Normalization of Rings Greuel, Gert Martin; Laplagne, Santiago Jorge; Seelisch, Frank We present a new algorithm to compute the integral closure of a reduced Noetherian ring in its total ring of fractions. A modification, applicable in positive characteristic, where actually all computations are over the original ring, is also described. The new algorithm of this paper has been implemented in Singular, for localizations of affine rings with respect to arbitrary monomial orderings. Benchmark tests show that it is in general much faster than any other implementation of normalization algorithms known to us.

Bass' NK groups and cdh-fibrant Hochschild homology Cortiñas, Guillermo Horacio; Haesemeyer, C.; Walker, Mark E.; Weibel, C. The K-theory of a polynomial ring R[t] contains the K-theory of R as a summand. For R commutative and containing Q, we describe K∗(R[t])/K∗(R) in terms of Hochschild homology and the cohomology of Kähler differentials for the cdh topology. We use this to address Bass’ question, whether Kn(R) = Kn(R[t]) implies Kn(R) = Kn(R[t1,t2]). The answer to this question is affirmative when R is essentially of finite type over the complex numbers, but negative in general.

Análisis del control geológico en la torrencialidad del arroyo Las Lajas, Córdoba, a través de la modelización hidrológica; Analysis of the geological control on the Arroyo Las Lajas, Cordoba, flashiness through an hydrological modeling Doffo, Nelso; Eric, Carlos F.; Gonzalez Bonorino, Gustavo Se analiza la incidencia de factores litológicos, estructurales y bióticos en la respuesta hidrológica (torrencialidad) de una cuenca hídrica serrana aplicando el modelo matemático ARHymo. La cuenca alta del arroyo Las Lajas se encuentra en las sierras de Comechingones, entre 1.200 y 750 m s.n.m., con una superficie de 41 km2 y una red de drenaje de orden de Horton 6. La morfología de la cuenca está fuertemente controlada por la traza de la falla Las Lajas, una estructura de actividad reciente que separa un sustrato granítico de otro metamórfico. Para el modelado, la cuenca alta fue subdividida en 42 subcuencas. Para cada una de ellas se obtuvieron valores de curva número (CN). La torrencialidad de cada subcuenca fue estimada en base a los tiempos al pico (Tp) y a la distribución temporal de la onda de creciente reflejada en los hidrogramas. Se confrontaron las formas de los hidrogramas de subcuencas representativas y la distribución de las frecuencias de los tiempos al pico, con las características geológicas de la cuenca. Las subcuencas desarrolladas en metamorfitas con fuerte control estructural mostraron mayor torrencialidad que las ubicadas en el sustrato granítico.; The impact of lithological, structural and biotic factors in the hydrological response of a mountain drainage basin is analyzed using the mathematical model ARHymo. The upstream reach of the Las Lajas creek is located in the Comechingones Ranges, between 1,200 to 750 m a.s.l.; it has an area of 41 km2 and a drainage network of Horton order 6. The morphology of the basin is strongly controlled by the Las Lajas fault, a recently active structure that separates granitic from metamorphic substrates. The basin was subdivided into 42 subbasins and curve numbers were computed for each subbasin. The flashiness of the flood wave was estimated from time-to-peak data and from the shapes of hydrographs. Comparison of the shapes of the hydrographs of representative subbasins and the distribution of time-to-peak frequencies, with the geological features of the basin, suggests that the subbasins developed on metamorphic substrate show greater flashiness than those located on granitic substrate.

