Nanoinsecticidas: Nuevas perspectivas para el control de plagas Stadler, Teodoro; Buteler, Micaela; Weaver, David K. La agricultura de bajo impacto ambiental demanda nuevos pesticidas que deben ajustarse a las exigentes normativas internacionales. Parte de la búsqueda de nuevos productos bio-acionales se desarrolla por fuera del marco de la síntesis orgánica, explorando diferentes sustancias de origen natural como extractos vegetales, aceites insecticidas e insecticidas inorgánicos. Los polvos insecticidas representan el grupo más antiguo de sustancias utilizadas por el hombre para el control de plagas, cuya eficacia se basa principalmente en fenómenos físicos. Con el advenimiento de los insecticidas de síntesis, los polvos insecticidas fueron relegados por casi cinco décadas a la función de carriers de principios activos dentro de los insecticidas formulados. Con el desarrollo del caolín hidrófobo en la década de los 90´, los polvos inorgánicos resurgieron como insecticidas ?per se?, y, recientemente, a partir del descubrimiento de los nanoinsecticidas, afloran nuevas alternativas para expandir el espectro de aplicaciones de los polvos inorgánicos. El desarrollo y registro de nuevos productos a partir de nanomateriales manufacturados se basa en el paradigma ?lo mismo pero diferente?, ya que éstos difieren de las sustancias con idéntica estructura y composición química respecto de algunas propiedades como reactividad, área especifica, efectos cuánticos, carga eléctrica, etc. Estas sustancias con nuevas propiedades también se destacan como herramientas muy prometedoras para la protección de cultivos y la producción de alimentos y abren nuevas fronteras para el manejo de plagas con nanoinsecticidas. La alúmina nanoestructurada exhibe varias de las propiedades del insecticida ideal, ya que se trata de un producto natural desde el punto de vista químico, no reactivo, económico, con reducidas probabilidades de provocar resistencia en los insectos y su eficacia es mayor que la de otros polvos insecticidas como el caolín o la tierra de diatomeas. La masiva aparición de productos a base de nanomateriales en el mercado ha superado la velocidad a la que se evalúa su potencial impacto, de modo que la aplicación avanza por delante de la regulación para su uso. Esto sugiere la urgente necesidad de investigar los potenciales riesgos que surgen del empleo de estos productos en general, de los nanoinsecticidas en particular y sus efectos sobre organismos no blancos, así como sobre las nuevas tecnologías de aplicación más seguras y eficientes. Los actuales niveles de aplicación de nanopartículas y los desarrollos por venir, sugieren que la nanotecnología tendrá un efecto directo sobre las tendencias de la evolución de la agricultura para el control de plagas.; Sustainable agriculture demands new environmentally friendly pesticides that adhere to strict international regulations. Part of the research on new biorational pesticides focuses on natural products such as plant extracts, oils, and inorganic insecticides. Insecticidal dusts represent the oldest group of substances used by men for pest management, and their efficacy is based on physical phenomena. With the advent of synthetic pesticides, insecticidal dusts were used as carriers for other active ingredients in formulated insecticides. Organic dusts made a come-back as insecticides with the discovery of hidrophobic kaolin in the 90's. Recently, the discovery of nanoinsecticides brings new alternatives to expand the spectrum of applications of inorganic dusts. Development and registry of nanomaterials is based on the idea that they are not new materials, although they have different properties than the products with the same chemical structure, given that novel properties emerge from products when they are at the nanoscale. For example, reactivity, specific area, electric charge and quantum effects may differ. These substances with new properties are promising as tools for crop protection and food production, opening new frontiers for nanoinsecticides in pest management. For example, nanostructured alumina has been shown to have insecticidal properties, and it possesses some of the characteristics of an ideal insecticide, given that it is a natural product, not reactive, economical, with reduced probabilities of generating resistance in insects, and it is more effective than other commercially available insecticidal dusts. The current use of nanotechnology in a wide array of fields and products as well as the recent discovery of their potential in crop protection suggests that nanomaterials have a great potential for development of new products that will impact agriculture. Given the recent and widespread use of nanomaterials, there is an urgent need to study the impact of these products on human health and non target organisms, as well as to research more efficient and safer delivery technologies. The current levels of application of nanoparticles and the expected developments to come, suggest that nanotechnology will have a direct impact on the evolution of pest management practices in agriculture.

