Corrosion of Au–Pd–In alloy in simulated physiological solutions

The corrosion of Au–Pd–In alloy, which is of great importance in dentistry, has been studied using an electrochemical quartz crystal microbalance (EQCM) in simulated physiological solutions. The alloy was deposited on quartz substrates by means of magnetron sputtering (MS). Analysis performed using X-ray photoelectron spectroscopy showed that the chemical composition of the sputtered deposit was similar to that of the MS target made of conventional casting alloy. Investigations by X-ray diffraction indicated a crystalline structure of the MS alloy. The electrochemical and corrosion behaviour of the Au–Pd–In alloy was studied in three simulated physiological solutions: 0.9 M NaCl, 0.1 M NaCl + 0.1 M lactic acid and artificial saliva. Determination of break down potential was complicated by the anodic gold dissolution due to formation of a chloride complex. The onset of anodic currents, therefore, indicated not the potential at which the passive layer starts to be destroyed, but the exceeding of the Au/AuCl₄ ^– equilibrium potential, which does not directly reflect corrosion resistance. The EQCM measurements under open circuit conditions indicated corrosion as an increase in mass, caused by the accumulation of corrosion products on the alloy surface. The increase in mass in acidic solution (pH 2.2) was similar to that in neutral solution (pH 6.5), which implies dissolution of corrosion products to be insignificant.     

Scattering of electrons by confined interface polar optical phonons in a double-barrier heterostructure

It is shown that capture of the surface (interface) phonons can occur in a double-barrier heterostructure in addition to the capture of bulk polar optical phonons. The strength of interaction of electrons with confined interface phonons becomes lower as the thickness of the phonon well (a semiconductor layer where phonons are captured) is decreased. A new approach is suggested for reducing the scattering of electrons by polar optical phonons in a double-barrier quantum well; this approach is based on separate capture of phonons in narrow phonon wells. The calculated scattering rate with the capture of interface phonons into the GaAs/InAs/GaAs and AlAs/GaAs/AlAs quantum wells taken into account is found to be much lower than the rate obtained in the approximation of scattering of electrons by bulk phonons. A multifold decrease in the rate of electron-phonon scattering in the AlAs/GaAs/AlAs quantum well is obtained by separating this well by the monomolecular InAs layer that is transparent for electrons but acts as a reflecting barrier for polar optical phonons.     

Adhesion of graphene oxide on a transparent PET substrate: a study focused on the optimization process

The procedure with the aim to optimize a process of transfer of GO layer, formed by filtration on a PET substrate, was run out in two stages. First, using a Plackett–Burman experimental design strategy was to investigate the most significant technological parameters. Seven types of different interlayer materials (composed either of polymers or smaller organic molecules) were used to improve the quality of the operation. Using a quantitative structure property relationship strategy, it was stated that the hydrogen bonds play a very important role in the quality assurance of the process of GO transfer. However, hydrogen bonds formed between GO sheets and interlayer molecules influence only in the case when these molecules are sufficiently large. SEM images have shown that the morphology of GO layer after transfer is dependent on the interlayer material. Raman spectra revealed typical changes in the structure of GO layer using different interlayer materials. Arrangement of GO sheets in the layer and the structure of the GO single layer can be controlled by using appropriate interlayer materials. It was found that the main parameters, operating the quality of the process of GO transfer are: the thickness of interlayer, the coating thickness, and the temperature. At the second stage, using a simplex optimization strategy, a specific set of optimal values to obtain the best quality during the transfer procedure, was determined.     

Electrocatalytic activity of the nanostructured Au–Co catalyst deposited onto titanium towards borohydride oxidation

The nanostructured gold–cobalt catalysts were deposited onto titanium surface via galvanic displacement technique. The electrocatalytic activity of the as-prepared nanostructured Au(Co)/Ti catalysts was examined in respect to the oxidation of ₄BH⁻${{\text{BH}}_4}^{-}$ ions in alkaline medium by using of the cyclic voltammetry and chrono-techniques. The nanostructured catalysts were prepared via galvanic displacement reactions between hierarchical Co thin films prepared by electroless deposition and a solution of HAuCl₄. The surface morphology and composition of the samples were characterized using Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and X-ray diffraction. The prepared nanostructured Au(Co)/Ti catalysts exhibit an enhanced electrochemical activity towards the electro-oxidation of H₂ generated by catalytic sodium borohydride hydrolysis and oxidation of ₄BH⁻${{\text{BH}}_4}^{-}$ ions.     

