Formation d’acide cyanhydrique par action des ondes décimétriques sur des mélanges contenant de l’ammoniac, du méthane et un gaz rare ou de l’hydrogène

On a complété une étude antérieure portant sur la formation d’acide cyanhydrique à partir d’ammoniac, de méthane et d’argon en remplaçant ce dernier gaz rare par du néon, de l’hélium ou de l’hydrogène. Des essais en circuit fermé ont été ensuite effectués, et l’ensemble des résultats s’interprète par des mécanismes faisant intervenir les radicaux CH et CN, comme on l’avait envisagé précédemment

Étude de la formation d’acide cyanhydrique par action des ondes décimétriques sur des mélanges argon-ammoniac-méthane

On a étudié la formation d’acide cyanhydrique par l’action d’ondes décimétriques sur des mélanges d’argon, d’ammoniac et de méthane sous des pressions de quelques millimètres de mercure. La comparaison des mesures d’intensité lumineuse des bandes émises dans la décharge et des résultats des dosages chimiques a permis de mettre en évidence le rôle joué par les radicaux libres CH et CN. Les résultats sont interprétés en admettant que la décomposition du méthane fournit des radicaux CH. Les mécanismes conduisant à l’acide cyanhydrique seraient alors les suivants :CH + NH3 → CN + 2H2CH + H2 → HCN + HL’argon ne semble pas participer aux réactions

Memory-Efficient Training for Fully Unrolled Deep Learned PET Image Reconstruction with Iteration-Dependent Targets

We propose a new version of the forward-backward splitting expectation-maximisation network (FBSEM-Net) along with a new memory-efficient training method enabling the training of fully unrolled implementations of 3D FBSEM-Net. FBSEM-Net unfolds the maximum a posteriori expectation-maximisation algorithm and replaces the regularisation step by a residual convolutional neural network. Both the gradient of the prior and the regularisation strength are learned from training data. In this new implementation, three modifications of the original framework are included. First, iteration-dependent networks are used to have a customised regularisation at each iteration. Second, iteration-dependent targets and losses are introduced so that the regularised reconstruction matches the reconstruction of noise-free data at every iteration. Third, sequential training is performed, making training of large unrolled networks far more memory efficient and feasible. Since sequential training permits unrolling a high number of iterations, there is no need for artificial use of the regularisation step as a leapfrogging acceleration. The results obtained on 2D and 3D simulated data show that FBSEM-Net using iteration-dependent targets and losses improves the consistency in the optimisation of the network parameters over different training runs. We also found that using iteration-dependent targets increases the generalisation capabilities of the network. Furthermore, unrolled networks using iteration-dependent regularisation allowed a slight reduction in reconstruction error compared to using a fixed regularisation network at each iteration. Finally, we demonstrate that sequential training successfully addresses potentially serious memory issues during the training of deep unrolled networks. In particular, it enables the training of 3D fully unrolled FBSEM-Net, not previously feasible, by reducing the memory usage by up to 98% compared to a conventional end-to-end training. We also note that the truncation of the backpropagation (due to sequential training) does not notably impact the network’s performance compared to conventional training with a full backpropagation through the entire network

Argumentaire pour une utilisation plus large de la photochimiothérapie extracorporelle chez l’enfant

International audienceThe management of immune diseases in children remains challenging , although significant advances have been made. In addition to pharmacological approaches, extracorporeal photochemotherapy (ECP) is distinctive in its ability to provide immunomodulation without immune suppression or toxicity. However, in practice, this therapy is not widely used because of logistical issues and the lack of robust clinical pediatric studies. Here, we discuss the potential clinical applications of ECP in children and emphasize the need for a rigorous and specifically pediatric clinical evaluation of ECP. ß 2010 Elsevier Masson SAS. All rights reserved. Résumé Malgré l'apport des biothérapies, le traitement des maladies dysim-munitaires sévères et des conflits allogéniques de l'enfant reste difficile et entaché de nombreuses complications. Dans ce contexte, la photo-chimiothérapie extracorporelle (PCE) (thérapie cellulaire qui repose sur l'effet immunomodulateur des cellules mononucléées du patient, prélevées par aphérèse et exposées ex vivo aux rayons ultraviolets A [UVA] en présence de psoralène) a l'avantage notable d'induire une tolérance immunitaire sans générer d'immunosuppression systémique ni de toxicité a ` court, moyen ou long terme. Cette immunomodulation fait intervenir notamment la génération de lymphocytes T régulateurs (T reg). Malgré cela, la PCE est peu utilisée en raison de ses contraintes logistiques et du manque de données cliniques. Nous proposons une revue des indications reconnues et potentielles de la PCE en pédiatrie. Nous insistons sur la nécessité d'une e ´valuation clinique spécifique a ` l'enfant qui ne peut se concevoir sans la participation active des cliniciens pédiatres en particulier dans le domaine de la transplanta-tion et des maladies auto-immunes et inflammatoires

