Panizon E.,DellUniversity Genoa |
Ferrando R.,DellUniversity Genoa |
Ferrando R.,CNR Institute of Materials for Electronics and Magnetism
Physical Review B - Condensed Matter and Materials Physics | Year: 2015
Solid-solid transformations in Pd-Pt nanoalloys in the size range 32-38 atoms and for different compositions are computationally studied by the superposition approximation to the partition function, and by molecular dynamics simulations. A broad spectrum of transition types is shown to take place. These transition types are: (i) one-to-one type, in which the global minimum, which is dominant at low temperatures, transforms into another single isomer with increasing temperature; (ii) one-to-many type, in which the transition is from a single isomer to a family of other isomers; (iii) many-to-many type, in which the transition is between two different families of isomers; (iv) many-to-one type, in which the effect of vibrational entropy is to greatly reduce the number of relevant structures with increasing temperatures. We provide a rationale for these behaviors, which stem from the interplay between energetics and vibrational entropy effects. The vibrational entropy is explained by analyzing the vibrational density of states and the specific features of the normal modes. Quantum effects on the structural transitions are also discussed. © 2015 American Physical Society.
Foschi F.,DellUniversity Genoa |
Foschi F.,King's College London |
Conserva E.,University of Genoa |
Pera P.,University of Genoa |
And 3 more authors.
Journal of Biomaterials Applications | Year: 2012
Bone augmentation procedures rely on osteogenic/osteoconductive properties of bone graft material (BGM). A further improvement is represented by use of autologous bone marrow stromal cells (BMSC), expanded in vitro and seeded on BGM before implantation in the bone defect. The effect of different BGMs on BMSC osteogenic differentiation was evaluated. BMSC were cultured in vitro in the presence of different BGM (natural, synthetic, and mixed origins). Cellular morphology was analyzed with scanning electron microscopy. The capability of BMSC to differentiate was determined in vitro by alkaline phosphatase gene expression and enzyme activity at different time points (7, 14, and 28 days) and in vivo by ectopic bone formation of implanted tissue constructs in an immunodeficient murine model. BGM supports the cell adhesion and osteogenic differentiation of BMSC developing a useful tool in the bone tissue engineering. © The Author(s), 2010. Reprints and permissions: http://www.sagepub.co.uk/ journalsPermissions.nav.
Sole A.,University of Barcelona |
Oriols X.,Autonomous University of Barcelona |
Marian D.,University of Pisa |
Zanghi N.,DellUniversity Genoa
Fluctuation and Noise Letters | Year: 2016
Bohmian mechanics is a theory that provides a consistent explanation of quantum phenomena in terms of point particles whose motion is guided by the wave function. In this theory, the state of a system of particles is defined by the actual positions of the particles and the wave function of the system; and the state of the system evolves deterministically. Thus, the Bohmian state can be compared with the state in classical mechanics, which is given by the positions and momenta of all the particles, and which also evolves deterministically. However, while in classical mechanics it is usually taken for granted and considered unproblematic that the state is, at least in principle, measurable, this is not the case in Bohmian mechanics. Due to the linearity of the quantum dynamical laws, one essential component of the Bohmian state, the wave function, is not directly measurable. Moreover, it turns out that the measurement of the other component of the state - the positions of the particles - must be mediated by the wave function; a fact that in turn implies that the positions of the particles, though measurable, are constrained by absolute uncertainty. This is the key to understanding how Bohmian mechanics, despite being deterministic, can account for all quantum predictions, including quantum randomness and uncertainty. © 2016 World Scientific Publishing Company.
Oderji H.Y.,Dalian University of Technology |
Oderji H.Y.,University of Tehran |
Behnejad H.,University of Tehran |
Ferrando R.,dellUniversity Genoa |
Ding H.,Dalian University of Technology
RSC Advances | Year: 2013
Anti-Mackay icosahedral clusters of composition Ag32M 13, where M is either Cu, Ni, or Co, have been recently shown to possess special structural stability both by calculations and experiments. These nanoalloys assume a core-shell arrangement, with an icosahedral core of 13 M atoms surrounded by an Ag shell of anti-Mackay structure. In this paper we study the melting of these three nanoalloys, showing that, despite the close similarity of the structures, melting takes place through quite different mechanisms. In particular, we find that Ag32Co13 and Ag32Ni13 present a premelting phenomenon which involves only the shell of the cluster while the core melts at higher temperatures, in agreement with previous calculations. On the contrary, in Ag32Cu 13, melting occurs through stages that involve the shell and the core at the same time. These findings are rationalized in terms of the different features of the energy landscape of these nanoalloys. Our simulations, in which special care has been devoted to avoid non-ergodicity problems, show also that the particles keep their core-shell structures even in the liquid phase, indicating an incomplete miscibility of Ag with Ni, Co or Cu at the nanoscale up to quite high temperatures. This journal is © The Royal Society of Chemistry 2013.
