1,720,959 research outputs found
NMR applications for the diagnosis of female pathologies
No full textNuclear magnetic resonance (NMR) imaging (MRI) and spectroscopy (MRS) are powerful techniques that can be used to study the in-vivo human body and diseases. MRS allows for the quantification of metabolites and a chemical analysis of the analyzed sample, whereas MRI is a multi-parametric technique that provides detailed cross-sectional images of the body’s internal structures using non-ionizing radiation. In particular, Diffusion-Weighted imaging (DWI) allows the evaluation of the diffusion properties of water in biological tissues without requiring contrast agents and with excellent resolution dependent on diffusion length. These techniques applied in the brain studies have been revolutionizing the neuroimaging field, leading to important information related to the microstructure and function of the brain. To extract this information, the development of mathematical models has been the topic of greatest interest over the last 20 years. Indeed, in DWI the NMR signal is the Fourier transform of the motion propagator, which is easily calculated for free water, but it is more complex in biological tissues leading to the development of models such as the Intravoxel incoherent motion (IVIM) model and the Kurtosis representation. All these models were first applied and optimized for neurological application; hence the body application should be carried out considering these limitations (related to the structural and physiological differences between cerebral and ex cranial tissues) and adapting the models to the specific analyzed tissues to avoid the evaluation of parameters without physical sense. Sometimes, clinical NMR images are affected by high level of noise which imply the wrong evaluation of the NMR parameters. Hence, it is necessary to know the signal to noise ratio (SNR) of each image and perform a denoising if the SNR is too low.
In this thesis, a biophysical model with two perfusion compartments was adapted for placental tissues analysis to study the diffusion and perfusion properties of water in the placenta which is characterized by three main compartments: the fastest perfusion compartment due to the fetal villous-trees, a slower perfusion compartment related to the trophoblastic activity and a diffusion compartment linked to the maternal blood in the intra-villous space. The model was applied to evaluate the characteristics of the normal placental tissues and to find any differences between normal placentas and those affected by two specific pathologies: the fetal growth restriction disease (FGR) and the placental accretism. The application of this new model allowed the identification of new biomarkers non-obtainable applying the more known and used IVIM model, which nevertheless is able to highlight important perfusion features. Indeed, the IVIM model was used to study the differences between normal placentas and those belonging to women with SARS-CoV-2 infection, pinpointing substantial differences in the values of the diffusion coeffcient due to a damage to the microstructure of the tissue.
DWI also has important applications in the oncology field. In fact, it has been widely used to study the complexity of tumor tissues in the brain. In this work, DWI was adopted to study the cervical cancer and the endometrial cancer in particular. Generally, the diagnosis of these kinds of pathologies is performed by the histology which is an invasive technique and it is limited by the size of the taken tissue. In this thesis, tissue complexity and tumor grade were evaluated using the kurtosis representation combined with a clusterization based on the tissue differences in the same region of interest obtaining a higher variance of the kurtosis parameters in tumor tissues than in the healthy endometrium. Since the kurtosis representation is sensitive to image noise, a denoising was performed before applying the model and the non-dependence of the parameter to the noise was verified.
MRS was used to pinpoint early biomarkers in bone marrow and muscles to study the osteoporosis and osteoarthritis diseases, highlighting interesting differences in the fat lipid content and in the level of unsaturated fatty-acids in both bones and muscles, corroborating the hypothesis that these pathologies involve the whole musculoskeletal system.
Although the promising results, new perspectives should be considered for the diffusion model’s selection. Indeed, the dynamics underlying the studied system is crucial for the model selection since the application of the wrong model would bring the evaluation of physically no-sense parameters. In this work a preliminary experimental study was conducted on PEG to evaluate its true dynamics and then choose the right diffusion model applying a particular “recipe” conceived and developed in the NMR laboratory of the CNR-ISC & Sapienza where I carried out my PhD work. These last results underline the importance of the knowledge of the tissue diffusion properties a priori to perform more precise and faithful quantification of diffusion parameters indispensable for more precise and early clinical diagnostic
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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