Randomly Disassembled Nanostructure for Wide Angle Light Extraction of Top-Emitting Quantum Dot Light-Emitting Diodes.

The quantum dot light-emitting diode (QLED) represents one of the strongest display technologies and has unique advantages like a shallow emission spectrum and superior performance based on the cumulative studies of state-of-the-art quantum dot (QD) synthesis and interfacial engineering. However, research on managing the device's light extraction has been lacking compared to the conventional LED field. Moreover, relevant studies on top-emitting QLEDs (TE-QLEDs) have been severely lacking compared to bottom-emitting QLEDs (BE-QLEDs). This paper demonstrates a novel light extraction structure called the randomly disassembled nanostructure (RaDiNa). The RaDiNa is formed by detaching polydimethylsiloxane (PDMS) film from a ZnO nanorod (ZnO NR) layer and laying it on top of the TE-QLED. The RaDiNa-attached TE-QLED shows significantly widened angular-dependent electroluminescence (EL) intensities over the pristine TE-QLED, confirming the effective light extraction capability of the RaDiNa layer. Consequently, the optimized RaDiNa-attached TE-QLED achieves enhanced external quantum efficiency (EQE) over the reference device by 60%. For systematic analyses, current-voltage-luminance (J-V-L) characteristics are investigated using scanning electron microscopy (SEM) and optical simulation based on COMSOL Multiphysics. It is believed that this study's results provide essential information for the commercialization of TE-QLEDs.

Sintering Behavior of Copper Nanoparticle Ink by Laser in Air.

This paper presents a sintering technique using a laser in air which can provide heat for a few hundred milliseconds. In this study, a laser having a wavelength of 532 nm and a maximum-power output of 5 W was used. The effects of irradiated laser power at 104-282 W/cm² and sintering time of 50-330 milliseconds applied on spin-coated copper nanoparticle ink were investigated. The residual organic agent, oxidation, and specific resistance of the laser-sintered copper nanoparticle ink were characterized, and the sintering behavior was analyzed. For application, laser-sintered copper nanoparticle ink was confirmed to offer acceptable performance as a source and drain electrode in a thin-film transistor.

Consistent pattern in positional instability of polyfocal full-optics accommodative IOL.

PURPOSE: We describe cases of dislocation or subluxation of the WIOL-CF® polyfocal full-optics intraocular lens (IOL) and suggest a consistent pattern and possible mechanism for the IOL instability. METHODS: This is a retrospective case series of five consecutive eyes in three patients with WIOL-CF® IOL instability at Keimyung University Dongsan Medical Center and Kimkisan Eye Center from 2012 to 2014. The medical records and ocular exam data for these patients were analyzed. RESULTS: A 50-year-old male had uneventful phacoemulsification in both eyes with WIOL-CF® IOL implantation. At 27 months after surgery, the patient was referred to our clinic with a dislocated IOL in the left eye. The IOL in the right eye was dislocated in the same pattern 38 months after cataract surgery. Another 50-year-old male, who had phacoemulsification and WIOL-CF® IOL implantation in both eyes, was referred to our clinic following diagnosis of a subluxated IOL. Both IOLs were well centered; however, the infranasal aspect of the IOLs tilted posteriorly, and the supratemporal portion the IOLs tilted anteriorly, with overlying iris atrophy in a symmetric pattern. The inferonasal continuous curvilinear capsulorrhexis (CCC) edge was dragged superotemporally, and the supratemporal CCC edge was identified on the posterior surface of the IOL. A 16-year-old female had uneventful phacoemulsification and WIOL-CF® IOL implantation to treat a cataract in the right eye, and 3 years later, the IOL tilted with the same pattern as the previous case. CONCLUSIONS: Years after uncomplicated phacoemulsification, an implanted WIOL-CF® IOL may tilt and dislocate in the absence of trauma, in a consistent and characteristic pattern.

Surgical results of idiopathic and secondary epiretinal membrane.

