2,364 research outputs found
Collective Flows in a Transport Approach
We introduce a transport approach at fixed shear viscosity to entropy ratio
\etas to study the generation of collective flows in ultra-relativistic
heavy-ion collisions. Transport theory supplies a covariant approach valid also
at large \etas and at intermediate transverse momentum , where
deviations from equilibrium is no longer negligible. Such an approach shows
that at RHIC energies a temperature dependent \etas enhances significantly
the respect to the case of constant \etas. Furthermore if NJL
chiral dynamics is self-consistently implemented we show that it does not
modify the relation between and \etas.Comment: 4 pages, 4 figures, Proceedings of Hot Quarks 2010, 21-26 June 2010
Las Londe Les Maures; to appear in Journal of Physics: Conference Serie
Sumo Puff: Tidal Debris or Disturbed Ultra-Diffuse Galaxy?
We report the discovery of a diffuse stellar cloud with an angular extent
, which we term "Sumo Puff", in data from the Hyper
Suprime-Cam Subaru Strategic Program (HSC-SSP). While we do not have a redshift
for this object, it is in close angular proximity to a post-merger galaxy at
redshift and is projected within a few virial radii (assuming
similar redshifts) of two other galaxies, which we use to
bracket a potential redshift range of . The object's light
distribution is flat, as characterized by a low Sersic index (). It
has a low central -band surface brightness of mag
arcsec, large effective radius of (
kpc at and kpc at ), and an elongated
morphology (). Its red color () is consistent with a
passively evolving stellar population and similar to the nearby post-merger
galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We
offer two possible interpretations for the nature of this object: (1) it is an
extreme, galaxy-size tidal feature associated with a recent merger event, or
(2) it is a foreground dwarf galaxy with properties consistent with a quenched,
disturbed ultra-diffuse galaxy. We present a qualitative comparison with
simulations that demonstrates the feasibility of forming a structure similar to
this object in a merger event. Follow-up spectroscopy and/or deeper imaging to
confirm the presence of the bridge of tidal material will be necessary to
reveal the true nature of this object.Comment: 10 pages, 5 figures, submitted to PASJ for the HSC-SSP special issu
The nature of plasmon excitations in hole-doped cuprate superconductors
High Tc superconductors show a rich variety of phases associated with their
charge degrees of freedom. Valence charges can give rise to charge ordering or
acoustic plasmons in these layered cuprate superconductors. While charge
ordering has been observed for both hole- and electron-doped cuprates, acoustic
plasmons have only been found in electron-doped materials. Here, we use
resonant inelastic X-ray scattering (RIXS) to observe the presence of acoustic
plasmons in two families of hole-doped cuprate superconductors [La2-xSrxCuO4
(LSCO) and Bi2Sr1.6La0.4CuO6+d (Bi2201)], crucially completing the picture.
Interestingly, in contrast to the quasi-static charge ordering which manifests
at both Cu and O sites, the observed acoustic plasmons are predominantly
associated with the O sites, revealing a unique dichotomy in the behaviour of
valence charges in hole-doped cuprates.Comment: 11 pages, 7 figures + Supplementary Informatio
Berry phases and pairing symmetry in Holstein-Hubbard polaron systems
We study the tunneling dynamics of dopant-induced hole polarons which are
self-localized by electron-phonon coupling in a two-dimensional antiferro-
magnet. Our treatment is based on a path integral formulation of the adia-
batic approximation, combined with many-body tight-binding, instanton, con-
strained lattice dynamics, and many-body exact diagonalization techniques. Our
results are mainly based on the Holstein- and, for comparison, on the
Holstein-Hubbard model. We also study effects of 2nd neighbor hopping and
long-range electron-electron Coulomb repulsion. The polaron tunneling dynamics
is mapped onto an effective low-energy Hamiltonian which takes the form of a
fermion tight-binding model with occupancy dependent, predominant- ly 2nd and
3rd neighbor tunneling matrix elements, excluded double occupan- cy, and an
effective intersite charge interactions. Antiferromagnetic spin correlations in
the original many-electron Hamiltonian are reflected by an attractive
contribution to the 1st neighbor charge interaction and by Berry phase factors
which determine the signs of effective polaron tunneling ma- trix elements. In
the two-polaron case, these phase factors lead to polaron pair wave functions
of either -wave symmetry or p-wave symme- try with zero and
nonzero total pair momentum, respectively. Implications for the doping
dependent isotope effect, pseudo-gap and Tc of a superconduc- ting polaron pair
condensate are discussed/compared to observed in cuprates.Comment: 23 pages, revtex, 13 ps figure
Transient support from fibroblasts is sufficient to drive functional vascularization in engineered tissues
Formation of capillary blood vasculature is a critical requirement for native as well as engineered organs and can be induced in vitro by co-culturing endothelial cells with fibroblasts. However, whether these fibroblasts are required only in the initial morphogenesis of endothelial cells or needed throughout is unknown, and the ability to remove these stromal cells after assembly could be useful for clinical translation. In this study, we introduce a technique termed CAMEO (Controlled Apoptosis in Multicellular Tissues for Engineered Organogenesis), whereby fibroblasts are selectively ablated on demand, and utilize it to probe the dispensability of fibroblasts in vascular morphogenesis. The presence of fibroblasts is shown to be necessary only during the first few days of endothelial cell morphogenesis, after which they can be ablated without significantly affecting the structural and functional features of the developed vasculature. Furthermore, we demonstrate the use of CAMEO to vascularize a construct containing primary human hepatocytes that improved tissue function. In conclusion, this study suggests that transient, initial support from fibroblasts is sufficient to drive vascular morphogenesis in engineered tissues, and this strategy of engineering-via-elimination may provide a new general approach for achieving desired functions and cell compositions in engineered organs.R01 EB008396 - NIBIB NIH HHS; UH2 EB017103 - NIBIB NIH HHS; P30 CA014051 - NCI NIH HHS; R01 EB000262 - NIBIB NIH HHS; UH3 EB025765 - NIBIB NIH HHS; UG3 EB025765 - NIBIB NIH HHS; UH3 EB017103 - NIBIB NIH HHSAccepted manuscrip
Collective modes of asymmetric nuclear matter in Quantum HadroDynamics
We discuss a fully relativistic Landau Fermi liquid theory based on the
Quantum Hadro-Dynamics () effective field picture of Nuclear Matter
({\it NM}).
