Computer-Assisted Segmentation of Videocapsule Images Using Alpha-Divergence-Based Active Contour in the Framework of Intestinal Pathologies Detection

Visualization of the entire length of the gastrointestinal tract through natural orifices is a challenge for endoscopists. Videoendoscopy is currently the “gold standard” technique for diagnosis of different pathologies of the intestinal tract. Wireless Capsule Endoscopy (WCE) has been developed in the 1990's as an alternative to videoendoscopy to allow direct examination of the gastrointestinal tract without any need for sedation. Nevertheless, the systematic post-examination by the specialist of the 50,000 (for the small bowel) to 150,000 images (for the colon) of a complete acquisition using WCE remains time-consuming and challenging due to the poor quality of WCE images. In this article, a semiautomatic segmentation for analysis of WCE images is proposed. Based on active contour segmentation, the proposed method introduces alpha-divergences, a flexible statistical similarity measure that gives a real flexibility to different types of gastrointestinal pathologies. Results of segmentation using the proposed approach are shown on different types of real-case examinations, from (multi-) polyp(s) segmentation, to radiation enteritis delineation

Renormalization aspects of N=1 Super Yang-Mills theory in the Wess-Zumino gauge

The renormalization of N=1 Super Yang-Mills theory is analysed in the Wess-Zumino gauge, employing the Landau condition. An all orders proof of the renormalizability of the theory is given by means of the Algebraic Renormalization procedure. Only three renormalization constants are needed, which can be identified with the coupling constant, gauge field and gluino renormalization. The non-renormalization theorem of the gluon-ghost-antighost vertex in the Landau gauge is shown to remain valid in N=1 Super Yang-Mills. Moreover, due to the non-linear realization of the supersymmetry in the Wess-Zumino gauge, the renormalization factor of the gauge field turns out to be different from that of the gluino. These features are explicitly checked through a three loop calculation.Comment: 15 pages, minor text improvements, references added. Version accepted for publication in the EPJ

Implementing the Gribov-Zwanziger framework in N=1 Super Yang-Mills in the Landau gauge

The Gribov-Zwanziger framework accounting for the existence of Gribov copies is extended to N=1 Super Yang--Mills theories quantized in the Landau gauge. We show that the restriction of the domain of integration in the Euclidean functional integral to the first Gribov horizon can be implemented in a way to recover non-perturbative features of N=1 Super Yang--Mills theories, namely: the existence of the gluino condensate as well as the vanishing of the vacuum energy.Comment: 19 pages, no figure

Orbital order-disorder transition in La(1-x)Nd(x)MnO(3) (x = 0.0-1.0) and La(1-x-y)Nd(yx)Sr(y)MnO(3) (x = 0.1; y = 0.05,0.1)

The nature of orbital order-disorder transition has been studied in the La(1-x)Nd(x)MnO(3) (x = 0.0-1.0) series which covers the entire range between two end points - LaMnO(3) and NdMnO(3) - as well as in La(0.85)Nd(0.1)Sr(0.05)MnO(3) and La(0.8)Nd(0.1)Sr(0.1)MnO(3). It has been observed that the first-order nature of the transition gives way to higher order with the increase in "x" in the case of pure manganites. The latent heat (L) associated with the transition, first, drops with a steeper slope within x = 0.0-0.3 and, then, gradually over a range 0.3<x<0.9. This drop could, possibly, be due to evolution of finer orbital domain structure with "x". In the case of Sr-doped samples, the transition appears to be of higher-order nature even for a doping level 5 at%. In both cases, of course, the transition temperature T(JT) rises systematically with the drop in average A-site radius or rise in average Mn-O-Mn bond bending angle while no apparent correlation could be observed with doping induced disorder sigma^2. The cooperative nature of the orbital order, therefore, appears to be robust.Comment: 15 pages including 4 figures; pdf onl

