Viability of calcium alginate microencapsulated probiotic bacteria in Iranian yogurt drink (Doogh) during refrigerated storage and under simulated gastrointestinal conditions Mortazavian ,A. M.; Ehsani, M. R; Azizi, A.; Razavi, S. H.; Mousavi, S. M.; Sohrabvandi, S.; Reinheimer, Jorge Alberto The effects of microencapsulation of AB-type culture (Lactobacillus acidophilus LA-5 and Bifidobacterium lactis Bb-12) with calcium alginate on cell survival in Iranian yogurt drink (Doogh) during storage at 4°C for 42 days, as well as under simulated gastrointestinal conditions, were studied. The pH of the product at the beginning of storage was 4.53 and the final pH at the end of storage were 4.52 and 3.78 for the samples containing encapsulated and free cells, respectively. The acetic acid content in the encapsulated-cellcontaining Doogh increased by 0.01% (from 0.05 to 0.06%) during the storage period, whereas for free-cell-containing Doogh the increase was 0.04% (from 0.05 to 0.09%). At day 42, the viable counts of L. acidophilus and bifidobacteria in the samples containing encapsulated cells were 5.5 and 4.0 log cycles higher than those containing free cells, respectively. To evaluate the protective impact of encapsulation on cell survival in in vivo situations, the product was subjected to three simulated gastrointestinal conditions, including extreme conditions (pH 1.5, 90 min/2% bile, 90 min), intermediate conditions (pH 1.5, 90 min/1% bile, 90 min) and normal conditions, i.e. the situation in the gastrointestinal tract of a normal healthy person after the consumption of a probiotic-containing dairy drink, when the stomach has not been free for a relatively long time (pH 2.0, 30 min/0.6% bile, 60 min). The viability of the probiotic cells increased from 0.6% and 0.2% (L. acidophilus and bifidobacteria, respectively) as free cells to 18.0% and 9.5% under the extreme gastrointestinal conditions, after encapsulation. Under normal gastrointestinal conditions, the cell survival rates were 16.1% for L. acidophilus and 21% for bifidobacteria before encapsulation, and 26.3 and 34.0% (L. acidophilus and bifidobacteria, respectively) after encapsulation.

Dried cell-free fraction of fermented milks: new functional additives for the food industry Vinderola, Celso Gabriel The claimed health benefits of fermented functional foods areexerted either directly through ingested live microorganisms(probiotics) or indirectly as a result of ingestion of microbialmetabolites produced during the fermentation process. Severalreports are emerging concerning the immunomodulating capacityof the cell-free fraction of fermented milks. The solublemetabolites present in the whole non-bacterial fraction couldbe easily spray-dried and added as dried powders to foodmatrixes whose chemical composition or technological processof manufacture would seriously threaten the viability ofprobiotic bacteria. The relative technological easiness for incorporatingthe same biologically active metabolites presentin fermented milks, but as a dried cell-free fraction, into otherfood matrixes opens the doors to the development of a greatnew variety of functional foods using food matrixes notsuitable nowadays for viable probiotic bacteria. The abilityto bring functionality to ordinary food through the incorporationof ingredients from natural sources becomes increasinglyattractive to the food industry.

¿Qué bicho es? Tubaro, Pablo Luis; Díaz de Astarloa, Juan Martín Recientes avances en las tecnologías derivadas del conocimiento del ADN y la bioinformática han posibilitado el uso de una secuencia corta de una porción estandarizada del genoma como códigos de barras genéticos que ayude en la identificación y descubrimiento de nuevas especies.

Dynamical Functional Artificial Neural Network: Use of Efficient Piecewise Linear Functions Figueroa, Jose Luis; Cousseau, Juan Edmundo A nonlinear adaptive time series predictor has been developed using a new type of piecewise linear (PWL) network for its underlying model structure. The PWL Network is a D-FANN (Dynamical Functional Artificial Neural Network) the activation functions of which are piecewise linear. The new realization is presented with the associated training algorithm. Properties and characteristics are discussed. This network has been successfully used to model and predict an important class of highly dynamic and nonstationary signals, namely speech signals.

