Absorption enhancement due to scattering by dipoles into silicon waveguides

We develop an optical model for absorption enhancement and diffuse reflectance by metal nanoparticles on a siliconwaveguide. A point dipole treatment is used, including the effects of the waveguide on both the angular emission spectrum and scattering cross section of the dipoles. The model agrees very well with our experimental results of greatly enhanced electroluminescence and photocurrent from silicon-on-insulator light-emitting diodes and also gives very good agreement with previously reported diffuse reflectance measurements. The results suggest that the main mechanism in the enhancement of diffuse reflectance in this system is a dramatic enhancement in the scattering cross section of waveguided light, rather than a waveguide-mediated dipole-dipole interaction. We also put lower bounds on the radiative efficiency of scattering by the nanoparticles.One of the authors K.R.C. acknowledges the support of an Australian Research Council fellowship. The authors acknowledge the support of the Centre of Excellence for Advanced Silicon Photovoltaics and Photonics, supported by the Australian Research Council

जलकृषि में हरित जल प्रौद्योगिकी

कृपया पूरा लेखा पढ

Hydrological conditions of marine fish culture ponds and adjacent inshore waters of Palk Bay near Mandapam during the North-East Monsoon period

In recent years, attempts were being made in India to utilise the coastal lagoons, estuaries and other water bodies for fish culture practices by which the protein uptake of our masses could be increased. Tampi (1960) has proved that the coastal lagoons with low biological productivity can be developed into fish farm

Synthesis, Characterization and Activity of Sulphate-modified V2O5/SnO2 Catalysts

Sulphate-modified V2O5/SnO2 catalysts were prepared by a simple impregnation method and characterized using different physicochemical techniques, such as EDX, BET-SA, XRD, FT-IR, TGA and 51V NMR spectroscopy. A simple, effective and environmentally friendly method for the gas phase conversion of cyclohexanone oxime to ε-caprolactam by these modified catalysts is presented. The optimal protocol allows ε-caprolactam to be synthesized in excellent yields. NH3-TPD and cumene conversion reactions were used to determine the acid structural properties of the catalysts. Definite correlation was observed between the concentration of medium strength acid sites or Brønsted sites and the ε-caprolactam selectivity. Time-on-stream studies showed fast decline in the activity of the catalyst resulting fromthe basic nature of the reactant and product molecules.Keywords: Sulphated V2O5/SnO2 catalysts, acidity, vapour phase Beckmann rearrangemen

Pathway of human AS3MT arsenic methylation

A synthetic gene encoding human As(III) S-adenosylmethionine (SAM) methyltransferase (hAS3MT) was expressed, and the purified enzyme was characterized. The synthetic enzyme is considerably more active than a cDNA-expressed enzyme using endogenous reductants thioredoxin (Trx), thioredoxin reductase (TR), NADPH, and reduced glutathione (GSH). Each of the seven cysteines (the four conserved residues, Cys32, Cys61, Cys156, and Cys206, and nonconserved, Cys72, Cys85, and Cys250) was individually changed to serine. The nonconserved cysteine derivates were still active. None of the individual C32S, C61S, C156S, and C206S derivates were able to methylate As(III). However, the C32S and C61S enzymes retained the ability to methylate MAs(III). These observations suggest that Cys156 and Cys206 play a different role in catalysis than that of Cys32 and Cys61. A homology model built on the structure of a thermophilic orthologue indicates that Cys156 and Cys206 form the As(III) binding site, whereas Cys32 and Cys61 form a disulfide bond. Two observations shed light on the pathway of methylation. First, binding assays using the fluorescence of a single-tryptophan derivative indicate that As(GS)3 binds to the enzyme much faster than inorganic As(III). Second, the major product of the first round of methylation is MAs(III), not MAs(V), and remains enzyme-bound until it is methylated a second time. We propose a new pathway for hAS3MT catalysis that reconciles the hypothesis of Challenger ((1947) Sci. Prog., 35, 396-416) with the pathway proposed by Hayakawa et al. ((2005) Arch. Toxicol., 79, 183-191). The products are the more toxic and more carcinogenic trivalent methylarsenicals, but arsenic undergoes oxidation and reduction as enzyme-bound intermediates

Trends in the yield of exploited sciaenid fishery resources along the Indian coasts

In the present account a descriptive analysis is made on the recent trends in the yield of exploited sciaenid fishery resources along the coasts of India during the period, 1966-'84. The all-India state wise catch trends in the order of abundance during the period, 1966-'82 are summarized

उत्तर तमिलनाडु के कूटल्लूर, पषयार और कावेरिपट्टणम से तारली की भारी पकड

कृपया पूरा लेखा पढ

Rearing of prawn larvae for seed production

Rearing the newly hatched prawn larvae is the most demanding of the procedures in hatchery production of seeds. Freshly spawned eggs of the penaeid prawn hatch out into nauplii which pass through protozoea and mysis stages before metamorphosing into post larvae

Floral development and potential pollinators of Syzygium myhendrae (Bedd. ex Brandis) Gamble, a wild endemic tree of the Southern Western Ghats, India

Syzygium myhendrae, is a semi-evergreen, endemic and endangered tree species of the Southern Western Ghats, India which exhibits bi-annual mode of flowering and fruiting behaviour. This research is specifically aimed to observe the sequence of morphological processes occurring during floral development and to identify the potential pollinators from the different floral visitors. These aims are achieved by examining the individual trees of candidate species during their flowering season. Sticky traps, bee bowls, sweep nets and pan traps were used to capture floral visitors at the anthesis stage. Visitation frequency and visitor activity index were calculated to distinguish effective pollinators from visitor insects. The results showed nine stages in flower development starting from flower bud emergence to fruit ripening, which took 6-9 weeks. Nine species of insects were recorded as visitors. Honey bees (Apis cerana, ApisMdorsata and Tetragonula iridipennis), butterflies (Hypolimnas misippus,pachilopta pandiana), wasp species, beetle species, fly species were exclusively visiting the flowers of the candidate species. Among the honey bees, Apis dorsata showed high visitation frequency (0.40±0.01) followed by Apis cerana (0.31±0.02) and Tetragonula iridipennis (052±0.02). As per the visitation frequency, it can be concluded that Apis dorsata was the most frequent and effective pollinator

Handbook of training programmes

The Indian Council of Agricultural Research has established specialised Trainers' Training Centres in order to meet the demand of adequately trained teachers and trainers in agriculture and allied subjects to impart training on the principles of learning by doing. The TTCs offer in-service training courses for the trainers/instructors of the extension training centres, agricultural schools and teachers dealing with work experience and vocational courses in high schools and higher secondary schools. In addition to these programmes, the TTCs also offer skill oriented training programmes to entrepreneurs and progressive farmer