Pennsylvanian Bituminous Coal, North-Central Texas: Potential for Coalbed Methane Resource Development

Most recent U.S. Geological Survey National Coal Resources Data System (NCRDS) activities completed for the State of Texas by the Bureau of Economic Geology (BEG) focused on Wilcox Group deep coal (lignite) resources, including "Defining coalbed methane exploration fairways in East-Central Texas" (Tyler and Scott, 1999) and "Deep-basin coal (lignite) in Wilcox Group, Sabine Uplift, East Texas: potential for unconventional coalbed methane resource development" (Kim and Ruppel, 2001). The major objectives of these projects were to provide high-quality, organized digital information and interpretations on the location, quality, and quantity of the coal to be mined in the Wilcox Group, Texas Gulf Coast area, during the next several decades to meet the needs of the region and the nation for reliable, low-cost, environmentally compatible energy. The first commercial coalbed methane field in Texas, the Sacatosa coal bed methane field in Maverick County, was announced in 2001 by The Exploration Company. This field is currently being produced from bituminous coal and carbonaceous shale of the Upper Cretaceous Olmos Formation in the Maverick Basin. Although the Pennsylvanian bituminous coals of North-Central Texas are of higher rank than the Texas Gulf Coast lignites and are comparable to the most bituminous coals, very little current information exists on their occurrence, distribution, geological setting, or future potential for coalbed methane development. More detailed and updated information of the coal resource in this region is essential for inclusion in the NCRDS, utilizing digital databases of available data as well as digitized maps compiled in a Geographic Information System (GIS) platform. Providing updated digital data on the Pennsylvanian bituminous coals of North-Central Texas and assessing their potential for future coalbed methane resource development are the major objectives for this current study. Major accomplishments for FY02 included digitally compiling major background regional data for Pennsylvanian depositional systems and major coal resources such as the Strawn (Thurber) coals, as well as a comparison with current coalbed methane production from Olmos bituminous coals in the Maverick Basin. Future FY03 tasks to be completed include analysis of other coal resources such as the Canyon (Bridgeport) and Cisco (Newcastle) coals, as well as an overall future assessment of the coalbed methane potential of the Pennsylvanian bituminous coals of North-Central Texas.Bureau of Economic Geolog

Computation of supersonic jet mixing noise for an axisymmetric CD nozzle using k-epsilon turbulence model

The turbulent mixing noise of a supersonic jet is calculated for a round convergent-divergent nozzle at the design pressure ratio. Aerodynamic computations are performed using the PARC code with a k-epsilon turbulence model. Lighthill's acoustic analogy combined with Ribner's assumption is adopted. The acoustics solution is based upon the methodology followed by GE in the MGB code. The source correlation function is expressed as a linear combination of second-order tensors. Assuming separable second-order correlations and incorporating Batchelor's isotropic turbulence model, the source term was calculated from the kinetic energy of turbulence. A Gaussian distribution for the time-delay of correlation was introduced. The computational fluid dynamics (CFD) solution was used to obtain the source strength as well as the characteristic time-delay of correlation. The effect of sound/flow interaction was incorporated using the high frequency asymptotic solution to Lilley's equation for axisymmetric geometries. Acoustic results include sound pressure level directivity and spectra at different polar angles. The aerodynamic and acoustic results demonstrate favorable agreement with experimental data

A survey of the broadband shock associated noise prediction methods

Several different prediction methods to estimate the broadband shock associated noise of a supersonic jet are introduced and compared with experimental data at various test conditions. The nozzle geometries considered for comparison include a convergent and a convergent-divergent nozzle, both axisymmetric. Capabilities and limitations of prediction methods in incorporating the two nozzle geometries, flight effect, and temperature effect are discussed. Predicted noise field shows the best agreement for a convergent nozzle geometry under static conditions. Predicted results for nozzles in flight show larger discrepancies from data and more dependable flight data are required for further comparison. Qualitative effects of jet temperature, as observed in experiment, are reproduced in predicted results

Deep Basin Coal (Lignite) in WilcoxGroup, Sabine Uplift, East Texas: Potential for Unconventional Coal Gas Resource Development

The Wilcox Group in the Sabine Uplift, East Texas, contains relatively large amounts of deep-basin (220- to 2,000-ft depth) coal that may in turn contain large coalbed methane resources. The objective of the proposed study is to assemble and prepare data on coal resources in the Sabine Uplift area of East Texas for inclusion in the U.S. Geological Survey National Coal Resources Data System (NCRDS). Coal occurrence and lithofacies maps created in "The Wilcox Group (Paleocene-Eocene) in the Sabine Uplift Area, Texas: Depositional Systems and Deep-Basin Lignite" (Kaiser, 1990) were digitized and converted into a Geographic Information System (GIS) format. Associated data that were derived from geophysical logs to create these maps were then compiled into a digital spreadsheet. These digital maps and data enable prediction of coal seam thickness, geometry, and continuity and, therefore, areas of potential coalbed methane resources. The distribution of the Wilcox coals is depositionally controlled, and the stratigraphic framework of the targeted horizons defines coalbed methane exploration fairways. According to available data, the highest potential for coal bed methane production and development in the Sabine Uplift, East Texas, exists in the lower Wilcox Group coal seams in Panola and Shelby Counties.Bureau of Economic Geolog

