April 30

Known articles: Feed conversion ratio (FCR), Efficiency of food conversion (ECI)

The definitions given in the articles cited above either explicitly refer to mass (FCR, with the discussion noting that substantial problems exist with respect to dry/wet mass) or seem to be undefined (ECI). I am looking for conversion ratios that allow an understandable comparison for human food production. An example would be human consumable calories and human consumable protein (2 different values). The sum of the caloric input fed during the raising of an animal would be divided by the sum of all calories of products generated from the animal. Thus, the weight of bones and skin etc. would not go into the equation, neither would fodder not consumable by humans (grass) enter the equation. The desire for a "primary" conversion ratio relates to the case, where the fodder itself has a feed conversion ratio (raising fish from plant matter to be fed to other fish). Here the fodder would be accounted with the primary calories used to produce it. Do this or similar definitions exist? Do data for this or similar parameters exist? --Vigilius (talk) 09:26, 30 April 2017 (UTC)[reply]

A long time ago, I learned that bacterial and viral infections are relatively easy to treat. Bacterial infections can easily be treated with antibiotics. Viral infections can easily be prevented by and treated with vaccines. Then come fungal infections. Fungal infections are harder to treat, because they resemble animal cells. Then come parasitic infections, like worms. They are said to be difficult to treat, because they're multicellular. Why are multicellular organisms difficult to kill because they are multicellular? Also, if insects are treated with insecticides, then what would be used to treat large, vertebrate mammals (deer, rabbits, field mice, humans) who may steal food from produce farms, along with carnivorous, large, vertebrate, mammalian predators (wolves, foxes, cats, maybe humans from neighboring tribes) who may be attracted to the herbivorous prey on the farms? 50.4.236.254 (talk) 12:14, 30 April 2017 (UTC)[reply]

I would have to disagree with your statements that bacterial and viral infections are easy to treat. Some are, but both still kill plenty of people. As for why treating eukaryotic infections can be more difficult, they are more similar to human cells (eukaryotes as well, of course) than prokaryots. Therefore finding therapeutic targets in them that do not case unacceptable side effects on the host cells can be more difficult. Fgf10 (talk) 12:28, 30 April 2017 (UTC)[reply]

Note in particular that viral diseases are rarely treated using vaccines. Most vaccines targetting viral diseases are

vulvovaginal candidiasis [4], i.e. a fungal disease. (Although we should be careful about reading too much into what's being developed since it can reflect funding as much as anything.) Nil Einne (talk) 13:46, 30 April 2017 (UTC)[reply

]

Large, multi-cellular organisms are not necessarily and heartier, more resilient, or more difficult to kill than bacteria, such as prokaryotic. In fact, the opposite is likely true. Bacteria are quite resilient, and many can survive extreme conditions that few, if any, eukaryotes could survive. What you are talking about isn't the organisms' resilience, but rather our ability to treat them as infections. That's a very different problem. Antibiotics work great on bacteria because the mechanisms by which they were attack and kill bacteria, but do little to nothing against eukaryotic cells. This is because we are so different/distantly related from bacteria that we have a lot less in common with them. For example, penicillin attacks the peptidoglycan cell walls of bacteria, but we (humans) do not have peptidoglycan cell walls in our cells. Thus, something attacking peptidoglycan won't harm us. A fungal infection or, even more so, a parasitic worm is much harder to treat as it is more closely related to us. There are tons of things that are completely effective at killing fungi or parasitic worms, but most of them will kill you as well. A treatment isn't of much value if it kills the patient. This is even more apparent in cancer treatment; cancer cells ARE your cells, just slightly mutated, so almost anything really good at killing cancer cells is also really good at killing you. With cancer, we often have to accept a tradeoff of trying to find a chemotherapy that kills the cancer faster than it kills you, but that is why chemotherapy is often so unpleasant for the patient. Killing cancer is easy. We can light it on fire or expose it to cyanide, both of which will also kill a fungal infection or a parasitic worm... but would also kill you. Ideally, you'd want to do something like program the immune system to attack fungal infections, parasites, or, most especially, cancer cells, which is the basis of immunotherapy. Barring deficiencies, the immune system is excellent at discriminating between your own cells, which it wants to leave alone, and invading cells. So again, just to clarify, it isn't that fungi or parasites are any more resilient or difficult to kill than bacteria that makes them hard to treat, it's that they are difficult to kill without killing you because their cells and biochemistry are much close to our own. --OuroborosCobra (talk) 16:46, 30 April 2017 (UTC)[reply]

