title: Designing, measuring and modelling a small-scale coil and stimulation circuit for Transcranial Magnetic Stimulation (TMS)

authors: Khokhar, Farah Adeebah

abstract: In TMS rapid electromagnetic fields (EM) are applied to the brain. The fundamental effects of TMS are poorly understood so we need smaller coils to perform invasive measurements on mice. Based on established physics principles we designed and built cylindrical TMS coils consisting of 25 and 50 turns of 0.2 mm diameter copper wire around 5 mm diameter powdered iron cores and discharged a capacitor through these coils. We measured the magnetic flux densities (B-field) of 25 and 50 turn TMS coils with a Hall probe as 907 mT, 750 mT and the induced electric fields (E-field) with a wire loop as 10 – 27 V/m, 10 – 22 V/m at 50 V respectively. We have also modelled the coils with COMSOL Multiphysics which gave similar B-fields for 25 and 50 turn of around 900 mT, 700 mT and E- fields as 20 – 25 V/m, 15 – 20 V/m respectively. The temperature for 25 and 50 turn TMS coils increase by 52 °C and 71 °C respectively after 1200 pulses at 5 Hz. We tried to modulate the activity of a mouse brain slice by stimulating with the 50 turn TMS coil 3 mm above the mouse brain slice with 50 V using a B-field of 500 mT, 600 pulses at 5 Hz. There was no hint that the TMS has changed the activity. Although these coils perform better than previously constructed mouse coils, the EM fields are still considerably lower than human TMS coils of 2 T and 250 V/m.

text: Designing, measuring and modelling a small-scale coil and stimulation circuit for Transcranial Magnetic Stimulation (TMS) In TMS rapid electromagnetic fields (EM) are applied to the brain. The fundamental effects of TMS are poorly understood so we need smaller coils to perform invasive measurements on mice. Based on established physics principles we designed and built cylindrical TMS coils consisting of 25 and 50 turns of 0.2 mm diameter copper wire around 5 mm diameter powdered iron cores and discharged a capacitor through these coils. We measured the magnetic flux densities (B-field) of 25 and 50 turn TMS coils with a Hall probe as 907 mT, 750 mT and the induced electric fields (E-field) with a wire loop as 10 – 27 V/m, 10 – 22 V/m at 50 V respectively. We have also modelled the coils with COMSOL Multiphysics which gave similar B-fields for 25 and 50 turn of around 900 mT, 700 mT and E- fields as 20 – 25 V/m, 15 – 20 V/m respectively. The temperature for 25 and 50 turn TMS coils increase by 52 °C and 71 °C respectively after 1200 pulses at 5 Hz. We tried to modulate the activity of a mouse brain slice by stimulating with the 50 turn TMS coil 3 mm above the mouse brain slice with 50 V using a B-field of 500 mT, 600 pulses at 5 Hz. There was no hint that the TMS has changed the activity. Although these coils perform better than previously constructed mouse coils, the EM fields are still considerably lower than human TMS coils of 2 T and 250 V/m.

year: 2019

title: The development of a novel large area building integrated solar collector for pool heating

authors: Anderson, Timothy Nicholas

subjects: building integrated solar collector

abstract: Unglazed solar collectors have often been used a means of providing low cost heating to swimming pools. However, these systems are typically polymer style “mats” that are laid on top of a roof, often leading to poor aesthetics due to their lack of integration with the building itself. This study charts the development of a novel large area unglazed building integrated solar pool heating system (BIT), based on long run sheet metal roofing, from its initial conceptualisation through to its implementation. It discusses the design of the building integrated solar collector modules, the assessment of their performance through theoretical modelling and experimental validation. Subsequently, it shows the scaling of laboratory scale testing to a large area array through modelling and discusses the performance of the system in the “as-built” configuration. In doing this, it provides a succinct illustration of the design process for the development of the University of Waikato’s building integrated pool heating system.

text: The development of a novel large area building integrated solar collector for pool heating Unglazed solar collectors have often been used a means of providing low cost heating to swimming pools. However, these systems are typically polymer style “mats” that are laid on top of a roof, often leading to poor aesthetics due to their lack of integration with the building itself. This study charts the development of a novel large area unglazed building integrated solar pool heating system (BIT), based on long run sheet metal roofing, from its initial conceptualisation through to its implementation. It discusses the design of the building integrated solar collector modules, the assessment of their performance through theoretical modelling and experimental validation. Subsequently, it shows the scaling of laboratory scale testing to a large area array through modelling and discusses the performance of the system in the “as-built” configuration. In doing this, it provides a succinct illustration of the design process for the development of the University of Waikato’s building integrated pool heating system.

year: 2010

title: Tīaho mai

authors: Maxwell, Te Kahautu

abstract: Waiata ā Ringa (action song). Lyrics composed by Te Kahautu Maxwell. Performed by Ōpōtiki Mai Tawhiti (Kapa Haka group)

text: Tīaho mai Waiata ā Ringa (action song). Lyrics composed by Te Kahautu Maxwell. Performed by Ōpōtiki Mai Tawhiti (Kapa Haka group)

year: 2024