Direct inhibition of phospholipid scrambling activity in erythrocytes by potassium ions

The exposure of phosphatidylserine (PS) at the cell surface plays a critical role in blood coagulation and serves as a macrophage recognition moiety for the engulfment of apoptotic cells. Previous observations have shown that a high extracellular [K⁺] and selective K⁺ channel blockers inhibit PS exposure in platelets and erythrocytes. Here we show that the rate of PS exposure in erythrocytes decreases by ~50% when the intracellular [K⁺] increases from 0 to physiological concentrations. Using resealed erythrocyte membranes, we further show that lipid scrambling is inducible by raising the intracellular [Ca²⁺] and that K⁺ ions have a direct inhibitory effect on this process. Lipid scrambling in resealed ghosts occurs in the absence of cell shrinkage and microvesicle formation, processes that are generally attributed to Ca²⁺-induced lipid scrambling in intact erythrocytes. Thus, opening of Ca²⁺-sensitive K⁺ channels causes loss of intracellular K⁺ that results in reduced intrinsic inhibitory effect of these ions on scramblase activity. Received 11 September 2008; received after revision 17 October 2008; accepted 27 October 2008     

处理频率对TC4钛合金微弧氧化膜特性的影响

利用自制多功能微弧氧化膜的制备系统对TC4钛合金进行表面处理, 通过扫描电镜(SEM)和X射线衍射仪(XRD)研究脉冲频率(f)对氧化膜生长特性、 表面形貌和相组成的影响. 结果表明, 当f≤2 000 Hz时, 成膜速率随f增加迅速减小; 当2 000 Hz＜f＜4 000 Hz时, 成膜速率随f增加而减小的趋势变缓; 当f≥4 000 Hz时, 成膜速率不随f发生变化. 该氧化膜表面多孔, 随f的增加, 膜表面微孔尺寸逐渐减少, 微孔密度逐渐增加. 膜层主要由锐钛矿和金红石相TiO2及少量不饱和氧化物TiO2-x（0.02＜x＜0.07）相组成, 其中锐钛矿和金红石相TiO₂的相对含量随f的变化不明显, 而TiO_2-x的相对含量当f≤2 000 Hz时较高, 当f＞2 000 Hz时, TiO_2-x的相含量明显减少.      

动车组车体底边梁用6005A铝型材检验分析

6005A铝合金大截面复杂制品作为轨道车体的边梁或枕梁,对轨道车体的整体起连接和承重作用,是动车组车体的关键部位。采用电子万能试验机、铝型材压力试验机、光学显微镜等研究了速度达400 km·h^-1动车组车体底边梁用6005A铝型材的强度、显微组织和断口形貌等,旨在为动车组用铝挤压型材产品检验和工艺制度制定提供技术支持与指导。     

两种不同形貌FePO_4的制备及其正电极材料LiFePO_4的电化学性能

分别以Fe(NO_3)_3·9H_2O和FeSO_4·7H_2O为铁源,采用均相沉淀法和氧化-液相沉淀法制备了两种不同形貌的FePO_4粉体,再以FePO_4为前驱体,与LiOH·H_2O、蔗糖混合,采用碳热还原法合成了LiFePO_4正电极材料.用XRD和SEM对所制备的FePO_4粉体进行结构和表面形貌表征,测试了LiFePO_4样品的充放电性能.XRD和SEM测定结果表明,采用均相沉淀法制备的FePO_4为六方晶系纯相,颗粒形貌为圆片状,颗粒大小均匀;而液相氧化法制备的FePO_4也为六方晶系纯相,但颗粒形貌无规则.由圆片状FePO_4和无规则FePO_4所合成的LiFePO_4的颗粒形貌与其前驱体相同.充放电测试表明在0.5C下圆片状LiFePO_4的首次放电比容量为140 mAh/g,无规则LiFePO_4的首次放电比容量为89 mAh/g.经过50次循环后,前者的放电比容量仅下降1.43%,后者基本不变.     

浅谈城市供水系统的水质安全问题

从水质安全的角度出发,论述了供水系统中出现红虫、管道腐蚀、生物不稳定问题的原因,提出了防治措施以改善城市供水质量。     

系数优化在改善时间步进算法稳定性中的应用

隐式时间步进算法在求解二维物体的散射时,随着时间的推移,也会出现后时不稳定性的问题.文章在先五步后三步平均公式的基础上利用误差公式对系数进行筛选,改善了原公式在隐式时间步进算法中计算二维物体时产生的后时震荡情况；采用基于时域电场积分方程的隐式时间步进算法,分别计算了TM高斯脉冲入射到无限长导体圆柱和导体方柱时的导体表面...     

Effect of Si on austenite stabilization,martensite morphology,and magnetic properties in Fe-26%Ni-x%Si alloys

The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si (x=3.5, 5, and 6) alloys have been studied by means of transmission electron microscopy (TEM) and M?ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mssbauer spectroscopy. The M?ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.     

基于Soft多结构元素形态学的TM图像边缘检测

基于传统的数学形态学边缘检测算法,改进结构元素,提出Soft多结构元素算子。针对TM图像中存在噪声多和边缘形态多样性的特点,构建多结构元素,并结合Soft形态学方法,对TM图像进行形态学的腐蚀和膨胀,实现遥感图像的边缘检测。     

圆环圆拱承受均匀径向荷载时弹性失稳的加权余量解

本文用加权余量法推导出圆环和圆拱在均匀径向荷载作用下,发生弹性失稳时临界荷载q_(cr)的计算公式.