Science desk
< December 4	<< Nov \| December \| Jan >>	December 6 >

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.

December 5

causes of internal ache and chokeness along the throat

Removed request for medical advice. The only advice Wikipedia can give is to call a doctor and have a face-to-face meeting with him/her. Only a medical professional can give responsible medical advice.

Pyruvic Acid vs. Pyruvate as end product of Glycolysis

Most sources I've seen (incl. wiki) say that pyruvate is the end product of glycolysis. Except I was reviewing some biology in the Schaum's Outlines and it said pyruvic acid. According to wikipedia the formual for pyruvic acid is C(3) H(4) O (3) (I don't know how to do subscripts) and pyruvate is C (3) H(3) O(3), which makes sense given that pyruvate is the ionized form. In the glycolysis article it says pyruvate is the end product but if you look at the picture (glycolysis overview) then end product is has 4 hydrogen, which would make it pyruvic acid, not pyruvate. This makes more sense because after glycolysis if fermenation occurs the end product, supposedly pyruvate, is reduced twice by the two NAHDH to make a 6 hydrogen compound, which doesn't make sense because pyruvate reduced twice would only have five hydrogens. So my question is: is the end product of glycolysis pyruvate or pyruvic acid? Thanks, 76.95.117.123 (talk) 02:19, 5 December 2009 (UTC)[reply]

They are the same thing. Pyruvic acid is C₃H₄O₃, and pyruvate is the anion C₃H₃O₃^-. If you read the article on pyruvic acid, the second sentence of the lead tells you just that. Pyruvate is the form used by the Citric Acid Cycle. ~ Amory (u • t • c) 02:50, 5 December 2009 (UTC)[reply]

They are the same thing, and which form prevails basically depends on the pH in the cell. In this case it's most likely pyruvate - any pyruvic acid generated would have dissociated into pyruvate and proton anyway. Tim Song (talk) 02:59, 5 December 2009 (UTC)[reply]

So I could say either as the answer to the question? But if the pyruvic acid disassociated into pyruvate then fermentation wouldn't produce a 6 H compound. The only reason I'm curious is that I do Science Bowl and the question sometimes comes up. Which answer would be more correct? I kinda said that pyruvate is the ionized form of pyruvic acid in my question btw...66.133.196.152 (talk) 03:09, 5 December 2009 (UTC)[reply]

Say pyruvate because that is the form it will be in given the conditions. Also, pyruvate and H⁺ are among the reactants in anaerobic respiration. I saw you said that about the ions, apologies if you felt slighted. I just wanted to set up the proper subtext and background. ~ Amory (u • t • c) 03:25, 5 December 2009 (UTC)[reply]

If they say it's wrong based on that grounds you can always appeal. Pyruvate may be temporarily protonated in an enzyme at the active site, but usually what happens is that the COOH group has to be deprotonated. This gives the COO- system the electron it needs to expel the weak carbonyl-carbonyl bond and cleave as carbon dioxide. It can't cleave if it's protonated. ;-) The two-carbon molecule remaining (acetaldehyde) is further oxidised is attacked by the sulfur thiol of CoA to become acetyl CoA. John Riemann Soong (talk) 03:28, 5 December 2009 (UTC)[reply]

You can think of it like this: The proton of pyruvic acid helps supply protons to the proton pump in the electron transport chain. Note that NADH (reduced form of NAD+) carries 2 electrons but only one proton. The other "lost" proton has to come from deprotonating pyruvic acid. ;-) (As you might know, carboxylate is a weak base so it's not very good at taking back the lost proton.)

Decarboxylation (loss of CO2) donates a pair of energetic electrons (to NAD+) that will be used for the electron transport chain. The thermodynamic stability of CO2 helps drive the donation.

