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Optimized Loading for Particle-in-cell Gyrokinetic Simulations

Description: The problem of particle loading in particle-in-cell gyrokinetic simulations is addressed using a quadratic optimization algorithm. Optimized loading in configuration space dramatically reduces the short wavelength modes in the electrostatic potential that are partly responsible for the non-conservation of total energy; further, the long wavelength modes are resolved with good accuracy. As a result, the conservation of energy for the optimized loading is much better that the conservation of energy for the random loading. The method is valid for any geometry and can be coupled to optimization algorithms in velocity space.
Date: May 13, 2004
Creator: Lewandowski, J.L.V.
Partner: UNT Libraries Government Documents Department

Measurement of the Internal Magnetic Field of Plasmas using an Alpha Particle Source

Description: The internal magnetic fields of plasmas can be measured under certain conditions from the integrated v x B deflection of MeV alpha particles emitted by a small radioactive source. This alpha source and large-area alpha particle detector would be located inside the vacuum vessel but outside the plasma. Alphas with a typical energy of 5.5 MeV (241Am) can reach the center of almost all laboratory plasmas and magnetic fusion devices, so this method can potentially determine the q(r) profile of tokamaks or STs. Orbit calculations, background evaluations, and conceptual designs for such a vxB (or ''AVB'') detector are described.
Date: May 13, 2004
Creator: Zweben, S.J.; Darrow, D.S.; Ross, P.W.; Lowrance, J.L. & Renda, G.
Partner: UNT Libraries Government Documents Department

Turkmenistan: Recent Developments and U.S. Interests

Description: This report examines Turkmenistan's halting economic and political reforms under the authoritarian leadership of President Saparmurad Niyazov. It discusses U.S. policy and assistance, including support for grassroots democratization and advocacy for human rights, and provides basic facts and biographical information.
Date: May 13, 2004
Creator: Nichol, Jim
Partner: UNT Libraries Government Documents Department

Nuclear data and measurement series.

Description: It is well established that the high fluences of fast neutrons likely to be encountered in the environments of fusion reactors or fusion materials test facilities will generate substantial quantities of helium (both {sup 4}He and {sup 3}He isotopes), and that the presence of this gas in bulk material can produce serious damage in engineering structures due to swelling. The present study was undertaken to survey the current status (as of early 2004) of the available fast neutron cross section information for helium production in several major structural elements of interest for the development of fusion energy systems. The scope of this study encompasses both compiled experimental cross section data and evaluated cross sections available from major nuclear data libraries used in the analysis of fusion systems. The main conclusion from this work is that the contemporary knowledge of those individual neutron reaction cross sections important for helium production is, in general, very inadequate for the purpose of producing reliable designs for fusion reactors (e.g., ITER) and materials irradiation test facilities (e.g., IFMIF). Since the number of distinct neutron reactions that must be considered is large, and the capabilities (both experimental and theoretical) of the nuclear physics community to adequately determine the cross sections for specific reactions is limited for various reasons, it is recommended, as a consequence of the present investigation, that an engineering approach be undertaken to provide the data needed for system design purposes. The suggested technical approach would involve irradiating small specimens of candidate materials in high fluence neutron fields whose spectra resemble as closely as possible those to be encountered in real fusion facilities, and that direct integrated yield measurements then be made of helium production in these samples, inclusive of all the contributing neutron reaction channels.
Date: May 13, 2004
Creator: Smith, D. L.
Partner: UNT Libraries Government Documents Department

Complete photo-fragmentation of the deuterium molecule

Description: All properties of molecules, from binding and excitation energies to their geometry, are determined by the highly correlated initial state wavefunction of the electrons and nuclei. Perhaps surprisingly, details of these correlations can be revealed by studying the break-up of these systems into their constituents. The fragmentation might be initiated by the absorption of a single photon [1, 2, 3, 4, 5, 6], collision with a charged particle [7, 8] or exposure to a strong laser pulse [9, 10]. If the exciting interaction is sufficiently understood, one can use the fragmentation process as a tool to learn about the bound initial state [11, 12]. However, often the interaction and the fragment motions pose formidable challenges to quantum theory [13, 14, 15]. Here we report the coincident measurement of the momenta of both nuclei and both electrons from the single photon induced fragmentation of the deuterium molecule. The results reveal that the correlated motion of the electrons is strongly dependent on the inter-nuclear separation in the molecular ground state at the instant of photon absorption.
Date: May 13, 2004
Creator: Weber, Thorsten; Czasch, Achim O.; Jagutzki, Ottmar; Muller, Alkis K.; Mergel, Volker; Kheifets, A. et al.
Partner: UNT Libraries Government Documents Department

