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34 result(s) for "Regis, Daniele"
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Crustal reworking and hydration: insights from element zoning and oxygen isotopes of garnet in high-pressure rocks (Sesia Zone, Western Alps)
Subduction zones represent one of the most critical settings for fluid recycling as a consequence of dehydration of the subducting lithosphere. A better understanding of fluid flows within and out of the subducting slab is fundamental to unravel the role of fluids during burial. In this study, major and trace element geochemistry combined with oxygen isotopes were used to investigate metasediments and eclogites from the Sesia Zone in order to reconstruct the effect of internal and external fluid pulses in a subducted continental margin. Garnet shows a variety of textures requiring dissolution–precipitation processes in presence of fluids. In polycyclic metasediments, garnet preserves a partly resorbed core, related to pre-Alpine high-temperature/low-pressure metamorphism, and one or multiple rim generations, associated with Alpine subduction metamorphism. In eclogites, garnet chemical zoning indicates monocyclic growth with no shift in oxygen isotopes from core to rim. In metasediments, pre-Alpine garnet relics show δ18O values up to 5.3 ‰ higher than the Alpine rims, while no significant variation is observed among different Alpine garnet generations within each sample. This suggests that an extensive re-equilibration with an externally-derived fluid of distinct lower δ18O occurred before, or in correspondence to, the first Alpine garnet growth, while subsequent influxes of fluid had δ18O close to equilibrium. The observed shift in garnet δ18O is attributed to a possible combination of (1) interaction with sea-water derived fluids during pre-Alpine crustal extension and (2) fluids from dehydration reactions occurring during subduction of previously hydrated rocks, such as the serpentinised lithospheric mantle or hydrated portions of the basement.
Yo-yo subduction recorded by accessory minerals in the Italian Western Alps
High-pressure metamorphic rocks form during subduction of Earth’s crust to mantle depths at convergent plate margins. Their exposure at the surface of Earth today provides a record of the subduction zone process. In general, such metamorphic rocks record only a single cycle of subduction and exhumation, yet tectonic models suggest that individual rock units should undergo multiple subduction–exhumation cycles. Here we investigate the microstructure and chemical composition of metamorphic minerals in high-pressure rocks exposed in the Sesia zone in the Italian Western Alps. We find that the minerals white mica, garnet, allanite and zircon each exhibit multiple generations of mineral overgrowths. In particular, two generations of white mica with high-silicon content, indicative of formation at high pressure, are separated by an overgrowth with low-silicon content that formed during exhumation at low pressures. Furthermore, the trace-element signatures of distinct zones within zircon and allanite also reveal two episodes of high-pressure metamorphism, separated by a period of rapid exhumation. We use uranium–lead dating of zircon and allanite overgrowths to constrain the timing of this subduction–exhumation–subduction cycle to 79–65 Myr ago. We conclude that slices of the Sesia zone crust experienced two cycles of burial to mantle depths in less than 20 million years. The yo-yo subduction occurred during oblique convergence between the African and European plates, which involved a continental margin. Individual rock units are predicted by tectonic models to undergo numerous, complex cycles of subduction. Analysis of high-pressure rocks exposed in the Sesia zone, Italian Western Alps, suggest that slices of the crust underwent two distinct episodes of subduction to mantle depths in fewer than 20 million years.
Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?
Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U–Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P–T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U–Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure.
Geology of the Scalaro valley - Sesia Zone (Italian Western Alps)
In the Sesia Zone (Italian Western Alps), slivers of continental crust characterised by an Alpine high-pressure imprint are intermingled with abundant mafic rocks and Mesozoic metasediments. An extensive study of the central Sesia Zone was undertaken to identify and reconstruct the lithological setting of the mono-cyclic sediments of the Scalaro Unit. A new geological map (1:5000) and schematic cross sections across the Scalaro Unit and the adjoining Eclogitic Micaschist Complex are presented here. In order to delimit the size and shape of the mono-metamorphic unit and understand its internal geometry with respect to the poly-metamorphic basement, an integrated approach was used. Linking observations and data across a range of scales, from kilometres in the field down to petrological and chronological data obtained at micrometre scale, we define for the first time the real size and internal geometry of the Scalaro Unit, as well as its large-scale structural context.
