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2004 Catalysis Gordon Conference-June 27-July 2, (open access)

2004 Catalysis Gordon Conference-June 27-July 2,

The Conference was well-attended with 100 participants (attendees list included). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. The formal schedule and speaker program and the poster program is given. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
Date: August 17, 2005
Creator: Gray, Nancy Ryan & Stair, Peter C.
System: The UNT Digital Library
2004 Lasers Materials Interactions Gordon Research Conferences August 1-6, 2004 (open access)

2004 Lasers Materials Interactions Gordon Research Conferences August 1-6, 2004

The Report is Gordon Research Conferences Laser Interaction with materials.
Date: August 17, 2005
Creator: Dickinson, Nancy Ryan Gray J. Thomas
System: The UNT Digital Library
2005 Laser Diagnostics in Combustion Gordon Conference July 31-August 5, 2005 (open access)

2005 Laser Diagnostics in Combustion Gordon Conference July 31-August 5, 2005

The Gordon Research Conference (GRC) on LASER DIAGNOSTICS IN COMBUSTION was held at Mount Holyoke College from 7/31/2005 thru 8/5/2005. The Conference was well-attended with 121 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, ''free time'' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field. I want to personally thank you for your support of this Conference. As you know, in the interest of promoting the presentation of unpublished and frontier-breaking research, Gordon Research Conferences does not permit …
Date: August 1, 2005
Creator: Allen, Mark G.
System: The UNT Digital Library
3D Arcing for Offset Measurements with a Hamar Laser (Presentation material) (open access)

3D Arcing for Offset Measurements with a Hamar Laser (Presentation material)

This report is about 3D Arcing for Offset Measurements with a Hamar Laser on 7th International workshop on accelerator alignment.
Date: August 23, 2005
Creator: Fuss, B.
System: The UNT Digital Library
7Be(p,(gamma))8B S-factor From Ab Initio Wave Functions (open access)

7Be(p,(gamma))8B S-factor From Ab Initio Wave Functions

Nuclear structure of {sup 7}Be, {sup 8}B and {sup 7,8}Li is studied within the ab initio no-core shell model (NCSM). Starting from the high-precision CD-Bonn 2000 nucleon-nucleon (NN) interaction, wave functions of {sup 7}Be and {sup 8}B bound states are obtained in basis spaces up to 10{h_bar}{Omega} and used to calculate channel cluster form factors (overlap integrals) of the {sup 8}B ground state with {sup 7}Be+p. Due to the use of the harmonic oscillator (HO) basis, the overlap integrals have incorrect asymptotic properties. We fix this problem in two alternative ways. First, by a Woods-Saxon (WS) potential solution fit to the interior of the NCSM overlap integrals. Second, by a direct matching with the Whittaker function. The corrected overlap integrals are then used for the {sup 7}Be(p,{gamma}){sup 8}B S-factor calculation. We study the convergence of the S-factor with respect to the NCSM HO frequency and the model space size. Our S-factor results are in agreement with recent direct measurement data.
Date: August 15, 2005
Creator: Navratil, P; Bertulani, C & Caurier, E
System: The UNT Digital Library
Ab Initio Simulation of Materials under Extreme Conditions (open access)

Ab Initio Simulation of Materials under Extreme Conditions

The study of materials properties under extreme conditions has made considerable progress over the past decade due to both improvements in experimental techniques and advanced modeling methods. The availability of accurate models is crucial in order to analyze experimental results obtained in extreme conditions of pressure and temperature where experimental data can be scarce. Among theoretical models, ab initio simulations are playing an increasingly important role due to their ability to predict materials properties without the need for any experimental input. Ab initio simulations also allow for an exploration of materials properties in conditions that are unachievable using controlled experiments--such as e.g. the conditions prevailing in the core of large planets. In that limit, they constitute the only quantitative model of condensed matter available today. In this article, we review the current status of ab initio simulations and discuss examples of recent applications in which numerical simulations have provided an essential complement to experimental data.
Date: August 11, 2005
Creator: Gygi, F. & Galli, G.
System: The UNT Digital Library
An Accelerator Control Middle Layer Using Matlab (open access)

An Accelerator Control Middle Layer Using Matlab

None
Date: August 23, 2005
Creator: Portmann, G.; /LBL, Berkeley; Corbett, J.; Terebilo, A. & /SLAC, SSRL /SLAC
System: The UNT Digital Library
Active Control for Statistically Stationary Turbulent PremixedFlame Simulations (open access)

Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.
Date: August 30, 2005
Creator: Bell, J. B.; Day, M. S.; Grcar, J. F. & Lijewski, M. J.
System: The UNT Digital Library
Age-Based Methods to Explore Time-Related Variables in Occupational Epidemiology Studies (open access)

Age-Based Methods to Explore Time-Related Variables in Occupational Epidemiology Studies

Although age is recognized as the strongest predictor of mortality in chronic disease epidemiology, a calendar-based approach is often employed when evaluating time-related variables. An age-based analysis file, created by determining the value of each time-dependent variable for each age that a cohort member is followed, provides a clear definition of age at exposure and allows development of diverse analytic models. To demonstrate methods, the relationship between cancer mortality and external radiation was analyzed with Poisson regression for 14,095 Oak Ridge National Laboratory workers. Based on previous analysis of this cohort, a model with ten-year lagged cumulative radiation doses partitioned by receipt before (dose-young) or after (dose-old) age 45 was examined. Dose-response estimates were similar to calendar-year-based results with elevated risk for dose-old, but not when film badge readings were weekly before 1957. Complementary results showed increasing risk with older hire ages and earlier birth cohorts, since workers hired after age 45 were born before 1915, and dose-young and dose-old were distributed differently by birth cohorts. Risks were generally higher for smokingrelated than non-smoking-related cancers. It was difficult to single out specific variables associated with elevated cancer mortality because of: (1) birth cohort differences in hire age and mortality experience …
Date: August 31, 2005
Creator: Janice P. Watkins, Edward L. Frome, Donna L. Cragle
System: The UNT Digital Library
Aggregation kinetics in a model colloidal suspension (open access)

Aggregation kinetics in a model colloidal suspension

The authors present molecular dynamics simulations of aggregation kinetics in a colloidal suspension modeled as a highly asymmetric binary mixture. Starting from a configuration with largely uncorrelated colloidal particles the system relaxes by coagulation-fragmentation dynamics to a structured state of low-dimensionality clusters with an exponential size distribution. The results show that short range repulsive interactions alone can give rise to so-called cluster phases. For the present model and probably other, more common colloids, the observed clusters appear to be equilibrium phase fluctuations induced by the entropic inter-colloidal attractions.
Date: August 8, 2005
Creator: Bastea, S
System: The UNT Digital Library
Aging and weathering of cool roofing membranes (open access)

Aging and weathering of cool roofing membranes

Aging and weathering can reduce the solar reflectance of cool roofing materials. This paper summarizes laboratory measurements of the solar spectral reflectance of unweathered, weathered, and cleaned samples collected from single-ply roofing membranes at various sites across the United States. Fifteen samples were examined in each of the following six conditions: unweathered; weathered; weathered and brushed; weathered, brushed and then rinsed with water; weathered, brushed, rinsed with water, and then washed with soap and water; and weathered, brushed, rinsed with water, washed with soap and water, and then washed with an algaecide. Another 25 samples from 25 roofs across the United States and Canada were measured in their unweathered state, weathered, and weathered and wiped. We document reduction in reflectivity resulted from various soiling mechanisms and provide data on the effectiveness of various cleaning approaches. Results indicate that although the majority of samples after being washed with detergent could be brought to within 90% of their unweathered reflectivity, in some instances an algaecide was required to restore this level of reflectivity.
Date: August 23, 2005
Creator: Akbari, Hashem; Berhe, Asmeret A.; Levinson, Ronnen; Graveline,Stanley; Foley, Kevin; Delgado, Ana H. et al.
System: The UNT Digital Library
Alighment and Vibration Issues in TeV Linear Collider Design (open access)

Alighment and Vibration Issues in TeV Linear Collider Design

The next generation of linear colliders will require alignment accuracies and stabilities of component placement at least one, perhaps two, orders of magnitude better than can be achieved by the conventional methods and procedures in practice today. The magnitudes of these component-placement tolerances for current designs of various linear collider subsystems are tabulated. In the micron range, long-term ground motion is sufficiently rapid that on-line reference and mechanical correction systems are called for. Some recent experiences with the upgraded SLAC laser alignment systems and examples of some conceivable solutions for the future are described. The so called ''girder'' problem is discussed in the light of ambient and vibratory disturbances. The importance of the quality of the underlying geology is stressed. The necessity and limitations of particle-beam-derived placement information are mentioned.
Date: August 12, 2005
Creator: Fischer, G. E.
System: The UNT Digital Library
Alignment Tools Used to Locate a Wire and a Laser Beam in the VISA Undulator Project (open access)

