Dynamics of sonoluminescing bubbles within a liquid hammer device Urteaga, Raul; Garcia Martinez, Pablo Luis; Bonetto, Fabian Jose We studied the dynamics of a single sonoluminescing bubble (SBSL) in a liquid hammer device. In particular, we investigated the phosphoric acid–xenon system, in which pulses up to four orders of magnitude brighter than SBSL in water systems (about 1012 photons per pulse)have been previously reported [Chakravarty et al., Phys. Rev. E 69, 066317 (2004)]. We used stroboscopic photography and a Mie scattering technique in order to measure the radius evolution of the bubbles. Under adequate conditions we may position a bubble at the bottom of the tube (cavity) and a second bubble trapped at the middle of the tube (upper bubble). During its collapse, the cavity produces the compression of the liquid column. This compression drives impulsively the dynamics of the upper bubble. Our measurements reveal that the observed light emissions produced by the upper bubble are generated at its second collapse. We employed a simple numerical model to investigate the conditions that occur during the upper bubble collapse. We found good agreement between numerical and experimental values for the light intensity (fluence) and light pulse widths. Results from the model show that the light emission is increased mainly due to an increase in noble gas ambient radius and not because the maximum temperature increases. Even for the brightest pulses obtained (2x1013 photons, about 20 W of peak power) the maximum temperatures computed for the upper bubble are always lower than 20000 K.

Electrodeposition of CuInSe2 and In2Se3 on flat and nanoporous TiO2 substrates Valdes, Matias Hernan; Vazquez, Marcela Vivian; Goossens, A. In2Se3 and CuInSe2 films have been prepared by potentiostatic electrodeposition from deareated aqueous solutions. The substrate consisted of a duplex layer of dense and nanoporous TiO2 obtained by spray pyrolysis deposition (SPD) and doctor blading. In2Se3 thin films are electrodeposited in between the TiO2/CuInSe2 pn heterojunction to block the electron back flow and lower the interfacial recombination produced upon illumination. The films have been characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and optical transmission. Annealing the samples in Se atmosphere is essential to improve the crystallinity of the In2Se3 and CuInSe2 films. The combination of TiO2/In2Se3/CuInSe2 shows very good diode behavior with a rectification ratio higher than 100 at ±1 V.

Las empresas centenarias de Rosario y su región: Molino Victoria S.A. y Alabern Fábrega y Cía. S.A. de Marco, Miguel Angel L. La ubicación estratégica de la firma Molino Victoria. La localidad de María Juana en la década del 80 del siglo XIX. La familia Boero. Evolución del Molino. La relación de los Boero y la Bolsa de Comercio de Rosario. El siglo XX. Federico Alabern y los comienzos de la firma Alabern Fábrega y Cía. Ernesto Fábrega: la ampliación del campo de acción. La sociedad anónima. Los funcionarios de la firma y su inserción de las instituciones rosarinas. Los Weskamp: ciencia, empresa y vinculación internacional. La firma en la segunda mitad del siglo XX.

Fire retardant impregnants for woods based on alkaline silicates Pereyra, Andrea Marisa; Giudice, Carlos Alberto The aim of this paper was to determine the fire performance of wood panels (Araucaria angustifolia) impregnated in a pressure vessel with post-cured alkaline silicates (water glasses). Several commercial silicates based on sodium ions and potassium ions with 3.0/1.0 and 3.5/1.0 silica/alkali molar ratios were selected. Various treatments for curing were applied for polymerization, creating metal silicate polymers of high water insolubility. Experimental panels were tested in a limiting oxygen chamber (limiting oxygen index) and in a twofoot tunnel (flame-spread index and panel consumption). Test results displayed a high fire-retardant efficiency of some post-cured alkaline silicates.

50 años de CONICET: los avatares de la ciencia Hurtado de Mendoza, Diego Fabian; Feld, Adriana La historia del CONICET está marcada por una trayectoria errática. Nacido durante un gobierno dictatorial, el organismo estatal dedicado a la investigación científica y tecnológica sufrió las oscilaciones de la vida institucional del país, con gobiernos civiles y militares y la falta de una estrategia a largo plazo, que hoy intenta revertir, de cara a un proceso a futuro que vincule la indagación con la producción. Estos son algunos de los lineamientos que sigue este artículo.

