title: Enhancing Skin-Effect Using Surface Roughening and its Potential to Reduce RF Heating from Implant Leads

authors: Seshadri, Sinduja

abstract: Patients wearing Deep Brain Stimulators or Spinal Cord Stimulator implants experience heating at radio frequencies when subjected to an Magnetic Resonance Imaging (MRI) scan that operates at a frequency of 128MHz. One technique to mitigate this heating is applying the concept of loss due to skin-effect on an implant lead wire at MRI frequency. A coaxial resonator of quarter-wavelength with copper conductors was constructed to test the insertion loss using a Vector Network Analyser. The smooth inner copper rod was compared with rough inner copper rod to determine the difference between the quality factor of the resonator. Roughening the surface does enhance the skin-effect loss but the loss is insufficient to translate it to an implant lead which is inserted in a patient.

text: Enhancing Skin-Effect Using Surface Roughening and its Potential to Reduce RF Heating from Implant Leads Patients wearing Deep Brain Stimulators or Spinal Cord Stimulator implants experience heating at radio frequencies when subjected to an Magnetic Resonance Imaging (MRI) scan that operates at a frequency of 128MHz. One technique to mitigate this heating is applying the concept of loss due to skin-effect on an implant lead wire at MRI frequency. A coaxial resonator of quarter-wavelength with copper conductors was constructed to test the insertion loss using a Vector Network Analyser. The smooth inner copper rod was compared with rough inner copper rod to determine the difference between the quality factor of the resonator. Roughening the surface does enhance the skin-effect loss but the loss is insufficient to translate it to an implant lead which is inserted in a patient.

year: 2017

title: Production and assessment of Poly(Lactic Acid) matrix composites reinforced with regenerated cellulose fibres for fused deposition modelling

authors: Gauss, Christian

subjects: 3D printing technology

abstract: Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young's modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young's modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications.

text: Production and assessment of Poly(Lactic Acid) matrix composites reinforced with regenerated cellulose fibres for fused deposition modelling Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young's modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young's modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications.

year: 2022-09-23

title: Mouri matters Contextualizing mouri in Māori health discourse

authors: Penehira, Mera

abstract: The vision statement of Te Reo o Taranaki, “Tuku reo, tuku mouri: language, culture, crossing generations”, embodies the essence of an understanding of mouri which goes beyond the simple dictionary translations of “life force” or “life essence”. Indeed, there are numerous oral narratives—whakataukī (proverbs), waiata (songs), haka (dance), karanga (ceremonial call), whaikōrero (formal speech), karakia (prayers and incantations)—from the present day to our earliest records of Māori history that engage the notion of mouri. The purpose of this paper is to examine current understandings of mouri and, by linking the concept with linguistic, cultural and intergenerational terms—as in the Taranaki example—it will be argued that mouri is something of significance to our “being” and to our wellbeing.

text: Mouri matters Contextualizing mouri in Māori health discourse The vision statement of Te Reo o Taranaki, “Tuku reo, tuku mouri: language, culture, crossing generations”, embodies the essence of an understanding of mouri which goes beyond the simple dictionary translations of “life force” or “life essence”. Indeed, there are numerous oral narratives—whakataukī (proverbs), waiata (songs), haka (dance), karanga (ceremonial call), whaikōrero (formal speech), karakia (prayers and incantations)—from the present day to our earliest records of Māori history that engage the notion of mouri. The purpose of this paper is to examine current understandings of mouri and, by linking the concept with linguistic, cultural and intergenerational terms—as in the Taranaki example—it will be argued that mouri is something of significance to our “being” and to our wellbeing.

year: 2011