Effect of Luminance and Contrast Variation on Stereoacuity Measurements Using Smartphone Technology

Owing to the limitations of printed stereoacuity tests, the effects of luminance and contrast on stereopsis have not yet been sufficiently investigated, despite its important implications in designing stereoacuity measuring instruments, particularly for electronic devices. A stereopsis measurement system was established using two 4 K smartphones and a phoropter to evaluate the effects of luminance and contrast variations on the stereoacuity test. Seventeen young subjects with normal visual acuity and stereopsis were recruited. Two types of test symbols, contour-based and random-dot-based, were used in the experiment. Four series tests were established with different maximum brightness values, including 240 lux, 120 lux, 60 lux, and 30 lux. Each series test contained 19 pages with different contrasts between 95% and 5% and was calculated using the Michelson contrast formula. No significant difference was found for both contour-based and random-dot-based stereograms in any of the contrast groups with different maximum brightness. Similarly, no significant difference was found between contour-based and random-dot-based patterns under different contrasts of above 35%. As the contrast decreased below 30%, the stereopsis was significantly better in the contour-based pattern than in the random-dot-based pattern for some degrees of contrast. The luminance and contrast of the digital display are not critical factors for stereoacuity under normal circumstances. This implies that a standard monitor with a certain 3D technology can be used to measure the stereoacuity threshold without calibrating the luminance and contrast.

The FUor Star V2493 Cyg (HBC 722)—Eleven Years at Maximum Brightness

At the time of stellar evolution, young stellar objects go through processes of increased activity and instability. Star formation takes place in several stages during which the star accumulates enough mass to initiate thermonuclear reactions in the nucleus. A significant percentage of the mass of Sun-like stars accumulates during periods of increased accretion known as FUor outbursts. Since we know only about two dozen stars of this type, the study of each new object is very important for our knowledge. In this paper, we present data from photometric monitoring on a FUor object V2493 Cyg discovered in 2010. Our data were obtained in the optical region with BVRI Johnson–Cousins set of filters during the period from November 2016 to February 2021. The results of our observations show that during this period no significant changes in the brightness of the star were registered. We only detect variations with a small amplitude around the maximum brightness value. Thus, since 2013 V2493 Cyg remains at its maximum brightness, without a decrease in brightness. Such photometric behavior is not typical of other stars from FUor type. Usually, the light curves of FUors are asymmetrical, with a very rapid rise and gradual decline of the brightness. V2493 Cyg remains unique in this respect with a very rapid rise in brightness and prolonged retention in maximum light. Our period analysis made for the interval February 2013–February 2021 reveals a well-defined period of 914 ± 10 days. Such periodicity can be explained by dust structures remaining from star formation in orbit around the star.

FEATURES OF SELECTING DIELECTRIC LAYERS FOR ELECTROLUMINESCENT STRUCTURES

The paper considers an equivalent scheme of a thin-film electroluminescent emitter (TFELE), taking into account dielectric leaks, and proposes a criterion for the optimal choice of a dielectric in the structure to increase its efficiency. A calculation method is proposed for the optimal choice of material for dielectric films in an electroluminescent structure, taking into account their dielectric loss tangent. The algorithm for optimizing the parameters is based on the method of pairwise comparison of two dielectrics, provided that the charge flowing through the structure is constant or increased. The calculated data for materials are given in the form of a table according to the sequence of deterioration of their characteristics. The most attractive of the materials considered are PbTiO3, Ta2O5, Y2O3, as well as improved ceramics, which is confirmed by experiment. The possibility of applying the proposed model to explain the dependence of the luminosity of electroluminescent emitters on their excitation voltage is shown. A comparative analysis of the results of the calculation and experiment of the dependence of brightness on the applied voltage (B-V) for three types of TFELE based on a luminescent layer ZnS : Mn (0.5%) with a thickness of 0.6 μm, placed between two dielectric layers with a thickness of about 0.3- 0.35 μm with Ta2O5, Sm2O3 and Y2O3, respectively. It is established that the threshold luminescence excitation voltage correlates with the value of εE, and the maximum brightness with the value of εE / tg (δ). The table also shows the calculated characteristics of NdAlO3 and AlN films deposited by high-frequency magnetron sputtering. Higher brightness values can be expected from electroluminescent structures with such a dielectric than from structures with dielectric films with Sm2O3 and Y2O3. The results of such studies are presented in the form of a graph and table. This method can find practical application in the development of new materials and technologies for their production.

