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859
Small Animal Radionuclide Imaging With Focusing Gamma-Ray Optics
Significant effort currently is being devoted to the development of noninvasive imaging systems that allow in vivo assessment of biological and biomolecular interactions in mice and other small animals. While physiological function in small animals can be localized and imaged using conventional radionuclide imaging techniques such as single-photon emission tomography (SPECT) and positron emission tomography (PET), these techniques inherently are limited to spatial resolutions of 1-2 mm. For this reason, we are developing a small animal radionuclide imaging system (SARIS) using grazing incidence optics to focus gamma-rays emitted by {sup 125}I and other radiopharmaceuticals. We have developed a prototype optic with sufficient accuracy and precision to focus the 27.5 keV photons from {sup 125}I onto a high-resolution imaging detector. Experimental measurements from the prototype have demonstrated that the optic can focus X-rays from a microfocus X-ray tube to a spot having physical dimensions (approximately 1500 microns half-power diameter) consistent with those predicted by theory. Our theoretical and numerical analysis also indicate that an optic can be designed and build that ultimately can achieve 100 {micro}m spatial resolution with sufficient efficiency to perform in vivo single photon emission imaging studies in small animal.
Date:
February 27, 2004
Creator:
Hill, R; Decker, T; Epstein, M; Ziock, K; Pivovaroff, M J; Craig, W W et al.
Object Type:
Article
System:
The UNT Digital Library
Confined zone dispersion flue gas desulfurization demonstration. [Numerical data only; no text]
Report contains only numerical data, no text.
Date:
February 27, 1992
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Using Graphs for Fast Error Term Approximation of Time-varying Datasets
We present a method for the efficient computation and storage of approximations of error tables used for error estimation of a region between different time steps in time-varying datasets. The error between two time steps is defined as the distance between the data of these time steps. Error tables are used to look up the error between different time steps of a time-varying dataset, especially when run time error computation is expensive. However, even the generation of error tables itself can be expensive. For n time steps, the exact error look-up table (which stores the error values for all pairs of time steps in a matrix) has a memory complexity and pre-processing time complexity of O(n2), and O(1) for error retrieval. Our approximate error look-up table approach uses trees, where the leaf nodes represent original time steps, and interior nodes contain an average (or best-representative) of the children nodes. The error computed on an edge of a tree describes the distance between the two nodes on that edge. Evaluating the error between two different time steps requires traversing a path between the two leaf nodes, and accumulating the errors on the traversed edges. For n time steps, this scheme has …
Date:
February 27, 2003
Creator:
Nuber, C; LaMar, E C; Pascucci, V; Hamann, B & Joy, K I
Object Type:
Article
System:
The UNT Digital Library
Hyper-resistivity Theory in a Cylindrical Plasma
A model is presented for determining the hyper-resistivity coefficient that arises due to the presence of magnetic structures that appear in plasma configurations such as the reversed field pinch and spheromak. Emphasis is placed on modeling cases where magnetic islands pass from non-overlap to overlap regimes. Earlier works have shown that a diffusion-based model can give realistic transport scalings when magnetic islands are isolated, and this formalism is extended to apply to the hyper-resistivity problem. In this case electrons may either be in long or short mean-free-path regimes and intuitively-based arguments are presented of how to extend previous theories to incorporate this feature in the presence of magnetic structures that pass from laminar to moderately chaotic regimes.
Date:
February 27, 2001
Creator:
Berk, H. L.; Fowler, T. K.; LoDestro, L. L. & Pearlstein, L. D.
