Wikipedia:Reference desk/Archives/Science/2014 September 23

= September 23 =

Falling on your eye
When people fall on their eye, is the natural instinct to close the eye or try to dodge? Or stick their hands out like a regular fall, or try to block it with their hand? What I mean is if they slip and their eye is headed toward something pointy in the wall that looks like this:

What if it's a nail or a screw, putting the protect the nose instinct against the protect the eye instinct? (though unless you've got a bad nail protrusion length to nose length ratio, I think the danger to your eye is illusory. Sagittarian Milky Way (talk) 00:27, 23 September 2014 (UTC)
 * Obvious BS with no referenceable answer. μηδείς (talk) 02:39, 23 September 2014 (UTC)
 * How is it obvious BS? There could possibly be cases. I'd like to know what they did, even if selection effects prevent a referenceable answer as there'd be a strong bias to reporting when the subject did not in fact manage to prevent major harm of their eyeball. Sagittarian Milky Way (talk) 05:13, 23 September 2014 (UTC)


 * I hadn't been aware that assholes punching their partners and saying they fell is the major cause of such claims, or even of any claims. (Okay, now I think I have heard that before.) Anyway I was thinking of long protrusions smaller than the your eye socket, as that would be the scarier than a black eye. Sagittarian Milky Way (talk) 05:47, 23 September 2014 (UTC)

Salk polio vaccine tested in Russia?
The article Jonas Salk does not seem to mention testing of the polio vaccine in the Soviet Union, but I recall a tv documentary which said that there was testing of it in a large city in the USSR, and being surprised that the soviets would have allowed it. 1)Was there such Soviet testing before the announcement in the mid 1950's that it was safe and effective? 2) Did they followup initial administration of the Salk injected vaccine in the US with the Sabine oral vaccine, to the same children a year or so later, or did they stick to a Salk booster injection the next year for children who had the initial Salk injection? Edison (talk) 02:17, 23 September 2014 (UTC)


 * Here's a few freely accessible scientific articles on the topic. At a quick scan, these all seem to give dates 1958-1960 for studies in the USSR. Also, it seems that the tests done in USSR were for the live attenuated vaccine developed by Albert Sabin, not the Salk inactivated 'killed' vaccine.  . Here are a few documentaries on the topic if you want to follow up on that angle  . The second link, from the Smithsonian, seems to indicate that Salk's trials started in 1954 in the US, while Sabin's were in Europe.  SemanticMantis (talk) 16:41, 23 September 2014 (UTC)

Compensation of cost losses in the economy (Write-off of cost losses)
Obviously, that the expensive capitals are always more expensive than the cheap capitals in to its nominal value, so that, should the bourgeois capitalist economy do to equalize the costs of capitals?--Alex Sazonov (talk) 08:03, 23 September 2014 (UTC)


 * This is the Science Ref Desk. Only a madman would call economics a science. HiLo48 (talk) 08:40, 23 September 2014 (UTC)


 * Thanks. I suppose that economics is be a science! Should the bourgeois capitalist economy do to compensate the costs of the lost (unfulfilled) labor - work?--Alex Sazonov (talk) 08:45, 23 September 2014 (UTC)


 * All this questions are always be equal to the same. Should in the bourgeois capitalist economy a profitability of capitals be the equal, that is so, should in the bourgeois capitalist economy a rates of calculation (accrual) of profits on capital are be the equal?--Alex Sazonov (talk) 10:51, 23 September 2014 (UTC)


 * You mean "Write-off of cost losses" as lowering taxes tru Depreciation? Any number of n economists are usually blamed for having n+1 different opinions so "economics" indeed always has some difficulties with its claim to be science. Anyway this is a question of economic policy aka politics and this makes it an not fitting question here. --Kharon (talk) 11:04, 23 September 2014 (UTC)
 * Of course, the collapse (disintegration) of the Soviet Union (USSR) had objective reasons!--Alex Sazonov (talk) 11:41, 23 September 2014 (UTC)


