Bright Conditions Research Articles

Optimized scintillation imaging in low dose rate and bright room light conditions

Objective. To develop a robust method for non-contact surface dosimetry during Total Body Irradiation (TBI) that uses an optimally paired choice of scintillator material with camera photocathode and can work insensitively to the normal ambient room lighting conditions (∼500 Lux).Approach. This goal was approached by assessing the emission contrast of scintillator signal to background room ratio (SBR) detected by the camera, in the challening conditions of low dose rate TBI with high room lights. A total of 9 fast-response scintillators, 3 wavelength shifters, and 2 camera photocathodes were systematically tested to determine the optimal combination. The effects of room lights on the scintillator signal and the background signal were assessed to avoid signal saturation while retaining accurate dose measurement. A bandpass wavelength filter was then applied to reduce the effects on room lights and scintillator signal.Main Results. One scintillator (EJ262) combined with a blue-green sensitive photocathode camera and a 500 nm band pass filter produced the greatest available scintillator SBR of 95 with maximal room lights on. The caveat is that this design rejects all patient Cherenkov light, which can be useful for visualizing the patient treatment. Another option which retained the Cherenkov signal but produced less available scintillator signal was found with another scintillator (EJ-260) and a red photocathode camera with SBR of 35, but a narrow bandpass filter is required to make it work in ambient room lights, which addition will also remove most of the Cherenkov signal.Significance. Non-contact scintillator imaging can be used for surface dosimetry in TBI with appropriate pairing of scintillator emission spectrum and camera photocathode sensitivity or optical filtering range.

The effect of restricted and free-living conditions on light exposure and sleep in older adults

ABSTRACT During the COVID-19 pandemic, studies reported that restricted living conditions were associated with worse subjective sleep quality. This effect might have been caused by reduced light exposure during lockdowns. We investigated light exposure levels, subjective and objective sleep and physical activity levels in older adults during restricted and free-living conditions after the pandemic. Ninety-one participants (62.7 ± 8.4 years) recruited from the community using social media with 44 participants (63.4 ± 8.9 years) completed follow-up during free-living conditions. Participants wore an actigraphy device and completed sleep diaries for 7 days during each condition. Light values were extracted in hourly bins across the 24-h period and objective and subjective sleep were compared between the conditions. There was an increase in mean 24-h light exposure during restricted-living (1103.7 ± 1024.8 lux) compared to free-living (803.0 ± 803.6 lux; p < 0.001). This was partially related to participants spending 18 min more in bright light conditions (>1,000 lux) during wakefulness in restricted living (2.6 ± 1.9 h) compared to free-living (2.3 ± 2.0 h; p = 0.036). Despite differences in light exposure, there were no significant differences in objective and subjective sleep parameters between the two conditions. More research is required to better understand behaviours related to light exposure and how this may impact on sleep.

Light Exposure on Alertness after Wake-Up in Healthy Men: Comparing Dim, Bright, Red, and Blue Light

Introduction: Light is a key factor in moderating human alertness, both subjective and objective. However, the methodology applies in research on the effects of exposure to light of different wavelengths and intensities on objective and subjective alertness varies greatly and evidence on objective alertness in particular is still inconclusive. Thus, the present, highly standardized within-subject laboratory study on N = 44 healthy males explored how LED light of different intensities (dim vs. bright light) and wavelengths (red vs. blue) affected objective (reaction time/RT) as well as subjective (sleepiness) alertness in the morning after wake-up. Methods: Participants spent two separate nights in the laboratory and were exposed to either one of the two light intensities or colors for 60 min after wake-up. Additionally, they indicated their sleepiness on the Karolinska Sleepiness Scale and participated in an auditory RT task before and after light intervention. It was hypothesized that both bright and blue light would lead to greater subjective and objective alertness when compared to dim and red light, respectively. Results: Results indicated that average RTs were longer for participants in the bright light condition (p = 0.004, f2 = 0.07) and that RTs decreased post-light exposure irrespective of light being dim or bright (p = 0.026, f2 = 0.07). However, dim versus bright light and RT did not interact (p = 0.758, f2 = 0.07). Chronotype was a significant covariate in the interaction of dim versus bright light and subjective sleepiness (p = 0.008, f2 = 0.22). There was no difference in RTs when comparing exposure to red or blue light (p = 0.488, f2 = 0.01). Findings on subjective sleepiness and light of different wavelengths revealed that sleepiness was reduced after light exposure (p = 0.007, f2 = 0.06), although the wavelength of light did not appear to play a role in this effect (p = 0.817, f2 = 0.06). Conclusion: Hence, neither of the hypotheses could be confirmed. However, they indicated that evening types might benefit from exposure to bright light regarding sleepiness, but not morning types.

