The diffusion coefficient of propagating fronts with multiplicative noise

Recent studies have shown that in the presence of noise both fronts propagating into a metastable state and so-called pushed fronts propagating into an unstable state, exhibit diffusive wandering about the average position. In this paper we derive an expression for the effective diffusion coefficient of such fronts, which was motivated before on the basis of a multiple scale ansatz. Our systematic derivation is based on the decomposition of the fluctuating front into a suitably positioned average profile plus fluctuating eigenmodes of the stability operator. While the fluctuations of the front position in this particular decomposition are a Wiener process on all time scales, the fluctuations about the time averaged front profile relax exponentially.Comment: 4 page

Transcripción de la entonación de la variedad del andaluz de Álora según el sistema Sp_ToBI

In recent years, several studies about intonation have been developed based on the Autosegmental- Metrical framework established by Janet Pierrehumbert. The aim of this work is to describe the main intonational patterns in different sentence-types in the town of Álora (Málaga), a point located in a zone of confluence between the eastern and western Andalusian varieties. To this end, 224 sentences uttered by 7 local speakers were recorded using the Discourse Completion Task method. The contours were annotated using the Sp_ToBI transcription system. In addition to describing the intonation of the different sentence-types, this work compares the variety of Spanish spoken in Álora with the varieties of Central Peninsular Spanish, studied by Estebas-Vilaplana and Prieto, and with the variety spoken in Jerez, analyzed by Henriksen and García-Amaya. The results show that the variety of Álora is intonationally closer to the one of Jerez than to central peninsular Spanish, although it differs from the former in several sentence types (broad focus statements of more than one prosodic word, statements of the obvious, informationseeking wh- questions, insistent orders).En los últimos años se han ido desarrollando numerosos estudios sobre la entonación de las lenguas basados en el modelo métrico-autosegmental establecido por Janet Pierrehumbert. El objetivo de este trabajo es el de describir los principales contornos de F0 en diferentes tipos de enunciados de la localidad de Álora (Málaga), un punto situado en una zona de confluencia entre la variedad oriental y occidental andaluzas. Con ese fin, se han grabado mediante la técnica del Discourse Completion Task 224 oraciones producidas por 7 hablantes de esa localidad. Los contornos entonativos así obtenidos se han anotado mediante el sistema de transcripción Sp_ToBI. Además de describir la entonación de los diferentes tipos de enunciados, en este trabajo se realiza también una comparación con las variedades del espanol central peninsular, estudiado por Estebas-Vilaplana y Prieto, y del jerezano, analizado por Henriksen y García-Amaya. Los resultados indican que el habla de Álora se acerca entonativamente más al jerezano que al español peninsular central, aunque se diferencia del primero en varias modalidades oracionales (declarativas neutras de más de una unidad tonal, declarativas de obviedad, interrogativas parciales neutras, órdenes, vocativos insistentes)

Kinematic reduction of reaction-diffusion fronts with multiplicative noise: Derivation of stochastic sharp-interface equations

We study the dynamics of generic reaction-diffusion fronts, including pulses and chemical waves, in the presence of multiplicative noise. We discuss the connection between the reaction-diffusion Langevin-like field equations and the kinematic (eikonal) description in terms of a stochastic moving-boundary or sharp-interface approximation. We find that the effective noise is additive and we relate its strength to the noise parameters in the original field equations, to first order in noise strength, but including a partial resummation to all orders which captures the singular dependence on the microscopic cutoff associated to the spatial correlation of the noise. This dependence is essential for a quantitative and qualitative understanding of fluctuating fronts, affecting both scaling properties and nonuniversal quantities. Our results predict phenomena such as the shift of the transition point between the pushed and pulled regimes of front propagation, in terms of the noise parameters, and the corresponding transition to a non-KPZ universality class. We assess the quantitative validity of the results in several examples including equilibrium fluctuations, kinetic roughening, and the noise-induced pushed-pulled transition, which is predicted and observed for the first time. The analytical predictions are successfully tested against rigorous results and show excellent agreement with numerical simulations of reaction-diffusion field equations with multiplicative noise.Comment: 17 pages, 6 figure

Fluctuations and Bubble Dynamics in First-Order Phase Transitions

We numerically examine the effect of thermal fluctuations on a first-order phase transition in 2+1 dimensions. By focusing on the expansion of a single bubble we are able to calculate changes in the bubble wall's velocity as well as changes in its structure relative to the standard case where the bubble expands into a homogeneous background. Not only does the wall move faster, but the transition from the symmetric to the asymmetric phase is no longer smooth, even for a fairly strong transition. We discuss how these results affect the standard picture of electroweak baryogenesis.Comment: Latex, 30 pages, 11 ps figures, short discussion added in conclusions and minor clarifications, accepted to Phys Rev

Estilos de aprendizaje y evaluación formativa: Estudio con universitarios de Educación Física chilenos

