Surface-grafted silica linked with L-lactic acid oligomer: A novel nanofiller to improve the performance of biodegradable poly(L-lactide)

A new surface modification method by grafting L-lactic acid oligomer onto the surface silanol groups of silica nanoparticles has been developed. The surface-grafting reaction is confirmed by IR and Si-29 MAS NMR analyses. TEM and SEM results show that grafted SiO2 (g-SiO2) nanoparticles can be comparatively uniformly dispersed in chloroform or PLLA matrix, while the unmodified SiO2 nanoparticles tend to aggregate. The loading of g-SiO2 nanoparticles in poly(L-lactide) (PLLA) matrix greatly improves the toughness and tensile strength of this material. In contrast, the incorporation of un-grafted SiO2 nanoparticles into PLLA leads to the deterioration of its mechanical properties. DSC analysis shows that g-SiO2 nanoparticles can serve as a nucleating agent for the crystallization of PLLA in the composites. SEM characterization shows the tough characteristics and great interfacial combination strength for g-SiO2 (5wt%)/PLLA nanocomposites.

Effect of cations in solution on the oxidation of methanol on the surface of platinum electrode

The effect of metal cations in solution on the oxidation of methanol on the electrode surface of platinum is a neglected aspect to direct methanol fuel cell (DMFC). In this paper, a smooth platinum electrode absorbing metal cations as the working electrode was applied to investigate the methanol oxidation with the cyclic voltammetry (CV) in 1.0 mol L-1 H2SO4. From the analysis of experiment, it is found that the cations, Li+, Ce4+, Mn2+, Ni2+, Cu2+, have some negative effect on the catalytic oxidation of methanol on the surface of platinum. The degree of the effect from different cations was analyzed.

Characterization of the structural and functional changes of hemoglobin in dimethyl sulfoxide by spectroscopic techniques

Circular dichroism (CD), fourier transform infrared (FTIR), and fluorescence spectroscopy were used to explore the effect of dimethyl sulfoxide (DMSO) on the structure and function of hemoglobin (Hb). The native tertiary structure was disrupted completely when the concentration of DMSO reached 50% (v/v), which was determined by loss of the characteristic Soret CD spectrum. Loss of the native tertiary structure could be mainly caused by breaking the hydrogen bonds, between the heme propionate groups and nearby surface amino acid residues, and by disorganizing the hydrophobic interior of this protein. Upon exposure of Hb to 52% DMSO for ca. 12 h in a D2O medium no significant change in 1652 cm(-1) band of the FTIR spectrum was produced, which demonstrated that alpha-helical structure predominated. When the concentration of DMSO increased to 57%: (1) the band at 1652 cm(-1) disappeared with the appearance of two new bands located at 1661 and 1648 cm(-1); (2) another new band at 1623 cm(-1) was attributed to the formation of intermolecular beta-sheet or aggregation, which was the direct consequence of breaking of the polypeptide chain by the competition of S=O groups in DMSO with C=O groups in amide bonds. Further increasing the DMSO concentration to 80%, the intensity at 1623 cm(-1) increased, and the bands at 1684, 1661 and 1648 cm(-1) shifted to 1688, 1664 and 1644 cm(-1), respectively. These changes showed that the native secondary structure of Hb was last and led to further aggregation and increase of the content of 'free' amide C=O groups. In pure DMSO solvent, the major band at 1664 cm(-1) indicated that almost all of both the intermolecular beta-sheet and any residual secondary structure were completely disrupted. The red shift of the fluorescence emission maxima showed that the tryptophan residues were exposed to a greater hydrophilic environment as the DMSO content increased. GO-binding experiment suggested that the biological function of Hb was disrupted seriously even if the content of DMSO was 20%. (C) 1998 Elsevier Science B.V. All rights reserved.

