4,280 research outputs found
Cardiovascular MRI in clinical trials: expanded applications through novel surrogate endpoints
Recent advances in cardiovascular magnetic resonance (CMR) now allow the accurate and reproducible measurement of many aspects of cardiac and vascular structure and function, with prognostic data emerging for several key imaging biomarkers. These biomarkers are increasingly used in the evaluation of new drugs, devices and lifestyle modifications for the prevention and treatment of cardiovascular disease. This review outlines a conceptual framework for the application of imaging biomarkers to clinical trials, highlights several important CMR techniques which are in use in randomised studies, and reviews certain aspects of trial design, conduct and interpretation in relation to the use of CMR
Amine-terminated nanoparticle films: pattern deposition by a simple nanostencilling technique and stability studies under X-ray irradiation
Exploring the surface chemistry of nanopatterned amine-terminated nanoparticle films.</p
Predicting Scattering Scanning Near-field Optical Microscopy of Mass-produced Plasmonic Devices
Scattering scanning near-field optical microscopy enables optical imaging and
characterization of plasmonic devices with nanometer-scale resolution well
below the diffraction limit. This technique enables developers to probe and
understand the waveguide-coupled plasmonic antenna in as-fabricated
heat-assisted magnetic recording heads. In order validate and predict results
and to extract information from experimental measurements that is physically
comparable to simulations, a model was developed to translate the simulated
electric field into expected near-field measurements using physical parameters
specific to scattering scanning near-field optical microscopy physics. The
methods used in this paper prove that scattering scanning near-field optical
microscopy can be used to determine critical sub-diffraction-limited dimensions
of optical field confinement, which is a crucial metrology requirement for the
future of nano-optics, semiconductor photonic devices, and biological sensing
where the near-field character of light is fundamental to device operation.Comment: article: 18 pages, 5 figures; SI: 15 pages, 12 figure
The Active Nucleus of IC4970: A Nearby Example of Merger-Induced Cold-Gas Accretion
We present results from Chandra X-ray and Spitzer mid-infrared observations
of the interacting galaxy pair NGC6872/IC4970 in the Pavo galaxy group and show
that the smaller companion galaxy IC4970 hosts a highly obscured active
galactic nucleus (AGN). The 0.5-10 keV X-ray luminosity of the nucleus is
variable, increasing by a factor 2.9 to 1.7 x 10^{42} erg/s (bright state) on
~100 ks timescales. The X-ray spectrum of the is heavily absorbed (N_H = 3 x
10^{23} cm^{-2}) for power law models with Gamma = 1.5-2.0 and shows a clear
6.4 keV Fe Kalpha line with equivalent width of 144-195 eV. Limits on the
diffuse emission in IC4970 from Chandra X-ray data suggest that the available
power from Bondi accretion of hot interstellar gas may be an order of magnitude
too small to power the AGN. Spitzer images show that 8 micron nonstellar
emission is concentrated in the central 1 kpc of IC4970, consistent with high
obscuration in this region. The mid-infrared colors of the nucleus are
consistent with those expected for a highly obscured AGN. Taken together these
data suggest that the nucleus of IC4970 is a Seyfert 2, triggered and fueled by
cold material supplied to the central supermassive black hole as a result of
the off-axis collision of IC4970 with the cold-gas rich spiral galaxy NGC6872.Comment: 10 pages, 9 figures, submitted to ApJ, MIR flux conversion error
corrected in Table 4, MIR colors and paper text unchange
Mid-Infrared Galaxy Morphology Along the Hubble Sequence
The mid-infrared emission from 18 nearby galaxies imaged with the IRAC
instrument on Spitzer Space Telescope samples the spatial distributions of the
reddening-free stellar photospheric emission and the warm dust in the ISM.
These two components provide a new framework for galaxy morphological
classification, in which the presence of spiral arms and their emission
strength relative to the starlight can be measured directly and with high
contrast. Four mid-infrared classification methods are explored, three of which
are based on quantitative global parameters (colors, bulge-to-disk ratio)
similar to those used in the past for optical studies; in this limited sample,
all correlate well with traditional B-band classification. We suggest reasons
why infrared classification may be superior to optical classification.Comment: ApJS (in press), Spitzer Space Telescope Special Issue; 13 pages,
LaTeX (or Latex, etc); Figure 1ab is large, color plate; full-resolution
plates in .pdf format available at
http://cfa-www.harvard.edu/irac/publications
AEGIS: Infrared Spectral Energy Distributions of MIPS 70micron selected sources
We present 0.5 -160 micron Spectral Energy Distributions (SEDs) of galaxies,
detected at 70microns with the Multiband Imaging Photometer for Spitzer (MIPS),
using broadband imaging data from Spitzer and ground-based telescopes.
