1,137 research outputs found
A low-power/low-voltage CMOS wireless interface at 5.7 GHz with dry electrodes for cognitive networks
This paper describes a low-power/low-voltage CMOS
wireless interface (CMOS-WiI) at 5.7 GHz with dry electrodes for
congnitive networks. The electrodes are 4 x 4 microtip arrays and
acquire electroencephalogram (EEG) signals in key- points for
processing. The CMOS-WiI was fabricated in a UMC 0.18 µm
RF CMOS process and its total power consumption is 23mW with
a voltage-supply of only 1.5 V. The carrier frequency is digitally
selectable and it can be one of 16 possible values in the range
5.42–5.83 GHz, with 27.12 MHz steps. These multiple carriers
allow a better spectrum allocation as well as the acquisition,
processing and transmission of high-quality EEG signals from 16
electrode arrays. The microtips array was fabricated through bulk
micromachining of a -type silicon substrate in a potassium
hydroxide solution and avoids long subject preparations for EEG
data acquisition. The reactive sputtering of iridium dioxide (IrO)
on the surface of the array guarantees its biocompatibility. The
fabrication process was trimmed in a way that each microtip
presents solid angles of 54.7 , a width in the range 150–200 µm, a
height of 100–200 µm, and a microtip interspacing of 2 µm. The
microtips array coated with IrO together with the CMOS-WiI
permit the remote monitoring of EEG signals from freely-moving
subjects
Geometric approach to chaos in the classical dynamics of abelian lattice gauge theory
A Riemannian geometrization of dynamics is used to study chaoticity in the
classical Hamiltonian dynamics of a U(1) lattice gauge theory. This approach
allows one to obtain analytical estimates of the largest Lyapunov exponent in
terms of time averages of geometric quantities. These estimates are compared
with the results of numerical simulations, and turn out to be very close to the
values extrapolated for very large lattice sizes even when the geometric
quantities are computed using small lattices. The scaling of the Lyapunov
exponent with the energy density is found to be well described by a quadratic
power law.Comment: REVTeX, 9 pages, 4 PostScript figures include
Anti-de Sitter curvature radius constrained by quasars in brane-world scenarios
This paper is intended to investigate the luminosity due to accretion of gas
in supermassive black holes (SMBHs) in the center of quasars, using a
brane-world scenario naturally endowed with extra dimensions, whereon theories
formulated introduce corrections in the field equations at high energies. SMBHs
possess the necessary highly energetic environment for the introduction of
these corrections, which are shown to produce small deviations in all SMBH
properties and, consequentely, corrections in the accretion theory that
supports quasars radiative processes. The radiative flux observed from quasars
indicates these deviations, from which the magnitude of the AdS bulk
curvature radius, and consequently the extra dimension compactification radius
is estimated.Comment: 11 pages, RevTeX, Eq.(2) and (3) expanded, and comments thereon
update
CaracterÃsticas gerais de sistemas de produção realizados por produtores de caprinos leiteiros associados à s cooperativas de Jussara e Valente na Bahia.
Este trabalho teve como objetivo caracterizar os sistemas de produçao aplicados a caprinos leiteiros nas microrregioes de Jussara e Valente na Bahia. Utilizaram-se dados retirados de entrevistas com 45 produtores que utilizavam o leite para consumo proprio ou venda. As propriedades possuiam, em media, 55 hectares. Em 42% das propriedades, os animais se alimentavam em areas de fundo de pasto. 0 sistema de produçao animal pode ser caracterizado como urn sistema misto. A media de produçao obtida foi de 8,5 litros ao dia e a media da produçao comercializada mensalmente foi de 409 litros. Apenas 2 produtores fabricavam queijo e apenas 2 produtores fabricavam doce de leite.Grande parte dos dados obtidos apresentou altos valores de coeficiente de variaçao, refletindo a grande diversidade dos sistemas de produçao e comercializaçao
Hamiltonian dynamics of the two-dimensional lattice phi^4 model
The Hamiltonian dynamics of the classical model on a two-dimensional
square lattice is investigated by means of numerical simulations. The
macroscopic observables are computed as time averages. The results clearly
reveal the presence of the continuous phase transition at a finite energy
density and are consistent both qualitatively and quantitatively with the
predictions of equilibrium statistical mechanics. The Hamiltonian microscopic
dynamics also exhibits critical slowing down close to the transition. Moreover,
the relationship between chaos and the phase transition is considered, and
interpreted in the light of a geometrization of dynamics.Comment: REVTeX, 24 pages with 20 PostScript figure
Geometric dynamical observables in rare gas crystals
We present a detailed description of how a differential geometric approach to
Hamiltonian dynamics can be used for determining the existence of a crossover
between different dynamical regimes in a realistic system, a model of a rare
gas solid. Such a geometric approach allows to locate the energy threshold
between weakly and strongly chaotic regimes, and to estimate the largest
Lyapunov exponent. We show how standard mehods of classical statistical
mechanics, i.e. Monte Carlo simulations, can be used for our computational
purposes. Finally we consider a Lennard Jones crystal modeling solid Xenon. The
value of the energy threshold turns out to be in excellent agreement with the
numerical estimate based on the crossover between slow and fast relaxation to
equilibrium obtained in a previous work by molecular dynamics simulations.Comment: RevTeX, 19 pages, 6 PostScript figures, submitted to Phys. Rev.
