Edge Colourings of Graphs Avoiding Monochromatic Matchings of a Given Size

Let k and l be positive integers. With a graph G, we associate the quantity c(k,l)(G), the number of k-colourings of the edge set of G with no monochromatic matching of size l. Consider the function c(k,l) : N --> N given by c(k,l)(n) = max {c(k,l)(G): vertical bar V(G)vertical bar = n}, the maximum of c(k,l)(G) over all graphs G on n vertices. In this paper, we determine c(k,l)(n) and the corresponding extremal graphs for all large n and all fixed values of k and l.

Flow Visualization with Quantified Spatial and Temporal Errors Using Edge Maps

Robust analysis of vector fields has been established as an important tool for deriving insights from the complex systems these fields model. Traditional analysis and visualization techniques rely primarily on computing streamlines through numerical integration. The inherent numerical errors of such approaches are usually ignored, leading to inconsistencies that cause unreliable visualizations and can ultimately prevent in-depth analysis. We propose a new representation for vector fields on surfaces that replaces numerical integration through triangles with maps from the triangle boundaries to themselves. This representation, called edge maps, permits a concise description of flow behaviors and is equivalent to computing all possible streamlines at a user defined error threshold. Independent of this error streamlines computed using edge maps are guaranteed to be consistent up to floating point precision, enabling the stable extraction of features such as the topological skeleton. Furthermore, our representation explicitly stores spatial and temporal errors which we use to produce more informative visualizations. This work describes the construction of edge maps, the error quantification, and a refinement procedure to adhere to a user defined error bound. Finally, we introduce new visualizations using the additional information provided by edge maps to indicate the uncertainty involved in computing streamlines and topological structures.

EDGE-PRESERVING SPECKLE TEXTURE REMOVAL BY INTERFERENCE-BASED SPECKLE FILTERING FOLLOWED BY ANISOTROPIC DIFFUSION

Ultrasonography has an inherent noise pattern, called speckle, which is known to hamper object recognition for both humans and computers. Speckle noise is produced by the mutual interference of a set of scattered wavefronts. Depending on the phase of the wavefronts, the interference may be constructive or destructive, which results in brighter or darker pixels, respectively. We propose a filter that minimizes noise fluctuation while simultaneously preserving local gray level information. It is based on steps to attenuate the destructive and constructive interference present in ultrasound images. This filter, called interference-based speckle filter followed by anisotropic diffusion (ISFAD), was developed to remove speckle texture from B-mode ultrasound images, while preserving the edges and the gray level of the region. The ISFAD performance was compared with 10 other filters. The evaluation was based on their application to images simulated by Field II (developed by Jensen et al.) and the proposed filter presented the greatest structural similarity, 0.95. Functional improvement of the segmentation task was also measured, comparing rates of true positive, false positive and accuracy. Using three different segmentation techniques, ISFAD also presented the best accuracy rate (greater than 90% for structures with well-defined borders). (E-mail: fernando.okara@gmail.com) (C) 2012 World Federation for Ultrasound in Medicine & Biology.

Cutting Edge: Brazilian Pemphigus Foliaceus Anti-Desmoglein 1 Autoantibodies Cross-React with Sand Fly Salivary LJM11 Antigen

The environmental factors that contribute to the development of autoimmune diseases are largely unknown. Endemic pemphigus foliaceus in humans, known as Fogo Selvagem (FS) in Brazil, is mediated by pathogenic IgG4 autoantibodies against desmoglein 1 (Dsg1). Clusters of FS overlap with those of leishmaniasis, a disease transmitted by sand fly (Lutzomyia longipalpis) bites. In this study, we show that salivary Ags from the sand fly, and specifically the LJM11 salivary protein, are recognized by FS Abs. Anti-Dsg1 monoclonal autoantibodies derived from FS patients also cross-react with LJM11. Mice immunized with LJM11 generate anti-Dsg1 Abs. Thus, insect bites may deliver salivary Ags that initiate a cross-reactive IgG4 Ab response in genetically susceptible individuals and lead to subsequent FS. Our findings establish a clear relationship between an environmental, noninfectious Ag and the development of potentially pathogenic autoantibodies in an autoimmune disease. The Journal of Immunology, 2012, 189: 1535-1539.

