5,667 research outputs found
Population Growth and Other Statistics of Middle-sized Irish Towns. General Research Series Paper No. 85, April 1976
The basic aim of the study is the presentation of tables of comparative
statistical data relating to 97 towns with population 5OO-1O,OOO in
1971 and analyses of such data. The exclusion of the four County Boroughs
and Dun Laoghaire together with twelve other large towns and all small
towns and villages, was to impart a degree of homogeneity to the inquiry, as
regards function of town. The 97 towns range from Mullingar, the largest
with a population of 9,245 to Cootehill with 1,542
Elastic and thermal properties of hexagonal perovskites
We systematically investigate the mechanical and thermal properties of the P6₃cm hexagonal perovskites with composition A³+B³+O₃ for potential use in thermal barrier coatings. In spite of the structural anisotropy, the elastic constants are essentially isotropic. The thermal expansion is, however, strongly anisotropic, while the thermal conductivity is relatively isotropic. The thermal conductivities of the hexagonal perovskites are much larger than those of the orthorhombic perovskites
Engineering the free vacancy and active donor concentrations in phosphorus and arsenic double donor-doped germanium
In germanium, donor atoms migrate or form larger immobile clusters via their interaction with lattice vacancies. By engineering the concentration of free vacancies, it is possible to control the diffusion of the donor atoms and the formation of those larger clusters that lead to the deactivation of a significant proportion of the donor atoms. Electronic structure calculations in conjunction with mass action analysis are used to predict the concentrations of free vacancies and deactivated donor atoms in germanium doped with different proportions of arsenic and phosphorous. We find, for example, that at low temperatures, the concentration of free vacancies is partially suppressed by increasing the proportion of arsenic doping, whereas at high temperatures (above 1000 K), the concentration of free vacancies is relatively constant irrespective of the donor species. It is predicted that the free vacancy and active donor concentrations vary linearly with the arsenic to phosphorous ratio across a wide range of temperatures
Probing the extreme realm of AGN feedback in the massive galaxy cluster, RX J1532.9+3021
We present a detailed Chandra, XMM-Newton, VLA and HST analysis of one of the
strongest cool core clusters known, RX J1532.9+3021 (z=0.3613). Using new, deep
90 ks Chandra observations, we confirm the presence of a western X-ray cavity
or bubble, and report on a newly discovered eastern X-ray cavity. The total
mechanical power associated with these AGN-driven outflows is (22+/-9)*10^44
erg/s, and is sufficient to offset the cooling, indicating that AGN feedback
still provides a viable solution to the cooling flow problem even in the
strongest cool core clusters. Based on the distribution of the optical
filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map,
we suggest that the cluster harbours older outflows along the north to south
direction. The jet of the central AGN is therefore either precessing or
sloshing-induced motions have caused the outflows to change directions. There
are also hints of an X-ray depression to the north aligned with the 325 MHz
jet-like structure, which might represent the highest redshift ghost cavity
discovered to date. We further find evidence of a cold front (r=65kpc) that
coincides with the outermost edge of the western X-ray cavity and the edge of
the radio mini-halo. The common location of the cold front with the edge of the
radio mini-halo supports the idea that the latter originates from electrons
being reaccelerated due to sloshing induced turbulence. Alternatively, its
coexistence with the edge of the X-ray cavity may be due to cool gas being
dragged out by the outburst. We confirm that the central AGN is highly
sub-Eddington and conclude that a >10^10M_Sun or a rapidly spinning black hole
is favoured to explain both the radiative-inefficiency of the AGN and the
powerful X-ray cavities.Comment: Accepted for publication to ApJ (minor corrections), 16 pages, 16
figures, 5 tables. Full resolution at http://www.stanford.edu/~juliehl/M1532
From solid solution to cluster formation of Fe and Cr in -Zr
To understand the mechanisms by which Fe and Cr additions increase the
corrosion rate of irradiated Zr alloys, a combination of experimental (atom
probe tomography, x-ray diffraction and thermoelectric power measurements) and
modelling (density functional theory) techniques are employed to investigate
the non-equilibrium solubility and clustering of Fe and Cr in binary Zr alloys.
