Guidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project

Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the VS,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.Published2367-24205T. Sismologia, geofisica e geologia per l'ingegneria sismicaJCR Journa

The Spitzer c2d Survey of Weak-Line T Tauri Stars. III. The Transition from Primordial Disks to Debris Disks

We present 3.6 to 70 {\mu}m Spitzer photometry of 154 weak-line T Tauri stars (WTTS) in the Chamaeleon, Lupus, Ophiuchus and Taurus star formation regions, all of which are within 200 pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars (CTTS) which are located in the same star forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8 {\mu}m) and the 24 {\mu}m MIPS band. In the 70 {\mu}m MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTS survey in the mid to far infrared to date, and reveal the frequency of outer disks (r = 3-50 AU) around WTTS. The 70 {\mu}m photometry for half the c2d WTTS sample (the on-cloud objects), which were not included in the earlier papers in this series, Padgett et al. (2006) and Cieza et al. (2007), are presented here for the first time. We find a disk frequency of 19% for on-cloud WTTS, but just 5% for off- cloud WTTS, similar to the value reported in the earlier works. WTTS exhibit spectral energy distributions (SEDs) that are quite diverse, spanning the range from optically thick to optically thin disks. Most disks become more tenuous than Ldisk/L* = 2 x 10^-3 in 2 Myr, and more tenuous than Ldisk/L* = 5 x 10^-4 in 4 Myr.Comment: 40 pages, 13 figures, 4 tables. Accepted for publication in ApJ on September 20, 201

AIforCOVID: predicting the clinical outcomes in patients with COVID-19 applying AI to chest-X-rays. An Italian multicentre study

Recent epidemiological data report that worldwide more than 53 million people have been infected by SARS-CoV-2, resulting in 1.3 million deaths. The disease has been spreading very rapidly and few months after the identification of the first infected, shortage of hospital resources quickly became a problem. In this work we investigate whether chest X-ray (CXR) can be used as a possible tool for the early identification of patients at risk of severe outcome, like intensive care or death. CXR is a radiological technique that compared to computed tomography (CT) it is simpler, faster, more widespread and it induces lower radiation dose. We present a dataset including data collected from 820 patients by six Italian hospitals in spring 2020 during the first COVID-19 emergency. The dataset includes CXR images, several clinical attributes and clinical outcomes. We investigate the potential of artificial intelligence to predict the prognosis of such patients, distinguishing between severe and mild cases, thus offering a baseline reference for other researchers and practitioners. To this goal, we present three approaches that use features extracted from CXR images, either handcrafted or automatically by convolutional neuronal networks, which are then integrated with the clinical data. Exhaustive evaluation shows promising performance both in 10-fold and leave-one-centre-out cross-validation, implying that clinical data and images have the potential to provide useful information for the management of patients and hospital resources

CfA3: 185 Type Ia Supernova Light Curves from the CfA

We present multi-band photometry of 185 type-Ia supernovae (SN Ia), with over 11500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains the largest number of homogeneously-observed and reduced nearby SN Ia (z < 0.08) published to date. It more than doubles the nearby sample, bringing SN Ia cosmology to the point where systematic uncertainties dominate. Our natural system photometry has a precision of 0.02 mag or better in BVRIr'i' and roughly 0.04 mag in U for points brighter than 17.5 mag. We also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system BVRIr'i' photometry and 0.07 mag for U. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars, where available for the same SN, reveal agreement at the level of a few hundredths mag in most cases. We find that 1991bg-like SN Ia are sufficiently distinct from other SN Ia in their color and light-curve-shape/luminosity relation that they should be treated separately in light-curve/distance fitter training samples. The CfA3 sample will contribute to the development of better light-curve/distance fitters, particularly in the few dozen cases where near-infrared photometry has been obtained and, together, can help disentangle host-galaxy reddening from intrinsic supernova color, reducing the systematic uncertainty in SN Ia distances due to dust.Comment: Accepted to the Astrophysical Journal. Minor changes from last version. Light curves, comparison star photometry, and passband tables are available at http://www.cfa.harvard.edu/supernova/CfA3

Tomographie anisotrope du manteau superieur sous la Corne de l'Afrique: Implications geodynamiques du point chaud de l'Afar

