Ambient Light Levels Research Articles

Influence of different viewing conditions on the detection of fractured endodontic instruments using periapical radiographs at 3 projection angles

The objective of this study was to assess the influence of ambient lighting levels and horizontal viewing angle (HVA) on the radiographic detection of fractured endodontic instruments in root canals in extracted human mandibular molars. Thirty-two root canals were selected. Endodontic instrument fracture was induced in 24 canals, and all canals were endodontially treated. Periapical radiographs were obtained at orthoradial, mesioradial, and distoradial projection angles. Five oral radiologists examined the radiographs for detection of fractured endodontic instruments under 3 ambient lighting levels (high, 450 lux; medium, 28 lux; and low, 2.5 lux) and 3 HVAs (90°, 67.5°, and 45°). Area under the receiver operating characteristic curve (AUROC), accuracy, sensitivity, and specificity were calculated and compared by 2-way analysis of variance using Tukey post hoc tests (α = .05). AUROC data indicated that ambient lighting (P = .739) and HVA (P = .238) did not significantly influence the detection of fractured endodontic instruments. Overall mean diagnostic values were 0.745, 0.57, 0.46, and 0.90 for AUROC, accuracy, sensitivity, and specificity, respectively. The viewing conditions assessed in this study did not influence the radiographic detection of fractured endodontic instruments in root canals.

Dopamine-Mediated Circadian and Light/Dark-Adaptive Modulation of Chemical and Electrical Synapses in the Outer Retina.

The vertebrate retina, like most other brain regions, undergoes relatively slow alterations in neural signaling in response to gradual changes in physiological conditions (e.g., activity changes to rest), or in response to gradual changes in environmental conditions (e.g., day changes into night). As occurs elsewhere in the brain, the modulatory processes that mediate slow adaptation in the retina are driven by extrinsic signals (e.g., changes in ambient light level) and/or by intrinsic signals such as those of the circadian (24-h) clock in the retina. This review article describes and discusses the extrinsic and intrinsic modulatory processes that enable neural circuits in the retina to optimize their visual performance throughout day and night as the ambient light level changes by ~10 billion-fold. In the first synaptic layer of the retina, cone photoreceptor cells form gap junctions with rods and signal cone-bipolar and horizontal cells (HCs). Distinct extrinsic and intrinsic modulatory processes in this synaptic layer are mediated by long-range feedback of the neuromodulator dopamine. Dopamine is released by dopaminergic cells, interneurons whose cell bodies are located in the second synaptic layer of the retina. Distinct actions of dopamine modulate chemical and electrical synapses in day and night. The retinal circadian clock increases dopamine release in the day compared to night, activating high-affinity dopamine D4 receptors on cones. This clock effect controls electrical synapses between rods and cones so that rod-cone electrical coupling is minimal in the day and robust at night. The increase in rod-cone coupling at night improves the signal-to-noise ratio and the reliability of very dim multi-photon light responses, thereby enhancing detection of large dim objects on moonless nights.Conversely, maintained (30 min) bright illumination in the day compared to maintained darkness releases sufficient dopamine to activate low-affinity dopamine D1 receptors on cone-bipolar cell dendrites. This non-circadian light/dark adaptive process regulates the function of GABAA receptors on ON-cone-bipolar cell dendrites so that the receptive field (RF) surround of the cells is strong following maintained bright illumination but minimal following maintained darkness. The increase in surround strength in the day following maintained bright illumination enhances the detection of edges and fine spatial details.

Evidence That Pupil Size and Reactivity Are Determined More by Your Parents Than by Your Environment.

