The Dark Matter Radial Profile in the Core of the Relaxed Cluster A2589

We present an analysis of a Chandra--ACIS observation of the galaxy cluster A2589 to constrain the radial distribution of the total gravitating matter and the dark matter in the core of the cluster. A2589 is especially well-suited for this analysis because the hot gas in its core region (r < ~0.1 Rvir) is undisturbed by interactions with a central radio source. From the largest radius probed (r=0.07 Rvir) down to r ~0.02 Rvir dark matter dominates the gravitating mass. Over this region the radial profiles of the gravitating and dark matter are fitted well by the NFW and Hernquist profiles predicted by CDM. The density profiles are also described well by power laws, rho ~r^{-alpha}, where alpha=1.37 +/- 0.14 for the gravitating matter and alpha=1.35 +/- 0.21 for the dark matter. These values are consistent with profiles of CDM halos but are significantly larger than alpha ~0.5 found in LSB galaxies and expected from self-interacting dark matter models.Comment: 10 pages, 6 figures, To Appear in The Astrophysical Journal, March 20 issue, a few very minor changes to match copyedited versio

Opening Remarks

Opening remarks for the 2020 New England Graphic Medicine Conference by conference organizer A. David Lewis, MCPHS University

The superhero afterlife subgenre and its hermeneutics for selfhood through character multiplicity

Thesis (Ph.D.)--Boston UniversityComic book superheroes venture frequently into the afterlife, to the extent that the recurring conventions of such tales constitute a superhero subgenre. These generic elements help ensure that the stories can be read normatively by their audience (e.g. one's soul continues separately to function after the death of the body, existence after death is its own reality and discernible from illusion). The new subgenre, however, can also be regarded as masking an alternate understanding of narrative character and suggesting an alternative model of selfhood to readers. Beginning with the genre theory work of Paul Ricoeur, Tzvetan Todorov, and Peter Coogan, this project applies their perceived linkage between generic character and audience models for selfhood to the concerns of Helene Tallon Russell, J. Hillis Miller, and Karin Kukkonen. This second set of theorists warns against narrative characters being understood as whole and unified a priori when the presumably counterfactual idea of a multiple self better matches with the goals of religious pluralism and healthful self-understanding. Through these combined sets of theoretical lenses, the project focuses on popular recent depictions of the afterlife in the word-and-image medium of top-selling comics titles such as Thor, Green Lantern, Fantastic Four, Planetary, and Promethea. The comics, with their dual sign systems and 'low-art' fringe status, provide a consideration of personal multiplicity more naturally than prose does alone. Jeffery Burton Russell and Andrew Delbanco recount modern Americans' declining investment in the afterlife, one steeped in traditionally Augustinian models of singular selfhood. As H.T. Russell champions in Irigaray and Kierkegaard: On the Construction of the Self, this model may serve more as a hindering relic than as a useful system for consideration of one's full selfhood. This superhero subgenre offers a hermeneutic for integrating multiplicity into religious practices and considerations of the afterlife

Closing Remarks

Closing remarks for the 2020 New England Graphic Medicine Conference by conference organizer A. David Lewis, MCPHS University

PUBLIC CONSERVATION LAND AND EMPLOYMENT GROWTH IN THE NORTHERN FOREST REGION

As with many environmental issues, debates about increasing public conservation lands in the Northern Forest region frequently center on a perceived tradeoff between jobs and the environment. In particular, opponents of conservation lands often argue that employment will decline significantly when land is diverted from commodity-oriented uses such as wood products production. To evaluate this claim, we estimate a model of simultaneous employment and net migration growth using data on the 92 non-metropolitan counties comprising the region. Growth in employment and net migration are measured over the period 1990 to 1997 and the set of exogenous variables includes the 1990 share of the county land base in public conservation uses. We find that net migration rates were systematically higher in counties with more conservation lands, but the effects are relatively small. Public conservation lands were found to have no systematic effect on employment growth over the 1990 to 1997 period. Two extensions are considered. We examine the separate effects of preservationist and multiple-use lands. We also identify a "natural experiment" involving changes in national forest management that allows us to estimate the effects of diverting private forestland to public conservation uses. Our central conclusions are that existing public conservation lands have a positive, but small, effect on employment and migration in the Northern Forest region and that, over the range of our data, employment and migration are unlikely to be affected by timber harvest reductions resulting from the establishment of new conservation lands.Labor and Human Capital, Land Economics/Use,

Caveats to Cooley's Argument

Lewis responds to Cooley's essay

Role of vanguard counter-potential in terahertz emission due to surface currents explicated by three-dimensional ensemble Monte Carlo simulation

The discovery that short pulses of near-infrared radiation striking a semiconductor may lead to emission of radiation at terahertz frequencies paved the way for terahertz time-domain spectroscopy. Previous modeling has allowed the physical mechanisms to be understood in general terms but it has not fully explored the role of key physical parameters of the emitter material nor has it fully revealed the competing nature of the surface-field and photo-Dember effects. In this context, our purpose has been to more fully explicate the mechanisms of terahertz emission from transient currents at semiconductor surfaces and to determine the criteria for efficient emission. To achieve this purpose we employ an ensemble Monte Carlo simulation in three dimensions. To ground the calculations, we focus on a specific emitter, InAs. We separately vary distinct physical parameters to determine their specific contribution. We find that scattering as a whole has relatively little impact on the terahertz emission. The emission is found to be remarkably resistant to alterations of the dark surface potential. Decreasing the band gap leads to a strong increase in terahertz emission, as does decreasing the electronmass. Increasing the absorption dramatically influences the peak-peak intensity and peak shape. We conclude that increasing absorption is the most direct path to improve surface-current semiconductor terahertz emitters. We find for longer pump pulses that the emission is limited by a newly identified vanguard counter-potential mechanism: Electrons at the leading edge of longer laser pulses repel subsequent electrons. This discovery is the main result of our work