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41.
Michael Weiss 《Proceedings of the American Mathematical Society》1996,124(2):615-622
Upper bounds obtained by Gromov on the Betti numbers of certain closed Riemannian manifolds are shown to be upper bounds on the minimum number of cells in --spaces dominating such manifolds.
42.
Mattia Falconi Ruggero Gallimbeni Emanuele Paci 《Journal of computer-aided molecular design》1996,10(5):490-498
Summary Molecular dynamics (MD) simulations of 100 ps have been carried out to study the active-site behaviour of the Cu,Zn superoxide dismutase dimer (SOD) in water. The active site of each subunit was monitored during the whole simulation by calculating the distances between functional residues and the catalytic copper. The results indicate that charge orientation is maintained at each active site but the solvent accessibility varies. Analysis of the MD simulation, carried out by using the atomic displacement covariance matrix, has shown a different intra-subunit correlation pattern for the two monomers and the presence of inter-subunit correlations. The MD simulation presented here indicates an asymmetry in the two active sites and different dynamic behaviour of the two SOD subunits. 相似文献
43.
The reaction of acetone-4-chlorophenylhydrazone (6) with bromine in the presence of acetamide yields 2-bromo-2-(4-chlorophenylazo)-propane (7) and 2,2-bis(4-chlorophenylazo)propane (8). The unstable heteroallylic bromide7 was subjected without isolation to nucleophilic displacements with a series of heteronucleophiles thereby affording the corresponding 2-(4-chlorophenylazo)-2-propane derivatives9 with the azo- and heteroelement-functions in a geminal position to each other.
Herrn Prof. Dr. Dr. h. c.K. Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet. 相似文献
44.
A new effective approach to the synthesis of a small library of 2-amino-5-arylidene-1,3-thiazol-4(5H)-ones was reported using solvent-free reaction conditions under microwave irradiation. In the first step, rhodanines were subjected to Knoevenagel condensation with aryl aldimines according to a facile one-pot protocol. Then the (5Z)-5-arylidene rhodanine derivatives were transformed directly into the corresponding 2-amino-1,3-thiazol-4(5H)-ones by sulfur/nitrogen displacement reaction under microwaves with retention of configuration and good overall yields. 相似文献
45.
J. Grenet J. M. Saiter C. Vautier J. Bayard 《Journal of Thermal Analysis and Calorimetry》1992,38(4):557-565
The effect of ageing temperature (belowT
g) on physical ageing of glassy PET has been investigated by differential scanning calorimetry. The position of the glass transition endotherm was found to be strongly dependent on the annealing conditions (time, annealing temperature). A single relaxation time model is proposed for the analysis of physical ageing.The variations of the equilibrium relaxation time iso with annealing temperature allow the determination of the parameters of the model. Finally, using these constants, one can determine the thermal past and foresee the thermal future of unknown samples which are of prime importance in processes using temperatures around the glass transition temperature.
Zusammenfassung Mittels DSC wurde der Einfluß der Alterungstemperatur (unterhalbT g) auf das physikalische Altern von glasartigen PET untersucht. Die Lage der Glasumwandlungsendothermen hängt stark von den Temperungsbedingungen (Dauer, Temperungstemperatur) ab. Es wird ein Relaxationszeitmodell für die Analyse physikalischen Alterns vorgeschlagen.Die Parameter dieses Modelles knnen aus der Änderung der Gleichgewichtsrelaxationszeit iso mit der Temperungstemperatur ermittelt werden. Unter Benutzung dieser Konstanten kann die thermische Vergangenheit unbekannter Proben bestimmt und die thermische Zukunft derselben vorhergesagt werden, was für Vorgänge bei Temperaturen um den Glasumwandlungspunkt von primärer Wichtigkeit ist.相似文献
46.
Determining PPARγ-ligand binding affinity using fluorescent assay with cis-parinaric acid as a probe
Gao Zhenting Luo Haibin Chen Lili Shen Jianhua CHEN Kaixian JIANG Hualiang SHEN Xu 《中国科学B辑(英文版)》2005,48(2)
Upon the study of small-molecules binding to proteins, the traditional methods for calculating dissociation constants (Kd and Ki) have shortcomings in dealing with the single binding site models. In this paper, two equations have been derived to solve this problem. These two equations are independent of the total concentration or initial degree of saturation of receptor and the activity of the competitive molecule. Through nonlinear fitting against these two equations, Kd value of a probe can be obtained by binding assay, and Ki value of a ligand can be obtained by competitive assay. Moreover, only the total concentrations of receptor([R]t), ligand([L]t) and probe([P]t) are required for the data fitting. In this work, Ki values of some typical ligands of PPARγ were successfully determined by use of our equations, among which the Ki value of PPARγ-LY171883 was reported for the first time. 相似文献
47.
Seong-Je?Huang Jin-Kook?Lee Chang-Sik?HaEmail author 《Colloid and polymer science》2004,282(6):575-582
The object of this work was to prepare high-density polyethylene (HDPE)/ethylene–propylene–diene terpolymer (EPDM)/conductive carbon black (CB) composites by dynamic curing and to characterize the positive-temperature-coefficient (PTC) performances of the composites.EPDM and dicumyl peroxide were preblended in a research mill. The roll-milled strands were blended with HDPE and CB in a Haake mixer. The sheet resistivity and morphology of the HDPE/EPDM/CB composites with or without the dynamic curing process were investigated. It was concluded that the dynamically cured blends exhibit better PTC performance than the simple blends without dynamic curing. The effects of shear intensity and dicumyl peroxide content during the dynamic curing process were discussed for the PTC characteristics of the HDPE/EPDM/CB composites. 相似文献
48.
Xiao Hua WANG Han Zhi WANG Hui LIU Yuan KOU 《中国化学快报》2006,17(12):1531-1533
Recent years, crown ethers have been used in many fields, including phase transfer catalysis, chromatography stationary phase, ionselective electrode, and concentration of metal ions, etc1.. However, the toxicity of free crown ethers makes them unsuitable for industrial use2. Introduction of a crown ether as a functional group to functionalized ionic liquids has been reported3. These functionalized ionic liquids will combine the excellent properties of crown ether and ionic liquids without los… 相似文献
49.
The binding constants, K′, for the reaction between some alkyldimethylbenzylammonium bromide homologues (alkyl = methyl, ethyl, propyl, butyl, hexyl,
decyl, and dodecyl, respectively) and β-cyclodextrin in water at 25.0 ± 0.1 ∘C have been determined, by applying the spectral displacement technique with phenolphthalein as the displacing anion. It has
been shown that the ln K′ values increase linearly with the number of carbon atoms in the alkyl chain for the salts whose alkyl chain has at least
four carbon atoms. The ln K′ values estimated for the parent compound benzyltrimetylammonium bromide and its two nearest homologues are distinctly lower
than might be expected by extrapolation of the linear relation found for the higher homologues. Assuming that it is the organic
cation that undergoes association with β-cyclodextrin, then one may suppose that a change occurs in the mode of inclusion of the cation upon passing to higher homologues.
In the case of the lighter homologues, it is the phenylene group that undergoes inclusion. This model of inclusion is confirmed
by analysis of rotating-frame overhauser effect spectroscopy (ROESY) spectra. 相似文献
50.
Banach空间半线性发展方程的周期解 总被引:8,自引:2,他引:8
把上、下解方法引入到有序Banach空间中的半线性发展方程周期解问题,利用正算子半群特征与单调迭代程序,获得了最大周期解与最小周期解的存在性.所得的结果概括和推广了常微分方程与偏微分方程中的有关结论 相似文献