Purpose: A classic twin study to evaluate the relative contributions of genetic and environmental factors to resting pupil size and reactivity.Methods: Pupillometry was performed on 326 female twins (mean age 64 years) from the TwinsUK Adult Twin Registry, assessing resting pupil diameter in darkness and increasing levels of ambient light, alongside dynamic pupillary characteristics. Maximum-likelihood structural equation models estimated the proportion of trait variance attributable to genetic factors.Results: Mean (SD) pupil diameter in darkness was 5.29 mm (0.81), decreasing to 3.24 mm (0.57) in bright light. Pupil light reaction (PLR) had a mean (SD) amplitude of 1.38 mm (0.27) and latency of 250.34 milliseconds (28.58). Pupil size and PLR were not associated with iris colour, intraocular pressure or refractive error, but were associated with age (diameter β = −0.02, p = 0.016, constriction amplitude β = −0.01, p < 0.001, velocity β = 0.03, p < 0.001, and latency β = 0.98, p < 0.001). In darkness the resting pupil size showed a MZ intraclass correlation coefficient of 0.85, almost double that of DZ (0.44), suggesting strong additive genetic effects, with the most parsimonious model estimating a heritability of 86% [95% confidence interval (CI) 79–90%] with 14% (95% CI 10–21%) explained by unique environmental factors. PLR amplitude, latency and constriction velocity had estimated heritabilities of 69% (95% CI 54–79%), 40% (95% CI 21–56%), and 64% (95% CI 48–75%), respectively.Conclusion: Genetic effects are key determinants of resting pupil size and reactivity. Future studies to identify these genetic factors could improve our understanding of variation in pupil size and pupillary reactions in health and disease.

Analytical Evaluation of Signal-to-Noise Ratios for Avalanche- and Single-Photon Avalanche Diodes

Performance of systems for optical detection depends on the choice of the right detector for the right application. Designers of optical systems for ranging applications can choose from a variety of highly sensitive photodetectors, of which the two most prominent ones are linear mode avalanche photodiodes (LM-APDs or APDs) and Geiger-mode APDs or single-photon avalanche diodes (SPADs). Both achieve high responsivity and fast optical response, while maintaining low noise characteristics, which is crucial in low-light applications such as fluorescence lifetime measurements or high intensity measurements, for example, Light Detection and Ranging (LiDAR), in outdoor scenarios. The signal-to-noise ratio (SNR) of detectors is used as an analytical, scenario-dependent tool to simplify detector choice for optical system designers depending on technologically achievable photodiode parameters. In this article, analytical methods are used to obtain a universal SNR comparison of APDs and SPADs for the first time. Different signal and ambient light power levels are evaluated. The low noise characteristic of a typical SPAD leads to high SNR in scenarios with overall low signal power, but high background illumination can saturate the detector. LM-APDs achieve higher SNR in systems with higher signal and noise power but compromise signals with low power because of the noise characteristic of the diode and its readout electronics. Besides pure differentiation of signal levels without time information, ranging performance in LiDAR with time-dependent signals is discussed for a reference distance of 100 m. This evaluation should support LiDAR system designers in choosing a matching photodiode and allows for further discussion regarding future technological development and multi pixel detector designs in a common framework.

Determining the ambient influences and configuration of optimised environments for emotional wellbeing of older adults

It is now widely recognised that aspects such as tiredness or mood state can have an impact on an individual’s wellbeing. However, there also exist other less studied factors that might be influential, and whose analysis is important to maximise personal wellbeing. The aim of this study was to determine the influence of a set of 12 selected factors. Using the analysis of a 20-experiment case study by soft computing techniques the intention was to establish the most appropriate configuration for each factor to compose an optimal living environment to foster wellbeing. The analysis revealed that ambient lighting and stress level are the factors that most impact emotional wellbeing. To a lesser extent, being able to take a break, ambient temperature and ambient noise play a relatively determining role. The findings of this work can be used to establish a living environment for older persons that favours their emotional wellbeing. Practitioner summary: This study analyses the level of influence of a set of ambient factors on the emotional wellbeing of older people, conducting, to this end, a series of controlled experiments, and concluding that ambient lighting and stress level are the factors most relevant to promote a better living environment. KEY POINTS Older adults’ emotional interpretation of pictures depends on the environment and ambient factors. Ambient factors, such as lighting and stress, have a significant, positive effect on visual interpretation of stimuli and greater wellbeing. The use of soft computing techniques facilitates the quantification of the influence of factors affecting emotional wellbeing.

Movements and diving behaviour of white‐chinned petrels: Diurnal variation and implications for bycatch mitigation

Abstract Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries. Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white‐chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at‐sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered. The tracked white‐chinned petrels (n = 14) mostly performed shallow dives (&lt;3 m deep) of very short duration (&lt;5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface‐seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s−1), underlining the importance of using heavy line‐weighting to maximize hook sink rates, and bird‐scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.

