Luminance Levels Research Articles

Visual dysfunction of superior colliculus and lateral geniculate nucleus in idiopathic blepharospasm

BackgroundThe etiology and pathophysiology of idiopathic blepharospasm (BP) are still largely unknown. It has been hypothesized that BP is the consequence of a dysfunction of the basal ganglia loop, although cortical areas, cerebellum, and other brainstem structures may be involved. There is some evidence that the superior colliculus (SC), a sensorimotor brainstem structure, is involved in another adult-onset focal dystonia, the cervical dystonia. To date, there is no data concerning the implication of the SC in BP. ObjectivesOur study aims to investigate the role of the SC in people with idiopathic BP compared to controls using fMRI and a visual stimulation paradigm based on luminance contrast variations. MethodsPeople with idiopathic BP and controls underwent brain fMRI using a standardized protocol, allowing modulation of visual activity in the SC, the lateral geniculate nucleus (LGN), and the primary visual cortex (V1), at increasing luminance levels (1 %, 3 %, 5 %, 9 %). ResultsTen BP women and ten sex- and age-matched controls were enrolled. Compared to controls, the BP group showed no modulation of visual responses at all luminance levels (p < 0.05) in both SC and LGN. In BP, BOLD responses in V1 were significantly lower at 5 % (p = 0.001), and 9 % (p = 0.002) luminance level. ConclusionsOur findings support the concept of SC and LGN dysfunction in idiopathic BP. Brain fMRI, targeting these sub-cortical visual structures, could play a future important role both as a biomarker and in our understanding of the pathophysiology of adult-onset focal dystonias.

Clar's Aromatic π‐Sextet Rule for the Construction of Red Multiple Resonance Emitter

AbstractDespite the proliferation of multiple resonance (MR) materials in the blue to green spectral ranges, red MR emitters remain scarce in the literature, an area that certainly warrants attention for future applications. Here, through a clever application of classic Clar's aromatic π‐sextet rule, we triumphantly constructed the first red MR emitter by substituting the conventional benzene ring core with anthracene (fewer π‐sextets). Theoretical studies indicate that the quantity of π‐sextets ultimately determines the optical band gap of a molecule, rather than the number of fused benzene rings. Benefiting from the high photoluminescence quantum yield of ~94 % and horizontal dipole ratio of ~90 %, the corresponding narrowband red (luminescence wavelength: 608 nm) organic light‐emitting diode shows a high external quantum efficiency of 27.3 %, with only a slight decrease of 3.7 % at an elevated luminance level of 100,000 cd/m2.

Phosphor Screens Color Preferences Depending on Night Vision Experience and Luminance Level.

One of the most important factors affecting visual performance during vision aided by night vision goggles (NVGs) is image quality, which depends mainly on the image-intensifier technology used. Although NVGs with green image color (P43 phosphor) are only accepted in military aviation, white image (P45 phosphor) seems to be equally well-regarded by aviators. The aim of our study was to determine if the experience of using NVGs with the green screen affects image preference for that color, and if the screen color preference is related to luminance level. Subjects (127 military pilots, 26-56 yr, M = 37.2; 62 pilots with flight experience with NVG use) were asked to observe a model terrain board at two different luminance levels (corresponding roughly to ambient conditions during starlight and one-half moonlight) while using two types of NVGs (green P43 and white P45 phosphor screens). The pilots were asked to answer a questionnaire about their preference for NVG display color. The findings showed a significant difference between screen color preference and pilots' experience with the green-phosphor-based NVGs (43.5% vs. 23.1% for white screens). However, there was no relationship between screen color preference and luminance level. Previous NVG experience seems to play an important role in shaping a user's individual preference for a certain phosphor screen color, although green and white phosphor screens both provide satisfactory visibility. Nevertheless, when deciding, it is advisable to experiment with both colors and select the one that suits the user's preferences and needs. Lewkowicz R, Dereń-Szumełda J. Phosphor screens color preferences depending on night vision experience and luminance level. Aerosp Med Hum Perform. 2024; 95(10):749-757.

