Electrical conduction mechanism of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend film

The electrical conductivity of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend films have been measured by studying the I–V characteristics in the temperature range of 298–398 K. The results are shown by measuring the dependence of current on field, temperature, and blending compositions in the form of I–V characteristics and analysis has been made by interpretation of Poole–Frenkel, Schottky ln (J) vs. T plots, Richardson and Arrhenius plots. For individual polymers, the conduction mechanism observed to be a Poole–Frenkel type. On blending, the charge conduction appears to be the Schottky emission at lower temperature while Poole–Frenkel mechanism at higher temperature. The analysis of these results suggests that Pool–Frenkel mechanism is mainly responsible for the observed conduction. The conductivity was found to increase with an increase in the polysulfone concentration in the blend; it could be justified in terms of mobility of charge carriers. It is found that mobility of charge carriers increases with the increase in polysulfone concentration in the blend.     

Molecular beam study of photoionization of uranium and uranium oxide

Crossed laser molecular beam configuration was used to study the photoionization of U and UO by the UV-lines of an argon ion laser. Photoionization efficiencies of both U and UO were found to be line sensitive. Photoionization by the 3638 Å line was observed for the first time. Uranium atom ionization efficiency being higher for the 3345 Å and 3511 Å groups of lines, while UO ionization efficiency being maximum for the 3638 Å line. Dependence of photoion signal on laser power and relative photoionization efficiencies of the two isotopic species of uranium are also investigated.     

Some constrained shortest-route problems

Summary This paper treats five constrained shortest-route problems: 1) determining the shortest route when it is constrained to pass through a given set of specified nodes; 2) determining the shortest route when it is constrained to pass through a given set of specified nodes and the specified nodes are to be visited in a fixed order; 3) finding an optimal route for the travelling-salesman problem; 4) determining the shortest route throughK sets of specified nodes when at least one node of every set of specified nodes is to occur on the shortest route; and 5) finding the shortest route through the sets of specified nodes when at least one node of every set of specified nodes is to occur on the shortest route and the sets of specified nodes are to be visited in a fixed order. The functional equation technique of dynamic programming is employed to solve problems 1), 3), and 4), while problems 2) and 5) are solved through simpler algorithms. The methods are illustrated by examples.

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Zusammenfassung Es werden fünf Kürzeste-Wege-Probleme mit besonderen Bedingungen behandelt: 1) Bestimmung des kürzesten Weges unter der Bedingung, daß die in einer gegebenen Menge spezifizierten Knoten passiert werden müssen, 2) Bestimmung des kürzesten Weges, wobei die in einer gegebenen Menge spezifizierten Knoten in einer bestimmten Reihenfolge passiert werden müssen, 3) Ermittlung der optimalen Rundreise im Travelling-Salesman Problem, 4) Bestimmung des kürzesten Weges durchK Mengen von spezifizierten Knoten, wobei aus jeder Menge wenigstens ein Knoten passiert werden muß, und 5) Bestimmung des kürzesten Weges durch Mengen von spezifizierten Knoten, wobei aus jeder Menge wenigstens ein Knoten passiert und die Mengen in einer vorgegebenen Reihenfolge aufgesucht werden müssen. Zur Lösung der Probleme 1), 3) und 4) wird die Technik der dynamischen Optimierung angewandt, während die Probleme 2) und 5) mit einfacheren Algorithmen behandelt werden. Die Methoden werden an Beispielen erläutert.

     

Effect of electron-phonon interaction on the binding energy of a wannier exciton in a polarizable medium

A new phenomenological effective interaction potential between an electron and a hole of a Wannier exciton in a polarizable medium is proposed. Binding energies of Wannier excitons are calculated variationally using this potential in several polar crystals. A close agreement between the theoretical values thus calculated and the experimental values is found in all polar crystals including thallium halides.     

Ag-mediated synthesis of six-membered N-heterocycles

Abstract

One of the highly emerging and an important aspect of organic chemistry is the metal catalyzed synthesis of heterocycles. The methods used earlier for the synthesis of heterocycles were significant in the organic synthesis and developing cost-effective, improved and facial methods were beneficial to construct the complex architectures. For the both stereoselective and regioselective synthesis of six-membered nitrogen containing heterocycles, cyclic reactions that are Ag-mediated have known to be very efficient. The present review covers the applications of Ag in the formation of six-membered nitrogen containing heterocycles.     

Synthesis and Cytotoxicity Evaluation of Novel Andrographolide‐1,2,3‐Triazole Derivatives

A series of new andrographolide‐1,2,3‐triazole derivatives, 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , were synthesized from a natural bioactive labdane type diterpenoid, andrographolide. All the derivatives were screened against human cancer cell lines MCF7, MDA‐MB‐231, COLO205, HepG2, K562, Hela, and HEK293 to evaluate their cytotoxic activity. All the compounds showed anticancer activity selectively against K562 cell line, with IC₅₀ values ranging from 8.00 to 17.11 µM, and are inactive against the rest of the cell lines. Compounds 3c and 3d showed significant cytotoxicity among the synthesized derivatives. The in silico docking studies revealed compounds 3b and 3d with high binding affinity against the cancer target, transient receptor potential vanilloid 1.     

Franck-Condon effects in collision-induced electronic energy transfer: I2(E; v = 1,2) + He, Ar

Collisions of I2 in the E electronic state with rare gas atoms result in electronic energy transfer to the D, beta, and D' ion-pair electronic states. Rate constants for each of these channels have been measured when I2 is initially prepared in the J = 55, nu = 1 and 2 levels in the E state. The rate constants and effective hard sphere collision cross sections confirm the trends observed when nu = 0 in the E state is initially prepared: He collisions favor population of the D state, while Ar collisions favor population of the beta state. Final state vibrational level distributions are determined by spectral simulation and are found to be qualitatively consistent with the trends in the Franck-Condon factors. The experimental distributions are also compared to the recent quantum scattering calculations of Tscherbul and Buchachenko.     

Dye-sensitized solar cells concocted with dyes extracted from fresh and dried leaves of Henna using different solvents

Optical and Quantum Electronics - Nowadays, world is moving from conventional energy sources to non-conventional energy sources like solar energy, wind power, hydropower and those energy sources...     

Dynamic nuclear polarization at 9T using a novel 250 GHz gyrotron microwave source. 2003

In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9 T (250 GHz for g = 2 electrons, 380 MHz for ¹H). In these experiments, ¹H enhancements of up to 170 ± 50 have been observed in 1-¹³C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in ¹⁵N spectra of unoriented pf1-bacteriophage. Finally, enhancements of ∼17 have been obtained in two-dimensional ¹³C–¹³C chemical shift correlation spectra of the amino acid U–¹³C, ¹⁵N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments.