Linear-time list recovery of high-rate expander codes

We show that expander codes, when properly instantiated, are high-rate list recoverable codes with linear-time list recovery algorithms. List recoverable codes have been useful recently in constructing efficiently list-decodable codes, as well as explicit constructions of matrices for compressive sensing and group testing. Previous list recoverable codes with linear-time decoding algorithms have all had rate at most 1/2; in contrast, our codes can have rate $1 - \epsilon$ for any $\epsilon > 0$. We can plug our high-rate codes into a construction of Meir (2014) to obtain linear-time list recoverable codes of arbitrary rates, which approach the optimal trade-off between the number of non-trivial lists provided and the rate of the code. While list-recovery is interesting on its own, our primary motivation is applications to list-decoding. A slight strengthening of our result would implies linear-time and optimally list-decodable codes for all rates, and our work is a step in the direction of solving this important problem

Knöchelosteotomie - Die Osteotomie als Zugang

Zusammenfassung: Bei der Behandlung osteochondraler Läsionen am oberen Sprunggelenk stehen sowohl arthroskopische als auch offene Therapieverfahren zur Verfügung. Die Osteotomien rund um das obere Sprunggelenk haben sich als Zugangserweiterung bei der Behandlung weiter posterior gelegener osteochondraler Läsionen fest etabliert. Bei den relativ häufig anzutreffenden osteochondralen Läsionen im Bereich der medialen Talusschulter wird die mediale, schräge, monoplanare Knöchelosteotomie durchgeführt. Bei den weniger häufigen posterolateralen osteochondralen Läsionen kann die distale Fibulaosteotomie erfolgen. In der vorliegenden Arbeit werden die Indikationen für einzelne Osteotomieverfahren diskutiert und deren chirurgische Techniken beschriebe

Solución numérica del problema de transmisión de calor con cambio de fase

Este trabajo resume el estado del arte de la solución numérica de los problemas de transmisión de calor con cambio de fase. Su objetivo consiste en presentar algoritmos en función de su capacidad de encarar problemas ingenieriles, dejando de lado los aspectos teóricos referidos a la convergencia de la solución numérica a-la solución matemática clásica del problema. Se detallan las ventajas y desventajas de los diferentes esquemas para que se pueda efectuar la selección del método más conveniente para un problema determinado. Asimismo se indican cuáles son las tendencias de investigación actuales y las posibilidades futuras en el área. Se incluye una serie de ejemplos numéricos para remarcar los aspectos destacables de los métodos tratados en el trabajo.Peer Reviewe

Modelización del flujo invíscido alrededor de la pala de un aerogenerador mediante el método de los paneles

Se describe la formulación de un modelo computacional para determinar, bajo condiciones invíscidas, el flujo tridimensional alrededor de la pala de una turbina eólica de eje horizontal. Dicho modelo se basa en la representación mediante paneles de una pala rígida, delgada, torsionada y de envergadura finita. A estos paneles se asocian hilos vorticosos rectos, que conforman el sistema ligado a la pala, y un sistema de hilos vorticosos libres, que presentan trayectorias helicoidales de radios no constantes, que determinan una estela de configuración fija. Las velocidades inducidas por el sistema vorticoso completo son calculadas por la aplicación de la ley de Biot-Savart. Se presenta la metodología seguida para el cálculo de las distribuciones de circulación, velocidades inducidas y resultantes y cargas aerodinámicas a lo largo de la envergadura y cuerda de una pala de geometría definida, bajo una determinada condición de viento y rotación uniformes, sin la consideración de los efectos de interferencia.This work describes the formulation of a computational model to detemine, under inviscid conditions, the tri-dimensional flow field around the blade of an horizontal-axis wind turbine. The model is based upon a panel representation of a rigid, thin and twisted blade of finite span.The distribution of circulation is originated by a system of straight bound vortices associated to the blade and a system of free vortex filaments, having helical paths with non-constant radii, that generates a prescribed fixed wake. The velocities induced by that vortex system are calculated by the Biot-Savart law. The methodology followed in order to calculate the span and chordwise distributions of circulation, induced velocities and aerodynamic loads is presented for a blade whose geometry and working conditions are defined, without considering the interference effects.Peer Reviewe

Population size impacts host-pathogen coevolution

Ongoing host–pathogen interactions are characterized by rapid coevolutionary changes forcing species to continuously adapt to each other. The interacting species are often defined by finite population sizes. In theory, finite population size limits genetic diversity and compromises the efficiency of selection owing to genetic drift, in turn constraining any rapid coevolutionary responses. To date, however, experimental evidence for such constraints is scarce. The aim of our study was to assess to what extent population size influences the dynamics of host–pathogen coevolution. We used Caenorhabditus elegans and its pathogen Bacillus thuringiensis as a model for experimental coevolution in small and large host populations, as well as in host populations which were periodically forced through a bottleneck. By carefully controlling host population size for 23 host generations, we found that host adaptation was constrained in small populations and to a lesser extent in the bottlenecked populations. As a result, coevolution in large and small populations gave rise to different selection dynamics and produced different patterns of host–pathogen genotype-by-genotype interactions. Our results demonstrate a major influence of host population size on the ability of the antagonists to co-adapt to each other, thereby shaping the dynamics of antagonistic coevolution

Spectral approach to linear programming bounds on codes

We give new proofs of asymptotic upper bounds of coding theory obtained within the frame of Delsarte's linear programming method. The proofs rely on the analysis of eigenvectors of some finite-dimensional operators related to orthogonal polynomials. The examples of the method considered in the paper include binary codes, binary constant-weight codes, spherical codes, and codes in the projective spaces.Comment: 11 pages, submitte

Novel DNA methylation profiles associated with key gene regulation and transcription pathways in blood and placenta of growth-restricted neonates

BB/H012494/1/ Biotechnology and Biological Sciences Research Counci