Insertion/Deletion Polymorphisms in Indian Tribal Populations Veerraju, P.; Demarchi, Dario; Lakshmi, N.; Venkateswara Rao, T. Five Alu markers (Alu APO, PV 92, TPA 25, D1 and ACE) were studied in five tribal populations namely, Konda Reddi, Koya Dora and Konda Kammara of East Godavari district, Lambada and Chenchu of Mahaboobnagar district of Andhra Pradesh. All the five loci were found to be highly polymorphic. While the lowest heterozygosity was observed in the Chenchu the Lambadi shows the highest. Both Neighbour Joining tree and Principal Component analysis based on genetic distances suggest two broad clusters, one formed by the Lambada and Chenchu and the other by the Konda Reddi and Koya Dora with Konda Kammara as an outer element to this three-point cluster. Another cluster analysis carried out along with 19 other Indian populations brings out no distinct cluster of the 5 AP tribes; instead these AP tribal populations are integrated into different subclusters of the UP and Bengal suggesting lack of distinct genetic identity of these AP tribes as far as the few Alu markers are concerned.

A general tumour control probability model for non-uniform dose distributions González, Sara Josefina; Carando, Daniel Germán Perfectly uniform dose distributions over target volumes are almost impossible to achieve in clinical practice, due to surrounding normal tissues dose constraints that are commonly imposed to treatment plans. This article introduces a new approach to compute tumour control probabilities (TCPs) under inhomogeneous dose conditions. The equivalent subvolume model presented here does not assume independence between cell responses and can be derived from any homogeneous dose TCP model. To check the consistency of this model, some natural properties are shown to hold, including the so-called uniform dose theorem. In the spirit of the equivalent uniform dose (EUD) concept introduced by Niemierko (1997, Med. Phys., 24, 103–110), the probability-EUD is defined. This concept together with the methodology introduced to compute TCPs for inhomogeneous doses is applied to different uniform dose TCP models. As expected, the TCP takes into account the whole dose distribution over the target volume, but it is influenced more strongly by the low-dose regions. Finally, the proposed methodology and other approaches to the inhomogeneous dose scenario are compared.

Protesta social y cultura política: aportes para pensar los años ‘90 en Neuquén; Social protest and political culture: contributions for the interpretation of the 90´ in Neuquén Aiziczon, Fernando Cristian Durante la década del ´90 la provincia norpatagónica de Neuquén vive un intenso proceso caracterizado por una fuerte conflictividad social, anclada en un contexto particular y con diversos actores como protagonistas, con renovados contenidos y prácticas, aunque también impregnada por el rescate de ciertas tradiciones discursivas que remiten a un pasado combativo. Lo distintivo de Neuquén y que pretendo señalar aquí, parece ser la configuración de un campo de protesta social que se despliega en dos direcciones: a) como lugar simbólico para el resto de los fenómenos de protesta social en la Argentina de la década del ’90 (p.e. las organizaciones piqueteras), y b) como momento emergente de una cultura política que tras las puebladas cutralquenses de 1996/97 adquiere un claro perfil contestatario.; During the 90’s, the northern patagonic province of Neuquén goes through a very intense process, marked by strong social conflicts, anchored in a special context and with different kinds of actors in the leading roles. This process includes new practices and contents, though it is also permeated by certain speech traditions that reminds of a struggling pass. The distinctive tract of Neuquen –and I intend to point it here- seems to be the creation of a field for social protest that spreads towards two directions: a) as a symbolic place for the rest of the social protest phenomena in the 90’s of Argentina (v.g., the “piqueteros” (picketing) organizations), and b) as the emerging moment of a political culture that gets a clear defiant profile, after the village upraisings of Cutral Co during 1996/7.

How to Approximate the Heat Equation with Neumann Boundary Conditions by Nonlocal Diffusion Problems Cortazar, Carmen; Elgueta, Manuel; Rossi, Julio Daniel; Wolanski, Noemi Irene We present a model for nonlocal diffusion with Neumann boundaryconditions in a bounded smooth domain prescribing the flux throughthe boundary. We study the limit of this family of nonlocaldiffusion operators when a rescaling parameter related to thekernel of the nonlocal operator goes to zero. We prove that thesolutions of this family of problems converge to a solution of theheat equation with Neumann boundary conditions.

