Decrease In Luminance Research Articles

Eye tracking identifies biomarkers in α-synucleinopathies versus progressive supranuclear palsy

ObjectivesThis study (1) describes and compares saccade and pupil abnormalities in patients with manifest alpha-synucleinopathies (αSYN: Parkinson’s disease (PD), Multiple System Atrophy (MSA)) and a tauopathy (progressive supranuclear palsy (PSP)); (2) determines whether patients with rapid-eye-movement sleep behaviour disorder (RBD), a prodromal stage of αSYN, already have abnormal responses that may indicate a risk for developing PD or MSA.MethodsNinety (46 RBD, 27 PD, 17 MSA) patients with an αSYN, 10 PSP patients, and 132 healthy age-matched controls (CTRL) were examined with a 10-min video-based eye-tracking task (Free Viewing). Participants were free to look anywhere on the screen while saccade and pupil behaviours were measured.ResultsPD, MSA, and PSP spent more time fixating the centre of the screen than CTRL. All patient groups made fewer macro-saccades (> 2◦ amplitude) with smaller amplitude than CTRL. Saccade frequency was greater in RBD than in other patients. Following clip change, saccades were temporarily suppressed, then rebounded at a slower pace than CTRL in all patient groups. RBD had distinct, although discrete saccade abnormalities that were more marked in PD, MSA, and even more in PSP. The vertical saccade rate was reduced in all patients and decreased most in PSP. Clip changes produced large increases or decreases in screen luminance requiring pupil constriction or dilation, respectively. PSP elicited smaller pupil constriction/dilation responses than CTRL, while MSA elicited the opposite.ConclusionRBD patients already have discrete but less pronounced saccade abnormalities than PD and MSA patients. Vertical gaze palsy and altered pupil control differentiate PSP from αSYN.

Distribution Density-Aware Compensation for High-Resolution Stretchable Display

When a stretchable display is stretched, the area of the exposed substrate between the light-emitting diodes (LEDs) increases, decreasing the image luminance. Currently, this problem is not addressed in existing high-resolution display systems. Although the mean-based method and gamma correction method using general image processing techniques, which are first presented in this paper, can compensate for the decrease in luminance, these methods cannot be adaptively applied for stretchable display systems. Therefore, this paper proposes a novel image compensation method optimized for stretchable displays. The proposed distribution density-aware method (DDAM) compensates for the decrease in luminance particularly for the area involving the newly exposed substrate. The DDAM solves the saturation problem associated with the mean-based method and the problem of inaccurate luminance estimation associated with the gamma correction method. Compared with the mean-based method and the gamma correction method, the peak signal-to-noise ratio of the DDAM is 0.600 dB and 1.977 dB higher, respectively. The structural similarity index measure is also 0.055 and 0.057 higher, respectively. In addition, we develop a novel simulator to evaluate the stretching of high-pixel-per-inch displays, which are being actively researched, and use it to verify the performance of above mentioned luminance reduction compensation methods.

Coronary computed tomography versus coronary angiography for preoperative coronary assessment before valve surgery

