770 research outputs found
Algometry to measure pain threshold in the horse's back - An in vivo and in vitro study
Abstract Background The aim of this study was to provide information on algometric transmission of pressure through the dorsal thoracolumbar tissues of the equine back. Using a commercially available algometer, measurements were carried out with six different tips (hemispheric and cylindrical surfaces, contact areas 0.5Â cm2, 1Â cm2, and 2Â cm2). In nine live horses the threshold of pressure that lead to any reaction was documented. In postmortem specimens of five euthanized horses the transmission of algometer pressure onto a pressure sensor placed underneath the dorsal thoracolumbar tissues at the level of the ribs or the transverse lumbar processes respectively was measured. Results Algometer tips with a contact area of 1Â cm2 led to widely similar results irrespective of the surface shape; these measurements also had the lowest variance. Contact areas of 0.5Â cm2 resulted in a lower pressure threshold, and those of 2Â cm2 resulted in a higher pressure threshold. The hemispheric shape of the contact area resulted in a higher pressure threshold, than the cylindrical contact area. Compared to the thoracic region, a significantly higher pressure threshold was found in the lumbar region in the live horses. This result corresponds to the increased tissue thickness in the lumbar region compared to the thoracic region, also documented as less pressure transmission in the lumbar region on the in vitro specimens. Conclusions Algometry is an easily practicable and well tolerated method to quantify pain but it is important to consider the many factors influencing the results obtained
On the Role of Initial Conditions and Final State Interactions in Ultrarelativistic Heavy Ion Collisions
We investigate the rapidity dependence of the elliptical flow in heavy ion
collisions at 200 GeV (cms), by employing a three-dimensional hydrodynamic
evolution, based on different initial conditions, and different freeze-out
scenarios. It will be shown that the form of pseudo-rapidity ()
dependence of the elliptical flow is almost identical to space-time-rapidity
() dependence of the initial energy distribution, independent of the
freeze-out prescriptions
Cosmological weak lensing with the HST GEMS survey
We present our cosmic shear analysis of GEMS, one of the largest wide-field
surveys ever undertaken by the Hubble Space Telescope. Imaged with the Advanced
Camera for Surveys (ACS), GEMS spans 795 square arcmin in the Chandra Deep
Field South. We detect weak lensing by large-scale structure in high resolution
F606W GEMS data from ~60 resolved galaxies per square arcminute. We measure the
two-point shear correlation function, the top-hat shear variance and the shear
power spectrum, performing an E/B mode decomposition for each statistic. We
show that we are not limited by systematic errors and use our results to place
joint constraints on the matter density parameter Omega_m and the amplitude of
the matter power spectrum sigma_8. We find sigma_8(Omega_m/0.3)^{0.65}=0.68 +/-
0.13 where the 1sigma error includes both our uncertainty on the median
redshift of the survey and sampling variance.
Removing image and point spread function (PSF) distortions are crucial to all
weak lensing analyses. We therefore include a thorough discussion on the degree
of ACS PSF distortion and anisotropy which we characterise directly from GEMS
data. Consecutively imaged over 20 days, GEMS data also allows us to
investigate PSF instability over time. We find that, even in the relatively
short GEMS observing period, the ACS PSF ellipticity varies at the level of a
few percent which we account for with a semi-time dependent PSF model. Our
correction for the temporal and spatial variability of the PSF is shown to be
successful through a series of diagnostic tests.Comment: 17 pages, 16 figures. Version accepted by MNRA
Statistical hadronization phenomenology in fluctuations at ultra-relativistic energies
We discuss the information that can be obtained from an analysis of
fluctuations in heavy ion collisions within the context of the statistical
model of particle production. We then examine the recently published
experimental data on ratio fluctuations, and use it to obtain constraints on
the statistical properties (physically relevant ensemble, degree of chemical
equilibration, scaling across energies and system sizes) and freeze-out
dynamics (amount of reinteraction between chemical and thermal freeze-out) of
the system.Comment: Proceedings, SQM2009. Fig. 4, the main results figure, was wrong due
to editing mistake, now correcte
Evolution and Impact of Bars over the Last Eight Billion Years: Early Results from GEMS
Bars drive the dynamical evolution of disk galaxies by redistributing mass
and angular momentum, and they are ubiquitous in present-day spirals. Early
studies of the Hubble Deep Field reported a dramatic decline in the rest-frame
optical bar fraction f_opt to below 5% at redshifts z>0.7, implying that disks
at these epochs are fundamentally different from present-day spirals. The GEMS
bar project, based on ~8300 galaxies with HST-based morphologies and accurate
redshifts over the range 0.2-1.1, aims at constraining the evolution and impact
of bars over the last 8 Gyr. We present early results indicating that f_opt
remains nearly constant at ~30% over the range z=0.2-1.1,corresponding to
lookback times of ~2.5-8 Gyr. The bars detected at z>0.6 are primarily strong
with ellipticities of 0.4-0.8. Remarkably, the bar fraction and range of bar
sizes observed at z>0.6 appear to be comparable to the values measured in the
local Universe for bars of corresponding strengths. Implications for bar
evolution models are discussed.Comment: Submitted June 25, 2004. 10 pages 5 figures. To appear in Penetrating
Bars through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes a New Note,
eds. D. Block, K. Freeman, R. Groess, I. Puerari, & E.K. Block (Dordrecht:
Kluwer), in pres
Safe and complete contig assembly via omnitigs
Contig assembly is the first stage that most assemblers solve when
reconstructing a genome from a set of reads. Its output consists of contigs --
a set of strings that are promised to appear in any genome that could have
generated the reads. From the introduction of contigs 20 years ago, assemblers
have tried to obtain longer and longer contigs, but the following question was
never solved: given a genome graph (e.g. a de Bruijn, or a string graph),
what are all the strings that can be safely reported from as contigs? In
this paper we finally answer this question, and also give a polynomial time
algorithm to find them. Our experiments show that these strings, which we call
omnitigs, are 66% to 82% longer on average than the popular unitigs, and 29% of
dbSNP locations have more neighbors in omnitigs than in unitigs.Comment: Full version of the paper in the proceedings of RECOMB 201
System-size dependence of the pion freeze-out volume as a potential signature for the phase transition to a Quark Gluon Plasma
Hanburry-Brown-Twiss (HBT) correlation functions and radii of negatively
charged pions from C+C, Si+Si, Cu+Cu, and In+In at lower RHIC/SPS energies are
calculated with the UrQMD transport model and the CRAB analyzing program. We
find a minimum in the excitation function of the pion freeze-out volume at low
transverse momenta and around GeV which can be related to
the transition from hadronic to string matter (which might be interpreted as a
pre-cursor of the QGP). The existence of the minimum is explained by the
competition of two mechanisms of the particle production, resonance decays and
string formation/fragmentation.Comment: 12 pages, 4 fig
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