Electrochemical response of a composite Pt/TiO2 layer formed potentiodynamically on titanium surfaces

By potentiodynamic polarization of mechanically polished titanium in a diluted aqueous solution of hexachloroplatinic acid, nearly spherical Pt microparticles were grown, embedded into the simultaneously formed TiO₂ film. The real surface of platinum may be easily controlled by the number of potentiodynamic cycles, and roughness factors exceeding 100 were obtained. Within the potential region of both hydrogen and oxygen underpotential deposition, in both acidic and alkaline solutions, the electrode displayed an excellent electrochemical response characteristic of smooth polycrystalline platinum, unlike to highly dispersed platinum electrodes produced by other methods. The preparation method applied in this work presents an easy way to obtain an electrode surface combining the behaviour of smooth polycrystalline platinum with the behaviour of microdisc arrays. Its high electrocatalytic effectiveness was demonstrated for oxygen reduction and bromide ion adsorption/oxidation.     

Electrical properties of barium titanate stannate functionally graded materials

Barium titanate stannate (BTS) functionally graded materials (FGMs) with different tin/titanium concentration gradient were prepared by the powder-stacking method and uniaxially pressing process, followed by sintering. Impedance spectroscopy (IS) was used to determine the electrical characteristics of FGMs and ingredient BTS ceramics, as well as to distinguish the grain-interior and grain boundary resistivity of the ceramics. Activation energies of FGMs and ingredients were calculated. It has been established that for BTS ceramics the activation energy deduced from grain-interior conductivity (0.73–0.75 eV) is defined by chemical composition, while activation energy for grain boundary conductivity (1.07–1.25 eV) is influenced by microstructural development (density and average grain size). Furthermore, for FGMs, activation energy for grain-interior conductivity kept the intrinsic properties (0.74–0.78 eV) and did not depend on tin/titanium concentration gradient, while activation energy (1.03–1.29 eV) for grain boundary was determined by the microstructural gradient. No point dissipation was observed by IS, accordingly, no insulator interfaces (cracks and/or delamination) between graded layers were detected.     

Electrochemical properties of nanostructured Li1.2V3O8 in aqueous LiNO3 solution

The amorphous hydrated precursor of Li_1.2V₃O₈ was synthesized by soft chemistry method, and then heat-treated in air at several temperatures within the range 200–400 °C. The heat-treatment changed its morphological, structural and charging/discharging performance. The product obtained upon the treatment at 300 °C, consisting of uniform, rod-shaped particles, 100–150 nm in diameter and 300–800 nm in length, displayed the best electrochemical performance in aqueous LiNO₃ solution. Its initial discharge capacity amounted to 136.8 mAh g⁻¹ at a rate of C/5, which upon 50 charging/discharging cycles decreased for only 12%.     

Electrochemical polymerization of 2-methyl-1-naphthylamine

Summary 2-methyl-1-naphthylamine has been electropolymerized from the acidic aqueous solutions by three different synthetic routes. The polymerization products, deposited at a platinum working electrode as very adherent films, were characterized by cyclic voltammetry (CV), infrared spectroscopy (IR) and gel permeation chromatography (GPC). In a strongly acidic medium, the products display redox properties, in a form of two well-defined redox pairs with the formal potentials at 0.19 V and 0.47 V vs. SCE. IR-spectroscopy indicated that the polymerization occurs via the –NH₂ groups, by different coupling ways: N-C(4), N-C(5) and N-C(7), as well as that CIO ₄ ^- ions incorporate themselves into the product of electropolymerization. GPC of the polymerization products evidenced oligomeric chains with molar masses up to 1600 g/mol as main species.     