Alignment Tools Used to Locate a Wire and a Laser Beam in the VISA Undulator Project

The Stanford Linear Accelerator Center is evaluating the feasibility of placing a free electron laser (FEL) at the end of the linear accelerator. The proposal is to inject electrons two thirds of the way down the linac, accelerate the electrons for the last one third of the linac, and then send the electrons into the FEL. This project is known as the LCLS (Linac Coherent Light Source). To test the feasibility of the LCLS, a smaller experiment VISA (Visual to Infrared SASE (Self Amplified Stimulated Emission) Amplifier) is being performed at Brookhaven National Laboratory. VISA consists of four wiggler segments, each 0.99 m long. The four segments are required to be aligned to the beam axis with an rms error less than 50 {micro}m [1]. This very demanding alignment is carried out in two steps [2]. First the segments are fiducialized using a pulsed wire system. Then the wiggler segments are placed along a reference laser beam which coincides with the electron beam axis. In the wiggler segment fiducialization, a wire is stretched through a wiggler segment and a current pulse is sent down the wire. The deflection of the wire is monitored. The deflection gives information about the electron …
Date: August 17, 2005
Creator: Wolf, Z.; Ruland, R.; Dix, B. & Arnett, D.
System: The UNT Digital Library
Alignment without Magnet Fiducials (open access)

Alignment without Magnet Fiducials

Presently, the demand for high quality synchrotron radiation is increasing all over the world. One of the fascinating aspects of this novel tool is the broad range of scientific users interested in synchrotron radiation. They come from physics, chemistry, biology, and medicine, to name just a few. Third generation storage which recently became available for users will by far not be able to satisfy all the beam-time requests. In addition, it is also recognized that long-term scientific efficiency and technological success is heavily dependent on ease of access to a home based facility nearby and continuing fine-tuning of all components of a beam line. Based on the high quality user community in Switzerland and their prospective research activities, the Paul Scherrer Institute, in close collaboration with interested research groups from the Swiss universities and the Swiss Federal Institutes of Technology, has worked out a proposal to build an advanced synchrotron light source in Switzerland, which will come into operation in the year 2001. It has been named SLS as acronym for Swiss Light Source.
Date: August 17, 2005
Creator: Ruland, Robert; Mulhaupt, Gottfried; Rohrer, Martin & Wiegand, Peter
System: The UNT Digital Library
Amplification of surface temperature trends and variability in thetropical atmosphere (open access)

Amplification of surface temperature trends and variability in thetropical atmosphere

The month-to-month variability of tropical temperatures is larger in the troposphere than at the Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations, and is consistent with basic theory. On multi-decadal timescales, tropospheric amplification of surface warming is a robust feature of model simulations, but occurs in only one observational dataset. Other observations show weak or even negative amplification. These results suggest that either different physical mechanisms control amplification processes on monthly and decadal timescales, and models fail to capture such behavior, or (more plausibly) that residual errors in several observational datasets used here affect their representation of long-term trends.
Date: August 11, 2005
Creator: Santer, B. D.; Wigley, T. M. L.; Mears, C.; Wentz, F. J.; Klein, S. A.; Seidel, D. J. et al.
System: The UNT Digital Library
Analysis of stops with small stop-neutralino mass difference at a LC (open access)

Analysis of stops with small stop-neutralino mass difference at a LC

A compelling framework to explain dark matter and electroweak baryogenesis is supersymmetry with light scalar top quarks (stops) and a small mass difference between the stop and the lightest neutralino. In this work, the stop detection capability at the ILC for small mass differences between the stop and the neutralino is studied. The analysis is based on a fast and realistic detector simulation. Significant sensitivity for mass differences down to 5 GeV is obtained. It is discussed how the relevant parameters of the scalar tops can be extracted and used to compute the dark matter density in the universe.
Date: August 1, 2005
Creator: Milstene, C.; Carena, Marcela S.; Freitas, A.; Finch, A.; Sopczak, A. & Kluge, Hannelies
System: The UNT Digital Library
Analyzing Nuclear Fuel Cycles from Isotopic Ratios of Waste Products Applicable to Measurement by Accelerator Mass Spectrometry (open access)

