Anisotropic effects of background fields on Born-Infeld electromagnetic waves Aiello, Matias; Bengochea, Gabriel Roman; Ferraro, Rafael We show exact solutions of the Born–Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of the Born–Infeld equations generates an interaction between the background and the wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction—a behavior resembling the one of a wave in an anisotropic medium. This feature could open up a way to experimental tests of the Born–Infeld theory.

Is there an influence of short-term solar activity variations on mesopause region airglow? Scheer, Jurgen; Reisin, Esteban Rodolfo A-priori, rapid variations of solar activity that directly impact on the terrestrial environment should be expected to influence airglow brightness in the mesopause region via the photodissociative production of atomic oxygen, as it does on the time scale of the solar cycle. To find out whether this is supported by our midlatitude data, we analyze the strongest geoeffective solar activity events, in times when data from the Argentine airglow spectrometer were obtained. An alternative interaction path involving geomagnetic perturbations mediated by the solar wind can also be expected to affect the mesopause region. Daily mean values of different solar and geomagnetic activity indices, and more than 1400 nights of airglow brightness and rotational temperature measurements (mostly from El Leoncito, 31.8S) are available for this study. The diagnostic value of this investigation is augmented by using information corresponding to two different nominal altitudes (87 km for the OH(6–2) band, and 95 km for the O2b(0–1) band). Our approach ranks the (solar and airglow) events by their respective strength, which automatically provides emphasis on the more important cases. We conclude that if an airglow response to strong solar events exists, it is only short-lived and should therefore most easily be detectable by daytime observations. On the other hand, we did not find signatures in our airglow data that could convincingly be related to geomagnetic storms.

A Multiple Flare Scenario where the Classic Long-Duration Flare Was Not the Source of a CME Golf, C. P.; van Driel Gesztelyi, L.; Démoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, Cristina Hemilse; Klein, K. L.; Kurokawa, H. A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that “tether cutting” reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields.

The Essential Norm of Operators in the Toeplitz Algebra on Ap(Bn Suarez, Fernando Daniel Let Ap be the Bergman space on the unit ball Bn of Cn for 1

N-dimensional Hankel transform and complex powers of Bessel operator Trione, Susana Elena In this paper, we study a version of the n-dimensional Hankel transform on certain spaces ℋμ which were studied in [Molina, S., 2003, A generalization of the spaces ℋμ and and the space of multipliers. Actas del VII Congreso Dr. Antonio Monteiro, pp. 49–56.]. Moreover, we introduce an n-dimensional generalization of Bessel operator and we have studied its properties in relation to the Hankel transform. Moreover, we study some application to the study of the fractional powers of Bessel operator on L2 (Rn+).

The digestive adaptation of flying vertebrates: High intestinal paracellular absorption compensates for smaller guts Caviedes Vidal, Enrique Juan Raul; McWhorter, Todd J.; Lavin, Shana R.; Chediack, Juan Gabriel; Tracy, Christopher R.; Karasov, William Anecdotal evidence suggests that birds have smaller intestines than mammals. In the present analysis, we show that small birds and bats have significantly shorter small intestines and less small intestine nominal (smooth bore tube) surface area than similarly sized nonflying mammals. The corresponding >50% reduction in intestinal volume and hence mass of digesta carried is advantageous because the energetic costs of flight increase with load carried. But, a central dilemma is how birds and bats satisfy relatively high energy needs with less absorptive surface area. Here, we further show that an enhanced paracellular pathway for intestinal absorption of water-soluble nutrients such as glucose and amino acids may compensate for reduced small intestines in volant vertebrates. The evidence is that L-rhamnose and other similarly sized, metabolically inert, nonactively transported monosaccharides are absorbed significantly more in small birds and bats than in nonflying mammals. To broaden our comparison and test the veracity of our finding we surveyed the literature for other similar studies of paracellular absorption. The patterns found in our focal species held up when we included other species surveyed in our analysis. Significantly greater amplification of digestive surface area by villi in small birds, also uncovered by our analysis, may provide one mechanistic explanation for the observation of higher paracellular absorption relative to nonflying mammals. It appears that reduced intestinal size and relatively enhanced intestinal paracellular absorption can be added to the suite of adaptations that have evolved in actively flying vertebrates.

