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High-Throughput Analysis With 96-Capillary Array Electrophoresis and Integrated Sample Preparation for DNA Sequencing Based on Laser Induced Fluorescence Detection

Description: The purpose of this research was to improve the fluorescence detection for the multiplexed capillary array electrophoresis, extend its use beyond the genomic analysis, and to develop an integrated micro-sample preparation system for high-throughput DNA sequencing. The authors first demonstrated multiplexed capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) separations in a 96-capillary array system with laser-induced fluorescence detection. Migration times of four kinds of fluoresceins and six polyaromatic hydrocarbons (PAHs) are normalized to one of the capillaries using two internal standards. The relative standard deviations (RSD) after normalization are 0.6-1.4% for the fluoresceins and 0.1-1.5% for the PAHs. Quantitative calibration of the separations based on peak areas is also performed, again with substantial improvement over the raw data. This opens up the possibility of performing massively parallel separations for high-throughput chemical analysis for process monitoring, combinatorial synthesis, and clinical diagnosis. The authors further improved the fluorescence detection by step laser scanning. A computer-controlled galvanometer scanner is adapted for scanning a focused laser beam across a 96-capillary array for laser-induced fluorescence detection. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries. The limit of detection for fluorescein is 3 x 10{sup -11} M (S/N = 3) for 5-mW of total laser power scanned at 4 Hz. The observed cross-talk among capillaries is 0.2%. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components, and flexibility due to the independent paths for excitation and emission.
Date: December 31, 2001
Creator: Xue, Gang
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D and D of R Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Large quantities of mixed low level waste (MLLW) that fall under the Toxic Substances Control Act (TSCA) exist and will continue to be generated during D and D operations at DOE sites across the country. The standard process for destruction of MLLW is incineration, which has an uncertain future. The extraction and destruction of PCBs from MLLW was the subject of this research Supercritical Fluid Extraction (SFE) with carbon dioxide with 5% ethanol as cosolvent and Supercritical Waster Oxidation (SCWO) were the processes studied in depth. The solid matrix for experimental extraction studies was Toxi-dry, a commonly used absorbent made from plant material. PCB surrogates were 1.2,4-trichlorobenzene (TCB) and 2-chlorobiphenyl (2CBP). Extraction pressures of 2,000 and 4,000 psi and temperatures of 40 and 80 C were studied. Higher extraction efficiencies were observed with cosolvent and at high temperature, but pressure little effect. SCWO treatment of the treatment of the PCB surrogates resulted in their destruction below detection limits.
Date: April 1, 2002
Creator: Matthews, Michael A.; David A. Bruce,; Davis, Thomas A.; Thies, Mark C.; Weidner, John W. & White, Ralph E.
Partner: UNT Libraries Government Documents Department

Development of an integrated, in-situ remediation technology: Task 2--4, electrokinetic modeling. Topical report, September 26--May 25, 1996

Description: This report summarizes the work conducted in Tasks 2-4, which together make up the Electrokinetic Modeling carried out in this project. The modeling was divided into three main sections: thermal analysis, chemical species transport, and electrode geometry and soil heterogeneity issues. The thermal modeling consisted of development of the governing equations to incorporate Joule heating associated with electro-osmosis, heat conduction and convection, and temperature dependencies of electrical conductivity and electro-osmotic permeability. To model the transport of chemical species in the Lasagna{sup TM} process, a one-dimensional model was developed. This model is based on previous models, but includes additional mechanism to account for charge transfer in the double layer, pH buffering of the soil, and zeta potential dependency on pH and ionic strength. The results of this model and the corroboration by experimental measurement support some key assumptions made in the thermal model. An analysis was also conducted to compare the use of cylindrical electrodes to the plate geometry used in Phase I. In summary, cylindrical electrodes may be appropriate for anodes, because the do not intercept the flow. If used as cathodes, a planar treatment zone in their vicinity would probably be required. The cylindrical electrodes can operate at reasonable current densities without boiling water. Because the hottest region is at the electrode, cooling schemes could be used to operate at higher current densities. If iron anodes are used, they will have to be quite massive, and may not be economical compared to planar models. An example of soil heterogeneity was investigated when it was discovered that a steel pt was buried in the vicinity of the pilot test. There is some distortion of the field near the pit, but its effects on the test zone between the electrodes are minimal.
Date: May 1, 1997
Partner: UNT Libraries Government Documents Department

