Enzymatic Desizing of Polyvinyl Alcohol from Cotton Fabrics

Enzymatic degradation of polyvinyl alcohol (PVA) was used for the desizing of cotton fabrics. A mixture of two different PVA-degrading enzyme activities, including PVA oxidizing, was partially purified from the culture filtrate of a PVA-degrading mixed culture by ionic exchange chromatography. Optimum conditions for PVA-degradation by using this enzyme mixture were pH 8·0 and temperatures ranging from 30°C to 55°C. Cotton fabrics sized with a PVA solution (25 g dm⁻³) were desized with the enzyme mixture after a 1 h treatment at 30°C and pH 8·0. In this case, similar amounts of residual PVA in fabrics were detected in comparison with the conventional desizing process which uses hot water (80°C, 30 min). Minimum amounts of residual PVA were found when the enzymatic desizing time was extended to 6 h. Also, the PVA content in the liquid waste from the enzymatic desizing carried out during 4 h was negligible with a 7·4-fold increase in the biochemical oxygen demand as compared with the initial value. © 1997 SCI.     

Cloning and sequencing of kojibiose phosphorylase gene from Thermoanaerobacter brockii ATCC35047

A gene encoding kojibiose phosphorylase was cloned from Thermoanaerobacter brockii ATCC35047. The kojP gene encodes a polypeptide of 775 amino acid residues. The deduced amino acid sequence was homologous to those of trehalose phosphorylase from T. brockii and maltose phosphorylases from Bacillus sp. and Lactobacillus brevis with 35%, 29% and 28% identities, respectively. Kojibiose phosphorylase was efficiently overexpressed in Escherichia coli JM109. The DNA sequence of 3956 bp analyzed in this study contains three open reading frames (ORFs) downstream of kojP. The four ORFs, kojP, kojE, kojF, and kojG, form a gene cluster. The amino acid sequences deduced from kojE and kojF are similar to those of the N-terminal and C-terminal regions of a sugar-binding periplasmic protein from Thermoanaerobacter tengcongensis MB4. Furthermore, the amino acid sequence deduced from kojG is similar to that of a permease of the ABC-type sugar transport systems from T. tengcongensis MB4. Each of three amino acid substitutions, D362N, K614Q and E642Q, caused a complete loss of kojibiose phosphorylase activity. These results suggest that D362, K614 and E642 play an important role in catalysis. Another mutation, D459N, increased K(m) values for kojibiose (7-fold that for the wild type), beta-G1P (11-fold) and glucose (7-fold), whereas K(m) for inorganic phosphate was minimally affected by this mutation, suggesting that D459 may be involved in the binding to saccharides.     

声近场综合试验解析技术及其在车外噪声分析中的应用

开发了声近场综合试验解析技术,包括参考话筒位置选择,非相干源信号的特性辨识,各声源传播途径可视化,各声源对系统输出的贡献评价以及输出预测等方面的新方法。试验研究和实车应用的成功表明,这些新方法可以适用于复杂的工程实际。     

Synthesis and characterization of polytriphenylamine based graft polymers for photorefractive application

Novel graft copolymers, PTPA-g-PEAs containing poly(triphenylamine) (PTPA) backbone and poly(ethyl acrylate) (PEA) branches were synthesized by the oxidative coupling polymerization of triarylamine monomers followed by grafting of ethyl acrylate via an atom transfer radical polymerization (ATRP). Photorefractive (PR) composites based on the graft copolymers showed good static PR properties and fast response time under moderate conditions. The highest diffraction efficiency (19.7% at 45 V/μm) was observed with the composite containing the graft polymer with 18 mol% of graft density and 27 wt% of PTPA. And the fastest response (8 ms at 50 V/μm) was achieved when PTPA content was 68 wt%.     

