1,720,960 research outputs found
Intimal Hyperplasia. Experimental and Clinical Studies
Get PDFIntroduction: Intimal hyperplasia (IH) is recognized as the primary cause of reocclusion 2-24 months following vascular intervention and surgery, reportedly occurring in 30-50% of patients. It is an exaggerated form of the normal healing process of the iatrogenic trauma. The two main processes of IH are proliferation and migration of vascular smooth muscle cells (VSMCs) with a subsequent deposition of extracellular matrix. This accumulation of cells and matrix leads to a narrowing or, ultimately, occlusion of the lumen. IH usually affects arterial anastomoses, but a very distinct type of IH called pannus also exists. It occurs at the valvular annuli of the heart following implantation of valve prostheses and can obstruct valvular motion, thereby leading to acute heart failure. The treatment for IH is reintervention, resulting in major clinical issues for the patients and strain on the health care system. No prophylactic treatment currently exists. Heparins have demonstrated inhibitory effects in cell and animal experiments, but the results of clinical studies have been disappointing. There are no known predisposing factors enabling one to foresee who will develop clinically significant IH and who will not. This thesis sought to investigate the processes of IH in cell cultures, the effects of different heparins on these processes and the clinical manifestations in animals and patients. Paper I: The aim of this study was to investigate if heparin coated vascular grafts could improve patency and recruit less IH compared to uncoated grafts at a longer term in a sheep model. Twenty-eight common carotid arteries in fourteen sheep were bypassed with a luminal heparin-coated graft on one side and a control uncoated contralaterally. The grafts were explanted after six months. The thickness of IH in open grafts was measured with histomorphometrical methods. In conclusion, heparin coated grafts improved patency and recruited less IH compared to control uncoated grafts at six months in a sheep model. Paper II This study was designed to investigate the influence of heparin on the processes of IH of patient-derived vascular cell mono- and co-cultures. VSMCs and endothelial cells (ECs) were isolated from vessel wall biopsies from six patients. The cell cultures were treated with heparin and evaluated for effects on proliferation, migration and mitogen-activated protein kinase - extracellular signal-regulated kinase (MAPKERK) signal transduction using image-based cell enumeration, real-time migration monitoring and flow cytometry. Heparin inhibited proliferation and migration of patient-derived VSMC cultures, but only at concentrations exceeding clinical doses. The proliferative response of VSMCs to heparin was not affected by the presence of ECs. Heparin stimulated MAPK-ERK phosphorylation of VSMCs at lower concentrations in the presence of human fibroblast growth factor (hFGF). MAPK-ERK phosphorylation of unstimulated cultures was inhibited dose-dependently. Thus, heparin seems to influence patient-derived vascular cells through both a stimulatory hFGF-dependent and an inhibitory hFGF-independent pathway. These findings may explain the divergence of results between previous in vitro and clinical studies and provide a basis for new therapeutic strategies. Paper III This study was designed to investigate the effects of two low-molecular weight heparins (LMWHs), enoxaparin and dalteparin, compared to unfractioned heparin on proliferation, migration and MAPK-ERK signal transduction of patient-derived VSMCs. VSMCs were treated with the LMWHs in a range of concentrations and evaluated using image based cell enumeration, real time migration monitoring and flow cytometry. Series treated with unfractioned heparin were included as positive controls and untreated series as negative controls. This study demonstrated a difference in proliferative and migratory effects between the two LMWHs and unfractioned heparin in patient-derived VSMCs. The effects corresponded to the MAPK-ERK phosphorylation, suggesting different mechanisms of action. These results may explain why clinical trials using LMWHs to prevent IH have failed to observe a reduced incidence of restenosis and do not support prolonged therapeutic use to prevent it. Paper IV: The aim of this study was to analyse the incidence, treatment and results of acute prosthetic valve obstruction due to IH overgrowth originating from the periannular area (pannus), in a large series of patients with a Medtronic-Hall tilting disc aortic prosthesis. This was a retrospective study of patients seen at Haukeland University Hospital over the course of the last 30 years. Special attention was given potential predisposing factors of pannus development. This study demonstrated that females and younger patients are at higher risk for pannus development. When acute dysfunction of a mechanical aortic valve by pannus is suspected, an immediate echocardiogram and an emergency aortic valve replacement should be performed to prevent an otherwise fatal outcome
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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