Chemorheology and Curing Kinetics of a New RTM Benzoxazine Resin

The chemorheology and curing kinetics of a new high performance resin transfer molding benzoxazine resin was investigated. A chemorheological model based on a modified Arrhenius equation that describes the resin viscosity as a function of temperature and time was proposed. The model, which agreed well with the experimental data, can provide theoretical support for the mold-filling stage in the resin transfer molding process. The average activation energies of the polymerization reaction were obtained by means of gelation times at different temperatures based on the Arrhenius equation and from dynamic differential scanning calorimetry (DSC) results based on the Kissinger and Ozawa methods; the values were 96.0,84.0 and 87.8 KJ/mol, respectively. A plot of activation energy vs. conversion in the curing process was obtained using the Flynn-Wall-Ozawa model. The reaction orders were estimated from isothermal DSC based on a modified Kamal kinetics model which can describe both the autocatalytic and diffusion-controlled curing mechanism.     

2-Aryl-3,4-dihydropyrans as building blocks for organic synthesis: ring-opening reactions with nucleophiles

An electrophilic ring-opening reaction of 2-aryl-3,4-dihydropyran with many nucleophiles, such as thiophenols, thiols, benzenesulfinic acid, resorcin, 2-methylfuran, benzamide and allyltrimethylsilane, was developed. In the presence of an appropriate catalyst, a product that contains not only a moiety of the nucleophile but also a fragment of 1,3-dicarbonyl compound was obtained.     

Photocatalytic Inactivation Efficiency of Anatase Nano-TiO2 Sol on the H9N2 Avian Influenza Virus

This study was conducted to investigate efficiency of TiO₂nanomaterial as a novel environment-friendly disinfectant to control avian influenza (AI) by its photochemical sterilization ability. Anatase nano-TiO₂sol, a neutral, viscous aqueous colloid of 1.6% TiO₂, was synthesized from peroxotitanic acid solution according to the Ichinose method. Transmission electron microscope images showed that the TiO₂particles were spindle-shaped with an average size of 50 nm. X-ray diffraction patterns revealed that the crystal phase of TiO₂particles was anatase type with photocatalytic effect. A photocatalytic film of nano-TiO₂sol was tested as a means of inactivating H₉N₂avian influenza virus (AIV). Inactivation capabilities were examined with 365 nm ultraviolet (UV) radiation under black light by adjusting the UV intensity, the UV irradiation time and the quantity of AIV. The titer change of AIV was determined by hemagglutination tests. Cytopathic effect of Madin Darby canine kidney (MDCK) cells was monitored by inverted fluorescence microscope. The results showed that anatase nano-TiO₂sol significantly inactivated AIV under UV irradiation of 365 nm. The inactivation of AIV viruses reached up to 100%. Therefore, anatase nano-TiO₂sol is a potentially environment-friendly antivirus agent to prevent AI.     

Regioselective lipase-catalyzed acylation of 41-desmethoxy-rapamycin without vinyl esters

Selective lipase-catalyzed acylation of 41-desmethoxyrapamycin has been achieved with a quaternary carboxylic acid avoiding the use of vinyl ester activation. Among the acyl donors investigated, the novel butanedione-monooxime and the N-acetylhydroxamate ester proved to be the most efficient donors, comparable in reactivity to the undesired vinyl ester and allowing selective, preparative acylation on gram scale in excellent yields. These new donors are proposed as sustainable and process-friendly alternatives to the widely used vinyl ester substrate activation in lipase-catalyzed acylations of secondary alcohols.     

Structural determination of aspericins A?C,new furan and pyran derivates from the marine‐derived fungus Rhizopus sp. 2‐PDA‐61, by 1D and 2D NMR spectroscopy

Three new furan and pyran derivatives named aspericins A? C (1–3), as well as a known asperic acid (4), have been isolated from the marine‐derived fungus Rhizopus sp. 2‐PDA‐61. The complete ¹H and ¹³C NMR assignments for the new compounds were carried out using ¹H, ¹³C, DEPT, COSY, HMQC, HMBC, and NOESY NMR experiments. Compounds 1–3 were evaluated for their cytotoxic activities on P388, A549, HL‐60, and BEL‐7420 cell lines by the MTT and SRB methods. Copyright © 2009 John Wiley & Sons, Ltd.     

几种超弹性多次碰撞的讨论

本文分析了几种超弹性碰撞多次连续碰撞的过程，以期对照弹性碰撞的进一步理解．实现这些物理过程对物理教学是相当有趣的．     

Femtosecond fabrication of waveguide-like micro-structures in a photorefractive polymer

In this letter, we report on, for the first time, the successful femtosecond micro-fabrication of continuous waveguide-like channels in the photorefractive polymer consisting of the nonlinear chromophore 2,5-dimethyl-4-(p-nitrophenylazo)anisole (DMNPAA), the photosensitive compound 2,4,7-trinitro-9-flourenone (TNF), and the plasticiser N-ethylcarbazole (ECZ) all doped in the polymer matrix poly (methyl methacry-late) (PMMA). These channels are caused by the change in refractive index as a result of the localised heating of the polymer and therefore have an important potential for micro-photonic devices in future.     

Optimum convective heat transfer coefficient for diode-pumped laser slabs

It is important for laser designers to study the characteristics of heat transfer from the laser crystal slab to the coolant in high-power DPSS laser operations. We have simulated and obtained the optimum heat transfer coefficient and coolant flow rate for our cavity design, in which the circulating coolant is maintained at a constant temperature. It has been determined that the coolant temperature and the convective heat transfer coefficient (h) are important parameters in the thermal analysis. The coefficient h is affected by the coolant flow rate, the physical properties of the laser slab and the coolant and the pumping cavity geometry. Using analytical heat transfer equation, for cooling water temperature of 300 K, the optimum flow rate for our cavity geometry is found to be 390 cm³/s, corresponding to h=5 W/cm² K.