1,720,961 research outputs found
Charting new physics territories with cosmological observations
No full textIn questa Tesi sfruttiamo le più recenti osservazioni cosmologiche per vincolare scenari di fisica fondamentale che vanno oltre i modelli standard della cosmologia e della fisica delle particelle. Per cominciare consideriamo candidati di materia oscura macroscopica (MDM), che rappresentano una interessante alternativa ai modelli di materia oscura particellare. Ci concentriamo sul processo di cattura di protoni da parte della MDM e vincoliamo lo spazio dei parametri delle Macro sfruttando tre osservabili cosmologiche: (i) la variazione nella densità di barioni tra le epoche della Nucleosintesi Primordiale (BBN) e della Radiazione Cosmica di Fondo (CMB); (ii) la produzione di distorsioni spettrali nello spettro della CMB; (iii) l’accoppiamento tra la MDM carica e i barioni all’epoca del disaccoppiamento della CMB. Inoltre, mostriamo come esperimenti futuri per distorsioni spettrali, come PIXIE e SuperPIXIE, potranno migliorare i vincoli attuali. Successivamente ci concentriamo su particelle axion-like (d’ora in avanti assioni) termiche, che sono prodotte nell’Universo primordiale tramite processi di scattering tra particelle presenti nel plasma primordiale. A seconda della loro massa, gli assioni termici possono comportarsi come una componente di materia oscura calda, tiepida o fredda. Sfruttando le più recenti osservazioni delle anisotropie della CMB dal satellite Planck e delle Oscillazioni Acustiche Barioniche dalle survey di galassie, vincoliamo gli accoppiamenti degli assioni ai fotoni e ai gluoni. Questi risultati vengono poi confrontati con i vincoli ottenuti da esperimenti in laboratorio e tramite sorgenti astrofisiche. Nella seconda parte della Tesi ci concentriamo sulla polarizzazione della CMB per testare possibili violazioni di simmetrie fondamentali. Come prima cosa, consideriamo modelli che estendono l’elettrodinamica di Maxwell introducendo operatori rinormalizzabili che violano la simmetria di Lorentz. Questi consistono di due termini, uno dei quali viola anche la simmetria CPT. Sfruttando le più recenti osservazioni della polarizzazione della CMB, deriviamo vincoli molto stringenti sui coefficienti che parametrizzano la violazione di Lorentz. In particolare, per i coefficienti che violano CPT otteniamo i vincoli più forti ad oggi, anche considerando osservabili non cosmologiche. Per concludere, analizziamo gli effetti di teorie della gravità scalari-tensoriali che violano la parità durante l’inflazione, concentrandoci sulla non-Gaussianità delle onde gravitazionali primordiali. Calcoliamo la predizione teorica per il bispettro primordiale e discutiamo le prospettive per un’osservazione di questi effetti di violazione di parità tramite esperimenti di CMB futuri.In this Thesis we exploit the latest cosmological observations to constrain fundamental physics scenarios that go beyond the standard models of cosmology and particle physics. We start by considering Macroscopic Dark Matter (MDM) candidates, which represent an appealing
alternative to particle dark matter. We focus on the process of proton capture by MDM and constrain the parameter space of Macros using three cosmological probes: (i) the change in the baryon density between the epochs of the Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) decoupling; (ii) the production of spectral distortions in the CMB spectrum; (iii) the kinetic coupling between charged MDM and baryons at the time of CMB decoupling. We also show how future spectral distortions experiments, like PIXIE and SuperPIXIE, will allow us to improve these bounds. Then, we focus on thermal axion-like particles (hereafter axions), which are produced in the early Universe from scatterings between particles belonging to the primordial thermal bath. Depending on their mass, thermal axions can behave as a hot, warm or cold dark matter component. Using the latest observations of CMB anisotropies by Planck and of Baryon Acoustic Oscillations from galaxy surveys, we
constrain the couplings of axions to photons and gluons. We compare these bounds with the constraints derived from laboratory and astrophysical probes. In the second part of the Thesis, we focus on the polarization of the CMB as a probe to test possible violations of fundamental symmetries. First, we consider models that extend Maxwell’s electrodynamics by introducing renormalizable operators which break Lorentz invariance. These consist in two terms, one of which violates also CPT symmetry. Using the most recent observations of CMB polarization, we derive strong bounds on the Lorentz-violating coefficients. In particular, for the CPT-odd coefficients we obtain the strongest constraints to date, even considering non-CMB probes. Finally, we analyze the effects of chiral scalar-tensor theories of gravity during inflation, focusing on the non-Gaussianity of primordial gravitational waves. We compute the theoretical prediction for the primordial bispectrum and we discuss the prospects for detecting such parity-violating signatures with future CMB experiments
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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