title: Offsetting of CO₂ emissions by air capture in mine tailings at the Mount Keith Nickel Mine, Western Australia: Rates, controls and prospects for carbon neutral mining

authors: Wilson, Siobhan A.

subjects: Carbon accounting

abstract: The hydrated Mg-carbonate mineral, hydromagnesite [Mg₅(CO₃)₄(OH)₂•4H₂O], precipitates within mine tailings at the Mount Keith Nickel Mine, Western Australia as a direct result of mining operations. We have used quantitative mineralogical data and δ¹³C, δ¹⁸O and F¹⁴C isotopic data to quantify the amount of CO₂fixation and identify carbon sources. Our radiocarbon results indicate that at least 80% of carbon stored in hydromagnesite has been captured from the modern atmosphere. Stable isotopic results indicate that dissolution of atmospheric CO₂ into mine tailings water is kinetically limited, which suggests that the current rate of carbon mineralization could be accelerated. Reactive transport modeling is used to describe the observed variation in tailings mineralogy and to estimate rates of CO₂ fixation. Based on our assessment, approximately 39,800 t/yr of atmospheric CO₂ are being trapped and stored in tailings at Mount Keith. This represents an offsetting of approximately 11% of the mine's annual greenhouse gas emissions. Thus, passive sequestration via enhanced weathering of mineral waste can capture and store a significant amount of CO₂. Recommendations are made for changes to tailings management and ore processing practices that have potential to accelerate carbonation of tailings and further reduce or completely offset the net greenhouse gas emissions at Mount Keith and many other mines.

text: Offsetting of CO₂ emissions by air capture in mine tailings at the Mount Keith Nickel Mine, Western Australia: Rates, controls and prospects for carbon neutral mining The hydrated Mg-carbonate mineral, hydromagnesite [Mg₅(CO₃)₄(OH)₂•4H₂O], precipitates within mine tailings at the Mount Keith Nickel Mine, Western Australia as a direct result of mining operations. We have used quantitative mineralogical data and δ¹³C, δ¹⁸O and F¹⁴C isotopic data to quantify the amount of CO₂fixation and identify carbon sources. Our radiocarbon results indicate that at least 80% of carbon stored in hydromagnesite has been captured from the modern atmosphere. Stable isotopic results indicate that dissolution of atmospheric CO₂ into mine tailings water is kinetically limited, which suggests that the current rate of carbon mineralization could be accelerated. Reactive transport modeling is used to describe the observed variation in tailings mineralogy and to estimate rates of CO₂ fixation. Based on our assessment, approximately 39,800 t/yr of atmospheric CO₂ are being trapped and stored in tailings at Mount Keith. This represents an offsetting of approximately 11% of the mine's annual greenhouse gas emissions. Thus, passive sequestration via enhanced weathering of mineral waste can capture and store a significant amount of CO₂. Recommendations are made for changes to tailings management and ore processing practices that have potential to accelerate carbonation of tailings and further reduce or completely offset the net greenhouse gas emissions at Mount Keith and many other mines.

year: 2014

title: Electronic circuitry for shaping current pulses for small scale transcranial magnetic stimulation coils

authors: Raju, Soniya

abstract: Transcranial magnetic stimulation (TMS) uses electromagnetic induction to induce electric currents in brain tissue via a time-varying magnetic field from a coil, stimulating neuronal activity. While extensively studied in humans, small animal TMS coils are less explored, presenting challenges due to the high currents needed and heating issues from coil size and core hysteresis. This research focuses on the development of a new pulse generator tailored for TMS applications, with a specific emphasis on small-scale systems designed for animal studies. A supercapacitor-based design was implemented to serve as the power source, offering a compact, cost-effective solution for generating stable voltage pulses. The pulse generator demonstrated the ability to produce magnetic fields ranging 200 – 400 mT with an input of 1 V, making it a highly efficient tool for small animal TMS coils. In an effort to simplify pulse shaping without using complex circuitry, a mosfet was used as a dynamic element to control current. A triangular gate voltage waveform was introduced. This approach allowed for finer control over critical parameters such as rise time, fall time, and pulse width, which are key to TMS pulse optimization. In order to optimize pulse shape, a Matlab model to predict the behavior of coil current based on varying input gate voltage was developed. This model, which is based on a newly derived equation, align well with experimental data and enables the precise customization of pulse characteristics. It provides a valuable frame work for optimizing new and existing pulse shapes. This research demonstrates the supercapacitor-based pulse generator and its accompanying Matlab model for small-scale TMS applications. The flexibility in pulse generation and the ability to create custom pulse shapes provide a strong foundation for future exploration in TMS research, particularly for animal studies.

text: Electronic circuitry for shaping current pulses for small scale transcranial magnetic stimulation coils Transcranial magnetic stimulation (TMS) uses electromagnetic induction to induce electric currents in brain tissue via a time-varying magnetic field from a coil, stimulating neuronal activity. While extensively studied in humans, small animal TMS coils are less explored, presenting challenges due to the high currents needed and heating issues from coil size and core hysteresis. This research focuses on the development of a new pulse generator tailored for TMS applications, with a specific emphasis on small-scale systems designed for animal studies. A supercapacitor-based design was implemented to serve as the power source, offering a compact, cost-effective solution for generating stable voltage pulses. The pulse generator demonstrated the ability to produce magnetic fields ranging 200 – 400 mT with an input of 1 V, making it a highly efficient tool for small animal TMS coils. In an effort to simplify pulse shaping without using complex circuitry, a mosfet was used as a dynamic element to control current. A triangular gate voltage waveform was introduced. This approach allowed for finer control over critical parameters such as rise time, fall time, and pulse width, which are key to TMS pulse optimization. In order to optimize pulse shape, a Matlab model to predict the behavior of coil current based on varying input gate voltage was developed. This model, which is based on a newly derived equation, align well with experimental data and enables the precise customization of pulse characteristics. It provides a valuable frame work for optimizing new and existing pulse shapes. This research demonstrates the supercapacitor-based pulse generator and its accompanying Matlab model for small-scale TMS applications. The flexibility in pulse generation and the ability to create custom pulse shapes provide a strong foundation for future exploration in TMS research, particularly for animal studies.

year: 2025

title: Empowering Pacific and Māori students via Zoom

authors: Brown, Georgia

abstract: When discussing online teaching, a common refrain is that online teaching doesn’t suit Pacific and Māori students: they learn kanohi ki te kanohi. We present some experiences from students who attended a Zoom tutorial for Pacific students in 2023. These experiences show that a quality online learning experience is possible, and that Pacific and Māori students value and appreciate online options.

text: Empowering Pacific and Māori students via Zoom When discussing online teaching, a common refrain is that online teaching doesn’t suit Pacific and Māori students: they learn kanohi ki te kanohi. We present some experiences from students who attended a Zoom tutorial for Pacific students in 2023. These experiences show that a quality online learning experience is possible, and that Pacific and Māori students value and appreciate online options.

year: 2023