239 research outputs found
Kernels for Grassmann flops
We develop a generalization of the -construction of the first author, Diemer, and the third author for Grassmann flips. This generalization provides a canonical idempotent kernel on the derived category of the associated global quotient stack. The idempotent kernel, after restriction, induces a semi-orthogonal decomposition which compares the flipped varieties. Furthermore its image, after restriction to the geometric invariant theory semistable locus, "opens" a canonical "window" in the derived category of the quotient stack. We check this window coincides with the set of representations used by Kapranov to form a full exceptional collection on Grassmannians
Cardiac Computed Tomography: Application in Valvular Heart Disease
The incidence and prevalence of valvular heart disease (VHD) is increasing and has been described as the next cardiac epidemic. Advances in imaging and therapeutics have revolutionized how we assess and treat patients with VHD. Although echocardiography continues to be the first-line imaging modality to assess the severity and the effects of VHD, advances in cardiac computed tomography (CT) now provide novel insights into VHD. Transcatheter valvular interventions rely heavily on CT guidance for procedural planning, predicting and detecting complications, and monitoring prosthesis. This review focuses on the current role and future prospects of CT in the assessment of aortic and mitral valves for transcatheter interventions, prosthetic valve complications such as thrombosis and endocarditis, and assessment of the myocardium
In vitro and in vivo antitumor activity of crude extracts obtained from Brazilian Chromobacterium sp isolates
Elliptic flow from two- and four-particle correlations in Au + Au collisions at sqrt{s_{NN}} = 130 GeV
Elliptic flow holds much promise for studying the early-time thermalization
attained in ultrarelativistic nuclear collisions. Flow measurements also
provide a means of distinguishing between hydrodynamic models and calculations
which approach the low density (dilute gas) limit. Among the effects that can
complicate the interpretation of elliptic flow measurements are azimuthal
correlations that are unrelated to the reaction plane (non-flow correlations).
Using data for Au + Au collisions at sqrt{s_{NN}} = 130 GeV from the STAR TPC,
it is found that four-particle correlation analyses can reliably separate flow
and non-flow correlation signals. The latter account for on average about 15%
of the observed second-harmonic azimuthal correlation, with the largest
relative contribution for the most peripheral and the most central collisions.
The results are also corrected for the effect of flow variations within
centrality bins. This effect is negligible for all but the most central bin,
where the correction to the elliptic flow is about a factor of two. A simple
new method for two-particle flow analysis based on scalar products is
described. An analysis based on the distribution of the magnitude of the flow
vector is also described.Comment: minor text change
Transverse momentum and collision energy dependence of high hadron suppression in Au+Au collisions at ultrarelativistic energies
We report high statistics measurements of inclusive charged hadron production
in Au+Au and p+p collisions at \sqrtsNN=200 GeV. A large, approximately
constant hadron suppression is observed in central Au+Au collisions for
5\lt\pT\lt12 GeV/c. The collision energy dependence of the yields and the
centrality and \pT dependence of the suppression provide stringent constraints
on theoretical models of suppression. Models incorporating initial-state gluon
saturation or partonic energy loss in dense matter are largely consistent with
observations. We observe no evidence of \pT-dependent suppression, which may be
expected from models incorporating jet attentuation in cold nuclear matter or
scattering of fragmentation hadrons.Comment: Final journal version. Data tables for figures may be downloaded from
the STAR home page: http://www.star.bnl.gov --> Publications --> Access to
STAR published dat
Evidence from d+Au measurements for final-state suppression of high hadrons in Au+Au collisions at RHIC
We report measurements of single-particle inclusive spectra and two-particle
azimuthal distributions of charged hadrons at high transverse momentum (high
) in minimum bias and central d+Au collisions at =200 GeV.
The inclusive yield is enhanced in d+Au collisions relative to binary-scaled
p+p collisions, while the two-particle azimuthal distributions are very similar
to those observed in p+p collisions. These results demonstrate that the strong
suppression of the inclusive yield and back-to-back correlations at high
previously observed in central Au+Au collisions are due to final-state
interactions with the dense medium generated in such collisions.Comment: Final journal version. Data tables for figures may be downloaded from
the STAR home page: http://www.star.bnl.gov --> Publications --> Access to
STAR published dat
Azimuthally sensitive Hanbury Brown-Twiss interferometry in Au+Au collisions at sqrt(s_{NN}) = 200 GeV
We present the results of a systematic study of the shape of the pion
distribution in coordinate space at freeze-out in Au+Au collisions at RHIC
using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the
extracted HBT radii vs. emission angle indicate sources elongated perpendicular
to the reaction plane. The results indicate that the pressure and expansion
time of the collision system are not sufficient to completely quench its
initial shape.Comment: 6 pages, 4 figures, published versio
Pion-Xi correlations in Au-Au collisions at STAR
We present pion-Xi correlation analysis in Au-Au collisions at sqrt(s_NN)=
200 GeV and sqrt(s_NN) = 62.4 GeV, performed using the STAR detector at RHIC. A
Xi*(1530) resonance signal is observed for the first time in Au-Au collisions.
Experimental data are compared with theoretical predictions. The strength of
the Xi* peak is reproduced in the correlation function assuming that pions and
Xis emerge from a system in collective expansion.Comment: To appear in the proceedings of 18th Nuclear Physics Division
Conference of the EPS (NPDC18),Prague, 23.8.-29.8. 200
Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at s(NN)**(1/2) = 200-GeV
We present STAR measurements of the azimuthal anisotropy parameter and
the binary-collision scaled centrality ratio for kaons and lambdas
() at mid-rapidity in Au+Au collisions at
GeV. In combination, the and
particle-type dependencies contradict expectations from partonic energy loss
followed by standard fragmentation in vacuum. We establish
GeV/c as the value where the centrality dependent baryon enhancement ends. The
and values are consistent with
expectations of constituent-quark-number scaling from models of hadron
fromation by parton coalescence or recombination.Comment: 6 pages, 4 figures, 1 table. As published in PRL on Feb. 2, 2004;
Significant revisions have been made to the text and color has been added to
plot
Azimuthal anisotropy and correlations in the hard scattering regime at RHIC
Azimuthal anisotropy () and two-particle angular correlations of high
charged hadrons have been measured in Au+Au collisions at
=130 GeV for transverse momenta up to 6 GeV/c, where hard
processes are expected to contribute significantly. The two-particle angular
correlations exhibit elliptic flow and a structure suggestive of fragmentation
of high partons. The monotonic rise of for GeV/c is
consistent with collective hydrodynamical flow calculations. At \pT>3 GeV/c a
saturation of is observed which persists up to GeV/c.Comment: As publishe
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