Study on Preparation and Properties of La_2O_3/MC Nylon Nanocomposites

A series of La2O3/MC nylon nanocomposites were prepared via in situ polymerization. The effects of content of nano-La2O3 on the mechanical properties of nanocomposites were studied. Dispersion of nano-La2O3 in MC nylon matrix was observed with SEM. The crystal structure of nanocomposites was characterized by means of XRD. SEM analysis shows that La2O3 nanoparticles are uniformly dispersed in MC nylon matrix and little clustering exists when the content of nano- La2O3 is lower than 1%, however, when the content of nano-La2O3 is more than 1%, it begins to cluster. XRD analysis indicats that nano-La2O3 does not change the crystal structure of MC nylon. Mechanical properties tests show that the tensile strength, elongation at break, impact strength, flexural strength, and flexural modulus of nanocomposites first increase then decrease as the content of nano-La2O3 is increased. When the content of nano-La2O3 is 0.5%, the tensile strength and elongation at break of nanocomposites reach maximum, which are 17.9% and 52.1% higher respectively than those of MC nylon. When the content of nano-La2O3 is 1.0%, the impact strength, flexural strength and flexural modulus of nanocomposites reach maximum, which are 36.6 %, 12.7 % and 16.3 % higher respectively than those of MC nylon.

Preparation and Characterization of Chitosan/Ethylcellulose Complex Microcapsule

In this work a system which consists of chitosan microcores entrapped in ethylcellulose is presented.Vitamin D2 was eficiently entrapped in chitosan microcores with spray-drying method and was microencapsulated by coating of ethylcellulose.The average size of chitosan microspheres was 6.06μm.The morphology and release properties of microcapsules were tested.The results of release in vitro showed that the microcapsule could realize sustained release for 12h in artificial intestinal juice.

外国投资和经济现代化(1840—1937年)

[本文作者片面强调了外资对旧中国经济发展的积极作用,并指出旧中国经济发展缓慢的主要原因是政治动荡这一内因,在国外有一定代表性,现译出供研究参考。

Preparation and characterization of nanocrystalline SnO_2 thin film by electrodeposition technique

A novel process for preparing tin oxide thin films directly on copper foil by electrodeposition was developed. An optimal preparation technology to obtain SnO2 thin films was proposed with current density of 8mA/cm2, the time of deposition of 120min, the concentration of tin dichloride of 0.02mol/L and the concentration of dissociated acid of 0.03mol/L. The phase identification, microstructure and morphology of the thin films were investigated by thermogravimetric analysis and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectra,scanning electron microscopy and transmission electron microscopy. The as-deposited thin film was composed of SnO2·xH2O was obtained by drying at room temperature. Nanocrystalline SnO2 thin film having tetragonal structure with average grain size in the range of 8 to 20nm and porous, uniform surface was obtained by heat-treating the as-deposited film at 400℃ for 2h. Electrochemical characterization shows that SnO2 film can deliver a discharge capacity of 798 mAh/g and the SnO2 film with smooth surface and annealed at 400℃ for 2h has better cycle performance than that with rough surface and annealed at 150℃ for 10h.

Fractal Evolving Theory and Growing Model of Olefin Polymerization Process

The surface morphology of Ti-Mg supported catalyst and the polyethylene particles are studied using scanning electron microscope(SEM) technology.The results show that either the catalyst's surface or polymer particle's surface is irregular and has fractal characteristics,which can be described by fractal parameter.The more interesting discovery is that the surface fractal dimension values of the polymer particles vary periodically with the polymerization time.We call this phenomenon fractal evolution,which can be divided into the 'revolution' stage and the 'evolution' stage,And then we present polymerization fractal growing model(PFGM),and successfully describe and /or predict the whole evolving process of the polyethylene particle morphology under the different slurry polymerization(including pre-polymerization) conditions without H2.

Strengthening Foundation by Underwater Explosive Ram

Underwater explosive ram is adopted to treat the foundation in the project of petrochemical dock in Lanshan harbor. Feasibility of this kind of foundation reinforcement method in the project of petrochemical dock in Lanshan harbor is discussed based on the analysis and comparison of the difference of sea bottom elevation, physical and mechanical properties of sediments before and after explosive ram tests. The rational parameters of explosive ram are designed according to the result of the test. The quantitative data of underwater explosive ram are offered for large scale strengthening foundation of petrochemical dock in Lanshan harbor.

