Thin Ce Research Articles

Oxygen K near-edge-structure for thin Ce oxide films

Oxygen K-edge absorption studies are performed on thin oxidized Ce films on Ta substrates. The various absorption edges are identified as belonging to trivalent or tetravalent Ce oxides by use of previous photoemission results, and by use of the O K-edge absorption spectrum from formally tetravalent CeO 2, which is obtained by oxidizing a thick Ce film.

Ce-catalyzed oxidation of Ta(110).

Photoemission spectroscopy was used to investigate the initial oxidation of the Ce/Ta(110) interface at room temperature. The oxidation of Ta(110) is dramatically enhanced by a thin Ce overlayer. A Ta suboxide TaO{sub {chi}} (0.5{le}{chi}{le}1) is formed first in the interface, followed by the rapid formation of Ta{sub 2}O{sub 5} upon further oxygen exposure. A weak interface reaction exists in Ce/Ta(110), but is excluded as the main cause of the catalytic oxidation. An earlier suggestion is reconfirmed that the Ce layer converts O{sub 2} to oxygen ions and thus promotes the oxidation of the substrate.

Red Fork Sandstones (Lower Pennsylvanian) in Deeper Parts of Anadarko Basin, Oklahoma: ABSTRACT

Red Fork sandstones in the deeper part of the Anadarko basin are the downdip equivalents of fluvial and deltaic sandstones in the Cherokee Group. The sandstones have repetitive, ordered sequences of sedimentary structures in vertical section. Individual bedsets display sharp basal contacts, gradational tops, and contorted bedding. The characteristics indicate these basinal sandstones were deposited by turbidity currents. The sandstones occur as narrow, linear constructional channels that are dip-trending. The lateral change from channel-fill to overbank facies takes place abruptly. Channel sandstones display incomplete AE bedsets up to 12 ft (3.6 m) thick. Overbank deposits have thin BE, BCE, and CE Bouma sequences and generally are dominated by shale. The sandstones are very fine-grained litharenites with an average composition of 58% quartz, 8% feldspar, 17% rock fragments, 5% other grains, and 12% matrix. Cement consists mainly of calcite ranging from 2 to 40% of the bulk volume. Quartz content tends to decrease upward and matrix increases upward within bedsets. The compositional grading is accompanied by a decrease in grain size upward within bedsets, indicating deposition during a decreasing flow-regime. Red Fork sandstones are low-permeability reservoirs with an average porosity and permeability of 7.8% and 0.1 md, respectively. Natural gas reservoirs occur mainly in the thicker, channel sequences. The bedding character of the channel and overbank facies is reflected in gamma-ray log responses. Log characters of the two facies are used to interpret turbidite sections of uncored areas. The interpretations are adapted to the East Clinton field for prediction of constructional channel reservoirs. The interpretation of dip-trending turbidite deposits may aid in exploration and development of the Red Fork sandstones. End_of_Article - Last_Page 1328------------

Minimization of microprograms and algorithm schemes

Minimization of microprograms and algorithm schemes