粗粒料三轴试验橡皮膜嵌入量数值模拟

在粗粒料三轴试验中,橡皮膜嵌入量可造成显著的体积变形量测误差。本文针对颗粒材料的接触特点,利用Nagata Patch方法重建颗粒表面,基于重建曲面进行接触状态的判断和接触几何信息的计算,开发了高效的颗粒接触算法。该法采用dual mortar有限元方法处理颗粒与橡皮膜间的接触模拟,针对橡皮膜变形较大的特点,采用更新坐标的大变形计算格式,并根据重建的颗粒表面对颗粒-橡皮膜的距离进行几何修正,实现了颗粒-橡皮膜接触的精细化模拟,可较好地模拟计算“柔性”橡皮膜嵌入颗粒孔隙的过程。进行了Kramer钢球试验以及粗颗粒料和标准粗砂三轴试验橡皮膜嵌入过程的模拟计算,计算结果符合一般规律,与相应的试验结果吻合较好,验证了本文方法对于粗粒料膜嵌入问题的适用性。     

Differential Subcellular Distribution of Cytokinins: How Does Membrane Transport Fit into the Big Picture?

Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of “equilibrative nucleoside transporters” and “purine permeases”, which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness.     

Design,Synthesis, and Biological Evaluation of Novel 6H-Benzo[c]chromen-6-one Derivatives as Potential Phosphodiesterase II Inhibitors

Urolithins (hydroxylated 6H-benzo[c]chromen-6-ones) are the main bioavailable metabolites of ellagic acid (EA), which was shown to be a cognitive enhancer in the treatment of neurodegenerative diseases. As part of this research, a series of alkoxylated 6H-benzo[c]chromen-6-one derivatives were designed and synthesized. Furthermore, their biological activities were evaluated as potential PDE2 inhibitors, and the alkoxylated 6H-benzo[c]chromen-6-one derivative 1f was found to have the optimal inhibitory potential (IC₅₀: 3.67 ± 0.47 μM). It also exhibited comparable activity in comparison to that of BAY 60-7550 in vitro cell level studies.     

Dynamic “Molecular Portraits” of Biomembranes Drawn by Their Lateral Nanoscale Inhomogeneities

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 10³ nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties.     

Red-Blood-Cell-Membrane-Coated Metal-Drug Nanoparticles for Enhanced Chemotherapy

To overcome high toxicity, low bioavailability and poor water solubility of chemotherapeutics, a variety of drug carriers have been designed. However, most carriers are severely limited by low drug loading capacity and adverse side effects. Here, a new type of metal-drug nanoparticles (MDNs) was designed and synthesized. The MDNs self-assembled with Fe(III) ions and drug molecules through coordination, resulting in nanoparticles with high drug loading. To assist systemic delivery and prolong circulation time, the obtained MDNs were camouflaged with red blood cell (RBCs) membranes (RBCs@Fe-DOX MDNs) to improve their stability and dispersity. The RBCs@Fe-DOX MDNs presented pH-responsive release functionalities, resulting in drug release accelerated in acidic tumor microenvironments. The outstanding in vitro and in vivo antitumor therapeutic outcome was realized by RBCs@Fe-DOX MDNs. This study provides an innovative design guideline for chemotherapy and demonstrates the great capacity of nanomaterials in anticancer treatments.     

地下金属矿山斜坡道浆土路修筑工艺及应用研究

斜坡道是地下金属矿山的主要运输通道,其道路质量直接影响着矿山的安全运输和经济效益。针对斜坡道混凝土浇筑路面存在的筑路成本高、养护时间长、使用寿命短及维护困难等不足,引入浆土路修筑技术,开展了地下金属矿山斜坡道浆土路筑路材料配比试验、黏土搓条和崩解试验、水洗筛分试验,并在云南卡房分公司完成了浆土路试验路段的修筑。结果表明：浆土路筑路技术能够很好地应用于地下矿山道路修筑,具有施工工艺简单、筑路成本低、施工周期短、承载能力强、抑尘防滑和低碳环保等诸多优点,为地下金属矿山道路修筑提供了工程借鉴,对于矿山降本增效、节能减排及安全高效具有重要的意义。     

An experimental evaluation of the effects of ripple current generated by the power conditioning stage on a proton exchange membrane fuel cell stack

In this article, an impedance model of the proton exchange membrane fuel cell stack (PEMFCS) is proposed. The proposed study employs an equivalent circuit of the PEMFCS derived by the frequency response analysis technique. An equivalent circuit for the PEMFCS is developed to evaluate the effects of ripple currents generated by the power-conditioning unit. The calculated results are then verified by means of experiments using a commercially available PEMFCS. The relationship between ripple current and fuel cell performance, such as power loss and fuel consumption, is investigated. Experimental results show that the ripple current can contribute up to a 6% reduction in the available output power. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

液膜法分离富集,测定水中微量锶

用乳状液膜体系对锶进行分离富集，该体系包括协同流动载体（ＰＭＢＰ，ＴＢＰ），表面活性剂（ＳＰＡＮ８０）增强剂（丙三醇）溶剂（正己烷）和内相（１．２ｍｏｌ／Ｌ的盐酸溶液），实验表明，在适宜的条件下，锶的富集效率可达９９．５％以上，而在此条件下许多共存离子，如Ｆｅ＾３＋，Ａｌ＾３＋，Ｃａ＾２＋，Ｍｇ＾２＋，Ｂａ＾２＋，Ｃｒ＾３＋，ＣＯ＾２＋，Ｎｉ＾２＋，Ｚｒ＾４＋，Ｃｕ＾２＋，Ｚｎ＾２＋，Ｐｂ＾２＋和     

Zeolite based films, membranes and membrane reactors: Progress and prospects

The integration of reaction and separation in catalytic membrane reactors has received increasing attention during the past 30 years. The combination promises to deliver more compact and less capital-intensive processes with substantial savings in energy consumption. With the advent of new inorganic materials and processing techniques, there has been renewed interest in exploiting the benefits of membranes in many industrial applications. Zeolite membranes, however, have only recently been considered for catalytic membrane reactor applications. Despite the significant recent interest in these types of membranes there are relatively few reports of the application of such membranes in high-temperature catalytic membrane reactor applications. This can be attributed to a number of limitations that still need to be addressed such as the relatively high price of membrane units, the difficulty of controlling the membrane thickness, permeance, high-temperature sealing, reproducibility and the dilemma of upscaling. A number of research efforts, with some degree of success have been directed to finding solutions to the remaining challenges. This review makes a critical assessment of what has been achieved in the past few years in terms of hurdles that still stand in the way of the successful implementation of zeolite membrane reactors in industry.