Advances and new applications using the acousto-optic effect in optical fibers

This work presents a short review of the current research on the acousto-optic mechanism applied to optical fibers. The role of the piezoelectric element and the acousto-optic modulator in the excitation of flexural and longitudinal acoustic modes in the frequency range up to 1.2 MHz is highlighted. A combination of the finite elements and the transfer matrix methods is used to simulate the interaction of the waves with Bragg and long period gratings. Results show a very good agreement with experimental data. Recent applications such as the writing of gratings under the acoustic excitation and a novel viscometer sensor based on the acousto-optic mechanism are discussed

Terahertz Kerr nonlinearity analysis of a microribbon graphene array using the harmonic balance method

Transmission spectra of microribbon graphene arrays are investigated with a circuit model based on the transmission line method. The accuracy of the proposed method is comparable with full-wave electromagnetic simulation results versus chemical potential, incident angle, dimensions of microribbons and the permittivity of the substrate. This rigorous method takes less than a second to perform, therefore it can be employed to optimize other similar devices instead of numerical methods that involve heavy calculations. Furthermore, we depicted the Kerr effect with the harmonic balance method through calculating the parameters in steady state. The results of this novel approach exhibited an excellent agreement with full-wave simulation results

COVID-19 driven decline in emergency visits: Has it continued, is it permanent, and what does it mean for emergency physicians?

INTRODUCTION: Hospital-based emergency departments have been a sustained source of overall hospital utilization in the United States. In 2019, an estimated 150 million hospital-based emergency department (ED) visits occurred in the United States, up from 90 million in 1993, 108 million in 2000 and 137 million in 2015. This study analyzes hospital ED visit registration data pre and post to the COVID-19 pandemic describe the impact of on hospital ED utilization and to assess long-term implications of COVID and other factors on the utilization of hospital-based emergency services. METHODS: We analyze real-time hospital ED visit registration data from a large sample of US hospitals to document changes in ED visits from January 2020 through March 2022 relative to 2019 (pre-COVID baseline) to describe the impact of the COVID-19 pandemic on EDs and assess long-term implications. RESULTS: Our data show an initial steep reduction in ED visits during the first half of 2020 (compared to 2019 levels) with rebounding occurring in 2021, but never reaching pre-pandemic levels. Overall, ED visit volumes across the study states declined in each year since 2019: 2020 declined by -18%, 2021 by -10% and the first quarter of 2022 is -12% below 2019 levels. CONCLUSIONS: There is a wide range of potential long-term implications of the observed reduction in the demand for hospital-based emergency services not only for emergency physicians, but for hospitals, health plans and consumers