3,547 research outputs found
Flow probe of symmetry energy in relativistic heavy-ion reactions
Flow observables in heavy-ion reactions at incident energies up to about 1
GeV per nucleon have been shown to be very useful for investigating the
reaction dynamics and for determining the parameters of reaction models based
on transport theory. In particular, the elliptic flow in collisions of
neutron-rich heavy-ion systems emerges as an observable sensitive to the
strength of the symmetry energy at supra-saturation densities. The comparison
of ratios or differences of neutron and proton flows or neutron and hydrogen
flows with predictions of transport models favors an approximately linear
density dependence, consistent with ab-initio nuclear-matter theories.
Extensive parameter searches have shown that the model dependence is comparable
to the uncertainties of existing experimental data. Comprehensive new flow data
of high accuracy, partly also through providing stronger constraints on model
parameters, can thus be expected to improve our knowledge of the equation of
state of asymmetric nuclear matter.Comment: 20 pages, 24 figures, review to appear in EPJA special volume on
nuclear symmetry energ
QCD Viscosity to Entropy Density Ratio in the Hadronic Phase
Shear viscosity (eta) of QCD in the hadronic phase is computed by the coupled
Boltzmann equations of pions and nucleons in low temperatures and low baryon
number densities. The eta to entropy density ratio eta/s maps out the nuclear
gas-liquid phase transition by forming a valley tracing the phase transition
line in the temperature-chemical potential plane. When the phase transition
turns into a crossover, the eta/s valley gradually disappears. We suspect the
general feature for a first-order phase transition is that eta/s has a
discontinuity in the bottom of the eta/s valley. The discontinuity coincides
with the phase transition line and ends at the critical point. Beyond the
critical point, a smooth eta/s valley is seen. However, the valley could
disappear further away from the critical point. The eta/s measurements might
provide an alternative to identify the critical points.Comment: 16 pages, 4 figures. Minor typos corrected and references adde
Statistical Mechanics of Membrane Protein Conformation: A Homopolymer Model
The conformation and the phase diagram of a membrane protein are investigated
via grand canonical ensemble approach using a homopolymer model. We discuss the
nature and pathway of -helix integration into the membrane that results
depending upon membrane permeability and polymer adsorptivity. For a membrane
with the permeability larger than a critical value, the integration becomes the
second order transition that occurs at the same temperature as that of the
adsorption transition. For a nonadsorbing membrane, the integration is of the
first order due to the aggregation of -helices.Comment: RevTeX with 5 postscript figure
Fusion barrier distributions in systems with finite excitation energy
Eigen-channel approach to heavy-ion fusion reactions is exact only when the
excitation energy of the intrinsic motion is zero. In order to take into
account effects of finite excitation energy, we introduce an energy dependence
to weight factors in the eigen-channel approximation. Using two channel
problem, we show that the weight factors are slowly changing functions of
incident energy. This suggests that the concept of the fusion barrier
distribution still holds to a good approximation even when the excitation
energy of the intrinsic motion is finite. A transition to the adiabatic
tunneling, where the coupling leads to a static potential renormalization, is
also discussed.Comment: 9 pages, 4 figures, Submitted to Physical Review
Effects of Prescribed Fire Timing on Stocker Cattle Performance, Native Plant Composition, Forage Biomass, and Root Carbohydrate Reserves in the Kansas Flint Hills: Year One of Six
Objective: Our objective was to document the effects of prescribed fire timing on yearling beef cattle performance, native plant composition, and forage biomass accumulation in the Kansas Flint Hills.
Study Description: Our study took place at the Kansas State Beef Stocker Unit located northwest of Manhattan, KS. Pastures were assigned to one of three prescribed burn treatments: early spring (April), mid-summer (August), or early fall (October). Treatments were applied and yearling heifers (n = 360) were subsequently grazed from May to August. Native plant composition and forage biomass were evaluated annually in late June and early July.
The Bottom Line: The first year of data from a six-year study indicated that prescribed fire timing affected stocker cattle performance and forage biomass availability but not basal cover of forage grasses and forbs
Structure of 12Be: intruder d-wave strength at N=8
The breaking of the N=8 shell-model magic number in the 12Be ground state has
been determined to include significant occupancy of the intruder d-wave
orbital. This is in marked contrast with all other N=8 isotones, both more and
less exotic than 12Be. The occupancies of the 0 hbar omega neutron p1/2-orbital
and the 1 hbar omega, neutron d5/2 intruder orbital were deduced from a
measurement of neutron removal from a high-energy 12Be beam leading to bound
and unbound states in 11Be.Comment: 5 pages, 2 figure
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