Wikipedia:Reference desk/Archives/Science/2014 November 5

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November 5

7 or 10 listeria species?

I'm confused because in the beginning of the article is written that "Listeria is a genus of bacteria that contains seven species:", and later in this article itself:" The genus Listeria currently contains ten species: L. fleischmannii, L. grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. rocourtiae, L. seeligeri, L. weihenstephanensis and L. welshimeri.". so what's right? 213.57.99.33 (talk) 03:50, 5 November 2014 (UTC)

Another one: "the overt form of the disease has a mortality rate of about 20 percent" while in this article itself says: "The case fatality rate for those with a severe form of infection may approach 25%". it looks like as if many people the article without reading the previous things. 213.57.99.33 (talk) 03:55, 5 November 2014 (UTC)

Without getting into the specifics of this article; this may be the case of people (likely multiple different editors) adding information from multiple sources and different times. I would not be entirely surprised that different sources would disagree on exactly how many species of Listeria there were, or that different studies would come out with different data as to mortality/fatality rates (especially where the sources may not even be measuring comparable things). --Jayron32 04:00, 5 November 2014 (UTC)

If all the sources are reliable, the solution is to say there are 7-10 species with a 20-25% fatality rate. As for why they can't agree on the number of species, there could either be disagreement on whether 3 are listeria, or whether those 3 are separate species or just strains of other listeria species. StuRat (talk) 12:08, 5 November 2014 (UTC)

This all seems reasonable. I'll remind the OP that Wikipedia:Wikipedia_is_not_a_reliable_source, and this kind of thing is to be expected, especially in biology/taxonomy, where there are few universally "correct" answers. Even textbooks have this kind of issue, but they are written by experts who know when to leave out details, or know what study is most relevant for the current topic. SemanticMantis (talk) 15:52, 5 November 2014 (UTC)

Why does infusion bag need an expiration date?

I would like to understand why does "infusion bags" need an expiration date. What does it say when the date comes? it says this is a time it has a high potential to be contaminated? the same question about Oxygen tanks that have an expiration date. 213.57.99.33 (talk) 05:25, 5 November 2014 (UTC)

I suppose the assumption is that you expect those things to be "sterile", uncontaminated, fresh, etc with a HIGH degree of certainty. Under ideal conditions, I guess you'd expect the oxygen in a sealed tank to remain uncontaminated "oxygen" for a very, very long time, but there are seals, gaskets, perhaps lubricants, which do not last indefinitely. tanks can get knocked around, dropped, bags get handled, bent, folded... To be certain the item you have is "good" it should be below a certain age. Vespine (talk) 05:53, 5 November 2014 (UTC)

Also, plastic infusion bags may contain chemicals which slowly leak into the contents. The longer they sit, the more leaching occurs. And the manufacturers probably only test them to a certain age, so can't say one way or the other if they are good past that age. StuRat (talk) 12:05, 5 November 2014 (UTC)

It's commonly the case with medical supplies that the legal requirement to specify how long the product is good for is onerous for the manufacturers to test. If I come out with some new infusion bag, if I want to stick a 10 year expiration sticker on it - then I have to prove to the FDA that it'll still be OK in 10 years - and it could easily take me 10 years of testing to prove that...even if I know that the plastics it's made from should last for 1,000 years. Since I'll go bankrupt if I have to sit around for 10 years testing without being able to sell a single infusion bag, I'm much more likely to test for 1 year and put a 1 year sticker on it...even though the product might easily last 100 years.

The FDA created this rule in 1976 - and they weren't trying to be very subtle about it. So *all* drugs, *all* supplies and *all* medical devices are required to have an expiration date, even if they are some simple mechanical item or something that seems to be obviously safe - like a gas cylinder. This is why cotton balls used in hospitals cost twenty times what cotton balls sold to the general public for makeup removal cost...and have an expiration date of a few years - even though they are the exact same product you use at home with no expiration date.

