Tesis sobre el tema "Spatial control"
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Messin, Liam J. "Spatial control of microtubule shrinkage". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/94871/.
Texto completoLino, Christophe. "Virtual camera control using dynamic spatial partitions". Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00916835.
Texto completoNi, Jie. "Control of the spatial double inverted pendulum". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104855.
Texto completoLa stabilisation d'un double pendule spatiale inversé actionné à la hanche peut-être considérée comme un problème de contrôle de la posture d'un robot humanoïde. Basé sur un modèle existant de ce système mécanique sous-actionné avec quatre degrés de liberté, l'ultime objectif est de concevoir un régulateur approprié pour obtenir une stabilisation globale autour de l'instable position d'équilibre debout. Cette thèse présente un certain nombre d'algorithmes de contrôle et les résultats de simulation qui permettent une stabilisation locale ou semi-globale pivoter-vers-le-haut. Pour l'effort de stabilisation locale dans le voisinage de la position d'équilibre en position verticale, à la fois un contrôleur lqr et trois types de linéarisation basée sur des algorithmes de contrôle de mode glissant sont présentés. La région de la convergence du contrôleur lqr est étudiée. La performance et la robustesse du système sont comparées pour tous les contrôleurs. Afin de réaliser la strateǵie semi-globale pivoter-vers-le-haut, deux types d'approches de commande non linéaire de mode glissant sont explorés pour le balancement du système dans un essai pour amener le système dans la région de convergence locale des contrôleurs linéaires. L'approche hybride est proposée pour passer du contrôleur pour pivoter-vers-le-haut à un contrôleur linéaire local sous certaines conditions dans le voisinage de l'équilibre en position verticale afin de compléter l'effort de stabilisation. Toutefois, malgré des ajustements des contrôleurs, il n'a pas été possible de parvenir à une stabilisation globale avec une telle approche. Une enquête plus profonde est nécessaire pour résoudre ce problème. La contribution principale de cette thèse est la réussite une d'extension d'algorithmes de commande de 2-dimensions de mode glissant qui existent pour le cas de 3-D pour le contrôle du double pendule inversé spatial. Les contrôleurs de mode glissant basés sur un modèle du système linéarisé servent comme alternatives au contrôleur lqr pour la stabilisation locale. Les contrôleurs de mode glissant non-linéaires sont capables, à partir d'une configuration loin de l'équilibre de mettre le système dans la proximité de l'équilibre debout vertical utilisant le principe semi-global pivoter-vers-le-haut.
Gauthier, Thomas P. 1980. "Spatial control of cavitation in therapeutic ultrasound". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30171.
Texto completoIncludes bibliographical references (p. 60-65).
Inertial cavitation has been implicated as the primary mechanism for a host of emerging applications. In all these applications, the main concern is to induce cavitation in perfectly controlled locations in the field; this means specifically to be able to achieve cavitation threshold at the geometrical focus of the transducer without stimulating its near field. In this study, we make use of dual-frequency methods to preferentially lower the cavitation threshold at the focus relative to the rest of the field. One family of dual-frequency driving waveforms is evaluated in a bubble model incorporating rectified diffusion. Theoretical predictions based on Sokka's work (Sokka 2003a) are confirmed in vitro using Optison[TM], a commercially available contrast agent. The performance of the rest of acoustic field in suppressing cavitation when cavitation is induced at the focus is investigated theoretically and checked experimentally. This first part shows that dual-frequency phased arrays could be used to precisely control cavitation. Cavitation threshold is proved to be 1.2 times higher in the near field than at the focus. One of the main limitations of the aforementioned protocol is that it is tightly controlled. As an example, Optison[TM] has a mean bubble size of 2 - 4.5 [micro]m, which means that the initial bubble radii will fall in this range. Since cavitation threshold has been proved to depend on this parameter, using ultrasound contrast agents allows for more predictable results. Therefore, in the second half of this study, we propose a focused ultrasound protocol that induces and monitors gas bubbles at the focus and allows for ex vivo validation of the aforementioned theoretical results. The experiments involve fresh rabbit tissue and a statistical analysis is performed over data collected from back muscle.
(cont.) Moreover, the experimental apparatus is designed to be MRI-compatible to make future in vivo assessments feasible. This second half of the study demonstrates that the theoretical predictions made earlier can reliably be used to predict dual-frequency cavitation thresholds. It also suggests that clinical use of dual-frequency excitations might be a solution to the problem of spatial control of cavitation.
by Thomas P. Gauthier.
S.M.
Chen, Yiyang. "Iterative learning control for spatial path tracking". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/415865/.
Texto completoChen, Chih-Keng. "Nonholonomic control of coupled spatial multibody systems". Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057091907.
Texto completoFairbairn, Jonathan Paul. "Spatial and temporal dynamics of entomopathogenic nematodes". Thesis, University of Stirling, 2001. http://hdl.handle.net/1893/26685.
Texto completoLee, Yong Keat. "Active vibration control of a piezoelectric laminate plate using spatial control approach". Title page, abstract and table of contents only, 2005. http://hdl.handle.net/2440/37711.
Texto completoThesis (M.Eng.Sc.)--School of Mechanical Engineering, 2005.
Volpe, Giorgio. "Nanoscale spatial control of light in optical antennas". Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/96168.
