Optically Detected Magnetic Resonance for Selective Imaging of Diamond Nanoparticles.

While there is great interest in understanding the fate and transport of nanomaterials in the environment and in biological systems, the detection of nanomaterials in complex matrices by fluorescence methods is complicated by photodegradation, blinking, and the presence of natural organic material and other fluorescent background signals that hamper detection of fluorescent nanomaterials of interest. Optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond nanoparticles provides a pathway toward background-free fluorescence measurements, as the application of a resonant microwave field can selectively modulate the intensity from NV centers in nanodiamonds of various diameters in complex materials systems using on-resonance and off-resonance microwave fields. This work represents the first investigation showing how nanoparticle diameter impacts the NV center lifetime and thereby directly impacts the accessible contrast and signal-to-noise ratio when using ODMR to achieve background-free imaging of NV-nanodiamonds in the presence of interfering fluorophores. These results provide new insights that will guide the choice of optimum nanoparticle size and methodology for background-free imaging and sensing applications, while also providing a model system to explore the fate and transport of nanomaterials in the environment.

Correctional-Facility-Outbreak-Associated COVID-19 Cases Among Asymptomatic Persons Identified Through Universal Testing: Vermont, 2020.

On April 6, 2020, a confirmed COVID-19 case in a correctional facility employee (Staff A) was reported to the Vermont Department of Health (VDH). Staff A worked in the facility while symptomatic, without reporting symptoms, for 10 days. VDH and the facility conducted two facility-wide testing events, implemented symptom monitoring, and initiated contact tracing. All 197 incarcerated persons and 115 (71%) staff were tested for SARS-CoV-2; 45 (23%) incarcerated persons and 17 (10%) staff had positive results (confirmed case), of whom 37 (82%) incarcerated persons and 1 (6%) staff had asymptomatic infections. Case detection enabled isolation of incarcerated persons and staff, work exclusion of staff with COVID-19, and quarantine of staff and incarcerated persons who had close contact with persons with COVID-19. Broad-based SARS-CoV-2 testing identified more cases than symptom monitoring.