A sustainable process for biodiesel production using Zn/Mg oxidic species as active, selective and reusable heterogeneous catalysts Navas, Marisa Belén; Ruggera, José Fernando; Lick, Ileana Daniela; Casella, Mónica L. This paper describes the preparation and characterization of MgO and ZnO-based catalysts, pure and mixed in different proportions, supported on γ-Al2O3. Their catalytic performance was studied in the transesterification of soybean oil and castor oil with methanol and butanol, attempting to produce biodiesel. XRD (X-ray diffraction), SEM?EDS (scanning electron microscopy?energy dispersive X-ray spectroscopy), CO2-adsorption and N2-adsorption allowed characterizing the prepared catalysts. The characterization results were in all cases consistent with mesoporous solids with high specific surface area. All the catalysts exhibited good results, especially in the transesterification of castor oil using butanol. For this reaction, the reuse was tested, maintaining high FABE (fatty acid butyl esters) yields after four cycles. This good performance can be attributed to the basic properties of the Mg species, and simultaneously, to the amphoteric properties of ZnO, which allow both triglycerides and free fatty acids to be converted into esters. Using these catalysts, it is possible to obtain second-generation biodiesel, employing castor oil, a raw material that does not compete with the food industry. In addition, butanol can be produced from renewable biomass.

Un león entre la hacienda. Relaciones entre animales y humanos a partir del estudio de pumas embalsamados en la puna de Jujuy (Argentina); A lion in the flock. Relations between animals and humans from a study of embalmed pumas in the puna of Jujuy (Argentina) Rivet, María Carolina En distintos lugares de los Andes los félidos son calificados como animales predadores, criados por el cerro y a la vez son considerados pastores y protectores del ganado. En Coranzulí en particular (Jujuy, Argentina) en la actualidad se conservan pumas embalsamados en las casas de campo. Estos tienen la característica de poseer atributos materiales que los vinculan con los animales de los rebaños familiares. Los procedimientos técnicos, tanto para su caza como para la preparación del cuerpo, se plantearían como una de las condiciones necesarias para que sus capacidades otrora riesgosas devengan en propiciadoras. Así, una vez embalsamados, se integran a las sociabilidades familiares al participar activamente de la vida cotidiana de los pastores con agencias tales como la capacidad de multiplico, fertilidad y protección no sólo del ganado sino también del grupo familiar.; In different places of the Andes, felids are classified as predators, raised by Coquena, and at the same time, they are considered shepherds and livestock protectors. At present, especially in Coranzulí –Jujuy, Argentina– embalmed pumas are preserved in country houses. They have the distinctive characteristic of having material attributes connecting them to the animals of the flocks. The technical procedures for hunting and preparing the body will be considered one of the necessary conditions for their once risky capabilities to turn into enabling capabilities. Thus, once embalmed, they are integrated into family sociabilities by actively participating in the shepherds’ daily life with agencies such as the ability to multiply, fertility, and protection of livestock and the family group.

Two Late Cretaceous sauropods reveal titanosaurian dispersal across South America Hechenleitner, Esteban Martín; Leuzinger, Léa Sylvia; Martinelli, Agustín Guillermo; Rocher, Sebastian; Fiorelli, Lucas Ernesto; Taborda, Jeremías Ramón Alejandro; Salgado, Leonardo South American titanosaurians have been central to the study of the evolution of Cretaceous sauropod dinosaurs. Despite their remarkable diversity, the fragmentary condition of several taxa and the scarcity of records outside Patagonia and southwestern Brazil have hindered the study of continental-scale paleobiogeographic relationships. We describe two new Late Cretaceous titanosaurians from Quebrada de Santo Domingo (La Rioja, Argentina), which help to fill a gap between these main areas of the continent. Our phylogenetic analysis recovers both new species, and several Brazilian taxa, within Rinconsauria. The data suggest that, towards the end of the Cretaceous, this clade spread throughout southern South America. At the same locality, we discovered numerous accumulations of titanosaurian eggs, likely related to the new taxa. With eggs distributed in three levels along three kilometres, the new site is one of the largest ever found and provides further evidence of nesting site philopatry among Titanosauria.

