Synthesis and properties of novel random and block copolymers composed of phthalimidine‐ and perfluoroisopropylidene‐polyarylether‐sulfones

A series of novel polyarylethersulfone (AB) _n block copolymers with different segment lengths have been synthesized by nucleophilic solution polycondensation of phenoxide‐terminated and fluorine‐terminated oligomers; random copolymers have been prepared over the whole composition ranges. The structures of the resultant copolymers have been confirmed by FTIR, ¹³C NMR spectra and differential scanning calorimetry (DSC). Compared with two homopolymers and random copolymers, the block copolymers of this study possess excellent thermal stability (5% thermal decomposition under nitrogen atmosphere above 500 °C) and high glass transition temperatures, and have a wide melt‐processing temperature range. They may become a new class of mouldable high performance thermoplastics. © 2001 Society of Chemical Industry     

便携式电网在线检测仪设计

提出一种以TMS320F2812 DSP芯片为核心的便携式电网在线检测仪的设计方案,阐述了装置的基本结构及软硬件实现方法.对附加相位引起的功率测量误差采用了功率校正方法,采用微功耗16位ADS8320芯片作为A/D采样来代替TMS320F2812的内部A/D采样,克服了该DSP内部只有12位A/D的不足,提高了电力参数的测量精度.给出了交流取样调理电路、准同步采样电路和主程序流程.实验表明该装置精度达到0.2级,装置的功耗低、体积小的特点,满足便携式的要求.     

Small RNA F6 Provides Mycobacterium smegmatis Entry into Dormancy

Regulatory small non-coding RNAs play a significant role in bacterial adaptation to changing environmental conditions. Various stresses such as hypoxia and nutrient starvation cause a reduction in the metabolic activity of Mycobacterium smegmatis, leading to entry into dormancy. We investigated the functional role of F6, a small RNA of M. smegmatis, and constructed an F6 deletion strain of M. smegmatis. Using the RNA-seq approach, we demonstrated that gene expression changes that accompany F6 deletion contributed to bacterial resistance against oxidative stress. We also found that F6 directly interacted with 5′-UTR of MSMEG_4640 mRNA encoding RpfE2, a resuscitation-promoting factor, which led to the downregulation of RpfE2 expression. The F6 deletion strain was characterized by the reduced ability to enter into dormancy (non-culturability) in the potassium deficiency model compared to the wild-type strain, indicating that F6 significantly contributes to bacterial adaptation to non-optimal growth conditions.     

Mechanical properties of jute fibers and interface strength with an epoxy resin

Four different forms of jute fibers, namely untreated jute filament (UJF), sliver jute filament (SJF), bleached jute filament (BJF), and mercerized jute filament (MJF), have been subjected to tensile strength analysis following Weibull's theory. The MJF and BJF were obtained by the chemical modification of the UJF. A minimum of 50 fibers of each type, at three different gauge lengths, i.e., 15, 30, and 50 mm, were used to study the strength distribution and the effect of gauge length. The mean fiber strength was found to be the maximum for UJF followed, in the order, by BJF, MJF, and SJF (∼ 700, ∼ 660, ∼ 580, and ∼ 540 MPa, respectively, at 50‐mm gauge length). The strength was also found to decrease with an increase in gauge length. In all cases, good agreement was found with Weibull's statistical model. Single fiber composite tests, with an epoxy resin as the matrix, were carried out determine the critical fragment lengths and interfacial strength, following the Kelly–Tyson approach. The BJF was found to have the maximum interfacial adhesion (τ ≈ 140 MPa) followed by UJF, SJF, and MJF having τ values of ∼ 83, ∼ 57, and ∼ 47 MPa, respectively. Scanning electron microscope pictures showed the fiber surface was physically modified by the various treatments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1585–1596, 2000     

Nonporous monosize polymeric sorbents: Dye and metal chelate affinity separation of lysozyme

