Prince George's Community College

Urban development, industrialization, and vehicular emissions lead to the accumulation of heavy metals in urban soils. Background soils, those without direct pollution sources, reflect regional contaminant transport and industrial history. In soils, metals occur in distinct geochemical fractions that control their mobility and bioavailability. While metal speciation and bioavailability are well studied, cross-city variability in geochemical phase distributions is poorly understood. Pittsburgh (PGH) is a compelling case study for urban soil contamination given its legacy of steel production. New York City (NYC) and Los Angeles (LA), the only US cities with comparable datasets, provide a broader perspective on regional factors and metal distributions. Regional factors (local geology, soil properties, environmental conditions, and industrial history) shape metal enrichment and bioavailability. This study addresses this gap by evaluating total metal concentrations and geochemical phase distributions of Pb, Cd, Zn, Ni, and Mn in PGH, NYC, and LA. Sequential extractions of PGH soil samples were compared with similar analyses in NYC and LA, using the modified BCR method, to assess variations in metal partitioning across geochemical phases. We used the National Uranium Resource Evaluation (NURE) stream sediment dataset to assess regional Mn enrichment and geologic context. PGH exhibited higher Mn concentrations than NYC and LA. Industrial history contributes to Mn enrichment in PGH, but the patterns also suggest a possible role for vegetation in Mn retention and phase partitioning. In contrast, LA soils had the highest exchangeable metal fractions, suggesting greater metal bioavailability. Our findings highlight the complexity of urban soil metal contamination and the importance of considering both industrial legacies and environmental factors in determining metal bioavailability.

Bolt loosening is a significant concern in structural health monitoring (SHM), and the nonlinear wave modulation (NWM) technique shows promise for its detection. However, temperature variations affect piezoelectric sensors, complicating detection. This study examines thermal stress effects on NWM-based damage detection by simulating a beam with boundary loosening under thermal stress. A temperature compensation method was developed to mitigate these effects. A multibolt structure was also analyzed using a hybrid deep learning model combining convolutional neural networks (CNNs) and Dezert-Smarandache Theory (DSmT) for multisensor data fusion. Results show that thermal stress significantly reduces classification accuracy. At 60 °C, the Damage Index dropped to zero, and CNN classification accuracy fell from 87.5% (at 25 °C) to 27.08%. Applying the compensation algorithm restored CNN accuracy to 87.27%. Statistical tests confirmed the compensated results at 60 °C were comparable to those at 25 °C. The DSmT-based fusion model achieved 98.92% accuracy on average, and even at 60 °C, maintained 98.80% accuracy with compensation for a multibolted plate. It combines the probabilistic outputs of multiple CNNs using the PCR6 rule, which redistributes conflicting evidence to improve decision reliability. This fusion strategy effectively handles uncertainty across sensors and significantly enhances classification robustness under temperature variations. In conclusion, thermal stress adversely impacts SHM damage detection, but the proposed compensation method effectively restores performance. Moreover, integrating multisensor fusion with DSmT greatly enhances accuracy, offering a robust solution for SHM in varying thermal environments.

The analysis is a sociohistorical examination of entertainment media’s representation of black children from the 1970s to 2000s. Each decade of media production provides insight into the presentation of black children in regards to the stereotypes and biased messages conveyed. The analysis delineates the narrowly defined yet deviant manner in which black children have been depicted. Examples derived from motion picture films and television shows are set forth to illustrate the manner in which black children have traditionally been included, or perhaps excluded, in the perpetuation of racial stereotypes reflective of the coinciding stereotypes usually projected on to black adults.

We thank Jack Suess and Damian Doyle (UMBC Division of Information Technology)for their enthusiastic cooperation. Thanks to Richard Baldwin and Travis Scheponik for helpful comments. This project was supported in part by the National Science Foundation under SFS grants 1241576 and 1753681. Sherman was also supported by the National Science Foundation under SFS capacity grant 1819521 and by the U.S. Department of Defense under CAE-R grant H98230-17-1-0349 and CySP grants H98230-17-1-0387 and H98230-18-0321.

Stereotypes abound about the clash between newcomers to urban neighborhoods and their longstanding residents. In a case study of Columbia Heights in the District of Columbia, the preferences and attitudes of newcomers and longstanding residents are compared. The comparison will help assess the extent to which indirect displacement pressures in the domain of retail activity might be occurring in Columbia Heights. Data from surveys conducted in 2008 by the Howard University Center for Urban Progress (HUCUP) form the empirical base of this study. A total of 217 completed surveys were received, 116 from an Internet survey and 101 one-on-one street interviews. The sample was split into thirds (according to length of time that the participant lived in the neighborhood) leading to break points at two years and eight years of residency. All respondents who lived in the neighborhood two years or less or eight years or more were kept in the final sample. The former were defined as “newcomers and the latter were defined as “longstanding residents”. There were 77 newcomers and 74 longstanding residents in the final sample. The survey instrument inquired about respondents’ opinions about the availability and quality of stores by type, the variety of stores, and what types of stores they would like to see added to the neighborhood. Respondents were then asked their assessment of the new commercial developments and of the previously existing businesses in the corridor. Chi-square tests were used to test the hypotheses that there were differences between the two populations – newcomers and long-standing residents – in terms of preferences and attitudes. The findings demonstrated significant differences between the two groups in terms of their opinions about the commercial corridor, although both groups were generally pleased with the new retail developments. The analysis of these data weakly supports the hypothesis that indirect factors could heighten pressures for displacement of longstanding residents, but it is argued that the main focus of gentrification studies should continue to be on the direct economic factors affecting longstanding residents during neighborhood revitalization.

ABSTRACTRecently there have been reports of hot carrier thermoelectric response in nanostructured materials like graphene and MoS. We report observing that thermoelectric nanowire junctions detect light. In these experiments we employed devices composed of bismuth nanowire arrays which are capped with a transparent indium tin oxide electrode. The incident surface features very low optical reflectivity and enhanced light trapping. The unique attributes of the thermoelectric arrays are the combination of strong temporal and optical wavelength dependences of the photocurrent. Under infrared illumination, the signal can be completely described by “quasi-equilibrium” thermoelectric effects considering cooling rates given by heat diffusion through the array. The thermal diffusivity is found to be less (by a factor of 3.5) than in the bulk, a result that we discuss in terms of phonon confinement effects. In addition to a thermoelectric response, under visible illumination, we observe a photovoltaic response.

The following interview with Michèle Artigue was conducted in October 2013. Michèle Artigue obtained her degrees in mathematics from the École Normale Supérieure in Paris 1 and Université Paris 7. Her subsequent teaching and scholarly work were likewise connected with Université Paris 7, where she taught and in 1985-1988 was the director of IREM.KeywordsElementary SchoolMathematics EducationComputer Algebra SystemSecondary TeacherFrench MathematicianThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.