Correlation between the morphology of cobalt oxalate precursors and the microstructure of metal cobalt powders and compacts

Metal cobalt powders of well-controlled size and morphology were synthesized by thermal decomposition under hydrogen of precipitated cobalt oxalates. Green compacts were prepared by uniaxial pressing of metal powders at 290 MPa. The bending green strength of the metal compacts was measured. A precipitation from ammonium oxalate and oxalic acid gives rise to the formation of β-CoC2O4·2H2O particles of parallelepipedic and acicular morphology, respectively. An increase in the length to diameter ratio of the precursor particles favours an entanglement of the elementary grains during the thermal decomposition. Therefore, irregular and rough metal particles have been obtained. This specific morphology favours a mechanical interlocking of the particles during the compaction, leading to high values of green density and green strength of the metal compacts

SEPARATION OF THE INTER- AND INTRA-PARTICLE POROSITY IN IMAGES OF POWDER COMPACTS

Powder metallurgy is a highly developed and cheap method of manufacturing reliable materials, either metallic, ceramic or composite. This process was used to make green compacts of iron powders with a high porosity level. This study is part of a project aimed at describing the relationships between mechanical properties and morphological features of such compacts, with particular attention paid to the shape of the grains and the compaction pressure. In this report, a method is proposed to separate the intra grain porosity from the cavities located between particles. The approach is based on the covariogram of images obtained from the surface of the compacts by means of a laser roughometer. To achieve this separation, a model of the structure is proposed which assumes that the distributions of the grains and of the intra-particle cavities are random and independent. Each distribution is characterized by two parameters. A satisfactory agreement is obtained between experimental and calculated covariograms after identification of these parameters

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Chemical and structural evolution of nano-oxides from mechanical alloying to consolidated ferritic oxide dispersion strengthened steel

International audienceFerritic Oxides Dispersion Strengthened (ODS) steels are of great interest for nuclear fission and fusion power plants. The nano-oxides embedded into the matrix provide the main contribution to the ODS steel strength. Understanding of the precipitation mechanism of ODS steels is thus critical for optimizing the fabrication process, involving Mechanical Alloying (MA) of Fe-14Cr, Y2O3 and TiH2 powders. In this study, results from small-angle X-ray and neutron scattering, atom probe tomography and electron microscopy have been combined to investigate the nano-oxides evolution throughout the whole consolidation thermal treatment until 1100 °C. After MA clusters are observed, composed of Y, O and Ti. During heating these clusters grow and new ones nucleate, together with a sequential enrichment in Ti (from as-MA to 700 °C) and Y (between 900 and 1100 °C). A small quantity of Al is also found in the nano-oxides between 700 and 1100 °C. At 1100 °C the nano-oxides are found to be mainly Y2Ti2O7 and subsequently progressively transform to Y2TiO5 during isothermal holding. Nano-oxides display however an unchanged extremely low coarsening rate, demonstrating the outstanding stability of both Y2Ti2O7 and Y2TiO5 at 1100 °C

Paysages en réseaux

Diverses lois au cours de ces dernières décennies ont impulsé un renouveau et densifié l’affluence du paysage sur la scène politique, sociétale et scientifique. Elles ont concouru à l’émergence de savoirs scientifiques et techniques tout comme de pratiques professionnelles renouvelés au regard des nouveaux impératifs d’amélioration des connaissances, de la transversalité des politiques publiques et de la formation et montée en compétences professionnelles que porte la politique du paysage à l’échelle nationale. Pour autant, les politiques du paysage impliquent une visée démocratique et nécessitent de nouveaux dispositifs pour partager une culture toujours inscrite à la croisée des regards, favorisant ainsi une prise de distance par rapport au monde confiné et traditionnel de l’art des jardins d’une part et du seul savoir expert de l’autre. Le paysage se serait-il démocratisé ? C’est une des questions posées par ce numéro spécial « Paysage en réseau(x) ». Cette évolution nécessaire a amené, parfois sans le dire explicitement, à organiser et promouvoir des formes de partage, de mise en débat des enjeux des paysages à des échelles locales qui s’appuient sur des modalités de médiation dont les réseaux font sans nul doute partie. Ces réseaux, interprofessionnels et interdisciplinaires, seraient dès lors un vecteur et l’un des passages nécessaires pour renforcer la territorialisation des politiques du paysage qui jusqu’alors restaient fortement centralisées. Ce numéro vise à nourrir cette réflexion, illustrée par de nombreux exemples pris pour l’essentiel dans le sud-ouest de l’Europe. Le numéro thématique est complété par trois articles. Le premier propose de saisir l’atmosphère de Lisbonne en mobilisant largement poésies et odes à cette ville. Le deuxième article étudie comment l’événement touristique permet de renforcer l’attractivité d’une destination et d’accroître sa notoriété tout en étant un levier du projet urbain. Il propose de s’interroger sur le sens des aménagements fluviaux mis en place à la faveur de ce type d’événements dans deux villes bien distinctes, Québec et Saragosse. Enfin, un dernier article analyse la dissonance et la conflictualité qui existe entre projet urbain et projets d’habitants dans le cadre de l’aménagement culturel de Bordeaux

Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

Background Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation. Methods WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109. Findings Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0–4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2–6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital. Interpretation In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates

Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

Background: Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation. Methods: WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109. Findings: Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0-4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2-6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital. Interpretation: In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates. Funding: European Society of Intensive Care Medicine, European Respiratory Society

Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

International audienceBackground: Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation. Methods: WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109. Findings: Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0–4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2–6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital. Interpretation: In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates. Funding: European Society of Intensive Care Medicine, European Respiratory Society