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

Vibrational dynamics of rutile-type GeO2 from micro-Raman spectroscopy experiments and first-principles calculations

The vibrational dynamics of germanium dioxide in the rutile structure has been investigated by using polarized micro-Raman scattering spectroscopy coupled with first-principles calculations. Raman spectra were carried out in backscattering geometry at room temperature from micro-crystalline samples either unoriented or oriented by means of a micromanipulator, which enabled successful detection and identification of all the Raman active modes expected on the basis of the group theory. In particular, the Eg mode, incorrectly assigned or not detected in the literature, has been definitively observed by us and unambiguously identified at 525 cm − 1 under excitation by certain laser lines, thus revealing an unusual resonance phenomenon. First principles calculations within the framework of the density functional theory allow quantifying both wave number and intensity of the Raman vibrational spectra. The excellent agreement between calculated and experimental data corroborates the reliability of our findings

Different spectroscopic behavior of coupled and freestanding monolayer graphene deposited by CVD on Cu foil

The growth of graphene on copper foil has been performed, following the well-known low-pressure chemical vapor (LP-CVD) procedure. The as-deposited monolayer graphene clearly exhibits two different coupling behaviors with the metal substrate, as demonstrated by visual microscopic investigation and by other experimental techniques, like Scanning Electron Microscopy (SEM) and micro-Raman spectroscopy. The single graphene sheet shows both large areas where it is coupled to the metal substrate and others where it exhibits freestanding-like characteristics. This phenomenology appears to be related to oxidation of the copper surface. In addition, we demonstrate the possibility to induce a variation of the coupling state by visible-light irradiation above a proper power threshold. The resulting change of the coupling with the metal substrate is associated to a local variation of the work function. Applications in high-performance electronic devices can be suitably tailored by optical methods and, in principle, by any local probe producing "hot spots" such as Scanning Tunneling Microscopy (STM) tips and electron beams.</p

Lattice dynamics and anharmonicity of CaZrF6 from Raman spectroscopy and ab initio calculations

Very recently it has been found that CaZrF6 exhibits a very large and isotropic negative thermal expansion (NTE), even greater than the current most popular NTE materials. In this work, the vibrational dynamics of CaZrF6 has been investigated by temperature-dependent Raman spectroscopy combined with ab initio calculations. As expected on the basis of the group theory for CaZrF6, three Raman-active modes were identified: the F2g mode peaked at about 236 cm1, the Eg mode at around 550e555 cm1, and the Ag mode peaked at about 637 cm1. The temperature dependence of their frequencies follows an unusual trend: the F2g mode, due to bending vibrations of fluorine atoms in the linear Ca-F-Zr chain, is hardened with increasing temperature, while the Ag mode, corresponding to Ca-F-Zr bond stretching vibrations, is softened. We explain this anomalous behavior by separating implicit and explicit anharmonicity for both F2g and Ag modes. In fact, cubic anharmonicity (three-phonon processes) is observed to dominate the higher-frequency Ag phonon-mode, quartic anharmonicity (four-phonon processes) is found to dominate the lower-frequency F2g phonon-mode. As a result, the large NTE of CaZrF6 cannot be accurately predicted through the quasi-harmonic approximation

Co-encapsulation of vitamin D and rutin in chitosan-zein microparticles

© 2022 The Authors. Published by Springer. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1007/s11694-022-01340-2There is a growing interest in co-encapsulating multiple species to harness potential synergy between them, enhance their stability and efficacy in various products. The aim of this work was to co-encapsulate vitamin D3 and rutin inside chitosan-zein microparticles using a simple and easily scalable process for food fortification. This was achieved via anti-solvent precipitation coupled with spray-drying. Free-flowing powders of spherical microparticles with wrinkled surface and particle size < 10 μm were obtained. The encapsulation efficiency was 75% for vitamin D3 and 44% for rutin and this could be attributed to their different molecular size and affinity to the aqueous phase. The physicochemical properties were characterized by X-Ray powder diffraction and Fourier transform infrared spectroscopy. The two crystalline bioactive compounds were present in the microparticles in amorphous form, which would allow for better bioavailability when compared to non-encapsulated crystalline solid. Therefore, the obtained microparticles would be suitable for use as food ingredient for vitamin D3 fortification, with the co-encapsulated rutin acting as stability and activity enhancer.This work was supported by Regione Veneto FSE project No. 1695–16-11–2018.Published onlin

