Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

June 9

how the measurement in a dc potentiometer is being done??

how the unknown resistance is measured in a dc potentiometer? — Preceding unsigned comment added by 112.79.43.96 (talk) 03:47, 9 June 2013 (UTC)

Do the Wikipedia articles Potentiometer (measuring instrument) or Ohmmeter help? --Jayron32 04:25, 9 June 2013 (UTC)

You can use a potentiometer as part of a Wheatstone bridge in order to measure an unknown resistance. Red Act (talk) 05:27, 9 June 2013 (UTC)

Surveillance camera disruption

What thing can disrupt a surveillance camera other that an electromagnetic pulse and a fake footage? 76.88.39.179 (talk) 04:33, 9 June 2013 (UTC)

Shine a laser into the lens. Looie496 (talk) 04:44, 9 June 2013 (UTC)

Obstructing the lens? Disconnecting it? Moving it so it points in the wrong direction? I'm sure there are many other ways... AndyTheGrump (talk) 04:45, 9 June 2013 (UTC)

Solid state sensors CCTV's will suffer 'snow' in high radiation environments, e.g., within nuclear reactors. Volcanic gases can contain hydrofluoric acid. That really messes them up. 10 year old Homo sapiens armed with only curiosity and screw drivers render surveillance cameras completely defenceless. Maybe the OP would like to narrow down his question.--Aspro (talk) 13:16, 9 June 2013 (UTC)

Hang a piece of nylon that moves, then she will take 24 hours Picture , thanks water nosfim --81.218.91.170 (talk) 11:29, 10 June 2013 (UTC)

Resolved

--81.218.91.170 (talk) 04:52, 12 June 2013 (UTC)

F1=ma=mg=F2 or a=g

Why all objects in free fall have the same gravitational acceleration “g” when diverse masses (say from lightest to heaviest) require unlike forces to move the same distance and can be inferred in the Newton’s 2nd law of motion which states “The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object” i.e. a= F/m. So my question is when F1=ma=mg=F2 or a=g then why not a=g in the following example?

Example:

An acceleration of 4m/s/s is produced if a net 20N force “F1” is applied to block of mass of 5kg F1=ma; a=F/m=20/5=4m/s/s.

A constant gravitational acceleration of g=9.8 m/s/s is NOT produced by the same magnitude of 20N gravitational force”F2” if acted on free fall mass of 5kg F1 =ma=mg=F2=20=5x9.8 (Not congruent)

Shouldn't F1and F2 be dead on before making substitution/ elimination for a=g?74.200.19.65 (talk) 04:33, 9 June 2013 (UTC)Eclectic Eccentric Kamikaze

The magnitude of the acceleration of gravity is always the same. The magnitude of the force is the object's weight and is different for objects of different mass. a is always g in the absence of other forces (at least near the Earth's surface). In your case, your force is about 49 N for a 5 kg object.--Jasper Deng (talk) 04:37, 9 June 2013 (UTC)

(edit conflict) Why would F1 = F2 when you're using different accelerations in your calculations? Your accelerations are different (4 m/s/s vs. 9.8 m/s/s), so the forces necessary to produce that acceleration will also be different; It won't be a 20N force acting on the object in free fall. --Jayron32 04:45, 9 June 2013 (UTC)

The gravitational force between two objects (one of which happens to be a planet) is proportional to the product of the two masses. So a heavy object has more gravitational force applied to it than a lighter object. But acceleration is proportional to the force divided by the mass - so even though heavy objects have more force applied to them, they accelerate at exactly the same rate as lighter objects. When you're talking about acceleration, the mass elegantly cancels out and everything falls at the same rate. SteveBaker (talk) 02:02, 10 June 2013 (UTC)

What type of turtle

unknown turtle

What type of turtle is this? At first my wife thought it was a Diamondback terrapin but now doesn't know. Bubba73 ^{You talkin' to me?} 04:53, 9 June 2013 (UTC)

Hard to tell. Maybe a slider of some sort, possibly a pond slider? --Jayron32 04:57, 9 June 2013 (UTC)

I can give photos of the front and bottom if that will help. This is in coastal Georgia, about a kilometer from a salt marsh. We've had moderately heavy rain. Bubba73 ^{You talkin' to me?} 05:05, 9 June 2013 (UTC)

I'm going to guess river cooter. Unfortunately our article doesn't have a picture, but Google Image finds lots of them. Looie496 (talk) 05:31, 9 June 2013 (UTC)

This website is a good resource, he looks like some of them on that list, including the river cooter, and the map turtle, although those maps don't show them in brackish waters. It might be a worthwhile list of candidates though. Shadowjams (talk) 16:35, 9 June 2013 (UTC)

Thanks, looking at the photos at that website, I think it is a Florida Cooter. Bubba73 ^{You talkin' to me?} 18:09, 9 June 2013 (UTC)

A turtle expert identified it as a Yellow-bellied slider, a sub species of pond slider mentioned above. Bubba73 ^{You talkin' to me?} 14:36, 10 June 2013 (UTC)

I broke my soldering gun

I bought a cheap Am-Tech soldering gun and broke it by having it on for too long (I subsequently bought a Weller which came with instructions detailing its duty cycle which the cheap gun did not). Here is a photograph of the inside of the broken cheap soldering gun. Does that brown stuff suggest exactly what happened? Can I do anything with that chunk of metal? --78.144.192.116 (talk) 16:30, 9 June 2013 (UTC)

Donate the whole thing to your nearest recycling center. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:08, 9 June 2013 (UTC)

From the look of things, the transformer in your soldering gun overheated, melting the wire insulation in the windings. That brown stain is the melted resin, glue, or insulation, leaked out to the edges of the coil. When insulation between the windings melts, separate wires in the coil short together, potentially rendering the entire transformer as a short-circuit (or at least a less-effective transformer, depending on the short). It's also possible that the short blew the fuse, but the photo is too blurry to be sure. Nimur (talk) 21:37, 9 June 2013 (UTC)

Dude, Looks like your fuse is blown on that S1735! If so, bum a fuse somewhere. If it works, party on till it melts down again! If not, I'd pack everything up real neat like in the cheap grey case it came in then shit can the whole kit and kaboodle. 184.242.31.141 (talk) 22:02, 9 June 2013 (UTC)

184.242.31.141, are you honestly expecting anyone to believe that you can visually identify the make and model of a generic soldering-gun based only on a blurry photo of a disassembled unit? And if the fuse did blow, it indicates that the device drew too much current. Replacing the fuse may temporarily restore functionality to it, but it will not solve the root-cause of the problem.Nimur (talk) 22:26, 9 June 2013 (UTC)

Man, I'm telling you thats a S1735. They suck right out of the box, it's like they were invented to break down. Fortunately my trash compactor ate mine, but before it did, I was a fuse bummin bandit. Amtech makes some happenin solder, but they ain't got the brains to make nothing good to melt it with. 184.199.165.229 (talk) 22:32, 9 June 2013 (UTC)

The above user is a troll. Pay him no never-mind. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:47, 9 June 2013 (UTC)

I think I should point out that the "fuse" is actually a light bulb (so that the user can tell when the gun is switched on). There may be a (non-replaceable) thermal fuse inside the transformer. Tevildo (talk) 18:44, 10 June 2013 (UTC)

The OP said it was an Am-Tech, and the picture the OP gave does indeed look like an S1735.[1] Red Act (talk) 23:12, 10 June 2013 (UTC)

A special type of CRT?

The display on my intercom/video door phone is black and white, flickering and slightly bend (the top is closer to the front/viewer than the lower part of the display). The image is distorted if I move the receiver close to the screen, which I believe indicates that it is distorted by the magnetic field from the receiver. I understand how a regular CRT TV works, but I think the screen is too large (ca. 8 cm diagonal) for the depth (ca. 3 cm) of the device. Also this would not explain why the display is bend. So I was wondering whether in my case the electron beam is running in front of the screen vertically upwards. Since the screen is bend it could still hit different points on the screen requiring very little deflection (which is an advantage) in that direction. Not sure whether there is enough space for coils or condensator plates to achieve deflection in the other direction. So my questions is: Do I have a special type of CRT where the beam is running in front of the screen, or is it something else? bamse (talk) 20:56, 9 June 2013 (UTC)

Its condenser is on its way out. Replace.--Aspro (talk) 22:14, 9 June 2013 (UTC)

It would be easier to figure this out if you told us the make and model of the device. Walmart sells a Swann door phone that seems to match your description and uses a CRT screen. Looie496 (talk) 22:21, 9 June 2013 (UTC)

See also TV80 (and here's a photo and diagram of the CRT) --catslash (talk) 22:48, 9 June 2013 (UTC)

Thanks for the replies. @Aspro: Not sure what you mean, as far as I can see nothing is broken with it. It is designed this way. @Looie496: It is an older (15 years or so) commax, but can't see any model number on it. The Swann which you linked claims to be both a CRT and an LCD according to the description. @Catslash: That looks a lot like what I suspect. Only difference would be that the "Phosphor screen" is bend in my case, so one could perhaps get rid of the electric field between phosphor screen and "transparent thin oxide electrode". Not sure why a "Fresnel lens" is required here. bamse (talk) 15:05, 10 June 2013 (UTC)

what motor oil do i use for a 2001 bmw 740i with 159k miles in good condition? and other BMW questions

What kind of motor oil should i use on my BMW 740i? how do i get a manual for my car? What do i need to look at if the check engine light is on? And how do i open the glove compartment if the key won't work? How do i check the fluids? Are there any good diy fyi faq and how to guides that are free online? And also general owner's maintenance checklist and how to guide and videos? — Preceding unsigned comment added by 66.87.71.250 (talk) 23:12, 9 June 2013 (UTC)

You can always download a manual as a PDF file from [2]. Plasmic Physics (talk) 23:48, 9 June 2013 (UTC)

Too many questions! Let's break it down so that our experts can answer by the numbers:

1. What kind of motor oil should i use on my BMW 740i?
2. How do i get a manual for my car?
3. What do i need to look at if the check engine light is on?
4. And how do i open the glove compartment if the key won't work?
5. How do i check the fluids?
6. Are there any good diy fyi faq and how to guides that are free online?
7. And also general owner's maintenance checklist and how to guide and videos?

SteveBaker (talk) 01:56, 10 June 2013 (UTC)

I would suggest that getting a copy of the Owner's manual is the critical thing. It will certainly tell you what grade of oil to use, and how to check the fluids. Bad fluid levels could easily cause the check-engine light - and certainly that's what I'd check first. If the glove compartment has a lock - it's possible that the car was re-keyed at some time in the past and they didn't bother to re-key the glove compartment. That's kinda unfortunate, because that's probably where the owner's manual is!

So either you need to get a locksmith to pick the lock on the glovebox - or you need to force it open. Probably that gets you the owners' manual - and from that, most of your other questions will be answered.

