Oxygen variation

This oxygen variation and the Cu oxidation states play a very important role in the superconducting behavior of this compound. For example, the oxygen content (or x vacancy), the copper oxidation states, and the onset temperatures for superconductivity are listed below for different compositions. 

Melack, J. M., and T. R. Fisher. 1983. "Diel oxygen variations and their ecological implications in Amazon floodplain lakes." Archiv ftir Hydrobiologie 98 422-442. 

Brown G. H., Tranter M., Sharp M. J., Davies T. D., and Tsiouris S. (1993b) Dissolved oxygen variations in Alpine glacial meltwaters. Earth Surf. Process. Landforms 19, 247-253. 

Kump L. R., Kasting J. E., and Robinson J. M. (1991) Atmospheric oxygen variation through geologic time-introduction. Palaeogeogr. Palaeoclimatol. Palaeoecol. 97, 1-3. 

Lesson 2 -Reaction of elements of Period 3 with oxygen. -Variation in melting points of oxides of Period 3 elements. -Use of a spider concept map (Fig. 5) to test students prior knowledge. -Use of a concept map (Fig. 6) for formative assessment. -Use of a spider concept map (Fig. 7) for summarizing lesson and as an evaluative tool. 

Figure 12.16 Oxygen variation in the lead bath as a function ofthe quantity of electricity Q passing through the pump at 527 C.

Eds.), Atmospheric Oxygen Variation through Geologic Time. Global and Planetary Change 5 39-50 1991. 

Dyar MD, Colucci MT, Guidotti CV (1991) Forgotten major elements Hydrogen and oxygen variation in biotite from metapehte. Geology 19 1029-1032... 

When ethylene is oxidized over Ag, carbon dioxide may be formed either directly from ethylene, bypassing ethylene oxide, or by stepwise oxidation of ethylene oxide. To obtain confirmation for the occurrence of these reactions Margolis and Roginskii (118) carried out investigations with a mixture of C14-labeled ethylene, ethylene oxide, and oxygen. Variations in concentrations of initial compounds and reaction products as a function of the contact time were determined, as well as the activity distribution. 

Carbon dioxide may be sorbed reversibly only on an oxygen-covered surface, probably to form a (C03) complex. Twigg has shown that at temperatures about 200 to 250°C ethylene oxide will decompose in part to ethylene and adsorbed oxygen. Variations in the contact potential difference in adsorption of ethylene oxide at the above temperatures are indication that the electron work function will continuously increase with surface coverage. 

Various electrical and optical properties that have been measured for the wet thermal oxide on silicon carbide are summarised in TABLE 3. In general, no systematic variation of any of the oxide properties has been reported with oxide growth temperature in the range of 1000 to 1250°C. However, oxide grown with a wet process has been shown to have lower oxide charges than oxide grown in dry oxygen. Variations in the measured electrical properties... 

Gasification and combustion rates are usually low and the product gas may have a variable composition and even contain unconsumed oxygen. Variations of this method consist of breaking the coal by hand or drilling several holes into the seam and charging them with dynamite in the hope that the coal will be crushed in advance of the reaction zone by a series of explosions. 

Figure 7(b) SPC charts showing oxygen variation in as-milled and YjOj precipitated powder... 

Figure 5.2. Oxidation of Graphon with molecular oxygen. Variation of CO/CO2 partial pressure ratio with extent of coverage by surface oxygen complexes (p-molg ), from initial pressure of molecular oxygen (Pa) and bum-off (wt%) of the Graphon (adapted from Phillips et al, 1970).

Manthiram, A., Swiimea, J.S., Sui, Z.T., Steinfink, H., and Goodenough, JJl. (1987) The influence of oxygen variation on the crystal structure and phase composition of the superconductor yttrium barium copper oxide (YBa2Cu307 J. /. Am. 

The diffusion of nitrogen is slower than that of oxygen. Variations of hardness by heat treatment in oxygen and in nitrogen at 1200°C, show that nitrogen has a less decisive influence both at the surface and in the bulk of the metal (3). 

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