3,745 research outputs found
The impact of traffic on residential property values and retail sales in Champaign-Urbana
Prepared as a part of an investigation conducted by Dept. of Finance, University of Illinois, in cooperation with the State of Illinois Division of Highways and the U.S. Bureau of Public Roads, Project IHR-71; Impact of vehicular traffic on urban real estate.Bibliographical footnotes
The Spectral Energy Distribution of Normal, Starburst and Active Galaxies
We present the results of an extensive literature search of multiwavelength
data for a sample of 59 galaxies, consisting of 26 Starbursts, 15 Seyfert 2's,
5 LINER's, 6 normal spirals and 7 normal elliptical galaxies. The data include
soft X-ray fluxes, ultraviolet and optical spectra, near, mid/far infrared
photometry and radio measurements, selected to match as closely as possible the
IUE aperture (10" X 20"). The galaxies are separated into 6 groups with similar
characteristics, namely, Ellipticals, Spirals, LINER's, Seyfert 2's, Starbursts
of Low and High reddening, for which we create average spectral energy
distributions (SED). The individual groups SED's are normalized to the
7000\AA flux and compared, looking for similarities and differences
among them.The bolometric fluxes of different types of galaxies were calculated
integrating their SED's. These values are compared with individual waveband
flux densities, in order to determine the wavebands which contribute most to
the bolometric flux. Linear regressions were performed between the bolometric
and individual band fluxes for each kind of galaxy. These fits can be used in
the calculation of the bolometric flux for other objects of similar activity
type, but with reduced waveband information. We have also collected
multiwavelength data for 4 HII regions, a thermal supernova remnant, and a
non-thermal supernova remnant (SNR), which are compared with the Starburst
SED's.Comment: 29 pages, 13 postscript figures and 10 tables. To appear in The
Astronomical Journa
Development of a flash, bang, and smoke simulation of a shell burst
A large number of experiments (cue test firings) were performed in the definition of the cue concepts and packaging configurations. A total of 344 of these experiments were recorded with instrumentation photography to allow a quantitative analysis of the smoke cloud to be made as a function of time. These analyses were predominantly made using a short test site. Supplementary long range visibility tests were conducted to insure the required 3 kilometer visibility of the smoke signature
MODELING AND TOPOLOGY EVALUATION FOR RECTIFIER CIRCUITS IN MEDIUM VOLTAGE DIRECT CURRENT SYSTEM
Naval ship propulsion design is evolving from the traditional structure with a main engine driving a shaft through a reduction gear, to a new architecture that uses electric drives powered from a direct current (DC) power distribution system. The goal of this thesis is to compare different medium voltage rectifiers interfacing an alternate current (AC) generator to a DC bus which can power the ship propulsion system. Power quality and efficiency of the power converters are the parameters used to compare four different rectifier circuit topologies: 2-level converter, 3-level converter, modular multi-level converter, and modular multi-level rectifier. Converter operating principles, design trade-offs, modeling characteristics, performance, and naval shipboard applicability are discussed in detail. Using a power electronics simulation platform, the four power rectifier circuits and their controls are connected between a 6.6kV AC generator and a regulated DC bus that represents the shipboard platform. Inside each rectifier circuit, thermal properties of the chosen semiconductor switching devices and diodes are built in and losses are captured and analyzed in steady state operation. This study shows that the modular multi-level rectifier circuit is the most efficient, easiest to maintain, and the recommended topology for Naval shipboard applications.Lieutenant, United States NavyApproved for public release. Distribution is unlimited
THE EFFECT OF MEDIUM AND TASK ON DYADIC COMMUNICATION
A controlled laboratory study examined dyadic communication in face-to-face, telephone, and computer mediated text modes using high and low equivocal tasks. The dependent variables were decision time, consensus, change and communication satisfaction. The study failed to support media richness theory. While the findings support the hypothesis that decision time varies as a function of medium, they do not support similar hypotheses for consensus change and communication satisfaction. No support for hypothesized differences in decision time and consensus change as a function of the interaction of medium and task was found. However, there were consistent significant differences in all dependent measures based on task
Starbursts and Star Clusters in the Ultraviolet
Hubble Space Telescope ultraviolet (UV) images of nine starburst galaxies
reveal them to be highly irregular, even after excluding compact sources
