Ciencia y Tecnología
EBV primary infection in childhood and its relation to B-cell lymphoma development: a mini-review from a developing region
Chabay, Paola Andrea; Preciado, María Victoria
In most underdeveloped countries, the initial contact with Epstein Barr virus (EBV) usually happens in the first decade of life and results in an asymptomatic infection, whereas in developed areas, primary infection in adolescence or adulthood is accompanied by infectious mononucleosis in 50% cases. Although it is generally a harmless passenger, in some individuals, it is associated with B-cell lymphoma. In Argentina, EBV primary infection shows the classical pattern observed in developing populations, given that nearly 70% of patients are seropositive by the age of 2 years. However, EBV association with pediatric Hodgkin and Burkitt lymphoma resembles that observed in developed regions. Concerning diffuse large B-cell lymphoma, our series demonstrated higher EBV association than other adult ones from either developed or underdeveloped countries. Interestingly, the early EBV primary infection observed, characteristic of an underdeveloped population, together with the statistically significant EBV association with patients ≤10 years old demonstrated in all types of lymphoma studied, suggest a relationship between low age of EBV seroconversion and B-cell lymphoma development risk.
Un enfoque sistémico de la democracia deliberativa
Un enfoque sistémico de la democracia deliberativa; A sistemyc approach of deliberative democracy
Olivares, Nicolàs Emanuel
En el marco del debate teórico acerca de cuál es la concepción normativa más adecuada del modelo democrático deliberativo se han elaborado distintas propuestas rivales (1). Más recientemente, Jane Mansbridge y John Parkinson en su obra Deliberative Systems han explicitado una nueva e interesante perspectiva, a la que denominan sistémica. La misma, tiene por fin evaluar la legitimidad democrática de las decisiones políticas, para lo cual propone adoptar un enfoque de gran escala que tome en cuenta la interdependencia existente entre los distintos componentes del sistema democrático deliberativo (2). Este artículo tendrá por objetivos: 1) Reconstruir los presupuestos conceptuales y normativos del enfoque sistémico; 2) Explicitar las distintas interpretaciones o versiones que el mismo puede asumir; 3) Ensayar argumentos en defensa de una de dichas versiones. Todo ello a los fines de destacar el valioso aporte teórico que ha significado el novel en- foque deliberativo sistémico para la teoría democrática-deliberativa.; Under the theoretical debate about what is the most appropriate normative conception of the deliberative democratic model various rival proposals have been developed. More recently, Jane Mansbridge and John Parkinson in his work Deliberative Systems have explicit an interesting new perspective, which they called systemic. This new turn aims to assess the democratic legitimacy of political decisions, for which it proposes to adopt a large-scale approach that takes into account the interdependence between the different components of deliberative democratic system. This article will aim to: 1) Rebuild the conceptual and normative systemic approach; 2) Explain the different interpretations or versions that it can assume; 3) Rehearse ar- guments in defense of one of those versions. All this guided by the aim of highlighting the valuable theoretical contribution that the novel systemic deliberative approach has meant for the deliberative democratic theory.
Detección y genotipificación de Poliomavirus BK en muestras cloacales de la ciudad de Córdoba, Argentina
Detección y genotipificación de Poliomavirus BK en muestras cloacales de la ciudad de Córdoba, Argentina
Sosa, Julieta; Ferreyra, Leonardo; Giordano, Miguel; Barril, Patricia Angelica; Masachessi, Gisela; Isa, Maria Beatriz; Martinez, Laura Cecilia; Biganzoli, Patricia; Nates, Silvia Viviana; Pavan, Jorge
El virus BK (VBK) es un poliomavirus que es excretado en la orina por muchos individuos de la población humana y fue sugerido en otras partes del mundo como potencial marcador de contaminación con desechos humanos en muestras de aguas residuales. En este trabajo analizamos la prevalencia del VBK y sus genotipos en muestras de cloacas de la ciudad de Córdoba, Argentina. A lo largo de 2 años y medio se recolectaron 60 muestras cloacales en las cuales se detectó la presencia del virus por PCR. El 87% de las muestras resultaron positivas para VBK. De las muestras positivas, 19 fueron secuenciadas y genotipificadas, obteniendo trece genotipo I/b-1, cuatro genotipo I/a, uno genotipo II y el restante resultó genotipo IV. Se concluye que el VBK es altamente prevalente en muestras provenientes de las cloacas de la ciudad de Córdoba y el genotipo predominante es el I/b-1.
