Comparação dos filtros de velocidade e do operador WHLP-CRS na atenuação de múltiplas

A motivação geológica deste trabalho reside no imageamento de estruturas de bacias sedimentares da região Amazônica, onde a geração e o acúmulo de hidrocarboneto estão relacionados com a presença de soleiras de diabásio. A motivação sísmica reside no fato de que essas rochas intrusivas possuem grandes contrastes de impedância com a rocha encaixante, o que resulta em múltiplas, externas e internas, com amplitudes semelhantes as das primárias. O sinal sísmico das múltiplas podem predominar sobre o sinal das reflexões primárias oriundas de interfaces mais profundas, o que pode dificultar o processamento, a interpretação e o imageamento da seção sísmica temporal. Neste trabalho, estudamos a atenuação de múltiplas em seções sintéticas fonte-comum (FC) através da comparação de dois métodos. O primeiro método resulta da combinação das técnicas Wiener-Hopf-Levinson de predição (WHLP) e o de empilhamento superfície-de-reflexão-comum (CRS), e denominando WHLP-CRS, onde o operador é desenhado exclusivamente no domínio do tempo-espaço. O segundo método utilizado é o filtro de velocidade (ω-k) aplicado após o empilhamento superfície-de-reflexão (CRS), onde o operador é desenhado exclusivamente no domínio bidimensional de freqüência temporal-espacial. A identificação das múltiplas é feita na seção de afastamento-nulo (AN) simulada com o empilhamento CRS, e utiliza o critério da periodicidade entre primária e suas múltiplas. Os atributos da frente de onda, obtidos através do empilhamento CRS, são utilizados na definição de janelas móveis no domínio tempo-espaço, que são usadas para calcular o operador WHLP-CRS. O cálculo do filtroω-k é realizado no domínio da freqüência temporal-espacial, onde os eventos são selecionados para corte ou passagem. O filtro (ω-k) é classificado como filtro de corte, com alteração de amplitude, mas não de fase, e limites práticos são impostos pela amostragem tempo-espaço. Em termos práticos, concluímos que, para o caso de múltiplas, os eventos separados no domínio x-t não necessariamente se separam no domínio ω-k, o que dificulta o desenho de um operador ω-k semelhante em performance ao operador x-t.

Estudo geofísico para a caracterização geológica e hidrogeológica da subsuperfície rasa em área de deposição de rejeitos sólidos no município de Barcarena-PA

Este estudo foi realizado na Área de Depósito de Rejeitos Sólidos (ADRS) da ALBRAS (Alumínio Brasileiro S.A.), localizada no município de Barcarena, Estado do Pará. Os resultados alcançados permitiram estabelecer um padrão de caracterização da subsuperfície, a partir de medidas geofísicas, fornecendo informações sobre as camadas geológicas e sobre parâmetros hidrogeológicos, tais como direção e velocidade do fluxo subterrâneo. Na realização do trabalho foram utilizados três métodos geofísicos: os métodos elétricos (Potencial Espontâneo e Eletrorresitividade) e eletromagnético (Slingram). A distribuição dos potenciais medidos através do Método do Potencial Espontâneo indicaram o sentido do fluxo subterrâneo local. Durante o estudo, foi montado um experimento de infiltração de solução salina no solo e seu efeito foi monitorado através de imageamento elétrico. Esse experimento permitiu que se estimasse a velocidade e o sentido do fluxo subterrâneo local ao longo da linha de imageamento. Os modelos interpretativos obtidos através da inversão de dados de resistividade aparente obtidos em sondagens elétricas verticais apresentaram uma boa correlação com perfis de raios gama corridos em poços tubulares da área de estudo. Estas Sondagens Elétricas Verticais permitiram que se detalhasse as unidades litológicas rasas através da estimativa de seus valores de resistividade e espessura. A interpretação dos dados eletromagnéticos através da análise de perfis de medidas, sondagens eletromagnéticas e mapas de contornos permitiu identificar a presença de zonas mais condutivas (material argiloso) e zonas mais resistivas (material arenoso). Além disso, observou-se que o mapa de contornos para a freqüência de 14080 Hz apresentou uma boa correlação com o mapa de contornos do Potencial Espontâneo referente a mesma área.

