1,221 research outputs found

    Three Hopf algebras and their common simplicial and categorical background

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    We consider three a priori totally different setups for Hopf algebras from number theory, mathematical physics and algebraic topology. These are the Hopf algebras of Goncharov for multiple zeta values, that of Connes--Kreimer for renormalization, and a Hopf algebra constructed by Baues to study double loop spaces. We show that these examples can be successively unified by considering simplicial objects, cooperads with multiplication and Feynman categories at the ultimate level. These considerations open the door to new constructions and reinterpretation of known constructions in a large common frameworkPreprin

    Evolución de la energía de fractura de dos hormigones resistentes a la acción de ciclos hielo-deshielo

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    The current standards that regulate use of structural concrete have highlighted the durability of concrete. However, how the fracture energy of concrete evolves under the action of freeze-thaw cycles is not well known. The fracture energy of two types of concrete, one with an air-entraining additive and the other with silica fume addition, is studied after four, 14 and 28 freeze-thaw cycles. The results obtained show that the concrete with an air-entraining additive was undamaged and that fracture energy grew slightly. In addition to this, they also showed that the concrete with silica fume addition suffered severe surface scaling and its fracture energy changed due to the greater fracture areas generated.La actual normativa que rige el empleo de hormigón estructural ha puesto enfásis en la durabilidad del hormigón. Sin embargo, no se conoce cómo evoluciona la energía de fractura del hormigón sometido a ciclos hielo- deshielo, lo cual es de vital importancia para asegurar la durabilidad y el correcto comportamiento mecánico de las estructuras de hormigón en entornos con heladas durante su vida útil. Se ha estudiado la evolución de la energía de fractura de un hormigón con aireante y de un hormigón con humo de sílice después de 4, 14 y 28 ciclos hielo-deshielo realizando ensayos de fractura. Los resultados muestran cómo el hormigón con aireante no sufre daño por los ciclos hielo-deshielo y cómo la energía de fractura del mismo aumenta ligeramente. El hormigón con humo de sílice se daña por los ciclos hielo-deshielo y reduce su energía de fractura al aumentar el area fracturada

    The impact of European Union austerity policy on women's work in Southern Europe

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    Contrary to consolidated economic theory principles, in Europe (but also in other world regions), austerity policy has been implemented instead of stimulus measures which have proven to be successful in crisis associated with credit crunch and insufficient demand. These policies cannot be only considered as an "austericide" due to ideological blindness. They also need to be considered as a strategy for imposing an economic and social reform which proved too difficult to be implemented in the years previous to the great recession. The ongoing fiscal contraction policies include the typical adjustment measures which are now driving the European economy towards a new type of insertion within the international economy. And as a consequence, they imply deep changes on the gender division of work deepening gender inequality. This article analyses the different effects of European Union austerity policy on women and men’s participation in the labour markets in two Southern European countries beaten by the Debt crisis: Spain and Italy. During the first part of this economics crisis, unemployment grew higher for men than for women, but in the second phase with the all sectors hit by the recession and the implementation of harsh austerity policies affecting public-sector jobs, women are also losing their jobs at the same rate than men. We have estimated labour supply models for individuals aged 25 to 54 living in couples with or without children by gender by using the EU-SILC 2011 micro data for Spain and Italy. The analysis carried out shows a strong countercyclical added-worker effect for women in response to transitory shocks in partner’s earnings, in contrast with a procyclical discouraged-worker effect for men. However though the added-worker effect prevails for women in Spain, in Italy still the discouraged worker effect dominates. The results show also a positive effect of the provision of childcare services on women’s labour supply. A cut in social and care services due to austerity promotion may turn the tendency to a decline in women’s participation and employment rates in the labour force with the subsequent loss of total well-being, due to gender differences in education performance, and especially of women’s well-being

    Comunicación corta. Rhizoctonia solani, agente causal de la muerte de plántulas de acelga en España

