Abstract. An HR diagram indicating the positions of the HgMn and the Am stars analyzed by the senior author and his collaborators shows that the coolest HgMn stars and the hottest Am stars are found on the same stellar evolutionary tracks and hence the former must evolve into the later. The explanation of the dividing line between these two types of nonmagnetic chemically peculiar stars where the Hg abundances suddenly change their degree of overabundance is a major test of the theories which try to explain the anomalous abundances of such stars. Some other important relationships are found which can also serve as tests of theories which purport to explain the properties of these stars.

No abstract

We conducted an ecological analysis of childhood acute lymphoblastic leukaemia-incidence data from children p5 years old during 1992 -1998 from the Surveillance, Epidemiology, and End Results Program in 200 counties and Hawaii. The response variable was the count of cases in each county race -sex stratum, examined in relation to data from the United States Census and the United States Department of Agriculture. The final models for both sexes included race, proportion moved during 1985 -1990, and proportion of households with income X$5000 as potential predictors. Incidence was lower among black boys (rate ratio (RR) ¼ 0.5) and black girls (RR ¼ 0.4) than among other children of the same sex; no other significant racial differences were detected. Incidence was elevated among males (but not females) residing in counties where X50% of the population relocated (RR ¼ 1.5) and among females (but not males) residing in counties where o6% of the households had incomes o$5000 (RR ¼ 1.5). These sex differences in risk factors were unexpected.

No abstract