Full-sky CMB lensing reconstruction in presence of sky-cuts

We consider the reconstruction of the CMB lensing potential and its power spectrum of the full sphere in presence of sky-cuts due to point sources and Galactic contaminations. Those two effects are treated separately. Small regions contaminated by point sources are filled in using Gaussian constrained realizations. The Galactic plane is simply masked using an apodized mask before lensing reconstruction. This algorithm recovers the power spectrum of the lensing potential with no significant bias.Comment: Submitted to A&

Caractérisation de la microstructure des voies spinales humaines par IRM multiparamétrique

RÉSUMÉ La routine clinique en IRM pour le diagnostic ou le suivi de pathologies neurodégénératives telles que la sclérose en plaques ou la dégénérescence wallérienne ne se fait actuellement que par une évaluation visuelle basée sur des différences de contraste dans des images anatomiques. Il est donc difficile de déterminer précisément le degré des lésions. L’IRM quantitative (IRMq) se propose de quantifier l’évolution du tissu par des métriques sensibles et spécifiques aux différentes caractéristiques microstructurales. Très développé dans le cerveau, sa faisabilité et ses applications ont été démontrées dans la moelle. Toutefois, l’acquisition de telles métriques prend généralement trop de temps et est souvent trop exigeant en termes de force de gradients magnétiques pour entrer dans un cadre clinique. De plus, plusieurs sources d’erreurs sont susceptibles de baiser les mesures. Ce mémoire vise à mettre en place un protocole complet (de l’acquisition au traitement des données) permettant l’estimation de métriques IRMq spécifiquement à chaque voie spinale. Les principales métriques issues de ce protocole sont le Ratio de Transfert de Magnétisation (MTR), le temps de relaxation T1, le Volume de Tissu Macromoléculaire (MTV), les indices des modèles de diffusion NODDI (Neurite Orientation Dispersion and Density Imaging) et DTI (Imagerie par Tenseur de Diffusion), le g-ratio (ratio du diamètre axonal sur celui de la fibre incluant la gaine de myéline) et l’aire de section axiale. Le protocole développé est applicable en clinique et prend en compte les différentes sources d’erreurs connues qui peuvent s’introduire dans les mesures durant l’acquisition. De plus, basé sur le recalage d’un atlas des voies spinales sur chaque métrique, le protocole de traitement de données, rapide et quasi-automatique, permet de s’affranchir du biais lié à l’opérateur lors de la délimitation manuelle des régions d’intérêt. Quant à la méthode d’estimation, elle emploie des estimateurs tels que les estimateurs des moindres carrés et du maximum a posteriori permettant d’atténuer l’effet de volume partiel et du bruit ; elle est par ailleurs validée sur un fantôme synthétique. Finalement, le protocole complet est appliqué à une cohorte de 16 jeunes adultes (de 21 à 33 ans) et 14 adultes âgés (de 61 à 73 ans) sains afin d’évaluer sa sensibilité aux différentes microstructures dans la matière blanche de la moelle épinière. Pour toutes les métriques les estimations montrent des valeurs en accord avec la littérature. Toutes les métriques – excepté les fractions de volume intracellulaire, de volume----------ABSTRACT The current clinical MRI routine for the diagnosis or the screening of neurodegenerative pathologies such as multiple sclerosis or Wallerian degeneration, consists of a simple visual assessment based on contrast differences in anatomical images. Therefore it is hard to precisely assess the stage of the lesions. Quantitative MRI (qMRI) proposes to quantify the evolution of the tissue using metrics sensitive and specific to the different microstructural characteristics. Widely developed in the brain, its feasibility and applications have been demonstrated in the spinal cord. However, the acquisition of such metrics is too time-consuming and demanding in terms of magnetic gradient strength to apply in a clinical framework. Moreover, several sources of error are likely to bias the measures. This thesis aims to develop a comprehensive protocol (from the acquisition to the processing of the data) allowing the estimation of qMRI metrics specifically in each spinal pathway. The main metrics resulting from this protocol are the Magnetization Transfer Ratio (MTR), the relaxation time T1, the Macromolecular Tissue Volume (MTV), the diffusion indices from NODDI (Neurite Orientation Dispersion and Density Imaging) and DTI (Diffusion Tensor Imaging) models, the g-ratio (ratio of the inner diameter over the outer diameter of a fiber, including its myelin sheath) and the cross-sectional area. This protocol is applicable in a clinical framework and takes into account the different sources of error that are likely to affect the measures during acquisition. In addition, since it is based on the registration of a white matter atlas to each metric, the fast and almost automatic data processing pipeline allows to get rid of the usual user-related bias induced by the manual drawing of regions of interest. Moreover, the estimation method uses estimators such as the least square and the maximum a posteriori estimators allowing to mitigate the effect of partial volume and of noise; furthermore, a validation of the method is performed on a synthetic phantom. Finally, the whole protocol is applied to a cohort of 16 young (aged 21 to 33) and 14 elderly (aged 61 to 73) healthy adults in order to assess its sensitivity to different microstructures in the spinal cord white matter. For all metrics the estimations show values in agreement with the literature. All metrics – except the intracellular, the axonal and the fiber volume fractions – showed significant difference between the dorsal column and the corticospinal tract, as suggested by histology. However, only the MTR showed a significant decrease between young and elderly, in agreement wit

Structural role of PufX in the dimerization of the photosynthetic core complex of Rhodobacter sphaeroides.