Air stability of monolayer WSi2N4 in dark and bright conditions

Two-dimensional materials with chemical formula MA2Z4 are a promising class of materials for optoelectronic applications. To exploit their potential, their stability with respect to air pollution has to be analyzed under different conditions. In a first-principle study based on density functional theory, we investigate the adsorption of three common environmental gas molecules (O2, H2O, and CO2) on monolayer WSi2N4, an established representative of the MA2Z4 family. The computed adsorption energies, charge transfer, and projected density of states of the polluted monolayer indicate a relatively weak interaction between substrate and molecules resulting in an ultrashort recovery time of the order of nanoseconds. O2 and water introduce localized states in the upper valence region but do not alter the semiconducting nature of WSi2N4 nor its band-gap size apart from a minor variation of a few tens of meV. Exploring the same scenario in the presence of photogenerated electrons and holes, we do not notice any substantial difference except for O2 chemisorption when negative charge carriers are in the system. In this case, monolayer WSi2N4 exhibits signs of irreversible oxidation, testified by an adsorption energy of -5.5 eV leading to an infinitely long recovery time, a rearrangement of the outermost atomic layer bonding with the pollutant, and n-doping of the system. Our results indicate stability of WSi2N4 against H2O and CO2 in both dark and bright conditions, suggesting the potential of this material in nanodevice applications.

Transient eye closure and ocular preference in patients with intermittent exotropia

PurposeTo assess the relationship of sensory and motor ocular dominance to transient eye closure (TEC) under bright light conditions in patients with intermittent exotropia. MethodsForty patients (age range, 7-40 years) with intermittent exotropia were included in this prospective study. Motor and sensory ocular dominance were evaluated using the hole-in-the-card and Worth 4-Dot tests. Presence of any outward eye deviation or TEC was assessed and recorded in all participants under bright light conditions. Based on the fusion control grade of exodeviation, patients were assigned to good, fair, and poor control groups, and the results were compared. ResultsA total of 23 patients (58%) showed TEC under bright light: 18 (45%) in the good control group, 14 (35%) in the fair control group, and 8 (20%) in the poor control group. Eighteen patients (56%) with good and fair control showed TEC in the dominant eye. Five (63%) with poor control closed their nondominant eyes, and in all of them, outward eye deviation was observed before TEC. The angle of deviation at far and near and the degree of near stereopsis were not related to presence of TEC (P = 0.70, P = 0.06, and P = 0.34, resp.). ConclusionsIn patients with intermittent exotropia who exhibit TEC under bright light, those with good control tend to close the dominant eye, whereas in the majority of patients with poor control, spontaneous deviation occurs and is then followed by TEC of the nondominant eye.

Effect of Diurnal Light Conditions on Electroretinogram Responses to Red and Blue Flickering Light.

Bright light impacts the human circadian system such that exposure to bright light at night can suppress melatonin secretion, and exposure to bright light in the morning prevents light-induced melatonin suppression at night. The preventive effect of morning light may attenuate the prior history of light sensitivity of intrinsically photosensitive retinal ganglion cells (ipRGCs) that regulate the circadian system. In this study, we evaluated electroretinogram (ERG) responses to red and blue flickering lights following dim and bright daylight conditions. Eleven healthy females underwent ERG measurements during exposure to 33Hz flickering red or blue light under dim and bright daytime conditions. We averaged ERG waves for 50 flickering light pulses of the trigger signal data. We obtained the amplitude of the signal-averaged ERG by calculating the difference between the waves' peaks and bottoms. Although there was no significant dim and bright light difference in the amplitude of ERG waves, the ERG amplitude to flickering blue light under the bright light condition was significantly lower than to flickering blue light under the dim light condition. In this study, blue light stimulated mainly ipRGCs and S-cones. Since S-cones may contribute minimally to the light-adapted 33Hz flicker ERG results, our findings suggest that bright light during the daytime attenuates the sensitivity of human ipRGCs.

