期刊文献+
共找到639篇文章
< 1 2 32 >
每页显示 20 50 100
丙烯酰胺和N,N-二甲基丙烯酰胺反相乳液共聚动力学
1
作者 吴雨晨 陈浩 +3 位作者 朱良宇 苗贵兰 龚昀晗 王延梅 《功能高分子学报》 CAS CSCD 北大核心 2024年第4期332-337,共6页
以丙烯酰胺(AM)和N,N-二甲基丙烯酰胺(DMAA)作为单体,失水山梨醇单油酸酯(SPAN-80)为乳化剂,3号白油为连续相,过硫酸铵(APS)和四甲基乙二胺(TEMED)为氧化还原引发体系,通过反相乳液聚合得到AM和DMAA的共聚物,采用核磁共振氢谱对产物进... 以丙烯酰胺(AM)和N,N-二甲基丙烯酰胺(DMAA)作为单体,失水山梨醇单油酸酯(SPAN-80)为乳化剂,3号白油为连续相,过硫酸铵(APS)和四甲基乙二胺(TEMED)为氧化还原引发体系,通过反相乳液聚合得到AM和DMAA的共聚物,采用核磁共振氢谱对产物进行表征。结果表明,随着投料中n(DMAA)∶n(AM)的增加,聚合速率逐步加快,共聚物中DMAA物质的量多于投料中DMAA的物质的量;聚合速率随时间的变化曲线不存在恒速期,成核机理倾向于单体液滴成核;聚合速率方程为r_(p)=kcM^(1.74)cI^(0.82)cE^(0.77)(其中cM、cI、cE分别为单体总浓度、引发剂浓度和乳化剂浓度),表观活化能为20.53 kJ/mol。 展开更多
关键词 动力学 反相乳液 丙烯酰胺 n n-二甲基丙烯酰胺 成核机理
下载PDF
Cs_(2)LiYCl_(6):Ce探测器n-γ甄别及γ解谱方法
2
作者 苏丹 张时宇 《现代应用物理》 2024年第2期34-41,共8页
Cs_(2)LiYCl_(6):Ce(CLYC)晶体因其优异的线性响应、高光产额和较强的n-γ甄别能力,在瞬发γ射线中子活化分析技术(prompt gamma neutron activation analysis,PGNAA)中表现出极高的应用潜力。该技术可以用于元素无损分析、工业物料分... Cs_(2)LiYCl_(6):Ce(CLYC)晶体因其优异的线性响应、高光产额和较强的n-γ甄别能力,在瞬发γ射线中子活化分析技术(prompt gamma neutron activation analysis,PGNAA)中表现出极高的应用潜力。该技术可以用于元素无损分析、工业物料分析、环境监测及安全等诸多领域。本文针对CLYC探测器进行测试,旨在探究其在PGNAA领域的应用前景。通过Pu-C中子源和多种γ源(^(22)Na,^(60)Co,^(137)Cs,^(152)Eu)的实验测量对该探测器的性能进行测试。同时,开发了一套基于Gravel算法的γ解谱程序,以优化γ能谱分析。实验结果验证了CLYC探测器在n-γ混合场环境下的出色甄别能力,能有效剔除中子的干扰。γ能谱的解谱结果可以精确的反应入射γ能量信息,算法的平均相对偏差均小于1。通过多线性源解谱结果的可靠性确保了在复杂的伽马场环境中对伽马射线的精确识别和分析能力。 展开更多
关键词 CLYC探测器 n-γ甄别 能谱反演 PGnAA
下载PDF
冠心病心律失常的危险因素及cTnI、NT-proBNP、MMP-9的预测价值
3
作者 卢杨 葛蓓蓓 黄翔 《川北医学院学报》 CAS 2024年第5期624-627,共4页
目的:探讨冠心病患者发生心律失常的危险因素及心肌肌钙蛋白I(cTnI)、N末端B型脑钠肽前体(NT-proBNP)、基质金属蛋白酶-9(MMP-9)对心律失常的预测价值。方法:选取110例冠心病治疗后发生心律失常的患者作为心率失常组;选取同期150例冠心... 目的:探讨冠心病患者发生心律失常的危险因素及心肌肌钙蛋白I(cTnI)、N末端B型脑钠肽前体(NT-proBNP)、基质金属蛋白酶-9(MMP-9)对心律失常的预测价值。方法:选取110例冠心病治疗后发生心律失常的患者作为心率失常组;选取同期150例冠心病治疗后心律正常患者作为无心律失常组。对冠心病患者心律失常发生相关变量进行单因素、多因素Logistic回归分析。分析cTnI、NT-proBNP、MMP-9指标水平对心律失常的预测价值。结果:单因素分析显示,两组患者年龄、体质量、纽约心脏病协会(NYHA)分级、吸烟史、合并糖尿病、病变部位、合并慢性阻塞性肺疾病(COPD)、cTnI、NT-proBNP、MMP-9均有统计学差异(P<0.05)。多因素Logistic回归分析显示,年龄≥60岁、体质量≥60 kg、NYHA分级Ⅲ~Ⅳ级、存在吸烟史、合并糖尿病、右冠状动脉、合并COPD、cTnI≥4.50μg/L、NT-proBNP≥280 ng/L、MMP-9≥180μg/L均是影响冠心病患者发生心律失常的主要危险因素。ROC曲线显示,联合检测预测心律失常诊断效能高于cTnI、NT-proBNP、MMP-9单一检测。结论:cTnI、NT-proBNP、MMP-9是影响冠心病患者发生心律失常的主要关键性危险因素,三者对心律失常均具有较好的预测价值。 展开更多
关键词 冠心病 心律失常 心肌肌钙蛋白I n末端B型脑钠肽前体 基质金属蛋白酶-9
下载PDF
血清NT-pro-BNP、MMP-2水平与糖尿病合并急性脑梗死患者冠状动脉病变程度的关系
4
作者 赵建恒 牛红霞 +3 位作者 于洁 赵希哲 胥俊越 代丽丽 《中国急救复苏与灾害医学杂志》 2024年第6期777-781,共5页