El lugar de Aira. Algunos desplazamientos en el sistema de lectura de Punto de vista Sager, Valeria Pocas veces la revista Punto de vista menciona a César Aira, el lugar central que ocupa en la literatura argentina actual, inviste al largo silencio de gran significatividad. Este trabajo explora el sistema de lectura de la publicación, registra las formas del borramiento de Aira, e indaga las operaciones que recientemente han vuelto a considerar un universo poético que había sido denegado.; Punto de Vista mentions César Aira in few instances, his core position in present Argentine literature; resulting in a silence of great significance. This article explores the publication’s reading system, it also registers the ways of erasing Aira’s presence and examines the recent operations that have reconsidered the poetic universe which had been denied.

Tafonomía e icnología de los depósitos de tormenta de la Formación Bardas Blancas (Jurásico Inferior-Medio), Mendoza, Argentina; Taphonomy and ichnology from storm deposits in Bardas Blancas Formation (Lower-Middle Jurassic), Mendoza, Argentina Bressan, Graciela Susana; Palma, Ricardo Manuel Los depósitos de la Formación Bardas Blancas (Toarciano-Bajociano) de la Cuenca Neuquina, en el área del río Potimalal, son caracterizados sobre la base de criterios sedimentológicos, tafonómicos e icnológicos. Los atributos tafonómicos y su relación con las litofacies permiten distinguir cinco tipos de depósitos bioclásticos (DB): (1) DB1-Areniscas bioclásticas con estratificación cruzada tipo hummocky; (2) DB2-Concentraciones tabulares o lenticulares en areniscas finas-medias con estratificación cruzada tipo hummocky; (3) DB3-"Lags" bioclásticos; (4) DB4-Concentraciones complejas; (5) DB5-Concentraciones bioclásticas en areniscas finas macizas. Estos depósitos fueron interpretados como flujos de relajación de tormentas (DB3), tempestitas proximales (DB1 y DB2) y tempestitas distales (DB4 y DB5). Los taxa de moluscos incluyen pelecípodos, cefalópodos y gastrópodos, en orden de abundancia decreciente. Pholadomya cf. abbreviata Hupé, Meleagrinella cf. echinata (Sowerby) y Neocrassina andium (Gottsche) están presentes en las facies de areniscas mientras que Pholadomya laevigata Hupé y Trigonia (Trigonia) sp. son abundantes en las facies de pelitas. La icnofauna incluye los icnogéneros Skolithos y Ophiomorpha, asignados a la icnofacies de Skolithos, y Thalassinoides, Palaeophycus, Planolites y Chondrites, asignados a la icnofacies de Cruziana. En estos afloramientos se reconocieron tres secciones que se profundizan hacia el techo, promediando los 26, 17 y 25 m en espesor. El análisis y la interpretación de los rasgos sedimentológicos, tafonómicos e icnológicos permiten interpretar una plataforma dominada por tormentas, en una zona comprendida entre la anteplaya y la plataforma externa.; The Bardas Blancas Formation (Toarcian-Bajocian) of the Neuquen Basin in rio Potimalal area is characterized on the basis of sedimentologic, taphonomic and ichnologic criteria. The taphonomic attributes and their relation to the lithofacies allow us to distinguish five different bioclastic deposits (BD): (1) BD1, hummocky cross-stratified shell concentrations; (2) BD2, lenticular or tabular shell concentrations in hummocky cross-stratified sandstones; (3) BD3, shell “lags”; (4) BD4, complex shell beds; (5) BD5, shell beds in massive fine-medium grained sandstones. BD3 have been interpreted as storm relaxation flows, whereas BD1-BD2 has been interpreted as proximal tempestites and BD4-BD5 as distal tempestites. Molluscs taxa recorded include bivalves, cephalopods and gastropods, in order of decreasing of his relative abundance. Pholadomya cf. abbreviata Hupé, Meleagrinella cf. echinata (Sowerby) and Neocrassina andium (Gottsche) are present in sandstone facies while, Pholadomya laevigata Hupé and Trigonia (Trigonia) sp. are abundant in mudstone facies. Ichnofauna includes Skolithos and Ophiomorpha that may be assigned to the Skolithos ichnofacies, and Thalassinoides, Palaeophycus, Planolites and Chondrites, assigned to the Cruziana ichnofacies. In the study area, there are three deepening upward successions averaging 26, 17 and 25 m in thickness. The analysis and interpretation of sedimentologic, taphonomic and ichnologic features suggests a storm-dominated shelf, in a zone comprised from shoreface and outer shelf areas.

