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991.
992.
ZHANG Jie Yang Ke TAN DeYong ZENG JunYing Alan FINE 《科学通报(英文版)》2007,52(16):2210-2215
Constitutively expressed Fas ligand (FasL) in several distinct epithelial cell types appears to protect tissues by inducing apoptosis of Fas immune cells during inflammatory reactions. To study the rela-tionship of FasL and inflammation process in cornea,we examined the effects of inflammatory cytokine IL-1β on the FasL production,expression and cytotoxic function in corneal endothelial cells. In this paper,we demonstrate that IL-1β inhibits the FasL production and expression in corneal endothelial cells. The promoter activities of FasL in these cells are reduced by IL-1β in a dose-dependent manner. Finally,we also find that IL-1β block the cytotoxic effects of FasL derived from corneal endothelial cells to the Fas target cells. These data support the view that FasL derived from corneal endothelial cells modulate inflammation within cornea. 相似文献
993.
WU Song CHEN Hong GU JiaHua YU HongRut 《科学通报(英文版)》2007,52(17):2305-2309
This study deals with the sources of signal distortion of a piezoelectric transducer heated by measured gas flow. These signal distortions originate from both unloading of preload on a piezocrystal because of expansion of a diaphragm in the test apparatus and the pyroelectric effect of a heated piezoelectric crystal. A plastic film on the diaphragm of the transducer can effectively insulate the diaphragm and the piezocrystal within transducer from heating by gas flow, eliminating the sources of distortion. A method for evaluating the thickness of the film is proposed. 相似文献
994.
ZHAO DongMin ZHAO JiQuant ZHAO ShanShan HE LeQin WANG WeiYu 《科学通报(英文版)》2007,52(17):2337-2344
A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (III) complex was anchored onto the modified MCM-41 by a multi-step grafting method and two heterogenized catalysts with different Mn contents were obtained. The catalysts were characterized by XRD, N2 adsorption, ICP, FT-IR and DR UV-Vis. Their catalysis on asymmetric epoxidation of several olefins was studied with NaClO and m-CPBA as oxidants respectively. It was found that both the activity and enantioselectivity of the cata- lysts decreased after the homogeneous catalyst was heterogenized. The reasons resulting in the de- crease of catalytic performance were discussed. 相似文献
995.
Mechanism of the interaction between Au nanoparticles and polymerase in nanoparticle PCR 总被引:1,自引:0,他引:1
MI LiJuan ZHU HongPing ZHANG XiaoDong HU Jun FAN ChunHai 《科学通报(英文版)》2007,52(17):2345-2349
Nanoparticle PCR is a novel method to optimize DNA amplification. It performs well in improving specificity, enhancing sensitivity and speed. Several mechanisms were proposed in previous studies: one was based on the interaction between gold nanoparticles (AuNPs) and DNA while the other was attributed to the heat transfer property of AuNPs. In this paper, we propose that the interaction between AuNPs and DNA polymerase can significantly influence PCR. First, the addition of DNA polymerase can eliminate the inhibitory effects of excess AuNPs. Second, the addition of AuNPs will increase yield of the desired PCR product and make the optimum concentration of DNA polymerase move to higher value. Third, while excess polymerase might inhibit amplification efficiency, AuNPs can reverse this process and the yield of PCR amplification. Based on these results we propose a possible mechanism that AuNPs might modulate the activity of polymerase and improve PCR amplification. 相似文献
996.
On the monotone iterative method for set valued equation 总被引:2,自引:0,他引:2
This paper deals with the monotone iterative method for set-valued operator equation in ordered normed space. Some results
for the case of single valued operator are generalized here, as an application, a discontinuous nonlinear differential equation
problem is discussed.
Foundation item: Supported by the Naional Natural Sciences Foundation of China
Biography: TIAN Yan (1970-), male, Ph.D. candidate, research interests are in numerical analysis for PDE 相似文献
997.
香农采样定理可以恢复确定性频带有限信号.而真实信号经常是非频带有限的,这类信号可以被看作边带趋于无穷的频带有限信号.除了确定性型号,平稳的随机信号在许多领域发挥了重要作用.为了解决非频带有限的平稳过程的采样问题,借助香农采样定理,获得当功率在频域衰减时该类信号的采样级数,并求得该级数分别满足均方收敛和以概率1收敛的条件. 相似文献
998.
Detection and clarification of cause-effect relationships among variables is an important problem in time series analysis.This paper provides a method that employs both mutual information and conditional mutual information to identify the causal structure of multivariate time series causal graphical models.A three-step procedure is developed to learn the contemporaneous and the lagged causal relationships of time series causal graphs.Contrary to conventional constraint-based algorithm, the proposed algorithm does not involve any special kinds of distribution and is nonparametric.These properties are especially appealing for inference of time series causal graphs when the prior knowledge about the data model is not available.Simulations and case analysis demonstrate the effectiveness of the method. 相似文献
999.
Kai Xu 《系统科学与复杂性》2017,30(5):1173-1188
This paper is concerned with the problem of improving the estimator of covariance matrix under Stein’s loss. By the partial Iwasawa coordinates of covariance matrix, the corresponding risk can be split into three parts. One can use the information in the weighted matrix of weighted quadratic loss to improve one part of risk. However, this paper indirectly takes advantage of the information in the sample mean and reuses Iwasawa coordinates to improve the rest of risk. It is worth mentioning that the process above can be repeated. Finally, a Monte Carlo simulation study is carried out to verify the theoretical results. 相似文献
1000.
This paper considers the nonstandard renewal risk model in which a part of surplus is invested into a Black-Scholes market whose price process is modelled by a geometric Brownian motion, claim sizes form a sequence of not necessarily identically distributed and pairwise quasi-asymptotically independent random variables with dominatedly-varying tails.The authors obtain a weakly asymptotic formula for the finite-time and infinite-time ruin probabilities.In particular,if the claims are identically distributed and consistently-varying tailed,then an asymptotic formula is presented. 相似文献