Degree Department

44 Matching Results

Results open in a new window/tab.

Low-Income and Minority Serving Institutions: Department of Education Could Improve Its Monitoring and Assistance (open access)

Low-Income and Minority Serving Institutions: Department of Education Could Improve Its Monitoring and Assistance

A letter report issued by the Government Accountability Office with an abstract that begins "Congress has expanded the number of low-income and minority serving institutions eligible for grants under Titles III and V of the Higher Education Act and nearly doubled funding for these grants in the last 5 years to about $432 million in fiscal year 2004. Institutions eligible for funding under Titles III and V include Historically Black Colleges and Universities, Tribal Colleges, Hispanic Serving Institutions, Alaska Native Serving Institutions, Native Hawaiian Serving Institutions, and other postsecondary institutions that serve low-income students. Given the recent expansion, we examined these programs to determine (1) how institutions used their Title III and Title V grants and the benefits they received from using these grant funds, (2) what objectives and strategies the Department of Education (Education) has developed for Title III and Title V programs, and (3) to what extent Education monitors and provides assistance to Title III and Title V institutions."
Date: September 21, 2004
Creator: United States. Government Accountability Office.
Object Type: Report
System: The UNT Digital Library
Medicare Preventive Services: Most Beneficiaries Receive Some but Not All Recommended Services (open access)

Medicare Preventive Services: Most Beneficiaries Receive Some but Not All Recommended Services

Testimony issued by the Government Accountability Office with an abstract that begins "Preventive care depends on identifying health risks and on taking steps to control these risks. In contrast, Medicare, the federal health program insuring almost 35 million beneficiaries age 65 or older, was established largely to help pay beneficiaries' health care costs when they became ill or injured. Congress has broadened Medicare coverage over time to include specific preventive services, such as flu shots and certain cancer-screening tests, and the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (MMA) added coverage for several preventive services, including a one-time preventive care examination for new enrollees, which will start in 2005. GAO's work, done before MMA, included analyzing data from four national health surveys to examine the extent to which Medicare beneficiaries received preventive services through physician visits. GAO also interviewed officials from the Centers for Medicare & Medicaid Services (CMS) and other experts and reviewed the results of past demonstrations and studies to assess expected benefits and limits of different delivery options for preventive care, including a one-time preventive care examination."
Date: September 21, 2004
Creator: United States. Government Accountability Office.
Object Type: Text
System: The UNT Digital Library
Lithographically-directed self-assembly of nanostructures (open access)

Lithographically-directed self-assembly of nanostructures

The combination of lithography and self-assembly provides apowerful means of organizing solution-synthesized nanostructures for awide variety of applications. We have developed a fluidic assembly methodthat relies on the local pinning of a moving liquid contact line bylithographically produced topographic features to concentratenanoparticles at those features. The final stages of the assembly processare controlled first by long-range immersion capillary forces and then bythe short-range electrostatic and Van der Waal's interactions. We havesuccessfully assembled nanoparticles from 50 nm to 2 nm in size usingthis technique and have also demonstrated the controlled positioning ofmore complex nanotetrapod structures. We have used this process toassemble Au nanoparticles into pre-patterned electrode structures andhave performed preliminary electrical characterization of the devices soformed. The fluidic assembly method is capable of very high yield, interms of positioning nanostructures at each lithographically-definedlocation, and of excellent specificity, with essentially no particledeposition between features.
Date: September 21, 2004
Creator: Liddle, J. Alexander; Cui, Yi & Alivisatos, Paul
Object Type: Article
System: The UNT Digital Library
Probability Density and CFAR Threshold Estimation for Hyperspectral Imaging (open access)

Probability Density and CFAR Threshold Estimation for Hyperspectral Imaging

The work reported here shows the proof of principle (using a small data set) for a suite of algorithms designed to estimate the probability density function of hyperspectral background data and compute the appropriate Constant False Alarm Rate (CFAR) matched filter decision threshold for a chemical plume detector. Future work will provide a thorough demonstration of the algorithms and their performance with a large data set. The LASI (Large Aperture Search Initiative) Project involves instrumentation and image processing for hyperspectral images of chemical plumes in the atmosphere. The work reported here involves research and development on algorithms for reducing the false alarm rate in chemical plume detection and identification algorithms operating on hyperspectral image cubes. The chemical plume detection algorithms to date have used matched filters designed using generalized maximum likelihood ratio hypothesis testing algorithms [1, 2, 5, 6, 7, 12, 10, 11, 13]. One of the key challenges in hyperspectral imaging research is the high false alarm rate that often results from the plume detector [1, 2]. The overall goal of this work is to extend the classical matched filter detector to apply Constant False Alarm Rate (CFAR) methods to reduce the false alarm rate, or Probability of False …
Date: September 21, 2004
Creator: Clark, G A
Object Type: Report
System: The UNT Digital Library
FUDGE: A Program for Performing Nuclear Data Testing and Sensitivity Studies (open access)