BackgroundConventional coronary angiography (CAG) is currently the gold standard technique for the assessment of coronary arteries prior to cardiac valve surgery. Although CAG is a relatively safe procedure, however, it is still an invasive procedure, and it has potential hazards and complications. Coronary computed tomography angiography (CCTA) is a non-invasive technique that has emerged robustly as an excellent and attractive tool for delineating coronary anatomy. Therefore, we sought to evaluate the accuracy of CCTA when compared with the gold standard CAG in the evaluation of coronary arteries before valve surgery. We screened 111 consecutive patients with VHD undergoing a routine cardiac catheterization for preoperative evaluation of CAD. Fifty patients were eligible and underwent both CAG and CCTA. Significant coronary stenosis was defined as a luminal diameter decrease of ≥ 50%. Additionally, ectasia, calcifications, and congenital coronary anomalies were analyzed. Also, we compared both techniques regarding radiation dose, contrast volume, and complications. Non-evaluable segments were excluded from all levels of analysis. Sixty-one patients were excluded from the study due to various reasons.ResultsAmong the 50 patients of the study population, 27 (54%) were males. The prevalence of significant CAD in the study population was 19.6% according to the patient-based analysis, and CAG could have been avoided in 80.4% of patients with a true-negative CCTA result. Diagnostic accuracy of CCTA for detection of significant stenosis was evaluated regarding sensitivity and specificity, positive predictive value, negative predictive value, and overall accuracy of CCTA, which was 87.5%, 99.6%,87.5%, 99.6%, and 99.2%, respectively, for segmental-based analysis; 86%, 100%, 100%, 99%, and 99%, respectively, for vessel-based analysis; and 77.8%,100%,100%, 94.9%, and 95.7%, respectively, for patient-based analysis. Fewer rates of complications were encountered with CCTA. Additional information obtained like calcifications and congenital anomalies was diagnosed better with CCTA than CAG.ConclusionOwing mainly to its high negative predictive value, a well-performed CCTA exam is an excellent method to rule out coronary artery disease, specially in patients who are not at high risk of atherosclerosis.

Feature-based attention is not confined by object boundaries: Spatially global enhancement of irrelevant features.

Theories of visual attention differ in what they identify as the core unit of selection. Feature-based theories emphasize basic visual features (e.g., color, motion), demonstrated through enhancement of attended features throughout the visual field, while object-based theories propose that attention enhances all features belonging to the same object. These theories make distinct predictions about the processing of features that are not attended primarily: Object-based theories predict that such secondary, task-irrelevant features are enhanced within object boundaries, while feature-based theories predict enhancement of irrelevant features across locations, regardless of objecthood. To test these two accounts, we had participants attend a set of colored dots among distractor dots (moving coherently upward or downward) to detect brief luminance decreases, while simultaneously detecting speed changes in other sets of dots in the opposite visual field. In the first experiment, we demonstrate that participants have higher speed detection rates in the dot array that matched the motion direction of the attended color array, although motion direction was task-irrelevant. In a second experiment, we manipulated the probability that speed changes occurred in the matching motion direction and found that enhancement of the irrelevant motion direction persisted even when it was detrimental for task performance, suggesting that spatially global effects of feature-based attention cannot easily be flexibly adjusted. Overall, these results indicate that features that are not primarily attended are enhanced globally, surpassing object boundaries.

Colorimetric properties and structural evolution of cathodic electrochromic WO3 thin films

Cathodic amorphous tungsten trioxide (WO3) thin films have been deposited by reactive direct current magnetron sputtering and have been studied for their colorimetric and electrochromic properties. Those studies were carried out under two different potential cycling process: (i) switching mode (the response between coloration and bleaching in increasing potential steps) and (ii) modulation mode (the stepwise modulation to coloration with increasing potential and back to bleaching). Optical measurements, performed as a function of applied potential, showed excellent transmittance contrasts (∼80%) between colored and bleached states. The color stimuli and the changes that take place upon reversible switching or modulation were recorded based on the Commisson International de l’Éclairage (CIE) system. It was found that, under various potentials, significant changes occurred in the hue and saturation for WO3, as exhibited by the CIE 1931 xy chromaticity coordinates. As WO3 was reduced (W6+ + e– → W5+), a sharp decrease in luminance was observed. Excellent reversibility is demonstrated not only by colorimetric properties, but also by the corresponding intrinsic structures of the films, as investigated by µ-Raman spectroscopy. Furthermore, the WO3 films displayed a fast response time and good long-term cycling durability, which was attributed to their amorphous nature.

Visual continuity during blinks and alterations in time perception.

