Radiation damages in nuclear waste glasses: a « NMR point of view »

International audienceBorosilicate glasses have been recognized as valuable materials for the conditioning of nuclear wastes. An important issue for their long-term behaviour is radiation effects which may impact their performance and stability. To address these concerns, a fundamental understanding of the origin at the atomic scale of the macroscopic property evolutions must be established. Over the la st decade, magic-angle spinning nuclear magnetic resonance (MAS NMR) has firrrùy established itself as one of the most powerful tool to investigate a glass's structure. It offers several probes of the local structure, nuclei such as 11B, 23Na, 27 Al, 29Si and 17 0, to probe changes either in the glass network or in the alkali distribution. Recently, using external heavy ions irradiation (Xe, Au, Kr) ta simulate alpha decays,[1-3] dramatic changes in the local network structure were evidenced : conversion of tetrahedral B0 4 units into planar trigonal B0 3 units (l1B), appearance of high-coordination aluminum units (AlOs, AI0 6); glass depolymerisation e 9 Si) and changes in the distribution of alkali cations CZ 3 Na). Additionally, the spectra broaden globally which supports the hypothesis of an increased topological disorder after irradiation. AH these structural changes are similar to those observed with increasing the glass temperature or quenching rate and support therefore the model of ballistic disordering fast quenching events which induce a new glassy state with higher fictive temperature. Effects of external electronic (beta) irradiations will be also discussed. If NMR spectra variations show similar trends-but much less pronounced-they are mainly engendered by alkali migration phenomena and formation of molecular oxygen. Until recently, these studies were limited to externally irradiated samples (enabling the different components of irradiation to be dissociated for their precise investigation), but recently, the first MAS-NMR experiments could be performed on radioactive glass es (doped with 244Cm 0.1 % mol.) paving the way for future MAS NMR exarninations of self-irradiation damages in glasses. Experiments were performed at the Joint Research Centre Institute for Transuranium Elements (JRC-ITU) where a commercial NMR spectrometer were integrated with a radioactive glovebox and a MAS commercial probe. Pirst results will be presented. Competitive effects between the recoil nuclei and alpha decays were evidenced and the high resistance of the nuclear waste glasses corroborated

Sleep-Disordered Breathing and Cardiac Arrhythmias in Adults: Mechanistic Insights and Clinical Implications: A Scientific Statement From the American Heart Association

Sleep-disordered breathing (SDB), characterized by specific underlying physiological mechanisms, comprises obstructive and central pathophysiology, affects nearly 1 billion individuals worldwide, and is associated with excessive cardiopulmonary morbidity. Strong evidence implicates SDB in cardiac arrhythmogenesis. Immediate consequences of SDB include autonomic nervous system fluctuations, recurrent hypoxia, alterations in carbon dioxide/acid-base status, disrupted sleep architecture, and accompanying increases in negative intrathoracic pressures directly affecting cardiac function. Day-night patterning and circadian biology of SDB-induced pathophysiological sequelae collectively influence the structural and electrophysiological cardiac substrate, thereby creating an ideal milieu for arrhythmogenic propensity. Cohort studies support strong associations of SDB and cardiac arrhythmia, with evidence that discrete respiratory events trigger atrial and ventricular arrhythmic events. Observational studies suggest that SDB treatment reduces atrial fibrillation recurrence after rhythm control interventions. However, high-level evidence from clinical trials that supports a role for SDB intervention on rhythm control is not available. The goals of this scientific statement are to increase knowledge and awareness of the existing science relating SDB to cardiac arrhythmias (atrial fibrillation, ventricular tachyarrhythmias, sudden cardiac death, and bradyarrhythmias), synthesizing data relevant for clinical practice and identifying current knowledge gaps, presenting best practice consensus statements, and prioritizing future scientific directions. Key opportunities identified that are specific to cardiac arrhythmia include optimizing SDB screening, characterizing SDB predictive metrics and underlying pathophysiology, elucidating sex-specific and background-related influences in SDB, assessing the role of mobile health innovations, and prioritizing the conduct of rigorous and adequately powered clinical trials

Sleep-Disordered Breathing and Cardiac Arrhythmias in Adults: Mechanistic Insights and Clinical Implications: A Scientific Statement From the American Heart Association

Sleep-disordered breathing (SDB), characterized by specific underlying physiological mechanisms, comprises obstructive and central pathophysiology, affects nearly 1 billion individuals worldwide, and is associated with excessive cardiopulmonary morbidity. Strong evidence implicates SDB in cardiac arrhythmogenesis. Immediate consequences of SDB include autonomic nervous system fluctuations, recurrent hypoxia, alterations in carbon dioxide/acid-base status, disrupted sleep architecture, and accompanying increases in negative intrathoracic pressures directly affecting cardiac function. Day-night patterning and circadian biology of SDB-induced pathophysiological sequelae collectively influence the structural and electrophysiological cardiac substrate, thereby creating an ideal milieu for arrhythmogenic propensity. Cohort studies support strong associations of SDB and cardiac arrhythmia, with evidence that discrete respiratory events trigger atrial and ventricular arrhythmic events. Observational studies suggest that SDB treatment reduces atrial fibrillation recurrence after rhythm control interventions. However, high-level evidence from clinical trials that supports a role for SDB intervention on rhythm control is not available. The goals of this scientific statement are to increase knowledge and awareness of the existing science relating SDB to cardiac arrhythmias (atrial fibrillation, ventricular tachyarrhythmias, sudden cardiac death, and bradyarrhythmias), synthesizing data relevant for clinical practice and identifying current knowledge gaps, presenting best practice consensus statements, and prioritizing future scientific directions. Key opportunities identified that are specific to cardiac arrhythmia include optimizing SDB screening, characterizing SDB predictive metrics and underlying pathophysiology, elucidating sex-specific and background-related influences in SDB, assessing the role of mobile health innovations, and prioritizing the conduct of rigorous and adequately powered clinical trials

“What Should We Tell the Children About Relationships and Sex?” ©: Development of a Program for Parents Using Intervention Mapping

This article describes the development of an intervention that aims to increase the quantity and quality of parent-child communication about sex and relationships. The intervention has been designed as part of a local strategic approach to teenage pregnancy and sexual health. The process and findings of Intervention Mapping (IM), a tool for the development of theory-and evidence-based interventions, are presented. The process involves a detailed assessment of the difficulties parents experience in communicating with their children about sex and relationships. The findings are translated into program and change objectives that specify what parents need to do to improve their communication. Theory-based practical strategies most likely to bring about the desired behavioral change are then identified and pretested. The intervention developed consists of a six-session facilitator-led program that targets parents' attitudes, knowledge, communication skills, and self-efficacy. Following on from Bartholomew's seminal work on IM, this article develops and extends the application of this process by presenting explicit detail on the behavioral change techniques used and their theoretical underpinnings. The strengths and weaknesses of IM as a process for the development of health behavior interventions are discussed