Configurational lattice dynamics: The phase diagram of Rh − Pd

Free energies of Rh-Pd alloys as functions of both temperature and composition are calculated using quasiharmonic lattice dynamics. The free energy of the disordered solid is determined from an ensemble of a large number of randomly generated configurations. Both configurational and vibrational contributions to the entropy and enthalpy of mixing are taken into account. We study the convergence with the number of random configurations, and analyze the validity of the zero static internal stress approximation ZSISA, where only external strains are relaxed fully dynamically while internal stresses are relaxed in the static approximation. It is shown that the use of ZSISA allows an accurate calculation of free energies in a fraction of the time needed to carry out fully dynamic optimizations. From the values of free energies as functions of composition and temperature the phase diagram of Rh-Pd alloys is calculated, showing a good agreement with Monte Carlo simulations as well as with experiment. It is also shown that although free energies of mixing appear to be linear functions of temperature to a good approximation, the explicit expressions given by the configurational lattice dynamics method show that both enthalpies and entropies of mixing change appreciably with temperature.Fil: Cienfuegos, Clarisa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Isoardi, E. P.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Barrera, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentin

Area metropolitana e citta' diffusa: potenzialita' e limiti di un modello urbano

Recenti proposte parlamentari porpongono di mettere fine ad una discussione sulla città e/o area metropolitana di Roma, confermandone: • una dimensione d’area vasta coincidente con quella della provincia; • la sussidiarietà e la sostenibilità come principi ispiratori ed ordinatori dell’azione di governo del territorio; • le funzioni unitarie e complementari di livello territoriale (programmazione degli interventi per Roma Capitale, le opere di interesse statale, il patrimonio pubblico e privato nazionale ed internazionale, la valorizzazione e la gestione del sistema culturale, ambientale e del turismo, la ricerca e la formazione universitaria, le attività fieristico-congressuali-espositive, l’industria innovativa legata all’ICS); collocando la questione della scelta metropolitana per Roma ad un livello europeo, eppure intermedio tra la scala politica propria della città-capitale e i compiti di programmazione e gestione che il nostro ordinamento costituzionale attribuisce alle province (per l’Europa, le NUT 3). Rispetto a questo obiettivo, Roma non appare in posizione soddisfacente nella mappatura europea delle aree/città capitali metropolitane. Anche se, la spinta al policentrismo impressa dall’Unione potrebbe trovare già una base di corrispondenze nell’organizzazione – soprattutto spontanea - del territorio e dell’economia romana (non solo della Città). Se per un verso, dunque, c’è da augurarsi che attraverso un più stretto recepimento delle indicazioni europee (Cfr. strutture già cooperative su base policentrica), l’area vasta romana, cioè la provincia, diventi nel prossimo periodo 2007-2013 molto più visibile; la mancanza di strumenti appropriati al raggiungimento di questo obiettivo rappresenta un freno alla piena realizzazione di una metropoli diversa dalla semplice somma di progetti ed impostazioni negoziati “dall’alto”, di portata nazionale e regionale, che escludono, ad una lettura “fisica e formale” del territorio, la domanda di integrazione “dal basso”, cioè il riconoscimento, anche economico, delle forme insediative coese riconoscibili romane. In tal senso Roma e la sua provincia rappresentano il livello ideale per una lettura della programmazione territoriale europea, ma anche il livello sussidiario della mediazione tra una visione metropoitana globale e una locale, somma di insediamenti continui, diffusi o nucleari isolati (perirubanizzazione mista ad insediamento puntuale), attualmente privi di orientamento alla governance; lontani cioè da quell’insieme di regole con cui si attua la programmazione spaziale e fisica richiesta dall’Unione, entro cui ogni NUT offre il proprio contributo alla creazione di uno spazio integrato, anche attraverso scelte sussidiarie di metropolitanizzazione (cfr. Territorial Agenda 2007)

Removal of interleukin-1ß and tumor necrosis factor from human plasma by in vitro dialysis with polyacrylonitrile membranes

Contains fulltext : 4735.pdf (publisher's version ) (Open Access

Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale

We present a study of the HII regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197,637 individual spectra, using Integral Field Spectrocopy (IFS) recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ~2 effective radii (re ), sampling its morphological structures with unprecedented spatial resolution for a wide-field IFU. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogue of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allow us to estimate the typical mixing scale-length (rmix ~0.4 re ), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms, when comparing with simulations. We found evidence for an azimuthal variation of the oxygen abundance, that may be related with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.Comment: 13 pages, 7 Figurs, accepted for publishing in A&

Acceleration of the Universe driven by the Casimir force

We investigate an evolutional scenario of the FRW universe with the Casimir energy scaling like $(-)(1+z)^4$. The Casimir effect is used to explain the vacuum energy differences (its value measured from astrophysics is so small compared to value obtained from quantum field theory calculations). The dynamics of the FRW model is represented in terms of a two-dimensional dynamical system to show all evolutional paths of this model in the phase space for all admissible initial conditions. We find also an exact solution for non flat evolutional paths of Universe driven by the Casimir effect. The main difference between the FRW model with the Casimir force and the $\Lambda$CDM model is that their generic solutions are a set of evolutional paths with a bounce solution and an initial singularity, respectively. The evolutional scenario are tested by using the SNIa data, FRIIb radiogalaxies, baryon oscillation peak and CMB observation. We compare the power of explanation of the model considered and the $\Lambda$CDM model using the Bayesian information criterion and Bayesian factor. Our investigation of the information criteria of model selection showed the preference of the $\Lambda$CDM model over the model considered. However the presence of negative like the radiation term can remove a tension between the theoretical and observed primordial ${}^4$He and D abundance.Comment: RevTeX4, 17 pages, 9 figure

Abrupt Convergence and Escape Behavior for Birth and Death Chains

We link two phenomena concerning the asymptotical behavior of stochastic processes: (i) abrupt convergence or cut-off phenomenon, and (ii) the escape behavior usually associated to exit from metastability. The former is characterized by convergence at asymptotically deterministic times, while the convergence times for the latter are exponentially distributed. We compare and study both phenomena for discrete-time birth-and-death chains on Z with drift towards zero. In particular, this includes energy-driven evolutions with energy functions in the form of a single well. Under suitable drift hypotheses, we show that there is both an abrupt convergence towards zero and escape behavior in the other direction. Furthermore, as the evolutions are reversible, the law of the final escape trajectory coincides with the time reverse of the law of cut-off paths. Thus, for evolutions defined by one-dimensional energy wells with sufficiently steep walls, cut-off and escape behavior are related by time inversion.Comment: 2 figure

I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties

The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g. with unfavourable ion B ∇ direction. It is characterised by the development of a temperature pedestal while the density remains roughly as in the L-mode. This leads to a confinement improvement above the L-mode level which can sometimes reach H-mode values. This regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has been studied again since 2009 taking advantage of the development of new diagnostics and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold, pedestal characteristics and confinement, are independent of the heating method. The power required at the L-I transition exhibits an offset linear density dependence but, in contrast to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be mainly determined by the edge pressure gradient and the comparison between ECRH and NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often evolves gradually over a few confinement times until the transition to H-mode which offers a very interesting situation to study the transport reduction and its link with the pedestal formation. Exploratory discharges in which n = 2 magnetic perturbations have been applied indicate that these can lead to an increase of the I-mode power threshold by flattening the edge pressure at fixed heating input power: more heating power is necessary to restore the required edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in detail.European Commission (EUROfusion 633053