Monomeric and dimeric PufX-containing core complexes have been purified from membranes of wild-type Rhodobacter sphaeroides. Reconstitution of both samples by detergent removal in the presence of lipids leads to the formation of two-dimensional crystals constituted of dimeric core complexes. Two-dimensional crystals were further analyzed by cryoelectron microscopy and atomic force microscopy. A projection map at 26-A resolution reveals that core complexes assemble in an "S"-shaped dimeric complex. Each core complex is composed of one reaction center, 12 light-harvesting 1 alpha/beta-heterodimers, and one PufX protein. The light-harvesting 1 assemblies are open with a gap of density of approximately 30-A width and surround oriented reaction centers. A maximum density is found at the dimer junction. Based on the projection map, a model is proposed, in which the two PufX proteins are located at the dimer junction, consistent with the finding of dimerization of monomeric core complexes upon reconstitution. This localization of PufX in the core complex implies that PufX is the structural key for the dimer complex formation rather than a channel-forming protein for the exchange of ubiquinone/ubiquinol between the reaction center and the cytochrome bc1 complex

An observational assessment of the influence of mesoscale and submesoscale heterogeneity on ocean biogeochemical reactions

Numerous observations demonstrate that considerable spatial variability exists in components of the marine planktonic ecosystem at the mesoscale and submesoscale (100?km -1?km). The causes and consequences of physical processes at these scales (‘eddy advection’) influencing biogeochemistry have received much attention. Less studied, the non-linear nature of most ecological and biogeochemical interactions means that such spatial variability has consequences for regional estimates of processes including primary production and grazing, independent of the physical processes. This effect has been termed ‘eddy reactions’. Models remain our most powerful tools for extrapolating hypotheses for biogeochemistry to global scales and to permit future projections. The spatial resolution of most climate and global biogeochemical models means that processes at the mesoscale and submesoscale are poorly resolved. Modelling work has previously suggested that the neglected ‘eddy reactions’ may be almost as large as the mean field estimates in some cases. This study seeks to quantify the relative size of eddy and mean reactions observationally, using in situ and satellite data. For primary production, grazing and zooplankton mortality the eddy reactions are between 7% and 15% of the mean reactions. These should be regarded as preliminary estimates to encourage further observational estimates, and not taken as a justification for ignoring eddy reactions. Compared to modelling estimates, there are inconsistencies in the relative magnitude of eddy reactions and in correlations which are a major control on their magnitude. One possibility is that models exhibit much stronger spatial correlations than are found in reality, effectively amplifying the magnitude of eddy reactions

Dimensional Transmutation and Dimensional Regularization in Quantum Mechanics. II: Rotational Invariance

A thorough analysis is presented of the class of central fields of force that exhibit: (i) dimensional transmutation and (ii) rotational invariance. Using dimensional regularization, the two-dimensional delta-function potential and the $D$-dimensional inverse square potential are studied. In particular, the following features are analyzed: the existence of a critical coupling, the boundary condition at the origin, the relationship between the bound-state and scattering sectors, and the similarities displayed by both potentials. It is found that, for rotationally symmetric scale-invariant potentials, there is a strong-coupling regime, for which quantum-mechanical breaking of symmetry takes place, with the appearance of a unique bound state as well as of a logarithmic energy dependence of the scattering with respect to the energy.Comment: 29 pages. To appear in Annals of Physic

Monitoring the proportion of the population infected by SARS-CoV-2 using age-stratified hospitalisation and serological data: a modelling study.

BACKGROUND: Regional monitoring of the proportion of the population who have been infected by SARS-CoV-2 is important to guide local management of the epidemic, but is difficult in the absence of regular nationwide serosurveys. We aimed to estimate in near real time the proportion of adults who have been infected by SARS-CoV-2. METHODS: In this modelling study, we developed a method to reconstruct the proportion of adults who have been infected by SARS-CoV-2 and the proportion of infections being detected, using the joint analysis of age-stratified seroprevalence, hospitalisation, and case data, with deconvolution methods. We developed our method on a dataset consisting of seroprevalence estimates from 9782 participants (aged ≥20 years) in the two worst affected regions of France in May, 2020, and applied our approach to the 13 French metropolitan regions over the period March, 2020, to January, 2021. We validated our method externally using data from a national seroprevalence study done between May and June, 2020. FINDINGS: We estimate that 5·7% (95% CI 5·1-6·4) of adults in metropolitan France had been infected with SARS-CoV-2 by May 11, 2020. This proportion remained stable until August, 2020, and increased to 14·9% (13·2-16·9) by Jan 15, 2021. With 26·5% (23·4-29·8) of adult residents having been infected in Île-de-France (Paris region) compared with 5·1% (4·5-5·8) in Brittany by January, 2021, regional variations remained large (coefficient of variation [CV] 0·50) although less so than in May, 2020 (CV 0·74). The proportion infected was twice as high (20·4%, 15·6-26·3) in 20-49-year-olds than in individuals aged 50 years or older (9·7%, 6·9-14·1). 40·2% (34·3-46·3) of infections in adults were detected in June to August, 2020, compared with 49·3% (42·9-55·9) in November, 2020, to January, 2021. Our regional estimates of seroprevalence were strongly correlated with the external validation dataset (coefficient of correlation 0·89). INTERPRETATION: Our simple approach to estimate the proportion of adults that have been infected with SARS-CoV-2 can help to characterise the burden of SARS-CoV-2 infection, epidemic dynamics, and the performance of surveillance in different regions. FUNDING: EU RECOVER, Agence Nationale de la Recherche, Fondation pour la Recherche Médicale, Institut National de la Santé et de la Recherche Médicale (Inserm)

