不同数学模型模拟非均质土壤溶质大尺度运移的对比分析

利用长度为1250cm的非均质土柱中NaCl运移的试验资料,分别应用对流-弥散方程(CDE)、两区模型(TRM)、对流对数正态传递函数模型(CLT)、分数微分对流-弥散方程(FADE)和连续时间随机游走理论(CTRW)等数学模型对长土柱中溶质的运移过程进行模拟,对比各个模型的模拟结果,并从模型机理上分析模拟结果差异的原因,探讨各种模型描述非均质土壤中溶质大尺度运移的适用性。结果表明:CDE、CLT和FADE难以描述非均质土柱中的不规则穿透曲线,但FADE对穿透曲线尾部的模拟精度比CDE和CLT有所提高;与CDE、CLT和FADE相比,两者的模拟结果与实测值吻合更好,在穿透曲线尾部CTRW的模拟值略大于TRM的模拟结果;两者不仅较好地描述了穿透曲线的提前穿透和拖尾等不规则特征,而且捕捉到了非均质土柱中溶质不规则运移程度随着尺度增加而减弱的变化趋势。尽管TRM和CTRW均能很好地模拟长土柱试验所研究的饱和非均质土壤中保守性溶质的一维运移问题,但对于复杂的溶质运移问题的模拟,TRM和CTRW各有其优缺点。     

Colloidal transport phenomena in dynamic,pulsating porous materials

We study the transport phenomena of colloidal particles embedded within a moving array of obstacles that mimics a dynamic, time-varying porous material. While colloidal transport in an array of stationary obstacles (“passive” porous media) has been well studied, we lack the fundamental understanding of colloidal diffusion in a nonequilibrium porous environment. We combine Taylor dispersion theory, Brownian dynamics simulations, and optical tweezer experiments to study the transport of tracer colloidal particles in an oscillating lattice of obstacles. We discover that the dispersion of tracer particles is a nonmonotonic function of oscillation frequency and exhibits a maximum that exceeds the Stokes–Einstein–Sutherland diffusivity in the absence of obstacles. By solving the Smoluchowski equation using a generalized dispersion framework, we demonstrate that the enhanced transport of the tracers depends critically on both the direct interparticle interactions with the obstacles and the fluid-mediated, hydrodynamic interactions generated by the moving obstacles.     

支撑液膜法提取柠檬酸的研究

提出了用支撑液膜法从柠檬酸的发酵液中提取柠檬酸的新方法，实验结果表明用支撑液膜法提取柠檬酸是可行的．考察了膜的装配方法和载体浓度对传递通量及体系稳定性的影响，在该体系和一定的操作条件下，确定了合适的膜配方．     

Ady2p is essential for the acetate permease activity in the yeast Saccharomyces cerevisiae

To identify new genes involved in acetate uptake in Saccharomyces cerevisiae, an analysis of the gene expression profiles of cells shifted from glucose to acetic acid was performed. The gene expression reprogramming of yeast adapting to a poor non-fermentable carbon source was observed, including dramatic metabolic changes, global activation of translation machinery, mitochondria biogenesis and the induction of known or putative transporters. Among them, the gene ADY2/YCR010c was identified as a new key element for acetate transport, being homologous to the Yarrowia lipolytica GPR1 gene, which has a role in acetic acid sensitivity. Disruption of ADY2 in S. cerevisiae abolished the active transport of acetate. Microarray analyses of ady2Delta strains showed that this gene is not a critical regulator of acetate response and that its role is directly connected to acetate transport. Ady2p is predicted to be a membrane protein and is a valuable acetate transporter candidate.     

