Hydrothermal synthesis of nanostructured Cr-doped hematite with enhanced photoelectrochemical activity

[EN] Using the easily applicable hydrothermal method Cr-doped hematite thin films have been deposited polycrystalline on conductive glass substrates. The hydrothermal bath consisted of an aqueous solution containing a mixture of FeCl3.6H(2)O and NaNO3 at pH = 1.5. The samples were introduced in an autoclave and heated for a fixed time at a fixed temperature and then annealed in air at 550 degrees C. The concentration of the incorporated Cr atoms (Cr4+ ions) was controlled by varying the concentration of the Cr(ClO4)(3) precursor solution, varied from 0% to 20%. All samples followed morphological and structural studies using field-emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. Chronoamperometry measurements showed that Cr-doped hematite films exhibited higher photoelectrochemical activity than the undoped films. The maximum photocurrent density and incident photon conversion efficiencies (IPCE) were obtained for 16 at.% Cr-doped films. This high photoactivity can be attributed to both the large active surface area and increased donor density caused by Cr-doping in the alpha-Fe2O3 films. All samples reached their best IPCE at 400 nm. IPCE values for 16 at.% Cr-doped hematite films were thirty times higher than that of undoped samples. This high photoelectrochemical performance of Cr-doped hematite films is mainly attributed to an improvement in charge carrier properties. (C) 2017 Elsevier Ltd. All rights reserved.This work was supported by the Ministry of Higher Education and Scientific Research, Tunisia and Ministerio de Economia y Competitividad (ENE2016-77798-C4-2-R) and Generalitat Valenciana (Prometeus 2014/044).Bouhjar, F.; Mollar García, MA.; Chourou, M.; Marí, B.; Bessais, B. (2018). Hydrothermal synthesis of nanostructured Cr-doped hematite with enhanced photoelectrochemical activity. Electrochimica Acta. 260:838-846. https://doi.org/10.1016/j.electacta.2017.12.049S83884626

Coping with global environmental change, disasters and security : threats, challenges, vulnerabilities and risks

Book : vol 5 / hexagon series on human and environmental security and peac

It’s who you know that counts: Board connectedness and CSR performance

Highlights: We examine whether and how board connections affect the firm\u27s corporate social responsibilities (CSR). We find that board connectedness is positively associated with CSR performance. Our findings suggest firms that operate in a complex business environment or require more advising benefit more from a well-networked board. Firms that are poorly governed, have high stock return volatility, low market capitalization, or low institutional ownership tend to benefit more from the well-connected board when the cost of acquiring information is higher. In addition, we show that independent directors’ abilities to gather information and resources from their networks can facilitate the transmission of information. Overall, our study documents the informational advantage of a network as the predominant channel that allows a well-connected board to improve a firm’s CSR performance

Large-scale Nanostructure Simulations from X-ray Scattering Data On Graphics Processor Clusters

X-ray scattering is a valuable tool for measuring the structural properties of materialsused in the design and fabrication of energy-relevant nanodevices (e.g., photovoltaic, energy storage, battery, fuel, and carbon capture andsequestration devices) that are key to the reduction of carbon emissions. Although today's ultra-fast X-ray scattering detectors can provide tremendousinformation on the structural properties of materials, a primary challenge remains in the analyses of the resulting data. We are developing novelhigh-performance computing algorithms, codes, and software tools for the analyses of X-ray scattering data. In this paper we describe two such HPCalgorithm advances. Firstly, we have implemented a flexible and highly efficient Grazing Incidence Small Angle Scattering (GISAXS) simulation code based on theDistorted Wave Born Approximation (DWBA) theory with C++/CUDA/MPI on a cluster of GPUs. Our code can compute the scattered light intensity from any givensample in all directions of space; thus allowing full construction of the GISAXS pattern. Preliminary tests on a single GPU show speedups over 125x compared tothe sequential code, and almost linear speedup when executing across a GPU cluster with 42 nodes, resulting in an additional 40x speedup compared to usingone GPU node. Secondly, for the structural fitting problems in inverse modeling, we have implemented a Reverse Monte Carlo simulation algorithm with C++/CUDAusing one GPU. Since there are large numbers of parameters for fitting in the in X-ray scattering simulation model, the earlier single CPU code required weeks ofruntime. Deploying the AccelerEyes Jacket/Matlab wrapper to use GPU gave around 100x speedup over the pure CPU code. Our further C++/CUDA optimization deliveredan additional 9x speedup

