Precision limits of the twin-beam multiband URSULA

URSULA is a multiband astronomical photoelectric photometer which minimizes errors introduced by the presence of the atmosphere. It operates with two identical channels, one for the star to be measured and the other for a reference star. After a technical description of the present version of the apparatus, some measurements of stellar sources of different brightness, and in different atmospheric conditions are presented. These measurements, based on observations made with the 91 cm Cassegrain telescope of the Catania Astrophysical Observatory, are used to check the photometer accuracy and compare its performance with that of standard photometers

Metabolic syndrome and insulin resistance in pre-pubertal children with psoriasis

Psoriasis in adults is associated with an increased risk of metabolic disease. Various cardiometabolic comorbidities have been reported in childhood psoriasis, but only a few studies have analyzed the prevalence of metabolic syndrome. We performed a single-center prospective study investigating the prevalence of metabolic syndrome and insulin resistance in children with psoriasis. The prevalence of metabolic syndrome was evaluated in 60 pre-pubertal children with psoriasis (age: 3\u201310 years), accordingly to recently established criteria for the diagnosis of metabolic syndrome in children. Insulin resistance was considered altered when the homeostatic model assessment (HOMA-IR) for insulin resistance was 65 90th sex- and age-specific percentile and HOMA 2-IR was > 1.8. Eighteen (30%) children with psoriasis were found to have metabolic syndrome. Sixteen (27%) children were found to have insulin resistance. Conclusion: Our data underline the importance of assessing metabolic syndrome not only in adults and adolescents but also in young children with psoriasis.What is Known:\u2022 Psoriasis in adults is strongly associated with metabolic disease and insulin resistance.\u2022 Very limited data are available on the prevalence of metabolic syndrome and insulin resistance in pre-pubertal children with psoriasis.What is New:\u2022 This study reports that in pre-pubertal children with psoriasis, there is a high prevalence of metabolic syndrome and insulin resistance.\u2022 In children with psoriasis metabolic syndrome risk factors should be assessed

Widespread abiotic methane in chromitites

Recurring discoveries of abiotic methane in gas seeps and springs in ophiolites and peridotite massifs worldwide raised the question of where, in which rocks, methane was generated. Answers will impact the theories on life origin related to serpentinization of ultramafic rocks, and the origin of methane on rocky planets. Here we document, through molecular and isotopic analyses of gas liberated by rock crushing, that among the several mafic and ultramafic rocks composing classic ophiolites in Greece, i.e., serpentinite, peridotite, chromitite, gabbro, rodingite and basalt, only chromitites, characterized by high concentrations of chromium and ruthenium, host considerable amounts of 13C-enriched methane, hydrogen and heavier hydrocarbons with inverse isotopic trend, which is typical of abiotic gas origin. Raman analyses are consistent with methane being occluded in widespread microfractures and porous serpentine- or chlorite-filled veins. Chromium and ruthenium may be key metal catalysts for methane production via Sabatier reaction. Chromitites may represent source rocks of abiotic methane on Earth and, potentially, on Mars

Operation of a LAr-TPC equipped with a multilayer LEM charge readout

A novel detector for the ionization signal in a single phase LAr-TPC, based on the adoption of a multilayer Large Electron Multiplier (LEM) replacing the traditional anodic wire arrays, has been experimented in the ICARINO test facility at the INFN Laboratories in Legnaro. Cosmic muon tracks were detected allowing the measurement of energy deposition and a first determination of the signal to noise ratio. The analysis of the recorded events demonstrated the 3D reconstruction capability of ionizing events in this device in liquid Argon, collecting a fraction of about 90% of the ionization signal with signal to noise ratio similar to that measured with more traditional wire chambersComment: 9 pages, 7 Figure

