आँध्रप्रदेश की परुषकवचि (क्रस्टेशियाई) मात्स्यिकी संपदाएं

आँध्रप्रदेश की परुषकवचि (क्रस्टेशियाई) मात्स्यिकी संपदाए

Machine-Learned Potential Energy Surfaces for Free Sodium Clusters with Density Functional Accuracy: Applications to Melting

Gaussian Process Regression-based Gaussian Approximation Potential has been used to develop machine-learned interatomic potentials having density-functional accuracy for free sodium clusters. The training data was generated from a large sample of over 100,000 data points computed for clusters in the size range of N = 40 - 200, using the density-functional method as implemented in the VASP package. Two models have been developed, model M1 using data for N=55 only, and model M2 using additional data from larger clusters. The models are intended for computing thermodynamic properties using molecular dynamics. Hence, particular attention has been paid to improve the fitting of the forces. Interestingly, it turns out that the best fit can be obtained by carefully selecting a smaller number of data points viz. 1,900 and 1,300 configurations, respectively, for the two models M1 and M2. Although it was possible to obtain a good fit using the data of Na55 only, additional data points from larger clusters were needed to get better accuracies in energies and forces for larger sizes. Surprisingly, the model M1 could be significantly improved by adding about 50 data points per cluster from the larger sizes. Both models have been deployed to compute the heat capacities of Na55 and Na147 and to obtain about 40 isomers for larger clusters of sizes N = 147, 200, 201, and 252. There is an excellent agreement between the computed and experimentally measured melting temperatures. The geometries of these isomers when further optimized by DFT, the mean absolute error in the energies between DFT results and those of our models is about 7 meV/atom or less. The errors in the interatomic bond lengths are estimated to be below 2% in almost all the cases

Design and evaluation of sustained release matrix tablets of levofloxacin for effective treatment of microbial infections

The objective of present work was to formulate and evaluate sustained release matrix tablets of levofloxacin for treating microbial infections effectively. Levofloxacin is the active component of the racemate ofloxacin, and used for treating a variety of clinical conditions such as lower respiratory tract infections, acute sinusitis, uncomplicated skin and soft-tissue infections and complicated urinary tract infections. Different formulations were prepared by wet granulation method using various release rate controlling hydrophilic polymers. The formulations were evaluated for hardness, weight variation, friability and drug content uniformity. The in vitro release of drug from the formulations was studied in pH 1.2 acidic buffer and pH 6.8 phosphate buffer, and it was found that the prepared tablets were able to sustain the release of the drug. The release of levofloxacin from the tablets was diffusion controlled and the release mechanism was non-Fickian. For conclusion, the developed formulations may reduce the dosing intervals, reduce the dose related side effects and increase the drug’s efficacy for treating infections.Keywords: Matrix tablets, levofloxacin, HPMC, guar gum, xantham gum, locust bean gum, Amorphophallus starch

Intermolecular Coulombic decay by concerted transfer of energy from photoreceptors to a reaction center

Molecular mechanisms that enable concerted transfer of energy from several photoacceptors to a distinct reaction center are most desirable for the utilization of light-energy. Here we show that intermolecular Coulombic decay, a channel which enables non-local disposal of energy in photoexcited molecules, offers an avenue for such a novel energy-transfer mechanism. On irradiation of pyridine-argon gas mixture at 266 nm and at low laser intensities, we observed a surprisingly dominant formation of argon cations. Our measurements on the laser-power dependence of the yield of the Ar cations reveal that intermolecular Coulombic interactions concertedly localize the excitation energy of several photoexcited pyridines at the argon reaction center and ionize it. The density of the reaction center offers an efficient handle to optimize this concerted energy-transfer. This mechanism paves the way for a new $\pi$-molecular light-harvesting system, and can also contribute to biomolecular stability against photodamage

Selective Breeding and Development of Disease Resistant Broodstock of Black Tiger Shrimp Penaeus monodon Fabricius, 1798

The Indian tiger shrimp Penaeus monodon is the principal species being cultured. Of late hatchery sector is being dependent on wild gravid females due to non response of broodstock to eyestalk ablation. High cost of gravid females compelling the grow-out sector to stock pathogen carrier seeds. Hence domestication of tiger shrimp is essential to produce Specific Pathogen Free (SPF) broodstock / Disease Resistant (DR) broodstock. Merits and demerits of SPF versus DR broodstock are presented. Development of SPF broodstock involves stringent management of environment to arrest the entry of pathogens and more than one economic trait can be selected. Whereas in development of DR broodstockanimals are challenged with the pathogen and a selection of other economic traits are less possible. Resistance in shrimp exists at the species level as well as individual level. Experiment on domestication of P. monodon in which programme was advanced up to F3 generation has revealed the existence of resistance for WSSV at the individual level. Selective breeding programme for development of D R broodstock involves development of disease free base population, forming them into families, production of F1 generation family wise through inbreeding, challenging each family with WSSV at 3-5 g size and rearing survived individuals up to 100 g size, production of F2 generation by random inter crossing between families, advancing the programme up to F5 generation. Development of DR broodstock is imperative to ensure sustainable shrimp productio

