Axial Transition Form Factors and Pion Decay of Baryon Resonances

The pion decay constants of the lowest orbitally excited states of the nucleon and the $\Delta(1232)$ along with the corresponding axial transition form factors are calculated with Poincar\'e covariant constituent-quark models with instant, point and front forms of relativistic kinematics. The model wave functions are chosen such that the calculated electromagnetic and axial form factors of the nucleon represent the empirical values in all three forms of kinematics, when calculated with single-constituent currents. The pion decay widths calculated with the three forms of kinematics are smaller than the empirical values. Front and instant form kinematics provide a similar description, with a slight preference for front form, while the point form values are significantly smaller in the case of the lowest positive parity resonances.Comment: 18 pages, 5 figures. Slightly revised, accepted in Phys. Rev.

Aplicação da termometria por infravermelho a irrigação do feijoeiro (Phaseolus vulgaris L.): parâmetros fisiológicos.

Avaliou-se no campo a resposta de plantas de feijao (Phaseolus vulgaris L.) cv Carioca submetidas a quatro regimes de irrigacao, visando adotar um indicador fisiologico que permitisse determinar o momento de se efetuar a irrigacao, tanto na fase vegetativa quanto na reprodutiva. Registraram-se significativas relacoes entre os decrescimos do potencial hidrico foliar e os acrescimos na resistencia estomatica ao longo do dia, e desta com os aumentos na temperatura do dossel, que foram maiores nas plantas sob deficiencia hidrica mais acentuada. Os maiores diferenciais de temperatura do dossel foram observados entre o controle irrigado e o tratamento mais seco. Tambem foram registrados para cada tratamento, diferenciais de temperatura do dossel em relacao a temperatura do ar, obtendo-se diferenciais positivos apenas nas plantas sob menor frequencia de irrigacao na condicao maxima de tensao de agua no solo. Os resultados indicam que o diferencial de temperatura do dossel entre uma parcela de plantas bem irrigadas e outra submetida ao estresse hidrico foi o parametro fisiologico mais apropriado para monitorar a irrigacao

OB Stars in the Solar Neighborhood I: Analysis of their Spatial Distribution

We present a newly-developed, three-dimensional spatial classification method, designed to analyze the spatial distribution of early type stars within the 1 kpc sphere around the Sun. We propose a distribution model formed by two intersecting disks -the Gould Belt (GB) and the Local Galactic Disk (LGD)- defined by their fundamental geometric parameters. Then, using a sample of about 550 stars of spectral types earlier than B6 and luminosity classes between III and V, with precise photometric distances of less than 1 kpc, we estimate for some spectral groups the parameters of our model, as well as single membership probabilities of GB and LGD stars, thus drawing a picture of the spatial distribution of young stars in the vicinity of the Sun.Comment: 28 pages including 9 Postscript figures, one of them in color. Accepted for publication in The Astronomical Journal, 30 January 200

The Nature of the Gould Belt from a Fractal Analysis of its Stellar Population

The Gould Belt (GB) is a system of gas and young, bright stars distributed along a plane that is inclined with respect to the main plane of the Milky Way. Observational evidence suggests that the GB is our closest star formation complex, but its true nature and origin remain rather controversial. In this work we analyze the fractal structure of the stellar component of the GB. In order to do this, we tailor and apply an algorithm that estimates the fractal dimension in a precise and accurate way, avoiding both boundary and small data set problems. We find that early OB stars (of spectral types earlier than B4) in the GB have a fractal dimension very similar to that of the gas clouds in our Galaxy. On the contrary, stars in the GB of later spectral types show a larger fractal dimension, similar to that found for OB stars of both age groups in the local Galactic disk (LGD). This result seems to indicate that while the younger OB stars in the GB preserve the memory of the spatial structure of the cloud where they were born, older stars are distributed following a similar morphology as that found for the LGD stars. The possible causes for these differences are discussed.Comment: 20 pages including 7 figures and 1 table. ApJ (in press

