Search

The Ma_MISS miniaturized spectrometer is integrated within the Drilling System of the ExoMars Rosalind Franklin Rover for Mars exploration. Here we focus on the on ground calibration campaign to obtain radiometric and linearity calibrations of the Ma_MISS instrument, while the first paper dealt with the spectral calibration [De Angelis et al., Rev. Sci. Instrum. 93, 123704 (2022)]. The experimental setup used to carry out radiometric calibration is described, as are the methods used for data processing and key parameter retrieval. In particular, the Spectrometer Transfer Function (Responsivity), Signal-to-Noise Ratio, and detector linearity are determined. In a third paper [De Sanctis et al., Planet. Sci. J. 3, 142 (2022)], validation of the Ma_MISS calibration results through spectral measurements performed on rock and synthetic targets during the radiometric calibration campaign is described. [ABSTRACT FROM AUTHOR]

The aim of this work is to characterize, from a thermophysical perspective, the dark resistant unit (DRU) characterizing Germania Lacus in the Oxia Planum Region, providing new insights to constrain the nature of the materials which compose this unit. We investigated the temperature distribution of the DRU by adopting common values of the thermophysical parameters of the basalt and by exploring several values of porosity. As an additional case, we also explore a composition made of pebbles. The numerical model developed here represents a follow-up of the work recently published by Formisano et al. 2021, and it takes into account a large-scale topography of the site and assumes a diurnal temperature profile for the atmosphere rather than a constant value (unlike Formisano et al. 2021). Comparisons with Mars Pathfinder and Viking data as well as numerical models are also reported. The methodology described here could be useful to characterize as well other sites on Mars' surface with available small-scale topographic data. [ABSTRACT FROM AUTHOR]

The Mars Multispectral Imager for Subsurface Studies (Ma_MISS) instrument is a miniaturized visible and near-infrared spectrometer that is integrated into the drilling system of the ESA Rosalind Franklin rover, which is devoted to subsurface exploration on Mars. Ma_MISS will acquire spectral data on the Martian subsurface from excavated borehole walls. The spectral data collected by Ma_MISS on unexposed rocks will be crucial for determination of the composition of subsurface rocks and optical and physical properties of materials (i.e., grain size). Ma_MISS will further contribute to a reconstruction of the stratigraphic column and acquire data on subsurface geological processes. Ma_MISS data may also inform with regard to the presence of potential biomarkers in the subsurface, given the presence of organic matter that may affect some spectral parameters. In this framework, we performed a wide range of measurements using the laboratory model of the Ma_MISS to investigate mineral/organic mixtures in different proportions. We prepared mixtures by combining kaolinite and nontronite with glycine, asphaltite, polyoxymethylene, and benzoic acid. These organic compounds show different spectral characteristics in the visible and near-infrared; therefore their presence can be detected by the Ma_MISS instrument. Our results indicate that the Ma_MISS instrument can detect organic material down to abundances of around 1 wt %. In particular, the data collected on low-concentration mixtures show that, by analyzing sediments with a grain size smaller than the Ma_MISS spatial resolution, the instrument can still discern those points where organic matter is present from points with exclusive mineral composition. The results also show that a collection of multiple contiguous measurements on a hypothetical borehole wall could help indicate the presence of organic matter in clay-rich soils if present. [ABSTRACT FROM AUTHOR]

