Wikipedia:Reference desk/Archives/Science/2014 November 29

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November 29

What are the chances of getting hpv from oral sex?

[Note the OP has rephrased this question more to his liking as of Dec 3, below]

What are the chances of getting hpv from oral sex, not the chances of oral cancer from hpv? I asked a similar question a few days ago. Whereismylunch (talk) 04:28, 29 November 2014 (UTC) ″

Fairly sure the answer will depend on factors like whether any form of barrier protection was used, the sex of the recepient, and whether you're referring to the risk to the receiving or giving/performing partner. Also the presence or absence of open sores or wounds on the mouth of the performing partner, the number of times and whether the people involved have HPV or at high risk of it (e.g. sex workers). The difficulty of seperating these means some figures will be averages of them (for example, I don't think anyone is going to try to come up with a figures for a person who's received oral sex 1x, 2x, 3x, 4x.... during their lives), but I don't think anyone is going to come up with a random single figure for the risk of getting HPV from oral sex. Nil Einne (talk) 13:36, 29 November 2014 (UTC)

But on wikipedia they have a random single figure for aids from anal sex.Whereismylunch (talk) 18:11, 29 November 2014 (UTC)

The question is not from receiving, but from giving oral sex, and I think we can just assume average numbers, not specific risk factors. Basically, the OP seems to be asking, of those who get oral cancer, how many can attribute it to a sexually transmitted HPV infection, not "what are my odds of getting oral cancer if I service a guy wearing a condom", which we wouldn't answer anyway. That being said, my understanding is the risk is measurable, but I have no Idea where I read that, so I am not about to venture a guess. I suspect I read it somewhere that was advocating that not only girls get the HPV vaccine. μηδείς (talk) 03:23, 30 November 2014 (UTC)

Where was it stated it was from receiving not giving oral sex? It wasn't even stated the sex of the receiving partner. And so average numbers for what? I don't get the relevance of most of your later stuff. The point is that the OP hasn't sufficiently defined what they're asking for this to be answered in any meaningful way. (Note also as stated below there are multiple subtypes of HPV and I'm not sure these are always considered together.) In terms of your middle point, this [1] easily found from a simple search says "every year, over 9,000 men are affected by cancers caused by HPV". This includes those affecting "the anus, mouth/throat (oropharyngeal cancer), and penis". I'm sure you could come up with a value for those only affecting the mouth/throat. However it would be silly to assume the HPV always came from sexual contact, and even more flawed to assume that the sexual contact was from giving oral sex. Nil Einne (talk) 04:05, 30 November 2014 (UTC)

I mistook this thread for the almost identical one that had just archived. μηδείς (talk) 22:14, 1 December 2014 (UTC)

Your question is not specific enough. It is better to ask, what are the chances of acquiring a HPV infection of subtype N by the person giving oral sex from the person receiving oral sex provided that the latter person has an active HPV infection with subtype N? The chances are probably high—in the range of tens of percent. However the vast majority of such infection are asymptomatic and will resolve on their own in a few months. Only a very small fraction will become chronic and potentially cancerogenic and only of subtype 16. Ruslik_Zero 03:40, 30 November 2014 (UTC)

If I WP:AGF you are correct, then that should be fixed ASAP. It makes zero sense for any article on wikipedia to say that. For starters, while many people with HIV will eventually get AIDS, it's complicated and can take a while. For this reason, it's far better to talk about the chance of getting HIV not the chance of getting AIDS and few, if any, will talk about the chance of getting AIDS.

Secondly, nearly every single source will differentiate between the receiving or receptive partner and performing or insertive partner when it comes to the risk, as these can vary quite significantly.

Thirdly, the sex of the receiving receiving partner probably may not have a significant effect on the risk for anal sex in the generalised case. In the real world it may have an effect because the person may have a different risk profile and other factors. But actually this would apply to the giving partner in the oral sex case which I didn't mention because I was going to mention the later issues. (In "anal sex" practices where the insertive/giving partner is female like pegging, these normally aren't considered when it comes to anal sex. And female/male here refers to the sexual organs of simple cases. For intersex and other individuals where the partner may have a penis despite being female, I didn't mention that complexity.) In the oral sex case, it's quite important that we differentiate between fellatio and cunnilingus, both are which quite correctly and commonly described as oral sex yet are likely to have difference risk profiles, hence why I said the sex of the receiving partner is significant. (To be fair, anilingus]] may also be included which would include both sexes and isn't something I really mentioned.)

