Tensor decomposition of polarized seismic waves

National audienceIn antenna array processing, tensor decompositions allow to jointly estimate sources and their location. But these rechniques can be used only if data are recorded as a function of at least three diversities, which are usually time, space and space translation. The approach presented therein is based on polarization diversity, a very attractive alternative when the antenna array does not enjoy space invariance. Then we derive Cramér-Rao bounds in this context, by resorting to differentiation conventions for real-complex mixed variables.En traitement d'antenne, les décompositions tensorielles permettent d'estimer conjointement les sources et de les localiser. Pour que ces dernières puissent être utilisées, il faut que les données présentent au moins trois diversités, qui sont habituellement le temps, l'espace, et la translation dans l'espace. L'approche présentée ici est basée sur la diversité de polarisation, une alternative très attractive lorsque l'antenne de jouit pas d'invariance spatiale. Nous dérivons ensuite les bornes de Cramér-Rao dans ce contexte, en nous appuyant sur des conventions de différentiation de variables mixtes réelles et complexes

Wideband multilinear array processing through tensor decomposition

International audienceOur goal is to devise a wideband High-Resolution technique that does not require a priori knowledge of DoA rough estimates, and that is able to exploit multiple spatial invariances.Existing tensor array processing techniques are limited to the narrowband case. On the other hand, wideband Esprit has only been proposed with focusing matrices, requiring a priori DoA knowledge.We resort to the decomposition of tensors built on space, space translation and frequency diversities, and demonstrate the good behavior of the algorithm proposed

Specifics of cardiac magnetic resonance imaging in children

SummaryThis review points out three specific features of cardiac magnetic resonance imaging (MRI) in children: the small size of the heart modifies the usual balance between signal-to-noise ratio and spatial resolution; the higher and more variable heart rate limits tissue characterization and temporal resolution; and motion artefacts (notably respiratory motions) must be dealt with. In the second part of this review, we present the current and future practices of cardiac magnetic resonance (CMR) in children, based on the experience of all French paediatric cardiac MRI centres

Prekäre Politik. Hannah Arendt zur Flüchtlingsfrage

Hannah Arendt hat sich wie kaum eine andere politische Theoretikerin mit der Situation von Flüchtlingen und Staatenlosen in der ersten Hälfte des 20. Jahrhunderts auseinandergesetzt. Ihre Hauptwerke lassen sich dabei als Reaktion auf diese Phänomene deuten: Ausgehend von einer Kritik des Souveränitätsparadigmas entwickeln sie ein Rechts- und Politikverständnis, das die Möglichkeit eines solchen radikalen Ausschlusses unterlaufen soll. Der Beitrag macht dabei vor allem zwei Linien in Arendts Werk aus, die im Kontext der Gegenwärtigen sog. „Flüchtlingskrise“ fruchtbar gemacht werden können: Ihre Kritik am souveränen Nationalstaat und der Entwurf eines alternativen Konstitutionalismus sowie die Grundzüge einer Politik von outcasts, die nicht mehr länger an institutionell abgesicherte Kontexte gebunden ist

Staaten und Körper in der Pandemie: Rezension zu "Die Ordnung der Berührung. Staat, Gewalt und Kritik in Zeiten der Coronakrise" von Gesa Lindemann

Gesa Lindemann: Die Ordnung der Berührung: Staat, Gewalt und Kritik in Zeiten der Coronakrise. Weilerswist: Velbrück Wissenschaft 2020. 978395832226

Structural communication between the GTPase Sec4p and its activator Sec2p: Determinants of GEF activity and early deformations to nucleotide release

Ras GTPases are molecular switches that cycle between OFF and ON states depending on the bound nucleotide (i.e. GDP-bound and GTP-bound, respectively).The Rab GTPase, Sec4p, plays regulatory roles in multiple steps of intracellular vesicle trafficking. Nucleotide release is catalyzed by the Guanine Nucleotide Exchange Factor (GEF) Sec2p.Here, the integration of structural information with molecular dynamics (MD) simulations addressed a number of questions concerning the intrinsic and stimulated dynamics of Sec2p and Sec4p as well as the chain of structural deformations leading to GEF-assisted activation of the Rab GTPase.Sec2p holds an intrinsic ability to adopt the conformation found in the crystallographic complexes with Sec4p, thus suggesting that the latter selects and shifts the conformational equilibrium towards a pre-existing bound-like conformation of Sec2p.The anchoring of Sec4p to a suitable conformation of Sec2p favors the Sec2p-assisted pulling on itself of the a1/switch 1 (SWI) loop and of SWI, which loose any contact with GDP. Those deformations of Sec4p would occur earlier. Formation of the final Sec2p-Sec4p hydrophobic interface, accomplishes later. Disruption of the nucleotide cage would cause firstly loss of interactions with the guanine ring and sec-ondly loss of interactions with the phosphates.The ease in sampling the energy landscape and adopting a bound-like conformation likely favors the catalyzing ability of GEFs for Ras GTPases.(c) 2022 Published by Elsevier B.V. on behalf of Research Network of Computational and Structural Bio-technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/)

