Oxidation-Reduction Condition

This Study has shown that reasonably uniform platinum crystallites can be made on y-alumlna, and that platinum and palladium can be segregated and maintained In that form for the most part even after exposure to high temperature oxidation-reduction conditions. Highly dispersed clusters of palladium, nickel, cobalt, and Iron can be observed. Cluster size determination could not be accurately made because of the lack of contrast between the cluster and the support. The marginal detectability by EDS for these clusters enabled elemental Identification to be made, however, mass uniformity determinations could not be made. 

Thick sedimentary pile from middle Miocene to late Pliocene is exposed in the Oga Peninsula, northern Honshu, Japan (Fig. 1.153). Age of the sedimentary rocks has been determined by microfossil data. Thus, the sedimentary rocks in the Oga Peninsula where type localities of Miocene sedimentary rocks in northern Japan are well exposed have been studied to elucidate the paleoenvironmental change of the Japan Sea (Watanabe et al., 1994a,b). Kimura (1998) obtained geochemical features of these rocks (isotopic and chemical compositions) and found that regional tectonics (uplift of Himalayan and Tibetan region) affect paleo-oceanic environment (oxidation-reduction condition, biogenic productivity). However, in their studies, no detailed discussions on the causes for the intensity and periodicity of hydrothermal activity, and temporal relationship between hydrothermal activity, volcanism and tectonics in the Japan Sea area were discussed. They considered only the time range from ca. 14 Ma to ca. 5 Ma. 

Beydilli MI, Pavlostathis SG, Tincher WC (2000) Biological decolorization of the azo dye Reactive Red 2 under various oxidation-reduction conditions. Wat Env Res 72 698-705... 

The color of soil gives an indication of its oxidation-reduction conditions and the amount of OM present. Well-aerated soils will be under oxidizing conditions iron will be in the Fe3+ state, less soluble and thus less available for chemical reaction. Under water-saturated conditions, soil will be under reducing conditions as indicated by increased yellow colorings, gleying, and mottling. Iron will be in the Fe2+ state, which is more soluble and thus more available for chemical reaction. Under these conditions, reduced species such as methane (CH4), hydrogen, (H2), and sulfides will be found. 

The colors in rare earth glasses are caused by the ion being dissolved and they behave uniquely because the 4 f electrons are deeply buried. Their colors depend on transitions taking place in an inner electronic shell while in other elements such as the transition metals, the chemical forces are restricted to deformation and exchanges of electrons within the outer shell. Since the rare earth s sharp absorption spectra are insensitive to glass composition and oxidation-reduction conditions, it is easy to produce and maintain definite colors in the glass making process. ( )... 

Most kinetic studies (e.g., 29) and a thermodynamic study (30) of nuclear waste host dissolution focus on heterogeneous reactions with major concern for temperature, pH, and complexation. We believe that strongly reducing conditions are necessary to inhibit the undesirable U(IV)-U(VI) oxidation in nuclear waste matrices. Therefore, nuclear waste matrices should incorporate reductants or oxidation-reduction Eh buffers to maintain very low oxygen partial pressure, and leach studies should be conducted under oxidation-reduction conditions that nearly match repository conditions. 

AuCl2- or even a higher order complex. While it is possible that the enhanced capacity of Au1 for complexation with soft ligands may account for the disparate distributions of Ag and Au, fractionation of Au and Ag may also be caused by a significant Aum chemistry in seawater. The major species of Au111 in seawater are expected to be Au(OH)3 or Au(OH)3C1 (Baes and Mesmer, 1976). Although the analysis ofTumer etal. (1981) indicated that the field of Aum stability is somewhat outside the oxidation-reduction conditions encountered in seawater, a paucity of direct formation-constant observations for both Aum and Au1 creates substantial uncertainties. Furthermore, with respect to thermodynamic predictions of oxidation-reduction behaviour the ocean is not a system at equilibrium. 

Moldowan et al (5) investigated a sediment core, spanning a depth range of 5m, of Lower Toarcian shales from W. Germany specifically at a transition zone from a rather oxidized, shallow-marine, marly sediment to an organic matter-rich, black shale. Variations in distributions of isoprenoid hydrocarbons, steranes and monoaromatic steroids were observed and were related to variations in oxidation/reduction conditions during and shortly after sedimentation. 

The oxidation-reduction conditions of formation of iron compounds can... 

James considered all the typical parageneses of the BIF to be primary sedimentary and distinguished oxide, silicate, carbonate, and sulfide facies, deposited at different depths of the basin, where different oxidation-reduction conditions existed. 

Oxidation-reduction conditions are important in the geologic transport and deposihon of uranium. Oxidized forms of uranium (U[VI]) are relatively soluble and can be leached from the rocks to migrate in the environment. When strong reducing conditions are encountered (e.g., presence of carbonaceous materials or H2S), precipitahon of the soluble uranium will occur. 

Figure 4 Summary of oxidation-reduction conditions in three saline lakes of the Great Basin, USA (source Domagalski et al., 1990) (reproduced by The Geochemical Society from...

Formation of the amber chromophore is affected not only by oxidation-reduction conditions of melting, but also by the basic glass composition due to the related activity of oxygen ions this is increased for instance by adding Na20 at the expense of Si02 and the chromophore content then decreases (Harding, 1972),... 

Pourbaix diagram Pourbaix diagrams are often used to grab quickly an idea of which species predominates at specific pH and Eh (oxidation-reduction) conditions. The Pourbaix diagram is commonly used by corrosion engineers to determine the pH and potential where a metal will either be stable to corrosion, will corrode, or will form a passivating layer. 

Compound Alternative formula Oxidations Reduction Conditions Solvent pH Reference... 

Redox potential (Eh) characterises the oxidation-reduction condition of a soil. This in turn provides a means to assess soil genesis, soil fertility and status of soil contaminants (Liu Yu 1984). Redox potential is well known to be difficult to measure precisely with conventional methods, for reasons ranging from slow electrode response to soil condition, especially for poorly poised (redox capacity) soils (Bohn 1971 Ponnamperuma 1972). Usually measurements are made under specified conditions, with values being dependent on the experimental conditions. As the measured value is conditional, it may not be sufficiently precise for some physicochemical studies. Nevertheless, there is unique information about soil condition that can be derived by measuring the redox potential. 

The major disposal alternatives for dredged sediments and their modifications are listed in Table 7-3 (Gambrell et al., 1978) These categories differ primarily in the biological population exposed to the contaminated sediments, oxidation-reduction conditions, and transport pro-... 

The Cu complexation parameters for Wells 1 and 4 showed the most similarity in both model ligand concentrations and conditional stability constants. These waters also showed the greatest differences in oxidation-reduction conditions (oxic and post-oxic), while the ground water with the intermediate dissolved oxygen concentration seemed to be the outlier. However, all complexation parameters agreed within an order of magnitude for all three ground waters. 

Table 13.4. Influence of the container on the oxidation-reduction condition of a red wine stored for 8 months (Vivas and Glories, 1993a)...

Gambrell, R. R, R. A. Khalid, and W. H. Patrick, Jr. 1980. Chemical availability of mercury, lead, and zinc in Mobile Bay sediment suspension as affected by pH and oxidation-reduction conditions. Environ. Sci. Technol. 14 431-436. 

The integration of the His-tag might in addition reduce the expression level of the protein and oxidative reductive conditions inside the column might lead to metal-induced cleavage of the protein. The number of large-scale applications of IMAC is therefore limited and the biggest potential should be seen in proteins not intended for human use. 

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