Air-Stable Ultrabright Inverted Organic Light-Emitting Devices with Metal Ion-Chelated Polymer Injection Layer

Here, this work presents an air-stable ultrabright inverted organic light-emitting device (OLED) by using zinc ion-chelated polyethylenimine (PEI) as electron injection layer. The zinc chelation is demonstrated to increase the conductivity of the PEI by three orders of magnitude and passivate the polar amine groups. With these physicochemical properties, the inverted OLED shows a record-high external quantum efficiency of 10.0% at a high brightness of 45,610 cd m−2 and can deliver a maximum brightness of 121,865 cd m−2. Besides, the inverted OLED is also demonstrated to possess an excellent air stability (humidity, 35%) with a half-brightness operating time of 541 h @ 1000 cd m−2 without any protection nor encapsulation.

A Multi-wavelength Analysis of Small-scale Brightenings Observed by IRIS

Small-scale brightenings in solar atmospheric observations are a manifestation of heating and/or energy transport events. We present statistical characteristics of brightenings from a new detection method applied to 1330, 1400, and 2796 Å IRIS slit-jaw image time series. A total of 2377 events were recorded that coexist in all three channels, giving high confidence that they are real. Of these, ≈1800 were spatially coherent, equating to event densities of ∼9.7 × 10−5 arcsec−2 s−1 within a 90″ × 100″ FOV over 34.5 minutes. Power-law indices estimates are determined for total brightness (2.78 < α < 3.71), maximum brightness (3.84 < α < 4.70), and average area (4.31 < α < 5.70) distributions. Duration and speed distributions do not obey a power law. A correlation is found between the events’ spatial fragmentation, area, and duration, and a weak relationship with total brightness, showing that larger/longer-lasting events are more likely to fragment during their lifetime. Speed distributions show that all events are in motion, with an average speed of ∼7 km s−1. The events’ spatial trajectories suggest that cooler 2796 Å events tend to appear slightly later and occupy a different position/trajectory than the hotter channel results. This suggests that either many of these are impulsive events caused by reconnection, with subsequent rapid cooling, or that the triggering event occurs near the TR, with a subsequent propagating disturbance to cooler atmospheric layers. The spatial distribution of events is not uniform, with broad regions devoid of events. A comparison of spatial distribution with properties of other atmospheric layers shows a tentative connection between high magnetic field strength, the corona’s multi-thermality, and high IRIS brightening activity.

