1,720,963 research outputs found
Hydraulic Detrusor for Artificial Bladder Active Voiding
No full text: The gold standard treatment for bladder cancer is radical cystectomy that implies bladder removal coupled to urinary diversions. Despite the serious complications and the impossibility of controlled active voiding, bladder substitution with artificial systems is a challenge and cannot represent a real option, yet. In this article, we present hydraulic artificial detrusor prototypes to control and drive the voiding of an artificial bladder (AB). These prototypes rely on two actuator designs (origami and bellows) based either on negative or positive operating pressure, to be combined with an AB structure. Based on the bladder geometry and size, we optimized the actuators in terms of contraction/expansion performances, minimizing the liquid volume required for actuation and exploring different actuator arrangements to maximize the voiding efficiency. To operate the actuators, an ad hoc electrohydraulic circuit was developed for transferring liquid between the actuators and a reservoir, both of them intended to be implanted. The AB, actuators, and reservoir were fabricated with biocompatible flexible thermoplastic materials by a heat-sealing process. We assessed the voiding efficiency with benchtop experiments by varying the actuator type and arrangement at different simulated patient positions (horizontal, 45° tilted, and vertical) to identify the optimal configuration and actuation strategy. The most efficient solution relies on two bellows actuators anchored to the AB. This artificial detrusor design resulted in a voiding efficiency of about 99%, 99%, and 89%, in the vertical, 45° tilted, and horizontal positions, respectively. The relative voiding time was reduced by about 17, 24, and 55 s compared with the unactuated bladder
A Soft Robotic Detrusor Based on Balloon Hydraulic Actuators for Artificial Bladder Voiding
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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
Design and optimization of an actuation strategy for urinary bladder systems
No full textBladder cancer ranks ninth among the most frequently diagnosed cancers worldwide. Disease progression often necessitates radical cystectomy, i.e., complete surgical removal of the urinary bladder, with considerable impact on patients’ quality of life. Current clinical solutions involve either urinary diversion, redirecting urine through an external collection bag, or reconstruction of a neobladder using autologous tissue to replicate the storage function of the native bladder. However, these procedures do not provide patients with sensory feedback regarding bladder fullness, and urine drainage is frequently managed through intermittent catheterization, which often results in recurrent infections. Moreover, these approaches generally offer limited storage capacity of approximately 200 mL. For these reasons, the development of a fully implantable artificial urinary system capable of replicating bladder functions, namely urine storage, fullness sensation and voiding, is highly desirable.
In this context, the aim of this thesis is to develop a novel actuation strategy to be integrated into an existing origami-based artificial bladder, enabling efficient and on-demand voiding. The proposed solution employs a soft, hydraulic, kirigami-inspired actuation system to be integrated along the lateral walls of the artificial bladder. The kirigami-patterned actuator features a planar geometry with strategically arranged triangular subunits created through patterned cuts. Rectangular cross-section channels are embedded within the regions between the cuts: when vacuum is applied, these channels collapse, thereby generating the compressive force required to drive the micturition process of the artificial bladder. Conversely, when these channels are filled with fluid, the actuators relax allowing the artificial bladder to expand and fill with urine. The soft actuators are made of silicone material to ensure safe interaction with surrounding organs in the abdominal cavity.
Initially, the actuator design was defined through finite element (FEM) simulations in Ansys Mechanical to determine optimal geometric (e.g., number of subunits) and structural parameters (e.g., channel dimension). In particular, two geometries were evaluated, incorporating 4 and 12 cuts respectively, with channel widths of 4 mm and 6 mm and heights of 1 mm and 2 mm, yielding to eight distinct design configurations. FEM simulations were analyzed in terms of actuation volume and generated force to identify the optimal configuration. Each configuration was evaluated in different elastomeric materials (Ecoflex 00-50, Moldstar 15, Dragonskin 30, and SmoothSil 936) in ascending order of stiffness to optimize the performance while minimizing resistance to bladder expansion during filling.
The optimal combination of actuator design (i.e. 12 cuts, wall thicknesses of 1 mm, channel dimensions of 4 × 2 mm, and actuation fluid volume of 9.2 mL) and material (Moldstar 15 and Dragonskin 30) were subsequently fabricated and tested on bench. Molding fabrication was performed using a two-step process in which the silicone was poured into two separate molds corresponding to one of the lateral walls and the remaining structure with the embedded channels. After curing, the two layers were bounded together using additional silicone to form a single, integrated structure. This approach allowed preventing air entrapment within the mold, which could otherwise compromise the integrity of the thin-walled structure.
Two experimental phases were conducted: (i) actuator characterization and (ii) voiding performance upon integration on the artificial bladder. The actuator characterization involved the measurement of forces generated during depressurization of the channels using a load-cell setup enabling validation of the FEM simulation results. In particular, a mean absolute error of 0.186 N was showed between the FEM simulations and the experimental results. In addition, elastic and hydraulic contributions were assessed (90% and 10%, respectively, for an elongation of 20 mm). The complete actuation system, composed of four actuators positioned in pairs on the later walls of the artificial bladder, was then integrated and tested. The actuators performed well in both the best-case configuration, with the bladder urethra aligned horizontally, achieving a mean post-void residual volume (PVR) of 12.73 ± 5.59 mL, and the worst-case configuration, with the urethra elevated of 3 cm with respect to the bladder, resulting in a mean PVR of 31.98 ± 5.59 mL. In both cases, the system achieved the clinically relevant target of a PVR below 50 ml. Similarly, the voiding time was always in line with the state of the art of artificial detrusors for artificial bladders (120 ± 4 s and 120 ± 8 s, respectively).
Future investigation should focus on evaluating the durability of the actuation system under cyclic operation conditions and more realistic in-body condition to determine its suitability for long-term implantation. Moreover, integration with artificial sphincters and a sensing system for continuous monitoring of bladder fullness, along with miniaturized electronics for actuator fluid management, would enable the development of the first fully implantable artificial bladder with restored all physiological functions
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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