From the linearized kinetic equations we get the dispersion relations of the
propagating collective modes. We focus our attention on the dynamical effects
of the interplay between scalar and vector channel contributions. A beautiful
``mirror'' structure in the form of the dynamical response in the
isoscalar/isovector degree of freedom is revealed, with a complete parallelism
in the role respectively played by the compressibility and the symmetry energy.
All that strongly supports the introduction of an explicit coupling to the
scalar-isovector channel of the nucleon-nucleon interaction. In particular we
study the influence of this coupling (to a -meson-like effective field)
on the collective response of asymmetric nuclear matter (). Interesting
contributions are found on the propagation of isovector-like modes at normal
density and on an expected smooth transition to isoscalar-like oscillations at
high baryon density. Important ``chemical'' effects on the neutron-proton
structure of the mode are shown. For dilute we have the isospin
distillation mechanism of the unstable isoscalar-like oscillations, while at
high baryon density we predict an almost pure neutron wave structure of the
propagating sounds.Comment: 18 pages (LATEX), 8 Postscript figures, uses "epsfig
Observation of a charged charmoniumlike structure in at GeV
We study the process at a
center-of-mass energy of 4.26GeV using a 827pb data sample obtained with
the BESIII detector at the Beijing Electron Positron Collider. Based on a
partial reconstruction technique, the Born cross section is measured to be
pb. We observe a structure near the
threshold in the recoil mass spectrum, which we denote as the
. The measured mass and width of the structure are
MeV/c and MeV, respectively. Its
production ratio is determined to be . The first uncertainties
are statistical and the second are systematic.Comment: 7 pages, 4 figures, 1 table; version accepted to be published in PR
Search for Baryonic Decays of \psi(3770) and \psi(4040)
By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482
pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt
s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the
BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic
final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0,
\Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0,
\Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits
are set at the 90% confidence level.Comment: 9 pages, 3 figure
Search for the Lepton Flavor Violation Process at BESIII
We search for the lepton-flavor-violating decay of the into an
electron and a muon using events
collected with the BESIII detector at the BEPCII collider. Four candidate
events are found in the signal region, consistent with background expectations.
An upper limit on the branching fraction of (90% C.L.) is obtained
First observation of the M1 transition
Using a sample of 106 million \psi(3686) events collected with the BESIII
detector at the BEPCII storage ring, we have made the first measurement of the
M1 transition between the radially excited charmonium S-wave spin-triplet and
the radially excited S-wave spin-singlet states: \psi(3686)\to\gamma\eta_c(2S).
Analyses of the processes \psi(2S)\to \gamma\eta_c(2S) with \eta_c(2S)\to
\K_S^0 K\pi and K^+K^-\pi^0 gave an \eta_c(2S) signal with a statistical
significance of greater than 10 standard deviations under a wide range of
assumptions about the signal and background properties. The data are used to
obtain measurements of the \eta_c(2S) mass (M(\eta_c(2S))=3637.6\pm
2.9_\mathrm{stat}\pm 1.6_\mathrm{sys} MeV/c^2), width
(\Gamma(\eta_c(2S))=16.9\pm 6.4_\mathrm{stat}\pm 4.8_\mathrm{sys} MeV), and the
product branching fraction (\BR(\psi(3686)\to \gamma\eta_c(2S))\times
\BR(\eta_c(2S)\to K\bar K\pi) = (1.30\pm 0.20_\mathrm{stat}\pm
0.30_\mathrm{sys})\times 10^{-5}). Combining our result with a BaBar
measurement of \BR(\eta_c(2S)\to K\bar K \pi), we find the branching fraction
of the M1 transition to be \BR(\psi(3686)\to\gamma\eta_c(2S)) = (6.8\pm
1.1_\mathrm{stat}\pm 4.5_\mathrm{sys})\times 10^{-4}.Comment: 7 pages, 1 figure, 1 tabl
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