Anchoring selenido-carbonyl ruthenium clusters to functionalised silica xerogels

Silica Xerogels containing carbonyl Ru3Se2 nido clusters were prepared in three different ways. The simple dispersion of [Ru3(mu3-Se)2(CO)7(PPh 3)2] via sol gel process produces an inhomogeneous material; by contrast, homogeneous xerogels were obtained by reaction of [Ru3(mu3-Se)2(CO)8(PPh 3)] with functionalised xerogels containing grafted diphenylphosphine moieties and by reaction of [Ru3(CO)12] with a xerogel containing grafted phosphine-selenide groups. The reaction between [Ru3(CO)12] and dodecyldiphenylphosphine selenide led to the formation of four selenido carbonyl clusters, which are soluble in hydrocarbon solvents and can be deposited as thin films from their solution by slow evaporation. Xerogéis de silica contendo carbonilas metálicas polinucleares (clusters) com estrutura nido Ru3Se2 foram preparadas através de três rotas diferentes. A simples dispersão do cluster [Ru3(mi3-Se)2(CO)7(PPh 3)2] pelo processo sol gel produz um material não homogêneo. Xerogéis homogêneos foram obtidos através da reação de [Ru3(mi3-Se)2(CO)8(PPh 3)] com xerogéis funcionalizados contendo fragmentos difenilfosfino enxertados, e pela reação do [Ru3(CO)12] com um xerogel contendo grupos fosfinoseleneto enxertados. A reação entre [Ru3(CO)12] e seleneto de dodecildifenilfosfinoseleneto resultou na formação de quatro clusters contendo ligantes carbonil e seleneto, solúveis em solventes apolares e que podem ser empregados na confecção de filmes

Record Processing in ITACA, the New Italian Strong-Motion Database

The development of the new Italian strong-motion database ITACA (ITalian AC-celerometric Archive, http://itaca.mi.ingv.it) is in progress under the sponsorship of the National Department of Civil Protection (DPC) within Project S4, in the framework of DPC-INGV 2007–2009 research agreement. This work started from the alpha version of ITACA [8], where 2,182 3-component records from 1,004 earthquakes, mainly recorded by the National Accelerometric Network, RAN, operated by DPC, were processed and included in the database. Earthquake metadata, recording station information and reports on the available geologicalgeophysical information of 452 recording sites, corresponding to about 70% of the total, were also included. Subsequently, ITACA has been updated and will reach its final stage by the end of Project S4, around mid-2010, with additional features, improved information about recording stations, and updated records, including the Mw6.3 L’Aquila earthquake. All records were re-processed with respect to the alpha version [9], with a special care to preserve information about late-triggered events and to ensure compatibility of corrected records, i.e., velocity and displacement traces obtained by the first and second integral of the corrected acceleration should not be affected by unrealistic trends. After a short introduction of ITACA and its most relevant features and statistics, this paper mainly deals with the newly adopted processing scheme, with reference to the problems encountered and the solutions that have been devised

The Three-dimensional Evolution of Rising, Twisted Magnetic Flux Tubes in a Gravitationally Stratified Model Convection Zone

We present three-dimensional numerical simulations of the rise and fragmentation of twisted, initially horizontal magnetic flux tubes which evolve into emerging Omega-loops. The flux tubes rise buoyantly through an adiabatically stratified plasma that represents the solar convection zone. The MHD equations are solved in the anelastic approximation, and the results are compared with studies of flux tube fragmentation in two dimensions. We find that if the initial amount of field line twist is below a critical value, the degree of fragmentation at the apex of a rising Omega-loop depends on its three-dimensional geometry: the greater the apex curvature of a given Omega-loop, the lesser the degree of fragmentation of the loop as it approaches the photosphere. Thus, the amount of initial twist necessary for the loop to retain its cohesion can be reduced substantially from the two-dimensional limit. The simulations also suggest that as a fragmented flux tube emerges through a relatively quiet portion of the solar disk, extended crescent-shaped magnetic features of opposite polarity should form and steadily recede from one another. These features eventually coalesce after the fragmented portion of the Omega-loop emerges through the photosphere.Comment: 17 pages, 17 figures, uses AAS LaTeX macros v5.0. ApJ, in pres

Toward Reliable Characterization of Sites With Pronounced Topography and Related Effects on Ground Motion

Here we present first results of a joint effort undertaken in ongoing European project NERA -JRA1, which aims at establishing scientifically solid and practically acceptable propositions to incorporate surface topography effects in seismic hazard estimates. We assembled a dataset of both ambient vibration and earthquake recordings acquired at 40 European sites with pronounced topography. It comprises a wide variety of sites including populated hills and even extreme cases of unstable rock slopes in Alpine regions. Results of the polarisation analysis for the two sites presented here show the peculiarity of the topographic site effects

