Local deformation in a hydrogel induced by an external magnetic field

The aim of this study is to prove the feasibility of a system able to apply local mechanical loading on cells seeded in a hydrogel for tissue engineering applications. This experimental study is based on a previously developed artificial cartilage model with different concentrations of poly(vinyl alcohol) (PVA) that simulates the cartilage extracellular matrix (ECM). Poly(l-lactic acid) (PLLA) microspheres with dispersed magnetic nanoparticles (MNPs) were produced with an emulsion method. These microspheres were embedded in aqueous PVA solutions with varying concentration to resemble increased viscosity of growing tissue during regeneration. The ability to induce a local deformation in the ECM was assessed by applying a steady or an oscillatory magnetic field gradient to different PVA solutions containing the magnetic microparticles, similarly as in ferrogels. PLLA microparticle motion was recorded, and the images were analyzed. Besides, PVA gels and PLLA microparticles were introduced into the pores of a polycaprolactone scaffold, and the microparticle distribution and the mechanical properties of the construct were evaluated. The results of this experimental model show that the dispersion of PLLA microparticles containing MNPs, together with cells in a supporting gel, will allow applying local mechanical stimuli to cells during tissue regeneration. This local stimulation can have a positive effect on the differentiation of seeded cells and improve tissue regeneration.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the MAT2013-46467-C4-1-R project, including the Feder funds. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. The authors thank "Servicio de Microscopia Electronica" of Universitat Politecnica de Valencia for their invaluable help. The translation of this paper was funded by the Universitat Politecnica de Valencia, Spain.Vikingsson, L.; Vinals Guitart, Á.; Valera Martínez, A.; Riera Guasp, J.; Vidaurre Garayo, AJ.; Gallego Ferrer, G.; Gómez Ribelles, JL. (2016). Local deformation in a hydrogel induced by an external magnetic field. Journal of Materials Science. 51(22):9979-9990. https://doi.org/10.1007/s10853-016-0226-8S997999905122Eyre D (2002) Collagen of articular cartilage. Arthritis Res 4:30–35Roughley PJ, Lee ER (1994) Cartilage proteoglycans: structure and potential functions. Microsc Res Tech 28:385–397Gillard GC, Reilly HC, Bell-Booth PG, Flint MH (1979) The influence of mechanical forces on the glycosaminoglycan content of the rabbit flexor digitorum profundus tendon. 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Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Nouveau champ de vitesses GNSS RENAG22

International audienceLe Réseau National GNSS (Résif-Rénag) vient d'achever une nouvelle solution combinée appelée RENAG22. Elle a pour objectif de compiler et de comparer toutes les estimations de vitesse GNSS des stations Résif-Rénag et, par extension, de toutes les stations GNSS permanentes sur le territoire métropolitain. Au total, la solution combinée RENAG22 rassemble des estimations de vitesse pour 693 stations GNSS

Estimation des mouvements verticaux de l'écorce terrestre par GPS dans un repère géocentrique, dans le cadre du projet TIGA.