目的探讨血清N末端脑钠肽前体(NT-pro BNP)、基质金属蛋白酶-2(MMP-2)水平与糖尿病合并急性脑梗死(ACI)患者冠状动脉病变程度的关系。方法选择首都医科大学电力教学医院2021年1月—2022年12月收治的126例糖尿病合并ACI患者为观察组,其... 目的探讨血清N末端脑钠肽前体(NT-pro BNP)、基质金属蛋白酶-2(MMP-2)水平与糖尿病合并急性脑梗死(ACI)患者冠状动脉病变程度的关系。方法选择首都医科大学电力教学医院2021年1月—2022年12月收治的126例糖尿病合并ACI患者为观察组,其中单支病变62例,双支病变33例,三支病变31例,轻度狭窄37例,中度狭窄43例,重度狭窄46例。另将同期于我院体检的60例单纯糖尿病患者纳为对照组以及60例健康体检者设为正常组。比较三组心肌肌钙蛋白I(cTnI)、肌酸激酶同工酶MB(CK-MB)、NT-pro BNP、MMP-2、I型胶原交联羧基末端肽(ICTP)水平;以ROC分析NT-pro BNP、MMP-2诊断糖尿病患者并发ACI的价值;比较不同冠状动脉病变支数及不同冠状动脉狭窄程度患者NT-pro BNP、MMP-2、ICTP水平;以Spearman秩相关分析NT-pro BNP、MMP-2、ICTP水平与冠状动脉病变支数、冠状动脉狭窄程度之间的相关性。结果观察组cTnI、CK-MB、NT-pro BNP、MMP-2、ICTP水平显著高于对照组(P<0.05),对照组cTnI、CK-MB、NT-pro BNP、MMP-2、ICTP水平显著高于正常组(P<0.05)。ROC结果显示,NT-pro BNP、MMP-2诊断糖尿病患者并发ACI训练集的曲线下面积为0.953、0.872,测试集的曲线下面积为0.902、0.842(P均<0.05)。NT-pro BNP、MMP-2、ICTP水平随着冠状动脉病变支数的增加及冠状动脉狭窄程度的加重而上升(P<0.05)。NT-proBNP、MMP-2、ICTP水平与糖尿病合并ACI患者冠状动脉病变支数、冠状动脉狭窄程度呈正相关(均有P<0.05)。结论NT-pro BNP、MMP-2、ICTP水平与糖尿病合并ACI患者冠状动脉病变支数、冠状动脉狭窄程度呈正相关,临床关注以上指标可对糖尿病合并ACI患者冠状动脉病变程度进行评估。 展开更多
关键词 糖尿病 急性脑梗死 冠状动脉病变 n末端脑钠肽前体 基质金属蛋白酶2
下载PDF
基于SR-FSDAF多源影像融合的内陆水体NH_(3)-N反演研究
5
作者 马玉荣 柯美如 《无线电工程》 北大核心 2023年第11期2482-2491,共10页
利用遥感影像进行大范围水体NH_(3)-N动态监测和时空分析,可快速实时发现由NH_(3)-N引起的富营养化和发黑发臭等一系列问题。为了克服单一卫星观测无法同时获取高空间和高时相分辨率影像的问题,在FSDAF模型的基础上,提出了改进的时空融... 利用遥感影像进行大范围水体NH_(3)-N动态监测和时空分析,可快速实时发现由NH_(3)-N引起的富营养化和发黑发臭等一系列问题。为了克服单一卫星观测无法同时获取高空间和高时相分辨率影像的问题,在FSDAF模型的基础上,提出了改进的时空融合模型SR-FSDAF,基于ESPCN重构空间变化预测图像,生成由Landsat-8与MODIS影像融合的高空间和高时相分辨率影像,结合水质监测数据和遥感反射率光谱信息建立水体NH_(3)-N浓度反演模型以获取多时段大范围水体NH_(3)-N浓度值。以信阳市的主干河流为例进行了NH_(3)-N浓度的反演和时空分析,结果表明研究区域整体水体NH_(3)-N浓度呈现略微下降趋势,并有明显季节特征,潢河与浉河等支流部分河段由于工厂排污的影响导致氨氮污染较严重,需加强水质监测和污染治理。 展开更多
关键词 氨氮反演 时空融合模型 SR-FSDAF Landsat-8 MODIS
下载PDF
Ti_(n+1)C_(n)T_(x)-MXenes二维材料的制备及其陶瓷基复合材料的研究现状 被引量:2
6
作者 吕功业 梁峰 +4 位作者 邱丹阳 谷昊辉 吴帅兵 王晓函 张海军 《陶瓷学报》 CAS 北大核心 2023年第1期28-37,共10页
二维钛碳化物(Ti_(n+1)C_(n)T_(x)-MXenes)具有独特的层状结构、优异的电学性能、良好的化学稳定性和较高的比表面积,被广泛应用于能源、存储、医学、电磁屏蔽和传感器等领域。通过液相法选择性刻蚀钛基MAX相中的A位元素,可制得Ti_(n+1)... 二维钛碳化物(Ti_(n+1)C_(n)T_(x)-MXenes)具有独特的层状结构、优异的电学性能、良好的化学稳定性和较高的比表面积,被广泛应用于能源、存储、医学、电磁屏蔽和传感器等领域。通过液相法选择性刻蚀钛基MAX相中的A位元素,可制得Ti_(n+1)C_(n)T_(x)-MXenes。Ti_(n+1)C_(n)T_(x)-MXenes作为增强相,与陶瓷材料有效复合形成陶瓷基复合材料,进而改善陶瓷材料的使用性能。目前,绿色高效制备无氟Ti_(n+1)C_(n)T_(x)-MXenes的研究尚处于起步阶段,且Ti_(n+1)C_(n)T_(x)-MXenes陶瓷基复合材料的增强机理和高温使用性能仍有待探究。综述了Ti_(n+1)C_(n)T_(x)-MXenes的制备方法,同时介绍了Ti_(n+1)C_(n)T_(x)-MXenes在陶瓷基复合材料中的应用,并对Ti_(n+1)C_(n)T_(x)-MXenes的发展趋势和面临的问题进行了展望。 展开更多
关键词 Ti_(n+1)C_(n)T_(x)-MXenes 二维材料 制备方法 陶瓷基复合材料
下载PDF
DATA TRANSFORMATION OF FAULT TREE BY USING MATRIX OPERATION 被引量:2
7
作者 CaiJiakun ChenJinshui 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2003年第3期260-263,共4页
