Wikipedia:Reference desk/Archives/Science/2010 April 5

= April 5 =

HEADACE
Whats known cure for head ace and flu KENNEDY NEWTON (talk • contribs) 00:05, 5 April 2010 (UTC)


 * [medical advice removed --Tango (talk) 00:40, 5 April 2010 (UTC)]


 * We can't give medical advice, I'm afraid. There are lots of head ache and flu treatments available. I suggest you ask a pharmacist, they will almost certainly be able to help. --Tango (talk) 00:40, 5 April 2010 (UTC)


 * Moved discussion to Wikipedia_talk:Reference_desk. --Tango (talk) 19:22, 5 April 2010 (UTC)


 * And the spelling you are looking for is most likely headache --Polysylabic Pseudonym (talk) 10:57, 5 April 2010 (UTC)


 * If we're removing Cyclonemin's answer, I'll at least reference our articles Headache and Influenza, which has all the information that was contained in his response. Buddy431 (talk) 22:37, 5 April 2010 (UTC)


 * Or better yet, these: Headache, Management of chronic headaches, and Influenza treatment. Buddy431 (talk) 22:42, 5 April 2010 (UTC)

Restoring non-medical advice response, per talk page consensus: StuRat (talk) 19:39, 6 April 2010 (UTC)


 * Headache's vary significantly in type, but are usually relieved by some sort of analgesic (such as paracetamol) if they're minor. More serious types of headaches exist and depending on the type, various types of drugs can be given such as stronger analgesics or vasodilators. Sometimes headaches are indications of further, more serious diseases and act as a diagnosis aid. Influenza is a virus which is usually unpleasant but killed off by your immune system, and thus does not usually require treatment. However, in immunocompromised individuals (that is to say, those with a weaker immune system such as the elderly, AIDS patients, transplant patients etc) are often at greater risk because their immune systems may not be able to deal with the rapid replication of the virus. In such cases, doctors prescribe antivirals specific to the current influenza virus to try and boost your immune systems removal of the virus. Regards, --— Cyclonenim | Chat 10:59, 5 April 2010 (UTC)
 * bottom line: if aspirin or another nsaid doesn't make your headache or other ache (i.e. flu) go away, then modern medicine is more or less out of options. (not applicable to migraines, though)Gzuckier (talk) 06:23, 8 April 2010 (UTC)

Electrochemistry
"A biological cell is immersed in a 70. mM solution of NaCl at 37°C. The cell's membrane is permeable only to Na+ ions. When the system reaches equilibrium, a potential difference of 55.4 mV is measured between the inside and the outside of the cell, where the inside has the higher (more positive) potential. Calculate [Na+] inside the cell, assuming the amount of Na+ ions transferred is negligible compared to the total amount of Na+ ions in the solution."

I'm aware that, at equilibrium, the chemical potential of Na+ inside the cell equals the chemical potential of Na+ outside the cell, according to m = m° + RT ln a + ZFo. But what are F and o? I plugged in the values but don't get the answer. —Preceding unsigned comment added by 70.68.120.162 (talk) 01:59, 5 April 2010 (UTC)


 * I think Fo refers in this context to the Faraday constant. I might be wrong, though, because I haven't done any electrochem calculations in a long time.  FWiW 24.23.197.43 (talk) 02:20, 5 April 2010 (UTC)


 * Let me just note that our Nernst potential article covers this. Looie496 (talk) 05:19, 5 April 2010 (UTC)

Cat Behavior - combination of "playing the piano" and mate mounting?
One of my adult female cats has exhibited a new behavior pattern for the past several months that I've never seen before. She has always occasionally "played the piano", the rhythmic massaging of invisible mammaries done by adult cats that were weaned too early. Recently, however, she has combined that with the neck-bite-and-hold that male cats do when they mount the female to mate. So, when I'm laying on the sofa or in bed under a blanket, she will mount my leg and firmly bite the blanket, then begin simultaneously massaging my leg with her forepaws while purring most determinedly. Has anyone else ever seen a cat (especially female) exhibit this behavior? Does anyone have any idea what sort of "needs" are behind this? I can understand both components alone, but together seems a bit odd! 61.189.63.142 (talk) 03:04, 5 April 2010 (UTC)


 * I'm not aware there's any real understanding of why cats knead. There are plenty of theories, of which yours is one, but we don't really know which one is correct (there may be multiple reasons). This is a key point because unless we know why cats knead, any speculation of why that occurs with some other behaviour is going to be speculation upon speculation. If you think these two behaviours don't go together because the cat is doing X for reason Y, if it's actually reason B this may change things completely. Purr is a somewhat related example. If you think your cat is purring because it's contented, what about if it's purring when it's sick, injured or dying? (Personally I like to jokingly say my cat is purring because he broke his bones ) BTW if you are concerned about any recent change in your cats behaviour, you should see a vet. Nil Einne (talk) 04:04, 5 April 2010 (UTC)
 * Note that female cats also grab their kittens by the loose skin on the back of the neck when carrying them. So, she may have kittens on the brain.  This "broody" behavior seems especially common right after they are fixed. StuRat (talk) 04:11, 5 April 2010 (UTC)