Two complementary techniques coexist today to observe sea-level variations. Satellite altimetry observes sea-level on near-global and regular spatial and temporal sampling. However, this technique has not more than a few decades of existence. Due to inter-decadal variations in sea-level, altimetry does not provide access to long-period signals or secular changes. Long-term sea-level variations are accessible today by tide gauge measurements, having some of them continuous records since the 19th century. This technique is therefore the only way to directly observe the sea-level change during the 20th century, which represents a good indicator of climate change. However, the tide gauge estimates are contaminated by long-term vertical movements of the Earth's crust. To obtain the absolute long-term sea-level variation, the vertical movements of tide gauges can now be determined by the GPS technique. This approach is explored in practice since 2001 by the TIGA (Tide Gauge Benchmark Monitoring) pilot project of the International GNSS Service (IGS). Since 2002, the Consortium ULR (University of La Rochelle and the French National Geographic Institute) takes part in this project as a TIGA Analysis Center. Currently, more than 300 GPS stations globally distributed are processed, from which more than 200 are co-located with a tide gauge. My doctoral thesis work deals with the methodological study to improve the estimation of vertical velocities of GPS stations. A first part of my work has involved the study of the best processing strategy of the GPS data. Various models have been tested as, for example, the effects of antennae phase center variation and the tropospheric delay. Due to the large number of stations, the distribution into sub-networks is necessary for processing. An optimal and dynamical distribution of GPS stations has been developed and tested. The results showed that this procedure has greatly improved the quality of the GPS processing. Following the application of this new processing strategy, we obtained and exported products such as the station positions, the satellite orbits, the orientation parameters of the Earth, and the apparent motion geocenter, to be combined within the first GPS data reanalysis campaign of the IGS. The comparison of these products with other high-quality estimates provided a validation of the GPS processing strategy implemented as well as some clues for future improvement. In addition, the participation in this campaign has extended the International Terrestrial Reference Frame (ITRF) to tide gauges. The second part of my work involved the study of the GPS vertical velocity estimation. The coupled effect of periodic signals and discontinuities on the estimated velocities has been highlighted, showing the need to estimate these parameters in a consistent and rigorous way. Particularly, the effect of discontinuities has been reported as the current largest source of error in velocity estimation. The realistic velocity uncertainties were analyzed in depth by taking into account the correlated noise content in time series. By comparing the results of this rigorous analysis with the previous ULR solution, it was found a significant reduction in the correlated noise content. This is mainly due to the improved data processing strategy. The noise analysis has led to the demonstration that the temporal correlation of homogeneously reprocessed time series depends on the data epoch. In this way, it was shown that the noise content of long GPS time series is mainly due to the noise level of the oldest data. However, to get the smallest formal velocity uncertainty, it is necessary to use all the available data. It has been shown that by using the noise model most appropriate for each time series, the formal uncertainty of the velocity field agrees with the velocity differences obtained with respect to the next realization of the International Terrestrial Reference Frame, the ITRF2008.Deux techniques complémentaires coexistent aujourd'hui pour observer les variations du niveau des mers. L'altimétrie par satellite permet une observation quasi globale avec un échantillonnage temporel et spatial régulier. Cependant, cette technique n'a pas plus de quelques décennies d'existence. A cause des variations inter-décennales du niveau des mers, elle ne donne donc pas accès aux signaux de longue période ou aux variations séculaires. Les variations du niveau des mers à long terme sont accessibles aujourd'hui que grâce aux mesures marégraphiques, certains marégraphes fournissant des enregistrements continus depuis le XIXème siècle. Cette technique constitue donc le seul moyen d'estimer, à partir de la mesure directe, les variations du niveau des mers pendant le XXème siècle, donnée qui représente un bon indicateur du changement climatique. Cependant, les estimations marégraphiques sont contaminées par des mouvements verticaux à long terme de la croûte terrestre. Afin d'obtenir les variations absolues à long terme du niveau des mers, les mouvements verticaux des marégraphes peuvent maintenant être déterminés par la technique GPS. Cette approche est explorée en pratique depuis 2001 par le projet pilote TIGA (Tide Gauge benchmark monitoring) du Service International des GNSS (IGS). Dès 2002, le Consortium ULR (Université de La Rochelle et Institut Géographique National) contribue à ce projet en tant que Centre d'Analyse TIGA. Actuellement, plus de 300 stations GPS globalement reparties sont traitées, parmi lesquelles plus de 200 sont co-localisées avec un marégraphe. Mes travaux de thèse s'inscrivent dans l'étude méthodologique visant à améliorer l'estimation des vitesses verticales des stations GPS. Une première étape de mes travaux a donc consisté en l'étude de la meilleure stratégie de traitement des données GPS. Différentes modélisations ont été testées comme, par exemple, les effets de variation de phase des antennes et du retard troposphérique. A cause du grand nombre de stations du réseau, une répartition en sous-réseaux est imposée pour le traitement. Une répartition optimale des stations GPS selon une approche dynamique a été élaborée et testée. Les résultats ont montré que cette procédure améliore grandement la qualité du traitement GPS. A l'issue de l'application de cette nouvelle stratégie de calcul, on a obtenu et exporté des produits dérivés comme les positions des stations, les orbites des satellites, les paramètres d'orientation de la Terre, et le mouvement apparent du géocentre, pour être combinés dans le cadre de la première campagne de retraitement des données GPS de l'IGS. La confrontation de ces produits avec les produits d'autres analyses de très haute qualité (la grande majorité des Centres d'Analyse IGS y participent) on fourni une validation de la stratégie de traitement GPS implémentée et aussi des indications pour de futures améliorations. La participation à cette campagne a permis en plus de densifier et d'étendre le repère international de référence terrestre (ITRF) aux marégraphes. La deuxième étape de mes travaux a consisté en l'étude de l'estimation de vitesses verticales GPS. L'effet couplé des signaux périodiques et des discontinuités sur les vitesses estimées a été mis en évidence, montrant la nécessité d'estimer ces paramètres d'une manière cohérente et rigoureuse. Particulièrement, l'effet des discontinuités a été signalé comme la source d'erreur la plus importante aujourd'hui pour l'estimation de vitesses. Les incertitudes réalistes des vitesses estimées ont été analysées en profondeur en prenant en compte le contenu de bruit corrélé dans les séries temporelles. En comparant rigoureusement les résultats de cette analyse avec la précédente solution ULR, on constate une réduction significative du contenu du bruit corrélé. Ceci est dû principalement à l'amélioration du traitement des données. Cette analyse du bruit a abouti à la démonstration que la corrélation temporelle des données retraitées de façon homogène dépend de l'époque des données. De cette façon, il a été démontré que le contenu du bruit dans les séries temporelles GPS longues s'explique principalement par le niveau de bruit des données les plus anciennes. Toutefois, pour obtenir l'incertitude formelle de vitesse la plus petite possible, il est nécessaire d'incorporer toutes les données disponibles. Il a été montré qu'en utilisant le modèle de bruit le plus approprié pour la série temporelle de chaque station, l'incertitude formelle du champ de vitesse estimé est en accord avec les différences de vitesse obtenues par rapport à la prochaine réalisation du repère international de référence terrestre, l'ITRF2008

