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61.
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63.
S.L Segal 《Historia Mathematica》1980,7(1):46-56
In 1934 Helmut Hasse became Professor of Mathematics at Göttingen. Hasse's attitudes and behavior during the Nazi period were representative of the ambiguous position of much of the mathematical community at that time. Various aspects of Hasse's situation make him appear to be almost the ideal example of the apolitical conservative and ideologically naive German academic in extremis. The purpose of this article is to present him as such an example. 相似文献
64.
<正>In this paper we give an overview of the present state of fast solvers for the solution of the incompressible Navier-Stokes equations discretized by the finite element method and linearized by Newton or Picard's method.It is shown that block preconditioners form an excellent approach for the solution,however if the grids are not to fine preconditioning with a Saddle point ILU matrix(SILU) may be an attractive alternative. The applicability of all methods to stabilized elements is investigated.In case of the stand-alone Stokes equations special preconditioners increase the efficiency considerably. 相似文献
65.
Dr. Gao Li Wu-Yue Yang Wen-Hao Li Yun-Yi Luo Yeh-Jun Lim Prof. Dr. Yang Li Dr. Ashim Paul Prof. Dr. Daniel Segal Liu Hong Prof. Dr. Yan-Mei Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(16):3499-3503
It has been reported that many molecules could inhibit the aggregation of Aβ (amyloid-β) through suppressing either primary nucleation, secondary nucleation, or elongation processes. In order to suppress multiple pathways of Aβ aggregation, we screened 23 small molecules and found two types of inhibitors with different inhibiting mechanisms based on chemical kinetics analysis. Trp-glucose conjugates ( AS2 ) could bind with fibril ends while natural products ( D3 and D4 ) could associate with monomers. A cocktail of these two kinds of molecules achieved co-inhibition of various fibrillar species and avoid unwanted interference. 相似文献
66.
The authors present a kinetic investigation of the generation of manganese ferrite by the ageing of some coprecipitates in contact with the residual solution. 相似文献
67.
A.S. Segal A.V. Kondratyev S.Yu. Karpov D. Martin V. Wagner M. Ilegems 《Journal of Crystal Growth》2004,270(3-4):384-395
A simple quasi-thermodynamic model of surface chemistry in GaN hydride vapor phase epitaxy (HVPE) is presented. The model is coupled with the detailed 3D simulations of species transport in a horizontal-tube reactor and validated by the comparison with the data on the GaN growth rate obtained by laser reflectometry. Parametric study of the growth rate as a function of temperature and species flow rates has been performed over a wide range of growth conditions. The important role of species transport in an HVPE reactor is demonstrated. In particular, a strong effect of the natural concentration convection resulting in the formation of recirculation zones and in a non-uniform vapor composition is revealed by modeling. The impact of these effects on the GaN growth rate and V/III ratio on the growth surface is discussed in detail. 相似文献
68.
The unique capabilities of multiple collector inductively coupled mass spectrometry (MC-ICP-MS) for high precision isotope
ratio measurements in light elements as Li, Mg, Ca, and Cu are reviewed in this paper. These elements have been intensively
studied at the Geological Survey of Israel (GSI) and other laboratories over the past few years, and the methods used to obtain
high precision isotope analyses are discussed in detail. The scientific study of isotopic fractionation of these elements
is significant for achieving a better understanding of geochemical and biochemical processes in nature and the environment. 相似文献
69.
A sensitive and specific assay aimed at measuring the oxidized nucleic acids, 8-oxoguanine (8-oxoGua), fapy-guanine (Fapy-Gua), 8-oxoguanosine (8-oxoGuo), 8-oxo-2'-deoxyguanosine (8-oxodG) has been developed by coupling reversed phase liquid chromatography (HPLC) with electrospray tandem mass spectrometry detection (MS/MS) and isotope dilution. The HPLC-MS/MS approach with multiple reaction monitoring (MRM) allowed for the sensitive determination of 8-oxoGua, Fapy-Gua, 8-oxoGuo, and 8-oxodG in human urine samples. There is no sample preparation needed except for the addition of buffer and (13)C- and (15)N-labeled internal standards to the urine prior to sample injection into the HPLC-MS/MS system. This method was tested in urine samples from non-smokers, smokers, non-smokers with chronic kidney disease (CKD) and smokers with CKD, to assess the level of oxidative damage to nucleic acids. Markers of both RNA and DNA damage were significantly increased in the smokers with and without CKD compared to their respective control subjects. These findings suggest that a highly specific and sensitive analytical method such as isotope dilution HPLC-MS/MS may represent a valuable tool for the measurement of oxidative stress in human subjects. 相似文献
70.
Daniel S. Freed Gregory W. Moore Graeme Segal 《Communications in Mathematical Physics》2007,271(1):247-274
In the ordinary quantum Maxwell theory of a free electromagnetic field, formulated on a curved 3-manifold, we observe that
magnetic and electric fluxes cannot be simultaneously measured. This uncertainty principle reflects torsion: fluxes modulo
torsion can be simultaneously measured. We also develop the Hamilton theory of self-dual fields, noting that they are quantized
by Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is -graded, so typically contains both bosonic and fermionic states. Significantly, these ideas apply to the Ramond-Ramond field
in string theory, showing that its K-theory class cannot be measured. 相似文献