Wikipedia:Reference desk/Archives/Science/2012 August 23

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August 23

Breast size and milk production

Do both correlate in female humans? OsmanRF34 (talk) 00:09, 23 August 2012 (UTC)

Only in that breasts do swell during lactation. StuRat (talk) 00:11, 23 August 2012 (UTC)

Yes, but if small breast have less potential for swelling, then, a woman with small breast will produce less milk? That might not be that important if maternal milk substitutes are available, although across evolution it could have been relevant. OsmanRF34 (talk) 00:24, 23 August 2012 (UTC)

Surely they must correlate, isn't it obvious? I saw a doco on breast feeding recently and one lady was shown with quite ample breasts who had to express every day even more then her child could drink to get the swelling down, she had litres and litres of the stuff in her freezer, that is just an anecdote and very well could have been a special case, but I don't believe it was presented as such. As to what kind of source you could find to support it, beats me! Vespine (talk) 01:32, 23 August 2012 (UTC)

Huh huh you said "support" —Tamfang (talk) 00:05, 25 August 2012 (UTC)

Interesting, it might actually not be as simple as that, if you google do big boobs make more milk you'll find some interesting reading. I'm not going to google that at work but I did on my phone and it appears, from a cursory browse, that in fact milk production might not correlate with big boobs, but big boobs certainly can HOLD more milk. Vespine (talk) 02:00, 23 August 2012 (UTC)

Breast size is mainly determined by the amount of fat, not by the amount of milk gland. As you would expect, there would have been strong evolutionary pressure to ensure that almost all females to have enough milk galnd tissue to support a baby, but the fat is just there to protect the glands from impact from falls, and make them attractive to males. An indication of how small the milk glands are when not feeding occurs when females get breast cancer. These days, for stage 1 (ie not yet spread to lymph nodes) cancer, treatment is to surgically remove all gland tissue and a 1 cm margin of tissue around the lump. This happened to my daughter in law and she went down just one bra size. As milk glands only occupy a small part of the breast, you would expect little or no correlation of mik capacity with breast size. Ratbone124.182.134.244 (talk) 03:24, 23 August 2012 (UTC)

The great apes do just fine breastfeeding their offspring. Human breast and penis size is a result of sexual selection. μηδείς (talk) 03:36, 23 August 2012 (UTC)

What's curious to me is that no one seems to care. There are some quality studies on the correlation between milk production and the increase in breast size that occurs during pregnancy ([1] for example), but I'm finding precious little on the the relationship between raw size (pre- or post-pregnancy) and milk production. But what's most curious about this is that the data has certainly been collected, the researchers simply aren't discussing it, which implies they don't find the data interesting. Looking at some other sources around the internet, mostly self-published ones (although by physicians or pediatricians), seems to suggest that there is no correlation, provided you remove from your data set outliers on the size chart that are only there because they have a breast-related medical condition. Someguy1221 (talk) 03:38, 23 August 2012 (UTC)

I suspect that the reason for not studying it is that any scientist who wants to study breast size risks being thought of as a pervert (although, if it was for some important reason, like the risk of breast cancer, then maybe not). StuRat (talk) 04:54, 23 August 2012 (UTC)

I suspect the reason no one studies it is that most healthy females are not really constrained by how much milk they could produce. The milk production is determined by consumption and is capable of going much higher in the case of twins, triplets or even (bizarrely) an adult partner breast feeding. Of course malnourishment and other problems may limit production and perhaps correlate but the general principle is that it is not an issue. --BozMo talk 06:04, 23 August 2012 (UTC)

There are studies that have to do with breast size and inheritable tendencies toward certain types of cancer. I have only read of them in newspapers, so have no specific references, but do recall them quite clearly. One type of cancer ran in Jewish families. For pictures of how small ape breast are in breastfeeding mothers, see these pictures of gorillas and these pictures of chimps. μηδείς (talk) 03:52, 24 August 2012 (UTC)