Crowned eagles rarely prey on livestock in central Argentina: persecution is not justified Sarasola, José Hernán; Santillán, Miguel Ángel; Galmes, Maximiliano Adrian Raptors have been reported to prey on livestock, causing considerable conflicts between birds of prey and local human communities. Previous studies have documented that human persecution is the most important threat to the endangered crowned eagle Harpyhaliaetus coronatus in central Argentina, due to a local belief that crowned eagles heavily and consistently prey on livestock. However, there are no empirical data supporting this assertion. Such information is crucial to evaluating possible measures to mitigate this human–wildlife conflict. We evaluated the feeding ecology of crowned eagles in semiarid habitats of central Argentina during the breeding seasons of 2002 to 2009. We also evaluated whether eagles are responsible for livestock predation and examined spatial-temporal variation in crowned eagles’ food habits. We identified 598 prey items consisting almost entirely of native prey: mammals (67.7%), reptiles (16.2%), birds (3.3%), fish (2.5%), and invertebrates (16.9%). We only recorded 1 (0.17%) occurrence of livestock prey remains, belonging to a domestic goat Capra hircus. Occurrences of the 4 main prey groups were not affected by habitat type or season. However, reptiles were recorded in higher numbers at sites where the diet of eagles was addressed by direct observation and video recording. Contrary to other human–predator conflicts worldwide, and assuming that the single livestock prey was not scavenged, our results show that crowned eagles rarely prey on livestock. We advocate reducing human–wildlife conflicts by implementing management and conservation measures and by educating local communities with respect to the ecological role of crowned eagles and other predators.

Effect of abomasal glucose infusion on plasma concentrations of gut peptides in periparturient dairy cows Larsen, M.; Relling, Alejandro Enrique; Reynolds, C.K.; Kristensen, N. B. Six Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in the portal vein, hepatic vein, mesenteric vein, and an artery were used to study the effects of abomasal glucose infusion on splanchnic plasma concentrations of gut peptides. The experimental design was a randomized block design with repeated measurements. Cows were assigned to one of 2 treatments: control or infusion of 1,500. g of glucose/d into the abomasum from the day of parturition to 29 d in milk. Cows were sampled 12 ± 6 d prepartum and at 4, 15, and 29 d in milk. Concentrations of glucose-dependent insulinotropic polypeptide, glucagon-like peptide 1(7-36) amide, and oxyntomodulin were measured in pooled samples within cow and sampling day, whereas active ghrelin was measured in samples obtained 30. min before and after feeding at 0800. h. Postpartum, dry matter intake increased at a lower rate with infusion compared with the control. Arterial, portal venous, and hepatic venous plasma concentrations of the measured gut peptides were unaffected by abomasal glucose infusion. The arterial, portal venous, and hepatic venous plasma concentrations of glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1(7-36) amide increased linearly from 12 d prepartum to 29 d postpartum. Plasma concentrations of oxyntomodulin were unaffected by day relative to parturition. Arterial and portal venous plasma concentrations of ghrelin were lower postfeeding compared with prefeeding concentrations. Arterial plasma concentrations of ghrelin were greatest prepartum and lowest at 4 d postpartum, giving a quadratic pattern of change over the transition period. Positive portal venous-arterial and hepatic venous-arterial concentration differences were observed for glucagon-like peptide 1(7-36) amide. A negative portal venous-arterial concentration difference was observed for ghrelin pre-feeding. The remaining portal venous-arterial and hepatic venous-arterial concentration differences of gut peptides did not differ from zero. In conclusion, increased postruminal glucose supply to postpartum transition dairy cows reduced feed intake relative to control cows, but did not affect arterial, portal venous, or hepatic venous plasma concentrations of gut peptide hormones. Instead, gut peptide plasma concentrations increased as lactation progressed. Thus, the lower feed intake of postpartum dairy cows receiving abomasal glucose infusion was not attributable to changes in gut peptide concentrations.

