title: Technique to assess the compatibility of medical implants to the RF Field in MRI

authors: McCabe, Steven Owen

subjects: Magnetic resonance imaging

abstract: The standard technique for determining the compatibility of medical implants to the magnetic and RF fields present in Magnetic Resonance Imaging (MRI), requires access to an MRI machine. For implants comprising metals of mostly the non-ferrous kind, it is only the RF field of an MRI machine that is of concern. Implant electrodes can concentrate the RF field in the surrounding tissue and give rise to joule heating. The inherent design of Spinal Cord Stimulators (SCS) and Deep Brain Stimulators (DBS) makes these implants particularly susceptible to hazardous levels of RF heating. We propose a technique that offers a quick and indicative assessment of the compatibility of implant leads to the RF field in 3-Tesla MRI, without needing access to an MRI machine. A dipole antenna, driven by a power amplifier and Continuous Wave (CW), injects RF energy into a gelled saline phantom. The heating in the gel near a test implant electrode is monitored with a fiber optic thermometer. The results are calibrated against measurements made in a 3-Tesla MRI machine.

text: Technique to assess the compatibility of medical implants to the RF Field in MRI The standard technique for determining the compatibility of medical implants to the magnetic and RF fields present in Magnetic Resonance Imaging (MRI), requires access to an MRI machine. For implants comprising metals of mostly the non-ferrous kind, it is only the RF field of an MRI machine that is of concern. Implant electrodes can concentrate the RF field in the surrounding tissue and give rise to joule heating. The inherent design of Spinal Cord Stimulators (SCS) and Deep Brain Stimulators (DBS) makes these implants particularly susceptible to hazardous levels of RF heating. We propose a technique that offers a quick and indicative assessment of the compatibility of implant leads to the RF field in 3-Tesla MRI, without needing access to an MRI machine. A dipole antenna, driven by a power amplifier and Continuous Wave (CW), injects RF energy into a gelled saline phantom. The heating in the gel near a test implant electrode is monitored with a fiber optic thermometer. The results are calibrated against measurements made in a 3-Tesla MRI machine.

year: 2015

title: The temperature optima of enzymes: a new perspective on an old phenomenon

authors: Daniel, Roy M.

subjects: temperature optima

abstract: Careful analysis of the dependence of enzyme activity on assay temperature has revealed that some enzymes might have real temperature optima in which the decrease in catalytic rate at temperatures above the optimum is not primarily a result of irreversible thermal inactivation. The ‘equilibrium model’ has been formulated to describe genuine temperature optima, and to suggest a simple experimental method by which to distinguish these cases from those in which enzyme instability is the major determinant of temperature optima.

text: The temperature optima of enzymes: a new perspective on an old phenomenon Careful analysis of the dependence of enzyme activity on assay temperature has revealed that some enzymes might have real temperature optima in which the decrease in catalytic rate at temperatures above the optimum is not primarily a result of irreversible thermal inactivation. The ‘equilibrium model’ has been formulated to describe genuine temperature optima, and to suggest a simple experimental method by which to distinguish these cases from those in which enzyme instability is the major determinant of temperature optima.

year: 2001-04

title: Homeless Māori Men: Re-connection, Re-joining, and Re-membering Ways of Being

authors: King, Pita Richard Wiremu

subjects: Māori psychology

abstract: There are a range of interventions and programmes to address the on-going issue of Māori homelessness. This thesis explores a gardening project hosted by a Ngāti Whātua marae (communal complex used for everyday Māori life) in Auckland for homeless Māori men. The garden project facilitates a sense of belonging, dignity, purpose, meaning and connectedness with other Māori people. It provides insights into how culturally-patterned relationships are centrally important to resolving the overrepresentation of indigenous peoples’ in homelessness populations. I employ the use of semi-structured interviews, reflective journaling, and photography as techniques to record and document the daily interactions in the marae gardens. Participants came from three distinct groups, which include: homeless Māori men, the Auckland City Mission, and Ngāti Whātua o Orakei. A total of eight participants were formally interviewed, along with another six who engaged in casual conversations, in this research, with ages ranged from 30 to 70 years of age. Key findings from this research relate to the construction and preservation of Māori identity while in a state of homelessness, the functioning of marae as spaces of care that foster the wellbeing of Māori, and the role of food in the reproduction of Māori cultural values in everyday life. The broader significance of my work is to use indigenous concepts to build an understanding of the activities, needs and relationships of homeless Māori men that they can recognise themselves from.

text: Homeless Māori Men: Re-connection, Re-joining, and Re-membering Ways of Being There are a range of interventions and programmes to address the on-going issue of Māori homelessness. This thesis explores a gardening project hosted by a Ngāti Whātua marae (communal complex used for everyday Māori life) in Auckland for homeless Māori men. The garden project facilitates a sense of belonging, dignity, purpose, meaning and connectedness with other Māori people. It provides insights into how culturally-patterned relationships are centrally important to resolving the overrepresentation of indigenous peoples’ in homelessness populations. I employ the use of semi-structured interviews, reflective journaling, and photography as techniques to record and document the daily interactions in the marae gardens. Participants came from three distinct groups, which include: homeless Māori men, the Auckland City Mission, and Ngāti Whātua o Orakei. A total of eight participants were formally interviewed, along with another six who engaged in casual conversations, in this research, with ages ranged from 30 to 70 years of age. Key findings from this research relate to the construction and preservation of Māori identity while in a state of homelessness, the functioning of marae as spaces of care that foster the wellbeing of Māori, and the role of food in the reproduction of Māori cultural values in everyday life. The broader significance of my work is to use indigenous concepts to build an understanding of the activities, needs and relationships of homeless Māori men that they can recognise themselves from.

year: 2014