Geotechnique, Physico-chemical Behaviour and a New Erosion Model for Mine Tailings under Environmental Loading

Comprehensive geotechnical characterisation of mine tailings is required for the design, construction and safe operation of mine waste management facilities against the large number of potential failure risks. It is important that the characterization is carried out under the stress range and drainage conditions relevant to those encountered in the field. The present research utilized mine tailings samples from a copper/nickel base-metal mine. Kaolinite and bentonite clays were added to the mine tailings in order to study the effect of clay percentage and clay mineralogy on the behaviour of saturated tailings/clay systems with varying composition. Slurries with moderate or high concentration of solids were prepared in the laboratory by mixing distilled water with mine tailings or artificial tailings/clay soils. Beds with different composition, thickness and age were sedimented from these slurries and tested under a stress range below 1 kPa, and under different degrees of drainage ranging from undrained to fully drained. The primary consolidation of the pure tailings beds was complete in approximately one hour and negligible volume changes occurred in the beds during secondary compression. The effect of adding kaolinite or bentonite to the tailings was to increase the time for primary consolidation of the mixed beds, but the rate of increase was greater when bentonite was used. The undrained shear strength of the beds was measured using an automated fall cone device at a depth interval of 1 cm below bed surface. It was found that the undrained strength increased, whereas the water content and void ratio decreased with depth within the beds. The factor controlling the undrained strength of the beds was the vertical effective stress, with the water content also having some secondary effect. A specially built Tilting Tank was used to measure the shear strength of the beds under drained and partially drained conditions that were simulated by varying the loading rate. Bed failure within the Tank always occurred at a plane parallel to the surface of the bed and at a depth of 0.4 to 2.5 cm. Linear drained and partially drained shear strength envelopes with zero cohesion intercept were defined, with the partially drained (total) friction angle always remaining lower than the drained (effective) friction angle. The latter varied from 35.2° for the tailings/bentonite mixtures to 40.4° for the pure tailings, depending on the percentage and mineralogy of the clay fraction. It was found that adding clay to the mine tailings generally caused a decrease in the frictional resistance of the mixtures, with the effect being more pronounced for the bentonite additive. Time for consolidation did not influence the shear strength of the tailings and tailings/kaolinite mixtures, but produced an increase of 2.1° in the frictional resistance of the tailings/bentonite mixtures. A critical stress for erosion as a function of depth was estimated for each bed using existing formulations for cohesive and noncohesive sediments and mixtures of both. A linear correlation between the undrained shear strength and the critical stress for erosion, with parameters dependent on the composition of the mixtures was proposed

Evaluation of GaN and InGaN semiconductors as potentiometric anion selective electrodes

Ion selective electrodes (ISEs) are chemical sensors primarily used for in situ analysis and monitoring of air, water, and land. Despite their easy fabrication, low cost, and simple usage, ISEs still suffer from the sensitivity of their response to temperature variations, solution turbidity, interferences from other ions in solution, drift of the electrode potential, membrane fouling, and short lifetime. As a result, investigating new materials to develop ISEs that can address some of these limitations is a worthwhile and challenging topic of research. The excellent mechanical, thermal and chemical stability of gallium nitride (GaN) and indium gallium nitride (InGaN) semiconductors, coupled with their resistance to corrosion and low toxicity if dissolved, are some of the properties that make these materials prime candidates for a variety of sensor applications, particularly at high temperatures and in harsh environments. This thesis evaluates the potential of these two semiconductor materials for replacing conventional ISE membranes with a solid-state semiconductor surface/solution interface. The benefits gained from this novel design of the ISE sensing element are assessed

Treatment of Adult Spasticity With Botox (onabotulinumtoxinA): Development, Insights, and Impact

Upper and lower limb spasticity (ULS, LLS) often occur following a stroke or in patients with other neurological disorders, leading to difficulties in mobility and daily living and decreased quality of life. Prior to the use of onabotulinumtoxinA, antispastic medications had limited efficacy and often caused sedation. Phenol injections were difficult for physicians to perform, painful, and led to tissue destruction. The success of onabotulinumtoxinA in treating cervical dystonia led to its use in spasticity. However, many challenges characterized the development of onabotulinumtoxinA for adult spasticity. The wide variability in the presentation of spasticity among patients rendered it difficult to determine which muscles to inject and how to measure improvement. Another challenge was the initial refusal of the Food and Drug Administration to accept the Ashworth Scale as a primary endpoint. Additional scales were designed to incorporate a goal-oriented, patient-centered approach that also accounted for the variability of spasticity presentations. Several randomized, double-blind, placebo-controlled trials of post-stroke spasticity of the elbow, wrist, and/or fingers showed significantly greater improvements in the modified Ashworth Scale and patient treatment goals and led to the approval of onabotulinumtoxinA for the treatment of ULS in adult patients. Lessons learned from the successful ULS trials were applied to design an LLS trial that led to approval for the latter indication. Additional observational trials mimicking real-world treatment have shown continued effectiveness and patient satisfaction. The use of onabotulinumtoxinA for spasticity has ushered in a more patient-centered treatment approach that has vastly improved patients\u27 quality of life

Efficacy and safety of onabotulinumtoxinA with standardized physiotherapy for the treatment of pediatric lower limb spasticity: A randomized, placebo-controlled, phase III clinical trial.

BackgroundSpasticity is common in cerebral palsy and can result in pain and diminished health-related quality of life.ObjectiveTo evaluate the safety and efficacy of onabotulinumtoxinA for lower limb spasticity treatment in children with cerebral palsy.MethodsIn this registrational phase 3, multinational, randomized, double-blind, placebo-controlled trial (NCT01603628), children (2-< 17 years) with cerebral palsy and ankle spasticity (Modified Ashworth Scale-Bohannon [MAS] score≥2) were randomized 1 : 1 : 1 to standardized physical therapy and onabotulinumtoxinA (4 or 8 U/kg), or placebo. Primary endpoint was average change from baseline at weeks 4 and 6 in MAS ankle score. Secondary endpoints included the Modified Tardieu Scale (MTS) and Global Attainment Scale (GAS).Results381 participants were randomized. MAS scores averaged at weeks 4 and 6 were significantly reduced with both onabotulinumtoxinA doses (8 U/kg: -1.06, p = 0.010; 4 U/kg: -1.01, p = 0.033) versus placebo (-0.8). Significant improvements in average dynamic component of spasticity, measured by MTS, and in function, measured by GAS, were observed at several time points with both onabotulinumtoxinA doses versus placebo. Most adverse events were mild or moderate.ConclusionsOnabotulinumtoxinA was well tolerated and effective in reducing lower limb spasticity and improving functional outcomes versus placebo in children