Estimating the viscosity of volcanic melts from the vibrational properties of their parental glasses

Abstract The numerical modelling of magma transport and volcanic eruptions requires accurate knowledge of the viscosity of magmatic liquids as a function of temperature and melt composition. However, there is growing evidence that volcanic melts can be prone to nanoscale modification and crystallization before and during viscosity measurements. This challenges the possibility of being able to quantify the crystal-free melt phase contribution to the measured viscosity. In an effort to establish an alternative route to derive the viscosity of volcanic melts based on the vibrational properties of their parental glasses, we have subjected volcanologically relevant anhydrous glasses to Brillouin and Raman spectroscopic analyses at ambient conditions. Here, we find that the ratio between bulk and shear moduli and the boson peak position embed the melt fragility. We show that these quantities allow an accurate estimation of volcanic melts at eruptive conditions, without the need for viscosity measurements. An extensive review of the literature data confirms that our result also holds for hydrous systems; this study thus provides fertile ground on which to develop new studies of the nanoscale dynamics of natural melts and its impact on the style of volcanic eruptions

Thermal Annealing and Phase Transformation of Serpentine-Like Garnierite

This study is focused on the vibrational and microstructural aspects of the thermally induced transformation of serpentine-like garnierite into quartz, forsterite, and enstatite occurring at about 620 °C. Powder specimens of garnierite were annealed in static air between room temperature and 1000 °C. The kinetic of the transformation was investigated by means of thermogravimetric and differential thermal analysis, and the final product was extensively characterized via micro-Raman spectroscopy and X-ray diffraction. Our study shows that serpentine-like garnierite consists of a mixture of different mineral species. Furthermore, these garnierites and their composition can provide details based on the mineralogy and the crystalline phases resulting from the thermal treatment

Effect of the alkali vs. iron ratio on glass transition temperature and vibrational properties of synthetic basalt-like glasses

Volcanic eruptions generate huge amounts of material with a wide range of compositions and therefore different physicochemical properties. We present a combined Raman and calorimetric study carried out on four synthetic basaltic glasses with different alkali vs. iron ratio which spans the typical compositions of basalts on Earth. Differential scanning calorimetry shows that changes of this ratio modify the glass transition interval whereas Raman spectra allow to gain insight about the structure of the glass in the microscopic and macroscopic range. Indeed, our Raman analysis is extended from the high frequency region, characterized by the molecular peaks, to the very low frequency region where glasses exhibit the boson peak. Spectra show a variation of the non-bridging oxygens number that affects the medium range order of the glass and the network interconnections. In the considered substitution interval, the boson peak shape is conserved while its position shift upwards. This means that increasing the alkali vs. iron content the elastic medium hardens but it does not change nature. This study emphasizes the importance of considering the full-range spectra when analysing multicomponent or natural systems with small chemical variations

A nanocomposite based on multi-walled carbon nanotubes grafted by molecularly imprinted poly(methacrylic acid–hemin) as a peroxidase-like catalyst for biomimetic sensing of acetaminophen

In the present study the synthesis of a nanocomposite based on multi-walled carbon nanotubes grafted by poly(methacrylic acid–hemin) is described. The presence of functional groups in the nanocomposite was evaluated by FT-IR, while morphological, textural and thermal stability data were evaluated by means of SEM, TEM, nitrogen adsorption–desorption assays and TGA, respectively. The material was evaluated as a biomimetic and catalytic sensor toward the electrochemical determination of acetaminophen (AC) by depositing it onto a glassy carbon electrode surface. Acetaminophen has been widely used as an analgesic and antipyretics drug and for patients with a high sensitivity to aspirin; therefore the development of analytical methods for AC determination in pharmaceutical formulations is of paramount importance for quality control. The biomimetic electrochemical sensor operation is similar to that of the biosensor based on horseradish peroxidase, where the hemin in the presence of H2O2 catalyses the oxidation of acetaminophen into N-acetyl-p-benzoquinoneimine, which in turn is reduced back to AC on the electrode at a potential of −0.27 V. The variables that exert influence on the performance of the biomimetic response, including H2O2 concentration (300 μmol L−1), pH (8.0) and concentration (0.1 mol L−1) and type of buffer solution (Trizma) were investigated. Under optimized conditions the electrochemical determination of AC using multi-walled carbon nanotubes grafted by poly(methacrylic acid–hemin) immobilized on the surface of the glassy carbon electrode was carried out by square wave voltammetry (SWV), showing a limit of detection of 1.1 μmol L−1. The selectivity of material, ascribed to imprinted effect, was assured by comparison to a non-imprinted material (NIP). The proposed method was applied to AC determination in a pharmaceutical formulation, whose obtained values were very similar to those declared and statistically equal to the HPLC method, thus illustrating the feasibility of method for analysis of real samples.6342875128760CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIG481669/2013-2, 305552/2013-9, 472670/2012-325/2014573672/2008-

