UNTANGLING LIGHT IN “NOISY” LUMINOUS ENVIRONMENTS

Electric light sources, including displays and luminaires, often exhibit rapid light fluctuations called temporal light modulation (TLM). TLM can be seen as their electrical footprint. This work demonstrates that TLM can be remotely detected and used to perform in situ photometric and spectroradiometric measurements of very low light levels superimposed to intense backgrounds. Illuminance levels about 500 000 times smaller than the background were reliably measured by lock-in detection, allowing photometric measurements to be performed during daytime, even with sunny conditions. Using a new type of optical lock-in spectrometer, it becomes possible to retrieve spectral quantities through the TLM of the light source. The spectral distribution of an LED lamp was measured against a daylit background more than 1500 times brighter. Lock-in detection is an excellent technique to perform in situ measurements of electric light, even at very low level, in the presence of daylight and other background lights, opening interesting opportunities to characterize anthropogenic light pollution.

In hyperspectral remote sensing measurements, the spectral effective information extracted under different measurement light source conditions will produce differences, which in turn affects the robustness of the constructed models. Therefore, it is important to study the differences between hyperspectral estimation models under different measurement light source conditions to construct a general hyperspectral model of vegetation parameters under different light source conditions. In this paper, hyperspectral models are constructed from artificial and natural light sources, and the hyperspectral reflectance and the corresponding SPAD values of artificial and natural light sources under winter wheat, corn and tea tree were measured under the same time period and the same light measurement angle and height. The collected data were used to construct models for the four vegetation indices with better results after screening and to explore how to reduce model variability under different measured light source conditions. The results show that the difference between the artificial light source and natural light source models is significant (the coefficient of determination R2 is significantly different between the artificial light source and natural light source models), and the influence of different light sources on the construction of hyperspectral estimation models can be reduced by selecting vegetation indices. The linear regression equation model constructed by NDVI can effectively reduce the influence of different light sources on the construction of SPAD hyperspectral models and make the model more general. This study can provide new ideas and methods to investigate the differences in spectral models under different measurement light sources.

Temporal Light Modulation (TLM) can induce undesirable effects (flicker, stroboscopic, and phantom array effects), discomfort, headaches, and seizures in photosensitive population. We explored literature to understand impacts of TLM on human viewers, approaches for measuring their effects, and to help drive design of workstations with automated scanning stations. Findings indicate that existing standards recommend thresholds for frequency and modulation depth. We not only provide recommendations to ensure safe implementation of TLM systems but also discuss potential approaches for assessing discomfort. Future studies need to examine high frequency TLM and long-term implications to ensure comfortable workspaces.

Numerous efforts have been made to investigate how light source color rendition affects color preference. Though the effect of light level on color appearance (known as the Hunt effect) was found in 1952, most studies investigating color preference under light sources only employed a single illuminance level and the illuminance levels were typically between 200 and 1000 lux. This article reports two psychophysical experiments that were designed to investigate how light source color rendition affected color preference across a wide range of illuminance levels, from 20 to 15,000 lux. The observers compared the color appearance of an artwork under nine nearly metameric light stimuli with a correlated color temperature (CCT) of 3000 K at different illuminance levels. These light stimuli were carefully designed to have different abilities to enhance the chroma of red and green colors, so that they had different gamut areas R g (between 100 and 124 in Experiment 1 and between 99 and 117 in Experiment 2). It was found that the illuminance level significantly affected the observers’ judgments, with a light stimulus with a greater R g being preferred at a lower light level. The light stimuli with an R g beyond 100 were preferred at the light levels from 20 to 5000 lux, whereas those with an R g around 100 were preferred at very high light levels (i.e., 10,000 and 15,000 lux). This suggested that the preference to the stimuli with an R g beyond 100, as found in many past studies, was likely due to the relatively lower illuminance levels in comparison to the daylight illuminance levels. In addition, the calculations of the color attributes of the artwork under the preferred stimuli suggested that CIECAM02 may overestimate the effect of light level on color appearance, especially when the light level was very high, which merits further investigations.