On the base of study of the correlation of fault tree's main data-minimum cutsets, minimum path sets, non-intersect minimum cut sets and non-intersect minimum path sets,transformation method among main data are fo... On the base of study of the correlation of fault tree's main data-minimum cutsets, minimum path sets, non-intersect minimum cut sets and non-intersect minimum path sets,transformation method among main data are found, i.e. the transformation can be realized by theoperation of cut sets matrixes. This method provides anew way to reduce 'NP' difficulty and simplifyFTA. 展开更多
关键词 Fault tree Cut sets matrix non-intersect D operation n operation
下载PDF
Transport properties of a binary mixture of CO_2-N_2 from the pair potential energy functions based on a semi-empirical inversion method 被引量:1
8
作者 宋渤 王晓坡 +1 位作者 杨富鑫 刘志刚 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第4期370-377,共8页
The potential energy snrface of a CO2-N2 mixture is determined by using an inversion method, together with a new collision integral correlation [J. Phys. Chem. R@ Data 19 1179 (1990)]. With the new invert potential,... The potential energy snrface of a CO2-N2 mixture is determined by using an inversion method, together with a new collision integral correlation [J. Phys. Chem. R@ Data 19 1179 (1990)]. With the new invert potential, the transport properties of CO2-N2 mixture are presented in a temperature range front 273.15 K to 3273.15 K at low density by employing the Chapman-Enskog scheme and the Wang Chang-Uhlenbeck de Boer theory, consisting of a viscosity coefficient, a thermal conductivity coefficient, a binary diffusion coefficient, and a thermal diffusion factor. The accuracy of the predicted results is estimated to be 2% for viscosity, 5% for thermal conductivity, and 10% for binary diffusion coefficient. 展开更多
关键词 inversion method potential energy surface C02 n2 mixture transport property
下载PDF
Processing and performance of 2D fused-silica fiber reinforced porous Si_3N_4 matrix composites 被引量:1
9
作者 Guifang Han Litong Zhang Laifei Cheng 《Journal of University of Science and Technology Beijing》 CSCD 2008年第1期58-61,共4页
Two-dimension (2D) fused-silica fiber reinforced porous silicon nitride matrix composites were fabricated using slurry impregnation and cyclic infiltration with colloidal silica sol. The microstructure and fracture ... Two-dimension (2D) fused-silica fiber reinforced porous silicon nitride matrix composites were fabricated using slurry impregnation and cyclic infiltration with colloidal silica sol. The microstructure and fracture surface were characterized by SEM, the mechanical behavior was investigated by three-point bending test, and the dielectric constant was also measured