Statistical equilibrium in simple exchange games I

Simple stochastic exchange games are based on random allocation of finite resources. These games are Markov chains that can be studied either analytically or by Monte Carlo simulations. In particular, the equilibrium distribution can be derived either by direct diagonalization of the transition matrix, or using the detailed balance equation, or by Monte Carlo estimates. In this paper, these methods are introduced and applied to the Bennati-Dragulescu-Yakovenko (BDY) game. The exact analysis shows that the statistical-mechanical analogies used in the previous literature have to be revised.Comment: 11 pages, 3 figures, submitted to EPJ

Protein accumulation in the endoplasmic reticulum as a non-equilibrium phase transition

Several neurological disorders are associated with the aggregation of aberrant proteins, often localized in intracellular organelles such as the endoplasmic reticulum. Here we study protein aggregation kinetics by mean-field reactions and three dimensional Monte carlo simulations of diffusion-limited aggregation of linear polymers in a confined space, representing the endoplasmic reticulum. By tuning the rates of protein production and degradation, we show that the system undergoes a non-equilibrium phase transition from a physiological phase with little or no polymer accumulation to a pathological phase characterized by persistent polymerization. A combination of external factors accumulating during the lifetime of a patient can thus slightly modify the phase transition control parameters, tipping the balance from a long symptomless lag phase to an accelerated pathological development. The model can be successfully used to interpret experimental data on amyloid-\b{eta} clearance from the central nervous system

ISM composition through X-ray spectroscopy of LMXBs

The diffuse interstellar medium (ISM) is an integral part of the evolution of the entire Galaxy. Metals are produced by stars and their abundances are the direct testimony of the history of stellar evolution. However, the interstellar dust composition is not well known and the total abundances are yet to be accurately determined. We probe ISM dust composition, total abundances, and abundance gradients through the study of interstellar absorption features in the high-resolution X-ray spectra of Galactic low-mass X-ray binaries (LMXBs). We use high-quality grating spectra of nine LMXBs taken with XMM-Newton. We measure the column densities of O, Ne, Mg, and Fe with an empirical model and estimate the Galactic abundance gradients. The column densities of the neutral gas species are in agreement with those found in the literature. Solids are a significant reservoir of metals like oxygen and iron. Respectively, 15-25 % and 65-90 % of the total amount of O I and Fe I is found in dust. The dust amount and mixture seem to be consistent along all the lines-of-sight (LOS). Our estimates of abundance gradients and predictions of local interstellar abundances are in agreement with those measured at longer wavelengths. Our work shows that X-ray spectroscopy is a very powerful method to probe the ISM. For instance, on a large scale the ISM appears to be chemically homogeneous showing similar gas ionization ratios and dust mixtures. The agreement between the abundances of the ISM and the stellar objects suggests that the local Galaxy is also chemically homogeneous.Comment: 13 pages, 10 figures, 5 tables, accepted to A&

EAPC task force on education for psychologists in palliative care

It is argued that psychological aspects of care and psychosocial problems are essential components of palliative care. However, the provision of appropriate services remains somewhat arbitrary. Unlike medical and nursing care, which are clearly delivered by doctors and nurses respectively, psychological and psychosocial support in palliative care are not assigned exclusively to psychologists. It is generally expected that all professionals working in palliative care should have some knowledge of the psychological dynamics in terminal illness, as well as skills in communication and psychological risk assessment. On the one hand, palliative care education programmes for nurses and doctors comprise a considerable amount of psychological and psychosocial content. On the other hand, only a few palliative care associations provide explicit information on the role and tasks of psychologists in palliative care. Psychologists’ associations do not deal much with this issue either. If they refer to it at all, it is in the context of the care of the aged, end-of-life care or how to deal with grief

