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1,695 Matching Results
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Prediction of atmospheric δ13CO2 using fossil plant tissues. Reviews of Geophysics, 46/2006RG0002.(view/download pdf)
To summarize the content: we presented the results of laboratory experiments designed to quantify the relationship between plant tissue δ13C and δ13CO2 values under varying environmental conditions, including differential pCO2 ranging from 1 to 3 times today’s levels. As predicted, plants grown under elevated pCO2 showed increased average biomass compared to controls grown at the same temperature. Across a very large range in δ13Ca (≈ 24 ‰) and pCO2 (≈ 740 ppmv) we observed a consistent correlation between δ13Ca and δ13Cp (p<0.001). We show an average isotopic depletion of −25.4 ‰ for above-ground tissue and −23.2 ‰ for below-ground tissue of Raphanus sativus L. relative to the composition of the atmosphere under which it formed. For both above- and below-ground tissue, grown at both ~23 ˚C and ~29 ˚C, correlation was strong and significant (r2 ≥ 0.98, p<0.001); variation in pCO2 level had little or no effect on this relationship.
Date:
June 30, 2008
Creator:
A.H. Jahren, N.C. Arens and S.A. Harbeson
Object Type:
Report
System:
The UNT Digital Library
Measurement of b-jet Shapes in Inclusive Jet Production in p anti-p Collisions at s**(1/2) = 1.96-TeV
We present a measurement of the shapes of b-jets using 300 pb{sup -1} of data obtained with the upgraded Collider Detector at Fermilab (CDF II) in p{bar p} collisions at center of mass energy {radical}s = 1.96 TeV. This measurement covers a wide transverse momentum range, from 52 to 300 GeV/c. Samples of heavy-flavor enhanced jets together with inclusive jets are used to extract the average shapes of b-jets. The b-jets are expected to be broader than inclusive jets. Moreover, b-jets containing a single b-quark are expected to be narrower than those containing a b{bar b} pair from gluon splitting. The measured b-jet shapes are found to be significantly broader than expected from the pythia and HERWIG Monte Carlo simulations. This effect may arise from an underestimation of the fraction of b-jets originating from gluon splitting in these simulations.
Date:
June 1, 2008
Creator:
Aaltonen, T.
Object Type:
Article
System:
The UNT Digital Library
Forward-Backward Asymmetry in Top Quark Production in ppbar Collisions at sqrt{s}=1.96 TeV
Reconstructable final state kinematics and charge assignment in the reaction p{bar p} {yields} t{bar t} allows tests of discrete strong interaction symmetries at high energy. We define frame dependent forward-backward asymmetries for the outgoing top quark in both the p{bar p} and t{bar t} rest frames, correct for experimental distortions, and derive values at the parton-level. Using 1.9 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron, we measure forward-backward top quark production asymmetries in the p{bar p} and t{bar t} rest frames of A{sub FB}{sup p{bar p}} = 0.17 {+-} 0.08 and A{sub FB}{sup t{bar t}} = 0.24 {+-} 0.14.
Date:
June 1, 2008
Creator:
Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; Alvarez Gonzalez, B.; Amerio, S. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for long-lived particles decaying into electron or photon pairs with the D0 detector
In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, like hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark.
Date:
June 1, 2008
Creator:
Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T. et al.
Object Type:
Article
System:
The UNT Digital Library
Feedback damper system for quadrupole oscillations after transition at RHIC.
The heavy ion beam at RHIC undergoes strong quadrupole oscillations just after it crosses transition, which leads to an increase in bunch length making rebucketing less effective. A feedback system was built to damp these quadrupole oscillations and in this paper the characteristics of the system and the results obtained are presented and discussed.
Date:
June 23, 2008
Creator:
Abreu, N.; Blaskiewicz, M.; Brennan, J. M. & Schultheiss, C.
Object Type:
Article
System:
The UNT Digital Library
The effect of head-on beam-beam compensation on the stochastic boundaries and particle diffusion in RHIC.