“Living” Free Radical Polymerization in Tubular Reactors. I. Modeling of the Complete Molecular Weight Distribution Using Probability Generating Functions Asteasuain, Mariano; Soares, Matheus; Lenzi, Marcelo K; Cunningham, Michael; Sarmoria, Claudia; Pinto, José Carlos; Brandolin, Adriana This is the first of a series of works aiming at developing a tool for designing “living” free radical polymerization processes in tubular reactors, in order to achieve tailor‐made MWDs. A mathematical model of the nitroxide‐mediated controlled free radical polymerization is built and implemented to predict the complete MWD. It is shown that this objective may be achieved accurately and efficiently by means of the probability generating function (pgf) transformation. Comparison with experimental data is good. The potential of the resulting model for optimization activities involving the complete MWD is also shown.

Structure of hard-hypersphere fluids in odd dimensions Rohrmann, Rene Daniel; Santos, Andrés The structural properties of single component fluids of hard hyperspheres in odd space dimensionalities d are studied with an analytical approximation method that generalizes the rational function approximation earlier introduced in the study of hard-sphere fluids. The theory makes use of the exact form of the radial distribution function to first order in density and extends it to finite density by assuming a rational form for a function defined in Laplace space, the coefficients being determined by simple physical requirements. Fourier transform in terms of reverse Bessel polynomials constitute the mathematical framework of this approximation, from which an analytical expression for the static structure factor is obtained. In its most elementary form, the method recovers the solution of the Percus-Yevick closure to the Ornstein-Zernike equation for hyperspheres at odd dimensions. The present formalism allows one to go beyond by yielding solutions with thermodynamic consistency between the virial and compressibility routes to any desired equation of state. Excellent agreement with available computer simulation data at d=5 and d=7 is obtained.

Diseño urbano sustentable de conjuntos habitacionales Papparelli, Alberto Hermes; Kurban, Alejandra Silvia El trabajo describe dos métodos de aplicación en el diseño urbano sustentable de conjuntos de viviendas en propiedad horizontal en altura, basados en el reconocimiento de la ciudad como un sistema ambiental. Estos métodos, combinados entre sí, permiten el abordaje del diseño urbano con el objetivo de colaborar con la apropiación de los espacios públicos y semi-públicos, procurando ciudades inclusivas y no selectivas. Dichos métodos: Leyes de Generación Espaciofuncional y Sistema de Umbrales Urbanos, son empleados desde hace más de una década en los Talleres de Arquitectura IV(A) y V(B) de la Facultad de Arquitectura, Urbanismo y Diseño (UNSJ - Argentina), período durante el cual fueron verificados y ajustados en sus conceptos teóricos y en su praxis. Si bien resultan de utilidad en el diseño urbano de conjunto de viviendas multifamiliares, también pueden ser usados como herramienta en el diseño de conjuntos edilicios institucionales y culturales, en entornos urbanos de complejidad media y alta.; The work describes two methods to be applied in the sustainable urban design of a group of multi-storey dwellings in common property, based on the recognition of the city as an environmental system. These methods combined between them, let the approach of the urban design in order to collaborate with the appropriation of the public and semi-public spaces, offering inclusive and non selective cities. Such methods: Patterns of Spatial-Functional Generation and System of Urban Range are used since a decade in the Architectural Workshops IV (A) and V (B) of the Faculty of Architecture, Urbanism and Design (UNSJ - Argentina), period during which they were verified and adjusted in their theoretical concepts and in their practice. Although they are useful in the urban design of groups of multifamiliar dwellings, they can be used as tools in the design of groups of institutional and cultural buildings in urban environments of middle and high complexity.

Characterization and catalytic performance of PtSn catalysts supported on Al2O3 and Na-doped Al2O3 in n-butane dehydrogenation de Miguel, Sergio Ruben; Bocanegra, Sonia Alejandra; Vilella, Irene María Julieta; Ruiz Guerrero, Ana María; Scelza, Osvaldo Antonio PtSn/Al2O3 and PtSn/Al2O3-Na catalysts display important modifications of the metallic phase with respect to Pt/Al2O3 one. In this sense, TPR and XPS results show the presence of strong interactions between Pt and Sn, with probable alloy formation, which would be responsible for the decrease of the reaction rate and the increase of the activation energy in cyclohexane dehydrogenation. Besides the experiments of cyclopentane hydrogenolysis show that the alkali metal addition to bimetallic PtSn/Al2O3 catalysts completely eliminates the hydrogenolytic ensembles, which could be due to a geometric modification of the metallic phase. These important modifications in the nature of the metallic function due to the simultaneous addition of Na and Sn to Pt/Al2O3 are responsible for the excellent catalytic performance in the n-butane dehydrogenation, thus giving high conversions, selectivities to butenes higher than 95%, and lower deactivation capacity than those corresponding to bimetallic PtSn catalysts (with different Sn contents) supported on undoped alumina. The excellent stability of PtSn/Al 2O3-Na catalysts would be due to a low carbon formation during the reaction, such as it was observed from pulse experiments.

