Dynamical instabilities in density-dependent hadronic relativistic models

Unstable modes in asymmetric nuclear matter (ANM) at subsaturation densities are studied in the framework of relativistic mean-field density-dependent hadron models. The size of the instabilities that drive the system are calculated and a comparison with results obtained within the non-linear Walecka model is presented. The distillation and anti-distillation effects are discussed.Comment: 8 pages, 8 Postscript figures. Submitted for publication in Phys. Rev.

Electron--phonon coupling and anharmonic effects in metal clusters

The periods of the harmonic oscillations of the ion core of charged sodium clusters around the equilibrium shapes are considered. It is found that these periods are of the order of magnitude of the experimentally measured relaxation times of the plasmons, which suggests the importance of the electron-ion coupling and stresses the role played by the electron-phonon interaction in the dissipation of the plasmon energy. The relation of the process to fission is briefly discussed.Comment: 6 pages, no figures, to appear in EPLetter

Isospin Constraints on the Parametric Coupling Model for Nuclear Matter

We make use of isospin constraints to study the parametric coupling model and the properties of asymmetric nuclear matter. Besides the usual constraints for nuclear matter - effective nucleon mass and the incompressibility at saturation density - and the neutron star constraints - maximum mass and radius - we have studied the properties related with the symmetry energy. These properties have constrained to a small range the parameters of the model. We have applied our results to study the thermodynamic instabilities in the liquid-gas phase transition as well as the neutron star configurations.Comment: 11 pages, 10 figure

Low density expansion and isospin dependence of nuclear energy functional: comparison between relativistic and Skyrme models

In the present work we take the non relativistic limit of relativistic models and compare the obtained functionals with the usual Skyrme parametrization. Relativistic models with both constant couplings and with density dependent couplings are considered. While some models present very good results already at the lowest order in the density, models with non-linear terms only reproduce the energy functional if higher order terms are taken into account in the expansion.Comment: 16 pages,6 figures,5 table

Nicorandil preserves the function of the mitochondrial phosphorylative and oxidative system in an animal model of global ischemia-reperfusion

Ischemia followed by reperfusion (IR) negatively affects mitochondrial function. At the level of the oxidative-phosphorylative system, IR inhibits the respiratory complexes and ATP synthase, and increases the passive leak of protons through the inner mitochondrial membrane, uncoupling respiration from phosphorylation, decreasing mitochondrial potential and, consequently, ATP production. Drugs that minimize the mitochondrial damage induced by IR may prove to be clinically effective. In the present work, we analyzed the impact of nicorandil, a mitochondrial ATP-sensitive potassium channel agonist, on mitochondrial dysfunction at the level of the oxidative-phosphorylative system of rat hearts subjected to IR. The decrease in the respiratory control ratio (RCR) induced by IR leads to the conclusion that IR has a negative impact on the activity of the mitochondrial respiratory system, uncoupling oxidation from phosphorylation. This effect is reversed by nicorandil, which increases not only RCR, but also the ADP/O ratio. Regarding respiratory rate, state 3 rate was approximately the same for all the experimental groups, while state 4 rate was lower for the group where IR was induced in the presence of nicorandil. This result is in accordance with the data obtained for the RCR and ADP/O. State 4 rate is most affected by uncoupling, given that it is controlled by proton leak. Mitochondria subjected to IR in the presence of nicorandil have a lower state 4 rate, i.e. they are less uncoupled. From these results we conclude that nicorandil preserves the function of mitochondria subjected to IR in terms of both respiration and phosphorylative capacity

Warm and dense stellar matter under strong magnetic fields

We investigate the effects of strong magnetic fields on the equation of state of warm stellar matter as it may occur in a protoneutron star. Both neutrino free and neutrino trapped matter at a fixed entropy per baryon are analyzed. A relativistic mean field nuclear model, including the possibility of hyperon formation, is considered. A density dependent magnetic field with the magnitude $10^{15}$ G at the surface and not more than $3\times 10^{18}$ G at the center is considered. The magnetic field gives rise to a neutrino suppression, mainly at low densities, in matter with trapped neutrinos. It is shown that an hybrid protoneutron star will not evolve to a low mass blackhole if the magnetic field is strong enough and the magnetic field does not decay. However, the decay of the magnetic field after cooling may give rise to the formation of a low mass blackhole.Comment: 17 pages, 10 figures, 3 tables, submitted to Phys. Rev.

Light clusters and the pasta phase

The effects of including light clusters in nuclear matter at low densities are investigated within four different parametrizations of relativistic models at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase) are described for neutral nuclear matter with fixed proton fractions. We discuss the effect of the density dependence of the symmetry energy, the temperature and the proton fraction on the non-homogeneous matter forming the inner crust of proto-neutron stars. It is shown that the number of nucleons in the clusters, the cluster proton fraction and the sizes of the Wigner Seitz cell and of the cluster are very sensitive to the density dependence of the symmetry energy.Comment: 14 pages, 14 figures; Accepted for publication in Phys. Rev.

Instabilities in asymmetric nuclear matter

The existence of phase transitions from liquid to gas phases in asymmetric nuclear matter (ANM) is related with the instability regions which are limited by the spinodals. In this work we investigate the instabilities in ANM described within relativistic mean field hadron models, both with constant and density dependent couplings at zero and finite temperatures. In calculating the proton and neutron chemical potentials we have used an expansion in terms of Bessel functions that is convenient at low densities. The role of the isovector scalar $\delta$-meson is also investigated in the framework of relativistic mean field models and density dependent hadronic models. It is shown that the main differences occur at finite temperature and large isospin asymmetry close to the boundary of the instability regions.Comment: 13 pages, 5 figures; to appear in Phys. Rev.

High-risk pulmonary embolism with right heart thrombi

Accuracy is essential to surface quality control when a range sensor is applied to measure the 3D shape of an automotive body part. A sensor's viewing pose, including location and orientation, is related to measurement accuracy. It is usually difficult to find an optimal solution by manual control of sensor viewpoints. A CAD-guided robot view planner developed previously can automatically generate viewpoints. Measurement accuracy can be satisfied in a certain range. However, the unpredictable image noises, especially in regions with low intensity contrast, cannot be compensated by the CADguided robot view planner. In another aspect, measurement accuracy is evaluated all over the part surface. The local accuracy of a small patch may exceed the measurement tolerance. In this paper, feedback design is applied to the CADguided robot sensor planning system. The feedback controller can evaluate the accuracy of obtained point clouds, identify problem regions, and generate new viewpoints. This process is recursively executed until the measurement accuracy reaches to a tolerant value. This feedback-based inspection system had been implemented in previous work to fill holes of a point cloud, which are caused by shadows and light reflections. In this paper, the feedback controller is specifically designed to improve the measurement accuracy. Experimental results show the success of applying this feedback system for dimensional inspection of an automotive body part. © 2007 IEEE.Link_to_subscribed_fulltex