1,720,982 research outputs found
Patents and heart valve surgery - I : mechanical valves
No full textValvular heart disease, inherited or acquired, affects more than 5 million Americans yearly. Whereas medical treatment is beneficial in the initial stages of valvular heart disease, surgical correction provides symptomatic relief and long-term survival benefits. Surgical options include either repair or replacement using mechanical or bio-prosthetic valves. Patient age and the post-operative need for anticoagulation therapy are major determinants of the choice between use of mechanical or bio-prosthetic valves. Since the first mechanical valves were made available several decades ago, the incorporation of increasingly sophisticated materials and methodologies has led to substantial improvements in the valve design, and has catalyzed a parallel increase in the amount of patents issued for these emerging technologies. In this paper, we have chronologically reviewed such patents, briefly discussed various challenges that mechanical heart valve implementation is faced with and finally reviewed some of the strategies employed to overcome such obstacles. An ideal prosthetic heart valve would comprehensively mimic the natural hemodynamics and physiology of the native heart valve. Additionally, such a valve would be easily implantable, associated with a minimal risk of thrombosis and thus need for anti-coagulation, and with a proven long-term durability. With cutting edge technological advancements in the recent times, the ongoing innovative and collaborative efforts of physicians, scientists, and engineers will not seize until an ideal mechanical heart valve becomes a reality
Combining stem cells and tissue engineering in cardiovascular repair - a step forward to derivation of novel implants with enhanced function and self-renewal characteristics
No full textThe use of stem and progenitor cells in cardiovascular therapy has been proposed as a feasible option to promote repair of tissue damage by ischemia, or to devise definitive artificial tissue replacements (valves, vessels, myocardium) to be surgically implanted in patients. Whereas in other medical branches such as dermatology and ophthalmology the use of ex vivo grown tissues is already accessible to a large degree, the use of bio-artificial implants in cardiovascular surgery is still marginal. This represents a major limitation in cardiovascular medicine at present. In fact, the limited durability and the lack of full compatibility of current implantable devices or tissues prevent a long-term resolution of symptoms and often require re-intervention thereby further increasing the economic burden of the cardiovascular disease. Stem cell technology can be of help to derive tissues with improved physiologic function and permanent durability. Specifically, the intrinsic ability of stem cells to produce tissue-specific "niches", where immature cells are perpetuated while differentiated progenitors are continuously produced, makes them an ideal resource for bioengineering approaches. Furthermore, recent advancements in biocompatible material science, designing of complex artificial scaffolds and generation of animal or human-derived natural substrates have made it feasible to have ex vivo reproduction of complex cell environment interactions - a process necessary to improve stem cells biological activity. This review focuses on current understanding of cardiovascular stem cell biology as well as tissue engineering and explores their interdisciplinary approach. By reviewing the relevant recent patents which have enabled this field to advance, it concentrates on various design substrates and scaffolds that grow stem cells in order to materialize the production of cardiovascular implants with enhanced functional and self-renewal characteristics
Patents and Heart Valve Surgery - III : Percutaneous Heart Valves
No full textAdvancements in technology for the treatment of valvularcardiac diseases seek to provide solutions for high risk patients in the form of percutaneous valve insertion for patients with complicated valvular disease not amenable to more traditional options. Within the last decade, cardiac valves designed for percutaneous insertion have emerged rapidly as a treatment option for valvular disease. This procedure serves as an alternative to open heart surgery, which is more invasive and requires longer ICU stay. Thus, the percutaneous valve insertion procedure has been used on older, frailer patients who are poor candidates for open heart surgery. Designs for percutaneous valve insertion systems have been in development for decades, but have only recently been approved by the FDA for use. Important considerations include stent design, valve design, balloon catheter design, and deployment method
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
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