2,146 research outputs found
A Case of Reactive Cervical Lymphadenopathy with Fat Necrosis Impinging on Adjacent Vascular Structures.
A tender neck mass in adults can be a diagnostic challenge due to a wide differential diagnosis, which ranges from reactive lymphadenopathy to malignancy. In this report, we describe a case of a young female with an unusually large and tender reactive lymph node with fat necrosis. The diagnostic imaging findings alone mimicked that of scrofula and malignancy, which prompted a complete workup. Additionally, the enlarged lymph node was compressing the internal jugular vein in the setting of oral contraceptive use by the patient, raising concern for Lemierre's syndrome or internal jugular vein thrombosis. This report shows how, in the appropriate clinical context, and especially with the involvement of adjacent respiratory or neurovascular structures, aggressive diagnostic testing can be indicated
Non-Markovian entanglement dynamics of quantum continuous variable systems in thermal environments
We study two continuous variable systems (or two harmonic oscillators) and
investigate their entanglement evolution under the influence of non-Markovian
thermal environments. The continuous variable systems could be two modes of
electromagnetic fields or two nanomechanical oscillators in the quantum domain.
We use quantum open system method to derive the non-Markovian master equations
of the reduced density matrix for two different but related models of the
continuous variable systems. The two models both consist of two interacting
harmonic oscillators. In model A, each of the two oscillators is coupled to its
own independent thermal reservoir, while in model B the two oscillators are
coupled to a common reservoir. To quantify the degrees of entanglement for the
bipartite continuous variable systems in Gaussian states, logarithmic
negativity is used. We find that the dynamics of the quantum entanglement is
sensitive to the initial states, the oscillator-oscillator interaction, the
oscillator-environment interaction and the coupling to a common bath or to
different, independent baths.Comment: 10 two-column pages, 8 figures, to appear in Phys. Rev.
Mapping Monte Carlo to Langevin dynamics: A Fokker-Planck approach
We propose a general method of using the Fokker-Planck equation (FPE) to link
the Monte-Carlo (MC) and the Langevin micromagnetic schemes. We derive the
drift and disusion FPE terms corresponding to the MC method and show that it is
analytically equivalent to the stochastic Landau-Lifshitz-Gilbert (LLG)
equation of Langevin-based micromagnetics. Subsequent results such as the time
quantification factor for the Metropolis MC method can be rigorously derived
from this mapping equivalence. The validity of the mapping is shown by the
close numerical convergence between the MC method and the LLG equation for the
case of a single magnetic particle as well as interacting arrays of particles.
We also found that our Metropolis MC is accurate for a large range of damping
factors , unlike previous time-quantified MC methods which break down
at low , where precessional motion dominates.Comment: 4 pages, 4 figures. Accepted for publication in Phys. Rev. Let
Angular position of nodes in the superconducting gap of YBCO
The thermal conductivity of a YBCO single crystal has been studied as a
function of the relative orientation of the crystal axes and a magnetic field
rotating in the Cu-O planes. Measurements were carried out at several
temperatures below T_c and at a fixed field of 30 kOe. A four-fold symmetry
characteristic of a superconducting gap with nodes at odd multiples of 45
degrees in k-space was resolved. Experiments were performed to exclude a
possible macroscopic origin for such a four-fold symmetry such as sample shape
or anisotropic pinning. Our results impose an upper limit of 10% on the weight
of the s-wave component of the essentially d-wave superconducting order
parameter of YBCO.Comment: 10 pages, 4 figure
Submillimeter emission from the hot molecular jet HH 211
We observed the HH 211 jet in the submillimeter continuum and the CO(3-2) and
SiO(8-7) transitions with the Submillimeter Array. The continuum source
detected at the center of the outflow shows an elongated morphology,
perpendicular to the direction of the outflow axis. The high-velocity emission
of both molecules shows a knotty and highly collimated structure. The SiO(8-7)
emission at the base of the outflow, close to the driving source, spans a wide
range of velocities, from -20 up to 40 km s^{-1}. This suggests that a
wide-angle wind may be the driving mechanism of the HH 211 outflow. For
distances greater than 5" (1500 AU) from the driving source, emission from both
transitions follows a Hubble-law behavior, with SiO(8-7) reaching higher
velocities than CO(3-2), and being located upstream of the CO(3-2) knots. This
indicates that the SiO(8-7) emission is likely tracing entrained gas very close
to the primary jet, while the CO(3-2) is tracing less dense entrained gas. From
the SiO(5-4) data of Hirano et al. we find that the SiO(8-7)/SiO(5-4)
brightness temperature ratio along the jet decreases for knots far from the
driving source. This is consistent with the density decreasing along the jet,
from (3-10)x10^6 cm^{-3} at 500 AU to (0.8-4)x10^6 cm^{-3} at 5000 AU from the
driving source.Comment: 3 pages, 3 figures. Accepted by Astrophysical Journal Letter
Noise robust distillation of self-supervised speech models via correlation metrics
Compared to large speech foundation models, small distilled models exhibit
degraded noise robustness. The student's robustness can be improved by
introducing noise at the inputs during pre-training. Despite this, using the
standard distillation loss still yields a student with degraded performance.