A Novel Gaze Input System Based on Iris Tracking With Webcam Mounted Eyeglasses

AbstractDue to the high cost of eye-tracking systems based on pupillary corneal reflections, efforts to develop a webcam-based eye-tracking system have increased to provide an affordable alternative to disabled people in recent years. However, due to the camera specification and location, ambient light changes and positional changes of the users, the gazing point of the eyes has not yet been determined precisely by such a system. Therefore, only 8 different gaze directions or up to 10 gaze regions could be detected in the previous webcam-based human–computer interaction studies. In this study, a novel gaze input system has been proposed to make the best use of the limited performance of webcam-based eye tracking and offer an economical alternative for disabled people. To reduce the impact of head movements, the webcam has been mounted to an ordinary glasses frame and positioned in front of the eye. For estimation of the gaze regions, a feature-based method (Hough transformation) was used by considering the circular shape of the iris and the contrast between the iris and sclera. The central coordinates of the iris image captured by the webcam were given to the k-nearest neighbor classifier. We performed a series of experiments with 20 subjects to determine the performance of the system and to investigate the effect of ambient light on the system’s accuracy. The 23 regions that were gazed at by subjects were determined with an average accuracy of 99.54%. When the ambient light level was reduced by half, the accuracy decreased to 94.74%. As a result, it has been found that the proposed prototype allows more accurate recognition of a larger number of regions on the screen than previous webcam-based systems. It has been observed that system performance decreases if the ambient light is reduced byhalf.

Spatial Augmented Reality Based Customer Satisfaction Enhancement and Monitoring System

This research proposes a customer-interaction scheme that enhances customer-satisfaction through spatial-augmented-reality and deep-learning-based emotion-recognition for restaurant 4.0, by monitoring user-experience levels using facial expressions. The customer-satisfaction analytical-model provides environmental knowledge-based dynamic capabilities to the human-centered dining environment, which is also utilized as an input to logistics 4.0 supply chain management, business-processes, and decision-support-systems for future analytics. The perception of the quality of food was enhanced by the recreation of the live environment on the preparation of the menu ordered, utilizing the waiting time after each ordering session. The dishes are being portrayed in three-dimensional (3D) virtual menu also, adding SAR features in a special angle creating a 3D illusion to the naked eye. Menu suggestions are also proposed depending on the recommendations of the analytical model. The deep learning model monitors customer-satisfaction levels through emotion recognition. The performance was analyzed with numerous experimental evaluations with ambient light levels and desired viewing angles, where we found optimal angle values for spatial augmented reality applications. A survey was carried out to analyze user perception on evaluating the proposed system. The results revealed 87.5% of responders were very satisfied with the 3D virtual experience. 79.2% indicated rareness of feedback on food and service and more than 50% liked a system that will automatically measure their satisfaction. The results indicate enhanced customer-satisfaction levels compared to existing schemes. The resulting insights may lay a foundation for a novel approach towards the management of user-experience, business-processes, decision support systems, and supply chain management of restaurant 4.0.

Acoustic characterization of juvenile Pacific salmon distributions along an eco-engineered seawall

A mobile dual-frequency identification sonar (DIDSON) was used to characterize juvenile Pacific salmon (Oncorhynchus spp.) daytime use of armored and eco-engineered seawall habitats along an urbanized shoreline in Puget Sound, Washington, USA. Eco-engineering included intertidal benches to elevate the seafloor, a textured seawall to provide refuge and encourage invertebrate colonization, and glass blocks in an overhanging sidewalk to increase ambient light. A DIDSON multibeam sonar gave salmon counts twice that of visual surveys, and was thus deemed effective as a mobile sampling tool for small fish (~40-90 mm) and can be advantageous relative to visual methods depending on research goals, habitats, and ambient light levels. Increased salmon presence in the eco-engineered intertidal corridor relative to traditional seawall and pier habitats showed that the combination of increased light, reduced infrastructure (e.g. pier pilings), increased texture, and a shallower seafloor improves habitat function for juvenile salmon. High densities of juvenile salmon along pier ends show that salmon also use alternative migration pathways, with unknown energetic costs and predations risks.

