A cornerstone in the history of hypertension: The seventieth anniversary of the discovery of angiotensin Milei, Jose In 1939, two independent teams, in Buenos Aires and Indianapolis, identified the polypeptide angiotensin. In 1934, Goldblatt et al. demonstrated that partial occlusion of the renal arteries produces hypertension in dogs, and Houssay in 1936 predicted the presence of a humoral mechanism and, with Fasciolo, demonstrated that the ischemic kidneys released a pressor substance that increased the recipient's blood pressure. Later on, Taquini proved that the rise in blood pressure that follows the re-establishment of circulation in kidneys was also produced by a plasmatic substance from the venous blood of acute ischemic kidneys and it was called 'hypertensin'. Then, they proved that it was the result of an enzymatic reaction in which renin was the enzyme and plasma the substrate. At the same time, in 1939, Page et al. postulated that renin activated by plasma becomes vasoactive and the substance was called 'angiotonin'. Page's group began in 1937, with the purification of renin, studying its renal hemodynamic effects. Later on, Page et al. acknowledged in 1943 the enzymatic nature of the system and renamed their so-called renin-activator as renin substrate. Both groups fused the two original names into 'angiotensin' during a meeting at Michigan in 1958, making the 'adventure of the discovery of angiotensin' a reality. © 2010 Italian Federation of Cardiology.

The involvement of transition metal ions on iron-dependent lipid peroxidation Repetto, Marisa Gabriela; Ferrarotti, Nidia Fatima; Boveris, Alberto Antonio The metals iron (Fe) and copper (Cu) are considered trace elements, and the metals cobalt (Co) and nickel (Ni) are known as ultra-trace elements, considering their presence in low to very low quantity in humans. The biologic activity of these transition metals is associated with the presence of unpaired electrons that favor their participation in redox reactions. They are part of important enzymes involved in vital biologic processes. However, these transition metals become toxic to cells when they reach elevated tissue concentrations and produce cellular oxidative damage. Phospholipid liposomes (0.5 mg/ml, phosphatidylcholine (PC)/phosphatidylserine (PS), 60/40) were incubated for 60 min at 37°C with 25 μM of Fe2+ in the absence and in the presence of Cu2+, Co2+, and Ni2+ (0-100 μM) with and without the addition of hydrogen peroxide (H 2O2, 5-50 μM). Iron-dependent lipid peroxidation in PC/PS liposomes was assessed by thiobarbituric acid-reactive substances (TBARS) production. Metal transition ions promoted lipid peroxidation by H 2O2 decomposition and direct homolysis of endogenous hydroperoxides. The Fe2+-H2O2-mediated lipid peroxidation takes place by a pseudo-second order process, and the Cu 2+-mediated process by a pseudo-first order reaction. Co2+ and Ni2+ alone do not induce lipid peroxidation. Nevertheless, when they are combined with Fe2+, Fe2+-H2O 2-mediated lipid peroxidation was stimulated in the presence of Ni2+ and was inhibited in the presence of Co2+. The understanding of the effects of transition metal ions on phospholipids is relevant to the prevention of oxidative damage in biologic systems. © 2009 Springer-Verlag.

Semantics-based Color Assignment in Visualization Larrea, Martin Leonardo; Martig, Sergio R.; Castro, Silvia Mabel The active use and manipulation of visual representations makes many complex and in tensive cognitive tasks feasible. A visual representation is able to convey relationships among many elem ents in parallel and it provides an individual with directly observable memory. A successful visualization allows the user to gain insight into the data, that is, to communicate different aspects of the data in an effective way. Even with today’s visualization systems that give the user a considerable control over the visualization process, it can be difficult to produce an effective visualization. To obtain useful results, a user has to interr ogate the visual ization very precisely. A strategy to improve this situation is to guide the user with the selection of the parameters involved in the visualization. This paper presents the initial effort dedicated to achieve a visualiz ation system that assists the user in the configuration and preparation of the visualization by considering bot h the semantic of the data and the semantic of the stages through all the visualization process. In this article we present a visualization system for file hierarchies where color assignment is made by a reasoning process through the use of an ontology. This work sets the way forward to integrate the visualization process with a reasoning process and configure a visualization based on the reasoner’s results.