I know this is a very hypothetical question, but since I was a child I thought that the idea life couldn't exist in extreme environments was ridiclous. And now we are finding life in more and more environments.

So, based on our knowledge of physics could it be possible for a life form to exist on a star? 95.148.212.198 (talk) 14:22, 30 April 2017 (UTC)[reply]

I don't believe we have the knowledge to answer that at present. However, the complex magnetic fields on stars could be one possible indication of "life". StuRat (talk) 14:46, 30 April 2017 (UTC)[reply]

Stu, did you make that theory up or do you have a reference? Henry^Flower 20:14, 30 April 2017 (UTC)[reply]

As I said "I don't believe we have the knowledge to answer that at present". Also, see emergence. StuRat (talk) 23:56, 30 April 2017 (UTC)[reply]

You must be having trouble sitting after that one. Ian.thomson (talk) 00:01, 1 May 2017 (UTC)[reply]

How should we know about life in the universe? We checked out one system and about half of its planets and moons. We are also still about to discover/develop our first/own artificial intelligence. Maybe wait 20-30 years and ask them! --Kharon (talk) 22:50, 30 April 2017 (UTC)[reply]

My reason for asking is because scientists (maybe more scientific press) say that life needs certain conditions, but conditions for our lifeforms don't mean that is necessary for other life. Thanks for replies anyway 95.148.212.198 (talk) 13:53, 1 May 2017 (UTC)[reply]

"

There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know" (Donald Rumsfeld, 2002). :-) Alansplodge (talk) 16:09, 1 May 2017 (UTC)[reply

]

It would be nice to know some unknown unknowns sometime before i pass on :-) 95.148.212.198 (talk) 16:25, 1 May 2017 (UTC)[reply]

Oh, we will probably, but everyone will find it disappointing. Humans have mastered telepathy, but we complain it is too expensive. Tigraan^{Click here to contact me} 15:20, 2 May 2017 (UTC)[reply]

@Tigraan No, Telephony != Telepathy. Blooteuth (talk) 22:32, 2 May 2017 (UTC)[reply]

• The answer is quite simply "no". While life could take many forms, it would be hard to imagine any form of life which does not rely at least basically on
  condensed matter, that is where atoms and molecules combine in some way to form stable forms such as liquids and solids. Stars are, quite simply, too hot for any condensed matter to form, the consists mostly of a form of matter called plasma, where even neutral atoms find it hard to exist; such matter consists mostly of ions and free electrons. There's no way for life to self-organize in such an environment (a pre-requisite for Abiogenesis) , or indeed to maintain any semblance of order. Any solid matter would be vaporized in short order if placed close enough to a star such as the Sun. --Jayron32 15:32, 2 May 2017 (UTC)[reply
  ]

What about flattened-flatfish shaped (the gravity!) life on the surface of neutron stars based on the strong force? Or would that only be science fiction? Sagittarian Milky Way (talk) 21:08, 2 May 2017 (UTC)[reply]

The last one. --Jayron32 21:17, 2 May 2017 (UTC)[reply]

Thanks for the links. I still hope life can exist in very extreme conditions but you answered my question (i.e. based on our current knowledge of physics) 95.148.212.198 (talk) 20:41, 2 May 2017 (UTC)[reply]

I have seen a solution from the solution book (translation):

...