Setting research priorities for preconception care in low- and middle-income countries: aiming to reduce maternal and child mortality and morbidity
Setting research priorities for preconception care in low- and middle-income countries: aiming to reduce maternal and child mortality and morbidity
Dean, Sohni; Rudan, Igor; Althabe, Fernando; Webb Girard, Aimee; Howson, Christopher; Langer, Ana; Lawn, Joy; Reeve, Mary Elizabeth; Teela, Katherine C.; Toledano, Mireille; Venkjatraman, Chandra Mouli; Belizan, Jose; Car, Josip; Chan, Kit Yee; Chatterjee, Subidita; Chitekwe, Stanley; Doherty, Tanya; Donnay, France; Ezzati, Majid; Humayun, Khadija; Jack, Brian; Lassi, Zohra S.; Martorelli, Reynaldo; Poortman, Ysbrand; Bhutta, Zulfiqar A.
Preconception care means providing care before pregnancy is established. Women and couples of reproductive age are generally unaware of the effects that their own health conditions and health-related behaviors may have on the fetus during pregnancy. Although antenatal care is set in the maternal, newborn, and child health (MNCH) continuum [1], it neglects the most critical time of embryonic development, which often occurs before a woman even knows she is pregnant [2]. The evidence increasingly points to earlier care before pregnancy to improve women´s health, and better pregnancy outcomes for the mother and newborn.
Characterization of the atmospheric depth profile using the ground-level temperature: The case of Malargüe, Argentina
Characterization of the atmospheric depth profile using the ground-level temperature: The case of Malargüe, Argentina
Moreno, Juan Cruz; Sciutto, Sergio Juan
We present a study of the atmospheric depth profile and the dependence with its characteristic parameters. We introduce a new model, named GAMMA, based on a parameterization that allows us to obtain the atmospheric depth profile specifying only one simple physical parameter, namely the temperature at ground. The GAMMA model consists of a multilayer representation of the atmosphere that can be adjusted conveniently via constrained fits that are built to ensure interlayer continuity for both atmospheric depth and density profiles. Our analysis uses experimental data collected at Malargüe, Argentina by meteorological radiosondes. The GAMMA model can reproduce the averaged atmospheric depth profiles in all the cases available for analysis with good accuracy. The relative differences between model predictions and averaged data are always less than approximately 0.7%.
Seasonal variation in genetic population structure of sábalo (Prochilodus lineatus) in the Lower Uruguay River
Seasonal variation in genetic population structure of sábalo (Prochilodus lineatus) in the Lower Uruguay River
Rueda, Eva Carolina; Carriquiriborde, Pedro; Monzón, Alexander; Somoza, Gustavo Manuel; Ortí, Guillermo
Prochilodus lineatus is a highly migratory fish species that sustains the most important commercial fishery of Parana-Paraguay basin. Migratory patterns are poorly known and only few population genetic studies are avaliable for this species in the Upper Parana. To assess genetic population structure, we genotyped a sample of 93 individuals from the Lower Uruguay River close to Gualeguaychu city (Entre Rıos, Argentina) at three different times, July 2008 (Winter), September 2008 (Spring) and May 2009 (Fall). All individuals were genotyped for 12microsatellite loci previously found to be informative to assess populations of P. lineatus. Our results show seasonal variation of the genetic sub-structuring at this locality that may be related to the presence of different migratory stocks throughout the year. The Fall sample includes an additional genetic cluster of individuals not detected in Winter and Spring, suggesting that this species should be considered a mixed stock fishery.