In order to estimate the visibility of temporal light modulation (TLM), also known as "flicker", various metrics are employed in research and commerce. The metrics, however, are not easily calculated, and occasionally the values change depending on sampling rates. This study investigates the complexities involved in processing data from TLM waveform metrics and then calculating metrics. It explores the sensitivity of each metric to sampling rate, and recommendations are then provided for how to increase the accuracy and consistency of the metrics by using appropriate sampling rates. The analyses in this study are based on noise-free and stable ideal waveforms; however, sampling rate effects also exist for real-world waveforms.

One of the key developments in the renaissance in solid-state laser technology has been the rapid improvement of diode laser pump sources.1–3 Some of the advantages of diode-pumping relative to lamp-pumping of solid-state lasers include higher overall efficiency, reduced thermal loading of the gain medium, higher reliability, and reduced size. In addition, there are other important differences between these two types of pump sources. For example, diode lasers have higher spectral and spatial brightness, in other words, the diode laser output is narrowband spectrally, and it is directional. The consequence is that much higher volumetric pumping density can be achieved using diode-laser pumps even with low power single-stripe diode lasers relative to high-power lamps. The high pump densities has led to the demonstration of good laser performance at room temperature of several transitions that performed only poorly or not at all at room temperature under lamp pumping. These transitions in rare-earth ions include the 4F3/2- 4I9/2 near 0.94 µm in Nd3+,4–6 the 5I7 - 5I8 near 2.1 µm in Ho3+,7–10 the 3F4 -3H6 near 2.0 µm in Tm3+,11–13 the 4I13/2 - 4I15/2 near 1.5 µm in Er3+,13,14 and the 2F5/2 - 2F7/2 near 1.0 µm in Yb3+ (refs. 15, 16) as shown in Fig. 1. The common element in these laser transitions is that the lower laser levels are in the ground-state multiplet which means that the lower laser levels are only a few hundred cm-1 above the ground state. Thus the lower levels have significant population in thermal equilibrium at room temperature since kT is 207 cm-1 at 300 K. This is in contrast to the common four-level Nd3+ transition near 1.06 µm which has a lower level about 10kT above the ground-state at 300 K thus can be considered unpopulated in thermal equilibruim, or ruby in which the lower laser level is the ground-state. With lamp-pumping, these lasers with lower levels in the ground-state manifold were typically operated at cryogenic temperatures to reduce the lower-level population in thermal equilibruim; at sufficiently low temperature these lasers become four-level lasers and efficient, low threshold performance was obtained.

Poot, H., B. J. Ens, H. de Vries, M. A. H. Donners, M. R. Wernand, and J. M. Marquenie. 2008. Green light for nocturnally migrating birds. Ecology and Society 13(2): 47. https://doi.org/10.5751/ES-02720-130247

Background: Salvia miltiorrhiza Bunge has been used in traditional medicine. The type of light source has an effect on the growth properties and composition of functional compounds in plants. In this study, we analyzed the effects of different artificial light sources on the growth characteristics as well as antioxidant and antimicrobial activities of S. miltiorrhiza.<BR>Methods and Results: Seedlings of S. miltiorrhiza were grown under various artificial light sources, including fluorescent light (FL), light emitting diode (LED), and microwave electrodeless light (MEL), for 8 weeks. Growth characteristics were the best in plants treated with MEL. DPPH scavenging activity of the shoot was more pronounced with the FL treatments, while the roots were more active in plants grown under single wavelength lights (i.e., blue and red LEDs). Among the different light source treatments, the blue LED resulted in a higher total phenolic content in the plants. Furthermore, growing plants growth under the red LED enhanced their total flavonoid content. Notably, the antimicrobial properties of plants varied significantly between light source treatments in this study. Except for E. coli, all the tested microorganisms were susceptible to the plant extracts.<BR>Conclusions: The type of light source may be an important parameter for the enhancement of plant growth and functional compounds in S. miltiorrhiza.