The aim of the study is to compare the surgical results of patients with an idiopathic and secondary epiretinal membrane (ERM) after pars plana vitrectomy and membranectomy. The medical records of 51 consecutive patients with ERM who underwent pars plana vitrectomy and membranectomy with a follow-up >1 year were reviewed retrospectively. Age, sex, best-corrected visual acuity (BCVA, logMAR), lens status, presence of additional removal of internal limiting membrane (ILM), and recurrence rate within 1 year after the operation were compared in the idiopathic and secondary ERM groups. Forty-one eyes had idiopathic ERM and 10 eyes had secondary ERM. Preoperative average BCVA values in the two groups were 0.47 and 0.70, respectively, and the postoperative average BCVA values were 0.28 and 0.18, respectively, with significant improvement postoperatively in both groups (p < 0.01, p < 0.01). The recurrence rate within 1 year after surgery in the idiopathic group was 4.88 % and that in the secondary group was 20 % (p = 0.03). The recurrence rate was 4.3 % in the idiopathic group with ILM removal and it was 5.9 % without ILM removal (p = 0.03). No case recurred within 1 year in the secondary group with ILM removal but the recurrence rate was 33.3 % in the group without ILM removal (p = 0.01). Although patients with secondary ERM gained better visual acuity improvement postoperatively, the recurrence rate was higher within 1 year than that of patients with idiopathic ERM. Removal of the ILM may lower recurrence rates.

Deep Learning-Based Inkjet Droplet Detection for Jetting Characterizations and Multijet Synchronization.

Inkjet printing is a powerful direct material writing process. It can be used to deposit microfluidic droplets in designated patterns at submicrometer resolution, which reduces materials usage. Nonetheless, predicting jetting characterizations is not easy because of the intrinsic complexity of the ink-nozzle-air interactions. Thus, inkjet processes are monitored by skilled engineers to ensure process reliability. This is a bottleneck in industry, resulting in high labor costs for multiple nozzles. To address this, we present a deep learning-based method for jetting characterizations. Inkjet printing is recorded by an in situ CCD camera and each droplet is detected by YOLOv5, a 1-stage detector using a convolutional neural network (CNN). The precision, recall, and mean average precision (mAP) at a 0.5 intersection over the union (IoU) threshold of the trained model were 0.86, 0.89, and 0.90, respectively. Each regression result for a detected droplet is accumulated in chronological order for each class of droplet and nozzle. The quantified information includes velocity, diameter, length, and translation, which can be used to synchronize multinozzle jetting and, eventually, the printed patterns. This demonstrates the feasibility of autonomous real-time process testing for large-scale electronics manufacturing, such as the high-resolution patterning of biosensor electrodes and QD display pixels while exploiting big data obtained from jetting characterizations.

Two-Year Follow-Up Study of Patients with Neovascular Age-Related Macular Degeneration Undergoing Anti-VEGF Treatment during the COVID-19 Pandemic.

BACKGROUND: regular intravitreal anti-vascular endothelial growth factor (VEGF) treatment is crucial for patients with neovascular age-related macular degeneration (nAMD), and delayed treatment can exacerbate disease progression. METHODS: we compared the outcomes of on-time versus delayed intravitreal anti-VEGF treatment for patients with nAMD. This study was conducted during the coronavirus disease 2019 (COVID-19) pandemic with a 2-year follow-up period. The best-corrected visual acuity (BCVA) and anatomical findings were evaluated before the pandemic, during the pandemic, and at 6-, 12-, 18-, and 24-months post-pandemic. RESULTS: The delayed and on-time groups comprised 54 and 72 patients, respectively. After the pandemic, the injection interval increased by 0.65 ± 1.51 months (p = 0.003), with 22.2% of the patients in the delayed group switching to the treat-and-extended regimen (p < 0.001). The delayed group showed greater mean BCVA deterioration (p = 0.027) and central subfield thickness (p = 0.037) at 6 months and worse maximum subretinal fluid height (p = 0.022) at 18 months than the on-time group. No difference was observed between the groups in the second year. CONCLUSION: the negative effects of delaying anti-VEGF treatment because of the COVID-19 pandemic can be ameliorated by changing the treatment regimen and shortening treatment intervals.

Comparison of the Effectiveness of Intravitreal Bevacizumab Injections with and without Simultaneous Cataract Surgery in Diabetic Patients with Macular Edema.