Investigating causal effects of pupil size on visual discrimination and visually evoked potentials in an optotype discrimination task.

Pupil size primarily changes to regulate the amount of light entering the retina, optimizing the balance between visual acuity and sensitivity for effective visual processing. However, research directly examining the relationship between pupil size and visual processing has been limited. While a few studies have recorded pupil size and EEG signals to investigate the role of pupil size in visual processing, these studies have predominantly focused on the domain of visual sensitivity. Causal effects of pupil size on visual acuity, therefore, remain poorly understood. By manipulating peripheral background luminance levels and target stimulus contrast while simultaneously recording pupillometry and EEG signals, we examined how absolute pupil size affects visual discrimination and visually evoked potentials (VEP) in a task using optotype mimicking the Snellen eye chart, the most common assessment of visual acuity. Our findings indicate that both higher background luminance levels and higher target contrast were associated with improved target discrimination and faster correct reaction times. Moreover, while higher contrast visual stimuli evoked larger VEPs, the effects of pupil size on VEPs were not significant. Additionally, we did not observe inter-individual correlations between absolute pupil size and discrimination performance or VEP amplitude. Together, our results demonstrate that absolute pupil size, regulated by global luminance level, played a functional role in enhancing visual discrimination performance in an optotype discrimination task. The differential VEP effects of pupil size compared to those of stimulus contrast further suggested distinct neural mechanisms involved in facilitating visual acuity under small pupils.

Experimental study on effect of pavement background on obstacle visibility in LED lighting environment of road tunnel

The tunnel pavement is generally made of asphalt or concrete. Due to the relatively fixed material of pavement, the effect of tunnel pavement setting on the lighting environment and visual performance of drivers has not received sufficient attention, especially the impact on the visual performance of drivers during driving has not been revealed. Therefore, experimental research on the visual recognition performance of an obstacle on asphalt and concrete pavements inside tunnels during dynamic driving was conducted in this study. The results indicate that under the same pavement illumination, the luminance on concrete pavement is higher than that on asphalt pavement due to the higher reflectance of concrete. The visible distance of the human eyes for a gray obstacle with a reflectance of 0.2 on the concrete pavement is greater than that on the asphalt pavement, and the visible distance of the obstacle on the concrete pavement increases by more than 28%. When the color of the obstacle and the pavement are close, it can be challenging for observers to recognize the obstacle, and the pavement and obstacle need to have a higher level of luminance for the recognition. During dynamic driving, the visible distance at a speed of 60 km/h is 1.2 to 1.4 times that at a speed of 80 km/h, which means the influence of vehicle speed on the human eye’s recognition of obstacles on asphalt and concrete pavements should be taken into consideration in the design of road tunnel lighting. The correlated color temperature and S/P value of LED light have little impact on the visible distance of human eyes to the obstacle on the asphalt and concrete pavements, but it does create different visual perceptions. As the correlated color temperature and S/P value increase, the lighting environment of the tunnel gradually gives a brighter feeling to drivers.

The effects of emotional arousal on pupil size depend on luminance

Pupillometry is widely used to measure arousal states. The primary functional role of the pupil, however, is to respond to the luminance of visual inputs. We previously demonstrated that cognitive effort-related arousal interacted multiplicatively with luminance, with the strongest pupillary effects of arousal occurring at low-to-mid luminances (< 37 cd/m2), implying a narrow range of conditions ideal for assessing cognitive arousal-driven pupillary differences. Does this generalize to other forms of arousal? To answer this, we assessed luminance-driven pupillary response functions while manipulating emotional arousal, using well-established visual and auditory stimulus sets. At the group level, emotional arousal interacted with the pupillary light response differently from cognitive arousal: the effects occurred primarily at much lower luminances (< 20 cd/m2). Analyses at the individual-participant level revealed qualitatively distinct patterns of modulation, with a sizable number of individuals displaying no arousal response to the visual or auditory stimuli, regardless of luminance. Together, our results suggest that effects of arousal on pupil size are not monolithic: different forms of arousal exert different patterns of effects. More practically, our findings suggest that lower luminances create better conditions for measuring pupil-linked arousal, and when selecting ambient luminance levels, consideration of the arousal manipulation and individual differences is critical.

