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排序方式: 共有1383条查询结果,搜索用时 15 毫秒
131.
Mingming Zou Ying Li Jun Wang Qi Wang Yumei Kong Jingqun Gao Ping Fan 《Journal of solution chemistry》2013,42(4):849-865
The interaction between bovine serum albumin (BSA) and FeIII complexes with three binary organic acid (biorga) ligands, [FeIII(oxa)(H2O)4]+ (oxa = oxalic acid), [FeIII(pra)(H2O)4]+ (pra = propanedioic acid) and [FeIII(sua)(H2O)4]+ (sua = succinic acid), as well as the sonocatalytic damage of BSA in the presence of these three FeIII–biorga complexes under ultrasonic irradiation, were studied by UV–vis and fluorescence spectra. The experimental results show that the fluorescence quenching process of BSA caused by three FeIII–biorga complexes are all static quenching and the corresponding quenching rate constants (K q), equilibrium constants (K A) and the binding site numbers (n) were calculated. The results reveal that, under ultrasonic irradiation, the BSA molecules were obviously damaged by these FeIII–biorga complexes. In addition, the effects of several factors on the damage of BSA molecules were examined. The experimental results demonstrate that the damage degree of BSA increased with an increase of ultrasonic irradiation time, FeIII–biorga complex concentration, and ionic strength. In comparison, [FeIII(pra)(H2O)4]+ exhibited higher sonocatalytic activity than [FeIII(oxa)(H2O)4]+ and [FeIII(sua)(H2O)4]+. Finally, the extent of generation of $ \cdot {\text{O}}_{2}^{ - } $ · O 2 ? and ·OH during sonocatalytic processes was estimated. Perhaps, the results will be significant for promoting sonodynamic treatment (SDT) of tumors at the molecular level. 相似文献
132.
鲨鱼软骨血管形成抑制因子的分离纯化及其活性的初步研究 总被引:4,自引:0,他引:4
以广东阳江鲨鱼软骨为原料,研究了鲨鱼软骨新生血管形成抑制因子的分离纯化方法,并对其生物学活性进行了初步研究.采用盐酸胍抽提、膜超滤、丙酮分级沉淀、SephadexG-75柱层析和C4反相高效液相色谱等步骤,分离纯化出一种新的鲨鱼软骨血管生成抑制因子-a(SharkCartilageAngiogenesisInhibitor-a,SCAI-a),分子量为12600,能显著抑制鸡胚绒毛尿囊膜血管的形成. 相似文献
133.
134.
Tetraarylthiophenes were prepared by regioselective Suzuki cross-coupling reactions of tetrabromothiophene. 相似文献
135.
136.
韩团香 《科技情报开发与经济》2003,13(11):108-108,163
固定资产的价值在使用中是越来越减少的,要真正体现出单位固定资产的实有价值,像企业一样建立固定资产的折旧制度是非常必要的,同时还必须分清提取折旧和提取修购基金是相同用途的不同提取方法。 相似文献
137.
Yumei Hou Suresh P. Sethi Hanqin Zhang 《Journal of Mathematical Analysis and Applications》2006,317(2):398-428
We consider a production planning problem for a jobshop with unreliable machines producing a number of products. There are upper and lower bounds on intermediate parts and an upper bound on finished parts. The machine capacities are modelled as finite state Markov chains. The objective is to choose the rate of production so as to minimize the total discounted cost of inventory and production. Finding an optimal control policy for this problem is difficult. Instead, we derive an asymptotic approximation by letting the rates of change of the machine states approach infinity. The asymptotic analysis leads to a limiting problem in which the stochastic machine capacities are replaced by their equilibrium mean capacities. The value function for the original problem is shown to converge to the value function of the limiting problem. The convergence rate of the value function together with the error estimate for the constructed asymptotic optimal production policies are established. 相似文献
138.
The problem of kink stability of isothermal spherical self-similar flow in newtonian gravity is revisited. Using distribution
theory we first develop a general formula of perturbations, linear or non-linear, which consists of three sets of differential
equations, one in each side of the sonic line and the other along it. By solving the equations along the sonic line we find
explicitly the spectrum, k, of the perturbations, whereby we obtain the stability criterion for the self-similar solutions. When the solutions are smoothly
across the sonic line, our results reduce to those of Ori and Piran. To show such obtained perturbations can be matched to
the ones in the regions outside the sonic line, we study the linear perturbations in the external region of the sonic line
(the ones in the internal region are identically zero), by taking the solutions obtained along the line as the boundary conditions.
After properly imposing other boundary conditions at spatial infinity, we are able to show that linear perturbations, satisfying
all the boundary conditions, exist and do not impose any additional conditions on k. As a result, the complete treatment of perturbations in the whole spacetime does not alter the spectrum obtained by considering
the perturbations only along the sonic line. 相似文献
139.
对某小型无人直升机的增稳动力学进行了精确的建模,鉴于稳定杆对飞行动力学有很重要的影响,本文对旋翼和稳定杆系统分别进行建模.通过仿真的比较和分析表明,稳定杆引起了姿态系统的小阻尼和峰值,采取加入陷波器的方法进行补偿,使姿态系统的性能得到了明显的优化. 相似文献
140.
We are concerned with the shock structure in viscoelasticity of rate type. The existence of a shock profile, which in the vanishing relaxation limit becomes an elastic shock, is demonstrated by an explicit construction of the solution of viscoelastic equations provided that the equilibrium stress–strain relation is governed by a parabolic law. For a more general stress–strain law which does not differ substantially from a parabolic one, the solution is obtained from a perturbation expansion. 相似文献