Wikipedia:Reference desk/Archives/Science/2013 August 20

= August 20 =

Hypothermic/hypothermia surgery
I have found Google information about the use of deliberate hypothermia in brain and cardiac surgery. It is apparently being used in Ecuador for, for example, foot surgery, but I can't find any references to this technique. Anybody out there have better sources and or knowledge? Thanks Bielle (talk) 02:57, 20 August 2013 (UTC)
 * Cryotherapy would be a good place to start. 24.23.196.85 (talk) 04:20, 20 August 2013 (UTC)
 * Thank you, but cryosurgery is used only for very small parts of the body. The description I was given was of some sort of "ice machine" which "froze" the whole lower half of the body. This cannot be literally true, because of the response of cells to freezing. Any other suggestions? Bielle (talk) 16:15, 20 August 2013 (UTC)


 * Wikipedia Has An Article On Everything! - see Therapeutic hypothermia. Alansplodge (talk) 17:49, 20 August 2013 (UTC)

sun setting at different times
A couple of weeks ago while I was driving home (Central Ontario, Canada), I pulled over to take a picture of an amazing sunset. Later, I sent the pic to my friend in Ghana and noted that the pic was taken at about 8:30 pm. She was surprised as the sun set in Ghana at about 4:30 pm. When I look at a map I see that Ghana is much closer to the equator than Canada is. Does this explain why the sun set at different times in the two countries? 173.35.158.194 (talk) 03:25, 20 August 2013 (UTC)


 * The short answer is "yes". See Sunset for a better one. Bielle (talk) 03:33, 20 August 2013 (UTC)


 * Are you sure that she said sunset was at 4:30 p.m. in Ghana? Does she live behind a big hill?  Ghana is not on a time zone significantly ahead of its local time.    D b f i r s   11:24, 20 August 2013 (UTC)


 * Sunrise and sunset in Ghana is never far away from six o'clock, it is quite close to the equator and in an appropriate timezone. I was wondering if they were referring to what the time was in Ghana when there was a sunset in Ottawa, it is four hours out currently but unfortunately the wrong way for this so I haven't the foggiest what's happening. Dmcq (talk) 11:40, 20 August 2013 (UTC)


 * Time zones and daylight savings time could also shift sunset times by up to 2 hours in Ghana relative to Canada. There could also be differences in how "sunset" is defined.  It could be when the first part of the Sun goes below the horizon, or the last bit, or when the sky goes black. StuRat (talk) 14:33, 20 August 2013 (UTC)


 * There is no way the sun sets in Ghana at 4:30 PM. Dauto (talk) 14:53, 20 August 2013 (UTC)


 * Day length explains how surise and sunset vary by latitude and where the earth is in its annual orbit around the sun. Ecliptic explains the cause behind it. Hope this helps.Diwakark86 (talk) 18:50, 20 August 2013 (UTC)


 * Ghana runs on GMT all year, and no region is very far from the meridian (between four degrees west and two degrees east), so if the friend in Ghana really did mean 4:30 local time then the only explanation is that she lives just east of a hill, and perhaps just east of a tall forest. Local terrain can significantly affect the time at which the sun apparently sets, though daylight will remain for much longer.    D b f i r s   20:31, 20 August 2013 (UTC)


 * Tomorrow, the sun will set at 6:12 pm local time in Accra, Ghana.  That's not 8:30 pm, but it's a far cry from 4:30.  --74.43.43.6 (talk) 03:03, 21 August 2013 (UTC)

Thanks everyone. I suspect that it is a combination of definition and language. 173.35.158.194 (talk) 02:27, 22 August 2013 (UTC)


 * There are various websites that allow computation of times of sunrise and sunset, simply by nominating latitude, longitude and timezone. I have successfully used the following site to compute a table of sunrise and sunset in Ghana for the whole of 2013: Sunrise, Sunset and Twilight Times. Dolphin  ( t ) 23:29, 22 August 2013 (UTC)

