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11.
The electrochemical copolymerization of furan and thiophene was performed at a constant electrode potential in a binary solvent system consisting of boron trifluoride/ethyl ether and an additional amount of ethyl ether (molar ratio = 1 : 2). The obtained homopolymers and copolymers were characterized with cyclic voltammetry and infrared spectroscopy. The influence of the applied electropolymerization potential and the monomer feed ratio of furan and thiophene on the copolymers was investigated. The furan–thiophene copolymers showed good stability of the redox activity in an acetonitrile‐based electrolyte solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
12.
Rudolf Felix 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(2):129-135
Real world applications of a decision model of relationships between goals based on fuzzy relations are presented. In contrast
to other approaches the relationships between decision goals or criteria for each decision situation are represented and calculated
explicitly. The application fields are decision making for financial services and optimization of production sequences in
car manufacturing. 相似文献
13.
Michael Kofink Menelaos Papagiannopoulos Rudolf Galensa 《European Food Research and Technology》2007,225(3-4):569-577
The enantiomers of catechin and epicatechin were separated by chiral capillary electrophoresis using modified cyclodextrins
as chiral selectors. Various conditions for the separation system were optimized, including the pH value and the concentration
of the running buffer. A baseline separation of the catechin and epicatechin enantiomers could be achieved by using 0.1 mol l−1 borate buffer (pH 8.5) with 12 mmol l−1 (2-hydroxypropyl)-γ-cyclodextrin as chiral selector, a fused-silica capillary with 40 cm effective length (75 μm I.D.), +18 kV
applied voltage, a temperature of 20 °C and direct UV detection at 280 nm. The method was applied to different plant food
samples. (+)-Catechin and (−)-epicatechin could be verified as the most common flavan-3-ols. In the case of guaraná, however,
we were able to identify all four enantiomers, both (+)- and (−)-catechin and (+)- and (−)-epicatechin, as naturally occurring
compounds. This finding was verified by further isolation and purification of the flavan-3-ols and subsequent LC–MS analysis.
This method allows for the identification of the authenticity of guaraná through the analysis of the catechin and epicatechin
enantiomers, additionally to the conventional methods like HPLC. 相似文献
14.
Rudolf E. Schmitt Johann Haas und Renato Amadò 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1988,187(2):121-124
Zusammenfassung Zur Bestimmung biogener Amine aus Schlachtgeflügel wird ein einfach durchzuführendes Analysenverfahren beschrieben. Die Amine wurden mit 0,6m-Perchlorsäure extrahiert, nach Dansylierung auf einer RP-18 Säule aufgetrennt und bei 254 nm detektiert. Innerhalb von 7 min konnte eine gute Auftrennung von 8 Aminen erreicht werden. Zur quantitativen Erfassung von Spermin und Spermidin mußte der Extrakt zusätzlich über Amberlite CG 50 gereinigt werden. Die Wiederfindungsraten betrugen 82% bis 96%, die Nachweisgrenzen 0,2 bis 0,5 g pro g Hühnerhaut. Bei Schlachtgeflügel eignen sich Putrescin und Cadaverin gut als Leitsubstanzen für den einsetzenden Verderb, da sie bereits ab Gesamtkoloniezahlen von etwa 105 pro cm2 nachweisbar sind, und ihre Konzentration mit zunehmendem Verderb rasch ansteigen.
Determination of biogenic amines by RP-HPLC for monitoring microbial spoilage of poultry
Summary A simple high-performance liquid chromatographic (HPLC) analysis is described for the determination of biogenic amines in broiler carcasses. The clean-up procedure consists of an extraction with 0.6M-perchloric acid, formation of dansyl derivatives, separation by a RP-18 column and UV detection at 254 nm. Within 7 min eight amines could be separated. The quantitative determination of spermidine and spermine requires an additional ion-exchange clean-up with Amberlite CG 50 after the extraction. This procedure gives recoveries of 82%–96% with detection limits of 0.2–0.5 g/g of broiler skin. Putrescine and cadaverine are good indicators for the onset of spoilage of poultry carcasses, since both amines could be detected at total colony counts of 105 cfu/cm2 and their concentration increases rapidly with advancing decomposition.相似文献
15.
Rudolf Rothen 《特种铸造及有色合金》2005,(Z1):140
全新的工艺数据永久记录,对压铸过程进行最优化控制满足适用并易于使用的市场需求.布勒公司新的dat@net控制系统(见图1和图2),综合了传统技术,实时操作,工业耐用性和稳定性,以及当今最先进的PCj技术的优点.精心的硬、软件匹配允许使自动化方案不受约束.也是首次,这种控制系统使压铸设备能够按照客户需求完全协调. 相似文献
16.
Summary The effect of tert-butyl chloride in the polymerizations of isobutylene carried out in the presence of SnCl4 in dichloromethane at temperatures-20°C and-78°C was investigated. Synthesized polyisobutylene samples showed a bimodal molecular
weight distribution (MWD) and it was found that the weight content of the lowermolecular weight (LMW) fraction increased with
increasing t-BuCl concentration in the polymerization mixture. The effect of ageing of the initiation mixture t-BuCl/SnCl4 in CH2Cl2 prepared in advance on MWD of the PIB samples was also studied. Ageing of the initiation system supports the formation of
the LMW fraction and this oily PIB is the only product of the polymerization at-20°C,
. 相似文献
17.
Smokers Richard Gense Raymond Rijkeboer Rudolf Dijkhuizen Arjan 《Topics in Catalysis》2004,30(1-4):439-443
Topics in Catalysis - This paper presents the results of a quantitatively substantiated “expert judgement” concerning the potential for further reduction of the exhaust emissions of... 相似文献
18.
In Winkel (2001) a generalization of Bernstein polynomials and Bézier curves based on umbral calculus has been introduced. In the present paper we describe new geometric and algorithmic properties of this generalization including: (1) families of polynomials introduced by Stancu (1968) and Goldman (1985), i.e., families that include both Bernstein and Lagrange polynomial, are generalized in a new way, (2) a generalized de Casteljau algorithm is discussed, (3) an efficient evaluation of generalized Bézier curves through a linear transformation of the control polygon is described, (4) a simple criterion for endpoint tangentiality is established. 相似文献
19.
Rudolf H. Scheffrahn Ruei-Ching Hsu Nan-Yao Su Jacob B. Huffman Sharon L. Midland James J. Sims 《Journal of chemical ecology》1988,14(3):765-776
The heartwood of bald cypress,Taxodium distichum (L.) Rich., resisted feeding attack by the Formosan subterranean termite,Coptotermes formosanus Shiraki. Hexane-extracted heartwood, however, was consumed at > 12 times the amount of sound heartwood eaten. A bioassay usingT. distichum sapwood as a feeding substrate was employed to assess the antitermitic activity of successive hexane, acetone, and methanol extracts of heartwood shavings and isolates derived from the active hexane extract. Two fractions, eluted from the crude hexane extract by liquid chromatography, significantly reduced termite feeding compared to the parent extract, while a third fraction was less active than the original hexane extract. Each fraction contained one major component. All three components were structurally related diterpenes. The two most active heartwood constituents were identified by GC-MS and NMR as ferruginol and manool, while the third and least active, but most prevalent, compound in heartwood was identified as nezukol. Results of bioassays suggest that these allelochemicals act principally as feeding deterrents with accompanying termite mortality due to starvation. 相似文献
20.