Texto completoEl control dinámico y determinístico de la luz en una escala espacial por debajo de la longitud de onda es un requisito clave para ampliar los conceptos y las funcionalidades de la macro-óptica hasta la escala nanométrica. Un mayor nivel de control también tendrá implicaciones importantes en nuestra comprensión de los fenómenos ópticos en la nanoescala. Uno de los principales problemas en nano-óptica tiene como objetivo describir cómo y con qué precisión es posible controlar la distribución espacial de la luz de forma dinámica en la nanoescala. Desafortunadamente, un límite fundamental de la física – el límite de difracción de la luz – afecta nuestra capacidad de seleccionar ópticamente puntos separados por menos de media longitud de onda de la luz. El campo de la plasmónica ofrece una oportunidad única para cerrar la brecha entre el límite de difracción y la escala nanométrica. Nanoantenas metálicas pueden acoplarse eficientemente a luz propagante y focalizarla en volúmenes nanométricos, y viceversa. Además, estas nanoantenas prometen mejorar significativamente la eficiencia de procesos como le fotodetección, la emisión de luz, sensores, transferencia de calor, y espectroscopía a la escala nanométrica. Aprender a controlar de forma precisa la respuesta óptica de estas nanoantenas representa un enfoque muy prometedor para controlar la distribución espacial y temporal de la luz a la escala nanométrica. Tradicionalmente, se han desarrollado dos principales estrategias para el control de la respuesta óptica de nanoantenas plasmónicas: la primer estrategia (estrategia estática) tiene como objetivo la optimización del diseño geométrico de las nanoantenas acorde a su aplicación, mientras que la segunda estrategia (estrategia dinámica) tiene como objetivo la modulación reversible del campo cercano de una nanoestructura dada a través de la manipulación de la luz de excitación en el tiempo y el espacio. El trabajo presentado en esta Tesis extiende el estado del arte de estas dos estrategias, y desarrolla nuevas herramientas, tanto experimentales como teóricas, para ampliar el nivel de control que tenemos sobre la distribución espacial de la luz debajo del límite de difracción. Después de presentar una visión general de los principios básicos de nano-óptica y de la óptica de lo plasmones de superficie, el Capítulo 1 repasa los avances en el control de la respuesta óptica de nanoestructuras metálicas – sea por una estrategia estática o dinámica – en el momento en que se inició este trabajo de investigación. La modificación de la geometría y las dimensiones de las nanpartículas metálicas sigue siendo un ingrediente fundamental para controlar las resonancias plasmónicas y los campos de luz a la escala nanométrica. Como ejemplos novedosos de control estático, por lo tanto, los Capítulos 2 y 3 estudian nuevos diseños de estructuras plasmónicas con capacidades sin precedentes de modelar campos de luz a la escala nanométrica, en particular un diseño fractal y una nanoantena unidireccional tipo Yagi-Uda. Los Capítuols 4 y 5 describen una nueva herramienta teórica y experimental para el control dinámico y determinístico de la respuesta óptica de nanoantenas basada en la modulación espacial de la fase de la luz de excitación: el campo óptico cercano, que resulta de la interacción entre la luz y las nanoestructuras plasmónicas, es normalmente determinado por la geometría del sistema metálico y las propiedades de la luz incidente, como su longitud de onda y su polarización; sin embargo, el control exacto y dinámico del campo óptico cercano debajo de límite de difracción de la luz – independientemente de la geometría de la nanoestructura – es también un ingrediente importante para el desarrollo de futuros dispositivos nano-ópticos y para ampliar los conceptos y las funcionalidades de la óptica macroscópica a la escala nanométrica. Finalmente, la Conclusión resume los resultados de este trabajo y ofrece una visión general de algunos estudios paralelos a esta tesis. Algunas de las observaciones finales permiten echar un vistazo a las perspectivas y estrategias futuras para complementar el control estático y el control dinámico en una única herramienta, que podría avanzar enormemente nuestra capacidad de controlar la respuesta óptica de nanoantennas debajo del límite de difracción.
Bullock, Adrian. "SPACE : SPatial Access Control for collaborative virtual Environments". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285675.
Texto completoZaidi, Syed Ali Mustafa. "Accelerating control-flow intensive code in spatial hardware". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708878.
Texto completoBrown, Gillian Louise. "Spatial control of ligand presentation on biomaterial surfaces". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/57669.
Texto completoIncludes bibliographical references (leaves 201-211).
Adhesion of many cell types to the extracellular matrix or to synthetic bioactive surfaces is mediated by transmembrane integrin receptors. Integrin clustering is believed to be closely associated with focal contact formation and signaling, as assessed by the behavior of cells on surfaces presenting relatively uniform ligand distributions. It has therefore been hypothesized that controlled clustering of 2, 3.....n integrins might be achieved by controlling the spatial distribution of adhesion ligands on biomaterial surfaces. Substrates were prepared on which cell-surface interactions are controlled by modifying non-adhesive poly(ethylene oxide) (PEO) hydrogels with the minimal cell-adhesion peptide sequence GRGDY (RGD). The peptide is tethered to the hydrogel surfaces via star PEO molecules, producing surfaces on which the ligands are presented to cells in "clusters", or domains of high concentration. The substrates are compared with others on which the RGD peptide is uniformly distributed. Control of the RGD cluster size was achieved by varying the relative concentrations of reactants in solution. The binding of RGD-modified stars to surfaces was found to be a non-linear function of its concentration in solution and degree of modification, and is reasonably explained by a Langmuir model of competitive adsorption. Quantitative techniques for visualizing the ligand distribution on the surface were developed, and indicated that surfaces to which ligands had been tethered via star molecules showed a significant deviation from normal, random distribution. Thus, control of the ligand spatial distribution was achieved. In addition, preliminary biological testing suggests that substrates on which adhesion ligands are presented to cells in a clustered format produces more physiological behaviour than those on which ligands are uniformly distributed at the same average ligand density. Thus, we have fabricated surfaces which, because of their resistance to non-specific cell interactions and the control of specific interactions at the molecular level, can serve as a model for artificial matrix development and can be used for fundamental in vitro studies.
by Gillian L. Brown.
