exchemist

If this is for amateur chemistry, in say 100-250ml beakers etc, you can buy a magnetic hotplate and stirrer for about £50 or so. These are standard lab gear and work fine for low viscosity mixtures and solvents.

Arf arf.

I don't know if we have any polymer chemists here. I would think it quite hard to find a polymer with very different solubilities in water and ethanol since polarity and hydrogen bonding is so much a feature of both these solvents, though more for water obviously. I'm not surprised you are having difficulty identifying one.

That view is a bit of a simplification. Because electrons are wave/particle quantum entities, although they are detected only as "whole" particles, they also behave as if they are "smeared out" throughout the volume of the atom around the nucleus. One speaks of "clouds" of "electron density". This cloud is pretty diffuse in terms of mass density, because electrons are light particles compared to the nucleus, but it is not really true to say there is a lot of "empty" space in the atom.

Off-topic gibberish.

Ah yes, according to Wiki that is indeed one of the applications for it. Hope you don't spill any on your clothes.

What are you doing with butyric acid, if you don't mind me asking. It's got a pretty horrible smell (rancid butter, vomit etc).

I don’t know but I would expect the solubility to be quite good. I’m not sure I would expect full miscibility, as the alkyl group of butyric acid is quite big and might reduce the hydrogen bonding of propylene glycol too much.

Sure, but having a long neck also shapes how giraffes evolve. I do not see that intelligence is qualitatively different from having a long neck, as far as its effect on further evolution is concerned. The organism population does not choose its evolutionary path, even though the choices its members make may affect that path.

It seems to me you are artificially separating intelligence from other evolved traits, without justification. Of course a creature with intelligence will respond to its environment in ways a less intelligent one might not. But then a creature with keen sight will make different choices from one that has poor vision. But a more important objection is that it is the responses of individual creatures in individual circumstances that are "guided" by intelligence, if you will. There is no way for a creature to apply its intelligence to the evolution of the population of which it is a member, which is what would be need to it to be correctly termed "guided evolution". A population of intelligent creatures can't make choices about how it evolves.

This seems a bit meaningless. Animal intelligence is, like other traits, a product of evolution. All such traits obviously play a role in determining the future evolution of the organism. But as we don’t say evolution is “guided” by the presence of, say, a sense of smell, or a pair of legs, why should it suddenly be termed “guided” when an organism has evolved a degree of intelligence? It seems quite arbitrary.

Thanks yes it could be it, except my mystery message says "help me" instead of C-19. But if it's a bot or scammer that posts a PM and then gets banned he, she or it has done it to me twice now with the same message. But at any rate, from reading the previous thread on your mystery messages, it seems I need not worry too much about malware or hacking.

For the second time now in recent weeks, when logging in I get a message towards the bottom of the screen saying "help me", with a note that I have a personal message. This message disappears after a few seconds, without any further keystrokes from me. On neither occasion has there been any unread personal message in my In box. I don't like this. Is it a feature, a bug, or has the forum, or my laptop, been hacked?

What I said was if there is no sign of life I don't think an extrapolation can be made.

OK thanks. (The link you supplied takes one to the middle of some piffling argument with a creationist, but scrolling to the top makes it clearer.) But that's just about Mars. If there continues to be no sign of life there, I don't think it provides a basis for extrapolation to other bodies we have not yet detected. Of course it does detect evidence of past life, that's highly significant, hence the interest.

You will need to explain the relevance of that link. No, that is wrong. We do not know what the "normal" density of life is. We have no way to assess what is "normal" for the universe, due to the difficulty of detecting life elsewhere. According to my understanding (I am not a specialist in exobiology) the best we can currently do is look for the signatures of molecules that are relevant to the biochemistry we know from Earth, in the absorption spectra of planetary atmospheres. That is very hard to do, as planets are themselves too small to detect around anything other than very close stars, let alone measuring the absorption spectra of their atmospheres. The general default principle of cosmology, that there is no reason to think why our own solar system or galaxy should be special, suggests that since life has arisen here it will have arisen elsewhere, on planets with similar conditions. The question then becomes one of how common such planets are. That is a question people sometimes try to estimate but, given the size of the cosmos, it seems unlikely that these conditions occur nowhere.

What you say you have noticed is wrong. We simply do not know whether life occurs elsewhere, due to the difficulty of making the necessary observations.

Your blunder is to ignore the role of observation in science.

As I understand it, the thing about evolution through genetic drift is that it is not adaptive. Not all evolutionary processes are. They can be neutral or have negligible benefit and still become established in a population.

My understanding is that genetic drift is now a recognised mechanism in the evolution of organisms. Evolution simply means change over time, does it not? It is Darwinian evolution that relies on natural selection. That is just one kind of evolution, surely?

There are people here better qualified than me to answer this but, to get the ball rolling, my understanding is that cholesterol in the diet is not particularly well absorbed by the body. A lot is esterified (cholesterol is an alcohol) and not absorbed. The body makes a lot of its own cholesterol. The main bad actors seem to be elements in the diet that elevate levels of low density lipoproteins. These are emulsified droplets with fatty (lipid) cores and water-soluble outer layers. The low density ones have a big core and a small outer layer, i.e. carry a lot of lipid per unit protein. The lipid cores can dissolve cholesterol and transport it around the body for tissue synthesis and so on. (There are also VLDLs, IDLs and HDLs as well, all with different ratios of fat to protein.) What I have read is that eggs in the diet (egg yolks, specifically, as those are where the cholesterol is found) are not a problem in moderation. It is chiefly eating saturated fat, leading to creation of an excess of low density lipoprotein particles in the blood, that is the problem. Actually, from what I read it is not clear to me that the cholesterol molecule itself is a problem at all! It seems to be the breakdown of these excess LDL particles - which contain a great deal besides cholesterol - that leads to arterial plaque. But perhaps someone more knowledgeable will swing by and clarify this.

Very well. It would be imprudent to extend the advice given, on the basis of a singe substance with MSDS provided, to a blanket statement for an entire category on which we do not have the details. We cannot know what some suppliers may add to their silicone greases, or fail to remove from them. You should be able to appreciate that, I hope.

Ah yes could well be. It's been a while......

Well done for the research. Indeed, this level only makes sense to study if one has done some more basic chemistry first. Otherwise it will appear to be gobbldegook. In fact, all the listed reactions seem to be examples of nucleophilic substitutions (some of which will proceed by SN1 and some by SN2 mechanisms). My guess is that knowledge of these substitutions is what the exercise is designed to test. But our poster hasn't said a word about that and doesn't seem to have the knowledge even to write the formulae out. It looks as if it's pitched at quite the wrong level.

I've been deeply bored by computing ever since I was made to futz about with Fortran statements on punched cards at Oxford in the mid 70s. Christ it was dull. We had a ghastly and rather tyrannical S. African teacher called Sonya, I remember, whom we nicknamed "Biltong". To this day, my eyes water with boredom whenever the subject crops up, I'm afraid.