I recall some vague reason for suspicion that feeding a pregnant mother milk from cows fed on linseed oil or safflowers could put a hex on her daughter's breast size and milk production, but I'm not finding strong evidence presently, but that might be because I'm snowed under here [2] and haven't looked carefully. (See conjugated linoleic acid, [3], [4] for background) Wnt (talk) 13:04, 25 August 2012 (UTC)

Airspeed

Why do pilots use airspeed instead of ground speed? Clover345 (talk) 10:40, 23 August 2012 (UTC)

Pilots need and use both. Ground speed is used for navigation purposes. Air speed is critical, because winds at flying altitudes are significant. For example, an airliner cruising at 10,000m has a cruising air speed typically 800 km/hr, has a stall speed in cruise configuration 700 to 750 km/hr, and will encounter tradewinds typicallly 200 km/hr. They need ground speed for navigation, but for safety and optimum fuel consumption air speed is what counts. Ratbone121.215.38.12 (talk) 11:26, 23 August 2012 (UTC)

Until the arrival of GPS technology there was no way to directly and accurately measure ground speed in the aircraft in real time - there is no "ground speedometer" in an aircraft instrument panel. Roger (talk) 12:29, 23 August 2012 (UTC)

Not true. I remember being invited to the flight deck of an airliner 40 years ago. The pilot showed me two things showing ground speed: a ground-speed indicator based on auto-correlation radar, and a Distance Measuring Equipment (DME) display, which was also counting off the miles to the next airport at 4-place accuracy like the odometer in a car. DME is based on special ground transmitters installed for the purpose. See http://en.wikipedia.org/wiki/Distance_measuring_equipment. In any case, a trained navigator can calculate ground speed from bearings and timings to purpose built radio beacons, radio and TV stations, planets, stars, etc. And there were all manner of radio navigation aids invented in World War 2 and just after. The Germans had an effective radio navigation for accurately bombing English targets regardless of weather - well it was accutate until the Poms put up their own transmitters on the same frequencies to confuse the Germans. It's just that the technology of the day required large expensive equipment, unlike your cheap hand held GPS. Ratbone121.215.38.12 (talk) 12:55, 23 August 2012 (UTC)

It is true that long-range airliners, business jets and military aircraft have, for several decades, had equipment that provides the pilot(s) with an accurate indication of ground speed. The great majority of aircraft are smaller, simpler general aviation aircraft and, until the advent of low-cost GNSS equipment, they didn't have access to equipment providing an accurate indication of ground speed. More importantly, they didn't need it, and they don't really need it now. When flying under the Visual Flight Rules the only use for ground speed is as an aid to navigation - but who cares if the pilot arrives at his destination a few minutes before or after he originally calculated. Of much greater importance to the pilot of a general aviation aircaft is his airspeed in relation to the stalling speed, speed for best rate of climb, speed for best fuel consumption etc. These speeds are all airspeeds, not ground speeds. Dolphin (t) 13:18, 23 August 2012 (UTC)

Often when 'airspeed' is referred to, what is meant is indicated airspeed (IAS) - the speed as shown on the airspeed indicator, which only corresponds to true airspeed (TAS) under specific conditions. It is however the most useful measurement in regard to stall speed and other limiting speeds. See also V speeds, Equivalent airspeed and calibrated airspeed for more on the subject. AndyTheGrump (talk) 13:22, 23 August 2012 (UTC)

Why doesn't kilometers per hour have a special name?

