Developments and achievements in atmospheric sciences and space meteorology in India

Space research in India began in the early sixties, with the establishment of the Thumba Equatorial Rocket Launching Station. Indigenously developed rocket payloads were carried in foreign rockets and flown for studying various atmospheric parameters, which are unique to the tropics. In the seventies, Indian-made rockets became available. Since then, there has been rapid progress in the technical advancement, which helped the atmospheric scientists in taking up more challenging and contemporary problems, related to mesospheric winds, ionospheric irregularities, stratospheric ozone, role of aerosols in atmospheric radiative transfer, etc. India entered into the satellite era in 1975, with the development of the Aryabhatta satellite, the first Indian experimental satellite, followed by Bhaskara-1 in 1979, which carried a microwave radio meter for retrieval of atmospheric water vapour and cloud liquid water contents. Since then, there have been several satellites, such as the INSAT series for meteorology and communication, Indian Remote Sensing (IRS) satellite series, and Stretched Rohini Satellite System (SROSS) for in situ observation of the ionosphere, which are all built in India and launched from Indian soil. High quality data being obtained from these satellite missions are helping scientists in taking up problems that are of regional and global scales and in studying the changes that are taking place in the earth atmosphere system, in a more holistic way. This paper attempts to provide an overview of the scientific developments and highlights some results

Some aspects of the hydrographical conditions of the backwaters around Willingdon Island (Cochin)

The Cochin backwaters which form more or less a northward extension of the Vembanad lake have all the characteristics of a typical estuary. On the southern side of the backwaters there is the influx of waters of the Pampa river and on the northern side, the Periyar. The channel to the west opening out into the Arabian Sea is the main area for the exchange between the sea and the estuary. These backwaters thus form a very interesting subject of study not only from the point of view of the seasonal variation in the various hydrographic parameters, but also this is an area where there is considerable scope for a theoretical study of magnitude of exchanges across the transition. The tidal exchanges across the channel are fairly high, as also the influx of freshwater. Apart from the influence of monsoon rains and the considerable amount of evaporation during hot months in this shallow environment, the influence of various types of phenomena in the Arabian Sea such as upwelling, sinking, coastal piling etc. is quite considerable and these result in certain characteristic variations in the hydrographical and associated conditions in this area. The present paper is an attempt to work out the main pattern of distribution of the various parameters—spatial as well as temporal and to indicate the mixing processes which make this area quite interesting not only to the hydrographer but to the biologist as well

Hydrographical features of the continental shelf waters off Cochin during the years 1958 and 1959

The hydrographical features and the seasonal variations in the physical and chemical conditions of the shelf waters off Cochin form an interesting subject of study. In this region, as well as in other areas along this coast, the influence of the southwest monsoon is very profound while that of the north-east monsoon is at best indirect. The changes in the conditions of these waters from time to time more or less reflect the changing pattern in the climatic conditions. The main circulation in the Arabian Sea results in the establishment of a surface current along this coast which reverses itself in the course of the year. This stream is southerly (i.e., towards south) when the circulation in the open part of the Arabian Sea is clockwise and northerly when the circulation is counter-clockwise. Associated with these drifts are the upwelling and sinking along this coast. The existence of these phenomena has been pointed out earlier by Sastry and Myrland (1960). In a preliminary analysis of the wind data during the period when upwelling is in evidence Jayaraman (1959) has pointed out that the prevailing winds are somewhat favourable for upwelling to take place, while Banse (1959) has regarded the prevailing current system and not the wind to be the main cause of the upwelling. It is not, however, the purpose of the present paper to discuss in detail the possible causes for upwelling or sinking along this coast, but it is intended to indicate that these various phenomena and the associated water movements could provide an explanation for the hydrographical features and their seasonal variations in the shelf waters along this coast. The interest is all the greater because Banse has shown that the demersal fisheries along this coast are fully dependent upon the prevailing hydrographic conditions

Autonomous Motility of Active Filaments due to Spontaneous Flow-Symmetry Breaking

