880 research outputs found
Double neutron-proton differential transverse flow as a probe for the high-density behavior of the nuclear symmetry energy
The double neutron-proton differential transverse flowtaken from two reaction
systems using different isotopes of the same element is studied at incident
beam energies of 400 and 800 MeV/nucleon within the framework of an isospin-
and momentum-dependent hadronic transport model IBUU04. The double differential
flow is found to retain about the same sensitivity to the density dependence of
the nuclear symmetry energy as the single differential flow in the more
neutron-rich reaction. Because the double differential flow reduces
significantly both the systematic errors and the influence of the Coulomb
force, it is thus more effective probe for the high-density behavior of the
nuclear symmetry energy.Comment: 12 pages, 6 figures, version accepted for publication in Phys. Rev.
Triton-3He relative and differential flows and the high density behavior of nuclear symmetry energy
Using a transport model coupled with a phase-space coalescence after-burner
we study the triton-3He relative and differential transverse flows in
semi-central 132Sn+124Sn reactions at a beam energy of 400 MeV/nucleon. We find
that the triton-3He pairs carry interesting information about the density
dependence of the nuclear symmetry energy. The t-3He relative flow can be used
as a particularly powerful probe of the high-density behavior of the nuclear
symmetry energy.Comment: 6 pages, 2 figures, Proceeding of The International Workshop on
Nuclear Dynamics in Heavy-Ion Reactions and the Symmetry Energ
Single and double pi^{-}/pi^{+} ratios in heavy-ion reactions as probes of the high-density behavior of the nuclear symmetry energy
Based on an isospin- and momentum-dependent hadronic transport model IBUU04,
effects of the nuclear symmetry energy on the single and double
pi^{-}/pi^{+}ratios in central reactions of ^{132}Sn+^{124}Sn and
^{112}Sn+^{112}Sn at a beam energy of 400 MeV/nucleon are studied. It is found
that around the Coulomb peak of the single pi^{-}/pi^{+} ratio the double
pi^{-}/pi^{+} ratio taken from the two isotopic reactions retains about the
same sensitivity to the density dependence of nuclear symmetry energy. Because
the double pi^{-}/pi^{+}ratio can reduce significantly the systematic errors,
it is thus a more effective probe for the high-density behavior of the nuclear
symmetry energy.Comment: 11 pages, 3 figures, to appear in Physics Review
Inadequate Dissemination of Phase I Trials: A Retrospective Cohort Study
François Chapuis and colleagues examine a cohort of clinical trial protocols approved by French ethics committees, and show that Phase I trials are less frequently published than other types of trials
Progress Towards Determining the Density Dependence of the Nuclear Symmetry Energy Using Heavy-Ion Reactions
The latest development in determining the density dependence of the nuclear
symmetry energy using heavy-ion collisions is reviewed. Within the IBUU04
version of an isospin- and momentum-dependent transport model using a modified
Gogny effective interaction, recent experimental data from NSCL/MSU on isospin
diffusion are found to be consistent with a nuclear symmetry energy of
at subnormal densities.
Predictions on several observables sensitive to the density dependence of the
symmetry energy at supranormal densities accessible at GSI and the planned Rare
Isotope Accelerator (RIA) are also made.Comment: 10 pages. Talk given at the 21st Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, USA, Feb. 5-12, 2005. To appear in Heavy-Ion Physics
(2005
Systematic review of melanoma incidence and prognosis in solid organ transplant recipients
Cutaneous melanoma carries the potential for substantial morbidity and mortality in the solid organ transplant population. We systematically reviewed the literature published from January 1995 to January 2012 to determine the overall relative risk and prognosis of melanoma in transplant recipients. Our search identified 7,512 citations. Twelve unique non-overlapping studies reported the population-based incidence of melanoma in an inception cohort of solid organ transplant recipients. Compared to the general population, there is a 2.4-fold (95% confidence interval, 2.0 to 2.9) increased incidence of melanoma after transplantation. No population-based outcome data were identified for melanoma arising post-transplant. Data from non-population based cohort studies suggest a worse prognosis for late-stage melanoma developing after transplantation compared with the general population. For patients with a history of pre-transplant melanoma, one population-based study reported a local recurrence rate of 11% (2/19) after transplantation, although staging and survival information was lacking. There is a need for population-based data on the prognosis of melanoma arising pre- and post-transplantation. Increased incidence and potentially worse melanoma outcomes in this high-risk population have implications for clinical care in terms of prevention, screening and reduction of immunosuppression after melanoma development post-transplant, as well as transplantation decisions in patients with a history of pre-transplant melanoma
Differential isospin-fractionation in dilute asymmetric nuclear matter
The differential isospin-fractionation (IsoF) during the liquid-gas phase
transition in dilute asymmetric nuclear matter is studied as a function of
nucleon momentum. Within a self-consistent thermal model it is shown that the
neutron/proton ratio of the gas phase becomes {\it smaller} than that of the
liquid phase for energetic nucleons, although the gas phase is overall more
neutron-rich. Clear indications of the differential IsoF consistent with the
thermal model predictions are demonstrated within a transport model for
heavy-ion reactions. Future comparisons with experimental data will allow us to
extract critical information about the momentum dependence of the isovector
strong interaction.Comment: Rapid Communication, Phys. Rev. C (2007) in pres
Probing nuclear symmetry energy at high densities using pion, kaon, eta and photon productions in heavy-ion collisions
The high-density behavior of nuclear symmetry energy is among the most
uncertain properties of dense neutron-rich matter. Its accurate determination
has significant ramifications in understanding not only the reaction dynamics
of heavy-ion reactions especially those induced by radioactive beams but also
many interesting phenomena in astrophysics, such as the explosion mechanism of
supernova and the properties of neutron stars. The heavy-ion physics community
has devoted much effort during the last few years to constrain the high-density
symmetry using various probes. In particular, the pion-/pion+ ratio has been
most extensively studied both theoretically and experimentally. All models have
consistently predicted qualitatively that the pion-/pion+ ratio is a sensitive
probe of the high-density symmetry energy especially with beam energies near
the pion production threshold. However, the predicted values of the pion-/pion+
ratio are still quite model dependent mostly because of the complexity of
modeling pion production and reabsorption dynamics in heavy-ion collisions,
leading to currently still controversial conclusions regarding the high-density
behavior of nuclear symmetry energy from comparing various model calculations
with available experimental data. As more pion-/pion+ data become available and
a deeper understanding about the pion dynamics in heavy-ion reactions is
obtained, more penetrating probes, such as the kaon+/kaon0 ratio, eta meson and
high energy photons are also being investigated or planned at several
facilities. Here, we review some of our recent contributions to the community
effort of constraining the high-density behavior of nuclear symmetry energy in
heavy-ion collisions. In addition, the status of some worldwide experiments for
studying the high-density symmetry energy, including the HIRFL-CSR external
target experiment (CEE) are briefly introduced.Comment: 10 pages, 10 figures, Contribution to the Topical Issue on Nuclear
Symmetry Energy in EPJA Special Volum
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