Social isolation and stress related hormones modulate the stimulating effect of ethanol in preweanling rats Arias Grandio, Carlos; Solari, Ana Clara; Mlewski, Estela Cecilia; Miller, Stacie; Haymal, Olga Beatriz; Spear, Norman E.; Molina, Juan Carlos Preweanling rats are highly sensitive to the locomotor stimulation induced by relatively high ethanol doses. In adult mice this ethanol effect is modulated by stress. The goal of the present study was to analyze the role of stress and corticosterone in the stimulating effect of ethanol in preweanling rats. In Experiment 1 15-day-old rats were separated from the mother during a period of 4 h in which subjects remained isolated or paired with a littermate. In a third condition pups remained in the home-cage with the dam. After this isolation period pups were given ethanol (0 or 2.5 g/kg) and were tested in a novel environment. Previous data have shown that a similar period of isolation is enough to increase corticosterone levels in preweanling rats. Experiment 2 evaluated the effect of exogenous administration of corticosterone (0, 3 or 6 mg/kg) along with ethanol, and Experiment 3 tested ethanol-mediated locomotor activation in adrenalectomized preweanling rats. The last experiment aimed to test the role of corticotropic releasing factor 1 (CRF1) receptors in locomotion induced by ethanol in isolated pups. According to our results there is a synergism between stress or corticosterone and ethanol in preweanling rats. The interaction between stress (induced by social isolation) and ethanol seems to be mediated by CRF, since blockade of CRF1 receptors cancelled the effect of ethanol in isolated pups. This study highlights the importance of considering stress as a possible intervening variable in studies evaluating ethanol effects in developing animals when maternal separation is used in the experimental procedure.

Vibrational spectra of magnesium oxalates D'Antonio, Maria C.; Mancilla Haselbach, Nancy Beatriz; Wladimirsky, Alejandra; Palacios, Daniel; Gonzalez Baro, Ana Cecilia; Baran, Enrique José The infrared and Raman spectra of anhydrous MgC2O4 as well as those of the two polymorphic forms of the dihydrated oxalate, α-MgC2O4·2H2O and β-MgC 2O4·2H2O, were recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of natural α-MgC2O4·2H2O (the mineral glushinskite). Some comparisons between these polymorphs and with other, previously investigated, oxalate complexes were made. The IR spectra of partially deuterated samples of α-MgC2O4· 2H2O were also discussed, reinforcing some of the performed assignments.

Calidad de agua para la producción de especies animales tradicionales y no tradicionales en Argentina; Water quality for the production of traditional and non traditional animal species in Argentina Fernandez Cirelli, Alicia; Moscuzza, Carlos Hernán; Pérez Carrera, Alejo Leopoldo; Volpedo, Alejandra La calidad de agua es un factor determinante de la producción de especies animales tradicionales y no tradicionales, debido a su relación con los requerimientos nutricionales de cada especie. Los criterios que habitualmente se consideran para la determinación de la calidad del agua de bebida son sus propiedades físicoquímicas y organolépticas, la presencia de compuestos tóxicos y de bacterias patógenas, y el exceso de minerales. En este trabajo se presenta una revisión de los estudios de calidad de agua para las producciones animales tradicionales (producción de carne y leche bovinas) y no tradicionales (acuicultura y pesca de captura) para diferentes regiones de Argentina con el objetivo de analizar las carencias de información y proponer la intensificación de estudios que permitan mejorar los sistemas de producción animal de nuestro país.; Water quality is a determining factor in the production of both traditional and nontraditional animal species since it is related to the nutritional requirements of each species. Water quality criteria often include physical- chemical and organoleptic properties, the presence of toxic compounds and pathogenic bacteria as well as mineral excess. The aim of this work is to review studies on water quality for the production of traditional (bovine meat and milk) and non-traditional animal species (aquaculture and capture fisheries) in different regions of Argentina. The identification of information gaps will be the basis for new studies to improve animal production systems in Argentina.

La Facultad va a la Escuela del Barrio. Una experiencia de interacción con la comunidad escolar a través de talleres de Ciencias Naturales Bab, Marisa Alejandra; Borrajo, R.; Brusasco, Carlos Gaston; Calcaferro, Leila Magdalena; Castiglioni, José Luis; Garcia, Maria Soledad; Lavalle, M. del C.; Pastor, Veronica Estela; Pernici, M.; Rebón, Lorena; Richard, Diego; RodrÍguez Torres, Claudia Elena; Vampa, V. La Facultad va a la Escuela del Barrio es un proyecto de extensión acreditado por las Facultades de Ciencias Naturales y Museo, y Ciencias Exactas de la UNLP, que realiza sus actividades en forma continuada desde el año 2002. En el mismo se desarrollan actividades en el ámbito escolar tendientes a fomentar la experimentación como parte integral de la enseñanza de las Ciencias Naturales en la escuela. El proyecto está formado por un equipo interdisciplinario y de los distintos claustros universitarios, y constituye un ámbito de formación integral de profesionales comprometidos con la sociedad.

