Optical differentiation of amoebic ectoplasm and endoplasmic flow

Optical activity differentiating the flowing and nionflowing amoebic cytoplasm was detected. This evidence indicates mtiolecular alignment in the flow stream and can be used to provide data on the direction of alignmtient. The results were obtained by utilizing a dynamnic polarized-light detection system which is sensitive only to specimenis which possess a preferred axis.     

Evidence for biased gene conversion in concerted evolution of ribosomal DNA

Concerted evolution is the production and maintenance of homogeneity within repeated families of DNA. Two mechanisms--unequal crossing over and biased gene conversion--have been the principal explanations of concerted evolution. Concerted evolution of ribosomal DNA (rDNA) arrays is thought to be largely the result of unequal crossing over. However, concerted evolution of rDNA in parthenogenetic lizards of hybrid origin is strongly biased toward one of two parental sequences, which is consistent with biased gene conversion as the operative mechanism. The apparent gene conversions are independent of initial genome dosage and result in homogenization of rDNA arrays across all nucleolar organizer regions.     

Textural and crystal-fabric anisotropies and the flow of ice masses

Accurate modeling and prediction of glacier response requires a better understanding of the influence of physical anisotropies on creep. To investigate the effects of variations in the degree of preferred crystallographic orientation and ice crystal size on creep, 19 samples of anisotropic glacier ice were deformed in simple shear. Results indicate that the time required for ice samples to reach the minimum strain rate decreases as crystal size increases; an increase in crystal-fabric development from an isotropic fabric to one with a strong single maximum results in an enhancement of the minimum strain rate by a factor of 4; and a doubling of the crystal size results in about a ninefold increase in the minimum strain rate.     

Stratospheric ozone, middle ultraviolet radiation, and carbon-14 measurements of marine productivity

The effects of increased ultraviolet radiation, due to decreased stratospheric ozone, on marine phytoplankton have been investigated with the use of static bottle in situ carbon-14 productivity measurements. The relative biological efficiency for photoinhibition may be used to calculate biologically effective doses and resultant amplification factors. The carbon-14 technique (short-term incubations) is inadequate for assessment of possible large amplification factor photoprocesses that may be ecologically significant.