Estimating the viscosity of volcanic and binary melts from the vibrational properties of their parental glasses

The knowledge of the viscosity of magmas as a function of melt composition and temperature is central in the numerical modeling of the magmatic dynamics and eruptive scenarios. Recent studies suggest that the measure of the viscosity of volcanic melts is affected by the occurrence of nano-scale modification (i.e., crystallization) of the melt structure during the measurement. This challenges the possibility of being able to quantify the crystal-free melt phase contribution to the measured viscosity. Herein we provide a new strategy that allows an accurate estimation of the melt viscosity at eruptive conditions starting from the Brillouin and Raman scattering of parental glasses. Our results show that the ratio between bulk and shear moduli and the boson peak position of glass embed the melt fragility. However, at the moment there are no known reasons why some of these quantities are linked together in such multicomponent systems. At this effort, we also provided a mean to evaluate whether the local structure of glasses may justify this correlation by testing the well-known prototypical binary system Na2O-SiO2. Concluding, our strategy allows the estimation of the melt viscosity as a function of temperature avoiding its direct measurement, ridding also the measurement from unwished crystallization

H+-dependent inorganic phosphate uptake in Trypanosoma brucei is influenced by myo-inositol transporter.

Trypanosoma brucei is an extracellular protozoan parasite that causes human African trypanosomiasis or "sleeping sickness". During the different phases of its life cycle, T. brucei depends on exogenous inorganic phosphate (Pi), but little is known about the transport of Pi in this organism. In the present study, we showed that the transport of 32Pi across the plasma membrane follows Michaelis-Menten kinetics and is modulated by pH variation, with higher activity at acidic pH. Bloodstream forms presented lower Pi transport in comparison to procyclic forms, that displayed an apparent K0.5 = 0.093 ± 0.008 mM. Additionally, FCCP (H+-ionophore), valinomycin (K+-ionophore) and SCH28080 (H+, K+-ATPase inhibitor) inhibited the Pi transport. Gene Tb11.02.3020, previously described to encode the parasite H+:myo-inositol transporter (TbHMIT), was hypothesized to be potentially involved in the H+:Pi cotransport because of its similarity with the Pho84 transporter described in S. cerevisiae and other trypanosomatids. Indeed, the RNAi mediated knockdown remarkably reduced TbHMIT gene expression, compromised cell growth and decreased Pi transport by half. In addition, Pi transport was inhibited when parasites were incubated in the presence of concentrations of myo-inositol that are above 300 μM. However, when expressed in Xenopus laevis oocytes, two-electrode voltage clamp experiments provided direct electrophysiological evidence that the protein encoded by TbHMIT is definitely a myo-inositol transporter that may be only marginally affected by the presence of Pi. These results confirmed the presence of a Pi carrier in T. brucei, similar to the H+-dependent inorganic phosphate system described in S. cerevisiae and other trypanosomatids. This transport system contributes to the acquisition of Pi and may be involved in the growth and survival of procyclic forms. In summary, this work presents the first description of a Pi transport system in T. brucei