Spin-Electron-Phonon Excitation in Re-based Half-Metallic Double Perovskites

A remarkable hardening (~ 30 cm-1) of the normal mode of vibration associated with the symmetric stretching of the oxygen octahedra for the Ba2FeReO6 and Sr2CrReO6 double perovskites is observed below the corresponding magnetic ordering temperatures. The very large magnitude of this effect and its absence for the anti-symmetric stretching mode provide evidence against a conventional spin-phonon coupling mechanism. Our observations are consistent with a collective excitation formed by the combination of the vibrational mode with oscillations of local Fe or Cr 3d and Re 5d occupations and spin magnitudes.Comment: 12 pages, 4 figure

Power spectrum characterization of the continuous gaussian ensemble

The continuous Gaussian ensemble, also known as the ν-Gaussian or ν-Hermite ensemble, is a natural extension of the classical Gaussian ensembles of real (ν=1), complex (ν=2), or quaternion (ν=4) matrices, where ν is allowed to take any positive value. From a physical point of view, this ensemble may be useful to describe transitions between different symmetries or to describe the terrace-width distributions of vicinal surfaces. Moreover, its simple form allows one to speed up and increase the efficiency of numerical simulations dealing with large matrix dimensions. We analyze the long-range spectral correlations of this ensemble by means of the δn statistic. We derive an analytical expression for the average power spectrum of this statistic, Pkδ̅ , based on approximated forms for the two-point cluster function and the spectral form factor. We find that the power spectrum of δn evolves from Pkδ̅ ∝1/k at ν=1 to Pkδ̅ ∝1/k2 at ν=0. Relevantly, the transition is not homogeneous with a 1/fα noise at all scales, but heterogeneous with coexisting 1/f and 1/f2 noises. There exists a critical frequency kc∝ν that separates both behaviors: below kc, Pkδ̅ follows a 1/f power law, while beyond kc, it transits abruptly to a 1/f2 power law. For ν>1 the 1/f noise dominates through the whole frequency range, unveiling that the 1/f correlation structure remains constant as we increase the level repulsion and reduce to zero the amplitude of the spectral fluctuations. All these results are confirmed by stringent numerical calculations involving matrices with dimensions up to 10

Raman phonons as a probe of disorder, fluctuations and local structure in doped and undoped orthorhombic and rhombohedral manganites

We present a rationalization of the Raman spectra of orthorhombic and rhombohedral, stoichiometric and doped, manganese perovskites. In particular we study RMnO3 (R= La, Pr, Nd, Tb, Ho, Er, Y and Ca) and the different phases of Ca or Sr doped RMnO3 compounds as well as cation deficient RMnO3. The spectra of manganites can be understood as combinations of two kinds of spectra corresponding to two structural configurations of MnO6 octahedra and independently of the average structure obtained by diffraction techniques. The main peaks of compounds with regular MnO6 octahedra, as CaMnO3, highly Ca doped LaMnO3 or the metallic phases of Ca or Sr doped LaMnO3, are bending and tilt MnO6 octahedra modes which correlate to R-O(1) bonds and Mn-O-Mn angles respectively. In low and optimally doped manganites, the intensity and width of the broad bands are related to the amplitude of the dynamic fluctuations produced by polaron hopping in the paramagnetic insulating regime. The activation energy, which is proportional to the polaron binding energy, is the measure of this amplitude. This study permits to detect and confirm the coexistence, in several compounds, of a paramagnetic matrix with lattice polaron together with regions without dynamic or static octahedron distortions, identical to the ferromagnetic metallic phase. We show that Raman spectroscopy is an excellent tool to obtain information on the local structure of the different micro or macro-phases present simultaneously in many manganites.Comment: Submitted to PR

Cumplimiento de las recomendaciones de práctica de actividad física y percepción de barreras en estudiantes de bachillerato

