A New Isomalabaricane Triterpenoid from Sponge Jaspis sp.

From the marine sponge Jaspis sp., a new isomalabaricane triterpenoid 22, 23-dihydrostellettin D (1) was isolated, and its structure was established on the basis of IR, MS and extensive 2D NMR spectroscopic analysis. It is a unique skeleton compound rarely obtained from Chinese marine organisms.     

Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li⁺, Na⁺, K⁺, and Cs⁺ ions and the study of the influence of alkali metal cations on CO₂ adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs⁺) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO₂ adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li⁺ or K⁺ cations.     

STUDIES ON STEROIDAL PLANT-GROWTH REGULATORS (ⅩⅦ)——A NEW SYNTHESIS OF HOMOBRASSINOLIDE AND (22S,23S)-22,23-EPI-HOMOBRASSINOLIDE

Homobrassinolide (2) and (22S, 23S)-22,23-epi-homobrassinolide (4) were synthesized fromstigmasterol in seven steps respectively in 4.7% and 24.1% overall yields. The ratio of 2 to 4is 1:5. The key step is the highly regioselective formation of the B--homo-7-oxa-lactone ringby oxidation of an enol silyl ether with 3--chloro-peroxybenzoic acid.     

Cu-Pd/MCM-22催化剂上二甲醚低温水解反应

 考察了分子筛的类型、硅铝比及Cu和Pd改性对分子筛催化剂上二甲醚低温水解活性的影响. 结果表明,酸性的MCM-22和HZSM-5分子筛催化剂具有较高的二甲醚水解活性,且其活性随着分子筛硅铝比的增加而降低. 这表明分子筛的类型及酸性对催化剂性能有重要影响,具有超笼结构的MCM-22分子筛上B酸中心的良好可接近性,使得该分子筛催化剂的水解活性较相同硅铝比的HZSM-5分子筛高. 与改性前相比, Cu和Pd改性后的MCM-22催化剂显示出更高的二甲醚水解活性.     

Gammaspektrometrische Schnellbestimmung von Thorium in Wolfram-Schwei?elektroden

Zusammenfassung Die Methode wurde für ThO₂-Gehalte von 1–5% in stabförmigen Wolfram-Schweiß-elektroden ausgearbeitet. Die gammaspektrometrische Aktivitätsmessung kann unter Verwendung eines einfachen Einkanal-Gammaspektrometers mit NaJ (Tl)-Bohrlochkristall erfolgen. Der günstigste Meßbereich umfaßt224xp22/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-Energien von 30–500 keV. Eine Zählzeit von 5–40 sec ist je nach ThO₂-Gehalt und Elektrodendurchmesser ausreichend. Chemische Eichanalysen für aus verschiedenen ThO₂-Chargen hergestellte Elektroden sind unerläßlich. Brauchbare Messungen werden erst 1 Woche nach der Sinterung der Elektroden erhalten. Dies erscheint jedoch für die Endkontrolle auszuliefernder Elektroden unwesentlich. Untersuchungen betreffend die radiale und axiale ThO₂-Verteilung an verschiedenen Elektroden wurden durchgeführt. Dank. Für wertvolle Diskussionen sowie für die Aufnahme von224xp22/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-Spektren mit hoher Auflösung sind wir Herrn Dr. Danneberg der Osram Studiengesellschaft in München zu aufrichtigem Dank verpflichtet, ebenso Herrn Dipl.-Ing. Christ vom Metallwerk Plansee für seine Rechenhilfe.     

On fermion gauge groups,current algebras and Kac-Moody algebras

Representations of groups of loops in U(N), SO(N) and various subgroups are studied. The representations are defined on fermion Fock spaces, and may be regarded as local gauge groups in the context of the two-dimensional many-particle Dirac theory for charged or neutral particles with rest mass m0. For m=0, the representations are shown to give rise to type I factors, while for m>0 hyperfinite, type III₁ factors arise. A key point in the structure analysis is a convergence result: We prove that suitably rescaled representers of certain nonzero winding number loops converge to the free Dirac fields. We also present applications to cyclicity and irreducibility questions concerning the Dirac currents, and to the representation theory of a class of Kac-Moody Lie algebras.     

On locking materials

This work is devoted to the study of variational problems encountered in the theory of locking materials introduced by Prager. In a first step, we are interested in the dual principles governing the equilibrium state of an elastic-locking material. We establish the inf-sup equality by means of a penalty method. In a second step, we introduce and discuss the locking limit analysis problem. This problem allows one to determine which displacements can be imposed on a locking body before complete locking. We show the equivalence of the statical and the kinematical methods. Two appendices close the paper. The first one focuses the attention on stress concentrations in a problem of torsion, and the second is devoted to materials with limited compressibility which lead to simpler mathematical problems.

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Résumé Ce travail est consacré à l'étude des problèmes variationnels posés par les matériaux à blocage introduits par Prager. Dans un premier temps nous nous intéressons aux principes duaux qui gouvernent l'équilibre d'un milieu élastique à blocage. Nous établissons l'égalité Inf-Sup par une méthode de pénalisation. Dans un deuxième temps nous introduisons et discutons l'analyse limite de blocage qui permet de déterminer les déplacements susceptibles d'être imposés au corps avant son blocage complet. On montre que les approches statiques et cinématiques conduisent à la même valeur de la charge limite de blocage. Le travail se termine par deux annexes: l'une met l'accent sur la possibilité de concentration de contraintes (qui sont alors des mesures) dans un problème de torsion; l'autre étudie les matériaux à compressibilité limitée pour lesquels les problèmes mathémqtiques se simplifient notablement.

     

Characterization of hydrotreated Cu-ZSM-5 catalyst for the selective catalytic reduction of NO by n-decane

The steam treatment of Cu-ZSM-5 prepared by solid ion exchange involves an important decrease of the NO conversion. Characterization of the solids by NO-TPD, H₂-TPR, ²⁷Al MAS NMR shows that the catalyst deactivation is mainly due to change in copper species rather than the collapse of the zeolite framework.This revised version was published online in December 2005 with corrections to the Cover Date.     

Notes on pre-Frölicher spaces

In this work we introduce a class of Sikorski differential spaces (M, D) called pre-Fr¨olicher spaces, on which the process of yielding a Fr¨olicher structure on the underlying set M is D preserving, their category we denote by preFrl. We investigate some algebraic properties on these spaces whose subsequent geometric properties are mostly similar to those of smooth manifolds, except for the invariance of dimension, and also that preFrl naturally induces a Cartesian closed subcategory of the category Frl in which there is no discrete object. Using this Cartesian property, it is shown that the Gelfand representation is a smooth map, that the tangent as well as cotangent bundles are made smooth spaces in an unusual but more natural way via smooth curves.