Antioxidant response of tobacco (Nicotiana tabacum) hairy roots after phenol treatment Sosa Alderete, Lucas Gastón; Agostini, Elizabeth; Medina, Maria Inés Phenol is released to the environment from a wide variety of industrial effluents and it causes severe problems to human health and ecosystem. In the present study, we determined that Nicotiana tabacum hairy roots (HRs) double transgenic (DT) for two peroxidase genes (tpx1 and tpx2) showed higher phenol removal efficiency than wild type (WT) HRs after 120 h of phenol treatment at the expense of endogenous H 2O 2. Besides, to determine whether phenol could induce oxidative stress on tobacco HRs, we analyzed the antioxidant response, superoxide anion (O 2 -) localization and malondialdehyde (MDA) levels. Both HRs treated with phenol, showed significant increases in peroxidase (PX) activity mainly at the end of the assay (120 h) being PX activity from transgenic HRs 40% higher than that of WT HRs. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities showed significant increases from 24 to 120 h of phenol treatment. PX, SOD and APX isoforms were also analyzed and slight changes were observed only in PX patterns. Both HRs showed significant differences in total glutathione (TGSH) content during treatment, being higher in DT HRs than in WT HRs. At the end of the assay, a greater accumulation of O 2 - in different root zones was observed in WT and DT HRs. Moreover, phenol was able to increase the MDA levels in WT HRs from 48 to 120 h of the treatment, but no significant changes were observed in DT HRs. Results suggest that under these experimental conditions, DT HRs would be more tolerant to phenol than WT HRs.

Vibrational spectra of Tris(maltolato)gallium(III): A new interesting antitumoral agent Wagner, Claudia Cecilia; Parajón Costa, Beatriz Susana; Baran, Enrique José The FTIR and FT-Raman spectra of the gallium(III) complex of 3-hydroxy-2-methyl-4-pyrone (maltol), tris(maltolato)gallium(III), a new very promising antitumoral drug, were recorded and briefly discussed by comparison with the spectra of uncoordinated maltol and with some related species.

The space-bandwidth product in the joint transform correlator optical encryption setup Cuadrado Laborde, Christian Ariel; Lancis, Jesús In this work we study the joint transform correlator (JTC) optical encryption setup through the Wigner function. We found analytical expressions for the spatial and spatial frequency extent of the encrypted signal. Since the JTC is inherently an asymmetrical optical system, different expressions were found for each spatial axis and for their associated spatial frequency axes. We also compare these results with the dual random phase encoding technique. Finally, we found an analytical expression for the minimum separation between channels that avoids crosstalk in a wavelength multiplexing JTC architecture.

