Science desk
< February 6	<< Jan \| February \| Mar >>	February 8 >

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.

February 7[edit]

Phases of matter[edit]

What determines the phase (solid, liquid or gas) of matter emanating from the human lower tract?--31.92.250.145 (talk) 00:38, 7 February 2017 (UTC)[reply]

The presence of gas, or flatulence, is caused by production of gas by microbes present in the gastrointestinal tract. These microbes are always present, in every person, though the degree to which they produce gas varies with a person's own diet. With regard to liquid versus solid, or basically solid feces versus diarrhea (though medically speaking, that means at least three liquid bowel movements a day), this is determined by water absorption by the colon. Digestive products reach the colon in a liquid state, but normally exit the body as a moist solid due to the absorption of water by the colon. Many different factors can cause the colon to fail to remove water from feces, and some of these are discussed in the article I linked. Illness, injury and sudden changes in diet could do it, for example. Someguy1221 (talk) 00:48, 7 February 2017 (UTC)[reply]

Oh, and anyone passing plasma from their lower tract should probably consult their physician. See also Phase (matter).{The poster formerly known as 87,.81.230.195} 94.12.94.189 (talk) 05:25, 7 February 2017 (UTC)[reply]

Warning: Keep out of reach of children. In case of ingestion consult a funeral home. Sagittarian Milky Way (talk) 07:10, 7 February 2017 (UTC)[reply]

The phase of any particular chemical substance is determined by temperature and pressure. In the colon, that is pretty much the same for all of the many substances present - which is why faecal matter is a varying mixture of solids, liquids and gases. It would not be accurate to talk about faeces having a particular phase, as it is not a chemically uniform substance. The water is always liquid, the methane is always gaseous, and the coin the baby swallowed is always solid. The consistency at any particular time depends on the mixture of substances actually present - and that depends on the factors mentions above. Wymspen (talk) 12:43, 7 February 2017 (UTC)[reply]

Wikipedia has articles on feces, diarrhea, and flatulence. No one here will stop you from reading them yourself. --Jayron 32 13:08, 7 February 2017 (UTC)[reply]

meta discussion on WP:OVERLINK
All three of those articles were already linked in a response given ten minutes after the question was asked. Did someone here stop you from reading Someguy1221's reply? Matt Deres (talk) 16:03, 7 February 2017 (UTC)[reply] Nope, just the fact that I'm a terrible example a of human with nothing useful to contribute. Carry on. --Jayron 32 17:00, 7 February 2017 (UTC)[reply]

How many oxygen molecule in any molecule of hemoglobin de facto?[edit]

How many oxygen molecule in any molecule of hemoglobin? I know that hemoglobin has 4 irons which each one of them carry on one molecule of oxygen (totaly 4 oxygens for one hemoglobin) but what I don't understand is if any hemoglobin is 'busy' and binds 4 molecules of oxygen (O2) in normal condition or it's just the ability and in fact it is not what happening? 93.126.88.30 (talk) 15:23, 7 February 2017 (UTC)[reply]

This paper should answer your questions. --Jayron 32 15:31, 7 February 2017 (UTC)[reply]

Unfortunately I don't have access to this PDF file. 93.126.88.30 (talk) 15:49, 7 February 2017 (UTC)[reply]

I made a detour by this headache-giving paper, but eventually found Oxygen–hemoglobin dissociation curve. Does it answer the question? Tigraan^{Click here to contact me} 17:07, 7 February 2017 (UTC)[reply]

To put that graph in context, you may have encountered pulse oximetry at a doctor's office -- the little thing they put on your finger and hopefully it reads ninety-something, or sometimes, 100 or more. Arterial blood is generally going to have all four oxygens in place. Moreover, because of cooperative binding, even if you had a group of hemoglobin proteins with an average of 50%, they would be more likely to have some with all four oxygens and some with all four empty than you would expect by random chance. (How much more, I'd have to look up some specific numbers and set up a bunch of calculations I scarcely remember to figure out...) Wnt (talk) 17:22, 7 February 2017 (UTC)[reply]

