9,903 research outputs found
Stress waves in transversely isotropic media: The homogeneous problem
The homogeneous problem of stress wave propagation in unbounded transversely isotropic media is analyzed. By adopting plane wave solutions, the conditions for the existence of the solution are established in terms of phase velocities and directions of particle displacements. Dispersion relations and group velocities are derived from the phase velocity expressions. The deviation angles (e.g., angles between the normals to the adopted plane waves and the actual directions of their propagation) are numerically determined for a specific fiber-glass epoxy composite. A graphical method is introduced for the construction of the wave surfaces using magnitudes of phase velocities and deviation angles. The results for the case of isotropic media are shown to be contained in the solutions for the transversely isotropic media
Wave propagation in anisotropic medium due to an oscillatory point source with application to unidirectional composites
The far-field displacements in an infinite transversely isotropic elastic medium subjected to an oscillatory concentrated force are derived. The concepts of velocity surface, slowness surface and wave surface are used to describe the geometry of the wave propagation process. It is shown that the decay of the wave amplitudes depends not only on the distance from the source (as in isotropic media) but also depends on the direction of the point of interest from the source. As an example, the displacement field is computed for a laboratory fabricated unidirectional fiberglass epoxy composite. The solution for the displacements is expressed as an amplitude distribution and is presented in polar diagrams. This analysis has potential usefulness in the acoustic emission (AE) and ultrasonic nondestructive evaluation of composite materials. For example, the transient localized disturbances which are generally associated with AE sources can be modeled via this analysis. In which case, knowledge of the displacement field which arrives at a receiving transducer allows inferences regarding the strength and orientation of the source, and consequently perhaps the degree of damage within the composite
Aspectos clínicos e endócrinos da puberdade, ciclo estral, gestação, parto e puerpério em búfalos tipo Baio (Bubalus bubalis) criados na região amazônica (FCAP/UFPA/EMBRAPA: 06270301).
Phase transition of a two dimensional binary spreading model
We investigated the phase transition behavior of a binary spreading process
in two dimensions for different particle diffusion strengths (). We found
that cluster mean-field approximations must be considered to get
consistent singular behavior. The approximations result in a continuous
phase transition belonging to a single universality class along the phase transition line. Large scale simulations of the particle density
confirmed mean-field scaling behavior with logarithmic corrections. This is
interpreted as numerical evidence supporting that the upper critical dimension
in this model is .The pair density scales in a similar way but with an
additional logarithmic factor to the order parameter. At the D=0 endpoint of
the transition line we found DP criticality.Comment: 8 pages, 10 figure
Programa de melhoramento genético de búfalos da Embrapa Amazônia Oriental.
bitstream/item/61933/1/Oriental-Doc29.pd
Final Analysis and Results of the Phase II SIMPLE Dark Matter Search
We report the final results of the Phase II SIMPLE measurements, comprising
two run stages of 15 superheated droplet detectors each, the second stage
including an improved neutron shielding. The analyses includes a refined signal
analysis, and revised nucleation efficiency based on reanalysis of
previously-reported monochromatic neutron irradiations. The combined results
yield a contour minimum of \sigma_{p} = 4.2 x 10^-3 pb at 35 GeV/c^2 on the
spin-dependent sector of WIMP-proton interactions, the most restrictive to date
from a direct search experiment and overlapping for the first time results
previously obtained only indirectly. In the spin-independent sector, a minimum
of 3.6 x 10^-6 pb at 35 GeV/c^2 is achieved, with the exclusion contour
challenging the recent CoGeNT region of current interest.Comment: revised, PRL-accepted version with slightly weakened limit contour
Global fixed point proof of time-dependent density-functional theory
We reformulate and generalize the uniqueness and existence proofs of
time-dependent density-functional theory. The central idea is to restate the
fundamental one-to-one correspondence between densities and potentials as a
global fixed point question for potentials on a given time-interval. We show
that the unique fixed point, i.e. the unique potential generating a given