The use of instantaneous phase for improving sparse arrays images

Sparse arrays have pitch larger than half-wavelength (lambda/2) and there is a reduced number of elements in comparison with a full-populated array. Consequently, there is a reduction in cost, data acquisition and processing. However, conventional beamforming techniques result in large side and grating lobes, and consequently in image artifacts. In this work the instantaneous phase of the signals is used in a beamforming technique instead of the instantaneous amplitudes to improve images obtained from sparse arrays configurations. A threshold based on a statistical analysis and the number of signals used for imaging is applied to each pixel, in order to determine if that pixel is related to a defect or not. Three sets of data are used to evaluate the technique, considering medical and non-destructive testing: a simulated point spread function, a medical phantom and an aluminum plate with 2 lambda-, 7 lambda- and lambda-pitch, respectively. The conventional amplitude image is superposed by the image improved by the instantaneous phase, increasing the reflectors detectability and reducing artifacts for all cases, as well as dead zone for the tested plate.

Analysis of 25 mutual eclipses and occultations between the Galilean satellites observed from Brazil in 2009

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Escape through a time-dependent hole in the doubling map

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Instantaneous Phase Threshold for Reflector Detection in Ultrasonic Images

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Inspeção de materiais compósitos utilizando ondas acústicas guiadas

Pós-graduação em Engenharia Elétrica - FEIS

Phase transition from a dx2-y2 to a dx2-y2+dxy superconductor

We study the phase transition from a dx2-y2 to a dx2-y2+dxy superconductor using the tight-binding model of two-dimensional cuprates. As the temperature is lowered past the critical temperature Tc, first a dx2-y2 superconducting phase is created. With further reduction of temperature, the dx2-y2+dxy phase is created at temperature T=Tc1. We study the temperature dependencies of the order parameter, specific heat, and spin susceptibility in these mixed-angular-momentum states on a square lattice and on a lattice with orthorhombic distortion. The above-mentioned phase transitions are identified by two jumps in specific heat at Tc and Tc1. ©1999 The American Physical Society.

Termodinâmica do modelo Bouncer: um gás unidimensional simplificado

Pós-graduação em Física - IGCE

Gas-phase reactivity of protonated 2-oxazoline derivatives: mass spectrometry and computational studies

RATIONALE: Oxazolines have attracted the attention of researchers worldwide due to their versatility as carboxylic acid protecting groups, chiral auxiliaries, and ligands for asymmetric catalysis. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of five 2-oxazoline derivatives has been conducted, in order to understand the influence of the side chain on the gas-phase dissociation of these protonated compounds under collision-induced dissociation (CID) conditions. METHODS: Mass spectrometric analyses were conducted in a quadrupole time-of-flight (Q-TOF) spectrometer fitted with electrospray ionization source. Protonation sites have been proposed on the basis of the gas-phase basicity, proton affinity, atomic charges, and a molecular electrostatic potential map obtained on the basis of the quantum chemistry calculations at the B3LYP/6-31 + G(d, p) and G2(MP2) levels. RESULTS: Analysis of the atomic charges, gas-phase basicity and proton affinities values indicates that the nitrogen atom is a possible proton acceptor site. On the basis of these results, two main fragmentation processes have been suggested: one taking place via neutral elimination of the oxazoline moiety (99 u) and another occurring by sequential elimination of neutral fragments with 72 u and 27 u. These processes should lead to formation of R+. CONCLUSIONS: The ESI-MS/MS experiments have shown that the side chain could affect the dissociation mechanism of protonated 2-oxazoline derivatives. For the compound that exhibits a hydroxyl at the lateral chain, water loss has been suggested to happen through an E2-type elimination, in an exothermic step. Copyright (C) 2012 John Wiley & Sons, Ltd.