Ph.D.
Falk, Jill E. "Mechanisms underlying spatial control of exit from mitosis". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103238.
Texto completoDVD-ROM contains 4 supplemental movies (mov.) for Chapter III.
Both MIT Institute Archives and Science Library copy: with DVD-ROM.
Cataloged from PDF version of thesis.
Includes bibliographical references.
During mitosis, cells must accurately segregate their genome in order to produce healthy daughter cells. In budding yeast, cells align their anaphase spindle along a predetermined axis of division in order to partition their genome into the daughter cells. In the event that the spindle becomes mispositioned, cells will prevent exit from mitosis by inhibiting the mitotic exit network (MEN). The MEN functions to regulate the localization of the essential phosphatase Cdc 4. Control of the MEN by spindle position is established through MEN inhibitory signals in the mother cell compartment (such as the kinase Kin4), MEN promoting signals in the bud (such as Ltel) and a GTPase sensor (Tem1) that moves between them. While the molecular functions of Kin4 and Tem1 are well defined, the function of Ltel has remained unclear. In the first part of this thesis I attribute a function to Ltel in promoting exit from mitosis. I show that Ltel functions to prevent Kin4 from inappropriately localizing to SPBs (spindle pole bodies) in the bud cell compartment. I find that these two proteins interact and that the Nterminus of Kin4 mediates this interaction. This work highlights the importance of spatial restriction of Ltel in the bud and Kin4 in the mother for the proper execution of chromosome segregation in anaphase. In the second part of this thesis I investigate the role of cytoplasmic microtubules in spatial regulation of the MEN. It has been proposed that spatial regulation of the MEN functions as a checkpoint that requires contact between cytoplasmic microtubules (cMTs) and the budneck to arrest cells in anaphase. Loss of cMT-budneck contact was reported to lead to checkpoint failure resulting in anucleate and multinucleate cells. In contradiction to these results, I find that Cdc14 release is responsible for the loss of cMT-budneck interactions that precede inappropriate exit from mitosis. Lastly, through the generation of cells with two nuclei, I show that the coupling of spindle position to exit from mitosis is established in a dual manner through both inhibitory signals in mother cell compartment and through activating signals in the bud.
by Jill E. Falk.
Ph. D.
Brand, Samuel P. C. "Spatial and stochastic epidemics : theory, simulation and control". Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56738/.
Texto completoUhl, Brecken. "Direct Spatial Antenna Modulation for Wideband Phase Control". International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/604278.
Texto completoDirect spatial antenna modulation (DSAM) is a new approach to phased array control that opens up new "smart antenna" architecture possibilities. The DSAM technique leverages the inherent spatial differences of excitation in an antenna in a novel way to achieve the equivalent of conventional modulation and beam control effects. Smart antenna techniques are of potentially increasing importance to test range operations given a trend toward more flexible, internetworked, and autonomous test activities. The DSAM technique has been demonstrated through several generations of analysis, simulation, and prototyping, but has previously only been applied to narrowband antenna designs. Furthermore, the IQ DSAM approach in particular has not been previously implemented in hardware. This paper details the application of IQ DSAM to achieve wideband phase control using a commercial off the shelf (COTS) antenna. The phase control performance of IQ DSAM over a range of 1.5 GHz to 4 GHz is measured across relative field control angles of +/- 45 degrees. The measured IQ DSAM performance is compared to what could be expected from a conventional phased array element control architecture.
Schultheis, Holger. "Computational cognitive modeling of control in spatial cognition". Lengerich Berlin Bremen Miami, Fla. Riga Viernheim Wien Zagreb Pabst Science Publ, 2009. http://d-nb.info/998029661/04.
Texto completoDylla, Frank. "An agent control perspective on qualitative spatial reasoning : towards more intuitive spatial agent development /". [Berlin] : Aka, 2008. http://d-nb.info/989997510/04.
Texto completoHargrave, Stephen Mark. "Spatial material transport and processing systems : modelling, simulation and control". Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322919.
Texto completoWeger, Ulrich Wolfgang. "Spatial and linguistic control of eye movements during reading". Diss., Online access via UMI:, 2005.
Buscar texto completoHowarth, Richard J. "Spatial representation, reasoning and control for a surveillance system". Thesis, Queen Mary, University of London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369664.
Texto completoJackson, David P. "Spatial control of transcription in flowers of Antirrhinum majus". Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292659.
Texto completoHinder, Steven. "The compositional and spatial control of self-assembled monolayers". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364666.
Texto completoZheng, Xiao. "Mid-spatial frequency control for automated functional surface processing". Thesis, University of Huddersfield, 2018. http://eprints.hud.ac.uk/id/eprint/34723/.
Texto completoAtwood, Emma Katherine. "Spatial Dramaturgy and Domestic Control in Early Modern Drama". Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104813.
