2,013 research outputs found
Particle-size characteristics of the vertical dust profiles of two contrasting dust events in the Channel Country of western Queensland, Australia
Spatial and temporal variations in vegetation and soil surface conditions of rangelands add a level of complexity to wind erosion processes which is often difficult to model or measure. Butler and colleagues have developed a methodology which combines computer simulation and experimental measurement to analyse how spatial and temporal changes in dust source area emission rates and atmospheric conditions affect vertical dust concentration profiles during wind erosion events in the Queensland Channel Country. This methodology has not, however, taken into account how variations in dust source area particle-size can affect vertical dust concentration profiles.
The present paper examines how the particle-size characteristics of dust source soils affect both vertical dust concentration profiles and the vertical distribution of particle-sizes in two contrasting wind erosion events in the Queensland Channel Country. Comparisons are made between computer simulations of these events and the results of field measurements (of vertical dust concentration profiles) and laboratory measurements (of dust particle-size). Computer simulations of the particle-size emissions from the different dust source areas during the two events produce vertical distributions of dust particle-sizes which are similar to the measured dust particle-sizes for these events. These results indicate that erodibility-induced spatial and temporal variations in particle-size emissions of dust source areas have important influences upon: dust fluxes, vertical dust concentration profiles and the vertical distribution of dust particle-sizes within these profile
An Inexpensive High-Temporal Resolution Electronic Sun Journal for Monitoring Personal Day to Day Sun Exposure Patterns
Exposure to natural sunlight, specifically solar ultraviolet radiation contributes to lifetime risks of skin cancer, eye disease and diseases associated with vitamin D insufficiency. Improved knowledge of personal sun exposure patterns can inform public health policy; and help target high risk population groups. Subsequently, an extensive number of studies have been conducted to measure personal solar ultraviolet exposure in a variety of settings. Many of these studies however use digital or paper-based journals (self-reported volunteer recall), or employ cost prohibitive electronic ultraviolet dosimeters (that limit the size of sample populations), to estimate periods of exposure. A cost effective personal electronic sun journal built from readily available infrared photodiodes is presented in this research. The electronic sun journal can be used to complement traditional ultraviolet dosimeters that measure total biologically effective exposure by providing a time stamped sun exposure record. The electronic sun journal can be easily attached to clothing and data logged to personal devices (including fitness monitors or smartphones). The electronic sun journal improves upon self-reported exposure recording and is a cost effective high temporal resolution option for monitoring personal sun exposure behavior in large population studies
Sauropod dinosaur tracks from the Purbeck Group (Early Cretaceous) of Spyway Quarry, Dorset, UK
Dinosaur tracks have a long history of discovery and study in the UK, but track sites for sauropodomorph dinosaursâthe group that included the giant, graviportal herbivorous sauropodsâare comparatively rare. Here, we provide a description of a sauropod dinosaur track site at Spyway Quarry in Dorset, southern England. The tracks at Spyway were discovered in the late 1990s and occur in the Stair Hole Member of the Durlston Formation in the Purbeck Limestone Group, of earliest Cretaceous age. More than 130 individual tracks of large sauropod dinosaurs are present at the site, but they are generally poorly preserved and do not form clear trackways, although it is likely that they represent multiple individuals. They provide further evidence for sauropods living in or passing through coastal lagoonal environments. Although poorly preserved, Spyway represents the largest in situ dinosaur track site currently accessible within the Purbeck Group, with considerable potential for further discoveries through ongoing quarrying in the surrounding area
Reduced glomerular filtration in diabetes is attributable to loss of density and increased resistance of glomerular endothelial cell fenestrations
Modelling the perceptual similarity of facial expressions from image statistics and neural responses
The ability to perceive facial expressions of emotion is essential for effective social communication. We investigated how the perception of facial expression emerges from the image properties that convey this important social signal, and how neural responses in face-selective brain regions might track these properties. To do this, we measured the perceptual similarity between expressions of basic emotions, and investigated how this is reflected in image measures and in the neural response of different face-selective regions. We show that the perceptual similarity of different facial expressions (fear, anger, disgust, sadness, happiness) can be predicted by both surface and feature shape information in the image. Using block design fMRI, we found that the perceptual similarity of expressions could also be predicted from the patterns of neural response in the face-selective posterior superior temporal sulcus (STS), but not in the fusiform face area (FFA). These results show that the perception of facial expression is dependent on the shape and surface properties of the image and on the activity of specific face-selective regions