FUDGE: A Program for Performing Nuclear Data Testing and Sensitivity Studies

We have developed a program called FUDGE that allows one to modify data from LLNL's nuclear database. After modifying data, FUDGE can then be instructed to process the data into the formats used by LLNL's deterministic (ndf) and the Monte Carlo (MCAPM) transport codes. This capability allows users to perform nuclear data sensitivity studies without modification of the transport modeling codes. FUDGE is designed to be user friendly (object-oriented) and fast (the modification and processing typically takes about a minute). It uses Python as a front-end, making it flexible and scriptable. Comparing, plotting and printing of the data are also supported. An overview of FUDGE will be presented as well as examples.
Date: September 21, 2004
Creator: Beck, B R
Object Type: Article
System: The UNT Digital Library
Neutrino Factory and Beta Beam Experiments and Development. (open access)

Neutrino Factory and Beta Beam Experiments and Development.

The long-term prospects for fully exploring three-flavor mixing in the neutrino sector depend upon an ongoing and increased investment in the appropriate accelerator R&D. Two new concepts have been proposed that would revolutionize neutrino experiments, namely the Neutrino Factory and the Beta Beam facility. These new facilities would dramatically improve our ability to test the three-flavor mixing framework, measure CP violation in the lepton sector, and perhaps determine the neutrino mass hierarchy, and, if necessary, probe extremely small values of the mixing angle {theta}{sub 13}. The stunning sensitivity that could be achieved with a Neutrino Factory is described, together with our present understanding of the corresponding sensitivity that might be achieved with a Beta Beam facility. In the Beta Beam case, additional study is required to better understand the optimum Beta Beam energy, and the achievable sensitivity. Neither a Neutrino Factory nor a Beta Beam facility could be built without significant R&D. An impressive Neutrino Factory R&D effort has been ongoing in the U.S. and elsewhere over the last few years and significant progress has been made towards optimizing the design, developing and testing the required accelerator components, and significantly reducing the cost. The recent progress is described here. There …
Date: September 21, 2004
Creator: Albright, C.; Berg, J. S.; Fernow, R.; Gallardo, J.; Kahn, S.; Kirk, H. et al.
Object Type: Report
System: The UNT Digital Library
Segregation of Uranium Metal from K Basin Sludge: Results from Vendor Testing (open access)

Segregation of Uranium Metal from K Basin Sludge: Results from Vendor Testing

Under contract to Fluor Hanford, Pacific Northwest National Laboratory directed laboratory, bench-scale, and pilot-scale vendor testing to evaluate the use of commercial gravity mineral concentration technology to remove and concentrate uranium metal from Hanford K Basin sludge. Uranium metal in the sludge corrodes by reacting with water to generate heat and hydrogen gas, and may constrain shipment and disposal of the sludge to the Waste Isolation Pilot Plant as remote-handled transuranic waste. Separating uranium metal from the K Basin sludge is expected to be similar to some gold recovery operations. Consequently, the capabilities of commercial gravity mineral concentration technologies were assessed for their applicability to K Basin sludge streams. Overall, the vendor testing demonstrated the technical feasibility of using gravity concentration equipment to separate the K Basin sludge into a high-volume uranium metal-depleted stream and a low-volume uranium metal-rich stream. I n test systems, more than 96% of the uranium metal surrogate was concentrated into 10 to 30% of the sludge mass (7 to 24% of the sludge volume). With more prototypical equipment and stream recycle, higher recoveries may be achieved.
Date: September 21, 2004
Creator: Schmidt, Andrew J.; Elmore, Monte R. & Delegard, Calvin H.
Object Type: Report
System: The UNT Digital Library
Laser- and Radar-based Mission Concepts for Suborbital and Spaceborne Monitoring of Seismic Surface Waves (open access)

