Light Threshold Research Articles

Periodically asymmetric responses of deep chlorophyll maximum to light and thermocline in a clear monomictic lake: Insights from monthly and diel scale observations

Deep chlorophyll maximum (DCM), a chlorophyll peak in the water column, has important implications for biogeochemical cycles, energy flow and water surface algal blooms in deep lakes. However, how an observed periodically asymmetric DCM response to environmental variables remains unclear, limiting our in-depth understanding and effective eco-environmental management of deep lakes. Based on both monthly field investigations in 2021 and diel continuous observations in 2021–2023 in clear, monomictic Lake Fuxian, Southwest China, the temporal dynamics and drivers of DCM were examined and periodic features of DCM were found, with a formation period (FP, February–July) and a weakening period (WP, August–December). On the monthly scale, although DCM dynamics were partly attributed to thermocline structures, the role of light penetration depths varied with period. In the FP, the influence of light on DCM was direct, i.e., increased depth and thickness but decreased magnitude. Differently, the influence of light mainly occurred by affecting thermocline structures in the WP, where water quality was another important driver. On the diel scale, light was a major reason for a thicker and lower (magnitude) DCM during day than at night, and the response of DCM to environmental factors between the FP and WP differed also more during day. This periodically asymmetric response of daytime DCM not only being caused by light but possibly also related to other physical factors such as lake surface water temperature, wind speed and precipitation. Bayesian network modelling suggested that water darkening and stratification intensification may promote a shallower, thinner and larger (magnitude) DCM in both FP and WP, but achieving such changes in DCM requires different light and thermocline thresholds. Our findings provide new information valuable for modelling DCM and for predicting the related surface algal blooms in deep lakes under climate change and eutrophication.

Light sensitivity of the circadian system in the social Highveld mole-rat Cryptomys hottentotus pretoriae.

Highveld mole-rats (Cryptomys hottentotus pretoriae) are social rodents that inhabit networks of subterranean tunnels. In their natural environment, they are rarely exposed to light, and consequently their visual systems have regressed over evolutionary time. However, in the laboratory they display nocturnal activity, suggesting that they are sensitive to changes in ambient illumination. We examined the robustness of the Highveld mole-rat circadian system by assessing its locomotor activity under decreasing light intensities. Mole-rats were subjected to seven consecutive light cycles commencing with a control cycle (overhead fluorescent lighting at 150lx), followed by decreasing LED lighting (500, 300, 100, 10 and 1lx) on a 12h light:12h dark (L:D) photoperiod and finally a constant darkness (DD) cycle. Mole-rats displayed nocturnal activity under the whole range of experimental lighting conditions, with a distinct spike in activity at the end of the dark phase in all cycles. The mole-rats were least active during the control cycle under fluorescent light, locomotor activity increased steadily with decreasing LED light intensities, and the highest activity was exhibited when the light was completely removed. In constant darkness, mole-rats displayed free-running rhythms with periods (τ) ranging from 23.77 to 24.38 h, but was overall very close to 24 h at 24.07 h. Our findings confirm that the Highveld mole-rat has a higher threshold for light compared with aboveground dwelling rodents, which is congruent with previous neurological findings, and has implications for behavioural rhythms.

Band structure regulation for improving the photoinduced cathodic protection performance of TiO2/ZnxIn2S3+x heterojunctions

The degree of band matching is crucial for the photoelectric conversion performance of heterojunctions. In this work, TiO2/ZnxIn2S3+x (TO/ZIS-X, X=1, 2, 3, 4) heterostructures and their electrochemical and photoelectrochemical tests were studied. According to the energy band analysis of a series of TO/ZIS-X, it is found that I-type heterojunction can be formed between TO and ZIS-1, while Z-type heterojunction would be formed between TO and ZIS-2, ZIS-3 and ZIS-4. The photoinduced potential drop associated with current density of TO/ZIS-2 in 3.5 wt% NaCl are 505.82 mV and 18.61 μA·cm−2, respectively. This result is much higher than those of homogeneous TO and single-phase ZIS-X. The desirable photoelectrochemical cathodic protection performance of the photoelectrode is owing to the loading of ZnxIn2S3+x, which broadens the light absorption threshold and improves the electrochemical activity area. Besides, the construction of Z-type heterojunction retains the photogenerated electrons/holes with strong reduction/oxidation ability, which greatly promotes the photoelectrochemical cathodic protection capability on 316 L stainless steel.