 * If you look at Reference_desk you see economics falls under the Reference_desk/Humanities. Post there as you are unlikely to get a sensible answer on this desk.--Salix alba (talk): 11:07, 23 September 2014 (UTC)


 * Very much thanks, I don’t know about it. So I been suppose, that is been obviously, that the profitability of economies as also economic actors could not be the equal, otherwise, at the expense of someone will had to cover the losses. Thanks a lot for all.--Alex Sazonov (talk) 11:24, 23 September 2014 (UTC)

Nose shaping
There have been spate of so called "nose shaping" devices flooding the market like Nasofix. Nose Magic, Nose Up etc... They claim that the cartilage in nose which gives it's shape is actually malleable if pressed for a period of time everyday and that too at a particular temperature. How true is it ?? — Preceding unsigned comment added by 119.235.54.187 (talk) 11:07, 23 September 2014 (UTC)


 * i'm not sure about the products but i don't think "malleable" is the right word to describe cartilage; iirc it's displaced during a nose job, not moulded?  ~Helicopter  Llama~  11:54, 23 September 2014 (UTC)


 * It certainly is flexible, but that's not quite the same thing. I'd say it will undergo elastic deformation, not plastic deformation.  You can do an experiment.  Buy a whole chicken.  You will find cartilage on the tip of the breastbone quite similar to nose cartilage.  Bend it for as long and as much as you like.  When you stop bending it, does it go back to the original shape ?  (Of course, even if you can get it to change shape permanently, you may not be willing to expose your nose to the same level of force for the same period of time.)


 * Now, the nostrils are a bit different. Since there's no cartilage on the sides of the nose, those areas could be stretched out, over time.  Some primitive cultures stretch out their lips in a similar way.  StuRat (talk) 17:41, 26 September 2014 (UTC)

More questions on Newton's Laws
First, there is the rule that the phase space coordinates are positions and velocities, that is, with these, all future states of the system are determined. Is this somehow a consequence of Newton's Laws?

Second, it is often stated that energy conservation is a consequence of the time-invariance of physical laws. This seems lacking to me, though I may be wrong. If we have a dissipative system that obeys Newton's Laws, the rules governing the system are time-invariant but energy isn't conserved. Is a more accurate statement that energy conservation follows from physical laws being conservative and time-invariant?--Leon (talk) 12:07, 23 September 2014 (UTC)


 * Regarding the first question: no Newton's laws of motion do not necessarily lead to determinism. They describe how masses are influenced by forces and how momentum is conserved, but they don't say anything about what kinds of forces exist or what mechanisms give rise to these forces. They do not exclude the possibility of random/unpredictable forces. Of course gravity, as described by Newton, is a predictable force, but Newton would never have claimed that gravity is the only type of force. - Lindert (talk) 12:32, 23 September 2014 (UTC)
 * Sorry, I was unclear. I mean do Newton's Laws suggest that a mechanical system is specified completely by positions and velocities, and higher-order derivatives do not need to be stated? I know Newton's Laws do not suggest determinism--Leon (talk) 13:18, 23 September 2014 (UTC)


 * It is been always assumed that Newton's Laws are stored in nuclear physics, so that Newton's mathematical model is been stored in nuclear physics.--Alex Sazonov (talk) 15:04, 23 September 2014 (UTC)


 * Yes, you could say that if you separate the mechanical system from the forces acting upon it. Newton's second law basically defines forces as the second-order time derivative of the space co-ordinates per unit of mass. So if you say that the future states of the system are determined by the 'mechanical system' plus the forces acting upon it (or if forces are absent), then yes, by definition the mechanical system does not include anything but the positions and velocities of the particles. - Lindert (talk) 15:31, 23 September 2014 (UTC)


 * The answer to your second question is Noether's theorem. If the physics is described by a Lagrangian and it doesn't explicitly depend on the time, then there is a conserved quantity that is, essentially by definition, the total energy.


