887 research outputs found

    Adaptive immunity in a human chronic inflammatory disorder: phenotypic and functional characterization of T lymphocytes in a cohort of Chronic Granulomatous Disease patients

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    La malattia granulomatosa cronica è una rara immunodeficienza primitiva, dovuta a mutazioni di uno dei quattro geni che codificano per le componenti catalitiche e regolatorie della NADPH ossidasi, un enzima coinvolto nella produzione dei ROS, necessari per mediare l’uccisione del patogeno fagocitato da neutrofili, monociti e macrofagi. I pazienti sono quindi caratterizzati dall’avere un’aumentata suscettibilità ad infezioni dovute a microrganismi catalasi-positivi come batteri (es. Staphylococcus aureus) e funghi (es. Aspergillus fumigatus e Candida albicans). Inoltre, i pazienti soffrono di infiammazioni acute e croniche, con fibrosi e formazione di lesioni granulomatose in vari organi quali fegato, pelle, tratto digerente e urogenitale, linfonodi e nei casi più gravi cervello. Questi danni cronici, non direttamente riconducibili ad infezioni microbiche, sono probabilmente causati da alterazioni delle risposte immunitarie che coinvolgono anche altre cellule diverse dai fagociti. Ci sono pochi studi immunologici sui linfociti nei pazienti affetti da CGD, ma un recente lavoro condotto sul modello murino di CGD con aspergillosi invasiva, ha mostrato che nella fase acuta dell’infezione, i linfociti produttori di IL-17A vanno incontro ad una espansione incontrollata, con una ridotto numero di cellule effettrici IFN-γ +e di cellule regolatorie IL-10+. Inoltre la diminuita frequenza di linfociti Th17, produttrici di IL-17 è stata associata con l’aumento di infezioni batteriche e di Candida in due malattie croniche come la sindrome da iper IgE (HIES) e la candidiasi mucocutanea cronica. In questo studio abbiamo investigato il potenziale coinvolgimento dei linfociti T nella patogenesi della CGD, comparando: test di linfoproliferazione, quantificazione dell’espressione del mRNA e della produzione delle citochine, e l’analisi del fenotipo linfocitario, tra pazienti e controlli sani. Nonostante la grande variabilità nella risposta tra tutti i soggetti analizzati, i pazienti hanno mostrato un significativo aumento di proliferazione indotta dal lisato di C. albicans e un significativo aumento nella produzione di IL-10 con stimolazione da parte d A. fumigatus, ma anche un lieve aumento di produzione di IFN-γ e IL-17A dopo stimolazione con antigeni fungini, rispetto alla popolazione di controllo. L’ aumentata produzione di IL-17A diventava significativa quando dalla corte dei pazienti si escludeva un paziente particolare, che aveva un’infiammazione cronica intestinale. Anche l’espressione del mRNA per l’IL-17A è stata trovata aumentata nei PBMC non stimolati dei pazienti, rispetto ai controlli, indicando un possibile coinvolgimento di questa citochina nella patogenesi della CGD come mostrato nel modello animale. Inoltre, in accordo con il suo ruolo protettivo nell’infezione da A. fumigatus, la produzione di IFN-γ indotta dal fungo, era ridotta nei pazienti che avevano subito un’aspergillosi, rispetto agli altri CGD, ma simile rispetto ai controlli, mentre i pazienti che non avevano avuto aspergillosi, producevano livelli più elevati d’IFN-γ rispetto ai controlli, indicando che un aumentato livello d’IFN-γ è probabilmente richiesto per compensare la ridotta degradazione del fungo presente nei pazienti con CGD. Rispetto ai controlli, i PBMC dei pazienti stimolati con lieviti e ife di C. albicans, producevano livelli simili d’IFN-γ, ma aumentati livelli di IL-17A e IL-10, indicando che l’aumentata frequenza alle infezioni di Candida nei CGD forse richiede un meccanismo diverso rispetto alla HIES , che non dipende dalla diminuita frequenza di linfociti Th17. I PBMC dei due pazienti con HIES, rispetto a quelli dei CGD, producevano livelli più bassi d’IFN-γ dopo stimolo con tutti gli antigeni. Per quanto riguarda l’IL-17A, diversamente dal paziente HIES con mutazione di STAT3 che non produceva affatto, il paziente HIES senza mutazione, dopo stimolazione con lieviti e ife di C. albicans produceva livelli di IL-17A simili a quelli trovati per i pazienti CGD e maggiori rispetto a quelli dei controlli. Quindi è plausibile che la ridotta frequenza d’infezioni da Candida nei pazienti CGD, rispetto ai pazienti