344 research outputs found

    Note on Moufang-Noether currents

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    The derivative Noether currents generated by continuous Moufang tranformations are constructed and their equal-time commutators are found. The corresponding charge algebra turns out to be a birepresentation of the tangent Mal'ltsev algebra of an analytic Moufang loop.Comment: LaTeX2e, 6 pages, no figures, presented on "The XVth International Colloquium on Integrable Systems and Quantum Symmetries, Prague, 15-17 June, 2006

    Crescimento da pescada-foguete (Macrodon ancylodon): aspecto quantitativo

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    We determined the age of the commercial marine fish "pescada-foguete" (Macrodon ancylodon, Bloch 1801) caught by trawls along the southern coast of Brazil (28ºS-34ºS), from 1961 to 1963, by means of the annuli in otoliths (CHUGUNOVA, 1959). We correlated the mean total length (L) in centimetres with the age (t) in years by means of the BERTALANFFY expression adjusted by FORD-WALFORD method (BEVERTON & HOLT, 1957). The mean total length was correlated with the mean weight (W) in grams, by means of the expression W = aLb adjusted by least square method, after a logarithmic transformation. Results

    Migração da pescada-foguete, Macrodon ancylodon

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    The "pescada-foguete" fish presented (1961-1964) migration along the southern coast of Brazil (from 28ºS to 34ºS), according to the following expression, adjusted by the least squares method: y = 30.2 + 1.7 cos 30 (x - 1.5) where: y - latitude with maximum production per unit effort (ºS) X = 1, % .... 12, months of the yea

    Análise da pesca da pescada-foguete na costa centro-sul do Brasil

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    In this paper data on catch and effort by gear are analysed, for weakfish (Macrodon ancylodon) landed at Santos from January 1959 to December 1963. The region studied was a narrow band about 30 nautical miles wide, along the southern coast of Brazil, between 23º S and 34º S. From the analysis of monthly data of production per unit-effort by squares of 1º on a side, we divided the studied region in two areas: area I (from 23º S to 27º S) and area II (from 28º S to 34º S). The index of unit-effort production and the effort concentration index were computed grouping the data by quarters. From the results we may drow the following conclusions: 1 - In a general way, the effort for catch weak-fish has been applied satisfactorily because the medium and large parejas have operated almost in areas with average density on¹ higher than average density; 2 - The production per unit-effort in the area I is smaller than the production in area II, which suggests that the index of abundance is higher in area II; 3 - The decrease in production per unit-effort, in area II, suggests a decrease in the abundance or availability of weak-fish in this area; 4 - In the area I, the index of production per unit-effort remained approximately at the same level

    Helminth parasites of the oceanic horse mackerel Trachurus picturatus Bowdich 1825 (Pisces: Carangidae) from Madeira Island, Atlantic Ocean, Portugal

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    The helminth parasite fauna of the oceanic horse mackerel Trachurus picturatus Bowdich 1825, caught off the Madeira Islands was composed of six different taxa. Prevalence and abundance of larval Anisakis sp. (Nematoda: Anisakidae) and Nybelinia lingualis (Trypanorhyncha: Tentaculariidae), the most common parasite taxa, were 24.3%, 0.9 and 37.9%, 0.7, respectively. Bolbosoma vasculosum (Acanthocephala: Polymorphidae) and the monogeneans Heteraxinoides atlanticus (Monogenea: Heteraxinidae) and Pseudaxine trachuri (Monogenea: Gastrocotylidae) were comparatively rare. The depauperate helminth fauna of the oceanic horse mackerel at Madeira compared to other geographical regions of the north-eastern Atlantic, namely the Azores banks and the West African coast, may be attributed to the paucity of nutrients off oceanic islands and to a low density of the fish population.This work was partially supported by the Portuguese Foundation for Science and Technology (FCT) Pluriannual Programs.info:eu-repo/semantics/publishedVersio

    Fractalization of Torus Revisited as a Strange Nonchaotic Attractor

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    Fractalization of torus and its transition to chaos in a quasi-periodically forced logistic map is re-investigated in relation with a strange nonchaotic attractor, with the aid of functional equation for the invariant curve. Existence of fractal torus in an interval in parameter space is confirmed by the length and the number of extrema of the torus attractor, as well as the Fourier mode analysis. Mechanisms of the onset of fractal torus and the transition to chaos are studied in connection with the intermittency.Comment: Latex file ( figures will be sent electronically upon request):submitted to Phys.Rev. E (1996

    Multifractal Scaling, Geometrical Diversity, and Hierarchical Structure in the Cool Interstellar Medium

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    Multifractal scaling (MFS) refers to structures that can be described as a collection of interwoven fractal subsets which exhibit power-law spatial scaling behavior with a range of scaling exponents (concentration, or singularity, strengths) and dimensions. The existence of MFS implies an underlying multiplicative (or hierarchical, or cascade) process. Panoramic column density images of several nearby star- forming cloud complexes, constructed from IRAS data and justified in an appendix, are shown to exhibit such multifractal scaling, which we interpret as indirect but quantitative evidence for nested hierarchical structure. The relation between the dimensions of the subsets and their concentration strengths (the "multifractal spectrum'') appears to satisfactorily order the observed regions in terms of the mixture of geometries present: strong point-like concentrations, line- like filaments or fronts, and space-filling diffuse structures. This multifractal spectrum is a global property of the regions studied, and does not rely on any operational definition of "clouds.'' The range of forms of the multifractal spectrum among the regions studied implies that the column density structures do not form a universality class, in contrast to indications for velocity and passive scalar fields in incompressible turbulence, providing another indication that the physics of highly compressible interstellar gas dynamics differs fundamentally from incompressible turbulence. (Abstract truncated)Comment: 27 pages, (LaTeX), 13 figures, 1 table, submitted to Astrophysical Journa

    Site adaptations of Acanthogyrus (Acanthosentis) tilapiae: Observations through light and scanning electron microscopy

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    Acanthogyrus (Acanthosentis) tilapiae parasites were collected from the intestines of 300 fish belonging to three tilapia species sourced at the River Nile, Giza, Egypt. The proboscis of the parasite was characterized by three rows of hooks that curved towards the posterior of the body. The first row is supported by unmodified hooks. The parasite tegument has a series of alternative folds and a large number of pores. Sensory ganglia are located on the surface of the proboscis and body. Acanthogyrus (Acanthosentis) tilapiae provokes an aggressive host response indicated by hyperplasia of the intestinal goblet cells and focal eosinophil infiltrations. This acanthocephalan parasite shows a highly modified adaptation to its site of host infection
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