137 research outputs found
An Analysis of Four-quark Energies in SU(2) Lattice Monte Carlo using the Flux-tube Symmetry:
Energies of four-quark systems calculated by the static quenched SU(2)
lattice Monte Carlo method are analyzed in bases for square,
rectangle, tilted rectangle, linear and quadrilateral geometry configurations
and in bases for a non-planar geometry configuration. For small
interquark distances, a lattice effect is taken into account by considering
perimeter dependent terms which are characterized by the cubic symmetry. It is
then found that a parameter - that can be identified as a gluon field
overlap factor - is rather well described by the form , where and are the area and
perimeter mainly defined by the positions of the four quarks, is the
string constant in the 2-quark potentials and are constants.Comment: (19 pages of Latex - 1 page of figures not included - sent on
request). Preprint HU-TFT-94-2
Nutritional composition of omnivorous and carnivorous wild freshwater fish from Tagus river basin
Portugal is one of the countries in the world with highest per capita fish consumption (59.9 kg/year) (1), mainly saltwater fish from Atlantic Northwest and marine aquaculture. However, in the interior of Portugal is traditional the consumption of wild freshwater fish (common carp [CC], iberian barbel [IB], crucian carp [CrC] and largemouth bass [LB]). These species are very interesting as game fishing and also very important in the local cuisine due to their characteristic flavor.CERNAS-IPCB [UIDB/00681/2020] funding by the Portuguese National Funding Agency for Science, Research and Technology (FCT).info:eu-repo/semantics/publishedVersio
The influence of lifestyle and gender on sickness absence in Brazilian workers
Background: Despite an increasing body of knowledge concerning gender and lifestyle factors as determinants of sickness absence in well-developed countries, the relationship between these variables has not been elucidated in emerging econ
Infinitesimal and local convexity of a hypersurface in a semi-Riemannian manifold
Given a Riemannian manifold M and a hypersurface H in M, it is well known
that infinitesimal convexity on a neighborhood of a point in H implies local
convexity. We show in this note that the same result holds in a semi-Riemannian
manifold. We make some remarks for the case when only timelike, null or
spacelike geodesics are involved. The notion of geometric convexity is also
reviewed and some applications to geodesic connectedness of an open subset of a
Lorentzian manifold are given.Comment: 14 pages, AMSLaTex, 2 figures. v2: typos fixed, added one reference
and several comments, statement of last proposition correcte
-Strands
A -strand is a map for a Lie
group that follows from Hamilton's principle for a certain class of
-invariant Lagrangians. The SO(3)-strand is the -strand version of the
rigid body equation and it may be regarded physically as a continuous spin
chain. Here, -strand dynamics for ellipsoidal rotations is derived as
an Euler-Poincar\'e system for a certain class of variations and recast as a
Lie-Poisson system for coadjoint flow with the same Hamiltonian structure as
for a perfect complex fluid. For a special Hamiltonian, the -strand is
mapped into a completely integrable generalization of the classical chiral
model for the SO(3)-strand. Analogous results are obtained for the
-strand. The -strand is the -strand version of the
Bloch-Iserles ordinary differential equation, whose solutions exhibit dynamical
sorting. Numerical solutions show nonlinear interactions of coherent wave-like
solutions in both cases. -strand equations on the
diffeomorphism group are also introduced and shown
to admit solutions with singular support (e.g., peakons).Comment: 35 pages, 5 figures, 3rd version. To appear in J Nonlin Sc
Análisis paleontológicos a través límite Ediacárico-Cámbrico, Grupo Alto Corumbá, Brasil
