A New Approach for Synthesis of 2-Thioxocytosine-5-carbonitrile as Antimicrobial Agents

Russian Journal of General Chemistry - A highly efficient synthetic methodology for the preparation of 2-thioxocytosine was achieved by the nucleophilic addition of thiourea to...     

Biosynthesis and Anti-Mycotoxigenic Activity of Zingiber officinale Roscoe-Derived Metal Nanoparticles

Mycotoxigenic fungi have attracted special attention due to their threat to food security and toxicity to human health. Aqueous extract of Zingiber officinale Roscoe was used as reducing and capping agent for the synthesis of silver (AgNPs), copper (CuNPs), and zinc oxide (ZnONPs) nanoparticles. UV-Visible spectra of the AgNPs, CuNPs, and ZnONPs showed absorption peaks at λ_max 416 nm, 472 nm, and 372 nm, respectively. Zeta potential of AgNPs, CuNPs, and ZnONPs were −30.9, −30.4 and −18.4 mV, respectively. ZnONPs showed the highest activity against Aspergillus awamori ZUJQ 965830.1 (ZOI 20.9 mm and MIC 24.7 µg/mL). TEM micrographs of ZnONPs-treated A. awamori showed cracks and pits in the cell wall, liquefaction of the cytoplasmic content, making it less electron-dense. The sporulation and ochratoxin A production of A. awamori was inhibited by ZnONPs in a concentration-dependent pattern. The inhibition percentage of OTA were 45.6, 84.78 and 95.65% for 10, 15, 20 of ZnONPs/mL, respectively.     

Numerical study for the electrified instability of viscoelastic cylindrical dielectric fluid film surrounded by a conducting gas

The linear electrohydrodynamic cylindrical instability of annular Walters B^′${\mathrm{B}}^{\prime }$ viscoelastic dielectric fluid layer surrounded by a conducting gas in the presence of radial electric field is investigated. The obtained dispersion relation is found to be complicated and cannot be treated theoretically easily. Two limiting cases of interest are investigated, when the inertia is dominant, and when both the kinematic viscosity and viscoelasticity are high, and the corresponding new stability conditions are obtained for both cases. We solve the eigenvalue problem numerically using the continuation method which gives better results than the classical non-linear solvers such as Newton and Secant methods. It is found that the applied radial electric field has a dual role on the stability of the considered system, depending of the chosen wavenumbers range. Both the kinematic viscoelasticity and liquid depth are found to have stabilizing effects, while both the kinematic viscosity and surface tension have destabilizing effects on the considered system. The stability or instability breaks down for critical wavenumber values at which the growth rate vanishes. The behaviors of both the maximum growth rate and the corresponding dominant wavenumber are discussed in detail corresponding to the effect of all physical parameters. Finally a comparison between the results obtained here for Walters B^′${\mathrm{B}}^{\prime }$ viscoelastic fluids, and those obtained here too if the fluid is replaced by a Rivlin–Ericksen viscoelastic one is achieved. The limiting cases of absence of electric field and/or kinematic viscoelasticity are also investigated in detail.     

Hydromagnetic parametric resonance instability of two superposed conducting fluids in porous medium

Rayleigh–Taylor instability of a heavy fluid supported by a lighter one through porous medium, in the presence of a uniform, horizontal and oscillating magnetic field is studied. The fluids are taken as viscous (obeying Darcy's law), uniform, incompressible, and infinitely conducting. The amplitude of the oscillating part of the field is taken to be small compared with its steady part. The dispersion relation is obtained in the form of a third-order differential equation, with time as the independent variable and with periodic coefficients, for the vertical displacement of the surface of separation of the two fluids from its equilibrium position. The oscillatory magnetic field of frequency ω$\omega$ and steady part _H0$H_0$ has a stabilizing influence on a mode of disturbance which is unstable in a steady magnetic field of strength _H0$H_0$. It is found that the oscillatory magnetic field and porosity of the porous medium have stabilizing effects, while the medium permeability has a destabilizing influence on the considered system. For a constant value of any of these physical parameters, the system has been found to be unstable (for small wavenumbers) as well as stable afterwards after a definite wavenumber value. The marginal stability case of parametric resonance holds when _M1=_M2=0$M_1=M_2=0$ (and hence m=0$m=0$), in which the characteristic exponents, and the corresponding solutions for u$u$ break down, is also investigated in detail. It is found, to order ?$?$, that the effect of an oscillating magnetic field has no stabilizing influence on a disturbance which is marginally stable in the steady magnetic field; while to order ?²${?}^2$, and when the magnetic field oscillates, a resonance between this mode of disturbances and the oscillating field leads to instability when _ρ2>_ρ1${\rho }_2>{\rho }_1$. It is found also, in this resonant case, that all the constant or varied physical parameters, mentioned above, have destabilizing influences on the considered system. Finally, the other two resonance points appear in non-porous media (i.e., when m=±iω$m=\pm \mathrm{i}\omega$ and m=±2iω$m=\pm 2\mathrm{i}\omega$), are disappeared here due to the presence of the porous medium.     