Self-organized criticality in MHD driven plasma edge turbulence

We analyze long-range time correlations and self-similar characteristics of the electrostatic turbulence at the plasma edge and scrape-off layer in the Tokamak Chauffage Alfven Bresillien (TCABR), with low and high Magnetohydrodynamics (MHD) activity. We find evidence of self-organized criticality (SOC), mainly in the region near the tokamak limiter. Comparative analyses of data before and during the MHD activity reveals that during the high mHD activity the Hurst parameter decreases. Finally, we present a cellular automaton whose parameters are adjusted to simulate the analyzed turbulence SOC change with the MHD activity variation. (C) 2011 Published by Elsevier B.V.

On the optical properties of copper nanocubes as a function of the edge length as modeled by the discrete dipole approximation

This Letter reports an investigation on the optical properties of copper nanocubes as a function of size as modeled by the discrete dipole approximation. In the far-field, our results showed that the extinction resonances shifted from 595 to 670 nm as the size increased from 20 to 100 nm. Also, the highest optical efficiencies for absorption and scattering were obtained for nanocubes that were 60 and 100 nm in size, respectively. In the near-field, the electric-field amplitudes were investigated considering 514, 633 and 785 nm as the excitation wavelengths. The E-fields increased with size, being the highest at 633 nm. (c) 2012 Elsevier B.V. All rights reserved.

Electronics and Optics of Graphene Nanoflakes: Edge Functionalization and Structural Distortions

The effects of edge covalent functionalization on the structural, electronic, and optical properties of elongated armchair graphene nanoflakes (AGNFs) are analyzed in detail for a wide range of terminations, within the framework of Hartree-Fock-based semiempirical methods. The chemical features of the functional groups, their distribution, and the resulting system symmetry are identified as the key factors that determine the modification of strutural and optoelectronic features. While the electronic gap is always reduced in the presence of substituents, functionalization-induced distortions contribute to the observed lowering by about 35-55% This effect is paired with a red shift of the first optical peak, corresponding to about 75% of the total optical gap reduction. Further, the functionalization pattern and the specific features of the edge-substituent bond are found to influence the strength and the character of the low-energy excitations. All of these effects are discussed for flakes of different widths, representing the three families of AGNFs.

Bifurcation effects on the plasma edge of tokamaks with ergodic limiter.

In the present paper, we solve a twist symplectic map for the action of an ergodic magnetic limiter in a large aspect-ratio tokamak. In this model, we study the bifurcation scenarios that occur in the remnants regular islands that co-exist with chaotic magnetic surfaces. The onset of atypical local bifurcations created by secondary shearless tori are identified through numerical profiles of internal rotation number and we observe that their rupture can reduce the usual magnetic field line escape at the tokamak plasma edge.

In-situ XANES experiments on Ni K-edge in mesoporous ZrO2-CeO2:Ni.

Ordered mesoporous ZrO2-CeO2 mixed oxides are potential candidates for catalytic applications. These systems, used as anodes in solid oxide fuel cells (SOFC), may lead to better performance of SOFCs, due to an enhancement on surface area, aiming to achieve a lower working temperature. The aim of this studies is to evaluate the reduction capacity of Ni2+ to Ni in ZrO2-x(mol)%CeO2 (x=50 and 90) samples impregnated with 60(wt.)%NiO. The synthesis was made with Zr and Ce chloride precursors, HCl aqueous solution, Pluronic P123, NH4OH to adjust the pH (3-4) and a teflon autoclave to perform a hydrothermal treatment (80oC/48h). The samples were dried and calcined, until 540oC in N2 and 4 hours in air. The NiO impregnation was made with an ethanol dispersion of Ni(NO3)£6H2O. The powder was calcinated in air until 350oC for 2 hours. Temperature-resolved XANES data at the Ni K-edge were collected at the DXAS beam line of the LNLS in transmission mode, using a Si(111) monochromator and a CCD detector. Sample preparation consisted of mixing »6mg of the powder samples with boron nitride and pressing into pellets. The data were acquired during an experiment of temperature programmed reduction (TPR) under a 5% H2/He until 600oC and mixtures of 20%CH4:5%O2/He, at temperatures from 400 to 600oC. All the reactions were monitored with a mass spectrometer. The data was analyzed with a linear combination fit of 2 standards for each valence number using Athena software. The Ni K-edge experiments demonstrated that for both contents of CeO2, NiO embedded in the porous zirconia-ceria matrix reduces at lower temperatures than pure NiO, revealing that the ZrO2-CeO2 support improves the reduction of impregnated NiO. Ni was oxidized to NiO after all reactions with methane and oxygen. Hydrogenated carbonaceous species were detected, but under reducing conditions, the hydrocarbon compounds are removed. The reaction of total oxidation of methane CH4:O2 (1:2 ratio) was observed at lower temperatures (around 400oC) for both samples.

