Science desk
< January 14	<< Dec \| January \| Feb >>	January 16 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 15[edit]

Is there such as "aspiration center" in nerve system?[edit]

(I'm not surely back) Like sushi 49.135.2.215 (talk) 00:48, 15 January 2016 (UTC)[reply]

I don't quite understand your question, further information about the context would be needed. Maybe what you are looking for is an aspiration center. This is a physical location in a hospital where some medical procedure like needle aspiration biopsy) is performed. --Denidi (talk) 01:20, 15 January 2016 (UTC)[reply]

I don't know what's up either, but this paper [1] discusses "fine needle aspiration biopsies of the central nervous system", so it might be helpful to OP. SemanticMantis (talk) 16:09, 15 January 2016 (UTC)[reply]

"Aspiration" has ~~two~~ three very different meanings. Aspiration can mean "ambition" (as in my son aspires to be a scientist). Aspiration can also mean "drawing in" or "removing by suction" by creating a negative air pressure difference in a hollow surgical instrument. And, finally, aspiration can mean the act of drawing in breath. Which one is it? :) Dr Dima (talk) 17:52, 15 January 2016 (UTC)[reply]

Aspiration in the first sense (that is, ambition) is thought to be functionally associated with frontal lobe; or at least one of the symptoms associated with prefrontal cortex / frontal lobe damage is the lack of ambition. Aspiration in the third sense - breathing in - is governed by the respiratory center in the brain stem. --Dr Dima (talk) 18:17, 15 January 2016 (UTC)[reply]

Is there such as "motive entropy"?[edit]

(I'm not surely back) Like sushi 49.135.2.215 (talk) 00:49, 15 January 2016 (UTC)[reply]

As above, the question is difficult to understand. Motive is usually a term used in law or psychology while entropy is a term usually used in physics, specifically thermodynamics. I have not come across those two words being used together to describe anything. If this misses your question entirely, you could try asking the question in your native language and someone might be able to translate it for you. Vespine (talk) 04:59, 15 January 2016 (UTC)[reply]

Two seconds of googling reveals it to be a phrase used by Carnot, hence something to do with thermodynamics. Greglocock (talk) 08:28, 15 January 2016 (UTC)[reply]

Motive can also be an adjective meaning "relating to motion and/or to its cause". Just like a locomotive is not generally a reason why loco people commit crimes, it's unlikely that "motive entropy" has anything at all to do with the law or psychology term. ;) --Link ^(t•c•m) 11:42, 15 January 2016 (UTC)[reply]

Of course it can! Fail on my part. Vespine (talk) 22:50, 17 January 2016 (UTC)[reply]

Hm, electromotive force, magnetomotive force, Projectile#Motive_force all speak to the usage in physics of "motive" in a different sense than the psychological/behavioral sense of motivation. Some of these terms (esp. motive force) may be losing currency, but were very popular not that long ago. SemanticMantis (talk) 16:06, 15 January 2016 (UTC)[reply]

Here [2] is a 2003 article, freely accessible, that explains a concept of "motive entropy", with references, thusly:

“

Only the potential energy and zero-point vibrational energies, E0, and the degeneracy term, [math notation for terms] contribute to A so Frank suggested they should be called ‘motive enthalpy’ and ‘motive entropy’ after Carnot to distinguish work terms from the heat terms now called ‘thermal’ terms.

”

Here's another recent (2008) paper that defines the concept formally (eq. A20). The idea seems to be to separate "thermal" and "motive" portions of entropy, the latter of which is independent of temperature (or perhaps adiabatic?). The physical scope of these articles is is a bit over my head, but these should provide good sources for anyone who wants to explain further. (Also if anyone wants to help me out on a related sub-question - is this distinction at all analogous to latent heat vs. sensible heat? I'm fine with the math but fairly ignorant of thermodynamics) SemanticMantis (talk) 16:06, 15 January 2016 (UTC)[reply]

Norovirus and Pathogenic Escherichia coli[edit]

Does immersion in boiling water inactivate these two pathogens, and how long does it take? Edison (talk) 05:09, 15 January 2016 (UTC)[reply]

Yes, I found this article has some details. All common enteric pathogens are readily inactivated by heat, although the heat sensitivity of microorganisms varies. It appears that for most viruses they take just several seconds (~10 seconds) to be inactivated in boiling water. Just keep in mind that just putting a potato (for example) into boiling water for 10 seconds doesn't guarantee all virus will be inactivated. There could be a virus caught in a crack or cavity that is too small for water to get into, and the potato can act like a heatsink for long enough to cause the virus not to reach a high enough temp. Vespine (talk) 05:53, 15 January 2016 (UTC)[reply]