Groundwater travel time in the freshwater lenses of Samborombón Bay, Argentina; Temps de transfert hydrogéologique dans les lentilles d'eau douce de la Baie de Samborombón, Argentine Carol, Eleonora Silvina; Kruse, Eduardo Emilio; Roig, Alejandro The Samborombón Bay area (Argentina) is a coastal plain environment that contains groundwater resources with high salinity. In addition, there are local freshwater lenses associated with shell ridges and sand sheets in the region. In this work, the groundwater travel time in these freshwater lenses is estimated based on their geological conditions, which include hydraulic conductivity, recharge, morphology and discharge to surface freshwater or to saline groundwater. Groundwater travel times in the freshwater lenses were calculated from the equations developed by Chesnaux andAllen. The travel times estimated for the different scenarios were relatively short. The results indicate that the groundwater flow tends to be strongly dependent on the recharge conditions, with an excess of water in the water balance. The results can be applied to help design sustainable management methods to exploit this water resource system and also to assess the impact of contaminant plumes on this groundwater resource.; La zone de la Baie de Samborombón (Argentine) est un environnement de plaine côtière qui contient des ressources en eaux souterraines dont la salinité est élevée. En outre, il existe des lentilles d’eau douce locales associées aux crêtes de coquillages et feuilles de sable dans la région. Dans ce travail, le temps de transfert des eaux souterraines dans ces lentilles d’eau douce est estimé en fonction de leurs conditions géologiques, notamment la conductivité hydraulique, la recharge, la morphologie et la décharge vers les eaux de surface ou vers les eaux souterraines salines. Les temps de transfert des eaux souterraines dans les lentilles d’eau douce ont été calculés à partir des équations développées par Chesnaux et Allen. Les temps de transfert estimés pour les différents scénarios sont relativement faibles. Les résultats indiquent que l’écoulement des eaux souterraines a tendance à être fortement dépendant des conditions de recharge, avec un excès d’eau dans le bilan hydrologique. Les résultats peuvent être appliqués pour aider à concevoir des méthodes de gestion durable pour l’exploitation de ce système de ressources en eau et aussi pour évaluer l’impact de panaches de contaminants sur cette ressource en eaux souterraines.

Heterogeneous MNC subsidiaries and technological spillovers: Explaining Marin, Anabel; Subash Sasidharan One of the most intriguing aspects of the recent empirical literature on FDI-related spillover effects is the increasing identification of mixed results. A few studies, particularly in advanced countries have found positive effects; however, a more common scenario in recent studies is the prevalence of insignificant or even negative effects. This is despite the fact that theory predicts substantial positive effects in association with a supposed technological superiority of MNCs relative to domestic firms, particularly in the context of less advanced countries. In this paper, by distinguishing subsidiaries according to their orientation to carry out creative vs. exploitation activities in the host economy, we are able to distinguish situations with positive and negative spillover effects, and we explain why they may be emerging. More specifically, we find that only subsidiaries that are oriented to technologically creative activities have a significantly positive effect in India. In contrast, subsidiaries oriented mostly to technologically exploitative activities generate negative effects in some circumstances. The implications for theory and policy are discussed.

Insurance Regulation and the Credit Crisis: What's New? Ferro, Gustavo Adolfo Prior to the 2008 global credit crisis, some developments had occurred in the regulation of the insurance industry worldwide. At different speeds, the world was heading toward a more risk-based solvency regulation and some convergence on principles and criteria. We see a common thread in the present discussion and in the way events happened. We consider that the great debate in the industry is a fundamental decision: whether to engage in other than core business activities. If the industry focuses on its insurance business, the argument for specialized regulation and the continuity of a conservative and prudent line of business is strong. Instead, if the industry deepens its identification with other lines of financial business, the specialized supervision arrangement does not hold. The move entails both possibilities of new, riskier and promising business, but also perils, since the industry “buys” the systemic characteristics that distinguish other financial institutions.