Chandra imaging of the ∼\simkpc extended outflow in 1H 0419-577

The Seyfert 1 galaxy 1H 0419-577 hosts a $\sim$kpc extended outflow that is evident in the [\ion{O}{iii}] image and that is also detected as a warm absorber in the UV/X-ray spectrum. Here, we analyze a $\sim$30 ks Chandra-ACIS X-ray image, with the aim of resolving the diffuse extranuclear X-ray emission and of investigating its relationship with the galactic outflow. Thanks to its sub-arcsecond spatial resolution, Chandra resolves the circumnuclear X-ray emission, which extends up to a projected distance of at least $\sim$16 kpc from the center. The morphology of the diffuse X-ray emission is spherically symmetrical. We could not recover a morphological resemblance between the soft X-ray emission and the ionization bicone that is traced by the [\ion{O}{iii}] outflow. we argue that the photoionized gas nebula must be distributed mostly along the polar directions, outside our line of sight. In this geometry, the X-ray/UV warm absorber must trace a different gas component, physically disconnected from the emitting gas, and located closer to the equatorial plane.Comment: accepted for publications A&

Epistemic Logic Programs: A Study of Some Properties

Epistemic logic programs (ELPs), extend answer set programming (ASP) with epistemic operators. The semantics of such programs is provided in terms of world views, which are sets of belief sets, that is, syntactically, sets of sets of atoms. Different semantic approaches propose different characterizations of world views. Recent work has introduced semantic properties that should be met by any semantics for ELPs, like the Epistemic Splitting Property, that, if satisfied, allows to modularly compute world views in a bottom-up fashion, analogously to "traditional"ASP. We analyze the possibility of changing the perspective, shifting from a bottom-up to a top-down approach to splitting. We propose a basic top-down approach, which we prove to be equivalent to the bottom-up one. We then propose an extended approach, where our new definition: (i) is provably applicable to many of the existing semantics; (ii) operates similarly to "traditional"ASP; (iii) provably coincides under any semantics with the bottom-up notion of splitting at least on the class of Epistemically Stratified Programs (which are, intuitively, those where the use of epistemic operators is stratified); (iv) better adheres to common ASP programming methodology

Epistemic Logic Programs: an Approach to Semantic Comparison

Epistemic Logic Programs (ELPs) extend Answer Set Programming (ASP) with epistemic operators. The semantics of such programs is provided in terms of world views, which are sets of belief sets. Several semantic approaches have been proposed over time to characterize world views. Recent work has introduced semantic properties that should be met by any semantics for ELPs. We propose a new method, easy but, we believe, effective, to compare the different semantic approaches

Epistemic Logic Programs: a Novel Perspective and Some Extensions

Epistemic Logic Programs (ELPs), which propose an extension to Answer Set Programming (ASP) with epistemic operators, have their semantic defined, in various ways, in terms of world views, which are sets of belief sets. Several semantic approaches have in fact been proposed over time to characterize world views, and, recently, to also characterize semantic properties that should be met by any semantics for ELPs. We propose a new semantics, easy also from the computational point of view, but effective, also in order to compare the different semantic approaches. We also propose a significant extension to the ELP approach, by allowing epistemic atoms in rule heads

Fast Prototyping of a Solver for Reduct-based ELP Semantics

Several semantic approaches have been proposed over time for Epistemic Logic Programs (ELPs), which is an extension to Answer Set Programming (ASP) with epistemic operators. ELP semantics has been defined, in various ways, in terms of world views, which are sets whose elements are sets of atoms. Several semantic approaches are Reduct-based, i.e., extend to ELPs what done for ASP, in the sense that in order to find the world views of a given program they propose to: start with a candidate world view; build the reduct of the program with respect to this candidate world view, according to some specific definition of such reduct; compute the set of stable models of the reduct; check whether the candidate world view is indeed a world view, which is the case if it coincides with the set of stable models of the reduct. Solvers have been developed for some of these approaches, but new semantics/variations have been introduced, and are likely to be introduced in the future, as there is no consensus yet on the “right” semantics. We propose a fast-prototyping approach to obtain a solver for any reduct-based semantics, with the advantage to be able to experiment the approach on small/medium programs, and not only on very small programs as done so far, prior to undertaking the costly process of developing a dedicated solver