Kinetic studies of the dry reforming of methane over the Rh/La 2O3-SiO2 catalyst Múnera Agudelo, John Fernando; Cornaglia, Laura Maria; Vargas Cesar, Deborah; Schmal, Martin; Lombardo, Eduardo Agustin Rh(0.6%)/La2O2(27%)-SiO2 is one of the best catalysts used in membrane reactors for the CO2 reforming of methane. A reliable rate equation is needed to model the system. Hence, the fresh and used/catalysts were duly characterized using several instrumental techniques (TPD, DRIFTS, and XPS). The kinetic behavior of the catalysts in the reforming reaction was investigated as a function of temperature and partial pressure of CH4 and CO2. The rate of methane consumption showed fractional order dependency on the partial pressures of both reactants. A reaction mechanism adopted from the literature and supported by the characterization data presented here led to a kinetic equation that fits the experimental data obtained. This study contributes to a better qualitative and quantitative understanding of the dry reforming of methane occurring on Rh catalysts supported on La-containing oxides.

A novel function for CRISP1 in rodent fertilization: involvement in sperm-zona pellucida interaction Busso,Dolores; Cohen, Debora Juana; Maldera, Julieta Antonella; Dematteis, Andrea; Cuasnicu, Patricia Sara Epididymal protein CRISP1 participates in rat and mouse gamete fusion through its interaction with complementary sites on the egg surface. Based on in vivo observations, in the present study we investigated the possibility that CRISP1 plays an additional role in the sperm-zona pellucida (ZP) interaction that precedes gamete fusion. In vitro fertilization experiments using zona-intact rat and mouse eggs indicated that the presence of either an antibody against rat CRISP1 (anti-CRISP1) or rat native CRISP1 (rCRISP1) during gamete co-incubation produced a significant decrease in the percentage of fertilized eggs. However, differently to that expected for a protein involved in gamete fusion, no accumulation of perivitelline sperm was observed, suggesting that the inhibitions occurred at the sperm-ZP interaction level. Bacterially expressed recombinant CRISP1 (recCRISP1) also significantly inhibited egg fertilization. In this case, however, an increase in the number of perivitelline sperm was observed. Subsequent experiments evaluating the effect of anti-CRISP1 or rCRISP1 on the number of sperm bound per egg indicated that the protein is involved in the initial step of sperm-ZP binding. In agreement with these functional studies, indirect immunofluorescence experiments revealed that although rCRISP1 is capable of binding to both the ZP and the oolema, recCRISP1 only binds to the egg surface. The finding that deglycosylated rCRISP1 behaves as the untreated protein, whereas the heat-denatured rCRISP1 associated only with the oolema, indicates that the protein ZP-binding ability resides in the conformation rather than in the glycosydic portion of the molecule. The interaction between rCRISP1 and the ZP reproduces the sperm-ZP-binding behavior, as judged by the failure of the protein to interact with the ZP of fertilized eggs. Together, these results support the idea that CRISP1 participates not only in sperm-egg fusion but also in the prior stage of sperm-ZP interaction.

Imágenes de indígenas con pasaporte abierto: del Gran Chaco a la Tierra del Fuego; Images of natives with an open passport: from Gran Chaco to Tierra del Fuego Alvarado, Margarita; Giordano, Mariana Lilian Este trabajo tiene como objetivo principal exponer las reflexiones y análisis de un conjunto de fotografías de fines del siglo XIX y comienzos del siglo XX, de realidades culturales muy distantes geográficamente – región del Gran Chaco y la zona de Tierra del Fuego (América del Sur) – pero cercanas en cuanto a sus formas de producción e interpretación de lo visible. Nuestra hipótesis es que a partir de un conjunto de imágenes de indígenas sometidos a lo que hemos llamado una “trashumancia iconográfica”, se ha contribuido a moldear e influir en la construcción de identidades étnicas y sociales con relación a lo llamado “chaqueño” y “fueguino”. Planteamos que las maneras en que se ha definido la “otredad” visual de estos grupos están sometidas a ciertos mecanismos de construcción e interpretación de identidades y etnicidades, así como también de transmisión de memorias pre-moldeadas, en donde se manifiestan características visuales específicas para organizar la diferencia y por lo tanto las formas de “imaginarizarlas”. La fotografía puede ser pensada como una producción cultural donde la memoria social o colectiva busca referentes, huellas y marcos de contención. Estas imágenes constituyen memorias delineadas sobre el “otro” en espacios disímiles pero que han sido intercambiados por la circulación que se les ha dado.; This work is devoted to expound the thoughts and analyses we have been carrying out from a group of photographs of the late XIXth and early XXth centuries, which show two cultural realities that, though extremely distant if seen from a geographical point of view, are really close if focused from their ways of producing and interpreting the visible world. Our hypothesis is that, thanks to a group of images of natives that were subjected to what we have called ‘an iconographic transhumance’, there has been a contribution to the modelling and construction of the ethnic and social identities regarding the so-called ‘Chaqueño’ and ‘Fueguino’ natives. We state that the ways in which the visual ‘otherness’ of these groups have been defined are subjected to certain mechanisms of construction and interpretation of identities and ethnicities, as well as to others of transmission of pre-moulded memories, in which certain specific visual features become manifest in order to organize the difference and, thus, the ways of ‘imaginaryzing’ them. Photography can be thought of as a cultural production where the social or collective memory looks for referents, traces, and retaining frameworks. These images are memories that were outlined over the ‘other’ within dissimilar spaces, which have nonetheless been interchanged through the circulation they have been subdued to.

