You, Graphite and Diamonds

Living things, including you and me, and diamonds, are made of the same substance: the element carbon (C). Carbon atoms in our bodies are bound to other atoms, such as hydrogen and oxygen, in organic molecules, while those in a diamond are bound to other carbon atoms to form a pure crystalline structure. Another form of pure carbon is graphite. ...

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The Incredible Capacity Of The Immune System

By age two, infants in the US can receive up to 20 vaccinations. In view of that, concerns had been raised that too many immunizations could overwhelm an infant's immune system. ... Continue reading


You Can Learn A Lot From A Microbe.

You can learn a lot from a microbe. Right now, a tiny critter from the Dead Sea is teaching scientists new things about biotechnology, cancer, possible life on other worlds. And that's just for ... Continue reading


Malaria and Sickle Cell Anemia

Sickle cell anemia is a genetic disorder in which the red blood cells collapse into a 'sickle' shape and cannot carry oxygen very well. They also tend to get stuck in narrow blood vessels, causing ... Continue reading


The Self-less Gene?

The dictionary defines altruism as 'an unselfish concern for the welfare of others.' That's the kind of behavior that rescue workers showed in the 9-11 attack on the World Trade Center, and many of ... Continue reading


Why Is Blood Pressure Two Numbers?

WhyIsBloodPressureTwoNumbersBlood pressure might better be called heart pressure, for the heart's pumping action creates it. To measure blood pressure, health workers determine how hard the blood is pushing at two different times: when the heart contracts, called systole; and when the heart relaxes, called diastole. The contraction of the ventricles during systole gives the blood a strong push, like the rush of water through a hose when the spigot is turned on. The force propels the blood through the arteries; it also pushes against artery walls. The first number in a blood pressure reading is the systole number. It is a larger number because the pressure of blood against artery walls is greater with the push of the heart's contraction behind it. Diastole is the relaxation phase of heartbeat. Pressure diminishes within the relaxing ventricles. The pressure that blood exerts on artery walls decreases, too. This is the second number in a blood pressure measurement. It is always smaller than the first.

Blood pressure is not the same in all parts of the body, so to make comparisons meaningful, blood pressure is usually measured in the main artery of the upper arm. Also, blood pressure increases with exercise, stress, or exertion, so its readings are most accurate when the subject is lying down and relaxed. Other factors besides position and exercise can affect blood pressure. The amount of blood in the system, the strength of the heart's flexing, and the pliancy of artery walls all play a part. Emotions such as fright, excitement, or worry increase blood pressure. Blood pressure can fall in people who are depressed, lonely, or grieving.

Blood pressure is measured in millimeters of mercury. A blood pressure of less than 120 mm. over 80 mm. is considered a normal reading for adults. Until recently, pressures below 140/90 were thought acceptable. Now, new guidelines for physicians define pressure that stays between 120-139 systolic or 80-89 diastolic as 'prehypertension.' For people with pressures in that range, the risk of developing hypertension, or blood pressure high enough to require treatment, is elevated.