning by keeping the bananas in a bag, but I don't know if the banana actually respires enough to build up CO2 in a bag. (the truth is out there, but I might go bananas trying to track it down) This is essentially a pigmentation reaction, producing melanin - though the details are not quite the same as the reaction in insects, the basic function of responding to injury or infection using a pigmentation reaction is the same. Wnt (talk) 15:49, 27 April 2011 (UTC)

Thanks for that information. You've well answered how the browning happens. "What happens is that the plant senses damage,..." How it does that (how it figures out that it's cold outside and to start doing what you described, which has a side effect of making them appear brown) would be a mechanism of interest. 20.137.18.50 (talk) 17:21, 27 April 2011 (UTC)

Blood supply to the dartos muscle

Does the dartos muscle in the scrotum have a named blood supply?

This is mostly for personal interest, but should possibly be referenced in the article. Kind Regards, Captain n00dle\^Talk 14:47, 27 April 2011 (UTC)

I did a quick search:

"The blood supply to the skin of the penis and the anterior scrotal wall are from the external pudendal arteries. The blood supply to the posterior aspects of the scrotum is from the posterior scrotal arteries, which is a branch of the perineal artery, which is a further branch of the internal pudendal arteries (5) (Fig. 2.1)

Branching off the medial aspect of the femoral artery are the superficial/ superior branches and the deep/inferior branches of the external pudendal artery. These superficial external pudendal branches pass from lateral to medial, in a variable pattern, across the femoral triangle, and within Scarpa's fascia (a loose membrane of superficial fascia; Fig. 2.2).

After giving off scrotal branches to the anterior scrotum, the superficial external pudendal artery cross the spermatic cord and enter the base of the penis as posterolateral and anterolateral axial branches. Together with interconnecting, perforating branches, they form an arterial network within the Dartos fascia. The Dartos fascia is not really the blood supply; it is more accurate to visualize the fascia as a trellis and the blood supply as the vine entwined on the trellis. At the base of the penis, branches from the axial penile arteries form a subdermal plexus which supplies the distal penile skin and prepuce (Fig. 2.3). There are perforating connections between the subcutaneous and subdermal arterial plexuses. These connections typically are minimal and very fine and, thus, a relatively avascular plane can be developed between the Dartos and Buck's fascia. Because the fascial plexus is the true blood supply to the penile skin flaps that we use in urethral reconstruction, the flaps are considered axial, penile skin island flaps that can therefore be mobilized widely and transposed aggressively.^[16]

I would like to copy the images from the book here, as not everyone will find themselves able to access this page from Google each time they check the link; but unfortunately, I don't think that Wikipedia's Fair Use image policy has thus far extended to uploading local Fair Use images for the Ref Desk archives. If people think we have a chance, this might be time to press the issue on behalf of one or more images. Alternatively, they might be redrawn from the source at some low level of quality (it really is pretty schematic as it is, presumably due to some anatomic variation that they discuss after the section I quoted). Wnt (talk) 22:14, 27 April 2011 (UTC)

Thank you very much for your answer, that was more than helpful! Regards, Captain n00dle\^Talk 11:47, 28 April 2011 (UTC)

Selling spent nuclear fuel

Why don't states that practice nuclear reprocessing buy the nuclear waste from states that don't? Is it uneconomical? (If so, by how much?) Or is it just political? I can see why the US would not sell to China, for example, because there is always a chance that any plutonium reprocessed in China could be alleged to enter into their nuclear stockpile, which would be political poison to whomever proposed it in the US. But there are other, safeguards states, like the Netherlands, or Japan, where this wouldn't presumably be a problem. Has this ever been seriously proposed? --Mr.98 (talk) 15:43, 27 April 2011 (UTC)

For perspective, clothing worn by technicians who work in laboratories near hallways connected to the reactor core is considered "low level nuclear waste" and can't be driven on non-Federal roadways without police escort. (A bit of hyperbole, perhaps, but not much - that's the regulatory environment that years of paranoia and FUD have created). The prospect of actually exporting actual nuclear material is so far off the political table right now, I can't imagine it ever being discussed by a serious high-level legislator. See Radioactive Waste from the US Nuclear Regulatory Commission for more information about relevant policy and procedure; particularly, transportation guidelines for spent fuel. Nimur (talk) 15:53, 27 April 2011 (UTC)