by impedance analysis. The microstructure showed that the fiber and the matrix had a physical bonding, forming a clearance interface. The mechanical behavior suggested that the porous matrix acted as crack deflection, and the fracture surface had a lot of fiber pull-out. However, the interlaminar shear strength was not so good. The dielectric constant of the composites at room temperature was about 2.8-3.1. The relatively low dielectric constant and non-catastrophic failure indicated the potential application in the radome materials field. 2008 University of Science and Technology Beijing. All rights reserved. 展开更多
关键词 porous matrix composites fused-silica fiber SI3n4 mechanical behavior dielectric constant
下载PDF
Dirichlet-to-Neumann Map for a Hyperbolic Equation
10
作者 Fagueye Ndiaye Mouhamadou Ngom Diaraf Seck 《Journal of Applied Mathematics and Physics》 2023年第8期2231-2251,共21页
In this paper, we provide an explicit expression for the full Dirichlet-to-Neumann map corresponding to a radial potential for a hyperbolic differential equation in 3-dimensional. We show that the Dirichlet-Neumann op... In this paper, we provide an explicit expression for the full Dirichlet-to-Neumann map corresponding to a radial potential for a hyperbolic differential equation in 3-dimensional. We show that the Dirichlet-Neumann operators corresponding to a potential radial have the same properties for hyperbolic differential equations as for elliptic differential equations. We numerically implement the coefficients of the explicit formulas. Moreover, a Lipschitz type stability is established near the edge of the domain by an estimation constant. That is necessary for the reconstruction of the potential from Dirichlet-to-Neumann map in the inverse problem for a hyperbolic differential equation. 展开更多
关键词 Hyperbolic Differential Equation Calderón’s Problem Schrödinger Operator POTEnTIAL inverse Potential Problem Dirichlet-to-neumann Map numerical Simulations Lipschitz Stability
下载PDF
Kohn-Sham Density Matrix and the Kernel Energy Method 被引量:1
11
作者 POLKOSNIK Walter MASSA Lou 《物理化学学报》 SCIE CAS CSCD 北大核心 2018年第6期656-661,共6页
The kernel energy method(KEM) has been shown to provide fast and accurate molecular energy calculations for molecules at their equilibrium geometries.KEM breaks a molecule into smaller subsets,called kernels,for the p... The kernel energy method(KEM) has been shown to provide fast and accurate molecular energy calculations for molecules at their equilibrium geometries.KEM breaks a molecule into