Agreed. This is why food has to be cooked right through. One more thing to mention is that even though cooking may kill the pathogenic organisms, it won't necessarily inactivate their toxins. -- The Anome (talk) 08:42, 15 January 2016 (UTC)[reply]

Douglas Baldwin's rather wonderful book on sous vide has both the full pasteurisation time/temperature tables for the internal temperature of the food (in the section linked), and timings for how long it would take to reach those temperatures given the meat, thickness, and water bath temperature (in the individual sections for the meats). E coli is considered in the beef, lamb and pork section. The point about toxins is a very valid one - and there are some pathogens (such as Clostridium botulinum) which will just spore up at cooking temperatures, and then continue to reproduce when the temperature drops. MChesterMC (talk) 09:22, 15 January 2016 (UTC)[reply]

The general recommendation in food preparation is to avoid the "Danger zone", which is reported as 5-60 celsius, which would imply that holding food at above 60 C is generally regarded as safe; since boiling is at 100 C, you're probably good. --Jayron 32 13:22, 15 January 2016 (UTC)[reply]

Except that food in boiling water is not at 100C (or if it is, it's horribly overcooked!). Looking at my ref above, the pasteurisation times for actual cuts of meat are much higher than the government pasteurisation tables - because it can take several hours for the centre of a joint to get to a safe temperature. This will be a lot quicker at boiling than at typical sous vide temperatures, but the boiling water is the heat source, not the thing you're trying to kill bacteria in. Your best bet is to get a meat thermometer, and measure the internal temperature of your food - if it's above 70C, you're good. If it's been above 60C for 10 minutes, or 65C for 1 minute, you're good. Add 5C to each of those for poultry. Of course, full pasteurisation is overkill for most foods - steak cooked at medium or below won't be pasteurised throughout unless it's dove very slowly, but for the most part it doesn't matter since most of the bacteria are on the surface, which gets hot enough to kill them.

Also, while holding food at 60C is safe (since most dangerous bacteria can't grow), just getting food to 60 and then eating it may not be - the pasteurisation time at 60C is about half an hour for fatty poultry, so a short time at 60C isn't going to change much. MChesterMC (talk) 14:43, 18 January 2016 (UTC)[reply]

I see that a restaurant chain plans to reduce the incidence of e coli and norovirus illness as follows "Onions will be dipped in boiling water to kill germs before they're chopped.... Cilantro will be added to freshly cooked rice so the heat gets rid of microbes in the garnish." Past outbreaks of food-born illness have identified irrigation water or produce-washing water which might be contaminated as a source of germs, and presumably if the contamination is only on the surface of the plant material, there would be a decrease in the likelihood of illness, if not a guarantee. Edison (talk) 16:06, 15 January 2016 (UTC)[reply]

Question about Quarks[edit]

Hello! I was thinking about particle physics, when a thought occurred to me: "How did Quarks form in the early universe? I know that we are pretty certain that they are elementary, so why were they there in the universe, at that time? Are they little balls of energy or did some force (like Gravity) cause space-time to collapse on its self to form Quarks?" So how did they form then? By the way, I only know basic physics, so explain any "complicated stuff" to me. Megaraptor12345 (talk) 15:53, 15 January 2016 (UTC)[reply]

I'm not sure we have a very good idea. You might want to read up on baryogenesis (and by that I mean not just the Wikipedia article, but as a concept to focus your research on outside of Wikipedia as well), but the main take-away I've always had is that we have very general, broad, and not-at-all in focus ideas about what went on during this epoch of the early universe, and that there are several competing (consistent but as yet not well supported) theories on what really went down. --Jayron 32 17:09, 15 January 2016 (UTC)[reply]

You actually have to page back quite a few epochs from the quark epoch to reach the legendary grand unification epoch, which lays somewhat west of the Wicked Witch of the West, perhaps. Our article is not very informative due to the lack of accepted grand unification theory. But it wasn't until the quark epoch that they (mostly) lacked more massive competition like W and Z, I suppose. Wnt (talk) 17:15, 15 January 2016 (UTC)[reply]

Sorry, what is W and Z? Megaraptor12345 (talk) 22:05, 15 January 2016 (UTC)[reply]

The bosons in the image below, I think. SemanticMantis (talk) 22:28, 15 January 2016 (UTC)[reply]

I'll have to check it out on my next trip to the Big Bang Burger Bar. --Jayron 32 17:30, 15 January 2016 (UTC)[reply]

@Megaraptor12345: The W and Z bosons are mentioned in the previous epoch before the quark epoch, the Electroweak epoch. Note that electroweak theory has been tested and is pretty well agreed upon ... whether that means that period of the universe is well agreed on, I don't know. Wnt (talk) 23:09, 15 January 2016 (UTC)[reply]

