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The aim of this paper is to present a review of the development and application of superhydrophobic insulation for outdoor high voltage applications. The methods of preparing insulation exhibiting superhydrophobic properties in order to mitigate the pollution problem under high voltages in the outdoors are explored. In addition, existing evaluation techniques at the material development stage are reviewed and potential new modifications are discussed. The self-cleaning and anti-icing properties, the electrical performance and prospects of superhydrophobic insulators are also addressed. Although superhydrophobic insulators may show promising behavior in small-scale laboratory conditions that do not employ electrical stress, the effect of surface micro-nano structure responsible for the superhydrophobicity on performance under the actual outdoor and weathering conditions under voltage remains to be fully understood and verified. Therefore, there is a need to verify the feasibility of superhydrophobic insulators for outdoor high voltage applications with a solid evaluation protocol, while employing material screening methods in the laboratory, and with reference to field experience.

Purpose: This work investigates the visual and anatomical outcomes of full-thickness macular hole (FTMH) repair surgery using air in comparison to gas tamponade. Methods: A retrospective consecutive review of medical records was undertaken of all patients undergoing pars plana vitrectomy for idiopathic FTMH at an academic practice from January 2010 to May 2017. Each operative report was reviewed to investigate the agent used for tamponade at the end of the surgery. Preoperative hole duration and size as measured using optical coherence tomography as well as successful postoperative hole closure were recorded. Use of gas or air was not randomized and was instilled at surgeon discretion. Results: The final analysis included 211 eyes. Gas was used as the tamponade agent in 171 of the 211 eyes; most of these eyes (144 of 171) received sulfur hexafluoride (SF6) and the remainder received perfluoropropane (C3F8). Forty eyes underwent only a complete fluid-air exchange without any gas placement following vitrectomy. There was no statistically significant difference between the 2 groups in mean preoperative macular hole size ( P = .43). Nine of the 171 macular holes receiving gas tamponade failed to close (5.3%). One of the 40 macular holes receiving only air failed to close (2.5%). There was no statistically significant difference in hole closure rates between the 2 groups ( P = .45). Conclusions: Air served as an equally efficacious internal tamponade agent in comparison to nonexpansile gas following idiopathic FTMH repair surgery.

Temperature and electric field along the stress grading system of a form wound coil under repetitive impulse voltage are studied using 2D axisymmetric and 3D models in COMSOL¯ 5.3a. The validity of the 3D model is shown by comparing the results with the measured temperature profile along the stress grading system. The evaluation of both temperature and electric field shows that using a stress grading system based on a micro-varistor characteristic reduces the maximum temperature; however, with an increase in the electric field, which can be reduced to an acceptable level. An optimization on the initial conductivity of the micro-varistor characteristic confirms that desired electric field and temperature rise are achievable by selecting an optimized conductivity characteristic. 2D and 3D simulations show that a proposed stress grading system, which is a combination of an optimized stress grading tape conductivity and minimum conductive armor tape length, has a good temperature and electrical performances under repetitive impulse voltage.

Evaluation of thermal and electrical characteristics of a 13.8 kV rotating machine stress grading system shows that a reduced length of conductive armor tape (CAT) from the slot exit reduces the electric field and temperature rise under pulsed voltage. Although, the electric field in stress grading tape (SGT) increased slightly, with a shorter length of CAT during the rise time of the pulse voltage, it decreased during the DC portion of the pulse voltage. The temperature profile of the stress grading system under pulsed voltage at room, elevated room, and near typical operating temperatures are measured and simulated for several CAT lengths; results show lower temperatures for shorter CAT length. The partial discharge inception voltage is unchanged for shorter CAT lengths. A lower temperature rise is desirable as this leads to a longer life in the absence of partial discharges.

BACKGROUND AND OBJECTIVE: This paper reports 3-year intraocular pressure (IOP) outcomes of the Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study. PATIENTS AND METHODS: The prospective, controlled, observational study included 80 eyes of 40 participants undergoing routine pars plana vitrectomy. Study patients underwent preoperative evaluation and multimodal testing of the study (surgical) and fellow (control) eye. This testing was repeated at 3 months postoperatively and then annually for 3 years. RESULTS: Thirty-two of 40 patients (80%) completed 3-year follow-up. At 3 years postoperatively, there was no difference in IOP measurements in surgical eyes overall from baseline ( P = .36). Subgroup analysis of pseudophakic eyes at baseline showed a significant elevation in IOP from 14.3 mm Hg ± 2.9 mm Hg at baseline to 16.8 mm Hg ± 3.2 mm Hg at 3-year follow-up ( P < .029). Fellow eyes did not experience a significant change from baseline. CONCLUSION: The authors' 3-year results show that IOP is consistently and significantly elevated in pseudophakic eyes compared to baseline following routine vitrectomy. [ Ophthalmic Surg Lasers Imaging Retina . 2019;50:371–376.]

The thermal and electrical characteristics of a stress grading system are studied by simulations and measurements of the electric field and temperature distributions in the overhang region of a form wound medium voltage motor coil. Simulations show that a highly conductive stress grading tape (SGT) reduces the maximum electric field in this region but increases heat production and temperature. In contrast, a highly conductive armor tape (CAT) decreases the maximum electric field in this region and also reduces the heat production and temperature in the stress grading system but also produces a slight increase in the electric field in the SGT region. For the simulation studies, accurate measurements of the electrical and thermal conductivities of materials are made, taking into account the effects of the vacuum pressure impregnation (VPI) process, temperature, and tape builds. The electrical conductivity of single and double half-lap layers of CAT and SGT are measured from 30 to 100 °C. For the evaluation of the simulation model, the temperature profile along the stress grading system was measured and simulated under pulsed voltage at room and near typical operating temperatures.