 * All the female cats I've had exhibit this behaviour, which I haven't seen in any of the male cats. If she's biting and kneading at the same time, she's probably trying to suckle. I associate it with being relaxed - it usually happens before she goes to sleep. --TammyMoet (talk) 08:45, 5 April 2010 (UTC)


 * Thanks everyone! 61.189.63.142 (talk) 22:15, 5 April 2010 (UTC)


 * errr... I hate to suggest it, but it's possible you might be in the line for some kittens.  pregnant cats tend to display some odd behavior.  have you noticed her carrying small objects from one part of the room to another?  -- Ludwigs 2  22:40, 5 April 2010 (UTC)
 * My experience suggests the behaviour happens in spayed females more than in entire females, so don't rule out the possibility unless you know she's been done! --TammyMoet (talk) 09:26, 6 April 2010 (UTC)

bioinformatics question
I need to compare amino acid and/or genetic sequences at work and it seems that my bioinformatics and BLAST skills are a little rusty. Can you point me to articles (better if they are fully accessible) regarding similarity, identity and homology of sequences? --121.54.2.188 (talk) 07:44, 5 April 2010 (UTC)
 * Do you mean BLAST, sequence alignment, BLOSUM ? --Rajah (talk) 10:55, 5 April 2010 (UTC)
 * Also relevant: Homology (biology), Conserved sequence, and Substitution matrix. -- Scray (talk) 11:30, 5 April 2010 (UTC)
 * Also keep in mind that Pubmed provides entire open-access books, e.g. Koonin & Galperin, the NCBI Handbook, Coffin, Hughes, & Varmus. -- Scray (talk) 15:18, 5 April 2010 (UTC)


 * This page from NCBI seems to be a good resource for everything BLAST related. It also has an email address and a link to a mailing list in case you need more specialist advice: 131.111.185.75 (talk) 21:42, 5 April 2010 (UTC)
 * Sweet :) I think I'll be reading those articles and books this week.--121.54.2.188 (talk) 01:40, 6 April 2010 (UTC)

longest wavelength of EM radiation
In Electromagnetic spectrum, it is stated that the longest wavelength can be the size of the universe. If we use the equation relating frequency and Planck's constant then shouldn't the longest wavelength be 300,000 km ? as the energy of the photon must be integral multiples of Plankck's Constant. Also, the EM spectrum article states that it's continuous, but how can that be if energy is quantized. Maybe this is covered in another article like wave - particle duality, but I don't know. Can someone shed some light on this issue? Thanks! --Rajah (talk) 10:50, 5 April 2010 (UTC)
 * Energy does not have to a multiple of Planck's constant. You have assumed that lowest frequency is 1 Hz. Graeme Bartlett (talk) 11:51, 5 April 2010 (UTC)


 * You're confused. The energy spectrum is not quantised. Photons of any energy, no matter how big or small, can exist. Once you pick a photon frequency, then the number of photons for that frequency is quantised that is no fractions of photons are allowed. Dauto (talk) 12:17, 5 April 2010 (UTC)


 * Energy levels for a certain system, like an electron in an atom, will be quantised, but that doesn't mean that energy in general is quantised. If your photons are being emitted by an excited atom, then there will be a minimum photon energy corresponding to the smallest gap between energy levels of the atom, but there are other ways for photons to be created and, once they have been created, their energies can change (we call that redshift or blueshift). --Tango (talk) 14:30, 5 April 2010 (UTC)


 * Tango, the energy levels of an atom have an accumulation point as the energy aproaches the continuum (free particles) so the smallest gap between energy levels tend to zero. Dauto (talk) 14:37, 5 April 2010 (UTC)