Anchors unzipping
I've recently watched The Eiger Sanction with a friend of the family, and he told me that he found the final scene implausible: he said that when anchors unzip from the top because of excessive strain, they all go, so it would be impossible for Clint to remain hanging from his rope while the other three fall to their death. However, I have my doubts about this -- if the bottommost anchor was driven in much more firmly than the others, I don't see why it can't remain in place. Neither of us is a professional mountaineer, so I'd like some educated commentary on the subject. Thanks in advance! 24.23.196.85 (talk) 04:34, 20 August 2013 (UTC)
 * The Eiger article has an unsourced comment saying that the film crew included experienced climbers to ensure the accuracy of the climbing scene. The novel was written before the invention of spring loaded camming device so I'm not sure, but I would say that with modern equipment having 3 anchors fail and the fourth hold would be possible - after all, even if they fail the other anchors should slow down the fall - but I don't recall even seeing such a thing happen (I've seen one or two anchor failures happen though, with modern equipment trad climbing). Not having seen the movie, I have a hard time imagining how that situation would let one member survive but not the others; also note that even if the fourth anchor holds, the distance fallen essentially doubles with every missed anchor, and if there is any angular momentum the climber would likely kill themselves by crashing into the cliff. Effovex (talk) 15:12, 20 August 2013 (UTC)
 * A well placed cam can stop a fall of well over 10 kN. I would guess a well placed pitons would be able to hold at least as much and probably more, as the problem with pitons isn't their strength but the damage they cause to the surface (see Clean climbing). If you can provide a description of the distance between the pitons and the weight of the climbers, I'm sure someone could calculate the maximum amount of force that would be exercised on the remaining anchor. Are they climbing strictly vertically? Effovex (talk) 15:23, 20 August 2013 (UTC)
 * This climbing forum gives a generally favourable review to the film; there are a few quibbles but nobody mentions the failing pegs. John Cleare is mentioned as an advisor. Our Eiger article also states (with a reference) that Dougal Haston, and Hamish MacInnes were involved. Alansplodge (talk) 17:42, 20 August 2013 (UTC)
 * Thanks! So I guess this situation would be possible but unlikely? 24.23.196.85 (talk) 06:29, 23 August 2013 (UTC)

Human body maximum performance
I read an article which claimed that the human body overall performs at its best between ages 25 and 28. Is this true? Does it differ between people, gender race etc? Clover345 (talk) 10:21, 20 August 2013 (UTC)
 * What kind of performance are you talking about? 163.202.48.126 (talk) 11:26, 20 August 2013 (UTC)


 * Aging and athletic performance. The physical peak for "most sports" is 25 to 35. This is likely to be lower for women - I doubt you'll find anything concrete for the different races. Some sports however do require more training than others and you might find that older players tend to do better than younger ones (e.g. golf). Also . If you're talking about academic performance or something else then the answer will be different. 163.202.48.125 (talk) 12:11, 21 August 2013 (UTC)

examples of organs which made of some kinds of tissues
Could you give me some examples for organs which made of some kinds of tissues And some examples for tissue which made of some kinds of cells? Thank you a lot!176.13.161.70 (talk) 16:55, 20 August 2013 (UTC)
 * You may wish to read our articles on organ (anatomy), tissue (biology), and cell (biology) to help you do your homework. DMacks (talk) 17:01, 20 August 2013 (UTC)
 * By the very definition of tissue, all organs are "made of some kinds of tissues". So just pick an organ, and find out how it is constituted. Plasmic Physics (talk) 00:17, 21 August 2013 (UTC)

doing a blood test for who did mastectomy
Today I was in the clinic for blood tests, and I saw that the nurses said to a woman who made mastectomy in one side, that she is allowed to make a blood test only in the another side, because she don't has limph nodes in the side of mastectomy. I also was in the room when it happened but I ashamed to ask about... even it's intresting me. So, here I feel good to ask about:) My questions are: 1. What is the problem or danger to make a blood test in the side of the mastectomy (this is the side where there is not limph nodes). 2. What have to do when a woman made mastectomy in her two sides breasts, can she not be taken a blood test at all, or is there any solution for her? (p.s. It's not medical advice, because I'm a man and just intersting to know the issue. So, please don't note about). thank you. 95.35.232.184 (talk) 17:46, 20 August 2013 (UTC)
 * Reference desk/Archives/Science/2013 August 12 got no responses, but that question does include an answer to the question #1 here. DMacks (talk) 17:56, 20 August 2013 (UTC)
 * Googling finds lots of hospital (or similar) patient-advice webpages talking about it. They mention a problem with the cuff causing lymphedema (consistent with my previous link). And note pros and cons of the obvious alternative of measuring blood pressure "somewhere else" or "by means other than compression cuff". DMacks (talk) 18:07, 20 August 2013 (UTC)