Acetyl-CoA is a useful anabolic building block (if you want to build sugars or fatty acid]]), but if you want to oxidise it all the way (use all its energetic electrons) it's kinda hard to oxidise and pull electrons (via evolving CO2) out of a molecule to nothingness (converting acetaldehyde to formaldehyde and formic acid would be a pretty bad idea), so it goes through the citric acid cycle. John Riemann Soong (talk) 03:57, 5 December 2009 (UTC)[reply]

Ok thanks John Riemann Soong! The first explanation you gave helped me alot. And if I challenge I say the wiki ref desk told me :-)

66.133.196.152 (talk) 04:11, 5 December 2009 (UTC)[reply]

heat modelling

this code has come as an outcome of modelling of spot modelling process.i have arrived at eqation (1).If we take initial heat (due to atmospheric conditions) in each point as unity.this in coded in initialisation section. Now dq is sent to ode45 for solving in a prescribed time domain and with initial condition y0=0.

function dq = heat(t,q)
p=5;%number of variables
%--------------------------
% generation of const matrix
%---------------------------
A = [5 4 3 2 1]';----------------------------------------arbitrarily chosen constant A,B,C,D
B = [5 4 3 2 1]';------------------------------------------------
C = [5 4 3 2 1]';------------------------------------------------
D = [5 4 3 2 1 ]';------------------------------------------------
%----------------------------------
dq = zeros(p,1); 
%-----------initialisation-----------------
for i=1:p
   q(i) =1;
end
%----------------------------------------
    dq(1) = A(1)*q(2) + B(1)*q(1) + D(1);
for i=2:p-1
    dq(i) = A(i)*q(i+1) + B(i)*q(i) + C(i)*q(i-1) + D(i); -----------------(1)
end

here 'i' represents the weld number.code has considered the contribution from a point before ,a point after the point 'i', and contribution of heat added in next point.now my problem is that i want to optimise this process i.e. minimize dq.i.e.i need the welding to be cooled fastly.so what parameter should i consider for optimisation and what method should i adopt. SCI-hunter (talk) —Preceding undated comment added 03:01, 5 December 2009 (UTC).[reply]

See this duplicate inquiry at WP:RD/Math. Takes your pick but not both. You are in a little maze of twisty passages. hydnjo (talk) 03:49, 5 December 2009 (UTC)[reply]

I have formatted the code for readability. Nimur (talk) 04:45, 5 December 2009 (UTC) [reply]

The code seems rather nonsensical - the first 'for' loop sets all members of q(1..p) to 1. So surely the second loop sets every element of dq(n) to A(n)+B(n)+C(n)+D(n) ? Why so much complication? You don't say what language this is written in - but what C-like programming language has arrays that start from index 1? This suggests that whatever this code is intended to do...it's not doing it. SteveBaker (talk) 16:16, 5 December 2009 (UTC)[reply]

It was subtly implied that it was Matlab code; between the syntax and the reference to ode45; the OP might want to read our guide on asking for help with code. Nimur (talk) 19:11, 5 December 2009 (UTC)[reply]

its written in matlab and its approxmately functioning correctly.please help now 220.225.98.251 (talk) —Preceding undated comment added 16:28, 5 December 2009 (UTC).[reply]

What do you mean by "minimize dq" ? dq is a function (vector in your code).

More broadly, try following the following steps:

Formulate a clear mathematical statement of the physical problem you are trying to solve.
Derive (or pick) a mathematical solution/algorithm for the problem (or its discretized/approximate version)
Write Matlab code for the algorithm. Test and debug it.

Right now, you seem to be at step 3, and it is not clear (at least to us) if you have followed the previous steps. As such, your code does what it does, but we cannot determine if it actually implements the algorithm derived in step 2, and if the algorithm solves the problem in step 1 (remember GIGO).

PS: You should consult fellow students for tips on better Matlab coding; your current code is pretty poor. For example, the function takes in inputs t and q, and then doesn't use either. Instead it simply defines q. Also your first loop can be replaced by q = ones(p,1). Note that this review is intended to guide, not criticize. Hope it helps. Abecedare (talk) 16:52, 5 December 2009 (UTC)[reply]

Abecedare, dq is not a function. That is the syntax for declaring a return value. The function, heat(t,q), returns a vector whose local name is dq. This is standard MATLAB code style. What is unclear is why the code overwrites q, which is an input; and why it does that overwrite in such an inefficient and convoluted way. I suspect the OP used "pseudocode" or dummy assignments instead of writing a comment or actually implementing the correct physics. If the OP reviews Abecedare's and others' suggestions, and our software help guidelines, it will greatly help us answer the problem. I'm also going to posit that the simulated annealing article may be conceptually helpful, as well as the heat equation article. Nimur (talk) 19:40, 5 December 2009 (UTC)[reply]

I meant to indicate that dq is not scalar valued, so it doesn't make sense to try and minimize it. My language was ambiguous though; thanks for pointing it out. Abecedare (talk) 19:54, 5 December 2009 (UTC)[reply]

I guess if not otherwise specified, minimizing a vector implies minimizing its L2 norm. Nimur (talk) 22:30, 5 December 2009 (UTC)[reply]

Bohr Magneton Number for Copper Sulphate.

