Wikipedia:Reference desk/Archives/Science/2014 February 28

= February 28 =

Great Heck train wreck
If both engineers in the Great Heck train wreck (What the Heck, no article?! This can't be -- it's on the main page!) were killed in the collision, then how did Andrew Hill, the instructor who was riding in the cab of the freight train, manage to survive? 24.5.122.13 (talk) 06:08, 28 February 2014 (UTC)


 * The article is Great Heck rail crash. HiLo48 (talk) 06:11, 28 February 2014 (UTC)


 * Fixed it for you. Don't know if anyone can answer "who lives/who dies" question.  There were fatalities and injuries.  He wasn't the "sole survivor" nor were the drivers the only fatalities so it seems it's random/speculation.  --DHeyward (talk) 06:33, 28 February 2014 (UTC)


 * He survived because he didn't sustain fatal injuries - what more is there to say? Richerman    (talk) 10:10, 28 February 2014 (UTC)
 * It could be instructive to find out how someone survives or doesn't, for the purpose of making safety recommendations for the future. ←Baseball Bugs What's up, Doc? carrots→ 12:58, 28 February 2014 (UTC)
 * As a writer of disaster novels, I find it very instructive to learn how a person can survive an otherwise fatal event. How did Shadrach, Meshach, and Abednego survive being burned alive in a furnace?  How did Vesna Vulovic survive falling from a plane without a parachute (assuming, of course, that her story is true)?  How did Joe Simpson survive falling down the mountainside?  All these things naturally pique my curiosity -- and with luck, maybe discovering the secret and telling the world about it might save a life or two down the road... 24.5.122.13 (talk) 01:43, 1 March 2014 (UTC)
 * As was the case for all serious rail accidents in the UK, this crash was undoubtably investigated closely by Her Majesty's Railway Inspectorate, whose official Railway Accident Report will likely elucidate the matter. (I say "was" because this function has latterly been taken over by the Rail Accident Investigation Branch.) {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:40, 28 February 2014 (UTC)


 * Indeed, the full report is linked from the article in question. Incidentally, "train wreck" is too colloquial for an article title. I hope not all rail crash articles will be made redirects from the equivalent "train wreck" pages.--Shantavira|feed me 15:09, 28 February 2014 (UTC)


 * "Train wreck" is the standard American nomenclature for events of this type -- "rail crash" is AFAIK an exclusively British term. And what, may I ask, is wrong with providing a redirect, as long as the article's actual title remains the same? 24.5.122.13 (talk) 01:29, 1 March 2014 (UTC)


 * "It could be instructive to find out how someone survives or doesn't" It certainly would be instructive for the the crash investigators, but my point is that editors who contribute to this page are unlikely to have access to that information. Richerman    (talk) 19:04, 28 February 2014 (UTC)
 * Are British accident reports made available to the public? ←Baseball Bugs What's up, Doc? carrots→ 19:53, 28 February 2014 (UTC)
 * All the RAIB's reports are public, they're on http://www.raib.gov.uk  20:21, 28 February 2014 (UTC)

Yes it's linked to the article, as Shantavira says above. I've just scanned through The track obstruction by a road vehicle and subsequent train collisions at Great Heck 28 February 2001: A report of the Health and Safety Executive investigation and although it states that the instructor survived (p. 30), it doesn't say why specifically. It does say "It [the freight locomotive] was heavily damaged on the front and right side, and below the cab in the vicinity of the missing right buffer, with part of the DVT [the passenger loco] embedded below the right front window. The interior of the leading cab was mainly intact, but all the windows were broken. The two drivers seats were undamaged and fixed to the floor. The survival space about the right-hand seat had been reduced below waist level" (p. 28). It goes on to say that "The exit for drivers from the locomotive cab is not easy. The driver has to move forward, around the control pedestal, before gaining access to the inward opening door in the rear wall of the cab. This opens into a cross passage that could be used as a refuge during a collision" (p. 29) It seems to me that the damage was all on the driver's side (the right) and the instructor on the left was saved by not being directly involved in the impact. An alternative is that the instructor got up and ran back into the "refuge", but I think that they would have mentioned this were it the case. Alansplodge (talk) 20:31, 28 February 2014 (UTC)


