Monolayer graphene exhibits extraordinary properties owing to the unique, regular arrangement of atoms in it. However, graphene is usually modified for specific applications, which introduces disorder. This article presents details of graphene structure, including sp2 hybridization, critical parameters of the unit cell, formation of σ and π bonds, electronic band structure, edge orientations, and the number and stacking order of graphene layers. We also discuss topics related to the creation and configuration of disorders in graphene, such as corrugations, topological defects, vacancies, adatoms and sp3-defects. The effects of these disorders on the electrical, thermal, chemical and mechanical properties of graphene are analyzed subsequently. Finally, we review previous work on the modulation of structural defects in graphene for specific applications.

There is ever-increasing interest yet grand challenge in developing programmable untethered soft robotics. Here we address this challenge by applying the asymmetric elastoplasticity of stacked graphene assembly (SGA) under tension and compression. We transfer the SGA onto a polyethylene (PE) film, the resulting SGA/PE bilayer exhibits swift morphing behavior in response to the variation of the surrounding temperature. With the applications of patterned SGA and/or localized tempering pretreatment, the initial configurations of such thermal-induced morphing systems can also be programmed as needed, resulting in diverse actuation systems with sophisticated three-dimensional structures. More importantly, unlike the normal bilayer actuators, our SGA/PE bilayer, after a constrained tempering process, will spontaneously curl into a roll, which can achieve rolling locomotion under infrared lighting, yielding an untethered light-driven motor. The asymmetric elastoplasticity of SGA endows the SGA-based bi-materials with great application promise in developing untethered soft robotics with high configurational programmability.

The biogeochemical cycling and chemical transformation of Se in Chinese environments is reviewed, especially with regard to the formation of low-Se environments. The occurrence, distribution, concentration and flux of Se in Chinese environments are reported in comparison to those in the rest of the world. Low-Se regions in China can be classified into 4 categories. In the NE, organic matter in the soil affects bioavailability of Se in soil. In the Huabei plain, the concentration of soil Se is strongly influenced by leaching and hydrological transport processes and Se deficient regions are mostly located on the hill-slopes due to leaching. In the Loessial Plateau, low-Se soils have developed on the low-Se parent material with a very low flux of Se between soil and plants. Low-Se regions in the SW have soils derived from weathered materials of lower Se contents. Both the lowest and highest concentrations and the flux of Se in environments are reported for China. #

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Effects of arsenite, arsenate and vanadate on human erythrocyte membrane have been assessed according to their routes passing through the membrane, their binding modes to the membrane and their influences on membrane proteins and lipids. The uptake of arsenate (1.0 mM) by cells approached a limit with intracellular arsenic of about 0.2 mM in 5 h, and was strongly inhibited (;95%) by 4,49-diisothiocyano-2,29-disulfonic stilbene (DIDS), indicating that arsenate, similar to vanadate, passed across the membrane through the anion exchange protein, band 3. Arsenite (1.0 mM) influx reached a maximum of about 0.4 mM in 30 min, and was not inhibited by DIDS. The transformed species of arsenite bound to the membrane from cytosol. In contrast, arsenate bound rapidly from the outside, followed by releasing and re-binding. The binding to the membrane via sulfhydryl was indicated by the decrease of the sulfhydryl level of membrane proteins. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) analysis revealed that the proteins, bands 1-3, were among the targets of arsenite, arsenate and vanadate. Their binding to the membrane also induced changes in the fluidity of membrane lipids and in the negative charge density in the outer surface of the membrane. q2000 Elsevier Science Inc. All rights reserved.

Selenium-containing proteins or their subunits in human serum were separated and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the amount of selenium in each protein band was determined by HPLC with a fluorescence detector after derivatization with 2,4-diaminonaphthalene (DAN). This procedure provides a detection limit of 0.06 ng in a linear range of 0-1.5 ng. A protein is defined as a selenium-containing protein if its mean Se content exceeds twice the detection limit (0.12 ng) and twice the standard deviation of three replicates in sample determination. At least 4 selenium-containing bands with apparent molecular masses of 57-74, 46-56, 40-42 and 21-22 kDa could be detected from human serum collected from 4 volunteers.

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