Functional groups and common pyrolysate products of Odontopteris cantabrica (index fossil for the Cantabrian Substage, Carboniferous)
Zodrow, Eewin L; D`angelo, José Alejandro; Helleur, Robert; Simunek, Zbynek
Foliage of the tree-fern Odontopteris cantabrica (Order: Medullosales) is considered a reliable plant-fossil index for the Cantabrian Substage (Carboniferous, 306 Ma). Compared are two preservation states from Canada (fossilized cuticles) and the Czech Republic (compression-cuticles), representing relatively uncommon and common preservation states, respectively. The main objective is deriving spectrochemical parameters for refining the taxonomic circumscription of the species. For the comparison, five sample categories (fossilized-cuticle, macerated fossilized-cuticle, compression, cuticle, and alkaline solution) are analyzed by methods of Fourier transform infrared (FTIR) spectroscopy, complemented by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) for the Canadian sample. Variation of FTIR data in the latter sample is explained by the geochemical model for the formation of fossilized-cuticles by natural maceration.As a result, we propose a set of semi-quantitative FTIR ratios (spectral regions 1800-1000 cm-1 and 3000-2800 cm-1) as spectrochemical-taxonomic parameters for the index fossil: CH2/CH3, Al/Ox, C=O/C=C, C=O cont, Ar/Al and Ar/C=C. They contain molecular structural information related to aliphatic, aromatic and oxygen-bearing moieties. As expected, small overall spectrochemical differences occur, given converging preservation states, or similar fossilization trends for the cantabrica-plant inhabiting the Variscan Forelands of the ancestral Canada-Czech geographical regions. Some chemical differences occurred due to preservations in the sample categories (i.e., fossilized-cuticle and compression) with the oxygen-bearing structures, the length and branching of polymethylenic side chains and aromatic structures. A biomacropolymeric structure is confirmed by Py-GC/MS, and deduced for the Czech sample from the higher CH2/CH3 ratios.
Digestión anaeróbica mesofílica de la fracción orgánica de residuos sólidos domiciliarios. Reactor de alimentación semicontinua
Bres, Patricia; Beily, María Eugenia; Crespo, Diana
Este trabajo se enfocó en el monitoreo de un reactor anaeróbico semicontínuo, alimentado a velocidad de carga constante (VC= 1,1 kgSV m-3d-1), con la fracción orgánica de residuos sólidos domiciliarios y restos de verdulería durante 12 meses. Para ello se midió la producción de biogás y se analizaron en el efluente diferentes variables físicoquímicas y los indicadores de estabilidad (IE): alcalinidad parcial/total (AT) y ácidos grasos volátiles/AT. El rendimiento de biogás fue de 112 lkgSV-1en condiciones normales de temperatura y presión (CNPT), resultando este valor menor al obtenido con otros sustratos en el mismo reactor. Los IE mostraron un buen desarrollo del proceso anaeróbico durante todo el ensayo. Además, los porcentajes de remoción del 77% y 47,5% para la demanda química de oxígeno (DQO) y sólidos volatiles (SV) respectivamente, indicaron una eficiente degradación de la materia orgánica. Sin embargo los altos valores de DQO en el efluente, muestran la necesidad de ser tratado antes de su descarga.