Brownian Motions on Metric Graphs

Brownian motions on a metric graph are defined. Their generators are characterized as Laplace operators subject to Wentzell boundary at every vertex. Conversely, given a set of Wentzell boundary conditions at the vertices of a metric graph, a Brownian motion is constructed pathwise on this graph so that its generator satisfies the given boundary conditions.Comment: 43 pages, 7 figures. 2nd revision of our article 1102.4937: The introduction has been modified, several references were added. This article will appear in the special issue of Journal of Mathematical Physics celebrating Elliott Lieb's 80th birthda

Superconducting nanowire photon number resolving detector at telecom wavelength

The optical-to-electrical conversion, which is the basis of optical detectors, can be linear or nonlinear. When high sensitivities are needed single-photon detectors (SPDs) are used, which operate in a strongly nonlinear mode, their response being independent of the photon number. Nevertheless, photon-number resolving (PNR) detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication, the PNR functionality is key to many protocols for establishing, swapping and measuring entanglement, and can be used to detect photon-number-splitting attacks. A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, e.g. in long-distance optical communications, fluorescence spectroscopy, optical time-domain reflectometry. We demonstrate here a PNR detector based on parallel superconducting nanowires and capable of counting up to 4 photons at telecommunication wavelengths, with ultralow dark count rate and high counting frequency

Deregulation of the protocadherin gene FAT1 alters muscle shapes: implications for the pathogenesis of facioscapulohumeral dystrophy.

International audienceGeneration of skeletal muscles with forms adapted to their function is essential for normal movement. Muscle shape is patterned by the coordinated polarity of collectively migrating myoblasts. Constitutive inactivation of the protocadherin gene Fat1 uncoupled individual myoblast polarity within chains, altering the shape of selective groups of muscles in the shoulder and face. These shape abnormalities were followed by early onset regionalised muscle defects in adult Fat1-deficient mice. Tissue-specific ablation of Fat1 driven by Pax3-cre reproduced muscle shape defects in limb but not face muscles, indicating a cell-autonomous contribution of Fat1 in migrating muscle precursors. Strikingly, the topography of muscle abnormalities caused by Fat1 loss-of-function resembles that of human patients with facioscapulohumeral dystrophy (FSHD). FAT1 lies near the critical locus involved in causing FSHD, and Fat1 mutant mice also show retinal vasculopathy, mimicking another symptom of FSHD, and showed abnormal inner ear patterning, predictive of deafness, reminiscent of another burden of FSHD. Muscle-specific reduction of FAT1 expression and promoter silencing was observed in foetal FSHD1 cases. CGH array-based studies identified deletion polymorphisms within a putative regulatory enhancer of FAT1, predictive of tissue-specific depletion of FAT1 expression, which preferentially segregate with FSHD. Our study identifies FAT1 as a critical determinant of muscle form, misregulation of which associates with FSHD

Measures of kidney function by minimally invasive techniques correlate with histological glomerular damage in SCID mice with adriamycin-induced nephropathy

Maximising the use of preclinical murine models of progressive kidney disease as test beds for therapies ideally requires kidney function to be measured repeatedly in a safe, minimally invasive manner. To date, most studies of murine nephropathy depend on unreliable markers of renal physiological function, exemplified by measuring blood levels of creatinine and urea, and on various end points necessitating sacrifice of experimental animals to assess histological damage, thus counteracting the principles of Replacement, Refinement and Reduction. Here, we applied two novel minimally invasive techniques to measure kidney function in SCID mice with adriamycin-induced nephropathy. We employed i) a transcutaneous device that measures the half-life of intravenously administered FITC-sinistrin, a molecule cleared by glomerular filtration; and ii) multispectral optoacoustic tomography, a photoacoustic imaging device that directly visualises the clearance of the near infrared dye, IRDye 800CW carboxylate. Measurements with either technique showed a significant impairment of renal function in experimental animals versus controls, with significant correlations with the proportion of scarred glomeruli five weeks after induction of injury. These technologies provide clinically relevant functional data and should be widely adopted for testing the efficacies of novel therapies. Moreover, their use will also lead to a reduction in experimental animal numbers