Using patterns in the automatic marking of ER-Diagrams

This paper illustrates how the notion of pattern can be used in the automatic analysis and synthesis of diagrams, applied particularly to the automatic marking of ER-diagrams. The paper describes how diagram patterns fit into a general framework for diagram interpretation and provides examples of how patterns can be exploited in other fields. Diagram patterns are defined and specified within the area of ER-diagrams. The paper also shows how patterns are being exploited in a revision tool for understanding ER-diagrams

Hot Populations in M87 Globular Clusters

We have obtained HST/STIS far- and near-UV photometry of globular clusters in four fields in the gE galaxy M87. To a limit of m(FUV) = 25 we detect a total of 66 globular clusters (GCs) in common with the deep HST optical-band study of Kundu et al. (1999). Despite strong overlap in V- and I-band properties, the M87 GCs have UV/optical properties that are distinct from clusters in the Milky Way and in M31. M87 clusters, especially metal-poor ones, produce larger hot HB populations than do Milky Way analogues. Cluster mass is probably not a factor in these distinctions. The most metal-rich M87 GCs in our sample are near Z_sun and overlap the local E galaxy sample in estimated Mg_2 line indices. Nonetheless, the clusters produce much more UV light at a given Mg_2, being up to 1 mag bluer than any gE galaxy in (FUV-V) color. The M87 GCs do not appear to represent a transition between Milky Way-type clusters and E galaxies. The differences are in the correct sense if the clusters are significantly older than the E galaxies. Comparisons with Galactic open clusters indicate that the hot stars lie on the extreme horizontal branch, rather than being blue stragglers, and that the EHB becomes well populated for ages > 5 Gyr. We find that 43 of our UV detections have no optical-band counterparts. Most appear to be UV-bright background galaxies, seen through M87. Eleven NUV variable sources detected at only one epoch in the central field are probably classical novae. [Abridged]Comment: 70 pages, 25 figures (including 4 jpgs), 7 tables. To appear in AJ. Full resolution version available at http://www.astro.virginia.edu/~rwo/m87/m87-hotpops.pd

Experiments in the automatic marking of ER-Diagrams

In this paper we present an approach to the computer understanding of diagrams and show how it can be successfully applied to the automatic marking (grading) of student attempts at drawing entity-relationship (ER) diagrams. The automatic marker has been incorporated into a revision tool to enable students to practice diagramming and obtain feedback on their attempts

The Mini AGN at the Center of the Elliptical Galaxy NGC 4552 with HST

The complex phenomenology shown by the UV-bright, variable spike first detected with the Hubble Space Telescope (HST) at the center of the otherwise normal galaxy NGC 4552 is further investigated with both HST imaging (FOC) and spectroscopy (FOS). HST/FOC images taken in 1991, 1993, and 1996 in the near UV have been analyzed in a homogeneous fashion, showing that the central spike has brightened by a factor ~4.5 between 1991 and 1993, and has decreased its luminosity by a factor ~2.0 between 1993 and 1996. FOS spectroscopy extending from the near UV to the red side of the optical spectrum reveals a strong UV continuum over the spectrum of the underlying galaxy, along with several emission lines in both the UV and the optical ranges. In spite of the low luminosity of the UV continuum of the spike (~3*10^5 Lsolar), the spike is definitely placed among AGNs by current diagnostics based on the emission line intensity ratios, being just on the borderline between Seyferts and LINERs. Line profiles are very broad, and both permitted and forbidden lines are best modelled with a combination of broad and narrow components, with FWHM of ~3000 km s^-1 and ~700 km s^-1, respectively. This evidence argues for the variable central spike being produced by a modest accretion event onto a central massive black hole (BH), with the accreted material having possibly being stripped from a a star in a close fly by with the BH. The 1996 broad Halpha luminosity of this mini-AGN is ~5.6*10^37 erg s^-1, about a factor of two less than that of the nucleus of NGC 4395, heretofore considered to be the faintest known AGN.Comment: 40 pages, LaTeX, with 12 PostScript figures. Accepted for publication in the Astrophysical Journa

Galactic Extinction from Colors and Counts of Field Galaxies in WFPC2 Frames: An Application to GRB 970228

We develop the ``simulated extinction method'' to measure average foreground Galactic extinction from field galaxy number-counts and colors. The method comprises simulating extinction in suitable reference fields by changing the isophotal detection limit. This procedure takes into account selection effects, in particular, the change in isophotal detection limit (and hence in isophotal magnitude completeness limit) with extinction, and the galaxy color--magnitude relation. We present a first application of the method to the HST WFPC2 images of the gamma-ray burster GRB 970228. Four different WFPC2 high-latitude fields, including the HDF, are used as reference to measure the average extinction towards the GRB in the F606W passband. From the counts, we derive an average extinction of A_V = 0.5 mag, but the dispersion of 0.4 mag between the estimates from the different reference fields is significantly larger than can be accounted by Poisson plus clustering uncertainties. Although the counts differ, the average colors of the field galaxies agree well. The extinction implied by the average color difference between the GRB field and the reference galaxies is A_V = 0.6 mag, with a dispersion in the estimated extinction from the four reference fields of only 0.1 mag. All our estimates are in good agreement with the value of 0.81\pm0.27 mag obtained by Burstein & Heiles, and with the extinction of 0.78\pm0.12 measured by Schlegel et al. from maps of dust IR emission. However, the discrepancy between the widely varying counts and the very stable colors in these high-latitude fields is worth investigating.Comment: 14 pages, 2 figures; submitted to the Astrophysical Journa

