Texas Racing Commission Annual Report: 2008 (open access)

Texas Racing Commission Annual Report: 2008

Annual report of the Texas Racing Commission describing goals, activities, and accomplishments during fiscal year 2008.
Date: June 22, 2009
Creator: Texas Racing Commission
Object Type: Report
System: The Portal to Texas History
Computer-Aided Content-Based Cueing of Remotely Sensed Images with the Image Content Engine (ICE) (open access)

Computer-Aided Content-Based Cueing of Remotely Sensed Images with the Image Content Engine (ICE)

Human analysts are often unable to meet time constraints on analysis and interpretation of large volumes of remotely sensed imagery. To address this problem, the Image Content Engine (ICE) system currently under development is organized into an off-line component for automated extraction of image features followed by user-interactive components for content detection and content-based query processing. The extracted features are vectors that represent attributes of three entities, namely image tiles, image regions and shapes, or suspected matches to models of objects. ICE allows users to interactively specify decision thresholds so that content (consisting of entities whose features satisfy decision criteria) can be detected. ICE presents detected content to users as a prioritized series of thumbnail images. Users can either accept the detection results or specify a new set of decision thresholds. Once accepted, ICE stores the detected content in database tables and semantic graphs. Users can interactively query the tables and graphs for locations at which prescribed relationships between detected content exist. New queries can be submitted repeatedly until a satisfactory series of prioritized thumbnail image cues is produced. Examples are provided to demonstrate how ICE can be used to assist users in quickly finding prescribed collections of entities (both …
Date: June 22, 2004
Creator: Weinert, G F; Brase, J M & Paglieroni, D W
Object Type: Article
System: The UNT Digital Library
Lawrence Livermore National Laboratory Experience Using 30-Gallon Drum Neutron Multiplicity Counter for Measuring Plutonium-Bearing Salts (open access)

Lawrence Livermore National Laboratory Experience Using 30-Gallon Drum Neutron Multiplicity Counter for Measuring Plutonium-Bearing Salts

Lawrence Livermore National Laboratory (LLNL) has been performing accountability measurements of plutonium (Pu) -bearing items with the 30-gallon drum neutron multiplicity counter (NMC) since August 1998. A previous paper focused on the LLNL experience with Pu-bearing oxide and metal items. This paper expands on the LLNL experience with Pu-bearing salts containing low masses of Pu. All Pu-bearing salts used in this study were measured using calorimetry and gamma isotopic analyses (Cal/Iso) as well as the 30-gallon drum NMC. The Cal/Iso values were treated as being the true measure of Pu content because of the inherent high accuracy of the Cal/Iso technique, even at low masses of Pu, when measured over a sufficient period of time. Unfortunately, the long time period required to achieve high accuracy from Cal/Iso can impact other required accountability measurements. The 30-gallon drum NMC is a much quicker system for making accountability measurements of a Pu-bearing salt and might be a desirable tradeoff. The accuracy of 30-gallon drum NMC measurements of Pu-bearing salts, relative to that of Cal/Iso, is presented in relation to the mass range and alpha associated with each item. Conclusions drawn from the use of the 30-gallon drum NMC for accountability measurements of salts …
Date: June 22, 2004
Creator: Dearborn, D M & Keeton, S C
Object Type: Article
System: The UNT Digital Library
Room temperature continuous-wave operation of GaInNAs long wavelength VCSELs (open access)