Genetic linkage map of bay scallop, Argopecten irradians irradians (Lamarck 1819)

The bay scallop (Argopecten irradians irradians Lamarck 1819) has become one of the most important aquaculture species in China. Genetic improvement of cultured bay scallop can benefit greatly from a better understanding of its genome. In this study, we developed amplified fragment length polymorphisms (AFLPs) and simple sequence repeat markers from expressed sequence tags (EST-SSRs) for linkage analysis in bay scallop. Segregation of 390 AFLP and eight SSR markers was analysed in a mapping population of 97 progeny. Of the AFLP markers analysed, 326 segregated in the expected 1:1 Mendelian ratio, while the remaining 74 (or 19.0%) showed significant deviation, with 33 (44.6%) being deficient in heterozygotes (A/a). Among the eight polymorphic EST-SSR loci, one marker (12.5%) was found skewing from its expected Mendelian ratios. Eighteen per cent of the markers segregating from female parent were distorted compared with 21% of the markers segregating from male parent. The female map included 147 markers in 17 linkage groups (LGs) and covered 1892.4 cM of the genome. In the male map, totally 146 AFLP and SSR markers were grouped in 18 LGs spanning 1937.1 cM. The average inter-marker spacing in female and male map was 12.9 and 13.3 cM respectively. The AFLP and SSR markers were distributed evenly throughout the genome except for a few large gaps over 20 cM. Although preliminary, the genetic maps presented here provide a starting point for the mapping of the bay scallop genome.

岩石类材料静态、动态拉伸弹性模量测试方法研究——以巴西圆盘试验和霍普金森压杆、效应为手段

As we all know, rock-like materials will absolutely show very different mechanical properties under the compressive stress and tensile stress respectively. Similarly, under the dynamic compressive stress or dynamic tensile stress, the characteristics of the dynamics showed by the rock-like materials also have great differences from the mechanical behavior under static force. Studying their similarities and differences in rock mechanics theory and practical engineering will be of great significance. Generally, there are compression modulus of elasticity and tensile modulus of elasticity corresponding to compressive stress state and the tensile stress state in the rock. Both the two kinds of elastic modulus play an extremely important role in calculation of engineering mechanics. Their reliability directly affects the accuracy and reliability of the calculation results of internal stress field and displacement field of engineering rock mass. At present, it is easy to obtain the compression modulus of elasticity in laboratory; but it is very difficult to determine the tensile modulus of elasticity with direct tensile test due to that direct tensile test is difficult to perform in laboratory in general. In order to solve this problem, this thesis invents and develops several indirect test methods to determine the static or dynamic tensile modulus of elasticity of rock-type materials with high reliability and good interoperability. For the static tensile modulus of elasticity, the analytical stress field solution has been given out for the Brazilian disc under the radial and linear concentration load with Airy stress function method. At the same time, the stress field has been modeled for the Brazilian disc test by using the finite element software of ANSYS and ADINA. The analytical stress field solution is verified to be right by comparatively researching the analytical stress field solution and the numerical stress field solution. Based on the analytical stress field solution, this thesis proposes that a strain gauge is pasted at the Brazilian disc center along the direction perpendicular to the applied force to indirectly determine the static tensile modulus of elasticity, and related measurement theory also has been developed. The method proposed here has good feasibility and high accuracy verified by the experimental results. For the dynamic tensile modulus of elasticity, two measuring methods and theories are invented here. The first one is that the Split Hopkinson Pressure Bar is used to attract the Brazilian disc to generate the dynamic load, make the dynamic tensile stress is formed at the Brazilian disc center; and also a strain gauge is pasted at the Brazilian disc center to record the deformation. The second is that, in the Hopkinson effect phenomenon, the reflection tensile stress wave is formed when the shock wave propagates to the free end of cylindrical rock bar and reflect, which can make the rock bar is under dynamic tensile stress state; and some strain gauges are pasted at the appropriate place on the rock bar to record the strain coursed by the tensile or compressive stress wave. At last, the dynamic tensile modulus of elasticity can be determined by the recorded strain and the dynamic tensile stress which can be determined by related theories developed in this thesis.