The November 2017 Mw 5.5 Pohang earthquake: a possible case of induced seismicity in South Korea

The Mw 5.5 earthquake that struck South Korea in November 2017 was one of the largest and most damaging events in this country over the last century. Its proximity to an Enhanced Geothermal Systems site, where high pressure hydraulic injection had been performed during the previous two years, raises the possibility that this earthquake was anthropogenic. We have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks, constrain the geometry of this seismic sequence and shed light on its casual factors. According to our analysis it seems plausible that the occurrence of this earthquake was influenced by these industrial activities. Finally we found that the earthquake transferred static stress to larger nearby faults, potentially increasing the seismic hazard in the area

A prototype of a large tunable Fabry–Pérot interferometer for solar spectroscopy

Large Fabry-Pérot Interferometers (FPIs) are used in a variety of astronomical instrumentation, including spectro-polarimeters for 4 m class solar telescopes. In this work we comprehensively characterize the cavity of a prototype 150 mm FPI, sporting a novel, fully symmetric design. Of particular interest, we define a new method to properly assess the gravity effects on the interferometer's cavity when the system is used in either the vertical or horizontal configuration, both typical of solar observations. We show that the symmetric design very effectively limits the combined effects of pre-load and gravity forces to only a few nm over a 120 mm diameter illuminated surface, with gravity contributing ~2 nm peak-to-valley (~0.3 nm rms) in either configuration. We confirm a variation of the tilt between the plates of the interferometer during the spectral scan, which can be mitigated with appropriate corrections to the spacing commands. Finally, we show that the dynamical response of the new system fully satisfies typical operational scenarios. We conclude that large, fully symmetric FPIs can be safely used within solar instrumentation in both, horizontal and vertical position, with the latter better suited to limiting the overall volume occupied by such an instrument

Insight into the solar plage chromosphere with DKIST

The strongly coupled hydrodynamic, magnetic, and radiation properties of the plasma in the solar chromosphere makes it a region of the Sun's atmosphere that is poorly understood. We use data obtained with the high-resolution Visible Broadband Imager (VBI) equipped with an H$\beta$ filter and the Visible Spectro-Polarimeter (ViSP) at the Daniel K. Inouye Solar Telescope to investigate the fine-scale structure of the plage chromosphere. To aid the interpretation of the VBI imaging data, we also analyze spectra from the CHROMospheric Imaging Spectrometer on the Swedish Solar Telescope. The analysis of spectral properties, such as enhanced line widths and line depths explains the high contrast of the fibrils relative to the background atmosphere demonstrating that H$\beta$ is an excellent diagnostic for the enigmatic fine-scale structure of the chromosphere. A correlation between the parameters of the H$\beta$ line indicates that opacity broadening created by overdense fibrils could be the main reason for the spectral line broadening observed frequently in chromospheric fine-scale structures. Spectropolarimetric inversions of the ViSP data in the Ca II 8542 {\AA} and Fe I 6301/6302 {\AA} lines are used to construct semiempirical models of the plage atmosphere. Inversion outputs indicate the existence of dense fibrils in the Ca II 8542 {\AA} line. The analyses of the ViSP data show that the morphological characteristics, such as orientation, inclination and length of fibrils are defined by the topology of the magnetic field in the photosphere. Chromospheric maps reveal a prominent magnetic canopy in the area where fibrils are directed towards the observer.Comment: 17 pages, 11 figures, accepted in Ap

Caratteristiche dei dati accelerometrici registrati durante la sequenza sismica aquilana

