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Actinide Spectroscopy Workshop (open access)

Actinide Spectroscopy Workshop

Actinide materials present an extreme scientific challenge to the materials research community. The complex electronic structures of actinide materials result in many unusual and unique properties that have yet to be fully understood. The difficulties in handling, preparing, and characterizing actinide materials has frequently precluded investigations and has the limited the detailed understanding of these relevant, complex materials. However, modern experiments with actinide materials have the potential to provide key, fundamental information about many long-standing issues concerning actinide materials. This workshop focused on the scientific and technical challenges posed by actinide materials and the potential that synchrotron radiation approaches available at the ALS can contribute to improving the fundamental understanding of actinides materials. Fundamental experimental approaches and results, as well as theoretical modeling and computational simulations, were part of the workshop program.
Date: December 5, 2004
Creator: Tobin, J.G. & Shuh, D.K.
System: The UNT Digital Library
Intelligent Signal Processing for Detection System Optimization (open access)

Intelligent Signal Processing for Detection System Optimization

A wavelet-neural network signal processing method has demonstrated approximately tenfold improvement over traditional signal-processing methods for the detection limit of various nitrogen and phosphorus compounds from the output of a thermionic detector attached to a gas chromatograph. A blind test was conducted to validate the lower detection limit. All fourteen of the compound spikes were detected when above the estimated threshold, including all three within a factor of two above the threshold. In addition, two of six spikes were detected at levels of 1/2 the concentration of the nominal threshold. Another two of the six would have been detected correctly if we had allowed human intervention to examine the processed data. One apparent false positive in five nulls was traced to a solvent impurity, whose presence was subsequently identified by analyzing a solvent aliquot evaporated to 1% residual volume, while the other four nulls were properly classified. We view this signal processing method as broadly applicable in analytical chemistry, and we advocate that advanced signal processing methods should be applied as directly as possible to the raw detector output so that less discriminating preprocessing and post-processing does not throw away valuable signal.
Date: December 5, 2004
Creator: Fu, C. Y.; Petrich, L. I.; Daley, P. F. & Burnham, A. K.
System: The UNT Digital Library
Raman spectroscopy under extreme conditions (open access)

Raman spectroscopy under extreme conditions

We report the results of Raman measurements of various materials under simultaneous conditions of high temperature and high pressure in the diamond anvil cell (DAC). High temperatures are generated by laser heating or internal resistive (ohmic) heating or a combination of both. We present Raman spectra of cubic boron nitride (cBN) to 40 GPa and up to 2300 K that show a continuous pressure and temperature shift of the frequency of the transverse optical mode. We have also obtained high-pressure Raman spectra from a new noble metal nitride, which we synthesized at approximately 50 GPa and 2000 K. We have obtained high-temperature spectra from pure nitrogen to 39 GPa and up to 2000 K, which show the presence of a hot band that has previously been observed in CARS measurements. These measurements have also allowed us to constrain the melting curve and to examine changes in the intramolecular potential with pressure.
Date: November 5, 2004
Creator: Goncharov, A F & Crowhurst, J C
System: The UNT Digital Library
Surface Sensitivity of Fast Superconducting Ion Detectors for Time-of-Flight Mass Spectrometry (open access)

Surface Sensitivity of Fast Superconducting Ion Detectors for Time-of-Flight Mass Spectrometry

We are developing the spatial uniformity of superconducting tunnel junction detectors with a size of 200 {micro}m is improved by increasing the Al thickness of the Nb/Al proximitized electrodes in an energy range of 5-10 keV, which is in the same order as an acceleration energy in time-of-flight mass spectroscopy (TOF-MS). It has been confirmed in TOF experiments with Ta ions and Ta clusters that the proximitized junction detectors clearly separate different ionic states and multi-hit events in impact energy spectra, and moreover can reveal a difference in ion species or ion-surface collision dynamics. However, a better spatial uniformity is not always good for TOF-MS, because a detector with the thicker Al layers has a lower superconducting energy gap, which results in improper detector operation because of a temperature rise due to heat radiation.
Date: November 5, 2004
Creator: Ohkubo, M; Ukibe, M; Saito, N; Kushino, A; Ichimura, S & Friedrich, S
System: The UNT Digital Library
Acceleressence: Dark energy from a phase transition at the seesawscale (open access)