smaller subsets,called kernels,for the purposes of calculation.The results from the kernels are summed according to an expression characteristic of KEM to obtain the full molecule energy.A generalization of the kernel expansion to density matrices provides the full molecule density matrix and orbitals.In this study,the kernel expansion for the density matrix is examined in the context of density functional theory(DFT) Kohn-Sham(KS) calculations.A kernel expansion for the one-body density matrix analogous to the kernel expansion for energy is defined,and is then converted into a normalizedprojector by using the Clinton algorithm.Such normalized projectors are factorizable into linear combination of atomic orbitals(LCAO) matrices that deliver full-molecule Kohn-Sham molecular orbitals in the atomic orbital basis.Both straightforward KEM energies and energies from a normalized,idempotent density matrix obtained from a density matrix kernel expansion to which the Clinton algorithm has been applied are compared to reference energies obtained from calculations on the full system without any kernel expansion.Calculations were performed both for a simple proof-of-concept system consisting of three atoms in a linear configuration and for a water cluster consisting of twelve water molecules.In the case of the proof-of-concept system,calculations were performed using the STO-3 G and6-31 G(d,p) bases over a range of atomic separations,some very far from equilibrium.The water cluster was calculated in the 6-31 G(d,p) basis at an equilibrium geometry.The normalized projector density energies are more accurate than the straightforward KEM energy results in nearly all cases.In the case of the water cluster,the energy of the normalized projector is approximately four times more accurate than the straightforward KEM energy result.The KS density matrices of this study are applicable to quantum crystallography. 展开更多
关键词 Kohn SHAM density matrix KERnEL energy method n-REPRESEnTABILITY QUAnTUM CRYSTALLOGRAPHY Watercluster
下载PDF
General calculation formulas and recurrence relations of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 被引量:1
12
作者 CHENChang-yuan LUFa-lin SUNDong-sheng 《原子与分子物理学报》 CAS CSCD 北大核心 2004年第3期432-440,共9页
In this paper, the general calculation formulas of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 are obtained, and the recurrence relation of different power order radial matrix eleme... In this paper, the general calculation formulas of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 are obtained, and the recurrence relation of different power order radial matrix elements are also derived. 展开更多