HIES, sia dovuta alla maggior protezione mediata da più alti livelli d’IFN-γ. Inoltre, poiché i pazienti HIES con mutazione STAT3 non producono IL-17A, noi pensiamo che l’utilizzo di test immunologici in vitro, possa servire a meglio indirizzare le future indagini molecolari nei pazienti con sospetta HIES.Chronic granulomatous disease (CGD) is a rare primary immunodeficiency syndrome characterized by mutations in one of the four genes that encode the subunits of NADPH oxidase, a enzyme principally involved in the ROS mediated pathogen killing. The patients are characterized by life-threatening and recurrent infections mainly by catalase-positive microorganisms, due to the inability of their phagocytes to express a respiratory burst against invading bacteria (e.g. Staphylococcus aureus) and fungi (e.g. Aspergillus fumigatus and Candida albicans). Patients, also suffer from a variety of sterile inflammatory conditions as acute and/or chronic inflammation with fibrosis containing non-caseous granulomas in the intestinal tract, liver, lymph nodes, urogenital tract, skin, and brain, most probably caused by an intrinsic dysregulation of the inflammatory mechanisms that can involve other cell types than the known defective phagocytes. Although in literature there are few immunological studies about cell function in CGD, a recent work on CGD animal model, has highlighted that in acute fungal infection, a dysregulation of IL-17-secreting cells, coupled with a decrease IFN-γ-producing effector cells and of IL-10-producing regulatory cells, could have a pathogenic role. Moreover, a decreased frequency of a specific T lymphocytes compartment, called Th17, for their characteristic IL-17A production, was associated with increased susceptibility to fungal end bacterial infection in several human chronic disease as hyper IgE syndrome (HIES) and chronic mucocutaneous candidiasis. In this study, we have investigated the potential involvement of T lymphocyte deregulation in CGD manifestations, by comparison of proliferation, mRNA expression, cytokine production and T lymphocyte phenotype upon fungal and bacterial antigen stimulation, of peripheral blood mononuclear cells (PBMC) between a cohort of CGD patients and of healthy controls. Despite a very large variability in functional responses found in both patient and controls, we showed a statistical significant increased of proliferation upon C. albicans lysate and of IL-10 production upon A. fumigatus in CGD patients, coupled with a slight increase of IFN-γ and IL-17A upon fungal stimulation. Furthermore, upon A. fumigatus in the CDG cohort was found a statistically significant increased of IL-17A production, excluded one patient with chronic inflammation, and increased IL-17A mRNA expression, in agreement with an involvement of IL-17A+ cells in CGD pathogenesis, as shown by the CGD animal model of invasive aspergillosis. We also observed that, in agreement with a protective role of IFN-γ, CGD patients that experienced severe aspergillosis expressed low IFN-γ production compared with other patients, but similar to controls, while patient that not experienced severe aspergillosis had increased IFN-γ production compared to controls, demonstrating that a compensatory IFN-γ increased was need to protect patients with defect of ROS-mediated killing. Concerning the responses to C. albicans yeast and hyphae stimulation, we observed similar amount of IFN-γ and increased of IL-17A and IL-10 levels, compared to controls, showing that probably different pathological mechanism lead to increased Candida albicans infections in CGD with respect to HIES, because it would not be dependent on a decrease of IL17A response to fungal antigens. Moreover, in comparison to CGD patients, HIES patients expressed lower value of IFN-γ for all antigens, but differently to STAT3-mutated HIES patient, that not express IL-17A upon all kinds of stimulation, in STAT3-wt HIES patient IL-17A production upon both C. albicans yeast and hyphae was similar to CGD and increased compared to age-matched healthy controls. Thus the reduced frequencies of C. albicans infection in CGD compared to STAT3-wt HIES, may be explained through the main protective level of IFN-γ. Moreover we believe that in vitro immunological test can help us to exclude a STAT3 mutation, in patients who have a positive score for HIES, before performing a molecular analysis of the gene

