ZnO powders as multi-facet single crystals

Oxides are most commonly found in divided forms with properties difficult to control since their crystallographic orientations usually escape analysis. To overcome this an appropriate model system can be provided by ZnO smoke which, obtained by combustion of Zn in air, exhibits nanoparticles with well-defined surface facets. The present work focuses on the interaction of water with ZnO smokes by combining density functional theory based simulations and infrared spectroscopy measurements with applied pressures from 10(-7) to 1 mbar. We demonstrate that the use of ultra-high vacuum allows the analysis of the very first stages of the adsorption, and report on water structures on ZnO(11 (2) over bar0) for the first time. We further show that ZnO powders behave as multi-facet single crystals involving (10 (1) over bar 10), (11 (2) over bar0), (0001), and (000 (1) over bar) surfaces with the polar orientations corresponding to 25% of the total surface area. A great deal of cross-agreements between experimental results and simulation provides a simple approach for the examination of hydroxylated/hydrated ZnO smokes and can be widely applied on other ZnO-related powders

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Association of respiratory symptoms and lung function with occupation in the multinational Burden of Obstructive Lung Disease (BOLD) study

Background Chronic obstructive pulmonary disease has been associated with exposures in the workplace. We aimed to assess the association of respiratory symptoms and lung function with occupation in the Burden of Obstructive Lung Disease study. Methods We analysed cross-sectional data from 28 823 adults (≥40 years) in 34 countries. We considered 11 occupations and grouped them by likelihood of exposure to organic dusts, inorganic dusts and fumes. The association of chronic cough, chronic phlegm, wheeze, dyspnoea, forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1)/FVC with occupation was assessed, per study site, using multivariable regression. These estimates were then meta-analysed. Sensitivity analyses explored differences between sexes and gross national income. Results Overall, working in settings with potentially high exposure to dusts or fumes was associated with respiratory symptoms but not lung function differences. The most common occupation was farming. Compared to people not working in any of the 11 considered occupations, those who were farmers for ≥20 years were more likely to have chronic cough (OR 1.52, 95% CI 1.19–1.94), wheeze (OR 1.37, 95% CI 1.16–1.63) and dyspnoea (OR 1.83, 95% CI 1.53–2.20), but not lower FVC (β=0.02 L, 95% CI −0.02–0.06 L) or lower FEV1/FVC (β=0.04%, 95% CI −0.49–0.58%). Some findings differed by sex and gross national income. Conclusion At a population level, the occupational exposures considered in this study do not appear to be major determinants of differences in lung function, although they are associated with more respiratory symptoms. Because not all work settings were included in this study, respiratory surveillance should still be encouraged among high-risk dusty and fume job workers, especially in low- and middle-income countries.publishedVersio

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation

Réactivité de nanoparticules d'oxydes d'orientations définies

The analysis of adsorption from the first stage to saturation is necessary to understand gas/solid interactions. This is the motivation for surface analysis under vacuum. The common approach of dispersed materials surfaces is incomplete since working pressures, that are high enough to achieve reasonable reaction times, do not allow studies of powder surfaces from bare to fully covered. The aim of the present work is to examine the successive changes of ZnO, MgO and ZnxMg1-xO nanopowders upon exposure to water or hydrogen from UHV to the ambient by FTIR. It is shown that ZnO smokes behave in a same way as a collection of single crystals which exhibit (0001), (0001̅), (101̅0) and (112̅0) faces with a non-polar/polar ratio of 75/25. Combining FTIR with XPS and TPD techniques, three stages of hydroxylation were identified on MgO smokes: point defects (10-8 mbar), steps (10-6 mbar) then terraces (> 10-5 mbar). Results indicate a reorganisation of surface structure showing that water adsorption on MgO(100) is an irreversible process. The common model of MgO as a series of (100) facets is questioned. At low concentrations of zinc, the mixed oxide ZnxMg1-xO consists of crystals with similar structure as MgO. A segregation of Zn2+ toward low coordinated surface sites is suggested to explain the changes in reactivity of the ZnxMg1-xO with respect to water and hydrogen at low coverages. Furthermore, the mixture ZnO-MgO produced by combustion of ZnMg alloy combines the antibacterial properties of ZnO and the biocompatibility of MgO, interesting for potential applications. The overall results demonstrate the relevance of the study of powders in ultra-high vacuum conditions.La connaissance d’un système gaz/solide requiert l’analyse de l’adsorption, du premier stade jusqu’à saturation. C’est la motivation de l’analyse des surfaces sous vide. L’approche des surfaces divisées est souvent tronquée. Pratiquée à des pressions suffisamment élevées pour être compatible avec un temps de réaction raisonnable, elle ne permet pas l'analyse de la surface nue à la monocouche. L’objectif du présent travail a été d’établir une continuité d’observation par FTIR, de l’UHV à la pression ambiante, de poudres de MgO, ZnO et ZnxMg1-xO exposées à l’eau ou à l’hydrogène. Il a été montré que les fumées de ZnO se comparent à des cristaux présentant les faces (0001), (0001̅), (101̅0), (112̅0), avec un rapport non-polaire/polaire de 75/25. Par FTIR combinée à la photoémission et à la désorption thermique, trois étapes de l’hydroxylation des fumées de MgO ont été identifiées : défauts ponctuels (10-8 mbar), marches (10-6 mbar) puis terrasses (> 10-5 mbar), avec une restructuration qui prouve que l’eau change la structure de surface de MgO. La représentation commune de la surface de MgO par une suite de facettes (100) est mise en cause. Aux faibles teneurs en zinc, l’oxyde mixte ZnxMg1-xO est formé de cristallites cubiques de même structure que MgO. Le zinc en substitution tend à ségréger vers les sites de basse coordinence où il affecte les propriétés d’adsorption d’eau et d’hydrogène. Par ailleurs, le mélange ZnO-MgO obtenu par combustion d’alliage ZnMg offre une possibilité d’application grâce aux propriétés bactéricides de ZnO et de faible toxicité de MgO. L’ensemble des résultats montre la pertinence de l’étude des poudres pratiquée dans les conditions de l’UHV