The eruption of the submarine Hunga Tonga-Hunga Haʻapai (Hunga Tonga) volcano on 15 January 2022, was one of the largest volcanic explosions recorded by modern geophysical instrumentation. The eruption was notable for the broad range of atmospheric wave phenomena it generated and for their unusual coupling with the oceans and solid Earth. The event was recorded worldwide across the Global Seismographic Network (GSN) by seismometers, microbarographs and infrasound sensors. The broad-band instrumentation in the GSN allows us to make high fidelity observations of spheroidal solid Earth normal modes from this event at frequencies near 3.7 and 4.4 mHz. Similar normal mode excitations were reported following the 1991 Pinatubo (Volcanic Explosivity Index of 6) eruption and were predicted, by theory, to arise from the excitation of mesosphere-scale acoustic modes of the atmosphere coupling with the solid Earth. Here, we compare observations for the Hunga Tonga and Pinatubo eruptions and find that both strongly excited the solid Earth normal mode 0S29 (3.72 mHz). However, the mean modal amplitude was roughly 11 times larger for the 2022 Hunga Tonga eruption. Estimates of attenuation (Q) for 0S29 across the GSN from temporal modal decay give Q  = 332 ± 101, which is higher than estimates of Q for this mode using earthquake data (Q  = 186.9 ± 5). Two microbarographs located at regional distances (<1000 km) to the volcano provide direct observations of the fundamental acoustic mode of the atmosphere. These pressure oscillations, first observed approximately 40 min after the onset of the eruption, are in phase with the seismic Rayleigh wave excitation and are recorded only by microbarographs in proximity (<1500 km) to the eruption. We infer that excitation of fundamental atmospheric modes occurs within a limited area close to the site of the eruption, where they excite select solid Earth fundamental spheroidal modes of similar frequencies that are globally recorded and have a higher apparent Q due to the extended duration of atmospheric oscillations. [ABSTRACT FROM AUTHOR]

Severe acquired brain injury (sABI) leads to a wide range of functional limitations in cognitive, moto and behavioural abilities. These changes impact the patient's family in terms of the feeling of emotional and physical health, social life and financial condition. Caregivers are often intensely involved in the patient's management exposing them to negative effects of caregiving including stress, mood disorders and decreased quality of life. Implementing forms of active involvement of caregivers in the rehabilitative program could be useful. Thus, in the present study, therapeutic educational workshops (TEWs) for caregivers during the post-acute intensive hospitalization were organized during the post-acute intensive hospitalization of patients with sABI. The caregivers were asked to participate in the workshops to actively involve them in the patient's care and neurorehabilitation program. Each workshop session provided indications regarding the management of the patient with aphasia, neglect, behavioural and swallowing disorders. A questionnaire of 22 items has been designed in order to represent possible indicators of usefulness and effectiveness of the TEWs. The primary aim of this study was to develop a reliable and valid questionnaire able to assess the caregivers' satisfaction with the modalities of carrying out the TEW as a novel activity during the post-acute hospitalization of patients with sABI. The second aim was to assess the caregivers' satisfaction with the utility of the TEW as a tool to enhance their skills in the management of patients' disabilities. 100 caregivers of patients with sABI who attended at least one TEW session and completed the questionnaire were included in the analysis. In conclusion the administered questionnaire has proven to be a valid and reliable tool to evaluate sABI caregivers' satisfaction with TEW. Moreover, caregivers were satisfied with the organization of the TEW and with their usefulness in the management of the patients with sABI. [ABSTRACT FROM AUTHOR]

The Ma_MISS spectrometer is integrated within the drilling system of the Rosalind Franklin ExoMars rover. This paper reports the on-ground calibration campaign performed on the spectrometer. Here, we focus on the spectral calibration of the instrument. The experimental setup used to carry out calibration is described, and the methods used for data processing and key parameters retrieval are explained. In particular, the spectral parameters such as (i) pixel central wavelengths, (ii) spectral response function, (iii) spectral resolution, (iv) sampling, and (v) range are determined. In a follow-up paper, the linearity and radiometric calibrations are described, while in De Sanctis et al. [Planet. Sci. J. 3, 142 (2022)], the validation of spectral measurements performed on synthetic and natural rock targets is presented. [ABSTRACT FROM AUTHOR]

