Collisions and turbulence in optical rogue wave formation

We discuss optical rogue wave generation in terms of collisions and turbulence processes. Simulations of picosecond pulse propagation in optical fibres show rogue soliton generation from either third-order dispersion or Raman scattering independently. Simulations of rogue soliton emergence with dispersive perturbation in the long-distance limit are also presented.     

快速简便测定有机电致发光材料HOMO能级的电化学方法

采用多层结构有利于提高有机电致发光 (ｏｒ ｇａｎｉｃｅｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｃｅ ,ＯＥＬ)器件的效率和寿命[1 3] 。为了有依据地选择多层有机材料 ,就要准确表征其能带。表征有机材料能带的一些方法有的因为得不到理想结果、有的因为仪器昂贵未被普遍采用[4] 。而用电化学方法 (如循环伏安法 )表征有机材料的能带所用仪器设备简单 ,操作方便 ,被广泛使用。常用ＯＥＬ器件中所选用有机物的氧化、还原电位较大 ,体系中的少量杂质 (如水、氧气等 )的电化学活性就会表现出来。因此 ,须保证体系在测定时水、氧气的含量足够低。…     

NH4H2PO4掺杂改性纳米TiO2的光催化性能

利用钛酸丁酯水解浸渍方法制备了几种不同浓度NH4H2PO4掺杂改性的TiO2纳米复合粉体材料并作了XRD、BET等表征。以正己烷的气相光催化氧化降解为探针反应研究了NH4H2PO4掺杂TiO2催化剂的光催化活性。并和未掺杂TiO2及商品TiO2 Degussa P-25作了比较．结果表明。掺杂NH4H2PO4能够显著地细化TiO2的晶粒度。增大TiO2的比表面积。同时，适量掺杂NH4H2PO4对TiO2的光催化活性也有较大的促进作用。     

Silvestrol and episilvestrol, potential anticancer rocaglate derivatives from Aglaia silvestris

Two cytotoxic rocaglate derivatives possessing an unusual dioxanyloxy unit, silvestrol (1) and episilvestrol (2), were isolated from the fruits and twigs of Aglaia silvestris by bioassay-guided fractionation monitored with a human oral epidermoid carcinoma (KB) cell line. Additionally, two new baccharane-type triterpenoids, 17,24-epoxy-25-hydroxybaccharan-3-one (3) and 17,24-epoxy-25-hydroxy-3-oxobaccharan-21-oic acid (4), as well as eleven known compounds, 1beta,6alpha-dihydroxy-4(15)-eudesmene (5), ferulic acid (6), grasshopper ketone (7), apigenin, cabraleone, chrysoeriol, 1beta,4beta-dihydroxy-6alpha,15alpha-epoxyeudesmane, 4-hydroxy-3-methoxyacetophenone, 4-hydroxyphenethyl alcohol, ocotillone, and beta-sitosterol 3-O-beta-D-glucopyranoside, were also isolated and characterized. The structures of compounds 1-4 were elucidated by spectroscopic studies and by chemical transformation. The absolute stereochemistry of silvestrol (1) was established by a X-ray diffraction study of its di-p-bromobenzoate derivative, and the structure of 3 was also confirmed by single-crystal X-ray diffraction. The isolates and chemical transformation products were evaluated for cytotoxicity against several human cancer cell lines, and silvestrol (1) and episilvestrol (2) exhibited potent in vitro cytotoxic activity. Silvestrol (1) was further evaluated in vivo in the hollow fiber test and in the murine P-388 leukemia model.     

Iron-assisted nucleophilic aromatic substitution on solid phase

Iron-assisted S(N)Ar reactions were performed for the first time on solid phase, and a library of 36 unsymmetrically substituted phenylpiperazines and phenyl-1,4-diazepanes was synthesized with this novel strategy. The scope of iron-assisted S(N)Ar reactions on solid phase was investigated, and reactions of representative nucleophiles from groups VI (O, S, and Se) and V (N and P) of the periodic table were examined. Decomplexation of resin-bound iron complexes was achieved with 1,10-phenanthroline under irradiation, thereby overcoming the notorious disadvantages of decomplexation observed in solution-phase chemistry.     

Preparation and properties of polyamides containing p-terphenyl units

Novel polyamides that contained p-terphenyl units were prepared with inherent viscosities in the range of 0.4–1.7 dL/g by the polycondensation of 4,4″-dichloroformyl-p-terphenyl with aromatic diamines and 4,4″-diamino-p-terphenyl with aromatic dicarbonyl chlorides. Polyamides composed of only paraoriented phenylene units were insoluble in all solvents and showed a high degree of crystallinity. A series of polyamides that contained p-terphenyl units were more thermostable than corresponding polymers with p-phenylene or biphenylene linkages.     

1-methyl-2-undecyl-4(1H)-quinolone as an irreversible and selective inhibitor of type B monoamine oxidase

The inhibitory compound of monoamine oxidase (MAO) activity was isolated from the CH(2)Cl(2) fraction of the fructus of Evodia rutaecarpa and identified as 1-methyl-2-undecyl-4(1H)-quinolone (1). Compound 1 showed a selective inhibition of type B MAO (MAO-B) activity with the IC(50) value of 15.3 microM using a substrate kynuramine, but did not inhibit type A MAO (MAO-A) activity. The kinetic analysis using Lineweaver-Burk plots indicated that compound 1 competitively inhibited MAO-B activity with the K(i) value of 9.91 microM. The inhibition of MAO-B by compound 1 was found to be irreversible by dialysis of the incubation mixture. These results suggest that compound 1 is a potent irreversible inhibitor of MAO-B, and may regulate catecholamine content in the neurons.     

Temperature-dependent micellar structures in poly(styrene-b-isoprene) diblock copolymer solutions near the critical micelle temperature

The temperature dependence of the micelle structures formed by poly(styrene-b-isoprene) (SI) diblock copolymers in the selective solvents diethyl phthalate (DEP) and tetradecane (C14), which are selective for the PS and PI blocks, respectively, have been investigated by small angle neutron scattering (SANS). Two nearly symmetric SI diblock copolymers, one with a perdeuterated PS block and the other with a perdeuterated PI block, were examined in both DEP and C14. The SANS scattering length density of the solvent was matched closely to either the core or the corona block. The resulting core and corona contrast data were fitted with a detailed model developed by Pedersen and co-workers. The fits provide quantitative information on micellar characteristics such as aggregation number, core size, overall size, solvent fraction in the core, and corona thickness. As temperature increases, the solvent selectivity decreases, leading to substantial solvent swelling of the core and a decrease in the aggregation number and core size. Both core and corona chains are able to relax their conformations near the critical micelle temperature due to a decrease in the interfacial tension, even though the corona chains are always under good solvent conditions.     

Enhanced luminescence of SiO2:Eu3+ by energy transfer from ZnO nanoparticles

ZnO nanoparticles embedded into SiO(2) by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5-10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.