Feasibility of biodegradable PLGA common bile duct stents: An in vitro and in vivo study

The current study investigates the feasibility of using a biodegradable polymeric stent in common bile duct (CBD) repair and reconstruction. Here, poly(l-lactide-co-glycolide) (PLGA, molar ratio LA/GA = 80/20) was processed into a circular tube- and dumbbell-shaped specimens to determine the in vitro degradation behavior in bile. The morphology, weight loss, and molecular weight changes were then investigated in conjunction with evaluations of the mechanical properties of the specimen. Circular tube-shaped PLGA stents with X-ray opacity were subsequently used in common bile duct exploration (CBDE) and primary suturing in canine models. Next, X-ray images of CBD stents in vivo were compared and levels of serum liver enzymes and a histological analysis were conducted after stent transplantation. The results showed that the PLGA stents exhibited the required biomedical properties and spontaneously disappeared from CBDs in 4-5 weeks. The degradation period and function match the requirements in repair and reconstruction of CBDs to support the duct, guide bile drainage, and reduce T-tube-related complications.

微观结构对溶胶-凝胶法合成的La_(0.67)Sr_(0.33)MnO_3电磁性能影响

采用溶胶-凝胶法制备了不同烧结温度的钙钛矿类锰氧化物La0.67Sr0.33MnO3样品。实验结果表明,在1573 K以上烧结的样品,晶粒出现异常长大,晶界效应明显。随着烧结温度的提高,磁化强度逐渐增大,但样品的居里温度基本不变。此外,在1173和1573 K温度下烧结的样品,均出现了低于居里温度的金属-半导体导电行为转变。在合适的烧结条件下,可以观察到隧道磁电阻(TMR)和超大磁电阻(CMR)2种磁电阻效应。实验表明,自旋电子的输运,不仅与样品平均粒径的大小和密度有关,而且与晶界的微观结构有密切关系。

Sudies on non-isothermal melt crystallization kinetics in PET/PEN/DBS blends

Macrokinetic models, namly the modified Avrami, Ozawa and Zibicki models, were applied to study the non-isothermal melt crystallization process of PET/PEN/DBS blends by DSC measurement. The modified Avrami model was found to describe the experimental data fairly well. With the cooling rates in the range from 5 to 20 K/min, Ozawa model could be well used to describe the early stages of crystallization. However, Ozawa model did not fit the polymer blends during the late stages of crystallization, because it ignored the influence of secondary crystallization. The crystallization ability of the blends decreases with increasing the DBS content from analysis by using Ziabicki kinetic model, which is similar to the results based on calculation of the effective energy barrier of the blends.

Synthesis, properties and structural characterization of an intermolecular photosensitive complex: (HGly-Gly)(3)PMo12O40 center dot 4H(2)O

The first heteropoly acid-dipeptide complex, (HGly-Gly)(3)PMo12O40.4H(2)O, was synthesized and characterized by elemental analysis, IR, UV, H-1 NMR and single crystal X-ray diffraction. The X-ray crystallographic study showed that the crystal structure was constructed from N-H...O and O-H...O hydrogen bonds among the (HGly-Gly)(+), H2O and PMo12O403- units. This structure represents a model interaction between polyoxometalates and proteins. The complex has photosensitivity under irradiation by sunlight. The fluorescent activity of this compound is also reported.

Structure, electric and magnetic properties of new compounds CdYMWO7 (M = Cr and Mn)

Two new compounds with the formula of CdYMWO7 (M = Cr, Mn) were prepared by solid state reaction. They crystallized with orthorhombic structure with the cell parameters of a = 11.7200 Angstrom, b = 7.1779 Angstrom, c = 6.9805 Angstrom (CdYCrWO7), and a = 11.7960 Angstrom, b = 6.1737 Angstrom, c = 7.6530 Angstrom (CdYMnWO7). These compounds are insulators with high resistivities at room temperature. The temperature dependence of the magnetic susceptibility of CdYMWO7 (M = Cr and Mn) show Curie-Weiss Law's behaviors from 80 to 300 K. The magnetic moments at room temperature fit very well with those corresponding to Cr3+ and Mn3+ ions. This suggests that both Cr and Mn ions exist in + 3 oxidation state in CdYMWO7 compounds. (C) 1998 Elsevier Science Ltd. All rights reserved.