Participación de los inmigrantes bolivianos en espacios específicos de la producción hortícola argentina; Migrations, Work and Agricultural Global Chains
Benencia, Roberto Rodolfo
La horticultura en fresco en la Argentina ha sido producida históricamente por mano de obra migrante; fuera ésta europea durante las primeras décadas del siglo XX o bien limítrofe a inicios del siglo XXI. En la actualidad, podría afirmarse que la corriente migratoria proveniente de Bolivia cuasi hegemoniza no sólo la oferta de mano de obra en dicha producción en casi todos los cinturones verdes del país, sino que, además, en algunos nichos clave domina los eslabones más importantes de esta cadena agroalimentaria. Desde finales del siglo XX e inicios del XXI, los inmigrantes bolivianos, apoyándose en la tradición de la inmigración europea, están hoy ejerciendo el predominio en la producción y en la comercialización de la horticultura en fresco. Si bien en otras provincias se registra la incorporación temprana de los inmigrantes bolivianos a la horticultura en el interior del país antes de los ’80 -cuando se detecta su llegada a Buenos Aires-, podría decirse que es a partir de esta última fecha que el fenómeno se generaliza y se expande, y en los últimos años -particularmente a partir de la crisis económico-social del 2002- se puede apreciar un fuerte avance de estas familias sobre el eslabón comercial de la cadena agroalimentaria de esta producción. En este trabajo se procurará describir el proceso histórico que posibilitó la ocurrencia del fenómeno a partir de la constitución de enclaves étnicos en distintos territorios hortícolas de la Argentina.; Fresh horticulture in Argentina has historically been produced by immigrant labor, from European countries during the first decades of the twentieth century or from borderline countries at the beginning of XXI century. At present, it could be argued that the migratory flow from Bolivia quasi hegemonizes not only the supply of labor in this production in almost all the green belts of the country, but also in some key niches dominates the most important links the food chain. Since the late twentieth and early twenty-first Bolivian immigrants, drawing on the tradition of European immigration, are now exerting dominance in the production and marketing of fresh horticulture. While other provinces have recorded the early incorporation of Bolivian immigrants in horticulture at the interior of the country before the ‘80s, when it detects its arrival in Buenos Aires, it can be argued that from the latter date the phenomenon is widespread and growing, and in recent years, particularly from the economic-social crisis of 2002, we can see a strong development of these families on the commercial link in the food chain of this production. In this paper we attempt to describe the historical process that allowed the occurrence of the phenomenon based on the formation of ethnic enclaves in different territories horticultural Argentina.
The Alternative Epac/cAMP Pathway and the MAPK Pathway Mediate hCG Induction of Leptin in Placental Cells
Maymo, Julieta Lorena; Pérez Pérez, Antonio; Maskin, Bernardo; Dueñas, José Luis; Calvo, Juan Carlos; Sánchez Margalet, Víctor; Varone, Cecilia Laura
Pleiotropic effects of leptin have been identified in reproduction and pregnancy, particularly in the placenta, where it works as an autocrine hormone. In this work, we demonstrated that human chorionic gonadotropin (hCG) added to JEG-3 cell line or to placental explants induces endogenous leptin expression. We also found that hCG increased cAMP intracellular levels in BeWo cells in a dose-dependent manner, stimulated cAMP response element (CRE) activity and the cotransfection with an expression plasmid of a dominant negative mutant of CREB caused a significant inhibition of hCG stimulation of leptin promoter activity. These results demonstrate that hCG indeed activates cAMP/PKA pathway, and that this pathway is involved in leptin expression. Nevertheless, we found leptin induction by hCG is dependent on cAMP levels. Treatment with (Bu)2cAMP in combination with low and non stimulatory hCG concentrations led to an increase in leptin expression, whereas stimulatory concentrations showed the opposite effect. We found that specific PKA inhibition by H89 caused a significant increase of hCG leptin induction, suggesting that probably high cAMP levels might inhibit hCG effect. It was found that hCG enhancement of leptin mRNA expression involved the MAPK pathway. In this work, we demonstrated that hCG leptin induction through the MAPK signaling pathway is inhibited by PKA. We observed that ERK1/2 phosphorylation increased when hCG treatment was combined with H89. In view of these results, the involvement of the alternative cAMP/ Epac signaling pathway was studied. We observed that a cAMP analogue that specifically activates Epac (CPT-OMe) stimulated leptin expression by hCG. In addition, the overexpression of Epac and Rap1 proteins increased leptin promoter activity and enhanced hCG. In conclusion, we provide evidence suggesting that hCG induction of leptin gene expression in placenta is mediated not only by activation of the MAPK signaling pathway but also by the alternative cAMP/Epac signaling pathway.
Determinación de un coeficiente térmico desconocido a través de una sobre-condición convectiva en el borde fijo
Tarzia, Domingo Alberto
Se usa el modelo de región pastosa de Solomon-Wilson-Alexiades (Letters Heat Mass Transfer, 9 (1982), 319- 324) y el método dado en Tarzia (Int. J. Heat Mass Transfer, 26 (1983), 1151-1157; Int. Comm. Heat Mass Transfer, 14 (1987), 219-228) para la determinación de un coeficiente térmico desconocido de un material semi-infinito a través de un proceso de cambio de fase con una sobre-condición convectiva en el borde fijo. Se encuentran fórmulas para los seis coeficientes desconocidos y la condición necesaria y suficiente para la existencia de la solución.; We use the Solomon-Wilson-Alexiades’ mushy zone model (Letters Heat Mass Transfer, 9 (1982), 319-324) and the method given in Tarzia (Int. Heat Mass Transfer, 26 (1983), 1151-1157; Int. Comm. Heat Mass Transfer, 14 (1987), 219-228) for the determination of one unknown thermal coefficient of a semi-infinite material through a phase-change process with an overspecified convective boundary condition on the fixed face. We also find formulas for the six unknown coefficients, and the necessary and sufficient condition for the existence of the solution.