Development and Validation of a High-Performance Thin-Layer Chromatographic Method for the Assay of Ternary Mixtures Containing Cetirizine Dihydrochloride in Pharmaceutical Dosage Forms

JPC – Journal of Planar Chromatography – Modern TLC - A highly validated and selective high-performance thin-layer chromatography (HPTLC) method was developed for the determination of...     

An efficient and facile multicomponent synthesis of 4,6-diarylpyridine derivatives under solvent-free conditions

We present an efficient and facile synthesis of 4,6-diaryl-2-oxo-1,2-dihydropyridine-3-carbonitriles (5a–j) via a four-component system of aromatic aldehydes (1), acetophenones (2), ethyl cyanoacetate (3), and ammonium acetate (4). The short reaction time coupled with the simplicity of the reaction procedure and clean reaction make this method one of the most efficient methods for synthesis of this class of compounds.     

Nano nickel [1,2,4]-triazole-3-thiones complex: Design,sonochemical synthesis,and antimicrobial evaluation

A series of new 1,2,4-triazole-3-thiones were synthesized by calm, benign, no risk, eco-friendly, and energy efficient sequential reaction methodology like grinding and ultrasonic (US). In addition, 1,2,4-triazoles were prepared under conventional method and comparative study was done. The synthesized 1,2,4-triazoles were complexed with Ni(II) to produce nanoparticles complexes (NPC's) with average particle size vary from 55 to 100 nm (using scanning electron microscope technique) with good yields via both US and conventional techniques. X-ray diffraction technique and spectra analysis techniques were used to confirm the square planer geometry of the synthesized NPC's. Antimicrobial activity of the prepared 1,2,4-triazoles and their nickel complexes were studied which evaluated a high activity with complexes instead their triazoles.     

Determination of dissolved organic nitrogen in natural waters using high-temperature catalytic oxidation

Studies on nitrogen in natural waters have generally focussed on dissolved inorganic nitrogen (DIN), primarily because of relative ease of analysis and the important influence of DIN on water quality. Advances in analytical techniques now permit the systematic study of dissolved organic nitrogen (DON), and this work has shown that DON is quantitatively significant in many waters. This article describes the sampling and analytical protocols required for rapid, precise and reliable determinations of DON, involving high-temperature catalytic oxidation (HTCO), coupled to chemiluminescence detection. This approach simultaneously determines dissolved organic carbon (DOC) and total dissolved nitrogen (TDN), and DON is derived by subtraction of DIN measured by colorimetry. The DON determination is simple to perform, exhibits excellent precision (<1% for C and 1.5% for N) and is applicable to a wide range of natural waters.     

Structural and short-range order analysis of glassy system

To understand the effects of structural features and to locate their signatures in the As-Ag-Te glassy system, various properties were studied as a function of average coordination number, 〈r〉. The structure of the sample is analyzed by X-ray diffraction technique and is found to be crystalline. The d-spacing and the lattice parameters of the samples were calculated. The structural parameters were discussed on the basis of Ag (silver) effect on As-Ag-Te glassy system. Structural investigations on these compositions revealed the polycrystalline nature of compositions with the presence of hexagonal As-Ag-Te phases. Grain size increased with the Ag content and parameters of unit cell are determined. The variations in the mean atomic volume, V, and the glass transition temperature, T_g, for glass transition, with composition have been reported. The change in thermal parameters was measured using differential thermal analysis (DTA). The results of the program are in agreement with those of analytical method and realized by binding energy represented by the cohesive energy values. The generalized ‘8-n’ rule was used to estimate the average coordination number. Obtained results were treated in the frame of chemical bond approach. We estimated some of physical parameters viz. mean bond energy, glass transition temperature, cohesive energy, average single bond energy, density, compactness and molar volume of all bulk samples. Our experimental and theoretical results were discussed in light of the topological bonding structure, which involves a hierarchy of correlation ranges in short-range order.