¿Tratar o no tratar? la controversia científica sobre el tratamiento para los enfermos de chagas crónico; To treat or not to treat? scientific controversy about the treatment for chronic chagas' disease patients Kreimer, Pablo Rafael; Romero, Lucia Ana; Bilder, Paula Rosana La enfermedad de Chagas es una de las principales endemias de América Latina, cuyo desarrollo se manifiesta en 3 etapas diferenciadas, que han sido caracterizadas por los especialistas como aguda, indeterminada y crónica. Hacia mediados de la década de 1960, dos laboratorios transnacionales desarrollaron dos drogas, cuya eficacia ha sido valorada como contundente en el caso de los enfermos agudos. En cambio, los pacientes crónicos quedaron al margen de este tratamiento específico porque entre los especialistas en el tema no existía acuerdo sobre su efectividad. Mientras unos juzgaron que las drogas ya no eran efectivas en este estadio de la enfermedad, otros lo valoraron efectivo y preventivo de la evolución de la enfermedad y de sus síntomas clínicos. Así, desde 1980 y hasta la actualidad, el tratamiento de los enfermos crónicos de Chagas es objeto de una controversia científico-médica. Esta controversia moviliza diferentes conocimientos, es motorizada por actores diversos (médicos cardiólogos, investigadores científicos, funcionarios del estado nacional, organismos internacionales) y tiene consecuencias sobre los propios enfermos, ya que, según quién los atienda o a qué instituciones acudan, será el tipo de tratamiento que recibirán. En este trabajo caracterizamos los posicionamientos de los diferentes actores involucrados en el desarrollo de la controversia, analizando  los enunciados y conocimientos científicos puestos en cuestión por ellos. Se identifican y especifican las distintas etapas de la controversia, con el objetivo de comprender sus consecuencias sociales y políticas, al nivel de las prácticas de tratamiento, de sus respectivas reglamentaciones y en cuanto al tipo de configuración médica y social del paciente. Mostramos así, que lo que se pone en cuestión y es objeto de disputa, son las concepciones mismas de “enfermedad” y de “cura”, tanto en el campo científico médico local como en el espacio más amplio de organismos nacionales e internacionales de políticas de salud.; Chagas disease is one of the main endemic illnesses in Latin America. Since 1969 up to the present, the treatment of chronic Chagas patients has been the object of a scientific-medical controversy mobilizing several bodies of knowledge and actors. The resolution of the controversy has direct effects on the health of patients; however, they have been systematically excluded of public debates. In this paper we identified and specified four different steps of the controversy, showing the different positions adopted by the actors implicated, analyzing their statements, the scientific knowledge mobilized during the debates and the consequences for the establishment of norms for the treatment. We conclude showing that what makes up the central issue of the controversy is not what the actors implicated explicitly state as it but the criteria (technical and cognitive) through which are measured and defined «illness» and «cure» states. This research is about a case study in Argentina.

Formas de la sobrepoblación relativa y políticas sociales: La política asistencial durante el primer gobierno Kirchnerista (2003-2007) Seiffer, Tamara; Matusevicius, Jorgelina El artículo intenta ser una aproximación crítica a la política asistencial implementada durante el primer gobierno kirchnerista. Parte de reconocer el papel de la política social en el modo de producción capitalista y su relación con la conformación de una sobrepoblación relativa, para llegar al análisis de los tres planes nacionales sobre los que se erigió la política asistencial en el período estudiado.; The article tries to be a critical approach to social policy implemented during the first Kirchner government. It starts by recognizing the role of social policy in the capitalist mode of production and its relation to the conformation of a relative surplus population, in order to analyze the three national plans that organize assistential policy in the period under study.