Inversion of prestack seismic data using FISTA
Perez, Daniel Omar; Velis, Danilo Ruben; Sacchi, Mauricio Dino
In this work we present a new inversion method to obtain AVA high-resolution attributes from prestack seismic data. The method aims to find a series of sparse reflectors that, when convolved with the source wavelet, fit the observed data. To perform the inversion, we propose the use of the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA). FISTA, which can be viewed as an extension of the classical gradient algorithm, provides sparse solutions minimizing both the misfit between the modeled and the observed data, and the l1-norm of the solution. The advantage of FISTA over other methods is that no inversion over any matrix is needed, making it numerically stable, easy to apply, economic in computational terms, and adequate for solving large-scale problems even with dense matrix data. Results on synthetic and field data show that the proposed method is capable to provide high-resolution AVA attributes that honor the observed data under noisy conditions, making it an interesting alternative to other known methods.
The Socio-Historical Construction of Corruption: Examples from Police, Politics and Crime in Argentina
Miguez, Daniel Pedro
This paper proposes that corruption results from particular historical and social conditions. Specifically, it sustains that the stability and credibility of a society’s institutional system, the perception of a shared fate by most members of society, the levels of inequality and the perception of fair opportunities for personal progress are all elements that may deter or promote corruption. In order to show the association between these social conditions and corruption we analyse socially and historically the way that state agents such as the police, members of the judiciary and the political system relate to each other and to normal citizens. Although the examples are taken from the argentine context, they constitute a tool to understand, heuristically, why corruption is prominent in many parts of the underdeveloped world.
Physiological and biochemical responses to drought stress and subsequent rehydration in the symbiotic association peanut-Bradyrhizobium sp
Furlan, Ana Laura; Llanes, Analia Susana; Luna, Maria Virginia; Castro, Stella Maris
Drought stress is one of the most important environmental factors that regulate plant growth and development and limit its production. Peanut (Arachis hypogaea L.) is an agriculturally valuable plant with widespread distribution in the world serving as a subsistence food crop as well as a source of various food products. The aims of this work were to evaluate growth and nodulation as well as some physiological and biochemical stress indicators in response to drought stress and subsequent rehydration in the symbiotic association peanut-Bradyrhizobium sp. SEMIA6144. Drought stress affected peanut growth reducing shoot dry weight, nodule number, and dry weight as well as nitrogen content, but root dry weight increased reaching major exploratory surface. Besides, this severe water stress induced hydrogen peroxide production associated with lipid and protein damage; however, the plant was able to increase soluble sugar and abscisic acid contents as avoidance strategies to cope with drought stress. These physiological and biochemical parameters were completely reversed upon rehydration, in a short period of time, in the symbiotic association peanut-Bradyrhizobium sp. Thus, the results provided in this work constitute the initial steps of physiological and biochemical responses to drought stress and rehydration in this nodulated legume.
