1,582 research outputs found
Observation of small scale structure using sextupole lensing
Weak gravitational lensing seeks to determine shear by measuring induced
quadrupole (elliptical) shapes in background galaxy images. Small impact
parameter (a few kpc) gravitational lensing by foreground core masses between 2
10^{9} and 2 10^{12} M_\odot will additionally induce a sextupole shape with
the quadrupole and sextupole minima aligned. This correlation in relative
orientation of the quadrupole and sextupole provides a sensitive method to
identify images which have been slightly curved by lensing events. A general
theoretical framework for sextupole lensing is developed which includes several
low order coefficients in a general lensing map. Tools to impute map
coefficients from the galaxy images are described and applied to the north
Hubble deep field. Instrumental PSFs, camera charge diffusion, and image
composition methods are modelled in the coefficient determination process.
Estimates of Poisson counting noise for each galaxy are used to cut galaxies
with signals too small to reliably establish curvature. Curved galaxies are
found to be spatially clumped, as would be expected if the curving were due to
small impact parameter lensing by localized ensembles of dark matter haloes.
Simulations provide an estimate of the total required lensing mass and the
acceptable mass range of the constituent haloes. The overdensities and
underdensities of visible galaxies and their locations in the Hubble foreground
is found to be consistent with our observations and their interpretation as
lensing events.Comment: 40 pages, 44 figure
The Chemical Basis of Pharmacology
ABSTRACT: Molecular biology now dominates pharmacology so thoroughly that it is difficult to recall that only a generation ago the field was very different. To understand drug action today, we characterize the targets through which they act and new drug leads are discovered on the basis of target structure and function. Until the mid-1980s the information often flowed in reverse: investigators began with organic molecules and sought targets, relating receptors not by sequence or structure but by their ligands. Recently, investigators have returned to this chemical view of biology, bringing to it systematic and quantitative methods of relating targets by their ligands. This has allowed the discovery of new targets for established drugs, suggested the bases for their side effects, and predicted the molecular targets underlying phenotypic screens. The bases for these new methods, some of their successes and liabilities, and new opportunities for their use are described. So dominant has the molecular biology view of pharmacology become that it is difficult to remember that even 25 years ago it was little more than an aspiration. Today we understand the activity of drugs and reagents first through the specific, clonable receptor molecules with which they interact. To understan
Management of Children With Chronic Wet Cough and Protracted Bacterial Bronchitis CHEST Guideline and Expert Panel Report
BACKGROUND: Wet or productive cough is common in children with chronic cough. We formulated recommendations based on systematic reviews related to the management of chronic wet cough in children (aged METHODS: We used the CHEST expert cough panel\u27s protocol for systematic reviews and the American College of Chest Physicians (CHEST) methodologic guidelines and GRADE framework (the Grading of Recommendations Assessment, Development and Evaluation). Data from the systematic reviews in conjunction with patients\u27 values and preferences and the clinical context were used to form recommendations. Delphi methodology was used to obtain consensus for the recommendations/suggestions made. RESULTS: Combining data from the systematic reviews, we found high-quality evidence in children aged 4 weeks\u27 duration) wet/productive cough that using appropriate antibiotics improves cough resolution, and further investigations (eg, flexible bronchoscopy, chest CT scans, immunity tests) should be undertaken when specific cough pointers (eg, digital clubbing) are present. When the wet cough does not improve following 4 weeks of antibiotic treatment, there is moderate-quality evidence that further investigations should be considered to look for an underlying disease. New recommendations include the recognition of the clinical diagnostic entity of protracted bacterial bronchitis. CONCLUSIONS: Compared with the 2006 Cough Guidelines, there is now high-quality evidence for some, but not all, aspects of the management of chronic wet cough in specialist settings. However, further studies (particularly in primary health) are required
Spatial Variations of Jovian Tropospheric Ammonia via Ground-Based Imaging
Optical bandpass-filter observations can be simply processed to determine
similar horizontal ammonia distributions above the Jovian cloud tops as
mid-infrared and microwave observations. Current understanding of this
distribution and its relationship to aerosol opacity, cloud-top pressure, and
circulation is provided by atmospheric retrieval models using observations from
major ground-based facilities and spacecraft. These techniques recover high
fidelity information on the ammonia distribution but are limited in spatial and
temporal coverage. Part of this coverage gap - upper tropospheric abundance -
can be bridged by using continuum-divided ammonia and methane absorption images
as suggested by Combes and Encrenaz [1979]. In 2020-21, Jupiter was imaged in
the 645 nm ammonia absorption band and adjacent continuum bands, demonstrating
that the spatially-resolved optical depth in that band could be determined with
a 0.28-m Schmidt-Cassegrain telescope (SCT). In 2022, a 620 nm filter was added
to include methane absorption images in the same wavelength range. Methane
abundance provides a constant reference against which to determine the ammonia
abundance, specifically the column-averaged mole fraction above the clouds.
VLT/MUSE results are compared to these SCT results and those from the TEXES
mid-infrared spectrometer used on the IRTF and the Gemini telescopes.