Room temperature continuous-wave operation of GaInNAs long wavelength VCSELs

Vertical cavity surface-emitting lasers (VCSELs) are becoming increasingly important for short-haul optical fiber transmission systems. Given the commercial success of GaAs-based 850nm VCSELs, dramatic enhancements in transmission bandwidth and distance can be achieved in conventional single- and multi-mode fiber by extending the emission wavelength to the 1300nm-1550nm range. GaInNAs is a promising active layer material grown on GaAs that can achieve 1300nm emission [l], and electrically pulsed broad-area GaInNAs VCSELs [2,3] have been realized. Here we take advantage of the properties of GaAs-based materials-thermally-conductive high contrast mirrors and AlAs-oxide current apertures-to demonstrate for the first time low-threshold ({approx}1 mA) GaInNAs VCSELs emitting at a wavelength of 1200 nm under continuous-wave room temperature operation. The device structure is shown schematically in figure 1. The bottom mirror consists of a 22.5-period n-doped GaAs/AlAs distributed Bragg reflector (DBR) designed for a center wavelength {lambda} near 1200nm, the top mirror is a 22-period p-doped DBR whose reflectance is enhanced by a Ti/Au contact electrode, and the GaAs {lambda} cavity contains three 70{angstrom}, Ga{sub 0.3}In{sub 0.7}N{sub 0.02}As{sub 0.98} quantum wells (QWs) separated by 200{angstrom} GaAs barriers. The epilayers were grown by molecular beam epitaxy using solid-source arsenic and a rf nitrogen plasma source. After growth, …
Date: June 22, 2000
Creator: Larson, M C; Coldren, C W; Spruytte, S G; Peterson, H E & Harris, J S
Object Type: Article
System: The UNT Digital Library
Archaeological Excavation Report for Proposed Well 199-K-131 in Support of the 100-KR-4 Pump-and-Treat Project (open access)

Archaeological Excavation Report for Proposed Well 199-K-131 in Support of the 100-KR-4 Pump-and-Treat Project

An archaeological excavation was conducted at the site of proposed groundwater monitoring well 199-K-131 in support of the 100-KR-4 Pump-and-Treat Project between June 2 and 3, 2004. Excavations confirmed that there were no intact cultural deposits at the proposed well location. This report was prepared to document the findings of the test excavation.
Date: June 22, 2004
Creator: Woody, Dave M. & Prendergast-Kennedy, Ellen L.
Object Type: Report
System: The UNT Digital Library
Combining Evolutionary Algorithms With Oblique Decision Trees to Detect Bent Double Galaxies (open access)

Combining Evolutionary Algorithms With Oblique Decision Trees to Detect Bent Double Galaxies

Decision trees have long been popular in classification as they use simple and easy-to-understand tests at each node. Most variants of decision trees test a single attribute at a node, leading to axis-parallel trees, where the test results in a hyperplane which is parallel to one of the dimensions in the attribute space. These trees can be rather large and inaccurate in cases where the concept to be learnt is best approximated by oblique hyperplanes. In such cases, it may be more appropriate to use an oblique decision tree, where the decision at each node is a linear combination of the attributes. Oblique decision trees have not gained wide popularity in part due to the complexity of constructing good oblique splits and the tendency of existing splitting algorithms to get stuck in local minima. Several alternatives have been proposed to handle these problems including randomization in conjunction with deterministic hill climbing and the use of simulated annealing. In this paper, they use evolutionary algorithms (EAs) to determine the split. EAs are well suited for this problem because of their global search properties, their tolerance to noisy fitness evaluations, and their scalability to large dimensional search spaces. They demonstrate the technique …
Date: June 22, 2000
Creator: Cantu-Paz, E & Kamath, C
Object Type: Article
System: The UNT Digital Library
Computational Prediction of Aerodynamic Forces for a Simplified Integrated Tractor-Trailer Geometry (open access)

Computational Prediction of Aerodynamic Forces for a Simplified Integrated Tractor-Trailer Geometry

None
Date: June 22, 2004
Creator: Salari, K; Ortega, J & Castellucci, P
Object Type: Article
System: The UNT Digital Library
U.S. Energy Flow Trends: 2002 (open access)

U.S. Energy Flow Trends: 2002

None
Date: June 22, 2004
Creator: Kaiper, Gina V.
Object Type: Report
System: The UNT Digital Library
Carbon Resistor Pressure Gauge Calibration at Low Stresses (open access)