It is believed that in the period prior to 10⁻⁶ seconds after the Big Bang (the quark epoch), the universe was filled with quark–gluon plasma, as the temperature was too high for hadrons to be stable. Such a quark-gluon plasma was reportedly produced in the Large Hadron Collider in June 2015. However the quark has not been directly observed, it is a category of Elementary particle introduced in the Standard model as parts of an ordering scheme for hadrons that appears to give verifiable predictions of particle interactions, but as yet we have no agreed explanation why there are three generations of quarks and leptons nor can we explain the masses of particular quarks and leptons from first principles. AllBestFaith (talk) 18:25, 15 January 2016 (UTC)[reply]

This is all very well, but I am not sure I put my question right. Let me start again. How did matter form? I thought in my original question that quarks were the original particle, but they were not, were they? So how did any sort of matter form? Did it appear as a personification of energy or as globs of some force? Megaraptor12345 (talk) 22:14, 15 January 2016 (UTC)[reply]

Quarks will appear spontaneously through pair production and other interactions when enough energy is available. They are just a particular mode of vibration of the quantum field, and all of the vibrational modes are coupled together in complicated ways, so if there's enough energy there will unavoidably be quarks. If inflationary cosmology is correct (which it may not be), that energy came from the inflaton [sic] field, and where that came from is anyone's guess. -- BenRG (talk) 22:50, 15 January 2016 (UTC)[reply]

What is a "quantum field"? Megaraptor12345 (talk) 16:49, 16 January 2016 (UTC)[reply]

It's a field (physics), like the electromagnetic field but with more oscillatory degrees of freedom that correspond to particles other than the photon. It isn't really the field that's quantum, it's the world that's quantum. Because the world is quantum, oscillations of any field are quantized, and each quantum of oscillation energy is called a particle. The properties of the field tell you everything about physics at ordinary energies; all particles and interactions are oscillations of the field. The physics is described by the Standard Model Lagrangian and (the quantum version of) Lagrangian mechanics. -- BenRG (talk) 21:50, 16 January 2016 (UTC)[reply]

More specifically, it's one of the set of fields predicted by quantum field theory. This video focuses on the Higgs mechanism, but touches a bit on QFT, as you need to understand the basics to understand why physicists care about the Higgs. --71.119.131.184 (talk) 08:09, 18 January 2016 (UTC)[reply]

This isn't my field, but here's the perception I have: The universe is a bit like a three ring circus. New kinds of physics come in, stay a while, and eventually are ushered offstage. The way this ushering occurs is that there is physics for very high-energy particles that occurs on a very short time scale and physics for lower energy particles that occurs on a longer time scale. If proton decay occurs, and there is no end of cosmic expansion/heat death of the universe etc., then one day all of our protons and neutrons may be considered just some weird high energy physics that happened during the first few moments after the Big Bang, before the universe settled into steadier assemblages of neutrinos interacting at a more measured pace. Whereas if you look far enough back, there was a time when an ordinary photon of radiated heat had enough energy to make Z and W particles, and perhaps quarks were a minor constituent - something like neutrinos to us in that they didn't carry as much mass and so might have seemed relatively irrelevant ... though I'm not sure the analogy really makes sense due to quarks' charge - certainly I have no guess of how relevant charge was in the era before electromagnetic and weak forces were distinguishable. While free quarks can't exist in our space, back then there was so much energy crammed so close together that the quarks were in quark-gluon plasma, which is tolerable, so basically any thermal photon could make quarks and antiquarks spontaneously. But I don't think anyone knows just how many acts there were at the beginning of this circus, or even if it had a beginning, rather than just smaller and smaller intervals of time in a convergent series. Wnt (talk) 23:09, 15 January 2016 (UTC)[reply]

Crude Oil[edit]

Will the crude oil rate slash down further? — Preceding unsigned comment added by 59.88.196.26 (talk) 17:44, 15 January 2016 (UTC)[reply]

Maybe, maybe not. Please see WP:CRYSTAL; we cannot speculate on this. Here [3] is a relevant article from the Economist published today that you might be interested in. Other respondents may choose provide references that speculate on this, but they should not speculate here. SemanticMantis (talk) 17:50, 15 January 2016 (UTC)[reply]

The report I heard on NPR said that prices may well drop further, yes. They based that on current stockpile levels and the slow rate at which oil production facilities (and alternative substitutes production, like natural gas) currently are reducing production. Eventually, those production levels will be brought down to match demand, and then you can expect prices to stabilize. StuRat (talk) 22:10, 15 January 2016 (UTC)[reply]

The price of oil, or of any commodity for that matter, will either go up, or down, or remain stable. Guaranteed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:58, 16 January 2016 (UTC)[reply]

Today sanctions against Iran were dropped, allowing them to sell their substantial oil reserves on the world market. This can be predicted to lower prices due to increased supply. StuRat (talk) 22:05, 16 January 2016 (UTC)[reply]