Synthèse de couches ultra-minces de siliciures sur silicium cristallin et endommagé étudiée par microscopie et profilométrie en profondeur

Les siliciures métalliques constituent un élément crucial des contacts électriques des transistors que l'on retrouve au coeur des circuits intégrés modernes. À mesure qu'on réduit les dimensions de ces derniers apparaissent de graves problèmes de formation, liés par exemple à la limitation des processus par la faible densité de sites de germination. L'objectif de ce projet est d'étudier les mécanismes de synthèse de siliciures métalliques à très petite échelle, en particulier le NiSi, et de déterminer l’effet de l’endommagement du Si par implantation ionique sur la séquence de phase. Nous avons déterminé la séquence de formation des différentes phases du système Ni-Si d’échantillons possédant une couche de Si amorphe sur lesquels étaient déposés 10 nm de Ni. Celle-ci a été obtenue à partir de mesures de diffraction des rayons X résolue en temps et, pour des échantillons trempés à des températures critiques du processus, l’identité des phases et la composition et la microstructure ont été déterminées par mesures de figures de pôle, spectrométrie par rétrodiffusion Rutherford et microscopie électronique en transmission (TEM). Nous avons constaté que pour environ la moitié des échantillons, une réaction survenait spontanément avant le début du recuit thermique, le produit de la réaction étant du Ni2Si hexagonal, une phase instable à température de la pièce, mélangée à du NiSi. Dans de tels échantillons, la température de formation du NiSi, la phase d’intérêt pour la microélectronique, était significativement abaissée.Currently metal silicide constitutes a crucial component in the formation of electrical contacts for transistors that forms the heart of modern day integrated circuits. As we reduce the dimensions of the latter, we are faced with serious problems of formation, related for example to the process limitation due to the weak density of germination sites. The objective of this project is to study at small scale the synthesis mechanisms of metal silicide, in particular NiSi, and to determine the effect of Si implantation damage on the phase sequence. We have determined the different phase sequences of the Ni-Si system for samples composed of a 10 nm Ni surface layer deposited on a-Si. These were obtained by time resolved x-ray diffraction (TR-XRD) measurements. As for samples quenched at critical temperatures we identified the different phases, their composition and their microstructure were determined by pole figures, Rutherford back scattering (RBS) spectrometry and transmission electron microscopy (TEM). We noted that for approximately half the samples, a spontaneous reaction happened before annealing. The result of the reaction was hexagonal Ni2Si, a phase unstable at room temperature, mixed with NiSi. In theses samples, the temperature of formation for the phase of interest, the NiSi, was lower

Links Between Metabolic and Structural Changes in the Brain of Cognitively Normal Older Adults: A 4-Year Longitudinal Follow-Up

We aimed to longitudinally assess the relationship between changing brain energy metabolism (glucose and acetoacetate) and cognition during healthy aging. Participants aged 71 ± 5 year underwent cognitive evaluation and quantitative positron emission tomography (PET) and magnetic resonance imaging (MRI) scans at baseline (N = 25) and two (N = 25) and four (N = 16) years later. During the follow-up, the rate constant for brain extraction of glucose (Kglc) declined by 6%–12% mainly in the temporo-parietal lobes and cingulate gyri (p ≤ 0.05), whereas brain acetoacetate extraction (Kacac) and utilization remained unchanged in all brain regions (p ≥ 0.06). Over the 4 years, cognitive results remained within the normal age range but an age-related decline was observed in processing speed. Kglc in the caudate was directly related to performance on several cognitive tests (r = +0.41 to +0.43, allp ≤ 0.04). Peripheral insulin resistance assessed by the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly inversely related to Kglc in the thalamus (r = −0.44, p = 0.04) and in the caudate (r = −0.43, p = 0.05), and also inversely related to executive function, attention and processing speed (r = −0.45 to −0.53, all p ≤ 0.03). We confirm in a longitudinal setting that the age-related decline in Kglc is directly associated with declining performance on some tests of cognition but does not significantly affect Kacac

Upregulated IL-32 expression and reduced gut short chain fatty acid caproic acid in people living with HIV with subclinical atherosclerosis

