title: Preface: Enhancing tephrochronology and its application (INTREPID project): Hiroshi Machida commemorative volume

authors: Lowe, David J.

subjects: tephrochronology

abstract: Tephrochronology is the characterization and use of tephras – the explosively-erupted, unconsolidated, pyroclastic products of volcanic eruptions – or cryptotephras (glass-shard and/or crystal concentrations not visible as layers) as a unique stratigraphic linking, synchronizing, and dating tool. The word ‘tephra’ is derived directly from the Greek word tephra meaning ‘ashes’. Although the method is founded in stratigraphy, tephrochronology relies also on characterizing or ‘fingerprinting’ inherent tephra-derived components using laboratory-based analysis to complement field-based evidence. Such analysis includes the petrographic identification of mineral assemblages and the geochemical assay of glass shards, melt inclusions, or crystals (minerals including plagioclase, olivine, pyroxenes, amphiboles, biotite, or Fe–Ti oxides such as titanomagnetite) using the electron microprobe and other instruments including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) ( [Lowe, 2011] and [1] ). These data are supported by the derivation of numerical ages on tephras/cryptotephras using a range of techniques including radiometric (e.g., radiocarbon, fission track, luminescence), incremental (e.g., layering in ice cores, varves, dendrochronology), age-equivalence (e.g., orbital tuning, magnetopolarity, palynostratigraphy), relative dating (e.g., obsidan hydration), and historical observation. Ages are also obtained using Bayesian-based flexible depositional modelling and wiggle matching (e.g., [Lowe et al., 2007] and Lowe et al., 2008 D.J. Lowe, P.A.R. Shane, B.V. Alloway and R.M. Newnham, Fingerprints and age models for widespread New Zealand tephra marker beds erupted since 30,000 years ago: a framework for NZ-INTIMATE.. Quaternary Science Reviews,  27  (2008), pp. 95–126. [Lowe et al., 2008] ).

text: Preface: Enhancing tephrochronology and its application (INTREPID project): Hiroshi Machida commemorative volume Tephrochronology is the characterization and use of tephras – the explosively-erupted, unconsolidated, pyroclastic products of volcanic eruptions – or cryptotephras (glass-shard and/or crystal concentrations not visible as layers) as a unique stratigraphic linking, synchronizing, and dating tool. The word ‘tephra’ is derived directly from the Greek word tephra meaning ‘ashes’. Although the method is founded in stratigraphy, tephrochronology relies also on characterizing or ‘fingerprinting’ inherent tephra-derived components using laboratory-based analysis to complement field-based evidence. Such analysis includes the petrographic identification of mineral assemblages and the geochemical assay of glass shards, melt inclusions, or crystals (minerals including plagioclase, olivine, pyroxenes, amphiboles, biotite, or Fe–Ti oxides such as titanomagnetite) using the electron microprobe and other instruments including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) ( [Lowe, 2011] and [1] ). These data are supported by the derivation of numerical ages on tephras/cryptotephras using a range of techniques including radiometric (e.g., radiocarbon, fission track, luminescence), incremental (e.g., layering in ice cores, varves, dendrochronology), age-equivalence (e.g., orbital tuning, magnetopolarity, palynostratigraphy), relative dating (e.g., obsidan hydration), and historical observation. Ages are also obtained using Bayesian-based flexible depositional modelling and wiggle matching (e.g., [Lowe et al., 2007] and Lowe et al., 2008 D.J. Lowe, P.A.R. Shane, B.V. Alloway and R.M. Newnham, Fingerprints and age models for widespread New Zealand tephra marker beds erupted since 30,000 years ago: a framework for NZ-INTIMATE.. Quaternary Science Reviews,  27  (2008), pp. 95–126. [Lowe et al., 2008] ).

year: 2011

title: Bio-composites materials from engineered natural fibres for structural applications

authors: Mohd Ghazali, Aruan Efendy

subjects: Aligned discontinuous natural fibre composites

abstract: The large environmental footprint caused by conventional synthetic fibre reinforced petrochemical-derived polymer composites along with potential improvement in mechanical properties for natural fibre reinforced bio-derived polymer composites, have long been a motivation for further research and innovation in natural fibre composites. Harakeke and hemp fibres, amongst other natural fibres, possess respectable mechanical properties along with other advantages such as low cost, low production energy requirements and abundant availability. Polylactic acid (PLA), a sustainable alternative to petrochemical-derived polymers, is produced on a mass scale from 100% renewable resources and can be degraded at end of life by simple hydrolysis under the appropriate conditions. It has high stiffness, strength, thermal and UV stability, but is low in toughness. Limited applications of natural fibre reinforced PLA composites so far is mainly due to low mechanical properties of discontinuous fibre composites made using injection moulding or compression moulding using randomly oriented fibre mats attributed to poor fibre orientation and fibre-matrix incompatibility. Presented in this study are experimental investigations of the properties of PLA reinforced aligned discontinuous harakeke and hemp fibre mats produced using a dynamic sheet former (DSF) to provide improved performance of discontinuous fibre composites.