Intravitreal bevacizumab (IVB), often injected during cataract surgery, is currently the main treatment for diabetic macular edema. This retrospective study aimed to compare the effectiveness of IVB injections alone and during cataract surgery in patients with diabetic macular edema. We examined 43 eyes in 40 patients who underwent cataract surgery with simultaneous IVB injections 3-12 months after IVB injections alone. Best-corrected visual acuity and central subfield macular thickness (CMT) were measured 1-month post-injection. The CMTs of the same eyes with IVB-only first and combined-treatment procedures later were 384 ± 149 vs. 315 ± 109 µm pretreatment (p = 0.0002), and after 1 month, they were 319 ± 102 vs. 419 ± 183 µm (p < 0.0001). In the IVB-only procedure, 56.1% of eyes had CMT < 300 µm 1 month after the injection compared to 32.5% after the combined treatment. Therefore, on average, when IVB was administered during cataract surgery, CMT increased, whereas after IVB injection alone, it effectively decreased. More prospective trials with large sample sizes are needed to evaluate the effectiveness of IVB injection performed simultaneously with cataract surgery.

Measurement of inkjet droplet size based on Fraunhofer diffraction.

Inkjet printers have started to manufacture OLED/QLED pixel arrays for the display industry, and the precise measurement and control of ink droplet volume during the printing process has become important. We investigated the feasibility of Fraunhofer diffraction analysis as a volume measurement tool for fast-moving inkjet droplets. To confirm the basic idea, two Fraunhofer diffraction-based methods were used to calculate the wire diameters of well-known sized and steady-positioned metal wires. The first method was to curve-fit the whole measured diffraction intensity curve with the extensive Fraunhofer diffraction equation. The second one was to use the simple approximate diameter calculation equation with the measured position data of minimum diffraction intensity. The metal wire diameters calculated by the two methods showed less than 1.17% error. For the size measurement of fast-moving inkjet droplets, the first method showed 24.5 µm diameter and 7.7 pL volume, while the second method showed 25.4 µm diameter and 8.58 pL volume. We found that the second method was more suitable for real-time inkjet monitoring because its average computer calculation time was 33 ms, and the first method took an average of 34 ms, about 1000 times more CPU time. Hence, Fraunhofer diffraction analysis as an inkjet droplet volume measurement tool was feasible with a good balance of measurement time and measurement accuracy.

Correlation between Severity of Idiopathic Epiretinal Membrane and Irvine-Gass Syndrome.

A higher risk of pseudophakic cystoid macular edema (PCME) has been reported in patients with preoperative idiopathic epiretinal membrane (ERM); however, whether the formation of PCME depends on the grade of ERM has not been well established. We conducted a retrospective case-control study of 87 eyes of 78 patients who were preoperatively diagnosed with idiopathic ERM and had undergone cataract surgery. Patients were divided into two groups: PCME and non-PCME groups. After cataract surgery, the ERM status was graded using the Gass and Govetto classifications. Both the central macular thickness (CMT) and ERM grade increased after surgery, and higher preoperative CMT and ERM grades were found in the PCME group. The association between higher-grade ERM and the development of PCME was significant in the Govetto classification (grade 2, odds ratio (OR): 3.13; grade 3, OR: 3.93; and grade 4, OR: 16.07). The study results indicate that close attention should be given to patients with ERM with the presence of an ectopic inner foveal layer before cataract surgery.

The Effect of Pre-Stretched Substrate on the Electrical Resistance of Printed Ag Nanowires.

One-dimensional nanomaterials have drawn attention as an alternative electrode material for stretchable electronics. In particular, silver nanowires (Ag NWs) have been studied as stretchable electrodes for strain sensors, 3D electronics, and freeform-shaped electronic circuits. In this study, Ag NWs ink was printed on the pre-stretched silicone rubber film up to 40% in length using a drop-on-demand dispenser. After printing, silicone rubber film was released and stretched up to 20% as a cyclic test with 10-time repetition, and the ratios of the resistance of the stretched state to that of the released state (Rstretched/Rreleased) were measured at each cycle. For Ag NWs electrode printed on the pre-stretched silicone rubber at 30%, Rstretched/Rreleased at 10% and 20% strain was 1.05, and 1.57, respectively, which is significantly less than about 7 for Ag NWs at the 10% strain without pre-stretched substrate. In the case of 10% strain on the 30% pre-stretched substrate, the substrate is stretched and the contact points with Ag NWs were not changed much as the silicone rubber film stretched, which meant that Ag NWs may slide between other Ag NWs. Ag NWs electrode on the 40% pre-stretched substrate was stretched, strain was concentrated on the Ag NWs electrode and failure of electrode occurred, because cracks occurred at the surface of silicone rubber film when it was pre-stretched to 40%. We confirmed that printed Ag NWs on the pre-stretched film showed more contact points and less electric resistance compared to printed Ag NWs on the film without pre-stretching.

