An inquiry into the nature of the gamma-ray source 3EG J1828+0142 Punsly, Brian; Romero, Gustavo Esteban; Torres, Diego F.; Combi, Jorge Ariel The unidentified, low-latitude, gamma -ray source 3EG J1828+0142 presents high levels of variability and a steep spectral index Gamma ~ 2.7. Here we propose a model for this source where the high-energy emission is produced by a galactic Kerr-Newman black hole. The model takes into account electron-positron annihilation losses in the calculation of the expected spectral energy distribution and can reproduce the observational features, including the absence of a strong radio counterpart. We also report the discovery of a nearby supernova remnant that could be associated with the original supernova explosion that created the black hole. Several faint radio sources were also detected in the radio field within the inner gamma -ray confidence contour and their spectral index estimated. Some of these sources could be the expected weak radio counterpart.

Geomorfología de estuarios: una visión diferente Piccolo, Maria Cintia; Perillo, Gerardo Miguel E. Los estuarios son una de las mas importantes caracteristicas de las zonas costeras sujetas a fuertes procesos de interaccion mar-continente en un amplio rango de escalas espacio-temporales. En general, estos ambientes ocupan las areas costeras menos expuestas ala accion marina, permitiendo el desarrollo de puertos, facilidades recreacionales 0 apropiados emprendimientos de acuicultura, Sin embargo, dentro de los estuarios los procesos dinamicos son significativos imponiendo un marc ado stress sobrela biota, ya sea pennanente 0 temporaria, la morfologia y las construccione.

Integración, fronteras y movilidad espacial de la población Meichtry, Norma Cristina Se analizan los posibles argumentos que pudieran respaldar los procesos de cambios que se vienen registrando en la frontera entre Argentina y Paraguay, desde el punto de vista de la teoría de la nueva división del trabajo en el marco de un sistema mundial o de la teoría de la generalización de las crisis socioeconnómicas a partir de los procesos de reestructuración de la economía.

Análisis empírico de algoritmos de inversión de matrices, aplicados al cálculo de propiedades moleculares. Godoy, María Viviana; Provasi, Patricio Federico; Aucar, Gustavo Adolfo En este articulo se evahia la performance en cuanto a tiempos de ejecuci6n de dos algoritmos de inversi6n de matrices: uno tradicionalmente utilizado en calculos de propiedades moleculares y uno nuevo implementado en nuestro grupo de investigaci6n y que utiliza un desarrollo en sene de potencias de los elementos matriciales. Se probaron distintas plataformas, sistemas operativos, compiladores y subrutinas de algebra lineal (BLAS). Se realizaron calculos para compuestos modelo que requieren el tratamiento de matrices conteniendo entre 80.000 y 4.000.000 de elementos. Se obtuvieron los tiempos de ejecuci6n de dichos algoritmos a traves de la evaluaci6n con el metodo de propagadores de polarizaci6n de propiedades moleculares tipo triplete y singulete. Se observ6 que el rendimiento del algoritmo de la serie aumenta al crecer la dimensi6n de la matriz a invertir. Para todas las plataformas utilizadas se obtuvo una performance ganancioso de la serie con respecto al algoritmo tradicional.; In this article, the performance of two algorithms for matrix inversion are evaluated considering as a parameter the times of execution: one traditionally used in the calculations of molecular properties and a new one implemented in our research group, that makes use of a series development of matrix elements. Different platforms, operating sistems, compilers and subroutines of lineal algebra (BLAS) were investigated. Calculations for model compounds that require the treatment of matrix containing a number of elements between 80.000 and 4.000.000 was carried out. The calculation of molecular properties of both, singlet and triplet type was used to evaluate the execution time of these algorithms. It was observed that the performance of the series algorithm increases when the dimension of the given matrix grows. For all plataforms, a gainful performance of the series was obtained, compared to the tradicional algorithm.

Transmetallations between aryltrialkyltins and borane: Synthesis of arylboronic acids and organotin hydrides Faraoni, María Belén; Koll, Liliana Cristina; Mandolesi, Sandra Delia; Zuñiga, Adriana Elena; Podestá, Julio Cesar Aryltrialkyltin compounds react with borane in THF to give mixtures of trialkyltin hydrides and arylboranes, which on hydrolysis give arylboronic acid in high yields. The arylboronic acids are easily separated and obtained free of organotins.