经治艾滋病患者免疫恢复和免疫无应答相关研究进展

有效的抗反转录病毒治疗(antiretroviral therapy, ART)可以持续抑制HIV-1复制,同时促进HIV-1感染者的免疫恢复。然而不同疾病阶段的艾滋病患者经ART后的预后不同,大部分HIV-1感染者免疫恢复较好,但仍有15%~30%左右的HIV-1感染者无法实现有效的免疫重建,即免疫无应答者(immunological non-responders, INRs)。本文重点介绍了免疫恢复的分类及定义,导致INRs的可能原因以及针对INRs治疗的临床试验进展,以期为INRs的诊断和治疗寻找潜在的方向。

国际语境下的高丽晚期外交再思考

引言学界近来的讨论使得我们对高丽晚期的外交有了重新理解。有些学者强调了该时期的文化多样性,一些学者则重新审视了高丽的朝堂政治,还有些学者考察了高丽在国际秩序中的地位。本文以14世纪后期蒙古帝国的灭亡和欧亚大陆后蒙古秩序的发端这一重要历史时期为时间点考察了高丽晚期,讨论了高丽与外部世界之间的联系,快速求变的需求以及高丽在14世纪下半叶的选择范围。最后本文试图讨论,与其关注高丽晚期外交中空洞的政治话语,不如考察其背后的动机原因。

Effect of Yb_2O_3 Additive on Transformation Behavior of Anatase for TiO_2/(O′+β′)-Sialon Multi phase Ceramics

TiO2/（O＇ ＋ β＇）-Sialon multiphase ceramics were prepared with nano TiO2 （anatase） powder and （O＇ ＋ β＇）-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/（O＇ ＋ β＇）-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3 ： some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows： some Yb^n＋ enter TiO2 lattice and replace Ti^4＋ , as well as the redox reaction between Yb^3＋ and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and Ti- O-Yb bond is formed by the coaction of Yb^3＋ and TiO2, which inhibit the process.

雪莲薯提取物及其成分的促精子发生作用

AIM: Smallanthus sonchifolius (Yacon) has been used as a food and folk medicine in the Andes region. It was screened the pharmacological effects of a 50% ethanol extract of Yacon on spermatogenesis in rats. This study is carried out to evaluate the possibility of using Yacon tubers extracts as a fertility agent to treat infertility caused by spermatogenic disorders. METHODS: The dried, pulverized Yacon tubers were extracted with 50% ethanol at 50 ℃ for 5 h under sonication. The Yacon extracts were analyzed by using HPLC system on a Kromasil C18 column (250 mm×4.6 mm). The Yacon tubers extracts, chlorogenic acid and ferulic acid were administrated to rats once daily by oral gavage. The number of sperm heads in the testis was assessed by counting the number of sperm heads using slight modification of the procedure reported by Toth et al (1989). RESULTS: After administration of chlorogenic acid and Yacon tuber extracts to rat for 5 weeks, the number of sperm in epididymis were increased by 20.33% and 34.48%, respectively. The ferulic acid which was reported as a metabolite of chlorogenic acid and constituent of Yacon to estimate the spermatogenic activity was also administered. After administration of ferulic acid and Yacon tubers extracts, the sperm number were increased by 37.87% and 43.33%, respectively. Spermatogenic effects of chlorogenic acid and ferulic acid were 0.59 times and 0.87 times of Yacon tubers extracts, respectively. CONCLUSION: The spermatogenic effect of Yacon tubers extracts may result from the combined effect of chlorogenic acid or its analogues and their metabolites.

Purification and Biochemical Characterization of D-hydantoinase and D-N-carbamoylase from Burkholderia cepecia.njut01

Hydantoinase and N-carbamoylase play important rol es in the production of optically pure amino acids from racemic 5-monosubstitut ed hydantoins. In this report, hydantoinase and the N-carbamoylase from Burkh olderia cepecia.njut01 were purified to homogeneity by chromatography (Pharma cia Explorer 100 system). The substrate specificity, enantioselectivity, pH depe ndence of activity and temperature stability of the activity were characterized. The results show that the hydantoinase and N-carbamoylase induced from Burkh olderia cepecia.njut01 are both strict D-stereo selective enzymes. They both hydrolyze substrates with side chains containing aliphatic and aromatic res idues with higher activity and affinity toward aromatic than aliphatic substitu ted substrates. The hydantoinase is a homotetramer with subunit molecular weight near 52,000 and is active between pH 6.5 and 10 with an optimum near pH 9.0. The en zyme is active at temperatures up to 60°C, however,it appears instable at h ig her temperatures. The subunit molecular weight of N-carbamoylase is about 35KD. The N-carbamoylase is active in the pH range from 6.0 to 9.5. The optim-pH is 7.2 and the optimizing bioconversion temperature of the N-carbamyolase is 52 °C.

Adaptive Biorthogonal Local Discrete Cosine Transform for Interference Excision in Direct Sequence Spread Spectrum Communications

A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine trans form (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional trans form domain excision algorithms is that the basis functions are not fixed but ca n be adapted to the time-frequency structure of the interfering signal. It is w e ll suited to transform domain compression and suppression of various types of in terference. Compared to the discrete wavelet transform (DWT) that provides logar ithmic division of the frequency bands, the adaptive BLDCT can provide more flex ible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) perf ormance and the increased robustness of the receiver.