Dose-dependent change in biomarkers during neoadjuvant endocrine therapy with fulvestrant: results from NEWEST, a randomized Phase II study

NEWEST (Neoadjuvant Endocrine Therapy for Women with Estrogen-Sensitive Tumors) is the first study to compare biological and clinical activity of fulvestrant 500 versus 250 mg in the neoadjuvant breast cancer setting. We hypothesized that fulvestrant 500 mg may be superior to 250 mg in blocking estrogen receptor (ER) signaling and growth. A multicenter, randomized, open-label, Phase II study was performed to compare fulvestrant 500 mg (500 mg/month plus 500 mg on day 14 of month 1) versus fulvestrant 250 mg/month for 16 weeks prior to surgery in postmenopausal women with ER+ locally advanced breast cancer. Core biopsies at baseline, week 4, and surgery were assessed for biomarker changes. Primary endpoint: change in Ki67 labeling index (LI) from baseline to week 4 determined by automated computer imaging system (ACIS). Secondary endpoints: ER protein expression and function; progesterone receptor (PgR) expression; tumor response; tolerability. ER and PgR were examined retrospectively using the H score method. A total of 211 patients were randomized (fulvestrant 500 mg: n = 109; 250 mg: n = 102). At week 4, fulvestrant 500 mg resulted in greater reduction of Ki67 LI and ER expression versus 250 mg (-78.8 vs. -47.4% [p < 0.0001] and -25.0 vs. -13.5% [p = 0.0002], respectively [ACIS]); PgR suppression was not significantly different (-22.7 vs. -17.6; p = 0.5677). However, H score detected even greater suppression of ER (-50.3 vs. -13.7%; p < 0.0001) and greater PgR suppression (-80.5 vs. -46.3%; p = 0.0018) for fulvestrant 500 versus 250 mg. At week 16, tumor response rates were 22.9 and 20.6% for fulvestrant 500 and 250 mg, respectively, with considerable decline in all markers by both ACIS and H score. No detrimental effects on endometrial thickness or bone markers and no new safety concerns were identified. This provides the first evidence of greater biological activity for fulvestrant 500 versus 250 mg in depleting ER expression, function, and growth.

A novel linkage map of sugarcane with evidence for clustering of retrotransposon-based markers

Background: The development of sugarcane as a sustainable crop has unlimited applications. The crop is one of the most economically viable for renewable energy production, and CO2 balance. Linkage maps are valuable tools for understanding genetic and genomic organization, particularly in sugarcane due to its complex polyploid genome of multispecific origins. The overall objective of our study was to construct a novel sugarcane linkage map, compiling AFLP and EST-SSR markers, and to generate data on the distribution of markers anchored to sequences of scIvana_1, a complete sugarcane transposable element, and member of the Copia superfamily. Results: The mapping population parents ('IAC66-6' and 'TUC71-7') contributed equally to polymorphisms, independent of marker type, and generated markers that were distributed into nearly the same number of co-segregation groups (or CGs). Bi-parentally inherited alleles provided the integration of 19 CGs. The marker number per CG ranged from two to 39. The total map length was 4,843.19 cM, with a marker density of 8.87 cM. Markers were assembled into 92 CGs that ranged in length from 1.14 to 404.72 cM, with an estimated average length of 52.64 cM. The greatest distance between two adjacent markers was 48.25 cM. The scIvana_1-based markers (56) were positioned on 21 CGs, but were not regularly distributed. Interestingly, the distance between adjacent scIvana_1-based markers was less than 5 cM, and was observed on five CGs, suggesting a clustered organization. Conclusions: Results indicated the use of a NBS-profiling technique was efficient to develop retrotransposon-based markers in sugarcane. The simultaneous maximum-likelihood estimates of linkage and linkage phase based strategies confirmed the suitability of its approach to estimate linkage, and construct the linkage map. Interestingly, using our genetic data it was possible to calculate the number of retrotransposonscIvana_1 (similar to 60) copies in the sugarcane genome, confirming previously reported molecular results. In addition, this research possibly will have indirect implications in crop economics e. g., productivity enhancement via QTL studies, as the mapping population parents differ in response to an important fungal disease.

