840 research outputs found

    A doubly nonlinear Cahn-Hilliard system with nonlinear viscosity

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    In this paper we discuss a family of viscous Cahn-Hilliard equations with a non-smooth viscosity term. This system may be viewed as an approximation of a "forward-backward" parabolic equation. The resulting problem is highly nonlinear, coupling in the same equation two nonlinearities with the diffusion term. In particular, we prove existence of solutions for the related initial and boundary value problem. Under suitable assumptions, we also state uniqueness and continuous dependence on data.Comment: Key words and phrases: diffusion of species; Cahn-Hilliard equations; viscosity; non-smooth regularization; nonlinearities; initial-boundary value problem; existence of solutions; continuous dependenc

    Linked Data approach for selection process automation in Systematic Reviews

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    Background: a systematic review identifies, evaluates and synthesizes the available literature on a given topic using scientific and repeatable methodologies. The significant workload required and the subjectivity bias could affect results. Aim: semi-automate the selection process to reduce the amount of manual work needed and the consequent subjectivity bias. Method: extend and enrich the selection of primary studies using the existing technologies in the field of Linked Data and text mining. We define formally the selection process and we also develop a prototype that implements it. Finally, we conduct a case study that simulates the selection process of a systematic literature published in literature. Results: the process presented in this paper could reduce the work load of 20% with respect to the work load needed in the fully manually selection, with a recall of 100%. Conclusions: the extraction of knowledge from scientific studies through Linked Data and text mining techniques could be used in the selection phase of the systematic review process to reduce the work load and subjectivity bia

    Characterization of Rome’s rainwater in the early of 2018 aiming to find correlations between chemical-physical parameters and sources of pollution: a statistical study

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    Analysis of rainwater in historical cities plays a key role to save ancient monuments from atmospheric agents. In this study we sampled the Rome’s rainwater from February to July of 2018 and we analysed them to determine their chemical and physical parameters: pH, redox potential, conductivity, temperature, and the concentration of the main inorganic ions (Na+, K+, Ca++, Mg++, F−, Cl−, NO3−, SO4−−). The volume of the daily fallen rainwater, the speed and direction of the wind in the sampling site were also collected. In order to find a correlation between all the above data we used the Principal Component Analysis (PCA). Results evidenced that there aren’t authentic “acid rains” as the minimum pH value that we found is 5.2. In some cases high concentrations of nitrates and sulphates were found with maximum values of 12.4 ppm and 18.7 ppm respectively. We also found no correlation between the rainwater’s composition and the seasonal period; on the contrary, the speed and direction of the wind, especially when coming from the sea or industrial country near Rome, play a noticeable role on the rainwater composition. [Figure not available: see fulltext.] © 2020, The Author(s)

    Semantic Enrichment for Recommendation of Primary Studies in a Systematic Literature Review

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    A Systematic Literature Review (SLR) identifies, evaluates, and synthesizes the literature available for a given topic. This generally requires a significant human workload and has subjectivity bias that could affect the results of such a review. Automated document classification can be a valuable tool for recommending the selection of studies. In this article, we propose an automated pre-selection approach based on text mining and semantic enrichment techniques. Each document is firstly processed by a named entity extractor. The DBpedia URIs coming from the entity linking process are used as external sources of information. Our system collects the bag of words of those sources and it adds them to the initial document. A Multinomial Naive Bayes classifier discriminates whether the enriched document belongs to the positive example set or not. We used an existing manually performed SLR as benchmark data set. We trained our system with different configurations of relevant documents and we tested the goodness of our approach with an empirical assessment. Results show a reduction of the manual workload of 18% that a human researcher has to spend, while holding a remarkable 95% of recall, important condition for the nature itself of SLRs. We measure the effect of the enrichment process to the precision of the classifier and we observed a gain up to 5%

    Cascade Superfluorescence in Er:YLF

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    We report the analysis of paired photon pulses arising from two cascading transitions in continuously pumped Erbium-doped YLiF4_4 1% and 0.01% crystals at 1.6 K. The dependence of the pulse peak intensity on the squared number of involved Erbium ions, between 1011^{11} and 1013^{13}, definitely identifies the cooperative nature of the two pulsed emissions, that are generated by the subsequent, spontaneous formation of coherent states. The observed fluctuations of the time interval between the paired pulses and, most importantly, its correlation with the second pulse duration, demonstrate that the Erbium ions coherence is indeed seeded by vacuum fluctuations

    Tracing Resource Usage over Heterogeneous Grid Platforms: A Prototype RUS Interface for DGAS

