Spontaneous reduction of a hydroborane to generate a B-B single bond using a Lewis pair

The ansa‐aminohydroborane 1‐NMe2‐2‐(BH2)C6H4 crystallizes in an unprecedented type of dimer containing a B−H bond activated by one FLP moiety. Upon mild heating and without the use of any catalyst, this molecule liberates one equivalent of hydrogen to generate a diborane molecule. The synthesis and structural characterization of these new compounds, as well as the kinetic monitoring of the reaction and the DFT investigation of its mechanism, are reported

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Comportement thermique d'enrobés bitumineux de déchets radioactifs

The production of nuclear energy generates aqueous effluents during the treatment of spent nuclear fuel. The principle of reprocessing of certain effluents is based on the insolubilization of the radionuclides contained in these effluents by co-precipitation, using salts having a particular chemical affinity for them. The resulting suspension is called «sludge». This sludge is then immobilized in a bituminous matrix by means of a temperature extrusion process, which allows the evaporation of the water contained in the sludge and ensures an intimate mixing between the salts thus recrystallized and the matrix. The resulting bitumen mixes can therefore be described as a dispersion of inorganic salts within a bituminous matrix.However, these salts can present an exothermic reactivity following interactions that can occur with the bituminous matrix or between the different species that constitute them. It is therefore necessary to bring elements of knowledge to the safety study related to the risk of fire inherent in the bituminous waste throughout their life (transport, storage, disposal).Thus, this work aims to study the behavior of bituminous mixes under external thermal stress in order to obtain elements of physicochemical and thermokinetic understanding related to their degradation, with the objective of feeding their knowledge file. However, bituminous mixes incorporate a wide variety of chemical species, and understanding their thermal behavior can be complex.This study was therefore conducted in a preliminary manner on pure bitumen and on simulated bituminous mixes incorporating only nitrate salts. Experimental data were acquired by means of thermal analysis (differential and thermogravimetric) and then modeled by isoconversional methods in order to obtain the thermokinetic parameters associated with the behavior of the studied materials. The nature of the gases emitted during thermal stress was also determined by coupling with gas chromatography. The materials were characterized before and after thermal solicitation, by various solid-state characterization techniques such as infrared spectroscopy, X-ray diffraction and scanning electron microscopy.When pure bitumen is thermally stressed under anaerobic conditions, an endothermic event caused by its pyrolysis is observed. Under aerobic conditions, the bitumen is the site of several phenomena: two exothermic stages of low temperature oxidation (LTO), followed by an endothermic stage of cracking by fuel deposition (FD) and an exothermic stage of high temperature oxidation (HTO). The activation energies associated with the pyrolysis and FD step, obtained by isoconversional modeling of the experimental data, show close values.The study of the thermal behavior of simplified bitumen incorporating nitrate salts (of sodium or magnesium) under anaerobic conditions has revealed an exothermic reactivity. This exothermicity is increased for bitumen containing sodium nitrate. At low conversion degrees, the bitumen incorporating sodium nitrate shows a behavior similar to that of pure bitumen under anaerobic conditions. As the degree of conversion increases and nitrates are available to be engaged in redox reactions, bituminous mixes exhibit a behavior