关键词 n-dimensional hydrogen atom-type potential Klein-Cordon equation Radial matrix dements GEnERAL calculation FORMULAS RECURREnCE relations
下载PDF
Certain <i>pl</i>(<i>m</i>,<i>n</i>)-Kummer Matrix Function of Two Complex Variables under Differential Operator
13
作者 Ayman Shehata 《Applied Mathematics》 2013年第1期91-96,共6页
The main aim of this paper is to define and study of a new matrix functions, say, the pl(m,n)-Kummer matrix function of two complex variables. The radius of regularity, recurrence relation and several new results on t... The main aim of this paper is to define and study of a new matrix functions, say, the pl(m,n)-Kummer matrix function of two complex variables. The radius of regularity, recurrence relation and several new results on this function are established when the positive integers p is greater than one. Finally, we obtain a higher order partial differential equation satisfied by the pl(m,n)-Kummer matrix function and some special properties. 展开更多
关键词 HYPERGEOMETRIC matrix FUnCTIOn pl(m n)-Kummer matrix FUnCTIOn matrix Differential Equation
下载PDF
the phase-dependent gain without inversion in a Doppler broadened open four-level system
14
作者 刘中波 贾克宁 +2 位作者 梁颖 仝殿民 樊锡君 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第6期227-233,共7页
It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase ... It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase between the probe field and the driving field; the atomic exit rate (R0) and the ratio (S) of the atomic injection rates have a considerable modulation effect on the phase-dependent GWI. GWI first increases and then decreases with R0 increasing; in a certain value range of S, GWI increases monotonically with S increasing; by adjusting the values of R0 and S, in an open system a much larger GWI can be obtained than in the corresponding closed system [2011 Phys. Rev. A 83 043805]. The modulation effects of R0 and S on the phase-dependent GWI in the case with the counter-propagating probe and driving fields are stronger than those in the co-propagating case, GWI in the co-propagating case is much larger than that in the counter-propagating case. 展开更多
关键词 open n-type four-level system spontaneously generated coherence relative phase Doppler broadening gain without inversion
下载PDF
N-Summet-k and Its Application in the Construction of Pascal Triangle and Pascal Matrix
15
