Wikipedia:Reference desk/Archives/Science/2015 January 3

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January 3

Any one here proficient about Histamine & Appetite regulation?

Please see Talk:Histamine; The article could grow better if an expert in the field would add some data on this subject. Ben-Natan (talk) 06:39, 3 January 2015 (UTC)

why does listerine packaging say not to rinse mouth straight from bottle?

is it a weird cross contamination issue or what? 212.96.61.236 (talk) — Preceding undated comment added 11:37, 3 January 2015 (UTC)

Probably as a legalistic thing, i.e. to discourage you from absent-mindedly drinking it. Like other seemingly idiot-proofing warnings, like on those little moisture absorbing packets that say "Do not eat". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:00, 3 January 2015 (UTC)

This, from Google Images, is a ca.2011 warning label. I don't see anything that says not to take it straight from the bottle, only a warning "do not swallow". Or is your label more recent? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:09, 3 January 2015 (UTC)

Our bottle from yesterday says "Do not dilute, swallow, or swig from the bottle". From various talk pages; While the product will kill any germs in the "backwash" from the mouth to the bottle, it will eventually discolour and taste bad (worse). Fiddlersmouth (talk) 13:56, 3 January 2015 (UTC)

Also, a swig from a large bottle may tend to splash in your eyes, burning quite badly, I imagine. StuRat (talk) 00:11, 4 January 2015 (UTC)

There might be a clue in their use of that term "swig", which means a big gulp.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:20, 4 January 2015 (UTC)

A swig is between a sip and a mouthful (an unswallowed gulp), where I'm from. A reasonable amount for rinsing. It seems to me they just don't want your lip microbes screwing up their concoction. Might never happen, but there are a lot of filthy lips out there, and germs evolve every day. If something gets terribly funky (or just less effective) and a lawyer pursues it, they can tell him they warned you and hang up.

As for "don't dilute", they just want you to replace it sooner. Nothing wrong with water and mouthwash. Watery milk's no fun, though. InedibleHulk (talk) 23:46, 4 January 2015 (UTC)

Does it really say "swig"? I can't wait till I next have a reason to go buy store-brand Listerine and look at the overpriced brand-named product's label. μηδείς (talk) 03:09, 7 January 2015 (UTC)

Couldn't you just hit up a nearby DR and look at a label for free? I think another idea is that they want to discourage you from attempting to get wasted off of it. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 16 Tevet 5775 18:42, 7 January 2015 (UTC)

Here's a label: [2]. It says to use a cup, but doesn't use the word "swig". I also found other Listerine labels that don't specify to use a cup. StuRat (talk) 20:27, 7 January 2015 (UTC)

What is the way that EDTA prevents the clotting in the blood samples?

I read in the article here (EDTA) the next sentence but it dosn't explane the way: "EDTA is used extensively in the analysis of blood. It is an anticoagulant for blood samples for CBC/FBEs." 194.114.146.227 (talk) 15:15, 3 January 2015 (UTC)

It binds (aka sequesters aka chelates) calcium ions disolved in the plasma so that they are no longer available for the clotting cascade, in which calcium ions play a key role. No free calcium ions, no clotting. Dominus Vobisdu (talk) 15:19, 3 January 2015 (UTC)

science(cooking,heating)

Can a heating source (ie electrical hotplate) mantain the heat of an extremely hot pot with food in it forever, however it would not be able to bring something that was cold to that heat? — Preceding unsigned comment added by Neil rybak (talk • contribs) 16:55, 3 January 2015 (UTC)

I suppose so, in a theoretical sense. There is a certain equilibrium temperature which will be reached when the heat source and cooling are equivalent. However, the cooling rate depends on the temperature difference between the food and the environment. Combine these together and the temperature will asymptotically approach the equilibrium temperature. Depending on if the heated object starts above or below that equilibrium object, it will theoretically take forever to get to it, meaning that those two objects will never be the same temperature. However, the reality is that, after some period of time, the temps would be so close they could no longer be distinguished by any instruments we have. (Note that I ignored other factors such as all the water boiling off the food, which then changes the equilibrium temperature.)

To illustrate, here's a chart of how temps might change on 3 objects starting below, at, or above the equilibrium temperature:

Obj1  Obj2  Obj3
====  ====  ==== 
100   200   300
150   200   250
175   200   225
188   200   212
194   200   206
197   200   203
198   200   202
199   200   201
199.5 200   200.5
199.7 200   200.3
199.8 200   200.2
199.9 200   200.1

So now for some practical cooking advice. It can take very long to get food to the desired temperature using something with a low heat output like a hotplate. That means it will be warm, but not hot, for a long time, and bacteria can grow during that period. Thus, it's safer to initially heat the food elsewhere, like in a microwave oven, to quickly get it past that dangerous temperature and into the safe range, then move it to the hot plate to keep it in the safe range. StuRat (talk) 17:28, 3 January 2015 (UTC)

Pretty much in a practical sense, too. A good example is the hotplates that keep coffeepots warm under electric coffee makers. They have enough power to maintain temperature, but generally not enough to bring cold water up to the serving temperature for coffee (at least in a reasonable timeframe), nor enough to bring the coffee to a full boil. The power is carefully selected to balance cooling and heating. Dominus Vobisdu (talk) 18:04, 3 January 2015 (UTC)

Yes, they won't reach the same temp in a practical amount of time, and theoretically, they will never reach the same temp. StuRat (talk) 18:46, 3 January 2015 (UTC)

That's true for a low output hotplate, but an 1100 watt radiant cooker ring - also known as a hotplate - can get very hot and can boil a pan of water from cold fairly quickly. Richerman (talk) 21:21, 3 January 2015 (UTC)

From a physics point of view, the answer is "no". If the hot plate can maintain something at a particular temperature, it can eventually heat that thing to that temperature. As StuRat notes, the approach is slow and asymptotic. How long it takes to reach the target temperature depends on how closely you define the target's tolerances. Arguing that the food never reaches the equilibrium temperature is sensible mathematically, but physically is nonsense. Every measurement has some uncertainty, and most physical properties have fundamental uncertainties too. Even if you start with the food hot, you can never exactly maintain it at one particular temperature, to infinite precision. See also Zeno's paradox#Dichotomy paradox.--Srleffler (talk) 02:51, 5 January 2015 (UTC)