A Low Complexity Indoor Visible Light Positioning Method

The continuous positioning of a mobile user equipment (MU) in a prompt way is a fundamental requirement in several indoor applications related to ubiquitous computation, assisted living environments, and security/surveillance systems. Motivated by this fact, the current contribution reports a low-complexity visible light positioning (VLP) method suitable for indoor environments in the Big Data era. The proposed architecture consists of multiple light-emitting diodes (LEDs) as light sources and an MU equipped with a photodiode (PD). To guarantee higher spectral efficiency, the LEDs emit sinusoidal waveforms at slightly different predetermined frequencies. The light intensity received at the PD from every LED is continuously estimated after applying a short-time Fourier transformation. To this end, a grid-based numerical technique is proposed to recover the unknown MU position. Additionally, a closed-form solution is presented for the particular case of three LEDs that overrides the need for training points in the grid arrangement. Further, a method for handling noisy signals is proposed, based on averaging the calculated positions from densely overlapping received signals. Finally, a Kalman filter is employed as a post-processing precision improving tool. The proposed VLP efficiency is quantified through respective Monte Carlo simulations that allow the setting of different LED frequencies, received signal processing parameters, MU speed, and noise levels. The results reveal that the suggested approach is robust with significant tolerance in high ambient light levels, computationally efficient, and exhibits low positional error. Finally, to evaluate the performance improvements the new method introduces, we make comparisons against widely-used fingerprint approaches.

Survey of monitor specification and viewing conditions in breast screening units in the North West of England

IntroductionMonitor specification and viewing conditions are important factors affecting image assessment in mammography. This survey evaluates the different viewing conditions and monitor specifications that exist in acquisition and reporting rooms in UK breast screening units. MethodsStatic (n = 10) and mobile (n = 2) breast screening units were evaluated in North West England. Room illumination levels were measured in 3 locations for each room using a calibrated Lux meter and the specification of 122 monitors recorded. Room layout, wall colour, location and number of doors, windows and light sources were recorded. ResultsIn reporting rooms, 90/91 of monitors had similar technical specifications and were compliant to guidelines. The ambient light levels ranged from 10 to 25.8 lux. The mean illuminance was 12.32 ± 4.6 lux. In acquisition rooms, great variances appeared in monitor specification and ambient light levels. The majority of monitors (24/34) had 3 megapixel (MB) optimum resolution but the ambient light level ranged from 10 to 1020 lux. The mean illuminance was 105.3 ± 178.8 lux. The mobile units were consistent with each other and compliant with guidelines. ConclusionA lack of consistency and great variances appeared in terms of ambient light levels and monitor specifications in the image acquisition rooms. However, there was excellent consistency among the illumination measurements and the monitors’ technical specifications in the reporting rooms. Implications for practiceThis research demonstrates, for the first time, the need for further research and specialised guidelines for acquisition rooms.

Measuring dose in a tailored lighting intervention to improve sleep and mood in Alzheimer's disease patients

AbstractBackgroundDaytime light helps consolidate sleep in persons with Alzheimer's disease and related dementia (ADRD), but light levels required are high and available lighting fixtures cannot deliver the light level and spectrum needed for the circadian system. Moreover, ambient light levels cannot be measured to determine treatment dose. The present study tested whether a tailored lighting intervention could improve sleep in eight ADRD patients living in long‐term care facilities and used a novel device to measure light dose (RAD).MethodIn a crossover, repeated‐measures design, we exposed ADRD participants (MMSE&lt;24) to an active (circadian stimulus, CS=0.3) and inactive (CS=0.1) tailored lighting intervention for successive 4‐week periods, spaced by a 4‐week washout period. RAD devices, calibrated to measure circadian light, were placed in spaces where the intervention was administered. The lighting intervention was energized from wake time until 6:00 pm. Measures of sleep disturbances (Pittsburgh Sleep Quality Index, PSQI and actigraph) and mood (Cornell Scale for Depression in Dementia, CSDD) were collected at baseline and during the last weeks of each intervention periods.ResultCompared to their respective baseline conditions, the active lighting intervention significantly decreased wake percent and increased sleep percent. Compared to baseline and to the inactive intervention, PSQI scores reduced in the active intervention. Depression scores were significantly lower after the active than after the inactive intervention. The mean ± SEM PSQI scores was 10.9±1.1 and 7.3±0.7 at baseline and after active intervention and 10.0±1.0 and 10.3±1.6 at baseline and after the inactive intervention. The mean ± SEM CSDD scores was 9.0±1.7 and 8.0±1.3 at baseline and after active intervention and 12.0±1.6 and 12.0±2.1 at baseline and after the inactive intervention.ConclusionWhen carefully delivered to patients’ eyes and monitored with a calibrated instrument, daytime light can improve sleep and mood in nursing home residents with AD/ADRD. Additional data need to be collected to extend these preliminary results.