Mise au point d'outils de prévision de l'évolution de la stabilité de la structure de sols sous l'effet de la gestion organique des sols; Developping tools to predict soil aggregate stability as influenced by soil organic matter management; Desarrollo de herramientas de previsión de la evolución de la estabilidad estructural de los suelos bajo efecto de la gestión orgánica de los suelos Chenu, Claire; Abiven, Samuel; Annabi, Mohamed; Barray, S.; Bertrand, M.; Bureau, F.; Cosentino, Diego; Darboux, F.; Duval, O.; Fourrié, L.; Francou, C.; Houot, S.; Jolivet, C.; Laval, K.; Le Bissonnais, Y.; Lemée, L.; Menasseri, S.; Pétraud, J. P.; Verbèque, B. La estabilidad estructural está una propiedad física importante de los suelos, indicadora de su sensibilidad al sellado superficial del suelo y a la erosión. Los suelos limosos, que cubren superficies importantes en Francia y en el norte de Europa tienen debido a su textura y a su bajo contenido en materias orgánicas, una baja estabilidad estructural. En un contexto donde hay preocupación de la disminución de contenido en materia orgánica y donde se diversifica prácticas y sistemas de cultivo, aparece necesario desarrollar herramientas de predicción de la estabilidad estructural en función de la cuantidad y de la calidad de materias orgánicas. Desarrollamos una función de pedotransferencia (o relación estadística) que liga estabilidad de la estructura a su constitución, en particular el contenido en carbono orgánico, a partir de una base de datos Agresta de 480 suelos reunidos durante el proyecto. El examen de 7 ensayos de larga duración o de redes de parcelas sobre suelos limosos mostró mejoramientos de la estabilidad de la estructura en algunos años con prácticas que permiten un aumento del contenido en C en el horizonte de superficie (no laboreo, praderas temporarias, scv, aportes repetidos de compostas). El contenido en C total del horizonte está así un mejor indicador de la estabilidad estructural que las fracciones orgánicas (azucares solubles al agua caliente, materias orgánicas en partículas) o que la biomasa de los microorganismos. Experimentaciones de aporte de materias orgánicas (residuos de cultivos, compostas…) en suelos al laboratorio permitieron confirmar que le papel de estos aportes estuvo esencialmente indirecto, por la estimulación de los microorganismos del suelo que su descomposición lleva; estos microorganismos que agregan las partículas de los suelos por sus secreciones o mecánicamente. Propusimos un modelo predictivo de la estabilidad estructural seguido a aportes orgánicos cuyos se conoce la calidad bioquímica: Cantis-Stab, que copla un modelo de descomposición de materias orgánicas con una función estadística. Como la gestión de las materias orgánicas constituye un volante de acción mayor para actuar sobre la sensibilidad de los suelos limosos al sellado superficial y a la erosión, las herramientas propuestas pueden servir de base a preocupaciones agronómicas o al aporte razonado de productos residuales orgánicos al suelo.; La stabilité structurale est une propriété physique des sols importante, indicatrice de leur sensibilité à la battance et à l’érosion. Les sols limoneux, qui couvrent des surfaces importantes en France et dans le Nord de l’Europe ont, du fait de leur texture et de leur faible teneur en matières organiques, une stabilité structurale faible. Dans un contexte où l’on se préoccupe de la diminution de la teneur en matière organique des sols, où se développe l’apport de produits résiduaires organiques au sol et où se diversifient les pratiques culturales et les systèmes de culture, il apparaît nécessaire de développer des outils de prédiction de la stabilité structurale en fonction de la quantité et de la qualité des matières organiques. Nous avons développé une relation statistique qui relie la stabilité de la structure à la constitution des sols, en particulier à leur teneur en carbone organique (C), à partir d’une base de données AGRESTA de 480 sols assemblée pendant cette étude. Cependant sa faible capacité prédictive ne permet pas de l’utiliser comme fonction de pédotransfert. L’examen de 7 essais de longue durée ou réseaux de parcelles sur sols limoneux a montré des améliorations de la stabilité de la structure en quelques années avec des pratiques qui permettent une augmentation de la teneur en C dans l’horizon de surface (non labour, prairies temporaires, semis direct sous couvert végétal (SCV), apports répétés de composts). La teneur en C totale de l’horizon est souvent un meilleur prédicteur de la stabilité structurale que des fractions organiques (carbohydrates solubles à l’eau chaude, matières organiques particulaires) ou que la biomasse des microorganismes. Des expérimentations réalisées en laboratoire d’apport de matières organiques (résidus de culture, composts) à des sols limoneux, nous ont permis de confirmer que le rôle de ces apports était essentiellement indirect, par la stimulation des microorganismes du sol que leur décomposition entraîne. Les microorganismes agrégent les particules de sols par leur sécrétions ou mécaniquement. Nous avons proposé un modèle prédictif de la stabilité structurale suite à des apports organiques dont on connaît la qualité biochimique : CANTIS-STAB, qui couple un modèle de décomposition des matières organiques à une fonction statistique. Comme la gestion des matières organiques constitue un volant d’action majeur pour agir sur la sensibilité de sols limoneux à la battance et à l’érosion, les outils proposés doivent être développés, afin de servir de base à des préconisations agronomiques ou à l’apport raisonné de produits résiduaires organiques au sol.; Aggregate stability is a major soil physical property, which is a good indicator of the sensitivity of soils to crusting and erosion. Silty soils, which cover large surface areas in France and Northern Europe, have a low aggregate stability, because of their texture and of their frequent low organic matter contents. In the present context of (i) soil organic matter content depletion, (ii) development of organic wastes application to soils and (iii) diversification of cropping systems, it is necessary to have tools to predict changes in soil aggregate stability with changes in soil organic matter content and quality. Using a data base of 480 soils, established during this study, we developed a statistical relationship which relates soil aggregate stability with soil characteristics, in particular with its organic carbon (C) content. However, its low predictive capacity does not allow to use it as a pedotransfer function. Based on 7 in situ long term experiments or cultivated plots series, we found rapid increased of soil aggregate stability when practices that increases the soil C content in the surface layer are implemented (no till, rotations with leys, permanent coverage of soil with plants, repeated compost additions). The total C content of soil was often better correlated to aggregate stability than other organic variables, such as hot water soluble polysaccharides, particulate organic matter contents, or microbial biomass C. Laboratory experiments, in which a wide range of organic materials (crop residues, composts) were added to soil showed that the effect of the organic materials was indirect, through the stimulation of the microbial decomposers, which aggregated the soil. We proposed a new model to simulate the temporal changes in aggregate stability after organic matter additions of given biochemical qualities and in controlled amounts. “CANTIS-STAB” couples a decomposition model with a statistical function. Managing organic matter in soils is a powerful option to decrease the sensitivity of silty cultivated soils to crusting and erosion. The different tools proposed in this program will be developed further, to serve as a basis to optimize agronomic practices and organic wastes addition in this perspective.

