1,179 research outputs found
Retrodiction as a tool for micromaser field measurements
We use retrodictive quantum theory to describe cavity field measurements by
successive atomic detections in the micromaser. We calculate the state of the
micromaser cavity field prior to detection of sequences of atoms in either the
excited or ground state, for atoms that are initially prepared in the excited
state. This provides the POM elements, which describe such sequences of
measurements.Comment: 20 pages, 4(8) figure
Burning of CP Titanium (Grade 2) in Oxygen-Enriched Atmospheres
The flammability in oxygen-enriched atmospheres of commercially pure (CP) titanium rods as a function of diameter and test gas pressure was determined. Test samples of varying diameters were ignited at the bottom and burned upward in 70% O2/balance N2 and in 99.5+% O2 at various pressures. The burning rate of each ignited sample was determined by observing the apparent regression rate of the melting interface (RRMI) of the burning samples. The burning rate or RRMI increased with decreasing test sample diameter and with increasing test gas pressure and oxygen concentratio
Quantum probability rule : a generalization of the theorems of Gleason and Busch
Buschs theorem deriving the standard quantum probability rule can be regarded as a more general form of Gleasons theorem. Here we show that a further generalization is possible by reducing the number of quantum postulates used by Busch. We do not assume that the positive measurement outcome operators are effects or that they form a probability operator measure. We derive a more general probability rule from which the standard rule can be obtained from the normal laws of probability when there is no measurement outcome information available, without the need for further quantum postulates. Our general probability rule has prediction-retrodiction symmetry and we show how it may be applied in quantum communications and in retrodictive quantum theory
Red Optical Planet Survey : A radial velocity search for low mass M dwarf planets
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedWe present radial velocity results from our Red Optical Planet Survey (ROPS), aimed at detecting low-mass planets orbiting mid-late M dwarfs. The similar to 10 ms(-1) precision achieved over 2 consecutive nights with the MIKE spectrograph at Magellan Clay is also found on week long timescales with UVES at VLT. Since we find that UVES is expected to attain photon limited precision of order 2 ms-1 using our novel deconvolution technique, we are limited only by the
Psychometric Properties of the Altarum Consumer Engagement (ACE) Measure of Activation in Patients with Prediabetes.
BackgroundPatient activation is associated with better outcomes in chronic conditions.ObjectiveWe evaluated the psychometric properties of the 12-item Altarum Consumer Engagement™ Measure (ACE-12) in patients with prediabetes.ParticipantsACE-12 was administered to patients in the Prediabetes Informed Decisions and Education Study.Main measuresWe conducted an exploratory factor analysis followed by confirmatory factor analytic models. We evaluated item response categories using item characteristic curves. Construct validity was assessed by examining correlations of the ACE-12 scales with education, depressive symptoms, self-rated health, hemoglobin A1c, body mass index, and weight loss.Key resultsParticipants (n = 515) had a median age of 58; 56% were female; 17% Hispanic; 54% were non-White. The scree plot and Tucker and Lewis reliability coefficient (0.95) suggested three factors similar to the original scales. One item loaded on the navigation rather than the informed choice scale. Ordinal alpha coefficients for the original scales were commitment (0.75); informed choice (0.71); and navigation (0.54). ICCs indicated that one or more of the response categories for 5 of the 12 items were never most likely to be selected. Patients with lower education were less activated on the commitment (r = - 0.124, p = 0.004), choice (r = - 0.085, p = 0.009), and overall score (r = - 0.042, p = 0.011). Patients with depressive symptoms had lower commitment (r = - 0.313, p ≤ 0.001) and overall scores (r = - 0.172, p = 0.012). Patients with poorer health scored lower on the Commitment (r = - 0.308, p ≤ 0.001), Navigation (r = - 0.137, p ≤ 0.001), and overall score (r = - 0.279, p ≤ 0.001).ConclusionThe analyses provide some support for the psychometric properties of the ACE-12 in prediabetic patients. Future research evaluating this tool among patients with other chronic conditions are needed to determine whether Q1 (I spend a lot of time learning about health) should remain in the informed choice or be included in the navigation scale. Additional items may be needed to yield acceptable reliability for the navigation scale
Interference in dielectrics and pseudo-measurements
Inserting a lossy dielectric into one arm of an interference experiment acts
in many ways like a measurement. If two entangled photons are passed through
the interferometer, a certain amount of information is gained about which path
they took, and the interference pattern in a coincidence count measurement is
suppressed. However, by inserting a second dielectric into the other arm of the
interferometer, one can restore the interference pattern. Two of these
pseudo-measurements can thus cancel each other out. This is somewhat analogous
to the proposed quantum eraser experiments.Comment: 7 pages RevTeX 3.0 + 2 figures (postscript). Submitted to Phys. Rev.
Spectroscopic characterisation of CARMENES target candidates from FEROS, CAFE and HRS high-resolution spectra
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with
Near-infrared and optical Echelle Spectrographs) started a new planet survey on
M-dwarfs in January this year. The new high-resolution spectrographs are
operating in the visible and near-infrared at Calar Alto Observatory. They will
perform high-accuracy radial-velocity measurements (goal 1 m s-1) of about 300
M-dwarfs with the aim to detect low-mass planets within habitable zones. We
characterised the candidate sample for CARMENES and provide fundamental
parameters for these stars in order to constrain planetary properties and
understand star-planet systems. Using state-of-the-art model atmospheres
(PHOENIX-ACES) and chi2-minimization with a downhill-simplex method we
determine effective temperature, surface gravity and metallicity [Fe/H] for
high-resolution spectra of around 480 stars of spectral types M0.0-6.5V taken
with FEROS, CAFE and HRS. We find good agreement between the models and our
observed high-resolution spectra. We show the performance of the algorithm, as
well as results, parameter and spectral type distributions for the CARMENES
candidate sample, which is used to define the CARMENES target sample. We also
present first preliminary results obtained from CARMENES spectra
Propagation of squeezed radiation through amplifying or absorbing random media
We analyse how nonclassical features of squeezed radiation (in particular the
sub-Poissonian noise) are degraded when it is transmitted through an amplifying
or absorbing medium with randomly located scattering centra. Both the cases of
direct photodetection and of homodyne detection are considered. Explicit
results are obtained for the dependence of the Fano factor (the ratio of the
noise power and the mean current) on the degree of squeezing of the incident
state, on the length and the mean free path of the medium, the temperature, and
on the absorption or amplification rate.Comment: 8 pages, 4 figure
- …