Analyses of the mechanical properties and microstructure of bamboo epoxy composites

Bamboo reinforced epoxy possesses reasonably good properties to waarrant its use as a structural material, and is fabricated by utilizing bamboo, an abundant material resource, in the technology of fibre composites. Literature on bamboo-plastics composites is rare. This work is an experimental study of unidirectional bamboo-epoxy laminates of varying laminae number, in which tensile, compressive, flexural and interlaminar shear properties are evaluated. Further, the disposition of bamboo fibre, the parenchymatous tissue, and the resin matrix under different loading conditions are examined. Our results show that the specific strength and specific modulus of bamboo-epoxy laminates are adequate, the former being 3 to 4 times that of mild steel. Its mechanical properties are generally comparable to those of ordinary glass-fibre composites. The fracture behaviour of bamboo-epoxy under different loading conditions were observed using both acoustic emission techniques and scanning electron microscopy. The fracture mode varied with load, the fracture mechanism being similar to glass and carbon reinforced composites. Microstructural analyses revealed that natural bamboo is eligibly a fibre composite in itself; its inclusion in a plastic matrix will help solve the problems of cracking due to desiccation and bioerosion caused by insect pests. Furthermore, the thickness and shape of the composite can be tailored during fabrication to meet specific requirements, thereby enabling a wide spectrum of applications.

The influence of buoyancy on the oscillatory thermocapillary convection with small bond number

This work is an experimental study of unidirectional bamboo-epoxy laminates of varying laminae number, in which tensile, compressive, flexural and interlaminar shear properties are evaluated. Further, the disposition of bamboo fibre, the parenchymatous tissue, and the resin matrix under different loading conditions are examined. Our results show that the specific strength and specific modulus of bamboo-epoxy laminates are adequate, the former being 3 to 4 times that of mild steel. Its mechanical properties are generally comparable to those of ordinary glass-fibre composites. The fracture behaviour of bamboo-epoxy under different loading conditions were observed using both acoustic emission techniques and scanning electron microscopy. The fracture mode varied with load, the fracture mechanism being similar to glass and carbon reinforced composites. Microstructural analyses revealed that natural bamboo is eligibly a fibre composite in itself; its inclusion in a plastic matrix will help solve the problems of cracking due to desiccation and bioerosion caused by insect pests. Furthermore, the thickness and shape of the composite can be tailored during fabrication to meet specific requirements, thereby enabling a wide spectrum of applications.

酚醛树脂激波管试验的高温热解研究

使用激波管作为加热手段研究酚醛树脂在1200～1800K温度范围内的热解特征.气相产物中主要碳氢产物是甲烷、乙烯、乙炔、苯和甲苯.获得试验温度范围内主要碳氢产物分布随热解温度的变化关系.结果表明,在试验温度范围内随着热解温度的升高酚醛树脂的热解机理发生重大变化.1400K以下热解断键过程主要发生在亚甲基桥链结构上;1400K以上芳环开环成为主要的热解通道,生成大量的乙炔.

酚醛树酯的热解动力学模型

建立了一种利用热重峰值分析进行酚醛树酯热解动力学研究的方法,这种方法利用热重谱峰上几个特征点的数据来确定动力学参数.根据酚醛树酯热解DTG曲线的特点,把酚醛树酯的热解过程分解成三个阶段,用峰值分析法对每个反应阶段分别建模,通过三个反应阶段的叠加得到了一个酚醛树酯分阶段热解动力学模型,该模型能够很好地描述酚醛树酯的热解过程.

激波管在酚醛树脂高温热解动力学研究中的应用

使用激波管作为加热手段,利用其加热速率快的优点,突破了传统方法在加热速率上的限制,研究了酚醛树脂在1400～1700K温度范围内的热解动力学.主要碳氢产物是甲烷、乙烯、乙炔和苯.通过对反应扩散过程的分析,考察了扩散对热解过程的影响.结果表明,实验中酚醛树脂的反应扩散过程迅速达到稳态,扩散影响可以忽略,首次获得了酚醛树脂在芳环开环热解机制下的热解速率常数.

