Atomic Data for Permitted Resonance Lines of Atoms and Ions from H to Si, and S, Ar, Ca and Fe

We list vacuum wavelengths, energy levels, statistical weights, transition probabilities and oscillator strengths for permitted resonance spectral lines of all ions of 18 astrophysically important elements (H through Si, S, Ar, Ca, Fe). Using a compilation of experimental energy levels, we derived accurate wavelengths for 5599 lines of 1828 ground-term multiplets which have gf-values calculated in the Opacity Project. We recalculated the Opacity Project multiplet gf-values to oscillator strengths and transition probabilities of individual lines. For completeness, we added 372 resonance lines of NeI, ArI, FeI and FeII ions which are not covered by the Opacity Project. Intercombination and forbidden lines are not included in the present compilation.Comment: 6 pages of text, latex, 1 figure, 4 tables; tables in ASCII format available at ftp://asta.pa.uky.edu/dima/lines/ or at http://www.pa.uky.edu/~verner/atom.html Accepted by Atomic Data Nucl. Data Table

Elucidating the Correlation of the Quasar \ion{Fe}{2}/\ion{Mg}{2} Ratio with Redshift

Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from quasars has a major cosmological motivation. Both Fe and Mg are produced by short-lived massive stars. In addition, Fe is produced by accreting white dwarf supernovae somewhat after star formation begins. Therefore, we expect that the Fe/Mg ratio will gradually decrease with redshift. We have used data from the Sloan Digital Sky Survey to explore the dependence of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio on redshift and on luminosity in the redshift range of $0.75< z< 2.20$, and we have used predictions from our 830-level model for the \ion{Fe}{2} atom in photoionization calculations to interpret our findings. We have split the quasars into several groups based upon the value of their \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios, and then checked to see how the fraction of quasars in each group varies with the increase of redshift. We next examined the luminosity dependence of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio, and we found that beyond a threshold of \ion{Fe}{2}(UV)/\ion{Mg}{2} =~ 5, and $M_{2500} < -25\rm mag$, the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio increases with luminosity, as predicted by our model. We interpret our observed variation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio with redshift as a result of the correlation of redshift with luminosity in a magnitude limited quasar sample.Comment: ApJL accepte

A NEGATIVE-COST APPROACH TO THE FORMULATION OF A TRANSHIPMENT PROBLEM

Agribusiness,

Skeletal Biomechanics and Response to Mechanical Load: A Comparative Approach in the Mouse and Chukar Partridge

Dynamic mechanical loading plays an important role in regulating bone geometry and strength. A healthy skeleton adapts to the bone tissue strain profile and magnitude of loads it experiences on a daily basis in order to maintain reasonable safety factors. In skeletal diseases, such as osteoporosis, a bone’s ability to adapt and maintain structural integrity in response to increased mechanical strains is apparently impaired, which allows skeletal resorption to progress unabated and could eventually lead to mechanical failure. In order to develop better treatments for bone wasting diseases, it is important to understand the mechanobiology of how the healthy skeleton responds to mechanical load. The non-invasive, axial compressive murine tibial loading model has been used extensively to study skeletal adaptation, but sole use of rodent models propagates a large gap in understanding skeletal sensitivity and response to load across terrestrial vertebrate groups. The avian skeleton exhibits several features that make it unique compared to the mammalian rodent skeleton, and these differences could affect how the avian skeleton responds to mechanical load relative to the rodent skeleton. To begin expanding our understanding of skeletal sensitivity across vertebrate species, we developed a novel non-invasive avian tibiotarsal (TBT) loading model using the chukar partridge to complement the use of the murine tibial loading model. For both the mouse and the bird, relatively similar increases in strain stimuli via experimentally applied loads were determined through a combination of in vivo strain gauging and finite element models. The cross-sectional strain distributions during locomotion and experimental loading were further characterized in the bird TBT after validating the use of planar strain theory for cortical bone loaded in bending. In response to several weeks of experimentally applied loading, the mouse tibia adapted its geometry and mass. In contrast, the birds adapted their cross-sectional geometry without complementary increases in bone mass while suppressing normal endocortical bone growth. Lastly, in order to study cortical bone’s response to mechanical load without the potentially confounding effects of varied systemic factors across species, we developed a novel isolated cortical bone culture model that can be mechanically loaded in vitro. We validated that osteocytes in a murine tibial bone segment maintained adequate survival over a five day culture period, and comprehensively characterized the load induced strain profile. Overall, this work takes novel steps to develop and validate comparative in vivo and in vitro models for comparatively assessing skeletal sensitivity across terrestrial vertebrate species. Continued work in this direction will enhance our understanding of how a healthy skeleton is regulated to maintain adequate bone strength

High-Resolution Spectroscopy from 3050 to 10000 A of the HDF-S QSO J2233-606 with UVES at the ESO VLT

We report on high-resolution observations ($\Re \simeq 45000$) of the Hubble Deep Field South QSO J2233-606 obtained with the VLT UV-Visual Echelle Spectrograph (UVES). We present spectral data for the wavelength region $3050 < \lambda < 10000$ \AA. The $S/N$ ratio of the final spectrum is about 50 per resolution element at 4000 \AA, 90 at 5000 \AA, 80 at 6000 \AA, 40 at 8000 \AA. Redshifts, column densities and Doppler widths of the absorption features have been determined with Voigt-profile fitting. A total of 621 lines have been measured. In particular 270 Ly-alpha lines, 41 Ly-beta and 24 systems containing metal lines have been identified. Together with other data in the literature, the present spectrum confirms that the evolution of the number density of Ly-alpha lines with $\log N($\huno$) > 14$ has an upturn at $z \sim 1.4-1.6$.Comment: 34 pages Latex, with 3 PostScript figures. Astronomical Journal, in press. A few revised upper limit

Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions

We present a complete set of analytic fits to the non-relativistic photoionization cross sections for the ground states of atoms and ions of elements from H through Si, and S, Ar, Ca, and Fe. Near the ionization thresholds, the fits are based on the Opacity Project theoretical cross sections interpolated and smoothed over resonances. At higher energies, the fits reproduce calculated Hartree-Dirac-Slater photoionization cross sections.Comment: 24 pages including Postscript figures and tables, uses aaspp4.sty, accepted for publication in Astrophysical Journal. Misprint in Eq.(1) is correcte