Wikipedia:Reference desk/Archives/Science/2012 April 19

= April 19 =

Peat pod fungus
Do Jiffy peat pods contain the fungus that causes rose gardeners disease,Sporothrix schenckii ? Here is an example of them  http://www.seedandgarden.com/shop/products/Jiffy-Professional-Greenhouse-Kit-36.html

I have been having fungus grow on the  Peat, and a quick Google search shows that this is a common problem and I'm wondering if it is the fungus Sporothrix schenckii  growing? — Preceding unsigned comment added by 64.38.226.88 (talk) 01:34, 19 April 2012 (UTC)


 * They are unlikely to contain any fungus at all, considering that the manufacturing process includes drying at high temperatures. The mold you see growing on them is far more likely to be an air contaminant, most likely from spores from your own environment or o the seeds themselves. What it is is anyones guess. Sporothrix is possible, but so are thousands of other species, few of which are pathogenic to humans or plants. I did have peat pots grow mushrooms out of them once. Specifically, Coprinellus micaceus. Dominus Vobisdu (talk) 09:50, 19 April 2012 (UTC)


 * Most of these products are "sterile" and advertised as such -it looks like your products might be made of Coco peat or something similar - not real peat.
 * eg http://www.jiffygroup.com/assets/files/Jiffypot/Jiffypot-USA-Salesheet%201%20sided-06-10LR.pdf - is this your product - if not try the "jiffy" website to find - they have data sheets. This one states the "jiffy pots" are coir (anther name for cocoa peat). Most sources seem to indicate that the jiffy pots are sterile. I don't know if this extends to your fungus spores. The pots may not be the source of the spores- it is probably irrelevant as the fungus may be present just about anywhere.
 * I don't think anyone will be able to identify the fungus with out more decription.Oranjblud (talk) 23:19, 19 April 2012 (UTC)

Finland's class size ratios
Yesterday, on someone else's computer, I found a government report (I think it was from Scotland) which stated:


 * 1) Finland has the best public school educational outcomes in the world;
 * 2) Finland spends about the same per-pupil as most other European public school systems; but
 * 3) Finland caps their has average class sizes of 19 students in 1st and 2nd grade, and 21 students in the other grades, which is several students below the European average.

Now I can not find that report and I can't get to the browser history which would have it. Can anyone confirm or deny those statements? 71.212.237.94 (talk) 02:00, 19 April 2012 (UTC)

Update: it has to have been two different reports; this report confirms #1 (Figure 2.1) and #2 (Figures 2.2, 2.3, and 2.4) but amazingly Finland's class sizes are missing from its Figure 2.6 so I just need to find some other document with those class size caps. 71.212.237.94 (talk) 02:06, 19 April 2012 (UTC)

Got it! "We don’t have legislation limiting class size, but the average class size for all grades is 21. In first- and second-grade, it’s 19." -- Henna Virkkunen, Finland’s Minister of Education; confirmed within epsilon in, , and.

Tohoku earthquake's shift
Tohoku earthquake reportedly shifted Primorye area 4 cm towards the quake's epicenter. How it's possible when the earthquake is expected to shift the objects away from epicenter?--176.241.247.17 (talk) 11:33, 19 April 2012 (UTC)


 * Before the earthquake, when the subducting Pacific Plate was still locked to the overlying Eurasian Plate (some debate about exactly how to name the plates in this area, but bear with me), continued movement effectively dragged the eastern side of Honshu with it (to the west) causing a lot of strain to develop. When the earthquake happened this strain was released and the leading edge of the Eurasian Plate jumped eastwards, see elastic-rebound theory. Mikenorton (talk) 11:48, 19 April 2012 (UTC)


 * I'll add an illustration. You can see that subduction involves both movement of the subducting plate to (in this case) the left and movement of the overriding plate to the right—toward the area in which quakes will occur. Deor (talk) 12:10, 19 April 2012 (UTC)
 * The locations of earthquake hypocenters along the plate interface actually remain beneath the same part of the overriding plate. That part of the crust is shortened and uplifted during the locked phase - one of the things that made the 2011 tsunami worse was the subsidence along the coast as this temporary uplift disappeared. Mikenorton (talk) 12:21, 19 April 2012 (UTC)

