The Coalfields of the Republic of South Africa (RSA) discharge approximately 360 Ml d-1 of mine impacted water, referred to as Acid Mine Drainage (AMD), requiring neutralization to reduce risk to the environment. High Density Sludge Process (HDSP) is commonly used to treat AMD, and neutralization is typically with either limestone (CaCO3) alone to save costs, or with limestone plus hydrated lime (Ca(OH)2) to effectively reduce acidity and improve metal removal. This water either needs to be further treated to reduce metal content and salinity, or a potential option is to use it for irrigation. Since, it would be possible to lime a soil and irrigate directly with AMD as this would be potentially easy to manage than an HDS plant and save costs on the plant. The treatment process produces a circum-neutral mine water that requires further treatment with reverse osmosis to potable water. Suitability of these waters for irrigation can be evaluated with the Irrigation Water Quality Decision Support System (IWQDSS) for RSA. This study therefore evaluated the two specific mine impacted waters for irrigation. The treatment process also generates gypseous products, referred to as High Density Sludges (HDS), which may be classified as hazardous, based on metal (Mn, Ni, Pb) content, in which case expensive waste storage is required. However, these sludges may have some value for use in agriculture since they are gypseous. Four out of six sludges considered in this study were investigated for potential use in agriculture since their chemical characteristics depend on the quality of AMD and the treatment process. If hazardous, a potential approach was to add phosphate to them since this has been shown before to immobilize metals. The influence of phosphate on the availability of elements in sludges was therefore investigated. Hence, the objectives were to investigate; 1) the fitness for use of AMD and circum-neutral mine impacted waters for irrigation with IWQDSS, 2) chemical and physical properties of sludges, 3) hazardous status of sludges using the RSA waste classification system including those of the United States Environmental Protection Agency (USEPA), Australia, China and Canada, 4) phosphate potential in reducing the solubility of metals in sludges, 5) crop and soil response to sludges applied on their own as soil amendments and when co-applied with phosphate, 6) the influence of phosphate co-applied with sludges to the phyto-availability and uptake of Ni and Pb, including food safety. Assessment with IWQDSS showed that both waters were not fit for irrigation because of some quality issues. However, AMD can only be used if the soil can be limed and used as a reactor and further showed that there would be no leaf scorching. The circum-neutral mine water was found to be not effectively saline. Micro irrigation should not be considered for these waters due to suspended solids they contain. Four of the six sludges assessed for agricultural use included; a Ferriferrous Gypseous sludge (GypFeMnNi) with Fe, Mn and Ni from a limestone process, and three others generated from three stages of a limestone plus hydrated lime process; Ferriferrous Gypseous sludge with Mn (GypFeMn), Gypseous sludge with Brucite (GypB) and Gypseous sludge (Gyp) with Fe removed. Chemically, the sludges, GypFeMn, GypB and Gyp showed pH values of 8.2, 9.4 and 9.5, exhibiting CaCO3 equivalents (CCE) of 510, 601, 617 mg kg-1. The sludge, GypFeMnNi, had a pH of 5.5 and a CCE of 250 mg kg-1. All four sludges showed to be largely gypsum (72 – 95 %) composed. Physically, all sludges had particle sizes falling between 0.4 to 906 µm. These four sludges were further considered for hazardous assessment, including two sludges; GypFeNi and GypFe from a different limestone process. USEPA rated all six sludges non-hazardous, while Canada and China found GypFeNi as hazardous based on Ni solubility, Australia found GypFeMn as hazardous. RSA considered GypFeMnNi and GypFeNi hazardous, based on Ni and Mn solubility. Limestone was therefore less effective in reducing the solubility of Ni and Mn in the sludges than limestone plus hydrated lime. The sludges found hazardous (GypFeMnNi and GypFeMn) were then phosphated to reduce Mn and Ni solubility. Their solubility was reduced in both sludges. GypFeMnNi and Gyp, were further considered for use as soil amendments and selection was based on differences in the treatments that generates them. A pot trial was conducted where both were applied at 10 and 20 