Detecting and Characterising Small-Scale Brightenings in Solar Imaging Data

Observations of small-scale brightenings in the low solar atmosphere can provide valuable constraints on possible heating and heat transport mechanisms. We present a method for the detection and analysis of brightenings, and demonstrate its application to time-series imagery of the Interface Region Imaging Spectrograph (IRIS) in the extreme ultraviolet (EUV). The method is based on spatio-temporal band-pass filtering, adaptive thresholding and centroid tracking, and records an event’s spatial position, duration, total brightness and maximum brightness. Spatial area, brightness, and position are also recorded as functions of time throughout the event’s lifetime. Detected brightenings can fragment, or merge, over time – thus the number of distinct regions constituting a brightening event is recorded over time, and the maximum number of regions recorded as $N_{\mathit{frag}}$ N frag , which is a simple measure of an event’s coherence or spatial complexity. A test is made on a synthetic datacube composed of a static background based on IRIS data, Poisson noise and $\approx 10^{4}$ ≈ 10 4 randomly-distributed, moving, small-scale Gaussian brightenings. Maximum brightness, total brightness, area, and duration follow power-law distributions, and the results show the range over which the method can successfully extract information. The test shows that the recorded maximum brightness of an event is a reliable measure for the brightest and most accurately detected events, with an error of 6%. Event area, duration and speed are generally underestimated by around 15% and have an uncertainty of 20–30%. The total brightness is underestimated by 30%, and has an uncertainty of 30%. Applying this detection method to real IRIS quiet-sun data spanning 19 minutes over a $54.40''\times 55.23''$ 54.40 ″ × 55.23 ″ field of view (FOV) yields 2997 detections, 1340 of these detections either remain un-fragmented or fragment to two distinct regions at least once during their lifetime ($N_{\mathit{frag}}\le 2$ N frag ≤ 2 ), equating to an event density of $3.96\times 10^{-4}$ 3.96 × 10 − 4 arcsec−2 s−1. The method will be used for a future large-scale statistical analysis of several quiet-sun (QS) data sets from IRIS, other EUV imagers, and other types of data including H$\alpha $ α and visible photospheric imagery.

Simple Synthesis of Red Iridium(III) Complexes with Sulfur-Contained Four-Membered Ancillary Ligands for OLEDs

Phosphorescent iridium(III) complexes have been widely researched for the fabrication of efficient organic light-emitting diodes (OLEDs). In this work, three red Ir(III) complexes named Ir-1, Ir-2, and Ir-3, with Ir-S-C-S four-membered framework rings, were synthesized efficiently at room temperature within 5 min using sulfur-containing ancillary ligands with electron-donating groups of 9,10-dihydro-9,9-dimethylacridine, phenoxazine, and phenothiazine, respectively. Due to the same main ligand of 4-(4-(trifluoromethyl)phenyl)quinazoline, all Ir(III) complexes showed similar photoluminescence emissions at 622, 619, and 622 nm with phosphorescence quantum yields of 35.4%, 50.4%, and 52.8%, respectively. OLEDs employing these complexes as emitters with the structure of ITO (indium tin oxide)/HAT-CN (dipyra-zino[2,3-f,2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile, 5 nm)/TAPC (4,4′-cyclohexylidenebis[N,N-bis-(4-methylphenyl)aniline], 40 nm)/TCTA (4,4″,4″-tris(carbazol-9-yl)triphenylamine, 10 nm)/Ir(III) complex (10 wt%): 2,6DCzPPy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(mpyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) achieved good performance. In particular, the device based on complex Ir-3 with the phenothiazine unit showed the best performance with a maximum brightness of 22,480 cd m−2, a maximum current efficiency of 23.71 cd A−1, and a maximum external quantum efficiency of 18.1%. The research results suggest the Ir(III) complexes with a four-membered ring Ir-S-C-S backbone provide ideas for the rapid preparation of Ir(III) complexes for OLEDs.

The altitude of sprites observed over South Africa

Sprites are mesospheric optical emissions that are mostly produced by large, positive cloud-to-ground lightning discharges. Sprites appear in different morphologies such as carrot, jellyfish and column, and are typically in the altitude range of ~40–100 km above the Earth’s surface. Sprites are a subset of transient luminous events and they contribute to the global electric circuit. South Africa has large convective thunderstorms, which typically occur in the summer months of every year. Peak current, time and geographical position of lightning strokes were obtained from the South African Weather Service. Sprite observations were recorded in South Africa for the first time on 11 January 2016 from Sutherland in the Northern Cape using a night-vision television camera from the South African National Space Agency’s Optical Space Research laboratory. We report the first estimates of the top altitude, and the altitude of maximum brightness, of 48 sprites over South Africa. We found that the average top altitude and the altitude of maximum brightness of sprites are approximately 84.3 km and 69 km, respectively, which is consistent with estimates made elsewhere. We also found a moderately high positive and a weak positive correlation between the top altitude and the altitude of maximum brightness, respectively, of sprites and the lightning stroke charge moment change.