Electrokinetic removal of uranium from contaminated, unsaturated soils

Description: Electrokinetic remediation of uranium-contaminated soil was studied in a series of laboratory-scale experiments in test cells with identical geometry using quartz sand at approximately 10 percent moisture content. Uranium, when present in the soil system as an anionic complex, could be migrated through unsaturated soil using electrokinetics. The distance that the uranium migrated in the test cell was dependent upon the initial molar ratio of citrate to uranium used. Over 50 percent of the uranium was recovered from the test cells using the citrate and carbonate complexing agents over of period of 15 days. Soil analyses showed that the uranium remaining in the test cells had been mobilized and ultimately would have been extracted. Uranium extraction exceeded 90 percent in an experiment that was operated for 37 days. Over 70 percent of the uranium was removed from a Hanford waste sample over a 55 day operating period. Citrate and carbonate ligand utilization ratios required for removing 50 percent of the uranium from the uranium-contaminated sand systems were approximately 230 moles ligand per mole uranium and 1320 moles ligand per mole uranium for the waste. Modifying the operating conditions to increasing the residence time of the complexants is expected to improved the utilization efficiency of the complexing agent.
Date: January 1, 1997
Creator: Booher, W.F.; Lindgren, E.R. & Brady, P.V.
Partner: UNT Libraries Government Documents Department

Positron production in multiphoton light-by-light scattering

Description: A signal of 106 {+-} 14 positrons above background has been observed in collisions of a low-emittance 46.6-GeV electron beam with terawatt pulses from a Nd:glass laser at 527 nm wavelength in an experiment at the Final Focus Test Beam at SLAC. Peak laser intensities of {approximately} 1.3 {times} 10{sup 18} W/cm{sup 2} have been achieved corresponding to a value of 0.3 for the parameter {Upsilon} = {var_epsilon}*/{var_epsilon}{sub crit} where {var_epsilon}* = 2{gamma}{var_epsilon}{sub lab} is the electric field strength of the laser transformed to the rest frame of the electron beam and {var_epsilon}{sub crit} = m{sup 2}c{sup 3}/e{bar h} = 1.3 {times} 10{sup 16} V/cm is the QED critical field strength. The positrons are interpreted as arising from a two-step process in which laser photons are backscattered to GeV energies by the electron beam followed by a collision between the high-energy photon and several laser photons to produce an electron-positron pair. These results are the first laboratory evidence for a light-by-light scattering process involving only real photons.
Date: March 1997
Creator: Bula, C.
Partner: UNT Libraries Government Documents Department

ELECTROKINETIC DENSIFICATION OF COAL FINES IN WASTE PONDS

Description: The objective of this research is to demonstrate that electrokinetics can be used to remove colloidal coal and mineral particles from coal-washing ponds and lakes without the addition of chemical additives such as salts and polymeric flocculants. In this experimental and analytical study the authors elucidate the transport processes that control the rate of concentrated colloidal particle removal, demonstrate the process on a laboratory scale, and develop the scale-up laws needed to design commercial-scale processes. They then address the fundamental problems associated with particle-particle interactions (electrical and hydrodynamic), the effects of particle concentration on the applied electric field, the electrochemical reactions that occur at the electrodes, and the prediction of power requirements.
Date: April 30, 1997
Creator: Davis, E. James
Partner: UNT Libraries Government Documents Department

