Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: A review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.     

天然盐渍土冻融循环时水盐迁移规律及强度变化试验研究

通过对新疆喀什地区12处天然盐渍土室内基本性质试验分析,选取典型天然盐渍土,在开放系统中进行反复冻融循环条件下的试验研究。研究了天然盐渍土在多次冻融循环时的水分和盐分迁移规律及强度变化特征。试验结果表明:经多次冻融循环,低液限粘土试样水分重分布与盐分重分布有很大的一致性,水分和盐分自下而上迁移;试样粘聚力自下而上线形减小,内摩擦角呈s形分布。含砂低液限粘土试样冻融循环过程中,易溶盐均随水分向冷端面迁移,离子剖面呈现中间大两端小的趋势;试样粘聚力呈反s形分布,内摩擦角均呈s形分布。     

Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C₃H₅NS₂)] was synthesized and characterized by chemical and spectroscopic measurements, DFT studies and biological assays. Infrared (IR) and ¹H, ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on DFT confirmed nitrogen coordination to gold(I) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Thermal decomposition starts at temperatures near 160 °C, leading to the formation of Au⁰ as the final residue at 1000 °C. The gold(I) complex with 2-mercaptothiazoline (Au-MTZ) is soluble in dimethyl sulfoxide (DMSO), and is insoluble in water, methanol, ethanol, acetonitrile and hexane. The antibacterial activities of the Au-MTZ complex were evaluated by an antibiogram assay using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of the cytotoxic effect of the Au-MTZ complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a potent cytotoxic activity, inducing 85% of cell death at a concentration of 2.0 μmol L⁻¹.     

The development of an integrated platform to identify breast cancer glycoproteome changes in human serum

Protein glycosylation represents one of the major post-translational modifications and can have significant effects on protein function. Moreover, changes in the carbohydrate structure are increasingly being recognized as an important modification associated with cancer etiology. In this report, we describe the development of a proteomics approach to identify breast cancer related changes in either concentration and/or the carbohydrate structures of glycoprotein(s) present in blood samples. Diseased and healthy serum samples were processed by an optimized sample preparation protocol using multiple lectin affinity chromatography (M-LAC) that partitions serum proteins based on glycan characteristics. Subsequently, three separate procedures, 1D SDS-PAGE, isoelectric focusing and an antibody microarray, were applied to identify potential candidate markers for future study. The combination of these three platforms is illustrated in this report with the analysis of control and cancer glycoproteomic fractions. Firstly, a molecular weight based separation of glycoproteins by 1D SDS-PAGE was performed, followed by protein, glycoprotein staining, lectin blotting and LC–MS analysis. To refine or confirm the list of interesting glycoproteins, isoelectric focusing (targeting sialic acid changes) and an antibody microarray (used to detect neutral glycan shifts) were selected as the orthogonal methods. As a result, several glycoproteins including alpha-1B-glycoprotein, complement C3, alpha-1-antitrypsin and transferrin were identified as potential candidates for further study.     

An adsorption study of Sr2+ from saline sources by coconut shell charcoal

The adsorption potential of charcoal for the removal of heavy metal ions is well documented in the literature. However, its exploration for uptake of technologically valuable metal ions such as Sr²⁺ is poorly known. In this work, the batch adsorption study of Sr²⁺ ion from aqueous solution as well as from saline matrix (>3% of NaCl) onto charcoal has been carried out. The experiments were conducted with two charcoals, i.e., our prepared charcoal (coconut shell charcoal) and commercial charcoal. Strontium adsorption has been investigated as a function of its initial concentration, contact time, and varied mass of adsorbent. Equilibrium adsorption data were evaluated for Langmuir and Freundlich isotherm models. The adsorption capacities (mg/g) of Sr²⁺ present in the salt matrix onto coconut shell charcoal and commercial charcoal was found to be 18.4 and 22.2, respectively. Uptake of Sr²⁺ from subsoil brine onto coconut shell charcoal has been successfully demonstrated in this work.     

316L不锈钢在Saline溶液中的微动磨蚀行为研究

采用球－平面接触微动磨损试验设备考察了轧制固溶３１６Ｌ不锈钢在Ｓａｌｉｎｅ溶液中的微动磨蚀行为。研究表明,３１６Ｌ不锈钢的微动过程存在显著的阶段性;微动初期为磨合期,第一稳定阶段摩擦副处于高摩擦应力状态,伴随着不锈钢表面缝隙腐蚀与弹塑性损伤的积累;第二过渡阶段和第二稳定阶段不锈钢表面呈微断裂剥层特征,腐蚀引起的微断裂不可忽视,不锈钢微动损伤表面形貌同微动损伤速率之间存在对应关系。     

Numerical Simulation of the Movement of Saltwater under Skimming and Scavenger Pumping in the Pleistocene Aquifer of Gaza and Jericho Areas, Palestine

The Pleistocene aquifers are important sources of water supply in both the Gaza and Jericho areas of Palestine. The aquifers are saline with freshwater lenses floating on saline bodies of water. It is important to investigate how to exploit these freshwater lenses without causing unnecessary mixing of the fresh and saline waters. The objective of this research is to investigate the feasibility of applying skimming and scavenger pumping as a means to exploit the freshwater lenses and to control saline water upconing in the aquifers. This study is the first to examine the movement of fresh and saline waters underneath skimming and scavenger wells in the aquifers of Gaza and Jericho. Two simulation models that couple density-dependent fluid flow and solute transport have been used to simulate and predict the movement of saltwater under different hydrogeological and operational conditions of skimming and scavenger wells in the two aquifers. The results show (for the Jericho Aquifer) that: the location of well screen has a strong control on the steady-state position of the fresh/saline water transition zone; the upconing mechanism appears to continue under skimming pumping until saline water enters the well screen even when the pumping rate is reduced; and for better salinity control it is necessary to place well screen against the gravel layers only and locate one screen segment in the saline water zone. The study shows (for the Gaza coastal aquifer) that the most important parameters affecting the movement of saline water under scavenger pumping are the relationship between recharge and pumping rates, the location of the well screen within the saturated thickness, the vertical permeability; and the transverse dispersivity. This study shows that saltwater upconing in Gaza aquifer can be controlled by operating a second well in the saline water zone so that the optimal ratio between saline water and freshwater pumping is 1:2 respectively.     

黄河三角洲盐生草甸白茅(Imperata cylindrica var. major)群落季节性动态的研究

采用定位研究的方法研究了生长季白茅(Imperata cylidrica var. major)群落的主要特征和动态。群落的种类组成较简单,其盖度一般在七月中旬达到100％。群落的高增长及地上生产量符合逻辑斯蒂增长模型(Logistic model),并主要受环境中水分和温度因子的影响。群落的最大高度为59cm,出现在八月中旬;地上生产量最大值为干重563g/m~2,出现在九月中旬。     

Free convection flow over a truncated cone embedded in a porous medium saturated with pure or saline water at low temperatures

Steady free convection boundary layer about a truncated cone embedded in a porous medium saturated with pure or saline water at low temperatures has been studied in this paper. The governing coupled partial differential equations are solved numerically using a very efficient finite-difference method. Several new parameters arise and the results are given for some specific values of these parameters. The obtained results for a Boussinesq fluid are compared with known results from the open literature and it is shown that the agreement between these results is very good.