Influences of permeation of vanadium ions through PVDF-g-PSSA membranes on performances of vanadium redox flow batteries

The preparation and physical characterization of a poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid) (PVDF-g-PSSA) membrane prepared by a solution-grafting method were described. These membranes exhibited high conductivity with a value 3.22 x 10(-2) S/cm at 30 degrees C. ICP studies revealed that the PVDF-g-PSSA membrane showed dramatically lower vanadium ion permeability compared to Nafion 117. Trivalent vanadium ions had the highest permeability through all these membranes in contrast to pentavalent vanadium ions with the lowest. The VRB with the low-cost PVDF-g-PSSA membrane exhibited a higher performance than that with Nafion 117 under the same operating conditions, and its energy efficiency reached 75.8% at 30 mA/cm(2). The performance of VRB with the PVDF-g-PSSA membrane can be maintained after more than 200 cycles at a current density of 60 mA/cm(2).     

Surface tension effect on transmembrane channel stability in a model membrane

The effect of surface tension on the lipid bilayer membrane is a question that has drawn considerable research effort. This interest has been driven both by the desire to determine the surface tension effects on the lipid bilayer and from the suggestion that adding finite surface tension to a small membrane system may provide more realistic lipid properties in molecular dynamics simulations. Here, the effect of surface tension on a palmitololelylphosphatidylcholine (POPC) bilayer membrane containing a four-helix transmembrane alamethicin peptide bundle is investigated. Simulations of 10 ns were undertaken for two different ensembles, NPT and NP(z)gammaT with a surface tension, gamma, of 20 mN m(-1) per interface, which is near the pore-forming region. The significance of differences between the tension-free and surface tension simulations was determined using nonparametric statistical analysis on replicate simulations with different initial conditions. The results suggest that, when the membrane is under surface tension, the peptide helical structure is perturbed from that in the tension-free state but that the bundle conformation is more stable than that in the tension-free state, with hydrogen bonding playing an important stabilizing role. Surface tension counteracts the influence of the transmembrane helix bundle on nearby lipid order, making the lipid order more uniform throughout the membrane in the tension state. Conversely, the lipid mobility was less uniform in the tension state, with lipids far from the bundle being significantly more mobile than those near the bundle. One general implication of the results is that surface tension can affect the membrane nonuniformly, in that the properties of lipids near the peptide are different from those further away.     

Boomerang‐Type Substitution Reaction: Reactivity of Fullerene Epoxides and a Halofullerenol

The C_s‐symmetric fullerene chlorohydrin C₆₀(Cl)(OH)(OOtBu)₄ reacts with 4‐dimethylaminopyridine (DMAP) and 1,4‐diazabicyclo[2.2.2]octane (DABCO) to yield two isomers with the formula C₆₀(O)(OOtBu)₄ in good yields. These isomers differ with respect to the location of the epoxy functionality. The one from DMAP is C_s symmetric, whereas that from DABCO is C₁ symmetric with the epoxy group on the central pentagon. Two different mechanisms are proposed to explain the chemoselectivity of these reactions. The reaction with DMAP involves single‐electron transfer as the key step; DMAP acts as the electron donor. A combination of an oxygen‐atom shift and S_N2′′ processes (boomerang substitution) are responsible for the formation of isomer with DACBO. Various related reactions support the proposed mechanisms. The structures of new fullerene derivatives were determined by spectroscopy, single‐crystal X‐ray analysis, and chemical correlation experiments.     

Synthesis,structures and properties of two novel copper(II) complexes with hydrogen bonding supramolecular networks

Two novel complexes, [Cu(HL)₂(H₂O)]₂(OH)₂(ClO₄)₂·1.5H₂O (1) and [Cu(HL)₂]Cl₂·4H₂O (2), have been prepared by reacting copper salts with the 4-amino-3-ethyl-1,2,4-triazole-5-thione (HL) ligand in neutral solution and in HCl (6 mol L^–1) medium, respectively. They were characterized by FT-IR and u.v.–vis. spectra, and the structures were determined by single crystal X-ray diffraction techniques. In both complexes, the triazole ligand chelated the metal ions through the amine and thione substituents on the five-membered ring. Complex (1) has a square-pyramidal copper(II) ion coordinated by two triazole ligands and one water molecule. Unlike (1), the Cu²⁺ ion in (2) displays its characteristic Jahn–Teller distortion with the distance of the Cl^– anions to metal ion further away than that of the triazole ligands. The most intriguing structural features of the title complexes are that the HL ligands chelate copper(II) ions through the N(1) and S(1) atoms, in a cis mode in (1) and a trans mode in (2). In both cases, self-assembled crystals, by supramolecular contacts simultaneously, form two multi-dimensional frameworks.     

