8,548 research outputs found
The Redshift Distribution of FIRST Radio Sources at 1 mJy
We present spectra for a sample of radio sources from the FIRST survey, and
use them to define the form of the redshift distribution of radio sources at
mJy levels.We targeted 365 sources and obtained 46 redshifts (13 per cent of
the sample). We find that our sample is complete in redshift measurement to R
, corresponding to . Early-type galaxies represent the
largest subset (45 per cent) of the sample and have redshifts 0.15\la z \la
0.5 ; late-type galaxies make up 15 per cent of the sample and have redshifts
0.05\la z \la 0.2; starbursting galaxies are a small fraction ( per
cent), and are very nearby (z\la 0.05). Some 9 per cent of the population
have Seyfert1/quasar-type spectra, all at z\ga 0.8, and there are 4 per cent
are Seyfert2 type galaxies at intermediate redshifts (). Using our
measurements and data from the Phoenix survey, we obtain an estimate for
at mJy and compare this with model predictions. At
variance with previous conclusions, we find that the population of starbursting
objects makes up \la 5 per cent of the radio population at S mJy.Comment: 20 pages, sumbitted to MNRA
Planning assistance for the 30/20 GHz program, volume 3
The three basic experiment categories and consolidated experiments proposed by members of the Carrier Working Group are defined by category and by carrier. The three experiment categories are: (1) Possible Service (PS); (2) Possible Service and Technology (PSAT); and (3) Possible Technology (PT). Under Task 9 Western Union provided review, recommendations and critique of the NASA generated Statement of Work (SOW) defining the technical requirements governing design, launch and operation of the 30/20 GHz experimental systems
Planning assistance for the 30/20 GHz program, volume 1
Functional requirements for the 30/20 GHz communication system, planning assistance for the 30/20 GHz program, and a review of specified conceptual designs and recommendations are provided
Preventing transition to turbulence: a viscosity stratification does not always help
In channel flows a step on the route to turbulence is the formation of
streaks, often due to algebraic growth of disturbances. While a variation of
viscosity in the gradient direction often plays a large role in
laminar-turbulent transition in shear flows, we show that it has, surprisingly,
little effect on the algebraic growth. Non-uniform viscosity therefore may not
always work as a flow-control strategy for maintaining the flow as laminar.Comment: 9 pages, 8 figure
Mesoscopic Effects in Quantum Phases of Ultracold Quantum Gases in Optical Lattices
We present a wide array of quantum measures on numerical solutions of 1D
Bose- and Fermi-Hubbard Hamiltonians for finite-size systems with open boundary
conditions. Finite size effects are highly relevant to ultracold quantum gases
in optical lattices, where an external trap creates smaller effective regions
in the form of the celebrated "wedding cake" structure and the local density
approximation is often not applicable. Specifically, for the Bose-Hubbard
Hamiltonian we calculate number, quantum depletion, local von-Neumann entropy,
generalized entanglement or Q-measure, fidelity, and fidelity susceptibility;
for the Fermi-Hubbard Hamiltonian we also calculate the pairing correlations,
magnetization, charge-density correlations, and antiferromagnetic structure
factor. Our numerical method is imaginary time propagation via time-evolving
block decimation. As part of our study we provide a careful comparison of
canonical vs. grand canonical ensembles and Gutzwiller vs. entangled
simulations. The most striking effect of finite size occurs for bosons: we
observe a strong blurring of the tips of the Mott lobes accompanied by higher
depletion, and show how the location of the first Mott lobe tip approaches the
thermodynamic value as a function of system size.Comment: 13 pages, 10 figure
Acute post-disaster medical needs of patients with diabetes: emergency department use in New York City by diabetic adults after Hurricane Sandy.
OBJECTIVE: To evaluate the acute impact of disasters on diabetic patients, we performed a geospatial analysis of emergency department (ED) use by New York City diabetic adults in the week after Hurricane Sandy.
RESEARCH DESIGN AND METHODS: Using an all-payer claims database, we retrospectively analyzed the demographics, insurance status, and medical comorbidities of post-disaster ED patients with diabetes who lived in the most geographically vulnerable areas. We compared the patterns of ED use among diabetic adults in the first week after Hurricane Sandy\u27s landfall to utilization before the disaster in 2012.
RESULTS: In the highest level evacuation zone in New York City, postdisaster increases in ED visits for a primary or secondary diagnosis of diabetes were attributable to a significantly higher proportion of Medicare patients. Emergency visits for a primary diagnosis of diabetes had an increased frequency of certain comorbidities, including hypertension, recent procedure, and chronic skin ulcers. Patients with a history of diabetes visited EDs in increased numbers after Hurricane Sandy for a primary diagnosis of myocardial infarction, prescription refills, drug dependence, dialysis, among other conditions.
CONCLUSIONS: We found that diabetic adults aged 65 years and older are especially at risk for requiring postdisaster emergency care compared to other vulnerable populations. Our findings also suggest that there is a need to support diabetic adults particularly in the week after a disaster by ensuring access to medications, aftercare for patients who had a recent procedure, and optimize their cardiovascular health to reduce the risk of heart attacks
The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
The contribution of the Unresolved Extragalactic Radio Sources to the diffuse
brightness of the sky was evaluated using the source number - flux measurements
available in literature. We first optimized the fitting function of the data
based on number counts distribution. We then computed the brightness
temperature at various frequencies from 151 MHz to 8440 MHz and derived its
spectral dependence. As expected the frequency dependence can be described by a
power law with a spectral index , in agreement with the
flux emitted by the {\it steep spectrum} sources. The contribution of {\it flat
spectrum} sources becomes relevant at frequencies above several GHz. Using the
data available in literature we improved our knowledge of the brightness of the
unresolved extragalactic radio sources. The results obtained have general
validity and they can be used to disentangle the various contributions of the
sky brightness and to evaluate the CMB temperature.Comment: Accepted for publication in the Astrophysical Journa
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