Domain specific software design for decision aiding

McDonnell Aircraft Company (MCAIR) is involved in many large multi-discipline design and development efforts of tactical aircraft. These involve a number of design disciplines that must be coordinated to produce an integrated design and a successful product. Our interpretation of a domain specific software design (DSSD) is that of a representation or framework that is specialized to support a limited problem domain. A DSSD is an abstract software design that is shaped by the problem characteristics. This parallels the theme of object-oriented analysis and design of letting the problem model directly drive the design. The DSSD concept extends the notion of software reusability to include representations or frameworks. It supports the entire software life cycle and specifically leads to improved prototyping capability, supports system integration, and promotes reuse of software designs and supporting frameworks. The example presented in this paper is the task network architecture or design which was developed for the MCAIR Pilot's Associate program. The task network concept supported both module development and system integration within the domain of operator decision aiding. It is presented as an instance where a software design exhibited many of the attributes associated with DSSD concept

Interview with Kirby Phillips

Kirby Phillips talks about his involvement with the 4H Clubhttps://digital.kenyon.edu/ps_interviews/1020/thumbnail.jp

Episodic starbursts in dwarf spheroidal galaxies: a simple model

Dwarf galaxies in the Local Group appear to be stripped of their gas within 270 kpc of the host galaxy. Color-magnitude diagrams of these dwarfs, however, show clear evidence of episodic star formation (\Delta{}t ~ a few Gyr) over cosmic time. We present a simple model to account for this behaviour. Residual gas within the weak gravity field of the dwarf experiences dramatic variations in the gas cooling time around the eccentric orbit. This variation is due to two main effects. The azimuthal compression along the orbit leads to an increase in the gas cooling rate of ~([1+\epsilon]/[1-\epsilon])^2. The Galaxy's ionizing field declines as 1/R^2 for R>R_disk although this reaches a floor at R~150 kpc due to the extragalactic UV field ionizing intensity. We predict that episodic SF is mostly characteristic of dwarfs on moderately eccentric orbits (\epsilon>0.2) that do not come too close to the centre (R>R_disk) and do not spend their entire orbit far away from the centre (R>200 kpc). Up to 40% of early infall dwarf spheroidals can be expected to have already had at least one burst since the initial epoch of star formation, and 10% of these dwarf spheriodals experiencing a second burst. Such a model can explain the timing of bursts in the Carina dwarf spheroidal and restrict the orbit of the Fornax dwarf spheroidal. However, this model fails to explain why some dwarfs, such as Ursa Minor, experience no burst post-infall.Comment: 8 pages, 8 figures. ApJ accepte

Multi-Element Abundance Measurements from Medium-Resolution Spectra. I. The Sculptor Dwarf Spheroidal Galaxy

We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way. This is the largest sample of individual alpha element (Mg, Si, Ca, Ti) abundance measurements in any single dSph. The measurements are made from Keck/DEIMOS medium-resolution spectra (6400-9000 A, R ~ 6500). Based on comparisons to published high-resolution (R >~ 20000) spectroscopic measurements, our measurements have uncertainties of sigma([Fe/H]) = 0.14 and sigma([alpha/Fe]) = 0.13. The Sculptor [Fe/H] distribution has a mean = -1.58 and is asymmetric with a long, metal-poor tail, indicative of a history of extended star formation. Sculptor has a larger fraction of stars with [Fe/H] < -2 than the Milky Way halo. We have discovered one star with [Fe/H] = -3.80 +/- 0.28, which is the most metal-poor star known anywhere except the Milky Way halo, but high-resolution spectroscopy is needed to measure this star's detailed abundances. As has been previously reported based on high-resolution spectroscopy, [alpha/Fe] in Sculptor falls as [Fe/H] increases. The metal-rich stars ([Fe/H] ~ -1.5) have lower [alpha/Fe] than Galactic halo field stars of comparable metallicity. This indicates that star formation proceeded more gradually in Sculptor than in the Galactic halo. We also observe radial abundance gradients of -0.030 +/- 0.003 dex per arcmin in [Fe/H] and +0.013 +/- 0.003 dex per arcmin in [alpha/Fe] out to 11 arcmin (275 pc). Together, these measurements cast Sculptor and possibly other surviving dSphs as representative of the dwarf galaxies from which the metal-poor tail of the Galactic halo formed.Comment: Accepted to ApJ on 2009 Sep 15, 22 pages, 23 figure

On the parabolic equation method in internal wave propagation

A parabolic equation for the propagation of periodic internal waves over varying bottom topography is derived using the multiple-scale perturbation method. Some computational aspects of the numerical implementation are discussed. The results of numerical experiments on propagation of an incident plane wave over a circular-type shoal are presented in comparison with the analytical result, based on Born approximation.Comment: Submitted to Coastal Engineering. 16 pages, 5 figures. One figure was excluded from article because of size problem

Temperature-dependent release of ATP from human erythrocytes: Mechanism for the control of local tissue perfusion

