2,143 research outputs found
Observation of String Breaking in QCD
We numerically investigate the transition of the static quark-antiquark
string into a static-light meson-antimeson system. Improving noise reduction
techniques, we are able to resolve the signature of string breaking dynamics
for n_f=2 lattice QCD at zero temperature. This result can be related to
properties of quarkonium systems. We also study short-distance interactions
between two static-light mesons.Comment: 27 pages, 22 figures, changed decimal place of errors in 3 entries of
Table, corrected reference
Flavour singlet pseudoscalar masses in N_f = 2 QCD
We perform a lattice mass analysis in the flavour singlet pseudoscalar
channel on the SESAM and TXL full QCD vacuum configurations, with 2 active
flavours of dynamical Wilson fermions at beta = 5.6. At our inverse lattice
spacing, a^-1 = 2.3 GeV, we retrieve by a chiral extrapolation to the physical
light quark masses the value m_eta' = 3.7(+8)(-4) m_pi. A crude extrapolation
from (N_f = 3) phenomenology would suggest m_eta' \approx 5.1 m_pi for N_f = 2
QCD. we verify that the mass gap between the singlet state eta' and the pi
flavour triplt state is due to gauge configurations with non-trivial topology.Comment: 8 pages, 10 figure
Silicate Treatment to Inhibit Corrosion of Hot, Potable Water Systems, Phase I
Research has been conducted to determine the variables involved in the use of the sodium silicate treatment technique and in the design of a system which utilizes or controls these variables for the efficient control of corrosion of steel, galvanized steel, and copper piping exposed to hot, potable water. Test loops were designed and constructed at nine selected sites to investigate the influence that temperature flow velocity, water chemistry, and silicate formulation and dosage have on the effectiveness of sodium silicate as a corrosion inhibitor for steel, galvanized steel, and copper piping exposed to heat (140°F and 180°F) in aggressive, potable
water of four different compositions. Recommendations are made to conduct further research to determine ( 1) silicate treatment variables involved in treating low alkalinity and low hardness water; {2) the practicality of employing silicate treatment of hard water; (3) the effectiveness of zinc salts as a supplement to silicate; and (4) the corrosion resistance of ASTM A-268 Grade 409 stainless steel.AIR FORCE WEAPONS LABORATORY - Air Force Systems Command - Kirtland Air Force Base, New MericoOpe
The nucleon to Delta electromagnetic transition form factors in lattice QCD
The electromagnetic nucleon to Delta transition form factors are evaluated
using two degenerate flavors of dynamical Wilson fermions and using dynamical
sea staggered fermions with domain wall valence quarks. The two subdominant
quadrupole form factors are evaluated for the first time in full QCD to
sufficient accuracy to exclude a zero value, which is taken as a signal for
deformation in the nucleon-Delta system. For the Coulomb quadrupole form factor
the unquenched results show deviations from the quenched results at low q^2
bringing dynamical lattice results closer to experiment, thereby confirming the
importance of pion cloud contributions on this quantity.Comment: 15 pages, 8 Figure
Far-Ultraviolet Color Gradients in Early-Type Galaxies
We discuss far-UV (1500 A) surface photometry and FUV-B color profiles for 8
E/S0 galaxies from images taken with the Ultraviolet Imaging Telescope,
primarily during the Astro-2 mission. In three cases, the FUV radial profiles
are more consistent with an exponential than a de Vaucouleurs function, but
there is no other evidence for the presence of a disk or of young, massive
stars. In all cases except M32 the FUV-B color becomes redder at larger radii.
There is a wide range of internal radial FUV-B color gradients. However, we
find no correlation between the FUV-B color gradients and internal metallicity
gradients based on Mg absorption features. We conclude that metallicity is not
the sole parameter controlling the "UV upturn component" in old populations.Comment: 11 pages; tar.gz file includes LaTeX text file, 3 PostScript figures.
Paper to be published in ApJ Letter
Ultraviolet Imaging of the Globular Cluster 47 Tucanae
We have used the Ultraviolet Imaging Telescope to obtain deep far-UV (1620
Angstrom), 40' diameter images of the prototypical metal-rich globular cluster
47 Tucanae. We find a population of about 20 hot (Teff > 9000 K) objects near
or above the predicted UV luminosity of the hot horizontal branch (HB) and
lying within two half-light radii of the cluster center. We believe these are
normal hot HB or post-HB objects rather than interacting binaries or blue
stragglers. IUE spectra of two are consistent with post-HB phases. These
observations, and recent HST photometry of two other metal-rich clusters,
demonstrate that populations with rich, cool HB's can nonetheless produce hot
HB and post-HB stars. The cluster center also contains an unusual diffuse
far-UV source which is more extended than its V-band light. It is possible that
this is associated with an intracluster medium, for which there was earlier
infrared and X-ray evidence, and is produced by C IV emission or scattered
light from grains.Comment: 13 pages AASLaTeX including one postscript figure and one bitmapped
image, JPEG format. Submitted to the Astronomical Jorunal. Full Postscript
version available at http://www.astro.virginia.edu/~bd4r
Relative sound localisation abilities in human listeners
Spatial acuity varies with sound-source azimuth, signal-to-noise ratio, and the spectral characteristics of the sound source. Here, the spatial localisation abilities of listeners were assessed using a relative localisation task. This task tested localisation ability at fixed angular separations throughout space using a two-alternative forced-choice design across a variety of listening conditions. Subjects were required to determine whether a target sound originated to the left or right of a preceding reference in the presence of a multi-source noise background. Experiment 1 demonstrated that subjects' ability to determine the relative location of two sources declined with less favourable signal-to-noise ratios and at peripheral locations. Experiment 2 assessed performance with both broadband and spectrally restricted stimuli designed to limit localisation cues to predominantly interaural level differences or interaural timing differences (ITDs). Predictions generated from topographic, modified topographic, and two-channel models of sound localisation suggest that for low-pass stimuli, where ITD cues were dominant, the two-channel model provides an adequate description of the experimental data, whereas for broadband and high frequency bandpass stimuli none of the models was able to fully account for performance. Experiment 3 demonstrated that relative localisation performance was uninfluenced by shifts in gaze direction
Political brand identity: an examination of the complexities of Conservative brand and internal market engagement during the 2010 UK General Election campaign
This paper seeks to build an understanding of the importance of internal communications when building a strong political brand. Using Kapferer’s brand prism as a conceptual framework, the paper explores UK Conservative Party members’ attitudes towards the development of the Conservative brand as personified by David Cameron. There are clear implications for political strategists as the findings suggest that it is crucial to engage the internal market in the co-creation of the marketing communications strategy for as brand evangelists they interpret the brand promise at the local level
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