Urban modelling as storytelling: using simulation models as a narrative

This article examines the distinctions between empirical and simulation models using the metaphors of argument and narrative. It argues that all argumentation is contextualized within a narrative that is either inferred or communicated. The paper provides another semantic structure for urban models that applies elements of systems- dynamic method to construct "stories" of the past and possible futures of communities in a watershed in southern Arizona. By constructing such narratives this paper demonstrates how computer-based urban models can "tell a story"

Measuring the Slope of the Dust Extinction Law and the Power Spectrum of Dust Clouds Using Differentially-Reddened Globular Clusters

We present 3 methods for measuring the Galactic dust extinction law slope R_V and a method for quantifying fine structure in dust clouds in the direction of differentially-reddened globular clusters. We apply these methods to the low- latitude globular cluster NGC4833 which displays variable extinction/reddening about a mean ~ 1. A set of Monte Carlo simulations is used to characterize the efficacy of the methods. The essence of the first 2 methods is to determine, for an assumed value of R_V, the relative visual extinction delta(A_V) of each cluster horizontal branch (HB) star with respect to an empirical HB locus; the locus is derived from the CMD of a subset of stars near the cluster center in which differential reddening is small. A star-by-star comparison of delta(A_V) from the (B-V,V) CMD with that from the (V-I,V) CMD is used to find the optimal R_V. In the third method, R_V is determined by minimizing the scatter in the HB in the (B-V, V) CMD after correcting the photometry for extinction and reddening using the Schlegel et al. (1998) dust maps. The weighted average of the results from 3 methods gives R_V = 3.0 +/- 0.4 for the dust towards NGC4833. The dust fine structure is quantified via the difference, Delta(A_V)_ij = [delta(A_V)]_i - [delta(A_V)]_j, between pairs of cluster HB stars (i,j) as a function of their angular separation r_ij. The variance of Delta(A_V)_ij is found to have a power- law dependence on angular scale: var(r) \propto r^(+0.9 +/- 0.1). This translates into an angular power spectrum P(kappa) \propto kappa^(-1.9 +/- 0.1) for r ~ 1' - 5', where kappa = 1/r. The dust angular power spectrum on small scales (from optical data) matches smoothly onto the larger-scale power spectrum derived from Schlegel et al.'s far-infrared map of the dust thermal emission.Comment: 36 pages, 15 figures, 1 table. Accepted for publication in the Astronomical Journal (July 2004

Keck Spectroscopy of Dwarf Elliptical Galaxies in the Virgo Cluster

Keck spectroscopy is presented for four dwarf elliptical galaxies in the Virgo Cluster. At this distance, the mean velocity and velocity dispersion are well resolved as a function of radius between 100 to 1000 pc, allowing a clear separation between nuclear and surrounding galaxy light. We find a variety of dispersion profiles for the inner regions of these objects, and show that none of these galaxies is rotationally flattened.Comment: 4 pages, 2 figures, to appear in the proceedings of the Yale Cosmology Workshop "The Shapes of Galaxies and their Halos", (ed. P. Natarjan

Keck Studies of M31's Stellar Halo

We present Keck 10-meter/LRIS spectra of candidate red giants in the halo of M31, located at a projected radius of R=19kpc on the minor axis. These spectroscopic targets have been selected using a combination of UBRI-based and morphological screening to eliminate background galaxies. Radial velocity measurements are used to separate M31 halo giants from foreground Milky Way dwarf stars, M31 disk stars, and residual background galaxies. The metallicity of each M31 halo giant is measured using standard photometric and spectroscopic techniques, the latter based on the strength of the CaII triplet. The various [Fe/H] estimates are in rough agreement with one another. The data reveal a large spread (>2dex) in [Fe/H] in M31's halo; there is no strong radial [Fe/H] gradient. LRIS and HIRES spectra are also presented for red giants in five dwarf spheroidal satellites of M31: AndI, AndIII, AndV, AndVI, and AndVII. There appears to be a significant metallicity spread in AndVI and possibly in AndI. The new radial velocity data on these outer dwarfs are used to constrain the total mass of M31: the best estimate is under 10^(12)Msun, somewhat less than the best estimate for the Milky Way.Comment: 12 pages, 7 figures, Proceedings of SPIE Conference: Discoveries and Research Prospects with 8-10 Meter Class Telescopes (Munich March 2000

Discovery of Super-Li Rich Red Giants in Dwarf Spheroidal Galaxies

Stars destroy lithium (Li) in their normal evolution. The convective envelopes of evolved red giants reach temperatures of millions of K, hot enough for the 7Li(p,alpha)4He reaction to burn Li efficiently. Only about 1% of first-ascent red giants more luminous than the luminosity function bump in the red giant branch exhibit A(Li) > 1.5. Nonetheless, Li-rich red giants do exist. We present 15 Li-rich red giants--14 of which are new discoveries--among a sample of 2054 red giants in Milky Way dwarf satellite galaxies. Our sample more than doubles the number of low-mass, metal-poor ([Fe/H] <~ -0.7) Li-rich red giants, and it includes the most-metal poor Li-enhanced star known ([Fe/H] = -2.82, A(Li)_NLTE = 3.15). Because most of these stars have Li abundances larger than the universe's primordial value, the Li in these stars must have been created rather than saved from destruction. These Li-rich stars appear like other stars in the same galaxies in every measurable regard other than Li abundance. We consider the possibility that Li enrichment is a universal phase of evolution that affects all stars, and it seems rare only because it is brief.Comment: 6 pages, 3 figures, accepted to ApJ Letters, version 3 includes additional references and minor typographical change

Patterns and Rates of Land Use Land Cover Change: A Case Study of Ambos Nogales (Arizona and Sonora), 1985-2004

Abstract The continued expansion of the paired U.S.–Mexican border cities of Ambos Nogales presents many environmental management and urban planning challenges. This study focuses on a comparative study of spatial patterns and rates of land-use and land-cover change, in relation to land degradation, deforestation, and urban growth over different time periods. Based on historical data the study suggests that both cities have experi- enced high land degradation; however, land on the Arizona-side has been more stable and less degraded. However, there were more severely degraded areas found in Nogales, Arizona, than in Nogales, Sonora. The delineation of land use change and the severity of land degradation provide important information to planners about areas that should be targeted for development and other areas that require restoration to natural settings. Keywords: Nogales, land use land cover, urban growth, land degradation Resumen La expansión continua de las ciudades gemelas de Ambos Nogales (USA-Mexico) presenta muchos desafíos de planificación urbana y manejo ambiental. Este estudio se concentra en un análisis comparativo de los patrones espaciales y velocidad de cambios de uso del suelo con relación a la degradación del terreno, deforestación, y crecimiento urbano durante distintos períodos de tiempo. Basado en datos históricos el estudio sugiere que ambas ciudades han experimentado alta degradación de tierra, pero la tierra en el lado de Arizona ha sido más estable y menos degradada. Sin embargo, en Nogales Arizona, habían áreas severamente más degradadas que en Nogales, Sonora. Palabras clave: Nogales, crecimiento urbano, uso de suelo, degradación de tierra

Natural Language Processing: The Future of Content Generation and It's Applications

Natural Language Processing (NLP) is a field of artificial intelligence and computer science that deals with the interaction between computers and humans in the form of natural language. It involves using algorithms and statistical models to analyze, generate, and understand human language, enabling computers to interpret and respond to human requests naturally and intelligently