Three Dimensional Angular Distributions of X‐Rays in a 4 kJ Plasma Focus Device for Different Anode Tips Using TLD‐100 Dosimeters

Time and energy integrated measurements of the 3‐D angular distribution of X‐rays emission within the chamber of a 4 kJ Mather‐type plasma focus is investigated employing four different anode shapes and using nitrogen as the filling gas by the TLD‐100 thermoluminescence dosimeters. The distributions of X‐ray radiation in the energy range of 5 keV to several hundred keV were bimodal for all of the anode tips, peaked approximately at ±15°. The intensity of X‐rays decreased abruptly along the central axis of the device where the quasi cylindrical plasma pinch was formed. High intensity of X‐ray was observed in the case of a tapered ?at‐end anode, whereas less was obtained with the cylindrical hollow‐end anode. The maximum nitrogen X‐rays were for the tapered flat‐end anode at 4.5 mbar and 13 kV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Disiline-doped boron nitride nanotubes: A computational study

The properties of the electronic structure of the Disiline-doped boron nitride nanotubes (Disiline-BNNTs) are investigated by a density functional theory (DFT) calculation. The structural forms are firstly optimized and the CS tensors calculated. Subsequently, the chemical-shielding isotropic (CS^I) and chemical shielding anisotropic (CS^A) parameters are found. The shielding values of boron (B) and nitrogen (N) atoms were calculated by Gauge-Including Atomic Orbital (GIAO), Continuous Set of Gauge Transformations (CSGT) and Individual Gauges for Atoms in Molecules (IGAIM) methods, using B3LYP/6-311+G*. The B3LYP level of theory with IGAIM was the best method to evaluate the theoretical chemical shifts for studied models. The results reveal a significant effect of Disiline doping on the chemical shielding tensors at the sites of those ¹¹B and ¹⁵N nuclei located in the nearest neighborhood of the Disiline-doped ring. Furthermore, the values of dipole moments and HOMO-LUMO gaps change in the Disiline-doped models in comparison with the original pristine model.     

Design,Synthesis, and Antibacterial Evaluation of Some Novel 3′-(Phenylamino)-1′H-spiro[indoline-3,2′-quinazoline]-2,4′(3′H)-dione Derivatives

A combinatorial synthesis and evaluation of antibacterial activity against clinically isolated resistant strains of Gram-positive and Gram-negative bacteria of 3′-(phenylamino)-1′H-spiro[indoline-3,2′-quinazoline]-2,4′(3′H)-dione derivatives is described.     

Remarkable Improvement of Methylglyoxal Synthase Thermostability by His–His Interaction

Lately it has been proposed that interaction between two positively charged side chains can stabilize the folded state of proteins. To further explore this point, we studied the effect of histidine–histidine interactions on thermostability of methylglyoxal synthase from Thermus sp. GH5 (TMGS). The crystal structure of TMGS revealed that His23, Arg22, and Phe19 are in close distance and form a surface loop. Here, two modified enzymes were produced by site-directed mutagenesis (SDM); one of them, one histidine (TMGS-HH^O), and another two histidines (TMGS-HHH^O) were inserted between Arg22 and His23 (H^O). In comparison with the wild type, TMGS-HH^O thermostability increased remarkably, whereas TMGS-HHH^O was very unstable. To explore the role of His23 in the observed phenomenon, the original His23 in TMGS-HHH^O was replaced with Ala (TMGS-HHA). Our data showed that the half-life of TMGS-HHA decreased in relation to the wild type. However, its half-life increased in comparison with TMGS-HHH^O. These results demonstrated that histidine–histidine interactions at position 23 in TMGS-HH^O probably have the main role in TMGS thermostability.     

Passive walking biped robot model with flexible viscoelastic legs

Nonlinear Dynamics - To simulate the complex human walking motion accurately, a suitable biped model has to be proposed that can significantly translate the compliance of biological structures. In...     

A combined experimental and density functional theory study on the complexation ability of 15-crown-5 with Li+, Na+, K+, and NH4 + cations

The complexation processes among Li⁺, Na⁺, K⁺, and NH₄ ⁺ cations with the macrocyclic ligand, 15-crown-5 (15C5) have been studied in acetonitrile–methanol binary mixtures at different temperatures using conductometric method. The stability constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at various temperatures. The values of thermodynamic parameters ( $ \Updelta H_{\text{c}}^{^\circ } $ and $ \Updelta S_{\text{c}}^{^\circ } $ ) for the formation of the complexes were obtained from temperature dependence of the stability constants of complexes using van’t Hoff plots. In addition, a theoretical study has been carried out using density functional theory to obtain the stability of the complexes and the geometrical structure of the 15C5 and its complexes with Li⁺, Na⁺, K⁺ and NH₄ ⁺ cations in the gas phase. We compared the experimental data with those obtained by quantum chemistry calculations to investigate the effect of the solvent on complexation process.     

Oxygen decorating at the one ring and at the N-mouth of (10, 0) aluminum nitride nanotube: A DFT investigation

We have investigated oxygen decorating in the (10, 0) aluminum nitride nanotube (AlNNT) by density functional theory. Band gaps, total (TDOS) and partial (PDOS) densities of state and chemical-shielding isotropic (CSI) and chemical-shielding anisotropic (CSA) have been calculated or determined in three models of the investigated (10, 0) AlNNT: pristine (model.0), O-decorating at the one ring in the middle of AlNNT (Model.1) and O-decorating at the nitrogen mouth of AlNNT (Model.2). The results indicated that the dipole moment does not detect the significant effects of dopant whereas TDOS, PDOS and band gap energies detect notable effects. The CSI and CSA values for the Al and N atoms-contributed to the Al-O bonds or those atoms close to the decorated region, in both models of O-decorated AlNNTs are changed.      

Enhancement of Fluorescence Intensity of Tramadol and Its Main Metabolites in LC Using Pre-Column Derivatization with 9-Fluorenylmethyl Chloroformate

Tramadol was found to exhibit weak fluorescence with a maximum emission at 300 nm when excited at 200 nm. Also, fluorescence spectra of the drug and its two main metabolites, O-desmethyltramadol and N-desmethyltramadol are not practically identical. Thus low and different sensitivities have been reported for the drug and its metabolites in previously published work. In the present method using 9-fluorenylmethyl chloroformate (FMOC-Cl) as labeling agent, equal and magnified fluorescence intensity were obtained for the analytes. The drug, its metabolites and an internal standard (oseltamivir phosphate) were extracted from serum by dichloromethane. Pre-column derivatization of the analytes was achieved using FMOC-Cl in the presence of borate buffer (0.1 M, pH 7.5). Liquid chromatography with a mobile phase consisting of a mixture of 0.05 M phosphate buffer containing triethylamine (2 ml L^?1; pH = 3.0) and methanol (54:46; v/v) and a Shimpack CLC-ODS column were used for analytical separation of the analytes. The fluorescence of the column effluent was monitored at an excitation and emission wavelengths of 265 and 315 nm, respectively. The analytical method was linear over the concentration range of 1.0–1,280 ng mL^?1 of the parent drug and its metabolites and limit of quantification of 1.0 ng mL^?1 was obtained for the analytes using 10 μL injection. The method validation was studied and the validated method applied in a bioequivalence study of 2 different tramadol preparations in 24 healthy volunteers.