196,020 research outputs found
Neuropsychological study of the consequences of closed cranial trauma with coma in children
No full textThe authors have selected two samples from a larger group of children having suffered from a cranial trauma: 1) the first one is composed of eleven subjects in mesencephalic coma; 2) the second one is composed of twelve subjects in severe diencephalo-mesencephalic coma. All these cases have been followed up during three years after the trauma with periodical neuro-psychometric controls. These controls have brought to light differences between the two groups letting appear a less severe attack of the cognitive functions in the second group
Dipole dynamics of an interacting bosonic mixture
No full textWe unravel the coupled dipole dynamics of a two-species Bose-Einstein
condensate with tunable interspecies interaction. We produce a degenerate
mixture of K-Rb in an optical trap and we study the dipole
oscillations of both atomic species in the linear response regime. Varying the
interspecies interaction from the weakly to the strongly attractive side, we
measure the frequencies and the composition of the two dipole eigenmodes. For
enough strong interactions, even beyond the mean-field collapse, we find that
the frequency of the low-energy eigenmode is determined only by the bare trap
frequencies and the species population imbalance. The experimental results are
well reproduced by numerical simulations based on two coupled Gross-Pitaevskii
equations. Our findings provide a detailed picture of the dipole excitations in
asymmetric bosonic mixtures.Comment: 8 pages, 4 figure
Effective expression of the Lee-Huang-Yang energy functional for heteronuclear mixtures
No full textWe consider a homogeneous heteronuclear Bose mixture with contact interactions at the mean-field collapse, i.e., with interspecies attraction equal to the mean geometrical intraspecies repulsion. We show that the Lee-Huang-Yang (LHY) energy functional is accurately approximated by an expression that has the same functional form as in the homonuclear case. The approximated energy functional is characterized by two exponents, which can be treated as fitting parameters. We demonstrate that the values of these parameters which preserve the invariance under permutation of the two atomic species are exactly those of the homonuclear case. Deviations from the exact expression of the LHY energy functional are discussed quantitatively and a specific application is described
A passively regulated full-toroidal continuously variable transmission
No full textThis work presents a novel self-regulated toroidal continuously variable transmission (ART-CVT) that features a passive control of the speed ratio, achieved with no need for supplementary actuation system. The proposed transmission system is based on a full-toroidal CVT topology which combines a specially shaped geometry of the conjugate profiles with a pre-load system to create a correlation between the speed ratio and the input torque. Such a solution is conceived to reduce the complexity that is usually associated with active regulated systems and it is envisaged to be applicable to low-power/low-cost systems such as small wind turbines, powered-two-wheelers, or bicycles. We illustrate a simplified mathematical model that is able to describe the response of the proposed ART-CVT in quasi-static steady-state operational conditions. Additionally, we propose a case-study in a realistic scenario: a design for an ART-CVT that matches the requirements of a low-power wind turbine coupled with a synchronous generator directly connected to the grid without additional power converters. The achieved results show that an ART-CVT is able to reach working conditions close to the maximum theoretical aerodynamic performance without any active regulation
Observation of quantum droplets in a heteronuclear bosonic mixture
No full textWe report on the formation of heteronuclear quantum droplets in an attractive bosonic mixture of 41K and 87Rb. We observe long-lived self-bound states, both in free space and in an optical waveguide. In the latter case, the dynamics under the effect of a species-dependent force confirms their bound nature. By tuning the interactions from the weakly to the strongly attractive regime, we study the transition from expanding to localized states, in both geometries. We compare the experimental results with beyond-mean-field theory and we find good agreement in the full range of explored interactions. Our findings provide access to the production of long-lived droplets with important implications for further research
Effect of interactions in the interference pattern of Bose Einstein condensates
No full textUnderstanding the effect of interactions in the phase evolution of expanding
atomic Bose Einstein condensates is fundamental to describe the basic
phenomenon of matter wave interference. Many theoretical and experimental works
tackled this problem, always with the implicit assumption that the mutual
interaction between two expanding condensates rigidly modifies the phase
evolution through an effective force. In this paper, we present a combined
experimental and theoretical investigation of the interference profile of
expanding Rb condensates, with a specific focus on the effect of
interactions. We come to the different conclusion that the mutual interaction
produces local modifications of the condensate phase only in the region where
the wavepackets overlap.Comment: 10 pages, 14 figures; published versio
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Dynamics of laser-induced Cesium atom desorption from porous glass
No full textThe dynamics of short pulsed infrared laser-induced desorption of Cesium atoms from porous silica samples has been investigated. We find most probable kinetic energies of 69 ± 6 meV for desorption laser fluences between 60 and 190 mJ/cm2, significantly higher compared to those obtained for Cs desorption from plain glass, 40 ± 2 meV, but lower compared to those observed for Na and Rb desorption from polymeric surfaces, 200 meV. This is explained qualitatively by scattering of the desorbing atoms with the silica nanochannels, thus suggesting different pulsed laser photodesorption processes for atoms embedded in hard porous dielectrics as compared to polymeric thin films. © 2006 Elsevier B.V. All rights reserved
Dynamical Formation of Multiple Quantum Droplets in a Bose-Bose Mixture
No full textWe report on the formation of multiple quantum droplets in a heteronuclear K41-Rb87 mixture released in an optical waveguide. By a sudden change of the interspecies interaction from the noninteracting to the strongly attractive regime, we initially form a single droplet in an excited compression-elongation mode. The latter axially expands up to a critical length and then splits into two or more smaller fragments, recognizable as quantum droplets. We find that the number of formed droplets increases with decreasing interspecies attraction and increasing atom number. We show, by combining theory and experiment, that this behavior is consistent with capillary instability, which causes the breakup of the stretching droplet due to the surface tension. Our results open new possibilities to explore the properties of quantum liquids and systems of multiple quantum droplets in two-component bosonic mixtures
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