Monotone versions of countable paracompactness

One possible natural monotone version of countable paracompactness, MCP, turns out to have some interesting properties. We investigate various other possible monotone versions of countable paracompactness and how they are related.     

Volatile phase profiling of mainstream smoke by glass capillary gas-chromatographic techniques

A heated injection system for a microprocessor-controlled GC has been developed for the (GC)² analysis of the volatile phase of whole smoke of a cigarette. Effects of injection port temperature and the presence of a Cambridge filter pad are demonstrated. Chromatograms are shown for smoke samples with and without a Cambridge Filter with the sample valve oven at 25°, 165° and 205°C. The use of a flame ionization and a nitrogen-phosphorous detector is illustrated.     

Spectrophotometric determination of palladium(II) with 2-diethylaminoethanethiol hydrochloride and the simultaneous determination of rhodium and palladium

2-Diethylaminoethanethiol hydrochloride is proposed for spectrophotometric determination of palladium(II). The sensitivity of the reaction is 0.0085 smg/cm² and the yellow colored complex shows absorption maxima at 258 mμ and 303 mμ. Color development is slow in the cold but complete after heating for 10–15 min. The optimum pH range is 3.5 to 5.5 and the system adheres to Beer's law between 0.2 and 16.8 p.p.m. of palladium. The average and maximum relative standard deviations were 0.60% and 1.40% respectively. Interferences due to other platinum metals were studied and a procedure is suggested for the simultaneous determination of rhodium and palladium.     

基于时频分布的盲信号分离方法研究长骨中的多模式导波信号

由于超声导波对长骨皮质骨的材料特性及厚度变化非常敏感,因此用导波评价长骨状况的研究已成为近年来的一个研究热点。在接收到的导波中,往往多种模式混叠在一起,使得进一步求取每种导波模式的群速度等与骨质状况密切相关的参数时遇到困难。本文采用基于时频分布的盲信号分离(TFBSS)方法对长骨中混叠的多模式进行分离,然后对分离后的单一导波模式求取群速度。研究结果表明TFBSS方法能够准确的分离出混叠的多模式导波,且实验测量的群速度与其理论值吻合。利用导波的群速度就可以得到长骨皮质骨的厚度,这对诊断其骨质状况具有重要意义。     

膜流动电位测试中Ag-AgCl电极的制备及稳定性研究

膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。     

Monopolar surfaces

Following the development of a methodology for determining the apolar components as well as the electron donor and the electron acceptor parameters of the surface tension of polar surfaces, surfaces of a number of quite common materials were found to manifest virtually only electron donor properties and no, or hardly, any electron acceptor properties. Such materials may be called monopolar; they can strongly interact with bipolar materials (e.g., with polar liquids such as water); but one single polar parameter of a monopolar material cannot contribute to its energy of cohesion. Monopolar materials manifesting only electron acceptor properties also may exist, but they do not appear to occur in as great an abundance. Among the electron donor monopolar materials are: polymethylmethacrylate, polyvinylalcohol, polyethyleneglycol, proteins, many polysaccharides, phospholipids, nonionic surfactants, cellulose esters, etc. Strongly monopolar materials of the same sign repel each other when immersed or dissolved in water or other polar liquids. The interfacial tension between strongly monopolar surfaces and water has a negative value. This leads to a tendency for water to penetrate between facing surfaces of a monopolar substance and hence, to repulsion between the molecules or particles of such a monopolar material, when immersed in water, and thus to pronounced solubility or dispersibility. Monopolar repulsion energies can far outweigh Lifshitz-van der Waals attractions as well as electrostatic and "steric" repulsions. In aqueous systems the commonly observed stabilization effects, which usually are ascribed to "steric" stabilization, may in many instances be attributed to monopolar repulsion between nonionic stabilizing molecules. The repulsion between monopolar molecules of the same sign can also lead to phase separation in aqueous solutions (or suspensions), where not only two, but multiple phases are possible. Negative interfacial tensions between monopolar surfactants and the brine phase can be the driving force for the formation of microemulsions; such negative interfacial tensions ultimately decay and stabilize at a value very close to zero. Strongly monopolar macromolecules or particles surrounded by oriented water molecules of hydration can still repel each other, albeit to an attenuated degree. This repulsion was earlier perceived as caused by "hydration pressure". A few of the relevant colloid and surface phenomena are reviewed and re-examined in the light of the influence of surface monopolarity on these phenomena.     

镁掺杂氧化铈整体式催化剂催化CO2和CH3OH直接合成碳酸二甲酯

采用共沉淀法成功地合成了不同Mg掺杂量的Ce_1-xMg_xO₂(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO₂晶格中Mg的含量,可以调控所制备的Ce_1-xMg_xO₂催化材料的粒径、比表面积、表面缺陷等。其中Ce_0.90Mg_0.10O₂展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g^-1)以及最高的表面氧含量(31.98%)。将Ce_1-xMg_xO₂催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO₂和CH₃OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce_0.90Mg_0.10O₂整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO₂和其余的Ce_1-xMg_xO₂(x=0.05、0.15、0.20)催化材料。