Modelo de predicción espacial para el índice de aridez en una transecta del centro argentino; Spatial predictive model for the aridity index in a transect of the center of Argentina Nardecchia, Graciela Lucia; Diblasi, Angela Magdalena; Gonzalez Loyarte, Maria Margarita El procesamiento de imágenes satelitarias, conjuntamente con metodologías de los procesos estocásticos espaciales, ofrecen información sobre el comportamiento de variables cuyos valores son inexistentes. Particularmente, la obtención de un índice de aridez (IA) es imposible en puntos donde se carece de estaciones meteorológicas. Se utiliza la información de las imágenes NOAA-AVHRR NDVI (índice verde) para construir un modelo espacial predictivo para el NDVI en la transecta entre 69.51º W y 58.79º W y 34.40ºS y 38.07ºS. Mediante este modelo se obtienen predicciones de NDVI en los puntos de esta transecta donde se encuentran estaciones meteorológicas que permiten calcular el IA. Este índice es explicado mediante un modelo lineal por el NDVI. El modelo ajustado es aplicado luego a otros puntos dentro de la transecta para predecir valores del IA en puntos donde no existen estaciones meteorológicas. Así, mediante supuestos de continuidad espacial, se analizan patrones globales de comportamiento de aridez.; Satellite image data jointly with Spatial Stochastic Process methodologies offer information about the behaviour of variables whose values do not exist. Particularly, it is impossible to calculate values of the Aridity Index (AI) in points where there are no meteorological stations. Information based on NOAA-AVHRR NDVI images is used to build a predictive model for NDVI in the transect between 69.51º W and 58.79º W, and 34.40º S and 38.07º S. In the points where the meteorological stations are located, NDVI predictive values from this model are obtained. Then, a Linear Model is fitted to the NDVI predictive values to explain the calculated AI values in these points. This model is applied to obtain values of AI in points where there are no meteorological stations. Thus, aridity patterns are analyzed under spatial continuity assumptions.

Distribución de Chironomidae en dos sistemas fluviales ritrónicos (andino-serrano) de Argentina; Chironomidae (Diptera) distribution in two fluvial rhitronic systems (Andean and hilly streams), Argentina Medina, Ana Irene; Scheibler, Erica Elizabeth; Paggi, Analia Constancia Se presentan los primeros registros sobre el estado actual de la composición faunística de larvas de la familia Chironomidae en dos sistemas fluviales: río Mendoza (Mendoza) y río Grande (San Luis), a la misma latitud en una zona cuyana. Se analizaron los patrones de distribución y se comparó su taxocenosis, con sistemas fluviales similares de tipo ritrónicas. En el caso del río Mendoza la subfamilia Orthocladiinae presentó la mayor riqueza genérica (5) siguiéndole Podonominae con tres géneros; mientras que el resto de las subfamilias halladas compuestas por: Chironominae (2), Diamesinae (2) y Tanypodinae (1), exhibieron las densidades genéricas más bajas. En el río Grande el patrón de distribución de las subfamilias mostró que la riqueza genérica máxima la obtuvo siempre Chironominae (11), le siguió Tanypodinae (8) y por último Orthocladiinae (5). Se encontraron diferencias  tanto entre los grupos taxanómicos, la riqueza genérica como en la abundancia relativa de las subfamilias para la región neotropical. En cuanto a la composición faunística, ambos ríos muestran una marcada diferencia, el río Mendoza está predominantemente constituido por elementos patagónicos, en cambio la fauna encontrada en el río Grande está constituida por elementos brasílicos.; The first records are presented concerning the current status of faunal composition for Chironomidae larvae (Diptera) from two river systems: Mendoza River (Mendoza) and Grande River (San Luis), at the same latitude in the Cuyo region. Distribution patterns were analyzed and larvae assemblage compared with similar rhitronic river systems. In the case of Mendoza River, the subfamily Orthocladiinae exhibited the highest generic richness (5) followed by Podonominae with three genera; whereas the other subfamilies found, composed of: Chironominae (2), Diamesinae (2) and Tanypodinae (1), exhibited the lowest generic densities. In the Grande River, the distribution pattern of subfamilies always showed the highest generic density for Chironominae (11), followed by Tanypodinae (8) and finally Orthocladiinae (5). Differences between these two environments were found among taxonomic groups in generic richness and relative abundance for the Neotropical region. The faunal composition found in the Mendoza River was made up of Patagonian elements and the Grande River was dominated by brasilic elements.