The mild degassing and effusion that characterizes open‐vent volcanoes can be interrupted by episodes of sustained explosive activity known as paroxysms. Here, we present observations from a seismic array deployment during the 2021 eruption of Mt. Etna, Italy. During the observation period, degassing dominated surface activity at the central and northeast summit craters; lava flows, Strombolian explosions, and fire fountaining, accompanied by ash plumes, characterized eruption in the southeast sector of Mt. Etna. Seismic array locations showed changes associated with shifts in the style and location of activity across multiple craters at Mt. Etna. We observed changes in array locations between the north‐northeast and southeast directions that consistently anticipated the onset of paroxysmal activity in the southeast sector. Our results demonstrate the potential of seismic arrays to resolve vent‐specific activity and shed light on precursory patterns leading up to paroxysmal activity. Plain Language Summary: In this study we present analyses of seismic data collected at Mt. Etna, Italy, during a period of paroxysmal eruptive activity in the summer of 2021. Throughout the period under investigation, activity at the volcano was characterized by shifts in both style and location across the multiple summit craters. Analyses of seismic data recorded by a cluster of tightly spaced seismometers, or seismic array, allowed to track the location of seismic tremor throughout the study period. We show, with unprecedented resolution, that migration of the tremor source systematically anticipated the onset of the most intense phases of eruption. Our results are consistent with previously proposed models of a branched conduit system within the shallow plumbing at Mt. Etna; different branches of the conduit system feed activity from different vents within the multiple summit craters, each with a distinctive style of eruption. The results of our study demonstrate that seismic arrays can shed light on precursory patterns leading up to paroxysmal activity at Mt. Etna, and other similar volcanoes worldwide. We surmise that seismic arrays are a powerful monitoring tool with clear potential to improve volcano early warning practices and protocols. Key Points: Seismic arrays track degassing and explosive activity at multi‐vent volcanoesSystematic shifts in seismic tremor locations anticipate the onset of paroxysmal activity at Mt. EtnaShifts in tremor locations and style of surface activity at Mt. Etna are consistent with previous models of a branched conduit system [ABSTRACT FROM AUTHOR]

Numerical simulations are required to thermophysically characterize Oxia Planum, the landing site of the mission ExoMars 2022. A drilling system is installed on the ExoMars rover, and it will be able to analyze down to 2 meters in the subsurface of Mars. The spectrometer Ma_MISS (Mars Multispectral Imager for Subsurface, Coradini and Da Pieve, 2001) will investigate the lateral wall of the borehole generated by the drill, providing hyperspectral images. It is not fully clear if water ice can be found in the subsurface at Oxia Planum. However, Ma_MISS has the capability to characterize and map the presence of possible ices, in particular water ice. We performed simulations of the subsurface temperatures by varying the thermal inertia, and we quantified the effects of self-heating. Moreover, we quantified the heat released by the drilling operations, by exploring different frictional coefficients and angular drill velocities, in order to evaluate the lifetime of possible water ice. [ABSTRACT FROM AUTHOR]

Dental implant placement is a predictable therapy for replacing teeth. Nevertheless, mechanical, biological, and aesthetic complications frequently occur. The aim of this study was to compare the clinical outcomes of a xenogeneic collagen matrix (XCM) used at the time of implant placement as an alternative to a subepithelial connective tissue graft (SCTG), for soft tissue augmentation. This was a prospective clinical trial with 12 months of follow-up. In the control group, soft tissue augmentation at the time of implant placement was performed with a SCTG, while in the test group, a XCM was employed. At 12 months postoperative, all xenografts showed no postoperative complications. In both groups, a significantly greater thickness was observed on the buccal and occlusal sides from preoperative to 3 months postoperative (P < 0.05). No statistically significant difference in pink aesthetic score (P = 0.379, 6 months postoperative) or marginal bone loss (P = 0.449 at 3 months postoperative, P = 0.778 at 6 months postoperative) was observed between the groups. Statistically significant differences in pain perceived by the patients (P < 0.0001) and the time to complete the surgical procedure (P = 0.0008) were detected. At 12 months after surgery, XCM provided similar clinical results in terms of soft tissue augmentation on the buccal and occlusal sides as compared with the SCTG. [ABSTRACT FROM AUTHOR]

