Artificial Illumination Research Articles

Underwater image enhancement by combining color constancy and dehazing based on depth estimation

The physical properties which are present in the underwater environment affects the images captured by the visual sensors. As a consequence of these properties, the captured image includes non-uniform illumination. This non-uniform illumination cause color distortion, low contrast, white regions, and color casts. An underwater image enhancement method is proposed by combining a color constancy framework and dehazing. In the color constancy framework, both the white patch retinex and gamma correction are used to illuminate a non-hardware based balanced artificial illumination in the reference image. A chromatic adaptation technique (CAT) is adapted to correct the color cast caused by the non-uniform illumination. The color transferred image is then transformed into HSI with gamma correction in the Intensity (I)-component. This gamma correction enhances the intensity of the color transferred image. The gamma-corrected HSI image is converted to an RGB image. The dehazing is based on the estimation of artificial background light and transmission map depth. The depth is estimated from the difference of channel intensity prior (DCIP), which is the difference between the maximum and minimum intensity priors. Further, normalization of the DCIP with the histogram stretching enhances the contrast of the estimated depth. A saturation correction factor is proposed for color correction. This correction factor, estimates the artificial background light, and solves the non-uniform illumination limitations in the turbid image. A guided and rolling guidance filter is adapted to refine the estimated transmission map depth. Finally, the recovered image is transformed into HSI image with gamma correction on the I-component. The gamma-corrected HSI image is transformed to an RGB image. The recovered RGB image results with enhanced contrast and brightness. The proposed method enhances the contrast, preserves the visual information such as texture smoothing, edge-preserving, no halo effect, and decreases artifacts. We experimented the proposed method with that of the existing methods and observed that the proposed method resulted in a substantially improved image quality for the human visual perception.

Africa's protected areas are brightening at night: A long-term light pollution monitor based on nighttime light imagery

As the cornerstone of biodiversity conservation, the core value of protected areas (PAs) is to maintain an area’s natural conditions (both day and night) and to restrict human-caused disturbances to biology and the environment. Although the value of PAs has been universally recognized, light pollution within them is worsening as a result of the widespread use of artificial illumination devices. Previous studies have focused on light pollution in PAs and evaluated light radiation using nighttime light imagery. However, given the scale and span of these studies (national scale and over short periods), PA light pollution research should be advanced further. In this paper, we conducted long-term (1992–2018) monitoring and evaluation of light pollution in African PAs using aligned multi-sensor NTL data. The results showed that 1) Africa PAs were impacted by increasingly severe artificial lights during 1992–2018, with all three light indices showing an accelerating increasing trend. 2) The number of light-polluted PAs also rapidly increased, with more than 80% of PAs experiencing aggravated light pollution as of 2018. Different types of PAs had heterogeneous light pollution, which penetrates indiscriminately into all PA regulation levels. 4) Light pollution in African PAs was divided into three types, including outside invasion, internal sources, and mixed pollution. 5) Human activity intensity surrounding the PAs was highly correlated with light pollution within them, with a maximum effect distance of approximately 245 km. This paper provides new approaches for understanding the patterns of light pollution within PAs, and is a valuable reference for future PA planning.

A Theoretical Framework for Informal 3D Rendered Analysis of the RomanLarariumfrom Apollonia-Arsuf

AbstractDigital reconstruction and visualization of archaeological sites are beneficial not only for public edification and admiration, but they can also significantly contribute to the site interpretation process. By going beyond basic modeling scenarios, one can apply 3D analyses for accurately testing visibility and lighting parameters, among other aspects. Based on the results of these tests, further insights can be extrapolated about the lived experience of culturally specific ancient peoples. The case of a Roman “villa” at Apollonia-Arsuf in Israel presents the opportunity to apply these informal techniques to a household shrine, or niche-stylelararium, found within the building in order to ascertain sightline visibility based on the architectural plan and visual impact as a result of artificial illumination from ceramic lamps. This paper also considers how photorealistic visualizations aid in phenomenological areas of research through sensory archaeology and sense of place, which in turn encourages reflection on the political, social, and religious meanings of the built environment. When we combine the power and diverse applications of 3D visualization technology with decades of research about Roman architecture, culture, religion, and social norms, the result is a step closer to recreating archaeological remnants and, in turn, understanding the ancient experience.

