On the entropy for group actions on the circle

We show that for a finitely generated group of $C^2$ circle diffeomorphisms, the entropy of the action equals the entropy of the restriction of the action to the non-wandering set.Comment: 13 pages. To appear in Fundamenta Mat

Magnetic fields in Bok globules: Multi-wavelength polarimetry as tracer across large spatial scales

[abridged] The role of magnetic fields in the process of star formation is a matter of continuous debate. Clear observational proof of the general influence of magnetic fields on the early phase of cloud collapse is still pending. First results on Bok globules with simple structures indicate dominant magnetic fields across large spatial scales (Bertrang+2014). The aim of this study is to test the magnetic field influence across Bok globules with more complex density structures. We apply near-infrared polarimetry to trace the magnetic field structure on scales of 10^4-10^5au in selected Bok globules. The combination of these measurements with archival data in the optical and sub-mm wavelength range allows us to characterize the magnetic field on scales of 10^3-10^6au. We present polarimetric data in the near-infrared wavelength range for the three Bok globules CB34, CB56, and [OMK2002]18, combined with archival polarimetric data in the optical wavelength range for CB34 and CB56, and in the sub-millimeter wavelength range for CB34 and [OMK2002]18. We find a strong polarization signal (P>2%) in the near-infrared and strongly aligned polarization segments on large scales (10^4-10^6au) for all three globules. This indicates dominant magnetic fields across Bok globules with complex density structures. To reconcile our findings in globules, the lowest mass clouds known, and the results on intermediate (e.g., Taurus) and more massive (e.g., Orion) clouds, we postulate a mass dependent role of magnetic fields, whereby magnetic fields appear to be dominant on low and high mass but rather sub-dominant on intermediate mass clouds.Comment: 7 pages, 6 figures; Accepted by A&

At-sea abundance and distribution of skuas and jaegers (Charadriiformes: Stercorariidae) at coastal waters off central Chile

Indexación: Web of Science; Scielo.BACKGROUND: Skuas and jaegers (Charadriiformes: Stercorariidae) are seabirds breeding at moderate to high latitudes and some perform extensive post-breeding transequatorial migrations. Most species overwinter and perform significant portions of their migratory flyways along the Pacific coast of South America, but scant information is available on their at-sea ecology in this waters. Our aims in this study were to determine: 1) the timing of occurrence and fluctuations in abundance of skua and jaeger species, 2) their spatial distribution within the coastal zone and 3) at-sea behavior of birds, including flock size and interactions with other seabird species. RESULTS: Between July 2006 and October 2013, we conducted at-sea bird counts at Valparaiso Bay (33°S) in central Chile and confirmed the occurrence of Chilean skuas (Stercorarius chilensis), Brown skuas (S. antarcticus), and Parasitic jaegers (S. parasiticus). Parasitic jaegers are regular austral summer visitors (November to March), whereas Brown skuas occur in the area only in winter (July to October). Chilean skuas were regularly recorded year-round in the area with higher abundances between late winter and early spring (August to October). Brown and Chilean skuas where observed comparatively offshore, whereas Jaegers presented a more coastal distribution, probably associated to host presence. Chilean skuas kleptoparasitized similar-sized (shearwaters and fulmars) and larger seabird species (boobies), whereas jaegers chased only smaller coastal birds (gulls and terns). Brown skuas engaged in no kleptoparasitic behaviors. All three species were observed mostly as solitary individuals. CONCLUSIONS: Skuas and jaegers showed in general a marked seasonality in their occurrence and abundance (only Chilean skua occurs year-round) and use this area as a commuting and stopover zone within their extensive migratory flyway along the southeastern Pacific.http://ref.scielo.org/p7thp

Factors that affect motivation towards english language acquisition in seventh grade students of a public elementary school in Parral

Tesis (Magíster en la enseñanza del inglés como lengua extranjera)The research presents the results of the identification and analysis of factors that characterize the motivation for the English Foreign Language Acquisition of seventh year students who belong to a Public Elementary school of Parral, seventh region, Maule in Chile. To investigate the factors that influence students’ motivation a mixed method research was carried out. The data was collected and analysed through qualitative approach and organized and presented in a quantitative manner represented by graphics. The information was compiled by two previously validated instruments, which consisted of a questionnaire for the teachers of the different subjects of the class and the psychosocial team who works with the students. A personal interview was applied to each student. Two major conclusions were obtained from the results of the analysis of the data collection; firstly students present a lack of motivation towards the subject of English as a Foreign Language as a product of the sociocultural environment in which they are immersed, secondly learners are exposed to language learning from puberty and not from the beginning of their first learning stages as postulates the Critical Period Hypothesis (CPH).La investigación presenta los resultados de la identificación y análisis de los factores que caracterizan la motivación hacia la adquisición del inglés como lengua extranjera de alumnos de séptimo año básico pertenecientes a un colegio básico y público de la comuna de Parral, séptima región del Maule en Chile. Para investigar los factores que inciden en la motivación de los estudiantes se utilizó un enfoque mixto tanto cualitativo para la recolección y análisis de los datos y cuantitativo para la organización y presentación de la información representada en gráficos. La obtención de la información se hizo mediante dos instrumentos previamente validados, los cuales consistieron en un cuestionario para los profesores de los diferentes sectores de aprendizaje del curso y para el equipo sicosocial que trabaja con los estudiantes. Una entrevista personal fue aplicada a cada alumno. Dos grandes conclusiones se obtuvieron del resultado del análisis de la recolección de datos; la primera es la falta de motivación de los alumnos hacia la asignatura de inglés como lengua extranjera producto del entorno sociocultural en el cual están inmersos y la segunda es que los alumnos son expuestos al aprendizaje de la lengua desde el inicio de la pubertad y no desde sus primeras etapas de aprendizaje como postula la hipótesis del período crítico

Improved ontology for eukaryotic single-exon coding sequences in biological databases

Indexación: Scopus.Efficient extraction of knowledge from biological data requires the development of structured vocabularies to unambiguously define biological terms. This paper proposes descriptions and definitions to disambiguate the term 'single-exon gene'. Eukaryotic Single-Exon Genes (SEGs) have been defined as genes that do not have introns in their protein coding sequences. They have been studied not only to determine their origin and evolution but also because their expression has been linked to several types of human cancer and neurological/developmental disorders and many exhibit tissue-specific transcription. Unfortunately, the term 'SEGs' is rife with ambiguity, leading to biological misinterpretations. In the classic definition, no distinction is made between SEGs that harbor introns in their untranslated regions (UTRs) versus those without. This distinction is important to make because the presence of introns in UTRs affects transcriptional regulation and post-transcriptional processing of the mRNA. In addition, recent whole-transcriptome shotgun sequencing has led to the discovery of many examples of single-exon mRNAs that arise from alternative splicing of multi-exon genes, these single-exon isoforms are being confused with SEGs despite their clearly different origin. The increasing expansion of RNA-seq datasets makes it imperative to distinguish the different SEG types before annotation errors become indelibly propagated in biological databases. This paper develops a structured vocabulary for their disambiguation, allowing a major reassessment of their evolutionary trajectories, regulation, RNA processing and transport, and provides the opportunity to improve the detection of gene associations with disorders including cancers, neurological and developmental diseases. © The Author(s) 2018. Published by Oxford University Press.https://academic.oup.com/database/article/doi/10.1093/database/bay089/509943