t ha-1 each to a soil with pH 3.75 and co-applied with phosphate at application rates of 40 and 100 kg ha-1. Maize (Zea mays) was planted and harvested at physiological maturity. Effect on soil showed that both sludges marginally increased pH, with Gyp at 20 t ha-1 and 100 kg ha-1 P increasing it the most by 0.46 units. This pH was still not suitable for plant growth. The sludge, Gyp increased soil salinity the most from 7.8 mS m-1 to 728 mS m-1, suitable only for salt tolerant crops. The effect on the maize showed that both sludges on their own marginally increased plant height and biomass, but co-application with phosphate increased these parameters. Grain was present only in treatments where phosphate was co-applied with either sludge. The highest grain yield was obtained when Gyp was applied at 20 t ha-1 with 100 kg ha-1 P. With food safety, Ni and Pb concentrations in the grain were below thresholds regarded as toxic. It is suggested that irrigation with AMD may be possible on condition that the soil is limed and used as treatment reactor to prevent the reduction of soil pH. Also, micro irrigation systems are to be avoided when irrigating with AMD and circum-neutral mine impacted waters because they contain suspended solids that can clog them. Irrigation should be with an appropriate leaching fraction to reduce accumulation of salts in the soil profile. It can also be concluded that two of the sludges from a limestone only HDSP were found to be hazardous by the RSA waste classification system due to Mn and Ni solubility., whereas international systems felt these materials were non-hazardous. The RSA waste classification system was found to be overly cautious compared to international systems and should be revisited. Sludges from HDSP can rather be used as soil amendments instead of being classified hazardous and destined to expensive waste management sites. If certain trace elements are excessively available, the study demonstrated that phosphating reduces mobility and toxicity, ensuring the safety of produce from soils treated with HDS. Keywords: AMD, HDS, Circum-neutral mine water, waste classification, amendment / Thesis (PhD (Soil Science)--University of Pretoria, 2020. / WRC / Plant Production and Soil Science / PhD (Soil Science) / Unrestricted

Background: Age-related macular degeneration (AMD) is a leading cause of visualimpairment in the world. AMD is a retinal degenerative condition that affects themacular area of the retina and thus the central vision. Ocular exposure to the bluelight can cause the retina to start produce reactive oxygen species (ROS), whichcauses damage to the retina and can thus increase the risk of developing AMD. Withage, the crystalline lens of the eye becomes more yellow and less transparent. Thetransmittance of the blue light is thus reduced because the lens shows naturalfiltering properties for the blue light. In cataract surgery, the crystalline lens isremoved and usually replaced by a clear intraocular lens (IOL). Blue light-filteringintraocular lenses (BLF-IOLs) have, among other things, been developed with theaim of reducing the risk of developing retinal dysfunction and AMD. Purpose: The aim of this study was to investigate whether blue light filteringintraocular lenses (BLF-IOL) could help minimize the risk of developingage-related macular degeneration (AMD). Material and method: This review was based on four studies obtained from thedatabases PubMed and Web of Science. When searching for data, the publicationdates were limited to a period between 2018-2022 and the articles had to beavailable in "free full text". The search terms used were "Blue light IOL and AMD"and "Cataract and IOL and AMD". Articles that were excluded were judged not tobe relevant to the study as they did not include BLF-IOL and AMD. To answer thequestion, we compared studies where patients who received BLF-IOLs and patientswho received conventional IOLs implanted after cataract surgery were analyzed. Results: Three of the studies indicate that there was no significant differencebetween BLF-IOLs and non-BLF-IOLs regarding the risk of developing AMD. Inone of the studies, it was concluded that oxidative stress was reduced in the presenceof BLF-IOL. Conclusion: The question of whether blue-light-filtering intraocular lenses reducethe risk of developing age-related macular degeneration still remains since enoughevidence has not been found that it works. / Bakgrund: Åldersrelaterad makuladegeneration (AMD) är en ledande orsak