Ultrastructure and potential taxonomic importance of euspermatozoa and paraspermatozoa in the volutid gastropods Zidona dufresnei and Provocator mirabilis (Caenogastropoda, Mollusca) Giménez, Juliana; Healy, John M.; Hermida, Gladys Noemí; Lo Nostro, Fabiana Laura; Penchaszadeh, Pablo Enrique The ultrastructure of mature spermatozoa is investigated for the first time in the Volutidae, based on the commercially significant South American species Zidona dufresnei (Donovan, 1823) (fresh material) and supplemented with observations on testicular (museum) material of the deep sea New Zealand species Provocator mirabilis (Finlay, 1926). Euspermatozoa of Z. dufresnei (ex sperm duct) consist of: (1) a tall-conical acrosomal vesicle (with short basal invagination, constricted anteriorly) which is flattened anteriorly and associated with an axial rod, centrally perforate basal plate and short accessory membrane; (2) a rod-shaped, solid and highly electron-dense nucleus (with short basal fossa containing centriolar complex and initial portion of a 9 + 2 axoneme); (3) an elongate midpiece consisting of the axoneme sheathed by 5–6 helical mitochondrial elements, each exhibiting a dense U-shaped outer layer; (4) an elongate glycogen piece (axoneme sheathed by nine tracts of putative glycogen granules); (5) a dense annulus at the junction of the midpiece and glycogen piece and (6) a short free tail region (axoneme surrounded only by plasma membrane). Paraspermatozoa of Z. dufresnei are vermiform and dimorphic: the first type contains approximately 14–20 axonemes (arranged peripherally and interspersed with microtubules) and numerous oblong dense vesicles, numerous less dense (round) vesicles, occasional, large lipid-like vesicles, and scattered mitochondria; the second type contains 25–31 axonemes (peripherally arranged, interspersed with microtubules), occasional mitochondria and extensive cytoplasm. Results obtained for P. mirabilis from testis material are essentially as observed in Z. dufresnei, although the euspermatozoan acrosome still has to achieve its compressed transverse profile. Observations on paraspermatozoa were limited by fixation quality of available (testis) tissues, but these cells are similar to the first type of Zidona paraspermatozoa. Although most of the euspermatozoal features are also observed in many neotaenioglossans and neogastropods, the U-shaped outer layer of each mitochondrial element has not previously been reported and may prove a diagnostic feature of the Volutidae, the subfamily Zidoniinae or possibly only the Zidonini (in which Z. dufresnei and P. mirabilis are currently placed).

Acerca de una inhumación temprana (CA. 2500 AP) en el sitio Cruz Chiquita 3 (Valle de Salsacate, Córdoba, Argentina) Pastor, Sebastián Se presentan los resultados del estudio de una inhumación localizada en el sitio Cruz Chiquita 3, en el valle de Salsacate, al occidente de la provincia de Córdoba (Argentina). La misma cuenta con una datación temprana -ca. 2500 AP- obtenida por AMS a partir de la fracción de colágeno de una muestra ósea. Se busca contextualizar el caso considerando los tratamientos mortuorios a escala regional. En tal sentido, se evalúan tendencias homogeneizantes y diversificadoras, así como continuas y discontinuas, observadas en torno a dichos tratamientos a lo largo de un extenso período. Por otra parte, el análisis de los fitolitos asociados al tártaro de las piezas dentarias permitió reconocer la presencia de maíz (Zea mays), en una fecha temprana para las Sierras de Córdoba y en general para el área Andina Meridional. A partir de la información disponible a escala regional y macro-regional, se considera la conveniencia de interpretar o no estos datos en términos de una producción agrícola local.; This paper presents the study of a burial found in Cruz Chiquita 3, a site located in Salsacatevalley, in the western sector of Córdoba province, Argentina. AMS dating of a human bone samplereveals an antiquity of 2500 BP. The mortuary practices are evaluated on a regional scale in order tocontextualize the case. We analyze the degree of diversity/homogeneity, and continuity/discontinuityof the trends regarding mortuary practices for a long period. In parallel, the phytolithic analysis ofteeth reveals the presence of maize (Zea mays), in an early time for Córdoba Hills and in general for theSouth Andes region. We evaluate the potential existence of a local agricultural production, in accordancewith available information at a regional and macro-regional scale.