Detecting and mapping buried buildings with Ground-Penetrating Radar at an ancient village in northwestern Argentina Bonomo, Nestor Eduardo; Osella, Ana Maria; Ratto, Norma Rosa We describe an archaeo-geophysical investigation performed near the Palo Blanco archaeological site, Catamarca, Argentina. A large area beyond the northern limit of the site was explored with the Ground-Penetrating Radar (GPR) method in order to detect new buildings. The exploration showed signals of mud-walls in a sector that was located relatively far from the previously known buildings. A detailed survey was performed in this sector, and the results showed that the walls belonged to a large dwelling with several rooms. The discovery of this dwelling has considerably extended the size of the site, showing that the dwellings occupied at least twice the originally assumed area. High-density GPR surveys were acquired at different parts of the discovered building in order to resolve complex structures. Interpreted maps of the building were obtained. Different characteristics of the walls were satisfactory determined, in spite of the low contrast of the dielectric constant at their interfaces and the noticeable spatial fluctuations of the signals due to wall collapses.Systematic excavations confirmed the GPR maps providing further relevant information about the characteristics of the walls and the occupational floor, as well as material for radiocarbon analyses. These analyses indicated that the discovered building was occupied until about AD 880. This fact extends 180 years the previously known period for the village, and also for the settlements in the region (formerly, AD 200 to AD 700). The performed investigations moreover confirmed different architectural characteristics assumed for Palo Blanco, related to the internal and external layouts. Interconnection between the rooms without intermediary courtyards seems to indicate a better use of the internal spaces and a more integrated spatial conception in Palo Blanco than in other villages of the region. © 2010 Elsevier Ltd.

Nonequilibrium electronic transport in a one-dimensional Mott insulator Heidrich-Meisner, F.; González, Ignacio; Al-Hassanieh, K.A.; Feiguin, Fabian Marcelo; Rozenberg, Marcelo Javier; Dagotto, Elbio We calculate the nonequilibrium electronic transport properties of a one-dimensional interacting chain at half filling, coupled to noninteracting leads. The interacting chain is initially in a Mott insulator state that is driven out of equilibrium by applying a strong bias voltage between the leads. For bias voltages above a certain threshold we observe the breakdown of the Mott insulator state and the establishment of a steady-state electronic current through the system. Based on extensive time-dependent density-matrix renormalization-group simulations, we show that this steady-state current always has the same functional dependence on voltage, independent of the microscopic details of the model and we relate the value of the threshold to the Lieb-Wu gap. We frame our results in terms of the Landau-Zener dielectric breakdown picture. Finally, we also discuss the real-time evolution of the current, and characterize the current-carrying state resulting from the breakdown of the Mott insulator by computing the double occupancy, the spin structure factor, and the entanglement entropy. © 2010 The American Physical Society.

