Alkali basalts and enclosed ultramafic xenoliths near Ushuaia, Tierra Del Fuego, Argentina

At the southernmost part of Tierra del Fuego a few outcrops and erratic boulders of alkali basaltic rocks with ultramafic enclaves have been studied. Alkali basalt plugs or pipes hitherto identified are scarce, and host rocks are constituted by slates that belong to Mesozoic deposition. The petrography, texture and composition of the basalt and xenoliths were investigated by petrographic microscope and electron microprobe analysis. Xenocrysts of amphibole and alkali feldspar, phenocrysts of nepheline, olivine, spinel, phlogopite and Fe–Ti minerals (10 %) and a diversity of xenoliths, mainly lherzolitic, pyroxenite and wehrlitic nodules (15 %), but also from metamorphic rocks provenance, are contained in the basalt groundmass (75 %). This finer-grained material is made up of laths or needles of plagioclase, pyroxene, opaque minerals, apatite and glass, with intersertal, hyalopilitic and pilotaxitic. Locally, rock has an even granoblastic texture. Former amygdules are filled by analcite, zeolites, sodalite and calcite. The normative classification, based on nepheline content, conclude that this rock is an alkali basalt. The chemical classification, considering immobile elements as Zr/TiO2 versus Nb/Y indicate an alkali basalt too and plots over the TAS diagram fall in the foidite (Na-rich or nephelinite) and basanite fields. The REE patterns are fractionated (La/Yb primitive mantle normalized is approximately 30). The K–Ar isotopic technique on individual macrocrysts gave ages of 146 ± 5 Ma (amphibole) and 127 ± 4 Ma (alkali feldspar); and K–Ar whole rock datum reported 8.3 ± 0.3 Ma. Nevertheless, fertile samples show geochemical features typical of deep derived material thus, based on the position in the actual tectonic setting, indicate that the basalt is older than its isotopic age.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

A megacryst- and xenolith-rich camptonite basalt from Ushuaia, Tierra del Fuego, Argentina

Isolated pods of volcanic breccias with alkalinecomposition are hosted in the metaturbidites of the Yahgan Formation to west ofUshuaia, Isla Grande de Tierra del Fuego, Argentina. The briefly exposed outcropsare almost partially covered by bushy vegetation, whence identification of its scarceapparitions is hampered. Field features display sinuous chilled margins withpinch and swell phenomena or show uneven shape with irregular branching andsegmentation into discrete blobs. Pods of breccias, possibly components of apipe-cluster, seem to represent incipient explosion of the melt that wouldgiven rise to a fully developed vent. Unique horned ends may occur, whichtotally preclude any tectonic explanation for the off-set, even in an Andeanfolded environment. Country rocks are not apparently altered by contact around theigneous boulders. The former may perhaps have acted as a long-lives feeder tolavas, so allowing the hostess to heat up graduatelly. The rock is constituted by macrocrysts of cognatedkaersutite (146 ±5 Ma) and K-feldspar (127 ±4 Ma), phenochrysts of olivine andTi-augite in a groundmass of the same minerals, with plagioclase andfeldspathoids. Texture is mostly aphyric and richly porphyritic both, withfine-grained black matrix. Carbonation is common as secondary alteration. Alkalimetasomatism is marked by developing of kaersutite, feldspathoids and zeolites. The presence of xenoliths, mainly of lherzolitic,pyroxenitic and wehrlitic composition, is the most prominent characteristic ofthese eruptive bodies (Acevedo, 2016). The geochemical plotting of Ce/Yb ratio vs Sm contentsshown these rocks not belong to a specified field in the lamprophyre branches. On the other hand, from a petrographic and petrologic outlook,the mineral arrangement places this rock as a broad volatile-enriched alkalibasalt or camptonite that reflects the mantle upwelling during the stage ofhorizontal extension of the back-arc basin in middle times of the Jurassic-Cretaceoustransition in Tierra del Fuego.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaEGU General AssemblyVienaAustriaEuropean Geosciences Unio

Assessing Mechanical Performance of Dissimilar Steel Systems Made Via Wire-Arc Additive Manufacturing

Hot stamping is part of a specific type of metalworking procedure widely used in the automotive industry. This research seeks to help make hot stamp tooling component production more cost-effective by using large-scale additive manufacturing. Additive manufacturing can produce dissimilar steel components that can be more cost-effective and time-efficient and allow for complex geometries to be made. A dissimilar steel system consisting of 410 martensitic stainless steel and AWS ER70S-6 mild steel is proposed to make hot stamps, making them more cost-efficient. However, the material interface\u27s mechanical behavior in 410SS-mild steel additively manufactured material systems is not well understood. This research seeks to find how these dissimilar hot stamps can potentially fail during service. To assess the mechanical behavior of the material interface, mechanical testing by way of hardness testing, thermal expansion testing, fatigue testing, and microscopic imaging were performed. Samples were heat-treated, and fatigue tests were designed to run for 1200 cycles at a temperature range of 200-600$^{\circ}$C. Fatigue test results show that, as expected, all four samples went through plastic deformation, with hardness test results used to confirm this behavior. Microscopy was done to show the post-test microstructure that shows potential evidence of plastic deformation sites. One of the materials in the dissimilar system did not meet the hardness requirements for hot stamping applications, but recommendations are made to address this

