Effect of vitamin A deprivation on the cholesterol side-chain cleavage enzyme activity of testes and ovaries of rats (Short Communication)

The cholesterol side-chain cleavage enzyme activity is decreased considerably at the mild stage of vitamin A deficiency in rat testes and ovaries and the decrease in activity becomes more pronounced with progress of deficiency. Supplementation of the deficient rats with retinyl acetate, but not retinoic acid, restores the enzyme activity to normal values. The cholesterol side-chain cleavage enzyme of adrenals is not affected by any of the above treatments.

Mesospheric temperature response to variations in geomagnetic activity

Temperature data collected over several years from rocket grenade and other experiments at Point Barrow (Alaska), Fort Churchill (Canada) and Wallops Island (Virginia) have been analysed to determine the effect of geomagnetic activity on the neutral temperature in the mesosphere and to study the latitudinal variation of this effect. An analysis carried out has revealed almost certainly significant correlations between the temperature and the geomagnetic indicies Kp and Ap at Fort Churchill and marginally significant correlations at Barrow and Wallops. This has also been substantiated by a linear regression analysis. The results indicate two types of interdependence between mesospheric temperature and geomagnetic field variations. The first type is the direct heating effect, during a geomagnetic disturbance, which has been observed in the present analysis with a time lag of 3–15 hr at the high latitudes and 36 hr at the middle latitudes. The magnitude of this heating effect has been found to decrease at the lower altitudes. The second type of interrelation which has been observed is temperature perturbations preceding geomagnetic field variations, both presumably caused by a disturbance in atmospheric circulation at these levels.

The effect of solar activity on temperatures in the equatorial mesosphere

A study of the response of neutral temperatures in the equatorial mesosphere to variations in solar activity has been carried out by investigating the correlation between the 10.7 cm solar radio flux and temperatures obtained from a series of 51 rocket soundings conducted over Thumba, India (8°N, 77°E) during the period December 1970–December 1971. A strong positive correlation between these two parameters has been obtained, indicating mesospheric heating effects caused by day-to-day variations in solar EUV emission. The correlation analysis indicates that this response persists over several days and that the peak correlation between the temperatures and the F10.7 index occurs with a time lag of less than 24 hr.

An association and Wilson activity coefficient model for solubilities of aromatic solid pollutants in supercritical carbon dioxide

The solubilities of various solid pollutants in supercritical carbon dioxide were investigated. The intermolecular interactions play a significant role in determining the solubilities of solids in supercritical carbon dioxide. A new model equation was derived by using the concepts of association and activity coefficient model to correlate the solubilities of solids. The model equation combines the association and Wilson activity coefficient models and includes the interaction potentials between the molecules, which are useful in understanding the behavior of the solid solutes in SCCO2. The new model equation involves five adjustable parameters to correlate the solubilities of solids by incorporating the interactions between the molecules. The equation correlated 75 solid systems with an average AARD of around 9%, which was better than the correlations obtained from standard models such as Mendez Santiago-Teja (MT) model and association model. (C) 2012 Elsevier B.V. All rights reserved.