Linfomas asociados con la infección por el virus de la inmunodeficiencia humana: subtipos histológicos y asociación con los virus de Epstein Barr y Herpes-8.; AIDS related lymphomas: histopathological subtypes and association with Epstein Barr virus and Human Herpes virus type-8 Corti, Marcelo; de Dios Soler, Marcela; Baré, Patricia; Villafañe, Maria F.; de Tezanos Pinto, Miguel; Pérez Bianco, R.; Narbaitz, Marina Los linfomas no Hodgkin (LNH) constituyen la segunda neoplasia definitoria de Sida más frecuente. En el presente trabajo se evaluaron 48 casos de linfomas asociados con la enfermedad debida al virus de la inmunodeficiencia humana (HIV) diagnosticados en la División Histopatología del Instituto de Investigaciones Hematológicas de la Academia Nacional de Medicina. Se incluyeron en la investigación 5 mujeres y 43 hombres con una mediana de edad al momento del diagnóstico de la neoplasia de 37 años. La evaluación morfológica se realizó en cortes coloreados con hematoxilina-eosina, estudio inmunohistoquímico para la detección del virus de Epstein Barr (VEB) en 48/48 casos, y mediante sonda oligonucleotídica biotinilada para la detección del ADN del Herpes virus humano tipo-8 (HHV-8) en 14/14 linfomas plasmoblásticos (LP). Todos fueron linfomas de fenotipo B, con un curso clínico agresivo y enfermedad neoplásica avanzada al momento del diagnóstico. Se pudo demostrar la fuerte asociación del VEB con los linfomas asociados al sida, con frecuencias que variaron según el subtipo histológico: 16/21 (76%) para los linfomas difusos de grandes células; 1/3 casos (33%) de linfomas de Burkitt y 3/4 (75%) en los linfomas primarios del sistema nervioso central. Globalmente, el genoma del VEB se detectó en 20/28 (71%) de las muestras de biopsias de LNH de esta serie. La detección del HHV-8 resultó negativa en los 14 LP. Los linfomas de Hodgkin fueron más frecuentes en varones,18/20 (90%), con un curso clínico agresivo y franco predominio de los subtipos histológicos de peor pronóstico (90% de casos). En estas neoplasias también se comprobó una frecuente asociación patogénica con el VEB (90% de casos).; Non-Hodgkin lymphomas (NHL) of the B-cell type are the second most common neoplasm among patients with human immunodeficiency virus (HIV) infection and AIDS. Here, we evaluated 48 cases of AIDS-related lymphomas (ARL) diagnosed at the Histopathological Division of the Instituto de Investigaciones Hematológicas of the National Academy of Medicine. Five were females and 43 were males with a median of age of 37 years at the time of the diagnosis. Micrometer sections were prepared and stained with hematoxilin-eosin; immunohistochemical examination for the presence of Epstein-Barr virus (EBV) was carried out in 48/48 cases. Additionally, biotinilated oligonucleotides were used to determine the presence of DNA of the Human Herpes virus type-8 (HHV-8) in 14/14 biopsy smears corresponding to plasmablastic lymphomas (PL). All were fenotype B cell lymphomas with an aggressive course and advanced neoplasm disease at the time of diagnosis. Virological findings showed the strong association between EBV and AIDS-related NHL. According to the histopathological subtype, the EBV genome was detected in 16/21 (76%) diffuse large B cell lymphomas, 1/3 Burkitt lymphoma and 3/4 (75%) of primary central nervous system lymphomas. Globally, EBV genome was detected in 20/28 NHL of this series. Detection of HHV-8 was negative in all cases of PL. Hodgkin lymphoma were more frequent in males 18/20 (90%), with an aggressive clinical course and a significant predominance of the subtypes associated with worse prognosis (90% of cases). We detected a significant association between EBV and HL (90% of cases). We consider that all cases of AIDS related lymphomas should be assessed for the presence of EBV because its presence may play a role in the prognosis.

Characterization of the Earwig, Doru lineare , as a Predator of Larvae of the Fall Armyworm, Spodoptera frugiperda : A Functional Response Study Romero Sueldo, Mabel; Bruzzone, Octavio Augusto; Virla, Eduardo Gabriel Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) is considered as the most important pest of maize in almost all tropical America. In Argentina, the earwig Doru lineare Eschscholtz (Dermaptera: Forficulidae) has been observed preying on S. frugiperda egg masses in corn crops, but no data about its potential role as a biocontrol agent of this pest have been provided. The predation efficiency of D. lineare on newly emerged S. frugiperda larva was evaluated through a laboratory functional response study. D. lineare showed type II functional response to S. frugiperda larval density, and disc equation estimations of searching efficiency and handling time were (a) = 0.374 and (t) = 182.9 s, respectively. Earwig satiation occurred at 39.4 S. frugiperda larvae.

