山西霍山森林群落主要种生态位的研究

将山西霍山每50m海拔段作为一个样方调查区,作四个100m~2的样方。从山蔍海拔900m到山顶2354m,共作样方52个。将海拔作为一条反映水、热、土壤等环境因子的综合资源轴,将群落类型作为反映种群互惠、竞争关系的另一综合资源轴。选择该区12种乔木,15种灌木,计测其在两条轴上的资源选择性系数(L)生态位宽度(B),和乔木之间,灌木之间以及乔灌木之间的生态重叠值(O)。结果表明L值愈小,B值愈大,物种的资源利用能力愈强,生态幅度愈大,对某一资源的依赖性愈小,反之亦然。比较同一资源轴上的不同的L值和B值,可反映物种的优势程度和区分能力。相同生活型种间的重叠值既可作为反映种间生态学相似性的指标。也可作为判断种间有无竞争可能的参考。不同生活型种间重叠值的的大小则可作为判断种间依存和相似程度的指标。     

振动机械的亚谐分叉研究

研究了一类非线性振动磨机的动力学行为，利用平均法，得到分岔方程，并分析其稳定性；利用奇异性理论研究了分叉方程的普适开折，全面分析了系统在整个参数空间上的各种行为，为设计振动磨机提出了理论依据。     

重载运输中扼流变压器容量配置预算的理论基础

在电气化铁道中，钢轨既是机车牵引电流回流的通道，又是自动闭塞系统传输信息的通道，两者之间存在着电磁兼容性的问题。本文首先介绍了一种现场模拟产生大牵引电流的方法，然后在实测数据的基础上，分析了钢轨回流随牵引电流的变化关系．根据轨流在一定范围内随牵引电流呈线性变化这一关系，可以在己有测试数据的基础上预测出重载运输牵引电流下，钢轨回流的大小，确定沿线扼流变压器容量的配置。这为扼流变压器容量的预先配置计算奠定了电流特性方面的理论基础。     

Structure of the Sec23/24-Sar1 pre-budding complex of the COPII vesicle coat

COPII-coated vesicles form on the endoplasmic reticulum by the stepwise recruitment of three cytosolic components: Sar1-GTP to initiate coat formation, Sec23/24 heterodimer to select SNARE and cargo molecules, and Sec13/31 to induce coat polymerization and membrane deformation. Crystallographic analysis of the Saccharomyces cerevisiae Sec23/24-Sar1 complex reveals a bow-tie-shaped structure, 15 nm long, with a membrane-proximal surface that is concave and positively charged to conform to the size and acidic-phospholipid composition of the COPII vesicle. Sec23 and Sar1 form a continuous surface stabilized by a non-hydrolysable GTP analogue, and Sar1 has rearranged from the GDP conformation to expose amino-terminal residues that will probably embed in the bilayer. The GTPase-activating protein (GAP) activity of Sec23 involves an arginine side chain inserted into the Sar1 active site. These observations establish the structural basis for GTP-dependent recruitment of a vesicular coat complex, and for uncoating through coat-controlled GTP hydrolysis.     

Normal faulting in central Tibet since at least 13.5 Myr ago

Tectonic models for the evolution of the Tibetan plateau interpret observed east-west thinning of the upper crust to be the result of either increased potential energy of elevated crust or geodynamic processes that may be unrelated to plateau formation. A key piece of information needed to evaluate these models is the timing of deformation within the plateau. The onset of normal faulting has been estimated to have commenced in southern Tibet between about 14 Myr ago and about 8 Myr ago and, in central Tibet, about 4 Myr ago. Here, however, we report a minimum age of approximately 13.5 Myr for the onset of graben formation in central Tibet, based on mineralization ages determined with Rb-Sr and 40Ar-39Ar data that post-date a major graben-bounding normal fault. These data, along with evidence for prolonged activity of normal faulting in this and other Tibetan grabens, support models that relate normal faulting to processes occurring beneath the plateau. Thinning of the upper crust is most plausibly the result of potential-energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath Tibet. This is supported by recent geophysical and geological data, which indicate that spatial heterogeneity exists in both the Tibetan crust and lithospheric mantle.     

木果楝挥发油成分的GC-MS分析

采用气相色谱-质谱联用技术,首次对木果楝叶子和果实挥发油进行了成分分析,从木果楝叶子和果实分别鉴定出了33和36种化合物,分别占挥发油的99.11%和97.63%.两个部位中挥发油化学组成各有异同,但其主要成分均是倍半萜类化合物b-桉叶烯和γ-桉叶烯.本研究结果可为木果楝的综合开发利用提供理论依据.     

海南岛东部地区砖红壤中微量元素含量的纵向分异研究

对海南岛东部地区发育典型的6个砖红壤剖面的微量元素的组成特征及其纵向变化规律进行研究发现,土壤母质是决定砖红壤微量元素含量的主要原因,区内花岗岩砖红壤中Cu、Sr、Zn、Pb含量明显高于砂页岩砖红壤,而砂页岩砖红壤中的As含量相对较高.砂页岩砖红壤剖面中的微量元素含量的纵向变化规律具有相似性,并显示出B层>C层>A层的特征,而花岗岩砖红壤微量元素在各层中的纵向分异规律不甚明显.区内的人类活动对海南岛东部砖红壤剖面中的部分微量元素的分布具有一定的影响,农药及老鼠药的大量使用,可致使大量的As元素进入土壤表层富集,并造成土壤中As含量超标,成为区内环境的重要隐患.     

生物材料应用于脊髓损伤修复的研究进展

脊髓损伤是人类致残率最高的疾患之一。治疗脊髓损伤的趋势是联合应用多种技术和手段,创造出最适宜神经细胞再生恢复的环境,达到功能恢复的目的。生物材料在结构和功能上的优良性质使得它在脊髓损伤和修复中具有很好的应用前景。近年来兴起的组织工程学方法更为脊髓损伤的治疗带来新思路,即通过种子细胞—支架材料—神经营养因子复合物修复受损脊髓。本文回顾了近年来组织工程支架和细胞载体系统在脊髓损伤修复中的应用,展示了生物材料在组织工程和细胞分子治疗策略中的优越性。