Evaluation of Pd/La2O3 catalysts for dry reforming of methane Fernandes Junior, Luiz Carlos P.; de Miguel, Sergio Ruben; García Fierro, José Luis; Rangel, Maria do Carmo Lanthana-supported palladium catalysts with different metal loads were evaluated in carbon dioxide of methane (dry reforming). A strong interaction between palladium and lanthana was noted. The catalysts produced low hydrogen to carbon monoxide molar ratio and thus the reaction can be combined with methane steam reforming to adjust this ratio for several purposes. The catalyst with 1 Pd was the most active leading to conversion above 80 and hydrogen to carbon monoxide molar ratio of 0.4.

Lateralization as a symmetry breaking process in birdsong Trevisan, Marcos Alberto; Cooper, B; Goller, Franz; Mindlin, Bernardo Gabriel The singing by songbirds is a most convincing example in the animal kingdom of functional lateralization of the brain, a feature usually associated with human language. Lateralization is expressed as one or both of the bird's sound sources being active during the vocalization. Normal songs require high coordination between the vocal organ and respiratory activity, which is bilaterally symmetric. Moreover, the physical and neural substrate used to produce the song lack obvious asymmetries. In this work we show that complex spatiotemporal patterns of motor activity controlling airflow through the sound sources can be explained in terms of spontaneous symmetry breaking bifurcations. This analysis also provides a framework from which to study the effects of imperfections in the system' s symmetries. A physical model of the avian vocal organ is used to generate synthetic sounds, which allows us to predict acoustical signatures of the song and compare the predictions of the model with experimental data. © 2007 The American Physical Society.

La fiesta del sentido. Observaciones acerca de la esenciade la alegría a partir del pensamiento de M. Scheler, V. Jankélévitch y H. Rombach; The celebration of meaning. Observations on the essence of happiness from M.Scheler’s, V. Jankélévitch’s and H. Rombach’s thinking Garrido Maturano, Ángel Enrique El artículo estudia primero el paradigma religioso de Scheler, el ético de Jankélévitch y el ontológico de Rombach de la alegría, intentando en cada caso despejar los rasgos formales esenciales que definen el fenómeno en todos ellos. Redefine luego estos rasgos valiéndose de las nociones de sincronía y sintonía y muestra el trasfondo estético propio de los diferentes paradigmas de la alegría. Finalmente se refiere al enamoramiento como un modo abierto a todo hombre de experimentar la alegría en su esencia.; The article first deals with Scheler’s religious, Jankélévitch’s ethical, and Rombach’s ontological paradigm on happiness, and describes the essential formal traits that define the phenomenon in the three patterns. Second, it articulates these traits by resorting to the notions of synchrony and syntony, and shows the aesthetic backgound proper to the different paradigms of happiness. Finally, the article refers to the act of falling in love as a mood open to every human being in order to experience happiness in its essential nature.