High performance composite phosphor-in-glass film for laser-driven warm white light on patterned sapphire substrate

Phosphor-in-glass film (PiF) based on sapphire substrate (SS) is a promising laser-driven color converter. Herein, by using an optimized silicon borate glass component, high-performance Y3Al5O12:Ce3+ PiFs are successfully prepared on both flat sapphire substrate (FSS) and patterned sapphire substrate (PSS) surfaces. Compared with planar structure of FSS, PSS has a periodic arrangement of conical structures on its surface, which effectively increases the contact area between the PiF and the substrate by approximately 56%, thereby forming a more robust film composite structure. The blue laser light is affected by the structure of PSS and produces a typical diffraction effect, which realizes the dispersion of the convergent beam. This significantly expands the laser spot on PSS-PiF and improves the uniformity of light. The saturation power density of PiF-PSS (6.29 W/mm2) is found to be 91% higher than that of PiF-FSS, while maintaining a high luminous efficiency (220 lm/W) and a low correlated color temperature (4500 K). Finally, the thermal quenching mechanism of PiF with different substrate surface morphologies is compared and analyzed. The present results provide important support for designing the interface structure between SSs and PiF to achieve higher efficiency and higher saturation threshold for warm white light.

Design of 1450-1500nm Bismuth-doped Fiber Laser

With the rapid development of information technology, people's demand for the transmission capacity of fiber optic communication networks is increasing. How to broaden the bandwidth of communication systems has become one of the key issues in the field of communication. Researchers have found that the operating bandwidth of amplifiers mainly limits the bandwidth of communication systems. Although multiple solutions have been proposed and implemented to address this issue, there are still many gaps in the design of full-band multi wavelength-related light sources. By studying the three-level system of bismuth ions, the rate equation and power transfer equation of a bismuth ion doped fiber laser are simulated, and the pump power threshold and output power are calculated. Using MATLAB for simulation experiments, the relationship between laser power and pump power, as well as their variation with propagation distance, were ultimately obtained. The simulation results show that under 830 pump lights, the pump light threshold power is 10W. After reaching the threshold power, the pump light power and laser power have a linear relationship, and as the propagation distance increases, the pump light power gradually decreases and the laser power gradually increases. The analysis shows that the power generated by the signal light in this band meets the theoretical standards, which verifies the correctness of the scheme.

Relationship between sensation and balance and gait in multiple sclerosis patients with mild disability

BackgroundPatients with Multiple Sclerosis (PwMS) often experience sensory, balance, and gait problems. Impairment in any sensation may increase imbalance and gait disorder in PwMS. This study aimed to (1) compare foot plantar sensations, knee position sense, balance, and gait in PwMS compared to Healthy Individuals (HI) and (2) examine the relationship between plantar sensations, knee position sense, balance, and gait in PwMS. MethodsThirty PwMS with mild disability and 10 HI participated in this study. Light touch threshold, two-point discrimination, vibration duration, and knee position sense were examined on the Dominant Side (DS) and Non-Dominant Side (NDS). Balance and spatio-temporal gait analysis were evaluated in all participants. ResultsPwMS had higher postural sway with eyes closed on the foam surface, longer swing phase of DS, longer single support phase of NDS, and shorter double support phase of DS compared to HI (p < 0.05). The results of regression analysis showed that the light touch thresholds of the 1st and 5th toes of the DS were associated with postural sway in different sensory conditions (p < 0.05). In contrast, the light touch thresholds of the 1st and 5th toes, two-point discrimination of the heel, vibration duration of the 1st metatarsal head and knee position sense of the NDS, and light touch threshold in the medial arch of both sides were associated with the gait parameters (p < 0.05). ConclusionPwMS, even with mild disabilities needs neurorehabilitation to improve plantar sensation and knee position sense.

