Can anyone explain to me how Deuterium slows down neutrons?

nukeman

Hey all,

First off, am I correct in saying (generally) that Deuterium slows down neutrons? That's why nuclear reactors use it because its easier to catch neutrons that are going slower. ??

Does this apply to all neutrons?

Example, lets say I drank a nice tall glass of delicious Heavy Water :). When the Deuterium interacts with whatever it comes in contact with in my body, will it slow down the neutrons of it?

Can someone explain to me how deuterium does slow down neutrons?

Thanks everyone.

russ_watters

Your body doesn't have any free neutrons.

nukeman

Thank you

nukeman

I am trying to find a whole collection of possible solutions HOW deuterium could possibly slow down the circadian clock.

berkeman

Say which what? Have you read something (reliable) that you can post a link to?

nukeman

http://warmingsystem.blogspot.ca/201...deuterium.html

the link to the original post on physorg is down right now...

M Quack

http://www.ncbi.nlm.nih.gov/pubmed/1330336

Have not read the article, so I don't know if they say anything about the mechanism.

sigoldberg1

It's pretty simple. The special thing about deuterium is that it does not absorb (thermal) neutrons (very much, compared to hydrogen), i.e. the thermal neutron absorption (also called capture) cross section for deuterium is 3E(-4) vs 2E(-1) for ordinary hydrogen H(1). So the only thing that the neutrons can do is scatter. See the table near the end of
http://en.wikipedia.org/wiki/Neutron_cross_section . Note that Oxygen(16) also does not absorb much. So heavy water D2O scatters energetic thermal neutrons with little absorbing. It is the scattering of the hot neutrons off of the room temperature deuterium oxide (heavy water) "moderator" which slows them down. For reactors, the neutrons are then absorbed by Uranium, which then undergoes fission.

So why are deuterium and oxygen such poor absorbers compared say with elements with an odd number of nucleons? It is because of the magic numbers 2 and 16 in their atomic weights. The reason is a combination of quantum mechanics and spherical dynamics, and on a deeper level Lie Groups (I think) and somewhat similar to why Helium (with two electrons this time and Argon with 18 electrons) are "noble" gases and are basically unreactive chemically. The big philosophical point is that in this instance, Pythagoras (550 BC) was pretty much completely correct, "All [elementary structure] [really] is [integer] number" on the deepest level. To me this is perpetually amazing. On the other hand, in retrospect what else could it have been?

Pretty much all of the neutrons in your body are locked up inside the nuclei of atoms. Heavy water won't affect them at all. It is only the free neutrons released from radioactive transmutation of the elements (e.g. decay) that are affected.

sigoldberg1

Oops, sorry, never mind the above. While true, I completely missed your circadian rhythm question.

I do not know much about the enzymes involved in the mechanism of circadian rhythm but there are many known "kinetic isotope effects" involving enzymes in biology, some involving isotope substitution in the solvent, but most in the substrate. If we are looking at a pure heavy water effect in the solvent, I suppose alterations in hydrogen bonding might be one possible mechanism, or involvement of a water molecule in the active site of a particular enzyme. The altered mass of the heavy isotope compound is the reason for the difference, sometimes via tunneling. Vibrations also differ.

Since 1992 very much indeed has been learn about circadian rhythm, esp. in drosophila. You might look for genetics of circadian rhythm. A quick search shows no real biochemistry experiments yet.

Drakkith

I don't see anything here about circadian clocks, where are you getting that from?

nukeman

http://cbn.eldoc.ub.rug.nl/FILES/roo...Oklejewicz.pdf

Drakkith

Well, how does the circadian clock work in the first place?

K^2

Circadian Rhythm.

Protons and deuterons diffuse at very different rates. Heavy water and regular water diffuse at noticeably different rates. Since so many metabolic processes are regulated by diffusion, fact that heavy water can alter various biological cycles is not surprising.