Since I can't find what you referred to (may be it's already been removed), I'll give a current example. Our HIV/AIDS#Sexual has risks. But it does differentiate between receptive and insertive partner. (And receptive is quite a large range.) It also assumes no barrier protection (condoms) were used. It's also referring to an average per act risk, and exposure to an infected source. And if you read the text, it gives further complications such as whether it's a low or high income country, and the presence of other STIs, and whether commercial sex work including prostitution is involved. This is an example of the complexity involved and why the article you referred to which gave a single figure probably should be changed. Note our article also mentions a value for oral sex (again differentating between receptive and insertive) but makes it clear it's referring to cases where the insertive partner is male. (The high/low income thing is interesting and not something I was aware of although I guess not surprising. Since we're talking about cases where condoms weren't used and the partner has HIV, these obviously aren't the reason. I would guess it's because of how well the HIV is controlled, the relative health of both partners, the number of conurrent STIs, perhaps also stuff like the usage of and type of lubrication and a bunch of other factors.)

Nil Einne (talk) 04:05, 30 November 2014 (UTC)

I will re formulate my question and make it clearer. Just forget what I asked. What are the chances of catching the hpv virus from giving oral sex for men to someone who is infected? I already googled it yesterday and it said in one study it was less than 10 per 1000 person months for healthy men. — Preceding unsigned comment added by Whereismylunch (talk • contribs) 22:00, 30 November 2014 (UTC) Men giving it to women, not men giving it to men.Whereismylunch (talk) 22:07, 30 November 2014 (UTC)

Hydrogen roasting

Molybdenum and tungsten is produced by roasting the oxides under hydrogen gas. What makes the ore of one metal better qualified over the ore of another? Which ores were this technique first applied to, for the purpose of refining the metals? Plasmic Physics (talk) 09:13, 29 November 2014 (UTC)

Metals are smelted from ore using the chemical process of reduction. The material used as a reducing agent depends on the electronegativity of the metal. Some metals (like the ones in your example) have very low electronegativity and require extreme conditions to accomplish ore extraction, such as protecting the entire process within a reducing atmosphere. Mihaister (talk) 07:19, 30 November 2014 (UTC)

Metals are normally smelted, but not always. In hydrogen roasting, hydrogen plays the role of the primary reducing agent, not just the reducing atmosphere. The key difference between smelting and roasting, is that smelting involves a molten phase at some point in the process, whereas roasting does not. An example would be the hydrogen roasting of chalcocite:

Cu
₂S + H
₂ → Cu + H
₂S

Plasmic Physics (talk) 07:42, 30 November 2014 (UTC)

I stand corrected. Mihaister (talk) 07:51, 1 December 2014 (UTC)

If you mean What makes the ore of one metal better qualified over the ore of another – for roasting as opposed to smelting. It would be the melting point of the metal (and to some extent I suppose, the ticklish problem of removing unwanted other elements that occur in the ore, if refining was attempted in the molten state). After all, what would one line the crucible with to stop the crucible from melting? Even ZrO2 Ceramic Properties only go up to 2400°C!!! --Aspro (talk) 02:23, 1 December 2014 (UTC)

OK, thanks. How was the process historically applied? I'm after some light trivia to write into an article where this process is somewhat important in explaining the main topic. Plasmic Physics (talk) 02:32, 1 December 2014 (UTC)

In that case you have come to the right place - I specialize in trivia - whatever its mass happens to be. Have a read of [2] Chapter One, page 1 & [3] page 143. As I vaguely recalled, it appears that the ore needs to be chemically purified before roasting. --Aspro (talk) 06:43, 1 December 2014 (UTC)

Red Bull Stratos

The person might have been burned during re-entry. But he did not. But spacecrafts get fire during re-entry. Please explain why? --IEditEncyclopedia (talk) 10:39, 29 November 2014 (UTC)

See Aerodynamic heating. The guy probably got warm from the friction, but he wasn't going fast enough to cause combustion. The typical "shooting star" comes into the atmosphere at a very high speed and burns quickly. Speed seems to be the key issue. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:27, 29 November 2014 (UTC)

Also, try this: Rub your hands together very fast... Do they get warm? That's why things get hot on re-entry. Friction causes objects to heat up, the faster something is "rubbing" against something else, the more heat is generated. An object such as a meteor or a space craft is moving very fast indeed, and as such, generates a lot of friction with the air of the earth's atmosphere. --Jayron32 13:28, 29 November 2014 (UTC)

