1,125 research outputs found
First-order transitions and triple point on a random p-spin interaction model
The effects of competing quadrupolar- and spin-glass orderings are
investigated on a spin-1 Ising model with infinite-range random -spin
interactions. The model is studied through the replica approach and a phase
diagram is obtained in the limit . The phase diagram, obtained
within replica-symmetry breaking, exhibits a very unusual feature in magnetic
models: three first-order transition lines meeting at a commom triple point,
where all phases of the model coexist.Comment: 9 pages, 2 ps figures include
Development of an active orthosis prototype for lower limbs
ARAUJO, Márcio V. ; ALSINA, Pablo J. ; MEDEIROS, Adelardo A. D. ; PEREIRA, Jonathan P.P. ; DOMINGOS, Elber C. ; ARAÚJO, Fábio M.U. ; SILVA, Jáder S. . Development of an Active Orthosis Prototype for Lower Limbs. In: INTERNATIONAL CONGRESS OF MECHANICAL ENGINEERING, 20., 2009, Gramado, RS. Proceedings… Gramado, RS: [s. n.], 2009This paper presents the development of a prototype of an active orthosis for lower limbs. The proposed orthosis is an orthopedical device with the main objective of providing walking capacity to people with partial or total loss of limbs movements. In order to design the kinematics, dynamics and the mechanical characteristics of the prototype, the
biomechanics of the human body was analized. The orthosis was projected to reproduce the movements of human gait. The movements of the joints of the orthosis are controlled by DC motors equipped with mechanical reductions, whose purpose is to reduce rotational speed and increase the torque, thus generating smooth movements. An embedded electronic system for sensory data acquisition and motor control was projected. The gait movements of the orthosis will be controlled by high level commands from a human-machine interface based on processings of electroencephalogram signals, speech
recognition or joystic
Alternativas culturais para o manejo do nematoide das lesões radiculares durante a entressafra da soja no Mato Grosso.
O objetivo do trabalho foi avaliar os efeitos de diferentes práticas culturais adotadas na entressafra sobre a população do nematoide das lesões radiculares (Pratylenchus brachyurus) e os danos causados por ele na soja na safra 2012/2013
Superconductivity in the SU(N) Anderson Lattice at U=\infty
We present a mean-field study of superconductivity in a generalized N-channel
cubic Anderson lattice at U=\infty taking into account the effect of a
nearest-neighbor attraction J. The condition U=\infty is implemented within the
slave-boson formalism considering the slave bosons to be condensed. We consider
the -level occupancy ranging from the mixed valence regime to the Kondo
limit and study the dependence of the critical temperature on the various model
parameters for each of three possible Cooper pairing symmetries (extended s,
d-wave and p-wave pairing) and find interesting crossovers. It is found that
the d- and p- wave order parameters have, in general, very similar critical
temperatures. The extended s-wave pairing seems to be relatively more stable
for electronic densities per channel close to one and for large values of the
superconducting interaction J.Comment: Seven Figures; one appendix. Accepted for publication in Phys. Rev.
Coexistence of antiferromagnetism and superconductivity in the Anderson lattice
We study the interplay between antiferromagnetism and superconductivity in a
generalized infinite- Anderson lattice, where both superconductivity and
antiferromagnetic order are introduced phenomenologically in mean field theory.
In a certain regime, a quantum phase transition is found which is characterized
by an abrupt expulsion of magnetic order by d-wave superconductivity, as
externally applied pressure increases. This transition takes place when the
d-wave superconducting critical temperature, , intercepts the magnetic
critical temperature, , under increasing pressure. Calculations of the
quasiparticle bands and density of states in the ordered phases are presented.
We calculate the optical conductivity in the clean limit. It
is shown that when the temperature drops below a double peak structure
develops in .Comment: 18 pages, 13 figure
Caracterização do módulo de crescimento do pinhão-manso (Jatropha curcas L.) na microregião geográfica de Teresina-Piauí.
