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41.
An unusual reaction manifold for cyclopropylcarbinyl cations, uncovered using B3LYP and MP2 calculations, is described. This reaction is a hybrid of a [1,2] sigmatropic hydrogen shift and a two-electron electrocyclic ring opening. These two processes occur through a single transition structure (i.e., they are concerted), although they are not synchronous. We call these reactions "hiscotropic" rearrangements. The potential energy surfaces for these reactions are often complicated, in some cases involving flat plateaus and bifurcations. Torquoselectivity occurs in some cases as a result of favorable orbital interactions between the breaking C-C and C-H bonds. 相似文献
42.
Afonso?S.?Bandeira Megan?E.?Lewis Dustin?G.?MixonEmail author 《Journal of Fourier Analysis and Applications》2018,24(4):935-956
We develop new discrete uncertainty principles in terms of numerical sparsity, which is a continuous proxy for the 0-norm. Unlike traditional sparsity, the continuity of numerical sparsity naturally accommodates functions which are nearly sparse. After studying these principles and the functions that achieve exact or near equality in them, we identify certain consequences in a number of sparse signal processing applications. 相似文献
43.
Dhimankrishna Ghosh Dustin Lippert Oleg Krokhin John P. Cortens John A. Wilkins 《Journal of mass spectrometry : JMS》2010,45(1):1-25
The present study was initiated to define the composition of the membrane proteome of the Natural Killer (NK) like cell line YTS. Isolated membranes were treated with reagents that have been reported to remove peripheral membrane proteins. Additional steps involving trifluoroethanol (TFE) were introduced in an effort to remove remaining nonintegral membrane proteins. This treatment resulted in the release of a subset of proteins without any apparent disruption of membrane integrity. The membranes were solubilized and digested with trypsin in 25% TFE. The resulting peptides were separated using an off‐line two‐dimensional reversed phase LC technique at alkaline and acidic pHs. Mass spectrometric analysis identified 1843 proteins with high confidence scores. On the basis of the presence of transmembrane regions or evidence of posttranslational modifications and prediction algorithms, approximately 40% of the identified proteins were predicted as plausible membrane proteins. The remaining species were largely involved in cellular processes and molecular functions that could be predicted to be transiently associated with membranes. The analytical approaches presented in this study offer robust generic methods for the identification and characterization of membrane proteins. These observations highlight the fact that the membrane is a dynamic entity that is composed of integral and stably associated proteins. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
44.
Johnson JP Bringley DA Wilson EE Lewis KD Beck LW Matzger AJ 《Journal of the American Chemical Society》2003,125(48):14708-14709
The Bergman cyclization has long been known to produce polymers as side products. More recently, this attribute has been harnessed for the production of conjugated materials. However, the structures of these polymers have not been established. To resolve this question, the metal-catalyzed polymerization of 1,4-dibromonaphthalene and thermal polymerization of o-diethynylbenzene were conducted. Two distinct polymers were obtained. Comparison of IR spectroscopy, MALDI-TOF MS, solid-state NMR spectroscopy, UV-vis reflectance spectroscopy, and pyrolysis GC-MS data indicates that only one of the polymers is consistent with poly(1,4-naphthalene). 相似文献
45.
[reaction: see text] A concise synthesis of the spinosyn A tricyclic nucleus 27 has been developed by a route featuring a one-pot tandem intramolecular Diels-Alder reaction and intramolecular vinylogous Morita-Baylis-Hillman cyclization in which five stereocenters in tricycle 10 are set with excellent selectivity. 相似文献
46.
In a work by L. Fuchs, W. Heinzer and B. Olberding, a decomposition of ideals in a commutative ring as intersections of primal
isolated component ideals is investigated. In subsequent work by L. Fuchs and R. Reis, these ideas are developed in multiplicative
lattices. The object of this note is to point out that, when specialized to the lattice of ideals of a commutative ring, the
decomposition of L. Fuchs and R. Reis does not give the decomposition obtained in the paper by Fuchs, Heinzer and Olberding,
and to give two variations of the decomposition of Fuchs and Reis. One of these variations, when specialized to the lattice
of ideals of a ring, does give the decomposition obtained by Fuchs, Heinzer and Olberding, and the other one gives a decomposition
which is superior in some ways.
Received December 2, 2004; accepted in final form February 17, 2005. 相似文献
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