作者 Neelam Jeevan Kumar 《Journal of Applied Mathematics and Physics》 2016年第1期169-177,共9页
Summetor is an operator used in the mathematics to calculate the special numbers like binomial coefficients and combinations of group elements. It has many applications in algebra, matrices like calculation of pascal ... Summetor is an operator used in the mathematics to calculate the special numbers like binomial coefficients and combinations of group elements. It has many applications in algebra, matrices like calculation of pascal triangle elements and pascal matrix formation, etc. This paper explains about its functions and properties of N-Summet-k. The result of variation between N and k is shown in tabulation. 展开更多
关键词 Summetor n-Summet-k Binomial Coefficients Pascal’s Triangle Pascal’s matrix
下载PDF
N-乙酰半胱氨酸等对基质金属蛋白酶在大鼠慢性阻塞性肺疾病模型气道细胞外基质重塑中的作用 被引量:15
16
作者 李红梅 崔德健 +3 位作者 佟欣 高亚兵 崔雪梅 王德文 《解放军医学杂志》 CAS CSCD 北大核心 2002年第7期593-596,I002,共5页
53只Wistar大鼠随机分为对照组、慢性阻塞性肺疾病 (COPD)模型组及N 乙酰半胱氨酸 (NAC)组、蛋白激酶C(PKC)抑制剂H7组及转移生长因子 (TGF) β单抗组 ;研究基质金属蛋白酶 (MMPs)及其组织抑制剂 (TIMP 1)在COPD模型气道细胞外基质 (E... 53只Wistar大鼠随机分为对照组、慢性阻塞性肺疾病 (COPD)模型组及N 乙酰半胱氨酸 (NAC)组、蛋白激酶C(PKC)抑制剂H7组及转移生长因子 (TGF) β单抗组 ;研究基质金属蛋白酶 (MMPs)及其组织抑制剂 (TIMP 1)在COPD模型气道细胞外基质 (ECM)重塑中的作用及NAC、H7及TGF β单抗等干预因素的影响。结果表明 ,模型组气道壁以Ⅰ型胶原为主的细胞外基质及羟脯氨酸 (Hy)含量、粘膜下成纤维细胞 (Fb)数、MMP 9、2、TIMP 1及TGF βⅠ、Ⅱ受体在支气管肺组织中蛋白和 (或 )mRNA表达较对照组显著增高 ,72kDMMP 2及 92kDMMP 9酶活性亦显著增高 ,NAC组及TGF β单抗组Hy含量及Fb数较模型组显著降低 ,H7组Hy含量则显著增高 ,三个干预组MMP 2、9及TIMP 1和MMP 9、2酶活性表达均较模型组显著减弱 ,三个干预组TGF βⅠ、Ⅱ受体亦有不同程度减弱。MMP 9、2及TIMP 1表达增强表明COPD大鼠模型ECM降解及合成代谢异常活跃 ,与气道ECM重塑密切相关。拮抗氧自由基或TGF β对MMPs、TIMP 1及气道重塑具有调节和减轻作用 ,为探索防治气道细胞外基质重塑的途径提供了一定依据。H7由于具有强抑制胶原酶作用而使胶原沉积增多。 展开更多
关键词 细胞外基质 基质金属蛋白酶 n-乙酰半胱氨酸 慢性阻塞性肺疾病 COPD
下载PDF
精确计算重整化N-圈传播子的新计算方法 被引量:12
17
作者 张忠灿 蒋再富 +3 位作者 方祯云 高飞 蒋敏 陈文锁 《重庆大学学报(自然科学版)》 EI CAS CSCD 北大核心 2006年第9期89-93,共5页
采用核子N(反核子N-)与中性介子π0相互作用的Lorentz不变耦合模型,对N-N-圈图传播子在“动量重整化方案”中的“动量正规化”作了深入细致的分析与考证,发现可以采用“矩阵函数展开法”来替代通常采用的“传统减除法”,并由此对N-N-圈... 采用核子N(反核子N-)与中性介子π0相互作用的Lorentz不变耦合模型,对N-N-圈图传播子在“动量重整化方案”中的“动量正规化”作了深入细致的分析与考证,发现可以采用“矩阵函数展开法”来替代通常采用的“传统减除法”,并由此对N-N-圈图传播子函数中的“发散量”与“有限量”作了十分简捷有效的分离,获得了“重整化有限量”的一个具有“明确计算含义”的表达式.进而,又对所获得的结果采用“大动量积分极限法”作了十分有效的计算处理,获得了可供作“严格解析计算”的一个“一维积分计算表达式”———这将为“精确计算”N-N-圈图传播子重整化有限量提供出简捷可行的有效计算途径与方法. 展开更多
关键词 n--↑n单圈传播子 动量重整化 动量正规化 Feynman收敛积分 矩阵函数展开法 大动量积分极限法
下载PDF
Modulation of atomic exit and injection rates on the phase-dependent gain without inversion in a Doppler broadened open four-level system
18
作者 刘中波 贾克宁 +2 位作者 梁颖 仝殿民 樊锡君 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第6期231-237,共1页