Impact of Delayed Intravitreal Anti-Vascular Endothelial Growth Factor (VEGF) Therapy Due to the Coronavirus Disease Pandemic on the Prognosis of Patients with Neovascular Age-Related Macular Degeneration.

This study estimated the outcome of delayed intravitreal anti-vascular endothelial growth factor (VEGF) therapy due to the coronavirus (COVID-19) disease pandemic on the prognosis of patients with neovascular age-related macular degeneration (nAMD). This study retrospectively enrolled 57 nAMD patients whose intravitreal anti-VEGF injections were delayed for >2 weeks between February and June 2020. Best-corrected visual acuity (BCVA), central subfield thickness (CST), and anatomical characteristics were evaluated before (baseline), on the day, and at 2, 4, and 6 months after the delayed injection, and risk factors were identified. The average injection interval before and after treatment delay was 3.05 ± 1.45 and 2.41 ± 1.46 months, respectively (p = 0.002). The CST at baseline and on the day of delayed injection was 227.82 ± 62.46 and 267.26 ± 77.74 µm, respectively (p < 0.001). The average BCVA decreased from 0.29 ± 0.29 logMAR (baseline) to 0.38 ± 0.31 logMAR (6 months) (p = 0.001). The maximum subretinal fluid (SRF) height increased from 84.32 ± 89.33 µm (baseline) to 121.38 ± 103.36 µm (6 months) (p = 0.027). A higher baseline maximum SRF height was associated with less SRF height deterioration 6 months later (p < 0.001). Delayed intravitreal anti-VEGF therapy caused by the COVID-19 pandemic has worsened BCVA and residual SRF in nAMD patients after a temporary recovery. The baseline SRF reduce the degree of SRF height deterioration.

Deep-Learning-Based Microfluidic Droplet Classification for Multijet Monitoring.

Inkjet printing, the deposition of microfluidic droplets on a specified area, has gained increasing attention from both academia and industry for its versatility and scalability for mass production. Inkjet printing productivity depends on the number of nozzles used in a multijet process. However, droplet jetting conditions can vary for each nozzle due to multiple factors, such as the surface wetting condition of the nozzle, properties of the ink, and variances in the manufacturing of the nozzle head. For these reasons, droplet jetting conditions must be continuously monitored and evaluated by skillful engineers. The present study presents a deep-learning-based method to identify the droplet jetting status of a single-jet printing process. A convolutional neural network (CNN)-based on the MobileNetV2 model was employed with optimized hyperparameters to classify the inkjet frames containing images captured with a CCD camera. By accumulating the classified class data in order by frame time, the jetting conditions could be evaluated with high accuracy. The method was also successfully demonstrated with a multijet process, with a test time of less than a second per image.

Clinical Significance of Choroidal Thickness in Eyes with Ocular Ischemic Syndrome.

PURPOSE: To determine the clinical significance of choroidal thickness and evaluate changes in choroidal thickness over time in eyes affected by ocular ischemic syndrome (OIS). METHODS: Medical records of 16 patients diagnosed with OIS between November 2017 and August 2019 were retrospectively reviewed. In every nine areas of the Early Treatment Diabetic Retinopathy Study grid, we compared the differences in choroidal thickness between the eyes with OIS and unaffected eyes, and its change in the OIS eyes during the follow-up period using swept-source optical coherence tomography. We analyzed the best-corrected visual acuity, intraocular pressure, fluorescein angiography (FAG) parameters, systemic diseases, and the duration of symptoms. Correlation between FAG parameters and the choroidal thickness value ratio in the OIS eyes and the unaffected eyes, and changes in the choroidal thickness in the OIS eyes during follow-up were investigated. RESULTS: Median age of the subjects was 67.5 years. In the OIS eyes, all FAG parameters were delayed at the initial examination. Best-corrected visual acuity and intraocular pressure were significantly different between the OIS and unaffected eyes. While the choroidal thickness in every nine areas of Early Treatment Diabetic Retinopathy Study in the OIS eyes was lesser than the unaffected eyes, the choroidal thickness of inner temporal, outer nasal, and outer temporal area showed statistically significant difference. During follow-up, changes in choroidal thickness of OIS eyes as well as correlation between the FAG parameters and the choroidal thickness value ratio between the OIS eyes and the unaffected eyes were not found to be statistically significant. CONCLUSIONS: The choroidal thickness of the eyes with OIS was significantly less compared with the unaffected eyes. We inferred that choroidal thinning takes place in the early phase of the disease as the changes in choroidal thickness during the follow-up period were not significant.