Meridional and longitudinal features are examined, including the Equatorial
Zone (EZ) ammonia enhancement, the North Equatorial Belt (NEB) depletion,
depletion above the Great Red Spot (GRS), and suggested enhancements over
bright plumes in the northern EZ. This work demonstrates meaningful ammonia
monitoring that can provide synoptic coverage and continuity between spacecraft
or major ground-based facility campaigns.Comment: 23 pages, 8 figure
Neural modelling, control and optimisation of an industrial grinding process
This paper describes the development of neural model-based control strategies for the optimisation of an industrial aluminium
substrate disk grinding process. The grindstone removal rate varies considerably over a stone life and is a highly nonlinear function
of process variables. Using historical grindstone performance data, a NARX-based neural network model is developed. This model
is then used to implement a direct inverse controller and an internal model controller based on the process settings and previous
removal rates. Preliminary plant investigations show that thickness defects can be reduced by 50% or more, compared to other
schemes employed
The photometric properties of a vast stellar substructure in the outskirts of M33
We have surveyed sq.degrees surrounding M33 with CFHT MegaCam in the
g and i filters, as part of the Pan-Andromeda Archaeological Survey. Our
observations are deep enough to resolve the top 4mags of the red giant branch
population in this galaxy. We have previously shown that the disk of M33 is
surrounded by a large, irregular, low-surface brightness substructure. Here, we
quantify the stellar populations and structure of this feature using the PAndAS
data. We show that the stellar populations of this feature are consistent with
an old population with dex and an interquartile range in
metallicity of dex. We construct a surface brightness map of M33 that
traces this feature to mags\,arcsec. At these low surface
brightness levels, the structure extends to projected radii of kpc from
the center of M33 in both the north-west and south-east quadrants of the
galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns
with the orientation of the HI disk warp. We calculate a lower limit to the
integrated luminosity of the structure of mags, comparable to a
bright dwarf galaxy such as Fornax or AndII and slightly less than $1\$ of the
total luminosity of M33. Further, we show that there is tentative evidence for
a distortion in the distribution of young stars near the edge of the HI disk
that occurs at similar azimuth to the warp in HI. The data also hint at a
low-level, extended stellar component at larger radius that may be a M33 halo
component. We revisit studies of M33 and its stellar populations in light of
these new results, and we discuss possible formation scenarios for the vast
stellar structure. Our favored model is that of the tidal disruption of M33 in
its orbit around M31.Comment: Accepted for publication in ApJ. 17 figures. ApJ preprint forma
The Implications of M Dwarf Flares on the Detection and Characterization of Exoplanets at Infrared Wavelengths
We present the results of an observational campaign which obtained high time
cadence, high precision, simultaneous optical and IR photometric observations
of three M dwarf flare stars for 47 hours. The campaign was designed to
characterize the behavior of energetic flare events, which routinely occur on M
dwarfs, at IR wavelengths to milli-magnitude precision, and quantify to what
extent such events might influence current and future efforts to detect and
characterize extrasolar planets surrounding these stars. We detected and
characterized four highly energetic optical flares having U-band total energies
of ~7.8x10^30 to ~1.3x10^32 ergs, and found no corresponding response in the J,
H, or Ks bandpasses at the precision of our data. For active dM3e stars, we
find that a ~1.3x10^32 erg U-band flare (delta Umax ~1.5 mag) will induce <8.3
(J), <8.5 (H), and <11.7 (Ks) milli-mags of a response. A flare of this energy
or greater should occur less than once per 18 hours. For active dM4.5e stars,
we find that a ~5.1x10^31 erg U-band flare (delta Umax ~1.6 mag) will induce
<7.8 (J), <8.8 (H), and <5.1 (Ks) milli-mags of a response. A flare of this
energy or greater should occur less than once per 10 hours. No evidence of
stellar variability not associated with discrete flare events was observed at
the level of ~3.9 milli-mags over 1 hour time-scales and at the level of ~5.6
milli-mags over 7.5 hour time-scales. We therefore demonstrate that most M
dwarf stellar activity and flares will not influence IR detection and
characterization studies of M dwarf exoplanets above the level of ~5-11
milli-mags, depending on the filter and spectral type. We speculate that the
most energetic megaflares on M dwarfs, which occur at rates of once per month,
are likely to be easily detected in IR observations with sensitivity of tens of
milli-mags.Comment: Accepted in Astronomical Journal, 17 pages, 6 figure
Probabilistic classification of acute myocardial infarction from multiple cardiac markers
Logistic regression and Gaussian mixture model (GMM) classifiers have been trained to estimate the probability of acute myocardial infarction (AMI) in patients based upon the concentrations of a panel of cardiac markers. The panel consists of two new markers, fatty acid binding protein (FABP) and glycogen phosphorylase BB (GPBB), in addition to the traditional cardiac troponin I (cTnI), creatine kinase MB (CKMB) and myoglobin. The effect of using principal component analysis (PCA) and Fisher discriminant analysis (FDA) to preprocess the marker concentrations was also investigated. The need for classifiers to give an accurate estimate of the probability of AMI is argued and three categories of performance measure are described, namely discriminatory ability, sharpness, and reliability. Numerical performance measures for each category are given and applied. The optimum classifier, based solely upon the samples take on admission, was the logistic regression classifier using FDA preprocessing. This gave an accuracy of 0.85 (95% confidence interval: 0.78–0.91) and a normalised Brier score of 0.89. When samples at both admission and a further time, 1–6 h later, were included, the performance increased significantly, showing that logistic regression classifiers can indeed use the information from the five cardiac markers to accurately and reliably estimate the probability AMI
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