Novel in-situ Ag-decorated trithiocyanuric acid polymer with superior visible light photocatalytic activity

A novel Ag-decorated trithiocyanuric acid polymer (Ag-TTCA) was fabricated via a photocatalytic reduction method based on the strong affinity between Ag ion and trithiocyanic acid (TTCA). The as-prepared photocatalysts were characterized, and the paralleled experiments were conducted on the photocatalytic oxidation of bisphenol A (BPA) to evaluate the photocatalytic activity. Compared with TTCA, Ag-TTCA has a much higher photocatalytic activity. The 0.08Ag-TTCA catalyst can remove BPA (20 mg L−1) in 240 min with a degradation efficiency as high as 96.4 %. The improved photocatalytic performance of Ag-TTCA can be attributed to the dispersed nanoparticle morphology and unique electronic structure. The dispersed nanoparticle morphology of Ag-TTCA can provide more active sites for the adsorption and degradation of pollutants. After silver modification, the light absorption threshold of TTCA is redshifted from 466 nm to 522 nm, and the corresponding band gap is reduced from 2.74 eV to 2.54 eV, which broadens the light absorption range of the photocatalyst and significantly enhances the light absorption capacity. Moreover, metal silver can trap photogenerated electrons and generate surface plasmon resonance (SPR) when illuminated by sunlight, which can effectively promote the separation of electron-hole pairs. Trapping experiment indicates that photogenerated holes, singlet oxygen and superoxide free radicals are the main active species in photocatalytic system.

Phototoxicity of low doses of light and influence of the spectral composition on human RPE cells

Light is known to induce retinal damage affecting photoreceptors and retinal pigment epithelium. For polychromatic light, the blue part of the spectrum is thought to be the only responsible for photochemical damage, leading to the establishment of a phototoxicity threshold for blue light (445 nm). For humans it corresponds to a retinal dose of 22 J/cm2. Recent studies on rodents and non-human primates suggested that this value is overestimated. In this study, we aim at investigating the relevance of the current phototoxicity threshold and at providing new hints on the role of the different components of the white light spectrum on phototoxicity. We use an in vitro model of human induced pluripotent stem cells (hiPSC)-derived retinal pigment epithelial (iRPE) cells and exposed them to white, blue and red lights from LED devices at doses below 22 J/cm2. We show that exposure to white light at a dose of 3.6 J/cm2 induces an alteration of the global cellular structure, DNA damage and an activation of cellular stress pathways. The exposure to blue light triggers DNA damage and the activation of autophagy, while exposure to red light modulates the inflammatory response and inhibits autophagy.

Construction of yield loss indicators for cold vortex, light-temperature-water combined stress during the flowering period of rice in Northeast China.

The construction of a yield loss evaluation index for the cold vortex type light-temperature-water composite adversity during rice flowering period in Northeast China is important for elucidating the impacts of cold vortex type composite disasters on rice yield loss in middle and high latitude areas. Moreover, it can provide meteorological support to ensure safe production of high-quality japonica rice in China and contribute to regional disaster reduction and efficiency improvement. By combining growth period data, meteorological data, and yield data, we delineated and constructed the composite stress occurrence index of cold vortex type light-temperature-water at the flowering stage of japonica. We analyzed the relationship between factors causing disasters and yield structure, as well as the relationship between different yield structures and yield by employing BP neural network method. We further dissected the processes involved in the causation of combined disasters. Based on the K-means clustering method and historical typical disaster years, we quantified the critical thresholds and disaster grades, and established an evaluation index and model for assessing yield loss caused by combined stress from cold vortex type light-temperature-water. Finally, we examined the spatial and temporal variations of low temperature, abundant rainfall, and reduced sunlight during the flowering period in the three provinces of Northeast China. Results showed that the critical thresholds for light, temperature, and water stress index during the flowering stage of mild, moderate, and severe cold vortex types were [0, 0.21), [0.21, 0.32), and [0.32, 0.64], respectively. The rates of yield loss were [0, 0.03), [0.03, 0.08), and [0.08, 0.096], respectively. Based on the verification results of a total of 751 samples in 11 random years from 1961 to 2020, the percentage of stations for which the production reduction grade, as calculated by the composite index developed in this study, aligning with the actual production reduction grade was 63.7%, consistently exceeding 58.0% annually. Moreover, the proportion of sites with a similarity or difference level of 1 stood at 88.3%, surpassing 85.0% in each year. The index could effectively assess the extent of rice yield loss caused by cold vortex disasters in Northeast China.

