The Stability of an Isentropic Model for a Gaseous Relativistic Star

We show that the isentropic subclass of Buchdahl's exact solution for a gaseous relativistic star is stable and gravitationally bound for all values of the compactness ratio $u [\equiv (M/R)$, where $M$ is the total mass and $R$ is the radius of the configuration in geometrized units] in the range, $0 < u \leq 0.20$, corresponding to the {\em regular} behaviour of the solution. This result is in agreement with the expectation and opposite to the earlier claim found in the literature.Comment: 9 pages (including 1 table); accepted for publication in GR

Induction of sex conversion in male Vitis

Shoot girdling, widely different levels of nitrogen and photoperiod and a number of chemical agents were ineffective in promoting sex conversion in a male V. vinifera (sylvestris) clone 030-44.The cytokinins SD 8339, zeatin, benzyladenine and kinetin converted sex from male to hermaphrodite in the clone 030-44. The first two cytokinins were more effective than the others. A concentration of 1000 ppm of SD 8339 was the most effective, followed in decreasing order by 500 and 100 ppm. Treatment was most effective at the time of megaspore mother cell formation.SD 8339 also induced sex conversion in other male clones and seedling vines of V. vinifera L. (sylvestris) and in male clones of other Vitis species, and a species hybrid 'Ganzin 1'.In male clones and seedling vines of V. vinifera L. (sylvestris), there was no correlation in frequency of natural sex conversion and that induced by SD 8339, but such a correlation was found in male clones. of other Vitis species and a species hybrid.The cytokinins did not affect pollen viability and the seeds obtained germinated normally.Association of natural sex conversion with endogenous cytokinins in male vines of Vitis is discussed.Two possible practical applications of this method of sex conversion by cytokinins are also mentioned

Studies on sex conversion in male Vitis vinifera L. (sylvestris)

The appearance of functionally hermaphroditic flowers and mature seeded berries on otherwise male vines was defined as a natural sex conversion from functionally male to functionally hermaphroditic flowers. Sex conversion was investigated in vegetatively propagated vines of the wild male V. vinifera clone 030-44 derived from a seed sample collected in Iran. Frequency of sex conversion varied markedly among inflorescences on the same vine, among vines side by side, and from season to season, which implicated the effect of environment, both local and seasonal.Studies on vegetative selection for high fruitfulness revealed that sex conversion was not due to somatic mutation or any vegetative syndrome within the vine

Conversion and determination of sex in Vitis vinifera L. (sylvestris)

Sex conversion in the male V. vinifera (sylvestris) clone 030-44 could not be attributed to germinal mutation of the major gene for sex. The differences in sex expression among male seedling vines can best be explained on the basis of an undetermined number of minor modifying genes able to shift a very sensitive threshold. The frequency of sex conversion within a given seedling vine was greatly influenced by environmental, both local and seasonal, conditions. The following facts were established in Vitis vinifera L. (sylvestris): (1) the male sex is heterogametic and is inherited as a simple Mendelian factor, maleness being completely dominant;(2) homozygous males are as viable as heterozygous males, they are phenotypically alike and can only be identified by breeding tests;(3) pure and hermaphroditic males are genetically alike as far as the major gene for sex is concerned;(4) sex chromosomes are not differentiated, either morphologically or physiologically.A pair of alleles, SuF and Sum, were used to explain the results obtained on selfing the hermaphroditic male clone 030-44. The gene SuF determines maleness and its allele Sum in homozygous condition determines femaleness. The gene SuF is completely dominant over its allele Sum. The genotypes of the homozygous and heterozygous males are SuF SuF and SuF Sum respectively, and that of the female is Sum Sum. The evolution of cultivated V. vinifera hermaphrodites in the light of present results is discussed

Theory of defect-mediated ionic transport in Li, Na and K beta and beta prime prime aluminas

Alkali metal $\beta$/$\beta^{\prime\prime}$ aluminas are among the fastest ionic conductors, yet little is understood about the role of defects in the ion transport mechanism. Here, we use density functional theory (DFT) to investigate the crystal structures of $\beta$ and $\beta^{\prime\prime}$ phases, and vacancy and interstitial defects in these materials. We find that charge transport is likely to be dominated by alkali metal interstitials in $\beta$-aluminas and by vacancies in $\beta^{\prime\prime}$ aluminas. Lower bounds for the activation energy for diffusion are found by determining the minimum energy paths for defect migration. The resulting migration barriers are lower than the experimental activation energies for conduction in Na $\beta$ and $\beta^{\prime\prime}$ aluminas, suggesting a latent potential for optimization. The lowest activation energy of about 20 meV is predicted for correlated vacancy migration in K $\beta^{\prime\prime}$ alumina

Evaluation of Snow Parameters using Passive Microwave Remote Sensing

The study of snow characteristics using conventional techniques for vast, rugged andremote snow covered areas of Himalayas is very difficult. In the present study, the satellite dataof SSM/I sensor has been used. Changes in snow accumulation result in related variations inpassive microwave brightness temperature. This study attempts to develop new algorithms usingbrightness temperature for snow water equivalent (SWE) and snow depth that will suit theIndian Himalayan conditions. The snow and meteorological data recorded in the field is usedto determine the empirical coefficients, which have been further used in the algorithmdevelopment. The parameters evaluated can be used as the input for the avalanche risk analysis,as one can estimate average snow depth and SWE of the area which are main input for avalancheforecasting. Algorithms are further used for the prediction of snow depth and SWE for subsequentwinters using the brightness temperature. A good correlation was found between the predictedand the observed values from the ground observatory data