Lighting Research Articles

Artificial Light at Night and Type 2 Diabetes Mellitus.

The widespread and pervasive use of artificial light at night (ALAN) in our modern 24-hour society has emerged as a substantial disruptor of natural circadian rhythms, potentially leading to a rise in unhealthy lifestyle-related behaviors (e.g., poor sleep; shift work). This phenomenon has been associated with an increased risk of type 2 diabetes mellitus (T2DM), which is a pressing global public health concern. However, to date, reviews summarizing associations between ALAN and T2DM have primarily focused on the limited characteristics of exposure (e.g., intensity) to ALAN. This literature review extends beyond prior reviews by consolidating recent studies from 2000 to 2024 regarding associations between both indoor and outdoor ALAN exposure and the incidence or prevalence of T2DM. We also described potential biological mechanisms through which ALAN modulates glucose metabolism. Furthermore, we outlined knowledge gaps and investigated how various ALAN characteristics beyond only light intensity (including light type, timing, duration, wavelength, and individual sensitivity) influence T2DM risk. Recognizing the detrimental impact of ALAN on sleep health and the behavioral correlates of physical activity and dietary patterns, we additionally summarized studies investigating the potential mediating role of each component in the relationship between ALAN and glucose metabolism. Lastly, we proposed implications of chronotherapies and chrononutrition for diabetes management in the context of ALAN exposure.

Recycle, repair and reuse in Roman Napoca

The archaeological rescue excavations carried out between 1992 and 2001 and again in 2012 in Roman Napoca (Cluj-Napoca, Romania), on the site from Victor Deleu Street revealed important information regarding the life of the ancient town and its residential areas. One of the most interesting discoveries is represented by an assemblage of twelve metal objects: a statue, a statuette, three fragmentary metal vessels, four pieces belonging to lighting equipment (candlesticks and a lamp base), a pair of scissors fragmentarily preserved and two decorated bronze plates. They were identified on the floor of an annex belonging to a private residence, in a context which can be dated during the fourth–fifth decades of the 3rd century AD. The paper is a preliminary analysis of the assemblage. The objects are all high-quality imports and most of them present traces of repair or were recomposed from different parts coming from other objects. They attest the existence of a ‘antiquarian-restorer’ in Roman Napoca and reveal a clear concern for selecting, collecting, recycling, repairing and refunctioning good quality objects.

Anthropogenic noise and light pollution decrease the repeatability of activity patterns and dampen expression of chronotypes in a free-living songbird

Anthropogenic environmental change is introducing a suite of novel disturbance factors, which can have wide-ranging effects on mean behavior and behavioral repeatability. For example, exposure to sensory pollutants, such as anthropogenic noise and artificial light at night (ALAN), may affect consistent and repeatable individual-level timing of daily activity, which is referred to as chronotypes. Although chronotypes have been increasingly documented in wild animal populations and may affect fitness, evidence for long-term stability across life-history stages and seasons is notably lacking. Furthermore, how multiple anthropogenic stressors may interact to erode or magnify the expression of chronotypes remains unclear. We tested for existence of chronotypes across life-history stages and seasons in suburban female great tits (Parus major), using emergence time from nest boxes in the morning as a proxy for activity onset. We then examined joint effects of noise pollution and ALAN on expression of chronotypes, and tested for effects of noise, ALAN, and weather conditions on mean emergence time. We found repeatability of daily activity patterns (emergence times) across life-history stages and seasons, providing evidence of chronotypes, as well as interactive effects of anthropogenic disturbance factors and weather conditions on population mean behavior. Furthermore, across-season repeatability of emergence times was approximately double in magnitude in low light and low noise conditions, relative to in conditions with higher light and/or noise pollution. Thus, joint exposure to these sensory pollutants tends to erode expression of chronotypes. This effect was driven by higher among-individual variance in the relatively undisturbed environment and collapse of this variance in the more disturbed environments. Decreased repeatability in environments with high disturbance levels may reduce potential for behavioral traits, such as chronotype, to be the target of selection and limit adaptability.