Acceleressence: Dark energy from a phase transition at the seesawscale

Simple models are constructed for ''acceleressence'' dark energy: the latent heat of a phase transition occurring in a hidden sector governed by the seesaw mass scale v{sup 2}/M{sub Pl}, where v is the electroweak scale and M{sub Pl} the gravitational mass scale. In our models, the seesaw scale is stabilized by supersymmetry, implying that the LHC must discover superpartners with a spectrum that reflects a low scale of fundamental supersymmetry breaking. Newtonian gravity may be modified by effects arising from the exchange of fields in the acceleressence sector whose Compton wavelengths are typically of order the millimeter scale. There are two classes of models. In the first class the universe is presently in a metastable vacuum and will continue to inflate until tunneling processes eventually induce a first order transition. In the simplest such model, the range of the new force is bounded to be larger than 25 {micro}m in the absence of fine-tuning of parameters, and for couplings of order unity it is expected to be {approx} 100 {micro}m. In the second class of models thermal effects maintain the present vacuum energy of the universe, but on further cooling, the universe will ''soon'' smoothly relax to a matter dominated …
Date: October 5, 2004
Creator: Chacko, Z.; Hall, Lawrence J. & Nomura, Yasunori
System: The UNT Digital Library
The effect of thin film thickness on the incorporation of Mn interstitials in Ga{sub 1-x}Mn{sub x}As (open access)

The effect of thin film thickness on the incorporation of Mn interstitials in Ga{sub 1-x}Mn{sub x}As

We have investigated the effect of film thickness on the distribution of Mn atoms at various lattice sites in Ga{sub 1-x}Mn{sub x}As thin films. We find that the growth surface acts as a sink facilitating the out-diffusion of Mn interstitials (Mn{sub I}), and thus reducing its concentration in the film. The out-diffused Mn{sub I} accumulate on the surface in a surface oxide layer and do not participate in the ferromagnetism of the film. For thin films less than 15 nm thick, no Mn{sub I} can be detected. Because of the absence of compensating Mn{sub I} defects, higher T{sub C} can be achieved for such extremely thin Ga{sub 1-x}Mn{sub x}As layers. These results agree with our previously suggested Fermi-level-governed upper limit of the T{sub C} of III-Mn-V ferromagnetic semiconductors.
Date: October 5, 2004
Creator: Yu, K. M.; Walukiewicz, W.; Wojtowicz, T.; Denlinger, J.; Scarpulla, M. A.; Liu, X. et al.
System: The UNT Digital Library
Improved Energy Coupling into the Gain Region of the Ni-Like Pd Transient Collisional X-Ray Laser (open access)

Improved Energy Coupling into the Gain Region of the Ni-Like Pd Transient Collisional X-Ray Laser

We present within this paper a series of experiments, which yield new observations to further our understanding of the transient collisional x-ray laser medium. We use the recently developed technique of picosecond x-ray laser interferometry to probe the plasma conditions in which the x-ray laser is generated and propagates. This yields two dimensional electron density maps of the plasma taken at different times relative to the peak of the 600ps plasma-forming beam. In another experimental campaign, the output of the x-ray laser plasma column is imaged with a spherical multilayer mirror onto a CCD camera to give a two-dimensional intensity map of the x-ray laser output. Near-field imaging gives insights into refraction, output intensity and spatial mode structure. Combining these images with the density maps gives an indication of the electron density at which the x-ray laser is being emitted at (yielding insights into the effect of density gradients on beam propagation). Experimental observations coupled with simulations predict that most effective coupling of laser pump energy occurs when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for Ni-like schemes). This can increase the output intensity by more than an order of magnitude relative to …
Date: October 5, 2004
Creator: Smith, R.; Dunn, J.; Filevich, J.; Moon, S.; Nilsen, J.; Keenan, R. et al.
System: The UNT Digital Library
Iridium-192 Production for Cancer Treatment (open access)

Iridium-192 Production for Cancer Treatment

The purpose of this work is to settle a laboratory for Iridium -192 sources production, that is, to determine a wire activation method and to build a hot cell for the wires manipulation, quality control and packaging. The paper relates, mainly, the wire activation method and its quality control. The wire activation is carried out in our nuclear reactor, IEA- R1m.
Date: October 5, 2004
Creator: Rostelato, M.E.C.M.; Silva, C.P.G.; Rela, P.R.; Zeituni, C.A.; Lepki, V. & Feher, A.
System: The UNT Digital Library
IRRADIATION EFFECTS ON THE PHYSICAL CHARACTERISTICS OF SEWAGE SLUDGE (open access)

