Diffractive,refractive optics or anything more? Comparative analysis and trends of development

Abstract

The development of diffractive and refractive optics from ancient times (2000 years ago) to the present is traced from a theoretical and practical point of view. A comparative analysis of the possibilities of the two fields in optics is presented. The possibility for achromatization and corrections that exceed the boundary of diffractive and refractive optical elements is pointed out.     

Electrochemical synthesis and characterization of TiO2-polyaniline composite layers

The electrochemical formation of TiO₂-polyaniline (PANI) composite layers was studied by anodic polymerization of aniline in the presence of TiO₂ nanoparticles. The composite layers were investigated for their electrochemical, photoelectrochemical, and surface morphological characteristics. It was found that thick composite layers showed no photoresponse, whereas thin layers, prepared by a few potentiodynamic scans, have small photocurrents almost independent of the layer thickness. Due to the small photocurrents of the composite single-layers, bi-layered structures consisting of a first pristine PANI layer followed by an outer TiO₂-PANI composite layer were also studied. The bi-layered structures were found to have up to threefold larger photocurrents than the composite single layers. The TiO₂-PANI composite layers were additionally modified by deposition of platinum particles using galvanostatic electroreduction or photoreduction in the presence of hexachloroplatinate anions.     

Extracts of plant cell cultures of <Emphasis Type="Italic">Lavandula vera</Emphasis> and <Emphasis Type="Italic">Rosa damascena</Emphasis> as sources of phenolic antioxidants for use in foods

Ethanolic extracts of plant cell cultures of lavender (Lavandula vera) and rose (Rosa damascena) have been examined as potential food antioxidants. The L. vera cell extract quenched the radicals Fremy’s salt, DPPH (2,2-diphenyl-1-picrylhydrazyl radical), and ABTS^·+ (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic) radical) more efficiently than the R. damascena extract. Also the L. vera extract inhibited lipid oxidation in a methyl linoleate emulsion more efficiently than the R. damascena extract. However, the L. vera extract had a prooxidative effect on the iron-based Fenton reaction in an aqueous model system. A similar effect was observed for pure rosmarinic acid, but not for the R. damascena extract. The addition of L. vera extract to minced chicken meat reduced lipid oxidation (measured as thiobarbituric acid reactive species) and the loss of α-tocopherol during cold storage after the meat was cooked. This suggests the antioxidative properties of L. vera extracts dominate in a real food system.     

Full scale plume rise modeling in calm and low wind velocity conditions

A variety of models and software products are in use for computer simulation of pollutant dispersion for air pollution assessment. All of them need to calculate the so called effective stack height, but problems are encountered in calm and low wind velocity conditions. The present research aims at such meteorological situations. Based on a full scale numerical simulation, the plume rise has been investigated in sub-adiabatic and near-adiabatic conditions. The influence of the emission and stack parameters, the ground level air temperature, the temperature gradient of the atmosphere, and the surface wind velocity in the range from 0.0 to 1.0 m/s is studied. A computational fluid dynamics problem has been formulated and solved for planned combinations of meteorological conditions and emission parameters. For each numerical simulation the height of the plume center line and hence, the plume rise has been assessed. The results obtained have been used to work out new mathematical models for plume rise calculation.     

In vitro host response assessment of biomaterials for cardiovascular stent manufacture

The deployment of a vascular stent during angioplasty has greatly reduced the risks of restenosis. However, the presence of the device still induces a host response as well as a mechanical action on the blood vessel wall and an alteration of the haemodynamics. Platelet and inflammatory cells can adhere on the stent surface and be activated to produce biochemical signals able to stimulate an excessive proliferation of the smooth muscle cells with the consequent obstruction of the vessel lumen. For these reasons, the host response to two of the materials used in stent manufacture, stainless steel and diamond-like carbon, was investigated in vitro. The data showed that stainless steel induced a higher level of host response both in terms of platelet aggregation and macrophage activation. However, the spreading of inflammatory cells was more accentuated on diamond-like carbon. The inflammatory cells produced levels of platelet-derived growth factor, a key signal in smooth muscle cell proliferation, similar to stainless steel thus suggesting that carbon coatings may not be able to prevent restenosis.     

Electrochemically Phosphating of Aluminum Surfaces in $${\text{MoO}}_{{\text{4}}}^{{{\text{2}} - }}$$ -Containing Solutions

Protection of Metals and Physical Chemistry of Surfaces - Effects of concentration (2.0, 4.0, 7.0 and 11.0 vol %) and operating temperature (20.0, 40.0 and 60.0°C) on phosphate coatings formed...     

Kinetics of temperature programmed reduction of Fe3O4 promoted with copper: application of iso-conversional methods

The temperature-programmed reduction of Cu/Fe₃O₄ in hydrogen was analyzed. The values of the apparent activation energy characteristic of this process were determined using the most widely known iso-conversional methods. In all cases a variation of the apparent activation energy with the degree of reduction was shown.The values of the pre-exponential factor were evaluated assuming various kinetic models. In all cases both the apparent activation energy and pre-exponential factor depend on the degree of reduction. Their values vary according to the relationship of the compensation effect: ln A = a · E + b. The analysis of the data suggested that the reduction of Cu/Fe₃O₄ takes place passing through three consecutive stages, in which the reduction mechanisms are different. The existence of these reduction stages was tentatively explained taking into account the possible structural changes, which accompany the increase of the reduction degree.     

Artisanal cheeses relying on spontaneous fermentation as sources of unusual microbiota – The example of the Bulgarian ‘mehovo sirene’ skin bag cheese

The Bulgarian ‘mehovo sirene’ cheese is a type of regional artisanal cheese prepared from raw ewe milk in a skin bag relying on spontaneous fermentation. A metagenomics study revealed an unusual microbiome comprising beneficial bacteria such as Staphylococcus equorum, Lactococcus lactis, Streptococcus thermophilus, Lactobacillus delbrueckii, Lactobacillus kefiranofaciens, Lactococcus raffinolactis, Lactiplantibacillus plantarum, Limosilactobacillus fermentum and Loigolactobacillus coryniformis. Our findings suggest that ‘mehovo sirene’ could have some functional food properties and is a source of beneficial microorganisms.