Formic Acid reductant-Sodium Lauryl Sulphate Surfactant enhanced photogalvanic effect of Indigo Carmine dye sensitizer for simultaneous solar energy conversion and storage

The aim of this study is to harness and store solar energy through Indigo Carmine dye–Formic acid photogalvanic cells. The photogalvanic cells based on photo-sensitizer Indigo Carmine dye-surfactant Sodium Lauryl Sulphate-reductant Formic acid–NaOH alkaline medium has shown encouraging and very impressive improvement in solar energy conversion and storage. This combination of chemicals has shown harnessing of 985.6 μW maximum powers with a storage capacity of 115 min as half change time from the 10.4 mWcm−2 artificial and low illumination intensity. In this study, the observed optimum cell performance in terms of the maximum potential, maximum photocurrent, and short-circuit current is 1086 mV, 6400 μA, and 3800 μA, respectively.

Comparisons between yellow and green leaves of sweet potato cultivars in chlorophyll fluorescence during various temperature regimes under high light intensities

• Two sweet potatoes plants were illuminated with 1,000 and 2,000 μmol m−2 s−1 at 10, 25, and 35°C for 30 min. • Wide variations in Fv/Fm and NPQ levels of yellow- and green-leaved plants under temperatures in response to light intensities were observed. • Green-leaved plants showed greater E and P values than yellow-leaved plants, but lower D value than yellow-leaved plants at 35°C under 1,000 μmol m−2 s−1. • Green-leaved plants showed negative correlations of NPQ with Fv’/Fm’ and ΔF/Fm’, and of D with P, but positive relationship between E and P of green leaves. • Manipulation of light harvesting and its regulation by photo-protection might be key to increase bioenergy and food crop yields. The objective of this work was to study changes in the chlorophyll fluorescence (ChlF) components of two sweet potatoes ( Ipomoea batatas L. Lam) cultivars ‘Taoyaun 2’ (green leaf) and ‘CN1927’ (yellow leaf) in response to varying light intensities and temperatures. Cuttings were grown in potting soil under a controlled greenhouse for 4 weeks and moved to a dark room overnight. Plants were then illuminated with 1,000 and 2,000 μmol m −2 s −1 of photosynthetic photon flux density (PPFD) at 10, 25, and 35°C for 30 min with a cool light source, followed by a 30 min dark recovery period at each measured temperature. ChlF was measured immediately before illumination and every 2~5 min during illumination until the end of dark recovery. All measurements were performed at 2 min intervals during the temperature exposure period. The accumulation of chlorophyll affected the leaf colors, and those ChlF indices of yellow- and green-leaved plants treated under various temperatures in response to various light intensities over time, showing wide variations in maximal chlorophyll fluorescence Fv/Fm (in darkness), Fv’/Fm’ (in the light), and non-photochemical fluorescence quenching (NPQ) levels. Moreover, green-leaved plants showed greater the fraction of excess energy in PS II (E) and fraction of light absorbed in PSII antennae (P) than yellow-leaved plants, but lower the fraction of light absorbed in PSII antennae that is dissipated thermally (D) than yellow-leaved plants at 35°C under 1,000 μmol m −2 s −1 . As temperature increased, P values of all plants increased but D values decreased. The values of qE% in green leaves were significantly higher than those in yellow leaves, whereas qI% in yellow leaves was significantly higher than in green leaves under 2,000 μmol m −2 s −1 at all temperatures. There were significant and negative correlations of NPQ with Fv’/Fm’ and ΔF/Fm’, and of D with P of green leaves, but significant and positive relationship was detected between E and P of green-leaved plants. Manipulation of light harvesting and its regulation by photo-protection might be a key to increase bioenergy and food crop yields. The effective management of ChlF parameters in response to the light intensity provides a better understanding of the photosynthetic characteristics of leafy vegetables grown in controlled environments with various combinations of varying temperatures and high light intensities. Fv/Fm and Fv’/Fm’, obtained before illumination and after 30 min of artificial illumination and a subsequent dark recovery for 30 min, followed by extension to 150 min at room temperature, for green-leaved (●) and yellow-leaved (○) sweet potato cultivars under 1,000 and 2,000 μmol m −2 s −1 at 10, 25, and 35°C.

An Overview for Zero‐Dimensional Broadband Emissive Metal‐Halide Single Crystals

AbstractThe high‐profile candidacy of low‐dimensional metal‐halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low‐dimensional metal‐halide single crystals, zero‐dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling have been further translated into near‐unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal‐halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications.

