22 research outputs found
Large-scale mass wasting in the western Indian Ocean constrains onset of East African rifting
Faulting and earthquakes occur extensively along the flanks of the East African Rift System, including an offshore branch in the western Indian Ocean, resulting in remobilization of sediment in the form of landslides. To date, constraints on the occurrence of submarine landslides at margin scale are lacking, leaving unanswered a link between rifting and slope instability. Here, we show the first overview of landslide deposits in the post-Eocene stratigraphy of the Tanzania margin and we present the discovery of one of the biggest landslides on Earth: the Mafia mega-slide. The emplacement of multiple landslides, including the Mafia mega-slide, during the early-mid Miocene is coeval with cratonic rifting in Tanzania, indicating that plateau uplift and rifting in East Africa triggered large and potentially tsunamigenic landslides likely through earthquake activity and enhanced sediment supply. This study is a first step to evaluate the risk associated with submarine landslides in the region
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS measured from stellar occultations
This work aims at constraining the size, shape, and geometric albedo of the
dwarf planet candidate 2002 MS4 through the analysis of nine stellar
occultation events. Using multichord detection, we also studied the object's
topography by analyzing the obtained limb and the residuals between observed
chords and the best-fitted ellipse. We predicted and organized the
observational campaigns of nine stellar occultations by 2002 MS4 between 2019
and 2022, resulting in two single-chord events, four double-chord detections,
and three events with three to up to sixty-one positive chords. Using 13
selected chords from the 8 August 2020 event, we determined the global
elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the
object's rotational information from the literature, constrains the object's
size, shape, and albedo. Additionally, we developed a new method to
characterize topography features on the object's limb. The global limb has a
semi-major axis of 412 10 km, a semi-minor axis of 385 17 km, and
the position angle of the minor axis is 121 16. From
this instantaneous limb, we obtained 2002 MS4's geometric albedo and the
projected area-equivalent diameter. Significant deviations from the fitted
ellipse in the northernmost limb are detected from multiple sites highlighting
three distinct topographic features: one 11 km depth depression followed by a
25 km height elevation next to a crater-like depression with an
extension of 322 39 km and 45.1 1.5 km deep. Our results present an
object that is 138 km smaller in diameter than derived from thermal
data, possibly indicating the presence of a so-far unknown satellite. However,
within the error bars, the geometric albedo in the V-band agrees with the
results published in the literature, even with the radiometric-derived albedo
Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016
Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft.
Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015.
Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 ÎŒbar to 10 nbar).
Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4â7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere
Efficacy and Safety of Sofosbuvir-Based Antiviral Therapy to Treat Hepatitis C Virus Infection After Kidney Transplantation
International audienceThere is no approved therapy for hepatitis C virus (HCV) infection after kidney transplantation, and no data regarding the use of newâgeneration direct antiviral agents (DAAs) have been published so far. The aims of this pilot study were to assess the efficacy and safety of an interferonâfree sofosbuvirâbased regimen to treat chronic HCV infection in kidney transplant recipients. Twentyâfive kidney transplant recipients with chronic HCV infection were given, for 12 (nâ=â19) or 24 weeks (nâ=â6), sofosbuvir plus ribavirin (nâ=â3); sofosbuvir plus daclatasvir (nâ=â4); sofosbuvir plus simeprevir, with (nâ=â1) or without ribavirin (nâ=â6); sofosbuvir plus ledipasvir, with (nâ=â1) or without ribavirin (nâ=â9); and sofosbuvir plus pegylatedâinterferon plus ribavirin (nâ=â1). A rapid virological response, defined by undetectable viremia at week 4 after starting DAA therapy, was observed in 22 of the 25 patients (88%). At the end of therapy, HCV RNA was undetectable in all patients. At 4 and 12 weeks after completing DAA therapy, all had a sustained virological response. The tolerance to antiâHCV therapy was excellent and no adverse event was observed. A significant decrease in calcineurin inhibitor levels was observed after HCV clearance. Newâgeneration oral DAAs are efficient and safe to treat HCV infection after kidney transplantation
Design, Fabrication and Characterization of a Novel Piezoresistive Pressure Sensor for Blast Waves Monitoring
International audienceIn several side-on configurations, the monitoring of blast wave requires sensor with very low response time (< 1 ”s). The sensing area of commercial sensors are too high to fulfill this specification. New transducers are focused on miniature membrane (diameter < 100 ”m), but with optical transduction which suffers from low integration capabilities for multiple transducers. In this communication, a miniature piezoresistive pressure transducer based on silicon membrane and silicon gauges is designed and fabricated. Shock tube characterizations of the sensor have shown promising dynamic behavior, with a rise time of 30 ns and a response time lower than 1 ”s thanks to the membrane fundamental resonant frequency of 20 MHz. Undesirable mechanical effects leading to the response drift after 1 ”s are discussed and interpreted as the result of the holder deformation
