Wikipedia:Reference desk/Archives/Science/2015 October 22

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October 22

Does alcohol take 30 minutes to kill bacteria?

Per the question, does alcohol kill "bacteria" quickly, or does it take 30 minutes as this website which is affiliated with the Washington State University College of Veterinary Medicine states: "Alcohol takes about 30 minutes before bacteria are killed, so just swiping the hair with alcohol is not effective in killing bacteria." A CDC website says many named things are killed in 10 to 15 seconds by certain typical alcohol mixtures, but mention that a "culture phase" of some named things takes 20 minutes to die. Are the 20 minute holdouts the "bacteria" that WSU is worried about, and are they correct to dismiss the ability of alcohol to quickly kill the named species? Is it just reassurance and theatre when nurses clean an arm or the top of a vial with alcohol before doing an injection, when they don't wait 30 minutes before doing an injection? Edison (talk) 03:12, 22 October 2015 (UTC)

It's a vague question. The diversity of bacterial life is possibly greater than the other kingdoms of the tree of life, so asking a general question like "does X kill bacteria" is basically meaningless. Which bacteria? There are different species of bacteria more different from each other than you are from a jellyfish.--Jayron32 03:22, 22 October 2015 (UTC)

I think it's clear from the context of the linked page that the bacteria in question are those which might be [1] found on a cat's skin and [2] potentially pathogenic in an immunocompromised cat. - Nunh-huh 04:09, 22 October 2015 (UTC)

Hand sanitizer has some relevant info. I think the answer is both. A lot of bacteria is killed quickly, some bacteria is more resistant. That seems to be precisely what the article you linked says. Vespine (talk) 04:01, 22 October 2015 (UTC)

I agree, and suggest that the linked page is simply saying, "if you have an immunocompromised cat, don't rely on alcohol to sterilize injection sites, we have other things that work faster." Also, generally, when discussing antiseptic solutions, you need to specify the concentration of the solution for the discussion to have much meaning. - Nunh-huh 04:09, 22 October 2015 (UTC)

Too "ridiculously vague?" Apologies. Sorry to have provoked the bitey response. Should have specified Becton Dickinson Alcohol Swabs, no. 326895, 70% isopropyl Alcohol, inactive ingredient water, intended for use as an "antiseptic skin cleanser." Do they kill all important pathogens in a few seconds, or does it take "30 minutes" to kill "bacteria" as the Washington State University site states. WSU suggests that they are a waste of time unless you wait 30 minute , a practice which I doubt is ever done. Would they kill "all bacteria" even in the absurd 30 minutes wait scenario? Clearly they don't kill all dangerous pathogens since in recent well publicized cases similar non-sterilized swabs carried bacillus cereus and actually caused serious or fatal infections. Why aren't such swabs sterilized as well as being saturated with 70% isopropyl alcohol? Edison (talk) 04:30, 22 October 2015 (UTC)

Unfortunately, Jayron has taken it upon himself to ridicule others on the Ref Desk, and any excuse will do. Your Q was fine. If he needed clarification, then he should have asked for it, without the ridicule. StuRat (talk) 14:24, 22 October 2015 (UTC)

The Bacillus cereus contamination is undoubtedly a result of survival of the spore form of the organism, which can survive 90% solutions of ethanol for months [1]. Another point to consider is that these days diabetics are generally told that swabbing the skin before testing glucose/injecting insulin is a useless exercise. Though diabetics are immunocompromised by definition, they are presumably less so, or compromised in a rather different way, than the cats in the original page.[2] ("Several studies have reported that there is no increased risk of infection from single-use syringes, pen needles, or lancets when alcohol swabs are not used. Most current practice guidelines, including those from the American Association of Diabetes Educators, no longer recommend the use of alcohol swabs, which can lead to dry skin.") - Nunh-huh 06:31, 22 October 2015 (UTC)

Re: "diabetics are immunocompromised by definition". In what way ? Poor circulation to the extremities is common, and that might lead to increased risk of infection there, since the immune response depends on the circulatory system. Is this what you refer to ? In that case, since diabetics inject insulin into fatty areas on the abdomen, not the extremities, that shouldn't be a concern there. StuRat (talk) 14:19, 22 October 2015 (UTC)

