Teacher-children interaction and concept development in kindergarten Rosemberg, Celia Renata; Silva, María Luisa This article analyzes the interaction between teachers and children in kindergarten classrooms in order to identify and describe the discursive strategies of teachers that retrieve children's previous expressions to clarify and specify concepts represented in them. Data analyzed include 90 situations of teacher–children exchanges in 7 kindergarten classrooms located in marginal urban neighborhoods in the outskirts of the city of Buenos Aires, Argentina. The analysis followed a qualitative procedure: the constant comparative method (CitationGlaser & Strauss, 1967; CitationStrauss & Corbin, 1991). This allowed the authors to identify and describe the various ways in which teachers reconceptualize information offered by the children in ways that allow them to gradually specify, define, and characterize concepts underlying the words they use, albeit with a limited meaning. It also leads children to develop a finer differentiation and integration between concepts. Such development promotes processes of generalization and construction of hierarchical taxonomies.

The species of Megaphragma Timberlake (Hymenoptera: Trichogrammatidae) from Argentina Viggiani, Gennaro; Luft Albarracin, Erica Beatriz; Virla, Eduardo Gabriel Trichogrammatidae are an almost worldwide family of egg parasitoids that consist of 88 genera (Pinto 2006). Species of Megaphragma Timberlake (tribe Oligositini) are egg parasitoids of Thysanoptera. Fifteen species are assigned to Megaphragma, but only three have been reported from the Neotropical region (Noyes 2002). Megaphragma mymaripenne Timberlake (1924) has been recorded previously from Argentina (De Santis 1970), but M. striatum Viggiani (1997) was known only from Mexico, and M. caribea Delvare (1993) is known only from Guadeloupe (Noyes 2002; Pinto 2006). Recently, one of us (E. Luft) reared Megaphragma sp. from eggs of Thysanoptera on corn in San Miguel de Tucumán, Argentina, and this record instigated a review of all material of the genus recorded from Argentina. We searched for specimens deposited in the major entomological collections of Argentina: Instituto Fundación Miguel Lillo (San Miguel de Tucumán) (IMLA), Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Buenos Aires city) (MBA), and Museo de Ciencias Naturales de La Plata (La Plata, Buenos Aires province) (MLPA), but found specimens only in MLPA. In addition, one of us (G. Viggiani) studied material of Megaphragma from Argentina preserved in two other collections, that of the University of California Riverside (UCR) and of the Universidad Rómulo Gallegos, Venezuela (URGV). The results of this study are presented here.

A meteorite crater on Earth formed on September 15, 2007: The Carancas hypervelocity impact Tancredi, G.; Ishitsuka, J.; Schultz, P. H.; Harris, R. S.; Brown, P.; Revelle, D. O.; Antier, K.; Pichon, A. Le; Rosales, D.; Vidal, E.; Varela, Maria Eugenia; Sánchez, L.; Benavente, S.; Bojorquez, J.; Cabezas, D.; Dalmau, A. On September 15, 2007, a bright fireball was observed and a big explosion was heard by many inhabitants near the southern shore of Lake Titicaca. In the community of Carancas (Peru), a 13.5 m crater and several fragments of a stony meteorite were found close to the site of the impact. The Carancas event is the first impact crater whose formation was directly observed by several witnesses as well as the first unambiguous seismic recording of a crater-forming meteorite impact on Earth. We present several lines of evidence that suggest that the Carancas crater was a hypervelocity impact. An event like this should have not occurred according to the accepted picture of stony meteoroids ablating in the Earth's atmosphere, therefore it challenges our present models of entry dynamics. We discuss alternatives to explain this particular event. This emphasizes the weakness in the pervasive use of "average" parameters (such as tensile strength, fragmentation behavior and ablation behavior) in current modeling efforts. This underscores the need to examine a full range of possible values for these parameters when drawing general conclusions from models about impact processes.

