Effect of competition intensity on recruitment of palatable and unpalatable grasses García, Andrés; Scarfó, María Cecilia; Loydi, Alejandro; Distel, Roberto Alejandro In this study, we made an attempt to reveal how competition intensity from established plants impacts on palatable and unpalatable grass seedlings recruitment, in a natural mesic grassland of central Argentina. Our objective was to assess the seedling recruitment of a palatable species (Chascolytrum subaristatum) and an unpalatable species (Nassella trichotoma) in microsites differing in competition intensity from established plants. Identity (C. subaristatum and N. trichotoma) and defoliation severity were used as surrogate for competition intensity. In March 2017, we permanently marked established individuals of N. trichotoma and C. subaristatum and placed two circular plots adjacent to each individual. In one plot we added seeds of N. trichotoma and in the other seeds of C. subaristatum. After seeding, established plants were randomly assigned to one of three level of defoliation: without defoliation, low defoliation severity and high defoliation severity. From April to November 2017 (i.e. over a complete annual growing cycle), we measured seedling density, recruitment and growth. Our results supported the hypothesis that seedlings of palatable grasses are more competitive than seedlings of unpalatable grasses. Seedling of the palatable grass C. subaristatum recruited successfully regardless the intensity of competition from established plants, whereas seedlings of the unpalatable grass N. trichotoma recruited better under low competitive pressure from established plants. Our results suggest that the availability of microsites with low competitive pressure from the established vegetation, created by selective grazing of palatable grasses, promotes the recruitment of unpalatable grass seedlings. This mechanism may contribute to the species replacement process commonly observed in heavy grazed grasslands.

Adsorption of norfloxacin on a hexagonal mesoporous silica: isotherms, kinetics and adsorbent reuse Ortiz Otalvaro, Julian Andres; Brigante, Maximiliano Eduardo; Avena, Marcelo Javier The adsorption of the antibiotic norfloxacin (NFX) on MCM-41 type mesoporous silica has been studied in batch experiments by performing adsorption kinetics and isotherms under different conditions. Regeneration of the adsorbent and reuse studies were also carried out and are discussed. On the one hand, the adsorption is very fast and strongly dependent on pH, increasing from 30.6 µmol g−1 at pH 3.0 to 192.3 µmol g−1 at pH 7.0 and then decreasing up to 29.6 µmol g−1 as pH increases. The adsorption takes place by direct binding of NFX to silica active sites through electrostatic interactions and H-bonds formations, as deduced from adsorption experiments at several ionic strengths and temperatures. The hydrophobic conformation of the antibiotic zwitterion seems to play also a key role on the maximum adsorption at neutral pH. The presence of calcium ions strongly increases the adsorption of NFX at pH > 4.5 due to the formation of ternary NFX-Ca2+-MCM-41 complexes by calcium-bridging. After the first cycle of regeneration through washing using several solvents, the studied solid significantly reduces its removal efficiency—up to 60%—but then it remains constant for another three cycles. The analysis of thermodynamic parameters suggests that the adsorption is exothermic (− 28.8 kJ mol−1) and spontaneous in nature. On the other hand, the capacity of MCM-41 to remove a concentration of the antibiotic commonly-found in water environments is still being too low if it compares with other adsorbents. Improving the silica surface reactivity should be the main goal by the researchers in order to use the material as adsorbent of this kind of molecules in the future.

Discrimination of hydrologic variations for spatial distribution of fish assemblage in a large subtropical temperate river Espínola, Luis Alberto; Abrial, Elie; Rabuffetti, Ana Pia; Simoes Da Silva, Nadson Ressyé; Amsler, Mario Luis; Blettler, Martin Cesar Maria; Eurich, María Florencia; Paira, Aldo Raul This study examines the effects of the flow and flood pulses on spatialdispersion of fish assemblages in the floodplain of the Paraná River in Argentina. Wetested the hypothesis that high water levels and greater lateral connectivity promotefish dispersal and spatial homogenization of assemblage structure. We sampled foursites during different phases of the annual hydrologic cycle from 2010 to 2016. Watersurface in the area was estimated during each phase. We computed multivariatestatistics and estimates of ß-diversity to analyze assemblage variations in relation tohydrological phases. Three hydrological phases were defined: low flow pulses (waterlevels between 2.3 and 3.2, approximately 10% of the floodplain covered by water),high flow pulses(between 3.2 and 4.5, from 11 to 84%), and floods (> 4.5 m, morethan 84%). Although difference between high flow pulses and flood was notsignificant, ß-diversity values for these stages were higher than for low flow pulses.This suggests that floods and high flow pulses increase the spatial variability of fishassemblages, whereas homogenization processes occur later during low flowperiods. This work provides further knowledge about the flood homogenization effectin a large unregulated floodplain where lateral connectivity still plays a significant roleon ecological structuring processes.