Analyzing Nuclear Fuel Cycles from Isotopic Ratios of Waste Products Applicable to Measurement by Accelerator Mass Spectrometry

An extensive study was conducted to determine isotopic ratios of nuclides in spent fuel that may be utilized to reveal historical characteristics of a nuclear reactor cycle. This forensic information is important to determine the origin of unknown nuclear waste. The distribution of isotopes in waste products provides information about a nuclear fuel cycle, even when the isotopes of uranium and plutonium are removed through chemical processing. Several different reactor cycles of the PWR, BWR, CANDU, and LMFBR were simulated for this work with the ORIGEN-ARP and ORIGEN 2.2 codes. The spent fuel nuclide concentrations of these reactors were analyzed to find the most informative isotopic ratios indicative of irradiation cycle length and reactor design. Special focus was given to long-lived and stable fission products that would be present many years after their creation. For such nuclides, mass spectrometry analysis methods often have better detection limits than classic gamma-ray spectroscopy. The isotopic ratios {sup 151}Sm/{sup 146}Sm, {sup 149}Sm/{sup 146}Sm, and {sup 244}Cm/{sup 246}Cm were found to be good indicators of fuel cycle length and are well suited for analysis by accelerator mass spectroscopy.
Date: August 24, 2005
Creator: Biegalski, S R; Whitney, S M & Buchholz, B
System: The UNT Digital Library
Analyzing the scalar top co-annihilation region at the ILC (open access)

Analyzing the scalar top co-annihilation region at the ILC

The Minimal Supersymmetric Standard Model opens the possibility of electroweak baryogenesis provided that the light scalar top quark (stop) is lighter than the top quark. In addition, the lightest neutralino is an ideal candidate to explain the existence of dark matter. For a light stop with mass close to the lightest neutralino, the stop-neutralino co-annihilation mechanism becomes efficient, thus rendering the predicted dark matter density compatible with observations. Such a stop may however remain elusive at hadron colliders. Here it is shown that a future linear collider provides a unique opportunity to detect and study the light stop. The production of stops with small stop-neutralino mass differences is studied in a detailed experimental analysis with a realistic detector simulation including a CCD vertex detector for flavor tagging. Furthermore, the linear collider, by precision measurements of superpartner masses and mixing angles, also allows to determine the dark matter relic density with an accuracy comparable to recent astrophysical observations.
Date: August 1, 2005
Creator: Carena, M.; /Fermilab; Finch, A.; U., /Lancaster; Freitas, A.; Milstene, C. et al.
System: The UNT Digital Library
Angular resolution of the Pierre Auger Observatory (open access)

Angular resolution of the Pierre Auger Observatory

We studied the angular resolution of the Pierre Auger Detector using data collected from January 2004 to May 2005. The detector consists of two independent components, the fluorescence detector and the surface detector. Hybrid events, observed simultaneously by both components, have smaller reconstruction uncertainties than the events observed with only one component. The hybrid resolution is extracted from artificial showers generated by laser shots, while the surface detector angular accuracy is then determined from the comparison of the hybrid geometrical fit with the one obtained from the surface detector alone. We used adjacent surface detector stations to cross check our methods. The angular reconstruction accuracy of the surface detector events is given as a function of station multiplicity.
Date: August 1, 2005
Creator: Bonifazi, C.
System: The UNT Digital Library
Anisoplanatism in adaptive optics systems due to pupil aberrations (open access)

Anisoplanatism in adaptive optics systems due to pupil aberrations

Adaptive optics systems typically include an optical relay that simultaneously images the science field to be corrected and also a set of pupil planes conjugate to the deformable mirror of the system. Often, in the optical spaces where DM's are placed, the pupils are aberrated, leading to a displacement and/or distortion of the pupil that varies according to field position--producing a type of anisoplanatism, i.e., a degradation of the AO correction with field angle. The pupil aberration phenomenon is described and expressed in terms of Seidel aberrations. An expression for anisoplanatism as a function of pupil distortion is derived, an example of an off-axis parabola is given, and a convenient method for controlling pupil-aberration-generated anisoplanatism is proposed.
Date: August 1, 2005
Creator: Bauman, B
System: The UNT Digital Library
Anisotropic flow nu2 in Au + Au collisions at RHIC (open access)

