Nuclear expansion and symmetry energy of hot nuclei

The decrease in the symmetry energy of hot nuclei populated in $^{58}$Ni + $^{58}$Ni, $^{58}$Fe + $^{58}$Ni and $^{58}$Fe + $^{58}$Fe reactions at beam energies of 30, 40, and 47 MeV/nucleon, as a function of excitation energy is studied. It is observed that this decrease is mainly a consequence of increasing expansion or decreasing density rather than the increasing temperature. The results are in good agreement with the recently reported microscopic calculation based on the Thomas-Fermi approach. An empirical relation to study the symmetry energy of finite nuclei in various mass region is proposed.Comment: 10 pages, 2 figure

Analysis of fragment yield ratios in the nuclear phase transition

The critical phenomena of the liquid-gas phase transition has been investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon using the Landau free energy approach with isospin asymmetry as an order parameter. Fits to the free energy of fragments showed three minima suggesting the system to be in the regime of a first order phase transition. The relation m =-{\partial}F/{\partial}H, which defines the order parameter and its conjugate field H, has been experimentally verified from the linear dependence of the mirror nuclei yield ratio data, on the isospin asymmetry of the source. The slope parameter, which is a measure of the distance from a critical temperature, showed a systematic decrease with increasing excitation energy of the source. Within the framework of the Landau free energy approach, isoscaling provided similar results as obtained from the analysis of mirror nuclei yield ratio data. We show that the external field is primarily related to the minimum of the free energy, which implies a modification of the source concentration \Delta used in isospin studies

Proton induced reaction cross section measurements on Se isotopes for the astrophysical p process

As a continuation of a systematic study of reactions relevant to the astrophysical p process, the cross sections of the 74,76Se(p,gamma)75,77Br and 82Se(p,n)82Br reactions have been measured at energies from 1.3 to 3.6 MeV using an activation technique. The results are compared to the predictions of Hauser-Feshbach statistical model calculations using the NON-SMOKER and MOST codes. The sensitivity of the calculations to variations in the optical proton potential and the nuclear level density was studied. Good agreement between theoretical and experimental reaction rates was found for the reactions 74Se(p,gamma)75Br and 82Se(p,n)82Br.Comment: 9 pages, 6 figures (in 12 eps files), accepted for publication in Phys. Rev C, RevTeX styl

Analysis of fragment yield ratios in the nuclear phase transition

The critical phenomena of the liquid-gas phase transition has been investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon using the Landau free energy approach with isospin asymmetry as an order parameter. Fits to the free energy of fragments showed three minima suggesting the system to be in the regime of a first order phase transition. The relation m =-{\partial}F/{\partial}H, which defines the order parameter and its conjugate field H, has been experimentally verified from the linear dependence of the mirror nuclei yield ratio data, on the isospin asymmetry of the source. The slope parameter, which is a measure of the distance from a critical temperature, showed a systematic decrease with increasing excitation energy of the source. Within the framework of the Landau free energy approach, isoscaling provided similar results as obtained from the analysis of mirror nuclei yield ratio data. We show that the external field is primarily related to the minimum of the free energy, which implies a modification of the source concentration \Delta used in isospin studies

Sensitivity of intermediate mass fragment flows to the symmetry energy

The NIMROD-ISiS array was used to study the transverse flow of intermediate mass fragments in 35 MeV/nucleon ${}^{70}\mathrm{Zn}+{}^{70}\mathrm{Zn}$, ${}^{64}\mathrm{Zn}+{}^{64}\mathrm{Zn}$, and ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ reactions. The intermediate mass fragment flow was previously shown to be sensitive to the density dependence of the symmetry energy. To explore the model dependence of the results, the antisymmetrized molecular dynamics, constrained molecular dynamics, and stochastic mean-field models were each compared to the experimental results to extract information on the form of the symmetry energy. The results demonstrate that sensitivity of the models to the nuclear equation of state can vary significantly based on the treatment of the nuclear dynamics. Despite the differences in the sensitivity, improved agreement with the experimental data is observed for each model with a stiff density dependence of the symmetry energy

Investigation of transverse collective flow of intermediate mass fragments

The transverse flow of intermediate mass fragments (IMFs) has been investigated for the 35 MeV/u ${}^{70}\mathrm{Zn}+{}^{70}\mathrm{Zn}$, ${}^{64}\mathrm{Zn}+{}^{64}\mathrm{Zn}$, and ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ systems. A transition from the IMF transverse flow strongly depending on the mass of the system, in the most violent collisions, to a dependence on the charge of the system, for the peripheral reactions, is shown. This transition was shown to be sensitive to the density dependence of the symmetry energy using the antisymmetrized molecular-dynamics model. The results present an observable, the IMF transverse flow, that can be used to probe the nuclear equation of state. Comparison with the simulation demonstrated a preference for a stiff density dependence of the symmetry energy

ACR Appropriateness Criteria® Spinal Bone Metastases

The spine is a common site of involvement in patients with bone metastases. Apart from pain, hypercalcemia, and pathologic fracture, progressive tumor can result in neurologic deterioration caused by spinal cord compression or cauda equina involvement. The treatment of spinal bone metastases depends on histology, site of disease, extent of epidural disease, extent of metastases elsewhere, and neurologic status. Treatment recommendations must weigh the risk-benefit profile of external beam radiation therapy (EBRT) for the particular individual's circumstance, including neurologic status, performance status, extent of spinal disease, stability of the spine, extra-spinal disease status, and life expectancy. Patients with spinal instability should be evaluated for surgical intervention. Research studies are needed that evaluate the combination or sequencing of localized therapies with systemic therapies including chemotherapy, hormonal therapy (HT), osteoclast inhibitors (OI), and radiopharmaceuticals. The roles of stereotactic body radiation therapy (SBRT) in the management of spinal oligometastasis, radioresistant spinal metastasis, and previously irradiated but progressive spinal metastasis are emerging, but more research is needed to validate the findings from retrospective studies. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140115/1/jpm.2012.0376.pd