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101.
Sanghera N Correia BE Correia JR Ludwig C Agarwal S Nakamura HK Kuwata K Samain E Gill AC Bonev BB Pinheiro TJ 《Chemistry & biology》2011,18(11):1422-1431
The prion protein (PrP) resides in lipid rafts in?vivo, and lipids modulate misfolding of the protein to infectious isoforms. Here we demonstrate that binding of recombinant PrP to model raft membranes requires the presence of ganglioside GM1. A combination of liquid- and solid-state NMR revealed the binding sites of PrP to the saccharide head group of GM1. The binding epitope for GM1 was mapped to the folded C-terminal domain of PrP, and docking simulations identified key residues in the C-terminal region of helix C and the loop between strand S2 and helix B. Crucially, this region of PrP is linked to prion resistance in?vivo, and structural changes caused by lipid binding in this region may explain the requirement for lipids in the generation of infectious prions in?vitro. 相似文献
102.
In this paper, the design-oriented two-stage and data-analysis one-stage multiple comparison procedures for successive comparisons of exponential location parameters under heteroscedasticity are proposed. One-sided and two-sided simultaneous confidence intervals are also given. We also extend these simultaneous confidence intervals for successive differences to a larger class of contrasts of the location parameters. Upper limits of critical values are obtained using the recent techniques given in Lam [Lam, K., 1987. Subset selection of normal populations under heteroscedasticity. In: Proceedings of the Second International Advanced Seminar/Workshop on Inference Procedures Associated with Statistical Ranking and Selection, Sydney, Australia; Lam, K., 1988. An improved two-stage selection procedure. Communications in Statistics Simulation and Computation. 17 (3), 995-1006]. These approximate critical values are shown to have better results than the approximate critical values using the Bonferroni inequality developed in this paper. Finally, the application of the proposed procedures is illustrated with an example. 相似文献
103.
We describe a hierarchy of approximations (MP2[x]) that allow one to estimate second-order M?ller-Plesset (MP2) energies in a large basis set from small-basis calculations. The most cost-effective approximation, MP2[K], is significantly cheaper than full MP2 but numerical tests on small atoms and molecules indicate that it is nonetheless accurate. We conclude that MP2[K] is an attractive level of theory for large systems. 相似文献
104.
105.
106.
We construct a generalization of Maxwell's equations associated with the proper-time of the source which accounts for radiation reaction without any assumptions concerning the nature of the source. The theory leads to a new invariance group, related to the Lorentz group, which leaves the proper-time of the source fixed for all observers. 相似文献
107.
Tepper L. Gill Woodford W. Zachary James Lindesay 《International Journal of Theoretical Physics》1998,37(10):2573-2613
Our purpose in this paper is to provide theframework for a generalization of classical mechanicsand electrodynamics, including Maxwell's theory, whichis simple, technically correct, and requires noadditional work for the quantum case. We first show thatthere are two other definitions of proper-time, eachhaving equal status with the Minkowski definition. Weuse the first definition, called the proper-velocity definition, to construct a transformationtheory which fixes the proper-time of a given physicalsystem for all observers. This leads to a new invariancegroup and a generalization of Maxwell's equations left covariant under the action of this group.The second definition, called the canonical variablesdefinition, has the unique property that it isindependent of the number of particles. This definition leads to a general theory of directlyinteracting relativistic particles. We obtain theLorentz force for one particle (using its proper-time),and the Lorentz force for the total system (using theglobal proper-time). Use of the global proper-time tocompute the force on one particle gives the Lorentzforce plus a dissipative term corresponding to thereaction of this particle back on the cause of itsacceleration (Newton's third law). The wave equation derivedfrom Maxwell's equations has an additional term, firstorder in the proper-time. This term arisesinstantaneously with acceleration. This shows explicitly that the longsought origin of radiationreaction is inertial resistance to changes in particlemotion. The field equations carry intrinsic informationabout the velocity and acceleration of the particles in the system. It follows that our theory isnot invariant under time reversal, so that the existenceof radiation introduces an arrow for the (proper-time ofthe) system. 相似文献
108.
We present a network of delay log2N, whose comparators have only log2N different lengths with maximum length N/2. This network is log-sequential in that it will sort N data items when they are passed through it log2Ntimes. The design, which is related to the Batcher odd-even merge, is distinctly different from the first known example of a log-delay log-sequential network, due to Dowd, Perl, Rudolf, and Saks. It is quite probably the best possible sorting network. 相似文献
109.
M E Heyde D Gill R G Kilponen L Rimai 《Journal of the American Chemical Society》1971,93(25):6776-6780
110.
Philip E. Gill Walter Murray Michael A. Saunders G. W. Stewart Margaret H. Wright 《Mathematical Programming》1985,33(2):172-186
Given a rectangular matrixA(x) that depends on the independent variablesx, many constrained optimization methods involve computations withZ(x), a matrix whose columns form a basis for the null space ofA
T(x). WhenA is evaluated at a given point, it is well known that a suitableZ (satisfyingA
T
Z = 0) can be obtained from standard matrix factorizations. However, Coleman and Sorensen have recently shown that standard orthogonal factorization methods may produce orthogonal bases that do not vary continuously withx; they also suggest several techniques for adapting these schemes so as to ensure continuity ofZ in the neighborhood of a given point.This paper is an extension of an earlier note that defines the procedure for computingZ. Here, we first describe howZ can be obtained byupdating an explicit QR factorization with Householder transformations. The properties of this representation ofZ with respect to perturbations inA are discussed, including explicit bounds on the change inZ. We then introduceregularized Householder transformations, and show that their use implies continuity of the full matrixQ. The convergence ofZ andQ under appropriate assumptions is then proved. Finally, we indicate why the chosen form ofZ is convenient in certain methods for nonlinearly constrained optimization.The research of the Stanford authors was supported by the U.S. Department of Energy Contract DE-AM03-76SF00326, PA No. DE-AT03-76ER72018; the National Science Foundation Grants MCS-7926009 and ECS-8312142; the Office of Naval Research Contract N00014-75-C-0267; and the U.S. Army Research Office Contract DAAG29-84-K-0156.The research of G.W. Stewart was supported by the Air Force Office of Scientific Research Contract AFOSR-82-0078. 相似文献