Minimum classification error learning for sequential data in the wavelet domain Tomassi, Diego Rodolfo; Milone, Diego Humberto; Forzani, Liliana Maria Wavelet analysis has found widespread use in signal processing and many classification tasks. Nevertheless, its use in dynamic pattern recognition have been much more restricted since most of wavelet models cannot handle variable length sequences properly. Recently, composite hidden Markov models which observe structured data in the wavelet domain were proposed to deal with this kind of sequences. In these models, hidden Markov trees account for local dynamics in a multiresolution framework, while standard hidden Markov models capture longer correlations in time. Despite these models have shown promising results in simple applications, only generative approaches have been used so far for parameter estimation. The goal of this work is to take a step forward in the development of dynamic pattern recognizers using wavelet features by introducing a new discriminative training method for this Markov models. The learning strategy relies on the minimum classification error approach and provides re-estimation formulas for fully non-tied models. Numerical experiments on phoneme recognition show important improvement over the recognition rate achieved by the same models trained using maximum likelihood estimation.

Risk assessment of genetically modified lactic acid bacteria using the concept of substantial equivalence Leblanc, Jean Guy Joseph; van Sinderen, Douwe; Hugenholtz, Jeroen; Piard, Jean Christophe; Sesma, Fernando Juan Manuel; Savoy, Graciela The use of food-grade microorganisms such as lactic acid bacteria (LAB) is one of the most promising methods for delivering health promoting compounds. Since it is not always possible to obtain strains that have the ability to produce specific compounds naturally or that produce them in sufficient quantities to obtain physiological responses, genetic modifications can be performed to improve their output. The objective of this study was to evaluate if previously studied genetically modified LAB (GM-LAB), with proven in vivo beneficial effects, are just as safe as the progenitor strain from which they were derived. Mice received an elevated concentration of different GM-LAB or the native parental strain from which they were derived during a prolonged period of time, and different health parameters were evaluated. Similar growth rates, hematological values, and other physiological parameters were obtained in the animals that received the GM-LAB compared to those that were fed with the native strain. These results demonstrate that the GM-LAB used in this study are just as safe as the native strains from which they were derived and thus merit further studies to include them into the food chain.

The oldest lower Upper Cretaceous plesiosaurs (Reptilia, Sauropterygia) from southern Patagonia, Argentina; Los Plesiosaurios (Reptilia, Sauropterygia) más antiguos del Cretácico Superior bajo de la Patagonia Austral, Argentina O'gorman, Jose Patricio; Varela, Augusto Nicolás Plesiosaurs are recorded for the first time from the lower section of Mata Amarilla Formation, Santa Cruz Province, Patagonia, Argentina. The stratigraphic succession consists of mudstones and siltstones interbedded with medium to fine-grained sandstone, deposited in a littoral environment during the Cenomanian-Santonian; therefore the material is the oldest record of plesiosaurs from the lower Late Cretaceous rocks of Argentina. The remains include teeth, some vertebrae, and one propodium assigned to Elasmosauridae indet. and Plesiosauria indet. The status of Polyptychodon patagonicus Ameghino, 1893, as well as its stratigraphic position are discussed, leading to the conclusion that the material described by Ameghino is probably from the Mata Amarilla Formation and can only be referred to Plesiosauria indet. Analysis of sedimentologic features suggests that the material described here was deposited in an estuarine environment, strongly influenced by tides. The characters of the inferred environment are consistent with the type of preservation of the materials; Se dan a conocer los primeros registros claramente referibles a plesiosaurios de la sección inferior de la Formación Mata Amarilla en la provincia de Santa Cruz, Argentina. Los niveles portadores están compuestos por limolitas y arcillitas grises y negruzcas, que alternan con bancos de areniscas finas y medianas. Dichos niveles se depositaron en un ambiente litoral durante el intervalo Cenomaniano-Santoniano, siendo por tanto el registro más antiguo de plesiosaurios del Cretácico Superior de Argentina. Los restos hallados corresponden a dientes, vértebras y un propodio asignados a Elasmosauridae indet. y a Plesiosauria indet. Se discute el estatus de Polyptychodon patagonicus Ameghino, 1893 y su posición estratigráfica, concluyendo que el material descripto por Ameghino es sólo referible a Plesiosauria indet. y que proviene de la sección inferior de la Formación Mata Amarilla. El análisis sedimentológico indica que los materiales que se describen aquí fueron depositados en un ambiente estuarino con fuerte influencia mareal. Las características del ambiente de depositación de esta sección son consistentes con el estado de preservación de los materiales

