Model-based iterative reconstruction in pediatric chest CT: assessment of image quality in a prospective study of children with cystic fibrosis

Background: The potential effects of ionizing radiation are of particular concern in children. The model-based iterative reconstruction VEOTM is a technique commercialized to improve image quality and reduce noise compared with the filtered back-projection (FBP) method. Objective: To evaluate the potential of VEOTM on diagnostic image quality and dose reduction in pediatric chest CT examinations. Materials and methods: Twenty children (mean 11.4years) with cystic fibrosis underwent either a standard CT or a moderately reduced-dose CT plus a minimum-dose CT performed at 100kVp. Reduced-dose CT examinations consisted of two consecutive acquisitions: one moderately reduced-dose CT with increased noise index (NI = 70) and one minimum-dose CT at CTDIvol 0.14mGy. Standard CTs were reconstructed using the FBP method while low-dose CTs were reconstructed using FBP and VEO. Two senior radiologists evaluated diagnostic image quality independently by scoring anatomical structures using a four-point scale (1=excellent, 2=clear, 3=diminished, 4=non-diagnostic). Standard deviation (SD) and signal-to-noise ratio (SNR) were also computed. Results: At moderately reduced doses, VEO images had significantly lower SD (P < 0.001) and higher SNR (P < 0.05) in comparison to filtered back-projection images. Further improvements were obtained at minimum-dose CT. The best diagnostic image quality was obtained with VEO at minimum-dose CT for the small structures (subpleural vessels and lung fissures) (P < 0.001). The potential for dose reduction was dependent on the diagnostic task because of the modification of the image texture produced by this reconstruction. Conclusions: At minimum-dose CT, VEO enables important dose reduction depending on the clinical indication and makes visible certain small structures that were not perceptible with filtered back-projectio

Generation of a genomic tiling array of the human Major Histocompatibility Complex (MHC) and its application for DNA methylation analysis

Background: The major histocompatibility complex (MHC) is essential for human immunity and is highly associated with common diseases, including cancer. While the genetics of the MHC has been studied intensively for many decades, very little is known about the epigenetics of this most polymorphic and disease-associated region of the genome.Methods: To facilitate comprehensive epigenetic analyses of this region, we have generated a genomic tiling array of 2 Kb resolution covering the entire 4 Mb MHC region. The array has been designed to be compatible with chromatin immunoprecipitation (ChIP), methylated DNA immunoprecipitation (MeDIP), array comparative genomic hybridization (aCGH) and expression profiling, including of non-coding RNAs. The array comprises 7832 features, consisting of two replicates of both forward and reverse strands of MHC amplicons and appropriate controls.Results: Using MeDIP, we demonstrate the application of the MHC array for DNA methylation profiling and the identification of tissue-specific differentially methylated regions (tDMRs). Based on the analysis of two tissues and two cell types, we identified 90 tDMRs within the MHC and describe their characterisation.Conclusion: A tiling array covering the MHC region was developed and validated. Its successful application for DNA methylation profiling indicates that this array represents a useful tool for molecular analyses of the MHC in the context of medical genomics

Regional Brain Responses in Nulliparous Women to Emotional Infant Stimuli

Infant cries and facial expressions influence social interactions and elicit caretaking behaviors from adults. Recent neuroimaging studies suggest that neural responses to infant stimuli involve brain regions that process rewards. However, these studies have yet to investigate individual differences in tendencies to engage or withdraw from motivationally relevant stimuli. To investigate this, we used event-related fMRI to scan 17 nulliparous women. Participants were presented with novel infant cries of two distress levels (low and high) and unknown infant faces of varying affect (happy, sad, and neutral) in a randomized, counter-balanced order. Brain activation was subsequently correlated with scores on the Behavioral Inhibition System/Behavioral Activation System scale. Infant cries activated bilateral superior and middle temporal gyri (STG and MTG) and precentral and postcentral gyri. Activation was greater in bilateral temporal cortices for low- relative to high-distress cries. Happy relative to neutral faces activated the ventral striatum, caudate, ventromedial prefrontal, and orbitofrontal cortices. Sad versus neutral faces activated the precuneus, cuneus, and posterior cingulate cortex, and behavioral activation drive correlated with occipital cortical activations in this contrast. Behavioral inhibition correlated with activation in the right STG for high- and low-distress cries relative to pink noise. Behavioral drive correlated inversely with putamen, caudate, and thalamic activations for the comparison of high-distress cries to pink noise. Reward-responsiveness correlated with activation in the left precentral gyrus during the perception of low-distress cries relative to pink noise. Our findings indicate that infant cry stimuli elicit activations in areas implicated in auditory processing and social cognition. Happy infant faces may be encoded as rewarding, whereas sad faces activate regions associated with empathic processing. Differences in motivational tendencies may modulate neural responses to infant cues

