813 research outputs found

    Planificación, políticas públicas y el proceso decisorio en la gestión gubernamental

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    Siendo la planificación, la determinación de políticas y la forma de toma de decisiones, la base sobre la cual gira el desarrollo del país, es de suma importancia realizar el análisis de este tema para poder efectuar observaciones, obtener conclusiones y presentar recomendaciones. Con el propósito de entender el proceso decisorio, en el sentido de comprender el grado en que se cumplen las acciones previstas por la planificación de carácter nacional, regional y local, es necesario examinar los aspectos fundamentales del método de planificación tradicional, así como de las innovaciones metodológicas que se están incorporando al proceso de planificación, especialmente por parte del CONADE, como en las oficinas de planificación de ministerios y entidades públicas que forman parte del sistema de planificación. La utilidad del estudio será el presentar un análisis sobre la forma en que se ha venido tratando estos temas durante el último periodo democrático del país; servirá de instrumento y guía para que se enmienden errores, se mejore lo que está bien y se establezca una directriz para el futuro

    Polyfluorinated Cyclopentadienones as Lewis Acids

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    The ability of 2,3,4,5-tetrakis(trifluoromethyl)cyclopenta-2,4-dien-1-one and 2,3,4,5-tetrakis(pentafluorophenyl)cyclopenta-2,4-dien-1-one to act as organic Lewis acids in the field of frustrated Lewis pair (FLP) chemistry was evaluated. Whereas the former ketone formed zwitterionic adducts with all phosphines studied, the latter did not react with bulky phosphines and, instead, gave completely organic FLPs. Unfortunately, these did not activate dihydrogen, even under high pressures

    Local Casimir Energies for a Thin Spherical Shell

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    The local Casimir energy density for a massless scalar field associated with step-function potentials in a 3+1 dimensional spherical geometry is considered. The potential is chosen to be zero except in a shell of thickness δ\delta, where it has height hh, with the constraint hδ=1h\delta=1. In the limit of zero thickness, an ideal δ\delta-function shell is recovered. The behavior of the energy density as the surface of the shell is approached is studied in both the strong and weak coupling regimes. The former case corresponds to the well-known Dirichlet shell limit. New results, which shed light on the nature of surface divergences and on the energy contained within the shell, are obtained in the weak coupling limit, and for a shell of finite thickness. In the case of zero thickness, the energy has a contribution not only from the local energy density, but from an energy term residing entirely on the surface. It is shown that the latter coincides with the integrated local energy density within the shell. We also study the dependence of local and global quantities on the conformal parameter. In particular new insight is provided on the reason for the divergence in the global Casimir energy in third order in the coupling.Comment: 16 pages, revtex 4, no figures. Major additions, clarifications, and corections, references adde

    Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

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    Metal phosphonates are multifunctional solids with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, a new family of isostructural 2D layered compounds based on lanthanide nitrilotris-methylphosphonates is reported. These compounds have been isolated at room temperature and have the general formula Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb). The coordination environment of Ln3+ is composed by eight oxygen atoms from three different ligands and two oxygens from bound waters. This connectivity creates positive charged layers connected to sulfate ions through hydrogen-bonds. These compounds show promising proton conductivity with values ranging between 7.6·10-2 and 3.8·10-2 S·cm-1 at 80 °C and 95% RH and low activation energy corresponding to Grotthuss-type proton transfer mechanism. In addition, a structural transformation occurs at T > 70 °C accompanied by a remarkable enhanced conductivity. Studies on the structure-properties relationships will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO: MAT2016-77648-R Junta Andalucía: P12-FQM-1656 y FQM-11

    Insetos bentônicos do Rio El Tala (Catamarca, Argentina): Variação longitudinal de sua estrutura e seu uso para avaliar a qualidade da água