Carbon Resistor Pressure Gauge Calibration at Low Stresses

The 470 Ohm carbon resistor gauge has been used in the stress range up to approximately 4-5 GPa for highly heterogeneous materials and/or divergent flow experiments. The attractiveness of the gauge is due to its rugged nature, simple construction, low cost, reproducibility, and survivability in dynamic events. The associated drawbacks are a long time response to pressure equilibration and gauge resistance hysteresis. In the range below 0.4 GPa, the gauge calibration has been mainly extrapolated into this regime. Because of the need for calibration data within this low stress regime, calibration experiments were performed using a split-Hopkinson bar, drop tower apparatus, and a gas pressure chamber. Since the performance of the gauge at elevated temperatures is a concern, the change in resistance due to heating at atmospheric pressure was also investigated. Details of the various calibration arrangements and the results will be discussed and compared a calibration curve fit to previously published calibration data.
Date: June 22, 2001
Creator: Cunningham, B; Vandersall, K S; Niles, A M; Greenwood, D W; Garcia, F & Forbes, J W
Object Type: Article
System: The UNT Digital Library
Using Data Mining to Find Bent-Double Radio Galaxies in the FIRST Survey (open access)

Using Data Mining to Find Bent-Double Radio Galaxies in the FIRST Survey

In this paper, the authors describe the use of data mining techniques to search for radio-emitting galaxies with a bent-double morphology. In the past, astronomers from the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey identified these galaxies through visual inspection. This was not only subjective but also tedious as the on-going survey now covers 8000 square degrees, with each square degree containing about 90 galaxies. In this paper, they describe how data mining can be used to automate the identification of these galaxies. They discuss the challenges faced in defining meaningful features that represent the shape of a galaxy and their experiences with ensembles of decision trees for the classification of bent-double galaxies.
Date: June 22, 2001
Creator: Kamath, C.; Cantu-Paz, E.; Fodor,I & Tang,N A
Object Type: Article
System: The UNT Digital Library
On the design and implementation of a parallel, object-oriented, image processing toolkit (open access)

On the design and implementation of a parallel, object-oriented, image processing toolkit

Advanced in technology have enabled us to collect data from observations, experiments, and simulations at an ever increasing pace. As these data sets approach the terabyte and petabyte range, scientists are increasingly using semi-automated techniques from data mining and pattern recognition to find useful information in the data. In order for data mining to be successful, the raw data must first be processed into a form suitable for the detection of patterns. When the data is in the form of images, this can involve a substantial amount of processing on very large data sets. To help make this task more efficient, they are designing and implementing an object-oriented image processing toolkit that specifically targets massively-parallel, distributed-memory architectures. They first show that it is possible to use object-oriented technology to effectively address the diverse needs of image applications. Next, they describe how we abstract out the similarities in image processing algorithms to enable re-use in the software. They will also discuss the difficulties encountered in parallelizing image algorithms on massively parallel machines as well as the bottlenecks to high performance. They will demonstrate the work using images from an astronomical data set, and illustrate how techniques such as filters and denoising …
Date: June 22, 2000
Creator: Kamath, Chandrika; Baldwin, Chuck H.; Fodor, Imola K. & Tang, Nu A.
Object Type: Article
System: The UNT Digital Library
Rapid growth of Very Large KDP and KD*P Crystals in Support of the National Ignition Facility (open access)

Rapid growth of Very Large KDP and KD*P Crystals in Support of the National Ignition Facility

