30,980 research outputs found
Bernardo Secchi : libri e piani
No full textIl quaderno raccoglie gli esiti di un ciclo di seminari che si è svolto presso l’Università Iuav di Venezia tra marzo e giugno 2015. Dodici giornate, quasi un semestre, in cui si è offerta a studenti e dottorandi l'occasione di riflettere sui temi e le questioni che Bernardo Secchi ha delineato lungo la sua vita di studioso ripercorrendo alcune tappe della sua ricerca teorica e progettuale, attraverso la rilettura di alcuni dei suoi più significativi libri e piani da parte di ventinove studiosi, allievi e colleghi.
I sei libri selezionati e discussi in questo testo sono le monografie scritte da Bernardo Secchi dagli anni settanta fino al 2013 e consentono di ripercorrere le principali ipotesi interpretative che hanno caratterizzato la sua riflessione e hanno rappresentato delle tappe importanti nel suo percorso professionale.
I sei piani qui riletti costituiscono una selezione circoscritta dell’attività professionale di Secchi e dello studio Secchi-Viganò (a partire dal 1990): quattro piani italiani che coprono gli anni ottanta e novanta, due piani all’estero che segnano gli anni 2000 e anche il definitivo riconoscimento dello studio alla scala internazionale. Il piano di Jesi (1983-1987), che – nelle parole di Patrizia Gabellini – “inaugura l’urbanistica di Bernardo Secchi”, i tre piani degli anni novanta Prato (1993-1999), Pesaro e Brescia (1996-1998) che sperimentano e sedimentano al contempo una vasta esplorazione della città contemporanea; infine lo Structure Plan di Anversa (2003-2007) e la partecipazione alla consultazione internazionale del Grand Paris (2008-2009) con i quali la riflessione si apre a temi urgenti e emergenti nel dibattito internazionale
Angelo Secchi, gesuita e scienziato
No full textBreve biografia del gesuita Angelo Secchi (1818-1878), pioniere dell'astrofisica e innovatore in diverse discipline scientifiche
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
Concorso internazionale per la riqualificazione della base di sottormarini Keroman a Lorient - progetto menzionato
No full textProgetto per la riconversione del patrimonio architettonico costituito della base di sottomarini Keroman, parte del complesso sistema difensivo tedesco sulla costa altlantica durante la seconda guerra mondiale. Il progetto prevede la riqualificazione degli elementi architettonici e del territorio circostante della penisola di Keroman nella città di Lorient (FR). Il concorso ha visto la partecipazione di 192 progetti, Il progetto ha ottenuto una menzione speciale (7° classificato). Gruppo di Progettazione: N. Privileggio (capogruppo), C. Macchi Cassia, P. Macchi Cassia, M. Orsini, M. Secchi
Geometric Optics for Surface Waves on the Plasma–Vacuum Interface
No full textWe consider the free boundary problem for a plasma–vacuum interface
in ideal incompressible magnetohydrodynamics, where the Maxwell equations for
electric and magnetic fields are considered in the vacuum region. Under a neces-
sary and sufficient stability condition for a piecewise constant background state, we
construct approximate solutions at any arbitrarily large order of accuracy to the free
boundary problem in three space dimensions when the initial discontinuity displays
high frequency oscillations. Moreover, such approximate surface waves have non-
trivial residual non-oscillatory components. The content of this paper summarizes
the result in Secchi and Yuan (2022)
A novel role for heparanase in the onset of liver fibrosis establishment
No full textHeparan sulfate proteoglycans are important structural and functional components of basal membranes composed of a core protein (soluble or transmembrane) covalently linked to highly sulfated chains of glycosaminoglycans called heparan sulfate. Heparanase is the only endoglucuronidase capable of cleaving heparan sulfate chains of heparan sulfate proteoglycans. It exerts its enzymatic activity by catalyzing the cleavage of the β(1,4)-glycoside bond between glucuronic acid and glucosamine residues, generating fragments of about 5–7kDa. At intracellular level (endosomal and lysosomal), heparanase participates in the turnover of membrane-associated heparan sulfate proteoglycans, while secreted enzyme is involved in the remodeling and degradation of extracellular matrix. Given the electrostatic interaction of heparan sulfate with growth factors, cytokines and enzymes, heparanase cleavage indirectly facilitates the release and diffusion of these molecules. Heparanase exerts also non-enzymatic functions since it regulates gene expression by the activation of specific signaling pathways. Through degradation of heparan sulfate chains and heparan sulfate-independent functions, HPSE regulates several physiological and pathological processes. In particular, heparanase has a significant role in tumor progression and in renal glomerular diseases. In addition, it was recently shown its involvement also in bowel and kidney chronic inflammation as well as in tubulo-interstitial fibrosis. In general, fibrosis is an unregulated process of tissue repair that occurs in response to persistent damage and chronic inflammation. In the liver, the progressive accumulation of extracellular matrix can lead to cirrhosis and organ failure. In this process, activated Kupffer cells and hepatic stellate cells (HSCs) play a fundamental role, the first in the inflammatory response, the latter in fibrogenesis.
The involvement of heparanase in the development of chronic liver disease has not been demonstrated so far. Given the reproducibility of the mechanisms that contribute to the development of chronic diseases, this study was aimed to: i) investigate whether heparanase is up-regulated during chronic liver disease, ii) study the possible regulation of its expression and iii) study the possible effects on the development of the disease.
