Wikipedia:Reference desk/Archives/Science/2013 December 2

= December 2 =

RMWI?
Hello, as a part of my grade 11 chemistry assignment, we have to write a report on the arsenic levels in chicken, and how much of it is consumed in a sample of ten people. One of the questions it deals with is to find the "Recommended Maximum Weekly Intake (RMWI) for each person." Now, the only thing we were given was the toxicological reference value (TRV) of chicken being 0.024µg As/kg BW per day, and so we had to research the RMWI ourselves. This link gives the formula:

$$\frac{TRV \times BW \times 7}{CF}$$ , where TRV = toxicological reference value (µg/kg body weight/day) BW = body weight (kg) CF = concentration in food.

I tried the equation, using the TRV value given (0.024 µg/kg) and the weight of a sample person (68kg), but I do not have the concentration in food, nor could I find it online. Does anyone have any idea of what this concentration could be, or if there is a better formula available? Thanks. 50.101.203.177 (talk) 00:19, 2 December 2013 (UTC)


 * I'm not absolutely sure, but I think your 0.024 ug/kg is the 'concentration in food' where the people are concerned, and what you still need to get is the reference value for how much arsenic a person can consume in ug/kg body weight/day.... nay, wait a minute, the figure you gave is an intake per day for the chicken, hmmm. Are you sure about that?  Which are you calculating this for - what maximum intake of ?grain? is needed to keep the chicken meat below a specific arsenic concentration, or what the maximum intake of chicken is to keep the level of arsenic in the humans below a certain level (and if so what level?) Wnt (talk) 01:49, 2 December 2013 (UTC)
 * Quick reality check:   has people talking about 0.6 to 3 micrograms of arsenic per kg of chicken, with the organic people crowing and cackling about the lower level in their product because they don't use roxarsone.  Jeesh, the commercial folks should take a page from the laetrile salesmen and call it "vitamin As" :)  Anyway, I have to recognize you are giving me a ug/kg/day figure then, not a ug/kg figure.  I think there's something missing in the definition of this problem. Wnt (talk) 01:54, 2 December 2013 (UTC)
 * Oh, and according to the dosage of roxarsone is "22.7 to 45.4 g roxarsone/ton feed"; assuming a metric ton (1000 kg) for now, that is 22.7 to 45.4 mg/kg of roxarsone, which is 75/263 arsenic... hmmm, that seems waaay higher than the figure given.  Even the organic chickens ought to be getting much more.  Hmmm, I should return here and see if I slipped up. Wnt (talk) 02:00, 2 December 2013 (UTC)


 * I'm guessing the CF in this case would refer to arsenic concentration in chicken meat, and the TRV to maximum arsenic intake from chicken alone (considering that other foods and drinks may also contain As). In that case you still need the arsenic concentration in chicken meat; the FDA limit is 500 ppb or 500 ug/kg (and 2000 ppb for chicken liver). But that's huge in comparison with 0.024 microgram/kg BW /day, it gives you an RMWI of only 22.8 gram for someone weighing 68 kg. This study from 2006 lists arsenic content in chicken meat from several suppliers. In uncooked chicken the maximum found was 21.2 ppb, In fast food chicken the Church's chicken thighs contained 46.5 ppb. The 21.2 would result in an RMWI of 530 grams for the same person. So it all depends on which value you take for CF...  Ssscienccce  (talk) 16:27, 2 December 2013 (UTC)

California coastal oak balls
I am going nuts. Every year I see the acorns on the ground & I see them in the trees. However, I also see these perfectly round balls on the ground & for the life of me I can't find any in the tree. Where do they come from? Are they formed from the acorn top left in the tree? Many thanks! — Preceding unsigned comment added by 24.23.237.218 (talk) 01:37, 2 December 2013 (UTC)
 * They are probably some type of oak gall. μηδείς (talk) 02:47, 2 December 2013 (UTC)
 * Maybe, but it would be helpful to have a picture. Looie496 (talk) 16:39, 2 December 2013 (UTC)

