Wikipedia:Reference desk/Archives/Science/2015 May 13

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May 13

STDs and nutrition in developing countries

Can it be said that in developing countries, stds are more common partly due to poor nutrition? Obviously it's also things like less condom use, less developed medicine etc but can poor nutrition also be a factor? If so, why and is there any evidence for this? — Preceding unsigned comment added by 194.66.246.78 (talk) 01:41, 13 May 2015 (UTC)

Well, poor nutrition can hinder the immune system, and that could be a factor. StuRat (talk) 02:19, 13 May 2015 (UTC)

here is a pub med article that credits malnutrition (as) the most common cause of immunodeficiency worldwide. I don't see any reason why this would not apply to STDs along with all other diseases. Vespine (talk) 04:41, 13 May 2015 (UTC)

Automated Milk Harvester

They enter "of their own free will". (This is found about 2 minutes into the video.) Why do they go in? Bus stop (talk) 02:13, 13 May 2015 (UTC)

Having a full udder is uncomfortable, much like having a full bladder. They know that they will feel better after they are milked. StuRat (talk) 02:21, 13 May 2015 (UTC)

How often has your udder been full, Stu? I won't embarrass my relatives by bringing them in to refute you. See SB's response below. μηδείς (talk) 04:57, 13 May 2015 (UTC)

Some cows LIKE being milked. When I was a kid, visiting my great-uncle's dairy farm, the two dozen cows in his small dairy herd were able to judge when it was milking time, they'd walk into the dairy and go straight to their preferred stalls without any human intervention. There was an entry from the field for them to do that. SteveBaker (talk) 04:13, 13 May 2015 (UTC)

I've seen these in operation. I've also seen cows milked in free stalls and in milking parlors. So far, what has been said is accurate. With both free stalls and parlors, the cows know when they need to come to get milked. They learn the times just like your cat or dog might learn when they get dinner or go for a walk. Additionally, the cows will start to "let down" their milk when they expect to be milked. If their udder is especially full, the teats will leak milk without being actively milked. There are some cows who don't let down as readily and the farmer will then have to give them an injection of oxytocin. It's the hormone that would naturally trigger the let down, so there's no need for reporting of it like there is with rBST or things of that ilk.

Getting back to the automated milking machines though, the cows do get to a level of discomfort if they haven't been milked in some time. Dismas|^(talk) 06:24, 13 May 2015 (UTC)

I suspect that the main reason that cows like being milked is that, in most systems, they get fed something tasty at the same time. Dbfirs 07:20, 13 May 2015 (UTC)

Any lactating mammal, including humans, will suffer discomfort if the milk built up is not released. Cows aren't so dumb. They know the machines will relieve their discomfort. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:58, 13 May 2015 (UTC)

How many total distinct living organisms exist within a typical human body at any given time?

This is probably extremely variable from person to person and from day to day in a single person, not to mention very difficult to accurately estimate, but in principle I imagine there is a finite (though unfathomably large) value that is the average total number of living organisms with genomes separate from the genome of the human body which they occupy, i.e. counting all bacteria, protozoa, intestinal parasites, gut flora, epidermal fungi, etc. Anything with a set of genetic material such that the organism constitutes a species distinct from the human host (I will exclude viruses simply because they would make the estimate that much larger and harder to determine, though if anyone has any estimates with viruses included, that would be interesting, too). I'm not just looking for the total number of distinct organisms, but more specifically the total number of individuals of each type of distinct organism; for example, total number of individuals of E. coli + total number of individuals of Candida albicans and so on, for all distinct species that are currently alive in a typical healthy adult human body at any given moment in time. Hopefully this is a reasonable question? — Preceding unsigned comment added by PJsg1011 (talk • contribs) 06:15, 13 May 2015 (UTC)

Estimates of the total cells range up to a hundred million million, with over 90% of them not human, but I've no idea how many of each species. I wonder if anyone has done research on this. Our article Human microbiota doesn't give actual numbers. Dbfirs 07:16, 13 May 2015 (UTC)