    Adaptive immunity in a human chronic inflammatory disorder: phenotypic and functional characterization of T lymphocytes in a cohort of Chronic Granulomatous Disease patients

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    La malattia granulomatosa cronica è una rara immunodeficienza primitiva, dovuta a mutazioni di uno dei quattro geni che codificano per le componenti catalitiche e regolatorie della NADPH ossidasi, un enzima coinvolto nella produzione dei ROS, necessari per mediare l’uccisione del patogeno fagocitato da neutrofili, monociti e macrofagi. I pazienti sono quindi caratterizzati dall’avere un’aumentata suscettibilità ad infezioni dovute a microrganismi catalasi-positivi come batteri (es. Staphylococcus aureus) e funghi (es. Aspergillus fumigatus e Candida albicans). Inoltre, i pazienti soffrono di infiammazioni acute e croniche, con fibrosi e formazione di lesioni granulomatose in vari organi quali fegato, pelle, tratto digerente e urogenitale, linfonodi e nei casi più gravi cervello. Questi danni cronici, non direttamente riconducibili ad infezioni microbiche, sono probabilmente causati da alterazioni delle risposte immunitarie che coinvolgono anche altre cellule diverse dai fagociti. Ci sono pochi studi immunologici sui linfociti nei pazienti affetti da CGD, ma un recente lavoro condotto sul modello murino di CGD con aspergillosi invasiva, ha mostrato che nella fase acuta dell’infezione, i linfociti produttori di IL-17A vanno incontro ad una espansione incontrollata, con una ridotto numero di cellule effettrici IFN-γ +e di cellule regolatorie IL-10+. Inoltre la diminuita frequenza di linfociti Th17, produttrici di IL-17 è stata associata con l’aumento di infezioni batteriche e di Candida in due malattie croniche come la sindrome da iper IgE (HIES) e la candidiasi mucocutanea cronica. In questo studio abbiamo investigato il potenziale coinvolgimento dei linfociti T nella patogenesi della CGD, comparando: test di linfoproliferazione, quantificazione dell’espressione del mRNA e della produzione delle citochine, e l’analisi del fenotipo linfocitario, tra pazienti e controlli sani. Nonostante la grande variabilità nella risposta tra tutti i soggetti analizzati, i pazienti hanno mostrato un significativo aumento di proliferazione indotta dal lisato di C. albicans e un significativo aumento nella produzione di IL-10 con stimolazione da parte d A. fumigatus, ma anche un lieve aumento di produzione di IFN-γ e IL-17A dopo stimolazione con antigeni fungini, rispetto alla popolazione di controllo. L’ aumentata produzione di IL-17A diventava significativa quando dalla corte dei pazienti si escludeva un paziente particolare, che aveva un’infiammazione cronica intestinale. Anche l’espressione del mRNA per l’IL-17A è stata trovata aumentata nei PBMC non stimolati dei pazienti, rispetto ai controlli, indicando un possibile coinvolgimento di questa citochina nella patogenesi della CGD come mostrato nel modello animale. Inoltre, in accordo con il suo ruolo protettivo nell’infezione da A. fumigatus, la produzione di IFN-γ indotta dal fungo, era ridotta nei pazienti che avevano subito un’aspergillosi, rispetto agli altri CGD, ma simile rispetto ai controlli, mentre i pazienti che non avevano avuto aspergillosi, producevano livelli più elevati d’IFN-γ rispetto ai controlli, indicando che un aumentato livello d’IFN-γ è probabilmente richiesto per compensare la ridotta degradazione del fungo presente nei pazienti con CGD. Rispetto ai controlli, i PBMC dei pazienti stimolati con lieviti e ife di C. albicans, producevano livelli simili d’IFN-γ, ma aumentati livelli di IL-17A e IL-10, indicando che l’aumentata frequenza alle infezioni di Candida nei CGD forse richiede un meccanismo diverso rispetto alla HIES , che non dipende dalla diminuita frequenza di linfociti Th17. I PBMC dei due pazienti con HIES, rispetto a quelli dei CGD, producevano livelli più bassi d’IFN-γ dopo stimolo con tutti gli antigeni. Per quanto riguarda l’IL-17A, diversamente dal paziente HIES con mutazione di STAT3 che non produceva affatto, il paziente HIES senza mutazione, dopo stimolazione con lieviti e ife di C. albicans produceva livelli di IL-17A simili a quelli trovati per i pazienti CGD e maggiori rispetto a quelli dei controlli. Quindi è plausibile che la ridotta frequenza d’infezioni da Candida nei pazienti CGD, rispetto ai pazienti HIES, sia dovuta