To compensate the effects from the head-on beam-beam interactions in the polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), an electron lens (elens) is proposed to collide head-on with the proton beam. We used an extended version of SixTrack for multiparticle beam-beam simulation in order to study the effect of the e-lens on the stochastic boundary and also on diffusion. The stochastic boundary was analyzed using Lyapunov exponents and the diffusion was characterized as the increase in the rms spread of the action. For both studies the simulations were performed with and without the e-lens and with full and partial compensation. Using the simulated values of the diffusion an attempt to calculate the emittance growth rate is presented.
Date:
June 23, 2008
Creator:
Abreu,N.; Beebe-Wang, J.; FischW; Luo, Y. & Robert-Demolaize, G.
Object Type:
Article
System:
The UNT Digital Library
Energy loss of coasting gold ions and deuterons in RHIC.
The total energy loss of coasting gold ion beams was measured at RHIC at two energies, corresponding to a gamma of 75.2 and 107.4. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.
Date:
June 23, 2008
Creator:
Abreu,N.; Blaskiewicz, M.; Brown, K.A.; Butler, J.J.; FischW; Harvey, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Confirmatory Survey for the Partial Site Release at the ABB Inc. CE Winsor Site, Windsor, CT
The objectives of the confirmatory surveys were to confirm that remedial actions had been effective in meeting established release criteria and that documentation accurately and adequately describes the final radiological conditions of the PSR Impacted Areas.
Date:
June 27, 2008
Creator:
Adams, W.C.
Object Type:
Report
System:
The UNT Digital Library
Outlook and Challenges for Chinese Coal
China has been, is, and will continue to be a coal-powered economy. The rapid growth of coal demand since 2001 has created deepening strains and bottlenecks that raise questions about supply security. Although China's coal is 'plentiful,' published academic and policy analyses indicate that peak production will likely occur between 2016 and 2029. Given the current economic growth trajectory, domestic production constraints will lead to a coal gap that is not likely to be filled with imports. Urbanization, heavy industry growth, and increasing per-capita consumption are the primary drivers of rising coal usage. In 2006, the power sector, iron and steel, and cement accounted for 71% of coal consumption. Power generation is becoming more efficient, but even extensive roll-out of the highest efficiency units could save only 14% of projected 2025 coal demand. If China follows Japan, steel production would peak by 2015; cement is likely to follow a similar trajectory. A fourth wedge of future coal consumption is likely to come from the burgeoning coal-liquefaction and chemicals industries. New demand from coal-to-liquids and coal-to-chemicals may add 450 million tonnes of coal demand by 2025. Efficient growth among these drivers indicates that China's annual coal demand will reach 4.2 to …
Date:
June 20, 2008
Creator:
Aden, Nathaniel T.; Fridley, David G. & Zheng, Nina
Object Type:
Report
System:
The UNT Digital Library
Recent experience in the fabrication and brazing of ceramic beam tubes for kicker magnets at FNAL
Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermi National Accelerator Laboratory. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil (titanium/incusil) alloy brazing material are stacked in the furnace and then brazed in the furnace at 1000 C. The ceramic specified is 99.8% Alumina, Al{sub 2}O{sub 3}, a strong recrystallized high-alumina fabricated by slip casting. Recent experience at Fermilab with the fabrication and brazing of these tubes has brought to light numerous problems including tube breakage and cracking and also the difficulty of brazing the tube to produce a leak-tight joint. These problems may be due to the ceramic quality, voids in the ceramic, thinness of the wall, and micro-cracks in the ends which make it difficult to braze because it cannot fill tiny surface cracks which are caused by grain pullout during the cutting process. Solutions which are being investigated include lapping the ends of the tubes before brazing to eliminate the micro-cracks and also metallization of the tubes.
Date:
June 1, 2008
Creator:
Ader, C. R.; Jensen, C.; Reilly, R.; Snee, D. & Wilson, J. H.