Clar's Aromatic π-Sextet Rule for the Construction of Red Multiple Resonance Emitter.

Despite the proliferation of multiple resonance (MR) materials in the blue to green spectral ranges, red MR emitters remain scarce in the literature, an area that certainly warrants attention for future applications. Here, through a clever application of classic Clar's aromatic π-sextet rule, we triumphantly constructed the first red MR emitter by substituting the conventional benzene ring core with anthracene (fewer π-sextets). Theoretical studies indicate that the quantity of π-sextets ultimately determines the optical bandgap of a molecule, rather than the number of fused benzene rings. Benefiting from the high photoluminescence quantum yield of ~94% and horizontal dipole ratio of ~90%, the corresponding narrowband red (luminescence wavelength: 608 nm) organic light-emitting diode shows a high external quantum efficiency of 27.3%, with only a slight decrease of 3.7% at an elevated luminance level of 100,000 cd/m2.

Reading comfort in relation to monitor and ambient luminance levels: A study using continuous rating scale and paired comparison methodology

In this work, it is investigated how reading comfort is influenced by monitor and ambient luminance levels, when employing high-luminance monitors. High-luminance monitors can be used to get more light on the eye and elicit non-image-forming effects. However, this might lead to reduced reading comfort. Two psychophysical methods, a continuous rating scale and paired comparison, were employed to investigate reading comfort in relation to the luminance of the monitor and the ambient environment. The results of 18 observers for the continuous rating scale experiment (aged 20 y to 30 y) and 20 observers for the paired comparison experiment (aged 20 y to 37 y) indicate that reading comfort is significantly influenced by both monitor and ambient luminance levels The paired comparison methodology provided more distinctive capabilities and thus offered a deeper insight. In contrast to prior work suggesting a linear relation between monitor luminance and preferred ambient luminance, the current results indicate that the reading comfort level reaches a tipping or saturation point. A monitor luminance level of 260 cd m−2 combined with an ambient luminance level of 68 cd m−2 provided the highest reading comfort. This reading comfort could not be matched when employing a higher monitor luminance level of 700 cd m−2.

Manipulating excited states for constructing ultraviolet hybridized local and charge transfer fluorophores and non-doped OLEDs with high color purity

The development of efficient ultraviolet (UV) organic light-emitting materials and devices holds paramount significance for their practical applications. Nonetheless, attaining a short-wavelength electroluminescence peak of less than 390 nm while maintaining high color purity in non-doped devices remains a formidable challenge. In this work, we have successfully designed and synthesized two UV hybridized local and charge transfer fluorophores, specifically 4DBF-CZCN and 2DBF-CZCN, which are comprised of cyanide-modified phenylcarbazole and a weak electron donor dibenzofuran. And the properties of excited state are well regulated through the different linking site of dibenzofuran. The resulting non-doped devices exhibit not only emission peak wavelengths of 390 and 388 nm, accompanied by narrow full-width-at-half-maximums of 42 and 38 nm, respectively, corresponding to color coordinates of (0.164, 0.034) and (0.164, 0.036), but also admirable external quantum efficiencies of 3.00 % and 2.86 % at high luminance levels of 1910 and 1252 cd m−2, respectively.

Evaluating the perceived brightness of chromatic stimuli with backgrounds of varying luminance

AbstractReproducing near‐gamut colors on an emissive display often causes them to appear brighter than an achromatic color of the same luminance. This phenomenon can be explained by the Helmholtz–Kohlrausch (H–K) effect, which describes an increase in perceived brightness when increasing the chroma of a stimulus. Although recent studies have attempted to incorporate the H–K effect into their modeling, none of these studies have directly explored how the perception of chromatic stimuli changes with background luminance. In this article, we present results from a psychophysical brightness‐matching experiment conducted across different levels of background luminance. The experimental results show the magnitude of the H–K effect upon simultaneous lightness contrast for high chroma colors. We, then, compare our results to CAM16 and other published models that propose modifications to CAM16 to account for the H–K effect. The findings reveal that CAM16 overestimates the perceived rate of lightness change by more than double for highly saturated, low luminance colors with increasing background luminance levels. Despite the progress made in incorporating the H–K effect into models, our study indicates the need for further data to establish a more accurate and robust modeling of this phenomenon.

