Easy Strategy for the Synthesis of New 5,6-Dihydro-[1,2,4]triazolo[4,3-a][1,3,5]triazine Derivatives

Russian Journal of Organic Chemistry - New substituted 5,6-dihydro[1,2,4]triazolo[4,3-a][1,3,5]triazines were synthesized by cyclocondensation of...     

Origin of the Raman mode at 379 cm−1 observed in ZnO thin films grown on sapphire

In this work, we present a detailed Raman scattering study to clarify the origin of the mode at 379 cm⁻¹ which is observed in Raman spectra of the ZnO films grown on c‐sapphire substrates and generally attributed to the A₁‐transverse optical (A₁‐TO) mode of ZnO. The studied ZnO films were deposited by metal‐organic chemical vapor deposition on c‐sapphire and (0001) ZnO substrates. In the z(−,−)z̄ backscattering configuration, the A₁‐TO mode is forbidden, while the 379 cm⁻¹ peak is still observed in the as‐deposited film grown on sapphire substrate. However, this mode is not observed in Raman spectra of the as deposited film grown on ZnO substrate. We suggest that the peak at 379 cm⁻¹ is the E_1g mode of the sapphire substrate which is allowed in z(−,−)z̄ backscattering configuration. The effects of annealing, the substrate and the collection cross‐section on Raman active modes were analyzed. Copyright © 2011 John Wiley & Sons, Ltd.     

Spherical Bessel functions and explicit quadrature formula

An evaluation of the derivative of spherical Bessel functions of order at its zeros is obtained. Consequently, an explicit quadrature formula for entire functions of exponential type is given.

     

Quadrature formulae using zeros of Bessel functions as nodes

A gaussian type quadrature formula, where the nodes are the zeros of Bessel functions of the first kind of order (), was recently proved for entire functions of exponential type. Here we relax the restriction on as well as on the function. Some applications are also given.

     

Electronic and optical properties of quaternary selenides for optoelectronic applications: Insights from DFT+U-computations

The optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe₃, CsUCuSe₃, CsZrCuSe₃, and CsGdZnSe₃ compounds have been calculated by using the full potential and linear augmented plane wave (FP-LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound's structure of these was (A = Cs, Ba; Ln = Zr, Gd, U; M = Cu, Zn) is composed of (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization between the s, p, and d states of Zr, Gd, and Cu atoms. Around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer's Kronig correlations with the imaginary part dielectric function. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75–2.25, which is indication that the material used in optoelectronic devices.     

Automated Scanning Probe Microscopy as a New Tool for Combinatorial Polymer Research: Conductive Carbon Black/Poly(dimethylsiloxane) Composites

A systematic investigation into the surface properties of siloxane rubber/carbon black (CB) nanocomposites has been performed, using an automated scanning probe microscope. In this way the influence of CB concentration and curing rate of the siloxane rubber matrix on roughness and conductivity of the composites was studied. Decreasing the curing rate while keeping the CB concentration resulted in a decrease in both roughness and surface conductivity, which can be explained by an additional siloxane‐rubber layer formed during curing.

     

Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules

Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in ^1,3Σ, ^1,3Π, and ^1,3Δ symmetries are presented. Adiabatic results are also reported for ²Σ, ²Π, and ²Δ electronic states of the molecular ion LiNa⁺ dissociating into Li (2s, 2p, 3s, and 3p) + Na⁺ and Li⁺  + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s²) and Na (1s²2s²2p⁶) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and LiNa⁺ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between electronic states of ²Σ and ²Π symmetries is related to the charge transfer process between the two ionic systems Li⁺Na and LiNa⁺.     

Theoretical investigation of the stability of highly charged C60 molecules produced with intense near-infrared laser pulses

We theoretically investigated the stability of highly charged C(60) (z+) cations produced from C(60) with an ultrashort intense laser pulse of lambda approximately 1800 nm. We first calculated the equilibrium structures and vibrational frequencies of C(60) (z+) as well as C(60). We then calculated key energies relevant to dissociation of C(60) (z+), such as the excess vibrational energy acquired upon sudden tunnel ionization from C(60). By comparing the magnitudes of the calculated energies, we found that C(60) (z+) cations up to z approximately 12 can be produced as a stable or quasistable (microsecond-order lifetime) intact parent cation, in agreement with the recent experimental report by V. R. Bhardwaj et al. [Phys. Rev. Lett. 93, 043001 (2004)] that almost only intact parent C(60) (z+) cations up to z=12 are detected by a mass spectrometer. The results of Rice-Ramsperger-Kassel-Marcus calculation suggest that the lifetime of C(60) (z+) drastically decreases by ten orders of magnitude as z increases from z=11 to z=13. Using the time-dependent adiabatic state approach, we also investigated the vibrational excitation of C(60) and C(60) (z+) by an intense near-infrared pulse. The results indicate that large-amplitude vibration with energy of >10 eV is induced in the delocalized h(g)(1)-like mode of C(60) (z+).     

