Wikipedia:Reference desk/Archives/Science/2007 October 9

= October 9 =

Banned airlines
I was just looking at our list of air carriers banned in the EU. Is there an equivalent list for the US? I couldn't find one.--Shantavira|feed me 10:03, 9 October 2007 (UTC)


 * I can't find a US airline blacklist either; apparently there isn't one. FAA does have a country-level assessment, International Aviation Safety Assessment Program. Weregerbil 11:30, 9 October 2007 (UTC)

The winter plumage of large gulls...
My local black-backed gulls have now fully moulted into their winter plumage (basically, their heads and necks become streaked with diffuse greys and browns and look 'dirty' from a distance). I was watching them feed today and I found myself wondering if this plumage feature is related in any way to the solid black/brown 'hoods' that some species of gull (e.g. Black-headed Gull, Mediterranean Gull) display in the summer months. A genetic vestige of something from a common 'proto-gull' ancestor, altered by evolution over millions of years, perhaps? Some LBB/Herring Gulls have many more darker feathers on their heads than others - in certain birds, it almost looks as though they have the 'hood' anyway. Anyone know for sure/have any ideas? Cheers. --Kurt Shaped Box 10:10, 9 October 2007 (UTC)


 * Hi, Kurt. That's an interesting idea. I have no idea if there is a connection. However, it might be relevant that black-headed gull species lose much of their dark cap in their winter plumage, the opposite of white-headed gull species. Also, the related terns have the same pattern as black-headed gulls: black cap in summer that is greatly reduced in winter. What does that mean? I don't know. I'll have to look up some information on gull evolution. I'm not at home right now, so I don't have any of my bird books handy.--Eriastrum 15:40, 9 October 2007 (UTC)


 * So, did you manage to find out anything interesting? --Kurt Shaped Box 19:52, 13 October 2007 (UTC)

Oop! Sorry Kurt. I didn't find anything that seemed relevant. Tons of stuff on plumages, but nothing on whether the black cap is a derived or ancestral character. I'll dig some more.--Eriastrum 15:39, 14 October 2007 (UTC)


 * Okay man, no worries... :) --Kurt Shaped Box 07:41, 15 October 2007 (UTC)

Degradation of Ubiquitin
Though vast information is available about the role played by ubiquitin in the degradation of proteins, very little literature is available on the degradation of the ubiquitin molecule itself. Generally, after degradation of a protein, the ubiquitin molecules are recycled for another round of protein degradation. But, how is ubiquitin ultimately degraded?

Swellbeing24

link for ubiquitin mediated degradation of proteins: http://en.wikipedia.org/wiki/Ubiquitin —Preceding unsigned comment added by Swellbeing24 (talk • contribs) 12:48, 9 October 2007 (UTC)


 * Here is a starting point in the literature that you can download: Ubiquitin Depletion as a Key Mediator of Toxicity by Translational Inhibitors. My guess is that cells normally produce an excess of ubiquitin and when there is "excesss", more of it gets destroyed by proteasomes because less effort is put into removing ubiquitin from proteins that are degraded. If ubiquitin becomes depleted, then changes are made to the proteasomes that increase the efficiency of releasing ubiquitin which can then be re-used. See A ubiquitin stress response induces altered proteasome composition. --JWSchmidt 15:58, 9 October 2007 (UTC)

That was extremely helpful. The NCBI article provided just the hint I was looking for- 'The proteasome-associated deubiquitinating enzyme Ubp6, which spares ubiquitin from proteasomal degradation, is induced by ubiquitin deficiency'. Thanks! Swellbeing24

mass of phosphorus
What is the molecular mass of phosphorus? I don't want molar mass. --MKnight9989 13:16, 9 October 2007 (UTC)
 * There are several allotropes of phosphorus, but white phosphorus=P4 appears to be the only one that comes in molecules. 31P seems to be the only isotope found in nature, so unless your molecule comes from a nuclear reactor or something, it will have a relative molecular mass of (very very slightly less than) 124. Algebraist 13:37, 9 October 2007 (UTC)


