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Computational Characterization of the Substrate-Binding Mode in Coproporphyrinogen III Oxidase

Silva, Pedro J.; Ramos, Maria João
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
45.84%
Oxygen-dependent coproporphyrinogen III oxidase catalyzes the sequential decarboxylation of the propionate substituents present on the A and B rings of coproporphyrinogen III in the heme biosynthetic pathway. Although extensive experimental investigation of this enzyme has already afforded many insights into its reaction mechanism, several key features (such as the substrate binding mode, the characterization of the active site, and the initial substrate protonation state) remain poorly described. The molecular dynamics simulations described in this paper enabled the determination of a very promising substrate binding mode and the extensive characterization of the enzyme active site. The proposed binding mode is fully consistent with the known selectivity of the active site toward substituted tetrapyrroles and explains the lack of activity of the H131A, R135A, D274A, and R275A mutants and the reasons behind the nonoccurrence of catalysis on the C and D rings of the tetrapyrrole. An important role in this binding mode is fulfilled by G276, as its carbonyl oxygen intervenes in the substrate anchoring by hydrogen bonding its ring D pyrrole NH group. The presence of this interaction (which is only possible with the protonated NH pyrrole group) and the absence of positively charged side chains close to the pyrrole nitrogen (which might stabilize the N-deprotonated pyrrole postulated in some mechanistic proposals) show that the pyrrole ring is very unlikely to undergo deprotonation during the catalytic cycle and allow the discrimination between the previously postulated mechanistic proposals.

A biomimetic piezoelectric pump: Computational and experimental characterization

LIMA, Cicero R. de; VATANABE, Sandro L.; CHOI, Andres; NAKASONE, Paulo Henrique; PIRES, Rogerio Felipe; SILVA, Emilio Carlos Nelli
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.04%
Flow pumps have been developed for classical applications in Engineering, and are important instruments in areas such as Biology and Medicine. Among applications for this kind of device we notice blood pump and chemical reagents dosage in Bioengineering. Furthermore, they have recently emerged as a viable thermal management solution for cooling applications in small-scale electronic devices. This work presents the performance study of a novel principle of a piezoelectric flow pump which is based oil the use of a bimorph piezoelectric actuator inserted in fluid (water). Piezoelectric actuators have some advantages over classical devices, such as lower noise generation and ease of miniaturization. The main objective is the characterization of this piezoelectric pump principle through computational simulations (using finite element software), and experimental tests through a manufactured prototype. Computational data, Such as flow rate and pressure curves, have also been compared with experimental results for validation purposes. (C) 2009 Elsevier B.V. All rights reserved.

Aplicação da espectroscopia de infravermelho próximo na caracterização de petróleo: simulação de uma unidade de destilação atmosférica.; Application of near infrared spectroscopy in the characterization of crude petroleum: simulation of an atmospheric distillation unit.

Falla Sotelo, Francisco
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/10/2006 PT
Relevância na Pesquisa
35.89%
A contínua mudança na qualidade da carga de alimentação das unidades de destilação atmosférica introduz incertezas na operação do processo de refino. A caracterização precisa do petróleo bruto, cuja composição varia devido à sua natureza intrínseca e às condições de transporte e armazenamento nas refinarias, poderia auxiliar na redução destas incertezas. O processo clássico de caracterização, baseado nas curvas de destilação TBP (True Boiling Point, Ponto de Ebulição Verdadeiro), ainda não permite detectar essas mudanças de modo mais dinâmico, o que reduz a precisão da simulação do processo e, portanto, uma menor confiabilidade nas condições de operação determinadas a partir dela. No Brasil, petróleo pesado é produzido de forma predominante, que é misturado freqüentemente com petróleo leve importado antes do refino. Como conseqüência, nas refinarias brasileiras as características do petróleo mudam em média, a cada três dias, sendo esta taxa de variação incompatível com a determinação das curvas de destilação TBP. A análise SimDis (Simulated Distillation, Destilação Simulada) é atualmente a técnica de laboratório alternativa para aproximar as curvas de destilação. Porém...