Extreme and Exposed Points of Spaces of Integral Polynomials Boyd, Christopher; Lassalle, Silvia Beatriz We show that if E is a real Banach space such that E has the approximation property and such that 1 → n,s, E, then the set of extreme points of the unit ball of PI (nE) is equal to {±φn : φ ∈ E , φ = 1}. Under the additional assumption that E has a countable norming set, we see that the set of exposed points of the unit ball of PI (nE) is also equal to {±φn : φ ∈ E , φ = 1}.

2-Filteredness and The Point of Every Galois Topos Dubuc, Eduardo Julio A connected locally connected topos is a Galois topos if the Galois objects generate the topos. We show that the full subcategory of Galois objects in any connected locally connected topos is an inversely 2-filtered 2-category, and as an application of the construction of 2-filtered bi-limits of topoi, we show that every Galois topos has a point.

Classical membrane progesterone receptors in murine mammary carcinomas: agonistic effects of progestins and RU-486 mediating rapid non-genomic effects. Bottino, Maria Cecilia; Cerliani, Juan Pablo; Rojas, Paola Andrea; Giulianelli, Sebastian Jesus; Soldati, Rocío; Mondillo, Carolina; Gorostiaga, Maria Alicia; Pignataro, Omar Pedro; Calvo, Juan Carlos; Gutkind, Silvio J.; Amornphimoltham, Panomwat; Molinolo, Alfredo A.; Luthy, Isabel Alicia; Lanari, Claudia Lee Malvina In this article, we demonstrate the expression of functional progesterone binding sites at the cell membrane in murine mammary carcinomas that are stimulated by progestins and inhibited by antiprogestins. Using confocal immunofluorescence, ligand binding and cell compartment-specific western blots, we were able to identify the presence of the classical progesterone receptors. Medroxyprogesterone acetate (MPA) and RU-486 (1 × 10(-11) and 1 × 10(-8) M) behaved as agonists activating extracellular signal-regulated kinases (ERKs) and progestin-regulated proteins, except for Cyclin D1 and Tissue factor which failed to increase with 1 × 10(-8) M RU-486, an experimental condition that allows PR to bind DNA. These results predicted a full agonist effect at low concentrations of RU-486. Accordingly, at concentrations lower than 1 × 10(-11) M, RU-486 increased cell proliferation in vitro. This effect was abolished by incubation with the ERK kinase inhibitor PD 98059 or by OH-tamoxifen. In vivo, at a daily dose of 1.2 μg/kg body weight RU-486 increased tumor growth, whereas at 12 mg/kg induces tumor regression. Our results indicate that low concentrations of MPA and RU-486 induce similar agonistic non-genomic effects, whereas RU-486 at higher concentrations may inhibit cell proliferation by genomic-induced effects. This suggests that RU-486 should be therapeutically administered at doses high enough to guarantee its genomic inhibitory effect.

Transient simulation of a storage floor with a heating/cooling parallel pipe system Flores Larsen, Silvana Elinor; Filippin, Maria Celina; Lesino, Graciela The exact 2-D transient solution of a slab with an embedded array of parallel circular pipes for heating/cooling is developed. The boundary and initial conditions are: constant temperature at the pipe surface, upper slab surface subjected to convection heat transfer, thermal insulation at the slab bottom, and constant initial temperature. The analytical solution of the transient bi-dimensional problem is obtained together with the fluid temperature. A calculation example is analysed at the end of the paper to enlighten practical issues appearing in the computation of the analytical solution.

