18,111 research outputs found
Intensity correlations and entanglement by frequency doubling in a dual ported resonator
We show that non-classical intensity correlations and quadrature entanglement
can be generated by frequency doubling in a resonator with two output ports. We
predict twin-beam intensity correlations 6 dB below the coherent state limit,
and that the product of the inference variances of the quadrature fluctuations
gives an Einstein-Podolsky-Rosen (EPR) correlation coefficient of V_EPR = 0.6 <
1. Comparison with an entanglement source based on combining two frequency
doublers with a beam splitter shows that the dual ported resonator provides
stronger entanglement at lower levels of individual beam squeezing.
Calculations are performed using a self-consistent propagation method that does
not invoke a mean field approximation. Results are given for physically
realistic parameters that account for the Gaussian shape of the intracavity
beams, as well as intracavity losses.Comment: 12 pages, 9 figures, normalization corrected, fig 3 and fig 7 update
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IMRT QA using machine learning: A multi-institutional validation.
PurposeTo validate a machine learning approach to Virtual intensity-modulated radiation therapy (IMRT) quality assurance (QA) for accurately predicting gamma passing rates using different measurement approaches at different institutions.MethodsA Virtual IMRT QA framework was previously developed using a machine learning algorithm based on 498 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3 mm with 10% threshold at Institution 1. An independent set of 139 IMRT measurements from a different institution, Institution 2, with QA data based on portal dosimetry using the same gamma index, was used to test the mathematical framework. Only pixels with â„10% of the maximum calibrated units (CU) or dose were included in the comparison. Plans were characterized by 90 different complexity metrics. A weighted poison regression with Lasso regularization was trained to predict passing rates using the complexity metrics as input.ResultsThe methodology predicted passing rates within 3% accuracy for all composite plans measured using diode-array detectors at Institution 1, and within 3.5% for 120 of 139 plans using portal dosimetry measurements performed on a per-beam basis at Institution 2. The remaining measurements (19) had large areas of low CU, where portal dosimetry has a larger disagreement with the calculated dose and as such, the failure was expected. These beams need further modeling in the treatment planning system to correct the under-response in low-dose regions. Important features selected by Lasso to predict gamma passing rates were as follows: complete irradiated area outline (CIAO), jaw position, fraction of MLC leafs with gaps smaller than 20 or 5 mm, fraction of area receiving less than 50% of the total CU, fraction of the area receiving dose from penumbra, weighted average irregularity factor, and duty cycle.ConclusionsWe have demonstrated that Virtual IMRT QA can predict passing rates using different measurement techniques and across multiple institutions. Prediction of QA passing rates can have profound implications on the current IMRT process
Entanglement and statistics in Hong-Ou-Mandel interferometry
Hong-Ou-Mandel interferometry allows one to detect the presence of
entanglement in two-photon input states. The same result holds for
two-particles input states which obey to Fermionic statistics. In the latter
case however anti-bouncing introduces qualitative differences in the
interferometer response. This effect is analyzed in a Gedankenexperiment where
the particles entering the interferometer are assumed to belong to a
one-parameter family of quons which continuously interpolate between the
Bosonic and Fermionic statistics.Comment: 7 pages, 3 figures; minor editorial changes and new references adde
Filling the Void: A Low Cost, High-Yield Method to Addressing Incidental Findings in Trauma Patients
In this study we:
Report the incidence of incidental findings in a suburban trauma center treating primarily blunt and elderly trauma
Propose simple solutions to increase the rate of disclosure to patientshttps://jdc.jefferson.edu/patientsafetyposters/1070/thumbnail.jp
Experimental realization of strange nonchaotic attractors in a quasiperiodically forced electronic circuit
We have identified the three prominent routes, namely Heagy-Hammel,
fractalization and intermittency routes, and their mechanisms for the birth of
strange nonchaotic attractors (SNAs) in a quasiperiodically forced electronic
system constructed using a negative conductance series LCR circuit with a diode
both numerically and experimentally. The birth of SNAs by these three routes is
verified from both experimental and their corresponding numerical data by
maximal Lyapunov exponents, and their variance, Poincar\'e maps, Fourier
amplitude spectrum, spectral distribution function and finite-time Lyapunov
exponents. Although these three routes have been identified numerically in
