1,720,996 research outputs found
Electron tomography of heterogeneous catalysts
No full textEMAG conferences are biennial events organised by the Electron Microscopy and Analysis Group of the Institute of Physics. The aim of the EMAG conference series is to provide a forum for discussion of the latest developments in instrumentation, techniques and applications of electron and scanning probe microscopies. EMAG 2003, the latest conference in this series, was held at the University of Oxford in September 2003. Electron microscopy is now a mainstay characterisation tool for solid state physicists and chemists as well as materials scientists. This volume is intended as a reference covering current developments in this field mainly in the UK but also further afield
Differentiation of tin oxides using electron energy-loss spectroscopy
Full text linkWe have used electron energy-loss spectroscopy to search for differences in the energy-loss near-edge structure of SnO, SnO 2, and an intermediate oxide, with a view to distinguishing them unambigously. We have found that the oxygen K edge exhibits clear differences that can be used for fingerprinting each phase. The oxygen edge appears at the same position for each phase whereas a chemical shift of the Sn M 4,5 edge of about 3.5 eV was observed between phases with Sn in 2+ and 4+ oxidation states. Both observations can be used to distinguish between the three phases, allowing their on-line identification within nanostructured materials.Fil: Moreno, Mario Sergio Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Egerton, R.F.. University of Alberta; CanadáFil: Midgley, P.A.. University of Cambridge; Reino Unid
THREE-DIMENSIONAL FIELD MODELS FOR REVERSE BIASED P-N JUNCTIONS.
Full text linkIn order to obtain reliable quantitative information on the electrostatic field associated with reverse-biased p-n junctions and on the distribution of dopants, the physics of the so-called ''dead layer'' and the influence of charged oxide layers are of paramount importance. To this purpose, experimental observations near the edge of a TEM sample can be useful. In these conditions, however, phase computations required to interpret the experimental results are very challenging as the problem is intrinsically three-dimensional. In order to cope with this problem, a mixed analytical-numerical approach is presented and discussed
High-resolution scanning transmission electron tomography and elemental analysis of zeptogram quantities of heterogeneous catalyst
No full textThe ability to visualize the three-dimensional structure of an object is of central importance in many branches of science and engineering. Recording an angular series of two-dimensional projections (images) and subsequently applying tomographic reconstruction methods has proven to be extremely successful at many lengthscales. Using scanning transmission electron microscopy (STEM) high angle annular dark field (HAADF) imaging, we describe how the three-dimensional distribution of bimetallic nanocatalysts (such as Ru10Pt2, diameter ~1 nm, mass 10-21 g) within mesoporous hosts may be precisely determined. Moreover, the simultaneous retrieval of the elemental composition (from electron-stimulated X-ray emission spectra) of individual catalytic nanoparticles was achieved
The chemical application of high-resolution electron tomography: Bright field or dark field?
No full textSingle-step conversion of dimethyl terephthalate into cyclohexanedimethanol with Ru5PtSn, a trimetallic nanoparticle catalyst
No full textHigh-performance nanocatalysts for single-step hydrogenations
No full textThis article discusses the usage of nanoporous silica support for anchoring bimetallic nanoparticle catalysts, which display high activity and selectivity in single-step hydrogenation reactions. Research reveals that the methodology is applicable to other solids possessing nanopores in the range of 3-30 nanometers, such as carbon nanoporous arrays for dispersing platinum nanoparticle
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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