Chilean swallows (Tachycineta meyeni) adjust the number of feathers added to the nest with time of breeding Liljesthrom, Marcela; Schiavini, Adrian Carlos Miguel; Reboreda, Juan Carlos Tachycineta swallows nest in secondary cavities and build nests made of a mat of dry grasses with a nest cup lined with feathers. The insulative quality of feathers may prevent hypothermia of the chicks and increase chick growth, but also may raise the risk of nestling hyperthermia if ambient temperature is high. The number of feathers added to the nest should vary throughout the breeding season according to ambient temperature. We describe nest structure and timing of nest building of Chilean Swallows (Tachycineta meyeni) nesting in Tierra del Fuego, Argentina. We analyzed the association between number of feathers in the nest and (1) daily ambient temperature during the period swallows add feathers to the nest, and (2) hatching success of eggs and survival and growth of the chicks. There was a negative association between number of feathers added to the nest and average daily ambient temperature during the nesting cycle. Hatching success was not associated with number of feathers at start of laying or at the end of incubation. There was no association between number of feathers and chick survival or between number of feathers and average weight of the chicks when they were 12 and 15 days of age. Chilean Swallows make temporal adjustments to the number of feathers added to the nest. We suggest these adjustments may help maintain reproductive success throughout the breeding season.

Effect of oxalate on the growth of cuprous oxide layers on copper electrodes: ellipsometric and isoelectric point study Zerbino, Jorge Omar; Torres Sanchez, Rosa Maria; Sustersic, Maria Gisela The effect of the addition of oxalate to the growth of a cuprous oxide layer on copper electrodes was analysed at potential near that of the open circuit, in borax solutions (7 < pH < 9) by cyclic voltammetry, ellipsometry and surface charge techniques. The oxide formation is explained as a sequence of Cu2 O layer growth, ippl, cationic defect accumulation and Cu(II) adsorption on the oxide/solution interface, and a dissolution/precipitation step similar to the mechanism previously reported in oxalate free solutions. The oxalate adsorption at pH = 9 increases the dissolution rate and a greater thickness of the outer layer, oppl, is obtained. Nevertheless, the oxalate adsorption at pH = 7 decreases the cationic defect on the cuprous oxide/electrolyte interface, promoting the Cu2 O growth. For copper particles immersed in solutions of pH between 7 and 9, the measured isoelectric point values, iep, (11.8 < iep < 11.5) shifts in the presence of oxalate to pH between 11.6 and 11.0, respectively. This shift in the iep to a lower pH value indicates oxalate adsorption on the Cu/ Cu2 O particles.

Energy efficiency of double skin façades: an approach to Brazilian climates; Energieeffizienz von doppelschaligen Fassaden: eine Annäherung an brasilianische Klimabedingungen Leão, Marlon; Huckemann, Volker; Borges Leão, Érika F.; Fisch, Manfred Norbert; Kuchen, Ernesto The heat gains and daylight transmitted through windows directly influence the building's energy demand. High performance façades, when correctly specified, produce a great potential of energy savings by using daylight efficiently and controlling heat gains and/or losses. In Brazil, the lack of natural ventilation associated with large glass areas in office buildings exhibits substandard results concerning energy efficiency. This article demonstrates an approach to highly ventilated double skin façades in Brazil, investigating the potential of natural ventilation in accordance with the local climate. Applying the Light Design and Ideal Window Area methodologies, window areas as a function of different types of high performance glass are thermally simulated in the program EnergyPlus. The simulations are run for 10 cities in Brazil, in one of those cities, Curitiba (–25° 25′ 40'′), the annual results of hourly simulations demonstrate the building energy demand as a function of window area, glass type, room ratio and size. The results concerning the energy efficiency perspective only illustrated that double skin façades could be applied for southern regions in Brazil and under certain criteria.; Die ansteigende Temperatur und das Tageslicht, das ungehindert durch die Fenster tritt, beeinflussen den Energiehaushalt eines Gebäudes. Moderne Hochleistungsfassaden bieten bei korrekter Auslegung ein großes Potential zur Energieeinsparung, indem sie Tageslichtnutzung zulassen und solare Gewinne kontrollieren. Das Fehlen von natürlichen Belüftungsmöglichkeiten und der hohe Anteil großflächiger Glasfassaden in Bürogebäuden führen in Brasilien zu unterdurchschnittlicher Energieeffizienz. Der Beitrag beschäftigt sich mit belüfteten doppelschaligen Fassaden in Brasilien, indem das Potential von natürlicher Belüftung unter den lokalen Klimabedingungen geprüft wird. In Anlehnung an Regeln der Kunstlichtplanung und zur Ermittlung der idealen Fensterfläche werden unterschiedliche Fensterflächenanteile unter Variation der Glasqualitäten in dem Programm EnergyPlus thermisch simuliert. Die Simulationen wurden für 10 brasilianische Städte durchgeführt. Die Jahresergebnisse der stündlichen Simulationen für Curitiba (–25° 25’ 40’’) zeigen, dass der Energiebedarf des Gebäudes von der Größe der Fensterflächen, der Art der Glasscheiben sowie der Raumproportion und -größe abhängt. Die Ergebnisse bezüglich der Einschätzung der Energieeffizienz weisen ferner darauf hin, dass doppelschalige Fassaden in südlichen Regionen von Brasilien und vergleichbaren Klimaten unter bestimmten Bedingungen angewendet werden können.

