Metamorfose planar via métodos Level Set e Particle Level Set para a reconstrução de superfícies tridimensionais

Evolving interfaces were initially focused on solutions to scientific problems in Fluid Dynamics. With the advent of the more robust modeling provided by Level Set method, their original boundaries of applicability were extended. Specifically to the Geometric Modeling area, works published until then, relating Level Set to tridimensional surface reconstruction, centered themselves on reconstruction from a data cloud dispersed in space; the approach based on parallel planar slices transversal to the object to be reconstructed is still incipient. Based on this fact, the present work proposes to analyse the feasibility of Level Set to tridimensional reconstruction, offering a methodology that simultaneously integrates the proved efficient ideas already published about such approximation and the proposals to process the inherent limitations of the method not satisfactorily treated yet, in particular the excessive smoothing of fine characteristics of contours evolving under Level Set. In relation to this, the application of the variant Particle Level Set is suggested as a solution, for its intrinsic proved capability to preserve mass of dynamic fronts. At the end, synthetic and real data sets are used to evaluate the presented tridimensional surface reconstruction methodology qualitatively.Inicialmente centralizadas na solução de problemas em Dinâmica dos Fluidos, as fronteiras dinâmicas, com o advento da modelagem mais robusta provida pelo método Level Set, expandiram os limites originais de sua aplicabilidade. Especificamente à área de Modelagem Geométrica, os trabalhos até então apresentados, relacionando o Level Set à reconstrução de superfícies tridimensionais, concentram-se na reconstrução a partir de uma nuvem de dados dispersos no espaço; a abordagem baseada em fatias planas paralelas e transversais ao objeto a ser reconstruído evidencia-se ainda incipiente. Este trabalho propõe-se, logo, a analisar a viabilidade do Level Set para a reconstrução tridimensional, oferecendo uma metodologia que agregue, simultaneamente, as ideias comprovadamente eficientes já publicadas sobre a aproximação em questão e as propostas para contornar as limitações inerentes ao método ainda não satisfatoriamente tratadas, em particular a suavização excessiva de características finas dos contornos em evolução sob o Level Set. Relativamente a esse ponto, o emprego da variante Particle Level Set é sugerido como uma solução, por sua intrínseca capacidade comprovada para a preservação de massa de fronteiras dinâmicas. Ao final, conjuntos de dados sintéticos e reais são utilizados para avaliar a metodologia de reconstrução de superfícies tridimensionais apresentada qualitativamente.291303Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Location of the Energy Levels of the Rare-Earth Ion in BaF2 and CdF2

The location of the energy levels of rare-earth (RE) elements in the energy band diagram of BaF2 and CdF2 crystals is determined. The role of RE3+ and RE2+ ions in the capture of charge carriers, luminescence, and the formation of radiation defects is evaluated. It is shown that the substantial difference in the luminescence properties of BaF2:RE and CdF2:RE is associated with the location of the excited energy levels in the band diagram of the crystals

Quenching of the Haldane gap in LiVSi2O6 and related compounds

Abstract.: We report results of susceptibility χ and 7Li NMR measurements on LiVSi2O6. The temperature dependence of the magnetic susceptibility χ(T) exhibits a broad maximum, typical for low-dimensional magnetic systems. Quantitatively it is in agreement with the expectation for an S=1 spin chain, represented by the structural arrangement of V ions. The NMR results indicate antiferromagnetic ordering below TN=24 K. The intra- and interchain coupling J and Jp for LiVSi2O6, and also for its sister compounds LiVGe2O6, NaVSi2O6 and NaVGe2O6, are obtained via a modified random phase approximation which takes into account results of quantum Monte Carlo calculations. While Jp is almost constant across the series, J varies by a factor of 5, decreasing with increasing lattice constant along the chain direction. The comparison between experimental and theoretical susceptibility data suggests the presence of an easy-axis magnetic anisotropy, which explains the formation of an energy gap in the magnetic excitation spectrum below TN, indicated by the variation of the NMR spin-lattice relaxation rate at T≪T

