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91.
Rafael Abela Christopher Baines Xavier Donath Dierk Herlach David Maden Ivan D. Reid Dieter Renker György Solt Ulrich Zimmermann 《Hyperfine Interactions》1994,87(1):1105-1110
TheSR Facility Instruments presently available at PSI and the envisaged medium- and long-term developments are presented. The plans focus on further upgrades of the existing instruments and the development of new techniques using the very high fluxes becoming available at PSI, in particular the setup of a beamline with a fast kicker for muons on request (MORE) and the development of very low energy muon beams. 相似文献
92.
Dieter Jungnickel Marialuisa J. de Resmini Scott A. Vanstone 《Designs, Codes and Cryptography》1996,8(1-2):159-165
We consider the problem of embedding the even graphical code based on the complete graph onn vertices into a shortening of a Hamming code of length 2m-1, wherem = h(n) should be as small as possible. As it turns out, this problem is equivalent to the existence problem for optimal codes with minimum distance 5, and optimal embeddings can always be realized as graphical codes based onK
n. As a consequence, we are able to determineh(n) exactly for alln of the form 2
k
+ 1 and to narrow down the possibilities in general to two or three conceivable values.Dedicated to Hanfried Lenz on the occasion of his 80th birthdayThe research for this note was done while the first author was visiting the University of Waterloo and the University of Rome, respectively. He thanks his colleagues there for their hospitality and also acknowledges the financial support of the Consiglio Nazionale delle Ricerche (Italy). The third author acknowledges the support of the National Science and Engineering Research Council of Canada given under grant #0GP0009258. 相似文献
93.
Dieter Erle 《Journal of mathematical chemistry》1998,24(4):365-378
For a class of dynamical systems of the form
, we prove boundedness of all solutions in the positive time direction. We discuss the existence of stable limit cycles for the simplest autocatalytic reaction involving two internal and two external reactants, as well as for a number of other models arising in applications. 相似文献
94.
95.
96.
97.
The “Thermo-Stat” — a new device for the determination of catalyticaily active substancesA device for the determination of catalytically active substances, called a “ThermoStat”, is described. An additional heater is used to keep constant an arbitrarily preset temperature gradient between the reaction mixture and a cooling coil. Any heat produced by the catalysed reaction induces a deviation from the preset parameter and thus cuts out the additional heater. These breaks are plotted versus time by an integrating recorder. The slope of the reaction curve obtained is a measure of the concentration of the catalyst. As examples, determinations of copper in the range 0.1–2.0μg and molybdenum in the range 5–50 μg are discussed. 相似文献
98.
Beiträge zur Chemie der Pyrrolpigmente, 70. Mitt.: Zum aktiven Transport mit tripyrrinoiden Liganden
The tripyrrin carboxylic acid6 exhibits a pronounced efficiency for carrier mediated proton driven secondary active transport (counter transport) for a series of toxic or valuable cations in a bulk chloroform membrane. In case of Zn++ ions the mechanism including complete concentration profiles forNerst diffusion layers and bulk phase have been established. This compound might be used for detoxification or enrichment of precious metals using membrane separation systems.
Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
99.
Adam W Alsters PL Neumann R Saha-Möller CR Seebach D Beck AK Zhang R 《The Journal of organic chemistry》2003,68(21):8222-8231
The epoxidation of allylic alcohols is shown to be efficiently and selectively catalyzed by the oxidatively resistant sandwich-type polyoxometalates, POMs, namely [WZnM(2)(ZnW(9)O(34))(2)](q)(-) [M = OV(IV), Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], with organic hydroperoxides as oxygen source. Conspicuous is the fact that the nature of the transition metal M in the central ring of polyoxometalate affects significantly the reactivity, chemoselectivity, regioselectivity, and stereoselectivity of the allylic alcohol epoxidation. For the first time, it is demonstrated that the oxovanadium(IV)-substituted POM, namely [ZnW(VO)(2)(ZnW(9)O(34))(2)](12-), is a highly chemoselective, regioselective, and also stereoselective catalyst for the clean epoxidation of allylic alcohols. A high enantioselectivity (er values up to 95:5) has been achieved with [ZnW(VO)(2)(ZnW(9)O(34))(2)](12)(-) and the sterically demanding TADOOL-derived hydroperoxide TADOOH as regenerative chiral oxygen source. Thus, a POM-catalyzed asymmetric epoxidation of excellent catalytic efficiency (up to 42 000 TON) has been made available for the development of sustainable oxidation processes. The high reactivity and selectivity of this unprecedented oxygen-transfer process are mechanistically rationalized in terms of a peroxy-type vanadium(V) template. 相似文献
100.
A new base-labile anchoring group, derived from 9-(hydroxymethyl)fluorene-4-carboxylic acid (HO2CFmoH or HOFmCO2H; 7), for polymer-supported peptide synthesis os described. The synthesis of 7 starting from 2,2′-biphenyldicarboxylic acid ( 1 ) proceeds in an overall yield of 53%. The group HO2CFmo exhibits properties similar to the well known Fmoc protecting group: It is stable to acidic conditions and cleavable by 15% piperidine in DMF. In combination with acid labile Nα-protecting groups (e.g. Boc, Ddz, Bpoc, Nps etc.), it renders more flexibility to the stepwise synthesis using polymer supports. The versatility of the new anchoring group in solid- and liquid-phase peptide synthesis is demonstrated for the synthesis of a model peptide. 相似文献