alla maggior protezione mediata da più alti livelli d’IFN-γ. Inoltre, poiché i pazienti HIES con mutazione STAT3 non producono IL-17A, noi pensiamo che l’utilizzo di test immunologici in vitro, possa servire a meglio indirizzare le future indagini molecolari nei pazienti con sospetta HIES.Chronic granulomatous disease (CGD) is a rare primary immunodeficiency syndrome characterized by mutations in one of the four genes that encode the subunits of NADPH oxidase, a enzyme principally involved in the ROS mediated pathogen killing. The patients are characterized by life-threatening and recurrent infections mainly by catalase-positive microorganisms, due to the inability of their phagocytes to express a respiratory burst against invading bacteria (e.g. Staphylococcus aureus) and fungi (e.g. Aspergillus fumigatus and Candida albicans). Patients, also suffer from a variety of sterile inflammatory conditions as acute and/or chronic inflammation with fibrosis containing non-caseous granulomas in the intestinal tract, liver, lymph nodes, urogenital tract, skin, and brain, most probably caused by an intrinsic dysregulation of the inflammatory mechanisms that can involve other cell types than the known defective phagocytes. Although in literature there are few immunological studies about cell function in CGD, a recent work on CGD animal model, has highlighted that in acute fungal infection, a dysregulation of IL-17-secreting cells, coupled with a decrease IFN-γ-producing effector cells and of IL-10-producing regulatory cells, could have a pathogenic role. Moreover, a decreased frequency of a specific T lymphocytes compartment, called Th17, for their characteristic IL-17A production, was associated with increased susceptibility to fungal end bacterial infection in several human chronic disease as hyper IgE syndrome (HIES) and chronic mucocutaneous candidiasis. In this study, we have investigated the potential involvement of T lymphocyte deregulation in CGD manifestations, by comparison of proliferation, mRNA expression, cytokine production and T lymphocyte phenotype upon fungal and bacterial antigen stimulation, of peripheral blood mononuclear cells (PBMC) between a cohort of CGD patients and of healthy controls. Despite a very large variability in functional responses found in both patient and controls, we showed a statistical significant increased of proliferation upon C. albicans lysate and of IL-10 production upon A. fumigatus in CGD patients, coupled with a slight increase of IFN-γ and IL-17A upon fungal stimulation. Furthermore, upon A. fumigatus in the CDG cohort was found a statistically significant increased of IL-17A production, excluded one patient with chronic inflammation, and increased IL-17A mRNA expression, in agreement with an involvement of IL-17A+ cells in CGD pathogenesis, as shown by the CGD animal model of invasive aspergillosis. We also observed that, in agreement with a protective role of IFN-γ, CGD patients that experienced severe aspergillosis expressed low IFN-γ production compared with other patients, but similar to controls, while patient that not experienced severe aspergillosis had increased IFN-γ production compared to controls, demonstrating that a compensatory IFN-γ increased was need to protect patients with defect of ROS-mediated killing. Concerning the responses to C. albicans yeast and hyphae stimulation, we observed similar amount of IFN-γ and increased of IL-17A and IL-10 levels, compared to controls, showing that probably different pathological mechanism lead to increased Candida albicans infections in CGD with respect to HIES, because it would not be dependent on a decrease of IL17A response to fungal antigens. Moreover, in comparison to CGD patients, HIES patients expressed lower value of IFN-γ for all antigens, but differently to STAT3-mutated HIES patient, that not express IL-17A upon all kinds of stimulation, in STAT3-wt HIES patient IL-17A production upon both C. albicans yeast and hyphae was similar to CGD and increased compared to age-matched healthy controls. Thus the reduced frequencies of C. albicans infection in CGD compared to STAT3-wt HIES, may be explained through the main protective level of IFN-γ. Moreover we believe that in vitro immunological test can help us to exclude a STAT3 mutation, in patients who have a positive score for HIES, before performing a molecular analysis of the gene

