ewmon

My 2¢ worth: Spontaneous human combustion. Why don't we ever here about it happening to other animals? Considering that the world contains 16 billion chickens, complete with easy-to-light feathers, we don't hear from a chicken farm: "Hey Joe, another chicken just burst into flames." Or mice. Or ants (except those in front of kids with magnifying glasses). I'm guessing the answer is that humans drink alcohol, often habitually, and sometimes to excess. Alcohol might act as starter fluid or an accelerant. Besides, less dense fat would float on water or watery body fluids, and would burn like floating candles.

Someone else needs to answer this. I've used Student t tests to compare populations, but this is unfamiliar to me.

What's the whole question regarding t-percentiles?

Just convert the percent to probability, then use the P[Z<z] table in reverse, and then, knowing the mean and SD, convert the z into the length.

I'm thinking airports use ground-based units because that's where airplanes fly close to the ground and might crash (ie, unintended contact with terrain) due to air turbulence. The 1966 BOAC incident was actually air turbulence that caused the craft to disintegrate in midair (ie, tore it to pieces). How often do such disintegrations occur?

Some ground-based radar systems already detect microbursts, wind shear and other air turbulence. Does the history of navigation support the need (and the cost and maintenance) for aircraft-based systems?

There are universally-compatible (no blood-type matching) oxygen-transporting blood substitutes produced from non-human blood that lasts for years at room temperature, and it would seem easy enough to produce human hemoglobin artificially using recombinant DNA.

Bingo!

Nexium Tao, thanks for the reminder. I did spell it out, but Tony had led Akash Kagi to the Aluminum conductors section in Wikipedia's article on Electrical wiring, which says the same thing. I also think it's dangerous for a modern textbook to suggest that bare aluminum conductors are safe. I agree with Random because I also have not heard of uninsulated aluminum wiring.

Today's students have the world's knowledge at their fingertips. I googled aluminium wires not insulated, and the answer appeared in the first entry on the google results page (without even clicking on the link!) --

Regulation. Thanks CharonY. It seems to work the other way too, because fertilized eggs don't grow flagella as sperm do, which means that the "gametic" genes are turned off after fertilization. Which leads me to my last point ... And the differences between X sperm and unfertilized eggs (ie, secondary oocytes)? Do they essentially have the same chromosomal components. There's size differences and also the sperm's flagella which the egg lacks. So it seems like it might be the hormonal/chemical environment the starter cells are in that differentiates them into sperm and eggs. So, would an oogonium undergo spermatogenesis if transplanted into a male (or subjected to male hormonal levels), and likewise, would a spermatogonium undergo oogenesis if transplanted into a female (or subjected to female hormonal levels)? Or does differentiation go back further than that?

I've studied developmental biology, but I have not yet seen anything that explains how gametes actually "live". I think of DNA as the software of the cells. We know that gametes (sperm and unfertilized eggs) are alive and perform various functions; however, ... Has science uncovered how their DNA operates? Is their existence as gametes simply the "default" consequence of having only half of their DNA? Or (because gametes of diverse species behave very similarly) do gametes simply suppress their "organism" DNA/software (which runs after fertilization occurs)? So, do gametes (and, by extension, do all cells in our bodies) have two sets of software -- what might be called gametic and somatic? What especially puzzles me is that X sperm and unfertilized eggs seem to have the same DNA (ie, 23 chromosomes including an X sex chromosome), yet they develop and behave very differently. Why? How?

Uh, nope. Sorry, let me re-phrase the logic involved because all the cumulative probabilities are for "less than" a value of z (ie, P[Z<z], as shown in my diagram). "less than z = 1.25" means P[Z<1.25], which you correctly found to equal 0.89435. "less than z = –1.50" means P[Z<-1.50], which you know means 1 – P[Z<1.50]. So, look up P[Z<1.50] in the table, and subtract it from 1. Hopefully, when you draw the bell curve and shade the areas, you'll see how to calculate "less than z = 1.25" BUT NOT "less than z = –1.50". The value of P[Z<a] refers to the area under the curve from –∞ to a, like this: The graph below is different because the shaded area shows the final answer in graphic form. If you know the areas representing P[Z<1.25] and P[Z<–1.50], then what must you do to find the answer? And be careful converting probabilities into percentages; a probability of 1.00 equals 100%, a probability of 0.50 equals 50%, etc. Merry Christmas.

Applejack (ie, concentrated hard cider) is made by fermenting the cider and then letting it partially freeze. Freezing separates the alcohol from water due to differences in their freezing points (–114°C versus 0°C), as compared to distilling, which separates the alcohol from water due to differences in their boiling points (78°C versus 100°C). Water will freeze at a much higher temperature than alcohol (ie, it'll "freeze first" as the mixture cools), and it will do so from the outside in, so you'll see ice (mostly frozen water with a little alcohol) around the edges of the container with a mixture in the center of a higher alcoholic content. Interestingly, as the water freezes out of the mixture, the alcoholic content of the remaining mixture increases, and so, lowers its freezing point. The remaining mixture can be poured off (or the ice removed), and the process repeated. Hard cider has an alcoholic concentration similar to beer or wine, but applejack can have a higher concentration similar to brandy (ie, distilled wine).