Assessment contributes to students learning. Formative assessment is a useful strategy of the initial teacher training. Perceptions about the assessment of Chilean university Physical Education students (n = 95), depending on their learning style, gender and academic course were analyzed. The Learning Styles Questionnaire and the Spanish version of the Assessment Experience Questionnaire were used. The results showed negative perceptions about the assessment process. Significant differences were observed in the perceptions about the use of feedback depending on the learning style of the students (F = 1.062, p =. 004). Significant differences were observed in the perception about the amount of effort (F = 5.888, p =. 000), the suitability of the evaluation (F = 3.282, p =. 015) and the shallow approach to the learning (F = 5.472, p =. 001), depending on the academic course. Gender was not a determinant of perceptions. The findings suggest the use of traditional procedures of assessment (summative assessment) with the students. On the other hand, findings show the influence of learning stylesand the academic course on student perceptionsand learning styles and feedback. This information contributes to a deeper understanding of the learning mode of the students according to their characteristics and context.La evaluación contribuye a la formación del aprendizaje, facilitando el avance del estudiante. La evaluación formativa se presenta como una estrategia eficaz dentro de la formación inicial docente. Se analizaron las percepciones sobre la evaluación de universitarios de Educación Física chilenos (n = 95), en función de su estilo de aprendizaje, género y curso académico. Se utilizaron el Cuestionario de Estilos de Aprendizaje y la versión en castellano del Assessment Experience Questionnaire. Los resultados mostraron percepciones negativas sobre el proceso evaluativo. Se observaron diferencias significativas en las percepciones sobre el uso del feedback en función del estilo de aprendizaje (F= 1.062, p = .004). Se observaron diferencias significativas en la percepción de la cantidad de esfuerzo (F= 5.888, p = .000), la adecuación de la evaluación (F= 3.282, p = .015)y la aproximación superficial al aprendizaje (F= 5.472, p = .001), en función del curso académico. El género no fue determinante de las percepciones. Los hallazgos sugieren la utilización de procedimientos de evaluación tradicional con los encuestados. Se encontraron relaciones entre el estilo de enseñanza y el feedback, y entre el curso académico y las percepciones de evaluación. Esta información contribuye a un entendimiento más profundo del modo de aprender de los estudiantes en función de sus características y contexto

Percolation thresholds in chemical disordered excitable media

The behavior of chemical waves advancing through a disordered excitable medium is investigated in terms of percolation theory and autowave properties in the framework of the light-sensitive Belousov-Zhabotinsky reaction. By controlling the number of sites with a given illumination, different percolation thresholds for propagation are observed, which depend on the relative wave transmittances of the two-state medium considered

No association between chronic musculoskeletal complaints and Val158Met polymorphism in the Catechol-O-methyltransferase gene. The HUNT study

BACKGROUND: The Catechol-O-methyltransferase (COMT) gene contains a functional polymorphism, Val158Met, that has been found to influence human pain perception. In one study fibromyalgia was less likely among those with Val/Val genotype. METHODS: In the 1995–97 Nord-Trøndelag Health Study (HUNT), the association between Val/Met polymorphism at the COMT gene and chronic musculoskeletal complaints (MSCs) was evaluated in a random sample of 3017 individuals. RESULTS: The distribution of the COMT Val158Met genotypes and alleles were similar between controls and the twelve different chronic MSCs groups. Even when the Met/Met and Val/Met genotypes were pooled, the distribution of the Val/Val genotype and other genotypes were similar between controls and the chronic MSCs groups. CONCLUSION: In this population-based study, no significant association was found between Val/Met polymorphism at the COMT gene and chronic MSCs

Mechanical Systems with Symmetry, Variational Principles, and Integration Algorithms

This paper studies variational principles for mechanical systems with symmetry and their applications to integration algorithms. We recall some general features of how to reduce variational principles in the presence of a symmetry group along with general features of integration algorithms for mechanical systems. Then we describe some integration algorithms based directly on variational principles using a discretization technique of Veselov. The general idea for these variational integrators is to directly discretize Hamilton’s principle rather than the equations of motion in a way that preserves the original systems invariants, notably the symplectic form and, via a discrete version of Noether’s theorem, the momentum map. The resulting mechanical integrators are second-order accurate, implicit, symplectic-momentum algorithms. We apply these integrators to the rigid body and the double spherical pendulum to show that the techniques are competitive with existing integrators

Selection for growth is associated in gilthead sea bream (Sparus aurata) with diet flexibility, changes in growth patterns and higher intestine plasticity

Farmed gilthead sea bream (Sparus aurata) is able to grow efficiently with new feed formulations based on plant ingredients. Here, two experimental diets with standard and high inclusion levels of plant ingredients were formulated to assess the suited use of plant-based diets in fish with different growth genetic backgrounds. To pursue this issue, a long-term feeding trial (12-months) was conducted with fish (17 g initial body weight) of 16 families coming from the broodstock of PROGENSA project, that were grown communally in the IATS-CSIC experimental facilities. All fish in the study (2545) were PIT-tagged, and their pedigree was re-constructed with 96% success by using a SMsa1 multiplex of 11 microsatellites, which revealed the main parents contributions of 5 females and 6 males. Each diet was randomly assigned to replicate 3000 L tanks, gathering each replicate a similar family composition through all the feeding trial. Data on growth performance highlighted a strong ge- netic effect on growth trajectories, associated with enhanced growth during winter in fish selected for faster growth. No main dietary effects were found on growth rates or condition factor, and regression-correlation analyses of growth rates across families on both diets suggest that genome by diet interaction was weak, while genetic variation accounted for most of the growth phenotypic variation. Hepatosomatic index (HSI) and me- senteric fat index (MSI) of five families, covering the growth variability of the population, were regulated nu- tritionally and genetically, but without statistically significant genome by diet interactions. Fish from faster growing families showed shorter intestines after being fed the control diet, but this phenotype was masked by the enriched plant-based diet. Collectively, the results demonstrate that selection for faster growth is associated in gilthead sea bream with different growth trajectories and a high diet flexibility and intestine plasticity.Versión del editor2,04

Thermomechanical couplings in shape memory alloy materials

In this work we address several theoretical and computational issues which are related to the thermomechanical modeling of shape memory alloy materials. More specifically, in this paper we revisit a non-isothermal version of the theory of large deformation generalized plasticity which is suitable for describing the multiple and complex mechanisms occurring in these materials during phase transformations. We also discuss the computational implementation of a generalized plasticity based constitutive model and we demonstrate the ability of the theory in simulating the basic patterns of the experimentally observed behavior by a set of representative numerical examples