    Higgs Boson Production in Association with a Photon in Vector Boson Fusion at the LHC

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    Higgs boson production in association with two forward jets and a central photon at the CERN Large Hadron Collider is analyzed, for the Higgs boson decaying into a b bbar pair in the m_H <= 140 GeV mass region. We study both irreducible and main reducible backgrounds at parton level. Compared to the Higgs production via vector-boson fusion, the request of a further photon at moderate rapidities dramatically enhances the signal/background ratio. Inclusive cross sections for p_T^\gamma >= 20 GeV can reach a few tens of fb's. After a suitable choice of kinematical cuts, the cross-section ratio for signal and irreducible-background can be enhanced up to >= ~1/10, with a signal cross section of the order of a few fb's, for m_H ~ 120 GeV. The request of a central photon radiation also enhances the relative signal sensitivity to the WWH coupling with respect to the ZZH coupling. Hence, a determination of the cross section for the associated production of a Higgs boson decaying into a b bbar pair plus a central photon in vector-boson fusion could help in constraining the b bbar H coupling, and the WWH coupling as well. A preliminary study of QCD showering effects points to a further significant improvement of the signal detectability over the background.Comment: 30 pages, 8 figures, 8 tables; minor corrections to the text; version appeared in Nuclear Physics

    The Deep Plumbing System of Ischia: a Physico-chemical Window on the Fluid-saturated and CO2-sustained Neapolitan Volcanism (Southern Italy)

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    Ischia, a volcanic island located 18 miles SW of Naples (Southern Italy), is a densely populated active caldera that last erupted in AD 1302. Melt inclusions in phenocrysts of the Vateliero and Cava Nocelle shoshonite-latite eruptive products (6th to 4th centuries BC) constrain the structure and nature of the Ischia deep magmatic feeding system. Their geochemical characteristics make Ischia a natural borehole for probing the physico-chemical conditions of magma generation in mantle contaminated by slab-derived fluids or melts, largely dominated by CO2. Volatile concentrations in olivine-hosted melt inclusions require gas-melt equilibria at between 3 and 18 km depth. In agreement with what has already been demonstrated at the other neighboring Neapolitan volcanoes (Procida, Campi Flegrei caldera and Somma-Vesuvius volcanic complex), a major crystallization depth at 8-10 km has been identified.The analyzed melt inclusions provide clear evidence for CO2-dominated gas fluxing and consequent dehydration of magma batches stagnating at crustal discontinuities. Gas fluxing is further supported by selective enrichment in K owing to fluid-transfer during magma differentiation.This takes place under oxidized conditions (Fe3+/EFe>=0·3) that can be fixed by an equimolar proportion of divalent and trivalent iron in the melt if post-entrapment crystallization of the host olivine is discarded. The melt inclusion data, together with data from the literature for other Neapolitan volcanoes, show that magmatism and volcanism in the Neapolitan area, despite differences in composition and eruption dynamics, are closely linked to supercritical CO2-rich fluids.These fluids are produced by devolatilization of subducting terrigenous-pelagic metasediments and infiltrate the overlying mantle wedge, generate magmas and control their ascent up to eruption. Geochemical characteristics of Ischia and the other Neapolitan volcanoes reveal that the extent of fluid or melt contamination of the pre-subduction asthenospheric mantle wedge was similar among these volcanoes. However, differences in the isotopic compositions of the erupted magmas (more enriched in radiogenic Sr at Ischia, Campi Flegrei and Somma-Vesuvius with respect to Procida) and the amount of H2O in the plumbing system of these volcanoes (almost double at Ischia, Campi Flegrei and Somma-Vesuvius than at Procida) reflect the different flow-rates of deep slab-derived fluids or melts through the mantle wedge, which, in turn, control the amount of generated magma.The high bulk permeability of the lithosphere below Ischia, Campi Flegrei and Somma-Vesuvius, determined by the occurrence of intersecting NW-SE and NE-SW regional fault systems, favours fluid ascent and accumulation at crustal levels, with consequent larger magma production and storage than at Procida, located along the NE-SW system