If by any chance the owner's manual isn't in there - you can find them on eBay all the time for under $20. SteveBaker (talk) 01:56, 10 June 2013 (UTC)

Or you can one for free, from the link I gave. Plasmic Physics (talk) 01:58, 10 June 2013 (UTC)

In some cars the entire glovebox assembly can be removed, then unlocked from the inside. I have no idea if it is possible in your car, but the procedure would be given in a service manual that you can buy at an auto parts store. The store should also be able to plug in their diagnostic scanner to see what is making the check engine light come on and give you advice on what it means. 209.131.76.183 (talk) 11:37, 10 June 2013 (UTC)

June 10

Can time really be depicted with space in continuum?

What is the spatial distance between the two positions of a stationary object separated by one second in its world line and how this can be represented geometrically in the light cone? 74.200.19.65 (talk) 01:04, 10 June 2013 (UTC)Eclectic Eccentric Kamikaze

Time and space can be depicted in many ways. Physicists commonly use a graph to represent position versus time. A stationary object, as observed in some reference frame, would have zero spatial distance between its start- and end- positions over time. That is the definition of stationarity. It could be drawn as a stationary point or as a line with constant position on the space-axis, depending on how you visually represent time and space in a diagram. Do you need help finding introductory articles to these subjects? I recommend starting with Galilean transforms first, to develop familiarity with the use of algebraic geometry to represent time and position. Nimur (talk) 01:35, 10 June 2013 (UTC)

Also relevant is Minkowski space, which provides the geometric underpinning for the concept of space-time. --Jayron32 01:40, 10 June 2013 (UTC)

(ec) Your two questions (the one in the section heading and the other in the text) are not the same question, so I'll answer both.

1. Space and time must be regarded together as part of the same spacetime continuum to maintain consistency. To try to separate them is no different from separating the x-axis from the y-axis on a geometric plane, due to the arbitrariness of the direction in which you can choose to draw them. The relationship between the t-axis and the x-axis is slightly different, but in this respect it is the same. If you have a mathematical bent, articles like Minkowski space may be interesting.
2. The word-line of an object stationary with respect to the observer is depicted as a vertical line in a spacetime diagram, parallel to the time axis in the top diagram in Minkowski space and Special relativity. Any given time may be depicted by a horizontal plane in the diagram (as for this observer – planes representing an instant in time for other moving observers will be seen as tilted from the horizontal by the first observer). Planes one second apart will intersect the object's world line, defining two points (or "events"), one straight above the other in the diagram. The spatial distance between these two points (as seen by this observer) is the horizontal separation between these points, and is hence zero. Any moving observer will see the object's world line as tilted, and hence the spatial separation of two distinct points on the object's world line as seen by such an observer will be non-zero.

— Quondum 01:54, 10 June 2013 (UTC)

I think the OP is asking if there is any meaningful correlation between distance in space and "distance" in time. I've always assumed that 1 second equates to 1 light-second in the other three axes, but I don't know if this is at all justified. Rojomoke (talk) 14:53, 10 June 2013 (UTC)

The ratio between distance in space and "distance" in time is called speed. As quondum said above, if an oject is stationary, its speed is zero and so is the distance traveled. Dauto (talk) 20:43, 10 June 2013 (UTC)

speed of aurora video

Are these videos in real time or are they sped up? Bubba73 ^{You talkin' to me?} 02:09, 10 June 2013 (UTC)

Thanks for asking this. I've often wondered about the same thing. HiLo48 (talk) 02:13, 10 June 2013 (UTC)

If you take a few seconds to click the links on the APOD page, you find the author's website. That video is made from a time-lapse sequence of few hundred frames, each with an exposure of 3 to 6 seconds, or, played back at about 100x natural speed. Nimur (talk) 02:17, 10 June 2013 (UTC)

Thanks. Would that be the case for all videos of auroras? They all seem similarly fast. Having never seen a real aurora, it would be nice if they all carried some explanation. HiLo48 (talk) 02:23, 10 June 2013 (UTC)

Here are viewing tips from University of Alaska's Geophysical Institute, providing guidance on what real aurora observations are like for the average enthusiast. Actual aurora are often quite dim; brightness varies widely based on geomagnetic activity. The speed that the aurora move through the sky is also quite slow. At least from a purely aesthtetic perspective, aurora are similar to clouds: somewhat slow and boring. Of course the physical process is totally different from clouds, and if you've never seen an aurora, the novelty is greater; but there are many natural novelties in the polar regions. Personally, I found the novelty of midnight sun more fascinating; when I was in Fairbanks, (which is not even above the Arctic circle), the late sunsets were very unusual to me. There were several days that we remained outside and actively working well past midnight, because without a clock to tell us otherwise, it seemed like late afternoon. Of course we understand the science quite well, but there is an aesthetic quality that perhaps must be experienced.

Ideal aurora-viewing is of course during the winter months, because it is darker more often; but the aurora can occur at any time of year, and even at any time of the day. The vanishing daytime E-layer may make aurora slightly more common at night. Nimur (talk) 02:52, 10 June 2013 (UTC)

I have seen real-life auroral displays that appear to move at a similar rate to that shown in the time-lapse video linked above, but usually affecting only smallish regions at a time, not sweeping across the whole sky as we see there. Part of the fun of watching aurorae is the suddenness with which the character or behaviour of a display can change from moment to moment.—Odysseus1479 02:50, 10 June 2013 (UTC)

(Edit Conflict) Actually, the first two or three segments of that video are not speeded up to the same extent as the latter few: this is evident from the differing speeds at which the background stars can be seen moving: such visible movement is a crude indication of time lapse having been employed, but could not be measured to calculate the degree of speeding up unless parameters of the lenses used were known.

Obviously different aurora videos may be sped up to different degrees (or may be in real time). As one who used to observe them regularly in Scotland (while studying Astronomy at University) where they're more frequent than most people realise, I can say that although the gross movement of the green curtains in that video are obviously sped up, occasionally some details in some auroras can be seen moving almost as quickly as in the opening segments. I agree that it would be useful if the degree of speed-up were more frequently mentioned in such videos. {The poster formerly known as 87.81.230.195} 5.66.247.129 (talk) 02:56, 10 June 2013 (UTC)

Resolved

Thank you. Bubba73 ^{You talkin' to me?} 02:32, 10 June 2013 (UTC)

Birds as pest control

Is it feasible to use insectivorous birds as a supplementary (not primary) method of broad-spectrum insect control? This source says no, but many wiki articles suggest otherwise (for example, the article about the sand martin suggests that it eats many harmful insects). So which of these is right? 24.23.196.85 (talk) 05:36, 10 June 2013 (UTC)

One can find many sources which show that people build houses for purple martins because they believe them to keep down insects, but this paper which reviews much of the literature indicates that mosquitoes are not one of the insects that it eats; mosquitoes being one of the most harmful insects. --Jayron32 05:40, 10 June 2013 (UTC)

Yes, this makes sense because mosquitoes mostly fly at night, and martins hunt only in daylight. But what about nightjars -- do they eat a lot of mosquitoes? 24.23.196.85 (talk) 05:54, 10 June 2013 (UTC)

And the armchair speculation continues... even published studies have similar issues. Bats eat an enormous amount of insects, but the endemic mosquito population in malaria zones is probably not gonna change anytime soon. Shadowjams (talk) 09:32, 10 June 2013 (UTC)

That martins eat lots of insects is undisputed. It is true that they don't eat many mosquitoes, but they they can generally suppress insect populations, including plant pest species. Also, the goal of control is not always eradication, often you just want to reach the economic threshold. So don't dismiss martins as pest control just because they don't eat mosquitoes. SemanticMantis (talk) 16:08, 10 June 2013 (UTC)

It really depends on what you mean by control, and how you classify "harmful insects." For the agricultural side of things, here's some refs: "Sustainable pest regulation in agricultural landscapes: a review on landscape composition, biodiversity and natural pest control" [3], which says "In 74% ... of the studies reviewed ... natural enemy populations were higher and pest pressure lower in complex landscapes versus simple landscapes." (Natural enemy includes insectivorous birds) There's also a review article on the topic, "Past and Current Attempts to Evaluate the Role of Birds as Predators of Insect Pests in Temperate Agriculture" [4]. The former article is basically about how insectivorous birds can reduce pest loads in agriculture. However, rather than trying to put birds in fields directly, the strategy is to attract them by having structurally and biologically diverse landscapes. The birds will naturally come and eat insects if the habitat is right. If you want to do more searching on the idea, this is known in academia as integrated pest management. So - though it is tough to get specific numbers to quantify exactly how effective they are, there is plenty of evidence that insectivorous birds can help manage pests. SemanticMantis (talk) 15:56, 10 June 2013 (UTC)

• Guinea fowl are ground birds bought specifically for pest control, see google and University of Connecticut. μηδείς (talk) 18:25, 10 June 2013 (UTC)

Geese are quite popular for pest control in vinyards and orchards.[5][6][7] -- Roger (Dodger67) (talk) 20:22, 10 June 2013 (UTC)

Geese shit constantly from their high-fiber diets and are considered a major pest of lawns in the U.S. Northeast Canada_goose#Relationship_with_humans. μηδείς (talk) 00:41, 11 June 2013 (UTC)

And they cause plane crashes... 24.23.196.85 (talk) 00:45, 12 June 2013 (UTC)

Mosquitos simply do not make much of a meal. I suspect it's just not worth the effort to catch them, except passivley, like a spider's web. They would be just as hard if not harder catch then many other insects and a single moth, beetle or fly would weigh as much as dozens of mosquitos. Vespine (talk) 00:39, 11 June 2013 (UTC)

Which is why I asked if whippoorwills catch them on a regular basis -- from what I know about whippoorwills, they can fly through a swarm of mosquitos (or other bugs) with open mouth and just suck them in, like a whale swallowing krill. That would be a fairly efficient way to catch mosquitos, which would allow whippoorwills to at least supplement their menu with mosquitos. (Not to mention that whippoorwills are nocturnal birds, so they hunt precisely when mosquitos are active.) 24.23.196.85 (talk) 00:45, 12 June 2013 (UTC)

Greater blue-ringed octopus size

How big is the greater blue-ringed octopus? The article doesn't address the size, so I decided to find it via Google and add it; I've found several pages with size information, such as 1, 2, and 3, but none of them appear to be reliable sources. I don't know where to find reliable sources on cephalapods. Nyttend (talk) 15:28, 10 June 2013 (UTC)

According to Aquarium of the Pacific (Online Learning Center Species Print Sheet), "the body of H. lunulata is about the size of a grape seed at birth and that of a golf ball at maturity. Adults are usually less than 5 cm (1.97 in) long with arms to 7 cm (2.8 in) when extended. They weigh 10-100 g, avg. 55 g (0.35-3.5 oz, avg. 1.9 oz). Females are slightly larger than males". Brandmeister^talk 16:00, 10 June 2013 (UTC)

The Australian Museum website at http://www.australianmuseum.net.au/ may be of assistance. --220 of ^Borg 18:10, 10 June 2013 (UTC)

Yep ! "Size range: Body to 5cm, arms to 10cm." from above website at Southern-Blue-lined-Octopus-Hapalochaena-fasciata ---220 of ^Borg 18:14, 10 June 2013 (UTC)

Why Dewar flask cannot be considered a truly isolated system?