Texto completoThesis advisor: Andrew Sofer
Spatial Dramaturgy and Domestic Control in Early Modern Drama explores the social components of early modern domestic architecture and the spatial practices that helped to dramatize them. Each chapter examines a particular domestic feature—doors, windows, galleries, studies—and considers its role in a variety of early modern plays. Methodologically, I bridge the gaps between literary study, dramaturgy, and history by analyzing the palimpsest of the physical stage (e.g., the upper playing balcony) and the fictional spaces produced in performance (e.g., Juliet’s window). My work takes its influence from literary scholars, primarily Lena Cowen Orlin and Patricia Fumerton; theater historians, primarily Tim Fitzpatrick, Alan Dessen, Leslie Thompson, and Mariko Ichikawa; and architectural historians, primarily Mark Girouard and Alice T. Friedman. Bringing together these fields of study allows me to reconsider the theory of the unlocalized early modern stage that has largely dominated scholarly and theatrical approaches to early modern theater for half a century. In my first chapter, “Doors and Keys: Enclosure and Spatial Control,” I argue that doors and keys operate in productive tension with the spatial flexibility of the “unlocalized” stage, troubling the fantasy of domestic spatial control in plays such as A Woman Killed With Kindness and The Comedy of Errors. In my second chapter, “Windows: Locus, Platea, and Contested Authority,” I explore the way window scenes in plays such as Romeo and Juliet and Women Beware Women provide a liminal space between house and street where the tiring house façade and the apron of the stage could intersect. My third chapter, “Galleries: Feigned Soliloquy and Interiority,” shows how playwrights used gallery settings to stage feigned soliloquy, exposing the limits of private speech and the struggle to access another person’s most inner thoughts. My final chapter, “Studies: Hauntings and Impossible Privacy,” looks at plays that feature ghosts or devils in studies, such as Doctor Faustus and Friar Bacon and Friar Bungay, to argues that these supernatural elements reflect the ease with which playwrights could violate presumably protected spaces. In turn, these hauntings explore the danger presented in early modern humanism: that the most haunted place of all is one’s own mind
Thesis (PhD) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: English
Hegarty-Cremer, Solene G. "Spatial control and cell guidance in evolving biological tissues". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207246/1/Solene_Hegarty-Cremer_Thesis.pdf.
Texto completoDai, Jing. "Efficient Concurrent Operations in Spatial Databases". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28987.
Texto completoPh. D.
Wang, Xuan. "Contrôle de forme d'un miroir spatial par actionneurs piézoélectriques". Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0043/document.
Texto completoThe next generation of space-based observation systems will make use of larger primary mirrors to achieve higher image resolution. Large primary mirrors lead to the increase of structural flexibility and are more susceptible to distortions. Thus maintaining optical tolerances across the mirror surface becomes increasingly difficult. The techniques of active shape control may be required for spatial mirror surfaces in future space observation systems. Piezoelectric actuators are often studied as embedded elements for the active control of mirror structures due to their excellent properties. However, unwanted nonlinear effects in piezoelectric actuators, i.e., hysteresis and creep, severely limit the service performance. This thesis aims at developing openloopcontrol laws to compensate hysteresis and creep effects in piezoelectric actuators. The studies led during this thesis are applied to the shape control of spatial mirror surfaces. An experimental setup with a small-scale mirror test structure involving multiple piezoelectric actuators is first developed and is used as support for all the measurements conducted during this thesis. Then the open-loop control methodologies of creep compensation, hysteresis compensation, and simultaneous compensation of both the nonlinear effects in a single piezoelectric actuator are respectively developed. To compensate creep, a nonlinear viscoelastic model is used to portray creep, and a new inverse model of creep based on the concept of “voltage relaxation” is proposedRegarding the hysteresis compensation, the classical Preisach model is modified by adding a derivative term in parallel to describe hysteresis more accurately with relatively few measurements, and the new inverse model is constructed in the similar way. For the simultaneous compensation of the two nonlinear effects, the hysteresis is first compensated and then, the creepof the hysteresis-compensated piezoelectric actuator is attenuated by open-loop control. The methodology is first developed for a single actuator. Finally, the shape control of a mirror surface with several piezoelectric actuators is achieved by actuating the points on the mirror surface in such a way as to reach the required displacements. The mirror test structure involving multiplepiezoelectric actuators compensated in hysteresis and creep is considered as a linear system on which the superposition principle can be applied. The influence coefficients characterizing the coupling effect between the piezoelectric actuators are determined by measurements. The influence coefficient matrix is first constructed using the superposition principle, and is then inverted. By insertion of the inverse matrix in cascade with multiple piezoelectric actuators with hysteresis and creep compensation, a feed-forward control approach to actuate the multiple interesting points of the mirror surface is developed. A number of experimental results demonstrate that the developed control methodologies are effective and feasible in practice
Oscarsson, Joakim. "A spatial presence of thoughtfulness : Electrolux experience". Thesis, Konstfack, Industridesign, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-2834.
Texto completoExamensarbete Industridesign kandidatexamensarbete
Kircali, Omer Faruk. "Active Vibration Control Of A Smart Beam: A Spatial Approach". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607555/index.pdf.
Texto completoNewman, Lisa J. "MYB misexpression links the spatial control of lignification with photomorphogenesis". Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365719.
Texto completoHsieh, Shulan. "Shifting task 'set' : exploring non-spatial aspects of intentional control". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316858.
Texto completoWebb, Richard Davis 1957. "Spatial frequency based closed-loop control of sheet metal forming". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14827.
Texto completoGuo, Ruey-Shan. "Modeling, optimization, and control of spatial uniformity in manufacturing processes". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13459.
Texto completoGossain, Hrishikesh. "Power Control and Spatial Reusability in Mobile Ad Hoc Networks". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115308673.
Texto completoHarvey, Sean [Verfasser]. "Nanoscale spatial control and application of poly(catecholamines) / Sean Harvey". Ulm : Universität Ulm, 2021. http://d-nb.info/1225400945/34.