 * Thanks! This last comment pretty much answers my question -- the instructor probably survived because he was sitting in the left (fireman's) seat, and the express train hit the freight train on the right side. 24.5.122.13 (talk) 01:25, 1 March 2014 (UTC)
 * You're welcome. Alansplodge (talk) 01:33, 1 March 2014 (UTC)

Anxiety Symptoms From Different Sources Cause Anxiety
This is not a request for medical advice, it's a request for information about something I'm curious about from personal observation. That said: at one point in time, I had an anxiety disorder, I've noticed that now, years later, various anxiety attack effects can sometimes trigger a small anxiety attack. For example, I'd feel cold and a bit shaky when I had an episode, if I go outside and there is an extreme temperature differential, I get cold and shaky, which sometimes makes me feel like I'm having an anxiety attack. The same thing can happen if I purposely hyperventilate. Etc. This is not a constant thing, and when it does trigger anything, it's relatively minor; I'd be curious if any research has ever been done on this, the mechanisms for it, etc. Thank you for any help:-) *And, again: I'm not looking for a diagnosis, cure, etc. I'm quite fine; just curious about how it all works under the hood.Phoenixia1177 (talk) 10:54, 28 February 2014 (UTC)
 * Clarification: I realize that having anxiety in a situation can cause a link with that situation and anxiety. My curiosity is that this is directly linked to replication of symptoms, is not consistent, generally milder, and rather obvious - making it seem like it might be a separate type of thing/association.Phoenixia1177 (talk) 11:01, 28 February 2014 (UTC)
 * Our article on panic disorder does describe a mechanism of that type: "Another mediator is hypochondriacal concerns, which mediate the relationship between anxiety sensitivity and panic symptomatology; thus, anxiety sensitivity affects hypochondriacal concerns which, in turn, affect panic symptomatology".  The reference given for that statement is . Looie496 (talk) 14:28, 28 February 2014 (UTC)

This type of generalisation of symptomology is common in anxiety problems. Your reaction to the sensation of shivering is recalling a time when such shivering was a part of panic/anxiety. This is a learned behaviour and will take some time to unlearn. Recognise what is happening and allow yourself to feel the reaction while keeping calm. Self-analysis of your reaction sometimes helps. If however the reaction triggers real panic it may be advisable to seek some support with a professional. Think clearly about what occurs, try to acknowledge to yourself that it is a memory of anxiety not actual anxiety. After encountering the stimulus several time without getting badly anxious the stimulus should stop being so worrying. Try looking for reports on controlled breathing and positive visualisation to provide techniques to sooth anxiety reactions. shad darra — Preceding unsigned comment added by Shaddarra (talk • contribs) 05:27 1 Mar 2014

Sump pumps that work better
I would like to use a sump pump to drain water off my sidewalk where it accumulates during snow melt. However, it doesn't seem to work unless I have several inches of water there. It sucks in air instead. So I have to find other ways to clear the water. I know that digging a pit off the edge of the sidewalk on the lowest spot and putting the sump pump down there would work, but is there any way to get one to work short of excavations ? Do they make any designed for this situation ? StuRat (talk) 14:45, 28 February 2014 (UTC)


 * A sump pump needs a sump (which on its own will help to drain the sidewalk), but it only needs to be a few inches deep. Otherwise you would need a wet vac.--Shantavira|feed me 15:17, 28 February 2014 (UTC)


 * Yes, I've used a wet vac there before, but that's rather painful. Seems like a version of a sump pump that can pump down to a mm of water ought to exist. StuRat (talk) 16:19, 28 February 2014 (UTC)


