24,479 research outputs found
Ion and polymer dynamics in polymer electrolytes PPO-LiClO4: insights from NMR line-shape analysis
We investigate ion and polymer dynamics in polymer electrolytes PPO-LiClO4
performing 2H and 7Li NMR line-shape analysis. Comparison of temperature
dependent 7Li and 2H NMR spectra gives evidence for a coupling of ion and
polymer dynamics. 2H NMR spectra for various salt concentrations reveal a
strong slow down of the polymer segmental motion when the salt content is
increased. The 2H NMR line shape further indicates that the segmental motion is
governed by dynamical heterogeneities. While the width of the distribution of
correlation times G(log tau) is moderate for low and high salt content, an
extremely broad distribution exists for an intermediate salt concentration 15:1
PPO-LiClO4. For the latter composition, a weighed superposition of two spectral
components, reflecting the fast and the slow polymer segments of the
distribution, describes the 2H NMR line shape over a broad temperature range.
Analysis of the temperature dependent relative intensity of both spectral
components indicates the existence of a continuous rather than a discontinuous
distribution G(log tau). Such continuous distribution is consistent with
gradual fluctuation of the local salt concentration and, hence, of the local
environments of the polymer segments, whereas it is at variance with the
existence of large salt-depleted and salt-rich domains featuring fast and slow
polymer dynamics, respectively. Finally, for all studied mixtures PPO-LiClO4,
the 2H NMR line shape strongly depends on the echo delay in the applied
echo-pulse sequence, indicating that the structural relaxation of the polymer
segments involves successive rotational jumps about small angles gamma<20
degree.Comment: 11 pages, 11 figure
Limit on T-violating P-conserving rhoNN interaction from the gamma decay of Fe-57
We use the experimental limit on the interference of M1 and E2 multipoles in the γ decay of 57Fe to bound the time-reversal-violating parity-conserving ρNN vertex. Our approach is a large-basis shell-model calculation of the interference. We find an upper limit on the parameter g¯ρ, the relative strength of the T-violating ρNN vertex, of close to 10^(-2), a value similar to the best limits from other experiments
Nonclassicality filters and quasiprobabilities
Necessary and sufficient conditions for the nonclassicality of bosonic
quantum states are formulated by introducing nonclassicality filters and
nonclassicality quasiprobability distributions. Regular quasiprobabilities are
constructed from characteristic functions which can be directly sampled by
balanced homodyne detection. Their negativities uncover the nonclassical
effects of general quantum states. The method is illustrated by visualizing the
nonclassical nature of a squeezed state.Comment: Significantly revised version, more emphasis on practical applicatio
Space shuttle navigation analysis. Volume 1: GPS aided navigation
Analytical studies related to space shuttle navigation are presented. Studies related to the addition of NAVSTAR Global Positioning System user equipment to the shuttle avionics suite are presented. The GPS studies center about navigation accuracy covariance analyses for both developmental and operational phases of GPS, as well as for various orbiter mission phases
Experimental determination of a nonclassical Glauber-Sudarshan P function
A quantum state is nonclassical if its Glauber-Sudarshan P function fails to
be interpreted as a probability density. This quantity is often highly
singular, so that its reconstruction is a demanding task. Here we present the
experimental determination of a well-behaved P function showing negativities
for a single-photon-added thermal state. This is a direct visualization of the
original definition of nonclassicality. The method can be useful under
conditions for which many other signatures of nonclassicality would not
persist.Comment: 4 pages, 4 figure
How violent video games communicate violence: A literature review and content analysis of moral disengagement factors
Mechanisms of moral disengagement in violent video game play have recently received considerable attention among communication scholars. To date, however, no study has analyzed the prevalence of moral disengagement factors in violent video games. To fill this research gap, the present approach includes both a systematic literature review and a content analysis of moral disengagement cues embedded in the narratives and actual game play of 17 top-ranked first-person shooters (PC). Findings suggest that moral disengagement factors are frequently embedded in first-person shooters, but their prevalence varies considerably. Most violent video games include justifications of the portrayed violence, a distorted portrayal of consequences, and dehumanization of opponents. Implications of the findings for research on violent games are discussed
Statistical uncertainty in quantum optical photodetection measurements
We present a complete statistical analysis of quantum optical measurement
schemes based on photodetection. Statistical distributions of quantum
observables determined from a finite number of experimental runs are
characterized with the help of the generating function, which we derive using
the exact statistical description of raw experimental outcomes. We use the
developed formalism to point out that the statistical uncertainty results in
substantial limitations of the determined information on the quantum state:
though a family of observables characterizing the quantum state can be safely
evaluated from experimental data, its further use to obtain the expectation
value of some operators generates exploding statistical errors. These issues
are discussed using the example of phase-insensitive measurements of a single
light mode. We study reconstruction of the photon number distribution from
photon counting and random phase homodyne detection. We show that utilization
of the reconstructed distribution to evaluate a simple well-behaved observable,
namely the parity operator, encounters difficulties due to accumulation of
statistical errors. As the parity operator yields the Wigner function at the
phase space origin, this example also demonstrates that transformation between
various experimentally determined representations of the quantum state is a
quite delicate matter.Comment: 18 pages REVTeX, 7 figures included using epsf. Few minor corrections
made, clarified conclusion
The AGN and Gas Disk in the Low Surface Brightness Galaxy PGC045080
We present radio observations and optical spectroscopy of the giant low
surface brightness (LSB) galaxy PGC 045080 (or 1300+0144). PGC 045080 is a
moderately distant galaxy having a highly inclined optical disk and massive HI
gas content. Radio continuum observations of the galaxy were carried out at 320
MHz, 610 MHz and 1.4 GHz. Continuum emission was detected and mapped in the
galaxy. The emission appears extended over the inner disk at all three
frequencies. At 1.4 GHz and 610 MHz it appears to have two distinct lobes. We
also did optical spectroscopy of the galaxy nucleus; the spectrum did not show
any strong emission lines associated with AGN activity but the presence of a
weak AGN cannot be ruled out. Furthermore, comparison of the H flux and
radio continuum at 1.4 GHz suggests that a significant fraction of the emission
is non-thermal in nature. Hence we conclude that a weak or hidden AGN may be
present in PGC 045080. The extended radio emission represents lobes/jets from
the AGN. These observations show that although LSB galaxies are metal poor and
have very little star formation, their centers can host significant AGN
activity. We also mapped the HI gas disk and velocity field in PGC 045080. The
HI disk extends well beyond the optical disk and appears warped. In the HI
intensity maps, the disk appears distinctly lopsided. The velocity field is
disturbed on the lopsided side of the disk but is fairly uniform in the other
half. We derived the HI rotation curve for the galaxy from the velocity field.
The rotation curve has a flat rotation speed of ~ 190 km/s.Comment: Paper contains 14 figures and 4 tables. Figures 8, 10 (color) and 13
supplied separately. Accepted for publication in MNRA
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