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High impact technologies for endovascular treatment of chronic total occlusions
No full textMedical Instruments & Bio-Inspired Technolog
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
Design of the flexible HORSE morcellator for the surgical treatment of Cushing's disease in horses
No full textThesis on the design of a flexible morcellator for the surgical treatment of Cushing's disease in horses. Currently there is no surgical treatment possible in horses due to lack of a surgical approach and tools. In this study a new innovative flexible tool is developped in combination with a surgical approach that can be used for the surgical treatment. The prototype was succesfully tested, allowing for surgical treatment of Cushing's disease in horses in the near future.BMEBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Endovascular crossing of Chronic Total Occlusions using impact force: An explorative design-study
No full textBackground: Chronic Total Occlusions (CTOs) are the most challenging lesions of Percutaneous Coronary Intervention (PCI). The most common failure mode is the inability to cross the lesion with a guidewire. Crossing is complicated by the lack of guidewire stiffness and the high penetration force of the fibrous proximal cap of the CTO, often causing guidewire buckling during penetration attempts. Therefore, the goal of this study was to explore a novel method to puncture the proximal cap of the CTO. Methods: Theoretical analysis and modelling of the clinical case and crossing action resulted in the selection of the "impact method", comprising the application of impact force onto the CTO that potentially causes fracture of the proximal cap without (large) environmental disturbance through an inelastic collision. This method was transformed into a functional prototype design, which was subsequently evaluated on its mechanical performance and puncture effectiveness, by means of High Speed Video (HSV) analysis, peak force measurements, and tests with different developed CTO models, representing variable CTO material characteristics. Results: The developed prototype (Ø 2 mm) uses a distal spring-loaded indenter (of different shapes) with a novel reload mechanism to exert impact force onto the CTO. The maximum indenter momentum and mean peak force, at 1 mm object distance and with maximized spring force, were experimentally determined at 1.3 mNs (mass 0.39 grams, mean velocity 3.4 m/s (n = 5)) and 19 N (n = 10), respectively. The puncture effectiveness of the indenter strike was found to be dependent on material characteristics of the targeted CTO model and the indenter tip shape. Proximal cap models with hard and brittle characteristics were fractured most effectively; on average in less than three indenter strikes with non-pointed indenter tip shapes. Conclusions: The impact method and prototype have shown potential to fracture fibrocalcific cap models. However, to draw final conclusions on potential (safe) endovascular crossing of CTOs, and the most optimal design (parameters) of the instrument, more knowledge on biomechanical properties of CTOs, or an in-vivo experiment, is needed. Nevertheless, it is believed that continued research and development of the method may, in time, improve the endovascular treatment possibilities of coronary CTOs.BMDBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
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
Design of a Soft Bio-Inspired Tissue Transport Mechanism
No full textIn the medical field, it is essential to remove delicate tissues from the body without damaging them or disturbing the surroundings. Current tissue transport mechanisms depend on the tissue composition and shape of the transported tissue, which results in problems such as clogging. This study presents a soft transportation mechanism for tissues inspired by the longitudinal muscles associated with the peristaltic movement of the gastrointestinal tract. The mechanism is designed as a conveying toroid that turns itself inside out in a continuous motion. A fabrication method was developed to manufacture a small-sized silicone toroid, filled with lubricating liquid. Comparable to the peristaltic movement, the silicone toroid adapts its shape to the transported tissue which results in a soft seal around the tissue. The toroid conveys the tissue while locking it at a stationary spot. A prototype was built to evaluate the transport efficiency of the conveying toroid in differently curved pathways. The preliminary experiments showed good transport efficiency, revealing the potential of the proposed soft transport mechanism for medical, and other transport applications.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired TechnologyTransport Engineering and Logistic
First steps in developing a novel catheter for cardiac catheterization with variable stiffness capabilities in two degrees of freedom
No full textAs their name suggests, variable stiffness mechanisms are mechanical systems that are capable of altering their stiffness. They can do this in order to adapt their interaction with the environment. One of the applications where variable stiffness can offer advantages is in healthcare. Specifically in minimally invasive surgical procedures, such as cardiac catheterization. In cardiac catheterization a catheter is maneuvered to a target location where it is to perform its task, which can be diagnostic or interventional. Currently, catheters are preceded by guidewires, which navigate the vasculature before the catheter follows. During the navigation of the tortuous vasculature, situations, such as a very tight bend, may present themselves that the guidewire cannot comply with in terms of stiffness. The guidewire is then to be replaced by one that does conform to the required stiffness for that situation. However, swapping guidewires takes time and imposes stresses upon the patient, which is not beneficial. It is then desirable to develop a catheter that does not depend so heavily on guidewires, such that it can navigate the vasculature practically by itself. After the navigation the catheter should still be able to perform its tasks as other currently used catheters. In order to comply to the different scenarios that the catheter may encounter during navigation or procedural tasks, the catheter should be able to vary the stiffness characteristics of some of its degrees of freedom.An analysis was conducted of which degrees of freedom are key during interactions between the catheter and the vasculature and what their desirable behaviour should be in a number of scenarios. It was identified that mainly the axial and bending degrees of freedom undergo loading during interactions with the vasculature. The two degrees of freedom should be able to obtain both a flexible state and a rigid state. In the flexible state the behaviour of the degrees of freedom should pose a minimal chance of causing significant harm to the vascular environment. The rigid state allows the catheter to resist more of the contact forces without deforming, thus leaving the catheter able to better transfer force upon the environment. In some scenarios it is vital that one degree of freedom is in the flexible state, while the other is in its rigid state.The identified requirements were used to develop a number of conceptual solutions, of which the most promising were further developed. Eventually, the concept with the most potential was fabricated into a prototype and its stiffness behaviour of the separate degrees of freedom validated. After validation, the final prototype was designed which serves as an interpretation of how the novel catheter may be used in the medical field.The fabricated prototype was tested by subjecting the tip to axial and bending load cases. The magnitude of deflection due to the imposed load showed the stiffness characteristics of each degree of freedom. It was found that the stiffness of both degrees of freedom was able to be varied using the working principles of the developed concepts. Also, the results showed that a stiffness variation in one degree of freedom did not significantly influence the stiffness characteristics of the other degree of freedom.From the results following the tests of a prototype based on the developed concepts, it was concluded that the novel catheter is be able to adapt the stiffness of the axial and bending degrees of freedom, such that it can comply to several scenarios. Compliance to these scenarios allows the catheter to navigate through the vasculature without inducing significant harm, but also to apply force along a certain degree of freedom to the environment when necessary. The implementation of the stiffness variation methods into real life application would benefit both patient and operator in terms of decreased procedural time and elimination of stresses associated with guidewire replacement.Mechanical Engineerin
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
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