La vida cotidiana ante el COVID-19: Modos diferenciales de usar y valorar el espacio en el Gran Buenos Aires durante la fase 1 del ASPO, 2020 Marcus, Juliana; Boy, Martín Guillermo; Benitez, Joaquín Andrés; Berardo, Martina Daniela; Felice, Magdalena Inés; Marquez, Agustina; Peralta, María Agustina; Vazquez, Diego Ezequiel La llegada del COVID-19 a la Argentina y la política de Aislamiento Social Preventivo y Obligatorio (ASPO) transformaron los usos y valoraciones en torno al espacio público y privado. Este artículo focaliza en la dimensión espacial de la política sanitaria con el objetivo de analizar cómo las/os habitantes del Gran Buenos Aires (GBA) modificaron su relación con el espacio urbano y el espacio doméstico a partir de la medida del ASPO. Sobre la base de una encuesta online realizada durante las primeras semanas de la Fase 1 de ASPO a residentes del GBA mayores de 18 años con secundario completo o más, se indaga cómo el género, la composición del hogar, la zona geográfica de residencia y la disponibilidad de espacios exteriores en la vivienda inciden en los modos de usar y valorar el espacio público y privado. Entre los resultados, se destaca que la pandemia profundizó desigualdades preexistentes referidas tanto a los usos del espacio doméstico como a las formas de valorar el espacio público, de modo tal que son las mujeres quienes experimentan con mayores cargas laborales y emocionales este período del ASPO.

Colinas Sagradas y Arte Rupestre Escandinavo en Tanum (Suecia) Ceruti, Maria Constanza Situado al sudoeste de Suecia, el paraje de Tanum sobresale mundialmente por la riqueza y variedad de su arte rupestre, que se remonta a la Edad del Bronce Escandinava (1800 a 500 BC) y comprende alrededor de quinientos sitios y más de diez mil motivos grabados sobre superficies rocosas alisadas por glaciares. Los petroglifos revelan aspectos vinculados a la vida social, las experiencias espirituales, las creencias religiosas y los rituales de los antiguos habitantes escandinavos.Uno de los más famosos paneles rupestres se encuentra en Vitlycke, donde se nuclean decenas de motivos incisos que incluyen barcos, discos solares, líneas de puntos, antropomorfos, zoomorfos (renos) y tacitas, entre otros. Se destaca por su plasticidad una escena de duelo fúnebre y una escena con dos personajes abrazados, a los que se denomina coloquialmente Los Amantes. También se distingue un motivo antropomorfo que ha sido interpretado como una deidad del clima. El panel de Litsleby se destaca por el gran tamaño de una representación masculina denominada La Deidad de la Lanza, precursora de la figura del dios nórdico Odín, que constituye el petroglifo antropomorfo más grande de Escandinavia. También aparecen en Litsleby representaciones de barcas, discos solares y pisadas humanas, y en un panel vecino, motivos de jinetes a caballo con escudos y lanzas. La colina de Aspeberget merece el calificativo de montaña sagrada, según la folletería de Tanum. Se encuentra cubierta con motivos incisos que representan barcas y discos solares, escenas de caza, acróbatas a bordo de barcos, entre otros. El presente trabajo analiza e interpreta el arte rupestre de Tanum en relación con la importancia ritual y simbólica de la montaña, en los ritos fúnebres, las prácticas shamánicas y los depósitos de ofrendas votivas en la antigua Escandinavia.

Aportes de la Comisión Central de Señoras Cooperadoras Salesianas Argentinas al financiamiento del proyecto salesiano (Buenos Aires, 1900-1929); Financial contributions of the Comisión Central de Señoras Cooperadoras Salesianas Argentinas to the salesian project (Buenos Aires, 1900-1929) Bracamonte, Lucia Desde fines del siglo XIX, las cooperadoras fueron importantes para conseguir recursos destinados a los proyectos de los salesianos y las Hijas de María Auxiliadora en la Argentina, ya fuera de manera individual o grupal. El objetivo específico de este artículo es analizar los ingresos monetarios de la Comisión Central de Señoras Cooperadoras Salesianas Argentinas entre 1900 y 1929, a fin de identificar la extensión de la asistencia proveída y las fuentes de financiamiento. Desde el análisis de esta entidad, aborda el problema de la relación entre los grupos confesionales femeninos y la intervención estatal en el área asistencial.; Since the end of the 19th Century, the women cooperators were important to obtain financial resources, working individually or in group, for the projects of the salesians and the congregation Hijas de María Auxiliadora in Argentina. The main objective of this paper is to analyze the monetary income of the Comisión Central de Señoras Cooperadoras Salesianas Argentinas in the period 1900-1929, in order to determine the financial sources and the extensionof the assistance provided. With the analysis of this entity, the relation between the confesional feminine groups and the State participation in the social assistance area is studied.

