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Bloch k-selective resonant inelastic scattering of hard X-rays from valence electrons of 3d-metals
Full text linkDie Form von resonant angeregen Valenz-Fluoreszenzspektren hängt sowohl vonder Energie der einfallenden Strahlung, als auch von Größe und Richtung desImpulsübertrags q ab, falls harte Röntgenstrahlen benutzt werden. DieserEffekt ist auf die elektronische Bandstruktur der Valenz- undLeitungselektronen der Probe, in Kombination mit der Energie- undImpulserhaltung des Streuprozesses zurückzuführen, woraus dieBloch-k-Impulserhaltung des resonant inelastischen Streuprozesses folgt.In dieser Arbeit wird die Gültigkeit der Bloch-k-Impulserhaltung im Bereichder harten Röntgenstrahlen und ihre Anwendbarkeit auf metallische Probengezeigt. Dazu werden die K-Kante von Cu und die K-Kante von Ni in NiAluntersucht. Ausgehend von einer LAPW Bandstrukturrechnung werden resonantangerege Valenz-Fluoreszensspektren berechnet. Diese stimmen gut mit dengemessenen Spektren überein.Weiterhin werden mehrere Effekte untersucht, die den Bloch-k-erhaltendenresonant inelasischen Röntgenstreuprozess beeinflussen.Im Gegensatz zur Streuung im Bereich der weichen Röntgenstrahlung ist an derK-Kante von Cu keine Zerstörung der Bloch-k-Erhaltung durchElektron-Phonon-Wechselwirkung im Zwischenzustand meßbar. In der Tat ist nurein kleiner nicht-k-erhaltender Anteil von wenigen Prozent zu erwarten, dadie Lebensdauer des 1s Rumpf-Lochs von Cu kürzer als dieElektron-Phonon-Wechselwirkungszeit ist.Mit Hilfe einer Superzellen-Rechnung an Cu wird gezeigt, daß die Abschirmungdes 1s-Rumpf-Lochs keinen Einfluß auf den Streuprozeß hat, falls an denK-Kanten der schweren 3d-Übergangsmetalle angeregt wird. DieSuperzellen-Methode wird im Detail beschrieben, und die Konvergenz derLadungsdichte bezüglich der Größe der Superzelle wird ausführlichuntersucht.Die Intensität des 3d-nach-1s-Quadupolübergangs relativ zum4p-nach-1s-Dipolübergang wird durch die Berechnung der entsprechendenÜbergangs-Matrixelemente bestimmt. Das Ergebnis wird anhand von Ga, Ge undAs überprüft, indem berechnete Floreszenzspektren mit gemessenen verglichenwerden, da für diese Elemente die 3d-Fluoreszenzlinie von der4p-Fluoreszenzlinie getrennt ist. Ferner wird die Abschirmung des3d9-Endzustands im Fall des 3d-nach-1s-Quadrupolübergangs untersucht. Damitist es möglich, sowohl die Intensität als auch die energetische Position desQuadrupolbeitrags zur Fluoreszenz für Cu zu bestimmen.Die Valenz-Fluoreszenzlinie der schweren 3d-Übergangsmetalle wird teilweisevom radiativen KNN Auger-Satelliten ueberdeckt. Die Intensität diesesSatelliten, dem ein Doppelionisationsprozess während der Emission einesFluoreszenzphotons zugrunde liegt, wird für die Elemente Co bis Asuntersucht. Um die Satellitenlinie in der Auswertung von Bloch-k-selektivenValenz-Fluoreszenzspektren richtig berücksichtigen zu können, wird derKNN-Satellit im Rahmen eines semiempirischen Modells behandelt, das aus demresonant inelastischen Streuquerschnitt hergeleitet und anhand derradiativen KMN- und KMM-Auger-Satelliten von Cu bestätigt wird Darüber hinaus werden die Cu K beta' und Cu K beta'' Satelliten der Cu Kbeta_1,3 Fluoreszenzlinie untersucht. Diese Satelliten stammen von einemDoppelionisationsprozeß während der Absorption eines Photons. Aus ihrerSchwellenenergie kann geschlossen werden, daß ihnen ein3d-Zuschauer-Lochzustand zugrunde liegt, während der kurze Sättigungsbereichdarauf hindeutet, daß diese Satelliten von shakeup-Prozessen dominiertwerden.The shape of resonantly excited valence fluorescence spectra depends on theenergy of the incident radiation as well as on the size and the direction ofthe momentum transfer q if hard x-rays are used. This effect is due to theelectronic band structure of the valence and conduction electrons of thesample in combination with the energy and momentum conservation of thescattering process, giving rise to the law of Bloch k-momentum conservationof the resonant inelastic scattering process.In this thesis, the validity of the Bloch k-momentum conservation in thehard x-ray regime and its applicability to metallic samples are demonstratedby probing the K edge of Cu and the K edge of Ni in NiAl. Based on a LAPWbandstructure calculation resonantly excited valence fluorescence spectraare calculated. These agree well with the measured spectra.Four effects influencing the Bloch k-conserving resonant inelastic x-rayscattering process have been investigated. In contrast to scattering in the soft x-ray regime a destruction of thek-conservation due to electron-phonon interaction in the intermediate stateis not measurable at the K edge of Cu. Indeed, only a small k-unselectivefraction of a few percent is expected, since the lifetime of the 1s corehole in Cu is shorter than the electron-phonon interaction time.By means of a supercell calculation of Cu it is found that screening of the1s core hole does not alter the scattering process if the K edges of thelate 3d elements are probed. A detailed description of the supercellapproach is given. The convergence of the charge density with respect to thesize of the supercell is thoroughly investigated.The intensity of the quadrupolar 3d-to-1s transition relative to the dipolar4p-to-1s transition is obtained from the calculation of the correspondingtransition matrix elements. The result is verified by comparing calculatedto measured fluorescence spectra in the case of Ga, Ge, and As, where the 3dfluorescence line is separated from the 4p fluorescence line. Moreover, thescreening of the 3d9 final state configuration in case of the quadrupolar3d-to-1s transition is investigated. This allows to determine properly theintensity and the energetic position of the quadrupolar fluorescencecontribution in the case of Cu.The valence fluorescence lines of the late 3d elements is partly obscured bythe KNN radiative Auger satellite. The intensity of this satellite line,which is due to a double ionization process during the emission of afluorescence photon, is investigated for the elements from Co to As. Inorder to be properly considered in the interpretation of the Blochk-selective valence floresence spectra, the shape of the KNN satellite isaccounted for by a semiempirical model, which is derived from the resonantinelastic scattering cross section. The model is confirmed by investigatingthe KMN and KMM radiative Auger satellites of Cu.Moreover, the Cu K beta' and Cu K beta'' satellites of the Cu K beta_1,3fluorescence line are examined. These satellites stem from a doubleionization process during the absorption of a photon. From their thresholdenergy it is possible to confirm that they are due to a 3d spectator hole.The short saturation range indicates that these satellites are dominated byshakeup processes
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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