5,106 research outputs found
Thirty-fold: Extreme gravitational lensing of a quiescent galaxy at
We report the discovery of eMACSJ1341-QG-1, a quiescent galaxy at
located behind the massive galaxy cluster eMACSJ1341.92442 (). The
system was identified as a gravitationally lensed triple image in Hubble Space
Telescope images obtained as part of a snapshot survey of the most X-ray
luminous galaxy clusters at and spectroscopically confirmed in
ground-based follow-up observations with the ESO/X-Shooter spectrograph. From
the constraints provided by the triple image, we derive a first, crude model of
the mass distribution of the cluster lens, which predicts a gravitational
amplification of a factor of 30 for the primary image and a factor of
6 for the remaining two images of the source, making eMACSJ1341-QG-1 by
far the most strongly amplified quiescent galaxy discovered to date. Our
discovery underlines the power of SNAPshot observations of massive, X-ray
selected galaxy clusters for lensing-assisted studies of faint background
populations
The size-star formation relation of massive galaxies at 1.5<z<2.5
We study the relation between size and star formation activity in a complete
sample of 225 massive (M > 5 x 10^10 Msun) galaxies at 1.5<z<2.5, selected from
the FIREWORKS UV-IR catalog of the CDFS. Based on stellar population synthesis
model fits to the observed restframe UV-NIR SEDs, and independent MIPS 24
micron observations, 65% of galaxies are actively forming stars, while 35% are
quiescent. Using sizes derived from 2D surface brightness profile fits to high
resolution (FWHM_{PSF}~0.45 arcsec) groundbased ISAAC data, we confirm and
improve the significance of the relation between star formation activity and
compactness found in previous studies, using a large, complete mass-limited
sample. At z~2, massive quiescent galaxies are significantly smaller than
massive star forming galaxies, and a median factor of 0.34+/-0.02 smaller than
galaxies of similar mass in the local universe. 13% of the quiescent galaxies
are unresolved in the ISAAC data, corresponding to sizes <1 kpc, more than 5
times smaller than galaxies of similar mass locally. The quiescent galaxies
span a Kormendy relation which, compared to the relation for local early types,
is shifted to smaller sizes and brighter surface brightnesses and is
incompatible with passive evolution. The progenitors of the quiescent galaxies,
were likely dominated by highly concentrated, intense nuclear star bursts at
z~3-4, in contrast to star forming galaxies at z~2 which are extended and
dominated by distributed star formation.Comment: 6 pages, 4 figures, accepted for publication in Ap
Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor
The upgrade of the cold neutron triple-axis spectrometer FLEXX is described.
We discuss the characterisation of the gains from the new primary spectrometer,
including a larger guide and double focussing monochromator, and present
measurements of the energy and momentum resolution and of the neutron flux of
the instrument. We found an order of magnitude gain in intensity (at the cost
of coarser momentum resolution), and that the incoherent elastic energy widths
are measurably narrower than before the upgrade. The much improved count rate
should allow the use of smaller single crystals samples and thus enable the
upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table
Trace ideals for Fourier integral operators with non-smooth symbols II
We consider Fourier integral operators with symbols in modulation spaces and
non-smooth phase functions whose second orders of derivatives belong to certain
types of modulation space. We establish continuity and Schatten-von Neumann
properties of such operators when acting on modulation spaces.Comment: 25 page
A prospective observational longitudinal study of new-onset seizures and newly diagnosed epilepsy in dogs
BACKGROUND: Seizures are common in dogs and can be caused by non-epileptic conditions or epilepsy. The clinical course of newly diagnosed epilepsy is sparsely documented. The objective of this study was to prospectively investigate causes for seizures (epileptic and non-epileptic) in a cohort of dogs with new-onset untreated seizures, and for those dogs with newly diagnosed epilepsy to investigate epilepsy type, seizure type and the course of disease over time, including the risk of seizure recurrence. Untreated client-owned dogs experiencing new-onset seizures were prospectively enrolled in a longitudinal observational study including clinical investigations and long-term monitoring at the Copenhagen University Hospital for Companion Animals. A baseline clinical assessment was followed by investigator/owner contact every eight weeks from inclusion to death or end of study. Inclusion of dogs was conducted from November 2010 to September 2012, and the study terminated in June 2014. RESULTS: One hundred and six dogs were included in the study. Seventy-nine dogs (74.5%) were diagnosed with epilepsy: 61 dogs (77.2%) with idiopathic epilepsy, 13 dogs (16.5%) with structural epilepsy and five dogs (6.3%) with suspected structural epilepsy. A non-epileptic cause for seizures was identified in 13 dogs and suspected in 10 dogs. Four dogs in which no cause for seizures was identified experienced only one seizure during the study. In dogs with idiopathic epilepsy 60% had their second epileptic seizure within three months of seizure onset. Twenty-six dogs with idiopathic epilepsy (43%) completed the study without receiving antiepileptic treatment. The natural course of idiopathic epilepsy (uninfluenced by drugs) was illustrated by highly individual and fluctuating seizure patterns, including long periods of remission. Cluster seizures motivated early treatment. In a few dogs with a high seizure frequency owners declined treatment against the investigators advice. CONCLUSIONS: Epilepsy is the most likely diagnosis in dogs presenting with new-onset seizures. The course of idiopathic epilepsy is highly individual and might not necessarily require long-term treatment. This must be considered when advising owners about what to expect with regard to treatment and prognosis
Increasing safe design practice within the engineering curriculum
