Wikipedia:Reference desk/Archives/Science/2011 April 24

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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)