1.3. Let us first consider how evaporation will occur if the glass is covered with a lid and pumped out all air from under it. While the water vapor under the lid is small, the liquid will evaporate. Water molecules will always fly out of the water, and a couple of molecules will return to the water, that is, condense. After a while, a dynamic equilibrium will be established in the glass: the number of molecules emitted from the water will be equal to the number of molecules returning from the water. If you remove the lid, the water starts to evaporate continuously, and the number of emitted molecules will be the same as when the glass was covered, because the evaporation process depends only on the movement of molecules in the water, the number of molecules returning to the water depends on the amount of water vapor in the air Over a glass.

Let us estimate the number of molecules emitted from the water per unit time at equilibrium. It is simpler to calculate not this number, but the number of condensing molecules of vapor equal to it.

Let the unit volume of air above the lid contain n water vapor molecules. The number n depends only on the air temperature, it was measured experimentally; There are tables of the dependence of n on temperature. During the time interval t of the surface of the water, only those molecules of vapor (the velocity of the molecule v) that were at the initial instant of time no more than ${\displaystyle v_{B}t}$ (${\displaystyle v_{B}}$ — Vertical velocity of the molecule). In other words, the water surfaces reach those molecules that are in the volume ${\displaystyle Sv_{B}t}$ Above the glass (S-cross-sectional area of ​​the glass). Consequently, ${\displaystyle (1/2)nSv}$ of vapor molecules is condensed per unit time.

As already noted, the number of evaporating molecules with the lid removed will be the same as when the lid is closed. But the number of condensable molecules depends on how many molecules of vapor are contained in a unit volume of air above the surface of the liquid. We assume that the air humidity is close to normal. Humidity (relative) refers to the ratio of the number of water vapor molecules contained in air at a given instant of time to the maximum possible (that is, the number of vapor molecules per unit volume at equilibrium). Normal humidity is about 60 - 80%. We assume that the air humidity is 50%, that is, per unit volume of air contains n / 2 molecules of water vapor. In this case, as follows from the previous consideration, ${\displaystyle (1/4)nSv}$ molecules should condense into the water from the vapor. However, it would be so only if there are only water vapor over the water, and not a mixture of air and steam. In the presence of air, the molecules from the water fly off without collision only by the mean free path ${\displaystyle \lambda }$ (This distance is ${\displaystyle ~3\cdot 10^{-5}cm}$, see problem 1.1), they move further from the surface of the liquid at a very low rate (in comparison with the thermal one). Therefore, the number of condensable molecules is determined not by the density of the vapor at a great distance from the water, but by the density of the vapor at a distance of the mean free path. Assuming that the vapor density in the direction perpendicular to the surface of the water changes linearly, and at a distance of about 1 cm it is already n / 2, we find that the density of water vapor at a distance ${\displaystyle \lambda }$ Is approximately equal to

${\displaystyle {\tfrac {n}{2}}+{\tfrac {n}{2}}(1-\lambda )=n(1-{\tfrac {\lambda }{2}})}$

Thus, about ${\displaystyle n\lambda Sv/4}$water molecules per unit time evaporate from the surface of the water. After this consideration, we can answer the questions posed in the problem.

A) The water glass contains ${\displaystyle n_{B}Sh}$ water molecules, where ${\displaystyle n_{B}=3\cdot 10^{22}cm^{-3}}$ is the number of water molecules per cm3 (see previous problem), and h is the height of the glass, which we assume to be 10 cm. All the water evaporates in a time ${\displaystyle {\tfrac {4n_{B}h}{\lambda nv}}=0.6\cdot 10^{6}sec=7days}$

(at ${\displaystyle t=25^{\circ }C,v=60000cm/sec,n=10^{18}cm^{-3}}$)

—  MEPhI , Solutions (Google Translate)

I think that the approach is taken from lecture 39 and speed ${\displaystyle v}$ and number density ${\displaystyle n}$ are not known. I have made a solution from specific heat of evaporation (for water ${\displaystyle 2\cdot 10^{6}{\text{J/kg}}}$). Also the power of the sun = ${\displaystyle 1000{\text{W/m}}^{2}}$. And assuming area of the glass as ${\displaystyle 16{\text{cm}}^{2}}$ I got 6 days. But I want to calculate somehow the power of heating by air (if the glass is put not at direct sun rays). How to do this?