There was a case some time ago (see [1]) when the US military had a small mountain of drugs that they'd stockpiled in case of some hypothetical emergency - which were due to expire quite soon, or which had already expired. The cost of dumping all of those drugs lead them to actually test their viability and they found that 15 years after the expiration date, 90% of the kinds of drugs they had were still just as good as the day they were purchased...so they extended the expiration dates. But it's rare for organizations to have such gigantic stock-piles of unused drugs (or infusion bags or whatever), so the cost of re-testing them by far exceeds the cost of tossing them out and replacing them. So in general, tons of completely usable, safe, materials are dumped just because nobody can afford to keep testing them.

SteveBaker (talk) 16:22, 5 November 2014 (UTC)

Wouldn’t disagree with anything Steve said yet to add only that infusion bags can become contaminated over time by the plasticisers used in plastic that the bag is made from. See the section PVC and DEHP in medical products: [2]--Aspro (talk) 22:16, 6 November 2014 (UTC)

the Oxygen in the tanks is in liquid or gas condition?

213.57.99.33 (talk) 08:40, 5 November 2014 (UTC)

The critical point of oxygen is -118.56°C (ref Wolfram Alpha). Thus it needs to be kept below that temperature to be liquefied. LOX (liquid oxygen) is used for rockets, but not generally for other purposes. CS Miller (talk) 12:23, 5 November 2014 (UTC)

supercritical oxygen could be thought of as a liquid if it is condensed to the density to be expected of liquid oxygen; but it would still (even under those conditions) more closely resemble a gas, as the molecules will still have enough kinetic energy to overcome the bonding energy necessary to hold the molecules in a true "liquid" phase. That's the molecular definition of a supercritical fluid: the temperature at which the kinetic energy of the molecules is greater than the energy needed to hold the molecules together. --Jayron32 13:42, 5 November 2014 (UTC)

Liquid at 200-300 bar. --Kharon (talk) 12:24, 5 November 2014 (UTC)

Why would you say that, Kharon? With a critical point of 154.581 K, 5.043 MPa = 50.43 bar, room temperature (non-cryogenic) O2 at 200 bar is a supercritical fluid, but it is far above its critical temperature, and at a pressure where its molar volume is still four times that liquid oxygen, so as Jayron32 points out, its physical behavior will be very gas-like. Were you, perhaps, thinking of carbon dioxide? -- ToE 08:08, 9 November 2014 (UTC)

Both. You can get industrial/hospital oxygen in both compressed gas ranges and liquid ranges. The large Dewer tanks are liquid and have oxygen vapor that is extracted. Most hospitals will have liquid as the refill requirements does not require purging. Compressed oxygen in a tank (like portable ones) need to be evacuated and have a vacuum pulled on them to meet codes for medical oxygen refills. --DHeyward (talk) 21:28, 10 November 2014 (UTC)

Man turns mobile off whilst committing crime?

I've taken the liberty of moving this to Wikipedia:Reference desk/Humanities#Man turns mobile off whilst committing crime?, which discusses legal and social matters. Wnt (talk) 13:31, 5 November 2014 (UTC)

Note: if you are actually interested in how precisely companies can determine when a cell phone was off, I'd probably recommend the Computing refdesk, but be clearer when you ask that you're interested in technical capabilities rather than admissibility. Wnt (talk) 13:38, 5 November 2014 (UTC)

How common are capacitors that can hold a charge for several days?

Are there any household machines (or anything that private people use) that use these? The wash-machine maybe, the car? How much electricity can they be charged with?--Senteni (talk) 18:36, 5 November 2014 (UTC)

I can't answer with numbers, but proper safety practice calls for adding Bleeder resistors. Ariel. (talk) 19:54, 5 November 2014 (UTC)

Old televisions (CRT type) have large capacitors. Rmhermen (talk) 22:17, 5 November 2014 (UTC)

There are few (if any) modern household appliances that do this - mostly because it's potentially dangerous. I have a couple of laser cutters that have capacitors that retain enough charge after a couple of hours to produce a three inch spark at a few thousand volts...these are hardly "household" appliances but plenty of hobbyists have them. so they fit the "anything that private people use" category.