Limited associations between passive range of motion and gross motor function in ambulant/semi-ambulant children and adolescents with cerebral palsy: A cross-sectional study

Background and aimCerebral palsy (CP) is the most common childhood motor disability, and the Cerebral Palsy Follow-Up Program (CPUP) in Nordic countries uses a traffic light system for passive range of motion (ROM) assessment to aid interpretation and guide decisions regarding interventions. However, the arbitrary chosen ROM threshold values and their potential clinical impact are uncertain. We investigated whether lower extremity ROM values were positively associated with gross motor function and whether gross motor function scores differ between the CPUP ROM thresholds. MethodsThis was a cross-sectional analysis of CPUP data for 841 ambulatory children and adolescents with CP, at a mean (SD) age of 9 (3). Regression analyses were employed to explore the relationship between gross motor capacity and performance (using the Gross Motor Function Measure (GMFM-66) and the Functional Mobility Scale (FMS) 5/50/500 m, respectively) and lower extremity ROM, measured with a goniometer. ROM was assessed both as continuous and categorical variables. ResultsWe found that two out of ten continuous ROM measures were positively associated with gross motor function. Limited differences in gross motor function between the ROM thresholds were seen for seven out of ten ROM measures. The CPUP traffic light thresholds primarily differentiated gross motor function between the red and green categories, predominantly for the subgroup of participants with bilateral spastic CP. ConclusionLimited associations between passive ROM and gross motor function in children and adolescents with CP were observed, indicating that there is more to consider than ROM when identifying whether interventions are needed.

Induced seismicity traffic light protocol at the Alberta No. 1 geothermal project site

The Alberta No. 1 Geothermal Project (ABNo1) is a renewable energy project in Canada; it will use deep geothermal energy for electrical power generation and direct-use thermal power. However, concerns regarding induced seismicity must be addressed. This study proposes implementing the Traffic Light Protocol (TLP) as a risk management tool for conventional geothermal projects in Alberta. We focus on determining an appropriate TLP red-light threshold, employing a risk-informed approach for the Leduc Formation - one of the geothermal reservoirs proposed for development by ABNo.1. The recommended red-light threshold of ML 3.5 signifies the level at which operations must be halted (i.e., the red light) to mitigate nuisance impact, damage, and personal risk. The recommended yellow light threshold of ML 1.5 signifies the level at which assessment of injection operations must be re-assessed, the regulator must be informed, and a risk mitigation analysis must be undertaken to re-evaluate operations to keep induced seismicity at a low magnitude. Comparison to induced seismicity near the project site highlights key factors requiring consideration during the project's design phase: injection volume, chances of basement fault reactivation, and delayed seismic activity onset. Effective mitigation entails controlling injection rate, continuous fluid balance monitoring, allowing gradual and appropriate pressure dissipation rates, and potentially the use of tracer tests to deconvolve pathways. This study provides insights for stakeholders involved in injection projects, aiding risk mitigation and ensuring safe, sustainable energy extraction while also prioritizing the local community's well-being.

Impacts of the stochastically perturbed parameterization on the precipitation ensemble forecasts of the Betts–Miller–Janjić (BMJ) scheme in Eastern China

This study investigated the impact of stochastic perturbations on precipitation forecasts generated by the Betts-Miller-Janjic (BMJ) cumulus parameterization scheme. Two types of stochastic perturbation approaches were compared. The first approach involved perturbing the temperature and humidity tendencies derived from the BMJ scheme. The second approach focused on perturbing the reference profiles of temperature and humidity estimated within the BMJ scheme. These profile perturbations led to reference profiles becoming either warmer and wetter or colder and drier. Ten precipitation cases occurring in eastern China during the summer of 2019 were selected to evaluate the different perturbation methods. The default BMJ scheme exhibited a significant wet bias at the light rain threshold due to overestimating entropy change and a dry bias at the heavier rain threshold. The tendency perturbation approach, which perturbed the temperature and humidity, did not affect the entropy change and produced precipitation placement similar to its unperturbed counterpart. These attributes resulted in a small ensemble spread and relatively low forecast skill scores. Perturbing the reference profiles, conversely, influenced the entropy change in the BMJ scheme, leading to a larger ensemble spread and higher forecast skill scores regarding the spatial distribution of precipitation. Asymmetrically perturbing the reference profiles considered the wet bias, which increased the grid points with negative entropy change and outperformed the symmetric perturbation. The asymmetric perturbation also increased the chance of heavier rain because more water was retained in the air, alleviating the corresponding dry bias.