A triangular finite element with local remeshing for the large strain analysis of axisymmetric solids Castello, Walter Braulio; Flores, Fernando Gabriel In this work a three-node triangular finite element with two degrees of freedom per node for the large strain elasto-plastic analysis of axisymmetric solids is presented. The formulation resorts to the adjacent elements to obtain a quadratic interpolation of the geometry over a patch of four elements from which an average deformation gradient is defined. Thus the element formulation falls within the framework of assumed strain elements or more precisely of F-bar type formulations. The in-plane behavior of the element is similar to the linear strain triangle, but without the drawbacks of the quadratic triangle, e.g. contact or distortion sensitivity. The element does not suffer of volumetric locking in problems with isochoric plastic flow and the implementation is simple. It has been implemented in a finite element code with explicit time integration of the momentum equations and tools that allow the simulation of industrial processes. The widely accepted multiplicative decomposition of the deformation gradient in elastic and plastic components is adopted here. An isotropic material with non-linear isotropic hardening has been considered. Two versions of the element have been implemented based on a Total and an Updated Lagrangian Formulation respectively. Some approximations have been considered in the latter formulation aimed to reduce the number of operations in order to increase numerical efficiency. To consider bulk forming, with large geometric changes, an automatic local remeshing strategy has been developed. Several examples are considered to assess the element performance with and without remeshing.

A new search strategy for microquasar candidates using NVSS/2MASS and XMM-Newton data Combi, Jorge Ariel; Albacete Colombo, Juan Facundo; Martí, Josep Aims.Microquasars are ideal natural laboratories for understanding accretion/ejection processes, studying the physics of relativistic jets, and testing gravitational phenomena. Nevertheless, these objects are difficult to find in our Galaxy. The main goal of this work is to increase the number of known systems of this kind, which should allow better testing of high-energy phenomena and more realistic statistical studies of this galactic population to be made. Methods: We have developed an improved search strategy based on positional cross-identification with very restrictive selection criteria to find new MQs, taking advantage of more sensitive modern X-ray data. To do this, we made combined use of the radio, infrared, and X-ray properties of the sources, using different available catalogs. Results: We find 86 sources with positional coincidence in the NVSS/XMM catalogs at galactic latitudes |b| ¡Ü 10¡ã. Among them, 24 are well-known objects and the remaining 62 sources are unidentified. Out of 86 sources, 31 have one or two possible infrared counterparts in the 2MASS catalog. For the fully coincident sources, whenever possible, we analyzed color-color and hardness ratio diagrams and found that at least 3 of them display high-mass X-ray binary characteristics, making them potential microquasar candidates.

La savia del tiempo. Apuntes para una concepción relacional del tiempo; The sap of time. Notes for a relational conception of time Garrido Maturano, Ángel Enrique El artículo primero «abre» la tijera del tiempo y muestra por qué tiempo cósmico y tiempo vivido son irreductibles uno a otro. En segundo lugar «afila» las hojas de la tijera y analiza tanto tiempo cósmico cuanto tiempo vivido como categorías relacionales y la alteridad como conditio sine qua non de la efectividad del tiempo. En tercer lugar «cierra» la tijera señalando los rasgos formales comunes a tiempo cósmico y vivido. Finalmente se pregunta en qué medida estos rasgos comunes presuponen un sentido religioso último del tiempo; The article first «opens» the scissors of time, and shows why cosmic time and lived time are irreducible one to another. Second, it «sharpens» the blades of the scissors an analyzes both cosmic time and lived time as relational categories, and alterity as the conditio sine qua non of the actuality of time. Third, the article «closes» the scissors by pointing out the formal traits common to cosmic and lived time. Fainally, it raises the question about how far these common features presuppose an ultimate religious meaning of time.