The impact of birth order on behavior in contact team sports: Evidence of rugby teams Delbianco, Fernando Andrés; Fioravanti, Federico; Tohmé, Fernando Abel Several studies have shown that birth order and the sex of siblings may have an influence on individual behavioral traits. In particular, it has been found that second brothers (of older male siblings) tend to have more disciplinary problems. If this is the case, this should also be shown in contact sports. To assess this hypothesis, we use a data set from the South Rugby Union from the region of Bahía Blanca, Argentina, and information obtained by surveying more than 400 players of that league. We find a statistically significant positive relation between being a second-born male rugby player with an older male brother and the number of yellow cards received.

Precariedad, crisis y nuevas miradas sobre el Estado Condiciones de trabajo en el ámbito teatral platense antes y durante la pandemia; Precariedade, crise e novos olhares sobre o Estado Condições de trabalho no teatro de La Plata antes e durante a pandemia; Precariousness, crisis and new views about the State Labor conditions in La Plata theater before and during the pandemic del Mármol, Mariana; Díaz, Juliana En este artículo abordaremos el caso del teatro independiente de la ciudad de La Plata (Buenos Aires, Argentina) con el objetivo de describir y analizar cómo impactó la crisis producida a partir la pandemia del COVID 19 y la medida de Aislamiento Social Preventivo y Obligatorio decretada por el gobierno nacional, en los procesos de identificación de los/as teatristas como trabajadores/as, su organización colectiva para enfrentar la situación de emergencia y sus relaciones de articulación y demanda respecto de los organismos del Estado dedicados a la promoción y protección de la cultura. El trabajo surge como parte de dos investigaciones paralelas y en diálogo que abordan problemas en torno al trabajo artístico en La Plata dentro de los últimos cinco años. Los datos que analizamos en este caso provienen del trabajo de campo realizado antes del ASPO; de observaciones y análisis documental realizadas en este último período, utilizando los dispositivos tecnológicos que tenemos a nuestro alcance y de una encuesta no probabilística impulsada por una organización de Profesores/as de Artes Escénicas Autogestivas recientemente creada en la ciudad, cuyo diseño, procesamiento y análisis de datos estuvo a cargo de una de las autoras de este artículo. Todo esto lo hemos puesto en diálogo con bibliografía afín a la temática laboral en general y como del trabajo artístico en particular.; Neste artigo abordaremos o caso do teatro independente da cidade de La Plata (Buenos Aires, Argentina) com o objetivo de descrever e analisar como a crise produzida a partir da pandemia COVID 19 e a medida de Isolamento Social Preventivo e Obrigatório (ASPO) decretada pelo governo nacional, impactou nos processos de identificação dos atores teatrais como trabalhadores, sua organização coletiva para o enfrentamento da situação de emergência e sua articulação e cobrança de relações com os órgãos do Estado voltados à promoção e proteção do cultura. A obra surge como parte de duas investigações paralelas e em diálogo que abordam problemas em torno do trabalho artístico em La Plata nos últimos cinco anos. Os dados que analisamos, neste caso, vêm do trabalho de campo realizado antes da ASPO; de observações e análises documentais realizadas neste último período, recorrendo aos dispositivos tecnológicos de que dispomos e de um inquérito não probabilístico promovido por uma organização de Professores de Artes Performativas Autogeridas recentemente criada na cidade, cujo desenho, processamento e análise os dados ficaram a cargo de um dos autores deste artigo. Colocamos tudo isso em diálogo com a bibliografia relacionada ao tema do trabalho em geral e do trabalho artístico em particular.; In this article, we will address the case of the independent theater in La Plata (Buenos Aires, Argentina) to describe and analyze how the crisis produced by the COVID 19 pandemic and the Preventive and Obligatory Social Isolation (ASPO) national government decree, impacted on the processes of identifying theaters as workers, their collective organization to face the emergency and their relations of articulation and demand concerning the State agencies dedicated to the promotion and protection of culture. The work emerges as part of two parallel and dialogical investigations that address problems surrounding artistic work in La Plata within the last five years. The data that we analyze in this case comes from the fieldwork carried out before the ASPO; from observations and documentary analysis made in this last period, using the technological devices that we have at our disposal, and from a non-probabilistic survey promoted by an organization of Teachers of Self-Managed Performing Arts recently created in the city, whose design, processing and data analysis were in charge of one of the authors of this article. We have put all this into dialogue with the bibliography related to labor issues in general and artistic work in particular.

