红细胞衰老过程中微观流变学行为的研究

作者在用抗体诱发动物急性溶血的方法建立的红细胞在体同步衰老模型的基础上，对红细胞衰老过程中的微观流变学行为进行了研究。用激光衍射法对高粘悬浮介质（ＰＶＰ）和低粘悬浮介质（ＰＢＳ）流场中的微观流变学指标ＤＩ、ＩＤＩ、（ＤＩ）ｄ、（ＤＩ）ｏｒ进行测量，结果显示四项指标随红细胞年龄的增加均呈下降趋势，但并不呈线性关系。表现为在生命周期中的前期变化较小，后期变化较大。提示老化过程中红细胞的流变学行为的变化主要发生在其生命过程的后半期。但各指标变化的规律不尽相同。与本室以往的研究结果进行比较，这些结果提示，在红细胞生命的初期，其膜的力学性质基本不变。而整个红细胞生命过程中红细胞力学性质的变化，可能来自红细胞的形状。

小鼠网织红细胞微观流变学特性的研究

按Bishop方法,在小鼠血液里诱导生成大量网织红细胞,然后提取网织红细胞,对其电泳率、渗透脆性、膜的流动性、细胞的变形能力和取向性进行了系统研究。研究结果表明网织红细胞在转变为成熟红细胞的短短时间内,其微观流变学特性发生了明显的变化:电泳率变小、渗透脆性变好、膜的流动性变大、细胞的变形能力变强、取向性变好,最终发育成具有全面功能的成熟红细胞。

树突状细胞的微观流变学特性研究

树突状细胞(Dendritic Cells,DCs)是一种特化的抗原呈递细胞,它在启动和放大天然和适应性免疫应答方面发挥着关键作用。细胞的微观流变学特性能够反映细胞的结构和功能之间的关系。DCs在其复杂的生命过程中显示出不同的免疫学功能和微观流变学特性,而且肿瘤来源的抑制性细胞因子能够通过损伤DCs的微观流变学特性来抑制其免疫功能,是肿瘤逃脱免疫监视的方式之一。作者着重介绍了北京大学基础医学院血流变学研究中心近几年在此研究领域的一些进展。

诃子醇提物对急性血瘀大鼠微观血液流变学的影响

目的通过血液流变学的实验研究,探讨诃子醇提物对大鼠微观血液流变学指标的影响。方法选取SD雄性大鼠随机分为对照组、血瘀模型组、诃子醇提物组,阳性对照组(复方丹参片)。采用皮下注射肾上腺素加冰水冷浴法造大鼠血瘀模型,通过测定全血粘度、血浆粘度,红细胞压积,红细胞在不同切变率下的变形、取向指数,红细胞膜的渗透脆性等血液流变学指标来观察诃子醇提物对大鼠微观血液流变学的影响。结果正常对照组,诃子醇提物组,阳性对照组各血液流变学指标间的差异不明显。但与血瘀模型组比较,诃子醇提物能明显降低全血粘度、血浆粘度、红细胞压积,增强红细胞变形、取向能力,提高红细胞的抗低渗能力。结论诃子醇提物可以有效改善急性应激性血瘀大鼠的微观血液流变学特性。

红细胞衰老过程的研究进展

本文介绍了近年来研究红细胞衰老所采用的各种模型及其优缺点。

Effects of technical parameters of continuous semisolid rolling on microstructure and mechanical properties of Mg-3Sn-1Mn alloy

A sloping semisolid rheo-rolling process of Mg-3Sn-1Mn alloy was developed, and the effects of process parameters on the microstructure and mechanical properties of Mg-3Sn-lMn alloy strip were studied. The results show that the primary grain average diameter of the strip increases with the increase of the roll speed. The primary grain average diameter decreases firstly and then increases with the increase of the vibration frequency, and the tensile strength and elongation of the strip increase firstly and then decrease with the increase of the vibration frequency. The primary grain average diameter increases with the increase of casting temperature, and the tensile strength and elongation of the strip decrease correspondingly. When the casting temperature is 670℃, the roll speed is 52 mm/s, and the vibration frequency is 60 Hz, Mg-3Sn-1Mn alloy strip with good properties is produced. The mechanical properties of the present product are higher than those of Mg-3Sn-lMn alloy casting with the addition of 0.87% Ce （mass fraction）.

Effects of rheoforming on microstructures and mechanical properties of 7075 wrought aluminum alloy

It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competitiveness of this emerging technology in the manufacture of wrought aluminum alloy.High quality semi-solid slurry was produced,in which primary α(Al) presents in diameter of 62 μm and shape factor of 0.78 and features no eutectics entrapped.Higher forming pressure results in small grain size,improved shape factor and higher density.Especially,rheoforming can effectively reduce the occurrence of hot tearing.The average yield strength and elongation of the rheoformed samples in the T6 condition are 483 MPa and 8%,respectively.

Microstructure, morphology, crystallization and rheological behavior of impact polypropylene copolymer

Impact polypropylene copolymer (IPC), named polypropylene catalloy, not only possesses excellent impact property, but also presents good rigidity. Its superior performances result from the complicated composition and microstructure. In the present article, recent progress in the studies on microstructure, morphology, crystallization and rheological behavior of IPC is summarized, and findings of the authors and their collaborators are reported. In general, IPC is divided into three components, i.e., ethylene-propylene random copolymer (EPR), a series of different segment lengths ethylene-propylene copolymer (EbP) and propylene homopolymer. The reasonable macromolecular structures of EbP and a multilayered core-shell model of dispersed phase structure in IPC were proposed, in which the dispersed phase consists of an outer EbP shell, an inner EPR layer and an EbP core. It is found that the annealing at melt-state may lead to an abnormal phase inversion, and the phase inversion disappears when temperature cools down to room temperature. The cause of phase inversion is ascribed to the existence of EbP component, which results in the stronger activity of the dispersed phase. The crystalline structure and morphologic results confirm the formation of β-iPP in IPC. Furthermore, it is found that the ethylene content in IPC and cooling rate of the samples have an important influence on the formation of β-iPP. Based on the crystallization kinetics analyzed by Lauritzen-Hoffman theory, crystallization behavior of different IPC samples is discussed and it is proposed that the dilution effect of ethylene propylene copolymer has a more remarkable influence on surface nucleation than on crystal growth. In addition, annealing at high temperature can result in the changes of chain structure for IPC, and this instability is ascribed to the oxidative degradation and crosslink reaction mainly in iPP component.

Rheology and microstructure effects of waste spent coffee grounds in modifying asphalt binder

Herein the biowaste by-product spent coffee grounds(SCGs)from coffee industry were incorporated into asphalt binders for performance enhancement.From the analysis of Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),dynamic shear rheometer(DSR),and Brookfield viscosity rheometer,it is confirmed that SCGs have potential prospects as bio-waste modifiers in the application of sustainable pavements.Results demonstrated that the modification process was mainly based on physical reinforcement.Compared with that of the neat asphalt,the shearing stress-resistant ability and high-temperature performance of the SCGs modified binders with the appropriate addition presented a bit of improvement;whereas the binders with 1%and 3%SCGs exhibited remarkably enhanced low-temperature stability.However,notable weaknesses of practical performance were shown for the binder with excessive content of SCGs,indicating the necessity of proportion selecting before application.