Descent theory and Morita theory for ultrametric Banach modules

In this paper we consider ultrametric Banach modules over commutative ultrametric Banach algebras with unit. We study the descent problem along a morphism f: R --> S of such algebras and show that descent morphisms coincide with weak retracts. We give further conditions for having an effective descent morphism or for having a Morita equivalence between the corresponding categories of ultrametric Banach modules

Synthèse et caractérisation structurale de composés oxalate à base d'actinides

L acide oxalique est un ligand mis en avant pour la récupération quantitative des actinides séparés des produits de fission. En particulier, la co-précipitation oxalique facilite l incorporation des actinides mineurs dans des matériaux céramique dédiés à leur transmutation grâce à la formation contrôlée de composés oxalate mixtes, précurseurs des solutions solides oxyde souhaitées. Les méthodes de croissance cristalline existantes n étant pas adaptables à la chimie du système actinide-oxalate et aux conditions de manipulation en boîte-à-gants, plusieurs méthodes de synthèse originales ont été conçues puis développées sur les lanthanides et les actinides légers (uranium, thorium). Quatre méthodes originales, basées sur des stratégies de mise en contact lente des réactifs, ont ainsi été optimisées. Après développement sur les simulants, elles ont été adaptées aux spécificités (notamment redox) des actinides plus lourds tels le plutonium ou l américium. Elles ont permis la synthèse de nombreux monocristaux d oxalates d actinide et d oxalates mixtes An1(IV)-An2(III) mais aussi An1(IV)-An2(IV). Finalement, les premières caractérisations structurales poussées de ces composés par DRX sur monocristal, EXAFS ou micro-RAMAN permettent d acquérir des informations structurales indispensables à l enrichissement de la base de données structurales relativement pauvre concernant les oxalates d actinides. Cette dernière est pourtant indispensable à une meilleure compréhension des futurs cycles du combustible actuellement à l étude.Oxalic acid is a well-known reagent to recover actinides thanks to the very low solubility of An(IV) and An(III) oxalate compounds in acidic solution. Therefore, considering mixed-oxide fuel or considering minor actinides incorporation in ceramic fuel materials for transmutation, oxalic co-conversion is convenient to synthesize mixed oxalate compounds, precursors of oxide solid solutions. As the existing oxalate single crystal syntheses are not adaptable to the actinide-oxalate chemistry or to their manipulation constrains in gloves box, several original crystal growth methods were developed. They were first validate and optimized on lanthanides and uranium before the application to transuranium elements. The advanced investigations allow to better understand the syntheses and to define optimized chemical conditions to promote crystal growth. These new crystal growth methods were then applied to a large number of mixed An1(IV)-An2(III) or An1(IV)-An2(IV) systems and lead to the formation of the first original mixed An1(IV)-An2(III) and An1(IV)-An2(IV) oxalate single crystals. Finally thanks to the first thorough structural characterizations of these compounds, single crystal X-ray diffraction, EXAFS or micro-RAMAN, the particularly weak oxalate-actinide compounds structural database is enriched, which is essential for future studied nuclear fuel cycles.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Etude des mécanismes de compensation de charge dans les solutions solides d'oxalates d'actinides

