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World Trade Organization: China's Membership Status and Normal Trade Relations Issues
A letter report issued by the General Accounting Office with an abstract that begins "GAO provided information on efforts to grant China membership in the World Trade Organization (WTO), focusing on: (1) the status of negotiations for China to join WTO; (2) the results of the negotiations as compared to U.S. objectives for these negotiations; and (3) trade and legal considerations about granting China permanent normal trade relations status."
Date:
March 17, 2000
Creator:
United States. General Accounting Office.
Object Type:
Report
System:
The UNT Digital Library
Women's Pay: Gender Pay Gap in the Federal Workforce Narrows as Differences in Occupation, Education, and Experience Diminish
A letter report issued by the Government Accountability Office with an abstract that begins "Although the pay gap between men and women in the U.S. workforce has narrowed since the 1980s, numerous studies have found that a disparity still exists. In 2003, we found that women in the general workforce earned, on average, 20 cents less for every dollar earned by men in 2000 when differences in work patterns, industry, occupation, marital status, and other factors were taken into account. Other research indicates that this disparity existed for federal workers as well. For example, a 1998 study showed that the pay gap between men and women in the federal workforce decreased significantly between 1976 and 1995, but in 1995 white women still earned 14 cents less for every dollar earned by white men and African-American women earned 8 cents less for every dollar earned by African-American men after available factors related to pay were taken into account. In light of concerns that a pay gap may continue to exist between men and women in the workplace, Congress asked us to examine pay disparity issues and the role the federal government has played in enforcing anti-discrimination laws. In agreement with Congressional …
Date:
March 17, 2009
Creator:
United States. Government Accountability Office.
Object Type:
Report
System:
The UNT Digital Library
Global War on Terrorism: Reported Obligations for the Department of Defense
Correspondence issued by the Government Accountability Office with an abstract that begins "Since 2001, Congress has provided the Department of Defense (DOD) with hundreds of billions of dollars in supplemental and annual appropriations for military operations in support of the Global War on Terrorism (GWOT). DOD's reported annual obligations for GWOT have shown a steady increase from about $0.2 billion in fiscal year 2001 to about $139.8 billion in fiscal year 2007. To continue GWOT operations, the President requested $189.3 billion in appropriations for DOD in fiscal year 2008. Through December 2007, Congress has provided DOD with about $86.8 billion of this request, including $16.8 billion for Mine Resistant Ambush Protected vehicles. As of February 2008, Congress has not taken action on the remaining $102.5 billion. The United States' commitments to GWOT will likely involve the continued investment of significant resources, requiring decision makers to consider difficult trade-offs as the nation faces an increasing long-range fiscal challenge. The magnitude of future costs will depend on several direct and indirect cost variables and, in some cases, decisions that have not yet been made. DOD's future costs will likely be affected by the pace and duration of operations, the types of facilities …
Date:
March 17, 2008
Creator:
United States. Government Accountability Office.
Object Type:
Text
System:
The UNT Digital Library
The NSF Scientific Collections Survey: A Brief Overview of Findings
This white paper describes the state of digital collections resulting from NSF funded research in biodiversity, ecology, environmental health, environmental education, and environmental resource management.
Date:
March 17, 2009
Creator:
National Science Foundation (U.S.)
Object Type:
Text
System:
The UNT Digital Library
Digitral Down Conversion Technology for Tevatron Beam Line Tuner at FNAL
Fermilab is presently in Run II collider operations and is developing instrumentation to improve luminosity. Improving the orbit matching between accelerator components using a Beam Line Tuner (BLT) can improve the luminosity. Digital Down Conversion (DDC) has been proposed as a method for making more accurate beam position measurements. Fermilab has implemented a BLT system using a DDC technique to measure orbit oscillations during injections from the Main Injector to the Tevatron. The output of a fast ADC is downconverted and filtered in software. The system measures the x and y positions, the intensity, and the time of arrival for each proton or antiproton bunch, on a turn-by-turn basis, during the first 1024 turns immediately following injection. We present results showing position, intensity, and time of arrival for both injected and coasting beam. Initial results indicate a position resolution of {approx}20 to 40 microns and a phase resolution of {approx}25 ps.
