Evaluation of physicochemical properties of a new group of SiO2/silane/POSS hybrid materials

Preparation of a new group of hybrid fillers, of SiO₂/silane/oligomeric silsesquioxane type, characterised by specific desirable physicochemical properties, was studied. Synthetic SiO₂ was precipitated by the emulsion method. At first, as a result of improved adhesion between SiO₂ and selected POSS compound, SiO₂ surface was functionalised with alkoxysilanes containing characteristics functional groups. Functionalised SiO₂ was used in the process of hybrid filler preparation according to hydrolytic condensation using methacryl POSS® mixture. To evaluate potential application of such fillers, SiO₂ systems, bifunctionalised using innovative method, were thoroughly characterised to determine their physicochemical properties as well as the effectiveness of functionalisation with silanes and POSS compound. Proposed method of SiO₂ surface modification using selected alkoxysilanes and oligosilsesquioxanes is innovative and gives very promising results. Bifunctionalisation of inorganic fillers with those compounds will substantially extended the range of their applications and probably will lead to improvement of mechanical properties of final polymer composites and reduction in the cost of their production which is the main feature of this research. Copyright © 2013 John Wiley & Sons, Ltd.     

May thermal imaging be useful in the assessment of dental anaesthesia? Preliminary study

Journal of Thermal Analysis and Calorimetry - The main goal of this study was to find out if thermal imaging may be useful in the evaluation of two types of anaesthetic injections—with and...     

Laccase–gold nanoparticle assisted bioelectrocatalytic reduction of oxygen

It was found that homogeneous activity of Trametes hirsuta laccase is considerably diminished in the presence of gold nanoparticles (Au-NPs). Heterogeneous electron transfer studies revealed that Au-NPs facilitate direct electron transfer (DET) between the T1 copper site of the laccase and the surface of Au-NP modified electrodes. DET was characterized by the standard heterogeneous ET constant of 0.5 ± 0.6 s^?1 at Au-NPs with an average diameter of 50 nm. As a consequence of this a well pronounced DET based bioelectrocatalytic oxygen reduction with current densities of 5–30 µA cm^?2 has been achieved at the laccase–Au-NP modified electrodes.     

Thermal analysis of nanostructured calcite crystals covered with fatty acids

The way of precipitation process conducting is crucial for the final product properties and its further applications. In present experiments, the CaCO₃ powders, produced by controlled fast precipitation trough gaseous CO₂ absorption in Ca(OH)₂ slurry, have been covered by two fatty acids: dodecanoic (lauric) acid and tetradecanoic (myristic) acid. This multiphase reaction was conducted in a new rotating disc reactor unit which enables to control inter- and intra-face mass and energy transfer as well as the macro- and micromixing effects in the reacting system. The obtained nanopowders have been observed by the use of the scanning electron microscope. The X-ray diffraction technique as well as the dynamic light scattering (DLS) and the thermogravimetric method (TG) were further used for its deep analyses. The experimental data have allowed for distinction between different fatty acid molecules species present on calcite surface (chemisorbed ones, inter-located between adsorbed to surface, formed mono- and bilayers and the soap) or free fatty acids molecules if presented in the sample. The amount of fatty acid species forming different layers on calcite as well as the size and distribution of fatty acid coated CaCO₃ powders have been also calculated.     

Analysis of charge transport in gels containing polyoxometallates using methods of different sensitivity to migration

Two methods have been used for examination of transport of charge in gels soaked with DMF and containing dissolved polyoxometallates. The first method is based on the analysis of both Cottrellian and steady-state currents and therefore is capable of giving the concentration of the electroactive redox centres and their transport (diffusion-type) coefficient. The second method provides the real diffusion coefficients, i.e. transport coefficients free of migrational influence, for both the substrate and the product of the electrode reaction. Several gels based on poly(methyl methacrylate), with charged (addition of 1-acrylamido-2-methyl-2-propanesulphonic acid to the polymerization mixture) and uncharged chains, have been used in the investigation. The ratio obtained for the diffusion coefficient (second method) and transport coefficient (first method) was smaller for the gels containing charged polymer chains than for the gels with uncharged chains. In part these changes could be explained by the contribution of migration to the transport of polyoxomatallates in the gels. However, the impact of the changes in the polymer-channel capacity at the electrode surface while the electrode process proceeds was also considered. These structural changes should affect differently the methods based on different time domains.     

