90,950 research outputs found
Optical communications system Patent
Specifications and drawings for semipassive optical communication syste
Looking for a gift of Nature: Hadron loops and hybrid mixing
We investigate how coupling of valence q qbar to meson pairs can modify the
properties of conventional q qbar and hybrid mesons. In a symmetry limit the
mixing between hybrids and conventional q qbar with the same J^PC is shown to
vanish. Flavor mixing between heavy and light q qbar due to meson loops is
shown to be dual to the results of gluon mediated pQCD, and qualitatively
different from mixing involving light flavors alone. The validity of the OZI
rule for conventional q qbar and hybrid mesons is discussed.Comment: v2: added important references and discussion of previous literature;
results and conclusions unchanged. 8 pages, 2 figure
Mariner 9 data storage subsystem flight performance summary
The performance is summarized of the Mariner 9 Data Storage Subsystem (DSS) throughout the primary and extended missions. Information presented is limited to reporting of anomalies which occurred during the playback sequences. Tables and figures describe the anomalies (dropouts, missing and added bits, in the imaging data) as a function of time (accumulated tape passes). The data results indicate that the performance of the DSS was satisfactory and within specification throughout the mission. The data presented is taken from the Spacecraft Team Incident/Surprise Anomaly Log recorded during the mission. Pertinent statistics concerning the tape transport performance are given. Also presented is a brief description of DSS operation, particularly that related to the recorded anomalies. This covers the video data encoding and how it is interpreted/decoded by ground data processing and the functional operation of the DSS in abnormal conditions such as loss of lock to the playback signal
The effect of induced charges on low-energy particle trajectories near conducting and semiconducting plates
The effect of the induced charge was found on particles less than 1 eV as they passed through simulated parallel, grounded channels that are comparable in dimension to those that are presently in space plasma instruments which measure the flux of low-energy ions. Applications were made to both conducting and semiconducting channels that ranged in length from 0.1 to 50 mm and in aspect ratio from 1 to 100. The effect of the induced charge on particle trajectories from simple straight lines. Several configurations of channel aspect ratio and detector locations are considered. The effect is important only at very low energies with small dimensions
Van Hove singularities in the paramagnetic phase of the Hubbard model: a DMFT study
Using the dynamical mean-field theory (DMFT) we study the paramagnetic phase
of the Hubbard model with the density of states (DOS) corresponding to the
three-dimensional cubic lattice and the two-dimensional square lattice, as well
as a DOS with inverse square root singularity. We show that the electron
correlations rapidly smooth out the square-root van Hove singularities (kinks)
in the spectral function for the 3D lattice and that the Mott metal-insulator
transition (MIT) as well as the magnetic-field-induced MIT differ only little
from the well-known results for the Bethe lattice. The consequences of the
logarithmic singularity in the DOS for the 2D lattice are more dramatic. At
half filling, the divergence pinned at the Fermi level is not washed out, only
its integrated weight decreases as the interaction is increased. While the Mott
transition is still of the usual kind, the magnetic-field-induced MIT falls
into a different universality class as there is no field-induced localization
of quasiparticles. In the case of a power-law singularity in the DOS at the
Fermi level, the power-law singularity persists in the presence of interaction,
albeit with a different exponent, and the effective impurity model in the DMFT
turns out to be a pseudo-gap Anderson impurity model with a hybridization
function which vanishes at the Fermi level. The system is then a generalized
Fermi liquid. At finite doping, regular Fermi liquid behavior is recovered.Comment: 7 pages, 9 figure
Comparison of simple mass estimators for slowly rotating elliptical galaxies
We compare the performance of mass estimators for elliptical galaxies that
rely on the directly observable surface brightness and velocity dispersion
profiles, without invoking computationally expensive detailed modeling. These
methods recover the mass at a specific radius where the mass estimate is
expected to be least sensitive to the anisotropy of stellar orbits. One method
(Wolf et al. 2010) uses the total luminosity-weighted velocity dispersion and
evaluates the mass at a 3D half-light radius , i.e., it depends on the
GLOBAL galaxy properties. Another approach (Churazov et al. 2010) estimates the
mass from the velocity dispersion at a radius where the surface
brightness declines as , i.e., it depends on the LOCAL properties. We
evaluate the accuracy of the two methods for analytical models, simulated
galaxies and real elliptical galaxies that have already been modeled by the
Schwarzschild's orbit-superposition technique. Both estimators recover an
almost unbiased circular speed estimate with a modest RMS scatter (). Tests on analytical models and simulated galaxies indicate that the local
estimator has a smaller RMS scatter than the global one. We show by examination
of simulated galaxies that the projected velocity dispersion at could
serve as a good proxy for the virial galaxy mass. For simulated galaxies the
total halo mass scales with as with RMS scatter
.Comment: 19 pages, 14 figures, 4 tables, accepted for publication in MNRA
Statistics of reversible bond dynamics observed in force-clamp spectroscopy
We present a detailed analysis of two-state trajectories obtained from
force-clamp spectroscopy (FCS) of reversibly bonded systems. FCS offers the
unique possibility to vary the equilibrium constant in two-state kinetics, for
instance the unfolding and refolding of biomolecules, over many orders of
magnitude due to the force dependency of the respective rates. We discuss two
different kinds of counting statistics, the event-counting usually employed in
the statistical analysis of two-state kinetics and additionally the so-called
cycle-counting. While in the former case all transitions are counted,
cycle-counting means that we focus on one type of transitions. This might be
advantageous in particular if the equilibrium constant is much larger or much
smaller than unity because in these situations the temporal resolution of the
experimental setup might not allow to capture all transitions of an
event-counting analysis. We discuss how an analysis of FCS data for complex
systems exhibiting dynamic disorder might be performed yielding information
about the detailed force-dependence of the transition rates and about the time
scale of the dynamic disorder. In addition, the question as to which extent the
kinetic scheme can be viewed as a Markovian two-state model is discussed.Comment: 25 pages, 10 figures, Phys. Rev. E, in pres
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