 * For the first question: Newton's laws have no time derivatives higher than order 2. Assuming that's true of your forces as well, you can convert the differential equations to first order by substituting v'(t) for x'&apos;(t) and adding constraints of the form x'(t) = v(t). Then you can use something like the Picard–Lindelöf theorem to show that initial values for x and v are enough to guarantee a unique solution. In general, if the forces have nth time derivatives (n ≥ 2) then you will need initial values for the zeroth to (n-1)th derivatives. -- BenRG (talk) 19:41, 23 September 2014 (UTC)

Is the speed of the electrons is not been enough?
Is it right to consider that the speed of electron (the speed of flow of electrons) is insufficient by compared to the speed of light, although all nuclear physics just is been based on the speed of the electrons (on the speeds of flow of electrons)?--Alex Sazonov (talk) 13:04, 23 September 2014 (UTC)
 * Who says so? ←Baseball Bugs What's up, Doc? carrots→ 13:41, 23 September 2014 (UTC)
 * However, I suppose, that the division of nuclei and atoms (nuclear decay) always had been a high-speed output of flow of electrons instead of light energy output.--Alex Sazonov (talk) 14:50, 23 September 2014 (UTC)
 * Our article on beta particles says that their speed is typically greater than 0.75c. Gandalf61 (talk) 15:07, 23 September 2014 (UTC)
 * Thank you Gandalf61. The intensity of the electromagnetic fields is always been determines the speed of the electrons (the speeds of flow of electrons).--Alex Sazonov (talk) 15:15, 23 September 2014 (UTC)
 * It also depends on what you mean by speed. The speed of a single electron in isolation is rarely a useful thing to know when modeling the behavior of matter.  What you want is the Root-mean-square speed of electrons in a given environment.  -- Jayron  32  16:19, 23 September 2014 (UTC)
 * Under the speed of electron, I been mean the permissible speed acceleration of electron.--Alex Sazonov (talk) 17:16, 23 September 2014 (UTC)


 * This is explained by bremsstrahlung: "The total power radiated in the two limiting cases is proportional to $$\gamma^4$$ ($$a \perp v$$) or $$\gamma^6$$ ($$a \parallel v$$). Since $$E = \gamma m c^2$$, we see that the total radiated power goes as $$m^{-4}$$ or $$m^{-6}$$, which accounts for why electrons lose energy to bremsstrahlung radiation much more rapidly than heavier charged particles" Count Iblis (talk) 18:40, 23 September 2014 (UTC)
 * Also relevant to Iblis's link is Larmor formula. -- Jayron  32  18:55, 23 September 2014 (UTC)
 * As far as I know the resonances of the electric current and dynamics of the electric current in the gases are always had been not so great dynamics as in the metal alloys. Therefore, gases are not been the environment on which we can speak.--Alex Sazonov (talk) 19:22, 23 September 2014 (UTC)
 * Still, the natural environment of all electrons are always been metals!--Alex Sazonov (talk) 03:14, 24 September 2014 (UTC)
 * I suppose, that in this physical-mathematical formula of Einstein the speed of light been plays the role of a possible speed acceleration of the electrons.--Alex Sazonov (talk) 05:33, 24 September 2014 (UTC)
 * I suppose, that the speed of light is been achieved by ionization of electrons.--Alex Sazonov (talk) 17:00, 26 September 2014 (UTC)

Question about iud study
Question moved from "Question about iud study" on the Miscellaneous desk. -- EronTalk 16:52, 23 September 2014 (UTC)

In one study about iud on the internet, it said that 1.8 percent of teenagers became pregnant while using mirena iud. Do they mean that the first year failure rate for teens using it is 1.8, or do they mean that 1.8 percent of teens became pregnant over the course of the study? It said they used descriptive statistics to determine the failure rate within first year of use.199.7.159.41 (talk) 03:41, 22 September 2014 (UTC)


 * Complications and Continuation of Intrauterine Device Use Among Commercially Insured Teenagers


