The effect of light on the electrical conduction of pure and doped poly(methyl methacrylate)

Thin films of pure and doped poly(methyl methacrylate) (PMMA) with thicknesses ranging from 0·1 to 0·2 mm were prepared by the casting method. The effect of light on the electrical conduction of these films was studied using a specially designed electrical cell. The results showed that the resistivity of PMMA decreases gradually with increasing exposure time and the effect was found to be reversible. The doped samples showed more stability against the light effect. The current-voltage (I–V) characteristics indicated that the mechanism of conduction of PMMA depends on the presence of localized states or trapping levels arising from lack of order. Some physical parameters such as fermi energy, E_f, trap energy, E_t, density of charge carriers, n₀, ion mobility, μ, as well as the electrical conductivity of the test samples were calculated.     

Herstellung und thermisches Verhalten einiger Polyarylsilane

Ohne Zusammenfassung     

Synthesis and reactions of some 6-(2-hydroxy-1-naphthyl)-1,2,4-triazines

4,5-Benzocoumaran-2,3-dione condenses with semicarbazide and thiosemicarbazide at the 3-position and the products obtained were converted to the corresponding 6-(2-hydroxy-1-naphthyl)-1,2,4-triazines. Reactions of these triazines with some reagents are described.     

An approach to biologically important S‐heterocycles,dithiocarbamyls, and their relevant phosphono derivatives

The feasibility of insertions of carbanions between two sulfur atoms has been reported when 5‐(4‐chlorophenyl)‐4‐cyano‐1,2‐dithiol‐3‐thione ( 1 ) and tetramethylthiuram disulfide ( 17 ) were allowed to react with unsaturated 2a,b and active phosphonium salts 11a,b . The reactions afforded, mainly, 1,3‐dithiols 4a,b and 14a,b together with substituted thiophenes 10a,b and 16a,b . Reactions of 1 and 17 with α‐alkylthiomethyl phosphonates 24a,b afforded the phosphonates 25a,b and 26a,b , respectively.     

Synthesis and characterization of copper(I) halide/pseudohalide adducts of 2-benzoylpyridine and x-ray crystal structure of [di-μ-iodo-bis(N,O-2-benzoylpyridine)dicopper(I)]

Dark-brown copper(I) complexes of the type CuXL, for X = Cl, Br, I, SCN and N₃, and orange-yellow complexes of the type (CuX)₂L, for X = Cl or Br, where L = 2-benzoylpyridine, have been prepared and characterized. All complexes exhibit strong CT bands in the visible region and gave non-conducting solutions in acetone and nitrobenzene. The IR spectral data suggest that 2-benzoylpyridine acts as a monodentate ligand in the orange-yellow complexes and as a bidentate chelating ligand in the brown complexes, whereas bridging halides and pseudohalides exist in both types. The structure of the 1 : 1 black iodide complex, as determined by X-ray crystallography, features a discrete, centrosymmetric [CuI(2-benzoylpyridine)]₂ molecule with a short CuCu distance of 2.587(1) Å. Each copper atom in the dimeric molecule is tetrahedrally coordinated by two μ-iodine atoms and the carbonyl oxygen and nitrogen atoms of the chelating 2-benzoylpyridine ligand. The orange-yellow complexes display visible emission when excited in the UV region, whereas the brown complexes do not.     

Determination of amlodipine besylate by adsorptive square-wave anodic stripping voltammetry on glassy carbon electrode in tablets and biological fluids

The adsorptive and electrochemical behavior of amlodipine besylate on a glassy carbon electrode were explored in Britton-Robinson buffer solution by using cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step and fundamentally controlled by adsorption. The solution conditions and instrumental parameters were optimized for the determination of the authentic drug by adsorptive square-wave stripping voltammetry. Amlodipine besylate gave a sensitive adsorptive oxidation peak at 0.510 V (versus Ag/AgCl). The oxidation peak was used to determine amlodipine besylate in range 4.0×10⁻⁸ to 2.0×10⁻⁶ with a detection limit of 1.4×10⁻⁸ M. The procedure was successfully applied for the assay of amlodipine besylate in tablets (Norvasc)^®. The percentage recoveries were in agreement with those obtained by the reference method. Applicability to assay the drug in urine and serum samples was illustrated. The mean percentage recoveries were 96.31±1.18 and 96.98±1.17, respectively. The proposd method used for monotoring clinically relevant concntrations of drug in human urine and serum.     

Mössbauer and magnetic studies of nanocrystalline zinc ferrites synthesized by microwave combustion method

Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mössbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 ^°C and 900 ^°C. Both the saturation magnetization (Ms) and the remnant magnetization (Mr) were found to be highly dependent upon the annealing temperature. Mössbauer studies show magnetic ordering in the powder even at room temperature. The Mössbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite.     

Validated UPLC method for the determination of guaiphenesin,oxeladin citrate,diphenhydramine, and sodium benzoate in their quaternary mixture used in treatment of cough,in the presence of guaiphenesin-related substance (guaiacol)

Accurate, precise, and sensitive UPLC method was developed and validated for the simultaneous determination of a quaternary mixture containing guaiphenesin (GUP), oxeladin citrate (OXC), diphenhydramine (DPH), and sodium benzoate (SOB) in the presence of GUP-related substance, guaiacol (GUA). Chromatographic separation was achieved using NUCLEOSHELL^® column—C₁₈ (4.0?×?50.0 mm, 2.7 μm). Isocratic elution at a flow rate 1.0 mL/min was performed using a mobile phase consisting of acetonitrile:phosphate buffer pH 3.5?±?0.1 (25.0:75.0, v/v). The specificity of the developed method was investigated by analyzing of laboratory-prepared mixtures containing different ratios of the four drugs, in the presence of GUA as well as their combined pharmaceutical formulation. The obtained results were statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p?=?0.05.     

Synthesis and bioactivity evaluation of new pyrimidinone-5-carbonitriles as potential anticancer and antimicrobial agents

Research on Chemical Intermediates - New series of pyrimidinone-5-carbonitriles 3a–i, 4a–e, 5a–c, 6 and 7 have been synthesized and explored for their activities as anticancer,...     

Prepared and properties of filled and pozzolanic-filled cements from marble dust waste and granulated slag

Journal of Thermal Analysis and Calorimetry - Marble processing produces immense amounts of solid waste, which causes environmental issues. This work aims to “recycle marble dust waste”...