Adaptative machine vision with microsecond-level accurate perception beyond human retina

Visual adaptive devices have potential to simplify circuits and algorithms in machine vision systems to adapt and perceive images with varying brightness levels, which is however limited by sluggish adaptation process. Here, the avalanche tuning as feedforward inhibition in bionic two-dimensional (2D) transistor is proposed for fast and high-frequency visual adaptation behavior with microsecond-level accurate perception, the adaptation speed is over 104 times faster than that of human retina and reported bionic sensors. As light intensity changes, the bionic transistor spontaneously switches between avalanche and photoconductive effect, varying responsivity in both magnitude and sign (from 7.6 × 104 to −1 × 103 A/W), thereby achieving ultra-fast scotopic and photopic adaptation process of 108 and 268 μs, respectively. By further combining convolutional neural networks with avalanche-tuned bionic transistor, an adaptative machine vision is achieved with remarkable microsecond-level rapid adaptation capabilities and robust image recognition with over 98% precision in both dim and bright conditions.

Informing solar blind radioluminescence imaging through a calibrated spectrum

While direct radiation detection methods offer great insight into the origin of ionizing particles and photons, their use to locate contaminated areas or concealed radioactive sources can lead to undue exposure of personnel and equipment to ionizing radiation or the potential for contamination. These same sources induce ultraviolet (UV) optical photon fluorescence in air – a process referred to as radioluminescence – that may be imaged from low dose regions over larger attenuation lengths than ionizing radiation. However, most optical detection methods are limited to low lighting conditions to image the more abundant ultraviolet-A (UV-A) photons. To extend this capability to room light or daytime conditions, the solar blind region (Ultraviolet-C (UV–C), <280 nm) can be tapped. Though the emission yield of UV-C photons is roughly two orders of magnitude lower than that in the UV-A regime, the UV-C offers dramatic improvements in signal-to-noise ratios under bright lighting conditions due to decreased background interferences. The yield of specific UV-C lines, if present in the literature at all, varies widely, which has a large impact in modeling and analyzing standoff UV-C measurement scenarios. Thus, we have captured improved radioluminescence spectra over 250–400 nm and identified observed emission peaks in ambient air. Many of the UV-C photons produced by ionizing radiation excitation result from high-energy, molecular nitrogen Gaydon-Herman transitions which have had limited study to date for this application. Relating these findings to published UV-A yields, we estimate emissions between 0.15 and 0.19 photons/MeV over 250–280 nm. We also use a commercial corona-discharge imaging camera to demonstrate outdoor UV-C radiation mapping of alpha and gamma emitters from 50 to 75 m standoffs, respectively. The imaged “counts” are compared to optically modeled values and show the same trend over distance.

Delineation of gastrointestinal tumors biopsies using a fluorescence lifetime imaging optical fiber probe.

Autofluorescence spectroscopy has emerged in recent years as a powerful tool to report label-free contrast between normal and diseased tissues, both in vivo and ex-vivo. We report the application of an instrument employing an optical fiber probe and capable of performing real-time autofluorescence lifetime imaging at a macroscopic scale, under bright background conditions. We validate and demonstrate the practicality of this technology to discriminate healthy against neoplastic tissue in freshly excised tumor biopsies. The capability of delineating tumor margins through processing the fluorescence decays in the phasors domain was demonstrated on four different types of cancer, highlighting the broad range of potential clinical applications for the proposed approach. The presented results suggest that our autofluorescence lifetime imaging probe, together with phasor analysis, can offer a real-time tool to observe lifetime contrast on tissues and, thus, is a suitable candidate for improving in situ tissue diagnostics during surgery.