Cr occupies both interstitial and substitutional sites in the {\alpha}-Zr
lattice, Fe favours interstitial sites, and a low-symmetry site that was not
previously modelled is found to be the most favourable for Fe. Lattice
expansion as a function of alloying concentration (in the dilute regime) is
strongly anisotropic for Fe additions, expanding the -axis while contracting
the -axis. Defect clusters are observed at higher solution concentrations,
which induce a smaller amount of lattice strain compared to the dilute defects.
In the presence of a Zr vacancy, all two-atom clusters are more soluble than
individual point defects and as many as four Fe or three Cr atoms could be
accommodated in a single Zr vacancy. The Zr vacancy is critical for the
increased solubility of defect clusters, the implications for irradiation
induced microstructure changes in Zr alloys are discussed.Comment: 15 pages including figure, 9 figures, 2 tables. Submitted for
publication in Acta Mater, Journal of Nuclear Materials (2015
A Composite HST Spectrum of Quasars
We construct a composite quasar spectrum from 284 HST FOS spectra of 101
quasars with redshifts z > 0.33. The spectrum covers the wavelengths between
350 and 3000 A in the rest frame. There is a significant steepening of the
continuum slope around 1050 A. The continuum between 1050 and 2200 A can be
modeled as a power law with alpha = -0.99. For the full sample the power-law
index in the extreme ultraviolet (EUV) between 350 and 1050 A is alpha = -1.96.
The continuum flux in the wavelengths near the Lyman limit shows a depression
of about 10 percent. The break in the power-law index and the slight depression
of the continuum near the Lyman limit are features expected in Comptonized
accretion-disk spectra.Comment: 10 figures To appear in the February 1, 1997, issue of the Ap.
Diffusion and defect reactions between donors, C, and vacancies in Ge. II. Atomistic calculations of related complexes
Electronic structure calculations are used to study the stability, concentration, and migration of vacancy-donor (phosphorus, arsenic, and antimony) complexes in germanium, in the presence of carbon. The association of carbon with mobile vacancy-donor pairs can lead to energetically favorable and relatively immobile complexes. It is predicted that the complexes formed between lattice vacancies, carbon, and antimony substitutional atoms are more stable and less mobile compared to complexes composed of vacancies, carbon, and phosphorus or arsenic atoms. Then, with the use of mass action analysis, the relative concentrations of the most important complexes are calculated, which depend also on their relative stability not just their absolute stability. Overall, the theoretical predictions are consistent with experimental results, which determined that the diffusion of vacancy-donor defects is retarded in the presence of carbon, especially in samples with a high concentration of carbon. In addition, the calculations provide information on the structure and the equilibrium concentration of the most important complexes and details of their association energies
The Determination of Nuclear Level Densities from Experimental Information -
A novel Information Theory based method for determining the density of states
from prior information is presented. The energy dependence of the density of
states is determined from the observed number of states per energy interval and
model calculations suggest that the method is sufficiently reliable to
calculate the thermal properties of nuclei over a reasonable temperature range.Comment: 7 pages + 6 eps figures, REVTEX 3.
Observation of Ground-State Two-Neutron Decay
Neutron decay spectroscopy has become a successful tool to explore nuclear
properties of nuclei with the largest neutron-to-proton ratios. Resonances in
nuclei located beyond the neutron dripline are accessible by kinematic
reconstruction of the decay products. The development of two-neutron detection
capabilities of the Modular Neutron Array (MoNA) at NSCL has opened up the
possibility to search for unbound nuclei which decay by the emission of two
neutrons. Specifically this exotic decay mode was observed in 16Be and 26O.Comment: To be published in Acta Physica Polonica
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