Ammonium phyllosilicates have been identified on the dwarf planet Ceres, thanks to infrared telescopic and orbital data from the Dawn mission, by means of the 3.06 μm spectral feature. Nevertheless, it is not known which ammonium‐bearing phyllosilicate species are present, nor the thermal processing they underwent throughout Ceres history. Identifying the NH4+‐hosting mineral species is important for deciphering Ceres' surface mineralogy, which provides a link to its interior and putative different evolutionary pathways. Ammoniated species can have formed in the presence of water/ammonia‐rich fluids in different conditions in the interior of the planet; in case of an exogenous outer Solar System origin, they can have undergone heating at depth. In this work, we study the visible‐infrared spectra of several NH4‐treated/untreated phyllosilicates in the range 0.35–5 μm, acquired in vacuum and at temperatures between 298 and 723 K. Previously NH4‐phyllosilicates have been mostly studied at ambient condition, preventing the characterization of the NH4+ band at 3.06 μm, due to overlapping bands of water. With this new set of measurements, we investigate how the NH4‐phyllosilicates spectra are modified when the mineral's water is lost, and which temperature is the limit for the releasing of NH4+. We present the first high‐temperatures/high vacuum 3‐μm reflectance spectra of ammonium phyllosilicates. Our measurements indicate that Mg‐phyllosilicates are the best candidates for the ammonium‐bearing species. Moreover, the almost complete disappearing of NH4+ absorption feature at ∼3.06 μm for ammoniated phyllosilicates heated at the highest temperatures indicates that such species on Ceres could not have experienced temperatures higher than 623 K. Plain Language Summary: Hydrated/ammonium minerals have been observed on Ceres thanks to the Dawn mission instruments. This indicates that Ceres accreted volatile materials and ammonia from the outer Solar System during its formation. Ammonium minerals are observed with spectrometers on Ceres, thanks to the sunlight they reflect in the visible‐infrared interval. The spectrum of such minerals, the way they absorb light at different frequencies, depends on physical parameters such as composition, temperature, pressure, radiations. Different types of phyllosilicates could host ammonium, with implications for the thermal evolution of the planet. It is not well constrained which the hosting species is, nor the maximum temperature it underwent, or the formation environment. It is important to characterize in laboratory such materials in various conditions that can simulate the ambient on Ceres' surface. Here we investigated in laboratory, the visible‐infrared spectra of hydrated‐ammonium minerals, subject to different experimental conditions; we studied minerals in vacuum and at high‐temperatures, with the aim of removing water from the minerals for a better comparison with mission data. Data acquired in laboratory on dehydrated samples will be helpful for comparison with data from missions, in order to identify the ammonium minerals and to give clues on the thermal evolution of Ceres. Key Points: Reflectance spectra of NH4‐phyllosilicates measured in the 0.35–5 μm range, in high vacuum and at temperatures up to 723 KAmmonium band at 3.1 μm is almost completely lost in the temperature range 623–723 KSpectra of dehydrated NH4‐phyllosilicates compared with Ceres infrared data from Dawn mission; 3‐μm band in NH4‐saponites above 623 K can match with Ceres spectrum [ABSTRACT FROM AUTHOR]

The primary aim is to verify the effectiveness of an aquatic training (AT) in inpatients with severe Traumatic Brain Injury (sTBI) on balance. The secondary aims are to explore the effects on gait, activities of daily living, and quality of life, comparing to a land-based conventional protocol. Two-arm, randomized controlled trial. Twenty inpatients with sTBI, Glasgow Coma Scale score ≤8, and Level of Cognitive Functioning ≥7 were recruited and randomly assigned to the aquatic therapy group (ATG) or to the Conventional Training Group (CTG). Patients underwent 12 individual rehabilitation sessions (3 days/week, 4 weeks), in a rehabilitation pool during the post-acute intensive neurorehabilitation. The primary outcome measure was the Berg Balance Scale (BBS). Secondary outcome measures were the Modified Barthel Index (MBI), Disability Rating Scale (DRS), Tinetti Gait Balance Scale (TBG) and Quality of Life After Brain Injury (QOLIBRI). All the evaluations were performed at the baseline and after 4 weeks of training. The within-subjects analysis showed a significant improvement both in ATG and CTG in MBI, BBS, TBG, and QOLIBRI. Our results may support the use of AT during post-acute phase to improve motor functions and quality of life in patients with sTBI. [ABSTRACT FROM AUTHOR]