Cuentas y Tembetás Malacológicos de los grupos cazadores-recolectores prehispánicos del humedal del Paraná inferior; Shell beads and tembetás from prehispanic hunter-gatherers of low Paraná wetland Buc, Natacha; Acosta, Alejandro Alberto; Loponte, Daniel Marcelo Entre los grupos cazadores-recolectores que ocuparon el humedal del río Paraná inferior durante el Holoceno tardío, el conjunto más numeroso de adornos es el de las cuentas y tembetás hechos sobre valvas de moluscos. En trabajos previos observamos que estos elementos presentan similitudes morfológicas a nivel intersitio, con pequeñas variaciones formales. En este trabajo evaluamos la posibilidad de que estos elementos hayan funcionado como demarcadores sociales. En este sentido esperamos un patrón homogéneo tanto en la forma general y sus atributos, como en el tamaño. Para ello analizamos métrica y morfológicamente los conjuntos malacológicos provenientes de diez sitios arqueológicos del área. Los resultados muestran tendencias diferentes para las cuentas y los tembetás. Las primeras se distribuyen de manera homogénea en el espacio con un patrón morfológico y métrico compartido que sólo excluye uno de los sitios arqueológicos. Los tembetás, por su parte, son menos frecuentes y presentan dos variantes morfométricas que pueden responder a variaciones individuales o reflejar parcialidades étnicas.; Among hunter-gatherer groups that inhabited the low Paraná wetland during Late Holocene, the most numerous assemblages of ornaments are composed by shell beads and tembetás. In previous works we observed that the assemblages show inter-site morphological similarities with little formal variations. In this paper we test the idea that these elements were used as social markers. Consequently, we expect an homogeneous pattern in the general form and the form of their attributes, as well as the metrical values. For this purpose, we analyse metrical and morphological data of shell assemblages from ten archaeological sites of the study area. Results show different tendencies for shell beads and tembetás. Shell beads are homogenously distributed in the region with a shared morphologic and metric pattern that only excludes one of the archaeological sites. Tembetás are less frequent and show two morpho-metric variants that could be a response either to individual variability or to ethnic identification.

Intuitionistic fuzzy set and fuzzy mathematical morphology applied to color leukocytes segmentation Bouchet, Agustina; Montes, Susana; Ballarin, Virginia Laura; Díaz, Irene This work presents a new algorithm based on Atanassov’s intuitionistic fuzzy sets and fuzzy mathematical morphology to leukocytes segmentation in color images. The main idea is based on modeling a color image as an Atanassov’s intuitionistic fuzzy set using the hue component in the HSV color space. Then, a pixel labeled as leukocyte is selected and compared to the whole image with a similarity measure. Thus, the leukocyte is segmented and separated from the rest of the image. The experimental results show that the algorithm has a good performance, reaching a value of 99.41% for the correctclassification of leukocytes and a 99.23% for the correct classification of the background. Other metrics such as accuracy, precision and recall have been calculated obtaining 99.32%, 99.41% and 99.24%, respectively. The algorithm presents two important characteristics: It works directly over the color images without the need of converting the image in gray scale, and it does not produce false colors because fuzzy morphological operators guarantee it.

