We report the experimental demonstration of time-resolved relativistic electron diffraction. Single shot diffraction patterns from a single crystal gold sample were recorded using ultrashort 3.5 MeV electron bunches from a radio frequency photoinjector. By scanning the pump pulse time-delay, we studied the Bragg peaks amplitude change due to the laser-induced melting of the sample. The observed time scale matches the one predicted using a simple two temperature model of the heating of the thin foil. Time-resolved relativistic electron diffraction using megaelectronvolt electron beams with 107 particles in 100 fs bunch length opens exciting possibilities in ultrafast structural dynamics.

In this paper we report on the experimental demonstration of using relativistic electron diffraction and an radiofrequency deflecting cavity to capture in a single shot the entire time-history of the ultrafast laser-induced heating and melting of a single crystal gold sample. By recording the time variation in the Bragg peaks on the streak image of a 16 ps long electron beam it is possible to reconstruct with 400 fs temporal resolution the evolution of the sample structure induced by a 35 mJ/cm2 400 nm laser pump pulse.

To effectively respond to the COVID-19 pandemic, California had to quickly mobilize a substantial number of case investigators (CIs) and contact tracers (CTs). This workforce was comprised primarily of redirected civil servants with diverse educational and professional backgrounds. The purpose of this evaluation was to understand whether the weeklong, remote course developed to train California's CI/CT workforce (i.e., Virtual Training Academy) adequately prepared trainees for deployment. From May 2020 to February 2021, 8,141 individuals completed the training. A survey administered ~3 weeks post-course assessed two measures of overall preparedness: self-perceived interviewing proficiency and self-perceived job preparedness. Bivariate analyses were used to examine differences in preparedness scores by education level, career background, and whether trainees volunteered to join the COVID-19 workforce or were assigned by their employers. There were no significant differences in preparedness by education level. Compared to trainees from non-public health backgrounds, those from public health fields had higher self-perceived interviewing proficiency (25.1 vs. 23.3, p < 0.001) and job preparedness (25.7 vs. 24.0, p < 0.01). Compared to those who were assigned, those who volunteered to join the workforce had lower self-perceived job preparedness (23.8 vs. 24.9, p = 0.02). While there were some statistically significant differences by trainee characteristics, the practical significance was small (<2-point differences on 30-point composite scores), and it was notable that there were no differences by education level. Overall, this evaluation suggests that individuals without bachelor's degrees or health backgrounds can be rapidly trained and deployed to provide critical disease investigation capacity during public health emergencies.

Context: School closures in California due to COVID-19 have had a negative impact on the learning advancement and social development of K-12 students. Since March 2020, the achievement gap has grown between high-income and low-income students and between White students and students of color. Program: In November 2020, a team from the California Department of Public Health, University of California, San Francisco, and University of California, Los Angeles, developed the School Specialist training for local health department and state employee redirected staff to the COVID-19 response to equip them to support schools as they reopen. Implementation: A pilot of the virtual School Specialist training was carried out in December 2020, which informed subsequent biweekly half-day virtual trainings. The training consisted of lectures from experts and skill development activities led by trained facilitators. Evaluation: The objectives of the evaluation of the training were to understand whether (1) knowledge of key concepts improved from pre- to posttraining; (2) confidence in skills central to the role of a School Specialist improved from pre- to posttraining; and (3) course learners who were activated to work as School Specialists felt the training adequately prepared them for the role. The School Specialist training team sent pre- and posttraining surveys to learners between February 8 and May 18, 2021. Of the 262 learners who responded, a significant improvement was seen in knowledge, with a mean score increase of 15.6%. Significant improvement was also observed for confidence, with a 20.1% score improvement seen posttraining. Discussion: Overall, the School Specialist training was shown to be effective in increasing knowledge and confidence in preparation for School Specialist deployment. Adequate training and partnerships for local health department and school staff are critical to keep K-12 students safe and to reduce the learning achievement gap during the ongoing COVID-19 pandemic.