Aspects of tautomerism. Part II. Reactions of the pseudo-acid chloride of o-benzoylbenzoic acid with nucleophiles

Reactions of fourteen nucleophiles with the pseudo-acid chloride of o-benzoylbenzoic acid in two solvents have been studied. The nucleophiles that react primarily at the tetrahedral carbon atom to give pseudo derivatives, are weaker than those that react at the carbonyl carbon atom causing opening of the lactone ring. An explanation for this phenomenon is advanced.

The physical properties of SnS films grown on lattice-matched and amorphous substrates

The development of high-quality tin monosulphide (SnS) layers is one of the crucial tasks in the fabrication of efficient SnS-based optoelectronic devices. Reduction of strain between film and the substrate by using an appropriate lattice-matched (LM) substrate is a new attempt for the growth of high-quality layers. In this view, the SnS films were deposited on LM Al substrate using the thermal evaporation technique with a low rate of evaporation. The as-grown SnS films were characterized using appropriate techniques and the obtained results are discussed by comparing them with the properties of SnS films grown on amorphous substrate under the same conditions. From structural analysis of the films, it is noticed that the SnS films deposited on amorphous substrate have crystallites that were oriented along different directions. However, the SnS crystallites grown on Al substrate exhibited epitaxial growth along the 101] direction. Photoluminescence (PL) and Raman studies reveal that the films grown on Al substrate have better optical properties than those of the films grown on amorphous substrates. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Role of PbO in lithium ion transport in Li2O-PbO-B2O3 glasses

Abstract: A wide range of compositions of grasses in the ternary Li2O-PbO-B2O3 glass system was prepared, and de and ac conductivity measurements were carried out on these glasses. The presence of lead leads to a decrease in de conductivities and an increase in the activation energies. This is likely to be due to the increase of the partial charges on the oxygen atoms and to the presence of the lone pair on the Pb atom; both of these factors impede lithium ion motion. The ac conductivity and dielectric behavior of these glasses support such a conjecture. (C) 2000 Elsevier Science Ltd.

A checking method for probabilistic seismic-hazard assessment: case studies on three cities

The conventional Cornell's source-based approach of probabilistic seismic-hazard assessment (PSHA) has been employed all around the world, whilst many studies often rely on the use of computer packages such as FRISK (McGuire FRISK-a computer program for seismic risk analysis. Open-File Report 78-1007, United States Geological Survey, Department of Interior, Washington 1978) and SEISRISK III (Bender and Perkins SEISRISK III-a computer program for seismic hazard estimation, Bulletin 1772. United States Geological Survey, Department of Interior, Washington 1987). A ``black-box'' syndrome may be resulted if the user of the software does not have another simple and robust PSHA method that can be used to make comparisons. An alternative method for PSHA, namely direct amplitude-based (DAB) approach, has been developed as a heuristic and efficient method enabling users to undertake their own sanity checks on outputs from computer packages. This paper experiments the application of the DAB approach for three cities in China, Iran, and India, respectively, and compares with documented results computed by the source-based approach. Several insights regarding the procedure of conducting PSHA have also been obtained, which could be useful for future seismic-hazard studies.

Physics-Based Band Gap Model for Relaxed and Strained 100] Silicon Nanowires

In this paper, we propose a physics-based simplified analytical model of the energy band gap and electron effective mass in a relaxed and strained rectangular 100] silicon nanowires (SiNWs). Our proposed formulation is based on the effective mass approximation for the nondegenerate two-band model and 4 x 4 Luttinger Hamiltonian for energy dispersion relation of conduction band electrons and the valence band heavy and light holes, respectively. Using this, we demonstrate the effect of the uniaxial strain applied along 100]-direction and a biaxial strain, which is assumed to be decomposed from a hydrostatic deformation along 001] followed by a uniaxial one along the 100]-direction, respectively, on both the band gap and the transport and subband electron effective masses in SiNW. Our analytical model is in good agreement with the extracted data using the extended-Huckel-method-based numerical simulations over a wide range of device dimensions and applied strain.

Computational investigations on covalent dimerization/oligomerization of polyacenes: Is it relevant to soot formation?

We have postulated a novel pathway that could assist in the nucleation of soot particles through covalent dimerization and oligomerizations of a variety of PAHs. DFT calculations were performed with the objective of obtaining the relative thermal stabilities and formation probabilities of oligomeric species that exploit the facile dimerization that is known to occur in linear oligoacenes. We propose that the presence of small stretches of linear oligoacence (tetracene or longer) in extended PAH, either embedded or tethered, would be adequate for enabling the formation of such dimeric and oligomeric adducts; these could then serve as nuclei for the growth of soot particles. Our studies also reveal the importance of p-stacking interactions between extended aromatic frameworks in governing the relative stabilities of the oligomeric species that are formed. (c) 2012 Wiley Periodicals, Inc.

MolBridge: a program for identifying nonbonded interactions in small molecules and biomolecular structures

Identification and analysis of nonbonded interactions within a molecule and with the surrounding molecules are an essential part of structural studies, given the importance of these interactions in defining the structure and function of any supramolecular entity. MolBridge is an easy to use algorithm based purely on geometric criteria that can identify all possible nonbonded interactions, such as hydrogen bond, halogen bond, cation-pi, pi-pi and van der Waals, in small molecules as well as biomolecules. The user can either upload three-dimensional coordinate files or enter the molecular ID corresponding to the relevant database. The program is available in a standalone form and as an interactive web server with Jmol and JME incorporated into it. The program is freely downloadable and the web server version is also available at http://nucleix.mbu.iisc.ernet.in/molbridge/index.php.

Capturability Analysis of a 3-D Retro-PN Guidance Law for Higher Speed Nonmaneuvering Targets

This brief presents the capturability analysis of a 3-D Retro-proportional navigation (Retro-PN) guidance law, which uses a negative navigation constant (as against the usual positive one), for intercepting targets having higher speeds than interceptors. This modification makes it possible to achieve collision conditions that were inaccessible to the standard PN law. A modified polar coordinate system, that makes the model more compact, is used in this brief for capturability analysis. In addition to the ratio of the target to interceptor speeds, the directional cosines of the interceptor, and target velocity vectors play a crucial role in the capturability. The existence of nontrivial capture zone of the Retro-PN guidance law and necessary and sufficient conditions, for capturing the target in finite time, are presented. A sufficient condition on the navigation constant is derived to ensure finiteness of the line-of-sight turn rate. The results are more extensive than those available for 2-D engagements, which can be obtained as special cases of this brief. Simulation results are given to support the analytical results.