Jury compose de: M. Claude JAUPART (President du Jury), M. Michel CARA, M. Pierre-Yves GILLOT, M. Jeannot TRAMPERT.In a geologically rich region of the African continent, we are attending to the birth of a new ocean. Indeed, sincenearly 30Ma, a mantle plume coming from a still undetermined depth, could have initiated the extension in the Horn of Africa. In order to define the role of the Afar Hotspot in the North Africa geodynamics, a tomographic study was carried out using fundamental mode of surface waves. The mean phase velocities along each great circle epicenter-station path are calculated using a new nonlinear inverse algorithm. The simultaneous inversion of Rayleigh and Love waves enable us to retrieve the perturbations of SV-waves velocities, the fast axis directions of azimuthal anisotropy and the radial anisotropy. The azimuthal anisotropy displays a complex pattern around the Afar Hotspot. This characteristic is more pronounced at shallow depth. The fast axis directions are in good agreement with the fast polarization direction of the shear-wave splitting of previous studies. Fast velocities are attributed to the cratons downto about 250km, a result also consistent with previous studies.We observe a negative anomaly of strong amplitude below the Afar Hotspot. A second hotspot located on the East-African rift is also visible at great depths (300km). Contrary to the ethiopian rift and the Red sea, the Gulf of Aden is associated with slow velocities only to 150km depth. The hotspots of North Africa seem to have a superficial signature and could be a consequence of small-scale and edge-driven convection. The E-W heterogeneous structure, characterized by a succession of positive and negative contrasts, supports this idea.Dans une region geologiquement tres riche du continent Africain, un nouvel ocean est en train de naitre. En effet, il y a pres de 30Ma, l'arrivee en surface d'un panache mantellique provenant d'une profondeur encore non determinee aurait initie l'extension dans la Corne de l'Afrique. Le but de cette these est de definir le role du point chaud de l'Afar dans la geodynamique du Nord de l'Afrique. Une etude tomographique a partir du mode fondamental des ondes de surface a ete realisee dans cette intention. Les vitesses de phase moyennes le long des grands cercles reliant les epicentres aux stations sont calculees a partir d'un nouvel algorithme d'inversion non-lineaire. L'inversion simultanee des ondes de Rayleigh et des ondes de Love permet non seulement de retrouver les perturbations de vitesses d'ondes SV et les directions d'axe rapide d'anisotropie azimutalemais egalement d'acceder a l'information sur l'anisotropie radiale. La distribution des directions d'axe rapide d'anisotropie azimutale est tres perturbee au voisinage du point chaud et cette caracteristique est accentuee aux faibles profondeurs. Elles restent neanmoins en accord avec de precedentes etudes d'ondes SKS. Les cratons affichent des vitesses rapides jusqu'a 250km coherentes avec des resultats anterieurs. On observe une anomalie negative de forte amplitude sous le point chaud de l'Afar. La signature persiste clairement jusqu'a350km. Un second point chaud situe sur le rift Est-Africain est aussi visible a grande profondeur (300km). Contrairement aux traces profondes du rift ethiopien et de la mer Rouge, le Golfe d'Aden met en evidence des vitesses lentes jusqu'a seulement 150km. Les points chauds d'Afrique du Nord semblent egalement de nature superficielleet pourraient s'averer etre une consequence de convection secondaire a petite echelle. La structure heterogene alternant entre un contraste positif et negatif selon l'orientation Est-Ouest vient appuyer cette idee

Tomographie anisotrope du manteau supérieur sous la Corne de l' Afrique (implications géodynamiques du point chaud de l' Afar)