Our article mentions the flash unit on a disposable camera as containing a potentially lethal capacitor...those things are becoming rare - but you still probably still find them in people's homes.

I once got electrocuted by one of those. It went in one side of the finger and came out the same side, close by. It kind melted a bit of skin, turned that part white from pinkish yellow and made a burnt skin smell. Holy crap, those things can kill? (If the heart is in the path and it can't be restarted in time is the easiest I assume). Sagittarian Milky Way (talk) 21:53, 9 November 2014 (UTC)

Supercapacitors can store immense charges - but they start to blur the line with rechargeable batteries, which, in a sense are just capacitors too. SteveBaker (talk) 23:58, 5 November 2014 (UTC)

Just to help us get a feel for it, can you quantify the size of your capacitors? Are we talking a few Farads, or many? SemanticMantis (talk) 15:22, 6 November 2014 (UTC)

• If the two ends of a capacitor are very well insulated from each other, its ability to hold charge is determined by its leakage rate. I believe that most ordinary capacitors are capable of holding a charge for days without major loss. Low-leakage capacitors can hold a charge for months. The maximum charge that a capacitor can hold is determined by its dielectric breakdown point, which depends on the quality of construction. Looie496 (talk) 16:25, 6 November 2014 (UTC)

understanding the waveform representation

If an oscillogram depicts a wave around the x axis, and there are values that are positive and negative for the y-axis. The y-axis represents frequency, but how can the frequency be negative? And don't we need multiple values at the same time on the y-axis for all frequencies? Think https://en.wikipedia.org/wiki/Praat#mediaviewer/File:Spectrogram_-_mot%C3%A1ngo_mwa_basod%C3%A1.png --Senteni (talk) 19:57, 5 November 2014 (UTC)

An oscilligram depicts amplitude vs. time (not frequency vs. time). Typically, there is some sensitive element that responds to sound waves (such as a microphone transducer), and the y-axis is proportional to the back and forth fluctuations in that element caused by passing sound waves. Dragons flight (talk) 20:04, 5 November 2014 (UTC)

On the image in question, the upper trace is an oscillogram (with positive and negative y-axis values), and the lower trace is a spectrogram (with only positive y-values). Tevildo (talk) 20:12, 5 November 2014 (UTC)

That's a confusing plot to say the least. The upper window appears to be the time history of the sound waveform, in black. As such it will oscillate around 0 Pa. I suspect the vertical blue lines represent the occurence of peaks in the time history, the interval of which is plotted as its reciprocal in the blue curve in the lower plot. The lower plot is what I'd call a spectogram, a 2d representation with frequency on the y axis, time on the x axis, and intensity of that frequency and time represented by grey scale. I do not understand the left and right hand y axis notations, the red dots appear to be some sort of peak picking algorithm. Greglocock (talk) 22:38, 5 November 2014 (UTC)

It's not confusing if you are familiar with spectrograms. I would go so far as to call this a "standard" plot format for certain types of digital signal processing. Nimur (talk) 22:34, 5 November 2014 (UTC)

Oh yes, try explaining to an engineer why there are two y axis scales and no explanation as to which data uses which one! Greglocock (talk) 22:38, 5 November 2014 (UTC)

Regarding the plot arrangement: there are two plots. One who is familiar with waveform analysis will very quickly visually identify that the two plots correspond to a waveform and a spectrogram. One who is unfamiliar would do well to read the caption.

Regarding the colors: the image has a caption:

• light blue line = pitch (as documented)
• dark blue lines = pulses
• red dots = formants (as documented)

Here is a link to the Praat software tool official website.