Milicias y fronteras en la formación del Estado argentino: la regulación de la Guardia Nacional de Buenos Aires (1852-1880)
Literas, Luciano
El artículo analiza la normativa de la Guardia Nacional entre 1852 y 1880, con el propósito de explorar la complejidad de su desarrollo de acuerdo a las disputas facciosas entorno al proyecto nacional y el avance de la frontera sobre los territorios indígenas en el contexto de organización y consolidación del Estado argentino. Sin el poder suficiente para monopolizar el poder coercitivo, el gobierno nacional debió depender de la capacidad de convocatoria militar de los gobiernos locales. Así se instauró y adquirió relevancia la Guardia Nacional formada por campesinos y vecinos domiciliados obligados a realizar ejercicios militares de forma regular y listos para acudir a todo llamado, so pena de cumplir servicio en el Ejército de Línea. Esto se sitúa en la dinámica general de progresiva dominancia del Estado como forma de integración socio política, mediante la apropiación de ámbitos funcionales en los diversos planos de la interacción social y que hacia finales del período de estudio implicó la sustitución del marco institucional provincial como principal eje articulador de relaciones sociales y la subordinación de la Guardia Nacional al Estado nacional. Los principales documentos utilizados fueron las leyes y decretos en materia militar elaborados entre 1852 y 1880, los diarios de sesiones del Congreso nacional entre 1862 y 1874 y las memorias del ministerio de Guerra y Marina entre 1868 y 1881.; The article discusses the National Guards rules between 1852 and 1880, in order to explore the complexity of their evolution, according to factional conflicts about the national political project and the ocuppation of indigenous territories. Without the capacity to monopolize coercive power, the national government depended on the local goverments military deployments. Thus the National Guard was established with peasants forced to do military exercises and ready to go to every call, under the penality of being sent to the border army. This happened during the gradual supremacy of the national state in social and political integration and that meant for one hand the replacement of the local frameworks as the hub of social relations and for other hand the National Guard subordination. The main documents used were the military laws and decrees between 1852 and 1880, the diaries of the national Congress sessions between 1862 and 1874, and the reports of the War and Marine department between 1868 and 1881.
Integración de los paneles de vuelo del satélite Cubebug-1
Bolzi, Claudio Gustavo; Bruno, C. J.; Cabot, P.; Carella, E.; Di Santo, J.; Duran, Julio Cesar; Fernández Vázquez, J.; Godfrin, Elena María; Goldbeck, V.; Gonzalez, L.; Moglioni, A.; Muñoz, S.; Olima, José María; Plá, Juan Francisco Esteban; Perez, J. I.; Raggio, D.; Socolovsky, Hernan Pablo; Tamasi, Mariana Julia Luisa
Se describe la integración de los paneles de vuelo de la misión satelital CUBEBUG-1. Éstos se integraron a partir de un convenio firmado entre la CNEA y la empresa DISARMISTA SRL para la integración de 6 módulos solares de esta misión satelital. Los paneles están constituidos por 3 módulos con 2 subcadenas conectadas en serie y 3 módulos de una subcadena cada uno Estos módulos se realizaron con celdas de de triple juntura (ATJ) marca EMCORE de descarte Se presentan los parámetros eléctricos más relevantes de las celdas utilizadas y las verificaciones funcionales que se realizaron luego de la integración de los paneles.; The integration of flight solar panels of CUBEBUG-1 satellital mission is presented. This panels has been integrated from a agreement between CNEA and DISARMISTA SRL for the integration of 6 flight solar panels for CUBEBUG-1 satellital mission. The panels integration has been done using substrings of 2 solar cells connected in series, the cells used was from EMCORE advance triple junction (ATJ) non flight solar cells. The panels itself, are constituted for 3 modules with 2 substrings connected in series and 3 modules with one substring each one. The solar cells relevant electrical parameters and the curves of functional verifications after the integration are presented.
Geografía y Sistemas de Información Geográfica (SIG) en la escuela secundaria: reflexiones y propuestas para el trabajo en las aulas de la República Argentina
Buzai, Gustavo Daniel; Baxendale, Claudia Alicia; Cacace, Graciela Patricia; Humacata, Luis Miguel; Caloni, Nicolas; Cruz, María del Rosario
Con el inicio del siglo XXI la dimensión espacial ha cobrado particular importancia al momento de analizar y comprender el mundo que nos rodea. El desarrollo tecnológico actual ha posibilitado la aparición de las denominadas Tecnologías de la Información Geográfica (TIG) que llevan a configurar el marco de vínculos globales basados en el formato digital, en el cual la tecnología de los Sistemas de Información Geográfica (SIG) ocupa una posición destacada. El presente trabajo analiza la potencialidad que presentan los SIG como sustento aplicativo de la geografía en el aula y como herramienta fundamental que contribuye a apoyar el desarrollo de la inteligencia espacial de los alumnos. Para lograrlo se considera al SIG en su papel aplicativo que apoya una revolución tecnológica (métodos y técnicas) y una revolución intelectual (teoría y epistemología). En este sentido se analiza su surgimiento como resultado del desarrollo científico-tecnológico, los paradigmas geográficos que le brindan sustento, la formación docente necesaria para utilizarlos y los conceptos fundamentales del análisis espacial. El camino recorrido encuentra su síntesis en una propuesta de práctica didáctica orientada a la modelización digital urbana, formalizando conceptos fundamentales en diferentes niveles de complejidad posibles de ser aplicados a la Educación secundaria.; With the beginning of the XXI century the spatial dimension has been particularly important when analyzing and understanding the world around us. Current technological development has enabled the emergence of so-called Geographic Information Technologies (GIT) leading to configure the framework of global linkages based on digital format, in which the technology of Geographic Information Systems (GIS) occupies a prominent position. This paper examines the potential offered by GIS as a support application of GIT in the classroom and essential tool that helps to support the development of spatial intelligence of students. To achieve this, GIS is considered in its application role that supports a technological revolution (methods and techniques) and an intellectual revolution (theory and epistemology). In this sense its emergence is analyzed as a result of scientifictechnological developments, geographical paradigms that provide support, teacher training needed to its use and the basic concepts of spatial analysis. The path is synthesized in a proposal of a teaching practice —oriented as a digital urban modeling—, formalizing key concepts at different levels of complexity possible to be applied to secondary education.