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    During September 2011, post-emergence damping off of Swiss chard (Beta vulgaris subsp. cicla L.) was observed in a greenhouse in Villa del Prado (Spain). About 20% of the seedlings showed damping off symptoms. Lesions were initially water soaked, dark brown necrosis of crown tissue, irregular in shape and sunken in appearance on large plants, causing the infected seedlings to collapse and eventually die. Rhizoctonia solani was isolated consistently from symptomatic plants. After morphological and molecular identification of the isolates, pathogenicity was tested by placing agar plugs of four isolates adjacent to the stem at the three or four true leaf stage. In inoculated plants, brown crown and stem necrosis occurred while control plants did not show disease symptoms. Pathogenicity using non-germinated seeds was also tested. All four isolates produced extensive damping off when inoculated on non-germinated seeds. To our knowledge, this is the first report of damping off of Swiss chard caused by R. solani in Europe.En el mes de septiembre de 2011, se observó muerte de plántulas en acelgas cultivadas en un invernadero en Villa del Prado (España). Cerca del 20% de los semilleros mostraban síntomas de caída de plántulas. Las lesiones iniciales tenían un aspecto húmedo y consistían en una necrosis del tejido de la corona de color marrón oscuro, de bordes irregulares y deprimidos en las plantas adultas, produciendo el colapso de las plántulas y, ocasionalmente, la muerte de las mismas. Rhizoctonia solani se aisló de manera consistente de las plantas sintomáticas. Tras una identificación morfológica y molecular, la patogenicidad de los aislados se probó colocando discos de agar adyacentes al tallo de la planta en estados de tres o cuatro hojas verdaderas. En las plantas inoculadas se observó un oscurecimiento de la corona y la necrosis del tallo en todos los casos, síntomas que no mostraron las plantas control. Por otro lado, se comprobó la patogenicidad de los aislados en semillas no germinadas. Los cuatro aislados produjeron muerte de plántulas cuando se inocularon en semillas no germinadas. Hasta donde hemos podido comprobar, este trabajo parece ser la primera cita de muerte de plántulas de acelga causada por R. solani en Europa

    The multidimensionality of poverty: Time poverty in Spain

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    In the last few years the concept of poverty has evolved from simply being a measure of income poverty to a multidimensional measure that takes into consideration essential aspects for the attainment of certain levels of wellbeing. This paper assesses how the incorporation of time can contribute to the measurement of poverty. To this end, we reviewed the time poverty literature and focused on the Spanish case. We use the Spanish Time-Use Survey 2009-2010 to analyse time poverty in Spain, and estimate a probit model to assess the probability of being time poor in Spain and identify key factors associated with time poverty in Spain

    Magnetic study on biodistribution and biodegradation of oral magnetic nanostructures in the rat gastrointestinal tract

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    We have undertaken a magnetic study on the oral biodistribution and biodegradation of nude maghemite nanoparticles of 10 nm average size (MNP) and probiotic bacteria, Lactobacillus fermentum, containing thousands of these same nanoparticles (MNP-bacteria). Using AC magnetic susceptibility measurements of the stomach, small intestine, cecum and large intestine obtained after rat sacrifice, and iron content determination by ICP-OES, we have monitored the biodistribution and biodegradation of the maghemite nanoparticles along the gastrointestinal tract, after oral administration of both MNP and MNP-bacteria. The results revealed that the amount of magnetic nanoparticles accumulated in intestines is sensibly higher when MNP-bacteria were administered, in comparison with MNP. This confirms our initial hypothesis that the use of probiotic bacteria is a suitable strategy to assist the magnetic nanoparticles to overcome the stomach medium, and to achieve their accumulation in intestines. This finding opens doors to different applications. Since iron absorption in humans takes place precisely in the intestines, the use of MNP-bacteria as an iron supplement is a definite possibility. We have actually illustrated how the administration of MNP-bacteria to iron-deficient rats corrects the iron levels after two weeks of treatment

    Identifying Ultra-Cool Dwarfs at Low Galactic Latitudes: A Southern Candidate Catalogue