Integrated ecotoxicological assessment of bottom sediments from the Paraná basin, Argentina
Integrated ecotoxicological assessment of bottom sediments from the Paraná basin, Argentina
Peluso, María Leticia; Abelando, Mariana; Apartin, Carina Diana; Almada, Pablo; Ronco, Alicia Estela
Paraná River, the six largest in the world, is receptor of pollution loads from tributaries traversing urban and industrialized areas, and extensive agriculture, particularly in its middle and low stretch along the Argentinean sector, where most of the productive activities of the country develop. Within the frame of monitoring surveys, the quality of bottom sediments from distal positions of twenty tributaries and three of the main course was evaluated. The assessment covered testing lethal and sublethal effects with the Hyalella curvispina based toxicity test, a benthic macrofauna survey and physicochemical variables of sediment matrix composition. A multivariate statistical analysis approach permitted integrating the obtained data from the different survey lines of evidence, explaining potential causes of the measured biological effects. The main perturbations detected were associated to tributaries in the middle sector of the basin, where anoxic conditions with high sulfide contents prevail mostly related to organic matter inputs of diverse combined activities, where sediments induce high lethality, and a consequent strong reduction of the benthic community population and diversity. The integrated survey approach proved being a robust tool in the assessment of causative—adverse effects relationships.
Thermotropic mesomorphism of mixed-valent diruthenium aliphatic carboxylates with axial anion bearing two aliphatic chains
Thermotropic mesomorphism of mixed-valent diruthenium aliphatic carboxylates with axial anion bearing two aliphatic chains
Bottazzi, Tamara Paula; Cecchi, Florencia; Zelcer, Andrés; Benoit, Heinrich; Donnio, Bertrand; Guillon, Daniel; Cukiernik, Fabio Daniel
A homologous series of binuclear mixed-valent diruthenium tetracarboxylates, Ru2(O2C(CH2)n-2CH3)DHDP, (DHDP=di(hexadecyl)phosphate axial anion, n=10,12,14,16 and 18), have been synthesized and characterized, and liquid crystallines properties of these compounds were examined. All the compounds exhibit a room-temperature crystallines lamellar phase and a high temperature (above 140º) Col_h mesophase. Another, probably semi-crustallines lamellar intermediate phase has also been found for all the studied compounds but for the n=18 derivative. Comparison with related mesogenic homologous series where the equatorial ligands are alsolinear carboxylates, but the axial anion bear just one aliphatic chain (carboxylates, octylslfonate, and dodecylsulfate), shows that the presence of a second aliphatic chain in the axial anion both lowers the transition temperatures and modifies the nature of the intermediate lamellar phase. Structural models at the molecular level are suggested for the crystallines lamellar en the Col_h phases.
Andean cat in northern Patagonia: linking conservation and research
Andean cat in northern Patagonia: linking conservation and research
Palacios, Rocio
Postcranial anatomy and phylogenetic relationships of Mussaurus patagonicus (Dinosauria, Sauropodomorpha)
Postcranial anatomy and phylogenetic relationships of Mussaurus patagonicus (Dinosauria, Sauropodomorpha)
Otero, Alejandro; Pol, Diego
The transition from basal sauropodomorphs to sauropods is one of the most dramatic evolutionary transformations in the history of dinosaurs. Constituent taxa of this transition were recorded mainly in South Africa and South America, and to a lesser extent in North America. We describe here the postcranial anatomy of four specimens of basal sauropodomorphs from the Late Triassic of Patagonia, Argentina, and identify them as adult individuals of Mussaurus patagonicus. The material is composed of one subadult and three adult specimens and was originally identified as Plateosaurus. The completeness of the material provides more complete knowledge of this taxon and allows us to introduce aspects of basal sauropodomorph anatomy that were poorly understood until now, such as the configuration and arrangement of the distal carpal elements. The phylogenetic relationships of Mussaurus patagonicus are tested through a cladistic analysis of basal sauropodomorphs based on the anatomy of these specimens rather than on the post-hatchling and juvenile specimens previously known for this taxon. Mussaurus is recovered as a non-sauropod anchisaurian, being the sister group of Aardonyx plus more derived sauropodomorphs and is depicted outside the ‘quadrupedal clade,’ given the presence of plesiomorphic features such as a humerus/femur ratio <0.8, a curved femoral shaft in lateral view, and a nearly circular femoral midshaft cross-section. Mussaurus patagonicus adds new and valuable information that helps to clarify the core of the basal sauropodomorph-sauropod transition.
