2250 CVC热连轧机支持辊辊形研究

针对2250 CVC热连轧机支持辊磨损严重、不均匀且出现剥落问题,提出与2250热连轧机CVC工作辊相匹配的支持辊新辊形CVR（CVC-VCR Compounded Roll）,采用通用有限元软件ANSYS建立辊系三维弹性变形模型,并在F3机架上进行工业轧制试验。研究结果表明：与原辊形配置相比,CVR辊形配置不仅增加了弯辊力的调控范围,辊缝横向刚度增加11.5%以上,而且轧制过程服役前期和后期的辊间压力分布不均匀度分别降低28.17%和29.1%,辊间压力峰值分别下降27.56%和24.49%;新支持辊CVR自保持性较好,可稳定发挥其性能。     

带有临界Sobolev-Hardy指标椭圆问题的径向解

设Ω(∪)RN是球心在原点半径为R的球形区域,N≥3,0≤s＜2,2*(s)=2(N-s)/N-2,μ≥0,λ＞0.运用变分方法和分析技巧,证明了带有Dirichlet边界条件的奇异临界问题-△u-μu/|x|2=|u|2*(s)-2/|x|s u+λu的无穷多个径向解的存在性.这些解都带有不同个数的节点.     

Luminol-H2O2化学发光法测定司帕沙星

基于在碱性介质中,司帕沙星对Luminol-H2O2化学发光体系有较强的增敏作用,建立了司帕沙星的流动注射化学发光分析法.结果表明:司帕沙星浓度在9.0×10-12~7.6×10-8mol/L范围内,线性关系良好,检出限为4.8×10-12mol/L(n=11).本方法快捷、简便,且具有很高的灵敏度,用于司帕沙星片剂中司帕沙星含量的测定,回收率在96.8%~114.5%之间,结果满意.     

Neural correlates of short-term perceptual learning in orientation discrimination indexed by event-related potentials

The current work investigated the neural correlates of visual perceptual learning in grating orientation discrimination by recording event-related potentials (ERPs) from human adults. Subjects were trained with a discrimination task of grating orientation in three consecutive training sessions within 2 h. While reaction times (RTs) were shortened gradually across training sessions, the N1 was decreased and the P2 was increased over the parietal and occipital areas. A broadly distributed P3 was increased along with more practices. In addition, the time course of learning reflected in the P2 and P3 amplitudes was in line with the changes of reaction times and exhibited a stable level during later training. The impli- cations of these results to the neural mechanisms subserving perceptual learning were discussed.     

Inhibiting effect of melittin on pathogens of crops

The spectrum of antimicrobial effects of melittin were investigated on 19 pathogens by using a cylin-der-plate method with serial dilutions. Bacteriostatic efficiency and possible mechanistic effects were monitored via growth curves. The mechanism of inhibition was further analyzed by SDS-PAGE, flow cytometry and electron microscopy. Melittin had a wide inhibition spectrum and killed pathogens ef-fectively, and bacteriostatic action was influenced by factors such as pH and temperature. We eluci-dated three inhibitory mechanisms: melittin integrated with the cell membrane causing cell bursting and cytoplasm release, inhibited the synthesis of proteins and caused the cytoplasm to condense, and delayed pathogens in phase I (or phase G1) so that they could not complete the cell cycle. These re-sults suggest that melittin could serve as a broad-spectrum biological pesticide with fast-action and high-efficiency.     

Recent temperature increase recorded in an ice core in the source region of Yangtze River

Interests on climate change in the source region of Yangtze River have been raised since it is a region with the greatest warming over the Tibetan Plateau (TP). A 70-year history of precipitation δ~(18)O has been recovered using an ice core record retrieved in a plat portion of the firn area in the Guoqu Glacier (33°34′37.8″N, 91°10′35.3″E, 5720 m a.s.l.), Mt. Geladaindong (the source region of Yangtze River), in November, 2005. By using a significant positive relationship between ice core δ~(18)O record and summer air temperature (July to September) from the nearby meteorological stations, a history of summer air temperature has been reconstructed for the last 70 years. Summer temperature was relatively low in 1940s and high in 1950s to the middle of 1960s. The lowest temperature occurred in the middle of 1970s. Temperature was low in 1980s and dramatically increased since 1990s, keeping the trend to the begin-ning of the 21st century. The warming rate recorded in the ice core with 0.5℃/10 a since 1970s is much higher that that in the central TP and the Northern Hemisphere (NH), and it becomes 1.1℃/10 a since 1990s which is also higher than these from the central TP and the NH, reflecting an accelerated warm-ing and a more sensitive response to global warming in the high elevation region.     