(In actual truth, there are only three locations that are legally permitted to accept incoming shipments of low level nuclear waste, including dirty laundry from nuclear facilities). My exaggeration in the previous paragraph was not that far off the mark. Nimur (talk) 15:57, 27 April 2011 (UTC)

Sellafield's Thermal Oxide Reprocessing Plant provided reprocessing for material from several nations: Japan, Germany, Switzerland, Spain, Sweden, Italy, Netherlands and Canada. [17] Waste was (and may still be) processed for a fee and returned to the origin. Polititally it seems undesirable for any nation to accept radioactive waste from another nation without a promise to return it. There are also numerous problems with transporting it, not least of which is the reluctance of intervening countries to let nuclear waste pass through, and while some of the public grudgingly admit the need for nuclear power, the need for reprocessing is less obvious. --Colapeninsula (talk) 16:01, 27 April 2011 (UTC)

According to Peak_uranium#Reprocessing_and_Recycling, mining uranium is far cheaper than reprocessing nuclear waste, so it does not make economic sense to buy waste in order to reprocess it. --Colapeninsula (talk) 16:06, 27 April 2011 (UTC)

Though you could imagine states like the US, who have literally zero long term waste policy at the moment (other than "store it on site at every individual reactor"), might find the service itself to be worth paying a premium for, well beyond what it would get them in terms of fuel. --Mr.98 (talk) 21:15, 27 April 2011 (UTC)

Part of the economic theory which justified the design of THORP in the 1970s was that there would be a market (subject to NNPT restrictions) for plutonium for fast breeder reactors.(ref:NewScientist 4 Aug 1977). But the UK didn't build a generation of commercial fast breeder reactors (ref: Bulletin of the Atomic Scientists March 1993), and they didn't really catch on elsewhere either. And given that nuclear weapons delivery systems have become so accurate, and the mania for competing in megatonnage has gone with SALT, START etc., the declared nuclear powers have a surplus of Pu anyway (and so have come to realise that it's a liability rather than a boon). If the proposed new generation FBRs catches on, there might after all be a decent market for Pu, but there seems to be quite a lot of it sitting around anyway (from military applications and existing reprocessing). This paper(from 2001) gives numbers then for surplus Pu and describes the plutonium fuel business as uneconomic and over-subsidised. -- Finlay McWalter ☻ Talk 21:50, 27 April 2011 (UTC)

ISS lights

I have been able to spot the ISS in the Earth's shadow with binos quite often. In fact, it is always observable when it is higher than about 20° above the horizon. I would say that it is roughly magnitude +8 when it is at 45° altitude, which by my calculations corresponds to a lightsource of about 30 Watt. Because over the last three years, the brightness is similar, I think that there is an outside lightsource on the ISS and it isn't light escaping through the windows. Does anyone know more about the lights of the ISS? Count Iblis (talk) 17:40, 27 April 2011 (UTC)

What makes you think it isn't just reflecting some combination of the ambient light reaching it from the Earth/Moon/Sun. It has giant solar panels and a shiny metal skin. I think it'd be a pretty decent reflector, and wouldn't need a porch light to be visible at night with some binoculars. --Jayron32 18:09, 27 April 2011 (UTC)

I doubt any external lights are normally on. They would serve no purpose except during an EVA, robotic operations, or docking/undocking with a visiting vehicle. You're probably seeing reflected earthshine. anonymous6494 18:25, 27 April 2011 (UTC)

Also, solar panels provide a limited amount of power. And every extra light fixture implies extra wiring, extra fixtures, etc, each one of them having a small chance of breaking and/or becoming a hazard and/or becoming a nuisance to do something else. Also, extra control circuits and extra items in your maintenance checklist. --Enric Naval (talk) 13:51, 28 April 2011 (UTC)

It is usually visible for a considerable time after the sun has set at the ground observer's location. Just because it's dark where you are does not mean the ISS is not in sunlight when you see it. Roger (talk) 18:29, 27 April 2011 (UTC)

I know, but if the ISS is not in the Earth's shadow it is magnitude -3.7 or so, easly visible to the naked eye (as bright as Venus). E.g. a few days ago, I could see it entering the Earth's shadow already above the Western horizon, and then it became invisible to the naked eye (brightness dropping rapidly from -3.7 to about +8). In binoculars it is then still visible. Then, when it rises toward the Zenith it actually brightens a bit to magnitude +7 or so and then, when it moves toward the East and starts to set, it becomes less bright. Count Iblis (talk) 18:50, 27 April 2011 (UTC)