Internal anatomy of an erg sequence from the aeolian-fluvial system of the De La Cuesta Formation (Paganzo Basin, northwestern Argentina) Spalletti, Luis Antonio; Limarino, Carlos Oscar; Colombo Piñol, Ferran Permian red beds of the De La Cuesta Formation in the Sierra de Narváez (Paganzo Basin, northwestern Argentina) are essentially composed of sandstones associated with mudstones and subordinate conglomerates. Facies distributions and stacking patterns indicate that these sediments resulted from the interaction between aeolian and ephemeral fluvial systems, and are represented by aeolian dune, dry aeolian interdune and aeolian sand sheet, mudflat, wet aeolian interdune, and fluvial deposits. The De La Cuesta Formation is characterised by aeolian (erg) sequences alternating with non-aeolian (terminal alluvial fan - mudflat) sequences. Each erg sequence is bounded at its base by a regionally extensive sand-drift surface and at the top by an extinction surface. A number of architectural elements, including aeolian dunes limited by interdunes, grouped crescentic aeolian dunes, longitudinal dunes, and draa with superimposed crescentic dunes are recognised in the erg sequences. The sand sea developed during phases of increasing aridity, whereas non-aeolian deposition might have occurred during more humid phases. Thus, the styles of aeolian-fluvial interaction are considered to result from cyclical climatic changes. Within the drier hemicycles, the rhythmic alternation between draa deposits and aeolian dune and interdune deposits indicates higher frequency cycles that could be attributed to subtle climatic oscillations and/ or changes in sand supply and availability. The development of the Permian sand sea in the inland Paganzo Basin seems to be related to the growth of a volcanic chain to the west. This topographic barrier separated the Paganzo Basin from the Chilean Basin, located along the western margin of Gondwana and characterised by shallow marine carbonate sedimentation. The correlation between the Permian erg and the shallow marine carbonates suggests a regional warming period during the Middle Permian in western Gondwana.

Patrones de actividad en dos monos araña negro, Ateles paniscus, en la Reserva Experimental Horco Molle, Tucumán, Argentina: comparación con sus congéneres silvestres; Activity patterns in two black spider monkeys, Ateles paniscus, in the Experimental Horco Molle Reserve, Tucumán, Argentina: Comparison with wild relatives Lambruschi, Daniel Andrés; Halloy, Monique El estudio del comportamiento y de los patrones de actividad en vertebrados puede brindar herramientas que pueden ser útiles para estimar su bienestar. Cuánto más se asemejen estos patrones entre animales silvestres y en cautiverio, mayores serán las probabilidades de que estos últimos se encuentren en buen estado. Realizar actividades de enriquecimiento ambiental contribuye al bienestar de los animales cautivos. En este trabajo, se describen los comportamientos de dos individuos de mono araña negro, Ateles paniscus, un macho y una hembra, que habitan una pequeña isla artificial de 1400 m 2 en la Reserva Experimental Horco Molle, Tucumán. Se reportan patrones de actividad durante dos semanas no consecutivas y se realizan experimentos de enriquecimiento durante una semana intermedia con el objetivo de evaluar su bienestar y sugerir opciones de manejo orientadas a mejorar su calidad de vida. Los monos expresaron conductas típicas de la especie y con frecuencias similares a las citadas para poblaciones silvestres, indicio importante de su bienestar. Esto puede deberse en parte a donde están viviendo, una isla con árboles altos, lo que les da más espacio y diversidad. Los compor tamientos más frecuentes fueron descansar, estar alerta, locomoción y forrajear. A diferencia de sus congéneres silvestres, estuvieron la mayor parte del tiempo en el suelo. Dado el gran interés que mostraron ante los distintos enriquecimientos y dado que la búsqueda de comida constituye una actividad importante, generalmente realizada en el dosel de los árboles en monos silvestres, acciones destinadas a incrementar éstos podrían mejorar aún más su calidad de vida.; The study of behavior and activity patterns in vertebrates can provide tools that may be useful in estimating their well-being. The more these patterns are similar between wild and captive animals, the greater the probability that the latter are in good condition. Providing enrichment activities can contribute to the well-being of these animals. In this study, behaviors of two black spider monkeys, Ateles paniscus, a male and a female, residing in a small artificial island of 1400 m 2 in the Experimental Reserve of Horco Molle, Tucumán, are described. Activity patterns are reported for two non-consecutive weeks, with enrichment experiments performed during an intermediate week, in order to evaluate their well-being and suggest strategies that may contribute to their quality of life. The monkeys expressed typical behaviors for the species, with similar frequencies to those cited for wild populations, an important indication of its well-being. This may be due in part to the fact that they live on an island with trees, which gives them more space and diversity. The most frequent behaviors were resting, being alert, moving, and foraging. Contrary to their wild counterparts, they were most of the time on the ground. Given the great interest they showed when presented with different enrichment activities and given that the search for food is an impor tant activity, generally taking place in the canopy of trees in wild monkeys, actions destined to increase these activities could improve even more their quality of life.

