Wikipedia:Reference desk/Archives/Science/2018 March 13

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.

March 13

What is the reason that it's not recommended to put hot foods in the refrigerator?

Normally people don't put hot food in the refrigerator. Is there a basis for that? if there is, what is the reason for that? 93.126.116.89 (talk) 00:34, 13 March 2018 (UTC)

If the food's too hot and too big (i.e. it has too much thermal energy), it can warm up the contents of the refrigerator so rapidly that the cooling equipment can't keep up, so you'll end up warming the refrigerator's interior too much. Nyttend (talk) 00:40, 13 March 2018 (UTC)

Hot food will produce allot of water vapor that will condense and freeze at the cooling element, building up a growing ice coat around it which prevents the fridge to cool down the air effective. Its also a waste of energy because the hot food will cool down fast without investing additional electrical energy with the fridge. Additionally the whole concept of preservation with a refrigerator is to keep the temperature low enough to keep all microorganisms in a Hibernation state. Every time the food gets warm again the microorganisms start eating and reproducing, thereby cutting down the time of the food they are on to the state of spoiled. So its no imminent drama if you put some hot food into your fridge but its still wrong in many ways. --Kharon (talk) 05:23, 13 March 2018 (UTC)

Also the water vapor from the hot food will condense ON the hot food as well and make it soggy. 2601:646:8E01:7E0B:0:0:0:64DA (talk) 06:41, 13 March 2018 (UTC)

Also, if the hot food is in a type of container that will crack from thermal shock, you don't want that to happen. --69.159.62.113 (talk) 16:54, 13 March 2018 (UTC)

I used to keep pot of boiled milk in refrigerator. Did so every day for a week or two. The acrylic sheet on which I used to keep the pot gradually developed cracks due to sudden temperature difference. Now I let it cool down a bit but when it is still hot I put in refrigerator to cool it quickly to prevent growth of microbes. manya (talk) 07:45, 13 March 2018 (UTC)

The best way to cool an item like this is to immerse it in cold water for a while, rather than put it in the refrigerator, for the reasons listed above. --TammyMoet (talk) 13:05, 13 March 2018 (UTC)

The problem that the contents of the fridge will heat up if you put hot stuff into it, is a lot worse with modern fridges that are a lot more energy efficient compared to older ones. Old fridges with poor thermal insulation can more easily deal with hot food, because they are pumping out heat at a much faster rate anyway. To store freshly prepared food you should cool it asap using e.g. cold water as suggested above. I usually put the food cooled in this way in the freezing compartment of the fridge, not to freeze it but to cool it rapidly down to just above freezing point. Also, the freezing compartment is isolated from the rest of the fridge, and the fridge will start to work immediately if you put something in there, while if you put something in the fridge, it will only start to cool the contents if the temperature rises above a set point. The faster you cool the food to below 10 C the better, a rule of thumb is that every hour at room temperature takes away about one day of safe storage time at fridge temperatures. Count Iblis (talk) 18:35, 13 March 2018 (UTC)

I just stick it outside for a few minutes. At −37 °C (−35 °F) it don't take long. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 23:03, 13 March 2018 (UTC)

Err. What do you do in those few short and very long summer days in Cambridge Bay when temperature it gets up into in to the 80's ? Do you just eat Eat MacDonald's hamburgers and French fry takeaways? Come on. You must have fridge, otherwise you beer will go off. Oh! That is providing you're allowed to drink beer up there  :¬) --Aspro (talk) 16:27, 15 March 2018 (UTC)

I'm not sure the last time I saw 80 °F (27 °C). Couple of summers ago we were in Hay River, Northwest Territories and it was 25 °C (77 °F) and that was more than hot enough. For MacDonald's I would need to go to Yellowknife and the return fare is over $2,000 so not really worth it. Of course we can get take-out burgers and fries from any of the 5 restaurants in town. Beer is allowed here but again you have to get it from Yellowknife, so hard liquor gives you the best value. And every house has a fridge and most houses will have a chest freezer as well. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 12:44, 16 March 2018 (UTC)