similar to that of pure bitumen stressed under aerobic conditions. These results suggest a role of fuel for the bitumen and oxidizer for the nitrates.La production d'énergie d'origine nucléaire génère des effluents aqueux lors du traitement du combustible nucléaire usé. Le principe de retraitement de certains effluents repose sur l'insolubilisation des radionucléides qu'ils contiennent par co-précipitation, au moyen de sels ayant une affinité chimique particulière avec eux. La suspension résultante est qualifiée de « boue ». Cette boue est ensuite immobilisée dans une matrice bitumineuse au moyen d'un procédé d'extrusion en température, qui permet l'évaporation de l'eau contenue dans la boue et assure un mélange intime entre les sels ainsi recristallisés et la matrice. Les enrobés bitumineux résultants peuvent donc être décrits comme une dispersion de sels inorganiques au sein d'une matrice bitumineuse.Ces sels peuvent cependant présenter une réactivité exothermique suite à des interactions qui peuvent se produire avec la matrice bitumineuse ou entre les différentes espèces qui les constituent. Il est donc nécessaire d'apporter des éléments de connaissance à l'étude de sûreté relative au risque d'incendie inhérent aux déchets bitumés pendant toute leur durée de vie (transport, entreposage, stockage). Ainsi, ce travail vise à étudier le comportement des enrobés bitumineux sous sollicitation thermique externe afin d'obtenir des éléments de compréhension physico-chimiques et thermocinétiques liés à leur dégradation, dans l'objectif d'alimenter leur dossier de connaissances. Toutefois, les enrobés bitumineux incorporant une grande variété d'espèces chimiques, la compréhension de leur comportement thermique peut s'avérer complexe.Cette étude a donc été menée de manière préliminaire sur la matrice bitumineuse seule et des enrobés simulés incorporant uniquement des sels de nitrates. Des données expérimentales ont été acquises au moyen d'analyses thermiques (différentielle et thermogravimétrique), puis ont été modélisées par des méthodes isoconversionnelles afin d'obtenir les paramètres thermocinétiques associés au comportement des matériaux étudiés. La nature des gaz émis au cours de la sollicitation thermique a également été déterminée par couplage avec une chromatographie en phase gazeuse. Les matériaux ont été caractérisés avant et après sollicitation thermique, par diverses techniques de caractérisation du solide telles que la spectroscopie infrarouge, la diffraction des rayons X et la microscopie électronique à balayage.Lorsque le bitume pur est sollicité thermiquement en condition anaérobie, un événement endothermique causé par sa pyrolyse est observé. En condition aérobie, le bitume est le siège de plusieurs phénomènes : deux étapes exothermiques d'oxydation à basse température (LTO), suivies d'une étape endothermique de craquage par dépôt de combustible (FD) et une étape exothermique d'oxydation à haute température (HTO). Les énergies d'activations associées à la pyrolyse et l'étape FD, obtenues par modélisation isoconversionnelle des données expérimentales, présentent des valeurs proches.L'étude du comportement thermique d'enrobés simplifiés incorporant des sels de nitrates (de sodium ou de magnésium) en condition anaérobie a permis de mettre en évidence une réactivité exothermique. Cette exothermicité est accrue pour le bitume contenant du nitrate de sodium. À de faibles degrés de conversion, le bitume incorporant du nitrate de sodium présente un comportement similaire à celui du bitume pur sollicité en condition anaérobie. Lorsque le degré de conversion augmente et que les nitrates sont disponibles pour être engagés dans les réactions d'oxydo-réduction, l'enrobé présente un comportement similaire à celui du bitume pur sollicité en condition aérobie. Ces résultats suggèrent un rôle de combustible pour le bitume et de comburant pour les nitrates