Laser- and Radar-based Mission Concepts for Suborbital and Spaceborne Monitoring of Seismic Surface Waves

The development of a suborbital or spaceborne system to monitor seismic waves poses an intriguing prospect for advancing the state of seismology. This capability would enable an unprecedented global mapping of the velocity structure of the earth's crust, understanding of earthquake rupture dynamics and wave propagation effects, and event source location, characterization and discrimination that are critical for both fundamental earthquake research and nuclear non-proliferation applications. As part of an ongoing collaboration between LLNL and JPL, an advanced mission concept study assessed architectural considerations and operational and data delivery requirements, extending two prior studies by each organization--a radar-based satellite system (JPL) for earthquake hazard assessment and a feasibility study of space- or UAV-based laser seismometer systems (LLNL) for seismic event monitoring. Seismic wave measurement requirements include lower bounds on detectability of specific seismic sources of interest and wave amplitude accuracy for different levels of analysis, such as source characterization, discrimination and tomography, with a 100 {micro}m wave amplitude resolution for waves nominally traveling 5 km/s, an upper frequency bound based on explosion and earthquake surface displacement spectra, and minimum horizontal resolution (1-5 km) and areal coverage, in general and for targeted observations. For a radar system, corresponding engineering and operational …
Date: September 21, 2004
Creator: Foxall, W; Schultz, C A & Tralli, D M
Object Type: Article
System: The UNT Digital Library
MATRIX PRODUCT VARIATIONAL FORMULATION FOR LATTICE GAUGE THEORY. (open access)

MATRIX PRODUCT VARIATIONAL FORMULATION FOR LATTICE GAUGE THEORY.

For hamiltonian lattice gauge theory, we introduce the matrix product ansatz inspired from density matrix renormalization group. In this method, wavefunction of the target state is assumed to be a product of finite matrices. As a result, the energy becomes a simple function of the matrices, which can be evaluated using a computer. The minimum of the energy function corresponds to the vacuum state. We show that the S = 1/2 Heisenberg chain model are well described with the ansatz. The method is also applied to the two-dimensional S = 1/2 Heisenberg and U(1) plaquette chain models.
Date: September 21, 2004
Creator: SUGIHARA,T.
Object Type: Article
System: The UNT Digital Library
Proceedings of the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring (open access)

Proceedings of the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring

These proceedings contain papers prepared for the 26th Seismic Research Review: Trends in Nuclear Explosion Monitoring, held 21-23 September, 2004 in Orlando, Florida. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), Air Force Research Laboratory (AFRL), US Army Space and Missile Defense Command, and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.
Date: September 21, 2004
Creator: Chavez, Francesca C.; Benson, Jody; Hanson, Stephanie; Mark, Carol & Wetovsky, Marvin A.
Object Type: Article
System: The UNT Digital Library
Reducing Complexity in Parallel Algebraic Multigrid Preconditioners (open access)

Reducing Complexity in Parallel Algebraic Multigrid Preconditioners

Algebraic multigrid (AMG) is a very efficient iterative solver and preconditioner for large unstructured linear systems. Traditional coarsening schemes for AMG can, however, lead to computational complexity growth as problem size increases, resulting in increased memory use and execution time, and diminished scalability. Two new parallel AMG coarsening schemes are proposed, that are based on solely enforcing a maximum independent set property, resulting in sparser coarse grids. The new coarsening techniques remedy memory and execution time complexity growth for various large three-dimensional (3D) problems. If used within AMG as a preconditioner for Krylov subspace methods, the resulting iterative methods tend to converge fast. This paper discusses complexity issues that can arise in AMG, describes the new coarsening schemes and examines the performance of the new preconditioners for various large 3D problems.
Date: September 21, 2004
Creator: De Sterck, H; Yang, U M & Heys, J
Object Type: Article
System: The UNT Digital Library
Microbial Metabolite Production for Accelerated Metal and Radionuclide Bioremediation (Microbial Metabolite Production Report) (open access)

Microbial Metabolite Production for Accelerated Metal and Radionuclide Bioremediation (Microbial Metabolite Production Report)