It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase betw... It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase between the probe field and the driving field; the atomic exit rate (R0) and the ratio (S) of the atomic injection rates have a considerable modulation effect on the phase-dependent GWI. GWI first increases and then decreases with R0 increasing; in a certain value range of S, GWI increases monotonically with S increasing; by adjusting the values of R0 and S, in an open system a much larger GWI can be obtained than in the corresponding closed system [2011 Phys. Rev. A 83 043805]. The modulation effects of R0 and S on the phase-dependent GWI in the case with the counter-propagating probe and driving fields are stronger than those in the co-propagating case, GWI in the co-propagating case is much larger than that in the counter-propagating case. 展开更多
关键词 open n-type four-level system spontaneously generated coherence relative phase Doppler broadening gain without inversion
全文增补中
普伐他汀治疗AMI急诊PCI术后CHF患者血浆NT-proBNP和MMP-2的变化及与左室重构的关系 被引量:14
19
作者 黄宇 雷海芳 +3 位作者 魏盟 邱建平 邱耕 陆纪德 《上海交通大学学报(医学版)》 CAS CSCD 北大核心 2010年第3期336-339,共4页
目的观察他汀类药物普伐他汀对急性心肌梗死(AMI)急诊经皮冠状动脉介入术(PCI)后较为稳定的慢性心力衰竭(CHF)患者氨基末端脑钠肽前体(NT-proBNP)、基质金属蛋白酶-2(MMP-2)和左室重构的影响及相关性。方法96例AMI急诊PCI术后CHF患者(N... 目的观察他汀类药物普伐他汀对急性心肌梗死(AMI)急诊经皮冠状动脉介入术(PCI)后较为稳定的慢性心力衰竭(CHF)患者氨基末端脑钠肽前体(NT-proBNP)、基质金属蛋白酶-2(MMP-2)和左室重构的影响及相关性。方法96例AMI急诊PCI术后CHF患者(NYHA分级Ⅱ/Ⅲ)随机分为普伐他汀20 mg组(普伐他汀20 mg/d治疗,n=52)和普伐他汀40 mg组(普伐他汀40 mg/d治疗,n=44),比较两组治疗前一般资料、两组治疗前和治疗18个月后血浆NT-proBNP和MMP-2水平以及左室重构相关指标的变化,并分析其相关性。结果两组治疗后血浆NT-proBNP和MMP-2水平均较治疗前显著降低(P<0.05),治疗后普伐他汀40 mg组血浆NT-proBNP和MMP-2水平显著低于普伐他汀20 mg组(P<0.05)。普伐他汀治疗后,两组左室质量指数(LVMI)、左室舒张末期内径(LVEDD)、舒张末左室后壁厚度(LVPWT)较治疗前均显著降低(P<0.01),普伐他汀40 mg组LVMI、LVEDD、LVPWT显著小于普伐他汀20 mg组(P<0.01);两组舒张末室间隔厚度(IVST)、左室短轴缩短率(FS)、左室平均周径缩短率(MVCF)、二尖瓣口多普勒舒张早期最大流速与舒张末期最大流速比率(E/A)较治疗前均显著增加(P<0.01),普伐他汀40 mg组IVST、FS、MVCF、E/A显著大于普伐他汀20 mg组(P<0.01)。两组治疗前后血浆NT-proBNP和MMP-2的下降水平均与LVMI、LVEDD、LVPWT减少呈正相关,均与IVST、FS、MVCF、E/A增加呈负相关;NT-proBNP、MMP-2下降水平两者呈正相关(均P<0.05)。结论他汀类药物普伐他汀对AMI急诊PCI术后较为稳定的CHF患者心功能改善有益,这可能与其抑制MMP-2、减轻左室重构作用相关。 展开更多
关键词 普伐他汀 急性心肌梗死 慢性心力衰竭 氨基末端脑钠肽前体 左室重构 基质金属蛋白酶-2
下载PDF
3×n阶网络等效电阻的再研究 被引量:18
20
作者 谭志中 罗达峰 杨建华 《南通大学学报(自然科学版)》 CAS 2011年第2期67-72,共6页
通过网络分析构建了三元差分方程组模型,提出了一种矩阵变换方法,得到了电阻网络中的电流分布规律.基于不同的边界条件,获得了3×n阶网络等效电阻的2个新的普适公式,该公式适用于网格数为一切自然数的情形,同时得到的无穷3×n... 通过网络分析构建了三元差分方程组模型,提出了一种矩阵变换方法,得到了电阻网络中的电流分布规律.基于不同的边界条件,获得了3×n阶网络等效电阻的2个新的普适公式,该公式适用于网格数为一切自然数的情形,同时得到的无穷3×n阶网络的2个等效电阻是由无理数表示的常数.通过将所得结论与实际结果比较,说明了该公式的正确性. 展开更多
关键词 3×n阶网络 差分方程模型 矩阵变换 等效电阻
下载PDF
上一页 1 2 32 下一页 到第
使用帮助 返回顶部