Purpose To determine plasma metabolite and metabolic pathway differences between patients with type 2 diabetes with diabetic retinopathy (DR) and without retinopathy (diabetic controls), and between patients with proliferative DR (PDR) and nonproliferative DR (NPDR). Methods Using high-resolution mass spectrometry with liquid chromatography, untargeted metabolomics was performed on plasma samples from 83 DR patients and 90 diabetic controls. Discriminatory metabolic features were identified through partial least squares discriminant analysis, and linear regression was used to adjust for age, sex, diabetes duration, and hemoglobin A1c. Pathway analysis was performed using Mummichog 2.0. Results In the adjusted analysis, 126 metabolic features differed significantly between DR patients and diabetic controls. Pathway analysis revealed alterations in the metabolism of amino acids, leukotrienes, niacin, pyrimidine, and purine. Arginine, citrulline, glutamic γ-semialdehyde, and dehydroxycarnitine were key contributors to these pathway differences. A total of 151 features distinguished PDR patients from NPDR patients, and pathway analysis revealed alterations in the β-oxidation of saturated fatty acids, fatty acid metabolism, and vitamin D3 metabolism. Carnitine was a major contributor to the pathway differences. Conclusions This study demonstrates that arginine and citrulline-related pathways are dysregulated in DR, and fatty acid metabolism is altered in PDR patients compared with NPDR patients.

The development of leakage current on vertical and horizontal strings of RTV coated porcelain suspension insulators in a salt-fog chamber are presented in this paper. Strings comprising of three-units, fully coated, and bottom surface coated, are investigated for leakage current development over a 1000 hour test period. The bottom surface coated insulator strings are used to examine the merits of half-coated insulators in comparison to fully coated insulator strings. Two coating formulations, containing ground quartz in one system, and alumina trihydrate in the other, both at the same filler level, are studied to determine whether filler type affects the development of leakage current, flashover, and their ability to prevent erosion under dry-band arcing.

Simulation studies under pulse voltage using a 2D axisymmetric model in COMSOL® 5.3a on the temperature and electric field along the stress grading system (SGS) of a form wound coil are reported in this work. The validity of the 2D model is shown by comparing the results with the measured temperature profile along the SGS. The effect of the nonlinearity of stress grading tape (SGT) conductivity is evaluated on both temperature and electric field. The results show that increasing the level of the nonlinearity of the SGT conductivity reduces the maximum electric field. On the other hand, the temperature rise is decreased by reducing the level of the nonlinearity of the SGT conductivity. As such, the effect of nonlinearity changes are not mutually compatible in controlling both the electric field and temperature profiles.

Surface partial discharges on the stress grading system of a medium voltage form-wound coil fed by an inverter can lead to insulation failure. Reducing the maximum surface electric field is therefore essential for prolonging insulation life. Under square waves in simulations using COMSOL Multiphysics, this work studies how floating metal foils added to the stress grading tape (SGT) affect electric field and temperature distributions. The results show that the metal foils make the electric field uniform but increase the temperature, due to increased current density in the stress grading tape. However, the temperature rise is below that considered to be detrimental to the insulation.

The Infectious Diseases Society of America recommends ophthalmologic examinations for everyone with positive Candida blood culture results (candidemia) to screen for endophthalmitis, a practice that remains controversial because of multiple concerns for its limited usefulness and potential for harm.To determine guideline efficacy by reconciling discrepancies in the incidence of endophthalmitis and evaluating outcomes of studies assessing ophthalmologic screening for candidemia.PubMed literature searches, including the search terms candidemia, fungemia, chorioretinitis, and endophthalmitis, identified longitudinal studies prior to 2018 of patients who underwent ophthalmologic evaluations in the setting of positive fungal blood culture results regardless of symptoms or clinical status. Additional studies not captured by these queries were found by manually scanning references within the articles captured by the queries. Ambiguous studies of patients with concomitant bacterial or viral infections were excluded.Thirty-eight applicable studies of 7472 patients who underwent ophthalmologic screening for candidemia or fungemia were identified. Criteria were compared with the conventional definition of endophthalmitis based on present (concordant) or absent (discordant) frank vitreous involvement. Concordant (59 of 6693 [0.9%]) and discordant (114 of 779 [14.6%]) endophthalmitis incidence rates differed by 13.8% (95% CI, 11.4%-16.4%; P .001). Visual acuity for each case was recorded verbatim as subjective report provided by each study, when available. None of the concordant endophthalmitis cases reported direct, intraocular, microscopic evidence of Candida or other fungal organisms. Outcomes were available for 19 patients with concordant endophthalmitis; 6 died within 4 weeks of screening. The rate of substantial vision loss was associated (φ = 0.58; 95% CI, 0.01-0.86; P = .046) with additional invasive intervention (3 of 6 [50.0%]) compared with medical management alone (0 of 6).In this systematic review without meta-analysis, inconsistent definitions of endophthalmitis accounted for discrepancies of its incidence and overreporting among patients with candidemia, contributing to bias and resulting in the construction of guidelines. As few as 3 of 7472 patients had potential improvement, while routine examination overall could lead to additional interventions and harm in this population. These findings suggest that indiscriminate screening based on candidemia alone does not appear to be supported by the literature and should be reevaluated for inclusion as a recommendation from the Infectious Diseases Society of America.

