Space time fractional KdV Burgers equation for dust acoustic shock waves in dusty plasma with non-thermal ions

The KdV–Burgers equation for dust acoustic waves in unmagnetized plasma having electrons, singly charged nonthermal ions, and hot and cold dust species is derived using the reductive perturbation method. The Boltzmann distribution is used for electrons in the presence of the cold(hot) dust viscosity coefficients. The semi-inverse method and Agrawal variational technique are applied to formulate the space–time fractional KdV–Burgers equation which is solved using the fractional sub-equation method. The effect of the fractional parameter on the behavior of the dust acoustic shock waves in the dusty plasma is investigated.     

Structural and optical properties of lithium borobismuthate glasses

Glasses with compositions 25Li₂O-(75−x)Bi₂O₃-x B₂O₃, with 0?x?30 mol%, have been prepared using the melt quenching technique. The density and the molar volume have been determined. IR spectroscopy is used as a structural probe of the nearest neighbor environment in the glass network. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400-1100 nm. The values of the optical band gap E_g^opt for indirect transition and refractive index have been determined for 0?x?30 mol%. The average electronic polarizability of the oxide ion α_o²⁻ and the optical basicity have been estimated from the calculated values of the refractive indices. Variations in the different physical parameters such as the density, molar volume, optical band gap, refractive index, average electronic polarizability of the oxide ion and optical basicity with B₂O₃ content have been analyzed and discussed in terms of the changes in the glass structure.     

Quantum chemical studies on structures and spectra of 2,5-distyrylpyrazine (DSP) laser dye

Semiempirical (MNDO and PM3) molecular orbital calculations have been undertaken to study the structures of the ground and excited states of 2,5-distrylpyrazine dye to assess its activity as a laser dye. In the ground and first excited singlet states, the trans-trans structure of C_2h symmetry is the most stable structure in the gas phase and in DMSO, which agrees with the experimental findings. Upon excitation, the flexibility of the molecule decreases, leading to a subsequent decrease in the radiationless deactivation pathway and this increases the fluorescence efficiency of DSP. The absorption, excitation, and emission spectra have been calculated at the MNDO level using the PM3 optimized geometries in DMSO. At this level the agreement between theory and experiment is quite good. An estimated absorption band at 377 nm (expt 380 nm) is assigned to the S₀→S₁ transition. The excited state absorption band at 457 nm (expt 460 nm) is assigned to the S₁→S₁₂ transition. The emission band at 458 nm (expt 460 nm) is assigned to the S′₁→S′₀ transition. The overlap between the emission and the excited-state absorption spectra is presumably the main reason behind the reduced laser activity of the investigated dye. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 585–592, 1998     

Synthesis and antimicrobial evaluation of novel 1,3-thiazoles and unsymmetrical azines

Research on Chemical Intermediates - 1,3-Thiazol derivatives have been synthesized via reaction of 1-(1-(5,6-dimethoxy-2-oxobenzo[d]thiazol-3(2H)-yl)propan-2-ylidene)-4-substituted...     

Acid-Promoted Oxygen-Atom Transfer from a Novel Dihydroisoquinoline-Derived Oxaziridine Substituted at Position 1

N-Alkyl-oxaziridines react in the presence of a nucleophile as an oxygenating agent; in the absence of a nucleophile, an isomerization reaction is observed. This study describes the synthesis of two new dihydroisoquinoline oxaziridines and their reactivity in an acid-promoted reaction in the presence and absence of sulfides.     

Synthesis,antiviral and antimicrobial screening of some new 2-oxoindoline derivatives

New 3-(2-(5-(aryldiazenyl)-4-methylthiazol-2-yl)hydrazono)indolin-2-ones were prepared by the reaction of isatin β-thiosemicarbazone with different hydrazonoyl chlorides. Imide derivatives were prepared by the reaction of isatin hydrazone with various anhydrides, and a series of new sulfonimides was also synthesized. All new compounds were tested for their biological activities.     

Snail Hepatopancreatic Lipase: A New Member of Invertebrates Lipases' Group

Higher animal's lipases are well characterized; however, much less is known about lipases from mollusks. A lipolytic activity was located in the land snail (Eobania vermiculata) digestive glands (hepatopancreas), from which a snail digestive lipase (SnDL) was purified. Pure SnDL has a molecular mass of 60 kDa; it does not present the interfacial activation phenomenon. It was found to be more active on short-chain triacylglycerols than on long-chain triacylglycerols. The NH₂-terminal sequence of the SnDL shows 66% of identity with the 17 NH₂-terminal amino acids of a putative lipase from sea urchin (Strongylocentrotus purpuratus). No sequence identity was found with known lipases. Interestingly, neither colipase nor bile salts were detected in the snail hepatopancreas. This suggests that colipase evolved in vertebrates simultaneously with the appearance of an exocrine pancreas and a true liver which produces bile salts. Altogether, these results suggest that SnDL is a member of a new group of digestive lipases belonging to invertebrates.     

Catalytic Decomposition of H2O2over Supported ZnO

 Transition metal sulfates of Cu(II), Co(II), Ni(II), Cr(III), Mn(II), and Fe(III) supported on ZnO were prepared and characterized by SEM, EDX, and XRD. The kinetics of the heterogeneous decomposition of H₂O₂ over these supported catalysts was investigated. The reaction rate is correlated with both the amount of supported metal ion and its redox potential. The rate of reaction increases with increasing initial concentration of H₂O₂, attains a maximum, and decreases thereafter. It also increases with pH and reaches a maximum at high pH values. A reaction mechanism is proposed that implies the formation of a peroxo intermediate at the early stages of the reaction. A second intermediate is assumed to be formed at high [H₂O₂]_o which inhibits the progress of the reaction.     

ITSTUDIES ON THE EFFECT OF UREA ON THE COMPATIBILITY OF PMMA/PVC MIXTURES IN DMF BY A DILUTE- SOLUTION VISCOMETRY METHOD

The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea.     

Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO2

Direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated. The synthesized catalyst has been characterized by means of FTIR and XRD. Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC. However, DMC formation is limited by the reaction with co-produced water. DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2. As for the reactions in gas phase, it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature, owing to the decomposition of DMC at high temperatures. High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane (DMM) and methyl formate (MF).