Use of Pigments Present in the Crude Aqueous Extract of the Spinach for the Simultaneous Solar Power and Storage at Natural Sun Intensity

The photogalvanic (PG) solar cell technique discussed in the present study has potential for both solar energy conversion and solar power storage at a time. The harvesting of the solar energy using costly, polluting, and synthetic dye sensitizers cannot be a sustainable method. Furthermore, the sensitizers including the natural sensitizers must be capable of showing simultaneous solar energy and conversion at natural sunlight intensity. With this aim, therefore, the PG cell using cheap and easily obtainable aqueous crude spinach extract for harvesting natural sunlight for solar power generation and storage is fabricated and studied. Herein, it is shown that this extract can also be an efficient sensitizer in the PG cell technique for harvesting energy from the natural sunlight by following the same cell fabrication principles as applicable for the synthetic dye photosensitizers at artificial and low illumination intensity. A very good open‐circuit potential (1.088 V), steady‐state current (50 mA cm−2), power output (13.05 mW cm−2), and efficiency obtainable (≈13%) at a peculiar external load resistance (322.2 Ω) are observed during the natural sunlight illumination.

Impact of light pollution on moth morphology–A 137-year study in Germany

Increasing artificial illumination during night has multifaceted effects on species. Moths are shown to be distracted and attracted by artificial light sources, leading to increased mortality through predation or exhaustion. Increased mortality can be expected to increase selection pressure on morphology, particularly those being functional in light detection and flight ability. We were thus interested if intraspecific traits differ between areas and times with differing light pollution values. We chose the moth Agrotis exclamationis, a common species in the Berlin-Brandenburg region, Germany, a region that offers very different levels of light pollution across space and time. We examined body length, eye size and forewing length, traits likely targeted through selection due to light pollution. We examined moths collected over the past 137 years. We predicted decreasing forewing length, body and eye size, in response to increasing light pollution and expected to see trait changes from the past to today, and from rural to urban areas, representing temporal and spatial gradients of increasing light pollution. In order to determine current levels of light pollution, we used radiance values of the years 2012 to 2019. These values were the base to extrapolate previous radiance values for all sample sites and years. We observed no trait differences along the spatial gradient, but trait and sex dependant changes along the temporal gradient. We could not confirm a direct causal link between changes in body size and female eye size. However, we revealed indirect effects of light pollution, and assume habitat fragmentation and host-plants to be the main drivers for these effects. A trend towards smaller-eyed females in ‘medium’ and ‘high’ light-polluted areas over time could be a first indication that morphological trait changes to light pollution are taking place.

From traditional to distance learning: hygienic problems of vision protection of students

Introduction. Electronic devices (ED) are widespread among adolescents, filling their daily lives. The trend towards digitalization of all aspects of life is a global trend with the inevitable involvement of young people. The lack of existing preventive measures necessitates scientific research and intensification of work to promote a healthy lifestyle. Materials and methods. In 2019, an online survey was conducted of 200 schoolchildren in grades 9-11, 498 students in 1-6 courses, and 251 parents. In April 2020, an online survey was conducted of 1587 students of 1-6 classes and 500 parents. Measurements of physical factors were carried out at the Dolgoprudnenskaya gymnasium and the N.I. Pirogov Russian National Research Medical University. One thousand sixty-six schoolchildren and students were examined by an ophthalmologist with the help of the device “ARMISm”. Results. Negative tendencies in the state of the organ of vision, observed by students, are primarily associated with increased use of stationary and mobile ED in all age groups. Students use various ED in places with insufficient artificial illumination. In educational institutions, such places are corridors, halls, recreation, where students use their electronic devices. There are currently no separate requirements for artificial lighting by using information and communication technologies outside of classrooms or work premises. During the period of distance learning, schoolchildren and students have been established to use one more ED in comparison with the period of traditional education. The long-term effect of using mobile ED is still unknown. Conclusions. As a preventive hygienic measure for the protection of vision, it is recommended to use ED only in places with a good level of illumination, including artificial, with limited duration of continuous use of ED, with gymnastics for the eyes during breaks.

Biochemical Composition of Chlorella vulgaris Grown on Sugarcane Molasses

The quest for green and sustainable biofuel to serve as alternative to the conventional fossil fuel have remained a grey area in biotechnology. The Chlorella vulgaris was isolated from the African Regional Aquacultural Centre Aluu, Port Harcourt, Nigeria. Sugarcane Molasses modified Bold Basal medium was used to cultivate the Microalgae mixotrophically. The algal culture was incubated at room temperature for 15 days with continuous aeration and 12:12 hour photoperiod under artificial illumination of 2000 lux. The proximate composition of the biomass showed 6.28%wt, 67.37% wt and 11.35%wt of moisture, volatile organic matter and Fixed carbon content respectively. The ultimate composition of Chlorella biomass revealed that Carbon was 42.46% while Oxygen content was 27.93%. Nitrogen content was 6.62% while Sulphur content was 0.82% while hydrogen content was 6.74%. The study further identified that algal biomass from C. vulgaris has the potential of serving as both nutraceuticals and bioenergy feedstock. There is need for further studies around the algae oil oriented optimization as a veritable tool for biotechnological advancements.