 * And red phosphorus is P4 chains giving a molecular mass of 124 x N, ... the others are macromolecules87.102.18.10 14:41, 9 October 2007 (UTC)

Peroxide blocking
In the TUNEL assay, hydrogen peroxide is added for the purpose of "peroxide blocking". Why (or how do I find out why) is this blocking necessary? --137.120.90.152 13:41, 9 October 2007 (UTC)
 * TUNEL assay says, "dUTPs that are secondarily labeled"; in particular, the nucleotides used in the assay can be biotinylated and then once the biotinylated nucleotides are enzymatically incorporated into cells they can be detected with Streptavidin coupled to horseradish peroxidase (HRP). However, some cells/tissues contain endogenous peroxidase activity. So before adding the Streptavidin-HRP, it is often useful to "block" the endogenous peroxidase activity. See this article. --JWSchmidt 14:30, 9 October 2007 (UTC)

Comet ETA
When can we expect the next comet to pass by Earth? Halley isn't due until 2061, and the Great Daylight Comet won't be back until 4144877 AD. Beekone 16:50, 9 October 2007 (UTC)
 * What so you mean by 'pass by Earth'? If you mean be bright and impressive when seen with the naked eye, then Great Comet explains that it is hard to predict when they will occur, but they do so about once a decade, the most recent being Comet McNaught this year. If you're happy with comets visible with binoculars, then that happens all the time: c/2006 vz13 right now for example. Algebraist 17:15, 9 October 2007 (UTC)
 * No it isn't, that's out of date. Algebraist 17:18, 9 October 2007 (UTC)
 * That's exactly what I mean. Visible by binocular is cool too, but i prefer a reason to drive to the country and lie in a pasture.  Is there a solid date on that kind of action? Beekone 17:34, 9 October 2007 (UTC)
 * Quoting Algebraist above:
 * Great Comet explains that it is hard to predict when they will occur, but they do so about once a decade, the most recent being Comet McNaught this year.
 * &mdash; Lomn 17:47, 9 October 2007 (UTC)
 * So there's absolutely no way to predict when another comet will be coming? I get that it's "hard" but that should mean "speed bump" when it comes to science.  Should the aforementioned quote read "...it is impossible to predict..."?  Thanks for treating me like an idiot though, Lomn, that was pretty  cool.  Does anyone else know when another comet will be coming? Beekone 18:13, 9 October 2007 (UTC)
 * I'm sorry I offended you, but it's likewise "cool" to ignore the answer (and reference) you've been given just because it's not the one you wanted -- twice now. In case any doubt remains, no, there is no way to predict a Great Comet.  Orbital mechanics are fine for determining when a comet is observable in astronomical terms, but determining that a comet will be daylight-visible like McNaught is guesswork.  &mdash; Lomn 19:16, 9 October 2007 (UTC)
 * "Orbital mechanics are fine for determining when a comet is observable in astronomical terms" This is actually a great start, this is exactly the info I'm looking for! You can tell because I previously said "When can we expect the next comet to pass by Earth?"  So, using orbital mechanics, when can we expect another Great Comet to pass by Earth?  Beekone 19:33, 9 October 2007 (UTC)
 * (de-indent) We don't know. We can't know, because predicting a comet is not at all the same thing as predicting a Great Comet.  In the last 200 years, only two Great Comets (Comet Hale-Bopp and Comet Halley in 1910) were even known to exist more than 6 months prior to perihelion, and only Halley anticipated prior to that.  Many were discovered less than 3 months before perihelion, and even HB had less than two years' foreknowledge.  Additionally, the history of comets is rife with expected Great Comets that fizzled (for example, Comet Halley in 1986) as well as Great Comets that no one expected until they suddenly brightened.  Obviously, orbital mechanics are no good at predicting something when we don't know what its orbit is.  As for "when will the next comet pass by Earth?" (do you see the distinction?) -- comets are observed in astronomical contexts on a near-constant basis. &mdash; Lomn 20:13, 9 October 2007 (UTC)

