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Summary: This paper presents an ultrahigh input impedance, low noise, and wide bandwidth four‐channels analog front‐end (AFE) for low‐power neural recording systems. To achieve high input impedance, the buffer channels are placed between the electrodes and the main amplifier stage of the AFE. The buffer is designed with low noise and low power consumption to obtain high input impedance of overall AFE while maintaining low input‐referred noise and low power consumption. A chopper capacitively coupled chopper instrumentation amplifier (CCIA) is placed after the buffer as the main amplifier stage of the AFE to improve the common mode rejection ratio (CMRR) and the input‐referred noise of the overall AFE design. A new chopper stabilization control technique is proposed and used in the CCIA stage to reduce the charge injection and clock feedthrough and consequently the high‐frequency ripple of the AFE output signal. A programmable gain amplifier (PGA) is designed as the third stage to adjust the overall gain of the AFE. Benefiting from PGA, the AFE can adapt its gain with both action potential and local field potential signals. To reduce the number of the electrode to be implanted and reduce the impedance mismatch that causes the degradation on overall CMRR performance, two AFE channels shared a reference electrode followed by a reference buffer. The proposed AFE is designed and simulated using a standard 180 nm CMOS process and operates in a wide frequency band of 2.1 to 2500 Hz with low input‐referred noise of 1.6 μVrms and a CMRR over 80 dB at 2.1 Hz. The total power consumption is lower than 4.3 μW per channel. With the proposed structure of AFE, the input impedance is 35 GΩ @ 21 Hz and the minimum impedance over operational bandwidth is 75 MΩ @ 2.5 kHz. [ABSTRACT FROM AUTHOR]

Influenza virus seasonality, synchronicity, and vaccine supply differ substantially between temperate and tropical settings, and optimal vaccination strategy may differ on this basis. Many national vaccine recommendations focus on high-risk groups, elderly populations, and healthcare workers despite previous analyses demonstrating broad benefits to vaccinating younger high-contact age groups. In this study, we parameterized an age-structured nonseasonal asynchronous epidemiological model of influenza virus transmission for a tropical low-income setting. We evaluated timing and age allocation of vaccines across vaccine supplies ranging from 10 to 90% using decade-based age groups. Year-round vaccination was beneficial when compared with more concentrated annual vaccine distribution. When targeting a single age group for vaccine prioritization, maximum vaccine allocation to the 10-19 high-contact age group minimized annual influenza mortality for all but one vaccine supply. When evaluating across all possible age allocations, optimal strategies always allocated a plurality of vaccines to school-age children (10-19). The converse, however, was not true as not all strategies allocating a plurality to children aged 10-19 minimized mortality. Allocating a high proportion of vaccine supply to the 10-19 age group is necessary but not sufficient to minimize annual mortality as distribution of remaining vaccine doses to other age groups also needs to be optimized. Strategies focusing on indirect benefits (vaccinating children) showed higher variance in mortality outcomes than strategies focusing on direct benefits (vaccinating the elderly). However, the indirect benefit approaches showed a lower mean mortality and a lower minimum mortality than vaccination focused on the elderly., (© The Author(s) 2024. Published by Oxford University Press on behalf of National Academy of Sciences.)