Human capital as a location factor: An empirical investigation of relocating firms and their labour force in the Netherlands

This paper examines the role of human capital as a location factor in the context of long‐distance firm relocations. Using rich register data on single‐plant firms in the Netherlands 2006–2011, the paper enquires into whether relocation is motivated by the wish to improve the access to employees and the quality of labour force. Not disrupting existing spatial relationships is a prominent consideration of relocating firms, yet in general, relocation does not result in a better spatial match. Some evidence is found for firm‐specific human capital functioning as a keep factor. Relocating firms retain predominantly highly skilled employees, but general human capital itself functions neither as a keep factor nor as a pull factor.     

Electron mobility and drift velocity in selectively doped InAlAs/InGaAs/InAlAs heterostructures

An increase in the electron mobility and drift velocity in high electric fields in quantum wells of selectively doped InAlAs/InGaAs/InAsAs heterostructures is obtained experimentally via controlling the composition of semiconductors forming the interface. The electron mobility at the interface in the In_0.8Ga_0.2As/In_0.7Al_0.3As metamorphic structure with a high molar fraction of In (0.7–0.8) is as high as 12.3 × 10³ cm² V⁻¹ s⁻¹ at room temperature. An increase in the electron mobility by a factor of 1.1–1.4 is attained upon the introduction of thin (1–3 nm) InAs layers into a quantum well of selectively doped In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructures. A maximal drift velocity attains 2.5 × 10⁷ cm/s in electric fields of 2–5 kV/cm. The threshold field F _th for the intervalley Γ-L electron transfer (the Gunn effect) in the InGaAs quantum well is higher than in the bulk material by a factor of 2.5–3. The effect of two- to threefold decrease in the threshold field F _th in the InGaAs quantum well is established upon increasing the molar fraction of In in the InAlAs barrier, as well as upon the introduction of thin InAs inserts into the InGaAs quantum well.     

Structural and pharmacological characterization of phenylalanine-based AMPA receptor antagonists at kainate receptors

Continued efforts into the discovery of ligands that target ionotropic glutamate receptors (iGluRs) are important for studies of the physiological roles of the various iGluR subtypes as well as for the search for drugs that can be used in the treatment of diseases of the central nervous system. A new series of phenylalanine derivatives that target iGluRs was reported to bind AMPA receptors. Herein we report our studies of these compounds at the kainate receptors GluK1-3. Several compounds bind with micromolar affinity at GluK1 and GluK3, but do not bind GluK2. The crystal structure of the most potent compound in the ligand binding domain of GluK1 revealed different modes of binding to GluK1 and GluA2, due primarily to residues Ser741 (GluK1) and Met729 (GluA2). The compound was shown to be slightly more potent at GluK1 than at AMPA receptors and to induce a domain closure similar to that observed in GluK1 structures with partial agonists.     

Rapid method to determine suitability of ABS plastics for metallisation

In this study, the metallisation of acrylonitrile–butadiene–styrene (ABS) plastics has been investigated. The adhesion of the metallic layer on ABS was studied by the cross-cut test. Raman spectroscopy was used to evaluate the components of ABS plastics. The results indicate that Raman spectroscopy can be applied for rapid determination of suitability of ABS plastics for metallisation.     

Development of bigel based dysphagia-oriented products,structured with collagen and carnauba wax: characterisation and rheological behaviour

The aim of the study was to design composition of the bigels with required rheological properties that responds the needs of the dysphagia patients. Bigels were prepared with carnauba wax and different collagen concentrations in the hydrogel phase (40, 60%) as well as by changing oleogel to hydrogel ratio from 40:60 to 60:40. The stability, physical and rheological properties of obtained bigels were evaluated after their preparation and after 14 days storage. All obtained bigels were stable without phase separation and had a pleasant taste and good mouth-feel, exept bigels with the higher oleogel fraction. Viscosity values at 50 s⁻¹ divided formulated bigels into two groups: honey-like and spoon thick. An increase of oleogel fraction caused an increase in the consistency index and elastic modulus. Higher firmness and cohesiveness values were obtained in the samples with the higher collagen concentration. It was also obtained that all rheological parameters increased after 14 days of storage. The present work develops a novel bigel-based product with strong shear-thinning behaviour and high protein concentration (16–36%). It is believed that such product could not only ensure the safe swallowing process but also reduce the risk of malnutrition development.