John L. Bratten Oral History

An oral history interview of military veteran John L. Bratten originally conducted under the auspices of the Library of Congress Veterans History Project

Effects of Microstructure on the Oxidation Behavior of A3 Matrix-Grade Graphite

The oxidation behavior of matrix-grade graphite in air- or steam-ingress accident scenarios is of great interest for high-temperature gas reactors (HTGRs). In this study, the microstructures of two variants of matrix-grade graphite based on the German A3-3 and A3-27 formulations were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and correlated to oxidation behavior observed through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Through TEM imaging and selected area electron diffraction (SAED), a higher volume fraction of partially graphitized carbon was identified in the A3-3 type graphite than in the A3-27 type. This structure is believed to have contributed to the accelerated oxidation exhibited by A3-3 in the chemical reaction-controlled oxidation regime

The ratting of North America: A 350-year retrospective on <i>Rattus</i> species compositions and competition

While the impacts of black (Rattus rattus) and brown (Rattus norvegicus) rats on human society are well documented—including the spread of disease, broad-scale environmental destruction, and billions spent annually on animal control—little is known about their ecology and behavior in urban areas due to the challenges of studying animals in city environments. We use isotopic and ZooMS analysis of archaeological (1550s–1900 CE) rat remains from eastern North America to provide a large-scale framework for species arrival, interspecific competition, and dietary ecology. Brown rats arrived earlier than expected and rapidly outcompeted black rats in coastal urban areas. This replacement happened despite evidence that the two species occupy different trophic positions. Findings include the earliest molecularly confirmed brown rat in the Americas and show a deep ecological structure to how rats exploit human-structured areas, with implications for understanding urban zoonosis, rat management, and ecosystem planning as well as broader themes of rat dispersal, phylogeny, evolutionary ecology, and climate impacts