Wikipedia:Reference desk/Archives/Science/2014 November 28

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November 28

Most viewed health topics on Wikipedia

I recently read in a news article that Wikipedia allows free access to its data on the most frequently searched topics. As I understand it, this information can also be broken down according to language (but not to geographical location).

If this is the case, I would like to know which health topics are most commonly viewed on Wikipedia in both English and Arabic. A list of up to about 2,000 topics in each language would be ideal, but otherwise I would settle for a shorter list!

Alternatively, if it’s not possible to stratify according to health topics specifically, I would also be interested in the same lists in a similar category (e.g. medicine, science, biology, etc). — Preceding unsigned comment added by 14.203.101.110 (talk) 00:39, 28 November 2014 (UTC)

The main portal for page stats is http://stats.grok.se/ Which will let you look up individual pages or download count files for all requests. There is a top list but it doesn't seem to have been updated in several months and shows some spurious requests (probably due to bots and other automated web processes). The most visited pages on a month to month basis are often typical issues that are being highlighted in the news (e.g. new movies, celebrities, wars, etc.) As far as medicine goes, I suspect that the Ebola related pages have rated very highly in recent months. As far as I know, there are no preexisting subcategorized lists of page views for medicine or any other topic. In principle one could be created though, either by hand, or by selecting a subset of pages that are already labeled with categories associated with medicine. That would presumably take someone with a bit of programming skill however. Dragons flight (talk) 01:24, 28 November 2014 (UTC)

See Category:Lists of popular pages by WikiProject.

—Wavelength (talk) 03:11, 28 November 2014 (UTC)

You may also want WP:5000; it only gives results per week, not long-term, but since most health topics generally don't get a ton of spikes from news coverage, you'll be able to make a decent guess on "most popular" by checking a few weeks' entries. If you have a bot or a way to scrape content, you can easily amalgamate statistics by months or years. Nyttend (talk) 03:58, 28 November 2014 (UTC)

Using Wavelength's link, you can see a list of the 1000 most popular WikiProject Medicine pages at Wikipedia:WikiProject Medicine/Popular pages. John M Baker (talk) 15:35, 28 November 2014 (UTC)

What's the thickness of a clothing to prevent mosquito bites?

I want to visit South America, and I want to protect myself from mosquito bites. How thick should a clothing be to prevent the piercing of a southern american mosquito? What is the minimum thickness? How deep can southern american mosquitoes pierce into the human skin? 173.33.183.141 (talk) 03:31, 28 November 2014 (UTC)

I don't think it's primarily a question of thickness, but more of the quality and density of the weave. I've never experienced mosquitos biting through a normal dress shirt, but I'd be less sure about a t-shirt, even if technically thicker. If you want to be sure, use something like DEET or Icaridin on the skin and Permethrin on clothing and mosquito nets. Famous brands here in Germany are NoBite and Autan, but international branding seems to vary a lot. --Stephan Schulz (talk) 03:48, 28 November 2014 (UTC)

Thanks. Do southern american mosquitos have longer piercing heads than the north american mosquitos? 173.33.183.141 (talk) 21:30, 29 November 2014 (UTC)

Sublimation and temperature change

Take a quantity of water and evaporate some of it, and the rest cools to an extent. Take a quantity of ice and sublimate some of it; will the rest become colder? Nyttend (talk) 19:25, 28 November 2014 (UTC)

Yes, the ice becomes colder. It is this same phenomena which is used to cool spacesuits. That is why NASA came to over-look the presence of water on the moon during the Apollo era. The H2O that the NASA scientists found in the moon samples, they concluded was just man-made contamination. However, the Soviets knew but the Americans never read their science papers.--Aspro (talk) 20:18, 28 November 2014 (UTC)

Function generator design

Function generators are usualy designed with the primary waveform generated being a triangle wave created by charging a capacitor with a constant current. At higher frequencies than about 3-5 MHz, however, the comparator used has to be very fast and the triangle wave distorted to operate the comparator as fast as possible. I was wondering if there were any function generator designs that used a square wave produced by a voltage controlled oscillator as the primary waveform. Triangles can then be produced by integrators and sine by shaping the triangle as usual. Are ther any problems with this approach and are there any manufacturers using this technique especially for fast (20MHz) generators?--86.157.138.192 (talk) 19:32, 28 November 2014 (UTC)

That might have been true 40 years ago, but any modern function generator will be purely digital, using a DAC to create the waveforms. Apart from the audiophile market (which is more art than engineering), there's very little analog equipment for use at low frequencies available these days. However, I'm sure it would be possible to design an analog function generator along those lines, it just wouldn't be a commercially viable proposition. Tevildo (talk) 21:13, 28 November 2014 (UTC)

20MHz triangle and sine from a DAC??--86.157.138.192 (talk) 21:22, 28 November 2014 (UTC)

120 MHz! It's amazing what they can do these days ("these days" starting in about 1995). Tevildo (talk) 21:42, 28 November 2014 (UTC)

Indeed! Our article is direct digital synthesis. And if you have unlimited budget, you can get direct digital synthesizers deep into microwave bands - arbitrary digital waveform synthesis at tens and hundreds of gigahertz! Such devices are used for satellite communication and microwave RADAR design and test.