基于生态系统的管理如何融入城市环境政策——以西华盛顿为例

全球范围内城市聚落的增长影响着人类对自然资源的管理,从而促使自然科学和社会科学的学者们提倡以基于生态系统的途径来管理人类聚落。尽管过往有不少探讨基于生态系统管理(ecosystem-based management,以下简称EBM)的文献,但在制定环境政策时,却极少有城市和区域规划师将EBM因素考虑在内。本文对西华盛顿州的城市规划师在审视关于环境政策的科研数据时,在多大程度上运用EBM原则进行评估。笔者采用了现成文献中对EBM的定义,采访了42位在西华盛顿工作的环境规划师,询问其在审视有关科研数据时会考虑哪些EBM因素,并对访谈数据进行内容分析。结果显示,规划师们在审视与制定环境政策相关的科学文献时,会考虑监测、机构间合作、生态边界、价值取向乃至适应性管理等因素,但对于尺度、生态完整性和机构改革等因素,则会遇到阻碍或者说不会明确考虑。本文还阐述了为何有些EBM因素得到重视而另一些却被忽略,最后对通过应用EBM原则来改良城市环境政策的制定提出了建议。

20世纪晚期人类学的亲属研究

回顾了20世纪晚期人类学领域有关亲属研究的进展,特别注意到20世纪70年代以来理论的发展和方法论与研究目的的转变。突出了马克思主义、女性主义和历史学的研究方法,强调亲属研究的回归和对同性恋亲属关系的各个方面及新生育技术所导致的问题的研究。当代亲属研究倾向于以历史为基础,集中在对性别、权力和差异的日常体验、理解和表述上,并着重分析矛盾、对立和模棱两可的主题。

Hepatic differentiation from embryonic stem cells in vitro

OBJECTIVE: To investigate an method for hepatic differentiation from embryonic stem cells (ES cells) in vitro and the resulting differentiation ratio, in order to develop a procedure for producing a new type of hepatocyte for hepatocyte replacement therapy in the treatment of liver failure. METHODS: ES cells from Balb/C mice were cultured and maintained in an undifferentiated state in gelatin-coated dishes using Dulbecco's modified Eagle's medium (DMEM) containing 1000 U/ml leukemia inhibitory factor (LIF). Then, LIF was withdrawn from the DMEM to allow the ES cells to develop into embryonic bodies (EBs). EBs were plated onto tissue culture dishes, and growth factors such as acidicfibroblast growth factor (aFGF) and hepatocyte growth factor (HGF) were added to the medium to promote directional differentiation. The course of development and differentiation was observed dynamically using an inversion microscope. The expression of hepatic proteins, such as alpha-fetoprotein (AFP), albumin (ALB), cytokeratin 8 (CK8), cytokeratin 18 (CK18), in cytoplasm was analyzed by immunocytochemistry (ICC). The concentration of ALB in the medium was determined dynamically by radioimmunoassay (RIA). RESULTS: ES cells replicated as clones, without differentiating, in DMEM containing LIF. They developed into EBs in medium without LIF. Our ICC assay showed that differentiating cells did not express hepatic proteins, such as AFP, ALB, CK8, and CK18 until day 7, day 9, day 11, and day 11, respectively (up to 2 days later when growth factors are not present). The concentration of AFP in the medium was first detected on day 8, at a concentration of 3.4 ng/ml, and increased to 22.8 ng/ml by day 15. The concentration of ALB in the medium was 0.2 micro g/ml on day 11, and increased to 2.2 micro g/ml by day 15. ALB-positive cells under ICC manifest morphological structures were consistent with normal mouse hepatocytes. The differentiation ratio of hepatocytes in the ES cell differentiation system was 30% on day 15 (significantly lower without the presence of growth factors). CONCLUSIONS: ES cells can differentiate into mature hepatocytes. Growth factors, such as aFGF and HGF, can enhance this differentiation and produce sufficient numbers of functional hepatocytes. This method may be a reliable new way of differentiating ES cells into hepatocytes for use in replacement therapy in the treatment of liver failure.

A PRECONDITIONER FOR DOMAIN DECOMPOSITION METHODS WITH MORTAR LAGRANGE MULTIPLIERS

In this paper we consider the domain decomposition methods with mortar element Lagrange multipliers to two-dimensional elliptic problems.We shall construct a kind of simple preconditioners for the corresponding interface equation.It will be shown that condition number of the preconditioned interface matrix is almost optimal.

观念如何对政策产生因果效应

政治科学中意义取向的行为主义者与观念制度主义者,批评新现实主义与博弈论回避决策中的认知复杂性难题,指出它们的理性假设模型由于忽视思维活动而无法充分认识观念及信念对于政策制定的重要意义。行为主义与制度主义由于偏重对可观测和可验证的行为展开实证分析,致使其忽略为观念赋予因果效应的主体间意义和符号话语,而且对观念性因果机制或因果能力的认识也受到方法论层面的限制。与此同时,建构性与话语性分析路径集中关注诠释性理解,在分析观念自身的符号语言与主体间意义方面具有方法论优势,但其缺陷是重诠释意义而轻探究原因。本文认为当前研究一方面应推进行为主义与制度主义探讨那些促使观念产生因果效应的机制和能力,另一方面应推进建构性与话语性分析路径对观念要素所造成的效果作出因果说明或准因果说明,以此更好地阐释观念对政策产生的因果效应。