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    The aim of this work was to determine the structure of the benthic entomofauna and its variation along the El Tala River (Catamarca, Argentina). Five sampling stations were established, considering the location of nearby housing with respect to the watercourse. The following variables were determined in situ: altitude, latitude and longitude, bedstream width, river depth, river-current speed, water and air temperatures. Benthic insects were collected with a square parcel sampler of 0.09-m2 area and 300-μm net opening and identified to the family level. Faunal density, richness, and diversity exhibited a longitudinal variation. From sampling Stations 1 (reference site) to 3, the number of orders and families decreased, whereas in sampling Station 4 those values increased and continued to do so through to Station 5 (downstream station). Station 5 showed the highest family richness (17) and the highest value for the Shannon-Wiener index (2.74) and the lowest value in Simpson's Dominance index (D = 0.22). These values could be explained because of the self-cleansing capabilities of the river downstream. The water quality of El Tala River is Class I (very clean and non-impacted), according to the results obtained from the application of the biotic Biological-Monitoring-Working-Party and Average-Store-per-Taxon indices.O objetivo deste trabalho foi determinar a estrutura da entomofauna bentônica do Rio El Tala (Catamarca, Argentina) e sua variação longitudinal. Cinco estações de amostragem foram estabelecidas considerando-se a localização da habitação em relação ao curso de água. As seguintes variáveis foram determinadas in situ: altitude, latitude e longitude; largura do leito; profundidade do rio; velocidade da correnteza, e temperatura da água e do ar. Insetos bentônicos foram coletados em cinco estações de amostragem, utilizando-se um coletor tipo Surber de 0,09 m2 , com rede de malha 300 μm, tendo sido identificados em laboratório até o nível de Família. Densidade, riqueza e diversidade da fauna exibiram variação longitudinal. Da estação de amostragem 1 (site de referência) à 3, uma tendência decrescente no número de ordens e famílias foi observada, enquanto que as estações de amostragem 4 e 5 apresentaram uma tendência crescente. As amostras da estação 5 (estação rio abaixo) apresentaram a maior riqueza de famílias (17), o valor mais elevado do Índice de Shannon (2,74) e o menor valor de Dominância de Simpson (D = 0,22). Estes valores podem ser explicados pela capacidade de autopurificação de rio a jusante. A qualidade da água do Rio El Tala é Classe I (muito limpo e água sem impacto), de acordo com os resultados obtidos pela aplicação de índices bióticos BMWP’ e ASPT’.Facultad de Ciencias Naturales y Muse

    Insetos bentônicos do Rio El Tala (Catamarca, Argentina): Variação longitudinal de sua estrutura e seu uso para avaliar a qualidade da água

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    The aim of this work was to determine the structure of the benthic entomofauna and its variation along the El Tala River (Catamarca, Argentina). Five sampling stations were established, considering the location of nearby housing with respect to the watercourse. The following variables were determined in situ: altitude, latitude and longitude, bedstream width, river depth, river-current speed, water and air temperatures. Benthic insects were collected with a square parcel sampler of 0.09-m2 area and 300-μm net opening and identified to the family level. Faunal density, richness, and diversity exhibited a longitudinal variation. From sampling Stations 1 (reference site) to 3, the number of orders and families decreased, whereas in sampling Station 4 those values increased and continued to do so through to Station 5 (downstream station). Station 5 showed the highest family richness (17) and the highest value for the Shannon-Wiener index (2.74) and the lowest value in Simpson's Dominance index (D = 0.22). These values could be explained because of the self-cleansing capabilities of the river downstream. The water quality of El Tala River is Class I (very clean and non-impacted), according to the results obtained from the application of the biotic Biological-Monitoring-Working-Party and Average-Store-per-Taxon indices.O objetivo deste trabalho foi determinar a estrutura da entomofauna bentônica do Rio El Tala (Catamarca, Argentina) e sua variação longitudinal. Cinco estações de amostragem foram estabelecidas considerando-se a localização da habitação em relação ao curso de água. As seguintes variáveis foram determinadas in situ: altitude, latitude e longitude; largura do leito; profundidade do rio; velocidade da correnteza, e temperatura da água e do ar. Insetos bentônicos foram coletados em cinco estações de amostragem, utilizando-se um coletor tipo Surber de 0,09 m2 , com rede de malha 300 μm, tendo sido identificados em laboratório até o nível de Família. Densidade, riqueza e diversidade da fauna exibiram variação longitudinal. Da estação de amostragem 1 (site de referência) à 3, uma tendência decrescente no número de ordens e famílias foi observada, enquanto que as estações de amostragem 4 e 5 apresentaram uma tendência crescente. As amostras da estação 5 (estação rio abaixo) apresentaram a maior riqueza de famílias (17), o valor mais elevado do Índice de Shannon (2,74) e o menor valor de Dominância de Simpson (D = 0,22). Estes valores podem ser explicados pela capacidade de autopurificação de rio a jusante. A qualidade da água do Rio El Tala é Classe I (muito limpo e água sem impacto), de acordo com os resultados obtidos pela aplicação de índices bióticos BMWP’ e ASPT’.Facultad de Ciencias Naturales y Muse

    Aerodynamic reconstruction of the primitive fossil bat Onychonycteris finneyi (Mammalia: Chiroptera)