Comportement thermique d'enrobés bitumineux de déchets radioactifs

The production of nuclear energy generates aqueous effluents during the treatment of spent nuclear fuel. The principle of reprocessing of certain effluents is based on the insolubilization of the radionuclides contained in these effluents by co-precipitation, using salts having a particular chemical affinity for them. The resulting suspension is called «sludge». This sludge is then immobilized in a bituminous matrix by means of a temperature extrusion process, which allows the evaporation of the water contained in the sludge and ensures an intimate mixing between the salts thus recrystallized and the matrix. The resulting bitumen mixes can therefore be described as a dispersion of inorganic salts within a bituminous matrix.However, these salts can present an exothermic reactivity following interactions that can occur with the bituminous matrix or between the different species that constitute them. It is therefore necessary to bring elements of knowledge to the safety study related to the risk of fire inherent in the bituminous waste throughout their life (transport, storage, disposal).Thus, this work aims to study the behavior of bituminous mixes under external thermal stress in order to obtain elements of physicochemical and thermokinetic understanding related to their degradation, with the objective of feeding their knowledge file. However, bituminous mixes incorporate a wide variety of chemical species, and understanding their thermal behavior can be complex.This study was therefore conducted in a preliminary manner on pure bitumen and on simulated bituminous mixes incorporating only nitrate salts. Experimental data were acquired by means of thermal analysis (differential and thermogravimetric) and then modeled by isoconversional methods in order to obtain the thermokinetic parameters associated with the behavior of the studied materials. The nature of the gases emitted during thermal stress was also determined by coupling with gas chromatography. The materials were characterized before and after thermal solicitation, by various solid-state characterization techniques such as infrared spectroscopy, X-ray diffraction and scanning electron microscopy.When pure bitumen is thermally stressed under anaerobic conditions, an endothermic event caused by its pyrolysis is observed. Under aerobic conditions, the bitumen is the site of several phenomena: two exothermic stages of low temperature oxidation (LTO), followed by an endothermic stage of cracking by fuel deposition (FD) and an exothermic stage of high temperature oxidation (HTO). The activation energies associated with the pyrolysis and FD step, obtained by isoconversional modeling of the experimental data, show close values.The study of the thermal behavior of simplified bitumen incorporating nitrate salts (of sodium or magnesium) under anaerobic conditions has revealed an exothermic reactivity. This exothermicity is increased for bitumen containing sodium nitrate. At low conversion degrees, the bitumen incorporating sodium nitrate shows a behavior similar to that of pure bitumen under anaerobic conditions. As the degree of conversion increases and nitrates are available to be engaged in redox reactions, bituminous mixes exhibit a behavior similar to that of pure bitumen stressed under aerobic conditions. These results suggest a role of fuel for the bitumen and oxidizer for the nitrates.La production d'énergie d'origine nucléaire génère des effluents aqueux lors du traitement du combustible nucléaire usé. Le principe de retraitement de certains effluents repose sur l'insolubilisation des radionucléides qu'ils contiennent par co-précipitation, au moyen de sels ayant une affinité chimique particulière avec eux. La suspension résultante est qualifiée de « boue ». Cette boue est ensuite immobilisée dans une matrice bitumineuse au moyen d'un procédé d'extrusion en température, qui permet l'évaporation de l'eau contenue dans la boue et assure un mélange intime entre les sels ainsi recristallisés et la matrice. Les enrobés bitumineux résultants peuvent donc être décrits comme une dispersion de sels inorganiques au sein d'une matrice bitumineuse.Ces sels peuvent cependant présenter une réactivité exothermique suite à des interactions qui peuvent se produire avec la matrice bitumineuse ou entre les différentes espèces qui les constituent. Il est donc nécessaire d'apporter des éléments de connaissance à l'étude de sûreté relative au risque d'incendie inhérent aux déchets bitumés pendant toute leur durée de vie (transport, entreposage, stockage). Ainsi, ce travail vise à étudier le comportement des enrobés bitumineux sous sollicitation thermique externe afin d'obtenir des éléments de compréhension physico-chimiques et thermocinétiques liés à leur dégradation, dans l'objectif d'alimenter leur dossier de connaissances. Toutefois, les enrobés bitumineux incorporant une grande variété d'espèces chimiques, la compréhension de leur comportement thermique peut s'avérer complexe.Cette étude a donc été menée de manière préliminaire sur la matrice bitumineuse seule et des enrobés simulés incorporant uniquement des sels de nitrates. Des données expérimentales ont été acquises au moyen d'analyses thermiques (différentielle et thermogravimétrique), puis ont été modélisées par des méthodes isoconversionnelles afin d'obtenir les paramètres thermocinétiques associés au comportement des matériaux étudiés. La nature des gaz émis au cours de la sollicitation thermique a également été déterminée par couplage avec une chromatographie en phase gazeuse. Les matériaux ont été caractérisés avant et après sollicitation thermique, par diverses techniques de caractérisation du solide telles que la spectroscopie infrarouge, la diffraction des rayons X et la microscopie électronique à balayage.Lorsque le bitume pur est sollicité thermiquement en condition anaérobie, un événement endothermique causé par sa pyrolyse est observé. En condition aérobie, le bitume est le siège de plusieurs phénomènes : deux étapes exothermiques d'oxydation à basse température (LTO), suivies d'une étape endothermique de craquage par dépôt de combustible (FD) et une étape exothermique d'oxydation à haute température (HTO). Les énergies d'activations associées à la pyrolyse et l'étape FD, obtenues par modélisation isoconversionnelle des données expérimentales, présentent des valeurs proches.L'étude du comportement thermique d'enrobés simplifiés incorporant des sels de nitrates (de sodium ou de magnésium) en condition anaérobie a permis de mettre en évidence une réactivité exothermique. Cette exothermicité est accrue pour le bitume contenant du nitrate de sodium. À de faibles degrés de conversion, le bitume incorporant du nitrate de sodium présente un comportement similaire à celui du bitume pur sollicité en condition anaérobie. Lorsque le degré de conversion augmente et que les nitrates sont disponibles pour être engagés dans les réactions d'oxydo-réduction, l'enrobé présente un comportement similaire à celui du bitume pur sollicité en condition aérobie. Ces résultats suggèrent un rôle de combustible pour le bitume et de comburant pour les nitrates