Despite the success of antiretroviral therapy (ART), people living with HIV (PLWH) are still at higher risk for cardiovascular diseases (CVDs) that are mediated by chronic inflammation. Identification of novel inflammatory mediators with the inherent potential to be used as CVD biomarkers and also as therapeutic targets is critically needed for better risk stratification and disease management in PLWH. Here, we investigated the expression and potential role of the multi-isoform proinflammatory cytokine IL-32 in subclinical atherosclerosis in PLWH (n=49 with subclinical atherosclerosis and n=30 without) and HIV- controls (n=25 with subclinical atherosclerosis and n=24 without). While expression of all tested IL-32 isoforms (α, β, γ, D, ϵ, and θ) was significantly higher in peripheral blood from PLWH compared to HIV- controls, IL-32D and IL-32θ isoforms were further upregulated in HIV+ individuals with coronary artery atherosclerosis compared to their counterparts without. Upregulation of these two isoforms was associated with increased plasma levels of IL-18 and IL-1β and downregulation of the atheroprotective protein TRAIL, which together composed a unique atherosclerotic inflammatory signature specific for PLWH compared to HIV- controls. Logistic regression analysis demonstrated that modulation of these inflammatory variables was independent of age, smoking, and statin treatment. Furthermore, our in vitro functional data linked IL-32 to macrophage activation and production of IL-18 and downregulation of TRAIL, a mechanism previously shown to be associated with impaired cholesterol metabolism and atherosclerosis. Finally, increased expression of IL-32 isoforms in PLWH with subclinical atherosclerosis was associated with altered gut microbiome (increased pathogenic bacteria; Rothia and Eggerthella species) and lower abundance of the gut metabolite short-chain fatty acid (SCFA) caproic acid, measured in fecal samples from the study participants. Importantly, caproic acid diminished the production of IL-32, IL-18, and IL-1β in human PBMCs in response to bacterial LPS stimulation. In conclusion, our studies identified an HIV-specific atherosclerotic inflammatory signature including specific IL-32 isoforms, which is regulated by the SCFA caproic acid and that may lead to new potential therapies to prevent CVD in ART-treated PLWH

6. Les revues systématiques mixtes

Les revues systématiques mixtes sont des revues de littérature utilisant une approche systématique pour combiner des études quantitatives, qualitatives et mixtes. Elles sont de plus en plus populaires, car elles permettent une compréhension approfondie des phénomènes et interventions complexes. Dans ce chapitre, huit étapes de la revue systématique mixte sont présentées : (a) formulation d’une question de recherche, (b) définition des critères d’éligibilité, (c) identification des sources documentaires, (d) (élaboration de stratégie de recherche documentaire,(e) sélection des études pertinentes, (f) évaluation de la qualité des études retenues, (g) extraction des données des études retenues et (h) synthèse des données extraites. Ces étapes sont illustrées à partir d’un exemple tiré d’une revue systématique mixte sur les conséquences non intentionnelles d’une intervention reposant sur le financement basé sur les résultats. De plus, afin de guider l’intégration des données quantitatives et qualitatives, quatre devis de synthèse sont présentés : (a) devis de synthèse convergent avec intégration au niveau des données, (b) devis de synthèse convergent avec intégration au niveau des résultats de synthèse, (c) devis de synthèse convergent avec intégration au niveau de l’interprétation et (d) devis de synthèse séquentiel. Enfin, quelques défis des revues systématiques mixtes sont présentés dans l’analyse réflexive.Systematic mixed studies reviews are literature reviews using a systematic approach to combine quantitative, qualitative and mixed methods studies. They are growing in popularity owing to their potential to provide a deep understanding of complex health interventions and problems. In this chapter, eight steps of systematic mixed studies reviews are presented: (a) formulate a review question, (b) define eligibility criteria, (c) identify sources of information, (d) select relevant studies, (e) appraise the quality of studies, (f) extract data and (g) synthesize extracted data from included studies. These steps are illustrated using an example of systematic mixed studies review on unintended consequences of performance-based financing intervention. Also, to provide guidance on how to combine qualitative and quantitative evidence, four synthesis designs are presented: (a) data-based convergent synthesis design, (b) results-based convergent synthesis design, (c) parallel-results convergent synthesis design, and (d) sequential synthesis design. This chapter ends with some challenges that can be encountered when conducting a systematic mixed studies review.Las revisiones sistemáticas de estudios mixtos son revisiones de la literatura que utilizan un enfoque sistemático para combinar estudios cuantitativos, cualitativos y de métodos mixtos. Su popularidad va en aumento debido a su potencial para proporcionar una comprensión profunda de las intervenciones y los problemas de salud complejos. En este capîtulo se presentan ocho pasos de revisiones sistemáticas de estudios mixtos : (a) formular una pregunta de revisión, (b) definir los criterios de elegibilidad, (c) identificar las fuentes de información, (d) seleccionar los estudios pertinentes,(e) evaluar la calidad de los estudios, (f) extraer los datos y(g) sintetizar los datos extraídos de los estudios incluidos. Estos pasos se ilustran con un ejemplo de revisión sistemática de estudios mixtos sobre las consecuencias no deseadas de la intervención financiera basada en el desempeño. Además, para proporcionar orientación sobre cómo combinar la evidencia cualitativa y cuantitativa, se presentan cuatro diseños de síntesis : a) diseño de sintesis convergente basado en datos, b) diseño de sintesis convergente basado en resultados, c) diseño de sintesis convergente basado en resultados paralelos, y d) diseño de síntesis secuencial. Este capítulo termina con algunos de los desafíos que se pueden encontrar al realizar una revisión sistemática de estudios mixtos