Yes, flawless execution. Thank you for the explanation Beekone 20:23, 9 October 2007 (UTC)


 * This won't answer your question, but to give you an idea of the complexity of the problem, take a look at this site . For example, it says that so far in 2007, 77 comets alone were newly discovered! The author of the site includes his email address, so you could contact him and see if he can give you some kind of idea of when the next "wow" comet might be visible. He also includes a number of links you could explore to see if you can find anything.--Eriastrum 23:05, 9 October 2007 (UTC)

Influenza vs Common Cold
hi, can anyone explain to me the difference between influenza and the common cold? thanks a lot. —Preceding unsigned comment added by 193.195.187.186 (talk) 16:53, 9 October 2007 (UTC)
 * From influenza: 'Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus.' Try the two linked articles for more details. Come back here if you still have questions. Algebraist 17:10, 9 October 2007 (UTC)
 * As noted, they are caused by different viruses. And although the symptoms are similar, fever is rare in colds, common in flu, generalized aches and pains are rare in colds, common in flu, weakness is far more severe in flu, and the potential complications of influenza are more severe. Other differences: you can be vaccinated against the flu, but not against colds. - Nunh-huh 06:26, 10 October 2007 (UTC)

Difference between seagulls with white and dark heads
Is it just a coincidence that gulls with white heads are bigger and more predatory than the ones with dark heads? --84.69.19.94 23:27, 9 October 2007 (UTC) Remember to WP:AGF D: --⁪frotht
 * There are lots of species of Gull. If you look at the gallery at the bottom of the article, it looks like there are a number of species with black/grey heads.  I can't think of any reason why having a dark head would be related to size or aggressiveness, but then I know absolutely nothing about birds.  By the way, the Black-headed Gull - which is a particular species, and the most common one with a black head where I live - only has a black head in winter summer (oops, that was stupid), so maybe there is some kind of seasonal change in its behaviour? Bistromathic 20:28, 10 October 2007 (UTC)
 * In the northern hemisphere, there are 16 very closely-related species of 'large white-headed gull'. Have a look at the gull article for the species names - but the familiar Herring Gull (the archetypical 'seagull') is one of them. IIRC, they're that genetically close that most of them are capable of interbreeding and producing fertile hybrids. They're all very big, bulky, aggressive, cocky (around humans), somewhat (or outright, depending on the species) predatory birds. Most other gulls are smaller and daintier-looking in comparison to this lot - and it happens that some of those have the 'hoods' in summer. --Kurt Shaped Box 21:53, 10 October 2007 (UTC)
 * EDIT: There is one hooded species (that I know of), the Great Black-headed Gull, which in terms of size and behaviour could easily go to-to-toe with the Great Black-backed Gull. --Kurt Shaped Box 21:57, 10 October 2007 (UTC)

Hydrogen fuel
I've heard some people talk about Hydrogen based fuel (with no pollution and all that stuff). How would we get the hydrogen? I've read somewhere that extracting hydrogen from water takes more energy than what is released by the combustion of hydrogen. Is that true?

I've got some other questions:
 * How can neutrinos have antiparticles even though they have zero electric charge?
 * I know that bosons are force carriers but how can certain isotopes of elements be bosons? What force do they carry?

