Microstructure and mechanical properties of Mg-12.3Zn-5.8Y-1.4Al alloy

Microstructure and mechanical properties of as-cast and heat-treated Mg-12.3Zn-5.8Y-1.4Al (ZYA1261) alloy were investigated. The phase compositions of the as-cast alloy are alpha-Mg, Mg3YZn6 (I-phase), Mg(3)y(2)Zn(3) (W-phase), Mg12YZn (Z-phase), Mg24Y5, MgZn and a small quantity of Al-containing phase.

Metallic Cation Induced One-Dimensional Assembly of Poly(acrylic acid)-1-Dodecanethiol-Stabilized Gold Nanoparticles

In this work, we report a simple approach for controllable synthesis of one-dimensional (ID) gold nanoparticle (AuNP) assemblies in solution. In the presence of divalent metallic ions, poly(acrylic acid)-1-dodecanethiol-stabilized AuNPs (PAA-DDT@AuNPs) are found to form I D assemblies in aqueous solution by an ion-templated chelation process; this causes an easily measurable change in the absorption spectrum of the particles. The assemblies are very stable and remain suspended in solution for more than one month without significant aggregation.

New process for the preparation of 3,5-dihydroxy-1-pentylbenzene

A new process for the preparation of 3,5-dihydroxy-1-pentylbenzene, which is used as medicinal intermediate and raw material for the synthesis of HIV restrainer, is proposed in this paper. Technical 3,5-dimethoxybenzoic acid reacted with lithium hydride to form a salt (I) which acylated n-butyllithium directly to give 1-(3,5-dimethoxyphenyl)-1-pentanone (II) in 85.06% yield. Then (II) was reduced through a Wolff-K-Huangminglong reaction at 210 degrees C to give 3,5-dimethoxy-1-pentylbenzene (III). Finally, (III) refluxed with melt pyridine hydrochloride at 200 degrees C for 2 h to afford the target product 3,5-dihydroxy-1-pentylbenzene (IV). The total yield of (IV) amounted to 61.50% and its mass percentage was 98.22%. The products were characterized by means of IR, H-1-NMR, GC and HLPC-MS. The results indicated that this synthetic route was feasible, characterized by simple process and higher yield, and superior to the published ones.

Diacetatobis[2-(2-furyl)-1H-imidazo[4,5-f]-[1,10]phenanthroline]cadmium(II)

In the title complex, [Cd(C2H3O2)(2)(C17H10N4O)(2)], the central Cd-II ion (site symmetry 2) shows an uncommon eight-coordinate CdN4O4 coordination geometry arising from two N,N-chelating 2-(2-furyl)-1H-imidazo[4,5-f]-1,10-phenanthro-line molecules and two O, O-bidentate acetate anions.

The chemical resolution of racemic cis-2-hydroxymethyl-5(cytosine-1 '-yl)-1,3-oxathiolane (BCH-189)-one direct method to obtain lamivudine as anti-HIV and anti-HBV agent

Racemic cis-BCH-189 can be resolved to (-)-enantiomer (lamivudine) and (+)-enantiomer by esterification of cis-2-hydroxymethyl-5-(N-4(')-acetylcytosine-1'-yl)-1,3-oxathiolane and (+)-menthyl chloroformate in CH3CN with pyridine as base. The two diastereomers of ester were seperated by recrystallization in methanol at 0degreesC. Lamivudine was obtained by deprotection of (-)-diastereomer with high yield.

The nature of the interaction between polyaniline and 2,5-dimercapto-1,3,4-thiadiazole in electrochemical redox processes

The interaction between polyaniline (PAn) and 2,5-dimercapto-1,3,4-thiadiazole (DMcT) was investigated by means of cyclic voltammetry and UV-visible spectroscopy. The results show that the polymerization-depolymerization reaction of DMcT or its dilithium salt Li(2)DMcT is a kinetically quasi-reversible process. PAn exhibits very weak electrochemical activity in neutral propylene carbonate. After doping with protonic acid, such as hydrochloric acid or maleic acid etc., however, it shows an extensively enhanced electroactivity. For the complex system, PAn-DMcT or PAn-Li(2)DMcT, polyaniline has no catalytic activity for the electrochemical polymerization-depolymerization reaction of DMcT or DMcT(2-). Instead, the enhancement of the electrochemical redox activity of PAn-DMcT system compared with that of PAn, DMcT, Li(2)DMcT, and PAn-Li(2)DMcT comes from the protonic doping of PAn by DMcT.

Investigation of the electrocatalytic effect of polyaniline on the redox reaction of 2,5-dimercapto-1,3,4-thiadiazole by cyclic voltammetry

Electrochemical polymerized polyaniline(PAn) film electrode was used to investigate the electrocatalytic effect of PAn on the electrochemical redox reaction of 2,5-dimercapto-1,3,4-thiadiazole (DMcT), PAn film electrode was electrochemically treated or immersed in DMcT solution before it was scanned in 1.0 mol/L HCl electrolyte. The cyclic voltammograms of PAn film electrode in 1.0 mol/L HCl solution changed with the above treatment, implying the electrocatalytic effect of PAn on the redox reaction of DMcT, The formation of electron-donor-acceptor adducts through the interaction between thiol or disulfide groups of DMcT and amine or imine groups of PAn during the treatment was probably the reason of the catalysis, The electrochemical properties of the adduct were different from those of PAn and DMcT, The adduct possessed a higher electrochemical activity and a better electrochemical reversibility than DMcT or PAn used alone.

