Characterisation of anisotropic etching in KOH using network etch rate function model: influence of an applied potential in terms of microscopic properties

Using the network etch rate function model, the anisotropic etch rate of p-type single crystal silicon was characterised in terms of microscopic properties including step velocity, step and terrace roughening. The anisotropic etch rate data needed have been obtained using a combination of 2 wagon wheel patterns on different substrate and 1 offset trench pattern. Using this procedure the influence of an applied potential has been investigated in terms of microscopic properties. Model parameter trends show a good correlation with chemical/electrochemical reaction mechanism and mono- and dihydride terminated steps reactivity difference. Results also indicate a minimum in (111) terrace roughening which results in a peak in anisotropic ratio at the non-OCP applied potential of −1250 mV vs OCP

Influence of applied potentials on anisotropic etching of silicon described using kinematic wave etch model

Anisotropic etch rates of silicon in KOH solutions were studied as a function of an externally applied potential. A combination of three micromachined samples consisting of predry-etched wagon-wheel patterns and masked trench offset patterns was used to measure the etch rates at a large number of crystal orientations simultaneously. The measured data was described in terms of microscopic properties, including step velocities, terrace roughening, and step anisotropy, using the kinematic wave etch model. All parameters show distinct changes due to the applied potential and resulting additional electrochemical reaction path. A decrease in step velocity shows the electrochemical oxidation and subsequent passivation of the Si surface. Trends in terrace roughening show a minimum in roughness and a corresponding change in anisotropic etch-rate ratio at the non-open-circuit potential of −1250 mV vs saturated calomel electrode. The observed decrease in step anisotropy and subsequent step-anisotropy reversal at more positive potentials indicates an anisotropy in not only chemical etching but also electrochemical oxidation of (111) surface steps.\u

Placental growth factor and its potential role in diabetic retinopathy and other ocular neovascular diseases.

The role of vascular endothelial growth factor (VEGF), including in retinal vascular diseases, has been well studied, and pharmacological blockade of VEGF is the gold standard of treatment for neovascular age-related macular degeneration, retinal vein occlusion and diabetic macular oedema. Placental growth factor (PGF, previously known as PlGF), a homologue of VEGF, is a multifunctional peptide associated with angiogenesis-dependent pathologies in the eye and non-ocular conditions. Animal studies using genetic modification and pharmacological treatment have demonstrated a mechanistic role for PGF in pathological angiogenesis. Inhibition decreases neovascularization and microvascular abnormalities across different models, including oxygen-induced retinopathy, laser-induced choroidal neovascularization and in diabetic mice exhibiting retinopathies. High levels of PGF have been found in the vitreous of patients with diabetic retinopathy. Despite these strong animal data, the exact role of PGF in pathological angiogenesis in retinal vascular diseases remains to be defined, and the benefits of PGF-specific inhibition in humans with retinal neovascular diseases and macular oedema remain controversial. Comparative effectiveness research studies in patients with diabetic retinal disease have shown that treatment that inhibits both VEGF and PGF may provide superior outcomes in certain patients compared with treatment that inhibits only VEGF. This review summarizes current knowledge of PGF, including its relationship to VEGF and its role in pathological angiogenesis in retinal diseases, and identifies some key unanswered questions about PGF that can serve as a pathway for future basic, translational and clinical research

COVID-19 and immunosuppression: a review of current clinical experiences and implications for ophthalmology patients taking immunosuppressive drugs

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 in Wuhan city, Hubei province, China. This is the third and largest coronavirus outbreak since the new millennium after SARS in 2002 and Middle East respiratory syndrome (MERS) in 2012. Over 3 million people have been infected and the COVID-19 has caused more than 217 000 deaths. A concern exists regarding the vulnerability of patients who have been treated with immunosuppressive drugs prior or during this pandemic. Would they be more susceptible to infection by the SARS-CoV-2 and how would their clinical course be altered by their immunosuppressed state? This is a question the wider medical fraternity-including ophthalmologists, rheumatologists, gastroenterologist and transplant physicians among others-must answer. The evidence from the SARS and MERS outbreak offer some degree of confidence that immunosuppression is largely safe in the current COVID-19 pandemic. Preliminary clinical experiences based on case reports, small series and observational studies show the morbidity and mortality rates in immunosuppressed patients may not differ largely from the general population. Overwhelmingly, current best practice guidelines worldwide recommended the continuation of immunosuppression treatment in patients who require them except for perhaps high-dose corticosteroid therapy and in patients with associated risk factors for severe COVID-19 disease.Ophthalmic researc