The VIIth Blois workshop: Theory summary and factorization issues

Description: Theory presentations at this workshop have covered a wide range of topics. In addition to the traditional topics of elastic and diffractive scattering, the workshop has had a variety of interesting talks coming under the broad umbrella of ``Recent Advances in Hadron Physics.`` These have included review talks on lattice gauge theory, techniques for high-order perturbative QCD calculations, strong interaction effective field theories, the current status of QED and the construction of theories beyond the Standard Model. While the author briefly describes some topics covered, a ``review of reviews`` is in no way a substitute for the original reviews which also appear, of course, in this same volume. Among the more traditional topics covered are: BFKL physics -- higher-order corrections and jet cross-sections; unitarity and eikonal screening -- mainly in deep-inelastic diffraction but also in soft diffraction; elastic scattering phenomenology -- including real parts, the pomeron intercept and small-t oscillations. Also discussed is the role of factorization, i.e. both Regge pole factorization and perturbative QCD factorization theorems in the definition of a pomeron structure function and in the formulation of a parton model description of diffractive hard physics. The author focuses on one gluon versus two gluons as illustrating the issues involved.
Date: September 17, 1997
Creator: White, A.R.
Partner: UNT Libraries Government Documents Department

Electrokinetic pumps and actuators

Description: Flow and ionic transport in porous media are central to electrokinetic pumping as well as to a host of other microfluidic devices. Electrokinetic pumping provides the ability to create high pressures (to over 10,000 psi) and high flow rates (over 1 mL/min) with a device having no moving parts and all liquid seals. The electrokinetic pump (EKP) is ideally suited for applications ranging from a high pressure integrated pump for chip-scale HPLC to a high flow rate integrated pump for forced liquid convection cooling of high-power electronics. Relations for flow rate and current fluxes in porous media are derived that provide a basis for analysis of complex microfluidic systems as well as for optimization of electrokinetic pumps.
Date: March 1, 2000
Creator: Paul, Phillip M.
Partner: UNT Libraries Government Documents Department

ELECTROKINETIC DENSIFICATION OF COAL FINES IN WASTE PONDS

Description: The objective of this research is to apply electrokinetics to remove colloidal coal and mineral particles from coal washing ponds without the addition of chemical additives. Colloidal particles do not settle gravitationally, but because their surfaces are charged one can produce settling by applying an external electric field. Of specific interest is a lake near Centralia, Washington used to wash coal prior to combustion in an electrical power generation facility. Laboratory experiments have demonstrated that electrokinetic treatment is feasible, so this project is examining how to scale up laboratory results to an industrial level. Electrode configurations, power requirements, and system properties are being studied.
Date: April 1, 1996
Creator: Davis, E. James
Partner: UNT Libraries Government Documents Department

Residual meson-meson interaction from lattice gauge simulation in a simple QED{sub 2+1} model

Description: The residual interaction for a meson-meson system is computed utilizing the cumulant, or cluster, expansion of the momentum-space time correlation matrix. The cumulant expansion serves to define asymptotic, or free, meson-meson operators. The definition of an effective interaction is then based on a comparison of the full (interacting) and the free (noninteracting) time correlation matrices. The proposed method, which may straight forwardly be transcribed to other hadron-hadron systems, here is applied to a simple 2+1 dimensional U(1) lattice gauge model tuned such that it is confining. Fermions are treated in the staggered scheme. The effective interaction exhibits a repulsive core and attraction at intermediate relative distances. These findings are consistent with an earlier study of the same model utilizing L{umlt u}scher's method where scattering phase shifts are obtained directly.
Date: August 1, 1995
Creator: Canosa, J. & Fiebig, H.
Partner: UNT Libraries Government Documents Department

Studies of Nonlinear QED in Collisions of 46.6 Electrons with Intense LaserPulses

