The genetic legacy of African Americans from Catoctin Furnace.

Few African Americans have been able to trace family lineages back to ancestors who died before the 1870 United States Census, the first in which all Black people were listed by name. We analyzed 27 individuals from Maryland's Catoctin Furnace African American Cemetery (1774-1850), identifying 41,799 genetic relatives among consenting research participants in 23andMe, Inc.'s genetic database. One of the highest concentrations of close relatives is in Maryland, suggesting that descendants of the Catoctin individuals remain in the area. We find that many of the Catoctin individuals derived African ancestry from the Wolof or Kongo groups and European ancestry from Great Britain and Ireland. This study demonstrates the power of joint analysis of historical DNA and large datasets generated through direct-to-consumer ancestry testing.

Exposure indicator degradation from CR plate processing delays.

PURPOSE: To determine the percentage of exposure indicator (EI) degradation that occurs during a delay between exposure and processing of the imaging receptor. METHODS: Twenty-six images of a hand phantom, stepwedge and resolution test tool were created using a computed radiography (CR) system (Agfa Impax 6.3.1 SU5 CR, Agfa-Gevaert NV, Mortsel, Belgium). To control variables, exposures were made using the same technique, resulting in an EI of 2.0. The radiographic equipment, Agfa algorithms and processor and display monitor were held constant, and all imaging plates (IPs) were exposed and processed initially to rule out EI variation. Consecutive experimental exposures were made and each IP labeled by number and the time processed. To control ambient conditions, the exposed IPs were secured at room temperature in a radiation-free area until they were processed. RESULTS: The EI degraded 8% within the first hour of delay in processing. After 24 hours, degradation was 16%, demonstrating that the EI initially drops quickly following exposure, but degrades at a slower pace as the processing delay increases. CONCLUSION: This study supports current literature by showing that more than half of the degradation that occurs in the first 24 hours happens within the first hour of delay in processing.