Usos y apropiaciones de TICs desde la subalternidad: El COVID19 y la gestión del IFE; Uses and appropriations of ICTs from subalternity: COVID19 and the management of the IFE Noscue Mera, Eliana En este artículo se consigna avances investigativos en torno a los usos y apropiaciones de TICs por parte de los habitantes del barrio periférico Villa Castells, La Plata, BsAs; en relación a las gestiones que tuvieron que adelantar para obtener 0el Ingreso Familiar de Emergencia (IFE) decretado por el Estado Nacional Argentino ante la contingencia del COVID-19 durante el primer semestre del 2020. Los antecedentes teóricos incorporados, devienen de hallazgos y continuidades propuestos en el marco de un recorrido posdoctoral, desde donde se reconocen diferentes niveles de exclusión de lo transmediático como un entramado sistemático entre lo tecnológico, político-económico y sociocultural histórico al interior de grupos sociales particulares. La “Alfabetización Transmediática Situada” (Noscué, 2019) es una composición conceptual como base para interpretar y analizar comunicacional y socio antropológicamente las experiencias de este grupo social y las diligencias digitales que debieron adelantar para obtener el IFE. Además, se incorporan otros conceptos como son Usos y Apropiaciones de Tics, Subalternidades Históricas y Desigualdades. El desarrollo metodológico priorizó las indagaciones desde un enfoque Etnográfico Digital adecuado al cumplimiento del Aislamiento Social Preventivo Obligatorio y (ASPO), es decir, que el acercamiento al proceso se logró a través de diferentes vías comunicacionales. Los hallazgos preliminares se ubican en torno a las desigualdades reconocidas en la problemática delimitada, las tácticas individuales y colectivas implementadas por los actores sociales participes en los procesos de gestión.; In this article, investigative advances are recorded on the uses and appropriations of ICTs by the inhabitants of the peripheral neighborhood Villa Castells, La Plata, BsAs; in relation to the steps they had to take to obtain the Emergency Family Income (IFE) decreed by the Argentine National State in the face of the contingency of COVID-19 during the first semester of 2020. The theoretical background incorporated comes from findings and proposed continuities within the framework of a postdoctoral journey, from which different levels of exclusion of the transmedia are recognized as a systematic framework between the technological, political-economic and historical socio-cultural within particular social groups. The “Situated Transmedia Literacy” (Noscué, 2019) is a conceptual composition as a basis for interpreting and analyzing communicationally and socio-anthropologically the experiences of this social group and the digital procedures that they had to carry out to obtain the IFE. In addition, other concepts such as ICT Uses and Appropriations, Historical Subalternities and Inequalities are incorporated. The methodological development prioritized the inquiries from a Digital Ethnographic approach appropriate to the fulfillment of Mandatory Preventive Social Isolation and (ASPO), that is, the approach to the process was achieved through different communication channels. The preliminary findings are located around the inequalities recognized in the defined problem, the individual and collective tactics implemented by the social actors participating in the management processes.

Molecular phylogenetics of Doraditos (Aves, Pseudocolopteryx ): Evolution of cryptic species, vocal and mechanical sounds Jordan, Emilio Ariel; Tello, José G.; Benitez Saldivar, Maria Juliana; Areta, Juan Ignacio While bird vocalizations (produced by the syrinx) have been the focus of countless studies, mechanical sounds (produced by external body structures) have received much less attention. In particular, the evolutionary interplay between these two modes of acoustic communication remains largely unstudied. Here, we present the first species-level molecular phylogeny of the doraditos (Pseudocolopteryx), reconstruct the evolutionary history of acoustic vocal and non-vocal characters, elucidate their relationship to feather modifications and aerial displays, and explore the influence of acoustics in the speciation of cryptic species. Our well-resolved phylogeny using four genes (ND2, COI, MB and ODC), recovered the monophyly of Pseudocolopteryx, resolving the relationships among its five species: ((((P. sclateri) P. acutipennis) P. dinelliana) P. citreola, P. flaviventris). Repetition and translocation of acoustic elements were commonplace in the evolution of Pseudocolopteryx. Songs were composed of introductory syllables and a final flourish. Bill-snapping sounds of P. sclateri were functionally homologous to introductory vocal syllables of the other species. The song of P. dinelliana evolved to high levels of complexity and repetition and is the syntactically most complex song in Pseudocolopteryx (and perhaps in the Tyrannidae). Aerial displays, mechanical wing sounds and modifications of primary feathers coevolved in three species: P. sclateri, P. acutipennis and P. dinelliana. Wing sounds documented for P. acutipennis and P. dinelliana differed markedly, and their production mechanisms might differ. The two cryptic and sibling species P. flaviventris and P. citreola diverged ∽60,000 Ya were not reciprocally monophyletic and are a case of extremely rapid evolutionary acoustic differentiation with morphological stasis.