Antibodies anti-Shiga toxin 2 B subunit from chicken egg yolk: Isolation, purification and neutralization efficacy Parma, Yanil Renee; Chacana, Pablo Anibal; Rogé, Ariel Diego; Kahl, Alan Jonatan; Cangelosi, A.; Geohgegan, P.; Lucchesi, Paula Maria Alejandra; Fernandez Miyakawa, Mariano Enrique Shiga toxins (Stx1 and Stx2) are the main virulence factors of enterohemorrhagic Escherichia coli (EHEC), a foodborne pathogen associated with diarrhea, hemorrhagic colitis and hemolytic uremic syndrome. The aim of this study was to evaluate the antibodies against Stx2 obtained from egg yolks of laying hens immunized with a recombinant Stx2B subunit. A high specific response in serum was observed 25 days after the first immunization and IgY antibodies were extracted from day 47th and purified from egg yolk. A concentration of 0.84 mg of total IgY/ml of egg yolk was obtained, of which 8% were antigen specific. The ability of anti-Stx2B IgY to recognize Stx2B and Stx2 either in solid-phase or in solution were evaluated and compared with anti-Stx2B rabbit antibodies by Western blotting and ELISA. The protective efficacy of IgY against Stx2 was determined by in vitro and in vivo experiments. The results show that IgY was able to recognize Stx2B and Stx2 in denatured conditions, attached to a solid-phase and free in solution. The anti-Stx2B IgY could effectively block the biological activity of Stx2 on Vero cells and protect mice from Stx2 challenge. The data suggest that immunization of hens with Stx2B could be a strategy to obtain at low cost a relatively high concentration of anti-Stx2 egg yolk IgY, able to neutralize Stx2 lethal activity. IgY technology could be an useful tool for research, diagnosis and therapy of EHEC infection.

Fredi Guthmann: el extranjero entre nosotros Venturini, Santiago El poeta franco argentino Fredi Guthmann –Alfredo Jonás Guthmann (San Isidro, 1911- Mar del Plata, 1995)– continúa siendo, una década después de su aparición en la escena literaria, una figura excéntrica, excentricidad que puede leerse tanto en relación con el canon como con el relato mítico que la delinea. Este trabajo llevará a cabo una doble lectura: de la poética de Guthmann y de la inclusión de esa poética en el sistema literario argentino, a través de “refracciones” críticas y de la operación inclusiva por excelencia: la traducción.