But we don't even have to look into wacky aerospace and defense technologies to find such circuitry! Chances are high that you've got one of these K-band digital synthesizers - or one like it - built into your home computer!

Nimur (talk) 00:04, 29 November 2014 (UTC)

Universe - universe = 0?

If our universe was created from nothing, and we dont seem to have found much antimatter so far, is it possible that an anti universe was created at the same time as the matter universe? --86.157.138.192 (talk) 21:35, 28 November 2014 (UTC)

But if there was nothing ("0") befor, what created or caused the universe? The theory of an antiuniverse is scientificly as bad (not proven) as the famouse Bigbang theory. Some astrophysists still belive in the theory that this universe has simply always been here. --Kharon (talk) 01:55, 29 November 2014 (UTC)

Mathematically, that notion doesn't work. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:03, 29 November 2014 (UTC)

In fact, the idea that the universe "has always been there", strikes me as the cosmic equivalent of the "Turtles all the way down" story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:32, 29 November 2014 (UTC)

Well, as explained in the antimatter article, the idea is apparently not totally dead even that antimatter could exist in large amounts somewhere in our observable universe. It is also possible that the observable universe encompasses a large region that is entirely matter, but that there is a variation on a larger scale even than the entire universe we see, so that other regions may be mixed or entirely antimatter (which isn't far from the OP's suggestion really, except the two were once connected as a single region of space but now "you can't get there from here" due to cosmic inflation). But CP violation in baryogenesis is still the more likely looking answer, since there are observed deviations. Wnt (talk) 04:52, 29 November 2014 (UTC)

The concept of a zero-energy universe does not depend on equal amounts of matter and antimatter. -- ToE 16:51, 29 November 2014 (UTC)

Question About the Elimination of Energy

Since energy can be neither created nor destroyed therefore does Einstein’s energy equation equitable with any other forms of energy such as P.E, K.E, Work Done….....?162.157.249.151 (talk) 22:22, 28 November 2014 (UTC)eek

Yes. However, while Einestein's equation says that the total energy of a system remains constant, it does not say that it cannot be converted into other forms of energy. Potential energy is frequently converted into kinetic energy (dropping objects, burning fuel, electrical discharge, etc.) and vice versa. Is this what you are asking? --T H F S W (T · C · E) 23:27, 28 November 2014 (UTC)

By equating, I meant eliminate energy E from E=mc^2 and any other equation of energy of any form. Although physicists don’t agree but here is the example if units are interchangeable in dimensional analyses of the following?

1- Energy, E= mc^2 ----- Eq. (A)

2- E = mv^2 --------Eq. (B) as if “Joule is equal to the energy transferred (or work done) when applying a force of one newton through a distance of one meter (1 newton meter or N·m:)” - [ Wikipedia]. Since, joule = N.m = [(Kg.m)/sec^2].m = Kg.m^2/sec^2 therefore this means Energy; E = mv^2 as L/T is the unit of velocity. We get mv^2 = mc^2 after eliminating “E” from Eq. (A) and (B) and hence v=c unless unit of energy is defined differently in relativity and classical physics

Since you mentioned conversion therefore would the energy released from the burning of 1kg mass (nearly =1lit) of gasoline be = mc^2162.157.249.151 (talk) 04:39, 30 November 2014 (UTC)eek

The answer to your last sentence is "no", because only a very small portion of the mass of gasoline is converted to energy. The combustion products also have mass, which is almost identical to the original mass of the gasoline and oxygen. In nuclear reactions, a much larger portion of the mass is converted to energy, and the decay products have lower mass than the parent product, but even complete radioactive decay of a kilogram of plutonium, for example, will yield much less than 9*10^16J of energy.--Wikimedes (talk) 11:04, 30 November 2014 (UTC)

Ok thankx, I thought E would be different upon changing the mass in e=mc^2. 162.157.249.151 (talk) 16:05, 30 November 2014 (UTC)eek

E=mc^2 can be used to calculate the energy released when mass is converted to energy. In the case of burning gasoline, most of the mass is instead converted to another form of mass (water and carbon dioxide), so the energy released is more easily calculated directly from calorimetry. (A freshman or high school chemistry book might be more useful for understanding basic calorimetry of combustion than the Wikipedia article). E=mc^2 is used to calculate energy released in nuclear reactions, but the mass entered into the equation is not the starting mass, but the difference between the starting and ending mass. In a matter-antimatter reaction, all the mass can be converted to energy, and the use of E=mc^2 is more easily applied.--Wikimedes (talk) 01:58, 1 December 2014 (UTC)