Biogeochemical activity is an ongoing and dynamic process due to bacterial activity in the subsurface. Bacteria contribute significantly to biotransformation of metals and radionuclides. As basic science reveals more information about specific mechanisms of bacterial-metal reduction, an even greater contribution of bacteria to biogeochemical activities is realized. An understanding and application of the mechanisms of metal and radionuclide reduction offers tremendous potential for development into bioremedial processes and technologies. Most bacteria are capable of biogeochemical transformation as a result of meeting nutrient requirements. These assimilatory mechanisms for metals transformation include production of small molecules that serve as electron shuttles for metal reduction. This contribution to biogeochemistry is small however due to only trace requirements for minerals by bacteria. Dissimilatory metal reducing bacteria (DMRB) reduce oxidized metals and insoluble mineral oxides as a means for biological energy production during growth. These types of bacteria offer considerable potential for bioremediation of environments contaminated with toxic metals and radionuclides because of the relatively large amount of metal biotransformation they require for growth. One of the mechanisms employed by some DMRB for electron transfer to insoluble metal oxides is melanin production. The electrochemical properties of melanin provide this polymeric, humic-type compound with electron shuttling …
Date: September 21, 2004
Creator: TURICK, CHARLES
Object Type: Report
System: The UNT Digital Library
Effect of Nitrate on the Repassivation Potential of Alloy 22 in Chloride Containing Environment (open access)

Effect of Nitrate on the Repassivation Potential of Alloy 22 in Chloride Containing Environment

The study of Alloy 22 was undertaken in several selected nitrate/chloride (NO{sub 3}{sup -}/Cl{sup -}) electrolytes with chloride concentrations [Cl{sup -}] of 1.0, 3.5 and 6.0 molal with [NO{sub 3}{sup -}]/[Cl{sup -}] ratios of 0.05, 0.15 and 0.5 at temperatures up to 100 C. The repassivation potentials increased with increase in [NO{sub 3}{sup -}]/[Cl{sup -}] ratio and decreased with increase in temperature. The absolute [Cl{sup -}] was found to have less of an effect on the repassivation potential compared with temperature and the [NO{sub 3}{sup -}]/[Cl{sup -}]. Regression analyses were carried out to describe the relationship between the repassivation potential, temperature, [Cl{sup -}] and [NO{sub 3}{sup -}] for the conditions tested.
Date: September 21, 2004
Creator: Ilevbare, G.; King, K.; Gordon, S.; Elayat, H.; Gdowski, G. & Summers, T.
Object Type: Article
System: The UNT Digital Library
Fundamental Surface Reaction Mechanisms in Fluorocarbon Plasma-Based Processing: Final report (open access)

Fundamental Surface Reaction Mechanisms in Fluorocarbon Plasma-Based Processing: Final report

This report provides a summary of results obtained in research supported by contract ''Fundamental Surface Reaction Mechanisms in Fluorocarbon Plasma-Based Processing'' (Contract No. DE-FG0200ER54608). In this program we advanced significantly the scientific knowledge base on low pressure fluorocarbon plasmas used for patterning of dielectric films and for producing fluorocarbon coatings on substrates. We characterized important neutral and ionic gas phase species that are incident at the substrate, and the processes that occur at relevant surfaces in contact with the plasma. The work was performed through collaboration of research groups at three universities where significantly different, complementary tools for plasma and surface characterization, computer simulation of plasma and surface processes exist. Exchange of diagnostic tools and experimental verification of key results at collaborating institutions, both experimentally and by computer simulations, was an important component of the approach taken in this work.
Date: September 21, 2004
Creator: Oehrlein, Gottlieb S.; Anderson, H.; Cecchi, J. & Graves, D.
Object Type: Report
System: The UNT Digital Library
Quantum physics in neuroscience and psychology: A neurophysicalmodel of the mind/brain interaction (open access)

Quantum physics in neuroscience and psychology: A neurophysicalmodel of the mind/brain interaction