Precipitation of niobium carbonitrides in ferrite: chemical composition measurements and thermodynamic modelling

High-resolution transmission electron microscopy and electron-energy loss spectroscopy have been used to characterize the structure and chemical composition of niobium carbonitrides in the ferrite of a Fe–Nb–C–N model alloy at different precipitation stages. Experiments seem to indicate the coexistence of two types of precipitates: pure niobium nitrides and mixed substoichiometric niobium carbonitrides. In order to understand the chemical composition of these precipitates, a thermodynamic formalism has been developed to evaluate the nucleation and growth rates (classical nucleation theory) and the chemical composition of nuclei and existing precipitates. A model based on the numerical solution of thermodynamic and kinetic equations is used to compute the evolution of the precipitate size distribution at a given temperature. The predicted compositions are in very good agreement with experimental results

Solution-Based Assembly of Conjugated Polymers into Nanofibers for Organic Electronics

Solution-based crystallization of conjugated polymers offers a scalable and attractive route to develop hierarchical structures for electronic devices. The introduction of well-defined nucleation sites into metastable solutions provides a way to regulate the crystallization behavior, and therefore the morphology of the material. A crystallization method for generating metastable solutions of poly(3-hexylthiophene) (P3HT) was established. These metastable solutions allow P3HT to selectively crystallize into nanofibers (NFs) on graphene-coated surfaces. It was found that the crystallization kinetics is faster with increasing P3HT molecular weight and concentration. Through in situ atomic force microscopy, it was confirmed that NFs grow vertically in a face-on chain orientation (i.e., the π orbitals parallel to the substrate normal) from highly oriented pyrolytic graphite and graphene. Moreover, the P3HT crystal structure observed on the surface of graphene was identified to be the same one formed by solution crystallization. However, as confirmed by X-ray scattering and scanning electron microscopy the crystals transitioned from face-on to edge-on orientation (i.e., the π orbitals perpendicular to the substrate normal) as the film grew thicker. As determined by X-ray scattering. the initial face-on conformation was partially preserved by embedding the P3HT structures in an indene C60 bisadduct matrix when compared to pristine P3HT films. The resulting organic field effect transistors had hole mobilities (μ = 20 x 10-3 cm2 V-1 s-1) two orders of magnitude higher than the devices fabricated from spin casted P3HT (μ = 0.9 x 10-3 cm2 V-1 s-1). The solution-processable fabrication of electrodes and semiconductors is potentially scalable and amenable to roll-to-roll manufacturing

Catálogo de los meteoritos hallados en territorio argentino

Es presentado aquí el primer catálogo de meteoritos argentinos. El listado actualizado incluye varios especímenes no reportados previamente. En total se mencionan setenta y cuatro ejemplares, caídos ó encontrados. Fueron omitidos deliberadamente otros seis, de dudosa existencia, más siete pseudometeoritos. Este catálogo brinda las informaciones básicas de cada especímen tales como su procedencia (ubicación geográfica en coordenadas históricas y mapa), clasificación, imagen, peso total, custodios y si fue visto caer ó encontrado casualmente. El trabajo entrega asimismo una completa bibliografía en cada caso. Por otra parte, se anuncia que, con el objeto de impedir el contrabando de meteoritos, el 14 de noviembre de 2007 fue sancionada la Ley Nacional n° 26.306. Gracias a ella, los meteoritos caídos en territorio argentino han sido declarados bienes culturales de la Nación y su comercialización está expresamente prohibida. En las conclusiones se menciona una realidad evidente, que el mayor avistamiento de meteoroides se ha producido en las zonas más pobladas del país, con la excepción de la Provincia de Buenos Aires, donde es comparable al de Patagonia.The first Catalogue of Meteorites from Argentina is presented here. The updated list includes many new specimens previously never reported. The total number of specimens mentioned is seventy four (74), fallen or found. Six doubtful specimens and seven pseudometeorites were deliberately omitted. The catalogue gives the basic information about each specimen, including its provenience (in historical co-ordinates and map), classification, image, total weight, the institution who keeps it, and if it was seen to fall or was found. Our work brings also a complete bibliography about each specimen. We also remark, with the aim to stop the illegal trade of meteorites, that in November 14, 2007, it was dictated a new law, Ley Nacional number 26.306. This law declares that all the meteorites are considered cultural properties of the Argentina’s Nation and their commercial trade is totally forbidden. In the conclusions we indicate that the largest numbers of sightseers of meteoroids were placed in the most populated zones of the country, with the exception of Buenos Aires province in which they were like those of Patagonia’s.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Rocca, Maximiliano. Fundacion de Historia Natural Felix de Azara; Argentin

A very unusual cluster of multiple small impact craters probably created by the impact of a split cometary nucleus in Patagonia