Spectroscopic redshifts, in the range 0.2<z<1.5, have been measured as part of
the Deep Extragalactic Evolutionary Probe2 (DEEP2) project. Based on the SEDs
we explore the nature and physical properties of the sources. Using the optical
spectra we derive Hbeta and [OII]-based Star Formation Rates (SFR) which are
10-100 times lower than SFR estimates based on IR and radio. The median offset
in SFR between optical and IR is reduced by a factor of ~3 when we apply a
typical extinction corrections. We investigate mid-to-far infrared correlations
for low redshift (>0.5) and high redshift (0.5<z<1.2) bins. Using this unique
``far-infrared'' selected sample we derive an empirical mid to far-infrared
relationship that can be used to estimate the infrared energy budget of
galaxies in the high-redshift universe. Our sample can be used as a template to
translate far-infrared luminosities into bolometric luminosities for high
redshift objects.Comment: 4 pages, 5 figures, accepted for publication in AEGIS ApJL Special
Issu
Extended Fermi coordinates
We extend the notion of Fermi coordinates to a generalized definition in
which the highest orders are described by arbitrary functions. From this
definition rises a formalism that naturally gives coordinate transformation
formulae. Some examples are developped in which the extended Fermi coordinates
simplify the metric components.Comment: 16 pages, 1 figur
The Bright End of the z~9 and z~10 UV Luminosity Functions using all five CANDELS Fields
The deep, wide-area (~800-900 arcmin**2) near-infrared/WFC3/IR + Spitzer/IRAC
observations over the CANDELS fields have been a remarkable resource for
constraining the bright end of high redshift UV luminosity functions (LFs).
However, the lack of HST 1.05-micron observations over the CANDELS fields has
made it difficult to identify z~9-10 sources robustly, since such data are
needed to confirm the presence of an abrupt Lyman break at 1.2 microns. We
report here on the successful identification of many such z~9-10 sources from a
new HST program (z9-CANDELS) that targets the highest-probability z~9-10 galaxy
candidates with observations at 1.05 microns, to search for a robust
Lyman-break at 1.2 microns. The potential z~9-10 candidates are preselected
from the full HST, Spitzer/IRAC S-CANDELS observations, and the
deepest-available ground-based optical+near-infrared observations. We
identified 15 credible z~9-10 galaxies over the CANDELS fields. Nine of these
galaxies lie at z~9 and 5 are new identifications. Our targeted follow-up
strategy has proven to be very efficient in making use of scarce HST time to
secure a reliable sample of z~9-10 galaxies. Through extensive simulations, we
replicate the selection process for our sample (both the preselection and
follow-up) and use it to improve current estimates for the volume density of
bright z~9 and z~10 galaxies. The volume densities we find are 5(-2)(+3)x and
8(-3)(+9)x lower, respectively, than found at z~8. When compared with the
best-fit evolution (i.e., dlog_{10} rho(UV)/dz=-0.29+/-0.02) in the UV
luminosities densities from z~8 to z~4 integrated to 0.3L*(z=3) (-20 mag),
these luminosity densities are 2.6(-0.9)(+1.5)x and 2.2(-1.1)(+2.0)x lower,
respectively, than the extrapolated trends. Our new results are broadly
consistent with the "accelerated evolution" scenario at z>8, as seen in many
theoretical models.Comment: 23 pages, 15 figures, 7 tables, updated to match the version in
press, including some minor textual corrections identified at the proof stag
Star formation in z>1 3CR host galaxies as seen by Herschel
We present Herschel (PACS and SPIRE) far-infrared (FIR) photometry of a
complete sample of z>1 3CR sources, from the Herschel GT project The Herschel
Legacy of distant radio-loud AGN (PI: Barthel). Combining these with existing
Spitzer photometric data, we perform an infrared (IR) spectral energy
distribution (SED) analysis of these landmark objects in extragalactic research
to study the star formation in the hosts of some of the brightest active
galactic nuclei (AGN) known at any epoch. Accounting for the contribution from
an AGN-powered warm dust component to the IR SED, about 40% of our objects
undergo episodes of prodigious, ULIRG-strength star formation, with rates of
hundreds of solar masses per year, coeval with the growth of the central
supermassive black hole. Median SEDs imply that the quasar and radio galaxy
hosts have similar FIR properties, in agreement with the orientation-based
unification for radio-loud AGN. The star-forming properties of the AGN hosts
are similar to those of the general population of equally massive non-AGN
galaxies at comparable redshifts, thus there is no strong evidence of universal
quenching of star formation (negative feedback) within this sample. Massive
galaxies at high redshift may be forming stars prodigiously, regardless of
whether their supermassive black holes are accreting or not.Comment: 30 pages, 13 figures, 4 tables. Accepted for publication in A&
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