A Sex Change (Dramatically) Changing One's Sexuality?
Is it possible for a sex change (especially the hormone replacement therapy, et cetera) to (dramatically) change one's sexuality (such as previously being completely or predominantly attracted to females and then becoming completely or predominantly attracted to males)? Also, if so, then how frequently does such a (dramatic) change in one's sexuality occur in such cases? Thank you very much. Futurist110 (talk) 05:18, 2 December 2013 (UTC)
 * Yes, I have seen a documentary (I'll look for it) where female to male post-transexuals have changed orientation. This article suggests heterosexual males who have transitioned to females become attracted to males at a significant rate (6 out of 20). μηδείς (talk) 05:37, 2 December 2013 (UTC)
 * This article suggests that 40% of presumably female-attracted female to male transexuals become attracted to gay men to some extent within 10 years of transitioning. μηδείς (talk) 05:41, 2 December 2013 (UTC)


 * It must depend on the person's will to change. There is probably a placebo effect.  The effect of hormone therapy vis-a-vis sexual attraction may reduce with age.  The reason why I don't believe that hormone therapy inherently changes sexual preference is that a standard and commonly used treatment for men with prostate cancer for 40 years has been hormonal therapy (there are other treatments - eg surgery) as prostate cancer is hormone dependent.  The hormone dosage is sufficient to stimulate breast growth, and in some cases the breasts can be quite prominent.  A workmate of mine aquired breasts about size 42C - looked at little odd on a 6 foot 3 inch muscular man.  But such men do not change partner preference.   There is usually some loss of libido.  If the man has difficulty getting an erection (say due to circulatory issues or diabetes), the hormone treatment may kill it off completely, but they are still men and they still want real females.  There is of course no way that other sex change procedures (eg cosmetic surgery) can change one's preference. 58.169.252.71 (talk) 10:16, 2 December 2013 (UTC)
 * Hormone replacement therapy is more than just estrogen pills. A trans woman who has not had reassignment surgery or an orchiectomy will still produce testosterone, which is why she would also be on spirolactone or some other androgen antagonist. If she elects for one of those surgeries, then her body will no longer produce testosterone at all. Her estrogen dose would also be designed to raise her bodie's estrogen level to one similar to other women. Progesterone is also commonly used to encourage some of the physical feminization. This means you can't just compare the medical effects of estrogen for prostate cancer to those for HRT. The majority of trans people I know have had confusion about their orientation in the past, likely due to gender issues, and then settle on something as they figure themselves out during transition. In my case I went from thinking i was straight man to a bi man, then realizing I was a woman and for a while identifying primarily as a lesbian right in the middle of the hard parts of the realization and early transition, then back to being a bi woman as things settled down, and that was all pre-HRT. I would describe those shifts (except for maybe straight to bi) as real, and they had nothing to do with transition related medical procedures - it was all personal development as I learned more about who I am. Hormones and other procedures end up having a profound mental effect on trans people, so even if there isn't a direct medical link, I can understand the personal development that comes along with finally having a body that matches one's gender identity leading to changes in orientation. K ati e R  (talk) 12:47, 2 December 2013 (UTC)
 * This doesn't sound treatment-wise much different to hormone therapy for prostate cancer. Such treatment includes drugs to stop testosterone production (it won't stop it completely, but then neither will sex change therapy, in any case some testosterone is present in natural females) plus optionally an estrogen or estrogen analogue course.  Other androgen receptor blocking drugs are also used in some cases. It sounds from your post that rather than the hormone treatment driving a change in partner preference and persona, it just made it mentally easier to achieve an orientation you wanted or subconsciously had built in anyway.  In contrast, men with prostate cancer don't want to change partner preference or their own sex persona, and are not a feminine person trying to get out, so they don't change, regardless of the treatment.  All the best for your future though Katie. 58.169.252.71 (talk) 15:28, 2 December 2013 (UTC)
 * That's interesting to know - I've heard the estrogen side mentioned several times, but not the anti-androgens, but I've never really looked into prostate cancer treatment. It just happens to come up in discussions of HRT sometimes. But yes, aside from pointing out what I thought was different in the treatments, the main point I was trying to make was that there is a lot going on on the mental side of things, and even if a specific procedure doesn't have a direct medical link to orientation changes it can still trigger the change as a part of the personal development going on at the same time. I think we agree there - I just wanted to explain to the OP how those sorts of changes can happen during transition regardless of the specific medical procedures involved, because it sounded like he might be interested in orientation changes in general, even though he mentioned medical procedures in the question. K ati e R  (talk) 16:12, 2 December 2013 (UTC)