Here's a tutorial, Praat Sound Window, from UNC's computational linguistics program.

Nimur (talk) 22:44, 5 November 2014 (UTC)

Black Holes, Dark Matter, General Relativity

It is clear from the statements on the user's page that this is just trolling

Why aren't dark matter, black holes and general relativity labeled as pseudoscience? All three concepts fit the description of pseudoscience very well. We do not need to delete these articles, just label them correctly. Wavyinfinity (talk) 21:28, 5 November 2014 (UTC)

Who says they're pseudoscience? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:35, 5 November 2014 (UTC)

Because e.g. black holes are not pseudoscience. Our article defines: "Pseudoscience is a claim, belief or practice which is falsely presented as scientific, but does not adhere to a valid scientific method, lacks supporting scientific evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status."

Black holes are considered plausible by the astrophysics community. They have plenty of scientific evidence for their existence and most published results about them conform to the scientific method. We even have a whole section on Black_hole#Observational_evidence. The same goes for dark matter and general relativity (they are topics in science, not pseudoscience), which I think you'd know if you'd read the articles carefully. I'm assuming good faith here, but you should know that your question sounds a bit like trolling. SemanticMantis (talk) 21:37, 5 November 2014 (UTC)

(edit conflict)No, they don't fit the description you claim, because they are attempts to explain observations. Science starts with evidence and develops theory to explain it. (I agree that sometimes speculative science puts forward a theory that goes beyond the available evidence, but it then looks for evidence to confirm or refute the extended theory.) Have you read the articles that you link? (Do you believe in infinity? ) Dbfirs 21:38, 5 November 2014 (UTC)

Read the essay on the user's page and it will be clearer where he's coming from . ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:41, 5 November 2014 (UTC)

The definition of pseudoscience (at least according to Wiktionary) is:

"Any body of knowledge purported to be scientific or supported by science but which fails to comply with the scientific method."

(Other dictionaries define it similarly)

So:

1. Do these fields of study "purport to be scientific"? Well, yes...duh!
2. Do they "comply with the scientific method"? Yes, they do. They propose hypotheses, they make predictions that are (at least in principle) testable, they don't make unfalsifiable claims, they perform experiments and/or observations in an effort to prove (or disprove) those predictions. They publish results in peer-reviewed mainstream journals. Experiments and/or observations are repeated independently where possible. This is "THE SCIENTIFIC METHOD" at it's finest.

Now, it's very possible that any or all of these things might turn out to be false. But that's not the acid test of pseudoscience.

Pseudoscience is something like Homeopathy where they make scientific claims (in this case that diluting some active ingredient to the point where there is none left leaves a stable 'imprint' in the water - and that the resulting water can cure illnesses) - but they do not create working hypotheses, they do not perform experiments (like a double-blind drug trial would do), they don't do peer reviews and publish results in mainstream journals. They are making clearly testable scientific claims yet NOT following the scientific method...so they are pseudosciences.

A religion, on the other hand does NOT make scientifically testable claims (their claims are generally non-falsifiable) - so the scientific method is inapplicable, even in principle - so they are not pseudoscience.

Pseudoscience is NOT the same thing as bad science or unproven science or disproven science. So even if you believe that black holes do not exist - that doesn't make the field of study "pseudoscience".

Cold fusion is a good case in point. It was claimed to occur, they tried to do experiments to prove it, the experiments were written up, peer reviewed and published, efforts to repeat the experiments failed - and now it's (generally) believed to be false. But it's definitely science and not pseudoscience because they followed the scientific method. Our article correctly labels it as "pathological science" - but not pseudoscience.

Wikipedia has very clear rules about pseudoscience and how it's determined and labelled - and the things you mention are not remotely it.

If you want a target to attack, you might try Freudian psychoanalysis (for example) - which makes scientific claims and has historically failed to do serious experimentation to back up those claims.

