Reduced parabolic model for radical addition reactions

The transition state of addition of free radicals and atoms to multiple bonds is considered as a result of intersecting of two parabolic potential curves. One of them characterizes the stretching vibration of the attacked multiple bond, and another curve characterizes the stretching vibration of the bond formed in the transition state. The force constant of the latter is calculated by an empirical equation that correlates the force constant with the bond dissociation energy. In the framework of this model, the thermally neutral activation energy (E _e0) and the elongation of the attacked and formed bonds (r _e) in the transition state were calculated from the experimental data (activation energy (E _e) and enthalpy of reaction (H _e)) for the addition of an H atom and methyl, alkoxyl, aminyl, triethylsilyl, and peroxyl radicals to the C=C bond and the addition of H and CH₃ to the C=O and CC bonds. Analysis of the data obtained showed that E _e0 depends linearly on the |H _e| + E_e sum, i.e., E_e0/kJ mol^–1 = 14.2 + 0.61 · (E_e – H _e), and the bond elongation in the transition state for addition of the most part of radicals to ethylene and acetylene vary within (0.65–0.87)·10_–10 m. The factors affecting the activation energy of the radical addition reactions are discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1542–August, 2004.     

Optimization of on-chip elongation for fabricating double-stranded DNA microarrays

The sequence-specific recognitions between DNA and proteins are playing important roles in many biological functions. The double-stranded DNA microarrays (dsDNA microarrays) can be used to study the sequence-specific recognitions between DNAs and proteins in highly parallel way. In this paper, two different elongation processes in forming dsDNA from the immobilized oligonucleotides have been compared in order to optimize the fabrication of dsDNA microarrays: (1) elongation from the hairpins formed by the self-hybridized oligonucleatides spotted on a glass; (2) elongation from the complementary primers hybridized on the spotted oligonucleatides. The results suggested that the dsDNA probes density produced by the hybridized-primer extension was about four times lower than those by the self-hybridized hairpins. Meanwhile, in order to reduce the cost of dsDNA microarrays, we have replaced the Klenow DNA polymerase with Taq DNA polymerase, and optimized the reaction conditions of on-chip elongation. Our experiements showed that the elongation temperature of 50 °C and the Mg²⁺ concentration of 2.5 mM are the optimized conditions in elongation with Taq DNA polymerase. A dsDNA microarray has been successfully constructed with the above method to detect NF-kB protein.     

应变速率对8090Al-Li合金拉伸性能的影响

用动态拉伸的方法研究了应变速率对 80 90 Al— L i合金拉伸性能的影响 ,应变速率的范围为 10 - 3～ 10 3s- 1。结果表明 ,合金的强度和塑性随应变率的增加而增加。试样的 SEM和 TEM分析发现 :准静态下的断裂为沿晶断裂 ;随着应变率的增加 ,断裂从穿晶准解理断裂过渡到由显微空穴聚集而成的韧窝断裂。高应变率下80 90 Al- L i合金强度和塑性的提高与其变形机制和晶界无沉淀区 (PFZ)的变化有关     

低捻转杯纺纱实验与理论分析--提高低捻转杯纱强力探索

研究在转杯纺加捻区中加装阻扭件,然后选用相同的棉条纺制不同捻系数的转杯纱(加装阻扭件和不加装阻扭件)和环锭纱,并测试其成纱的强伸性能、表面形态和扭转性能.测试结果表明,加装阻扭件的转杯纱可以适当改善转杯纺的加捻效果,进而适当提高了转杯纱的成纱强力.     

汞、镉、铅胁迫对油菜的毒害效应

研究了不同浓度(200mg·L-1-500mg·L-1)Hg2+、Cd2+、Pb2+处理对油菜种子萌发、根伸长、叶绿素含量及叶绿素a/b值等指标的影响.结果表明:在Hg2+、Cd2+胁迫下,随着重金属浓度的增加,处理时间的延长,油菜种子的萌发率、根生长速率、叶绿素含量和叶绿素a/b比值持续下降.而低浓度(50mg·L-1-200mg·L-1)的Pb2+对油菜叶绿素合成则具有一定的促进作用,叶绿素含量明显高于对照.在相同浓度条件下,重金属对根伸长的抑制作用大于对种子萌发的抑制.     

侯西铁路线K81＋061立交桥梁体后张法预应力筋伸长值偏差探讨与计算机辅助计算

结合工程实例,从施工材料和施工技术、混凝土弹性模量增长滞后、设计伸长值等方面,对后张法预应力筋伸长值超限问题进行了系统的论述,最终采用理论计算的手段解决了该问题,并针对理论计算的难度及特点提出了计算机高级语言辅助计算的解决方法与思路。     

Elongation method with intermediate mechanical and electrostatic embedding for geometry optimizations of polymers

The elongation method with intermediate mechanical and electrostatic embedding (ELG-IMEE) is proposed. The electrostatic embedding uses atomic charges generated by a charge sensitivity analysis (CSA) method and parameterized for three different population analyses, namely, the Merz–Singh–Kollman scheme, the charge model 5, and the atomic polar tensor. The obtained CSA models were tested on two model systems. Test calculations show that the electrostatic embedding provides several times of decrease in the difference of energies of testing and reference calculations in comparison with the conventional elongation approach (ELG). The mechanical embedding is implemented in a combination of the conventional elongation method and the ONIOM approach. Moreover, it was demonstrated that the geometry optimization with the ELG-IMEE reduces the errors in the optimized structures by about one order in root-mean-square deviation, when compared to ELG.     

融合人工智能的图书馆资源建设问题反思

以乐山师范学院为例,应用人工智能的方法研究了图书馆资源建设利用现状和存在的问题,并采用机器学习理论对乐山师范学院图书馆读者伸长特性构建模型,为高校图书馆的管理和建设提供指导。