2,284 research outputs found

    Insights Into the Eruptive Dynamics of Small Caldera-Forming Eruptions: The Case Study of the Welded Scoriae of Vulcano (Aeolian Islands, Italy)

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    A multi-disciplinary study, integrating volcanological field observations, petrography, whole rock geochemistry and textural and compositional analyses on plagioclase crystals has been carried out on the products of Monte Luccia, Spiaggia Lunga, and Quadrara eruptions, occurred between 48 and 21 kyrs on the island of Vulcano. These products are all characterized by welded scoria blankets, and their eruptions have been generally related to the formation and/or re-activation of ring faults bordering the "Il Piano" caldera. The aim of the work is to reconstruct the pre- and syn-eruptive dynamics acting within their magma plumbing systems and the related link with the phases of caldera collapse. At the bottom of the stratigraphic sequences, the presence of base surge deposits suggests that all the eruptions started with a phreatomagmatic phase fed by a shallow reservoir. Textural and microanalytical study of plagioclase crystals of Spiaggia Lunga eruption revealed that the phreatomagmatic event activated the ascent of a volatile-rich, basaltic magma residing at 5–11 km of depth. This basaltic magma mixed with the resident shallow one, and was poured out during the course of the eruption producing a sustained lava-fountaining phase. The subsequent caldera collapse, identified by a layer of chaotic breccia interbedded in the scoriae deposit, has been linked to the partial emptying of the shallow magma reservoir. In contrast to what observed for recent eruptive events at Vulcano, the onset of the magmatic phase would be attributed to a self-activation due to volcano-tectonic events, and not to a pressurization of the plumbing system related to the ascent of deep magma batches. As concerns the Mt. Luccia deposits, bordering the eastern rim of the "Il Piano" caldera, the absence of plagioclase in the mineralogical assemblage suggests the eruption of a deeper magma (>11 km b.s.l.), rapidly ascending through the re-activated ring faults of "Il Piano" caldera. At Quadrara eruption, the occurrence of a layer of white biotite-bearing latitic pumices overlying the basal phreatomagmatic deposits suggests the involvement a shallow, isolated reservoir where the increase of volatile pressure allowed the crystallization of hydrous phases. A deeper shoshonitic magma was involved later in the eruption, forming the welded scoria level at the top of the sequence

    Expanding the knowledge related to flavors and fragrances by means of three-dimensional preparative Gas Chromatography and Molecular Spectroscopy

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    As universally known, gas chromatography (GC) coupled with mass spectrometry (MS) allows us to acquire spectra that can be searched in specific databases to attain qualitative information on a peak of interest. When not present in databases, structure elucidation is required before including a new component in a library: from that moment, scientists all around the world will be able to identify the new molecule with analytical confidence after GC-MS analysis. Conversely, if data are not shared in commercial databases, even if a molecule is studied and elucidated, it appears to be unknown or only identifiable on the basis of third-party data taken from the literature, which is a serious limitation. The present paper deals with a case that confirms this assumption. A component of Myrtus communis L. volatile fraction was tentatively identified based on literature data. Despite this, reliable identification could not be achieved due to the lack of a corresponding spectrum in commercial MS databases. Afterwards, the target component was isolated in a reasonable quantity and with a high degree of purity for downstream characterization by spectroscopic techniques. For this purpose, preparative (prep) GC may appear insufficient for the isolation of volatile components from highly complex samples. In this study, a prep-MDGC system was implemented for the isolation of the compound of interest from myrtle oil, consisting of three wide-bore columns of different selectivity coupled by means of Deans switch transfer devices. Based on the NMR and GC-FTIR data acquired, the unknown compound was identified as 2,2,5,5,7,7-hexamethyl-3,7-dihydro-1-benzofuran-4,6(2H,5H)-dione. Noticeably, this is a known molecule, yet its mass spectrum had never been registered into MS databases and thus was not available to the scientific community. Finally, the spectrum was included for the first time in a commercial library, namely the FFNSC 5.0 MS database. The aim of the present study was to highlight the opportunity to make analytical data quickly available in a reliable way by registering them in searchable MS databases to improve the identification means for researchers all over the worl

    Biokemijska svojstva topljivih i vezanih peroksidaza ekstrahiranih iz glavica i lišća artičoke