Thermal behavior of bituminized waste products

La production d'énergie d'origine nucléaire génère des effluents aqueux lors du traitement du combustible nucléaire usé. Le principe de retraitement de certains effluents repose sur l'insolubilisation des radionucléides qu'ils contiennent par co-précipitation, au moyen de sels ayant une affinité chimique particulière avec eux. La suspension résultante est qualifiée de « boue ». Cette boue est ensuite immobilisée dans une matrice bitumineuse au moyen d'un procédé d'extrusion en température, qui permet l'évaporation de l'eau contenue dans la boue et assure un mélange intime entre les sels ainsi recristallisés et la matrice. Les enrobés bitumineux résultants peuvent donc être décrits comme une dispersion de sels inorganiques au sein d'une matrice bitumineuse.Ces sels peuvent cependant présenter une réactivité exothermique suite à des interactions qui peuvent se produire avec la matrice bitumineuse ou entre les différentes espèces qui les constituent. Il est donc nécessaire d'apporter des éléments de connaissance à l'étude de sûreté relative au risque d'incendie inhérent aux déchets bitumés pendant toute leur durée de vie (transport, entreposage, stockage). Ainsi, ce travail vise à étudier le comportement des enrobés bitumineux sous sollicitation thermique externe afin d'obtenir des éléments de compréhension physico-chimiques et thermocinétiques liés à leur dégradation, dans l'objectif d'alimenter leur dossier de connaissances. Toutefois, les enrobés bitumineux incorporant une grande variété d'espèces chimiques, la compréhension de leur comportement thermique peut s'avérer complexe.Cette étude a donc été menée de manière préliminaire sur la matrice bitumineuse seule et des enrobés simulés incorporant uniquement des sels de nitrates. Des données expérimentales ont été acquises au moyen d'analyses thermiques (différentielle et thermogravimétrique), puis ont été modélisées par des méthodes isoconversionnelles afin d'obtenir les paramètres thermocinétiques associés au comportement des matériaux étudiés. La nature des gaz émis au cours de la sollicitation thermique a également été déterminée par couplage avec une chromatographie en phase gazeuse. Les matériaux ont été caractérisés avant et après sollicitation thermique, par diverses techniques de caractérisation du solide telles que la spectroscopie infrarouge, la diffraction des rayons X et la microscopie électronique à balayage.Lorsque le bitume pur est sollicité thermiquement en condition anaérobie, un événement endothermique causé par sa pyrolyse est observé. En condition aérobie, le bitume est le siège de plusieurs phénomènes : deux étapes exothermiques d'oxydation à basse température (LTO), suivies d'une étape endothermique de craquage par dépôt de combustible (FD) et une étape exothermique d'oxydation à haute température (HTO). Les énergies d'activations associées à la pyrolyse et l'étape FD, obtenues par modélisation isoconversionnelle des données expérimentales, présentent des valeurs proches.L'étude du comportement thermique d'enrobés simplifiés incorporant des sels de nitrates (de sodium ou de magnésium) en condition anaérobie a permis de mettre en évidence une réactivité exothermique. Cette exothermicité est accrue pour le bitume contenant du nitrate de sodium. À de faibles degrés de conversion, le bitume incorporant du nitrate de sodium présente un comportement similaire à celui du bitume pur sollicité en condition anaérobie. Lorsque le degré de conversion augmente et que les nitrates sont disponibles pour être engagés dans les réactions d'oxydo-réduction, l'enrobé présente un comportement similaire à celui du bitume pur sollicité en condition aérobie. Ces résultats suggèrent un rôle de combustible pour le bitume et de comburant pour les nitrates.The production of nuclear energy generates aqueous effluents during the treatment of spent nuclear fuel. The principle of reprocessing of certain effluents is based on the insolubilization of the radionuclides contained in these effluents by co-precipitation, using salts having a particular chemical affinity for them. The resulting suspension is called «sludge». This sludge is then immobilized in a bituminous matrix by means of a temperature extrusion process, which allows the evaporation of the water contained in the sludge and ensures an intimate mixing between the salts thus recrystallized and the matrix. The resulting bitumen mixes can therefore be described as a dispersion of inorganic salts within a bituminous matrix.However, these salts can present an exothermic reactivity following interactions that can occur with the bituminous matrix or between the different species that constitute them. It is therefore necessary to bring elements of knowledge to the safety study related to the risk of fire inherent in the bituminous waste throughout their life (transport, storage, disposal).Thus, this work aims to study the behavior of bituminous mixes under external thermal stress in order to obtain elements of physicochemical and thermokinetic understanding related to their degradation, with the objective of feeding their knowledge file. However, bituminous mixes incorporate a wide variety of chemical species, and understanding their thermal behavior can be complex.This study was therefore conducted in a preliminary manner on pure bitumen and on simulated bituminous mixes incorporating only nitrate salts. Experimental data were acquired by means of thermal analysis (differential and thermogravimetric) and then modeled by isoconversional methods in order to obtain the thermokinetic parameters associated with the behavior of the studied materials. The nature of the gases emitted during thermal stress was also determined by coupling with gas chromatography. The materials were characterized before and after thermal solicitation, by various solid-state characterization techniques such as infrared spectroscopy, X-ray diffraction and scanning electron microscopy.When pure bitumen is thermally stressed under anaerobic conditions, an endothermic event caused by its pyrolysis is observed. Under aerobic conditions, the bitumen is the site of several phenomena: two exothermic stages of low temperature oxidation (LTO), followed by an endothermic stage of cracking by fuel deposition (FD) and an exothermic stage of high temperature oxidation (HTO). The activation energies associated with the pyrolysis and FD step, obtained by isoconversional modeling of the experimental data, show close values.The study of the thermal behavior of simplified bitumen incorporating nitrate salts (of sodium or magnesium) under anaerobic conditions has revealed an exothermic reactivity. This exothermicity is increased for bitumen containing sodium nitrate. At low conversion degrees, the bitumen incorporating sodium nitrate shows a behavior similar to that of pure bitumen under anaerobic conditions. As the degree of conversion increases and nitrates are available to be engaged in redox reactions, bituminous mixes exhibit a behavior similar to that of pure bitumen stressed under aerobic conditions. These results suggest a role of fuel for the bitumen and oxidizer for the nitrates

