MPEG-PLLGA多孔支架制备影响因素研究

采用热致相分离法制备了MPEG-PLLGA(单甲氧基聚乙二醇-聚左旋丙交酯乙交酯)多孔支架。讨论了丙交酯/乙交酯(LA/GA)配比、聚合物质量浓度、预冻温度等因素对支架的孔径、孔隙率和力学性能的影响。结果表明,当聚合物质量浓度为0.03g/mL时,不同n(LA)/n(GA)比的MPEG-PLLGA支架的孔形貌相差较大,而当聚合物质量浓度为0.04g/mL和0.05g/mL时,3种n(LA)/n(GA)比的MPEG-PLLGA支架的孔形貌和孔径没有明显差异,且在相同聚合物质量浓度下,随着n(LA)/n(GA)比升高,所得支架的压缩强度增大;随聚合物溶液质量浓度的提高,3种n(LA)/n(GA)比支架的孔隙率、孔径均呈变小趋势,压缩强度逐渐增大;随预冻温度的降低,所得支架的孔径、孔隙率逐渐变小,压缩强度逐渐增大。     

采用聚醚酯制备多孔支架的条件控制

采用热致相分离(TIPS)结合冷冻干燥技术制备了聚醚酯(聚对苯二甲酸丁二醇酯-co-聚对苯二甲酸环己烷二甲醇酯-b-聚乙二醇)(PTCG)多孔支架,研究了聚合物质量浓度、粗化温度和溶剂组成等相分离参数对多孔支架形貌结构的影响.结果表明,制备出的多孔支架孔间相互贯通,支架表面(与空气接触面)的孔径大于底面(与玻璃接触面)的孔径;随着聚合物质量浓度的增大,支架的孔径和孔隙率减小.由于分相过程中热力学推动力增大和相区融合阻力增加的相互作用,孔径随着粗化温度的降低呈现先升后降的趋势,并在0℃时出现最大值.在DO中加入不良溶剂H2O,溶液分相温度的升高导致多孔支架孔径的增大.通过控制相分离参数可以制备不同形貌结构的PTCG多孔支架.     

聚-DL/L-丙交酯(30DL/70L)纳米纤维的电纺研究

对生物可吸收聚-DL/L-丙交酯(30DL/70L)体系进行了静电纺丝.研究了聚-DL/L-丙交酯(30DL/70L)的浓度,加料速度,电压,喷头与接收体之间的距离等因素对纤维形态的影响,制备出纳米纤维膜,并用扫描电镜(SEM)等对纤维膜进行表征.结果表明,电纺溶液浓度和溶剂对纤维直径影响比较明显,减小电纺溶液浓度和采用复合溶剂CHCl3/DMF可得到更细的纳米纤维;一定范围内适当的增加电压、减小距离和减小加料速度有利于减小纤维直径.在聚-DL/L-丙交酯(30DL/70L)浓度为5g/100mL溶剂、加料速度1mL/h、喷头与接收体之间的距离6cm、电压15kV电纺条件下,可制备直径50nm左右的聚-DL/L-丙交酯(30DL/70L)纳米纤维膜.     

水辅助法制备左旋聚乳酸/聚乙烯醇复合多孔膜及其力学性能

以左旋聚乳酸(PLLA)/聚乙烯醇(PVA)为成膜材料,利用水辅助法制备了PLLA/PVA复合多孔膜。研究了溶剂及其组成、环境湿度和聚合物浓度对形成多孔膜的形貌影响。筛选出可完全溶解PLLA/PVA体系的二甲亚砜(DMSO)/二氯甲烷(DCM)混合溶剂。V(DMSO)/V(DCM)=1/9为溶剂得到孔径大小为(2.45±0.31)μm的规整蜂窝孔,且随着DMSO含量增多,孔径变小,孔分布变得无序。环境湿度从43%增加到91%,孔径大小由(1.43±0.63)μm增加到(4.30±0.63)μm,孔径与环境湿度基本上呈现一阶线性关系。与纯PLLA多孔膜相比,PLLA/PVA复合多孔膜的拉伸强度和断裂伸长率分别从33.32MPa和12.46%增加到40.66MPa和32.57%。PLLA/PVA复合多孔膜有利于细胞的粘附与生长,因而有望作为组织工程支架材料。     

聚己内酯多级孔径支架的相分离/盐析复合工艺研究

采用相分离和盐析复合工艺,通过改变冷却温度、溶液浓度、溶剂/水比例、造孔剂用量等工艺制备聚己内酯多孔支架,通过扫描电镜观察支架形貌,采用压汞仪测量支架孔隙率及孔径,研究各工艺条件对支架多级孔径结构的影响.研究表明冷却温度-70℃、PCL溶液浓度10%、溶剂/水比例95/5、80%质量含量的粒径100～200μm NaCl造孔剂为最佳实验条件,可制备出具有100～350μm大孔、5～30μm小孔及＜10nm微孔的聚己内酯复合多级孔径支架,孔隙率高,连通性好,可应用于骨组织工程支架.     