IRRADIATION EFFECTS ON THE PHYSICAL CHARACTERISTICS OF SEWAGE SLUDGE

The radiation effects on the physical characteristic of the sewage sludge were studied in order to obtain information which will be used for study on the enhancement of the sludge's dewaterability. Water contents, capillary suction time, zeta potential, irradiation dose, sludge acidity, total solid concentration, sludge particle size and microbiology before and after irradiation were investigated. Irradiation gave an effect on physical characteristics sludge. Water content in sludge cake could be reduced by irradiation at the dose of 10kGy.
Date: October 5, 2004
Creator: Lee, M. J.; Lee, J. K.; Yoo, D. H. & Ho, K.
System: The UNT Digital Library
Pressure Gradient Effects On Two-Dimensional Plasma Expansion (open access)

Pressure Gradient Effects On Two-Dimensional Plasma Expansion

Recent advances in interferometry has allowed for the characterization of the electron density expansion within a laser produced plasma to within 10 {micro}m of the target surface and over picosecond timescales. This technique employs the high brightness output of the transient gain Ni-like Pd collisional x-ray laser at 14.7 nm to construct an effective moving picture of the two-dimensional (2-D) expansion of the plasma. We present experimentally measured density profiles of an expanding Al plasma generated through laser irradiation in a 14mm line focus geometry. Significant lateral expansion was observed at all times as well as a pronounced on-axis electron density dip. Detailed modeling with a 2-D plasma physics code gives good agreement to experimental observations. Large pressure gradients associated with the tight focal spot conditions are calculated to dominate in shaping the plasma density profile.
Date: October 5, 2004
Creator: Moon, S.; Smith, R. F.; Dunn, J.; Keenan, R.; Nilsen, J.; Hunter, J. R. et al.
System: The UNT Digital Library
Targetry at the LANL 100 MeV Isotope Production Facility: Les-Sons Learned From Facility Commissioning (open access)

Targetry at the LANL 100 MeV Isotope Production Facility: Les-Sons Learned From Facility Commissioning

The new Isotope Production Facility (IPF) at Los Alamos National Laboratory has been commissioned during the spring of 2004. Commissioning activities focused on the establishment of a radionuclide database, the review and approval of two specific target stack designs, and four trial irradiation runs with subsequent chemical processing and data analyses. This paper highlights some aspects of the facility and the targetry of the two approved target stacks used during the commissioning process.
Date: October 5, 2004
Creator: Nortier, F. M.; Fassbender, M. E.; DeJohn, M.; Hamilton, V. T.; Heaton, R. C.; Jamriska, D. J. et al.
System: The UNT Digital Library
2004 Molecular and Ionic Clusters Gordon Conference - September 5-10, 2004 (open access)

2004 Molecular and Ionic Clusters Gordon Conference - September 5-10, 2004

This Report is Gordon Conference Molecular and Ionic Clusters Final Report and Agenda.
Date: September 5, 2004
Creator: Zwier, Timoty S.
System: The UNT Digital Library
Accuracy of Density Functional Theory for First-Principles Simulations of Water (open access)

Accuracy of Density Functional Theory for First-Principles Simulations of Water

None
Date: August 5, 2004
Creator: Schwegler, E.; Grossman, J.; Draeger, E.; Allesch, M.; Gygi, F. & Galli, G.
System: The UNT Digital Library
cctbx news: Geometry restraints and other new features (open access)

cctbx news: Geometry restraints and other new features

None
Date: August 5, 2004
Creator: Grosse-Kunstleve, Ralf W.; Afonine, Pavel V. & Adams, Paul D.
System: The UNT Digital Library
Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX (open access)

Coefficient of Thermal Expansion of the Beta and Delta Polymorphs of HMX

Dimensional changes related to temperature cycling of the beta and delta polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the beta and delta phases are measured and reported in this work over a temperature range of -20 C to 215 C. In addition, dimensional changes associated with the phase transition were measured, both through the transition and back down. Initially, differential scanning calorimetry (DSC) was used to investigate back conversion of the delta phase to the beta phase polymorph. The most successful approach was first to measure the amount of the beta to delta conversion, then after a given cooling period a repeat analysis, to measure the heat consumed by a second pass through the beta to delta phase transition. In addition, TMA is used to measure the dimensional change of a 0.20-gram sample of HMX during its initial heating and then three days later during a 2nd heating. This HMX shows the beta to delta phase transition a second time, thereby confirming the back conversion from delta to beta phase HMX.
Date: August 5, 2004
Creator: Weese, R K; Burnham, A K & Maienschein, J L
System: The UNT Digital Library
''CPT Theorem'' for Accelerators (open access)

