计及轴向压力的方管节点塑性铰线模型

塑性铰线分析模型已成功用于估计由弦杆表面屈服控制的各种管节点的强度；然而弦杆自身的轴向压力对节点承载力的影响仍然是用一个经验折减系数来考虑的．为了计算在轴向压力作用下沿倾斜塑性铰线的极限弯矩，研究者们提出了各种理论模型．该文对这些模型进行了分析和对比．结果表明，采用简化假设的阶梯形塑性铰线模型用于评价T形方管市点的慢度与试验结果和有限元计算结果符合得最好．

激光辅助预应力成形的相似性问题

根据激光辅助预应力成形的物理模型,以激光辅助预应力成形过程中的温度场、成形效率、弹性能转化比等物理量为目标,通过方程分析法以及量纲分析,提出了一组无量纲参数,确定了相似准则.使用有限元方法分析了满足几何相似和物理相似的模型比为1:3两个模型.结果表明,满足相似准则的两个模型,在相应的输入参量下,其物理量相似.

溶胶-凝胶条波导Sagnac环的乙醇蒸气传感特性

采用有机/无机混合溶胶-凝胶法制作条形光波导,并将条波导接入光纤Sagnac 环中,测量了输出光功率随环境气氛中乙醇蒸气体积分数变化的特性,表明在实验研究的范围内,输出信号与乙醇蒸气体积分数呈正弦变化。根据Sagnac环结构输出特性的基本关系,反映了溶胶-凝胶条波导在乙醇蒸气气氛下产生了双折射效应。观察到双折射相移与乙醇体积分数的亚线性关系。对实验数据拟合,计算了偏振相移的线性项和二次项系数,得到所制备的条波导的双折射对乙醇体积分数的响应为Δn≈4.4×10-2。测量了信号变化的时间演变特性,典型的上升和

Lancifodilactone F: A novel nortriterpenoid possessing a unique skeleton from Schisandra lancifolia and its anti-HIV activity

Lancifodilactone F (1), possessing an unprecedented rearranged pentanortriterpenoid backbone derived from cycloartane, was isolated from the leaves and stems of Schisandra lancifolia (Rehd. et Wils) A. C. Smith. Its structure was established by comprehensive NMR and MS spectroscopic analysis, coupled with single-crystal X-ray experiment. Compound 1 exerted minimal cytotoxicity against C8166 cells (CC50 > 200 mu g/mL) and showed anti-HIV activity with EC50 = 20.69 +/- 3.31 mu g/mL and a selectivity index > 6.62.

Compounds from Kadsura heteroclita and related anti-HIV activity

Phytochemical investigation of the stems of Kadsura heteroclita led to isolation of 16 compounds, including the triterpenoid named longipcdlactone J (2), and two dibenzocyclooctadiene type lignans named heteroclitin I and J (3, 4). Compounds 8-10, 14, and

腐生型眼虫Astasia longa 两种TIM 同工酶cDNA的克隆和分析

　利用3′2 RACE 和5′2 RACE 技术, 从腐生型眼虫长变胞藻( Astasia longa) 克隆了磷酸丙糖异构酶 ( TIM) 的两个同工酶cDNA 全序列。分析表明: 它们分别编码定位于细胞质的胞质型TIM (cTIM) 和定位于质 体的质体型TIM (p TIM) ; 后者的N 端具有引导该酶定位到质体中去的典型“前导序列”。根据这些事实我们推 测腐生型眼虫A . longa 质体中可能存在功能性的TIM , 并进一步认为该质体可能不只是一般意义上的“叶绿体 退化的残迹”, 而仍是一种至少有TIM 参与其代谢活动的功能性细胞器[动物学报50 (3) : 414 - 419 , 2004 ] 。

香溪河库湾枝角类的种类组成及垂直分布

中国科学院知识创新工程重要方向项目(KSCX2-SW-111); 国家自然科学基金重点项目(30330140); 国家重点基础研究发展规划(973)项目(2002CB412300); 淡水生态与生物技术国家重点实验室开放基金资助项目(2004FB03)

In-plane optical anisotropy of symmetric and asymmetric (001) GaAs/Al(Ga)As superlattices and quantum wells

Two sensitive polarized spectroscopies, reflectance difference spectroscopy and photocurrent difference spectroscopy, are used to study the characteristic of the in-plane optical anisotropy in the symmetric and the asymmetric (001) GaAs/Al(Ga)As superlattices (SLs). The anisotropy spectra of the symmetric and the asymmetric SLs show significant difference: for symmetric ones, the anisotropies of the 1HH-->1E transition (1H1E) and 1L1E are dominant, and they are always approximately equal and opposite; while for asymmetric ones, the anisotropy of 1H1E is much less than that of 1L1E and 2H1E, and the anisotropy of 3H2E is very strong. The calculated anisotropy spectra within the envelope function model agree with the experimental results, and a perturbation approach is used to understand the role of the electric field and the interface potential in the anisotropy. (C) 2001 American Institute of Physics.

从气候标准的改变分析西北地区的气候变化

IEECAS SKLLQG

Sn-modified Pt/SAPO-11 catalysts for selective hydroisomerization of n-paraffins

The hydroconversion of n-paraffins is a key reaction in hydrodewaxing of lubricating base oil. In this paper, we investigate the performance of Pt/SAPO-11 catalysts for isomerization of n-paraffins by the model compound of n-dodecane. Under this experimental condition, yields of feed isomers as well as cracking products are a function of the total n-dodecane conversion. Primary products are methylundecane while multi-brancheds and cracking products are formed in successive reactions. The result shows that the addition of Sn increases the selectivity for isomerization reaction. The most ideal experimental data for hydroconversion of n-dodecane is that the selectivity of isomerized products gets 90% when conversion of n-dodecane is 90% for the Sn-promoted Pt/SAPO-11 catalyst.