The Chemical Compositions Of RR Lyrae Type C Variable Stars

We present a detailed chemical abundance study of eight RR Lyrae variable stars of subclass c (RRc). The target RRc stars chosen for study exhibit "Blazhko-effect" period and amplitude modulations to their pulsational cycles. Data for this study were gathered with the echelle spectrograph of the 100 inch du Pont telescope at Las Campanas Observatory. Spectra were obtained throughout each star's pulsation cycle. Atmospheric parameters-effective temperature, surface gravity, microturbulent velocity, and metallicity-were derived at multiple phase points. We found metallicities and element abundance ratios to be constant within observational uncertainties over the pulsational cycles of all stars. Moreover, the alpha-element and Fe-group abundance ratios with respect to iron are consistent with other horizontal-branch members (RRab, blue and red non-variables). Finally, we have used the [Fe/H] values of these eight RRc stars to anchor the metallicity estimates of a large-sample RRc snapshot spectroscopic study being conducted with the same telescope and instrument combination employed here.NSF AST-0908978, AST-1211585Baker Centennial Research EndowmentJohn W. Cox Endowment for the Advanced Studies in AstronomyMcDonald Observator

A Simulation of Demand-Driven Dataflow: Translation from Lucid into MDC Language

Message Driven Computation (MDC) is a model of computation with which they have been experimenting at the Illinois Institute of Technology. The authors aim to prove the viability of MDC in practice for the expression of parallel algorithms and the implementation of functional and dataflow programming languages. In the paper they discuss their implementation of the Lucid programming language in MDC. The discussion presents a subset of Lucid which illustrates the principles of Lucid, Message Driven Computing, and the translation into and the interpretation of dataflow graphs

Factorization of e+e- Event Shape Distributions with Hadronic Final States in Soft Collinear Effective Theory

We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory.Comment: 21 pages. Journal version. Defined an explicit thrust axis operator; clarified meaning of a delta function operato

We Have the Spaceship; But Where's the Start Button: Human Engineering Issues in the Age of Long Duration Space Exploration

As long duration space exploration and habitation becomes more commonplace, a number of Human Engineering factors (Gravitational Adaptation, 2-D to 3-D Movement Adaptation, Design Form/Function, and Space Ergonomics to name a few) will become more pronounced. More research and development is needed in these areas or the explorers may find themselves in painful or dangerous situations

Rh single atoms on TiO2 dynamically respond to reaction conditions by adapting their site.

Single-atom catalysts are widely investigated heterogeneous catalysts; however, the identification of the local environment of single atoms under experimental conditions, as well as operando characterization of their structural changes during catalytic reactions are still challenging. Here, the preferred local coordination of Rh single atoms is investigated on TiO2 during calcination in O2, reduction in H2, CO adsorption, and reverse water gas shift (RWGS) reaction conditions. Theoretical and experimental studies clearly demonstrate that Rh single atoms adapt their local coordination and reactivity in response to various redox conditions. Single-atom catalysts hence do not have static local coordinations, but can switch from inactive to active structure under reaction conditions, hence explaining some conflicting literature accounts. The combination of approaches also elucidates the structure of the catalytic active site during reverse water gas shift. This insight on the real nature of the active site is key for the design of high-performance catalysts

The prevalence of BANA‐hydrolyzing periodontopathic bacteria in smokers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99012/1/j.1600-051X.1999.tb02526.x.pd

Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes

Employing spectra obtained with the new Keck I HIRES near-UV sensitive detector, we have performed a comprehensive chemical composition analysis of the binary blue metal-poor star CS29497-030. Abundances for 29 elements and upper limits for an additional seven have been derived, concentrating on elements largely produced via neutron-capture nucleosynthesis. Included in our analysis are the two elements that define the termination point of the slow neutron-capture process, lead and bismuth. We determine an extremely high value of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the single-feature result obtained in previous studies. We also detect Bi for the first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with those predicted from the most recent FRANEC calculations of the slow neutron-capture process in low-mass AGB stars. We find that the neutron-capture elemental abundances of CS29497-030 are best explained by an AGB model that also includes very significant amounts of pre-enrichment of rapid neutron-capture process material in the protostellar cloud out of which the CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and ``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can be further constrained by the abundance of the light odd-element [Na/Fe] which is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to appear in ApJ Letters; additional jpeg figure available at ftp://www.astro.caltech.edu/users/iii/cs2949703

Radial Velocities and Pulsation Ephemerides of 11 Field RR Lyrae Stars

We present new radial velocities, improved pulsation periods and reference epoch s of 11 field RR Lyrae ab-type variables: AS Vir, BS Aps, CD Vel, DT Hya, RV Oct, TY Gru, UV Oct, V1645 Sgr, WY Ant, XZ Aps and Z Mic. This study is based on high resolution spectra obtained with the echelle spectro graph of the 2.5-m du Pont telescope at Las Campanas Observatory. We obtained ~200 spectra per star (i.e, total of ~2300 spectra) distributed more or less uniformly throughout their pulsation cycles. Radial velocity curves and photometric lightcurves phased to our new ephemerides are presented for all program stars. In a subsequent paper, we will use these spectra to derive stellar atmospheric parameters and chemical compositions throughout the pulsational cycles, based purely on spectroscopic constraints.Comment: 28 pages, 14 figures, 5 tables. Accepted for publication in ApJ