偶联剂KH和聚合物PVA在硫铝酸盐—MDF水泥中的作用机理

以硫铝酸盐水泥为基材，采用有机聚合物ＰＶＡ，并且在ＭＤＦ水泥中添加偶联剂ＫＨ，制备出抗折强度大于１７０ＭＰａ，抗压强度达２４０ＭＰａ的新型ＭＤＦ水泥。同时，借助于Ｘ射线光电子能谱分析（ＸＰＳ），红外光谱分析（ＩＲ）等测试手段研究了偶联剂ＫＨ和聚合物ＰＶＡ的硫铝酸盐－ＭＤＦ水泥中的作用机理。     

应用带HSV－TK基因的重组腺病毒的肺癌基因治疗的研究

带有单纯疱疹病毒脱氧胸苷激酶基因（ＨＳＶ－ｔｋ）的腺病毒结合ｇａｎｃｉｃｌｏｖｉｒ（ＧＣＶ）对分裂细胞有很强的杀伤作用。本文报道在感染复数（Ｍ．Ｏ．Ｉ,ＭｕｌｔｉＰｌｉｃｉｔｙｏｆＩｎｆｅｃｔｉｏｎ）达到１０００时对人体肺腺癌细胞Ａ５４９的杀伤几乎达到回１００％。四种人体肺癌细胞株（Ａ５４９,ＬＡＸ,ＳＰＣ,ＳＫＹ）对带ＨＳＶ－ｔｋ的腺病毒（ＡＤＶ／ＲＳＶ－ｔＫ）的杀伤作用表现不同的敏感性。另外,Ａｃｙｃｌｏｖｉｒ（ＡＣＶ）和ＧＣＶ对感染了重组腺病毒ＡＤＶ／ＲＳＶ－ｔＫ的细胞都有一定杀伤作用,但杀伤效果有很大差别;就Ａ５４９而言,ＧＣＶ的杀伤作用比ＡＣＶ高７—８倍。此外ＡＤＶ／ＲＳＶ－ｔｋ结合ＧＣＶ杀伤肿瘤细胞时有“旁观者效应”,即感染了ＡＤＶ／ＲＳＶ－ｔｋ的细胞与未感染细胞混合后,后者也明显地遭到杀伤。     

石墨－MDF水泥基复合材料屏蔽电磁波性能

研究了石墨、聚合物（ＰＶＡ）及材料厚度对石墨－ＭＤＦ（Ｍａｃｒｏ－Ｄｅｆｅｃｔ－Ｆｒｅｅ）水泥基复合材料屏蔽电磁波性能的影响及其机理．结果表明；当石墨添加量超过１８ｖ．％时，材料对２００—１６００ＭＨｚ的电磁波有１０—４０ｄＢ的衰减效果，屏蔽效率Ｓ随材料中聚合物增加而降低，随材料厚度增加而升高，随电磁波的频率ｆ的增加有升高的趋势．当石墨在水泥基体里形成导电网络时，材料的电阻车ρｖ发生显著变化，即出现渗滤阈值（ＰｅｃｏｌａｔｉｏｎＴｈｒｅｓｈｏｌｄ）现象后，具有较好的屏蔽性能，屏蔽电磁波主要以吸收电磁波为主．     

理光XR－X3PF手动聚焦单反相机

理光ＸＲ－Ｘ３ＰＦ手动聚焦单反相机蒋宁在内置自动输片装置的手动聚焦３５ｍｍＳＬＲ中，功能较为齐全的有康泰克斯（ＣＯＮＴＡＸ）１６７ＭＴ、佳能（ＣＡＮＯＮ）Ｔ９０、企能（ＣＨＮＯＮ）ＣＰ—７Ｍ、尼康（ＮＩＫＯＮ）Ｆ—６０１Ｍ、以及理光（ＲＩＣＯＨ）ＸＲ...     