Date:
March 17, 2008
Creator:
Schappert, W.; Lorman, E.; Scarpine, V.; Ross, M.C.; Sebek, J.; Straumann, T. et al.
Object Type:
Article
System:
The UNT Digital Library
Active Damping of the E-P Instability at the Los Alamos Proton Storage Ring
A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). The feedback system configuration, setup procedures, and optimization of performance are described. Results of several experimental tests of system performance are presented including observations of instability threshold improvement and grow-damp experiments, which yield estimates of instability growth and damping rates. A major effort was undertaken to identify and study several factors limiting system performance. Evidence obtained from these tests suggests that performance of the prototype was limited by higher instability growth rates arising from beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback.
Date:
March 17, 2008
Creator:
Macek, R. J.; Assadi, S.; Byrd, J. M.; Deibele, C. E.; Henderson, S. D.; Lee, S. Y. et al.
Object Type:
Article
System:
The UNT Digital Library
Independent Verification Survey Report for the Operable Unit-1 Miamisburg Closure Project, Miamisburg, OH
The objectives of the independent verification survey were to confirm that remedial actions have been effective in meeting established release criteria and that documentation accurately and adequately describes the current radiological and chemical conditions of the MCP site.
Date:
March 17, 2008
Creator:
Weaver, P.
Object Type:
Report
System:
The UNT Digital Library
Downregulation of Protein 4.1R impairs centrosome function,bipolar spindle organization and anaphase
Centrosomes nucleate and organize interphase MTs and areinstrumental in the assembly of the mitotic bipolar spindle. Here wereport that two members of the multifunctional protein 4.1 family havedistinct distributions at centrosomes. Protein 4.1R localizes to maturecentrioles whereas 4.1G is a component of the pericentriolar matrixsurrounding centrioles. To selectively probe 4.1R function, we used RNAinterference-mediated depletion of 4.1R without decreasing 4.1Gexpression. 4.1R downregulation reduces MT anchoring and organization atinterphase and impairs centrosome separation during prometaphase.Metaphase chromosomes fail to properly condense/align and spindleorganization is aberrant. Notably 4.1R depletion causes mislocalizationof its binding partner NuMA (Nuclear Mitotic Apparatus Protein),essential for spindle pole focusing, and disrupts ninein. Duringanaphase/telophase, 4.1R-depleted cells have lagging chromosomes andaberrant MT bridges. Our data provide functional evidence that 4.1R makescrucial contributions to centrosome integrity and to mitotic spindlestructure enabling mitosis and anaphase to proceed with the coordinatedprecision required to avoid pathological events.
Date:
March 17, 2006
Creator:
Spence, Jeffrey R.; Go, Minjoung M.; Bahmanyar, S.; Barth,A.I.M. & Krauss, Sharon Wald
Object Type:
Article
System:
The UNT Digital Library
A CCD Camera with Electron Decelerator for Intermediate Voltage Electron Microscopy
Electron microscopists are increasingly turning to Intermediate Voltage Electron Microscopes (IVEMs) operating at 300 - 400 kV for a wide range of studies. They are also increasingly taking advantage of slow-scan charge coupled device (CCD) cameras, which have become widely used on electron microscopes. Under some conditions CCDs provide an improvement in data quality over photographic film, as well as the many advantages of direct digital readout. However, CCD performance is seriously degraded on IVEMs compared to the more conventional 100 kV microscopes. In order to increase the efficiency and quality of data recording on IVEMs, we have developed a CCD camera system in which the electrons are decelerated to below 100 kV before impacting the camera, resulting in greatly improved performance in both signal quality and resolution compared to other CCDs used in electron microscopy. These improvements will allow high-quality image and diffraction data to be collected directly with the CCD, enabling improvements in data collection for applications including high-resolution electron crystallography, single-particle reconstruction of protein structures, tomographic studies of cell ultrastructure and remote microscope operation. This approach will enable us to use even larger format CCD chips that are being developed with smaller pixels.