 * Here's part one of at least on of the documentaries of which I was thinking above: http://www.youtube.com/watch?v=-c9ZnpMppHQ. μηδείς (talk) 02:05, 3 December 2013 (UTC)
 * If you watch part 3/4 of this documentary, the men and women discuss for a bit the statistics and their personal experience with orientation changes after to the physical changes. It is very interesting that heterosexual men tend, if they change, to become heterosexual women, while lesbian females often become gay males. μηδείς (talk) 01:45, 4 December 2013 (UTC)

Thank you very much for all of this information. I will definitely check out all of it in a little bit. Sorry for the late reply, but I was pretty busy with school-related things in the last couple of days. Futurist110 (talk) 16:57, 6 December 2013 (UTC)

Autonomous vehicle
Has any autonomous vehicle, other than spacecraft, circumnavigated the world? --140.180.255.56 (talk) 08:07, 2 December 2013 (UTC)


 * There is nothing listed at List of circumnavigations but it looks as though such a feat is now theoretically possible .--Shantavira|feed me 12:28, 2 December 2013 (UTC)


 * Yes, and I can think of 3 different ways: airplane (although here fuel might run short), helium or hydrogen balloon, and boat. A land vehicle would also be possible, if not for the fact that the trip would be interrupted by oceans. StuRat (talk) 12:41, 2 December 2013 (UTC)


 * You can think of 3 ways, but have any of them ever been done? --Bowlhover (talk) 22:07, 2 December 2013 (UTC)

There is a team working on a robotic, solar powered boat that will, or has done this. I remember reading about it some time ago. 217.158.236.14 (talk) 13:36, 2 December 2013 (UTC)


 * Doubt it has happened yet, some google results about the idea itself (forums etc), but nothing on it having been achieved. Shouldn't be too hard for a balloon or airship, specially if you make it buoyancy neutral at some fixed height. Judging by the global wind patterns all you need then is launch it with the trade winds. Ssscienccce  (talk) 16:49, 2 December 2013 (UTC)


 * This has actually been done by a superpressure balloon (a type of stratospheric weather balloon), but I forgot the name of the reference. 24.23.196.85 (talk) 00:32, 3 December 2013 (UTC)


 * From Aerobot:
 * The French had already conducted extensive experiments with solar Montgolfieres, performing over 30 flights from the late 1970s into the early 1990s. The Montgolfieres flew at an altitude of 35 kilometers, where the atmosphere was as thin and cold as it would be on Mars, and one spent 69 days aloft, circling the Earth twice.
 * but I agree with Dismas below that this wouldn't meet the requirement of being being autonomous. -- ToE 13:32, 4 December 2013 (UTC)


 * I am not sure what you mean by autonomous, but Steve Fossett flew around the world in a balloon. μηδείς (talk) 21:26, 2 December 2013 (UTC)


 * He means an unmanned vehicle that isn't remotely controlled. See for example autonomous underwater vehicle or autonomous car Ssscienccce  (talk) 22:39, 2 December 2013 (UTC)


 * There has been discussions of using a novel wave-powered craft to do this - without the need to carry fuel, and with simple satellite navigation, it seems plausible that a very small craft could make the trip. That would make it a fairly cheap device (by the standards of other circumnavigation efforts) - but there are no reported successes as yet.  Liquid Robotics have a device called "Wave Glider" that is a semi-submersible powered by waves and solar cells.  The craft is around 7 feet long and looks like a surf-board with solar panels on the top.   The Wave glider has successfully travelled 9,000 miles on a year-long autonomous mission as a part of the "PacX" challenge to cross the pacific and holds the current Guinness world record for autonomous travel.  The accepted minimum distance for a "circumnavigation" is 24,800 miles (40,000km) - so this craft has managed more than a third of that and there is no reason to assume that it couldn't complete the entire journey if so desired.  The Suntory Mermaid II (manned trimaran) demonstrates that even a 3 tonne vessel can be propelled by wave-power alone at between 1 and 2 knots - so even if a much larger vessel is required, this is clearly "do-able".  But at a speed of 1 to 2 knots - covering the required 40,000 km will take at least 11,000 hours and probably more like 22,000 hours (30 months!).  That means that the reliability of the craft - especially in extreme conditions - becomes a critical matter.  Having something that can survive the worst weather conditions continuously for two or more years at sea is not such a simple problem to solve I suspect!