Resolved

I'm currently trying to calculate the dimensionless Bohr Magneton number p_eff for CuSO₄·5H₂O. The formulae I have are:

$\mu _{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}}}\right)^{\frac {1}{2}}$

$p_{eff}={\frac {\mu _{eff}}{\mu _{B}}}$

and $\mu _{B}={\frac {eh}{4\pi m_{e}}}$

Where all the symbols have usual meanings and values. From this, p_eff should be:

$p_{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}\mu _{B}}}\right)^{\frac {1}{2}}$

However, the formula I have been given for the dimensionless Bohr magneton number is:

$p_{eff}=\left({\frac {3kt\chi _{M}^{\prime }}{N_{A}\mu _{0}\mu _{B}^{2}}}\right)^{\frac {1}{2}}$

Where the fundamental constant of magnetism of an electron is squared in the denominator, how can this be? Thanks for any help 188.221.55.165 (talk) 13:32, 5 December 2009 (UTC)[reply]

When you substituted, you forgot about that square root. Outside the square root use

\mu _{B}

but if you move it inside the parenthesis you have to square it.. Graeme Bartlett (talk) 21:30, 5 December 2009 (UTC)[reply]

Oh, yeah....simple....thanks Alaphent (talk) 08:26, 6 December 2009 (UTC)[reply]

And I thought I would have to understand Bohr Magnet(r)on number, but actually only algebra was needed! Graeme Bartlett (talk) 05:58, 7 December 2009 (UTC)[reply]

Does rice water has chemical reaction with mineral water's plastic bottle?

I had collect some rice water after washing rice for watering plants.
Because of keep raining these few days, I kept the rice water in plastic bottles to watering plants later.
But I found that after about two weeks, the plastic bottles had been harden and bloat.
The base of the bottle also bloat until hardly to stand on a flat surface.
I'm wondering is there any chemical reaction between rice water and mineral plastic bottle?
I'm curious and wish to know more about this condition, and also the reason why the bottle becomes like this.
Can anyone helps to find out the reason?

There is some problem statements i wish to know:
1. What is the fators affecting the bottle to bloat and harden?
2. What is the effect (positvely and negetively)
2. Does the chemical reaction brings harm to human?
3. Does it brings harm to plants if i watering plant with the rice water in it?

This is the condition i kept the rice water for about 2 weeks:
1. Date I kept the rice water in plastic bottles: 21/12/2009 to 5/12/2009 (I discovered out the condition on 5/12/2009)
2. Temperature: about 27 degree celsius to 33 degree celsius (sometimes in air-conditioned of 24 degree celsius)
3. Place I kept it: in a cupboard in my room
4. Not exposed to sunlight.

And these are few of the pictures of the bottle's condition:

This picture shows the difference of the base of original plastic bottle and the plastic bottle with rice water inside.
This picture shows that the plastic bottle with rice water inside hardly stand on a flat surface.
This picture shows the upper part of bottle also had bloat.
This picture shows that I kept the bottles with rice water inside in a book shelf with glass windows.

--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)[reply]

We can't look at the pictures unless you put them somewhere that we all have access to - upload to Commons or somewhere equally accessible. Mikenorton (talk) 17:14, 5 December 2009 (UTC)[reply]

Your links are inaccessible as well. bibliomaniac 1 5 18:00, 5 December 2009 (UTC)[reply]

Thanks, that's much better. Mikenorton (talk) 18:51, 5 December 2009 (UTC)[reply]

I'm sorry about previous condition. I'm still a newbie in wikipedia, that's why I'm keep finding the instructions and ways to fix those problems. And thank you for your help to guide me. Just now, I'm still finding the ways to reply.--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)[reply]

Perhaps you are inadvertantly making rice wine? 75.41.110.200 (talk) 18:06, 5 December 2009 (UTC)[reply]

I have to agree that fermentation of rice starch in the water, creating carbon dioxide, is a likely cause of this. Mikenorton (talk) 18:58, 5 December 2009 (UTC)[reply]