This work presents the results of a palaeontological analysis focused on twenty-six species sampled in five sections of the Tamengo and Guaicurus formations, Corumbá and Ladário regions: Corcal and Laginha quarries, Porto Sobramil, Porto Figueiras and Ecoparque Cacimba. Besides, palaeoecological and palaeoenvironmental inferences are presented based on the occurrence of this fossil assemblage. Cloudina carinata Cortijo et al., 2010, previously documented in Spain and Siberia, presents an unprecedented occurrence in the American continent, in siltstones of the Tamengo Formation at Porto Figueiras section, Municipality of Corumbá, Mato Grosso do Sul State, Brazil. The biota of the Tamengo Formation is updated and composed of three biomineralizing metazoans, including poriferan spicules, putative sponge gemmule, and a sessile epibiontic prokaryotic colony. The present work also deals with the taxonomy and stratigraphic distribution of four ichnospecies and three vendotaenid species that integrate the updated benthic fauna for the upper portion of Corumbá Group. The species diversity of the Tamengo Formation was complemented by the occurrence of sixteen microfossil species that possibly represent a marine planktic assemblage. A dramatic change was identified in the palaeoenvironmental conditions of the Tamengo to Guaicurus formations, followed by a mass extinction event, possibly linked to the global Ediacaran- Cambrian mass extinction. In addition, organic-walled microfossils were prepared and analyzed from sections of three countries: nine species from the Nomtsas Formation, Namibia; four species from the Tagatiya Guazu Formation, Paraguay; and six species from the Dengying Formation, China. An international biostratigraphic essay consisting of six biozones is proposed for the uppermost Ediacaran and one biozone for the earliest Cambrian.Se presenta en este trabajo el análisis paleontológico de 26 especies fósiles muestradas en cinco cortes de las Formaciones de Tamengo y Guaicurus en las regines de Corumbá y Ladário: canteras de Corcal y Laginha, Porto Sobramil, Porto Figueiras y Ecoparque Cacimba. Además, se añaden varias interpretaciones paleoecológicas y ambientales, basadas en el registro fósil. Cloudina carinata Cortijo et al., 2010, previamente citada en España y Siberia, aparece por primera vez en el continente Americano, concretamente en limolitas de la Formación Tamengo en el corte de Porto Figueiras, Corumbá, Estado de Mato Grosso do Sul, Brasil. La biota de la Formación Tamengo incluye tres metazoos mineralizados, que incluyen espículas de poríferos, posibles gémulas de esponjas y una colonia sésil de procaiotas epibentónicos. Este trabajo se centra en la taxonomía y distribución estratigráfica de cuatro icnoespecies y tres especies de vendoténidos que forman la fauna bentónica de la parte superior del Grupo de Corumbá. La biodiversidad de la Formación Tamengo ha sido completada con el registro de 16 especies microfósiles que representan posiblemente una asociación plantónica marina. Se ha identificado un cambio drástico en las condiciones ambientales de las Formaciones Tamengo y Guaicurus, que culminan en un evento de extincinón masiva posiblemente relacionado con la extincición en masa que marca el tránsito global Ediácarico- Cámbrico. Por otro lado, se han extraído microfósiles de pared orgánica de varios afloramientos: nueve especies de la Formación de Nomtsas (Namibia), cuatro de la Formación Tagatiya Guazu (Paraguay) y seis de la Formación Dengying (China). Se propone un marco bioestratigráfico para el Ediacárico terminal que incluye seis biozonas y una biozona para el Cámbrico basal
Rotational Surfaces in and Solutions in the Nonlinear Sigma Model
The Gauss map of non-degenerate surfaces in the three-dimensional Minkowski
space are viewed as dynamical fields of the two-dimensional O(2,1) Nonlinear
Sigma Model. In this setting, the moduli space of solutions with rotational
symmetry is completely determined. Essentially, the solutions are warped
products of orbits of the 1-dimensional groups of isometries and elastic curves
in either a de Sitter plane, a hyperbolic plane or an anti de Sitter plane. The
main tools are the equivalence of the two-dimensional O(2,1) Nonlinear Sigma
Model and the Willmore problem, and the description of the surfaces with
rotational symmetry. A complete classification of such surfaces is obtained in
this paper. Indeed, a huge new family of Lorentzian rotational surfaces with a
space-like axis is presented. The description of this new class of surfaces is
based on a technique of surgery and a gluing process, which is illustrated by
an algorithm.Comment: PACS: 11.10.Lm; 11.10.Ef; 11.15.-q; 11.30.-j; 02.30.-f; 02.40.-k. 45
pages, 11 figure
Cover plants and mineral nitrogen: effects on organic matter fractions in an oxisol under no-tillage in the cerrado
Sulfur K‐edge XANES Spectroscopy as a Tool for Understanding Sulfur Dynamics in Soil Organic Matter
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