And of course there is more than one type of hemoglobin, and each type has its own dissociation curve. . . - Nunh-huh 22:30, 7 February 2017 (UTC)[reply]

There are oxygen atoms in both heme and the globin chains, but no oxygen molecules. There need be no oxygen molecules (reversibly) bound to the heme, and even at a high partial pressure of oxygen are they ever actually "in" the hemoglobin? Arguably not. Klbrain (talk) 00:22, 11 February 2017 (UTC)[reply]

@Klbrain: Well, I think I have to give you this one! I checked our article on hemoglobin and it's apparent there's some chemistry ongoing which I haven't kept up with. The discussion of the oxidation state there favors the idea that the oxygen molecule is in fact converted to superoxide ion, and the iron(II) at the center of the heme is converted to iron(III) - but only while the superoxide is bound, because otherwise that's methemoglobin. Well, you can read it there, just learned it myself. An oxygen molecule vanishes into the innards of each monomer, and an oxygen molecule comes out again later, but while it's out of our view... it's something else. That's science for you! Wnt (talk) 01:57, 11 February 2017 (UTC)[reply]

Is blood pressure considered as a hydrostatic pressure?[edit]

I watched this video on Youtube and I noticed that the blood pressure is similar but I'm not sure about that. 93.126.88.30 (talk) 15:46, 7 February 2017 (UTC)[reply]

Sounds like we need a link to hydrostatic pressure. The first sentence in that sections says: "In a fluid at rest, all frictional and inertial stresses vanish and the state of stress of the system is called hydrostatic." Since normally blood is not at rest, BP is not measuring hydrostatic pressure alone (the fact that it varies during each heartbeat is a clue here). However, there may be a hydrostatic pressure component, and when they stop the heart during heart surgery, that may come into play, affecting the bleeding rate. StuRat (talk) 15:52, 7 February 2017 (UTC)[reply]

What we call "blood pressure" is the hydrostatic pressure exerted by our blood on our blood vessels. In the realm of the circulatory system, we differentiate between hydrostatic and oncotic pressure. While it may not agree perfectly with the Wikipedia article, hydrostatic pressure in the circulatory system refers to the pressure of a liquid in a closed system. It is normally higher pressure at the bottom of the system and lower pressure at the top (gravity). 209.149.113.5 (talk) 20:15, 7 February 2017 (UTC)[reply]

Even oncotic pressure doesn't account for the difference between systolic pressure and diastolic pressure, called pulse pressure, which is due to the active pumping of the heart. StuRat (talk) 22:39, 7 February 2017 (UTC)[reply]

Oncotic is the opposing pressure to hydrostatic pressure. While systolic and diastolic are pressures and part of the circulatory system, they are not part of the hydrostatic-oncotic relationship. They do affect it because the entire circulatory system is all related, but they are separate. I noticed that in the link to the article you included in your first response, the very next entry notes that in medical usage, hydrostatic has a different meaning than common hydrostatic pressure. 209.149.113.5 (talk) 13:25, 8 February 2017 (UTC)[reply]

Hydrostatics#Medicine, yes. StuRat (talk) 16:22, 8 February 2017 (UTC)[reply]

Human Body vs. Gorilla Body[edit]

In this comparison image, the human looks very lean. The abdomen appears flat, and there is very little space for the intestines. In contrast, the gorilla seems to have a huge space at the abdominal region. Do gorillas have bigger digestive tracts than humans do; or do they have more fat than humans? And why is the gorilla's ilium longer than the human's? 66.213.29.17 (talk) 18:52, 7 February 2017 (UTC)[reply]

Do gorillas have bigger digestive tracts than humans do?

"Milton [1987, p. 101] notes that "...the size of the human gut relative to body mass is small in comparison with other anthropoids" [1]. That link contains a nice discussion of human/ape digestive systems, along with an informative diagram. SemanticMantis (talk) 19:06, 7 February 2017 (UTC)[reply]

Long story short: while the human species has evolved to be omnivorous, gorillas are herbivores; plants are harder to digest than meat, so herbivores in general need relatively larger/longer digestive tracts than omnivores (or carnivores).

