Extending the Colloidal Transition Metal Dichalcogenide Library to ReS2 Nanosheets for Application in Gas Sensing and Electrocatalysis

Among the large family of transition metal dichalcogenides, recently ReS₂ has stood out due to its nearly layer‐independent optoelectronic and physicochemical properties related to its 1T distorted octahedral structure. This structure leads to strong in‐plane anisotropy, and the presence of active sites at its surface makes ReS₂ interesting for gas sensing and catalysts applications. However, current fabrication methods use chemical or physical vapor deposition (CVD or PVD) processes that are costly, time‐consuming and complex, therefore limiting its large‐scale production and exploitation. To address this issue, a colloidal synthesis approach is developed, which allows the production of ReS₂ at temperatures below 360 °C and with reaction times shorter than 2h. By combining the solution‐based synthesis with surface functionalization strategies, the feasibility of colloidal ReS₂ nanosheet films for sensing different gases is demonstrated with highly competitive performance in comparison with devices built with CVD‐grown ReS₂ and MoS₂. In addition, the integration of the ReS₂ nanosheet films in assemblies together with carbon nanotubes allows to fabricate electrodes for electrocatalysis for H₂ production in both acid and alkaline conditions. Results from proof‐of‐principle devices show an electrocatalytic overpotential competitive with devices based on ReS₂ produced by CVD, and even with MoS₂, WS₂, and MoSe₂ electrocatalysts.     

Analysis of Xanthate Derivatives by Vacuum Ultraviolet Laser-Time-of-Flight Mass Spectrometry

A series of liquid O,S-dialkyl dithiocarbonates (xanthate esters) have been synthesized, and time-of-flight (TOF) mass spectra were recorded for their vapors using both ultraviolet (UV) and vacuum ultraviolet (VUV) laser excitation. These compounds are chemical derivatives of low vapor pressure xanthate salts which have found important commercial application as collectors in mineral sulfide flotation circuits. Our experiments demonstrate that esters ionized by short-wavelength VUV light can be detected by parent mass with high efficiency and minimal fragmentation. In contrast, the mass spectra of the same compounds obtained by UV light excitation exhibit a large number of low molecular mass peaks. A preliminary quantitative analysis of the composition of a gas-phase mixture of xanthate esters has also been achieved, which indicates possible subfemtomole detection limits.     

Monte Carlo algorithms for evaluating Sobol’ sensitivity indices

Sensitivity analysis is a powerful technique used to determine robustness, reliability and efficiency of a model. The main problem in this procedure is the evaluating total sensitivity indices that measure a parameter’s main effect and all the interactions involving that parameter. From a mathematical point of view this problem is presented by a set of multidimensional integrals. In this work a simple adaptive Monte Carlo technique for evaluating Sobol’ sensitivity indices is developed. A comparison of accuracy and complexity of plain Monte Carlo and adaptive Monte Carlo algorithms is presented. Numerical experiments for evaluating integrals of different dimensions are performed.     

Applying variable precision rough set model for clustering student suffering study’s anxiety

Computational models of the artificial intelligence such as rough set theory have several applications. Data clustering under rough set theory can be considered as a technique for medical decision making. One possible application is the clustering of student suffering study’s anxiety. In this paper, we present the applicability of variable precision rough set model for clustering student suffering studies anxiety. The proposed technique is based on the mean of accuracy of approximation using variable precision of attributes. The datasets are taken from a survey aimed to identify of studies anxiety sources among students at Universiti Malaysia Pahang (UMP). At this stage of the research, we show how variable precision rough set model can be used to groups student in each study’s anxiety. The results may potentially contribute to give a recommendation how to design intervention, to conduct a treatment in order to reduce anxiety and further to improve student’s academic performance.     

Visualizing multiple error-sensitivity fields for single camera positioning

In many data acquisition tasks, the placement of a real camera can vary significantly in complexity from one scene to another. Optimal camera positioning should be governed not only by least error sensitivity, but in addition to real-world practicalities given by various physical, financial and other types of constraints. It would be a laborious and costly task to model all these constraints if one were to rely solely on fully automatic algorithms to make the decision. In this work, we present a study using 2D and 3D visualization methods to assist in single camera positioning based on error sensitivity of reconstruction and other physical and financial constraints. We develop a collection of visual mappings that depict the composition of multiple error sensitivity fields that occur for a given camera position. Each camera position is then mapped to a 3D visualization that enables visual assessment of the camera configuration. We find that the combined 2D and 3D visualization effectively aids the estimation of camera placement without the need for extensive manual configuration through trial and error. Importantly, it still provides the user with sufficient flexibility to make dynamic decisions based on physical and financial constraints that can not be encoded easily in an algorithm. We demonstrate the utility of our system on two real-world applications namely snooker analysis and camera surveillance.     

Generalized Damped Wave Approach for Evaluating Seismic Shear Demands

This paper presents a new analytical approach for simple and explicit computation of the seismic base shear demand of structural systems that can be idealized by a uniform shear-beam model. The approach is based on a Green’s function representation for the relative displacement response that is assumed to be composed of exponentially decaying wave sequences. Explicit solutions for both the strain and displacement response are derived in terms of an effective ground velocity and displacement that can be computed incrementally from the ground acceleration. A physical interpretation for the damping mechanism is proposed. The method is further generalized to form a class of physically motivated shear-beam systems referred to as the continuous spring-dashpot (CSD) model. The response characteristics of three cases of the CSD model along with a shear beam equipped with a mass-proportional external damping are compared and discussed for the case of near-field earthquake excitation.     

Immobilization of glucose oxidase and acetylcholinesterase onto modified polyamide sorbent

Two types of polyamide (PA) sorbents with high specific area were prepared. The effects of solvent type, concentrations of formic acid, and polymer on the porosity characteristics were studied. The sorbent with the highest specific area was obtained by using C₂H₅OH—HCOOH solvent (60% HCOOH) and the rest of the experiments were carried out with this type of sorbent. The possibility of applying the PA sorbent as carrier for immobilization of glucose oxidase (GOD) and acetylcholinesterase (AChE) was investigated. In order to increase the active groups content (necessary for enzyme immobilization), the sorbent was modified with dimethylaminoethylmethacrylate (DMAEM) and 2-acrylamido-2-methylpropensulfonic acid. The amount of the active groups introduced during the modification and the degree of hydrophilicity were determined. The quantity of bound protein and relative activity of GOD and AChE immobilized onto unmodified and modified sorbents were studied. Optimum pH and temperature of the immobilized GOD and AChE were also determined. The influence of three phosphoroorganic compounds on the activity of the immobilized AChE was investigated. Tetrachlorvinvos was found to be the strongest inhibitor, while AChE immobilized onto PA sorbent modified with DMAEM showed the highest stability. The possibility of using immobilized GOD and AChE in a flow-injection system for determination of the concentrations of glucose and phosphoroorganic compounds was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:323–329, 1998     

Decoupling of Confined Normal 3He

Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined ³He. For pure ³He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid’s inertial contribution was negligible, indicating a complete decoupling of the ³He from the pendulum.