1,721,077 research outputs found
Recommended from our members
Angiographic Assessment of Flow Divertors as Treatment for Cerebral Aneurysms: Results in the Rabbit Elastase-Induced Aneurysm Model
No full textCerebral aneurysms are abnormal focal dilations of the cerebral vasculature that may rupture and cause a hemorrhagic stroke. More than a decade after seminal experimental studies showed the feasibility of successfully treating cerebral aneurysms by flow diversion, the potential of this modality is gradually being recognized in the clinical arena. A flow divertor is a metallic meshed tube that has its porosity (ratio of metal-free surface area to total surface area) and pore density (number of pores per unit surface area) optimized to facilitate occlusion of aneurysms. An appropriately designed flow divertor severely attenuates the flow exchange between the parent vessel and an aneurysm, resulting in the formation of intra-aneurysmal flow stasis zones which promote thrombosis. This study reports the results from implantation of three different configurations of a novel flow-diverting device in thirty elastase-induced aneurysm models in rabbits. Ten animals per device configuration were followed-up at 3 weeks (n=3), 3 months (n=3), and 6 months (n=4) and tissue explanted post-sacrifice was sent for histology. High-speed angiographic sequences were acquired before and immediately after device implantation, and at follow-up for each animal. Temporal variations in the angiographic contrast intensity within the aneurysms were recorded and subsequently corrected for respiratory motion. These aneurysmal contrast washout curves were fit to a mathematical model whose parameters served to quantify device performance. Angiographic quantification was supplemented by histomorphometric data to derive composite scores of the performance of each device configuration in effecting stable aneurysm occlusion. Performance scores showed that the device with a porosity of 70%, filament diameter of 38 microns, and pore density of 18 pores/mm^2 performed better than devices with 65% porosity, 51 micron filament diameter, 14 pores/mm^2 and 70% porosity, 51 micron filament diameter, 12 pores/mm^2 with relative efficacies of 100%, 86%, and 79%, respectively. Angiographic quantification further suggested a parameter, which could be employed to estimate long-term aneurysm occlusion probabilities immediately after treatment with any flow diversion device. A value of this parameter less than 30 predicts greater than 97% angiographic aneurysm occlusion over a period of six months with a sensitivity of 73% and specificity of 82%. Larger data sets are required to improve the validity of this test. The pore density of flow divertors, rather than porosity, was seen to be a critical modulating factor of device efficacy. Refinement of the best device configuration by further optimizing the pore density may yield yet better results.</p
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
Endovascular treatment of intracranial aneurysms: current status
No full textAlthough treatment of a ruptured aneurysm is accepted as an emergency, indication for treatment of unruptured intracranial aneurysms (IAs) is still being discussed
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
Brain aneurysms and arteriovenous malformations: advancements and emerging treatments in endovascular embolization
No full textBACKGROUND AND PURPOSE: Brain aneurysms and vascular malformations can cause cerebral hemorrhages, with devastating consequences for the patients and their families. Since the development of microcatheters and materials used for endovascular embolization, we have witnessed a rapid advancement in the technology and in the number or patients treated with this approach. The aim of this review is to survey recent data relevant to new technologies and emerging treatment strategies in these areas. SUMMARY OF REVIEW: Clinical trials assessing the safety and efficacy of coil embolization for cerebral aneurysms were based on the use of bare platinum, helical coils. Since then, endovascular operators have been testing and using new materials such as bioactive coils, expandable coils, and complex-shaped coils. Based on the data so far obtained, third and fourth generation coil designs are rapidly emerging and will be ready for clinical application in the near future. Balloon- and stent-assisted coil embolization is enabling the treatment of complex, large-neck aneurysms and the vascular reconstruction of lesions previously considered not treatable. New open- and closed-cell designs allow the navigation and deployment of stents in extremely tortuous vessels. With regards to the embolization of vascular malformations, it is possible to safely navigate microcatheters and microwires through very small arteries previously considered not accessible. In addition, embolization materials such as n-butyl cyanoacrylate and ethylene-vinyl alcohol copolymer are now routinely injected to safely reduce or obliterate large and complex arteriovenous malformations and fistulae. CONCLUSIONS: Advancements in technology are rapidly improving the endovascular approach to the treatment of cerebral aneurysms and arteriovenous malformations
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
- …