Synthesis of cis-(+/-)-2-hydroxymethyl-5-(cytosine-1 '-yl)-1,3-oxathiolane (BCH-189)

The target compound BCH-189 was synthesized with high yield via four steps from benzoyloxy acetylaldehyde and p-dithiane-2,5-diol as starting materials. The synthetic route is preferable to what literature reported.

Poly(ethylene glycol) block poly(butyl acrylate) .1. Synthesis

Prepolymers of poly(ethylene oxide) (Pre-PEG) were synthesized by reacting azoisobutyronitrile (AIBN) with poly(ethylene glycol) (PEG), and their structures were characterized by IR and UV. The molecular weight of pre-PEG was related to the feed ratio and reaction time. These prepolymers can be used to prepare block copolymers - poly(ethylene oxide)-block-poly(butyl acrylate) (PEO-b-PBA) by radical polymerization in the presence of butyl acrylate (BA). Solution polymerization was a suitable technique for this step. The yield and the molecular weight of the product were related to the ratio of the prepolymer to BA, the reaction time, and temperature. GPC showed that the molecular weight increased with a higher ratio of BA to pre-PEO. The intrinsic viscosity of the copolymers was only slightly dependent on reaction time, but decreased at higher reaction temperatures, as did the amount of PEA homopolymer. (C) 1997 John Wiley & Sons, Inc.

DICHLORO(ETA(5)-CYCLOPENTADIENYL)([1-(4-METHOXYPHENYL)CYCLOHEXYL]-ETA(5)-CYCLOPENTADIENYL)TITANIUM(IV)

The title molecule, [TiCl2(C5H5)(C18H21O)], has a pseudotetrahedral bent metallocene structure in which the cyclopentadienyl ring is symmetrically bonded to Ti [range of Ti-C distances 2.36(1)-2.41(1)Angstrom], but the substituted cyclopentadienyl ring adopts asymmetrical bonding [Ti-C 2.33(1)-2.48(1)Angstrom] due to the interaction of the large substituent with the Cl(2) atom. The angle C(11)-C(1)-C(21) is 111.1(8)degrees with the large substituent occupying a cis position with respect to the substituted ring.

钴-4-(5-氯-2-吡啶偶氮)-1,3-二氨基苯-Triton X-100体系的析相富集及痕量钴的光度测定

本文研究了TritonX-100在浊点条件下对钴-4-(5-氯-2-吡啶偶氮)-1,3-二氨基苯(5-Cl-PADAB)络合物的析相条件,在pH4.0～6.0介质中,将胶束溶液加热到92±1℃,保持40min,络合物即被TritonX-100相富集。富集液在575nm测定吸光度,钴含量在0～4μg/5ml范围内服从比尔定律,干扰离子可在TritonX-100析相液中加入H_2SO_4消除。拟定的方法灵敏、简捷,已用于不经分离直接测定人发及自来水中痕量钴。

BLENDS OF POLY[3,3-BIS(CHLOROMETHYL)OXETANE] WITH POLY(VINYL ACETATE) .1. THERMAL AND MECHANICAL-PROPERTIES

Blends of poly[3,3-bis(chloromethyl)oxetane] (Penton) with poly(vinyl acetate) were prepared. Compatibility, morphology, thermal behavior, and mechanical properties of blends with various compositions were studied using differential scanning calorimetry (DSC), dynamic mechanical measurements (DMA), tensile tests, and scanning electron microscopy (SEM). DMA study showed that the blends have two glass transition temperatures (T(g)). The T(g) of the PVAc rich phase shifts significantly to lower temperatures with increasing Penton content, suggesting that a considerable amount of Penton dissolves in the PVAc rich phase, but that the Penton rich phase contains little PVAc. The Penton/PVAc blends are partially compatible. DSC results suggest that PVAc can act as a beta-nucleator for Penton in the blend. Marked negative deviations from simple additivity were observed for the tensile strength at break over the entire composition range. The Young's modulus curve appeared to be S-shaped, implying that the blends are heterogeneous and have a two-phase structure. This was confirmed by SEM observations.

SIMULATION OF THE OXYGEN-ATOM VACANCY IN THE HIGH-TEMPERATURE SUPERCONDUCTOR TIBA2CAN-1CUNO2N+2.5(N = 1)

These simulation calculations for the oxygen-atom vacancy in the high temperature superconductor TlBa2Ca(n-1)Cu(n)O2n+2.5(n = 1) have been performed by means of the tight-binding approximation based on the EHMO method. The results indicate that the effect of the oxygen-atom vacancy on the charge distributions at the Tl-, Ba-, Cu- and O-atom sites is appreciably different and that there may exist two kinds of Cu cation with different net charges (approximately + 3.0 or approximately + 1.0) due to the oxygen-atom vacancy in the lattice. The electric field gradient at the site of the oxygen-atom vacancy has been calculated. The position of the oxygen-atom vacancy which favours the high temperature superconductivity of TlBa2Ca(n-1)Cu(n)O2n+2.5(n = 1) has been discussed.