 * Since we have had successful non-stop circumnavigations in an aircraft (Virgin Atlantic GlobalFlyer), it ought to be possible to program a drone-pilot to make the same trip in a similar craft (the necessary additional computers, cameras and batteries being lighter than the pilot and engineer from the manned trip) - but since there isn't really a compelling record to be broken, I doubt people are working towards doing that. SteveBaker (talk) 00:12, 3 December 2013 (UTC)


 * As far as surviving bad weather at sea, I suggest a boat that can detect bad weather and submerge to a safe depth until it passes. StuRat (talk) 08:04, 3 December 2013 (UTC)


 * You are probably not going to have an autonomous vehicle transiting the canals (what, with robotic line handlers in Panama?), so it would circumnavigate via the great capes, and what passes for good weather in the southern ocean is bad weather elsewhere. Boats there expect to sail during typical gale force winds, and only heave to or tow warps or drogues during stronger storms.  Insolation is limited, what with the high latitude and cloud cover, so I suspect that a Wave Glider could cross the Pacific back and forth a dozen times easier than it could circumnavigate via the great capes.  Generating electrical power from wind turbines or towed water generators is very practical at those latitudes, and would mesh well with solar generation used is the low winds of the equatorial Atlantic, so it shouldn't be too difficult to build an autonomous sailboat which powers its own sail controls from these sources, but, as others have mentioned, reliability would be the big issue.  You need a design which can go for many months in all types of conditions without human assistance unjamming caught lines, replacing chaffed and broken ones, and stitching up torn sails. -- ToE 13:32, 4 December 2013 (UTC)
 * I wouldn't discount the possibility of one of these devices making it through the Panama and Suez canals. The machine is capable of navigating via predetermined GPS waypoints - so all it would take would be some arrangement where it would call ahead to request the canal locks being operated for it.  But since it's only about the size of a surfboard, it could probably be programmed to sneak into the locks with some larger ship.


 * Even if it had to go past the capes, because it has no fuel issues, it could loiter until the weather was optimal to do the trip...so now the question is whether the best weather at the cape is worse than the worst weather it successfully managed during an entire year in the Pacific. SteveBaker (talk) 00:45, 5 December 2013 (UTC)


 * How about an autonomous, parasitic boat, called the Remora, which suctions onto the hull of ships to go where it wants. Perhaps it could read the ship's transponders and look up the shipping records via satellite to figure out which ship is going where it wants to go. StuRat (talk) 09:23, 6 December 2013 (UTC)


 * Speaking to the idea of releasing a balloon into the trade winds, that doesn't seem like it would fit the OP's requirement of the vehicle being autonomous. "Autonomous", in every case I've seen, at least implies that the thing has some sort of control over its own workings.  A balloon simply set adrift on the winds has no way of making any changes to altitude, speed, or heading.  Dismas |(talk) 05:13, 3 December 2013 (UTC)


 * That's a good point, but how much would it have to do to qualify ? If it just monitors it's progress and then releases gas to descend when it reaches the target, would that qualify ?  (I bet it would need to do more than that, though, like change altitude to avoid weather, get into the proper wind currents, etc.) StuRat (talk) 08:01, 3 December 2013 (UTC)


 * Certainly you could imagine a vehicle that can inflate or deflate a balloon to control altitude being described as "autonomous" - but only if it does so in order to achieve some degree of control over the flight path. It could perhaps be informed of the wind speeds at different altitudes at its location and autonomously control altitude in order to control direction.  However, the amount of information available to it about wind speed versus direction over the entire earth might be problematic...so then you'd have to imagine it either measuring that information with some kind of doppler-effect thing - or perhaps moving up and down to experimentally discover the best height to be at.  This seems like a fairly challenging problem - so I doubt that this kind of gadget would be the first autonomous circumnavigation.  My bet is definitely on the Liquid Robotics boat - it's already travelled 9,000 miles and since it doesn't require fuel, there is no particular reason to assume that it couldn't go the whole distance...although reliability issues over a 2 to 3 year voyage, and some lack of desire on behalf of the owner to actually make the attempt might prevent it from being the first to do this. SteveBaker (talk) 15:13, 3 December 2013 (UTC)


 * I would think "navigate" would be a factor whether a human program or artificial intelligence (animals wouldn't count). Dropping a bottle with a message into the ocean might traverse the globe but it has no navigational ability.  Ferdinand Magellan and Juan Sebastián Elcano made navigation decisions to circumnavigate the globe. Similarly, simply tracking a whale wouldn't count either.  --DHeyward (talk) 09:21, 4 December 2013 (UTC)