Solid State Neutral Particle Analyzer Array on NSTX

Description: A Solid State Neutral Particle Analyzer (SSNPA) array has been installed on the National Spherical Torus Experiment (NSTX). The array consists of four chords viewing through a common vacuum flange. The tangency radii of the viewing chords are 60, 90, 100, and 120 cm. They view across the three co-injection neutral beam lines (deuterium, 80 keV (typ.) with tangency radii 48.7, 59.2, and 69.4 cm) on NSTX and detect co-going energetic ions. A silicon photodiode used was calibrated by using a mono-energetic deuteron beam source. Deuterons with energy above 40 keV can be detected with the present setup. The degradation of the performance was also investigated. Lead shots and epoxy are used for neutron shielding to reduce handling any hazardous heavy metal. This method also enables us to make an arbitrary shape to be fit into the complex flight tube.
Date: May 13, 2004
Creator: Shinohara, K.; Darrow, D.S.; Roquemore, A.L.; Medley, S.S. & Cecil, F.E.
Partner: UNT Libraries Government Documents Department

Observation of a High Performance Operating Regime with Small Edge-Localized Modes in the National Spherical Torus Experiment

Description: We report observation of a high performance scenario in the National Spherical Torus Experiment with very small edge-localized modes (ELMs). These ELMs have no measurable impact on stored energy and are consistent with high bootstrap current operation with line average density approaching Greenwald scaling. The ELM perturbation is observed to typically originate near the lower divertor region, as opposed to the outer midplane for ELMs described in the literature. If extrapolable, this scenario would provide an attractive operating regime for next step fusion experiments
Date: May 13, 2004
Creator: Maingi, R.; Tritz, K.; Fredrickson, E.D.; Menard, J.E.; Sabbagh, S.A.; Stutman, D. et al.
Partner: UNT Libraries Government Documents Department

Phenomenology of Compressional Alfven Eigenmodes

Description: Coherent oscillations with frequency 0.3 {le} {omega}/{omega}{sub ci} {le} 1, are seen in the National Spherical Torus Experiment [M. Ono, S.M. Kaye, Y-K.M. Peng, et al., Nucl. Fusion 40, 557 (2000)]. This paper presents new data and analysis comparing characteristics of the observed modes to the model of compressional Alfven eigenmodes (CAE). The toroidal mode number has been measured and is typically between 7 < n < 9. The polarization of the modes, measured using an array of four Mirnov coils, is found to be compressional. The frequency scaling of the modes agrees with the predictions of a numerical 2-D code, but the detailed structure of the spectrum is not captured with the simple model. The fast ion distribution function, as calculated with the beam deposition code in TRANSP [R.V. Budny, Nucl. Fusion 34, 1247 (1994)], is shown to be qualitatively consistent with the constraints of the Doppler-shifted cyclotron resonance drive model. This model also predicts the observed scaling of the low frequency limit for CAE.
Date: May 13, 2004
Creator: Fredrickson, E.D.; Gorelenkov, N.N. & Menard, J.
Partner: UNT Libraries Government Documents Department

OpenAD : algorithm implementation user guide.

Description: Research in automatic differentiation has led to a number of tools that implement various approaches and algorithms for the most important programming languages. While all these tools have the same mathematical underpinnings, the actual implementations have little in common and mostly are specialized for a particular programming language, compiler internal representation, or purpose. This specialization does not promote an open test bed for experimentation with new algorithms that arise from exploiting structural properties of numerical codes in a source transformation context. OpenAD is being designed to fill this need by providing a framework that allows for relative ease in the implementation of algorithms that operate on a representation of the numerical kernel of a program. Language independence is achieved by using an intermediate XML format and the abstraction of common compiler analyses in Open-Analysis. The intermediate format is mapped to concrete programming languages via two front/back end combinations. The design allows for reuse and combination of already implemented algorithms. We describe the set of algorithms and basic functionality currently implemented in OpenAD and explain the necessary steps to add a new algorithm to the framework.
Date: May 13, 2004
Creator: Utke, J.
Partner: UNT Libraries Government Documents Department

Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

Description: Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.
Date: May 13, 2004
Creator: Ji, Hantao; Fox, William; Pace, David & Rappaport, H.L.
Partner: UNT Libraries Government Documents Department

Final Technical Report ''Double discontinuities in space plasma''

