6,912 research outputs found
The extraordinary mid-infrared spectral properties of FeLoBAL Quasars
We present mid-infrared spectra of six FeLoBAL QSOs at 1<z<1.8, taken with
the Spitzer space telescope. The spectra span a range of shapes, from hot dust
dominated AGN with silicate emission at 9.7 microns, to moderately obscured
starbursts with strong Polycyclic Aromatic Hydrocarbon (PAH) emission. The
spectrum of one object, SDSS 1214-0001, shows the most prominent PAHs yet seen
in any QSO at any redshift, implying that the starburst dominates the mid-IR
emission with an associated star formation rate of order 2700 solar masses per
year. With the caveats that our sample is small and not robustly selected, we
combine our mid-IR spectral diagnostics with previous observations to propose
that FeLoBAL QSOs are at least largely comprised of systems in which (a) a
merger driven starburst is ending, (b) a luminous AGN is in the last stages of
burning through its surrounding dust, and (c) which we may be viewing over a
restricted line of sight range.Comment: ApJ, accepte
High-power AlGaAs channeled substrate planar diode lasers for spaceborne communications
A high power channeled substrate planar AlGaAs diode laser with an emission wavelength of 8600 to 8800 A was developed. The optoelectronic behavior (power current, single spatial and spectral behavior, far field characteristics, modulation, and astigmatism properties) and results of computer modeling studies on the performance of the laser are discussed. Lifetest data on these devices at high output power levels is also included. In addition, a new type of channeled substrate planar laser utilizing a Bragg grating to stabilize the longitudinal mode was demonstrated. The fabrication procedures and optoelectronic properties of this new diode laser are described
Monolithic microwave integrated circuits: Interconnections and packaging considerations
Monolithic microwave integrated circuits (MMIC's) above 18 GHz were developed because of important potential system benefits in cost reliability, reproducibility, and control of circuit parameters. The importance of interconnection and packaging techniques that do not compromise these MMIC virtues is emphasized. Currently available microwave transmission media are evaluated to determine their suitability for MMIC interconnections. An antipodal finline type of microstrip waveguide transition's performance is presented. Packaging requirements for MMIC's are discussed for thermal, mechanical, and electrical parameters for optimum desired performance
The Statistical Approach to Quantifying Galaxy Evolution
Studies of the distribution and evolution of galaxies are of fundamental
importance to modern cosmology; these studies, however, are hampered by the
complexity of the competing effects of spectral and density evolution.
Constructing a spectroscopic sample that is able to unambiguously disentangle
these processes is currently excessively prohibitive due to the observational
requirements. This paper extends and applies an alternative approach that
relies on statistical estimates for both distance (z) and spectral type to a
deep multi-band dataset that was obtained for this exact purpose.
These statistical estimates are extracted directly from the photometric data
by capitalizing on the inherent relationships between flux, redshift, and
spectral type. These relationships are encapsulated in the empirical
photometric redshift relation which we extend to z ~ 1.2, with an intrinsic
dispersion of dz = 0.06. We also develop realistic estimates for the
photometric redshift error for individual objects, and introduce the
utilization of the galaxy ensemble as a tool for quantifying both a
cosmological parameter and its measured error. We present deep, multi-band,
optical number counts as a demonstration of the integrity of our sample. Using
the photometric redshift and the corresponding redshift error, we can divide
our data into different redshift intervals and spectral types. As an example
application, we present the number redshift distribution as a function of
spectral type.Comment: 40 pages (LaTex), 21 Figures, requires aasms4.sty; Accepted by the
Astrophysical Journa
Image Coaddition with Temporally Varying Kernels
Large, multi-frequency imaging surveys, such as the Large Synaptic Survey
Telescope (LSST), need to do near-real time analysis of very large datasets.
This raises a host of statistical and computational problems where standard
methods do not work. In this paper, we study a proposed method for combining
stacks of images into a single summary image, sometimes referred to as a
template. This task is commonly referred to as image coaddition. In part, we
focus on a method proposed in previous work, which outlines a procedure for
combining stacks of images in an online fashion in the Fourier domain. We
evaluate this method by comparing it to two straightforward methods through the
use of various criteria and simulations. Note that the goal is not to propose
these comparison methods for use in their own right, but to ensure that
additional complexity also provides substantially improved performance
Exercise rehabilitation following intensive care unit discharge for recovery from critical illness: executive summary of a Cochrane Collaboration systematic review
Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society of Sarcopenia, Cachexia and Wasting DisordersSkeletal muscle wasting and weakness are major complications of critical illness and underlie the profound physical and functional impairments experienced by survivors after discharge from the intensive care unit (ICU). Exercise-based rehabilitation has been shown to be beneficial when delivered during ICU admission. This review aimed to determine the effectiveness of exercise rehabilitation initiated after ICU discharge on primary outcomes of functional exercise capacity and health-related quality of life. We sought randomized controlled trials, quasi-randomized controlled trials, and controlled clinical trials comparing an exercise intervention commenced after ICU discharge vs. any other intervention or a control or ‘usual care’ programme in adult survivors of critical illness. Cochrane Central Register of Controlled Trials, Medical Literature Analysis and Retrieval System Online (MEDLINE), Excerpta Medica Database, and Cumulative Index to Nursing and Allied Health Literature databases were searched up to February 2015. Dual, independent screening of results, data extraction, and quality appraisal were performed. We included six trials involving 483 patients. Overall quality of evidence for both outcomes was very low. All studies evaluated functional exercise capacity, with three reporting positive effects in favour of the intervention. Only two studies evaluated health-related quality of life and neither reported differences between intervention and control groups. Meta-analyses of data were precluded due to variation in study design, types of interventions, and selection and reporting of outcome measurements. We were unable to determine an overall effect on functional exercise capacity or health-related quality of life of interventions initiated after ICU discharge for survivors of critical illness. Findings from ongoing studies are awaited. Future studies need to address methodological aspects of study design and conduct to enhance rigour, quality, and synthesis
The Near-Infrared Number Counts and Luminosity Functions of Local Galaxies
This study presents a wide-field near-infrared (K-band) survey in two fields;
SA 68 and Lynx 2. The survey covers an area of 0.6 deg., complete to
K=16.5. A total of 867 galaxies are detected in this survey of which 175 have
available redshifts. The near-infrared number counts to K=16.5 mag. are
estimated from the complete photometric survey and are found to be in close
agreement with other available studies. The sample is corrected for
incompleteness in redshift space, using selection function in the form of a
Fermi-Dirac distribution. This is then used to estimate the local near-infrared
luminosity function of galaxies. A Schechter fit to the infrared data gives:
M, and Mpc (for H Km/sec/Mpc and q). When
reduced to , this agrees with other available estimates of the local
IRLF. We find a steeper slope for the faint-end of the infrared luminosity
function when compared to previous studies. This is interpreted as due to the
presence of a population of faint but evolved (metal rich) galaxies in the
local Universe. However, it is not from the same population as the faint blue
galaxies found in the optical surveys. The characteristic magnitude
() of the local IRLF indicates that the bright red galaxies ( mag.) have a space density of Mpc and hence,
are not likely to be local objects.Comment: 24 pages, 8 figures, AASTEX 4.0, published in ApJ 492, 45
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