1,720,981 research outputs found
Study of metal surfaces in operando conditions by means of near-ambient-pressure scanning tunneling microscopy
Full text linkTitle: Study of metal surfaces in operando conditions by means of near-ambient- pressure scanning tunneling microscopy Author: Petr Dlabaja Department: Department of Surface and Plasma Science Supervisor: RNDr. Peter Matvija, Ph.D., Department of Surface and Plasma Science Abstract: The thesis covers investigation of monocrystalline surfaces of metals Cu(111) and Pt(111) in high pressures. These surfaces were exposed to oxygen and carbon monoxide gasses of pressures between 1 × 10−10 mbar and 5 mbar. Changes in the structure of the surfaces was monitored using scanning tunneling microscopy, low-energy electron diffraction and X-ray photoelectron spectroscopy. Acquired results showed that reactive gasses at pressures ≈ 5 mbar affect the structure of the surfaces more prominently than the same gasses of lower pres- sures. The surface of Cu(111) at room temperature and 5 mbar pressure of O2 strongly oxidized. The surface of Pt(111) at pressure 5 mbar of gass O2 oxidized only locally, under the influence of the STM tip. Increased pressure of carbon mo- noxide induces creation of nanometric clusters on the surface of Cu(111), which agglomerate into small islands. These islands are distributed evenly on the whole surface of Cu(111). In contrast increased pressure of carbon monoxide mainly changes the shapes of..
Atomic-Scale View of Water Chemistry on Nanostructured Iron Oxide Films
No full textThe interaction of water with solid surfaces is crucial for a wide range of disciplines, including catalysis, environmental science, corrosion, geology, and biology. In this study, we present a combined experimental and theoretical investigation that elucidates the interaction of water with a model iron oxide surface under near ambient conditions (i.e., room temperature and water vapor in the mbar range). Our findings reveal that surface hydroxylation can be controlled at the nanoscale by the local properties of the oxide film, such as local rumpling and electrostatic potential. The iron oxide surface presents alternating hydrophilic and hydrophobic domains, creating after water exposure a hexagonal pattern with a pitch of approximately 3 nm, where the highly hydroxylated regions act as nucleation centers for nanoconfined water molecule clusters
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
Interaction of simple organic molecules with cerium oxide surfaces
No full textIn this work we prepare well defined thin epitaxy layers of cerium oxide (CeO2) and cerium oxide with nanoparticles of platinum (CeO2/Pt) on the Cu(111) substrate. The surface was characterized before exposition by ethanol molecules, after exposition, after annealing at 725 K in UHV and after annealing in O2 atmosphere at pressure p = 5×10−7 mbar at 725 K by LEED (low-electron energy diffraction), XPS (x-ray photoelectron di- ffraction) and STM (scanning tunnelling microscopy). Layer of CeO2/Pt was also exposed to 2 mbar of methane and 2, 5 mbar of methane and oxygen mixture in a ratio 1:1. This layer was observed by NAP-STM in higher pressures. In this work we have discovered that a disordered layer is formed on the CeO2 surface after exposure to the mixture of air and ethanol. Interaction of adsorbed molecules and ceria is increased during annealing in UHV, when carbon desorbs from the surface and cerium is reduced. After annealing in oxygen cerium is reoxidized. However, even after reoxidation, the surface contains a large number of defects of various types. Significant increase in brightness was observed in the proximity of domain interfaces of cerium oxide layers during scanning at higher pressures of oxygen. This effect will be studied more closely in our future experiments. 1Práca sa zaoberá tenkými epitaxnými vrstvami oxidu céru (CeO2) a oxidu céru s nanočasticami platiny (CeO2/Pt) pripravenými na substráte Cu(111). Povrch vrstiev bol charakterizovaný pred expozíciou molekulami etanolu, po expozícii, po ohreve v UHV na 725 K a po ohreve na 725 K v O2 atmosfére pri tlaku p = 5 × 10−7 mbar pomocou metód LEED (nízko-energetická elektrónová difrakcia), XPS (röntgenová fotoelektrónová spektroskopia) a STM (skenovacia tunelová mikroskopia). Vrstvu CeO2/Pt sme okrem etanolu vystavili aj 2 mbar metánu a 2, 5 mbar zmesi metánu a kyslíku v pomere 1:1. Tento povrch sme pozorovali pomocou metódy NAP-STM za zvýšeného tlaku plynov. Zo získaných výsledkov vyplynulo, že jednoduché organické molekuly pri izbovej tep- lote na povrchu vytvárajú súvislú neusporiadanú vrstvu. Výraznejšie vrstva CeO2 s or- ganickými molekulami interaguje počas ohrevu v UHV, kedy atómy uhlíku desorbujú z povrchu a cér sa redukuje. Po ohreve v kyslíku sa cér reoxiduje. Aj po reoxidácii však povrch obsahuje veľké množstvo defektov rôzneho typu. Behom skenovania povrchu za prítomnosti zmesi kyslíku a metánu bolo pozorované výrazné zvýšenie jasu okolia doménových rozhraní vrstvy oxidu céru. Tento efekt bude podrobnejšie skúmaný v našich budúcich experimentoch. 1Katedra fyziky povrchů a plazmatuDepartment of Surface and Plasma ScienceFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult
Study of the Growth of Iron Oxide on the Surface of Cerium Oxide
No full textCerium oxide (ceria) is widely used catalytic material known for its oxygen storage capacity. Iron-modified ceria-based catalysts find applications in various reactions, such as the oxidation of CO or NO. However, the existing knowledge about these catalysts is limited to relatively undefined powder samples. The aim of this Bachelor's thesis is to create well-defined model surfaces of iron oxide on ceria and characterize these surfaces using various methods such as Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and Low-Energy Electron Diffraction (LEED). In our work we found the following procedure for preparing the FeO(111)/ CeO2(111) surface on the Cu(111) substrate: Initially, metallic Fe is deposited onto the surface of CeO2(111) at room temperature, followed by annealing in ultra-high vacuum (UHV) up to 700 K. At room temperature, iron tends to form clusters con- sisting of both neutral Fe0 and ionic Fe3+ or Fe2+ states. After annealing in UHV up to 700 K, iron gets fully oxidized, resulting in the formation of a 2D FeO layer. This process gives rise to a moiré pattern observed in STM and LEED due to the overlay of the FeO and CeO2 lattices. By measuring the parameters of the moiré pattern, the periodicity and orientation of the deposited FeO..
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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