Dinámica espacio-temporal de usos del suelo en sistemas ecológicos de la región pampeana austral, Argentina: Agriculturización en el Partido de Tandil; Space-Temporal Dynamics of Land Use in Ecological Systems in the Southern Pampean Region, Argentina: Agriculturization in Tandil Country; Dynamique spatio-temporaire de l'utilisation des terres dans les sistèmes écologiques de la region du sud de pampean, Argentine: Agriculturation dans le Parti Tandil Somoza, Ailin; Vazquez, Patricia Susana; Zulaica, Maria Laura; Sacido, Monica Benita El proceso de agriculturización, como caso particular y frecuente de cambio en el uso de la tierra, es uno de los propulsores del Cambio Global y causante de transformaciones ambientales. Los sistemas ecológicos de la Región Pampeana Austral han sufrido radicales cambios en sus usos del suelo cuyas externalidades no fueron consideradas. Surge como objetivo analizar los cambios en el uso del suelo en un Partido representativo de la región (Tandil) a fin de dar cuenta de la dinámica del proceso de agriculturización en los diferentes sistemas ecológicos que lo caracterizan. Se analizan las transformaciones acontecidas en 1989 - 2004 - 2019. Se obtuvieron imágenes satelitales corregidas radiométricamente, se realizaron clasificaciones supervisadas y relevamientos de campo. El proceso de agriculturización se confirma particularmente en el sistema ecológico de Llanura periserrana y recientemente en las Serranías y Planicie distal. Se enfatiza en la necesidad de generar propuestas de gestión ambiental tendientes al desarrollo de agroecosistemas sostenibles.; The agriculturization as particular process of change in the use of land is one of the drivers of the Global Change and consequently it causes environmental transformations. The ecological systems of the Southern Pampean Region have undergone radical changes in their land uses whose externalities were not considered. The aim is to analyze the changes in land use in a representative Country of the region (Tandil) in order to account for the dynamics of the agricultural process in the different ecological systems that characterize it. Were analyzed the transformations that took place in 1989 – 2004 - 2019 when the production patterns reflect the general trends of the region. Three satellite images were obtained and were radiometrically corrected. Then, supervised classifications were carried. The process of agriculturization is particularly confirmed in the ecological system of the Rolling Plain and recently in the Hills and Depressed Plain. It emphasizes the need to generate environmental management proposals aimed at the development of sustainable agroecosystems.; L'agriculturización en tant que processus particulier de changement dans l'utilisation des terres est l'un des moteurs du changement global et, par conséquent, provoque diverses transformations de l'environnement. Les systèmes écologiques de la région du sud de la Pampée ont subi des changements radicaux dans leurs utilisations des terres, dont les externalités n'ont pas été prises en compte. L'objectif est d'analyser les changements d'utilisation des terres dans un parti représentatif de la région (Tandil) afin de rendre compte de la dynamique du processus agricole dans les différents systèmes écologiques qui le caractérisent. Les transformations qui se sont produites en 1989 - 2004 - 2019 sont analysées. L'agriculturización est particulièrement confirmé dans le système écologique de la Plaine Periserrana et récemment dans les Serranías et Plaines Distales. Il souligne la nécessité de générer des propositions de gestion environnementale visant au développement d'agroécosystèmes durables.

Devulcanization of natural rubber industry waste in supercritical carbon dioxide combined with diphenyl disulfide Asaro, Lucía; Gratton, Michel; Poirot, Nathalie; Seghar, Said; Ait Hocine, Nourredine The elimination of rubber wastes without affecting the environment is one of the most important challenges of the 21st century waste management. Accordingly, the present work is focused on the recycling of natural rubber (NR) industry waste by means of devulcanization in supercritical carbon dioxide (scCO2) atmosphere. With that aim, a novel device allowing to perform rubber devulcanization was developed. It consists of a triaxial compression reactor integrated into a dynamic hydraulic universal testing machine with a heating chamber. NR industry waste was devulcanized in the mentioned device at different temperatures, in scCO2 by using diphenyl disulfide (DD) as devulcanizing reagent. The devulcanization degree and quality of the treated materials were evaluated by the swelling test combined with the Horikx theory. It was appeared that a successful devulcanization, with almost no degradation, was obtained, and the devulcanization degree reached maximum value of ~90%. Thermogravimetric tests and scanning electron microscopy (SEM) images strengthened these results. Finally, it was concluded that the developed device is appropriate to perform rubber recycling, which contributes to the progress in the environmental protection.