Harvesting the tuning mechanism of strategic polychrome and white light emission in NapH dye based on excited state intermolecular proton transfer

Organic white light emitting (WLE) materials have sparked a research boom due to their promising applications in display devices, artificial lighting, and molecular sensors. However, the complex luminescence mechanism of full-spectra emitting materials has limited the development of white light materials with high stability and reproducibility. In this study, building on the full-spectra luminescent naphthimide dye (NapH) introduced by Xu et al., (Chin. Chem. Lett. 35(2024), 108348), we report the solvent-sensitive excited state proton transfer (ESPT) properties and white light emission mechanism in NapH. Our theoretical research results show that the ESPT process of NapH molecule is hindered in the low-polar solvent tetrahydrofuran (THF), so only the blue fluorescence from the Enol* is observed in the experiment. In contrast, in polar solvents such as water (H2O) and methanol (MeOH), the formation of strong intermolecular hydrogen bonds successfully initiates the ESPT process, leading to the dual fluorescence observed in experiments, with blue emission from the Enol* and red emission from the Nap anion. In essence, different solvent environments can adjust several emission colors. Furthermore, we theoretically verify that the optimal white light emission can be achieved when the mixed solvent ratio of dimethyl sulfoxide (DMSO) and dioxane (DIOX) is 5:5, which aligns well with experimental results. More importantly, we elucidate the specific WLE mechanism from multiple perspectives, including potential energy curves and electron spectra. Our work not only displays the interaction models of NapH molecule in various solvents, but also reveals the underlying luminescence mechanism, thus providing a valuable theoretical reference for the development and advancement of new white light materials.

Efficient Daylighting: The Importance of Glazing Transmittance and Room Surface Reflectance

This study quantitatively analyzes the influence of the spectral characteristics, reflectance or transmittance, of different materials on the lighting of an interior space with natural and artificial light. For this purpose, a three-dimensional simulated classroom is used, where each of the components is assigned specific materials with an associated reflectance or transmittance. Additionally, two types of lighting are available: 6500 K daylight and light from six continuous spectrum LED luminaires. The lighting is evaluated on two planes: the work plane and the corneal plane (80 cm and 120 cm from the floor, respectively). Three versions of the same classroom were analyzed by varying the walls (white, blue, and red), each with a different neutral-colored floor. Furthermore, calculations were performed in each situation considering two different types of glazing in the windows, with 20% and 88% transmittance. The photopic and melanopic lighting analysis was carried out with the ALFA calculation program to verify the necessary requirements for adequate lighting. The results show that the white classroom is the best lit, followed by the blue and finally the red, due to the reflectance characteristics of the walls and floor although slight differences among them are found. It was found that in some cases, additional auxiliary luminaires would be required for proper lighting depending on the transmittance of the glazing. This study highlights the critical role of material selection in optimizing both photopic and melanopic lighting, with practical implications for energy efficiency and occupant well-being in educational spaces.

Dim light at night unmasks sex-specific differences in circadian and autonomic regulation of cardiovascular physiology

Shift work and artificial light at night disrupt the entrainment of endogenous circadian rhythms in physiology and behavior to the day-night cycle. We hypothesized that exposure to dim light at night (dLAN) disrupts feeding rhythms, leading to sex-specific changes in autonomic signaling and day-night heart rate and blood pressure rhythms. Compared to mice housed in 12-hour light/12-hour dark cycles, mice exposed to dLAN showed reduced amplitudes in day-night feeding, heart rate, and blood pressure rhythms. In female mice, dLAN reduced the amplitude of day-night cardiovascular rhythms by decreasing the relative sympathetic regulation at night, while in male mice, it did so by increasing the relative sympathetic regulation during the daytime. Time-restricted feeding to the dim light cycle reversed these autonomic changes in both sexes. We conclude that dLAN induces sex-specific changes in autonomic regulation of heart rate and blood pressure, and time-restricted feeding may represent a chronotherapeutic strategy to mitigate the cardiovascular impact of light at night.