Harakeke and hemp fibres were treated using either a solution of 5 wt% or 10 wt% NaOH or combination of 5 wt% NaOH with 2 wt% Na2SO3 at elevated temperatures in a small pressure vessel. Treated fibres were assessed using single fibre tensile testing, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It was found that 5 wt% NaOH/2 wt% Na2SO3 and 5 wt% NaOH effectively removed non-cellulosic materials from harakeke and hemp fibre surfaces, respectively, giving good fibre separation without greatly reducing the tensile strength of the fibres. It was also found that these treatments lead to a higher crystallinity index and improved thermal stability of fibres.

Fibre alignment in fibre mats produced using a DSF was observed using light microscopy. Visual observation supported that the fibre alignment had occurred. Fibre orientation factors (Kɵ) determined for harakeke and hemp composites using the Bowyer-Bader model were found higher compared to Kɵ values obtained for other natural composites prepared using injection and compression moulding. Improved fibre orientation resulted in improved reinforcement giving large increases for tensile strengths up to approximately 90 and 60% for harakeke and hemp composites reinforced with inclusion of 30 and 25 wt% fibre respectively. 

The effect of silane and peroxide as additional fibre treatments and MA-g-PLA as a coupling agent was evaluated by scanning electron microscopy (SEM), composite swelling analysis, tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Scanning electron micrographs of fractured composite surfaces revealed that the gaps between fibres and matrix for composites with fibres treated using silane and peroxide and composites coupled with MA-g-PLA were smaller compared to the surfaces for composites with fibres treated using just alkali. Improved interfacial strength was also supported by lower swelling indices, lower peaks on tan δ and higher residual composites weights, compared to those values obtained for composites with fibres treated using just alkali, which was found to lead to higher composite tensile strengths.

Harakeke and hemp fibre composites were plasticised using hyper-branched polymer (HBP) and assessed using SEM, tensile and impact testing. SEM micrographs for plasticised composites revealed longer pultruding fibres than un-plasticised composites, with gaps between the fibre and matrix appearing to be slightly larger, indicating a weaker interface between fibres and matrix compared to those composites without plasticiser. Improved composite ductility and impact strength were demonstrated for plasticised composites without dramatic reduction of composite tensile strength.

text: Bio-composites materials from engineered natural fibres for structural applications The large environmental footprint caused by conventional synthetic fibre reinforced petrochemical-derived polymer composites along with potential improvement in mechanical properties for natural fibre reinforced bio-derived polymer composites, have long been a motivation for further research and innovation in natural fibre composites. Harakeke and hemp fibres, amongst other natural fibres, possess respectable mechanical properties along with other advantages such as low cost, low production energy requirements and abundant availability. Polylactic acid (PLA), a sustainable alternative to petrochemical-derived polymers, is produced on a mass scale from 100% renewable resources and can be degraded at end of life by simple hydrolysis under the appropriate conditions. It has high stiffness, strength, thermal and UV stability, but is low in toughness. Limited applications of natural fibre reinforced PLA composites so far is mainly due to low mechanical properties of discontinuous fibre composites made using injection moulding or compression moulding using randomly oriented fibre mats attributed to poor fibre orientation and fibre-matrix incompatibility. Presented in this study are experimental investigations of the properties of PLA reinforced aligned discontinuous harakeke and hemp fibre mats produced using a dynamic sheet former (DSF) to provide improved performance of discontinuous fibre composites.

Harakeke and hemp fibres were treated using either a solution of 5 wt% or 10 wt% NaOH or combination of 5 wt% NaOH with 2 wt% Na2SO3 at elevated temperatures in a small pressure vessel. Treated fibres were assessed using single fibre tensile testing, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It was found that 5 wt% NaOH/2 wt% Na2SO3 and 5 wt% NaOH effectively removed non-cellulosic materials from harakeke and hemp fibre surfaces, respectively, giving good fibre separation without greatly reducing the tensile strength of the fibres. It was also found that these treatments lead to a higher crystallinity index and improved thermal stability of fibres.

Fibre alignment in fibre mats produced using a DSF was observed using light microscopy. Visual observation supported that the fibre alignment had occurred. Fibre orientation factors (Kɵ) determined for harakeke and hemp composites using the Bowyer-Bader model were found higher compared to Kɵ values obtained for other natural composites prepared using injection and compression moulding. Improved fibre orientation resulted in improved reinforcement giving large increases for tensile strengths up to approximately 90 and 60% for harakeke and hemp composites reinforced with inclusion of 30 and 25 wt% fibre respectively. 