Estructura interna de la franja migmatítica del núcleo cristalino de las Sierras Pampeanas Septentrionales del norte argentino; Internal structure of the migmatitic belt in the crystalline core of the northern Sierras Pampenas Northwestern Argentina Cisterna, Clara Eugenia; Mon, Ricardo; Mena, Rodolfo El Complejo Las Cañas (LCC), en la sierra de Aconquija (Sierras Pampeanas Septentrionales, NO de Argentina) está integrado por rocas del basamento cristalino, representadas por migmatitas y en menor proporción por esquistos, que se hallan como resistatos ellas. Las migmatitas varían desde metatexitas a diatexitas y muestran una foliación gnéisica, acompañada de pliegues intrafoliales formados bajo condiciones de elevado metamorfismo, con fusión parcial y anatéxis. La sobreimpresión de un segundo plegamiento genera figuras de interferencia, ante condiciones de elevada ductilidad de los materiales plegados. Finalmente, se reconoce un episodio de deformación por cizallamiento dúctil, que afecta heterogéneamente a las migmatitas. Las observaciones de campo, estructurales y petrográficas permiten definir sobre estas rocas episodios pre, sin y post deformacionales y hacer interpretaciones sobre la evolución del basamento cristalino del noroeste de Argentina.; The Las Cañas Complex located in Aconquija Range (Sierras Pampeanas Septentrionales) is formed by rocks of the crystalline basement, mainly migmatites and, in smaller proportion, schists which are as resisters included in the migmatites. The migmatites range from metatexites to diatexites. They show a migmatitic foliation accompanied by intrafoliated folds generated under high metamorphic conditions, with partial melt and anatexis. A later superposed folding episode under high ductile conditions generated interference patterns. Finally a brittle-ductile shear episode involving the migmatites is recognized. It affects some portions more intensively than others; its distribution is not uniform. The structural and petrographic observations in the field and in microscope allow the recognition of pre, syn and post migmatization deformation episodes. This tectonic evolution occurred along a significant stretch of the crystalline basement of NW Argentina in a mobile belt along the west border of supercontinent Gondwana, where the recognized deformation episodes correspond to the Pampean Orogeny (550 - 500 Ma) and to the superposed Famatinian Orogeny (500 - 440 Ma).

Algunos comentarios sobre muestreo de Poblaciones Bernoulli Lencina, Viviana Beatriz En este trabajo se aborda el problema de Inferencia en Poblaciones Bernoulli, y se muestra cómo, en el proceso de obtener los datos de la población mediante un muestreo aleatorio simple, diferentes fuentes de variabilidad producen parámetros en las variables aleatorias que serán observadas (muestra) que pueden no coincidir directamente con los parámetros en la población bajo estudio.