Dielectric and ferroelectric properties evolution of (1−x)(Bi0.5Na0.5TiO3)–xK0.5Na0.5NbO3 piezoceramics Prado Espinosa, Fabiola Andrea; Rubio Marcos, Fernando; Ramajo, Leandro Alfredo; Castro, Miriam Susana In this work, piezoceramics of (1-x)(Bi0.5Na0.5)TiO3-x(K0.5Na0.5)NbO3, (1-x)BNT-xKNN, composition with x=0.01, 0.02, 0.03, 0.04, 0.05, 0.06 and 0.07 were prepared by a mechanochemically activated solid-state method. The structural phase formation and microstructural, dielectric and ferroelectric properties were studied. Although changes, in symmetry of the perovskite structure, were not detected with the composition (that is, from a perspective of its intrinsic properties), the microstructural evolution was strongly dependent on the content of the KNN phase (that is, based on its extrinsic properties). Specifically, KNN favoured the formation of a microstructure with cubic grains, typical morphology of the alkaline niobate ceramics. After KNN addition, both the maximum permittivity temperature and the long-range to short-range ordered transition temperature were reduced. Additionally, ferroelectric loops and strain deformation curves also reflect the long-range to short-range order evolution with KNN addition and temperature.

Conduction mechanisms in epitaxial NiO/Graphene gas sensors Niavol, Somayeh Saadat; Budde, Melanie; Papadogianni, Alexandra; Heilmann, Martin; Moghaddam, Hossain Milani; Aldao, Celso Manuel; Ligorio, Giovanni; List-Kratochvil, Emil J.W.; Lopes, Joao Marcelo J.; Barsan, Nicolae; Bierwagen, Oliver; Schipani, Federico Integrated, highly sensitive and reversible sensor devices for toxic and hazardous gases in environmental pollution monitoring can be realized with graphene-based materials. Here we show that, single layer graphene grown on SiC can be utilized to implement sensor devices being extremely sensitive towards NO2 showing an n-type response. A second type of sensor with an added NiO layer on top of the single layer graphene changed its response to p-type but did not reduce its sensitivity. We show that the conduction switch from n-type to p-type was not a consequence of an alteration of the graphene layer but is found to be an effect of the NiO layer. We find that the NiO leads to lowering of the Fermi level to a point that a crossing of the Dirac Point in the graphene switched the conduction type. These sensors were tested in the 100 ppb NO2 regime, showing good response and a detection limit extrapolated to be below 1 ppb. This new NiO/graphene/SiC configuration can be an attractive p-type sub-ppb sensor platform for NO2 and related gases.

Cincuenta años de la primera ley de Tobler: revisión de sus aportes teóricos y prácticos a la ciencia geográfica Celemin, Juan Pablo En el año 2020 se cumplen cincuenta años de la enunciación de la Primera Ley en Geografía o la Primera Ley de Tobler que ha realizado importantes aportes tanto en los aspectos teóricos como prácticos de la disciplina geográfica. Su aparición ha generado amplios debates conceptuales en la Geografía que continúan hasta la actualidad. Es innegable la importancia de este principio en el desarrollo de los Sistemas de Información Geográfica y en la autocorrelación espacial. En este marco el presente trabajo resalta la importancia del tema a partir de una rigurosa revisión bibliográfica que rescata los dichos de los investigadores directamente involucrados en el tema, lo contextualiza temporal y conceptualmente y destaca su significancia en la discusión teórica de la Geografía y en su parte práctica, en particular con la autocorrelación espacial y en los SIG.