Factors that modify early and late reproductive phases in oilseed rape (Brassica napus L.): Its impact on seed yield and oil content Gomez, Nora Valentina; Miralles, Daniel Julio Oilseed rape yield potential could be improved lengthening the duration of the late reproductive phase by increasing the number of grains per unit area. Photoperiod sensitivity could be used as a tool to manipulate the reproductive phase and thereby the number of grains. The aim of this study was to assess (i) the effects of different combinations of photoperiod on the duration of different phases and (ii) analyze how the changes in that duration affect yield (and its components) as well as oil seed content in oilseed rape. Field experiments were conducted in a factorial combination of three cultivars and three photoperiod regimes: natural photoperiod (NP) which represents the control and extended photoperiod of 6h over NP (NP+6) during emergence (E)-flower buds visible (FBV) and FBV-maturity (M) arranged in a randomized complete block design with three replicates, during two years representing three environments. Results showed that oilseed rape evidenced photoperiod responses during vegetative and early reproductive phases. Due to the lack of correlation between the duration of the vegetative and reproductive phases, it is possible to speculate the vegetative period may be altered independently of the modification of the rest of the phases. The positive relationship between grain number per m2 and the duration of the late reproductive phase suggests that yield could be increased by lengthening the duration of that phase. Thus, regardless of the effect on the previous phase, the photoperiod sensitivity found in the early reproductive phase opens the possibility to manipulate the relative durations of vegetative and reproductive phases. Therefore, the length of the reproductive phase will be increased at the expense of a reduction in the duration of the vegetative phase, but without changing the whole duration of the crop cycle. This strategy could increase yield in oilseed rape in the future. Variations in yield were mostly explained by changes in the grain number per unit area without significant correlation with grain weight. However, a negative relationship between grain weight and grain number was found, showing a slight counterbalance in yield, by decreasing the grain weight. Since oil concentration appeared to be a more conservative attribute, increases in crop yield through a higher grain number per unit area would be a suitable strategy for improving oil yield as no reductions in oil concentration can be expected.

Briefing: Collaborative management for sustainable beaches Faggi, Ana Maria This briefing describes examples of integrated coastal zone management systems carried out along the Atlantic coastal strip in Argentina. The programmes helped to limit negative impacts and to regulate uses, applying adaptive management based on a holistic approach. This briefing forms part of the 'current trends in municipal engineering' series.

Metodología UV para la determinación de los antichagásicos Nifurtimox y Benznidazol en sangre; UV methodology for determination of antichagasic drugs Nifurtimox and Benznidazol in blood; Metodologia UV para a determinação dos antichagásicos Nifurtimox e Benznidazol em sangue Bulffer, Romina Fernanda; Castro, Jose Alberto; Fanelli, Silvia Laura El Mal de Chagas es una enfermedad parasitaria endémica en América del Sur y Central. Existen dos fármacos disponibles para el tratamiento médico de la enfermedad, el Nifurtimox (Nfx) y el Benznidazol (Bz). No existen protocolos estandarizados, validados y accesibles en laboratorios regionales para determinar niveles de los antichagásicos en sangre. En este trabajo, se presenta un método espectrofotométrico para la determinación de Nfx y Bz en sangre. Los metabolitos en sangre se Extraen con columnas Extrelut®. Los extractos se evaporan, se redisuelven en mezclas de metanol/agua y se analizan espectrofotométricamente a 400nm y a 320nm para Nfx y Bz, respectivamente. Se cuantifica comparando con soluciones estándar de Nfx o Bz en el solvente. La metodología utilizada fue validada entre 0,5 y 50 μg/ml sangre para Nfx y entre 0,5 y 100 μg/ml sangre para Bz. La exactitud, precisión, linealidad y robustez del método fueron satisfactorias. Se aplicó el procedimiento determinando concentraciones sanguíneas post administración de ambos fármacos a ratas.; Chagas’ Disease is an endemic parasitic disease in South and Central America. There are two drugs available for medical treatment of the disease, Nifurtimox (Nfx) and Benznidazol (Bz). There are no standardized or accessible protocols in regional laboratorios to determine the levels of antichagasic drugs in blood. A spectrophotometric method for Nfx and Bz determination in blood is presented in the present work. Blood metabolites are extracted through Extrelut® columns. Extracts are evaporated, redissolved in metanol/water mixanalysed by spectrophotometry at 400 nm and 320 nm for Nfx and Bz, respectively. They are quantified comparing with standard Nfx or Bz solutions in the solvent. The methodology used was validated between 0.5 and 50 µg/mL of blood for Nfx, and between 0.5 and 100 µg/mL of blood for Bz. The accuracy, precision, lineality and robustness of the method were satisfactory. The procedure was applied determining blood concentrations after administration of both drugs to rats.; Mal de Chagas é uma doença parasitária endêmica na América do Sul e Central. Existem dois fármacos disponíveis para o tratamento médico da doença, o Nifurtimox (Nfx) e o Benznidazol (Bz). Não existem protocolos padronizados, validados e acessíveis em laboratórios regionais para determinarem níveis dos antichagásicos em sangue. Neste trabalho se apresenta um método espectrofotométrico para a determinação de Nfx e Bz em sangue. Os metabólitos em sangue são extraídos com colunas Extrelut®. Os extratos se evaporam, são redissolvidos em misturas de metanol/água e se analisam espectrofotometricamente a 400 nm e a 320 nm para Nfx e Bz, respectivamente. São quantificados comparando com soluções padrão de Nfx ou Bz no solvente. A metodologia utilizada foi validada entre 0,5 e 50 µg/mL de sangue para Nfx e entre 0,5 e 100 µg/mL de sangue para Bz. A exatidão, precisão, linearidade e robustez do método foram satisfatórias. Aplicou-se o procedimento determinando concentrações sanguíneas pós- administração de ambos os fármacos em rato

