Magneto-thermoelastic problem in non-homogeneous isotropic cylinder

The present paper concerns the investigation of the stress, temperature and magnetic fields in an isotropic elastic cylinder in a primary magenetic field when the curved surface of the cylinder subject to certain boundary conditions.The system of fundamental equations is solved by means of a finite difference method and the numerical calculations are carried out for the temperature, the components of displacement and the components of stresses with time and through the thickness of the cylinder. The results indicate that the effects of inhomogeneity and magnetic field are very pronounced.     

The Utility of Carbon Disulphide and Lawesson's Reagent for Synthesis of Different Fused Heterocycles for Antimicrobial Evaluation

Hexahydroquinolines 1a , 1b reacted with carbon disulphide in different conditions to yield the corresponding adducts 2a , 2b and 3a , 3b . Carrying out the same reactions in acetone as solvent produced the modified new products 4a , 4b . The interaction of pyrazolopyridine derivatives 5a , 5b , 5c , 5d with carbon disulphide under the same previous conditions furnished the isolated products 6a , 6b , 6c , 6d , 7a , 7b , 7c , 7d , and 8a , 8b , 8c , 8d . Studying the behavior of 1a , 1b or 5a , 5b , 5c , 5d toward Lawesson's reagent (LR) formed the final adducts 11a , 11b or 12a , 12b , 12c , 12d . The structure of synthesized compounds was confirmed with the spectroscopic and microanalytical data. The biological activities of 2a , 4a , 4b , 7a , 7c , 8d , 11a , 11b , 12b , and 12c were tested for antimicrobial evaluation.     

On the Electrochemical Reduction of α-Cyanothioacetamide Derivatives (I) Polarographic Behaviour of 2-Arylhydrazono-2-Cyanothioacetamides

The polarographic reduction of a series of 2-aryl-hydrazono-2-cyanothioacetamides ((Ia-e) has been examined in 50% ethanolic buffer solutions. The obtained data indicate that these compounds are in the hydrazono form and that they are reduced to give an amino acid and the corresponding primary aromatic amine. A mechanism has been proposed and discussed. Recombination and dissociation rate constants (k_r) and (k_d) have been computed using the appropriate spectrophotometric, potentiometric and apparent acid equilibrium constants.     

Characterization of an Exopolygalacturonase from <Emphasis Type="Italic">Aspergillus niger</Emphasis>

Polygalacturonase (PGI) from Aspergillus niger NRRL3 was purified about 12.0-fold from the cell-free broth using diethylaminoethyl-Sepharose and Sephacryl S-200 columns. The molecular weight of the PGI was 32,000 Da as estimated by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PGI had an isoelectric point of 7.6 and an optimum pH of 5.0. PGI was active on polygalacturonic acid and esterified pectins, but the activity on pectin decreased with an increase in degree of esterification. PGI had higher affinity (low Km) and turnover number (Vmax/Km and Kcat/Km) toward polygalacturonic acid. PGI was found to have a temperature optimum at 40 degrees C and was approximately stable up to 30 degrees C. All the examined metal cations had partial inhibitory effects on PGI, while Mn+2 at 5 mM caused a complete inhibition for the enzyme. Comparison of viscosity reduction rates with release of reducing sugars indicated that the enzyme from A. niger is exoacting. The storage stability study of PGI showed that the enzyme in powder form retained 56% of its activity after 9 months of storage at 4 degrees C. The above properties of PGI may be suitable for food processing.     

Molecular dynamics and conduction mechanism of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) terpolymer containing ionic liquid

Dielectric spectroscopy (DS) measurements were performed to probe the segmental dynamics and ion mobility of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) terpolymer dopped with different amounts of tetrabutylammonium tetrafluoroborate ([TBA] [BF₄]) ionic liquid (IL). Differential scanning calorimetry (DSC) was also employed to trace the change in the glass transition temperature (T_g) at different loads of IL. The DSC measurements revealed a remarkable reduction in the PVVH T_g from 344 to 310 K just by adding 20 wt% of IL. The DS measurements revealed three relaxation processes named α, β₁, and β₂. The α-process is related to the segmental motion of PVVH while the β₁ and β₂ are due to the restricted local dynamics of side chains. The segmental relaxation times (α-relaxation) speed up with increasing the concentration of IL due to the plasticization effect of IL on polymer chains. The temperature dependence of α-relaxation follows the Vogel-Fulcher-Tammann (VFT) relation with dynamic glass transition between 323 and 294 K in agreement with the DSC measurements. The β₁ and β₂-relaxations have an Arrhenius temperature dependence. The temperature dependence of ionic conductivity obeys the VFT behavior indicating the coupling between the segmental motion of PVVH chains and ion transport. Polaronic tunneling is the predominant conduction mechanism in PVVH and its composites. The specific capacitance increases with increasing both the temperature and IL concentration.     