石墨—MDF水泥基复合材料屏蔽电磁波性能

研究了石墨、聚合物（ＰＶＡ）及材料厚度对石墨－ＭＤＦ（Ｍａｃｒｏ－Ｄｅｆｅｃｔ－Ｆｒｅｅ）水泥基复合材料屏蔽电磁性能的影响及其机理。结果表明：当石墨添加量超过１８ｖ．％时，材料对２００１６００ＭＨｚ的电磁波有１０－４０ｄＢ的衰减效果，屏蔽效率Ｓ随材料中聚合物增加而降低，随材料厚度增加而升高，随电磁波的频率ｆ的增加有升高的趋势。当石墨在水泥基体里形成导电网络时，材料的电阻率ｐｖ发生显著变化，即出现渗     

超高压处理HDPE的微硬度及DSC研究

用维氏微硬度测定仪和ＤＳＣ对超高压自理的ＨＤＰＥ进行了研究。发现随着处理压力的增大,ＨＤＰＥ的微硬度ＨＶ）提高,在处理时升高温度（ＴＣ）,更有利于ＨＶ的提高。当Ｐｃ＝４．０ＧＰａ,Ｔｃ＝１８０℃时,ＨＶ达最大值１７８．４ＭＰａ,比处理前的的７２．５ＭＰａ提高了１４６％,ＤＳＣ结果表明,ＨＤＰＥ经超高压处理后,结晶度增大,而且除了在１３２℃出现１个普通的强度较大的融吸热峰外,还在１３４℃处附近出现１     

新型渗透汽化透水膜的研制（II）：膜的结构和性能

确定聚合物共混的相容性最常用的方法是通过测定共混物的玻璃化转变温度（Ｔｇ），本文利用ＤＳＣ－７（Ｅｐｓｏｎ）测定了不同共混比的ＰＶＡ，ＣＳ共混物的玻璃化转变温度，结果表明ＰＶＡ，ＣＳ之间有良好的相容性。本文利用扫描电子显微镜（ＳＥＭ），红外光谱（ＩＲ）和Ｘ－射线衍射（ＸＲＤ）等现代分析仪器，对研制的多元酸交联的ＰＶＡ－ＣＳ／ＰＳＦ膜结构进行了观察测试，探讨了膜结构与性之间的关系。     

照相机使用二则

照相机使用二则章玉梅如何使用两段式自动调焦照相机最近几年，很多中、低档自动照相机使用可见光两段式自动调焦机构。我国市场上“拍得丽”ＰＣ－８００，ＰＣ－８００Ｄ，“享利”（ＨＡＮＩＭＥＸ）３５ＲＡＦ，“西马克”（ＣＩＭＡＲＫ）Ｂ－１０ＡＦ，卡蒙（ｃａｍ...     

聚苯胺复合导电膜的制备

报导了经苯胺溶胀后的聚乙烯醇（ＰＶＡ）薄膜与酸性三氯化铁水溶液氧化聚合制备出聚苯胺／聚乙烯醇（ＰＡｎ／ＰＶＡ）复合导电膜。复合膜的表面电阻率可达１０１（Ω·ｃｍ），拉伸强度为２０ＭＰａ，断裂伸长率为１２７％。并通过ＸＰＳ及ＳＥＭ对膜的表面形貌及微观结构进行了研究。     

一个编码XAP2同源蛋白的人视网膜cDNA的克隆

用同源筛选法从人视网膜ｃＤＮＡ分子库中克隆到一个与ＸＡＰ２ｃＤＮＡ有高度同源的ｃＤＮＡ序列,长１３８６ｂｐ,其第１７—１１７１ｎｔ为一个完整的开放阅读框（ＯＲＦ）,编码３８４个氨基酸,其Ｃ端较ＸＡＰ２长５５个氨基酸;３ＵＴＲ长２１８ｂｐ,１３５５—１３６０ｎｔ为加尾信号序列ＡＡＴＡＡＡ,１３７７—１３８６ｎｔ为ＰｏｌｙＡ序列。由该ｃＤＮＡＯＲＦ推导的蛋白质被命名为ＡＩＰＨ,它在ＧｅｎＢａｎｋ的登录号为：ＡＦ０３８４３７。它与ＸＡＰ２的氨基酸一致率为４２％,相似率为６１．７％。计算机分析结果显示：推导的ＡＩＰＨ蛋白与乙肝病毒Ｘ蛋白（ＨＢＸ）有三个较高同源的区域。其中两个对应于ＨＢＸ的反式转录激活功能结构域。ＡＩＰＨｃＤＮＡ与人体１６种组织ｍＲＮＡ的Ｎｏｒｔｈｅｒｎ杂交结果显示：这个来源于视网膜的转录本也可在骨骼肌和心脏中见到,杂交带长度约１．９Ｋｂ;此外在骨骼肌和心脏及其它１４种组织中还可见到另一个长约５．８Ｋｂ的杂交带     