Description: We report on measurements of quantum electrodynamic processes in an intense electromagnetic wave, where nonlinear effects (both multiphoton and vacuum polarization) are prominent. Nonlinear Compton scattering and electron-positron pair production have been observed in collisions of 46.6 GeV and 49.1 GeV electrons of the Final Focus Test Beam at SLAC with terawatt pulses of 1053 nm and 527 nm wavelengths from a Nd:glass laser. Peak laser intensities of approximately 0.5 x 10{sup 18} W/cm{sup 2} have been achieved, corresponding to a value of approximately 0.4 for the parameter {eta} = eE{sub rms}/m{omega}{sub 0}c, and to a value of approximately 0.25 for the parameter {Upsilon}{sub e} = E{sub rms}/E{sub crit} = eE{sub rms}{h_bar}/m{sup 2}c{sup 3}, where E{sub rms} is the rms electric field strength of the laser in the electron rest frame. We present data on the scattered electron spectra arising from nonlinear Compton scattering with up to four photons absorbed from the field. A convolved spectrum of the forward high energy photons is also given. The observed positron production rate depends on the fifth power of the laser intensity, as expected for a process where five photons are absorbed from the field. The positrons are interpreted as arising from the collision of a high-energy Compton scattered photon with the laser beam. The results are found to be in agreement with theoretical predictions.
Date: February 16, 1999
Creator: McDonald, Kirk T.
Partner: UNT Libraries Government Documents Department

Return to the shorted and shunted quartz gauge problem: Analysis with the SUBWAY code

Description: Simulations with finite element models of well controlled impact experiments with x-cut quartz gauges have been performed with the transient electromechanics code SUBWAY. Comparisons of measured gauge output current with calculated output current were made for four fully-electroded gauge configurations, involving two different can spacings and potting materials. The observed good agreement between measured and calculated currents provides a basis for confidence in the basic capabilities of the code.
Date: September 1, 1995
Creator: Montgomery, S.T.; Graham, R.A. & Anderson, M.U.
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D&D of R. Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Collaborating researchers at the University of South Carolina (USC), Clemson University (CU), and the Savannah River Site (SRS) are investigating the fundamentals of a combined extraction and destruction process for the decontamination and decommissioning (D&D) of PCB-contaminated materials as found at DOE sites. Currently, the volume of PCBs and PCB contaminated wastes at DOE sites nationwide is approximately 19,000 m3. While there are a number of existing and proposed processes for the recovery and/or destruction of these persistent pollutants, none has emerged as the preferred choice. Therefore, this research focuses on combining novel processes to solve the problem. The research objectives are to investigate benign dense- fluid extraction with either carbon dioxide (USC) or hot water (CU), followed by destruction of the extracted PCBs via either electrochemical (USC) or hydrothermal (CU) oxidation. Based on the results of these investigations, a combined extraction and destruction process that incorporates the most successful elements of the various processes will be recommended for application to contaminated DOE sites.
Date: June 1, 2000
Creator: Matthews, Michael A.
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D&D of R. Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Collaborating researchers at the University of South Carolina (USC), Clemson University (CU), and the Savannah River Site (SRS) are investigating the fundamentals of a combined extraction and destruction process for the decontamination and decommissioning (D&D) of PCB-contaminated materials as found at DOE sites. Currently, the volume of PCBs and PCB contaminated wastes at DOE sites nationwide is approximately 19,000 m3. While there are a number of existing and proposed processes for the recovery and/or destruction of these persistent 4 pollutants, none has emerged as the preferred choice. Therefore, this research focuses on combining novel processes to solve the problem. The research objectives are to investigate benign dense-fluid extraction with either carbon dioxide (USC) or hot water (CU), followed by destruction of the extracted PCBs via either electrochemical (USC) or hydrothermal (CU) oxidation. Based on the results of these investigations, a combined extraction and destruction process that incorporates the most successful elements of the various processes will be recommended for application to contaminated DOE sites.
Date: June 1, 1999
Creator: Hamilton, Edward A.; Bruce, David A.; Oji, Lawrence; White, Ralph E.; Matthews, Michael A. & Thies, Mark C.
Partner: UNT Libraries Government Documents Department

