Fabrication and redesign of a meso-scale six-axis nano-positioner system

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaf 38).The industry's need for low-cost nano-positioners led MIT's Precision Compliant Systems lab to design a system of 10 six-axis meso-scale nano-positioners. They devised a system that could revolutionize the nano-scale industry, by making massive parallel positioning at the nanometer/micro-radian possible at a low cost. In order to test the design, the alpha prototype was built and tested. The fabrication and the assembly processes provided insight into possible redesign changes that would facilitate future manufacturing, as well as improve the performance of the nano-positioner. The fabrication of the prototype also allowed for the exploration of the accuracy of conventional machining methods and their effect on the device performance. Traditional manufacturing was necessary in order to achieve the lowest cost possible. The design was also analyzed from a business perspective and modified to begin the transformation from prototype to profitable product. The construction of the prototype and the proposed changes to the design are important to the development of the project.by Maria J. Telleria.S.B

Design rules and models for the synthesis and optimization of cylindrical flexures

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis. Page 210 blank.Includes bibliographical references (p. 195-197).Cylindrical flexures (CFs) are defined as systems composed of flexural elements whose length is defined by the product of their radius of curvature, R, and sweep angle, [phi]. CFs may be constructed out of a cylindrical stock which leads to geometry, manufacturability, and compatibility advantages over planar flexures. However, CFs present a challenge because their mechanics differ from those of straight beams, and although the modeling of curved beams has been researched in detail [1-4], it has yet to be distilled into compliant element and system creation rules. The lack of relevant design rules has inhibited the process of concept generation and optimization of CF systems, preventing these systems from becoming pervasive in engineering applications. The design guidelines and models developed in this work enable (i) the rapid generation of multiple concepts, (ii) the efficient analysis of different designs and selection of the best design, and (iii) the effective optimization of the chosen concept. The CF synthesis approach presented in this thesis has three components: (i) analysis of element mechanics models to reveal key parameters, (ii) understanding of how the key parameters affect the flexure performance and (iii) guidelines as to how to assemble and optimize CF systems. With the knowledge generated designers will be able to rapidly layout possible designs using the element building blocks and system creation rules, and then use the identified key parameters to optimize a design. The synthesis guidelines were established and tested through the development of two case study flexures: a CF linear guide and an x-y-[theta]z stage. The case studies demonstrate the increased design space of CF systems, which makes it possible for these new flexure mechanisms to meet functional requirements that could not be met using traditional straight-beam flexures.by Maria J. Telleria.Ph.D

Construction of Empirical Care Pathways Process Models from Multiple Real-World Datasets

Care pathways (CPWs) are "multidisciplinary care plans that detail essential care steps for patients with specific clinical problems." While CPWs impact on health or cost outcomes is vastly studied, an in-depth analysis of the real-world implementation of the CPWs is an area that still remains underexplored. The present work describes how to apply an existing process mining methodology to construct the empirical CPW process models. These process models are a unique piece of information for health services research: for example to evaluate their conformance against the theoretical CPW described on clinical guidelines or to evaluate the impact of the process in health outcomes. To this purpose, this work relies on the design and implementation of a solution that a) synthesizes the expert knowledge on how health care is delivered within and across providers as an activity log, and b) constructs the CPW process model from that activity log using process mining techniques. Unlike previous research based on ad hoc data captures, current approach is built on the linkage of various heterogeneous real-world data (RWD) sets that share a minimum semantic linkage. RWD, defined as secondary use of routinely collected data as opposite to ad hoc data extractions, is a unique source of information for the CPW analysis due to its coverage of the caregiving activities and its wide availability. The viability of the solution is demonstrated by constructing the CPW process model of Code Stroke (Acute Stroke CPW) in the Aragon region (Spain)

Understanding the drivers for the development of design rules for the synthesis of cylindrical flexures

Cylindrical flexures (CFs), defined as flexures with only one finite radius of curvature loaded normal to the plane of curvature, present an interesting research direction in compliant mechanisms. CFs are constructed out of a cylindrical stock which leads to geometry, manufacturability, and compatibility advantages. Synthesis rules must be developed to design these new systems effectively. Current knowledge in flexure design pertains to straight-beam flexures or curved flexures loaded along the plane of curvature. CFs present a challenge because their mechanics differ from those of straight beams, and although their modelling has been researched thoroughly it has yet to be distilled into element and system creation rules. This paper uses models and finite element analysis to demonstrate that current design rules for straight-beam flexures are insufficient and inadequate for the design of CF systems. The presented discussion will show that CFs differ both at the element and systems levels, and therefore future research will focus on developing the three components of the building block approach: (i) reworking of element mechanics models to reveal the parameters which cause the kinematics of the curved beam to differ from those of the straight beam, (ii) development of a visual stiffness representation, and (iii) formation of system creation rules

Mifepristone increases mRNA translation rate, triggers the unfolded protein response, increases autophagic flux, and kills ovarian cancer cells in combination with proteasome or lysosome inhibitors