American Robin (Turdus migratorius) feeding young at night in an area of artificial light

American Robin (Turdus migratorius) feeding young at night in an area of artificial light

Maintaining KEAP1 levels in retinal pigment epithelial cells preserves their viability during prolonged exposure to artificial blue light

Exposure to artificial blue light, one of the most energetic forms of visible light, can increase oxidative stress in retinal cells, potentially enhancing the risk of macular degeneration. Retinal pigment epithelial (RPE) cells play a crucial role in this process; the loss of RPE cells is the primary pathway through which retinal degeneration occurs. In RPE cells, Kelch-like ECH-associated protein 1 (KEAP1) is located in both the nucleus and cytosol, where it binds to nuclear factor erythroid 2-related factor 2 (NRF2) and p62 (sequestosome-1), respectively. Blue light exposure activates the NRF2-heme oxygenase 1 (HMOX1) axis through both canonical and noncanonical p62 pathways thereby reducing oxidative damage, and initiates autophagy, which helps remove damaged proteins. These protective responses may support the survival of RPE cells. However, extended exposure to blue light drastically decreases the viability of RPE cells. This exposure diminishes the ability of KEAP1 to bind to p62 and reduces the level of KEAP1. Inhibition of autophagy does not prevent KEAP1 degradation, the NRF2-HMOX1 axis, or blue-light-induced cytotoxicity. However, proteasome inhibitor along with a transient increase in the amount of KEAP1 in RPE cells, partially restores the p62-KEAP1 complex and reduces blue-light-induced cytotoxicity. In vivo studies confirmed the downregulation of KEAP1 in damaged RPE cells. Mice subjected to periodic blue light exposure exhibited significant atrophy in the outer retina, particularly in the peripheral areas. Additionally, there was a significant decrease in c-wave electroretinography and pupillary light reflex, indicating functional impairments in both visual and nonvisual physiological processes. These data underscore the essential role of KEAP1 in managing oxidative defense and autophagy pathways triggered by blue light exposure in RPE cells.

Vertical Farming: A Promising Solution to Urban Agriculture

Urban agriculture refers to the agricultural activities such as plant production for home consumption and income generation in the urban areas especially cities. The concept of urban agriculture has been popularizing but in today’s century it is also facing certain problems such as limited land resources, population increase etc. Vertical farming is a type of urban agriculture, through which we could seek solutions to the problems that urban agriculture has been facing in the recent times. Vertical farming refers to the growing of crops in vertically stacked structures especially under controlled environmental conditions and using a suitable growing medium to increase the crop production per square metre by utilizing the vertical space for cultivation [1]. A wide range of crops can be cultivated in vertical farming with the use of techniques such as hydroponics, aeroponics, aquaponics, artificial lighting, inside the controlled environment of a greenhouse. Vertical farming is needed to provide solution to the problems of urban agriculture in terms of providing food security to the growing population, efficient land utilization, water conservation, increased crop production etc. However, vertical farming has certain disadvantages as well such as high initial investment cost, high energy cost and high maintenance cost. Therefore, further research and development strategies are necessary to overcome such disadvantages for increasing its effectiveness to meet the food demands of the growing population as well as the future generation in a sustainable manner.

Computational fluid dynamics (CFD) simulation modeling for the cultivation of microalgal monoculture in axenic enclosed bubble column photobioreactor (BCPBR)

Researchers are more concerned with axenic-enclosed PBRs, where there is less or no chance of contamination during the production of biochemical and highly valuable metabolites, and monocultures of microalgae are being grown more frequently. It is a closed, manufactured vessel that aids in the photosynthesis of microalgal cells using artificial light or sunlight as the energy source. In this study, the bubble column PBR (BCPBR) was selected because it possessed some advantages over other PBRs for the growth of Chlorella vulgaris. The BCPBR system prevents contact between the enclosed microalgal cells and the environment, allowing the culturing of microalgae species that are difficult to grow in open pond systems. To compare BCPBR performance quantitatively, the efficient mixing expected in BCPBR, as discussed in the literature, was applied to the CFD model. The experimental results observed during the cultivation of C. vulgaris with restaurant wastewater (RWW) in BCPBR clearly showed better mixing, high growth, and improved treatment efficiency. CFD analysis was conducted on the evolution of bubbles in the BCPBR. The Pressure-Implicit with Splitting of Operators (PISO) pressure correction method is used for velocity and pressure coupling. A geo-reconstruct approach is used to construct the interface, and a second-order upwind calculation technique is used to determine the flow parameters. Therefore, CFD simulation in this study will contribute to the following aspects: (i) the volume fraction contours and velocity contours are going to validate the experimental study as the homogenous mixing favors the growth and productivity, (ii) To study how the size of the nozzle and inlet velocity affect the turbulence generated by bubbles in a BCPBR to identify the optimal nozzle size and velocity for the required turbulence.

