6,378 research outputs found

    Reducing the parameter space for Unparticle-inspired models using white dwarf masses

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    Based on astrophysical constraints derived from Chandrasekhar's mass limit for white-dwarfs, we study the effects of the model on the parameters of unparticle-inspired gravity, on scales ΛU>1  TeV\Lambda_U > 1 \; TeV and dU1d_U \approx 1.Comment: 4 pp., 4 Fig., to appear in PR

    Produção de tomateiro orgânico irrigado por aspersão e gotejamento, em cultivo solteiro e consorciado com coentro.

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    O uso eficiente da água e a diversificação ambiental são fundamentais para o equilíbrio e a sustentabilidade dos sistemas orgânicos de produção de tomate. O presente estudo teve por objetivo avaliar a produção de tomate de mesa em cultivo solteiro e consorciado com coentro com irrigação por aspersão e gotejamento, em sistema orgânico. O experimento foi conduzido em área de produção orgânica no Distrito Federal. O delineamento foi blocos ao acaso, com tratamentos dispostos num arranjo fatorial 2 x 2 (dois sistemas de irrigação x dois sistemas de cultivo). Não houve interação significativa entre os fatores avaliados, assim como não houve efeito do sistema de cultivo sobre as variáveis avaliadas. Embora o ciclo do tomateiro irrigado por gotejamento tenha diminuído, a produtividade de frutos não foi afetada pelos sistemas de irrigação. A maior redução de estande verificada na aspersão foi compensada por um aumento no número de frutos por planta, sem variação na massa por fruto. O menor volume de solo explorado pelas raízes do tomateiro associado à maior incidência de traça-o-tomateiro (Tuta absoluta) e principalmente de oídio (Leveillula taurica) pode ter limitado a produtividade do tomateiro irrigado por gotejamento. A taxa de frutos podres na aspersão foi o dobro da verificada no sistema por gotejamento

    Sporopollenin as an efficient green support for covalent immobilization of a lipase

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    Sporopollenin exine capsules (SECs), derived from the spores of Lycopodium clavatum, have been functionalised with 1,n-diamines and the resulting aminoalkyl microcapsules used to immobilize Candida antarctica lipase B (Cal B) via a glutaradehyde-based diimine covalent linker. The supported enzyme efficiently catalyzes the esterification of oleic acid with ethanol. Initial rates using the SEC-CalBs were comparable to the commercial enzyme Novozym 435, but displayed up to 20-fold higher specific activity. The supported enzymes could also be recycled and after four cycles displayed only a modest decrease in conversions. In a kinetic resolution the SEC-CalBs efficiently acetylated rac-1-phenylethanol, with conversions up to 37% after 5 hours and product enantiomeric excesses of >99%. Related to this, the dynamic resolution of rac-1-phenylethylamine, in the presence of Pd-BaSO₄ and ammonium formate, led to the acetylated amine with a 94% conversion and >99% ee

    Width/length–weight relationships and condition factor of seven decapod crustaceans in a Brazilian tropical estuary

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    The analysis of body relationships and condition factors are useful tools in studies of marine populations, and they have been widely used in fishery research and management. In this study, width–weight (WWR) and length–weight (LWR) relationships and Fulton's condition factors were analyzed for six commercially important decapod crustacean species from the Paraguaçu River estuary (Todos os Santos Bay), eastern Brazil, namely Callinectes danae, C. exasperatus, C. marginatus, C. ornatus, Goniopsis cruentata and Ucides cordatus, and one non-indigenous species, Charybdis helleri. In total 5,704 individuals were measured and weighed during five years (2012–2017). The three allometric growth types for the crustacean species were observed, being most frequently the negative allometric growth. The analysis of covariance (ANCOVA) revealed significant differences between the sexes and climatic seasons in WWR/LWRs for the four species of the genus Callinectes, C. helleri, G. cruentata and U. cordatus, except for females and males of C. danae in WWR. The means for condition factor were generally higher for females than for males during the dry period, and in general, indicating good conditions for crustacean species. This study provided morpho-biometric parameters information will contribute stock management of traditional artisanal fisheries, and enable future comparative studies of populations of the same species.9 página

    Topological Line Defects around Graphene Nanopores for DNA Sequencing

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    Topological line defects in graphene represent an ideal way to produce highly controlled structures with reduced dimensionality that can be used in electronic devices. In this work we propose using extended line defects in graphene to improve nucleobase selectivity in nanopore-based DNA sequencing devices. We use a combination of QM/MM and non-equilibrium Green's functions methods to investigate the conductance modulation, fully accounting for solvent effects. By sampling over a large number of different orientations generated from molecular dynamics simulations, we theoretically demonstrate that distinguishing between the four nucleobases using line defects in a graphene-based electronic device appears possible. The changes in conductance are associated with transport across specific molecular states near the Fermi level and their coupling to the pore. Through the application of a specifically tuned gate voltage, such a device would be able to discriminate the four types of nucleobases more reliably than that of graphene sensors without topological line defects.Comment: 6 figures and 6 page

    Magnetic field decay in black widow pulsars

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    We study in this work the evolution of the magnetic field in 'redback-black widow' pulsars. Evolutionary calculations of these 'spider' systems suggest that first the accretion operates in the redback stage, and later the companion star ablates matter due to winds from the recycled pulsar. It is generally believed that mass accretion by the pulsar results in a rapid decay of the magnetic field when compared to the rate of an isolated neutron star. We study the evolution of the magnetic field in black widow pulsars by solving numerically the induction equation using the modified Crank-Nicolson method with intermittent episodes of mass accretion on to the neutron star. Our results show that the magnetic field does not fall below a minimum value ('bottom field') in spite of the long evolution time of the black widow systems, extending the previous conclusions for much younger low-mass X-ray binary systems. We find that in this scenario, the magnetic field decay is dominated by the accretion rate, and that the existence of a bottom field is likely related to the fact that the surface temperature of the pulsar does not decay as predicted by the current cooling models. We also observe that the impurity of the pulsar crust is not a dominant factor in the decay of magnetic field for the long evolution time of black widow systems.Instituto de Astrofísica de La Plat
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