The National Ignition Facility will require hundreds of very large single crystals (boules) of KDP and KD*P for the amplifier and frequency conversion optics. Rapid growth now routinely produces 250-300 kg boules of KDP. Technical hurdles overcome during the past year include inclusion formation and spurious nucleation. Areas of continued interest are control of asymmetry and aspect ratio. Variations in KDP concentration on the pm scale at the growing crystal steps can cause inclusions of growth solution. Microscopic investigations, hydrodynamic modeling, and theoretical modeling have been combined to provide a good mechanistic understanding of the formation of inclusions. Modifications to rotation regimes to improve hydrodynamics can eliminate or minimize the effects of these instability mechanisms, and can increase the inclusion-free growth rate by 20-40% over previously observed growth rates. Aspect ratio and boule asymmetry remains of great interest. Small changes in asymmetry can result in significant increases in maximum yields for boules of the same mass. Reasons for the observed changes in aspect ratio during growth will be presented, along with methods to control or influence aspect ratio and boule asymmetry.
Date: June 22, 2000
Creator: Hawley-Fedder, Ruth; Robey, Harry; Biesiada, Tom; DeHaven, Martin; Floyd, Randy & Burnham, Alan
Object Type: Article
System: The UNT Digital Library
Experimental Design for Laser Produced Shocks in Diamond Anvil Cells (open access)

Experimental Design for Laser Produced Shocks in Diamond Anvil Cells

Laser driven shock measurements have been performed on pre-compressed samples. A diamond anvil cell (DAC) has been used to statically compress water to 1 GPa and then strong shocked with an energetic laser. The use of intense laser irradiation can drive shocks in targets making it possible to study the equation of state (EOS) of samples well into the hundreds of GPQ regime. Generally, such experiments employ a sample initially at normal density and standard pressure. Therefore providing data on the principal Hugoniot. In this experiment the initial state of the sample was varied to provide data off the principal Hugoniot. We report the work that was done on the Vulcan laser and describe a method to achieve off principal Hugoniot data.
Date: June 22, 2001
Creator: Moon, S. J.; Cauble, R.; Collins, G. W.; Celliers, P. M.; Hicks, D.; Da Silva, L. B. et al.
Object Type: Article
System: The UNT Digital Library
Metals Far From Equilibrium: From Shocks to Radiation Damage (open access)

Metals Far From Equilibrium: From Shocks to Radiation Damage

Shock waves and high-energy particle radiation can each drive materials far from thermodynamic equilibrium and enable novel scenarios in the processing of materials. A large number of theoretical and experimental studies of shock deformation have been performed on polycrystalline materials, but shock deformation in single crystals has only recently been studied in some detail. We present Molecular Dynamics (MD) simulations of the shock response of single crystal copper, modeled using an embedded atom potential that reproduces both defect formation and high pressure behavior. Shock-induced plasticity will also be discussed. Predicting the in-service response of ferritic alloys in future fusion energy environments requires a detailed understanding of the mechanisms of defect accumulation and microstructure evolution in harsh radiation environments, which include a high level of He generation concurrent with primary damage production. The second half of this paper describes results of atomistic MD and kinetic Monte Carlo simulations to investigate the role of He on point defect cluster behavior and damage accumulation in bcc Fe. The goal of these simulations is to study the mechanisms responsible for the formation of vacancy-He clusters which serve as He bubble and void nuclei in fusion reactor materials.
Date: June 22, 2002
Creator: Bringa, E. M.; Wirth, B. D.; Caturla, M. J.; Stolken, J. & Kalantar, D.
Object Type: Article
System: The UNT Digital Library
Iron site occupancies in magnetite-ulvospinel solid solution: A new approach using XMCD (open access)

Iron site occupancies in magnetite-ulvospinel solid solution: A new approach using XMCD

