A posteriori error estimation for the dual mixed finite element method for the pp-Laplacian in a polygonal domain

International audienceFor the discrete solution of the dual mixed formulation for the $p$-Laplace equation, we define two residues $R$ and $r$. Then we bound the norm of the errors on the two unknowns in terms of the norms of these two residues. Afterwards, we bound the norms of these two residues by functions of two error estimators whose expressions involve at the very most the datum and the computed quantities. We next explain how the discretized dual mixed formulation is hybridized and solved. We close our paper by numerical tests for $p$=1.8 and $p$=3 firstly to corroborate the orders of convergence established by M. Farhloul and H. Hanouzi [1], and secondly to experimentally verify the reliability of our a posteriori error estimates

A posteriori error estimates of the stabilized Crouzeix-Raviart finite element method for the Lamé-Navier equations

International audienceWe obtain a posteriori error estimates for a variant of (non-locking) stabilized non-conforming methods based on the Crouzeix-Raviart element introduced by P. Hansbo and M.G. Larson in [M2AN 37 (2003) 63-72]. We derive upper and lower a posteriori error bounds which are robust with respect to the nearly incompressible materials

Plasma neuregulin 1 as a synaptic biomarker in Alzheimer's disease: a discovery cohort study

BACKGROUND: Synaptic dysfunction is an early core feature of Alzheimer's disease (AD), closely associated with cognitive symptoms. Neuregulin 1 (NRG1) is a growth and differentiation factor with a key role in the development and maintenance of synaptic transmission. Previous reports have shown that changes in cerebrospinal fluid (CSF) NRG1 concentration are associated with cognitive status and biomarker evidence of AD pathology. Plasma biomarkers reflecting synaptic impairment would be of great clinical interest. OBJECTIVE: To measure plasma NRG1 concentration in AD patients in comparison with other neurodegenerative disorders and neurological controls (NC) and to study its association with cerebrospinal fluid (CSF) core AD and synaptic biomarkers. METHODS: This retrospective study enrolled 127 participants including patients with AD at mild cognitive impairment stage (AD-MCI, n = 27) and at dementia stage (n = 35), non-AD dementia (n = 26, Aβ-negative), non-AD MCI (n = 19), and neurological controls (n=20). Plasma and CSF NRG1, as well as CSF core AD biomarkers (Aβ 42/Aβ 40 ratio, phospho-tau, and total tau), were measured using ELISA. CSF synaptic markers were measured using ELISA for GAP-43 and neurogranin and through immunoprecipitation mass spectrometry for SNAP-25. RESULTS: Plasma NRG1 concentration was higher in AD-MCI and AD dementia patients compared with neurological controls (respectively P = 0.005 and P < 0.001). Plasma NRG1 differentiated AD MCI patients from neurological controls with an area under the curve of 88.3%, and AD dementia patients from NC with an area under the curve of 87.3%. Plasma NRG1 correlated with CSF NRG1 (β = 0.372, P = 0.0056, adjusted on age and sex). Plasma NRG1 was associated with AD CSF core biomarkers in the whole cohort and in Aβ-positive patients (β = -0.197-0.423). Plasma NRG1 correlated with CSF GAP-43, neurogranin, and SNAP-25 (β = 0.278-0.355). Plasma NRG1 concentration correlated inversely with MMSE in the whole cohort and in Aβ-positive patients (all, β = -0.188, P = 0.038; Aβ+: β = -0.255, P = 0.038). CONCLUSION: Plasma NRG1 concentration is increased in AD patients and correlates with CSF core AD and synaptic biomarkers and cognitive status. Thus, plasma NRG1 is a promising non-invasive biomarker to monitor synaptic impairment in AD

Smartphone applications are used for self-management, telerehabilitation, evaluation and data collection in low back pain healthcare: a scoping review [version 2; peer review: 2 approved]

Background Smartphone use has grown in providing healthcare for patients with low back pain (LBP), but the literature lacks an analysis of the use of smartphone apps. This scoping review aimed to identify current areas of smartphone apps use for managing LBP. We also aimed to evaluate the current status of the effectiveness or scientific validity of such use and determine perspectives for their potential development. Methods We searched PubMed, PEDro and Embase for articles published in English up to May 3rd, 2021 that investigated smartphone use for LBP healthcare and their purpose. All types of study design were accepted. Studies concerning telemedicine or telerehabilitation but without use of a smartphone were not included. The same search strategy was performed by two researchers independently and a third researcher validated the synthesis of the included studies. Results We included 43 articles: randomised controlled trials (RCTs) (n=12), study protocols (n=6), reliability/validity studies (n=6), systematic reviews (n=7), cohort studies (n=4), qualitative studies (n=6), and case series (n=1). The purposes of the smartphone app were for 1) evaluation, 2) telerehabilitation, 3) self-management, and 4) data collection. Self-management was the most-studied use, showing promising results derived from moderate- to good-quality RCTs for patients with chronic LBP and patients after spinal surgery. Promising results exist regarding evaluation and data collection use and contradictory results regarding measurement use. Conclusions This scoping review revealed a notable interest in the scientific literatures regarding the use of smartphone apps for LBP patients. The identified purposes point to current scientific status and perspectives for further studies including RCTs and systematic reviews targeting specific usage

Détail d'une structure régionale majeure par méthodes géophysiques combinées - cas de la faille de Fécamp-Lillebonne (Seine-Maritime, France)