    Erwinia oleae sp. nov., isolated from olive knots caused by Pseudomonas savastanoi pv. savastanoi

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    Three endophytic bacterial isolates were obtained in Italy from olive knots caused by Pseudomonas savastanoi pv. savastanoi. Phenotypic tests in combination with 16S rRNA gene sequence analysis indicated a phylogenetic position of these isolates in the genus Erwinia or Pantoea, and revealed two other strains with highly similar 16S rRNA gene sequences (> 99 %), CECT 5262 and CECT 5264, obtained in Spain from olive knots. Rep-PCR DNA fingerprinting of the five strains from olive knots with BOX, ERIC and REP primers revealed three groups of profiles that were highly similar to each other. Multilocus sequence analysis (MLSA) based on concatenated partial atpD, gyrB, infB and rpoB gene sequences, indicated that the strains constitute a single novel species in the genus Erwinia. The strains showed general phenotypic characteristic of Erwinia, and whole genome DNA-DNA hybridization data confirmed they represent a single novel Erwinia species. The strains showed a DNA G+C base composition ranging from 54.7 to 54.9 mol%. They could be discriminated from the phylogenetically related Erwinia species by their ability to utilise potassium gluconate, L-rhamnose and D-arabitol, but not glycerol, inositol and D-sorbitol. The name Erwinia oleae (type strain DAPP-PG 531T = LMG 25322T = DSM 23398T) is proposed for this new taxon

    An update of the on-sky performance of the Layer-Oriented wave-front sensor for MAD

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    The Multi-conjugate Adaptive optics Demonstrator, MAD, successfully demonstrated on sky the MCAO technique both in Layer Oriented and Star Oriented modes. As results of the Guaranteed Time Observations in Layer Oriented mode quality astronomy papers have been published. In this paper we concentrate on the instrumentation issues and technical aspects which stay behind this success.Comment: 12 pages, 10 figures, Proceedings of the SPIE conference "Adaptive Optics Systems II", 27 June 2010, San Diego, California, US

    Redox behavior of degassing magmas: critical review and comparison of glass-based oxybarometers with application to Etna volcano

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    Glass/melt inclusions are repositories of polybaric magma physiochemical interactions. They are fundamental to retrieve the conditions of fluid saturation and magma oxidation state. The latter is usually reported as oxygen fugacity, which is a key thermodynamic variable: involved in such polybaric physiochemical interactions, fO2f\mathrm{O}_{2} affects melt saturation properties and fixes the speciation of fluids discharged by magmatic systems either up to volcanic craters or feeding hydrothermal systems. Several oxybarometers have been proposed, based on iron and sulfur oxidation states. In this study I summarize their main features and show their performances for 1-bar and fluid-saturated andesitic and basaltic melts. I then show that any assessment of magma redox behavior that does not account for the melt reactivity, driven by melt polymerization and the so-called oxygen electrode in association with iron or sulfur redox couples, may fail in determining the actual contribution of the composition to the observed variations of iron and sulfur oxidation states, resulting in potentially biased fO2f\mathrm{O}_{2} estimates. In the case of Etna volcano, by using a well-established ionic-polymeric approach we show that a major control is the dehydration taking place during magmatic differentiation and magma ascent. Dehydration determines a slight iron oxidation down to around 2.5 wt% in dissolved water, but further dehydration taking place up to the surface results in iron reduction. This dual behavior, related to a change of trivalent iron speciation, is reproduced by reactive ionic-polymeric approaches and for the Etna basalt it is predicted also for constant fO2f\mathrm{O}_{2}. Such a modulation of the redox state due to water dissolution cannot be reproduced by empirical formulations

