944 research outputs found
Auditory frequency threshold comparisons of humans and pre-adolescent chimpanzees
Auditory frequency threshold comparisons of humans and pre-adolescent chimpanzee
The refractive characteristics and intraocular tensions of colony chimpanzees Technical report, Aug. 1965
Refraction and intraocular pressure tests of colony chimpanzees - age relationshi
Ultrasound and phakometry measurements of the primate eye Technical report, Aug. 1965
Ultrasonic testing and phakometry measurements of primate ey
Effect of continuous gamma-ray exposure on performance of learned tasks and effect of subsequent fractionated exposures on blood-forming tissue
Sixteen monkeys trained to perform continuous and discrete-avoidance and fixed-ratio tasks with visual and auditory cues were performance-tested before, during, and after 10-day gamma-ray exposures totaling 0, 500, 750, and 1000 rads. Approximately 14 months after the performance-test exposures, surviving animals were exposed to 100-rad gamma-ray fractions at 56-day intervals to observe injury and recovery patterns of blood-forming tissues. The fixed-ratio, food-reward task performance showed a transient decline in all dose groups within 24 hours of the start of gamma-ray exposure, followed by recovery to normal food-consumption levels within 48 to 72 hours. Avoidance tasks were performed successfully by all groups during the 10-day exposure, but reaction times of the two higher dose-rate groups in which animals received 3 and 4 rads per hour or total doses of 750 and 1000 rads, respectively, were somewhat slower
Strain balancing of MOVPE InAs/GaAs quantum dots using GaAs0.8P0.2
MOVPE growth of stacked InAs/
GaAs QDs with and without GaAs
0.8
P
0.2
strain balancing layers has been
studied. The GaAsP layers reduce the accumulated strain whilst
maintaining the electrical characteristics. This should
enable closer stacking of QD layers leading to higher gain and improved laser performance
Strain Balancing of Metal-Organic Vapour Phase Epitaxy InAs/GaAs Quantum Dot Lasers
Incorporation of a GaAs0.8P0.2 layer allows strain balancing to be achieved in self-assembled InAs/GaAs quantum dots (QDs) grown by metal organic vapor phase epitaxy. Tuneable wavelength and high density are obtained through growth parameter optimization, with emission at 1.27 μm and QD layer density 3 × 10 10 cm-2. Strain balancing allows close vertical stacking (30 nm) of the QD layers, giving the potential for increased optical gain. Modeling and device characterization indicates minimal degradation in the optical and electrical characteristics unless the phosphorus percentage is increased above 20%. Laser structures are fabricated with a layer separation of 30 nm, demonstrating low temperature lasing with a threshold current density of 100 A/cm2 at 130 K without any facet coating
Dark Solitons in High Velocity Waveguide Polariton Fluids
We study exciton-polariton nonlinear optical fluids in the high momentum waveguide regime for the first
time. We demonstrate the formation of dark solitons with the expected dependence of width on fluid
density for both main classes of soliton-forming fluid defects. The results are well described by numerical
modeling of the fluid propagation. We deduce a continuous wave nonlinearity more than ten times that on
picosecond time scales, arising due to interaction with the exciton reservoir
Probing the Sensitivity of Electron Wave Interference to Disorder-Induced Scattering in Solid-State Devices
The study of electron motion in semiconductor billiards has elucidated our
understanding of quantum interference and quantum chaos. The central assumption
is that ionized donors generate only minor perturbations to the electron
trajectories, which are determined by scattering from billiard walls. We use
magnetoconductance fluctuations as a probe of the quantum interference and show
that these fluctuations change radically when the scattering landscape is
modified by thermally-induced charge displacement between donor sites. Our
results challenge the accepted understanding of quantum interference effects in
nanostructures.Comment: 8 pages, 5 figures, Submitted to Physical Review
Spin injection from Co2MnGa into an InGaAs quantum well
We have demonstrated spin injection from a full Heusler alloy Co2MnGa thin film into a (100) InGaAs quantum well in a semiconductor light-emitting diode structure at a temperature of 5 K. The detection is performed in the oblique Hanle geometry, allowing quantification of the effective spin lifetime and spin detection efficiency (22 +/- 4%). This work builds on existing studies on off-stoichiometric Heusler injectors into similar light-emitting-diode structures. The role of injector stoichiometry can therefore be quantitatively assessed with the result that the spin injection efficiency increases by a factor of approximately 2 as compared with an off-stoichiometric Co2.4Mn1.6Ga injector. (C) 2008 American Institute of Physics
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