9,936 research outputs found
Patient-maintained sedation for oral surgery using a target-controlled infusion of propofol - a pilot study
OBJECTIVE: To assess the safety and efficacy of a new patient-maintained propofol system for conscious sedation in dentistry. DESIGN: Prospective clinical trial SETTING: Department of Sedation, Glasgow Dental Hospital and School, 2001 SUBJECTS AND METHODS: Patients scheduled for oral surgery with conscious sedation. Exclusions included ASA IV -V, inability to use the handset, opioid use and severe respiratory disease. INTERVENTIONS: Patients were given intravenous propofol to a level of 1.0 microg/ml (reducing from 1.5 microg/ml) using a target controlled infusion system, they then controlled their sedation level by double-clicking a handset which on each activation increased the propofol concentration by 0.2 microg/ml. MAIN OUTCOME MEASURES: Oxygen saturation, patient satisfaction, and surgeon satisfaction. RESULTS: Twenty patients were recruited, 16 female and four male. Nineteen patients completed sedation and treatment successfully. Mean lowest oxygen saturation was 94%. No patients were over-sedated. All patients successfully used the system to maintain a level of sedation adequate for their comfort. Patient and surgeon satisfaction were consistently high. CONCLUSIONS: Initial experience with this novel system has confirmed safety, patient satisfaction and surgeon satisfaction
An efficient semiparametric maxima estimator of the extremal index
The extremal index , a measure of the degree of local dependence in
the extremes of a stationary process, plays an important role in extreme value
analyses. We estimate semiparametrically, using the relationship
between the distribution of block maxima and the marginal distribution of a
process to define a semiparametric model. We show that these semiparametric
estimators are simpler and substantially more efficient than their parametric
counterparts. We seek to improve efficiency further using maxima over sliding
blocks. A simulation study shows that the semiparametric estimators are
competitive with the leading estimators. An application to sea-surge heights
combines inferences about with a standard extreme value analysis of
block maxima to estimate marginal quantiles.Comment: 17 pages, 7 figures. Minor edits made to version 1 prior to journal
publication. The final publication is available at Springer via
http://dx.doi.org/10.1007/s10687-015-0221-
A fitting formula for the non-Gaussian contribution to the lensing power spectrum covariance
Weak gravitational lensing is one of the most promising tools to investigate
the equation-of-state of dark energy. In order to obtain reliable parameter
estimations for current and future experiments, a good theoretical
understanding of dark matter clustering is essential. Of particular interest is
the statistical precision to which weak lensing observables, such as cosmic
shear correlation functions, can be determined. We construct a fitting formula
for the non-Gaussian part of the covariance of the lensing power spectrum. The
Gaussian contribution to the covariance, which is proportional to the lensing
power spectrum squared, and optionally shape noise can be included easily by
adding their contributions. Starting from a canonical estimator for the
dimensionless lensing power spectrum, we model first the covariance in the halo
model approach including all four halo terms for one fiducial cosmology and
then fit two polynomials to the expression found. On large scales, we use a
first-order polynomial in the wave-numbers and dimensionless power spectra that
goes asymptotically towards for , i.e., the result for
the non-Gaussian part of the covariance using tree-level perturbation theory.
On the other hand, for small scales we employ a second-order polynomial in the
dimensionless power spectra for the fit. We obtain a fitting formula for the
non-Gaussian contribution of the convergence power spectrum covariance that is
accurate to 10% for the off-diagonal elements, and to 5% for the diagonal
elements, in the range and can be used for
single source redshifts in WMAP5-like cosmologies.Comment: 23 pages, 15 figures, submitted to A&
A redshift distortion free correlation function at third order in the nonlinear regime
The zeroth-order component of the cosine expansion of the projected
three-point correlation function is proposed for clustering analysis of cosmic
large scale structure. These functions are third order statistics but can be
measured similarly to the projected two-point correlations. Numerical
experiments with N-body simulations indicate that the advocated statistics are
redshift distortion free within 10% in the non-linear regime on scales
~0.2-10Mpc/h. Halo model prediction of the zeroth-order component of the
projected three-point correlation function agrees with simulations within ~10%.