GROWTH RESPONSE OF INDOOR ORNAMENTAL PLANT SPECIES TO VARIOUS ARTIFICIAL LIGHT INTENSITIES (LED) IN AN INDOOR VERTICAL GARDEN

Urban population spends most of their time indoors leading to multiple problems. Making an indoor vertical garden and associating people to this new concept will help build the indoor environment with improved energy efficiency, indoor air quality, their improved health and well-being. Of all of the factors affecting plant growth in interiors, adequate light is by far the most important. LED is an efficient, energy-saving light source widely used in artificial light plant production systems. Lack of scientific information regarding the light intensity requirement for optimum growth of the indoor ornamental plant species under Indian conditions makes the study of utmost importance. Five indoor ornamental plant species namely, Schefflera arboricola, Dracaena godseffiana, Philodendron salloum, Syngonium podophyllum and Scindapsis aureus were planted in pots (5”) with soil less media arranged as vertical structures (6?11”x4?3”) aligned to interiors walls of a room. Four such structures/frames were fabricated, fertigated with 100 % of the Hoagland solution and artificially illuminated using LED lighting system (PWM controlled) with different light intensities i.e. 700-1100 lux (LI I), 1100-1500 lux (LI II), 1500- 1900 lux (LI III) and LI IV had no artificial light illumination (control). From the most effective positive response of plant species under study on the basis of their growth response towards different light intensities, it was concluded that Philodendron salloum responded best to LI I (700-1100 lux), Scindapsis aureus to LI II (1100-1500 lux), Dracaena godseffiana, Schefflera arboricola and Syngonium podophyllum to LI III (1500-1900 lux).

Spectral composition of artificial illuminants and their effect on eye growth in chicks

In broadband light, longitudinal chromatic aberration (LCA) provides emmetropization signals from both wavelength defocus and the resulting chromatic cues. Indoor illuminants vary in their spectral output, potentially limiting the signals from LCA. Our aim is to investigate the effect that artificial illuminants with different spectral outputs have on chick emmetropization with and without low temporal frequency modulation.In Experiment 1, two-week-old chicks were exposed to 0.2 Hz, square-wave luminance modulation for 3 days. There were 4 spectral conditions: LED strips that simulated General Electric (GE) LED “Soft” (n = 13), GE LED “Daylight” (n = 12), a novel “Equal” condition (n = 12), and a novel “High S” condition (n = 10). These conditions were all tested at a mean level of 985 lux. In Experiment 2, the effect of intensity on the “Equal” condition was tested at two other light levels (70 lux: n = 10; 680 lux: n = 7). In Experiment 3, the effect of temporal modulation on the “Equal” condition was tested by comparing the 0.2 Hz condition with 0 Hz (steady). Significant differences were found in axial growth across lighting conditions. At 985 lux, birds exposed to the “Equal” condition showed a greater reduction in axial growth (both p < 0.01) and a greater hyperopic shift compared to “Soft” and “Daylight” (both p < 0.01). The “High S” birds experienced more axial growth compared to “Equal” (p < 0.01) but less than in “Soft” and “Daylight” (p < 0.01). Axial changes in “Equal” were only observed at 985 lux with 0.2 Hz temporal modulation, and not with lower light levels or steady light. We conclude that axial growth and refraction were dependent on the lighting condition in a manner predicted by wavelength defocus signals arising from LCA.

