The mini trawl fishery of Kerala

Mini trawl operation started in Kerala during 1987, is another post motorisation innovation like the ring seine by the artisanal fishers. During 1987-2002, annual mini trawl landings ranged between 1,500 and 18,600 tonnes. The minimum landing was in 1987, when this gear was introduced for the first time in Kerala and the peak landings of 18,600 tonnes was during 1997. The low investment of the mini trawls at the initial stage has attracted more fishermen. A trend in component group landings and seasonal trends have been cited in this information. They could earn more for their livelihood with less investment. Prawns which come to the nearby shore for breeding, are caught by this gear. Appropriate management measures need to be taken to regulate this fishery for ensuring sustrainbility and better livelihood for the artisanal sector

Broadband energy-efficient optical modulation by hybrid integration of silicon nanophotonics and organic electro-optic polymer

Silicon-organic hybrid integrated devices have emerging applications ranging from high-speed optical interconnects to photonic electromagnetic-field sensors. Silicon slot photonic crystal waveguides (PCWs) filled with electro-optic (EO) polymers combine the slow-light effect in PCWs with the high polarizability of EO polymers, which promises the realization of high-performance optical modulators. In this paper, a broadband, power-efficient, low-dispersion, and compact optical modulator based on an EO polymer filled silicon slot PCW is presented. A small voltage-length product of V{\pi}*L=0.282Vmm is achieved, corresponding to an unprecedented record-high effective in-device EO coefficient (r33) of 1230pm/V. Assisted by a backside gate voltage, the modulation response up to 50GHz is observed, with a 3-dB bandwidth of 15GHz, and the estimated energy consumption is 94.4fJ/bit at 10Gbit/s. Furthermore, lattice-shifted PCWs are utilized to enhance the optical bandwidth by a factor of ~10X over other modulators based on non-band-engineered PCWs and ring-resonators.Comment: 12 pages, 4 figures, SPIE Photonics West Conference 201

Oxidation studies. I. Oxidation of primary alcohols by peroxydisulfate

Results on the oxidation of primary alcohols (methanol, ethanol, n-propanol, n-butanol and isobutanol) by peroxydisulfate in aqueous solution in the temperature range 50°-80°, under uncatalysed, Ag+ catalysed and deaerated conditions are presented. Oxygen was found to have a retarding effect on the rate of peroxydisulfate disappearance, -RS2O3−, and the inhibition period was a maximum in the case of ethanol and isobutanol. Both under uncatalysed and Ag+ catalysed conditions -RS2O3− varied with [S2O8-]3/2 for all the alcohols; -RS2O3− was independent of alcohol concentration for all the alcohols except for methanol and ethanol where a one-half order with respect to [alcohol] was observed. In the Ag+ catalysed oxidation -RS2O3− varied as [Ag+]½ with all the alcohols. The effect of [H+], ionic strength, temperature, initially added product of the reaction on the rate are discussed and the stoichiometries of the reactions determined. In the light of the observed results, reaction mechanisms are postulated with SO4•− as the reactive species formed by thermal decomposition of S2O8− under uncatalysed conditions and by the interaction of Ag+ and S2O8- under Ag+ catalysed conditions. The existence of Ag++ in catalysed reactions is postulated. The values of rate constants, frequency factors, energies of activation entropies of activation, etc., were evaluated

Vortex behavior near a spin vacancy in 2D XY-magnets

The dynamical behavior of anisotropic two dimensional Heisenberg models is still a matter of controversy. The existence of a central peak at all temperatures and a rich structure of magnon peaks are not yet understood. It seems that the central peaks are related, in some way, to structures like vortices. In order to contribute to the discussion of the dynamical behavior of the model we use Monte Carlo and spin dynamics simulations as well analytical calculations to study the behavior of vortices in the presence of nonmagnetic impurities. Our simulations show that vortices are attracted and trapped by the impurities. Using this result we show that if we suppose that vortices are not very much disturbed by the presence of the impurities, then they work as an attractive potential to the vortices explaining the observed behavior in our simulations.Comment: 4 pages, 6 figure

Monte Carlo study of the critical temperature for the planar rotator model with nonmagnetic impurities

We performed Monte Carlo simulations to calculate the Berezinskii-Kosterlitz-Thouless (BKT) temperature $T_{BKT}$ for the two-dimensional planar rotator model in the presence of nonmagnetic impurity concentration $(\rho)$. As expected, our calculation shows that the BKT temperature decreases as the spin vacancies increase. There is a critical dilution $\rho_c \approx 0.3$ at which $T_{BKT} =0$. The effective interaction between a vortex-antivortex pair and a static nonmagnetic impurity is studied analytically. A simple phenomenological argument based on the pair-impurity interaction is proposed to justify the simulations.Comment: 5 pages, 5 figures, Revetex fil

1H-1,2,4-Triazol-4-ium (3,4-dichloro­phen­yl)methane­sulfonate

In the title molecular salt, C2H4N3 +·C7H5Cl2O3S−, C—C—S angle [112.25 (18)°] deviates slightly from that expected for ideal sp 3-hybridization geometry. In the crystal, the components are linked by N—H⋯O and bifurcated N—H⋯(O,O) hydrogen bonds into chains parallel to [110]

Marine fisheries of the south-west coast of India during 2008

The south-west region comprising the states of Kerala, Karnataka and Goa with a coastline of 994 km and 7.83 lakh fishermen population, had been the most productive and the largest contributor to the country’s total marine fish landings. Marine fish production in this region during the year 2008 has been estimated as 11.11 lakh t, contributing about 34.5% to the all India landing

Estimated marine fish landings (in tonnes)in India during 2002 and 2003

Estimated marine fishing landing in India during 2002 and 2003 is 2.59 and 2.58 millon tonnes respectively. Gear wise landing were also estimated during this period

Discommensurational and Inhomogeneous States Induced by a Strong Magnetic Field in Low-Dimensional Antiferromagnets

Anisotropic antiferromagnetic systems of dimensionality greater than one in an external field are shown to exhibit a complicated array of ground states depending on the spin structure of the surface. The simplest structure that exhibits these effects is the spin ladder with the surface being the ladder end, which can be either compensated or non-compensated spins. The structure with the compensated end has a surface spin flop phase, the non-compensated end has a discommensurational phase, and the transition to these phases can be either first or second order with a tricritical point.Comment: 10 page