Description: This research used high-resolution magnetic field data to examine the interior structures of MHD shocks in interplanetary space and in the magnetotail; we discovered that a slow-mode shock is often followed by an adjoining rotational discontinuity layer on the postshock side. The thickness of each layer is of the order of a few ion inertial lengths. Such a compound structure is known as a double discontinuity. When the magnetic field rotates by several degrees per ion inertial length inside a thin layer, the Hall current term becomes important in the generalized Ohm's law. Steady state solutions based on the Hall-MHD theory have been obtained to show the merging of a rotational layer and a slow shock layer to form a compound structure like the observed double discontinuities.
Date: May 13, 2004
Creator: Whang, Yun Chow
Partner: UNT Libraries Government Documents Department

Order-to-chaos transition in rotational nuclei

Description: The authors have studied the narrow (valley-ridge) structure in the {gamma}-ray spectrum following a heavy-ion fusion reaction that produces several ytterbium nuclei. The intensity of this structure can be quantitatively related to the average chaotic behavior in these nuclei and they have traced this behavior from nearly fully ordered to nearly fully chaotic.
Date: May 13, 2004
Creator: Stephens, F.S.; Deleplanque, M.A.; Lee, I.Y.; Macchiavelli, A.O.; Ward, D.; Fallon, P. et al.
Partner: UNT Libraries Government Documents Department

Spatial and temporal patterns of beetles associated with coarse woody debris in managed bottomland hardwood forests.

Description: For. Ecol. and Mgt. 199:259-272. Malaise traps were used to sample beetles in artificial canopy gaps of different size (0.13 ha, 0.26 ha, and0.50 ha) and age in a South Carolina bottomland hardwood forest. Traps were placed at the center, edge, and in the surrounding forest of each gap. Young gaps (ý 1 year) had large amounts of coarse woody debris compared to the surrounding forest, while older gaps (ý 6 years) had virtually none. The total abundance and diversity of wood-dwelling beetles (Buprestidae, Cerambycidae, Brentidae, Bostrichidae, and Curculionidae (Scolytinae and Platypodinae)) was higher in the center of young gaps than in the center of old gaps. The abundance was higher in the center of young gaps than in the surrounding forest, while the forest surrounding old gaps and the edge of old gaps had a higher abundance and diversity of wood-dwelling beetles than did the center of old gaps. There was no difference in wood-dwelling beetle abundance between gaps of different size, but diversity was lower in 0.13 ha old gaps than in 0.26 ha or 0.50 ha old gaps. We suspect that gap size has more of an effect on woodborer abundance than indicated here because malaise traps sample a limited area. The predaceous beetle family Cleridae showed a very similar trend to that of the woodborers. Coarse woody debris is an important resource for many organisms, and our results lend further support to forest management practices that preserve coarse woody debris created during timber removal.
Date: May 13, 2004
Creator: Ulyshen, M., D.; Hanula, J., L.; Horn, S.; Kilgo, J., C. & Moorman, C., E.
Partner: UNT Libraries Government Documents Department

Business-Owned Life Insurance: More Data Could Be Useful in Making Tax Policy Decisions

Description: A letter report issued by the General Accounting Office with an abstract that begins "Business-owned life insurance is permanent insurance held by employers on the lives of their employees, and the employer is the beneficiary of these policies. Its attractive features, common to all permanent life insurance, generally include both tax-deferred accumulation of earnings on the policies' cash value and tax-free receipt of the death benefit. Legislators have expressed concerns about the ability of employers to receive tax-favored treatment from insuring their employees' lives. GAO was asked to discuss (1) the prevalence and use of business-owned life insurance, (2) federal and state regulation and oversight of these policies, and (3) the potential usefulness of and costs associated with obtaining more comprehensive data on business-owned life insurance."
Date: May 13, 2004
Creator: United States. General Accounting Office.
Partner: UNT Libraries Government Documents Department

Military Operations: DOD's Fiscal Year 2003 Funding and Reported Obligations in Support of the Global War on Terrorism

Description: A letter report issued by the General Accounting Office with an abstract that begins "The Global War on Terrorism--principally involving operations in Afghanistan and Iraq--was funded in fiscal year 2003 by Congress's appropriation of almost $69 billion. To assist Congress in its oversight of spending, GAO is undertaking a series of reviews relating to contingency operations in support of the Global War on Terrorism. In September 2003, GAO issued a report that discussed fiscal year 2003 obligations and funding for the war through June 2003. This report continues the review of fiscal year 2003 by analyzing obligations reported in support of the Global War on Terrorism and reviews whether the amount of funding received by the military services was adequate to cover DOD's obligations for the war from October 1, 2002, through September 30, 2003. GAO will also review the war's reported obligations and funding for fiscal year 2004."
Date: May 13, 2004
Creator: United States. General Accounting Office.
Partner: UNT Libraries Government Documents Department