Thermal behaviour of Bituminized Waste Products

International audienceIn France, bitumen was chosen during the 60's as an efficient embedding material for low and medium activity nuclear waste (sludges), owing to its high chemical inertness, impermeability, and confining ability. In the scope of the nuclear safety process, the thermal behavior of these bituminized sludges should be investigated during their whole life: it is thus crucial to study the physicochemical and thermochemical phenomena involved when they are exposed to heat. Thermogravimetric analysis coupled to differential thermal analysis was used to assess kinetic parameters related to reactions that occur when these materials are exposed to non-isothermal heat conditions, in various atmospheres (nitrogen, air). Firstly, a simplified system, pure bitumen, was studied. The degree of complexity of the studied system was then increased, by taking into account salts present in significant quantities in the nuclear sludges, in particular sodium nitrate.Under nitrogen atmosphere, pure bitumen shows a single thermal event, which is attributed to its pyrolysis. Under air, it undergoes three exothermal and one endothermal events that result from combustion and cracking reactions, respectively. Under nitrogen, bitumen embedding sodium nitrate shows an exothermic peak due to the combustion reaction of the bitumen by the nitrates. Activation energy for each event has been determined using several kinetic methods from non-isothermal heat conditions

Objective assessment of covid-19 severity affecting the vocal and respiratory system using a wearable, autonomous sound collar

International audienceIntroduction Since the outbreak began in January 2020, Covid-19 has affected more than 161 million people worldwide and resulted in about 3.3 million deaths. Despite efforts to detect human infection with the virus as early as possible, the confirmatory test still requires the analysis of sputum or blood with estimated results available within approximately 30 minutes; this may potentially be followed by clinical referral if the patient shows signs of aggravated pneumonia. This work aims to implement a soft collar as a sound device dedicated to the objective evaluation of the pathophysiological state resulting from dysphonia of laryngeal origin or respiratory failure of inflammatory origin, in particular caused by Covid-19. Methods In this study, we exploit the vibrations of waves generated by the vocal and respiratory system of 30 people. A biocompatible acoustic sensor embedded in a soft collar around the neck collects these waves. The collar is also equipped with thermal sensors and a cross-data analysis module in both the temporal and frequency domains (STFT). The optimal coupling conditions and the electrical and dimensional characteristics of the sensors were defined based on a mathematical approach using a matrix formalism. Results The characteristics of the signals in the time domain combined with the quantities obtained from the STFT offer multidimensional information and a decision support tool for determining a pathophysiological state representative of the symptoms explored. The device, tested on 30 people, was able to differentiate patients with mild symptoms from those who had developed acute signs of respiratory failure on a severity scale of 1 to 10. Conclusion With the health constraints imposed by the effects of Covid-19, the heavy organization to be implemented resulting from the flow of diagnostics, tests and clinical management, it was urgent to develop innovative and safe biomedical technologies. This passive listening technique will contribute to the non-invasive assessment and dynamic observation of lesions. Moreover, it merits further examination to provide support for medical operators to improve clinical management