CONTEXT The Australian Work Health and Safety Strategy 2012-2022 contains two national Action Areas of direct relevance to Engineering Educators: Healthy and safe by design and Health and safety capabilities. The need for designs to be safe, and for student engineers to develop competencies in this area, is not new. However, poor design of machinery plant and powered tools continues to kill and injure Australian workers. Safe Work Australia (2014) reports that between 2006 and 2011, 63 workrelated deaths were determined to be caused by the unsafe design of machinery plant and power tools, or design-related factors contributed to the fatality. A further 125 fatalities were considered as possibly design-related. It is sad fact that many of these deaths were preventable with existing design solutions. Good design can eliminate (or minimise the impact of) the major physical, biomechanical and psychosocial hazards associated with work. From an engineering education perspective it is necessary to increase awareness amongst educators and students of these processes such that consideration of safe design is inherent to the engineering design process and not simply an added regulatory requirement. PURPOSE Safe design is not a separate activity or series of activities, but is integral to the engineering process regardless of sector or discipline. This paper reviews the role of engineering educators in understanding, promoting and embedding safe design principles within the engineering curricula. APPROACH The paper explores how safe design has been incorporated into engineering education since the early 1990s, and assesses the effectiveness of available resources and teaching practice. Changes to the legislative environment throughout this time are also described, to provide context and articulate implications for engineering educators. RESULTS The importance of safe design is recognised and resources do exist to support engineering educators to embed safe design principles within curriculum. The paper provides a series of recommendations to mainstream the available resources, highlights characteristics of effective practice and identifies areas for further professional development of engineering educators who are not familiar with safe design principles. CONCLUSIONS In order to develop graduates who are safe design practitioners, the model of engineering design introduced within the engineering curriculum must demonstrate that safe design is an inherent user requirement for all projects. This requires engineering educators to be familiar with human centred engineering design and how this impacts traditional technical design outcomes.Bernadette Foley, Prue Howard, Yvonne Toft and Mike Hur
Distant red galaxies in the Hubble Ultra Deep Field
We take advantage of the Hubble Ultra Deep Field (UDF) data to study the
restframe optical and ultra violet (UV) morphologies of the novel population of
Distant Red Galaxies (DRGs). Six galaxies with J-Ks > 2.3 are found to Ks=21.5,
five of which have photometric redshifts z_phot > 2, corresponding to a surface
density of 0.9/arcmin^2. The surface brightness distributions of the z_phot > 2
galaxies are better represented by exponential disks than R^{1/4}-laws. Two of
the z_phot > 2 galaxies are extended, while three have compact morphologies.
The restframe optical morphology of the z_phot > 2 galaxies is quite different
from the restframe UV morphology: all the galaxies have red central components
which dominate in the NICMOS H_{160}-band images, and distinct off-center blue
features which show up in (and often dominate) the ACS images. The mean
measured effective radius of the z_phot > 2 galaxies is =1.9+/-1.4 kpc,
similar (within the errors) to the mean size of LBGs at similar redshifts. All
the DRGs are resolved in the ACS images, while four are resolved in the NICMOS
images. Two of the z_phot > 2 galaxies are bright X-ray sources and hence host
AGN. The diverse restframe optical and UV morphological properties of DRGs
derived here suggest that they have complex stellar populations, consisting of
both evolved populations that dominate the mass and the restframe optical
light, and younger populations, which show up as patches of star formation in
the restframe UV light; in many ways resembling the properties of normal local
galaxies. This interpretation is supported by fits to the broadband SEDs, which
for all five z_phot > 2 are best represented by models with extended star
formation histories and substantial amounts of dust.Comment: Accepted for publication in APJ
The Optical - Infrared Colors of CORALS QSOs: Searching for Dust Reddening Associated With High Redshift Damped Lyman Alpha Systems
The presence of dust in quasar absorbers, such as damped Lyman alpha (DLA)
systems, may cause the background QSO to appear reddened. We investigate the
extent of this potential reddening by comparing the optical-to-infrared (IR)
colors of QSOs with and without intervening absorbers. Our QSO sample is based
on the Complete Optical and Radio Absorption Line System (CORALS) survey of
Ellison et al (2001). We have obtained near-simultaneous B and K band
magnitudes for subset of the CORALS sample and supplemented our observations
with further measurements published in the literature. To account for
redshift-related color changes, the B-K colors are normalized using the Sloan
Digital Sky Survey (SDSS) QSO composite. The mean normalized B-K color of the
DLA sub-sample is +0.12, whereas the mean for the no-DLA sample is -0.10; both
distributions have RMS scatters ~0.5. Neither a student's T-test nor a KS test
indicate that there is any significant difference between the two color
distributions. Based on simulations which redden the colors of QSOs with
intervening DLAs, we determine a reddening limit which corresponds to E(B-V) <
0.04 (SMC-like extinction) at 99% confidence (3 sigma), assuming that E(B-V) is
the same for all DLAs. Finally, we do not find any general correlation between
absorber properties (such as [Fe/Zn] or neutral hydrogen column density) and
B-K color. One of these two QSOs shows evidence for strong associated
absorption from X-ray observations, an alternative explanation for its very red
color. We conclude that the presence of intervening galaxies causes a minimal
reddening of the background QSO.Comment: Accepted for publication in A
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