Factors Underlying Technology Adoption in Academic Libraries in Kuwait

The study analysed factors shaping adoption of technology in academic libraries in Kuwait. The research was based on interviews conducted with library directors, staff and users, combined with observation and document analysis. A major aspect of the Kuwaiti context was a relative lack of financial restraints and an enthusiasm for technology within society as a whole. Other important influences shaping technology adoption specifically within libraries were the top down decision making style and a quest for prestige, in a context of a lack of library culture among users, shortage of professional staff and a strong, perhaps exaggerated, faith in technology as a solution to problems

Combining theory and experiment for X-ray absorption spectroscopy and resonant X-ray scattering characterization of polymers

An improved understanding of fundamental chemistry, electronic structure, morphology, and dynamics in polymers and soft materials requires advanced characterization techniques that are amenable to in situ and operando studies. Soft X-ray methods are especially useful in their ability to non-destructively provide information on specific materials or chemical moieties. Analysis of these experiments, which can be very dependent on X-ray energy and polarization, can quickly become complex. Complementary modeling and predictive capabilities are required to properly probe these critical features. Here, we present relevant background on this emerging suite of techniques. We focus on how the combination of theory and experiment has been applied and can be further developed to drive our understanding of how these methods probe relevant chemistry, structure, and dynamics in soft materials

"ETHNIKTAG: ART, CONSTRUCTION Et PARTICIPATION": Séminaire sémantique en contexte « le sens entre l'homme et les hommes » <br />Dir. Prof. Michael Rinn (Université de Bretagne occidentale), Prof. Ioannis kanellos (Ecole Nationale Supérieure des Télécommunication Bretagne)

National audienceNotre étude d' « Ethniktag » s'appuie sur une approche sémiotique de la communication interactive à travers la « re-construction » évolutive du sens. Nous mettrons en valeur les différentes possibilités de perception et d'évolution de la matière plastique.Nous allons dans un premier temps définir l'expression artistique « Ethniktag » et sa logique de construction évolutive.Ensuite, nous verrons la mise en espace de ces productions sur le web 2.0 par l'étude du fonctionnement en réseau de deux Blogs Ethniktag : « Ethniktag est une expression artistique mélangeant Tag et Graf avec une plastique ethnique. Des inscriptions en acrylique, des dessins et des graphiques proches de l'écriture sont griffonnés sur un support non-urbain : toile collée sur bois. »Ethniktag est une conception de l'art développant une logique de construction qui s'appuie sur des articulations mathématiques, géométriques et topologiques (addition, multiplication, soustraction, division, déplacement, rotation, pivotement...) afin de former des figures symétriques, asymétriques, quasi cristallines asymptotiques. Cet art conceptuel met en place un « signifiant pluriel » évoluant en 5 parcours :- 1er cursus : « le modus operandi »- 2ème cursus : l'empreinte- 3ème cursus : les chorégraphies picturales ou les variations topologiques- 4ème cursus : le montage plastique virtuel par des règles mathématiques et géométriques- 5ème cursus : le montage plastique réel par l'application de règles mathématiques et topologique

: Conférence présentée dans le cadre de la MSHB (Maison des Sciences Humaines de Bretagne), Groupe de recherche « Analyse des discours de prévention en santé publique » sous la direction du Prof. Michael Rinn (Université de Bretagne Occidentale) et Prof. Marcel Calvez (Université Rennes II)

International audienceSuperman a été créé par Jerry Siegel et Joe Shuster comme réponse fantastique face à un problème réél la montée de l'antisémitisme lors de la 2ème guerre mondiale. Nous avons proposé une analyse sémiotique de cet héros dans un double corpus : les campagnes sociales de l'association de lutte contre le sida AIDES et les campagnes commerciales de VW, Warner Bros et Vespa.Superman est un héros qui développe un couble parcours :l'invulnérabilité en marketing commercial avec une amplification des compétences, performances positives et parcours narratif itératif ; et la vulnérabilité en marketing social avec une diminution des compétences, des performances négatives et un parcours narratif inédit