Finite element simulation of the physical gelation of rennet casein(酶凝干酪素物理凝胶化过程的有限元模拟)

以酶凝干酪素的凝胶化过程为对象,利用有限元方法数值分析了在凝胶化过程中温度场的空间分布和时间演变规律.在此基础上,基于一阶的凝胶化动力学方程,数值模拟了凝胶体系的复剪切模量场,进而分析了材料配方、体系尺寸与冷却方案对复剪切模量场的影响规律.模拟结果表明,由于热阻的差异,体系表面的冷却速率大于内部,表面首先发生凝胶化;而由于预凝胶化阶段的平均冷却速率决定了无穷复剪切模量的值,最终体系内部的复剪切模量超过表面的.

Synthesis and characterization of novel sulfonated poly(arylene ether ketone) copolymers with pendant carboxylic acid groups for proton exchange membranes

A series of novel side-chain-type sulfonated poly(arylene ether ketone)s with pendant carboxylic acid groups copolymers (C-SPAEKs) were synthesized by direct copolymerization of sodium 5,5'-carbonyl-bis(2-fluorobenzenesulfonate), 4,4'-difluorobenzophenone and 4,4'-bis(4-hydroxyphenyl) valeric acid (DPA). The expected structure of the sulfonated copolymers was confirmed by FT-IR and H-1 NMR. Membranes with good thermal and mechanical stability could be obtained by solvent cast process. It should be noted that the proton conductivity of these copolymers with high sulfonation degree (DS > 0.6) was higher than 0.03 S cm(-1) and increased with increasing temperature. At 80 degrees C, the conductivity of C-SPAEK-3 (DS = 0.6) and C-SPAEK-4 (DS = 0.8) reached up to 0.12 and 0.16 S cm-1, respectively, which were higher than that of Nafion 117 (0.10 S cm(-1)).

Sensitive and Selective Sensor for Biothiols in the Cell Based on the Recovered Fluorescence of the CdTe Quantum Dots-Hg(II) System

Herein, a sensitive and selective sensor for biothiols based on the recovered fluorescence of the CdTe quantum dots (QDs)-Hg(II) system is reported. Fluorescence of QDs could be quenched greatly by Hg(II). In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), however, Hg(H) preferred to react with them to form the Hg(II)-S bond because of the strong affinity with the thiols of biothiols rather than quenching the fluorescence of the QDs. Thus, the fluorescence of CdTe QDs was recovered. The restoration ability followed the order GSH > Hcy > Cys due to the decreased steric hindrance effect. A good linear relationship was obtained from 0.6 to 20.0 mu mol L-1 for GSH and from 2.0 to 20.0 mu mol L-1 for Cys, respectively. The detection limits of GSH and Cys were 0.1 and 0.6 mu mol L-1, respectively. In addition, the method showed a high selectivity for Cys among the other 19 amino acids. Furthermore, it succeeded in detecting biothiols in the Hela cell.

Raspberry-like Hierarchical Au/Pt Nanoparticle Assembling Hollow Spheres with Nanochannels: An Advanced Nanoelectrocatalyst for the Oxygen Reduction Reaction

In this contribution, we for the first time report the synthesis of raspberry-like hierarchical Au/Pt nanoparticle (NP) assembling hollow spheres (RHAHS) with pore structure and complex morphology through one in situ sacrificial template approach without any post-treatment procedure. This method has some clear advantages including simplicity, quickness, high quality, good reproducibility, and no need of a complex post-treatment process (removing templating). Furthermore, the present method could be extended to other metal-based NP assembling hollow spheres. Most importantly, the as-prepared RHAHS exhibited excellent electrocatalytic activity for oxygen reduction reaction (ORR). For instance, the present RHAHS-modified electrode exhibited more positive potential (the half-wave potential at about 0.6 V), higher specific activity, and higher mass activity for ORR than that of commercial platinum black (CPB). Rotating ring-disk electrode (RRDE) voltarnmetry demonstrated that the RHAHS-modified electrode could almost catalyze a four-electron reduction of O-2 to H2O in a 0.5 M air-saturated H2SO4 solution.

Study of self-assembly of symmetric coil-rod-coil ABA-type triblock copolymers by self-consistent field lattice method

The self-assembly of symmetric coil-rod-coil ABA-type triblock copolymer melts is studied by applying self-consistent field lattice techniques in a three-dimensional space. The self-assembled ordered structures differ significantly with the variation of the volume fraction of the rod component, which include lamellar, wave lamellar, gyroid, perforated lamellar, cylindrical, and spherical-like phases. To understand the physical essence of these phases and the regimes of occurrence, we construct the phase diagram, which matches qualitatively with the existing experimental results. Compared with the coil-rod AB diblock copolymer, our results revealed that the interfacial grafting density of the separating rod and coil segments shows important influence on the self-assembly behaviors of symmetric coil-rod-coil ABA triblock copolymer melts. We found that the order-disorder transition point changes from f(rod)=0.5 for AB diblock copolymers to f(rod)=0.6 for ABA triblock copolymers. Our results also show that the spherical-like and cylindrical phases occupy most of the region in the phase diagram, and the lamellar phase is found stable only at the high volume fraction of the rod.

