Design, Development and Application of a Modular Electromagnetic Induction (EMI) Sensor for Near-Surface Geophysical Surveys

Low-frequency electromagnetic induction (EMI) is a non-invasive geophysical method that is based on the induction of electromagnetic (EM) waves into the subsurface to quantify changes in electrical conductivity. In this study, we present an open (design details and software are accessible) and modular system for the collection of EMI data. The instrument proposed allows for the separations between the transmitter to be adjusted and up to four receiving antennas as well as the acquisition frequency (in the range between 3 and 50 kHz) to permit measurements with variable depth of investigation. The sensor provides access to raw data and the software described in this study allows control of the signal processing chain. The design specifications permit apparent conductivity measurements in the range of between 1 mS/m and 1000 mS/m, with a resolution of 1.0 mS/m and with a sampling rate of up to 10 samples per second. The sensor allows for a synchronous acquisition of a time stamp and a location stamp for each data sample. The sensor has a mass of less than 5 kg, is portable and suitable for one-person operation, provides 4 h of operation time on one battery charge, and provides sufficient rigidity for practical field operations

Shedding Some Light in the Dark : A Comparison of Personal Measurements with Satellite-Based Estimates of Exposure to Light at Night among Children in the Netherlands

BACKGROUND: Exposure to light at night (LAN) can perturb the biological clock and affect sleep and health. Previous epidemiological studies have evaluated LAN levels measured by satellites, but the validity of this measure as a proxy for personal LAN exposure is unclear. In addition, outdoor satellite-measured LAN levels are higher in urban environments, which means that this measure could potentially represent a proxy for other, likely urban, environmental exposures. OBJECTIVES: We evaluated correlations of satellite-assessed LAN with measured bedroom light levels and explored correlations with other environmental exposures, in particular, air pollution, green space, and area-level socioeconomic position (SEP). METHODS: We compared satellite measurements with evening and nighttime bedroom measurements of illuminance (in units of lux) for 256 children, and we evaluated correlations between satellite-based measures and other urban exposures such as air pollution, area-level SEP, and surrounding green space for 3,021 children. RESULTS: Satellite-measured LAN levels (nanowatts per centimeter squared per steradian) were not correlated with measured evening or nighttime lux levels [Spearman correlation coefficients ([Formula: see text]) [Formula: see text] to 0.04]. There was a weak correlation with measurements during the darkest time period if parents and their children reported that outdoor light sometimes or usually influenced indoor light levels ([Formula: see text], [Formula: see text]). In contrast, satellite-measured LAN levels were correlated with air pollution ([Formula: see text] with [Formula: see text], [Formula: see text] with [Formula: see text]), and surrounding green space ([Formula: see text] for green space within [Formula: see text] of the home). A weak correlation with area-level SEP was also observed ([Formula: see text]). CONCLUSIONS: Outdoor satellite-assessed outdoor LAN exposure levels were correlated with urban environmental exposures, but they were not a good proxy for indoor evening or nighttime personal exposure as measured in our study population of 12-y-old children. Studies planning to evaluate potential risks from LAN should consider such modifying factors as curtains and indoor lighting and the use of electronic devices and should include performing indoor or personal measurements to validate any exposure proxies. The moderate-to-strong correlation of outdoor LAN with other environmental exposures should be accounted for in epidemiological investigations. https://doi.org/10.1289/EHP3431

Shedding Some Light in the Dark-A Comparison of Personal Measurements with Satellite-Based Estimates of Exposure to Light at Night among Children in the Netherlands