The Genetic Basis of Strokes in Pediatric Populations and Insight into New Therapeutic Options

Strokes within pediatric populations are considered to be the 10th leading cause of death in the United States of America, with over half of such events occurring in children younger than one year of life. The multifactorial etiopathology that has an influence on stroke development and occurrence signify the importance of the timely recognition of both modifiable and non-modifiable factors for adequate diagnostic and treatment approaches. The early recognition of a stroke and stroke risk in children has the potential to advance the application of neuroprotective, thrombolytic, and antithrombotic interventions and rehabilitation strategies to the earliest possible timepoints after the onset of a stroke, improving the outcomes and quality of life for affected children and their families. The recent development of molecular genetic methods has greatly facilitated the analysis and diagnosis of single-gene disorders. In this review, the most significant single gene disorders associated with pediatric stroke are presented, along with specific therapeutic options whenever they exist. Besides monogenic disorders that may present with stroke as a first symptom, genetic polymorphisms may contribute to the risk of pediatric and perinatal stroke. The most frequently studied genetic risk factors are several common polymorphisms in genes associated with thrombophilia; these genes code for proteins that are part of the coagulation cascade, fibrolysis, homocystein metabolism, lipid metabolism, or platelets. Single polymorphism frequencies may not be sufficient to completely explain the stroke causality and an analysis of several genotype combinations is a more promising approach. The recent steps forward in our understanding of the disorders underlying strokes has given us a next generation of therapeutics and therapeutic targets by which to improve stroke survival, protect or rebuild neuronal connections in the brain, and enhance neural function. Advances in DNA sequencing and the development of new tools to correct human gene mutations have brought genetic analysis and gene therapy into the focus of investigations for new therapeutic options for stroke patients.     

Carbonized polyaniline nanotubes/nanosheets-supported Pt nanoparticles: Synthesis, characterization and electrocatalysis

Nitrogen-containing carbonized polyaniline nanotubes/nanosheets were used to synthesize a novel type of supported Pt nanoparticles electrocatalyst PtNPs/Carb-nanoPANI, with the Pt nanoparticles of ~ 9 nm in diameter. PtNPs/Carb-nanoPANI nanocomposite was characterized by transmission electron microscopy, cyclovoltammetry, thermogravimetric and XRD analyses. Its electrocatalytic activity towards the oxygen reduction reaction in both the alkaline and acidic solutions was studied by a rotating disc technique. In acidic media, this electrocatalyst was compared to both smooth platinum and commercial C-supported Pt-based electrocatalyst. Its higher specific electrocatalytic activity, which amounted to ~ 1 mA cm^− 2 in the region of diffusion control, was proved. High electrocatalytic activity of PtNPs/Carb-nanoPANI towards the ethanol oxidation reaction in acidic medium was also evidenced.     

Monitoring for exposures to TENORM sources in Vojvodina region

TENORM are found in a wide variety of waste materials, some raw mineral ores and in some consumer products (in trace amounts) where molecules of radionuclides may be bound to specific minerals used in the manufacturing process and can result in increases in radiation exposures to workers and the public. The aim of this paper is to understand this problem and to develop effective ways to protect humans and the environment from harmful exposure to the radiation in TENORM materials in the Vojvodina region. The results of measurement of indoor radon concentration in schools and kindergartens and dose-rate and gamma-spectrometry measurements of the workplace with TENORM materials are presented.     

Approximation of the carrier generation rate in illuminated silicon

In order to shorten the calculation time for solar cell properties, the light generation rate usually expressed as a sum of individual contributions over the whole solar spectrum is replaced by a curve-fitted approximation. This approximation is represented by a series of three to five exponential terms resulting in an analytical solution of the continuity equation which has the same form as for the actual generation rate. Using the proposed approximation the calculated contribution of the base region to the short-circuit current fits closely the result obtained with the actual generation rate.     

Electrochemical Oxidation of Phenol on Metal‐Impregnated Zeolite Electrodes

Nanodispersed metallic clusters of platinum, silver and cobalt were incorporated into NaX zeolite cavities by impregnation with acetone solution of corresponding acetylacetonates and solvent evaporation followed by acetylacetonate thermal decomposition. The mixture of modified zeolites and 10 wt % of carbon black, in the form of a thin layer, was pasted onto a glassy carbon surface by Nafion. With such electrode materials, the phenol oxidation in neutral, alkaline and acid solution was studied by cyclovoltammetry. Deactivation of all electrodes in both neutral and alkaline medium was observed, indicating that polymerization reaction might be the main reaction pathway of phenol at higher pH values. Formation of quinine‐type structures was obtained during electro‐oxidation at lower pH values, being more significant in acidic solutions.