Effects of Self—coiling of Organic Molecules on Intramolecular Exciplex Formation and Fluoresscence Quenching in DX—H2O Solvent System

Effects of self-coiling of organic molecules on intramolecular exciplex formation of compound I,in which the carbazole chromophore and terephthalic acid methylester acceptor group are linked by one (CH2)10 chain,and the decrease of the fluorescence intensities of compounds Ⅱ，Ⅲ，and Ⅳ,in which the carbazole chromophore and 3,5-dinitrobenzoate are connected by one aliphatic chain of (CH2)10 (Ⅱ），（CH2）12（Ⅲ）,or (CH2)4(Ⅳ）,have been studied in the dioxane (DX)-H2O binary system.The results show that self-coiling of organic molecules in DX-H2O facilitates intramolecular exciplex formation of I and induces the decrease of fluorescence intensities of Ⅱ,bacause of the proximity effect brought about by selfcoiling of organic molecules under hydrophobic-lipophilic interaction(HLI) between the excited carbazole chromophore and the acceptor.Since the similar effects are observed even when the concentration of the probes are less than their CAgCs(critical aggregate concentrations )in the DX-H2O mixture with the same φ values,formation of the intermolecular exciplex has been excluded.The effects are found to be strongly depended on φ values,indication that they are mainly driven by HLI.The properties of the acceptors can also affect the intramolecular exciplex formation.With terephthalic acid methylester moiety as the acceptor,the carbazole chromophore exhibits the fluorescence spectra of the exciplex,while with 3,5-dinitrobenzoate moiety as the acceptor,only the fluorescence spectra of excited carbazolyl chromophore are observed.     

Synthesis and Characterization of Ag2S Nanocrystals in Hyperbranched Polyurethane at Room Temperature

Ag₂S nanoparticles in hyperbranched polyurethane matrix were prepared through the in situ reaction with thioacetamide as the sulfur source at room temperature. Transmission electron microscopic analysis revealed a uniform spherical shape for Ag₂S nanoparticles, with an average size of about 4-10 nm and a narrow size distribution. X-ray powder diffraction and UV-vis spectroscopy were also used to characterize the obtained nanoparticles     

三烃基锡肟类化合物的合成及生物活性

共合成了１３个未见文献报道的三烃基锡肟衍生物，测定了它们的＾１ｈ，（＾１３Ｃ，＾１１９Ｓｎ）ＮＭＲ，ＩＲ和ＭＳ。结果表明此类化合物为四配位锡单体结构，生物活性测定结果表明部分化合物同时兼有杀菌、杀螨、除草多种活性。     

Optical properties of human prostate at 732 nm measured in mediated photodynamic therapy

Characterization of the tissue light penetration in prostate photodynamic therapy (PDT) is important to plan the arrangement and weighting of light sources so that sufficient light fluence is delivered to the treatment volume. The optical properties (absorption [mu(a)], transport scattering [mu(s)'] and effective attenuation [mu(eff)] coefficients) of 13 patients with locally recurrent prostate cancer were measured in situ using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu)-mediated PDT in four quadrants. Optical properties were derived by applying the diffusion theory to the fluence rates measured at several distances (0.5-5 cm) from a point source. mu(a) and mu(s)' varied between 0.07 and 1.62 cm(-1) (mean 0.37 +/- 0.24 cm(-1)) and 1.1 and 44 cm(-1) (mean 14 +/- 11 cm(-1)), respectively. mu(a) was proportional to the concentration of MLu measured by an ex vivo fluorescence assay. We have observed, on average, a reduction of the MLu concentration after PDT, presumably due to the PDT consumption of MLu. mu(eff) varied between 0.91 and 6.7 cm(-1) (mean 2.9 +/- 0.7 cm(-1)), corresponding to an optical penetration depth (delta = 1/micro(eff)) of 0.1-1.1 cm (mean 0.4 +/- 0.1 cm). The mean penetration depth at 732 nm in human prostate is at least two times smaller than that found in normal canine prostates, which can be explained by a four times increase of the mean value of mu(s)' in human prostates. The mean light fluence rate per unit source strength at 0.5 cm from a point source was 1.5 +/- 1.1 cm(-2), excluding situations when bleeding occurs. The total number of measurements was N = 121 for all mean quantities listed above. This study showed significant inter- and intraprostatic differences in the optical properties, suggesting that a real-time dosimetry measurement and feedback system for monitoring light fluences during treatment should be considered for future PDT studies.     

Application of magdala red as a fluorescence probe in the determination of nucleic acids

A fluorescence quenching method was developed for the rapid determination of DNA and RNA using magdala red as fluorescence probe. In weakly acidic medium, the fluorescence of magdala red (lambdaex/lambdaem = 540/555 nm) can be largely quenched by DNA or RNA. The calibration graphs are linear over the range 0.01-1.2 microg/mL for both calf thymus DNA (CT DNA) and salmon DNA (SM DNA), and 0.015-1.0 microg/mL for yeast RNA, respectively. The corresponding detection limits are 6.0 ng/mL for CT DNA, 7.0 ng/mL for SM DNA and 15.0 ng/mL for yeast RNA, respectively. CT DNA could be determined in the presence of 20% (w/w) yeast RNA, and the relative standard deviation of six replicate measurements is 3.18% for 400 ng/mL of CT DNA. Interference from coexisting substances in the determination of DNA was also examined. Real samples were determined with satisfactory results.     

微量元素硒在肿瘤防治中的作用及应用前景

硒作为人类必需的必需元素，人们对其重要性的认识日益提高，已经将将缺硒与增加癌症风险联系在一起。本文就硒在肿瘤防治中的可能作用及其应用进展，从流行病学调查、实验室和人群试验三个方面作一综述。尽管对其作用仍然存在不同观点的争论，但多数报道提示硒在抗癌领域有良好的应用前景。