642 research outputs found
Aharonov-Bohm interference in quantum ring exciton: effects of built-in electric fields
We report a comprehensive discussion of quantum interference effects due to
the finite structure of excitons in quantum rings and their first experimental
corroboration observed in the optical recombinations. Anomalous features that
appear in the experiments are analyzed according to theoretical models that
describe the modulation of the interference pattern by temperature and built-in
electric fields.Comment: 6 pages, 7 figure
Características dos anéis de crescimento de Drimys brasiliensis e Podocarpus sellowi em áreas de floresta ombrófila densa das Terras Baixas e Altomontana, no Estado do Paraná.
Resumo
On the Formation of Copper Linear Atomic Suspended Chains
We report high resolution transmission electron microscopy and classical
molecular dynamics simulation results of mechanically stretching copper
nanowires conducting to linear atomic suspended chains (LACs) formation. In
contrast with some previous experimental and theoretical work in literature
that stated that the formation of LACs for copper should not exist our results
showed the existence of LAC for the [111], [110], and [100] crystallographic
directions, being thus the sequence of most probable occurence.Comment: 4 pages, 3 figure
Plasmídios em Bacillus thuringiensis: tamanho, mecanismo de replicação e papel na atividade entomopatogênica.
bitstream/item/39148/1/DOC262-09.pd
Electric field inversion asymmetry: Rashba and Stark effects for holes in resonant tunneling devices
We report experimental evidence of excitonic spin-splitting, in addition to
the conventional Zeeman effect, produced by a combination of the Rashba
spin-orbit interaction, Stark shift and charge screening. The
electric-field-induced modulation of the spin-splitting are studied during the
charging and discharging processes of p-type GaAs/AlAs double barrier resonant
tunneling diodes (RTD) under applied bias and magnetic field. The abrupt
changes in the photoluminescence, with the applied bias, provide information of
the charge accumulation effects on the device.Comment: 4 pages, 2 figure
Crescimento diamétrico de Blepharocalyx salicifolius em remanescente de Floresta Ombrófila Mista Aluvial, Paraná.
Buscou-se avaliar o incremento diamétrico de Blepharocalyx salicifolius (Kunth) O. Berg (Myrtaceae) a partir de cintas dendrométricas fixadas em 11 indivíduos de um remanescente de Floresta Ombrófila Mista Aluvial na Região Metropolitana de Curitiba-PR. Concomitantemente às leituras de incremento, foi avaliado o comportamento fenológico desses indivíduos, durante 24 meses. O incremento diamétrico médio mensal de B. salicifolius variou de 0,36 mm a praticamente nulo nos meses mais frios (de junho a agosto) e até 1,78 mm, durante os meses mais favoráveis (de novembro a março). A taxa média de incremento anual foi de 4,52 mm. O crescimento ainda pouco expressivo nos meses de setembro e outubro pode ser justificado pelo pico de floração e frutificação. A correlação do incremento mensal intraespécie foi alta (r = 0,55), indicando boa sincronia dos dados. A correlação entre o incremento médio, as variáveis meteorológicas e as fenofases apontou que a temperatura média responde por 42% da variação do incremento médio e da frutificação
Hamiltonian structure of real Monge-Amp\`ere equations
The real homogeneous Monge-Amp\`{e}re equation in one space and one time
dimensions admits infinitely many Hamiltonian operators and is completely
integrable by Magri's theorem. This remarkable property holds in arbitrary
number of dimensions as well, so that among all integrable nonlinear evolution
equations the real homogeneous Monge-Amp\`{e}re equation is distinguished as
one that retains its character as an integrable system in multi-dimensions.
This property can be traced back to the appearance of arbitrary functions in
the Lagrangian formulation of the real homogeneous Monge-Amp\`ere equation
which is degenerate and requires use of Dirac's theory of constraints for its
Hamiltonian formulation. As in the case of most completely integrable systems
the constraints are second class and Dirac brackets directly yield the
Hamiltonian operators. The simplest Hamiltonian operator results in the
Kac-Moody algebra of vector fields and functions on the unit circle.Comment: published in J. Phys. A 29 (1996) 325
Universal Quantum Cloning in Cavity QED
We propose an implementation of an universal quantum cloning machine [UQCM,
Hillery and Buzek, Phys. Rev. A {\bf 56}, 3446 (1997)] in a Cavity Quantum
Electrodynamics (CQED) experiment. This UQCM acts on the electronic states of
atoms that interact with the electromagnetic field of a high cavity. We
discuss here the specific case of the cloning process using either a
one- or a two-cavity configuration
Spathodea campanulata (Bignoniaceae): flower visitors and nectar characteristics.
Spathodea campanulata is an exotic plant often used in arborisation of Brazilian cities.Its flower resources are toxic for insects, including bees. In order to investigate this westudied a tree located at Embrapa Semiárido (Petrolina) in July-August 2017-2018
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