''CPT Theorem'' for Accelerators

In this paper we attempt to reveal common features in evolution of various colliders' luminosity over commissioning periods. A simplified formula, ''CPT theorem'' or CP = T, is proposed which relates the time needed for commissioning T, the ''complexity'' of the machine C and performance increase goal P.
Date: August 5, 2004
Creator: Shiltsev, Vladimir
System: The UNT Digital Library
Development of the third harmonic SC cavity at Fermilab (open access)

Development of the third harmonic SC cavity at Fermilab

The third harmonic 3.9 GHz superconducting cavity was recently proposed by DESY for a new generation of high brightness photo-injector (TTF photoinjector-2) to compensate nonlinear distortion of the longitudinal phase space due to RF curvature of the 1.3 GHz TESLA cavities [1,2]. Installation of the 3rd harmonic cavity will allow us to generate ultra-short (<50 {micro}m rms) highly charged electron bunches with an extremely small transverse normalized emittance (<1 {micro}m). This is required to support a new generation of linear colliders, free electron lasers and synchrotron radiation sources. In this paper we present the current status of the 3rd harmonic cavity being developed at Fermilab. We discuss the design procedure, the building and testing of the copper and niobium half-cells and components, the design of input and HOM couplers.
Date: August 5, 2004
Creator: al., Nikolay Solyak et
System: The UNT Digital Library
Mechanical design and engineering of the 3.9 GHZ, 3rd harmonic SRF system at Fermilab (open access)

Mechanical design and engineering of the 3.9 GHZ, 3rd harmonic SRF system at Fermilab

The mechanical development of the 3.9 GHz, 3rd Harmonic SRF System is summarized to include: the development of a full scale copper prototype cavity structure; the design of the niobium 3 cell and niobium 9 cell structures; the design of the helium vessel and cryostat; the HOM coupler design; and a preliminary look at the main coupler design. The manufacturing processes for forming, rolling, and e-beam welding the HOM coupler, cavity cells, and end tubes are also described. Due to the exotic materials and manufacturing processes used in this type of device, a cost estimate for the material and fabrication is provided. The 3rd harmonic design is organized via a web-based data management approach.
Date: August 5, 2004
Creator: al., Don Mitchell et
System: The UNT Digital Library
Overview of the Coupled Model Intercomparison Project (CMIP) (open access)

Overview of the Coupled Model Intercomparison Project (CMIP)

The Coupled Model Intercomparison Project (CMIP) is designed to allow study and intercomparison of multi-model simulations of present-day and future climate. The latter are represented by idealized forcing of compounded 1% per year CO2 increase to the time of CO2 doubling near year 70 in simulations with global coupled models that contain, typically, components representing atmosphere, ocean, sea ice and land surface. Results from CMIP diagnostic subprojects were presented at the Second CMIP Workshop held at the Max Planck Institute for Meteorology in Hamburg, Germany, in September, 2003. Significant progress in diagnosing and understanding results from global coupled models has been made since the First CMIP Workshop in Melbourne, Australia in 1998. For example, the issue of flux adjustment is slowly fading as more and more models obtain stable multi-century surface climates without them. El Nino variability, usually about half the observed amplitude in the previous generation of coupled models, is now more accurately simulated in the present generation of global coupled models, though there are still biases in simulating the patterns of maximum variability. Typical resolutions of atmospheric component models contained in coupled models is now usually around 2.5 degrees latitude-longitude, with the ocean components often having about twice …
Date: August 5, 2004
Creator: Meehl, Gerald A.; Covey, Curt; McAvaney, Bryant; Latif, Mojib & Stouffer, Ronald J.
System: The UNT Digital Library
A Prehistorical Record of Cultural Eutrophication from Crawford Lake, Canada (open access)

A Prehistorical Record of Cultural Eutrophication from Crawford Lake, Canada

Cultural eutrophication--the process by which human activities increase nutrient input rates to aquatic ecosystems and thereby cause undesirable changes in surface-water quality--is generally thought to have begun with the start of the industrial era. The prehistoric dimension of human impacts on aquatic ecosystems remains relatively undescribed, particularly in North America. Here we present fossil plankton data (diatoms and rotifers), organic and inorganic carbon accumulations, and carbon isotope ratios from a 1000-yr sediment core record from Crawford Lake, Ontario, Canada. The data documents increased nutrient input to Crawford Lake caused by Iroquoian horticultural activity from A.D. 1268 to 1486 and shows how this increased nutrient input elevated lake productivity, caused bottom-water anoxia, and irreversibly altered diatom community structure within just a few years. Iroquoian settlement in the region declined in the fifteenth century, yet diatom communities and lake circulation never recovered to the predisturbance state. A second phase of cultural eutrophication starting in A.D. 1867, initiated by Canadian agricultural disturbance, increased lake productivity but had comparatively less of an impact on diatom assemblages and carbon-storage pathways than the initial Iroquoian disturbance. This study deepens our understanding of the impact of cultural eutrophication on lake systems, highlights the lasting influence of initial …
Date: August 5, 2004
Creator: Ekdahl, E J; Teranes, J; Guilderson, T; Turton, C L; McAndrews, J H; Wittkop, C A et al.
System: The UNT Digital Library
Preparation of Peptide p-Nitroanilides using an Aryl Hydrazine Solid Support (open access)