tillsynnedsättning i världen. AMD är ett retinalt degenerativt tillstånd som påverkarnäthinnans makulära område och således det centrala seendet. Okulär exponering avdet blå ljuset kan leda till att näthinnan börjar producera reaktiva syrearter (ROS),vilket orsakar skador i näthinnan och kan på så vis ge ökad risk för utveckling avAMD. Ögats kristallina lins gulnar och blir mindre transparent med åren.Transmittansen av det blå ljuset minskar därmed eftersom ögats lins visar naturligafiltreringsegenskaper för det blå ljuset. Vid en kataraktoperation avlägsnas denkristallina linsen och ersätts oftast av en klar intraokulär lins (IOL).Blåljus-filtrerande intraokulära linser (BLF-IOL) har bland annat tagits fram i syfteatt minska risken för att utveckla retinal dysfunktion och AMD. Syfte: Syftet med denna litteraturstudie var att undersöka om blåljus-filtrerandeintraokulära linser (BLF-IOL) kunde minska risken att utveckla åldersrelateradmakuladegeneration (AMD). Material och metod: Denna litteraturstudie baserades på fyra studier som erhöllsfrån databaserna PubMed och Web of Science. Vid sökning av data avgränsadespubliceringsdatumen till en period mellan 2018- 2022 samt att artiklarna skulle varatillgängliga i “free full text”. Sökorden som användes var "Blue light IOL andAMD” och “Cataract and IOL and AMD”. Artiklar som exkluderades bedömdesinte vara av relevans till studien då de inte omfattade BLF-IOL och AMD. För attbesvara frågeställningen analyserades studier där man jämfört patienter som fåttBLF-IOL med patienter som fått konventionella IOL implanterat efter enkataraktoperation. Resultat: Tre av studierna visade att ingen signifikant skillnad fanns mellan BLF-IOL och icke-BLF-IOL vad gäller risken att utveckla AMD. I en av studiernakom man fram till att oxidativ stress minskades vid närvaro av BLF-IOL. Slutsats: Frågan huruvida blåljus-filtrerande intraokulära linser minskar risken föratt utveckla åldersrelaterad makuladegeneration kvarstår fortfarande eftersom manännu inte funnit tillräckligt med bevis på att det fungerar.

The Internet of Things (IoT) consists of a network of physical devices that are connected over the internet for the purpose of exchanging data with other devices and systems. IoT platforms, such as Node-RED, have been introduced in recent times to facilitate communication between different IoT devices. Hosting Node-RED on a cloud service provider might result in the confidentiality of sensitive data on Node-RED being violated by malicious attackers, since users are forced to entrust their sensitive data with the cloud service providers. Using trusted execution environments, such as AMD-SEV and Intel SGX, can mitigate several potential attacks from exposing sensitive information in Node-RED. This thesis investigates if AMD-SEV and Intel SGX are viable options to protect sensitive data in Node-RED when hosted on a cloud service provider. The work in this thesis investigates difficulties encountered when deploying Node-RED on AMD-SEV and Intel SGX, from a usability perspective. Usability is measured by running Node-RED in AMDSEV and Intel SGX, and then recording the complexity of the process. Several performance tests are conducted to measure the performance overhead of Node-RED caused by AMD-SEV. A literature review is also conducted to investigate potential vulnerabilities in AMD-SEV and Intel SGX that could undermine the security of user’s data in Node-RED. The results from this thesis finds that AMD-SEV is a viable option to protect sensitive data in Node-RED when hosted on a cloud service provider. Deploying Node-RED on AMD-SEV is found to be a relatively simple process from a usability perspective. There are some noticeable performance overhead with regards to CPU utilization and TCP throughput, but all other metrics show marginal performance overhead. The potential vulnerabilities in AMD-SEV are not found to be significant enough to make AMD-SEV unviable. The thesis finds Intel SGX to be an unviable solution primarily due to usability. The process of running Node-RED in an Intel SGX enclave is extremely complex and the results show that for most users of Node-RED, this is not viable. The security vulnerabilities found from the literature review, are not significant enough to make Intel SGX an unviable option to protect sensitive user data inNode-RED. / Internet of Things (IoT) är en nätverk av fysiska enheter som är sammankopplade via internet för att kunna skicka data till andra fysiska enheter eller