Texto completoAslani, Pegah. "Active Control of Cylindrical Shells Using the Weighted Sum of Spatial Gradients (WSSG) Control Metric". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6454.
Texto completoMoore, Brandon Joseph. "Cooperative strategies for spatial resource allocation". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180971769.
Texto completoShrekenhamer, David. "Dynamic Control of Metamaterials at Terahertz Frequencies". Thesis, Boston College, 2013. http://hdl.handle.net/2345/3152.
Texto completoProgress in the field of metamaterials has started coming to a point where the field may finally begin to emerge as a viable solution to many electromagnetic challenges facing the community. No where is that more true then at terahertz frequencies where there lies an immense opportunity for growth. The development of mature technologies within this region of the electromagnetic spectrum would provide a valuable resource to become available for a multitude of applications. In order to achieve this, the necessary first steps of identifying viable materials and paths to integrate these with metamaterials will need to be completed. In this dissertation, we examine several different paths to achieve dynamic metamaterial electromagnetic response at terahertz frequencies, and demonstrate several paths to package these devices into imaging systems. In Chapter 1, we introduce the basic theory and design principles of metamaterials. We also describe the experimental techniques involved in the study of terahertz metamaterials. Chapter 2 presents a computational and experimental study investigating the integration of high electron mobility transistors with metamaterials allowing for high speed modulation of incident terahertz radiation. In Chapters 3 and 4, we investigate several different paths to create tunable terahertz metamaterial absorbers. Chapter 3 presents an investigation where we encapsulate a metametarial absorber unit cell with liquid crystals. We study both computationally and experimentally the tuning mechanism of the absorber as the liquid crystal refractive index is controlled as a function of the applied electric field strength and modulation frequency. In Chapter 4, we form a doped semiconducting metamaterial spatial light modulator with multi-color super-pixels composed of arrays of electronically controlled terahertz metamaterial absorbers. We computationally and experimentally study the independent tunability of each pixel in the spatial array and demonstrate high speed modulation. Chapter 5 introduces a multiplex imaging approach by using a terahertz spatial light modulator to enable terahertz imaging with a single pixel detector. We demonstrate the capability for high speed image acquisition, currently only limited by the commerical software used to reconfigure the spatial masks. We also configure the system to capture high fidelity images of varying complexity. In Chapter 6, we show how a metamaterial absorber can be implemented into a detector focal plane array for high sensitivity, low mutual coupling, and broad angle performance. Finally, we summarize in Chapter 7 the achievments of the research presented and highlight the direction of future work
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
Gupta, Maneesh Kumar. "Stimuli-responsive hybrid nanomaterials: spatial and temporal control of multifunctional properties". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45920.
Texto completoSinclair, Scott. "Pattern formation and control of spatial structures in optical parametric oscillators". Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249142.
Texto completoTekin, Halil. "Microengineered responsive platforms for spatial and geometrical control of multicellular organizations". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79222.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references.
Living systems are composed of complex multicellular organizations containing various cell types spatially distributed in defined microenvironments. The intricate cell-cell and cell-matrix interactions in these microenvironments regulate the cell fate, differentiation of the cells, and functions of the associated tissues. Recreating these complex associations in vitro can be highly useful for fabricating biomimetic tissues for regenerative medicine, disease models for drug discovery, and models to study embryogenesis. This thesis focused on developing microscale responsive platforms for spatial and geometrical control of multicellular organizations. The first part of the thesis describes methods to fabricate spherical and stripe microtissues of single cell types and their temperature-controlled retrieval. These microtissues were scaffold-free and can potentially produce homotypic cell-cell interactions. Microwells fabricated from poly(Nisopropylacrylamide) (PNIPAAm) responded to temperature by changing their shapes. Spherical microtissues of a single cell type were formed in responsive microwells and recovered by using shape changing properties of microwells. Elastomeric microgrooves were conformally coated with PNIPAAm to first generate stripe microtissues of a single cell type, and then harvest them by exploiting the temperature-dependent hydrophilicity and swelling change of PNIPAAm film. The second part of the thesis introduces techniques to control spatial and geometrical distribution of multiple cell types in scaffold-free and scaffold-based tissues. Shape changing properties of dynamic microwells facilitated the sequential patterning of multicompartment hydrogels. Different cell types were spatially arranged in different compartments of microgels which may lead to complex cell-matrix interactions replicating native tissues. Shape changing properties of dynamic microwells were also employed to seed different cell types at different temperatures within defined geometries to control spatial and geometrical organization of multiple cell types. Resulting scaffold-free tissues can potentially produce homotypic and heterotypic cell-cell interactions. Dynamic microstructures with different geometries could be used to recapitulate complex native tissues with controlled cell-cell and cell-matrix interactions. The techniques presented in this thesis are versatile and may potentially be useful for replicating biological complexities for a wide range of applications in tissue engineering, regenerative medicine, drug discovery, developmental biology, and cancer biology.
by Halil Tekin.
Ph.D.
Chao, Ling Ph D. Massachusetts Institute of Technology. "Spatial and temporal control of lipid-membrane morphology induced by sphingomyelinase". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51670.
Texto completoThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 195-201).
