University of Patras

About: University of Patras is a education organization based out in Pátrai, Greece. It is known for research contribution in the topics: Population & Catalysis. The organization has 13372 authors who have published 31263 publications receiving 677159 citations. The organization is also known as: Panepistímio Patrón.

Pathways of solar light-induced photocatalytic degradation of azo dyes in aqueous TiO2 suspensions

Abstract: The photocatalytic degradation of aqueous solutions of Acid Orange 7 in TiO 2 suspensions has been investigated with the use of a solar light simulating source. The photoreaction was followed by monitoring the degradation of the dye and the formation of intermediates and final products, as functions of time of irradiation, both in solution and on the photocatalyst surface. It has been found that the dye adsorbs on TiO 2 and undergoes a series of oxidation steps, which lead to decolorization and formation of a number of intermediates, mainly aromatic and aliphatic acids. These molecules are further oxidized toward compounds of progressively lower molecular weight and, eventually, to CO 2 and inorganic ions, such as sulfate, nitrate and ammonium ions. A TiO 2 -mediated photodegradation mechanism for Acid Orange 7 is proposed on the basis of quantitative and qualitative detection of intermediate compounds.

Hydrogen sulfide and nitric oxide are mutually dependent in the regulation of angiogenesis and endothelium-dependent vasorelaxation

Abstract: Hydrogen sulfide (H2S) is a unique gasotransmitter, with regulatory roles in the cardiovascular, nervous, and immune systems. Some of the vascular actions of H2S (stimulation of angiogenesis, relaxation of vascular smooth muscle) resemble those of nitric oxide (NO). Although it was generally assumed that H2S and NO exert their effects via separate pathways, the results of the current study show that H2S and NO are mutually required to elicit angiogenesis and vasodilatation. Exposure of endothelial cells to H2S increases intracellular cyclic guanosine 5′-monophosphate (cGMP) in a NO-dependent manner, and activated protein kinase G (PKG) and its downstream effector, the vasodilator-stimulated phosphoprotein (VASP). Inhibition of endothelial isoform of NO synthase (eNOS) or PKG-I abolishes the H2S-stimulated angiogenic response, and attenuated H2S-stimulated vasorelaxation, demonstrating the requirement of NO in vascular H2S signaling. Conversely, silencing of the H2S-producing enzyme cystathionine-γ-lyase abolishes NO-stimulated cGMP accumulation and angiogenesis and attenuates the acetylcholine-induced vasorelaxation, indicating a partial requirement of H2S in the vascular activity of NO. The actions of H2S and NO converge at cGMP; though H2S does not directly activate soluble guanylyl cyclase, it maintains a tonic inhibitory effect on PDE5, thereby delaying the degradation of cGMP. H2S also activates PI3K/Akt, and increases eNOS phosphorylation at its activating site S1177. The cooperative action of the two gasotransmitters on increasing and maintaining intracellular cGMP is essential for PKG activation and angiogenesis and vasorelaxation. H2S-induced wound healing and microvessel growth in matrigel plugs is suppressed by pharmacological inhibition or genetic ablation of eNOS. Thus, NO and H2S are mutually required for the physiological control of vascular function.

Lipids of oleaginous yeasts. Part I: Biochemistry of single cell oil production.

Abstract: In the first part of this review, the biochemistry of lipid accumulation in the oleaginous microorganisms is depicted. Lipid biosynthesis form sugars and related substrates is a secondary anabolic activity, conducted after essential nutrient (usually nitrogen) depletion in the medium. Due to this exhaustion, the carbon flow is directed towards the accumulation of intracellular citric acid that is used as acetyl-CoA donor in the cytoplasm. Acetyl-CoA generates cellular fatty acids and subsequently triacylglycerols. Lipid accumulation from hydrophobic substrates is a growth associated process, being independent from nitrogen exhaustion in the medium. Medium fatty acids are incorporated with various incorporation rates and are either dissimilated for growth needs or become “substrate” for intracellular biotransformations. “New” fatty acid profiles (in both extra- and intracellular lipids) that did not previously exist in the medium are likely to be produced. Oleaginous microorganisms consume their own storage lipids when their metabolic abilities cannot be saturated by the extracellular carbon source. Reserve lipid breakdown is independent from the type of the carbon source used for lipid accumulation. In most cases it is accompanied by lipid-free biomass production. Lipid mobilization is a specific process, as preferential degradation of the neutral lipid fractions is observed.

Selective CO oxidation over CuO-CeO2 catalysts prepared via the urea-nitrate combustion method

Abstract: CuO-CeO2 catalysts have been proposed as a promising candidate catalytic system for CO removal from reformed fuels via selective oxidation. In this work, the performance of CuO-CeO2 catalysts, synthesized via the urea–nitrate combustion method, in the reaction of selective CO oxidation in the presence of H2 has been investigated. The combustion method was found to be a simple and fast route for the synthesis of ultrafine, nanocrystalline CuO-CeO2 catalysts. The influence of the fuel/oxidant (urea/nitrate) ratio and the Cu content on the catalytic properties of CuO-CeO2 catalysts has been studied and optimal values of these parameters have been determined. Compared to CuO-CeO2 catalysts prepared with other techniques, the catalysts prepared via the combustion method exhibited similar catalytic performance, remaining very active and stable, remarkably selective and with good tolerance towards CO2 and H2O.