Effect of fat supplementation on leptin, insulin-like growth factor I, growth hormone, and insulin in cattle Becu, Damasia; Garcia Tornadu, Isabel Andrea; Shroeder, G.; Salado, E.E.; Gagliostro,G.; Delavaud C; Chilliard, Y; Lacau, Isabel María We investigated the effect of fat supplementation on plasma levels of hormones related to metabolism, with special attention to leptin, in cows in early lactation and in feedlot steers. In experiment 1, 34 lactating cows received no fat or else 0.5 or 1.0 kg of partially hydrogenated oil per day in addition to their basal diet from day 20 before the expected calving date to day 70 postpartum. In experiment 2, part of the corn in the basal concentrate was replaced with 0.7 kg of the same oil such that the diets were isocaloric; 18 cows received the fat-substituted diet and 18 a control diet from day 20 before the expected calving date to day 75 postpartum. In experiment 3, calcium salts of fatty acids were added to the basal diet of 14 feedlot steers for 80 d; another 14 steers received a control diet. The basal plasma levels of leptin were higher in the cows than in the steers. Dietary fat supplementation did not affect the leptin levels in the lactating cows but lowered the levels in the feedlot steers despite greater energy intake and body fatness (body weight) in the steers receiving the supplement than in those receiving the control diet. The levels of insulin-like growth factor I and insulin were decreased with dietary fat supplementation in the lactating cows but were unaffected in the steers, suggesting that responses to fat ingestion depend on the physiological state of the animal, including age and sex. Finally, no effects of supplementary fat on the level of growth hormone were demonstrated in any of the models; L’effet de l’ajout de gras sur les niveaux plasmatiques d’hormones reliées au métabolisme, avec une attention particulière à la leptine, a été étudié chez des vaches en début de lactation et chez des bouvillons en parc d’engraissement. Dans l’expérience 1, 34 vaches en lactation n’ont reçu aucun gras ou bien 0,5 ou 1 kg/jour d’huile partiellement hydrogénée en supplément de leur ration de base commençant 20 jours avant la date prévue de vêlage et allant jusqu’à 70 jours post-partum. Dans l’expérience 2, une partie du maïs dans le concentré de base a été remplacé par 0,7 kg de la même huile de manière à ce que les diètes soient isocaloriques; 18 vaches ont reçu la diète avec le substitut de gras et 18 une diète témoin débutant 20 jours avant la date prévue de vêlage et allant jusqu’à 75 jours post-partum. Dans l’expérience 3, des sels de calcium d’acides gras ont été ajoutés à la diète de base de 14 bouvillons d’embouche pendant 80 jours; 14 autres bouvillons ont reçu une diète témoin. Les niveaux plasmatiques de base de leptine étaient plus élevés chez les vaches que chez les bouvillons. Un supplément de gras alimentaire n’a pas affecté les niveaux de leptine chez les vaches en lactation mais a diminué les niveaux chez les bouvillons d’embouche malgré un plus grand apport calorique et plus de gras corporel (poids corporel) chez les bouvillons recevant le supplément que chez ceux recevant la diète témoin. Les niveaux du facteur de croissance similaire à l’insuline de type I et l’insuline étaient diminués chez les vaches laitières recevant le supplément en gras mais non-modifiés chez les bouvillons, ce qui suggère que les réponses à l’ingestion de gras dépendent de l’état physiologique de l’animal, incluant son âge et le sexe. Finalement, l’ajout de gras n’a démontré aucun effet sur les niveaux d’hormone de croissance dans tous les modèles étudiés.

Influence of weather conditions and density of Doru luteipes (Dermaptera: Forficulidae) on Diatraea saccharalis (Lepidoptera: Crambidae) egg mortality Fenoglio, Maria Silvina; Trumper, Eduardo The infuence of weather factors and the predator Doru luteipes Scudder density on Diatraea saccharalis (F.) egg predation was studied. Mortality of D. saccharalis eggs was determined by artiÞcially infesting maize plots with egg masses at various times within each of two maize-growing seasons. Each egg cohort was monitored every 24Ð48 h to determine the fate of eggs, and predation rates were calculated. Doru luteipes were sampled every 7Ð10 d, and the mean air temperature, the minimum percentage of relative humidity, and rainfall accumulations were recorded during the egg exposure period. To test the effects of abiotic and biotic variables on egg predation, we used a generalized linear model (GLM). Diatraea saccharalis egg predation was negatively associated with rainfall, whereas D. luteipes density and mean temperature were positively correlated with mortality. The implications of these Þndings for the management of D. saccharalis are discussed.

