Rapid determination of atrazine in environmental water samples by a novel liquid phase microextraction

A novel method was described for the rapid determination of atrazine using dispersive liquid phase microextraction in combination with high performance liquid chromatography （HPLC）. Possible impact parameters such as sample pH, extraction and disperser solvents, salting-out effect, and extraction time were investigated. The experimental results indicated that proposed method possessed an excellent analytical performance, The linear range, detection limit, and precision （R.S.D.） were 0.1- 50 ng mL- 1 （R2 = 0.9955）, 0.601 ng mL- 1 and 6,4%, respectively. The proposed method was validated with the real water samples, and the spiked recoveries were in the range of 69.9-89.8%, respectively. These results indicated that the established method with high enrichment factor, short extraction time was an excellent alternative for the routine analysis of atrazine in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A Graded and Individualized Teaching and Learning method

Taking the programming course as an example,a comprehensive solution for individualized and precise teaching has been proposed.Firstly,graded teaching strategy is performed.The students are divided into three groups according to their base of learning and the degree of acceptance of knowledge.Designed teaching resources are provided for the teaching mode of low starting points and high landing points.Secondly,a process evaluation method combining online and offline has been proposed.An“evaluation-feedback-improvement”mechanism based on the analysis of students’learning data has been adopted.The practice in Harbin Institute of Technology has shown that the proposed method can not only help students achieve individualized learning goals,but also help teachers achieve precise teaching.

Carbon nanotube-based photothermal membrane for efficient cold air heating and removal of particulate matter and airborne bacteria

Indoor heating results in high energy consumption and severe atmospheric pollution.Although the development of solar air heaters provides a sustainable route for indoor thermal comfort,such heaters still face challenges in terms of adequate heat exchange and filtering of atmospheric pollutants.Inspired by solar-driven interfacial evaporation,we propose a multifunctional carbon nanotube-based photothermal membrane for efficient cold air heating and purification via ventilation.Carbon nanotubes endow the membrane with high light absorption and thermal conversion capabilities,thereby sufficiently heating the approaching cold air.With the hierarchical structure formed by phase inversion,the thin upper skin of the composite membrane intercepts micropollutants via the size-sieving effect,whereas the finger-like pores and interpenetrating macrovoids inside the membrane ensure that the heated clear air passes through quickly.A proof-of-principle experiment indicated a cold airflow of 1 L/min across the membrane,yielding a temperature increase of ca.37℃ as well as a PM 2.5 rejection always higher than 93%.Further antibacterial experiments demonstrated that the membrane effectively removed airborne bacteria.This multifunctional carbon nanotube-based photothermal membrane with specific microstructures not only improves the indoor living quality but also provides a sustainable development scheme to coordinate the relationship among energy utilization,building heating,and air purification.

Construction of multiple concentration gradients for single-cell level drug screening

Isolation and manipulation of single cells play a crucial role in drug screening.However,previously reported single-cell drug screening lacked multiple-dose concentration gradient studies,which limits their ability to predict drug performance accurately.To solve this problem,we constructed a multiconcentration gradient generator in which a Tai Chi-spiral mixer can accelerate solution mixing in a short time and produce a linear concentration gradient.Later,a gradient generator combined with a single-cell capture array was adopted to investigate the effects of single or combined doses of 5-fluorouracil and cisplatin on human hepatoma cells and human breast carcinoma cells(at the single-cell level).The results showed that both drugs were effective in inhibiting the growth of cancer cells,and the combination was more effective for human hepatoma cells.In addition,the relationship between the biomechanical heterogeneity(e.g.,deformability and size)of tumor cells and potential drug resistance at the single-cellevel was investigated,indicating that small and/or deformable cells were more resistant than large and/or less deformable cells.The device provides a simple and reliable platform for studying the optimal dosage of different drug candidates at the single-cell level and effectively screening single-agent chemotherapy regimens and combination therapies.