But I just kept the rice water after I wash the rice. At first my motive is just to watering the plants later because the past few days were raining. Until yesterday only i found out that the shape of bottle had change and had harden. Err..does it means that I'm accidentally make of rice wine which produce carbon dioxide, and the carbon dioxide had harden the bottle?--perfection is not intact.. (talk) 19:26, 5 December 2009 (UTC)[reply]

Two weeks at that sort of temperature is certainly enough to ferment the starch. The bottle should have a bit of pressure inside, when you open the top it will outgas. There should be some nasty smell associated, your result is probably not drinkable. But plants may be able to tolerate it. Graeme Bartlett (talk) 21:25, 5 December 2009 (UTC)[reply]

Yes!!I just try to open the cap and it releases gases..so is it carbon dioxide release?I don't have lime water at home,so unable to test it.And there is nasty smell too!But after I open the cap and the gas had releases, the bottle had back to it's softness. So, can I conclude that rice water under the condition of high pressure and the temperature will results in fermentation? Does it apart of anaerobic respiration reaction?But there is no yeast inside.Besides that, does bacteria inside the bottles can replaced the yeast? --perfection is not intact.. 06:28, 6 December 2009 (UTC)

I doubt that the bottle itself has changed its hardness. It's just that the contents are under such high pressure that they're pushing out against the walls of the bottle really hard.

Incidentally, it's only a matter of time before those bottles burst and spray that rice water all over the place. It might not be a good idea to store them so close to a bunch of books. APL (talk) 21:52, 5 December 2009 (UTC)[reply]

Thanks for reminding me. =) I had placed the bottle in a bucket.I had an crazy idea..I wonder that if i still keeping the rice water in that bottle, how long does it takes to burst or does it will burst. It may test the "toughness" of the bottle too..haha xD --perfection is not intact.. 06:28, 6 December 2009 (UTC)

The yeast naturally arrives from the air. 75.41.110.200 (talk) 18:15, 6 December 2009 (UTC)[reply]

Indeed it does: in Belgium, Lambic beers are fermented by allowing wild yeasts (and some bacteria) to drift in and 'infect' the wort, rather than by adding cultivated yeasts as in more conventional brewing. On a similar note, I find that if I partly consume a carton of pure orange juice, but then leave it in my refrigerator for a couple of weeks, it begins to ferment, adding a not-unpleasant tang to the taste. 87.81.230.195 (talk) 00:50, 7 December 2009 (UTC)[reply]

Eye water

What is the substance composed of that wets and lubricates the human eye? Mac Davis (talk) 16:26, 5 December 2009 (UTC)[reply]

See tears. The standard "wetness" is referred to as "basal tears" and according to the article it contains contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Matt Deres (talk) 16:38, 5 December 2009 (UTC)[reply]

It is also called lachrymal fluid. Googlemeister (talk) 15:54, 7 December 2009 (UTC)[reply]

classical music and emotions

I find it very strange which songs trigger strong emotions in myself — e.g., I get flushing waves of "tingles" whenever I hear Pachelbel's Canon, even though I can't recall having any strong memories associated with the song. Bits of Wagner hit me similar. I would probably generalize that it is probably only classical music that affects me in this particular way (the waves of "tingles," whatever that is), but I'm not a particularly big fan of classical at all (and haven't spent long amounts of time listening or playing it or anything along those lines), and generally do not think of myself as a terribly sentimental person (nor someone who is unusually appreciative of or interested in music). What causes this? Is it just some sort of long-lost association to music playing in stores around Christmastime when I was a child? Some property of this type of music itself—mathematical "problems" being proposed and solved? Just a sign of how complicated and weird the human brain is? I know there has been a lot written and researched on music and the brain, but I'd love a summary, if someone out there has thought about it much. --Mr.98 (talk) 16:45, 5 December 2009 (UTC)[reply]

Anything in the music psychology article give you any clues? Between cultural conditioning and a biological predisposition to perceive rhythm, tonal scales, and harmonics, music can inspire a strong psychological response. It's pretty much impossible to pinpoint what exactly triggers this response for you, but a lot of research has been done on music and psychology. Nimur (talk) 19:15, 5 December 2009 (UTC)[reply]

I have heard the term aural orgasm used to describe this, although I can't find any particularly reliable sources that define it. Mitch Ames (talk) 02:57, 6 December 2009 (UTC)[reply]

Isn't this sensation the basic meaning of the word "thrill"? --Anonymous, 04:55 UTC, December 6, 2009.

