Sleep in a live-in mining operation: The influence of start times and restricted non-work activities

The amount of sleep obtained between shifts is influenced by numerous factors including the length of work and rest periods, the timing of the rest period relative to the endogenous circadian cycle and personal choices about the use of non-work time. The current study utilised a real-world live-in mining environment to examine the amount of sleep obtained when access to normal domestic, family and social activities was restricted. Participants were 29 mining operators (26 male, average age 37.4 ± 6.8 years) who recorded sleep, work and fatigue information and wore an activity monitor for a cycle of seven day shifts and seven night shifts (both 12 h) followed by either seven or fourteen days off. During the two weeks of work participants lived on-site. Total sleep time was significantly less (p < 0.01) while on-site on both day (6.1 ± 1.0 h) and night shifts (5.7 ± 1.5 h) than days off (7.4 ± 1.4 h). Further, night shift sleep was significantly shorter than day-shift sleep (p < 0.01). Assessment of subjective fatigue ratings showed that the sleep associated with both days off and night shifts had a greater recovery value than sleep associated with day shifts (p < 0.01). While on-site, participants obtained only 6 h of sleep indicating that the absence of competing domestic, family and social activities did not convert to more sleep. Factors including shift start times and circadian influences appear to have been more important.     

HACH: Heuristic Algorithm for Clustering Hierarchy protocol in wireless sensor networks

Wireless sensor networks (WSNs) require energy management protocols to efficiently use the energy supply constraints of battery-powered sensors to prolong its network lifetime. This paper proposes a novel Heuristic Algorithm for Clustering Hierarchy (HACH), which sequentially performs selection of inactive nodes and cluster head nodes at every round. Inactive node selection employs a stochastic sleep scheduling mechanism to determine the selection of nodes that can be put into sleep mode without adversely affecting network coverage. Also, the clustering algorithm uses a novel heuristic crossover operator to combine two different solutions to achieve an improved solution that enhances the distribution of cluster head nodes and coordinates energy consumption in WSNs. The proposed algorithm is evaluated via simulation experiments and compared with some existing algorithms. Our protocol shows improved performance in terms of extended lifetime and maintains favourable performances even under different energy heterogeneity settings.     

Work hours, workload, sleep and fatigue in Australian Rail Industry employees

Research suggests that less than 5 h sleep in the 24 h prior to work and/or more than 16 h of wakefulness can significantly increase the likelihood of fatigue-related impairment and error at work. Studies have also shown exponential safety declines with time on shift, with roughly double the likelihood of accident or injury after 10 h relative to the first 8 h. While it is acknowledged that reduced sleep, increased wakefulness and longer work hours produce work-related fatigue, few studies have examined the impact of workload on this relationship. Studies in the rail industry have focused on drivers. This study investigated fatigue in a large sample of Australian Rail Industry Employees. Participants were from four companies (n = 90: 85m, 5f; mean age 40.2 ± 8.6 y). Data was analysed for a total of 713 shifts. Subjects wore wrist actigraphs and completed sleep and work diaries for 14-days. They also completed the Samn–Perelli Fatigue Scale at the beginning and end of shifts, and the NASA-TLX workload scale at least twice during each shift. Average (±SD) sleep length (7.2 ± 2.6 h), prior wake at shift end (12.0 ± 4.7 h), shift duration (8.0 ± 1.3) and fatigue (4.1 ± 1.3, “a little tired, less than fresh”) were within limits generally considered acceptable from a fatigue perspective. However, participants received 5 h or less sleep in the prior 24 h on 13%, were awake for at least 16 h at the end of 16% and worked at least 10 h on 7% of shifts. Subjects reported that they felt “extremely tired, very difficult to concentrate,” or “completely exhausted, unable to function effectively” on 13% of shifts. Sleep length (OR = 0.88, p < 0.01), shift duration (OR = 1.18, p < 0.05), night shift (REF = morning shift, OR = 2.12, p < 0.05) and workload ratings (OR = 1.2, p < 0.05) were significant predictors of ratings of extreme tiredness/exhaustion (yes/no). While on average, sleep loss, extended wakefulness, longer work hours and work-related fatigue do not appear problematic in this sample, there is still a notable percentage of shifts that are likely to be associated with high levels of work-related fatigue. Given the size of the Australian Rail Industry, with thousands of shifts occurring each day, this is potentially of operational concern. Further, results indicate that, in addition to sleep length, wakefulness and work hours, workload significantly influences fatigue. This has possible implications for bio-mathematical predictions of fatigue and for fatigue management more generally.     

Influence of back angle on the quality of sleep in seats

Nocturnal sleep was assessed electroencephalographically in 9 males aged between 29 and 48 (mean 36·5) years in bed and in three seats with back angles to the vertical of 49·5° (sleeperette), 37·0° (reclining seat) and 17·5° (armchair).

Sleep in the sleeperette did not differ from that in bed, but in the reclining seat the duration of sleep was reduced and the amount of awake activity was increased. Sleep in the armchair was markedly worse than in any of the other three conditions. Total sleep time was shorter and awake activity was increased with more awakenings. Sleep efficiency was also reduced.

It would appear that adequate sleep may be obtained in seats as long as the back angle with the vertical approaches 40°.     

