Galactic Halo substructure in the Sloan Digital Sky Survey: the ancient tidal stream from the Sagittarius dwarf galaxy

Two studies have recently reported the discovery of pronounced Halo substructure in the Sloan Digital Sky Survey (SDSS) commissioning data. Here we show that this Halo substructure is almost in its entirety due to the expected tidal stream torn off the Sagittarius dwarf galaxy during the course of its many close encounters with the Milky Way. This interpretation makes strong predictions on the kinematics and distances of these stream stars. Comparison of the structure in old horizontal branch stars, detected by the SDSS team, with the carbon star structure discovered in our own survey, indicates that this halo stream is of comparable age to the Milky Way. It would appear that the Milky Way and the Sagittarius dwarf galaxy have been a strongly interacting system for most of their existence. Once complete, the SDSS will provide a unique dataset with which to constrain the dynamical evolution of the Sagittarius dwarf galaxy, it will also strongly constrain the mass distribution of the outer Milky Way.Comment: 7 pages, 3 figures (1 color figure chunky due to PS compression), minor revisions,accepted by ApJ

The early evolutionary history of neo-sex chromosomes in Neotropical grasshoppers, Boliviacris noroestensis (Orthoptera: Acrididae: Melanoplinae)

Neo-sex chromosomes are an important component of chromosome variation in Orthoptera, particularly South American Melanoplinae species, which have proven to be outstanding experimental model system to study the mechanism of sex chromosome evolution in this group of insects. In terms of their origin, most derived sex chromosome mechanisms involve a Robertsonian fusion (i.e. translocation) between the ancestral X chromosome and an autosome. In the grasshopper, Boliviacris noroestensis Ronderos & Cigliano (1990) (Orthoptera: Acrididae: Melanoplinae), our results point to a small degree of differentiation (conserved homology between the XR arm and the neo-Y) of the neo-XY chromosomes, which may be of recent evolutionary origin. However, a simple centric fusion model does not explain their origin, mainly because of the observed reduction in the fundamental number (FN) of arms. We propose two models which, we hope, clarify the genesis of B. noroestensis neo-sex chromosomes. Records of karyotype variation in related species due to multiple rearrangements support our models. We propose a possible adaptive advantage for neo-sex chromosome carriers, such changes perhaps representing the primary force that increases their frequency within natural populations compared with non-fused translocated forms, and occurring without apparent detriment to the microevolutionary forces that may also act, at least at the beginning of the evolutionary history of individuals bearing such neo-sex chromosomes.Fil: Castillo, Elio Rodrigo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Taffarel, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Marti, Dardo Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentin

Tipo de cambio flexible y fijación de metas inflacionarias en Chile: experiencia y aspectos resaltantes

(Disponible en idioma inglés) Los primeros cinco años del régimen de tipo de cambio flexible y la fijación de metas inflacionarias en Chile han arrojado resultados positivos. La inflación está controlada, el tipo de cambio ha evolucionado a la par de las condiciones externas, la política monetaria ha sido de tipo anticíclico y todo indica que el ciclo se ha suavizado. Aunque ha aumentado la inestabilidad del tipo de cambio, tal como cabría anticipar con un sistema flexible, lo mismo ha ocurrido en otros países de características similares. Este aumento de la inestabilidad muestra valoraciones extremas del tipo de cambio real más bajas que en el pasado y también se aprecia en otros países con sistemas cambiarios distintos. Avances importantes en la profundización del mercado de derivados, así como una menor transmisión del tipo de cambio a la inflación, han contribuido a mejorar la credibilidad y la viabilidad del actual marco de políticas, al tiempo que se minimizan los costos potenciales derivados de ese marco.

