19,727 research outputs found
Spectroscopy of Ultra-diffuse Galaxies in the Coma Cluster
We present spectra of 5 ultra-diffuse galaxies (UDGs) in the vicinity of the
Coma Cluster obtained with the Multi-Object Double Spectrograph on the Large
Binocular Telescope. We confirm 4 of these as members of the cluster,
quintupling the number of spectroscopically confirmed systems. Like the
previously confirmed large (projected half light radius 4.6 kpc) UDG, DF44,
the systems we targeted all have projected half light radii kpc. As
such, we spectroscopically confirm a population of physically large UDGs in the
Coma cluster. The remaining UDG is located in the field, about Mpc behind
the cluster. We observe Balmer and Ca II H \& K absorption lines in all of our
UDG spectra. By comparing the stacked UDG spectrum against stellar population
synthesis models, we conclude that, on average, these UDGs are composed of
metal-poor stars ([Fe/H] ). We also discover the first UDG with
[OII] and [OIII] emission lines within a clustered environment, demonstrating
that not all cluster UDGs are devoid of gas and sources of ionizing radiation.Comment: 5 pages, 4 figure
Exploring the Revenue Mix of Nonprofit Organizations -- Does it Relate to Publicness
Nonprofit organizations offer a wide range of goods and services and seek funding from a variety of revenue sources. Our working theory n this paper is that the sources of funding are related to the services a nonprofit provides - specifically whether services are public, private, or mixed in the nature of their benefits. Using multiple subfields from three major fields in the National Taxonomy of Exempt Entities (NTEE), this study divides nonprofits according to service type, and estimates the impact of service character on particular revenue streams and overall level of revenue diversification. Generally, the proportion of revenues generated by program fees is lowest for the category deemed public, highest for those with mostly private benefits, and midway for "mixed" services which are private in character but entail substantial public benefits. Similarly, the more public a nonprofit's services, the greater the proportion of revenues it generates through donations. However, we also identify some puzzling results that suggest the need for continued investigation of the determinants of the sources and mixes of nonprofit income. Working Paper 07-3
Nutrient requirements and other factors involved in the culture of human kidney cells on microcarrier beads
The culture of human kidney cells on microcarrier beads in the Bioprocessing Laboratory at the Johnson Space Center is described. These were the first series of studies performed before and during 1983 to determine optimum conditions, including medium type, bead type and density. The composition of several medium types and the molecular weights of some common culture medium supplements and cellular proteins are included. The microgravity cell-to-bead attachment experiment performed on Space Transportation System Flight 8 is described
Numerical simulations of supersonic flow through oscillating cascade sections
A finite difference code was developed for modeling inviscid, unsteady supersonic flow by solution of the compressible Euler equations. The code uses a deforming grid technique to capture the motion of the airfoils and can model oscillating cascades with any arbitrary interblade phase angle. A flat plate cascade is analyzed, and results are compared with results from a small perturbation theory. The results show very good agreement for both the unsteady pressure distributions and the integrated force predictions. The reason for using the numerical Euler code over a small perturbation theory is the ability to model real airfoils that have thickness and camber. Sample predictions are presented for a cascade of loaded airfoils and show appreciable differences in the unsteady surface pressure distributions when compared with the flat plate results
Numerical analysis of supersonic flow through oscillating cascade sections by using a deforming grid
A finite difference code was developed for modeling inviscid, unsteady supersonic flow by solution of the compressible Euler equations. The code uses a deforming grid technique to capture the motion of the airfoils and can model oscillating cascades with any arbitrary interblade phase angle. A flat plate cascade is analyzed, and results are compared with results from a small-perturbation theory. The results show very good agreement for both the unsteady pressure distributions and the integrated force predictions. The reason for using the numerical Euler code over a small-perturbation theory is the ability to model real airfoils that have thickness and camber. Sample predictions are presented for a section of the rotor on a supersonic throughflow compressor designed at NASA Lewis Research Center. Preliminary results indicate that two-dimensional, flat plate analysis predicts conservative flutter boundaries
Multi-region relaxed magnetohydrodynamics with anisotropy and flow
We present an extension of the multi-region relaxed magnetohydrodynamics
(MRxMHD) equilibrium model that includes pressure anisotropy and general plasma
flows. This anisotropic extension to our previous isotropic model is motivated
by Sun and Finn's model of relaxed anisotropic magnetohydrodynamic equilibria.
We prove that as the number of plasma regions becomes infinite, our anisotropic
extension of MRxMHD reduces to anisotropic ideal MHD with flow. The
continuously nested flux surface limit of our MRxMHD model is the first
variational principle for anisotropic plasma equilibria with general flow
fields.Comment: 11 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1401.307
DEVELOPING REGIONAL INPUT-OUTPUT MODELS FROM THE U.N. FORMAT ADOPTED BY THE U.S. IN THE NEW 1972 INPUT-OUTPUT MODEL
International Relations/Trade,
A high-speed digital camera system for the observation of rapid H-alpha fluctuations in solar flares
Researchers developed a prototype digital camera system for obtaining H-alpha images of solar flares with 0.1 s time resolution. They intend to operate this system in conjunction with SMM's Hard X Ray Burst Spectrometer, with x ray instruments which will be available on the Gamma Ray Observatory and eventually with the Gamma Ray Imaging Device (GRID), and with the High Resolution Gamma-Ray and Hard X Ray Spectrometer (HIREGS) which are being developed for the Max '91 program. The digital camera has recently proven to be successful as a one camera system operating in the blue wing of H-alpha during the first Max '91 campaign. Construction and procurement of a second and possibly a third camera for simultaneous observations at other wavelengths are underway as are analyses of the campaign data
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