A robust clustering method for detection of abnormal situations in a process with multiple steady-state operation modes Maestri, Mauricio Leonardo; Farall, Rodolfo Andres; Groisman, Pablo Jose; Cassanello, Miryan; Horowitz, Gabriel Ignacio Many classical multivariate statistical process monitoring (MSPM) techniques assume normal distribution of the data and independence of the samples. Very often, these assumptions do not hold for real industrial chemical processes, where multiple plant operating modes lead to multiple nominal operation regions. MSPM techniques that do not take account of this fact show increased false alarm and missing alarm rates. In this work, a simple fault detection tool based on a robust clustering technique is implemented to detect abnormal situations in an industrial installation with multiple operation modes. The tool is applied to three case studies: (i) a two-dimensional toy example, (ii) a realistic simulation usually used as a benchmark example, known as the Tennessee?Eastman Process, and (iii) real data from a methanol plant. The clustering technique on which the tool relies assumes that the observations come from multiple populations with a common covariance matrix (i.e., the same underlying physical relations). The clustering technique is also capable of coping with a certain percentage of outliers, thus avoiding the need of extensive preprocessing of the data. Moreover, improvements in detection capacity are found when comparing the results to those obtained with standard methodologies. Hence, the feasibility of implementing fault detection tools based on this technique in the field of chemical industrial processes is discussed.

Digital Closed-Loop High-Speed Thyristor Firing System for Line-Commutated Converters Maestri, Sebastian Oscar; Benedetti, Mario; Uicich, Gustavo Cesar; Gomez Costa, Jose Luis This report presents the implementation of an all-digital high-speed closed-loop thyristor firing system based on the Cassel technique. Different aspects associated to digital implementations, like sampling frequency, synchronism and finite word-length are analyzed. Experimental results obtained on a CERN GEREG crate are presented.

¿Cómo tratan los psiquiatras argentinos la depresión bipolar? Encuesta a una muestra de 359 psiquiatras acerca de sus hábitos prescriptivos para el tratamiento farmacológico; How do argentinean psychiatrists treat bipolar depression? Mazaira, Silvina; Leiderman, Eduardo A.; Nemirovsky, Martín; Vigo, Daniel Eduardo; Wikinski, Silvia Ines Se presentan los resultados de una encuesta realizada a una muestra de 359 psiquiatras argentinos en el marco del Congreso Nacional de Psiquiatría llevado a cabo en la Ciudad Autónoma de Buenos Aires entre el 26 y 29 de septiembre de 2007. El objetivo de la encuesta fue estudiar los hábitos prescriptivos de los psiquiatras asistentes en lo referente al tratamiento de la depresión bipolar. La discusión se centra en la comparación de las respuestas obtenidas con las conductas de tratamiento sugeridas en las principales guías, consensos y autores de referencia. Las diferencias halladas señalan una distancia observada con frecuencia entre las guías y consenso de tratamiento (realizados en base a poblaciones de pacientes seleccionadas para los ensayos clínicos controlados) y el mundo real de la práctica clínica cotidiana a la que se enfrenta el psiquiatra.; We show the results of a survey on bipolar depression treatment using a sample of 359 argentine psychiatrists in the context of The National Psychiatry Congress that took place in the City of Buenos Aires, between September 26th and 29th , 2007. The objective was to study the attendant psychiatrists’s prescribing habits in the treatment of bipolar depression. The discussion is based on the comparison between the answers and the recommendations taken from the main consensus, guidelines and from articles published by experts. The differences found point to the distance often present between guidelines and expert consensus series (based on patients meeting the strict criteria used in randomized controlled studies) on one hand, and a clinician’s everyday real world practice, on the other hand.

