加入 WTO对我国道路运输业的影响及应对之策

入世后，我国道路运输业打入国际市场，参与国际竞争的困难比较大。文章对入世后道路运输业面临的压力和机遇进行了正反两方面分析，提出了道路运输业应采取的应对措施。     

第一周期双原子分子电荷密度心的计算

分子电荷密度分布对了解分子结构及性能的关系具有重要意义。实验及理论计算的各种电荷密度图广泛用于化学键的研究,其中密度差图有重要价值。本文中引进了电荷密度心概念,并计算了一些第一周期双原子分子的电荷密度心,旨在对电荷密度分布作一些简洁、定量的解析和应用。     

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG₂₀₀₀cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems.Received 4 March 2005; accepted 14 April 2005     

Increased mitochondrial palmitoylcarnitine/carnitine countertransport by flavone causes oxidative stress and apoptosis in colon cancer cells

Cancer cell metabolism is characterized by limited oxidative phosphorylation in order to minimize oxidative stress. We have previously shown that the flavonoid flavone in HT-29 colon cancer cells increases the uptake of pyruvate or lactate into mitochondria, which is followed by an increase in O₂^−.. production that finally leads to apoptosis. Similarly, a supply of palmitoylcarnitine in combination with carnitine induces apoptosis in HT-29 cells by increasing the mitochondrial respiration rate. Here we show that flavone-induced apoptosis is increased more than twofold in the presence of palmitoylcarnitine due to increased mitochondrial fatty acid transport and the subsequent metabolic generation of O₂^−. in mitochondria is the initiating factor for the execution of apoptosis. Received 12 August 2005; received after revision 12 October 2005; accepted 14 October 2005     

Particle methods for multiscale simulation of complex flows

The multi-scale structures of complex flows have been great challenges to both theoretical and engineering researches, and multi-scale modeling is the natural way in response. Particle methods (PMs) are ideal constitutors and powerful probes of multi-scale models, owing to their physical insight and computational simplicity. In this paper, the role of different PMs for multi-scale modeling of complex flows is critically reviewed and possible development of PMs in this background is prospected, with the emphasis on pseudo-particle modeling (PPM). The performances of some different PMs are compared in simulations and new development in the fundamentals and applications of PPM is also reported, demonstrating PPM as a unique PM for multi-scale modeling.     

不同溶剂对七台河煤萃取效果的影响

采用常压沸点下回流萃取方法,选用6种不同的有机溶剂对七台河煤进行了萃取研究,并利用CC／MS联用法对各萃取物的组成进行了分析。但不同的有机溶剂对七台河煤的萃取率相差很大。溶剂的电子受—授能力、溶解度参数、沸点、酸碱性都会对萃取效果产生不同程度的影响。实验证明,在萃取过程中,含有良好的氢键受体、很强的电负性羰基氧的有机溶剂,含n个孤对电子的胺类有机溶剂对七台河煤的萃取率都较大;溶剂萃取过程遵循“相似相溶”规律;呈碱性的有机溶剂对七台河煤的萃取率较大。结果表明,利用有机溶剂萃取法从煤中得到高附加值产品在技术上是可行的。     

Fusion between a myogenic cell in the satellite cell position and undamaged adult myofibre segments

In this report we demonstrate for the first time that differentiating myogenic cells, geographically located between the plasmalemma and external lamina of myofibres in the satellite cell position³, can fuse directly with the plasmalemma of undamaged segments of mature myofibres.     

近底泥沙通量的处理方法及适用性

为了正确理解悬沙运动方程底边界条件即近底泥沙通量的诸多处理方法的物理意义和适用性,避免泥沙理论分析和数值计算带来的偏差,归纳总结了近底泥沙通量的各种表达式,对它们的适用性和合理性进行分析.结果表明:以挟沙力、切应力、参考浓度或临界速度等方法处理近底泥沙通量,表达形式虽然多样,或将临界切应力换成对应的临界速度表示,或加入一些修正系数,但其物理本质不变,只是为了处理一些具体问题而做的简化或修正;挟沙力方法和切应力方法的经典形式用于描述近底泥沙通量更具一般性,这2种方法描述的物理过程有差别.