2020 Dataset on local gambling regulations in Italy

The dataset provides the complete enumeration of gambling policies implemented by Italian Municipalities between 2003 and 2021. The dataset comprises information on all municipalities existing in 2017 and following years (thus considering also merging). The following variables are available: Municipality ISTAT Code (ID), Municipality Name (Name) Province, Region, Researcher, and a series of variables identifying the number and the type of rulings adopted ('regolamento', 'ordinanza' and 'delibera'). The rulings are distinguished between identified and downloaded or only identified (because the document is no longer available). Additional variables describe municipal activism with other administrative acts (Anti-gambling Manifesto, events, projects or tax reductions). Overall, the dataset comprises 8031 units

Levantamento pedológico e sistema de informações geográficas naavaliação do uso das terras em sub-bacia hidrográfica de Minas Gerais Pedologic survey and geographic information system for evaluation of land use within a small watershed, Minas Gerais State, Brazil

A aptidão agrícola das terras consiste em uma classificação técnica que identifica o potencial agrícola de utilização das mesmas, considerando as limitações do solo em níveis de manejo diferenciados a partir das informações geradas em um levantamento pedológico. O cruzamento dos dados de aptidão agrícola e uso atual das terras em ambiente SIG (Sistema de Informações Geográficas) consiste numa ferramenta adequada de planejamento, pois permite determinar a inadequação entre uso e aptidão agrícola, dando bases sustentáveis à exploração. Neste estudo, foram realizadas a avaliação da aptidão agrícola das terras e seu uso atual com auxílio de imagens de satélite e observações de campo, e a identificação de Áreas de Preservação Permanente (APPs) em uma sub-bacia hidrográfica da Bacia do Alto Rio Grande, MG. Com base no levantamento de solos, a utilização do sensoriamento remoto, por meio de imagens de satélites, aliado ao ambiente SIG, constituem-se em ferramentas adequadas para avaliação da aptidão agrícola e uso atual das terras, e permitem o monitoramento das áreas da sub-bacia hidrográfica. O levantamento pedológico forneceu uma base segura e real para que, com o auxílio de ferramentas de geoprocessamento, os mapas resultantes tivessem melhor qualidade e representassem com acurácia os diferentes ambientes naturais na paisagem da sub-bacia hidrográfica. Ocorreu o predomínio de usos da terra menos intensivos que os das classes de aptidão agrícola encontradas. As Áreas de Preservação Permanente (APPs) estão recebendo os mais diferentes usos agrícolas, caracterizando uma inadequação entre a legislação ambiental e o uso atual da terra.<br>The land agricultural suitability is a technical classification that identifies the agricultural potential of land use, considering the soil limitations at differential management levels from the information generated in a pedologic survey. The cross reference of data involving land agricultural suitability and land use in Geographical Information System (GIS) is an adequate tool for planning, because it allows to determine the inadequacy between land use and land agricultural suitability, giving bases to sustainable exploration. Therefore, we evaluated in this work the land agricultural suitability and the current use of the land mediated by satellite images and field observations, for the identification of permanent preservation areas (PPAs) in a small watershed from Alto Rio Grande basin - MG. Based on soil survey, the utilization of remote sensing, by means of satellite images, in association with GIS, constitutes adequate tools to evaluate the land suitability and current use, and allows monitoring areas of the small watershed. The pedologic survey supplied a secure and real basis for this purpose and with the help of geoprocessing tools, the resulting maps had better quality and represented with accuracy the different natural environments in the landscape of the hydrographic small watershed. We observed a dominance of less intensive land use in relation to the agricultural suitability classes found here. The permanent preservation areas (PPAs) are receiving a variety of agricultural uses, which characterizes an inadequacy between the environmental legislation and the current land use

2020 Dataset on local gambling regulations in Italy

The dataset provides the complete enumeration of gambling policies implemented by Italian Municipalities between 2003 and 2021. The dataset comprises information on all municipalities existing in 2017 and following years (thus considering also merging). The following variables are available: Municipality ISTAT Code (ID), Municipality Name (Name) Province, Region, Researcher, and a series of variables identifying the number and the type of rulings adopted (“regolamento”, “ordinanza” and “delibera”). The rulings are distinguished between identified and downloaded or only identified (because the document is no longer available). Additional variables describe municipal activism with other administrative acts (Anti-gambling Manifesto, events, projects or tax reductions). Overall, the dataset comprises 8031 units