Object Type:
Report
System:
The UNT Digital Library
Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of the Effect of Mn on the Nanostructural Features formed in Irradiated Fe-Cu-Mn Alloys
The size, number density and composition of the nanometer defects responsible for the hardening and embrittlement in irradiated Fe-0.9wt.% Cu and Fe-0.9wt.% Cu-1.0wt% Mn model reactor pressure vessel alloys were measured using small angle neutron scattering and positron annihilation spectroscopy. These alloys were irradiated at 290 C to relatively low neutron fluences (E > 1 MeV, 6.0 x 10{sup 20} to 4.0 x 10{sup 21} n/m{sup 2}) in order to study the effect of manganese on the nucleation and growth of copper rich precipitates and secondary defect features. Copper rich precipitates were present in both alloys following irradiation. The Fe-Cu-Mn alloy had smaller precipitates and a larger number density of precipitates, suggesting Mn segregation at the iron matrix-precipitate interface which reduces the interfacial energy and in turn the driving force for coarsening. Mn also retards the precipitation kinetics and inhibits large vacancy cluster formation, suggesting a strong Mn-vacancy interaction which reduces radiation enhanced diffusion.
Date:
February 27, 2003
Creator:
Glade, S C; Wirth, B D; Asoka-Kumar, P; Odette, G R; Sterne, P A & Howell, R H
Object Type:
Article
System:
The UNT Digital Library
Feature Selection in Scientific Applications
Numerous applications of data mining to scientific data involve the induction of a classification model. In many cases, the collection of data is not performed with this task in mind, and therefore, the data might contain irrelevant or redundant features that affect negatively the accuracy of the induction algorithms. The size and dimensionality of typical scientific data make it difficult to use any available domain information to identify features that discriminate between the classes of interest. Similarly, exploratory data analysis techniques have limitations on the amount and dimensionality of the data that can be effectively processed. In this paper, we describe applications of efficient feature selection methods to data sets from astronomy, plasma physics, and remote sensing. We use variations of recently proposed filter methods as well as traditional wrapper approaches where practical. We discuss the importance of these applications, the general challenges of feature selection in scientific datasets, the strategies for success that were common among our diverse applications, and the lessons learned in solving these problems.
Date:
February 27, 2004
Creator:
Cantu-Paz, E; Newsam, S & Kamath, C
Object Type:
Article
System:
The UNT Digital Library
Characterization of Contaminant Transport by Gravity, Capillarity and Barometric Pumping in Heterogeneous Vadose Zones
This final report summarizes the work and accomplishments of our three-year project. We have pursued the concept of a Vadose-Zone Observatory (VZO) to provide the field laboratory necessary for carrying out the experiments required to achieve the goals of this research. Our approach has been (1) to carry out plume release experiments at a VZO allowing the acquisition of several different kinds of raw data that (2) are analyzed and evaluated with the aid of highly detailed, diagnostic numerical models. The key feature of the VZO constructed at Lawrence Livermore National Laboratory (LLNL) is the variety of plume-tracking techniques that can be used at a single location. Electric resistance tomography (ERT) uses vertical arrays of electrodes across the vadose zone that can monitor electrical resistance changes in the soil as a plume moves downward to the water table. These resistance changes can be used to provide ''snapshots'' of the progress of the plume. Additionally, monitoring wells have been completed at multiple levels in the vicinity of a central infiltration site. Sensors emplaced at different levels include electrically conducting gypsum blocks for detecting saturation changes, thermistors for monitoring temperature changes and pressure transducers for observing barometric changes at different levels in …
Date:
February 27, 2001
Creator:
Carrigan, C R; Martins, S A; Ramirez, A L; Daily, W D; Hudson, G B; Ralsont, D et al.
Object Type:
Report
System:
The UNT Digital Library
Open and Closed Magnetic Confinement Systems: Is There a Fundamental Difference in Their Transport Properties?