Diabetics are classified as immunocompromised on the basis of empirical evidence showing increased susceptibility to frequent and protracted infections. There are also differences in which organisms are likely to cause a specific syndrome in diabetics vs. euglycemic individuals. The observation was made first, and the explanations later. There are several immunological abnormalities that have been described in diabetes. I think the most prominent are defects in complement-mediated opsonization and phagocytosis. T lymphocytes may also be implicated. Lowered secretion of inflammatory cytokines and disorders of humoral immunity and neutrophil function have also been noted. All of these are worse when the hyperglycemia/diabetes is poorly controlled. The circulatory difficulties are as you note, and can cause difficulties in treating skin ulcers/osteomyelitis or other infections, but aren't considered "immune" problems. While diabetics typically inject insulin into the abdomen or upper thigh, they still do glucose testing on fingertips (though that hurts a great deal more than testing on, say, a forearm; the fingertip testing is more reliable during episodes of hypoglycemia). - Nunh-huh 22:27, 22 October 2015 (UTC)

Based on personal experience, I think we are talking about hyperglycemia encouraging persistent sores, not diabetes causing actual leukocytic immunosuppression. Having lost over 60 lbs and finding I actually have to work hard at raising my blood sugar over 120, as a controlled type II diabetic, I doubt it is the condition, rather than the symptom, which is the problem here. μηδείς (talk) 04:23, 24 October 2015 (UTC)

The alcohol would all have evaporated after a few minutes so a 30 minutes wait would be pointless. There is some useful information about alcohol as an antiseptic here under Mechanisms of action:Alcohol. Richerman (talk) 15:30, 22 October 2015 (UTC)

But just as comparative statistics on infection rates were used to promote the sterile method for surgical practice in the 1870's,greatly reducing strep and staph infections at incision sites, someone must have done a study of post-injection infection rates with and without an alcohol wipe of the site before it became common practice. An 1882 manual on hypodermic injections made no mention of sterilizing the needle or of using sterile liquid for making solutions to inject, let alone wiping the site with alcohol.The author did caution against using a needle on someone again after it had been used on "an infected person." So when did the swipe before the jab become common practice? By 1915a nursing manual called for wiping the skin with alcohol or another antiseptic before doing an injection. beforeSwipe before jab has been the only practice I have seen used in a doctor's office, neglecting the recommendations listed above against alcohol wipes for diabetics who are doing pricks for blood testing or who are injecting insulin or diabetic meds under the skin. What do peer-reviewed studies and recent medical textbooks say about complication/infection rates with and without alcohol wipes before subcutaneous or intramuscular jabs or placement of IVs? This is a general scientific question going beyond diabetics or immunocompromised cats. If some doctor says "I did 5000 injections without cleaning the skin and there were no infections," I wonder how many of the patients were examined to determine if there was in fact an infection, or if the doctor was merely unaware of any infections, though some might have occurred without the patient making his way back to the office for followup. Patients might think that some soreness, redness or a bump under the skin were to be expected after an injection. WHO (2010) ,"Best practices" calls for alcohol wipe before injections.A 2003 WHO publication says it is unnecessary, as do many websites. How can these divergent recommendations all be correct and evidence based? Edison (talk) 23:27, 23 October 2015 (UTC)

The "Best practices" paper you link relates to injections in health-care and related facilities, while the 2nd WHO paper seemingly relates to all injections, but with an eye to "transitional and developing countries". The setting of the injections may bear upon the recommendations; organisms found in health care facilities are often more virulent than those found on one's own skin at home. Different areas also have different standards of personal cleanliness. Note that the (2nd) best practice recommendation states it is based on "expert consensus and theoretical rationale" rather than "well-designed studies", and the (1st) best practice recommendation fails to identify its basis. - Nunh-huh 00:23, 24 October 2015 (UTC)

I wonder if anyone has considered the possibility that alcohol may kill benign bacteria, allowing more dangerous microorganisms to grow on the skin. StuRat (talk) 04:32, 24 October 2015 (UTC)

ADP engine

Any idea what this "ADP engine"[3] is referring to? It's from a free MIT source material site[4], but I can't figure out which chapter it came from. I came across the picture from here[5], with no link to the actual webpage containing it. 731Butai (talk) 08:23, 22 October 2015 (UTC)

Advanced Ducted Propfan according to goooooooogle. DMacks (talk) 08:34, 22 October 2015 (UTC)

Correct, or "Advanced Ducted Propulsor". Wikimedia has a picture of it: File:Pratt & Whitney Advanced Ducted Propulsor engine test.jpg, and it's briefly described in the Popular Mechanics magazine of Oct. 1993, p. 28 - Lindert (talk) 08:38, 22 October 2015 (UTC)

Trans-species?