Analysis and Evaluation of Artificial Lighting in the Passenger Spaces of a 500 Gt Ro-Ro Ferry

Lighting is an important design criterion for ships, including the ro-ro ferry. The ship’s lighting system must meet certain standards. Therefore, the present study analysed and evaluated the artificial lighting of an Indonesian ro-ro ferry. The analysed ship in the present research was a 500 GT ro-ro ferry named KMP. Takabonerate that operated across the Selayar Islands of Indonesia. The artificial lighting systems in this ship’s three passenger spaces, which are reclining seat room, sofa seat room, and passenger open space, were evaluated and analysed. The main parameter to be investigated was the room illuminance produced by the ship’s lighting system. In order to achieve the study objective, the illuminance in those rooms was calculated using analytical formulas. The calculation results were validated using direct measurements and computer simulation. The direct measurements were conducted using a luxmeter, while computer simulations were performed using DIAlux Evo 10.0 software. With this software, the artificial lighting in the passenger spaces was also simulated and realistically visualized. The research results showed that the illuminance in the reclining seat room and the sofa seat room had met the minimum illuminance value set by the Indonesian National Standard (SNI), American Bureau of Shipping (ABS), and Indonesian Classification Bureau (BKI) standards. For the passenger open space, a re-arrangement of the lighting system was conducted to improve the light distribution so that all space illumination can meet the specified standards.

Optimal Light Intensity for Lettuce Growth, Quality, and Photosynthesis in Plant Factories.

In agriculture, one of the most crucial elements for sustained plant production is light. Artificial lighting can meet the specific light requirements of various plants. However, it is a challenge to find optimal lighting schemes that can facilitate a balance of plant growth and nutritional qualities. In this study, we experimented with the light intensity required for plant growth and nutrient elements. We designed three light intensity treatments, 180 μmol m-2 s-1 (L1), 210 μmol m-2 s-1 (L2), and 240 μmol m-2 s-1 (L3), to investigate the effect of light intensity on lettuce growth and quality. It can be clearly seen from the radar charts that L2 significantly affected the plant height, fresh weight, dry weight, and leaf area. L3 mainly affected the canopy diameter and root shoot ratio. The effect of L1 on lettuce phenotype was not significant compared with that of the others. The total soluble sugar, vitamin C, nitrate, and free amino acid in lettuce showed more significant increases under the L2 treatment than under the other treatments. In addition, the transpiration rate and stomatal conductance were opposite to each other. The comprehensive evaluation of the membership function value method and heatmap analysis showed that lettuce had the highest membership function value in L2 light intensity conditions, indicating that the lettuce grown under this light intensity could obtain higher yield and better quality. This study provides a new insight into finding the best environmental factors to balance plant nutrition and growth.

Optimization of the Design of a Greenhouse LED Luminaire with Immersion Cooling

Modern agriculture, with the use of artificial lighting, requires high-intensity LED luminaires with compact dimensions. In this regard, new approaches to the design of LED luminaires using both new materials and technical solutions have been considered. The theoretical evaluation of the influence of different materials on the efficiency of removal of thermal energy from LEDs was shown. A new material PMS-5 is proposed and evaluated as an immersion liquid, which can be used as an effective heat sink in the lower part of the luminaire up to the level of LEDs located in the top light LED luminaires. The proposed polymethylsiloxane PMS-5 liquid has more than twice the thermal conductivity (0.167 W/(m·K)) of HFE7200 and NS15 liquids used in immersion-cooled LED luminaires. Based on the theoretical evaluation, the requirements for parameters, such as metal profile area, immersion liquid volume, wall thickness area, and external area of the cylinder, are highlighted and shown. The noted parameters have a key role in the design of an efficient top light LED luminaire. It has been shown that the design of the metal profile significantly affects the efficiency of the removal of thermal energy from LEDs and it is necessary to use specialized profiles optimized for the diameter of the LED luminaire cylinder. A number of LED luminaire designs were proposed, depending on the thermal properties of the construction materials, technical and economic performance, as well as actual operating and installation conditions. The analysis of the presented theoretical evaluations allowed overlay of the design basis of LED luminaires within the presented concept and top light.

