1,720,958 research outputs found
Development and validation of structural Magnetic Resonance Imaging (MRI)-based biomarkers for diagnosis and prognosis of prodromal Alzheimer's disease
No full textAlzheimer's disease (AD) is a neurodegenerative disease and the most common cause of dementia. Currently in Canada, there are about 750,000 people living with dementia with more than 60,000 new cases diagnosed each year. Considering the relative failures in recent clinical trials, combined with the promising prospect of life-style changes, early prediction of the future onset of dementia in the early stages of Alzheimer's disease continuum can be highly beneficial. Advances in better identifying future progressors may both enhance population design for clinical trials and better identify the at-risk populations for life-style interventions. This thesis focuses on enhancement of dementia onset in patients with Mild Cognitive Impairment (MCI) using structural Magnetic Resonance Images (MRI) driven markers. The volume of the hippocampus is one of the best-known MRI-based biomarkers for Alzheimer's disease. Here, it is investigated using four different automatic hippocampus segmentation methods, each enhanced with bias error correction. Results show that multi-atlas-based hippocampus segmentation methods are accurate and show high conformity with manual delineation, and they can be further enhanced using a bias correction technique. The methods compared are not significantly different in their ability to capture AD related pathology. The Cohen's d group difference in hippocampal volume between patients with Alzheimer's dementia and healthy controls is high for all the methods and is of medium size between patients with MCI who convert to dementia in the near future and to those who remain stable for all the methods.Due to the wide-spread use of hippocampal volume a recent effort has been made by researchers in the field to harmonize the hippocampus segmentation protocol. The resulting new protocol, known as the EADC-ADNI harmonized protocol or the HarP, needs more validation. I validate the protocol using a large multi-center database designed for AD biomarker research. The results show that the HarP-based automatic segmentation is an accurate hippocampal segmentation which can be used in AD-related research to capture the Alzheimer's pathology. The methods described above are used in a novel model to predict the onset of dementia in an MCI population during different follow-up periods. The model combines information from MRI-driven markers from the hippocampus and entorhinal cortex with cognitive scores at baseline and tries to predict the diagnostic stage of each subject in different time intervals following the baseline visit. The model produces promising results using information from both cognitive scores and MRI markers to reach higher performance. MRI markers are more sensitive, while cognitive scores bring specificity to the prediction. Furthermore, for a follow-up period of 5 years, the model reaches an area under the receiver operating curve of 0.92 and an accuracy of 87%. Therefore, the prognostic model demonstrates promise as a candidate to be used in the clinic to identify subjects with prodromal Alzheimer's dementia at the MCI stage. Finally, I show that the AD-related atrophy pattern is even present in cognitively normal subjects and can be captured through hippocampal-based markers. I show that there is a small effect size (as measured by Cohen's d) between hippocampal volume in subjects who progress to MCI and/or dementia or subjects who maintain their normal cognition, while the effect is of medium size for the hippocampal grade. This thesis evaluates different automatic and manual hippocampus segmentation techniques and validates hippocampus volume as the most widely used AD marker. Moreover, I present a model to predict the onset of dementia in subjects MCI. I further validate hippocampal driven markers as an Alzheimer's biomarker in very early stages of the disease. Therefore, the results of this work will improve early detection of Alzheimer's leading to decrease the prevalence of the disease.La maladie d'Alzheimer (MA) est une maladie neurodégénérative et la cause la plus fréquente de la démence. Compte tenu du vieillissement de la population, le fardeau social et économique de MA augmente chaque jour. Les échecs relatifs des récents essais cliniques et la perspective prometteuse de changements de mode de vie indiquent que la prédiction précoce de l'apparition future de la démence aux premiers stades de MA peut être très bénéfique. Cette thèse vise à améliorer la prédiction de l'apparition de démence chez les patients atteints de troubles légers de la cognition (TLC) à l'aide de marqueurs structurels de l'imagerie par résonance magnétique (IRM).Le volume de l'hippocampe est l'un des biomarqueurs les plus connus de MA. Dans cette étude, il est évalué à l'aide de quatre méthodes différentes de segmentation automatique de l'hippocampe. Les résultats montrent que les méthodes de segmentation de l'hippocampe sont précises, en comparaison a plusieurs atlas d'imagerie. Elles paraissent conformes à la délimitation manuelle et peuvent être améliorées par la technique de correction de biais. Cependant, les différentes méthodes ne montrent pas de différences significatives dans leur capacité à identifier des modifications pathologiques liées à MA. En raison de l'utilisation répandue du volume de l'hippocampe en IRM en tant que biomarqueur de choix de MA des chercheurs ont récemment tenté d'harmoniser le protocole de segmentation de l'hippocampe. Le protocole proposé, appelé protocole d'harmonisation EADC-ADNI ou le HarP, nécessite davantage de validation. Cette thèse valide le protocole en utilisant une grande base de données multicentriques conçue pour la recherche de biomarqueurs de MA. Les résultats montrent que la segmentation automatique basée sur le HarP est une segmentation précise de l'hippocampe qui peut être utilisée dans la recherche liée à la MA pour identifier des modifications pathologiques induites par la MA. En plus, un nouveau modèle est proposé pour prédire l'apparition de démence dans la population TLC au cours de différentes périodes de suivi. Le modèle combine des informations provenant de marqueurs IRM de l'hippocampe et du cortex entorhinal avec des scores cognitifs au départ. Le modèle intègre des informations provenant de scores cognitifs et de marqueurs d'IRM pour atteindre des performances plus élevées. Les marqueurs d'IRM sont plus sensibles, alors que les scores cognitifs apportent une meilleure spécificité à la prédiction. Pour une période de suivi de 5 ans, le modèle atteint une aire sous la courbe ROC de 0,92 et une précision de 87%. Par conséquent, le modèle pronostique s'avère prometteur en tant que candidat à une utilisation en clinique pour identifier les sujets atteints de démence d'Alzheimer débutante au stade TLC.Enfin, le modèle d'atrophie liée à la MA est enfin retrouvé chez les sujets ayant des fonctions cognitives normales et peut être identifiée avec les marqueurs IRM de l'hippocampe. Un effet taille de faible ampleur (mesuré par le d de Cohen) est retrouvé entre le volume de l'hippocampe chez les sujets évoluant vers le TLC et/ou la démence ou les sujets conservant leur cognition normale, alors que l'effet est d'ampleur moyenne pour le grade hippocampique. Cette thèse évalue différentes techniques de segmentation automatique et manuelle de l'hippocampe et valide le volume de l'hippocampe en tant que marqueur MA le plus largement utilisé. De plus, un modèle permettant de prédire l'apparition de démence chez les sujets présentant une déficience cognitive légère est présentée dans cette thèse. Les marqueurs IRM de l'hippocampe en tant que biomarqueurs de MA sont valides aux tout premiers stades de la maladie. Par conséquent, les résultats de ces travaux amélioreront la détection précoce de la démence d'Alzheimer, ce qui, avec des interventions efficaces, pourrait permettre de réduire la prévalence de la démence et de réduire le fardeau social et économique de la maladie
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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