Combustion of GAP/HMX and GAP/TAGN Energetic Composite Materials

Energetic composite materials (ECM) have high thermodynamic potential and flexible design capability. Two types of ECM were formulated as mixtures of glycidyl azide polymer (GAP) and crystalline materials. The crystalline materials evaluated were cyclotetramethylene tetranitramine (HMX) and triaminoguanidine nitrate (TAGN). The thermochemical properties of HMX and TAGN were different to each other: HMX is a high energy material but the burning rate is lower than that of TAGN. TAGN produces hydrogen as a combustion product and the thermodynamic potential becomes high even though the flame temperature is low. The results of burning rate measurement tests indicate that the burning rates of both ECM are decreased significantly by the addition of HMX and TAGN even though the burning rates of GAP, HMX, and TAGN are higher than those of the ECM. The temperature sensitivity of burning rate of GAP is reduced significantly by the addition of HMX and remains unchanged by the addition of TAGN. The reduced burning rates of GAP/HMX and GAP/TAGN are caused by the reduced heat flux transferred back from the gas phase to the burning surface. The reduced heat release at the burning surface of GAP/HMX is responsible for the reduced temperature sensitivity.     

Combustion of GAP Based Energetic Pyrolants

Glycidyl azide polymer (GAP) is a high energy material used as a fuel component and binder of propellants and gas generators. High temperature products are formed by the scission of the chemical bond N₃ when GAP is decomposed. The major decomposition products are N₂, CO, and C. Though GAP contains no oxidizer fragments in its products, an addition of metal particles increases the energy of GAP. A mixture of GAP and metal particles forms a high energy metal based GAP pyrolant, i.e. GAP/metal pyrolant. The metals examined are Al, Mg, B, Ti, and Zr. The results indicate that the thermal decomposition and burning rate are dependent on the type of metals mixed.     

Ensuring fairness among ECN and non‐ECN TCP over the Internet

Explicit Congestion Notification (ECN) has been proved to provide a fast indication of incipient congestion and thus better the performance of a TCP/IP network. In this work, we carry out investigations on gateway or router performance in providing fairnesss when both FIM ECN‐capable and non‐ECN‐capable connections are employed. We propose a new packet‐dropping scheme called Fair In‐time Dropping (FID) which drops packets from a connection upon detecting an incipient indication of congestion depending on its share of gateway or router buffer occupancy. We also show that a combination of FIM and FID offers the best fairness compared with a combination of FIM along with other dropping schemes. Copyright © 2003 John Wiley & Sons, Ltd.     

Coupling effects on the conductance fluctuations in GaAs/AlGaAs double quantum dots

Electron wave interference effects in GaAs/AlGaAs coupled quantum dots have been studied at 30 mK in magnetic fields with different coupling strength between two dots. In a strong coupling regime, the existence of global trajectories which span two dots was suggested, while in a weak coupling regime, the trajectories were found to be limited in each single dot.     

Effect of internal donors in propylene polymerization analyzed with the two‐site model

The effect of internal donors of Ziegler‐Natta catalyst on stereoregularity in propylene polymerization was analyzed with the aid of the two‐site model analysis system. The amount of internal donor and that of external donor were varied. The probability in the selection of d (or l) monad in asymmetric site is contributed by both the amount of internal donor and that of external donor. With respect to the fraction of asymmetric site, the two‐site model enabled us to conceive that the new kinds of active centres are generated in specific cases where external donor is believed to be replacing weaker internal donor during polymerization. The effect of hydrogen concentration during polymerization is also discussed. © 2002 Society of Chemical Industry.     

滚石离散元数值模拟的参数反演

 离散元法(DEM)是数值模拟崩塌落石运动的一个有力方法,但确定离散元输入参数是个难题。提出一个基于已知落石轨迹的离散元参数的反演计算方法。落石轨迹可以通过现场落石试验或者野外实地调查实际落石过程获得。该方法的特征为反演得到的离散元参数可以间接反映边坡与落石冲击时的变形以及植被缓冲效应。建议的几个保证解的有效性得到验证,稳定性措施效果良好。室内落石试验结果和现场落石工程实录验证证明了该算法的有效性和实用性。