生物医用微孔高分子涂层的制备及其初始降解形貌的研究

主要研究了316L不锈钢基体表面微孔聚丙交酯/乙交酯(PLGA)高分子载药涂层的制备技术,探索出空气湿度、温度、涂膜液的浓度等参数对涂层表面的孔径影响的规律,制备出孔径均匀的不锈钢表面PLGA涂层,并对微孔涂层在人工模拟体液(hank's溶液)中的初始降解(3个星期)形貌进行了考察,从而为开发心血管介入治疗不锈钢支架上的微孔载药涂层技术奠定基础.     

冠脉支架表面PLGA涂层制备及其血液相容性研究

采用静电喷涂沉积(electrospray deposition ESD)法在冠脉支架表面制备了PLGA涂层.采用OLYMPUS体式显微镜、原子力显微镜(AFM)观察了涂层宏观表面形貌及三维形貌;通过对涂层支架进行球囊扩张考察了PLGA涂层与支架的结合力;通过血小板粘附实验和动态凝血时间测定研究PLGA涂层的血液相容性.结果表明:ESD法在冠脉支架表面制备PLGA涂层,支架筋拐角处无明显的聚合物胶体缠绕、粘连且涂层表面光滑;PLGA涂层将316L不锈钢基体的微坑覆盖,基体Ra=16.174nm,PLGA涂层Ra=0.149nm,涂层表面粗糙度小;涂层支架撑开后在最大塑性变形位置无涂层撕裂、翘起等缺陷,涂层与支架有良好结合力;PLGA涂层血小板粘附量少,变形小,未引起血小板激活,动态凝血时间长,直到50min未产生凝血,PLGA涂层具有较好的血液相容性.     

地塞米松-乙交酯丙交酯共聚物作为药物洗脱支架的涂层研究

采用溶液浇注法制备了以乙交酯丙交酯共聚物(PLGA)为载体、地塞米松为药物的载药薄膜。傅立叶红外光谱(FT-IR)结果显示地塞米松被有效地分散在PLGA中;水接触角测试结果表明相比于PLGA薄膜,地塞米松的引入增加了薄膜的亲水性。载药薄膜的体外药物释放行为表明地塞米松存在突释现象,6d后呈现出较好的线性释放特征。体外生物学评价表明装载地塞米松的PLGA表面既对血小板的粘附与激活具有一定的抑制作用,又显著地抑制平滑肌细胞的粘附与增殖。采用超声雾化喷涂法制备了地塞米松药物洗脱支架,扫描电镜观察表明支架表面涂层光滑均匀且连续,支架撑开后没有产生剥落和裂纹。     

金属表面聚合物涂层在模拟体液中的失效

使用硅烷偶联剂在316L不锈钢管及用于介入治疗的血管内支架上面用浸涂与喷涂两种方法制备高分子涂层.在PLGA溶液中介入少量偶联剂制备涂层,与不加偶联剂的涂层进行对比,并用体外循环冲刷的方法对制备的聚合物涂层支架进行评价,对其动态降解过程及失效机制进行分析.     

含氟聚合物在溶液中的聚集行为与其固化后表面性质

含氟高分子材料的优异表面性能主要依赖于含氟组分在表面的富集和排列。高分子溶液经常用来制备各种材料,在固化过程中含氟高分子在溶液缔合状态影响含氟组分在表面的富集。文中主要综述了含氟组分组成、结构、溶剂等对含氟聚合物分子在溶液中聚集形态的影响,以及聚合物聚集形态对其固化后表面结构性能影响的研究进展。     

等离子体处理乙丙交酯共聚物表面固定胶原的研究

选择等离子体对乙丙交酯共聚物(PLGA)表面进行活化处理来接枝胶原.通过测定等离子体处理后PLGA材料表面水接触角确定最佳处理功率为60W,时间5min.XPS分析确定胶原表面的羧基与PLGA表面等离子体激活的羟基发生了反应生成酯基,而使胶原接枝到PLGA表面.选用小鼠胚胎内皮成纤维细胞(3T3)在PLGA材料表面培养...     

在类仿生溶液中电沉积羟基磷灰石涂层的性能

在类仿牛溶液中用电沉积法在阳极氧化处理后的钛基体上电沉积均一的羟基磷灰石涂层,研究了阳极氧化处理后对HA涂层耐蚀性能、沉积效率和结合强度的影响.结果表明:用该方法沉积的HA涂层结构单元的排列与人骨类似,具有优良的生物诱导性能.经过阳极氧化后钛表面生成均匀的纳米孔洞结构,增强了与HA涂层的机械结合和涂层的阻抗值,提高了涂层的结合强度和耐腐蚀性能.同时,在类仿生溶液中二氧化钛吸附羟基,通过库仑力和氢键作用大大提高了沉积效率,并因其纳米孔洞结构促进HA的形核,形成更加细小、致密的针状HA晶体结构,提高了涂层的结合强度和耐腐蚀性能.     

表面预氧化镍钛丝微弧氧化涂层的研究

通过微弧氧化法(MAO)在表面预氧化镍钛(NiTi)丝(直径(0)0.5mm)表面制备含Ca、P的均匀微孔涂层,对不同处理时间形成的涂层进行扫描电镜(SEM)形貌观察和电子探针(EPMA)成分分析,并探查了涂层的血液相容性.实验结果表明,表面预氧化的NiTi丝在微弧氧化处理时,随微弧氧化时间的延长,氧化层中Ti/Ni提高,Ca、P含量也提高.微弧氧化20s时,涂层质量较好,微孔均匀分布,微孔孔径1μm左右,表面没有裂纹,而且此时涂层有较好的生物相容性.     

PLGA携载紫杉醇涂层包被TiNi合金的表面特性与生物性能

系统研究了PLGA携载紫杉醇包被TiNi合金的表面特性与生物性能。采用原子力显微镜(AFM)和X射线光电子能谱(XPS)研究了药物涂层的表面形貌及化学成分;采用高效液相色谱(HPLC)研究了在pH为7.4的PBS溶液中紫杉醇从TiNi合金表面涂层中释放特性,并通过血小板粘附试验研究了药物涂层的血液相容性。试验结果表明经涂覆后TiNi合金表面化学组成及结构随着载药量的增加而改变。紫杉醇在涂层降解初期释放较快,随着时间的延长,累积释放量增加缓慢。血小板粘附试验表明载药量为0%、10%、20%和30%时涂膜样品表面血小板粘附数量均小于未涂膜样品表面。而随着载药量的增加,涂膜样品表面粘附的血小板数量增加,血小板变形严重,当载药量为30%时,血小板出现明显的聚集现象。     

聚丙交酯-乙交酯聚合物(PLGA)涂层体外降解行为研究

为了防止心血管支架植入后再狭窄的发生,目前采用将抑制平滑肌细胞生长的药物通过高分子载体涂在支架表面.由于支架植入体内后,涂层受到血液冲刷作用.本工作采用可降解高分子材料PLGA作为载体,将PLGA薄膜置于体外循环冲刷装置中,在37℃、pH7.4的Hank's模拟体液、模拟血流冲刷作用下的体外降解,并与静态降解作为对比.采用SEM、GPC、1H-NMR和DSC技术研究了聚合物在降解过程中形貌、分子量及分子量分布、失重率、组成和热性能的变化,并对降解机理进行探讨.与静态降解相比较,在流动体液中,高分子载体表面形貌、失重率以及分子量变化均较慢.上述结果与表面微环境有关.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...