Aims. We study the surface of Ceres at visible wavelengths, as observed by the Visible and InfraRed mapping spectrometer (VIR) onboard the Dawn spacecraft, and analyze the variations of various spectral parameters across the whole surface. We also focus on several noteworthy areas of the surface of this dwarf planet. Methods. We made use of the newly corrected VIR visible data to build global maps of a calibrated radiance factor at 550 nm, with two color composites and three spectral slopes between 400 and 950 nm. We have made these maps available for the community via the Aladin Desktop software. Results. Ceres' surface shows diverse spectral behaviors in the visible range. The color composite and the spectral slope between 480 and 800 nm highlight fresh impact craters and young geologic formations of endogenous origin, which appear bluer than the rest of the surface. The steep slope before 465 nm displays very distinct variations and may be a proxy for the absorptions caused by the O2− → Fe3+ $\textrm{O}_2^-\,{\longrightarrow}\,{\textrm{Fe}_{3}}^{+}$ O 2 −   →   Fe 3 + or the 2Fe3+ → Fe2+ + Fe4+ charge transfers, if the latter are found to be responsible for the drop in this spectral range. We notice several similarities between the spectral slopes and the abundance of phyllosilicates detected in the infrared by the VIR, whereas no correlation can be clearly established with carbonate species. The region of the Dantu impact crater presents a peculiar spectral behavior – especially through the color and the spectral slope before 465 nm – suggesting a change in composition or in the surface physical properties that is not observed elsewhere on Ceres. [ABSTRACT FROM AUTHOR]

Rapid assessment of the volume and the rate at which gas and pyroclasts are injected into the atmosphere during volcanic explosions is key to effective eruption hazard mitigation. Here, we use data from a dense infrasound network deployed in 2017 on Mt. Etna, Italy, to estimate eruptive volume flow rates (VFRs) during small gas‐and‐ash explosions. We use a finite‐difference time‐domain approximation to compute the acoustic Green's functions and perform a full waveform inversion for a multipole source, combining monopole and horizontal dipole terms. The inversion produces realistic estimates of VFR, on the order of 4 × 104 m3/s and well‐defined patterns of source directivity. This is the first application of acoustic waveform inversion at Mt. Etna. Our results demonstrate that acoustic waveform inversion is a mature and robust tool for assessment of source parameters and holds potential as a tool to provide rapid estimates of VFR in near real time. Plain Language Summary: Rapid and realistic assessment of the volume of erupted material, and the rate at which gas and pyroclasts are injected into the atmosphere during volcanic explosions, is crucial for effective monitoring and hazard mitigation. These parameters, for instance, are key inputs into models of atmospheric rise and transport of volcanic plumes. Volcanic explosions, among many other phenomena, generate atmospheric pressure waves known as infrasound. These sound waves that propagate at frequencies below 20 Hz, represent a powerful tool to investigate the dynamics and source mechanisms of volcanic explosions. Here, we demonstrate how recordings of acoustic infrasound generated by explosions at Mt. Etna can be used to assess the volume flow history of these events. We introduce and apply a data modeling workflow that could be implemented in near real time at Mt. Etna and other volcanoes worldwide. Key Points: This is the first application of acoustic waveform inversion for small explosions at Mt. Etna volcano, ItalyWe demonstrate the feasibility of applying this inversion method for large volcanoes using up to 14 stationsAcoustic waveform inversion holds potential for volume flow estimation in near real time at Mt. Etna and other volcanoes [ABSTRACT FROM AUTHOR]