The Role of a Hot Gas Environment on the Evolution of Galaxies

Most spiral galaxies are found in galaxy groups with low velocity dispersions; most E/S0 galaxies are found in galaxy groups with relatively high velocity dispersions. The mass of the hot gas we can observe in the E/S0 groups via their thermal X-ray emission is, on average, as much as the baryonic mass of the galaxies in these groups. By comparison, galaxy clusters have as much or more hot gas than stellar mass. Hot gas in S-rich groups, however, is of low enough temperature for its X-ray emission to suffer heavy absorption due to Galactic HI and related observational effects, and hence is hard to detect. We postulate that such lower temperature hot gas does exist in low velocity dispersion, S-rich groups, and explore the consequences of this assumption. For a wide range of metallicity and density, hot gas in S-rich groups can cool in far less than a Hubble time. If such gas exists and can cool, especially when interacting with HI in existing galaxies, then it can help link together a number of disparate observations, both Galactic and extragalactic, that are otherwise difficult to understand.Comment: 16 pages with one figure. ApJ Letters, in pres

The economic impact of chronic fatigue syndrome in Georgia: direct and indirect costs

<p>Abstract</p> <p>Background</p> <p>Chronic fatigue syndrome (CFS) is a debilitating chronic illness affecting at least 4 million people in the United States. Understanding its cost improves decisions regarding resource allocation that may be directed towards treatment and cure, and guides the evaluation of clinical and community interventions designed to reduce the burden of disease.</p> <p>Methods</p> <p>This research estimated direct and indirect costs of CFS and the impact on educational attainment using a population-based, case-control study between September 2004 and July 2005, Georgia, USA. Participants completed a clinical evaluation to confirm CFS, identify other illnesses, and report on socioeconomic factors. We estimated the effect of CFS on direct medical costs (inpatient hospitalizations, provider visits, prescription medication spending, other medical supplies and services) and loss in productivity (employment and earnings) with a stratified sample (n = 500) from metropolitan, urban, and rural Georgia. We adjusted medical costs and earnings for confounders (age, sex, race/ethnicity, education, and geographic strata) using econometric models and weighted estimates to reflect response-rate adjusted sampling rates.</p> <p>Results</p> <p>Individuals with CFS had mean annual direct medical costs of $5,683. After adjusting for confounding factors, CFS accounted for$3,286 of these costs (p < 0.01), which were driven by increased provider visits and prescription medication use. Nearly one-quarter of these expenses were paid directly out-of pocket by those with CFS. Individuals with CFS reported mean annual household income of $23,076. After adjustment, CFS accounted for$8,554 annually in lost household earnings (p < 0.01). Lower educational attainment accounted for 19% of the reduction in earnings associated with CFS.</p> <p>Conclusions</p> <p>Study results indicate that chronic fatigue syndrome may lead to substantial increases in healthcare costs and decreases in individual earnings. Studies have estimated up to 2.5% of non-elderly adults may suffer from CFS. In Georgia, a state with roughly 5.5 million people age 18-59, illness could account for $452 million in total healthcare expenditures and$1.2 billion of lost productivity.</p

A non-Markovian quantum trajectory approach to radiation into structured continuum

We present a non-Markovian quantum trajectory method for treating atoms radiating into a reservoir with a non-flat density of states. The results of an example numerical simulation of the case where the free space modes of the reservoir are altered by the presence of a cavity are presented and compared with those of an extended system approach

Toy models of crossed Andreev reflection

We propose toy models of crossed Andreev reflection in multiterminal hybrid structures containing out-of-equilibrium conductors. We apply the description to two possible experiments: (i) to a device containing a large quantum dot inserted in a crossed Andreev reflection circuit. (ii) To a device containing an Aharonov-Bohm loop inserted in a crossed Andreev reflection circuit.Comment: 5 pages, 9 figures, minor modification

BS196: an old star cluster far from the SMC main body

We present B and V photometry of the outlying SMC star cluster BS196 with the 4.1-m SOAR telescope. The photometry is deep (to V~25) showing ~3 mag below the cluster turnoff point (TO) at Mv=2.5 (1.03 Msun). The cluster is located at the SMC distance. The CMD and isochrone fittings provide a cluster age of 5.0+-0.5 Gyr, indicating that this is one of the 12 oldest clusters so far detected in the SMC. The estimated metallicity is [Fe/H]=-1.68+-0.10. The structural analysis gives by means of King profile fittings a core radius Rc=8.7+-1.1 arcsec (2.66+-0.14 pc) and a tidal radius Rt=69.4+-1.7 arcsec (21.2+-1.2 pc). BS196 is rather loose with a concentration parameter c=0.90. With Mv=-1.89+-0.39, BS196 belongs to the class of intrinsically fainter SMC clusters, as compared to the well-known populous ones, which starts to be explored.Comment: 8 pages, 10 figures; accepted by MNRA