Eye blinks strongly attenuate visual input, yet we perceive the world as continuous. How this visual continuity is achieved remains a fundamental and unsolved problem. A decrease in luminance sensitivity has been proposed as a mechanism but is insufficient to mask the even larger decrease in luminance because of blinks. Here we put forward a different hypothesis: visual continuity can be achieved through shortening of perceived durations of the sensory consequences of blinks. Here we probed the perceived durations of the blackouts caused by blinks and visual stimuli interrupted by blinks. We found that the perceived durations of blackouts because of blinks are about half as long as artificial blackouts immediately preceding or following the blink. Stimuli interrupted by blinks were perceived as briefer than uninterrupted stimuli, by about the same duration as the interruption-but so were stimuli interrupted by optically simulated blinks. There was a difference between real and simulated blinks, however: The decrease in perceived duration depended on the duration of the interruption for simulated, but not for real, blinks. These profound modifications in time perception during blinks show a way in which temporal processing contributes to the solution of an essential perceptual problem. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Effects of pupillary light and darkness reflex on the generation of pro- And anti-saccades.

Saccades are often directed toward a stimulus that provides useful information for observers to navigate the visual world. The quality of visual signals of a stimulus is influenced by global luminance, and the pupil constricts or dilates after a luminance increase or decrease, respectively, to optimize visual signals for further information processing. Although luminance level changes regularly in the real environment, saccades are mostly studied in the luminance-unchanged setup. Whether pupillary responses triggered by global luminance changes modulate saccadic behavior are yet to be explored. Through varying background luminance level in an interleaved pro- and anti-saccade paradigm, we investigated the modulation of pupillary luminance responses on the generation of reflexive and voluntary saccades. Subjects were instructed to either automatically look at the peripheral stimulus (pro-saccade) or to suppress the automatic response and voluntarily look in the opposite direction from the stimulus (anti-saccade). Level of background luminance was increased (light), decreased (dark), or unchanged (control) during the instructed fixation period. Saccade reaction time distributions of correct pro- and anti-saccades in the light and dark conditions were differed significantly from those in the control condition. Moreover, the luminance condition modulated saccade kinematics, showing reduced performances in the light condition than in the control condition, particularly in pro-saccades. Modeling results further suggested that both pupil diameter and pupil size derivative significantly modulated saccade behavior, though effect sizes were small and mainly mediated by intersubject differences. Together, our results demonstrated the influence of pupillary luminance responses on the generation of pro- and anti-saccades.

Hybrid Tandem White OLED with Long Lifetime and 150 Lm W−1 in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter

AbstractModern lighting requires high efficiency and long lifetime simultaneously. In this paper, highly efficient white organic light emitting diodes (WOLEDs) are demonstrated based on a modified hybrid tandem structure constructed with a phosphorescent yellow‐red unit using an exciplex host and a blue‐red unit based on a thermally activated delayed fluorescence (TADF) blue emitter, and the devices are properly built with internal and external light extraction structures. The resulting four‐color WOLED exhibits an external quantum efficiency and luminous efficacy of 126.2% and 150.7 Lm W−1, respectively, and the color rendering index is close to 80 at a brightness of 1000 cd m−2. This device also shows a very good color stability with increasing luminance up to 15 000 cd m−2 and there is only a small angular color variation for viewing angles changing from 0° to 70°. The T50 lifetime (defined as the time corresponding to 50% decrease in luminance from an initial value) of the WOLED at an initial luminance of 1000 cd m−2 is extrapolated as 12 600 h.

Relationship between the immunohistological examination and fluorescence visualization of oral squamous cell carcinoma.