 * From a practical point of view, it is very hard to generate electromagnetic waves with wavelengths much larger than an antenna. As such, it is pretty uncommon on Earth to ever observe EM waves as low as, say, 100 Hz; but ultra low frequency and extremely low frequency waves do exist, often related to geological and geomagnetic processes, interactions between Earth and its solar environment, or extraterrestrial/extrasolar sources.  Nimur (talk) 15:24, 5 April 2010 (UTC)
 * Oh, yes, I apologise for my mistake. I should look these things up rather than try an remember my one course in Quantum Mechanics several years ago. --Tango (talk) 15:30, 5 April 2010 (UTC)
 * There does not seem to be any lower limit for EM waves. They could be orders of magnitude lower in frequency that 1/second. This is despite the effect that an antenna for efficient transmission and reception would have to be beyond humongous. The only limit wold be one of definition. Edison (talk) 18:53, 5 April 2010 (UTC)
 * You really think that EM waves less than 100 Hz are "pretty uncommon"? Well, just take your portable radio and stand under a high-voltage power line, and see what it does to the reception!  The fact is, EM waves with a frequency of exactly 60 Hz are actually pretty darn common on Earth -- any high-voltage power line generates them to a greater or lesser extent.  Now it's true that such low-frequency sources only radiate very weakly in relation to the amount of current flowing through them, and that it would take an antenna that's "beyond humongous" in length to transmit such waves -- but if you're talking about a transmission line that's part of the national grid, it would typically be hundreds of miles long (thus forming essentially a super-duper-long wire antenna) and carrying hundreds of millions of amps at maybe 750,000 volts, which would emit a significant amount of 60 Hz radio waves even if only a fraction of a percent of the total energy was radiated.  24.23.197.43 (talk) 04:55, 6 April 2010 (UTC)
 * Do you understand that your portable radio is picking up harmonics of 60 Hz, and not 60 Hz? Unless your portable radio antenna is about 5000 kilometers long, and connected to a tuned circuit that resonates at such low frequencies, you are not picking up 60Hz waves.  Nimur (talk) 20:56, 6 April 2010 (UTC)
 * OK, I may be wrong about the radio picking up the 60 Hz waves; but that doesn't change the fact that the 60 Hz waves are indeed emitted by the power line, along with the higher harmonics that are the ones responsible for radio interference. It's pretty much the same thing as when a plane crashes in the ocean but there's nobody around to hear it... 24.23.197.43 (talk) 02:23, 7 April 2010 (UTC)
 * One or two thousand amperes, more like. --Heron (talk) 18:20, 6 April 2010 (UTC)
 * The U.S. and Soviet/Russian navies used "super low frequency" or "extremely low frequency" transmissions at 76 Hz and 82 Hz respectively to send messages to their submerged submarines. The Sovs put the ground electrodes 60 kilometers apart. The U.S. used electrodes 52 km apart. The input power was a reported 660 kilowatts, while the radiated power was only a few watts, since the antenna was a tiny fraction of a wavelength, but the encrypted transmissions could be received worldwide by deeply submerged submarines. (The submarines couold not reply at that frequency, but could let up a radio bouy to send at more normal frequencies if stealth was not a concern). There were concerns about the effects on humans and animals of the resulting widespread electromagnetic fields. The system could be used to send nuclear attack authorization to ballistic missile submarines, so it had to transmit signals all the time, and could not be kept in standby non-transmitting. To suddenly start transmitting during a time of world tensions would have been a giveaway that something was up. Edison (talk) 15:26, 6 April 2010 (UTC)

Wasn't the bandwidth really low on that comm method? Googlemeister (talk) 16:37, 6 April 2010 (UTC)

Experimental psychology effect - can't remember name
I've had no luck with Google and I really need an answer to this question, so I'm going to be obnoxious and cross-post it from the humanities desk to draw some attention.


 * I'm trying to find the name of a psychological effect I remember reading about a while ago. (It might have been in SuperFreakonomics, a book I no longer have.) The effect was that people tend to prefer to work for free over working for a small amount of money, because working for free feels like charity but working for very little feels like devaluing your accomplishments. Anyone know what the name of this effect is, or a citation for the experiment?

Please don't kill me. I'm really a nice guy, you know. « Aaron Rotenberg « Talk « 17:40, 5 April 2010 (UTC)
 * I can't say I know that this effect has a name, but Dan Ariely writes about this kind of thing in Predictably Irrational, which unfortunately I don't have on hand.--Rallette (talk) 18:19, 5 April 2010 (UTC)
 * I think your thinking of:Cognitive dissonance theory (Leon Festinger and Carlsmith 1959) which shows that getting a zero reward can increase liking for the task compared with receiving a small positive reward. see also:--Aspro (talk) 18:38, 5 April 2010 (UTC)
 * Of course, free t-shirts are a more powerful motivator than either low pay or charity. :-) &mdash;ShadowRanger (talk 19:04, 5 April 2010 (UTC)
 * Who said free t-shirts? Where?  What do I need to do?!  Dismas |(talk) 20:40, 5 April 2010 (UTC)
 * Dismas you want to volunteer at the Great British Beer Festival and you will get your free staff T-shirt! --TammyMoet (talk) 09:24, 6 April 2010 (UTC)


