The composition dependence of electrical switching behavior of Ge7Se93−xSbx glasses

Bulk Ge₇Se_93?xSb_x (21 ? x ? 32) glasses are prepared by melt quenching method and electrical switching studies have been undertaken on these samples to elucidate the type of switching and the composition and thickness dependence of switching voltages. On the basis of the compressibility and atomic radii, it has been previously observed that Se-based glasses exhibit memory switching behavior. However, the present results indicate that Ge₇Se_93?xSb_x glasses exhibit threshold type electrical switching with high switching voltages. Further, these samples are found to show fluctuations in the current–voltage (I–V) characteristics. The observed threshold behavior of Ge₇Se_93?xSb_x glasses has been understood on the basis of larger atomic radii and lesser compressibilities of Sb and Ge. Further, the high switching voltages and fluctuations in the I–V characteristics of Ge–Se–Sb samples can be attributed to the high resistance of the samples and the difference in thermal conductivities of different structural units constituting the local structure of these glasses. The switching voltages of Ge₇Se_93?xSb_x glasses have been found to decrease with the increase in the Sb concentration. The observed composition dependence of switching voltages has been understood on the basis of higher metallicity of the Sb additive and also in the light of the Chemically Ordered Network (CON) model. Further, the thickness dependence of switching voltages has been studied to reassert the mechanism of switching.     

Possibility of room-temperature multiferroism in Mg-doped ZnO

Room-temperature multiferroic properties in Mg-doped ZnO samples are reported wherein Mg replaces Zn in the ZnO matrix and retains hexagonal wurtzite structure. The saturation magnetisation is increased from ～2×10^?4 emu/g to 3×10^?4 emu/g for the dilute doping of 2 % Mg in pure ZnO and the ferroelectricity is also increased. Higher concentration of Mg does not lead to a significant enhancement in the magnetisation but improves the ferroelectric properties. An X-ray absorption spectroscopic study shows an enhancement in O vacancies with dilute doping of Mg. The origin of the multiferroic behaviour is understood based on their crystal and electronic structures.     

Structural,dielectric and ac conductivity properties of Ni-doped HoFeO3 before and after gamma irradiation

A series of samples of HoFe_1?x Ni _x O₃ (x = 0.0, 0.1, 0.3) were prepared using the solid-state reaction technique to understand the structural, dielectric and conductivity properties before and after gamma irradiation of accumulated dose of 625 KGy. The X-ray diffraction confirms that all the samples exist in single-phase orthorhombic structure having space group Pbnm. With increasing dopant Ni, the unit cell volume and lattice parameters undergo small change. X-ray analysis show change in the interplanar spacing and full width at half maximum values after gamma irradiation. The Raman spectra of the samples show modifications after gamma irradiation. It can be easily seen that after gamma irradiation intensity, peak width are completely altered by gamma-absorbed dose. Measurement of dielectric loss and dielectric constant at room temperature was performed before and after gamma irradiation in the frequency range of 20 Hz–1 MHz. It is observed that the value of dielectric constant decreases after irradiation. The ac conductivity is estimated from the dielectric constant and loss tangent. Exposure to gamma radiation results in substantial modification in the physical properties of the Ni-doped Ho-based orthoferrites.     

Synthesis,molecular modeling,and pharmacological evaluation of new 2-substituted benzoxazole derivatives as potent anti-inflammatory agents

Structural Chemistry - In the present work, 2-substituted benzoxazole derivatives were synthesized from 2-(benzo[d]oxazol-2-yl) aniline. All the synthesized compounds were purified and...     