Future changes in drought characteristics over southern South America projected by a CMIP5 multi-model ensemble
Future changes in drought characteristics over southern South America projected by a CMIP5 multi-model ensemble
Penalba, Olga Clorinda; Rivera, Juan Antonio
The impact of climate change on drought main characteristics was assessed over Southern South America. This was done through the precipitation outputs from a multi-model ensemble of 15 climate models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The Standardized Precipitation Index was used as a drought indicator, given its temporal flexibility and simplicity. Changes in drought characteristics were identified by the difference for early (2011-2040) and late (2071-2100) 21st century values with respect to the 1979-2008 baseline. In order to evaluate the multi-model outputs, model biases were identified through a comparison with the drought characteristics from the Global Precipitation Climatology Centre database for the baseline period. Future climate projections under moderate and high-emission scenarios showed that the occurrence of short-term and long-term droughts will be more frequent in the 21st century, with shorter durations and greater severities over much of the study area. These changes in drought characteristics are independent on the scenario considered, since no significant differences were observed on drought changes. The future changes scenario might be even more dramatic, taking into account that in most of the region the multi-model ensemble tends to produce less number of droughts, with higher duration and lower severity. Therefore, drought contingency plans should take these results into account in order to alleviate future water shortages that can have significant economic losses in the agricultural and water resources sectors of Southern South America.
Constructivismo y sociología: siete tesis de Bruno Latour
Constructivismo y sociología: siete tesis de Bruno Latour; Constructivism and sociology: seven theses of Bruno Latour
de Grande, Pablo Ernesto
Bruno Latour postula que la sociología contemporánea se dedica en buena medida a explicar cómo ciertas configuraciones sociales (tales que las jerarquías de poder o las desigualdades estructurales) afectan el funcionamiento de otros ámbitos en sus contenidos no sociales (tales que el derecho, la religión o el arte). Como consecuencia de esto, la misma habría abandonado su misión primaria de explicar lo social por sí mismo, además de estar produciendo explicaciones repetitivas y poco interesantes. El presente artículo reúne elementos teóricos de diferentes obras de Bruno Latour en función de elaborar siete tesis sobre su crítica radical a la sociología contemporánea. La propuesta principal de Latour es reformular la investigación social, abriendo la ‘caja negra' en la que lo social ha venido a convertirse. Finalmente se realizan algunas consideraciones sobre usos y limitaciones de las posiciones de Bruno Latour.; Bruno Latour argues that contemporary sociology is largely devoted to explain how certain social configurations (such as power hierarchies or structural inequalities) affect other non-social activities (such as law, religion or arts). As a result, sociology would have had abandoned its primary mission to explain the social itself, and it would be producing repetitive and uninteresting explanations. This paper puts together theoretical elements from different works of Bruno Latour in order to state seven theses on his radical critique to contemporary sociology. The main goal of Latour's proposal is reformulating social research, opening the black box in which the Social would have become. Finally, the article concludes summarizing usages and limitations of the perspective of Bruno Latour.
Fabricación de estándares de calibración para microsondas nucleares
Fabricación de estándares de calibración para microsondas nucleares; Calibration standars of nuclear microprobes
Arena, S.; Faya, T.; Lell, J.; Vega, N.; Davidson, Jorge; Nesprias, Francisco Jose Gabriel; Debray, M.
