Comparative petrology of Tertiary sandstones of southern Piceance Creek Basin, Colorado
Lacustrine and fluvial sandstones of the Wasatch and Green River Formations are described as they outcrop at several localities along the southern margin of the Piceance Creek basin. The description combined with petrographic analyses of thin-section samples provide a basis for determining the provenance of the sand, as well as crude comparison of compositional and textural features that resulted from differences in depositional processes. The sandstones in marginal lacustrine settings in the Wasatch and Green River Formations are proven reservoirs for significant hydrocarbon reserves in the Uinta and Piceance Creek basins. (JMT)
Stratigraphy of the Evacuation Creek Member (Green River Formation), Piceance Creek Basin, Northwestern Colorado
The Evacuation Creek Member occupies 2 , 6 0 0 square miles of the Piceance Creek basin of northwestern Colorado. The Green River Formation within the Piceance Creek basin fo rms a high table-land known a s the Roan Plateau. The Evacuation Creek Member i s the uppermost member of the Green River Formation and i s exposed everywhere throughout the basin. The lithology of the Evacuation Creek Member consists mainly of discontinuous sandstones, sil tstones, and marlstones. Correlation a c r o s s the basin i s possible once the base of the Evacuation Creek Member i s established, but becomes increasingly difficult upward through the Member . The Evacuation Creek Member represents the final regress ive cycle of lake deposition. The sediments were derived from the crystall ine rocks in the adjacent uplifts and from pre-existing sediments derived from the surrounding borderlands during previous uplifts.
Comparative study of in vitro flow characteristics between a human aortic valve and a designed aortic valve and six corresponding types of prosthetic heart valves.
A model of a pulsatile cardiovascular system is described including an electronic control, a hydraulic driving unit, a volume storage, a peripheral resistance and measuring equipment. Six different artificial heart valves, a designed aortic valve (Aachen pockett valve II) and a human aortic valve have been tested in the outflow position of the pump. Three of them are presently being used in clinical applications. Measurements of pressure and volume flow have been obtained for different frequencies n, pump volumes Vp and time ratios between pressure and suction phase. From the experimental results a comparative evaluation was deducted for different working conditions. In comparison to natural human aortic valve (NK) large volume flow is verified by the Aachen pocket valve II (AT), the Gott-Dagget value (GD), the Starr-Edwards valve (SE) and the Lillehei-Kaster valve (LK). The Gott-Daggett valve has the smallest back flow volume. The Smeloff-Cutter and in particular the Wada-Cutter valve have the largest regurgitation. This is to be expected since the Cutter valves are purposely so designed that they do not close tightly in order to avoid blood sedimentation. The human aortic valve, the Gott-Daggett valve and the Aachen pocket valve demonstrate the most favourable opening-closing characteristics. The human aortic valve achieves a negligible pressure loss, followed by the Björk-Shiley and the Lillehei-Kaster valve.