Demagnetization via Nucleation of the Nonequilibrium Metastable Phase in a Model of Disorder

We study both analytically and numerically metastability and nucleation in a two-dimensional nonequilibrium Ising ferromagnet. Canonical equilibrium is dynamically impeded by a weak random perturbation which models homogeneous disorder of undetermined source. We present a simple theoretical description, in perfect agreement with Monte Carlo simulations, assuming that the decay of the nonequilibrium metastable state is due, as in equilibrium, to the competition between the surface and the bulk. This suggests one to accept a nonequilibrium "free-energy" at a mesoscopic/cluster level, and it ensues a nonequilibrium "surface tension" with some peculiar low-T behavior. We illustrate the occurrence of intriguing nonequilibrium phenomena, including: (i) Noise-enhanced stabilization of nonequilibrium metastable states; (ii) reentrance of the limit of metastability under strong nonequilibrium conditions; and (iii) resonant propagation of domain walls. The cooperative behavior of our system may also be understood in terms of a Langevin equation with additive and multiplicative noises. We also studied metastability in the case of open boundaries as it may correspond to a magnetic nanoparticle. We then observe burst-like relaxation at low T, triggered by the additional surface randomness, with scale-free avalanches which closely resemble the type of relaxation reported for many complex systems. We show that this results from the superposition of many demagnetization events, each with a well- defined scale which is determined by the curvature of the domain wall at which it originates. This is an example of (apparent) scale invariance in a nonequilibrium setting which is not to be associated with any familiar kind of criticality.Comment: 26 pages, 22 figure

Piperacillin/tazobactam vs. cefoperazone/sulbactam in adult low-risk febrile neutropenia cases

WOS: 000330113500014PubMed ID: 24372736AimThe aim of this study was to compare the efficacy of piperacillin/tazobactam (P/T) and cefoperazone/sulbactam (C/S) in the empirical treatment of adult neutropenic fever. MethodsData and outcomes of low-risk adult cases with neutropenic fever and treated with P/T (4.5gq6h) or C/S (2gq8h) between 2005 and 2011 June were extracted from our database. Risk evaluation was made according to criteria of Multinational Association for Supportive Care in Cancer (MASCC) and a score of 21 was considered as low risk. Data were collected prospectively by daily visits and evaluated retrospectively. Primary outcome was - fever defervescence at 72h in combination with success without modification (referring to episodes where the patient recovered from fever with disappearance of signs of infection without modification to initial empirical treatment). All-cause mortality referred to death resulting from a documented or presumed infection or unidentified reason during the treatment and 30-day follow-up period. ResultsA total of 172 patients (113 cases P/T and 59 cases C/S) fulfilled the study inclusion criteria. Persistent response in P/T arm was 73.5%, whereas it was 64.5% in C/S arm (p>0.05). Rates of any modification were also similar in both treatment arms. All-cause mortality during the treatment and 30-day follow-up period was not significantly different (P/T: 4/113 vs. C/S: 2/59, p>0.05). There was no severe adverse effect requiring antibiotic cessation in both cohorts. ConclusionIn conclusion, our data suggest that C/S may be a safe alternative to P/T in the empirical treatment of adult low-risk febrile neutropenia cases