Low-Light Image Enhancement Method for Electric Power Operation Sites Considering Strong Light Suppression

Insufficient light, uneven light, backlighting, and other problems lead to poor visibility of the image of an electric power operation site. Most of the current methods directly enhance the low-light image while ignoring local strong light that may appear in the electric power operation site, resulting in overexposure and a poor enhancement effect. Aiming at the above problems, we propose a low-light image enhancement method for electric power operation sites by considering strong light suppression. Firstly, a sliding-window-based strong light judgment method was designed, which used a sliding window to segment the image, and a brightness judgment was performed based on the average value of the deviation and the average deviation of the subimages of the grayscale image from the strong light threshold. Then, a light effect decomposition method based on a layer decomposition network was used to decompose the light effect of RGB images with the presence of strong light and eliminate the light effect layer. Finally, a Zero-DCE (Zero-Reference Deep Curve Estimation) low-light enhancement network based on a kernel selection module was constructed to enhance the low-light images with reduced or no strong light interference. Comparison experiments using the electric power operation private dataset and the SICE (Single Image Contrast Enhancement) Part 2 public dataset showed that our proposed method outperformed the current state-of-the-art low-light enhancement methods in terms of both subjective visual effects and objective evaluation metrics, which effectively improves the image quality of electric power operation sites in low-light environments and provides excellent image bases for other computer vision tasks, such as the estimation of operators’ posture.

Diel vertical migration in Pacific sand lance (Ammodytes personatus)—a pelagic forage fish associated with benthic substrates

AbstractDiel vertical migration (DVM) in marine organisms is an evolved response to maximize foraging opportunities and minimize predation risk. This pattern in vertical distribution is a widely observed phenomenon and common in pelagic forage fish species. Modelling these dynamics has important relevance to understanding marine ecosystem dynamics, predator–prey interactions, and marine food webs. We examine DVM in sand lance—an ecologically important taxa of forage fishes throughout northern hemisphere marine systems and target of commercial fisheries. Much remains unknown about their diurnal emergence from sediments. We apply data from autonomous stereo-camera deployments and tank observations to provide new insight to DVM patterns in Pacific sand lance (Ammodytes personatus). We model emergence curves using beta regression models with random effects, depicting important differences in the shape of ascent and descent. Our observations and analyses document crepuscular movement patterns, suggesting pelagic foraging occurs primarily at dawn and dusk. Results suggest critical light thresholds are necessary to initiate and maintain pelagic foraging. Results also suggest the importance of seasonality and life stage, such that adult fish exhibit reduced pelagic foraging in the fall relative to juvenile fish. These results constitute a comprehensive evaluation of DVM in this species, better define the physical drivers, and mathematically depict the pattern and shape of emergence timing.

A Mo doping WO3/CdZnS heterojunction photoelectrode for boosting electron storage capacity

Most of the photoelectrodes for photoelectrochemical cathodic protection (PECCP) technology reported at present cannot store electrons, leading to the inability to protect metals in the absence of light, which becomes the main defect that limits the practical application of PECCP. In this work, a Mo doping WO3/CdZnS heterojunction photoelectrode with electrons storage capability was prepared, by which the PECCP can be kept running in the absence of light. The result of theoretical calculation of density functional validates that Mo doping can introduce new doping levels into WO3, leading to modifications in the intrinsic electronic structure associated with increasing capacitance and conductivity. The compounding of CdZnS can not only broaden the light absorption threshold of the photoelectrode, but also charge the Mo-WO3. Besides, the construction of heterojunction also facilitates the oriented separation and migration of photogenerated carriers. The 0.3%Mo-WO3/CdZnS-2 composite photoelectrode with desirable capacity of electron storage can store the quantity of electric charge about 1.87 × 10−3 C after 100 s illumination, which is about 1.5 times of WO3/CdZnS-2 without Mo doping. In the meanwhile, the persistent PECCP performance in the absence of light was also prolonged from 481 s to 584 s.

