Environmental deterioration in Lakshadweep and need for conservation of living resources

The Lakshadweep Archipelago is located on the Laccadive - Chagos ridge, believed to be the submarine extension of the Aravalli mountains. The various atolls rise from a depth ranging from 1500 to 4000 m. The Lakshadweep Archipelago consists of 12 atolls, 3 reefs and 5 submerged banks, all of coral formations. The total land area is about 32 sq km. The height of islands vary from 1 to 1.4 m from MSL

Magnetic Field Uniformity Across the GF 9-2 YSO, L1082C Dense Core, and GF 9 Filamentary Dark Cloud

The orientation of the magnetic field (B-field) in the filamentary dark cloud GF 9 was traced from the periphery of the cloud into the L1082C dense core that contains the low-mass, low-luminosity Class 0 young stellar object (YSO) GF 9-2 (IRAS 20503+6006). This was done using SOFIA HAWC+ dust thermal emission polarimetry (TEP) at 216 um in combination with Mimir near-infrared background starlight polarimetry (BSP) conducted at H-band (1.6 um) and K-band (2.2 um). These observations were augmented with published I-band (0.77 um) BSP and Planck 850 um TEP to probe B-field orientations with offset from the YSO in a range spanning 6000 AU to 3 pc. No strong B-field orientation change with offset was found, indicating remarkable uniformity of the B-field from the cloud edge to the YSO environs. This finding disagrees with weak-field models of cloud core and YSO formation. The continuity of inferred B-field orientations for both TEP and BSP probes is strong evidence that both are sampling a common B-field that uniformly threads the cloud, core, and YSO region. Bayesian analysis of Gaia DR2 stars matched to the Mimir BSP stars finds a distance to GF 9 of 270 +/- 10 pc. No strong wavelength dependence of B-field orientation angle was found, contrary to previous claims.Comment: 18 pages, 6 figures ApJ, accepte

Evaluation of brightness temperature from a forward model of ground-based microwave radiometer

Ground-based microwave radiometers are getting great attention in recent years due to their capability to profile the temperature and humidity at high temporal and vertical resolution in the lower troposphere. The process of retrieving these parameters from the measurements of radiometric brightness temperature (TB) includes the inversion algorithm, which uses the background information from a forward model. In the present study, an algorithm development and evaluation of this forward model for a ground-based microwave radiometer, being developed by Society for Applied Microwave Electronics Engineering and Research (SAMEER) of India, is presented. Initially, the analysis of absorption coefficient and weighting function at different frequencies was made to select the channels. Further the range of variation of TB for these selected channels for the year 2011, over the two stations Mumbai and Delhi is discussed. Finally the comparison between forward-model simulated TBs and radiometer measured TBs at Mahabaleshwar (73.66°E and 17.93°N) is done to evaluate the model. There is good agreement between model simulations and radiometer observations, which suggests that these forward model simulations can be used as background for inversion models for retrieving the temperature and humidity profiles

Preliminary report on a reconnaissance survey of the major coastal and marine ecosystems in Gulf of Kutch

The region of Gulf of Kutch was possibly more an arid zone in the pleistocene, almost approaching to a desert condition, than what it is at present. The gulf is believed to be the result of a wide indentation or subsidence that allowed encroachment of the sea in the geological past. The whole area is still supposed to be seismically unstable. The Gulf of Kutch covers an area of circa 7,350 sq. km with a maximum depth of 60 m. The tidal range varies from 3.06 to 5.89 m with an average of 4 m. The intertidal zones are sandy and muddy or with sandstones of vast expanse and prolonged exposure

A timeline for massive star-forming regions via combined observation of o-H2_2D+^+ and N2_2D+^+