电离辐射对Jurkat T细胞周期进程的影响

目的:探讨电离辐射诱导Jurkat T细胞损伤过程中细胞周期进程的变化规律。方法:采用流式细胞术(FCM)检测低剂量(0.075 Gy)和较大剂量(0.5、1.0、2.0、4.0及6.0 Gy)X射线照射后Jurkat T细胞周期进程变化的时间-效应关系和剂量-效应关系。结果:时间-效应关系研究发现,2.0 Gy X射线照射后JurkatT细胞相继发生S期延迟和G2期阻滞,S期细胞百分率于照射后立即增加(P<0.001),而G2+M期细胞百分率照射后8 h开始显著增加(P<0.001)。剂量-效应关系研究发现,75 mGy低剂量X射线照射即可诱导JurkatT细胞发生S期延迟(P<0.001)和G2期阻滞(P<0.05);0.5~6.0 Gy较大剂量X射线照射后,Jurkat T细胞发生S期延迟和G2期阻滞。与假照组相比较,G0/G1期细胞百分率显著降低(P<0.001),在0.5~6.0 Gy内具有剂量依赖性,而S期和G2+M期细胞百分率显著升高(P<0.05或P<0.001)。结论:X射线照射可以改变Jurkat T细胞周期进程,诱导其相继发生S期延迟和G2期阻滞,在0.5~6.0 Gy内具有剂量依赖性。

Electro-assisted precipitation of electrolytes in poly(3,4-ethylenedioxythiophene) film

The electrolyte, NaBF4, can be enriched into the matrix of poly(3,4-ethylenedioxythiophene) (PEDOT) film during the p-doping potential cycling between 0.6 and -0.9 V. It has been demonstrated that this enrichment is originated from the mixed ion transfer between doping and dedoping, i.e. BF4- anion migrate into the PEDOT film during the oxidation process, the Ne cation insert into the film during the reduction process, and then, the electrolyte is accumulated into the film matrix after the multiple CV cycling. The quantitative analysis of energy-dispersive X-ray spectroscopy (EDX) confirmed the enrichment of NaBF4 in the PEDOT film.

Viscous-force-dominated tensile deformation behavior of oriented polyethylene

High-density polyethylene with shish-kebab structure, prepared by a melt extrusion drawing, was employed to investigate the effect of the well-defined lamellar orientation on the deformation characteristics under uniaxial tensile deformation along the drawing direction. This was done by investigating the true stress-true strain dependencies at different strain rates, recovery properties, and stress relaxation measurements. Measurements were complemented by recording in-situ wide-angle X-ray scattering patterns during the deformation process. The oriented samples showed not only a higher modulus, but different from analogous isotropic samples, a homogeneous deformation without necking. The true strain associated with the onset of fibrillation was determined. Because of the preorientation, it is shifted to 0.3, which is below the value 0.6 of the isotropic counterpart. The main finding is a strong enhancement of the Viscous force, as was revealed by stress relaxation experiments; the viscous force takes up 70% of the total stress. The presence of shish-kebabs, i.e., interconnected lamellae in a stack, seems to be responsible for the high viscous force in the oriented samples. The absence of necking has to be ascribed to the high viscous force.

Up-conversion spectrum properties of the oxy-fluoride glass co-doped with Er3+ and Yb3+

Up-conversion of 45PbF(2)-45GeO(2)-10WO(3) oxy-fluoride glasses co-doped with Yb3+ and Er3+ ions were prepared by fusion method through melting at 1223 K and then annealing at 653 K for 4 h. Transmittance of the undoped host glass was beyond 73% in a range of 0.6-2.5 mu m and the co-doped glasses still provided good transmittance beyond 50%. Refractive indices of the host and co-doped glasses were 1.517 and 1.650, respectively. Blue, green and red fluorescence spectra were observed in a range of 400-700 nm under 980 nm diode laser excitation. Up-conversion spectra at about 410, 518, 530and 650 nm were assigned to the 4f electron transitions of H-2(9/2) -> I-4(15)/(2), H-2(15/2) -> I-4(15/2) S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) of Er3+ ion, respectively. The mechanism of energy transfer between Yb3+ and Er3+ ions in the glass was analyzed. Raman shift shows the non-radiative relaxation of the glass sample is low.