Discépolo o el arte de la inversión
Dalbosco, Dulce María
El objetivo de este artículo es abordar la presencia de lo grotesco y de sus códigos en la obra tanguera de Enrique Santos Discépolo. En ella hallamos algunos textos que invierten los tópicos de ciertos motivos estereotipados del tango, mecanismo que da lugar a auténticas acuarelas grotescas. En esta ocasión nos interesa descifrar los artilugios utilizados por el autor para producir tal efecto, con el fin de comprender, en última instancia, cuál es su concepción de lo grotesco. Atenderemos tanto a las composiciones que pertenecen a lo que la crítica ha denominado “vertiente grotesca” (Conde 2003, Gobello 2004) como a la presencia de rasgos o de recursos de lo grotesco presentes en otros tangos de su autoría.
The effect of aluminium alloy secondary phases on aniline-based silane
Trueba, Mónica; Trasatti, Stefano P.; Flamini, Daniel Omar
Commercial wrought Al alloys with high content of intermetallic phases, namely, AA5083-H111, AA2024-T3 and AA7075-T6, were treated with N-(3-trimethoxysilylpropyl) aniline (AnSi) by a simple procedure. Characterization studies and corrosion experiments indicate that the hybrid film protection capacity is related in a complex way to the macromolecular network structure linked to the Al substrate composition. Nevertheless, barrier protection enhanced by a buffer effect and galvanic coupling, as aided by aniline units within the hybrid film, is indicated mostly. Results overall demonstrate synergistic effect against Al alloy corrosion by combining at a molecular level monomers of conducting polymers and silane functionalities.
Differential participation of phospholipase A2 isoforms during iron-induced retinal toxicity. Implications for age-related macular degeneration
Rodriguez Diez, Guadalupe; Uranga, Romina Maria; Mateos, Melina Valeria; Giusto, Norma Maria; Salvador, Gabriela Alejandra
Both elevated iron concentrations and the resulting oxidative stress condition are common signs in retinas of patients with age-related macular degeneration (AMD). The role of phospholipase A2 (PLA2) during iron-induced retinal toxicity was investigated. To this end, isolated retinas were exposed to increasing Fe2+ concentrations (25, 200 or 800 μM) or to the vehicle, and lipid peroxidation levels, mitochondrial function, and the activities of cytosolic PLA2 (cPLA2) and calcium-independent PLA2 (iPLA2) were studied. Incubation with Fe2+ led to a time- and concentration-dependent increase in retinal lipid peroxidation levels whereas retinal cell viability was only affected after 60 min of oxidative injury. A differential release of arachidonic acid (AA) and palmitic acid (PAL) catalyzed by cPLA2 and iPLA 2 activities, respectively, was also observed in microsomal and cytosolic fractions obtained from retinas incubated with iron. AA release diminished as the association of cyclooxigenase-2 increased in microsomes from retinas exposed to iron. Retinal lipid peroxidation and cell viability were also analyzed in the presence of cPLA2 inhibitor, arachidonoyl trifluoromethyl ketone (ATK), and in the presence of iPLA2 inhibitor, bromoenol lactone (BEL). ATK decreased lipid peroxidation levels and also ERK1/2 activation without affecting cell viability. BEL showed the opposite effect on lipid peroxidation. Our results demonstrate that iPLA2 and cPLA2 are differentially regulated and that they selectively participate in retinal signaling in an experimental model resembling AMD.