Context: In cold and dense gas prior to the formation of young stellar objects, heavy molecular species (including CO) are accreted onto dust grains. Under these conditions H$_3^+$ and its deuterated isotopologues become more abundant, enhancing the deuterium fraction of molecules such as N$_2$H$^+$ that are formed via ion-neutral reactions. Because this process is extremely temperature sensitive, the abundance of these species is likely linked to the evolutionary stage of the source. Aims: We investigate how the abundances of o-H$_2$D$^+$ and N$_2$D$^+$ vary with evolution in high-mass clumps. Methods: We observed with APEX the ground-state transitions of o-H$_2$D$^+$ near 372 GHz, and N$_2$D$^+$(3-2) near 231 GHz for three massive clumps in different evolutionary stages. The sources were selected within the G351.77-0.51 complex to minimise the variation of initial chemical conditions, and to remove distance effects. We modelled their dust continuum emission to estimate their physical properties, and also modelled their spectra under the assumption of local thermodynamic equilibrium to calculate beam-averaged abundances. Results: We find an anticorrelation between the abundance of o-H$_2$D$^+$ and that of N$_2$D$^+$, with the former decreasing and the latter increasing with evolution. With the new observations we are also able to provide a qualitative upper limit to the age of the youngest clump of about 10$^5$ yr, comparable to its current free-fall time. Conclusions: We can explain the evolution of the two tracers with simple considerations on the chemical formation paths, depletion of heavy elements, and evaporation from the grains. We therefore propose that the joint observation and the relative abundance of o-H$_2$D$^+$ and N$_2$D$^+$ can act as an efficient tracer of the evolutionary stages of the star-formation process

Preliminary report on a reconnaissance survey of the major coastal and marine ecosystems in Gulf of Kutch

The region of Gulf of Kutch was possibly more an arid zone in the pleistocene, almost approaching to a desert condition, than what it is at present. The Gulf of Kutch covers an area of circa 7,350 sq. km with a maximum depth of 60 m. The tidal range varies from 3.06 to 5.89 m with an average of 4 m. The intertidal zones are sandy and muddy or with sandstones of vast expanse and prolonged exposure. The present report is based on a six weeks survey carried out in the Gulf of Kutch mainly around Okha and Jamnagar in 1978 with a view to obtaining additional information on the major marine and coastal habitats, particularly the coral formations and the mangroves. The prevailing physical features,animal communities and the visible ecological impact on the ecosystems due to human interference are briefly discussed. The most important physical factor that at present aifect the marine life of Gulf of Kutch seems to be the high degree of sedimentation. Existence of extreme physical conditions such as prolonged exposure due to very high tidal amplitude is a major factor that applies constraints on the colonization of many marine animals. The higher rate of sedimentation in the inshore waters of Gulf of Kutch appears to be the most deleterious physical factor that affect the marine fauna at present

On the occurrence of Acanthaster planci (the crown-of-thorns) at Minicoy Atoll.

The predation of coral-polyps by the multi-armed star fish Acanthaster planci is identified during the last two decades as a major biological factor that causes large scale death to reef corals at several parts of the Indo-Pacific. During a recent visit by a team of scientists from Central Marine Fisheries Research Institute,the presence of this star fish in the lagoon of Minicoy Atoll was noticed in November, 1979.Many control measures of star fishes have been practised elsewhere in the Pacific. However, hand-picking of the adults with the aid of pointed spears and killing them with formalin or ammonia solution is the most eifective.Careful search among the corals is required, since the crown-of-thorns hide under the crevices during day time

Fishery, biology and stock assessment of small tunas

Fishery Survey of India has brought out publications on the results of the operations of chartered vessels in the oceanic tuna fishery (Sudarsan el. al., 1991; FSI, 1992) and a bibliography of tuna fisheries in Indian seas (John and Bhargava, 1992). These publications have updated our information on the coastal and oceanic tuna fishery resources from the Indian EEZ

Enhanced emission from Si-based light-emitting diodes using surface plasmons

Excitation of surface plasmons on metallic nanoparticles has potential for increasing the absorption and emission from thin Si devices. We report an eight-fold enhancement in electroluminescence from silicon-on-insulator light-emitting diodes at 900nm via excitation of surface plasmon resonance in silvernanoparticles, along with a redshift in the electroluminescence by 70nm by overcoating the nanoparticles with ZnS. The enhancement is due to coupling between the electromagnetic excitations of the silvernanoparticles and the waveguide modes.The Centre of Excellence for Advanced Silicon Photovoltaics and Photonics is supported under the Australian Research Council’s Centres of Excellence Scheme

Frequency of occurrence of Heterosaccus indicus(Rhizocephala) on the edible crab Neptunus pelagicus in the Gulf of Mannar

Heterosaccus indicus Boschma parasitises the blue swimming crab Neptunus pelagicus. During January 1967, the authors examined 1836 crabs caught by crab titps in the vicinity of the Regional Centre of Central Marine Fisheries Research Institute, Mandapam Camp. While 12.2 per cent of the total population examined was found to be infe^d, 28.1 per cent of the females had parasites. The ratio of female hosts to male was 1:1.3.: It was also observed that S .8 per cent of the infested crabs possessed more than one parasite