Mapping of initiatives to increase membership in mutual health organizations in Benin

Abstract Introduction Mutual health organizations (MHO) have been implemented across Africa to increase access to healthcare and improve financial protection. Despite efforts to develop MHOs, low levels of both initial enrolment and membership renewals continue to threaten their financial viability. The purpose of this study was to map initiatives implemented to increase the pool of MHO members in Benin. Methods A multiple case study was conducted to assess MHOs supported by five major promoters in Benin. Three months of fieldwork resulted in 23 semi-structured interviews and two focus groups with MHO promoters, technicians, elected members, and health professionals affiliated with the MHOs. Fifteen non-structured interviews provided additional information and a valuable source of triangulation. Results MHOs have adopted a wide range of initiatives targeting different entry points and involving a variety of stakeholders. Initiatives have included new types of collective health insurance packages and efforts to raise awareness by going door-to-door and organizing health education workshops. Different types of partnerships have been established to strengthen relationships with healthcare professionals and political leaders. However, the selection and implementation of these initiatives have been limited by insufficient financial and human resources. Conclusions The study highlights the importance of prioritizing sustainable strategies to increase MHO membership. No single MHO initiative has been able to resolve the issue of low membership on its own. If combined, existing initiatives could provide a comprehensive and inclusive approach that would target all entry points and include key stakeholders such as household decision-makers, MHO elected members, healthcare professionals, community leaders, governmental authorities, medical advisors, and promoters. There is a need to evaluate empirically the implementation of these interventions. Mechanisms to promote dialogue between MHO stakeholders would be useful to devise innovative strategies, avoid repeating unsuccessful ones, and develop a coordinated plan to promote MHOs.</p

Adiposity and pulmonary function: Relationship with body fat distribution and systemic inflammation

Purpose: Obesity is associated with changes in pulmonary function and increased systemic inflammation. We explored the relationships among adiposity, body fat distribution indices, serum inflammatory markers and pulmonary function. Methods: This was a post-hoc cross-sectional analysis that included subjects who had previously participated in randomized studies on obesity at our centre. Non-smoking sedentary men (282 subjects, mean age 42) without respiratory diseases were studied. BMI, waist circumference (WC), visceral and subcutaneous adipose tissue (AT), lung residual volume (RV), vital capacity (VC) and expiratory reserve volume (ERV) were measured. Serum leptin, adiponectin, tumor necrosis factor alpha (TNF-α) and high-sensitive C-reactive protein (hs-CRP) levels were measured. Results: In subjects with metabolic syndrome (n=124), percent predicted ERV and RV were significantly associated with BMI (ERV: r=-0.19, p=0.02, RV: r=-0.28, p=0.0007), WC (r=-0.20, p=0.02, r=-0.26, p=0.002), visceral (r=-0.22, p=0.007, r=-0.25, p=0.002) and subcutaneous AT (r=-0.19, p=0.02, r=-0.28, p=0.0007). Percent predicted VC correlated with visceral (r=-0.20, p=0.02) and subcutaneous AT (r=-0.18, p=0.03). Leptin was strongly correlated with BMI (MS/no-MS: r=0.52, p=0.0005/r=0.62, p < 0.0001), WC (r=0.41, p=0.008/r=0.49, p < 0.0001), visceral (r=0.27,p=0.09/0.43, p < 0.0001) and subcutaneous AT (r=0.46, p=0.003/r=0.66, p < 0.0001), while adiponectin levels were associated in subjects with no-MS with WC (r=-0.20, p=0.01), visceral (r=-0.22, p=0.008), and subcutaneous AT (r=-0.17, p=0.05). When adjusted for anthropometric measures, neither ERV, RV nor VC was significantly correlated with serum leptin, adiponectin, TNF-α, or hs-CRP levels. Conclusion: These results suggest that the influence of obesity on lung function in healthy subjects is mostly mediated by mechanical factors. Furthermore, not only BMI but also the pattern of fat distribution should be considered when studying associations between adiposity indices and mechanical or inflammatory variables potentially associated with pulmonary function