Cormorant identification

Cormorants at the Jamestown Ferry

What species are these? They looked more like Phalacrocorax auritus than any other North American species I found, but these look green, not the black of this species. But maybe it's my colorblindness, making me imagine that I'm seeing a dark green when it's really black. Nyttend (talk) 00:35, 13 March 2018 (UTC)

I'm not good with cormorants, but these don't appear green to me. However, while I have perfect colour vision, I'm not sure we can trust this image's colours as it has clearly been altered to compensate for the low-light. Matt Deres (talk) 02:03, 13 March 2018 (UTC)

Well, I used flash, but it's just as it came from the camera; I don't have any photo-editing software aside from Windows Paint. Nyttend (talk) 02:27, 13 March 2018 (UTC)

Yes, but the camera itself has built-in imaging software that takes the picture from raw data to jpeg. - Nunh-huh 05:29, 13 March 2018 (UTC)

Ah, okay; I thought this meant that it had been photoshopped. Nyttend (talk) 12:11, 13 March 2018 (UTC)

That definitely looks like a Double-crested cormorant to me. Though in the image given in that linked article, there are clearly some green shades. Polyamorph (talk) 12:17, 13 March 2018 (UTC)

Sterilizing hamsters

Miniature hamsters I bought (here in China) used to breed. Now they do not. I buy new ones when they die of old age. I suspect the wholesaler gives them some drug just before selling them to stop them from breeding. Is this possible. Anna Frodesiak (talk) 13:07, 13 March 2018 (UTC)

The answer may be more simple. “Warning. The following may read like something that has just come out of the Twilight Zone.“ You know how the Monsanto company spend billions convincing us that the GM's are safe and they are, - aren’t they? Because Monsanto spend billions cherry picking scientific proof that shows no health issues. But what about the Glyphosate herbicides? I just had to google Hamsters, Glyphosate, and Infertility and loads of stuff comes up. American human fertility rates are plummeting ( there could be other reasons for this but this includes couples that are desperately trying to start a family). What are you feeding your hamster on? The cheap GM stuff from the pet store? Make your own mind up. Please report back on how you got them breeding again. --Aspro (talk) 14:56, 13 March 2018 (UTC)

@Aspro: I just had to google Hamsters, Glyphosate, and Infertility and loads of stuff comes up. If you googled "moon landing hoax" or "electrosensibility health scandal" or "homeopathy discredited by Big Pharma" or "Holocaust did not happen" or "how dowsing works" or anything of the kind you would also have seen loads of stuff come up. You inconsciously preselected what conclusion you expected, the query reflected that and the results obliged.

Now I know next to nothing about hamsters, fertility, and glyphosphate, and it may well be that you are correct. But you should really, really, really have put up sources rather than giving a rant with vague pointers (and prefacing it with a warning that is is a rant does not make it any less a rant).

For instance, here's a serious-looking source that says (see paragraph I.C) that GM crops in China are mostly limited to cotton and papaya (at least until 2010), i.e. not stuff hamsters eat. Presumably the OP's hamsters are fed on local (=Chinese) pet food. Tigraan^{Click here to contact me} 16:53, 13 March 2018 (UTC)

• As this is the science desk, I need to point out that Aspro's rant above has no basis in peer-reviewed science. Read it at your own peril. Fgf10 (talk) 18:44, 13 March 2018 (UTC)

Perhaps they stopped selling you females? Greglocock (talk) 15:45, 13 March 2018 (UTC)

I have not heard of terminator technology being used on livestock, but I cannot formally rule it out. I know of less-than-reversible sorts of male contraception like cottonseed oil that affect humans ... no idea how it affects a miniature hamster. I also have no idea if the entire randy colony of hamsters has simply caught a bad case of chlamydia (apparently Chlamydia muridarum does infect hamsters, according to our article), nor whether that sterilizes hamsters. In biology anything is possible, but not much is likely. Wnt (talk) 23:31, 13 March 2018 (UTC)

Just to let you all know, we feed the hamsters grains we buy, like whole oats, and also vegetables and peanuts. No pet store food.

