3,445 research outputs found
Bragg Spectroscopy of Vortex Lattices in Bose-Einstein condensates
We have measured the velocity field of a vortex lattice within a sodium
Bose-Einstein condensate using Bragg scattering. The phase gradient of the
macroscopic wavefunction was mapped into the spatial structure of the
diffracted atom cloud, allowing for single shot measurement of the rotation
parameters. A combination of spectral and spatial information yields a complete
description of the superfluid flow, coarse-grained over the lattice structure,
including direct and independent measurements of the rate and sense of
rotation. Signatures of the microscopic quantum rotation have also been
observed.Comment: 5 pages, 5 Figures, A movie built from the CM data is available in
our Webpage: http://www.physics.gatech.edu/chandra/index.htm; added Fig.5
presents new data, showing signatures of the microscopic vortex structure in
the diffracted clou
The Nature and Validity of the RKKY limit of exchange coupling in magnetic trilayers
The effects on the exchange coupling in magnetic trilayers due to the
presence of a spin-independent potential well are investigated. It is shown
that within the RKKY theory no bias nor extra periods of oscillation associated
with the depth of the well are found, contrary to what has been claimed in
recent works. The range of validity of the RKKY theory is also discussed.Comment: 10, RevTe
Sample size and classification error for Bayesian change-point models with unlabelled sub-groups and incomplete follow-up.
Many medical (and ecological) processes involve the change of shape, whereby one trajectory changes into another trajectory at a specific time point. There has been little investigation into the study design needed to investigate these models. We consider the class of fixed effect change-point models with an underlying shape comprised two joined linear segments, also known as broken-stick models. We extend this model to include two sub-groups with different trajectories at the change-point, a change and no change class, and also include a missingness model to account for individuals with incomplete follow-up. Through a simulation study, we consider the relationship of sample size to the estimates of the underlying shape, the existence of a change-point, and the classification-error of sub-group labels. We use a Bayesian framework to account for the missing labels, and the analysis of each simulation is performed using standard Markov chain Monte Carlo techniques. Our simulation study is inspired by cognitive decline as measured by the Mini-Mental State Examination, where our extended model is appropriate due to the commonly observed mixture of individuals within studies who do or do not exhibit accelerated decline. We find that even for studies of modest size ( n = 500, with 50 individuals observed past the change-point) in the fixed effect setting, a change-point can be detected and reliably estimated across a range of observation-errors.This work was supported by the Medical Research Council (Unit Programme number U105292687)
Emergência de plântulas de moringa em diferentes substratos.
bitstream/CPATC-2010/21515/1/bp-56.pd
Adição de metionina protegida da degrabilidade ruminal em rações para cordeiros alimentados com dois níveis de ptoteína não degradável no rúmen: degrabilidade ruminal da matéria seca1.
bitstream/CPATC/19776/1/f_14_2007.pd
Explaining the water: holding capacity of biochar by scanning electron microscope images.
O objetivo deste estudo foi identificar biocarvão com melhor desempenho de promover o aumento da capacidade de retenção de água no solo, com base em evidências de laboratório e avaliação de porosidade microestructural
On quantum traversability of wormholes
In this paper we study the possibility of non-relativistic quantum particles
to traverse the generalized Ellis-Bronnikov wormholes by considering quantum
effects, such as tunneling. We have used the generalized Ellis-Bronnikov
wormhole metric and found that for we have a single barrier shaped
effective potential centered at the throat of the wormhole for any value of
orbital angular momentum. For we have a symmetric double barrier
shaped potential when the orbital angular momentum is zero and a single barrier
for nonzero angular orbital momentum. Analytical solutions for the
Schr\"{o}dinger equation in the generalized Ellis-Bronnikov spacetime could be
found only for . Such solutions were given in terms of the confluent Heun
functions. Finally, by using a delta-barrier approximation we could find the
transmission and reflection coefficients for a non-relativistic particle to
traverse the generalized Ellis-Bronnikov wormhole.Comment: 5 pages, two columuns, 3 figure
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