Reconstruction of panoramic dental Iimages through Bézier function optimization

The authors were grateful to CAPES, CNPq, and FAPESP for their financial support.Computed tomography (CT) and X-ray images have been extensively used as a valuable diagnostic tool in dentistry for surgical planning and treatment. Nowadays, dental cone beam CT has been extensively used in dental clinics. Therefore, it is possible to employ three-dimensional (3D) data from the CT to reconstruct a two-dimensional (2D) panoramic dental image that provides a longitudinal view of the mandibular region of the patient, avoiding an additional exposure to X-ray. In this work, we developed a new automatic method for reconstructing 2D panoramic images of the dental arch based on 3D CT images, using Bézier curves and optimization techniques. The proposed method was applied to five patients, some of them with missing teeth, and smooth panoramic images with good contrast were obtained.info:eu-repo/semantics/publishedVersio

Localized versus itinerant magnetic moments in Na0.72CoO2

Based on experimental 59Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23Na- and 59Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution corb to the d-electron susceptibility. At low temperatures corb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.Comment: 8.7 pages, 6 Figures, submitted to Phys. Rev.

NMR and dc-susceptibility studies of NaVGe2O6

We report the results of measurements of the dc magnetic susceptibility chi(T) and of the 23Na nuclear magnetic resonance (NMR) response of NaVGe2O6, a material in which the V ions form a network of interacting one-dimensional spin S=1 chains. The experiments were made at temperatures between 2.5 and 300 K. The chi(T) data suggest that the formation of the expected low-temperature Haldane phase is intercepted by an antiferromagnetic phase transition at 18 K. The transition is also reflected in the 23Na NMR spectra and the corresponding spin-lattice relaxation rate 1/T1(T). In the ordered phase, 1/T1(T) decreases by orders of magnitude with decreasing temperature, indicating the formation of a gap of the order of 12 K in the magnetic excitation spectrum.Comment: 10 pages, 15 figures; v2 with minor revisions of the tex

Unconventional Charge Ordering in Na0.70CoO2 below 300 K

We present the results of measurements of the dc-magnetic susceptibility chi(T) and the 23Na-NMR response of Na_{0.70}CoO_{2} at temperatures between 50 and 340 K. The chi(T) data suggest that for T > 75 K, the Co ions adopt an effective configuration of Co^{3.4+}. The 23Na-NMR response reveals pronounced anomalies near 250 and 295 K, but no evidence for magnetic phase transitions is found in chi(T). Our data suggest the onset of a dramatic change in the Co 3d-electron spin dynamics at 295 K. This process is completed at 230 K. Our results maybe interpreted as evidence for either a tendency to electron localization or an unconventional charge-density wave phenomenon within the cobalt oxide layer, CoO_2, 3d electron system near room temperature.Comment: 4 pages, 4 figures, re-submitted to Physical Review Letters. The manuscript has been revised following the recommendations of the referees. The discussion section contains substantial change

ALS-linked mutant SOD1 damages mitochondria by promoting conformational changes in Bcl-2.

In mutant superoxide dismutase (SOD1)-linked amyotrophic lateral sclerosis (ALS), accumulation of misfolded mutant SOD1 in spinal cord mitochondria is thought to cause mitochondrial dysfunction. Whether mutant SOD1 is toxic per se or whether it damages the mitochondria through interactions with other mitochondrial proteins is not known. We previously identified Bcl-2 as an interacting partner of mutant SOD1 specifically in spinal cord, but not in liver, mitochondria of SOD1 mice and patients. We now show that mutant SOD1 toxicity relies on this interaction. Mutant SOD1 induces mitochondrial morphological changes and compromises mitochondrial membrane integrity leading to release of Cytochrome C only in the presence of Bcl-2. In cells, mouse and human spinal cord with SOD1 mutations, the binding to mutant SOD1 triggers a conformational change in Bcl-2 that results in the uncovering of its toxic BH3 domain and conversion of Bcl-2 into a toxic protein. Bcl-2 carrying a mutagenized, non-toxic BH3 domain fails to support mutant SOD1 mitochondrial toxicity. The identification of Bcl-2 as a specific target and active partner in mutant SOD1 mitochondrial toxicity suggests new therapeutic strategies to inhibit the formation of the toxic mutant SOD1/Bcl-2 complex and to prevent mitochondrial damage in ALS