红枫湖溶解有机质的分离富集、地球化学特征和环境效应

作为全球碳循环的主要组成部分，溶解有机质在水生生态系统的各种物理、化学和生物过程中起着十分重要的作用：它是湖泊异养型生物所需能量的主要提供者；是湖泊水体pH的调节剂和控制因素；能够与金属离子或有机污染物相互作用，从而影响它们的迁移转化、毒性和生物可利用性；溶解有机质也是饮用水氯化工艺中生成具有致癌作用消毒副产品的主要前驱物质。溶解有机质组成和结构十分复杂，一般由腐殖质和非腐殖质物质组成，相应的环境地球化学特征和行为也各不相同。因此，研究溶解有机质各分离组分的结构特征和环境效应，将有助于我们对溶解有机质复杂化学结构、循环特征及行为特征的深入理解；有助于揭示溶解有机质对环境中微量污染物的迁移、转化、毒性和生物有效性的影响机理和贡献因素；为水环境评价、预测、控制和管理提供科学依据。 本论文选择云贵高原山区湖泊—红枫湖为研究对象，利用XAD树脂分离技术，把湖泊水体中溶解有机质按极性的不同分成了疏水性酸、碱、中性物质和亲水性酸、碱、中性物质等六种有机组分。主要运用元素分析、有机碳分析仪、傅立叶变换红外光谱、紫外－可见分光光度，高效液相体积排阻色谱、三维荧光光谱和稳定同位素质谱仪等现代分析方法和手段，对各有机组分的地球化学特征及来源的进行了表征和探讨。同时利用荧光猝灭滴定技术研究了溶解有机质分离组分与铜的相互作用，利用顶空气相色谱法测定了各分离组分与氯气反应活性的大小，并确立了生成消毒副产物的主要前驱物质。本论文的研究成果主要有以下几点： 1.改进了分离流程：在XAD－8树脂分离溶解有机质流程的基础上，引入XAD－4树脂，对贵州红枫湖水体中溶解有机质进行了富集分离，得腐殖酸、富里酸、疏水性中性物质、亲水性酸、亲水性碱、亲水性中性物质等六种有机组分，回收率为82%。各分离组分的组成与其它天然水体的组成接近，其中以富里酸为主，占分离组分的51%。 2.溶解有机质分离组分化学结构特征的研究：元素分析表明疏水性组分具有较高的碳和硫含量，而亲水性组分O/C比较高，含有较多的含氧官能团；傅立叶变换红外光谱表明各分离组分在3424－3434 cm-1具有O-H和N-H的吸收峰，腐殖酸组分主要为含氮和聚糖物质，富里酸和亲水性酸表现强的羧基吸收峰。高效体积排阻色谱表明各六种有机组分的分子量较小，重均(Mw)和数均(Mn)分子量分别集中在1688-2355Da和1338-1928Da之间，其中Mw和紫外吸收比值(E2/E3)之间呈负相关关系；三维荧光光谱显示六种有机组分表现了4种不同类型的荧光峰，紫外区类富里酸荧光峰peakA和可见区类富里酸荧光峰peakC；疏水性中性物质还表现了两种类蛋白荧光峰peakB和peakD。荧光强度与紫外吸光系数SUVA254之间呈显著正相关关系，说明了产生荧光和紫外的物质具有某些相似的官能团，其中芳香官能团和共轭双键在这两类光谱的产生中具有重要作用。本研究进一步揭示了溶解有机质不同有机组分的分子量分布、荧光光谱特征和紫外吸收特征之间的一致性，反映了各有机组分之间的亲水、疏水与分子量、光谱特征之间的内在联系，本研究有助于加我们深对溶解有机质复杂性和相似性及化学结构与行为的进一步认识。 3.溶解有机质分离组分来源问题的探讨：我们利用δ13C及C/N比值并结合荧光光谱特征来指示溶解有机质的来源。各分离组分的δ13C及C/N比值表明富里酸主要来自陆源C3植被形成的土壤有机质，而腐殖酸、疏水性中性物质、亲水性酸、亲水性碱、亲水性中性物质属于陆源和内源的混合来源，其中腐殖酸、亲水性酸、亲水性碱接近红枫湖藻类一端，而疏水性中性物质和亲水性中性物质接近陆源一端。荧光光谱表明疏水性中性物质中含有类蛋白荧光峰，可能暗示了该组分还与人类活动有关。该研究加深了对溶解有机质来源的多样性和影响因素复杂性的认识。 4.溶解有机质分离组分与铜离子的相互作用，利用荧光猝灭滴定技术研究了分离组分与铜离子的相互作用，结果表明溶解有机质滴加铜离子后荧光强调显著降低，同时发射波长Em发生蓝移，而激发波长Ex基本不变，说明了分离有机组分在与铜离子相互作用后，π电子减少，共轭性和芳香型降低，直线型分子向非直线型分子转变；溶解有机质分离组分与铜相互作用的滴定曲线与修正的Stern-Volmer模型十分吻合；分离组分的稳定常数logK介于4.73-5.16之间（C峰）和4.64-5.24之间（A峰），logKA与logKC与总酸度以及与酚羟基之间存在显著相关性, 与羧基含量之间也有弱相关关系，说明铜离子优先与配体中强配位点（酚羟基）络合，其次为弱配位基（羧基）。该研究揭示了云贵高原山区湖泊溶解有机质分离组分与金属离子相互作用的差异性和影响因素，为水环境中金属离子迁移转化和毒性的评价提供理论依据。 5.溶解有机质分离组分卤代活性的比较：我们运用顶空气相色谱法测定了红枫湖分离组分与消毒剂反应生成有机卤代物的情况。结果表明红枫湖分离组分氯化消毒副产物主要以三氯甲烷(CHCl3)和二溴一氯甲烷(CHBr2Cl)为主，富里酸是生成三卤甲烷的主要前驱物质，同时富里酸的卤代反应活性也最强。该研究揭示了云贵高原山区湖泊中富里酸是生成消毒副产物的主要前驱物质，该组分以陆源有机质输入为主。因此，该研究对饮用水消毒具有一定的现实意义。