Design and synthesis of some new tri-substituted pyrazole derivatives as anticancer agents

A new series of tri-substituted pyrazole derivatives were designed as anti-cancer agents and synthesized, starting with the formylation of semicarbazone via the Vilsmeier–Haack reaction to give 3-(4-bromophenyl)-1H-pyrazole-4-carbaldehyde I which was the precursor of compounds 1–9. The new chemical entities were screened for their anti-cancer activity on various human cancer cell lines, namely: hepatocellular carcinoma HepG2, breast cancer MCF-7, lung carcinoma A549 and prostatic cancer PC3. Most of the synthesized compounds showed remarkable activity on the tested cell lines, while compound 2 had the highest potency against the HepG2 cell line with an IC₅₀ of 9.13 µM compared with doxorubicin (IC₅₀ = 34.24 µM), the reference standard used in this study, and compound 7 was the most active on the rest of the three cell lines; MCF-7, A549 and PC3 (IC₅₀ = 16.52, 6.52 and 9.13 µM, respectively) relative to IC₅₀ = 20.85, 5.93 and 38.02 µM of the standard. Thus, some of the synthesized tri-substituted pyrazole derivatives, specially 2 and 7, have the potential to be developed into potent anticancer agents.     

Surface and Bulk Structure of Thin Spin Coated and Plasma-Polymerized Polystyrene Films

Polystyrene (PS) spin coated thin films were modified by O₂ and Ar plasma as well as by UV irradiation treatments. The modified PS samples were compared with plasma polymerized and commercial polystyrene. The effects of plasma (O₂ and Ar) and UV irradiation treatments on the surface and the bulk properties of the polymer layers were discussed. The surface properties were evaluated by X-ray Photoelectron Spectroscopy and Contact angle measurements and the bulk properties were investigated by FTIR and dielectric relaxation spectroscopy. As a result only one second treatment time was sufficient to modify the surface. However, this study was also dedicated to understand the effect of plasma and plasma irradiation on the deposited layers of plasma polymers. The dielectric measurements showed that the plasma deposited films were not thermally stable and underwent an undesired post-plasma chemical oxidation.     

Transient magneto-thermoviscoelastic plane waves in a non-homogeneous anisotropic thick strip subjected to a moving heat source

The aim of this paper is to study the transient wave propagations in a non-homogeneous anisotropic thermoviscoelastic thick strip placed in a constant primary magnetic field and subjected to a moving heat source. The governing equations for temperature and displacement fields are solved by means of a dual reciprocity boundary element method (DRBEM). In the case of plane deformation, a numerical scheme for the implementation of the method is presented and the numerical computations are carried out for the temperature, displacement components and thermal stress components. The validity of DRBEM is examined by considering a magneto-thermo-visco-elastic thick strip occupies a rectangular region and good agreement is obtained with existent results. The results obtained are presented graphically to show the effect of inhomogeneity on the displacement components and thermal stress components. Relevant results of previous investigations are deduced as special cases from this study.     

Spectroscopic Study of Solvent Polarity on the Optical and Photo-Physical Properties of Novel 9,10-bis(coumarinyl)anthracene

Novel 7,7′-((anthracene-9,10-diylbis(methylene))bis(oxy))bis(4-methyl-2H-chromen-2-one) (BisCA) was prepared as fluorescent probe. The chemical structure of the novel BisCA was confirmed by spectroscopic data as well as elemental analyses. The solvatochromic characteristics of the new proble and its precursors were investigated in different solvents including, ethanol, DMF and toluene as protic polar, aprotic polar and non-polar solvents, respectively. Photo-physical parameters of probes, such as fluorescence quantum yields, fluorescence lifetime of excited state, radiative and non-radiative decay, were assessed in different media. The intermolecular H-bond effect on absorption and excitation spectra of the novel probe was reported in different solvents. Also, Onsager cavity radius and dipole moment of ground state and excited state of the probe were calculated as described by Bakhshiev and Reichardt methods.     

A Mössbauer investigation of zirconium distribution and diffusion in ball milled nanocrystalline iron powders

Ball milled nanocrystalline iron with minor zirconium additions was examined using ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction. Powder samples were synthesized using 0, 5, and 10 wt.% zirconium additions and milled at room temperature for periods up to 24 h. Progressive decrease in grain size as determined by X-ray diffraction was observed as a function of milling time. Mössbauer spectroscopy indicates increased iron-zirconium coordination with increased milling time. After milling, the powder samples were then heat treated in an inert atmosphere of argon at up to 925 K for various times up to 25 min. Analysis of X-ray peak line width (FWHM) was used to characterize grain size and grain growth kinetics as a function of heat treatment, milling time, and alloy content and reveal an increasingly finer post-heated structure in the alloy samples containing more zirconium. Mössbauer measurements were made and suggest Zr is steadily distributed into the Fe lattice with milling and rapidly diffuses to the grain boundaries with heat treatment. The impurity-rich grain boundaries appear to considerably stabilize the refined structure.