A utilização da química computacional em processos químicos relacionados à ionização por electrospray; The use of computational chemistry in the studies of chemical processes involved in electrospray ionization

Lourenço, Ricardo Vessecchi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/06/2009 PT
Relevância na Pesquisa
35.87%
Nas últimas décadas, o desenvolvimento das técnicas de ionização à pressão atmosférica impulsionou a espectrometria de massas, na caracterização e elucidação estrutural de compostos de grande massa molecular. O surgimento dessas técnicas foi o responsável pela amplitude nas aplicações e estudos de espectrometria de massas, sendo a ionização por electrospray a mais versátil dentre essas fontes de ionização. O caráter eletrolítico da fonte de ionização por electrospray permite-se obter íons provenientes de três processos químicos: i) ácido-base; ii) redox e iii) complexação. A extensão com que cada um desses processos ocorrerá dependerá de fatores relacionados à operação da fonte de ionização e grandezas termoquímicas do analito. O notável progresso em técnicas experimentais, processamento de dados e integração entre as mais diversas áreas de aplicação da química, tem estimulado e beneficiado a aplicação da química teórica em estudos de reações em fase gasosa. A aplicação da química computacional fornece uma compreensão quantitativa das variações estruturais e energéticas dos possíveis íons formados durante a ionização da amostra, permitindo também a compreensão das possíveis vias de dissociação. É neste sentido...

Caracterização de estado sólido e análise computacional de uma nova forma cristalina do fármaco antifilariose dietilcarbamazina: um sal de ácido maleico; Characterization of solid state and computational analysis of a new crystalline form of the antifilarial drug diethylcarbamazine: a maleic acid salt

Ribeiro, Leandro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/08/2011 PT
Relevância na Pesquisa
35.93%
A caracterização no estado sólido de insumos farmacêuticos constitui uma parte muito importante no entendimento de suas propriedades físicas, químicas e farmacológicas. A partir da análise estrutural por difração de raios X em monocristal, pode-se identificar a conformação no estado sólido do fármaco, assim como sua densidade eletrônica. Estes estudos podem ser complementados com dados provenientes da Modelagem Molecular, que compreende um número de ferramentas e métodos computacionais e teóricos que têm como objetivos compreender e prever o comportamento de sistemas reais. Nesse contexto, visando compreender melhor as propriedades de estado sólido apresentadas pelo fármaco anti-filariose dietilcarbamazina (DEC), foi obtido um novo sal, o maleato de dietilcarbamazina (DEC maleato), cujas propriedades foram comparadas com as das estruturas já reportadas, DEC citrato e DEC pura. A DEC maleato foi caracterizada por difração de raios X em monocristal, espectroscopias Raman e Infravermelho e análise térmica. A DEC maleato cristaliza no grupo espacial triclínico PI com dois confôrmeros da molécula de DEC na unidade assimétrica, ambos exibindo caudas etílicas na conformação syn em relação ao anel piperazina...

Abordagem Computacional para Identificar Novos SNVs em Bases de Dados de ESTs; Computational Approach to Identify new SNVs in ESTs Data Set

Sousa, Rodrigo Guarischi Mattos Amaral de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/08/2012 PT
Relevância na Pesquisa
35.89%
Indivíduos não relacionados apresentam apenas 1% de diferenças entre seus genomas. Estas variações ocorrem na forma de substituições, inserções, deleções, rearranjos complexos ou até estruturais. Dentre essas variações, aquelas que apresentam uma frequência populacional acima de 1% são denominadas de polimorfismos. Tais variações são responsáveis por diferenças que vão desde a resposta imunológica até o tratamento com drogas, incluindo sensitividade das células tumorais, níveis de plasma, efeitos colaterais e toxicidade. A forma mais comum de polimorfismo genético entre humanos são os polimorfismo de base única ou Single Nucleotide Polymorphisms (SNPs), sendo mais de 47 milhões descritos no dbSNP, um banco de dados de pequenos polimorfismos do NCBI. No presente estudo, foi estabelecida uma abordagem computacional, com etapas de exclusão de regiões parálogas ou de baixa qualidade, com o objetivo de identificar variantes genéticas em sequências expressas gerados pelo método de Open Reading Frame ESTs (ORESTES) durante o Projeto Genoma Humano do Câncer. Diferentemente de outros softwares de detecção de polimorfismos, a abordagem computacional descrita neste estudo leva em consideração a informação a priori do número de bibliotecas distintas que reportaram a mesma variação. Foram identificadas 1900 mutações (853 sinônimas e 1047 não-sinônimas) presentes em duas ou mais bibliotecas distintas...