So there's being transgender, which is a gender identity issue. But is there a condition in which people feel they are the wrong species. Born a human but with the brain or mind of a sheep, dog, cat whatever. It seems like people naturally have a very strong connection with animals and maybe that's part of it. Any name for this or exampleS? — Preceding unsigned comment added by 80.195.27.47 (talk) 11:40, 22 October 2015 (UTC)

Zoanthropy is the term for the psychological condition, this is sometimes informally known as Species dysphoria. Otherkin is the popculture concept.--Jayron32 11:54, 22 October 2015 (UTC)

Note that it's possible to have the brain of the opposite gender, and this can happen due to hormone levels during development, etc. However, having the brain of another species isn't actually possible, AFAIK. If this is possible, then it would only be between closely linked species, like dogs and wolves. StuRat (talk) 14:28, 22 October 2015 (UTC)

Note, however, that mind =/= brain. --Jayron32 14:42, 22 October 2015 (UTC)

<flame bait>I'm tempted to ask whether physicians offer species reassignment surgery to deal with the problem, and whether government entities are enlightened enough to recognize this in legal documents, dog licenses &c. Wnt (talk) 15:55, 22 October 2015 (UTC)</flame bait>

See Dennis Avner. Note that his appearance is rather - striking. Tevildo (talk) 21:29, 22 October 2015 (UTC)

If you knew if was flame bait, why the fuck'd you post it? AlexTiefling (talk) 21:48, 22 October 2015 (UTC)

Because it's interesting. Wnt (talk) 22:05, 22 October 2015 (UTC)

Understanding time

There is no request for information in here. Looie496 (talk) 11:52, 22 October 2015 (UTC)

One of the things showed to me was our real time. It seems the Gregorian calendar is incorrect. The problem with it is time. There is no account for the speed the earth is traveling around the sun, and for the sun rotation around the galactic center. This gives us a quarter of a day extra a year. Einstein explained it with his theories of relativity. Once a person reaches the speed of light, time will stop. The earth travels around and gains a quarter of a free day a year. The creator lets it build up and releases every four years on the Gregorian calendar date July the 25th. This day repeats itself. It is a day that has no time. Because we are moving slower than the speed of light we gain time. When you exceed the speed of light we can travel backwards in time. This leads to the famous "twin paradox" in which one twin is rocketed at high speeds flies across the galaxy and back home. Even at a velocity close to the speed of light, the journey would take tens of thousands of years from the vantage point of Earth, but because of his high relative motion the astronaut would age more slowly than he or she would than on Earth, and would return home only a few years older. His twin would be long dead. In a 1905 Einstein predicted that because of the rotation speed of Earth, clocks would also run slower at the Equator than the poles, but that turned out to be wrong. See Einstein actually understood time. I think with a little bit more time Einstein would have figured this out too. E=mc2 and set the speed of light, 186,000 miles per second, as the cosmic speed limit - allows for time to stop. So if you are going slower than the speed of light it will move you forward. Everyone is a time traveler on our ship earth. There are 26 hours in the day. 13 hours of light 13 hours of dark 1 hour = 52 min 1 min = 52 sec 1sec = 52 nanosec 3 times 7 = 21 + 1 for god=22 7/22 = PI PI=3.142857 364 days a year times PI = 1144 Perfect rotation! It is in the math. Every four years we get a free click. The day with no time. 28 days times 13 months = 364 days 12 ages/ 1 age = 2166.7 earth years 26,000 earth years around galaxy 125 years a click = 1 min on watch Remember we have to take in the account that we are moving slower than the speed of light. The faster you go towards the speed of light you gain extra time. Once you exceed the speed of light you can travel backwards in time. So all of you hopeful time travelers you will need to build a craft that can go faster than the speed of light to go back. This is almost impossible, but can be done. In order to go back you need to bend space which allows the astronaut to move faster than the speed of light. In order to bend space you need to create your own gravity. I have drawn a replica watch of earth’s correct time. I guess you can tell I ate the apple of knowledge??? — Preceding unsigned comment added by 5.0.88.207 (talk) 11:44, 22 October 2015 (UTC) If you have a question about the nature of time, please ask a question. This is not the place for your essay. You might also enjoy reading about the arrow of time or time travel. SemanticMantis (talk) 16:29, 22 October 2015 (UTC)

what is name of light-flashlike "things" seeing during closed eyes in dark

floating light-dark thing, not describable, seeing stars?Mahfuzur rahman shourov (talk) 15:41, 22 October 2015 (UTC)

I'm tempted to say "orgones" -- but no. Honestly, I think it's a phosphene/"Prisoner's cinema.

