微量元素与脑卒中(2)

脑卒中是目前中国最重要的公共卫生问题,正以其高发病率、高死亡率对我国造成巨大的社会、经济困难。从脑卒中的流行病学特征、脑卒中发病的危险因素、脑卒中患者的微量元素失衡及微量元素检测的临床意义四个方面阐述了微量元素与脑卒中的关系。     

中美高中化学教科书支撑同一知识的实验设计和内容呈现比较——以“影响化学反应速率的因素”为例

以人教版、苏教版、鲁科版高中化学教科书以及美版教科书中支撑"影响化学反应速率的因素"这一知识内容所涉及的实验内容为研究对象，从实验的设计和内容呈现等方面进行系统地比较，结果表明：国内的教科书中设计的实验探究性更强，对于学生能力的培养更加全面，美国教科书中设计的实验更注重吸引学生的注意力，激发学生的学习兴趣。最后综合分析了不同版本教科书的优缺点，并对实际教学提出一些建议。     

Crystal planes and reciprocal space in Clifford geometric algebra

This paper discusses the geometry of kD crystal cells given by (k+ 1) points in a projective space ?^{n+ 1}. We show how the concepts of barycentric and fractional (crystallographic) coordinates, reciprocal vectors and dual representation are related (and geometrically interpreted) in the projective geometric algebra Cl(?^{n+ 1}) (see (Die Ausdehnungslehre von 1844 und die Geom. Anal. Teubner: Leipzig, 1894)) and in the conformal algebra Cl(?^{n+ 1, 1}). The crystallographic notions of d‐spacing, phase angle, structure factors, conditions for Bragg reflections, and the interfacial angles of crystal planes are obtained in the same context. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetics of the radical scavenging activity of β-carotene-related compounds

To clarify the non-enzymatic radical-scavenging activity of β-carotene-related compounds and other polyenes, we used differential scanning calorimetry to study the kinetics of radical polymerization of methyl methacrylate (MMA) by 2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) in the absence or presence of polyenes under nearly anaerobic conditions at 70°C, and analyzed the results with an SAR approach. The polyenes studied were all-trans retinol, retinol palmitate, calciferol, β-carotene and lycopene. Polyenes produced a small induction period. The stoichiometric factor (n) (i.e. the number of radicals trapped by each inhibitor molecule) of polyenes was close to 0. Tetraterpenes (β-carotene, lycopene) suppressed significantly more of the initial rate of polymerization (R ^inh) than did diterpenes (retinol, retinol palmitate). The inhibition rate constants (k ^inh) for the reaction of β-carotene with AIBN-or BPO-derived radicals were determined to be 1.2–1.6?×?10⁵ l?/?mol?s, similar to published values. A linear relationship between k ^inh and the kinetic chain length (KCL) for polyenes was observed; as k ^inh increased, KCL decreased. KCL also decreased significantly as the number of conjugated double bonds in the polyenes increased. Polyenes, particularly β-carotene and lycopene, acted as interceptors of growing poly-MMA radicals.     

加热方式及原料配比对介孔CeO2结构及其光催化性能的影响

以P123（聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物）为模板剂,Ce（NO₃）₃为反应原料,通过考察加热方式、加热温度、原料配比等因素,合成了结构性能较好、表面羟基含量较高的介孔CeO₂材料。利用XRD,N₂吸附-脱附,TEM,Raman,FT-IR等技术对合成样品的结构性能进行了表征,结果表明,当P123与Ce（NO₃）₃物质的量之比为1：10,在110℃水热下合成的CeO₂结构性能最好。以酸性橙7（AO7）为探针分子,对合成介孔CeO₂的光催化性能进行评价。光催化结果证明,由于表面羟基含量较高、介孔及氧缺位的形成,所合成结构性能较好的CeO₂,利用可见光可彻底催化降解溶液中的AO7。     

Mechanism and Influencing Factors of Wettability Alteration of Water-Wet Sandstone Surface by CTAB

Different experimental methods including ellipsometry, zeta potential measurements, imbibition studies, and contact angle measurements were used to study the mechanism and influencing factors of wettability alteration of water-wet sandstone surface caused by CTAB (hexadecyl trimethyl ammonium bromide). Results show that when the concentration of CTAB reaches a certain level (below CMC), due to the electrostatic attraction between the positively charged head groups of CTAB and the negatively charged sandstone surface, the monolayer of CTAB is formed and hydrophobic chains of CTAB molecules are toward the aqueous phase, making the solid surface oil-wet. When the concentration of CTAB continues to increase (above CMC), due to the hydrophobic interaction, the compact bilayer of CTAB is formed and hydrophilic head groups of CTAB molecules are toward the aqueous phase, rendering the solid surface water-wet. The contact angles between the oil–water interface and the surface treated with CTAB increase with the increase of the concentration of NaCl and CaCl_2. Compared to NaCl, the inorganic salt CaCl₂ has a greater impact on the contact angle. In addition, the contact angles increase with the increase of temperature and decrease with the increase of pH value of the aqueous solution.     

Handling of Environmental and Biological Samples via Pre-Column Technologies

Abstract

Sample handling is still a weak point in chromatography and in analytical chemisty in general. One consideration is the automation potential of new procedures. Solid-liquid extraction techniques in combination with pre-column technology are particularly promising in this regards. The construction and geometry of pre-columns both for conventional and narrow-bore HPLC are of major importance, since band broadening should be kept at a minimum for an optimal functioning of the analytical system. The various operations that can be carried out with such a pre-column are trace-enrichment, clean-up of the sample which depends on the type of adsorbents used in the precolumn, i.e., polar or apolar materials, ion exchangers or metal covered surfaces, etc., protection of the analytical column, field sampling and storage of samples and as a substrate for on-column chemical derivatizations. These various operations are demonstrated with practical examples from the fields of environmental and biological analysis. The selectivity can be further enhanced by coupling precolumn technology with selective detection modes such as diode array UV, electrochemical or fluorescence detection. This enables the construction of optimal and integrated analysis sytems which are fully automated and microprocessor controlled. They can also be made compatible with miniaturized LC-technology.