1,720,971 research outputs found
Espressione delle potenzialità dei Laser ad elettroni liberi attraverso esperimenti innovativi
No full textThe advent of X-Ray Free Electron Lasers (FELs) has opened a new era for exploring the fundamental properties of matter. These machines are the 4th generation light sources and combine the exceptional properties of conventional lasers and synchrotrons, allowing to probe the ultra-fast dynamics of atoms and molecules in simple and complex systems at a nano-scale level. This thesis work is divided in two main branches: at first, it reviews the basic theory behind FELs and points out possible improvement of these sources. Secondly, it presents some results obtained during new and peculiar experiments performed between 2017 and 2020 in different FELs facilities while showing how further improvements are needed in order to accomplish state of art results unreachable with the current state of synchrotrons and FELs. In Chapter 1, the reader is introduced to the charged particle accelerator theory culminating with its application on one of the main component of a FEL: the undulator. In order to provide its special radiation output, a FEL light source makes use of interactions between charged particles and a self-generated electromagnetic radiation inside an undulator. To let the reader easily understand the mechanism behind the radiation generated and its properties, this thesis opens with an approach to the laws of physics that rule the dynamics of the particles. Coupling the Lorentz equation with Maxwell equations we show the collective dynamics of electrons throughout the all FEL structure in Chapter 2. In Chapter 3 we present the two main places where this work of thesis has been built: the FERMI FEL in Italy and the SwissFEL machine based at the Paul Scherrer Institute in Switzerland. Here we explore the secrets of their layouts, beamlines and main experiment performed. Once the reader mastered the fundamental properties of a FEL, we show the main results achieved during this research period at the FERMI FEL and at the SwissFEL. In Chapter 4 we present the very first successfull attempt at X-Ray Transient Grating Spectroscopy on Bismuth Germanate Oxide. In order to confirm some of the results obtained through the X-ray Transient Grating technique, a few satellite measurements and simulations were also performed on the Bismuth Germanate Oxide sample, which are presented in Chapter 5. In Chapter 6 we present what we called a Real-time visualization of ibuprofen dimer vibrations with element- and enantiomeric- selectivity: here we exploit the potential of FELs through an ultrafast soft X-Ray absorption experiment that allows the visualization and disentangling of several low-frequency and near lying vibrational modes, involving specific carbon atoms in a racemic mixture of Ibuprofen. In Chapter 7 we explore the world of soft matter: here we introduce the problematics affecting the protein structure research by showing the main re- results obtained at two synchrotron facilities. Afterward, given the results we obtained, we explore the possibility to overcome such problems by introducing the Coherent and Incoherent Diffraction Imaging techniques at FELs combined to a new approach on protein bidimensional crystallization. Furthermore, we introduce a rather similar approach to a technique aiming at Catching Conical Intersection through Electronic Coherence and Noise Correlation Spectroscopy: we explore the possibility to use the TRUECARS technique to directly visualize the conical intersection dynamics, which regulates the photo-chemestry of most molecules. Chapter 8 opens with an introduction on Resonant Inelastic X-ray Spettroscopy (RIXS). Here we show the results of the application of RIXS exploiting the Ultrafast charge trapping dynamics in Cu2O in-gap states: we investigated the charge trapping dynamics in the defect-related in-gap states of Cu2O, following photoexcitation across the band gap. Finally, the thesis culminates with the Design of a soft X-Rays RIXS spectrometer for the SwissFEL's new beamline FURKA.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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