1,720,952 research outputs found
Development of Vessel Connectors for Coronary Bypass Surgery
No full textMechanical Maritime and Materials Engineerin
Instrument for fine-mechanical or surgical applications
No full textThe invention relates to an instrument for high-precision or surgical applications of a minimally invasive nature, comprising a distally positioned directable head, a shaft upon which the head is positioned, and a proximally positioned handgrip for operating the head, wherein a ring of cables comprising longitudinally extending cables connects to the head, wherein each cable of the ring of cables is disposed such that at least a part of both sides is in direct contact with another cable of the ring of cables, and wherein the cables are fixedly secured in the radial direction.Mechanical, Maritime and Materials Engineerin
Design of a Steerable Laparoscopic Aspirator-Irrigator: FlowFlex
No full textLaparoscopy is a type of minimally invasive surgery in which instruments with long, slender shafts between handle and end effector are inserted through small incisions in the abdominal wall. A laparoscopic aspirator-irrigator (LAI) has a hollow shaft used to evacuate undesirable substances using a vacuum pressure, rinse tissue using a stream of pressurized saline, and manipulate adherent tissue.Although laparoscopic instruments typically have a steerable tip to compensate for the loss of maneuverability due to the small incision, all currently available laparoscopic aspirator-irrigators lack a steerable tip. This lack is associated with sub-optimal aspiration and irrigation efficacy, mechanical trauma resulting from interference with obstructive tissue, interference with other instruments, and a lack of fine motor control of the tip. Although LAI’s with a steerable tip are known from patent literature [1]–[6], they all seem to have been abandoned, which suggests that the implementation of a steerable tip on an LAI tends to compromise performance relative to cost. Therefore, the objective of the current study is to design a new laparoscopic aspirator-irrigator (FlowFlex) with a steerable tip that mitigates the limitations of a conventionally rigid, straight tip to the extent of warranting its additional cost.To meet the objective, design requirements have been generated, tentative prototypes have been designed and evaluated, and a Final Prototype has been designed based on the superior tentative prototypes. Its steerable tip consists of an inner tube that is rigid and straight and an outer tube with an elastic, pre-curved silicone tip. Whereas the inner tube is stationary, the user can rotate, retract, or protract the outer tube by moving the tip control wheel on its proximal end using the index or middle finger, causing the tip to rotate, straighten, or deflect.The Final Prototype meets all important design requirements; it is cost-effective, due to the particularly simple and cheap steerable tip, it has ample flow rate capacity, it is unsusceptible to clogging, and it is sufficiently maneuverable. Although its main limitation is the low stiffness of its pre-curved tip, the ability of the tip to be rigidized by straightening makes it at least as capable of manipulating tissue as a conventional laparoscopic aspirator-irrigator.Mechanical Engineerin
Design and development of the Hornet: a new suturing device for laparoscopic surgery
No full textLaparoscopic suturing is one of the most difficult and time-consuming tasks in laparoscopic surgery. The long instrument shafts, two-dimensional view, and limited space for movement make simple actions, such as grasping and manipulating the needle and thread, difficult in the laparoscopic setting. To simplify the suturing process, the Hornet project was started by DEAM. The company was asked by two gynecologists to create a laparoscopic suturing device that simplifies the closure of the vaginal cuff during a total laparoscopic hysterectomy. The first prototypes that were created had promising design elements, but their suturing techniques proved difficult to execute. The modified sewing machine suturing technique was created to solve these issues, resulting in the aim of this thesis: to develop a laparoscopic suturing instrument that uses the modified sewing machine suturing technique to simplify the closure of the vaginal cuff. A new prototype of the Hornet was designed based on a list of Product Specifications. This instrument, Hornet prototype B3, was built and subsequently tested in a series of design verification tests to determine if the design meets the Product Specifications. Additionally, a series of user tests was executed to verify whether the design simplifies the closure of the vaginal cuff. In the tests, the participants placed sutures with both the Hornet and with the regular suturing method. Participants with different levels of suturing and laparoscopic experience were included to determine the effect of experience on the suturing results with the Hornet. The tests showed that the prototype simplifies the suturing process. All participants were able to place a closed suture with the Hornet, whereas only 43% of the participants placed a closed suture with the regular suturing method. The participants without laparoscopic experience had significantly shorter suturing times with the Hornet compared to regular suturing, indicating that the suturing method with the Hornet is simpler to learn. The participants with laparoscopic experience performed similarly with the Hornet and the regular suturing method, indicating that the first time the Hornet is used gives similar results to experience with regular laparoscopic suturing. From this research, it can be concluded that the Hornet prototype B3 simplifies the closure of the vaginal cuff when compared to regular suturing. To further confirm this claim, additional development and testing of the prototype is needed. Some alterations to the prototype design are required to improve its functioning and to ensure that all the product specifications are met. Additional tests are needed to investigate the extent in which the prototype simplifies the suturing process and to determine the learning curve of the Hornet.Biomedical Engineerin
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 Biopsy Containuer: The development and evaluation of an endoscopic biopsy storage instrument
No full textBackground: Colonoscopy is a successful screening method to prevent colorectal cancer (CRC). Biopsies are performed from suspicious tissue spots during the colonoscopic procedure to find cancerous polyps in an early stage of the disease. However, taking multiple biopsies is rather time-consuming and requires many repetitious actions from the gastroenterologist. The current state of the art instruments either do not solve this issue or do not meet the user requirements. The goal of this study was, therefore, to design a new endoscopic instrument to store multiple biopsies during a colonoscopy. Methods: The input from different gastroenterologists, together with risk analyses, has resulted in the lists of requirements for the device. These requirements have defined the design space for the development of the instrument. The tip functionalities were subdivided into five design challenges: integrate, transport, remove, store and secure. The solutions for these challenges were combined to generate concept directions. Within these directions, concepts have been created and analysed, which resulted in the final design, 'the Biopsy Containuer'. Different prototypes have been made from this design to evaluate the functionalities of the instrument and receive the opinion of potential users. Results: The evaluation showed that the developed prototype is able to remove a biopsy from the biopsy forceps and store five biopsies without loss or change of order inside the container of the instrument. Besides, potential failure movements were investigated, and they did not result in breakage or malfunctions. The participating gastroenterologists in the user assessment were, in general, pleasantly surprised about the potential of this instrument. Performing six biopsies using the Biopsy Containuer results in a time reduction of 44 %. Discussion and conclusion: When taking the learning effect found during the user assessment analysis into account, the time to perform six biopsies is reduced by 57 %. More research is required to evaluate the influence of bowel tissue on the instrument functionalities and the most suitable handle design. The next prototype iteration can include the use of one single polytetrafluoroethylene (PTFE) tube and laser cutting to create the tip structures. The Biopsy Containuer is able to store multiple biopsies during a colonoscopy, and the potential purpose in endoscopic procedures besides colonoscopy could be useful.Mechanical Engineering | BioMechanical Desig
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
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