Friction is too much of an over simplification when it comes to de-orbiting craft and lumps of comic rock. At these velocities the air stops moving before it gets to the leading surface (called something like the stagnation point). So low flow, low friction! The bulk of the heating comes from compression in this case. The temperature of this air at this point (when it has been turned to plasma) is enough to vaporize all known materials. Fortunately it is not in direct contact with the heat shield (because there is no flow) and so most of the thermal energy radiates away. At lower speeds, the air conducts away much of the heat caused by friction alone, because it is in contact and thus convention is the main method of heat transport. --Aspro (talk) 14:53, 29 November 2014 (UTC)

An important point (not mentioned yet) is that the intrepid Mr Baumgartner only _fell_ to Earth, he was never in orbit. A spacecraft in orbit will be moving much more quickly on re-entry than one which has just been launched straight up, so there's much more energy to dissipate in atmospheric heating on reentry. Tevildo (talk) 15:17, 29 November 2014 (UTC)

Absolutely! That's the huge difference between the two examples. For skydiving from orbit (via an emergency, one man, inflatable reentry device), see MOOSE.-- ToE 16:46, 29 November 2014 (UTC)

I agree. The free fall from a high altitude balloon is much slower than typical orbital speeds. For a somewhat analogous situation see also space elevator. Mihaister (talk) 23:22, 29 November 2014 (UTC)

It's not about the height you fall from - it's about the speed you were travelling when you started to fall.

When you start off at zero speed, you accelerate until you reach "terminal velocity", at which point the force due to the pressure of the air equals the force of gravity, and you stop going any faster. As the air gets progressively denser, your terminal velocity gradually decreases, and at no point are you going fast enough to produce significant problems. That's also why SpaceShipOne was able to get back to Earth without the need to heat-resistant tiles or an ablative heat shield. In the Baumgartner jump, the fastest speed he ever reached was around 850 mph.

When you start off in low-earth-orbit, you're initially moving at between 15,000 and 18,000 mile per hour...when you reach the atmosphere, you're already moving vastly faster than terminal velocity...and you are going so fast that you're reaching the denser air before you've shed enough speed.

Looked at another way, the amount of kinetic energy you have to burn off to reach the ground at a safe speed from orbit is phenomenal. Kinetic energy is proportional to the SQUARE of the speed...so not only is an orbital craft moving twenty times faster than Felix Baumgartner did - but the amount of energy needing to be shed (per kilogram of mass) was 400 times greater.

In terms of how that energy gets turned into heat, it's a bit complicated because some of the energy goes into heating up the object itself, and some into heating the air around it...and playing with the shape of the craft, the angle of re-entry, the nature of it's surfaces, makes it possible to dissipate most of the energy into the air rather than into the craft itself...but regardless of that, it's clear that there is so much more energy to get rid of when you fall from orbital speeds than if you fell from the same height but without being in orbit.

SteveBaker (talk) 14:54, 2 December 2014 (UTC)

Thanks for the explanation, SteveBaker. --IEditEncyclopedia (talk) 10:51, 4 December 2014 (UTC)

Snow-resistant buildings

Steeply pitched, gabled roofs in Northern Europe

How can buildings be constructed to be able to support four meters of snow without being damaged?

• New York's Cuomo warns snow-hit Buffalo of risk to roofs—Reuters (November 24, 2014)

—Wavelength (talk) 17:32, 29 November 2014 (UTC) and 19:10, 29 November 2014 (UTC)

Use a steeper roof pitch. Plasmic Physics (talk) 21:36, 29 November 2014 (UTC)

How steep would it have to be to avoid all snow accumulation ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:30, 29 November 2014 (UTC)

Houses built in Northern latitudes typically have steep roofs for this exact purpose. This image is from the main article on roofs. Mihaister (talk) 23:30, 29 November 2014 (UTC)

Perhaps the section heading is misleading. My question is about buildings actually supporting an accumulation of four meters of snow on their roofs, and not about techniques for deliberately avoiding snow accumulation.
—Wavelength (talk) 00:28, 30 November 2014 (UTC)

In snow-bound areas, the solution to building damage from snow accumulation is to build structures where snow does not accumulate. If the snow crushes your roof in, the more sensible problem is to build a roof to allow the snow to slide off, rather than to accumulate. Does that mean that sometimes people in such areas sometimes build structures in an unintelligent way, so that the snow builds up and then caves in the roof? Yes, they do. But the best solution is to avoid letting snow accumulate in the first place. You can build structures to support the weight of the snow, After all, if you can build a bridge to support multi-ton trucks rumbling across them all day, you can apply the same principles to support multiple tons of anything, including snow. Any structure that will support the weight will support the weight. The question is whether such structures are economically sensible, or whether it just makes more sense to pitch your roof so snow doesn't gather. --Jayron32 01:49, 30 November 2014 (UTC)

