Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules.

Although the effect of son preference on sex composition of children ever born is undetectable in national-level estimates that aggregate across all families, this article provides empirical evidence from India that son preference has two pronounced and predictable family-level effects on the sex composition of children ever born. First, data from India show that smaller families have a significantly higher proportion of sons than larger families. Second, socially and economically disadvantaged couples and couples from the northern region of India not only want but also attain a higher proportion of sons, if the effects of family size are controlled.

This article examines the effects of girls' early marriage on their risk of acquiring HIV/AIDS. By comparing several underlying HIV risk factors, it explores the counterintuitive finding that married adolescent girls in urban centers in Kenya and Zambia have higher rates of HIV infection than do sexually active unmarried girls. In both countries, we find that early marriage increases coital frequency, decreases condom use, and virtually eliminates girls' ability to abstain from sex. Moreover, husbands of married girls are about three times more likely to be HIV-positive than are boyfriends of single girls. Although married girls are less likely than single girls to have multiple partners, this protective behavior may be outweighed by their greater exposure via unprotected sex with partners who have higher rates of infection. These results challenge commonly held assumptions about sex within marriage.

There was no increase in the risk of vaccine-associated Guillain-Barré syndrome from 1992-1993 to 1993-1994. For the two seasons combined, the adjusted relative risk of 1.7 suggests slightly more than one additional case of Guillain-Barré syndrome per million persons vaccinated against influenza.