Theory and application of left-handed metamaterials

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Vita.Includes bibliographical references (p. 223-244).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Materials with simultaneously negative permittivity and permeability over a certain frequency band were first studied by Veselago in 1968, who termed such media left-handed (LH) due to the LH triad formed by the electric field vector, the magnetic field vector, and the phase propagation vector. However, since no such naturally occurring materials were known, Veselago's work laid dormant for nearly 30 years. Recently though, a composite material, also known as a metamaterial, consisting of the periodic arrangement of metallic rods and split-rings has been shown to exhibit left-handed properties. Because the dimension of the rods and rings that makeup the metamaterial are small compared to the wavelength of interest, it is possible to approximately describe their bulk electromagnetic properties using an effective permittivity and an effective permeability. In this thesis, the properties and potential applications of LH media are explored. In addition, various tools are presented for the purpose of characterizing metamaterial designs. Before studying their metamaterial realization, the basic properties of propagation, radiation, and scattering through homogeneous LH media are studied. Many of the basic properties of LH media are in contrast to those typically encountered in right-handed media. For example, using a rigorous plane wave analysis of propagation and transmission into a dispersive LH medium from a RH medium, it is shown that power refracts at a negative angle, without violating causality. Second, the perfect lens concept is studied through a Green's function analysis. It is shown that under the perfect lens requirement, that a single source outside a LH media slab will generate two perfect images.(cont.) Interestingly though, the time-averaged power flow inside the slab forms a sink. However, it is shown that while the introduction of loss eliminates this behavior, the lens becomes imperfect. It is seen that even a small amount of loss can destroy the imaging properties of the LH media lens. In terms of scattering, the Mie solution for plane wave scattering by a LH medium sphere is examined. It is shown that where applicable, care must be taken in choosing the appropriate algebraic signs of the wavenumbers in the evaluation of the Mie coefficients. In addition, it is then shown that a sphere composed of a LH medium will focus incoming energy into a spot inside the sphere. Finally, because the metamaterials studied in this thesis are anisostropic, the effects of aniostropy on reflection and transmission are examined. Next, various tools for understanding and characterizing left-handed metamaterials are presented. First, the accuracy of approximate analytic models of the rods and split-rings is investigated by using two-dimensional FD-TD simulations to compare transmission characteristics. It is shown that the rods tend to agree more favorably with their analytic model than the split-rings do. Next, in order to better understand the behavior of the rods and rings separately, numerical simulations of rods (or rings) embedded in homogeneous mag- netic (or electric) plasma media were performed. Using the transmission characteristics, it is shown that in order to obtained left-handed features, the plasma in the immediate vicinity of the rods or rings needed to be removed, ...by Joe Pacheco, Jr.Ph.D

Finite difference techniques for body of revolution radar cross section

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 267-272).Although a number of radar cross section prediction techniques have been developed which exploit body of revolution symmetry, the use of finite-difference techniques with these geometries has not been throughly explored. This thesis investigates several finite-difference approaches which vary both in the approximations they introduce as well as the computational resources they require. These techniques include body of revolution finite-difference time-domain methods with both staircase and conformal grids, a hybrid FD-TD/geometrical optics method, and a body of revolution parabolic wave equation method. In addition, the use of the monostatic-bistatic equivalence principle is explored in approximating monostatic RCS at multiple angles from a single FD-TD simulation. Both canonical and more realistic BOR targets are modeled. The results from these techniques are compared, with each other and with method of moment predictions, physical theory of diffraction predictions, and analytic results. From these comparisons the tradeoffs possible between accuracy and computation with this collection of finite-difference tools is determined.by Joe Pacheco, Jr.M.Eng

Integrated analysis of microRNA regulation and its interaction with mechanisms of epigenetic regulation in the etiology of systemic lupus erythematosus

The aim of this study was to identity in silico the relationships among microRNAs (miRNAs) and genes encoding transcription factors, ubiquitylation, DNA methylation, and histone modifications in systemic lupus erythematosus (SLE). To identify miRNA dysregulation in SLE, we used miR2Disease and PhenomiR for information about miRNAs exhibiting differential regulation in disease and other biological processes, and HMDD for information about experimentally supported human miRNA-disease association data from genetics, epigenetics, circulating miRNAs, and miRNA-target interactions. This information was incorporated into the miRNA analysis. High-throughput sequencing revealed circulating miRNAs associated with kidney damage in patients with SLE. As the main finding of our in silico analysis of miRNAs differentially expressed in SLE and their interactions with disease-susceptibility genes, post-translational modifications, and transcription factors; we highlight 226 miRNAs associated with genes and processes. Moreover, we highlight that alterations of miRNAs such as hsa-miR-30a-5p, hsa-miR-16-5p, hsa-miR-142-5p, and hsa-miR-324-3p are most commonly associated with post-translational modifications. In addition, altered miRNAs that are most frequently associated with susceptibility-related genes are hsa-miR-16-5p, hsa-miR-374a-5p, hsa-miR-34a-5p, hsa-miR-31-5p, and hsa-miR-1-3p

The Future of Heliophysics Research through Targeted use of Constellations

This white paper seeks to outline the benefits and challenges of constellations, ranging from the Heliophysics System Observatory, to constellations consisting of a small number of spacecraft, to large-number constellations. In moving toward this constellation era, investments are required by our sponsors to best enable our continued scientific advancement in Solar and Space Physics

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

4to. Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad. Memoria académica

Este volumen acoge la memoria académica de la Cuarta edición del Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad, CITIS 2017, desarrollado entre el 29 de noviembre y el 1 de diciembre de 2017 y organizado por la Universidad Politécnica Salesiana (UPS) en su sede de Guayaquil. El Congreso ofreció un espacio para la presentación, difusión e intercambio de importantes investigaciones nacionales e internacionales ante la comunidad universitaria que se dio cita en el encuentro. El uso de herramientas tecnológicas para la gestión de los trabajos de investigación como la plataforma Open Conference Systems y la web de presentación del Congreso http://citis.blog.ups.edu.ec/, hicieron de CITIS 2017 un verdadero referente entre los congresos que se desarrollaron en el país. La preocupación de nuestra Universidad, de presentar espacios que ayuden a generar nuevos y mejores cambios en la dimensión humana y social de nuestro entorno, hace que se persiga en cada edición del evento la presentación de trabajos con calidad creciente en cuanto a su producción científica. Quienes estuvimos al frente de la organización, dejamos plasmado en estas memorias académicas el intenso y prolífico trabajo de los días de realización del Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad al alcance de todos y todas