The results of five decades of experimental investigations of open-ended and closed magnetic confinement geometries are examined to see if intrinsic topology-dependent differences in their cross-field transport can be discerned. The evidence strongly supports a picture in which closed systems (stellarators, tokamaks, reversed-field pinches, etc.) are in all cases studied to date characterized by some level of plasma turbulence, leading to substantial deviations from purely classical cross-field transport. This transport is often describable as a Bohm-like scaling with plasma temperature and magnetic field intensity. By contrast, open systems have in many significant examples been able to approach closely to classically predicted cross-field transport, including cases where the transport appeared to be more than five orders of magnitude slower than the Bohm-diffusion rate. To explain these differences the following tentative hypothesis is put forward: The differences arise from two sources: (1) differences in the instability driving terms arising from free-energy sources, such as current flow along the field lines, etc. and, (2) differences in the nature of the boundary conditions for the various unstable waves that may be stimulated by these free energy sources within the plasma. By analogy with a laser, closed systems, with their flux tubes returning on themselves, …
Date:
February 27, 2001
Creator:
Post, R F
Object Type:
Article
System:
The UNT Digital Library
High Resolution Radionuclide Imaging Using Focusing Gamma-Ray Optics
Significant effort is being devoted to the development of noninvasive imaging systems that allow in vivo assessment of biological and biomolecular interactions in mice and other small animals. Although single-photon emission tomography (SPECT) and positron emission tomography (PET) are well-matched to the study of physiological function in small animals, the spatial resolutions of 1-2 mm currently achievable with these techniques limits the types of research possible. For this reason, we are developing a small animal radionuclide imaging system using grazing incidence optics to focus the low-energy gamma-rays emitted by {sup 125}I, {sup 95m}Tc, {sup 96}Tc, and {sup 99m}Tc. We compare this approach to the more traditional use of absorptive collimation.
Date:
February 27, 2004
Creator:
Pivovaroff, Michael; Craig, William; Ziock, Klaus; Barber, William; Funk, Tobias; Hasegawa, Bruce et al.
Object Type:
Article
System:
The UNT Digital Library
Texas Preventable Disease News, Volume 48, Number 8, February 27, 1988
Newsletter of the Texas Bureau of Disease Control and Epidemiology discussing the news, activities, and events of the organization and other information related to health in Texas.
Date:
February 27, 1988
Creator:
Texas. Bureau of Disease Control and Epidemiology.
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History
Maximally Concentrating Optics for Photovoltaic Solar Energy Conversion
The use of a two-stage concentrator with a fresnel lens primary and a non-imaging dielectric totally internally reflecting secondary, has unique advantages for photovoltaic concentration. This new design has a much larger acceptance angle than the conventional lens-cell concentrating system. In the continuation of this research, an optimally designed prototype which employs a 13.6-cm diameter flat fresnel tons as the primary focusing device, a dielectric compound hyperbolic concentrator (DCHC) as secondary and a 1-cm diameter high-concentration cell for electricity conversion has been built, tested and analyzed. Measurements under sunlight show that it has an angular acceptance of [plus minus]3.6 degrees, which is dramatically better than the [plus minus]0.5 degree achievable without a secondary concentrator. This performance agrees well with theoretical ray-tracing predictions. The secondary shows an optical efficiency of (91[plus minus]2)% at normal incidence. Combining with the primary fresnel tens which has an optical efficiency of (82[plus minus]2)%, tho two-stage system yields a total optical efficiency of (7l[plus minus]2)%. The measurement of the system electrical performance yielded a net electrical efficiency of 11.9%. No problems associated with non-uniform cell illumination were found, as evidenced by the excellent fill factor of (79[plus minus]2)% measured under concentration. The secondary geometrical properties and …
Date:
February 27, 1986
Creator:
Winston, R.; O'Gallagher, J. & Ning, X.
Object Type:
Report
System:
The UNT Digital Library
Confined zone dispersion flue gas desulfurization demonstration
The confined zone dispersion (CZD) process involves flue gas post-treatment, physically located between a boiler's outlet and its particulate collector, which in the majority of cases is an electrostatic precipitator. The features that distinguish this process from other similar injection processes are: Injection of an alkaline slurry directly into the duct, instead of injection of dry solids into the duct ahead of a fabric filter. Use of an ultrafine calcium/magnesium hydroxide, type S pressure-hydrated dolomitic lime. This commercial product is made from plentiful, naturally occurring dolomite. Low residence time, made possible by the high effective surface area of the Type S lime. Localized dispersion of the reagent. Slurry droplets contact only part of the gas while the droplets are drying, to remove up to 50 percent of the S0{sub 2} and significant amounts of NO{sub x}. The process uses dual fluid rather than rotary atomizers. Improved electrostatic precipitator performance via gas conditioning from the increased water vapor content, and lower temperatures. Supplemental conditioning with S0{sub 3} is not believed necessary for satisfactory removal of particulate matter.