This lays the ground work for using these functions to perform joint analyses
with the projected two-point correlation functions, exploring galaxy clustering
properties in the framework of the halo model and relevant extensions.Comment: 10 pages, 6 figs; MNRAS accepte
The Impact of Non-Gaussian Errors on Weak Lensing Surveys
The weak lensing power spectrum carries cosmological information via its
dependence on the growth of structure and on geometric factors. Since much of
the cosmological information comes from scales affected by nonlinear
clustering, measurements of the lensing power spectrum can be degraded by
non-Gaussian covariances. Recently there have been conflicting studies about
the level of this degradation. We use the halo model to estimate it and include
new contributions related to the finite size of lensing surveys, following
Rimes and Hamilton's study of 3D simulations. We find that non-Gaussian
correlations between different multipoles can degrade the cumulative
signal-to-noise for the power spectrum amplitude by up to a factor of 2 (or 5
for a worst-case model that exceeds current N-body simulation predictions).
However, using an eight-parameter Fisher analysis we find that the marginalized
errors on individual parameters are degraded by less than 10% (or 20% for the
worst-case model). The smaller degradation in parameter accuracy is primarily
because: individual parameters in a high-dimensional parameter space are
degraded much less than the volume of the full Fisher ellipsoid; lensing
involves projections along the line of sight, which reduce the non-Gaussian
effect; some of the cosmological information comes from geometric factors which
are not degraded at all. We contrast our findings with those of Lee & Pen
(2008) who suggested a much larger degradation in information content. Finally,
our results give a useful guide for exploring survey design by giving the
cosmological information returns for varying survey area, depth and the level
of some systematic errors.Comment: To appear in MNRAS, 22 pages, 12 figures. Minor modifications made
according to the referee comment
Automated metamorphic testing on the analyses of feature models
Copyright © 2010 Elsevier B.V. All rights reserved.Context: A feature model (FM) represents the valid combinations of features in a domain. The automated extraction of information from FMs is a complex task that involves numerous analysis operations, techniques and tools. Current testing methods in this context are manual and rely on the ability of the tester to decide whether the output of an analysis is correct. However, this is acknowledged to be time-consuming, error-prone and in most cases infeasible due to the combinatorial complexity of the analyses, this is known as the oracle problem.Objective: In this paper, we propose using metamorphic testing to automate the generation of test data for feature model analysis tools overcoming the oracle problem. An automated test data generator is presented and evaluated to show the feasibility of our approach.Method: We present a set of relations (so-called metamorphic relations) between input FMs and the set of products they represent. Based on these relations and given a FM and its known set of products, a set of neighbouring FMs together with their corresponding set of products are automatically generated and used for testing multiple analyses. Complex FMs representing millions of products can be efficiently created by applying this process iteratively.Results: Our evaluation results using mutation testing and real faults reveal that most faults can be automatically detected within a few seconds. Two defects were found in FaMa and another two in SPLOT, two real tools for the automated analysis of feature models. Also, we show how our generator outperforms a related manual suite for the automated analysis of feature models and how this suite can be used to guide the automated generation of test cases obtaining important gains in efficiency.Conclusion: Our results show that the application of metamorphic testing in the domain of automated analysis of feature models is efficient and effective in detecting most faults in a few seconds without the need for a human oracle.This work has been partially supported by the European Commission(FEDER)and Spanish Government under CICYT project SETI(TIN2009-07366)and the Andalusian Government project ISABEL(TIC-2533)
Self calibration of photometric redshift scatter in weak lensing surveys
Photo-z errors, especially catastrophic errors, are a major uncertainty for
precision weak lensing cosmology. We find that the shear-(galaxy number)
density and density-density cross correlation measurements between photo-z
bins, available from the same lensing surveys, contain valuable information for
self-calibration of the scattering probabilities between the true-z and photo-z
bins. The self-calibration technique we propose does not rely on cosmological
priors nor parameterization of the photo-z probability distribution function,
and preserves all of the cosmological information available from shear-shear
measurement. We estimate the calibration accuracy through the Fisher matrix
formalism. We find that, for advanced lensing surveys such as the planned stage
IV surveys, the rate of photo-z outliers can be determined with statistical
uncertainties of 0.01-1% for galaxies. Among the several sources of
calibration error that we identify and investigate, the {\it galaxy
distribution bias} is likely the most dominant systematic error, whereby
photo-z outliers have different redshift distributions and/or bias than
non-outliers from the same bin. This bias affects all photo-z calibration
techniques based on correlation measurements. Galaxy bias variations of
produce biases in photo-z outlier rates similar to the statistical
errors of our method, so this galaxy distribution bias may bias the
reconstructed scatters at several- level, but is unlikely to completely
invalidate the self-calibration technique.Comment: v2: 19 pages, 10 figures. Added one figure. Expanded discussions.