 * Hmmm, that reminds me: what is the theoretical limit of capillary action given a specified volume to work in? I assume that if you completely lined the sidewalk with towels with their lower edges in the water, they would take it up.  But assuming someone wants to pound a few poles into the ground up and down the length of the sidewalk, how do you calculate the theoretical maximum of the water they could take up and evaporate?  Trees, of course, are good but not necessarily good enough for this; then again they aren't really designed to maximize water loss at all costs, and besides, wooden poles just don't seem to do it.  I look at the brick in capillary action and think... if you could just make that work better, and have better surface area to evaporate from...  is there theoretically (or even practically) a way, with the right marvel material? Wnt (talk) 16:24, 28 February 2014 (UTC)


 * Is there some way you could use some variation of a french drain to direct the water away from the sidewalk? -- Jayron  32  18:46, 28 February 2014 (UTC)


 * That's what I was going to recommend too. A photo would help with the geometry, but all he should really need to do is dig a trench, fill it with gravel, and let gravity do its work. Probably no pump required! SemanticMantis (talk) 19:31, 28 February 2014 (UTC)


 * That rather depends on the geology. Here in London, we have London clay which is "relatively impermeable to water" according to our clay article. But then, we haven't had any snow at all this year. Alansplodge (talk) 20:36, 28 February 2014 (UTC)


 * You might be able to attach some sort of tube with a small bore on one end to your existing sump pump. Ensuring you keep any air out of the system might allow the pump to work as desired. There do seem to be some pumps designed to work with low water levels, fountain pumps, or surface water pumps.--Salix alba (talk): 06:32, 1 March 2014 (UTC)

The sidewalk has several low spots, and I'd like to be able to pump water out of those before it freezes into ice. I suppose I could dig several trenches, one by each low spot, and put a sump pump into each, but that doesn't seem very practical. Same with connecting the various low spots with a long trench. The low spots all tend to be at seams between slabs of cement, so there is a "micro-trench" between each seam, and a small enough tube sucking in water slowly enough might work there, although it would take hours at that rate, especially if more melt-water was pouring in.

So far I've just been pouring salt on the ice when it forms, but that kills the adjacent plants. StuRat (talk) 23:24, 1 March 2014 (UTC)

Hiv virus
Why are used needles such a large risk for HIV if the only method of transmission, during sexual activity is direct contact between blood, Semen or vaginal fluid or a mucous membrane. Surely the risk is lower for needles as the virus is unlikely to have survived on it. — Preceding unsigned comment added by 94.13.141.182 (talk • contribs)


 * Not on it, but in it. IV drug users usually shoot into a vein and draw in a little blood before injecting to make sure they have it one. μηδείς (talk) 21:23, 28 February 2014 (UTC)


 * Read also about mass Hepatitis C infections in healthcare settings. here's one. There have been other cases where a contaminated syringe is used to draw medication from a vial and the vial becomes contaminated.  Here is another one .  I don't know if hepatitis C is more or less resilient than HIV but they have common pathways for transmission (they are also very different in mechanism).  The flu virus can live on hands and surfaces so viruses can have a lifetime outside the body (flu virus seems obviously more hardy than either hep C or HIV, though).  HIV can survive longer than 6 weeks in a syringe.  --DHeyward (talk) 07:48, 1 March 2014 (UTC)


 * Now there's a statistic that we should hear more often in public service announcements. I thought about this, and my guess was that because syringes have a rubber plunger, when you finish injecting a drug, there will be some resilience pulling blood back up.  I would imagine that opiate addicts might be particularly avid about pressing out every last microliter...  looking this up led me to low dead space syringe, which actually does seem to reduce transmission risk considerably.   It is amazing that so many people have died over such a tiny issue in careless design (though of course primary blame goes to the foolishness of drug prohibition to begin with). Wnt (talk) 11:40, 2 March 2014 (UTC)