Search for gravitational waves from binary inspirals in S3 and S4 LIGO data
We report on a search for gravitational waves from the coalescence of compact
binaries during the third and fourth LIGO science runs. The search focused on
gravitational waves generated during the inspiral phase of the binary
evolution. In our analysis, we considered three categories of compact binary
systems, ordered by mass: (i) primordial black hole binaries with masses in the
range 0.35 M(sun) < m1, m2 < 1.0 M(sun), (ii) binary neutron stars with masses
in the range 1.0 M(sun) < m1, m2 < 3.0 M(sun), and (iii) binary black holes
with masses in the range 3.0 M(sun)< m1, m2 < m_(max) with the additional
constraint m1+ m2 < m_(max), where m_(max) was set to 40.0 M(sun) and 80.0
M(sun) in the third and fourth science runs, respectively. Although the
detectors could probe to distances as far as tens of Mpc, no gravitational-wave
signals were identified in the 1364 hours of data we analyzed. Assuming a
binary population with a Gaussian distribution around 0.75-0.75 M(sun), 1.4-1.4
M(sun), and 5.0-5.0 M(sun), we derived 90%-confidence upper limit rates of 4.9
yr^(-1) L10^(-1) for primordial black hole binaries, 1.2 yr^(-1) L10^(-1) for
binary neutron stars, and 0.5 yr^(-1) L10^(-1) for stellar mass binary black
holes, where L10 is 10^(10) times the blue light luminosity of the Sun.Comment: 12 pages, 11 figure
Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using Data from the Second, Third, and Fourth LIGO Runs
We present the results of a search for short-duration gravitational-wave
bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray
satellite experiments during LIGO's S2, S3, and S4 science runs. The search
involves calculating the crosscorrelation between two interferometer data
streams surrounding the GRB trigger time. We search for associated
gravitational radiation from single GRBs, and also apply statistical tests to
search for a gravitational-wave signature associated with the whole sample. For
the sample examined, we find no evidence for the association of gravitational
radiation with GRBs, either on a single-GRB basis or on a statistical basis.
Simulating gravitational-wave bursts with sine-gaussian waveforms, we set upper
limits on the root-sum-square of the gravitational-wave strain amplitude of
such waveforms at the times of the GRB triggers. We also demonstrate how a
sample of several GRBs can be used collectively to set constraints on
population models. The small number of GRBs and the significant change in
sensitivity of the detectors over the three runs, however, limits the
usefulness of a population study for the S2, S3, and S4 runs. Finally, we
discuss prospects for the search sensitivity for the ongoing S5 run, and beyond
for the next generation of detectors.Comment: 24 pages, 10 figures, 14 tables; minor changes to text and Fig. 2;
accepted by Phys. Rev.
A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO
The first simultaneous operation of the AURIGA detector and the LIGO
observatory was an opportunity to explore real data, joint analysis methods
between two very different types of gravitational wave detectors: resonant bars
and interferometers. This paper describes a coincident gravitational wave burst
search, where data from the LIGO interferometers are cross-correlated at the
time of AURIGA candidate events to identify coherent transients. The analysis
pipeline is tuned with two thresholds, on the signal-to-noise ratio of AURIGA
candidate events and on the significance of the cross-correlation test in LIGO.
The false alarm rate is estimated by introducing time shifts between data sets
and the network detection efficiency is measured with simulated signals with
power in the narrower AURIGA band. In the absence of a detection, we discuss
how to set an upper limit on the rate of gravitational waves and to interpret
it according to different source models. Due to the short amount of analyzed
data and to the high rate of non-Gaussian transients in the detectors noise at
the time, the relevance of this study is methodological: this was the first
joint search for gravitational wave bursts among detectors with such different
spectral sensitivity and the first opportunity for the resonant and
interferometric communities to unify languages and techniques in the pursuit of
their common goal.Comment: 18 pages, IOP, 12 EPS figure
Searching for gravitational waves from known pulsars
We present upper limits on the amplitude of gravitational waves from 28
isolated pulsars using data from the second science run of LIGO. The results
are also expressed as a constraint on the pulsars' equatorial ellipticities. We
discuss a new way of presenting such ellipticity upper limits that takes
account of the uncertainties of the pulsar moment of inertia. We also extend
our previous method to search for known pulsars in binary systems, of which
there are about 80 in the sensitive frequency range of LIGO and GEO 600.Comment: Accepted by CQG for the proceeding of GWDAW9, 7 pages, 2 figure
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