Avances en el desarrollo de un biofungicida: caracterización físicoquímica y actividad antifúngica de propóleos; Advances in the development of a biofungicide: physical-chemical characterization and antifungal activity of propolis Cibanal, Irene Laura; Fernández, Leticia A.; Krepper, Gabriela; Pellegrini, Cecilia Noemí; Gallez, Liliana María El propóleos constituye, gracias a sus propiedades antimicrobianas, una alternativa para el control de fitopatógenos. En este trabajo se realizó, mediante técnicas convencionales, la caracterización sensorial y físico-química de cuatro muestras de propóleos provenientes de diferentes regiones de Argentina y de sus respectivos extractos hidroalcohólicos. Asimismo, se evaluó in vitro la actividad antifúngica de los extractos sobre el hongo Penicillium sp. causante de la ??mufa del ajo?? (Allium sativum). Los propóleos en bruto presentaron aroma resinoso, coloración marrón con diferentes tintes y aspecto de trozos irregulares. El análisis de las muestras evidenció diferencias significativas en los parámetros ceras (9,43 - 31,16 %), pérdidas por calentamiento (1,04 - 1,46 %), cenizas (0,98 - 7,18 %) y temperatura media de fusión (63,16 - 67,5 °C). En los extractos hidroalcohólicos de propóleos también se detectaron diferencias estadísticas en el extracto seco (5,50 - 9,30 %), contenido de fenoles (23,44 - 53,91 %), flavonoides totales (1,12 - 1,58 %) e índice de oxidación (2,25 - 4,33 segundos). Los espectros UV-VIS exhibieron un perfil de absorción con una banda amplia entre 240 nm y 340 nm. Todos los tratamientos a base de extractos de propóleos tuvieron un efecto inhibidor superior al 99 % sobre el desarrollo de unidades formadoras de colonias fúngicas. Los resultados permiten concluir que si bien los propóleos y extractos analizados en este trabajo presentaron diferentes características, coincidieron en la excelente actividad antifúngica sobre Penicillium sp.. Esto demuestra la potencialidad de los propóleos para el desarrollo de un biofungicida de uso agrícola.; Propolis is a viable alternative for chemical control of plant pathogens due to its antimicrobial properties. The present study was conducted to determine the sensorial, physical and chemical characteristics of four propolis from Argentina, and their respective hydroalcoholic extracts. In vitro antifungal activity of hydroalcoholic propolis extracts against Penicillium sp. that cause the decay of garlic (Allium sativum) was also studied. All propolis samples were composed of irregular fragments. The aroma was mainly resinous. The predominant colour was brown. The analysis of the raw samples showed differences in the parameters wax content (9.43-31.16 %), loss by heating (1.04-1.46 %), ashes (0.98-7.1 8 %) and melting point (63.16-67.5 °C). The hydroalcoholic extracts of propolis also differ in the dry residue (5.50-9.30 %), content of phenols (23.44-53.91 mg eq galic/g propolis), total flavonoids (11.23-15.88 mg eq quercetin/g propolis) and oxidation index (2.25- 4.33 seconds). The evaluation of the antifungal activity demonstrated that all the treatments containing propolis had an inhibitory effect over 99 % on fungi colony-forming units’ development. Although the physical and chemical study showed significant differences between propolis samples, all exhibited excellent antifungal activity against Penicillium sp. This demonstrates the potential of different propolis for the development of a biofungicide for agricultural use.

Empirical mode decomposition of multiphase flows in porous media: Characteristic scales and speed of convergence Echebarrena, Nicolas; Mininni, Pablo Daniel; Moreno, Gustavo Ariel We apply a proper orthogonal decomposition (POD) to data stemming from numerical simulations of a fingering instability in a multiphase flow passing through obstacles in a porous medium, to study water injection processes in the production of hydrocarbon reservoirs. We show that the time evolution of a properly defined flow correlation length can be used to identify the onset of the fingering instability. Computation of characteristic lengths for each of the modes resulting from the POD provides further information on the dynamics of the system. Finally, using numerical simulations with different viscosity ratios, we show that the convergence of the POD depends non-trivially on whether the fingering instability develops or not. This result has implications on proposed methods to decrease the dimensionality of the problem by deriving reduced dynamical systems after truncating the system’s governing equations to a few POD modes.