I've noticed that there are several derived units have special names (like the Newton, Pascal, Joule, Ohm, Tesla, etc.), but why doesn't Kilometers per hour have one? Being one of the most commonly used units, it can be surprising that it does not have a special name unlike the other derived units. Narutolovehinata5 ^tccsdnew 12:05, 23 August 2012 (UTC)

If any speed unit had a special name, it would be metres per second would it not? It is usually the more complex derived units that have special names. Most people understand m/s (or km/h), but not many know what a (kg·m²)/(s²·A) is. Dbfirs 12:11, 23 August 2012 (UTC)

Knot (unit) would appear to be a special name for a speed? So would Mach. --BozMo talk 20:58, 23 August 2012 (UTC)

Both of those have special histories, though. Knots, if the story I've heard is correct, were measured by laying out knotted rope into the water and counting how fast they go past. And Mach number is not a measure of speed per se, but of speed relative to the local speed of sound, which is of importance for predicting the way air behaves as the craft passes through it. --Trovatore (talk) 21:25, 23 August 2012 (UTC)

Momentum has way more credence than speed. Plasmic Physics (talk) 12:30, 23 August 2012 (UTC)

Special names e.g., newtons, are good for scientists, engineers, and other boffins who use them on daily basis and can get used to them, and they are shorter than the full form, saving the boffins some writing. But for ordinary people, km/hr is a lot more informative, almost as short, & easier to use. Also, there is only one way to cite speed, distance per time, but the special name units generally have alternative ways: E.g, Tesla = V.s / m = N / A.m = Wb / m² = kg / C.s = kg / A.s = N.s/Cm . Some of these alternates make the meaning a bit obscure, so a special name helps. Ratbone121.215.38.12 (talk) 12:41, 23 August 2012 (UTC)

121.215 hits the name on the head. Any basic unit can always be reduced to a relation between core SI units, like meter, second, Ampere, and kilogram. Nearly all of our "named" units like Newtons or Joules or Henrys are quite complex in terms of reducability to core SI units (the Joule, for example, is kg*m²*s^-2 while the Henry is kg*m²*s^-2*A^-2. Also, the more complex the measurement, the more ways to express it, as Ratbone notes with the Tesla, I always think of the measurement of Energy, which commonly has units of the Joule (reducable to base SI units), the calorie (normalized to the specific heat of water), and the liter-atmosphere (used in many forms of the universal gas constant) as ones I use on a regular basis as a Chemistry teacher. With speed, I use only meters per second and kilometers per hour, both of which are simple enough to conceptualize for most people. For measurements which are reducable to two base units, there isn't a need to name them. --Jayron32 12:52, 23 August 2012 (UTC)

Jayron, feel free to call me Ratbone. Ratbone121.215.38.12 (talk) 13:05, 23 August 2012 (UTC)

Also note that "kilometers per hour" is a little bit long for some people who shorten it to "kilometers an hour", "kilometers", "clicks" or just omit the units all together as in, "Honestly officer, according to my speedo I was sitting on a hundred..." 203.27.72.5 (talk) 21:29, 23 August 2012 (UTC)

In the context where kilometres per hour are most frequently discussed, vehicle speeds, the "name" of the unit is simply omitted. For example, "I was doing about 95 when this idiot overtook me over double lines." All listeners know what the unmentioned units are. That's a pretty effective short cut. HiLo48 (talk) 17:17, 23 August 2012 (UTC)

With, of course, the caveat that even if "speed" is understood by all listeners (a supposition which may not be true, depending on context), the particular units are not so. — Lomn 17:43, 23 August 2012 (UTC)

Derived units are based on the SI base units (which are rooted in part in the MKS system of units), and neither kilometre nor hour are MKS. It effectively introduces a 1000⁄3600 (5⁄18) constant into the mix, making dimensional analysis as silly as if you were using imperial or U.S. customary units. Km/h is a consequence of legislation, and there's no compelling reason to give it an SI derived unit name. BigNate37_(T) 21:12, 23 August 2012 (UTC)

I was going to suggest calling them Volts after the Chevy Volt. Given that is already taken, how about calling them Slows? μηδείς (talk) 01:42, 24 August 2012 (UTC)

Which mobile standards uses OFDM?