分级多孔结构聚乳酸支架的制备与性能研究

以左旋聚乳酸为原料,1,4-二氧六环/水为溶剂,采用热致相分离法制备了具有分级多孔结构的组织工程支架。研究了溶剂配比、粗化时间对支架结构和性能的影响。溶剂比为87/13(1,4-二氧六环/水),PLLA浓度5%,粗化1h时,制备出大孔孔径达300μm,小孔嵌在大孔孔壁上且孔径在10μm以下的高连通分级多孔支架。粗化时间的延长使大孔孔径有所增大。细胞实验表明分级多孔支架有助于细胞长入支架内部,促进细胞的增殖。     

聚乳酸立构复合物规整度对其降解性能的影响

通过开环聚合法,利用D,L-丙交酯合成不同规整度(XD)的左旋聚乳酸PLLA和右旋聚乳酸PDLA。用溶液浇铸法制得不同规整度的聚乳酸立构复合物SC-PLA,并在50℃缓冲溶液中进行降解。通过分析剩余质量、溶液pH值、热性能(DSC)、表面形貌(SEM)、电离子喷雾质谱(ESI-MS)等评价SC-PLA的降解性能。结果表明:相同规整度时,SC-PLA降解速率小于PLLA,但pH值变化大于PLLA,立构复合物SC的存在使材料比常见PLLA更耐水解;立构规整度下降会使SC-PLA的结晶度降低,材料的降解速率加快;降解使材料的结晶度上升,立构复合物晶体SC与均聚物晶体HC熔点降低;高规整度SC-PLA相对于相同规整度PLLA及低规整度SC-PLA,其降解产物分子链长度更短。     

聚乳酸和聚己内酯共混物多孔支架超临界流体技术制备

以二氯甲烷作为聚合物溶剂,利用超临界CO_2诱导相分离-循环干燥过程制备了质量比为1∶1的聚乳酸和聚己内酯混合物组织工程用多孔支架,同时考察了过程操作压力和温度、溶液浓度、CO_2流量及循环干燥时间等操作参数对孔径大小和形态的影响。结果表明,溶液浓度、操作压力和温度及CO_2流量对孔结构的影响较大。溶液浓度增大、操作温度升高均会引起混合物支架孔径的减小。操作压力升高,混合物多孔支架孔径逐渐增大,孔径分布越来越不均匀。随CO_2流量升高,混合物支架的孔径不断减小。循环干燥时间虽然对混合物支架的孔结构影响不大,但对超临界CO_2诱导相分离-循环干燥过程的可实现性有重要的影响。实验范围内,当混合物溶液浓度为25%(质量分数),循环干燥用CO_2流量为31kg/h,操作压力和温度分别为12 MPa和45℃的操作条件下,制备的混合物多孔支架更有利于组织工程的应用。     

单一热致相分离法制备聚乳酸纳米纤维大孔支架

在不结合其它致孔方法的条件下,基于单一的热致相分离的方法,采用聚左旋乳酸(PLLA),二氧六环,水三元体系,测量了体系的浊点和凝胶点,并在此基础之上系统地研究了溶液浓度,溶剂配比,凝胶温度,凝胶时间对支架大孔,纳米纤维的影响,在质量分数为5%,m(溶剂配比二氧六环)/m(水)=87/13,凝胶温度25℃,凝胶时间15min的条件下,制备了含有100μm以上大孔,同时孔壁上分布均匀的纳米纤维的PLLA支架,孔隙均匀,连通性很好。     

PLA-PEG共聚物三维多孔支架的制备及表征

将D,L-丙交酯(D,L-LA)与聚乙二醇(PEG)共聚制备了一系列共聚物,并用IR、GPC和1H-NMR对其进行了表征.在此基础上,采用溶剂浇铸-柱子沥滤技术和层叠技术制备了具有一定空间形状的三维多孔组织工程支架,并研究了致孔剂颗粒尺寸及其用量对多孔支架的孔径、孔隙率的影响.结果表明,PLA-PEG共聚物的分子量随着原料中PEG含量的增加而减小;以PLA-PEG共聚物为原料制备多孔支架时,孔径的大小与致孔剂颗粒尺寸有一定的对应关系,孔隙率随着致孔剂用量的增加而增加;采用层叠技术制备的具有一定形状的三维多孔支架符合组织工程对支架材料的一般要求.     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

Development and challenges of planning and scheduling for petroleum and petrochemical production

Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint.     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

Error and uncertainty in modeling and simulation

This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics.     

Density and viscosity of tetralin and trans-decalin

New measurements are reported for the density and viscosity of tetralin and trans-decalin. The density was determined from room temperature to 60°C for tetralin and to 95°C for trans-decalin. The kinematic viscosity was measured up to temperatures slightly above 100°C. Our results improve upon the values recommended by the American Petroleum Institute for these liquids.     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

SMC／BMC的回收与再利用

SMC／BMC废弃物对工业及环境造成了很大影响，指出了SMC／BMC回收再利用的紧迫性。通过对目前国际上SMC／BMC回收再利用的3种典型途径优缺点的对比，参照国外SMC／BMC回收再利用的先进方法，对我国SMC／BMC回收再利用提供了可行的建议．     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.