Modelo probabilistico de la aridez en la provincia de Mendoza a partir de la fenología foliar a escala regional; Probabilistic model of the aridity in Mendoza province derived from foliar phenology ar regional scale Gonzalez Loyarte, Maria Margarita; Diblasi, Angela Magdalena; Menenti, Massimo Se plantea un modelo espacial continuo del índice de aridez (P/ETP) en función de la actividad de la vegetación (fenología foliar) a escala regional. Como medida de la fenología foliar usamos los parámetros obtenidos de la descomposición de una serie temporal de 9 años de imágenes mensuales de índice verde (NOAA-AVHRR NDVI) mediante la Transformada Rápida de Fourier (TRF). La TRF descompone la serie en una señal media y componentes sinusoidales (nuevas imágenes). Se seleccionan los parámetros de Fourier índice verde medio, amplitud a 3 y 1 año. Se ajusta luego un modelo de regresión linear múltiple con P/ETP como variable respuesta y los parámetros de Fourier como predictivas para los sitios con estación meteorológica. El modelo de regresión explica el 77% de la variabilidad de P/ETP. Este modelo es aplicado entonces a las imágenes completas para obtener un mapa de índice de aridez para la provincia de Mendoza.

The basement of the Central Andes: The arequipa and related terranes Ramos, Victor Alberto The basement of the Central Andes provides insights for the dispersal of Rodinia, the reconstruction of Gondwana, and the dynamics of terrane accretion along the Pacific. The Paleoproterozoic Arequipa terrane was trapped during collision between Laurentia and Amazonia in the Mesoproterozoic. Ultrahigh-temperature metamorphism correlates with the collapse of the Sunsás-Grenville orogen after ∼1000 Ma and is related to slab break-off and dispersal of Rodinia. The Antofalla terrane separated in the Neoproterozoic, forming the Puncoviscana basin. Its closure was coeval with the collision of the eastern Sierras Pampeanas. The rift-drift transitions of the early Paleozoic clastic platform showed a gradual younging to the north, in agreement with counterclockwise rotation based on paleomagnetic data of Antofalla. North of Arequipa arc magmatism and high-grade metamorphism are linked to collision of the Paracas terrane in the Ordovician, during the Famatinian orogeny in the Sierras Pampeanas. The early Paleozoic history of the Arequipa massif is explained by a backarc, which further south changed to open oceanic conditions and subsequent collision. The Antofalla terrane reaccreted to the continental margin by the late Ordovician. These accretions and subsequent separations during the Mesoproterozoic, Neoproterozoic-early Cambrian, and late Cambrian-middle Ordovician are explained by changes in absolute motion of the Gondwana supercontinent during plate global reorganization.