Date:
March 17, 2008
Creator:
Downing, Kenneth H; Downing, Kenneth H. & Mooney, Paul E.
Object Type:
Article
System:
The UNT Digital Library
Microbunching and Beam Break Up in DUV FEL Accelerator
We present the results of electron beam longitudinal modulation studies in the DUV-FEL accelerator. For bunch length determination we used the 'zero-phasing' method, based on a measurement of the chirped electron bunch energy spectra. The measurements revealed a spiky structure in the longitudinal phase space [1]. A model based on space charge effect is considered [2] to explain of the obtained phenomena. The analysis of the energy spectra has shown a sensitivity of the structure to the electron beam peak current, energy and longitudinal non-uniformity of the RF gun drive laser. Analytical calculations have demonstrated a qualitative agreement with experimental observations. Several experiments have been made to compare with theory; measured results are reviewed in this paper. The obtained effect is briefly discussed in relation to high brightness accelerators.
Date:
March 17, 2008
Creator:
Shaftan, T.; Carr, L.; Loos, H.; Sheehy, B.; Graves, William S.; Huang, Z. et al.
Object Type:
Article
System:
The UNT Digital Library
A Lattice with Larger Momentum Compaction for the NLC Main Damping Rings
Previous lattice designs for the Next Linear Collider Main Damping Rings [1] have met the specifications for equilibrium emittance, damping rate and dynamic aperture. Concerns about the effects of the damping wiggler on the beam dynamics [2] led to the aim of reducing the total length of the wiggler to a minimum consistent with the required damping rate, so high-field dipoles were used to provide a significant energy loss in the arcs. However, recent work has shown that the wiggler effects may not be as bad as previously feared. Furthermore, other studies have suggested the need for an increased momentum compaction (by roughly a factor of four) to raise the thresholds of various collective effects. We have therefore developed a new lattice design in which we increase the momentum compaction by reducing the field strength in the arc dipoles, compensating the loss in damping rate by increasing the length of the wiggler. The new lattice again meets the specifications for emittance, damping rate and dynamic aperture, while having the benefit of significantly higher thresholds for a number of instabilities.
Date:
March 17, 2008
Creator:
Woodley, M.; Raubenheimer, Tor O.; Wu, J.; Wolski, A. & /SLAC /LBL, Berkeley
Object Type:
Article
System:
The UNT Digital Library
Fragmentation Cross Sections of 290 and 400 MeV/nucleon 12C Beamson Elemental Targets
Charge-changing and fragment production cross sections at 0circ have been obtained for interactions of 290 MeV/nucleon and 400MeV/nucleon carbon beams with C, CH2, Al, Cu, Sn, and Pb targets. Thesebeams are relevant to cancer therapy, space radiation, and the productionof radioactive beams. We compare to previously published results using Cand CH2 targets at similar beam energies. Due to ambiguities arising fromthe presence of multiple fragments on many events, previous publicationshave reported only cross sections for B and Be fragments. In this work wehave extracted cross sections for all fragment species, using dataobtained at three distinct values of angular acceptance, supplemented bydata taken with the detector stack placed off the beam axis. A simulationof the experiment with the PHITS Monte Carlo code shows fair agreementwith the data obtained with the large acceptance detectors, but agreementis poor at small acceptance. The measured cross sections are alsocompared to the predictions of the one-dimensional cross section modelsEPAX2 and NUCFRG2; the latter is presently used in NASA's space radiationtransport calculations. Though PHITS and NUCFRG2 reproduce thecharge-changing cross sections with reasonable accuracy, none of themodels is able to accurately predict the fragment cross sections for allfragment species and target materials.