Deformation and extensional exhumation of 1.9 Ga high-pressure granulites along the Wholdaia Lake shear zone, south Rae Craton, Northwest Territories, Canada
The origin of high-pressure granulites in the south Rae craton and Snowbird tectonic zone (STZ) is highly enigmatic. Current models for their formation and exhumation envisage continental collision at 2.55 Ga and intracratonic orogenesis at 1.9 Ga, or collision and exhumation at ca. 1.9 Ga. As an attempt to reconcile these disparate models, we conducted a regional and detailed mapping program along a geophysical discontinuity 100 km west of the STZ within the south Rae craton of the Northwest Territories, Canada. This work presents the discovery of a new crustal-scale shear zone, the Wholdaia Lake shear zone (WLsz), which deformed and transposed host rocks into a 20-km-wide and 300-km-long ductile high-strain zone. U-Pb zircon geochronology was utilized to establish host-rock crystallization ages, timing of deposition of metasedimentary rocks, and age constraints of metamorphism and ductile shearing. Hanging-wall metasedimentary rocks have a new depositional range of 1.98-1.93 Ga and contain abundant metamorphic zircon at 1.91 Ga. The protoliths of the footwall mafic granulite orthogneisses crystallized at 2.6 Ga and were metamorphosed at 1.9 Ga, which extends the known footprint of 1.9 Ga metamorphism 100 km west of the STZ. During and after 1.9 Ga metamorphism, the WLsz began progressively exhuming footwall rocks in three distinct stages, associated with (1) normal-oblique shearing at high-pressure granulite-facies conditions, (2) normal-oblique shearing accompanied by mylonitization at amphibolite-facies conditions, and (3) normal-oblique shearing with ultramylonite development at amphibolite- to greenschist-facies conditions. Ductile shearing was waning by 1.86 Ga, based on ages obtained from late syn- to postkinematic crosscutting dikes. Collectively, the WLsz in concert with other regional structures aided both extensional and thrust-sense exhumation of a large high-grade terrane at 1.9 Ga in the south Rae craton.
Homogalacturonan From Yellow Passion Fruit Peel Ameliorates Intestinal Injury in DSS‐Induced Colitis in Mice
Ulcerative colitis is a chronic inflammatory bowel disease characterised by persistent inflammation of the colonic mucosa. Symptoms include bloody diarrhoea and abdominal pain, which have a significant impact on quality of life. Current treatments mainly alleviate symptoms and maintain remission, but natural therapeutic alternatives are still needed. To investigate the therapeutic effect of pectic polysaccharides from the peel of Passiflora edulis on DSS‐induced ulcerative colitis in mice, focusing on colonic histoarchitecture, collagen remodelling, MUC‐2 expression and immune cell distribution. Mice were assigned to a control group, a group with DSS‐induced colitis, or a group with HPE treatment (P. edulis homogalacturonan, 100 mg/kg). Histomorphometric, histopathologic, and immunohistochemical analyses of the colonic wall, evaluation of collagen remodelling and MUC‐2 expression, quantification of immune cells and in silico tests were performed. DSS caused atrophy of the muscular and submucosal layers, hypertrophy of the mucosa, increased crypt depth and decreased enterocyte height. HPE improved muscular and submucosal thickness, partially restored enterocyte height, reduced crypt depth and collagen deposition and increased intraepithelial lymphocytes. DSS significantly decreased MUC‐2 expression in goblet cells, while HPE significantly restored it. Pharmacokinetic and toxicological predictions indicated a favourable safety profile for HPE, and molecular docking analyses suggested interactions with proteins involved in maintaining the integrity of the intestinal barrier. HPE effectively attenuated DSS‐induced colon damage and restored MUC‐2 expression, contributing to epithelial barrier restoration and supporting its therapeutic potential in ulcerative colitis.
Women in construction: shortcomings, difficulties, and good practices
Purpose On average, only 10 percent workers at construction sites are women. This percentage, however, is not due to a lack of interest or capacity, but to discrimination against women, sexual harassment and work safety. The purpose of this paper is to identify the main issues and current difficulties of women workers at construction sites, as well as good practices that might provide a better environment for them. Design/methodology/approach Interviews were carried out with workers and engineers who work/have worked at construction sites, to gather material for a discussion about the gender gap in this environment. The interviews were structured and analyzed around the following topics: acceptance, well-being, installations, gender perception and good practices. Findings The hiring of women usually occurs at the end of the construction period, which brings up the issue of sexual division of labor. Effects of the glass ceiling and the leaky pipeline phenomena were evident, as well as harassment, discrimination and sexism. Originality/value Studies about women in engineering have been become relative common, but studies about female workers on construction sites are still scarce. The women interviewed see themselves as warriors, symbolizing the gain of space within the construction sector and in society. It is hoped that the results can contribute to raising awareness about the benefits of gender mainstreaming at construction sites and to promote the health and well-being of women in these environments.