If the drag coefficient is not constant then what is the point of the equation?
According to drag coefficient, the drag coefficient in the drag equation $$\vec F_\mathrm d = -\tfrac12 \rho {\vec v}^2 C_\mathrm d A $$ is not constant but is instead a function of a number of variables, notably including velocity and density (which are also part of the drag equation). Why then the equation $$\vec F_\mathrm d = -\tfrac12 \rho {\vec v}^2 C_\mathrm d A $$? Why not simply $$\vec F_\mathrm d = \vec{C_\mathrm d} A $$? Furthermore, what is the usefulness of this equation? (if velocity is changing then it would be completely useless.) Widener (talk) 13:06, 19 April 2012 (UTC)
 * As an aside, I don't think the equation given in that article is strictly correct from a mathematical perspective, since you cannot "square" a vector conventionally (although I guess you could define such an operation). Maybe $$\vec F_\mathrm d = -\tfrac12 \rho ||{\vec v}||\vec{v} C_\mathrm d A$$ would be better. Widener (talk) 13:15, 19 April 2012 (UTC)


 * For a fixed body shape relative to fluid flow, the drag coefficient tends to be approximately constant for turbulent flows at low Mach number. Since this describes many common situations (e.g. driving a car), it is often adequate to assume that the drag coefficient is a constant.  You might be confused by the article since the definition of the drag coefficient given there is simply a restatement of the drag equation.  In general, the drag coefficient is not a strongly varying function of velocity or density over most common ranges of interest.  Dragons flight (talk) 15:09, 19 April 2012 (UTC)
 * The coefficient of thermal expansion varies with temperature but it's still useful. 203.27.72.5 (talk) 20:41, 19 April 2012 (UTC)

Fluorine(I)
Oxidation number states:

"Fluorine is always -1. Other halogens are usually -1 except when bonded to oxygen or fluorine."

But wouldn't fluorine have an oxidation number of +1 in difluorofluoronium, F—F+—F (because the charge of the central fluorine is +1 and it is bonded to two other fluorines), and difluorine mononeonide, F—Ne—F (because neon is more electronegative than fluorine)? Whoop whoop pull up Bitching Betty 17:56, 19 April 2012 (UTC)
 * Stuff doesn't really exist though does it? You can make F5+ in an ionisation chambers etc - that's not an isolable chemical compound... Fluorine (F2) is 0. 178.78.88.114 (talk) 18:00, 19 April 2012 (UTC)
 * Oxidation number is a heuristic bookkeeping method which is a powerful tool for predicting the sturcture and reactivity of many chemical compounds. Like all heuristics, however, it is still a rough approximation, and there are lots of cases where it doesn't work.  Pay those instances no mind.  Oxidation number is just a way of keeping track of the organization of electrons in chemical reactions, but doesn't represent anything close to physical reality anymore than a lewis dot diagram does.  For any highly simplified model of a complex system (and oxidation number is a very highly simplified model of a very complex system), there are going to be many ways to find exceptions and contradictions.  It doesn't necessarily make the model invalid: oxidation number is useful because it usually works, and though there are carefully constructed examples where it doesn't make sense, don't let those rare exceptions make you lose sight of the usefulness of the model.  If you are studying chemistry at the level below a professional chemist, the "Fluorine is always -1" rule is good enough to get you through what you're going to need to do with it.  If you ever get to the point of having to work regularly in situations where it doesn't work, you're going to have long abandoned the oxidation number heuristic anyways.  -- Jayron  32  20:06, 19 April 2012 (UTC)
 * To be pedantic the centre F in 'difluorofluoronium' is +1, compare the isoelectronic : Oxygen difluoride which has O in a formal +2 oxidation state (not -2). The compound is a possibility as a real world stable compound under suitably stabilising conditions. Neon difluoride is a non-starter as a real compound. As of today however the original statement remains true.Oranjblud (talk) 23:26, 19 April 2012 (UTC)
 * It would be +1 (if it existed), as the formal oxidation state of an element is the sum of the charge (here 1) and the bond orders to more electronegative elements (here 0) minus those to less electronegative ones (here 0). Ne is of unknown EN, so nobody knows how it'd be. Alfa-ketosav (talk) 13:42, 7 April 2021 (UTC)
 * Ne is more electronegative than F. Double sharp (talk) 08:04, 13 April 2021 (UTC)