Nouveau champ de vitesses GNSS RENAG22

International audienceLe Réseau National GNSS (Résif-Rénag) vient d'achever une nouvelle solution combinée appelée RENAG22. Elle a pour objectif de compiler et de comparer toutes les estimations de vitesse GNSS des stations Résif-Rénag et, par extension, de toutes les stations GNSS permanentes sur le territoire métropolitain. Au total, la solution combinée RENAG22 rassemble des estimations de vitesse pour 693 stations GNSS

Automatic offset detection using R open source libraries

International audienceLong GNSS position time series contain offsets typically at rates between 1 and 3 offsets per decade. We may classify the offsets whether their epoch is precisely known, from GNSS station log files or Earthquake databases, or unknown. Very often, GNSS position time series contain offsets for which the epoch is not known a priori and, therefore, an offset detection/removal operation needs to be done in order to produce continuous position time series needed for many applications in geodesy and geophysics. A further classification of the offsets corresponds to those having a physical origin related to the instantaneous displacement of the GNSS antenna phase center (from Earthquakes, antenna changes or even changes of the environment of the antenna) and those spurious originated from the offset detection method being used (manual/supervised or automatic/unsupervised). Offsets due to changes of the antenna and its environment must be avoided by the station operators as much as possible. Spurious offsets due to the detection method must be avoided by the time series analyst and are the focus of this work.Even if manual offset detection by expert analysis is likely to perform better, automatic offset detection algorithms are extremely useful when using massive (thousands) GNSS time series sets. Change point detection and cluster analysis algorithms can be used for detecting offsets in a GNSS time series data and R offers a number of libraries related to performing these two. For example, the "Bayesian Analysis of Change Point Problems" or the "bcp" helps to detect change points in a time series data. Similarly, the "dtwclust" (Dynamic Time Warping algorithm) is used for the time series cluster analysis. Our objective is to assess various open-source R libraries for the automatic offset detection