NMR basic problem

I have a relatively basic NMR question, but I am having trouble figuring it out. The chemical formula is C5H10O. The chemical shifts are 1.3 (singlet, integration 2 cm), 1.9 (singlet, integration .3 cm), 5.0 (doublet, .2 cm), 5.2 (doublet, .2 cm), 6.0 (doublet of doublets, .2 cm). The problem also says the peak at 1.9 ppm is solvent and concentration dependent. Does this mean it is -OH? I know there is a C=O. The spin spin splitting is throwing me off. — Preceding unsigned comment added by Pinterc (talk • contribs) 22:34, 28 November 2014 (UTC)

Do you know if that's the molecular formula, or the empirical formula? That is, do you know if the molecular weight is ~86, or could the compound be something like C₁₀H₂₀O₂ or C₁₅H₃₀O₃? (Getting mass spectroscopy results greatly helps NMR determination.) You may want to also double-check your integrations. As written, they sum to 2.9, meaning that each proton should account for ~0.3 (assuming 10 protons) - which means you're getting something like a 6:1:1:1:1 ratio, and a fair amount of error on integration amounts. (Although if you're using an empirical formula, you might be running 30 protons, with possibly more like a 20:2:4:2:2 or 21:2:3:2:2 ratio.) But if the "2 cm" is a typo for "0.2 cm", then you're summing to 1.1, and getting more of a 2:2:2:2:2 ratio. All this, of course, is complicated by the solvent and concentration dependance of the 1.9ppm peak. You may want to figure out what about the peak is concentration/solvent dependent: is it just chemical shift, just integration, or both? You're pretty saturated, though, so that's going to limit you. Do work it out yourself, but I think the carbonyl requirement is going to take up your unsaturation allotment. The splitting pattern itself isn't too hard to accommodate. (You have to remember that if a proton is split, it's going to be splitting another proton in turn, so that constrains how the doublet of doublets and the two doublets are related to each other. Do you have the J values for the coupling constants? In this example it's probably going to be uninteresting, but matching the J values of the coupling constants can be used to figure out which proton is splitting which other proton.) The concern I might have about the split peaks is their shift - ca. 5 ppm and a general lack of unsaturation in the molecule implies some sort of relationship to the oxygen(s). You also have quite a small number of peaks in comparison to the number of protons (especially for larger multiples of an empirical formula) - that usually (but not always) implies a high degree of symmetry in your molecule. -- One suggestion I would make is to break the problem into parts: list a bunch of different molecular fragments which can account for different portions of the data at hand. Then see if you can come up with a way to merging those fragments together to account for all the data. -- 160.129.138.186 (talk) 00:03, 29 November 2014 (UTC)

There's already some confusing idea if C5H10O is the actual molecular formula: the proposed C=O is the oxygen atom, so there's no other oxygen left to be the OH oxygen. DMacks (talk) 05:10, 29 November 2014 (UTC)

Per NMR spectroscopy, "Coupling to additional spins will lead to further splittings of each component of the multiplet e.g. coupling to two different spin ½ nuclei with significantly different coupling constants will lead to a doublet of doublets." This alone implies a CH - CHR - CH structure. I don't see a good table at chemical shift; we should have something like [1]. I fooled around with this for a bit and couldn't think of any ideas; [2] is a useful link but I'm stumped. Someone ought to be able to recommend some searchable NMR database that might come through here. Wnt (talk) 01:47, 29 November 2014 (UTC)

Chemical shift is the general idea, not specifically 1H. For information specific to that, see Proton NMR. But the table there is confusing as hell...seems entirely focused on "what else is attached to the C with the H", making it hard to identify the aldehyde structure as such and except for that case omitting all other H that are not on sp³ C (no vinyl or aryl or OH or NH themselves, just the C_α to it). DMacks (talk) 05:18, 29 November 2014 (UTC)

• You've also got 5 peaks, which implies 5 unique carbons. What are the splitting constants? You can sometimes match neighboring bits by matching splitting constants... --Jayron32 13:32, 29 November 2014 (UTC)

Hmmm, I'd hoped someone would clarify the issues with the problem ... the last I looked at this my closest guess was CC1=CC(O)C=C1, which on the prediction site above gives the right doublet of doublets and two doublets and a peak at 1.9 from the methyl... the problem was, it has one doublet too high and the peak at 5.2 is a doublet of doublets and the 1.3 peak is absent, not to mention it's missing two hydrogens. Wnt (talk) 17:29, 1 December 2014 (UTC)

There can only be one degree of unsaturation, because C5H10 is only 2 hydrogens short of the saturated alkane (C5H12, or pentane). That means you can't have 2 double bonds. --Jayron32 19:09, 1 December 2014 (UTC)

Yes, but try to come up with a model that involves only singlets, doublets, and doublets of doublets... Wnt (talk) 03:05, 2 December 2014 (UTC)