 * That's good enough. The "introducing a penalty for parents who are late picking up their children from kindergarten can actually increase tardiness" example is one of the ones I remember reading about. I guess there isn't a standardized name for the specific effect, though. Thanks! « Aaron Rotenberg « Talk « 23:26, 5 April 2010 (UTC)

Cracking a Chest
When doctors refer to cracking a person's chest open, what is the technical name for this surgical procedure? Thanks 92.11.43.155 (talk) 21:28, 5 April 2010 (UTC)


 * Well, when they're operating on the heart or nearby related organs, it's called open heart surgery. Not sure if there are other operations that use this technique. &mdash;ShadowRanger (talk 21:43, 5 April 2010 (UTC)


 * May be sternotomy. Dauto (talk) 21:49, 5 April 2010 (UTC)


 * That's right, it's a specific type of thoracotomy. By the way the definition of open heart surgery on the cardiac surgery page contradicts that on the median sternotomy page. Someone should probably check that out, but I'm afraid I can't as I'm not really meant to be editing wikipedia at all at the moment. (self imposed wikibreak due to exams, and yes I know that I shouldn't be posting this now) 131.111.185.75 (talk) 21:53, 5 April 2010 (UTC)


 * Thanks. Thoracotomy was just what I was looking for. 92.11.43.155 (talk) 01:01, 6 April 2010 (UTC)


 * (ecX2) See Cardiac_surgery. StuRat (talk) 21:51, 5 April 2010 (UTC)

Railroad Engineering
Hi,

I was developing some content for a train-simulation program..

I have a LOT of questions..

I'm asking because I was developing some content for a train-sim and wanted to make the objects 'look' accurate.

i) Does anyone here have a simple formula for converting an axle loading value into a rail weight? (It's something the article on axle loading should maybe have but doesn't)

ii) Typical weights and "rail profiles" for typical 2ft industrial lines would be? ( I've got links to some data for typical US profiles, although I imagine the 'official' standards are tightly controlled.) I am guessing that US logging lines used heavier rails then the Welsh Slate lines though :)

iii) An ISBN or citation for a standard (preferably metric) work on how you lay out trackwork for various gauge construction.. Such works also usally have the formulae for curve limit calculation for various gauges and wheelbases..

iv) A general reading list on the subject of 'industrial' narrow gauge railways ShakespeareFan00 (talk) 23:18, 5 April 2010 (UTC)


 * Interesting! I actually worked on commercial railroad simulators for Burlington Northern back in the early 1990's - and we didn't need any information in that much detail!  Sadly, that means I'm of no help whatever in answering your questions - sorry. SteveBaker (talk) 02:44, 6 April 2010 (UTC)


 * How is 2 feet an "industrial" gauge? It is less than half standard gauge, and sounds like something you might find at a narrow gauge museum or a little toy ride-on train at an amusement park. Google Book search is your friend for old technical information, because some of it is fully viewable, unlike technical information from recent years. See "Railway engineering" (1899), "Railway engineeering" (1908), "Railway maintenance engineering" (1919), "Steel rails" (1913), "Manual of the American Railway Engineering Society" (1921), Manual of recommended practice for railway engineering  and maintenance of way" (1907)  and in a limited view "Practical railway engineering" (2005). A cursory search through some of the old and the one new ref did not turn up the terms "axle loading" or "rail weight," though. Where did you find the terms in use? Edison (talk) 14:47, 6 April 2010 (UTC)
 * Searching Google books for "axle loading" "rail weight" turned up one reference: "Operation and maintenance of diesel-electric locomotives", U.S. Army, (1989)‎ - Page 174 which says "allowable axle loading varies with the weight of the rail, speed of operation, and other factors." "Rails weighing 60 pounds per yard or less will handle about 500 pounds of axle load (2 wheels) per pound of rail weight (that is, about 30,000-pound axle loading for 60 pound rail, 25,000-pound axle loading for 50 pound rail). As rails become heavier, the allowable axle loading increases to an approximate value of 700 pounds per pound of rail for 90 pound rails (that is 63,000 pounds)." No idea if the data extrapolate down to very small and light rails. Incidentally, U.S. practice has been 8 wheels (4 axles) per car, while I have seen old European railstock with 2 axles per car. Edison (talk) 15:03, 6 April 2010 (UTC)


 * Hmm, Thanks for the first set links, they don't seem to be on 'full' view in the UK though (longer copyright terms perhaps:.

2ft Guage certainly WAS an industrial guage, and something similar is still used in some parts of Europe, IIRC parts of New England also had 2ft lines associated with 'forestry'? 212.225.121.81 (talk) 23:34, 6 April 2010 (UTC)


 * Indeed, there are plenty of induxtrial lines in our Category:Two foot gauge railways. DuncanHill (talk) 08:59, 7 April 2010 (UTC)