“Atravesando fronteras”: Prácticas compartidas e identidades sociales negociadas durante el tardío prehispánico. Una discusión desde la alfarería ordinaria del valle del Bolsón (Belén, Catamarca); “Traversing frontiers”: shared practices and negotiated social identities in the late prehispanic. A discussion on common pottery from the valle del Bolsón (Belén, Catamarca)
Puente, Veronica
La alfarería ordinaria, del mismo modo que cualquier otro ítem de la cultura material, tiene un papel activo en la producción y reproducción de relaciones y significaciones sociales. El propósito de este trabajo es contribuir en el estudio de las prácticas sociales de producción y consumo de estos objetos como instancias que permiten debatir la construcción de identidades sociales en procesos de interacción macrorregional durante el tardío prehispánico en el área valliserrana del NOA. Para ello se presentan y sintetizan las características estéticas visuales –morfología, tratamiento de superficie, iconografía– y petrográficas de los conjuntos cerámicos ordinarios recuperados en dos asentamientos ubicados en el valle del Bolsón (Belén, Catamarca). Estos resultados son puestos en relación con los obtenidos en regiones vecinas, y a partir de ellos planteo la existencia de patrones estéticos y tecnológicos compartidos que atraviesan las fronteras regionales y también estilísticas planteadas tradicionalmente para el área y período cronológico mencionado.; Common pottery, like any other item of material culture, plays an active role in the production and reproduction of social relations and meanings. This paper contributes to the study of the social practices of production and consumption of these objects as instances that allow us to discuss the construction of social identities in macro-regional interaction processes during the late Prehispanic in the Valliserrana region of Northwestern Argentina. Thus, we present and synthesize the visual aesthetic characteristics -morphology, surface treatment, iconography- and petrography of the ceramic assemblages from two settlements in the Bolsón valley (Belén, Catamarca). We compare these results with those of neighboring regions and posit the existence of shared aesthetic and technological models that cross the regional and stylistic boundaries traditionally applied to this area and for this chronological period.
Skeletal development and adult osteology of Hypsiboas pulchellus (Anura: Hylidae)
Hoyos, Julio M.; Sánchez-Villagra, Marcelo; Carlini, Alfredo Armando; Mitgutsch, Christian
Osteological and skeletal characters have long been proven to be particularlyinformative in taxonomic and systematic research. Furthermore, ossification sequencesare assumed to be a potential tool to investigate developmental states and developmentalmodes of fossil and extant skeletal specimens. Herein, we provide a detailed accounton adult osteology and skeletogenesis in the Montevideo treefrog, Hypsiboas pulchellus(Anura: Hylidae) based on evaluation of a series of cleared and stained specimens.A consensus sequence of ossification, i.e., the order of appearance of mineralized elementsuntil early metamorphosis could be determined as (parasphenoid, presacral vertebraeI-VII, frontoparietal, exoccipital) ? transverse processes of presacral vertebraeI-VIII ? sacral vertebra ? (humerus, radioulna, ilium, femur, tibiofibula, scapula) ?(cleithrum, clavicle, coracoids, metacarpals, tarsals, metatarsals, phalanges, hypochord)? (prootic, angulosplenial, dentary, maxilla, premaxilla, squamosal). Comparing thestate of mineralized elements in individual specimens, a number of skeletal elements,including the exoccipital, frontoparietal, parasphenoid and prootic, as well as elementsof the shoulder and pelvic girdles, and the phalanges, were found to vary intraspecificallyregarding the relative time of their ossification within the ossification sequence.
