A hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes

Aims. We aim at creating a Bayesian model to infer the coefficients of PL or PLZ relations that propagates uncertainties in the observables in a rigorous and well founded way. Methods. We propose a directed acyclic graph to encode the conditional probabilities of the inference model that will allow us to infer probability distributions for the PL and PL(Z) relations. We evaluate the model with several semi-synthetic data sets and apply it to a sample of 200 fundamental mode and first overtone mode RR Lyrae stars for which Gaia DR1 parallaxes and literature Ks-band mean magnitudes are available. We define and test several hyperprior probabilities to verify their adequacy and check the sensitivity of the solution with respect to the prior choice. Results. The main conclusion of this work is the absolute necessity of incorporating the existing correlations between the observed variables (periods, metallicities and parallaxes) in the form of model priors in order to avoid systematically biased results, especially in the case of non-negligible uncertainties in the parallaxes. The tests with the semi-synthetic data based on the data set used in Gaia Collaboration et al. (2017) reveal the significant impact that the existing correlations between parallax, metallicity and periods have on the inferred parameters. The relation coefficients obtained here have been superseded by those presented in Muraveva et al. (2018a), that incorporates the findings of this work and the more recent Gaia DR2 measurements.Comment: 14 pages, 12 figures. Submitted to A&

Optimal Design of Silicon-based Chips for Piezo-induced Ultrasound Resonances in Embedded Microchannels

AbstractWe present a variational formulation of the governing equations and introduce global indicators to describe the behavior of acoustofluidic devices driven at resonance frequencies by means of a piezoelectric transducer. The individuation of the correct Lagrangian densities for the different parts constituting the device (the piezo transducer, the silicon walls, the fluid-filled microchannel, and the glass lid) allows for the introduction of the weak formulation used in the finite element discretization of the equations describing the system in its oscillatory regime. Additionally, the knowledge of the Lagrangian density leads to the derivation of the correct structure of the Hamiltonian density, i.e. the energy density, which is important for the quantification of the energy content of the whole system and its individual parts. Specifically, the energy content of the embedded microchannel is quantified by means of the acoustofluidic yield η defined as the ratio between the energy in the channel and the total energy. From the standpoint of acoustophoretic application, the introduction of the acoustophoretic mean orientation allows us to identify the frequencies for which an acoustophoretic effect, i.e. the lateral motion of particle dragged by the axial main flow, is particularly strong. Finally, the connection between the mechanical and electrical degrees of freedom of the system is addressed. This is important for proper determination of the dissipated power, and it may lead to the detection of resonance states by means of purely electrical measurements. Numerical simulations and preliminary experimental results show some features of the model introduced

Costruire in pietra, pratica e storia. Laboratorio di stereotomia - Palermo 2016

Il volume raccoglie i contributi presentati in occasione del seminario introduttivo al Laboratorio di stereotomia, tenutosi presso il Dipartimento di Architettura dell'Università degli studi di Palermo nel mese di aprile del 2016, e un contributo che illustra quest'ultima esperienza. Nel complesso, i diversi saggi ruotano intorno al tema della costruzione in pietra nell'ambito dell'architettura tardogotica, con particolare attenzione alle volte, osservata da diversi punti di vista e ambiti disciplinari che spaziano dalla storia, al disegno, alla storia della costruzione. Ricerca e didattica si intrecciano e concorrono a fare nuova luce su esperienze costruttive di primo piano nella storia dell'architettura europea, secondo una modalità già sperimentata da José Carlos Palacios Gonzalo nel Laboratorio di costruzione gotica dell'Universidad Politecnica di Madrid e replicata a Palermo nel Laboratorio di stereotomiaThis volume collects the contributions presented at the introductory seminar at Laboratory of stereotomy, held at the Department of Architecture of the University of Palermo in April of 2016, and a contribution that illustrates this last experience. All the essays deal with the theme of the stone building in late Gothic architecture, with particular attention to the vaults, observed from different points of view and disciplines ranging from history, to drawing, to construction history . Research and teaching are intertwined and help to shed new light on experiences prominent in the history of European architecture, according to a methodology already tested by José Carlos Gonzalo Palacios in the Gothic building Laboratory of the Universidad Politecnica de Madrid and replicated in Palermo in the Laboratory of stereotomy