Sphingomyelinase (SMase) has been shown to be involved in a variety of cell regulation processes. It can convert sphingomyelin (SM) to ceramide (Cer) and has been suggested to influence the cellular processes by reorganizing the cell membrane morphology. This thesis aims at a more comprehensive understanding of how sphingomyelinase (SMase) can regulate lipid membrane heterogeneity. We develop corralled model raft membranes in a microfluidic device to study the complex phase phenomena induced by SMase. The mass balance of lipid molecules in each confined corral greatly helps us to interpret results. By using the corralled membrane arrays, we are able to obtain the overall statistical distribution of the induction time of a slow domain nucleation and therefore fairly compare the membrane responses caused by different factors. In addition, the flow control by a microfluidic device solves the difficulty of distributing SMase uniformly to membrane systems. Furthermore, the laminar flow in a microchannel allows us to create model membrane arrays with a variety of lipid membrane compositions or solution conditions, which can serve as a screening tool to study a broad range of parameters associated with the interactions between lipid membranes and SMase or other peripheral proteins. We report that SMase can induce both a reaction-induced and a solvent-mediated phase transformation, causing switches of three stationary membrane morphologies and multiple-time-domain ceramide generation in model raft membranes.
(cont.) During the reaction-induced phase transformation, the ceramide generated by SMase causes the disintegration of pre-existing rafts rich in sphingomyelin and cholesterol, and recruit sphingomyelin to form SM-enriched domains which are relatively inaccessible to SMase. Once most of the sphingomyelin is physically trapped in SM-enriched domains and the SM concentration in the SMase-accessible region becomes low, the morphology pauses. The pause situation is resolved after the formation of a 3-D feature, rich in SMase, sphingomyelin (SMase's substrate), and ceramide (SMase's product), which triggers the solvent-mediated phase transformation. This 3-D feature is hypothesized as a slowly nucleating SMase-enriched phase where SMase processes sphingomyelin at low concentration more efficiently. The disparate time-scales of the formation of these SMase-features and the SM-enriched domains allow for the development of a significant duration of the middle pause morphology between the two transformations. The results show that SMase can be actively involved in the lipid membrane phase changes. The SMase-induced multi-stage morphology evolution is not only due to the membrane compositional changes caused by SMase,but also due to the selective binding of SMase, and SMase's special phase behavior during the solvent-mediated phase transformation. We further demonstrate that lipid membrane composition and SMase concentration can be used to tune the two phase transformations and therefore the intervals and spatial patterns of Smase-induced multi-stage morphology evolution.
(cont.) At a physiologically relevant concentration of SMase, we observe that membrane composition can influence the formation of SM-enriched domains and the nucleation of SMase-features at different extents of time scale and thus significantly tune the stable duration of the middle pause morphology. More importantly, the induction time of SMase-feature nucleation can be significantly decreased by increasing the supersaturating level of its three components in the membrane system. We further model the spatio-temporal morphology change during the solvent-mediated phase transformation. Three major kinetic processes are described in the model: the consumption of SM by the enzymatic reaction at an SMase-feature, the diffusion of SM from SM-enriched domains to an SMase-feature, and the release of SM due to the dissolution of SM-enriched domains. We combine MATLAB coding with Comsol, a software using finite element method to solve partial differential equations, to solve the model numerically due to the complex geometry and the moving boundary of our membrane systems. The non-dimensionality of the model allows the system to be characterized by three non-dimensional parameters. We show all of the possible scenarios of spatial pattern change during the phase transformation. The modeling results are shown to be consistent with our experimental results and can provide insights into the system parameters which are difficult to measure.
by Ling Chao.
Ph.D.
Kurup, Abhishek. "Spatial awareness| how cells respond and control extracellular matrix stiffness topography". Thesis, University of California, Irvine, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3727444.
Texto completoThe mechanical properties of the extracellular matrix (ECM) have shown to regulate key cellular processes. However, current tools studying cell-ECM biophysical interactions revolve around cell-mediated traction forces, which, as I will show, are not appropriate in natural matrices due to matrix remodeling. I used active microrheology (AMR) to, instead, measure ECM stiffness in order to quantify these interactions in various cell-ECM systems.
In the first system, I evaluated a commonly used 3D cell-culture method in breast cancer research. I show that this model produces a large physical asymmetry in ECM stiffness, which resulted in altered cellular morphology, adhesion-mediated signaling, and phenotype. Importantly, a hallmark result obtained in this culture method was not repeatable once the asymmetry was removed, highlighting the importance of considering biophysical interactions in cell-culture models.
In the second system, my work, in collaboration with Dr. Stephen Weiss, led to the discovery that stem cells are not passive recipients of ECM stiffness signals as previously thought. Rather they can deliberately alter local (pericellular) stiffness with matrix metalloproteinases as a control for cellular functions. In particular, we found that skeletal stem cells competent in their ability to degrade collagen, increased pericellular stiffness via matrix remodeling to activate ?1 integrin signaling pathways and thus controlled their own lineage commitment to osteogenic fates. Cells without the ability to degrade their local matrix lost this functionality and were restricted in lineage commitment to adipogenic or chondrogenic fates.
For the third system, I quantified the contributions of cell contractility and matrix metalloproteinases in matrix remodeling for developing a normal mechanical topography in smooth muscle cells. I also provide evidence that it is the distribution of pericellular stiffness rather than a bulk value that instructs cellular behavior. In order to accomplish this task, I automated the AMR system (aAMR) for a tenfold decrease in measurement time. Importantly, aAMR reduces the complexity of AMR to a few mouse clicks, can create stiffness maps over large distances and provides metrics to assess the distribution of stiffness in the pericellular space within the volume of a natural, fibrous hydrogel.
Stringer, Bryan Pascal. "Cities Divided: The Spatial Legacy of Apartheid". Ohio University Honors Tutorial College / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors155628942846541.
Texto completoBonham, John G. "Effects of Spatial Information on Estimated Farm Nonpoint Source Pollution Control Costs". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34797.
