Modeling of a reacting nanofilm on a composite substrate

This article provides a detailed computational analysis of the reaction of dense nanofilms and the heat transfer characteristics on a composite substrate. Although traditional energetic compounds based on organic materials have similar energy per unit weight, non-organic material in nanofilm configuration offers much higher energy density and higher flame speed. The reaction of a multilayer thin film of aluminum and copper oxide has been studied by varying the substrate material and thicknesses. The numerical analysis of the thermal transport of the reacting film deposited on the substrate combined a hybrid approach in which a traditional two-dimensional black box theory was used in conjunction with the sandwich model to estimate the appropriate heat flux on the substrate accounting for the heat loss to the surroundings. A procedure to estimate this heat flux using stoichiometric calculations is provided. This work highlights two important findings. One is that there is very little difference in the temperature profiles between a single substrate of silica and a composite substrate of silicon silica. Secondly, with increase in substrate thickness, the quenching effect is progressively diminished at a given speed. These findings show that the composite substrate is effective and that the average speed and quenching of flames depend on the thickness of the silica substrate, and can be controlled by a careful choice of the substrate configuration. (C) 2011 Elsevier Ltd. All rights reserved.

Application of selective F-1 decoupled H-1 NMR for enantiomer resolution and accurate measurement of enantiomeric excess at low chiral substrate/auxiliary concentration

The higher substrate and chiral auxiliary concentration is a pre-requisite to obtain efficient separation of H-1 NMR signals of enantiomers. The higher concentration of chiral lanthanide shift reagents provides broadened spectral lines resulting in a severe loss of resolution between the enantiomer resonances. In order to circumvent such difficulties, herein we present the application and the usefulness of a selective F-1 decoupled correlation (COSY) experiment which yields proton decoupled proton spectra in the indirect dimension. The potentiality of the experiment is demonstrated on several chiral compounds possessing different functional groups, employing either a lanthanide shift reagent or a solvating reagent as chiral auxiliaries. (C) 2011 Elsevier B.V. All rights reserved.

High-Q, Ag-doped 123 resonator on unbuffered sapphire substrate

The microwave performance of an Ag-doped YBa2Cu3O7-x, thin-film X-band microstrip resonator on unbuffered sapphire substrate is reported. Q-values of 2400 and 1200 have been obtained al 15R and 77K, respectively, which correspond to R(s) values of 330 mu Omega and 680 mu Omega.

Effect of substrate on particle arrangement in arrays formed by self-assembly of polymer grafted nanoparticles

We show that the substrate affects the interparticle spacing in monolayer arrays with hexagonal order formed by self-assembly of polymer grafted nanoparticles. Remarkably, arrays with square packing were formed due to convective shearing at a liquid surface induced by miscibility of colloidal solution with the substrate.

Monoclonal antibodies in the study of architecture of plant viruses

Monoclonal antibodies have been used as probes to study the architecture of several plant viruses over the past decade. These studies complement the information obtained through X-ray crystallography and help in delineating epitopes on the surface of the virus. The monoclonal antibodies that recognize distinct epitopes also aid in unravelling the mechanisms of assembly/disassembly of virus particles. Group-specific and strain-specific monoclonal antibodies are widely used in the classification of viruses. The significant developments made in this emerging area are reviewed here with specific examples.

Structural and optical properties of nonpolar (11-20) a-plane GaN grown on (1-102) r-plane sapphire substrate by plasma-assisted molecular beam epitaxy

We report the structural and optical properties of a-plane GaN film grown on r-plane sapphire substrate by plasma-assisted molecular beam epitaxy. High resolution X-ray diffraction was used to determine the out-of-plane and in-plane epitaxial relation of a-plane GaN to r-plane sapphire. Low-temperature photoluminescence emission was found to be dominated by basal stacking faults along with near-band emission. Raman spectroscopy shows that the a-GaN film is of reasonably good quality and compressively strained. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ultrasonic wave characteristics of a monolayer graphene on silicon substrate

The present work deals with an ultrasonic type of wave propagation characteristics of monolayer graphene on silicon (Si) substrate. An atomistic model of a hybrid lattice involving a hexagonal lattice of graphene and surface atoms of diamond lattice of Si is developed to identify the carbon-silicon bond stiffness. Properties of this hybrid lattice model is then mapped into a nonlocal continuum framework. Equivalent force constant due to Si substrate is obtained by minimizing the total potential energy of the system. For this equilibrium configuration, the nonlocal governing equations are derived to analyze the ultrasonic wave dispersion based on spectral analysis. From the present analysis we show that the silicon substrate affects only the flexural wave mode. The frequency band gap of flexural mode is also significantly affected by this substrate. The results also show that, the silicon substrate adds cushioning effect to the graphene and it makes the graphene more stable. The analysis also show that the frequency bang gap relations of in-plane (longitudinal and lateral) and out-of-plane (flexural) wave modes depends not only on the y-direction wavenumber but also on nonlocal scaling parameter. In the nonlocal analysis, at higher values of the y-directional wavenumber, a decrease in the frequency band gap is observed for all the three fundamental wave modes in the graphene-silicon system. The atoms movement in the graphene due to the wave propagation are also captured for all the tree fundamental wave modes. The results presented in this work are qualitatively different from those obtained based on the local analysis and thus, are important for the development of graphene based nanodevices such as strain sensor, mass and pressure sensors, atomic dust detectors and enhancer of surface image resolution that make use of the ultrasonic wave dispersion properties of graphene. (C) 2011 Elsevier Ltd. All rights reserved.

