Activation of dispersed PtSn/C nanoparticles by tungsten oxide matrix towards more efficient oxidation of ethanol

A novel electrocatalytic system for oxidation of ethanol, in which carbon-supported PtSn nanoparticles were modified with ultra-thin films/deposits of tungsten oxide, was proposed, fabricated and characterized here using electrochemical as well as spectroscopic (X-ray diffraction) and microscopic (transmission electron) techniques. The enhancement effect was evident from comparative diagnostic electrochemical experiments utilizing WO₃-modified and bare (unmodified) PtSn nanoparticles in acid medium (0.5 mol dm⁻³ H₂SO₄) at room temperature in the presence of ethanol. It is noteworthy that, the chronoamperometric electrocatalytic currents measured at potentials as low as 0.3 V (vs. RHE) were significantly larger for WO₃-modified PtSn/C relative to bare PtSn/C. In another diagnostic “stripping” experiment, it was found that oxidation of CO-adsorbate occurred in the presence of WO₃ at potentials almost 100 mV lower in comparison to the unmodified system. The overall activation effect may have origin in interactions of tungsten oxide with tin (from PtSn alloy nanoparticles) leading to stabilization of the catalytic tin oxo species. WO₃ may also provide large population of reactive oxo groups at the Pt/Sn-based electrocatalytic interface.     

Characterizing temporal development of biofilm porosity using artificial neural networks

We used artificial neural networks (ANN) to compute parameters characterising biofilm structure from biofilm images and to interpolate a limited number of experimental data characterising the effects of nutrient concentration and flow velocity on the areal porosity of biofilms. ANN were trained using a set of experimental data characterising structural parameters of biofilms of Pseudomonas aeruginosa (ATCC #700829), Pseudomonas fluorescens (ATCC #700830) and Klebsiella pneumoniae (ATCC #700831) for various flow velocities and glucose concentrations. We used 80% of the data to train ANN and 10% of the data to validate the results, which is routinely carried out as a countermeasure against overtraining. Trained ANN were used to interpolate into the data set and evaluate the missing 10% of the data. To compare ANN accuracy in evaluating the missing data with the accuracies achieved using other interpolation algorithms, we used spline, cubic, linear and nearest-neighbour interpolation algorithms to evaluate the missing data. ANN estimates were consistently closer to the experimental data than the estimates made using the other methods.     

EXISTENCE OF A GENERALIZED SOLUTION IN THERMOELASTICITY WITH TWO RELAXATION TIMES,PART II

The existence of a generalized solution to a natural stress-temperature initial-boundary value problem of linear thermoelasticity with two relaxation times is established in a functional space of the Sobolev type.     

Thermal stability of poly(2-ethylhexyl acrylates) used as plasticizers for medical application

This article discusses thermal analysis of different molecular weight poly(2-ethylhexyl acrylates) synthesized by radical polymerization of 2-ethylhexyl acrylate. The main aim of this work was to investigate the thermal properties and degradation process of synthesized acrylic homopolymers and forming of thermal degradation products during their pyrolysis. As investigated method pyrolysis combined with gas chromatography was used. Poly(2-ethylhexyl acrylates) are used as plasticizers for pressure-sensitive adhesives applied in medical area.     