Dans une région géologiquement très riche du continent Africain, un nouvel océan est en train de naître. En effet, il y a près de 30Ma, l'arrivée en surface d'un panache mantellique provenant d'une profondeur encore non déterminée aurait initié l'extension dans la Corne de l'Afrique. Le but de cette thèse est de définir le rôle du point chaud de l'Afar dans la géodynamique du Nord de l'Afrique. Une étude tomographique à partir du mode fondamental des ondes de surface a été réalisée dans cette intention. Les vitesses de phase moyennes le long des grands cercles reliant les épicentres aux stations sont calculées à partir d'un nouvel algorithme d'inversion non-linéaire. L'inversion simultanée des ondes de Rayleigh et des ondes de Love permetnon seulement de retrouver les perturbations de vitesses d'ondes Sv et les directions d'axe rapide d'anisotropie azimutale mais également d'accéder à l'information sur l'anisotropie radiale. La distribution des directions d'axe rapide d'anisotropie azimitale est très perturbée au voisinage du point chaud et cette caractéristique est accentuée aux faibles profondeurs. Elles restent néanmoins en accord avec de précédentes études d'ondes SKS. Les cratons affichent des vitesses rapides jusqu'à 250km cohérentes avec des résultats antérieurs. On observe une anomalie négative de forte amplitude sous le point chaud de l'Afar. La signature persiste clairementjusqu'à 350km. Un second point chaud situé sur le rift Est-Africain est aussi visible à grande profondeur (300km). Contrairement aux traces profondes du rift éthiopien et de la mer Rouge, le Golfe d'Aden met en évidence des vitesses lentes jusqu'à seulement 150km. Les points chauds d'Afrique du Nord semblent également de nature superficielle et pourraient s'avérer être une conséquence de convection secondaire à petite échelle. La structure hétérogène alternant entre un contraste positif et négatif selon l'orientation Est-Ouest vient appuyer cette idéeIn order to define the role of the Afar Hotspot in the North Africa geodynamics, a tomography was carried out using fundamental mode of surface waves. The mean phase velocities along each path are calculated using a new nonlinear inverse algorithm. The simultaneaous inversion of Rayleigh and Love waves enable us to retrieve the perturbations of velocities, the azimutal anisotropy and the radial anisotropy. The azimuthal anisotropy displays a complex pattern close to the Afar Hotspot and is in good agreement with studies of shear-wave splitting. The Gulf of Aden is associates with slow velocities down to 150km depth. We observe a negative anomaly of strong amplitude below the Afar Hotspot. A second plume located on the ethiopian rift is visible down to 300km. The hotspots of North Africa seem to have a superficial signature and could be a consequence of edge-driven convectionPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Discussion on ‘Palaeoseismic structures in Quaternary sediments, related to an assumed fault zone north of the Permian Peissen-Gnutz salt structure (NW Germany) – Neotectonic activity and earthquakes from the Saalian to the Holocene’ (Grube, 2019)

International audienceWe discuss the significance of deformation structures in Quaternary sediments observed by Grube (2019) in the Peissen quarries (NW Germany) in light of the geological context. Evidence for polygonal patterns visible in aerial images in the study area shows that the wedge structures interpreted by Grube (2019) as earthquake-induced sand blows may rather correspond to thermal contraction cracks filled with aeolian sand in a permafrost environment. In the study sites, brittle deformations caused by (i) the rise of a salt diapir, (ii) salt dissolution, (iii) the development of Pleistocene permafrost and (iv) possibly, water circulation under pressure in the Scandinavian ice sheet margin may have coexisted. We support the idea that, while the morphology of deformation generally makes it possible to determine the stress state to which the sediments have been subjected and the quantity of water available in the system at the time of deformation, the nature of the factors causing the stresses remains difficult to identify. In the end, we highlight other useful criteria that should be privileged for palaeoseismic research in such complex geological settings

Best practices in teaching information technology development

Programming is one of the most fundamental and central topics in the information technology curriculum. Because of its importance it is crucial to understand how to effectively teach development students. In this panel we share best practices for teaching programming to a variety of populations, including freshman, non-majors, and community college students. Various pedagogical approaches including pair programming, studiobased instruction, peer instruction, active learning, cooperative learning, project-based pedagogy, high-impact education practices, and CS Unplugged type activities are included

Experimental soft-sediment deformation caused by fluidization and intrusive ice melt in sand

(IF 3.41; Q1)International audienceIdentifying the driving mechanisms of soft‐sediment deformation in the geological record is the subject of debate. Thawing of ice‐rich clayey silt above permafrost was proved experimentally to be among the processes capable of triggering deformation. However, previous work failed so far to reproduce similar structures in sand. This study investigates fluidization and intrusive ice formation from soil models in the laboratory. Experimental conditions reproduce the growth of ice‐cored mounds caused by pore water pressure increase during freeze‐back of sand in permafrost context. Excess pore water pressure causes hydraulic fracturing and the development of water lenses beneath the freezing front. Later freezing of the water lenses generates intrusive ice. The main structures consist of sand dykes and sills formed when the increase in pore water pressure exceeds a critical threshold, and soft‐sediment deformations induced by subsidence during ice melt. The combination of processes has resulted in diapir‐like structures. The experimental structures are similar to those described in Pleistocene sites from France. These processes constitute a credible alternative to the seismic hypothesis evoked to explain soft‐sediment deformation structures in other European regions subjected to Pleistocene cold climates