2,164 research outputs found
Ion implantation and low-temperature epitaxial regrowth of GaAs
Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ion‐implanted GaAs and the crystal quality following capless furnace annealing at low temperature (∼400 °C). The implantation‐induced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 Å. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (<400 Å) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the low‐temperature annealing of GaAs
Epitaxial regrowth of thin amorphous GaAs layers
Channeling and transmission electron microscopy have been used to investigate the parameters that govern the crystal quality following capless funace annealing at low temperature (~ 400 °C) in ion-implanted GaAs. From the results obtained, we concluded that the crystal quality after annealing depends strongly on the thickness of the amorphous layer generated by ion implantation and the number of residual defects increases linearly with the thickness of the implanted layer. Single-crystal regrowth free of defects detectable by megaelectron volt He + channeling was achieved for a very thin amorphous layer (<~ 400 Å)
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Potential Sinks for Geologic Storage of CO2 Generated in the Carolinas
This document summarizes a scoping study of the current state of knowledge of carbon storage options for our geographic area.
The focus is on one aspect of carbon capture and storage—identification of deep saline aquifers in which carbon dioxide (CO2
) generated in the Carolinas might be stored. The study does not address other aspects of CO2 storage projects, such as capture and compression of the gas, well construction and development, or injection. Transport of CO2 is touched upon in this study but has not been fully addressed.
The information contained in this document is primarily from review of published geologic literature and unpublished data. No field data collection has been completed as part of this study. Further work will be necessary to increase confidence in the suitability of the potential CO2 storage sites identified in this report. This study does not address the regulatory, environmental, or public policy issues associated with carbon storage, which are under development at this time.Duke Energy, Progress Energy, Santee Cooper Power, South Carolina Electric and Gas, Electric Power Research Institute (EPRI), Southern States Energy Board (SSEB)Bureau of Economic Geolog
Natural resources inventory and monitoring in Oregon with ERTS imagery
Multidiscipline team interpretation of ERTS satellite and highflight imagery is providing resource and land use information needed for land use planning in Oregon. A coordinated inventory of geology, soil-landscapes, forest and range vegetation, and land use for Crook County, illustrates the value of this approach for broad area and state planning. Other applications include mapping fault zones, inventory of forest clearcut areas, location of forest insect damage, and monitoring irrigation development. Computer classification is being developed for use in conjunction with visual interpretation
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Optimal Geological Environments for Carbon Dioxide Disposal in Brine Formations (Saline Aquifers) in the United States Pilot Experiment in the Frio Formation, Houston Area
This Environmental Assessment (EA) provides the results of an evaluation of the potential environmental consequences of a field experiment and injection of CO2 into a subsurface brine-bearing formation, a process known as geologic sequestration. The U.S. Department of Energy (DOE) is proposing to fund this project to determine if geologic sequestration of CO2 is safe and effective in reducing atmospheric releases, and if the sequestration process can be modeled, measured, and monitored. If approved, DOE would provide the $3.4 million cost of the project.
This project was proposed by the Bureau of Economic Geology as Phase III of a DOE-initiated competitive solicitation DE-RA26-98FT35008. Phase I and Phase II assessed the optimal geological environments for geologic sequestration in brine formations in the onshore U.S., and found that the upper Texas Gulf Coast was a region with excellent potential for geologic sequestration. Phase III will test the Phase I and Phase II conclusions with a field experiment.
Increasing concentrations of CO2 in the atmosphere are thought to have the potential to force change toward a warmer global climate. These changes may have negative impacts on human systems as well as ecosystems. DOE is developing an understanding of environmentally acceptable options.
Geologic sequestration is one of the highly ranked technologies for stabilizing the amount of CO2 released to the atmosphere as waste from combustion of fossil fuel. In this method, CO2 is captured from a stationary industrial source of CO2, compressed, and injected into the subsurface. The injection site must be selected to have the geologic properties that will assure that the CO2 will remain trapped in the subsurface and isolated from the atmosphere for thousands of years. The natural capacity of the subsurface to trap and retain buoyant fluids such as oil and natural gas is well known. Technologies for injection of fluids into the subsurface are widely applied both for waste disposal and for enhancing recovery of oil.
This field experiment is designed to closely monitor the performance of the subsurface in holding CO2. To reduce risks, the injection is designed using the minimum volume of CO2 that can be measured in the subsurface using a wide variety of techniques, and to be completed over a short period of time (less than 1 year). The results obtained from monitoring a small volume will provide assurance that in a similar geologic environment, a large volume can be safely and effectively injected and monitored over a longer time frame. Monitoring and modeling tools have been designed and will be tested at this site by researchers from Lawrence Berkeley National Laboratory (LBNL), Oak Ridge National Laboratory (ORNL), Lawrence Livermore National Laboratory (LLNL), and National Energy Technology Laboratory (NETL).Bureau of Economic Geolog
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Potential sinks for geologic storage of carbon dioxide generated by power plants in North and South Carolina
Duke Energy
Progress Energy
Santee Cooper Power
SCANA CorporationBureau of Economic Geolog
The comparative evaluation of ERTS-1 imagery for resource inventory in land use planning
The author has identified the following significant results. Multidiscipline team interpretation and mapping of resources for Crook County is nearly complete on 1:250,000 scale enlargements of ERTS-1 imagery. Maps of geology, landforms, soils and vegetation-land use are being interpreted to show limitations, suitabilities and geologic hazards for land use planning. Mapping of lineaments and structures from ERTS-1 imagery has shown a number of features not previously mapped in Oregon. A timber inventory of Ochoco National Forest has been made. Inventory of forest clear-cutting practices has been successfully demonstrated with ERTS-1 color composites. Soil tonal differences in fallow fields shown on ERTS-1 correspond with major soil boundaries in loess-mantled terrain. A digital classification system used for discriminating natural vegetation and geologic materials classes has been successful in separation of most major classes around Newberry Cauldera, Mt. Washington and Big Summit Prairie. Computer routines are available for correction of scanner data variations; and for matching scales and coordinates between digital and photographic imagery. Methods of Diazo film color printing of computer classifications and elevation-slope perspective plots with computer are being developed
The comparative evaluation of ERTS-1 imagery for resource inventory in land use planning
The author has identified the following significant results. Multidiscipline team interpretation and mapping of resources for Crook County is complete on 1:250,000 scale enlargements of ERTS imagery and 1:120,000 hi-flight photography. Maps of geology, soils, vegetation-land use and land resources units were interpreted to show limitations, suitabilities, and geologic hazards for land use planning. Mapping of lineaments and structures from ERTS imagery has shown a number of features not previously mapped in Oregon. A multistage timber inventory of Ochoco National Forest was made, using ERTS images as the first stage. Inventory of forest clear-cutting practices was successfully demonstrated with color composites. Soil tonal differences in fallow fields correspond with major soil boundaries in loess-mantled terrain. A digital classification system used for discriminating natural vegetation and geologic material classes was successful in separating most major classes around Newberry Caldera, Mt. Washington, and Big Summit Prairie
Pharmacology of DB844, an orally active aza analogue of pafuramidine, in a monkey model of second stage human African trypanosomiasis
Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-yl]-nicotinamide (DB820), exhibiting plasma C(max) values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible
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