膳食多酚对淀粉消化吸收的影响

近年来基于食品成分之间相互作用调节食品质地与功能特性的研究成为食品学科的研究热点。多酚与淀粉的相互作用在食品中广泛发生,二者的相互作用对调控加工食品的风味和质地、提高多酚的生物利用度、抑制淀粉的老化以及降低淀粉的消化吸收速度等具有重要作用。综述了多酚与淀粉的复合作用、多酚对淀粉消化酶活性的抑制以及多酚对肠道葡萄糖吸收转运的抑制作用,为利用食物成分与淀粉的相互作用开发预防和控制高血糖症的新型食品提供了参考。     

FlexGrid标准研究进展及应用分析

针对电力企业数据业务流量爆炸性增长所引发的骨干网络带宽资源瓶颈问题,在对国家电网公司光传输网（optical transport network,OTN）大容量骨干传输网络承载业务需求分析基础上,从频谱管理方法、交叉连接设备、混合线速传输、控制平面等方面出发,探索FlexGrid技术在电力通信网络中的应用模式,可为电力通信骨干网络提供光层粒度的精细划分与动态调整能力.在此基础上,提出在多种约束条件下根据频谱资源利用度动态调节调制的信道资源管理方法,可有效改善现有骨干传输网络采用的固定带宽分配和管理模式造成网络灵活性差,带宽资源利用效率低下的现状.     

Membrane transport in an osmotically fragile mutant of Saccharomyces cerevisiae

Transport properties of the osmotically fragile strain VY1160 of Saccharomyces cerevisiae were compared with those of the parent S288c strain. Mediated diffusion of 6-deoxy-D-glucose was practically unaffected; membrane-potential-dependent transport of D-glucosamine was very much depressed in the fragile strain. The H+-driven transport of L-lysine and L-proline, as well as that of the hitherto uninvestigated D-glucose-6-phosphate, were also very depressed. 2-Deoxy-D-glucose transport displayed slightly different kinetic parameters. Primary H+ extrusion by the plasma membrane H-ATPase was not diminished although the ATP-splitting activity was depressed by about 50%. The overall proton-motive force (pmf) of the fragile mutant at pH 5.5 was only 20 mV while in the parent strain it was 108 mV. In parallel with this, spontaneous acidification of the external medium (a CO2-associated event) was only about 2% of that in the parent strain. The defect in this, together with the inability to stimulate transport protein synthesis by glucose, may account for the generally poorer transport performance of the fragile mutant.     

Exploration of the oxygen transport behavior in non-precious metal catalyst-based cathode catalyst layer for proton exchange membrane fuel cells

High cost has undoubtedly become the biggest obstacle to the commercialization of proton exchange membrane fuel cells (PEMFCs), in which Pt-based catalysts employed in the cathodic catalyst layer (CCL) account for the major portion of the cost. Although non-precious metal catalysts (NPMCs) show appreciable activity and stability in the oxygen reduction reaction (ORR), the performance of fuel cells based on NPMCs remains unsatisfactory compared to those using Pt-based CCL. Therefore, most studies on NPMC-based fuel cells focus on developing highly active catalysts rather than facilitating oxygen transport. In this work, the oxygen transport behavior in CCLs based on highly active Fe-N-C catalysts is comprehensively explored through the elaborate design of two types of membrane electrode structures, one containing low-Pt-based CCL and NPMC-based dummy catalyst layer (DCL) and the other containing only the NPMC-based CCL. Using Zn-N-C based DCLs of different thickness, the bulk oxygen transport resistance at the unit thickness in NPMC-based CCL was quantified via the limiting current method combined with linear fitting analysis. Then, the local and bulk resistances in NPMC-based CCLs were quantified via the limiting current method and scanning electron microscopy, respectively. Results show that the ratios of local and bulk oxygen transport resistances in NPMC-based CCL are 80% and 20%, respectively, and that an enhancement of local oxygen transport is critical to greatly improve the performance of NPMC-based PEMFCs. Furthermore, the activity of active sites per unit in NPMC-based CCLs was determined to be lower than that in the Pt-based CCL, thus explaining worse cell performance of NPMC-based membrane electrode assemblys (MEAs). It is believed that the development of NPMC-based PEMFCs should proceed not only through the design of catalysts with higher activity but also through the improvement of oxygen transport in the CCL.     

一体化运输安装船系泊状态下运动响应分析

通过MOSES软件对运输安装船建立三维模型并模拟多种抛锚方式,对系泊状态下的船体进行时域分析。研究不同海况下不同数量锚链、不同抛锚方式的运动响应。结果表明,锚链数量及抛锚方式会影响浮体运动响应;8根锚链且交叉抛锚方式是最有利的系泊布置方式,纵摇、纵荡、垂荡加速度等运动响应均优于其他抛锚方式。