Hidrografia de la columna de agua en puerto cuatreros Menendez, Maria Clara; Vitale, Alejandro José; Piccolo, Maria Cintia; Hoffmeyer, Monica Susana Se analizó la variación de las condiciones hidrográficas en la columna de agua en relación al ciclo de mareas en Puerto Cuatreros. Durante el periodo comprendido entre diciembre de 2004 y diciembre de 2005 se midieron perfil les verticales de temperatura y salinidad y se obtuvieron muestras de agua en dos profundidades para determinar la concentración de sedimentos en suspensi6n. Los parámetros meteorológicos y la marea se obtuvieron en forma continua. La temperatura del agua presento un suave gradiente vertical en bajamar, en tanto que en pleamar el sistema se homogeneizó producto de la mezcla turbulenta de la marea. La temperatura superficial del agua presento una variación a 10 largo del ciclo de marea can mayor amplitud en los meses cálidos. La salinidad presentó un notorio gradiente vertical en bajamar. En creciente y pleamar la salinidad fue similar a la de la plataforma continental interior, mientras que en bajante y bajamar disminuyó por influencia de la descarga de agua dulce de arroyos próximos a la zona. En meses con altas precipitaciones la salinidad decreció significativamente y en días con altas temperaturas aumentó por el efecto de la evaporaci6n. Las mayores concentraciones de sedimento en suspensión se registraron con precipitaciones máximas y en marea bajante. Si bien la marea es el principal agente que influye sobre las características de la columna de agua, el factor meteorológico contribuye a generar variabilidad sobre las características hidrográficas en Puerto Cuatreros.; The variation of the bydrogrlphic con ditions in the water column in relation to the tidal cycle in Cuatreros Port was analyzed. Vertical profiles of temperature and salinit y were measured belween December 2004 and December 2005. Water samples were also obtained to de termine the suspended sediment concentration. Meteorological parameters and tides were registered continuously. Water temperature showed a smooth vecrtical gradient during low tide, while in high tide the system became homogenous as a consequence of tidal mixing. The surface water temperature showed a variation throug hout the tidal cycle with the greatest amplitude in the warm months. The salinitys howed a significant vertical gradient in low tide. During flood and high tide salinity was similar to the typical values of the inner continental shelf, while in ebb and low tide it diminished because of the influence of freshwater discharges of near by streams. In months with high precipitations, salinity decreased significantly and in days with high temperatures it increased by effect of evapomtion. The highest concentrations of suspended sediment were registered with maximum precipitations and during ebb tide. Although the tide is the main agent that influences the characteristics of the water column, the meteorological factor contributes to generate variability on the hydrographic conditions in Cuatreros PorI.

Historias rojas: Los intelectuales comunistas y el pasado nacional en los años 1930s Cattaruzza, Alejandro En este artículo estudiaremos las interpretaciones del pasado que los intelectuales comunistas plantearon en la Argentina entre 1930 y 1943. El cambio crucial en las mismas, que hizo posible una lectura comunista desplegada del pasado argentino, se explica por un proceso de incorporación del Partido Comunista al campo político nacional, más importante y profundo que los sucesivos cambios de línea tácticos decididos por la Internacional.; In this article we will analyse the interpretations of the past offered by the communist intellectuals in Argentina between 1930 and 1943. We argue that the most important change in those interpretations -which made a detailed communist vision of the national past possible- must be explained by the incorporation of the Communist Party to the national political field during this period: a more important and deeper process than the various tactical changes decided by the Communist International.

A model for capturing and representing the engineering design process Gonnet, Silvio Miguel; Henning, Gabriela Patricia; Leone, Horacio Pascual This paper presents a Collaborative Model for capturing and representing the engineering Design process (CoMoDe). CoMoDe is a deductive object-oriented model that, in relation to an engineering design process, is able to capture the different elements that participate in a design process in an integrated fashion. In particular, it is able to represent (i) the activities, operations, and actors that have generated each design product, (ii) the imposed requirements, and (iii) the rationale behind each decision. Furthermore, it also offers an explicit mechanism to represent and trace the different model versions that have participated in the design process. On such a basis, this proposal introduces specific procedures to handle various situations appearing in cooperative environments. They are: (i) different design teams perform independent concurrent activities on ‘‘a priori’’ independent parts of the artefact being designed and afterwards their results need to be made consistent; (ii) distinct teams concurrently work on slightly coupled parts of the artefact being designed and conflict handling must be addressed along their ‘‘parallel’’ course of actions.

