Scaling behavior of plasmon coupling in Au and ReO3 nanoparticles incorporated in polymer matrices

Polymer nanocomposites containing different concentrations of Au nanoparticles have been investigated by small angle X‐ray scattering and electronic absorption spectroscopy. The variation in the surface plasmon resonance (SPR) band of Au nanoparticles with concentration is described by a scaling law. The variation in the plasmon band of ReO₃ nanoparticles embedded in polymers also follows a similar scaling law.

     

Orbital order in ZnV(2)O(4)

In view of recent controversy regarding the orbital order in the frustrated spinel ZnV(2)O(4), we analyze the orbital and magnetic ground state of this system within an ab initio density functional theory approach. While local density approximation+Hubbard U calculations in the presence of a cooperative Jahn-Teller distortion stabilize an A-type staggered orbital order, the consideration of relativistic spin-orbit (SO) effects unquenches the orbital moment and leads to a uniform orbital order with a net magnetic moment close to the experimental one. Our results show that ab initio calculations are able to resolve the existing discrepancies in previous theories and that it is the SO coupling along with electronic correlations which play a significant role in determining the orbital structure in these materials.     

Propagation of very short pulses at millimeter wavelengths through rain filled medium

Distortion of pulses with pulse widths ranging from 0.1 to 1 ns propagating with carrier frequencies in the range 10–100 GHz through rain filled medium has been estimated considering the absorptive and dispersive effects produced by rain drops on the propagation of millimeter waves. It is found that the rain induced broadening or compression can be quite appreciable for very short pulses in the window region of millimeter wave band under intense and extensive raining conditions.     

Probing microstructure of polymer electrolyte-salt complex through impedance spectroscopy

In study of polymer-salt complexes usually one is interested in the dc conductivity, which can be extracted from impedance spectroscopy. However, impedance spectroscopy yields a host of additional information, for example, frequency variation of the measured admittance or impedance, nature of the Cole-Cole plot and dielectric function. Proper analysis of this information reveals details of the microstructure and transport processes in the sample. This in turn, will lead to development of better solid electrolytes with tailor-made properties. The polymer electrolyte PEO-NH₄ClO₄ shows an interesting variation in its properties in two different regimes, (1) where salt concentration is below ∼ 19 wt.% and (2) above this concentration. In the present paper we suggest an equivalent circuit incorporating a constant phase element (CPE), which reproduces the complex admittance behavior at different salt fractions. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Higher-order solution for dust acoustic solitary waves in an unmagnetized dusty plasma

The effect of higher-order nonlinearity on dust acoustic solitary waves is studied taking into account the dust-charge variation. The model of charge fluctuation, taken here, is of the formI _e+I _i=0,I _e andI _i being the electronic and ionic currents. The dust charge is determined self consistently from the current-balance equation. It is found that the higher-order correction modifies the amplitude and width of the dust acoustic solitary waves. The effect of dust-charge streaming is also discussed.     

Thermoanalytical and gas chromatographic properties of the copper(II) complexes of alkyl-substituted Schiff's bases

Summary A study is presented of the thermoanalytical and gas chromatographic (GC) properties of the copper(II) complexes of twenty four tetradenate Schiff's bases. Variations in thermal stability, volatility and GC retention of the complexes are discussed in terms of stereo-electronic effects of the substituents. Although some complexes decomposed extensively during vaporization above 250°C all, apparently, survive chromatography intact at 200°C. Certain complexes were separated as distinct regio-isomers by GC. Fluorinated ligands still appear to be the most suitable derivatizing reagents for Cu(II).     

On correlated electron-nuclear dynamics using time-dependent density functional theory

We discuss possibilities and challenges for describing correlated electron and nuclear dynamics within a surface-hopping framework using time-dependent density functional theory (TDDFT) for the electron dynamics. We discuss the recent surface-hopping method proposed by Craig et al. [Phys. Rev. Lett. 95, 163001 (2005)] that is based on Kohn-Sham potential energy surfaces. Limitations of this approach arise due to the Kohn-Sham surfaces generally having different gradients than the true TDDFT-corrected ones. Two mechanisms of the linear response procedure cause this effect: we illustrate these with examples.     

A simple and general strategy for the design of fluorescent cation sensor beads

[Structure: see text] Chenodeoxycholic acid based PET sensors for alkali metal ions have been immobilized on Merrifield resin and on Tentagel. The fluorescence of the sensor beads is enhanced upon binding the cations. The modular nature of the sensor allows designing different sensors based on this concept.     

Selective and unusual fluoride ion complexation by a steroidal receptor using OH...F- and CH...F- interactions: a new motif for anion coordination?

[structure: see text] A novel cholaphane has been synthesized from a naturally occurring bile acid in just two steps. It has an ability to bind two fluoride ions selectively utilizing the glycolate motif in chloroform. This "inside-out" cyclodextrin analogue encapsulates fluoride through O-H...F(-) and C-H...F(-) interaction.     

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: potential therapeutics for type II diabetes

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.