Screening for the obstructive sleep apnea syndrome among guards in alternating work shifts
This study was conducted to appraise the prevalence of OSAS among individuals employed in alternating work shifts. The tentative diagnosis suggested by screening was validated by testing in a sleep laboratory; afflicted individuals received appropriate treatment and follow -up care. S creening conducted by administering a questionnaire suggested OSAS in 23 per cent of 218 subjects employed as sentries/guards in alternating work shifts. Individuals identified by screen ing underwent polysomnography in a sleep diagnostics laboratory in or der to confirm the tent ative diagnosis. Advanced OSAS is associated with abnormal enhancement of daytime sleepiness, which results in significant impairment of attention, mental concentration, vigilance, cognitive and job performance in afflicted individua ls employed in alternating work shifts.
Selected mapping (SLM) and partial transmit sequence ::: (PTS) are well-known techniques for peak-power reduction ::: in orthogonal frequency-division multiplexing (OFDM). We ::: derive a simplified maximum likelihood (ML) decoder for SLM ::: and PTS that operates without side information. This decoder ::: exploits the fact that the modulation symbols belong to a given ::: constellation and that the multiple signals generated by the PTS or ::: SLM processes are widely different in a Hamming distance sense. ::: Pairwise error probability (PEP) analysis suggests how SLM and ::: PTS vectors should be chosen. The decoder performs well over ::: additive white Gaussian noise (AWGN) channels, fading channels, ::: and amplifier nonlinearities.