Search results for "oxidation"
showing 10 items of 1913 documents
Über die Autoxydation gesättigter makromolekularer Kohlenwasserstoffe
1973
Die Autoxydation in Losung von isotaktischem Polypropylen bzw. Polyputylen-1 gehorcht einer anderen kinetischen Beziehung als die entsprechende Autoxydation von ataktischem Polypropylen, Polybutylen-1 und Polyathylen. Die Autokatalyse der Autoxydation isotaktischer Produkte wird durch einen bimolekularen Kettenstart der gebildeten Hydroperoxyde hervorgerufen, wahrend bei ataktischen Produkten ein monomolekularer Kettenstart beobachtet wird. Die unterschiedliche Kinetik der Autoxydation kann eindeutig auf Taktizitatsunterschiede zuruckgefuhrt werden. The autoxidation of isotactic polypropylene and poly-butylene-1 in solution shows a kinetic difference from that of atactic fractions of these …
Die oxydation von polyepoxiden mit molekularem sauerstoff
1966
Polypropylenoxid, Polybutylen-1-oxid und Polystyroloxid wurden dargestellt und mit Hilfe von Losungsmitteln in verschiedene taktische Fraktionen getrennt. Diese Fraktionen und Polyathylenoxide mit verschiedenem Molekulargewicht wurden in Substanz autoxydiert und die fluchtigen Reaktionsprodukte gaschromatographisch identifiziert. Die Autoxydation dieser Polymeren in Losung wurde durch Messung der Sauerstoffaufnahme verfolgt. Die Bruttoaktivierungsenergien der taktischen Fraktionen der Polymeren sind groser als die der ataktischen Fraktionen. Die Kinetik der Autoxydation des Polybutylen-1-oxides wurde aufgeklart. Polypropyleneoxide, polybutene-1-oxide, and polystyreneoxide were prepared and …
Selective oxidation of aromatic alcohols in the presence of C3N4 photocatalysts derived from the polycondensation of melamine, cyanuric and barbituri…
2021
AbstractA set of C3N4 samples has been prepared by using melamine, cyanuric acid and barbituric acid as the precursors. The materials were subjected both to physical and chemical characterization and were used as photocatalysts for the selective oxidation of aromatic alcohols in water suspension under UV and visible irradiation. The photoactivity of the materials versus the partial oxidation of four substituted benzyl alcohols was investigated. The type and position of the substituents in the aromatic molecule influenced conversion and selectivity to the corresponding aldehyde. The presence of barbituric and cyanuric acids in the preparation method has changed the graphitic-C3N4 structure, …
Potential role of branched-chain amino acid catabolism in regulating fat oxidation.
2013
Insulin-resistant or obese individuals have increased serum branched-chain amino acid (BCAA) levels. Recent findings relate increased BCAA catabolism to increased fatty acid oxidation and better metabolic health in physically active individuals. We hypothesize that, via glyceroneogenesis, BCAA catabolism mediates increased constitutive use of fatty acids for β-oxidation in subjects with increased inherent or acquired aerobic capacity both during exercise and at rest.
Alkyl- and aryl-substituted corroles. 5. Synthesis, physicochemical properties, and X-ray structural characterization of copper biscorroles and porph…
2004
The synthesis and characterization of cofacial copper biscorroles and porphyrin-corroles linked by a biphenylenyl or anthracenyl spacer are described. The investigated compounds are represented as (BCA)Cu(2) and (BCB)Cu(2) in the case of the biscorrole (BC) derivatives and (PCA)Cu(2) and (PCB)Cu(2) in the case of porphyrin (P)-corrole (C) dyads, where A and B represent the anthracenyl and biphenylenyl bridges, respectively. A related monomeric corrole (Me(4)Ph(5)Cor)Cu and monomeric porphyrin (Me(2)Et(6)PhP)Cu that comprise the two halves of the porphyrin-corrole dyads were also studied. Electron spin resonance (ESR), (1)H NMR, and magnetic measurements data demonstrate that the copper corr…
THEORETICAL INSIGHTS ON O2 AND CO ADSORPTION ON NEUTRAL AND POSITIVELY CHARGED GOLD CLUSTERS
2006
With the aim of understanding the elementary steps governing the oxidation of CO catalyzed by dispersed or supported gold nanoclusters, the adsorption of molecular species, such as O2 and CO, on model neutral and positively charged clusters (Au(n)(m+) n = 1, 9, and 13; m = 0, 1, and 3) has been studied using an ab initio approach. The computed structural and thermodynamic data related to the binding process show that molecular oxygen interacts better with neutral clusters, acting as an electron acceptor, while CO more strongly binds to positively charged species, thus acting as an electron donor.
Response to ozone in two lettuce varieties on chlorophyll a fluorescence, photosynthetic pigments and lipid peroxidation.
2004
The effect of different O3 concentrations on two lettuce (Lactuca sativa L.) varieties (Valladolid and Morella) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthetic pigments (Chl a, b and total carotenoid), lipid peroxidation and crop yield. Ozone fumigation caused: a decrease in maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) in mature leaves, a reduction in the non-cyclic electron flow (phiPSII) and a lower capacity to reoxidize the QA pool (qP). These reductions were significant in the Valladolid var. but not in the Morella var. A significant decrease in Chl a, b and in the total carotenoids was observed in the Valladolid var. but not…
Determination of sterols, oxysterols, and fatty acids of phospholipids in cells and lipoproteins: A one-sample method
1998
In addition to fatty acids, especially polyunsaturated species, cholesterol oxidizes and leads to various oxygenated derivatives, named oxysterols. They display a wide range of adverse biological properties. Monitoring oxysterols is important in the evaluation of the potential risks associated with lipid oxidation. In the present study, a quick and reliable method was developed for analysis of oxysterols, sterols, and fatty acid composition of phospholipids in the same biological sample. Total lipid extraction was determined after addition of several internal standards (epicoprostanol for sterols, 19-hydroxy-cholesterol for oxysterol and di-heptadecanoyl-phosphatidylcholine for phospholipid…
Effect of extrusion and photoxidation on polyethylene/clay nanocomposites
2009
Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) …
Effect of natural antioxidants and modified atmosphere packaging in preventing lipid oxidation and increasing the shelf-life of common dolphinfish (C…
2015
We investigated the effects of natural antioxidants and modified atmosphere packaging (MAP) on the quality and shelf-life of Coryphaena hippurus (common dolphinfish) fillets. Fillets of the control group (CO) were simply placed on trays and not sealed. Fillets of the second group (MAP) were preserved in modified atmosphere (45% CO2, 50% N2, 5% O2), and fillets of the third group (MAP-AOX) were preserved by combining natural antioxidants from halophytes with modified atmosphere. All samples were stored in a refrigerator at 1 ± 0.5 C for 18 days. Analyses were conducted at T0 and after 3, 6, 12, 15 and 18 days of storage. According to sensory tests and colour analyses, the fillets in the MAP …