New record of a stranded sperm whale (physeter macrocephalus) and a review of strandings along the continental Argentine coast; Nuevo registro de un cachalote (Physeter macrocephalus) varado y una revisión de varamientos en las costas de Argentina continental Degrati, Mariana; Garcia, Nestor Anibal; Grandi, Maria Florencia; Leonardi, María Soledad; Loizaga de Castro, Rocio; Vales, Damián Gustavo; Dans, Silvana Laura; Pedraza, Susana Noemi; Crespo, Enrique Alberto Presentamos un nuevo registro de un cachalote, con notas sobre la dieta, la determinación de edad y la presencia de parásitos, junto con una revisión de los varamientos a lo largo de toda la costa continental argentina. El animal varado fue un macho maduro de 64+ años. Este es el individuo más longevo registrado para esta especie en el Atlántico Sudoccidental. En el contenido estomacal se colectaron 302 picos inferiores de cefalópodos. Los únicos parásitos presentes fueron cestodes en la capa de grasa; no se encotraron helmintos gastrointestinales.; We present a new record of sperm whale with notes on diet, age determination and a review of strandings along the continental Argentine coast. A complete necropsy was made in the field, and morphometric data were taken. The specimen stranded was a mature male of 64+ years old. This is the oldest specimen determined for a sperm whale in the Southwest Atlantic coast. In the stomach contents a total of 302 cephalopod lower beaks were recovered. Cestodes were present in the blubber but parasites were not found in stomach and intestine contents.

Razón gubernamental, biopolítica y mecanismos de capitalización de la praxis indígena en Mendoza Katzer Molina, Maria Leticia En un mundo en constante transformación, los dispositivos pedagógicos también se modifican. La escuela produce nuevas formas de regular las conductas, distintas a las que conocimos en las sociedades disciplinarias. Para dar cuenta de esos cambios, focalizaremos la atención en algunas situaciones discursivas de los docentes, padres y estudiantes en la escuela, que nos permiten aproximarnos a las prácticas de regulación cotidianas y también a las formas de oposición, de contraconductas o conductas en la escuela del siglo XXI.; In a constantly changing world, educational devices also change. The school produces new forms of behavior regulation, different from those we met in disciplinary societies. To give an account of these changes we will focus on certain school situations through discursive practices of teachers, parents and students, which will allow us to approach day-to-day regulatory practices and also the forms of opposition, counter-conducts or conducts that in its generality cannot take place in the XXIth century school.

Características del olivar en los valles áridos del noroeste de Argentina Gomez del Campo, M. V.; Morales Silleros, A. M.; Vita Serman, Alberto Facundo; Rousseaux, Maria Cecilia; Searles, Peter Stoughton

Acute and Chronic Effects of Copper, Chromium and Insecticide-Endosulfan on Littoral Cladocera, Pseudosida Variabilis Gutierrez, Marìa Florencia; Gagneten, Ana María; Paggi, Juan Cesar Recent works have emphasized on the serious problems caused by the toxicity of pesticides and heavy metals on aquatic ecosystems due to human activities. The aim of this work was to evaluate the toxicities of an insecticide with endosulfan as active element and the metals copper and chromium on the littoral cladocera ctenopoda, Pseudosida variabilis. The lethal and sublethal effects on eight biological endpoints were analyzed paying special attention to the intrinsic rate of increase (r). The EC50 values to copper, chromium and endosulfan were: 29; 133.2 and 1.75 μl l-1 at 24 h and 12; 52.5 and 1.04 μg l-1 at 48 h respectively. A comparison with other freshwater cladocerans revealed that P. variabilis would be an appropriate species to be used as a test organism in ecotoxicological studies. A detailed analysis of each life history trait showed that copper, chromium and endosulfan had negative effects on several life history parameters. However, the r value was not the most appropriate endpoint of copper and chromium toxicity, when it was compared with other individual and population parameters. Survival, longevity, age of first reproduction and mean brood size were the most appropriate parameters for both metals. On the contrary, in case of endosulfan, this endpoint was severely affected, and the population consequences are discussed. The results suggest that multiple biological endpoints and an extended period of exposure are needed in order to achieve a better screening of metal and insecticide toxicity.