Prevalence and Odds of Depressive and Anxiety Disorders and Symptoms in Children and Adults With Alopecia Areata

Importance Two recent meta-analyses reported a high prevalence of both anxiety and depression in patients with alopecia areata (AA), as well as a positive association of AA with anxiety and depression, without distinguishing between disorders and symptoms. Yet, depression and anxiety can manifest either as symptoms identified in questionnaires or as specific diagnoses defined by Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) or International Statistical Classification of Diseases and Related Health Problems, Tenth Revision criteria. Objective To perform a large meta-analysis separating the prevalence of depressive and anxiety disorders from that of depressive and anxiety symptoms in patients with AA. Data Sources PubMed, ScienceDirect, the Cochrane Library, Embase, and PsycINFO databases were searched from inception through August 1, 2020. Study Selection Studies that contained data on the prevalence of depressive or anxiety disorders or symptoms were included. Data Extraction and Synthesis The Meta-analysis of Observational Studies in Epidemiology ( MOOSE ) reporting guidelines were used. Pooled prevalence was calculated with a random effects model meta-analysis that took into account between- and within-study variability. Meta-regressions were used to study the association between variations in prevalence and study characteristics. Main Outcomes and Measures The prevalence of depressive and anxiety disorders and symptoms in patients with AA. Results Thirty-seven articles (29 on depression and 26 on anxiety) that met the inclusion criteria were identified. By distinguishing between disorders and symptoms, the prevalence of both depressive disorders (9%) and unspecified anxiety disorders (13%) in patients with AA was shown to be greater than that in the general population. The prevalence and odds ratio (OR) of depressive disorders (prevalence, 9%; OR, 1.38) and anxiety disorders of which each category had been specifically studied (prevalence, 7%-17%; OR, 1.51-1.69) were markedly lower than that of depressive symptoms (prevalence, 37%; OR, 2.70) and anxiety symptoms (prevalence, 34%; OR, 3.07). Meta-regressions showed that variations in prevalence were mainly associated with methodological differences between studies. Conclusions and Relevance In this systematic review and meta-analysis, the separate analyses showed that 7% to 17% of patients with AA had depressive or anxiety disorders that require psychiatric care, including specific medication. Additionally, more than one-third of patients had symptoms that are warning signs and that need monitoring because they can develop into disorders

Incidence of Chronic Radiodermatitis after Fluoroscopically Guided Interventions: A Retrospective Study

International audiencePurpose: To assess the incidence and risk factors for chronic radiodermatitis after fluoroscopically guided interventions (FGIs) in high-risk patients.Materials and methods: Between 2010 and 2016, of 55,782 patients who underwent FGIs, 359 had a risk procedure for skin injury (maximal skin dose > 3 Gy, air kerma > 5 Gy, dose area product [DAP] > 500 Gy.cm2, or fluoroscopy time > 60 minutes). Ninety-one of these patients were examined by a dermatologist for radiodermatitis (median time after procedure, 31.2 months [95% confidence interval, 14.2-50.7]). In each case, the clinical features and topography of the skin lesions were recorded and their incidence calculated. The characteristics of the patients and of the FGIs were tested as risk factors.Results: Eight patients (8.8%) had chronic radiodermatitis; 19 (20.9%) had acute radiodermatitis. Body mass index, DAP value, and air kerma were the only risk factors identified.Conclusions: This study shows that chronic radiodermatitis may be considered a frequent side effect in an at-risk population. The lesions are commonly benign, but extensive sclerosis can occur. Patients should be better informed about the side effects and offered a skin exam periodically