It is important to understand recent lighting and fenestration history and its development. Before the era of on-tap electrical energy supply for lighting, when artificial lighting sources were inefficient, fenestration was used as a means of providing working illuminance in addition to its many other well-documented functions. Daylighting technology developed firstly from a need to ease natural light into buildings in order to illuminate tasks and interior spaces. High ceiling heights with tall windows were favored and roof lighting, to provide working illuminance, became extensively used in industrial premises. With the advent of the fluorescent lamp, and its rapid rise to prominence during the 1950s, buildings were freed from many configuration constraints and the use of fenestration, as a means of providing working illuminance, diminished. Within a further decade, artificial lighting levels soared, especially in the USA. Levels of 2,000 lux were not uncommon as the philosophy that more light is better propagated rapidly. Controversy abounded concurrently with these developments. One area of controversy was associated with the trend toward seemingly unnecessary ever higher interior illuminances. The lighting industry was blamed for producing a body of opinion which favored higher illuminance and, hence, higher financial returns to the industry. Then the 1970s energy crisis materialized. It was already known that the then popular deep office building, illuminated almost totally by artificial lighting, was a prime offender in the excess energy consumption league. The high lighting levels used in these buildings came under immediate attack, resulting in large-scale delamping, which resulted in widespread but scarcely acknowledged complaints about difficulties due to observed fenestration brightness.

Artificial light at night may affect mortality risk in prey from visually oriented predators because the effect of the artificial light spectrum may differ for a predator’s visual prey detection and for prey evasiveness. To test this, we conducted two types of experiment. First, we assessed the reaction distance and swimming speed of juvenile rudd (Scardinius erythrophthalmus) allowed to forage on juvenile Daphnia pulex × pulicaria under three artificial light sources: halogen, high pressure sodium (HPS), and metal halide bulbs, at the same light intensity. Second, we assessed the evasiveness of D. pulex × pulicaria under the same artificial light sources and in darkness (as a control), in the presence and absence of chemical information on predation risk (kairomones) of juvenile rudd. We found that while both reaction distance and swimming speed of fish was greater under halogen compared to HPS, and similar under metal halide light compared to halogen and HPS, the evasiveness of Daphnia was greater under halogen and HPS-generated light than under metal halide light. The results suggest a possible mismatch of Daphnia’s behavioural response under metal halide light to predicted predation risk, and thus a possible threat to predator–prey balance in a lake ecosystem.

Despite centuries of use, artificial light at night has only recently been recognized as a cause for environmental concern. Its global extent and ongoing encroachment into naturally lit ecosystems has sparked scientific interest into the many ways in which it may negatively affect human health, societal attitudes, scientific endeavors, and biological processes. Yet, perhaps because sources of artificial light are largely land based, the potential for artificial light pollution to interfere with the biology of the ocean has not been explored in any detail. There is little information on how light pollution affects those species, behaviors, and interactions that are informed by the intensity, spectra, and periodicity of natural nighttime light in marine ecosystems. Here, we provide an overview of the extent of marine light pollution, discuss how it changes the physical environment, and explore its potential role in shaping marine ecosystems.

AB0484 TROUGH LEVELS OF TNF-Α INHIBITORS AND THEIR IMMUNOGENICITY IN THE TREATMENT OF RHEUMATIC DISEASES AND INFLAMMATORY BOWEL DISEASES