Prospección de enfermedades de la soja en la provincia de Tucumán y zonas de influencia durante las campañas 2009/2010 y 2010/2011 Gonzalez, Victoria del Valle; Ploper, Leonardo Daniel; Hecker, Luis; de Lisi, Vicente; Reznikov, Sebastian; Gimenez, Cynthia; Stegmayer, Carlos A.; Diaz, Santiago Personal de la Sección Fitopatología de la Estación Experimental Agroindustrial Obispo Colombres (EEAOC) monitorea anualmente en forma intensiva los lotes de soja [Glycine max (L.) Merr.] de la provincia de Tucumán y sus zonas de influencia (oeste de Santiago del Estero y sudeste de Catamarca), con el objetivo de evaluar su estado sanitario. En el presente trabajo se presentan los resultados de las prospecciones realizadas durante las campañas 2009/2010 y 2010/2011. Durante la campaña 2009/2010 la producción de soja en el NOA resultó muy favorable en lo que se refiere a las condiciones climáticas, registrándose precipitaciones apropiadas en cantidad y distribución para el crecimiento y desarrollo de los cultivos en la mayor parte de la región. La ocurrencia y los daños ocasionados por las enfermedades fueron mínimos a pesar de haberse presentado condiciones favorables para el desarrollo de las mismas a lo largo de la campaña. Las patologías foliares mostraron valores de severidad que no superaron el 30%. La pústula bacteriana (Xanthomonas axonopodis pv. glycines) y el mildiu (Peronospora manshurica) presentaron mayores valores de severidad (30%) en relación a las otras enfermedades evaluadas. La roya de la soja (Phakopsora pachyrhizi) no tuvo importancia alguna; apareció en forma tardía y progresó muy lentamente. En cuanto a la campaña 2010/2011, con condiciones ambientales que también fueron favorables para el cultivo, se detectaron incrementos en la severidad de las patologías foliares, incluyendo tizón por Cercospora (Cercospora kikuchii), mancha anillada (Corynespora cassiicola) y mancha por Myrothecium (Myrothecium roridum). La mancha anillada y mancha por Myrothecium fueron detectadas en la localidad de San Agustín sólo en la última campaña. En contraste, la roya de la soja no tuvo importancia alguna en la campaña, en parte, por su tardía detección a fines de marzo.

Estrategias de estudio y aprendizaje en estudiantes de nivel medio y universitario; Learning Strategies in College and High School Students Uriel, Fabiana Edith; Carreras, María Alejandra; Ongarato, Paula; Stover, Juliana Beatriz; Fernandez Liporace, Maria Mercedes Los bajos niveles de rendimiento académico alcanzados en el nivel superior de educación han sido tema de análisis en los últimos años a la luz de la marcada distancia entre la formación previa de los ingresantes y las competencias requeridas para cursar aquellos estudios. numerosas variables influyen en este cuadro de situación. dentro de la psicología de la educación, un tópico habitualmente contemplado para abordar esta cuestión son las estrategias de aprendizaje. este constructo se analizó en estudiantes de psicología de dos universidades públicas argentinas (n=193) y de dos escuelas medias estatales de Buenos aires (n=155), contemplando diferencias en su uso (p>0,01) según variables sociodemográficas (sexo, nivel educativo, grupo de convivencia y educación parental). se encontró que las mujeres refieren mayor ansiedad y recurren a técnicas de ayuda al estudio más asiduamente que los varones. se verificó un mayor uso de todas las estrategias en los alumnos universitarios, a excepción de ansiedad y preocupación por el rendimiento. no se verificaron diferencias según grupo de convivencia y educación parental. Los resultados se analizan a la luz de hallazgos precedentes.; Low academic achievement in College and the big distance between freshmen’s previous training and skills required in this educational level are considered an important issue. this situation can be explained by a certain number of variables. in spite of this, educational psychology points to learning strategies to address the question. a comparison between High school (n=155, public schoolers from Buenos aires City) and College students (n=193, from two public argentinean universities) is presented. differences in learning strategies are analyzed (p<0,01) by socio-demographic variables (sex, cohabitation group, educational level and parental education). Females show more anxiety and use helping study techniques more frequently than males. Comparing strategies employed by highschoolers and College students, significant differences in every strategy, favouring College participants, were verified, except in anxiety and concerns on achievement. differences were not verified in any strategy, neither by cohabitation group, nor by parental educational level. results are discussed taking into account recent findings.