Highlights • Laboratory experiments were made to study the NH 4 -carrier phase detected on Ceres. • An ammoniation technique was tested on ten different phyllosilicate samples. • The ammonium treated samples were analysed by means of VIS-NIR spectroscopy. • Only the smectite samples incorporated the ammonium ion in their structure. • A scenario for the thermal evolution of a smectite-bearing surface is presented. Abstract The identification of NH 4 -bearing phyllosilicates on Ceres poses the question on the NH 4 -carrier phase(s) and in this study we describe the laboratory production and IR spectroscopic measurements of a suite of ten NH 4 -phyllosilicates, starting from the corresponding NH 4 -free minerals. For each mineral, we prepared three types of powder samples: raw (R), ammoniated (A), and leached (L). All samples have been spectrally characterized by means of visible/infrared spectroscopy in the INAF-IAPS laboratories with the FieldSpec Pro in the 0.35–2.5 µm range, and with the FT-IR, using a Vertex 80 spectrometer operating in the range of 2–14 µm. The samples were also measured with the SPectral IMager, an imaging spectrometer operating in the spectral range 0.2–5.1 µm, which is a replica of the VIR spectrometer on-board Dawn spacecraft. Reflectance spectra of the ammoniated clays show bands near 1.56 µm, 2.05 µm, 2.12 µm, 3.06 µm, 3.25 µm, 3.55 µm, 4.2 µm, 5.7 µm and 7.0 µm that are related to the presence of nitrogen complexes. Treatment of phyllosilicates with ammonia shows that different minerals behave in different ways: NH 4 + ions are easily accepted by the smectites, while other non-expandable structures do not accept these ions. The obtained results can be used to better constrain the NH 4 -bearing species present on Ceres and, possibly, other bodies of the solar system. [ABSTRACT FROM AUTHOR]

Microimaging spectroscopy is going to be the new frontier for validating reflectance remote sensed data from missions to solar system bodies. In this field, microimaging spectroscopy of Martian meteorites can provide important and new contributions to interpret data that will be collected by next instruments onboard rover missions to Mars, such as for example Exomars‐2020/Ma_MISS spectrometer. In this paper, a slab from the Northwest Africa (NWA) 8657 shergottite was studied using the SPectral IMager (SPIM) microimaging spectrometer, in the visible‐infrared (VIS‐IR) range, with the aim to subsequently validate the spectral data by means of different independent techniques. The validation was thus carried out, for the first time, comparing SPIM spectral images, characterized by high spatial and spectral resolution, with mineralogical–petrological analyses, obtained by scanning electron microscopy (SEM). The suitability of the SPIM resolution to detect and map augite, pigeonite, maskelynite, and other minor phases as calcite, Ca‐phosphates, and troilite/pyrrhotite with no loss of information about mineral distribution on the slab surface, was ascertained. The good agreement found between spectral and mineralogical data suggests that spectral‐petrography of meteorites may be useful to support in situ investigations on Martian rocks carried out by MaMiss spectrometer during Exomars2020 mission. Moreover, micro spectral images could be also useful to characterize, in a nondestructive way, Martian meteorites and other rare minerals occurring in meteorites. The results obtained in this work represent not only a methodological contribution to the study of meteorites but furnish also elements to reconstruct the history of this sample. The finding of zoned pyroxene, symplectitic texture, amorphous phases as maskelynite, and Fe‐merrillite permits us to hypothesize four stages, i.e., (1) igneous formation of rimmed pyroxenes and other minerals, (2) retrograde metamorphism, (3) shock by impact, and (4) secondary minerals by terrestrial contamination. [ABSTRACT FROM AUTHOR]