The experimenting (or torturing) physician in Clockwork Orange was surprised at the strong reaction the young thug Alex had to classical music. Stanley Kubrick seemed to be making the same point: Alex epitomised unsentimentality and was not particularly well educated, but he responded to Beethoven, not pop, with bliss. BrainyBabe (talk) 19:37, 6 December 2009 (UTC)[reply]

Showering with contact lenses

Why do most manufacturers of soft contact lenses warn against showering with them in or using tap water to rinse out the lens case? What negative effects could showering with them in have on the lenses? Thanks! --98.108.36.186 (talk) 20:27, 5 December 2009 (UTC)[reply]

It's to do with contaminating the lenses. Normal tap water carries bacteria that, in the normal way of things, isn't a problem for most people. However, if it gets on your lenses the bacteria will be in contact with your eyes for hours at a time, and your tears can't wash it away properly. If these are lenses you wear for more than one day, the bacteria will continue to breed and grow, feeding on bits you haven't properly washed off the lens. And they'll still be there, more plentiful than ever, when you next put them on. It can potentially blind the lens wearer. Here [1]. 86.166.148.95 (talk) 21:51, 5 December 2009 (UTC)[reply]

Thank you! —Preceding unsigned comment added by 98.108.32.19 (talk) 01:45, 7 December 2009 (UTC)[reply]

Raccoon

I was just walking back across campus and I saw a small animal on the path ahead. I assumed it was a cat, but the nose was the wrong shape, so I assumed it was an opossum. No biggie; opossums are vicious, but they aren't likely to have rabies. Then when I was close enough to clearly make out the raccoon's markings (it's at night), I noticed that it was so content on drinking the contents of the puddle that it didn't notice me. I must have passed within five feet of it. It is a college campus, so perhaps it's just abnormally tame, but isn't an early sign of rabies an intense thirst? I did look at the article, but I can't tell whether the thirst comes before or after the animal is unable to drink. Just as a note, I did report it to campus police. Falconus^{p t c} 23:31, 5 December 2009 (UTC)[reply]

You seem to have been checking it out quite intently -- perhaps you're into raccoon drinking-voyeurism? :) I'm just saying that it's very easy to jump from "it was drinking and didn't see me" to "it must have a rabid thirst for it to not have seen me." DRosenbach ^{(Talk | Contribs)} 00:50, 6 December 2009 (UTC)[reply]

Well, I thought it odd, as most wild animals will at least look at you when you walk within a few feet. Falconus^{p t c} 00:56, 6 December 2009 (UTC)[reply]

Have you ever spent some time around racoons, even wild ones? Most that live close to people generally behave exactly as you describe, in my experience. When I was growing up, it was not uncommon to have racoons in my yard picking through the trash. They frequently didn't even pay me any attention, even if i yelled, threw rocks, whatever. I had to get close enough to grab them, and they would move far enough away for me to pick up all the trash. Then they went back to picking through it as soon as I walked away. They simply don't seem to pay humans much mind, and they certainly weren't much afraid of me. --Jayron32 01:08, 6 December 2009 (UTC)[reply]

My experience with urban raccoons is that they don't care very much about humans and regularly ignore them. (Dogs are another matter.) They are tough animals that nobody hunts near cities. --Mr.98 (talk) 01:34, 6 December 2009 (UTC)[reply]

Well, I guess I made a big deal out of nothing. I have just never seen an animal do that. Falconus^{p t c} 01:52, 6 December 2009 (UTC)[reply]

A little known fact about raccoons is that they wear raccoon coats not for fashion reasons. Bus stop (talk) 02:02, 6 December 2009 (UTC)[reply]

I often see raccoons around the house, and they are pretty intelligent creatures. They aren't likely to regard you with anything more than peripheral vision unless you do something problematic. Vranak (talk) 04:15, 6 December 2009 (UTC)[reply]

I don't know, I frequently see raccoons peering in through the bottom panel of my glass door at night. They're pretty curious. Looie496 (talk) 17:45, 6 December 2009 (UTC)[reply]

That's because you've got stuff they'd like to eat and rummage through, not because they care about you. --Mr.98 (talk) 20:10, 6 December 2009 (UTC)[reply]