Latitudinal gradients in macroalgal biodiversity in the Southwest Atlantic between 36 and 55°S Liuzzi, Maria Gabriela; López Gappa, Juan José; Piriz, Maria Luz Different groups of marine benthic organisms show contrasting latitudinal patterns of biodiversity. The widely accepted paradigm of increasing biodiversity towards the tropics does not seem to be valid for macroalgal floras of the Southern Hemisphere. We compiled a database summarizing the distributional ranges of macroalgae along the coast of Argentina to test whether biodiversity decreases towards lower latitudes, as in the Pacific coast of South America, and whether breaking points in the geographical distribution can be recognized in one or more areas of the Southwest Atlantic south of 36°S. We found a clear trend of decreasing biodiversity with decreasing latitude. The interpretation of some biodiversity declines is confounded by changes in the intensity of the sampling effort. A 51% reduction in algal species richness between 42 and 41°S coincides with the boundary between the Argentine and Magellanic Zoogeographic Provinces. This sharp breaking point is related to a thermal anomaly caused by long residence times of water masses within San Matías Gulf, suggesting an upper thermal tolerance limit for most Antarctic/sub-Antarctic seaweeds. A further reduction occurs at 38-37°S. This breaking point can be explained by the disappearance of suitable hard substrata, since rocky outcrops give place to wide extensions of sandy beaches. The impoverished algal assemblage inhabiting the northern coast of Argentina is mainly related to the reduction or disappearance of the Antarctic/sub-Antarctic floristic component. This area is characterised by a predominance of widely distributed species, Chlorophytes and opportunistic filamentous or foliose algae.

Consistent effects of a major QTL for thermal resistance in field-released Drosophila melanogaster Loeschcke, Volker; Kristensen, Torsten Nygaard; Norry, Fabian Marcelo Molecular genetic markers can be used to identify quantitative trait loci (QTL) for thermal resistance and this has allowed characterization of a major QTL for knockdown resistance to high temperature in Drosophila melanogaster. The QTL showed trade-off associations with cold resistance under laboratory conditions. However, assays of thermal tolerance conducted in the laboratory may not necessarily reflect performance at varying temperatures in the field. Here we tested if lines with different genotypes in this QTL show different thermal performance under high and low temperatures in the field using a release recapture assay. We found that lines carrying the QTL genotype for high thermal tolerance were significantly better at locating resources in the field releases under hot temperatures while the QTL line carrying the contrasting genotype were superior at cold temperatures. Further, we studied copulatory success between the different QTL genotypes at different temperatures. We found higher copulatory success in males of the high tolerance QTL genotype under hot temperature conditions, while there was no difference in females at cold temperatures. The results allow relating components of field fitness at different environmental temperatures with genotypic variation in a QTL for thermal tolerance.