Dynamical renormalization group methods in theory of eternal inflation

Dynamics of eternal inflation on the landscape admits description in terms of the Martin-Siggia-Rose (MSR) effective field theory that is in one-to-one correspondence with vacuum dynamics equations. On those sectors of the landscape, where transport properties of the probability measure for eternal inflation are important, renormalization group fixed points of the MSR effective action determine late time behavior of the probability measure. I argue that these RG fixed points may be relevant for the solution of the gauge invariance problem for eternal inflation.Comment: 11 pages; invited mini-review for Grav.Cos

Exploitation of penaeid shrimp resources by small mechanised trawlers off Visakhapatnam, Andhra Pradesh

Small trawlers (9-11 m OAL) fit for short-term cruises (2-7 days) exploit penaeid shrimps up to a depth of 70 m in the Bay of Bengal off Visakhapatnam both in the northern and southern directions. During the period 2001 to 2010, average annual fishing effort was 5,97,412 h. Penaeid shrimp catch varied from 703 t to 4,323 t with average catch per hour (cph) being 3.54 kg. The contribution of penaeid shrimps to total fish landings ranged from 6.7 to 18.32%, both fishing effort and landings of the resource showing increasing trend. Penaeid shrimp landing was supported by 24 species, dominated by Metapenaeus monoceros followed by Metapenaeus dobsoni. Mean annual species composition and cph for each species were estimated for two spells i.e., 2001 to 2005 and 2006 to 2010. Catch per hour for five species declined whereas it increased for the rest 19 species. The cph for penaeid shrimps increased by 103% from spell 1 to spell 2. Expected catch for each year was estimated by Schaefer production model (CEDA; r2=0.72) which showed that the resource was under exploitated during 2001-2005 and overexploited during 2006-2010, which indicate the necessity for restricting fishing effort at present level

Trends in penaeid shrimp landings by sona boats at Visakhapatnam Fishing Harbour, Andhra Pradesh

Sona boats operate mostly in the northern part of the Bay of Bengal up to sand heads. The boats (13-15 m OAL) worthy to conduct voyage fishing for 10-20 days exploit resources upto a depth of 100 m. The present study analysed the trends in penaeid shrimp landings by sona boats at Visakhapatnam Fishing Harbour, for the period from 2001 to 2010. During the period, annual fishing effort ranged from 4,77,710 to 16,31,507 h with an average of 10,15, 230 h. Annual penaeid shrimp catch varied from 1,409 to 7,496 t, average being 4,892 t. Average catch per hour (CPH) was estimated at 4.81 kg. Annual penaeid shrimp contribution from the sona boats to the total fish landings was 10.2 to 22% (average 15.9). Both fishing effort and penaeid shrimp catch showed increasing trend during the period. Penaeid shrimp fishery was supported by 14 genera/species dominated by Metapenaeus monoceros followed by M. dobsoni. Mean annual species composition and CPH for each species were computed for two span, first being 2001-2005 and the second during 2006-2010. The CPH for the penaeid shrimps increased by 1.5% from span-1 to span-2. CPH for smaller shrimp species declined whereas increased for commercial species. Expected catch for each year estimated by Schaefer production model (CEDA; r2=0.72) showed underexploitation during 2001 and 2004; optimum state of exploitation for four years during 2005, 2006, 2007 and 2009 and overexploitation for four years during 2002, 2003, 2008 and 2010. In terms of total fish landings, 2001 and 2002 showed underexploitation, optimum state during six years i.e., 2003, 2006, 2007, 2008, 2009 and 2010; while overexploitation during 2004 and 2005. Considering the exploitation rate of both penaeid shrimps and total fish, by sona boats, the study suggests restriction of fishing effort at the 2009-2010 level to ensure sustainability of the resources

Radiating dipoles in photonic crystals

The radiation dynamics of a dipole antenna embedded in a Photonic Crystal are modeled by an initially excited harmonic oscillator coupled to a non--Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the Photonic Crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes.Comment: Phys. Rev. E, accepte

Fishery and biology of Plesionika quasigrandis Chace, 1985 off Sakthikulangara, south-west coast of India

The fishery and biology of Plesionika quasigrandis Chace, 1985 from Sakthikulangara Fishing Harbour was studied for the period 2006-2008. The average annual catch was 2400 t, forming 28% of the total deep sea shrimp landings at Sakthikulangara. August to November was the most productive period in terms of catch and catch rate. The growth parameters L∞ and K y-1 for males and females were 124 mm, 0.7 and 130 mm, 0.8 respectively. The growth performance index (φ’) and t0 were 4.032, -0.0036 and 4.131, -0.00275 for males and females, respectively with a longevity of 5 years. Recruitment pattern was bimodal with two peaks, one in March and the other in June. The relationship between total length (TL) and total weight (W) revealed an isometric growth in case of females and allometric growth in males. The length at recruitment (Lr) and length at 50% capture (Lc50) was 73; 84.8 mm (males) and 78; 93.4 mm (females), respectively which corresponded to an age (tc) of 1.6 years. The natural mortality, fishing mortality, total mortality, exploitation ratio, exploitation rate and Emax were 0.81, 2.14, 2.95, 0.62, 0.72, 0.90 and 0.88, 2.97, 3.85, 0.71, 0.77, 0.93 for males and females, respectively. The rate of exploitation for P. quasigrandis was found to be lower than the Emax which indicates sustainable utilisation of the resource