A compact AAA-compatible multispectral solar simulator based on spherical cap chamber

Rapidly developing thin-film solar cells prompts the demand for artificial narrow-band spectral illumination. Here, an LED-based compact spherical cap solar simulator is proposed to provide multiple independent color channels, while compatible with the traditional broadband IEC60904-9 standard in terms of illumination non-uniformity, stability and solar-like spectrum. Firstly, a one-dimensional model is established and then validated to analyze locations of maximum power point which may degenerate the spatial homogeneity. Secondly, the LED layout is optimized by Monte Carlo ray tracing, and it is found that a good illumination uniformity can be achieved if they are rotational symmetrically distributed. Thirdly, another two structural parameters, including output slot size and cavity height, are simulated to balance the output uniformity and output power. Finally, an instance simulator based on the structure is developed for performance verification. In the implementation, heat dissipation strategies are introduced to stabilize the system, including the use of heat sinks and flip-connected printed circuit boards to keep heat sources away from the optical chamber, thereby ensuring 0.052% short-term and 1.13% long-term stability. In addition, seven types of LEDs are adopted to simulate the solar spectrum, and its maximum deviation between the AM 1.5G is −8.82%. A control system consisting of a graphical user interface, STM32 microprocessor and constant current sources is developed to configure the current of different color channels. As a result, in predominant area of the entire output slot, six narrow-band and broadband illuminations can achieve 2% non-uniform, which is of interest for testing thin film solar cells.

Artificial illumination influences niche segregation in bats

Artificial light at night (ALAN) is a pervasive form of pollution largely affecting wildlife, from individual behaviour to community structure and dynamics. As nocturnal mammals, bats are often adversely affected by ALAN, yet some “light-opportunistic” species exploit it by hunting insects swarming near lights. Here we used two potentially competing pipistrelle species as models, Kuhl’s (Pipistrellus kuhlii) and common (Pipistrellus pipistrellus) pipistrelles, both known to forage in artificially illuminated areas. We set our study in a mountainous area of central Italy, where only recently did the two species become syntopic. We applied spatial modelling and radiotracking to contrast potential vs. actual environmental preferences by the two pipistrelles. Species distribution models and niche analysis showed a large interspecific niche overlap, including a preference for illuminated areas, presenting a potential competition scenario. Pipistrellus pipistrellus association with ALAN, however, was weakened by adding P. kuhlii as a biotic variable to the model. Radiotracking showed that the two species segregated habitats at a small spatial scale and that P. kuhlii used artificially illuminated sites much more frequently than P. pipistrellus, despite both species potentially being streetlamp foragers. We demonstrate that ALAN influences niche segregation between two potentially competing species, confirming its pervasive effects on species and community dynamics, and provide an example of how light pollution and species’ habitat preferences may weave a tapestry of complex ecological interactions.

Total quality control of the cyber-physical production using machine vision technologies

The total control is made for each separate unit of the item being manufactured to prevent any scrap. The automatic control tools are a part of information, measurement and controlling sub-systems, which use the machine vision technology. The information sub-system is done with the cyber-physical production calculation potency. The measurement sub-system is a set of digital cameras (optical detectors) and the artificial illumination semiconductor sources. The controlling sub-system regulates the item position with turning mechanisms inside the closed cyber-physical system technological chamber. A set of sub-systems performs a non-destructible item quality control with the item surface photographic images and stereo-maps program analysis, which should not contain non-homogeneous sections like scars, fissures, inclusions and other and any deviations of geometrical dimensions. The calculator three-dimension item image is formed with reconstruction algorithms of two-dimension photographs received in different views and illumination conditions and the means of laser scanning. The item surface quality requirements in the enlightened areas and obscured ones are defined with rendering equation, which are permitted for the item digital twin with calculator numerous methods. The quality control requires to compare with the reference energy and color measurement item surface characteristics, which are defined with mathematical calculations and optical measurement means. There is a scheme given of information, measurement and controlling cyber-physical system channels, which engage the machine vision technologies to control the item quality.

INSTALLATION FOR PHYSICAL SIMULATION OF LASER LOCATION PROCESSES

A device for physical modeling of laser ranging processes has been developed, taking into account aerosol interference phenomena of natural and artificial origin and active background illumination. The installation simulates the processes of object detection and recognition by a laser information-measuring system (LIMS) under conditions of external destabilizing factors and obstacles in the atmospheric channel.

Sustainable City Lighting Impact and Evaluation Methodology of Lighting Quality from a User Perspective

High quality artificial lighting of public places is one of the necessary functions of sustainable cities. It is much more than just providing sufficient light intensity with reduced energy consumption and low environmental impact. The solution to this challenge is not only technological, but also requires the consideration of the subjective approach, such as psychological, sociological, and aesthetic-functional. The article presents the SEC (Suitable for everyone, Environmentally-accepted, Cost-effective) methodology and model, which are placed in the context of sustainable city lighting. A holistic assessment approach of user environmental perception, priorities, and spatial responses is required to evaluate the impact of artificial night illumination. Lighting efficiency was expressed as the correspondence between environmental perception and spatial utilization during day and night. Ten sites with different urban background and illumination characteristics were selected. It was assumed that artificial night lighting influences the perception, priorities, and responsiveness of users. The validity of this argument was demonstrated at a relevant statistical level of p &lt;0.05. The research results provided useful information about the current state, which is needed to prepare a sustainable lighting strategy, and could be compared between different or similar sites. Based on the obtained results, it can be concluded that the artificial lighting of urban open spaces is of high quality when the difference in the spatial perception and spatial utilization between day and night is as small as possible.