The synthetic steroid mifepristone blocks the growth of ovarian cancer cells, yet the mechanism driving such effect is not entirely understood. Unbiased genomic and proteomic screenings using ovarian cancer cell lines of different genetic backgrounds and sensitivities to platinum led to the identification of two key genes upregulated by mifepristone and involved in the unfolded protein response (UPR): the master chaperone of the endoplasmic reticulum (ER), glucose regulated protein (GRP) of 78 kDa, and the CCAAT/enhancer binding protein homologous transcription factor (CHOP). GRP78 and CHOP were upregulated by mifepristone in ovarian cancer cells regardless of p53 status and platinum sensitivity. Further studies revealed that the three UPR-associated pathways, PERK, IRE1α, and ATF6, were activated by mifepristone. Also, the synthetic steroid acutely increased mRNA translation rate, which, if prevented, abrogated the splicing of XBP1 mRNA, a non-translatable readout of IRE1α activation. Moreover, mifepristone increased LC3-II levels due to increased autophagic flux. When the autophagic–lysosomal pathway was inhibited with chloroquine, mifepristone was lethal to the cells. Lastly, doses of proteasome inhibitors that are inadequate to block the activity of the proteasomes, caused cell death when combined with mifepristone; this phenotype was accompanied by accumulation of poly-ubiquitinated proteins denoting proteasome inhibition. The stimulation by mifepristone of ER stress and autophagic flux offers a therapeutic opportunity for utilizing this compound to sensitize ovarian cancer cells to proteasome or lysosome inhibitors.Fil: Zhang, Lei. University Of South Dakota; Estados UnidosFil: Hapon, María Belén. University Of South Dakota; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Goyeneche, Alicia A.. University Of South Dakota; Estados Unidos. McGill University; CanadáFil: Srinivasan, Rekha. University Of South Dakota; Estados UnidosFil: Gamarra Luques, Carlos Diego. University Of South Dakota; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Callegari, Eduardo A.. University Of South Dakota; Estados UnidosFil: Drappeau, Donis D.. University Of South Dakota; Estados UnidosFil: Terpstra, Erin J.. University Of South Dakota; Estados UnidosFil: Pan, Bo. University Of South Dakota; Estados UnidosFil: Knapp, Jennifer R.. University of Kansas; Estados UnidosFil: Chien, Jeremy. University of Kansas; Estados UnidosFil: Wang, Xuejun. University Of South Dakota; Estados UnidosFil: Eyster, Kathleen M.. University Of South Dakota; Estados UnidosFil: Telleria, Carlos Marcelo. University Of South Dakota; Estados Unidos. McGill University; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Modeling and implementation of solder-activated joints for single actuator, centimeter-scale robotic mechanisms

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 139-140).This thesis explains when, and why, solder-based phase change materials (PCMs) are best-suited as a means to modify a robotic mechanism's kinematic and elastomechanic behavior. The preceding refers to mechanisms that possess joints which may be thermally locked and unlocked via a material phase change within the joint. Different combinations of locked and unlocked joints yield different one-DOF mechanisms states. A single actuator is used to control motion allowed by the different states. By reducing the number of required actuators, solderlocking joints enable the creation of compliant centimeter-scale mechanisms that can perform a multiplicity of tasks. Herein, this thesis presents physics-based design insights that provide understanding of how solder-based material properties and joint design dominate joint performance characteristics. First order models are used to demonstrate selection of suitable PCMs and how to set initial joint geometry prior to fine tuning via detailed FEA models and experiments. The first order models result in order-of-magnitude estimates of the locking and unlocking times for the joints. The insights and models are discussed in the context of two case studies. Squishbot1 is a crawling robot that uses a single spooler motor and three solder-locking joints to crawl and steer. Squishbot 1 is able to reconfigure its joints in approximately 10 seconds. SquishTendons utilizes solder-locking joints to actuate a compliant structure with a single motor. The second robot used the complete set of models and rules to improve on the performance of Squishbotl. SquishTendons can unlock and lock its joints in less than 6 seconds.by Maria J. Telleria.S.M

Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa

Distinct breeding populations of migratory species may overlap both spatially and temporally, but differ in patterns of habitat use. This has important implications for population monitoring and conservation. To quantify the extent to which two distinct breeding populations of a migratory shorebird, the Black-tailed Godwit Limosa limosa, overlap spatially, temporally and in their use of different habitats during winter. We use mid-winter counts between 1990 and 2001 to identify the most important sites in Iberia for Black-tailed Godwits. Monthly surveys of estuarine mudflats and rice-fields at one major site, the Tejo estuary in Portugal in 2005-2007, together with detailed tracking of colour-ringed individuals, are used to explore patterns of habitat use and segregation of the Icelandic subspecies L. l. islandica and the nominate continental subspecies L. l. limosa. In the period 1990-2001, over 66 000 Black-tailed Godwits were counted on average in Iberia during mid-winter (January), of which 80% occurred at just four sites: Tejo and Sado lower basins in Portugal, and Coto Dontildeana and Ebro Delta in Spain. Icelandic Black-tailed Godwits are present throughout the winter and forage primarily in estuarine habitats. Continental Black-tailed Godwits are present from December to March and primarily use rice-fields. Iberia supports about 30% of the Icelandic population in winter and most of the continental population during spring passage. While the Icelandic population is currently increasing, the continental population is declining rapidly. Although the estuarine habitats used by Icelandic godwits are largely protected as Natura 2000 sites, the habitat segregation means that conservation actions for the decreasing numbers of continental godwits should focus on protection of rice-fields and re-establishment of freshwater wetlands