Single-Molecule Sensing of Acidic Catecholamine Metabolites Using a Programmable Nanopore

Acidic catecholamine metabolites, which could serve as diagnostic markers for many diseases, demonstrate an importance of accurate sensing. However, they share a highly similar chemical structure, which is a challenge in the design of sensing strategies. A nanopore may be engineered to sense these metabolites in a single molecule manner. To achieve this, a recently developed programmable nano-reactor for stochastic sensing (PNRSS) technique adapted with a phenylboronic acid (PBA) adaptor was applied. Three acidic catecholamine metabolites, including 3,4-dihydroxyphenylacetic acid (DOPAC), 3,4-dihydroxymandelic acid (DHMA) and 3-methoxy-4-hydroxymandetic acid (VMA) were investigated by PNRSS. Specifically, DHMA, which contains an α-hydroxycarboxylate moiety and an adjacent cis-hydroxyl groups on its benzene ring, reports two binding modes simultaneously resolvable by PNRSS. Assisted with the high resolution of PNRSS, direct regulation of these two binding modes by pH can also be observed. A custom machine learning algorithm was also developed to achieve automatic event classification.     

Assessing political second screening behavior and personality traits: The roles of economic development,freedom of expression and monochromatic vs. polychromatic cultures

This study focuses on an emerging media multitasking phenomenon called second screening or dual screening. Employing two-wave panel-data from 19 countries, we test whether the Big Five personality traits help explain the use of an additional screen or device while watching political content on TV to discuss the program with others or to look up for additional information. Results show that extraversion positively predicts political second screening. In contrast, agreeableness and openness to new experience are negatively related to political second screening. Moreover, multilevel analysis is performed to test whether the between-country variation is related to economic, political and cultural indicators.     

PSO-LSSVM对LIBS定量分析精度的提高

针对土壤定量分析受基体效应影响大，LIBS定量分析精度不佳等问题，采用粒子群算法对LSSVM进行优化，提高模型的精确度。选取Pb Ⅰ 405.78 nm和Cr Ⅰ 425.44 nm作为分析谱线进行分析。采集十二个不同浓度样品的特征光谱，每个浓度样品在不同点采集20组数据，将其中17组数据设为训练集，3组数据设为预测集，用LSSVM和PSO-LSSVM两种方法建立定标模型。对比两种模型的拟合相关系数（R2）、训练集均方根误差（RMSEC）和预测集均方根误差(RMSEP)。由于自吸收效应的影响，随着浓度的增加，预测值逐渐低于实际值，LSSVM定标模型的拟合程度较低，无法达到实验要求，模型性能有待提高。利用粒子群算法对LSSVM的模型参数惩罚系数和核函数参数进行优化，得到最佳的参数组合，Pb元素为(8 096.8, 138.865 7)，Cr元素为(4 908.6, 393.563 5)，用最佳的参数组合构建LSSVM的定标模型。相比于LSSVM，PSO-LSSVM定标模型的精确度更高，Pb和Cr元素的R2提高到了0.982 8和0.985 0，拟合效果明显提升。Pb和Cr元素的训练集均方根误差由0.026 0 Wt%和0.027 2 Wt%下降到0.022 4 Wt%和0.019 1 Wt%，预测集均方根误差由0.101 8 Wt%和0.078 8 Wt% 下降到0.045 8 Wt%和0.042 0 Wt%，模型的稳定性进一步提高。说明PSO-LSSVM算法能够更好地降低土壤基体效应和自吸收效应带来的影响，提高分析结果的精确度与稳定性。     

Solvent‐free inkjet printing process for the fabrication of conductive,transparent, and flexible ionic liquid‐polymer gel structures

A new and solvent‐free process for the fabrication of inkjet printed ionic liquid‐polymer gel microstructures with high‐resolution (line widths of ～40 μm), good electrical conductivity (5–30 mS cm^?1), optical transparency, and mechanical flexibility is presented. Carrying out the printing and polymerization process in nitrogen atmosphere eliminates the inhibiting influence of oxygen and guarantees homogeneously gelled structures. Careful selection and combination of ionic liquids (ILs) and unsaturated monomers makes it possible to achieve low viscosities which are printable with commercially available inkjet printers and printheads without adding extra solvents. By using different types and amounts of ILs and monomers the resulting properties of the printed IL‐polymer gels can be controlled in terms of ionic conductivity, optical transmission, and mechanical flexibility. Higher conductivities are possible by using a bifunctional instead of a monofunctional monomer, which allows one to lower the amount of monomer without loss in mechanical strength. Cast samples make it possible to obtain data of transmission (～90% for 170‐μm thick films) and mechanical flexibility (E = 0.02–0.23 MPa) of bulk material. Comparing electrical conductivity of printed and cast samples, the higher values of printed samples indicate the conductivity enhancing influence of moisture absorbed from the surrounding atmosphere after the fabrication process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