Increased color preference through the introduction of luminance noise in chromatic stimuli

Humans exhibit consistent color preferences that are often described as a curvilinear pattern across hues. The recent literature posits that color preference is linked to the preference for objects or other entities associated with those colors. However, many studies examine this preference using isoluminant colors, which don’t reflect the natural viewing experience typically influenced by different light intensities. The inclusion of random luminance levels (luminance noise) in chromatic stimuli may provide an initial step towards assessing color preference as it is presented in the real world. Employing mosaic stimuli, this study aimed to evaluate the influence of luminance noise on human color preference. Thirty normal trichromats engaged in a two-alternative forced-choice paradigm, indicating their color preferences between presented pairs. The chromatic stimuli included saturated versions of 8 standard hues, presented in mosaics with varying diameters under different luminance noise conditions. Results indicated that the inclusion of luminance noise increased color preference across all hues, specifically under the high luminance noise range, while the curvilinear pattern remained unchanged. Finally, women exhibit a greater sensitivity to the presence of luminance noise than men, potentially due to differences between men and women in aesthetic evaluation strategies.

Redesign of the electrical power and lighting network at ice cream parlor located in the city of Quito

Abstract This article proposes the redesign of the electrical power and lighting network in an Ice Cream Parlor located in the city of Quito to ensure continuity in the electrical service and a luminous level according to the UNE 12464.1 Standard, established in the country. For this purpose, a survey of all the electrical load installed in the organization was carried out, where the nominal parameters of each equipment were identified with the help of the nameplate of each one of them. Using the specifications of the Ecuadorian Construction Standard (NEC) and the data obtained from the electrical load survey, five (5) circuits for outlets were proposed, considering a possible expansion of small equipment and the ten (10) maximum outlets established by the aforementioned standard. Additionally, four (4) circuits were proposed to feed the power load. With respect to the lighting network, the DIAlux software is used to determine the number of lamps, luminaires and their location to comply with the luminous level indicated. Therefore, it was necessary to propose six (6) circuits in order not to exceed the fifteen (15) lighting points established by the NEC. For each circuit, the following was calculated: conductor cross section, overcurrent protection, type of insulation and the diameter of the corresponding conduit to protect the conductors. Finally, quotations were made for the materials required for the implementation of the project. From these, an organization is selected, based on the availability of the necessary materials, their cost and accessibility, compared to other suppliers. The total amount of the proposal is US$2,518.24.

Manipulating the photophysical properties of multi-donor molecules for fast reverse intersystem crossing in solution-processed OLED devices

The slow reverse intersystem crossing (RISC) rate in thermally activated delayed fluorescence (TADF) emitters result in extended exciton lifetime and pronounced efficiency loss at high luminance level. To address this limitation, we have developed and characterized a series of novel compounds featuring triazine cores substituted with tert-butyl carbazole moieties at various positions and quantities. The objective here is to fine-tune the charge transfer properties, thereby enhancing the efficiency of the RISC process. Our studies reveal that through-space charge transfer is more effective than long-range through-bond charge transfer in minimizing the singlet-triplet energy gap and accelerating RISC. The optimized compound, 4tCzTrz, exhibits an exceptionally fast RISC rate of 1.02 × 107 s−1 and a high photoluminescence quantum yield of up to 100 %. Solution-processed organic light-emitting diodes (OLEDs) incorporating this molecule have achieved outstanding maximum external quantum efficiencies of around 20 %, whether used as an emitter directly or as a sensitizer to boost overall emission efficiency.

