31,359 research outputs found
Modeling the chemical evolution of Omega Centauri using three-dimensional hydrodynamical simulations
We present a hydrodynamical and chemical model for the globular cluster Omega
Cen, under the assumption that it is the remnant of an ancient dwarf spheroidal
galaxy (dSph), the bulk of which was disrupted and accreted by our Galaxy ~10
Gyr ago. We highlight the very different roles played by Type II and Type Ia
supernovae (SNe) in the chemical enrichment of the inner regions of the
putative parent dSph. While the SNe II pollute the interstellar medium rather
uniformly, the SNe Ia ejecta may remain confined inside dense pockets of gas as
long as succesive SNe II explosions spread them out. Stars forming in such
pockets have lower alpha-to-iron ratios than the stars forming elsewhere. Owing
to the inhomogeneous pollution by SNe Ia, the metal distribution of the stars
in the central region differs substantially from that of the main population of
the dwarf galaxy, and resembles that observed in Omega Cen. This inhomogeneous
mixing is also responsible for a radial segregation of iron-rich stars with
depleted [alpha/Fe] ratios, as observed in some dSphs. Assuming a star
formation history of ~1.5 Gyr, our model succeeds in reproducing both the iron
and calcium distributions observed in Omega Cen and the main features observed
in the empirical alpha/Fe versus Fe/H plane. Finally, our model reproduces the
overall spread of the color-magnitude diagram, but fails in reproducing the
morphology of the SGB-a and the double morphology of the main sequence.
However, the inhomogeneous pollution reduces (but does not eliminate) the need
for a significantly enhanced helium abundance to explain the anomalous position
of the blue main sequence. Further models taking into account the dynamical
interaction of the parent dwarf galaxy with the Milky Way and the effect of AGB
pollution will be required.Comment: 15 pages, 13 figures. MNRAS accepte
Three-body structure of the system with coupling
The structure of the three-body system, which has been observed
recently by the HypHI collaboration, is investigated taking coupling explicitly into account. The and interactions employed in
this work reproduce the binding energies of H, H
and He. We do not find any bound state, which
contradicts the interpretation of the data reported by the HypHI collaboration.Comment: To be publsihed in PRC as a Rapid communicatio
Two-dimensional oscillating airfoil test apparatus
A two dimensional oscillating airfoil test apparatus is presented as a method of measuring unsteady aerodynamic forces on an airfoil or rotor blade section. The oscillating airfoil test rig, which is being built for use in an 11 X 11-foot transonic wind tunnel (speed range M = 0.4 - 1.4), will allow determination of unsteady loadings and detailed pressure distributions on representative airfoil sections undergoing simulated pitching and flapping motions. The design details of the motion generating system and supporting structure are presented. This apparatus is now in the construction phase
Three-nucleon interactions: A frontier in nuclear structure
Three-nucleon interactions are a frontier in understanding and predicting the
structure of strongly-interacting matter in laboratory nuclei and in the
cosmos. We present results and discuss the status of first calculations with
microscopic three-nucleon interactions beyond light nuclei. This coherent
effort is possible due to advances based on effective field theory and
renormalization group methods in nuclear physics.Comment: 7 pages, 11 figures, talk at International Symposium on New Facet of
Three-Nucleon Force (FM50), Tokyo, October, 200
Importance of Baryon-Baryon Coupling in Hypernuclei
The coupling in --hypernuclei and coupling in --hypernuclei produce novel
physics not observed in the conventional, nonstrange sector. Effects of
conversion in H are reviewed.
The role of coupling suppression in the
--hypernuclei due to Pauli blocking is highlighted, and the
implications for the structure of B are explored.
Suppression of conversion in He is hypothesized as the reason that the
matrix element is small. Measurement of H is
proposed to investigate the full interaction. The
implication for analog states is discussed.Comment: 17 pages LATEX, 1 figure uuencoded postscrip
On Dwarf Galaxies as the Source of Intracluster Gas
Recent observational evidence for steep dwarf galaxy luminosity functions in
several rich clusters has led to speculation that their precursors may be the
source of the majority of gas and metals inferred from intracluster medium
(ICM) x-ray observations. Their deposition into the ICM is presumed to occur
through early supernovae-driven winds, the resultant systems reflecting the
photometric and chemical properties of the low luminosity dwarf spheroidals and
ellipticals we observe locally. We consider this scenario, utilising a
self-consistent model for spheroidal photo-chemical evolution and gas ejection
via galactic superwinds. Insisting that post-wind dwarfs obey the observed
colour-luminosity-metallicity relations, we conclude that the bulk of the ICM
gas and metals does not originate within their precursors.Comment: 43 pages, 8 figures, LaTeX, also available at
http://msowww.anu.edu.au/~gibson/publications.html, to appear in ApJ, Vol
473, 1997, in pres
System maintenance manual for master modeling of aerodynamic surfaces by three-dimensional explicit representation
A system of computer programs has been developed to model general three-dimensional surfaces. Surfaces are modeled as sets of parametric bicubic patches. There are also capabilities to transform coordinate to compute mesh/surface intersection normals, and to format input data for a transonic potential flow analysis. A graphical display of surface models and intersection normals is available. There are additional capabilities to regulate point spacing on input curves and to compute surface intersection curves. Internal details of the implementation of this system are explained, and maintenance procedures are specified
A systematic review of worldwide cancer nursing research: 1994 to 2003
Kelly contributed to the conduct and choice of papers for the study, carried out a systematic review of one sixth of all the papers, contributed to the conclusion and helped to edit the final version of this paper
Dissociation of Action and Object Naming: Evidence From Cortical Stimulation Mapping
This cortical stimulation mapping study investigates the neural representation of action and object naming. Data from 13 neurosurgical subjects undergoing awake cortical mapping is presented. Our findings indicate clear evidence of differential disruption of noun and verb naming in the context of this naming task. At the individual level, evidence was found for punctuate regions of perisylvian cortex subserving noun and verb function. Across subjects, however, the location of these sites varied. This finding may help explain discrepancies between lesion and functional imaging studies of noun and verb naming. In addition, an alternative coding of these data served to highlight the grammatical class vulnerability of the target response. The use of this coding scheme implicates a role for the supramarginal gyrus in verb-naming behavior. These data are discussed with respect to a functional-anatomical pathway underlying verb naming
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