Brote de intoxicación alimentaria en la localidad de El Huecú, provincia de Neuquén; Foodborne disease outbreak in El Huecú community, province of Neuquén Lopez, C.; Feltri, A.; Leotta, Gerardo Anibal; Gonzalez, G.; Manfredi, E.; Gottardi, G.; Elder, M.; De Las Carreras, S.; Patri, C.; Guajardo, F.; San Martín, A.; Rivas, M. En febrero de 2006 ocurrió un brote epidémico de gastroenteritis aguda de origen alimentario, en ocasión de un festejo popular en una pequeña localidad de la provincia de Neuquén, Argentina. Aproximadamente 800 personas participaron de un almuerzo en las instalaciones del Gimnasio Municipal, y unas tres horas después de finalizado, cerca de 150 asistentes consultaron al hospital local, afectados por síndrome gastroentérico agudo. Se realizó una investigación epidemiológica caso-control a través de un muestreo representativo no probabilístico. Los resultados epidemiológicos establecieron un brote de ETA a fuente común, con una relación caso-control de 1:1,8. Los principales síntomas fueron cólicos abdominales (88%), vómitos (73,5%) y diarrea (60%). La torta que se sirvió en ese evento fue identificada como el alimento causal (OR 9,79; IC 95%; 2,66-36,00; valor p = 0,0001), sujeto a condiciones higiénico-sanitarias insatisfactorias en los diferentes procesos de elaboración, conservación y manipulación. De una porción de la torta se aisló una cepa de Staphylococcus aureus subespecie aureus, coagulasa positiva, enterotoxigénica, con un recuento de 2,4x10 UFC/g, y también se aisló este microorganismo de tres muestras de manos y narinas de personas involucradas en la preparación y el servicio. Las cepas aisladas de un operador y de la torta portaron el gen sea y presentaron el mismo patrón de SmaI-PFGE. Se atribuyó el brote de ETA a la contaminación durante el proceso de preparación de la torta consumida durante ese almuerzo popular, lo que podría estar relacionado con deficiencias en aspectos higiénicos y con la falta de refrigeración y de mantenimiento de la cadena de frío.; In the summer of 2006, an epidemic outbreak of acute gastrointestinal illness related to food consumption occurred in a small town in the province of Neuquén, Argentina. During a popular feast, approximately 800 local residents attended lunch held in the facilities of the Municipal Gymnasium. About three hours later, nearly 150 attendees sought medical assistance at the local hospital due to acute gastroenteritis. A case-control epidemiological investigation was conducted using representative non-probability sampling. The epidemiological investigation showed a common-source foodborne disease outbreak with a case-control ratio of 1:1.8. The main symptoms were abdominal cramps (88%), vomiting (73.5%) and diarrhea (60%). The cake was identified as the source of infection (OR 9.79; IC 95%, 2.66-36.00; p = 0.0001), and unsatisfactory hygienic conditions in food production, conservation and handling steps were identified. Coagulase positive, enterotoxigenic Staphylococcus aureus, subspecies aureus was detected in a piece of cake, with a count of 2.4x106 CFU/g, and in samples from the hands and nostrils of three people involved in food preparation and service. The strains isolated from both the cake and one of the food handlers carried the sea gene, and presented the same SmaI-PFGE pattern. The foodborne disease outbreak was considered to be due to contamination in the preparation process of the cake consumed at the feast, which was related to inadequate hygienic conditions, lack of refrigeration and cold chain disruption.