Object Type:
Article
System:
The UNT Digital Library
The Neutrino Flux Prediction at MiniBooNE
The Booster Neutrino Experiment (MiniBooNE) searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations using the {Omicron}(1 GeV) neutrino beam produced by the Booster synchrotron at the Fermi National Accelerator Laboratory (FNAL). The Booster delivers protons with 8 GeV kinetic energy (8.89 GeV=c momentum) to a beryllium target, producing neutrinos from the decay of secondary particles in the beam line. We describe the Monte Carlo simulation methods used to estimate the flux of neutrinos from the beamline incident on the MiniBooNE detector for both polarities of the focusing horn. The simulation uses the Geant4 framework for propagating particles, accounting for electromagnetic processes and hadronic interactions in the beamline materials, as well as the decay of particles. The absolute double differential cross sections of pion and kaon production in the simulation have been tuned to match external measurements, as have the hadronic cross sections for nucleons and pions. The statistical precision of the flux predictions is enhanced through reweighting and resampling techniques. Systematic errors in the flux estimation have been determined by varying parameters within their uncertainties, accounting for correlations where appropriate.
Date:
June 1, 2008
Creator:
Aguilar-Arevalo, A. A.
Object Type:
Article
System:
The UNT Digital Library
Alignment of the Pixel and SCT Modules for the 2004 ATLAS Combined Test Beam
A small set of final prototypes of the ATLAS Inner Detector silicon tracking system(Pixel Detector and SemiConductor Tracker), were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignmentof the silicon modules is of the order of 5 mm in their most precise coordinate.
Date:
June 2, 2008
Creator:
Ahmad, A.; Andreazza, A.; Atkinson, T.; Baines, J.; Barr, A. J.; Beccherle, R. et al.
Object Type:
Article
System:
The UNT Digital Library
Developing Supersonic Impactor and Aerodynamic Lens for Separation and Handling of Nano-Sized Particles
A computational model for supersonic flows of compressible gases in an aerodynamic lens with several lenses and in a supersonic/hypersonic impactor was developed. Airflow conditions in the aerodynamic lens were analyzed and contour plots for variation of Mach number, velocity magnitude and pressure field in the lens were evaluated. The nano and micro-particle trajectories in the lens and their focusing and transmission efficiencies were evaluated. The computational model was then applied to design of a aerodynamic lens that could generate focus particle beams while operating under atmospheric conditions. The computational model was also applied to airflow condition in the supersonic/hypersonic impactor. Variations of airflow condition and particle trajectories in the impactor were evaluated. The simulation results could provide understanding of the performance of the supersonic and hypersonic impactors that would be helpful for the design of such systems.
Date:
June 30, 2008
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
High-Performance Systems Biology and Associated Combinatorial Scientific Computing Problems
Presentation discussing a metabolomics study focused on a hydrogen-producing green alga and the problems encountered that are addressable using combinatorial scientific computing methods.
Date:
June 1, 2008
Creator:
Alber, D.
Object Type:
Presentation
System:
The UNT Digital Library
Timpson & Tenaha News (Timpson, Tex.), Vol. 26, No. 23, Ed. 1 Thursday, June 5, 2008
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
June 5, 2008
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 26, No. 24, Ed. 1 Thursday, June 12, 2008
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
June 12, 2008
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 26, No. 25, Ed. 1 Thursday, June 19, 2008
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
June 19, 2008
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
Timpson & Tenaha News (Timpson, Tex.), Vol. 26, No. 26, Ed. 1 Thursday, June 26, 2008
Weekly newspaper from Timpson, Texas that includes local, state, and national news along with advertising.