Lamin A/C Mechanotransduction in Laminopathies

Mechanotransduction translates forces into biological responses and regulates cell functionalities. It is implicated in several diseases, including laminopathies which are pathologies associated with mutations in lamins and lamin-associated proteins. These pathologies affect muscle, adipose, bone, nerve, and skin cells and range from muscular dystrophies to accelerated aging. Although the exact mechanisms governing laminopathies and gene expression are still not clear, a strong correlation has been found between cell functionality and nuclear behavior. New theories base on the direct effect of external force on the genome, which is indeed sensitive to the force transduced by the nuclear lamina. Nuclear lamina performs two essential functions in mechanotransduction pathway modulating the nuclear stiffness and governing the chromatin remodeling. Indeed, A-type lamin mutation and deregulation has been found to affect the nuclear response, altering several downstream cellular processes such as mitosis, chromatin organization, DNA replication-transcription, and nuclear structural integrity. In this review, we summarize the recent findings on the molecular composition and architecture of the nuclear lamina, its role in healthy cells and disease regulation. We focus on A-type lamins since this protein family is the most involved in mechanotransduction and laminopathies

Equality of Effort via Algorithmic Recourse

This paper proposes a method for measuring fairness through equality of effort by applying algorithmic recourse through minimal interventions. Equality of effort is a property that can be quantified at both the individual and the group level. It answers the counterfactual question: what is the minimal cost for a protected individual or the average minimal cost for a protected group of individuals to reverse the outcome computed by an automated system? Algorithmic recourse increases the flexibility and applicability of the notion of equal effort: it overcomes its previous limitations by reconciling multiple treatment variables, introducing feasibility and plausibility constraints, and integrating the actual relative costs of interventions. We extend the existing definition of equality of effort and present an algorithm for its assessment via algorithmic recourse. We validate our approach both on synthetic data and on the German credit dataset

Transient disappearance of RAS mutant clones in plasma: A counterintuitive clinical use of EGFR inhibitors in RAS mutant metastatic colorectal cancer

Genomic studies performed through liquid biopsies widely elucidated the evolutionary trajectory of RAS mutant clones under the selective pressure of EGFR inhibitors in patients with wild type RAS primary colorectal tumors. Similarly, the disappearance of RAS mutant clones in plasma has been more recently reported in some patients with primary RAS mutant cancers, supporting for the first time an unexpected negative selection of RAS mutations during the clonal evolution of mCRC. To date, the extent of conversion to RAS wild type disease at the time of progression has not been clarified yet. As a proof of concept, we prospectively enrolled mCRC patients progressing under anti-VEGF based treatments. Idylla™system was used to screen RAS mutations in plasma and the wild type status of RAS was further confirmed through IT-PGM (Ion Torrent Personal Genome Machine) sequencing. RAS was found mutant in 55% of cases, retaining the same plasma mutation as in the primary tumor at diagnosis, while it was found wild-type in 45%. Four patients testing negative for RAS mutations in plasma at the time of progression of disease (PD) were considered eligible for treatment with EGFR inhibitors and treated accordingly, achieving a clinical benefit. We here propose a hypothetical algorithm that accounts for the transient disappearance of RAS mutant clones over time, which might extend the continuum of care of mutant RAS colorectal cancer patients through the delivery of a further line of therapy

MiR-33a Controls hMSCS Osteoblast Commitment Modulating the Yap/Taz Expression Through EGFR Signaling Regulation

Mesenchymal stromal cells (hMSCs) display a pleiotropic function in bone regeneration. The signaling involved in osteoblast commitment is still not completely understood, and that determines the failure of current therapies being used. In our recent studies, we identified two miRNAs as regulators of hMSCs osteoblast differentiation driving hypoxia signaling and cytoskeletal reorganization. Other signalings involved in this process are epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) signalings through the regulation of Yes-associated protein (YAP)/PDZ-binding motif (TAZ) expression. In the current study, we investigated the role of miR-33a family as a (i) modulator of YAP/TAZ expression and (ii) a regulator of EGFR signaling during osteoblast commitments. Starting from the observation on hMSCs and primary osteoblast cell lines (Nh-Ost) in which EMT genes and miR-33a displayed a specific expression, we performed a gain and loss of function study with miR-33a-5p and 3p on hMSCs cells and Nh-Ost. After 24 h of transfections, we evaluated the modulation of EMT and osteoblast genes expression by qRT-PCR, Western blot, and Osteoimage assays. Through bioinformatic analysis, we identified YAP as the putative target of miR-33a-3p. Its role was investigated by gain and loss of function studies with miR-33a-3p on hMSCs; qRT-PCR and Western blot analyses were also carried out. Finally, the possible role of EGFR signaling in YAP/TAZ modulation by miR-33a-3p expression was evaluated. Human MSCs were treated with EGF-2 and EGFR inhibitor for different time points, and qRT-PCR and Western blot analyses were performed. The above-mentioned methods revealed a balance between miR-33a-5p and miR-33a-3p expression during hMSCs osteoblast differentiation. The human MSCs phenotype was maintained by miR-33a-5p, while the maintenance of the osteoblast phenotype in the Nh-Ost cell model was permitted by miR-33a-3p expression, which regulated YAP/TAZ through the modulation of EGFR signaling. The inhibition of EGFR blocked the effects of miR-33a-3p on YAP/TAZ modulation, favoring the maintenance of hMSCs in a committed phenotype. A new possible personalized therapeutic approach to bone regeneration was discussed, which might be mediated by customizing delivery of miR-33a in simultaneously targeting EGFR and YAP signaling with combined use of drugs