Desarrollo de un modelo de ahorro de energía en edificios de vivienda y determinación de valores límite de calidad térmica para la República Argentina Czajkowski, Jorge Daniel La definición de valores admisibles de uso normativo es de características especiales ya que poseen un cierto grado de arbitrariedad. Esto depende de muchos factores entre los que podemos mencionar los de carácter técnico, científico, práctico y político. La definición de estándares se complejiza por la variabilidad climática y la necesidad de compatibilizar modelos y procedimientos desarrollados para diferentes escalas de aplicación. Se presenta el modelo desarrollado, se discute sobre las dificultades encontradas en la determinación de los valores admisibles para los diversos climas de la Argentina y se comentan las resistencias para su aplicabilidad como normativa.; The acceptable values definition of normative use is of special characteristics since they have a certain arbitrariness degree. This depends on many factors, technical, scientific, practical and political. The standard definition turns more complex by the climatic variability and the necessity to compatibilize models and procedures developed for different application degrees. The developed model is presented, the difficulties found in the acceptable values determination for the Argentine diverse climates are discussed and the resistances for its applicability as normative is commented.

Chronic stress influences the immune system through the thyroid axis Cremaschi, Graciela Alicia; Gorelik, Gabriela Judith; Klecha, Alicia Juana; Lysionek, Alexis E.; Genaro, Ana Maria The aim of the present work was to analyze the effect of chronic stress on thyroid axis and its influence on the immune response. For this purpose a murine model of chronic stress was developed to evaluate and to correlate thyroid hormone levels with humoral alloimmune response. Results show a reduction in serum levels of thyroid hormones, specially a significant decrease in serum levels of tri-iodotyronine (T3) in stressed animals. On the other hand, alloimmunization was not able to induce an early increment in T3 and thyroxine (T4) levels as it was previously reported in normal animals. In addition, lower titers of alloantibodies were obtained in animals under stress conditions as compared to normal mice. The sustitutive T4 treatment in stressed animals increased significantly alloantibody production as well as the early increment in thyroid hormones after antigenic challenge. These findings suggest that chronic stress induces an alteration of the function of thyroid axis that alters the immune response. (C) 2000 Elsevier Science Inc.

Isobutane/Butene Alkylation:regeneration of solid acid catalysts Querini, Carlos Alberto The regeneration of Y-zeolite catalysts used during the isobutane alkylation reaction is studied. Coke is characterized by temperature-programmed techniques and measuring the H/C ratio. The coke deposited under supercritical conditions is very similar (TPO profile and amount) to the coke deposited in liquid phase. The regeneration was carried out in many ways. Air was used for heating with at a low rate, and holding the temperature at low values for long times. Platinum was incorporated in the zeolite to catalyze the coke combustion or to provide an additional route for coke gasification, such as hydrogenation. Ozone was used to remove most of the coke, followed by a second step with H2 or He. Hydrogen peroxide was studied as an alternative low-temperature oxidation compound. It was found that the ozone treatment, followed by a hydrogen treatment, is an effective way to regenerate this microporous catalyst. The ozone not only eliminates a large fraction of the coke but also changes the characteristics of the small amount of coke left on the catalyst, making it easier to be burnt. The treatment with hydrogen peroxide at 90°C also removes a large fraction of coke, but without changing significantly the characteristics of the coke left after the treatment.

Conversiones religiosas, conversiones seculares: Comparando las estrategias de transformación de identidad en programas de minoridad e iglesias pentecostales Miguez, Daniel Pedro Uno de los problemas que últimamente enfrenta la sociedad argentina es el del crecimiento de su tasa de delincuencia. El delito se ha incrementado en todas sus formas, y dentro de él la delincuencia juvenil no ha sido una excepción. Frente al crecimiento de la delincuencia juvenil, el sistema argentino de minoridad ha implementado una diversidad de políticas, entre las cuales se destaca la de la descentralización de los grandes institutos de menores con regímenes carcelarios cerrados, hacia instituciones más pequeñas, con regímenes abiertos o semi-abiertos. Tal como pasó en los primeros años con la experiencia de Massachussets, las estadísticas muestran que no existen grandes diferencias en los niveles de reincidencia pese al cambio de política. Sin embargo, algunos trabajos estadísticos muestran que las iglesias pentecostales si logran mayores niveles de eficacia, disminuyendo significativamente la reincidencia. El artículo analiza las razones de esta diferencia a partir de la noción de identidad y de ‘organizaciones transformadoras de la identidad’ planteadas por Greil y Rudy.