O pinhao-manso (Jatropha curcas L.) e uma oleaginosa bastante promissora para producao de oleo. Entretanto, pesquisas com essa Euforbiacea na regiao Meio-Norte do Brasil praticamente nao existem, e atualmente ha uma forte demanda por parte dos empresarios para obter informacoes tecnicas sobre o manejo dessa planta para a producao de oleo (biodiesel). Para a exploracao racional dessa especie de forma economica, ambiental e socialmente sustentada, ainda faltam informacoes basicas, exigindo a experimentacao em diversas areas e dentre essas se destaca a da fisiologia de producao..
Quantum dot to disordered wire crossover: A complete solution in all length scales for systems with unitary symmetry
We present an exact solution of a supersymmetric nonlinear sigma model
describing the crossover between a quantum dot and a disordered quantum wire
with unitary symmetry. The system is coupled ideally to two electron reservoirs
via perfectly conducting leads sustaining an arbitrary number of propagating
channels. We obtain closed expressions for the first three moments of the
conductance, the average shot-noise power and the average density of
transmission eigenvalues. The results are complete in the sense that they are
nonperturbative and are valid in all regimes and length scales. We recover
several known results of the recent literature by taking particular limits.Comment: 4 page
Comportamento de açaizeiro (Euterpe precatoria Mart.) submetido a sombreamento com bananeira em diferentes arranjos.
O objetivo deste trabalho foi avaliar o comportamento de açaizeiro (Euterpe precatoria Mart.) em cultivo a pleno sol e submetido ao sombreamento disponibilizado por bananeira em diferentes densidades de plantio, nas condições edafoclimáticas do estado do Acre
Crescimento de mudas de açaizeiro (Euterpe precatoria Mart.) em diferentes condições de sombreamento.
Para açaizeiro solteiro não há relatos acerca do sombreamento adequado para a produção de mudas, por isso o objetivo foi avaliar o comportamento de açaizeiro (Euterpe precatoria Mart.) em diferentes níveis de sombreamento
Adsorptive stripping voltammetric determination of trace level Ricin in castor seeds using a boron-doped diamond electrode.
Ricin, (Ricinus communis agglutinin, RCA) is one of the most poisonous of naturally occurring substances and has great potential for bioterrorism because no antidote exists. Fast detection at low concentrations is a challenge, and vital to the development of proper countermeasures. In this study, a square wave adsorptive stripping voltammetric (SWAdSV) method for determining RCA using a cathodically polarized boron-doped diamond (BDD) electrode is presented. An irreversible electrochemical RCA oxidation peak was identified on the BDD electrode by different voltammetric techniques using both direct and adsorptive stripping modes. An adsorption-controlled (slope log Ip vs log v of 0.80) pHdependent process was observed. For values of 1.0pH 9.0, the numbers of protons and electrons associated with the oxidation reaction were estimated (ca. 1.0) by differential pulse voltammetry. The RCA oxidation step may correspond to the oxidation of tryptophan amino acid residues, and occurs in a complex mechanism. The excellent analytical performance of the cathodically polarized BDD electrode in combination with the stripping mode ramp was verified with RCA by using a short deposition time in an open circuit potential (120 s). Under optimized analysis conditions, a linear response in the range of (3.3?94.0)3109 mol L1 (r2=0.9944) and a limit of detection of 6.231010 mol L1 were estimated. This LOD is lower than several methods found in the literature. For example, it is 168 times lower than that obtained by using square wave voltammetric with a glassy carbon electrode. Moreover, an even lower LOD might be achieved by using the SWAdSV method with a higher pre-concentration time. In addition, trace levels of RCA were successfully determined in different castor seed cultivars with an overall average recovery from 99.2 1.6% for the three different RCA-A concentration levels. The high accuracy of the analytical data highlights the use of the proposed method for determining RCA in other samples
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