A multilayer microperforated panel prototype for broadband sound absorption at low frequencies

Microperforated panel (MPP) absorbers are one of the most promising alternatives to porous sound absorbing materials. However, these structures cannot achieve high and broadband absorption at low frequencies. To be effective, once defined the material properties the geometrical parameters of the absorber need to be optimized to match the prescribed absorption level. This paper presents a multiple layer MPP absorber with a high sound absorption coefficient and broadband absorption at low frequencies. An electro-acoustical equivalent circuit model was used for a parametric analysis to study the relationships between the absorption mechanism and the absorbers geometrical parameters in the proposed multilayer MPP. A prototype of this absorber was machined and tested in an impedance tube test ring and the experimental acoustical properties in terms of absorption coefficient were extracted using the transfer function method. It was demonstrated that the five-layer MPP absorber was capable of guaranteeing a high absorption (constantly over 90%) in a frequency range from 400 to 2000 Hz. The results indicate that the proposed multilayer MPP absorber provides a good alternative for sound absorption applications.</p

Real-time thermography system for composite welding:Undamaged baseline approach

The aerospace industry's current focus on recyclable materials and low-cost processes has accelerated research and implementation of thermoplastics matrix composites (TPC). In the last decades, researchers have researched weldability of these materials as a valid alternative to conventional mechanical fastening and adhesives, for improving the strength of the joint. Automatic induction welding of carbon fiber TPCs is one of the most promising techniques due to its numerous benefits, such as elevated energy efficiency and highly localised heat. As for all the manufacturing techniques, the importance of efficiently detecting the presence of defects during TPCs welding has pushed the need for automated real-time non-destructive evaluation (NDE) systems. This paper focuses on the development of an efficient NDE technique able to detect the presence of alterations and defects in real-time during the welding process. This technique relies on Infrared (IR) active thermography inspections performed using the induction welding heat as the source and an undamaged baseline methodology to detect differences in the heat field. The procedure was experimentally analysed by means of an apparatus capable of automatic welding of samples, performing the real-time NDE during the process. Results show the efficiency of the method to localise the damaged area and characterise the defects during the welding. The undamaged baseline methodology was proven to better clarify shape and location of defects, allowing for an efficient detection of damaged samples and areas where more detailed inspections can be performed after the welding process by means of the same IR apparatus.</p

Static and dynamic heterogeneities in a model for irreversible gelation

We study the structure and the dynamics in the formation of irreversible gels by means of molecular dynamics simulation of a model system where the gelation transition is due to the random percolation of permanent bonds between neighboring particles. We analyze the heterogeneities of the dynamics in terms of the fluctuations of the intermediate scattering functions: In the sol phase close to the percolation threshold, we find that this dynamical susceptibility increases with the time until it reaches a plateau. At the gelation threshold this plateau scales as a function of the wave vector $k$ as $k^{\eta -2}$, with $\eta$ being related to the decay of the percolation pair connectedness function. At the lowest wave vector, approaching the gelation threshold it diverges with the same exponent $\gamma$ as the mean cluster size. These findings suggest an alternative way of measuring critical exponents in a system undergoing chemical gelation.Comment: 4 pages, 4 figure

VST - VLT Survey Telescope Integration Status

The VLT Survey Telescope (VST) is a 2.6m aperture, wide field, UV to I facility, to be installed at the European Southern Observatory (ESO) on the Cerro Paranal Chile. VST was primarily intended to complement the observing capabilities of VLT with wide-angle imaging for detecting and pre-characterising sources for further observations with the VLT.Comment: 2 pages, 2 figures, conferenc

Dynamical heterogeneity in a model for permanent gels: Different behavior of dynamical susceptibilities

