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1.
R. Baeza Luis M. Gugliotta A. M. R. Pilosof 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):81-93
The role of the non-gelling polysaccharide, propyleneglycol alginate (PGA), on the dynamics of gelation and gel properties of β-lactoglobulin (β-lg) under conditions where the protein alone does not gel (6%) was analyzed. To this end, the kinetics of gelation, aggregation and denaturation of β-lg in the mixed systems (pH 7) were studied at different temperatures (64–88 °C). The presence of PGA increased thermal stability of β-lg. The rate of β-lg denaturation was decreased and the onset and peak denaturation temperatures increased by 2.2–2.4 °C. PGA promoted the formation of larger aggregates that continued to grow in time. An average aggregate diameter of approximately 300 nm is reached at the gel point in the mixed β-lg+PGA systems, irrespective of the heating temperature. Comparing the activation energies for the aggregation (193 kJ/mol), denaturation (422 kJ/mol) and formation of the primary gel structure (1/tgel) (256 kJ/mol) processes in the mixed protein–polysaccharide system, it can be concluded that the rate determining step in the formation of the primary gel structure would be the aggregation of protein. Ea values for the processes after the gel point (solid phase gelation) suggest a diffusion limited process because of the high viscosity of the solid gelling matrix. The characteristics of the mixed β-lg+PGA gels in terms of rheological and textural parameters, water loss and microstructure were studied as a function of heating temperature and time. The extent of aggregation and the type of interactions involved, prior to denaturation seem to be very important in determining the gel structure and its properties. 相似文献
2.
二阶非线性电路中的不相容性 总被引:1,自引:0,他引:1
为了研究动力学系统和混沌中产生的跳跃随机性,利用能量平衡原理分析了二阶非线性电路的退化方程。发现了动力学系统中的连续不相容性是电路状态发生跳跃的原因之一,这种连续不相容性是指解依约束方程电路的状态轨迹运动进入某一区域时,其任何运动与停止都是与该约束方程相矛盾的:电路状态是处于既不能向前,又不能后退,也不能停止不动的境地,而在该区域外的临近区域,它的运动都与约束方程相容。同时发现动力学系统中的非线性函数项(或非线性元件)能够发生跳跃随机性和产生跳跃随机曲线,以使电路的状态轨迹达到与约束方程相容的状态。 相似文献
3.
Bernhard A. Wolf 《Macromolecular theory and simulations》2010,19(1):36-43
The calculation of phase diagrams for blends of linear and branched polymers made up of identical monomeric units is modeled using an approach that subdivides the mixing process into two steps: i) contact formation between the different components, keeping their chain conformations and the volume of the system constant; and, ii) relaxation of the macromolecules into their equilibrium state by molecular rearrangements. It is assumed that step (ii) causes shape‐induced polymer incompatibility and that the degree of branching can be quantified in terms of the volumes the isolated coils of the branched polymer occupy in relation to the volume the linear product with the same molecular weight occupies. Under these premises, it is possible to work out how the critical conditions depend on the molar masses of the components and on the degree of branching of the non‐linear polymer by means of only one system‐specific parameter, measuring the effects of conformational relaxation. Detailed phase diagrams show how the binodal and spinodal conditions reflect the conformational variability of the blend components.
4.
多评价特征基元可拓集研究 总被引:20,自引:2,他引:20
杨春燕 《数学的实践与认识》2005,35(9):203-208
在单评价特征基元可拓集的基础上,研究多评价特征基元可拓集的构造方法及其关联函数的建立方法,为多特征综合评价和多特征不相容问题求解提供理论依据和可操作的形式化、定量化方法,使多特征不相容问题的智能化处理成为可能. 相似文献
5.
以信号量机制、管程机制、会合技术、Petri网这四种控制机制为基础,对经典的进程同步问题:生产者-消费者模型进行了分析,并给出了该问题基于不同机制的解决方案,对四种控制机制进行了比较研究. 相似文献
6.
大白菜(BrasicacampestrisssppekinensisOlsson)冠-291花期自交授粉后,花粉管在柱头乳突细胞表面盘曲,乳突细胞中出现胼胝质反应。蕾期自交授粉能克服自交不亲和性,但受精作用,胚胎发育较冠-291×石-851迟缓,单果鲜重及种子数仅为后者的一半。电助授粉未见明显效果。 相似文献
7.
R. Chen F. Chu C. Gauthier L. Chazeau I. Chaduc E. Bourgeat‐Lami M. Lansalot 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2329-2339
Ethyl cellulose (EC) was incorporated into copolymer latexes via miniemulsion polymerization. The effects of EC viscosity and EC content on droplet size, particle size, and polymerization kinetics were investigated. The higher the EC content and viscosity, the larger the droplet size and the less stable the latex suspension. Small droplets that could be efficiently nucleated were formed for the lower‐viscosity EC but the latex still showed limited colloidal stability. This was attributed to some phase‐incompatibility between EC and the acrylic polymer. These stability issues were overcome by using an oil‐soluble initiator and a crosslinker. The later enabled to physically entrap EC inside the polymer particles, whereas the former allowed in situ grafting of the growing acrylic radicals to the EC backbone decreasing thereby the extent of phase separation. Thermal‐mechanical analyses evidenced that the films obtained from the hybrid latexes displayed better properties than the EC‐free latex films or the physical blends. This supports the hypothesis of formation of hybrid latexes that synergistically combine the properties of the acrylic matrix and the EC polymer. Interestingly, a significant increase of the elastic modulus was observed between 50 and 90 °C. This mechanical reinforcement was tentatively attributed to the formation of a percolating EC‐based hybrid phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2329–2339, 2010 相似文献
8.
研究发现在临床上磷酸川芎嗪的各种剂型里使用最多的是注射给药.相关报道中注射用磷酸川芎嗪在使用时经常与其他药物配合使用,且联合用药时易发生配伍变化.对这些配伍变化进行归纳总结,旨在提醒广大医药工作者在研究和使用磷酸川芎嗪注射液时应给予重视. 相似文献
9.
Beatriz Casta?eda William Ortiz‐Cala Cecilia Gallardo‐Cabrera Norma Sbarbati Nudelman 《Journal of Physical Organic Chemistry》2009,22(9):807-814
An HPLC method was developed to determine the stability of alprazolam (AL) as a pure drug and in monodrug pharmaceutical tablets. The main degradation product of AL tablets was isolated and fully characterized as triazolaminoquinoleine (TAQ). For a quantitative evaluation of the excipient effects in the pharmaceutical formulations, a 2k fractionated factorial design was applied in the preparation of the different samples. The kinetic of degradation of AL in each formulation was followed by UV spectrophotometry. It was found that excipients like CMC and magnesium stearate favour degradation, while the rate of the reaction is decreased when lactose and starch were used as excipients. A mechanism for the interactions of AL with some excipients is postulated that explains the observed results. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
本文介绍Noll和Wang等人用理性力学观点建立的变形体非协调理论(即缺陷的连续统理论)。这理论表明,本构方程完全确定物质流形的几何结构。因而,几何结构是理论的自然结果,而不是作为理论出发点的最初假设。 相似文献