Also, this sterility is present in the last few groups of around 8 hamsters we bought. We just got a new group and they are still too young to breed. We shall see. Anna Frodesiak (talk) 01:07, 14 March 2018 (UTC)

Ooh, I just found Chemical castration. Could the wholesaler get a hold of some of these chemicals, like SpayVac? Anna Frodesiak (talk) 01:09, 14 March 2018 (UTC)

Chemical castration isn't really permanent, and it seems like an added expense is implausible. I mean, it seems more conceivable (or at least more amusing) to picture a hamster assembly line passing beneath automated robot assembly probes that implant intrauterine devices in all the females. (I suppose every once in a while they get a male by accident, or the maintenance technician's finger, with tragic results) Wnt (talk) 03:11, 14 March 2018 (UTC)

But suppose a wholesaler could give the hamsters something in their food just before sale that would stop them from having babies. Their sales would increase. Anna Frodesiak (talk) 12:10, 14 March 2018 (UTC)

I was going to say I never heard of any such thing and doubted it was possible, but naturally I just had to try a quick web search first... came across [1]. Here is the PubChem entry. Says it causes ovarian tumors in mice but not in rats, and "in mice, the ED50 for the reduction in small oocytes by 4-vinylcyclohexene was 2.7 mmol/kg, whereas, no detectable oocyte loss occurred in rats at the highest dose of 4-vinylcyclohexene (7.4 mmol/kg)." PubChem as a compilation isn't exceptionally reliable, but it copied that abstract from here. Another study says " 4-vinylcyclohexene diepoxide (VCD, 40 mg/kg), was used to induce premature ovarian failure (POF). Methylparaben (MP, 100 mg/kg), propylparaben (PP, 100 mg/kg), and butylparaben (BP, 100 mg/kg) dissolved in corn oil were treated in female 8-week-old Sprague-Dawley rat for 5 weeks." [2] It also has some effect on hamsters: "Siberian hamsters were treated with VCD (240mg/kg i.p. daily for 10 days) during short days, and outcomes were compared with reproductively active females that were maintained and treated in long days. Primordial follicle numbers were significantly reduced by VCD under both day lengths, and reproductive quiescence in short days did not appear to render the ovaries less susceptible to VCD-induced follicle depletion." [3] I don't know if it works on proles but given the widespread use as an industrial chemical I imagine the data should be available. Wnt (talk) 15:30, 14 March 2018 (UTC)

Holy moly, Wnt. I think that may be it. Anna Frodesiak (talk) 19:24, 18 March 2018 (UTC)

Thank you all for the very thoughtful answers! Anna Frodesiak (talk) 19:24, 18 March 2018 (UTC)

Discarded plastic bags everywhere while there is a shortage of fuel

I watched a documentary, and it showed people using discarded plastic bags as cooking fuel. The people were breathing fumes. Is there a cooker that can burn old plastic bags without harming people? Anna Frodesiak (talk) 13:10, 13 March 2018 (UTC)

Bags are, in general, polyethylene. As a fuel it's pretty clean. As a pure hydrocarbon it contains only carbon and hydrogen, so the exhaust products will be carbon dioxide and water vapour. At worst, if burned in restricted airflow, carbon monoxide.