Criterios de asignación de género gramatical en toba Censabella, Marisa Ines El género es uno de los tipos de categorización nominal que se diferencia de otros -los clasificadores nominales, por ejemplo- por exigir concordancia entre una clase 'controladora' y la/s clase/s 'meta' (Corbett, 1991; Aikhenvald, 2000). En toba (familia Guaycurú), la marcación de género natural y gramatical se organiza en la oposición masculino / femenino, y se manifiesta por medio de afijos en los dependientes demostrativos o en los mismos nombres, cuando estos son derivados. En este trabajo presentamos las clases de palabras que expresan el género y sus reglas de asignación semántica, fonológica y morfológica. Las reglas de asignación semántica y fonológica no presentan problemas para su identificación. En cuanto a la asignación morfológica, cada sufijo nominalizador selecciona la misma marca de género gramatical, salvo los nombres derivados que utilizan el sufijo -ki 'lugar cerrado, posición vertical', caso en que puede seleccionar tanto uno como otro género; además se observa procesos de nombres, cuando estos son derivados. En este trabajo presentamos las clases de palabras que expresan el género y sus reglas de asignación semántica, fonológica y morfológica. Las reglas de asignación semántica y fonológica no presentan problemas para su identificación. En cuanto a la asignación morfológica, cada sufijo nominalizador selecciona la misma marca de género gramatical, salvo los nombres derivados que utilizan el sufijo -ki 'lugar cerrado, posición vertical', caso en que puede seleccionar tanto uno como otro género; además se observa procesos de reanálisis de sufijos indicadores de forma en marcadores de género natural. Finalmente, se presenta la expresión del género en préstamos y su comportamiento en casos de homofonía.; 'Genders' or 'noun classes' are noun categorization devices that obligatory need agreement between 'controller' and 'target' classes (Corbett, 1991; Aikhenvald, 2000). In Toba (Guaykuruan), grammatical and natural gender are expressed in the opposition 'masculine / feminine' observed in the target classes (demonstrative dependents and pronominal demonstrative dependents) with non-derivate nouns, and also in the controller morpheme when it is constructed by derivation. In this paper we present the expression of gender (in target and controller classes), and the semantic, phonological and morphological rules of gender assignment in Toba. Semantic and phonological assignment rules are clearly identifiable but morphological assignment rule are more complex. Each derivational suffix selects always the same gender with one exception, the suffix -ki. This suffix that could be interpreted as nominal classifier controls masculine or feminine gender on the basis of semantic criteria, as shape or volume. Also related to the morphological assignment rules, we have identified processes of reanalysis where derivational suffixes associated with shape information are reinterpreted as gender markers. Finally, we present the gender assignment in Spanish loans and in cases of homophony.

An Experimental and Theoretical Study of the Synthesis of Bioninspired Copololymers of Vinylbenzylthymine and Vinyl triethylammnonium Chloride Casis, Natalia; Luciani, Carla Vanesa; Vich Berlanga, Javier; Martino, Debora Marcela; Estenoz, Diana Alejandra; Meira, Gregorio Raul ‘Bioinspired’ copolymers based on vinylbenzyl thymine (VBT) and an ionically-charged monomer, such as vinylbenzyl triethylammonium chloride (VBA), were synthesized and theoretically investigated. These watersoluble copolymers are polystyrene (PS)-based, and their structure mimics DNA. In the presence of shortwavelength UV light, the thymine groups dimerize into non-toxic, environmentally benign, and biodegradable photo-resist materials. Copolymerizations with different comonomer ratios were carried out at 658C. Samples were taken along the reactions to determine monomer conversion, chemical composition, and molecular weight distribution. While average molecular weights fall along the reaction, the average composition remains almost constant and coincident with the initial comonomer ratios, thus indicating a similar reactivity of all the comonomer radicals. The developed mathematical model simulates the synthesis of the base biopolymer, in the sense of predicting the evolution of the global reaction variables and molecular structure of the polymer. The termination and propagation kinetic constants were adjusted to the experimental data. The resulting values are quite different to those of a normal styrene homopolymerization, thus suggesting a noticeable effect between the solvent and the comonomer pending groups.