Ordering of Fe{sup 3+} and Fe{sup 2+} between octahedral (Oh) and tetrahedral (Td) sites in synthetic members of the magnetite (Fe{sub 3}O{sub 4}) - ulvoespinel (Fe{sub 2}TiO{sub 4}) solid-solution series was determined using Fe L{sub 2,3}-edge X-ray magnetic circular dichroism (XMCD) coupled with electron microprobe and chemical analysis, Ti L-edge spectroscopy, Fe K-edge EXAFS and XANES, Fe{sub 57} Moessbauer spectroscopy, and unit cell parameters. Microprobe analysis, cell edges and chemical FeO determinations showed that the bulk compositions of the samples were stoichiometric magnetite-ulvoespinel solid-solutions. Surface sensitive XMCD showed that the surfaces of these oxide minerals were more sensitive to redox conditions and some samples required re-equilibration with suitable solid-solid buffers. Detailed site-occupancy analysis of these samples gave XMCD-Fe{sup 2+}/Fe{sup 3+} ratios very close to stoichiometric values. L{sub 2,3}-edge spectroscopy showed that Ti{sup 4+} was restricted to Oh sites. XMCD results showed that significant Fe{sup 2+} only entered Td when the Ti content was > 0.40 apfu while Fe{sup 2+} in Oh increased from 1 a.p.f.u in magnetite to a maximum of {approx}1.4 apfu in USP45. As the Ti content increased from this point, the steady increase in Fe{sup 2+} in Td sites was clearly observable in the XMCD spectra, concurrent …
Date: June 22, 2009
Creator: Pearce, C. I.; Henderson, C. M. B.; Telling, N. D.; Pattrick, R. A.D.; Vaughan, D. J.; Charnock, J. M. et al.
Object Type: Article
System: The UNT Digital Library
Design of Mega-Voltage X-ray Digital Radiography and Computed Tomography Performance Phantoms (open access)

Design of Mega-Voltage X-ray Digital Radiography and Computed Tomography Performance Phantoms

A number of fundamental scientific questions have arisen concerning the operation of high-energy DR and CT systems. Some of these questions include: (1) How deeply can such systems penetrate thickly shielded objects? (2) How well can such systems distinguish between dense and relatively high Z materials such as lead, tungsten and depleted uranium and lower Z materials such as steel, copper and tin? (3) How well will such systems operate for a uranium material which is an intermediate case between low density yellowcake and high density depleted uranium metal? These questions have led us to develop a set of phantoms to help answer these questions, but do not have any direct bearing on any smuggling concern. These new phantoms are designed to allow a systemic exploration of these questions by gradually varying their compositions and thicknesses. These phantoms are also good probes of the blurring behavior of radiography and tomography systems. These phantoms are composed of steel ({rho} assumed to be 7.8 g/cc), lead ({rho} assumed to be 11.4 g/cc), tungsten ({rho} assumed to be 19.25 g/cc), uranium oxide (UO{sub 3}) ({rho} assumed to be 4.6 g/cc), and depleted uranium (DU) ({rho} assumed to be 18.9 g/cc). There are five …
Date: June 22, 2009
Creator: Aufderheide, M B; Martz, H E & Curtin, M
Object Type: Report
System: The UNT Digital Library
FEA Analysis of AP-0 Target Hall Collection Lens (Current Design) (open access)

FEA Analysis of AP-0 Target Hall Collection Lens (Current Design)

The AP-0 Target Hall Collection Lens is a pulsed device which focuses anti-protons just downstream of the Target. Since the angles at which the anti-protons depart the Target can be quite large, a very high focusing strength is required to maximize anti-proton capture into the downstream Debuncher Ring. The current design of the Collection Lens was designed to operate with a focusing gradient of 1,000 T/m. However, multiple failures of early devices resulted in lowering the normal operating gradient to about 750 T/m. At this gradient, the Lens design fares much better, lasting several million pulses, but ultimately still fails. A Finite Element Analysis (FEA) has been performed on this Collection Lens design to help determine the cause and/or nature of the failures. The Collection Lens magnetic field is created by passing high current through a central conductor cylinder. A uniform current distribution through the cylinder will create a tangential or azimuthal magnetic field that varies linearly from zero at the center of the cylinder to a maximum at the outer surface of the cylinder. Anti-proton particles passing through this cylinder (along the longitudinal direction) will see an inward focusing kick back toward the center of the cylinder proportional to …
Date: June 22, 2001
Creator: Hurh, P.G. & Tang, Z.
Object Type: Report
System: The UNT Digital Library
100 Area D4 Project Semi-Annual 2006 Building Completion Report, August 2005 - April 2006 (open access)