Taxonomic status of Apterodytes ictus AMEGHINO, 1901 (Aves; Sphenisciformes) from the early miocene of patagonia, Argentina Acosta Hospitaleche, Carolina Ileana Alicia A proximal end of a humerus collected by C. AMEGHINO was designated as the holotype of Apterodytes ictus AMEGHINO, 1901 in the monotypic genus Apterodytes AMEGHINO, 1901. Later, AMEGHINO (1905) transferred this species to the new genus Palaeoapterodytes AMEGHINO, 1905. The validity and affinity of this species has been discussed controversial, not only on account of the poor preservation of the material, but also because of the characters used in its diagnosis and description. A systematic revision of Aptenodytes ictus (AMEGHINO, 1901) is presented. This is a proximal end of a right humerus strongly weathered that was interpreted as a complete humerus with an unique morphology. The characters included in the original diagnosis and the description are inadequate to compare with those of other species as they are based mainly on the assumption of the atrophy of a humerus that is in fact fractured and incomplete. Its morphology allows its confidant assignment to the family Spheniscidae, although it is not well enough preserved to assign it to any known genus. Therefore, this fossil is not appropriate to found a species on and Palaeoapterodytes ictus (AMEGHINO, 1901) must be considered as a nomen dubium.

Rheological properties of a two phase lipid monolayer at the air/water interface: Effect of the composition of the mixture Wilke, Natalia; Vega Mercado, Franco; Maggio, Bruno Many biologically relevant monolayers show coexistence of discrete domains of a long-range ordered condensed phase dispersed in a continuous, disordered, liquid-expanded phase. In this work, we determined the viscous and elastic components of the compressibility modulus and the shear viscosity of monolayers exhibiting phase coexistence with the aim at elucidating the contribution of each phase to the observed monolayer mechanical properties. To this purpose, mixed monolayers with different proportions of distearoylphosphatidylcholine (DSPC) and dimyristoylphosphatidylcholine (DMPC) were prepared and their rheological properties were analyzed. The relationship between the phase diagram of the mixture at 10 mN m-1 and the rheological properties was studied. We found that the monolayer shear viscosity is highly dependent on the presence of domains and on the domain density. In turn, the monolayer compressibility is only influenced by the presence of domains for high domain densities. For monolayers that look homogeneous on the micrometer scale (DSPC amount lower that 23 mol %), all the analyzed rheological properties remain similar to those observed for pure DMPC monolayers, indicating that in this proportion range the DSPC molecules contribute as DMPC to the surface rheology in spite of having hydrocarbon chains four carbons longer.

Contratos de estado, inversión extranjera y derecho internacional público Castillo Argañarás, Luis Fernando El objetivo de éste artículo es responder al siguiente interrogante: ¿Es posible aplicar Derecho Internacional Público a los contratos de Estado? En ese sentido, se analizará la naturaleza jurídica de estos contratos y luego la vinculación de éste tipo de instrumentos jurídicos con el Derecho Internacional Público. También se considerará el arbitraje internacional.; O objetivo deste artigo é responder à seguinte questão: É possível aplicar o Direito Internacional Público a contratos do Estado. Nesse sentido, vamos analisar a natureza jurídica dos contratos do Estado e, a seguir, relacionar estes tipos de contratos com o Direito Internacional. Também ser considerada uma arbitragem internacional.; The purpose of this paper is to answer the following question: Is it possible to apply Public International Law to State Contracts? In this sense, the legal nature of State contracts will be analysed and then the link between Public International Law and this type of contracts will be established. International arbitration will be considered.

Experiencias y discursos sobre organización política y laboral de las y los jóvenes. Un acercamiento histórico-etnográfico a los procesos de socialización-apropiación contemporáneos Scarfó, Gabriela Fernanda; Enrique, Iara Nuria El objetivo de este artículo consiste en analizar, desde un enfoque histórico-antropológico, la particularidad de algunas experiencias y reflexiones relativas a la vida política y laboral de las y los jóvenes adolescentes, en dos contextos de socialización diferenciados: una organización no gubernamental dedicada a la formación de la juventud en el mundo del trabajo y una organización de segundo grado que procura aglutinar al llamado movimiento estudiantil secundario en la Ciudad de Buenos Aires.; The aim of this paper is to analyze from a historical-anthropological approach the particularity of some experiences and reflections relative to the political life and the world of the work of the young people in two different contexts of socialization: an non-governmental organization dedicated to the education of young people in the world of work and an organization of the second degree that tries to agglutinate the so called student secondary movement in the City of Buenos Aires.