Se hace aquí un análisis detallado del evento de impacto cósmico de Bajada del Diablo (S 42º 45’, W 67º 30’). El evento ocurrió probablemente en el Pleistoceno Medio (780.000 a 130.000 años atrás), y originalmente unos 550 cráteres de impacto de menos de 400 metros de diámetro fueron creados simultáneamente en unárea de 480 kilómetros cuadrados en Bajada del Diablo, Chubut, Patagonia central. Hoy solo sobreviven a los procesos erosivos que han actuado desde el evento de impacto unos 200 cráteres de impacto. La ausencia de una clara elipse de impacto en la distribución de planta de los cráteres de impacto evidencia el impacto de un objeto que ya venía muy fragmentado antes de entrar en la atmósfera terrestre. La ausencia en el sitio mismo de fragmentos de meteoritos (tanto pétreos como metálicos) apunta a que el objeto que impacto estaba principalmente compuesto por hielos, y probablemente era un núcleo helado de cometa fragmentado. Luego de un análisis lógico se favorece el origen de estos cráteres de impacAn analysis of the impact event that created the Bajada del Diablo (S 42º 45’, W 67º 30’) impact crater strewn field is presented. At mid Pleistocene (780,000 to 130,000 years ago), about 550 impact craters of less than 400 meters in diameter were created simultaneously in an area of about 480 square kilometres at Bajada del Diablo in central Patagonia. Absence in the maps of craters of a clear dispersion ellipsoid in the area points toward the idea of the impact of a very fragmented small cosmic object. Cosmic impactor could have been: 1) a “rubble pile” type Near Earth Asteroid or 2) a small split cometary nucleus. The absence of meteorites in the area is in conflict with the hypothesis of the impact of a rocky Near Earth Asteroid. More probably, an ice comet nucleus was the responsible of the impact since the impact of such an icy object would not have left visible traces of itself after more than 130,000 years. After some analysis the impact of a small 200 meters wide split ice comet nucleus is presented as the most probable scenario.Fil: Rocca, Maximiliano. No especifíca;Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Cavlectometry: Towards Holistic Reconstruction of Large Mirror Objects

We introduce a method based on the deflectometry principle for the reconstruction of specular objects exhibiting significant size and geometric complexity. A key feature of our approach is the deployment of an Automatic Virtual Environment (CAVE) as pattern generator. To unfold the full power of this extraordinary experimental setup, an optical encoding scheme is developed which accounts for the distinctive topology of the CAVE. Furthermore, we devise an algorithm for detecting the object of interest in raw deflectometric images. The segmented foreground is used for single-view reconstruction, the background for estimation of the camera pose, necessary for calibrating the sensor system. Experiments suggest a significant gain of coverage in single measurements compared to previous methods. To facilitate research on specular surface reconstruction, we will make our data set publicly available

The importance of teachers and high school students’ interaction in the English classroom to enhance EFL learning in a public school in the municipality of El Peñol

El propósito de este artículo es mostrar la influencia de la interacción entre el profesor y los estudiantes en un aula de inglés como lengua extranjera. El trabajo investigativo se llevon a cabo con un grupo de alumnos de octavo y noveno grado, en una escuela pública ubicada en El Peñol, Antioquia. Este estudio utiliza un método de investigación cualitativo y se centra principalmente en la realización de un estudio de caso, que nos permite describir, comparar, evaluar y comprender diferentes aspectos de este fenómeno de investigación. Los métodos de recolección de datos involucraron diarios de clase, observaciones no participantes y entrevistas semiestructuradas, lo que ayudó a los investigadores a conocer el alcance de la clase, la perspectiva del docente a través del diario de campo, la opinión de un tercero a través de observaciones y entrevistas, las cuales fueron desarrollados para explorar las experiencias y percepciones de los estudiantes sobre la interacción en las clases. Los hallazgos presentados en el estudio sugieren que la interacción entre los estudiantes y el profesor juega un papel importante en el aprendizaje de los estudiantes ya que a través de la interacción, los estudiantes pueden sentirse motivados a estar interesados ​​en participar en la clase de inglés. Además, también se convierte en un tema de discusión ya que a través de la interacción entre ambos agentes, el docente puede acercarse a los estudiantes teniendo en cuenta los factores que influyen en su interacción en el aula para potenciar su aprendizaje sobre el idioma inglés en el aula.The purpose of this paper is to show the influence of the interaction between teacher and students in an EFL classrooms. We work with a group of eighth and ninth graders, in a public school located in El Peñol, Antioquia. This study uses a qualitative research method and it is mainly focused on conducting a case study, which allows us to describe, compare, evaluate and understand different aspects of this research phenomenon. The data collection methods involved class journals, non-participant observations and semi-structured interviews, which helped the researchers to get to know the scope of the class, the teacher's perspective through the field journal, the opinion of a third party through observations and interviews which were developed to explore the students’ experiences and perceptions of the interaction in the classes. The findings presented in the study suggest that the interaction between both students and the teacher, it plays an important role in student learning since through the interaction, students can feel motivated to being interested in get engage in the English class. Moreover, it also becomes a subject matter since through the interaction between both agents, the teacher can approach students by taking into account the factors that influence their interaction in the classroom in order to boost their learning about the English language in the classroom