Rounding of a first-order quantum phase transition to a strong-coupling critical point

We investigate the effects of quenched disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong-disorder renormalization group, we demonstrate that quenched disorder rounds the first-order quantum phase transition to a continuous one for both weak and strong coupling between the colors. In the strong-coupling case, we find a distinct type of infinite-randomness critical point characterized by additional internal degrees of freedom. We investigate its critical properties in detail and find stronger thermodynamic singularities than in the random transverse field Ising chain. We also discuss the implications for higher spatial dimensions as well as unusual aspects of our renormalization-group scheme. DOI: 10.1103/PhysRevB.86.214204

ORAL MUCOSITIS PREVENTION BY LOW-LEVEL LASER THERAPY IN HEAD-AND-NECK CANCER PATIENTS UNDERGOING CONCURRENT CHEMORADIOTHERAPY: A PHASE III RANDOMIZED STUDY

Purpose: Oral mucositis is a major complication of concurrent chemoradiotherapy (CRT) in head-and-neck cancer patients. Low-level laser (LLL) therapy is a promising preventive therapy. We aimed to evaluate the efficacy of LLL therapy to decrease severe oral mucositis and its effect on RT interruptions. Methods and Materials: In the present randomized, double-blind, Phase III study, patients received either gallium-aluminum-arsenide LLL therapy 2.5 J/cm(2) or placebo laser, before each radiation fraction. Eligible patients had to have been diagnosed with squamous cell carcinoma or undifferentiated carcinoma of the oral cavity, pharynx, larynx, or metastases to the neck with an unknown primary site. They were treated with adjuvant or definitive CRT, consisting of conventional RT 60-70 Gy (range, 1.8-2.0 Gy/d, 5 times/wk) and concurrent cisplatin. The primary endpoints were the oral mucositis severity in Weeks 2, 4, and 6 and the number of RT interruptions because of mucositis. The secondary endpoints included patient-reported pain scores. To detect a decrease in the incidence of Grade 3 or 4 oral mucositis from 80% to 50%, we planned to enroll 74 patients. Results: A total of 75 patients were included, and 37 patients received preventive LLL therapy. The mean delivered radiation dose was greater in the patients treated with LLL (69.4 vs. 67.9 Gy, p = .03). During CRT, the number of patients diagnosed with Grade 3 or 4 oral mucositis treated with LLL vs. placebo was 4 vs. 5 (Week 2, p = 1.0), 4 vs. 12 (Week 4, p = .08), and 8 vs. 9 (Week 6, p = 1.0), respectively. More of the patients treated with placebo had RT interruptions because of mucositis (6 vs. 0, p = .02). No difference was detected between the treatment arms in the incidence of severe pain. Conclusions: LLL therapy was not effective in reducing severe oral mucositis, although a marginal benefit could not be excluded. It reduced RT interruptions in these head-and-neck cancer patients, which might translate into improved CRT efficacy. (C) 2012 Elsevier Inc.

Signatures of quantum phase transitions in parallel quantum dots: Crossover from local moment to underscreened spin-1 Kondo physics

We study a strongly interacting "quantum dot 1" and a weakly interacting "dot 2" connected in parallel to metallic leads. Gate voltages can drive the system between Kondo-quenched and non-Kondo free-moment phases separated by Kosterlitz-Thouless quantum phase transitions. Away from the immediate vicinity of the quantum phase transitions, the physical properties retain signatures of first-order transitions found previously to arise when dot 2 is strictly noninteracting. As interactions in dot 2 become stronger relative to the dot-lead coupling, the free moment in the non-Kondo phase evolves smoothly from an isolated spin-one-half in dot 1 to a many-body doublet arising from the incomplete Kondo compensation by the leads of a combined dot spin-one. These limits, which feature very different spin correlations between dot and lead electrons, can be distinguished by weak-bias conductance measurements performed at finite temperatures.