Neuropsychological research on the neural basis of behavior generally posits that brain mechanisms will ultimately suffice to explain all psychologically described phenomena. This assumption stems from the idea that the brain is made up entirely of material particles and fields, and that all causal mechanisms relevant to neuroscience can therefore be formulated solely in terms of properties of these elements. Thus terms having intrinsic mentalistic and/or experiential content (e.g., ''feeling,'' ''knowing,'' and ''effort'') are not included as primary causal factors. This theoretical restriction is motivated primarily by ideas about the natural world that have been known to be fundamentally incorrect for more than three quarters of a century. Contemporary basic physical theory differs profoundly from classical physics on the important matter of how the consciousness of human agents enters into the structure of empirical phenomena. The new principles contradict the older idea that local mechanical processes alone can account for the structure of all observed empirical data. Contemporary physical theory brings directly and irreducibly into the overall causal structure certain psychologically described choices made by human agents about how they will act. This key development in basic physical theory is applicable to neuroscience, and it provides neuroscientists and psychologists with …
Date: September 21, 2004
Creator: Schwartz, Jeffrey M.; Stapp, Henry P. & Beauregard, Mario
Object Type: Article
System: The UNT Digital Library
Irradiation Induced Precipitation and Dissolution of Intermetallics in Zr Alloys Studied Using Synchrotron Radiation (open access)

Irradiation Induced Precipitation and Dissolution of Intermetallics in Zr Alloys Studied Using Synchrotron Radiation

The overall aim of this project is to investigate the irradiation induced precipitation of alloying elements and dissolution of second phase particles in Zr alloys using a combination of (1) synchrotron radiation examination of bulk samples using the Advanced Photon Source (APS) at Argonne National Laboratory and (2) in-situ irradiation of model alloys using the IVEM/Tandem Facility also located at Argonne
Date: September 21, 2004
Creator: Motta, Arthur T.
Object Type: Report
System: The UNT Digital Library
2003 Archaea: Ecology, Metabolism and Molecular Biology (open access)

2003 Archaea: Ecology, Metabolism and Molecular Biology

The Gordon Research Conference (GRC) on 2003 Archaea: Ecology, Metabolism and Molecular Biology was held at Proctor Academy, Andover, NH from August 3-8, 2003. The Conference was well-attended with 150 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, ''free time'' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field. I want to personally thank you for your support of this Conference. As you know, in the interest of promoting the presentation of unpublished and frontier-breaking research, Gordon Research …
Date: September 21, 2004
Creator: Shand, Richard F.
Object Type: Article
System: The UNT Digital Library
2003 Plant Cell Walls Gordon Conference (open access)

2003 Plant Cell Walls Gordon Conference

This conference will address recent progress in many aspects of cell wall biology. Molecular, genetic, and genomic approaches are yielding major advances in our understanding of the composition, synthesis, and architecture of plant cell walls and their dynamics during growth, and are identifying the genes that encode the machinery needed to make their biogenesis possible. This meeting will bring together international scientists from academia, industry and government labs to share the latest breakthroughs and perspectives on polysaccharide biosynthesis, wood formation, wall modification, expansion and interaction with other organisms, and genomic & evolutionary analyses of wall-related genes, as well as to discuss recent ''nanotechnological'' advances that take wall analysis to the level of a single cell.
Date: September 21, 2004
Creator: Cosgrove, Daniel J.
Object Type: Article
System: The UNT Digital Library
Process to Accomplish Autothermal or Steam Reforming Via a Reciprocating Compression Device (open access)

Process to Accomplish Autothermal or Steam Reforming Via a Reciprocating Compression Device

The invention provides a method and apparatus for producing a synthesis gas from a variety of hydrocarbons. The apparatus (device) consists of a semi-batch, non-constant volume reactor to generate a synthesis gas. While the apparatus feeds mixtures of air, steam, and hydrocarbons into a cylinder where work is performed on the fluid by a piston to adiabatically raise its temperature without heat transfer from an external source.
Date: September 21, 2004
Creator: Lyons, David K.; James, Robert; Berry, David A. & Gardern, Todd
Object Type: Patent
System: The UNT Digital Library
Local search strategies for equational satisfiability. (open access)

Local search strategies for equational satisfiability.