New remains of Notosuchus terrestris Woodward, 1896 (Crocodyliformes: Mesoeucrocodylia) from Late Cretaceous of Neuquén, Patagonia, Argentina; Novos restos de Notosuchus terrestris Woodward, 1896 (Crocodyliformes: Mesoeucrocodylia) do Cretáceo Superior de Neuquén, Patagônia, Argentina Fiorelli, Lucas Ernesto; Calvo, Jorge New materials of Notosuchus terrestris are here described. They were found on Bajo de la Carpa Formation outcrops, near the Universidad Nacional del Comahue, Neuquén City. Descriptions were based on five specimens, one of them the only specimen of Notosuchus with postcranial remains articulated to the skull. As in Sphagesaurus, it presents triangular teeth in cross-section and oblique molariforms with worn facet surface. As in Mariliasuchus, it possesses procumbent mandibular incisiform teeth and, like in other notosuchians and basal crocodyliforms, it was able of proal mandibular movement. The centra of cervical vertebrae possess ventral keel as in Chimaerasuchus. Elongated cervical neural spines and suprapostzygapophyseal laminae in cervicodorsal vertebrae are observed. The scapular dorsal end is greatly enlarged, while the coracoid ventromedial process end is moderately developed. The dorsal surface of the ilium is lateromedially wide with a greatly expanded acetabular roof and a prominent anteromedial process in the femoral shaft. Based on diverse cranial and postcranial characters, we infer that Notosuchus possessed facial and perioral musculature well developed and an herbivore diet, confirming the suggestions of previous authors. Notosuchus represents, based on phylogenetic studies, the sister taxon of Mariliasuchus and the monophyly of Notosuchia is demonstrated. Paleobiogeographycally, the occurrence of Chimaerasuchus in China evidences the faunistic interchange between Gondwana and Central Asia during the Early Cretaceous.; Novos materiais de Notosuchus terrestris são aqui descritos. Eles provêm de afloramentos da Formação Bajo de la Carpa, localizados próximos à Universidad Nacional del Comahue, na cidade de Neuquén. As descrições foram baseadas em cinco exemplares, um deles o único espécime de Notosuchus com restos pós-cranianos articulados ao crânio. Como em Sphagesaurus, N. terrestris apresenta dentes triangulares em seção cruzada e molariformes oblíquos com superfície da faceta com desgaste. Como em Mariliasuchus, a espécie possui dentes mandibulares incisiformes procumbentes e, como em outros notossúquios e crocodiliformes basais, era possível realizar o movimento antero-posterior mandibular. Os centros das vértebras cervicais possuem uma quilha ventral como em Chimaerasuchus. Espinhos neurais cervicais alongados e lâminas suprapószigapofiseais em vértebras cérvico-dorsais são observados. A extremidade escapular dorsal é amplamente alargada, enquanto a extremidade do processo ventro-medial do coracóide é pouco desenvolvida. A superfície dorsal do ilium é larga látero-medialmente com um teto acetabular amplamente expandido e processo ântero-medial proeminente na diáfise femoral. Baseado em diversos caracteres cranianos e pós-cranianos, infere-se que Notosuchus apresentava grande desenvolvimento da musculatura facial e perioral e tinha uma dieta herbívora, confirmando o que foi sugerido anteriormente por outros autores. Notosuchus representa, baseado em estudos filogenéticos, o táxon irmão de Mariliasuchus e a monofilia de Notosuchia é demonstrada. Paleobiogeograficamente, a ocorrência de Chimaerasuchus na China evidencia o intercâmbio faunístico entre o Gondwana e a Ásia Central durante o Cretáceo Inferior.

A new name for Celeus lugubris castaneus Olrog Fraga, Rosendo Manuel; Dickinson; E.

Reseña bibliográfica de Florencia Garramuño, Modernidades primitivas. Tango, samba y nación, Buenos Aires, Fondo de Cultura Económica, 2007, 269 páginas Sosa, Carlos Hernán El texto sintetiza los aspectos temáticos y metodológicos más relevantes, empleados por Florencia Garramuño al analizar el proceso de constitución del tango y el samba, como exponentes de la música nacional en la Argentina y el Brasil, entre fines del siglo XIX y comienzos del XX.