International audienceLa faille de Lillebonne-Fécamp est une faille normale-décrochante dextre (Hauchard et Laignel, 2008 ; Wazi, 1988), orientée N150° (orientation armoricaine) à regard vers l'ouest, à rejet vertical variable (150 m dans le secteur de Bolbec, 40 m dans le secteur de Lillebonne). Il s'agit d'une structure géologique régionale majeure qui traverse le Pays de Caux sur plus de 25 km et se prolonge en Manche au large de Fécamp en prenant progressivement une orientation E-O. Au sud, cette structure n'atteindrait pas la Seine et viendrait buter contre l'accident de Notre-Dame-de-Gravenchon-Villequier, orienté N060° (orientation varisque). A l'échelle du Bassin de Paris, cette structure s'inscrit dans la continuité des failles de la Seine, de Rambouillet et d'Etampes, et présente la même orientation que la structure du Bray. Dans le paysage structural du Pays de Caux, la faille de Lillebonne-Fécamp est également associée à de larges structures plicatives à faible pendage, globalement parallèles à la faille (Ragot, 1988). En 2017, des investigations géophysiques ont été réalisées par le BRGM dans le secteur de Bolbec pour améliorer les connaissances géologiques et structurales dans la zone. L'interprétation et la corrélation conjointe des profils géo-électriques, sismiques et de la carte gravimétrique a permis de confirmer la thèse de Ragot sur la géométrie en faisceau de la faille, et de proposer une nouvelle carte structurale pour le secteur de Bolbec

A Pragmatic, Data-Driven Method to Determine Cutoffs for CSF Biomarkers of Alzheimer Disease Based on Validation Against PET Imaging

OBJECTIVE: To elaborate a new algorithm to establish a standardized method to define cuff-offs for CSF biomarkers of Alzheimer's disease (AD) by validating the algorithm against CSF classification derived from PET imaging. METHODS: Low and high levels of CSF phosphorylated tau were first identified to establish optimal cut-offs for CSF amyloid-β peptide (Aβ) biomarkers. These Aβ cut-offs were then used to determine cut-offs for CSF tau and phosphorylated tau markers. We compared this algorithm to a reference method, based on tau and amyloid PET imaging status (ADNI study), and then applied the algorithm to 10 large clinical cohorts of patients. RESULTS: A total of 6,922 subjects with CSF biomarkers data were included (mean (SD) age: 70.6 (8.5) years, 51.0% women). In the ADNI study population (n=497), the agreement between classification based on our algorithm and one based on amyloid/tau PET imaging was high with Cohen's kappa coefficient between 0.87 and 0.99. Applying the algorithm to 10 large cohorts of patients (n=6,425), the proportion of persons with AD ranged from 25.9% to 43.5%. DISCUSSION: The proposed novel, pragmatic method to determine CSF biomarkers cut-offs for AD does not require assessment of other biomarkers or assumptions concerning the clinical diagnosis of patients. Use of this standardized algorithm is likely to reduce heterogeneity in AD classification

Initial results from a hydroacoustic network to monitor submarine lava flows near Mayotte Island

In 2019, a new underwater volcano was discovered at 3500 m below sea level (b.s.l.), 50 km east of Mayotte Island in the northern part of the Mozambique Channel. In January 2021, the submarine eruption was still going on and the volcanic activity, along with the intense seismicity that accompanies this crisis, was monitored by the recently created REVOSIMA (MAyotte VOlcano and Seismic Monitoring) network. In this framework, four hydrophones were moored in the SOFAR channel in October 2020. Surrounding the volcano, they monitor sounds generated by the volcanic activity and the lava flows. The first year of hydroacoustic data evidenced many earthquakes, underwater landslides, large marine mammal calls, along with anthropogenic noise. Of particular interest are impulsive signals that we relate to steam bursts during lava flow emplacement. A preliminary analysis of these impulsive signals (ten days in a year, and only one day in full detail) reveals that lava emplacement was active when our monitoring started, but faded out during the first year of the experiment. A systematic and robust detection of these specific signals would hence contribute to monitor active submarine eruptions in the absence of seafloor deep-tow imaging or swath-bathymetry surveys of the active area

Human Muscle Satellite Cells as Targets of Chikungunya Virus Infection

BACKGROUND: Chikungunya (CHIK) virus is a mosquito-transmitted alphavirus that causes in humans an acute infection characterised by fever, polyarthralgia, head-ache, and myalgia. Since 2005, the emergence of CHIK virus was associated with an unprecedented magnitude outbreak of CHIK disease in the Indian Ocean. Clinically, this outbreak was characterized by invalidating poly-arthralgia, with myalgia being reported in 97.7% of cases. Since the cellular targets of CHIK virus in humans are unknown, we studied the pathogenic events and targets of CHIK infection in skeletal muscle. METHODOLOGY/PRINCIPAL FINDINGS: Immunohistology on muscle biopsies from two CHIK virus-infected patients with myositic syndrome showed that viral antigens were found exclusively inside skeletal muscle progenitor cells (designed as satelllite cells), and not in muscle fibers. To evaluate the ability of CHIK virus to replicate in human satellite cells, we assessed virus infection on primary human muscle cells; viral growth was observed in CHIK virus-infected satellite cells with a cytopathic effect, whereas myotubes were essentially refractory to infection. CONCLUSIONS/SIGNIFICANCE: This report provides new insights into CHIK virus pathogenesis, since it is the first to identify a cellular target of CHIK virus in humans and to report a selective infection of muscle satellite cells by a viral agent in humans