Date:
March 17, 2007
Creator:
Zeitlin, C.; Guetersloh, S.; Heilbronn, L.; Miller, J.; Fukumura,A.; Iwata, Y. et al.
Object Type:
Article
System:
The UNT Digital Library
On Sub-linear Convergence for Linearly Degenerate Waves in Capturing Schemes
A common attribute of capturing schemes used to find approximate solutions to the Euler equations is a sub-linear rate of convergence with respect to mesh resolution. Purely nonlinear jumps, such as shock waves produce a first-order convergence rate, but linearly degenerate discontinuous waves, where present, produce sub-linear convergence rates which eventually dominate the global rate of convergence. The classical explanation for this phenomenon investigates the behavior of the exact solution to the numerical method in combination with the finite error terms, often referred to as the modified equation. For a first-order method, the modified equation produces the hyperbolic evolution equation with second-order diffusive terms. In the frame of reference of the traveling wave, the solution of a discontinuous wave consists of a diffusive layer that grows with a rate of t{sup 1/2}, yielding a convergence rate of 1/2. Self-similar heuristics for higher order discretizations produce a growth rate for the layer thickness of {Delta}t{sup 1/(p+1)} which yields an estimate for the convergence rate as p/(p+1) where p is the order of the discretization. In this paper we show that this estimated convergence rate can be derived with greater rigor for both dissipative and dispersive forms of the discrete error. In …
Date:
March 17, 2008
Creator:
Banks, J W; Aslam, T & Rider, W J
Object Type:
Article
System:
The UNT Digital Library
A Parallel Code for Lifetime Simulations in Hadron Storage Rings in the Presence of Parasitic Beam-Beam Interactions
The usual approach to predict particle loss in storage rings in the presence of nonlinearities consists in the determination of the dynamic aperture of the machine. This method, however, will not directly predict the lifetimes of beams. We have developed a code which can, by parallelization and careful speed optimization, predict lifetimes in the presence of 100 parasitic beam-beam crossings by tracking > 10{sup 10} particles-turns. An application of this code to the anti-proton lifetime in the Tevatron at injection is discussed.
Date:
March 17, 2008
Creator:
Kabel, A. C.; Cai, Y.; Erdelyi, B.; Sen, T. & Xiao, M.
Object Type:
Article
System:
The UNT Digital Library
The Shewanella oneidensis MR-1 Fluxome under Various OxygenConditions
The central metabolic fluxes of Shewanella oneidensis MR-1were examined under carbon-limited (aerobic) and oxygen-limited(micro-aerobic) chemostat conditions using 13C labeled lactate as thesole carbon source. The carbon labeling patterns of key amino acids inbiomass were probed using both GC-MS and 13C-NMR. Based on the genomeannotation, a metabolic pathway model was constructed to quantify thecentral metabolic flux distributions. The model showed that thetricarboxylic acid (TCA) cycle is the major carbon metabolism route underboth conditions. The Entner-Doudoroff and pentose phosphate pathways weremainly utilized for biomass synthesis (flux below 5 percent of thelactate uptake rate). The anapleurotic reactions (pyruvate to malate andoxaloacetate to phosphoenolpyruvate) and the glyoxylate shunt wereactive. Under carbon-limited conditions, a substantial amount of carbonwas oxidized via the highly reversible serine metabolic pathway. Fluxesthrough the TCA cycle were less whereas acetate production was more underoxygen limitation than under carbon limitation. Although fluxdistributions under aerobic, micro-aerobic, and shake-flask cultureconditions were dramatically different, the relative flux ratios of thecentral metabolic reactions did not vary significantly. Hence, S.oneidensis metabolism appears to be quite robust to environmentalchanges. Our study also demonstrates the merit of coupling GC-MS with 13CNMR for metabolic flux analysis to reduce the use of 13C labeledsubstrates and to obtain more accurate flux values.