酚醛树脂高温热解的激波管实验研究

采用激波管方法研究了酚醉树脂在温度1100K～1800K范围之间的热解过程.在激波管高温和短实验时间条件下,分析了实验样品颗粒在高温气相中的传热过程,讨论了样品颗粒达到热平衡的条件.通过色谱和质谱方法检测热解产物,获得了酚醛树脂高温热解产物分布和热解速率常数.酚醛树脂高温热解最主要的产物为水、一氧化碳、氢、乙炔和苯.温度1400 K将酚醛树脂热解分为高温和低温区,分别表现出不同的热解速率常数与温度的关系.

植物结构专题研究

1． 裸子植物次生韧皮部中晶体的分布类型及其意义 应用偏光镜检术和扫描电境一一能谱分析等手段对1 1科30种裸子植物次生韧皮部中晶体的形状、大小、分布类型和化学成分进行了系统研究。结果发现，所有的观察种类都具有晶体，钙是晶体的主要成分。在苏铁科、银杏科和松科，晶体存在于韧皮薄壁组织细胞的胞腔中：在其他各科，晶体则主要存在于韧皮细胞的胞壁上;通常胞腔中的晶体通常比胞壁上的大．苏铁科、银杏科和松科的晶体形状分别足棱形晶体、晶簇和柱状晶体或方形晶体．其他各科的晶体形状均为沙晶，但分布的部位各不相同。在杉科、柏科、和罗汉松科的韧皮部中，品体主要嵌埋在各类细胞的径向壁上：在三尖杉科的韧皮部，晶体主要存在于部分薄壁组织细胞的弦向壁上：在红豆杉科（澳洲红豆杉属除外），晶体嵌埋在韧皮纤维的外侧壁上;在麻黄科、买麻藤科，晶体主要存在于薄壁细胞间的胞间隙中，偶尔也在薄壁组织细胞的内侧，但在裸子植物的韧皮部，未见典型的针晶。根据晶体的上述变化，将晶体分布类型分成棱形晶体在薄壁组织细胞腔内、簇晶在溥壁组织细胞腔内、柱形晶体在薄壁组织细胞腔内、沙品在韧皮细胞壁上、沙品在韧皮纤维壁上和沙晶在韧皮薄壁组织细胞间的胞间隙内等六大类型，并依此讨论了它们在裸予植物各类群中的分类意义． 在红豆杉科中，晶体仪存在于厚壁组织细胞类的韧皮纤维上。根据该五属韧皮纤维．L晶体的比较观察，发现红豆杉属、白豆杉属的韧皮纤维具六角形和方形两种晶体，穗花杉属和榧树属仅具方形一种晶体，澳洲红豆杉属不具晶体．从晶体的有无和晶体的类型，讨论了它们在红豆杉科各属间的分类意义． 2． 长苞铁杉的结构及其系统发育的研究 长苞铁杉足我国特有的珍稀濒危植物。自发现以来，其分类位置曾几度变迁．1931年，郑万钧将其归属于铁杉属。1948年，Gaussen ＆van Campo-Duplan认为它是云南油杉和铁杉的杂交种，主张建立铁油杉属(Ts uga -Keteleeria). 1951年，胡先驌认为长苞铁杉与其他铁杉区别明显，提出建立新属- Nothotsuga. 1957年，喻诚鸿根据木材解剖的结果，认为长苞铁杉木质部缺乏正常树脂道，与铁杉属没有本质上的区别，建议将它归人铁杉属．<<中国植物志>>第七卷设长苞铁杉组(Sect. Heopeuce)，与铁杉组(Sect. Tsuga)平行，同归于铁杉属。 本课题对长苞铁杉营养器官的结构做了研究，发现长苞铁杉成熟部位的次生木质部具正常树脂道，创伤树脂道除切向连续分布外还有单个独生的现象，早晚材过渡不明显，射线管胞不发达，交叉场纹孔以杉木型为主，韧皮部中具树脂腔(Resin caviLy)。叶片气孔雨面生，维管束鞘明显，细胞大小均匀，树脂道1个边生。 上述特征都与铁杉属存在明显区别，因而作者支持胡先驌(1951)、Frankis(1989)、Faljon(1990)等关于建立长苞铁杉属的主张。 3． 白皮松的结构及其系统发育的研究 按<<中国植物志>>第七卷的分类系统，白皮松隶属单维管束亚属白皮松组，但其对分类位置曾有不同看法． 本课题通过白皮松营养体结构的研究，发现它在许多方面与单维管束亚属的其他种类有显著差异，白皮松针叶的气孔分布于背腹雨面，气孔间连结细胞的雨侧具石细胞，副卫细胞为近四方形且数目比较恒定，角质层内表面具深波浪状的胞间凸缘：次生木质部的射线管胞内壁具微锯齿状突起，交叉场纹孔松木型，管胞内表面及纹孔部分具明显的瘤层结构;树皮薄，其最外侧仅保留一层周皮，无内皮外皮之分，外侧的韧皮薄壁组织细胞与射线有明显的扩展与弯曲现象，韧皮薄壁组织细胞中的晶体有长柱形和短柱形雨种类型．依据上述结构特征结合前人从染色体、心边材抽提物化学成分析的研究结果，作者支持将白皮松从单维管束亚属中独立出来，成立白皮松亚属的主张。 4． C02浓度升高对植物生长的影响 大气中C02浓度的升高以及所引起的温室效应已成为了人们普遍关注的焦点。预计到21世纪下半叶，C02浓度将增加一倍(Gates，1983).由于C02是植物光合作用的重要原料， 它的变化将直接影响植物的生长和发育，进而引起生物圈乃至整个生态系统的变化。 本项目通过在人工气候室内增加C02浓度，观察大豆与黄麻的生长及其内部结构的影响。结果表明：在短期内，C02浓度升高对两种植物的生长有促进作用，对植物内部结构也有较明显的影响。其中包括种子的发芽率提高，幼苗生长加快，植株明显增高，叶面积增大，叶片加厚（栅栏组织层数增加），根系数量增多，气孔数量减少，茎干增粗、生长轮加宽，韧皮纤维和木纤维增长、大豆结实率增高。但C02浓度升高对两种植物的长期作用仍有待于进一步研究。 本项目还在进行之中。