Since, according to isolated system, "truly isolated systems cannot exist in nature". 93.174.25.12 (talk) 15:49, 10 June 2013 (UTC)

Have you answered your own question here? — Preceding unsigned comment added by 217.158.236.14 (talk) 16:01, 10 June 2013 (UTC)

The Dewar flask is well-insulated, but not perfectly so. Even if it were sealed after filling so that it were entirely surrounded by vacuum, and kept in space where the inside would need no point of support, no mirror is perfectly reflective. Wnt (talk) 16:14, 10 June 2013 (UTC)

Yes, and no vacuum is perfect. SemanticMantis (talk) 18:02, 10 June 2013 (UTC)

Actually, I am a little unsure about that. You'd think that you could literally remove every single light isotope atom period from a container ... with enough skill. Now, true, I suppose that even if you make an evacuated container out of tungsten, there will be a chance of individual stray atoms in a vapor phase - is it possible though to somehow measure the container and prove that, for some moments, none are present? Wnt (talk) 06:49, 14 June 2013 (UTC)

It is often still possible to do measurements involving perfectly isolated systems, even though they don't exist. What you then use is that they exist in some ideal limit; you can do experiments in better and and better isolated systems and extrapolate the results to the ideal limit. Count Iblis (talk) 18:46, 10 June 2013 (UTC)

Dopamine chemistry

I've been working on our article on dopamine, and I can handle the biological aspects, but my weakness at chemistry is causing me difficulties. I'd be grateful if anybody can help me with these two questions:

• The solubility of dopamine is listed as 60g/100ml. Is it appropriate to describe that as "moderately soluble"? Would there be sources that tell whether there are factors that affect the solubility (pH, or example)? Is it possible to find out the solubility in substances other than water?

• When dopamine in solution is mixed with hydrochloric acid, it becomes protonated and forms a highly soluble hydrochloride salt. That means that dopamine is a base, right? Is it an organic base? Is there any way of finding out its alkalinity?

Thanks for any responses. Looie496 (talk) 17:06, 10 June 2013 (UTC)

Dopamine is a by definition of "that which reacts with acid", but also as usual for most amines. And this property causes there to be an effect of pH on solubility (also discussed in the section I linked). The key parameter to report would be the pKa value, and there is a chembox field for it. A solubility of 60g/mL in water at room temp is 50% more by mass than what NaCl does (but only a little over half compared to NaCl by moles).

I'm not sure what other properties you have in mind, but temperature always affects solubility, but that's not a notable detail for most chemicals (unless it's strongly altered at near physiologic conditions or during storage/transport to affect product formulation, for example). There may be other solubility data available (temperature or solvent); anyone can predict them computationally, but that would not meet WP:RS unless published/validated in the scientific literature. DMacks (talk) 17:25, 10 June 2013 (UTC)

Hmm. The literature says that dopamine is usually supplied as a hydrochloride salt because it is much more soluble than the unreacted form. I wonder whether that number actually refers to the hydrochloride salt? I'll see what I can find out -- anyway your information has already been very helpful, thanks. (Basically I want the article to contain everything that is important to large numbers of readers and supported by good sources.) Looie496 (talk) 17:36, 10 June 2013 (UTC)

If it's going to be administered orally, it doesn't make any difference, since your stomach acid will turn it into the hydrochloride salt anyways. --Jayron32 23:37, 10 June 2013 (UTC)

As far as I know the only direct medical use for dopamine is intravenous injection. It's useful for emergency treatment of heart failure or shock, especially in infants. Looie496 (talk) 04:48, 11 June 2013 (UTC)

Did he say anything about eating it? I don't know what would happen - I know dopamine solutions tend to be unstable (akin to melanin...) if you keep them at room temperature. Wnt (talk) 03:36, 11 June 2013 (UTC)

Turtles

What is the ideal sand porosity for sea turtle nesting? Does the ideal sand porosity vary between species? — Preceding unsigned comment added by 99.146.124.35 (talk) 18:53, 10 June 2013 (UTC)

This article:

• FOLEY, ALLEN M., SUE A. PECK, and GLENN R. HARMAN. "Effects Of Sand Characteristics And Inundation On The Hatching Success Of Loggerhead Sea Turtle (Caretta Caretta) Clutches On Low-Relief Mangrove Islands In Southwest Florida." Chelonian Conservation & Biology 5.1 (2006): 32-41. Academic Search Premier. Web. 10 June 2013.

states that "sand porosity [was] negatively related to sand water salinity," and that "hatching success decreased as inundations, sand water content, and sand water salinity increased" in clutches that were inundated by sea water, but in clutches that were not inundated sand water content and salinity were not related to hatching success. The mean sand porosity the study found at 47 nest sites was 42%, with a range of 30.2 to 60.1%.

This one:

• Yalçin-Ozdilek, Şükran, Hasan Göksel Ozdilek, and F. Sancar Ozaner. "Possible Influence Of Beach Sand Characteristics On Green Turtle Nesting Activity On Samandağ Beach, Turkey." Journal Of Coastal Research 23.6 (2007): 1379-1390. Science Full Text Select (H.W. Wilson). Web. 10 June 2013.

says "Green turtles are noted to prefer nesting in areas with uniform sand grain sorting. Good sand packing appears to prevent nesting of this species because of a number of reasons, such as porosity and specific yields."

I also found this article:

• Brock, Kelly A., Joshua S. Reece, and Llewellyn M. Ehrhart. "The Effects Of Artificial Beach Nourishment On Marine Turtles: Differences Between Loggerhead And Green Turtles." Restoration Ecology 17.2 (2009): 297-307. Academic Search Premier. Web. 10 June 2013.

It says "artificial beach nourishment projects modify ecosystem components," including porosity, but doesn't directly relate sand porosity to nesting success. All three articles are pretty high level (a little over my head, really) and all have their own lists of references that may provide additional information. If you can track them down online or at your library, they may be worth a look to you. --some jerk on the Internet (talk) 20:59, 10 June 2013 (UTC)

Does switching to a different diet require extra energy in humans?

When you cultivate bacteria like E.coli, and switch from one carbon source to the other, growth lags. This is because new proteins need to be synthesized to deal with the new carbon source. Does something similar happen in humans? For instance, recently I became a vegetarian. I felt a bit weak the first 3 days. After that I was fine. I wonder if my body had to make large changes to adapt to my diet.137.224.239.102 (talk) 19:54, 10 June 2013 (UTC)

Your gut flora will have changed. But I don't know the answer to your main question. Thincat (talk) 22:47, 10 June 2013 (UTC)

Things like the Atkins diet depend on changing one's metabolism and blood chemistry. Just changing from meat and plants to plants as the source of one's sugars, fats and amino acids in a normal balance shouldn't have any effect on a healthy person's body's metabolism, since it is much more complex than a bacterium's and is already digesting those things.

But we have absolutely no knowledge of your health concerns, actual diet, or metabolism. It's quite possible you may have a disorder, need or missing nutrient we don't know about, so you should seek professional medical advice. μηδείς (talk) 00:35, 11 June 2013 (UTC)

I'd say it differently: "The body's digestion process is less efficient for some time after switching to a new diet". This explains why many diets work, at first, but very few are successful in the long run. Once your body adjusts, you can get just as many calories out of a variety of sources. StuRat (talk) 02:13, 11 June 2013 (UTC)

I agree. I think in part (or even mostly) it is due to the gut flora not having had time to optimise towards efficiently fermenting undigested carbohydrates in the new food mix. Thincat (talk) 07:58, 11 June 2013 (UTC)

Of course if someone changes to a weight-loss diet they may be highly motivated to start with and so initially eat less and lose weight more rapidly. However, that is not what the original poster was asking about nor what any of the answers have been dealing with. Thincat (talk) 08:08, 11 June 2013 (UTC)

Thanks for the answers guys! This wasn't a medical question btw. Just interested. [OP on another PC] 137.224.252.10 (talk) 14:04, 11 June 2013 (UTC)

Heat storage

I believe more porous sands would hold less heat then less porous sands. Is this true? — Preceding unsigned comment added by 99.146.124.35 (talk) 20:05, 10 June 2013 (UTC)

Heat per mass? heat per volume? heat per surface area? Dauto (talk) 20:35, 10 June 2013 (UTC)

Besides, it's the fluids that count. Are you concerned with total thermal flow, or only thermal conductivity by the solid substrate? Nimur (talk) 20:47, 10 June 2013 (UTC)

It depends on what's in the pores. --Jayron32 23:27, 10 June 2013 (UTC)

Bufotenine - Medicinal Uses in China?

Extracts of toad venom, containing bufotenin and other bioactive compounds, have been used in some traditional medicines such as ch’an su (probably derived from Bufo gargarizans), which has been used medicinally for centuries in China according:

http://en.wikipedia.org/wiki/Bufotenin

but is NOT native to China so any suggestions on how that is possible? Sincere curiosity.

http://en.wikipedia.org/wiki/Colorado_River_toad

I came here after a search for the word Bufotenine which I came across in a novel I am reading:

"American Gods: The Tenth Anniversary Edition authored by Neil Gaiman.

On the Kindle, this word appears at location 927 but does not appear in the Kindle dictionary. A web search led me here.

Learning is my passion, a day without learning something new is a day wasted.

After reading the pages listed above I am now curious as to how this toad, which is native to a small portion of the US, could have been used for medicinal uses as stated centuries in China. Or

Also stated in the book is this: 'A character in the book is smoking synthetic toad-skins and inquires of the main character, Shadow, if he is aware that its possible to synthesize bufotenine now?'

True or author's fiction?