Computational methods for gene characterization and genomic knowledge extraction; Métodos computacionais para a caracterização de genes e extração de conhecimento genómico

Gaspar, Paulo Miguel da Silva
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
36.01%
Motivation: Medicine and health sciences are changing from the classical symptom-based to a more personalized and genetics-based paradigm, with an invaluable impact in health-care. While advancements in genetics were already contributing significantly to the knowledge of the human organism, the breakthrough achieved by several recent initiatives provided a comprehensive characterization of the human genetic differences, paving the way for a new era of medical diagnosis and personalized medicine. Data generated from these and posterior experiments are now becoming available, but its volume is now well over the humanly feasible to explore. It is then the responsibility of computer scientists to create the means for extracting the information and knowledge contained in that data. Within the available data, genetic structures contain significant amounts of encoded information that has been uncovered in the past decades. Finding, reading and interpreting that information are necessary steps for building computational models of genetic entities, organisms and diseases; a goal that in due course leads to human benefits. Aims: Numerous patterns can be found within the human variome and exome. Exploring these patterns enables the computational analysis and manipulation of digital genomic data...

Experimental and Computational Characterization of Biological Liquid Crystals: A Review of Single-Molecule Bioassays

Eom, Kilho; Yang, Jaemoon; Park, Jinsung; Yoon, Gwonchan; Soo Sohn, Young; Park, Shinsuk; Yoon, Dae Sung; Na, Sungsoo; Kwon, Taeyun
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 10/09/2009 EN
Relevância na Pesquisa
35.93%
Quantitative understanding of the mechanical behavior of biological liquid crystals such as proteins is essential for gaining insight into their biological functions, since some proteins perform notable mechanical functions. Recently, single-molecule experiments have allowed not only the quantitative characterization of the mechanical behavior of proteins such as protein unfolding mechanics, but also the exploration of the free energy landscape for protein folding. In this work, we have reviewed the current state-of-art in single-molecule bioassays that enable quantitative studies on protein unfolding mechanics and/or various molecular interactions. Specifically, single-molecule pulling experiments based on atomic force microscopy (AFM) have been overviewed. In addition, the computational simulations on single-molecule pulling experiments have been reviewed. We have also reviewed the AFM cantilever-based bioassay that provides insight into various molecular interactions. Our review highlights the AFM-based single-molecule bioassay for quantitative characterization of biological liquid crystals such as proteins.

Outer membrane phospholipase A in phospholipid bilayers: A model system for concerted computational and experimental investigations of amino acid side chain partitioning into lipid bilayers

Fleming, Patrick J.; Freites, J. Alfredo; Moon, C. Preston; Tobias, Douglas J.; Fleming, Karen G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.93%
Understanding the forces that stabilize membrane proteins in their native states is one of the contemporary challenges of biophysics. To date, estimates of side chain partitioning free energies from water to the lipid environment show disparate values between experimental and computational measures. Resolving the disparities is particularly important for understanding the energetic contributions of polar and charged side chains to membrane protein function because of the roles these residue types play in many cellular functions. In general, computational free energy estimates of charged side chain partitioning into bilayers are much larger than experimental measurements. However, the lack of a protein-based experimental system that uses bilayers against which to vet these computational predictions has traditionally been a significant drawback. Moon & Fleming recently published a novel hydrophobicity scale that was derived experimentally by using a host-guest strategy to measure the side chain energetic perturbation due to mutation in the context of a native membrane protein inserted into a phospholipid bilayer. These values are still approximately an order of magnitude smaller than computational estimates derived from molecular dynamics calculations from several independent groups. Here we address this discrepancy by showing that the free energy differences between experiment and computation become much smaller if the appropriate comparisons are drawn...