(I'm going to assume that you meant -7 in the post above). The apparent brightness of the ISS viewed with the naked eye or through binoculars will depend on a number of factors. Less atmospheric haze, skyglow, or residual twilight on a given evening and time will make the station appear proportionately brighter because it will be seen against a darker background sky. Less haze and good seeing will also scatter less of the station's light on its way to you, meaning that it will be genuinely brighter as viewed, even if the amount of light it reflects is unchanged. Of course, it's not a good idea to assume that the amount of reflected light is unchanged—in fact it will vary quite a bit. The amount of light reflected will depend quite heavily on the relative position and orientation of station, Sun, and Earth-based observer. The moderately-experienced stargazer will be familiar with the swift (and often periodic) variations in apparent brightness associated with inactive satellites and other tumbling space debris that rapidly change their orientation relative to the Sun and Earth. While the ISS isn't tumbling, it's apparent orientation relative to the observer changes as it arcs across the sky. Usually this effect is subtle, but if one is in the right place at the right time one can get very bright specular reflections off the broad, flat solar panels. These so-called satellite flares are most often associated with the Iridium communication satellites, but observers have also recorded ISS flares—this short article has some incredible photographs. TenOfAllTrades(talk) 14:12, 28 April 2011 (UTC)

diminished brightness when closer to the horizon could be caused by the greater distance that the reflected light has to pass through the air to reach you.190.148.133.64 (talk) 21:28, 27 April 2011 (UTC)

There is a reason why distant objects appear brighter: Viewed from the moon it self the moon dust is quite dark, but from the earth the moon looks so bright it shines, I think that's probably part of the effect you're noticing. have a look at the pics on our ISS article, and if you're still not convinced, do a google image search for telescope iss photo, there are no obvious external lights to be seen. Vespine (talk) 23:27, 27 April 2011 (UTC)

Virtualy all the light you see reflected from the ISS is from the sun. This can be demonstrated by the fact that the brightness (and thus visibility) of the passes over a particular spot on the earth's surface are related to the passage of the station through the still present sunlight high above the observer, although the ground is in darkness. The station is never visible from the ground by naked eye more than about three hours after sunset because it passes throught the earth's full shadow when observed by a ground observer more than (say) three hours after sunset. The same principle applies before dawn. The station is visible from earth during evenings or pre-dawn periods even when there is no visible moon. I get my info from here Richard Avery (talk) 07:58, 28 April 2011 (UTC)

I think this thread is going off the rails a bit, perhaps I was not so clear in my postings here :) I'm talking about the ISS being in the complete shadow of the Earth, and then it is "invisible", but actually not quite invisible, you can still see it in binoculars. It seems consistently magnitude +8 to me when it is 45° above the horizon (and obviously a bit brighter when it is higher in the sky, but I have fewer observations of such cases and because it is then moving fast, it more difficult to estimate brightness). If you attribute that to a lightsource on board the ISS, you can compute that you need that lightsource to be about 30 Watt. You can easily imagine that 30 Watt can escape through the windows, or you could postulate that there is an outboard light that is always burning.

Now, Jayron32 says that it could be due to reflection of ambient light from the Moon, the Earth etc. But we can discount the Moon, because you can see the ISS in the shadow just as well during New Moon. Also, if the ISS is in the Earth's shadow, you won't have reflected sunlight from the Earth shining on the ISS. Then what remains are city lights. Now, where I live, there is a fair degree of light pollution, so you could imagine that this is possible.

To make the ISS appear to be magnitude +8, you need a total of 15 Watts reflecting off it (half of the 30 Watt because that 30 Watts was assumed to radiate isotropically). But to get 15 Watts of city-lights reflecting off the ISS, you need quite a bit more than of 10 GigaWatt of lights on the ground near a radius of a few hundred kilometers of where I am (I get 14 Gigagawatts when I compute flux by taking the reflecting area of the ISS its width times its length, which is obviously a big overestimate, and then assuming that most light sources are where the ISS apears 45° above the horizon, which is also not realistic). If I assume that most city lights have a luminous efficacy of 60 lumens/Watt instead of the 15 lumens/watt I've been assuming all along, you still are left with at least about 3 GigaWatts of street lighting which still doesn't sound realistic to me.

