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排序方式: 共有85条查询结果,搜索用时 250 毫秒
21.
Davis MI Wasinger EC Decker A Pau MY Vaillancourt FH Bolin JT Eltis LD Hedman B Hodgson KO Solomon EI 《Journal of the American Chemical Society》2003,125(37):11214-11227
22.
Truong Nguyen-Ba Han Hao Hemza Yagoub Rémi Vaillancourt 《Journal of Applied Mathematics and Computing》2011,35(1-2):363-378
The HBT(10)9 method for ODEs is expanded into HBT(10)9DAE for solving nonstiff and moderately stiff systems of fully implicit differential algebraic equations (DAEs) of arbitrarily high fixed index. A scheme to generate first-order derivatives at off-step points is combined with Pryce scheme which generates high order derivatives at step points. The stepsize is controlled by a local error estimator. HBT(10)9DAE uses only the first four derivatives of y instead of the first 10 required by Taylor’s series method T10DAE of order 10. Dormand–Prince’s DP(8,7)13M for ODEs is extended to DP(8,7)DAE for DAEs. HBT(10)9DAE wins over DP(8,7)DAE on several test problems on the basis of CPU time as a function of relative error at the end of the interval of integration. An index-5 problem is equally well solved by HBT(10)9DAE and T10DAE. On this problem, the error in the solution by DP(8,7)DAE increases as time increases. 相似文献
23.
Jarrod D. Edwards Jim E. Morel Dana A. Knoll 《Journal of computational physics》2011,230(4):1198-1214
We apply the Trapezoidal/BDF2 (TR/BDF2) temporal discretization scheme to nonlinear grey radiative diffusion. This is a scheme that is not well-known within the radiation transport community, but we show that it offers many desirable characteristics relative to other second-order schemes. Several nonlinear variants of the TR/BDF2 scheme are defined and computationally compared with the Crank–Nicholson scheme. It is found for our test problems that the most accurate TR/BDF2 schemes are those that are fully iterated to nonlinear convergence, but the most efficient TR/BDF2 scheme is one based upon a single Newton iteration. It is also shown that neglecting the contributions to the Jacobian matrix from the cross-sections, which is often done due to a lack of smooth interpolations for tabular cross-section data, has a significant impact upon efficiency. 相似文献
24.
Dr. Sang Min Lim Dr. Kenneth D. Westover Dr. Scott B. Ficarro Rane A. Harrison Dr. Hwan Geun Choi Dr. Michael E. Pacold Dr. Martin Carrasco Dr. John Hunter Dr. Nam Doo Kim Ting Xie Dr. Taebo Sim Dr. Pasi A. Jänne Dr. Matthew Meyerson Dr. Jarrod A. Marto Dr. John R. Engen Dr. Nathanael S. Gray 《Angewandte Chemie (International ed. in English)》2014,53(1):199-204
We report the synthesis of a GDP analogue, SML‐8‐73‐1, and a prodrug derivative, SML‐10‐70‐1, which are selective, direct‐acting covalent inhibitors of the K‐Ras G12C mutant relative to wild‐type Ras. Biochemical and biophysical measurements suggest that modification of K‐Ras with SML‐8‐73‐1 renders the protein in an inactive state. These first‐in‐class covalent K‐Ras inhibitors demonstrate that irreversible targeting of the K‐Ras guanine‐nucleotide binding site is potentially a viable therapeutic strategy for inhibition of Ras signaling. 相似文献
25.
Zeolite-like metal-organic frameworks as platforms for applications: on metalloporphyrin-based catalysts 总被引:1,自引:0,他引:1
Alkordi MH Liu Y Larsen RW Eubank JF Eddaoudi M 《Journal of the American Chemical Society》2008,130(38):12639-12641
The extra-large cavities of zeolite-like metal-organic frameworks (ZMOFs) offer great potential for their exploration in applications pertinent to larger molecules, like porphyrins. The anionic nature of the framework allowed for facile in situ encapsulation of a cationic free-base porphyrin, and the alpha-cage of our (In-imidazoledicarboxylate)-based rho-ZMOF is ideally suited to the isolation of one porphyrin molecule per cage, which prevents the oxidative self-degradation associated with self-dimerization common in homogeneous catalysis and upon aggregation in solid supports like mesoporous silicates or polymers. The encapsulation of a free-base porphyrin [5,10,15,20-tetrakis(1-methyl-4- pyridinio)porphyrin] and the stability of the rho-ZMOF to metalation conditions, allows for the preparation of a variety of metalloporphyrins (i.e., Mn, Cu, Co, Zn ions) with the ZMOF serving as a platform. The Mn-metallated porphyrin encapsulated in rho-ZMOF shows catalytic activity toward the oxidation of cyclohexane, with turn-over numbers, to the best of our knowledge, higher than reported for similar heterogeneous systems, and our system can be recycled up to 11 cycles, which represents a longer lifetime than reported for any other system. 相似文献
26.