Disorders of the oral mucosa are considered easy to diagnose since they can be visualized and examined directly. A change in the color of the oral mucosa reflects histopathological changes and is an important diagnostic parameter. However, the subjective perception of color varies. To determine the extent of resection for oral mucosa conditions, it is necessary to digitize the color and perform objective assessments. In recent years, fluorescence visualization devices and analysis software that measure tissue luminance G have been employed for the identification of oral mucosa diseases. Fluorescence visualization is presumably based on the decrease in epithelial flavin adenine dinucleotide content and luminance G values due to the destruction of collagen cross-links [fluorescence visualization loss (FVL)]. However, cases with differences between luminance values and histopathological presentation exist. Therefore, additional factors may affect fluorescence visualization. The present study used a portable, non-contact oral mucosa fluorescence visualization device for luminance measurements in seven patients with oral squamous cell carcinoma. Furthermore, Picro-Sirius Red and immunohistochemical staining were performed for CK13, CK17, Ki67, p53 and E-cadherin in the FVL(+) (lesion) and FVL(−) (resection stump) areas to elucidate the principle of fluorescence visualization. Fluorescence was significantly lower in the FVL(+) than in the FVL(−) areas, and the mean luminance G value was 56. The Picro-Sirius Red stain revealed collagen destruction in the FVL(+) areas but no collagen disruption in the FVL(−) areas. CK13 was negative in the FVL(+) and positive in the FVL(−) areas, whereas the opposite pattern was observed for CK17. In the FVL(+) area, p53 staining was positive. E-cadherin expression was enhanced in the FVL(−) areas and reduced in the FVL(+) areas. Furthermore, the luminance G value tended to be lower in cases with weaker E-cadherin staining. The aforementioned results suggest that decreased E-cadherin expression may be a factor that regulates fluorescence visualization.

High-resolution nonfluorescent imaging with structured illumination for patterned surface measurement

Surface patterning is widely performed in various applications, and hence high-resolution, high-throughput, and nondestructive measurement of patterned surfaces is required. The current optical methods used for such measurements are constrained, in terms of spatial resolution, by the diffraction limit. In this study, structured illumination was employed for high-resolution wide-field imaging measurements. Structured illumination microscopy is well known as a fluorescent bio-imaging technique. For nonfluorescent imaging and industrial measurement applications, however, speckle noise, generated by the structured illumination pattern, environmental vibrations, and thermal drift, causes problems for the high-precision positioning and control of the illumination pattern. To solve these problems, we developed a structured illumination microscope that detects the phase of the structured illumination as a fringe signal by using an additional interferometric measurement system. In this system, a low-coherence light source is employed for illumination pattern generation and high-resolution imaging with low speckle noise. The constructed optical system consists of multiple Michelson interferometers that allow the manipulation of low-coherence interference fringes at the sample position and the detection of the phase via another sensor. Robust imaging can be implemented by feeding back the structured illumination phase through super-resolution image processing. We experimentally achieved high-resolution nonfluorescent imaging with low speckle noise and resolved patterned surfaces beyond the diffraction limit without high-precision positioning stages. Furthermore, the image reconstruction algorithm typically used in structured illumination microscopy was improved by adopting a Fourier ptychography approach. Thus, artifact reduction, as well as decreases in luminance and pitch errors, was achieved, and this result represents a step forward in the development of practical measurement methods for patterned surfaces.

Spatial Contrast Sensitivity to Polarization and Luminance in Octopus.

While color vision is achieved by comparison of signals of photoreceptors tuned to different parts of light spectra, polarization vision is achieved by comparison of signals of photoreceptors tuned to different orientations of the electric field component of visible light. Therefore, it has been suggested that polarization vision is similar to color vision. In most animals that have color vision, the shape of luminance contrast sensitivity curve differs from the shape of chromatic contrast sensitivity curve. While luminance contrast sensitivity typically decreases at low spatial frequency due to lateral inhibition, chromatic contrast sensitivity generally remains high at low spatial frequency. To find out if the processing of polarization signals is similar to the processing of chromatic signals, we measured the polarization and luminance contrast sensitivity dependence in a color-blind animal with well-developed polarization vision, Octopus tetricus. We demonstrate that, in Octopus tetricus, both luminance and polarization contrast sensitivity decrease at low spatial frequency and peak at the same spatial frequency (0.3 cpd). These results suggest that, in octopus, polarization and luminance signals are processed via similar pathways.