Stiff oscillatory systems, delta jumps and white noise

Two model problems for stiff oscillatory systems are introduced. Both comprise a linear superposition of N >> 1 harmonic oscillators used as a forcing term for a scalar ODE. In the first case the initial conditions are chosen so that the forcing term approximates a delta function as N tends to infinity, and in the second case so that it approximates white noise. In both cases the fastest natural frequency of the oscillators is O(N). The model problems are integrated numerically in the stiff regime where the time step is of size O(1/N). The convergence of the algorithms is studied in this case in the limit of N tending to infinity and the time step tending to zero. For the white noise problem both strong and weak convergence are considered

Effect of particle shape on biomass pyrolysis in a bubbling fluidized bed

The effect of biomass particle shape on the conversion of beech wood during pyrolysis in a bubbling fluidized bed (BFB) was experimentally quantified. A lab-scale BFB installed on a high-precision scale was used to characterize the mass loss of the biomass particles immersed in the bed. The scale could monitor the mass loss of the beech wood particles while moving freely inside the bed, which was operated at 2.5 times the minimum fluidization velocity of the bed material employed. The tests were performed at 500 and 600 °C using beech wood particles of the same mass, but different in shape. All particles used were cylindrical in shape, with the same mass, and differing in their aspect ratio, analyzing particles from typical biomass chips to standard biomass pellets. The experimental results indicate that the velocity of pyrolysis for the different particles is proportional to the characteristic heat transfer length of the particles, with pyrolysis times ranging from 27 to 53 s for a bed temperature of 600 °C and from 43 to 85 s for a bed temperature of 500 °C. The minimum pyrolysis time was obtained for particles with a diameter of 20 mm and a length of 2 mm pyrolyzing in a bed at 600 °C, whereas the maximum pyrolysis time corresponds to particles of 10 mm in diameter and 8 mm in length converting in a bed at 500 °C. Estimations of the conversion time obtained from a Shrinking Unreacted Particle Model (SUPM), assuming a constant density and reducing volume of biomass during conversion, and a Uniform Conversion Model (UCM), considering uniform volume and decreasing density of biomass along the conversion process, were compared to experimental measurements of the conversion time. Qualitative agreement was found between the experimental values and the predictions of the conversion time from the simplified models, obtaining in all cases conversion times proportional to the characteristic length of heat transfer of each particle shape

Eficiência produtiva de usinas de açúcar e álcool do estado de São Paulo.

O objetivo desse artigo e realizar uma avaliação da eficiência produtiva da agroindústria canavieira paulista. As atividades canavieiras foram beneficiadas, desde seu surgimento, por proteção governamental. Com a modificação estrutural da economia brasileira ocorrida no início dos anos de 1990 as firmas que compõem o setor viram-se obrigadas a apresentar desempenho compatível com o das organizações acostumadas a sobreviver em mercados competitivos. Tal modificação no ambiente tomou a eficiência e a competitividade questões importantes para as organizações. Esse trabalho visa estabelecer rankings de eficiência das firmas que compõem a agroindústria canavieira paulista utilizando técnicas de programação matemática. No seu desenvolvimento são promovidas discussões sobre o grau de heterogeneidade dos níveis de eficiência dessas firmas sob vários enfoques, dentre os quais a concentração regional das firmas eficientes, a relação entre eficiência e escala de produção e possíveis causas para a ineficiência. A fonte dos dados utilizados nesta pesquisa foi a publicação " Anuário Jornal Cana"

Vigilancia de la lepra en España en 2017-2018 y situación mundial

[ES] En este boletín se presentan los datos del Registro Nacional de lepra en España de los años 2017 y 2018, así como los últimos datos globales publicados por la Organización Mundial de la Salud (OMS). En estos dos años se notificaron 15 casos incidentes, 9 en 2017 y 6 en 2018, de los cuales, 12 eran personas procedentes de otros países. Hubo 25 casos prevalentes en 2017 y 17 en 2018. [EN] This article shows the leprosy cases reported to the Spanish National Leprosy Register (SNLR), as well as the latest global data published in 2017 by the World Health Organization (WHO). In these two years 15 incident cases were reported, 9 in 2017 and 6 in 2018, of which 12 were in foreign-born people. There were 25 prevalent cases in 2017 and 17 in 2018