    Redox behavior of degassing magmas: critical review and comparison of glass-based oxybarometers with application to Etna volcano

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    Glass/melt inclusions are repositories of polybaric magma physiochemical interactions. They are fundamental to retrieve the conditions of fluid saturation and magma oxidation state. The latter is usually reported as oxygen fugacity, which is a key thermodynamic variable: involved in such polybaric physiochemical interactions, fO2f\mathrm{O}_{2} affects melt saturation properties and fixes the speciation of fluids discharged by magmatic systems either up to volcanic craters or feeding hydrothermal systems. Several oxybarometers have been proposed, based on iron and sulfur oxidation states. In this study I summarize their main features and show their performances for 1-bar and fluid-saturated andesitic and basaltic melts. I then show that any assessment of magma redox behavior that does not account for the melt reactivity, driven by melt polymerization and the so-called oxygen electrode in association with iron or sulfur redox couples, may fail in determining the actual contribution of the composition to the observed variations of iron and sulfur oxidation states, resulting in potentially biased fO2f\mathrm{O}_{2} estimates. In the case of Etna volcano, by using a well-established ionic-polymeric approach we show that a major control is the dehydration taking place during magmatic differentiation and magma ascent. Dehydration determines a slight iron oxidation down to around 2.5 wt% in dissolved water, but further dehydration taking place up to the surface results in iron reduction. This dual behavior, related to a change of trivalent iron speciation, is reproduced by reactive ionic-polymeric approaches and for the Etna basalt it is predicted also for constant fO2f\mathrm{O}_{2}. Such a modulation of the redox state due to water dissolution cannot be reproduced by empirical formulations

    Polymerisation, basicity, oxidation state and their role in ionic modelling of silicate melts

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    In order to describe and quantify the reactivity of silicate melts, the ionic notation provided by the Temkin formalism has been historically accepted, giving rise to the study of melt chemical equilibria in terms of completely dissociated ionic species. Indeed, ionic modelling of melts works properly as long as the true extension of the anionic matrix is known. This information may be attained in the framework of the Toop-Samis (1962a,b) model, through a parameterisation of the acid-base properties of the dissolved oxides. Moreover, by combining the polymeric model of Toop and Samis with the «group basicity» concept of Duffy and Ingram (1973, 1974a,b, 1976) the bulk optical basicity (Duffy and Ingram, 1971; Duffy, 1992) of molten silicates and glasses can be split into two distinct contributions, i.e. the basicity of the dissolved basic oxides and the basicity of the polymeric units. Application to practical cases, such as the assessment of the oxidation state of iron, require bridging of the energetic gap between the standard state of completely dissociated component (Temkin standard state) and the standard state of pure melt component at P and T of interest. On this basis it is possible to set up a preliminary model for iron speciation in both anhydrous and hydrous aluminosilicate melts. In the case of hydrous melts, I introduce both acidic and basic dissociation of the water component, requiring the combined occurrence of H+ cations, OH- free anions and, to a very minor extent, of T-OH groups. The amphoteric behaviour of water revealed by this study is therefore in line with the earlier prediction of Fraser (1975)

    Uma experiência com resolução de problemas e demonstração de um fato matemático no ensino médio

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    Neste artigo descrevemos e analisamos uma atividade que foi elaborada com o intuito de contribuir para o desenvolvimento do raciocínio lógico e da capacidade de resolver problemas, objetivos centrais do ensino de matemática, e de introduzir um trabalho com demonstração de fatos matemáticos com alunos de ensino médio. Em sua aplicação, em uma turma de segundo ano da escola Centro Municipal de ensino médio e Profissionalizante Osmar Passarelli Silveira da cidade de Paulínia (SP), no 1º semestre de 2011, os alunos foram divididos em duplas e receberam a atividade cujo objetivo era encontrar e expressar em linguagem matemática a relação entre o número de diagonais e lados de um polígono convexo. Os dados foram analisados a partir da observação etnográfica, registrado em um diário de bordo, e do registro das respostas dos alunos às questões propostas na atividade
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