 * It is a matter of balancing risk. For a woman with a recent mastectomy, the risk of penetrating the skin on the arm on the mastectomy side, as is required to get a blood sample, is that infections will be more complicated, as part of the role of lymph nodes is to prevent the spread of infection.  Infection toxins may build up in the arm due to the poor lymph drainage.  For the same reason, women with mastectomies involving the removal of lymph nodes are advised to give up gardening or any activity that has a risk of scratches (or at least wear arm length gloves).  After a few years the lymph channels adapt and new lymph nodes grow, reducing the risk.  For a woman who has had a mastectomy and lymph nodes removed on both sides, normally the mastectomies will be some years apart.  Use the oldest surgery side for blood pressure taking, blood taking, and injections, as this lowers the risk.  Note that for mastectomies, whether no lymph nodes are removed, some lymph nodes are removed, or all lymph nodes are removed, depends on the facts of the case, and the judgement and experience of the surgeon.  If the cancer is discovered by feel or mammogram and is considered early, only the sentinel lymph nodes in the chest might be removed, and there is no more risk to the arm than for any other woman.  Many women who have had breast cancer will have had chemotherapy via a drip in the other side arm.  In some cases this will have "burnt out" the surface veins in that arm, making getting a blood sample difficult.  The woman should insist that an experienced phlebotomist does it, and not just some ordinary general duties nurse.  However, if only a general nurse is available, it's only a matter of risk, nothing to get too uptight about.  A blood sample for lab testing can be taken from any surface vein on a limb.  If the woman has no lymph nodes in both armpits from a double mastectomy (which is very unusual) blood can be taken from a leg or foot vein.  However, as gravity will markedly increase the risk of uncontrolled bleeding, this should only be done in a hospital (or other situation where medical staff can get it under control) under the supervison of a doctor, and the woman will have to remain there until it is certain she won't bleed. — Preceding unsigned comment added by 1.122.245.38 (talk) 00:20, 21 August 2013 (UTC)

Raid Fly Spray
I seem to have an infestation of some kind with Blue bottles and got home from work today with my dining room full of them. So I grabbed a can of Raid fly killer (it may be this product but in the UK it's a blue can marketed as a fly and wasp killer) and sprayed at them directly wherever they were, including walls and windows, shut the doors and returned 15 mins later.

Then I read the directions on the can and part of the warnings state 'keep spray at least 1 metre from all surfaces and walls'. I certainly sprayed a good few surfaces as that's where the flies were sitting. I'm just wondering why, as it's an aerosol, it specifically states not to spray a wall even though spraying it the air leaves the insecticide on all sorts of surfaces.

Is it simply in case the spray rebounds off the surface you're aiming at? I'd think it's still better to aim at the problem rather than spray an antire room in the air and have the spray land on every surface

Thanks in advance --46.208.198.216 (talk) 21:59, 20 August 2013 (UTC)


 * If you have large numbers of them in your dining room, you'd better find the source... otherwise you can play with that can all you want and get nowhere. It's hard to comment on any potential toxicity without seeing ingredients for sure (not just 'something like it'), and even then it would be disallowed here as medical advice, but my pure guess is that if you can spray it in a room safely at >1m they must be more worried about the solvent than the chemical, i.e. for purposes of dissolving plastic, discoloring surfaces etc. Wnt (talk) 22:05, 20 August 2013 (UTC)
 * That makes sense thanks, I assumed it was potential toxins left in the home. I appreciate your advice that I should find the source, but this has happened a few times over maybe the past 8 years, this is the second time with flies and also I had a problem one year with bees (I work away from home and got back one weekend with dozens of tiny bees dead in front of the window). I've had pest control companies out and they were at a loss unfortunately --46.208.198.216 (talk) 22:28, 20 August 2013 (UTC)