Semiclassical approaches to nuclear dynamics

The extended Gutzwiller trajectory approach is presented for the semiclassical description of nuclear collective dynamics, in line with the main topics of the fruitful activity of V.G. Solovjov. Within the Fermi-liquid droplet model, the leptodermous effective surface approximation was applied to calculations of energies, sum rules and transition densities for the neutron-proton asymmetry of the isovector giant-dipole resonance and found to be in good agreement with the experimental data. By using the Strutinsky shell correction method, the semiclassical collective transport coefficients such as nuclear inertia, friction, stiffness, and moments of inertia can be derived beyond the quantum perturbation approximation of the response function theory and the cranking model.The averaged particle-number dependence of the low-lying collective vibrational states are described in good agreement with basic experimental data, mainly due to an enhancement of the collective inertia as compared to its irrotational flow value. Shell components of the moment of inertia are derived in terms of the periodic-orbit free-energy shell corrections. A good agreement between the semiclassical extended Thomas-Fermi moments of inertia with shell corrections and the quantum results is obtained for different nuclear deformations and particle numbers. Shell effects are shown to be exponentially dampted out with increasing temperature in all the transport coefficients.Comment: 83 pages, 39 figures, 4 tables, corrected typos and improved Englis

A critical examination of compound stability predictions from machine-learned formation energies

Machine learning has emerged as a novel tool for the efficient prediction of material properties, and claims have been made that machine-learned models for the formation energy of compounds can approach the accuracy of Density Functional Theory (DFT). The models tested in this work include five recently published compositional models, a baseline model using stoichiometry alone, and a structural model. By testing seven machine learning models for formation energy on stability predictions using the Materials Project database of DFT calculations for 85,014 unique chemical compositions, we show that while formation energies can indeed be predicted well, all compositional models perform poorly on predicting the stability of compounds, making them considerably less useful than DFT for the discovery and design of new solids. Most critically, in sparse chemical spaces where few stoichiometries have stable compounds, only the structural model is capable of efficiently detecting which materials are stable. The nonincremental improvement of structural models compared with compositional models is noteworthy and encourages the use of structural models for materials discovery, with the constraint that for any new composition, the ground-state structure is not known a priori. This work demonstrates that accurate predictions of formation energy do not imply accurate predictions of stability, emphasizing the importance of assessing model performance on stability predictions, for which we provide a set of publicly available tests

Quantum calculations of Coulomb reorientation for sub-barrier fusion

Classical mechanics and Time Dependent Hartree-Fock (TDHF) calculations of heavy ions collisions are performed to study the rotation of a deformed nucleus in the Coulomb field of its partner. This reorientation is shown to be independent on charges and relative energy of the partners. It only depends upon the deformations and inertias. TDHF calculations predict an increase by 30% of the induced rotation due to quantum effects while the nuclear contribution seems negligible. This reorientation modifies strongly the fusion cross-section around the barrier for light deformed nuclei on heavy collision partners. For such nuclei a hindrance of the sub-barrier fusion is predicted.Comment: accepted for publication in Physical Review Lette

A Monte Carlo Study of the Dynamical-Flucautation Property of the Hadronic System Inside Jets

A study of the dynamical fluctuation property of jets is carried out using Monte Carlo method. The results suggest that, unlike the average properties of the hadronic system inside jets, the anisotropy of dynamical fluctuations in these systems changes abruptly with the variation of the cut parameter \yct. A transition point exists, where the dynamical fluctuations in the hadronic system inside jet behave like those in soft hadronic collisions, i.e. being circular in the transverse plan with repect to dynamical fluctuations. This finding obtained from Jetset and Herwig Monte Carlo is encouraged to be checked by experiments.Comment: 8 pages, 3 figure

Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state

In this work, a self-consistent thermodynamic approach to micromagnetism is presented. The magnetic degrees of freedom are modeled using the Landau-Lifshitz-Baryakhtar theory, that separates the different contributions to the magnetic damping, and thereby allows them to be coupled to the electron and phonon systems in a self-consistent way. We show that this model can quantitatively reproduce ultrafast magnetization dynamics in Nickel.Comment: 5 pages, 3 figure

Death after smoking of fentanyl, 5F-ADB, 5F-MDMB-P7AICA and other synthetic cannabinoids with a bucket bong

Purpose: We report a case of a polydrug user who consumed various synthetic cannabinoids and fentanyl from a transdermal patch via a bucket bong. Toxicological results from postmortem matrices with special focus on synthetic cannabinoids are discussed in terms of their relevance to the death. Methods: The samples were analyzed by toxicological screening procedures involving immunoassays and gas chromatography–mass spectrometry (GC–MS) as well as quantitative analyses by means of GC–MS and high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS). Results: At the autopsy, coronary artery disease and signs of liver congestion were noted, in the absence of acute myocardial ischemic changes. Femoral blood concentrations of fentanyl and pregabalin were 14 ng/mL and 3,200 ng/mL, respectively. In addition, 2.7 ng/mL 5F-ADB and 13 ng/mL 5F-MDMB-P7AICA were detected together with relatively low amounts of 5 other synthetic cannabinoids in cardiac blood. A total number of up to 17 synthetic cannabinoids were detected in kidney, liver, urine and hair. Fentanyl and 5F-ADB were also detected in the water of the bucket bong. Conclusions: The cause of death could be attributed to an acute mixed intoxication by fentanyl and 5F-ADB (both Toxicological Significance Score (TSS) = 3) with a contribution of pregabalin and 5F-MDMB-P7AICA (TSS = 2), in a subject suffering from pre-existing heart damage. The most plausible mechanism of death consists in a respiratory depression. This case report demonstrates that use of opioids in combination with synthetic cannabinoids might be particularly dangerous