system. IoTplattformar, som Node-RED, har utvecklats för att förenkla kommunikationen mellan olika IoT- enheter. Att köra Node-RED på en molntjänst kan leda till att sekretessen av känslig data på Node-RED blir kränkt av en attack mot molntjänsten. Det är på grund av att användarna av Node-RED är tvungna att tillförlita deras känsliga data till molntjänsten, som deras data kan bli kränkt. Detta problem kan förminskas genom att användarna utnyttjar trusted execution environments som AMD-SEV och Intel SGX för att skydda sin känsliga data på molntjänsten. I denna avhandling, undersöks det om AMDSEV och Intel SGX kan användas för att skydda data i Node-RED när den körs på en molntjänst. Användarvänligheten av att köra Node-RED med AMD-SEV och Intel SGX undersöks genom att uppskatta hur komplicerad denna process är. Flera tester genomförs också för att mäta vilken påverkan AMD-SEV har på prestandan av Node-RED. En litteraturöversikt genomförs också för att undersöka potentiella sårbarheter i AMD-SEV och Intel SGX som skulle kunna utnyttjas för att komma åt känslig data i Node-RED. Resultaten från avhandlingen visar att AMD-SEV kan vara användbart för att skydda känslig data i Node-RED när den körs på en molntjänst. AMDSEV är väldigt användarvänlig när Node-RED ska köras. AMD-SEV har en märkbar påverkan på prestandan av processorn och TCP- genomströmning, men för de andra faktorerna som mäts har AMD-SEV ingen större påverkan. Litteraturöversikten finner inga sårbarheter som är tillräckligt farliga för att göra AMD-SEV oanvändbar för att skydda känslig data iNode-RED. Resultaten från avhandlingen visar dock att Intel SGX inte är särskilt användbar för att skydda känslig data i Node-RED när den körs på en molntjänst. Detta är främst för att det är väldigt komplicerat att köra Node-RED i en Intel SGX enklav från en användarvänlighet synpunkt. De flesta av Node-REDs användare skulle finna det för komplicerat att använda Intel SGX för att skydda sin känsliga data. Litteraturöversikten finner inga sårbarheter allvarliga nog för att göra Intel SGX oanvändbar.

This study investigates jarosite formation and stability patterns at the abandoned Davis Pyrite Mine in Rowe, Massachusetts. Jarosite, an iron-sulfate hydroxide, is found in acid mine drainage (AMD) environments, in acid sulfate soils, and on Mars. Jarosite and the iron oxides goethite and hematite are present at the site. Soil samples from the site were examined by XRD, SEM, and EDS. Five mineralogical areas were found, based on mineral abundance patterns. Jarosite exists in four of these areas. Two jarosite morphologies were identified. “Variable” jarosite, with partly-dissolved crystals of about 0.5 to 5 micrometers diameter, exists in spoil pile samples. “Donut” jarosite, with tightly-packed, sharp-edged crystals less than 0.5 micrometers that form a thin mantle on the surface of a second mineral, exists in native soil samples. Donut jarosite has not been previously characterized. These jarosite morphologies are controlled by the presence and relative mobility of pyrite oxidation products Fe and SO4, which in turn are controlled by water saturation levels. Three pathways are possible. On Path 1, both ions are mobile, go into solution, and variable jarosite forms at a distance from the pyrite source. On Path 2, only sulfur ions are mobile, an iron-oxide gossan develops. No jarosite forms. On Path 3, neither ion is mobile, and donut jarosite forms. On this path, Fe and SO4 ions are trapped in a thin film of stagnant water covering the pyrite. When sufficient ions are present, donut jarosite precipitates.

This thesis discusses pyridinium bisretinoid compounds (PBRs), which were prepared for two purposes: 1) to use them as standards for detection of novel fluorophores in human RPE cells, which may be involved in age-related macular degeneration (AMD), and 2) to use them in the development of a targeted and triggered drug delivery system for cancer therapy. We prepared a selection of PBRs using a one-pot biomimetic method; synthesis, mechanisms for formation, and characterization of these compounds is described. We also explored the photoreactivity of three novel PBR compounds and found that these PBRs form oxidation products under blue-light irradiation. The photoinduced cytotoxity of A2P and A2EE was examined in HL-60 cells. Results from this work suggest that the PBRs presented have the potential to be involved in AMD and to be developed into a targeted and triggered drug delivery system for cancer therapy.

