Wikipedia:Reference desk/Archives/Science/2012 September 25

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September 25

Can DNA be used for data storage ?

More information about using DNA as an data storage for electronics such as PC. Purine and Pyrimidine are used as 0 and 1. — Preceding unsigned comment added by 24.63.135.59 (talk) 00:30, 25 September 2012 (UTC)

I added a title. StuRat (talk) 00:44, 25 September 2012 (UTC)

It doesn't seem like a very good choice to me, as writing to and reading from DNA chains isn't very fast. It does store a lot of data in a small space, but there may be a way to store data as individual atoms embedded on the surface of crystals, which would allow for even denser data storage. StuRat (talk) 00:47, 25 September 2012 (UTC)

How would you read the crystal without breaking it apart? Seems like a form of write-only memory to me... Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:53, 25 September 2012 (UTC)

You wouldn't need to break it apart, just bounce some photons off the crystal, and you can tell what atoms are there based on the spectrum reflected back. It would be ROM, which I think is what this Q is about. Using DNA for active memory seems like an even worse idea. StuRat (talk) 01:00, 25 September 2012 (UTC)

As of last month, thanks to scientists at Harvard Medical School in Boston, the answer is YES. I'm guessing you didn't see this story last month? Vespine (talk) 01:24, 25 September 2012 (UTC)

Interesting. That's sort of a hybrid of the two ideas, by embedding DNA fragments on small glass chips. Unfortunately, they didn't say how fast it is. StuRat (talk) 02:10, 25 September 2012 (UTC)

I heard about it on a podcast and they said it's no where near fast enough to use as computer memory at this stage, it would only be useful as archival storage that could be kept for years or decades at a time. Vespine (talk) 03:54, 25 September 2012 (UTC)

By an amazing coincidence, that's how we use it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:41, 26 September 2012 (UTC)

endermologie

Shouldn't there be an article about endermologie? Endermologie is very different than liposuction. There's no "digging" involved. I've seen endermologie videos on YouTube. One featured Denise Austin. Another featured Brian Joubert. I have no medical expertise, what-so-ever. But somebody should do an article on endermologie. Who agrees?142.255.103.121 (talk) 08:23, 25 September 2012 (UTC)

doi:10.1007/s002669900085 might help to answer this question.--Stone (talk) 08:55, 25 September 2012 (UTC)

Crystalline ceramic vs. salt

How do I distinguish? Which one is chromium hydride? Plasmic Physics (talk) 11:27, 25 September 2012 (UTC)

Hey for the solid the answer is neither. Chromium hydride is crystalline. It is a metallic hydride conducting electricity and looking somewhat like a metal. The H to Cr ratio is not very fixed showing that there is not a + and - charge that needs to be balanced, so you would not call it a salt. Also it is not a ceramic formed by heating and cooling, and in fact it is destroyed by heat due to loss of hydrogen. Graeme Bartlett (talk) 12:35, 25 September 2012 (UTC)

What is it then, an alloy? I'm looking for a material science term. Plasmic Physics (talk) 12:57, 25 September 2012 (UTC)

If there's enough hydrogen in it to affect the material properties, you could call it a hydrogen-embrittled metal. It's an example of a transition metal hydride, though it's not mentioned explicitly in that article.--Wikimedes (talk) 08:43, 26 September 2012 (UTC)

That sounds very much like an alloy. Plasmic Physics (talk) 09:52, 26 September 2012 (UTC)

If I compare it with carbon steel. Plasmic Physics (talk) 10:20, 26 September 2012 (UTC)

(Carbon-embrittled iron). Plasmic Physics (talk) 13:51, 26 September 2012 (UTC)

According to Inorganic Chemistry by Wiberg, Holleman, and Viberg, p.259, the Cr-H bonds are metallic, so that would make it an alloy. (LiH, on the other hand, is called a saline hydride (i.e. salt) by Cotton and Wilkinson in Advanced Inorganic Chemistry p.206.)--Wikimedes (talk) 07:31, 27 September 2012 (UTC)