There's been a longstanding concern about trichinosis. We have known for some time that porcine physiology is fairly compatible with that of humans. An obvious concern exists that pigs act as vectors for human diseases (eg, swine flu). We use porcine insulin and heart valves in humans (however, some Jews and Muslims refuse these products). There's serious ongoing research to use more porcine body parts (including genetically altering pigs to reduce their rejection by humans) in xenotransplantations to help relieve the chronic shortages for transplants. Doesn't it seem as though everyone needs a kidney? I would hesitate to use the word "dirty" to describe the nature of pigs. The reputation given to pigs for their uncleanliness is undeserved because most of it results from humans placing them in small pens and typically adjacent to other pigpens. Pigs are highly intelligent and naturally clean. They are the only livestock that can control their urination and defecation, and some people keep miniature pigs as housebroken pets. Pigs will naturally use the coolest and darkest part of their area as their "toilet" and, if given enough space, will spend the rest of their time away from it, typically in the warm, sunny part of their area where they can eat, sleep and explore. Pigs are territorial, and they will mark the edges of their territory (ie, pens) with dung if they know there's other pigs nearby. Farmers put pigs in firmly-walled "pens" as compared to corrals, paddocks and pastures, because pigs enjoy digging and rooting around, and they would easily escape from corrals etc. Many pigs don't have much of what could be called fur or hair and they lack sweat glands, so they resort to methods to help warm and cool themselves, typically lying in the sun or the shade. Pigs can get sunburned. They should have a shelter for relief from the hot sun and inclement weather. They enjoy wallowing in water and mud as many livestock do, but more so, and they also enjoy getting watered down in hot weather.

I'd say oxygen input for two reasons: 1. Aerobic activities, such as marathoning, by definition, require oxygen and, when a marathoner does not receive enough oxygen, the metabolism becomes partially anaerobic and produces toxic by-products that result in fatigue. 2. Unlike oxygen intake, carbon dioxide output has multiple routes -- both carried by hemoglobin and dissolved in the plasma -- so it is not hemoglobin-limited the way oxygen input.

Your lookup for z = –1.50 is incorrect, so look up for z = 1.50 again. The entire area under the cumulative probability bell curve is normalized (ie, scaled or standardized) to 1 (because, by definition, the cumulative probability is 1 from z = –∞ to z = +∞). So, the reason to compute 1 – P(z) is to find the area in the "tail" which is the cumulative probability greater than z (which is the unshaded area under the bell curve I posted) --- but, more importantly here, it is also the as the same cumulative probability less than –z. Get it? Lightbulb? When you find the cumulative probability less than z = 1.25 (which you have already found) and the cumulative probability less than z = –1.50, I recommend that you draw a simple bell curve and graph these two probabilities (and shade them differently -- for example, shade lines that slant in one direction and in the other direction). (Remember that negative z values go to the left of z = 0.) From there, I hope the next step to perform is obvious from your graphing (ie, how to find the cumulative probability greater than z = –1.50 AND less than z = 1.25). One hint about this last step. The math you're using is not sophisticated enough to simply find the cumulative probability between two z values. (Think about it, "between" is a little sophisticated.) Instead, this math is only as simple as "less than" and "greater than." So that's why you need to convert your thinking of "between a and b" to "greater than a" AND "less than b." Bingo?

Most likely, the blood (being hydrophilic) would eventually dissolve/wash off the knife and/or the microbes in the lake would eventually ingest it, whereas the oils that compose the fingerprint (being hydrophobic) might survive longer. The time frame for these events is problematical (kinds and numbers of microbes, water temp, etc), but the knife "washing up on shore" means it was also subjected to currents, wave action and friction and saltation along the lake bottom which that would add to the "washing away" effect.

Bingo! I actually saw the lightbulb go on over your head.

Your thinking to this point is correct, except why did you look in the same column? You're looking up 1.50, not 1.55. When you find the correct area for z = –1.50, look again at the bell curve and think of what those areas represent, and your next step might come to you.

Using this table, you split your z value (let's say, 1.78) into two parts, the 1.70 (which you'll find to the left) and the 0.08 (which you'll find at the top). You'll find the cumulative probability (0.9625) of z = 1.78 where the "1.70" row and the "0.08" column intersect. This is for positive z values (as shown in the bell curve diagram). For negative z values (eg, –1.78), can you see what you would do with the 0.9625 value to obtain the cumulative probability for z = –1.78? (Look again at the bell curve diagram for a clue.)

When people began making clocks, perhaps they continued to follow the same convention as sundials. Most of the earth's land (and the origins of western civilization) is in the northern hemisphere, where the shadow of sundial gnomons (pointers) begins the day in the west and then moves toward the north and then the east. The same convention holds true for the sun that casts those shadows: someone north of the equator, when facing south, sees the sun rise at their left, then it travels somewhat overhead, and sets to their right.

Some sciences (or studies) involve some degree of interpretation. Astronomy - Probably the science that uses the greatest amount of interpretation. Astronomers cannot touch the objects of their study and cannot perform experiments; they can only observe. The science with the largest time frame (it apparently covers all of time) and the largest object of study (the universe). Geology - One step up from astronomy. Geologists can touch and examine/test objects, but cannot perform experiments. A science with a very large time frame, but not as large as astronomy's and not going back as far, and a much smaller object of study (the earth). Archeology - One step up from geology. Archeologists can touch and examine/test objects, but still cannot perform experiments; however, our current knowledge of recorded human history (and of human nature) allows us some insight ... maybe. It involves a much smaller and much more recent time frame than the above two sciences and a much smaller object of study (mankind).

Can you give some examples of other animals interbreeding?

Other animals (simians, dogs, etc) have blood factors similar to the human Rh blood factor, so some of the individuals of these species would be Rh negative. Also, other animals do not have an Rh factor in their blood, so the entire species would be Rh negative. I was wondering the importance of this information?