POC-SCALE TESTING OF A DRY TRIBOELECTROSTATIC SEPARATOR FOR FINE COAL CLEANING

Description: Numerous advanced coal cleaning processes have been developed in recent years that are capable of substantially reducing both ash- and sulfur-forming minerals from coal. However, most of the processes involve fine grinding and use water as the cleaning medium; therefore, the clean coal products must be dewatered before they can be transported and burned. Unfortunately, dewatering fine coal is costly, which makes it difficult to deploy advanced coal cleaning processes for commercial applications. As a means of avoiding problems associated with the fine coal dewatering, the National Energy Technology Laboratory (NETL) developed a dry coal cleaning process in which mineral matter is separated from coal without using water. In this process, pulverized coal is subjected to triboelectrification before being placed in an electric field for electrostatic separation. The triboelectrification is accomplished by passing a pulverized coal through an in-line mixer made of copper. Copper has a work function that lies between that of carbonaceous material (coal) and mineral matter. Thus, coal particles impinging on the copper wall lose electrons to the metal thereby acquiring positive charges, while mineral matter impinging on the wall gain electrons to acquire negative charges. The charged particles then pass through an electric field where they are separated according to their charges into two or more products depending on the configuration of the separator. The results obtained at NETL showed that it is capable of removing more than 90% of the pyritic sulfur and 70% of the ash-forming minerals from a number of eastern U.S. coals. However, the BTU recoveries were less than desirable. The laboratory-scale batch triboelectrostatic separator (TES) used by NETL relied on adhering charged particles on parallel electrode surfaces and scraping them off. Therefore, its throughput will be proportional to the electrode surface area. If this laboratory device is scaled-up as is, it ...
Date: April 30, 2001
Creator: Yoon, R.H.; Luttrell, G.H.; Yan, E.S. & Walters, A.D.
Partner: UNT Libraries Government Documents Department

Capillary Electrophoresis - Optical Detection Systems

Description: Molecular recognition systems are developed via molecular modeling and synthesis to enhance separation performance in capillary electrophoresis and optical detection methods for capillary electrophoresis. The underpinning theme of our work is the rational design and development of molecular recognition systems in chemical separations and analysis. There have been, however, some subtle and exciting shifts in our research paradigm during this period. Specifically, we have moved from mostly separations research to a good balance between separations and spectroscopic detection for separations. This shift is based on our perception that the pressing research challenges and needs in capillary electrophoresis and electrokinetic chromatography relate to the persistent detection and flow rate reproducibility limitations of these techniques (see page 1 of the accompanying Renewal Application for further discussion). In most of our work molecular recognition reagents are employed to provide selectivity and enhance performance. Also, an emerging trend is the use of these reagents with specially-prepared nano-scale materials. Although not part of our DOE BES-supported work, the modeling and synthesis of new receptors has indirectly supported the development of novel microcantilevers-based MEMS for the sensing of vapor and liquid phase analytes. This fortuitous overlap is briefly covered in this report. Several of the more significant publications that have resulted from our work are appended. To facilitate brevity we refer to these publications liberally in this progress report. Reference is also made to very recent work in the Background and Preliminary Studies Section of the Renewal Application.
Date: August 6, 2001
Creator: Sepaniak, M. J.
Partner: UNT Libraries Government Documents Department

Synthesis, Characterization, to application of water soluble and easily removable cationic pressure sensitive adhesives