Date:
February 27, 1992
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
High-pressure hydrogen apparatus for PCT studies up to approx. 700 MPa and 200/sup 0/C: preliminary results on LaCo/sub 5/H/sub 9/ /sub 0/ at 21/sup 0/C
An apparatus has been developed to react samples with hydrogen at pressures of up to 689.5 MPa (6805 atm) and temperatures of up to 200/sup 0/C. It is being used to determine whether RT/sub 5/ and RT/sub 3/ compounds (where R is a lanthanide element and T is a 3-d transition element, usually cobalt or nickel) ''fill up'' with hydrogen when subjected to high hydrogen pressures. Preliminary experiments with LaCo/sub 5/ in this apparatus showed a new (third) plateau at 126.7 MPa (1250 atm) in the PCT diagram; only two plateaus have previously been reported. There is an abrupt upturn at an H/LaCo/sub 5/ ratio of approximately 8.23. A second run showed an upturn at 8.76. The maximum loading is nine atoms of hydrogen.
Date:
February 27, 1976
Creator:
Lakner, J. F.; Steward, S. A. & Uribe, F.
Object Type:
Report
System:
The UNT Digital Library
Aircraft Nuclear Propulsion Project Quarterly Progress Report for Period Ending December 10, 1950
Technical report detailing expansion of the Aircraft Nuclear Propulsion at the Oak Ridge National Laboratory. Major facilities completed at this time were the Shielding Rector, the ANP Critical Facility, and the 86-in. Cyclotron. Outlines further need for radiation damage studies. [From Summary]
Date:
February 27, 1951
Creator:
Briant, R. C.; Ellis, C. B. & Cottrell, W. B.
Object Type:
Report
System:
The UNT Digital Library
[Program: Statewide Conference on Technical, Vocational, Adult Education 1980]
Program for the Statewide Conference on Technical, Vocational. Adult Education held February 12-13, 1980 including schedules, presenter biographies, general information, etc.
Date:
February 27, 1980
Creator:
Advisory Council for Technical-Vocational Education in Texas
Object Type:
Pamphlet
System:
The Portal to Texas History
Summary of the Stratigraphy, Sedimentology, and Mineralogy of Pennsylvanian and Permian Rocks of Oklahoma in Relation to Uranium-Resource Potential
Report describes the structural and stratigraphic framework, depositional environment, and petrology and petrography of the various Pennsylvanian-Permian time and rock units present in Oklahoma. This report identifies five geologic settings favorable for the localization of uranium, such as alluvial fan deposits, oil-productive structures where Permian sandstones are altered, tidal-flat sandstone-silstones, channel sandstones on gentle structural features, and oil-productive Cherokee sandstones.
Date:
February 27, 1976
Creator:
Shelton, John W. & Al-Shaieb, Zuhair
Object Type:
Report
System:
The UNT Digital Library
Lock.
Patent for "locking the control pedals of a motor vehicle from movement in either direction, the said lock being arranged between the pedals and arranged to simultaneously engage and lock both" (lines 9-14).
Date:
February 27, 1919
Creator:
Cameron, Robert G.
Object Type:
Patent
System:
The Portal to Texas History
Bulletin on Texas State Finance: 1987, Number 5
Periodic bulletin analyzing issues related to Texas legislation. This issue focuses on property appraisals for Texas.
Date:
February 27, 1987
Creator:
Texas Research League
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History
Wrench
Patent for tools used for construction, plumbing, machinery, home renovations, and many more.
Date:
February 27, 1923
Creator:
Edwards, Charles R.
Object Type:
Patent
System:
The Portal to Texas History