The spatial orientation of Planetary Nebulae within the milky way Weidmann, Walter Alfredo; Diaz, Ruben Joaquin We analyze the spatial orientation of a homogenous sample of 440 elongated Planetary Nebulae (PNe) in order to determine the orientation of their apparent major axis with respect to the Milky Way plane. We present some important geometrical and statistical considerations that have been overlooked by previous works on the subject. The global distribution of galactic position angles (GPA) of PNe is quantitatively not very different from a random distribution of orientations in the Galaxy. Nevertheless, we find that there is at least one region on the sky, toward the Galactic center, where a weak correlation may exist between the orientation of the major axis of some PNe and the Galactic equator, with an excess of axes with GPA ∼100°. Therefore, we confirm that "extrinsic" phenomena (i.e., global Galactic magnetic fields, shell compression from motion relative to the Interstellar Medium) do not determine the morphology of PNe on most of the sky, with a possible exception toward the Galactic center.

Aportes de la enseñanza de la autogestión a la construcción de proyectos de vida diferentes. Una experiencia con mujeres trabajadoras del conurbano bonaerense Miano, María Amalia; Heras Monner Sans, Ana Ines; Burin, David En este escrito analizamos una experiencia pedagógica que se desarrolló con mujeres en una localidad del conurbano bonaerense y que tuvo como objetivo enseñar a sus participantes algunos conceptos básicos acerca del cooperativismo de trabajo. Nos propusimos reflexionar sobre: 1) los aprendizajes incorporados por las mujeres en el proceso de la experiencia pedagógica en función de la historia de los grupos de trabajo que conforman y de las concepciones previas que tenían acerca del cooperativismo y, 2) los criterios y dispositivos que organizaron la enseñanza a partir de analizar las interacciones que tuvieron lugar en las jornadas de capacitación. Para esto nos preguntamos desde el enfoque etnográfico y la sociolinguística de la interacción ¿quién enseña qué, a quién y con qué resultados identificables, al menos a corto plazo?; In this article we analyze an educational experience aimed at teaching basic concepts on worker cooperatives to women living in a small town in the peripheral Buenos Aires area. We present our findings organized around two themes: (1) what this educational experience contributed to accessing knowledge on the basic procedures and ideas that ground worker cooperatives, by analyzing participants´ processes of change over time; (2) the educational tools and criteria that framed the educational process itself, by analyzing face to face interactions that took place during the teaching and learning experience. We have used an 2 ethnographic and interactional sociolinguistic approach to answer an underlying question: who teaches what, to whom, and with what identifiable results, at least in the short term?

Riesgo de erosión costera en el Balneario Parque Mar Chiquita, provincia de Buenos Aires; Coastal erosion risk in Buenos Aires Province, Argentina Merlotto, Alejandra; Verón, Eleonora Marta; Sabuda, Fernando Gabriel. El proceso de urbanización acelerada que se ha manifestado en las últimas décadas en el litoral marítimo bonaerense ha revelado la intensidad del fenómeno de erosión costera y la vulnerabilidad de dicha área al mismo. El área de estudio de este trabajo corresponde al Balneario Parque Mar Chiquita, localidad turística ubicada en el partido homónimo, provincia de Buenos Aires (Argentina). La misma presenta uno de los mayores valores de retroceso de la línea de costa, proceso que ha ocasionado importantes pérdidas económicas. De este modo, el objetivo ha sido evaluar el riesgo de erosión de la franja costera del balneario. Para ello se consideraron como componentes del riesgo a la vulnerabilidad y la peligrosidad, determinadas a partir de trabajos de campo. Luego se construyeron matrices de indicadores para obtener un valor índice del riesgo de erosión costera para cada unidad de análisis, el cual se volcó en un mapa. Los resultados permitieron terminar que el balneario presenta un importante riesgo de erosión costera, pudiéndose dentificar áreas con diferentes grados de riesgo.; The increasing complexity of nature-society relationship together with the estimates of climatic change and its effects on waves and coastal storms have asserted the importance of coastal phenomenon studies due to the particular vulnerability of both littoral areas and their population. Indices of the two components of risk, hazard and vulnerability, were constructed to assess coastal erosion risk in Buenos Aires Province. Based on different indicators, the indices allowed assessing the hazard characteristics (geomorphology, beach slope, erosion rates, etc.) and the population exposed to coastal erosion (quantity, sanitary condition, education level, etc.). The resulting zoning risk map outlined from very low to high hazard areas, and very low to moderate vulnerability. Coastal erosion risk is overall low in the study area although there are small sectors of moderate risk. The results reveal that risk assessment may develop practical and adequate tools for designing prevention and coastal erosion mitigation strategies according to the features of each sector.