Chameleonic Noise in GPS Position Time Series

International audienceIt has been a standard practice for about 2 decades to compute global positioning system (GPS) based station velocity uncertainties using the apparent noise statistics of the non linear position residuals rather than assume white noise (WN) behavior. The latter choice would yield unrealistic velocity uncertainties. The most common noise types used are power law, usually close to flicker noise (FN), over most frequencies mixed with WN at the shortest periods. The complicating impact of offsets in the position time series, mostly caused by equipment changes or tectonic events, has not been fully appreciated. These are far less benign than recently suggested. In addition to contributing a pseudo random walk noise (RW) component to the velocity errors, estimating offset parameters changes the apparent noise color toward whiter. Spectral power is effectively drained by offsets at periods longer than roughly the mean span between them. This consequently favors a Gauss Markov process as the apparently preferred noise model and, importantly, obscures the presence of RW and long period Earth deformation in the series. Both effects can lead to potentially under estimated velocity uncertainties. The full value of decadal long GPS time series for geodynamical applications is thereby greatly eroded by recurring offsets, especially when they occur quasi regularly. In addition, contrary to common assumption, the noise color is generally not fixed with time, but clearly becomes whiter in more recent data. The origin of the colored noise and its whitening over time remain elusive

3D GPS velocity field of the Iberian Peninsula

International audienceWe present a 3D crustal deformation velocity field of the Iberian Peninsula based on the analysis of more than 400 continuous GPS stations covering the period from 2010 to 2018 and distributed throughout the Iberian Peninsula, northern Africa and southern France. We describe the procedures followed to obtain a combined uniform velocity solution from daily GPS data using GAMIT/GLOBK and SARI software for post-processing the time series. The previous studies have estimated only the 2D horizontal rates, since the vertical component of deformation is more complicated to derive. Only the studies by Serpelloni et al. (2013) and Nguyen et al. (2016) have calculated the vertical rates of deformation in some limited areas of the Iberian Peninsula. In the present work, we provide the velocity vectors in horizontal and vertical directions. The calculated horizontal GPS velocities, in Eurasia fixed reference frame, indicate that the Iberian Peninsula presents a heterogeneous crustal deformation field, which can be roughly grouped into 7 distinct domains/blocks. Each domain can be related to the known geo-tectonic structural units of the Iberian Peninsula. The highest velocities, as well as the highest geodetic strain rates, are detected along the Iberia-Nubia plate boundary and the Eastern Betics Shear Zone (EBSZ), areas where the highest seismicity rates are observed. The obtained vertical velocity field has to be considered as preliminary, since a more careful treatment of various phenomena affecting the GPS vertical signal (e.g. ocean, tidal and atmospheric loading) should be performed in order to better resolve them. There are some locations with anomalously high rates that cannot be of a tectonic origin. These motions are related to local processes, often triggered by anthropogenic activities, such as the ongoing subsidence of 6 cm/yr in the Guadalentín basin near the city of Lorca (Murcia), caused by extensive groundwater extraction. The presented 3D velocity field provides useful information for multi-risk analysis since it can be used to identify zones and/or faults where the geodetic strain accumulates the most, contributing towards the improvement of seismic hazard assessment. This is especially relevant for evaluating long-term earthquake hazard in areas with slow deformation rates, like the Iberian Peninsula. The detected vertical motions are useful for studying long-term tectonic processes (uplift/subsidence), as well as, studying more short-term and local phenomena such as landslides, sediment settlement and/or anthropogenic activities (e.g. groundwater withdrawal, mining). This work is supported by the project PREVENT (CGL2015-66263-R) project financed by the Ministry of Economy, Industry and Competitiveness. G. Kh. was supported by the MUSE international mobility support program, within the framework of Explore 2018 and Salvador Madariaga mobility program of the Spanish Ministry of Education (PRX18/00586). We thank the operators of continuous GNSS networks that contributed data for this work: IGS (Global), IGN (Spain), RGP (France), Renep (Portugal) and regional networks of autonomous communities in Spain: CatNet (Catalonia), RAP (Andalucía), ARAGEA (Aragón), XGAIB (Baleares), Meristemum and REGAM (Murcia), Cantabria, ERVA (Valencia), GALNET (Galicia), ItaCyl (Castilla y León)