Synthesis of tamarixetin and isorhamnetin 3-O-neohesperidoside

Two isomeric flavonol 3-O-glycosides, tamarixetin and isorhamnetin 3-O-neohesperido side (1 and 2), were synthesized. The natural product from Costus spicatus assigned as the former compound is revised to the latter structure. (c) 2005 Elsevier Ltd. All rights reserved.

Entropy Loss is Maximal for Uniform Inputs

A secure sketch (defined by Dodis et al.) is an algorithm that on an input w produces an output s such that w can be reconstructed given its noisy version w' and s. Security is defined in terms of two parameters m and m˜ : if w comes from a distribution of entropy m, then a secure sketch guarantees that the distribution of w conditioned on s has entropy m˜ , where λ = m−m˜ is called the entropy loss. In this note we show that the entropy loss of any secure sketch (or, more generally, any randomized algorithm) on any distribution is no more than it is on the uniform distribution.

The legitimation of risk and democracy: A case study of Bt cotton in Andhra Pradesh, India

This thesis explores the inter-related attempts to secure the legitimation of risk and democracy with regard to Bt cotton, a genetically modified crop, in the state of Andhra Pradesh in India. The research included nine months of ethnographic fieldwork, extensive library and newspaper research, as well as university attendance in India, undertaken between June, 2010 and March, 2011. This comparative study (involving organic, NPM and Bt cotton cultivation) was conducted in three villages in Telangana, a region which was granted secession from Andhra Pradesh in July, 2013, and in Hyderabad, the state capital. Andhra Pradesh is renowned for its agrarian crisis and farmer suicides, as well as for the conflict which Bt cotton represents. This study adopts the categories of legitimation developed by Van Leeuwen (2007; 2008) in order to explore the theory of risk society (Beck, 1992; 1994; 1999; 2009), and the Habermasian (1996: 356-366) core-periphery model as means of theoretically analysing democratic legitimacy. The legitimation of risk and democracy in relation to Bt cotton refers to normative views on the way in which power should be exercised with regard to risk differentiation, construction and definition. The analysis finds that the more legitimate the exercise of power, the lower the exposure to risk as a concern for the collective. This also has consequences for the way in which resources are distributed, knowledge constructed, and democratic praxis institutionalised as a concern for social and epistemic justice. The thesis argues that the struggle to legitimate risk and democracy has implications not only for the constitution of the new state of Telangana and the region’s development, but also for the emergence of global society and the future development of humanity as a whole.

Diseño de una trayectoria hipotética de aprendizaje para la construcción de concepto de dependencia lineal

En esta comunicación se presenta la primera parte de una investigación cuyo objetivo fue analizar si un experimento de enseñanza diseñado ad hoc ayudó a la construcción de caracterizaciones equivalentes del concepto de dependencia lineal, en lenguaje geométrico y analítico. En primer lugar se diseñó un experimento de enseñanza en un contexto de geometría dinámica utilizando simultáneamente representaciones geométricas y analíticas del concepto y se describió una ‘trayectoria hipotética de aprendizaje’ en términos del mecanismo de ‘reflexión sobre la relación actividad-efecto’. En segundo lugar se describieron las trayectorias de aprendizaje de estudiantes de 2o de bachillerato (17-18 años) identificando las ‘acciones de generalización’ y las ‘generalizaciones de la reflexión’.