Narrow‐spectrum artificial light silences female fireflies (Coleoptera: Lampyridae)

AbstractThe rapid spread of artificial light at night (ALAN) poses myriad problems for nocturnal biodiversity.Bioluminescent taxa that communicate via glowing lures, warning signals, or courtship advertisements may have their signals obscured by artificial illumination, unless the added light is spectrally tuned to reduce its impact.Previous research has demonstrated that broad‐spectrum white light inhibits the production of courtship advertisements by male firefly beetles, yet the impact of varying wavelengths of artificial light on both members of the courtship dialogue is largely unknown.We exposed courting pairs ofPhotinus obscurellusfireflies to five colours of downwelling illumination, at two intensities, and recorded changes in male flash rate and flash intensity, female responsiveness, and the flash pattern composition of both sexes.All artificial light treatments significantly suppressed courtship activity.Bright amber light had the greatest impact, suggesting that ALAN which most overlaps the spectrum of firefly bioluminescence will most disrupt firefly courtship.Our findings contradict similar investigations of non‐bioluminescent taxa and raise concerns about the possibility of a universal standard for ecologically sustainable ALAN.

The influence of the light spectrum on the growth and development of greenhouse plants on the example of cucumber culture (Cucumissativus L., Cucurbitaceae family)

The aim of the work is to develop the lighting mode for the cucumber photoculture. The developed lighting mode should intensify production process by optimizing spectral characteristics of the light sources used at different stages of the life cycle of the plant. The authors conducted experiments on the cultivation of cucumber culture under conditions of ecosystems of small volume with artificial illumination. As the lighting sources, LED elements with phyto-oriented spectra were used. Based on dynamics of phenological and morphometric parameters and productivity of plants, the authors concludes that pre-sowing irradiation provided positive effect on seed germination. Artificial lighting sources with additional red LEDs (625nm in the ratio 9:2) accelerated the development of the vegetative and generative systems. Illumination by white spectrum LEDs (Ra80, CCT 3000 K) contributed to improving the efficiency of photosynthesis processes extended the period of active life of the plants. The authors proposed variants of artificial lighting with the use of light sources composed of LEDs of different spectra for the effective cultivation of cucumber according to different stages of plant life cycle.

Effects of Artificial Lighting at Night on Predator Density and Salmonid Predation

AbstractPredation of juvenile salmonids within California’s Sacramento–San Joaquin Delta (the Delta) has been identified as a contributing factor to low survival during out‐migration through the system. Artificial lighting at night (ALAN) may contribute to increased levels of salmonid predation by attracting predators and prey, increasing predator reaction distance, and boosting foraging success. To assess ALAN effects on predator (piscivorous fishes) density and the relative predation risk of Chinook Salmon Oncorhynchus tshawytscha smolts in the Delta, we preformed field‐based experiments with introduced ALAN. We used adaptive resolution imaging sonar cameras to generate predator density estimates in light and dark treatments throughout nightly experiments at 30‐min intervals. We simultaneously deployed predation event recorders to estimate the impact of ALAN intensity (lux) on relative predation risk of Chinook Salmon smolts. Early in the night (1–3 h past sunset), predator density and relative predation risk of smolts were unrelated to ALAN. However, late in the night (3–5 h past sunset), ALAN presence increased predator density, and the relative predation risk of juvenile salmonids increased with increasing lux. Predation risk was also positively related to predator density, and increased late‐night predator density under ALAN, coupled with late‐night foraging benefits of ALAN, likely contributed to the lux–risk relationship. The exact mechanism behind this discrepancy between early‐ and late‐night trends is unknown and could be a result of our experimental design or the predator community sampled here. However, if these temporal trends prove robust to future investigations, late‐night lighting reduction campaigns during out‐migration could maximize the human benefits of ALAN while minimizing the negative impacts on salmonids. Overall, our findings align with others and suggest that ALAN increases juvenile salmonid predation. Although many questions remain unanswered, it appears that reducing artificial illumination is a practical management strategy to reduce predation.