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121.
The first enantioselective reduction of aromatic 2H-azirines yields aziridines in up to 70% ee, using the aminoalcohol-[RuCl2(p-cymene)]2 catalyzed asymmetric transfer hydrogenation reaction. 相似文献
122.
123.
[reaction: see text] The synthesis of alpha-substituted alpha,beta-enones by a new metal iodide-promoted one-pot three-component reaction involving commercially available cyclopropyl ketones, aldehydes, and secondary amines followed by base treatment is described. 相似文献
124.
Volume Contents
Contents of Volume 68 (2002) 相似文献125.
126.
P Wormald B Lundgren K Andersson J W DePierre 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1992,46(1):100-102
Upon interaction of various glycerophospholipids with Rhodamine 6G in toluene, a typical difference spectrum with an absorption maximum at approximately 515 nm is obtained . This spectrum is obtained with phosphatidylcholine only after treatment with NaCl, which presumably weakens intra- and/or inter-molecular electrostatic binding between the negatively charged phosphate moiety and the protonated nitrogen in this molecule. Absorption at 515 nm was linear for all of the phospholipids investigated from a concentration of approximately 1.2 microM up to at least 50 microM. The highest extinction coefficient was obtained for diphosphatidylglycerol (251 mM-1 cm-1) and all of the compounds tested, with the exception of phosphatidylethanolamine, demonstrated extinction coefficients higher than that of palmitic acid. Thus, the absorption spectrum which results from the interaction of purified glycerophospholipids with Rhodamine 6G in organic solvent is a sensitive measure of the amount of phospholipid present. 相似文献
127.
Prof. Dr. K. Magnus 《Archive of Applied Mechanics (Ingenieur Archiv)》1980,49(5-6):295-308
übersicht Aktive Elemente in Kreiselsystemen k?nnen sich in verschiedenartigen Effekten auswirken. Allgemeine Bewegungsgleichungen werden
abgeleitet. Mit ihrer Hilfe lassen sich globale Aussagen zum Stabilit?tsverhalten von Kreiselsystemen mit Rotorantrieb gewinnen:
1) Konservative Systeme bleiben auch dann quasi-konservativ, wenn eine ideal wirkende Antriebsregelung vorhanden ist, die
die relativen Geschwindigkeiten zwischen den Rotoren und ihren Geh?usen konstant h?lt. 2) Eigenstabile Asynchron-Antriebe
machen ein grenzstabiles Kreiselsystem asymptotisch stabil bezüglich der Geschwindigkeiten. 3) Entsprechendes gilt für eigenged?mpfte
Synchron-Antriebe; hier gilt die asymptotische Stabilit?t auch für die Rotorwinkel selbst. Am Beispiel einer motorangetriebenen
Zentrifuge werden diese Ergebnisse durch Untersuchen der Eigenwerte pr?zisiert. Zugleich wird gezeigt, da? bezüglich der Lagewinkel
Instabilit?t infolge kinetischer Auswanderung auftreten kann.
Hans Ziegler zum 70. Geburtstag gewidmet 相似文献
Summary Due to active elements in gyroscopic systems various effects may occur. For their examination quite general equations of motion are derived, which allow some globale statements concerning the stability of gyro-systems with motor-driven rotors: 1) Conservative systems will behave quasi-conservative, if ideal working controllers are installed, which keep the relative rotational velocities of the rotors constant. 2) Asynchronous driving motors, which are stable for themselves, turn a marginal stable system into a system, asymptotically stable with respect to the velocities. 3) The same is valid for systems, in which the rotors are driven by damped synchronous motors; here asymptotic stability exists for the rotor-angles as well. As an example a motor-driven centrifuge is examined. The general results are proved and extended by calculating the eigenvalues. Furthermore it is shown that unstable behaviour with respect to the attitude angles is possible due to effects of kinetic drift.
Hans Ziegler zum 70. Geburtstag gewidmet 相似文献
128.
Energies of high spin states are calculated with the use of an oblate deformed oscillator potential with the purpose of finding possible yrast traps or isomers. Pairing forces are included and different methods of solving the pairing Hamiltonian (including the exact solution) are compared. The stability of the oblate regime against gamma vibrations is investigated with use of the random phase approximation. Pairing forces are included also here. 相似文献
129.
G. Andersson M. Areskoug H. -Å. Gustafsson G. Hyltén B. Schrøder E. Hagebø 《Zeitschrift für Physik A Hadrons and Nuclei》1979,293(3):241-251
Coincidence studies with silicon surface barrier detectors have been used to determine fragment kinetic energies, angular correlations and fission cross sections in the fission of Ag,139La,159Tb and U nuclei induced by 600 MeV protons. Symmetric mass distributions are deduced for Ag and Tb, whereas La shows an indication of a stable asymmetric mass distribution. We find no indication of the Businaro-Gallone point. Fission-spallation competition calculations are used to deduce values of macroscopic fission barrier heights and nuclear level density parameter values at deformations corresponding to the saddle point shapes. We find macroscopic fission barriers lower than those predicted by macroscopic theories. The total kinetic energies at symmetric mass divisions follow closely the Viola prediction. 相似文献
130.
The adsorption of C2H4 on Cu(100) at 80 K has been investigated by angle-dependent high-resolution electron energy loss spectroscopy (EELS) and low-energy electron diffraction (LEED). Our observations are consistent with a model where the ethene molecule is adsorbed in a configuration parallel to the Cu(100) surface. The molecule-metal interaction is weak and presumably of π character. 相似文献