1,225,759 research outputs found
A polyphonic acoustic vortex and its complementary chords
Using an annular phased array of eight loudspeakers, we generate sound beams that simultaneously contain phase singularities at a number of different frequencies. These frequencies correspond to different musical notes and the singularities can be set to overlap along the beam axis, creating a polyphonic acoustic vortex. Perturbing the drive amplitudes of the speakers means that the singularities no longer overlap, each note being nulled at a slightly different lateral position, where the volume of the other notes is now nonzero. The remaining notes form a tri-note chord. We contrast this acoustic phenomenon to the optical case where the perturbation of a white light vortex leads to a spectral spatial distribution
Realistic model of correlated disorder and Anderson localization
A conducting 1D line or 2D plane inside (or on the surface of) an insulator
is considered.Impurities displace the charges inside the insulator. This
results in a long-range fluctuating electric field acting on the conducting
line (plane). This field can be modeled by that of randomly distributed
electric dipoles. This model provides a random correlated potential with
decaying as 1/k . In the 1D case such correlations give essential
corrections to the localization length but do not destroy Anderson
localization
Measurement of helium-3 and deuterium stopping power ratio for negative muons
The measurement method and results measuring of the stopping power ratio of
helium-3 and deuterium atoms for muons slowed down in the D/He mixture are
presented. Measurements were performed at four values of pure He gas target
densities, (normalized to the
liquid hydrogen density) and at a density 0.0585 of the D/He mixture. The
experiment was carried out at PSI muon beam E4 with the momentum P MeV/c. The measured value of the mean stopping ratio is
. This value can also be interpreted as the value of mean reduced
ratio of probabilities for muon capture by helium-3 and deuterium atoms.Comment: 7 pages, 6 figure
The normalization of sibling violence: Does gender and personal experience of violence influence perceptions of physical assault against siblings?
Despite its pervasive and detrimental nature, sibling violence (SV) remains marginalized as a harmless and inconsequential form of familial aggression. The present study investigates the extent to which perceptions of SV differ from those of other types of interpersonal violence. A total of 605 respondents (197 males, 408 females) read one of four hypothetical physical assault scenarios that varied according to perpetrator–victim relationship type (i.e., sibling vs. dating partner vs. peer vs. stranger) before completing a series of 24 attribution items. Respondents also reported on their own experiences of interpersonal violence during childhood. Exploratory factor analysis reduced 23 attribution items to three internally reliable factors reflecting perceived assault severity, victim culpability, and victim resistance ratings. A 4 × 2 MANCOVA—controlling for respondent age—revealed several significant effects. Overall, males deemed the assault less severe and the victim more culpable than did females. In addition, the sibling assault was deemed less severe compared to assault on either a dating partner or a stranger, with the victim of SV rated just as culpable as the victim of dating, peer, or stranger-perpetrated violence. Finally, respondents with more (frequent) experiences of childhood SV victimization perceived the hypothetical SV assault as being less severe, and victim more culpable, than respondents with no SV victimization. Results are discussed in the context of SV normalization. Methodological limitations and applications for current findings are also outlined
3D Temperature Mapping of Solar Photospheric Fine Structure Using Ca II H Filtergrams
Context. The wings of the Ca II H and K lines provide excellent photospheric
temperature diagnostics. At the Swedish 1-meter Solar Telescope the blue wing
of Ca II H is scanned with a narrowband interference filter mounted on a
rotation stage. This provides up to 0"10 spatial resolution filtergrams at high
cadence that are concurrent with other diagnostics at longer wavelengths. Aims.
The aim is to develop observational techniques that provide the photospheric
temperature stratification at the highest spatial resolution possible and use
those to compare simulations and observations at different heights. Methods. We
use filtergrams in the Ca II H blue wing obtained with a tiltable interference
filter at the SST. Synthetic observations are produced from 3D HD and 3D MHD
numerical simulations and degraded to match the observations. The temperature
structure obtained from applying the method to the synthetic data is compared
with the known structure in the simulated atmospheres and with observations of
an active region. Cross-correlation techniques using restored non-simultaneous
continuum images are used to reduce high-altitude, small-scale seeing signal
introduced from the non-simultaneity of the frames when differentiating data.
Results. Temperature extraction using high resolution filtergrams in the Ca II
H blue wing works reasonably well when tested with simulated 3D atmospheres.
The cross-correlation technique successfully compensates the problem of
small-scale seeing differences and provides a measure of the spurious signal
from this source in differentiated data. Synthesized data from the simulated
atmospheres (including pores) match well the observations morphologically at
different observed heights and in vertical temperature gradients.Comment: Accepted the 10/10/2012 for publication in Astronomy & Astrophysics
in Section 9, The Sun. Published the 03/12/2012 v1 to v2: changed submission
metadata v2 to v3: small changes to match published versio
Surface-state electron dynamics in noble metals
Theoretical investigations of surface-state electron dynamics in noble metals
are reported. The dynamically screened interaction is computed, within
many-body theory, by going beyond a free-electron description of the metal
surface. Calculations of the inelastic linewidth of Shockley surface-state
electrons and holes in these materials are also presented. While the linewidth
of excited holes at the surface-state band edge () is
dominated by a two-dimensional decay channel, within the surface-state band
itself, our calculations indicate that major contributions to the
electron-electron interaction of surface-state electrons above the Fermi level
come from the underlying bulk electrons.Comment: 17 pages, 7 figures, to appear in Prog. Surf. Sc
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