Self-reported reasons for on-duty sleepiness among commercial airline pilots

Experimental and epidemiological research has shown that human sleepiness is determined especially by the circadian and homeostatic processes. The present field study examined which work-related factors airline pilots perceive as causing on-duty sleepiness during short-haul and long-haul flights. In addition, the association between the perceived reasons for sleepiness and actual sleepiness levels was examined, as well as the association between reporting inadequate sleep causing sleepiness and actual sleep-wake history. The study sample consisted of 29 long-haul (LH) pilots, 28 short-haul (SH) pilots, and 29 mixed fleet pilots (flying both SH and LH flights), each of whom participated in a 2-month field measurement period, yielding a total of 765 SH and 494 LH flight duty periods (FDPs) for analyses (FDP, a period between the start of a duty and the end of the last flight of that duty). The self-reports of sleepiness inducers were collected at the end of each FDP by an electronic select menu. On-duty sleepiness was rated at each flight phase by the Karolinska Sleepiness Scale (KSS). The sleep-wake data was collected by a diary and actigraph. The results showed that "FDP timing" and "inadequate sleep" were the most frequently reported reasons for on-duty sleepiness out of the seven options provided, regardless of FDP type (SH, LH). Reporting these reasons significantly increased the odds of increased on-duty sleepiness (KSS >= 7), except for reporting "inadequate sleep" during LH FDPs. Reporting "inadequate sleep" was also associated with increased odds of a reduced sleep-wake ratio (total sleep time/amount of wakefulnessPeer reviewe

Effect of the frequency spectrum of road traffic noise on sleep: A polysomnographic study

Spectrum of sound affects noise annoyance. Spectral differences of road traffic noise (RTN) transmitted indoors are usual because of spectrally different sound insulation of facades. The purpose was to compare the effect of RTN spectrum on sleep. Twenty-one volunteers slept three nights in a sleep laboratory in three sound conditions: low-frequency (LF) RTN, high-frequency (HF) RTN, and quiet (control). The A-weighted equivalent levels were 37, 37, and 17 dB LAeq,8h, respectively. The nocturnal time profiles of LF and HF were equal. Sleep was measured with polysomnography and questionnaires. HF and LF did not differ from each other in respect to their effects on both objective and subjective sleep quality. The duration of deep sleep was shorter, satisfaction with sleep lower, and subjective sleep latency higher in HF and LF than in quiet. Contrary to subjective ratings given right after the slept night, HF was rated as the most disturbing condition for sleep after the whole experiment (retrospective rating). The finding suggests the sound insulation spectrum of the facade construction might play a role regarding the effects of RTN. More research is needed about the effects of spectrum on sleep because the field is very little investigated

Carrier capture processes in strain-induced InxGa1-xAs/GaAs quantum dot structures

We investigate carrier capture processes in strain-induced quantum dot structures. The quantum dots consist of a near-surface InGaAs/GaAs quantum well in which a lateral confining potential is generated by the strain from InP stressor islands grown on the sample surface. Using photoluminescence spectroscopy, we show that the rate of carrier capture into the quantum dots increases dramatically when the energetic depth of the confinement potential is reduced by enlarging the quantum well/surface separation D. While carriers in the quantum well region between the quantum dots are found to experience D-dependent nonradiative surface recombination, this process seems to be negligible for carriers in the quantum dots, presumably due to the protecting InP islands.Peer reviewe

High-resolution spatial patterns and drivers of terrestrial ecosystem carbon dioxide, methane, and nitrous oxide fluxes in the tundra

Arctic terrestrial greenhouse gas (GHG) fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) play an important role in the global GHG budget. However, these GHG fluxes are rarely studied simultaneously, and our understanding of the conditions controlling them across spatial gradients is limited. Here, we explore the magnitudes and drivers of GHG fluxes across fine-scale terrestrial gradients during the peak growing season (July) in sub-Arctic Finland. We measured chamber-derived GHG fluxes and soil temperature, soil moisture, soil organic carbon and nitrogen stocks, soil pH, soil carbon-to-nitrogen (C/N) ratio, soil dissolved organic carbon content, vascular plant biomass, and vegetation type from 101 plots scattered across a heterogeneous tundra landscape (5 km2). We used these field data together with high-resolution remote sensing data to develop machine learning models for predicting (i.e., upscaling) daytime GHG fluxes across the landscape at 2 m resolution. Our results show that this region was on average a daytime net GHG sink during the growing season. Although our results suggest that this sink was driven by CO2 uptake, it also revealed small but widespread CH4 uptake in upland vegetation types, almost surpassing the high wetland CH4 emissions at the landscape scale. Average N2O fluxes were negligible. CO2 fluxes were controlled primarily by annual average soil temperature and biomass (both increase net sink) and vegetation type, CH4 fluxes by soil moisture (increases net emissions) and vegetation type, and N2O fluxes by soil C/N (lower C/N increases net source). These results demonstrate the potential of high spatial resolution modeling of GHG fluxes in the Arctic. They also reveal the dominant role of CO2 fluxes across the tundra landscape but suggest that CH4 uptake in dry upland soils might play a significant role in the regional GHG budget.</p

Quantifying the Detrimental Impacts of Land-Use and Management Change on European Forest Bird Populations

The ecological impacts of changing forest management practices in Europe are poorly understood despite European forests being highly managed. Furthermore, the effects of potential drivers of forest biodiversity decline are rarely considered in concert, thus limiting effective conservation or sustainable forest management. We present a trait-based framework that we use to assess the detrimental impact of multiple land-use and management changes in forests on bird populations across Europe. Major changes to forest habitats occurring in recent decades, and their impact on resource availability for birds were identified. Risk associated with these changes for 52 species of forest birds, defined as the proportion of each species' key resources detrimentally affected through changes in abundance and/or availability, was quantified and compared to their pan-European population growth rates between 1980 and 2009. Relationships between risk and population growth were found to be significantly negative, indicating that resource loss in European forests is an important driver of decline for both resident and migrant birds. Our results demonstrate that coarse quantification of resource use and ecological change can be valuable in understanding causes of biodiversity decline, and thus in informing conservation strategy and policy. Such an approach has good potential to be extended for predictive use in assessing the impact of possible future changes to forest management and to develop more precise indicators of forest health