Insulator-surface flashover conditioning: A streak photographicinvestigation

Conditioning behavior of surface flashover strength of a large-bandgap insulator (quartz) is investigated with the aid of streak photography in conjunction with electrical (voltage and current) and optical UV (phototube) diagnostics. The breakdown strength of the sample is found to be conditioned during the initial test as well as the subsequent test, performed after an overnight rest period. The results suggest that light emission during the initial test is dominated by visible light whereas during the subsequent test it is dominated by UV. The initial conditioning is attributed primarily to the desorption of absorbed molecules and rearrangement of the same by migration kinetics. Processes such as negative charge formation on the insulator surface and trapping of electrons in the deep traps are proposed to be responsible for the observed conditioning after the overnight rest period. The breakdown strength of the sample was found to degrade after experiencing breakdown at higher fields (i.e., after second day test). This deconditioning behavior is discussed in terms of evaporation of electrode material and deposition of the same on the insulator near the cathode end     

ketendithioacetals 39. Novel solvolytic rearrangements of 1,1-bis-(methylthio)-2,4-dimethyl-5-aryl (or styryl)-1,4-pentadien-3-ols to cyclopentenone derivative

Boron trifluoride etherate catalysed methanolysis of 1,1-bis (methylthio)-2,4-dimethyl-5-aryl ( or styryl)-1,4-pentadien-3-ols affords novel cyclopentenone derivatives.     

Synthesis,characterization, pharmacological,molecular modeling and antimicrobial activity evaluation of novel isomer quinoline derivatives

The structural and spectroscopic characteristics of the synthesized structurally novel compound 4-chloro-6-methylquinoline-2(1H)-one (4C6MQ) and its isomer 4-chloro-8-methylquinoline-2(1H)-one (4C8MQ) have been examined by means of experimental and computational quantum chemical methods like density functional theory (DFT). The crystal structure of the 4C6MQ compound has been brought to light by single-crystal x-ray diffraction (SCXRD) method which consists of two independent molecules (A and B) in the asymmetric unit with similar conformations. Both the isomer compounds are characterized spectroscopically by FTIR, FT-Raman, UV-Vis, and NMR spectrum and compared with DFT results. The geometries of the isomer compounds have been optimized by using DFT/B3LYP method with the 6-311G++(d,p) basis sets. From the optimized geometry of the compounds, geometric parameters (bond lengths, bond angles, and torsion angles); vibrational analysis; chemical shifts; and electronic absorption of the isomer compounds have been computed and compared with the experimental result. The detailed assignments of vibrational wave numbers have been prepared based on potential energy distribution (PED) which was carried out in the VEDA4 program. In addition, natural bonding orbital analysis, frontier molecular orbital, and molecular electrostatic potential have been explained theoretically. The in silico (absorption, distribution, metabolism, excretion and toxicity) studies were analyzed to identify the potential drug likeliness of the isomer compounds. The implications of the inhibitory activity of isomer compounds against DNA gyrase and lanosterol 14 α-demethylase enzyme by molecular docking are discussed. Further, the isomer compounds were screened for their antibacterial and antifungal activities.     

Facile preparation of potassium 32P-phosphonate

Simple and easy to operate experimental assemblies were for the first time designed for the successful preparation of potassium ³²P-phosphonate from ³²P-orthophosphate. Phosphate was first converted to phosphoryl chloride by reacting with phosphorus pentachloride. Then the phosphoryl chloride formed was reduced to phosphorus trichloride by heating with charcoal at 650 °C. The latter was absorbed in aqueous potassium hydroxide to obtain potassium ³²P-phosphonate at a yield of about 75%. The chemical purity of ³²P-phosphonate was assayed using ion-chromatography and the radiochemical purity was also determined.The authors thank Shri. J. K. Ghosh, Chief Executive, BRIT and Dr. N. Sivaprasad, General Manager, RPh & ILCJ, BRIT for their support and encouragement throughout this work.     

Study of the effect of SHI irradiation on nanocrystalline vacancy doped (La,Sr)(Mn,Fe)O system and its comparison with hydrostatic pressure using Mössbauer spectroscopy

The swift heavy ion irradiated La_0.9Mn_0.8Fe_0.2O₃ (La-deficient) system with 200 Mev Ag^16?+? ion beam at fluence 5 × 10¹² ions/cm² was studied with X-ray diffraction (XRD) and Mössbauer spectroscopic measurements. Comparison of Mössbauer parameters with those of unirradiated sample showed an increase in line width on irradiation which may be due to reduction in particle size as well as due to creation of defects. An increase in quadrupole splitting with no appreciable change in isomer shift showed ion-induced structural disorder in the material after irradiation. An attempt is made to compare the effect of fluence with the hydrostatic pressure on the sample.