Decoloración fotocatalítica del Rojo de Alizarina S empleando nanocatalizadores de hierro; Photocatalytic decoloration of Alizarin S Red employing iron nanocatalysts Lerici, Laura Carolina; Varela López, Claudio; Leal Marchena, Candelaria; Vinuesa, Ariel José; Diguilio, Eliana; Renzini, Maria Soledad; Campos Figueroa, Cristian Los colorantes constituyen una clase importante de compuestos orgánicos que encuentran numerosas aplicaciones en nuestra vida cotidiana. El teñido produce efluentes que contienen entre el 10 y 15% del colorante que finalmente se depositan en los cuerpos de agua. Se sintetizaron y caracterizaron nanotubos de alúmina impregnados con 2, 6 y 10 % de hierro (Fe-NT), para ser empleados en la decoloración fotocatalítica del Rojo de Alizarina S (ARS). Por DRX se verificaron las señales características de la γ-Al2O3. El área superficial disminuyó con el aumento del contenido hierro oscilando entre 87 y 116 m2/g. La presencia de hierro fue confirmada por Absorción Atómica. Además, por TEM, se confirmó la estructura tipo nanotubo. Los materiales fueron evaluados catalíticamente en la decoloración del ARS obteniendo porcentajes de decoloración del 50% para el Fe-NT 2% y 85-90 % para los nanotubos con 6 y 10 % de hierro, respectivamente.; Dyes are an important organic compounds that find numerous applications in our daily lives. The dyeing produces effluents that contain between 10 and 15% of the dye that are finally deposited in the bodies of water. Alumina nanotubes impregnated with 2, 6 and 10% of iron (Fe-NT) were synthesized and characterized to be used in the photocatalytic degradation of Alizarine Red S (ARS). By XRD, the characteristic signals of γ-Al2O3 were verified. Surface area varying from 87 to 116 m2/g. The presence of iron was confirmed by Atomic Adsorption. In addition, the nanotube structure of the support was confirmed by TEM. The materials were evaluated catalytically in the degradation of the ARS obtaining percentages of degradation of 50% for the Fe-NT 2% and 85-90% for the nanotubes with 6 and 10% of iron, respectively.

El rompecabezas de la integración sudamericana: intereses corporativos, política exterior y estrategia en el COSIPLAN- UNASUR; The South American Integration Puzzle: Corporative Interests, Foreign Policy and Strategy in COSIPLAN-UNASUR Barrenengoa, Amanda Carolina Nos proponemos indagar en los actores sociales presentes en los procesos de integración suramericana reciente, desde la Unión de Naciones Suramericanas (UNASUR) y el Consejo Suramericano de Infraestructura y Planeamiento (COSIPLAN). Buscamos reconstruir una porción de un gran rompecabezas que reúne a diversos actores sociales, para dar cuenta de un entramado que excede los márgenes estatales e involucra a gobiernos, empresas, organismos de financiamiento, bancos, sectores productivos, funcionarios estatales, poblaciones. A partir del caso brasileño ponemos el foco en los intereses de la clase dominante y la forma en que se vinculan con los Estados, encontrando un amplio repertorio de problemas y dimensiones. De aquí se desprenden conflictos que nos llevan a preguntarnos por las limitaciones, los factores externos e internos y las contradicciones que enmarcaron los gobiernos de Lula. Desde una metodología cualitativa, damos cuenta de una multiplicidad de actores de las clases dominantes, cuyos intereses y acciones se hallaron, en principio, entrelazados con las estrategias impulsadas desde el propio Estado. Mientras avanzaba la dinámica social y política, las perspectivas y posiciones de estos actores se vieron modificadas, por diversos motivos. Como resultado de estas indagaciones, pudimos observar las múltiples formas de manifestación de sus intereses y relaciones.; This article aims to contribute to the investigation about social actors in the South American Integration Process of the last decade from the Union of South American Nations (UNASUR) and the South American Infrastructure and Planning Council (COSIPLAN). It focus on reconstructing a part of a big puzzle that brings together a number of social actors, to show a network that exceeds the state’s margins and involves governments, companies, financing agencies, banks, productive sectors, state officials and populations. Starting at the Brazilian case, attention is paid to the interests of the ruling class and the way they are linked to the States, finding a wide repertoire of problems and dimensions. At this point, conflicts arise, which lead us to ask ourselves about the limitations, the external and internal factor and those contradictions with which the governments of Lula encountered. From a qualitative methodology, we were able to account for a multiplicity of actors of ruling clases, whose interests and actions were intertwined with the strategies promoted by the Brazilian State itself. While the social and political dynamics advanced, the perspectives and positions of these actors were modified, for various reasons. As a result of these inquiries, we could observe the multiple forms of manifestation of their interests and relationships.

Picosecond laser interference patterning of periodical micro architectures on metallic molds for hot embossing Fu, Yangxi; Soldera, Marcos Maximiliano; Wang, Wei; Voisiat, Bogdan; Lasagni, Andrés Fabián In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.