Health effects of Tobacco

In the forementioned article, explicitly defined were several chemical reactions producing compounds both carcino- and mutagenic in nature discovered by medical research. Some of those reactions appear to be considered inconsequential or deliberately omitted for the general purpose of the theme of the essay. This appears to be the gospel according to the temple of the A.M.A. Several tobacco companies (Boo, Hiss) have been raked over the coals for the modifications in the additive qualities of cigarettes and was deemed adulteration. What I do not see within the article is the effects upon the chemical reactions when an oxidizer is made to be introduced into the manufacture process (an Adulteration). In the state of Oklahoma, under state statute euphamistically defined as Fire Safety Code, Chapter 40, though I am unaware as to what extent such legislation has expanded throughout the Union at this time, every cigarette sold within this state is required to be so treated by law. Under Chapter 40, the Oklahoma Fire Marshal is required to receive and accept performance data as to cigarette combustion and certify said results prior to affording tax stamps. One such requirement, I am given to understand, is self snuffing or extinguishment obtained through an oxididzer to alter combustion characteristics. Specifically, an oxidizing compound, when ignited, produces a controlled thermal range so that the original composite compounds burn at differing rates designed to produce excess residual tars, in concentration. Thereby, having accumulated sufficient residue, produces extinguishment. In the text which I have examined, carefully withheld is what exactly is the oxidizing chemical or compound used in the adulteration? Does the administration of the chemical or compound alter the composition with the introduction of the energy source (combustion) to produce reactions which are not disclosed in the article? Can those reactions create a greater toxic effect than the orginal Tobacco or in greater concentration? In a nation known for having performed unconsented human experimentation, both federal and state entities have negated the individuals' right of consent. Having been made a scapegoat, who is next, besides the overweight? — Preceding unsigned comment added by 98.160.104.90 (talk) 17:06, 25 September 2012 (UTC)

Wouldn't adding an oxidizer just make the fire burn hotter and faster, the exact opposite of any proposed self-extinguishing capability? Rmhermen (talk) 17:13, 25 September 2012 (UTC)

You may be interested in our article Fire safe cigarette. I don't know if it fully addresses your question, but it does mention possible health impacts. It does not seem from a casual reading of the article that these cigarettes work the way you describe. I agree with Rmhermen that it is not likely that they make fire-safe cigarettes by adding an oxidizer. Rather, it looks like these cigarettes are designed to reduce oxygen availability to the burning material.--Srleffler (talk) 17:40, 25 September 2012 (UTC)

According to Phillip Morris, they don't use any materials in their fire-standards compliant cigarettes that were not used in the earlier non-compliant ones.[1]--Srleffler (talk) 17:45, 25 September 2012 (UTC)

• Personally, I can't help but think that the tobacco companies, despite their many lethal sins, were treated wrongly in FDA v. Brown & Williamson Tobacco Corp. The idea of Y1 (tobacco) was to provide twice the nicotine in the same amount of tobacco with the same amount of tar. The FDA portrayed this as "manipulating tobacco to be more addictive". But I don't see why this can't equally well be seen as being 50% of the way toward switching the addicts over to an "electronic cigarette". It would seem like they could get the same fix with half the cancer risk (though nicotine still kills by heart disease). It is ironic that after so many decades of lying and misleading and killing people, when one tobacco company tries on a lark to do a good deed, that is what gets them all punished. Wnt (talk) 23:53, 25 September 2012 (UTC)
  
  • If you want to reduce the cancer risk, it would be better to require the tobacco companies to reduce the level of nicotine in cigarettes, phasing it out over the course of a year or two from current levels to zero. Anyone who wants to continue smoking would be free to do so, but no one would be addicted.--Srleffler (talk) 16:44, 26 September 2012 (UTC)

Prohibition never works. Near beer never really caught on. If your scheme were implemented, people would hoard the powerful cigarettes, sell them at an increasing premium as the others became weaker, and eventually transition to a full black market as with other drugs. While cigarettes are obviously not a healthy solution, we have yet to experience the horrors of people warring over black market nicotine used by intravenous injection. Wnt (talk) 15:34, 27 September 2012 (UTC)

baking soda would have an extinguishing effect by producing CO₂ when heated. Sometimes used in home-made smoke bombs to slow combustion, or in slow fuses. But the problem is more the oxidizer added to the paper to keep it burning. Hand rolled cigarettes using thin untreated paper go out unless you take a puff once or twice a minute. Ssscienccce (talk) 08:18, 26 September 2012 (UTC)

Leaf growth and development

The tree in question.

From the article linked by Jayron32 -- apparently these is considerable variation in leaf morphology.