Potential source regions of biogenic aerosol number concentration apportioning at King George Island, Antarctic Peninsula Alencar, Alexandre S.; Evangelista, Heitor; Dos Santos, Elaine A.; Correa, Sergio M.; Khodri, Myriam; Garcia, Virginia M. T.; Garcia, Carlos A. E.; Pereira, Enio B.; Piola, Alberto Ricardo; Felzenszwalb, Israel Nowadays it is well accepted that background aerosols in the boundary layer over remote oceans are of marine origin and not aged continental. Particularly in the Atlantic sector of the Southern Ocean at least four main important regions exhibit significant ocean primary productivity. They are the Bellingshausen-Amundsen Sea, the Weddell Sea, the southern Argentinean shelf and the southern Chilean coast. In this work, we have combined ground-based continuous atmospheric sampling of aerosol number concentration (ANC), over-sea dimethyl sulphide (DMS) measurements, chlorophyll a (chl a) concentration provided by Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite images, in situ meteorological data and monthly regional NCEP-NCAR re-analysis wind fields in order to investigate the relative contribution of each of the above regions to the apportionment of the ANC at King George Island (KGI), South Shetland Islands. Our results suggest that, at least during the period from September 1998-December 1999, the southern Argentinean shelf acted as the main contributor to the ANC measured in KGI.

First serological survey of antibodies against pathogenic viruses in a wild vicuña (Vicugna vicugna) population in the Argentinean Andean altiplano Marcoppido, Gisela Ariana; Parreño, Gladys Viviana; Vila, Bibiana Leonor Serum samples from 128 wild vicuñe; as (Vicugna vicugna) were tested for antibodies (Ab) to rotavirus (RV), bovine parainfluenza virus 3 (BPIV-3), bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV-1), foot-and-mouth disease virus (FMDV), bluetongue virus (BTV), equine herpesvirus-1 (EHV-1), and influenza A virus equine (EIV). Samples were collected in Cieneguillas Province of Jujuy, in northern Argentina. Feces from 44 vicuñe; as were also collected to investigate RV shedding. Llamas (Lama glama) and domestic cattle (Bos taurus) from the area studied also were tested for antibodies to these viruses. Antibodies against RV (100%) and BPIV-3 (37%) were detected in the vicuñe; as sampled. No RV antigen was detected in any of the fecal samples tested. One vicuñe; a was positive for Ab to BHV-1 (0.8%) and another for BVDV-1 (0.8%). The Ab prevalences detected in llamas were: 100% (16/16) for RV, 47% (8/17) for BPIV-3, 17.6% (3/17) for BHV-1, and 5.9% (1/17) for BVDV-1. However, domestic cattle had high antibody prevalences for RV and BPIV-3, 100% (13/13) and 73% (11/15), respectively, but were negative for Ab to BHV-1 and BVDV. No antibodies against FMDV, BTV, EHV-1, or EIV were detected in wild vicuñe; as or domestic species. Because no data of viral circulation on wild vicuñe; as are available, this report represents the first evidence of viral infection in wild vicuñe; as from the Argentinean Andean Puna.

Tauziehen um Genprobe Duran, Valeria Vanesa Während der letzten Militärdiktatur in Argentinien (1976 bis 1983) wurden nicht nur Tausende entführt, gefoltert und ermordet, sondern auch systematisch Kinder von Verschwundenen illegal adoptiert. In den meisten Fällen wissen die Kinder bis heute nichts von ihrer ursprünglichen Identität. Ein Fall steht zurzeit besonders im öffentlichen Interesse. Es geht um die Adoptivkinder der Hauptaktionärin der Clarín-Gruppe, dem mächtigsten Medienunternehmen des Landes.