 * Table 2 has the the percentage you listed, and the text associated says The frequency of complications within the first year of use was low among users of both types of IUDs in all age groups (Table 2)
 * -- looks like a first year failure rate of normal pregnancy to me (edit: there are other failure modes and complications that are also listed in the table, so, overall complications/"failures" due to any cause would be higher). SemanticMantis (talk) 14:27, 22 September 2014 (UTC)

But it says that out of 1528 teenagers, 28 became pregnant, which is close to 1.8 percent of 1528. If you look at table 1, you will see that the number of teens applying for a hormonal iud every two year period, adds up to 1528. My question is, how did they come up with 1.8 percent as the first year failure rate?24.207.79.50 (talk) 17:46, 22 September 2014 (UTC)

By the way, I'm the same person who posted the first question24.207.79.50 (talk) 17:47, 22 September 2014 (UTC)


 * Table 2 shows the frequency of various outcomes in the first year of use. Of 1528 subjects aged 15 to 19 years old at time of insertion, 28 became pregnant within one year. So the first year failure rate for this cohort was 1.8%. The key is that 28 did not become pregnant during the full study; 28 became pregnant within one year of having an IUD inserted. - EronTalk 18:08, 22 September 2014 (UTC)

I think i understand. what you are basically saying is that there were 28 teenagers who reported pregnancy after one year. Which means there could have been possibly more pregnancies during the entire period, but because they were after one year of use, they weren't mentioned, since the study was not looking for the total number of pregnancies during the entire period, but instead for the number of teens who reported pregnancy after their first year. — Preceding unsigned comment added by 24.207.79.50 (talk) 18:49, 22 September 2014 (UTC)


 * Yes. This is explicitly stated in the abstract: "A retrospective cohort study was conducted... to estimate the odds of experiencing complications, method failure, or early discontinuation within 12 months of insertion by age group and type of IUD inserted." - EronTalk 19:04, 22 September 2014 (UTC)

Anyway, my last question before i make myself look more foolish is, does that mean that the total number of pregnancies during the full study could have been even greater than the number of pregnancies reported after one year of use? Also, maybe this study should be cited in wikipedia — Preceding unsigned comment added by 24.207.79.50 (talk) 19:17, 22 September 2014 (UTC)


 * Yes, the total rate of pregnancies would be greater than the rate in the first year. - EronTalk 20:21, 22 September 2014 (UTC)

Anyways, thanks a lot for your answers. They really helpde, because for some reason, i was confused about the study, but i realized that it was because I didn't look at the study carefully enough. I still have some doubts about your answers,and i also still wonder why the percentage would be so high, but thank you24.207.79.50 (talk) 21:17, 22 September 2014 (UTC)

Also, would it be correct that out of each of the four numbers shown in table 1, 1.8 percent of them each became pregnant? or would it be correct if i divided 28 people or 1.8 percent by 8? According to table 1, 53 people applied from 2002-2003. When you add them all up it comes out as 1528, which is the total number of people in the study.24.207.79.50 (talk) 22:33, 22 September 2014 (UTC)


 * It wouldn't be correct to say that for each of the cohorts shown in table 1 exactly 1.8 percent of them became pregnant. That is the average value across all four cohorts. It may have been 1 from 2002-03, 2 from 2004-05, 7 from 2006-07 and 18 from 2008-09; but it could just as easily been 2, 3, 6, and 17, or 0, 1, 8, and 19, or other combinations that add up to 28.
 * That said, the farther the numbers for each cohort get from the 1.8% mean, the less statistically likely they are to be correct. It would be highly unlikely for there to have been be 0 pregnancies in three of the years and 28 in the fourth. So for that reason you would not want to divide 28 by four and say there were 7 pregnancies for each two-year period, as that would mean the percentage failure rates would have been 13%, 6%, 1.8%, and .7% respectively - this is not statistically likely. - EronTalk 00:25, 23 September 2014 (UTC)