In addition, humans have been processing at least some of their food before eating for something like 2 million years, initially by pounding and chopping and subsequently also by the application of heat, and have consequently evolved even smaller digestive tracts than would otherwise be the case, because such preparation (where appropriate) makes the food even easier to digest. {The poster formerly known as 87.81.230.195} 94.12.94.189 (talk) 22:43, 7 February 2017 (UTC)[reply]

Humans have been around for 2 million years?..... 64.170.21.194 (talk) 23:00, 7 February 2017 (UTC)[reply]

If you, like most paleoanthropologists, take the term "human" to be synonymous with Genus Homo. Even if you don't, the activity of food preparation extends from before the emergence of Homo sapiens, let alone our mutual subspecies Homo sapiens sapiens, and has therefore been influencing the evolution of the human (and, if you like, pre-human) digestive tract over the said 2 million years. {The poster formerly known as 87.81.230.195} 94.12.94.189 (talk) 23:42, 7 February 2017 (UTC)[reply]

Can criminal human behavior be predicted before they strike?[edit]

I know that finding patterns in the weather can predict tornados and hurricanes. Can humans predict criminal behavior in other humans before they strike? 66.213.29.17 (talk) 19:30, 7 February 2017 (UTC)[reply]

In broad ways yes. Just as the weather forecast may say "tornadoes are likely in this area today", they could also predict that "this serial killer is likely to strike again, around this date, in this area". However, the weather forecast won't tell you exactly where a tornado will hit, and neither could we predict exactly who a serial killer will attack. StuRat (talk) 19:33, 7 February 2017 (UTC)[reply]

On the individual human level, no. However, by studying risk factors for criminal behavior, one can predict how populations of people will produce trends in criminal behavior, which is why many policy makers look at crime prevention as an economic and social issue. Here is a report from the UK that looks at various risk factors for criminal behavior. Here is a book that purports to look at a variety of factors leading to criminal behavior. Here is a group based in the U.S. of scholars and economists that study the issue as well. Some of the experts in this area come from behavioral economics, you may want to read some Steven Levitt, either his scholarly work or his more popular-oriented stuff like Freakonomics. Sociologist Sudhir Venkatesh also looks at crime from a sociological (rather than economic) perspective, and his work is highly regarded in this field. --Jayron 32 19:52, 7 February 2017 (UTC)[reply]

I come from a background of statistical signal processing - the technical discipline that tries to guess correct answers to difficult problems by studying large amounts of input-data.

Using old mathematical techniques and new computers, we can predict anything! The more important question is, with what accuracy can we predict?

Review probability, and have a look at detection error tradeoff. If you don't care about confidence in your result, you can predict anything!

And for the interested reader, here's a fantastic historical monograph on predicting behavior: A Theorem for Prediction (Zlotnick, 1967), written by some folks who like to make intelligent predictions about bad behavior, particularly before the opposing team "strikes."

Nimur (talk) 20:20, 7 February 2017 (UTC)[reply]

We also have an article at Predictive policing. It's small, but you might find the references worth reading. Someguy1221 (talk) 22:48, 7 February 2017 (UTC)[reply]

(ec) This is a loaded question. Predicting in a sense of estimating a (relative) likelihood or an (absolute) probability - certainly yes. A criminal history and an occupation of a person are already significant indicators. For example, a blue-collar worker is less likely to commit a white-collar crime and vice versa. However, predicting and preventing a crime more than, say, 30 seconds before it happens - certainly not, as this is largely inconsistent with free will. There is experimental evidence (mostly from fMRI) that a person's brain forms a decision several (up to 30) seconds before the person can actually articulate that decision; however, this is not inconsistent with a free will (if anything, it is an evidence that person actually does think). However, if you could predict that person A will, beyond all reasonable doubt, murder person B a month from now -- this would be inconsistent with the free will as it is currently understood. If there is no free will, there is no meaning in punishment and reward, and thus no meaning in predicting the crime. Indeed, in absence of a free will, punishing a criminal is as effective as flogging the sea. On a related note, see The Minority Report. Does this help? Dr Dima (talk) 23:05, 7 February 2017 (UTC)[reply]

