Photochromism and Photoisomerization in Some 2,3,4,4,5,6-Hexasubstituted 4H-Thiopyrans

Photochromism and photoisomerization reactions of some new 2,3,4,4,5,6-hexasubstituted 4H-thiopyrans are described.     

碱性溶液中电聚酪胺-铜草酸盐纳米复合物修饰铜电极电催化甲醇氧化(英文)

A polytyramine-copper oxalate nanocomposite modified copper(PTCOxNMC) electrode prepared by electropolymerization was examined for electrocatalytic activity towards the oxidation of methanol in alkaline solution using cyclic voltammetry and impedance spectroscopy. The prepared PTCOxNMC electrode showed a significantly high response for adsorbed methanol oxidation. The effects of various parameters such as potential scan rate and methanol concentration on the electrocatalytic oxidation at the surface of the PTCOxNMC electrode were investigated. Spectrometry techniques such as Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine the surface physical characteristics of the modified electrode and revealed that the polytyramine-copper oxalate nanocomposite particles were highly dispersed on the surface of the copper electrode with a narrow size up to 40 nm. The very high current density obtained for the catalytic oxidation may have resulted from the high electrode surface area caused by modification with the poly-tyramine-copper oxalate nanocomposite.     

Synthesis,metal ion complexation and first use of a thia-aza substituted macrocyclic diamide as a novel sensing material for preparation of selective and sensitive poly(vinyl chloride)-membrane potentiometric sensors for Ag+ ion

A novel thia-aza substituted macrocyclic diamide 7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione (L) was synthesized and stability of its complexes with several alkaline earth, transition and heavy metal ions were studied conductometrically in methanol solution. The resulting 1:1 Ag⁺–L complex found to be the most stable one among all cation complexes studied. The optimized structures of the ligand and its Ag⁺ complex were also investigated. Based on the preliminary results thus obtained, L was used as an excellent sensing material to prepare polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes. The electrodes revealed a Nernstian behavior over wide Ag⁺ ion concentration ranges (i.e., 2.0 × 10^?6–1.0 × 10^?2 M for PME and 5.0 × 10^?7–1.0 × 10^?2 M for CGE). The potentiometric responses were independent of pH of the test solution in the range 2.9–6.8. The electrodes possessed advantages of low resistance, relatively fast response time, long lifetimes and, especially, good selectivity relative to a wide variety of other cations. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag⁺ ion in waste water, photographic emulsion, radiographic and photographic films and dental amalgams.     

Excitation of theΔ (1232)-resonance in proton-nucleus collisions

The excitation of theΔ resonance is observed in proton collisions on C, Nb and Pb targets at 0.8 and 1.6 GeV incident energies. The mass E₀ and widthΓ of the resonance are determined from the invariant mass spectra of correlated (p, π^±)-pairs in the final state of the collision: The mass E₀ is smaller than that of the free resonance, however by comparing to intra-nuclear cascade calculations, this reduction is traced back to the effects of Fermi motion, NN scattering and pion reabsorption in nuclear matter.     

Alumina-based fiber for solid phase microextraction of alcohols from gaseous samples.

On the basis of the affinity of alumina towards hydroxyl functional groups, a solid phase microextraction (SPME) fiber was constructed using alumina powder and poly(vinyl chloride) (PVC). Different compositions were tested and alumina:PVC (97:3) was selected as an optimun composition. A piece of silver wire was used as fiber support. The fiber producing was simple and could be completed in a few minutes. The mechanical durability of the fiber was so good that only a single fiber was used during this study. Ethanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol and cyclohexanol were selected as target analytes. Finally, ethanol concentration in the fruit juices and vinegar was measured using SPME-capillary gas chromatography followed by flame ionization detection.     

The Semileptonic Decay Modes {\bar{B} \rightarrow D\ell \bar{\nu}} and {\bar{B}_{s} \rightarrow D_{s} \ell \bar{\nu}}: A New Analysis in Potential Model

We consider the Schrödinger equation with a combination of Deng–Fan-type and harmonic terms. To solve the corresponding differential equation, we split the equation to two parts: the parent and the perturbation terms. We use the Nikiforov–Uvarov technique to solve the parent part. For the perturbation part, we apply the series expansion method. Next, using the calculated wave function, we investigate some bottom and charm mesons within the Isgur–Wise function formalism. We present especially semileptonic \({\bar{B} \rightarrow D\ell \bar{\nu}}\) and \({\bar{B}_{s} \rightarrow D_s \ell \bar{\nu }}\) decay widths, branching ratios and \({|V_{cb}|}\) (element of the CKM matrix). Masses of some pseudoscalar mesons are also indicated. Comparisons of our results with experimental values and other approaches are included.     

Study of Heavy-Light Mesons Properties Via the Variational Method for Cornell Interaction

Using the variational method we calculate mesonic wave function. We report masses and decay constants for heavy-light mesons. Leptonic decay widths of charmed and beauty mesons are also calculated. The obtained results are compared with the available experimental and theoretical data.     

Synthesis of functional polyethylene graft copolymers by nitroxide‐mediated living radical polymerization

This paper describes a new method to prepare graft copolymers, such as polyethylene‐g‐polystyrene (PE‐g‐PS), with a relatively well‐controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and m,p‐methylstyrene (m,p‐MS) to nitroxide‐mediated “living” free radical polymerization (LRFP) of styrene. The metallocene catalysis produces ethylene‐co‐m,p‐methylstyrene (EMS) random copolymers. Next, 1‐hydroxyl‐2,2,6,6‐tetramethylpiperidine (HO‐TEMPO) was synthesized by the reduction of TEMPO with sodium ascorbate. The macroinitiator (EMS‐TEMPO) was synthesized with the bromination reaction of EMS, and the following nucleofilic reaction with this functional nitroxyl compound. The resulting macroinitiator (EMS‐TEMPO) for LRFP was then heated in the presence of styrene to form graft copolymer. DSC, ¹H‐NMR, FTIR spectroscopy were employed to investigate the structure of the polymers. The results of Molau test showed that PE‐g‐PS could be a potential good compatilizer. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization, and crystal structures of α, α′-bis(substituted-benzylidene)cycloalkanone derivatives by nano-TiO<Subscript>2</Subscript>/HOAc

A new and economical synthesis of α, α′-bis(substituted-benzylidene)cycloalkanones has been achieved by the reaction of cycloalkanones with different aromatic aldehydes using nano-TiO₂/acetic acid as a catalyst in ethanol under reflux conditions with excellent yields. Five new products and three new single crystal structures are reported.     

Expedient Catalytic Access to Knöevenagel Condensation Using Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript> Nanocomposite in Room Temperature

Sr₃Al₂O₆ nanocomposite was prepared by sol gel method using aluminum isopropoxide, strontium nitrate, acetylacetone and polyethylene glycol as template, followed by calcination at 900 °C. This nanocomposite was characterized by various techniques including X-ray powder diffraction, infrared spectroscopy, elemental analysis, scanning transmission microscope and transmission electron microscope. It was found that Sr₃Al₂O₆ nanocomposite successfully catalyzes the Knöevenagel condensation of aromatic aldehydes with malononitrile in room temperature in ethanol. Expedient access to the corresponding Knöevenagel adducts in moderate to high yields within 6 min is promising. The recovered catalyst was reused for three times without significant loss of activity.