Anisotropic flow nu2 in Au + Au collisions at RHIC

Using the RQMD model, transverse momentum dependence of the anisotropic flow v{sub 2} for {pi}, K, nucleon, {phi}, and {lambda}, are studied for Au + Au collisions at {radical}s{sub NN} = 200 GeV. Both hydrodynamic hadron-mass hiragracy (hhmh) at low p{sub T} region and particle type dependence (baryon versus meson) at the intermediate p{sub T} region are reproduced with the model calculations although the model underpredicted the overall values of v{sub 2} by a factor of 2-3. As expected, when the rescatterings are turned off, all v{sub 2} becomes zero. The failure of the hadronic model in predicting the absolute values of hadron v{sub 2} clearly demonstrate the need of early dense partonic interaction in heavy-ion collisions at RHIC. At the intermediate p{sub T}, the hadron type dependence cold also be explained by the vacume hadronic cross sections within the frame of the model. The measurements of collective motion of hadrons from high-energy nuclear collisions can provide information on the dynamical equation of state information of the system [1, 2, 3]. Specifically, the strange and multi-strange hadron flow results have demonstrated the partonic collectivity [5] and the heavy-flavor flow will test the hypothesis of early thermalization in such collisions [4]. …
Date: August 20, 2005
Creator: Lu, Y.; Bleicher, M.; Liu, F.; Kiu, Z.; Sorensen, P.; Stocker,H. et al.
System: The UNT Digital Library
Aperture calculation of the Pierre Auger Observatory surface detector (open access)

Aperture calculation of the Pierre Auger Observatory surface detector

We determine the instantaneous aperture and integrated exposure of the surface detector of the Pierre Auger Observatory, taking into account the trigger efficiency as a function of the energy, arrival direction (with zenith angle lower than 60 degrees) and nature of the primary cosmic-ray. We make use of the so-called Lateral Trigger Probability function (or LTP) associated with an extensive air shower, which summarizes all the relevant information about the physics of the shower, the water tank Cherenkov detector, and the triggers.
Date: August 1, 2005
Creator: Allard, D.; Allekotte, I.; Armengaud, E.; Aublin, J.; Bertou, Xavier; Chou, A. et al.
System: The UNT Digital Library
Application of Sequence-based Methods in Human MicrobialEcology (open access)

Application of Sequence-based Methods in Human MicrobialEcology

Ecologists studying microbial life in the environment have recognized the enormous complexity of microbial diversity for many years, and the development of a variety of culture-independent methods, many of them coupled with high-throughput DNA sequencing, has allowed this diversity to be explored in ever greater detail. Despite the widespread application of these new techniques to the characterization of uncultivated microbes and microbial communities in the environment, their application to human health and disease has lagged behind. Because DNA based-techniques for defining uncultured microbes allow not only cataloging of microbial diversity, but also insight into microbial functions, investigators are beginning to apply these tools to the microbial communities that abound on and within us, in what has aptly been called the second Human Genome Project. In this review we discuss the sequence-based methods for microbial analysis that are currently available and their application to identify novel human pathogens, improve diagnosis of known infectious diseases, and to advance understanding of our relationship with microbial communities that normally reside in and on the human body.
Date: August 29, 2005
Creator: Weng, Li; Rubin, Edward M. & Bristow, James
System: The UNT Digital Library
Applying EVM principles to Tevatron Beam Position Monitor Project (open access)

Applying EVM principles to Tevatron Beam Position Monitor Project

At Fermi National Accelerator Laboratory (Fermilab), the Tevatron high energy particle collider must meet the increasing scientific demand of higher beam luminosity. To achieve this higher luminosity goal, U. S. Department of Energy (DOE) sponsored a major upgrade of capabilities of Fermilab's accelerator complex that spans five years and costs over fifty million dollars. Tevatron Beam Position Monitor (BPM) system upgrade is a part of this project, generally called RunII upgrade project. Since the purpose of the Tevatron collider is to detect the smashing of proton and anti-protons orbiting the circular accelerator in opposite directions, capability to detect positions of both protons and antiprotons at a high resolution level is a desirable functionality of the monitoring system. The original system was installed during early 1980s, along with the original construction of the Tevatron. However, electronic technology available in 1980s did not allow for the detection of significantly smaller resolution of antiprotons. The objective of the upgrade project is to replace the existing BPM system with a new system utilizing capabilities of modern electronics enhanced by a front-end software driven by a real-time operating software. The new BPM system is designed to detect both protons and antiprotons with increased resolution of …
Date: August 1, 2005
Creator: Banerjee, Bakul
System: The UNT Digital Library