The paper presents the results of surface charge measurements on insulation film samples with different surface resistivities. Polytetrafluoroethylene (PTFE) and Nylon 6 (PA6) as well as mica paper subjected to unipolar and bipolar square waves at different switching frequencies. The experimental data are presented to explain the differences observed in the times-to-failure of turn insulation when aged using unipolar and bipolar square waves. Time-to-failure experiments and COMSOL® simulations are used to estimate the accumulated charge on the surface of insulation films with different surface resistivities.

The paper examines the time-to-failure of enameled form-wound machine turn insulation subjected to unipolar and bipolar square waves at different switching frequencies. Partial discharge under the same square wave parameters are also reported using a point-to-plane geometry from which the measured PD features are related to the time-to-failure results of the turn insulation. The results show that the life of enameled turn insulation is considerably longer under bipolar square waves than for unipolar waves and that turn insulation lifetime is related to the power of the partial discharges. In addition, a frequency threshold in the time-to-failure results is observed corresponding to a decrease in PD power and the development of surface space charge that affects the PD features is discussed.

Limiting the temperature rise in the stress grading system in a medium voltage form-wound coil of a rotating machine driven by an adjustable speed drive is essential to prolong the life of a motor. The common way of increasing the electrical conductivity of the system, thereby to lower joule heat production and temperature rise, is to increase the build of the tape system. Simulation studies on various stress grading system builds on the heat production has been evaluated in this study. A good correlation between measured and simulated temperature profiles under pulse voltage condition confirms the validity of the simulation. The stress grading system has been simulated using the 2D axisymmetric module in COMSOL® 5.2a. The results show that increasing the number of layers of conductive armor tape can reduce the heat production in CAT region but by increasing the number of layers of stress grading tape leads to increase in heat production in SGT region. The study suggests that use of other non-linear tape materials for SGT may be needed to effectively lower the temperature rise in the stress grading system.

Evaluating the performance of the stress grading system by simulating the electric field and potential distributions in the overhang region shows that high conductive stress grading tape (SGT) reduces the maximum electric field at this region. For simulation studies, an accurate conductivity that takes into account the effects of vacuum pressure impregnation (VPI) process, temperature, and tape builds is measured. As the electric field on the SGT is enhanced under operating conditions, the conductivity of the SGT has been measured in a high electrical field condition under pulse conditions to minimize the effects of temperature rise on the SGT. The conductivity of a one half-lap layer and a double half-lap layer of SGT at different temperatures is measured. The results show that for both designs, the higher the tape conductivity the lower the maximum electric field in the SGT region. For evaluating the simulation model, the temperature profile along the stress grading system is measured and simulated under high frequency sinusoidal voltage.

The lifespans of enamelled turn insulation samples are studied when stressed with square waves characterized by different rise times, duty cycles, switching frequencies, and applied voltages. Partial discharge activities under these test conditions have also been recorded using an RF antenna in an effort to correlate the time to breakdown with material degradation under fast repetitive pulse aging. The aging and PD features were independent of rise time for a 50 % duty cycle; however, slightly faster times to failure were observed at a 15 % duty cycle for the faster rise times, for the considered range. The higher duty cycle and the higher number of applied cycles accelerated the aging.

This study presents both numerical and experimental results regarding the effects of pollution on the flashover performance of glass suspension-type insulators. The finite element method (FEM) was used for simulating polluted insulators both at power frequency and at lightning impulse voltages. Partially conductive epoxy resin with graphite powder was used for modeling pollution on the insulators, which enabled the measurement of the electrical potentials on the polluted insulators. Numerical studies demonstrated the variations in the field distributions caused by the location and severity of the pollution as well as by the type of voltage applied. The simulations, which were verified to a degree through measurement, showed that pollution conductivities greater than 10-6 S/m and 10-3 S/m alter field distributions for power frequency and lightning impulse voltages, respectively. Unlike the results obtained for partially polluted insulators, the voltage distribution was almost linear for fully polluted insulators. Experimental studies revealed that the location of the partial pollution plays an important role in flashover performance for lightning impulse voltages but has a negligible effect for power frequency voltages.

This paper describes the suppression of dry-band arcing erosion of silicone rubber by alumina tri-hydrate and silica fillers in the DC inclined plane test, employing the wavelet based multiresolution analysis of leakage current. The third detail component of the leakage current as decomposed by the wavelet-based multiresolution analysis is shown to be an indicator of the effectiveness of the filler type in suppressing erosion by dry-band arcing. The addition of alumina tri-hydrate or silica filler to silicone rubber increases the thermal conductivity of the composites, retarding the development of the eroding temperature, and thus the evolution of the third detail. Additional effect is also obtained for the dehydration enthalpy, of alumina tri-hydrate in silicone rubber at a filler level of 30 wt%, in impeding the development of hot spots on the tested surface. A reduction in the magnitude of the third detail is evident with filler level, indicating that the increasing volume of silica or alumina tri-hydrate reduces the temperature of the dry-band arcing plasma. Comparable levels of the leakage current third detail is found between 30 wt% alumina tri-hydrate and silica filled composites which suggests the water of hydration plays a minor role in diluting the SiR but at 58 wt% an internal oxidation mechanism that produces gases diluting the arcing phase appears to suppress erosion.