Date:
March 17, 2006
Creator:
Tang, Yinjie J.; Hwang, Judy S.; Wemmer, David E. & Keasling, Jay D.
Object Type:
Article
System:
The UNT Digital Library
Beam Dynamics Studies for the SPARC Project
The aim of the SPARC project, is to promote an R&D activity oriented to the development of a high brightness photoinjector to drive SASE-FEL experiments. We discuss in this paper the status of the beam dynamics simulation activities.
Date:
March 17, 2008
Creator:
Ferrario, M.; Biagini, Maria E.; Boscolo, M.; Fusco, V.; Guiducci, S.; Migliorati, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Positron Beam Propagation in a Meter Long Plasma Channel
Recent experiments and simulations have shown that positron beams propagating in plasmas can be focused and also create wakes with large accelerating gradients. For similar parameters, the wakes driven by positron beams are somewhat smaller compared to the case of an electron beam. Simulations have shown that the wake amplitude can be increased if the positron beam is propagated in a hollow plasma channel (Ref. 1). This paper, compares experimentally, the propagation and beam dynamics of a positron beam in a meter scale homogeneous plasma, to a positron beam hollow channel plasma. The results show that positron beams in hollow channels are less prone to distortions and deflections. Hollow channels were observed to guide the positron beam onto the channel axis. Beam energy loss was also observed implying the formation of a large wake amplitude. The experiments were carried out as part of the E-162 plasma wakefield experiments at SLAC.
Date:
March 17, 2008
Creator:
Marsh, K. A.; Blue, B. E.; Clayton, C. E.; Joshi, C.; Mori, W. B.; Decker, F. -J. et al.
Object Type:
Article
System:
The UNT Digital Library
Renewable Energy Development on Fort Mojave Reservation Feasiblity Study
The Ft. Mojave tribe, whose reservation is located along the Colorado River in the states of Arizona, California, and Nevada near the point where all three states meet, has a need for increased energy supplies. This need is a direct result of the aggressive and successful economic development projects undertaken by the tribe in the last decade. While it is possible to contract for additional energy supplies from fossil fuel sources it was the desire of the tribal power company, AHA MACAV Power Service (AMPS) to investigate the feasibility and desirability of producing power from renewable sources as an alternative to increased purchase of fossil fuel generated power and as a possible enterprise to export green power. Renewable energy generated on the reservation would serve to reduce the energy dependence of the tribal enterprises on off reservation sources of energy and if produced in excess of reservation needs, add a new enterprise to the current mix of economic activities on the reservation. Renewable energy development would also demonstrate the tribe’s support for improving environmental quality, sustainability, and energy independence both on the reservation and for the larger community.
Date:
March 17, 2008
Creator:
Russell Gum, ERCC analytics LLC
Object Type:
Report
System:
The UNT Digital Library
Electron Cloud Generation and Trapping in a Quadrupole Magnet at the Los Alamos Proton Storage Ring
Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the 'prompt' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the 'swept' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to 100 {micro}s. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the …
Date:
March 17, 2008
Creator:
Macek, Robert J.; Browman, Andrew A.; Ledford, John E.; Borden, Michael J.; O'Hara, James F.; McCrady, Rodney C. et al.
Object Type:
Article
System:
The UNT Digital Library
Coupling Correction and Beam Dynamics at Ultralow Vertical Emittance in the ALS
For synchrotron light sources and for damping rings of linear colliders it is important to be able to minimize the vertical emittance and to correct the spurious vertical dispersion. This allows one to maximize the brightness and/or the luminosity. A commonly used tool to measure the skew error distribution is the analysis of orbit response matrices using codes like LOCO. Using the new Matlab version of LOCO and 18 newly installed power supplies for individual skew quadrupoles at the ALS the emittance ratio could be reduced below 0.1% at 1.9 GeV yielding a vertical emittance of about 5 pm. At those very low emittances, additional effects like intra beam scattering become more important, potentially limiting the minimum emittance for machine like the damping rings of linear colliders.