different dynamical systems, the experimental observation of all these
mechanisms is reported for the first time to our knowledge and that too in a
single second order electronic circuit.Comment: 21 figure
Influence of blade aerodynamic model on prediction of helicopter rotor aeroacoustic signatures
Brownâs vorticity transport model has been used to investigate how the local blade aerodynamic model influences the quality of the prediction of the high-frequency airloads associated with bladeâvortex interactions, and thus the accuracy with which the acoustic signature of a helicopter rotor can be predicted. The vorticity transport model can accurately resolve the structure of the wake of the rotor and allows significant flexibility in the way that the blade loading can be represented. The Second Higher-Harmonic Control Aeroacoustics Rotor Test was initiated to provide experimental insight into the acoustic signature of a rotor in cases of strong bladeâvortex interaction. Predictions of two models for the local blade aerodynamics are compared with the test data. A marked improvement in accuracy of the predicted high-frequency airloads and acoustic signature is obtained when a lifting-chord model for the blade aerodynamics is used instead of a lifting-line-type approach. Errors in the amplitude and phase of the acoustic peaks are reduced, and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake, with the lifting-chord model producing the best representation of the distribution of sound pressure below the rotor
Bekenstein entropy bound for weakly-coupled field theories on a 3-sphere
We calculate the high temperature partition functions for SU(Nc) or U(Nc)
gauge theories in the deconfined phase on S^1 x S^3, with scalars, vectors,
and/or fermions in an arbitrary representation, at zero 't Hooft coupling and
large Nc, using analytical methods. We compare these with numerical results
which are also valid in the low temperature limit and show that the Bekenstein
entropy bound resulting from the partition functions for theories with any
amount of massless scalar, fermionic, and/or vector matter is always satisfied
when the zero-point contribution is included, while the theory is sufficiently
far from a phase transition. We further consider the effect of adding massive
scalar or fermionic matter and show that the Bekenstein bound is satisfied when
the Casimir energy is regularized under the constraint that it vanishes in the
large mass limit. These calculations can be generalized straightforwardly for
the case of a different number of spatial dimensions.Comment: 32 pages, 12 figures. v2: Clarifications added. JHEP versio
A dynamical systems approach to the tilted Bianchi models of solvable type
We use a dynamical systems approach to analyse the tilting spatially
homogeneous Bianchi models of solvable type (e.g., types VI and VII)
with a perfect fluid and a linear barotropic -law equation of state. In
particular, we study the late-time behaviour of tilted Bianchi models, with an
emphasis on the existence of equilibrium points and their stability properties.
We briefly discuss the tilting Bianchi type V models and the late-time
asymptotic behaviour of irrotational Bianchi VII models. We prove the
important result that for non-inflationary Bianchi type VII models vacuum
plane-wave solutions are the only future attracting equilibrium points in the
Bianchi type VII invariant set. We then investigate the dynamics close to
the plane-wave solutions in more detail, and discover some new features that
arise in the dynamical behaviour of Bianchi cosmologies with the inclusion of
tilt. We point out that in a tiny open set of parameter space in the type IV
model (the loophole) there exists closed curves which act as attracting limit
cycles. More interestingly, in the Bianchi type VII models there is a
bifurcation in which a set of equilibrium points turn into closed orbits. There
is a region in which both sets of closed curves coexist, and it appears that
for the type VII models in this region the solution curves approach a
compact surface which is topologically a torus.Comment: 29 page
Influence of blade aerodynamic model on the prediction of helicopter high-frequency airloads
Brownâs vorticity transport model has been used to investigate the inïŹuence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter bladeâvortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows signiïŹcant ïŹexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to bladeâvortex interactions as the computational grid is reïŹned, exposing the fundamental deïŹciencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach
Observation of twin beam correlations and quadrature entanglement by frequency doubling in a two-port resonator
We demonstrate production of quantum correlated and entangled beams by second
harmonic generation in a nonlinear resonator with two output ports. The output
beams at wavelength 428.5 nm exhibit 0.9 dB of nonclassical intensity
correlations and 0.3 dB of entanglement.Comment: 5 pages, 7 figure
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