Instead, assuming that you simply have 30 Watts of lights (or perhaps just 10 Watts of higher luminous efficacy light source than an incandescent light bulb), escaping from the ISS, sounds more realistic. The only thing then is that the ISS seems to have the same brightness consistently over the last few years when I have seen it in the Earth's shadow. So, that's why I was wondering whether there is a (small) light source on the outside of the ISS that is always switched on. Count Iblis (talk) 15:12, 28 April 2011 (UTC)

You may simply be seeing cabin light escaping through the laboratory science window, a 510mm diameter circular glass window on the ISS' Destiny module. Subsequent to STS-131, the WORF is installed at that location, and when it is in use it can be configured to entirely block cabin light entering the WORF (and thus escaping to be seen by you). If that's the case, if you can find a mission schedule that shows when the WORF is and isn't swung over the window, if that correlates with changes in the apparent brightness of the unilluminated ISS, then the window is implicated. But you'd probably need a better calibrated system than binoculars and human eyes, and quite a lot of observations, to be sure. 87.115.52.162 (talk) 15:40, 28 April 2011 (UTC)

...although they probably keep the external shutter on that window closed most of the time, to avoid it getting scuffed up unnecessarily (by micrometeorites). 87.115.52.162 (talk) 15:47, 28 April 2011 (UTC)

Do fluorescent lights have a preferred frequency when they flicker?

Resolved

As the title says, I'm wondering about the flicker in fluorescent lights. Not a flicker as they power up or down, but a sustained flicker that indicates something is not functioning properly. I observed this today, and while the pulses were not of even intensity (very bright pulses ~1/sec), I began to suspect the underlying frequency (almost too fast to notice) may be related to the 60 Hz of AC power. Is there any merit to this idea? Does the frequency of AC current have any effect on the frequency of flicker in the light? Thanks, SemanticMantis (talk) 21:47, 27 April 2011 (UTC)

See Fluorescent_light#Flicker_problems. Wnt (talk) 21:57, 27 April 2011 (UTC)

Oops, I should have checked there more thoroughly. Thanks! SemanticMantis (talk) 23:29, 27 April 2011 (UTC)

April 28

dna

Does DNA have physical potential energy in addition to chemical as it is coiled like a spring, similar to a rubber band that is twisted to form coils on coils? Is there tension within the structure of the DNA? —Preceding unsigned comment added by 98.221.254.154 (talk) 00:15, 28 April 2011 (UTC)

I don't think there is a clear distinction between "physical" and "chemical" on the molecular scale, at that scale isn't it all Electromagnetism?. Vespine (talk) 00:22, 28 April 2011 (UTC)

I'm pretty sure DNA does have potential energy associated with its springiness, twistiness, Writhe etc. See e.g. the first few papers here [18]. They discuss how stress, strain, torsion, and topology can influence gene expression. As Vespine alludes above, these forces are the result of chemical/electromagnetic interactions, but they can produce effects similar to what you see at the macroscopic scale. SemanticMantis (talk) 00:39, 28 April 2011 (UTC)

Generally this is termed as DNA supercoiling. But the energy involved is managed very actively - histones wrap the DNA around themselves, topoisomerases release tension, helicases unwrap the DNA so DNA polymerases can copy it, etc. Also see PCNA, a neat little object. There are bits of data (such as the physical binding of DNA polymerases on the leading strand and lagging strand) that make it pretty clear that the DNA in the cell really is handled more like the tape going through a tape recorder than as some immobile passive object as is sometimes implied by drawings you might see. Wnt (talk) 00:57, 28 April 2011 (UTC)

So is part of the DNAs mass this tensile energy? —Preceding unsigned comment added by 98.221.254.154 (talk) 01:55, 28 April 2011 (UTC)

Wow. Must be, but I don't even know how you formalize this. A strained supercoiled DNA must have higher-energy lowest-energy states for torsional vibrations of some sort, I suppose. You'd never be able to measure the difference in mass, I don't think - it would be something on the order of terahertz, I think. I hope there's a hard core biophysicist hero to chime in here. =) Wnt (talk) 02:11, 28 April 2011 (UTC)

Or just a softcore biophysicist that knows more than you. —Preceding unsigned comment added by 165.212.189.187 (talk) 14:56, 28 April 2011 (UTC) You might not be able to measure one strand but extrapolate that to a whole human body. —Preceding unsigned comment added by 98.221.254.154 (talk) 02:30, 28 April 2011 (UTC)

steel I-beam (H beam / double T beam) color?

