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排序方式: 共有578条查询结果,搜索用时 312 毫秒
101.
Sadeghi-Kohan Somayeh Hellebrand Sybille Wunderlich Hans-Joachim 《Journal of Electronic Testing》2021,37(5-6):715-728
Journal of Electronic Testing - Safety-critical systems have to follow extremely high dependability requirements as specified in the standards for automotive, air, and space applications. The... 相似文献
102.
103.
Athula Bandara Mohammad Abu-Haija Frank Höbel Helmut Kuhlenbeck Günther Rupprechter Hans-Joachim Freund 《Topics in Catalysis》2007,46(1-2):223-230
The adsorption of carbon monoxide (CO), propane (C3H8) and propene (C3H6) on V2O3(0001) films grown on Au(111) was studied by Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopy
(XPS). The “oxidized” surface (i.e., as prepared exhibiting V=O termination), the “reduced” surface (i.e., V=O groups being
removed by electron irradiation), as well as the oxygen pre-covered reduced surface were investigated. Both TPD and XPS indicate
that the oxidized surface has little affinity for CO adsorption, while the reduced surface readily binds CO (CO amount approx.
10 times higher). Accordingly, CO can be used to titrate the presence or absence of vanadyl oxygen (via adsorption on the
vanadium atoms) but also of defects like surface oxygen vacancies. For propane and propene, desorption of the parent molecules
was the major process, i.e., surface reactions were absent under the applied conditions. When oxygen was pre-adsorbed on the
reduced surface, the adsorption properties resembled that of the oxidized surface, i.e., the vanadyl groups were (partially)
re-established. TPD and XPS provide a handle to differentiate the binding sites on the V2O3 surface.
Dedicated to Prof. Konrad Hayek. 相似文献
104.
105.
Qiu L Zhang Y Krause HJ Braginski AI Usoskin A 《The Review of scientific instruments》2007,78(5):054701
Certain applications of superconducting quantum interference devices (SQUIDs) require a magnetic field measurement only in a very narrow frequency range. In order to selectively improve the alternating-current (ac) magnetic field sensitivity of a high-temperature superconductor SQUID for a distinct frequency, a single-coil LC resonant circuit has been used. Within the liquid nitrogen bath, the coil surrounds the SQUID and couples to it inductively. Copper coils with different numbers of windings were used to cover the frequency range from <1 to nearly 100 kHz. A superconducting coil made of YBa(2)Cu(3)O(7-delta) tape conductor was also tested. With the LC circuit, the signal-to-noise ratio of measurements could be improved typically by one order of magnitude or more in a narrow frequency band around the resonance frequency exceeding a few kilohertz. The best attained equivalent magnetic field resolution was 2.5 fT/radicalHz at 88 kHz. The experimental findings are in good agreement with mathematical analysis of the circuit with copper coil. 相似文献
106.
Pei Y Yu H Pei Z Theurer M Ammer C André S Gabius HJ Yan M Ramström O 《Analytical chemistry》2007,79(18):6897-6902
Photoderivatized polymer-coated gold surfaces have been developed following a perfluorophenylazide-based double ligation strategy. Gold-plated quartz crystal microbalance (QCM) crystals were initially covalently functionalized with a monolayer of poly(ethylene glycol) (PEG), using photo- or thermolytic nitrene formation and insertion. The polymer surfaces were subsequently used as substrates for photoinsertion of carbohydrate-derivatized photoprobes, yielding different recognition motifs for selective protein binding. The resulting robust and biocompatible sensor surfaces were applied to a flow-through QCM instrument for monitoring lectin-carbohydrate interactions in real time. The results clearly show the predicted lectin selectivity, demonstrating the applicability of the approach. 相似文献
107.
Melanie Wiebe Jürgen Kümmel Jan Prüß Hans-Joachim Warnecke 《European Journal of Lipid Science and Technology》1998,100(9):404-411
Continuous epoxidation of soybean oil: operational analysis and process development The epoxidation of refined soybean oil with peracetic acid is examined having special regard to the mass and heat transfer phenomena as well as to distribution coefficients depending on conversion and temperature. The process is described by a mathematic mechanistic model based on the cooled continuously stirred two-phase tank reactor. The process is limited by hydrodynamics and chemical kinetics. The main operation parameters feed temperature of coolant, volumetric rate of the lipoid phase, and residence time are optimized with respect to the space-time-yield. The two-stage countercurrent cascade of tank reactors leads to higher space-time-yields as well as higher epoxide yields. 相似文献
108.
Sandra Rudershausen Hans-Joachim Drexler Hans-Jürgen Holdt 《Advanced Synthesis \u0026amp; Catalysis》1998,340(5):450-454
Reductive dimerization of dodecylthio substituted 1,2-dithiole-3-thiones 6a–b and trithion-dithiacrown ethers 10a–c with triethyl phosphite furnished bis- and tetrakis (dodecylthio), and bis(dithiacrown ether) substituted thiodesaurines (E)- 11a–b and (E)- 12a–c . The stereochemistry of bis(dithia[15]crown-5)-thiodesaurine (E)- 12b has been determined by X-ray crystallographic analysis. 相似文献
109.
J. Deutsch M. Bartoszek M. Schneider V. Zabel Hans-Joachim Niclas 《Advanced Synthesis \u0026amp; Catalysis》1997,339(1):261-265
Tricarbonylchromium complexes 1 react with monosubstituted malonic acid esters 2 in DMSO at room temperature in the presence of KOtBu to give the complexes 3 . After oxidative demetalation, the appropriate aryl derivatives 4 are obtained in moderate to good overall yields. Diastereoselective arylations of chirally modified malonates such as 5a–c were studied. The stereoselectivity was highest for the products 6c/6c ′ (80:20) with (−)-8-phenylmenthol as alcohol component in the malonate 5 . 相似文献
110.
Kania-Korwel I Garrison AW Avants JK Hornbuckle KC Robertson LW Sulkowski WW Lehmler HJ 《Environmental science & technology》2006,40(12):3704-3710
The enantiomeric enrichment of polychlorinated biphenyl (PCB) atropisomers has been reported in both wildlife and in humans. The biological processes causing this enrichment are only poorly investigated, a fact that limits the use of enantiomeric fractions (EFs) as a tool to study various processes of environmental relevance. To further understand these enantioselective processes, this study investigates the tissue distribution and EFs of some PCB atropisomers after administration of PCB mixtures to immature male Sprague-Dawley rats. The mixtures selected for this study, Aroclor 1254 and an environmental mixture extracted from Chlorofen-contaminated soil, are qualitatively different and are known to induce different groups of hepatic enzymes. Animals were sacrificed 6 days after dosing, PCBs were extracted, and, whenever possible, the EFs of PCBs 84, 91, 95, 149, 174, and 176 were determined by chiral gas chromatography. The EFs of PCB 95 (adipose tissue, liver, and skin) and PCB 149 (adipose tissue, liver, skin, and blood) in tissues from Aroclor 1254-treated animals differed significantly from EFs in the Aroclor standard, while only EFs of PCB 95 (blood) and PCB 174 (adipose tissue) in tissues from soil-extract-treated animals were different from those of the Chlorofen soil extract. PCB 149 in tissues from soil-extract-treated animals underwent no statistically significant enantiomeric enrichment. These differences in the EFs clearly suggest that the enantioselective enrichment of PCB atropisomers may correlate with exposure history, and with the induction of hepatic enzymes, and that EFs may be useful chemical markers of physiologic and biochemical changes following exposure to PCBs. 相似文献