Another piece of the puzzle: The relationship between beliefs and practice in higher education organic chemistry Farré, Andrea Soledad; Lorenzo, Maria Gabriela An original study about beliefs, conceptions and discourse analyses of organic Chemistry teachers is presented. In order to examine conceptions of the nature of science, learning and teaching at university level, Likert questionnaires and discourse analysis were the methodological choices. A case study of four female teachers with different experience and teacher training was performed. The results show that when teachers were asked about their beliefs, they tended to express constructivist ideas, especially about the nature of science. However, in their practical discourse, during the classes, they exhibited more traditional positions. The discourse analyses then become a powerful tool which can be considered a "beliefsgate" to analyse conceptions.

Bacterial hydrocarbon-degrading consortium from Antarctic soils (short communication) Ruberto, Lucas Adolfo Mauro; Vázquez, Susana Claudia; Mac Cormack, Walter Patricio Removal of contaminants from polluted environments could be improved by taking advantage of the catabolic capacity of some microorganisms ina  process called bioremediation. Nowadays the use of microbial associations (also called microial consortia) is gaining attention, because they seem to have a wider degradation spectrum tan that exhibited by isolates strains. M10 is a bacterial consortium obtained from hydrocarbon-contaminated Antarctic soils whose components belong to the Pseudomonas and Sphingobacterium genera. In this short communication, transmision electron microscope (TEM) images are shown, evidencing the morphological diversity of these complex microbial association.

The Evolution of Song in the Phylloscopus Leaf Warblers (Aves: Sylviidae). A Tale of Sexual Selection, Habitat Adaptation, and Morphological Constraints Mahler, Bettina; Gil, Diego Differences in song between species of birds are often the most reliable criteria by which to identify them. Thus, the study of the evolution of bird song provides biologists with a powerful insight into the nature of speciation processes. Both adaptive and nonadaptive explanations have been proposed to account for the evolution of song differences in birds. In this study, we put several of these hypotheses to a test in the genus Phylloscopus, a species-rich group of Old World leaf warblers in which song is used by males for mate attraction and territory defense. We found that song characteristics contained significant amounts of phylogenetic information, although they were more labile than morphological traits. Song frequency characteristics were more phylogenetically preserved than temporal or song structure traits. Changes in body size between species were correlated with changes in maximum and minimum frequencies and frequency bandwidth: small-bodied species had higher frequencies and wider bandwidths than large-bodied species. Beak shape was not found to limit overall frequency patterns. We used an ecomorphological correlate of habitat use, the tarsus/beak ratio, to test for song adaptation to specific habitat sound transmission characteristics. We found that species with larger tarsus/beak ratio, typically inhabiting broadleaf habitats and understory vegetation, had lower emphasized frequencies in their songs, as expected if songs are adapted to maximize sound transmission. However, this relationship did not held when controlling for common descent. Song complexity, a wide-ranging measurement encompassing temporal and structural sound complexity estimates, was best explained by breeding latitude. We interpret this relationship as a correlate of increased sexual selection by mate choice toward more Northern latitudes. We failed to find a significant role of character displacement in the evolution of song in this group: sympatric pairs of species did not show larger differences in song than allopatric pairs of species. To sum up, superimposing upon large haphazard selection of song themes, selective pressures for higher song elaboration in areas of high sexual selection, and correlative change in song brought about by natural selection of body size, would explain some of the diversity of songs that are found within the genus Phylloscopus.