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    Bats are the only mammals capable of powered flight. One of the oldest bats known from a complete skeleton is Onychonycteris finneyi from the Early Eocene (Green River Formation, Wyoming, 52.5 Ma). Estimated to weigh approximately 40 g, Onychonycteris exhibits the most primitive combination of characters thus far known for bats. Here, we reconstructed the aerofoil of the two known specimens, calculated basic aerodynamic variables and compared them with those of extant bats and gliding mammals. Onychonycteris appears in the edges of the morphospace for bats, underscoring the primitive conformation of its flight apparatus. Low aerodynamic efficiency is inferred for this extinct species as compared to any extant bat. When we estimated aerofoil variables in a model of Onychonycteris excluding the handwing, it closely approached the morphospace of extant gliding mammals. Addition of a handwing to the model lacking this structure results in a 2.3-fold increase in aspect ratio and a 28% decrease in wing loading, thus greatly enhancing aerodynamics. In the context of these models, the rapid evolution of the chiropteran handwing via genetically mediated developmental changes appears to have been a key transformation in the hypothesized transition from gliding to flapping in early bats.Fil: Amador, Lucila Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Simmons, Nancy B.. American Museum of Natural History; Estados UnidosFil: Giannini, Norberto Pedro. American Museum of Natural History; Estados Unido

    Transcriptome and Biochemical Analysis of a Flower Color Polymorphism in Silene littorea (Caryophyllaceae)

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    Flower color polymorphisms are widely used as model traits from genetics to ecology, yet determining the biochemical and molecular basis can be challenging. Anthocyanin-based flower color variations can be caused by at least 12 structural and three regulatory genes in the anthocyanin biosynthetic pathway (ABP). We use mRNA-Seq to simultaneously sequence and estimate expression of these candidate genes in nine samples of Silene littorea representing three color morphs (dark pink, light pink, and white) across three developmental stages in hopes of identifying the cause of flower color variation. We identified 29 putative paralogs for the 15 candidate genes in the ABP. We assembled complete coding sequences for 16 structural loci and nine of ten regulatory loci. Among these 29 putative paralogs, we identified 622 SNPs, yet only nine synonymous SNPs in Ans had allele frequencies that differentiated pigmented petals (dark pink and light pink) from white petals. These Ans allele frequency differences were further investigated with an expanded sequencing survey of 38 individuals, yet no SNPs consistently differentiated the color morphs. We also found one locus, F3h1, with strong differential expression between pigmented and white samples (\u3e42x). This may be caused by decreased expression of Myb1a in white petal buds. Myb1a in S. littorea is a regulatory locus closely related to Subgroup 7 Mybs known to regulate F3h and other loci in the first half of the ABP in model species. We then compare the mRNA-Seq results with petal biochemistry which revealed cyanidin as the primary anthocyanin and five flavonoid intermediates. Concentrations of three of the flavonoid intermediates were significantly lower in white petals than in pigmented petals (rutin, quercetin and isovitexin). The biochemistry results for rutin, quercetin, luteolin and apigenin are consistent with the transcriptome results suggesting a blockage at F3h, possibly caused by downregulation of Myb1a

    Tuning the Lewis Acidity of Boranes in Frustrated Lewis Pair Chemistry: Implications for the Hydrogenation of Electron-Poor Alkenes

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    An analysis of the metal-free reduction of electron deficient olefins by frustrated Lewis pairs indicates that the rate-determining step might be either the heterolytic cleavage of H2 to form an -onium borohydride salt, or the subsequent transfer of the hydride moiety to the substrate following a Michael-type addition reaction. While the use of strong Lewis acids such as B(C6F5)3 facilitates the first of these processes, hydride transfer to the olefin should be contrarily favoured by the use of weak Lewis acids which, for this very same reason, might be unable to promote the prior H2 split. After systematic testing of several boranes of different Lewis acidity (assessed by using the Childs’ method) and steric demand, an optimal situation that employs tris(2,4,6-trifluorophenyl)borane was reached. Mixtures of this borane with 1,4-diazabicyclo[2.2.2]octane (DABCO) exhibited excellent catalytic activity for the hydrogenation of alkylidene malonates. In fact, this transformation could be achieved under milder conditions than those we reported previously. Moreover, the reaction scope could be expanded to other electron deficient olefins containing esters, sulfones or nitro functionalities as electron-withdrawing substituents

    Corrosion in 316L porous prostheses obtained by gelcasting

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    Gelcasting (GC) process, usually used for ceramic moulding, is adapted for producing spongy or porous metal osteosynthesis components destined to bone void filling. The main objective of the interconnected porosity is to improve the osteoconductive of metal matrix by ingrowth of bone. Further, porosity reduces metal density and Young module, which causes bone resorption, leading to implant failure, phenomenon known as stress shielding. The employed GC is based on the formulation of AISI 316L stainless steel powder suspension in an aqueous solution of organic polymers. This suspension is cast into porous ceramic shells, like those used in lost wax technique, wherein the polymer crosslinking is induced by heating. The shells, containing the resulting hydrogel–metal composite, are subjected to thermal cycle in order to dry, burn the organic phase, sinter the metal particles at 1200 °C, and cool down to room temperature under dry hydrogen permanent flow. The susceptibility to corrosion of 50-60 % porous pieces was analyzed. The results indicated that the lower relation between the open porosity and the total porosity, the lower the corrosion rate.International Congress of Science and Technology of Metallurgy and Materials, SAM – CONAMET 201
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