There's a tree outside my house in New Jersey and the leaves are lobed. But I noticed what appeared to be full grown leaves on the tree that are not lobed, suggesting that the leaves are not formed already lobed but rather become lobed after reaching a certain size. But then I noticed very small leaves that are already lobed -- they appear as miniature forms of the large lobed leaves. So do lobes form before, after, or both and it depends on which tree we're talking about? DRosenbach ^{(Talk | Contribs)} 17:30, 25 September 2012 (UTC)

What kind of tree is it? --Jayron32 17:44, 25 September 2012 (UTC)

I can't tell. DRosenbach ^{(Talk | Contribs)} 18:00, 25 September 2012 (UTC)

Could you take some pictures of the tree and of its leaves so maybe someone here could help? --Jayron32 18:15, 25 September 2012 (UTC)

There are many different types of variations in leaves over time and at different parts of a plant. Juvenile leaves are often different from mature leaves. In NJ, the young leaves of the Sassafras will have a single lobe, while leaves grown as the plant ages will look like mittens or have three or more lobes. The lowest leaves on holly trees have the most spines, while those at the top of a tree may even lack them. Cannabis leaves first develop with single leaflets, then leaves with three, five, seven, and more leaflets. We need to have a picture for a better explanation. μηδείς (talk) 19:14, 25 September 2012 (UTC)

To be fair, a cannabis "tree" would have likely caught the attention of someone of authority. --Jayron32 19:19, 25 September 2012 (UTC)

The green bark on young growth of a sassafras tree has a distinctive appearance and quite pleasant and allegedly carcinogenic flavor, so you should be able to tell us if that is the one you are interested in. Wnt (talk) 23:56, 25 September 2012 (UTC)

So, are we waiting for the OP to come back and say, yes, the bark tastes pleasantly carcinogenic? Hehehe. μηδείς (talk) 02:28, 26 September 2012 (UTC)

I'm not above nibbling on a bit of it myself in the woods - my feeling is that the allegation is probably overblown based on fear of what would happen if it were mass-produced as an artificial sweetener, or even due to its usefulness in producing MDMA. I see sassafras oil actually goes over this pretty well. Wnt (talk) 16:39, 26 September 2012 (UTC)

Another possibility is that you have two or more trees grown together, and you are looking at leaves from different species. StuRat (talk) 20:34, 25 September 2012 (UTC)

Besides the sassafras, another common tree (weed, really, in my part of the world) that has both lobed and unlobed leaves is the paper mulberry. I agree with Jayron and Medeis that we'd probably need to see a picture to identify your tree; but as far as I know, individual leaves don't "become" lobed—they're either lobed or unlobed from the beginning. Deor (talk) 00:32, 26 September 2012 (UTC)

Yes, we've got them all over and they leaves are a bit more varied in form than you can tell from the pictures in the article. μηδείς (talk) 02:30, 26 September 2012 (UTC)

I would hope it was clear I was giving examples of plants with different leaf growth forms, not suggesting those three were the OP's most likely candidates. I guess it wasn't. μηδείς (talk) 01:07, 26 September 2012 (UTC)

OP Here -- sorry about the delay but I didn't realize this would generate so much conjecture so soon and yesterday was YK and I couldn't get on. I've added a photo for identification and included my fingers in two shots to give you a sense of dimension. As you can see, there are small leaves with lobes and large ones without lobes, although most of the large ones are similar to the small one in that they have lobes. DRosenbach ^{(Talk | Contribs)} 14:52, 27 September 2012 (UTC)

• Looking at your pics, I'm gonna venture it is a White Mulberry. I used the tree identification guide at arborday.org which is very useful for these purposes. See Morus alba for that specific species. --Jayron32 15:03, 27 September 2012 (UTC)

Interesting -- after reading the article, it seems that there's some variation in the leaves, and I now suppose that this variation occurs not only between trees but also among the leaves of a single tree. Thanx! DRosenbach ^{(Talk | Contribs)} 18:29, 27 September 2012 (UTC)

Unidentified spiders from Brazil

• 
• 

I am unsure concerning the identification of these two spiders from Mato Grosso, Brazil.
The left one might be Lasiodora klugi or another Lasiodora species.
The one on the right sitting on the wall was approx. 8 cm big. It belongs to the Sparassidae family. It might be Polybetes sp., but this is only a guess. --Leyo 21:22, 25 September 2012 (UTC)

By what factor can a nose get desensitied to a smell?