Diversidad y distribución de los reptiles de la Provincia de Entre Ríos, Argentina; Diversity and Distribution of the Entre Ríos province Reptiles, Argentina Giménez, Esteban Mariano; Ayarrgaray, Matias; Manzano, Adriana Silvina . Los estudios sobre diversidad de especies en Argentina han aumentado considerablemente en los últimos años, sin embargo son pocos los trabajos referidos a la provincia de Entre Ríos y en particular a su fauna de reptiles. Con el propósito de caracterizar la composición de especies y su distribución geográfica se realizó una base de datos, con información obtenida a partir de la revisión de colecciones herpetológicas del país y complementada con datos bibliográficos, la cual fue asociada mediante un Sistema de Información Geográfica (SIG). Se realizó una lista de los reptiles de Entre Ríos y se confeccionaron mapas de distribución para las especies. Actualmente hay 73 especies y subespecies, lo cual representa el 23,3 % del total registrado para Argentina, siendo el grupo de las serpientes el de mayor número. En comparación con otras provincias del Litoral Argentino, Entre Ríos tiene la menor riqueza específica, particularmente en saurios y anfisbenas, lo cual puede deberse a la dificultad que presentan muchas aéreas para ser relevadas, ya sea por su topografía o por ser campos privados. Es necesario concretar un relevamiento general de la herpetofauna de la provincia, con el fin de obtener un panorama actualizado de su diversidad, el estado de conservación en el que se encuentran y su distribución actual, así como la repercusión del impacto de la modificación antrópica de los ambientes. Al conocer con mayor precisión estos aspectos podrá lograrse un acercamiento a la comprensión de la biodiversidad, que permita su conservación y utilización sostenible.; Studies related to the diversity of species in Argentina, have been increasing considerably in the last years, however there are few works referred to Entre Ríos province and in particular related to the fauna of Reptiles. With the purpose of characterizing the species composition and their geographical distribution, an information data base was made revising many Argentinean herpetological collections and complemented with bibliographical information, and was associated by means of a Geographic Information System (GIS). It was made a list of the reptile species in Entre Ríos and also maps of distribution for the species. There are 73 species and subspecies registered that represent the 23, 3% of the total reptiles for Argentina, being the snakes group the largest in number. Entre Ríos has the lowest species richness comparing with other provinces that integrate the “Litoral” region of Argentina, especially considering lizards and amphisbaenas. The difficulty to get to many areas because of the complicated topography or because they are private properties, could be an explanation of this lowest richness. Therefore, it is necessary to make a general survey of the herpetofauna in Entre Ríos and a revision of all the herpetological collections of our and border countries, with the goal of obtain an actualized perspective of it diversity, the conservation status, their actual distribution and the effects of the anthropic impact to the environment. Knowing all this aspects we will have an approach to the diversity comprehension that let us make a sustainable use of it.

Reflection and transmission in the ionosphere considering collisions in a first approximation Yesil, Ali; Aydogdu, Mehmet; Elias, Ana Georgina Reflection and transmission coefficients (R and T) of high frequency waves propagating in the ionosphere are studied taking collisions into account. This was done approximating the expression in the refractive index using binomial expansion and neglecting terms of order higher than is the ratio between the electron collision frequency and the wave frequency. R and T height profiles were assessed using the International Reference Ionosphere, IRI, to estimate the ionosphere plasma parameters. Although no significant differences are found between the estimation with and without collisions, the method employed to include collisions may be useful for other purposes where collisions should be taken into account.

Seven-year relative abundance in two syntopic neotropical lizards, Liolaemus quilmes and L. ramirezae (liolaemidae), from northwestern Argentina; Siete años de abundancia relativa en dos lagartos sinpáticos neotropicales, Liolaemus quilmes and L. ramirezae (liolaemidae), del noroeste argentino Robles, Cecilia Ines; Halloy, Monique Estudios sobre la abundancia relativa de poblaciones de lagartos simpátricos pueden ayudar a conocer sus historias de vida y, a largo plazo, a estimar potenciales problemas de conservación. A través de los años, pueden emerger patrones de coexistencia entre dos o más especies, tales como los efectos de una especie sobre la otra, o el efecto de las precipitaciones y la temperatura, o la abundancia de la presa y la presión de predación. Aquí reportamos un estudio de siete años sobre la abundancia relativa de dos especies Neotropicales del Noroeste de Argentina, Liolaemus quilmes y L. ramirezae. Estas dos especies se encuentran en sintopía en un sitio llamado Los Cardones. Monitoreamos un área de 60 x 60 m, dos a cinco días, cada uno o dos meses, a lo largo del período de actividad de los lagartos, desde el año 2000 al 2007. Durante este periodo, la abundancia relativa de L. quilmes, tomado como el número promedio de adultos avistados por monitoreo por mes, permaneció estable, mientras que la de L. ramirezae aumentó en los últimos dos años. La abundancia relativa de una población no afectó a la otra a lo largo de los años ni tampoco la de machos y hembras de L. quilmes. Aunque la cantidad de precitaciones varió significativamente a lo largo de los años, no estuvo asociada a la abundancia relativa de cada población. Las dos especies muestran diferencias en su uso del hábitat y en sus preferencias alimenticias lo cual podría facilitar la coexistencia. Sin embargo, a parte de considerar estos parámetros ecológicos, también habría que considerar limitantes históricos para poder explicar los patrones observados hoy.; Studies on the relative abundance of sympatric lizard populations can give insight into their life histories and, if long-term, can help estimate potential conservation problems. Through the years, patterns of coexistence between two or more species may emerge, such as the effect of one species over the other, or the effect of factors such as precipitation and temperature, or prey abundance and predator pressure. Here we report a seven-year study on the relative abundance of two Neotropical species from Northwestern Argentina, Liolaemus quilmes and L. ramirezae. These two species are found in syntopy at a site called Los Cardones. We monitored an area of 60 x 60 m, two to five days, every one or two months, throughout the activity period of the lizards, from 2000 to 2007. During that time, the relative abundance of L. quilmes, taken as the average number of adults sighted per survey per month, remained stable during the seven-year study whereas that of L. ramirezae increased in the last two years. The relative abundance of one population did not affect the other over the years nor did that of male and female L. quilmes. Although the amount of precipitation varied significantly over the years, it was not associated to the relative abundance of each population. The two species show differences in their habitat use and in prey preferences which may facilitate coexistence. However, besides taking into account these ecological parameters, historical constraints must also be considered in order to explain the patterns observed today.