Transformaciones urbanas y de la estructura social de un barrio de la ciudad de Buenos Aires; Urban transformations and transformations of the social structure of a neighborhood in the City of Buenos Aires Baer, Luis Enrique Algunos estudios urbanos abordan los procesos sociales que replantean la estructura, los usos del suelo y el paisaje de la ciudad; otros indagan los impactos de estos cambios en las condiciones de vida, las prácticas colectivas y las representaciones sociales. Este trabajo intenta ubicarse entre ambas perspectivas. Por un lado, recorremos las intervenciones urbanas que reestructuraron un barrio de la Ciudad de Buenos Aires entre 1998 y 2004, el “barrio del Abasto”. Esta transformación fue impulsada por el sector privado y consistió en el acondicionamiento de grandes emplazamientos urbanos para usos comerciales, residenciales y de entretenimiento. Por otro lado, indagamos los cambios urbanos desde las prácticas y representaciones cotidianas de los residentes de las “Torres de Abasto”, un grupo de personas que se mudó al barrio cuando ya había iniciado su reconversión. Específicamente, analizamos los vínculos y las representaciones que establecen en dicho complejo residencial y en el barrio que lo rodea.; Some scholars tace the urban processes that restate the structure, soil use and city landscape; some others analyze the effect of these changes on the life conditions, collective practices and social representations. This work tries to be halfway the aforementioned perceptions; we account the urban interventions which restructured a neighborhood in the city of Buenos Aires between 1998 and 2004, namely del Abasto neighborhood. This transformation was fostered by the private sector and it consisted of the adaptation of large urban sites for commercial, residential and leisure uses. We researched the urban changes from the quotidian practices and representations of the residents of the Torres de Abasto, a group of people who moved in the neighborhood when its reconversion had already begun. We analyzed the links and representations which are established in said residential complex and in the surrounding neighborhood.

Calidad de vida y políticas de hábitat: Programa de Mejoramiento Barrial en Córdoba, Argentina. Caso de estudio: barrio Malvinas Argentinas; Quality of Life and Housing Policy: Neighborhood Improvement Programs in Cordoba, Argentina. Case study: Malvinas Argentinas neighborhood Marengo, Maria Cecilia; Elorza, Ana Laura En este artículo analizamos los supuestos sobre la calidad de vida que orientan el Programa de Mejoramiento Barrial –Promeba– implementado en el medio local, y reflexionamos sobre el alcance que los mismos han tenido en términos de incidir positivamente en la calidad de vida de las familias destinatarias del programa. La base empírica de la investigación es un estudio de caso: el barrio Malvinas Argentinas, 1ª Sección (localizado en el área metropolitana de Córdoba, Argentina). La metodología consideró la triangulación en la recolección de datos. La articulación de esta doble información, la escrita y la recabada a partir de las valoraciones de los diferentes actores intervinientes, permitió comprender los supuestos que sustenta la política implementada y los alcances de su actuación.En este artículo, analizamos los supuestos sobre la calidad de vida que orientan el Programa de Mejoramiento Barrial (PROMEBA) implementado en el medio local, y por el otro, reflexionamos sobre el alcance que los mismos han tenido en términos de incidir positivamente en la calidad de vida de las familias destinatarias del programa. La base empírica de la investigación es un estudio de caso: el barrio Malvinas Argentinas Primera Sección (localizado en el área metropolitana de Córdoba- Argentina). La metodología consideró la triangulación en la recolección de datos. La articulación de esta doble información, la escrita y la recabada a partir de las valoraciones de los diferentes actores intervinientes, permitió comprender los supuestos que sustenta la política implementada y los alcances de su actuación. In the seventies the category quality of life takes importance as a measure and objective of countries development. From this re-thinking it begins to be the goal of public policy, globally promoted by international financing agencies through programs of poverty alleviation. In this article we analyze the assumptions about quality of life that guide the Program of Neighborhood Improvement (PROMEBA) implemented in the local arena, and we reflect on the extent they have had in terms of positives impacts in the quality of life of the targeting families. The empirical research is based on the case study: Malvinas Argentinas neighborhood (located in Córdoba metropolitan area, in Argentina). The methodology considered triangulation in data collection. The double articulation the information crossed -written and compiled from reviews of the different actors involved- allowed us to understand the assumptions behind the housing policy implemented and the extent of its performance.; In this article we analyze the assumptions about quality of life that guide the Program of Neighborhood Improvement –Promeba– implemented in the local arena, and we reflect on the extent to which they have had a positive impact on the quality of life of the targeted families. The empirical research is based on the case study: Malvinas Argentinas neighborhood (located in Córdoba metropolitan area, in Argentina). The methodology considered triangulation in data collection. The double articulation the information crossed –written and compiled from reviews of the different actors involved– allowed us to understand the assumptions behind the housing policy implemented and also its performance.