Identification of a C-type lectin from the bay scallop Argopecten irradians

C-type lectins are Ca2+ dependent carbohydrate-recognition proteins that play crucial roles in the invertebrate innate immunity, such as nonself recognition, activation of proPO system, antibacterial activity, promotion of phagocytosis and nodule formation. In this study, a novel C-type lectin of bay scallops Argopecten irradians (Ai Lec) was identified using expressed sequence tag (EST) and RACE techniques. The Ai Lec cDNA encoded a polypeptide of 171 amino acids with a putative signal peptide of 21 amino acid residues and a mature protein of 150 amino acids. The deduced amino acid sequence of Ai Lec was highly similar to those of the C-type lectins from other animals and contained a typical carbohydrate-recognition domain (CRD) of 131 residues, which has four conserved disulfide-bonded cysteine residues that define the CRD and two additional cysteine residues at the amino terminus. The expression of Ai Lec transcript was dominantly detected in the hepatopancreas and slightly detected in the haemocytes of normal scallops. 6 h after Vibrio anguillarum-challenge and 8 h after Micrococcus luteus-challenge, the temporal expression of Ai Lec mRNA in hemocytes was increased by 4.4- and 3.6-folds, respectively. The results suggested that Ai Lec was a constitutive and inducible acute-phase protein and might be involved in immune response to Gram-negative and Gram-positive microbial infection in bay scallop A. irradians.

Factors influencing hemolytic activity of venom from the jellyfish Rhopilema esculentum Kishinouye

In this study, hemolytic activity of venom from the jellyfish Rhopilema esculentum Kishinouye and some factors affecting it were assayed. The HU50 of R. esculentum full venom (RFV) against chicken erythrocytes was 3.40 mu g/ml and a Hill coefficient value was 1.73 suggesting at least two molecules participated in hemolytic activity. The hemolytic activity of RFV was affected by some chemical and physical factors such as divalent cations, EDTA, (NH4)(2)SO4, pH and temperature. In the presence of Mg2+, Cu2+, Zn2+, Fe2+, Ca2+ ( >= 2 mM), Mn2+ (>= 1 mM), EDTA (>= 2 mM) and (NH4)(2)SO4, the hemolytic activity of RFV was reduced. RFV had strong hemolytic activity at the pH 6-10 and the hemolytic ratios were 0.95-1.19. Hemolytic activity was temperature-sensitive and when RFV was pre-incubated at temperatures over 40 degrees C, it was sharply reduced. (c) 2007 Elsevier Ltd. All rights reserved.

藏鼠兔与高原鼠兔表型及分子性状的比较

本文应用限制性内切酶分析藏鼠兔和高原鼠兔的线粒体ＤＮＡ限制性片段长度多态性（ｍｔＤＮＡＲＦＬＰ），并结合形态、生境、地史和化石资料综合探讨两物种的异同。结果表明，形态上差异显著的两个物种，在分子水平上也同样具有明显的区别。用１６种酶分别消化各样品，共检出３０种限制性类型，两物种间存在丰富的多态性；它们的ｍｔＤＮＡ分子均为１７．９ｋｂ（千碱基对）左右；平均遗传距离为０．０４５５，分歧时间约为距今二百三十万年前的上新世晚期，相当于我国哺乳动物时代的榆社期晚期或泥河湾期早期。

Determination of aliphatic amines from soil and wastewater of a paper mill by pre-column derivatization using HPLC and tandem mass spectrometry (HPLC-MS/MS)