Well, when i divided 1.832460732984293 percent (28/1528) by 8, the result was 0.2290575916230366. When i calculated the failure rate using the pearl index, the result came out the same. And besides isn't that close to what the mirena iud failure is normally said to be?24.207.79.50 (talk) 00:56, 23 September 2014 (UTC)


 * The Pearl Index is ( (Number of pregnancies x 12) / (Number of women x Number of months) ) x 100. For this study, the number of pregnancies is 28, the number of women is 1528, and the number of months is 12. Remember, the study only reported pregnancies in the first 12 months after IUD insertion. Plug those numbers in and you get ( (28 x 12) / (1528 x 12) ) x 100 = 1.8. Don't be confused by the fact that there are data covering eight years. The reported pregnancy rate is only for the 12 months after insertion for each individual woman, not the rate over the full eight years. Regardless of what the Mirena failure rate is reported as, the rate reported in this study is 1.8%. - EronTalk 01:29, 23 September 2014 (UTC)

I wonder why the first year failure rate is so high according to the study then. Anyways, iforgot, yes 28 people got pregnant after one year, not during the full study.24.207.79.50 (talk) 01:51, 23 September 2014 (UTC)


 * The authors wondered that as well and they refer to these findings in the discussion section:
 * "It is possible that some pregnancies in our study were the result of luteal phase placements or spontaneous expulsions that were not coded. Additionally, our observation of elevated odds of pregnancy in younger women (15–19 year olds) compared with those 25 years and older may be the result of differences in fertility between the younger and older groups, leading to the observed differences.
 * "We used claims codes that indicated pregnancy for the outcome “normal pregnancy” but could not confirm the pregnancy in many cases. In addition, it was not always possible to determine whether pregnancy occurred as a result of spontaneous expulsion, because a claim may not have been made."
 * - EronTalk 03:15, 23 September 2014 (UTC)

Maybe i'll ask more tomorrow. Or perhaps move the qusetion to the science desk. How do i do that?199.119.235.162 (talk) 03:50, 23 September 2014 (UTC)


 * Don't move the question; you can just post a new one on the Science desk. - EronTalk 04:54, 23 September 2014 (UTC)

Is it ok to copy the answers from here to the new question?199.119.235.162 (talk) 14:21, 23 September 2014 (UTC)


 * Yes - in fact moving the question is OK too, I've just done that. - EronTalk 16:52, 23 September 2014 (UTC)


 * OP, what is your current question? It seems to me that Eron has sufficiently answered all the followups you've asked. Anyway, the quote above speculates a bit on why there is a higher rate of pregnancies for young women. It seems high compared to to other figures because many other sources will just report one figure for all ages, and given the data in table 2, that would be true for this study as well. SemanticMantis (talk) 17:17, 23 September 2014 (UTC)

Well, okay, here is thing. When i added up the number of pregnancies across the three age groups, the sum was 630, which is close to 0.9 percent of the sum of people using mirena from all the three age groups. That is still way above the yearly failure rate normally reported for mirena.199.7.159.55 (talk) 18:11, 23 September 2014 (UTC)


 * Yes it is. The authors asked the same question. They don't have an answer but suggested some possibilities, i.e. the IUD may have been placed during the luteal phase or the IUD may have been spontaneously expelled. The clinical trials that showed a 0.2% failure rate included 3330 women. We don't know the ages or other information of those women. We can surmise that as a clinical trial the results were probably carefully screened to eliminate pregnancies resulting from luteal phase placement or spontaneous expulsion. I would also expect the clinical trial did not include 15 to 19 year olds, the group that had the largest incidence of pregnancy in the study you originally referenced. - EronTalk 18:36, 23 September 2014 (UTC)
 * I agree. OP should keep in mind the difference between a retrospective study like the one cited, and studies based on clinical trials. The former simply cannot control as many variables as the latter. The data from a retrospective does not have the same quality control and quality assurance as a the data resulting from a controlled trial. Also, I'll point out that calculating a first year pregnancy rate is not the purpose of the cited study. Rather, the cited study has a goal of assessing safety of IUD for young women. The other stuff about pregnancy is just ancillary icing on the cake. Unless you are a specialist in the field, I would suggest trusting results from studies that were designed to find those results, over results that fall out of related studies. SemanticMantis (talk) 19:31, 23 September 2014 (UTC)