Electrochromic and colorimetric properties of anodic NiO thin films: Uncovering electrochromic mechanism of NiO

In this work anodic NiO electrochromism is investigated under two potential cycling modes: i) the response between coloration and bleaching in increasing potential steps (switching); ii) the stepwise modulation to coloration with increasing potential and back to bleaching (modulation). The films’ response is investigated by optical spectroscopy, colorimetry studies, Raman spectroscopy, XRD, cyclic voltammetry and chronoamperometry. Using the CIE (Commisson International de l’Éclairage) system of colorimetry the color stimuli of the films and the changes that take place upon reversible switching/modulation are recorded under various potentials. As shown by the CIE 1931 xy chromaticity coordinates, when NiO film is oxidized, a sharp decrease in luminance is observed. Optical measurements, performed as a function of applied potential, show excellent contrast between colored and bleached states. Up to now, for NiO, the coloration mechanism was considered as a surface phenomenon. Here, for the first time we show that upon ion insertion/extraction the lattice constant of NiO changes, proving that the EC coloration mechanism involves the unit cells in the bulk material. Furthermore, the fraction ratio of Li to Ni atoms (LiNi) is proposed. Considering the actual film fabrication conditions, the x value in LixNiO is found to be equal to 0.0046.

Binary Fate Choice between Closely Related Interneuronal Types Is Determined by a Fezf1-Dependent Postmitotic Transcriptional Switch

Many neuronal types occur as pairs that are similar in most respects but differ in a key feature. In some pairs of retinal neurons, called paramorphic, one member responds to increases and the other to decreases in luminance (ON and OFF responses). Here, we focused on one such pair, starburst amacrine cells (SACs), to explore how closely related neuronal types diversify. We find that ON and OFF SACs are transcriptionally distinct prior to their segregation, dendritic outgrowth, and synapse formation. The transcriptional repressor Fezf1 is selectively expressed by postmitotic ON SACs and promotes the ON fate and gene expression program while repressing the OFF fate and program. The atypical Rho GTPase Rnd3 is selectively expressed by OFF SACs and regulates their migration but is repressed by Fezf1 in ON SACs, enabling differential positioning of the two types. These results define a transcriptional program that controls diversification of a paramorphic pair.

Response anisocoria in the pupillary light and darkness reflex.

The pupil constricts or dilates in response to a luminance increase or decrease, and these transient pupillary responses are controlled by the parasympathetic and sympathetic pathways. Although pupillary responses of the two eyes are highly correlated, they are not always identical (referred to as anisocoria). For example, there are unequal direct and consensual pupillary constriction responses after an increase in luminance to one eye. While contraction anisocoria (i.e. constriction) has been demonstrated in the pupillary light reflex, it is not yet known if there is also dilation anisocoria in the pupillary darkness reflex. Unlike previous studies that focused on the pupillary light reflex, we examined response anisocoria in both pupillary light and darkness reflexes. While requiring participants to maintain central fixation, we presented a light or dark stimulus to either the right or left visual field to induce transient pupillary constriction or dilation. Both the pupillary light and darkness reflexes had significantly larger ipsilateral responses compared to the contralateral responses relative to the stimulated visual field. The observed ipsilateral effects occurred significantly faster in the light than darkness reflex, suggesting that larger ipsilateral pupillary dilation after a luminance decrease cannot be only attributed to the inhibition of the parasympathetic system, but is also mediated by the excitation of the sympathetic system. Together, our results demonstrated a larger ipsilateral pupil response in both the pupillary light and darkness reflex, indicating an asymmetry in ipsilateral and contralateral neural circuitry of the pupillary darkness reflex.

