Effect of changing mesopic and photopic light conditions on visual functions

AIM:To determine the effects of change in light conditions on refractive error and visual functions including visual acuity,stereopsis and contrast sensitivity.METHODS:This cross-sectional study was conducted in the optometry clinic of the Shahid Beheshti School of Rehabilitation on 48 students in 2021-2022.All of them had eye health and normal visual function and could have refractive errors or not.Light intensity of 4 lx was considered equivalent to photopic light condition and light intensity of 1 lx was considered to be equivalent to mesopic light condition.The amount of refractive error was checked by auto refractometer and its changes in mesopic light condition were subjectively measured.Also,visual acuity,stereopsis and contrast sensitivity(in five spatial frequencies of 1.5,3,6,12,and 18 cycles per degree),were measured first in photopic light condition and then in mesopic light condition,by Snellen control vision chart,stereo butterfly test and the M&S technology monitor test respectively.RESULTS:In the 48 student subjects with an average age of 22.69±3.56y,mean of refractive error as sphere equivalent,visual acuity and stereopsis were-1.25±1.74 diopters,0 logMAR,44.37±13.03 seconds of arc,respectively in photopic light condition while in mesopic light was equal to-1.56±1.75 diopters,0.12±0.09 logMAR and 50.62±33.35 seconds of arc,respectively.The mean of contrast sensitivity measured at spatial frequencies of 1.5,3,6,12,and 18 cycles per degree in photopic condition was equal to 2.38±0.04,2.37±0.07,2.04±0.21,1.27±0.32,0.82±0.27 logarithm of contrast sensitivity,respectively and in mesopic lighting condition was equal to 2.34±0.12,2.30±0.16,1.84±0.28,1.02±0.28,0.63±0.24 logarithm of contrast sensitivity,respectively.Statistical analysis showed a significant difference between the two lighting conditions in all evaluated variables[refractive error(P<0.001),visual acuity(P<0.001),stereopsis(P=0.008)and contrast sensitivity(P<0.001)].CONCLUSION:The refractive error of the student subjects in mesopic light condition change towards myopia,and its amount is clinically significant.Also,the examination and comparison of the factors of visual acuity,stereopsis and contrast sensitivity in these two lighting conditions show that the decrease in brightness level to the mesopic level causes a decrease in the aforementioned visual functions.

Light intensity regulates the sexual behaviors of oriental fruit fly Bactrocera dorsalis under laboratory conditions

The oriental fruit fly,Bactrocera dorsalis(Hendel),is a devastating pest of citrus fruits.After successful mating,adult females insert their eggs into the ripened fruit,resulting in moldy and rotten fruit and causing great economic losses for the citrus industry.In the field,flies initiate copulatory behaviors as twilight approaches,and decreasing light intensity in this period is the normal stimulus for copulation.In this study,ten light intensities ranging from 0–30000 lux were set to identify the typical intensity that strongly regulates the copulation behavior of B.dorsalis.Three light intensities found to regulate the copulation behavior were then selected to verify their effects on adult male wing fanning and female chemotaxis towards 2,3,5-trimethylpyrazine(TMP).At last,strong light and complete darkness were artificially combined in the lab to verify whether they could prevent copulation to inform behavioral manipulation of oriental flies in the future.The results indicated that adult flies generally initiated copulatory behaviors at low light intensity(<1000 lux).Stronger light significantly prevented copulation in proportion to intensity,with nearly no copulation events initiated when light intensity was above 20000 lux.Both male wing fanning and female chemotaxis towards TMP were attenuated as light intensity became stronger.However,at 10000 lux,males still fanned their wings to a certain extent while TMP completely lost its attractiveness to females.In the darkness,adults did not initiate any sexual behaviors,e.g.,copulation,wing fanning,or chemotaxis to TMP.One hour of strong light(10000 lux)combined with continuous darkness completely prevented mating.These results show that light condition is an essential factor for copulatory behaviors in the oriental fruit fly.Researchers could thus manipulate light conditions artificially or disrupt the molecular target in flies’light transduction pathway to develop environmentally-friendly techniques to control this pest.