Difference of diesel, bio-diesel, ethanol, gas and gasoline
Can a driver feel the difference when driving a car with these different fuels? I suppose that bio-diesel and diesel cannot be perceived as different, but what about the rest? XPPaul (talk) 22:13, 19 April 2012 (UTC)
 * You'll have to clarify what you mean by "gas". Is that LPG? You could definitely tell the difference between ethanol and gasoline, but I think you actually mean gasoline with enthanol in it vs pure gasoline. In the latter case you might notice if the performance ratings on the two fuels are different, but if all things are taken to be equal, it's doubtful that you could distinguish between them. 203.27.72.5 (talk) 23:26, 19 April 2012 (UTC)


 * Pure ethanol, not as an add-on to gasoline, is also a possibility: Ethanol fuel in Brazil. — Preceding unsigned comment added by 88.9.107.123 (talk) 06:03, 20 April 2012 (UTC)
 * I know that's a possibility, and as I said; you certainly can tell the difference between pure ethanol and gasoline. 203.27.72.5 (talk) 06:19, 20 April 2012 (UTC)
 * The engines of a diesel car and one running on gasoline sound different. If you include that in your "feel different" criteria, then yes for those two.  Dismas |(talk) 01:30, 20 April 2012 (UTC)


 * My truck (a 1999 Ford Ranger) seems to run a bit "better" (can't think of a way to describe how) on Ethanol, but the fact that it gets around half the gas mileage on Ethanol only makes it worth using when the price of gasoline is more than twice the price of Ethanol. Ks0stm  (T•C•G•E) 02:26, 20 April 2012 (UTC)
 * A plea to all. Don't use the word "gas" in these global articles on car fuels. It has two very different meanings in different parts of the world. HiLo48 (talk) 21:39, 20 April 2012 (UTC)


 * Can it run with any mixture of ethanol + gasoline, or even with ethanol alone? — Preceding unsigned comment added by 88.9.107.123 (talk) 06:06, 20 April 2012 (UTC)


 * There seems to be some reason why blends are better than 100% gasoline or 100% ethanol. I know 100% gasoline tends to get water accumulating in the fuel line.  I'm not sure what the problem is with 100% ethanol (is it degradation of rubber seals ?), but they generally only go up to E85, at 85% ethanol, so it sounds like there is some problem. StuRat (talk) 15:04, 20 April 2012 (UTC)


 * According to Common_ethanol_fuel_mixtures seems like ethanol freezing during cold weather is the only concern. 142.150.237.18 (talk) 18:40, 20 April 2012 (UTC)


 * Actually, the caption under the chart at Common_ethanol_fuel_mixtures says the problem is that the low vapor pressure makes cold starts difficult. StuRat (talk) 22:48, 20 April 2012 (UTC)

Helicopter and aircraft pilots record flying hour holders
Who are the world record holders for helicopter flying hours and aircraft flying hours? — Preceding unsigned comment added by Gdkbc (talk • contribs) 23:21, 19 April 2012 (UTC)
 * Evelyn Johnson has the most flying hours, but there's no distinction drawn between fixed wing and helicopters. 203.27.72.5 (talk) 23:33, 19 April 2012 (UTC)
 * "She is the female pilot with the most number of flying hours in the world." I interpreted that as: within the set of female pilots, she has the most number of flying hours. 99.245.35.136 (talk) 01:19, 20 April 2012 (UTC)
 * Also from the cited source: "Johnson holds the record for the most flight hours of any woman, 57,635.4 hours."99.245.35.136 (talk) 01:22, 20 April 2012 (UTC)
 * She also has the most hours of any living person. Handschuh-talk to me 03:39, 20 April 2012 (UTC)
 * According to CNN in 1998, the Guinness Book of Records credited Ed Long of Alabama with the most flying hours, over 64,000. Clarityfiend (talk) 02:25, 20 April 2012 (UTC)