And as a response to eron, the pregnancy failure rate for those aged 25-44 was 0.8 percent, which is also still a far cry. But, anyways, yes, i understand, the main purpose of this study was to assess safety for teens, not to determine the yearly failure rate.24.207.79.50 (talk) 20:45, 23 September 2014 (UTC)

I wonder then if there are other studies on the effectiveness of iud in teens24.207.79.50 (talk) 02:31, 24 September 2014 (UTC)

Probably the expulsion rate would be higher among teens due to their cervix?24.207.79.50 (talk) 02:45, 24 September 2014 (UTC)


 * Take a look at this: Adolescents and Long Acting Reversible Contraception. It is not a study, more of a medical guideline, but it references several studies. There is a good section on IUDs and adolescents and lots of references (not all are freely accessible, however.) Regarding expulsion, it notes "Intrauterine device expulsion rates range from 3% to 5% for all IUD users and from 5% to 22% in adolescents.". - EronTalk 04:18, 24 September 2014 (UTC)

Well, there is one study that says the cumulative pregnancy rate ranges from 2% at 6 months to 11% at 48 months. There is also another study which says that those using larc have the same risk of pregnancy regardless of age. Most of them aren't free, but from looking at some of the abstracts, i get a good picture of some the studies.199.7.159.55 (talk) 05:54, 24 September 2014 (UTC)
 * If you're trying to improve our article, you could ask for help accessing the full text of any specific studies you feel would beneficial at WP:REX. You could try here too, but REX would be the general go to place. It would be far better if you had an account though, so people can more easily contact you by email. Nil Einne (talk) 19:02, 24 September 2014 (UTC)

Explaining the speed of light travelling through matter. Clarification sought.
In the case of well made glass, or even clean air, light can travel very well without much scatter and giving every appearance of near perfection. I think for instance of using good quality binoculars to observe a star set in a quarter second through 400 odd km of varying atmosphere across a marine horizon at 15km. If one thinks of the passage through the air and then the binoculars and then the lens of the eye, such that a very clear and faithful message is seen by the brain; I am drawn to conclude that the speed of light in the three media (air, glass and human lens) is utterly systematic. The atoms in the three media are changing the speed of transmission in an extremely uniform way. Now the optics and the explanation for the refractions are all very well explained, but my impression is that explaining the physics of why light slows near matter is not explained at all. We have been thinking this normal for so long now, that it just normal, but not explained. Can I be corrected on this assumption of no explanation?

By no explanation, I mean that I am very happy with explanations for how light amplifiers work and the action of phonons, it all seems very logical. Are we missing a mystery here? Biezanek (talk) 20:32, 23 September 2014 (UTC)


 * Our article on refractive index has a description in the section Refractive_index. As light travels through a medium, electrons within the material respond to the changing electric and magnetic fields.  This means that the wave that travels is not just "bare" light, but a coherent, coordinated combination of an elecromagnetic wave with a wave propagating in the electrons in the material.  (In some cases, sound waves in the material also participate.)  You can think of this in terms of classical electromagnetic waves and a population of electrons that can be pushed around by the EM field.  You can also describe it in terms of Feynman diagrams in which the photon gets absorbed and re-emitted many times as it travels through the material.  Both pictures are describing the same thing. --Amble (talk) 21:50, 23 September 2014 (UTC)


 * In response to the statements "my impression is that explaining the physics of why light slows near matter is not explained at all" and "Are we missing a mystery here?", it seems to me that the contrary is the case. At some level, it might seem that every explanation is based on a leap of faith (axioms), but from the perspective of mathematically describing the phenomenon, refraction and related interactions of charged matter with electromagnetic fields are probably some of the best understood and explained phenomena of any. —Quondum 05:31, 24 September 2014 (UTC)