Thanks for your time, greatly appreciated. — Preceding unsigned comment added by Not1knowsme (talk • contribs) 20:07, 10 June 2013 (UTC)

You should read the article!  :) Seriously, it points to Asiatic toad, native to China. I should emphasize that it is important to distinguish between authentic traditional medicine and modern revivals with a different focus. (Just consider the difference between kava kava as pounded and extracted with water in the Pacific islands and its hazards when entrepreneurs put undesirable parts of the plant in a capsule to be swallowed because they have a high concentration of the "active ingredient"; or between native Americans who used tobacco to positively reinforce the rituals of their religion, and Westerners who seized on the dope and managed to kill themselves by the hundred million!) Wnt (talk) 00:40, 11 June 2013 (UTC)

citronella oil

Is citronella oil still usable and effective in burning torches if there is no yellow color to it?```` — Preceding unsigned comment added by 173.80.150.188 (talk) 21:06, 10 June 2013 (UTC)

Think it would help if you rephrased this. Citronella oil will, on flagration, produce sooty partials in the flame that iridesse at about 1,00 deg. C. I.e, Yellow. Try kerosene – its cheaper.--Aspro (talk) 22:19, 10 June 2013 (UTC)

But citronella oil smells a lot better, and also may have insect-repelling properties. 24.23.196.85 (talk) 23:25, 10 June 2013 (UTC)

I think the OP is asking about the color of the oil, not the flame. Citronella oil that I've seen for sale (and just double-checked with a quick google image search) usually has a yellow or amber color. I do not know if there are clear variants. I do think "effective" needs to be clarified. Effective at what? Just burning, or as an insect repellent as well? Citronella oil is commonly sold as a "tiki torch" fuel with the claim of it repelling insects, but our article only has information on it being used as a topical repellent. 209.131.76.183 (talk) 15:51, 11 June 2013 (UTC)

How spacecrafts estimate moon's and planet's internal structure

I thought once the spacecraft studies planet's and moon's surface they suppose to be able to tell what is inside a moon and planets. Do spacecraft not able to track all the information like how thick is the ice layers on gas giant's moons when trying to look at its interior? I thought once Galileo spacecraft went to Jupiter's four famous moons they have a special electric signals sends details to tell us what their moon's interior looks like. Then how spacecrafts measure how the celestial bodies interior looks like. Density? Chemical (Spectograph). When Cassini spacecraft went to Saturn do they use electric signal lighting to model what Titan have in interior, or they just build a variables to estimate what Titan might have inside. When Messenger went to Mercury did Messenger actually study its surface in detail?--69.233.254.115 (talk) 21:30, 10 June 2013 (UTC)

These interplanetary gizmos all employ variations of Remote sensing. --Aspro (talk) 22:55, 10 June 2013 (UTC)

Oh. And before anybody reminds me that the Huygens probe actually made 'physical' contact with the surface of Titan, let them tell me first, if the probe was able to transmit back, that it had landed on a vanilla, or a strawberry flavored crème brûlée. --Aspro (talk) 23:12, 10 June 2013 (UTC)

Per my favorite planetary science book, de Pater and Lissauer, geoscientists can use orbital parameters to determine moment of inertia and gravitational anomaly of a large celestial object. Then, they invert for a plausible geological internal substructure. This is why your usual model of a planetary interior is perfectly radially symmetric! In the book I linked (Planetary Sciences), an entire chapter is devoted to these techniques. Nimur (talk) 23:00, 10 June 2013 (UTC)

June 11

Does anyone provide solutions on solutions?

After reading up a bit on vodka sauce where ethanol is used, for lack of a better terms, in a Liquid–liquid extraction, I started to wonder about some of the other things I'm cooking with. Obviously non-polar compounds will be extracted by cooking in oil or fats in general, but the ethanol is a polar solvent that mixes well with water. This got me thinking about chemistry in general, and for purposes of enhancing or avoiding certain flavors (e.g. right now I'm making saltless tomato sauce that's coming out way too fruity) I'm wondering about timing of addition things like vinegar that change the pH and other chemical changes that would affect the extraction of flavors from onions/garlic/tomatoes/kumquats/etc... Is there a reference anywhere that answers some of these questions about flavor extractions in various food-grade solvents? 71.231.186.92 (talk) 01:39, 11 June 2013 (UTC)

The chemistry is sufficiently complex that making reliable predictions is difficult. Given the relatively low cost of a trial-and-error approach, I'd recommend that. I've come up with several recipes that way. Incidentally, regarding a salt-free tomato sauce, have you tried adding some capsaicin (hot peppers) ? StuRat (talk) 02:20, 11 June 2013 (UTC)

The most likely source is Nathan Myrhvold's Modernist Cuisine. But it ain't cheap. Looie496 (talk) 04:41, 11 June 2013 (UTC)

I believe these topics are addressed in On Food and Cooking, which generally has a nice balance of chemistry, history, and culinary lore. SemanticMantis (talk) 15:26, 11 June 2013 (UTC)

Is that cold or just the feeling of cold that brings thermogenesis ?

I have learned that the feeling of cold and heat is produced by the activation of certain peripheral "temperature" receptors. the question is. if a person got a knockout for the genes for these receptors and he feels neither cold or heat, and sometimes in his life, dives in an arctic water lake (for example), will this person have thermogenesis while in water?. my intuition says he won't have because there will be no signal to start all of this metabolic state. (i just haven't learned yet if a man could survive birth without temperature receptors). i am eager for your answers ! thanks Ben-Natan (talk) 02:54, 11 June 2013 (UTC)

As our article on thermoregulation states (very briefly), thermogenesis is driven by a small brain area called the preoptic nucleus of the hypothalamus, which contains cells that are exquisitely sensitive to core temperature. That area also receives input from temperature sensors on the body surface, but core temperature is much more important. So a knockout of skin sensors probably wouldn't greatly impact thermoregulation. No doubt there are other kinds of knockout that do, but I don't know anything about them. As far as I can tell, the molecular mechanism of thermosensation in the hypothalamus has not yet been established. Looie496 (talk) 03:21, 11 June 2013 (UTC)

Sensation of cold is mediated by TRPM8, and heat TRPV3 (there are others for each, though). The OMIM entry for TRPM8 doesn't mention body temperature changes, [8] and the OMIM entries for body temperature are other genes. [9] Logically there is just too much disconnect between when you feel cold (just rushed outside, say) and when you actually have a low body temperature; there needs to be some space between these mechanisms. Wnt (talk) 03:34, 11 June 2013 (UTC)

Ways to turn a hurricane?

Could any of these things possibly turn a hurricane? (Weather modification gives a good overview of some ideas to stop one, but from the narrow U.S. context, it is not actually necessary - in many cases it would be desirable simply to give the storm a shove somehow to make it turn a hundred miles sooner toward the northeast)

• Do cloud seeding in winds leading toward one side of the hurricane to make them drop some rain in advance. Since the condensation of moisture provides heat, could this put an asymmetric force on the storm?
• Release some kind of thickening agent into the storm with drones to increase the viscosity of the water and change the droplet size, and so hopefully the rate at which the water condenses, with the same effect?
• Fire lightning rockets up through one part of the hurricane to change the charge distribution with the notion of altering how minute droplets of water repel one another due to charge on them, with the same effect?
• Anchor some sort of kites designed to create turbulent air flow (I'm thinking a density very roughly around 1 per acre) with the notion that under some specific condition as the wind rises, the turbulence will propagate from each kite over a long distance, changing the amount of resistance the wind experiences against the sea? (No, I haven't modelled this in a wind tunnel! my subjective recollection is that there are specific circumstances for some objects where a little protrusion on a model can leave a long trail of disruption behind it, but I could be so wrong about this optimistic scenario ;) ...)
• Put some sort of biodegradable oil on the water (as the article mentions) but not at the center of the storm, rather at its distant extreme to change the wind resistance (can oil do that?)

Last but not least, does anyone ever actually go out and try to fool with a hurricane's path, with any technology of any kind? Wnt (talk) 05:50, 11 June 2013 (UTC)

Check this out. --Jayron32 06:06, 11 June 2013 (UTC)

Have you looked at the article on tropical cyclone track forecasting? The factors that are used to forecast a storm track are basically the things you would have to change in order to alter one. The most important ones are probably uncontrollable, but you might conceivably be able to exploit the Fujiwhara effect or something. Looie496 (talk) 06:12, 11 June 2013 (UTC)

There is some kind of gel which absorbs many times it's own weight in water, and the drops then dissolve in saltwater. A fleet of cargo planes working non-stop could conceivably drop enough of it into a hurricane to affect it. This would cost millions of dollars, but could possibly save billions in damage. Another option is to prevent the water from getting hot enough to spawn hurricanes, by placing reflective floating surfaces on it. Not sure if this would be practical, though, and there's the environmental impact when all this material eventually washes up on shores. StuRat (talk) 06:40, 11 June 2013 (UTC)

. --Jayron32 13:40, 11 June 2013 (UTC)

[10]. That says it only absorbs 20X the weight of the gel, but that seems much lower than I recall. Even a sponge absorbs that much, right ? StuRat (talk) 15:47, 11 June 2013 (UTC)

FYI: The water contained within a hurricane weighs about 240 million tons [11]. So if your gel absorbs 20x it's own weight, you're going to need 12 Million tons of gel (assuming you don't waste any by dumping too much of it in one place or missing the target or whatever). A Lockheed Martin C-130J transport plane can carry about 22 tons (See this). So we're going to need around a half million air transport missions to mop up the entire hurricane. The C-130 costs around $10,000 per hour to fly[12]...let's suppose it's a 4 hour mission - then the cost of doing this is about 20 billion dollars...plus the cost of the gel. That's actually cost-effective for Katrina-scale hurricanes that cost in the 100 billion dollar range - but not for a "typical" hurricane that does just a few billion in damage. It's plausible on cost benefits - but definitely not a slam-dunk.

But the problem is that we don't have a half a million aircraft - the US owns about 200 of these large cargo planes (See this) - and that would mean doing 2,500 flights each - if they take 4 hours plus an hour turn-around time, then it would take close to two years of non-stop work with the entire US airforce, navy and army C130 fleets to soak up just one hurricane! To put a stop to all of the atlantic hurricanes would require every man, woman and child in the US to become a C130 crewmember or support person! (Not to mention the gel-manufacturing nightmare!)

Obviously you wouldn't need to soak up the entire hurricane to put a stop to it - but even if you only had to soak up 10% of it - it's still wildly impractical.

Summary: Silly idea! Won't work. SteveBaker (talk) 16:46, 11 June 2013 (UTC)

As I said, I think it's much more than 20 times. Also, if you can attack the hurricane during formation, say by wiping out the eye wall whenever it tries to form, you might be able to keep it from organizing and keep it as only a tropical depression, with much less of an effort. And, yes, if we decided to do this, we'd need to build a large fleet of planes just for this purpose. Due to global warming, and the expectation of more devastating hurricanes, such an option may be more practical as time goes by. This might also be a good application of unmanned airplanes, as taking off, flying to a specific target, dropping the load, and then returning to base isn't beyond the capabilities of modern technology. If we mass produced such planes, hopefully the cost per hour to run them would go down dramatically. StuRat (talk) 04:48, 13 June 2013 (UTC)

The large practical problem here is that hurricane prediction is not an exact science. Your efforts to divert the hurricane would be far from exact too. Now, consider what happens if you divert a hurricane and cause it to hit a major city instead of missing it - 1800 people die and 100 billion dollars go down the toilet and it's all your fault! As with anything like this where you try to use a small force to create a large change, you have to apply that force as early as you can...but the problem is that's when storm prediction is least able to predict the path accurately. Even just three or four days before landfall, the best math models we have were predicting that Katrina would hit the Florida panhandle. So clearly, attempting to change the path even just a few days before landfall is as likely to cause a problem as to solve one. Leaving it until you're certain that you won't make matters worse is leaving it too late to have a measurable effect. Improving prediction times is tremendously difficult - even in principle - because the system is highly chaotic (in the chaos theory sense). SteveBaker (talk) 17:05, 11 June 2013 (UTC)

There's no harm thinking big, but practicality tends to intervene. Will Rogers posed what he claimed to be a great solution to the German U-Boat problem in WWI: "Boil the ocean!" Leaving the details up to the experts, of course. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:01, 11 June 2013 (UTC)

For what it's worth - in the last few years, there have been several special sessions at American Geophysical Union's annual meeting on the topic of geoengineering - that is, the task of working out the practical engineering considerations for earth-scale projects to intentionally affect climate and weather. It's already well-established that human activity does affect weather and climate. So, the task going forward is to design and engineer human activity to affect weather and climate in a controlled way. Serious scientists are expending serious thought on this issue - but it's still far from reality in the short term. Here's AGU's official position statement on geoengineering: Geoengineering the Climate System (2009). Excerpts: "proactive strategies could reduce the risks of climate change... (including) geoengineering: deliberately manipulating physical, chemical, or biological aspects of the Earth system"... Nimur (talk) 22:57, 11 June 2013 (UTC)

Hmmm - good detective work - thanks! Clearly this is nonsense. It can't possibly work...on cost grounds, on practicality grounds, on risk of doing more harm than good grounds...there are a million reasons why you can't do that.