Investigations on printed elastic resistors containing carbon nanotubes

This paper presents the results of authors investigations on elaboration of a new thick film composition filled with carbon nanotubes (CNTs). The polymer composition consists of polymer vehicle, which is the solution of organic resin in certain combination of solvents, and functional phase—carbon nanotubes well dispersed in the vehicle. The pastes were applied with screen-printing on several substrates and temperature cured. The properties of obtained layers were characterized. Series of samples were prepared with different amount of CNTs to evaluate electrical properties. Changes in resistance were investigated during periodic mechanical and temperature stresses, realized through cyclical bending and rapid temperature change. Tensometric effect was also investigated. Investigations have proved that polymer composites based on carbon nanotubes exhibit high resilience to stress factors. Resistance change in function of temperature was also investigated to evaluate temperature coefficient of resistance (TCR). All this aspects are important for elastic resistors fabrication in printed electronics microcircuits. Resistance and noise measurements in cryostats have also been involved. 1/f type noise has been observed. Noise intensity, calculated in decade frequency bands, rises significantly with increasing temperature. Activation energies of thermally activated noise sources (TANS) have been revealed using low-frequency noise spectroscopy. Relatively large value of negative TCR has been obtained from resistance versus temperature curve. Calculated dimensionless sensitivity is similar to that observed in cryogenic temperature sensors. However, bulk noise intensity of resistive layer is larger than obtained for lead containing RuO₂ based resistive layers.     

Processing and recognition of the thermal images using wavelet transforms

This paper presents methods for improving the quality of IR images that significantly facilitate the detection of physical and structural non-uniformities in layered objects. The methods are based on wavelets transformations. Both, discrete and continuous wavelet transforms were used. The space-scale representation of thermal image are used for the detection thermal non-uniformities in the objects examined. Examples of recorded and improved images are presented in this paper.     

Evaluating the Impact of Mine Groundwater on the Environment

Efficient monitoring of mine groundwater conducted with a standard methodology makes the evaluation of the influence of mine water on the environment easier. The paper examines problems of monitoring and proposes a groundwater monitoring system for existing and flooded abandoned mines. The final effect of mine waters monitoring enables ecochemical and economical evaluation. It also makes it possible to select and use the appropriate proecological technologies for mine waters.     

Calculation of the internal thermal resistance and ampacity of3-core screened cables with fillers

All 3-core cables require fillers to fill the space between insulated cores and the belt insulation or a sheath. The equations given in IEC 287 and in the Neher-McGrath paper (1957) for the internal thermal resistance of 3-core cables were developed for paper insulated cables. For such cables, it was assumed that the insulation and filler materials have the same thermal resistivities. In reality, in 3-core cables a variety of materials are used as fillers. The majority of these will have a higher thermal resistivity than the insulation. In the previous paper, a new formula was developed to compute the value of the internal thermal resistance of belted cables taking into account the thermal resistivity of the filler. In this paper, screened cables are considered and a new formula for the computation of the internal thermal resistance of such cables is presented. The effect of filler resistivity on cable ampacity is also discussed     

Sorption of heavy metal ions from aqueous solutions in the presence of EDTA on monodisperse anion exchangers

Conventional precipitation methods of industrial sewage and wastewater purification are not very effective and are insufficient in many cases. This implies the necessity of searching new, effective methods exploiting cheap, accessible and ecologically safe ion exchangers and sorbents. The paper presents the studies on removal of heavy metal ions — Cu(II), Zn(II), Co(II), Ni(II) and Fe(III) — from aqueous solutions in the presence of EDTA carried out on commercially available, strongly basic monodisperse anion exchangers with the polystyrene skeleton gel, Lewatit MonoPlus M 500; and the macroporous, Lewatit MonoPlus MP 500, which are more widely applied in water purification processes. The research results indicate a high affinity of the Lewatit MonoPlus M 500 and Lewatit MonoPlus MP 500 anion exchangers in the chloride form for copper(II), nickel(II), cobalt(II) and zinc(II) complexes with EDTA. The affinity series for the heavy metal complexes in the 0.001 M M(II)/(III)–0.001 M EDTA and 0.001 M M(II)/(III)–0.001M EDTA–0.001 M–0.002 M NaOH systems were found for the Lewatit MonoPlus M 500 anion exchanger in the chloride form to be as follows: Cu(II) > Ni(II) > Co(II) > Zn(II) Fe(III). In the case of the Lewatit MonoPlus MP 500 anion exchanger in the chloride form there was found the following affinity series: Cu(II) > Co(II) > Ni(II) > Zn(II) Fe(III). These anion exchangers can be applied in the removal of copper(II) complexes from waters and wastewaters.