PTA压力离心机转子的改造

介绍了PTA压力离心机的主要性能参数、工作原理、分离效果的影响因素。为了增大沉渣在过渡区及脱水区滞留的时问，同时为达到在过渡区及脱水区对沉渣加入纯净水进行再冲洗的目的，对螺旋送料转子、挡液环、进料管进行了改造。改造后，沉渣在脱水区的停留时间由0．44a增至0．72s，2．5～3t／h的冲洗水对脱水区的沉渣进行冲洗效果较好。产品中的杂质质量分数较改造前减少15％，产品优等品率提高到99％。     

Fabrication of nano-porous silicon oxide layers by plasma polymerisation methods

We report on the synthesis of nano-porous silicon oxide (SiO₂) layers by gas phase polymerisation reactions of hexamethy disiloxane and oxygen. The SiO₂ layers are deposited onto one or more layers of poly(methylmethacrylate) (PMMA) particles spin coated onto the substrate surface. Subsequent annealing of the films to high temperature (500 °C) leads to the pyrolysis of the polymeric particles resulting in a 3D nanoporosity in the film. X-ray Photoelectron (XPS) and Fourier Transform Infra Red Spectroscopy (FTIR) show an SiO₂-like surface chemistry and virtually complete removal of the organic components. These materials offer a very high surface area-to-volume ratio suitable for sensing applications.     

Negative effect of [bmim][PF6] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention

BACKGROUND: [bmim][PF₆] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF₆], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF₆] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF₆] on YADH by microemulsifying [bmim][PF₆]. RESULTS: The activity of YADH in the homogeneous solution formed by H₂O, CH₃CH₂OH and [bmim][PF₆] decreased rapidly with the increase of the molar fraction of [bmim][PF₆]. The inhibitory effect of [bmim][PF₆] on YADH was probably caused by the competition of the imidazole group of [bmim][PF₆] with the coenzyme NAD⁺ for the binding sites on YADH. In a water‐in‐[bmim][PF₆] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF₆] and avoided the direct inactivation of [bmim][PF₆] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L^?1 min^?1. CONCLUSION: [bmim][PF₆] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry     

Synthesis and two-photon absorption property of new π-conjugated dendritic fluorophores containing styrylpyridyl moieties

Four new multi-branched two-photon absorption chromophores, namely 1-(4-bromobenzal)-3,5-bis(4-((E)-2-(pyridin-4-yl)vinyl)phenyl)benzene (4), tris(4-((E)-2-(pyridin-4-yl)vinyl)phenyl)-benzene (5), 6-chloro-N²,N⁴-bis(4-((E)-2-(pyridin-4-yl)vinyl)phenyl)-1,3,5-triazine-2,4-diamine (6), tris-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine (7), have been synthesized and characterized. One-photon fluorescence, fluorescent quantum yields and two-photon fluorescence have been investigated. The experimental two-photon absorption cross-sections of 4–7 in DMF are 6, 11, 13 GM (pumped by 740 nm laser) and 19 GM (pumped by 800 nm laser), respectively. The calculated two-photon absorption cross-sections of 4–7 are 5.41, 7.67, 9.57 and 76.14 GM, respectively. The two-photon induced fluorescent peak wavelengths of 4–7 in DMF are 421, 425, 474 and 534 nm pumped by 680, 680, 740 and 800 nm laser, respectively. The results show that molecule 7 is a good two-photon absorption fluorophore possessing long two-photon fluorescent lifetime, good fluorescent quantum yield and large two-photon absorption cross-section. The two-photon absorption peak wavelength of molecule 7 is at 800 nm, which is favourable for initiating two-photon photopolymerization.     

Preparation,morphology, and mechanical properties of elastomers based on α,ω‐dihydroxy‐polydimethylsiloxane/polystyrene blends

α,ω‐Dihydroxy‐polydimethylsiloxane/polystyrene (PDMS/PS) blends were prepared by the solution polymerization of styrene (St) in the presence of α,ω ‐dihydroxy‐polydimethylsiloxane (PDMS), using toluene as solvent and benzoyl peroxide (BPO) as initiator. The PDMS/PS blends obtained by this method are a series of stable, white gums, which were vulcanized to elastomers at room temperature with methyl‐triethoxysilicane (MTES). The use level of MTES was far more than the necessary amount used to end‐link hydroxy‐terminated chains of PDMS, with the excess being hydrolyzed to crosslinked networks, which were similar to SiO₂ and acted as filler. Investigations were carried out on the elastomeric materials by extraction measurement, swelling measurement, and scanning electron microscopy. The extraction data show that at each composition the amount of soluble fraction is less than expected and the difference between experimental and theoretical values becomes more and more significant as PS content increases. This is mainly due to the grafting of PS onto PDMS and the entanglement of PS in the interpenetrating polymer network (IPN), which consists of either directly linked PDMS chains or chains linked via PS grafts and is formed by free radical crosslinking of PDMS during the radical polymerization of St. PS grafted on PDMS is insoluble and PS entangled in the IPN is difficult to extract. Both render the soluble fraction to be less than expected. As the St content in preparing PDMS/PS blends increases, the probability of grafting PS onto PDMS also increases, which may subsequently produce a higher crosslinking level of PDMS networks that linked via PS grafts by radical crosslinking. As a result, not only the amount of insoluble PS increases but also PS entangled in the IPN is more difficult to extract. Scanning electron microscopy demonstrates that the elastomer system has a microphase‐separated structure and a certain amount of PS remains in the PDMS networks after extraction, which is in accordance with the extraction data. Moreover, the mechanical properties of the elastormeric materials have been studied in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3542–3548, 2004     

函数S-粗集与规律F-隐藏

函数单向S-粗集(Function one direction singular rough sets)是用R-函数等价类定义的,函数是个规律;函数单向S-粗集具有规律特征、动态特征.利用函数单向S-粗集,给出规律F-隐藏概念,提出规律的F-隐藏定理,隐藏识别准则,给出规律的F-隐藏的应用.规律的F-隐藏是函数S-粗集中的一个新的应用研究方向,函数S-粗集是信息规律研究中的一个新理论与新工具.     

Pb(Zr0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties

Herein a useful methodology to synthesize the lead zirconate titanate (PZT) nanotubes via a dip-coating deposition process with anodic aluminum oxide (AAO) template is proposed. The nano-porous AAO templates were produced using a controlled two-step electrochemical anodization technique. The PZT/AAO composite was formed using the dip-coating wetting technique. The prepared PZT precursor solution was driven into the nanopore channels of AAO template under the driving force of capillary action, subsequently the sintering process of the as-filled templates was carefully tuned to obtain Pb(Zr_0.52Ti_0.48)O₃ nanotubes of crystalline tetragonal phase with uniform pore size and ordered arrange. Fourier transform infrared spectroscopy (FTIR) results show that in the 1200–1900 cm⁻¹ band, the composite structure of PZT/AAO has obvious absorption peaks at 1471.56 cm⁻¹ and 1556.09 cm⁻¹, the absorption intensity of the composite structure is about six times of pure AAO template. The unusual optical properties found in PZT/AAO composite will stimulate further theoretical and experimental interests in ferroelectric nanostructures.