Economic performance of variable structure control: A case study Figueroa, Jose Luis The operating point of a chemical process is usually computed by optimizing a steady-state objective function, e.g. the profit, subject to the steady-state characteristics of the plant. However, the resulting point typically lies in the boundary of the operating region. The presence of disturbances can easily cause constraint violations in the transient. Thus, it is necessary to move the operating point away from the active constraints into the feasible region. The magnitude of this back-off has a direct influence on the economic side. The purpose of this paper is to study the effect of the combination of a state-observer and controller designed using structure variable techniques at the economical level of the process control.

Potential involvement of C3 complement factor in amphibian fertilization Llanos, Ricardo Javier; Mansilla Whitacre, Cecilia; Miceli, Dora Cristina We have assessed the potential involvement of C3, the third complement factor, and its receptor in Bufo arenarum fertilization. We show that a polyclonal antibody against a B. arenarum C3-like factor (C3Ba) reacts specifically with components of the extracellular matrix (ECM) of coelomic eggs and the cell membrane of uterine eggs. Interestingly, we have identified a 163 kD protein immunoreactive with a monoclonal antibody against the CD11b α chain of the human C3 receptor on the cell membrane of the animal pole of uterine eggs, the site of entry of the sperm, but not in coelomic eggs (CR3Ba). Treatment of coelomic eggs with a pars recta oviductal-like protease, trypsin, induced the translocation of C3Ba from the ECM to the cell membrane. Furthermore, inhibition of CR3Ba by trypan blue, as well as inhibition of C3Ba by anti-C3Ba on uterine eggs impaired fertilization, whereas identical treatment on sperm cells did not alter percentage fertilization. Our results suggest, (A) that changes in the localization of C3Ba from the ECM to the cell membrane may be triggered by trypsin-like proteases during passage of eggs through the oviduct; and (B) that C3Ba/CR3Ba may be involved in B. arenarum fertilization.

Orally administered attenuated Salmonella enteritidis reduces chicken cecal carriage of virulent Salmonella challenge organisms Cerquetti, Maria Cristina; Gherardi, Maria Magdalena Chickens were immunized orally with 109 cfu of the temperature-sensitive (T(s)) mutant E/1/3 of Salmonella enteritidis at 1, 2, 3 and 7 days of age. The animals were challenged with wild-type strains of Salmonella of different serotypes 7 or 14 days following immunization. Chickens receiving multiple oral doses of the vaccine strain showed no signs of disease. Immunized animals shed the vaccine strain for at least 2 weeks after the last inoculation; on the other hand, colonization by the attenuated mutant of internal organs such as spleen and liver was limited. Early exposure of the immunized animals to the virulent bacteria resulted in a reduced cecal colonization by the pathogen. Visceral invasion by the wild-type strain of S. enteritidis or S. gallinarum was drastically diminished in birds challenged 14 days after immunization. Significant differences in the number of these Salmonella were found in the cecal contents, spleen and liver of immunized birds compared with the control animals. In addition, cecal colonization by the virulent strain was reduced in birds challenged with S. typhimurium. These results demonstrate that immunization of newly hatched chickens with live attenuated T(s) mutant E/1/3 of S. enteritidis is safe and reduces Salmonella shedding. (C) 2000 Elsevier Science B.V.

The indirect basal ganglia pathway in dopamine D2 receptor-deficient mice Murer, Mario Gustavo; Dziewczapolski, G.; Salin, P.; Vila, M.; Tseng, Kuei y; Ruberg, M.; Rubinstein, Marcelo; Kelly, M. A.; Grandy, D. K.; Low, M. J.; Hirsch, E.; Raisman Vozari, Rita; Gershanik, Oscar Samuel Recent pathophysiological models of basal ganglia function in Parkinson's disease predict that specific neurochemical changes in the indirect pathway would follow the lack of stimulation of D2 dopamine receptors. Post mortem studies of the basal ganglia in genetically modified mice lacking functional copies of the D2 dopamine receptor gene allowed us to test these predictions. When compared with their congenic N5 wild-type siblings, mice lacking D2 receptors show an increased expression of enkephalin messenger RNA in the striatum, and an increased activity and expression of cytochrome oxidase I in the subthalamic nucleus, as expected. In addition, D2 receptor-deficient mice display a reduced expression of glutamate decarboxylase-67 messenger RNA in the globus pallidus, as the basal ganglia model predicts. This reduction contrasts with the lack of change or increase in glutamate decarboxylase-67 messenger RNA expression found in animals depleted of dopamine after lesions of the mesostriatal dopaminergic system. Furthermore, D2 receptor-deficient mice show a significant decrease in substance P messenger RNA expression in the striatonigral neurons which form the direct pathway. Finally, glutamate decarboxylase-67 messenger RNA expression in the basal ganglia output nuclei was not affected by mutations in the D2 receptor gene, a fact that could probably be related to the absence of a parkinsonian locomotor phenotype in D2 receptor-deficient mice. In summary, these findings provide compelling evidence demonstrating that the lack of endogenous stimulation of D2 receptors is sufficient to produce subthalamic nucleus hyperactivity, as assessed by cytochrome oxidase I histochemistry and messenger RNA expression, and strongly suggest the existence of interactions between the basal ganglia direct and indirect pathways. (C) 2000 IBRO.