BACKGROUND: Exposure to light at night (LAN) can perturb the biological clock and affect sleep and health. Previous epidemiological studies have evaluated LAN levels measured by satellites, but the validity of this measure as a proxy for personal LAN exposure is unclear. In addition, outdoor satellite-measured LAN levels are higher in urban environments, which means that this measure could potentially represent a proxy for other, likely urban, environmental exposures. OBJECTIVES: We evaluated correlations of satellite-assessed LAN with measured bedroom light levels and explored correlations with other environmental exposures, in particular, air pollution, green space, and area-level socioeconomic position (SEP). METHODS: We compared satellite measurements with evening and nighttime bedroom measurements of illuminance (in units of lux) for 256 children, and we evaluated correlations between satellite-based measures and other urban exposures such as air pollution, area-level SEP, and surrounding green space for 3,021 children. RESULTS: Satellite-measured LAN levels (nanowatts per centimeter squared per steradian) were not correlated with measured evening or nighttime lux levels [Spearman correlation coefficients ([Formula: see text]) [Formula: see text] to 0.04]. There was a weak correlation with measurements during the darkest time period if parents and their children reported that outdoor light sometimes or usually influenced indoor light levels ([Formula: see text], [Formula: see text]). In contrast, satellite-measured LAN levels were correlated with air pollution ([Formula: see text] with [Formula: see text], [Formula: see text] with [Formula: see text]), and surrounding green space ([Formula: see text] for green space within [Formula: see text] of the home). A weak correlation with area-level SEP was also observed ([Formula: see text]). CONCLUSIONS: Outdoor satellite-assessed outdoor LAN exposure levels were correlated with urban environmental exposures, but they were not a good proxy for indoor evening or nighttime personal exposure as measured in our study population of 12-y-old children. Studies planning to evaluate potential risks from LAN should consider such modifying factors as curtains and indoor lighting and the use of electronic devices and should include performing indoor or personal measurements to validate any exposure proxies. The moderate-to-strong correlation of outdoor LAN with other environmental exposures should be accounted for in epidemiological investigations. https://doi.org/10.1289/EHP3431

Chronic Artificial Blue-Enriched White Light Is an Effective Countermeasure to Delayed Circadian Phase and Neurobehavioral Decrements

<div><p>Studies in Polar Base stations, where personnel have no access to sunlight during winter, have reported circadian misalignment, free-running of the sleep-wake rhythm, and sleep problems. Here we tested light as a countermeasure to circadian misalignment in personnel of the Concordia Polar Base station during the polar winter. We hypothesized that entrainment of the circadian pacemaker to a 24-h light-dark schedule would not occur in all crew members (n = 10) exposed to 100–300 lux of standard fluorescent white (SW) light during the daytime, and that chronic non-time restricted daytime exposure to melanopsin-optimized blue-enriched white (BE) light would establish an a stable circadian phase, in participants, together with increased cognitive performance and mood levels. The lighting schedule consisted of an alternation between SW lighting (2 weeks), followed by a BE lighting (2 weeks) for a total of 9 weeks. Rest-activity cycles assessed by actigraphy showed a stable rest-activity pattern under both SW and BE light. No difference was found between light conditions on the intra-daily stability, variability and amplitude of activity, as assessed by non-parametric circadian analysis. As hypothesized, a significant delay of about 30 minutes in the onset of melatonin secretion occurred with SW, but not with BE light. BE light significantly enhanced well being and alertness compared to SW light. We propose that the superior efficacy of blue-enriched white light versus standard white light involves melanopsin-based mechanisms in the activation of the non-visual functions studied, and that their responses do not dampen with time (over 9-weeks). This work could lead to practical applications of light exposure in working environment where background light intensity is chronically low to moderate (polar base stations, power plants, space missions, etc.), and may help design lighting strategies to maintain health, productivity, and personnel safety.</p></div

Circadian and neurobehavioral changes under SW and BE light condition over 9 weeks.

<p>Results were normalized to baseline SW1. <b>A</b>. Circadian phase was assessed using salivary DLMO. A delay in circadian phase of −0.64±0.21 h and −0.45±0.34 h was observed during weeks W5 and W9 respectively under SW light (p<0.05). The circadian phase delay observed on week W5 appears to be corrected during BE light on week BE7, and is observed again on week SW9 under SW light. <b>B</b>. Well being was increased by BE light (+9.7±12.8% and +14.5±14.9% on BE3 and BE7 respectively) compared to SW light (−2.9±12.8% and +3.2±11.2% during SW5 and SW9 respectively) (p<0.05). <b>C</b>. Subjective alertness was marginally increased on weeks BE3 and BE7 under BE light (p = 0.08) compared to SW light weeks SW5 and SW9.</p

Summary of sleep and phase shift results.

<p>Values are averages±SEM.</p>#<p>Statistics computed using the Wilcoxon matched pairs test.</p><p>*Phase angle  =  Sleep onset time - DLMO time.</p><p>All times are given in hh:mm.</p><p>In coherence with a significantly later circadian phase, lights off time, bed time were significantly delayed under SW light weeks in comparison to BE light weeks. On the other hand wake up time was not significantly different between lighting conditions, this leading to a significant decrease in sleep duration under SW light weeks. Sleep efficiency was not different between lighting conditions. Phase angle between DLMO and lights off was not different between lighting conditions.</p

Representative raster plot of continuous actigraphy over 9 weeks, and circadian phase.