Spontaneous formation of unilamellar vesicles based on the surfactant 1-methylimidazolium bis-(2-ethylhexyl) phosphate, evaluated as a function of pH and in saline solution Andrada, Heber Eduardo; Silva, Oscar Fernando; Morales, Gustavo Marcelo; Correa, Nestor Mariano; Falcone, Ruben Dario In this work, we report the formation of unilamellar vesicles in water based on the protic ionic liquid-surfactant 1-methylimidazolium bis-(2-ethylhexyl) phosphate (imim-DEHP) explored under different experimental conditions (surfactant concentration, pH and ionic strength). Surface tension measurements were made depending on the surfactant concentration at different pHs and in saline solution. The size of the vesicles was measured by dynamic light scattering (DLS) and images of the systems were obtained by atomic force microscopy (AFM). Our results showed that the surfactant self-assembled forming spontaneously vesicles at different pHs (from 2–8) and in saline solution. The vesicle formation, especially at pH ≥ 4, is independent of the imim-DEHP concentration and the ionic strength of the medium used, which demonstrates great stability in the systems formed. When the pH is lower than the pKa of the polar head group, the surfactant produces very large polydisperse aggregates, which is due to an agglomeration of smaller vesicles. Very interesting is that the dependence of the vesicle size with the pH value is reversible therefore, this system could be used as drug delivery under different conditions. In addition to this, imim-DEHP vesicles were coated with chitosan to improve biocompatibility and avoid possible effects of cytotoxicity of these systems. In summary, imim-DEHP is a promising surfactant to be used in biological applications, for example as a nanocarrier for the incorporation of bioactive compounds into living organisms.

Decrease in the occurrence of the South American fur seal (Arctocephalus australis) in San Matías Gulf after a sudden episode of reoccupation; Disminución en la ocurrencia del lobo marino sudamericano Arctocephalus australis en el Golfo San Matías después de un episodio repentino de reocupación Bartés, Saia Nahir; Svendsen, Guillermo Martin; Romero, Maria Alejandra; González, Raúl Alberto The colonies of South American fur seals,Arctocephalus australis (SAFS), are currently experiencing population recovery, and as a consequence many coastal areas have been reoccupied. These areas are often haul-out sites used by SAFS for resting during the post-reproductive (winterly) season, andmay be playing a key role in the population recovery process since they seem to be located close to winter feeding areas that are far from the breeding colonies. This study reports on the trend in abundance of SAFS in a recently reoccupied winter area, the San Matías Gulf (SMG). The trend was evaluated with generalized linear models between 2007 and 2017 in two sectors of the SMG, Islote Lobos, the only rookery of this species in the area, and the northwest marine area of the gulf. Both sectors showed a negative trend. For Islote Lobos, the best selected models estimated a mean annual rate between -12.2% and -17.6%, and for the northwest area, between -19.02% and -29.9%. The population context suggests that most SAFS observed in 2007 may have been selecting other habitats over the following years; however, simultaneous censuses throughout their distribution range are needed in order to understand the redistribution and recolonization processes.; Las colonias del lobo marinode dos pelos sudamericano, Arctocephalus australis(SAFS), están experimentando una recuperación poblacional y como consecuencia muchas áreas costeras han sido reocupadas nuevamente. Muchas de estas áreas son apostaderos utilizados por los SAFS para descansar durante la temporada post-reproductiva (invernal). Las mismas pueden estar jugando un papel clave en el proceso de recuperación ya que estarían ubicadas cerca de áreas de alimentación invernales que se encuentran distantes de las colonias reproductivas. El presente estudio reporta la tendencia en la abundancia de SAFS en un área invernal recientemente ocupada, el Golfo San Matías (GSM). La tendencia se evaluó con modelos lineales generalizados entre los años 2007 y 2017 para dos sectores del golfo: el Islote Lobos, el único apostadero de esta especie, y el área marina del noroeste del golfo. Ambos sectores mostraron una tendencia negativa. Para el Islote Lobos, los modelosseleccionados estimaron una tasa promedio anual entre -12.2% y -17.6%, y para el área marina noroesteentre -19.02% y -29.9%. El contexto a nivel poblacional sugiere que la mayoría de los SAFS observados en 2007 pueden haber seleccionado otros hábitats durante los siguientes años. Sin embargo, para comprender los procesos de redistribución y recolonización se necesitan censos simultáneos en todo su rango de distribución.

Silencios y pandemia Lavagnino, Nicolas Jose; Lamberti, Matias; Grupo de Filosofía de la Biología ¿Qué dice un silencio? En la canción Necesito de Sui Generis, la flauta y el piano de las primeras estrofas dan lugar a la voz de un Nito Mestre que hasta el undécimo compás permanece en silencio, aunque no ausente. Un Charly García ansioso y aga- zapado aguarda su momento para ingresar en el compás diecinueve. En el tiempo que dura la canción, voces como las de Nito y Charly cantan y callan, alternándose con la de otros instrumentos. En la partitura se indican unos y otros; sonidos y silencios como cara y contracara de la expresión artística. Lo interesante de la obra musical es que ninguna voz o instrumento desaparece de la partitura al silenciarse, sino que simplemente permanece en potencia a la espera de otros compases. La presencia incontestable de los silencios en la música los convierte en elementos ineludibles a la hora de explicar, comprender y ejecutar la totalidad de cualquier pieza musical. Resulta que, sin embargo, por fuera de la música, los silencios pueden no ser una contribución positiva a la comprensión de un todo complejo. Sobre esto y a propósito de los tiempos extraños de pandemia que nos tocan vivir trata el presente texto colectivo. Como ya deja entrever esta breve introducción, el trabajo surge de la convicción de que la reflexión acerca de la actual crisis y su administración al igual que la ejecución de una pieza musical? depende también de los silencios involucrados.