Los procesos de descentralización educativa y sus resultados: Un análisis para Argentina Formichella, Maria Marta; Krüger, Natalia Soledad; Rojas, Mara Leticia La expansión del acceso a la educación media se ha convertido en un importante objetivo de desarrollo para los países de América Latina. La formulación de una política acorde con esta meta, requiere un análisis exhaustivo del sistema educativo y sus interrelaciones con las distintas esferas sociales. Más aún, si se consideran los profundos procesos de reformas educativas acontecidas durante las últimas décadas y las consecuencias que los mismos han tenido sobre los resultados educativos. La presente investigación intenta contribuir con esta tarea, realizando un análisis de lo ocurrido en Argentina y estableciendo ciertas comparaciones con las transformaciones acaecidas en México en los últimos años.

The plastic phenomenon underlying the associative processes in the addictive properties of diazepam and other psychoactive drugs Ramirez, Oscar Angel; Perez, Mariela Fernanda Benzodiazepines are commonly prescribed for the therapy of disorders such as anxiety and sleep disturbance, but develop dependence in many patients. In this review we discuss the impact of different brain areas that modulate the reward system in the development of tolerance and dependence to benzodiazepine and the associative processes underlying those fenomena.

Alterations in glucocorticoid negative feedback following maternal Pb, prenatal stress and the combination: A potential biological unifying mechanism for their corresponding disease profiles Rossi-George, A.; Virgolini, Miriam Beatriz; Weston, D.; Cory-Slechta, D. A. Combined exposures to maternal lead (Pb) and prenatal stress (PS) can act synergistically to enhance behavioral and neurochemical toxicity in offspring. Maternal Pb itself causes permanent dysfunction of the body's major stress system, the hypothalamic pituitary adrenal (HPA) axis. The current study sought to determine the potential involvement of altered negative glucocorticoid feedback as a mechanistic basis of the effects in rats of maternal Pb (0, 50 or 150 ppm in drinking water beginning 2 mo prior to breeding), prenatal stress (PS; restraint on gestational days 16-17) and combined maternal Pb + PS in 8 mo old male and female offspring. Corticosterone changes were measured over 24 h following an i.p. injection stress containing vehicle or 100 or 300 μg/kg (females) or 100 or 150 μg/kg (males) dexamethasone (DEX). Both Pb and PS prolonged the time course of corticosterone reduction following vehicle injection stress. Pb effects were non-monotonic, with a greater impact at 50 vs. 150 ppm, particularly in males, where further enhancement occurred with PS. In accord with these findings, the efficacy of DEX in suppressing corticosterone was reduced by Pb and Pb + PS in both genders, with Pb efficacy enhanced by PS in females, over the first 6 h post-administration. A marked prolongation of DEX effects was found in males. Thus, Pb, PS and Pb + PS, sometimes additively, produced hypercortisolism in both genders, followed by hypocortisolism in males, consistent with HPA axis dysfunction. These findings may provide a plausible unifying biological mechanism for the reported links between Pb exposure and stress-associated diseases and disorders mediated via the HPA axis, including obesity, hypertension, diabetes, anxiety, schizophrenia and depression. They also suggest broadening of Pb screening programs to pregnant women in high stress environments. © 2008 Elsevier Inc. All rights reserved.

Micromechanical magnetometer using an all-silicon nonlinear torsional resonator Antonio, Dario; Dolz, Moira Ines; Pastoriza, Hernan In this work, a micromagnetometer employing a nonlinear torsional resonator with a high quality factor Q is presented experimentally. Oscillatory rotation of a conducting plate in the sensed magnetic field H induces eddy currents that dissipate energy. Due to the nonlinear response of the oscillator, the resulting mechanical damping originates frequency shifts in the resonance curve that depend on H. Nonlinearity results from the electrostatic detection, which introduces high order electrical spring constants. The device is fabricated with a standard silicon process and does not incorporate ferromagnetic materials. An analytical nonlinear model that correctly describes the device is also introduced.