Flight Testing Of A Single Point Frequency Sweeping Filtered Rayleigh Scattering Probe

"We present a successful in-flight application of filtered Rayleigh scattering (FRS) for temperature measurement in close proximity to the air plane using a newly developed single point, frequency sweeping probe. The temperature measurement is of relevance in the quantification of the density required for the evaluation of velocity from Pitot-probe measurements to obtain the true air speed (TAS). Laser optical air data sensors have the potential for contactless measurements outside the aerodynamic boundary layer. They are capable of self-diagnosis of fault conditions (e.g. signal loss, increased measurement uncertainty or spectral distortion for FRS) thereby increasing the safety of the aircraft. Compared to classical probes, they are less susceptible potential icing and blockage issues. The FRS-results presented here, are the outcome of two separate flight campaigns, carried out in the Alpine region as well as in the North Sea area. Measurement data provided information on the functionality of the FRS-system under various flight and weather conditions. Furthermore, the implementation of the FRS measurement system in the aircraft is presented; application aspects and improvements are discussed. In particular, the measurement accuracy at the actually achievable measurement rate was analyzed. For straight ahead flights at constant height, temperature mean values were in good agreement with the flight data system of the DLR research aircraft Dassault Falcon 20 (D-CMET). Aiming at in-flight air data measurements, the optical FRS measurement system requires a real-time temperature sample rate of a few Hz. We demonstrate that 2 FRS spectra per second can be acquired by a newly developed method using frequency sweeps for temperature determination. The low signal intensity of cw-laser based FRS is countered using a combined transmitter/receiver optic that focusses the entire cw-laser power into one measuring point. The light backscattered from the probe volume is collected by the same optics, filtered and imaged in a confocal arrangement onto a photomultiplier. An improved and miniaturized version of the presented FRS system could be a part of a future optical air data system (OADS). However, the strength of FRS signal relative to bright ambient conditions (e.g. sunlight, cloud backscatter) must be further improved in order to be able to measure well above cloud cover. The potential for further development is foreseen even if the accuracy required for flight data systems (~0.5 K) has not yet been achieved at a temperature measurement rate of 2 Hz. "

57‐4: Advanced Tone Mapping of Mini‐LED Backlit LCDs for Automotive Displays

Tone mapping and mini‐LED backlight algorithms are applied to enhance the sunlight readability of LCDs by fitting the human eye's functionality and increasing image uniformity. Both experimental and simulation results indicate that high luminance displays with an optimized gamma value help to distinguish low grayscale contents under bright ambient conditions.

49‐4: Invited Paper: Super High Ambient Contrast LCDs with Low Power Consumption

The most effective way to improve display visibility in ambient light is to suppress the reflectance of the display. After conducting a thorough analysis of the factors contributing to unwanted reflection, specific layers were identified that required improvement. Subsequently, these elements were carefully optimized, resulting in a significant reduction of internal reflection to 0.53% for our 12.3” FFS‐mode prototype, compared to 1.12% in conventional LCDs. This improvement was achieved without the use of circular polarizers and has been demonstrated to provide excellent visibility in bright ambient conditions while allowing for reduced backlight brightness and lower power consumption.

빛공해로 인한 자연생태계 교란방지를 위한 LED 조명디자인의 조향해석 및 시뮬레이션

Lighting lights such as streetlights and security lights are being illuminated outside the required area, disturbing the ecosystem of nature. In the case of LED lights that replace existing lighting lights, steering analysis and simulation of BUG (Back light, Up light, Glare) control technology that can prevent light pollution by securing left and right light, controlling light in the front and rear, and controlling upward light to prevent disturbance of the ecosystem of nature are performed. By doing so, we present an algorithm that can secure light from left to right, control light from the front to the back, and control light from the front and rear, and efficiently control upward light in the case of LED lighting. Through this, it is possible to effectively prevent light pollution through BUG control of nature-centered light environment and optical performance, such as reducing energy, and securing a uniformity of light pollution problems and the generation of lighting blind spots of conventional LED lights. As a result, it is possible to effectively prevent light pollution through BUG control of natural light environment and optical performance, such as securing a uniformity system for light pollution problems and the generation of lighting blind spots such as conventional LED lights. Various applications of lighting devices have recently been made possible based on powerful light sources through power LED devices. However, from the perspective of nature, industrialization and urbanization have destroyed the living grounds of many living things that coexist with humans, and in turn, they have come to realize that the harm can be brought back to humans. In particular, plants suffer from abnormal growth pains and fatigue syndrome because they cannot distinguish between night and day by using artificial lighting to excessively expand the lighting area to maintain bright conditions as day at night, and many scientific studies have shown that nocturnal animals are unable to hunt or mate properly as the food chain changes, resulting in disturbance of the ecosystem. For example, the use of LED lighting technology is applied according to the location and direction deemed essential, as migratory birds are lost, lost, or recovering from heartless poverty, reducing the population, or cicadas crying until late at night become pollution factors that destroy the natural ecosystem.