SteveBaker (talk) 23:37, 5 November 2014 (UTC)

It's nice that you all are trying here, but I feel the need to bring forth this rather reliably true aphorism: You cannot reason a person out of a position they did not arrive at via reason. The entire question above, and their entire main Wikipedia page screams "Science is hard and stuff, and it's easier to reject the things I don't understand than to either a) understand it or b) trust the people that do". It does no good to argue with people this far out of touch with reality. At best we can remind the rest of the world how silly they are. But people like this are a lost cause. --Jayron32 00:23, 6 November 2014 (UTC)

Given the following quote on the user's page, the full screen of discussion here is somewhat amusing:

"1. Hit and Run tactics. Post things on public forums like Einstein was an idiot, Stephen Hawking is a pawn for the mathematical priests of establishment. Do not respond to the replies, just post these things and then do something else with your time. You must insert ideas that can not be said otherwise because they are taboo. These taboo statements are incredibly dangerous to establishment."

MChesterMC (talk) 09:23, 6 November 2014 (UTC)

"The establishment", sure. It would be interesting to see a public opinion poll as to what percentage of the public either knows or cares about this subject. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:51, 6 November 2014 (UTC)

I suggest you take greater caution in the future. I'm not going to report you, but your topic ban seems very broad "everything related to astrophysics or cosmology" User talk:Wavyinfinity#Arbitration enforcement topic ban: Pseudoscience so it can likely be said to apply to the RD, particularly since, as many including the topic closer have suggested, you appear to be either trolling or soapboxing/POV pushing rather than asking a genuine question even if it's not clear you're trying to harm wikipedia by advocating for changing articles. I presume you know it's very broad, since you were blocked for fooling around with a wikiproject [3]. Nil Einne (talk) 18:01, 6 November 2014 (UTC)

How would Freud Interpret This Dream?

Just out of curiosity i always wanted to know how sigmund freud would interpret this dream, with his theory of dream analysis.The dream itself is something like this a man walks down a flight of stairs following a trail of blood to find his father lying in a pool of blood. This has always been something i wanted to know. Help from my fellow wikipedians would be greatly appreciated, THANKS. — Preceding unsigned comment added by 173.52.22.58 (talk) 22:45, 5 November 2014 (UTC)

We can never know what a dead person would think, but you can read about what he did think!

The Interpretation of Dreams (1900) is available at no cost in German from Project Gutenberg, and in English from other websites. Several other translations are listed in our article. Another of his works, Dream Psychology (1920) is available in English from Project Gutenberg.

I read The Interpretation of Dreams a long time ago. Reading Freud's own writing proved to me to be the most damning cases against Freudian psychology as a scientific enterprise. Nimur (talk) 22:52, 5 November 2014 (UTC)

If someone else's interpretation can help you, walking down stairs "might suggest being in control of a changing situation." Bleeding (from the same source) "could mean hurtful remarks, for instance being told we are not loved." Seeing a dead parent is "either the beginning of independence from parent or repression of the emotions they engendered in us."

In my absolutely unprofessional opinion, you murdered your father and mostly forgot about it. Also, your house is haunted. InedibleHulk (talk) 23:03, 5 November 2014 (UTC)

The dream is about anxiety. Now, donate 5 dollars to your favorite charity, in my name. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:11, 5 November 2014 (UTC)

• Of course we can't know what Freud would have said, but it isn't hard to guess. The fundamental tenet of Freud's theory was that all dreams consist of wish fulfilment. What sort of wish is being fulfilled in that dream? Well, another basic tenet of Freudian theory is that every male child has an Oedipal desire for his mother and therefore is jealous of his father. So this one is pretty easy. (My personal view is that the idea of dreams as wish fulfilment has some validity, but doesn't apply to all dreams and in any case Freud's use of it was utter bullshit.) Looie496 (talk) 16:12, 6 November 2014 (UTC)
  • I always figured Freud was into that, and assumed everyone else was too. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:29, 6 November 2014 (UTC)

Can an healthy man use a medical oxygen for breathing?