Even if it's something that's not a physical irritant such as chlorine shouldn't there be a limit to how much you can get used to it? Can you "get used to it" without conscious perception if it increases slowly enough? How long does it take to go back to the "maximum gain setting"? A genie once took a man into his lamp. He held his nose and said "How could you could live with this smell?" The genie said "Oh, you don't even notice it after a few hundred years." 96.246.70.87 (talk) 21:23, 25 September 2012 (UTC)

I once drove through Colorado, and reserved rooms ahead of time. I chose a hotel in Sterling, Colorado, because, for some reason, their rates were half all the other places. When I got there I discovered the reason, a huge cattle feed lot made the entire town smell like manure. I asked if it always smells like that, and they said "Smells like what ?". They weren't joking, apparently. StuRat (talk) 21:51, 25 September 2012 (UTC)

See sensory adaptation and olfactory fatigue. I can also tell you that having nasal polyps removed may result in a significant clinical loss of the sense of smell. μηδείς (talk) 22:32, 25 September 2012 (UTC)

It's an essential property of the olfactory system. If the olfactory system didn't adapt, you would never smell anything except the inside of your own nose. Looie496 (talk) 02:19, 26 September 2012 (UTC)

On occasion one does, with certain infections, smell one's throat or sinuses. μηδείς (talk) 02:25, 26 September 2012 (UTC)

...usually right before hacking up something green. StuRat (talk) 04:56, 26 September 2012 (UTC)

Charming. Don't you know it's rude to talk about that sorta stuff while people are eating their dinner? -- ♬ Jack of Oz ♬ ^{[your turn]} 07:48, 26 September 2012 (UTC)

Well thanks right back at you, now that I know I have to imagine you eating as you type your responses here. μηδείς (talk) 16:31, 26 September 2012 (UTC)

I drink lustily to your enjoyment of such imaginings. In fact, I think I'll have two extra turkeys in honour of this wonderful occasion. In some parts I'm known as La Plus Grande Bouffe, not without good reason. Nine years of Wikipedia and other sundry activities just have to be fitted in between gorgefuls as best I can. What a try-hard that Mr Creosote was. -- Jack of Oz (Talk) 09:48, 27 September 2012 (UTC)

Children and sugar

Most kids get all hyper after eating lots of sugar, while most adults do not. Why the difference ? StuRat (talk) 23:20, 25 September 2012 (UTC)

The idea that sucrose is a stimulant is a common myth, but it's still a myth. It provides food energy rather efficiently, but in and of itself does not cause hyperactivity or result in any other stimulant-like effects. See Sugar#Health effects. Evanh2008 ^{(talk|contribs)} 23:28, 25 September 2012 (UTC)

I think it is still unclear what the role of sugar is - see [2]. Oddly, the notion seems to be that sugar causes hyperactivity by causing hypoglycemia, leading to an adrenaline response when the food is too little to match the amount of insulin solicited by it. Now, two things I don't see mentioned there, which I'll just put out for discussion (not an answer): first, for diabetics, there is largely a lack of distinction between sugar and other carbohydrates, and so I have to wonder whether studies could show sugar to be "harmless" by comparison to other carbs. And second, given how many adults in modern times verge into prediabetes if not full blown type II diabetes - it seems possible that as the pancreas' response weakens, the adrenaline response no longer occurs, and so by that model the "hyper" reaction should end. Wnt (talk) 23:43, 25 September 2012 (UTC)

I only heard about it through American tv-series (Simpsons most likely). As far as I know, at least in Flanders (no pun intended) the concept was unknown. Ssscienccce (talk) 07:28, 26 September 2012 (UTC)

Have to agree with Ssscienccce that I don't think this is universal. While the idea apparently has some currency in NZ [3] [4], the more common claim (which may not be totally a myth) is that artificial colourings cause hyperactivity. As for sugar, as this says [5] the link is controversial at best, Hyperactivity notes the majority of studies show no linkage between sugar and hyperactivity. Nil Einne (talk) 08:01, 26 September 2012 (UTC)

By "hyper", I don't mean that it causes permanent hyperactivity, I just mean a temporary increase in activity level. StuRat (talk) 08:13, 26 September 2012 (UTC)

