title: Surface Roughening of Platinum Wire: An Electrochemical and Mechanical Approach

authors: Gygax, Stefan Manu

subjects: Surface Roughening

abstract: In order to make implanted electrodes MRI safe several methods have been explored. One of those methods involves increasing AC resistance by roughening the surface of the implanted platinum wires. This thesis explores an electrochemical and a mechanical approach to reliably induce 15 micro meter deep surface defects. The electrochemical approach dissolves the outermost layer of the wire and redeposits a porous layer on the surface that does not grow more than 2 micro meters thick. It is predicted that this layer may be grown to desired thickness if the source of platinum comes from within the solution treatment takes place in rather than the treated wire itself. The mechanical approach induces fatigue cracks that grow predictably and can be controlled to desired size. The limitations are the small amount of wire that may be treated at a time through rotational fatiguing, and the initial quality of the treated wire. High quality wire and an ultrasonic fatigue setup may remedy these limitations.

text: Surface Roughening of Platinum Wire: An Electrochemical and Mechanical Approach In order to make implanted electrodes MRI safe several methods have been explored. One of those methods involves increasing AC resistance by roughening the surface of the implanted platinum wires. This thesis explores an electrochemical and a mechanical approach to reliably induce 15 micro meter deep surface defects. The electrochemical approach dissolves the outermost layer of the wire and redeposits a porous layer on the surface that does not grow more than 2 micro meters thick. It is predicted that this layer may be grown to desired thickness if the source of platinum comes from within the solution treatment takes place in rather than the treated wire itself. The mechanical approach induces fatigue cracks that grow predictably and can be controlled to desired size. The limitations are the small amount of wire that may be treated at a time through rotational fatiguing, and the initial quality of the treated wire. High quality wire and an ultrasonic fatigue setup may remedy these limitations.

year: 2017

title: Students' Conceptions of Ionisation Energy: A Cross-cultural Study

authors: Tan, Kim Chwee Daniel

subjects: education

abstract: Previous studies have indicated that A-level students in the UK and Singapore have difficulty learning the topic of ionisation energy. A two-tier multiple-choice instrument developed in Singapore in an earlier study, the Ionisation Energy Diagnostic Instrument, was administered to A-level students in the UK, advanced placement high school students in the USA, and first-year university students in China, New Zealand, and Spain to determine whether the students from different countries and educational systems had similar conceptions and difficulties as the students in Singapore with the concepts assessed in the instrument. The results showed that, in general, the students in all six samples had similar alternative conceptions, which were grouped under the categories of octet rule framework, stable fully-filled and half-filled subshell conceptions, and conservation of force thinking. The students also resorted to relation-based thinking when answering items involving the trend of ionisation energies across Period 3. Implications for teaching and further research are discussed.

text: Students' Conceptions of Ionisation Energy: A Cross-cultural Study Previous studies have indicated that A-level students in the UK and Singapore have difficulty learning the topic of ionisation energy. A two-tier multiple-choice instrument developed in Singapore in an earlier study, the Ionisation Energy Diagnostic Instrument, was administered to A-level students in the UK, advanced placement high school students in the USA, and first-year university students in China, New Zealand, and Spain to determine whether the students from different countries and educational systems had similar conceptions and difficulties as the students in Singapore with the concepts assessed in the instrument. The results showed that, in general, the students in all six samples had similar alternative conceptions, which were grouped under the categories of octet rule framework, stable fully-filled and half-filled subshell conceptions, and conservation of force thinking. The students also resorted to relation-based thinking when answering items involving the trend of ionisation energies across Period 3. Implications for teaching and further research are discussed.

year: 2008

title: Hāwatewate

authors: Maxwell, Te Kahautu

abstract: Hāwatewate; this composition is in remembrance of the hanging of the Ōpōtiki missionary Rev Carl Sylvius Volkner by the Hauhau, Kereopa Te Rau of Ngāti Rangiwewehi of Te Arawa. As a consequence the Te Whakatōhea chief Mokomoko was wrongly convicted and executed by hanging in Mount Eden Prison 17 May 1866. 143870 acres of Te Whakatōhea land was confiscated under the New Zealand Settlements Act 1863. This item placed third in the Whakaeke discipline and was performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka Competition 2015.

text: Hāwatewate Hāwatewate; this composition is in remembrance of the hanging of the Ōpōtiki missionary Rev Carl Sylvius Volkner by the Hauhau, Kereopa Te Rau of Ngāti Rangiwewehi of Te Arawa. As a consequence the Te Whakatōhea chief Mokomoko was wrongly convicted and executed by hanging in Mount Eden Prison 17 May 1866. 143870 acres of Te Whakatōhea land was confiscated under the New Zealand Settlements Act 1863. This item placed third in the Whakaeke discipline and was performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka Competition 2015.

year: 2015-01-08