Hormigas (Hymenoptera: Formicidae) de la provincia de Santa Fe, Argentina; Ants (Hymenoptera: Formicidae) of Santa Fe province, Argentina Vittar, Fernando; Cuezzo, Fabiana del Carmen El presente trabajo pretende aportar una lista faunística actualizada de las subfamilias, tribus, géneros y especies de hormigas de la provincia de Santa Fe, Argentina. Si bien estos listados tienen poca duración temporal, contribuyen en gran medida a incrementar el conocimiento de un taxón determinado, despertando interés y brindando una herramienta fundamental para el desarrollo de estudios posteriores. Como resultado, nueve registros son nuevos para la Argentina y dos géneros y 18 citas de especies nuevas para la provincia de Santa Fe.; The present paper provides an updated faunistic list of the subfamilies, tribes, genera and species of ants of Santa Fe province, Argentina. To a great extent, these listings contribute to increase the knowledge of a specific taxa, awaking interest, and offering a fundamental tool for the development of subsequent studies. As a result, nine species are cited as new for Argentina, and two genera and 18 species are cited for Santa Fe province for the first time.

First record of Arctotherium (Ursidae, Tremarctinae) in northwestern Argentina: paleobiogeographic significance. Garcia Lopez, Daniel Alfredo; Ortiz, Pablo Edmundo; Madozzo Jaén, María Carolina; Moyano, Marcelo Sebastian Here we describe the first remains of Arctotherium from Late Pleistocene deposits of Catamarca Province, northwestern Argentina. This material narrows the geographical gap between two previously known fossiliferous localities separated by more than 1200 km. Institutional Abbreviations—BMNH, Natural History Museum, United Kingdom; GP, Museu Paulista, Universidade de Sâo Paulo, Brazil; MACN, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Buenos Aires, Argentina; MMMP, Museo Municipal de Mar del Plata ‘Lorenzo Scaglia’, Argentina; PVL, Colección Paleontología de Vertebrados Lillo, Tucumán, Argentina; UZM, Zoological Museum, University of Copenhagen, Denmark.

On the time of minimum ionization in the F2 region Ezquer, Rodolfo Gerardo; Cabrera, Miguel Angel; Mosert, Marta Estela; Radicella, Sandro María; Migoya Orue, Yenca Olivia Using measurements of the critical frequency of F2 region (foF2) the validity of the International Reference Ionosphere model to predict the time of minimum ionization is checked. Data obtained at different ionospheric stations have been considered. The CCIR and URSI options are used to model calculations. For CCIR option the results show that good predictions were obtained for about 40% of the considered cases. For the rest of the considered data, the model predicts the minimum at times earlier than that observed in the measurements. The percentages of good predictions obtained with URSI option are lower than those corresponding to CCIR one.