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Laser plasma interactions in fused silica cavities (open access)

Laser plasma interactions in fused silica cavities

The effect of laser energy on formation of a plasma inside a cavity was investigated. The temperature and electron number density of laser-induced plasmas in a fused silica cavity were determined using spectroscopic methods, and compared with laser ablation on a flat surface. Plasma temperature and electron number density during laser ablation in a cavity with aspect ratio of 4 increased faster with irradiance after the laser irradiance reached a threshold of 5 GW/cm{sup 2}. The threshold irradiance of particulate ejection was lower for laser ablation in a cavity compared with on a flat surface; the greater the cavity aspect ratio, the lower the threshold irradiance. The ionization of silicon becomes saturated and the crater depths were increased approximately by an order of magnitude after the irradiance reached the threshold. Phase explosion was discussed to explain the large change of both plasma characteristics and mass removal when irradiance increased beyond a threshold value. Self-focusing of the laser beam was discussed to be responsible for the decrease of the threshold in cavities.
Date: June 24, 2003
Creator: Zeng, Xianzhong; Mao, Xianglei; Mao, Samuel S.; Yoo, Jong H.; Greif, Ralph & Russo, Richard E.
System: The UNT Digital Library
Advances in lithium-ion batteries (open access)

Advances in lithium-ion batteries

The editors state in their introduction that this book is intended for lithium-ion scientists and engineers but they hope it may be of interest to scientists from other fields. Their main aim was to provide a snapshot of the state of the Lithium-ion art and in this they have largely succeeded. The book is comprised of a collection of very current reviews of the lithium ion battery literature by acknowledged experts that draw heavily on the authors' own research but are sufficiently general to provide the lithium ion researcher with enough guidance to the current literature and the current thinking in the field. Some of the literature references may be too current as there are numerous citations of conference proceedings which may be easily accessible to the lithium ion scientist or engineer but are not likely to be available to the interested chemist coming to the field for the first time. One author expresses the hope and expectation that properly peer-reviewed articles will appear in due course and the interested reader should look out for them in future. From the point of view of the lithium ion battery scientist and engineer, the book covers most of the topics that are …
Date: June 24, 2003
Creator: Kerr, John B.
System: The UNT Digital Library
A Binary Segmentation Approach for Boxing Ribosome Particles in Cryo EM Micrographs (open access)

A Binary Segmentation Approach for Boxing Ribosome Particles in Cryo EM Micrographs

Three-dimensional reconstruction of ribosome particles from electron micrographs requires selection of many single-particle images. Roughly 100,000 particles are required to achieve approximately 10 angstrom resolution. Manual selection of particles, by visual observation of the micrographs on a computer screen, is recognized as a bottleneck in automated single particle reconstruction. This paper describes an efficient approach for automated boxing of ribosome particles in micrographs. Use of a fast, anisotropic non-linear reaction-diffusion method to pre-process micrographs and rank-leveling to enhance the contrast between particles and the background, followed by binary and morphological segmentation constitute the core of this technique. Modifying the shape of the particles to facilitate segmentation of individual particles within clusters and boxing the isolated particles is successfully attempted. Tests on a limited number of micrographs have shown that over 80 percent success is achieved in automatic particle picking.
Date: June 24, 2003
Creator: Adiga, Umesh P. S.; Malladi, Ravi; Baxter, William & Glaeser, Robert M.
System: The UNT Digital Library
New Analysis Techniques for Estimating Impacts of Federal Appliance Efficiency Standards (open access)

New Analysis Techniques for Estimating Impacts of Federal Appliance Efficiency Standards

Impacts of U.S. appliance and equipment standards have been described previously. Since 2000, the U.S. Department of Energy (DOE) has updated standards for clothes washers, water heaters, and residential central air conditioners and heat pumps. A revised estimate of the aggregate impacts of all the residential appliance standards in the United States shows that existing standards will reduce residential primary energy consumption and associated carbon dioxide (CO{sub 2}) emissions by 89 percent in 2020 compared to the levels expected without any standards. Studies of possible new standards are underway for residential furnaces and boilers, as well as a number of products in the commercial (tertiary) sector, such as distribution transformers and unitary air conditioners. The analysis of standards has evolved in response to critiques and in an attempt to develop more precise estimates of costs and benefits of these regulations. The newer analysis elements include: (1) valuing energy savings by using marginal (rather than average) energy prices specific to an end-use; (2) simulating the impacts of energy efficiency increases over a sample population of consumers to quantify the proportion of households having net benefits or net costs over the life of the appliance; and (3) calculating marginal markups in distribution …
Date: June 24, 2003
Creator: McMahon, James E.
System: The UNT Digital Library
Evaluation of Uranium Co-precipitations with Sodium Aluminosilicate Phases (open access)