This paper investigates the erosion of silicone rubber composites filled with various fillers. The fillers under study are alumina tri-hydrate, magnesium hydroxide and silica in a liquid silicone ru bber. The inclined plane tracking and erosion test was used to compare the erosion of the composite materials at 50 wt% filler level and at 4.5 kV. Simultaneous thermogravimetric and differential thermal analyses are reported which shows various mechanisms by which the fillers can su ppress the dry­ band arcing erosion. The effect of water of hydration in the alumina tri-hyd rate and magnesium hydroxide is investigated and its effect on the suppression of the dry-band arcing erosion is reported for the composites filled with alumina tri-hydrate and magnesiu m hydroxide., 2017 IEEE Conference on Electrical Insulation and Dielectric Phenomenon (CEIDP), 22-25 October 2017, Fort Worth, TX, USA

The first polymer insulator for AC transmission lines was developed in the late 1950s. This insulator consisted of a flexibilized epoxy resin weathershed cast onto a fiberglass rod, and field trials on a 138-kV line took place in 1959. Insulators failed almost immediately on energization due to severe tracking and erosion of the bisphenol-A epoxy material, which was later, through inclined-plane tests, shown to be inherently unsuitable for use in outdoor insulation [1].

Purpose To report 1-year outcomes of the Prospective Retinal and Optic Nerve Vitrectomy Evaluation study. Design Prospective, controlled, observational study. Participants Eighty eyes of 40 participants undergoing pars plana vitrectomy for epiretinal membrane (ERM), macular hole (MH), or vitreous opacities. Methods Enrolled participants underwent baseline evaluation of the study (surgical) and fellow (control) eyes by a masked fellowship-trained glaucoma specialist; evaluation included intraocular pressure (IOP; Goldmann applanation and Tono-Pen), central corneal thickness, gonioscopy, and cup-to-disc ratio measurement. Baseline testing included bilateral color fundus and optic disc photography, fundus autofluorescence, automated perimetry, and optical coherence tomography (OCT) of the macula and optic nerve. Evaluations were repeated at 3 months and 1 year after surgery. Main Outcome Measures The primary outcome measure was changes in peripapillary retinal nerve fiber layer (pRNFL) thickness. Secondary outcomes included changes in macular thickness and IOP. Results Thirty-eight of 40 patients completed 1 year of follow-up. Mean visual acuity (VA) improved in study eyes from baseline ( P = 0.003) but remained worse than fellow eyes ( P P = 0.004). Mean IOP difference between study eyes and fellow eyes increased from baseline to 1 year. At 1 year, MH study eyes had higher mean IOP (16.0±3.7 mmHg) compared with fellow eyes (14.8±3.4 mmHg; P = 0.08). Mean IOP for pseudophakic study eyes increased from 14.5±3.2 mmHg at baseline to 16.0±2.8 mmHg at 1 year ( P = 0.04). Central subfield thickness (CST) and cube volume decreased in study eyes at 1 year but remained greater than that of fellow eyes ( P P P = 0.02) but remained worse than fellow eyes (−1.2; P = 0.002). Conclusions One year after vitrectomy, VA, CST, and MD improved in study eyes but not to the level of fellow eyes. Inferior pRNFL thickness decreased in study eyes. Reduction in CST from baseline correlated with degree of VA improvement. Pseudophakic study eyes demonstrated increased IOP when compared with baseline.

This paper describes an investigation into the dry-band arcing mechanism leading to erosion of filled silicone rubber in the DC inclined plane test. Good correlation is obtained between the formation of surface residue, hotspots and the eroding dry-band arcing. The hotspots detected by infrared camera correlates well with the temperature of degradation determined by thermogravimetric analysis and differential scanning calorimetry. To characterize the physical mechanism of dry-band arcing, wavelet-based multiresolution analysis up to seven levels of resolution is applied to the leakage current waveforms. The analysis shows that both stable and intense discharges characterize the eroding dry-band arcing. A time-to-eroding parameter is proposed to determine the relative resistance to the formation of residue. Faster accumulation of residue is evident under -DC than +DC. Earlier inception of erosion is obtained for the silica filled- as compared to the alumina tri-hydrate filled- silicone, in which the release of the water of hydration is postulated to suppress the residue formation.

Congenital hypertrophy of the retinal pigment epithelium is a benign pigmented lesion of the posterior pole with a unique clinical appearance. It is flat, round, and has sharp edges. While it is usually black, it may have internal lacunae without pigment. The lesion may also be all hypopigmented. Over many years, the lesions may grow slightly and change their pigmentation. Even though malignant transformation is extremely rare, annual examinations should be performed.