Cardiac mitochondrial nitric oxide: a regulator of heart rate? Fellet, Andrea L.; Boveris, Alberto Antonio; Arranz, Cristina Teresa; Balaszczuk, Ana María Alterations in autonomic control and myocardial nitric-oxide (NO) production are likely linked to the development and progression of heart dysfunction. By focusing on heart rate, the complexity of the actions of NO at distinct levels throughout the autonomic nervous system and its relationship with other regulators can be demonstrated. Given the multiple and opposing actions of NO on cardiac control, it is difficult to interpret a response after a global intervention in the NO system. The diversity of intracellular pathways activated by NO, and their differing sensitivities to different levels of NO, might account for some aspects of reported specific but opposite effects. We discuss factors that might contribute to this diversity of actions. A proper elucidation of the effects of NO on metabolic pathways and on energy generation could lead to novel therapeutic strategies aimed at the early treatment of heart dysfunction.

Los estudios sobre fatiga en Argentina: De Mosso a Palacios y Rimoldi Klappenbach, Hugo Alberto Arturo El trabajo analiza la conformación del campo de estudios sobre la fatiga a nivel internacional, especialmente en Europa. Seguidamente se examinan algunos trabajos tempranos sobre estudios de la fatiga en Estados Unidos. Finalmente se analizan los estudios de fatiga de Alfredo Palacios y en menor medida de Horacio Rimoldi, quienes abordaron la cuestión desde perspectivas diferentes. Palacios, se ocupó de los estudios sobre fatiga desde una matriz de pensamiento que articulaba el derecho laboral y la psicología experimental en un contexto de fuerte compromiso político socialista. Rimoldi, por su parte, se ocupó de la fatiga en un período posterior, a partir de la articulación de concepciones fisiológicas y psicológicas y a partir de su interés por las aplicaciones médicas.; This paper analyzes the early making of the studies around fatigue in an international setting, especially in Europe. Second, the early studies on psychological fatigue in the United States are examined. Finally, fatigue's studies by Alfredo Palacios and Horacio Rimoldi are analyzed. The interesting of both of them in fatigue's problems became from different approaches and motivations. Palacios, devoted himself to satigue studies from a wide approach that articulated both the labor right and the experimental psychology and with strong commitment towards socialist ideas. Rimoldi, on the other hand, researched on fatigue in a later period, starting from the articulation of physiological and psychological conceptions and worried about medical applications.

Nuevos resultados del estudio del sitio Ajej I: un aporte a la variabilidad de estrategias de los canoeros fueguinos Piana, Ernesto Luis; Vazquez, Martin Miguel; Alvarez, Myrian Rosa El estudio del sitio Ajej I, ubicado cronológicamente entre 1300 y 1400 años AP, es resultado de una excavación de rescate realizada en la costa norte del canal Beagle. La región fue ocupada desde el séptimo milenio AP por cazadores-recolectores litorales. Los análisis realizados permiten postular que el sitio se caracteriza por: a) una baja recurrencia de ocupación; b) la selectividad de caza de pinnípedos frente a otros recursos; c) su representación diferencial de partes anatómicas y d) una baja variabilidad actividades realizadas con el instrumental lítico. Asimismo proveyó una fecha temprana para la presencia del arco y la flecha en la región austral. Los resultados permiten discutir sobre la diversidad de estrategias implementadas por los cazadores-recolectores canoeros.; The study of the archaeological site Ajej I dated between 1300 and 1400 BP is the result of a rescue excavation carried out in the northern coast of the Beagle Channel, an area peopled by sea littoral hunter-gatherers since the seventh millennium BP. The analyses results pinpoint that the site is characterized by: a) a low redundant occupation; b) a selectivity of the pinnipeds as preys; c) a differential distribution of their anatomical parts; and d) a low diversity of activities carried with the lithic instruments. Besides, these studies provided an early date to the presence of bows and arrows in such an austral region. Results enable to discuss on the variability of the strategies carried on by those sea nomads.