Sava DF Kravtsov VCh Nouar F Wojtas L Eubank JF Eddaoudi M 《Journal of the American Chemical Society》2008,130(12):3768-3770
Two novel porous zeolitelike metal-organic frameworks (ZMOFs) were constructed via the single metal ion-based molecular building block approach from rigid and directional tetrahedral building units and pyrimidinecarboxylate bridging ligands; their ion exchange and hydrogen sorption properties were evaluated. 相似文献
27.
Gor'kov PL Chekmenev EY Li C Cotten M Buffy JJ Traaseth NJ Veglia G Brey WW 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,185(1):77-93
RF heating of solid-state biological samples is known to be a destabilizing factor in high-field NMR experiments that shortens the sample lifetime by continuous dehydration during the high-power cross-polarization and decoupling pulses. In this work, we describe specially designed, large volume, low-E 15N-1H solid-state NMR probes developed for 600 and 900 MHz PISEMA studies of dilute membrane proteins oriented in hydrated and dielectrically lossy lipid bilayers. The probes use an orthogonal coil design in which separate resonators pursue their own aims at the respective frequencies, resulting in a simplified and more efficient matching network. Sample heating at the 1H frequency is minimized by a loop-gap resonator which produces a homogeneous magnetic field B1 with low electric field E. Within the loop-gap resonator, a multi-turn solenoid closely matching the shape of the sample serves as an efficient observe coil. We compare power dissipation in a typical lossy bilayer sample in the new low-E probe and in a previously reported 15N-1H probe which uses a double-tuned 4-turn solenoid. RF loss in the sample is measured in each probe by observing changes in the 1H 360 degrees pulse lengths. For the same values of 1H B1 field, sample heating in the new probe was found to be smaller by an order of magnitude. Applications of the low-E design to the PISEMA study of membrane proteins in their native hydrated bilayer environment are demonstrated at 600 and 900 MHz. 相似文献
28.
The nonlinear Schr?dinger equation with attractive quintic nonlinearity in periodic potential in 1D, modeling a dilute-gas
Bose–Einstein condensate in a lattice potential, is considered and one family of exact stationary solutions is discussed.
Some of these solutions have an analog neither in the linear Schr?dinger equation nor in the integrable nonlinear Schr?dinger
equation. Their stability is examined analytically and numerically. 相似文献
29.
Jaehun Chun John S. McCloy Jarrod V. Crum Shanmugavelayutham K. Sundaram 《Rheologica Acta》2011,50(2):125-130
A novel millimeter wave (MMW) rheometry is developed to determine the viscosity of fluids based on an unsteady film flow on
an inclined plane. The method measures fringes due to MMW interference between the front and back surfaces of a fluid flowing
across the field of view of a ceramic wave guide coupled to a MMW receiver operating at 137 GHz. With knowledge of the dielectric
constant, the interference fringe spacing is used to calculate the thickness of the fluid layer. This thickness is then transformed
into the viscosity by means of a simple hydrodynamic theory. Our results show that the MMW rheometry can practically distinguish
between the 30, 100, and 200 Pa·s silicone oils. The geometry of the method allows for potential industrial applications such
as measuring viscosity of the flowing slag down the walls of coal gasifiers. The MMW rheometry with simple modifications can
be easily extended to measure important non-Newtonian fluid characteristics such as yield stress. 相似文献
30.
Cha JY Burnett GL Huang Y Davidson JB Pettus TR 《The Journal of organic chemistry》2011,76(5):1361-1371
This account details the synthesis of two scyphostatin analogues exhibiting a reactive polar epoxycyclohexenone core and various amide side chains outfitted for late-stage chemical derivatization into the desirable lipophilic tails. Our efforts highlight a key ipso-dearomatization process and provide new insights regarding the incompatibility and orthogonal reactivity of scyphostatin's functional groups. We further showcase the utility of resorcinol derived 2,5-cyclohexadienones as synthetic platforms capable of participating in selective chemical reactivity, and we further demonstrate their potential for rapid elaboration into complex structural motifs. 相似文献