Evaluation of Uranium Co-precipitations with Sodium Aluminosilicate Phases

This paper describes batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. We have found that conditions which favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to say just the formation of the aluminosilicates. Infrared spectra shows that sodium uranates, uranium silicates and other uranium solids are formed during the synthesis of sodium aluminosilicates structures in the presence of uranium. Both amorphous and sodalite aluminosilcate phases, unlike zeolite A phase, show appreciable affinity for uranium incorporation during their formation in the presence of uranium.
Date: June 24, 2003
Creator: Oji, L.N.
System: The UNT Digital Library
R&D Toward Neutrino Factories and Muon Colliders (open access)

R&D Toward Neutrino Factories and Muon Colliders

R&D aimed at the production, acceleration, and storage of intense muon beams is under way in the U.S., in Europe, and in Japan. Considerable progress has been made in the past few years toward the design of a ''Neutrino Factory'' in which a beam of 20-50 GeV mu- or mu+ is stored. Decay neutrinos from the beam illuminate a detector located roughly 3000 km from the ring. Here, we briefly describe the ingredients of a Neutrino Factory and then discuss the current R&D program and its results. A key concept in the design is ''ionization cooling,'' a process whereby the muon emittance is reduced by repeated interactions with an absorber material followed by reacceleration with high-gradient rf cavities. Plans to test this concept in the Muon Ionization Cooling Experiment (MICE) are well along and are described briefly.
Date: June 24, 2003
Creator: Zisman, Michael S.
System: The UNT Digital Library
Molecular Identification of a Functional Homologue of the Mammalian Fatty Acid Amide Hydrolase in Arabidopsis thaliana (open access)

Molecular Identification of a Functional Homologue of the Mammalian Fatty Acid Amide Hydrolase in Arabidopsis thaliana

Article on the molecular identification of a functional homologue of the mammalian fatty acid amide hydrolase in Arabidopsis thaliana.
Date: June 24, 2003
Creator: Shrestha, Rhidaya; Dixon, R. A. & Chapman, Kent D.
System: The UNT Digital Library
Corrosion Behavior of Alloy 22 in Oxalic Acid and Sodium Chloride Solutions (open access)

Corrosion Behavior of Alloy 22 in Oxalic Acid and Sodium Chloride Solutions

Nickel based Alloy 22 (NO6022) is extensively used in aggressive industrial applications, especially due to its resistance to localized corrosion and stress corrosion cracking in high chloride environments. The purpose of this work was to characterize the anodic behavior of Alloy 22 in oxalic acid solution and to compare its behavior to sodium chloride (NaCl) solutions. Standard electrochemical tests such as polarization resistance and cyclic polarization were used. Results show that the corrosion rate of Alloy 22 in oxalic acid solutions increased rapidly as the temperature and the acid concentration increased. Extrapolation studies show that even at a concentration of 10{sup -4}M oxalic acid, the corrosion rate of Alloy 22 would be higher in oxalic acid than in 1 M NaCl solution. Alloy 22 was not susceptible to localized corrosion in oxalic acid solutions. Cyclic polarization tests in 1 M NaCl showed that Alloy 22 was susceptible to crevice corrosion at 90 C but was not susceptible at 60 C.
Date: June 24, 2003
Creator: Day, S. D.; Whalen, M. T.; King, K. J.; Hust, G. A.; Wong, L. L.; Estill, J. C. et al.
System: The UNT Digital Library
High Field Magnet R&D in the USA (open access)

High Field Magnet R&D in the USA

Accelerator magnet technology is currently dominated by the use of NbTi superconductor. New and more demanding applications for superconducting accelerator magnets require the use of alternative materials. Several programs in the US are taking advantage of recent improvements in Nb{sub 3}Sn to develop high field magnets for new applications. Highlights and challenges of the US R&D program are presented along with the status of conductor development. In addition, a new R&D focus, the US LHC Accelerator Research Program, will be discussed.
Date: June 24, 2003
Creator: Gourlay, Stephen A.
System: The UNT Digital Library
Grafted polyelectrolyte membranes for lithium batteries and fuel cells (open access)

Grafted polyelectrolyte membranes for lithium batteries and fuel cells

Polyelectrolyte materials have been developed for lithium battery systems in response to the severe problems due to salt concentration gradients that occur in composite electrodes (aka membrane-electrode assemblies). Comb branch polymer architectures are described which allow for grafting of appropriate anions on to the polymer and also for cross-linking to provide for appropriate mechanical properties. The interactions of the polymers with the electrode surfaces are critical for the performance of the system and some of the structural features that influence this will be described. Parallels with the fuel cell MEA structures exist and will also be discussed.
Date: June 24, 2003
Creator: Kerr, John B.
System: The UNT Digital Library