植物根与茎输水结构的研究和功能分析

本文采用树脂复型法对裸子植物红豆杉的管胞，木本单子叶植物竹和棕榈藤木质部中各种管状分子（主要是导管和管胞）的内壁结构进行了研究;采用原子力显微镜对玉米和小麦根内皮层细胞内切向壁的表面结构进行了探索性的研究;用光学显微镜并结合荧光技术对典型的旱生、中生及水生植物根内皮层的次生加厚壁进行了比较观察;同时辅以传统的组织切片法对以上研究结果做了进一步的论证。 采用树脂复型法，不仅可观察到常规解剖法所能展示的结构，而且还可清晰地观察到管状分子间具缘纹孔对等常规方法所难以显示的三维构造，并对其各项结构参数进行了定量测量。结果表明：裸子植物管胞和竹、藤管状分子具缘纹孔的内、外口比例分别约为3:1 和1:1，其它各项结构参数均存在较大差别。此外，在云南省藤和桂竹等导管内壁上还观察到瘤层结构，瘤体直径大小为200-800纳米之间。 旱生植物内皮层细胞内切向壁的闪生加厚最为明显，水生植物的加厚程度最微弱，而中生植物则介于两类植物之间。玉米内皮层细胞内切向壁的内表面起伏不平，并具有70-90纳米的“孔状”质外体结构，其频率约为2，000个/平方微米。