Thanks in advance. --wj32 talk 23:59, 9 October 2007 (UTC)


 * To begin with, you're referring to a fuel cell. The hydrogen could be extracted from water through electrolysis, or alternatively from hydrocarbons.  And yes, extracting from water would consume more energy than recombination of hydrogen and oxygen would release.  If it didn't, you'd have a perpetual motion device on your hands (although the inventor of the water fuel cell would like you to believe that this is possible).  Antineutrinos are opposite their respectiveneutrinos in terms of helicity, not charge.  As for bosons, there are elementary bosons and composite bosons (both explained in boson).  The composite bosons are not force carriers, but they posses physical properties unique to bosons, such as independence from Pauli's exclusion principle.  This leads to bosonic matter displaying some very wierd characteristics (superfluidity and supersolidity).  Someguy1221 00:12, 10 October 2007 (UTC)
 * That answers all of my questions! Thanks a lot. --wj32 talk 00:29, 10 October 2007 (UTC)
 * To continue the fuel cell bit, it's worth noting the theoretical appeal of fuel cells if it's a net energy loss. As it stands now, the electricity needed to "crack" water tends to come from "dirty" sources -- coal-fired power plants and the like.  Burning coal to make clean hydrogen isn't really an improvement over burning oil directly in a car engine.
 * Suppose, however, that you've got a clean power source: perhaps solar in the small scale now or cold fusion someday (or fission now, but I'd prefer to avoid the debate as to whether or not that constitutes "clean"). Once you've got a ready eco-friendly power source to crack water, it's not a problem to accept the energy inefficiencies that come with generating hydrogen for portable fuel cells. &mdash; Lomn 02:21, 10 October 2007 (UTC)


 * I think it's reasonably true to say that most renewable energy sources (hydro, wind, waves, solar, geothermal) produce electricity. So does nuclear and (eventually) fusion power.  So it would be sensible to build electric cars.  The problem is that battery technology isn't up to the job for lots of reasons - and when you run out of charge, you might need HOURS to recharge the darned things.


 * So one alternative is to use electricity to crack water to make hydrogen in some big factory someplace - then put the hydrogen into a tank in the car and use a fuel cell to turn the hydrogen back into water + electricity - you can store quite a lot of hydrogen in your car, and refuelling might also be quick and easy - just like a gas station. Now, to be sure, the process of converting electricity to hydrogen and hydrogen back into electricity again is wasteful (both processes are about 80% efficient) - so you'll waste maybe 36% of the energy in the process.  However, that's still a lot better than gasoline powered cars - and all that comes out of the tail-pipe is warm water.  So if this can be perfected, it's a net win.  It would be much nicer if we could come up with a better battery technology though.


 * SteveBaker 02:35, 10 October 2007 (UTC)


 * Did you even read battery-electric vehicle? Battery electric cars are far more efficient than Hydrogen Cars. The latest models are capable of incredible performance as well. 0-60mph in 4 seconds, top speeds of over 200 mph, and ranges of 100-200 miles. Sometimes better. Of course those models are probably expensive. 64.236.121.129 13:25, 11 October 2007 (UTC)


 * And if you ran some refrigeration coils around and a big tank, you could have a drinking fountain in your car! Now that's novel. :) - Woo ty   [ Woot? ]  [Spam! Spam! Wonderful spam! ] 03:29, 10 October 2007 (UTC)
 * It would actually be kinda useful too - one of the challenges with fuel-cell hydrogen cars is how to warm up the hydrogen as the pressure is released. Keeping a fridge full of non-alcoholic beer frosty-cold would help! :-) SteveBaker 13:38, 10 October 2007 (UTC)


 * Actually, alcohol would do a better job because it takes much more energy to freeze it. DirkvdM 09:01, 11 October 2007 (UTC)


 * Steve, hydro- and windenergy don't strictly speaking produce electricity. It's just that that's a form of energy we have an extensive infrastructure for, so we convert the energy to that. Wind and rivers are both flows. We translate that into rotation and then use turbines to translate that into electricity. And then (in this case) into hydrogen again. Maybe efficiency would be served if we could translate the flow more directly into hydrogen. What about using the triboelectric effect? Alas, water and air aren't mentioned in the article, but what if we'd have a material that would build up a charge that can then be used for electrolysis to produce hydrogen? DirkvdM 09:01, 11 October 2007 (UTC)