Highlights • IR (0.8–4.2 μm) reflectance spectroscopy of Na-carbonates at low temperatures. • Anhydrous (Na 2 CO 3) and two hydrated species (Na 2 CO 3 •H 2 O, Na 2 CO 3 •10H 2 O) investigated. • CO 3 2− and OH−/H 2 O bands characterize spectra of samples. • Water bands in hydrated species split in many features at cryogenic temperatures. • H 2 O bands move at longer wavelengths for decreasing T; CO 3 2− at shorter wavelenghts. Abstract Recent space-based observations have revealed or suggested the existence of various types of carbonate salts in several Solar System bodies, such as Mars, Ceres, Enceladus, and Europa. Natrite is the main component of the crater Occator's faculae observed in detail by the Dawn spacecraft on the dwarf planet Ceres. Sodium carbonates are thought to form as precipitates in brines, originating in aqueous environments in the subsurface of Ceres and icy bodies. Here we report about near-infrared (0.8–4.2 μm) reflectance spectroscopic investigations on three compounds, namely natrite (anhydrous Na 2 CO 3), monohydrated sodium carbonate (Na 2 CO 3 •H 2 O, thermonatrite) and decahydrate sodium carbonate (Na 2 CO 3 •10H 2 O, natron). Spectral measurements have been carried out in the overall temperature range 93–279 K, representative of planetary surfaces. The analysis of diagnostic spectral signatures shows different temperature-dependent trends for several band parameters, as well as different behavior as a function of the grain size for a given temperature. While spectra of natrite are characterized by several CO 3 absorptions, broad and strong absorption features due to H 2 O dominate the spectra of heavily hydrated natron. The intermediate sample (monohydrated) shows multiple bands due to the overlap of CO 3 and H 2 O vibrational modes. Our temperature-dependent laboratory spectra are compared with Dawn-VIR spectra of Ceres and with Galileo-NIMS spectra of Europa. [ABSTRACT FROM AUTHOR]

Solid oxide cells (SOC) are electrochemical devices that can operate efficiently both in fuel cell (solid oxide fuel cell, SOFC) and electrolysis mode (solid oxide electrolysis cell, SOEC). However, long-term performance degradation hinder the widespread commercialization of this technology. Nickel coarsening is a major cause of the decrease of the cells' performance. Therefore, investigating and quantifying effects of nickel coarsening on the microstructural evolution in SOCs is crucial to understand the degradation processes occurring during operation. Focused-ion-beam scanning electron microscopy (FIB-SEM) tomography and phase field (PF) modelling are used to investigate the microstructure evolution of Ni/Yttria-Stabilized Zirconia (YSZ) SOC fuel electrodes. A cell, tested as part of a 25 cells stack for 9000 hours, and a reference cell (never operated) are reconstructed using FIB-SEM tomography. Microstructural parameters were calculated on the two cells showing that the percolated triple phase boundary (TPB) length in the cell decreases from 1.85 μm/μm³ for the reference cell to only 1.01 μm/μm³ for the long-term tested one. Phase field simulations were run on the reference cell geometry and microstructural parameters such as particle size distribution (PSD), TPB length and surface areas are computed and quantified on the simulated volumes. A trend of decreasing percolated TPB length with time is observed in the simulations. The numerical results are used to investigate the effects of nickel coarsening as well as to obtain information on the kinetics of the phenomenon. [ABSTRACT FROM AUTHOR]