Facet-dependent CuO/{010}BiVO4 S-scheme photocatalyst enhanced peroxymonosulfate activation for efficient norfloxacin removal

Rapid recombination of charge carriers and sluggish Cu2+/Cu+ conversion rate in Cu-based photocatalysts hinder the improvement of the peroxymonosulfate (PMS) activation efficiency. Herein, a novel S-scheme system was successfully built through hydrothermal and in-situ calcination methods to activate PMS for norfloxacin (NOR) degradation, which combined CuO with BiVO4 (BVO) containing surface heterojunction. The UV–vis spectra manifested that BVO displayed excellent visible light absorption performance after compounding with CuO, and the light absorption threshold of CuO/BVO was about 600 nm. Thanks to the existence of surface heterojunction in BVO, the photoinduced electrons, and holes would transfer to {010} and {110} facets, respectively. The construction of S-scheme heterojunction further facilitated the accumulation of electrons on CuO, thus realizing the spatial separation of charge carriers. In addition, the electrons gathered on the CuO expedited the Cu2+/Cu+ cycle, thereby improving the activation efficiency of PMS. On this basis, the NOR removal capacity of 5CuO/BVO composites was obviously enhanced, which was 3.65 and 2.45 times that of CuO and BVO. Moreover, the influence of ambient pH and PMS dosage on the photocatalytic performance of CuO/BVO was investigated. Through the analysis of NOR degradation pathways and degradation products, it was found that the toxicity threat of NOR to the environment was reduced during the degradation process. According to the XPS results, forming the S-scheme heterojunction accelerated the Cu2+/Cu+ redox cycle during the PMS activating process. Meanwhile, photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis demonstrated that the CuO/BVO composites exhibited eminent ability for charge separation. The possible mechanism of charge transfer was assumed by exploring reactive species and the energy band structure of catalysts. To sum up, this research provides a new perspective on boosting PMS activation to purify antibiotics in water.

Light limitation and coral mortality in urbanised reef communities due to sea-level rise

Sea-level rise (SLR) is expected to elevate the depth of seawater above shallow coral reefs, reducing light availability to the benthic environment, and impacting the survival and growth of corals especially on turbid reefs. However, the extent of impact at the deepest reef zones remains unknown. Coral growth could continue to keep pace above light thresholds as sea level rises, but mortality due to light limitation could vary between localities and local conditions. Here, we examine possible outcomes of corals inhabiting Singapore's turbid reefs in the years 2050 and 2100 by characterising their depth distributions and predicting potential mortality rates based on SLR projections. Our results reveal that in 2050, under both RCP4.5 and RCP8.5 sea level projections, up to 6.24% of colonies could face mortality if their growth is not considered. In 2100, up to 7.68% mortality under RCP4.5 and up to 10.7% mortality under RCP8.5 are predicted. When coral linear extension is considered, in 2050, under both RCP4.5 and RCP8.5 sea level projections, up to 1.03% of colonies could face mortality. In 2100, up to 0.87% mortality under RCP4.5 and up to 1.84% mortality under RCP8.5 are predicted. Species-specific losses could amount to 20% of colonies primarily at the deepest zones. The most vulnerable species exhibit a depth distribution with most colonies situated at the deeper parts of their depth ranges. Our findings suggest that sea-level rise may potentially result in the loss of coral cover for some species, but overall mortality could be low.

Reduced eye optical quality contributes to worse chromatic thresholds in aging.

