羟基乙酸均聚物PGA的合成及表征

以实验室合成的羟基乙酸二聚体乙交酯为原料，经乙交酯开环聚合合成高相对分子质量的聚羟基乙酸，对乙交酯在不同催化剂作用下的开环聚合成的均聚物进行了研究．结果表明，单体结晶次数、催化剂浓度、聚合时间等条件是影响聚合物特性黏度系数的重要因素．合成了满足要求的聚乙交酯，并提供了合理的工艺流程．     

乙交酯的悬浮聚合

利用悬浮聚合的方法,选用甲基硅油作为体系的分散介质,乙交酯 (GA)为单体,合成出了相对分子质量较高的聚乙交酯,其特性黏度[η]高达0.9。采用红外IR,DSC等方法表征了聚乙交酯的结构和性质。重点研究了聚合温度、反应时间、催化剂用量等因素对聚乙交酯的特性黏度的影响,确定了最佳工艺条件.     

乙交脂(GA)的合成及表征

以中试车间生产的羟基乙酸为原料，经溶剂萃取法提纯，通过羟基乙酸预聚再解聚制备乙交酯．研究表明，催化剂种类、催化剂用量、预聚时间、解聚时间对乙交酯的产率都有影响，为乙交酯的工业化生产提供了合理的工艺流程．     

生物降解材料—聚乙交酯医用纤维的研究

以乙醇酸为原料，合成α－乙交酯单体，进而再聚合成生物降解聚合物聚乙交酯（ＰＧＡ）。对聚合物进行纺丝成形，获得ＰＧＡ纤维。应用红外光谱（ＩＲ）、差示扫描量热分析（ＤＳＣ）、热重分析（ＴＧＡ）和Ｘ－射线衍射法，研究聚乙交酯的结构和性能。通过对ＰＧＡ纤维的生体内外的降解试验，发现其降解速度随浸渍液的ｐＨ值的增加而增大，特别是在碱性介质中重量损失最为明显。ＰＧＡ纤维埋入ＳＤ大白鼠体内，对机体无毒性，组织反应极小，６０天后能被机体完全吸收，对机体具有良好的相容性。     

乙交酯/ε-己内酯共聚物的合成和表征

以乙交酯和ε-己内酯为单体,辛酸亚锡为引发剂,通过本体开环聚合反应成功地合成了聚乙交酯/ε-己内酯共聚物;采用DSC、TG、1H/13C-NMR、XRD等技术对共聚物的结构性能进行了表征.结果表明,制备的共聚物的热性能、结晶性、两亲性等可以通过调节乙交酯和ε-己内酯单体的配比,来控制共聚物的组成,从而达到改善共聚物的加工性及控制生物降解性的目的.     

聚酯类生物降解材料的结构与性质

以精制的乙交酯(GA)、丙交酯(dl-LA)为单体制得了聚乙交酯(PGA)、聚丙交酯(PLA)和乙交酯与丙交酯以不同组成比的共聚物。用红外光谱、核磁共振、热分析和X-射线衍射分析确定了该系列聚合物的结构与性质。用毛细管流变仪研究了PGA和PGLA910熔体的粘弹性,这为选择合适的纺丝条件提供依据,并将该系列聚合物埋入动物体内进行体内降解试验。结果表明,该类聚合物无毒性,60天后可被动物体吸收。这是一类应用前景十分广阔的生物降解材料,可用作可吸收医用缝线,外科植入材料等。     

聚L-丙交酯的制备及其热稳定性能的研究

对聚丙交酯的合成和热稳定性进行了研究。单体重结晶次数、辛酸亚锡浓度、聚合时间等条件均是影响聚合物特性粘数的重要因素。热稳定剂对聚丙交酯的分子量几乎没有影响。优化聚合条件可以获得粘均分子量大于200000的聚丙交酯材料,聚合结果具有良好的重复性。实验表明在高于聚合物熔点温度以上,聚丙交酯表现出热不稳定性。热稳定剂ULTRONOX 626A能够有效降低聚丙交酯的热降解幅度。     

PLGA的合成、表征及其导管支架的制备

用质量百分比为80％的L-丙交酯与20％的乙交酯进行开环聚合,得到聚（L-丙交酯-CO-乙交酯）（80／20）,并用红外光谱和氢核磁共振光谱进行了表征．对合成条件与PLGA相对分子量的关系进行了研究．研究结果表明,合成高分子量PLGA的最优条件是：聚合温度为140℃,反应时间为48h,单体与引发剂的摩尔比（n（M）／n（I））为8000／1．结合溶液浇铸与盐沥滤技术,PLGA被制作成多孔导管支架．PLGA导管支架具有相互连通的孔墙结构．     

聚酯类可吸收型医用缝合线的单体——乙交酯及丙交酯的合成

可吸收型医用缝合线是一种能经受生物组织反应,经降解后被人体吸收的高分子材料。本文以α-羟基酸为原料合成了聚酯类可吸收型缝合线的单体:乙交酯和丙交酯,测定了它们的IR,NMR,MS以及DSC图谱。利用中间产物的质谱讨论了交酯生成的反应途径。运用DSC图谱以及加热红外光谱讨论了α-乙交酯、β-乙交酯的稳定性,得到α-乙交酯较为稳定的结论。     

聚(己内酯-乳酸)的直接熔融法合成及表征

以乳酸（LA）、ε-己内酯（CL）为单体,通过直接熔融共聚法合成可生物降解材料聚（己内酯-乳酸）[P（CL-co-LA）]．文中探讨了预聚时间、催化剂种类、熔融共聚时间等因素对产物特性粘数的影响．结果表明：以氯化亚锡（用量为0．5％（质量分数））为催化剂,外消旋乳酸（dl-LA）和CL以3：7（摩尔比）投料,将dl-LA和CL在180℃、70Pa下直接熔融共聚12h,可获得特性粘数为0．4733dL／g的聚（己内酯-乳酸）[P（CL-co-dl—LA）];将左旋乳酸（l-LA）和CL在同样条件下直接熔融共聚16h,可获得特性粘数为0．4121dL／g的聚（己内酯-乳酸）[P（CL-co-l-LA）]．与丙交酯开环聚合二步法相比,LA与CL直接熔融共聚的合成工艺简单易行．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that