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71.
Stephan Jüngling Rolf Mülhaupt Udo Stehling Hans-Herbert Brintzinger David Fischer Franz Langhauser 《Journal of polymer science. Part A, Polymer chemistry》1995,33(8):1305-1317
Propene was polymerized at 40°C and 2-bar propene in toluene using methylalumoxane (MAO) activated rac-Me2Si(Benz[e]Indenyl)2ZrCl2 ( BI ) and rac-Me2Si(2-Me-Benz[e]Indenyl)2ZrCl2 ( MBI ). Catalyst BI /MAO polymerizes propene with high activity to afford low molecular weight polypropylene, whereas MBI /MAO is less active and produces high molecular weight polypropylene. Variation of reaction conditions such as propene concentration, temperature, concentration of catalyst components, and addition of hydrogen reveals that the lower molecular weight polypropylene produced with BI /MAO results from chain transfer to propene monomer following a 2,1-insertion. A large fraction of both metallocene catalyst systems is deactivated upon 2,1-insertion. Such dormant sites can be reactivated by H2-addition, which affords active metallocene hydrides. This effect of H2-addition is reflected by a decreasing content of head-to-head enchainment and the formation of polypropylene with n-butyl end groups. Both catalysts show a strong dependence of activity on propene concentration that indicates a formal reaction order of 1.7 with respect to propene. MBI /MAO shows a much higher dependence of the activity on temperature than BI /MAO. At elevated temperatures, MBI /MAO polymerizes propene faster than BI /MAO. © 1995 John Wiley & Sons, Inc. 相似文献
72.
An automated method for the rapid determination of microorganisms using a flow-injection system is presented. Electrochemical measurement of a mediator reduced by microbial metabolism allowed the determination of fungi and bacteria in a few minutes. The lowest detection limit was 5 × 106 colony-forming units (cfu) ml?1 for Escherichia coli. Correlation between the flow-injection method and standard microbiological methods was excellent (r = 0.997, n = 4 for Beauveria bassiana; r = 0.997, n = 7 for E. coli). The flow-injection system was applied to the on-line control of an E. coli cultivation. 相似文献
73.
74.
Westman-Brinkmalm A Karlsson G Brive LM Hedberg-Fogel K Persson R Karlsson H Ekman R Blennow K 《Rapid communications in mass spectrometry : RCM》2005,19(24):3651-3658
In this study we have investigated whether micro-solution isoelectric focusing (microsol-IEF) can be used as a pre-fractionation step prior to liquid chromatography/tandem mass spectrometry (LC/MS/MS) and if extensive sample purification of the different fractions is required. We found that, in spite of the high concentrations of buffer and detergents, no clean up of the digested microsol-IEF fractions was necessary before analysis by LC/MS/MS. We also concluded that it is possible to identify at least twice as many proteins in a glioma cell lysate with the combination of microsol-IEF and LC/MS/MS than with LC/MS/MS alone. Furthermore, most of the proteins that were identified from one microsol-IEF fraction by using analytical narrow-range two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and peptide mass fingerprinting with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) were also identified by LC/MS/MS. Finally, we used the combination of microsol-IEF and LC/MS/MS to compare two sample preparation methods for glioma cells and found that several nuclear, mitochondria, and endoplasmic reticulum proteins were only present in the sample that had been subjected to lipid extraction by incubating the homogenized cells in chloroform/methanol/water. 相似文献
75.
Saalfrank RW Reimann U Göritz M Hampel F Scheurer A Heinemann FW Büschel M Daub J Schünemann V Trautwein AX 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(16):3614-3619
Starting from closely related metal-ligand combinations, completely different oligomeric metal clusters are synthesized. Whereas, picoline-tetrazolylamide HL(1) (1) and zinc or nickel acetate afforded [2x2] grids [M(4)(L(1))(8)] (2), slightly different N-(2-methylthiazole-5-yl)-thiazole-2-carboxamide HL(2) (5 a) and nickel acetate yielded the monometallic complex [Ni(L(2))(2)(OH(2))(2)] (6). In contrast, reaction of 5 a with zinc acetate produced the tetrametallic zinc cluster [Zn(4)O(L(2))(4)(OAc)(2)] (7). Even more surprising, when 3-methyl-substituted HL(3) (5 b) instead of 2-methyl-substituted HL(2) (5 a) was allowed to react under identical conditions with zinc acetate, the cluster [Zn(4)O(L(3))(4)Cl(2)] (8) crystallized from dichloromethane. Clusters 7 and 8 are isostructural. As for 7, in 8 two of the edges of the tetrahedron of zinc ions are doubly bridged, two are singly bridged, and the other two are nonbridged. On the other hand, when iron(II) acetate under aerobic conditions was allowed to react with 5 a, the unprecedented complex [[Fe(3)O(L(2))(2)(OAc)(4)](2)O] (9) was isolated. Cluster 9 is composed of two trimetallic, triangular mu(3)-O(2-)-centered [Fe(3)O(L(2))(2)(OAc)(4)](+) modules, linked by an almost linear mu(2)-O(2-) bridge. The M?ssbauer spectrum together with cyclic voltammetric and square-wave voltammetric measurements of 9 are reported, and 6-9 were characterized unequivocally by single-crystal X-ray structure analyses. 相似文献
76.