Rahul K Reddy,1 Maziar Lalezary,1 Stephen J Kim,1 Jeffrey A Kammer,1 Rachel W Kuchtey,1 Edward F Cherney,1 Franco M Recchia,2 Karen M Joos,1 Anita Agarwal,1 Janice C Law11Department of Ophthalmology, Vanderbilt University School of Medicine, Nashville, TN, USA; 2Tennessee Retina, PC, Nashville, TN, USABackground: The purpose of this paper is to report the 3-month findings of the Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study.Methods: Eighty eyes of 40 participants undergoing vitrectomy were enrolled. Participants underwent baseline evaluation of the study (surgical) and fellow (control) eye that included: intraocular pressure, central corneal thickness, gonioscopy, cup-to-disc ratio measurement, color fundus and optic disc photography, automated perimetry, and optical coherence tomography of the macula and optic nerve. Evaluation was repeated at 3 months. Main outcome measures were changes in macula and retinal nerve fiber layer (RNFL) thickness and intraocular pressure.Results: All participants completed follow-up. Mean cup-to-disc ratio of study and fellow eyes at baseline was 0.43 ± 0.2 and 0.46 ± 0.2, respectively, and 13% of participants had undiagnosed narrow angles. There was no significant change in intraocular pressure, cup-to-disc ratio, or pattern standard deviation in study eyes compared with baseline or fellow eyes at 3 months. Vision improved in all study eyes at 3 months compared with baseline (P = 0.013), but remained significantly worse than fellow eyes (P < 0.001). Central subfield and temporal peripapillary RNFL thickness were significantly greater in eyes with epiretinal membrane (P < 0.05), and resolution after surgery correlated with visual improvement (P < 0.05).Conclusion: The 3-month results do not indicate any increased risk for open-angle glaucoma but suggest that a relatively high percentage of eyes may be at risk of angle closure glaucoma. Temporal RNFL thickness and central subfield were increased in eyes with epiretinal membrane, and resolution correlated with degree of visual recovery.Keywords: vitrectomy, open-angle glaucoma, intraocular pressure, epiretinal membrane, macular hole

This paper presents the results of an examination of the erosion resistance of two-part room temperature vulcanizing (RTV) silicone rubber (SiR) nanocomposites. The SiR composites were filled with 7 nm size fumed silica and 1.5 μm size micro-silica. Separate samples were prepared using conventional mechanical mixing and an electrospinning technique, and their erosion resistances were compared. The electrospinning technique allows for a higher volume fraction of nanofiller and micro-filler in the composites as compared to the conventional samples. The erosion resistances were tested using both an infrared-laser-based source and the ASTM D2303 standard inclined plane tracking and erosion method (IPT). The experimental results for the eroded mass, tracking voltage, and tracking time show that the erosion resistances of electrospun samples are much greater than those of conventional samples. Scanning electron microscope (SEM) images and variable tracking patterns of the conventional samples after the IPT tests suggest an improvement in the dispersion of the fillers within the electrospun samples compared to the conventional samples. Power analysis during the IPT tests also shows that more power is required to track and erode electrospun samples before sample failure occurs than is needed for conventional samples, which suggests improved bonding between the fillers and the silicone rubber matrix. These findings also are supported by the results of thermo-gravimetric analysis.

In this paper, the performance of silicone rubber composites containing 0, 10 and 30 wt % loading of silica filler is investigated in the initial-tracking voltage test method of the inclined plane test under AC and DC showing the most inferior erosion class under +DC followed by -DC and then AC. DC as compared to AC dry-band arcing characteristics are analyzed by conducting leakage current measurements prior to and after the inception of dry-band arcing. At high test voltages, instability of the contaminant rivulet is found to be an important factor in the development of dry band arcing and, consequently, biasing the test outcomes when equal voltages of rms AC and DC are selected. The initial tracking voltage in ASTM D2303 is, therefore, proposed as a reliable approach by which +DC and -DC test voltages can be reliably selected. A coefficient of variation parameter is also proposed as a useful mean of selecting the equivalent DC voltages, and the validity of the parameter is verified experimentally using the initialtracking voltage test method. Erosion in the constant voltage method is investigated under DC by applying the equivalent voltages and compared to AC. Based on this methodology, it is suggested that an improvement in silicone rubber compositions is needed for DC. Moreover, the need to select the creepage distance of polymer insulators designed for AC, yet to be used under DC, with reference to tracking/erosion performance is highlighted.

PURPOSE The purpose of this report is to describe extensive acute macular neuroretinopathy lesions with atypical features. METHODS Retrospective case report. RESULTS A patient developed acute macular neuroretinopathy in the setting of multiple previously described associations including a flu-like illness, sympathomimetic exposure, overdose of norepinephrine reuptake inhibitors, anemia, thrombocytopenia, and hypotensive shock. The fundus lesions superficially resembled retinal hemorrhages in color and fluorescein angiography pattern. The lesions could be detected on autofluorescence and infrared imaging. Optical coherence tomography revealed outer plexiform layer opacification and photoreceptor abnormalities. CONCLUSION This case suggests a compounding effect of factors associated with acute macular neuroretinopathy, possible exacerbating insults and outer plexiform layer abnormalities that may correlate with the temporal course of this condition.

Purpose To develop an internationally valid skill-based rubric that can be used as a global standardized platform for teaching, training, and evaluation of panretinal photocoagulation (PRP) in training programs. Design A panel of educators and experts in retinal lasers was assembled to develop a standardized objective skill-based rubric. Participants Sixteen international educators and retina specialists. Methods The steps to performing slit-lamp delivery of PRP was described in detail. A group of 6 authors reviewed and agreed on the steps and assigned descriptors to expectation levels of novice, beginner, advanced beginner, and expert according to a modified Dreyfuss model. The tool then was vetted by an international panel of 10 retina specialists who are involved in training ophthalmologists in other countries. Main Outcome Measures Final version of the tool agreed on by the international review panel. Results The consecutive steps to performing PRP were outlined and broken down into preparation, procedure, and postoperative care. Descriptive words explaining what to expect from a novice, beginner, advanced beginner, and expert were listed for each step of PRP. Expert comments were incorporated, establishing face and content validity. Conclusions This group of authors clearly defined expectations of a trainee at 4 levels of training according to the modified Dreyfus model, and an international panel of retina specialists agreed to its accuracy. This tool, the International Council of Ophthalmology’s Ophthalmology Surgical Competency Assessment Rubric for Panretinal Photocoagulation, has face and content validity. It can be used globally in training programs both to teach and assess this important comprehensive skill in ophthalmic training.