Effect of boron on the microstructure of hydrogenated microcrystalline silicon thin films Dussan, A.; Koropecki, Roberto Roman In this work, a series of boron doped microcrystalline silicon films (µc-Si:H (B)) were deposited by plasma-enhanced chemical vapor deposition (PECVD), using silane (SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The concentration of B2H6 was varied in the range of 0–100 ppm. The microstructure and morphology of samples were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. A trend towards increasing crystalline volume fraction and grain size were observed as boron concentration in the samples increased; while the XRD spectra show that the peak intensity at 2? ˜ 47° decreases and becomes gradually amorphous with the increasing degree of doping. The doped microcrystalline silicon films presented a crystallographic preferential orientation in the plane (220). Correlations between structural and electric properties were also studied.

Propiedades estructurales y morfológicas de películas delgadas de uc-Si:H Dussan, A.; Koropecki, Roberto Roman Una serie de películas delgadas de silicio microcristalino dopadas con Boro (µc-Si:H (B)) fueron depositadas por el método de deposición química en fase de vapor asistida por plasma (PECVD). Las muestras fueron dopas con Boro. La microestructura y morfología de las muestras fue analizada por microscopía de fuerza atómica (AFM), difracción de rayos X y espectroscopía Raman. Se observó un incremento tanto en la fracción de volumen cristalina como en el tamaño de grano a medida que se incrementó la concentración de Boro en las muestras. Las películas de silicio microcristalino dopadas con Boro presentaron una orientación cristalográfica preferencial en el plano (220).; A series of films boron doped microcrystalline silicon (µc-Si:H (B)) was deposited by plasma-enhanced chemical vapor deposition (PECVD). The samples were Boron doped. The microstructure and morphology of samples were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. Trends of increasing crystalline volume fraction and grain size were observed with increasing boron concentration in the samples. The doped microcrystalline silicon films showed a preferential crystallographic orientation in the plane (220).

Sturmian functions in a L2 basis: critical nuclear charge for n-electron atoms Frapiccini, Ana Laura; Gasaneo, Gustavo; Colavecchia, Flavio Dario; Mitnik, Dario Marcelo Two particle Sturmian functions [M. Rotenberg, Ann. Phys., NY 19 (1962) 262; S.V. Khristenko, Theor. Math. Fiz. 22 (1975) 31 (Engl. Transl. Theor. Math. Phys. 22, 21)] for a short range potentials are obtained by expanding the solution of the Schrodinger equation in a finite ¨ L2Laguerretype basis. These functions are chosen to satisfy certain boundary conditions, such as regularity at the origin and the correct asymptotic behavior according to the energy domain: exponential decay for negative energy and outgoing (incoming or standing wave) for positive energy. The set of eigenvalues obtained is discrete for both positive and negative energies. This Sturmian basis is used to solve the Schrodinger equation for ¨ a one-particle model potential [A.V. Sergeev, S. Kais, J. Quant. Chem. 75 (1999) 533] to describe the motion of a loosely bound electron in a multielectron atom. Values of the two parameters of the potential are computed to represent the Helium isoelectronic series and the critical nuclear charge Zc is found, in good agreement with previous calculations.

A natural normalization for the eigenstates of a Hamiltonian with continuous spectrum Murgida, Gustavo Ezequiel; Castagnino, Mario Alberto G. J. A mathematical formalism that allows to deal with many problems on quantum systems with continuous evolution spectrum is presented. The usual Hilbert space is generalized to a prehilbert one T where singular states can be represented and an extended Dirac’s notation can be introduced. The obtained formalism contains the Van Hove one but in a more natural way. It allows to explain decoherence and other phenomena.

The Lee Friedrichs model: continuous limit and decoherence Laura, Roberto Domingo Eugenio; Castagnino, Mario Alberto G. J. We analyze the thermodynamic limit of the Hamiltonian, states and observables, of a system containing an oscillator interacting with a thermal bath We use the results to a compare environment and self induced decoherence.

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+).