Two common visual elements that meet the above definition could be Floaters (small specks of impurities in the vitreous humor of the eye) and Phosphenes, which are flashes of light caused by sources other than light itself (for example, by variations in pressure due to rubbing they eye, irritations to the optic nerve or retina, blows to the head, etc.) Both floaters and phosphenes could be benign, or COULD be a sign of underlying problems, if you have concerns, consult a medical professional such as an optometrist or an ophthalmologist. --Jayron32 16:06, 22 October 2015 (UTC)

Some information in our (rather sparse) flash blindness article. Alansplodge (talk) 16:08, 22 October 2015 (UTC)

See here. Richerman (talk) 16:33, 22 October 2015 (UTC)

Phosphenes appear gradually, they are more light phenomena than flashes. Photopsia on the other hand do flash and should be checked by a medical professional. Ssscienccce (talk) 21:10, 22 October 2015 (UTC)

@Wnt:OP has memory found article rationalwiki surfing 2011, 4 year past, less chaotic timeMahfuzur rahman shourov (talk) 17:00, 22 October 2015 (UTC)

• there's also the ability to see infrared when two photons hit the same pigment simultaneously: http://www.nature.com/news/photons-double-up-to-make-the-invisible-visible-1.16459. Interesting, although I doubt that fits the OP's criteria. μηδείς (talk) 19:25, 23 October 2015 (UTC)

Not directly responsive, but you may also be interested in Eigengrau. --Trovatore (talk) 01:05, 23 October 2015 (UTC)

As Ssscinccce mentioned, unexplained flashes can be a symptom of a serious condition such as retinal detachment or posterior vitreous detachment. We can't give medical advice, but anyone who has such flashes might seriously consider asking a professional about it. --Trovatore (talk) 03:53, 23 October 2015 (UTC)

Carbon nanotubes in clothing (NOW?)

This story [6] claims that carbon nanotubes are showing up in asthma patients, and says "Carbon nanotubes are often used in the production of computers, clothing and technologies for healthcare because of the material's highly durable and conductive properties." Our article on carbon nanotube mentions using it in bulletproof clothing (hypothetically) and web searching comes up with some story about using it against chemical weapons somehow ... but it seems like more of the same old same old. "You could do anything with carbon nanotubes, if you could do anything with carbon nanotubes." But what's the truth? Can people recommend a current source for where they are being used and what the environmental exposures really are? Wnt (talk) 16:36, 22 October 2015 (UTC)

The full journal article is freely accessible here [7]. At a skim, they claim that "Anthropogenic carbon nanotubes were found in all samples", but later acknowledge that "natural and anthropogenic sources might be an important component of [particulate matter]." This looks like sloppy writing at best. I don't think there's any way to distinguish a man-made nanotube from a naturally occurring one. Actually it's a bit of a fuzzy line, e.g. "These nanostructures are similar to those present in dusts and vehicle exhausts collected in Paris" - now technically those are man-made, but it's a side effect of combustion, not an intentional manufacture for use in a specific industry. It is conceivable to distinguish CNTs of intentional manufacture from CNTs that form from routine combustion by comparing statistical distributions of various features, but the authors of the Ebiomedicine article did not do that. I think the tech times' claim that "Carbon nanotubes are often used in the production of computers" is just false. Carbon_nanotube#Natural.2C_incidental.2C_and_controlled_flame_environments specifically discusses how they can be made accidentally by humans and even naturally by e.g. wildfire. SemanticMantis (talk) 16:58, 22 October 2015 (UTC)

Here's [8] a recent review of environmental exposure to CNT, human health effects, and some further refs. SemanticMantis (talk) 17:35, 22 October 2015 (UTC)

At a New Year party about a decade ago, someone asked whether Eric Drexler's new shirt was silk; no, he said, some kind of synthetic. "Buckytubes!" said I, and he laughed politely. —Tamfang (talk) 05:25, 23 October 2015 (UTC)

This looks like typical media spin on a normal journal article to me, tbh. Long on speculation about "what we don't know could be killing us" and short on facts. shoy (reactions) 13:43, 23 October 2015 (UTC)