In this article, we study the possibility that Ceres has, or had in the past, a crust heavier than a pure or muddy ice mantle, in principle gravitationally unstable. Such a structure is not unusual in the Solar system: Callisto is an example. In this work, we test how the composition (i.e. the volumetric quantity of ice) and the size of the crust can affect its survival during thermophysical evolution after differentiation. We have considered two different configurations: the first characterized by a dehydrated silicate core and a mantle made of pure ice, the second with a hydrated silicate core and a muddy mantle (ice with silicate impurities). In both cases, the crust is composed of a mixture of ice and silicates. These structures are constrained by a recent measurement of the mean density by Park et al. The Rayleigh–Taylor instability, which operates in such an unstable structure, could reverse all or part of the crust. The whole unstable crust (or part of it) can interact chemically with the underlying mantle and what is currently observed could be a partially/totally new crust. Our results suggest that, in the case of a pure ice mantle, the primordial crust has not survived until today, with a stability timespan always less than 3 Gyr. Conversely, in the case of a muddy mantle, with some ‘favourable’ conditions (low volumetric ice percentage in the crust and small crustal thickness), the primordial crust could be characterized by a stability timespan compatible with the lifetime of the Solar system. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The role of electrophysiology study in Brugada syndrome (BS) sudden cardiac death risk stratification remains controversial and seems to depend on the phenotypic expression of the channelopathy. Ajmaline has a key role in the diagnosis of BS. We observed that programmed electrical stimulation (PES) of the right ventricular outflow tract (RVOT), only when type 1 BS ECG is unmasked by ajmaline administration, induces ventricular arrhythmias. CASE REPORT: We describe a case of ventricular fibrillation induction by PES of the RVOT when type 1 BS ECG is revealed by ajmaline, in a patient with a baseline dynamic intermittent type 1 and 2 BS ECG. CONCLUSIONS: The heterogeneous clinical presentations of BS are due to the underlying mechanisms. PES of the RVOT during positive ajmaline test maximizes the channelopathy and therefore sudden cardiac death risk-stratification in BS. [ABSTRACT FROM AUTHOR]

A recent study of Fu et al. analysed the remaining magnetization in the eucrite meteorite Allan Hills A81001, which mostly likely has been produced during the cooling phase of the life of the asteroid Vesta, arguing that an ancient dynamo in the advective liquid metallic core could be set in. Using petrographic and paleomagnetic arguments, Fu et al. estimated a surface magnetic field of at least 2 μT. In this work, we verify the possibility that an early core dynamo took place in Vesta by analysing four different possible fully differentiated configurations of Vesta, characterized by different chondritic compositions, with the constraints on core size and density provided by Ermakov et al. We only incorporate the thermal convection, by neglecting the effects of the compositional convection, so our results in terms of magnetic Reynolds number and duration of the dynamo can be interpreted as a lower bound. The presence of a magnetic field would make Vesta a peculiar object of the Solar system, a 'small-Earth', since it has also a differentiated structure like Earth and the magnetic field has preserved Vesta from the space weathering. [ABSTRACT FROM AUTHOR]

Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a 4-year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 volcano-seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ~ 40 to ~ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) which are attributed to fracturing along the margins of the shallow, ascending spine. Further analysis indicates variable seismic velocities during the spine extrusion as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by previously published field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile deformation occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting sources, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes. [ABSTRACT FROM AUTHOR]

Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a four year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ~ 40 to ~ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) attributed to fracturing along the margins of the shallow, ascending plug. Further analysis indicates variable seismic velocities during spine extrusion, as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile failure occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting source, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes. [ABSTRACT FROM AUTHOR]

OBJECTIVE: ST-segment elevation in the right precordial electrocardiography (ECG) leads in Brugada syndrome (BS) can be unmasked by class I anti-arrhythmic drugs (sodium channel blockers) administration. It is still debated whether this ECG pattern is better explained by abnormal repolarization or ventricular conduction and depolarization. Conduction diseases can conceal type 1 BS-like ECG in standard V1-V3 leads. ECG alterations were found also in alternative leads. The role of electrophysiology study (EPS) in sudden cardiac death risk stratification remains controversial, and could depend on the phenotypic expression of the cardiac sodium channels disease. CASE REPORT: We describe unmasked diffuse J-point and ST-segment anomalies in peripheral and precordial ECG leads and ventricular fibrillation (VF) induction by EPS after ajmaline administration in a patient with pre-existing atypical right bundle branch block (RBBB) concealing subtle anomalies in standard V1-V3 leads. RBBB was influenced by the underlying BS-like ECG associating repolarization anomaly and pre-existing conduction disease. EPS induced VF when RBBB was associated with BS-like ECG, and failed to induce VF when RBBB was present alone. CONCLUSIONS: BS phenotype heterogeneity requires further studies to improve the knowledge of its pathophysiological mechanisms associated with conduction diseases in order to better identify an individual therapy and prognostic stratification. [ABSTRACT FROM AUTHOR]