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21.
Virginia Re Marco Bruni David R. Matravers Frances T. White 《General Relativity and Gravitation》2003,35(8):1351-1363
We develop an algebraic procedure to rotate a general Newman-Penrose tetrad in a Petrov type I spacetime into a frame with Weyl scalars 1 and 3 equal to zero, assuming that initially all the Weyl scalars are non vanishing. The new frame highlights the physical properties of the spacetime. In particular, in a Petrov type I spacetime, setting 1 and 3 to zero makes apparent the superposition of a Coulomb-type effect 2 with transverse degrees of freedom 0 and 4. 相似文献
22.
Frances Y. Jackson W. A. J. Luxemburg 《Proceedings of the American Mathematical Society》2003,131(1):185-199
We characterize the first three sundual spaces of , with respect to the translation group of .
23.
Gareth AD Hardy Nesrina Imami Mark R Nelson Ann K Sullivan Ron Moss Marlén MI Aasa-Chapman Brian Gazzard Frances M Gotch 《Journal of immune based therapies and vaccines》2007,5(1):6-12
Background
Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection. 相似文献24.
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27.
Herbert L. Holland Peter R. Andreana Reza Salehzadeh-Asl Aaron van Vliet Nancy J. Ihasz Frances M. Brown 《Monatshefte für Chemie / Chemical Monthly》2000,40(5):667-672
Biotransformation of a series of racemic N-benzoyl α-amino acids by the fungus Beauveria bassiana ATCC 7159 results in isolation of the corresponding D-amino acid benzamides in high enantiomeric purity and yield. 相似文献
28.
Frances Y. Kuo Grzegorz W. Wasilkowski Henryk Wo
niakowski 《Journal of Approximation Theory》2008,152(2):135-160
We study the worst case setting for approximation of d variate functions from a general reproducing kernel Hilbert space with the error measured in the L∞ norm. We mainly consider algorithms that use n arbitrary continuous linear functionals. We look for algorithms with the minimal worst case errors and for their rates of convergence as n goes to infinity. Algorithms using n function values will be analyzed in a forthcoming paper.We show that the L∞ approximation problem in the worst case setting is related to the weighted L2 approximation problem in the average case setting with respect to a zero-mean Gaussian stochastic process whose covariance function is the same as the reproducing kernel of the Hilbert space. This relation enables us to find optimal algorithms and their rates of convergence for the weighted Korobov space with an arbitrary smoothness parameter α>1, and for the weighted Sobolev space whose reproducing kernel corresponds to the Wiener sheet measure. The optimal convergence rates are n-(α-1)/2 and n-1/2, respectively.We also study tractability of L∞ approximation for the absolute and normalized error criteria, i.e., how the minimal worst case errors depend on the number of variables, d, especially when d is arbitrarily large. We provide necessary and sufficient conditions on tractability of L∞ approximation in terms of tractability conditions of the weighted L2 approximation in the average case setting. In particular, tractability holds in weighted Korobov and Sobolev spaces only for weights tending sufficiently fast to zero and does not hold for the classical unweighted spaces. 相似文献
29.
Dan Luo Yong Xiao Liam Hardwick Robert Snell Matthew Way Xavier Sanuy Morell Frances Livera Nicholas Ludford Chinnapat Panwisawas Hongbiao Dong Russell Goodall 《Entropy (Basel, Switzerland)》2021,23(1)
In the search for applications for alloys developed under the philosophy of the High Entropy Alloy (HEA)-type materials, the focus may be placed on applications where current alloys also use multiple components, albeit at lower levels than those found in HEAs. One such area, where alloys with complex compositions are already found, is in filler metals used for joining. In soldering (<450 °C) and brazing (>450 °C), filler metal alloys are taken above their liquidus temperature and used to form a metallic bond between two components, which remain both unmelted and largely unchanged throughout the process. These joining methods are widely used in applications from electronics to aerospace and energy, and filler metals are highly diverse, to allow compatibility with a broad range of base materials (including the capability to join ceramics to metals) and a large range of processing temperatures. Here, we review recent developments in filler metals relevant to High Entropy materials, and argue that such alloys merit further exploration to help overcome a number of current challenges that need to be solved for filler metal-based joining methods. 相似文献
30.
We describe real time observations of the behaviour of the silicon-oxide interface during oxidation in situ in an ultrahigh vacuum transmission electron microscope. We have formed clean, flat Si(111) surfaces by heating under UHV and allowed oxidation or oxygen etching to proceed in the microscope. We have examined the kinetics of both the oxidation and etching reactions using an imaging technique based on the use of forbidden reflections in silicon. We find that oxidation to form SiO2 occurs by the reaction of discrete monolayers with no flow of surface steps. This is in dramatic contrast to oxygen etching, during which the volatile oxide SiO evaporates preferentially from step edges. 相似文献