Effect of nickel loading on hydrogen adsorption capacity of different mesoporous supports Carraro, Paola María; Soria, Federico Ariel; Vaschetto, Eliana Gabriela; Sapag, Manuel Karim; Oliva, Marcos Iván; Eimer, Griselda Alejandra Pure siliceous and aluminosilicate mesoporous molecular sieves of MCM-41 type have been used as support for nickel incorporation (2.5 wt%) by wet impregnation method. The hydrogen adsorption capacities at 77 K of these materials have been studied. Various techniques such as X-ray diffraction, N2 adsorption–desorption, X-ray photoelectron spectroscopy, Temperature-Programmed Reduction, UV–Vis diffuse reflectance spectroscopy and adsorption of pyridine coupled to infrared spectroscopy were employed to characterize the materials. In addition, Density Functional Theory calculations were used in order to interpret the results of hydrogen adsorption. The results obtained show that isolated metallic species are capable to promote hydrogen favorable sites. Isolated mononuclear Ni2+ species on the surface strengthen the interaction with the H2, enhancing the hydrogen adsorption capacity.

Tamaño de grupo, argumentación y lectura de tablas en estudiantes universitarios; Group size, argumentation and table reading in university students Curcio, Juan Manuel; Peralta, Nadia Soledad; Castellaro, Mariano Andrés La argumentación es una variable importante para entender el aprendizaje. Aunque hay varios artículos al respecto, su relación con el tamaño del grupo es una novedad. Se analiza la relación entre el tamaño del grupo (díada-tríada) y la distribución argumental (simétrica-asimétrica) en lectura de tablas de doble entrada, y su relación con el tipo de respuesta utilizada. Se utilizó un diseño cuasi-experimental de solo post-test en una muestra de 89 estudiantes universitarios. Los resultados muestran distribuciones argumentales simétricas en las díadas, mientras que las tríadas obtuvieron mayores valores de asimetría. No se encontraron relaciones significativas entre el tamaño del grupo y el tipo de respuesta final como así tampoco entre la distribución argumental y el tipo de respuesta. Esto indicaría que el tamaño del grupo afecta la posibilidad de las personas de aportar argumentos durante la interacción, así como el tipo de tarea condicionaría el tipo de argumentos empleados.; Argumentation is an important variable to understand the learning process. Despite there are several papers about it, its relation with the group size is a novelty. The relationship between the group size (dyad-triad) and the argument distribution (symmetric-asymmetric) in a double-entry table reading task, in addition to its relationship with the type of answer used, are analyzed. A quasi-experimental design was used with only a post-test, in a sample of 89 university students. The results show that the dyads obtained the highest values of symmetry, whereas the triads obtained higher values of asymmetry. No significant relationships were found between the group size and the final answers types, neither between the group size and the answer type. This would indicate that the size of the group affects the possibility of people to provide arguments during the interaction, as well as the type of task that would condition the type of arguments used.

Data-driven estimation of the invisible energy of cosmic ray showers with the Pierre Auger Observatory Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Albury, J. M.; Gobbi, Fabián Jesús; Bertou, Xavier Pierre Louis; Etchegoyen, Alberto; Garcia, Beatriz Elena; Mariazzi, Analisa Gabriela; Ferreyro, Luciano Pablo; González, Nicolás Martín; Dasso, Sergio Ricardo; Sarmiento Cano, Christian Andres; Tueros, Matias Jorge; Platino, Manuel; Sanchez, Federico Andrés; Roulet, Esteban; Gomez Berisso, Mariano; Perlin, Matias; Mollerach, Maria Silvia; Golup, Geraldina Tamara; Micheletti, Maria Isabel; Almela, Daniel Alejandro; Lucero, Luis Agustin; Sciutto, Sergio Juan; Rovero, Adrian Carlos; Asorey, Hernán Gonzalo; Vergara Quispe, Indira Dajhana; Bonifazi, Carla Brenda The determination of the primary energy of extensive air showers using the fluorescence detection technique requires an estimation of the energy carried away by particles that do not deposit all their energy in the atmosphere. This estimation is typically made using Monte Carlo simulations and thus depends on the assumed primary particle mass and on model predictions for neutrino and muon production. In this work we present a new method to obtain the invisible energy from events detected by the Pierre Auger Observatory. The method uses measurements of the muon number at ground level, and it allows us to significantly reduce the systematic uncertainties related to the mass composition and the high energy hadronic interaction models, and consequently to improve the estimation of the energy scale of the Pierre Auger Observatory.

