title: Measurement of implant electrode leads using time-domain reflectometry to predict the resonant length for MRI heating

authors: McCabe, Steven Owen

abstract: Magnetic Resonance Imaging (MRI) machines can generate hazardous RF heating of patients with implanted neurostimulation leads. Consequently, most patients with these implants are contraindicated from having MRI scans. The level of RF heating has a strong dependence on lead length and is most severe when the length is close to a specific resonant length. Recent studies have shown that simple modifications to the lead construction and insulating material can alter the resonant length and significantly ameliorate this heating hazard, achieving MRI safety. We propose a technique using time domain reflectometry (TDR) to find the resonant length of an arbitrary lead such to minimise the amount of MRI machine time needed to find the length of highest heating. The results are compared with temperature measurements made in a 3-Tesla MRI machine and with a CW dipole radiator in the lab.

text: Measurement of implant electrode leads using time-domain reflectometry to predict the resonant length for MRI heating Magnetic Resonance Imaging (MRI) machines can generate hazardous RF heating of patients with implanted neurostimulation leads. Consequently, most patients with these implants are contraindicated from having MRI scans. The level of RF heating has a strong dependence on lead length and is most severe when the length is close to a specific resonant length. Recent studies have shown that simple modifications to the lead construction and insulating material can alter the resonant length and significantly ameliorate this heating hazard, achieving MRI safety. We propose a technique using time domain reflectometry (TDR) to find the resonant length of an arbitrary lead such to minimise the amount of MRI machine time needed to find the length of highest heating. The results are compared with temperature measurements made in a 3-Tesla MRI machine and with a CW dipole radiator in the lab.

year: 2016

title: Habituation and Dishabituation of Physical Activity

authors: Crawford, Demelza

subjects: habituation

abstract: Three experiments with single subject research designs were conducted to see whether habituation occurred as human participants completed physical activity. Experiment 1 had an arrangement where participant’s rates of stationary cycling were recorded throughout 20 minute sessions. Instead of habituation, stationary cycling rates increased over time, likely to be due to a rule that controlled behaviour derived from previous reinforced responding in the same setting as the experimental context. Experiment 2 was arranged similarly to Experiment 1 with an added concurrent task to disrupt the behaviour chain causing the rule-governed behaviour seen in Experiment 1. Despite this concurrent task, rates of stationary cycling again increased due to rule-governed behaviour. Experiment 3 had stationary cycling rates associated with a salient reinforcer that could lose its effectiveness to reinforce over time and thus habituate. Instead, Experiment 3 resulted in stable rates of stationary cycling consistent with task adherence, a rule-governed behaviour. With the failure of habituation to predict the results of this study, they are instead discussed from the more applicable perspective of motivating operations.

text: Habituation and Dishabituation of Physical Activity Three experiments with single subject research designs were conducted to see whether habituation occurred as human participants completed physical activity. Experiment 1 had an arrangement where participant’s rates of stationary cycling were recorded throughout 20 minute sessions. Instead of habituation, stationary cycling rates increased over time, likely to be due to a rule that controlled behaviour derived from previous reinforced responding in the same setting as the experimental context. Experiment 2 was arranged similarly to Experiment 1 with an added concurrent task to disrupt the behaviour chain causing the rule-governed behaviour seen in Experiment 1. Despite this concurrent task, rates of stationary cycling again increased due to rule-governed behaviour. Experiment 3 had stationary cycling rates associated with a salient reinforcer that could lose its effectiveness to reinforce over time and thus habituate. Instead, Experiment 3 resulted in stable rates of stationary cycling consistent with task adherence, a rule-governed behaviour. With the failure of habituation to predict the results of this study, they are instead discussed from the more applicable perspective of motivating operations.

year: 2015

title: Editorial

authors: Clarkin-Phillips, Jeanette

abstract: As New Zealand contemplates wholesale review of the formal schooling system and the leadership implications thereof, the winds of educational change begin to swirl. Not the persistent, yet gentle flutter of change that evolves the educational landscape in almost imperceptible ways, but tumultuous paradigmatic gales that potentially change it beyond all recognition. Heralded by politicians, economists and capitalists, there is little doubt that the 1989 neoliberal tempest wrought havoc on notions of community and profession. The whirlwind shift from social democracy to market competition, managerialism and performativity saw critical voices silenced and educators disparagingly positioned as self-interested providers. In the rush to legislate Tomorrow’s Schools, 18,000 submissions remained unanalysed and therein lies a crucial lesson: we ignore research at our peril. As educators, we have a moral obligation to generate, disseminate and critique understandings of leadership, policy and practice; to remain open to counter perspectives; and to contribute positively and hopefully to research that empowers and emancipates. Consistent with JELPP’s commitment to honouring diversity in leadership focus, setting, and authorship, articles in this year’s general edition offer fresh insight into topics of interconnected and perennial importance: native knowledge, instructional leadership, indigenous teachers, appraisal, professional values, and safe schools.

text: Editorial As New Zealand contemplates wholesale review of the formal schooling system and the leadership implications thereof, the winds of educational change begin to swirl. Not the persistent, yet gentle flutter of change that evolves the educational landscape in almost imperceptible ways, but tumultuous paradigmatic gales that potentially change it beyond all recognition. Heralded by politicians, economists and capitalists, there is little doubt that the 1989 neoliberal tempest wrought havoc on notions of community and profession. The whirlwind shift from social democracy to market competition, managerialism and performativity saw critical voices silenced and educators disparagingly positioned as self-interested providers. In the rush to legislate Tomorrow’s Schools, 18,000 submissions remained unanalysed and therein lies a crucial lesson: we ignore research at our peril. As educators, we have a moral obligation to generate, disseminate and critique understandings of leadership, policy and practice; to remain open to counter perspectives; and to contribute positively and hopefully to research that empowers and emancipates. Consistent with JELPP’s commitment to honouring diversity in leadership focus, setting, and authorship, articles in this year’s general edition offer fresh insight into topics of interconnected and perennial importance: native knowledge, instructional leadership, indigenous teachers, appraisal, professional values, and safe schools.

year: 2019