Application of multimodal machine learning to visual question answering

Master’s Degree in ICT Research and Innovation (i2-ICT)Due to the great advances in Natural Language Processing and Computer Vision in recent yearswith neural networks and attention mechanisms, a great interest in VQA has been awakened,starting to be considered as the ”Visual Turing Test” for modern AI systems, since it is aboutanswering a question from an image, where the system has to learn to understand and reasonabout the image and question shown. One of the main reasons for this great interest is thelarge number of potential applications that these systems allow, such as medical applicationsfor diagnosis through an image, assistants for blind people, e-learning applications, etc.In this Master’s thesis, a study of the state of the art of VQA is proposed, investigatingboth techniques and existing datasets. Finally, a development is carried out in order to try toreproduce the results of the art with the latest VQA models with the aim of being able to applythem and experiment on new datasets.Therefore, in this work, experiments are carried out with a first VQA model, MoViE+MCAN[1] [2] (winner of the 2020 VQA Challenge), which after observing its non-viability due toresource issues, we switched to the LXMERT Model [3], which consists of a pre-trained modelin 5 subtasks, which allows us to perform fine-tunnig on several tasks, which in this specificcase is the VQA task on the VQA v2.0 [4] dataset.As the main result of this Thesis we experimentally show that LXMERT provides similarresults to MoViE-MCAN (the best known method for VQA) in the most recent and demandingbenchmarks with less resources starting from the pre-trained model provided by the GitHubrepository [5]

Seismic structure and activity of the north-central Lesser Antilles subduction zone from an integrated approach: similarities with the Tohoku forearc

The 300 km long north-central segment of the Lesser Antilles subduction zone, including Martinique and Guadeloupe islands has been the target of a specific approach to the seismic structure and activity by a cluster of active and passive offshore-onshore seismic experiments coordinated within the ¿Thales was right¿ proposal to the European Union action (Laigle et al., Tectonophys., in rev.) The top of the subducting plate can be followed under the wide accretionary wedge by a dense grid of dip- and strike-lines of multichannel reflection seismics. This reveals the hidden updip limit of the contact of the upper plate crustal backstop thrust onto the slab. Two OBS refraction seismic profiles constrained a 26 km large crustal thickness from the volcanic arc throughout the forearc domain (Kopp et al., EPSL, 2011). These new observations imply a three times larger width of the potential interplate seismogenic zone under the marine domain of the Caribbean plate with respect to a regular intra-oceanic subduction zone, in the common assumption that the upper plate Moho contact on the slab is a proxy of its downdip limit. Towards larger depth under the mantle corner, the top of the slab imaged from the conversions of teleseismic body-waves and the locations of earthquakes from the dense temporary array of 80 OBS and land seismometers appears with kinks which increase the dip from 10-20° under the forearc domain, to 60° on the segment from 70 km depth down to under the volcanic arc. There, at 140 km depth just north of Martinique the 2007 M 7.4 earthquake, largest for half a century, was accompanied by an increased seismic activity over the whole depth range, which provides a new focused image thanks to the OBS and land deployments. A double-planed dipping slab seismicity is thus now resolved, as originally discovered in Tohoku ( NE Japan) and since in some other subduction zones. Other types of seismic activity uniquely observed in Tohoku, are resolved now here, such as ¿supraslab¿ earthquakes with normal-faulting focal mechanisms reliably located in the mantle corner and ¿deep flat-thrust¿ earthquakes at 45 km depth on the interplate fault under the Caribbean plate forearc mantle. None such types of seismicity should occur under the paradigm of a regular peridotitic mantle of the upper plate which is serpentinized by the fluids provided from the dehydrating slab beneath, and which is commonly considered as limiting the downward extent of the interplate seismic coupling. If the upper plate here comprised lithospheric segments related to the earlier formation of the Caribbean oceanic plateau by the material advection from a mantle plume, it could then be underlain by a correspondingly modified, heterogeneous mantle, which may impose regions of stick-slip behaviour on the interplate under the mantle corner among stable-gliding areas. The Tohoku 2011 M9 earthquake was unexpected not only in its slip reaching to the trench, but also in its slip reaching far under the mantle corner against the serpentinization decoupling paradigm, and its structural setting may be revisited for resolving corresponding structural heterogeneityPeer Reviewe

Slab segmentation controls the interplate slip motion in the SW Hellenic subduction: New insight from the 2008Mw 6.8 Methoni interplate earthquake

We present an integrated approach of the seismic structure and activity along the offshore SW Hellenic subduction from combined observations of marine and land seismic stations. Our imaging of the slab top topography from teleseismic receiver function analysis at ocean bottom seismometers supports a trenchward continuation of the along-dip slab faults beneath the Peloponnesus. We further show that their morphostructural control accounts for the backstepping of the thrust contact of the Mediterranean Ridge accretionary wedge over the upper plate. Local seismic activity offshore SW Peloponnesus constrained by ocean bottom seismometer observations reveals a correlation with specific features of the forearc: the Matapan Troughs. We study the Mw6.8 14.02.2008 interplate earthquake offshore SW Peloponnesus and show that its nucleation, rupture zone, and aftershocks sequence are confined to one slab panel between two adjacent along-dip faults and are thus controlled by not only the offshore slab top segmentation but also the upper plate sea-bottom morphology

