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161.
Ohne Zusammenfassung 相似文献
162.
163.
B. Peters 《Flow, Turbulence and Combustion》2005,73(3-4):217-229
The objective of this contribution is to investigate whether the mechanism of the thermal diffusion instability in gaseous
flames causing cellular flame structures also occurs during the combustion of porous solid fuel. Based on conservation for
mass and energy, the relevant set of differential equations was derived. Assuming thermal equilibrium between fuel and oxidiser,
a global energy equation was valid for both solid and gaseous phase. The resulting set of differential equations was discretised
by the Collocation method to arrive at a system of algebraic equations. In order to investigate into cellular flame structures,
an infinitesimal disturbance was superimposed onto the plane conversion front. Carrying out a linear instability analysis,
yielded eigenvalues dependent on the wave number of the disturbance. A critical wave number exists below which the real part
of the eigenvalues is positive, thus, indicating a regime of instability. Within this region, eigenvalues with a not-vanishing
imaginary part of the eigen value existed causing cellular flame structures. However, the growth rate of disturbances was
found to be small, which may explain the difficulty to investigate this phenomena experimentally. 相似文献
164.
Thomas Kull Dr. José Cabrera Dr. René Peters Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9132-9139
The development of the first trans‐selective catalytic asymmetric [2+2] cyclocondensation of acyl halides with aliphatic aldehydes furnishing 3,4‐disubstituted β‐lactones is described. This work made use of a new strategy within the context of asymmetric dual activation catalysis: it combines the concepts of Lewis acid and organic aprotic ion pair catalysis in a single catalyst system. The methodology could also be applied to aromatic aldehydes and offers broad applicability (29 examples). The utility was further demonstrated by nucleophilic ring‐opening reactions that provide highly enantiomerically enriched anti‐aldol products. 相似文献
165.
Michael Müller Prof. Dr. Markus Albrecht Verena Gossen Tanja Peters Andreas Hoffmann Prof. Dr. Gerhard Raabe Dr. Arto Valkonen Prof. Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(41):12446-12453
The directionality of interaction of electron‐deficient π systems with spherical anions (e.g,. halides) can be controlled by secondary effects like NH or CH hydrogen bonding. In this study a series of pentafluorophenyl‐substituted salts with polyhalide anions is investigated. The compounds are obtained by aerobic oxidation of the corresponding halide upon crystallization. Solid‐state structures reveal that in bromide 2 , directing NH–anion interactions position the bromide ion in an η1‐type fashion over but not in the center of the aromatic ring. The same directing forces are effective in corresponding tribromide salt 3 . In the crystal, the bromide ion is paneled by four electron‐deficient aromatic ring systems. In addition, compounds 4 and 6 , which have triiodide and the rare tetraiodide dianion as anions, are described. Computational studies reveal that the latter is highly unstable. In the present case it is stabilized by the crystal lattice, for example, by interaction with electron‐deficient π systems. 相似文献
166.
Peters RJ 《Natural product reports》2010,27(11):1521-1530
167.
Markus R. Meyer Jens Wilhelm Frank T. Peters Hans H. Maurer 《Analytical and bioanalytical chemistry》2010,397(3):1225-1233
In recent years, a new class of designer drugs has appeared on the drugs of abuse market in many countries, namely, the so-called
beta-keto (bk) designer drugs such as mephedrone (bk-4-methylmethamphetamine), butylone (bk-MBDB), and methylone (bk-MDMA).
The aim of the present study was to identify the metabolites of mephedrone in rat and human urine using GC-MS techniques and
to include mephedrone, butylone, and methylone within the authors’ systematic toxicological analysis (STA) procedure. Six
phase I metabolites of mephedrone were detected in rat urine and seven in human urine suggesting the following metabolic steps:
N-demethylation to the primary amine, reduction of the keto moiety to the respective alcohol, and oxidation of the tolyl moiety
to the corresponding alcohols and carboxylic acid. The STA procedure allowed the detection of mephedrone, butylone, methylone,
and their metabolites in urine of rats treated with doses corresponding to those reported for abuse of amphetamines. Besides
macro-based data evaluation, an automated evaluation using the automated mass spectral deconvolution and identification system
was performed. Mephedrone and butylone could be detected also in human urine samples submitted for drug testing. Assuming
similar kinetics in humans, the described STA procedure should be suitable for proof of an intake of the bk-designer drugs
in human urine. 相似文献
168.
169.
Andreas Wieczorek Brendan Roycroft Frank H. Peters Brian Corbett 《Optical and Quantum Electronics》2011,42(8):521-529
The film mode matching method was used to analyze the inter waveguide coupling losses in a passive asymmetric twin waveguide
caused by waveguide width and refractive index variation for both resonant and adiabatic coupling at a wavelength of 1,550 nm.
The reasons for power losses are shown. It is demonstrated that tapering the mode beating section of the resonant coupler
can increase the fabrication tolerance of resonant coupling without increasing the coupling length. 相似文献
170.
We consider several related set extensions of the core and the anticore of games with transferable utility. An efficient allocation is undominated if it cannot be improved, in a specific way, by sidepayments changing the allocation or the game. The set of all such allocations is called the undominated set, and we show that it consists of finitely many polytopes with a core-like structure. One of these polytopes is the $L_1$ -center, consisting of all efficient allocations that minimize the sum of the absolute values of the excesses. The excess Pareto optimal set contains the allocations that are Pareto optimal in the set obtained by ordering the sums of the absolute values of the excesses of coalitions and the absolute values of the excesses of their complements. The $L_1$ -center is contained in the excess Pareto optimal set, which in turn is contained in the undominated set. For three-person games all these sets coincide. These three sets also coincide with the core for balanced games and with the anticore for antibalanced games. We study properties of these sets and provide characterizations in terms of balanced collections of coalitions. We also propose a single-valued selection from the excess Pareto optimal set, the min-prenucleolus, which is defined as the prenucleolus of the minimum of a game and its dual. 相似文献