Some effects of jet-lag and their alleviation by melatonin

Abstract

Seventeen healthy volunteers (10 women and 7 men, aged 29-68) were flown from London to San Francisco between 20 November 1985 and 25 January 1986 and remained there for 14 days prior to flight home. Subjects took melatonin (N = 8, 5 women, 3 men) or placebo in a double-blind design, at 18.00h local time for three days before the return flight and at bedtime (22.00-24.00h) in Great Britain for four days. For three days before departure and on days 1-7,14,15, 21 and 22 after their return subjects collected 6-hourly sequential urine samples and kept a daily sleep log. They recorded mood and oral temperature 2 hourly and performed logical reasoning and letter cancellation tests 4 hourly from 08.00h (or wake up time) to 24.00h (or bedtime) whichever was the earlier. Urine was also collected for 48 h prior to departure from the U.S.A‥ On day 7 after their return subjects rated ‘jet lag’ (10 cm visual analogue scale—VAS) from 0 (insignificant) to 100 (very bad). Melatonin significantly improved ‘jet lag’ (p= 0.009). Comparisons by ANOVA between jet-lagged placebo subjects (N = 7) and melatonin (N = 8) showed decreased sleep latency with melatonin (p= 0.0397) which correlated positively with jet lag ratings, p< 0.001. Sleep quality was significantly improved in the melatonin group and correlated negatively with jet-lag ratings (p<0.001). No important differences were found in temperature, or performance data. Baseline differences were present in some performance ratings but no other variables. Melatonin treated subjects tended to be more alert than placebo subjects, especially at bedtime. They were also less depressed. Endogenous melatonin and Cortisol rhythms resyn-chronized more rapidly in melatonin subjects (p= 0.0216 and p= 0.0299 respectively, absolute acrophase shifts). Cortisol rhythms indicated adaptation to U.S.A. time in 14 days. These data suggest that MT can alleviate jet-lag after Eastward flight over eight time zones. Presumably its affects are primarily on sleep latency, quality, and directly or indirectly on some hormonal rhythms.     

Locomotive engineers and their spouses: coffee consumption,mood, and sleep reports

Locomotive engineers (train drivers) on irregular work schedules reported a general coffee consumption rate higher than that reported by a comparison sample of permanent shift factory workers. The present study examines the impact of this consumption on workday and non-workday sleep behaviour and mood ratings. Twenty-seven engineers and their spouses each completed daily logs for 30 consecutive days. Daily logs were then sorted into workday and non-workday categories. Workday sleep length was significantly shorter than non-workday sleep length for both engineers and spouses. For the engineers only, coffee consumption on workdays was higher than on non-workdays. This increased coffee consumption was correlated with longer sleep latency, increased negative mood, and decreased positive mood on both work and non-workdays. This was not true for spouses. These results may be related to a days-off carry-over effect of caffeine or a general consumption behaviour characteristic.     

Does the ‘forbidden zone’ for sleep onset influence morning shift sleep duration?

Shiftwork researchers have concentrated on the problems on the night shift, and have tended to neglect the truncation of sleep that can occur before morning, or ‘early’, shifts. We examined the sleep timing and duration between morning shifts of shiftworkers on a variety of shift systems. The extent of morning shift sleep truncation depended very largely on the time at which individuals had to leave home. Further, there was some suggestive evidence that the failure of individuals to compensate by going to sleep earlier was not simply due to social pressures to stay up. Rather it would appear to have depended, at least in part, on the biological clock determined ‘forbidden zone’ for sleep that occurs shortly before habitual sleep onset.     

嵌入式MCU的SOC设计中的低功耗设计

以Motorola龙珠系列中MXL芯片为例介绍了嵌入式MCU SOC设计中的低功耗设计技术。从加工工艺、硬件设计和软件设计方面来 阐述其中的低功耗设计技术。     

Gender influences on performance,mood and recovery sleep in fatigued aviators

Female aviators now are able to serve in combat roles, but few studies have addressed potential differences between the ability of males and females to withstand combat stressors. This study examined responses of men and women to one operational stressor, sleep deprivation. Pilots were tested on flight performance and mood during 40-h periods of sustained wakefulness. Baseline and recovery sleep also were examined. Gender produced no operationally significant effects on flight performance or recovery sleep. Although mood tests showed that women felt less tense and more energetic than men, there were no interactions between sleep deprivation and gender on either flight performance or psychological mood.     

The use of prophylactic naps and caffeine to maintain performance during a continuous operation

After a normal baseline night of sleep and a morning of baseline test performance, 24 young adult male subjects returned to bed from 16:00-20:00 prior to a 24?h period of sleep loss. Twelve subjects received caffeine 200?mg at 01:30 and 07:30. Performance tests (correctly completed addition problems, vigilance sensitivity, and logical reasoning correct responses) all indicated maintenance of baseline performance levels in the caffeine group after administration of caffeine while performance declined in the placebo group. Similar results were found for the Multiple Sleep Latency Test and Oral Temperature, which both remained near baseline levels throughout the observation period in subjects receiving caffeine. The results indicated that the combination of a prophylactic nap and caffeine was more effective in maintaining nocturnal alertness and performance than was the nap alone. Of more interest was the fact that the group which was given the combination of nap and caffeine was able to maintain alertness and performance at very close to baseline levels throughout a 24?h period without sleep.