Existential Theorems in Computational Complexity Theory: Size and Robustness

Zimand, Marius ; Hemaspaandra, Lane A.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Thesis; Technical Report
ENG
Relevância na Pesquisa
35.89%
Thesis (Ph. D.)--University of Rochester. Dept. of Computer Science, 1996. Simultaneously published in the Technical Report series.; How strong are the results in computational complexity that assert, under certain hypotheses, the existence of an object? Are there many such objects, or are there few? To what extent can we relax the hypotheses and still maintain the same conclusions? These are the types of questions that are studied in this thesis. More precisely, we investigate some of the central existential results in computational complexity from the point of view of size and robustness. Below is a sample of the results in the thesis. We show that for any effective enumeration of computational devices that cover the whole set of computable functions and for any complexity measure satisfying a single axiom, neither the set of speedable functions nor the set of functions that generate complexity gaps is small from a topological point of view. We show that, with probability one on the set of oracles, there is a set in NP^A that asymptotically splits in half any infinite set in P^A. This is the strongest currently known relativized separation of NP from P. We also show that most (in the resource-bounded measure sense) sets that are computable in exponential time do not have even very weak membership-related properties that are computable in polynomial time. We prove that in almost all relativized worlds...

Advanced methods for structural characterization and structure-property correlation for functional materials of layered compounds

Dürrschnabel, Michael Thomas
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
36.01%
A large number of functional materials have layered structures yielding anisotropic physical properties and an exciting physics of extended defects. For the understanding of both phenomena extensive computational methods are necessary for calculating anisotropic physical properties in an ab-initio approach. Calculating high-energy electron scattering is essential to yield quantitative results on defect structures by electron microscopy and spectroscopy. In this thesis superconducting ReBa2Cu3O7-x (ReBCO, Re = rare earth) coated conductors and thermoelectric Bi2Te3-related device-relevant materials were analyzed in detail. For both compounds various computational methods were applied to yield a quantitative structure-property correlation. The microstructure and the chemical composition of a material affecting its macroscopic physical properties is referred to as structure-property correlation. Coated conductors consist of multilayer thin film structures and are high-temperature superconducting (HTS) wires of the second generation. The analyzed coated conductors were grown by two methods: (i) chemical solution deposition (CSD) and (ii) inclined substrate deposition (ISD). In this work both materials were analyzed and compared to each other...

Computational Phenotyping of Two-Person Interactions Reveals Differential Neural Response to Depth-of-Thought

Xiang, Ting; Ray, Debajyoti; Lohrenz, Terry; Dayan, Peter; Montague, P. Read
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.94%
Reciprocating exchange with other humans requires individuals to infer the intentions of their partners. Despite the importance of this ability in healthy cognition and its impact in disease, the dimensions employed and computations involved in such inferences are not clear. We used a computational theory-of-mind model to classify styles of interaction in 195 pairs of subjects playing a multi-round economic exchange game. This classification produces an estimate of a subject's depth-of-thought in the game (low, medium, high), a parameter that governs the richness of the models they build of their partner. Subjects in each category showed distinct neural correlates of learning signals associated with different depths-of-thought. The model also detected differences in depth-of-thought between two groups of healthy subjects: one playing patients with psychiatric disease and the other playing healthy controls. The neural response categories identified by this computational characterization of theory-of-mind may yield objective biomarkers useful in the identification and characterization of pathologies that perturb the capacity to model and interact with other humans.