TIPS Is Not Associated with a Higher Risk of Developing HCC in Cirrhotic Patients:A Systematic Review and Meta-analysis

Background and Aims:The association between portalsystemic shunt and hepatocellular carcinoma(HCC)development in patients who have cirrhosis is still controversial.This systematic review with meta-analysis was performed to systematically clarify the potential role of portal-systemic shunt in the development of HCC.Methods:The PubMed,Embase,and Cochrane Library databases were searched for potentially eligible literature.Meta-analysis with random-effects model was performed to combine the incidence rates of HCC after portal-systemic shunt.Finally,seven studies were included.In the present review,we mainly focused on 859 patients(365 in the transjugular intrahepatic portal-systemic shunt(TIPS)group and 494 in the non-TIPS group)from five studies to analyze incidence rates after TIPS.Results:At the end of follow-up,there were 66(18%,66/365)patients who developed HCC after TIPS intervention and 63(13%,63/494)patients who developed HCC after non-TIPS treatments.Pooled estimates with random-effects model did not demonstrate a significant increase of incidence of HCC after TIPS(risk ratio:1.37[confidence interval(CI):0.96 to 1.97];p=0.08)compared with non-TIPS treatments.Subgroup analyses for those patients with transplanted liver also did not detect a significant difference between the TIPS group and non-TIPS group(risk ratio:1.10[CI:0.59 to 2.07];p=0.75).Conclusions:Current evidence suggests that portal-systemic shunt is not associated with a higher risk of HCC development in cirrhotic patients.

Determination of VOCs in groundwater at an industrial contamination site using a homemade low-density polyethylene passive difusion sampler

A home-made inexpensive passive diffusion bag （PDB） sampler, prepared by filling deionized water in low-density polyethylene （LDPE） tubes, was evaluated for volatile organic compounds （VOC） sampling in groundwater at industrial contamination sites. Impacts of environmentally relevant conditions on the sampling equilibration time and partitioning of VOCs between the sampler and the water sample were investigated. Sample salinity, agitation and temperature can influence the equilibration time, but generally sampling equilibration was obtained in 14 days under real field sampling of VOCs in groundwater. Both laboratory study and field testing in a contaminated site showed that the VOC concentrations in the developed sampler were equal to those in the water samples at equitibrium. Coupled with a purge and trap concentrator-gas chromatograph-mass spectrometer （P＆T-GC-MS）, the developed PDB sampler provided a low-cost sampling device for routine monitoring of VOCs in groundwater in wells, with LODs in the range of 2.9-10 μg/L. The proposed PDB was applied to determine VOCs in groundwater at an industrial contamination site, and the present results agreed well with those determined using conventional pump-and-sample monitoring. All the studied 13 VOCs were tested in the four wells in the industrial contamination sites, with their concentrations in the range of 12-73660 μg/L. In addition, while benzene and toluene were heavily contaminated up to a maximum concentration of 74000 μg/L and 6000 μg/L, respectively, 1,2,3-trichlorobenzene and bromobenzene had relatively low contamination levels （below 25 μg/L）.

Microfluidic Device： A Miniaturized Platform for Chemical Reactions

Microfluidic devices, as a new miniaturized platform stemming from the field of micro-electromechanical sys-tems, have been used in many disciplines. In the field of chemical reactions, microfluidic device-based microreac-tors have shown great promise in building new chemical technologies and processes with increased speed and reli- ability and reduced sample consumption and cost. This technology has also become a new and effective tool for precise, high-throughput, and automatic analysis of chemical synthesis processes. Compared with conventional chemical laboratory batch methodologies, microfluidic reactors have a number of features, such as high mixing ef- ficiency, short reaction time, high heat-transfer coefficient, small reactant volume, controllable residence time, and high surface-to-volume ratio, among others. Combined with recent advances in microfluidic devices for chemical reactions, this review aims to give an overview of the features and applications of microfluidic devices in the field of chemical synthesis. It also aims to stimulate the development of microfluidic device applications in the field of chemical reactions.

aging structures in the presence of incomplete deterioration information

The performance of an aging structure is commonly evaluated under the framework of reliability analysis, where the uncertainties associated with the structural resistance and loads should be taken into account. In practical engineering, the probability distribution of resistance deterioration is often inaccessible due to the limits of available data, although the statistical parameters such as mean value and standard deviation can be obtained by fitting or empirical judgments. As a result, an error of structural reliability may be introduced when an arbitrary probabilistic distribution is assumed for the resistance deterioration. With this regard, in this paper, the amount of reliability error posed by different choices of deterioration distribution is investigated, and a novel approach is proposed to evaluate the averaged structural reliability under incomplete deterioration information, which does not rely on the probabilistic weight of the candidate deterioration models. The reliability for an illustrative structure is computed parametrically for varying probabilistic models of deterioration and different resistance conditions, through which the reliability associated with different deterioration models is compared, and the application of the proposed method is illustrated.