<p>Subject (S7) had a relatively regular sleep wake cycle across the studyCircadian phase, assessed by DLMO (<b>*</b>), shows a phase delay under SW light condition (SW 8–9), but not under BE light condition (BE 6–7), compared to W1.</p

Characteristics of the lighting environments.

<p><b>A</b>. Spectra of ambient lightings used in the study. In a black straight line the spectrum of the control SW light used in weeks 1, 4, 5, 8 and 9 of the study. In a blue straight line the spectrum of the BE light used in weeks 2, 3, 6, and 7 of the study. <b>B</b>. Intensity (irradiance) and spectral composition of the lighting environments as measured in different locations of the Polar Station. BE light contained significantly more energy in the blue (p<0.001) and green (p<0.01) range of the light spectrum, and less red (p<0.001) compared to SW light. <b>C</b>. Intensity (irradiance) and spectral composition of the lighting environments as measured by the Lightwatcher device worn by the participants. The light spectra measured by the polar station workers under BE light contained significantly more short wavelength blue light (p<0.001) and less long wavelength red light (p<0.05) compared to SW light. Intensity of middle wavelength green light and IR light detected by the participants were not significantly different. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102827#pone.0102827.s011" target="_blank">Table S1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102827#pone.0102827.s002" target="_blank">Figures S2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102827#pone.0102827.s003" target="_blank">S3</a> for more details.</p

Impact of BE versus SW light on each participant's phase shift, subjective well being and alertness.

<p>Results were normalized to week SW1. Circadian phase advances (positive phase shifts) and delays (negative phase shifts) and increases and decreases in well being and alertness were averaged over the weeks of the same light condition (SW versus BE). <b>A</b>. On average DLMOs were significantly delayed during SW light weeks compared to BE light weeks (p<0.05). Average subjective well being (<b>B</b>) and alertness (<b>C</b>) were significantly increased under BE light weeks compared to SW light weeks (p<0.05).</p

Shedding Some Light in the Dark: A Comparison of Personal Measurements with Satellite-Based Estimates of Exposure to Light at Night among Children in the Netherlands

BACKGROUND: Exposure to light at night (LAN) can perturb the biological clock and affect sleep and health. Previous epidemiological studies have evaluated LAN levels measured by satellites, but the validity of this measure as a proxy for personal LAN exposure is unclear. In addition, outdoor satellite-measured LAN levels are higher in urban environments, which means that this measure could potentially represent a proxy for other, likely urban, environmental exposures. OBJECTIVES: We evaluated correlations of satellite-assessed LAN with measured bedroom light levels and explored correlations with other environmental exposures, in particular, air pollution, green space, and area-level socioeconomic position (SEP). METHODS: We compared satellite measurements with evening and nighttime bedroom measurements of illuminance (in units of lux) for 256 children, and we evaluated correlations between satellite-based measures and other urban exposures such as air pollution, area-level SEP, and surrounding green space for 3,021 children. RESULTS: Satellite-measured LAN levels (nanowatts per centimeter squared per steradian) were not correlated with measured evening or nighttime lux levels [Spearman correlation coefficients ([Formula: see text]) [Formula: see text] to 0.04]. There was a weak correlation with measurements during the darkest time period if parents and their children reported that outdoor light sometimes or usually influenced indoor light levels ([Formula: see text], [Formula: see text]). In contrast, satellite-measured LAN levels were correlated with air pollution ([Formula: see text] with [Formula: see text], [Formula: see text] with [Formula: see text]), and surrounding green space ([Formula: see text] for green space within [Formula: see text] of the home). A weak correlation with area-level SEP was also observed ([Formula: see text]). CONCLUSIONS: Outdoor satellite-assessed outdoor LAN exposure levels were correlated with urban environmental exposures, but they were not a good proxy for indoor evening or nighttime personal exposure as measured in our study population of 12-y-old children. Studies planning to evaluate potential risks from LAN should consider such modifying factors as curtains and indoor lighting and the use of electronic devices and should include performing indoor or personal measurements to validate any exposure proxies. The moderate-to-strong correlation of outdoor LAN with other environmental exposures should be accounted for in epidemiological investigations. https://doi.org/10.1289/EHP3431