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Fission and Fusion

In the nuclear fission process, a heavy atomic nucleus spontaneously splits apart, releasing energy and an energetic particle, and forms two smaller atomic nuclei. While this is a normal, natural process, it is in actuality an extremely rare process. Vastly more common is the opposite process of 'fusion', in which two very light atomic nuclei fuse ...

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FissionandFusion
Chemistry

Why Does Cement Set?

Concrete has been known for literally thousands of years. It is a testament to the enduring strength of this material that concrete structures from those long-ago times are still standing strong ... Continue reading

WhyDoesCementSet
Biology

Obesity: How much fat can your genes handle?

According to some experts, the popular formula for weight loss, 'eat less, and exercise more,' is not working for many Americans. Recent estimates say that about 34% of adults and 22% of preschool ... Continue reading

Obesity
Mathematics

Mobius Strip

A Mobius Strip is an amusing three-dimensional object whose surface has only one side. Huh? Well, most objects you can imagine have a surface with two sides. For example, an ordinary piece of paper ... Continue reading

MobiusStrip
Biology

The Art of Hunting

Most of us have seen a praying mantis. Two thousand species of praying mantis are scattered throughout the world, ranging in size from less than half an inch (1.27 cm) to more than five inches (12.7 ... Continue reading

PrayingMantis

A Sweaty Subject

SweatWhen human body temperature rises, tiny muscles around the sweat glands in the skin contract, squeezing perspiration - better known as sweat - out through the pores. Sweat is about 99 percent water. Dissolved in it are salts of sodium, potassium, and magnesium. Sweat also contains tiny amounts of waste materials such as urea (the major toxin in urine).

The skin of an adult contains some three to five million sweat glands, the combined total of two different types. Most abundant are the eccrine glands. About two million of them are distributed over the entire body. These glands empty directly onto the skin through pores. They help control body temperature and excrete waste material. The eccrine glands handle the body's heat-regulating functions. Exercise increases both the size and the efficiency of eccrine sweat glands. People who start an exercise program often notice that, after a few weeks, they start sweating at a lower body temperature and come to tolerate heat better.

The second kind, the apocrine glands, are inactive in childhood. They begin to work between the ages of 10 and 14 when the production of sex hormones increases. They empty into hair follicles, mostly in the armpits and groin. They produce a thick, colored fluid containing a complex mixture of fats, water, and proteins. The apocrine glands are especially sensitive to emotions. Antiperspirants work only on the apocrine glands. Perspiration itself is odorless, whether it comes from apocrine or eccrine glands. It's only when bacteria grow in sweaty places, such as under the arms, that odor occurs.