PVC, also used to make thin films for packaging, is another matter. The chlorine content is a problem if you're going to burn it, as are the plasticizers. Andy Dingley (talk) 16:24, 13 March 2018 (UTC)

The fact that the completely burned products are safe does not make burning the substance itself safe. One of the byproducts of incomplete combustion of polyethylene is surely going to be ethylene oxide. For that, the CDC states, "Ethylene oxide gas may produce immediate local irritation of the skin, eyes, and upper respiratory tract. At high concentrations, it may cause an immediate or delayed accumulation of fluid in the lungs. Inhalation of ethylene oxide can produce CNS depression, and in extreme cases, respiratory distress and coma. In some persons, ethylene oxide exposure may result in allergic sensitization, and future exposure may cause hives or a life-threatening allergic reaction." Looie496 (talk) 16:56, 13 March 2018 (UTC)

Whilst ethylene oxide wouldn't be a good thing, you're not going to produce that (or at least, not release a significant quantity of it) for a typical polyethylene flame in an adequate air supply. Andy Dingley (talk) 17:34, 13 March 2018 (UTC)

Google for diesel from waste plastic and take also a look on The Ocean Cleanup project. There are some people from India and also in Saxony, Germany. Buying meat in a super market today, You get a plastic package made from several plastics and coatings of several other plastics to keep fresh and save material. Conventional plastic recycling on this fails caused by the several different plastic types in one piece of plastic. Later production should be a process like performed in an oil refinery. --Hans Haase (有问题吗) 18:13, 13 March 2018 (UTC)

Plasticizer chemicals have a potential to be very harmful since they are suspected to interfere with human hormones. However "fuel" can contain very harmful chemicals as well, especially in developing countries where unrefined Crude oil is often used, since these can contain for example Naturally occurring radioactive materials and other poisons. --Kharon (talk) 12:14, 14 March 2018 (UTC)

"adequate air supply" may be the sticking point here. Many cooking fires are extremely inefficient.

Stoves, even simple camping stoves, with proper air-flow can greatly improve the quality of life for people still relying on cooking stoves. At least, that's the premise of a number of businesses and charities that supply such stoves to third-world countries. BioLite#HomeStove is the first one that comes to mind, but there are a few of them. ApLundell (talk) 00:09, 16 March 2018 (UTC)

Hi ApLundell. So, can that run on old plastic bags? Anna Frodesiak (talk) 07:15, 16 March 2018 (UTC)

"Improved cooking stoves" have been a stalwart of the appropriate technology movement since the start. Victor Papanek, for one, has written about them. Andy Dingley (talk) 10:19, 16 March 2018 (UTC)

Almost certainly not. A nice stove like that one will probably burn them more completely than normal cook fires, but plastics are too complicated, and unpredictable for an ordinary stove to reliably burn them safely. There's probably some specially made bio-plastics that would be OK in a good stove, but they would be a small minority, and there'd be no reliable way to identify them. ApLundell (talk) 22:15, 19 March 2018 (UTC)

What I'm getting at is a stove that safely runs on plastic bags. It would stop people from getting sick from fumes, would provide fuel, and kids would be running around gathering old bags for mom, which would clean up the environment too. Is there such a stove?

Anna Frodesiak (talk) 07:15, 16 March 2018 (UTC)

No, there is not. Almost every kind of plastic will release toxic fumes when burned, to a greater or lesser extent. They will burn, but they will not be safe to burn. Bastun^{Ėġáḍβáś₮ŭŃ!} 09:23, 16 March 2018 (UTC)

There are a couple companies apparently talking about offering stoves intended to burn plastic. The one that seems farthest along is the Energant K2, which claims to be able to safely burn fuel that is up to 8% plastic. [4] Modern high-efficiency stoves can reduce smoke by ~95%, and the same high efficiency helps to more thoroughly burn the fuel and reduce the number of toxic products. This would obviously be an advantage if one is going to try burning plastic. Of course, it also matters what you burn. Burning polyethylene is already much less hazardous than burning PVC or fluorinated plastics. However, it seems like their product development has stalled since they discussed it more than 3 years ago but it is still not available for purchase as far as I can tell. Perhaps the idea of a safe stove burning (small amounts) of plastic was still more wishful thinking than reality. Dragons flight (talk) 11:11, 16 March 2018 (UTC)