Structure of the Lesser Antilles subduction forearc and backstop from 3D seismic tomography

In 2007 the Sismantilles II experiment was conducted to constrain structure and seismicity in the central Lesser Antilles subduction zone. The seismic refraction data recorded by a network of 27 OBSs over an area of 65 km×95 km provide new insights on the crustal structure of the forearc offshore Martinique and Dominica islands. The tomographic inversion of first arrival travel times provides a 3D P-wave velocity model down to 15 km. Basement velocity gradients depict that the forearc is made up of two distinct units: A high velocity gradient domain named the inner forearc in comparison to a lower velocity gradient domain located further trenchward named the outer forearc. Whereas the inner forearc appears as a rigid block uplifted and possibly tilted as a whole to the south, short wavelength deformations of the outer forearc basement are observed, beneath a 3 to 6 km thick sedimentary pile, in relation with the subduction of the Tiburon Ridge and associated sea floor reliefs. North, offshore Dominica Island, the outer forearc is 70 km wide. It extends as far as 180 km to the east of the volcanic front where it acts as a backstop on which the accretionary wedge developed. Its width decreases strongly to the south to terminate offshore Martinique where the inner forearc acts as the backstop. The inner forearc is likely the extension at depth of the Mesozoic magmatic crust outcropping to the north in La Désirade Island and along the scarp of the Karukera Spur. The outer forearc could be either the eastern prolongation of the inner forearc, but the crust was thinned and fractured during the past tectonic history of the area or by recent subduction processes, or an oceanic terrane more recently accreted to the island arc.Peer Reviewe

Analytical tools for the multiplex rapid detection of SARS-CoV-2

There is a high demand for analytical tools that can readily be applied to effectively diagnose the Covid-19 but also to carry out screening and surveillance detection with enough frequency to get the transmission rates under control and thus help to timely tackling the disease. On the one hand, high throughput analytical benchtop approaches are still highly demanding for accelerating diagnostics. Such platforms are required to show multiplexed capabilities while in turn reducing the turnaround times of currently applied techniques such as the RT-PCR gold standard. On the other hand, massive screening and surveillance protocols still require for effective tools at the point of need that could reliably detect the virus in individuals after being exposed or the likelihood of being immunized after suffering from the disease. The rapid detection of coronavirus biomarkers, including RNA as well as spike and nucleocapsid proteins in nasopharyngeal and oropharyngeal samples, together with host biomarkers such as immunoglobulins and cytokines in serum has been addressed in this work. We aim to produce tools that provided with a global response to the diagnosis, prognosis and follow-up of the disease (Figure 1). All the biocomponents and corresponding bioassay protocols required for measuring these biomarkers have been tailored made and implemented in three different platforms. A calorimetric device based on a lateral flow assay format [1, 2] and a multiplex electrochemical platform comprising an electrochemical transducer array and a paper microfluidic component [3] have been adapted to produce tools to be used at the point of care. Likewise, a fluorescence microarray platform has been set up with the potential for high-throughput screening by recording molecular signatures thanks to the its multiplexing and miniaturization capabilities. REFERENCES [1] E. Polo et al. PCT, ES2013/070549 [2] E. Polo et al. Chem. Commun., 49 (2013) 3676 [3] C. Fernández-Sánchez et al. Application no. EP20382721.

About the lithospheric structure of central Tibet based on seismic data from the INDEPTH III profile

Signals from 11 shots and 8 earthquakes, and numerous teleseismic events were recorded along the 400-km seismic line INDEPTH III in central Tibet and interpreted together with previous seismic and tectonic data. The abnormal behavior of various mantle phases reveals a complex Moho-transition zone, especially in the northern part of the line, in the Changtang Block, where the lower crust and the mantle show unusually low velocities, a shingled appearance of Pn and no low-velocity layer in the upper crust. The strong east-west anisotropy in the Changtang Block is related to an easterly escape movement of the whole lithosphere, facilitated by the warm and weak layers in the lower crust and the upper mantle, bounded apparently by two prominent west-east running fault zones

Pliocene-Quaternary crustal melting in central and northern Tibet and insights into crustal flow

There is considerable controversy over the nature of geophysically recognized low-velocity-high-conductivity zones (LV-HCZs) within the Tibetan crust, and their role in models for the development of the Tibetan Plateau. Here we report petrological and geochemical data on magmas erupted 4.7-0.3 Myr ago in central and northern Tibet, demonstrating that they were generated by partial melting of crustal rocks at temperatures of 700-1,050°C and pressures of 0.5-1.5 GPa. Thus Pliocene-Quaternary melting of crustal rocks occurred at depths of 15-50 km in areas where the LV-HCZs have been recognized. This provides new petrological evidence that the LV-HCZs are sources of partial melt. It is inferred that crustal melting played a key role in triggering crustal weakening and outward crustal flow in the expansion of the Tibetan Plateau