The search for models of an algebra is an important and demanding aspect of automated reasoning. Typically, a model is represented in the form of a matrix or a set of matrices. When a model is found that satisfies all the given theorems of an algebra, it is called a solution model. This paper considers algebras that can be represented by using a single operation, by way of the Sheffer stroke. The characteristic of needing only one operation to represent an algebra reduces the problem by requiring a search through all instances of a single matrix. This search is simple when the domain size is small, say 2, but for a larger domain size, say 10, the search space increases dramatically. Clearly, a method other than a brute-force, global search is desirable. Most modern model-finding programs use a global search; instead of checking every possible matrix, however a set of heuristics is used that allows the search space to be dramatically smaller and thus increases the likelihood of reaching a solution. An alternative approach is local search. This paper discusses several local search strategies that were applied to the problem of equational satisfiability.
Date: September 21, 2004
Creator: Keefe, K.
Object Type: Report
System: The UNT Digital Library
Analysis of Radionuclide Migration through a 200-m Vadose Zone Following a 16-year Infiltration Event (open access)

Analysis of Radionuclide Migration through a 200-m Vadose Zone Following a 16-year Infiltration Event

The CAMBRIC nuclear test was conducted beneath Frenchman Flat at the Nevada Test Site on May 14, 1965. The nuclear device was emplaced in heterogeneous alluvium, approximately 70 m beneath the ambient water table, which is itself 220 m beneath the ground surface. Approximately 10 years later, groundwater adjacent to the test was pumped steadily for 16 years to elicit information on the migration of residual radionuclide migration through the saturated zone. The pumping well effluent--containing mostly soluble radionuclides such as tritium, {sup 14}C, {sup 36}Cl, {sup 85}Kr, {sup 129}I, and {sup 106}Ru--was monitored, discharged to an unlined ditch, and allowed to flow towards Frenchman Lake over one kilometer away. Discharged water and radionuclides infiltrated into the ground and created an unexpected second experiment in which the migration of the effluent through the unsaturated zone back to the water table could be studied. In this paper, the pumping and effluent data are being utilized in conjunction with a series of geologic data, new radionuclide measurements, isotopic age-dating estimates, and vadose zone flow and transport models to better understand the movement of radionuclides between the ditch and the water table. Measurements of radionuclide concentrations in water samples produced from a water …
Date: September 21, 2004
Creator: Tompson, A. B.; Hudson, G. B.; Smith, D. K. & Hunt, J. R.
Object Type: Article
System: The UNT Digital Library
The Baytown Sun (Baytown, Tex.), Vol. 83, No. 292, Ed. 1 Tuesday, September 21, 2004 (open access)

The Baytown Sun (Baytown, Tex.), Vol. 83, No. 292, Ed. 1 Tuesday, September 21, 2004

Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date: September 21, 2004
Creator: Cash, Wanda Garner
Object Type: Newspaper
System: The Portal to Texas History
North Texas Daily (Denton, Tex.), Vol. 89, No. 13, Ed. 1 Tuesday, September 21, 2004 (open access)

North Texas Daily (Denton, Tex.), Vol. 89, No. 13, Ed. 1 Tuesday, September 21, 2004

Daily student newspaper from the University of North Texas in Denton, Texas that includes local, state and campus news along with advertising.
Date: September 21, 2004
Creator: unknown
Object Type: Newspaper
System: The Portal to Texas History
T-REX: Thomson-Radiated Extreme X-rays Moving X-Ray Science into the ''Nuclear'' Applications Space with Thompson Scattered Photons (open access)

T-REX: Thomson-Radiated Extreme X-rays Moving X-Ray Science into the ''Nuclear'' Applications Space with Thompson Scattered Photons

The scattering of laser photons from relativistic electrons (Thomson scattering) has been demonstrated to be a viable method for the production of ultrashort-duration pulses of tunable radiation in the 10-keV to 100-keV range. Photons in this range are capable of exciting or ionizing even the most tightly bound of atomic electrons. A wide variety of atomistic scale applications are possible. For example, Thomson x-ray sources have been constructed at LLNL (PLEIADES) and LBL as picosecond, stroboscopic probes of atomic-scale dynamics and at Vanderbilt University as element-specific tools for medical radiography and radiology. While these sources have demonstrated an attractive ability to simultaneously probe on an atomic spatial and temporal scale, they do not necessarily exploit the full potential of the Thomson scattering process to produce high-brightness, high-energy photons. In this white paper, we suggest that the peak brightness of Thomson sources can scale as fast as the 4th power of electron beam energy and that production via Thomson scattering of quasi-monochromatic, tunable radiation in the ''nuclear-range'' between 100-keV and several MeV is potentially a much more attractive application space for this process. Traditional sources in this regime are inherently ultra-broadband and decline rapidly in brightness as a function of photon …
Date: September 21, 2004
Creator: Barty, C. P. & Hartemann, F. V.
Object Type: Report
System: The UNT Digital Library