I guess, You will find the information, You are looking for in Polyoxymethylene dimethyl ethers (OME), (in German Polyoxymethylendimethylether or Oxymethylendimethylether). --Hans Haase (有问题吗) 08:19, 17 March 2018 (UTC)

Bastun, never safe, understood. Dragons flight, only 8% max., and wishful thinking on the best stove yet, understood. Pity. Hans Haase, thank you dear, but I found nothing much there. Anna Frodesiak (talk) 19:36, 18 March 2018 (UTC)

Oh, well. Thank you all for taking the time. I guess Earth and its silly fools will all have to live with these trillions of plastic bags everywhere. (Oh, and I just saw someone buy a bundle of zippy bags in a larger zippy bag and the shopkeeper put them in a bag for the customer. I'm not kidding. I asked why, and he said because that bag had a handle. Sorry Earth. We're not that bright.) Anna Frodesiak (talk) 19:36, 18 March 2018 (UTC)

Look on the bright side. Plastic represents carbon that won't be entering our atmosphere any time soon.

Once the bag has been manufactured, and if reuse as a bag isn't an option, then it'd probably be better for the environment to just bury it somewhere rather than burn it and contribute to both global warming and local smog. ApLundell (talk) 22:07, 19 March 2018 (UTC)

I constructed a small tea light out of aluminium foil, using an asbestos fiber wick, and it appears to burn HDPE milk containers quite cleanly. ChemWarfare (talk) 11:26, 21 March 2018 (UTC)

Vitamin K

I switched to a multivitamin that does not have vitamin K like my old one, since I still want vitamin K I plan to get it from food. The vitamin k article lists vitamin k1 (mainly in certain vegetables) and k2 (mainly in meat and dairy), but my old vitamin just says vitamin k. Does it matter which one you take? I am also confused by how much you need, since my vitamin lists the amount you need in mcg but wiki lists it as IU, what is the conversion?--User777123 (talk) 18:58, 13 March 2018 (UTC)

In case you don't know, mcg is a terrible way of writing μg, the actual unit. That might help with your searches. Fgf10 (talk) 19:35, 13 March 2018 (UTC)

Actually, it is not a bad way, but you're right it won't do well in searches and is widely considered obsolete. I just tried out Google and got four different sets of results with µg (using the HTML version), μg, microgram, and mcg. But it could be worse ... in the old days people would use pre-Unicode word processors where µ is just an "m" in symbol font, and inevitably they would mess with their fonts at the last minute before submitting a draft, which means that any "mg" published in the 1990s is like as not to be micrograms. I suspect, but do not know, that the Venezuelan horses killed by selenium were victims of something similar involving their home pharmacy's special recipe. Wnt (talk) 21:57, 13 March 2018 (UTC)

Your body actually stores, and uses, vitamin K2 (unless you are really a vegetable). However, any K1 in your diet gets converted to K2 by the bacteria in your gut - so it makes no significant difference which one you take. Wymspen (talk) 23:28, 13 March 2018 (UTC)

I've seen claims vitamin K is not even something that needs to be supplemented in most people with ordinary diets, an attitude our article reports but not enthusiastically. There are many people on warfarin whom doctors believe need to have less vitamin K activity than their diet would naturally provide. On one hand, there is thrombosis, heart attacks and strokes, death; on the other side uncontrolled bleeding, shock, ischemia, hematomas, death. You pay your money and take your chances. Wnt (talk) 23:38, 13 March 2018 (UTC)

• Trying to answer the OP's question, I don't see where Wikipedia lists Vitamin K recomendations in IU. There may not be an IU measurement for Vitamin K (each vitamin has it's own IU standard that is developed individually, it's... confusing) and Vitamin K and Reference Daily Intake and Dietary Reference Intake list recommended Vitamin K intakes in micrograms. I'm not sure where on Wikipedia the OP is seeing it listed in IUs. But if they are looking for Vitamin K recomendations, there's three sources that list it in micrograms. --Jayron32 19:27, 14 March 2018 (UTC)