Low Thermal Expansion Coatings for Carbon/Carbon Composites

Two classes of materials are considered for low expansion protective coatings for carbon/carbon composites. They include composites containing particles which undergo allotropic phase transformations accompanied by negative volume changes with increasing temperature and anisotropic oxides which demonstrate low expansion due to microcracking. Conditions for failure of coatings by either cracking or spallation due to thermal mismatch are evaluated

University Lands Advanced Recovery Initative

Hydrocarbon production from West Texas lands held by The University of Texas System has been in decline since the 1960s (fig. 1). Nonetheless, analysis of resources on University lands indicates that of the 7,252 million stock tank barrels (MMSTB) of original oil in place, only 1,679 MMSTB has been recovered since production was established early in this century, and only 150 MMSTB of reserves exist. Unless advanced development practices are applied to University lands fields, some 5,423 MMSTB will therefore remain unrecovered in existing fields. Importantly, 2,140 MMSTB of this resource, nearly one-third of the original oil in place, is mobile oil that can be recovered using standard drilling and completion practices, provided that wellbores and completion intervals are geologically targeted to access this unrecovered resource (fig. 2). The goal of the University Lands Advanced Recovery Initiative is to characterize selected University Lands reservoirs to aid operators in geologically targeting the remaining hydrocarbon resource to stem the decline in University Lands production. This project is funded by The University of Texas (U.T.) System and by matching funds from operators of University Lands fields chosen for site-specific studies. The agreement between the Bureau of Economic Geology and the U.T. System was finalized on July 29, 1996. Three individual site-specific projects have been initiated in the first year of the project: (1) Fuhrman-Mascho Block 10 Unit, a San Andres-Grayburg carbonate and sandstone reservoir in Andrews County operated by Arrow Operating Company, (2) University Waddell Devonian field, a Devonian chert reservoir in Crane County operated by Pennzoil, and (3) North McElroy Grayburg field, a Grayburg carbonate reservoir in Crane and Upton Counties newly acquired by Apache Corporation (fig. 3). Fuhrman-Mascho and University Waddell fields have recovery efficiencies significantly below that of comparable fields within the same geologically based play. McElroy field, although producing at an efficiency above play average, contains an enormous 832 million barrels of unrecovered mobile oil (table 1).Bureau of Economic Geolog

Distribution of Matrix Cracks in a Uniaxial Ceramic Composite

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65596/1/j.1151-2916.1992.tb08181.x.pd

Arid Coastal Carbonates and the Phanerozoic Record of Carbonate Chemistry

Ocean chemistry and carbonate sedimentation link Earth's climate, carbon cycle, and marine pH. The carbonate system in seawater is complex and there are large uncertainties in key parameters in deep time. Here, we link sedimentary textures formed in arid coastal environments and preserved in the rock record to past seawater carbonate chemistry. Prior to the mid-Mesozoic, tepee structures and pisoids – features associated with peritidal environments – co-vary with available shelf area during cycles of supercontinent formation and rifting. In contrast, tepees and pisoids are consistently scarce after the mid-Mesozoic, which coincides with a radiation in pelagic calcifiers as well as the breakup of Pangea. Numerical models suggest that the global and temporal abundances of tepee structures and pisoids are correlated with secular shifts in seawater chemistry, and that trends likely reflect the underlying influence of tectonics and biotic innovation on marine alkalinity and the saturation states of carbonate minerals. As independent sedimentary proxies, tepees and pisoids serve as benchmarks for global carbon cycle models and provide a new proxy record of seawater chemistry that can help discern links among tectonics, biotic innovation, and seawater chemistry

Origin of Hysteresis Observed During Fatigue of Ceramic-Matrix Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66076/1/j.1151-2916.1990.tb05239.x.pd

Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa

Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its dietary overlap with native gastropods.A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) dietary overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Küster, 1841) and Melanoides tuberculata (Müller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed.The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research