Description: In recent years, the world has expressed an increasing interest in the recycling of waste paper to supplement the use of virgin fiber as a way to protect the environment. Statistics show that major countries are increasing their use of recycled paper. For example, in 1991 to 1996, the U.S. increased its recovered paper utilization rate from 31% to 39%, Germany went from 50% to 60%, the UK went from 60% to 70%, France increased from 46% to 49%, and China went from 32% to 35% [1]. As recycled fiber levels and water system closures both increase, recycled product quality will need to improve in order for recycled products to compete with products made from virgin fiber [2]. The use of recycled fiber has introduced an increasing level of metal, plastic, and adhesive contamination into the papermaking process which has added to the complexity of the already overwhelming task of providing a uniform and clean recycle furnish. The most harmful of these contaminates is a mixture of adhesives and polymeric substances that are commonly known as stickies. Stickies, which enter the mill with the pulp furnish, are not easily removed from the repulper and become more difficult the further down the system they get. This can be detrimental to the final product quality. Stickies are hydrophobic, tacky, polymeric materials that are introduced into the papermaking system from a mixture of recycled fiber sources. Properties of stickies are very similar to the fibers used in papermaking, viz. size, density, hydrophobicity, and electrokinetic charge. This reduces the probability of their removal by conventional separation processes, such as screening and cleaning, which are based on such properties. Also, their physical and chemical structure allows for them to extrude through screens, attach to fibers, process equipment, wires and felts. Stickies can break down and ...
Date: January 30, 2004
Creator: Technology, Institute of Paper Science
Partner: UNT Libraries Government Documents Department

SURFACE AREA, VOLUME, MASS, AND DENSITY DISTRIBUTIONS FOR SIZED BOMASS PARTICLES

Description: This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FC26-04NT42130 during the period July 01, 2004 to December 31, 2004 which covers the first six months of the project. Presently work is in progress to characterize surface area, volume, mass, and density distributions for sized biomass particles. During this reporting period, supply requests were processed and supplies including biomass test particles (hardwood sawdust AI14546) in the size range of 100-200 microns were obtained from a cofiring pilot plant research facility owned by Southern Company, Birmingham, AL. Morehouse has completed setting up of the gravimetric technique measurement system in the heat transfer laboratory, department of physics and dual degree engineering, Morehouse College. Simultaneously, REM, our subcontractor, has completed setting up of the electrodynamic balance (EDB) measurement system to characterize shape and mass for individual biomass particles. Testing of the gravimetric system, and calibration of the cameras and imaging systems using known sizes of polystyrene particles are in progress.
Date: May 1, 2004
Creator: Sampath, Ramanathan
Partner: UNT Libraries Government Documents Department

Atomic Physics Aspects of a Relativistic Nuclear Collider

Description: Atomic collision cross sections involving bare uranium nuclei are large at relativistic energies and will affect the design and operation of a relativistic nuclear collider (RNC). The most significant may be production of electron-positron pairs and muon pairs ({approx} 10{sup 8} per sec. and 2000 per sec. respectively for a 100 GeV/nucleon collider with a luminosity of 10{sup 27} cm{sup 2} s{sup -1}). Although the pair production is a direct measure of the luminosity it is also a large source of background and capture of an electron from the pair by one of the nuclei will result in the loss of the ion. Another important loss mechanism is Coulomb excitation of the giant nuclear dipole and giant nuclear quadrupole resonances. Storing and colliding bare and highly-stripped uranium opens up new possibilities for novel atomic physics experiments and an alternate approach for present experiments. As examples, the use of a collider for experiments to study spontaneous decay of the super-critical state (both positron production and x-ray production) of quasi-atoms of atomic number Z > 172, and a storage-ring measurement of the ground state hyperfine structure of hydrogen like thallium as a test of quantum electrodynamics (QED) are discussed.
Date: November 1, 1984
Creator: Gould, R.
Partner: UNT Libraries Government Documents Department

Ambient-Temperature Passive Magnetic Bearings for Flywheel Energy Storage Systems

Description: Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag forces, or from mechanical-hysteritic losses that may occur in the rotor. Our design problem thus becomes one of calculating and/or measuring the relevant stiffnesses and drag coefficients of the various elements and comparing our results with the theory so as to assure that the cited stability criteria are satisfied.
Date: May 26, 2000
Creator: Bender, D. & Post, R.
Partner: UNT Libraries Government Documents Department