Computational characterization and prediction of metal-organic framework properties

Coudert, François-Xavier; Fuchs, Alain H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.82%
In this introductory review, we give an overview of the computational chemistry methods commonly used in the field of metal-organic frameworks (MOFs), to describe or predict the structures themselves and characterize their various properties, either at the quantum chemical level or through classical molecular simulation. We discuss the methods for the prediction of crystal structures, geometrical properties and large-scale screening of hypothetical MOFs, as well as their thermal and mechanical properties. A separate section deals with the simulation of adsorption of fluids and fluid mixtures in MOFs.

Effective Strong Dimension, Algorithmic Information, and Computational Complexity

Athreya, Krishna B.; Hitchcock, John M.; Lutz, Jack H.; Mayordomo, Elvira
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.97%
The two most important notions of fractal dimension are {\it Hausdorff dimension}, developed by Hausdorff (1919), and {\it packing dimension}, developed by Tricot (1982). Lutz (2000) has recently proven a simple characterization of Hausdorff dimension in terms of {\it gales}, which are betting strategies that generalize martingales. Imposing various computability and complexity constraints on these gales produces a spectrum of effective versions of Hausdorff dimension. In this paper we show that packing dimension can also be characterized in terms of gales. Moreover, even though the usual definition of packing dimension is considerably more complex than that of Hausdorff dimension, our gale characterization of packing dimension is an exact dual of -- and every bit as simple as -- the gale characterization of Hausdorff dimension. Effectivizing our gale characterization of packing dimension produces a variety of {\it effective strong dimensions}, which are exact duals of the effective dimensions mentioned above. We develop the basic properties of effective strong dimensions and prove a number of results relating them to fundamental aspects of randomness, Kolmogorov complexity, prediction, Boolean circuit-size complexity, polynomial-time degrees...

On the possible Computational Power of the Human Mind

Zenil, Hector; Hernandez-Quiroz, Francisco
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.04%
The aim of this paper is to address the question: Can an artificial neural network (ANN) model be used as a possible characterization of the power of the human mind? We will discuss what might be the relationship between such a model and its natural counterpart. A possible characterization of the different power capabilities of the mind is suggested in terms of the information contained (in its computational complexity) or achievable by it. Such characterization takes advantage of recent results based on natural neural networks (NNN) and the computational power of arbitrary artificial neural networks (ANN). The possible acceptance of neural networks as the model of the human mind's operation makes the aforementioned quite relevant.; Comment: Complexity, Science and Society Conference, 2005, University of Liverpool, UK. 23 pages

Pure Nash Equilibria: Complete Characterization of Hard and Easy Graphical Games

Jiang, Albert Xin; Safari, MohammadAli
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/02/2010
Relevância na Pesquisa
35.97%
We consider the computational complexity of pure Nash equilibria in graphical games. It is known that the problem is NP-complete in general, but tractable (i.e., in P) for special classes of graphs such as those with bounded treewidth. It is then natural to ask: is it possible to characterize all tractable classes of graphs for this problem? In this work, we provide such a characterization for the case of bounded in-degree graphs, thereby resolving the gap between existing hardness and tractability results. In particular, we analyze the complexity of PUREGG(C, -), the problem of deciding the existence of pure Nash equilibria in graphical games whose underlying graphs are restricted to class C. We prove that, under reasonable complexity theoretic assumptions, for every recursively enumerable class C of directed graphs with bounded in-degree, PUREGG(C, -) is in polynomial time if and only if the reduced graphs (the graphs resulting from iterated removal of sinks) of C have bounded treewidth. We also give a characterization for PURECHG(C,-), the problem of deciding the existence of pure Nash equilibria in colored hypergraphical games, a game representation that can express the additional structure that some of the players have identical local utility functions. We show that the tractable classes of bounded-arity colored hypergraphical games are precisely those whose reduced graphs have bounded treewidth modulo homomorphic equivalence. Our proofs make novel use of Grohe's characterization of the complexity of homomorphism problems.; Comment: 8 pages. To appear in AAMAS 2010

Phase transition and computational complexity in a stochastic prime number generator