Design, Fabrication and Characterization of a Novel Piezoresistive Pressure Sensor for Blast Waves Monitoring
International audienceIn several side-on configurations, the monitoring of blast wave requires sensor with very low response time (< 1 ”s). The sensing area of commercial sensors are too high to fulfill this specification. New transducers are focused on miniature membrane (diameter < 100 ”m), but with optical transduction which suffers from low integration capabilities for multiple transducers. In this communication, a miniature piezoresistive pressure transducer based on silicon membrane and silicon gauges is designed and fabricated. Shock tube characterizations of the sensor have shown promising dynamic behavior, with a rise time of 30 ns and a response time lower than 1 ”s thanks to the membrane fundamental resonant frequency of 20 MHz. Undesirable mechanical effects leading to the response drift after 1 ”s are discussed and interpreted as the result of the holder deformation
Design, Fabrication and Characterization of a Novel Piezoresistive Pressure Sensor for Blast Waves Monitoring
International audienceIn several side-on configurations, the monitoring of blast wave requires sensor with very low response time (< 1 ”s). The sensing area of commercial sensors are too high to fulfill this specification. New transducers are focused on miniature membrane (diameter < 100 ”m), but with optical transduction which suffers from low integration capabilities for multiple transducers. In this communication, a miniature piezoresistive pressure transducer based on silicon membrane and silicon gauges is designed and fabricated. Shock tube characterizations of the sensor have shown promising dynamic behavior, with a rise time of 30 ns and a response time lower than 1 ”s thanks to the membrane fundamental resonant frequency of 20 MHz. Undesirable mechanical effects leading to the response drift after 1 ”s are discussed and interpreted as the result of the holder deformation
Risk Factors of Pneumocystis Pneumonia in Solid Organ Recipients in the Era of the Common Use of Posttransplantation Prophylaxis
International audiencePneumocystis pneumonia (PCP) in solid organ transplant (SOT) recipients becomes rare in the immediate posttransplantation period thanks to generalized prophylaxis. We aimed to identify the predictive factors for PCP in the era of universal prophylaxis and to propose a strategy for preventing PCP beyond the first year after transplantation. In a retrospective case-control study, 33 SOT cases with PCP diagnosed between 2004 and 2010 were matched with two controls each to identify risk factors for PCP by uni- and multivariate analysis. All the patients benefited from 6 months of posttransplantation trimethoprim-sulfamethoxazole prophylaxis. Most PCP in SOT patients occurred during the second year posttransplantation (33%). By univariate analysis, age, nonuse of tacrolimus, total and CD4 lymphocyte counts, gamma-globulin concentration and cytomegalovirus (CMV) infection appeared to be PCP risk factors. In the final multivariate analysis, age (adjusted odds ratio [OR] 3.7, 95% confidence interval [CI]: 1.3-10.4), CMV infection (OR: 5.2, 95% CI: 1.8-14.7) and total lymphocyte count (OR: 3.9, 95% CI: 1.4-10.7) were found to be independently associated with PCP. The second year posttransplantation appeared to be the new period of highest risk of PCP. Age, CMV viremia and lymphocytes were the most pertinent predictive criteria to evaluate the risk of PCP in clinical practice
Prevalence, Incidence and Risk Factors for Donor-Specific Anti-HLA Antibodies in Maintenance Liver Transplant Patients
International audienceAlthough large retrospective studies have identified the presence of donor-specific antibodies (DSAs) to be a risk factor for rejection and impaired survival after liver transplantation, the long-term predicted pathogenic potential of individual DSAs after liver transplantation remains unclear. We investigated the incidence, prevalence and consequences of DSAs in maintenance liver transplant (LT) recipients. Two hundred sixty-seven LT recipients, who had undergone transplantation at least 6 months previously and had been screened for DSAs at least twice using single-antigen bead technology, were included and tested annually for the presence of DSAs. At a median of 51 months (minâmax: 6â220) after an LT, 13% of patients had DSAs. At a median of 36.5 months (minâmax: 2â45) after the first screening, 9% of patients have developed de novo DSAs. The sole predictive factor for the emergence of de novo DSAs was retransplantation (OR 3.75; 95% CI 1.28â11.05, pâ=â0.025). Five out of 21 patients with de novo DSAs (23.8%) developed an antibody-mediated rejection. Fibrosis score was higher among patients with DSAs. In conclusion, monitoring for the development of DSAs in maintenance LT patients is useful in case of graft dysfunction and to identify patients with a high risk of developing liver fibrosis