"Seed+Expand": A validated methodology for creating high quality publication oeuvres of individual researchers

The study of science at the individual micro-level frequently requires the disambiguation of author names. The creation of author's publication oeuvres involves matching the list of unique author names to names used in publication databases. Despite recent progress in the development of unique author identifiers, e.g., ORCID, VIVO, or DAI, author disambiguation remains a key problem when it comes to large-scale bibliometric analysis using data from multiple databases. This study introduces and validates a new methodology called seed+expand for semi-automatic bibliographic data collection for a given set of individual authors. Specifically, we identify the oeuvre of a set of Dutch full professors during the period 1980-2011. In particular, we combine author records from the National Research Information System (NARCIS) with publication records from the Web of Science. Starting with an initial list of 8,378 names, we identify "seed publications" for each author using five different approaches. Subsequently, we "expand" the set of publication in three different approaches. The different approaches are compared and resulting oeuvres are evaluated on precision and recall using a "gold standard" dataset of authors for which verified publications in the period 2001-2010 are available.Comment: Paper accepted for the ISSI 2013, small changes in the text due to referee comments, one figure added (Fig 3

Concentration, Hold-Up and Information Revelation in Bank Lending: Evidence From Chilean Firms

In this paper we empirically study bank-client relationships using a sample of Chilean manufacturing firms. We examine whether concentration and the duration of bank-firm relationships affect the volume of bank lending. Our results indicate that lower concentration, measured by the number of banks a firm borrows from, is associated with a large and positive effect on borrowing. The length of borrower-lender relationships has a positive -although not always statistically significant- effect on the amount borrowed.

Effects of Donepezil on Behavioral Manifestations of Thalamic Infarction: A Single-Case Observation

Objective: To examine the effect of donepezil for the treatment of cognitive and behavioral disorders associated with thalamic lesions in a 45-year-old male who suffered an infarct in the left thalamus. Background: Recent studies suggest that donepezil may improve executive functions impairments due to subcortical ischemic lesions. Method: The effects of donepezil were analyzed in a single-case of thalamic infarction with cognitive and behavioral alterations in an open label study. Results: Significant behavioral modifications related to improved performances in executive functions were observed with the treatment. Conclusion: The results suggest that donepezil may have significant effect on executive functions that can alter behavioral outcomes after thalamic infarctions

Pax1 and Pax9 activate Bapx1 to induce chondrogenic differentiation in the sclerotome.

We have previously shown that the paired-box transcription factors Pax1 and Pax9 synergistically act in the proper formation of the vertebral column. Nevertheless, downstream events of the Pax1/Pax9 action and their target genes remain to be elucidated. We show, by analyzing Pax1;Pax9 double mutant mice, that expression of Bapx1 in the sclerotome requires the presence of Pax1 and Pax9, in a gene dose-dependent manner. By using a retroviral system to overexpress Pax1 in chick presomitic mesoderm explants, we show that Pax1 can substitute for Shh in inducing Bapx1 expression and in initiating chondrogenic differentiation. Furthermore, we demonstrate that Pax1 and Pax9 can transactivate regulatory sequences in the Bapx1 promoter and that they physically interact with the Bapx1 promoter region. These results strongly suggest that Bapx1 is a direct target of Pax1 and Pax9. Together, we conclude that Pax1 and Pax9 are required and sufficient for the chondrogenic differentiation of sclerotomal cells