Which standards for mobile phone communication HSDPA, HSPA+, 4G, etc. Makes use of OFDM ..? Most articles mentions line coding like 64QAM but doesn't mention if that's in a multi- or single carrier scheme. Electron9 (talk) 12:28, 23 August 2012 (UTC)

Our article mentions it is used in IEEE 802.20 (which appears to be dead), WiMAX and LTE. Do you have any reason to think it's used in the other standards or that it is otherwise incomplete? Nil Einne (talk) 14:00, 23 August 2012 (UTC)

The OFDM article only mentions "4G" which correspond to many different standards. It's like saying Television uses OFDM.. it's incomplete information. But I suspect various 3G standards like HSDPA also makes use of OFDM. 1G/2G is "OFDM free" however ;). Electron9 (talk)

Sorry but you're quite mistaken. I got all the information from the article as I suggested in my first post, which isn't surprising since I don't know much about the subject. And it has been there since long before you posted your message [5] [6]. Looking at the version from August 11, just before any of your edits, in fact Long Term Evolution is mentioned in 3 different places in the article (all 3 also mention the abbreviation LTE). WiMAX in 5 (3 of these also mention IEEE 802.16). IEEE 802.20 in 2 locations (both also mention MBWA), and as I said that's a dead standard. Excluding the external link, there's only one place where 4G is mentioned not in close proximity to the specific 4G standards in development that use OFDM, and that's in the intro. Since the intro doesn't mention any other specific standard which uses OFDM, it's entirely unresonable to expect it to mention any specific 4G standard in development (and 4G alone appears to be accurate since all current putative 4G standards, even as our article also mentions the dead UMB standard, plan to use OFDM). Given the number of standards that use it, it's unresonably generally to expect it to be in the intro anyway point blank. So while I'm sure the article is incomplete, it isn't as incomplete as you suggested, perhaps it is your reading that was incomplete. (Although I barely read the article myself and when composing my first reply IIRC I didn't even need to search yet still found the info.)

P.S. AFAIK, with the death of the UMB standard and the similar apparent death of 802.20, there's only two standards really competing to be 4G, LTE and WiMAX. Of course there may be extensions of 4G in the future which will be somewhat different standards, just as there was with 3G, but that seems way too far in the future to worry about, particularly since we're still a fairly long way from 4G.

P.P.S. I actually suspect you're mistaken on HSDPA as well. For starters our article strongly seems to imply OFDM is new to LTE etc when it comes to mobile communications. So do other sources. This one for example, [7] says things like

With LTE joining UMB and WiMAX in choosing OFDM as the underlying modulation technology, it could be argued that there is now little to choose between these cellular systems. Of the five major new cellular systems, only HSPA+ and EDGE Evolution do not use OFDM

(It's from 2008 so rather old but seems unlikely HSPA has changed that much.) Other sources like [8] say things like

According to sources, LTE is clearly the OFDM technology of choice for next-generation services; yet, HSPA is being driven to unleash tremendous wireless data throughput speeds. They anticipate that the majority of all operators who have deployed HSPA will upgrade to HSPA+ and will continue to enhance their networks through further evolutions for years to come, even as some may deploy LTE networks.

Of course as I said I don't know much about this, hence why I'm reluctant to definitely say HSPA etc don't use OFDM, there may be some subtleties on what the sources say when they refer to OFDM that I'm missing. Although my impression is it's just that it's not a simple matter combining OFDM with the needs of a mobile network so it wasn't used before now (and enhancements like HSPA couldn't change things too much), even if wifi etc were using it for a long time. Although I guess FLASH-OFDM and WiMAX have existed for a resonable while, albeit I believe real voice services for WiMAX only came fairly late and I'm not sure if they ever came for FLASH-OFDM.