In vitro plant regeneration from different seedling explants of blackgram [Vigna mungo (L.) Hepper] via organogenesis

Callus induction and morphogenesis from different blackgram explants were tested on MS basal medium supplemented with B5 vitamins, IAA, NAA, IBA, KIN and BAP individually and in combinations. The explants were hypocotyl, epicotyl, axillary bud, cotyledonary node and immature leaf. The optimal levels of the frequency of callus induction was 22.8 mu M of IAA or 16.1 mu M NAA and in combination with 2.2 mu M of BAP. Among the seedling explants, hypocotyl was found to be more efficient in producing callus. Shoots mere induced from callus cultures of hypocotyls, epicotyls, axillary bud, cotyledonary node and immature leaf with varying frequencies in the medium containing KIN (2.3-9.3 mu M) or BAP (2.2-8.8 mu M) and in combination with IAA (2.8 mu M) or NAA (2.6 mu M). Multiple shoots were obtained using cotyledonary node segments. The regenerated shoots rooted best on MS basal medium containing 9.8 mu M IBA. Seventy three per cent of the shoots produced roots, and 80-85% of the plantlets survived under greenhouse condition.

Cross-taxon surrogacy of biodiversity in the Indian Garhwal Himalaya

Biodiversity surveys were conducted in 13, 10x50 m(2) plots located between 1400 to 3100 in abode mean sea level in a range of habitats in temperate mixed Oak and Coniferous forests through sub-alpine to the alpine grasslands in Chamoli district of Uttaranchal state in the Indian Garhwal Himalaya. Cross-taxon congruence in biodiversity (alpha-diversity and beta-diversity) across macrolichens, mosses, liverworts, woody plants (shrubs and trees) and ants was investigated, so as to examine the extent to which these group, of organisms can function as Surrogates for each other. Although woody plants provided a major substrate for macrolichens and mosses, there was no species-specific association between them. Woody plant species richness was highly positively correlated with mosses (r(2) = 0.63, P < 0.001) but the relationship, as not particularly very strong with lichens and liverworts. While there was a significant correlation in the species turnover (β-diversity) of macrolichens with mosses (r(2) = 0.21 P < 0.005). the relationship was relatively poor with the woody plants. On the other hand. negative correlations emerged in the species richness of ants with those of macrolichens, mosses and woody plants (r(2) = -0.44 P < 0.05). but most of the complementarity (turnover) relationships among them were positive, Since diversity between taxonomic hierarchies within the group was consistently significantly positively correlated in all these taxa, the higher taxonomic categories Such as genus and family may be employed as surrogates for rapid assessment and monitoring of species diversity, Although no single group other than macrolichens has emerged as a good indicator of changes in species richness in all other groups, some concordant relationships between them conform to the hypothesis that species assemblages of certain taxonomic groups could still be used as surrogates for efficient monitoring of species diversity in other groups whose distribution may further predict the importance of conserving overall biodiversity in landscapes such as the Garhwal Himalaya. (C) 2002 Elsevier Science Ltd. All rights reserved.

Woody plant seedling distribution under invasive Lantana camara thickets in a dry-forest plot in Mudumalai, southern India

Lantana camara, a shrub of Central and South American origin, has become invasive across dry forests worldwide. The effect of the thicket-forming habit of L. camara as a dispersal and recruitment barrier in a community of native woody seedlings was examined in a 50-ha permanent plot located in the seasonally dry forest of Mudumalai, southern India. Sixty 100-m(2) plots were enumerated for native woody seedlings between 10-100 cm in height. Of these, 30 plots had no L. camara thickets, while the other 30 had dense thickets. The frequency of occurrence and abundance of seedlings were modelled as a function of dispersal mode (mammal, bird or mechanical) and affinities to forest habitats (dry forest, moist forest or ubiquitous) as well as presence or absence of dense L. camara thickets. Furthermore, frequency of occurrence and abundance of individual species were also compared between thickets and no L. camara. At the community level, L. camara density, dispersal mode and forest habitat affinities of species determined both frequency of occurrence and abundance of seedlings, with the abundance of dry-forest mammal-dispersed species and ubiquitous mechanically dispersed species being significantly lower under L. camara thickets. Phyllanthus emblica and Kydia calycina were found to be significantly less abundant under L. camara, whereas most other species were not affected by the presence of thickets. It was inferred that, by affecting the establishment of native tree seedlings, L. camara thickets could eventually alter the community composition of such forests.