Facile fabrication of flexible metal grid transparent electrode using inkjet-printed dot array as sacrificial layer.

In this study, we introduce a flexible metal grid transparent electrode fabricated using a lift-off process. This transparent electrode consisting of metal thin film with punched-like pattern by hole array was fabricated with 8 um separations. The separation of inkjet-printed etching resistant ink droplets was controlled in order to investigate the relationship between its electrical and optical properties of the electrodes. The aluminum areal density was defined to predict the electrical and optical properties of different arrays. A high and uniform transmittance spectrum appears to extend broadly into the UV region. The figure of merit of the transparent electrode was investigated in order to determine its performance as a transparent electrode. Moreover, there was no significant change in the resistance after 7000 bending cycles, indicating that the array conductor had superior stability. We also demonstrate transparent touch screen panels fabricated using the transparent electrode.

Bubble-free on-chip continuous-flow polymerase chain reaction: concept and application.

Bubble formation inside a microscale channel is a significant problem in general microfluidic experiments. The problem becomes especially crucial when performing a polymerase chain reaction (PCR) on a chip which is subject to repetitive temperature changes. In this paper, we propose a bubble-free sample injection scheme applicable for continuous-flow PCR inside a glass/PDMS hybrid microfluidic chip, and attempt to provide a theoretical basis concerning bubble formation and elimination. Highly viscous paraffin oil plugs are employed in both the anterior and posterior ends of a sample plug, completely encapsulating the sample and eliminating possible nucleation sites for bubbles. In this way, internal channel pressure is increased, and vaporization of the sample is prevented, suppressing bubble formation. Use of an oil plug in the posterior end of the sample plug aids in maintaining a stable flow of a sample at a constant rate inside a heated microchannel throughout the entire reaction, as compared to using an air plug. By adopting the proposed sample injection scheme, we demonstrate various practical applications. On-chip continuous-flow PCR is performed employing genomic DNA extracted from a clinical single hair root sample, and its D1S80 locus is successfully amplified. Also, chip reusability is assessed using a plasmid vector. A single chip is used up to 10 times repeatedly without being destroyed, maintaining almost equal intensities of the resulting amplicons after each run, ensuring the reliability and reproducibility of the proposed sample injection scheme. In addition, the use of a commercially-available and highly cost-effective hot plate as a potential candidate for the heating source is investigated.

Residual-Solvent-Induced Morphological Transformation by Intense Pulsed Light on Spin-Coated and Inkjet-Printed ZnO NP Films for Quantum-Dot Light-Emitting Diodes.

It was demonstrated through a comparison between the spin-coated and inkjet-printed quantum-dot light-emitting diodes' (QLED) performance analysis outcomes that the annealing temperature of a zinc oxide nanoparticle (ZnO NP) electron transport layer (ETL) optimized for intense pulsed light (IPL) via a post-treatment differs depending on the film-formation method used. For a naturally dried ZnO NP ETL formulated without annealing, different film morphologies were observed according to the film-formation method of spin coating and inkjet printing, and the surface-roughness root mean square (RMS) value was increased in an IPL post-treatment due to unevaporated residual solvent. Based on this phenomenon, we classified and analyzed different film profiles according to the deposition method, the presence or absence of annealing, and the annealing temperature.

A new optical coherence tomography method for subfoveal choroidal thickness measurement: A single-center observational study.