3D GPS velocity field of the Iberian Peninsula

International audienceWe present a 3D crustal deformation velocity field of the Iberian Peninsula based on the analysis of more than 400 continuous GPS stations covering the period from 2010 to 2018 and distributed throughout the Iberian Peninsula, northern Africa and southern France. We describe the procedures followed to obtain a combined uniform velocity solution from daily GPS data using GAMIT/GLOBK and SARI software for post-processing the time series. The previous studies have estimated only the 2D horizontal rates, since the vertical component of deformation is more complicated to derive. Only the studies by Serpelloni et al. (2013) and Nguyen et al. (2016) have calculated the vertical rates of deformation in some limited areas of the Iberian Peninsula. In the present work, we provide the velocity vectors in horizontal and vertical directions. The calculated horizontal GPS velocities, in Eurasia fixed reference frame, indicate that the Iberian Peninsula presents a heterogeneous crustal deformation field, which can be roughly grouped into 7 distinct domains/blocks. Each domain can be related to the known geo-tectonic structural units of the Iberian Peninsula. The highest velocities, as well as the highest geodetic strain rates, are detected along the Iberia-Nubia plate boundary and the Eastern Betics Shear Zone (EBSZ), areas where the highest seismicity rates are observed. The obtained vertical velocity field has to be considered as preliminary, since a more careful treatment of various phenomena affecting the GPS vertical signal (e.g. ocean, tidal and atmospheric loading) should be performed in order to better resolve them. There are some locations with anomalously high rates that cannot be of a tectonic origin. These motions are related to local processes, often triggered by anthropogenic activities, such as the ongoing subsidence of 6 cm/yr in the Guadalentín basin near the city of Lorca (Murcia), caused by extensive groundwater extraction. The presented 3D velocity field provides useful information for multi-risk analysis since it can be used to identify zones and/or faults where the geodetic strain accumulates the most, contributing towards the improvement of seismic hazard assessment. This is especially relevant for evaluating long-term earthquake hazard in areas with slow deformation rates, like the Iberian Peninsula. The detected vertical motions are useful for studying long-term tectonic processes (uplift/subsidence), as well as, studying more short-term and local phenomena such as landslides, sediment settlement and/or anthropogenic activities (e.g. groundwater withdrawal, mining). This work is supported by the project PREVENT (CGL2015-66263-R) project financed by the Ministry of Economy, Industry and Competitiveness. G. Kh. was supported by the MUSE international mobility support program, within the framework of Explore 2018 and Salvador Madariaga mobility program of the Spanish Ministry of Education (PRX18/00586). We thank the operators of continuous GNSS networks that contributed data for this work: IGS (Global), IGN (Spain), RGP (France), Renep (Portugal) and regional networks of autonomous communities in Spain: CatNet (Catalonia), RAP (Andalucía), ARAGEA (Aragón), XGAIB (Baleares), Meristemum and REGAM (Murcia), Cantabria, ERVA (Valencia), GALNET (Galicia), ItaCyl (Castilla y León)

Analysis of GNSS Displacements in Europe and Their Comparison with Hydrological Loading Models

International audienceThanks to the increasing number of permanent GNSS stations in Europe and their long records, we computed position solutions for more than 1000 stations over the last two decades using the REPRO3 orbit and clock products from the IGS CNES-CLS (GRGS) Analysis Center. The velocities, which are mainly due to tectonics and glacial isostatic adjustment (GIA), and the annual solar cycle have been estimated using weighted least squares. The interannual variations have been accounted for in the stochastic model or in the deterministic model. We demonstrated that the velocity and annual cycle, in addition to their uncertainties, depend on the estimation method we used and that the estimation of GPS draconitic oscillations minimises biases in the estimation of annual solar cycle displacements. The annual solar cycle extracted from GPS has been compared with that from loading estimates of several hydrological models. If the annual amplitudes between GPS and hydrological models match, the phases of the loading models were typically in advance of about 1 month compared to GPS. Predictions of displacements modelled from GRACE observations did not show this phase shift. We also found important discrepancies at the interannual frequency band between GNSS, loading estimates derived from GRACE, and hydrological models using principal component analysis (PCA) decomposition. These discrepancies revealed that GNSS position variations in the interannual band cannot be systematically interpreted as a geophysical signal and should instead be interpreted in terms of autocorrelated noise