Subjective and pupil responses to discomfort glare from small, high-luminance light sources

This study examined human subjective and pupil responses to small, high-luminance light sources seen against low-luminance backgrounds. Subjective judgements of glare using a seven-point rating scale and the change in pupil diameters following exposure to glare of 47 subjects were measured during evaluation of 36 conditions comprising three glare source luminances (20,000; 205,000; 750,000 cd/m2), two source positions (0°, 10°), two source sizes (10−5, 10−4 sr) and three background luminances (0.03; 0.3; 1 cd/m2). Data analysis suggests that the relative pupil size is correlated with subjective responses to discomfort glare to some extent (r = 0.659). Analysis of variance of relative pupil size measurements demonstrates a significant main effect of the background luminance suggesting that when the background luminance decreases, the relative pupil size increases. Relative pupil size shows the same trend as the relative change in illuminance at the eyes and the discomfort glare perception.

Visual complaints of patients with glaucoma and controls under optimal and extreme luminance conditions.

To determine (i) whether, compared to controls, visual complaints of glaucoma patients are more pronounced under extreme luminance conditions than in the optimal luminance condition and (ii) whether complaints belonging to different extreme luminance conditions are associated. We developed a luminance-specific questionnaire and sent it to 221 glaucoma patients (response rate 81%); controls (182) were primarily their spouses. Median (interquartile range) mean deviation of the visual field of the patients' better eye was -4.5 (-10.7 to -1.9) dB. Questions were addressing visual performance under five luminance conditions: presumed optimal (outdoor on a cloudy day), low, high, sudden decrease and sudden increase. We compared percentages of patients and controls who reported visual complaints while performing activities under different luminance conditions. Percentages of patients and controls with visual complaints were 4 versus 0% (p=0.02) for optimal luminance and 48 versus 6% (p<0.001), 22 versus 1% (p<0.001), 32 versus 1% (p<0.001) and 25 versus 3% (p<0.001) for low, high, sudden decrease and sudden increase in luminance. Within the group of glaucoma patients, the frequency of complaints increased significantly with increasing disease severity at a Bonferroni-corrected p value of 0.003 for all but one (p=0.005) luminance-specific questions that addressed extreme luminance conditions. The concept of (early stage) glaucoma as an asymptomatic disease is only valid with optimal luminance. Differences in visual complaints between glaucoma patients and controls are greater under extreme luminance conditions, especially in the dark. The fact that the cases were aware of their diagnosis could have induced bias.

Foveal light and dark adaptation in patients with glaucoma and healthy subjects: A case-control study.

IntroductionTo determine whether foveal light and dark adaptation are affected in glaucoma.MethodsCase-control study with 23 glaucoma patients and 51 controls. Light and dark adaptation were measured twice. After 10 minutes pre-adaptation to 0.0032 cd/m2, the background luminance increased stepwise to 320 (5 log unit step) or 10,000 cd/m2 (6.5 log unit step) for 10 minutes, then it decreased back to 0.0032 cd/m2 for 30 minutes. Foveal contrast sensitivity [CS]) as a function of time was determined using a 1.15 degree increment. Time resolution of the experiments was 30 seconds. Multiple linear regression was used to analyse the effect of glaucoma on the CS plateau and adaptation time (time to reach the plateau minus 3 dB); analyses were adjusted for age and gender.ResultsAfter light adaptation to 320 and 10,000 cd/m2, glaucoma patients had a 0.22 (P<0.001) and 0.13 (P = 0.010) log unit lower CS plateau than controls, respectively. After dark adaptation, this difference was 0.21 (P = 0.018) and 0.30 (P<0.001) log unit, respectively. Light adaptation occurred too fast to determine an accurate light adaptation time. Dark adaptation times of glaucoma patients and controls were similar, for both the 5 (7.2 versus 5.5 minutes; P = 0.10) and the 6.5 (18.2 versus 16.6 minutes; P = 0.14) log unit step.ConclusionAfter a sudden increase or decrease in luminance, the logCS adaptation curves of glaucoma patients are shifted downwards compared to the curves of healthy subjects. Glaucoma patients have a lower CS plateau than healthy subjects, for both light and dark adaptation; dark adaptation times are similar.