Just add extra dead load of the said snow while designing the slab thickness if the structure is RCC.162.157.249.151 (talk) 03:54, 30 November 2014 (UTC)EEK

Some of those roofs in the picture don't look very snow resistant. Specifically, the ones that are attached to their neighbours. The snow would accumulate in the valleys and cause a leak problem at thaw time. Richard Avery (talk) 07:50, 30 November 2014 (UTC)

I don't think your concerns are really a problem. Those valleys are supported by load bearing walls and there are clearly visible drainspouts to handle the meltwater. The picture shows a good design for adjoining buildings to handle heavy snow.

I can't really speak for houses, but warehouses and other buildings with large roof areas may simply opt for large support structures that can take the weight. When I toured a DC facility in Owen Sound, for example, there were these thick steel support structures, much larger than anything I'd seen elsewhere for the size of the roof they supported. They weren't visible from the outside, but inside they gave the place something of the appearance of an enormous ribcage. They're not much different than normal columns and OWSJ, just much more robust. Matt Deres (talk) 13:22, 30 November 2014 (UTC)

The method we use here in Finland is that the occupant buys a shovel. 88.112.50.121 (talk) 16:28, 30 November 2014 (UTC)

Yes, that works well when there are upwards of five feet of snow on the roof. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:59, 30 November 2014 (UTC)

It does work, although one would usually not let it get that thick, especially if it is older packed heavy snow. Shoveling a roof is easier than shoveling a similar amount from a driveway, as gravity helps a lot. 88.112.50.121 (talk) 17:20, 30 November 2014 (UTC)

When you get several feet in the space of a few hours, as with Buffalo recently, it's pretty hard to avoid the problem. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:58, 30 November 2014 (UTC)

New snow is pretty light and fluffy, I've never seen a real world problem with it. People have lived here in Finland for 10,000 winters, and the best technology we have for snow on the roof is a shovel. If you come up with a better solution, please do tell. Maybe we can share patent income! Basing all architecture on highly sloped roofs -- thanks but no thanks. 88.112.50.121 (talk) 20:49, 30 November 2014 (UTC)

Read what happened in Buffalo recently. And by the way, there is such a thing as a roof shovel, i.e. a scraper with a very long handle. But the citizens of Buffalo were overwhelmed by it all, and there many reports of collapsed roofs. That's probably what triggered the question here. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:51, 30 November 2014 (UTC)

Just reporting how people who deal with the issue every year handle it, sir. 88.112.50.121 (talk) 00:03, 1 December 2014 (UTC)

Helsinki gets 72 cm of snow a year - Buffalo gets 240 cm on average but in this storm got nearby Cowlesville got 223 cm in 3 days. Rmhermen (talk) 03:49, 1 December 2014 (UTC)

So I suggest getting a shovel and getting busy with it. The alternative of suddenly re-architechting all your buildings to have steep pointy roofs is ...yeah, well, good luck with that.

It is funny to see people struggling with a simple perfectly natural thing. Like someone who discovers he needs to mow his grass, or that dead leaves need to be raked. Memo to all: you got to shovel your snow! 88.112.50.121 (talk) 05:36, 1 December 2014 (UTC)

It seems that it isn't unheard of to have snow guards/snow barriers (and it's a legal requirement in some cases) on roofs in Finland to protect people under the roof from excessive falling snow & make sure the snow accumulates in a safe fashion with respect to the load bearing structures [4] [5] [6] and perhaps also to keep a minimum level of snow for insulation (per our article).

Not from Finland but as an alternative to shoveling [7]. (Although I'm not denying that shoveling is the most common method, albeit sometimes with assitance particularly for commercial buildings File:Snow removed from roof Keljo.jpg File:Snow removed from roof Keljo closeup.jpg & Commons:Category:Snow removal from roofs.)

That said, I think Rmhermen, BB et al do have a point that it's flawed to automatically assume there's something wrong just because people and structures are able to deal with something in one area when it causes greater problems in another area, particularly without considering how similar the situation actually is, the frequency of such events or how out of the ordinary it is, and the reasons such differences in the way things are dealt with might exist. In particular, most places have problems dealing with extremely rare events, I doubt Finland is any different.

Also e.g. [8] [9] (many of the articles relate to snow on roofs) or even our article snow removal has some info on snow on roofs.

It's not like roofs have never collapsed in Finland [10] or there isn't such concern [11]. In fact [12] is designed to provide warnings for when shovelling is necessary and appears to have been developed in Finland [13]. (Although more limited similar ideas may exist [14] [15].)