We present a systematic study of dynamical heterogeneity in a model for permanent gels, upon approaching the gelation threshold. We find that the fluctuations of the self intermediate scattering function are increasing functions of time, reaching a plateau whose value, at large length scales, coincides with the mean cluster size and diverges at the percolation threshold. Another measure of dynamical heterogeneities, i.e. the fluctuations of the self-overlap, displays instead a peak and decays to zero at long times. The peak, however, also scales as the mean cluster size. Arguments are given for this difference in the long time behavior. We also find that non-Gaussian parameter reaches a plateau in the long time limit. The value of the plateau of the non-Gaussian parameter, which is connected to the fluctuations of diffusivity of clusters, increases with the volume fraction and remains finite at percolation threshold.Comment: 11 pages, 14 figure

Sézary Syndrome: Different Erythroderma Morphological Features with Proposal for a Clinical Score System

Sézary syndrome is a rare subtype of cutaneous T-cell lymphoma characterized by erythroderma, peripheral lymphadenopathies, and circulating atypical cerebriform T-cells. To date, no definite staging system has been developed for these patients. In this retrospective analysis of the archive of the Dermatological Clinic of the University of Turin, Italy, erythrodermic SS patients were classified according to clinical records and photographs into three main presentations: erythematous, infiltrated, or melanodermic. The pattern of erythroderma was found to be associated with disease outcome, as better survivals were recorded in patients with erythematous and infiltrative erythroderma. Patients in the melanodermic group, though less represented in our investigation, seemed to show a worse trend in survival. According to this preliminary evidence, a new prognostic classification, with a revised score specific for Sézary syndrome patients, can be proposed to usefully integrate the current staging system. The correlation displayed in our research will be hopefully confirmed by prospective studies with larger cohorts, with the aim of identifying significant prognostic features in this subset of cutaneous T-cell lymphoma patients

Towards the periodization of the uses of Can Sadurní Cave (Begues, Catalonia) during the Middle Neolithic I. The contribution of bayesian modelling to radiocarbon dating sequences

Excavations at Can Sadurní Cave since 2012 have uncovered a complex stratigraphy for the Middle Neolithic phase (ca. 4700-4000 cal. BC). This was not in agreement with our expectations from the previous excavation of a trial trench, where only 4 layers (10, 10b,11 and 11b) were uncovered. After excavating a funerary layer with several in situ burials and further deposits containing multiple layers of burnt dung (fumier), the stratigraphy was revised and 5 episodes within layer 11 were detected. It became necessary to find a tool to refine the chronological sequence of these uses, under the premise that it is unlikely that the cave was used as a funerary area and a byre at the same time. Bayesian modelling allowed distinguishing these two phases, establishing an earlier use of the cave for animal herding purposes (ca. 4700-4450 cal. BC) and a funerary use of the cave in a more recent period (ca. 4400-4200 cal. BC)

Melanoma management during the covid-19 pandemic emergency: A literature review and single-center experience

Background: The current COVID-19 pandemic has influenced the modus operandi of all fields of medicine, significantly impacting patients with oncological diseases and multiple comorbidi-ties. Thus, in recent months, the establishment of melanoma management during the emergency has become a major area of interest. In addition to original articles, case reports and specific guidelines for the period have been developed. Purpose: This article aims to evaluate whether melanoma management has been changed by the outbreak of COVID-19, and if so, what the consequences are. We summarized the main issues concerning the screening of suspicious lesions, the diagnosis of primary melanoma, and the management of early-stage and advanced melanomas during the pandemic. Additionally, we report on the experience of our dermatological clinic in northern Italy. Methods: We performed a literature review evaluating articles on melanomas and COVID-19 published in the last two years on PubMed, as well as considering publications by major healthcare organizations. Concerning oncological practice in our center, we collected data on surgical and therapeutic procedures in patients with a melanoma performed during the first months of the pandemic. Conclusions: During the emergency period, the evaluation of suspicious skin lesions was ensured as much as possible. However, the reduced level of access to medical care led to a documented delay in the diagnosis of new melanomas. When detected, the management of early-stage and advanced melanomas was fully guaranteed, whereas the follow-up visits of disease-free patients have been postponed or replaced with a teleconsultation when possible