Contrast-dependent red-green balance shifts depend on S-cone activity.

Previous research from our lab has established that red-green-balanced yellow targets become greenish-brown as surround luminance increases, while red-green-balanced brown targets become reddish-yellow as surround luminance decreases. To help assess the generality and underlying processes of this contrast-dependent red-green hue shift, we investigated red-green hue shifts for target stimuli that appeared achromatic or blue as well as yellow/brown. Results confirmed that the red-green hue shift was largest for yellow/brown targets and was progressively reduced for achromatic and blue targets as target excitation of S cones increased. The magnitude of the hue shift could be predicted by the S/(L+M) excitation of the target when bright white surrounds are used. The hue shift also requires that the target and surround are presented to the same eye, consistent with processing in monocular pathways. Increased S-cone excitation by the surround was associated with red-green hue shifts for all targets equally. Thus, S-cone signals from bright white surrounds might play a role in the contrast-dependent red-green hue shift, but the source of the variation of the magnitude of the hue shift with variations in target S-cone excitation when presented on those surrounds is unknown.

The Role of Charge Balance and Excited State Levels on Device Performance of Exciplex-based Phosphorescent Organic Light Emitting Diodes

The design of novel exciplex-forming co-host materials provides new opportunities to achieve high device performance of organic light emitting diodes (OLEDs), including high efficiency, low driving voltage and low efficiency roll-off. Here, we report a comprehensive study of exciplex-forming co-host system in OLEDs including the change of co-host materials, mixing composition of exciplex in the device to improve the performance. We investigate various exciplex systems using 5-(3–4,6-diphenyl-1,3,5-triazin-2-yl)phenyl-3,9-diphenyl-9H-carbazole, 5-(3–4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9-phenyl-9H-3,9′-bicarbazole, and 2-(3-(6,9-diphenyl-9H-carbazol-4-yl)phenyl)-4-phenylbenzo[4,5]thieno[3,2-d]pyrimidine, as electron transporting (ET: electron acceptor) hosts and 9,9′-dipenyl-9H, 9′H-3,3′-bicarbazole and 9-([1,1′-biphenyl]-4-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole as hole transporting (HT: electron donor) hosts. As a result, a very high current efficiency of 105.1 cd/A at 103 cd/m2 and an extremely long device lifetime of 739 hrs (t95: time after 5% decrease of luminance) are achieved which is one of the best performance in OLEDs. Systematic approach, controlling mixing ratio of HT to ET host materials is suggested to select the component of two host system using energy band matching and charge balance optimization method. Furthermore, our analysis on exciton stability also reveal that lifetime of OLEDs have close relationship with two parameters; singlet energy level difference of HT and ET host and difference of singlet and triplet energy level in exciplex.

Histological effect of methomyl on rat brain and testis

Methomyl is a highly toxic carbamate insecticide and is used on a wide variety of crops. Prolonged exposure to these pesticides is known to cause teratogenic effect and decreased fertility in experimental animals. For this purpose, the present study was designed to investigate the effect of methomyl on the histological structure of brain and testes of male rats. Twenty four adult rats weighing about (250 – 300) gm and (8-10) weeks of age were used in this study, divided into four groups, six rats per group, first group serves as a control and three other groups were administered methomyl orally at three different doses (0.5 mg/kg B.W., 1 mg/kg B.W. and 2 mg/kg B.W.). At the end of the experiment period, the rats anesthetized and sections from brain and testes were prepared to investigate the histological effects of this insecticide. Various degrees of histological change in the structure of the brain and testes were observed in comparison with the control group. This alteration included degeneration of the nerve cells in the cerebrum and abnormal purkinje cells in the cerebellum with different degrees of valuation were seen, also the section from the seminiferous tubules of methomyl treated rats showed a reduction in the population of mature sperm cells, wider luminal diameter and decrease in leydig cells number in the interstitial spaces. These effects could impair the fertility potential of male