Date:
March 17, 2008
Creator:
Steier, Christoph; Robin, D.; Wolski, A.; Portmann, G.; Safranek, J. & /LBL, Berkeley /SLAC
Object Type:
Article
System:
The UNT Digital Library
General Relativistic Effects in Atom Interferometry
Atom interferometry is now reaching sufficient precision to motivate laboratory tests of general relativity. We begin by explaining the non-relativistic calculation of the phase shift in an atom interferometer and deriving its range of validity. From this we develop a method for calculating the phase shift in general relativity. This formalism is then used to find the relativistic effects in an atom interferometer in a weak gravitational field for application to laboratory tests of general relativity. The potentially testable relativistic effects include the non-linear three-graviton coupling, the gravity of kinetic energy, and the falling of light. We propose experiments, one currently under construction, that could provide a test of the principle of equivalence to 1 part in 10{sup 15} (300 times better than the present limit), and general relativity at the 10% level, with many potential future improvements. We also consider applications to other metrics including the Lense-Thirring effect, the expansion of the universe, and preferred frame and location effects.
Date:
March 17, 2008
Creator:
Dimopoulos, Savas; /Stanford U., Phys. Dept.; Graham, Peter W.; /SLAC /Stanford U., Phys. Dept.; Hogan, Jason M.; Kasevich, Mark A. et al.
Object Type:
Article
System:
The UNT Digital Library
Groundwater Level Status Report for Fiscal Year 2007 - Los Alamos National Laboratory
The status of groundwater level monitoring at Los Alamos National Laboratory in Fiscal Year 2007 is provided in this report. The Groundwater Level Monitoring Project was instituted in 2005 to provide a framework for the collection and processing of quality controlled groundwater level data. This report summarizes groundwater level data for 166 monitoring wells, including 45 regional aquifer wells, 25 intermediate wells, and 96 alluvial wells, and 11 water supply wells. Pressure transducers were installed in 133 monitoring wells for continuous monitoring of groundwater levels. Time-series hydrographs of groundwater level data are presented along with pertinent construction and location information for each well.
Date:
March 17, 2008
Creator:
Shannon P. Allen, Richard J. Koch
Object Type:
Report
System:
The UNT Digital Library
A comparison of water vapor quantities from model short-range forecasts and ARM observations
Model evolution and improvement is complicated by the lack of high quality observational data. To address a major limitation of these measurements the Atmospheric Radiation Measurement (ARM) program was formed. For the second quarter ARM metric we will make use of new water vapor data that has become available, and called the 'Merged-sounding' value added product (referred to as OBS, within the text) at three sites: the North Slope of Alaska (NSA), Darwin Australia (DAR) and the Southern Great Plains (SGP) and compare these observations to model forecast data. Two time periods will be analyzed March 2000 for the SGP and October 2004 for both DAR and NSA. The merged-sounding data have been interpolated to 37 pressure levels (e.g., from 1000hPa to 100hPa at 25hPa increments) and time averaged to 3 hourly data for direct comparison to our model output.
Date:
March 17, 2006
Creator:
Hnilo, J J
Object Type:
Report
System:
The UNT Digital Library
Parallel Simulation Algorithms for the Three Dimensional Strong-Strong Beam-Beam Interaction
The strong-strong beam-beam effect is one of the most important effects limiting the luminosity of ring colliders. Little is known about it analytically, so most studies utilize numeric simulations. The two-dimensional realm is readily accessible to workstation-class computers (cf.,e.g.,[1, 2]), while three dimensions, which add effects such as phase averaging and the hourglass effect, require vastly higher amounts of CPU time. Thus, parallelization of three-dimensional simulation techniques is imperative; in the following we discuss parallelization strategies and describe the algorithms used in our simulation code, which will reach almost linear scaling of performance vs. number of CPUs for typical setups.
Date:
March 17, 2008
Creator:
Kabel, A. C.
Object Type:
Article
System:
The UNT Digital Library