Stability Issues in Ambient-Temperature Passive Magnetic Bearing Systems

Description: The ambient-temperature passive magnetic bearing system developed at the Lawrence Livermore National Laboratory achieves rotor-dynamic stability by employing special combinations of levitating and stabilizing elements. These elements, energized by permanent magnet material, create the magnetic and electrodynamic forces that are required for the stable levitation of rotating systems, such as energy-storage flywheels. Stability criteria, derived from theory, describe the bearing element parameters, i.e., stiffnesses and damping coefficients, that are required both to assure stable levitation (''Earnshaw-stability''), and stability against whirl-type rotor-dynamic instabilities. The work described in this report concerns experimental measurements and computer simulations that address some critical aspects of this overall stability problem. Experimentally, a test device was built to measure the damping coefficient of dampers that employ eddy currents induced in a metallic disc. Another test device was constructed for the purpose of measuring the displacement-dependent drag coefficient of annular permanent magnet bearing elements. In the theoretical developments a computer code was written for the purpose of simulating the rotor-dynamics of our passive bearing systems. This code is capable of investigating rotor-dynamic stability effects for both small-amplitude transient displacements (i.e., those within the linear regime), and for large-amplitude displacements, where non-linear effects can become dominant. Under the latter conditions a bearing system that is stable for small-amplitude displacements may undergo a rapidly growing rotor-dynamic instability once a critical displacement is exceeded. A new result of the study was to demonstrate that stiffness anisotropy of the bearing elements (which can be designed into our bearing system) is strongly stabilizing, not only in the linear regime, but also in the non-linear regime.
Date: February 17, 2000
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

Electrodynamics at the highest energies

Description: At very high energies, the bremsstrahlung and pair production cross sections exhibit complex behavior due to the material in which the interactions occur. The cross sections in dense media can be dramatically different than for isolated atoms. This writeup discusses these in-medium effects, emphasizing how the cross section has different energy and target density dependencies in different regimes. Data from SLAC experiment E-146 will be presented to confirm the energy and density scaling. Finally, QCD analogs of the electrodynamics effects will be discussed.
Date: June 17, 2002
Creator: Klein, Spencer R.
Partner: UNT Libraries Government Documents Department

Thirteen years of pair production

Description: This talk surveys a thirteen-year collaboration with Chris Bottcher on various aspects of strong field electrodynamics. Most of the work centers on the atomic physics associated with the peripheral collisions of ultrarelativistic heavy atoms. The earliest, beginning in about 1979, dealt with the spontaneous emission of positrons from nuclear quasimolecules and touched briefly on the formation of axions as a possible explanation of the anomalous peaks in the spectrum. This work stimulated the extensive studies of particle production from coherent fields that laid the foundations for investigations of nuclear form factors, structure functions, and production mechanisms for the Higgs and other exotic particles. Chris conjectured that the strong fields that are present in these collisions would give rise to nonperturbative effects. Thus, during this time, Chris also worked to develop basis-spline collocation methods for solving dynamical relativistic fermions in super strong fields. This was perhaps one of the best of times for Chris; on these problems alone, he co-authored fifty articles with more than twenty different collaborators.
Date: December 31, 1994
Creator: Strayer, M.R.
Partner: UNT Libraries Government Documents Department

Topics in gauge theories and the unification of elementary particle interactions

Description: We report on work done by the principal investigators and their collaborators on phenomenology of low and medium p{sub t} physics, standard model results for macroscopic systems, same sign dilepton signals from massive Majorana neutrinos, Casimir effects for charged particles, further macroscopic effects in quantum electrodynamics, and n-particle amplitudes for large n beyond the tree approximation, renormalization group analysis of unified gauge theories.
Date: December 1, 1990
Creator: Srivastava, Y.N. & Vaughn, M.T.
Partner: UNT Libraries Government Documents Department