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York, J E; Young, A J; Radford, A N |
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Title |
Singing in the moonlight: dawn song performance of a diurnal bird varies with lunar phase |
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2014 |
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Biology letters |
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10 |
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1 |
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20130970 |
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animals; birds; signalling behaviour; photoperiod |
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It is well established that the lunar cycle can affect the behaviour of nocturnal animals, but its potential to have a similar influence on diurnal species has received less research attention. Here, we demonstrate that the dawn song of a cooperative songbird, the white-browed sparrow weaver (Plocepasser mahali), varies with moon phase. When the moon was above the horizon at dawn, males began singing on average 10 min earlier, if there was a full moon compared with a new moon, resulting in a 67% mean increase in performance period and greater total song output. The lack of a difference between full and new moon dawns when the moon was below the horizon suggests that the observed effects were driven by light intensity, rather than driven by other factors associated with moon phase. Effects of the lunar cycle on twilight signalling behaviour have implications for both pure and applied animal communication research. |
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LoNNe @ schroer @ |
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1609 |
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Stokkan, K.-A.; Folkow, L.; Dukes, J.; Neveu, M.; Hogg, C.; Siefken, S.; Dakin, S.C.; Jeffery, G. |
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Title |
Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer |
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Journal Article |
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2013 |
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Proceedings. Biological Sciences |
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Proc Biol Sci |
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280 |
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1773 |
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20132451 |
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Animals; Skyglow |
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Arctic reindeer experience extreme changes in environmental light from continuous summer daylight to continuous winter darkness. Here, we show that they may have a unique mechanism to cope with winter darkness by changing the wavelength reflection from their tapetum lucidum (TL). In summer, it is golden with most light reflected back directly through the retina, whereas in winter it is deep blue with less light reflected out of the eye. The blue reflection in winter is associated with significantly increased retinal sensitivity compared with summer animals. The wavelength of reflection depends on TL collagen spacing, with reduced spacing resulting in shorter wavelengths, which we confirmed in summer and winter animals. Winter animals have significantly increased intra-ocular pressure, probably produced by permanent pupil dilation blocking ocular drainage. This may explain the collagen compression. The resulting shift to a blue reflection may scatter light through photoreceptors rather than directly reflecting it, resulting in elevated retinal sensitivity via increased photon capture. This is, to our knowledge, the first description of a retinal structural adaptation to seasonal changes in environmental light. Increased sensitivity occurs at the cost of reduced acuity, but may be an important adaptation in reindeer to detect moving predators in the dark Arctic winter. |
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Department of Arctic and Marine Biology, University of Tromso, , Tromso, Norway, Institute of Ophthalmology, University College London, , 11-43 Bath Street, London EC1V 9EL, UK, Moorfields Eye Hospital, , London, UK |
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0962-8452 |
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PMID:24174115; PMCID:PMC3826237 |
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LoNNe @ kyba @ |
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1636 |
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Swaminathan, K.; Klerman, E.B.; Phillips, A.J.K. |
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Are Individual Differences in Sleep and Circadian Timing Amplified by Use of Artificial Light Sources? |
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2017 |
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Journal of Biological Rhythms |
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J Biol Rhythms |
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748730417699310 |
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Human Health |
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Within the human population, there is large interindividual variability in the timing of sleep and circadian rhythms. This variability has been attributed to individual differences in sleep physiology, circadian physiology, and/or light exposure. Recent experimental evidence suggests that the latter is necessary to evoke large interindividual differences in sleep and circadian timing. We used a validated model of human sleep and circadian physiology to test the hypothesis that intrinsic differences in sleep and circadian timing are amplified by self-selected use of artificial light sources. We tested the model under 2 conditions motivated by an experimental study (Wright et al., 2013): (1) a “natural” light cycle, and (2) a “realistic” light cycle that included attenuation of light due to living indoors when natural light levels are high and use of electric light when natural light levels are low. Within these conditions, we determined the relationship between intrinsic circadian period (within the range of 23.7-24.6 h) and timing of sleep onset, sleep offset, and circadian rhythms. In addition, we simulated a work week, with fixed wake time for 5 days and free sleep times on weekends. Under both conditions, a longer intrinsic period resulted in later sleep and circadian timing. Compared to the natural condition, the realistic condition evoked more than double the variation in sleep timing across the physiological range of intrinsic circadian periods. Model predictions closely matched data from the experimental study. We found that if the intrinsic circadian period was long (>24.2 h) under the realistic condition, there was significant mismatch in sleep timing between weekdays and weekends, which is known as social jetlag. These findings indicate that individual tendencies to have very delayed schedules can be greatly amplified by self-selected modifications to the natural light/dark cycle. This has important implications for therapeutic treatment of advanced or delayed sleep phase disorders. |
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School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia |
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0748-7304 |
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PMID:28367676 |
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SU @ spitschan @ |
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1648 |
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Bagan, H.; Borjigin, H.; Yamagata, Y. |
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Assessing nighttime lights for mapping the urban areas of 50 cities across the globe |
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2018 |
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Environment and Planning B: Urban Analytics and City Science |
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Environment and Planning B: Urban Analytics and City Science |
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2399808317752926 |
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Remote Sensing |
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Nighttime data from the Defense Meteorological Satellite Program Operational Linescan System have been widely used to map urban/built-up areas (hereafter referred to as “built-up area”), but to date there has not been a geographically comprehensive evaluation of the effectiveness of using nighttime lights data to map urban areas. We created accurate, convenient, and scalable grid cells based on Defense Meteorological Satellite Program/Operational Linescan System nighttime light pixels. We then calculated the density of Landsat-derived built-up areas within each grid cell. We explored the relationship between Defense Meteorological Satellite Program/Operational Linescan System nighttime lights data and the density of built-up areas to assess the utility of nighttime lights for mapping urban areas in 50 cities across the globe. We found that the brightness of nighttime lights was only in moderate agreement with the density of built-up areas; moreover, correlations between nighttime lights and Landsat-derived built-up areas were weak. Even in relatively sparsely populated urban regions (where the density of the built-up area is less than 20%), the highest correlation coefficient (R2) was only 0.4. Furthermore, nighttime lights showed lighted areas that extended beyond the area of large cities, and nighttime lights reduced the area of small cities. The results suggest that it is difficult to use the regression model to calibrate the Defense Meteorological Satellite Program/Operational Linescan System nighttime lights to fit urban built up areas. |
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2399-8083 |
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LoNNe @ kyba @; GFZ @ kyba @ |
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1795 |
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Preciado, O.; Manzano, E. |
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Spectral characteristics of road surfaces and eye transmittance: Effects on energy efficiency of road lighting at mesopic levels |
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2017 |
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Lighting Research & Technology |
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Lighting Research & Technology |
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147715351771822 |
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Vision; Lighting |
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In 2010, the CIE published a recommended system for mesopic photometry based on visual performance. According to this system, scenes illuminated at mesopic levels with light sources of high S/P ratio, will produce better visual performance than those illuminated with light sources of a lower S/P ratio at equal photopic luminance. However, there could be other factors affected by SPD that, when quantified, could lead to a contradictory final effect. The scope of this paper was to evaluate how road lighting is affected by the spectral road surface reflectance and by the human eye transmittance as people get older. Our results suggest that the benefits of considering the mesopic vision effect for light sources with high S/P ratios are totally counteracted by the other two effects at mesopic luminances between 0.75 cd/m2 and 1.73 cd/m2 for people between 20 and 60 years of age, depending on the light source and the age of observers. |
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1477-1535 |
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GFZ @ kyba @ |
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1862 |
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