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991.
Nickel(II) complexes of di-, tri- and tetra-peptides built up from Asp and/or Glu residues have been studied by potentiometric, UV–Vis and circular dichroism spectroscopic methods. The stoichiometry of the complexes are the same as in the case of common oligopeptides, but the presence of the side chain carboxylate groups results in differences in their stabilities and coordination modes. The presence of the β-carboxylate groups increases the metal binding affinity of the peptides in all cases. This is due to the coordination of the first, second and third aspartic acid residue in the case of the NiL, NiH−1L and NiH−2L complexes, respectively. The high negative charge of Asp4 suppresses the metal ion coordination of the third amide function, therefore the NiH−3L complex does not form with this tetra-peptide. In the case of peptides containing glutamic acid, no stability enhancement appears because there is only a weak interaction between the nickel(II) ion and the γ-carboxylate group, which is not able to compensate the disfavoured effect of the increasing negative charge of the complexes. 相似文献
992.
Y. Wu W. Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):305-312
The thermal and mechanical properties of Mg-Gd intermetallics MgGd,
MgGd2 and MgGd3 are studied using a modified analytical embedded
atom method. Calculated results agree well with the available experimental
data and other theoretical results. The results on the elastic constants
suggest that thermal softening behavior is observed as the temperature
increases and the bulk moduli of ordered phases are larger than that of
elemental Mg above 300 K. The heat capacities of MgGd, Mg2Gd and
Mg3Gd are 22.91, 23.04 and 23.09 J mol K-1, respectively, at 300 K.
Furthermore, the addition of Gd gives rise to an increase of c/a. With the
same content of Gd, the ratio c/a remains unchanged with increasing
temperature, whereas this phenomenon does not occur in pure Mg, which
indicates that the temperature-independent c/a restrains the occurrence of
non-basal slip and twinning. Hence the addition of Gd can enhance the
strength of Mg, in good agreement with experimental observation. 相似文献
993.
Due-date assignment and maintenance activity scheduling problem 总被引:1,自引:0,他引:1
In the scheduling problem addressed in this note we have to determine: (i) the job sequence, (ii) the (common) due-date, and (iii) the location of a rate modifying (maintenance) activity. Jobs scheduled before (after) the due-date are penalized according to their earliness (tardiness) value. The processing time of a job scheduled after the maintenance activity decreases by a job-dependent factor. The objective is minimum total earliness, tardiness and due-date cost. We introduce a polynomial (O(n4)) solution for the problem. 相似文献
994.
A thermodynamic framework for a mixture of two liquids 总被引:1,自引:0,他引:1
In this study, we extend a thermodynamic framework that has been used with some success for describing the response of a variety of single constituent continua. Using the thermodynamic framework, we obtain a model for the mixture of two compressible fluids that has a much simpler structure than the model obtained earlier within the context of mixture theory. We also investigate the response of a mixture of two fluids that is constrained to have a constant volume, using the same thermodynamic framework. 相似文献
995.
We study the rate of convergence of interpolating simultaneous
rational approximations with partially prescribed poles to so-called Nikishin systems of functions. To this end, a vector
equilibrium problem in the presence of a vector external field is
solved which is used to describe the asymptotic behavior of the
corresponding second-type functions which appear. 相似文献
996.
997.
本文使用OH激光诱导荧光方法研究了结构最简单的克里奇中间体CH2OO和CF3CF=CF2的反应动力学. 在压强为10 Torr条件下,测量了温度在283,298,308和318 K的反应速率常数,分别为(1.45±0.14)×10-13,(1.18±0.11)×10-13,(1.11±0.08)×10-13和(1.04±0.08)×10-13 cm3·molecule-1·s-1. 根据阿伦尼乌斯方程,获得该反应的活化能为(-1.66±0.21) kcal/mol. 在6.3∽70 torr压力范围内,未观察到该反应的速率常数存在压力相关. 相似文献
998.
M.G. Abd El Wahed M.A. Elmesallamy H.M. Kater M.M. El Gamel N.A. Khalil 《Arabian Journal of Chemistry》2011,4(2):169-178
The stability constants of the complexes of cyanopyridine and aminoantipyrine with some divalent transition metal chlorides were determined at different temperatures. The thermodynamic parameters were calculated; the obtained data reveal that the complexation is an endothermic process. Also it was found that the type of bonding between the ligands and the corresponding metal ion is mainly ionic in nature. The stoichiometry of the formed complexes was found to be M:L and M:2L. The structure of some prepared complexes was confirmed by IR, 1H NMR spectra as well as elemental analysis. Thermal stability was studied using TGA technique. 相似文献
999.
1000.
M. Baudequin G. Ryschenkow S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):157-162
Light fibrous materials composed of elastic fibers display a non-linear elastic behavior, where the non-linearity is due to
the increase in the number of contacts between fibers under compression. Testing glass wool under compression up to 95% shows
such a strongly non-linear behavior. A model is proposed to account for the divergence of the compressive stress as the strain approaches a threshold compression , with . Quantitative analysis of the experimental data on glass wool is fully consistent with this result.
Received 2 February 1999 相似文献