Copyright @ 2012 The AuthorsThis article has been made available through the Brunel Open Access Publishing Fund.Human limb muscle and skin blood flow increases significantly with elevations in temperature, possibly through physiological processes that involve temperature-sensitive regulatory mechanisms. Here we tested the hypothesis that the release of the vasodilator ATP from human erythrocytes is sensitive to physiological increases in temperature both in vitro and in vivo, and examined potential channel/transporters involved. To investigate the source of ATP release, whole blood, red blood cells (RBCs), plasma and serum were heated in vitro to 33, 36, 39 and 42°C. In vitro heating augmented plasma or ‘bathing solution’ ATP in whole blood and RBC samples, but not in either isolated plasma or serum samples. Heat-induced ATP release was blocked by niflumic acid and glibenclamide, but was not affected by inhibitors of nucleoside transport or anion exchange. Heating blood to 42°C enhanced (P < 0.05) membrane protein abundance of cystic fibrosis transmembrane conductance regulator (CFTR) in RBCs. In a parallel in vivo study in humans exposed to whole-body heating at rest and during exercise, increases in muscle temperature from 35 to 40°C correlated strongly with elevations in arterial plasma ATP (r2 = 0.91; P = 0.0001), but not with femoral venous plasma ATP (r2 = 0.61; P = 0.14). In vitro, however, the increase in ATP release from RBCs was similar in arterial and venous samples heated to 39°C. Our findings demonstrate that erythrocyte ATP release is sensitive to physiological increases in temperature, possibly via activation of CFTR-like channels, and suggest that temperature-dependent release of ATP from erythrocytes might be an important mechanism regulating human limb muscle and skin perfusion in conditions that alter blood and tissue temperature.This article is made available through the Brunel Open Access Publishing Fund

Spectroscopic versus Photometric Metallicities: Milky Way Dwarf Spheroidal Companions as a Test Case

Aims. The method of deriving photometric metallicities using red giant branch stars is applied to resolved stellar populations under the common assumption that they mainly consist of single-age old stellar populations. We explore the effect of the presence of mixed-age stellar populations on deriving photometric metallicities. Methods. We use photometric data sets for the five Galactic dwarf spheroidals Sculptor, Sextans, Carina, Fornax, and Leo II in order to derive their photometric metallicity distribution functions from their resolved red giant branches using isochrones of the Dartmouth Stellar Evolutionary Database. We compare the photometric metallicities with published spectroscopic metallicities based on the analysis of the near-infrared Ca triplet (Ca T), both on the metallicity scale of Carretta & Gratton and on the scale defined by the Dartmouth isochrones. In addition, we compare the photometric metallicities with published spectroscopic metallicities based on spectral synthesis and medium-resolution spectroscopy, and on high resolution spectra where available. Results. The mean properties of the spectroscopic and photometric metallicity samples are comparable within the intrinsic scatter of each method although the mean metallicities of dSphs with pronounced intermediate-age population fractions may be underestimated by the photometric method by up to a few tenths of dex in [Fe/H]. The star-by-star differences of the spectroscopic minus the photometric metallicities show a wide range of values along the fiducial spectroscopic metallicity range, with the tendency to have systematically lower photometric metallicities for those dwarf spheroidals with a higher fraction of intermediate-age populations. Such discrepancies persist even in the case of the purely old Sculptor dSph, where one would na\"ively expect a very good match when comparing with medium or low resolution metallicity measurements. Overall, the agreement between Ca T metallicities and photometric metallicities is very good in the metallicity range from ~ -2 dex to ~ -1.5 dex. We find that the photometric method is reliable in galaxies that contain small (less than 15%) intermediate-age stellar fractions. Therefore, in the presence of mixed-age stellar populations, one needs to quantify the fraction of the intermediate-age stars in order to assess their effect on determining metallicities from photometry alone. Finally, we note that the comparison of spectroscopic metallicities of the same stars obtained with different methods reveals similarly large discrepancies as the comparison with photometric metallicities.Comment: 17 pages, 12 figures; A&A accepte

Multi-Element Abundance Measurements from Medium-Resolution Spectra. IV. Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies

We derive the star formation histories of eight dwarf spheroidal (dSph) Milky Way satellite galaxies from their alpha element abundance patterns. Nearly 3000 stars from our previously published catalog (Paper II) comprise our data set. The average [alpha/Fe] ratios for all dSphs follow roughly the same path with increasing [Fe/H]. We do not observe the predicted knees in the [alpha/Fe] vs. [Fe/H] diagram, corresponding to the metallicity at which Type Ia supernovae begin to explode. Instead, we find that Type Ia supernova ejecta contribute to the abundances of all but the most metal-poor ([Fe/H] < -2.5) stars. We have also developed a chemical evolution model that tracks the star formation rate, Types II and Ia supernova explosions, and supernova feedback. Without metal enhancement in the supernova blowout, massive amounts of gas loss define the history of all dSphs except Fornax, the most luminous in our sample. All six of the best-fit model parameters correlate with dSph luminosity but not with velocity dispersion, half-light radius, or Galactocentric distance.Comment: 28 pages, 14 figures; accepted for publication in ApJ; very minor editorial corrections in v

Variability and star formation in Leo T, the lowest luminosity star-forming galaxy known today

We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way (MW) "ultra-faint" dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 10 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409 $^{+29}_{-27}$ kpc (distance modulus of 23.06 $\pm$ 0.15 mag) was derived from the galaxy's RR Lyrae star. Our V, V-I color-magnitude diagram of Leo T reaches V~29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the star formation history, based on the comparison of the observed V,V-I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex star formation history dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.Comment: 31 pages, 14 figures, accepted for publication in Ap