Optical properties and crystallization of glasses in the system Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–MoO<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>

The purpose of this work is to study the optical properties and crystallization of glasses in the ternary system Bi₂O₃–MoO₃–B₂O₃. In order to verify the obtaining of bismuth borate crystal phases several glass compositions have been selected for crystallization. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy and UV–Vis spectroscopy. The UV–Vis spectroscopy showed that the obtained glasses are transparent in the visible region. The values of optical band gap (E _opt) and changes in cut-off (λ_c) depending on composition are reported. It was established that the increase in the MoO₃ content led to decreasing the transmittance of the glasses. Moreover, the absorption edge shifts towards longer wavelength.     

Nanoparticles in low melting amorphous selenite materials

The aim of the present investigation is to establish the appropriate routе of nanoparticles formation during heat treatment of selected selenite glasses. Multicomponent compositions containing SeO₂, V₂O₅, TeO₂, MoO₃, ZnO and Ag₂O have been selected. Different preparation methods of the initial glass samples have been combined with heat treatment to influence the glass microstructure and formation of different types of microheterogeneites. TEM and SEM have been used to prove the formation of nanosized particles, randomly distributed in the amorphous matrix volume. Samples containing above 50 wt% Ag₂O show the formation of elementary silver with an average particle size of 50–100 nm. Glass-ceramic materials have been obtained after a long thermal treatment. The main crystal phases detected are Ag₂SeO₃, Ag₂TeO₃ and TeO₂.     

Deformation-based mapping of volume change from serial brain MRI in the presence of local tissue contrast change

This paper is motivated by the analysis of serial structural magnetic resonance imaging (MRI) data of the brain to map patterns of local tissue volume loss or gain over time, using registration-based deformation tensor morphometry. Specifically, we address the important confound of local tissue contrast changes which can be induced by neurodegenerative or neurodevelopmental processes. These not only modify apparent tissue volume, but also modify tissue integrity and its resulting MRI contrast parameters. In order to address this confound we derive an approach to the voxel-wise optimization of regional mutual information (RMI) and use this to drive a viscous fluid deformation model between images in a symmetric registration process. A quantitative evaluation of the method when compared to earlier approaches is included using both synthetic data and clinical imaging data. Results show a significant reduction in errors when tissue contrast changes locally between acquisitions. Finally, examples of applying the technique to map different patterns of atrophy rate in different neurodegenerative conditions is included.     

Comparison of the tribological and antimicrobial properties of CrN/Ag, ZrN/Ag, TiN/Ag, and TiN/Cu nanocomposite coatings

Nanocomposite coatings including CrN/Ag, ZrN/Ag, TiN/Ag and TiN/Cu with varying silver or copper contents were produced by co-deposition in a dual pulsed magnetron sputtering system. The compositions and structures of the coatings were characterised using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), and the physical and tribological properties were assessed by means of nanoindentation and thrust washer wear testing. Although increasing silver or copper content provided a reduction in the coefficient of friction, this was accompanied by reductions in hardness for all the coatings and wear resistance for some of the coatings. Zones of inhibition were used to determine the extent of silver ion release from the coating surfaces, and a NBT (nitro-blue tetrazolium) redox dye was used to determine the antimicrobial effectiveness of the coatings following incubation. The microorganisms tested were Pseudomonas aeruginosa and Staphylococcus aureus. For the NBT assays, significant reductions in the number of viable cells were observed with increasing Ag or Cu content, compared to the ‘pure’ nitride surfaces. Whilst no zones of inhibition were observed for S. aureus, on any of the surfaces, the diameter of the ‘kill’ zones generally increased with increasing silver content for P. aeruginosa.     

Mechanochemical synthesis of nanocrystalline ZnWO4 at room temperature

Single nanocrystalline ZnWO₄ powders were successfully synthesized by ball milling at room temperature. A stoichiometric mixture of ZnO and WO₃ in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill (Fritsch - Premium line - Pulversette No. 7) for a period varying from 5 to 300 min. The influence of the four different milling conditions was investigated on the formation of ZnWO₄. The products obtained were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmer-Teller (BET) surface area, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The synthesis of ZnWO₄ powder started after 5 min milling time and finished after 30 min milling time at a higher speed (1000 rpm). The mechanical treatment up to 300 min did not lead to phase and structure change of ZnWO₄. The product obtained contained nanoparticles with a size of about 50 nm. The photocatalytic activity of the ZnWO₄ powders obtained was investigated by degradation of a model aqueous solution of Malachite Green (MG) upon UV-light irradiation.     

Influence of the synthesis methods on the particle size of the LiVMoO<Subscript>6</Subscript> phase

The lithiated transition metal oxide LiVMoO₆ has been synthesized by a novel melt quenching method that presents some advantages as compared to the classical solid-state reaction and soft-combustion synthesis. These are: the short preparation time and the possibility to control the grain size of LiVMoO₆ powders. The local structure of LiVMoO₆ samples prepared in different ways was characterized by IR spectral analysis. The oxidation state of Li, V, and Mo was determined by X-ray photoelectron spectroscopy.     

Pattern memory involves both elemental and configural processes: Evidence from the effects of hippocampal lesions.

The formation of an integrated memory for a pattern of stimulation could be based on the elements of that pattern becoming directly linked to one another, or by each of the elements becoming linked to a shared separate configural representation. These 2 accounts have proven difficult to discriminate between. Here, rats received exposure to four patterns of stimulation, each consisting of an auditory stimulus, a visual context, and a time of day; and we examined whether pre-training lesions to the hippocampus influenced memory for the patterns. These lesions abolished pattern memory that required configural processes (Experiments 1A and 1B) but had no effect on pattern memory that could be supported by elemental processes (Experiment 2). This dissociation provides support for the views that elemental and configural processes ordinarily support pattern memory and that rats with lesions to the hippocampus are left reliant on elemental processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Proteolytic activity of conditionally pathogenic microorganisms causing food poisoning

A study was made of proteolytic activity of the microorganisms Proteus and Bac. cereus, as well as of infected extract from raw meat. Subject to study were also the effects of the temperature, storage and microbial association on the production of exoproteases. The results indicate an increase in the proteolytic activity in the course of storage at room and decreased temperatures and a lowering of the soluble protein amount in the samples, which attests to an active process of spoiling. Association of the bacteria in question appears to be a factor with a certain effect of protease repression. It is necessary to exercise control over the amount of the microorganisms in foods with a high content of protein, and to revise the times of meat storage in refrigerators.