Invasive ascidians: How predators reduce their dominance in artificial structures in cold temperate areas Giachetti, Clara Belen; Battini, Nicolás; Castro, Karen Lidia; Schwindt, Evangelina Artificial structures can provide suitable space for invasive species through a colonisable surface and refuge against predators. Besides several physical factors, invasive species can present different colonization success and dominance on structures that are connected to the sea floor (i.e. fixed) compared to structures that are suspended, depending on the differential predation pressure that affect both structures. Benthic and nektonic predators can reach fouling communities on fixed structures, while only nektonic predators can affect communities growing on suspended structures, depending on the distance to the sea floor. Only few studies tested both communities of predators at the same time in different artificial structures. In this study, we evaluated the effect of benthic and nektonic predators on the cover, composition and diversity on fouling communities and on the dominance of invasive ascidians on these communities, in two different types of artificial structures. We performed an experiment in the port area of Puerto Madryn (Southwestern Atlantic, Argentina) to compare the fouling community development between fixed and suspended structures and among different predator exclusion treatments. Results showed that benthic predators exerted a higher predation pressure than nektonic predators on the cover, composition and diversity of the fouling communities. In the absence of benthic predators, and even where nektonic predators were not excluded, communities were greatly dominated by two invasive ascidians, Ascidiella aspersa (Müller, 1776) and Ciona robusta Hoshino and Tokioka, 1967. Our results suggest that in this type of cold temperate ports, fouling organisms find refuge from benthic predators growing on suspended structures, where nektonic predators exert low predation pressure. We propose that, since benthic predators in temperate latitudes have an essential role decreasing invasive ascidians dominance and the cover of fouling communities, future studies should consider both predator communities, i.e. nektonic and benthic, in experimental designs performed to test biotic resistance and predation pressure.

Measurements and modeling of snow albedo at Alerce Glacier, Argentina: effects of volcanic ash, snow grain size and cloudiness Gelman Constantin, Julián; Ruiz, Lucas Ernesto; Villarosa, Gustavo; Outes, Ana Valeria; Bajano, Facundo N.; He, Cenlin; Bajano, Héctor; Dawidowski, Laura Elena The relevance of light absorbing impurities in snow albedo (and its effects in seasonal snow or glacier mass balance) have been under study for several decades. However, the effect of volcanic ash has been much less studied, and most articles studied only the effect of thick layers after direct deposition. There is also a knowledge gap in field measurements of seasonal snow and glaciers of the southern Andes, that only recently has started to be filled.We present here the first field measurements on Argentinian Andes, combined with albedo and mass balance modeling activities.Measured impurities content (1.1mgkg−1 to 30000 mgkg−1) varied abruptly in snow pits and snow/firn cores, due to high surface enrichment during ablation season and possibly local/regional wind driven resuspension and redeposition of dust and volcanic ash. In addition, we observed a high spatial hetereogeneity, due to seasonality, glacier topography and prevailing wind direction. Microscopical characterization showed that the major component was ash from recent Calbuco (2015) and Cordón Caulle (2011) volcanic eruption, with 10 minor presence of mineral dust and Black Carbon. We also found a wide range of measured snow albedo (0.26 to 0.81), whichreflected mainly the impurities content and the snow/firn grain size (due to aging). SNICAR model has been updated to model snow albedo taking into account the effect of cloudiness on incident radiation spectra, improving the match of modeled and measured values. We also ran sensitivity studies on the main measured parameters (impurities content and composition, snow grain size, layer thickness, etc) to assess which field measurements precision can improve the uncertainty of albedo modeling. Finally, we studied the impact of these albedo reductions in Alerce glacier using a spatially distributed surface mass-balance model. We found a large impact of albedo changes in glacier mass balance, and we estimated that the effect of observed ash concentrations can be as high as a 1.25mwe decrease in the glacier-wide annual mass balance (due to a 34 % of increase inthe melt during the ablation season).