Nobiletin, an activator of the pyruvate kinase isozyme M1/M2 protein, upregulated the glycolytic signalling pathway and alleviated depressive-like behaviour caused by artificial light exposure at night in zebrafish

We established a zebrafish model of depression-like behaviour induced by exposure to artificial light at night (ALAN) and found that nobiletin (NOB) alleviated depression-like behaviour. Subsequently, based on the results of a 24-h free movement assay, clock gene expression and brain tissue transcriptome sequencing, the glycolysis signalling pathway was identified as a potential target through which NOB exerted antidepressant effects. Using the ALAN zebrafish model, we found that supplementation with exogenous L-lactic acid alleviated depressive-like behaviour. Molecular docking and molecular dynamics simulations revealed an inter-molecular interaction between NOB and the pyruvate kinase isozyme M1/M2 (PKM2) protein. We then used compound 3 k to construct a zebrafish model in which PKM2 was inhibited. Our analysis of this model suggested that NOB alleviated depression-like behaviour via inhibition of PKM2. In summary, NOB alleviated depressive-like behaviour induced by ALAN in zebrafish via targeting of PKM2 and activation of the glycolytic signalling pathway.

The use of UV-A radiation for biofortification of lettuce and basil plants with antioxidant phenolic and flavonoid compounds

Stable plant production is a crucial concern of modern agriculture facing increasing food demands and the risk of less predictable weather conditions in the open field. Alternative approaches for plant production are greenhouses and indoor farming. Modern LED-based artificial lighting indoor facilities allow not only to fill the gap in the supply chain of food production, but to produce plants characterized with higher concentration of essential phytochemicals. Thus, in this study, we attempt to analyse the efficiency of short-term supplementation of spectrum within ultraviolet A light (UV-A, 365 nm) to increase the antioxidant potential of leafy plants, assessed by total phenolic (TPC) and flavonoid (TFC) content. To this end, two distinct cultivars of baby leaf lettuce (Lactuca sativa var. crispa L.) and microgreens basil (Ocimum basilicum L.) plants were grown under red-green-blue spectrum supplemented prior to harvest with low doses of UV-A radiation. Analyses showed that UV-A exposition enhanced TPC and TFC with green leaf cultivars, compared to dark-pigmented ones. The analysis also proved that plants exposed to UV-A presented higher overall antioxidant potential measured with 1,1-diphenyl-2-picrylhydrazil (DPPH). Results are crucial for better understanding the potential of UV-A supplementation to produce functional plants which are natural sources of dietary antioxidants.

An ultraviolet light data logger for studies of organismal ecology and physiology

Abstract Monitoring environmental conditions over time is essential for understanding how species regulate those conditions to satisfy their physiological needs. Variation in ultraviolet (UV) light exposure, for instance, is crucial for numerous taxa, influencing behaviour as well as essential physiological processes like vitamin D3 synthesis. Yet, despite these considerations, no commercially available data loggers exist to record UV exposures over time, preventing inquiry into this important but neglected fitness demand. To overcome this challenge, I designed the first UV data logger, custom built on the open‐source Arduino platform. This device logs UV exposures (in voltage or converted to UV index) and date‐time information for each UV reading, at user‐defined intervals. The integration of a low‐power timer into the assembly, and its weather‐resistant housing, enables long‐term use (at least several months). The cost of one device (including housing) is under £45/$55 USD. Calibration and performance tests reveal that this device is reliable under various weather conditions and produces accurate UV readings under both artificial lighting and sunlight. Both the device and its customised housing can be easily replicated and expanded upon (e.g. inclusion of additional sensors). Overall, this device represents a crucial first step in our ability to better characterise UV exposure patterns in habitats for physiological ecology studies. Exposure to UV light is adaptive for many types of organisms, both in the wild and in captivity (e.g. zoos and private hobbyists), and so I expect a broad array of scientific and public users alike to benefit from using this device.