Percolation Effects on Adsorption-Desorption Hysteresis López, Raúl Horacio; Vidales, Ana Maria; Zgrablich, Giorgio In the present work we study how the adsorption−desorption hysteresis loop of a mesoporous-disordered medium represented by a three-dimensional dual site-bond model is affected by percolation for different kinds of site and bond distributions. The behavior of the threshold pressure for the evaporation process, as a function of the separation between the site and bond distributions and their dispersions, suggests a method to determine them from experimental adsorption−desorption hysteresis curves.

Biosurfactant-enhanced degradation of residual hydrocarbons from ship bilge wastes Olivera, Nelda Lila; Commendatore, Marta Graciela; Morán, A. C.; Esteves, Jose Luis The use of Bacillus subtilis O9 biosurfactant (surfactin) and of bioaugmentation to improve the treatment of residual hydrocarbons from ship bilge wastes was studied. A biodegradation experiment was conducted in aquaria placed outdoors under non-aseptic conditions. Three treatments were examined: culture medium plus bilge wastes, bioaugmentation with microorganisms from bilge wastes, and bioaugmentation plus biosurfactant. Samples were analyzed for viable counts, aliphatic and aromatic hydrocarbon concentrations, n-C17/pristane and n-C18/phytane ratios. While the addition of biosurfactant stimulated hydrocarbon degradation, bioaugmentation did not produce any remarkable effect. At day 10, the remaining percentages of aliphatic and aromatic hydrocarbons in aquaria, which received biosurfactant, were 6.8 and 7.2, respectively, while it took 20 days to reach comparable results with the other treatments. The biosurfactant did not affect the preferential biodegradation of n-C17/pristane and n-C18/phytane. This biosurfactant, which can be produced in a relatively simple and inexpensive process, is a promising alternative in the optimization of hydrocarbon waste treatment.

Surface Characterization of Li-Modified Platinum/Tin Catalysts for Isobutane Dehydrogenation Casella, Mónica Laura; Siri, Guillermo Jorge; Santori, Gerardo Fabian; Ferretti, Osmar Alberto; Ramırez Corredores, Maria Magdalena The superficial properties of different Pt/γ-Al2O3 catalysts, modified by the addition of tin and/or lithium, were studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, BET, and 2-propanol transformation. The results obtained were correlated with the behavior of the catalysts in applied reactions such as the dehydrogenation of isobutane. To obtain very well defined bimetallic superficial phases, tin was introduced by means of surface organometallic chemistry on metals techniques and the nature of the bimetallic-active sites so obtained was compared with the ones prepared by conventional procedures. XPS measurements indicate that tin is present in both zeroth valent and oxidized states. The addition procedure of both tin and lithium has a marked influence on the characteristics of the surface of the catalysts. The order in which lithium is added generates solids having different properties in relation to texture, dispersion, and catalytic behavior, for both Pt and PtSn systems.

Diet selection by goats on a semi-arid shrubland in central Argentina Pisani, Jorge Marcelo; Distel, Roberto Alejandro; Bontti, Eliana E. The objective of this study was to determine diet selection by goats on a semi-arid shrubland in the central part of Argentina. Ten goats grazed on a pasture for 10-days periods in winter, spring, and summer. The botanical composition of the pasture was estimated by a combined measure of cover and biomass, whereas the botanical composition of the diet was determined by the microhistological technique complemented with direct observation. Two shrub species (Condalia microphylla and Prosopis caldenia) and five soft grasses (Piptochaetium napostaense, Poa spp., Stipa tennis, S. clarazii, and Pappophorum spp.) were highly selected by goats. Shrubs represented 32%, 40% and 74% of goat diets in winter, spring and summer, respectively. For each season, the rest of goat diets was composed by the soft grasses. Although coarse grasses represented most (> 80%) of the available biomass in all seasons, they were always highly avoided by goats. The results showed that goats behave as mixed-feeders (eat grasses and shrubs) on semi-arid shrublands in central Argentina.