Erythrolamprus reginae (Linnaeus, 1758). Culebra acuática de panza anaranjada
Arzamendia, Vanesa; Giraudo, Alejandro Raul; Bellini, Gisela Paola
Especie que presenta una amplia distribución tropical en áreas cisandinas de Sudamérica desde Colombia hasta el extremo norte de Argentina, también Trinidad y Tobago (Dixon, 1983). En Argentina presenta su límite de distribución meridional, siendo escasa en la mayoría de las localidades conocidas (con excepción del Parque Nacional Iguazú, Giraudo et al., 2009) en las provincias de Misiones, Salta, Jujuy (Parque Nacional Calilegua) y en el área de inundación de la presa de Yacyretá, en zonas limítrofes entre Paraguay y Corrientes (Álvarez et al., 1995; Giraudo, 2001; Giraudo y Scrocchi, 2002; Scrocchi et al., 2006; Arzamendia y Giraudo, obs. pers.). Habita en las ecorregiones Paranaense y de las Yungas, ambos ecosistemas con elevadas tasas de deforestación en Argentina, siendo además especialista en el uso del substrato (acuática), y en el uso de hábitat (arroyos y ríos rodeados con selvas y bosques fluviales). La población del área de Yacyretá ha sido fuertemente impactada por la represa que provocó la pérdida de su hábitat, y este grave impacto a los ecosistemas acuáticos y selvas del río Uruguay, se repetirá de construirse la represa de Garabí, donde la especie alcanza sus latitudes más meridionales en Argentina (Arzamendia y Giraudo, 2009). Las selvas en galería del Uruguay están modificadas por usos turísticos intensivos, represas (Salto Grande), forestaciones de exóticas, a pesar de ser un importante corredor biogeográfico de especies tropicales (Giraudo y Arzamendia, 2004). Adicionalmente, es afectada por atropellamientos en las rutas y eliminación por parte de las personas (Giraudo et al., 2009).
Topological synthesis of planar metamorphic mechanisms for low-voltage circuit breakers
Pucheta, Martín Alejo; Butti, Agostino; Tamellini, Valerio; Cardona, Alberto; Ghezzi. Luca
This article presents a systematic graph theory-based method for the topological synthesis of planar metamorphic mechanisms including metamorphic transformations of links and changes in the degrees-of-freedom. The parts to move, with input and output motion defined, and the topological design space, are represented by graphs of simple-jointed mechanisms. The topological requirements involving link transformations are expressed in terms of subgraphs with a given degrees-of-freedom containing prescribed input and output parts. The algorithm executes two subgraph searches inside atlases of mechanisms with different degrees-of-freedom. An application to the design of a family of low-voltage circuit-breaker mechanisms is shown.
Is foliar flammability of woody species related to time since fire and herbivory in northwest Patagonia, Argentina?
Blackhall, Melisa; Raffaele, Estela; Veblen, Thomas
Question: In northwest Patagonia burning of fire-resistant forests creates a community-level positive feedback towards increased fire occurrence because of successional replacement by fire-prone shrublands. We hypothesize that variability in plant traits related to time since last fire and to herbivory by cattle may affect foliar flammability, thus providing a flammability-promoting mechanism operating at the level of individual plants. We examine how plant foliar traits affecting flammability vary across species and at sites recovering from recent fires (<15 yr) vs sites not affected by fire for > 50 yr, both in the presence and absence of cattle. Location: Nahuel Huapi National Park, northwest Patagonia, Argentina. Methods: We measured four foliar traits expected to affect flammability: leaf moisture, leaf size, specific leaf area and leaf strength, and conducted tests of ignitability (time to ignition and duration of combustion) on leaves of six common tall shrub and small tree species: non-palatable Lomatia hirsuta and Diostea juncea, moderately palatable Nothofagus antarctica and Schinus patagonicus and highly palatable Maytenus boaria and Ribes magellanicum. We used ANOVA and PCA to examine potential relationships among species flammability traits, time since fire and presence or absence of cattle. Results: At plant level, variability in flammability-related foliar properties is strongly and consistently related to time since last fire, whereas effects of cattle are more variable across species and treatments. In comparison with unburned forests, the dominant woody species at shrubland sites showed reduced leaf moisture, leaf size and specific leaf area. Under pressure from cattle, N. antarctica, one of the most important woody species in these shrublands, showed changes in some foliar traits expected to enhance flammability (e.g. shorter time to ignition) but overall the influence of cattle on flammability was not consistent. Conclusions: The current study demonstrates that plant foliar traits vary between recently burned and unburned sites, and that these variations may enhance foliar flammability in shrubland communities. We hypothesize that variability in plant traits related to time since last fire and to herbivory by cattle may affect foliar flammability, thus providing a flammability-promoting mechanism operating at the level of individual plants. In northwestern Patagonia, Argentina, plant foliar traits vary between recently burned and unburned sites, and these variations may enhance foliar flammability in shrubland communities.