New Model for Electron-Impact Ionization Cross Sections of Molecules

A theoretical model for electron-impact ionization cross sections, which has been developed primarily for atoms and atomic ions, is applied to neutral molecules. The new model combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses minimal theoretical data for the ground state of the target molecule, which are readily available from public-domain molecular structure codes such as GAMESS. The theory is called the binary encounter Bethe (BEB) model, and does not, in principle, involve any adjustable parameters. Applications to 19 molecules, including H2, NO, CH2, C6H6, and SF6, are presented, demonstrating that the BEB model provides total ionization cross sections by electron impact from threshold to several keV with an average accuracy of 15% or better at the cross section peak, except for SiF3. The BEB model can be applied to stable molecules as well as to transient radicals

New Model for Electron-Impact Ionization Cross Sections of Molecules

A theoretical model for electron-impact ionization cross sections, which has been developed primarily for atoms and atomic ions, is applied to neutral molecules. The new model combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses minimal theoretical data for the ground state of the target molecule, which are readily available from public-domain molecular structure codes such as GAMESS. The theory is called the binary encounter Bethe (BEB) model, and does not, in principle, involve any adjustable parameters. Applications to 19 molecules, including H2, NO, CH2, C6H6, and SF6, are presented, demonstrating that the BEB model provides total ionization cross sections by electron impact from threshold to several keV with an average accuracy of 15% or better at the cross section peak, except for SiF3. The BEB model can be applied to stable molecules as well as to transient radicals

Spatial correlations in chaotic nanoscale systems with spin-orbit coupling

We investigate the statistical properties of wave functions in chaotic nanostructures with spin-orbit coupling (SOC), focussing in particular on spatial correlations of eigenfunctions. Numerical results from a microscopic model are compared with results from random matrix theory in the crossover from the gaussian orthogonal to the gaussian symplectic ensembles (with increasing SOC); one- and two-point distribution functions were computed to understand the properties of eigenfunctions in this crossover. It is found that correlations of wave function amplitudes are suppressed with SOC; nevertheless, eigenfunction correlations play a more important role in the two-point distribution function(s), compared to the case with vanishing SOC. Experimental consequences of our results are discussed.Comment: Submitted to PR

Transport and Strong-Correlation Phenomena in Carbon Nanotube Quantum Dots in a Magnetic Field

Transport through carbon nanotube (CNT) quantum dots (QDs) in a magnetic field is discussed. The evolution of the system from the ultraviolet to the infrared is analyzed; the strongly correlated (SC) states arising in the infrared are investigated. Experimental consequences of the physics are presented -- the SC states arising at various fillings are shown to be drastically different, with distinct signatures in the conductance and, in particular, the noise. Besides CNT QDs, our results are also relevant to double QD systems.Comment: 5 pages, 5 figure

Pituitary Adenylate-Cyclase Activating Polypeptide Regulates Hunger- and Palatability-Induced Binge Eating

While pituitary adenylate cyclase activating polypeptide (PACAP) signaling in the hypothalamic ventromedial nuclei (VMN) has been shown to regulate feeding, a challenge in unmasking a role for this peptide in obesity is that excess feeding can involve numerous mechanisms including homeostatic (hunger) and hedonic-related (palatability) drives. In these studies, we first isolated distinct feeding drives by developing a novel model of binge behavior in which homeostatic-driven feeding was temporally separated from feeding driven by food palatability. We found that stimulation of the VMN, achieved by local microinjections of AMPA, decreased standard chow consumption in food-restricted rats (e.g., homeostatic feeding); surprisingly, this manipulation failed to alter palatable food consumption in satiated rats (e.g., hedonic feeding). In contrast, inhibition of the nucleus accumbens (NAc), through local microinjections of GABA receptor agonists baclofen and muscimol, decreased hedonic feeding without altering homeostatic feeding. PACAP microinjections produced the site-specific changes in synaptic transmission needed to decrease feeding via VMN or NAc circuitry. PACAP into the NAc mimicked the actions of GABA agonists by reducing hedonic feeding without altering homeostatic feeding. In contrast, PACAP into the VMN mimicked the actions of AMPA by decreasing homeostatic feeding without affecting hedonic feeding. Slice electrophysiology recordings verified PACAP excitation of VMN neurons and inhibition of NAc neurons. These data suggest that the VMN and NAc regulate distinct circuits giving rise to unique feeding drives, but that both can be regulated by the neuropeptide PACAP to potentially curb excessive eating stemming from either drive

Electron Production in Proton Collisions: Total Cross Sections

Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given