In classic American cartoons I-beams are always reddish orange. It occurred to me recently that this is not the default color for steel. I decided I-beams were either previously this color for some reason unknown to me, or the cartoon illustrators used that color instead of black/dull gray because it looked better on the screen. Does anyone know the real reasons? The Masked Booby (talk) 01:26, 28 April 2011 (UTC)

Oxidation98.221.254.154 (talk) 01:52, 28 April 2011 (UTC)

Red lead paint for protection against oxidation.190.148.135.154 (talk) 02:08, 28 April 2011 (UTC)

Iron(III)oxide based primer paint. It's definitely not lead based paint unless the beams are older than your grandfather! Roger (talk) 14:36, 28 April 2011 (UTC)

Is dishwashing liquid safe on plastic water bottles?

Specifically, mine are from Nalgene Outdoors, #2's, and I'd consider buying #4's. Does dishwashing liquid cause leaching from those? Thanks. 66.108.223.179 (talk) 05:19, 28 April 2011 (UTC)

I don't see why they shouldn't cope with regular detergent, but read the instructions that came with the bottle and our article on Nalgene. Make sure you wash them out after your trip and that they're thoroughly dried before replacing the cap.--Shantavira|^{feed me} 15:10, 28 April 2011 (UTC)

Yeah. I've only bought their LDPE bottles so far. Their shipping and constant availability of coupon codes are very affordable. 66.108.223.179 (talk) 15:42, 28 April 2011 (UTC)

Hydrogen Sulfide

It is found in our bodies. Is it released? If so, how?

Is it found in air? The article says that in concentrations of more than 100 parts per million will produce a foul smell. Does that mean that it may or is found in air, but because it is so dilute, we cannot smell it?Curb Chain (talk) 05:35, 28 April 2011 (UTC)

Micro-organisms produce it in the guts under anaerobic conditions. Flatulence smells sometimes like H₂S. doi:10.1016/j.jchromb.2009.05.026; [19] might be a good read. --Stone (talk) 07:23, 28 April 2011 (UTC)

The human nose is very sensitive to the presence of thiols, which is why ethanethiol is added to natural gas to give the otherwise odorless gas it's characteristic smell - so you can detect even small leaks. The article hydrogen sulfide says that 0.00047 ppm in air is the point where 50% of people can detect the odor (Hydrogen Sulfide#Toxicity). At 100 ppm eye damage can occur, and the olfactory nerve is paralyzed. (So, actually, at concentrations above 100 ppm, you *no longer* will smell anything.) When you're talking about "found in our bodies" you might be talking about the statement "The human body produces small amounts of H2S and uses it as a signaling molecule", rather than just gut bacterial production. The section Hydrogen Sulfide#Function in the body notes that "The gas is produced from cysteine by the enzymes cystathionine beta-synthase and cystathionine gamma-lyase." I can't find the figures at the moment, but the concentrations which are active in signaling are very low; lower than the nasal detection limit, if I recall correctly. -- 174.31.219.218 (talk) 16:11, 28 April 2011 (UTC)

What are the most dangerous jobs with positions available?

If anyone or myself decides that there's no more hope for their lives and that it's no longer worth living, perhaps it should end only by serving others. The military would detect suicidal tendencies long before the soldier hits the battlefield, so what civilian occupations could one hope to die on the job from trying to do exactly what the job entails? --129.130.99.8 (talk) 10:59, 28 April 2011 (UTC)

Found an article that lists fishing as having the highest fatality rate: http://www.careerbuilder.com/Article/CB-777-Career-Growth-Change-Worlds-Most-Dangerous-Jobs/ - Also mentions, amongst others, roofing and logging. Darigan (talk) 11:07, 28 April 2011 (UTC)

"Farming is one of the most dangerous occupations in the United States. More than 700 lives were lost in farm-related activities last year. Another 150,000 agricultural workers suffered disabling injuries from work- related accidents," per this article. --Halcatalyst (talk) 13:24, 28 April 2011 (UTC)

President of the US seems pretty dangerous. 8 out of 44 US presidents have died in office (about 18,000 deaths per 100,000), and any US citizen over the age of 35 can try for that job in 1.5 years (though it is not an easy job to get by any metric). A job with a roughly 100% fatality rate is Pope, but it is hard to predict in advance when that job will have an opening. Googlemeister (talk) 13:40, 28 April 2011 (UTC)