Evaluación y calidad en los programas y cursos online en la enseñanza superior; Evaluation and quality at programmes and specific courses in higher education Constantino, Gustavo Daniel; Llull, Laura La Educación a Distancia (EAD) ha sido siempre considerada con cierto escepticismo en cuanto a la calidad de los programas en contraste con la enseñanza en presencia. La EAD basada en redes telemáticas ha logrado disminuir el recelo, pero no lo ha hecho desaparecer.La evaluación, como aspecto crítico de la calidad, hasta hoy no ha sido objeto de un examen profundo en relación a los nuevos contextos y en general se trasvasan los sistemas de evaluación convencionales y propios de la formación en presencia a los entornos online. Sin embargo, existe una intuición extendida en que tales sistemas no son del todo congruentes con la naturaleza de la enseñanza y del aprendizaje en comunidades virtuales, aspecto que ha sido particularmente sensible en el caso del Proyecto Alfa-Miforcal, ilustrándose con un par de ejemplos. El escenario de la educación online está cambiando dramáticamente con el surgimiento de nuevas formas de enseñar y aprender, pasando de modelos de reproducción de conocimientos a modelos del aprendizaje colaborativo y conocimiento compartido centrados en la actividad del estudiante en Comunidades Virtuales de Aprendizaje. En estas se puede llegar a un grado de interacción en el que la evaluación formativa alcanza niveles semejantes a los de la mejor orientación del aprendizaje en presencia.; Distance Education has been always considered with certain skepticism for the quality of the programs in contrast with the education in presence. The distance education based on virtual networks has managed to diminish the mistrust, but it has not made it disappear. The evaluation, as critical aspect of the quality, up to today has not been an object of a deep examination in relation to the new contexts, which implies that the conventional and proper systems of evaluation of the formation in presence are applied to the environments online. Nevertheless, there exists a widespread intuition in which such systems do not correspond completely to the nature of the education and of learning in virtual communities, Aspect that has been particularly sensitive in case of the Project Alfa-Miforcal, illustrated with a pair of examples. The scenario of the education online is changing dramatically with the emergence of new ways of teaching and of learning, going on from models of reproduction of knowledge to models of collaborative learning and shared knowledge focused on the activity of the student in Learning Virtual Communities. In these, it is possible to come to a grade of interaction in which the formative evaluation reaches similar levels to those of the best orientation of learning in presence.

El entorno sudamericano y su significado en la política exterior de los gobiernos de Duhalde y Kirchner Torres, Miguel Agustín La crisis institucional y socioeconómica que afectó a Argentina a fines de 2001 y principios de 2002 no solo implicó el agotamiento del modelo neoliberal implementado desde el comienzo de la década del noventa sino que también significó la posibilidad de revisar el esquema de inserción internacional que lo complementó. Esta reformulación de la política exterior incluía la oportunidad de replantear los vínculos con los países sudamericano y el rol del país dentro de MERCOSUR. En este aporte se analiza el significado que se asignó a las relaciones con los actores subregionales y a MERCOSUR en la política y exterior argentina luego de la crisis del 2001.; A crise institucional e sócio-econômicos que a Argentina sofreu no final de 2001 e início de 2002, não só representou o esgotamento do modelo neoliberal aplicado desde o início dos anos noventa, também significou a possibilidade de rever o esquema de inserção internacional que acompanhou esse modelo. Esta reformulação da política externa incluída a oportunidade de repensar os laços com os países da América do Sul eo papel do país no Mercosul. Esta contribuição analisa os significados atribuídos às relações com os atores subregionais e ao Mercosul na política externa da Argentina após a crise de 2001.