The tempo-spatial expression of heparanase was studied in mice with chronic hepatic damage induced by carbon tetrachloride (CCl4) administration for 1, 2, 8 and 12 weeks. The progression of chronic injury and fibrosis was assessed by Azan-Mallory and Hematoxylin-Eosin histological stainings. Extensive centrilobular areas with necro-inflammatory activity and fibrosis were observed after 1 and 2 weeks of treatment that progressively developed fibrotic septa and micronodular cirrhosis observed after 8 and 12 weeks of treatment. Analyses of gene expression (by real time RT-PCR) and protein expression (by western blot and immunofluorescence), showed a significant increase of heparanase expression in liver tissue after 1 and 2 weeks of treatment but not after 8 and 12 weeks suggesting a possible role in the early stages of chronic damage. Immunohistochemical analyses revealed the localization of heparanase in the centrilobular areas with necro-inflammatory damage and fibrosis. To identify the cellular source responsible for heparanase increase in tissue, in vitro analyses on cell cultures and co-immunofluorescence analyses on sections from 1 and 2 week-treated livers were performed. Given heparanase localization in fibrotic areas and the fundamental role of the HSCs in chronic liver disease, we wondered if the expression of heparanase increases in HSC during their activation. For this purpose, primary HSCs were isolated from rat livers and induced to activate through culture on plastic dishes. After 15 days of isolation, the levels of heparanase and transdifferentiation markers (α-SMA, fibronectin, TGF-β and collagen I) expression increased significantly compared to cells cultured for 7 days. However, despite immunofluorescence analyses on liver sections revealed the expression of heparanase by in vivo activated HSCs at 1 and 2 weeks of treatment with CCl4, a more significant degree of co-localization was observed with macrophages labeled with F4/80 and CD68.
Given the main involvement of macrophages in increasing hepatic heparanase in the sites of inflammation, an analysis of the possible mechanisms of heparanase up-regulation by inflammatory macrophages was then conducted. To this purpose, primary Kupffer cells were isolated from rat livers and treated with LPS and TNF-α, two important pro-inflammatory stimuli. In contrast to LPS, that did not alter the expression of heparanase, TNF-α induced a significant increase of heparanase expression. Also human U937 macrophages, treated with increasing concentrations of TNF-α, increased the heparanase gene and protein levels, in a dose-dependent mechanism. By Western blot on the conditioned media from cells treated or not with TNF-α, we also showed an increase of extracellular enzyme in the presence of TNF-α, indicating that this factor stimulates also heparanase secretion. In addition, two observations provided further evidence on the possible role of TNF-α as a regulator of heparanase expression in chronic liver disease: first, the significant increase in TNF-α expression in the liver tissue only at 1 and 2 weeks of intoxication by CCl4 and, secondly, its co-localization with heparanase at the same weeks of treatment. Among the other pro-inflammatory molecules tested, while IFN-γ stimulated heparanase gene transcription, IL-4 reduced its expression thus suggesting a different regulation of heparanase by macrophages depending on their state of M1 or M2 polarization.
The observation of enhanced heparanase expression in the early stages of chronic liver disease led to wonder what it could be its role in the process of fibrogenesis. Given the involvement of Kupffer cells in the activation of HSC through the release of pro-fibrotic stimuli, we examined whether a mechanism of regulation through the release of heparanase was also possible. For this purpose, LX-2 stellate cells were treated with the conditioned media of U937 cells that were previously induced to produce heparanase by stimulation with TNF-α. The involvement of heparanase in the activation of LX-2 has been verified using an heparanase inhibitor during treatment. The results showed that heparanase is able to regulate the expression of α-SMA and fibronectin by LX-2 cells.
Besides extracellular matrix degradation, the promotion of macrophage activation by heparanase is already known. In this study, using an in vitro migration assay, we demonstrated that heparanase is also able to stimulate the migration of macrophages.
Finally, to verify the involvement of heparanase also in human liver fibrosis, the levels of heparanase activity were measured in the plasma of healthy subjects and patients with chronic liver disease, of viral or autoimmune etiology and at different stages of fibrosis. Accordingly to the animal model, we showed that, regardless of the etiology of hepatic disease, heparanase plasma activity increased in patients with mild and moderate fibrosis compared to healthy subjects, but returned to baseline in patients with cirrhosis. In addition, in patients, plasma heparanase activity negatively correlated with the degree of liver stiffness.
Overall, our results indicate the involvement of heparanase in chronic liver disease but only in its early stages. Inflammatory macrophages and, to a lesser extent, activated HSCs are an important source of heparanase. In this context, secreted heparanase in the extracellular environment may play a role in the macrophage-mediated activation of HSCs and in the migration of macrophages themselves
Le lezioni di Fisica di Angelo Secchi: alcune note sui manoscritti ritrovati
No full textl'articolo analizza alcuni manoscritti inediti di Angelo Secchi ritrovati presso l'Osservatorio di Monte Porzio Catone. Tali manoscritti sono quasi certamente riconducibili agli anni di permanenza del Secchi a Loreto (1841-1844). Più precisamente vengono descritti e discussi in dettaglio i seguenti manoscritti: 1) "Prefazione alle lezioni di Fisica Matematica Sperimentale, Loreto 1842"; 2) "La piccolezza delle particelle che compongono i corpi, eccede ogni nostra immaginazione"; 3) Impenetrabilità dell'aria ed espansibilità"; 4) Dell'elasticità ed espansibilità dell'aria: descrizione ed uso della macchina pneumatica ad esaustione; 5) "Sul peso dell'aria"
Statistica Medica
No full textCuratela della traduzione del volume:
Martin Bland "An introduction to medical statistics" Oxford University Pres
Interacting Reinforced Urn Systems
No full textWe introduce a class of discrete time stochastic processes generated by interacting systems of reinforced urns. We show that such processes are asymptotically partially exchangeable and we prove a strong law of large numbers. Examples and the analysis of particular cases show that interacting reinforced urn systems are very °exible representations for modelling countable
collections of dependent and asymptotically exchangeable sequences of random variables
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