肝素钠树脂精制工艺的研究

利用D254树脂可以将原始粗品肝素钠的效价提高到179. 8 U SP U öm g, 进一步纯化可得201. 5 U SP U öm g 的精品, 其H2O 2 用量(1. 5% ) 和氧化时间(24 h) 均少于传统工艺, 产品光吸收和收率(85. 8% ) 最优。

Cloning, expression and characterization of aerolysin from Aeromonas hydrophila in Escherichia coli

Aerolysin is a toxin (protein in nature) secreted by the strains of Aeromonas spp. and plays all important role in the virulence of Aeromonas strains. It has also found several applications such as for detection of glycosylphosphatidylinositol (GPI)-anchored proteins etc. A. hydrophila is a ubiquitous Gram-negative bacterium which causes frequent harm to the aquaculture. To obtain a significant amount of recombinant aerolysin in the active form, in this study, we expressed the aerolysin in E. Coli Under the control of T7 RNase promoter. The coding region (AerA-W) of the aerA gene of A. hydrophila XS91-4-1. excluding partial coding region of the signal peptide was cloned into the vector pET32a and then transformed into E. coli b121. After optimizing the expression conditions, the recombinant protein AerA-W was expressed in a soluble form and purified using His-Bind resin affinity chromatography. Recombinant aerolysin showed hemolytic activity in the agar diffusive hemolysis test. Western blot analysis demonstrated good antigenicity of the recombinant protein.

Improvement and observation of immunoelectron microscopic method for the localization of frog Rana grylio virus (RGV) in infected fish cells

In this paper, to understand the roles of amorphous structures which were observed within the viromatrix of Rana grylio virus (RGV), an improved immunoelectron microscopy (IEM) method was developed to detect the localization of RGV in carp Epithelipma papulosum cyprinid (EPC) cells. Infected EPC cells were fixed with 4% paraformaldehyde-0.25% glutaraldehyde mixture, dehydrated completely, and embedded in LR White resin. This method allowed good ultrastructural preservation and specific labeling with anti-RGV antibodies. The results of IEM showed that colloidal gold mainly bound to the capsids of viral particles at the stage of viral assembly, while during the viral maturation colloidal gold bound to the envelop of virions. In addition, within the viromatrix, the amorphous structures, including dense floccules, membranous materials and tubules, also had strong colloidal gold signals, revealing that those amorphous structures were participated in RGV assembly. In contrast, no significant gold labeling signals were obtained in negative controls. The present study not only provided further evidence that amorphous structures within the viromatrix were involved in the process of RGV assembly, but also developed an improved IEM method for studying the interaction between iridovirus and host cells. (C) 2006 Elsevier Ltd. All rights reserved.

Simultaneous determination of chromium(VI) and chromium(III) of bioavailable fraction in bottom mud by flow injection-atomic absorption spectroscopy

A rapid and sensitive method for separation and determination of Cr(VI) and Cr(III) in bottom mud of lake by flow injection on-line preconcentrtion system and GFAAS was developed. The available Cr(VI) and Cr(III) were extracted by HOAc or EDTA + NH4 NO3 and adsorbed simultaneously by an anion and a cation resin microclummn and then eluted simultaneously by 2 mol/L NH4 NO3 + 0.05 mol/L ascorbate and 2 mol/L H2SO4, respectively. The elution was performed for 50 s after adsorption for 2 min, and the efficiencies of elution were 85.4% - 94.8% and 96.7% - 106% for Cr(VI) and Cr(M) respectively. The detection limits of the method were 0.9 mu g/L and 2.7 mu g/L with relative standard deviations of 3.5% and 6.4% for the determination of Cr(VI) and Cr(III) in sample, respectively.