The work by the American Geophysical Union isn't about attacking a single hurricane - it's about changing our society in ways that'll reduce our impact on global climate change - and some "Plan B" approaches to applying a bandaid to the problem if (as seems likely) we fail to do that. Things like injecting water vapor into the upper atmosphere to increase our planet's albedo. These are horribly dangerous things to consider doing - and it's unlikely that we could get international agreement to do that. But dialling down the surface temperature of the mid-atlantic ocean would reduce the amount of energy available for hurricane formation - which in turn would reduce the number and severity of hurricanes. Sure - that'll work - but it's not specifically a "fix" for hurricanes - it's a side-effect of a more general effort to engineer our impact on the planet. SteveBaker (talk) 13:55, 12 June 2013 (UTC)

I've tried to hold off responding because I've observed the OP editing a question is the kiss of death for getting more answers (hope this will be an exception!), but I should note that our article weather modification specifically mentions Dyn-O-Gel, claiming 1500x absorption, and if people are confident to debunk this at this point, please do. Myself, above, I didn't actually want to absorb the water, just change how droplets accrete or coalesce in some measurable way to affect how much heat of fusion enters a part of the storm; admittedly I doubt you can do that but I just don't know for sure. Of course, I admit that turning a hurricane in the Caribbean would be pretty useless - I'm thinking of the east coast U.S. in particular, where hurricanes often turn away and if they do they harm nobody but perhaps a few fishermen off Newfoundland. Wnt (talk) 16:11, 12 June 2013 (UTC)

...which is an excellent example showing that while some Wikipedia articles are excellent, some are crap. The reference cited in the article for Dyn-O-Gell is is a broken link. However the article is available on a paranormal/ghosts website at http://tech.dir.groups.yahoo.com/group/ParanormalGhostSociety/message/30659?var=1. Read it - you'll see it's rubbish. If that's not enough, it says the gell is made by the Dyn-O-Mat company. There is a domain name, dynomat.com registered but is inactive, and I could not find any evidence that the company exists. Note that Dynamat is a legit active company selling sound absorbent materials for automotive use. The History page for the Wikipedia article shaows that the Dyn-O-Gell bit was added on 7 April 2007 by editor Beland, apparently based on the paranormal/ghosts website (hard to tell for sure as the link Beland provided is not valid). The story was therein attributed to the Scripps Howard news service. You can search for old news reports on their website. There is no such story held by them. The story is just a load of rot, as I said before.

I just looked at this quickly and "Dyn-O-Storm" pulled up Discover Magazine saying the stuff is a polyacrylic acid derivative (sodium polyacrylate?) (I went off half-cocked a minute ago about polyacrylamide, but that's not the precise compound here) Wnt (talk) 06:28, 13 June 2013 (UTC)

I should say I like StuRat's notion of the floating mirror - in theory, if you had just the right material, you could spray a layer of highly reflective material that is just a few atoms thick, like a solar sail or something - I'd think you could do it with nanotech, but I bet some simpler but smarter engineering could make it able to self-organize and reorganize due to chemical properties, yet be ultimately biodegradable. It would be nice if it made use of iron so you could fertilize the ocean with the same intervention, thereby taking on the issue both long-term and short-term. :) Wnt (talk) 16:11, 12 June 2013 (UTC)

Chemistry and relativistic effects

I often hear the concept thrown into speculation in research reports, but have no idea what it actually means in a particular context. Here is an example: Unlike the lighter congeners, zinc(II), and cadmium(II) hydride, solid mercury(II) hydride is a molecular solid instead of a network solid. Apparently, it comes down to relativistic effects. What are those effects in this context, and how do those effects affect? Plasmic Physics (talk) 11:03, 11 June 2013 (UTC)

Electrons are not going to travel faster than the speed of light in an atom. For high charged nuclei the electrons will be travelling very fast near the nucleus, and would have greater effect for D or F orbitals. However this effect also can modify hydrogen atom spectra, causing splits in lines from higher shells. The result for the heavy elements is that they are softer and melt cooler. One effect is that the electrons are effectively heavier, and then moving slower, and reduce the Bohr radius, so densities are higher. Read Relativistic quantum chemistry for the article on this here. This explains that the 6S orbital in mercury is shrunken so that its bonds are weak. Graeme Bartlett (talk) 12:18, 11 June 2013 (UTC)

OK, thanks. Can you also please explain why mercury(I) chloride is Hg
₂Cl
₂, whereas mercury(I) hydride is just HgH? Plasmic Physics (talk) 14:06, 11 June 2013 (UTC)

You wrote that HgH was stable up to about 6K in matrix isolation. This gives a clue that the bond is extremely weak. Stable in isolation means that two molecules react with themselves. You can guess that the Hg₂H₂ is even more unstable and breaks apart to H₂ and Hg. Even if this Hg₂H₂ was stable enough in isolation it would be extra hard to make it in isolation as you need to get 4 atoms together in one place without extra reactive atoms. The bond in H₂ is much stronger than in HgH. What is your reference for dihydrido-1κH,2κH-dimercury existing? Graeme Bartlett (talk) 21:20, 11 June 2013 (UTC)

It's from the same paper by Andrews, and in a 2005 paper by Alireza Shayesteh (I think). From what I remember, the calculated enthalpy of formation for Hg
₂H
₂ for higher than for HgH, coupled with a low activation energy for the conversion to individual HgH. I don't remember about the energetics for total decomposition of Hg
₂H
₂ to the elements. It requires only a quarter of the energy to break the second bond of HgH
₂, than it does the first, and the first requires approximately two fifths of the energy to break on H-H bond. Plasmic Physics (talk) 22:30, 11 June 2013 (UTC)

Dissociation and eutectics

What is the eutectic point of a NO₂/N₂O₄ mixture? Is it even possible to liquefy such a mixture fast enough, before equilibrium is restored? Plasmic Physics (talk) 11:18, 11 June 2013 (UTC)

A related question: is it in theory possible to speed heat octosulfur to estimate it's boiling point? That is, heating it fast enough such that decomposition does not have significant blurring effect. Plasmic Physics (talk) 14:10, 11 June 2013 (UTC)

What if you heated octasulfur at a reduced pressure? That's pretty common for lots of things that can't be boiled at atmospheric pressure (because it's just too high-T to be convenient or because it thermally decomposes), either for measuring/reporting bp or simply for purification. There are heuristics for converting to other pressures, or it can simply be reported at whatever mmHg was used. DMacks (talk) 18:04, 11 June 2013 (UTC)

I suppose I could, but my question is concerned specifically with standard pressure. Monitoring the temperature differential of the substance over time, and looking for a step in such a plot. Plasmic Physics (talk) 23:08, 11 June 2013 (UTC)

Air oxidation of Ammonium iron(II) sulfate

Quoted from Ammonium iron(II) sulfate

In analytical chemistry, this salt is preferred over other salts of ferrous sulphate for titration purposes as it is much less prone to oxidation by air to iron(III). The oxidation of solutions of iron(II) is very pH dependent, occurring much more readily at low pH. The ammonium ions make solutions of Mohr's salt slightly acidic, which slows this oxidation process. [1]

So oxidation occurs readily at low pH. Ammonium ions make it acidic reducing the pH, which should make the oxidation happen much more readily. So how come is it slowing down? This is a contradiction.

What's correct?

--Gauravjuvekar (talk) 16:25, 11 June 2013 (UTC)

EDIT: Ammonium iron(III) sulfate says that it's abbrevated to FAS. Is FAS really Ammonium iron(III) sulfate(ferric) or ammonium iron(II) sulfate(ferrous)

--Gauravjuvekar (talk) 16:57, 11 June 2013 (UTC)

Low pH slows oxidation, so I have changed the article. Sulfuric acid is often added to solutions to stop them oxidising. Looking around for FAS it is used for Ammonium iron(II) sulfate more than for the ferric ammonium sulfate. [13] (232 hits) and [14] (54 hits). I would suggest that you don't use FAS alone as an abbreviation for this! Graeme Bartlett (talk) 21:57, 13 June 2013 (UTC)

Voltmeter and ammeter

Why do we combine voltmeter in parallel combination and ammeter in series combination? 106.209.208.31 (talk) 16:34, 11 June 2013 (UTC)

To answer simply: voltage is the same across parallel elements, but current is the same through elements in series. And vice versa: voltage differs across elements in series (except in the case when the impedances are identical) and current differs through parallel elements (except in the case when the impedances are identical). So if you connected the meter the wrong way, you wouldn't be measuring the thing you want to measure (not to mention any possible danger to your equipment and self)! You can make a deeper answer with regard to Maxwell's equations, but I assume you don't want that (not that I could give such an answer anyway). --Atethnekos (Discussion, Contributions) 16:58, 11 June 2013 (UTC)

Another way of thinking about it is to ask "what is voltage" and "what is current"? Voltage is a difference between two points, so you put your two meter probes on those two points to compare them. Current is flow, so you put your meter so that the electricity flows through it to measure that rate. DMacks (talk) 18:00, 11 June 2013 (UTC)

The hydraulic analogy is always useful in these cases. Voltage is like pressure in a system of water pipes - current is like the flow rate. If you need to measure pressure between two points you need to place your pressure gauge between those two points (although one point might be the ambient air pressure) - but for flow rate, you need to insert the flow meter into the pipe to measure how much water flows through it every second. SteveBaker (talk) 19:18, 12 June 2013 (UTC)

Are vaccines homeopathic?