Habilidades sociales y contexto sociocultural: Un estudio con adolescentes a través de la BAS-3; Social skills and sociocultural context: A study with adolescents through the BAS-3 Cohen Imach, Silvina; Esterkind de Chein, Ana Helena; Lacunza, Ana Betina; Caballero, Silvina Valeria; Martinenghi, Constanza El estudio tiene como objetivos: 1) describir las habilidades sociales en adolescentes de 11 y 12 años que viven en contextos de pobreza de Tucumán, Argentina; 2) explorar diferencias en las habilidades sociales en función del género; y 3) analizar la incidencia de variables vinculadas al grupo familiar en las habilidades sociales de los adolescentes estudiados. La muestra está constituida por 194 adolescentes de 11 y 12 años escolarizados de contextos de pobreza. Se trata de un estudio descriptivo realizado a través de la Batería de Socialización BAS-3 (Silva Moreno & Martorell Pallás, 2001) y una encuesta sociodemográfica elaborada por el equipo de investigación. Se analizan las habilidades sociales de los participantes según género y las características del grupo familiar (tipo de familia, posición del sujeto en la fratría, número de hermanos y cantidad de personas que viven en el hogar). En cuanto al género, los resultados señalan que difieren estadísticamente en la escala de Ansiedad social/Timidez, siendo más alta en mujeres que en varones. Respecto de las características de la familia, sólo se encuentra una relación negativa entre números de hermanos y la escala de Liderazgo. No se registran diferencias con respecto a las otras características del grupo familiar.; The study aims to: 1) describe social skills in adolescents of 11 to 12 years living in poverty contexts of Tucuman, Argentina, 2) analyze the social skills of participants by gender and 3) analyze the impact of variables related to the family in the social skills of adolescents studied. The sample consisted of 194 adolescents aged 11 and 12 years from schools in contexts of poverty. This is a descriptive study through Socialization Battery BAS-3 (Silva Moreno & Martorell Pallas, 2001) and a demographic survey developed by the research team. We analyze the social skills of participants by gender and household characteristics (family type, adolescent’s position in the sibling group, number of siblings and number of people living at home). In gender terms, the results show that differ statistically at the level of Social anxiety / shyness, being higher in females than in males. Regarding the characteristics of the family, is only a negative statistical relation between numbers of siblings and the scale of Leadership. No significant differences with respect to other characteristics of the household.

Screaming Cowbird parasitism on nests of Solitary Caciques and Cattle Tyrants Di Giacomo, Alejandro G.; Mahler, Bettina; Reboreda, Juan Carlos The Screaming Cowbird (Molothrus rufoaxillaris) is one of the most specialized brood parasites with only three known hosts: Baywing (Agelaioides badius), the main host throughout most of its range, and two alternative hosts in some areas of its distribution, Chopi Blackbird (Gnorimopsar chopi) and Brown-and-yellow Marshbird (Pseudoleistes virescens). We studied Screaming Cowbird parasitism in northeast Argentina where this parasite uses Baywings and Chopi Blackbirds as hosts. We monitored 69 nests of Baywings, 251 of Chopi Blackbirds, 31 of Solitary Caciques (Cacicus solitarius), and 30 of Cattle Tyrants (Machetornis rixosa). The frequency of Screaming Cowbird parasitism on Baywing nests was 80% and was 46% for Chopi Blackbirds. We recorded one event of Screaming Cowbird parasitism on one nest of Solitary Caciques and three events of Screaming Cowbird parasitism on one nest of Cattle Tyrants. The identities of parasitic eggs in both hosts were confirmed by sequencing the mtDNA control region. We propose these events of parasitism resulted from recognition errors by Screaming Cowbird females that regularly parasitize Baywings and Chopi Blackbirds. The nest of Solitary Caciques had been frequently visited by a pair of Baywings before Screaming Cowbird parasitism occurred, and the nest of Cattle Tyrants was near an active Chopi Blackbird nest that had been previously parasitized by Screaming Cowbirds.

