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21.
Stanislav S. Bielawski Stepan G. Mulyarchik Andrew V. Popov 《Journal of Computational and Applied Mathematics》1996,70(2):189-200
In this paper we show how an algebraically reduced system can be constructed, for which the preconditioned conjugate gradient method converges faster than for the original system. For this method it is necessary that the original matrix is symmetric positive-definite. Our approach is based on an efficient projection on a well-chosen subspace and we show an application in which a cyclically reduced system is one step further reduced by this novel technique. 相似文献
22.
C. Szwaj S. Bielawski M.-E. Couprie C. Bruni M. Hosaka A. Mochihashi M. Katoh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):451-455
We investigate the efficiency of the pulsed regime stabilization by
feedback control in a free electron laser (FEL) in oscillator
configuration. We show that a hidden dynamics remains in the
controlled FEL. Though not visible in the evolution of the pulse
envelope, this dynamics affects the internal pulse shape evolution,
and thus the FEL spectrum and coherence properties. The experimental
results obtained on the UVSOR FEL are interpreted in the framework
of a field master equation model. The stochastic nature of
spontaneous emission is taken into account, and appears as an
essential ingredient since the dynamics of the controlled structures
is governed by noise like the other stable regimes of the FEL. 相似文献
23.
[reaction: see text] New synthetic methodology to a variety of 1,2,4,5-tetraaminobenzenes and their corresponding benzobis(imidazolium) salts has been accomplished. Palladium-catalyzed coupling of various 1,2,4,5-tetrabromo- or 1,2,4,5-tetrachlorobenzenes with aryl- or tert-alkylamines afforded the respective tetrakis(N-substituted)aminobenzenes in excellent yields. This enabled comparative solid-state structural analyses of this elusive class of electron-rich arenes with their oxidized derivatives. The tetraamines were found to undergo formylative cyclization to the corresponding benzobis(imidazolium) salts in good to excellent yields. 相似文献
24.
Roger Bielawski 《Communications in Mathematical Physics》2008,284(3):675-712
We define and study certain hyperkähler manifolds which capture the asymptotic behaviour of the SU(2)-monopole metric in regions where monopoles break down into monopoles of lower charges. The rate at which these new metrics approximate the monopole metric is exponential, as for the Gibbons-Manton metric. 相似文献
25.
A 4n-dimensional Riemannian manifold (M, g) is hyperkählerif it possesses three anti-commuting complex structures I, J,K such that the metric g is Kähler with respect to eachof them. The reduced holonomy group of such a manifold is necessarilya subgroup of Sp(n) so the Ricci tensor of g vanishes and (M,g) can be regarded as a positive definite solution to Einstein'sequations in vacuum. 相似文献
26.
27.
J. F. Arambula R. McCall K. J. Sidoran D. Magda N. A. Mitchell C. W. Bielawski V. M. Lynch J. L. Sessler K. Arumugam 《Chemical science》2016,7(2):1245-1256
Ferrocene containing N-heterocyclic carbene (NHC) ligated gold(i) complexes of the type [Au(NHC)2]+ were prepared and found to be capable of regulating the formation of reactive oxygen species (ROS) via multiple mechanisms. Single crystal X-ray analysis of bis(1-(ferrocenylmethyl)-3-mesitylimidazol-2-ylidene)-gold(i) chloride (5) and bis(1,3-di(ferrocenylmethyl)imidazol-2-ylidene)-gold(i) chloride (6) revealed a quasi-linear geometry around the gold(i) centers (i.e., the C–Au–C bond angle were measured to be ∼177° and all the Au–Ccarbene bonds distances were in the range of 2.00 (7)–2.03 (1) Å). A series of cell studies indicated that cell proliferation inhibition and ROS generation were directly proportional to the amount of ferrocene contained within the [Au(NHC)2]+ complexes (IC50 of 6 < 5 < bis(1-benzyl-3-mesitylimidazol-2-ylidene)-gold(i) chloride (4)). Complexes 4–6 were also confirmed to inhibit thioredoxin reductase as inferred from lipoate reduction assays and increased chelatable intracellular zinc concentrations. RNA microarray gene expression assays revealed that 6 induces endoplasmic reticulum stress response pathways as a result of ROS increase. 相似文献
28.
Boydston AJ Pecinovsky CS Chao ST Bielawski CW 《Journal of the American Chemical Society》2007,129(47):14550-14551
A new series of highly photoluminescent benzobis(imidazolium) salts with tunable electronic and physical properties is described. Systematic structural manipulations provided a set of materials that were not only fluorescent in the condensed state but also displayed tunable glass transition temperatures ranging from -0.3 to 113 degrees C. Upon heating, these robust materials flowed while maintaining their emissive properties. Further phase tuning was demonstrated through the synthesis of two thermotropic liquid-crystalline fluorescent benzobis(imidazolium) salts. 相似文献
29.
Unsymmetric and symmetric diaryliodonium triflates are synthesized from both electron-deficient and electron-rich substrates in a fast, high yielding, and operationally simple protocol employing arenes and aryl iodides or iodine. 相似文献
30.
Shang Chen Shuiyin Chen Dengji Han Christopher W. Bielawski Jianxin Geng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(51):e202201580
Lithium (Li) metal has attracted significant attention in areas that range from basic research to various commercial applications due to its high theoretical specific capacity (3860 mA h g−1) and low electrochemical potential (−3.04 vs. standard hydrogen electrode). However, dendrites often form on the surfaces of Li metal anodes during cycling and thus lead to battery failure and, in some cases, raise safety concerns. To overcome this problem, a variety of approaches that vary the electrolyte, membrane, and/or anode have been proposed. Among these efforts, the use of three-dimensional frameworks as Li hosts, which can homogenize and minimize the current density at the anode surface, is an effective approach to suppress the formation of Li dendrites. Herein, we describe the development of using carbon-based materials as Li hosts. While these materials can be fabricated into a variety of porous structures, they have a number of intrinsic advantages including low costs, high specific surface areas, high electrical conductivities, and wide electrochemical stabilities. After briefly summarizing the formation mechanisms of Li dendrites, various methods for controlling structural and surface chemistry will be described for different types of carbon-based materials from the viewpoint of improving their performance as Li hosts. Finally, we provide perspective on the future development of Li host materials needed to meet the requirements for their use in flexible and wearable devices and other contemporary energy storage techniques. 相似文献