Morphofunctional Characteristics of the Hippocampus of White Rats in the Acute Period After Severe Traumatic Brain Injury During the Use of L-lysine Aescinat

Aim of study. The study is devoted to the effect of L-lysine aescinat on the nervous tissue of the CA1 and CA3 fields of the hippocampus of the brain of white rats in the acute period after severe traumatic brain injury (TBI).Material and methods. TBI was simulated by applying a blow to the parieto-occipital region with a freely falling weight weighing 200-250 grams from a height of 50 cm using a special rail rack. The objectives of the study were: 1) comparative morphometric assessment of the degree of hydration, cyto- and glioarchitectonics of different layers of CA1 and CA3 fields after ischemia without treatment; 2) the effect of L-lysine aescinat on these indicators. We used histological (staining of sections with hematoxylin-eosin and Nissl), immunohistochemical (for NSE, MAP-2 and GFAP) and morphometric methods. On thin (4 μm) serial frontal sections of the hippocampus, neurons, astrocytes, microvessels and neuropiles were studied in control (intact animals, n=5) and 1 and 3 days after injury without treatment (n=10, comparison group) and with treatment ( n = 10, main group). The number density of neurons was determined using the Nissl staining of cells and by the reaction to NSE. The cytoskeleton of neurons was studied by detecting MAP-2, and astroglia by GFAP. On color raster images (staining with hematoxylin and eosin, x100) using the Find Maxima plug-in filter, the zones of maximum brightness were determined, which were then analyzed using Analyze Particles from the ImageJ 1.52s program. Zones of maximum brightness corresponded to areas of the hippocampus with a high degree of hydration of the nervous tissue - edema-swelling. The nature of the distribution, statistical hypotheses, and plotting were checked using Statistica 8.0 software and R environment.Results. In control animals, normochromic neurons without signs of changes in the cytoskeleton prevailed in all layers of fields CA1 and CA3, and a low degree of hydration of the nervous tissue was noted (the relative proportion of zones of maximum brightness was 5–8%). One and 3 days after TBI, there was a statistically significant increase in the focal content of dystrophic and necrobiotically altered neurons (95% confidence interval: 52–78%), manifestations of reactive gliosis were noted, and the proportion of zones of maximum brightness increased to 16%. Statistically significant layer-by-layer differences were revealed between the CA1 and CA3 fields of the hippocampus. The use of L-lysine aescinat had a statistically significant effect on the morphometric parameters of the nervous tissue of the hippocampus.Conclusion. In the early post-traumatic period after TBI, the degree of hydration of the nervous tissue of the hippocampus increased. Heteromorphicity of dystrophic and necrobiotic changes in different layers of CA1 and CA3 fields was noted. L-lysine aescinate had a statistically significant positive effect on these changes. To a greater extent, this is typical for the CA3 field. The revealed changes are considered not only as patho-, but also as sanogenetic structural mechanisms of protection and reorganization of the hippocampus in the acute post-traumatic period.1. In the acute period (1−3 days) after severe traumatic brain injury, the degree of hydration of all components of the hippocampal nervous tissue increased. In the group without treatment, 3 days after injury, the relative volume of edema-swelling zones varied from 10 to 13% in CA1 (control 3-7%) and from 8 to 16% in CA3 (control 5–10%).2. The heteromorphism of hydropic changes in the molecular layer, the layer of pyramidal neurons and the polymorphic layer was established. The maximum increase in the volume of free water (more than twofold) was characteristic of the molecular and polymorphic layer CA1, as well as the polymorphic layer CA3.3. The use of L-lysine aescinat in the acute period significantly changed the manifestations of hydropic dystrophy. One day after injury, the volume of free water increased in comparison with animals without treatment, and then, after 3 days, decreased, but remained higher than in the comparison group. The maximum effect of the drug was noted in field CA3.