Iron Overload-induced Ferroptosis as a Target for Protection against Obliterative Bronchiolitis after Orthotopic Tracheal Transplantation in Mice.

The major complication of Obliterative Bronchiolitis (OB) is characterized by epithelial cell loss, fibrosis, and luminal occlusion of the terminal small airways, which limits the long-term survival of the recipient after lung transplantation. However, the underlying mechanisms are still not fully clarified. This research aims to investigate whether iron overload-induced ferroptosis is involved in OB development and provide a new target for OB prevention. Allograft orthotopic tracheal transplantation in mice was applied in our study. Ferrostatin-1 and deferoxamine were administrated to inhibit ferroptosis and get rid of ferric iron, while iron dextran was used to induce an iron overload condition in the recipient. The histological examination, luminal occlusion rate, collagen deposition, iron level, ferroptosis marker (GPX4, PTGS2), and mitochondrial morphological changes of the graft were evaluated in mice. Our research indicated that ferroptosis and iron overload contribute to OB development, while ferroptosis inhibition and iron chelator could reverse the changes. Iron overload exacerbated OB development after orthotopic tracheal transplantation via promoting ferroptosis. Overall, this research demonstrated that iron overload-induced ferroptosis is involved in OB, which may be a potential therapeutic target for OB after lung transplantation.

Color-appearance-matched data in high-dynamic-range luminance conditions

We report color-appearance-matched data under high-dynamic-range luminance conditions. The experimental method and apparatus proposed in a previous study [J. Opt. Soc. Am. A 36, 1940 (2019)JOAOD60740-323210.1364/JOSAA.36.001940] were used to measure perceptual color shifts in the R, G, B, Y, RB, BG, GY, and YR groups of 16 samples under four dual-illumination conditions at luminance levels of (300 and 4500cd/m2), (20 and 300cd/m2), (80 and 4500cd/m2), and (20 and 4,500cd/m2). We observed a decrease in lightness for all samples, and hue shifts toward blue in R, red in reddish YR, and green in BG samples when the luminance changed from low to high. Correlated changes in lightness and chroma, that is, an increase in lightness change and a decrease in chroma change under the highest luminance contrast (20 and 4500cd/m2), were observed for the Y, GY, and YR samples.

Luminance Contrast Affects the Binocular Color Fusion Limit

ABSTRACT When the color difference between the images perceived by the left eye and the right eye exceeds a certain threshold, the binocular rivalry could be activated, which is the main cause of visual fatigue. This threshold is referred to as the binocular color fusion limit. Past studies on the quantitative measurement of the binocular color fusion limit were always performed by presenting the stimulus (varying in color, disparity, size, etc.) under a dark background. To investigate how the background luminance and the luminance contrast influence the binocular color fusion limit, a series of forced-choice psychophysical experiments were conducted in a three-dimensional display for three luminance levels of both the stimulus and background. Under each luminance level, the color fusion limit for the D50 chromaticity point was measured on four opposite color directions in the CIE 1976 u F ’v F ’ uniform color space. The results show an increment of color fusion limit as the stimulus-background luminance contrast increases.

Genetic deletion of zinc transporter ZnT3 induces progressive cognitive deficits in mice by impairing dendritic spine plasticity and glucose metabolism.

Zinc transporter 3 (ZnT3) is abundantly expressed in the brain, residing in synaptic vesicles, where it plays important roles in controlling the luminal zinc levels. In this study, we found that ZnT3 knockout in mice decreased zinc levels in the hippocampus and cortex, and was associated with progressive cognitive impairments, assessed at 2, 6, and 9-month of age. The results of Golgi-Cox staining demonstrated that ZnT3 deficiency was associated with an increase in dendritic complexity and a decrease in the density of mature dendritic spines, indicating potential synaptic plasticity deficit. Since ZnT3 deficiency was previously linked to glucose metabolism abnormalities, we tested the expression levels of genes related to insulin signaling pathway in the hippocampus and cortex. We found that the Expression of glucose transporters, GLUT3, GLUT4, and the insulin receptor in the whole tissue and synaptosome fraction of the hippocampus of the ZnT3 knockout mice were significantly reduced, as compared to wild-type controls. Expression of AKT (A serine/threonine protein kinase) and insulin-induced AKT phosphorylation was also reduced in the hippocampus of ZnT3 knockout mice. We hypothesize that the ZnT3 deficiency and reduced brain zinc levels may cause cognitive impairment by negatively affecting glycose metabolism via decreased expression of key components of insulin signaling, as well as via changes in synaptic plasticity. These finding may provide new therapeutic target for treatments of neurodegenerative disorders.