El Micro-haz de iones Pesados (MiP) del laboratorio Tandar constituye un instrumento de características únicas en el país, pues puede proveer haces de iones pesados de dimensiones micrométricas acelerados hasta decenas de MeV de energía. La búsqueda de tamaños de haz más pequeños ha creado la necesidad de contar con estándares de calibración de elevada calidad de resolución. En el presente trabajo se desarrollaron los primeros prototipos para calibrar la focalización del haz: estructuras metálicas de cobre o niquel en forma de grilla con orificios cuadrados. Se emplearon dos métodos de fabricación. En el primero se utilizaron técnicas de fotolitografía convencional sobre un sustrato de silicio con foto-resina, mientras que en el segundo se utilizó el MiP para micro-mecanizar sustratos de Niobato de Litio (LiNbO3). En ambos casos se finalizó el proceso de fabricación del patrón con electrodeposición de cobre o níquel sobre la matriz desarrollada. Mediante la técnica fotolitográfica se fabricaron grillas de níquel que varían entre 130 y 180 mesh**. Mediante micro-mecanizado con el MiP se fabricaron grillas de cobre de entre 500 y 2000 mesh sobre sustratos de LiNbO3.; The Micro-heavy ion beam (MiP) at Tandar’s Lab is a unique instrument in the country, as it can provide heavy ion beams at micrometer-scale accelerated to tens of MeV energy. The quest for smaller beam sizes has created the need for calibration standards of high resolution quality. In this paper we developed the first prototypes to calibrate the beam focusing: metal structures of copper or nickel shaped grid with square holes. We used two methods of manufacture. Were used in the first conventional photolithography techniques on a silicon substrate with photoresin while the second was used for micromachining with MiP substrates of lithium niobate (LiNbO3). In both cases the process for the manufacture was finished with electro-deposition of copper or nickel on the matrix developed. By photolithographic technique nickel grids were manufactured varying between 130 and 180 mesh. By MiP micromachining copper grids were produced between 500 and 2000 mesh on LiNbO3 substrates.
El uso de zonas censales para medir la segregación residencial: contraindicaciones, propuesta metodológica y un estudio de caso: Argentina 1991-2001
El uso de zonas censales para medir la segregación residencial: contraindicaciones, propuesta metodológica y un estudio de caso: Argentina 1991-2001
Rodriguez, Gonzalo Martin
Medir la segregación residencial a partir de unidades espaciales arbitrarias construidas por los organismos censales conlleva ciertos inconvenientes vinculados a lo que se conoce como el Problema de la Unidad Espacial Modificable (PUEM). Este problema ha sido generalmente ignorado por la mayoría de los investigadores, como si no afectara los resultados de sus estudios. En este trabajo se discute la legitimidad de usar zonificaciones censales para medir la segregación residencial, y se propone el uso de técnicas de desagregación y reagrupamiento de datos (DRD) que podrían aportar a reducir los sesgos del PUEM. Una de estas técnicas es utilizada para medir la segregación residencial socioeconómica en la Argentina durante el período 1991-2001. Se concluye que en países como Argentina estas técnicas constituyen, sin embargo, una solución muy limitada, y que solo a partir de introducir cambios de política en la gestión de datos censales podrá mejorarse sustancialmente la calidad de los estudios en este y otros campos.; Attempts on measuring residential segregation using arbitrary spatial units constructed by census agencies carry certain drawbacks related to what is commonly known as the Modifiable Areal Unit Problem (MAUP). This problem has been generally ignored by urban researchers in this topic as if it would not affect the results of their studies. This paper discusses the legitimacy of using census zoning systems for measuring residential segregation, and proposes the use of data disaggregation and regrouping (DDR) techniques that may at some degree contribute in reducing MAUP biases. One of these techniques is used for measuring socioeconomic residential segregation trends in Argentina for the 1991-2001 period. We conclude that in countries like Argentina these techniques represent just a partial and limited solution to MAUP. Quality and precision of quantitative studies on residential segregation and other fields dealing with similar problems may be substantially improved only if better access to spatially disaggregated data is provided by census agencies.
Los procesos subjetivos en las reformas de las carreras universitarias
Los procesos subjetivos en las reformas de las carreras universitarias
Colella, Leonardo Javier
El artículo plantea la temática de la reproducción de la desigualdad a través de las instituciones educativas y problematiza las prácticas de dominios que desbordan la cuestión del contenido curricular. La problematización se sitúa en el contexto de las reformas de las carreras universitarias en la actualidad.
