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排序方式: 共有1296条查询结果,搜索用时 62 毫秒
941.
在pH=7.4的Tris-HCl介质中,利用荧光光谱和紫外吸收光谱法,研究了一种新型蒽环类抗癌药物柔红霉素衍生物(4′-O-(α-L-夹竹桃糖基)柔红霉素,ODNR)与小牛胸腺DNA(ctDNA)的相互作用。 通过离子强度的影响、KI荧光猝灭实验和单双链ctDNA作用的比较实验,分析了ODNR与ctDNA的相互作用模式。 结果表明,ODNR通过嵌插方式与ctDNA发生作用。 ctDNA对ODNR的荧光有明显的猝灭作用,其机理属于静态猝灭。 通过Scatchard方程求得不同温度下的结合常数和结合位点数,由热力学参数确定分子间作用力为疏水作用,也可能存在静电作用。 相似文献
942.
X. -Q. Feng 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(8):537-548
Summary Most of the conventional methods for estimating the overall elastic moduli of microcracked solids are defined based on the
concept of effective medium or effective field. The formal similarity of these methods is examined in this paper. A one-to-one
correspondence relation exists between the effective medium methods and the effective field methods in the sense that they
yield identical results. In addition to the conventional estimation techniques, any other number of such approaches may be
constructed by appropriately specifying the effective matrix compliance (or stiffness) tensor and the effective stress (or
strain) field which a microcrack is assumed to be subjected to. To generate continuous spectra of new methods for estimating
the effective elastic moduli, two simple and straightforward approaches are proposed, which contain one or two adjustable
parameters in order to yield results of good accuracy. The discussion in this paper can be extended to other kinds of heterogeneous
materials.
Received 4 October 2000; accepted for publication 30 January 2001 相似文献
943.
析因试验中交互作用分析的SAS技术 总被引:2,自引:0,他引:2
本文剖析了析因试验中交互作用的意义 ,并介绍了用 SAS软件对达显著的交互作用继续分析的两种方法 .此两法具有重要的实用价值 . 相似文献
944.
Parametric amplification of signal wave in a four-layered leaky waveguide configuration in Z-cut LiNbO 3 , where the pump and signal waves are guided modes and the idler is radiated into the substrate has been studied using coupled mode approach. It is shown that in this configuration, the signal gain can be greatly enhanced as compared to the case of a three-layered QPM Cerenkov-idler configuration. The studies show that by appropriately choosing the waveguide parameters, one can have a trade-off between signal gain bandwidth and the peak signal gain achieved. These studies should find application in designing optical parametric amplifiers and oscillators. 相似文献
945.
The forces and viscosity between calcium benzene sulfonate surfactant-coated mica surfaces in various hydrocarbon liquids
containing a polyamine-functionalized hydrocarbon polymer (M
W≈8000) have been measured using the surface forces apparatus technique. The polymer is found to adsorb to the substrate surfaces
by displacing the surfactant layer, and to produce forces that are monotonically repulsive. The forces have a maximum range
of 50–100 nm (>3R
H), indicating that tails play a particularly important role in the interaction of this relatively low molecular weight polymer.
The forces become steeply repulsive below about 10 nm (∼0.6R
H), at which point a “hard-wall” repulsion comes in that can sustain pressures greater than 100 atm. Thin-film viscosity measurements
indicate that the far-field positions of the slipping planes ΔH depend on the shear rate, showing that significant shear thinning/thickening effects occur within the outermost tail regions
of the adsorbed layers during shear. The position of the slipping plane, or hydrodynamic layer thickness ΔH, varies from 0.6R
H to 2R
H away from each surface (mica and surfactant-coated mica surfaces). Beyond the hydrodynamic layer the far-field fluid viscosity
is the same as that of the bulk polymer solution. At separations below D = 2ΔH the viscosity increases as each polymer layer is compressed. The static forces exhibited various time- and history-dependent
effects, which further indicate that a number of different relaxation/equilibration processes are operating simultaneously
in this complex multicomponent system. The results reveal that the interactions of tails of functionally adsorbed polymers
play a more important role than previously thought. This is especially true in this study where the adsorbed polymers are
of low molecular weight and where the tails may represent the largest fraction of interacting segments.
Received: 22 September 1998 Accepted: 11 January 1999 相似文献
946.
J. J. Ramsden 《Colloids and surfaces. B, Biointerfaces》1999,14(1-4):77-81
The interaction energy of a charged protein with zwitterionic and charged lipid bilayers is calculated and compared with recent experimental results. Calculations and available data suggest that the electrostatic (el) contribution to the binding of typical signal transduction proteins has been hitherto greatly exaggerated. 相似文献
947.
Nathalie Pannetier Jean-Pierre Habas Jean Peyrelasse Jeanne François 《Rheologica Acta》1999,38(3):241-250
Mixtures of lime/sucrose/water, at given compositions lead, to viscoelastic homogeneous pastes. The equilibrium state is
reached after a time, which decreases when either the water content decreases or the lime concentration increases. At equilibrium,
the general features of the spectromechanical analysis look like those for classical viscoelastic materials. Nevertheless,
while the frequency dependence of the loss modulus is as expected, the exponent of the variation of the storage modulus with
frequency is significantly lower than 2. It is clear that this system is not simply Maxwellian. The discussion deals with
the origin of this behaviour, caused either by the presence of lime particles in excess, or the approach of gelation.
Received: 9 October 1998 Accepted: 12 March 1999 相似文献
948.
原子-辐射场相互作用系统量子统计力学的相干态表述 总被引:2,自引:1,他引:1
用Heisenberg-weyle(简称H-W)群直积SU(2)群上的相干态表述了原子-辐射场相互作用系统的量子统计力学,引入一个新定义的分布函数,将平衡态下密度矩阵的Bloch方程转换成可分离变量的偏微分方程,给出了方程的形式解,算符和其平均值的表示。 相似文献
949.
950.
构建激发态取代基参数与1,4-二取代苯的紫外吸收波数之间的模型,成功地关联80个1,4-二取代苯的紫外吸收波数,其方程的相关系数为0.9805,标准偏差仅为672.27cm^-1.结果表明激发态取代基参数适用于1,4-二取代苯紫外吸收能量的研究.同时提供了研究芳香化合物的紫外吸收光谱的新方法,并有利于深入理解多取代共轭化合物的激发态物理化学性质中的取代基效应. 相似文献