No abstract

No abstract

A formula for the effective wavenumber in a dilute random array of identical scatterers in two dimensions is derived, based on Lax's quasi-crystalline approximation. This formula replaces a widely-used expression due to Twersky, which is shown to be based on an inappropriate choice of pair-correlation function.

When mixtures of semen containing an equal number of spermatozoa from two males are inseminated, the males usually sire disproportionate numbers of the offspring. In this study, when a mixture of equal numbers of spermatozoa from a Columbian (C) and a Leghorn (L1) cock was inseminated, the C male sired 34% of the offspring. The proportion of offspring was constant regardless of age of males, season, total number of spermatozoa, breed of hen or the interval from insemination to the time of egg-lay over a 15-day period after insemination. The proportion of C offspring observed from inseminating nine different ratios of spermatozoa arranged progressively from 1C :9L, 2C:8L and so on, was 10%, 20%, 23%, 34%, 38%, 44%, 58%, 74% and 82%. These results were in close agreement with mathematically derived estimates. It appears that the relationship between sperm ratios and the proportions of offspring sired by two males competing heterospermically is dependent on the ratio of the number of competing spermatozoa but not on total number, season, breed of hen or the interval from insemination to fertilization.

Assuming the existence of garbage collection makes it easier to design implementations of dynamic-sized concurrent data structures. However, this assumption limits their applicability. We present a methodology that, for a significant class of data structures, allows designers to first tackle the easier problem of designing a garbage-collection-dependent implementation, and then apply our methodology to achieve a garbage-collection-independent one. Our methodology is based on the well-known reference counting technique, and employs the double compare-and-swap operation.