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    We present an Ultra-Cool Dwarf (UCD) catalogue compiled from low southern Galactic latitudes and mid-plane, from a cross-correlation of the 2MASS and SuperCOSMOS surveys. The catalogue contains 246 members identified from 5042 sq. deg. within 220 deg. <= l <= 360 deg. and 0 deg. < l <= 30 deg., for |b| <= 15 deg. Sixteen candidates are spectroscopically confirmed in the near-IR as UCDs with spectral types from M7.5V to L9. Our catalogue selection method is presented enabling UCDs from ~M8V to the L-T transition to be selected down to a 2MASS limiting magnitude of Ks ~= 14.5 mag. This method does not require candidates to have optical detections for catalogue inclusion. An optimal set of optical/near-IR and reduced proper-motion selection criteria have been defined that includes: an Rf and Ivn photometric surface gravity test, a dual Rf-band variability check, and an additional photometric classification scheme to selectively limit contaminants. We identify four candidates as possible companions to nearby Hipparcos stars -- observations are needed to identify these as potential benchmark UCD companions. We also identify twelve UCDs within a possible distance 20 pc, three are previously unknown of which two are estimated within 10 pc, complimenting the nearby volume-limited census of UCDs. An analysis of the catalogue spatial completeness provides estimates for distance completeness over three UCD MJ ranges, while Monte-Carlo simulations provide an estimate of catalogue areal completeness at the 75 per cent level. We estimate a UCD space density of Rho (total) = (6.41+-3.01)x10^3/pc^3 over the range of 10.5 <= MJ ~< 14.9, similar to values measured at higher Galactic latitudes (|b| ~> 10 deg.) in the field population and obtained from more robust spectroscopically confirmed UCD samples.Comment: MNRAS accepted April 2012. Contains 30 figures and 11 tables. Tables 2 and 6 to be published in full and on-line only. The on-line tables can also be obtained by contacting the author

    DOSIS LETAL Y REDUCTIVA MEDIA CON RAYOS GAMMA EN Clitoria ternatea VAR. TEHUANA

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    The objective was to estimate the lethal and median reductive doses with gamma radiation, in seeds of Clitoria ternatea var. Tehuana, to induce genetic variation. Ten (10) doses of radiation (100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 Gy) were used, plus one control (without radiation). The experimental design was completely random with three repetitions. The germination was evaluated 12 days after sowing (das), while the survival, plant height, stem diameter, number of leaflets and leaf area, at 30 das. The data were analyzed through ANOVA and the means comparison with the Dunnett test. The LD50 and GR50 for plant survival and height were estimated through linear regression. The radiation did not influence the germination and stem diameter; however, the survival was reduced significantly starting at 300 Gy, compared with the control (39.16%). Meanwhile, for plant height, leaflet number and leaf area it was from 100, 200 and 400 Gy (15.24, 22.54 and 70.26 %). The LD50 and GR50 was estimated at 350.91 and 306.1 Gy. The dose of gamma radiation to induce genetic variation in Clitoria ternatea var. Tehuana is suggested at between 306 and 350 Gy.El objetivo fue estimar la dosis letal y reductiva media en semillas de Clitoria ternatea var. Tehuana con radiación gamma para inducir variación genética. Se utilizaron 10 dosis de radiación (100, 200, 300, 400, 500, 600, 700, 800, 900 y 1000 Gy) más un control (sin irradiar). El diseño experimental fue completamente al azar con tres repeticiones. Se evaluó la germinación a 12 días después de la siembra (dds), mientras que la supervivencia, altura de planta, diámetro de tallo, número de foliolos y área foliar, a los 30 dds. Los datos fueron analizados mediante ANOVA y la comparación de medias con la prueba de Dunnett. La DL50 y GR50 para supervivencia y altura de planta se estimaron mediante regresión lineal. La radiación no influyó en la germinación y diámetro de tallo; sin embargo, la supervivencia se redujo de manera significativa a partir de 300 Gy comparado con el testigo (39.16%). Mientras que, para altura de planta, número de foliolos y área foliar fue a partir de 100, 200 y 400 Gy (15.24, 22.54 y 70.26 %). La DL50 y GR50 se estimó a 350.91 y 306.1 Gy. La dosis de radiación gamma para inducir variación genética en Clitoria ternatea var. Tehuana se sugiere entre 306 y 350 Gy
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