Nonlinear Effects of a Gaussian Laser Beam on Megagauss Magnetic Field Generation in Laser Produced Plasma

The generation of megagauss magnetic field due to the time dependent part of the ponderomotive force of a self-focused Gaussian laser beam indicent on a plasma has been studied. Defocusing of the laser beam becomes possible due to diffraction divergence in the case of a weakly nonlinear medium. The influence of defocusing of a laser beam on magnetic field generation has also been investigated. It is found that the magnitude of the magnetic field due to self focusing of the beam is enhanced and is comparable with the observed values, while there is a reduction in the magnitude of the magnetic field when the beam defocuses due to diffraction divergence in the presence of weak nonlinearity.     

Reactions between hydroxylamines and aroyl cyanides

Aromatic hydroxylamines and sterically bulky aliphatic hydroxylamines react with aroyl cyanides to give exclusively the $\text{O}$-acyl derivatives.     

Dielectric relaxation of butyl acrylate—alcohol mixtures using time domain reflectometry

Dielectric relaxation measurements of butyl acrylate—alcohol mixtures at different concentrations and temperatures within the frequency range of 10 MHz to 10 GHz have been carried out using time domain reflectometry. Parameters such as the static permittivity, dielectric relaxation time, the Kirkwood correlation factor, the excess inverse relaxation time, and thermodynamic functions were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The value of the dielectric properties decreases with increasing butyl acrylate concentration in alcohol and systematically varies with the length of alcohol alkyl chain. Negative values of the excess inverse relaxation time found for all concentrations and at all temperatures studied may indicate that the effective dipoles rotate slowly.     

Montmorillonite KSF clay-promoted synthesis of enantiomerically pure 5-substituted pyrazoles from 2,3-dihydro-4H-pyran-4-ones

2,3-Dihydro-4H-pyran-4-ones derived from d-glucal undergo rapid condensation with aryl hydrazines in the presence of montmorillonite KSF clay under mild conditions to afford a novel class of chiral 5-substituted pyrazoles in good yields with high selectivity. The stereochemical assignments of the products were achieved by NMR studies.     

Synthesis of β-keto-sulfones using ionic liquid [TPA][Pro] as an efficient and reusable reaction medium

Facile and an efficient synthesis of β-keto-sulfones is described by the reaction of α-haloketone with sodium alkyl/aryl sulphinates in ionic liquid [TPA][Pro] as an efficient and reusable reaction medium to afford the corresponding β-keto-sulfones in excellent yields.     

LASER MEDIATED RELEASE OF DYE FROM LIPOSOMES

Liposomes made from phospholipids and containing sulforhodamine dye (1-50 mM) have been irradiated with nanosecond and picosecond laser pulses. Individual liposomes were locally heated by laser absorption of dye dimers during a single laser pulse, and heating was sufficient to release the liposome contents. The extent of dye release produced by a single laser pulse was shown to be quantitatively dependent on several interdependent variables, including dye concentration, liposome size, laser excitation parameters and initial temperature of the dye-liposome system. Fluorescence lifetime data having three components have been obtained and analyzed in terms of three dye environments. Quantitative estimates support a photo-induced thermal mechanism for liposome lysis and release of its contents. These results may be useful for laser induced delivery of therapeutic agents or other applications of lasers in biological systems.     

One-pot,solvent-free Pd(II)-catalyzed direct β-C-H arylation of carboxamides involving anhydrides as substrates via in situ installation of directing group

A one-pot, multicomponent-type, solvent-free Pd(II)-catalyzed direct β-C-H activation/arylation of carboxamides involving anhydrides as substrates via in situ installation of directing group (DG) is reported. Typically, the DG-assisted β-C-H activation/arylation of carboxamides is a two-step process comprising the installation of DG and Pd(II)-catalyzed CH arylation. We attempted a multicomponent-type reaction comprising an anhydride, a DG (e.g. 8-aminoquinoline), an aryl iodide in the presence of the Pd(II) catalyst and an appropriate additive. Different anhydrides, DGs, aryl iodides, catalysts and additives were screened to reveal the scope of this multicomponent-type CH arylation reaction process and various β-C-H arylated carboxamides were obtained in satisfactory to good yields.     

A theoretical study of the mechanism for the biogenesis of cofactor topaquinone in copper amine oxidases

In the present quantum chemical study, the biogenesis of the cofactor topaquinone (TPQ) has been studied using hybrid density functional theory (B3LYP). The suggested mechanism is divided into six steps and incorporates the observation of four crystallized intermediates. The experimental suggestion that the formation of the Cu(II)-peroxy species is the rate-limiting step is consistent with the results of the present study. Before the formation of the Cu(II)-peroxy species, dioxygen is suggested to first bind at the equatorial position on the copper metal center. A mechanism for the critical O-O bond cleavage is suggested, and this step is found to be driven by an unusually large exothermicity. A complex, spin-forbidden formation of H(2)O(2) with and without the involvement of the copper metal center is discussed. The results are discussed in detail, and comparisons are made to experimental findings and suggestions.     

Electrospray ionization studies of transition-metal complexes of 2-acetylbenzimidazolethiosemicarbazone using collision-induced dissociation and ion-molecule reactions

The complexes of transition-metal ions (M2+, where M = Fe, Co, Ni, Cu, Zn, Cd, and Hg) with 2-acetylbenzimidazolethiosemicarbazone (L) are studied under electrospray ionization (ESI) conditions. The ESI mass spectra of Fe and Co complexes showed the complex ions corresponding to [M+2L-2H]+, and those of Ni and Zn complexes showed [M+2L-H]+ ions, wherein the metal/ligand ratio is 1:2 and the oxidation state of the central metal ion is +3 in the case of Fe and Co and +2 in the case of Ni and Zn. The Cd and Cu complexes showed preferentially 1:1 complex ions, i.e., [M+L-H]+ or [M+L+Cl]+, whereas Hg formed both 1:1 and 1:2 complex ions. During formation of the above complex ions one or two ligands are deprotonated after keto-enol tautomerism, depending on the nature and oxidation state of central metal ion. The structures and coordination numbers of the metal ions in the complex ions were studied by their collision-induced dissociation spectra and ion-molecule reactions with acetonitrile or propylamine in the collision cell. Based on these results it is concluded that Fe, Co, Ni and Zn form stable octahedral complexes, whereas tetrahedral or square planar complexes are formed preferentially for other metals. In addition, the Cu complex showed a [2L+2Cu-3H]+ ion with a Cu-Cu bond.