Picoplankton structure in clear and turbid eutrophic shallow lakes: A seasonal study Silvoso, Julieta; Izaguirre, Irina; Allende, Luz The relative abundance of the different picoplankton components (eukaryotic picophytoplankton (Peuk), picocyanobacteria (Pcy) and bacterioplankton), and their relationships with the lake conditions were studied in three types of shallow lakes from the Pampa Plain (Argentina) that differ in their optical properties: clear-vegetated, phytoplankton-turbid and inorganic-turbid. All the selected lakes, but one, are characterized by their different alternative steady state (clear-vegetated and phytoplankton-turbid water phases) following the model proposed by Scheffer et al. (1993).Autotrophic and heterotrophic picoplankton abundances were analyzed seasonally in relation to environmental variables. All the lakes presented high concentrations of total nitrogen (TN) (>229μgL-1), total phosphorus (TP) (>46μgL-1) and dissolved organic carbon (DOC) (>13.7mgL-1). Clear-vegetated lakes were characterized by vertical diffuse PAR (photosynthetic active radiation) attenuation coefficient (kdPAR) lower than 11m-1, whereas inorganic-turbid lake always showed values higher than 21.1m-1. The euphotic zone depth (Z1%) was wider in clear-vegetated lakes (40-140cm) and thinner in the inorganic-turbid (10-20cm). The phytoplankton-turbid lakes presented a wide range in the values of these variables (kdPAR: 5.2-35.8m-1; Z1%: 10-90cm). Phytoplankton chlorophyll-a (Chl-a) strongly differed, ranging from 1.6 to 334.6μgL-1. Picophytoplankton was mainly represented by phycocianine-rich (PC-rich) Pcy in all cases, dominating over Peuk algae. The total and relative abundances of eukaryotic picophytoplankton, Pcy and bacterioplankton, as well as the size structure of the phytoplankton community differed among the water bodies. In general, clear-vegetated water bodies exhibited similar abiotic characteristics, picophytoplankton/bacterioplankton ratios, and phytoplankton size structure. Contrarily, no clear trend was identified for the group of turbid lakes. The contrasting results obtained for the importance of the picoplankton components in phytoplankton-turbid shallow lakes evidence that the availability of the energetical and nutrient resources cannot be solely considered to predict their relative importance in this type of shallow lake.

Smicridea mclachlan (Trichoptera: Hydropsychidae) from northwestern Argentina and bolivia: New species, redescription, association and new records Rueda Martin, Paola Alejandra; Sganga, Julieta Valeria Four new species of Smicridea (Rhyacophylax) are described from Argentina and Bolivia. Smicridea (Rhyacophylax) bifida sp. nov., S. (R.) elisae sp. nov. and S. (R.) valeni sp. nov. are described from the male; S. (R.) thermophyla sp. nov. is described as the first species of Smicridea from thermal springs. The larva and pupa of S. (R.) thermophila were associated using the metamorphotype method. New distributional records of S. (R.) dithyra, S. (R.) atrobasis, S. (R.) peruana and S. (R.) pampeana are included. Morphological characters of male S. (R.) peruana that were not mentioned before are included. Illustrations of all taxa named in this paper are included.

Delimitación y estudio de cuencas hidrográficas con modelos hidrológicos Geraldi, Alejandra Mabel; Piccolo, Maria Cintia; Perillo, Gerardo Miguel E. La cuenca Las Encadenadas del Oeste se localiza en el sudoeste de la provincia de Buenos Aires. Es una cuenca endorreica y un escenario de suma fragilidad ante eventos hidrológicos extremos, debido a su incapacidad para evacuar grandes vohlmenes de agua. Por esta razón, es de suma importancia el conocimiento y la delimitación de su cuenca hidrológica. El objetivo del presente trabajo es establecer la direccion de la escorrentta superfiCial a partir de la aplicación de modelos hidrol6gicos e identificar divisorias de aguas. Se aplicó el modelo «Hydrologic Modeling», de Arc Gis, el cual consiste en delerminar todas las celdas que drenan a una en particular. Se obtuvo una clasificación de las subcuencas en mayores, medias y conos aluviales activos. Los primeros formados por arroyos principales permanentes, las segundas jormadas por arroyos secundarios que nacen de carcavas y los conos aluviales sin cursos definidos, formados en la desembocadura de los arroyos principales y secundarios.; Las Encadenadas del Oeste basin is located in the southwestern of the Buenos Aires province. It is an endorheic basin and an extremely fragile scenario for its inability to pass large volumes of water. For this reason, it is very important to study and understand the hydrology of its watershed. The aim of this study is to establish the surface runoff direction of the basin using an hydrological model and to identify its watershed. The applied Arc Gis model was «Hydrologic Modeling». The model determines all cells that drain in a particular one. A classification of the sub-basins in larger, medium and active alluvial cones was obtained. Larger basins are permanent major rivers, medium ones are non permanent streams and the alluvial conos were the ones formed at the mouths of major and minor streams.