Nil Einne (talk) 03:05, 24 August 2012 (UTC)

jerry sandusky

how did they charge jerry sandusky? didnt the statute of limitations expire? --Wrk678 (talk) 14:35, 23 August 2012 (UTC)

Welcome to Wikipedia's Science Reference Desk. This page exists to help Wikipedia editors locate and understand reference material related to scientific articles in our encyclopedia. If you need help locating an Internet forum for general discussion, there are many links in our article. Nimur (talk) 14:44, 23 August 2012 (UTC)

Our article on Jerry Sandusky contains much of what you're looking for (including the grand jury's indictment), and a Google search for "statute of limitations sandusky" fills in the rest nicely. Particularly, the statute of limitations for Sandusky's crimes stretched to at least 1994, though there was at least one other victim who missed the statute cutoff. I don't see a specific duration listed, but based on the dates, I'd assume the statute of limitations in this case is roughly 18 years. — Lomn 15:00, 23 August 2012 (UTC)

Its is also notable that some of his crimes he was convicted of were committed as recently as 2009, which is not that long ago. --Jayron32 16:36, 23 August 2012 (UTC)

how dou explain this then http://espn.go.com/college-football/story/_/id/7920784/charge-penn-state-administrators-likely-dropped-change-jerry-sandusky-shower-allegations — Preceding unsigned comment added by Wrk678 (talk • contribs) 16:33, 23 August 2012 (UTC)

That's a different crime with a different statute of limitations against different people. That article is about possible criminal charges against Penn State administrators who may have covered up the abuses of Sandusky. It appears that the statute of limitations on what those two administrators would be charged with is shorter than the statute of limitations for what Sandusky did. --Jayron32 16:38, 23 August 2012 (UTC)

Hydrogen at Fukushima Daiichi

Can anyone tell me if there were passive hydrogen eliminators at Fukushima Daiichi or just active ones that required electricity to operate? RJFJR (talk) 18:48, 23 August 2012 (UTC)

According to [9], the primary containment was purged with N₂ to prevent hydorgen ignition, and the secondary containment had no provisions for hydrogen mitigation at all, as scary as that sounds. That' backed up by [10] which says in the hydrogen mitigation section, "Fukushima Dai-ichi units were equipped to deal with hydrogen: the building containments were inerted with nitrogen and a venting system...other plant designs assume passive autocatalytic recombiners as technique to mitigate the hydrogen..." 203.27.72.5 (talk) 21:20, 23 August 2012 (UTC)

Bird call identification?

At about 9,000 feet elevation in the Rocky Mountains (Colorado), looking for a bird that has a call that sounds like a whining dog. In fact, it sounds very much like the whines heard at the very beginning of this youtube video. It's extremely loud and can be heard across the valley. We also have a Red-Tailed Hawk that does its usual screech, which lives in this valley, and sometimes when it screeches, I can hear the dog-whine bird (I assume it's a bird) kick up its vocals. So maybe it's a deterrent? But the whining happens without the hawk as well. I don't think it's a starling, and I've listened to ruffed grouse and hermit thrushes online and nothing sounds remotely like the dog whining in the video—despite what others online have suggested. Any ideas? It's a new call, haven't heard it in previous years. Thanks!Reflectionsinglass (talk) 20:53, 23 August 2012 (UTC)

Is it a screech owl? --Jayron32 03:16, 24 August 2012 (UTC)

What an interesting response! We do have a Western Screech-Owl, and for several years, we've heard him with the call heard here... the sort of tremolo oow-oow-woowoowoowoo, but he disappeared a month ago—I'm not here all year 'round, so I'm not sure the owl's habitat patterns. I've never heard this wheezing whining dog sound before... but just from the power of the voice, I wouldn't at all be surprised if it's an owl. I will look into it further. Thank you for the suggestion!Reflectionsinglass (talk) 04:30, 24 August 2012 (UTC)

There are several dozen varieties of screech owl, and each has a distinct call. If your Western Screech-Owl moved out, perhaps another species has recently moved in. --Jayron32 05:22, 24 August 2012 (UTC)