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    Tracing resource usage by Grid users is of utmost importance especially in the context of large-scale scientific collaborations such as within the High Energy Physics (HEP) community to guarantee fairness of resource sharing, but many difficulties can arise when tracing the resource usage of distributed applications over heterogeneous Grid platforms. These difficulties are often related to a lack of interoperability of the accounting components across middlewares. This paper brie y describes the architecture and workflow of the Distributed Grid Accounting System (DGAS) [1] and evaluates the possibility to extend it with a Resource Usage Service (RUS) [2, 3] interface according to the Open Grid Forum (OGF) sped cation that allows to store and retrieve OGF Usage Records (URs) [4, 5] via Web Services. In this context the OGF RUS and UR sped cations are critically analyzed. Furthermore, a prototype of a RUS interface for DGAS (DGAS-RUS) is presented and the most recent test results towards a full interoperability between heterogeneous Grid platforms are outlined

    Enhanced atomic desorption of 209 and 210 Francium from organic coating

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    Controlled atomic desorption from organic Poly-DiMethylSiloxane coating is demonstrated for improving the loading efficiency of 209,210Fr magneto-optical traps. A three times increase in the cold atoms population is obtained with contact-less pulsed light-induced desorption, applied to different isotopes, either bosonic or fermionic, of Francium. A six times increase of 210Fr population is obtained with a desorption mechanism based on direct charge transfer from a triboelectric probe to the adatom-organic coating complex. Our findings provide new insight on the microscopic mechanisms of atomic desorption from organic coatings. Our results, obtained at room temperature so as to preserve ideal vacuum conditions, represent concrete alternatives, independent from the atomic species in use, for high-efficiency laser cooling in critical conditions

    Historical eye on IPF: a cohort study redefining the mortality scenario

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    RationaleTherapies that slow idiopathic pulmonary fibrosis (IPF) progression are now available and recent studies suggest that the use of antifibrotic therapy may reduce IPF mortality.ObjectivesThe aim of the study was to evaluate whether, to what extent, and for which factors the survival of IPF in a real-life setting has changed in the last 15 years.MethodsHistorical eye is an observational study of a large cohort of consecutive IPF patients diagnosed and treated in a referral center for ILDs with prospective intention. We recruited all consecutive IPF patients seen at GB Morgagni Hospital, Forlì, Italy between January 2002 and December 2016 (15 years). We used survival analysis methods to describe and model the time to death or lung transplant and Cox regression to model prevalent and incident patient characteristics (time-dependent Cox models were fitted).Measurements and main resultsThe study comprised 634 patients. The year 2012 identifies the time point of mortality shift (HR 0.58, CI 0.46–0.63, p < 0.001). In the more recent cohort, more patients had better preserved lung function, underwent cryobiopsy instead of surgery, and were treated with antifibrotics. Highly significant negative prognostic factors were lung cancer (HR 4.46, 95% CI 3.3–6, p < 0.001), hospitalizations (HR 8.37, 95% CI 6.5–10.7, p < 0.001), and acute exacerbations (HR 8.37, 95% CI 6.52–10.7, p < 0.001). The average antifibrotic treatment effect estimated using propensity score matching showed a significant effect in the reduction of all-cause mortality (ATE coeff −0.23, SE 0.04, p < 0.001), acute exacerbations (ATE coeff −0.15, SE 0.04, p < 0.001), and hospitalizations (ATE coeff −0.15, SE 0.04, p < 0.001) but no effect on lung cancer risk (ATE coeff −0.03, SE 0.03, p = 0.4).ConclusionAntifibrotic drugs significantly impact hospitalizations, acute exacerbations, and IPF survival. After the introduction of cryobiopsy and antifibrotic drugs, the prognosis of IPF patients has significantly improved together with our ability to detect IPF at an earlier stage

    Integrating Clinical Probability into the Diagnostic Approach to Idiopathic Pulmonary Fibrosis: An International Working Group Perspective

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    Background. When considering the diagnosis of idiopathic pulmonary fibrosis (IPF), experienced clinicians integrate clinical features that help to differentiate IPF from other fibrosing interstitial lung diseases, thus generating a “pre-test” probability of IPF. The aim of this international working group perspective was to summarize these features using a tabulated approach similar to chest HRCT and histopathologic patterns reported in the international guidelines for the diagnosis of IPF, and to help formally incorporate these clinical likelihoods into diagnostic reasoning to facilitate the diagnosis of IPF. Methods. The committee group identified factors that influence the clinical likelihood of a diagnosis of IPF, which was categorized as a pre-test clinical probability of IPF into “high” (70-100%), “intermediate” (30-70%), or “low” (0-30%). After integration of radiological and histopathological features, the post-test probability of diagnosis was categorized into “definite” (90-100%), “high confidence” (70-89%), “low confidence” (51-69%), or “low” (0-50%) probability of IPF. Findings. A conceptual Bayesian framework was created, integrating the clinical likelihood of IPF (“pre-test probability of IPF”) with the HRCT pattern, the histopathology pattern when available, and/or the pattern of observed disease behavior into a “post-test probability of IPF”. The diagnostic probability of IPF was expressed using an adapted diagnostic ontology for fibrotic interstitial lung diseases. Interpretation. The present approach will help incorporate the clinical judgement into the diagnosis of IPF, thus facilitating the application of IPF diagnostic guidelines and, ultimately improving diagnostic confidence and reducing the need for invasive diagnostic techniques