The adsorption of 1,3-butadiene on Pd/Ni multilayers: The interplay between spin polarization and chemisorption strength Gómez, Guillermina; Belelli, Patricia Gabriela; Cabeza, Gabriela Fernanda; Castellani, Norberto Jorge The adsorption of 1,3-butadiene (BD) on the Pd/Ni(1 1 1) multilayers has been studied using the VASP method in the framework of the density functional theory (DFT). The adsorption on two different configurations of the Pd n/Nim(1 1 1) systems were considered. The most stable adsorption sites are dependent on the substrate composition and on the inclusion or not of spin polarization. On Pd1Ni3(1 1 1) surface, diπcis and 1,2,3,4-tetra-σ adsorption structures are the most stable for non-spin polarized (NSP) and spin polarized (SP) levels of calculation, respectively. Conversely, on Pd3Ni1(1 1 1) surface, the 1,2,3,4-tetra-σ adsorption structure is the most stable for both NSP and SP levels, respectively. The magnetization of the Pd atoms strongly modifies the adsorption energy of BD and its most stable adsorption mode. On the other hand, as a consequence of BD adsorption, the Pd magnetization decreases. The smaller adsorption energies of BD and 1-butene on the Pd1Ni3(1 1 1) surface than on Pd(1 1 1) can be associated to the strained Pd overlayer deposited on Ni(1 1 1).

Self-assembled multilayers of polyethylenimine, DNA and gold nanoparticles. A study of electron transfer reaction Ferreyra, Nancy Fabiana; Bollo, Soledad; Rivas, Gustavo Adolfo The present manuscript describes studies of the electron transfer kinetics at gold electrodes modified by electrostatic self-assemblies of polyethylenimine (PEI), DNA and gold nanoparticles (NP) by Scanning Electrochemical Microscopy (SECM). Two redox mediators of similar structure, ferrocenemethanol (FcOH), and ferrocenecarboxylic acid (FcCOOH) were used to evaluate the effect of the electrode modification on the electron transfer process. For both redox probes, the observed electrochemical behavior was dependent of the charge of the external layer of the self-assembled structure. The corresponding apparent heterogeneous rate constant, k0, was determined. The effect of NP adsorption was also evaluated. Independently of the mediator used, an increase of the k0 was observed when NPs were incorporated, and the surfaces presented a conductive behavior similar to the bare gold electrode. SECM images using FcOH as redox mediator were also recorded. Variations in the normalized currents permitted to evaluate differences of the surface electroactivity due to the polymers and/or nanoparticles adsorption. © 2009 Elsevier B.V. All rights reserved.

Ultrasensitive detection of nitrogen oxides over a nanoporous membrane Prabhakar, Amlendu; Iglesias, Rodrigo Alejandro; Wang, Rui; Tsow, Francis; Forzani, Erica S.; Tao, Nongjian A nitrogen oxide (NOx; x = 1, 2) optical sensor with an extremely low detection limit in the range of fractions of ppbV (0.3 ppbV for 20 s sample injection) is presented. Phenylenediamine derivatives are utilized as molecular probes in the solid state on a nanoporous membrane to produce a miniaturized and low cost sensing platform for use as a wearable personal monitor.

Study of the water-gas shift reaction over Pt supported on CeO 2-ZrO2 mixed oxides Vignatti, Charito Ivana; Avila, Maria Sol; Apesteguia, Carlos Rodolfo; Garetto, Teresita Francisca The water gas shift (WGS) reaction was studied on Pt/CeO2, Pt/ZrO2 and Pt/CexZr1-xO2 catalysts. All the samples were characterized by a variety of physical and spectroscopic techniques. The catalyst activities were evaluated at 250 °C in a recirculating reactor through CO conversion versus time tests and also by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). The sample activity for the WGS reaction depended on chemical composition. Pt/CexZr1-xO2 catalysts with x ≥ 0.5 were more active than Pt/CeO2, probably because the addition of Zr to ceria increased both the surface area and the reducibility of ceria. The lowest CO conversion rates were obtained on Pt/ZrO2 and Zr-rich Pt/Ce xZr1-xO2 samples. Based on DRIFTS experiments, this result was interpreted by considering that in the WGS formate associative mechanism the stability of formate species is higher on Zr-rich supports.

Novel binderless zeolite-coated monolith reactor for environmental applications Zamaro, Juan Manuel; Miro, Eduardo Ernesto A novel structured catalyst based on a binderless zeolite film was developed onto a cordierite monolith. The zeolitic film was obtained performing a binderless washcoating which was followed by a hydrothermal treatment, which resulted in a coating with hybrid physicochemical properties, having a porous washcoat-like microstructure with an intergrowth between the aggregates. This combination confers to the zeolite coating an open structure which is an advantage of washcoats and a high mechanical stability characteristic of the zeolite growths. It should be emphasized that these desired properties are obtained without the use of binders. The physico-chemical properties were investigated through MIP (mercury intrusion porosimetry), SEM (scanning electron microscopy), ultrasonic adherence tests, NO-TPD (temperature-programmed desorption of NO) and EPMA (electron probe microanalysis). The catalytic properties of the monolith were evaluated in the selective catalytic reduction of NOx at high spatial velocities, showing promising results.