D'Elia M.,DellUniversity Pisa |
Mariti M.,DellUniversity Pisa |
Negro F.,DellUniversity Genoa
Physical Review Letters | Year: 2013
We investigate two flavor quantum chromodynamics (QCD) in the presence of CP-odd electromagnetic background fields and determine, by means of lattice QCD simulations, the induced effective θ term to first order in E→·B→. We employ a rooted staggered discretization and study lattice spacings down to 0.1 fm and Goldstone pion masses around 480 MeV. In order to deal with a positive measure, we consider purely imaginary electric fields and real magnetic fields, and then exploit the analytic continuation. Our results are relevant to a description of the effective pseudoscalar quantum electrodynamics - QCD interactions. © 2013 American Physical Society.
D'Elia M.,DellUniversity Pisa |
Negro F.,DellUniversity Genoa
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013
We study the phase diagram of non-Abelian pure gauge theories in the presence of a topological θ term. The dependence of the deconfinement temperature on θ is determined on the lattice both by analytic continuation and by reweighting, obtaining consistent results. The general structure of the diagram is discussed on the basis of large-N considerations and of the possible analogies and dualities existing with the phase diagram of QCD in the presence of an imaginary baryon chemical potential. © 2013 American Physical Society.
Marian D.,Autonomous University of Barcelona |
Marian D.,DellUniversity Genoa |
Colomes E.,Autonomous University of Barcelona |
Zanghi N.,DellUniversity Genoa |
Oriols X.,Autonomous University of Barcelona
Journal of Physics: Conference Series | Year: 2015
The interest on weak measurements is rapidly growing during the last years as a unique tool to better understand and predict new quantum phenomena. Up to now many theoretical and experimental weak-measurement techniques deal with (relativistic) photons or cold atoms, but there is much less investigation on (non-relativistic) electrons in up-to-date electronics technologies. We propose a way to perform weak measurements in nanoelectronic devices through the measurement of the total current (particle plus displacement component) in such devices. We study the interaction between an electron in the active region of a electron device with a metal surface working as a sensing electrode by means of the (Bohmian) conditional wave function. We perform numerical (Monte Carlo) simulations to reconstruct the Bohmian trajectories in the iconic double slit experiment. This work opens new paths for understanding the quantum properties of an electronic system as well as for exploring new quantum engineering applications in solid state physics.
Pallavicini M.,DellUniversity Genoa |
Pesce R.,DellUniversity Genoa |
Petrolini A.,DellUniversity Genoa |
Thea A.,DellUniversity Genoa
Astroparticle Physics | Year: 2012
We review the main issues that are relevant for the observation of extensive air showers from an Earth-orbiting satellite. Extensive air showers are produced by the interaction of ultra-high energy cosmic particles with the atmosphere and can be observed by an orbiting telescope detecting the air scintillation light. We provide the main analytical formulas and semi-analytical results needed to optimize the design of a suitable telescope and estimate the best-expected performance and the minimal necessary requirements for the observation. While we have in mind an EUSO-like general-purpose experiment, the results presented in this paper are useful for any kind of space-based experiment. © 2011 Elsevier B.V. All rights reserved.
Albareda G.,Autonomous University of Barcelona |
Marian D.,DellUniversity Genoa |
Benali A.,Autonomous University of Barcelona |
Yaro S.,Autonomous University of Barcelona |
And 2 more authors.
Journal of Computational Electronics | Year: 2013
It is shown that Bohmian mechanics applied to describe electron transport in open systems (in terms of waves and particles) leads to a quantum-trajectory Monte Carlo algorithm where randomness appears because of the uncertainties in the number of electrons, their energies and the initial positions of the trajectories. The usefulness of this formalism to provide predictions beyond DC, namely AC regime, transient and noise, in nanoelectronic devices, is proven and discussed in detail. In particular, we emphasize the ability of this formalism to provide a straightforward answer to the measurement of the total current and its advantages to deal with the many-body problem in electron transport scenarios. All the results presented along the manuscript have been obtained using the electron device simulator BITLLES. © 2013 Springer Science+Business Media New York.
Bruno D.,DellUniversity Genoa
Journal of Mathematical Physics | Year: 2011
The paper is devoted to prove the existence of a local solution of the Hamilton-Jacobi equation in field theory, whence the general solution of the field equations can be obtained. The solution is adapted to the choice of the submanifold where the initial data of the field equations are assigned. Finally, a technique to obtain the general solution of the field equations, starting from the given initial manifold, is deduced. © 2011 American Institute of Physics.