A subpixel edge detector applied to aortic dissection detection

[EN] The aortic dissection is a disease that can cause a deadly situation, even with a correct treatment. It consists in a rupture of a layer of the aortic artery wall, causing a blood flow inside this rupture, called dissection. The aim of this paper is to contribute to its diagnosis, detecting the dissection edges inside the aorta. A subpixel accuracy edge detector based on the hypothesis of partial volume effect is used, where the intensity of an edge pixel is the sum of the contribution of each color weighted by its relative area inside the pixel. The method uses a floating window centred on the edge pixel and computes the edge features. The accuracy of our method is evaluated on synthetic images of different hickness and noise levels, obtaining an edge detection with a maximal mean error lower than 16 percent of a pixel.

Shape design optimization of road acoustic barriers featuring top-edge devices by using Genetic Algotithms and Boundary Elements

[EN] This paper presents a Boundary Elements (BE) approach for the efficiency improvement of road acoustic barriers, mora specifically, for the shape design optimization of top-edge devices in the search for the best designs in terms of screening performance, usually represented by the insertion loss (IL).

Change in modal parameters of cracked single-edge notched plain concrete Beams

[EN]The aim of this work is looking into the possibility of capturing the change in the modal properties (natural frequencies, modal shapes and modal damping ratio) of plain concrete elements due to the presence of cracked areas by using a simple continuum damage zone numerical model.

Ab-initio determination of x-ray absorption near edge structure (xanes) spectra in an ultrasoft and norm conserving pseudopotentials scheme

X-ray absorption spectroscopy (XAS) is a powerful means of investigation of structural and electronic properties in condensed -matter physics. Analysis of the near edge part of the XAS spectrum, the so – called X-ray Absorption Near Edge Structure (XANES), can typically provide the following information on the photoexcited atom: - Oxidation state and coordination environment. - Speciation of transition metal compounds. - Conduction band DOS projected on the excited atomic species (PDOS). Analysis of XANES spectra is greatly aided by simulations; in the most common scheme the multiple scattering framework is used with the muffin tin approximation for the scattering potential and the spectral simulation is based on a hypothetical, reference structure. This approach has the advantage of requiring relatively little computing power but in many cases the assumed structure is quite different from the actual system measured and the muffin tin approximation is not adequate for low symmetry structures or highly directional bonds. It is therefore very interesting and justified to develop alternative methods. In one approach, the spectral simulation is based on atomic coordinates obtained from a DFT (Density Functional Theory) optimized structure. In another approach, which is the object of this thesis, the XANES spectrum is calculated directly based on an ab – initio DFT calculation of the atomic and electronic structure. This method takes full advantage of the real many-electron final wavefunction that can be computed with DFT algorithms that include a core-hole in the absorbing atom to compute the final cross section. To calculate the many-electron final wavefunction the Projector Augmented Wave method (PAW) is used. In this scheme, the absorption cross section is written in function of several contributions as the many-electrons function of the finale state; it is calculated starting from pseudo-wavefunction and performing a reconstruction of the real-wavefunction by using a transform operator which contains some parameters, called partial waves and projector waves. The aim of my thesis is to apply and test the PAW methodology to the calculation of the XANES cross section. I have focused on iron and silicon structures and on some biological molecules target (myoglobin and cytochrome c). Finally other inorganic and biological systems could be taken into account for future applications of this methodology, which could become an important improvement with respect to the multiscattering approach.

Pre-edge analysis of X-rays absorption spectra in TiO2 modified films

The thesis is mainly focused on the pre-edge analysis of XAS spectra of Ti HCF sample hexacyanocobaltate and hexacyanoferrate samples doped on a Indium Tin Oxide (ITO) thin film. The work is aimed at the determination of Ti oxidation state, as well as indication of various coordination number in the studied samples. The experiment have been conducted using XAFS (X-ray absorption fine structure)beamline at Elettra synchrotron, Trieste (Italy) under supervision of Professor Marco Giorgetti, Department of Industrial Chemistry, University of Bologna. The Master thesis accreditation to fullfill the ASC Master of Advanced Spectroscopy in Chemistry Degree requirement.