10,832 research outputs found
A Model for the Effectiveness of Aircraft Alerting and Warning Systems
The effectiveness of an alerting system with a single alert was analyzed. The pilot's decision behavior is modeled by the theory of signal detection and therefore accounts for different strengths of cross check information and different pilot criteria. The model includes the effects of the alerting and warning system (CAWS) error rate; the pilot's past experience with the CAWS accuracy; his reliance on the CAWS rather than independent monitoring; missed alerts; and adoption of a minimum error or Neyman-Pearson objective rather than minimum cost objective. It is showwn that for rare events: (1) the expected cost is greatly increased if the pilot ignores the a posteriori information in the existence of an alert; (2) the expected cost is insensitive to CAWS Type 1 errors; and (3) the expected cost is sensitive to CAWS type 2 errors only when the cross check information is ambiguous
Evaluation of the effects of space environment exposure on index of refraction and extinction coefficients of Apollo window materials
Temperature and radiation effects on index of refraction and extinction coefficients of Apollo window material
A low-loss, broadband antenna for efficient photon collection from a coherent spin in diamond
We report the creation of a low-loss, broadband optical antenna giving highly
directed output from a coherent single spin in the solid-state. The device, the
first solid-state realization of a dielectric antenna, is engineered for
individual nitrogen vacancy (NV) electronic spins in diamond. We demonstrate a
directionality close to 10. The photonic structure preserves the high spin
coherence of single crystal diamond (T2>100us). The single photon count rate
approaches a MHz facilitating efficient spin readout. We thus demonstrate a key
enabling technology for quantum applications such as high-sensitivity
magnetometry and long-distance spin entanglement.Comment: 5 pages, 4 figures and supplementary information (5 pages, 8
figures). Comments welcome. Further information under
http://www.quantum-sensing.physik.unibas.c
Ultra-bright and efficient single photon generation based on N-V centres in nanodiamonds on a solid immersion lens
Single photons are fundamental elements for quantum information technologies
such as quantum cryptography, quantum information storage and optical quantum
computing. Colour centres in diamond have proven to be stable single photon
sources and thus essential components for reliable and integrated quantum
information technology. A key requirement for such applications is a large
photon flux and a high efficiency. Paying tribute to various attempts to
maximise the single photon flux we show that collection efficiencies of photons
from colour centres can be increased with a rather simple experimental setup.
To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colour
centres on the flat surface of a ZrO2 solid immersion lens. We found stable
single photon count rates of up to 853 kcts/s at saturation under continuous
wave excitation while having excess to more than 100 defect centres with count
rates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we found
count rates up to 2.4 Mcts/s for time intervals of several ten seconds. It
seems to be a general feature that very high rates are accompanied by a
blinking behaviour. The overall collection efficiency of our setup of up to
4.2% is the highest yet reported for N-V defect centres in diamond. Under
pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a
click on the detector adding to 221 kcts/s thus opening the way towards diamond
based on-demand single photon sources for quantum applications
Ketoacidosis at Diabetes Onset Is Still Frequent in Children and Adolescents: A multicenter analysis of 14,664 patients from 106 institutions
Like-charge attraction through hydrodynamic interaction
We demonstrate that the attractive interaction measured between like-charged
colloidal spheres near a wall can be accounted for by a nonequilibrium
hydrodynamic effect. We present both analytical results and Brownian dynamics
simulations which quantitatively capture the one-wall experiments of Larsen and
Grier (Nature 385, p. 230, 1997).Comment: 10 pages, 4 figure
Contributors to the January Issue/Notes
Notes by John J. Killen, James H. Neu, John W. Hackett, Jr., James E. Diver, James C. Daner, Richard F. Swisher, and Leo L. Linck
Contributors to the January Issue/Notes
Notes by John J. Killen, James H. Neu, John W. Hackett, Jr., James E. Diver, James C. Daner, Richard F. Swisher, and Leo L. Linck
Incorporating Inductances in Tissue-Scale Models of Cardiac Electrophysiology
In standard models of cardiac electrophysiology, including the bidomain and
monodomain models, local perturbations can propagate at infinite speed. We
address this unrealistic property by developing a hyperbolic bidomain model
that is based on a generalization of Ohm's law with a Cattaneo-type model for
the fluxes. Further, we obtain a hyperbolic monodomain model in the case that
the intracellular and extracellular conductivity tensors have the same
anisotropy ratio. In one spatial dimension, the hyperbolic monodomain model is
equivalent to a cable model that includes axial inductances, and the relaxation
times of the Cattaneo fluxes are strictly related to these inductances. A
purely linear analysis shows that the inductances are negligible, but models of
cardiac electrophysiology are highly nonlinear, and linear predictions may not
capture the fully nonlinear dynamics. In fact, contrary to the linear analysis,
we show that for simple nonlinear ionic models, an increase in conduction
velocity is obtained for small and moderate values of the relaxation time. A
similar behavior is also demonstrated with biophysically detailed ionic models.
Using the Fenton-Karma model along with a low-order finite element spatial
discretization, we numerically analyze differences between the standard
monodomain model and the hyperbolic monodomain model. In a simple benchmark
test, we show that the propagation of the action potential is strongly
influenced by the alignment of the fibers with respect to the mesh in both the
parabolic and hyperbolic models when using relatively coarse spatial
discretizations. Accurate predictions of the conduction velocity require
computational mesh spacings on the order of a single cardiac cell. We also
compare the two formulations in the case of spiral break up and atrial
fibrillation in an anatomically detailed model of the left atrium, and [...].Comment: 20 pages, 12 figure
Engineering chromium related single photon emitters in single crystal diamond
Color centers in diamond as single photon emitters, are leading candidates
for future quantum devices due to their room temperature operation and
photostability. The recently discovered chromium related centers are
particularly attractive since they possess narrow bandwidth emission and a very
short lifetime. In this paper we investigate the fabrication methodologies to
engineer these centers in monolithic diamond. We show that the emitters can be
successfully fabricated by ion implantation of chromium in conjunction with
oxygen or sulfur. Furthermore, our results indicate that the background
nitrogen concentration is an important parameter, which governs the probability
of success to generate these centers.Comment: 14 pages, 5 figure
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