The thickness of Europa's icy shell, which controls its thermal and rheological structure, cannot currently be directly measured. However, it can be estimated through indirect methods, including ...geodynamic modeling. We simulate the crystallization of the ice shell from a liquid water ocean and its subsequent thermal equilibration in the presence of tidal heat. We evaluate the effects of solid‐state stagnant lid convection on the shell's thermal equilibrium thickness and shell formation timing. The thermal equilibrium thickness of the ice shell ranges from 5 to 30 km, depending on the imposed tidal flexure strain rate. The ice lithospheric thickness remains less than 8 km, independently of imposed tidal flexure strain rate, overall shell thickness, and surface temperature, suggesting the Europan ice lithospheric strength is globally uniform. Thermal convection significantly reduces the thermal equilibration time scale, with the Europan ice shell able to fully crystallize out from a liquid water ocean in less than 2 Myr. Heterogeneous thermal equilibrium thickness values across the satellite suggest that widespread crystallization and melting may occur at the base of the shell. Rapid melting and crystallization timing suggest that the young surface age of the Europan ice shell may be the result of rapid catastrophic whole‐shell melting and recrystallization entirely recycling the surface.
Plain Language Summary.
The icy shell of Jupiter's moon Europa rests on top of a water ocean that may harbor life. As space exploration probes to date were unequipped to measure ice shell thickness, which has important geological and astrobiological implications, we must rely on theoretical models to estimate that thickness. Due to the size of Jupiter and Europa's unique orbital path around it, the Europan ice is heated by especially strong tidal forces, which will eventually balance with ice cooling to halt freezing. Simulating this process allows us to estimate a stable shell thickness, as well as the time it takes for the Europan ice shell to fully form. Our ice shell model additionally is divided between a cold, rigid surface layer and a “warm”, ductile basal layer that may grow or shrink relative to each other. Depending on tidal heat, ice shell thickness may range from 5 to 30 km. However, the rigid upper layer remains at a constant geographic thickness of less than 8 km. We also find that the ice shell crystallizes much faster than previously thought, with crystallization times ranging from 200,000 years to 2 million years.
Key Points
Crystallization of a tidally heated planetary ice shell in a stagnant lid regime controls the equilibrium thickness of the Europan shell
Despite a wide range of possible ice shell thicknesses, the Europan shell lithosphere thickness is likely globally homogeneous
Ice convection leads to much faster crystallization rates when compared to conduction‐only ice shell growth
Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. ...This improvement opens the way to a directional Dark Matter detection, thus providing an innovative and complementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we provide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out threshold, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure.
The MU-RAY detector for muon radiography of volcanoes Anastasio, A.; Ambrosino, F.; Basta, D. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/2013, Letnik:
732
Journal Article, Conference Proceeding
Recenzirano
The MU-RAY detector has been designed to perform muon radiography of volcanoes. The possible use on the field introduces several constraints. First the electric power consumption must be reduced to ...the minimum, so that the detector can be solar-powered. Moreover it must be robust and transportable, for what concerns the front-end electronics and data acquisition. A 1m2 prototype has been constructed and is taking data at Mt. Vesuvius. The detector consists of modules of 32 scintillator bars with wave length shifting fibers and silicon photomultiplier read-out. A dedicated front-end electronics has been developed, based on the SPIROC ASIC. An introduction to muon radiography principles, the MU-RAY detector description and results obtained in laboratory will be presented.
We present preliminary tests of hybrid pixel detectors consisting of the Medipix2 readout chip bump-bonded to a 1-mm-thick CdTe pixel detector. This room temperature imaging system for single photon ...counting has been developed within the Medipix2 European Collaboration for various imaging applications with X-rays and gamma rays, including dental radiography, mammography, synchrotron radiation, nuclear medicine, and radiation monitoring in nuclear facilities. The Medipix2 + CdTe hybrid detector features 256 /spl times/ 256 square pixels, a pitch of 55 /spl mu/m, a sensitive area of 14/spl times/14 mm/sup 2/. We analyzed the quality of the detector and bump-bonding and the response to nuclear radiation of the first CdTe hybrids. The CdTe pixel detectors, with Pt ohmic contacts, showed an ohmic response when negatively biased up to less than 60 V (electrons collection mode). Tests were also performed in holes collection mode, where a nonresistive behavior was observed above +15 V. We performed a series of imaging tests at low voltage bias with gamma radioactive sources and with an X-ray tube. Under uniform irradiation, we observed for all detectors the presence of numerous, stable structures in the form of small circles of about 200 /spl mu/m diameter, with the central pixels showing a reduced counting efficiency with respect to the periphery (in electrons counting regime). Also long filament structures have been observed. Further investigations will reveal whether they are due to an intrinsic detector response (e.g., due to Te inclusions) or to the bump-bonding process.
Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly ...Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution.
The purpose of the MU-RAY project is to develop an innovative approach to the study of volcanoes and their monitoring based on a particle physics approach. The test site is Vesuvio: one of the higher ...risk volcanoes in the world. In this context, muon radiography is an innovative method of enormous impact. This is an imaging technique which relies on the measurement, by means of a cosmic ray telescope, of the absorption in the volcano of muons with near-horizontal trajectories, produced by the interactions of cosmic rays with the atmosphere. Since 2003 this technique has been successfully used on volcanoes in Japan, providing pictures of their vertices with resolutions much better than those obtained with the traditional techniques based on gravimeters. Researchers from Naples and Florence are currently involved in the construction and testing of a prototype telescope based on the use of bars of plastic scintillator with a triangular section whose scintillation light is collected by special fibres (wave length shifters) and transported to SiPM (Silicon photomultipliers). A complete prototype telescope, consisting of three xy scintillation planes and 1m2 active area has been assembled and is now under test.