Evolving consensus for immunomodulatory therapy in non-infectious uveitis during the COVID-19 pandemic

Background Immunomodulatory therapy (IMT) is often considered for systemic treatment of non-infectious uveitis (NIU). During the evolving coronavirus disease-2019 (COVID-19) pandemic, given the concerns related to IMT and the increased risk of infections, an urgent need for guidance on the management of IMT in patients with uveitis has emerged. Methods A cross-sectional survey of international uveitis experts was conducted. An expert steering committee identified clinical questions on the use of IMT in patients with NIU during the COVID-19 pandemic. Using an interactive online questionnaire, guided by background experience and knowledge, 139 global uveitis experts generated consensus statements for IMT. In total, 216 statements were developed around when to initiate, continue, decrease and stop systemic and local corticosteroids, conventional immunosuppressive agents and biologics in patients with NIU. Thirty-one additional questions were added, related to general recommendations, including the use of non-steroidal anti-inflammatory drugs (NSAIDs) and hydroxychloroquine. Results Highest consensus was achieved for not initiating IMT in patients who have suspected or confirmed COVID-19, and for using local over systemic corticosteroid therapy in patients who are at high-risk and very high-risk for severe or fatal COVID-19. While there was a consensus in starting or initiating NSAIDs for the treatment of scleritis in healthy patients, there was no consensus in starting hydroxychloroquine in any risk groups. Conclusion Consensus guidelines were proposed based on global expert opinion and practical experience to bridge the gap between clinical needs and the absence of medical evidence, to guide the treatment of patients with NIU during the COVID-19 pandemic.Ophthalmic researc

Holocene evolution of the Chan May coastal embayment, central Vietnam: Changing coastal dynamics associated with decreasing rates of progradation possibly forced by mid- to late-Holocene sea-level changes

Southeast Asian coastal environments are undergoing massive transformations with unprecedented population and infrastructure development. These transformations are occurring on a backdrop of intense natural and anthropogenic environmental change, which are increasing the risk to the burgeoning coastal population. Little is known about how central Vietnamese coastal environments have changed naturally since the mid-Holocene sea-level highstand and how recent anthropogenic change and sea-level variation have affected the coastal system. The Chan May embayment in central Vietnam allows us to examine how recent changes in both anthropogenic development and sea-level change have affected the coastline. The embayment preserves a series of prograding beach ridges and is subject to intense human pressures with the construction of a large economic and industrial park, and expansion of tourist facilities. Using ground penetrating radar and quartz optical dating we identify a switch from 6000 years of prograding beach ridges to transgressive dunes within the past century resulting in a decreasing rate of beach ridge progradation possibly in the last 100 years. The recent modes of sediment deposition through washovers and a transgressive dune indicates that coastal progradation has slowed and might have stopped

Search for patterns by combining cosmic-ray energy and arrival directions at the Pierre Auger Observatory

Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with E > = 6×1019 eV by analyzing cosmic rays with energies above E > = 5×1018 eV arriving within an angular separation of approximately 15°. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution. No significant patterns are found with this analysis. The comparison of these measurements with astrophysical scenarios can therefore be used to obtain constraints on related model parameters such as strength of cosmic-ray deflection and density of point sources

Influence of an Applied Potential on the Anisotropic Etch rates of Silicon in KOH

The anisotropic etch rate of p-type single crystal silicon has been systematically studied as a function of an externally applied electrical potential. Changes in overall etch rate are consistent with a combined chemical etching and electrochemical oxidation mechanism. Etch rate results of orientations close to (111) indicate that, at these surfaces, etching follows a step mechanism. Additionally it shows a difference in reactivity between monohydride and dihydride terminated steps towards both chemical etching and electrochemical oxidation. Morphology changes have also been observed, in particular on (110) surface, where the macroscopic surface becomes smoother at positive bias