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The Doppler Effect

As any object moves through the air, the air near the object is disturbed. The disturbances are transmitted through the air at a distinct speed called the speed of sound, because sound itself is just a sensation created in the human brain in response to small pressure fluctuations in the air. Sound moves through the air as a series of waves. When ...

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TheDopplerEffect
Medicine

Ultrasound In Medicine

In medical testing, ultrasound equipment is used to produce a sonogram, or a picture of organs inside the body. Ultrasound scanners do not use X-rays. They use waves of such high frequency that they ... Continue reading

UltrasoundInMedicine
Biology

The Dogma of Life

Dogmas are authoritative tenets common in religion and philosophy. But in molecular biology? Molecular biology has a central dogma, proposed by Francis Crick in 1953, that says that genetic ... Continue reading

MolecularBiology
Geology

The Importance of Cave and Karst Systems

Cave and karst systems are important for two major reasons. First, the overwhelming majority of the nation's freshwater resources is groundwater. About 25% of the groundwater is located in cave and ... Continue reading

ImportanceofCaveaKarstSystems
Biology

Batesian Mimicry

If you ever got stung by a wasp you would probably avoid all flying insects which resemble the brightly-colored yellow and black wasp. If you were a bird and certain types of butterflies gave you a ... Continue reading

BatesianMimicry

Is Heartburn a Heart Burn?

IsHeartburnaHeartBurnHeartburn is a bad name for a complaint that has nothing to do with the heart. TV ads call it acid indigestion. It's a burning sensation that begins under the breastbone and moves up into the throat. The pain may be at its worst when lying down or bending over. It may feel like bitter liquid rising into the throat or mouth. If it happens frequently, doctors call it GERD (for gastroesophageal reflux disease).

It happens when acid escapes back through the valve at the top of the stomach and moves up into the esophagus. Sixty million Americans say they get it at least once a month. Heartburn is common after a big meal, and some foods--such as tomato sauce, fried food, sour beverages, coffee, or soft drinks--trigger it in some people. It's more common among people who are overweight, smoke, or drink too much alcohol. It can be associated with a stomach ulcer or a hiatal hernia, which is a bulge of part of the stomach into the chest cavity. The hernia causes the stomach valve to work improperly.

Some people find they can avoid heartburn by watching what they eat and drink, learning to relax, and not eating two or three hours before bedtime. Over-the-counter antacids are effective for many. They make stomach acid less acid. When antacids fail, doctors recommend prescription drugs. In severe cases, a surgeon can stitch the stomach valve tighter, preventing the backup of acid.