Trajectorial market models: Arbitrage and pricing intervals Ferrando, Sebastian Esteban; González, Alfredo Lázaro; Degano, Iván Leonardo; Rahsepar, Massoomeh The paper develops general, non-probabilistic market models based on trajectory sets and minmax price bounds leading to price intervals for European options. The approach provides the trajectory based analogue of a martingale process as well as a generalization that allows a limited notion of arbitrage in the market while still providing coherent option prices. An illustrative example is described in detail. Several properties of the price bounds are obtained, in particular a connection with risk neutral pricing is established for trajectory markets associated to a continuous-time martingale model.

Multiscale constitutive model with progressive recruitment for nanofibrous scaffolds Caballero, Daniel; Montini Ballarin, Florencia; Gimenez, Juan Manuel; Urquiza, Santiago Adrian Biomedical applications need tailor-made scaffolds that exhibit biomimetic mechanical properties. In this context, electrospinning has emerged as a technique with promising features for their production. However, the electrospun scaffolds mechanical behavior as a function of the microstructure and nanofiber properties is still poorly understood. Besides, multiscale constitutive modeling appears as a powerful design tool, not only able to characterize electrospun structures, but also to determine the fiber properties and scaffold microstructure that would achieve the objective response. With focus in this last aspect, we developed a multiscale constitutive model for nanofibrous structures that takes into account the material constitutive properties, scaffold microstructure, and nanofiber progressive recruitment. A statistical approach of the nanofibers tortuosity with a modified Gaussian distribution was adopted, which allowed for reproducing the scaffolds macroscopic nonlinear mechanical behavior. It was observed that such behavior arises even if the nanofibers response is considered as mechanically linear. Experimental data from pressure vs. diameter inflation tests of electrospun tubular scaffolds was used to validate the model. In addition, the influence of the microstructural parameters upon the macroscopic constitutive behavior was studied. Finally, the model parameters were adjusted to obtain a vascular graft able to reproduce the mechanical response of a target natural tissue. The current study presents a step towards understanding, characterizing, and optimizing the mechanical properties of nanofibrous biomaterials.

The first record of Desmatochelys cf. D. lowii from the Late Cretaceous (Campanian) of Coahuila, Mexico López Conde, Oliver Ariel; Sterli, Juliana; Alvarado Ortega, Jesús; Chavarría Arellano, María L.; Porras Múzquiz, Héctor In this work we describe a new marine turtle from the clade Protostegidae from Mexico recognized as a new specimen of Desmatochelys. This specimen was collected in the San Carlos quarry, near Jiménez, Coahuila, in outcrops of the Austin Formation, Late Cretaceous (Lower Campanian). The quarries of this region are composed of marly limestones where numerous remains of fossil fish, shark teeth, ammonites and crabs were also found. This Protostegidae turtle from Mexico is a semi-articulated specimen in ventral position, that lacks the skull. This specimen is important because it preserves one of its forelimbs and both hindlimbs. The left anterior limb is fully articulated bringing new information of Desmatochelys and, in the same way, it is the first time that both articulated hindlimbs are reported. This new specimen of Desmatochelys is relevant because is the southernmost record for the genus along the Western Interior Seaway during the Late Cretaceous.

Mechanical performance of lightweight polycrystalline Ni nanotubes Rojas Nunez, Javier; Valencia, Felipe; Gonzalez, Rafael I.; Bringa, Eduardo Marcial; Allende, Sebastian; Palma, Juan L.; Pereira, Alejandro; Escrig Murúa, Juan Eduardo; Baltazar, Samuel E. The mechanical properties of metallic nanowires and nanotubes were investigated using atomistic molecular dynamics simulations on Ni polycrystalline structures, similar to those experimentally obtained by Atomic Layer Deposition. We studied the response of nanostructures under uniaxial deformations with different thickness, geometry, and crystalline degree. Plastic deformation is due to stacking fault and coherent twin boundary formation, and to grain boundary activity. Different fracture processes are obtained from these systems, being the thin nanotubes failing thanks to a mix of brittle failure by grain boundary decohesion and ductile fracture due to significantly more twins than with a thicker nanotube and nanowire during the ductile fracture. The stress-strain curves, atomic displacements, and defects formation were analyzed, finding that nanotubes with a fraction of the volumetric mass have practically the same Young modulus and ultimate tensile stress, while fracture strain is slightly larger for nanowire. From all these studied cases, it is remarkable the result where ultra-thin nanotubes can withstand a 21% of tensile stress-strain with a similar yield strength than nanowires, but with a volumetric mass reduction of 60%, offering a lightweight alternative to design mechanical nanodevices with minimal loss of mechanical performance.