In this paper, electrospinning is shown to be an effective method for overcoming the agglomeration of nanosilica in silicone rubber nanocomposites. Silicone rubber nanocomposites with 7 nm silica were produced using conventional mixing and electrospinning processes. Scanning electron microscopy is used to demonstrate homogenous filler dispersion in electrospun samples as compared to conventional mixed samples. Thermo-gravimetric analysis and infrared-laser-based thermal tests show significant improvements in thermal stability and heat transfer in electrospun nanocomposites. However, no significant improvements in either the mechanical properties or relative permittivity between the electrospun and conventional mixed samples were found. The improved thermal properties of the electrospun silicone rubber nanocomposites are attributed to the significantly reduced nanofiller agglomeration and their uniform dispersion.

The paper presents the results of inclined plane tests on ATH and silica composites of Silicone rubber (SiR) and EPDM to evaluate the effect of filler type and loading on the tracking and erosion resistance of the composites formed. The effect of test voltage on the outcome of the incline plane was also examined. A laser ablation test was also used to evaluate the various composites. A critical test voltage of 4.5 kV was shown to cause failures in samples which emphasizes the importance of testing composites at voltages above this critical level. In comparing the two test methods, both the inclined plane and laser ablation test methods showed the same order for EPDM composites of ATH and silica while the laser method showed silica SiR composites to perform somewhat better than in the inclined plane test which showed similar results.

Purpose To determine the baseline antibiotic susceptibility patterns of conjunctival and nasopharyngeal flora isolated from patients undergoing intravitreal (IVT) injections for choroidal neovascularization (CNV). Design Prospective, observational study. Participants Forty-eight eyes of 24 patients undergoing unilateral IVT injections for CNV. Methods Bilateral conjunctival and unilateral nasopharyngeal cultures on the treatment side were taken before application of any topical medications. Main Outcome Measures Bacterial isolates were identified and tested for antibiotic susceptibility to 16 different antibiotics using the Kirby-Bauer disc diffusion technique. Results A total of 57 bacterial isolates were obtained from the conjunctiva of 48 eyes. Coagulase-negative staphylococci (CNS) accounted for 37 of the 57 isolates (65%). The most common CNS organisms were Staphylococcus epidermidis and Staphylococcus lugdunensis accounting for 73% and 11% of CNS isolates, respectively. More than half of S. epidermidis isolates demonstrated some level of resistance to ofloxacin and levofloxacin, and 33% and 37% of isolates showed some level of resistance against gatifloxacin and moxifloxacin, respectively. Some 60% and 30% of CNS isolates were resistant to ≥3 and ≥5 antibiotics, respectively. Among the 24 nasopharyngeal cultures, 8 (33%) grew Staphylococcus aureus , and 1 of the 8 isolates (13%) was resistant to all penicillin, cephalosporin, macrolide, and fluoroquinolone antibiotics tested. Conclusions Our results demonstrate subtantial levels of resistance to third- and fourth-generation fluoroquinolones and multiresistance among ocular CNS isolated from patients undergoing IVT injections for CNV. Financial Disclosure(s) The authors have no proprietary or commercial interest in any materials discussed in this article.

The paper provides an analysis of the thermal stresses in medium-voltage form-wound motor coils that arise from pulsed width modulated, repetitive square-wave, and impulse voltages. The effects of the shape, repetition rate, and rise and fall time of the pulses are studied through experimental and computational work. Based on the frequency spectra of the pulse trains and their corresponding signal powers, it is shown that a set of sinusoidal high-frequency voltages of predetermined amplitudes can effectively produce consistent thermal stresses, and both the experimental and simulation results confirm the validity of the proposed scheme.

The paper addresses the ac modeling and anisotropic dielectric properties of stress grading and conductive armor tapes that are two crucial components in form-wound motor coils. The limitations of the conventional dc conductivity modeling and the necessities of using ac conductivity modeling and anisotropic properties of these materials at high frequencies and high electric field are discussed. The method of measurement of the dielectric parameters at high frequency and high electric field for 2D modeling is also presented. The transient FEM simulations from conventional modeling and the proposed ac modeling are compared to experimentally obtained results. Good agreement is only obtained from the latter modeling.

The paper discusses the mechanism by which nanofillers improve the erosion resistance of silicone rubber nanocomposites under simulated conditions of dry band arcing. Various micro-nano composites are studied, including microfiller, nanofiller, combinations of both, and with a commercial surfactant to improve the dispersion of the nanofiller. The thermal conductivity of the composites, measured using a standard method, shows higher thermal conductivity when the nanofiller is well dispersed. A thermal model is developed and solved with finite element method (FEM) to examine the temperature profile in the modelled nanocomposites under laser heating, which simulates the hot spot from dry band arcing. The hot spot is compared to the measured temperature profile by an infrared camera. SEM, EDAX, and XRD techniques are used to analyze the thermally decomposed silicone residue after laser heating to elucidate the protective mechanism in the silicone rubber nanocomposites.