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    Soluble (SP), ionically bound (IBP) and covalently bound (CBP) peroxidases (POD) from artichoke leaves and heads have been characterized for the main biochemical parameters. The three PODs, in both leaves and heads, showed the major apparent catalytic efficiency (vmax,app/Km,app) towards ferulic acid, even though, in some cases, they showed higher affinity (Km,app) for other substrates. In leaves, SP and IBP showed higher Km,app for ferulic and chlorogenic acids, and CBP for ferulic and caffeic acids. In heads, SP showed higher Km,app for chlorogenic acid, IBP for caffeic and ferulic acids, and CBP for ferulic acid. It was shown that pH optimum for PODs ranged between 5.0 and 6.0 in leaves. In heads, pH optimum for SP and IBP was 5.5, while CBP presented a very low activity in a wide pH range. All PODs showed high thermal stability but different ability to regenerate: the bound forms were more able to regenerate than the soluble one. The results obtained show that (i) CBP from heads is able to work under very different cellular conditions, (ii) all PODs, in both tissues, have a high apparent catalytic efficiency for ferulic acid, which could explain the effective involvement of POD in lignin biosynthesis, (iii) in heads, high Km,app of SP for chlorogenic acid, particularly abundant in artichoke, could justify the possible involvement of PODs in browning mechanism, and (iv) in heat-processed artichoke, the ability of PODs to regenerate could contribute to oxidation and loss of product quality.Okarakterizirana su mnoga biokemijska svojstva topljivih, ionski i kovalentno vezanih peroksidaza ekstrahiranih iz lišća i glavica artičoke. Sva tri oblika peroksidaza, iz lišća i glavica, pokazala su veliku prividnu katalitičku djelotvornost (vmax,app/Km,app) prema feruličnoj kiselini, iako su u nekoliko slučajeva imala veći afinitet (Km,app) prema drugim supstratima. Topljive i ionski vezane peroksidaze iz lišća artičoke imale su veći afinitet za feruličnu i klorogenu kiselinu, a kovalentno vezane za feruličnu i kafeinsku kiselinu. Topljive peroksidaze iz glavica artičoke pokazale su veći afinitet prema klorogenoj kiselini, ionski vezane prema kafeinskoj i feruličnoj, a kovalentno vezane peroksidaze samo prema feruličnoj kiselini. Optimalna pH-vrijednost za aktivnost peroksidaza iz lišća bila je od 5 do 6, a za aktivnost topljivih i ionski vezanih peroksidaza iz glavica 5,5. Kovalentno vezane peroksidaze ekstrahirane iz glavica artičoke imale su malu aktivnost pri svim pH-vrijednostima. Sve su peroksidaze imale veliku termostabilnost, ali različitu sposobnost regeneracije: vezani su se oblici bolje regenerirali od topljivih oblika. Iz dobivenih rezultata izvedeni su sljedeći zaključci: (i) kovalentno vezane peroksidaze iz glavica djeluju u različitim staničnim uvjetima, (ii) sve ekstrahirane peroksidaze imaju veliku prividnu katalitičku djelotvornost prema feruličnoj kiselini, što objašnjava ulogu peroksidaza u biosintezi lignina, (iii) veliki afinitet topljive peroksidaze iz glavica prema klorogenoj kiselini, osobito zastupljenoj u artičokama, mogao bi objasniti ulogu peroksidaza u posmeđivanju glavica i (iv) sposobnost regeneracije peroksidaza uzrokuje oksidaciju i gubitak kakvoće artičoke tijekom kuhanja

    Influence of Chemical Composition and Microvesiculation on the Chromatic Features of the Obsidian of Sierra de las Navajas (Hidalgo, Mexico)

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    The obsidian of Sierra de las Navajas is well known for its green color and gold hue. In order to relate these features with compositional and microtextural characteristics, we have carried out a microanalytical study by Wave Dispersion System associated to Electron Probe Micro-Analyzer, Scanning Electron Microscope observation, and X-rays micro-tomographic analyses of samples showing different colors (dark to light green, sometimes with bands of different color intensity) and hues (changing, uniform, no hue). In accordance with previous studies, the green color of the obsidian seems to be related to a high iron content, probably in its reduced state. However, no significant difference in composition occurs between dark and light green samples. The SEM observation and microtomographic study revealed the absence of microcrystals and the occurrence of vesicles of different size, shape, and orientation. Lighter green colors are shown by highly vesiculated surfaces, whereas non-vesiculated samples are darker. On the surfaces with a high concentration of coarse vesicles, a uniform golden hue is observed. Decreasing vesiculation gives a hue changing with the angle of incident light. However, when the vesicularity approaches zero, no hue is visible. The iso-orientation of vesicles along preferential directions and their distribution in bands determine the variation in color intensity and hue on differently oriented surfaces. Microvesiculation also influences other characteristics that were important features for the use of obsidian in the past, such as fracture, transparency, and roughness