A pre-column derivatization method for the sensitive determination of aliphatic amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) followed by HPLC with fluorescence detection and APCI/NIS identification in positive-ion mode has been developed. The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent was replaced by the 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing reagent, BCEOC, that could easily and quickly label amines. Derivatives were stable enough to be efficiently analyzed by HPLC and showed an intense protonated molecular ion corresponding m/z [M + H](+) with APCI/MS in positive-ion mode. The collision induced dissociation of the protonated molecular ion formed characteristic fragment ions at m/z 264.1, m/z 246.0 and m/z 218.1, corresponding to the cleavages of CH2CH2O-CO, CH2CH2-OCO, and N-CH2CH2O bonds. Studies on derivatization conditions demonstrated that excellent derivatization yields close to 100% were observed with a 3 to 4-fold molar reagent excess in acetonitrile solvent, in the presence of borate buffer (pH 9.0) at 40 degrees C for 10 min. In addition, the detection responses for BCEOC derivatives were compared with those obtained with CEOC and FMOC as labeling reagents. The ratios I-BCEOC/I-CEOC and I-BCEOC/I-FMOC were, respectively, 1.40-2.76 and 1.36-2.92 for fluorescence responses (here, I was the relative fluorescence intensity). Separation of the amine derivatives had been optimized on an Eclipse XDB-C-8 column. Detection limits calculated from an 0.10 pmol injection, at a signal-to-noise ratio of 3, were 18.65-38.82 fmol (injection volume 10 mu L for fluorescence detection. The relative standard deviations for intraday determination (n = 6) of standard amine derivatives (50 pmol) were 0.0063-0.037% for retention times and 3.36-6.93% for peak areas. The mean intra-and inter-assay precision for all amines were <5.4% and 5.8%, respectively. The recoveries of amines ranged from 96 to 113%. Excellent linear responses were observed with correlation coefficients of >0.9994. The established method provided a simple and highly sensitive technique for the quantitative analysis of trace amounts of aliphatic amines from biological and natural environmental samples.

液压反铲挖掘机工作装置有限元动态分析

针对挖掘机工作装置的结构特点 ,建立了其系统 3维有限元模型 ,通过分析得出了系统的固有频率和振型 ,以及结构动态响应各时刻的变形和应力分布规律。比较了工作装置在开挖难度较小和较大 2种情况下 ,挖掘阻力对系统动力响应的影响

基于自治及合作的整子制造系统

整子制造系统是智能制造计划中提出的一种未来的制造模式，本文对其概念、理论和研究状况进行了介绍和分析．整子是构造制造系统的一种模块，它具有自治性及合作性，而整子制造系统则追求快速适应环境变化的能力．整子制造系统采用了一种松弛的动态递阶控制结构．目前整子制造系统仍然处于对“下一代制造模式”的研究阶段，离实际应用还有一定的距离。

苔藓新老组织及其根际土壤的碳氮元素含量和同位素组成（δ^13C和δ^15N）对比

对细叶小羽藓（Haplocladium microphyllum）新老组织及其根际土壤的碳氮含量和同位素组成进行了分析,探讨了苔藓衰老过程控制元素和同位素变化的机制以及苔藓对土壤的贡献。同种组织碳氮含量之间的相关性反映了苔藓固碳能力和氮需求的相互联系。新生组织碳氮含量明显高于衰老组织且存在相关性,反映了苔藓衰老过程体内碳氮物质向新生组织迁移的生理特征。两种组织之间同位素组成（δ^13C和δ^15N）没有明显差异,说明组织间的物质迁移没有产生明显的同位素分馏,其原因可能在于细叶小羽藓形态结构简单,体内物质迁移对碳氮同位素组成的影响较小。相反,苔藓组织与根际土壤之间的有机碳/氮信息没有相关性,这可能与苔藓植物长期滞留营养物质、缓慢的分解和成土速度有关,反映了该研究区苔藓层对土壤碳氮累积的贡献较小.