Anomalous thermoelastic behaviour of orientationally disordered (NH4I)x(KI)1−x mixed crystals

We have incorporated the translational rotational (TR) coupling effects in the framework of three body force shell model (TSM) to develop an extended TSM (ETSM). This ETSM has been applied to reveal the second order elastic constants (C₁₁, C₁₂ and C₄₄) in the dilute regimes 0≤x≤0.50. Our theoretical results have reproduced well the observed variations of C₁₁ (x=0.14, 0.43) and C₁₂ (x=0.14, 0.43) with temperature. The anomalous elastic behaviour observed in C₄₄ below 150 K for x=0.43 has been predicted well by ETSM results in the orientationally disordered (NH₄I)_x(KI)_1−x mixed crystals. Our results for C₁₂ are in good agreement with the experimental data available for x=0.14 and 0.43. Besides, the third and fourth order elastic constants and the results on cohesive and thermophysical properties are also discussed.     

Synthesis, characterization, and antifungal activity of biaryl-based bis(1,2,3-triazoles) using click chemistry

Abstract  

Click chemistry was used to synthesize a series of biaryl-based bis(1,2,3-triazoles). Their antifungal activity was evaluated against three soil-borne plant pathogenic fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and Fusarium oxysporum, using the food poison technique at concentrations of 62.5–500 μg/cm³.     

Investigation of phase segregation in Zn1−xMgxO systems

The present work reports on the synthesis of the Zn_1?xMg_xO (x = 0, 0.02, 0.05, 0.10, 0.15 and 0.20) samples by sol–gel method and the investigations on their structural, morphological and optical properties. X-ray diffraction (XRD) data analysis confirms the formation of pure ZnO phase below 10% Mg doping and MgO related phases appears in 10% doped sample indicating that phase segregation of MgO starts at x ≥ 0.10 samples. The phase segregation observed through XRD analysis is also supported by results from Scanning Electron Microscopy (SEM), Raman spectroscopy and photoluminescence studies. Furthermore, the enhancement in optical band gap, with Mg doping, from 3.1 ± 0.1 eV to 3.5 ± 0.1 eV has been observed through UV–Vis spectroscopic analysis. Above results have been discussed on the basis of defects level observed through Raman and photoluminscence studies.     

Structural and polarization properties of polyimide/TiO2 nanocomposites

Polyimide (PI)/titanium dioxide (TiO₂) nanocomposite films were prepared by a solution mixing method with different contents of TiO₂ nanoparticles. The structural and thermal properties of pure PI and PI/TiO₂ nanocomposite films were studied by several techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermally stimulated depolarization current (TSDC). The SEM and AFM measurements show the uniform dispersion of TiO₂ nanoparticles in PI matrix, and it is also observed that the value of average roughness increases with increasing the contents of TiO₂ nanoparticles. The XRD pattern shows the presence of TiO₂ nanoparticles in PI matrix. It has been observed that the average crystallite size and percentage of crystallinity increase with content of the TiO₂ nanoparticles. FTIR spectra depict the position of different bonds in PI and nanocomposite samples. The TSDC results represent the modification of polarization phenomenon after filling of PI by titania nanoparticles.     

On the fractional chromatic number of monotone self-dual Boolean functions

We compute the exact fractional chromatic number for several classes of monotone self-dual Boolean functions. We characterize monotone self-dual Boolean functions in terms of the optimal value of an LP relaxation of a suitable strengthening of the standard IP formulation for the chromatic number. We also show that determining the self-duality of a monotone Boolean function is equivalent to determining the feasibility of a certain point in a polytope defined implicitly.     

Characterization of ammonium dichromate doped PVA films based waveguides

We report here the study of refractive index and Propagation loss of ammonium dichromate doped poly (vinyl alcohol) thin films by using a prism coupling technique. Transmissions of the doped films have been measured. It has been observed that doping of ammonium dichromate increase the refractive index. Propagation losses are found to decrease up to dye concentration 0.02% and thereafter increase rapidly.     

Heat capacities of linear macromolecules

The heat capacity of liquid selenium was measured from 500 K to 700 K. Three commercial dynamic differential calorimeters were used for the evaluation (du Pont, Mettler, Perkin-Elmer). Comparison with limited literature data by adiabatic calorimetry shows that all three instruments give data of better than ± 3 % accuracy. Differences among the instruments are thus mainly in the convenience of sample handling and calibration. The heat capacity measured shows a decreasing trend with increasing temperature, opposite to synthetic linear macromolecules.

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Zusammenfassung Die Wärmekapazität von flüssigem Selen wurde zwischen 500 und 700 K gemessen. Drei handelsübliche dynamische Differentialkalorimeter wurden zur Bewertung eingesetzt (du Pont, Mettler, Perkin-Elmer). Der Vergleich mit einigen Literaturangaben bezüglich adiabatischer Kalorimetrie zeigt für alle drei Instrumente eine höhere Genauigkeit als ± 3 %. Der Unterschied zwischen den Instrumenten besteht demnach hauptsächlich in der Leichtigkeit der Probenbehandlung und der Eichung. Die gemessene Wärmekapazität zeigt eine Abnahme mit steigender Temperatur, im Gegensatz zu synthetischen linearen Makromolekülen.

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Résumé On a mesuré la chaleur spécifique du sélénium liquide entre 500 et 700 K, à l'aide de trois analyseurs calorimétriques différentiels commerciaux (Du Pont, Mettler, Perkin-Elmer). La comparaison avec les données restreintes de la littérature, obtenues par calorimétrie adiabatique, a montré que les trois instruments donnent des résultats dont l'exactitude est meilleure que ± 3 %. Ainsi, les différences entre les instruments résident surtout dans la commodité de manipulation des échantillons et d'étalonnage. La chaleur spécifique ainsi mesurée tend à dimineur quand la température augmente, contrairement aux macromolécules synthétiques linéaires.

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500– 700 K. — , — . , , ±3%. , . , .

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Help by the du Pont Instruments Division, Wilmington, Delaware, in acquisition and operation of the du Pont 900 system is gratefully acknowledged.Thanks are expressed to Mr. H. J. Hoehn and to the Mettler, Instrument Corporation, Hightstown, N.J., for the opportunity to use and evaluate the TA 2000 system; and to Mr. G. Widmann of Mettler for the data used in this paper. Appreciation is also expressed to Dr. A. P. Gray, R. L. Fyans and the Perkin — Elmer Corporation, Norwalk, Conn. for their assistance in setting up the DSC-2 and providing us with the digital data recording facilities. This study was sponsored in part by a grant from the National Science Foundation (GH 42634X).     

Partition functions and dissociation constants for HeH+

Partition functions and dissociation equilibrium constants for HeH⁺ have been computed for temperatures between 2,000 and 16,000 K in steps of 100 K.