State of the art of macro-defect-free composites

Macro-defect-free (MDF) composites, developed and patented by scientists from Imperial Chemical Industries in the early 1980s, are very high strength cement–polymer composites. The preparation of MDF composites is different from the production of conventional cement paste in that high shearing with a roller mill as well as moderate pressure (about 5 MPa) and moderate temperature (about 80–100 °C) are applied during the production. Very low water/cement ratio (w/c) levels are achieved (as low as 0.10) in this composite, much lower than in other cement-based materials. Of the many unique properties exhibited by MDF composites, surely the most remarkable is their high flexural strength. This is generally attributed to their low porosity and to cross-linking reactions between cement and polymer. MDF composites may reach a flexural strength of 200–300 MPa levels, whereas ordinary cement pastes have generally around 5–10 MPa. However, serious durability problems are observed in MDF composites, particularly their significant reductions in strength when immersed in water. Comprehensive information about MDF composite research will help in understanding the reasons behind the high strength, microstructure and water sensitivity of MDF composites. This review summarizes the materials, production methods, properties, microstructure, hydration reactions, durability and potential application areas of MDF composites as published since 1981.     

High strength cement pastes

A study of the chemical reactions occurring in high strength cements is presented with particular reference to the cement-polymer interaction. The addition of small amounts (1.6%) of polyvinyl (alcohol/acetate) to the high alumina cement Secar 71 significantly retards the normal hydration reactions. At much larger doses (10% PVA) the crystalline hydrates are completely suppressed and the polymer reacts with the cement solution to form calcium acetate and a crosslinked polymeric product. In the case of high strength OPC/polyacrylamide pastes, the high pH of the cement solution converts the polymer to polyacrylic acid which reacts with the cations from the hydrated cement to form a crosslinked metal-polyacrylate. This latter system is analogous to reactions which occur in certain polyacrylic acid-based dental cements.     

Optimization of material characteristics of macro-defect free cement

Macro-defect free (MDF) cement is a high-strength cement-polymer composite produced by mixing cement (commonly calcium aluminate cement) with small amounts of polymer (commonly polyvinyl alcohol acetate) and water, applying high shear, and finally applying relatively low pressure (about 5 MPa) and modest temperature (about 80-100 °C). However, MDF cements lose considerable strength when exposed to water. The objective of this study was to explore the effects of cement and polymer compositions on flexural strength and water sensitivity. Calcium aluminate cements were used with Al₂O₃ contents between 42% and 79%. Production of MDF cement was successful with all cements, but the highest strength (268 MPa) was obtained with 70% Al₂O₃ cement. Secondly, PVAs were used that differed in their degree of hydrolysis between 73% and 99%. Of these, the one with a moderate degree of hydrolysis produced the highest strength (228 MPa). All mixtures had strength loss on exposure to water, but PVAs with moderate degrees of hydrolysis exhibited the lowest strength losses (50-60%).     