I mean mainstream vaccines and in the sense that you are using the same (homeo) substance as the illness (pathic). OsmanRF34 (talk) 23:58, 11 June 2013 (UTC)

No. Homeopathy is quackery designed to bilk money out of gullible people. Vaccines are proven to work. Big difference. Of course, if you read both articles, you'd already know that. If you're trying to work from the word "homeopathy" to make some connection, you'll also want to read etymological fallacy which explains nicely where you're going wrong there as well. --Jayron32 00:03, 12 June 2013 (UTC)

I do not dispute that what we buy as homeopathic is quackery or that vaccines work. But ignoring the etymological connection, and starting with the idea of "using the same substance as the illness to treat the illness", what's wrong with saying that it works, but only preventively, like a vaccine. OsmanRF34 (talk) 00:11, 12 June 2013 (UTC)

Homoeopathy doesn't use 'the same substance' - it uses water. Any 'substance' is diluted to the extent that you are highly unlikely to get a single molecule of it in the 'remedy' AndyTheGrump (talk) 00:23, 12 June 2013 (UTC)

Because the comparison is contrived and misleading. Vaccines have nothing to do with homeopathy whatsoever. The error you are making is a category error with the help of an eqivocating over-simplification. Saying that vaccines and homeopathy are similar because they "use the same substance as the illness to treat the illness" is like saying the planet Mars is like Stalin because they are both "red". Dominus Vobisdu (talk) 00:28, 12 June 2013 (UTC)

It's slightly completely opposite in approach and intent. To oversimplify each, one tries to induce a very mild case of the disease to prime the body to strongly fight the real one in the future. The other uses an unrelated agent that induces similar symptoms as a disease does to cure the disease in someone who is already sick. The commonality--"agent that can cause the symptoms"--is, as Dominus Vobisdu says, doesn't make them intrinsically related in any other way. DMacks (talk) 00:58, 12 June 2013 (UTC)

Also, the dilutions involved in homeopathy are such that not one single molecule of the "active ingredient" is actually present in the "treatment". That's emphatically not the case for a vaccine. You may get millions of weakened or killed viruses in a flu vaccine shot but not one single molecule of raw duck liver (yes, really!) in a homeopathic flu "treatment". Homeopathists would not regard a flu vaccination as a homeopathic dose. Conflating these two approaches can only lead to "Very Bad Things" happening! SteveBaker (talk) 13:42, 12 June 2013 (UTC)

The problem here is that "homeopathy" refers to two different things: the deceptive practices of Hahnemann and his ilk, and the much older vague principle of "similia similibus curantur" held by Paracelsus and other medieval physicians. [15] The concept of homeopathy as one of the ancient philosophies of medicine is legitimate though highly unreliable (as the Lancet mentions with the business of treating wounds with boiling oil). Vaccination can fairly be seen as an extension of that principle. Heuristically, it may still be a valid source of blue-sky inspiration, though I should emphasize that in biology there are no two things more similar than something's synonym and its antonym, and so homeopathy and allopathy, in the philosophical sense, are very closely related. (I know that is hard to wrap your head around, but by and large, to inhibit a biological process you need something that is almost but not quite the same as something that activates it!)

To comment on the social context, medicine is a racket but it has many mostly honest practitioners: the regulatory privileges held by its schools make them extremely valuable economically. Some, like allopaths, have managed to hold onto a high reputation, others, like osteopaths, seem to have a harder time holding on - and then there are the homeopaths, who have the same legal monopoly of "prescription" over their formulae of highly diluted water as the more common physicians hold over drugs that are actually needed. It is not impossible that one of the other schools could have been infiltrated and debased in the same way, but allopathy, with its tendency to provide quick obvious relief of symptoms, would have been harder to replace with water. Wnt (talk) 15:55, 12 June 2013 (UTC)

It should be noted that Wnt holds an idiosyncratic and unsupported view of mainstream medicine, and his unreferenced opinions should be taken with the largest grain of salt you can muster. --Jayron32 17:18, 12 June 2013 (UTC)

http://giantcrystals.strahlen.org/europe/merkers3.jpg

• Vaccination works for reasons that are easily understood, verified, tested and reproducible. Repeated, detailed studies show that most vaccines work very well in reducing the chance of their targetted disease occurring. Homeopathy (in all modern senses of the word) doesn't actually work at all (there is not one scientific study that demonstrates anything more than a placebo effect), and the means by which it's claimed to work are vague, contradicted by different practitioners and entirely unscientific.
• Allopathy also works fairly well in most cases - and usually (but not always) we understand why it works - and we're always careful to test it and measure things like side-effects. If you have a severe anaphylaxis attack, a shot of epinephrine will likely fix you right up. That's not a coincidence or a piece of luck - it's because we know that epinephrine is a vasoconstrictor. All of this is demonstrable in a scientific fashion - from the cause, to the cure to the reasons the cure works, the possible side-effects, the future prognosis, etc.
• All that the homeopathists can say is something about water being imprinted with the memory of something you added to it and then diluted to nothingness...they don't say why it works, they don't test to see if it actually does work, the whole thing is entirely made up of guesswork from people who are largely without any science training whatever.
• Osteopathy falls somewhere between the two. There have been a few studies that seem to show that it works better than placebo - but it's very hard to come up with a convincing placebo to compare it to - so that's a somewhat dubious claim - and there is little scientific explanation for how it works (if indeed it actually does). Discussing osteopathy is tricky because the term means radically different things in different countries. In the USA an osteopath does similar training to a conventional doctor - but in other places they may be regulated entirely differently - or not regulated at all - so the resulting mess makes it unlikely that the osteopathic treatment you get in those places is going to be any use anyway.

SteveBaker (talk) 19:10, 12 June 2013 (UTC)

I basically agree with all that, but I don't think any of it contradicts Wnt's assertion that "medicine is a racket but it has many mostly honest practitioners". It's a racket with a solid scientific basis, yes, but that doesn't keep it from being a conspiracy in restraint of trade, which indeed it is, and in that sense it's a "racket". --Trovatore (talk) 21:38, 12 June 2013 (UTC)

Is there a solid scientific basis for having prescription homeopathic medicines, which cannot legally be dispensed by ordinary people? Once you answer that: is there a solid scientific basis for having prescription regular medicines? For example, suppose that someone has high blood pressure and takes a drug daily to keep the dose low. He doesn't have money for a doctor that month, and by policy he can only receive so many refills for any medicine. Has someone done a scientific study that shows that it is safer for him to go off the high blood pressure medicine cold turkey than to be allowed to purchase a refill at his own risk based on his own personal decision making? Would an IRB even say it was ethical to conduct such a study? No. Profit comes first, and it really is that simple. Wnt (talk) 21:51, 12 June 2013 (UTC)

I meant there is a scientific basis for the treatments, not for the public policy. --Trovatore (talk) 22:21, 12 June 2013 (UTC)

@Wnt: There is no reason to have prescription-only homeopathic treatments. They are either water, alcohol and water, sugar pills or other placebo-like substances. Since they have no effect whatever on the body (which is why they don't work), you can't overdose on them - so they don't need to be prescription-only - and as far as I know they aren't. On the other hand most prescription medicines have potentially dangerous side-effects and have to be administered in carefully considered dosages (eg, the safe dosage may depend on your body weight, gender, age or life-style - it may be necessary to limit the duration of treatment to avoid addiction - or to encourage completion of a course of drugs in order to avoid drug-resistant diseases - or to avoid drug interactions). For those reasons, it's considered necessary to involve an expert (a doctor, for example) who can determine whether the risks and consequences of the side effects exceed the risk of not treating the condition - and who can determine an appropriate dosage. Limiting the ability to purchase such substances is considered a matter of public safety.

The issue of funding of conventional medicine is an entirely political/financial matter - not a matter on which science can reasonably rule. Your comment presumably comes from the perspective of a person living under a political system that values low taxation over universal health care. If you lived (for example) in Brunei (health-care costs a flat rate of about 80 US cents per consultation with no additional charges for drugs, hospitalization, surgery, etc) - your perspective on the nature of conventional medicine would undoubtedly be different. SteveBaker (talk) 02:45, 13 June 2013 (UTC)

I don't think the point is about funding. The point is about monopolistic practices. --Trovatore (talk) 04:04, 13 June 2013 (UTC)

What monopolistic practices? There are dozens of doctors and at least a couple of hospitals to choose from in every modern town or city - and once a drug comes out of patent protection, there are usually multiple manufacturers who compete on price to provide generics - there are even competing stores selling those drugs, who also compete vigorously on price. Sure, the drug company has a monopoly on the drug initially - but that's an issue of patent law, not the way that medicine works. You could certainly patent a homeopathic treatment if it actually worked - the manufacturers don't because patent battles between them would rapidly reveal that they're selling you bottles of water for $14 a pop - and bottles of water are not patentable. Besides, cutting the requirement to have a prescription out of the system wouldn't result in any more choice than you have now. SteveBaker (talk) 13:17, 13 June 2013 (UTC)

The AMA controls licensing and thereby restricts the supply of practitioners. Over the years, they have gotten rid of the general practitioner position (who didn't have to do a residency), and as I understand it are moving to restrict the supply of new nurse practitioners (allowed to prescribe) by making them get a doctorate. Obviously these measures reduce downwards pressure on pricing that the market would otherwise supply, especially if there were some sort of price transparency, and if tax incentives were not such that most routine medical care is provided through insurance (not what insurance is for!) so that the customer doesn't usually even know what the price is.

You may think that the measures that restrict supply also elevate quality, and who knows, perhaps they do. In a normal market situation, consumers are allowed to weigh such a purported benefit against the cost. --Trovatore (talk) 16:39, 13 June 2013 (UTC)

In a very limited sense, there are widely reported monopolistic-shenanigans by drug companies, up to and including use of the patent system to extend government patent protection (which is a form of endorsed monopoly that has its benefits to a point, so I'm not condemning the entire system),[16], [17], shady or too-cozy relationships with those that will prescribe the medication (over cheaper and often more effective medications), etc.[18] and [19], [20]. This sort of stuff isn't the tin-foil-hat crazy conspiracy stuff that Wnt seems to be on about when he condemns all doctors, and it shows up in mainstream media and well-respected scholarly studies all over the place. That being said, it is important to place the problems in the pharmaceutical industry into context, and it is still not reasonable to extend the well-documented shenanigans there with condemning doctors, nurses, midwives, PAs, and other front-line medical professionals who provide important, effective, and necessary care to the ailing. Doctors by-and-large are doing excellent work, and objections to the entire medical industry based on how some Big Pharma companies behave is unfounded. --Jayron32 13:56, 13 June 2013 (UTC)

Tinfoil hat conspiracy theory? I'm so relieved to hear that pharmacies really will refill a high blood pressure medicine prescription as a matter of compassion or respect if the person being treated can't afford to make a mandatory visit to the doctor two or three times a year - I must have been reading some of those wild internet conspiracy sites to think otherwise. Doubtless the marketing strategy for Oxycontin, the monopolization of Colcrys, the fads for hysterectomies and tonsillectomies and wisdom tooth extraction, and indeed, the marketing budget of pharmaceutical companies (and thus pretty near their entire budget) are all popular delusions without basis in fact. If not, do tell me what conspiracy theory you have in mind that I should recant? Wnt (talk) 16:26, 13 June 2013 (UTC)

Words don't always have the same meaning as you would guess from the literally meaning of their roots.

In modern English, Homeopathy refers to a pretty specific (discredited) branch of medicine.

The underlying philosophy of Homeopathy and vaccines have the superficial similarity you mention, but I think in general vaccines are more closely analogous to the age-old concept of building up a resistance to poison, but even that shouldn't be taken as more than a loose metaphor.

