1,720,958 research outputs found
Femtosecond Covariance Spectroscopy
Get PDFIn order to reveal a signal arising from a nonlinear interaction, several spectroscopic techniques are nowadays adopted. In spite of their practical and fundamental differences, they have in common to rely on pulse to pulse consistency to deliver information on a nonlinear process. With the work presented in this
thesis we show, instead, that we can successfully leverage upon experimental noise. To achieve this goal, we exploited the fact that a weak nonlinear signal introduces a strong spectral correlation, which can be revealed even when the output spectra fully spectrally and spatially overlap with the excitation pulse.
Based on these principles, we proposed a novel approach to a nonlinear spectroscopy experiment, called Femtosecond Covariance Spectroscopy. To provide a solid basis for the validation of the technique, we focused on a third order nonlinear process, inelastic light scattering, which is prompted by the mixing of intense electric fields in a transparent material. The interaction implies that the measured intensity at some point in the transmitted spectrum is statistically related to the intensity at other points of the spectrum, whenever their energy distance coincides with an energy level of the sample involved in
the scattering. We performed inelastic light scattering experiments from vibrational modes of a benchmark sample, quartz. We employed a near infrared laser with central wavelength in a transparency region of the sample, and bandwidth larger than its lowest energy vibrational modes. We found in
the correlation coefficient sidebands that reproduce the vibrational spectrum of the sample. Their lineshape changes according to the presence or absence of a non modulated portion of the spectrum, heterodyning the scattered radiation. In fact we find that a partial spectral randomization is most efficient in preparing a pulse with no pre-existent correlation, that, at the same time, provides a local oscillator for the sample-induced fluctuations to be amplified. In this scheme, the ultrashort pulse provides, at the same time, intense electric fields to stimulate a response, and noninteracting components to reveal it. The
self-heterodyned nature of the acquisition is accounted for in a fully quantum model.
The technique can be adapted to a pump - probe scheme by exciting the sample with a separate, intense and spectrally coherent, pump pulse. Our measurements of the average transmitted probe intensity performed using a pump to excite coherent vibrational states, reveal that oscillations in the response are initiated in-phase by the pump and evolve at the vibrational frequencies. Such a response is an ideal candidate to test a covariance based probe, as the spectrum undergoes a red-shift or a blue-shift alternatively in time, and the correlation
coefficient is found to oscillate in time at the phonon frequency. The investigation we started with this Thesis aims, primarily, at establishing the signatures in the correlation that resolve a thermal from a coherent vibrational state. In fact, if a quantum optics model describes accurately the results of a
standard pump probe experiment on quartz, the theoretical framework must be completed in order to describe a pump probe approach employing randomized pulses and a covariance based retrieval. The experiments have shown that consistent information is present in the correlation maps, but more incisive
analytical and conceptual tools are needed to assess the different contributions. The proposed method has proven to be a powerful probing scheme in a optical spectroscopy experiment, and can be successfully translated into the language of stochastic X-ray pulses, complex materials, electronic scattering processes.
To fully characterize the FCS technique there are still steps to take. Nonetheless we believe that the present work sets the basis for the development of a technique that successfully conveys information beyond traditional schemes
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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