The Basic Process of Lighting as Key Factor in the Transition towards More Sustainable Urban Environments

The design of lighting installations on roads and urban infrastructure has strictly followed the regulatory requirements of each country for a long time. Based on the traffic intensity, the presence of pedestrians and the nature of activities within the area, these regulations have been used to establish the luminance or illuminance levels from or on the pavement, the minimum average uniformity, the maximum glare and the minimum energy efficiency. Accurate values of these static parameters are supposed to ensure safety, security, and efficacy, and have traditionally been considered as the main targets of lighting installations. Therefore, compliance with these regulations indicates whether an installation is legal or not. Although this philosophy is operative, the reality is different due to two main issues. First, the progressive ageing of populations, mainly in North America and Europe, the changing circumstances of traffic flow and modalities and the presence of groves or socioeconomic factors, might have a strong impact on the safety, security and sustainability of cities. Secondly, the current regulations leave out perceived safety and security issues, as well as the well-being of people; that is, how people feel about the city independently of real danger. In this research, the Basic Process of Lighting (BPL) is formulated including, for the first time, the human factors involved when people develop their activities under public lighting. Using this framework, the potential factors influencing human wellbeing and feelings are summarized after being rated by people in a survey distributed among 133 participants. The results highlight a higher perceived impact of social factors compared to physical and visual ones.

Preservation of conjugated primary bile acids by oxygenation of the small intestinal microbiota in vitro.

Conjugated primary bile acids are produced by the liver and exist at high concentrations in the proximal small intestine, where they are critical for proper digestion. Deconjugation of these bile acids with subsequent transformation via dehydroxylation into secondary bile acids is regulated by the colonic gut microbiota and reduces their digestive function. Using an in vitro platform modeling the small intestinal microbiota, we analyzed the ability of this community to transform primary bile acids and studied the effect of physiological levels of oxygen normally found in the proximal small intestine (5%) on this metabolic process. We found that oxygenation of the small intestinal microbiota inhibited the deconjugation of primary bile acids in vitro. These findings suggest that luminal oxygen levels normally found in the small intestine may maintain the optimal role of bile acids in the digestive process by regulating bile acid conversion by the gut microbiota.

Continuous psychophysics shows millisecond-scale visual processing delays are faithfully preserved in movement dynamics.

Image differences between the eyes can cause interocular discrepancies in the speed of visual processing. Millisecond-scale differences in visual processing speed can cause dramatic misperceptions of the depth and three-dimensional direction of moving objects. Here, we develop a monocular and binocular continuous target-tracking psychophysics paradigm that can quantify such tiny differences in visual processing speed. Human observers continuously tracked a target undergoing Brownian motion with a range of luminance levels in each eye. Suitable analyses recover the time course of the visuomotor response in each condition, the dependence of visual processing speed on luminance level, and the temporal evolution of processing differences between the eyes. Importantly, using a direct within-observer comparison, we show that continuous target-tracking and traditional forced-choice psychophysical methods provide estimates of interocular delays that agree on average to within a fraction of a millisecond. Thus, visual processing delays are preserved in the movement dynamics of the hand. Finally, we show analytically, and partially confirm experimentally, that differences between the temporal impulse response functions in the two eyes predict how lateral target motion causes misperceptions of motion in depth and associated tracking responses. Because continuous target tracking can accurately recover millisecond-scale differences in visual processing speed and has multiple advantages over traditional psychophysics, it should facilitate the study of temporal processing in the future.