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

Rethinking Hudson-Meng: A Taphonomic Analysis of the Faunal Assemblage from 25SX115, Sioux County, Nebraska

Hudson-Meng (25SX115), located in the Oglala National Grassland, Sioux County, Nebraska, is a multi-component Cody complex site that was used for the procurement of bison between 10,500 and 11,250 years ago. The site was excavated in the 1970s and 1990s, which led to many, at times divergent, interpretations of the site’s origin and use by Cody complex peoples. Excavations between 2006 and 2012 have led to new evidence and interpretations regarding multiple episodes of site use. The faunal assemblage recovered from the most recent excavations was used for zooarchaeological and taphonomic studies, and is reported here. The identification of taphonomic characteristics, statistical analyses, and comparative studies were used to investigate the natural or cultural origin of the deposits, produce economic utility curves, and determine the faunal composition of the site. Both natural and cultural taphonomic characteristics were identified in this study of Hudson-Meng and along with other evidence of site use, confirm that Hudson-Meng is a multi-component cultural site. Two components were determined more likely to be natural based on a lack of cultural taphonomic characteristics. Economic utility curves produced for the components with adequate taxonomic information, showed that all of the components except one had identifiable elements representative of the unbiased utilization of animals. One component showed a bulk utilization of the animals represented at the site. It is possible that at least one of these economic utility curves was partly skewed by the deterioration and loss of less dense skeletal elements. The natural taphonomic characteristics identified for each of the components showed some slight differences between stratigraphically adjacent components that led to patterned clustering. This outcome demonstrates the possibility that the post-depositional processes that occurred within the first few years of the formation of each deposit were slightly different, which may reflect slight changes in the environment. The cultural taphonomic characteristics demonstrate that when only cultural processing was considered Components 3 and X were the most similar, followed by Component 2. In all cases where bone tool manufacturing characteristics or natural characteristics were considered with cultural processing characteristics Components 2 and 3 were the most similar, followed by Component X. Component X most likely represents a component from the same cultural phase as Component 3 or possibly Component 2

A Study on the Impact of Locality in the Decoding of Binary Cyclic Codes

In this paper, we study the impact of locality on the decoding of binary cyclic codes under two approaches, namely ordered statistics decoding (OSD) and trellis decoding. Given a binary cyclic code having locality or availability, we suitably modify the OSD to obtain gains in terms of the Signal-To-Noise ratio, for a given reliability and essentially the same level of decoder complexity. With regard to trellis decoding, we show that careful introduction of locality results in the creation of cyclic subcodes having lower maximum state complexity. We also present a simple upper-bounding technique on the state complexity profile, based on the zeros of the code. Finally, it is shown how the decoding speed can be significantly increased in the presence of locality, in the moderate-to-high SNR regime, by making use of a quick-look decoder that often returns the ML codeword.Comment: Extended version of a paper submitted to ISIT 201

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

EVALUACIÓN DE LAS COMPETENCIAS COGNITIVAS Y SOCIALES DE NIÑOS QUE HAN ESTADO EN SITUACIÓN DE CALLE

The following study is an exploratory approach to the population of street children of Montevideo. It involves 27 children of both sexes between 7 and 13 years. Sociodemographic variables were considered and it was evaluated the neuropsychological development, including the use of oral language, the relationship with the writing code, logical-mathematical reasoning skills, cognitive functioning and exploring some psychopathological indicators. The results show that this is a population with high levels of weaknesses and vulnerabilities, and a significant presence of behavioral disorders. In the cognitive aspect, there is some level of effectiveness in the implementation of intellectual nonverbal operations. In the verbal tasks, significant deficits for the low overall development of language were found. This would have a negative impact on school integration as well as on the capacity for self-regulation of behavior.En el siguiente estudio se busca una aproximación exploratoria a la población de los niños y niñas en situación de calle de Montevideo. Se trabajo con 27 niños de ambos sexos de entre 7 y 13 años. Se consideraron las variables sociodemográficas y se evaluó el desarrollo neuropsicológico, incluyendo la utilización del lenguaje oral, la relación con el código escrito, las habilidades de razonamiento lógico-matemático, el funcionamiento cognitivo general y la exploración de algunos indicadores psicopatológicos. Los resultados muestran que se trata de una población con un alto nivel de carencias y vulnerabilidades, y una importante presencia de trastornos comportamentales. En el aspecto cognitivo, se encuentra algún nivel de efectividad en la ejecución intelectual de operaciones no verbales. En las  tareas verbales, se comprobaría un déficit significativo por el escaso desarrollo general del lenguaje. Esto tendría consecuencias negativas en la inserción escolar así como en la capacidad de auto-regulación del comportamiento