(Sometimes "Homeopathy" is used (by advertisers) to mean all unproven herbal remedies, But that's not an accurate use of the word, and it has nothing to do with the word's roots.)APL (talk) 23:51, 12 June 2013 (UTC)

Although this doesn't really answer the original question, I think it's worth at the very least noting that not all homeopathic remedies are completely devoid of the alleged active ingredient, or source of memory, or whatever you want to call it. Some homeopathic preparations are not diluted to the point that the ingredient no longer exists. Others, through a combination of insolubility/immiscibility of the active ingredient and stupidly designed means of dilution, still contain active ingredient when they should not. This does not change the fact that homeopathy still has literally no basis is any valid science.

But then back to the question, I'll agree with most of the above that the similarities are superficial. They both began with the assumption that sources of similar illness may treat or prevent the same. Even that similarity is fuzzy, since homeopathy was looking at any two things that caused similar symptoms, whereas vaccination is using an infectious agent to prevent disease from the exact same infectious agent (with the rare exception of things like cowpox/smallpox, where a reason to believe vaccination would work already existed). And that is where the similarities end, because development of a vaccine is always followed by rigorous scientific experiments to prove its validity and improve its application, whereas homeopathy functions purely as a means of separating fools from their money. Someguy1221 (talk) 04:17, 13 June 2013 (UTC)

Homeopathists don't even agree amongst themselves. I edited the Homeopathy article for a while - and practicing homeopathists would often come to the talk page to complain about how our article is so "biassed" against them(!). One of them told us that our article was failing to explain that higher dilution rates were reserved for treatments that had to target a very specific part of the body and lower dilution rates were used for treatments that affected the entire body. I tried to find a reference for that claim and found that while some homeopathists claim that, others claim the exact opposite and yet others claim that increasing the dilution just makes the treatment more powerful and made no claim of targeted treatment with higher dilutions. This is true throughout homeopathy - almost any statement that one of them might make is found to be contradicted by others. Because there is no scientific basis - or concerted efforts to test these ideas, there is nothing preventing homeopathists from making wildly divergent claims - and since many of the leading proponents make money by writing books - they can make more money by "discovering" new things about homeopathy and writing about them. This results in an ever increasing spiral of wilder and wilder claims as each person has to find something new to write about to keep the gravy train running. Since none of the claims produce any actual clinical results (beyond placebo at least) - then all claims are equally valid and there is no means to distinguish "correct" from "incorrect" statements.

It's pretty hilarious to question a committed homeopathist from a scientific perspective: "So you claim that dilution of some initial substance makes the treatment stronger. But even the best quality distilled water contains some contaminants - and no matter how careful you are during your preparation, there are guaranteed to be things like metal ions leaching into the water in the initial dilution stages. Don't those contaminants undergo yet more dilution and also gain potency?"...and..."How do you clean the containers that you use to do the dilution? Doesn't washing them out at the end just leave an even more potent treatment left in the container?"...it's like shooting fish in a barrel! They don't like answering questions like that. SteveBaker (talk) 13:17, 13 June 2013 (UTC)

June 12

Mites and ticks

Is it true that mites and ticks find it harder to bite/sting musclier people? Clover345 (talk) 00:53, 12 June 2013 (UTC)

Probably, in general. Men are generally more muscular, and generally have thicker skin. B^e——C_ritical 01:04, 12 June 2013 (UTC)

But muscle isn't attached to skin so why would it have an effect? Clover345 (talk) 01:44, 12 June 2013 (UTC)

"Probably, in general." Is about as unspecific as you can get two words to be. Men are generally more muscular, What has the musculature of men have to do with tick bites? Are women more prone to tick bites? and generally have thicker skin. Do they? is that a guess too? I could almost believe if you had said that men on average have thicker skin on the palms of their hands because men on average they do more manual labour, but even then I wouldn't be totally convinced. And what does thick skin have to do with musculature?? Not a single word of that reply helps answer this question in any way. Now, subcutaneous fat I could believe plays a factor, less body fat makes a person appear more muscular but it is not correlated. You can have skinny weak people with little body fat or you can have huge muscular people with very high fat, like sumo wrestlers, so I doubt actual musculature has anything to do with it. A thinner skin and fat layer might make it harder for a tick to bite you, but for all we know, without a reference, it might make it easier for a tick to bite you. Taking a stab in the dark without any logical induction does not help at all. Vespine (talk) 05:48, 12 June 2013 (UTC)

I think Becritical was probably trying to make a joke. There is a statistical correlation between muscularity and thick skin, so there is probably a statistical correlation between muscularity and tick-bitability. This is a prime example of the fact that correlation does not in general imply causation. Looie496 (talk) 06:37, 12 June 2013 (UTC)

:D B^e——C_ritical 13:56, 12 June 2013 (UTC)

A tick can bite through cowhide with no problem. Human skin is much softer so I doubt a tick would find it harder - even in muscular people. I've had tick bite fever several times and I would say, as a generalization, that ticks seem to prefer the softer skin on your body - e.g. inner thigh groin area, under arm area and scalp. This may have nothing to do with the softness of the skin but rather that they can more easily hide in these areas and suck away unnoticed. This is based purely on my personal experience.196.214.78.114 (talk) 07:28, 12 June 2013 (UTC)

There are many species of mites and ticks - perhaps there is some variability in their bite capability? Certainly there are ticks that feast on cows - and those must be able to penetrate the thick hide on those animals. However, these kinds of blood-feeding pests aren't always able to cross species (eg dog fleas don't like to bite humans)...so it's possible that the kinds of tick that can bite through cowhide simply don't have what it takes to feed on humans for other reasons.

We need some solid evidence here - a decent reference would definitely help in answering this question accurately. SteveBaker (talk) 13:37, 12 June 2013 (UTC)

Agreed - it's very important to get the original folklore right before you try to confirm it. I don't know for example if what they mean is that someone who is active is harder for a tick to hang onto, etc. Wnt (talk) 15:39, 12 June 2013 (UTC)

I'm having trouble finding any study of the bitability of different people. There are plenty of papers on tick preferences, but most concern species preference. One paper states that, at least in South Africa, few ticks actually prefer humans, mostly feeding on other, larger animals[21]. Put that in the pile of things that suggest our skin should not be a problem at all. The one study I could find on preferences between different people was concerning adults vs. children, and concluded that behavior (time spent near tick habitats) rather than size or odor was the main driver of bite-rate differences. I seem to have misplaced that paper, so please forgive the lack of citation. I also question the very premise that muscle mass would even be associated with skin thickness. In at least one part of the body, skin thickness seems to be more associated with fat than muscle [22], which has an accompanying curious correlation between skin thickness and prognosis for kidney failure patients! Just another reminder that Looie's point is very important. So in the end, I question every aspect of this question, even the underlying claim - if the main determinant of tick bites is behavior, I'd expect people doing outdoor athletics, who may be more muscular, to get more tick bites. And if none of this has anything to do with skin thickness, which was not suggested by the OP, then I question it nonetheless, as the ticks are not biting through to muscle anyway. Someguy1221 (talk) 04:34, 13 June 2013 (UTC)

Sievert

In the article Sievert there are outdated quality factors which are superseded by ICRP 103 publication. — Preceding unsigned comment added by 217.21.43.22 (talk) 09:18, 12 June 2013 (UTC)

Well... update it? — Preceding unsigned comment added by 217.158.236.14 (talk) 09:31, 12 June 2013 (UTC)

Indeed, we encourage anyone who has a solid reference for a fact (and the ICRP publication would certainly count) to dive in and edit the encyclopedia to make it better. If you feel nervous about doing that, then you should at least report your findings on the "Talk" page for that article: Talk:Sievert - because this really isn't the right forum for that kind of thing. SteveBaker (talk) 13:32, 12 June 2013 (UTC)

It was mentioned there a couple of times, but nobody cares. -- 217.21.43.222 (talk) 16:59, 12 June 2013 (UTC)

Somebody cares - but anybody who works with radiation safety - and requires both precision and currency - should not be consulting a free online encyclopedia. Our encyclopedia article provides a thorough summary, and enough information to help guide anyone with more interest towards proper reference material. In fact, ICRP Publication 103 is the first reference listed in the sievert article. It is available for purchase, and a free excerpt is available online. Nimur (talk) 18:00, 12 June 2013 (UTC)

Basic rocket anatomy

Looking at this picture of the recently-launched Chinese rocket, I was just wondering, what is the main big tube most likely filled with and what about the smaller tubes on the sides? I see a number of types of setups at Rocket propellant. If one of those, e.g., LOX and kerosene, are the case here, are each of the tubes likely independently having all needed to be a thruster, or are the small tubes and the one big one having fully different ingredients only all together forming a working thrust system? 20.137.2.50 (talk) 14:23, 12 June 2013 (UTC)

According to our Long March (rocket family) article "the main stages and associated liquid rocket boosters use dinitrogen tetroxide as the oxidizing agent and UDMH as the fuel". Each of the liquid rocket boosters will be a self-contained rocket system, linked to a central thrust control. Gandalf61 (talk) 14:45, 12 June 2013 (UTC)

Long March seems to have a very similar booster arrangement to the R7/Soyuz rocket family, for which there's more public documentation available. Starsem's outline guide to Soyuz (here) shows internal diagrams for the Soyuz core stage and for its four strap on boosters (p22-). As Gandalf61 says for the LM, the Soyuz boosters run (essentially) the same engines as the core stage, and all four boosters and the core have their own fuel and oxidiser tanks. For the Soyuz, calling the core stage "stage 2" is a bit misleading, as its engines are lit at takeoff and burn (at about 50% power) all the time the boosters are running. Once the boosters are finished and gone the core throttles up to 100%. In contrast, this page says that the LM's core doesn't start until shortly before the boosters are shed. -- Finlay McWalterჷTalk 17:16, 12 June 2013 (UTC)

Main Battle Tank

I have a question which may seems to be a silly question , when you take a look on the turret before assembling it on the hull , you find that it is impossible for the loader in a tank like leopard 2 to reach the ammo storage at the left of the driver because , there is an obstruction between the loader and the ammo storage because of the extension of the turret inside the hull (the cylinder which contains the crew) as in the image on this page http://www.miscellaneoushi.com/Military/army/army_tanks_german_bundeswehr_leopard_2_1280x853_wallpaper_25616 — Preceding unsigned comment added by Tank Designer (talk • contribs) 14:47, 12 June 2013 (UTC)

You should explain what you're asking better. Simply looking at the picture I don't see an obvious obstruction, and the idea that the person loading the shells can't reach the ammo seems highly unlikely. Wnt (talk) 15:37, 12 June 2013 (UTC)

Note also that, in principle, it is not necessary for the loader to be able to easily reach all of the tank's ammunition. Tank designers could easily opt to shoehorn in additional ammunition in inconvenient spaces, with the understanding that it can be transferred into battle-ready storage when the tank is not engaged. I believe, but can't cite specifics, that some tank designs have even incorporated such storage in external compartments that cannot be reached unless the crew exits the vehicle. This method of ammunition storage has been used in other areas, such as the WW2-era Type VII U-Boat. — Lomn 17:20, 12 June 2013 (UTC)

