Spherical collapse with heat flow and without horizon

We present a class of solutions for a heat conducting fluid sphere, which radiates energy during collapse without the appearance of horizon at the boundary at any stage of the collapse. A simple model shows that there is no accumulation of energy due to collapse since it radiates out at the same rate as it is being generated.Comment: RevTeX, 3 page

Glimpses of the Emerging Technology, Genetic Engineering, and its Applications in Medical Sciences

The history of development of the Genetic Engineering Technology has been brought out with a brief description of the current status of some of the techniques used in gene cloning. The achievements and potential applications of the technology in medical sciences and its possible impact on the Society in future have been discussed, as far as possible, in a semitechnical language

Dynamical Origin of Extrasolar Planet Eccentricity Distribution

We explore the possibility that the observed eccentricity distribution of extrasolar planets arose through planet-planet interactions, after the initial stage of planet formation was complete. Our results are based on ~3250 numerical integrations of ensembles of randomly constructed planetary systems, each lasting 100 Myr. We find that for a remarkably wide range of initial conditions the eccentricity distributions of dynamically active planetary systems relax towards a common final equilibrium distribution, well described by the fitting formula dn ~ e exp[-1/2 (e/0.3)^2] de. This distribution agrees well with the observed eccentricity distribution for e > 0.2, but predicts too few planets at lower eccentricities, even when we exclude planets subject to tidal circularization. These findings suggest that a period of large-scale dynamical instability has occurred in a significant fraction of newly formed planetary systems, lasting 1--2 orders of magnitude longer than the ~1 Myr interval in which gas-giant planets are assembled. This mechanism predicts no (or weak) correlations between semimajor axis, eccentricity, inclination, and mass in dynamically relaxed planetary systems. An additional observational consequence of dynamical relaxation is a significant population of planets (>10%) that are highly inclined (>25deg) with respect to the initial symmetry plane of the protoplanetary disk; this population may be detectable in transiting planets through the Rossiter-McLaughlin effect.Comment: Accepted to ApJ, conclusions updated to reflect the current observational constraint

Morphological changes of Vibrio cholerae organisms in glucose saline

Morphological changes in Vibrio cholerae harvested from 18 hr growth on nutrient agar surface and incubated in glucose saline at 37° have been studied by electron microscopy using metal shadowing, uranyl staining and thin sectioning techniques. Within the 6 hr incubation period, a vacuolar region has been found to separate the cell wall from the protoplasmic body presumably at one polar end. Subsequently such separation has been found all round the periphery of the protoplasmic body, which assumes a round form of average dimension 0.4 ± 0.05 µ. Within the 24 hr incubation period, majority of the cells (60 to 70 %) are rounded and of these a significant fraction (15 to 20 %) contained bodies limited by one single membrane. It is suggested that these bodies represent the protoplasts of V. cholerae

Electron microscopic observations on the excretion of cell-wall material by Vibrio cholerae

Thin sections of Vibrio cholerae harvested during the logarithmic phase of growth in alkaline peptone water or in syncase medium have revealed an excretion process of the cell wall in the form of bulging out and pinching-off of portions. An identical phenomenon has also been revealed in cells harvested after a short period of incubation (1·5 hr) in glucose saline solution at 37°. Particles closely resembling the pinched-off cell-wall structures have been detected by metal shadowing and negative staining techniques in the bacteria-free filtrates of the log phase cultures (in both media) and the glucose saline incubation medium. These particles are in the range 400-1100 Å in size with a maximum frequency in the range 600-800 Å. No similar cell-wall changes have been detected in vibrios-harvested from the stationary phase of growth in any of the culture media, nor in vibrios undergoing plasmolysis. Turbidi-metric tests revealed no significant lysis of the vibrios when harvested during the logarithmic growth phase and incubated for several hours in saline or in Kellenberger buffer as compared to the lysis detected in distilled water. It is suggested that the cell-wall process described represents an excretory mechanism of V. cholerae, and the nature of the products released by the young vibrios and their probable relation with cholera toxin is discussed