Mechanical properties of BPDA-ODA polyimide fibers

An aromatic polyimide was synthesized via a one-step polycondensation reaction between biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) in p-chlorophenol. The polyimide (BPDA-ODA) solution dopes were spun into fibers by means of dry-jet wet spinning. The as-spun fibers were drawn and treated in heating tubes for improving the mechanical properties. The thermal treatment on the fibers resulted in a relatively high tensile strength and modulus. Thermal mechanical analysis (TMA) was employed to study the linear coefficient of thermal expansion (CTE). Thermal gravimetry analysis (TGA) spectra showed that the BPDA-ODA fibers possessed an excellent property of thermo-oxidative degradation resistance. The sonic modulus E_s of the polyimide fibers was measured.     

Solution-phase synthesis and electrochemical hydrogen storage of ultra-long single-crystal selenium submicrotubes

Ultra-long single-crystalline trigonal selenium submicrotubes were synthesized using a facile one-step solution-phase approach with the assistance of nonionic surfactant Polyoxyethylene(20)sorbitan monolaurate (Tween-20), which turned out to be significant for the formation of ultra-long Se submicrotubes. XRD, Raman, SEM, and TEM were adopted to characterize the morphology, structure and phase composition of the as-prepared Se products. It was found that the length of the obtained Se submicrotubes was over 100 microm. By variation of the experimental parameters, the t-Se spheres, nanowires, and broken microtubes can be prepared. The possible growth mechanism of the ultra-long selenium submicrotubes was explained. In addition, we have also demonstrated that the synthesized ultra-long t-Se submicrotubes using the Tween-20-assisted approach can electrochemically charge and discharge with the high capacity of 265 mAh/g (corresponding to 0.97 wt % hydrogen in SWNTs) under normal atmosphere at room temperature. Cyclic voltammetry was adopted to investigate the adsorption-oxidation behavior of ultra-long selenium submicrotubes. It was observed that the morphology of the synthesized selenium products had a remarkable influence on their capacity of electrochemical hydrogen storage. These differences in hydrogen storage capacity are likely due to the size and density of tubes as well as the microcosmic morphology of different Se samples. The as-obtained ultra-long Se submicrotubes are expected to find wide applications in hydrogen storage, high-energy batteries, and optoelectronic, biologic, and catalytic fields as well as in the studies of structure-property relationships. This simple Tween-assisted approach might be extended to the preparations of one-dimensional nanostructures of tellurium and other anisotropic materials.     

Preparation and characterization of molecularly imprinted electropolymerized carbon electrodes

Molecularly imprinted polymers (MIPs) selective for fluorescein, rhodamine or 2,4-dichlorophenoxyacetic acid (2,4-D) were electropolymerized onto graphite electrodes using an aqueous solution equimolar in resorsinol/ortho-phenylenediamine and in the presence of the template molecule. For the dyes, the MIP-coated electrodes showed higher affinity for their template molecule than for a non-template dye. The 2,4-D-MIP-coated electrode showed a concentration dependent response for 2,4-D as compared to the polymer-coated electrode prepared in the absence of template molecule.     

Synthesis of a highly reactive heterocyclic reactant and its unusual photochemistry; mechanistic and exploratory organic photochemistry

[reaction: see text] A unique new set of reactions has been observed in heterocyclic photochemistry. 2-Methyl-4,4-diphenyl-3,4-dihydropyrimidin-1(2H)-one has been synthesized and its photochemistry investigated. This compound has been found to lead to a rearranged, dimeric product arising from a unique bond-scission process.     

Potentiodynamic deposition of Prussian blue from a solution containing single component of ferricyanide and its mechanism investigation

Potentiodynamic techniques were used for the direct electrodeposition of Prussian blue nano-clusters from an acidic solution of ferricyanide. Electrochemical, EQCM, IR, AFM, and UV/vis measurements were carried out to characterize deposited nano-sized Prussian blue and to explore the formation mechanism. Results showed that ferricyanide could partially dissociate to free ferric and cyanide ions. The driving force of this dissociation is the formation of PB and the evolution of HCN. The optimal potential window for the potentiodynamic formation of PB from an acidic solution (pH 1.6) is between –0.5 V and 0.4 V. In addition, the influence of surface adsorption of CN^- ions on the formation of PB was discussed.Dedicated to Professor W. Vielstich on the occasion of his 80th birthday.     

Synthesis of tetrahydropyrido[2,3-b]pyrazine scaffolds from 2,3,5,6-tetrafluoropyridine derivatives

Reactions between N,N′-dimethylethylene diamine and a range of 2,3,5,6-tetrafluoropyridine derivatives provided ready access to the corresponding tetrahydropyrido[2,3-b]pyrazine systems if the substituent located at the 4-position of the pyridine ring was either hydrogen or an electron withdrawing substituent. In contrast, the presence of electron donating substituents at the 4-position made the formation of ring-fused products much more difficult. The two-step sequential nucleophilic substitution procedures from pentafluoropyridine gave convenient and adaptable methodology for the synthesis of polyfunctional tetrahydropyrido[2,3-b]pyrazine scaffolds of interest to the life science discovery arenas.     

茶叶中三氯螨杀醇残留量的快速HPLC测定法

用微量化技术处理茶叶样品，样品经石油醚提取、浓硫酸磺化后，用反相液相色谱分离、测定样品处理液中的三氯杀螨醇残留量，２３４ｎｍ检测，外标法定量。测定低限为０．５ｍｇ／ｋｇ，回收率为９１．５％～９９．３％，变异系数为１．５３％～６．９２％之间。     

甲氧羰基亚甲基三苯基胂与邻羟基芳醛,酮的反应-5,6-苯并-2-吡喃酮的合成

本文报道一种合成烃基取代5,6-苯并-2-吡喃酮的方法。甲氧羰基亚甲基三苯基胂与烃基取代的邻羟基芳醛、酮反应,首先生成α,β-不饱和酸酯,继而发生分子内环化,生成烃基取代的5,6-苯并-2-吡喃酮。     

In vivo optical analysis of quantitative changes in collagen and elastin during arterial remodeling

Altered collagen and elastin content correlates closely with remodeling of the arterial wall after injury. Optical analytical approaches have been shown to detect qualitative changes in plaque composition, but the capacity for detection of quantitative changes in arterial collagen and elastin content in vivo is not known. We have assessed fluorescence spectroscopy for detection of quantitative changes in arterial composition in situ, in rabbit models of angioplasty and stent implant. Fluorescence emission intensity (FEI) recorded at sites remote from the primary implant site was correlated with immunohistochemical (IH) analysis and extracted elastin and collagen. FEI was significantly decreased (P<0.05) after treatment with anti-inflammatory agents, and plaque area decreased on comparison with saline-treated rabbits after stent implant or angioplasty (Por=0.961) analysis were detected by multiple regression (MR) analysis. Good correlations also were found for FEI with elastin and collagen measured by high-performance liquid chromatography; MR analysis provided highly predictive values for collagen and elastin (R2>or=0.994). Fluorescence spectroscopic analysis detects quantitative compositional changes in arterial connective tissue in vivo, demonstrating changes at sites remote from primary angioplasty and stent implant sites.