Conductance of alpha-helical peptides trapped within molecular junctions

Self-assembled monolayers of alpha-helical peptides on a gold surface were employed as model systems for the investigation of mediated electron transfer. The peptides contained 14, 15, 16, and 17 amino acid residues. The measurements of electron transmission through single molecules of helical peptides were performed using scanning tunneling spectroscopy (STS). The molecules were trapped between the gold tip and the substrate. Electrical contact between the molecule and the gold probe was achieved by the use of peptides containing thiol groups present at each end of the helix. The conductance behavior of the peptides was examined as a function of tip-substrate distance at fixed bias voltage. Measurements performed with peptides containing different numbers of amino acid residues indicate that the distance dependence of electron transmission through an alpha-helix is weaker than that through simple n-alkyl bridges.     

Identification of some new clemastine metabolites in dog, horse, and human urine with liquid chromatography/tandem mass spectrometry

The metabolism of clemastine was studied in dogs, horses, and humans after a single dose of Tavegyl. The urine collected was extracted by solid-phase extraction or hydrolyzed with beta-glucuronidase and then extracted by liquid-liquid extraction, prior to analysis for unchanged drug and phase I and II metabolites by liquid chromatography/tandem mass spectrometry. The metabolites were identified by their molecular mass and interpretation of the product ion spectra, since no standard substances were available. Unchanged drug was recovered in urine samples from dogs and humans, but not from horses. In dogs and humans, the phase I metabolite, norclemastine, was identified, and clemastine metabolites with one and two additional oxygens were found in all three species. In horses and dogs monohydroxylation on one of the aromatic rings or the adjacent methyl group was favored while, in humans, the additional oxygen was positioned on either the aromatic or the aliphatic part of the structure, and the aliphatic reaction seemed to result in at least three isomers. In the metabolites with two additional oxygens, both the oxygens were found on the aliphatic fragment in humans and dogs, whereas they were situated on the aromatic part of the structure in horses. In human patients, glucuronidated monohydroxyclemastine was recovered, and in urine from horses both mono- and dihydroxyclemastine glucuronides were identified, while phase II metabolites could not be recovered from the dog urine. Clemastine metabolism in dogs and horses has, to our knowledge, not been studied before, and new metabolites from humans are presented in this article. Thus, the metabolites described in the present work have not been previously reported in the literature.     

Electrical behavior of molecular junctions incorporating alpha-helical peptide

We synthesized an alpha-helical peptide containing two terminal thiol groups and demonstrated the method of preparation of a self-assembled monolayer (SAM) on gold with uniform orientation of the molecules on the surface. The monolayers were employed as model systems for the investigations of mediated electron transfer. The measurements of electron transfer efficiency through the peptide were performed using scanning tunneling spectroscopy (STS). The molecules were trapped between the gold tip and the substrate using a Au-S linkage. The electron transfer behavior of the peptide was examined as a function of the tip-substrate distance at fixed bias voltage and as a function of bias voltage at a fixed distance between the tip and the substrate. The data obtained from these experiments indicated that the electron transfer through alpha-helical peptide is very efficient, and its conductivity is comparable to those observed for dodecanedithiol. There is also a directional dependence of electron transmission through the peptide, which is connected with the electric field generated by the molecular dipole of the helix.     

Electronic structure of bismuth terminated InAs(1 0 0)

Deposition of Bi onto (4 × 2)/c(8 × 2)-InAs(1 0 0) and subsequent annealing results in a (2 × 6) surface reconstruction as seen by low electron energy diffraction. The Bi condensation eliminates the original (4 × 2) surface reconstruction and creates a new structure including Bi-dimers. This surface is metallic and hosts a charge accumulation layer seen through photoemission intensity near the Fermi level. The accumulation layer is located in the bulk region below the surface, but the intensity of the Fermi level structure is strongly dependent on the surface order.