Keep in mind we can't easily point at some bacteria and say "this one is species X, that one is species Y" - If you look at the research, you'll see that instead, they use proxies for species identification, such as phylotypes or Operational_taxonomic_units. This Science paper found 395 phylotypes, just in the gut [1], and Figures 1,2 are slightly different ways of getting at your questions. This paper reports around 400 species of gut flora [2]. This is a fast growing and emerging field of research, we know that there is indeed much variation between and within humans, and also through time. This paper gives an overview of the diversity and function of normal human flora [3]. Your question is indeed reasonable and important, but there are no general easy answers yet. It is good to remember that most of the cells in and on your body are not human, though most of the mass is indeed human. Google scholar will be helpful here, and you can ask at WP:REX if you are having difficulty accessing the articles. SemanticMantis (talk) 13:55, 13 May 2015 (UTC)

Apropos, "most of the cells in and on your body are not human, though most of the mass is indeed human." Are there any estimates as to the mass of the non-human cells in human body ? I realize that this could be tricky (for example, does one count the food being digested?), and don't expect a precise number. Abecedare (talk) 14:15, 13 May 2015 (UTC)

Human microbiota says, with citation "The mass of microorganisms are estimated to account for 1-3% total body mass" - I'm pretty sure I've also seen larger estimates. Another claim I've seen is that a healthy adult male will have about 1L of gut flora at any given time, but I can't find a ref for that at the moment. Here's another good general ref on the function and metagenomics of gut flora [4], with the nice first sentence "It has been estimated that the microbes in our bodies collectively make up to 100 trillion cells, tenfold the number of human cells, and suggested that they encode 100-fold more unique genes than our own genome." So we have about 10X as many non-human cells as human cells, but the (usually prokaryotic) flora cells are about ~1000X smaller, so we get a floral mass of about a few percent. SemanticMantis (talk) 15:03, 13 May 2015 (UTC)

Thanks! That's exactly what I was looking for. Btw, the main Microbiota page has some inconsistent information in the article lead (one of the cited sources is a deadlink and, on a quick look, the other doesn't support the 200g estimate). Can you review and update, if necessary? Abecedare (talk) 15:30, 13 May 2015 (UTC)

Good call, the NYT pop science article isn't very reliable, and doesn't support the claim. I've taken the easy way out and deleted the claim and refs for now, will try to put in better refs and claims later. SemanticMantis (talk) 18:55, 13 May 2015 (UTC)

Is it dangerous to run a microwave oven while nothing is in it?

Is there any danger or issue in setting the microwave oven for a certain amount of time and turning it on with nothing inside? For example, let's say that I am cooking something on the regular conventional stove. I want to keep track of the time. So, I set the microwave for five minutes and turn it on, with nothing inside. After five minutes, the microwave oven will "ring". This ring will notify me that my five minutes are up and that I can remove the food from my conventional oven. So, in essence, I have simply used the microwave as an "alarm clock" or "timer". Is there any danger or any issue in doing this? I had assumed not. But, if I set the microwave for a long time (let's say, ten minutes), there is a funny smell. Thanks. Joseph A. Spadaro (talk) 14:56, 13 May 2015 (UTC)

When running the microwave empty, there is nothing there to absorb the microwave energy, so it's "absorbed" back into the magnetron and lead to potential overheating problems. Most electronic microwaves have a "Kitchen Timer" function that I use when I am cooking something in the over. Justin15w (talk) 14:59, 13 May 2015 (UTC)

If the question is about using the microwave oven as a kitchen timer, as Justin15w notes, there is nothing to absorb the head. The funny smell might be either the burning of burnt-on food in the microwave oven (neither good nor bad, unless a fire starts, in which case there was too much burnt-on food, creating a safety hazard anyway), or ozone (which is hazardous to health). I have three suggestions. First, as Justin15w advises, use a "Kitchen timer" function on the microwave oven itself. Second, use a feature on your cell phone as a kitchen timer. Third, buy and use a kitchen timer, which may be available for no more than $20 in the US, and is probably available for comparable prices in the Commonwealth, Europe, or Japan. Also, check whether you have too much burnt-on food in the microwave oven, and use steel wool or scouring powder to remove it. Robert McClenon (talk) 15:23, 13 May 2015 (UTC)