Reactivity of oxyde nanoparticles with defined orientations

La connaissance d’un système gaz/solide requiert l’analyse de l’adsorption, du premier stade jusqu’à saturation. C’est la motivation de l’analyse des surfaces sous vide. L’approche des surfaces divisées est souvent tronquée. Pratiquée à des pressions suffisamment élevées pour être compatible avec un temps de réaction raisonnable, elle ne permet pas l'analyse de la surface nue à la monocouche. L’objectif du présent travail a été d’établir une continuité d’observation par FTIR, de l’UHV à la pression ambiante, de poudres de MgO, ZnO et ZnxMg1-xO exposées à l’eau ou à l’hydrogène. Il a été montré que les fumées de ZnO se comparent à des cristaux présentant les faces (0001), (0001̅), (101̅0), (112̅0), avec un rapport non-polaire/polaire de 75/25. Par FTIR combinée à la photoémission et à la désorption thermique, trois étapes de l’hydroxylation des fumées de MgO ont été identifiées : défauts ponctuels (10-8 mbar), marches (10-6 mbar) puis terrasses (> 10-5 mbar), avec une restructuration qui prouve que l’eau change la structure de surface de MgO. La représentation commune de la surface de MgO par une suite de facettes (100) est mise en cause. Aux faibles teneurs en zinc, l’oxyde mixte ZnxMg1-xO est formé de cristallites cubiques de même structure que MgO. Le zinc en substitution tend à ségréger vers les sites de basse coordinence où il affecte les propriétés d’adsorption d’eau et d’hydrogène. Par ailleurs, le mélange ZnO-MgO obtenu par combustion d’alliage ZnMg offre une possibilité d’application grâce aux propriétés bactéricides de ZnO et de faible toxicité de MgO. L’ensemble des résultats montre la pertinence de l’étude des poudres pratiquée dans les conditions de l’UHV.The analysis of adsorption from the first stage to saturation is necessary to understand gas/solid interactions. This is the motivation for surface analysis under vacuum. The common approach of dispersed materials surfaces is incomplete since working pressures, that are high enough to achieve reasonable reaction times, do not allow studies of powder surfaces from bare to fully covered. The aim of the present work is to examine the successive changes of ZnO, MgO and ZnxMg1-xO nanopowders upon exposure to water or hydrogen from UHV to the ambient by FTIR. It is shown that ZnO smokes behave in a same way as a collection of single crystals which exhibit (0001), (0001̅), (101̅0) and (112̅0) faces with a non-polar/polar ratio of 75/25. Combining FTIR with XPS and TPD techniques, three stages of hydroxylation were identified on MgO smokes: point defects (10-8 mbar), steps (10-6 mbar) then terraces (> 10-5 mbar). Results indicate a reorganisation of surface structure showing that water adsorption on MgO(100) is an irreversible process. The common model of MgO as a series of (100) facets is questioned. At low concentrations of zinc, the mixed oxide ZnxMg1-xO consists of crystals with similar structure as MgO. A segregation of Zn2+ toward low coordinated surface sites is suggested to explain the changes in reactivity of the ZnxMg1-xO with respect to water and hydrogen at low coverages. Furthermore, the mixture ZnO-MgO produced by combustion of ZnMg alloy combines the antibacterial properties of ZnO and the biocompatibility of MgO, interesting for potential applications. The overall results demonstrate the relevance of the study of powders in ultra-high vacuum conditions