Structural and Spectroscopic Characterization of a Nanosized Sulfated TiO2 Filler and of Nanocomposite Nafion Membranes

Abstract: A large number of nano-sized oxides have been studied in the literature as fillers for polymeric membranes, such as Nafion®. Superacidic sulfated oxides have been proposed and characterized. Once incorporated into polymer matrices, their beneficial effect on peculiar membrane properties has been demonstrated. The alteration of physical-chemical properties of composite membranes has roots in the intermolecular interaction between the inorganic filler surface groups and the polymer chains. In the attempt to tackle this fundamental issue, here we discuss, by a multi-technique approach, the properties of a nanosized sulfated titania material as a candidate filler for Nafion membranes. The results of a systematic study carried out by synchrotron X-ray diffraction, transmission electron microscopy, thermogravimetry, Raman and infrared spectroscopies are presented and discussed to get novel insights about the structural features, molecular properties, and morphological characteristics of sulphated TiO2 nanopowders and composite Nafion membranes containing different amount of sulfated TiO2 nanoparticles (2%, 5%, 7% w/w)

Effect of Mn doping on the growth and properties of enstatite single crystals

Millimetric Mn-doped enstatite (MgSiO3) crystals have been grown by slow cooling in MoO3, V2O5, and Li2CO3 flux. Six starting mixture with different amount of manganese were slowly cooled from 1350 °C, 1050 °C and 950 °C down to 750 °C, 650 °C and 600 °C respectively. The enstatite crystals were characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy with energy-dispersive spectrometry (SEM/EDS). Mn-doped enstatite crystals were reddish in color, euhedral and elongate parallel to c-axis. The largest enstatite crystal obtained is 8.5 mm in length. The effects of growth parameters on yield and size of crystals were studied. Variations observed in crystal size were attributed to the amount of Mn doping. Further characterizations by μ-Raman spectroscopy (μ-R) and cathodoluminescence (CL) allowed to study the effect of Mn doping on some chemical/physical characteristics of the enstatite and to assess its potential in advanced technological applications

Lanthanide doped upconverting colloidal CaF2 nanoparticles prepared by a single-step hydrothermal method: toward efficient materials with near infrared-to-near infrared upconversion emission

Colloidal Er3+/Yb3+, Tm3+/Yb3+ and Ho3+/Yb3+ doped CaF2 nanoparticles have been prepared by a one-pot hydrothermal procedure and their upconversion properties have been investigated

A registry for Dravet syndrome: The Italian experience

Objectives: We describe the Residras registry, dedicated to Dravet syndrome (DS) and to other phenotypes related to SCN1A mutations, as a paradigm of registry for rare and complex epilepsies. Our primary objectives are to present the tools and framework of the integrative platform, the main characteristics emerging from the patient cohort included in the registry, with emphasis on demographic, clinical outcome, and mortality. / Methods: Standardized data of enrolled pediatric and adult patients were collected in 24 Italian expert centers and regularly updated at least on a yearly basis. Patients were prospectively enrolled, at registry starting, but historical retrospective data were also included. / Results: At present, 281 individuals with DS and a confirmed SCN1A mutation are included. Most patients have data available on epilepsy (n = 263) and their overall neurological condition (n = 255), based on at least one follow-up update. Median age at first clinical assessment was 2 years (IQR 0–9) while at last follow-up was 11 years (IQR 5–18.5). During the 7-year activity of the registry, five patients died resulting in a mortality rate of 1.84 per 1000-person-years. When analyzing clinical changes over the first 5-year follow-up, we observed a significant difference in cognitive function (P < 0.001), an increased prevalence of behavioral disorders including attention deficit (P < 0.001), a significant worsening of language (P = 0.001), and intellectual disability (P < 0.001). / Significance: The Residras registry represents a large collection of standardized national data for the DS population. The registry platform relies on a shareable and interoperable framework, which promotes multicenter high-quality data collection. In the future, such integrated platform may represent an invaluable asset for easing access to cohorts of patients that may benefit from clinical trials with emerging novel therapies, for drug safety monitoring, and for delineating natural history. Its framework makes it improvable based on growing experience with its use and easily adaptable to other rare and complex epilepsy syndromes