El objetivo de este estudio fue conocer los niveles de actividad física (AF) así como la percepción de barreras para la realización de AF en estudiantes de Bachillerato, analizando dichas variables en función del género, curso académico, práctica deportiva extraescolar y tipo de jornada. Se realizó un estudio descriptivo transversal en el que participaron 248 adolescentes, 120 chicos y 128 chicas ( M = 15.32; DT = 1.81), 144 de 1º de Bachillerato y 104 de 2º de Bachillerato. Se utilizó el Cuestionario Internacional de AF en su versión corta (IPAQ-SF) y la Escala de Barreras para la práctica de AF . Los resultados señalaron que menos del 30% de los estudiantes de Bachillerato alcanza las recomendaciones de práctica de AF, siendo el grado de cumplimiento más elevado en los chicos (38.3%), en el alumnado de 1º de Bachillerato (30.6%), en el alumnado que realiza práctica deportiva extraescolar (36.7%) y entre semana (31%). Por otro lado, las barreras referentes al tiempo fueron superiores en el alumnado de 2º de Bachillerato, mientras que las barreras relativas al disfrute fueron superiores en las chicas y en el alumnado que no realizaba práctica deportiva extraescolar. Los resultados destacan la importancia de promover la práctica regular de AF en Bachillerato, especialmente en las chicas y en los adolescentes de 2º curso, a través de programas de intervención que ayuden a mejorar la gestión del tiempo de ocio y estimulen el desarrollo de los procesos motivacionales. The aim of this study was to analyze physical activity (PA) levels and perceived barriers to PA in High School students. Similarly, differences in gender, academic year, out-of-school sport and type of day were analyzed among these variables. In this cross-sectional study, 248 adolescents, 120 boys and 128 girls (M = 15.32; SD = 1.81), were involved. The sample was made up of 144 12th grade students (58.1%) and 104 13th grade students. The International PA Questionnaire-Short Form (IPAQ-SF) and the Scale of Barriers to PA were used. The results showed that less than 30% of High School students comply with the PA guidelines, being higher in boys (38.3%), in the 12th High School students (30.6%), in the students who practiced extracurricular sports (36.7%) and weekdays (31%). On the other hand, barriers relating to time adolescents were higher in students of 13th High School, while barriers relate to enjoyment were higher in girls and students who did not practice extracurricular sports. The results highlight the importance of promoting PA in High School students, especially in girls and 12th High School, through intervention programs that help improve the management of their leisure time and development of motivational processes

Existence of orbital polarons in ferromagnetic insulating La1−x_{1-x}Srx_xMnO3_{3} (0.11<x<<x<0.14) evidenced by giant phonon softening

We present an inelastic light scattering study of single crystalline (La$_{1-y}$Pr$_y$)$_{1-x}$Sr$_{x}$MnO$_3$ ($0\leq x\leq0.14$,$y=0$ and $x=1/8$,$0\leq y\leq0.5$). A giant softening up to 20 - 30 cm$^{-1}$ of the Mn-O breathing mode has been observed only for the ferromagnetic insulating (FMI) samples ($0.11\leq x \leq 0.14$) upon cooling below the Curie temperature. With increasing Pr-doping the giant softening is gradually suppressed. This is attributed to a coupling of the breathing mode to orbital polarons which are present in the FMI phase.Comment: 4 pages, 5 figure

Inhomogeneous magnetism in La-doped CaMnO3. (I) Nanometric-scale spin clusters and long-range spin canting

Neutron measurements on Ca{1-x}La{x}MnO3 (0.00 <= x <= 0.20) reveal the development of a liquid-like spatial distribution of magnetic droplets of average size ~10 Angstroms, the concentration of which is proportional to x (one cluster per ~60 doped electrons). In addition, a long-range ordered ferromagnetic component is observed for ~0.05 < x < ~0.14. This component is perpendicularly coupled to the simple G-type antiferromagnetic (G-AFM) structure of the undoped compound, which is a signature of a G-AFM + FM spin-canted state. The possible relationship between cluster formation and the stabilization of a long-range spin-canting for intermediate doping is discussed.Comment: Submitted to Physical Review