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1.
In order to investigate the effects of chemical components and matrix structure on the destabilization of quenched wood, we
examined the physical and mechanical properties of steam-treated wood, hemicellulose-extracted wood, and delignified wood,
which were treated at different levels. For steam-treated and hemicellulose-extracted wood,the relative relaxation modulus
of the quenched sample was lower than that of the respective control sample. For delignified wood, the relative relaxation
modulus fell with weight loss and reached a minimum value at a certain weight loss, and subsequently increased significantly.
The hygroscopicity of all treated samples changed slightly by steaming, whereas increased with removing the component. More-over,
the average volumetric swelling per 1% MC at 100% relative humidity (RH) was less than at 75% RH and 93% RH for component-removed
wood. It was clear that a void structure existed. As a result, the destabilization evaluated by the fluidity (1 - E
t/E
0) of steam-treated wood was influenced by the amount of adsorbed water. For component-removed wood, destabilization increased
temporarily at lower weight loss because of nonuniform cohesive structure. At high weight loss, destabilization will decreased
because capillary-condensed water gathered in the voids and obstructed the motion of adsorbed water. However, the destabilization
of all treated wood changed less than that of chemically modified wood. 相似文献
2.
通过宏观检验观察、化学成分分析、硬度测试、金相检验和断口分析等方法对弹簧垫圈的断裂原因进行分析。结果表明:该弹簧垫圈热处理时产生淬火裂纹,镀锌时氢原子在裂纹尖端偏聚,这两种因素的共同作用导致弹簧垫圈在装配预紧过程中发生脆性断裂。 相似文献
3.
Fengling Cui Qiangzhai Zhang Hongxia Luo Lixia Qin Yan Lu 《Pesticide biochemistry and physiology》2008,90(2):126-134
The interaction of 5-Iodouracil with human serum albumin (HSA) was investigated in aqueous solution by fluorescence quenching spectrum in combination with UV absorption spectrum and modeling method. The quenching mechanism and binding characteristics of 5-Iodouracil with HSA were obtained from the fluorescence measurement. The binding constants were calculated according to the Lineweaver-Burk equation at different temperatures. And the thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), were calculated by thermodynamic equations. The results showed that the hydrophobic interaction played a major role in the binding of 5-Iodouracil with HSA. The binding distance was obtained according to Föster’s non-radiative energy transfer theory. The effect of some normal ions on the binding constants was discussed. Modeling method was applied to elucidate the interaction mode between 5-Iodouracil and HSA, which was agreed with the calculated result by thermodynamic method. Moreover, the synchronous fluorescence technique was successfully applied to quantify total protein in human body fluids including serum, urine, and saliva samples. The results showed that this method was stable, reliable, selective, sensitive, and practical for the determination of HSA. 相似文献
4.
5.
In order to understand the mechanism of destabilization occurring when wood is quenched, we applied chemical modifications,
and controlled the number of moisture adsorption sites in wood. The degree of destabilization was evaluated according to the
fluidity (1-E
t/E
0), increase in fluidity, and relative fluidity in relation to the nonmodified wood, and was discussed by comparing these quantities
with the hygroscopicity or swelling of wood. We found that destabilization of chemically modified wood was lower than that
in nonmodified wood, and the amount of adsorbed water controlled the magnitude of flow of wood. Moreover, according to the
analysis of water state by the Hailwood-Horrobin equation, it was shown that the function of dissolved water to the fluidity
is almost identical for both chemical modifications, whereas hydrated water has more effect on acetylated wood than on formaldehydetreated
wood. We speculate that the motion of water molecules due to quenching accompanied with the redistribution of energy resulting
from the exchange of their potential energy and movement to attain a new balance, and the introduced acetyl groups and cross-linking
restrict the water molecule movement.
An erratum to this article is available at . 相似文献
6.
荧光猝灭法测定甲硝唑片剂中的药物含量 总被引:2,自引:0,他引:2
本文利用甲硝唑可使十二烷基硫酸钠(SDS)的荧光强度猝灭,建立了荧光猝灭分光光度法测定甲硝唑含量的方法,实验结果表明:甲硝唑/SDS体系在pH=5~10缓冲溶液中,甲硝唑浓度在10μg/10mL~96μg/10mL 范围内与体系的荧光强度呈现良好的线性关系,R=0.9981.对浓度为23.44μg/10mL的甲硝唑进行11次平行的测定,RSD=0.92 ﹪,方法快速,简便,用于药物制剂中甲硝唑含量的测定,结果满意. 相似文献
7.
Denis Faure Yves Dessaux 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(3):353-365
Quorum sensing is a regulatory mechanism that connects gene expression to cell density in bacteria. Amongst proteobacteria,
numerous functions are regulated in this way, including pathogenicity in the Enterobacteriaceae genus Pectobacterium. In Pectobacterium, the signalling molecules involved in this regulatory process belong to the N-acyl-homoserine lactone class. Over the last
6 years, various studies have shown that these signal molecules could be degraded by other bacteria or by plant and animal
cells, opening the path to innovative biocontrol strategies. This review explores the various determinants of pathogenicity
in Pectobacterium and describes approaches that have been developed to quench the quorum-sensing-dependent pathogenicity in Pectobacterium. These approaches range from signal degradation by physicochemical constraints to the identification of signal-sensing inhibitors
and from the identification of enzymes degrading acyl-homoserine lactones to the construction of transgenic plants tolerant
to Pectobacterium. 相似文献
8.
本文对坦克履带销的失效形式进行了分析研究后,在不改变履带销用钢及技术要求条件下,对热处理工艺进行了优化设计,采用了非常规碳氮复合渗热处理新工艺,使履带销的使用寿命由原来的150-200摩托小时提高到600摩托小时以上,取得明显的军事和经济效益. 相似文献
9.
三种松树叶绿素荧光特征比较研究 总被引:1,自引:0,他引:1
以赤松、油松、白皮松3种松树为材料,利用便携式调制荧光仪MINI-PAM测定自然条件下其各叶绿素荧光参数Ft、Fm、Yield、ETR、qP、qN或NPQ和PAR指标的日变化。结果表明:3种松树各个时段荧光参数值在总体上差异不大,叶绿素荧光参数的变化依赖于PAR的变化。Ft、rETR、qN和NPQ的变化与PAR的变化趋势一致,Fm、Yield和qP的变化与PAR的变化相反。其中,白皮松的量子产量Yield、相对光合电子传递速率ETR、光化学淬灭系数qP、非光化学淬灭系数qN和NPQ均高于赤松和油松,说明其能通过增加热耗散来尽量降低光抑制程度,对当地环境较为适应。本研究为3种松树抗性研究、苗木管理、科学种植等提供了生理指标和依据。 相似文献
10.
用金相显微镜和扫描电镜(电子探针)等对发动机冷却水水泵泵轴淬火后出现的裂纹进行了宏观和微观分析。探讨了裂纹产生的影响因素,结果表明:淬火过程中产生的组织应力和热应力、工件的尺寸、带状碳化物和集中及分散分布的脆性非金属夹杂物是裂纹产生的主要原因。在上述观察和分析的基础上,对如何选材及确定正确的热处理工艺等提出了建设性意见。 相似文献