Foucault y Rancière como educadores: la explicación como técnica de sí mismo
Foucault y Rancière como educadores: la explicación como técnica de sí mismo
Colella, Leonardo Javier
La intención de este artículo es indagar sobre la posibilidad de interpretar algunos conceptos foucaultianos como antecedentes del pensamiento de Rancière, en referencia al estudio sobre los modos de subjetivación en la educación. El análisis de la lógica de la verdad en Foucault y su diagnóstico de las sociedades de normalización encuentran cierta continuidad en la crítica rancieriana a la explicación y a la sociedad del menosprecio. Ambos hacen foco en las prácticas que intervienen en la constitución subjetiva. Rancière restablece en el eje central del análisis filosófico-educativo lo que, paradójicamente, bajo el nombre de Foucault iba perdiendo vigor: el sujeto.
Hongos arbusculares (Glomeromycota) en la rizosfera de Atriplex lampa en dos ambientes salinos de Córdoba: influencia de la profundidad en la colonización radical y presencia de morfoespecies
Hongos arbusculares (Glomeromycota) en la rizosfera de Atriplex lampa en dos ambientes salinos de Córdoba: influencia de la profundidad en la colonización radical y presencia de morfoespecies
Soteras, María Florencia; Cofré, María Noelia; Bartoloni, José; Cabello, Marta Noemi; Becerra, Alejandra
Atriplex lampa es un arbusto halófito de la provincia fitogeográfica Chaqueña que constituye un recurso forrajero a lo largo de todo el año. Las plantas halófitas se benefician al asociarse con los hongos micorrícico arbusculares (HMA), ya que le proveen resistencia contra la salinidad y la sequía. En general, los estudios acerca de los HMA están restringidos a los primeros centímetros del suelo y existe poca información sobre su presencia a mayores profundidades. El objetivo de este trabajo fue estudiar la colonización, la concentración radical e identificar las morfoespecies de HMA en la rizosfera de A. lampa en dos ambientes salinos del norte de la provincia de Córdoba, durante dos estaciones del año, y en cinco profundidades del suelo. Aunque no se encontraron arbúsculos, A. lampa presentó colonización radical por HMA en todas las profundidades. El mayor valor de colonización micorrícica y de concentración radical se observó en las Salinas Grandes. Se identificaron 20 morfoespecies de HMA pertenecientes a los géneros: Acaulospora, Ambispora, Claroideoglomus, Diversispora, Funneliformis, Glomus, Septoglomus y Scutellospora. Este es el segundo registro en Argentina de la presencia de HMA en raíces de A. lampa. Es necesario realizar estudios que evalúen la respuesta de A. lampa frente a la inoculación con HMA para confirmar la funcionalidad de la simbiosis.; Arbuscular fungi (Glomeromycota) in the rhizosphere of Atriplex lampa at two saline environments of Córdoba (Argentina): depth infuence on root colonization and the presence of morphospecies. Atriplex lampa is a valuable fodder shrub available for browsing by livestock even during drought periods in the Chaco Phytogeographical Province. Halophytes may beneft from the association with arbuscular mycorrhizal fungi (AMF) through improved tolerance to drought and salt. Ecological studies of AMF are generally restricted to the main rooting zone. However, AMF vertical distribution and seasonal dynamics in natural saline soils of Argentina have been poorly studied. The aim of this work was to explore AMF root colonization, root concentration and to identify AMF morphoespecies in A. lampa rhizosphere in two saline environments (Salinas de Ambargasta and Salinas Grandes) of central Argentina, in fve soil depth levels, during the wet and dry seasons. Despite we did not fnd arbuscules, AMF were found colonizing A. lampa roots in all depth levels. Salinas Grandes showed the highest root colonization value, and showed the highest root concentration, during wet season. The 20 AMF morphospecies identifed in this work belonged to the genera: Acaulospora, Ambispora, Claroideoglomus, Diversispora, Funneliformis, Glomus, Septoglomus and Scutellospora. This is the second record in Argentina of AMF structures in A. lampa roots. Future studies that evaluate mycorrhizal dependency of the plant are necessary to confrm the function of the symbiosis.
Cell wall modifications and ethylene-induced tolerance to non-chilling peel pitting in citrus fruit
Cell wall modifications and ethylene-induced tolerance to non-chilling peel pitting in citrus fruit
Vicente, Ariel Roberto; Manganaris, George A.; Minas, Ioannis S.; Goulas, Vlasios; Lafuente, Maria T.