The SARS-CoV-2 pandemic has affected also the school environment. Prolonged closures and the weakness of available data prevent a definitive answer to the question of school transmission. We report ...our experience of responding to COVID-19 cases in the school setting, presenting a case study of the management of an outbreak in a large school.
The LHA/ASL Roma 1 has organized the School Units with a structure firmly rooted in the territory. At the local level, the District Unit mainly manages the relationship with schools, while the Hygiene and Public Health Service of the Prevention Department holds a coordinating and facilitating role. The HPHS carries out contact tracing activities facilitated by the schools, through the figure of the COVID-19 Contact Person, who is specifically trained to manage the preliminary stages of the reports.
Following several reports of COVID-19 suspect cases from two schools and, after a complex phase of contact tracing, it was possible to identify the major transmission chains. Furthermore, we performed a population-based screening on the entire school. Beyond the known transmission chains, for which quarantine was already in place, only five additional cases emerged, all asymptomatic, out of 1,231 swabs tested with RT-PCR.
Our experience confirms that an active interaction between the school and the School Unit made it possible to quickly control a potentially dangerous outbreak. The large-scale screening test demonstrated the substantial absence of collateral transmission chains. Effective contact tracing allowed to set forth a successful response. Our model of intervention can be used to support public health protocols regarding school outbreaks.
Abstract
Background
Myocardial work (MW) is estimated by pressure-strain loops using an implemented speckle tracking software. It has emerged as an index of LV contractile properties overcoming the ...load-dependency limit of left ventricular (LV) global longitudinal strain (GLS). This is particularly useful in clinical setting characterized by frequent hemodynamic variations, such as heart failure and valvular heart disease. However, the variation of MW parameters across different stages of primary mitral regurgitation (MR) and its impact on symptoms has never been investigated.
Objective
The aim of this observational study was to assess the variations of MW and deformation parameters of left heart chambers in mild, moderate and severe MR.
Methods
Consecutive patients with mild, moderate and severe MR were prospectively enrolled. Exclusion criteria were: chronic atrial fibrillation, valvular heart prosthesis, previous cardiac surgery.
Patients underwent clinical evaluation, blood sample tests, ECG and echocardiography. Speckle tracking analysis, completed by MW after inclusion of blood pressure values at the time of echocardiographic exam (Fig.1), ,was performed offline. Patients were then divided into groups first according to MR severity. Differences among the groups were analyzed by student T-test (or non-parametric tests for non-normally distributed variables) and predictors of symptoms (as NYHA class ≥ 2) were explored by logistic regression analysis and receiver operating characteristic (ROC) curves.
Results
Overall, 180 patients were enrolled (60 mild, 60 moderate, 60 severe MR). LV GLS and global PALS reduced according to MR severity. Global constructive work (GCW) and global wasted work (GWW) significantly improved in patients with moderate and severe MR, while global work efficiency (GWE) showed a trend towards reduction in patients with higher grades of MR. Global work index did not change significantly in the three groups (Fig.1). Among strain parameters, global PALS emerged as the best predictor of NYHA class (p<0.001; area under curve, AUC=0.75, Fig.2) These results are explained by the pathophysiology of MR, characterized by a mechanism of attempted LV compensation to volume overload with increased contractility parallel to the disease progress, although with low efficacy on increasing LV stroke volume and increased wasted work; while LA and diastolic function have an early reduction which is associated with the occurrence of symptoms.
Conclusions
myocardial deformation parameters of the left heart chambers vary accordingly to the pathophysiologic mechanisms of MR through increasing severity stages and are associate with the burden of symptoms.Fig.1Fig.2
Healthcare-associated infections (HAIs) surveillance is an essential part of any infection prevention and control programme. Repeated point prevalence surveys (PPSs) according to European Centre for ...Disease Prevention and Control (ECDC) protocol have been implemented in all Friuli Venezia Giulia (FVG) region (Italy) acute hospitals to reduce and control HAIs.
Using the repeated PPSs within a regional-healthcare system (RHS) to promote and evaluate infection prevention and control (IPC) programmes.
The standard versions of the ECDC PPS protocols were used in all four surveys (2011, 2013, 2015, 2017). All RHS public and private accredited hospitals were involved within the ‘safe care network’ programme.
The numbers of surveyed patients in the four PPSs were 3172, 3253, 2969 and 3036, respectively. Prevalence of HAIs and antimicrobial use (AU) decreased significantly from 2011: HAIs (P<0.05) 7.1%, 6.3%, 5.5%, 5.8% and AU (P<0.01) 40.4%, 39.2%, 36.0%, 37.2%, respectively. The appropriateness of duration of surgical prophylaxis increased significantly (<24 h increased through surveys related to one in 2011: odds ratio (OR), 95% confidence interval (CI) 1.29, 0.92–1.81; 1.95, 1.31–2.91; 1.78, 1.20–2.64, respectively). The most frequently detected HAIs were: bloodstream, urinary tract, pneumonia and surgical site (more than the 70% of HAIs in each PPS).
The FVG regional approach to HAIs and AU surveillance was able to contribute to reduce prevalence over a 7-year period. Furthermore, it was able to keep hospital attention on HAIs and AU through the years and to guarantee a standardized and comparable evaluation of HAIs and AU burden in all RHS hospitals, as well as impacting on HAIs and AU regional programmes.
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