Impact of Different Light Characteristics on the Growth and Lipid Content of Diatom Phaeodactylum tricornutum Transconjugant Strains

Light regulates important metabolic processes in microalgal cells, which can further impact the metabolism and the accumulation of biomolecules such as lipids, carbohydrates, and proteins. Different characteristics of light have been studied on various strains of the model diatom Phaeodactylum tricornutum, but not on transconjugant cells and information on wild-type strains is still limited. Therefore, we studied the impact of different light characteristics such as spectral quality, light intensity and light shift on the growth, and the composition in lipids and fatty acids of P. tricornutum cells to provide a comprehensive context for future applications. Initially, we tested the impact of spectral quality and light intensity on P. tricornutum transformed with an episomal vector (Ptev), harboring the resistance gene Sh ble. Results indicated that Ptev cells accumulated more biomass and overall lipids in spectral quality Red 1 (R1: 34% > 600 nm > 66%) more effectively as compared to Red 2 (R2: 8% > 600 nm > 92%). It was also detected that cell granularity was higher in R1 as compared to R2. Furthermore, by testing two light intensities 65 μmol·m-2·s-1 and 145 μmol·m-2·s-1 light, it was observed that 145 μmol·m-2·s-1 led to an increase in growth trend, total biomass and lipid content. Combining spectral qualities and light intensities, we show that the lipid accumulation raised by 2.8-fold. Studying the light intensity and spectral quality allowed us to optimize the light conditions to R1 spectral quality and light intensity 145 μmol·m-2·s-1. These initial results showed that red light R1 at 145 μmol·m-2·s-1 was the best condition for biomass and total lipids accumulation in Ptev cells. Next, we further combined these two-light optimizations with a third light characteristics, i.e. light shift, where the cultures were shifted during the early stationary phase to a different light environment. We studied Red light shift (Rs) to investigate how light condition variations impacted P. tricornutum transconjugants Ptev and with an episomal vector containing the reporter gene YFP (PtYFP). We observed that Rs induced growth and fatty acid eicosapentaenoic acid (EPA) in Ptev as compared to PtYFP. Altogether, the study shows that red light shift of R1 at 145 μmol·m-2·s-1 promoted biomass and total lipids accumulation in Ptev and PtYFP cells. The study provides a comprehensive approach to using different light characteristics with the aim to optimize growth and lipids, as well as to fatty acid production.

Light matters:Nest illumination alters egg rejection behavior in a cavity-nesting bird

Egg discrimination by cavity-nesting birds that build nests under dim light conditions was presumed to depend on nest luminance,although this hypothesis has rarely been tested.Tests of egg discrimination ability by cavity-nesting tits under dim light conditions may reveal the selection pressure from brood parasitism that they encounter under natural interactions.We manipulated the intensity of luminance of nests of the Green-backed Tit(Parus monticolus),a potential cuckoo host that possesses a strong discrimination ability of non-mimetic foreign eggs.We performed experiments to test their egg discrimination ability under different light conditions.Our results showed that Green-backed Tits discriminate against non-mimetic foreign eggs under normal light conditions in nest boxes,and this ability persisted at nest luminance as low as 4.78±1.31 lux that is several times lower than normal luminance(38.11±24.02 lux).However,egg discrimination by Green-backed Tits disappeared when nest luminance was reduced to a minimum of 0.35±0.15 lux.The latter value represents total darkness for humans.The present study shows that nest luminance plays a key role in egg discrimination by Green-backed Tits that build nests under dim light conditions.This study provides strong experimental evidence for nest illumination altering egg rejection behavior in cavity-nesting birds.

Effects of Light and Temperature on Uptake andDistribution of Nitrogen, Phosphorus and Potassiumof Cucumber in Solar Greenhouse

The influence of light and temperature conditions inside solar greenhouse of winter-spring and autumn-winter crop in northern China on uptake and distribution of nitrogen. phosphorus and potassium of cucumber was studied. The results showed that plant root development and uptake and distribution of N, P and K benefited more from inside light and temperature changes in winter-spring crop. Root volume and root activity increased more rapidly in winter-spring than in autumn-winter. Uptake of total N, P2O5 and K2O increased with plant development in winter-spring, and declined in autumn-winter crop. Distribution of total N, P2O5 and K2O at different part of cucumber at fruit bearing stage was significantly influenced by inside light and temperature of solar greenhouse. Total N, P2O5 and K2O were mainly distributed to leaves and stems at early stage, and increasingly to fruits after fruit bearing.