Well yes, but you can alter crime rates by altering social and economic conditions that lead to crime; increased access to education and employment opportunities, social safety nets, etc. Public policy decisions about such things are ABSOLUTELY based on what factors lead to crime, and how to combat crime by reducing its root causes. --Jayron 32 02:31, 8 February 2017 (UTC)[reply]

From Sherlock Holmes in The Sign of Four, "Winwood Reade is good upon the subject," said Holmes. "He remarks that, while the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty. You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. So says the statistician." Fiction, of course, and not quite an accurate quote from Reade, but to the point. Matt Deres (talk) 17:34, 8 February 2017 (UTC)[reply]

Holmes's thesis here was expanded upon in the Foundation Trilogy by Isaac Asimov. Still fiction, but the premise for the whole theory is that individual humans act unpredictably, but groups of humans behave in a statistically predictable manner. Asimov, as a chemist, based his concept on those from statistical thermodynamics such as the law of mass action and the kinetic theory and the like: the notion that a system can be studied and predictable statements made about its behavior even if the individual components of the system behave unpredictably. Ludwig Boltzmann made a career out of it. Our article on law of mass action even notes that some of the principles are applied by sociologists in their work. --Jayron 32 19:13, 8 February 2017 (UTC)[reply]

Surprisingly, in the 19th century it was the physicists that were inspired by sociologists in this respect. In the social sciences, the statistical approach had reliably described such phenomena as crime rates and ages of marriage in large populations even though behaviour of individual humans was obviously unpredictable, which stimulated both Maxwell and Boltzmann to take the same statistical approach with molecules.^[1] Jmchutchinson (talk) 21:13, 8 February 2017 (UTC)[reply]

Fascinating. I didn't know that. Thanks for sharing that reference. The interconnected nature of science is always interesting. --Jayron 32 23:57, 8 February 2017 (UTC)[reply]

Before "striking", most criminals will perform some sort of Surveillance or their target, and potential obstacles to successfully carrying out their crime, s well as both the strengths and vulnerabilities of their target. Countersurveillance measures are deemed a vital tool in protecting high-risk targets. I don't have a ref, other than reading it many times on Stratfor. Can anyone verify this? Eliyohub (talk) 15:26, 11 February 2017 (UTC)[reply]

Also, a lot of the research on the subject deals with attempts to predict the likelihood of a convicted criminal reoffending, and measures to mitigate this risk. In cases where the risk is deemed unable to be sufficiently mitigated, prisoners who have completed their sentence are sometimes held under Dangerous offender laws. Tools like STATIC-99 are somewhat useful in this regard.

There's probably a lot less research into predicting which individuals are going to offend in the first place, in the absence of any explicit indicators of concern.

One police officer who worked in the UK "pedophile unit" speculated that if so many offenders were claiming to have been victims in childhood themselves, and this connection was true, than we should initiate a general program for those who have experienced child sexual abuse to intervene in a therapeutic fashion before they strike, on the chance that they are a risk of turning to offending themselves. I found it an interesting idea, but obviously, any such initiative would require voluntary participation by the victim. Not sure whether experts would say the idea has merit as a way of reducing child sexual abuse, but abuse victims often need assistance anyways, and therapists doing such work could incorporate this in, I suppose. I think the idea of increased availability of psychological assistance for victims of sexual abuse is one which could be easily "sold" politically, and if it does help reduce the offending rate, so much the better. Eliyohub (talk) 15:40, 11 February 2017 (UTC)[reply]

References

^ Gigerenzer, Gerd; et al. (1989). The Empire of Chance: How Probability Changed Science and Everyday Life. Cambridge: Cambridge University Press. p. 62.

[1] Gigerenzer, Gerd; et al. (1989). The Empire of Chance: How Probability Changed Science and Everyday Life. Cambridge: Cambridge University Press. p. 62.

[1]