If you have a mobile phone you probably have a timer (or can install one for free). Short Brigade Harvester Boris (talk) 02:22, 14 May 2015 (UTC)

Yeah - it's definitely not a good idea to do this. As our microwave oven article points out: "Another hazard is the resonance of the magnetron tube itself. If the microwave is run without an object to absorb the radiation, a standing wave will form. The energy is reflected back and forth between the tube and the cooking chamber. This may cause the tube to overload and burn out. ". You will do damage to the microwave oven gradually over time - and it's also a colossal waste of energy. Also, if the magnetron does overload, it can crack the beryllium oxide insulators producing dust that is hazardous if handled or inhaled. So this is a very bad idea...don't do it. SteveBaker (talk) 15:31, 13 May 2015 (UTC)

(ec)If running the microwave oven really is the only way you can time something just put a mug of water in it, and turn the power down to the minimum. Roger (Dodger67) (talk) 15:47, 13 May 2015 (UTC)

A mug of water has little mass compared to Joe's pet cat, firstborn child, or favorite pair of shoes soaked in water and then filled with olive oil. Why not recommend that? Is there any sane reason why we are not simply advising Joe that if he wants advice on how to burn his abode down, to google the name of the oven manufacturer, and call their 800 customer service number and ask the horse directly? μηδείς (talk) 03:34, 14 May 2015 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 16:39, 18 May 2015 (UTC)

Is the following essay is considered as a scientific literature?

Is the following essay is considered as a scientific literature? I saw two people with two opinion about it (in another forum) that one of them brought it as a scientific literature but the second one told him that it's not scientific literature because it's opinion presentation. I would like to know if it's scientific literature or not. http://faculty.washington.edu/skalski/classes/QERM597/papers/Gavin.pdf 149.78.38.232 (talk) 16:14, 13 May 2015 (UTC)

It's clearly scientific literature; but it's not research findings. It's a discursive essay by a scientist about science. (On a grammar note, one wouldn't describe one essay as 'a literature'; it's literature.) AlexTiefling (talk) 16:19, 13 May 2015 (UTC)

The article seems to be a contribution to an ongoing discussion on methodological approaches in biology. As such it probably counts as scientific literature as defined in our article, though it is clearly advocating a position rather than presenting the results of research. RomanSpa (talk) 19:47, 13 May 2015 (UTC)

"Our early studies indicated that 25-50% of the breeding adults returned to the same field the following year to breed" -- research is being presented, summarized and discussed, though it does appear that this piece does not present novel research. The article is peer reviewed, appears in a scientific journal contains many references, and is squarely scientific literature. Many journals now have categories they place articles in to, e.g. in Nature, this would most likely be classified as "reviews and perspectives". From the "aims and scope" of J. Wildl. Manage. [5], "Also considered are theoretical and conceptual aspects of wildlife science, including development of new approaches to quantitative analyses, modeling of wildlife populations and habitats, and other topics that are germane to advancing wildlife science." - emphasis mine. SemanticMantis (talk) 20:15, 13 May 2015 (UTC)

It's a peer-reviewed article in an established scientific journal. Thus it's unquestionably a part of the scientific literature (which I think is what you mean). Short Brigade Harvester Boris (talk) 02:19, 14 May 2015 (UTC)

Yep. I suppose it's also worth mentioning that being part of the scientific literature doesn't impy anything about whether the article is any good, or useful, or valid as a citation in support of a specific claim. There's all kinds of scientific literature published. Some of it is is ground breaking, some is mostly hype and marketing, some is good, and some is not that useful. But even the not-that-useful scientific literature is still "scientific literature" ;) SemanticMantis (talk) 03:41, 14 May 2015 (UTC)

• As a side point, 149.78.38.232, "considered as" is incorrect usage here. "Considered" meaning "judged to be" takes no "as". "George washington was considered a good president." Considered as means viewed as a possible alternative. "A short invasion was considered as an option in the Iraq War, but Bush opted for a nation-building occupation." μηδείς (talk) 20:06, 16 May 2015 (UTC)