That extension doesn't appear solid - I don't see what obstruction you're referring to. There are a bunch of items inside that space - but it may well be that they are simply stowed there temporarily when the turret is removed (eg to make wiring harnesses easier or something). (Higher res version of that image is HERE). This image shows ammunition storage both behind the gunner in the turret and down in the front section of the hull. This article talks about how the ammo is reached and suggests that the rounds stored in the hull are the primary ones - with the additional rounds in the turret locked away behind an electrically operated door. SteveBaker (talk) 18:43, 12 June 2013 (UTC)

And while we're on the topic, why can't they devise a system for automatically loading shells, rather than requiring people to do it ? We've been able to do this with bullets since the Gatling gun (or earlier), after all. StuRat (talk) 04:30, 13 June 2013 (UTC)

See Autoloader, which are indeed used in many tanks. A common argument against autoloaders is that until recently, humans were actually about as fast as them anyway, for your typical tank-caliber guns. There were also concerns of the reliability of the autoloader, and the fact that incorporation of an autoloader into many existing tanks would require a dangerous relocation of the ammunition, such that accidental detonation of the ammo would be far more likely to kill everyone in the tank. That particular concern has been mitigated in many vehicles by more recent improvements to autoloader design, or by designing a new vehicle around an autoloading gun in a way that eliminates the problem. Someguy1221 (talk) 04:45, 13 June 2013 (UTC)

June 13

Non-circular replacement body joints

There's an ad on TV that shows people riding bicycles or driving cars, comically, with elliptical wheels, then the announcer says "Our replacement knee joints are round, because round is better". Ok, cute ad, but I'm left wondering why the other replacement knee joints are apparently elliptical. Are there advantages to that ? StuRat (talk) 04:36, 13 June 2013 (UTC)

I don't know the ad you are referring to, but are knee joints round? I don't know how anatomically correct an image like this is, but they certainly look quite eliptical to me. As to advantages, the knee doesn't move through 360 degrees, probably only about 140, if you compare a 140 degree arc of a circle to the 140 degrees arc of the kind of "not very eccentric" ellipse we see in the previous image, there's probably very little difference, they're both round arcs, you really need 180 degrees before an arc and a circle look much different (depending which arc you chose of course). One difference I can however imagine is weight distribution and this could play a large factor because wear of artifical knee joints is a main consideration, knee replacement is generally only offered to old people because young people would wear them out too quickly. Vespine (talk) 06:52, 13 June 2013 (UTC)

It's certainly not necessarily or obviously true that "round is better" anyway. Sure, for a wheel on a car, an elliptical wheel results in varying ride height and torque requirements that would be a disaster. But for a limb joint, it's not at all clear that there wouldn't be advantages. Just off the top of my head, I could imagine the following possibilities:

• Firstly, as an elliptically jointed limb rotates, the limb would change in length as the bearing point moves from the major to minor axis of the ellipse - but since the limb is only touching the ground during one part of the arc, that might not matter...but in a car wheel, this would result in massive vibrations at high speeds and sickening lurching at low speeds...also, since the wheels on front and back and either side of a car don't stay lined up - the car would rock from side to side and from front to back - and the suspension would be working continuously.

• Secondly, in a limb joint, when the minor axis of the ellipse is in place against the socket instead of the major axis, some fluid would presumably be trapped in that gap. This would result in fluid being continuously pumped in and out of the socket as you move the limb. That fluid flow might provide a lubrication function - or maybe deposit some material that resurfaces the socket over time - or perhaps have some other important biological function such as delivering oxygen or flushing out bacterial infections. Doing that wouldn't be necessary in an artificial limb - but it could very well be needed in nature.

• Thirdly, with wheels, the driving force is at the central axle - so the torque requirement from the motor would change as the wheel rotates and alternately raises and lowers the body of the car and the effective diameter of the wheel changes - this would clearly be a bad thing. But our limbs are powered by muscles that don't operate at the center of the joint - so the torque requirements wouldn't change significantly - and the idea that the amount of force required to move the limb would change over the arc that it swings through might actually work in favor of efficient motion. You could easily imagine a situation where your leg would be a little longer when in contact with the ground, gradually shortening as you moved it during a stride - this would allow your body weight to help propel the limb during the "power stroke" at the cost of increased torque as the leg is straightened to plant it back on the ground again. That could very easily reduce the load on the muscles and let you run faster.

I don't know whether any of those things are true...but the point is that it's very far from obvious that a round joint would be better than an elliptical one - and the analogy with car wheels is quite utterly bogus.

Since it's much harder to machine and polish an elliptical surface than a round one - I find it hard to believe that the other artificial joint manufacturers would have made elliptical joints if there wasn't good reason to do so.

SteveBaker (talk) 12:48, 13 June 2013 (UTC)

Triple integral integration by parts

We are all familiar with the integration by parts formula:

$\int f{\frac {dg}{dx}}dx=fg-\int g{\frac {df}{dx}}dx.$

Does there exist an "analogous" formula for the following case?

$\iiint f\left({\vec {\nabla }}\cdot g\right)dV=\cdots$

— Trevor K. — 04:46, 13 June 2013 (UTC)

You should post this on the math desk. Someguy1221 (talk) 04:51, 13 June 2013 (UTC)

$f\partial _{k}g_{k}=\partial _{k}\left(fg_{k}\right)-g_{k}\partial _{k}f$ Count Iblis (talk) 12:11, 13 June 2013 (UTC)

And if you're not familiar with the Einstein notation used by Count Iblis in his very concise answer, try

$f{\vec {\nabla }}\cdot {\vec {g}}={\vec {\nabla }}\cdot \left(f{\vec {g}}\right)-{\vec {g}}\cdot {\vec {\nabla }}f$. Dauto (talk) 14:16, 13 June 2013 (UTC)

And don't forget to use Gauss theorem to solve the integral of the divergent. Dauto (talk) 14:20, 13 June 2013 (UTC)

Naming an apple rust (fungus)

The apple tree in front of my work place (middle of Germany) started to look strange and on the under side of the leaves I found nice purple red looking marks. I made a few images and I need some help to give the little fungus the right name . It looks like some rust (fungus), but I could not find any images of a purple red one.

some apple rust

• 
  no magnification
• 
  5x
• 
  10x

--Stone (talk) 07:47, 13 June 2013 (UTC)

I think not. Google images for eriophyid mites. See http://www.whitecanker.net/Maple,%20Norway/Maple,%20Norway.asp and http://www.forestryimages.org/browse/detail.cfm?imgnum=5424246 It seems it is a Gall caused by mites. 196.214.78.114 (talk) 13:56, 13 June 2013 (UTC)

(Awesome pics BTW - hope you add them in the relevant sections.) 196.214.78.114 (talk) 14:02, 13 June 2013 (UTC)

Good call, it does look a little like a fungus, but I think mite gall is correct. Our article is at Eriophyidae, which only has a picture of a much larger type of gall. So the pics could probably be added there, even without a species-level ID. SemanticMantis (talk) 18:22, 13 June 2013 (UTC)

What's wrong with this one-pot synthesis?

We aren't going to advise you on how to synthesize drugs. Looie496 (talk) 19:44, 13 June 2013 (UTC)
The following discussion has been closed. Please do not modify it.
Recently I have used orgsyn problems as my crossword puzzles, and I like to find cheaper more feasible alternative routes to known drugs. So what's wrong with this one-pot synthesis -- it seems too simple or else it would have been more popular: Start with any essential oil containing mostly safrole (like the ones on eBay) Markovnikov acid-catalyzed hydration of safrole into a secondary alcohol Oxidize secondary alcohol into ketone using TEMPO and bleach React the ketone with N-Methylformamide (solvent) and formic acid (reagent, 5 equiv?) via the formamide form of the Eschweiler–Clarke reaction. Bleach will be destroyed, chlorine will be released (leave room) Add strong acid to hydrolyze the substituted formamide to release formate and MDMA. You can then recover the MDMA using the usual workup for amines, purify using chromatography etc. What's wrong? 71.2.172.65 (talk) 18:42, 13 June 2013 (UTC) Other than being illegal in many jurisdictions? --Jayron32 19:39, 13 June 2013 (UTC)

Genetic contributions of parentals in haplodiploidy

In the haplodiploidy section in the article of sex-determination it states:

"If a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems."

The premise is that female bees are diploid and male bees are diploid.

Here is what I do understand:

1. Daughters posses genetic material from both a father bee and a mother bee
2. Sons possess genetic material from a mother only

Here's what I don't understand:

1. If each (diploid) daughter possesses one of each chromosome from father bee and one of each from mother bee, how do they share 3/4 of their genes with each other? According to my calculation, they should have the potential to share 100% of their genes with siblings (if the same chromosome was receveived from mom) or 50% (if a different chromosome was received from mom) because they always have the same chromosomal contribution from haploid dad. Was the comment above meant as an average of 100% and 50%? That seems odd.
2. Do sisters in XY necessarily share only 50% of their genes? They necessarily share at least 50%, but can't they share 100%?
3. So it seems to me that in both haploploidy and XY, sisters can share 50% or 100%, but not 75%.

Thanks! DRosenbach ^{(Talk | Contribs)} 19:39, 13 June 2013 (UTC)

The 3/4 figure is the center of a range, but it isn't all that large of a range. The thing that you are missing is that meiosis (cell division for sexual reproduction) involves genetic recombination -- so the result has 50% of the parent's genome, but each chromosome is a mixture of the two that come from the parent. Looie496 (talk) 19:49, 13 June 2013 (UTC)

1) Yes, the 75% figure is the average, and the 100% or 50% are for each chromosome seperately, and due to interchanging sequences, even a single chromosome can be partly from one parent and partly from the other.

2)Sisters in the XY system (e.g. human sisters) can share anything between 0% and 100% of their genome (not counting the identical X-chromosome that they got from their father), but statistically the similarity is rarely far removed from 50%, except in the case of identical (or semi-identical) twins.

3)As mentioned before, the 75% is the average for the entire genome. - Lindert (talk) 20:20, 13 June 2013 (UTC)

(EC) No, male Hymenoptera are Haploid, females are diploid, that's why it's called haplodiploidy (Oops, I see now you probably just made a typo). Also, as Looie points out, there are ranges. You are correct that these are best viewed as averages, more precisely expected values. Human siblings share 50% of genes on average, but it can be higher and lower in individual cases. It is in fact highly unlikely that a given pair of human siblings share exactly 50% of their genes. And now that I've helped answer, I must point out that we are misusing the term "gene" here. Genes are loci, alleles are the information or "code" present at the loci. So really, we should say that bee sisters share 75% of their alleles, on average. SemanticMantis (talk) 20:23, 13 June 2013 (UTC)

What kind of microscope do oceanographers use?

Hi, I am from Kiribati, a small country in the Pacific Ocean and I'd love to study oceanography. Thank you. I'm 20 year old.