I think we could use the psychrometric tables to find temperature difference of air and water (for humidity 70% - average for Caltech location), and then use formula for heat conduction ${\displaystyle P={\tfrac {\lambda }{d}}A(T_{H}-T_{L})}$.

${\displaystyle P={\tfrac {0.2}{0.003{\text{ m}}}}0.0064{\text{ m}}^{2}(5{\text{ K}})=2{\text{ W}}}$.

Is it acceptable?

Username160611000000 (talk) 16:00, 30 April 2017 (UTC)[reply]

That sounds like one of those pieces of information "from the gut" or that "just feel right". However, could it be that a metal spoon in the glass changes the thermal shock on the glass? Metal is very good conductor of heat, and maybe it absorbs some heat avoiding a break. --Clipname (talk) 17:23, 30 April 2017 (UTC)[reply]

Yes, that's just common sense. The spoon also spreads the flow so that the temperature gradient in the glass is reduced. It's still possible to crack a cold glass with boiling water, of course, even with a silver spoon inside. Dbfirs 20:18, 30 April 2017 (UTC)[reply]

I'd think that the thermal shock would be so quick that the spoon wouldn't have enough time to make a difference. Sure, it's going to absorb some heat and then conduct it but it would take time to do that. Glasses break in the second you pour in too hot a liquid. 95.148.212.198 (talk) 14:01, 1 May 2017 (UTC)[reply]

Has anyone actually ever managed to break a glass by pouring in hot water, or dropping it into a bowl of hot water? Ever since I was warned against it as a child I've been trying to make it happen, and never succeeded. DuncanHill (talk) 14:21, 1 May 2017 (UTC)[reply]

Try putting it in the fridge first. If the glass is already warm, then the temperature gradient is lower, of course. It's probably easier to achieve (if that's your aim) with older, thicker glass. Dbfirs 15:29, 1 May 2017 (UTC)[reply]

Back in the 70s, McDonalds sold Star Wars glasses. They were very thin glass and easy to break by quickly making them either hot or cold. 209.149.113.5 (talk) 16:25, 1 May 2017 (UTC)[reply]

I broke two glasses by pouring in boiling water when I was younger, so it's definitely possible even without cooling the glass down beforehand. Maybe glass is more resilient now, but I stopped putting hot water into cold glasses after the second time one cracked.95.148.212.198 (talk) 16:35, 1 May 2017 (UTC)[reply]

I had a glass bowl that exploded (like shattered and sprayed glass around the kitchen) when I put hot mashed potatoes in it. It does happen. Also read this. --Jayron32 17:03, 1 May 2017 (UTC)[reply]

Whether it will shatter does depend both on the "starting temperature" of the cup (hence the suggestion to put it in the fridge first), and the type of glass. Duralex, for example, can handle significant temperature swings without cracking. 14:09, 2 May 2017 (UTC)

A

Prince Rupert's Drop is an interesting example of the stress in glass due to temperature change. DMacks (talk) 05:22, 3 May 2017 (UTC)[reply

]

Are there any living species with both evolved and separately living transitional form? That is, when one group parted ways with the other and retained transitional form, while the other group evolved further. Thanks.--212.180.235.46 (talk) 17:44, 30 April 2017 (UTC)[reply]

A neat way to see how you may have evolved is to lay your arm on a flat surface so that the underside and the palm of your hand face up. Touch and press together your pinky finger and thumb and then raise your hand up at the wrist just a little bit, as shown in the video. If there is a raised band in the middle of your wrist, you have a vestigial muscle in your forearm called the

palmaris longus. The ridge you see is a tendon that connects to it and that muscle is either absent from both arms, or missing from one arm, in an estimated 10-15% of the population. If you’re missing this muscle there’s no need to worry because it’s essentially useless! Studies have shown that it has absolutely no effect at all on a person’s grip or pinch strength.

— http://www.sun-gazing.com/tendon-protrude-wrist-like-means/

50.4.236.254 (talk) 19:02, 30 April 2017 (UTC)[reply