Undetected non-conformities in material processing led to a service failure in a casing hanger during pre-fracture operation Cirimello, Pablo Gabriel; Otegui, Luis Jose; Aguirre, Alberto; Carfi, Guillermo Rodolfo The failure of a 5″ casing hanger at an oil well led to costly workover operations and lost production. The brittle failure was due to the instantaneous propagation of a circumferential fracture, initiated at a geometrical stress raiser. Combined operation stresses from internal pressure, casing weight and tightening torque were close to the yield strength of the material. If the material had sufficient ductility, plastic deformation would have led to stress relaxation and redistribution. But a SAE/AISI 4140 steel with a low forging ratio, plus a poor heat treatment and incomplete quenching, led to a banded microstructure with both low strength and toughness, and a consequent limited capacity for plastic deformation. Geometric discontinuities due to elongated inclusions and other microestructural defects justify crack propagation at the reported service loads. Quality assurance failed to prevent unacceptable pieces. Some recommendations are provided to reduce the likelihood of recurrence in new hangers: an appropriate microstructure must be assured, controlling the forging stages and heat treatment parameters. The representativeness of test coupons used for quality control must be ensured. Re-evaluating the geometry of the casing hanger and switching to a steel with higher hardenability would lead to more defect - tolerant components.

On the Role of Finance in Sraffa’s System Dvoskin, Ariel; Feldman, Germán David We critically review the previous attempts to introduce money and finance into Sraffa’s price system, whose main difference is, we argue, their conception of the interest rate, either as an opportunity cost or as an effective cost of production. We examine the implications on three different grounds: (i) the formal consistency of the system; (ii) the possibilities to explicitly treat the financial industry as any other productive sector; and (iii) the validity of the so-called “monetary theory of distribution” (MTD). We then suggest a possible route, inspired by Schumpeter’s ideas on economic development, to introduce the banking sector through its role of granting credit to innovation. Unlike previous contributions, this reformulation allows us both to justify the basic nature of the financial sector and simultaneously preserve the validity of MTD.

Extensión universitaria y recreación: Transformaciones culturales en/desde un club deportivo Branz, Juan Bautista; Césaro, Aldo Román; Ferretty, Emmanuel; López, Andrés En este texto presentamos una experiencia colectiva e interdisciplinaria de extensión universitaria que se desarrolló durante tres años (2011-2013) en un club deportivo de la ciudad de La Plata, capital de la provincia de Buenos Aires, Argentina. Nuestro trabajo estrechó los lazos vecinales con el club favoreciendoprocesos de socialización y de identificación barrial en la trama de la cultura urbana platense. Para lograr este cometido impulsamos prácticas recreativas, artísticas y comunicacionales en una modalidad de taller como dispositivo participativo, abierto y gratuito.En la actualidad podemos observar como el club y sus actores incorporaron a la vida institucional algunos de los aspectos relevantes del proyecto de extensión.Ciertos acontecimientos y transformaciones nos dan indicios de los efectos permanentes de nuestras intervenciones y, de igual manera, abonan la posibilidad de construir una lógica social diferente a la del deporte en su faceta competitiva, selectiva, excluyente. En otro nivel de análisis, esta experiencia nos permitió reflexionar acerca de las articulaciones entre las instituciones estatales (universidad) y otras organizaciones tales como los clubes en la construcción de espacios públicos inclusivos en ciudades cada vez más desiguales.; In this text we present a collective and interdisciplinary experience of university extension that was developed during three years (2011-2013) in a sports club in the city of La Plata, capital of the province of Buenos Aires, Argentina. Our work strengthened the neighborhood ties with the club, favoring processes of socialization and neighborhood identification in the framework of the urban culture of La Plata. To achieve this goal, we promote recreational, artistic and communication practices in a workshop modality as a participatory, open and free device. Currently we can see how the club and its actors incorporated into institutional life some of the relevant aspects of the extension project. Certain events and transformations give us indications of the permanent effects of our interventions and, similarly, pay the possibility of constructing a social logic different from that of sport in its competitive, selective, exclusive aspect. At another level of analysis, this experience allowed us to reflect on the links between state institutions (universities) and other organizations such as clubs in the construction of inclusive public spaces in increasingly unequal cities.