(clusters and resolved stars). Most (7/9) are found to have a similar intrinsic
effective surface brightnesses, suggesting that a negative feedback mechanism
is setting an upper limit to the star formation rate per unit area. All
starbursts in our sample contain UV bright star clusters indicating that
cluster formation is an important mode of star formation in starbursts. On
average about 20% of the UV luminosity comes from these clusters. The brightest
clusters, or super star clusters (SSC), are preferentially found at the very
heart of starbursts. The size of the nearest SSCs are consistent with those of
Galactic globular clusters. The luminosity function of SSCs is well represented
by a power law with a slope alpha ~ -2. There is a strong correlation between
the far infrared excess and the UV spectral slope. The correlation is well
modeled by a geometry where much of their dust is in a foreground screen near
to the starburst, but not by a geometry of well mixed stars and dust.Comment: 47 pages, text only, LaTeX with aaspp.sty (version 3.0), compressed
postscript figures available at
ftp://eta.pha.jhu.edu/RecentPublications/meurer
Response of primary producers to nutrient enrichment in a shallow estuary
Shallow coastal systems worldwide are exhibiting increased algal growth in response to nutrient enrichment. This study evaluates primary production patterns in an estuarine system (Bass Harbor Marsh, ME, USA) receiving low levels of anthropogenic nitrogen. Biomass, areal coverage and in situ oxygen production of green macroalgae, Ruppia maritima, and phytoplankton were measured over a growing season to determine net ecosystem production. Macroalgae and R. maritima exhibited seasonal biomass curves with early summer peaks; however, peak biomass of macroalgae [150 g dry weight (wt) m-2] was substantially greater than R. maritima (33 g dry wt m-2). Phytoplankton biomass, measured as chlorophyll a, was low (\u3c1 µg l-1) early in the season and peaked (11 µg l-1) following a mid-summer decline in macroalgal biomass, suggesting a competitive interaction with macroalgae. Instantaneous net production rates varied over the growing season for all 3 primary producers. R. maritima net production ranged from near zero to 3.7 mg C g-1 dry wt h-1, with higher rates during summer and much of the seasonal variability explained by temperature. Macroalgal (0.88 to 5.0 mg C g-1 dry wt h-1) and phytoplankton (0 to 28 mg C m-3 h-1) net production did not exhibit any clear seasonal signal. Net primary production calculated on an areal basis demonstrated macroalgae\u27s dominance in the lower basin of Bass Harbor Marsh, with peak summer rates (400 mg C m-2 h-1) greatly exceeding maximum rates for both R. maritima (70 mg C m-2 h-1) and phytoplankton (12 mg C m-2 h-1). When compared to other New England estuarine sites with short residence times, nutrient loading and peak green macroalgal biomass in Bass Harbor Marsh are relatively low; however, the strong dominance of opportunistic green macroalgae is a pattern that is characteristic of shallow coastal systems undergoing eutrophication
First results from the VIMOS-IFU survey of gravitationally lensing clusters at z~0.2
We present the on-going observational program of a VIMOS Integral Field Unit
survey of the central regions of massive, gravitational lensing galaxy clusters
at redshift z~0.2. We have observed six clusters using the low-resolution blue
grism (R about 200), and the spectroscopic survey is complemented by a wealth
of photometric data, including Hubble Space Telescope optical data and near
infrared VLT data. The principal scientific aims of this project are: the study
of the high-z lensed galaxies, the transformation and evolution of galaxies in
cluster cores and the use of multiple images to constrain cosmography. We
briefly report here on the first results from this project on the clusters
Abell 2667 and Abell 68.Comment: 5 pages, 5 figures. To appear in "Sciences Perspectives for 3D
Spectroscopy. ESO Astrophysics Symposia". Ed by M.Kissler-Patig, M.M. Roth
and J.R. Wals
Inflammation as a Central Mechanism in Alzheimer\u27s Disease
Alzheimer\u27s disease (AD) is a progressive neurodegenerative disorder that is characterized by cognitive decline and the presence of two core pathologies, amyloid β plaques and neurofibrillary tangles. Over the last decade, the presence of a sustained immune response in the brain has emerged as a third core pathology in AD. The sustained activation of the brain\u27s resident macrophages (microglia) and other immune cells has been demonstrated to exacerbate both amyloid and tau pathology and may serve as a link in the pathogenesis of the disorder. In the following review, we provide an overview of inflammation in AD and a detailed coverage of a number of microglia-related signaling mechanisms that have been implicated in AD. Additional information on microglia signaling and a number of cytokines in AD are also reviewed. We also review the potential connection of risk factors for AD and how they may be related to inflammatory mechanisms
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