On weighting two criteria with a parameter in combinatorial optimization problems

Two criteria in a combinatorial problem are often combined in a weighted sum objective using a weighting parameter between 0 and 1. For special problem types, e.g., when one of the criteria is a bottleneck value, efficient algorithms are known that solve for a given value of the weighting parameter.     

缆机起重作业驾驶员的操作行为可靠性研究

缆机是大坝浇筑过程中的主要运输设备之一,缆机驾驶员操作水平直接关系缆机起重作业安全.为有效提高缆机起重作业驾驶员操作行为可靠性,预防起重作业安全事故,针对缆机起重作业周期性多维运动的特点,分解驾驶员操作流程;剖析操作行为失误,建立驾驶员行为模式;从时间角度量化操作流程,计算缆机驾驶员操作行为响应失误概率;构建操作行为可靠性分析模型,定量表达操作行为可靠性,分析人因失误对缆机起重作业安全事故的影响.结果表明,吊具与吊罐对接、混凝土卸料等作业过程的缆机驾驶员操作行为可靠性低,需加强安全培训,严格考核制度,从根本上提高缆机驾驶员操作行为的可靠性,以期提升缆机生产效率,实现预防安全事故的目标.     

Extreme learning machine approach for sensorless wind speed estimation

Precise predictions of wind speed play important role in determining the feasibility of harnessing wind energy. In fact, reliable wind predictions offer secure and minimal economic risk situation to operators and investors. This paper presents a new model based upon extreme learning machine (ELM) for sensor-less estimation of wind speed based on wind turbine parameters. The inputs for estimating the wind speed are wind turbine power coefficient, blade pitch angle, and rotational speed. In order to validate authors compared prediction of ELM model with the predictions with genetic programming (GP), artificial neural network (ANN) and support vector machine with radial basis kernel function (SVM-RBF). This investigation analyzed the reliability of these computational models using the simulation results and three statistical tests. The three statistical tests includes the Pearson correlation coefficient, coefficient of determination and root-mean-square error. Finally, this study compared predicted wind speeds from each method against actual measurement data. Simulation results, clearly demonstrate that ELM can be utilized effectively in applications of sensor-less wind speed predictions. Concisely, the survey results show that the proposed ELM model is suitable and precise for sensor-less wind speed predictions and has much higher performance than the other approaches examined in this study.     

几种吊钩中的力学问题探析

对吊装机械中使用的几种吊钩在吊装重物时的受力情况进行分析和比较,说明了各自的特点及其应用.     

A Disposable Homemade Screen Printed Electrochemical Sensor for Vitamin B1 Determination in Multivitamin Ampoules: Potentiometric and Surface Morphology Studies

Thiamine chloride hydrochloride (TCH) is one of the B‐complex vitamins which resemble a very biologically important group of biomolecules. The first screen‐printed graphite ion‐selective sensor for the determination of TCH was prepared and characterized. The sensor is based on TCH‐tetraphenylborate as electrode material. A number of parameters such as the type of solvent mediator, weight percent of the ion‐exchanger, test solution temperature and possible interferences were extensively studied. Moreover, the surface morphology of the prepared sensor was studied using scanning electron microscopy. The sensor shows a Nernstian slope of 30.60±0.07 mV/decade, a low LOD of 5.08×10⁻⁶ mol/L and a wide applicability range of 5.96×10⁻⁶‐1.00×10⁻² mol/L. The sensing graphite ink remains usable for at least one month. Fast potentiometric response was obtained within 5 s and remains stable for at least 60 s. The sensor was applied to the analysis of TCH in pure solutions and multivitamin ampoules from the Egyptian market using the standard addition method and high recovery values of 97–102 % were obtained. Low %RSD values (0.27‐1.30) indicate high precision of the proposed sensor. Our sensor provides the advantages of disposability, simple preparation procedures, sensitivity and easy storage and transportation.