The effect of silane and peroxide as additional fibre treatments and MA-g-PLA as a coupling agent was evaluated by scanning electron microscopy (SEM), composite swelling analysis, tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Scanning electron micrographs of fractured composite surfaces revealed that the gaps between fibres and matrix for composites with fibres treated using silane and peroxide and composites coupled with MA-g-PLA were smaller compared to the surfaces for composites with fibres treated using just alkali. Improved interfacial strength was also supported by lower swelling indices, lower peaks on tan δ and higher residual composites weights, compared to those values obtained for composites with fibres treated using just alkali, which was found to lead to higher composite tensile strengths.

Harakeke and hemp fibre composites were plasticised using hyper-branched polymer (HBP) and assessed using SEM, tensile and impact testing. SEM micrographs for plasticised composites revealed longer pultruding fibres than un-plasticised composites, with gaps between the fibre and matrix appearing to be slightly larger, indicating a weaker interface between fibres and matrix compared to those composites without plasticiser. Improved composite ductility and impact strength were demonstrated for plasticised composites without dramatic reduction of composite tensile strength.

year: 2016

title: Pilot study investigating pathway for practitioner engagement with whānau during a self-control activity: Implications for uptake in the home and for empowered engagement.

authors: Watson, Kaitlyn

subjects: Community psychology

abstract: There is a gap in youth mentoring services using the home environment of at-risk youth to encourage development of the skills worked on within mentoring. This thesis explores whether a game-based intervention situated in the home environment of youth may initiate changes in behaviour that coincide with their learning during mentoring. Participants were recruited through a private youth mentoring service within Whāngarei. Participants included whānau of youth who are enrolled in the Awhi Ako youth mentoring service and their respective mentors. The Awhi Ako mentoring service aims to support youth through their selected needs by a wider wraparound service.
A game was picked to introduce to whānau to play together at home. This game contained a mechanism that may reward self-control behaviours. Whānau were interviewed and asked to discuss their child’s self-control behaviours before the introduction of the game and any changes after playing the game. 
A principal focus of this thesis is on practitioner engagement with the whānau of mentored youth. Practitioner engagement with communities and people is an integral value underpinning Community psychology. Whānau within the youth mentoring service include Māori, Pasifika, Pākehā and mixed ethnic backgrounds. A core focus of this thesis is understanding the relationship between practitioner and participants and how this impacts upon uptake of the introduction of the activity. In accordance with community psychology underpinnings and values of cultural awareness, cultural respect and understanding this thesis aspires to provide evidence towards the importance of this relationship. Another key focus of this thesis is comprehending the multifaceted effects of an intervention within the home environment and how this impacts mentors, the home environment and the development of youth. Emphasizing a fundamental principle of community psychology of interconnectedness between all facets of a persons life. 
The conclusions drawn from this thesis illustrate the importance of developing a relationship with whānau a key focus to their willingness to participate and actively engage in this pilot study. The findings from this pilot study indicate that whānau experienced hardship and that whānau within at-risk environments had competing priorities that impeded the introduction of home-based activities.

text: Pilot study investigating pathway for practitioner engagement with whānau during a self-control activity: Implications for uptake in the home and for empowered engagement. There is a gap in youth mentoring services using the home environment of at-risk youth to encourage development of the skills worked on within mentoring. This thesis explores whether a game-based intervention situated in the home environment of youth may initiate changes in behaviour that coincide with their learning during mentoring. Participants were recruited through a private youth mentoring service within Whāngarei. Participants included whānau of youth who are enrolled in the Awhi Ako youth mentoring service and their respective mentors. The Awhi Ako mentoring service aims to support youth through their selected needs by a wider wraparound service.
A game was picked to introduce to whānau to play together at home. This game contained a mechanism that may reward self-control behaviours. Whānau were interviewed and asked to discuss their child’s self-control behaviours before the introduction of the game and any changes after playing the game. 
A principal focus of this thesis is on practitioner engagement with the whānau of mentored youth. Practitioner engagement with communities and people is an integral value underpinning Community psychology. Whānau within the youth mentoring service include Māori, Pasifika, Pākehā and mixed ethnic backgrounds. A core focus of this thesis is understanding the relationship between practitioner and participants and how this impacts upon uptake of the introduction of the activity. In accordance with community psychology underpinnings and values of cultural awareness, cultural respect and understanding this thesis aspires to provide evidence towards the importance of this relationship. Another key focus of this thesis is comprehending the multifaceted effects of an intervention within the home environment and how this impacts mentors, the home environment and the development of youth. Emphasizing a fundamental principle of community psychology of interconnectedness between all facets of a persons life. 
The conclusions drawn from this thesis illustrate the importance of developing a relationship with whānau a key focus to their willingness to participate and actively engage in this pilot study. The findings from this pilot study indicate that whānau experienced hardship and that whānau within at-risk environments had competing priorities that impeded the introduction of home-based activities.

year: 2024