Putting Poor People to Work: How the Work‐First Idea Eroded College Access for the Poor by Kathleen M. Shaw, Sara Goldrick‐Rab, Christopher Mazzeo, and Jerry A

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97252/1/j.1538-165X.2008.tb01783.x.pd

The Peculiar Type Ic Supernova 1997ef: Another Hypernova

SN 1997ef has been recognized as a peculiar supernova from its light curve and spectral properties. The object was classified as a Type Ic supernova (SN Ic) because its spectra are dominated by broad absorption lines of oxygen and iron, lacking any clear signs of hydrogen or helium line features. The light curve is very different from that of previously known SNe Ic, showing a very broad peak and a slow tail. The strikingly broad line features in the spectra of SN 1997ef, which were also seen in the hypernova SN 1998bw, suggest the interesting possibility that SN 1997ef may also be a hypernova. The light curve and spectra of SN 1997ef were modeled first with a standard SN~Ic model assuming an ordinary kinetic energy of explosion $E_{\rm K} = 10^{51}$ erg. The explosion of a CO star of mass $M_{\rm CO} \approx 6 M_\odot$ gives a reasonably good fit to the light curve but clearly fails to reproduce the broad spectral features. Then, models with larger masses and energies were explored. Both the light curve and the spectra of SN 1997ef are much better reproduced by a C+O star model with $E_{\rm K} =$ 8 \e{51} erg and $M_{\rm CO} = 10 M_\odot$. Therefore, we conclude that SN 1997ef is very likely a hypernova on the basis of its kinetic energy of explosion. Finally, implications for the deviation from spherical symmetry are discussed in an effort to improve the light curve and spectral fits.Comment: "To appear in the Astrophysical Journal, Vol.534 (2000)

Neighborhood Food Infrastructure and Food Security in Metropolitan Detroit

Concern about spatial access to food retailers and its relationship to household food security has increased in recent years, placing greater importance on understanding how proximity to food retailers is related to household food consumption. Using data from the Michigan Recession and Recovery Study (MRRS), a panel survey of working‐age adults in the Detroit Metropolitan Area, this article explores whether access to the food retailers is associated with food insecurity. We use unique data about food retailers in metropolitan Detroit to develop an array of food retailer access measures that account for distance to nearest retailer, density of retailers, commute times, mode of transit, and type of retailer. Across most measures, we find that many vulnerable population groups have greater or at least comparable spatial access to food resources as less vulnerable populations groups. There is little evidence, however, that greater access to food retailers is associated with food security

The significance of fathers for inner-city African-American teen mothers

Using the accounts of family life in young women's life stories, this qualitative study examined experiences with biological fathers for a sample of inner-city African-American teen mothers and a comparable sample of young women who were not parents. Distinguishing findings emerged about the pattern of young women's residential history with fathers, activity and interactions with fathers, and feelings about fathers. These qualitative findings were discussed in terms of their implications for services, policy, and research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44239/1/10560_2005_Article_BF01876206.pd

Spectral statistics of random geometric graphs

We use random matrix theory to study the spectrum of random geometric graphs, a fundamental model of spatial networks. Considering ensembles of random geometric graphs we look at short range correlations in the level spacings of the spectrum via the nearest neighbour and next nearest neighbour spacing distribution and long range correlations via the spectral rigidity Delta_3 statistic. These correlations in the level spacings give information about localisation of eigenvectors, level of community structure and the level of randomness within the networks. We find a parameter dependent transition between Poisson and Gaussian orthogonal ensemble statistics. That is the spectral statistics of spatial random geometric graphs fits the universality of random matrix theory found in other models such as Erdos-Renyi, Barabasi-Albert and Watts-Strogatz random graph.Comment: 19 pages, 6 figures. Substantially updated from previous versio

Dynamics and Excitation of Radio Galaxy Emission-Line Regions - I. PKS 2356-61

Results are presented from a programme of detailed longslit spectroscopic observations of the extended emission-line region (EELR) associated with the powerful radio galaxy PKS 2356-61. The observations have been used to construct spectroscopic datacubes, which yield detailed information on the spatial variations of emission-line ratios across the EELR, together with its kinematic structure. We present an extensive comparison between the data and results obtained from the MAPPINGS II shock ionization code, and show that the physical properties of the line-emitting gas, including its ionization, excitation, dynamics and overall energy budget, are entirely consistent with a scenario involving auto-ionizing shocks as the dominant ionization mechanism. This has the advantage of accounting for the observed EELR properties by means of a single physical process, thereby requiring less free parameters than the alternative scheme involving photoionization by radiation from the active nucleus. Finally, possible mechanisms of shock formation are considered in the context of the dynamics and origin of the gas, specifically scenarios involving infall or accretion of gas during an interaction between the host radio galaxy and a companion galaxy.Comment: 35 pages, LaTeX, uses aas2pp4.sty file, includes 9 PostScript figures. Two additional colour plates are available from the authors upon request. Accepted for publication in the Astrophysical Journa