Maybe the excitement of getting candy or the transition from one activity to another may have an effect? Children could be more active the first few minutes of any activity. Comparing their behaviour when they've been playing (or sitting in class) for an hour with the behaviour when they go back to playing (or class) may show a difference that isn't caused by sugar alone. Ssscienccce (talk) 08:40, 26 September 2012 (UTC)

Who's talking about permanent hyperactivity? Nil Einne (talk) 10:24, 26 September 2012 (UTC)

When you used the term "hyperactivity", that has that connotation, to me, of someone who is often hyper. The shortened form, "hyper", to me, means just one instance. StuRat (talk) 21:05, 26 September 2012 (UTC)

There is a reason I provided links.... Nil Einne (talk) 08:22, 27 September 2012 (UTC)

The studies I've heard about (I don't know what they are, so I couldn't provide sources) claim that children behaved differently because the responsible adults subconsciously treated them differently after they ate sugary foods (because of their belief that the sugar caused hyperactivity). The reason this doesn't happen to adults is because they aren't being given sugar by an authority figure. 146.87.16.182 (talk) 09:03, 26 September 2012 (UTC)

By googling "sugar rush" I found this site, which contains an experiment aimed at demonstrating a sugar rush. Make of it what you will. --TammyMoet (talk) 09:21, 26 September 2012 (UTC)

Eiyeiyei, that page is an example of how not to think about biology. Red food coloring is not blood, food is not digested in the blood, so... the rate at which food dissolves in water, without digestive enzymes present, has very little to do with the rate that nutrients eventually enter the bloodstream. And so in practice the difference between sugar and carbohydrate on blood glucose levels is not very much. Wnt (talk) 14:08, 26 September 2012 (UTC)

This page says; " In 1995 the Journal of the American Medical Association published a review of 23 comparatively rigorous studies conducted between 1982 and 1994... The results? No discernible relationship between sugar ingested and how the kids acted. It didn't matter how old they were, how much sugar they got, what their diets were like otherwise — nothing." Perhaps someone could find the original article - must dash now! Alansplodge (talk) 09:58, 26 September 2012 (UTC)

Here's the study: [6]. This is certainly persuasive, yet apparently it was not enough to close the issue. I should note that I am impressed that the control for all studies chosen was an artificial sweetener, not merely another food source. I haven't read the full study, but I should just mention that meta-analysis tends to be viewed with some skepticism, as it is not typically done unless there are some studies already published which have drawn the opposite conclusion. Nonetheless, their conclusions make sense - first, that the effects of sugar could be due more often to the expectation of parents, whose ways of controlling the kids are apparently not perfect. And second, their caveat that there could be a fraction of children who do become hyperactive in response to sugar, just not the majority. We know that the metabolic response to sugar is not perfectly regulated - some people become hypoglycemic, some become hyperglycemic, for example. It's not just that biology is imperfect - there's no perfect answer in the first place. Under varying circumstances over the course of evolution it may make sense to be sedate or hyperactive after eating, and I think the species will be equipped with a range of genetic responses. Wnt (talk) 14:21, 26 September 2012 (UTC)

I know that diabetics are advised, along with taking insulin, to exercise to burn off high blood sugar. So, yes, if children's systems aren't able to bring the BS level under control internally, then exercising to burn it off would be one way to prevent organ damage. So, that trait might very well have evolved, although I don't see why it would be limited to children. StuRat (talk) 21:11, 26 September 2012 (UTC)

Strangely, in my 1960s childhood, nobody ever suggested that eating lots of sugar made you behave badly, even though sugar was widely available. Alansplodge (talk) 00:21, 27 September 2012 (UTC)

I can think of at least 3 reasons

• Children are smaller than adults, so one can of a sugary drink will affect them more.
• Most sugary drinks are also caffinated, and its the caffeine that is causing the effect. Children tend to have a lower tolerance to caffeine that adults, through less habituation.
• Adults have better self-control than children, so even if they are feeling equally hyper, adults will show it less.

Of course, these are sweeping generalisations, and could be wrong; I'm just putting them up for discussion. CS Miller (talk) 21:42, 27 September 2012 (UTC)

Nil Einne and Alansplodge have provided well-sourced answers. Speculating based on loose associations does not add to reliable sources cited by them. -- Scray (talk) 16:11, 29 September 2012 (UTC)