Aging causes substantial changes in the intraocular lens, which leads to a reduction in chromatic perception. We aimed to measure the ocular light dispersion component in relation to the reduction in color vision by aging. Intraocular straylight was quantified psychophysically by C-Quant for light dispersion [Log(s)], reliability of the results (ESD), and psychometric sampling quality (Q). The Cambridge Color Test Trivector protocol measured the chromaticity thresholds for protan, deutan, and tritan color confusion axis in CIE 1976 u' v' units. We tested 224 subjects aged 24-68 years (106 men) with normal best-corrected visual acuity and without clinical evidence of cataracts. A significant positive correlation was found between ocular dispersion of light and chromaticity thresholds for protan (r = 0.42; p < 0.001), deutan (r = 0.49; p < 0.001) and tritan (r = 0.51; p < 0.0001) color confusion axes with a moderate effect size (η2 = 0.39). However, a weak contribution of the logarithm of the straylight in predicting the chromaticity threshold for protan (b = 0.15; p = 0.025), deutan (b = 0.27; p = 0.001) and tritan (b = 0.21; p = 0.001) color confusion axes was verified in the regression coefficients. The other two measurement quality parameters estimated in the C-Quant were not correlated with chromaticity thresholds, suggesting that there are no problems with the quality of the measurement performed. An increase in ocular light dispersion that occurs physiologically with aging negatively impacts the chromaticity threshold in a similar manner across all three color confusion axes. The weak regression effects suggest that neural rather than optical processes were more related to the reduction in chromaticity in aging.

New insights into the photocatalytic mechanism of pristine ZnO nanocrystals: From experiments to DFT calculations

Zinc oxide (ZnO) has been regarded as a promising photocatalytic candidate for the purification of wastewaters containing organic contaminants. In this study, six ZnO nanocrystals with the shapes of granule, flake, rod, porous flake, nanosheet-assembled flower, and nanorod-assembled flower were designed and synthesized to investigate the relationship between their photocatalytic activities and morphological features. All these different morphological samples had high-degree of crystallization and belonged to the hexagonal wurtzite structure of ZnO. The morphology had little effect on the light absorption threshold and band gap of these samples, but showed great effect on their adsorption performance, photocatalytic activity, and separation efficiency of photogenerated electrons and holes. The main reactive radicals generated during the photocatalytic process were O2–, OH, and holes. The theoretical calculations revealed that the polar crystal plane could facilitate the separation of charge carriers. The adsorption and distortion energies for O2 adsorbed onto different crystal planes were found to be much higher than those for H2O. These findings theoretically confirmed why O2– was the dominant group of reactive radicals.

Influence of ambient relative humidity on horizontal visibility in the two cities of western Nepal having contrasting urban-cum-industrial backgrounds and study of long-term variation

Atmospheric visibility, a measure of horizontal distance one can distinctly see with unaided eye, is affected by the scattering and absorption of visible light by the tiny particles (aerosols), or different gases present in the atmosphere. Thus, visibility is commonly considered a proxy for ambient air quality. The long-term trend of visibility may reflect the change in the air quality of a place over the period. In our study, we have analyzed historic climatological data (1977-2020) from the National Oceanic and Atmospheric Administration (NOAA) global hourly archive, for the two cities of west Nepal, namely, Bhairahawa (BWA, 27.506 °N, 83.416 °E) and Surkhet (SKH, 28.6 °N, and 81.617 °E). We have found that both of the synoptic stations exhibited persistent degraded visibility. BWA had poorer visibility conditions (poor air quality) than that of SKH since the beginning of the study period. Since 2014, the ‘annual good day’ (V ≥ 10 km ) at BWA is steadily near 0%, and the ‘annual bad day’ (V &lt; 5 km) is ≈ 60%, suggesting a degraded air quality. Similarly, we observed a notable decline in the 50th percentile of visibility in the mid-1980s at SKH, and a sharp decline of ‘good day’ since 2011. Meteorology modifies the optical properties of aerosol/ gaseous in the atmosphere, thereby, resulting in a change in visibility. In our study, we have investigated the influence of relative humidity (RH) on prevailing visibility. Although the relationship between them exists in both of the stations, it is more distinctly visible at BWA. We observed lower visibility conditions (V ≤ 3 km) occurring at an RH level as low as 50% at BWA. This indicates an abundance of specific hygroscopic aerosols, whose light extinction thresholds are as low. At BWA, the impact of RH is evident during the dry season. In contrast, the threshold value of RH is quite high (80%) at SKH and the relationship is prominent during the wet season. This alarmingly poor air quality at both stations requires a serious concern because of its adverse impact on various sectors like aviation, tourism, and public health.