    Performance of Circulating Placental Growth Factor as A Screening Marker for Diagnosis of Ovarian Endometriosis: A Pilot Study

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    The aim of this study is to compare the circulating placental growth factor (PlGF) concentration in women with and without endometrioma to verify the performance of this marker to diagnose the disease

    Bacterioplankton diversity and distribution in relation to phytoplankton community structure in the Ross Sea surface waters

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    © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cordone, A., D’Errico, G., Magliulo, M., Bolinesi, F., Selci, M., Basili, M., de Marco, R., Saggiomo, M., Rivaro, P., Giovannelli, D., & Mangoni, O. Bacterioplankton diversity and distribution in relation to phytoplankton community structure in the Ross Sea surface waters. Frontiers in Microbiology, 13, (2022): 722900, https://doi.org/10.3389/fmicb.2022.722900.Primary productivity in the Ross Sea region is characterized by intense phytoplankton blooms whose temporal and spatial distribution are driven by changes in environmental conditions as well as interactions with the bacterioplankton community. However, the number of studies reporting the simultaneous diversity of the phytoplankton and bacterioplankton in Antarctic waters are limited. Here, we report data on the bacterial diversity in relation to phytoplankton community structure in the surface waters of the Ross Sea during the Austral summer 2017. Our results show partially overlapping bacterioplankton communities between the stations located in the Terra Nova Bay (TNB) coastal waters and the Ross Sea Open Waters (RSOWs), with a dominance of members belonging to the bacterial phyla Bacteroidetes and Proteobacteria. In the TNB coastal area, microbial communities were characterized by a higher abundance of sequences related to heterotrophic bacterial genera such as Polaribacter spp., together with higher phytoplankton biomass and higher relative abundance of diatoms. On the contrary, the phytoplankton biomass in the RSOW were lower, with relatively higher contribution of haptophytes and a higher abundance of sequences related to oligotrophic and mixothrophic bacterial groups like the Oligotrophic Marine Gammaproteobacteria (OMG) group and SAR11. We show that the rate of diversity change between the two locations is influenced by both abiotic (salinity and the nitrogen to phosphorus ratio) and biotic (phytoplankton community structure) factors. Our data provide new insight into the coexistence of the bacterioplankton and phytoplankton in Antarctic waters, suggesting that specific rather than random interaction contribute to the organic matter cycling in the Southern Ocean.Samples were collected in the framework of Plankton biodiversity and functioning of the Ross Sea ecosystems in a changing Southern Ocean [P-ROSE – (PNRA16_00239)], and CDW Effects on glacial mElting and on Bulk of Fe in the Western Ross sea [CELEBeR – (PNRA16_00207)] projects – Italian National Antarctic Program – funded by the Ministry of Education, University and Research (MIUR), awarded to OM and PR, respectively. MM was supported by an Earth-Life Science Institute (Tokyo, Japan) visiting fellowship. This work was partially supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 948972) to DG

    Transcript Regulation of the Recoded Archaeal α-L-Fucosidase In Vivo

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    Genetic decoding is flexible, due to programmed deviation of the ribosomes from standard translational rules, globally termed “recoding”. In Archaea, recoding has been unequivocally determined only for termination codon readthrough events that regulate the incorporation of the unusual amino acids selenocysteine and pyrrolysine, and for −1 programmed frameshifting that allow the expression of a fully functional α-l-fucosidase in the crenarchaeon Saccharolobus solfataricus, in which several functional interrupted genes have been identified. Increasing evidence suggests that the flexibility of the genetic code decoding could provide an evolutionary advantage in extreme conditions, therefore, the identification and study of interrupted genes in extremophilic Archaea could be important from an astrobiological point of view, providing new information on the origin and evolution of the genetic code and on the limits of life on Earth. In order to shed some light on the mechanism of programmed −1 frameshifting in Archaea, here we report, for the first time, on the analysis of the transcription of this recoded archaeal α-l-fucosidase and of its full-length mutant in different growth conditions in vivo. We found that only the wild type mRNA significantly increased in S. solfataricus after cold shock and in cells grown in minimal medium containing hydrolyzed xyloglucan as carbon source. Our results indicated that the increased level of fucA mRNA cannot be explained by transcript up-regulation alone. A different mechanism related to translation efficiency is discusse
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