1,720,960 research outputs found
Synthesis of the Data on COVID-19 Skin Manifestations: Underlying Mechanisms and Potential Outcomes
Full text linkThe incidence of coronavirus disease 2019 (COVID-19)-related skin manifestations has progressively grown, in parallel with the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreading. The available evidence indicates that cutaneous signs are heterogeneous and can be divided as follows: a) erythematous rashes, b) lesions of vascular origin, c) vesicular rashes, d) urticarial rashes, and e) acute generalized exanthematous pustulosis (AGEP), erythema multiforme (EM) and other polymorphic/atypical reactions. Most cutaneous manifestations appear simultaneously or after respiratory and/or systemic symptoms such as fever, even if rarely urticaria has been reported as the first sign of the disease. It has been proposed that erythematous and vesicular rashes, as well as urticaria, are the result of immunological activation against Sars-CoV-2, similarly to other viral exanthems; alternatively, reactivation or co-infection of herpesviruses and drug hypersensitivity represent possible etiologic diagnosis that has to be considered. Regarding lesions of vascular origin, ischemic ones are the result of systemic hypercoagulability established in severe infections, whereas chilblains seem to be linked to the type I-interferon massively produced to halt virus replication. AGEP is triggered by drugs, whereas EM could represent a delayed immune response to the virus or a hypersensitivity reaction to drugs elicited by the inflammatory process built to fight the infection. A further pathogenic hypothesis is that the virus, or its particles detected in the skin (particularly in endothelium and eccrine glands), could be responsible for certain skin reactions, including chilblains and EM. From the available data, it appears that chilblains are correlated with younger age and less severe disease, while ischemic manifestations occur in the elderly with severe infection. In conclusion, larger studies are needed to confirm the suggested pathogenetic mechanisms of COVID-19-related skin reactions and to determine the potential prognostic significance of each one
What makes an inflammatory disease inflammatory? An overview of inflammatory mechanisms of allergic contact dermatitis, atopic dermatitis and psoriasis
No full textInflammatory response in the skin is important for host defence against a broad spectrum of insults including microorganisms, chemicals, radiation and physical trauma. When the inflammatory process becomes prolonged and self-perpetuating, illness occurs. In this review, we discuss recent findings regarding the complex inflammatory mechanisms in allergic contact dermatitis, atopic dermatitis and psoriasis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Advanced control strategies for active voltage balancing and load voltage control in flying capacitor multilevel converters
No full textLAUREA MAGISTRALEIn questa tesi vengono analizzate alcune strategie di controllo attivo per bilanciare le tensioni nei Convertitori Multilivello a Flying Capacitors (FCMLC) con filtro di uscita, operanti sia in configurazione DC/DC che DC/AC. In particolare è stato affrontato il problema delle cadute improvvise di tensione in ingresso, scenario comune nei sistemi ad energia rinnovabile e di accumulo. In questi casi, mantenere stabile la tensione di uscita è cruciale per evitare cali di prestazione nei carichi collegati e garantire l’efficienza del sistema di conversione.
Gli obiettivi principali di questo studio sono due: assicurare il bilanciamento delle tensioni nei flying capacitors, fondamentale per ridurre la distorsione delle forme d’onda e migliorare la stabilità del convertitore e mantenere la tensione di uscita desiderata nonostante le fluttuazioni dell’ingresso.
A tal fine, sono stati valutati e confrontati tre metodi di controllo: Feedback Linearization, Sliding Mode Control e un controllo basato su algoritmo. La feedback linearization si è dimostrata precisa e robusta in entrambe le configurazioni; lo sliding mode control offre ottime prestazioni in applicazioni DC/DC, ma è meno efficace in DC/AC. Il controllo basato su algoritmo, infine, garantisce maggiore efficienza computazionale e versatilità, ma essendo in anello aperto è meno robusto rispetto ai disturbi.
Poiché le cadute di tensione in ingresso sono imprevedibili e richiedono un lungo transitorio prima di stabilizzarsi, è stato sviluppato un metodo in grado di prevedere il loro valore finale fin dall’inizio della caduta. In questo modo, le tensioni dei flying capacitors seguono un riferimento a scalino e si stabilizzano rapidamente senza attendere le oscillazioni dell’ingresso. Questa tecnica ha un'accuratezza superiore al 99% e consente una regolazione in tempo reale che migliora la rapidità di risposta del convertitore.
I risultati ottenuti contribuiscono all’analisi e allo sviluppo dei sistemi di elettronica di potenza per applicazioni energetiche.This thesis investigates active control strategies for voltage balancing in a Flying Capacitor Multilevel Converter (FCMLC) with output filter operating under both DC/DC and DC/AC configurations. The study addresses a critical scenario often encountered in renewable energy and power storage systems: a sudden and unpredictable input voltage drop. In such cases, maintaining stable output voltage becomes essential, as voltage losses can compromise the performance of connected loads and the overall efficiency of the power conversion system. The primary objectives of this work are twofold: first, to ensure voltage balancing across the flying capacitors, crucial for minimizing waveform distortion and enhancing converter stability; and second, to maintain the desired output voltage level regardless of fluctuations in the DC input.
To meet these goals, the thesis evaluates three control methods: Feedback Linearization, Sliding Mode Control, and an algorithm-based control, with a comparative analysis of the strengths and limitations of each approach. Feedback Linearization achieves high precision and robust closed-loop control across both configurations, Sliding Mode Control demonstrates strong robustness and accuracy in DC/DC applications but underperforms in DC/AC scenarios and Algorithm-Based Control provides computational efficiency and greater adaptability, but no robustness against disturbances.
Managing capacitor voltage balancing is complex, as input voltage drops are unpredictable. For this reason in this thesis it has been developed a novel reference estimation technique that enables rapid capacitor voltage stabilization. Rather than waiting for DC voltage transients to end, this approach uses early-stage model identification to map the initial behavior of the DC voltage drop to its final stabilized value. This reference estimation method achieves over 99% accuracy, enhancing the converter’s response to sudden input variations by predicting and adjusting in real time.
These findings contribute advancing the field of power electronics for dynamic energy systems
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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