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Management and mitigation of acid mine drainage in South Africa : input for mineral beneficiation in Africa
This book ascertains that there are three schools of thought regarding the acid mine drainage (AMD) challenge in South Africa and elsewhere. The first school of thought, is that which has resigned itself to fate. The second school of thought is held by those who have hope that the problem can be managed, albeit with a considerable degree of difficulty. The third school comprises those that are energised to try (on a large scale) the various AMD remediation technologies and innovations brought to the fore by various research and development bodies. This book thus presents multifaceted potential channels for dealing with AMD challenges.
Book
Adjunctive Middle Meningeal Artery Embolization for Subdural Hematoma
In patients with subdural hematoma and an indication for surgical evacuation, middle meningeal artery embolization plus surgery led to a lower risk of reoperation for recurrence or progression within 90 days than surgery alone.
Journal Article
Modeling the Effects of Artificial Drainage on Agriculture‐Dominated Watersheds Using a Fully Distributed Integrated Hydrology Model
In agriculture‐dominated watersheds where natural drainage is poor, agricultural ditches (narrow engineered channels) and tile drains (perforated pipes) are widely employed to enhance surface and subsurface drainage, respectively. Despite their relatively small scale, these features exert substantial control over the hydro‐biogeochemical function of watersheds and their effects need to be represented in the models. We introduce a novel strategy to incorporate the effects of artificial agricultural drainage into a fully distributed basin‐scale integrated surface‐subsurface hydrology models. In our approach, narrow agriculture ditches for surface drainage are resolved efficiently using ditch‐aligned computational meshes that are hydrologically conditioned to ensure connectivity in the stream/ditch network. For tile drainage in the subsurface, we use the physically based Hooghoudt's drainage equation as a subgrid model and route the water drained through tiles to the nearest ditch. Without site‐specific calibration, this model reproduced observed streamflow in the Portage River Watershed (>1,000 km2) as recorded by a USGS gauge with good accuracy (normalized KGE = 0.81) and outperformed a calibrated SWAT model (normalized KGE = 0.68). Numerical experiments confirm that artificial drainage reduces surface inundations and effectively controls the water table. At the watershed scale, artificial drainage increases baseflow but has little effect on watershed discharges above the 90th percentile. The strong physical underpinnings and reduced need for calibration allow us to study the impacts of artificial drainage on distributed hydrological response in terms of fluxes and states and provide a platform for investigating watershed‐scale nutrient transport. Key Points Novel strategy is developed to incorporate effects of artificial drainage into fully distributed basin‐scale integrated hydrology model Without site‐specific calibration, our model reproduced observed streamflow well and outperformed calibrated SWAT model Numerical experiments reveal the effects of surface and surface drainage on various hydrological states and fluxes
Journal Article
Surface and subsurface runoff generation processes in a poorly gauged tropical coastal catchment : a study from Nicaragua : dissertation
Hydrological research in humid tropics is particularly challenging because of highly variable hydrological conditions and high socio-economic stresses caused by rapid population increase, as is the case of Nicaragua. The objective of this research is to understand the surface and subsurface runoff generation processes in a poorly gauged coastal catchment in Nicaragua under variable humid tropical conditions. Specifically, it focuses on identifying geomorphological and hydro-climatic controls on catchment response at different spatio-temporal scales and studies the link between hydrological processes and ecosystem conditions.
Book
Non-superiority of lumen-apposing metal stents over plastic stents for drainage of walled-off necrosis in a randomised trial
ObjectiveAlthough lumen-apposing metal stents (LAMS) are increasingly used for drainage of walled-off necrosis (WON), their advantage over plastic stents is unclear. We compared efficacy of LAMS and plastic stents for WON drainage.DesignPatients with WON were randomised to endoscopic ultrasound-guided drainage using LAMS or plastic stents. Primary outcome was comparing total number of procedures to achieve treatment success defined as symptom relief in conjunction with WON resolution on CT at 6 months. Secondary outcomes were treatment success, procedure duration, clinical/stent-related adverse events, readmissions, length of hospital stay (LOS) and costs.Results60 patients underwent LAMS (n=31) or plastic stent (n=29) placement. There was no significant difference in total number of procedures performed (median 2 (range 2–7) LAMS vs 3 (range 2–7) plastic, p=0.192), treatment success, clinical adverse events, readmissions, LOS and overall treatment costs between cohorts. Although procedure duration was shorter (15 vs 40 min, p<0.001), stent-related adverse events (32.3% vs 6.9%, p=0.01) and procedure costs (US$12 155 vs US$6609, p<0.001) were higher with LAMS. Significant stent-related adverse events were observed ≥3 weeks postintervention in LAMS cohort. Interim audit resulted in protocol amendment where CT scan was obtained at 3 weeks postintervention followed by LAMS removal if WON had resolved. After protocol amendment, there was no significant difference in adverse events between cohorts.ConclusionExcept for procedure duration, there was no significant difference in treatment outcomes between LAMS and plastic stents. To minimise adverse events with LAMS, patients should undergo follow-up imaging and stent removal at 3 weeks if WON has resolved.Trial registration number NCT02685865.
Journal Article
Endosonography-guided gallbladder drainage versus percutaneous cholecystostomy in very high-risk surgical patients with acute cholecystitis: an international randomised multicentre controlled superiority trial (DRAC 1)
ObjectiveThe optimal management of acute cholecystitis in patients at very high risk for cholecystectomy is uncertain. The aim of the current study was to compare endoscopic ultrasound (EUS)-guided gallbladder drainage (EUS-GBD) to percutaneous cholecystostomy (PT-GBD) as a definitive treatment in these patients under a randomised controlled trial.DesignConsecutive patients suffering from acute calculous cholecystitis but were at very high-risk for cholecystectomy were recruited. The primary outcome was the 1-year adverse events rate. Secondary outcomes include technical and clinical success, 30-day adverse events, pain scores, unplanned readmissions, re-interventions and mortalities.ResultsBetween August 2014 to February 2018, 80 patients were recruited. EUS-GBD significantly reduced 1 year adverse events (10 (25.6%) vs 31 (77.5%), p<0.001), 30-day adverse events (5 (12.8%) vs 19 (47.5%), p=0.010), re-interventions after 30 days (1/39 (2.6%) vs 12/40 (30%), p=0.001), number of unplanned readmissions (6/39 (15.4%) vs 20/40 (50%), p=0.002) and recurrent cholecystitis (1/39 (2.6%) vs 8/40 (20%), p=0.029). Postprocedural pain scores and analgesic requirements were also less (p=0.034). The technical success (97.4% vs 100%, p=0.494), clinical success (92.3% vs 92.5%, p=1) and 30-day mortality (7.7% vs 10%, p=1) were statistically similar. The predictor to recurrent acute cholecystitis was the performance of PT-GBD (OR (95% CI)=5.63 (1.20–53.90), p=0.027).ConclusionEUS-GBD improved outcomes as compared to PT-GBD in those patients that not candidates for cholecystectomy. EUS-GBD should be the procedure of choice provided that the expertise is available after a multi-disciplinary meeting. Further studies are required to determine the long-term efficacy.Trial registration number NCT02212717
Journal Article