Development of wear resistant carbidic austempered ductile iron (CADI) Laino, Sebastian; Sikora, Jorge Antonio; Dommarco, Ricardo The abrasion wear resistance of irons may be improved by the incorporation of an extra phase to the matrix, typically consistent of carbides. Nevertheless, the improvement in wear resistance is generally accompanied by a decrease in the impact toughness. The aim of this work is to study the methodology to obtain a controlled precipitation of carbides in a ductile cast iron that is subsequently austempered, obtaining the so called Carbidic Austempered Ductile Iron (CADI). This material is expected to offer high abrasion resistance but still retaining higher impact toughness than other reinforced irons, thanks to the particular characteristics of the matrix. A plate model with a copper chill allowed to evaluate both, the influence of a high cooling rate and the effect of alloying elements on carbide precipitation. Four different alloys with equivalent carbon close to the eutectic composition were used in order to evaluate the effect of chromium contents ranging from 1 to 2.5%. A detailed microstructural characterisation of the material was made, studying particularly carbide content and composition, besides their stability during the heat treatment. The abrasion wear resistance was evaluated by testing under the ASTM G 65 standard, obtaining relative wear resistance values ranging between 1.02 and 1.95 with respect to conventional ADI samples taken as reference material. The impact toughness decreased from about 138 – 101 J for ADI to about 26 – 7 J for CADI.

Adaptive management of alien invasive species: putting the theory into practice Zalba, Sergio Martín; Ziller, Sílvia R. Even though often based on scarce information, many actions due to conservation ofbiodiversity need to be carried out as matters of urgency. In the case of biological invasions, this is acommon situation, as the real possibilities for controlling an invasive alien species are significantlyreduced as it establishes and spreads over natural ecosystems. Adaptive management, that is, man-agement practices planned on a solid experimental basis, allows managers to tackle urgent problemsat the same time they generate essential information to test the effectiveness of control practices andthe precision of assessments of the impacts of invasive species over natural ecosystems or of the needto carry out complementary restoration practices. The basic principles of adaptive management arepresented in this paper with examples of its application in the control of invasive alien species in thepampas of Argentina.

Copper incorporation into recombinant CotA laccase from Bacillus subtilis: characterization of fully copper loaded enzymes Durão, Paulo; Chen, Zhenjia; Fernandes, André T.; Hildebrandt, Peter; Murgida, Daniel Horacio; Todorovic, Smilja; Pereira, Manuela M.; Melo, Eduardo P.; Martins, Lígia O. The copper content of recombinant CotA laccase from Bacillus subtilis produced by Escherichia coli cells is shown to be strongly dependent on the presence of copper and oxygen in the culture media. In copper-supplemented media, a switch from aerobic to microaerobic conditions leads to the synthesis of a recombinant holoenzyme, while the maintenance of aerobic conditions results in the synthesis of a copper-depleted population of proteins. Strikingly, cells grown under microaerobic conditions accumulate up to 80-fold more copper than aerobically grown cells. In vitro copper incorporation into apoenzymes was monitored by optical and electron paramagnetic resonance (EPR) spectroscopy. This analysis reveals that copper incorporation into CotA laccase is a sequential process, with the type 1 copper center being the first to be reconstituted, followed by the type 2 and the type 3 copper centers. The copper reconstitution of holoCotA derivatives depleted in vitro with EDTA results in the complete recovery of the native conformation as monitored by spectroscopic, kinetic and thermal stability analysis. However, the reconstitution of copper to apo forms produced in cultures under aerobic and copper-deficient conditions resulted in incomplete recovery of biochemical properties of the holoenzyme. EPR and resonance Raman data indicate that, presumably, folding in the presence of copper is indispensable for the correct structure of the trinuclear copper-containing site.

