Saving the Libby Hill Viewshed: Preserving and Enhancing One of Richmond’s Greatest Assets

The view from Libby Hill Park in Richmond\u27s Church Hill neighborhood has been identified as an endangered view, and the possibility of new development changing this view has increased in recent years. This plan explores what this view means to the identity of the neighborhood and the city and identifies ways to preserve the view while promoting development. The plan also identifies ways to make the park more accessible and open to all residents to increase its value to the city of Richmond, VA

Mood Disorders Lab: Honors Thesis Guidelines

Guidelines for any student who is considering completing an Honors Thesis within the Mood Disorders Laboratory. This is a work in progress and will likely evolve over time. We strongly encourage people who would like to conduct an honors thesis in the MDL to read this document first.Psycholog

The mass-L_x relation for moderate luminosity X-ray clusters

We present measurements of the masses of a sample of 25 moderate X-ray luminosity clusters of galaxies from the 160 square degree ROSAT survey. The masses were obtained from a weak lensing analysis of deep F814W images obtained using the Advanced Camera for Surveys (ACS). We present an accurate empirical correction for the effect of charge transfer (in)efficiency on the shapes of faint galaxies. A significant lensing signal is detected around most of the clusters. The lensing mass correlates tightly with the cluster richness. We measured the intrinsic scatter in the scaling relation between M_2500 and L_X and find the best fit power law slope and normalisation to be alpha=0.68+-0.07 and M_X=(1.2+-0.12)10^14M_sun (for L_X=2x10^44 erg/s). These results agree well with a number of recent studies, but the normalisation is lower compared to the study of Rykoff et al. (2008b). One explanation for this difference may be the fact that (sub)structures projected along the line-of-sight boost both the galaxy counts and the lensing mass. Such superpositions lead to an increased mass at a given L_X when clusters are binned by richness.Comment: accepted for publication in the Astrophysical Journal; 15 pages, 11 figure

Brief Note: Characterization of Hydrophobic Stream Bacteria Based on Adhesion to n-Octane

Author Institution: Department of Biological Sciences, Kent State UniversityThe purpose of this study was to characterize stream bacterial communities based on cell surface hydrophobicity. Because hydrophobicity is related to adhesion we hypothesized that more hydrophobic bacteria would be found on solid surfaces than in water. Water, rock, and sediment from two northeastern Ohio streams were sampled and bacteria were plated on modified nutrient agar. Hydrophobicity was determined by measuring adherence to n-octane. No difference was found in the proportion of hydrophobic bacteria among habitats. Two hydrophobic isolates were identified as Sphingomonas paucimobilis and Chryseomonas luteola. A large proportion of hydrophobic bacteria were gram positive and urease positive; none were gelatinase positive. More hydrophobic than hydrophilic bacteria were able to grow using manatose or malatose as the only carbon source. These physiological differences indicate that hydrophobic bacteria may be able to utilize resources not available to hydrophilic bacteria

Spitzer Observations of GX17+2: Confirmation of a Periodic Synchrotron Source

GX17+2 is a low-mass X-ray binary (LMXB) that is also a member of a small family of LMXBs known as "Z-sources" that are believed to have persistent X-ray luminosities that are very close to the Eddington limit. GX17+2 is highly variable at both radio and X-ray frequencies, a feature common to Z-sources. What sets GX17+2 apart is its dramatic variability in the near-infrared, where it changes by ΔK ~ 3 mag. Previous investigations have shown that these brightenings are periodic, recurring every 3.01 days. Given its high extinction (A_V≥9 mag), it has not been possible to ascertain the nature of these events with ground-based observations. We report mid-infrared Spitzer observations of GX17+2 which indicate a synchrotron spectrum for the infrared brightenings. In addition, GX17+2 is highly variable in the mid-infrared during these events. The combination of the large-scale outbursts, the presence of a synchrotron spectrum, and the dramatic variability in the mid-infrared suggest that the infrared brightening events are due to the periodic transit of a synchrotron jet across our line of sight. An analysis of both new, and archival, infrared observations has led us to revise the period for these events to 3.0367 days. We also present new Rossi X-Ray Timing Explorer (RXTE) data for GX17+2 obtained during two predicted infrared brightening events. Analysis of these new data, and data from the RXTE archive, indicates that there is no correlation between the X-ray behavior of this source and the observed infrared brightenings. We examine various scenarios that might produce periodic jet emission

Two Clusters with Radio-quiet Cooling Cores

Radio lobes inflated by active galactic nuclei at the centers of clusters are a promising candidate for halting condensation in clusters with short central cooling times because they are common in such clusters. In order to test the AGN-heating hypothesis, we obtained Chandra observations of two clusters with short central cooling times yet no evidence for AGN activity: Abell 1650 and Abell 2244. The cores of these clusters indeed appear systematically different from cores with more prominent radio emission. They do not have significant central temperature gradients, and their central entropy levels are markedly higher than in clusters with stronger radio emission, corresponding to central cooling times ~ 1 Gigayear. Also, there is no evidence for fossil X-ray cavities produced by an earlier episode of AGN heating. We suggest that either (1) the central gas has not yet cooled to the point at which feedback is necessary to prevent it from condensing, possibly because it is conductively stabilized, or (2) the gas experienced a major heating event $\gtrsim 1$ Gyr in the past and has not required feedback since then. The fact that these clusters with no evident feedback have higher central entropy and therefore longer central cooling times than clusters with obvious AGN feedback strongly suggests that AGNs supply the feedback necessary to suppress condensation in clusters with short central cooling times.Comment: ApJ Letter, in pres

Quaternary Ammonia Compounds in Disinfectant Products: Evaluating the Potential for Promoting Antibiotic Resistance and Disrupting Wastewater Treatment Plant Performance

Quaternary ammonium compounds (QACs) are a class of compounds that were widely used as disinfectants during the COVID-19 pandemic and continue to be used as disinfecting agents. After consumer usage, QAC concentrations are diluted in wastewater as they enter wastewater treatment plants. At sub-inhibitory concentrations, QACs may have unintended repercussions, including increased antibiotic resistance and inhibition of process performance in wastewater treatment plants. This review first summarizes how QACs inhibit bacteria and then highlights the mechanisms by which QACs can promote antibiotic resistance in general. Reported environmental concentrations of QACs are compared to concentrations that are suspected to impact antibiotic resistance, and the role QACs may have on antibiotic resistance proliferation in wastewater treatment is addressed. Finally, the specific impacts that QACs can have on biological wastewater processes (activated sludge and anaerobic digestion) are reviewed. We highlight key research gaps along with recommendations for future research. Of particular interest, research is needed to elucidate the relationship between the chemical structure of QACs and impacts on antibiotic resistance as well as process performance in wastewater treatment plants. Finally, the ability to mitigate (reverse) these impacts if QACs are removed needs to be determined