Hybrid stress analysis of boundary and finite elements by a super-element method

This paper is concerned with the hybrid method of boundary element and finite element techniques by means of an “external-super-element” function of the commercial finite element method code . The proposed super-element method preserves the modelling simplicity of the boundary element method and the generality of . Two- and three-dimensional elastostatic analyses are performed to demonstrate the accuracy of this method as well as its applicability to practical problems.     

Biosynthesis of citreothiolactone,citreopyrone and pyrenocine B

¹³C NMR spectroscopy using INADEQUATE pulse sequence method has been used to deduce the labelling patterns of the three metabolites of $\text{Penicillium citreo-viride}$ B. derived from [1,2-¹³C]acetate, indicating that their carbon skeletons consist of two different units [CH₃COCH₂COCH₂COS-Enzyme and CH₃COCH₂COS-Enzyme].     

Evidence for the importance of conformational equilibria in Rh-diphosphine complexes for the enantioselection in Rh-catalyzed asymmetric hydrogenation

The conformations of the chelate cycles in the X-ray structures of norbornadiene- and cyclooctadiene-rhodium complexes of (R,R)-1,2-bis[(o-methylphenyl)phenylphosphino]ethane are dramatically different. Nevertheless, they demonstrate the same sense of enantioselection in asymmetric hydrogenation of dehydroamino acids.     

Synthesis of 2-decenedioic acid (royal jelly acid) by sequential carbonylation of butadiene catalyzed by a palladium—phosphine complex and dicobalt octacarbonyl

Carbonylation of butadiene in t-butyl alcohol catalyzed by a palladium complex gave t-butyl-3,8-nonadienoate (I). Further carbonylation of I in methanol with Co₂(CO)₈ afforded t-butylmethyl-3-decenedioate (II) as the main product. Hydrolysis and base-catalyzed isomerization of II produced E-2-decenedioic acid.     

Living cationic polymerization of ethyl 2-(vinyloxy)ethoxyacetate: A vinyl ether with an ether and an ester function in the pendant

Ethyl 2-(vinyloxy)ethoxyacetate ( 4 ; CH₂?CH? OCH₂CH₂OCH₂? COOC₂H₅), a vinyl ether having both carboxylic acid ester and oxyethylene unit in its pendant, afforded well-defined living polymers when polymerized by the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?40°C. The polymers possessed a narrow molecular weight distribution (M _w/M _n ≤ 1.15), and their molecular weight (M _n) increased proportionally to monomer conversion or the molar ratio of the monomer to hydrogen iodide. The polymer molecular weight also increased upon addition of a fresh feed of the monomer to a completely polymerized reaction mixture. Polymers of high molecular weights (M _n > 5 × 10⁵) and broad molecular weight distributions were obtained by BF₃OEt₂ in toluene at ?40°C. Polymerization rate of 4 with HI/I₂ is ca. 100 times greater than that of the corresponding alkyl vinyl ether, and thus 4 was found to be one of the most reactive vinyl ethers thus far studied. Alkaline hydrolysis of the pendant ester groups of the polymers gave a vinyl ether-based polymeric carboxylic acid 6 with a narrow molecular weight distribution.     

Characterization of a lactate oxidase from a strain of gram negative bacterium from soil

A lactate oxidase was purified about 36-fold from a newly screened strain KY6 of gram negative bacterium from soil to yield a homogeneous protein. The native enzyme had a molecular mass of 204 kDa measured by Sephadex G-200 and that of subunit on the SDS-PAGE was found to be 45 kDa. The enzyme was optimally active at pH 7.7 and showed stability at pH range of 5.7 to 9.5 for 24 h at 4?C. The optimum temperature was 70?C and the enzyme activity was stable for 10 min up to 45?C. The half-life of the enzyme activity was about 10 min at 55?C. The best substrate of the enzyme was D-lactate and Km value for D-lactate was 0.14 mM. The Km value for DL-lactate was 0.20 mM. Substrate inhibition of the enzyme was observed at higher concentrations than 20 mM of DL-lactate and 10 mM of D-lactate.     

Star-shaped polymers by living cationic polymerization. VII. Amphiphilic graft polymers of vinyl ethers with hydroxyl groups: Synthesis and host–guest interaction

Amphiphilic graft polymers of vinyl ethers (VEs) ( 6 ) where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(alkyl vinyl ether) segment were prepared on the basis of living cationic polymerization, and their properties and functions were compared with the corresponding amphiphilic star-shaped polymers. In toluene at ?15°C, the HI/ZnI₂-initiated living block polymer 2 of an ester-containing VE (CH₂? CHOCH₂CH₂OCOCH₃) and isobutyl VE (IBVE) was terminated with the diethyl 2-(vinyloxy)ethylmalonate anion [ 3 ; ^ΦC(COOEt)₂CH₂CH₂OCH ? CH₂] ( 2/3 = 1/2 mole ratio) to give a macromonomer ( 4 ), H[CH₂CH(OCH₂CH₂OCOCH₃)] _m-[CH₂CH(OiBu)]_n? C(COOEt)₂CH₂CH₂OCH ? CH₂ (m = 5, n = 15; M?_n = 2600, M?_w/M?_n = 1.13, 1.10 vinyl groups/chain). Subsequently, 4 was homopolymerized with HI/ZnI₂ in toluene at ?15°C. In 3 h, 85% of 4 was consumed and a graft polymer ( 5 ) was obtained [M?_w = 15000, DP_n (for 4 ) = 6]. The apparent M?_w (10,900) of 5 by size-exclusion chromatography (SEC) is smaller than that by light scattering as well as that (18,300) by SEC of the corresponding linear polymer with the almost same molecular weight, indicating the formation of a multi-branched structure. Hydrolysis of the pendant esters in 5 gave the amphiphilic graft polymer 6 where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(IBVE) segment. The graft polymer 6 was found to interact specifically with small organic molecules (guests) with polar functional groups, and 6 differed in solubility and host-guest interaction from the corresponding star-shaped polymer. © 1993 John Wiley & Sons, Inc.     

Cationic oligomerization of styrene by solid acids. I. Catalysis by poly(styrenesulfonic acid) resin

Cationic oligomerizations of styrene by a solid acid [poly(styrenesulfonic acid) resin, Amberlyst 15] and by the corresponding soluble catalyst (p-toluenesulfonic acid) were compared with respect to their reactivity and the molecular weight distribution of products. The feature of Amberlyst 15 as oligomerization catalyst, in addition to its easy separation from products, was found to be was follows: The activity of Amberlyst 15 was 10 times larger than that of p-toluenesulfonic acid in benzene, although catalyst deactivation at high conversions was observed for Amberlyst 15 at high monomer concentrations. Styrene trimer and tetramer were dominantly produced by Amberlyst 15 at low monomer concentrations, whereas a linear dimer was obtained in 85% yield with p-toluenesulfonic acid. Characteristically, solvent polarity had almost no effect on the reaction rate and product composition in the Amberlyst 15-catalyzed oligomerization. These facts were discussed in relation to differences between the heterogeneous and homogeneous catalyses.