Different types of greenspace within urban parks and depressive symptoms among older U.S. adults living in urban areas

Access to greenspace in the form of urban parks is frequently used to study the mental health benefits of nature and may alleviate depression. However, there is a lack of research that considers the different types of vegetated and non-vegetated spaces that parks can provide. Our aim was to investigate whether different types of accessible park area, grassy; tree covered; and non-vegetated, were associated with depressive symptoms among older (≥50 years) urban US adults. We used interviews from the Health and Retirement Study spanning 2010 through 2016 as our primary data source. We calculated total grassy, tree covered, and non-vegetated park space accessible to participants using a comprehensive national database of US parks and a high resolution (10 m) landcover dataset. To measure depressive symptoms, we used the CESD-8 analyzed as a continuous scale. We used Poisson regression to estimate the percent difference in CESD-8 scores comparing quartiles of accessible park space. To control for confounding, we adjusted for sociodemographic characteristics, geography, and climate. Aggregated accessible park area was not substantively associated with depressive symptoms. However, having grassy park area near the home was associated with as much as 27 % fewer depressive symptoms. In contrast, non-vegetated park area was associated with up to 54 % more depressive symptoms. Our findings were robust to adjustment for air pollution, environmental noise, and artificial light at night. Different types of accessible park space may have disparate effects on mental health among older urban US adults.

Retraction Note: Design of fine motion control system for aerobics athletes based on light imaging equipment detection and image processing technology

Retraction Note: Design of fine motion control system for aerobics athletes based on light imaging equipment detection and image processing technology

Adipocyte sphingosine kinase 1 regulates histone modifiers to disrupt circadian function.

Circadian rhythms align biological functions with the 24-hour day-night cycle, but modern artificial light disrupts these patterns, contributing to health issues like obesity and cardiovascular disease. The circadian clock operates through a transcriptional-translational feedback loop involving core components such as BMAL1 and CLOCK. Recent research has shown circadian variations in sphingolipid metabolism, specifically sphingosine-1-phosphate (S1P), which plays crucial signaling roles. This study investigates the sphingolipid enzyme, sphingosine kinase 1 (SphK1), which converts sphingosine to S1P, as a circadian-regulated gene in adipocytes. We find that SphK1 expression and activity follow a circadian rhythm, regulated by BMAL1 and CLOCK binding to its promoter. Adipocyte-specific SphK1 knockout mice exhibit disrupted circadian rhythms, and impaired adipocyte function. Additionally, SphK1 deficiency leads to reduced histone acetylation and altered histone deacetylase (HDAC) localization, affecting gene regulation. These results highlight the critical role of SphK1 in linking lipid metabolism with circadian biology.

Light pollution: time to consider testicular effects.

Technological advances have led to a modern-day lighting and smartphone revolution, with artificial light exposure at night increasing to levels never before seen in the evolutionary history of living systems on Earth. Light as a pollutant, however, remains largely unrecognized, and the reproductive effects of light pollution are mostly if not entirely unconsidered. This is despite the reproductive system being intricately linked to metabolism and the circadian system, both of which can be disturbed even by low levels of light. Here, we aim to change this perspective by reviewing the physiological and pathophysiological mechanisms by which light exposure alters the intricate hormonal, metabolic and reproductive networks that are relevant to reproductive toxicology. Nascent human studies have recently identified the photoreceptors responsible for the light dose relationship with melatonin suppression and circadian re-entrainment, directly shown the association between the alignment of light-dark cycles with activity-rest cycles on metabolic health and provided proof-of-principle that properly timed blue light-enriched and blue light-depleted delivery can accelerate circadian re-entrainment. With these advances, there is now a need to consider testicular effects of light pollution.