We simulate the nonlocal Stokesian hydrodynamics of an elastic filament which is active due a permanent distribution of stresslets along its contour. A bending instability of an initially straight filament spontaneously breaks flow symmetry and leads to autonomous filament motion which, depending on conformational symmetry, can be translational or rotational. At high ratios of activity to elasticity, the linear instability develops into nonlinear fluctuating states with large amplitude deformations. The dynamics of these states can be qualitatively understood as a superposition of translational and rotational motion associated with filament conformational modes of opposite symmetry. Our results can be tested in molecular-motor filament mixtures, synthetic chains of autocatalytic particles, or other linearly connected systems where chemical energy is converted to mechanical energy in a fluid environment.Comment: 7 pages, 3 figures; contains supplemental text; movies at http://proofideas.org/rjoy/gallery; published in Physical Review Letter

Face selectivity in electrophilic additions to methylenenorsnoutanes: relative importance of through-space, through-bond and electrostatic interactions

4-Substituted 9-methylenenorsnoutanes undergo a variety of electrophilic additions with a small but consistent syn preference; ab initio MESP maps indicate that electrostatic factors and through-space interaction between the double bond and cyclopropane Walsh orbitals are unimportant in determining the face selectivity, while AM1 transition state energetics suggest that the observed preferences are determined primarily by through-bond interactions

Hydrography of the Laccadives offshore waters

The importance of the waters around the Laccadives ' with their special ecological conditions and their influence on the adjacent coastal waters of the mainland of India' has been indicated in an interesting review of the oceanographical investigations in the eastern section of the Arabian Sea by Jones (1959). The Laccadives region is particularly interesting to the oceanographer, because of the presence of the submarine ridge—the Laccadives-Chagos Ridge—which has a great influence on the circulation of the water masses in this part of the Indian Ocean. The ridge contributes, to some extent, to the enrichment of the upper waters of the mid-ocean as has been suggested by Cooper (1957). . To the fishery investigator, this region is equally interesting, as it is known to support a rich fishery, particularly of the pelagic type. A detailed hydrographic survey of this region is, therefore, considered necessary as it would help to throw light on several problems of oceanographical and fishery interest

Theory for Magnetic Anisotropy of Field-Induced Insulator-to-Metal Transition in Cubic Kondo Insulator YbB_{12}

Magnetization and energy gap of Kondo insulator YbB_{12} are calculated theoretically based on the previously proposed tight-binding model composed of Yb 5d$\epsilon$ and 4f $\Gamma_8$ orbitals. It is found that magnetization curves are almost isotropic, naturally expected from the cubic symmetry, but that the gap-closing field has an anisotropy: the gap closes faster for the field in (100) direction than in (110) and (111) directions, in accord with the experiments. This is qualitatively understood by considering the maximal eigenvalues of the total angular momentum operators projected on each direction of the magnetic field. But the numerical calculation based on the band model yields better agreement with the experiment.Comment: 4 pages, 4 figures, to appear in J. Phys. Soc. Jp

Towards Upcycling Biomass-Derived Crosslinked Polymers with Light

Photodegradable, recyclable, and renewable, crosslinked polymers from bioresources show promise towards developing a sustainable strategy to address the issue of plastics degradability and recyclability. Photo processes are not widely exploited for upcycling polymers in spite of the potential to have spatial and temporal control of the degradation in addition to being a green process. In this report we highlight a methodology in which biomass-derived crosslinked polymers can be programmed to degrade at ≈300 nm with ≈60 % recovery of the monomer. The recovered monomer was recycled back to the crosslinked polymer

Pressure-induced metallization in solid boron

Different phases of solid boron under high pressure are studied by first principles calculations. The $\alpha$-B$_{12}$ structure is found to be stable up to 270 GPa. Its semiconductor band gap (1.72 eV) decreases continuously to zero around 160 GPa, where the material transforms to a weak metal. The metallicity, as measured by the density of states at the Fermi level, enhances as the pressure is further increased. The pressure-induced metallization can be attributed to the enhanced boron-boron interactions that cause bands overlap. These results are consist with the recently observed metallization and the associated superconductivity of bulk boron under high pressure (M.I.Eremets et al, Science{\bf 293}, 272(2001)).Comment: 14 pages, 5 figure

DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers

Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein–DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents