Search results for "Reactive"
showing 10 items of 1469 documents
Improved co-oxidation of β-carotene to β-ionone using xanthine oxidase-generated reactive oxygen species in a multiphasic system
2007
beta-Ionone, an aroma compound exhibiting flower notes, can be obtained from beta-carotene in a cooxidation system utilizing xanthine oxidase-generated reactive oxygen species (ROS). ROS have to be controlled as, although they can give rise to beta-ionone, they may also degrade it. In this work, the biotransformation of beta-carotene into beta-ionone was investigated in systems containing variable proportions of decane to extract beta-ionone before degradation. The use of 50% or 90% decane resulted in increased production yields. Tween 80, which was added to further improve the production, slightly decreased the reactivity of the medium and the extraction of beta-carotene, but increased the…
Cytotoxicity of compounds from Xylopia aethiopica towards multi-factorial drug-resistant cancer cells.
2015
Abstract Introduction Multidrug resistance (MDR) in cancer represent a major hurdle in chemotherapy. Previously, the methanol extract of the medicinal spice Xylopia aethiopica displayed considerable cytotoxicity against multidrug resistant (MDR) cancer cell lines. Methods The present study was designed to assess the cytotoxicity of compounds, 16 α -hydroxy- ent -kauran-19-oic acid ( 2 ), 3,4′,5-trihydroxy-6″,6″-dimethylpyrano[2,3-g]flavone ( 3 ), isotetrandrine ( 5 ) and trans -tiliroside ( 6 ) derived from the methanol crude extract of Xylopia aethiopica against 9 drug-sensitive and -resistant cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of these c…
Sulfur Dioxide Oxidation Catalyzed by Photosensitized Ytterbium Diphthalocyanine
2008
Oxidation of SO2 into SO3 was found effectively catalyzed by photosensitized ytterbium diphthalocyanine, YbPc2 (Pc = phthalocyanine ligand, C32H16N8) when performed in air-saturated dimethylformamide (DMF) solution at 20 °C. The process follows according to a multi-step complex mechanism involving chemical induction as its driving force. Excitation energy of the sandwich molecular system in YbPc2 is used to promote the reaction by creating a reactive intermediate form of the ytterbium complex hosting up to eight SO2 molecules. The conversion of SO2 proved complete.
Cytotoxicity of the crude extract and constituents of the bark of Fagara tessmannii towards multi-factorial drug resistant cancer cells.
2019
Abstract Ethnopharmacological relevance Fagara tessmannii Engl. is an African medicinal plant used in Cameroonian traditional medicine to treat various types of cancers. Aim of the study This work was designed to determine the cytotoxicity of the crude extract (FTB), fractions (FTBa-d) and compounds isolated from the bark of Fagara tessmannii, namely lupeol (1), fagaramide (2), zanthoxyline (3), hesperidin (4), nitidine chloride (5), fagaridine chloride (6), and β-sitosterol-3-O-β-D-glucopyranoside (7). The study was extended to the mode of induction of apoptosis by FTB, compounds 5 and 6. Materials and methods The resazurin reduction assay was used to evaluate the cytotoxicity of samples. …
On the Effect of Surface Treatment to Improve Oxidation Resistance and Conductivity of Metallic Interconnects for SOFC in Operating Conditions
2008
International audience; Due to the reduction of operating temperature from 1000°C to 800°C, chromia forming alloys are the best candidates for interconnects in Solid Oxide Fuel Cells (SOFCs). These interconnects have to be operational in service conditions, at 800°C in air (cathode side) and in humidified hydrogen (anode side). The performance of the interconnect stainless steels is limited by the oxide scale formation (chromia), the low electronic conductivity of this scale and the possible volatility of chromium oxides. In the field of high temperature oxidation of metals, it is well known that the addition of a nanometric layer made of reactive element oxide such as, La2O3, Nd2O3 and Y2O…
Metallic interconnects for SOFC: competitive effect of water vapour and oxygen on the oxidation behaviour of ferritic stainless steel.
2009
Due to their low environmental impact, their high efficiency and their fuel flexibility, Solid Oxide Fuel Cells are studied for many years in order to supply electricity without fossil sources. The need of interconnect to create a stack (providing electrical connection between anode and cathode) and seal every single cell (having to avoid any contact between air and fuel) appears as a crucial point. Ferritic Stainless Steel (FSS) like Crofer22APU are considered as good candidates for interconnects. These chromia forming alloys have to be operational in the service conditions: 800°C in air (cathode side) and in humidified hydrogen (anode side). The performance of the interconnect stainless s…
Interconnecteurs métalliques de piles à combustible de type SOFC - Résistance à la corrosion et conductivité électrique à haute température
2009
The need of interconnect to connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. The main important criteria requires for interconnect is an excellent oxidation resistance in air and in H2/H2O. The goal of this study is to determine the influence on corrosion behaviour of a reactive element oxide coating (La2O3, Y2O3) realized by MOCVD on different metallic alloys like Crofer22APU, Haynes230 and Fe30Cr. The realisation of long ageing (7 700 and 15 400 hours) proved to be insightful. The corrosion kinetic experiments, the oxide scale characterisation and ASR measurements established that the presence of perovskite…
A comparative high-pressure jet-stirred reactor study on the oxidation of pentanol isomers: 1-, 2- and 3- pentanol
2018
International audience
An experimental and modelling study of the oxidation of 3-pentanol at high pressure
2018
International audience; High pressure oxidation of 3-pentanol is investigated in a jet-stirred reactor and in a shock tube. Experiments in the reactor were carried out at 10 atm, between 730 and 1180 K, for equivalence ratios of 0.35, 0.5, 1, 2, 4 and 1000 ppm fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were recorded using Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC). Ignition delay times were measured for 3-pentanol/O2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1000–1470 K and for equivalence ratios of 0.5, 1 and 2. The fuel did not show any low-temperature reactivity…
Possibilities of surface reaction coupling with transport phenomena
1977
International audience; The thermodynamic approach of nonequilibrium phenomena allows, through the construction of entropy production, appropriate fluxes generalized forces to be identified, and the possibility of coupling to be detected. For the interface phase the expression entropy production consists of two parts: one for irreversible phenomena in the surface (chemical reactions and transport); and the second for transport processes between volumic phases due to the discontinuity of intensive surface parameters. Accordingly in the linear range, the phenomenological relations establishing the thermodynamic coupling between fluxes and forces of the same tensorial order may cause couplings…