¿La gente prefiere paisajes naturales? Un estudio empírico en Chile

Existe una conciencia creciente de que la viabilidad de la planificación del paisaje depende del apoyo del público. Sin embargo, el conocimiento sobre percepciones y preferencias del público es generalmente limitado. Este estudio presenta una evaluación del paisaje basada en el observador y atributos físicos del paisaje. Para ello se aplicó un cuestionario en línea (n° respuestas = 643), a partir del cual se recolectó información sobre edad, género, lugar de residencia, nivel de ingresos y nivel educativo, y sobre las preferencias de los encuestados por diversas composiciones y niveles de belleza escénica de paisajes rurales del centro-sur de Chile, usando fotografías. Se analizaron los efectos de la composición y la belleza escénica sobre las respuestas (calificaciones individuales), así como los efectos de interacción entre esos atributos y características personales de los entrevistados mediante la aplicación de medidas multivariadas de repetición ANDEVA y prueba multivariada de Wilks. Las calificaciones tanto de la belleza escénica como de la composición del paisaje varían significativamente entre las fotografías, lo que revela una clara preferencia por paisajes dominados por vegetación nativa sobre paisajes dominados por plantaciones de árboles exóticos o tierras cultivadas. Una porción relativamente baja pero significativa de la variabilidad se explicó por diferencias en las preferencias derivadas de las características personales. Los resultados contribuyen a varios esfuerzos recientes para comprender la opinión pública sobre los cambios del paisaje rural. Específicamente, los resultados respaldan los efectos adversos de la pérdida de hábitats naturales en las apreciaciones de las personas.There is a growing consciousness that the viability of landscape-related policy depends on support from the general public. However, during planning stages, knowledge regarding landscape perceptions and preferences of people is generally absent or limited. This study presents an observer-based landscape assessment, applying a physical landscape attribute approach to measure visual preferences based on photographs. Data on age, gender, place of residence, income and education level were collected by means of a country-wide online questionnaire (n° answers=643), along with information from respondents on visual evaluations of images depicting various compositions and levels of scenic beauty of rural landscapes of south-central Chile. The effects of landscape composition and scenic beauty on responses (individual ratings), as well as the interaction effects between those attributes and personal characteristics, were tested by applying multivariate repeated measures ANOVA and Wilks multivariate tests. Ratings for both scenic beauty and landscape composition significantly varied across photographs, revealing a clear preference for landscapes dominated by native vegetation over landscapes dominated by exotic tree plantations or cultivated lands. A relatively low, nonetheless significant, portion of the rating variability was explained by subtle differences in preferences arising from personal characteristics. Results contribute to several recent efforts to understand public opinion regarding natural and rural landscape changes. Specifically, results sustain the adverse effects of loss of natural habitats on people’s appraisals of rural landscapes.Fil: Nahuelhual, Laura. Centro de Investigación en Dinámica de Ecosistemas Marinos de Altas Latitudes; Chile. Universidad Austral de Chile; ChileFil: Laterra, Pedro. Fundación Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jiménez, Dana. Centro de Ciencia del Clima y la Resiliencia; ChileFil: Báez, Andrea. Universidad Austral de Chile. Facultad de Ciencias Económicas. Instituto de Estadística; ChileFil: Echeverría, Christián. Millennium Nucleus Center for the Socioeconomic Impact of Environmental Policies; Chile. Universidad de Concepción; ChileFil: Fuentes, Rodrigo. Universidad de Concepción; Chil

Protein Repeats from First Principles

Some natural proteins display recurrent structural patterns. Despite being highly similar at the tertiary structure level, repeating patterns within a single repeat protein can be extremely variable at the sequence level. We use a mathematical definition of a repetition and investigate the occurrences of these in sequences of different protein families. We found that long stretches of perfect repetitions are infrequent in individual natural proteins, even for those which are known to fold into structures of recurrent structural motifs. We found that natural repeat proteins are indeed repetitive in their families, exhibiting abundant stretches of 6 amino acids or longer that are perfect repetitions in the reference family. We provide a systematic quantification for this repetitiveness. We show that this form of repetitiveness is not exclusive of repeat proteins, but also occurs in globular domains. A by-product of this work is a fast quantification of the likelihood of a protein to belong to a family.Fil: Turjanski, Pablo Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Parra, Rodrigo Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Espada, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Becher, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Ferreiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Genetically-inspired convective heat transfer enhancement in a turbulent boundary layer

The convective heat transfer in a turbulent boundary layer (TBL) on a flat plate is enhanced using an artificial intelligence approach based on linear genetic algorithms control (LGAC). The actuator is a set of six slot jets in crossflow aligned with the freestream. An open-loop optimal periodic forcing is defined by the carrier frequency, the duty cycle and the phase difference between actuators as control parameters. The control laws are optimised with respect to the unperturbed TBL and to the actuation with a steady jet. The cost function includes the wall convective heat transfer rate and the cost of the actuation. The performance of the controller is assessed by infrared thermography and characterised also with particle image velocimetry measurements. The optimal controller yields a slightly asymmetric flow field. The LGAC algorithm converges to the same frequency and duty cycle for all the actuators. It is noted that such frequency is strikingly equal to the inverse of the characteristic travel time of large-scale turbulent structures advected within the near-wall region. The phase difference between multiple jet actuation has shown to be very relevant and the main driver of flow asymmetry. The results pinpoint the potential of machine learning control in unravelling unexplored controllers within the actuation space. Our study furthermore demonstrates the viability of employing sophisticated measurement techniques together with advanced algorithms in an experimental investigation.Comment: 20 pages, 13 figure