Thus, this paper proposes improving student robustness via distillation with
correlation metrics. Teacher behavior is learned by maximizing the teacher and
student cross-correlation matrix between their representations towards
identity. Noise robustness is encouraged via the student's self-correlation
minimization. The proposed method is agnostic of the teacher model and
consistently outperforms the previous approach. This work also proposes an
heuristic to weigh the importance of the two correlation terms automatically.
Experiments show consistently better clean and noise generalization on Intent
Classification, Keyword Spotting, and Automatic Speech Recognition tasks on
SUPERB Challenge.Comment: 6 page
Efficacy of single and double SiNx interlayers on defect reduction in GaN overlayers grown by organometallic vapor-phase epitaxy
We report on the growth of and evolution of defects in GaN epilayers having single- and double-layer SiNx nanoporous insertion layers. The SiNx was formed in situ in the growth chamber of an organometallic vapor-phase epitaxy system by simultaneous flow of diluted silane and ammonia. The GaN epilayers and SiNx interlayers were grown on 6H-SiC substrates using three different nucleation layers, namely, low-temperature GaN, high-temperature GaN, and high-temperature AlN nucleation layers. X-ray-diffraction rocking curves and cross-sectional and plan-view transmission electron microscope analyses indicated that a nanoporous SiNx layer can reduce the dislocations density in the GaN overgrown layer to ∼3×108cm−2 range; below this level the defect blocking effect of SiNx would saturate. Therefore the insertion of a second SiNx layer becomes much less effective in reducing dislocations, although it continues to reduce the point defects, as suggested by time-resolved photoluminescence measurements. The insertion of SiNx interlayers was found to improve significantly the mechanical strength of the GaN epilayers resulting in a much lower crack line density
Aspects of Scalar Field Dynamics in Gauss-Bonnet Brane Worlds
The Einstein-Gauss-Bonnet equations projected from the bulk to brane lead to
a complicated Friedmann equation which simplifies to in the
asymptotic regimes. The Randall-Sundrum (RS) scenario corresponds to
whereas & give rise to high energy Gauss-Bonnet (GB) regime and
the standard GR respectively. Amazingly, while evolving from RS regime to high
energy GB limit, one passes through a GR like region which has important
implications for brane world inflation. For tachyon GB inflation with
potentials investigated in this paper, the scalar to
tensor ratio of perturbations is maximum around the RS region and is
generally suppressed in the high energy regime for the positive values of .
The ratio is very low for at all energy scales relative to GB inflation
with ordinary scalar field. The models based upon tachyon inflation with
polynomial type of potentials with generic positive values of turn out to
be in the observational contour bound at all energy scales varying
from GR to high energy GB limit. The spectral index improves for the
lower values of and approaches its scale invariant limit for in the
high energy GB regime. The ratio also remains small for large negative
values of , however, difference arises for models close to scale invariance
limit. In this case, the tensor to scale ratio is large in the GB regime
whereas it is suppressed in the intermediate region between RS and GB. Within
the frame work of patch cosmologies governed by , the behavior
of ordinary scalar field near cosmological singularity and the nature of
scaling solutions are distinguished for the values of .Comment: 15 pages, 10 eps figures; appendix on various scales in GB brane
world included and references updated; final version to appear in PR
Self-tuning experience weighted attraction learning in games
Self-tuning experience weighted attraction (EWA) is a one-parameter theory of learning in
games. It addresses a criticism that an earlier model (EWA) has too many parameters, by
fixing some parameters at plausible values and replacing others with functions of experience
so that they no longer need to be estimated. Consequently, it is econometrically simpler
than the popular weighted fictitious play and reinforcement learning models.
The functions of experience which replace free parameters “self-tune” over time, adjusting
in a way that selects a sensible learning rule to capture subjects’ choice dynamics. For
instance, the self-tuning EWA model can turn from a weighted fictitious play into an averaging
reinforcement learning as subjects equilibrate and learn to ignore inferior foregone
payoffs. The theory was tested on seven different games, and compared to the earlier parametric
EWA model and a one-parameter stochastic equilibrium theory (QRE). Self-tuning
EWA does as well as EWA in predicting behavior in new games, even though it has fewer
parameters, and fits reliably better than the QRE equilibrium benchmark
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