A comparative study of invasive Helianthus annuus populations in their natural habitats of Argentina and Spain; Poblaciones invasoras de Helianthus annuus en Argentina y España; Populations envahisseurs de Helianthus annuus en Argentine et en Espagne Poverene, María Mónica; Cantamutto, Miguel Ángel Wild Helianthus annuus is native to North America but it naturalized in other parts of the world as well. Although the origin of exotic populations is uncertain, they have probably evolved very differently in different countries. To unravel the origin of invasive populations from Argentina and Spain, morphological and agro-ecological data of nine populations from central Argentina, six from Andalusia and one from Gerona were collected in their natural habitats during three exploration trips in 2007 and 2008. In Argentina wild H. annuus was found mainly in disturbed areas between roads and fences. In a few cases the populations were located on the margins of cultivated fields. The Argentinean populations are spread across more than 50,000 m2 at a density of about 25 plants m-2. In Spain, the populations were found mainly in croplands. The largest population covered about 1,500 m2 and comprised no more than 200 plants. The Argentinean populations had taller plants with a higher number of heads of small size, while the Spanish populations were characterized by bigger heads with wider ligules and bracts. Plants were shorter and leaf size was larger in Gerona than in Andalusia. Multivariate analysis differentiated populations from Argentina and Spain by many traits. Wild-crop gene flow is likely the source of genetic variation among them. In Argentina, the populations keep the appearance of early wild introductions, while the Spanish populations are weedier and probably originated from pollen contamination of commercial seed with wild plants or crop-wild hybrids.

Testing detection and discrimination of vegetation chemical cues in the subterranean rodent Ctenomys talarum Schleich, Cristian; Zenuto, Roxana Rita Previous studies on the subterranean rodent Ctenomys talarum (tuco-tuco) have shown that this species has the ability to use olfaction to orient their digging while foraging. As a continuation of these works, we assess whether direct contact with vegetation chemical signals is required for food odour recognition, and whether this subterranean rodent is also able to discriminate plants of different nutritional quality by the chemical signals released by them into the soil. First, we test animal responses to plant extracts and controls (water) covered with a wire mesh or without it. Also, we assess individual digging response in an artificial Y-maze whose arms were filled with soil in which plants of different nutritional quality have been grown. The results of this study suggest that (i) volatile chemical cues allow food odour recognition and direct contact with the odour source does not enhance such recognition in C. talarum, and (ii) olfaction could play a key role in the finding of food patches, allowing individuals to direct their excavation towards plant species of high nutritional quality. © 2010 Dipartimento di Biologia Evoluzionistica dell'Universitá, Firenze, Italia.

Identification of the long polar fimbriae gene variants in the locus of enterocyte effacement-negative Shiga toxin-producing Escherichia coli strains isolated from humans and cattle in Argentina Galli, Lucía; Torres, Alfredo G.; Rivas, Marta The long polar fimbriae (Lpf) is one of few adhesive factors of Shiga toxin-producing Escherichia coli (STEC) and it is associated with colonization of the intestine. Studies have demonstrated the presence of lpf genes in several pathogenic E. coli strains, and classification of variants based on polymorphisms in the lpfA1 and lpfA2 genes has been adopted. Using a collection of Argentinean locus of enterocyte effacement (LEE)-negative STEC strains, we determined that the different lpfA types were present in a wide variety of serotypes with no apparent association between the types of lpfA1 or lpfA2 genes and the severity of human disease. The lpfA2-1 was the most prevalent variant identified, which was present in 95.8% of the isolates, and lpfA1-3 and lpfA2-2, proposed as specific biomarkers of E. coli O157:H7, were not found in any of the serotypes studied. The prevalence of lpf genes in a large number of strains is useful to understand the genetic diversity of LEE-negative STEC and to define the association of some of these isolates carrying specific lpf-variants with disease.