Determination and Temperature Dependence of Plateau Modulus for Polymerization of Propylene to Isotactic Polypropylene with Ultra-high Molecular Weight under Catalysis of Ziegler-Natta Catalyst

The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G") plots at 180 and 200 ℃versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0. 01-100 rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G"(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(ω) curve directly. For UHPPH, the G0N determined to be 4. 28×105 and 3. 62×105 Pa at 180and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G0N has no relation to the molecular weight.     

A Quasi-Interpolation Satisfying Quadratic Polynomial Reproduction with Radial Basis Functions

In this paper,a new quasi-interpolation with radial basis functions which satis- fies quadratic polynomial reproduction is constructed on the infinite set of equally spaced data.A new basis function is constructed by making convolution integral with a constructed spline and a given radial basis function.In particular,for twicely differ- entiable function the proposed method provides better approximation and also takes care of derivatives approximation.     

Synthesis and Characterization of Poly(ether imide)s Containing m-Methyl and Phthalazinone Moieties

Aromatic polyimides are distinguished for their excellent mechanical and thermal properties in many engineering fields1. However, aromatic polyimides are normally insoluble in common organic solvents, which restricts their applications in some fields. Many efforts have been taken to improve their solubility. Introducing bulky side groups and non-coplanar structure into polymers bone chains is a good way to obtain the polymers with excellent mechanical and thermal properties2. In this paper…     

An Efficient and Green Procedure for the Preparation of gem-Dicar- boxylates from Aldehydes Catalyzed by Fe_2(SO_4)_3·xH_2O

~~An Efficient and Green Procedure for the Preparation of gem-Dicar- boxylates from Aldehydes Catalyzed by Fe_2(SO_4)_3·xH_2O~~     

A New Quantum State

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Comparison of the Contributions of Tetrahydrofurfuryl Alcohol and PEG to a-Chymotrypsin Renaturation with High Performance Hydrophobic Interaction Chromatography

Theinvestigationofproteinrenaturation,orrefoldinghasbecomeaveryhotpointinbothliquidchromatography(LC)andlifesciencefields.Besidesusualdilutionanddialysismethods,manynewmethodsconcernproteinrenaturationhavebeenpresented,suchasreversemicelles1,chaperones2,polyethyleneglycol(PEG)3,surfactant4andantibodies5etc.Oneoftheauthorssuggestedhighperformancehydrophobicinter-actionchromatography(HPHIC)tobeanewtoolforproteinrenaturation6.Areviewonproteinrenaturationwithliquidchromatography(LC)wasrecentl…     

塞曼石墨炉原子吸收法定测血清、血浆、全血中锌

本文讨论了L■vov平台石墨炉原子吸收法对血样中锌的准确测定方法。针对石墨炉测锌时样品易被污染、线性范围窄、灵敏度过高,血基体干扰严重以及如何降低取血量以提高方法在临床上之实用价值等问题进行了较系统的探索。在μg/l级本方法测定变异系数为2.1%。     

Study on the Synthesis of Metabolite of Clausenamide （CM1）

(-) Clausenamide (1) showed strong nootropic action, while its (+) antipode had no such an action. The content of CM1(2) in the metabolites of (-)1 is much higher than that of (+)11. For comparing the nootropic activity of enantiomers, (+) and (-) CM1 were synthesized. CM1 is the hydroxylated product of the N-methyl group of clausenamide. Oxidation of the C3-OH and C6-OH protected clausenamide to introduce the hydroxyl group into the methyl was tried but unsuccessful. Then de novo s…     

Studies on Hepatocyte-Targeting Magnetic Resonance Imaging Macromolecular Contrast Media

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STUDY ON THE SYNTHESIS AND PHYSICOCHEMICAL PROPERTIES OF SUCROSE POLYESTER

1. INTRODUCTIONSucrose polyester (SPE) is neither metabolized nor absorbed, it makes no caloric contribution to the diet. Excessive dietary fat intake is associated with increasing risk of obesity, high blood cholesterol, hypertension, coronary heart disease and some types of cancer. At present, fat substitutes are fashionable all over the world. SPE is a new functional fat substitute, which is similar to ordinary oils in physical and chemical properties. In a word, the research and dev…