Regularity estimates for the solution and the free boundary to the obstacle problem for the fractional Laplacian

We use a characterization of the fractional Laplacian as a Dirichlet to Neumann operator for an appropriate differential equation to study its obstacle problem. We write an equivalent characterization as a thin obstacle problem. In this way we are able to apply local type arguments to obtain sharp regularity estimates for the solution and study the regularity of the free boundary

Local behavior of p-harmonic Green's functions in metric spaces

We describe the behavior of p-harmonic Green's functions near a singularity in metric measure spaces equipped with a doubling measure and supporting a Poincar\'e inequality

Broad emission lines for negatively spinning black holes

We present an extended scheme for the calculation of the profiles of emission lines from accretion discs around rotating black holes. The scheme includes discs with angular momenta which are parallel and antiparallel with respect to the black hole's angular momentum, as both configurations are assumed to be stable (King et al., 2005). We discuss line shapes for such discs and present a code for modelling observational data with this scheme in X-ray data analysis programs. Based on a Green's function approach, an arbitrary radius dependence of the disc emissivity and arbitrary limb darkening laws can be easily taken into account, while the amount of precomputed data is significantly reduced with respect to other available models.Comment: 7 pages, 6 figures; accepted by MNRAS for Publication, now matches the proof read versio

Targeting lipid rafts as a strategy against coronavirus

Lipid rafts are functional membrane microdomains containing sphingolipids, including gangliosides, and cholesterol. These regions are characterized by highly ordered and tightly packed lipid molecules. Several studies revealed that lipid rafts are involved in life cycle of different viruses, including coronaviruses. Among these recently emerged the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The main receptor for SARS-CoV-2 is represented by the angiotensin-converting enzyme-2 (ACE-2), although it also binds to sialic acids linked to host cell surface gangliosides. A new type of ganglioside-binding domain within the N-terminal portion of the SARS-CoV-2 spike protein was identified. Lipid rafts provide a suitable platform able to concentrate ACE-2 receptor on host cell membranes where they may interact with the spike protein on viral envelope. This review is focused on selective targeting lipid rafts components as a strategy against coronavirus. Indeed, cholesterol-binding agents, including statins or methyl-β-cyclodextrin (MβCD), can affect cholesterol, causing disruption of lipid rafts, consequently impairing coronavirus adhesion and binding. Moreover, these compounds can block downstream key molecules in virus infectivity, reducing the levels of proinflammatory molecules [tumor necrosis factor alpha (TNF-α), interleukin (IL)-6], and/or affecting the autophagic process involved in both viral replication and clearance. Furthermore, cyclodextrins can assemble into complexes with various drugs to form host–guest inclusions and may be used as pharmaceutical excipients of antiviral compounds, such as lopinavir and remdesivir, by improving bioavailability and solubility. In conclusion, the role of lipid rafts-affecting drugs in the process of coronavirus entry into the host cells prompts to introduce a new potential task in the pharmacological approach against coronavirus

Advances in the Pathophysiology of Thrombosis in Antiphospholipid Syndrome. Molecular Mechanisms and Signaling through Lipid Rafts

The pathological features of antiphospholipid syndrome (APS) are related to the activity of circulating antiphospholipid antibodies (aPLs) associated with vascular thrombosis and obstetric complications. Indeed, aPLs are not only disease markers, but also play a determining pathogenetic role in APS and exert their effects through the activation of cells and coagulation factors and inflammatory mediators for the materialization of the thromboinflammatory pathogenetic mechanism. Cellular activation in APS necessarily involves the interaction of aPLs with target receptors on the cell membrane, capable of triggering the signal transduction pathway(s). This interaction occurs at specific microdomains of the cell plasma membrane called lipid rafts. In this review, we focus on the key role of lipid rafts as signaling platforms in the pathogenesis of APS, and propose this pathogenetic step as a strategic target of new therapies in order to improve classical anti-thrombotic approaches with "new " immunomodulatory drugs