Date:
June 26, 2008
Creator:
Alexander, Nancy
Object Type:
Newspaper
System:
The Portal to Texas History
A kinetic approach to cosmic ray induced streaming instability at supernova shocks
We show here that a purely kinetic approach to the excitation of waves by cosmic rays in the vicinity of a shock front leads to predict the appearance of a non-alfvenic fastly growing mode which has the same dispersion relation as that previously found by Bell (2004) by treating the plasma in the MHD approximation. The kinetic approach allows us to investigate the dependence of the dispersion relation of these waves on the microphysics of the current which compensates the cosmic ray flow. We also show that a resonant and a non-resonant mode may appear at the same time and one of the two may become dominant on the other depending on the conditions in the acceleration region. We discuss the role of the unstable modes for magnetic field amplification and particle acceleration in supernova remnants at different stages of the remnant evolution.
Date:
June 1, 2008
Creator:
Amato, Elena; Observ., /Arcetri; Blasi, Pasquale & Sasso, /Arcetri Observ. /Fermilab /Gran
Object Type:
Article
System:
The UNT Digital Library
LARP Long Nb3Sn Quadrupole Design
A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb{sub 3}Sn conductor. The goal of these magnets is to be a proof of principle that Nb{sub 3}Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.
Date:
June 1, 2008
Creator:
Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S. et al.
Object Type:
Article
System:
The UNT Digital Library
Assembly and Test of a Support Structure for 3.6 m Long Nb3Sn Racetrack Coils
The LHC Accelerator Research Program (LARP) is currently developing 4 m long Nb{sub 3}Sn quadrupole magnets for a possible upgrade of the LHC Interaction Regions (IR). In order to provide a reliable test bed for the fabrication and test of long Nb{sub 3}Sn coils, LARP has started the development of the long racetrack magnet LRS01. The magnet is composed of two 3.6 m long racetrack coils contained in a support structure based on an aluminum shell pre-tensioned with water-pressurized bladders and interference keys. For the phase-one test of the assembly procedure and loading operation, the structure was pre-stressed at room temperature and cooled down to 77 K with instrumented, solid aluminum 'dummy coils'. Mechanical behavior and stress homogeneity were monitored with strain gauges mounted on the shell and the dummy coils. The dummy coils were replaced with reacted and impregnated Nb{sub 3}Sn coils in a second assembly procedure, followed by cool-down to 4.5 K and powered magnet test. This paper report on the assembly and loading procedures of the support structure as well as the comparison between strain gauge data and 3D model predictions.
Date:
June 1, 2008
Creator:
Ambrosio, G.; Anerella, M.; Caspi, S.; Cheng, D. W.; Felice, H.; Hafalia, A. R. et al.
Object Type:
Article
System:
The UNT Digital Library
Effect of Axial Loading on Quench Performance in Nb3Sn Magnets
A series of tests has been performed at Lawrence Berkeley National Laboratory (LBNL) and Fermi National Accelerator Laboratory (FNAL) with the goal of assessing the influence of coil axial pre-load on Nb{sub 3}Sn magnet training. The tests involved two subscale Nb{sub 3}Sn magnets: SQ02, a quadrupole magnet fabricated as part of the US LHC Accelerator Research Program (LARP), and SD01, a dipole magnet developed in collaboration between CEA/Saclay and LBNL. Both magnets used similar Nb{sub 3}Sn flat racetrack coils from LBNL Subscale Magnet Program, and implemented an axial support system composed of stainless steel end-plates and aluminum rods. The system was designed to withstand full longitudinal electro-magnetic forces and provide controllable preloads. Quench performances, training, and quench locations have been recorded in various axial loading conditions. Test results are reported.
Date:
June 1, 2008
Creator:
Ambrosio, G.; Bordini, B.; Caspi, S.; Dietderich, D. R.; Felice, H.; Hafalia, A. R. et al.
Object Type:
Article
System:
The UNT Digital Library
Southwest Retort, Volume 60, Number 9, June 2008
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
June 2008
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
The Newsletter of the Texas Chapter of the American Fisheries Society, Volume 34, Number 2, Summer 2008
Newsletter of the Texas Chapter of the American Fisheries Society containing information about the organization, membership, and field of aquaculture and ecosystem management.
Date:
June 2008
Creator:
American Fisheries Society. Texas Chapter.
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History