Three‐terminal perovskite/integratedbackcontactsilicon tandem solar cells under low light intensity conditions

The current climate and energy crisis urgently needs solar cells with efficiencies above the 29% single junction efficiency bottleneck.Silicon/perovskite tandem solar cells are a solution,which is attracting much attention.While silicon/perovskite tandem cells in 2-terminal and 4-terminal configurations are well documented,the three-terminal concept is still in its infancy.It has significant advantages under low light intensities as opposed to concentrated sunlight,which is the critical factor in designing tandem solar cells for low-cost terrestrial applications.This study pre-sents novel studies of the sub-cell performance of the first three-terminal perovskite/silicon selective band offset barrier tandem solar cells fabricated in an ongoing research project.This study focuses on short circuit current and operating voltages of the subcells under light intensities of one sun and below.Lifetime studies show that the perovskite bulk carrier lifetime is insensitive to illumination,while the silicon cell's lifetime decreases with decreasing light intensity.The combination of perovskite and silicon in the 3T perovskite-silicon tandem therefore reduces the sensitivity of V_(OC) to light intensity and maintains a relatively higher V_(OC) down to low light intensities,whereas silicon single-junction cells show a marked decrease.This technological advantage is proposed as a novel advantage of three-terminal perovkite/silicon solar cells for low light intensities of one sun or less.

Measuring light spectrum as a main indicator of artificial sources quality

Objective:To compare different artificial light sources in different places where plant breeding is conduced.Methods:Measurements were conducted outdoor,in room,in greenhouse,under four panels with light emitting diodes,in phytotron,in dark room with various light sources and inside Sanyo versatile environmental chamber.The measurements were made by using SpectraPen SP100(PSI,Czech Republic)device.Results:Our result showed that spectrum measured outdoor during sunny day had only one peak at the wavelength of 485 nm(ca.60000 relative units).On cloudy day,the trend of light spectrum curve was similar,but with lower values.At room conditions,the curve was more flat than outdoor.Under greenhouse conditions,the curve was similar to that measured outdoor.A few additional peaks on the curve appeared by adding high pressure sodium lamp.There were changes of curve under LED panels.Conclusions:It must be underlined that the most similar spectrum curve to daylight light has incandescent bulb and this light source should be preferred as support of daylight in greenhouses and as main source in phytotrons.Using high pressure sodium lamp in greenhouses as support of daylight cause increase in the red/far-red ratio and occurrence of a new peak on spectrum curve.The new possibilities are creating by LED panels with red and blue diodes.

Egg rejection based on egg size recognition as a specific strategy against parasitic cuckoos

In the coevolutionary interactions between avian brood parasites and their hosts,egg recognition based on color and/or pattern is a common and effective defense to counter parasitism.However,for egg recognition based on size,only a few studies have found affirmative results,and they do not provide unambiguous evidence that egg size recognition in hosts has evolved as an important and specific anti-parasite adaptation against parasite eggs.We studied the brood parasite system between the Asian emerald cuckoo Chrysococcyx maculatus and its host,the chestnut-crowned warbler Phylloscopus castaniceps.The cuckoo parasitizes the warbler using non-mimetic and larger eggs at a parasitism rate of 12.9%.The warbler nests used in this experiment were built in a dark environment with the nest illuminance near 0 lux.Experiments with 2 types of model eggs with colors and patterns resembling cuckoo eggs of different sizes(cuckoo egg size or host egg size)showed that the warblers were able to reject 63.6%of cuckoo model eggs under these dim light conditions.However,model eggs with the same color and pattern similar to the warbler egg size were always accepted.This study provides strong evidence supporting the theory that egg size recognition can be evolved in hosts as a specific anti-parasite adaptation against cuckoos.We suggest that the egg size recognition of the warbler is an outcome of the tradeoff between the costs of violating the parental investment rule and suffering cuckoo parasitism.