Dying while holding a job is not the same as dying because of a job. An accountant can die of cancer, and it doesn't mean that accountancy is what killed him. The cancer did. Contrawise, when a lumberjack dies because a tree lands on his head while working, it makes much more sense to say that he died of lumberjacking. As far as presidency goes, there have only been 4 assassinated presidents, rather than Presidents who died from health effects unrelated to being President. That's still a mortality rate of 9%, which is pretty high for any profession, however given that there have only been 44 presidents, that number has a fairly high margin of error. --Jayron32 14:06, 28 April 2011 (UTC)

Point taken. In any case, it is a very bad idea to take a dangerous job in the hopes that it will kill you because you would most likely putting others at risk. If you are a fisherman and go overboard, then someone might go into the water after you in an effort to rescue you and die because of it. As an additional question though, what if the stress of the job caused the accountant to have high blood pressure which was a contributing factor to a fatal heart attack? Would he count in the metric then? Googlemeister (talk) 14:40, 28 April 2011 (UTC)

An epidemiologist would call that the morbidity rate, not the mortality rate, to help keep the statistics straight. Nimur (talk) 17:09, 28 April 2011 (UTC)

Every fisherman knows not to go in after a man overboard, unless they want to die too! —Preceding unsigned comment added by 165.212.189.187 (talk) 14:54, 28 April 2011 (UTC)

If you are really serious about the " by serving others " part, there are numerous humanitarian aid organisations crying out for dedicated volunteers around the world. The Afrcan states. Sth. America, asia and many of those locations are quite dangerous. You might find something worthy of your last days, or heaven forbid, something worth living for.190.56.107.254 (talk) 18:08, 28 April 2011 (UTC)

Really? I thought for example the Peace Corps only takes a small fraction of applicants. Look up the details, and the "way you can help" always boils down to money. Capital is rare and precious, but humans are an unwanted waste product in any country. Wnt (talk) 19:12, 28 April 2011 (UTC)

The British charity Voluntary Service Overseas is only looking for "qualified professionals with at least two years’ post-qualification experience." Alansplodge (talk) 19:33, 28 April 2011 (UTC)

Astronaut or cosmonaut. I haven't done the numbers, but the fatalities rate - including the experimental phase - must be quite high. There might be experimental positions in teh future that benefit from someone willing to die. It is quite physically demanding, though, and as we know you can't just walk in. Depends what you mean by "positions available". Grandiose (me, talk, contribs) 18:19, 28 April 2011 (UTC)

Related is the one-way trip to Mars which, proponents say, is not a suicide mission but a colonization; there have been several hundred volunteers so far. Comet Tuttle (talk) 20:25, 28 April 2011 (UTC)

Or maybe you could do a tour of the blood donation centers (assuming your blood is usable).190.56.107.254 (talk) 20:37, 28 April 2011 (UTC)

Brain to Body Mass Ratio

Wikipedia currently contains an article on this subject that lists a small number of species. Where can I find, or can you provide, a more complete list, from the smallest animal for which data exists to the largest?Markfriedman28 (talk) 18:48, 28 April 2011 (UTC)

This chart gives a more complete picture of the data, at least for vertebrates. I've seen more extensive tables in books, but not on the web. Note that because the brain increases in size at a lower rate than the body as a whole, the brain-to-body-size ratio is widely considered not to be very meaningful. The vertebrate with the largest value is the hummingbird; the one with the smallest value is the blue whale. Most scientists consider a parameter called the encephalization quotient to be the most meaningful measure of the relation between brain and body size. Looie496 (talk) 21:42, 28 April 2011 (UTC)

Unidentified Flower (or maybe Fungi?)

Hi folks. I've been going through my old photos trying to find images suitable for WP articles. I came across the below photo, but was not able to identify the plant. This bloom appeared in September in the Robson Valley of British Columbia. It was growing in the shade of a black Spruce. Would appreciate any help in trying to identify this little guy. The Interior (Talk) 21:06, 28 April 2011 (UTC)

What am I?

Wow, cool specimen! I can't help much, but I'm pretty sure I see pistils and stamens in the flower, which rules out fungus. The only thing I can think of vaguely similar is Monotropa_uniflora; maybe that will help get us started. SemanticMantis (talk) 22:59, 28 April 2011 (UTC)

Drug that removes the ability to resist

A while ago I read about a drug that "removes one's ability to resist". Someone affected by the drug will obey most commands. It's powder form, begins with C and is common in South America. I can't remember what it's called, does anybody know?--92.251.167.28 (talk) 21:47, 28 April 2011 (UTC)

Scopolamine? 76.27.175.80 (talk) 23:17, 28 April 2011 (UTC)