And there are other risks besides the roof collapsing, as the presence of snow guards illustrate [16] [17] [18]. The shovelling itself obviously caries some risks [19] [20] (the video is from Estonia but the uploader appears to be from Finland). This Finnish person [21] seems to understand that albeit in relation to a different case.

Nil Einne (talk) 13:02, 1 December 2014 (UTC)

Another factor to remember is insulating the ceiling or roof. If the roof gets warm, the snow sticks to it more, and ice forms more. If the roof stays cold, the snow slides off more easily.122.108.177.30 (talk) 07:15, 1 December 2014 (UTC)

Actually, it's the opposite. If the snow disappears from the roof sooner than it does for your neighbors with similar roof styles, it means your house is improperly insulated - too much heat is escaping through the roof. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:13, 1 December 2014 (UTC)

Can you mix ants of the same species but of different ant colonies?

If you pick ants from one ant colony and place them in a totally distinct (but of the same species) ant colony, would they come well along? --Senteni (talk) 19:15, 29 November 2014 (UTC)

There has been considerable research on this topic. A Google Scholar search for 'ant colony recognition' will provide a starting point. [22] Ants communicate via scent (notably pheromones), and it seems that each colony (or possibly supercolony [23]) has a distinct scent. AndyTheGrump (talk) 20:30, 29 November 2014 (UTC)

Indeed, but the tolerances and differentiation vary amongst species and this may be a factor in which species form supercolonies and the degree of genetic uniformity within and between separate colonies. Further, there are some parasitic species who will intrude upon a closely-related colony and exist as a distinct genetic population within it without producing their own workers, and in these cases the parasitic species seems to be exploiting the fact that the pheromones employed are (apparently) innately known and universally recognized by the host species. But still other parasitic species will exploit the fact that some species have colonies that establish a scent that falls within certain constraints but varies from population to population, a scent that individuals are fine-tuned to recognize in development and which is therefore in a sense "learned" by the resulting superorganism; parasitic species in this context will sometimes attempt to install their own queen before the first broods are born, in order to either cohabitate with the, to completely leverage their work for themselves, or to simply leave the host colony disorganized until the physical burrows can be captured by a working population developed from their own offspring.

To answer the OP's question more directly and succinctly: in rare instances, yes -- one could integrate a migrant ant -- but not in most cases.Snow talk 02:16, 30 November 2014 (UTC)

Two examples: I was told by an entomology professor that an individual worker pharoah ant could be flown from NYC to LA (or Tokyo, etc) and could rejoin a colony there. Also the Argentine ant is thought to be so invasive in the USA because of a founder effect, wherein all invasions are related because they came from the same few queens. So, in their natural range they have small colonies that fight eachother, while in their introduced range different colonies aren't sensed as rivals, and giant supercolonies form. It all really depends on the specific species and how they sense kin/colony relationships. SemanticMantis (talk) 15:44, 30 November 2014 (UTC)

That is a fascinating aspect of the Argentine ant that I actually had forgotten about, but which perfectly demonstrates how divergent genetic variation and population size can be for the same species in different ecological niches. The Argentine ant proved so successful as an invasive species on several continents that one particular closely-interrelated (if massive) genetic population grew to encompass huge range of territory consisting of vast numbers of genetically similar individuals and colonies, while it stayed (relatively) constrained in it's orignal and more localized South American habitat, where it co-existed with other more closely-related and similarly capable subspecies and species, and other competitors/constraining species that it had co-evolved with. In other words, it might just as easily have been another similar population with most of the same traits but whom would be sharing their own unique phenotype for pheromones and leveraging their vast numbers to out-compete both the native species and any other Argentine subspecies/close relatives who might otherwise migrate. Snow talk 14:30, 1 December 2014 (UTC)

Ants also detect colony mates via signatures of hydrocarbons on the cuticle (which are different from pheremones). Some species will attack a con-colonial worker if she is washed off by humans. SemanticMantis (talk) 16:09, 30 November 2014 (UTC)

I had meant to mention as well that there are other types of chemoreceptors utilized by ants for communication and navigation. Although at the same time, ants are amongst the the very few organisms in which the role of pheromones is not overstated in popular science reporting; most all species of ant rely on them to some varying (but generally very significant) degree that is often well-documented; whereas the pheromones used, or purported to be used, in countless other species (vertebrate and invertebrate) are often overstated and/or not particularly well understood. Snow talk 14:30, 1 December 2014 (UTC)