100 Area D4 Project Semi-Annual 2006 Building Completion Report, August 2005 - April 2006

This report documents the decontamination, decommissioining (D&D) and the demolition of select facilities in the 100 Area of the Hanford Site as required by DOE G 430.1-4.
Date: June 22, 2006
Creator: Griff, B. C.
Object Type: Report
System: The UNT Digital Library
Development of a Novel Catalyst for NO Decomposition (open access)

Development of a Novel Catalyst for NO Decomposition

Air pollution arising from the emission of nitrogen oxides as a result of combustion taking place in boilers, furnaces and engines, has increasingly been recognized as a problem. New methods to remove NO{sub x} emissions significantly and economically must be developed. The current technology for post-combustion removal of NO is the selective catalytic reduction (SCR) of NO by ammonia or possibly by a hydrocarbon such as methane. The catalytic decomposition of NO to give N{sub 2} will be preferable to the SCR process because it will eliminate the costs and operating problems associated with the use of an external reducing species. The most promising decomposition catalysts are transition metal (especially copper)-exchanged zeolites, perovskites, and noble metals supported on metal oxides such as alumina, silica, and ceria. The main shortcoming of the noble metal reducible oxide (NMRO) catalysts is that they are prone to deactivation by oxygen. It has been reported that catalysts containing tin oxide show oxygen adsorption behavior that may involve hydroxyl groups attached to the tin oxide. This is different than that observed with other noble metal-metal oxide combinations, which have the oxygen adsorbing on the noble metal and subsequently spilling over to the metal oxide. This observation …
Date: June 22, 2007
Creator: Akyurtlu, Ates & Akyurtlu, Jale F.
Object Type: Report
System: The UNT Digital Library
Final Technical Report (open access)

Final Technical Report

The work under this grant consisted of encouraging community activities for the development of parallel programming patterns. This work was in conjunction with the research performed under the Pmodels award - where research was pursued on the development for new parallel programming models. Work on programming patterns does not have, as a goal, the invention of new technology. Rather, it is about codifying existing practice, so as to provide practitioners with a common language. This facilitates education and communication between practitioners. In addition, it helps in the design of new parallel frameworks and languages. One major issue in their design is expressiveness: To what extent does the language or framework facilitates the expression of common programming patterns. In order to assess expressiveness in any useful way, it is necessary to identify those common patterns.
Date: June 22, 2009
Creator: Snir, Marc
Object Type: Report
System: The UNT Digital Library
Optimal tuning and calibration of bendable mirrors with slope measuring profilers (open access)

Optimal tuning and calibration of bendable mirrors with slope measuring profilers

We describe a technique to optimally tune and calibrate bendable x-ray optics for sub-micron focusing. The focusing is divided between two elliptically cylindrical reflecting elements, a Kirkpatrick-Baez (KB) pair. Each optic is shaped by applying unequal bending couples to each end of a flat mirror. The developed technique allowsoptimal tuning of these systems using surface slope data obtained with a slope measuring instrument, the long trace profiler (LTP). Due to the near linearity of the problem, the minimal set of data necessary for the tuning of each bender, consists of only three slope traces measured before and after a single adjustment of each bending couple. The data are analyzed with software realizing a method of regression analysis with experimentally found characteristic functions of the benders. The resulting approximation to the functional dependence of the desired shape provides nearly final settings. Moreover, the characteristic functions of the benders found in the course of tuning, can be used for retuning to a new desired shape without removal from the beamline and re-measuring. We perform a ray trace, using profiler data for the finally tuned optics, predicting the performance to be expected during use of the optics on the beamline.
Date: June 22, 2009
Creator: McKinney, Wayne; Kirschman, Jonathan; MacDowell, Alastair; Warwick, Tony & Yashchuk, Valeriy
Object Type: Article
System: The UNT Digital Library
METHOD TO PREVENT SULFUR ACCUMULATION INSIDE MEMBRANE ELECTRODE ASSEMBLY (open access)