Lithium Depletion Boundary in a Pre-Main Sequence Binary System

A lithium depletion boundary is detected in HIP 112312 (GJ 871.1 A and B), a \~12 Myr old pre-main sequence binary system. A strong (EW 300 mA) Li 6708 A absorption feature is seen at the secondary (~M4.5) while no Li 6708 A feature is detected from the primary (~M4). The physical companionship of the two stars is confirmed from common proper motions. Current theoretical pre-main sequence evolutionary models cannot simultaneously match the observed colors, brightnesses, and Li depletion patterns of this binary system. At the age upper limit of 20 Myr, contemporary theoretical evolutionary models predict too slow Li depletion. If true Li depletion is a faster process than predicted by theoretical models, ages of open clusters (Pleiades, alpha Persei, and IC 2391) estimated from the Li depletion boundary method are all overestimated. Because of the importance of the open cluster age scale, development of self-consistent theoretical models to match the HIP 112312 data is desirable.Comment: Accepted in ApJL. 5 pages total (3 tables, 3 figures

Probabilistic Quantum Memories

Typical address-oriented computer memories cannot recognize incomplete or noisy information. Associative (content-addressable) memories solve this problem but suffer from severe capacity shortages. I propose a model of a quantum memory that solves both problems. The storage capacity is exponential in the number of qbits and thus optimal. The retrieval mechanism for incomplete or noisy inputs is probabilistic, with postselection of the measurement result. The output is determined by a probability distribution on the memory which is peaked around the stored patterns closest in Hamming distance to the input.Comment: Revised version to appear in Phys. Rev. Let

The early evolution of Globular Clusters: the case of NGC 2808

Enhancement and spread of helium among globular cluster stars have been recently suggested as a way to explain the horizontal branch blue tails, in those clusters which show a primordial spread in the abundances of CNO and other elements involved in advanced CNO burning (D'Antona et al. 2002). In this paper we examine the implications of the hypothesis that, in many globular clusters, stars were born in two separate events: an initial burst (first generation), which gives origin to probably all high and intermediate mass stars and to a fraction of the cluster stars observed today, and a second, prolonged star formation phase (second generation) in which stars form directly from the ejecta of the intermediate mass stars of the first generation. In particular, we consider in detail the morphology of the horizontal branch in NGC 2808 and argue that it unveils the early cluster evolution, from the birth of the first star generation to the end of the second phase of star formation. This framework provides a feasible interpretation for the still unexplained dichotomy of NGC 2808 horizontal branch, attributing the lack of stars in the RR Lyr region to the gap in the helium content between the red clump, whose stars are considered to belong to the first stellar generation and have primordial helium, and the blue side of the horizontal branch, whose minimum helium content reflects the helium abundance in the smallest mass (~4Msun)contributing to the second stellar generation. This scenario provides constraints on the required Initial Mass Function, in a way that a great deal of remnant neutron stars and stellar mass black holes might have been produced.Comment: 23 pages, 7 figures, in press on The Astrophysical Journa

Comparing the vibrational behaviour of e-kick scooters and e-bikes: Evidence from Italy

E-kick scooters are currently among the most popular emerging electric-powered Personal micro–Mobility Vehicles (e-PMVs) and have recently been equated to e-bikes. However, even if the dynamic behaviour of e-bikes is well studied, much less has been done to understand the behaviour of e-kick scooters. Furthermore, comparisons between the two vehicles have rarely been investigated and only based on mechanical models. This study covers this gap by proposing a novel framework that evaluates the vibrational behaviours of both vehicles when driven by different users and exposed to the pavement irregularities, using both real and simulated data. The experimental data are collected equipping an e-kick scooter and an e-bike with Inertial Measurement Units, and then processed by ISO 2631–1 method to obtain an objective evaluation of the comfort. Next, the experimental data are expanded to include uncertainty applying a Monte Carlo Simulation based on a two-layer feed-forward Artificial Neural Network. Afterwards, several statistical analyses are performed to understand the key factors affecting the vibrational magnitude (and their extent) for each vehicle. This framework was tested in an Italian city (Brescia) along urban paths with five different pavement surfaces. The results showed that the e-kick scooter appears to be globally more solicited than the e-bike in terms of vibrational magnitude. Moreover, pavement surface, sensor position, user gender, user height, and travel speed are identified as crucial factors explaining the vibrational magnitude for both vehicles. The overall findings challenge the recent European regulations that equated e-kick scooters with bikes. These findings may help public administrations in planning the circulation of e-bikes and e-kick scooters in cities and recommend that manufacturers improve the e-kick scooter design by including shock absorbers to increase comfort