Rotating Night Shift Work, Exposure to Light at Night, and Glomerular Filtration Rate: Baseline Results from a Chinese Occupational Cohort.

The misalignment between the circadian clock and behavioral cycles has been implicated in pathogenesis of many diseases. The main purpose of this study is to examine the association between rotating night shift work, exposure to light at night, and glomerular filtration rate among steelworkers in north China. A total of 6869 steelworkers, aged 22 to 60 years, were included in this study. Multivariable logistic regression was used to examine the association between night shift work, the brightness of bedroom ambient light at night (LAN), and estimated glomerular filtration rate (eGFR), with adjustment for potential confounders. Mediation analysis was performed to examine the mediation effect of potential mediators on the association of duration of night shifts and eGFR. Long duration of night shift work (≥29 years) had elevated odds of decreased eGFR (≤89 mL/min/1.73 m2) (odds ratio (OR), 1.37, 95% confidence interval (CI) 1.09–1.73) compared with day work after adjustment for potential confounders. The association between duration of night shifts and eGFR (continuous) was partially modified by diastolic blood pressure (average causal mediation effect (ACME), –0.077, 95% CI –0.134 to −0.030, p < 0.001). No significant associations were observed among the different brightness of bedroom ambient light levels: middle level (OR, 0.90, 95% CI 0.77–1.05), lightest level (OR, 0.94, 95% CI 0.75–1.18), and decreased eGFR compared with the darkest level. Long-term night-shift work, rather than the brightness of bedroom ambient LAN, is associated with early stage of renal dysfunction in steelworkers, and blood pressure may mediate the relationship between night shift work and decreased eGFR.

Low light intensities increase avoidance behaviour of diurnal fish species: implications for use of road culverts by fish.

Inadequately designed culverts can be physical barriers to fish passage if they increase the velocity of water flow in the environment, alter natural turbulence patterns or fail to provide adequate water depth. They may also act as behavioural barriers to fish passage if they affect the willingness of fish species to enter or pass through the structure due to altered ambient light conditions. To understand how reduced light intensity might affect fish behaviour in culverts, the authors performed a behavioural choice experiment quantifying the amount of time individual fish spent in dark and illuminated areas of a controlled experimental channel. They found that behavioural responses were largely reflective of the species' diel activity patterns; the diurnal species Craterocephalus stercusmuscarum and Retropinna semoni preferred illuminated regions, whereas the nocturnal/crepuscular Macquaria novemaculeata preferred the darkened region of the channel. Bidyanus bidyanus were strongly rheotactic, and their behaviour was influenced more by water flow direction than ambient light level. The authors then determined that a threshold light intensity of only c. 100-200 lx (cf. midday sunlight c. 100,000 lx) was required to overcome the behavioural barrier in c. 70% of the diurnally active C. stercusmuscarum and R. semoni tested. When these values were placed into an environmental context, 15 road-crossing (3.4-7.0 m long) box (c. 1 m × 1 m, height × width) and pipe (c. 1 m diameter) culverts sampled in Brisbane, Australia, recorded light intensities in the centre of the structure that were below the threshold for C. stercusmuscarum and R. semoni movement and could potentially be a barrier to their passage through the structure. Attention is required to better understand the impacts of low light intensity in culverts on fish passage and to prioritize restoration.

Circadian actions of orexins on the retinorecipient lateral geniculate complex in rat.

