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Hydropower Basics

Flowing water creates energy that can be captured and turned into electricity. This is called hydropower. Hydropower is currently the largest source of renewable power, generating nearly 10% of the electricity used in the United States. The most common type of hydropower plant uses a dam on a river to store water in a reservoir. Water released from ...

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HydropowerBasics
Biology

Genetic Testing And Discrimination

Genetic testing is the use of recombinant DNA technology to obtain information about a person's genome. The first genetic tests were conducted during the 1960s for the disease phenylketonuria (PKU). ... Continue reading

GeneticTestingAndDiscrimination
Medicine

The Placebo Effect

To test new drugs, researchers usually divide their subjects into two groups. One group receives the experimental drug. The other receives a placebo or 'sugar pill' that should have no effect on the ... Continue reading

PlaceboEffect
Biology

Gestation Periods of Mammals

Gestation period is the time from fertilization to the actual birth in animals. In humans this period is 266 days or approximately 9 months. ... Continue reading

GestationPeriodsofMammals
Biology

Luck Of The Irish?

In the 1800s many Irish were poor tenant farmers who farmed mainly for the landowner and relied on small plots for their own food. Because high yields of potatoes could be obtained from these small ... Continue reading

LuckOfTheIrish

Why Do We Call It A 'Vaccination?'

VaccinationSmallpox 'vaccinations' are in the news nowadays. What is smallpox and what is a vaccination? Smallpox is one of the oldest and most horrible diseases afflicting the human family. In the past, it killed twenty to sixty percent of victims, and left the survivors with disfiguring scars from the rash.

Early on people realized that survivors of smallpox were immune to further attacks. Over a hundred years before our present form of vaccination, a practice called 'variolation' was used, beginning in China and Asia and reaching Europe by the beginning of the 18th century. Variolation consisted of applying the pus or ground scabs from a patient who had a mild case of smallpox (also called variola, hence the name) to a scratch in the skin. This system wasn't very good: two or three percent of variolated people died of smallpox. But it was better than the 20-60 percent who might die in an epidemic. By the 18th century, people had noticed that those who had had a milder disease called cowpox were also immune from smallpox. Milkmaids often caught it from their cows.

So in the late 18th century, Edward Jenner invented the practice we now know as vaccination, so called from 'vaca', the latin word for 'cow'. Patients were innoculated with material from cowpox lesions, which is much safer than variolation because cowpox is a milder illness. Today, most adults over the age of 35 have a small round scar on their upper arm where they were vaccinated as children.