Genetic typing of equine arteritis virus isolates from Argentina Echeverria, Maria Gabriela; Diaz, Silvina; Metz, German Ernesto; Serena, Maria Soledad; Panei, Carlos Javier; Nosetto, Edgardo Omar We report the nucleotide sequence and genetic diversity of four Equine Arteritis Virus (EAV) ORF 5 and 6 from Argentina isolates, obtained from asymptomatic virus-shedding stallions. Nucleic acid recovered from the isolates were amplified by RT-PCR and sequenced. Nucleotide and deduced amino acid sequences from the Argentine isolates were compared with 17 sequences available from the GenBank. Phylogenetic analysis revealed that the Argentine isolates grouped together in a definite cluster near European strains. Despite the greater genetic variability among ORF 5 from different isolates and strains of EAV, phylogenetic trees based on ORF 5 and 6 are similar. Both trees showed that virus sequences from America and Europe segregate into distinct clades based on sequence analysis of either ORF 5 or 6. This study constitutes the first characterization of Argentine EAV isolates.

Characterization of Pd-CeOx interaction on α-Al2O3 support Gigola, Carlos Eugenio; Moreno, Mario Sergio Jesus; Costilla, Ignacio Oscar; Sanchez, Miguel Dario The Pd-Ce interaction was studied over CeO2 (0.3-2.5 wt.%)-Pd (1 wt.%)/α-Al2O3 catalysts used in the reforming reaction of CH4 with CO2. The samples were characterized by using high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The activity and selectivity behavior was in good agreement with that of other supported metal catalysts (Ni and Pd) modified with different promoters. The preliminary results of HRTEM would indicate that the CeOx forms small crystallites around the Pd particle. The XPS analysis for the regions of Ce 3d and Pd 3d, gives an account of Ce being present mostly as Ce3+ and a high binding energy for Pd 3d5/2 (335.3 eV), an evidence of Pd-Ce chemical interaction. The Pd/Al XPS intensity ratios vs. the Pd average particle size, determined by TEM, show an excellent correlation for fresh and used catalyst. These results indicate that the diminution of the Pd/Al ratios was due to Pd sintering. Consequently, the small amounts of CeOx species do not cover the Pd particle, in agreement with the HRTEM results. The overall results stand for the promoter action mechanism of the CeOx for the reforming reaction with CO2.

The Lévy fractional Brownian motion family as a new paradigm in the modeling of turbulent wave-front phase Pérez, Darío Gabriel; Zunino, Luciano José; Garavaglia, Mario Jose In Perez et al. [J. Opt. Soc. Am. A 21 (10), 2004] we have given a general formalism to model the turbulent wave-front phase by using fractional Brownian motion processes. Moreover, it extends classical results to non- Kolmogorov turbulence: the Strehl ratio and the angle-of-arrival variance are shown to be dependent on the dynamic state of the turbulence. Nevertheless, this model has its drawbacks as it is unable of handling the stationarity of the phase increments over the full inertial range. The Levy fractional Brownian motion (LfBm) family is then introduced here in order to overcome this problem.

Competitiveness of a Bradyrhizobium sp. Strain in Soils Containing Indigenous Rhizobia Bogino, Pablo Cesar; Banchio, Erika; Bonfiglio, Carlos; Giordano, Walter Fabian The success of rhizobial inoculation on plant roots is often limited by several factors, including environmental conditions, the number of infective cells applied, the presence of competing indigenous (native) rhizobia, and the inoculation method. Many approaches have been taken to solve the problem of inoculant competition by naturalized populations of compatible rhizobia present in soil, but so far without a satisfactory solution. We used antibiotic resistance and molecular profiles as tools to find a reliable and accurate method for competitiveness assay between introduced Bradyrhizobium sp. strains and indigenous rhizobia strains that nodulate peanut in Argentina. The positional advantage of rhizobia soil population for nodulation was assessed using a laboratory model in which a rhizobial population is established in sterile vermiculite. We observed an increase in nodule number per plant and nodule occupancy for strains established in vermiculite. In field experiments, only 9% of total nodules were formed by bacteria inoculated by direct coating of seed, whereas 78% of nodules were formed by bacteria inoculated in the furrow at seeding. In each case, the other nodules were formed by indigenous strains or by both strains (inoculated and indigenous). These findings indicate a positional advantage of native rhizobia or in-furrow inoculated rhizobia for nodulation in peanut.