Key points Rhythmic processes in living organisms are controlled by biological clocks. The orexinergic system of the lateral hypothalamus carries circadian information to provide arousal for the brain during the active phase.Here, we show that orexins exert an excitatory action in three parts of the lateral geniculate nucleus (LGN), in particular upon directly retinorecipient neurons in the non‐image forming visual structures.We provide evidence for the high nocturnal levels of orexins with stable circadian expression of predominant orexin receptor 2 in the LGN.Our data additionally establish the convergence of orexinergic and pituitary adenylate cyclase (PAC)‐activating peptide/PAC1 receptor systems (used by melanopsin‐expressing retinal ganglion cells), which directly regulates responses to the retinal input.These results help us better understand circadian orexinergic control over the non‐image forming subcortical visual system, forming the animal's preparedness for the behaviourally active night. The orexinergic system of the lateral hypothalamus is tightly interlinked with the master circadian clock and displays daily variation in activity to provide arousal‐related excitation for the plethora of brain structures in a circadian manner. Here, using a combination of electrophysiological, optogenetic, histological, molecular and neuronal tracing methods, we explore a particular link between orexinergic and visual systems in rat. The results of the present study demonstrate that orexinergic fibre density at the area of subcortical visual system exerts a clear day to night variability, reaching a maximum at behaviourally active night. We also show pronounced electrophysiological activations of neurons in the lateral geniculate nucleus by orexin A through 24 h, via identified distinct orexin receptors, with the ventrolateral geniculate displaying a daily cycle of responsiveness. In addition, for the first time, we provide a direct evidence for orexins to act on retinorecipient neurons with a high convergence of orexinergic and putatively retinal pituitary adenylate cyclase (PAC)‐activating peptide/PAC1 receptor systems. Altogether, the present study ties orexins to non‐image forming visual structures with implications for circadian orexinergic modulation of neurons, which process information on ambient light levels.

Are Sub-Saharan epileptic people less photosensitive? A Senegalese study of photoparoxysmal response in a reference epilepsy centre.

The photoparoxysmal response (PPR) is defined as the occurrence of generalized spike, spike-wave or polyspike-wave discharges consistently elicited by intermittent photic stimulation (IPS). PPR is not well studied in Sub-Saharan African people. We prospectively studied the epidemiological, clinical, and EEG characteristics of PPR among consecutive patients recorded at the clinical neurophysiology unit of Fann University Hospital (Dakar, Senegal). Among 6,808 EEG recordings including 3,065 pathological EEGs, we collected 56 EEGs with PPR (0.8% of all recorded EEGs and 1.8% of anormal EEGs), from 31 women and 25 men (sex ratio: 0.8). The mean age was 13.3 years (range: 8 months to 59 years). The peak of photosensitivity was found in the range of 6 to 10 years. Of the PPR cases, 12 had clinical manifestations during IPS. Generalized epilepsy was diagnosed in 23 (41%) patients and 18 (32%) had focal epilepsies. The most epileptogenic stimulation frequencies were between 12 and 24Hz (range: 1-28Hz). PPR were mainly triggered during eye closure (64%), and 41 patients (73% of PPR cases) were classified as Type 4 (Waltz classification). Our results confirm lower rates of photosensitivity in African Sub-Saharan people compared with others. Although the current data do not support a role of short-term ambient light levels, subject to consistent data from larger cohorts, it may be interesting to study the probable epigenetic-mediated protective role of sunshine against photosensitivity.

Experimental verification of consistency of micro-silica glass bead thermoluminescent detectors for mixed gamma/neutron irradiation

The thermoluminescent response of micro-silica glass beads has prompted their use as dosimeters across a variety of incident ionising radiations. This work presents the latest of a campaign to investigate, and confirm, the suitability of glass beads for neutron dosimetry applications. The impressive spatial resolution coupled with the linearity of dose response over a large dynamic range makes their use especially appropriate for applications requiring high levels of sensitivity. Data has been taken within the mixed radiation field of an americium-beryllium (241AmBe) source for two contrasting geometric configurations, investigating the fall-off of counts with respect to distance and the bead-to-bead variability to a uniform radiation dose from a mixed neutron/gamma radiation field. The study also considers the effect of experimental variations due to ambient light levels and the bead mounting itself.The exceptional spatial resolution previously demonstrated allows for observation of fine detail in the plot of dose versus distance from the source. Additionally, fine resolution peaks similar to those observed in previous simulations and data are observed again here. In this work, we can exclude the possibility that these response peaks are related to the source-bead distance.

