The effect of continuous volumetric direct-coupled nonequilibrium atmospheric microwave plasma discharge on swirl-stabilized premixed methane–air flames was investigated using quantitative OH planar laser-induced fluorescence and spectrally resolved emission. The plasma discharge was found to influence the dynamics of flame stabilization, i.e., plasma-assisted flames stabilized in the quiescent center body wake were relatively stable while swirl flames stabilized in the active inner shear layer were prone to local extinction due to aerodynamic shear. At coupled plasma powers corresponding to less than 3% of the thermal power output, in addition to the improved flame stability, significant improvement in the lean blow-out limit ( $\sim 43$ %) and OH number density ( $\sim 150$ %) was observed. The enhancements are shown to be nonequilibrium plasma effects and not predominantly ohmic heating as significant equivalence ratio dependence of OH number density in plasma-assisted flames was observed. Spectrographic measurements indicated nitrogen vibrational temperatures as high as 6100 K, suggesting both vibrational and electronic excitation of nitrogen molecules in the presence of a plasma discharge. The activation of highly reactive species through vibrational–vibrational relaxation and direct impact dissociation accelerates the combustion chemistry. It is demonstrated that microwave direct plasma coupling can drastically enhance the dynamic flame stability of swirl-stabilized flames, especially at very lean operating conditions.

Background: Morbidity and death due to coronavirus disease 2019 (COVID‐19) experienced by older adults in nursing homes have been well described, but COVID‐19's impact on community‐living older adults is less studied. Similarly, the previous ambulatory care experience of such patients has rarely been considered in studies of COVID‐19 risks and outcomes. Methods: To investigate the relationship of advanced age (65+), on risk factors associated with COVID‐19 outcomes in community‐living elders, we identified an electronic health records cohort of older patients aged 65+ with laboratory‐confirmed COVID‐19 with and without an ambulatory care visit in the past 24 months ( n = 47,219) in the New York City (NYC) academic medical institutions and the NYC public hospital system from January 2020 to February 2021. The main outcomes are COVID‐19 hospitalization; severe outcomes/Intensive care unit (ICU), intubation, dialysis, stroke, in‐hospital death), and in‐hospital death. The exposures include demographic characteristics, and those with ambulatory records, comorbidities, frailty, and laboratory results. Results: The 31,770 patients with an ambulatory history had a median age of 74 years; were 47.4% male, 24.3% non‐Hispanic white, 23.3% non‐Hispanic black, and 18.4% Hispanic. With increasing age, the odds ratios and attributable fractions of sex, race–ethnicity, comorbidities, and biomarkers decreased except for dementia and frailty (Hospital Frailty Risk Score). Patients without ambulatory care histories, compared to those with, had significantly higher adjusted rates of COVID‐19 hospitalization and severe outcomes, with strongest effect in the oldest group. Conclusions: In this cohort of community‐dwelling older adults, we provided evidence of age‐specific risk factors for COVID‐19 hospitalization and severe outcomes. Future research should explore the impact of frailty and dementia in severe COVID‐19 outcomes in community‐living older adults, and the role of engagement in ambulatory care in mitigating severe disease.

The data-rate requirement for a data center interconnect is being switched to 400 Gb/s. For the optical interface, the electro-optical transmitter chip designed in the CMOS process has been proposed rather than the BiCMOS process as technology advances. On the other hand, vertical-cavity surface-emitting laser (VCSEL) has been a popular candidate for the optical modulation device of the 400 GbE interconnect because of its cost and packaging efficiency [1] –[7]. However, the high operating voltage, nonlinear effects, and low bandwidth are problems to be overcome by the VCSEL driver to transmit high-speed pulse-amplitude-modulation-4 (PAM-4). The pattern-detecting equalization is proposed [3], [6] to compensate for the nonlinearity, and the driver combines MSB-LSB with a 1-bit DAC scheme to produce PAM-4 output [3], [5–6]. However, pattern detection requires power-consuming additional blocks. The combining at the driver needs an additional pre-driver and increases driver drain capacitance which lowers the bandwidth. This paper presents a PAM-4 64 Gb/s VCSEL transmitter (TX) for 400 GbE with 3-tap sub-UI asymmetric feed-forward equalizer (FFE) fabricated in 40 nm CMOS technology. The quarter-rate system and the PAM-4 combining 8:1 multiplexer (MUX) are employed for clocking power reduction. The sub-UI FFE and combining-ahead scheme compensate for low bandwidth. The TX achieves a power efficiency of 2.09 pJ/bit at PAM-4 64 Gb/s.