Fermion confinement induced by geometry
We consider a five-dimensional model in which fermions are confined in a
hypersurface due to an interaction with a purely geometric field. Inspired by
the Rubakov-Shaposhnikov field-theoretical model, in which massless fermions
can be localized in a domain wall through the interaction of a scalar field, we
show that particle confinement may also take place if we endow the
five-dimensional bulk with a Weyl integrable geometric structure, or if we
assume the existence of a torsion field acting in the bulk. In this picture,
the kind of interaction considered in the Rubakov-Shaposhnikov model is
replaced by the interaction of fermions with a geometric field, namely a Weyl
scalar field or a torsion field. We show that in both cases the confinement is
independent of the energy and the mass of the fermionic particle. We generalize
these results to the case in which the bulk is an arbitrary n-dimensional
curved space.Comment: 8 page
Conteúdo de minerais em ossos e no fÃgado de ovinos com ou sem periodontite
Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Zootecnia. Seropédica, RJ, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Zootecnia. Seropédica, RJ, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Zootecnia. Seropédica, RJ, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Veterinária. Seropédica, RJ, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Veterinária. Seropédica, RJ, Brasil.Universidade Federal Rural do Rio de Janeiro. Instituto de Veterinária. Seropédica, RJ, Brasil.Instituto Federal do Pará. Marabá, PA, Brasil.Instituto Federal do Pará. Marabá, PA, Brasil.Instituto Federal do Pará. Marabá, PA, Brasil.Universidade Federal do Sul e Sudoeste do Pará. Xinguara, PA, Brasil.Universidade Federal do Sul e Sudoeste do Pará. Xinguara, PA, Brasil.Universidade Federal do Sul e Sudoeste do Pará. Xinguara, PA, Brasil.Ministério da Saúde. Secretaria de Vigilância em Saúde e Ambiente. Instituto Evandro Chagas. Ananindeua, PA, Brasil.Ministério da Saúde. Secretaria de Vigilância em Saúde e Ambiente. Instituto Evandro Chagas. Ananindeua, PA, Brasil.Ministério da Saúde. Secretaria de Vigilância em Saúde e Ambiente. Instituto Evandro Chagas. Ananindeua, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Universidade Federal do Pará. Faculdade de Medicina Veterinária. Castanhal, PA, Brasil.Due to the supposed involvement of minerals in cases of ruminant periodontitis, this study aimed to analyze the concentrations of phosphorus (P) in bone, and cobalt (Co), copper (Co), iron (Fe), zinc (Zn) and selenium (Se) in liver of a cohort of sheep affected or not by periodontitis. From an outbreak of the disease in 2011 in Pará state, Brazil, rib and liver samples were obtained from 22 sheep with periodontitis and seven samples from healthy animals. Based on the concentrations of the different minerals in the tissues, we concluded that there was no relationship between periodontal disease in sheep with any mineral deficiency status. In contrast, most of the minerals in the tissues were above or within the recommended concentrations in bone and liver. Within the various aspects which until now have been studied regarding periodontitis in ruminants, the results obtained here corroborate the fact that periodontal disease in sheep is an infectious disease and it is not a consequence of the deficiency or excess of mineral elements in the diet
Theory on quench-induced pattern formation: Application to the isotropic to smectic-A phase transitions
During catastrophic processes of environmental variations of a thermodynamic
system, such as rapid temperature decreasing, many novel and complex patterns
often form.
To understand such phenomena, a general mechanism is proposed based on the
competition between heat transfer and conversion of heat to other energy forms.
We apply it to the smectic-A filament growth process during quench-induced
isotropic to smectic-A phase transition. Analytical forms for the buckling
patterns are derived and we find good agreement with experimental observation
[Phys. Rev. {\bf E55} (1997) 1655]. The present work strongly indicates that
rapid cooling will lead to structural transitions in the smectic-A filament at
the molecular level to optimize heat conversion. The force associated with this
pattern formation process is estimated to be in the order of
piconewton.Comment: 9 pages in RevTex form, with 3 postscript figures. Accepted by PR
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