Concentration level and distribution of polycyclic aromatic hydrocarbons in soil and grass around Mt. Qomolangma, China

High mountains may serve as a condenser for persistent organic pollutants. In the present study, soil and grass samples from Mt. Qomolangma region, China were collected from 4600 to 5620 m a.s.I and were analyzed for polycyclic aromatic hydrocarbons （PAHs） to determine if they are concentrated at colder, more elevated sites and to evaluate their possible resources and fractionation. The total PAHs concentration in soil samples was 〈 600 ng g^-1, the critical value to differentiate PAHs levels in remote and urban regions. This implied the PAHs levels at Mt. Qomolangma are relatively low and what one might expect in such a remote region of the world. These low values may represent a soil background for mid-latitude Northern Hemisphere soils away from the direct influence of an anthropogenic source. As for the distribution pattern, the low molecular weight PAHs were prone to accumulate at higher altitude, while the high molecular weight PAHs inversely related or unrelated with elevation. Based on high concentration of phenanthrene at elevated sample site and the ratios of individual PAHs, we deduced that home-heating combustion and vehicle emission may result in the constitution trait of PAHs in this mountain region. Monsoon traveling over India, Pakistan and other countries with dense population may carry contaminant to Mt. Qomolangma region.     

对自然科学社会化的整体认识

自然科学社会化是自然科学和社会发展的必然结果,两者之间存在着多方面的联系和不同的表现形式。随着科学研究的不断发展,对自然科学社会化所呈现出的新问题也提出了新的要求。只有深入研究科学的体系和结构、科学与社会的关系以及科学发展的政策,才能为自然科学社会化提供理论依据并加速其进程。     

钢筋混凝土双向受弯梁受剪承载力的计算方法探析

对于钢筋混凝土双向受弯梁斜截面受剪承载力的计算分析,一般是简化为按两个单向受弯梁的斜截面受剪承载力分别计算后再叠加的方法来确定。而对《混凝土结构设计规范》(GB50010-2002)中的双向受弯框架柱的计算方法,能否用来分析双向受弯梁的斜截面受剪承载力尚不清楚。基于已有的32根集中荷载作用下双向受弯梁的试验结果,本文采用上述两种方法对双向受弯梁的斜截面受剪承载力进行了对比分析,探讨了它们的适用性问题。研究结果表明,采用这两种方法计算分析双向受弯梁的斜截面受剪承载力所得结果误差较大且不安全,可以说是不适用的。     

耐盐能源植物海滨锦葵(Kostelezkya virginica)再生体系的建立

对海滨锦葵组织培养再生体系进行了研究，结果表明：1．海滨锦葵茎段外植体较好的愈伤组织诱导培养基组合为MS＋KT1．5mg／L＋IAA2．0mg／L或MS＋6-BA4．0mg／L＋IBA0．2mg／L＋Inositol50mg／L．2．海滨锦葵愈伤诱导不定芽的较好培养基组合为MS＋NAA2．0mg／L＋2iP5．0mg／L和MS＋NAA0．5mg／L＋2iP5．0mg／L．3．海滨锦葵腋芽分化不定芽的较好培养基组合为改良MS（含2倍有机营养）＋KT0．4mg／L＋IAA1．0mg／L．MS基本培养基中适当提高有机营养的含量对腋芽的增殖有促进作用，实验中以有机营养的含量为基本培养基2倍时效果较好．4．不定芽在1／ZMS的培养基中附加IBA1．0mg／L牛根最好．