48,204 research outputs found
Study of leakage currents in pCVD diamonds as function of the magnetic field
pCVD diamond sensors are regularly used as beam loss monitors in accelerators
by measuring the ionization of the lost particles. In the past these beam loss
monitors showed sudden increases in the dark leakage current without beam
losses and these erratic leakage currents were found to decrease, if magnetic
fields were present. Here we report on a systematic study of leakage currents
inside a magnetic field. The decrease of erratic currents in a magnetic field
was confirmed. On the contrary, diamonds without erratic currents showed an
increase of the leakage current in a magnetic field perpendicular to the
electric field for fields up to 0.6T, for higher fields it decreases. A
preliminary model is introduced to explain the observations.Comment: 6 pages, 16 figures, poster at Hasselt Diamond Workshop, Mar 2009,
accepted version for publicatio
Parental Functioning in Families for Behavioral Parent Training and Importance of Clinically Meaningful Change
Objective/Method: Statistically significant and clinically meaningful effects of behavioral parent training on parental functioning were examined for 20 children with ADHD and their parents who had successfully completed a psychosocial treatment for ADHD.
Results/Conclusion: Findings suggest that behavioral parent training resulted in statistically significant improvements in some domains of parenting behavior for both mothers and fathers and in reductions in most domains of parenting stress for mothers. Importantly, clinically meaningful change also was noted for these parental functioning areas, as well as for other domains of parental functioning that did not result in statistically significant findings. Clinical implications are discussed
Excitation Induced Dephasing in Semiconductor Quantum Dots
A quantum kinetic theory is used to compute excitation induced dephasing in
semiconductor quantum dots due to the Coulomb interaction with a continuum of
states, such as a quantum well or a wetting layer. It is shown that a frequency
dependent broadening together with nonlinear resonance shifts are needed for a
microscopic explanation of the excitation induced dephasing in such a system,
and that excitation induced dephasing for a quantum-dot excitonic resonance is
different from quantum-well and bulk excitons.Comment: 6 pages, 4 figures. Extensively revised text, two figures change
Electron spin relaxation in n-type InAs quantum wires
We investigate the electron spin relaxation of -type InAs quantum wires by
numerically solving the fully microscopic kinetic spin Bloch equations with the
relevant scattering explicitly included. We find that the quantum-wire size and
the growth direction influence the spin relaxation time by modulating the
spin-orbit coupling. Due to inter-subband scattering in connection with the
spin-orbit interaction, spin-relaxation in quantum wires can show different
characteristics from those in bulk or quantum wells and can be effectively
manipulated by various means.Comment: 8 pages, 6 figure
Oxidation and crystallization of an amorphous Zr60Al15Ni25 alloy
The amorphous ternary metallic alloy Zr60Al15Ni25 was oxidized in dry oxygen in the temperature range 310 ±C to 410 ±C. Rutherford backscattering (RBS) and cross-sectional transmission electron microscopy (TEM) studies suggest that during this treatment an amorphous layer of zirconium-aluminum-oxide is formed at the surface. Nickel was depleted in the oxide and enriched in the amorphous alloy near the interface. The oxide layer thickness grows parabolically with annealing duration, with a transport constant of 2.8 x 10^-5 m^2/s x exp(-1.7 eV/kT). The oxidation rate may be controlled by the diffusion of Ni in the amorphous alloy. At later stages of the oxidation process, precipitates of nanocrystalline ZrO2 appear in the oxide near the interface. Finally, two intermetallic phases nucleate and grow simultaneously in the alloy, one at the interface and one within the alloy. An explanation involving preferential oxidation is proposed
Diagnosis, prescription and prognosis of a Bell-state filter by quantum process tomography
Using a Hong-Ou-Mandel interferometer, we apply the techniques of quantum
process tomography to characterize errors and decoherence in a prototypical
two-photon operation, a singlet-state filter. The quantum process tomography
results indicate a large asymmetry in the process and also the required
operation to correct for this asymmetry. Finally, we quantify errors and
decoherence of the filtering operation after this modification.Comment: 4 pages, 4 figure
Nearby Gas-Rich Low Surface Brightness Galaxies
We examine the Fisher-Tully cz<1000 km/s galaxy sample to determine whether
it is a complete and representative sample of all galaxy types, including low
surface brightness populations, as has been recently claimed. We find that the
sample is progressively more incomplete for galaxies with (1) smaller physical
diameters at a fixed isophote and (2) lower HI masses. This is likely to lead
to a significant undercounting of nearby gas-rich low surface brightness
galaxies. However, through comparisons to other samples we can understand how
the nearby galaxy counts need to be corrected, and we see some indications of
environmental effects that probably result from the local high density of
galaxies.Comment: 12 page, 2 figures, to appear in Ap
Comment on "Fano Resonance for Anderson Impurity Systems"
In a recent Letter, Luo et al. (Phys. Rev. Lett. 92, 256602 (2004)) analyze
the Fano line shapes obtained from scanning tunneling spectroscopy (STS) of
transition metal impurities on a simple metal surface, in particular of the
Ti/Au(111) and Ti/Ag(100) systems. As the key point of their analysis, they
claim that there is not only a Fano interference effect between the impurity
d-orbital and the conduction electron continuum, as derived in Ujsaghy et al.
(Phys. Rev. Lett. 85, 2557 (2000)), but that the Kondo resonance in the
d-electron spectral density has by itself a second Fano line shape, leading to
the experimentally observed spectra. In the present note we point out that this
analysis is conceptually incorrect. Therefore, the quantitative agreement of
the fitted theoretical spectra with the experimental results is meaningless.Comment: 1 page, no figures. Accepted for publication in PRL; revised version
uploaded on November 18th, 200
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