The other thought I had was a loon of some sort; loons are shockingly loud. I'm most familiar having grown up with common loons, which have a call that sounds like a woman being attacked. It's unnerving. Again, perhaps a species of loon? --Jayron32 05:25, 24 August 2012 (UTC)

I left out some details in my original query: the bird (again, I'm completely assuming this is what it is) sounds as if it is coming from the trees. (I guess I should ask, then—because I'm not familiar with them beyond picturing lakes in Vermont—are loons water-fowl only?) The bird was behind our house yesterday up in the evergreens/lodgepole pines, and today was on the other side of the valley, so I'm assuming he's a bird. He'll go quiet for lengthy periods of time, so I give up looking for him flying from one location to another. And one last detail, I only hear him call during the day or early morning. Not at night. /Reflectionsinglass (talk) 06:41, 24 August 2012 (UTC)

Looking for a second bird

I spent quite some time listening to raptors online this evening and simply cannot find this one either. I was biking at an elevation of about 10,000 feet, same location, mountains with coniferous pines or evergreens, and I kept hearing the call of a loud bird that I'm convinced is a raptor. It was a whistle, though. Not the screech of a hawk, not the weak pips of an eagle, more like the whistles of an osprey, though the osprey calls I've listened to aren't right. To help me remember what the call sounded like, I immediately compared it to the Sound of Music song, Do-Re-Mi, in the part where the children sing, "Do Mi-Mi..." The whistle had the same tonal steps between do and mi... and then the pattern was similar: one twothree. Dit dotdot. But a steady whistling, not wavering too much, and not dropping off like the osprey's. Again, any ideas would be fantastic. Thanks! /Reflectionsinglass (talk) 06:41, 24 August 2012 (UTC)

lichens: as decomposers

I have always understood that lichens are slow growing decomposers. This is really not mentioned in the article, except regarding minerals? Isn't it true? What do they eat, if not.They are described in the article as epiphytes.Are they epiphytes when they grow on trees, or decomposers? I have understood also that they were the first producers of soil on earth by decomposing minerals. The description of the historical age of lichens doesn't seem to bear this out. What is the truth as we know it? Thanks. — Preceding unsigned comment added by 24.168.44.14 (talk) 21:55, 23 August 2012 (UTC)

Lichens are weird critters. They consist of a symbiotic pairing of a plant and a fungus: they get their energy, like all plants, from the sun via photosynthesis, with the fungus portion subsisting off of material provided by the plant portion. The fungus portion, IIRC, digests the substrate (the stuff the lichen is growing on) to provide non-Carbon nutrients to the pair. --Jayron32 21:59, 23 August 2012 (UTC)

Gephyromantis VS Mantidactylus

Gephyromantis VS Mantidactylus

Recently, I have been creating Gephyromantis genus articles to only find out the genus page redirects to Mantidactylus. So I redirected all the pages I made to Mantidactylus. The problem is though that I don't know which is the right genus or why it redirects. I also don't know why Mantidactylus sources are under the name Gephyromantis on IUCN. Frwiki has both genus and all the species. Commons also has categories for the genus's. I am very confused, any help would be appreciated. Also Amphibians of Madagascar has both species (which is where I found Gephyromantis was all redlinks and started creating them). -- Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 22:17, 23 August 2012 (UTC)

Blommersia, Boehmantis, Guibemantis, Spinomantis, Wakea (genus) also redirect to Mantidactylus -- Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 22:31, 23 August 2012 (UTC)

As far as I can work out, Blommersia (Dubois, 1992), Boehmantis (Glaw & Vences, 2006), Gephyromantis (Methuen, 1920), Guibemantis (Dubois, 1992), Spinomantis (Dubois, 1992) and Wakea (Glaw & Vences, 2006) are synonyms of Mantidactylus. Thine Antique Pen (talk) 09:51, 24 August 2012 (UTC)