Colacio E Lloret F Kivekäs R Suárez-Varela J Sundberg MR Uggla R 《Inorganic chemistry》2003,42(2):560-565
Two polymorphic cyano-bridged Au(I)-Ni(II) bimetallic complexes of formulas [Ni(en)2Au(CN)2][Au(CN)2] (1) and [Ni(en)2[Au(CN)2]2] (2) have been prepared from the 1:2 reaction between [Au(CN)2]- and either [Ni(en)2Cl2]Cl or [Ni(en)3]Cl2.2H2O, respectively. The structure of 1 consists of polymeric cationic chains of alternating [Au(CN)2]- and [Ni(en)2]2+ units running along the a axis and [Au(CN)2]- anions lying between the chains. The noncoordinated dicyanoaurate anions are aligned perpendicular to the ac plane and involved in aurophilic interactions with the bridging dicyanoaurate groups, ultimately leading to a 2D bimetallic grid. The structure of 2 consists of trinuclear molecules made of two [Au(CN)2]- anions linked to [Ni(en)2]2+ unit in trans configuration. Trinuclear units are joined by aurophilic interactions to form 1D zigzag chains. The magnetic properties of these compounds are strongly dominated by the local anisotropy of the octahedral Ni(II) ions, thus indicating that the magnetic exchange interaction mediated by dicyanoaurate bridging groups, if it exists, is very weak. To get insight into the electronic properties of the inter- and intramolecular interactions of the [Au(CN)2]- building blocks, the structures of different aggregates of dicyanogold units were optimized and then analyzed by making use of atoms-in-molecules (AIM) theory. Moreover, bond indices were calculated by methods based upon nonlinear population analysis. 相似文献
77.
78.
Kazuyoshi Yano Hiroshi Yoshitake Uwe T. Bornscheuer Rolf D. Schmid Kazunori Ikebukuro Kenji Yokoyama Yuzo Masuda Isao Karube 《Analytica chimica acta》1997,340(1-3):41-48
Piezoelectric quartz crystal sensors were developed using lipids with various properties for highly sensitive detection of chemical vapors. Lipids with varying lengths of alkyl chains were coated onto 10 MHz AT-cut quartz crystal resonators and the response of these modified crystals to chemical vapors were measured. It was shown that hydrophilic compounds, such as ethanol and methanol, could be recognized efficiently by lipids having shorter alkyl chains, whereas lipids with longer alkyl chains showed affinity to more hydrophobic vapors, such as toluene, hexane and cyclohexane. Frequency changes caused by adsorption of alcohols could be enhanced when cholesterol was co-immobilized in the lipid layer. To confirm the assumption that the sensor-response might be affected by the properties of lipids derived from acyl chains, we have examined the effects of two types of newly synthesized unusual lipids on sensor response. When lipids having one triple bond each at different positions on their alkyl chains were coated onto quartz crystals separately, lower responses were observed compared to responses obtained for a sensor with immobilized, saturated phosphatidylcholine. Lipids containing -branched acyl chains, however, showed good affinity for organic vapors, and sensor responses improved 4–5-fold. Moreover, these sensors were shown to have sensitivity of the same order as the humans' sense of smell (10−5–10−6 w/w in liquid paraffin) when measured using standard odorants (isovaleric acid, skatole, etc.) for an olfactometry established in Japan. 相似文献
79.
Teh-Chang Chou Holger Lange Rolf Gleiter Tibor Ggh Miroslav Krí Max H. Pfenninger Marian Valentíny Camille Ganter 《Helvetica chimica acta》1995,78(8):2011-2025
Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 . 相似文献
80.
Rolf C. Schulz 《Colloid and polymer science》1962,182(1-2):99-104
Zusammenfassung Durch Radikalketten-Polymerisation von Acrolein erhält man Polymere mit Aldehydgruppen. Diese sind zu vielfältigen Umsetzungen befähigt. In dieser Mitteilung werden nur zwei Arten von Reaktionen behandelt; nämlich die Reaktion der Aldehydgruppen untereinander, wobei unter Disproportionierung Polyhydroxypolycarbonsäuren entstehen. DieseCannizzaro-Reaktion tritt auch an der Oberfläche fester Polyacroleine ein. Eingehend behandelt wird die Umsetzung wäßriger Polyacrolein-Lösungen mit anderen Polymeren, welche Amino-, Hydroxyl-oder Mercaptangruppen enthalten. Die Kennzeichen der entstehenden Verbundpolymeren werden beschrieben und mit denWillstätterschen Symplexen verglichen. Auf Beziehungen dieser Reaktionen zu biochemischen Prozessen wird hingewiesen. Ferner wird die Diffusion von Polymeren durch Membranen mit reaktiven Gruppen (Agar-Agar und Gelatine) untersucht. In einigen Fällen tritt eine Oberflächen-Pfropfung ein.19. Mitt, üiber Polymere Acroleine, vorgetragen auf der 20. wissenschaftlichen Arbeitstagung der Kolloid-Gesellschaft vom 19. bis 20. 10. 1961 in Bad Oeynhausen; 18. Mitt, siehe Angew. Chem.72, 771 (1960).Fräulein Dr.Irmela Löflund und Herrn Dr.Mathias Marx, die an diesen Untersuchungen maßgebend beteiligt waren, möchte ich für ihre Mitarbeit herzlich danken. Herrn Prof. Dr.W. Kern, Direktor des Organisch-Chemischen Instituts, danke ich für mannigfache Förderung und anregende Diskussionen. Die Untersuchungen wurden durch Mittel des Fonds der Chemischen Industrie sowie der Firma Degussa, Frankfurt/Main, unterstützt, wofür ebenfalls herzlichst gedankt sei. 相似文献