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排序方式: 共有148条查询结果,搜索用时 15 毫秒
141.
An enantioselective aldol reaction of N-propionylthiazolidinethione and representative aldehydes is disclosed. The reaction is catalyzed by [Ni(S,S)-t-BuBox](Otf)2. Enolization is effected by 2,6-lutidine, and TMSOTf facilitates catalyst turnover. Syn diastereoselectivities range from 88:12 to 97:3, and enantioselectivities are 90% or greater. Both aromatic and enolizable aliphatic aldehydes are included within the scope of this aldol addition process. 相似文献
142.
We examine the randomness and triviality of reals using notions arising from martingales and prefix‐free machines. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
143.
We introduce techniques that allow us to embed below an arbitary nonlow2 recursively enumerable degree any lattice currently known to be embeddable into the recursively enumerable degrees.
Research partially supported by NSF Grants DMS-9204308, DMS-93-44740, a US-NZ binational grant NSF 90-20558, the U.S. ARO
through ACSyAM at the Mathematical Sciences Institute of Cornell Univrsity Contract DAAL03-91-C-0027 and the IGC of Victoria
University. 相似文献
144.
This paper describes a novel pneumatically operated diaphragmless shock tube valve that is capable of generating well-formed
shock waves within a driven tube which has a length to diameter ratio of 122. Its development was motivated by the requirement
for an automated shock tube—an application for which the conventional bursting diaphragm method is not suited. The valve operates
reliably, without any need for adjustment to its setup, over a wide range of driver pressures. Shock waves of up to Mach 2.4
have been generated in test gas at atmospheric pressure. A model for assessing the performance of the valve was developed
and calibrated with experimental data. It indicated that opening times in the region of 0.5 ms were attained. By comparison,
the opening time of a burst diaphragm is approximately 0.2–0.3 ms. Features of the valve include a streamlined flow path,
which helps optimise the efficiency of the shock tube, automated operation and a test turn around time of the order of a few
minutes. 相似文献
145.
Mirabella AC Pletnev AA Downey SL Florea BI Shabaneh TB Britton M Verdoes M Filippov DV Overkleeft HS Kisselev AF 《Chemistry & biology》2011,18(5):608-618
Proteasomes degrade the majority of proteins in mammalian cells, are involved in the regulation of multiple physiological functions, and are established targets of anticancer drugs. The proteasome has three types of active sites. Chymotrypsin-like sites are the most important for protein breakdown and have long been considered the only suitable targets for antineoplastic drugs; however, our recent work demonstrated that inhibitors of caspase-like sites sensitize malignant cells to inhibitors of the chymotrypsin-like sites. Here, we describe the development of specific cell-permeable inhibitors and an activity-based probe of the trypsin-like sites. These compounds selectively sensitize multiple myeloma cells to inhibitors of the chymotrypsin-like sites, including antimyeloma agents bortezomib and carfilzomib. Thus, trypsin-like sites are cotargets for anticancers drugs. Together with inhibitors of chymotrypsin- and caspase-like sites developed earlier, we provide the scientific community with a complete set of tools to separately modulate proteasome active sites in living cells. 相似文献
146.
应用Ahlfors覆盖曲面的方法,在单位圆内构造了代数体函数的一个新的奇异半径(称为T半径),并应用无穷级的型函数推广了亚纯函数奇异方向的相关结论. 相似文献
147.
148.
Douglas Cenzer Rodney G. Downey Jeffrey B. Remmel Zia Uddin 《Archive for Mathematical Logic》2009,48(1):115-140
We develop a theory of LOGSPACE structures and apply it to construct a number of examples of Abelian Groups which have LOGSPACE presentations. We show that all computable torsion Abelian groups have LOGSPACE presentations and we show that the groups , and the additive group of the rationals have LOGSPACE presentations over a standard universe such as the tally representation and the binary representation of the natural numbers.
We also study the effective categoricity of such groups. For example, we give conditions are given under which two isomorphic
LOGSPACE structures will have a linear space isomorphism.
相似文献