3,170 research outputs found
Nonequilibrium material effects on the behavior of polymeric composite matrices and their related composites
The effects of physical aging on the material properties of some linear and network macromolecular glasses are discussed. The free volume concept is used to describe this behavior. The effect of physical aging on properties of some uniaxial graphite/fiber epoxy resin composites is investigated using stress relaxation in both tensile and flexural modes. The matrix polymers used were resins both of which are based on a 4,4-methylenedianiline derivative of epichlorohydrin with diamino diphenyl sulfone (DDS) as the curing agent. The matrix resin, as used in the practical application in composites, not fully cured and the glass transition of the network was dependent on the curing schedule. The physical aging of the bulk crosslinked epoxy was found to depend on the annealing temperature, and the T sub g of the resin. The physical aging of the composite, monitored by the stress relaxation method, was found to be dependent on the testing direction
On accessibility for pro-p groups
We define the notion of accessibility for a pro- group. We prove that
finitely generated pro- groups are accessible given a bound on the size of
their finite subgroups. We then construct a finitely generated inaccessible
pro- group, and also a finitely generated inaccessible discrete group which
is residually -finite.Junior Research Fellowship, Clare Colleg
Profinite rigidity of graph manifolds and JSJ decompositions of 3-manifolds
There has been much recent interest into those properties of a 3-manifold
determined by the profinite completion of its fundamental group. In this paper
we give readily computable criteria specifying precisely when two orientable
graph manifold groups have isomorphic profinite completions. Our results also
distinguish graph manifolds among the class of all 3-manifolds and give
information about the structure of totally hyperbolic manifolds, and give
control over the pro- completion of certain graph manifold groups
The Deep SWIRE Field III. WIYN Spectroscopy
We present the results of spectroscopy using HYDRA on the WIYN 3.5m telescope
of objects in the deep SWIRE radio field. The goal of the project was to
determine spectroscopic redshifts for as many of the brighter objects in the
field as possible, especially those detected in the radio and at 24 microns.
These redshifts are primarily being used in studies of galaxy evolution and the
connection of that evolution to AGN and star-formation. Redshifts measured for
365 individual objects are reported. The redshifts range from 0.03 to 2.5,
mostly with z < 0.9. The sources were selected to be within the WIYN HYDRA
field of approximately 30' in radius from the center of the SWIRE deep field,
10h46m00s, 59d 01'00" (J2000). Optical sources for spectroscopic observation
were selected from a r-band image of the field. A priority list of
spectroscopic targets was established in the following order: 20cm detections,
24 micron detections, galaxies with r < 20 and the balance made up of fainter
galaxies in the field. We provide a table listing the galaxy positions,
measured redshift and error, and note any emission lines that were visible in
the spectrum. In practice almost all the galaxies with r < 19 were observed
including all of the radio sources and most of the 24 microns sources with r <
20 and a sample of radio sources which had fainter optical counterparts on the
r-band image.Comment: 6 pages, 3 tables, 2 figures, full electronic tables at
http://www.aoc.nrao.edu/~fowen/papers/SWIRE/WIYNpaper3/, accepted ApJ Suppl
Serie
A Summons to Memphis: Exploring the Life and Times of the Reverend Mr. George White (1802-1887)
A native of Charleston, S. C., he removed to Savannah, Georgia, in 1822. As principal of the Chatham Academy, and for fourteen years of his own Savannah Academy, he acquired fame; he is best remembered by the brilliant, Classical scholarship of his students. Ordained an Episcopal clergyman in 1836, he engaged in mission work, preaching to seamen and to the Negro population, also establishing a church. For over sixty years he was married to Elizabeth Millen of Savannah; they had eight children, three surviving them. As a charter member of the Georgia Historical Association, he wrote important early histories, his Statistics of Geotgia (1849) and Historical Collections of Georgia (1855. Between 1849 and 1858
he lived in Marietta, Georgia, served in relief or as missionary elsewhere in the state, and served a two-year rectorship at Trinity Church, Florence, Alabama. In 1858, he removed to Calvary Church in Memphis, which he served valiantly during the War Between the States and the yellow fever outbreak of 1878, which took his son, A tireless servant of the Church, and of God, he died Apr. 30, 1887,https://digitalcommons.georgiasouthern.edu/sav-bios-lane/1112/thumbnail.jp
The Cambridge-Cambridge ROSAT Serendipity Survey - I. X-ray-luminous galaxies
We report on the first results obtained from a new optical identification
programme of 123 faint X-ray sources with (0.5--2ergscm serendipitously detected in {\it ROSAT}
PSPC pointed observations. We have spectroscopically identified the optical
counterparts to more than 100 sources in this survey. Although the majority of
the sample (68 objects) are QSOs, we have also identified 12 narrow emission
line galaxies which have extreme X-ray luminosities (ergs). Subsequent spectroscopy reveals them to be a
mixture of starburst galaxies and Seyfert 2 galaxies in approximately equal
numbers. Combined with potentially similar objects identified in the {\it
Einstein} Extended Medium Sensitivity Survey, these X-ray-luminous galaxies
exhibit a rate of cosmological evolution, , consistent with that derived for X-ray QSOs. This
evolution, coupled with the steep slope determined for the faint end of the
X-ray luminosity function (), implies
that such objects could comprise 15--35 per cent of the soft (1--2keV)Comment: Accepted for publication in MNRAS. 7 pages including 5 figures;
uuencoded compressed postscript; RGO-21
Chandra Detection of Highest Redshift (z~6) Quasars in X-rays
We report on Chandra observations of three quasars SDSSP J083643+005453,
SDSSP J103027+052455, and SDSSP J130608+035626 at redshifts 5.82, 6.28 and 5.99
respectively. All the three sources are clearly detected in the X-ray band, up
to rest frame energies of ~55 keV. These observations demonstrate the
unprecedented sensitivity of Chandra to detect faint sources in relatively
short exposure times (5.7--8.2 ksec). The broad band X-ray properties of these
highest redshift quasars do not appear to be any different from their lower
redshift cousins. Spectra of the sources could not be determined with only few
counts detected. Observations with XMM-Newton will be able to constrain the
spectral shapes, if they are simple. Determination of complex spectra in a
reasonable amount of time, however, will have to await next generation of X-ray
missions.Comment: Submitted to ApJ Letter
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