This paper explores how the addition of inorganic nanofiller and microfiller to silicone rubber can impart resistance to erosion for overhead insulation applications. Various micro-nano composites were prepared for this study, namely microfiller, nanofiller, and the combination of microfiller and nanofiller with a commercial surfactant to improve the dispersion of the nanofiller. The effect of the surfactant on the surface wettability of the composites was analyzed with contact angle measurements. Salt-fog, inclined plane and laser ablation tests were conducted to evaluate the erosion resistance of the micro-nano filled composites. The results in all three tests showed that the combination of microfiller and nanofiller with surfactant resulted in composites with improved erosion resistance to dry band arcing, with the exception of the case where calcinated filler was used in the formulation.

The paper addresses the temperature and electric field dependence on the conductivity of the conductive armor and stress grading tapes on form-wound motor coils. The temperature and electric field dependence is measured in the laboratory, and the nonlinear dependency is used in transient FEM simulations of the potential distribution on the form-wound coils. The surface potential distribution, for various temperatures and applied voltages, is measured in the laboratory from which the surface electric stress is calculated. Good agreement between the simulated and measured stresses is obtained. A temperature of 155 °C is shown to have little influence on the stress grading, but the electric stress dependence on conductivity is shown to have a major influence on the stress grading of the motor coil examined in this study.

This paper reports on measurements of thermally stimulated depolarization current (TSDC) that is applied to characterize changes in the large motors and generators enamelled wires that have been exposed to aging under steep-front pulse voltage waveforms. The thermoelectrets are prepared at various polarizing fields, EP, and measurements of TSDC are carried out both as a function of time and temperature over the range of 23–200 °C. In addition, various TSDC parameters such as activation energy, ɛa, characteristic relaxation time, τ and the released charge, Q during the relaxation process have been determined by applying initial rise method. The experimental results for TSDC spectra of wire specimens have shown that the total stored charge in the insulation bulk increases significantly, as the number of insulation layers increases on the wire. The reason for such a higher concentration of trapped charges is more likely due to the presence of a broad distribution of the traps, which are occupied by the injected charges.

The results of erosion resistance, tensile strength, elongation at break, hardness, and thermal stability measurements are presented for silicone nanocomposites prepared using various nano and micro silica and alumina fillers in a two-part silicone rubber (SiR) matrix. The fillers are used to improve the erosion resistance of SiR, which is necessary for outdoor insulation housing applications. Good dispersion of the fillers is achieved using Triton/sup TM/, a common surfactant. An optimal surfactant concentration imparts good erosion resistance to the nanocomposites in laser heating tests without adverse effects, but excess surfactant has a negative impact on the mechanical properties of the silicone. Thermal gravimetric analysis demonstrated that nano fumed silica imparts better heat resistance to silicone than natural nano silica or nano alumina fillers. Fourier transform infrared spectroscopy analysis of the nanofillers indicated a significantly higher concentration of silanol groups in the nano fumed silica filler than in micro silica. The influence of the increased number of silanol groups on the erosion resistance of the nanocomposites and their mechanical properties is discussed.

The paper presents two different methods to calculate the current density along silicone rubber (SiR) insulator surface under salt-fog testing conditions. The first method which is based on field theory approach uses the commercial software COMSOL® to compute the current density. The conductivity of the contamination layer used in the calculations was extracted from the measured equivalent salt deposit density (ESDD) separately for different regions of the insulator surfaces. The second method is based on circuit theory approach. The insulator surface was divided into different sections for resistance calculations to account for different contamination levels. Rankings based on the calculated current densities based on segmentation of the insulator surface for ESDD measurements match with those extracted from measured leakage currents.

The paper reports on tests done on four commercial room temperature vulcanized (RTV) silicone rubber high voltage insulator coatings aimed at achieving information on the relative performance of the coatings with respect to aging. The initial characterization of the coatings includes the identification of the primary filler type, concentration of filler, the amount of free fluid, and the molecular species of the free fluid. Soxhlet extraction and gas chromatography tests show considerable depletion of fluid after accelerated aging tests in acid-water and the associated changes to the physical properties is assessed by standard mechanical tests on coupon size specimens. The effect of acid-water aging on the hydrophobicity is assessed by measurements of the static contact angle and the onset of leakage current in an incline plane test. Several field aged coatings are assessed for residual LMW fluid which is compared to accelerated aging tests.

This paper reports on the heat erosion resistance of various silicone rubber compositions under infrared laser heating that simulates the dry band arcing phenomenon on outdoor insulation. The composites are made using a two-part addition cure silicone rubber, with various amounts of alumina, natural silica, or fumed silica, nano-or micron size, and different amounts of Tritontrade X-100 surfactant. It is shown that the surfactant greatly improves the dispersion of nanosized particles, yielding composites that are more homogeneous, with improved resistance to heat ablation. Significantly improved dispersion in the presence of surfactant is confirmed by SEM analysis for some nanofillers, while very little effect is observed for others. The surfactant is beneficial up to the point where the filler surface is saturated with the additive. Fumed silica is shown to impart greater heat ablation resistance than natural silica and alumina. Furthermore, a distinct protection mechanism appears to be operative for fumed silica and natural silica as opposed to alumina.

