exchemist

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.

I have zero intention of interacting with ChatGPT. Ever.

All part of finding out what background the questioner has. These are very specific questions about organic synthesis, not the sort of thing I would expect to be relevant to many fields outside organic chemistry itself, hence the question. This sounds pretty bad. I'd have expected at least some course notes, maybe of lectures or presentations from the teacher. Anyway, I hope the 2 links I have provided (the Libretext one and the chemguide one) are helpful. But you will need to know a certain amount to even understand what links like this are saying. I sense you are struggling because you have been plunged into 6th Form or 1st year undergrad level organic chemistry without being taught any of the basics first. Seems a bit daft to me.

I've no idea what you are talking about, I'm pleased to say. 🤣

Ah so you are studying organic chemistry then, but just as a module of a broader course. Fair enough. This issue of what goes where in a chemical equation: the reactants go on the left and the products on the right, since the arrow denoting the direction of reaction goes by convention from left to right. There is no rule as to which reactant goes first. Some reactions are also equilibria that can go either way, depending on the conditions, concentrations, pressures etc. In such cases it does not even matter which you write as reactants and which as products. These are shown with double -headed arrows or more properly this symbol: ⇌ . Coming now to your example of t-Bu iodide reacting with cyanide, I don't understand your answer. This is a nucleophilic substitution. The iodine atom, being electronegative, comes off as iodide, I⁻ leaving a carbocation, which attracts CN⁻ so that it forms a bond in place of the iodide that has gone. It is described here (with bromine instead of iodine but it will be the same process): https://www.chemguide.co.uk/mechanisms/nucsub/cyanide.html So the product will be t-Bu-CN. But for some reason you are showing t-Bu-I as reacting with a further I⁻. That can't be right. What are you using as a learning aid? Do you have a textbook? If not, what does the course expect you to be using? It can help in gauging what kind of answer is likely to he helpful, if one has an idea of where the questioner is coming from. Especially in the homework section.

OK, that's useful guidance. I'll keep it in mind. If you can't tell by now, you must be thicker than I thought. 😁

What are you studying and why do you need to get answers to these organic chemistry questions?

Why are you sending us what looks like a screen shot of someone else asking the identical question?

I've a horrible feeling we are being suckered by a bot here. It makes no sense to speak of "solving" a chemical equation, nor of describing one as having "terms" in it. This is terminology from mathematical equations. The previous enquiries from mcrestroom were also odd. It's hard to think that anyone who is actually attending classes in organic chemistry would be asking these questions in the way he - or it - does. I think I'm going to send in a report, just in case.

Just trying to understand your point here, is it that what would constitute "improvement" in the program could only be defined by its human users, so the AI would not be able to improve itself without human feedback as to what to change?

OK. This abstract: https://www.nature.com/articles/s41581-021-00533-0 says that apart from hypertension it had effects on the kidneys (not surprising), brain and immune system. Not clear to me how many of these factors are knock-on effects of hypertension, as opposed to other direct effects of excess sodium. There will be others who know much more about this, e.g. @CharonY

From this account of its history, Iosepa does not seem to have relied on brackish water. They had intermittents streams and built a reservoir: https://issuu.com/utah10/docs/uhq_volume76_2008_number4/s/10217177

What settlements were these?

I have similar suspicions.

The opinion of the people here is that you can safely use the specific grease for which you provided an MSDS, for the purpose that you indicated. Period.

No they don't. But for you it makes a change from spontaneous combustion and exploding thymus glands, I suppose.

Energy is a book-keeping, conserved quantity, with dimensions ML²/T². Momentum is another book-keeping conserved quantity, but with dimensions ML/T. Because both are conserved properties, they are specially useful in analysing physical systems and processes. As for what it describes, that has already been mentioned: the capacity of a system to do work: lift a weight, light a bulb of a certain wattage for a certain time or whatever.