Non-chilling peel pitting (NCPP), a storage disorder resulting in the formation of depressed areas in the peel of many citrus cultivars, is reduced by ethylene treatments. We hypothesized that this effect may be associated with biochemical changes of cell wall components. Therefore, we extracted cell wall material from albedo and flavedo tissues of ‘Navelate’ oranges stored in air, conditioned with ethylene (2 L L−1) for 4 days and subsequently transferred to air, or continuously stored in an ethylene-enriched atmosphere (2 L L−1). Uronic acids and neutral sugars were extracted into five fractions enriched in specific wall polymers namely water-, CDTA-, Na2CO3-, and 1 and 4 M KOH-soluble fractions. Pectin insolubilization was found in control fruit at long storage times. Ethylene treatments, alleviating NCPP, increased polyuronide solubility in the albedo and had a slight effect on the flavedo. Ethylene-treated fruit showed greater content of water-soluble neutral sugars and a larger proportion of hemicelluloses readily extractable with 1 M KOH, with a concomitant reduction in the 4 M KOH-soluble fraction. This suggests that the protective role of ethylene on NCPP is associated with an increased solubilization of the wall of albedo cells.
Liquid phase densification of Al-4.5 wt.% Cu powder reinforced with 5 wt.% Saffil short fibers during hot pressing
Liquid phase densification of Al-4.5 wt.% Cu powder reinforced with 5 wt.% Saffil short fibers during hot pressing
Moreno, M. F.; Gonzalez Oliver, Carlos Julian R.
The Alumix 13 (wt.%) (Al–4.5 Cu 0.5 Mg 0.2 Si) powder with and without 5 wt.% Saffil short fibers specimens were hot pressed in the range 580–620 °C. The densification during pressure increase was fitted using the Konopicky model and an agreement with the associated linear plot P vs. ln(1/(1 − D) was found for both materials, where P is applied pressure and D is the relative density of the porous material. The transient liquid phase formed from the elemental Al and Cu powder particles above the eutectic temperature of 548 °C at low hot pressing pressures, allows to increase the densification due to the reduction in the yield stress of the porous material. The active liquid flow enhanced the deformation between Al particles in the beginning of the pressure ramp. For higher pressures, a sudden break to a higher slope in Konopicky plot was found. This hardening behavior was detected from 610 °C for pure Alumix 13 and it was systematically developed at 580, 600, 610 and 620 °C for the composites, and it can be assigned to diffusion of Cu into the Al grains. During the constant pressure stage the densification was well fitted using the Power Law Creep model with exponents of n = 1 and n = 2, which are related to Newtonian viscous flow and superplastic deformation, respectively. Besides, final hot pressed composites samples retained an important quantity of solidified liquid phase located in between the Saffil fibers agglomerates.
Los modos de ser contingentes de lo político en el acontecimiento teatral
Los modos de ser contingentes de lo político en el acontecimiento teatral
Sequeira, María Jazmín
Con la crisis del 2001 resurgieron cuestionamientos sobre el sentido político del teatro. Las preguntas y desacuerdos sobre el concepto que define lo político en el acontecimiento teatral reflejaron la incertidumbre frente a los rasgos inéditos de lo social y anunciaron la necesidad de crear renovadas claves de lectura según las demandas de los nuevos tiempos. Algunos interrogantes que continúan abiertos: ¿es pertinente asociar el teatro -siendo específicamente un acontecimiento poético- a un discurso político?, si es así: ¿qué tipo de discurso puede ser político y qué no?; ¿en qué sentido, de qué forma, puede ser político el acontecimiento poético de los cuerpos que excede las significaciones?; ¿existen grados distintos de politicidad?, o ¿todo es político?; ¿qué significa entonces lo político: lo concerniente al gobierno de la comunidad, lo concerniente al autogobierno en comunidad, lo concerniente a las ideologías y hechos sobre el estar con otros?; ¿es acaso la función del teatro en relación a lo social lo que significa su ser y reflexión políticos?, si es así: ¿qué función y qué utilidad se le atribuye? En este trabajo se propone tensionar estos interrogantes con algunos aportes de las teorías políticas de la corriente de pensamiento posfundacional estudiada particularmente por Oliver Marchart (2011).
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