Lysozyme adsorption onto dye‐attached nonporous monosize poly(2‐hydroxyethyl‐methacrylate‐methylmethacrylate) [poly(HEMA‐MMA)] microspheres was investigated. Poly(HEMA‐MMA) microspheres were prepared by dispersion polymerization. The monochloro‐triazine dye, Cibacron Blue F3GA, was immobilized covalently as dye–ligand. These dye‐affinity microspheres were used in the lysozyme adsorption–desorption studies. The effect of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye‐attached and metal‐chelated microspheres were studied in a batch reactor. Effect of Cu(II) chelation on lysozyme adsorption was also studied. The nonspecific adsorption of lysozyme on the poly(HEMA‐MMA) microspheres was 3.6 mg/g. Cibacron Blue F3GA attachment significantly increased the lysozyme adsorption up to 247.8 mg/g. Lysozyme adsorption capacity of the Cu(II) incorporated microspheres (318.9 mg/g) was greater than that of the Cibacron Blue F3GA‐attached microspheres. Significant amount of the adsorbed lysozyme (up to 97%) was desorbed in 1 h in the desorption medium containing 1.0M NaSCN at pH 8.0 and 25 mM EDTA at pH 4.9. In order to examine the effects of separation conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We conclude that dye‐ and metal‐chelate affinity chromatography with poly(HEMA‐MMA) microspheres can be applied for lysozyme separation without causing any significant changes and denaturation. Repeated adsorption/desorption processes showed that these novel dye‐attached monosize microspheres are suitable for lysozyme adsorption. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 115–124, 2000     

双酚F环硫-环氧树脂固化物的性能研究

以甲基六氢邻苯二甲酸酐(MeHHPA)为固化剂,N．N-二甲基苄胺为固化促进剂．在一定的固化条件下,对双酚F环硫-环氧树脂进行固化实验,探讨了固化机理。并对双酚F环硫-环氧树脂固化物的吸水性、拉伸强度、剥离强度和玻璃化温度进行分析测试,结果表明,与双酚F环氧树脂相比,相应的双酚F环硫-环氧树脂具有更高的拉伸强度、剥离强度和玻璃化温度以及较低的吸水性。     

18F-FBEM-NGA的合成及结构表征

以F-FBEM对新乳糖白蛋白(NGA)进行标记,探讨标记辅助基团标记蛋白或多肽的可行性.用18F-SFB与N-(2-氨基乙基)马来酰亚胺三氟乙酸盐反应合成了一种用于正电子发射计算机断层显像(PET)药物的辅助基团18F-FBEM,并进一步制得18F-FBEM-NGA.18F-FBEM的标记时间为2.5 h,经衰变校正后...     

折叠轴结构减振作用及其应用研究

把折叠轴单独作为一个子结构,建立了该子结构的有限元动力学模型,将有限元技术与模态综合理论相结合,研究了某航空发动机中一复杂齿轮传动系统的扭振特性,研究结果表明折叠轴对脉冲载荷有明显的减振作用,提出的结构合理,有限元模型是正确的。     

New metal chelate sorbent for albumin adsorption: Cibacron Blue F3GA-Zn(II) attached microporous poly(HEMA) membranes

Poly(2-hydroxyethyl methacrylate) [poly(HEMA)] membranes were prepared by UV-initiated photopolymerization of HEMA in the presence of an initiator (α-α′-azobis-isobutyronitrile, AIBN). The triazine dye Cibacron Blue F3GA was attached as an affinity ligand to poly(HEMA) membranes, covalently. These affinity membranes with a swelling ratio of 58% and containing 10.7 mmol Cibacron Blue F3GA/m² were used in the albumin adsorption studies. After dye-attachment, Zn(II) ions were chelated within the membranes via attached-dye molecules. Different amounts of Zn(II) ions [650–1440 mg Zn(II)/m²] were loaded on the membranes by changing the initial concentration of Zn(II) ions and pH. Bovine serum albumin (BSA) adsorption on these membranes from aqueous solutions containing different amounts of BSA at different pH was investigated in batch reactors. The nonspecific adsorption of BSA on the poly(HEMA) membranes was negligible. Cibacron Blue F3GA attachment significantly increased the BSA adsorption up to 92.1 mg BSA/m². Adsorption capacity was further increased when Zn(II) ions were attached (up to 144.8 mg BSA m²). More than 90% of the adsorbed BSA was desorbed in 1 h in the desorption medium containing 0.5M NaSCN at pH 8.0 and 0.025M EDTA at pH 4.9. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 657–664, 1998