Texto completoMaster of Science
Reuther, Cordula. "Patterning planar surfaces with motor proteins: Towards spatial control over motile microtubules". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-20916.
Texto completoDer räumlich kontrollierte Transport von nanoskaligen Objekten ist eine große Herausforderung auf dem Gebiet der Nanotechnologie. Ein auf molekularen Motoren und Filamenten des Zellskeletts basierendes Nanotransportsystem hat sich dabei als ein viel versprechender Ansatz erwiesen. Das Ziel der vorgelegten Arbeit war es daher, ebene Oberflächen so mit Motorproteinen zu strukturieren, dass eine kontrollierte und geführte Bewegung von Mikrotubuli-Transportern ermöglicht wird. Der erste Teil der Arbeit war insbesondere darauf fokussiert, Motorprotein-Spuren im Nanometerbereich zu erzeugen. Im zweiten Teil der Arbeit wurde eine Strukturierungsmethode zur Realisierung von benutzerdefinierten Musterdesigns untersucht und die erreichbare Auflösung bestimmt. Für die Nanometerstrukturierung von Oberflächen mit funktionalen Motorproteinen wurde ein neuer Ansatz demonstriert. Mit der Anwendung von Biotemplaten, wie hier der Mikrotubuli, konnte ein hoch-lokalisiertes und orientiertes Anbinden von Proteinen an Oberflächen sowie gleichzeitig geringer Proteindenaturierung erreicht werden. Durch spezifisches Stempeln beziehungsweise Binden von Motoren wurden Muster aus funktionellen Proteinen mit hoher Oberflächendichte hergestellt. Die erzeugten Motor-Spuren haben gezeigt, dass Nanometerstrukturierungen möglich sind und ohne topographische Barrieren zu zuverlässiger Führung von Mikrotubuli führen können. Bisher konnte die nicht-topographische Strukturierung von Oberflächen mit Kinesin-1-Motoren nur im Mikrometerbereich demonstriert werden. Wegen der hohen Steifigkeit der Mikrotubuli war die thermische Energie des Systems in diesen Fällen nicht ausreichend, um die führende Spitze der Mikrotubuli zurück auf das Gebiet mit den strukturierten Motoren zu biegen. Dieses Problem wird durch die kleine Breite der hier demonstrierten Motor-Nanospuren verhindert, da das Auftreffen der Mikrotubuli mit den Grenzlinien auf extrem flache Winkel begrenzt ist. Interessanterweise haben sich Spuren des nicht-prozessiven Motors Kinesin-14 für das Führen und den Transport im Nanometerbereich als noch zuverlässiger herausgestellt als Kinesin-1-Spuren. Es ist zu erwarten, dass nicht-topographisches Führen, wie es in dieser Arbeit gezeigt wurde, das Design und die Herstellung von Mikrotubuli-Transportsystemen deutlich vereinfacht und die Möglichkeit eröffnet, Cargo mit unlimitierter Größe, d.h. ohne Einschränkungen durch die Abmessungen der topographischen Führungskanäle, zu transportieren. Zusätzlich ist die biotemplierte Strukturierung ein viel versprechendes Werkzeug um das individuelle und das kooperative Arbeiten von Motorproteinen in vitro untersuchen und komplexe subzelluläre Maschinerien in synthetischer Umgebung rekonstituieren zu können. Dies wurde am Beispiel des gerichteten Gleitens des biomolekularen Motors Kinesin-14 gezeigt, der ein gerichtetes Gleiten zwischen antiparallelen Mikrotubuli und statisches Vernetzen zwischen parallelen Mikrotubuli hervorruft. Mit dem Ansatz des biotemplierten Strukturierens ist es jedoch nicht einfach möglich, benutzerdefinierte Spuren zu erzeugen. Daher wurde die photothermische Proteinstrukturierung als eine neue Methode für die frei programmierbare, hochauflösende und schnelle Herstellung von strukturierten Proteinoberflächen eingeführt. Auf diese Weise wurden Kinesin-1-Muster durch licht-induziertes Heizen einer licht-absorbierenden Substratschicht erzeugt. Die thermisch schaltbaren poly(N-isopropylacrylamid) (PNIPAM) Moleküle auf der Oberfläche kollabierten lokal und erlaubten es den Motorproteinen, in den beleuchteten Gebieten aus der Lösung an die Oberfläche zu binden. Die Bewegung gleitender Mikrotubuli bestätigte anschließend die erfolgreiche Strukturierung der Kinesin-1-Motoren und deren Funktionalität, da die Mikrotubuli an die strukturierten Motoren banden und ausschließlich in den strukturierten Gebieten transportiert wurden. Neben der Proteinstrukturierung wurde die lokalisierte Licht-zu-Wärme-Umwandlung kombiniert mit einer thermisch schaltbaren Polymerschicht auch für die lokale Aktivierung von Kinesin-1-Motoren auf der Oberfläche genutzt. Ein Vorteil der photothermischen Proteinstrukturierung ist die Möglichkeit, sichtbares Licht zu verwenden, da jede beliebige Wellenlänge angewendet werden kann und sichtbares Licht, im Vergleich zu anderen UV-basierten Photostrukturierungsmethoden, Proteine nicht schädigt. Modellierungen mit Hilfe der Finite-Elemente-Methode (implementiert in der Software COMSOL) haben gezeigt, dass die Lichtintensität und die Oberflächentemperatur speziell eingestellt werden müssen, um definierte Strukturgrößen zu erzielen. Während die derzeitig erzeugten Muster Größen im Bereich von zehn Mikrometern hatten, könnten durch höhere optische Intensitäten kombiniert mit Kühlung der Probe die Größenordnungen signifikant reduziert werden. Die reale experimentelle Auflösung wird jedoch auch von der Schaltcharakteristik des Polymers und der Proteinbindungsdynamik abhängen. Die hergestellten Muster können reversibel bei hohen beziehungsweise niedrigen Temperaturen aktiviert und deaktiviert werden. Zusätzlich können auf die gleiche Weise verschiedene Proteinsorten sequentiell auf einer Oberfläche strukturiert werden, ohne dass spezifische Bindungsmoleküle oder aufwändige Oberflächenpräparationen notwendig wären. Die Möglichkeit, Proteine reversibel an die Oberfläche zu binden, um geschriebene Muster wieder löschen zu können, wäre eine Weiterentwicklung und würde die Anwendungsmöglichkeiten der photothermischen Strukturierungsmethode erweitern. Außerdem würden optisch schaltbare Polymere das direkte Strukturieren von Motoren mit Licht ermöglichen und daher die Methode vereinfachen
Weber, Kimberly Diane. "Motor learning in the non-visual control of spatial orientation during locomotion". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24709.pdf.