Accepted to MNRA
Effects of halo substructure on the power spectrum and bispectrum
We study the effects of halo substructure and a distribution in the
concentration parameter of haloes on large-scale structure statistics. The
effects on the power spectrum and bispectrum are studied on the smallest scales
accessible from future surveys. We compare halo-model predictions with results
based on N-body simulations, but also extend our predictions to 10-kpc scales
which will be probed by future simulations. We find that weak-lensing surveys
proposed for the coming decade can probe the power spectrum on small enough
scales to detect substructure in massive haloes. We discuss the prospects of
constraining the mass fraction in substructure in view of partial degeneracies
with parameters such as the tilt and running of the primordial power spectrum.Comment: 9 pages, 10 figures; replaced with version published in MNRAS;
removed grey-scale versions of figures which were being included at the end
by the serve
Multicolor Photometry Study of the Galaxy Cluster A2589: Dynamics, Luminosity Function and Star Formation History
In this paper we present a multicolor photometry for A2589 () with
15 intermediate bands in the Beijing-Arizona-Taiwan-Connecticut (BATC) system
which covers an optical wavelength range from 3000 \AA\ to 10000 \AA. The
spectral energy distributions (SEDs) for more than 5000 sources are achieved
down to {\it V} 20 mag in about 1 deg field. A2589 has been also
covered by the Sloan Digital Sky Survey (SDSS) in photometric mode only. A
cross-identification of the BATC-detected galaxies with the SDSS photometric
catalog achieves 1199 galaxies brighter than mag, among which 68
member galaxies with known spectroscopic redshifts are found. After combining
the SDSS five-band photometric data and the BATC SEDs, the technique of
photometric redshift is applied to these galaxies for selecting faint member
galaxies. The color-magnitude relation is taken as a further restriction of
early-type cluster galaxies. As a result, 106 galaxies are newly selected as
member galaxies. Spatial distribution of member galaxies shows a north-south
elongation which agrees with the X-ray brightness profile and the orientation
of central cD galaxy, NGC 7647. No substructures are detected on the basis of
positions and radial velocities of cluster galaxies, indicating that A2589 is a
well-relaxed system. The luminosity function of A2589 exhibits a peak at mag and a dip at mag. The low-density outer regions
are the preferred habitat of faint galaxies. With the evolutionary population
synthesis model, PEGASE, the environmental effect on the star formation
properties for 68 spectroscopically confirmed member galaxies is studied. The
outlier faint galaxies tend to have longer time scales of star formation,
shorter mean stellar ages, and lower metallicities of interstellar medium,
which can be interpreted in the context of hierarchical cosmological scenario.Comment: 2011 Accepted to A
ROSAT X-ray sources in the field of the LMC I.Total LMC gas from the background AGN spectral fits
We analyzed a sample of 26 background X-ray sources in a ~60 square degree
field of the Large Magellanic Cloud observed with the ROSAT PSPC. The sample
has been selected from previously classified and optically identified X-ray
sources. In addition pointlike and spectrally hard sources with at least 100 to
200 observed counts have been used for the analysis. We performed X-ray
spectral fitting and derived total hydrogen absorbing column densities due to
LMC gas in the range 10^20 - 2. 10^21 cm^-2. We compared these columns with the
HI columns derived from a 21-cm Parkes survey of the LMC. For 7 optically
identified sources we find, within the uncertainties derived from the X-ray
spectral fit, agreement for both columns. For further 19 sources we constrain
the LMC columns from the X-ray spectral fit assuming that the powerlaw photon
index is that of AGN type spectra. We derive for 20 sources gas columns which
are within the uncertainties in agreement with the HI columns. We derive for
two background sources (RX J0536.9-6913 and RX J0547.0-7040) hydrogen absorbing
column densities due to LMC gas, which are in excess to the HI columns. These
sources - located in regions of large (~3. 10^21 cm^-2) LMC HI column densities
- could be seen through additional gas which may be warm and diffuse, cold or
molecular. For 10 sources we derive upper limits for the gas columns additional
to HI and constrain the molecular mass fraction to <(30-140)%.Comment: Accepted by A&
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