3,438 research outputs found
Acoustic Calibration of the Exterior Effects Room at the NASA Langley Research Center
The Exterior Effects Room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional audio and visual environment. The 3D audio system consists of 27 mid and high frequency satellite speakers and 4 subwoofers, driven by a real-time audio server running an implementation of Vector Base Amplitude Panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, baffled/unbaffled), and cross-over filtering
SANEPIC: A Map-Making Method for Timestream Data From Large Arrays
We describe a map-making method which we have developed for the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST) experiment, but which should
have general application to data from other submillimeter arrays. Our method
uses a Maximum Likelihood based approach, with several approximations, which
allows images to be constructed using large amounts of data with fairly modest
computer memory and processing requirements. This new approach, Signal And
Noise Estimation Procedure Including Correlations (SANEPIC), builds upon
several previous methods, but focuses specifically on the regime where there is
a large number of detectors sampling the same map of the sky, and explicitly
allowing for the the possibility of strong correlations between the detector
timestreams. We provide real and simulated examples of how well this method
performs compared with more simplistic map-makers based on filtering. We
discuss two separate implementations of SANEPIC: a brute-force approach, in
which the inverse pixel-pixel covariance matrix is computed; and an iterative
approach, which is much more efficient for large maps. SANEPIC has been
successfully used to produce maps using data from the 2005 BLAST flight.Comment: 27 Pages, 15 figures; Submitted to the Astrophysical Journal; related
results available at http://blastexperiment.info/ [the BLAST Webpage
Early respiratory viral infections in infants with cystic fibrosis
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Background
Viral infections contribute to morbidity in cystic fibrosis (CF), but the impact of respiratory viruses on the development of airway disease is poorly understood.
Methods
Infants with CF identified by newborn screening were enrolled prior to 4 months of age to participate in a prospective observational study at 4 centers. Clinical data were collected at clinic visits and weekly phone calls. Multiplex PCR assays were performed on nasopharyngeal swabs to detect respiratory viruses during routine visits and when symptomatic. Participants underwent bronchoscopy with bronchoalveolar lavage (BAL) and a subset underwent pulmonary function testing. We present findings through 8.5 months of life.
Results
Seventy infants were enrolled, mean age 3.1 ± 0.8 months. Rhinovirus was the most prevalent virus (66%), followed by parainfluenza (19%), and coronavirus (16%). Participants had a median of 1.5 viral positive swabs (range 0–10). Past viral infection was associated with elevated neutrophil concentrations and bacterial isolates in BAL fluid, including recovery of classic CF bacterial pathogens. When antibiotics were prescribed for respiratory-related indications, viruses were identified in 52% of those instances.
Conclusions
Early viral infections were associated with greater neutrophilic inflammation and bacterial pathogens. Early viral infections appear to contribute to initiation of lower airway inflammation in infants with CF. Antibiotics were commonly prescribed in the setting of a viral infection. Future investigations examining longitudinal relationships between viral infections, airway microbiome, and antibiotic use will allow us to elucidate the interplay between these factors in young children with CF
Analytical solution of a model for complex food webs
We investigate numerically and analytically a recently proposed model for
food webs [Nature {\bf 404}, 180 (2000)] in the limit of large web sizes and
sparse interaction matrices. We obtain analytical expressions for several
quantities with ecological interest, in particular the probability
distributions for the number of prey and the number of predators. We find that
these distributions have fast-decaying exponential and Gaussian tails,
respectively. We also find that our analytical expressions are robust to
changes in the details of the model.Comment: 4 pages (RevTeX). Final versio
Nitrogen turnover in the leaf litter and fine roots of sugar maple
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117199/1/ecy201091123456.pd
BLAST05: Power Spectra of Bright Galactic Cirrus at Submillimeter Wavelengths
We report multi-wavelength power spectra of diffuse Galactic dust emission
from BLAST observations at 250, 350, and 500 microns in Galactic Plane fields
in Cygnus X and Aquila. These submillimeter power spectra statistically
quantify the self-similar structure observable over a broad range of scales and
can be used to assess the cirrus noise which limits the detection of faint
point sources. The advent of submillimeter surveys with the Herschel Space
Observatory makes the wavelength dependence a matter of interest. We show that
the observed relative amplitudes of the power spectra can be related through a
spectral energy distribution (SED). Fitting a simple modified black body to
this SED, we find the dust temperature in Cygnus X to be 19.9 +/- 1.3 K and in
the Aquila region 16.9 +/- 0.7 K. Our empirical estimates provide important new
insight into the substantial cirrus noise that will be encountered in
forthcoming observations.Comment: Submitted to the Astrophysical Journal. Maps and other data are
available at http://blastexperiment.info
A Sample of Intermediate-Mass Star-Forming Regions: Making Stars at Mass Column Densities <1 g/cm^2
In an effort to understand the factors that govern the transition from low-
to high-mass star formation, we identify for the first time a sample of
intermediate-mass star-forming regions (IM SFRs) where stars up to - but not
exceeding - 8 solar masses are being produced. We use IRAS colors and Spitzer
Space Telescope mid-IR images, in conjunction with millimeter continuum and CO
maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely
to be precursors to Herbig AeBe stars and their associated clusters of low-mass
stars. IM SFRs constitute embedded clusters at an early evolutionary stage akin
to compact HII regions, but they lack the massive ionizing central star(s). The
photodissociation regions that demarcate IM SFRs have typical diameters of ~1
pc and luminosities of ~10^4 solar luminosities, making them an order of
magnitude less luminous than (ultra)compact HII regions. IM SFRs coincide with
molecular clumps of mass ~10^3 solar masses which, in turn, lie within larger
molecular clouds spanning the lower end of the giant molecular cloud mass
range, 10^4-10^5 solar masses. The IR luminosity and associated molecular mass
of IM SFRs are correlated, consistent with the known luminosity-mass
relationship of compact HII regions. Peak mass column densities within IM SFRs
are ~0.1-0.5 g/cm^2, a factor of several lower than ultra-compact HII regions,
supporting the proposition that there is a threshold for massive star formation
at ~1 g/cm^2.Comment: 61 pages, 6 tables, 20 figures. Accepted for publication in the
Astronomical Journa
Submillimeter Number Counts From Statistical Analysis of BLAST Maps
We describe the application of a statistical method to estimate submillimeter
galaxy number counts from confusion limited observations by the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST). Our method is based on a
maximum likelihood fit to the pixel histogram, sometimes called 'P(D)', an
approach which has been used before to probe faint counts, the difference being
that here we advocate its use even for sources with relatively high
signal-to-noise ratios. This method has an advantage over standard techniques
of source extraction in providing an unbiased estimate of the counts from the
bright end down to flux densities well below the confusion limit. We
specifically analyse BLAST observations of a roughly 10 sq. deg. map centered
on the Great Observatories Origins Deep Survey South (GOODS-S) field. We
provide estimates of number counts at the three BLAST wavelengths, 250, 350,
and 500 microns; instead of counting sources in flux bins we estimate the
counts at several flux density nodes connected with power-laws. We observe a
generally very steep slope for the counts of about -3.7 at 250 microns and -4.5
at 350 and 500 microns, over the range ~0.02-0.5 Jy, breaking to a shallower
slope below about 0.015 Jy at all three wavelengths. We also describe how to
estimate the uncertainties and correlations in this method so that the results
can be used for model-fitting. This method should be well-suited for analysis
of data from the Herschel satellite.Comment: Accepted for publication in the Astrophysical Journal; see associated
data and other papers at http://blastexperiment.info
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