Texto completoO'Rorke, Richard. "The spatial control of particles in microfluidic systems using surface acoustic waves". Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590299.
Texto completoTrukenbrod, Hans Arne. "Temporal and spatial aspects of eye-movement control : from reading to scanning". Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2014/7020/.
Texto completoBlickbewegungen stellen ein wichtiges Instrument dar, um kognitive Prozesse zu untersuchen. In den meisten Paradigmen ist allerdings wenig über die Entstehung von Sakkaden und Fixationen bekannt. Insbesondere die Kontrolle der Fixationsdauern wurde häufig außer acht gelassen. Eine wesentliche Ausnahme stellt die Leseforschung dar, in der sowohl zeitlichliche als auch räumliche Aspekte der Blickbewegungssteuerung im Detail betrachtet wurden. Dabei war der wissenschaftliche Diskurs durch drei Kontroversen gekennzeichnet, die untersuchten, (i), welchen Einfluss okulomotorische bzw. kognitive Prozesse auf die Blicksteuerung haben, (ii), ob Worte seriell oder parallel verarbeitet werden und, (iii), wie Fixationsdauern kontrolliert werden. Die vorliegende Arbeit zielt im wesentlichen darauf ab, die Dynamik von Fixationssequenzen zu erforschen. Ausgehend von den Erkenntnissen beim Lesen untersuchten wir Blickbewegungen in Nichtlese-Aufgaben, mit dem Ziel allgemeine Prinzipien der Blicksteuerung zu identifizieren. Zusätzlich versuchten wir mit Hilfe dieser Aufgaben, Erkenntnisse über Prozesse beim Lesen zu vertiefen. Unser Vorgehen war sowohl von der Durchführung von Experimenten als auch der Entwicklung und Evaluation computationaler Modelle geprägt. Die Hauptbefunde zeigten: Erstens, okulomotorische Phänomene des Lesens lassen sich in Suchaufgaben ohne Wortmaterial replizieren (Kapitel 2 & 4). Dabei bestimmen okulomotorische Prozesse die Fixationsposition innerhalb eines Objektes. Diese wiederum beeinflusst das nächste Sakkadenziel sowie die Fixationsdauer. Zweitens, wesentliche Vorhersagen von Modellen, in denen Blickbewegungen von seriellen Aufmerksamkeitsverschiebungen abhängen, konnten falsifiziert werden (Kapitel 3). Stattdessen legen unsere Erkenntnisse nahe, dass die Blicksteuerung von der parallelen Verarbeitung mehrerer Objekte abhängt. Drittens, Fixationsdauern werden asymmetrisch kontrolliert (Kapitel 4). Während hohe Verarbeitungsanforderungen Fixationsdauern unmittelbar verlängern können, führen niedrige Verarbeitungsanforderungen nur zeitlich verzögert zu einer Reduktion. Wir schlagen ein computationales Modell ICAT vor, um asymmetrische Kontrolle zu erklären. Grundlage des Modells ist ein autonomer Zeitgeber, der unabhängig von der momentanen Verarbeitung nach zufälligen Zeitintervallen Sakkaden initiiert. Unerwartet hohe Verarbeitungsanforderungen können die Initiierung der nächsten Sakkade hinauszögern, während unerwartet niedrige Verarbeitungsanforderungen den Beginn der nächsten Sakkade nicht verändern. Der Zeitgeber passt sich allerdings von Fixation zu Fixation neuen Verarbeitungsanforderungen an, so dass es zu einer zeitlich verzögerten Reduktion der Fixationsdauern kommen kann. In einer erweiterten Version des Modells überprüfen wir die Kompatibilität ICATs mit einer realistischen räumlichen Blicksteuerung. Die Ähnlichkeit von Blickbewegungsphänomenen über Aufgaben hinweg legt nahe, dass sie auf allgemeinen Prinzipien basieren. Grundlage der Blicksteuerung ist die verteilte Verarbeitung des visuellen Inputs, während die Kontrolle der Fixationsdauer auf den Prinzipien von ICAT beruht. Darüber hinaus tragen okulomotorische Phänomene wesentlich zur Variabilität der Blicksteuerung bei. Ein Verständnis dieses Zusammenspiels hilft entscheidend den Zusammenhang von Blickbewegungen und Kognitionen besser zu verstehen.
Weir, Clifford Ronald. "The role of extraocular afferent signals in oculomotor control and spatial localisation". Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390774.
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