I dati accelerometrici relativi alla sequenza sismica de L’Aquila, iniziata con l’evento del 6 Aprile alle ore 1.32 (MW 6.3), provengono dalla rete Rete Accelerometrica Nazionale (RAN), gestita dal Dipartimento della Protezione Civile (DPC) e da una rete temporanea installata il giorno dopo la scossa principale ad opera dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV MI-PV). I dati del DPC sono scaricabili dalla banca dati accelerometrica italiana ITACA (http://itaca.mi.ingv.it), mentre quelli dell'INGV sono accessibili dal sito Internet http://accel.mi.ingv.it/statiche/ABRUZZO-2009/main.html. Il terremoto de L’Aquila è il terzo evento più forte che abbia prodotto registrazioni accelerometriche in Italia, dopo i terremoti dell’Irpinia (1980, MW 6.9) e del Friuli (1976, MW 6.4). Questo evento, insieme alle 12 repliche più forti (MW > 4.0) ha fornito un insieme di dati accelerometrici unico in Italia, in particolare per la presenza di un numero consistente di registrazioni in zona epicentrale ("campo vicino"). Il data set è composto da circa 300 accelerogrammi digitali (di cui 270 provenienti dalla RAN), con un ottimo rapporto segnale/rumore, registrati da circa 70 stazioni, installate in varie condizioni di sito, a distanze comprese fra 0 e 300 km. L'importanza di questo data set, non solo a livello nazionale, è legato al contributo significativo che fornisce nel colmare una lacuna nella distribuzione magnitudo-distanza dei dati strong motion italiani e mondiali, soprattutto per quanto riguarda gli eventi con meccanismo di faglia normale (Ameri et al.; 2009). I dati registrati in campo vicino provengono da un transetto composto da 6 stazioni installato dalla Protezione Civile nel 2001 nella Alta Valle dell’Aterno, con lo scopo di investigare la variabilità del moto sismico rispetto alle condizioni geologiche locali, dalla stazione AQK, installata in prossimità del centro urbano e da una stazione (AQU) appartenente alla rete broad band Mednet (http://mednet.rm.ingv.it/data.php), situata nel castello de L’Aquila. Queste stazioni distano meno di 5 km dall’epicentro dell’evento principale, ricadendo all’interno della proiezione superficiale del piano di rottura. A queste si aggiungono le registrazioni delle repliche, ottenute dalle stazioni della rete temporanea INGV, installata in area epicentrale. In questo lavoro si presenta un resoconto delle principali caratteristiche dello scuotimento del suolo verificatosi durante la sequenza sismica aquilana, attraverso l’analisi dei dati accelerometrici relativi alla scossa principale e alle due repliche più forti. Si discutono in particolare la dipendenza di diversi parametri strong motion dalla distanza, dall’azimuth e dalle condizioni di sito, e l'effetto delle caratteristiche del moto in campo vicino sulla risposta strutturalePublished57-684.1. Metodologie sismologiche per l'ingegneria sismicaN/A or not JCRreserve

Coordinated and Interoperable Seismological Data and Product Services in Europe: the EPOS Thematic Core Service for Seismology

In this article we describe EPOS Seismology, the Thematic Core Service consortium for the seismology domain within the European Plate Observing System infrastructure. EPOS Seismology was developed alongside the build-up of EPOS during the last decade, in close collaboration between the existing pan-European seismological initiatives ORFEUS (Observatories and Research Facilities for European Seismology), EMSC (Euro-Mediterranean Seismological Center) and EFEHR (European Facilities for Earthquake Hazard and Risk) and their respective communities. It provides on one hand a governance framework that allows a well-coordinated interaction of the seismological community services with EPOS and its bodies, and on the other hand it strengthens the coordination among the already existing seismological initiatives with regard to data, products and service provisioning and further development. Within the EPOS Delivery Framework, ORFEUS, EMSC and EFEHR provide a wide range of services that allow open access to a vast amount of seismological data and products, following and implementing the FAIR principles and supporting open science. Services include access to raw seismic waveforms of thousands of stations together with relevant station and data quality information, parametric earthquake information of recent and historical earthquakes together with advanced event-specific products like moment tensors or source models and further ancillary services, and comprehensive seismic hazard and risk information, covering latest European scale models and their underlying data. The services continue to be available on the well-established domain-specific platforms and websites, and are also consecutively integrated with the interoperable central EPOS data infrastructure. EPOS Seismology and its participating organizations provide a consistent framework for the future development of these services and their operation as EPOS services, closely coordinated also with other international seismological initiatives, and is well set to represent the European seismological research infrastructures and their stakeholders withi

Applicability of Milne-Eddington inversions to high spatial resolution observations of the quiet Sun

The physical conditions of the solar photosphere change on very small spatial scales both horizontally and vertically. Such a complexity may pose a serious obstacle to the accurate determination of solar magnetic fields. We examine the applicability of Milne-Eddington (ME) inversions to high spatial resolution observations of the quiet Sun. Our aim is to understand the connection between the ME inferences and the actual stratifications of the atmospheric parameters. We use magnetoconvection simulations of the solar surface to synthesize asymmetric Stokes profiles such as those observed in the quiet Sun. We then invert the profiles with the ME approximation. We perform an empirical analysis of the heights of formation of ME measurements and analyze the uncertainties brought about by the ME approximation. We also investigate the quality of the fits and their relationship with the model stratifications. The atmospheric parameters derived from ME inversions of high-spatial resolution profiles are reasonably accurate and can be used for statistical analyses of solar magnetic fields, even if the fit is not always good. We also show that the ME inferences cannot be assigned to a specific atmospheric layer: different parameters sample different ranges of optical depths, and even the same parameter may trace different layers depending on the physical conditions of the atmosphere. Despite this variability, ME inversions tend to probe deeper layers in granules as compared with intergranular lanes.Comment: Accepted for publication in Astronomy and Astrophysic