Efficacy of a wearable night-vision aid in patients with concentric peripheral visual field loss: a randomized, crossover trial.

To investigate the efficacy of our wearable night-vision aid in patients with concentric peripheral visual field loss. Prospective, single blind, three-group, and three-period crossover clinical study. The study included patients with concentric peripheral visual field loss, a best-corrected visual acuity (decimal visual acuity) of 0.1 or higher in the better eye, and the presence of a central visual field. HOYA MW10 HiKARI® (HOYA Corporation), our original wearable night-vision aid, was used as the test device with three types of camera lenses (standard-, middle-, and wide-angle lenses). Under both bright and dark conditions, the angle of the horizontal visual field was measured using each of the three lens types for each group. The baseline angle was measured when each participant wore the night-vision aid (powered off). The study included 21 participants. Under bright condition, the perceived horizontal visual field was significantly wider than the baseline setup when using the standard-angle lens ("the standard lens"); the middle-angle lens ("the middle lens") was significantly wider than both the baseline setup and the standard lens; and the wide-angle lens ("the wide lens") was significantly wider than the other lenses. Under dark condition, the perceived horizontal visual field was again significantly wider when using the middle lens than the baseline setup and the standard lens, and when using the wide lens, the perceived horizontal visual field was again wider than when using the other lenses. The control in the bright condition was significantly wider (p < 0.001) than when used in the dark condition, while the standard-angle lens in the dark condition was significantly wider (p = 0.05) than when used in the bright condition. In regards to the middle and wide lenses, there was no statistically significant result emerging from either of the illumination conditions. Our wearable night-vision aid with a middle-angle or wide-angle lens appears to provide wider visual field images in patients with concentric peripheral visual field loss, regardless of whether the illumination conditions are bright or dark.

A Smart Clothes Drying Rack Roof Based on Arduino with Rain and Light Sensors

A smart clothesline roof prototype based on Arduino is equipped with rain sensor, light sensor, and servo motor for automated response against weather changes. This system is designed to automatically close the clothesline roof when rain is detected, thereby protecting clothes or items hung from risk of damage due to rainwater. Additionally, the light sensor plays a role in adjusting the clothesline roof position based on surrounding light intensity, allowing it to open widely in bright conditions to maximize clothes drying process when sunlight is adequate. The application of Arduino microcontroller provides flexibility in terms of programming intelligent algorithms in the system, while the servo motor is tasked with moving the clothesline roof precisely according to input commands sent by the Arduino. The testing results of the prototype demonstrate its ability in accurately responding to environmental and weather changes, where the rain sensor will trigger roof closure as soon as any raindrops or rain is detected, while the light sensor will adjust roof opening level to optimize drying when sunlight is intense enough. With this smart solution, efficiency and effectiveness of utilizing the clothesline roof can be enhanced and protection of clothes from rain exposure can be optimally maintained

Dual‐Functional X‐Ray Photochromic Phosphor: High‐Performance Detection and 3D Imaging

AbstractThis study explores the integration of X‐ray‐induced photochromism and photoluminescence in a single material, offering innovative multi‐mode applications in optical memory, anti‐counterfeiting, and X‐ray detection and imaging. The photochromic phosphor LiAlSi2O6:Sm3+ is synthesized, which undergoes a color change from white to dark green under bright field conditions and displays orange photoluminescence in dark field conditions after X‐ray exposure due to defect formation. The phosphor shows accelerated bleaching and recovery under 473 nm laser stimulation. The distinct X‐ray‐induced color contrast and luminescence intensity modification in LiAlSi2O6:Sm3+ highlight its potential in advanced luminescent material design. Moreover, a LiAlSi2O6:Sm3+‐based flexible film demonstrates “dual‐mode” 3D X‐ray imaging and detection capabilities, paving the way for future X‐ray detecting and imaging device research.

Autonomous Light Intensity Adaptation in an Energy‐Efficient Retinomorphic Organic Ferroelectric Neuristor

Autonomous Light Intensity Adaptation in an Energy‐Efficient Retinomorphic Organic Ferroelectric Neuristor

The contribution of carbon budget to masting intervals in Veratrum album populations inhabiting different elevations.