ABSTRACT: Several macular pathologies are associated with choroidal vascular supply and thus require choroidal thickness evaluation. However, there is no standard subfoveal choroidal thickness (SFCT) measurement method. This study investigated a new method of SFCT measurement, using optical coherence tomography.This is a single-center observational study. Eighty-two senior medical students participated as observers and independently measured the SFCT on 5 standard optical coherence tomography images of healthy adults in a tertiary care setting. They used 3 different methods: the observer's own method, the conventional method, perpendicular to the retinal pigment epithelium, and the new method, along a virtual line connecting the umbo with the most elevated point of the ellipsoid. Additionally, the SFCT angle-the angle between the measurement line and the vertical line of the image-was measured and compared between methods. The intraclass correlation coefficient was used to determine interpersonal variability.The intraclass correlation coefficients for SFCT, measured using methods 1, 2, and 3, were 0.853, 0.880, and 0.896, respectively (P < .001 for all). Method 3 was the highest. The intraclass correlation coefficients of the SFCT angles were 0.647, 0.842, and 0.307, respectively (P < .001 for all).The new method showed the lowest interpersonal variability and could therefore be a reliable standard for SFCT measurement, even in foveae with a steep slope on optical coherence tomography.Trial registration: Not applicable.

Effect of Time-Dependent Characteristics of ZnO Nanoparticles Electron Transport Layer Improved by Intense-Pulsed Light Post-Treatment on Hole-Electron Injection Balance of Quantum-Dot Light-Emitting Diodes.

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication and analysis of single carrier devices (SCDs), and it was confirmed that the time-dependent characteristics of the ZnO NPs affect the device characteristics of QLEDs. Stabilization of the ZnO NPs film properties for improvement of the charge injection balance in QLEDs was achieved by controlling the current density characteristics via filling of the oxygen vacancies by IPL post-treatment.

Orbital infarction syndrome after cerebral aneurysm surgery: A case series and literature review.

To report the clinical characteristics and retinal abnormalities associated with orbital infarction syndrome after cerebral aneurysm clipping surgery.In this retrospective case series, we evaluated 4 cases of orbital infarction syndrome using fluorescein angiography, optical coherence tomography, and computed tomography images from January 2011 to May 2014. The medical records of these patients including age, sex, laterality of the eyes, visual acuity, intraocular pressure, duration of the operation, location of the aneurysms, and surgical method with the type of approach used to reach the aneurysmal lesions were evaluated.Aneurysms were located in either the anterior or the posterior communicating artery. Two patients had subarachnoid hemorrhage arising from a ruptured aneurysm, whereas 2 other patients had unruptured aneurysms. Clipping was performed by 3 different surgeons using the pterional craniotomy. The mean time interval from aneurysmal clipping to awareness of vision loss was 10.75 ±â€Š13.8 days. In all patients, optic atrophy and irreversible deterioration of visual acuity ensued. Retinal edema, retinal vascular abnormality, or choroidal hypoperfusion was identified in these patients.Orbital infarction syndrome is a rare but devastating complication of brain aneurysm clipping surgery. The associated retinal ischemia is not only due to the involvement of the retinal vessels, but also the choroidal circulation.

Solution and Evaporation Hybrid Approach to Enhance the Stability and Pattern Resolution Characteristics of Organic Light-Emitting Diodes.

The solution process and vacuum evaporation, both fabrication methods for conventional organic light-emitting diodes (OLEDs), are intrinsically restricted with regard to their ability to enhance pattern resolutions and film stability outcomes. Here, we introduce a novel approach of the solution process followed by intense pulsed light (IPL) evaporation for producing high-resolution line patterns of OLEDs. Through control of the wettability between the banks and microchannels via a mask-free selective surface treatment, we successfully deposited phosphorescent green and red inks only into the microchannels. Then, high-resolution patterns of an emitting layer (EML) layer were uniformly evaporated onto the device substrate using IPL evaporation. Ultimately, we fabricated green and red phosphorescent OLED devices with a high pixel density of a line-patterned EML with a width of 6 µm and a pitch of 13.6 µm. In addition, we demonstrated that the IPL-evaporated films have many advantages compared to those fabricated by the conventional solution process. We also showed that the IPL evaporation process can be less sensitive to problems related to the aggregation of organic molecules during a drying or annealing process. Hence, the device performance and lifetime of the IPL-evaporated OLEDs were enhanced compared to those of the spin-coated OLEDs.