Influence oxidants

In 1929 Pfeil" published a most interesting account of the way layered structures form and the manner in which they influence oxidation rates. From detailed studies of the growth and composition of scales he was able to show clearly how the formation of barrier layers reduced scale formation by hindering outward diffusion of iron through the scale. Naturally, this work had to be largely based on the study of scales of sufficient thickness so that the mechanism of the early stages of oxidation could not be studied in this way. Pfeil analysed the outer, middle and inner layers of scales formed... 

The results found here indicate that although the changes in potential can markedly influence oxidation reaction energy through altering the energy of the electron product, differences in the interactions of the reactant (water) and product (hydroxyl) species with the interfacial electric field appear to have only a small effect on the... 

When the results for oxide growth and anion incorporation172,160 are compared with the kinetics of space charge accumulation in barrier and porous alumina films [see Section IV(1)], it can be concluded that anion incorporation modifies the electrostatics of the external oxide interface, thus influencing oxide dissolution and pore formation.172... 

Photochemistry often involves species that are electrochemically interesting. Excited states, radicals, and metals with light-influenced oxidation states are very common intermediates or products thus it is not surprising that numerous attempts have been made to study photochemical processes with electrochemical tools [66,67]. 

In the following sections, oxidation models for calculating oxide thickness and process variables that influence oxidation, as well as oxide structure, are discussed. 

This vitamin occurs in all living tissues, where it influences oxidation-reduction reactions. The major source of L-ascorbic acid in foods is vegetables and fmits (Table 9-13). 

In addition to the directed oxidation process responsible for the characteristic salmon flavor compound, carotenoids also were observed to Influence oxidation of polyunsaturated fatty acids In salmon oil systems (39). Typically, lipid oxidation of oils high In n-3 fatty acids produce Isomeric 2,4-heptadlenals as the major... 

The ionization potential of Ag and the dissociation energy of Ag + are the dominant factors influencing oxidation. It was concluded that with increase in cluster size the ionization potential decreases and the dissociation energy increases. 

Electrochemistry can be used to affect oxidation catalysis on metals and metallic oxides [13] in a very pronounced and reversible manner. The observed promotional phenomena are due to an electrochemically driven and controlled backspillover of ionic species on the catalyst surface. These species, which in some cases cannot form via gas phase adsorption, alter the catalyst work function and affect the binding strengths of chemisorbed reactants and intermediates in a pronounced and theoretically predictable manner. This electrochemically controlled variation in the binding strength of adsorbates causes the observed pronounced modification in catalytic activity and selectivity. The ability of solid electrolytes to act as reversible promoter donors to influence oxidation catalysis is of considerable theoretical and, potentially, practical interest. 

Although most fruits and vegetables have relatively small amounts of proteins and amino acids, these constituents may play an important role as synergists and primary flavor components, as well as influence oxidation of ascorbic acid and of other flavor compounds (2) Peroxidase has been associated with "off-flavors" in raw vegetables... 

A characteristic of the cytochromes c3 is a very low oxidation-reduction potential. Moreover, it is obvious from the multiheme nature of these cytochromes that the redox properties should be complex. In the simplest situation, four individual redox potentials could be expected, one for each heme. In addition to the axial ligands on the hemes, a number of factors are anticipated to influence the individual heme redox potentials. First and foremost, the environment of each heme can exert an influence on its oxidation-reduction potential. This influence will be manifested in two ways the packing of the specific amino acid side chains about each heme and the extent of solvent exposure of each heme. It is quite apparent from the structural data (Figures 1 and 2) that the four hemes, which are in nonequivalent environments, are expected to have different oxidation-reduction potentials. Moreover, at least with Miyazaki cytochrome c3> one of the hemes (heme II) is substantially more exposed to solvent, which may result in a lower oxidation-reduction potential (13). Finally, it is apparent that in a small molecule that contains four hemes within close proximity (< 18 A), heme-heme interactions, principally as a result of electrostatic interactions, are likely to influence oxidation-reduction potentials (14). Indeed, on electrostatic grounds the redox state of one heme should influence another. This influence results from the fact that addition of electrons changes the formal... 

The presence of inorganic particles such as hematite did not influence oxidation efficiency, and the error of analysis was evaluated with 10 samples of a few different concentrations in the range of... 