The paper presents the results of the study on the influence of insulator profile on the aging performance of silicone rubber (SIR) insulators in salt-fog. Experiments have been conducted on various two-shed arrangements at 35 V/mm average stress and 0.25 S/m salt-fog conductivity level. The work is also extended to include commercial 15 kV class insulators with different profiles. Shed spacing, shed diameter, alternate shed design and shed shape are the parameters investigated in this study. The low frequency harmonics of the leakage current, early aging period (EAP), and equivalent salt deposit density (ESDD), are used to evaluate the aging performance of different designs. Insulator profile is shown to greatly influence the aging performance of SIR insulators. Shed shape proves to be the most important parameter to be considered in designing non-ceramic insulators profiles. Also, as the shed spacing decreases, the performance of SIR insulators improves. Simulation results using FEMLAB show that the electric field on insulators is below the corona onset at both dry and wet conditions. Dry band arcing is therefore the main electrical cause for aging in distribution class insulators and it is possible to improve the pollution performance of SIR insulators using appropriate profiles as suggested in this work

The standard methods available to test tracking and erosion resistance of filled silicone rubber do not allow to delineate the fundamentals of the thermal degradation, although the heat from the dry band arcing is the main degradation factor. In this work a thermal imaging camera is used to investigate the performance of filled silicone rubber in an inclined plane test, and a scheme is established to relate the temperature and the electrical discharge energy. Further, an infrared laser technique, based on constant energy approach, is developed to study the material performance under laser heating. The technique consists of applying a certain amount of infrared laser energy during a set time period, in order to produce erosion in the silicone rubber samples. Through correlation studies the applicability of the proposed laser technique to rank silicone rubber samples with various fillers has been validated. The laser tests show identical ranking of samples when compared to samples ranked using inclined plane tests, yet offering significant advantages of being faster, simpler, and reproducible.

Local discharges in the vicinity of the mounting flange of composite bushings due to the electric field enhancement can cause insulating material degradation and finally lead to failure. In this paper, a proposed solution to this problem by employing a resistive silicone rubber coating on composite HV bushings was investigated. Finite Element Method (FEM) analysis of the electric field distribution along the surface of bushings by FEMLAB ® simulation and potential measurements by an electrostatic probe (ESP) technique confirmed that the stress grading effect of a 100 MΩ resistive coating results in a linear potential distribution and the tangential field is significantly reduced in the region of the mounting flange.

In this paper a parametric study of the dry-band arcing characteristics in the inclined plane tracking and erosion test is conducted under AC and DC voltages. The standard inclined plane testing apparatus is modified to promote stable and intense dry-band arcing, thereby analyzing the characteristics of the eroding dry-band arcing. The behavior of the liquid contaminant, which may bias the dry-band arcing current under equal AC and DC voltages, is investigated for different flow rates to determine suitable testing conditions. The highest leakage current magnitude is obtained under +DC followed by AC and -DC voltages, and reduced resistivity for the dry-band arcing column is shown under the +DC and AC as compared to the -DC voltages. The reduction in resistivity is speculated to be the result of metallic ions from electrode corrosion under +DC as compared to -DC, with less significant difference between +DC and AC. In addition, the inception behavior of the discharge influencing the length of the dry-band arc is found to be dependent on the voltage type. Reduced dry- band arcing length is measured for DC as compared to AC, with further reduction shown under +DC as compared to -DC. Thermal analysis is accordingly conducted, showing higher hot spot temperatures with dry-band arcing of a shorter length.

To determine the 1-year and 2-year likelihood of vitrectomy in diabetic patients undergoing initial pan retinal photocoagulation (PRP).Diabetic eyes receiving initial PRP for proliferative diabetic retinopathy (PDR) were analyzed to determine their risk for vitrectomy based on clinical findings.In total, 374 eyes of 272 patients were analyzed. The percentage of eyes undergoing vitrectomy 1 year and 2 years following initial PRP was 19.1% and 26.2%, respectively. Of the eyes in Group 1 (PDR alone), Group 2 (PDR and vitreous hemorrhage), and Group 3 (PDR and iris neovascularization, vitreous hemorrhage with traction or fibrosis, or fibrosis alone), the percentage receiving pars plana vitrectomy at 1 year and 2 years was 9.73% (18/185) and 15.7% (29/185), 26.9% (43/160) and 34.4% (55/160), and 37.9% (11/29) and 48.3% (14/29), respectively. Eyes in Group 2 had 2.78 times greater likelihood (P0.0001) and eyes in Group 3 had 3.54 times higher likelihood (P0.0001) of requiring pars plana vitrectomy within 2 years than those with PDR alone.Eyes receiving PRP for PDR with associated hemorrhage or traction were more likely to undergo pars plana vitrectomy within 1 year and 2 years following initial PRP compared with eyes with only PDR, providing important prognostic information for PRP-naive patients.

The paper presents the results of aging of medium voltage stator coil enamelled turn insulation under square waves having rise times of 270 ns and 4.5 μs. Unipolar square waves having a peak voltage of 2.5 kV and a switching frequency of 3 kHz were applied to enamelled wire samples while measuring online partial discharge. A two-parameter Weibull distribution was employed for analysis of the effect of rise time on insulation life. The tests were repeated at 6 kV peak with duty cycles of 15% and 50% for both rise times. The analysis indicates that insulation life is dependent on voltage rise time only when the DC component of the wave is short.