Insecticidal, Mutagenic and Genotoxic Evaluation of Annonaceous Acetogenins Álvarez Colom, Olga; Salvatore, Silvana Analia; Willink, Eduardo; Ordóñez, Roxana Mabel; Isla, Maria Ines; Neske, Adriana Neske; Bardon, Alicia del Valle Annonaceous acetogenins represent a class of bioactive compounds whose primary mode of action is the inhibition of NADHubiquinone oxidoreductase (Mitochondrial Complex I). Given the potential pesticidal use of these compounds, we evaluated the effects of seven acetogenins: squamocin (1), molvizarin (2), itrabin (3), almuñequin (4), cherimolin-1 (5), cherimolin-2 (6), and tucumanin (7) isolated from Annona cherimolia Mill. against Ceratitis capitata Wiedemann (Tephritidae). These acetogenins did not display insecticidal action at 250 µg of treatment per g of adult diet. However, the oviposition capacity of C. capitata females was significantly altered by some of the acetogenins at this concentration. The most potent compounds were itrabin, molvizarin and squamocin. Moreover, significant differences were detected in the preference of oviposition sites when itrabin and squamocin were spread on the surface of artificial fruits at doses of 30 µg/cm2 . Additionally, we investigated the mutagenic effects displayed by itrabin, as well as the phytotoxic and genotoxic action of squamocin and itrabin. Both compounds displayed slight phytotoxic and genotoxic effects on roots of Allium cepa at 2.5 µg/mL though no mutagenic effects were detected at 0.25, 0.5 and 2.5 µg/mL on Salmonella typhimurium strains TA98 and TA100.

Stenomicra (Diptera: Opomyzoidea) in Argentina, with information on the biology of the genus; Stenomicra (Diptera: Opomyzoidea) en Argentina, con información sobre la biología del género Campos, Raul Ernesto; Gramajo, Maria Cecilia; Lizarralde, Mercedes Sara This is the first literature record of the genus Stenomicra Coquillett (Diptera: Periscelididae) from South America (Neotropical Region). New information on the biological cycle of Stenomicra species in the wild is provided, and four species of the genus Eryngium L. (Apiaceae) are recorded as host plants for immature stages of this taxon. The specimens of Stenomicra sp. were collected in Sierra de la Ventana, Buenos Aires province, Argentina.; En este estudio, se publica por primera vez para Sudamérica (Región Neotropical) el género Stenomicra Coquillett (Diptera: Periscelididae). Se aporta información sobre su ciclo biológico en condiciones naturales y se mencionan cuatro especies del género Eryngium L. (Apiaceae), como plantas hospedadoras de los estados inmaduros. Los ejemplares de Stenomicra sp. fueron colectados en Sierra de la Ventana, Provincia de Buenos Aires, Argentina.

On the estimation of the cost of equity in Latin America Grandes, Martin; Panigo, Demian Tupac; Pasquini, Ricardo Aníbal This paper researches the sources of stock market risk influencing the pricing of 921 Latin American stocks and computes their corresponding opportunity cost (COE) over the period 1997–2004 by firm and sector. Running an adjusted version of the Capital Asset Pricing Model (CAPM) it finds that systematic risk accounts on average for more than 32% of COE total variance. This implies that potential CAPM mispricing related to undiversified idiosyncratic risk in Latin America has been relatively lower (but absolutely higher) than in United States and other European and Asian stock markets (such as the United Kingdom, Canada or Japan). A first robustness test for the omission of international sources of un-diversifiable risk suggests that both global market and real currencies portfolios do not add significant information to domestic market portfolios. Moreover, a second robustness check offers further evidence that well-diversified portfolios constructed by sorting stocks according to their size and book-to-market ratios a la Fama and French do not improve the goodness of fit in the regressions based on the adjusted version of CAPM.