Dans le cadre du développement des cycles nucléaires du futur, les recherches menées sur le recyclage des combustibles usés sont orientées vers des procédés de synthèse de solides mixtes d actinides pouvant être utilisés comme matières premières pour la fabrication de nouveaux combustibles ou cibles de transmutation. La co-conversion oxalique figure parmi les voies de synthèse d oxydes mixtes les plus étudiées. Les oxalates mixtes, composés d actinides IV et III, sont tout d abord produits avec de hauts rendements de précipitation compte tenu de leur grande insolubilité. Leur structure cristallographique est bâtie à partir d un réseau anionique, 2D ou 3D, dans lequel s insèrent des cations monochargés M+ pour assurer l électroneutralité du composé. Ce travail vise la compréhension des mécanismes de compensation de charge par les monocations M+, qui rentrent en jeu lors de la co-précipitation oxalique. L étude a été menée d abord sur un système modèle à base ThIV et NdIII exempt de toute interaction redox puis sur un système plus complexe purement à base d actinides, An1IV et An2III. Des techniques de caractérisation du solide par diffraction de RX, spectroscopie infrarouge et UV du solide, thermogravimétrie, MEB, granulométrie laser, ICP-AES, analyse CHN et dosages divers, ont été utilisés comme outil indispensable pour la compréhension des mécanismes de compensation de charge.Researches on future options for new nuclear cycles are oriented towards the synthesis of mixed actinide solids, which can be employed as precursors for the fabrication of new fuel or transmutation targets. Oxalic co-conversion is one of the most studied options for the synthesis of mixed oxides. Co-precipitated solids are commonly actinides III and IV compounds, because of their high yields of precipitation. They are able to develop 2D or 3D metal-oxalate frameworks, wherein single-charged cations are inserted to ensure the electroneutrality of the compound. The aim of this work is to better understand the charge compensation mechamisms during the oxalic co-precipitation of these mixed oxalates. The study has been first carried out on a model system, ThIV et NdIII, free of redox interactions, then applied to purely based actinides, An1IV and An2III, systems. Characterization techniques as powder X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy, thermogravimetry, SEM, Laser granulometry, ICP-AES, CHN analysis have been used as an indispensable tool for understanding charge compensation mechanisms.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Nouveaux peroxydes et peroxo-oxalates à base d'uranium, précurseurs d'oxydes (synthèse et caractérisation)

Les recherches actuelles sur les cycles nucléaires du futur sont axées notamment sur le traitement-recyclage du combustible nucléaire dit usé avec la préparation de solides mixtes à base d actinides, matières premières pour la fabrication de nouveaux combustibles. A l issue des cycles de séparation-purification lors du traitement du combustible, l étape de conversion des actinides en solution en oxyde mixte est une des étapes clés de cette démarche. Actuellement le plutonium est précipité sous forme oxalate et de nombreuses études de la précipitation et décomposition d oxalates mixtes ont été réalisées. Quant à l uranium, il est précipité sous forme de peroxyde d uranyle, l utilisation de peroxydes mixtes voire peroxo-oxalates comme précurseurs d oxydes est donc une voie à explorer. L objectif de cette étude est d instruire la potentialité d une telle voie peroxyde. Dans une première étape, l examen du système NH4+/UO22+/O22-/C2O42-, a mis en évidence la formation de plusieurs peroxydes et peroxo-oxalates sous forme de polyanions isolés ou de nanoclusters conduisant, par décomposition thermique, à des oxydes d uranium. Dans une seconde étape, partant de nanoclusters d uranyle et d ammonium des peroxydes d uranium et de lanthanides ou de thorium ont été préparés et caractérisés par diffraction X sur monocristal et sur poudre, par analyse ICP-AES, par microscopie électronique et par spectroscopies UV-visible et IR. Leur décomposition en oxydes mixtes a été étudiée sous différentes atmosphères.One of the current researches on future nuclear cycle is spent nuclear fuel treatment and recycling, where actinides mixed solids are prepared as raw materials for nuclear fuel refabrication. After separating-purification cycle during spent nuclear fuel treatment, the conversion step of actinides from solution to mixed oxide is one of the key stages. Currently, plutonium is recovered by oxalic precipitation and numerous studies on its precipitation and oxalate decomposition have been done. Meanwhile, in the case of uranium, a uranyl peroxide is precipitated. Therefore, a route to investigate is the use of peroxides or peroxo-oxalates as oxides precursors. The main goal of this study is to study the feasibility of such method. In a first step, examination of NH4+/UO22+O22-/C2O42- system has highlighted the evidence of many peroxides or peroxo-oxalates formed as polyanions or nanoclusters. These entities lead to uranium oxides after calcination. In a second step, using uranyl nanoclusters, mixed uranium - lanthanide or uranium - thorium compounds were prepared and characterised by single crystal and powder X-ray diffraction, ICP-AES analysis, electron microscopy, UV-Vis and IR spectroscopy. Their decomposition in mixed oxides has been studied under different atmospheres.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Single Crystal Synthesis Methods Dedicated to Structural Investigations of Very Low Solubility Mixed-Actinide Oxalate Coordination Polymers

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Actinide oxalates, solid state structures and applications

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Climate change would prevail over land use change in shaping the future distribution of Triturus marmoratus in France

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