Determination of biogenic amines by capillary electrophoresis with pulsed amperometric detection

The biogenic amines, putrescine, cadaverine, spermidine and spermine were separated and quantified by capillary electrophoresis with pulsed amperometric detection. Detection potential of the pulsed amperometric detection was optimized as 0.6 V Optimal separation of the biogenic amines was achieved using a separation buffer of 30 mM citrate at pH 3.5, while keeping the buffer in the detection cell as 20 mM NaOH. Using these conditions, the four biogenic amines were baseline separated. Extrapolated limits of detection for putrescine, cadaverime, spermidine and spermine were 400, 200, 100 and 400 nM for the standard mixture (polyamines dissolved in running buffer), respectively. These are lower than ultraviolet detection and comparable or even lower than laser-induced fluorescence detection results as reported in the literature. The number of theoretical plates was maintained at the 105 level, which is absolutely higher than any reported method. When applying capillary electrophoresis-pulsed amperometric detection to milk analysis, only spermidine was found in amounts varying between 0.1 and 0.5 mg/kg.

Conductive hybrids from water-borne conductive polyaniline and (3-glycidoxypropyl)trimethoxysilane

Free-standing conductive films of organic-inorganic hybrids were prepared employing the sol-gel process of (3-glycidoxypropyl)trimethoxysilane (GPTMS) and water-borne conductive polyaniline (cPANI) in water/ethanol solution. The hybrids displayed a percolation threshold for electrical conductivity at a volume fraction of 2.1% polyaniline (PANI); the maximum conductivity of the hybrids reached 0.6 S/cm. GPTMS showed good compatibility with water-borne cPANI during the sol-gel process, and freestanding conductive films were obtained at room temperature. Transmission electron microscopy images of the hybrids indicated that the cPANI was dispersed in the inorganic phase in nanoscale. Because of good confinement of cPANI chains in the inorganic network, water resistance of the hybrid films was significantly improved compared with that of pure cPANI; the electrical conductivity of the films kept stable for 6-7 days soaking in water, whereas it decreased sharply for 1 day soaking for the pure cPANI.

流动注射电化学发光法测定半胱氨酸和谷胱甘肽

采用流动注射分析技术研究了半胱氨酸和谷胱甘肽对鲁米诺微弱电化学发光的增敏行为。对影响电化学发光的各因素进行了试验和探讨 ,提出了可能的反应机理 ,并建立一种电化学发光测定半胱氨酸和谷胱甘肽的新方法。半胱氨酸和谷胱甘肽的浓度在 1 .0× 1 0 - 6 mol/L～ 5 .0× 1 0 - 5 mol/L和 1 .0× 1 0 - 6mol/L～ 2 .0× 1 0 - 5 mol/L之间呈良好的线性关系 ,相关系数分别为 0 .993和0 998,检出限分别为 0 .67μmol/L和 0 .72 μmol/L。对 1 .0× 1 0 - 5mol/L的半胱氨酸和谷胱甘肽进行 1 1次平行测定 ,相对标准偏差分别为 4.5 %和 3.7%。

降解聚β-羟基丁酸酯的真菌的研究

从不同来源的活性污泥中分离筛选出一株可降解聚β -羟基丁酸酯(PHB)的真菌 ,初步鉴定为青霉 (Penicillium .sp) ,编号DS 971 3 .降解特性研究表明 ,DS 971 3菌株对PHB膜的降解可分为两个阶段 ,即迟缓阶段和等速降解阶段 .PHB的非晶部分易于被降解 .该菌降解PHB膜的最适温度为 3 0℃ ,最适pH值为 6 0～ 6 8.

流动注射化学发光法测定葡萄糖

β-D-葡萄糖的检测是临床化学的常规分析项目 .化学发光分析法测定葡萄糖具有线性范围宽、灵敏度高等优点[1～ 3] .我们曾研究了鲁米诺 ( L uminol) -KIO4 -H2 O2 化学发光反应体系[4 ] ,发现 H2 O2 浓度在 2 .0× 1 0 - 7～ 6.0× 1 0 - 4mol/L范围内与发光强度有良好的线性关系 .本文将生成 H2 O2 的葡萄糖 -葡萄糖氧化酶 ( GOD)的酶促反应与鲁米诺 -KIO4 -H2 O2 的化学发光反应相偶合 ,结合流动注射技术 ,建立了一种流动注射化学发光测定葡萄糖的新方法 .方法的线性范围为 0 .6～ 1 1 0 mg/L ,相关系数为 0 .9997,检出限为 0 .0 8mg/L.对 1 0 mg/L葡萄糖 1 1次平行测定的相对标准偏差为 1 .3 % .该法用于人血清中葡萄糖含量的测定 ,结果令人满意 .β-D-C6 H12 O6 +O2 +H2 O GODp H =7.60 D-C5H11O5COOH+H2 O2L uminol+KIO4H2 O2p H=12 .97C6 H3NH2 ( COOH) 2 +hν仪器与试剂 :鲁米诺分析液...

水杨醛亚胺镍/MMAO催化降冰片烯加成聚合

用水杨醛亚胺镍 / MMAO催化降冰片烯聚合获得了热稳定、高分子量、可溶性的加成聚合产物 . Al、Ni摩尔比、单体浓度、反应温度与时间对催化剂的活性和聚合物分子量均有较大影响 .在优化条件下 ,催化剂的活性达 1 3 t/ (mol· h) ,聚降冰片烯的粘均分子量达 1× 1 0 6.