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 The relation coefficients obtained here have been superseded by those presented in Muraveva et al.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&

Variable stars and stellar populations in Andromeda XXI: II. Another merged galaxy satellite of M31?

B and V time-series photometry of the M31 dwarf spheroidal satellite Andromeda XXI (And XXI) was obtained with the Large Binocular Cameras at the Large Binocular Telescope. We have identified 50 variables in And XXI, of which 41 are RR Lyrae stars (37 fundamental-mode RRab, and 4 first-overtone RRc, pulsators) and 9 are Anomalous Cepheids (ACs). The average period of the RRab stars ( = 0.64 days) and the period-amplitude diagram place And~XXI in the class of Oosterhoff II - Oosterhoff-Intermediate objects. From the average luminosity of the RR Lyrae stars we derived the galaxy distance modulus of (m-M)$_0$=$24.40\pm0.17$ mag, which is smaller than previous literature estimates, although still consistent with them within 1 $\sigma$. The galaxy color-magnitude diagram shows evidence for the presence of three different stellar generations in And~XXI: 1) an old ($\sim$ 12 Gyr) and metal poor ([Fe/H]=$-$1.7 dex) component traced by the RR Lyrae stars; 2) a slightly younger (10-6 Gyr) and more metal rich ([Fe/H]=$-$1.5 dex) component populating the red horizontal branch, and 3) a young age ($\sim$ 1 Gyr) component with same metallicity, that produced the ACs. Finally, we provide hints that And~XXI could be the result of a minor merging event between two dwarf galaxies.Comment: accepted for publications in Ap

Waste heat to power conversion by means of thermomagnetic hydrodynamic energy harvester

Energy harvesting from extremely low enthalpy sources can play an important role in increasing the sustainability of future energy applications: low temperature differences are common and offer an abundant source, available both in the natural environment and as the result of a many industrial process. This paper presents the first closed-loop thermomagnetic hydrodynamic energy harvester, based on thermomagnetic advection and exploiting a commercial ferrofluid. The lab-scale prototype has a toroidal geometry adopted from the well-known tokamak inertial machines. Peltier modules are used to control the thermal gradient that is harvested and converted directly to electric energy, while permanent magnets trigger the advection. Temperature sensors are installed along the toroidal walls (thermistors) and are placed in contact with the rotating fluid (thermocouples). To extract and ensure the electrical energy output, the structure is wrapped-up with induction coils. Two coil configurations (purely poloidal and mixed poloidal/toroidal windings) are tested, in a heterogeneous two-phase flow from the combination of water carrier and ferrofluid packets, reaching a maximum extracted electrical power per unit of temperature difference of 10.4 μW/K. This positions the device close to 20% of the ideal Carnot efficiency of a thermal machine working on the same temperature drop. Numerical analysis of the system has been performed developing a Fortran™ code in a Eulerian framework, using a mixed Fourier-Galerkin/finite difference spatial discretization. The harvester is suitable for producing electricity from running engines, appliances, warm gas exhausts, exothermic processes

Changes in brain rhythms and connectivity tracking fear acquisition and reversal

Fear conditioning is used to investigate the neural bases of threat and anxiety, and to understand their flexible modifications when the environment changes. This study aims to examine the temporal evolution of brain rhythms using electroencephalographic signals recorded in healthy volunteers during a protocol of Pavlovian fear conditioning and reversal. Power changes and Granger connectivity in theta, alpha, and gamma bands are investigated from neuroelectrical activity reconstructed on the cortex. Results show a significant increase in theta power in the left (contralateral to electrical shock) portion of the midcingulate cortex during fear acquisition, and a significant decrease in alpha power in a broad network over the left posterior-frontal and parietal cortex. These changes occur since the initial trials for theta power, but require more trials (3/4) to develop for alpha, and are also present during reversal, despite being less pronounced. In both bands, relevant changes in connectivity are mainly evident in the last block of reversal, just when power differences attenuate. No significant changes in the gamma band were detected. We conclude that the increased theta rhythm in the cingulate cortex subserves fear acquisition and is transmitted to other cortical regions via increased functional connectivity allowing a fast theta synchronization, whereas the decrease in alpha power can represent a partial activation of motor and somatosensory areas contralateral to the shock side in the presence of a dangerous stimulus. In addition, connectivity changes at the end of reversal may reflect long-term alterations in synapses necessary to reverse the previously acquired contingencies

Integrated geophysical survey to recognize ancient Picentia’s buried walls, in the Archaeological Park of Pontecagnano – Faiano (Southern Italy)

There is no information on previous geophysical prospections carried out in the Archaeological Park of Pontecagnano- Faiano, in order to reconstruct the ancient settlement of Picentia, an Etrusco-Campanian and Roman settlement near Salerno (Southern Italy). Therefore, an integrated geophysical survey based on magnetic, geoelectric and ground-penetrating radar (GPR) prospections was executed in the Park. The methods provided a basic map of buried ancient structures at depth from 0.1-0.2 to about 1.5 meters. Magnetic data were processed analyzing the analytical signal of the vertical derivative of the measured gradient and this substantially reduced a strong fence effect. The results of the geophysical prospections showed archaeological structures located close to those discovered in the excavated areas. The shape of the anomalies are usually elongated with well-defined geometrical characteristics. Many anomalies are arranged along orthogonal directions and they are very coherent with the excavated structures, namely the quarters structures of the ancient Picentia

The role of juveniles in structuring demersal assemblages in trawled fishing grounds

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Management of self-inflicted orchiectomy in psychiatric patient. Case report and non-systematic review of the literature.

INTRODUCTION: Self-inflicted orchidectomy and auto-castration, also known as "Eshmun complex" is a rare phenomenon. The aim of our study it to present the management of a patient who performed a self orchiectomy and propose a non-systematic review of literature about self-orchiectomy. MATERIAL AND METHOD: A 27-years old male Patient with psychiatric disorder was admitted to our ward to have been cutted his scrotum with scissors and cut away his left testicle causing active bleeding from the left spermatic artery. The patient underwent emergency surgery with clamping of the spermatic cord and hemostasis of the wound. RESULTS: After surgery the clinical condition of the patient remained good during whole hospitalization. Urgent psychiatric evaluation was performed in order to administer proper therapy for acute management. To best of our knowledge, only 11 cases of self-orchidectomy are reported in literature and all of them except 1 case, underwent surgical exploration. CONCLUSIONS: Self-orchidectomy is an extremely rare phenomenon, often associated with psychiatric disorders, compounded by the use of drugs. In our opinion, emergency surgery should be the first choice of treatment, offering diagnostic and hemostatic purpose in a single act, aimed to prevent acute and postacute complications