Preparation of Peptide p-Nitroanilides using an Aryl Hydrazine Solid Support

Peptide p-nitroanilides are useful compounds for studying protease activity, however the poor nucleophilicity of p-nitroaniline makes their preparation difficult. We describe a new efficient approach for the Fmoc-based synthesis of peptide p-nitroanilides using an aryl hydrazine resin. Mild oxidation of the peptide hydrazide resin yields a highly reactive acyl diazene, which efficiently reacts with weak nucleophiles. We have prepared several peptide p-nitroanilides, including substrates for the Lethal Factor protease from B. anthracis.
Date: August 5, 2004
Creator: Kwon, Y; Welsh, K; Mitchell, A R & Camarero, J A
System: The UNT Digital Library
The QCD/SM Working Group: Summary Report (open access)

The QCD/SM Working Group: Summary Report

Among the many physics processes at TeV hadron colliders, we look most eagerly for those that display signs of the Higgs boson or of new physics. We do so however amid an abundance of processes that proceed via Standard Model (SM) and in particular Quantum Chromodynamics (QCD) interactions, and that are interesting in their own right. Good knowledge of these processes is required to help us distinguish the new from the known. Their theoretical and experimental study teaches us at the same time more about QCD/SM dynamics, and thereby enables us to further improve such distinctions. This is important because it is becoming increasingly clear that the success of finding and exploring Higgs boson physics or other New Physics at the Tevatron and LHC will depend significantly on precise understanding of QCD/SM effects for many observables. To improve predictions and deepen the study of QCD/SM signals and backgrounds was therefore the ambition for our QCD/SM working group at this Les Houches workshop. Members of the working group made significant progress towards this on a number of fronts. A variety of tools were further developed, from methods to perform higher order perturbative calculations or various types of resummation, to improvements in …
Date: August 5, 2004
Creator: al., M. Dobbs et
System: The UNT Digital Library
Results and Commissioning Issues From an Automated Demand Response Pilot (open access)

Results and Commissioning Issues From an Automated Demand Response Pilot

This paper describes a research project to develop and test Automated Demand Response hardware and software technology in large facilities. We describe the overall project and some of the commissioning and system design problems that took place. Demand Response (DR) is a set of activities to reduce or shift electricity use to improve the electric grid reliability purposes, manage electricity costs, and ensure that customers receive signals that encourage load reduction during times when the electric grid is near its capacity. There were a number of specific commissioning challenges in conducting this test including software compatibility, incorrect time zones, IT and EMCS failures, and hardware issues. The knowledge needed for this type of system commissioning combines knowledge of building controls with network management and knowledge of emerging information technologies.
Date: August 5, 2004
Creator: Piette, Mary Ann; Watson, Dave; Sezgen, Osman & Motegi, Naoya
System: The UNT Digital Library
Spatially Continuous Mixed P2-P1 Solutions for Planar Geometry (open access)

Spatially Continuous Mixed P2-P1 Solutions for Planar Geometry

Even-order Legendre polynomial (PN) expansion approximations of the neutron transport equation have historically seen only limited practical application. Research in the last decade [1] has resolved one of the historical theoretical objections [2] to the use of even-order PN approximations in planar geometry, namely the ambiguity in the prescription of boundary conditions as a result of an odd number of unknowns. This research also demonstrated the P2 approximation to be more accurate than the P1 approximation in planar geometry away from boundary layers and material interfaces. Neither the P1 nor the P2 approximation is convincingly more accurate near material interfaces. This progress motivated the reexamination of the multidimensional simplified P2 (SP2) approximation [3], the development of P2 approximations for planar geometry stochastic transport problems [4], and the examination of the P2 and SP2 approximations as a synthetic acceleration technique for the discrete ordinates equations.
Date: August 5, 2004
Creator: Brantely, P S
System: The UNT Digital Library