荧光法测定SD大白鼠不同脑区的单胺类神经递质

以荧光光谱法定量地研究了不同浓度的司考林作用下,鼠脑组织中去甲肾上腺素、多巴胺和5-羟色胺的定量变化,从而表达了中枢神经递质的变化规律.     

DNA-modified electrodes (VII)

Two kinds of DNA-modified electrodes were prepared by covalent and adsorptive immobilization of DNA onto self-assembled monolayers of 2, 2’-dithiodiethanol on gold electrodes and characterized by cyclic voltammetry, X-ray photoelectron spectroscopy and scanning tunneling microscopy. The results suggest that the methods are satisfactory for the immobilization of DNA on electrodes. Project supported by the National Natural Science Foundation of China (Grant Nos. 39370213; 39770220; 29773034), State Key Laboratory for Physical Chemistry of Solid Surfaces (Xiamen University), and Natural Science Foundation of Hubei Province (Grant NO. 96J037).     

Electrochemical performance of a nonaqueous rechargeable lithium-air battery

Nonaqueous rechargeable lithium-air battery has so high specific capacity and specific energy that it is being widely researched by academia, corporation, and different research institutes. When used in dried air and absorbing oxygen form the air, this battery is called lithium-air battery, and its specific capacity based on cathode active material (oxygen) is infinite. However, its cycle performance is very limited as reported by the state-of-the-art researches. This cycle problem is mainly caused by instability of electrolyte. Based on electroanalysis of materials’ electrochemical property, a stable electrolyte solvent (sulfolane) and a lithium salt LiBF₄ are selected as electrolytes in this work. Coupled with other eligible battery materials and careful assembly, the lithium-air battery exhibits favorable cycle performance. Above all, this lithium-air system is evaluated objectively in this paper.     

Oxygen production using La0.6Sr0.4Co0.2Fe0.8O3−α (LSCF) perovskite hollow fibre membrane modules

A phase-inversion/sintering technique has been employed in the production of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−α (LSCF) hollow fibre membranes, a bundle of which has then been placed in a high-temperature furnace for production of high purity oxygen from air at temperatures between 980 °C and 1060 °C. By applying a vacuum in the hollow fibre lumens, a product stream containing oxygen purity of 97.15% has been obtained. The downstream vacuum degree higher than 99 kPa shows negligible effect on the oxygen production rate. Studies on long-term operation suggest that the LSCF hollow fibre membranes are less stable for the oxygen production due to the segregation of the constituent membrane elements and the formation of new phases on the outer membrane surfaces. The effect of the operating cycle on the retrogression of membrane performance is much larger than that of duration used in a single cycle.     

Simultaneous Determination of Main Bioactive Components in Rosa multiflora Thunb. and Their Fragmentation Study by LC–MS

Five naturally bioactive compounds, belonging to the representative flavonoid and pentacyclic triterpenoid types, were separated by liquid chromatography and analyzed on-line with negative ion ESI–MS. Rutin, quercetin, and oleanolic acid in the extracts of Rosa multiflora Thunb. of China were identified by the comparison of their retention times and mass spectrometric data with those of authentic standards, and their contents were 0.22, 3.8, and 45 µg g^?1 of dry weight in rose hips, respectively. Five standards, including rutin, quercetin, kaempferol, lysionotin, and oleanolic acid were investigated by MS³, which facilitate further understanding of their structures.     

Synthesis, crystal structure and optical limiting properties of some W---Se---Cu clusters

A nest-shaped cluster [(C₄H₉)₄N]₂[WOSe₃Cu₃Br_1.67Cl_1.33] (1) and a cage-shaped cluster [(C₄H₉)₄N]₃[WSe₄Cu₃Br₂Cl₂] (2) were synthesized and their structures were determined by single-crystal X-ray diffraction. It was found that cluster 1 showed better optical limiting properties under an 8 ns pulsed laser at 532 nm but poorer optical limiting properties under a 35 ps pulsed laser compared with its analogue [(C₄H₉)₄N]₂[MoOS₃Cu₃BrCl₂]. The influence of the peripheral ligands of the cluster to the optical limiting properties was also discussed.     

Stability and approximations of eigenvalues and eigenfunctions for the Neumann Laplacian, Part 2

We extend the results obtained earlier in a joint paper with R. Banuelos, on the stability and approximations of the second Neumann eigenvalue and its corresponding eigenfunction, to the case when the second Neumann eigenvalue has multiplicity at least 2. We then show that our stability result can be applied to the Koch snowflake and the usual sequence of polygons approximating it from inside.     

A Review of the Integration of Science and Mathematics: Implications for Further Research

Building on the earlier analysis by Berlin (1991) , this paper reviews various studies on integrating mathematics and science in the 1990s and provides some implications for further research. The areas identified for further exploration include comparison of the nature of mathematics and science, epistemological debates in mathematics and in science education, the bases used to emphasize science over mathematics or vice versa, empirical evidence of effectiveness of integration, connections between teacher education programs for integration and teachers' subsequent classroom teaching practices, perceptions of integration on the part of teacher educators, contextual difficulties in implementing integrated approaches and possible solutions, and rationales of integrating mathematics and science through technology. In order to help all students become scientifically literate, which most reform documents call for, more focused attention on integration of curriculum and instruction is necessary.