Dietary Consumption of Phenolic Acids and Prostate Cancer: A Case-Control Study in Sicily, Southern Italy
Dietary polyphenols gained the interest of the scientific community due to their wide content in a variety of plant-derived foods and beverages commonly consumed, such as fruits, vegetables, coffee, tea, and cocoa. We aimed to investigate whether there was an association between dietary phenolic acid consumption and prostate cancer (PCa) in South Italy. We conducted a population-based case-control study from January 2015 to December 2016 in a single institution of the municipality of Catania, southern Italy (Registration number: 41/2015). Patients with elevated PSA and/or suspicious PCa underwent transperineal prostate biopsy. A total of 118 histopathological-verified PCa cases were collected and a total of 222 controls were selected from a sample of 2044 individuals. Dietary data were collected by using two food frequency questionnaires and data on the phenolic acids content in foods was obtained from the Phenol-Explorer database (www.phenol-explorer.eu). Association between dietary intake of phenolic acids and PCa was calculated through logistic regression analysis. We found lower levels of caffeic acid (2.28 mg/day vs. 2.76 mg/day; p < 0.05) and ferulic acid (2.80 mg/day vs. 4.04 mg/day; p < 0.01) in PCa when compared to controls. The multivariate logistic regression showed that both caffeic acid (OR = 0.32; p < 0.05) and ferulic acid (OR = 0.30; p < 0.05) were associated with reduced risk of PCa. Higher intake of hydroxybenzoic acids and caffeic acids were associated with lower risk of advanced PCa. High intake of caffeic acid and ferulic acid may be associated with reduced risk of PCa.
Development of RT-qPCR and semi-nested RT-PCR assays for molecular diagnosis of hantavirus pulmonary syndrome
Hantavirus Pulmonary Syndrome is an, often fatal, emerging zoonotic disease in the Americas caused by hantaviruses (family: Hantaviridae). In Brazil, hantavirus routine diagnosis is based on serology (IgM-ELISA) while RT-PCR is often used to confirm acute infection. A Semi-nested RT-PCR and an internally controlled RT-qPCR assays were developed for detection and quantification of four hantaviruses strains circulating in the Brazilian Amazon: Anajatuba (ANAJV) and Castelo dos Sonhos (CASV) strains of Andes virus (ANDV) species; and Rio Mamoré (RIOMV) and Laguna Negra (LNV) strains of LNV species. A consensus region in the N gene of these hantaviruses was used to design the primer sets and a hydrolysis probe. In vitro transcribed RNA was diluted in standards with known concentration. MS2 bacteriophage RNA was detected together with hantavirus RNA as an exogenous control in a duplex reaction. RT-qPCR efficiency was around 100% and the limit of detection was 0.9 copies/μL of RNA for RT-qPCR and 10 copies/μL of RNA for Semi-nested RT-PCR. There was no amplification of either negative samples or samples positive to other pathogens. To assess the protocol for clinical sensitivity, specificity and general accuracy values, both assays were used to test two groups of samples: one comprising patients with disease (n = 50) and other containing samples from healthy individuals (n = 50), according to IgM-ELISA results. A third group of samples (n = 27) infected with other pathogens were tested for specificity analysis. RT-qPCR was more sensitive than semi-nested RT-PCR, being able to detect three samples undetected by conventional RT-PCR. RT-qPCR clinical sensitivity, specificity and general accuracy values were 92.5%, 100% and 97.63%, respectively. Thus, the assays developed in this study were able to detect the four Brazilian Amazon hantaviruses with good specificity and sensitivity, and may become powerful tools in diagnostic, surveillance and research applications of these and possibly other hantaviruses.
Polysaccharides from Passion Fruit Peels: From an Agroindustrial By-Product to a Viable Option for 5-FU-Induced Intestinal Damage
Gastrointestinal mucositis is a serious and dose-limiting toxic side effect of oncologic treatment. Interruption of cancer treatment due to gastrointestinal mucositis leads to a significant decrease in cure rates and consequently to the deterioration of a patient’s quality of life. Natural polysaccharides show a variety of beneficial effects, including a gastroprotective effect. Treatment with soluble dietary fiber (SDF) from yellow passion fruit (Passiflora edulis) biomass residues protected the gastric and intestinal mucosa in models of gastrointestinal injury. In this study, we investigated the protective therapeutic effect of SDF on 5-FU-induced mucositis in male and female mice. Oral treatment of the animals with SDF did not prevent weight loss but reduced the disease activity index and preserved normal intestinal function by alleviating diarrhea and altered gastrointestinal transit. SDF preserved the length of the colon and histological damage caused by 5-FU. SDF significantly restored the oxidative stress and inflammation in the intestine and the enlargement and swelling of the spleen induced by 5-FU. In conclusion, SDF may be a promising adjuvant strategy for the prevention and treatment of intestinal mucositis induced by 5-FU.