density, is reached as the limiting point of an iterative procedure. The
one-to-one correspondence between densities and potentials is a straightforward
result provided that the response function of the divergence of the internal
forces is bounded. The existence, i.e. the v-representability of a density, can
be proven as well provided that the operator norms of the response functions of
the members of the iterative sequence of potentials have an upper bound. The
densities under consideration have second time-derivatives that are required to
satisfy a condition slightly weaker than being square-integrable. This approach
avoids the usual restrictions of Taylor-expandability in time of the uniqueness
theorem by Runge and Gross [Phys.Rev.Lett.52, 997 (1984)] and of the existence
theorem by van Leeuwen [Phys.Rev.Lett. 82, 3863 (1999)]. Owing to its
generality, the proof not only answers basic questions in density-functional
theory but also has potential implications in other fields of physics.Comment: 4 pages, 1 figur
On the violation of a local form of the Lieb-Oxford bound
In the framework of density-functional theory, several popular density
functionals for exchange and correlation have been constructed to satisfy a
local form of the Lieb-Oxford bound. In its original global expression, the
bound represents a rigorous lower limit for the indirect Coulomb interaction
energy. Here we employ exact-exchange calculations for the G2 test set to show
that the local form of the bound is violated in an extensive range of both the
dimensionless gradient and the average electron density. Hence, the results
demonstrate the severity in the usage of the local form of the bound in
functional development. On the other hand, our results suggest alternative ways
to construct accurate density functionals for the exchange energy.Comment: (Submitted on 27 April 2012
Avaliação de ganho de peso e peso a desmama em bezerros pantaneiros e pantaneiro X nelore, criados a pasto.
O bovino Pantaneiro é uma raça local brasileira que possui entre outras características, grande adaptabilidade às condições ambientais extremas aos quais são submetidos esses animais, no seu habitat natural, o Pantanal. Devido ao sério risco de extinção, a Embrapa Pantanal e parceiros têm dedicado suas pesquisas a conservação e uso desse patrimônio genético, divulgando suas potencialidades como forma de estimular a criação dessa raça em diferentes sistemas produtivos. Com o objetivo de avaliar o ganho de peso diário (GPD) e peso a desmama (PD) de animais da raça Pantaneiro e mestiços Pantaneiro X Nelore, foram coletados pesos de machos e fêmeas ao nascimento e próximo a idade de desmama. Não houve diferença de GPD entre os grupamentos raciais para ambos os sexos. A média de GPD de bezerras Pantaneiras e mestiças foi 0,575 kg/dia e 0,654 kg/dia, respectivamente. Para bezerros Pantaneiros e mestiços, os valores encontrados foram 0,643 kg/dia e 0,692 kg/dia, respectivamente. Não houve diferença de médias comparadas para o peso a desmama entre os grupamentos raciais para ambos os sexos. A média de PD, ajustado para 205 dias, de bezerras Pantaneiras e mestiças foi 148,3 kg e 161,6 kg, respectivamente. Para bezerros Pantaneiros e mestiços, os valores encontrados foram 161,7 kg e 172,3 kg, respectivamente. Os resultados encontrados foram semelhantes aos descritos na literatura para raça Nelore, principal raça bovina criada em sistema extensivo a pasto, em áreas de Cerrado. Sendo assim, considera-se que a inclusão de bovinos Pantaneiros pode ser uma alternativa viável do uso desse patrimônio genético em sistemas produtivos de cria
Pontine and Extrapontine Myelinolysis
Introdução: A mielinólise define-se como uma doença desmielinizante aguda, associada a
um quadro clínico de tetraplegia flácida e a incapacidade na fala e na deglutição. A patogenia em geral está associada a perturbações electrolíticas, particularmente hiponatrémia profunda e sua rápida correcção. A confirmação imagiológica do diagnóstico pode ser feita recorrendo à Ressonância Magnética Nuclear.
Objectivo: Os autores fazem a descrição do caso clínico, evidenciando a sua evolução e
programa de reabilitação instituído, realçando os ganhos da funcionalidade. São descritas também as intercorrências clínicas relevantes no atraso do diagnóstico.
Caso clínico: Apresenta-se uma doente com antecedentes psiquiátricos e polidipsia, internada na sequência de um quadro convulsivo resistente à medicação, tendo sido identificada hiponatrémia e feita a sua correcção. Após a correcção a doente desenvolveu um quadro de tetraplegia e hipotonia generalizada, tendo realizado uma Ressonância Magnética compatível com o diagnóstico de mielinólise centropôntica e extrapôntica
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