Air density at heights near 200 km from the orbit of 1969-20B

The rocket of Cosmos 268, 1969-20B, entered orbit on 5 March 1969, with an initial perigee height of 230 km and inclination of 48.40°. Accurate orbits were computed at RAE from all available observations. Using the values of perigee height from the RAE orbit and decay rates from Spacetrack bulletins, 103 values of density have been calculated between July 1969 and February 1970. On three occasions when geomagnetic activity was strong there were sudden increases in density. When the density was corrected to a fixed height, the semi-annual variation was apparent. There was a strong minimum in July 1969, a maximum in October–November 1969 and a weak minimum in January 1970.     

A comparison of the incidence of five pathological conditions in soft-shell clams, Mya arenaria, from environments with various pollution histories

The distribution of the occurrences and co-occurrences of five pathological conditions in samples of the soft-shell clam, Mya arenaria, from 17 locations on the east coast of the United States were compared by two different analytical techniques. 1. The relative fit of Poisson and Lagrange-Poisson distributions to the data were related to the mortality rate and spread of the pathological conditions. 2. A severity index based on a matrix of occurrences and co-occurrences, and the analysis of its eigenvectors were used to measure and to characterise the severity of the spread. These two techniques were compared with the help of a cluster analysis and discussed in the context of the pollution history of the seventeen locations studied. Although causal inferences cannot be drawn, the analyses suggested that crude oils and heavy metals had less effect on the incidence of hyperplasia and neoplasia than more refined petrochemicals. However, neoplasia was found in both clean and polluted environments.     

Biogeochemical climatologies in the Ross Sea, Antarctica: seasonal patterns of nutrients and biomass

The seasonal patterns of nutrient (nitrate and silicic acid) and chlorophyll distributions in the Ross Sea are formulated by two independent methods. The first procedure compiles all available data from cruises from 1970 to the present and generates a three-dimensional grid for the months from November through February using an iterative difference-correction scheme. The second method uses a three-dimensional circulation model and the phytoplankton standing stock climatology to investigate the effects of currents and phytoplankton uptake on nutrient distributions. The two approaches produced similar results, although the circulation model produced distributions that were more variable in space due to its finer resolution. The nutrient distributions were characterized by elevated concentrations in early spring and gradual reductions to ca. 15 and 40 μM (nitrate and silicic acid, respectively) in summer. Nutrient depletion did not occur despite the favorable growth conditions (elevated macronutrient concentrations, strong vertical stratification) in summer, suggesting that an alternative limitation (such as by dissolved iron concentrations) occurs. Chlorophyll concentrations reached ca. 6 μg l⁻¹ in December and declined thereafter. Seasonal primary production calculated from the nitrate deficits and the circulation model suggested that production was ca. 73 g C m⁻², slightly lower but similar to other estimates using independent methods. Using the nutrient climatology, losses (vertical flux plus respiration) through Feb. 15 from the upper 100 m were ca. 50% of the seasonal production, and the rest of the organic production was removed after that date. Results also suggest that carbon export from the surface layer may vary significantly in space and time.