METHOD TO PREVENT SULFUR ACCUMULATION INSIDE MEMBRANE ELECTRODE ASSEMBLY

HyS is conceptually the simplest of the thermochemical cycles and involves only sulfur chemistry. In the HyS Cycle hydrogen gas (H{sub 2}) is produced at the cathode of the electrochemical cell (or electrolyzer). Sulfur dioxide (SO{sub 2}) is oxidized at the anode to form sulfuric acid (H{sub 2}SO{sub 4}) and protons (H{sup +}) as illustrated below. A separate high temperature reaction decomposes the sulfuric acid to water and sulfur dioxide which are recycled to the electrolyzers, and oxygen which is separated out as a secondary product. The electrolyzer includes a membrane that will allow hydrogen ions to pass through but block the flow of hydrogen gas. The membrane is also intended to prevent other chemical species from migrating between electrodes and undergoing undesired reactions that could poison the cathode or reduce overall process efficiency. In conventional water electrolysis, water is oxidized at the anode to produce protons and oxygen. The standard cell potential for conventional water electrolysis is 1.23 volts at 25 C. However, commercial electrolyzers typically require higher voltages ranging from 1.8 V to 2.6 V [Kirk-Othmer, 1991]. The oxidation of sulfur dioxide instead of water in the HyS electrolyzer occurs at a much lower potential. For example, the …
Date: June 22, 2009
Creator: Steimke, J.; Steeper, T.; Herman, D.; Colon-Mercado, H. & Elvington, M.
Object Type: Report
System: The UNT Digital Library
Black ring deconstruction (open access)

Black ring deconstruction

We present a sample microstate for a black ring in four and five dimensional language. The microstate consists of a black string microstate with an additional D6-brane. We show that with an appropriate choice of parameters the piece involving the black string microstate falls down a long AdS throat, whose M-theory lift is AdS_3 x S2. We wrap a spinning dipole M2-brane on the S2 in the probe approximation. In IIA, this corresponds to a dielectric D2-brane carrying only D0-charge. We conjecture this is the firstapproximation to a cloud of D0-branes blowing up due to their non-abelian degrees of freedom and the Myers effect.
Date: June 22, 2007
Creator: Gimon, Eric; Gimon, Eric G. & Levi, Thomas S.
Object Type: Article
System: The UNT Digital Library
Regulating Intracellular Calcium in Plants: From Molecular Genetics to Physiology (open access)

Regulating Intracellular Calcium in Plants: From Molecular Genetics to Physiology

To grow, develop, adapt, and reproduce, plants have evolved mechanisms to regulate the uptake, translocation and sorting of calcium ions into different cells and subcellular compartments. Yet how plants accomplish this remarkable feat is still poorly understood. The spatial and temporal changes in intracellular [Ca2+] during growth and during responses to hormonal and environmental stimuli indicate that Ca2+ influx and efflux transporters are diverse and tightly regulated in plants. The specific goals were to determine the biological roles of multiple Ca pumps (ECAs) in the model plant Arabidopsis thaliana. We had pioneered the use of K616 yeast strain to functionally express plant Ca pumps, and demonstrated two distinct types of Ca pumps in plants (Sze et al., 2000. Annu Rev Plant Biol. 51,433). ACA2 represented one type that was auto-inhibited by the N-terminal region and stimulated by calmodulin. ECA1 represented another type that was not sensitive to calmodulin and phylogenetically distinct from ACAs. The goal to determine the biological roles of multiple ECA-type Ca pumps in Arabidopsis has been accomplished. Although we demonstrated ECA1 was a Ca pump by functional expression in yeast, the in vivo roles of ECAs was unclear. A few highlights are described. ECA1 and/or ECA4 are …
Date: June 22, 2008
Creator: Sze, Heven
Object Type: Report
System: The UNT Digital Library