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The use of prototypes as testing instruments has become a common strategy in the innovation of services and products and increasingly in the implementation of "smart" urban policies through living labs or pilots. As a technique for validating hypotheses about the future performance of products or policies, prototyping is based on the idea of generating original knowledge through the failures produced during the testing process. Through the study of an experimentation and prototyping project developed in Santiago de Chile called "Shared Streets for a Low-Carbon District," I analyse the technique of prototyping as a political device that can make visible (or invisible) certain entities and issues, determining what the experimental entities can do and say. I will show how the technique of prototyping defines modes of participation, what is visible and thinkable, what can be spoken and what is unspeakable. In this sense, I examine two ambivalent capacities of prototyping: as a mechanism of management and enrolment that seeks to prescribe normativities (problem-validating prototype) and as an event that can make frictions tangible, articulating matters of concern and ways to open up alternative scenarios (problem-making prototype).
(© 2019 London School of Economics and Political Science.)
It is technically demanding and requires rich experience to insert the translaminar facet screw(TFS) via the paramedian mini-incision approach. It seems that it is easy to place the TFS using computer-assisted design and rapid prototyping(RP) techniques. However, the accuracy and safety of these techniques is still unknown. The aim of this study is to assess the accuracy and safety of translaminar facet screw placement in multilevel unilateral transforaminal lumbar interbody fusion using a rapid prototyping drill guide template system. A patient-matched rapid prototyping translaminar facet screw guide was examined in fourteen cadaveric lumbar spine specimens. A three-dimensional (3D) preoperative screw trajectory was constructed using spinal computed tomography scans, from which individualized guides were developed for the placement of translaminar facet screws. Following bone tunnel establishment, the 3D positioning of the entry point and trajectory of the screws was compared to the preoperative plan as found in the Mimics software.Among 60 trajectories eligible for assessment, no cases of clinically significant laminar perforation were found. The mean deviation between the planned and the actual starting points on spinous process was 1.22 mm. The mean tail and submergence angle deviation was found to be 0.68°and 1.46°, respectively. Among all the deviations, none were found to have any statistical significance. These results indicate that translaminar facet screw placement using the guide system is both accurate and safe.
Purpose: To explore 3D printing for rapid development of prototype thin slab low-Z/density ionization chamber arrays viable for custom needs in radiotherapy dosimetry and quality assurance (QA).
Materials and Methods: We designed and fabricated parallel plate ionization chambers and ionization chamber arrays using an off-the-shelf 3D printing equipment. Conductive components of the detectors were made of conductive polylactic acid (cPLA) and insulating components were made of acrylonitrile butadiene styrene (ABS). We characterized the detector responses using a Varian TrueBeam linac at 95 cm SSD in slab solid water phantom at 5 cm depth. We measured the current-voltage (IV) curves, the response to different energy beam lines (2.5 MV, 6 MV, 6 MV FFF) for various dose rates and compared them to responses of a commercial Exradin A12 ionization chamber. We measured off-axis ratio (OAR) for several small field static multi-leaf collimators field sizes (0.5-3 cm) and compared them to OAR data obtained for commissioning of stereotactic radiotherapy. Results: We identified the printing capability and the limitations of a low-cost off-the-shelf 3D printer for rapid prototyping of detector arrays. The design of the array with sub-millimeter size features conformed to the 3D printing capabilities. IV-curve for the array showed a strong polarity effect (8%) due to the design. Results for the parallel plate and the array compared well with A12 chamber: monitor unit (MU) dependence for the array was within a few % and the response to different energy beam lines was within 1%. Off-axis dose profiles measured with the array were comparable to dose profiles obtained in water tank and stereotactic diode after accounting for the size of the chambers. Dose error was within 2% at the center of the profile and slightly larger at the penumbra. Conclusions: Rapid prototyping of ion chambers by means of low-cost 3D printing is feasible with certain limitations in the design and spatial accuracy of the printed details. (© 2019 American Association of Physicists in Medicine.)
A rapid and inexpensive method to produce high-resolution liquid metal patterns and electronics on stretchable substrates was introduced. Two liquid-phase gallium-indium (GaIn) alloy patterns, conductive lines, and interdigitated electrodes, were directly written or shadow mask-printed on a prestretched elastomeric substrate surface. Then, the prestretched substrate was released to recover its original length, and thus, electronic patterns simultaneously shrank on it. After these patterns were transferred to another prestretched substrate by the stamp printing method, the patterning resolution was demonstrated to increase by totally 50 times for the two successive stretch-release-shrink operations. Additionally, the resistance of the handwritten liquid metal conductive line traces remained nearly unchanged during the stretching process, which is believed to be feasible for electrical connections in stretchable electronics. The rapid prototyping of a serpentine strain sensor was successfully demonstrated to be highly sensitive and repeatable with a stretching ratio ranging from 0 to 200%. The proposed method paves a new way to fabricate stretchable electronic devices with high patterning resolution.
(Copyright © 2019 American Chemical Society.)
Statement Of Problem: Although closed hollow obturator prostheses provide the benefit of minimized weight, they also pose challenges. They are complex to fabricate, and contaminated water can easily enter the hollow section through the joined part, making them unsanitary and leading to malodor and increased weight.
Purpose: The purpose of this in vitro study was to investigate the hermeticity and durability of a hollow obturator model fabricated by using computer-aided design (CAD) and rapid prototyping (RP) techniques and to evaluate the possibility of its clinical use. Material and Methods: Leak testing was used to evaluate the hermeticity and durability of hollow spherical obturator specimens with an outer diameter of 30 mm and 2 different wall thicknesses (1.5 and 2.0 mm). Six specimens were fabricated for each of the wall thicknesses by using CAD and RP techniques. The accumulation of fluids in the hollow obturator specimens was evaluated every day by using megascopic observation with photoirradiation from the base of the specimens. The amount of water absorption and the rate of increase in the weight of the 2 specimens were calculated and compared. Statistical analysis was performed by using the Mann-Whitney U test (α=.05). Results: The application of CAD and RP techniques made it possible to fabricate a hollow obturator model specimen with completely unified parts. The 1.5-mm specimen showed an absorption rate (2.61%) that significantly exceeded that of the 2.0-mm specimen (2.53%) on day 130 (P=.006). By the end of the observation period, the 1.5-mm specimen exhibited large amounts of water absorption and destruction. The 1.5-mm-thick wall had reduced hermeticity than the 2.0-mm-thick wall. Conclusions: A fully unified hollow obturator model with 2.0-mm-thick walls was fabricated by using CAD and RP techniques. The absence of any joints prevented fluid accumulation, making this method suitable for the fabrication of hollow prostheses. (Copyright © 2019 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)
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