An homoplasmic large deletion in mtDNA control region: case report Motti, Josefina María Brenda; Alfaro, E. L.; Dipierri, Jose Edgardo; Muzzio, Marina; Ramallo, Virginia; Santos, María Rita; Irwin, J. A.; Scheible, M.; Saunier, J. L.; Coble, M. B.; Bailliet, Graciela; Bravi, Claudio Marcelo We report a new case of a large, homoplasmic Control Region deletion in human mitochondrial DNA. A missing 154 bp fragment spanning positions 16154?16307 was found in an apparently healthy blood donor from Salta (NW Argentina) whose maternal lineage was attributable to Native American haplogroup D1. The same mutation, to the best of our knowledge, has been independently reported before only twice, in both homoplasmic and heteroplasmic states.

Simple model for wet granular beds subjected to tapping Uñac, Rodolfo Omar; Vidales, Ana Maria; Pugnaloni, Luis Ariel We present a simple model to describe the response of a granular bed to a tapping-like excitation when grains can form capillary bridges due to the presence of interstitial liquid. We implement a pseudodynamic simulation of adhesive hard disks. The packing fraction and coordination number after the steady state of the tapping process has been reached are compared for different tapping intensities and liquid contents. We find some contrasting behavior with dry systems and qualitative agreement with experimental data.

Análisis tecno-morfológico y funcional del material lítico de superficie del sitio Las Vueltas 1 (norte de la Isla Grande De Tierra Del Fuego) Santiago, Fernando Carlos; Pal, Nélida Marcela; Salemme, Monica Cira A partir del estudio de las diferentes clases artefactuales (desechos de talla, núcleos y artefactos formatizados) recuperados en el sitio Las Vueltas 1, se intenta inferir las etapas de producción lítica desarrolladas por los cazadores-recolectores que ocuparon el sitio bajo estudio. De este modo, se busca definir las diversas actividades tecnológicas involucradas (e.g., explotación, aprovisionamiento, manufactura, uso y descarte) en la gestión de los recursos líticos. El análisis tecno-morfológico y funcional del material lítico permite explicitar las estrategias tecnológicas involucradas en el sitio bajo estudio y deslindar la existencia de diferentes trayectorias de producción de las materias primas presentes en el registro arqueológico. Hasta el momento, los resultados obtenidos permiten plantear el aprovechamiento de las materias primas disponibles localmente para la confección de artefactos con poca formatización como parte de una estrategia expeditiva en un sitio caracterizado como de matanza de guanacos.; The stages of lithic production developed by hunter-gatherers that occupied Las Vueltas 1 site are inferred from the study of different artifact classes (waste, nuclei and artifacts). It attempts to identify the technological activities involved (procurement, manufacturing, use and discard) in the management of lithic resources. The techno-morphological and functional analysis of lithic material allow us to interpret the technological strategies involved in the site under study, as well as to recognize the different production pathways of the recorded raw materials. Up to now, the results points to the use of local available raw materials for manufacturing artifacts with little formatting as part of an expedient strategy in a place characterized as a guanaco kill-site.

Reconstrucción de una Organización Matemática de referencia para el estudio del límite y la continuidad de funciones en la Universidad Parra, Verónica Ester; Otero, Maria Rita; Fanaro, Maria de Los Angeles En este trabajo se reconstruye y describe una Organización Matemática (OM) de referencia relativa a las nociones de límite y continuidad de funciones reales, para un curso de Cálculo del área Economía y Administración del primer año de la Universidad. El marco teórico adoptado es la Teoría Antropológica de lo Didáctico (TAD) (Chevallard, 1999, 2001). Se describe el sentido matemático, social, y cultural (Bosch et. al, 2006) de esta OM de referencia. Finalmente, se detallan los componentes prácticos-técnicos y tecnológicos-teóricos de la OM, es decir, los tipos de tareas, las técnicas matemáticas, las tecnologías y teoría.

Cronología, procesos de formación y ocupaciones humanas en el sitio El Tigre (curso inferior del Río Colorado, Partido de Patagones, Provincia de Buenos Aires) Martinez, Gustavo Adolfo; Stoessel, Luciana; Armentano, Gabriela Marisol El propósito de este trabajo es discutir la intensidad y redundancia de la ocupación humana en el sitio El Tigre durante el Holoceno tardío final a partir del estudio de los procesos de formación del sitio. En un trabajo anterior (Martínez et al. 2005) se propuso la existencia de un componente arqueológico superior (ca. 500 años AP) y se planteó la posible existencia de uno inferior. Esta discusión es retomada en este trabajo a partir del estudio de distintas líneas de análisis. Se discuten evidencias estratigráficas, cronológicas (14C y OCR), diagenéticas, y las distribuciones y frecuencias de los restos óseos y artefactos líticos a lo largo de la secuencia estratigráfica estudiada. Se analizan diversas variables a los efectos de identificar la acción de agentes y/o procesos tafonómicos. A través de este análisis se concluyó que solo puede proponerse la existencia del componente superior, y que su cronología sería de ca. 900-400 años AP.

