Dynamic neural cortical ensembles model

One-layered model of cortical neurons as a set of overlapping ensembles, each with a structure similar to Hopfield network, is proposed. Ensemble equilibrium equation is solved and formulas for connections weights calculation for given set of attractors are obtained. Concept of dynamic attractors that consists of consequent recalling of stored patterns with moving activity through the network is introduced. Role of dynamic attractors in long-term memory is discussed and mechanism for memory recovery after destruction of some neurons is proposed. Results of experiments on associative memory recovery after partial removal of neurons are shown.     

The use of the internet by older adults in Poland

Universal Access in the Information Society - It is generally accepted that it is young people who are particularly interested in information and communication technologies (ICT). Older adults...     

Reproducible comet assay of amorphous silica nanoparticles detects no genotoxicity

Genotoxicity of commercial colloidal and laboratory-synthesized silica nanoparticles was tested using the single cell gel electrophoresis or Comet assay. By using a carefully developed protocol and careful characterization of the nanoparticle dispersions, Comet assays were performed on 3T3-L1 fibroblasts with 3, 6, and 24 h incubations and 4 or 40 microg/ml of silica nanoparticles. No significant genotoxicity was observed for the nanoparticles tested under the conditions described, and results were independently validated in two separate laboratories, showing that in vitro toxicity testing can be quantitatively reproducible.     

Functional properties of Lactobacillus acidophilus metabolites

BACKGROUND: This study addressed the characteristics of metabolites synthesized by Lactobacillus acidophilus 5e2, with particular attention paid to exopolysaccharides, biosurfactants, proline peptidases and antibacterial compounds. RESULTS: The strain Lb. acidophilus 5e2 synthesizes low‐molecular‐mass polysaccharides (340 kDa) constituted by glucose, galactose and glucosamine at a ratio of 3.3:2.8:1.0, as well as biosurfactants with a molecular mass of 32 kDa built from a protein fraction, a polysaccharide fraction and phosphate groups. It additionally synthesizes extra‐ and intracellular proline peptidases, including prolyl endopeptidase and thermostable low‐molecular‐mass (<3.5 kDa) compounds with antimicrobiological activity against Escherichia coli strains. CONCLUSION: The strain Lb. acidophilus 5e2 may be applied to the production of functional food. Copyright © 2009 Society of Chemical Industry     

Identification of oat (<Emphasis Type="Italic">Avena sativa</Emphasis>) and buckwheat (<Emphasis Type="Italic">Fagopyrum esculentum</Emphasis>) proteins and their prolamin fractions using two-dimensional polyacrylamide gel electrophoresis

Total (non-fractionated) kernel proteins and the prolamin fraction (soluble in 75% ethanol) were extracted from oat (Avena sativa) var. Flämingstern kernel and from buckwheat (Fagopyrum esculentum) var. Kora kernel. As for buckwheat, extraction was effective only after kernel dehulling which allowed the removal of tannins and phenolic compounds that form complexes with proteins during extraction. The extracted proteins were analyzed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Gels of the prolamin fractions of oat and buckwheat were used as reference gels in order to detect prolamins on gels of total kernel proteins. The occurrence of 26 and 29 spots corresponding to prolamins was found on gels of total oat proteins and on gels of total buckwheat proteins, respectively. The electrophoretic images of oat and buckwheat prolamins revealed organized subregions containing spots with similar isoelectric points (pI) and various molecular weights (MW), mostly on oat prolamin gels and spots of similar molecular weights with various isoelectric points, mostly on buckwheat prolamin gels. Such organized subregions can be used as identifiers for the occurrence of prolamin fractions in total proteins (particularly as regards buckwheat proteins).     

Effect of parameters of the butt pressure welding process on the strength and ductile properties of polyvinylidene fluoride – PVDF – tubular joints

The method most often used for permanent joining of thermoplastic elements is that of butt pressure welding. So far, the investigations carried out at Instytut Spawalnictwa (The Welding Institute) have been focussed on the assessment of the quality of joints made in basic grades of thermoplastics, such as polyethylene (PE), and polypropylene (PP) by the fusion and pressure welding processes, and also, on the technology of these methods. These particular materials are widely used in a variety of plastic constructions such as gas, water and drain pipelines, chemical installations, installations for desulphurisation of combustion gases in power plants, and so on. As the use of plastics for more specific constructions increases, new materials of enhanced properties appear. They are characterised by their higher degrees of purity, a wider range of working temperatures, higher strength, resistance to ultraviolet radiation, etc. Polyvinylidene fluoride (PVDF) belongs to this group.     

The effect of copper on the selective carbon monoxide oxidation over alumina supported gold catalysts

The selective oxidation of CO in the presence of H₂ was investigated on Au catalysts promoted with different amounts of Cu. Au catalysts were prepared by the deposition–precipitation method and exhibited a satisfactory activity at low temperature with adequate selectivity. A considerable improvement in CO conversion was achieved when the O₂/CO ratio was increased from the value of 0.5–1.0. The addition of Cu to Au/Al₂O₃ catalysts caused an increase in the selectivity to CO oxidation due to an interaction between Au and Cu on the surface of the catalysts. However, this beneficial effect was limited to an optimal content of Cu. The catalysts were characterized by temperature programmed reduction and DRS UV–vis spectroscopy, indicating the formation of small bimetallic Au–Cu particles. The presence of water vapor in the feed stream played a positive effect in the CO conversion and selectivity while the CO₂ presence diminished the CO conversion and selectivity. In the case of a realistic reformate, when both H₂O and CO₂ are present, the positive effect of H₂O was able to compensate the negative effect of CO₂ depending on the temperature of reaction.     

Formation and stabilization of emulsion with A1, A2 and B β-casein genetic variants

The milk protein β-casein (β-CN) is a flexible, approximately random coil protein with a molecular mass of ∼24 kDa. It contains distinct charged and hydrophobic, non-charged regions in the primary structure. The strongly amphiphilic nature of β-casein causes it to concentrate at an interface, which is a prerequisite to form and stabilize emulsions. The emulsifying (particle-size distribution, turbidity measurement) and structural (surface coverage, CD) properties of β-casein genetic variants were studied at pH 6.7 and I = 75 mM (representative pH value for milk). β-Casein B variant produced bigger emulsion droplets than the A¹ and A² variant, having better emulsion-stabilizing properties than A² and A¹ variants. Significant differences were observed in the surface coverage of teflon droplets made with β-casein genetic variants. A relationship between the surface load and emulsion-stabilizing properties was found. An increased content of secondary structure, especially for β-CN B and A¹ variants, was found after adsorption onto the hydrophobic surface.     

The effect of glycosylation on emulsifying and structural properties of bovine β‐casein

A number of attempts have been made to improve the functional properties of milk proteins by chemical modifications. One of such modifications is glycosylation which was carried out to determine the effect of covalent binding of glucose molecules to β‐casein (βCN) on its emulsifying properties. It was found that up to six molecules of glucose were bound to one molecule of βCN. Glycosylated βCN produced smaller emulsion droplets than the intact βCN. Increases in emulsion‐forming and ‐stabilizing properties were observed. A prerequiste of proteins to form emulsions is their adsorption onto oil/water interface. Therefore the secondary structure of intact and glycosylated βCN, both in solution and adsorbed onto a hydrophobic teflon/water interface also were studied by far‐ultra violet circular dichroism (CD). It appeared, that after glycosylation the degree of helicity of intact βCN decreased and the incorporation of glucose moieties most likely resulted in a type β‐turn formation after adsorption onto the interface.