yes / Purpose: To demonstrate methods that enable visual field sensitivities to be compared with normative data without restriction to a fixed test pattern. Methods: Healthy participants (n = 60, age 19–50) undertook microperimetry (MAIA-2) using 237 spatially dense locations up to 13° eccentricity. Surfaces were fit to the mean, variance, and 5th percentile sensitivities. Goodness-of-fit was assessed by refitting the surfaces 1000 times to the dataset and comparing estimated and measured sensitivities at 50 randomly excluded locations. A leave-one-out method was used to compare individual data with the 5th percentile surface. We also considered cases with unknown fovea location by adding error sampled from the distribution of relative fovea–optic disc positions to the test locations and comparing shifted data to the fixed surface. Results: Root mean square (RMS) difference between estimated and measured sensitivities were less than 0.5 dB and less than 1.0 dB for the mean and 5th percentile surfaces, respectively. Root mean square differences were greater for the variance surface, median 1.4 dB, range 0.8 to 2.7 dB. Across all participants 3.9% (interquartile range, 1.8–8.9%) of sensitivities fell beneath the 5th percentile surface, close to the expected 5%. Positional error added to the test grid altered the number of locations falling beneath the 5th percentile surface by less than 1.3% in 95% of participants. Conclusions: Spatial interpolation of normative data enables comparison of sensitivity measurements from varied visual field locations. Conventional indices and probability maps familiar from standard automated perimetry can be produced. These methods may enhance the clinical use of microperimetry, especially in cases of nonfoveal fixation.

Yes / Depictions of vision with AMD in public information material typically show a central region of absolute vision loss. Patients with early and moderate disease frequently do not report this. We aimed to measure how a group of people with AMD perceive everyday scenes in order to produce accurate depictions. We report on six people aged 65-82 years with monocular AMD (visual acuity +0.04 to +1.64 logMAR) and normal vision in the fellow eye. Participants viewed 4 images monocularly, alternating between eyes. The image was digitally altered to approximate participants’ descriptions of their perception with the affected eye. The altered image was viewed with the unaffected eye, and compared with the original image viewed with the affected eye. This was repeated iteratively until a perceptual match was achieved between the modified image/unaffected eye and the original image/affected eye. For five AMD participants with visual acuity +0.04 to +0.50 logMAR the modified images did not resemble those in current public information material. Image modifications required to achieve perceptual similarity with the affected eyes included localised distortion, contrast reduction and blur. Widespread colour desaturation was also required in some cases. One participant with advanced geographic atrophy reported an absolute positive scotoma, similar to existing depictions. Vision in people with AMD may not conform to the common depiction of a central region of absolute vision loss. The accurate representations of AMD patients’ vision produced in this study will enable better understanding of the visual consequences of AMD. / College of Optometrists Postdoctoral Award; National Institute for Health Research Postdoctoral Fellowship

Yes / Purpose: To investigate how well visual field sensitivity predicts visual acuity at the same locations in macular disease, and to assess whether such predictions may be useful for selecting an optimum area for fixation training. Methods: Visual field sensitivity and acuity were measured at nine locations in the central 10° in 20 people with AMD and stable foveal fixation. A linear mixed model was constructed to predict acuity from sensitivity, taking into account within-subject effects and eccentricity. Cross validation was used to test the ability to predict acuity from sensitivity in a new patient. Simulations tested whether sensitivity can predict nonfoveal regions with greatest acuity in individual patients. Results: Visual field sensitivity (P < 0.0001), eccentricity (P = 0.007), and random effects of subject on eccentricity (P = 0.043) improved the model. For known subjects, 95% of acuity prediction errors (predicted − measured acuity) fell within −0.21 logMAR to +0.18 logMAR (median +0.00 logMAR). For unknown subjects, cross validation gave 95% of acuity prediction errors within −0.35 logMAR to +0.31 logMAR (median −0.01 logMAR). In simulations, the nonfoveal location with greatest predicted acuity had greatest “true” acuity on median 26% of occasions, and median difference in acuity between the location with greatest predicted acuity and the best possible location was +0.14 logMAR (range +0.04 to +0.17). Conclusions: The relationship between sensitivity and acuity in macular disease is not strongly predictive. The location with greatest sensitivity on microperimetry is unlikely to represent the location with the best visual acuity, even if eccentricity is taken into account. / College of Optometrists Postdoctoral Research Award (JD and ATA; London, UK) and National Institute for Health Research (NIHR) Postdoctoral Fellowship (ATA; London, UK). Presents independent research funded by the NIHR. / Research Development Fund Publication Prize Award winner, August 2018.

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