Microsoft Windows

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The world is now talking about the new replacement for "Windows". From the beginning, windows has improved, but has it's problems with Vista and 7. When asked which is the best, most agree that it is Windows XP. I am happy with XP and I know most others are also. There are minor improvements to be m

DC Stator Ring Question

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Hey guys:

I am creating a rotating magnetic field by constructing a steel stator ring with 6 coils and powered by either 3-phase AC power or DC power like in a brushless motor. My two questions are is there a formula to tell me how many turns per coil of the steel stator ring do I need to make

Bending PVC

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I want to bend a piece of 4-1/2" PVC pipe without collapsing it at the bend. The bend will be about 12" radius. My thought is to pack the pipe with sand and cap both ends; heat the pipe in hot water or steam and bend. Once cool, the caps and sand will be removed. Will this work?

BTW, I want to

Who are you calling weak? Human jaws are surprisingly strong and efficient | Not Exactly Rocket Science

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human_jaws

Stephen Wroe has built a career out of analysing some of the planet’s most formidable skulls. His group at the University of New South Wales have studied the strength, sturdiness and biting power of the sabre-toothed cat, the great white shark, and the Komodo dragon. Now, he has turned his attention to a predator whose skull is far less impressive but yields surprises all the same – us.

Humans, it is said, have relatively weak jaws that can’t inflict or withstand high bite forces. Some have suggested that we are adapted to eat foods that aren’t very tough, or that our use of tools and cooking has lessened the evolutionary pressure on maintaining sturdy jaws. Some have even suggested that our weedy jaw muscles made way for our large brains and thus facilitated their evolution. But according to Wroe, all of these explanations have a fatal flaw – our jaws aren’t weak at all. They’re actually remarkably efficient for a primate.

The notion of weak human chops was based on very unrefined models that treated our jaws as two-dimensional levers. Of course, in real life, we chew in three glorious dimensions. To really understand how strong our mandibles are, we need to add that third dimension to the models.

That’s exactly what Wroe did. He used his signature technique, called finite element analysis, to create a virtual model of a human skull (belonging to a San hunter-gatherer). The technique is commonly used by engineers to test the properties of machines and vehicles, but Wroe uses it to put animal skulls through a ‘digital crash-test’.

For good measure, Wroe also digitised the skulls of six other primates – the gorilla, chimpanzee, orang-utan and white-handed gibbon, and two extinct species, Australopithecus africanus and Paranthropus boisei. All of the skulls came from adult females. The images below show an example of these virtual models, displaying the forces that act upon the skulls as they chomp down on the second molar. The blue regions are those under the least amount of stress, while the red, pink and white regions are enduring the highest stresses.

The results revealed that human skulls, far from being weak, are quite tough and unusually efficient for their size. Our second molars can exert a bite force between 1,100 and 1,300 Newtons, beating the orang-utan, gibbon and Australopithecus but lagging behind the gorilla, chimp and Paranthropus. These forces are roughly what you’d expect for a primate of our size. We’re never going to bite with the sheer power of a Megalodon, or the predators that Wroe usually studies, but we’re no slouches when compared to closely related species.

And if you scale all the skulls to the same size, we suddenly become the leader of the pack. If all the jaw muscles clenched with the same force, our teeth would exert a bite force that’s at least 40% greater than any of the other primates, save the gibbon. So not only is our bite very respectable, our jaw muscles need to exert considerably less force from to produce it.

This explains some peculiar characteristics of our skulls. Our teeth are as tough as those of other primates because they still need to withstand the relatively high forces exerted by our bite. But the rest of our skull can afford to be comparatively flimsier. The jaw muscles attach to the skull and inflict stress upon it when they work. But our jaw muscles can produce a strong bite through less effort than those of other primates. As such, they inflict fewer stresses upon the skull, which can afford to abandon some of its sturdiness.

Reference: Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2010.0509

More on skulls and super-bites:

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NCBI ROFL: Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus? | Discoblog

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tips“To see whether estrus was really “lost” during human evolution (as researchers often claim), we examined ovulatory cycle effects on tip earnings by professional lap dancers working in gentlemen’s clubs. Eighteen dancers recorded their menstrual periods, work shifts, and tip earnings for 60 days on a study web site. A mixed-model analysis of 296 work shifts (representing about 5300 lap dances) showed an interaction between cycle phase and hormonal contraception use. Normally cycling participants earned about US$335 per 5-h shift during estrus, US$260 per shift during the luteal phase, and US$185 per shift during menstruation. By contrast, participants using contraceptive pills showed no estrous earnings peak. These results constitute the first direct economic evidence for the existence and importance of estrus in contemporary human females, in a real-world work setting. These results have clear implications for human evolution, sexuality, and economics.”

ovulatory

Thanks to David for today’s ROFL!

Photo: flickr/brh_images

Related content:
Discoblog: NCBI ROFL: Uh, no. Aunt Flo means no ho, bro!
Discoblog: NCBI ROFL: Sexy ladies sexing ladies
Discoblog: NCBI ROFL: scientist…or perv?

WTF is NCBI ROFL? Read our FAQ!


Personal RF Signals

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I have a theory that some persons or agencies can dial up your bodys personal signal. And really mess with your mind. Just like calling a cell phone. some people may be more susceptible than others.

Stator Ring Connection Question

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I am constructing a steel stator ring with 6-coils powered by 3-Phase AC power. However, I am unsure as to how to connect the three wires of the interconnected 6 coils to the AC power source to get a rotating magnetic field. Is there a certain automated switch that will change the AC coming out of a

Stator Field Coil Windings

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I am trying to find a program or formula that will help me figure out how many windings, turns of coil, are needed per coil on a 6 coil steel stator ring powered by 3-phase AC power to get a certain magnetic field strength, about 1.3T. Is there any way that you could help me find out how many windin