Synthesis,characterization, and antitumor activity of poly(maleic anhydride‐co‐vinyl acetate‐co‐acrylic acid)

The ternary copolymerization of maleic anhydride (MA), vinyl acetate (VA), and acrylic acid (AA) [P(MA‐co‐VA‐co‐AA)], which is considered to be an acceptor–donor–acceptor system, was carried out in 1,4‐dioxane with benzoyl peroxide as an initiator at 70°C under a nitrogen atmosphere. Constants of complex formation for the monomer systems in the study were determined by UV–visible (hydrogen‐bonding complex) and ¹H‐NMR (charge transfer complex) methods, respectively. The results show that polymerization of the P(MA‐co‐VA‐co‐AA) system proceeds by an alternating terpolymerization mechanism. It is shown that the synthesized copolymers have typical polyelectrolyte behavior, ability for reversible hydrolysis–anhydrization reactions, and semicrystalline structures. In these cases, including radical polymerization, and formation of semicrystalline structures, the hydrogen‐bonding effect plays a significant role. The in vitro cytotoxicities of the synthesized terpolymer and alternating copolymer were evaluated using Raji cells (human Burkitt lymphoma cell line). The antitumor activities of prepared anion‐active copolymers were studied using methyl–thiazol–tetrazolium colorimetric assay and 50% of the cytotoxic dose of each copolymer and terpolymer were calculated. Hydrolyzed P(MA‐co‐VA‐co‐AA) and P(MA‐alt‐AA) copolymers have sufficiently high antitumor activity, which depends on the amount of hydrogen‐bonding carboxylic groups and their regular distribution in the side chain of functional macromolecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3425–3432, 2006     

Ribosome display of mammalian receptor domains

Many mammalian receptor domains, among them a large number of potential therapeutic target proteins, are highly aggregation-prone upon heterologous expression in bacteria. This severely limits functional studies of such receptor domains and also their engineering towards improved properties. One of these proteins is the Nogoreceptor, which plays a central role in mediating the inhibition of axon growth and functional recovery after injury of the adult mammalian central nervous system. We show here that the ligand binding domain of the Nogoreceptor folds to an active conformation in ternary ribosomal complexes, as formed in ribosome display. In these complexes the receptor is still connected, via a C-terminal tether, to the peptidyl tRNA in the ribosome and the mRNA also stays connected. The ribosome prevents aggregation of the protein, which aggregates as soon as the release from the ribosome is triggered. In contrast, no active receptor was observed in phage display, where aggregation appears to prevent incorporation of the protein into the phage coat. This strategy sets the stage for rapidly studying defined mutations of such aggregation-prone receptors in vitro and to improve their properties by in vitro evolution using the ribosome display technology.     

森林生态税收体系研究现状

由于森林生态系统具有正的外部性,对其生态效益进行补偿就成为必须要考虑的问题。森林生态税作为一种为森林生态效益补偿筹集资金的手段,在发达国家已经有着不错的实施效果,而在我国基本上还处于空白。本文回顾了国内外对于森林生态税收体系的研究进展,比较了国内外在这一领域研究的异同,提出了在我国进行森林生态税研究的一些建议和看法。     

可控特征点对以及RANSAC的监视系统外参估算方法

为了提高基于机器视觉的监控系统的精度,立体视觉信息作为一种鲁棒性很高的参数被引入监控算法中.立体视觉信息的引入使得外参求解成为影响监控结果的一个重要环节.现存的应用于监视系统的外参自动估算方法均采用立体视觉中外参求解的方法.这些方法普遍存在特征点的数目完全由场景决定特点.为了解决在大部分监视系统应用的场景中,因为背景较为空旷、基线较长同时相机对之间的旋转量较大,由场景提供的特征点数量非常有限,导致计算结果并不理想这一问题,提出了一种基于视频序列的RANSAC外参求解方法.该方法不仅利用RANSAC算法有效的剔除外点,而且根据可控特征点对的动态性,利用时间上的积累获得了充足的位置可控、数量可控的可控特征点对,并据此得到精度较高的外参结果.根据实验,该方法可以将三维重建误差降低近50%.     

混凝土底板温度及温度应力影响参数分析

借助参数化设计语言(APDL)分析了水泥品种及标号、结构尺寸、外界约束对混凝土底板温度及温度应力的影响.结果表明:与普通硅酸盐水泥525相比,普通硅酸盐水泥425、矿渣水泥425可使底板最大拉应力分别减低约21%、37%;底板平面尺寸增大,压应力几乎保持不变,拉应力增大,发展较为平缓;底板厚度越大,出现最高温度的龄期越晚,底板降温时持续高温时间更长,且温度应力随厚度增大而增大.     

复杂环境下的施工项目管理探索

随着青岛城市建设的快速发展,旧城改造加速,一些城市多年的烂尾楼将逐个被解决.相应的如何解决在已建密集建筑群内进行施工管理的矛盾,就成了项目建设开发亟待解决的问题.由于新开发的项目在已成气候的中心商务区,项目施工将会受到很大的外部条件的限制,面临诸如：邻近建筑保护;地下室开挖的基坑边坡的安全问题;进出现场的土石方、建筑材料的管制;场地狭小布置临时设施及办公、宿舍困难;昼夜施工的扬尘、噪声扰民等等复杂环境.施工项目前期规划与预控制是在复杂环境下解决各种矛盾的重要方法.     

英屿沟Ⅱ号天桥的设计

为推广预应力混凝土箱梁结构在桥梁方面的应用研究,结合英屿沟Ⅱ号天桥实例,介绍了该组合结构在桥梁方面具体应用的设计思路,介绍了英屿沟Ⅱ号天桥波形钢腹板PC组合箱梁桥主梁结构、预应力体系、波形钢腹板、连接件、防腐、施工流程等的设计,为波形钢腹板PC组合箱梁结构应用于桥梁工程提供了设计经验.     

夏季极端环境下住宅墙体EPS保温体系热结构耦合分析

以居住建筑保温工程中一个典型开间的外墙为研究对象,采用有限元数值模拟方法,分析了EPS板薄抹灰外墙外保温复合墙体在夏季极端高温、骤降暴雨环境下的热结构耦合反应,结果表明:外界不利环境是引起裂缝或脱落的主要因素之一;聚苯板具有良好的隔热效果;窗洞四角变形较大,是容易出现问题的地方,应当引起重视;由于砂浆与EPS板的交界处变形不协调,裂缝会首先出现在砂浆层或者与EPS板的交界处.     

EPS板外墙保温系统的施工工艺

本文总结了EPS板薄抹灰外墙外保温系统施工工艺,根据施工程序提出了注意的事项、具体措施.     

等齿数平行轴外啮合同向传动齿轮的啮合传动分析

一种新型同向传动齿轮——平行轴外啮合同向传动齿轮的啮合传动原理.不同于传统齿轮,所研究的平行轴外啮合同向传动齿轮只需要2个齿轮就可以实现同向传动.采用机械原理分析方法对等齿数同向传动齿轮的正确啮合条件和连续传动条件进行了推导,并计算了重合度,最后给出同向传动齿轮的无侧隙啮合方程.研究结果表明平行轴外啮合同向传动齿轮可以实现同向传动.