6,491 research outputs found
The Optimal Single Copy Measurement for the Hidden Subgroup Problem
The optimization of measurements for the state distinction problem has
recently been applied to the theory of quantum algorithms with considerable
successes, including efficient new quantum algorithms for the non-abelian
hidden subgroup problem. Previous work has identified the optimal single copy
measurement for the hidden subgroup problem over abelian groups as well as for
the non-abelian problem in the setting where the subgroups are restricted to be
all conjugate to each other. Here we describe the optimal single copy
measurement for the hidden subgroup problem when all of the subgroups of the
group are given with equal a priori probability. The optimal measurement is
seen to be a hybrid of the two previously discovered single copy optimal
measurements for the hidden subgroup problem.Comment: 8 pages. Error in main proof fixe
Recurrence rates for SIDS - the importance of risk stratification
Objective:
To investigate the importance of stratification by risk factors in computing the probability of a second SIDS in a family.
Design: Simulation Study
Background:
The fact that a baby dies suddenly and unexpectedly means that there is a raised probability that the baby’s family have risk factors associated with Sudden Infant Death Syndrome (SIDS). Thus one cannot consider the risk of a subsequent death to be that of the general population. The Confidential Enquiry into Stillbirths and Deaths in Infancy (CESDI)6 identified three major social risk factors: smoking, age1, and unemployed/unwaged as major risk factors. It gave estimates of risk for families with different numbers of these risk factors. We investigate whether it is reasonable to assume that, conditional on these risk factors, the risk of a second event is independent of the risk of the first and as a consequence one can square the risks to get the risk of two SIDS in a family. We have used CESDI data to estimate the probability of a second SID in a family under different plausible scenarios of the prevalence of the risk factors. We have applied the model to make predictions in the Care of Next Infant (CONI) study7.
Results:
The model gave plausible predictions. The CONI study observed 18 second SIDS. Our model predicted 14 (95% prediction interval 7 to 21).
Conclusion:
When considering the risk of a subsequent SIDS in a family one should always take into account the known risk factors. If all risks have been identified, then conditional on these risks, the risk of two events is the product of the individual risks However for a given family we cannot quantify the magnitude of the increased risk because of other possible risk factors not accounted for in the model
A double-helix neutron detector using micron-size B-10 powder
A double-helix electrode configuration is combined with a B powder
coating technique to build large-area (9 in 36 in) neutron detectors.
The neutron detection efficiency for each of the four prototypes is comparable
to a single 2-bar He drift tube of the same length (36 in). One unit has
been operational continuously for 18 months and the change of efficiency is
less than 1%. An analytic model for pulse heigh spectra is described and the
predicted mean film thickness agrees with the experiment to within 30%. Further
detector optimization is possible through film texture, power size, moderator
box and gas. The estimated production cost per unit is less than 3k US\$ and
the technology is thus suitable for deployment in large numbers
ANALYSIS OF TRENDS AND FORECASTS IN COFFEE PRICES AND CONSUMER CONSUMPTION IN THE NORTHEAST AND UNITED STATES
Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,
AN ANALYSIS OF CONSUMER PREFERENCES FOR DELAWARE FARMER DIRECT MARKETS
Consumer/Household Economics,
Delensing Gravitational Wave Standard Sirens with Shear and Flexion Maps
Supermassive black hole binary systems (SMBHB) are standard sirens -- the
gravitational wave analogue of standard candles -- and if discovered by
gravitational wave detectors, they could be used as precise distance
indicators. Unfortunately, gravitational lensing will randomly magnify SMBHB
signals, seriously degrading any distance measurements. Using a weak lensing
map of the SMBHB line of sight, we can estimate its magnification and thereby
remove some uncertainty in its distance, a procedure we call "delensing." We
find that delensing is significantly improved when galaxy shears are combined
with flexion measurements, which reduce small-scale noise in reconstructed
magnification maps. Under a Gaussian approximation, we estimate that delensing
with a 2D mosaic image from an Extremely Large Telescope (ELT) could reduce
distance errors by about 30-40% for a SMBHB at z=2. Including an additional
wide shear map from a space survey telescope could reduce distance errors by
50%. Such improvement would make SMBHBs considerably more valuable as
cosmological distance probes or as a fully independent check on existing
probes.Comment: 9 pages, 4 figures, submitted to MNRA
Integral-Field Spectroscopy of the Post Red Supergiant IRC +10420: evidence for an axi-symmetric wind
We present NAOMI/OASIS adaptive-optics assisted integral-field spectroscopy
of the transitional massive hypergiant IRC +10420, an extreme mass-losing star
apparently in the process of evolving from a Red Supergiant toward the
Wolf-Rayet phase. To investigate the present-day mass-loss geometry of the
star, we study the appearance of the line-emission from the inner wind as
viewed when reflected off the surrounding nebula. We find that, contrary to
previous work, there is strong evidence for wind axi-symmetry, based on the
equivalent-width and velocity variations of H and Fe {\sc ii}
6516. We attribute this behaviour to the appearance of the complex
line-profiles when viewed from different angles. We also speculate that the Ti
{\sc ii} emission originates in the outer nebula in a region analogous to the
Strontium Filament of Carinae, based on the morphology of the
line-emission. Finally, we suggest that the present-day axisymmetric wind of
IRC +10420, combined with its continued blueward evolution, is evidence that
the star is evolving toward the B[e] supergiant phase.Comment: 22 pages, 9 figures, accepted for publication in ApJ. B&W-optimized
version can be downloaded from http://www.cis.rit.edu/~bxdpci/pubs.htm
Multipole expansion for H I intensity mapping experiments: simulations and modelling
We present a framework and an open-source python toolkit to analyse the
2-point statistics of 3D fluctuations in the context of HI intensity maps using
the multipole expansion formalism. We include simulations of the cosmological
HI signal using N-body and log-normal methods, foregrounds and their removal,
as well as instrumental effects. Using these simulations and analytical
modelling, we investigate the impact of foreground cleaning and the
instrumental beam on the power spectrum multipoles as well as on the Fourier
space clustering wedges. We find that both the instrumental beam and the
foreground removal can produce a quadrupole (and a hexadecapole) signal, and
demonstrate the importance of controlling and accurately modelling these
effects for precision radio cosmology. We conclude that these effects can be
modelled with reasonable accuracy using our multipole expansion technique. We
also perform an MCMC analysis to showcase the effect of foreground cleaning on
the estimation of the HI abundance and bias parameters. The accompanying python
toolkit is available at https://github.com/IntensityTools/MultipoleExpansion,
and includes an interactive suite of examples to aid new users.Comment: 21 pages, 14 figure
- …