Lacasa, Lucas; Luque, Bartolo; Miramontes, Octavio
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/12/2007
Relevância na Pesquisa
35.89%
We introduce a prime number generator in the form of a stochastic algorithm. The character of such algorithm gives rise to a continuous phase transition which distinguishes a phase where the algorithm is able to reduce the whole system of numbers into primes and a phase where the system reaches a frozen state with low prime density. In this paper we firstly pretend to give a broad characterization of this phase transition, both in terms of analytical and numerical analysis. Critical exponents are calculated, and data collapse is provided. Further on we redefine the model as a search problem, fitting it in the hallmark of computational complexity theory. We suggest that the system belongs to the class NP. The computational cost is maximal around the threshold, as common in many algorithmic phase transitions, revealing the presence of an easy-hard-easy pattern. We finally relate the nature of the phase transition to an average-case classification of the problem.; Comment: Submitted to New Journal of Physics

Computational Optical Imaging Systems: Sensing Strategies, Optimization Methods, and Performance Bounds

Harmany, Zachary Taylor
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2012
Relevância na Pesquisa
35.91%

The emerging theory of compressed sensing has been nothing short of a revolution in signal processing, challenging some of the longest-held ideas in signal processing and leading to the development of exciting new ways to capture and reconstruct signals and images. Although the theoretical promises of compressed sensing are manifold, its implementation in many practical applications has lagged behind the associated theoretical development. Our goal is to elevate compressed sensing from an interesting theoretical discussion to a feasible alternative to conventional imaging, a significant challenge and an exciting topic for research in signal processing. When applied to imaging, compressed sensing can be thought of as a particular case of computational imaging, which unites the design of both the sensing and reconstruction of images under one design paradigm. Computational imaging tightly fuses modeling of scene content, imaging hardware design, and the subsequent reconstruction algorithms used to recover the images.

This thesis makes important contributions to each of these three areas through two primary research directions. The first direction primarily attacks the challenges associated with designing practical imaging systems that implement incoherent measurements. Our proposed snapshot imaging architecture using compressive coded aperture imaging devices can be practically implemented...

Metamaterials for Computational Imaging

Hunt, John
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2013
Relevância na Pesquisa
36.05%

Metamaterials extend the design space, flexibility, and control of optical material systems and so yield fundamentally new computational imaging systems. A computational imaging system relies heavily on the design of measurement modes. Metamaterials provide a great deal of control over the generation of the measurement modes of an aperture. On the other side of the coin, computational imaging uses the data that that can be measured by an imaging system, which may limited, in an optimal way thereby producing the best possible image within the physical constraints of a system. The synergy of these two technologies - metamaterials and computational imaging - allows for entirely novel imaging systems. These contributions are realized in the concept of a frequency-diverse metamaterial imaging system that will be presented in this thesis. This 'metaimager' uses the same electromagnetic flexibility that metamaterials have shown in many other contexts to construct an imaging aperture suitable for single-pixel operation that can measure arbitrary measurement modes, constrained only by the size of the aperture and resonant elements. It has no lenses, no moving parts, a small form-factor, and is low-cost.

In this thesis we present an overview of work done by the author in the area of metamaterial imaging systems. We first discuss novel transformation-optical lenses enabled by metamaterials which demonstrate the electromagnetic flexibility of metamaterials. We then introduce the theory of computational and compressed imaging using the language of Fourier optics...

AVOA techniques for fracture characterization

Sabinin,Vladimir
Fonte: Instituto de Geofísica, UNAM Publicador: Instituto de Geofísica, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
Relevância na Pesquisa
36%
Different aspects of computational techniques for AVOA analysis (Amplitude Versus Offset and Azimuth) for fracture characterization are considered, in particular: using amplitudes instead of reflection coefficients, smoothing seismic data, and numerical methods for estimation of fracture directions. A new computational method and a new filter for smoothing are suggested. The different computational methods are compared in synthetic reflection surface data with noise, and without noise. Properties of the numerical methods in dependence on different sets of azimuths and offsets are obtained. It is shown a superiority of the new method.