In show caves, artificial lighting is intended to illuminate striking cave formations for visitors. However, artificial lighting also promotes the growth of novel and diverse biofilm communities, termed lampenflora, that obtain their energy from these artificial light sources. Lampenflora, which generally consist of cyanobacteria, algae, diatoms, and bryophytes, discolor formations and introduce novel ecological interactions in cave ecosystems. The source of lampenflora community members and patterns of diversity have generally been understudied mainly due to technological limitations. In this study, we investigate whether members of lampenflora communities in an iconic show cave—Lehman Caves—in Great Basin National Park (GRBA) in the western United States also occur in nearby unlit and rarely visited caves. Using a high-throughput environmental DNA metabarcoding approach targeting three loci—the ITS2 (fungi), a fragment of the 16S (bacteria), and a fragment of 23S (photosynthetic bacteria and eukaryotes)—we characterized diversity of lampenflora communities occurring near artificial light sources in Lehman Caves and rock surfaces near the entrances of seven nearby “wild” caves. Most caves supported diverse and distinct microbial-dominated communities, with little overlap in community members among caves. The lampenflora communities in the show cave were distinct, and generally less diverse, from those occurring in nearby unlit caves. Our results suggest an unidentified source for a significant proportion of lampenflora community members in Lehman Caves, with the majority of community members not found in nearby wild caves. Whether the unique members of the lampenflora communities in Lehman Caves are related to distinct abiotic conditions, increased human visitation, or other factors remains unknown. These results provide a valuable framework for future research exploring lampenflora community assemblies in show caves, in addition to a broad perspective into the range of microbial and lampenflora community members in GRBA. By more fully characterizing these communities, we can better monitor the establishment of lampenflora and design effective strategies for their management and removal.

The artificial light source is one of the most important factors in a controlled environment for vegetable production. It could provide new opportunities to improve growth and increase phytochemicals content in vegetables. Therefore, this study focused on the effects of artificial light sources on growth and phytochemicals in green oak lettuce (Lactuca sativa). The plants were grown under growth chamber with three artificial light sources, namely bar-LED (the 1:1:1 ratio of blue 460 nm : red 630 nm : red 660 nm), bulb-LED (the 2:1:1 ratio of blue 460 nm : red 630 nm : red 660 nm), and fluorescent lamp (FL) (the wavelength range 380-700 nm) for 4 weeks. The quality of bar-LED light was better than either bulb-LED or FL, when assessed by the parameters of photosynthetically active radiation (PAR), photosynthetic photon flux density (PPFD, 400-700 nm), PPFD-B (blue, 400-500 nm), PPFD-R (red, 600-700 nm), the yield photon flux density (YPFD), and the color of red. However, shoot and root (fresh and dry mass), leaf area, leaf number, and shoot/root ratio did not significantly differ between plants grown under bar-LED and bulb-LED, but they were significantly higher than plants grown under FL. Bulb-LED and bar-LED induced larger dry mass of the plants than FL. The dry mass per mole of artificial lighting was highest in plants grown under bar-LED. On the other hand, the fresh mass per mole of artificial lighting was highest in plants grown under bulb-LED. As regards power consumption, bar-LED provided the lowest consumption with 44.4% energy saving over the FL. Total phenolic content, 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenylpicrylhydrazyl (DPPH) activities were highest in plants grown under bar-LED. FL lighting gave the least contents of chlorophyll a and chlorophyll a + b. However, chlorophyll b and carotenoid contents did not significantly differ among the treatments. Thus, the results suggested that bar-LED has the potential to improve energy saving, and both growth and phytochemicals content of green oak lettuce grown in a controlled environment of vegetable production.

Artificial lighting at night (ALAN) is increasingly recognised as having negative effects on many organisms, though the exact mechanisms remain unclear. Glow worms are likely susceptible to ALAN because females use bioluminescence to signal to attract males. We quantified the impact of ALAN by comparing the efficacy of traps that mimicked females to attract males in the presence or absence of a white artificial light source (ALS). Illuminated traps attracted fewer males than did traps in the dark. Illuminated traps closer to the ALS attracted fewer males than those further away, whereas traps in the dark attracted similar numbers of males up to 40 m from the ALS. Thus, ALAN impedes females' ability to attract males, the effect increasing with light intensity. Consequently, ALAN potentially affects glow worms' fecundity and long-term population survival. More broadly, this study emphasises the potentially severe deleterious effects of ALAN upon nocturnal insect populations.