Biotechnological conversions of biodiesel derived waste glycerol by yeast and fungal species

Fifteen eukaryotic microorganisms were tested for their ability to assimilate biodiesel derived waste glycerol and convert it into value-added metabolic products. For this purpose yeast and Zygomycetes strains were cultivated in nitrogen-limited raw glycerol-based media (initial glycerol concentration 30 g/L). Yeasts tested accumulated restricted lipid quantities (up to ∼22%, wt/wt, in the case of Rhodotorula sp), while differentiations in their fatty acid composition were recorded in relation to the yeast strains employed and the fermentation time. On the contrary, fungi accumulated higher quantities of lipid inside their mycelia (ranging between 18.1 and 42.6%, wt/wt, of dry biomass) that contained in variable amounts the medically important GLA (γ-linolenic acid). Moreover, Yarrowia lipolytica, Pichia membranifaciens and Thamnidium elegans were further studied in media having increased initial glycerol concentrations. In these conditions Y. lipolytica secreted significant amounts of acetic acid (29.2 g/L), as well as mannitol (19.4 g/L) while P. membranifaciens reached 28.4 g/L of biomass at glycerol concentration 90 g/L. T. elegans produced 11.6 g/L of oil, with 71.1%, wt/wt, of fat in biomass, while the maximum concentration of GLA was 371 mg/L. Detailed analysis of T. elegans lipids indicated that the phospholipids fraction was particularly rich in polyunsaturated fatty acids.     

Photocatalysis and photoelectrocatalysis using nanocrystalline titania alone or combined with Pt,RuO<Subscript>2</Subscript> or NiO co-catalysts

Photocatalytic mineralization of ethanol in the presence of oxygen has been studied in aqueous photocatalyst suspensions by employing either pure nanocrystalline titania or TiO₂ combined with Pt, RuO₂ or NiO co-catalysts. Combined photocatalysts demonstrated a diverse behavior. Highest mineralization rates were obtained with Pt/TiO₂ and lowest with RuO₂/TiO₂ and NiO/TiO₂. These results were related with the photocatalysts’ behavior when used as photoanodes for the production of electricity in a photoactivated fuel cell running with ethanol as fuel. The highest current was obtained with pure titania. The current dropped in the case of Pt/TiO₂ and became much lower in the case of RuO₂/TiO₂ and NiO/TiO₂ photoanodes. Both current and voltage were lower in the presence of oxygen than in its absence. It is concluded that the presence of electron scavengers, like O₂, and/or the use of efficient photocatalysts, like titania-supported Pt, yield less electric power but assist ethanol mineralization process.     

Composition of Periclase and Calcium-Silicate Phases in Magnesia Refractories Derived from Natural Microcrystalline Magnesite

Mineralogical and microstructural properties of sintered and fused magnesia grains and refractory bricks derived from natural magnesite were examined. Although their CaO/SiO₂ ratios can be used to approximate their mineralogical compositions, detailed X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies revealed significant deviations from the expected phase assemblages. Their microstructures vary widely in terms of proportions of direct periclase bonding, amounts and phase constitution of the siliceous bonding, and the size and composition of the periclase crystals. An exceptionally high solid solubility of CaO in periclase crystals was detected. Most of the phases of the siliceous bond exhibit nearly stoichiometric compositions and show intriguing substitutions.     

Bioactivity of Greek honey extracts on breast cancer (MCF-7), prostate cancer (PC-3) and endometrial cancer (Ishikawa) cells: Profile analysis of extracts

Historically, honey has been important in Greek culture. The chemical composition and the potential of Greek honey extracts (thyme, pine and fir honey) to influence the oestrogenic activity and the cell viability of breast (MCF-7), endometrial (Ishikawa) and prostate (PC-3) cancer cells were investigated. All honeys contained total phenolics, phenolic acids and hydroxymethylfurfural, the levels being highest in thyme honey. Sugars and volatile compounds, but not fatty acids, were detected in all honey extracts. Thyme, pine and fir honey showed both antioestrogenic and a weak oestrogenic effect at low and high concentration, respectively, in MCF-7 cells. Thyme honey reduced the viability of Ishikawa and PC-3 cells, whereas fir honey stimulated the viability of MCF-7 cells. In conclusion, Greek honeys are rich in phenolic compounds, they modulate oestrogenic activity whereas a thyme honey-enriched diet may prevent cancer-related processes in breast, prostate and endometrial cancer cells.     

Optimal Communication Primitives on the Generalized Hypercube Network

Efficient interprocessor communication is crucial to increasing the performance of parallel computers. In this paper, a special framework is developed on thegeneralized hypercube, a network that is currently receiving considerable attention. Using this framework as the basic tool, a number of spanning subgraphs with special properties to fit various communication needs are constructed on the network. The importance of these spanning subgraphs is demonstrated with the development of optimal algorithms for four fundamental communication problems, namely, theone-to-allandall-to-all broadcastingand theone-to-allandall-to-all scattering. Broadcastingis the distribution of the same group of messages from a source processor to all other processors, andscatteringis the distribution of distinct groups of messages from a source processor to each other processor. We consider broadcasting and scattering from a single processor of the network (one-to-all broadcasting and scattering) and simultaneously from all processors of the network (all-to-all broadcasting and scattering). For the all-to-all broadcasting and scattering algorithms, a special technique is developed on the generalized hypercube so that messages originating at individual nodes are interleaved in such a manner that no two messages contend for the same edge at any given time. The communication problems are studied under thestore-and-forward, all-portcommunication model. Lower bounds are derived for the above problems under the stated assumptions, in terms of time and number of message transmissions, and optimal algorithms are designed.     

Dose performance evaluation of a charge coupled device and a flat-panel digital fluoroscopy system recently installed in an interventional cardiology laboratory

The purpose of the study was to evaluate the dose performance of a flat-panel (FP) and an image intensifier (II) charge coupled device (CCD) digital fluoroscopy X-ray systems newly installed in an Interventional Cardiology (IC) department. Filter entrance dose rate, detector dose rate (during fluoroscopy) and filter entrance dose per image were measured at 70 cm from the focus using 2 mm copper sheets to mimic normal size patient. Image quality was also evaluated. The patient dose survey included 277 patients, which had either a Coronary Angiography (CA) or a Percutaneous Transluminal Coronary Angioplasty (PTCA). Dose area product (DAP), fluoroscopy time (T) and total number of frames (F) values were also collected. The results showed that both systems performed within international recommendations with the exception of higher cine radiation doses, stressing the fact that neither specific protocols of measurement nor reference values for digital equipment were provided by the official bodies.