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Extra info for Ask the Experts (Scientific American Special Online Issue No. 25)

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Although male and female life habits have been converging in the industrial world, this convergence is not absolute. Females tend to smoke fewer cigarettes, drink less alcohol and drive more carefully. On average, their professional activities are less prejudicial to their health. In the past, women’s social status and life conditions, such as the hardships associated with childbirth, nullified their biological advantage. (In some countries, this effect continues today. ) But today, at least in industrial countries, economic and social advances have largely erased status inequalities, and women’s life expectancy is longer than that of men.

D. Barrera, McAllen, Tex. Many factors— from social to hormonal— could play a role when an expectant father experiences pregnancy side effects such as nausea, weight gain, mood swings and bloating. ” The prevalence of couvade is difficult to measure because of its varied definitions and the skewed rates of symptom reporting. In modern Western populations, estimates of couvade’s frequency range from less than 20 percent to more than 80 percent of expectant fathers. Only recently has this phenomenon received attention from biologists, spawning a variety of hypotheses.

The isotopes of particular interest for climate studies are 16O (with eight protons and eight neutrons); 18O (eight protons and 10 neutrons); 1H (with one proton and no neutrons); and 2H (one proton and one neutron, also known as deuterium, D). Using mass spectrometers, researchers measure the ratio of the oxygen and hydrogen isotopes in ice-core samples and compare the result with the isotopic ratio of an average ocean-water standard known as SMOW (standard mean ocean water). The water molecules in ice cores contain slightly less of the heavy isotopes than SMOW, and the difference compared with the standard is expressed as delta (or change of) 18O or D.

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Ask the Experts (Scientific American Special Online Issue No. 25) by Scientific American


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