植物纤维增强PS木塑复合材料的性能研究

以木纤维、竹纤维和聚苯乙烯为主要原料,加入偶联剂、润滑剂、增塑剂等加工助剂,经挤出注塑制备聚苯乙烯/木纤维复合材料。研究了植物纤维种类和添加质量分数、偶联剂KH-550添加质量分数对PS木塑复合材料力学性能的影响。结果表明：木纤维和偶联剂的加入都使复合材料的力学性能呈先增大后减小的趋势。当木纤维添加质量分数为25%,偶联剂KH-550添加质量为木纤维添加质量的1.5%时,复合材料具有最大的拉伸强度、弯曲强度和断裂伸长率,分别为30.2MPa,86MPa和8.74%,缺口冲击强度随木纤维添加质量分数的增加而减小。木纤维和竹纤维填充的两种复合材料的拉伸强度、弯曲强度和冲击强度相差不大。     

HAC/PVA基MDF材料中偶联剂作用机理研究

研究了在HAC/PVA基MDF复合材料中掺入硅烷偶联剂对其抗折性能和耐水性的影响,并用XPS方法研究了γ-甲基丙烯酰氧基丙基三甲氧基硅烷(A-174TM)与铝酸一钙(CaAl₂O₄)之间所进行的化学反应,据此探讨硅烷偶联剂在MDF复合材料中的增强与改善耐水性的机理。     

Stability of macrodefect-free cement

Abstract

The effect of water immersion on the strength and dimension stability of macrodefect-free (MDF) cement has been studied. The results show that the polymer phase in the MDF matrix is unstable in water. Prolonged immersion resulted in substantial expansion and leaching of the matrix. Microstructural changes were examined by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. The cause of weakening of the matrix is thought to be the modification of the cement/polymer interface through the hydration of anhydrous grains. Methods of improving the performance of MDF pastes in water have been considered.

MST/692     

Mechanism of cement paste reinforced by ultra-high molecular weight polyethylene powder and thermotropic liquid crystalline copolyester fiber with enhanced mechanical properties

In this study, a series of cementitious composites with high toughness and flexural strength was obtained by melt-dispersing ultra-high molecular weight polyethylene (UHMWPE) into a cement matrix followed by water immersion. The structure and chemical composition of the composites were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Three point bending tests showed that the flexural strengths of the composites were improved from 5.5 MPa to 18.2 MPa with the presence of 25 wt% UHMWPE, and could be further enhanced to 28.1 MPa with the addition of only 0.1 vol% oriented thermotropic liquid crystalline copolyester (TLCP) fibers. An adhesive test revealed that the interfacial binding force between polymer and fiber was much stronger than that between cement and fiber. Our findings provide a simple way for utilizing polymer to improve the interface between the fibers and cement matrix, consequently achieving a dramatic increase in the flexural strength and toughness.     

标准养护条件下铁尾矿制备RPC力学性能研究

标准养护条件下,采用固体废弃物铁尾矿砂代替石英砂设计制备RPC,研究其引入对RPC工作性能、强度和弯曲韧性的影响,通过XRD和SEM研究其对RPC水化反应和微观结构的影响。结果表明,标准养护条件下,铁尾矿砂RPC28d抗压强度和抗弯拉强度可分别达到117.5 MPa和24.2 MPa;铁尾矿砂的引入可降低RPC流动度、抗压强度和抗弯拉强度;采用美国ASTM C1609和日本JCI SF4评价测试铁尾矿砂RPC弯曲韧性,韧性指数I₁₀和σ_b分别为石英砂RPC的78.0%和77.8%;微观分析表明,少量铁尾矿砂对RPC内部水泥水化反应影响并不明显,继续增加铁尾矿砂的量会对水化反应产生不利影响。     

基于水泥水化度的混凝土早期力学性能发展预测

实验测量了3个强度等级混凝土(28d抗压强度分别为30MPa,50MPa和80MPa左右)在不同养护条件下典型龄期的P-CMOD曲线,借助断裂力学方法,获得了相应的混凝土开裂强度、抗拉强度和抗弯强度及其随龄期的发展规律,分析了养护条件对混凝土力学性能发展的影响。考虑混凝土内部湿度对水泥水化度的影响,对干燥环境下水泥水化度进行了修正,建立了基于水泥水化度的混凝土开裂强度,抗拉强度和抗弯强度的预测模型。