Differing estrogen activities in the organic phase of air particulate matter collected during sunny and foggy weather in a Chinese city detected by a recombinant yeast bioassay

Total air suspended particles (PM 100) collected from an urban location near a traffic line in Wuhan, China, were examined for estrogen using a recombinant yeast bioassay. Wuhan, located at the central part of China, is the fourth biggest city in China with 7 million populations. Today, Wuhan has developed into the biggest city and the largest traveling center of central China, becoming one of the important bases of industry, education and research. Wuhan is right at the confluent point of Yangzi River, the third longest river in the world, and its largest distributary Hanjiang, with mountains and more than 100 takes in downtown area. Therefore, by its unique landscape, Wuhan has formed clear four seasons with relatively long winter and summer and short spring and autumn. Foggy weather usually happen in early spring. The yeast line used in this assay stably expresses human estrogen receptor-alpha. Weak but clear estrogenic activities were detected in the organic phase of crude extracts of air particle materials (APM) in both sunny and foggy weather by 0.19-0.79 mug E2/gPM(100) which were statistically significantly elevated relative to the blank control responding from 20% to 50% of the maximum E2 response, and the estrogenic activity was much higher in foggy weather than in sunny weather. The estrogenic activities in the sub-fractions from chromatographic separation of APM sampled in foggy days were also determined. The results indicated that the responses of the fractions were obviously higher than the crude extracts. Since there is no other large pollution source nearby, the estrogenic material was most likely from vehicle emissions, house heating sources and oil fumes of house cooking. The GC/MS analysis of the PM100 collected under foggy weather showed that there were many phenol derivatives, oxy-PAHs and resin acids which have been reported as environmental estrogens. These results of the analysis of estrogenic potency in sunny and foggy weather in a subtropical city of China indicate that further studies are required to investigate the actual risks for the associated health and atmospheric system. (C) 2004 Elsevier Ltd. All rights reserved.

Hard magnetic properties of Sm3Fe26.7VxN4 and Sm3Fe26.7VxCy

Sm3Fe26.7V2.3N4 nitrides and Sm3Fe26.7V2.3Cy carbides have been synthesized by gas-solid phase reaction. Their hard magnetic properties have been investigated by means of additional ball-milling at room temperature. The saturation magnetization of Sm3Fe26.7V2.3N4 almost decreases linearly with increasing ball-milling time t, but that of Sm3Fe26.7V2.3Cy has no obvious change when the ball-milling time increases from t = 1 to 28 h. As a preliminary result, the maximum remanence B-r of 0.94 and 0.88 T, the coercivity mu(0i)H(C) of 0.75 and 0.25 T, and the maximum energy product (BH) of 108.5 and 39.1 kJ/m(3) for their resin-bonded permanent magnets are achieved, respectively, by ball-milling at 293 K. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

BIODIESEL PRODUCTION FROM DIFFERENT FEEDSTOCKS IN PILOT SCALE SYSTEM

In this study, the preparations of biodiesel from three different feedstocks, including rapeseed oil, high acidified Chinese wood oil and trap grease, were carried out in a pilot scale of 200 t yr(-1) biodiesel production system. The optimum operating conditions for transesterification of rapeseed oil in plug flow reactor were found to be as follows: the catalyst dosage is 1.2 wt%; the retention time is about 17 min; the bed temperature is 65 degrees C; the oil/methanol ratio is 1:6; the content of methyl ester is 96.33% under these conditions. A kind of ion exchange resin, a solid acid catalyst, filled in the fixed bed reactor was used as the esterification catalyst for the pretreating of high acidified oil. The acid value of Chinese wood oil could be reduced from 7 to 0.8 mg KOH.g(-1) after 88 min, the optimum operating conditions were obtained as follow: molar ratio of methanol to oil is about 6:1, the temperature of the fixed bed, 65 degrees C and the retention time, about 88 min. Also a kind of acidified oil, namely trap grease, with the acid value being 114 mg KOH.g(-1) could be equally converted to a good biodiesel product through this system. Generally, the refined biodiesel product generated through this system could meet China #0 Biodiesel Standard, as well as Germany Biodiesel Standard for most indexes. It indicates that the designed process in this system has a good adaptability for different kinds of oil.