The Pupillary Response of the Common Octopus (Octopus vulgaris).

Cephalopods have very conspicuous eyes that are often compared to fish eyes. However, in contrast to many fish, the eyes of cephalopods possess mobile pupils. To increase the knowledge of pupillary and thus visual function in cephalopods, the dynamics of the pupil of one of the model species among cephalopods, the common octopus (Octopus vulgaris), was determined in this study. We measured pupillary area as a function of ambient luminance to document the light and dark reaction of the octopus eye. The results show that weak light (<1 cd/m2) is enough to cause a pupil constriction in octopus, and that the pupil reacts fast to changing light conditions. The t50-value defined as the time required for achieving half-maximum constriction ranged from 0.45 to 1.29 s and maximal constriction from 10 to 20% of the fully dilated pupil area, depending on the experimental condition. Axial light had a stronger influence on pupil shape than light from above, which hints at a shadow effect of the horizontal slit pupil. We observed substantial variation of the pupil area under all light conditions indicating that light-independent factors such as arousal or the need to camouflage the eye affect pupil dilation/constriction. In conclusion, the documentation of pupil dynamics provides evidence that the pupil of octopus is adapted to low ambient light levels. Nevertheless it can quickly adapt to and thus function under brighter illumination and in a very inhomogeneous light environment, an ability mediated by the dynamic pupil in combination with previously described additional processes of light/dark adaptation in octopus.

IMPACT OF DAYLIGHT EXPOSURE ON HEALTH, WELL-BEING AND SLEEP OF OFFICE WORKERS BASED ON ACTIGRAPHY, SURVEYS, AND COMPUTER SIMULATION

ABSTRACT The purpose of this study is to examine how daylight exposure affects the health and well-being of office workers. Sleep actigraphy and health and well-being related survey data were the main dependent variables in this study. Research samples were composed of participants from the United States and South Korea, each set of workers divided into those having daylight at their workplaces and those without. Fifty participants in total wore for two weeks actiwatches equipped with light sensors to measure sleep quality and exposure to ambient light levels. Additional health and well-being measurements were taken using well established survey instruments such as the SF-36 for general and mental health, and the Pittsburg Sleep Quality Index (PSQI) for sleep. In order to estimate the levels of daylight participants were exposed to, computer simulation was used to generate the total annual daylight levels in each participant’s office. Our results seem to indicate that working in daylit office spaces would lead to higher sleep quality and higher scores of the health and well-being scales compared to those who do not work under daylight conditions. Our findings indicate that it is important to provide and maintain significant daylight levels at the workplace. Consequently, in terms of architectural design, building orientation, building dimensions, and the size and height of windows should be taken into consideration to optimize or maximize daylight exposure.

Motorcycle safety after-dark: The factors associated with greater risk of road-traffic collisions

The effect of ambient light level on road traffic collisions (RTCs) involving a motorcycle was investigated. Data were drawn from the STATS19 database of UK reported RTCs for the period 2005–2015. To isolate the effect of ambient light (daylight vs darkness) an odds ratio was used to compare RTCs at specific times of day in the weeks either side of the Spring and Autumn clock changes. This work extended previous studies by using a more precise method for distinguishing between RTCs in daylight and after dark, thus avoiding the ambiguity of twilight. Data for four-wheel motor vehicle (FWMV) RTCs were also investigated to provide a datum. As expected, the risk of an RTC occurring was significantly higher after dark compared to daylight for both motorcycles and FWMVs. Investigation of contextual factors suggests that risk after dark is significantly higher for motorcycles compared to FWMVs for RTCs with two-vehicles, on roads with low speed limits (≤30 mph), at T-junctions, and junctions controlled by a give way sign. These are the situations where visual aids for increasing conspicuity after dark have the greater potential for reducing motorcycle RTCs.