Mast flowering/seeding is often more extreme in lower-resource environments, such as alpine compared to lowland habitats. We studied a masting herb that had less extreme masting at higher elevations, and tested if this difference could be explained by higher photosynthetic productivity and/or lower reproductive investment at the higher-elevation sites. We examined the relationship between flowering intervals and carbon budget (i.e., the balance between reproductive investment and annual carbon fixation) in a masting herb, Veratrum album subsp. oxysepalum, across five lowland and six alpine populations in northern Japan. We evaluated the previous flowering histories of individual plants based on rhizome morphology and analyzed the masting patterns of individual populations. Total mass of the reproductive organs, as a proxy of reproductive investment, was compared between the lowland and alpine populations. Annual carbon fixation was estimated on the basis of photosynthetic capacity, total leaf area per plant, and seasonal transition of light availability. Interval between high-flowering years was shorter and total reproductive investment was smaller in the alpine than in the lowland populations. Owing to its high photosynthetic capacity and continuous bright conditions, annual carbon fixation per plant was 1.5 times greater in alpine habitat than in lowland habitat. These results suggest that V. album alpine populations have shorter flowering intervals than lowland populations due to faster recovery from energy loss after reproduction. Our study demonstrated that masting intervals in V. album populations can be explained by habitat-specific carbon budget balances.

Thriving on Mars: Potatoes as the Answer to Martian Challenges

Humans have committed themselves to the exploration of space and the quest for a habitable planet. Central to the development of a sustainable ecosystem that can provide essential resources like food and water is the implementation of space plant cultivation systems. In the pursuit of bio-regenerative life support systems for human space exploration, the inclusion of plants is imperative. This study focuses on assessing potential challenges associated with cultivating Potatoes (Solanum tuberosum) under simulated Martian conditions. Potatoes exhibit adaptability to extremely cold and dry environments, making them a promising candidate for extraterrestrial agriculture. The advantages of potatoes include their high yield, rich content of easily digestible carbohydrates, elevated protein levels, and simplicity of propagation. When induced to tuberize, potatoes can achieve a harvest index exceeding 80%, approximately double that of traditional grain crops. Notably, unlike certain crops such as soybeans and certain grains, potatoes do not necessitate elaborate processing procedures before consumption. The Potato, specifically varieties like Norland, Denali, and Russet Burbank, has garnered attention in research funded by the US National Aeronautics and Space Administration (NASA). Tests have revealed that these cultivars can successfully undergo tuberization even under constant bright light conditions, emphasizing their potential suitability for life support functions in space exploration contexts

Morphology of the cornea and iris in the Australian lungfish Neoceratodus forsteri (Krefft 1870) (Dipnoi): Functional and evolutionary perspectives of transitioning from an aquatic to a terrestrial environment.

The Australian lungfish, Neoceratodus forsteri (Krefft 1870), is the sole extant member of the Ceratodontidae within the Dipnoi, a small order of sarcopterygian (lobe-finned) fishes, that is thought to be the earliest branching species of extant lungfishes, having changed little over the last 100 million years. To extend studies on anatomical adaptations associated with the fish-tetrapod transition, the ultrastructure of the cornea and iris is investigated using light and electron (transmission and scanning) microscopy to investigate structure-function relationships and compare these to other vertebrate corneas (other fishes and tetrapods). In contrast to previous studies, the cornea is found to have only three main components, comprising an epithelium with its basement membrane, a stroma with a Bowman's layer and an endothelium, and is not split into a dermal (secondary) spectacle and a scleral cornea. The epithelial cells are large, relatively low in density and similar to many species of non-aquatic tetrapods and uniquely possess numerous surface canals that contain and release mucous granules onto the corneal surface to avoid desiccation. A Bowman's layer is present and, in association with extensive branching and anastomosing of the collagen fibrils, may be an adaptation for the inhibition of swelling and/or splitting of the stroma during its amphibious lifestyle. The dorsal region of the stroma possesses aggregations of pigment granules that act as a yellow, short wavelength-absorbing filter during bright light conditions. Desçemet's membrane is absent and replaced by an incomplete basement membrane overlying a monocellular endothelium. The iris is pigmented, well-developed, vascularised and contractile containing reflective crystals anteriorly. Based upon its ultrastructure and functional adaptations, the cornea of N. forsteri is more similar to amphibians than to other bony fishes and is well-adapted for an amphibious lifestyle.