Production, purification, and biochemical characterization of two beta-glucosidases from Sclerotinia sclerotiorum

The filamentous fungus Sclerotinia sclerotiorum produces beta-glucosidases in liquid culture with a variety of carbon sources, including cellulose (filter paper), xylan, barley straw, oat meal, and xylose. Analysis by native polyacrylamide gel electrophoresis (PAGE) followed by an activity staining with the specific chromogenic substrate, 5-bromo 4-chloro 3-indolyl beta-1,4 glucoside (X-glu) showed that two extracellular beta-glucosidases, designated as beta-glu1 and beta-glu2, were in the filter paper culture filtrate. Only one enzyme designated as beta-glu x was revealed by the same method in the xylose culture filtrate. Beta-glu1 and beta-glu2 were purified to homogeneity. The purification procedure consist of a common step of anion-exchange chromatography on DEAE-Sepharose CL6B, both high-performance liquid chromatography (HPLC) anion-exchange and gel filtration columns for beta-glu1 and only HPLC gel filtration for beta-glu2. Beta-glu1 has a molecular mass of 196 kDa and 96.5 kDa, as estimated by gel filtration and sodium dodecyl sulfate (SDS)-PAGE, respectively, suggesting that the native enzyme may consist of two identical subunits. The same analysis showed that beta-glu2 is a monomeric protein with an apparent molecular mass of about 76.5 kDa. Beta-glu1 and beta-glu2 hydrolyses PNPGlc and cellobiose, with apparent Km values respectively for PNPGlc and cellobiose of 0.1 and 1.9 mM for beta-glu1 and 2.8 and 8 mM for beta-glu2. Both enzymes exhibit the same temperature and pH optima for PNPGlc hydrolysis (60 degrees C and pH 5.0). beta-glu1 was stable over a pH range of 3-8 and kept 50% of its activity after 30 min of heating at 60 degrees C without substrate. It was further characterized by studying the effect of some cations and various reagents on its activity.     

Production, purification, and biochemical characterization of two β-glucosidases from Sclerotinia sclerotiorum

The filamentous fungus Sclerotinia sclerotiorum prudces ß-glucosidases in liquid culture with a variety of carbon sources, including cellulose (filter paper), xylan, barley straw, oat meal, and xylose. Analysis by native polyacrylamide gel electrophoresis (PAGE) followed by an activity staining with the specific chromogenic substrate, 5-bromo 4-chloro 3-indolyl ß-1,4 glucoside (X-glu) showed that two extracellular β-glucosidases, designated as ß-glul1 and \-glu2, were in the filter paper culture filtrate. Only one enzyme designated as ß-glus was revealed by the same method in the xylose culture filtrate. ß-glu1 and ß-glu2 were purified to homogeneity. The purification procedure consist of a common step of anion-exchange chromatography on DEAE-Sepharose CL6B, both high-performance liquid chromatography (HPLC) anion-exchange and gel filtration columns for ß-glu1 and only HPLC gel filtration for ß-glu2. ß-glu1 has a molecular mass of 196 kDa and 96.5 kDa, as estimated by gel filtration and sodium dodecyl sulfate (SDS)-PAGE, respectively, suggesting that the native enzyme may consist of two identical subunits. The same analysis showed that ß-glu2 is a monomeric protein with an apparent molecular mass of about 76.5 kDa. ß-glu1 and ß-glu2 hydrolyses PNPG1c and cellobiose, with apparent K _m values respectively for PNPGlc and cellobiose of 0.1 and 1.9 mM for ß-glu1 and 2.8 and 8 mM for ß-glu2. Both enzymes exhibit the same temperature and pH optima for PNPG1c hydrolysis (60°C and pH 5.0). ß-glu1 was stable over a pH range of 3–8 and kept 50% of its activity after 30 min of heating at 60°C without substrate. It was further characterized by studying the effect of some cations and various reagents on its activity.