In such a system, the rate of oxidation is influenced by the emulsion composition (relative concentrations of substrate and emulsifier) and especially, by the partition of the emulsifier between the interface and the water phases. Other factors influencing lipid oxidation in emulsions are particle size of the oil droplets, the ratio of oxidizable to non-oxidizable compounds in the emulsion droplets, and the packing properties of the surface-active molecules. In addition, the amount and composition of the oil phase in an emulsion are important factors that influence oxidative stability, formation of volatiles, and partition of the decomposition products, between the oil and water phase. 

C30H22O12, Mr 574.50, yellow-red crystals, decomp, at 264 °C. A hydroxynaphthoquinone produced by various species of fungi (e. g., Trichophyton, Penicillium, Aspergillus). X. is formed biosynthetically on the polyketide pathway and often occurs together with its precursors (e. g., semi-vioxanthin, vioxanthin, viomel-lein). X. is a mycotoxin, it has antibacterial and insecticidal activities and influences oxidative phosphorylation in rat liver mitochondria. 

Control of storage temperature post-fermentation is also important, particularly for white wines for which malolactic fermentation is undesirable. The storage temperature of wine influences oxidation (which is irreversible), the rate of which is reduced by approximately 20% for each 10°C reduction in temperature. The hydrolysis of carboxylic acid esters is similarly decreased by approximately 50% (White, 1989). It is now recommended that from crushing to bottling, the juice and wine should be stored at a controlled temperature in the range 10-18°C. 

AH of reaction (17) is an estimate since PuCl4(s) has not been synthesized AfH° [PuCl4(s)] = — 964 kJ is an estimate (Fuger et al. 1983). The dramatic difference in these enthalpies [Pu(IV) is more stable than Pu(III) in this complex chloride by -95-( —4) = - 91 kJ or almost 1.0 V, in comparison with the binary chloride] shows how acid-base effects influence oxidation-reduction properties. As noted above, there are few known lanthanide (IV) complex halides and no thermodynamic data on even these few halides, so no quantitative comparison can be made. Nevertheless it does show how complexation effects by basic complexants make high f-element oxidation states attainable. Perhaps the most dramatic evidence of the enhancement of high oxidation state by a basic fluoride is the existence of the Nd(IV) and Dy (IV) compounds such as Cs2(Cs, Rb, K) (Nd, Dy)Cl2 these AjRF, double fluorides are the only known Nd (IV) and Dy(IV) compounds. 

Several studies indicate that catechins and procyanidins are powerful scavengers of ROS. Some findings regarding the antioxidant activity of proanthocyanidins are listed in Ref. [100]. Other antioxidant mechanisms are the chelation of transition metals, as well as the mediation and inhibition of enzymes. The metal-chelating activity of proanthocyanidins is thought to be due to their capacity to reduce the concentration, and thus the oxidative activity, of hydroxyl radicals formed by Fenton reaction catalyzed by iron or copper. Flavanols also influence oxidative stress via enzyme modification and modulation of cell signaling pathways the extent of the effect relies greatly on flavanol structure-related protein reactivity [101]. 

Therefore, the advancement of diet design enriched with phenolic phytochemicals, LAB, and LAB phenolic phytochemical containing fermented products with enhanced antioxidant function can help combat enviromnent and lifestyle influence oxidation-linked diseases (Ljungh and Wadstrom 2006 McCue and Shetty 2005 Pyo etal. 2006 Havenaar and Veld, 1992). This can lead to consumption of combinations of wide variety of well characterized plant foods, in combination with LAB, for cost-effective prevention and modulation of various ox-... 

The conflicting results may be related to differences in formulas, meaning the aspartate/asparagine combination may have positively influenced oxidative metabolism, whereas potassimn aspartate had no effect at the given dose. 

The influence of environmental humidity at the used level of 1% specific humidity differed from alloy to alloy. However, it is weU known that humidity can influence oxidation/spallation kinetics and also evaporation of volatile products formed in the presence of humidity, especially in the case of chromia-forming alloys [11-14]. The strongest effect was observed in the case of the heat-treated specimens of P91 where increasing the environmental specific humidity up to 2% led to a breakaway type oxidation [15, 16]. Enhanced oxidation in this case does not lead to spallation of the oxide scale. For untreated P91 specimens, as well as for AISI441, Alloy 800H and CM247, virtually no effect of humidity on the oxidation/spallation kinetics and amount of spalled oxide could be found. 

Metals of changing valency influence oxidation rates by complex formation. The ligands are either substrate or enzyme protein molecules or both. Electron distribution is altered as well in the center as in the ligands, providing us with a number of catalysts of graded reactivity. As a consequence of one electron transfer, metal ions of changing valency may initiate chain reactions, whereby the rate of the oxidative process is greatly increased. 

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