Thermal behavior and hydration properties of yeast proteins from Saccharomyces cerevisiae and Kluyveromyces fragilis Otero, Miguel A.; Wagner, Jorge Ricardo; Vasallo, María C.; García, Lourdes; Añon, Maria Cristina High pressure homogenization of yeast cells followed by incubation at 50°C for the dissociation of ribonucleic acid-protein complexes resulted in a high denaturation degree of isolated proteins. Proteins in intact cells exhibited an ample endothermic peak with peak temperatures (T(P)) at 66.66 and 63.67°C for S. cerevisiae and K. fragilis, respectively. No differences were found with respect to the associated enthalpy changes for both studied species. The isolation of proteins from its biomass shifts T(P) to values around 50°C. Impurities such as nucleic acid, polysaccharides and other intracellular components seem to play a protective role upon denaturation. Isolated proteins showed solubilities lower than 40% but exhibited water retention properties and wettability from 3.5 to 7.0 ml of water/g of protein.

Clinical and epidemiologic characteristics of respiratory syncytial virus subgroups A and B infections in Santa Fe, Argentina Imaz, María S.; Sequeira, María D.; Videla, Cristina Mónica; Veronessi, Inés; Cociglio, Raquel; Zerbini, Elsa Virginia; Carballal, Guadalupe Respiratory Syncytial Virus (RSV) has two major antigenic groups, A and B. The implications of these variants in the epidemiology and pathogenesis of RSV infection are not well defined. This study was undertaken to compare the two RSV subgroups in patients admitted to hospital. Clinical and epidemiologic features of RSV subgroups in children under 30 months of age with proven RSV acute lower respiratory infections were examined during 4 winters from 1993 to 1996 in Santa Fe, Argentina. RSV typing was carried out with monoclonal antibodies in nasopharyngeal cells by indirect immunofluorescence. Of the 177 RSV positive nasopharyngeal aspirates obtained from 1993 to 1996, 85 (48%) were available for typing. Seventy-three (85.9%) specimens were identified as Subgroup A and 12 (14.1%) as Subgroup B. Except in 1993, in which only Subgroup A was detected, both variants circulated throughout the epidemic season. Subgroup A infections produced more severe disease than Subgroup B infections, as assessed by the length of the hospital stay and the use of respiratory support. This difference was age related, being evident in infants 0-6 months old. Patients with Subgroup B infections were also significantly less frequently breast-fed (95% vs. 75% for A and B subgroups, respectively; P = 0.04). It is concluded that the severity of disease in Argentinian patients admitted with acute RSV infections may be associated with Subgroup A strains as determined by a serogrouping method.

Gypsum-hydroboracite association in the sues formation (Miocene, NW Argentina): implications for the genesis of Mg-bearing borates Ortí, Federico; Alonso, Ricardo Narciso This paper deals with sedimentologic and diagenetic aspects of the evaporitic fades of the Sijes Formation (Miocene, central Andes, NW Argentina), which contains the largest known hydroboracite reserves in the world. In outcrop, the sulfate minerals are secondary gypsum and minor anhydrite, and the borate minerals are hydroboracite with subordinate inyoite and colemanite, and some ulexite. In the Monte Amarillo Member of the Sijes Formation it is possible to distinguish two coeval, shallow lacustrine subbasins, in which the gypsum accumulated in the margins and the hydroboracite in the centers, the intermediate zones being characterized by mixed gypsum-hydroboracite layers. In the depositional sequence, primary gypsum (gypsarenite) and syndepositional anhydrite, in association with limited amounts of calcium borates (colemanite, inyoite) precipitated first, followed by hydroboracite (calcium/magnesium borate). Alternations of gypsum and hydroboracite layers also formed. Hydroboracite is mainly a primary mineral, although it replaced some gypsum under synsedimentary conditions. The formation of colemanite, which occurred during early diagenesis, is linked to the precipitation of calcium sulfates (gypsum and anhydrite), whereas inyoite coexists with both calcium sulfates and magnesium-bearing borates. Transformations among the various borate minerals during burial diagenesis were not detected. Primary gypsum was transformed into anhydrite from early diagenesis to moderate burial diagenesis. The boron source of these deposits seems to be related to the volcanic/hydrothermal activity in the central Andes during the Miocene.