I've heard that using of a medical oxygen when it's not needed, is harmful. That's right and based on a reliable source? 213.57.99.33 (talk) 23:18, 5 November 2014 (UTC)

I think this is bordering on medical advice - and we're not allowed to provide that here on the ref desk. SteveBaker (talk) 23:22, 5 November 2014 (UTC)

The OP should consult Google, which I expect would have many references (albeit many of them bad information). ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 5 November 2014 (UTC)

No, the OP should consult a doctor. SteveBaker (talk) 23:38, 5 November 2014 (UTC)

Oh, please. The OP is seeking information, not advice, and even if advice were sought, we are at liberty to provide information not related to a specific case. Aside from pointing out that medical oxygen is essentially pure oxygen, the oxygen toxicity article linked by InedibleHulk below is probably a good place to start. Essentially, unless unusual conditions exist or where ambient pressure is elevated above that at sea level, there is no reason to suggest that breathing pure oxygen, especially over a limited period, would be harmful to the majority of individuals. —Quondum 00:09, 6 November 2014 (UTC)

I'm pretty sure we're allowed to say oxygen toxicity exists. InedibleHulk (talk) 23:46, 5 November 2014 (UTC)

Thank you. I've found this article: Oxygen therapy, and it refers this issue. (By the way, it's so interesting to understand why this information is bordering on medical advice - when it's in the article.213.57.99.33 (talk) 23:51, 5 November 2014 (UTC)

The issue is that what's in the article has been massaged over the years by many editors to be good, well sourced content. What gets written here is not in the same class. Anyone can write anything they think of here. Not to be trusted. (Not even my comments.) HiLo48 (talk) 00:01, 6 November 2014 (UTC)

Though if we refer people to that good, well-sourced content, it's not us they're trusting. If they even need to be trusting in the first place. The question didn't suggest "I'm considering taking oxygen I don't need. What should I do?" to me. Just looking for a source to verify whether it's generally harmful. Almost every question here can be taken with suspicions about the asker's reasons, but if they're not provided, I assume generic curiosity. Telling people to consult a doctor is medical and often financial advice, even if the assumption that they need one is correct. InedibleHulk (talk) 00:24, 6 November 2014 (UTC)

Hyperventilating with pure oxygen is necessary if you need to hold your breath for a long time. Count Iblis (talk) 04:29, 6 November 2014 (UTC)

• If the OP is a medical volunteer he should also ask his supervisor whether he should be researching such questions here. I had a friend training as an EMT in college who lost his job because he listed a patient's body temperature as 95F when tradition required it be rounded to the nearest even number. Should you suddenly come out with "but I was told on wikipedia that..." you may find yourself summarily dismissed. μηδείς (talk) 17:12, 6 November 2014 (UTC)

Our article on oxygen toxicity covers the main points that I'm aware of as a former clinical data analyst and biomedical engineering technologist. Further than that, I agree we oughtn't to be giving advice on when and how oxygen ought to be used to questioners. We don't know what their health status or their reasons for asking are, and any information beyond sourced material in the oxygen toxicity article falls under the general medical advice prohibition here.

It occurs to me that the OP seemed to be asking how safe medical oxygen was compared to, say, oxygen intended for SCUBA mix or welding oxygen. The same hazards listed in our article on oxygen toxicity apply regardless of whether the oxygen is USP (prepared according to the specs in the United States Pharmacopeia for medical use), non-medical oxygen for SCUBA or other nonmedical life support applications, or industrial oxygen (except that additional hazards may exist when industrial (welding) oxygen is used owing to impurities. loupgarous (talk) 01:02, 7 November 2014 (UTC)

Both oughtn't and ought not have become rare in North America. Oughtn't in particular may not be understood  :) Count Iblis (talk) 19:47, 7 November 2014 (UTC)