Mortalidad infantil y cobertura social: Análisis según escala urbana y regiones en la Argentina (2001) Velázquez, Guillermo Ángel; Vega, Andrea Este trabajo examina la relación entre Tasa de Mortalidad Infantil (TMI) y Cobertura de Salud de la población a nivel departamental (511 unidades) en la Argentina agrupando los departamentos de acuerdo a su categoría urbana y región de pertenencia. Los resultados muestran que, en general, a medida que se asciende en la categoría urbana disminuyen la TMI y la carencia de cobertura social. El análisis regional, por su parte, evidencia que la mejor situación relativa se presenta en la Patagonia y la peor en el Nordeste Argentino (NEA). Finalmente, al estudiar la relación entre ambos indicadores de salud y la escala urbana según regiones, tenemos que el efecto de combinar estas categorías no es lineal: la mejor situación relativa se presenta en las ciudades medias patagónicas, mientras que los pueblos pequeños y población rural cuyana sufren las peores condiciones.

El dimorfismo sexual en guanacos (Lama guanicoe). Una evaluación osteométrica de elementos poscraneales Kaufmann, Cristian Ariel; L'heureux, Gabriela Lorena En poblaciones vivas, los camélidos silvestres sudamericanos son sexados a partir de la observación de su conducta social y reproductiva. Por lo general, tanto biólogos como arqueólogos asumen la ausencia de caracteres morfológicos que evidencien un dimorfismo sexual marcado entre individuos adultos de guanaco (Lama guanicoe). Los principales estudios que evalúan las diferencias osteológicas entre machos y hembras en esta especie están basadosen análisis de variables morfométricas craneanas y en caracteres morfológicos de la pelvis. En este trabajo se evalúa la existencia y magnitud de variables osteométricas poscraneales de diferenciación sexual en una población moderna de guanacos procedente de la localidad Cinco Chañares, Provincia de Río Negro, Argentina. Se estudiaron 32 individuos (8 machos y 24 hembras) de más de 30 meses en los que se midieron 51 hemipelvis, 40 húmeros, 39 radioulnas, 40 fémures y 41 tibias. Los resultados mostraron que las principales diferencias osteológicas, vinculadas con el dimorfismo sexual, se relacionan con variaciones en el tamaño y la forma de la pelvis. En los huesos largos, las diferencias osteométricas significativas se registraron sólo en variables aisladas y no se pudieron definir diferencias osteométricas asociadas con el dimorfismo sexual. Igualmente se considera que esto deberá ser reevaluado con mayor profundidad considerando una muestra mayor de individuos machos.; In wild-living populations adult camelids are mainly sexed by observing their social and reproductive behavior, and on occasion, their genitalia. Both biologists and archaeologists usually assume the absence of clearly identifiable sexually dimorphic somatic and postcranial traits among adult guanaco (Lama guanicoe) specimens. The principal studies that evaluate the osteological differences between sexes in this species, had been carried out using qualitative morphological traits of the pelvis and morphometric traits of the skull. Therefore, the main objective of this paper is to contribute to the development of methodological tools aimed to accurately discriminate between sexes using morphometric techniques. In addition, we assess in this paper the existence and magnitude of the postcranial sex-related morphometric differences in a sample of modern guanaco specimens from Cinco Chañares, Río Negro, Argentina. The sample was composed by 32 individuals (8 males and 24 females) older than 30 month at the age of death. Fifty one hemipelvis, 40 humeri, 39 radioulnae, 40 femora, and 41 tibiae were measured. The obtained results show that the main morphometric differences between sexes are related to size and shape variation in the whole pelvis and acetabulum. In the appendicular skeleton no statistically significant differences between sexes were found, but this ought to be reevaluated increasing sample sizes of male specimens.