Emergency Preparedness: Federal Funds for First Responders

Description: Testimony issued by the General Accounting Office with an abstract that begins "The terrorist attacks of September 11, 2001, highlighted the critical role first responders play at the state and local level when a disaster or emergency strikes. In fiscal years 2002 and 2003, Congress appropriated approximately $13.9 billion for domestic preparedness. A large portion of these funds were for the nation's first responders to enhance their ability to address future emergencies, including potential terrorist attacks. These funds are primarily to assist with planning, equipment purchases, training and exercises, and administrative costs. They are available to first responders mainly through the State Homeland Security Grant Programs and Urban Area Security Initiative grants. Both programs are administered through the Department of Homeland Security's Office for Domestic Preparedness. In this testimony, GAO addressed the need to balance expeditious distribution of first responder funds to states and localities with accountability for effective use of those funds and summarized major findings related to funding distribution delays and delays involving funds received by local governments, as presented in reports issued by the Department of Homeland Security Office of Inspector General and the House Select Committee on Homeland Security. The testimony incorporated supporting evidence on first-responder funding issues based on ongoing GAO work in selected states."
Date: May 13, 2004
Creator: United States. General Accounting Office.
Partner: UNT Libraries Government Documents Department

Child And Family Services Reviews: States and HHS Face Challenges in Assessing and Improving State Performance

Description: Testimony issued by the General Accounting Office with an abstract that begins "In 2001, the Department of Health and Human Services' (HHS) Administration for Children and Families (ACF) implemented the Child and Family Services Reviews (CFSR) to increase states' accountability. The CFSR uses states' data profiles and statewide assessments, as well as interviews and an on-site case review, to measure state performance on 14 outcomes and systemic factors, including child well-being and the provision of caseworker training. The CFSR also requires progress on a program improvement plan (PIP); otherwise ACF may apply financial penalties. This testimony is based on our April 2004 report and addresses (1) ACF's and the states' experiences preparing for and conducting the statewide assessments and on-site reviews; (2) ACF's and the states' experiences developing, funding, and implementing items in PIPs; and (3) any additional efforts that ACF has taken beyond the CFSR to improve state performance. For the April 2004 report, we surveyed all 50 states, the District of Columbia, and Puerto Rico regarding their experiences throughout the CFSR process, visited 5 states to obtain first-hand information, and conducted a content analysis of all 31 available PIPs as of January 1, 2004. We also interviewed HHS officials--including those in all 10 regional offices--and key child welfare experts."
Date: May 13, 2004
Creator: United States. General Accounting Office.
Partner: UNT Libraries Government Documents Department

Nonproliferation: Further Improvements Needed in U.S. Efforts to Counter Threats from Man-Portable Air Defense Systems

Description: A letter report issued by the General Accounting Office with an abstract that begins "The proliferation of man-portable air defense systems (MANPADS) has been of growing concern to the United States and other governments. The United States is pursuing a wide variety of activities internationally and domestically to address this threat. GAO was asked to assess efforts by (1) the State Department to control global proliferation of MANPADS, (2) the Department of Defense (DOD) to monitor end-use of U.S.-exported Stingers, and (3) the Department of Homeland Security (DHS) to develop technical countermeasures to minimize the threat of a MANPADS attack."
Date: May 13, 2004
Creator: United States. General Accounting Office.
Partner: UNT Libraries Government Documents Department

Recommendations for Independent Science Review

Description: A document pertaining to water resource development projects in the United States. These projects are complex and the Corps of Engineers must balance local and national goals with a limited budget used to manage river and coastal systems.
Date: May 13, 2004
Creator: Environmental Advisory Board
Partner: UNT Libraries Government Documents Department

Oxidative DNA damage background estimated by a system model of base excision repair

Description: Human DNA can be damaged by natural metabolism through free radical production. It has been suggested that the equilibrium between innate damage and cellular DNA repair results in an oxidative DNA damage background that potentially contributes to disease and aging. Efforts to quantitatively characterize the human oxidative DNA damage background level based on measuring 8-oxoguanine lesions as a biomarker have led to estimates varying over 3-4 orders of magnitude, depending on the method of measurement. We applied a previously developed and validated quantitative pathway model of human DNA base excision repair, integrating experimentally determined endogenous damage rates and model parameters from multiple sources. Our estimates of at most 100 8-oxoguanine lesions per cell are consistent with the low end of data from biochemical and cell biology experiments, a result robust to model limitations and parameter variation. Our results show the power of quantitative system modeling to interpret composite experimental data and make biologically and physiologically relevant predictions for complex human DNA repair pathway mechanisms and capacity.
Date: May 13, 2004
Creator: Sokhansanj, B A & Wilson, III, D M
Partner: UNT Libraries Government Documents Department