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71.
A phenomenological approach was used to characterize the cure processes of epoxy resins (a diglycidyl ether of bisphenol A and its modifier CTBN) from dynamic experiments by DSC. Various kinetic parameters were obtained by using a modified Avrami expression. The resulting overall activation energies for the two systems agreed very well with the published data in the whole cure temperature range. In contrast with the isothermal results and the general dynamic models, a change in the exponent and the non-linear temperature dependence of the rate constant were also observed.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
72.
Using the standard truncated Painlevé expansion, the residual symmetry of the (2+1)-dimensional modified dispersive water-wave system is localized in the properly prolonged system with the Lie point symmetry vector. Some different transformation invariances are derived by utilizing the obtained symmetries. The symmetries of the system are also derived through the Clarkson-Kruskal direct method, and several types of explicit reduction solutions relate to the trigonometric or the hyperbolic functions are obtained. Finally, some special solitons are depicted from one of the solutions. 相似文献
73.
We propose a quantum-mechanical Brayton engine model that works between two superposed states, employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition principle, we obtain the explicit expressions of the power and efficiency, and find that the efficiency at maximum power is bounded from above by the function:η+ =θ/(θ+ 1), with being a potential-dependent exponent. 相似文献
74.
75.
依赖于天冬氨酸的半胱氨酸蛋白酶(caspase)在细胞凋亡途径中起着不可替代的关键酶作用.本研究采用原核表达载体pET32a表达和纯化了家蚕细胞Bm-caspase-1及粉纹夜蛾细胞Tni-caspase-1蛋白酶,序列分析表明二者具有相同的内部剪切识别序列,且酶活性位点均为QACQ↓G.纯化获得大量可溶性蛋白酶,Western-blotting分析表明Bm-caspase-1在大肠杆菌中已自我剪切活化,而Tni-caspase-1没有自我剪切,无酶活性;活性Bm-caspase-1蛋白酶对caspase-3特异性底物Ac-DEVD-AMC的降解酶活性可被Z-VAD-FMK呈剂量依赖性抑制,半抑制浓度约20nmol/L.此外,活性Bm-caspase-1蛋白酶能够转活化无活性的Tni-caspase-1蛋白酶原.结果揭示了昆虫细胞caspase同样具有与哺乳动物细胞caspase相似的底物降解活性并可相互剪切激活,为进一步研究昆虫细胞凋亡的分子途径奠定了基础. 相似文献
76.
Solving (2+1)-dimensional sine-Poisson equation by a modified variable separated ordinary differential equation method 下载免费PDF全文
By introducing a more general auxiliary ordinary differential equation (ODE), a modified variable separated ordinary differential equation method is presented for solving the (2+1)-dimensional sine-Poisson equation. As a result, many explicit and exact solutions of the (2+1)-dimensional sine-Poisson equation are derived in a simple manner by this technique. 相似文献
77.
胰岛素瘤相关蛋白1(INSM1)是一类转录调节蛋白,通过其C-端的锌指结构域(氨基酸250-510)来识别序列特异性的DNA分子.INSM1的C-端包含有5个串联的锌指结构域,然而这些结构域的结构及其如何识别DNA的分子机制目前仍不清楚.通过重组构建的质粒pET-32m-INSM1(424-497)表达的蛋白质(氨基酸424-497)包含了最后两个锌指结构域4和5,简称为ZF(4-5).该文详细研究了蛋白质ZF(4-5)的诱导表达条件,得到了较高产率的纯化蛋白.核磁共振(NMR)谱和圆二色谱(CD)揭示了Zn2+对稳定锌指蛋白结构的必要性,以及C2H2-Zn2+结合的组氨酸呈现为δ-异构方式. 相似文献
78.
The potential distribution between a grid and two plates is an electrostatic problem already solved for various applications such as MultiWire detectors used in Nuclear Physics, or electrostatic precipitators in Engineering. Since references and notations for this analytical solution are ancient and rather bewildering, the first part of this paper presents a revisit and a discussion of the formulations that assume a line charge on the wire. This is completed by establishing a ready-to use closed-form expression valid for the general configuration where the plates are not grounded. The second part is about the investigation of the line model accuracy close to the wires, using both analytical and numerical approaches. In the symmetric case where the grid is placed at equal distances between two grounded plates, it is shown that the error can be modelled using a quadrupole charge. For the asymmetric case, a larger discrepancy of the line model is brought to light, with an error featuring a dipole-like distribution. In order to cope with this small but not negligible error, a classical dipole model is implemented, leading to an accurate theoretical expression of the potential. 相似文献
79.
辐射阻抗是换能器的最重要辐射声场特性参数之一,影响着换能器的谐振频率、频带宽度、效率以及辐射声功率等。经典声学理论用一阶贝塞尔函数和斯特鲁夫函数给出了圆形活塞换能器辐射阻抗的数学表达式,但仅适用于无限大障板条件。该文用ANSYS有限元软件计算了无障板圆形活塞换能器的辐射阻抗,给出了数值解结果,通过与无限大障板条件下的理论结果相比较,显示了二者之间的偏离情况,尤其是在低频时差异显著。为了借助MATLAB工具模拟无障板圆形活塞换能器的辐射阻抗,并给出较准确的数学表达,选择了一系列初等函数以及它们的复合函数进行曲线拟合,最终给出了辐射阻和辐射抗关于ka的函数表达式,在ka值从0.08到20范围内与有限元计算结果很好吻合。 相似文献
80.