Science and Engineering Papers

This collection houses research from the School of Science and from the School of Engineering at the University of Waikato.

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    Bioinspired surface modification of mussel shells and their application as a biogenic filler in polypropylene composites
    (Journal Article, Elsevier BV, 2024-10) Xu, Jing; Mucalo, Michael R; Pickering, Kim L
    This study explores the potential of mussel shells (MS) as biogenic fillers in polymer composites. The chemical composition and crystal structures of MS were characterised. To improve MS filler dispersion and adhesion within a polypropylene (PP) matrix, three surface modification methods were evaluated: polydopamine (PDA) coating, maleic anhydride-grafted polypropylene (MAPP) modification, and PDA/MAPP co-modification. The PDA coating, inspired by the adhesive properties of mussel foot proteins, successfully functionalized the MS surface, as confirmed by X-ray photoelectron spectroscopy (XPS). Thermodynamic analysis, based on contact angle measurements, revealed that MAPP and PDA/MAPP modifications reduced surface energies and potential energy differences. These changes enhanced filler dispersion and interfacial bonding by increasing hydrophobicity and reducing agglomeration in the PP matrix. Consequently, PP composites with 20% PDA/MAPP-modified MS fillers exhibited a 2.9% increase in tensile strength and a 7.5% increase in flexural strength compared to neat PP. Scanning electron microscopy (SEM) also showed reduced filler-matrix debonding and fewer voids. The proposed mechanism attributes these macroscopic property enhancements to the ability of the PDA coating to facilitate chemical and hydrogen bonding between MS fillers and MAPP.
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    Examining the mid to long‐term variability in saturated hydraulic conductivity of sandy soils and its influencing factors under constant head test in the laboratory
    (Journal Article, American Geophysical Union (AGU), 2024) Nikghalb Ashouri, Saeed; Pittari, Adrian; Moon, Vicki; Shokri, Ali
    Saturated hydraulic conductivity (Ks) is a crucial parameter that influences water flow in saturated soils, with applications in various fields such as surface water runoff, soil erosion, drainage, and solute transport. However, accurate determination of Ks is challenging due to temporal and spatial uncertainties. This study addresses the knowledge gap regarding the long‐term behavior of Ks in sandy soils with less than 10% fine particles. The research investigates the changes in Ks over a long period of constant head tests and examines the factors influencing its variation. Two sandy samples were tested using a hydraulic conductivity cell, and the hydraulic head and discharge were recorded for over 50 days. The results show a general decline in Ks throughout the test, except for brief periods of increase. At the end of both tests, there are noticeable reductions in the saturated hydraulic conductivities of the samples, with one sample being 96% and the other sample 91% less than the maximum recorded saturated hydraulic conductivity during the tests. Furthermore, the relationship between flow rate and hydraulic head gradient does not follow the expected linear correlation from Darcy's law, highlighting the complex nature of sandy soil saturated hydraulic conductivity. The investigation of soil properties in three different sections of the samples before and after the tests revealed a decrease in the percentage of fine particles and a shift in specific gravity from the bottom to the top of the sample, suggesting particle migration along the flow direction. Factors such as clogging by fine particles and pore pressure variation contribute to the changes in Ks. The findings of this research show the importance of considering changes of saturated hydraulic conductivity during constant‐head laboratory tests. Therefore, this study provides evidence for the requirement to further assess the laboratory methods for measurement of the saturated hydraulic conductivity in sandy soil mixtures.
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    Neuroanatomy of a sex changing fish: the New Zealand spotty wrasse (Notolabrus celidotus) brain atlas
    (Journal Article, Informa UK Limited, 2024-06-15) Kamstra, Kaj; van der Burg, Chloé; Quertermous, Haylee M; Muncaster, Simon; Todd, Erica V; Jasoni, Christine L; Brown, Culum; Gemmell, Neil J
    For most vertebrates, sexual fate is genetically determined and remains fixed throughout life. However, for some teleost fishes sex is more plastic. Significant progress has been made in characterising the cellular and molecular processes that underpin gonadal sex change. The brain-mediated mechanisms that underlie and initiate this transformation, however, remain poorly understood. One reason for this is the current lack of a neuroanatomical reference work for sex changing fishes. Here, we present a brain atlas for the New Zealand (NZ) spotty wrasse (Notolabrus celidotus), developed from 10 wild caught specimens (2 male and 8 female). From each fish, coronal cryosections were collected and stained with cresyl violet solution. Photomicrographs were taken of each section using an inverted bright field microscope and 3D reconstructions were rendered of each brain for annotation and volumetric comparison of specific brain regions. The brain atlas describes the general features of the NZ spotty wrasse brain as well as its specificities. This atlas provides the necessary foundation for further investigation of the brain mechanisms driving protogyny in this species.
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    Effects of cortisol on female-to-male sex change in a wrasse
    (Journal Article, Public Library of Science (PLoS), 2022-09-01) Goikoetxea, Alexander; Todd, Erica V; Muncaster, Simon; Lokman, P Mark; Thomas, Jodi T; Robertson, Holly A; De Farias e Moraes, Carlos E; Gemmell, Neil J
    Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.
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    A new experimental model for the investigation of sequential hermaphroditism
    (Journal Article, Springer Science and Business Media LLC, 2021-12-01) Goikoetxea, A; Muncaster, Simon; Todd, E. V.; Lokman, P. M.; Robertson, H. A.; De Farias e Moraes, C. E.; Damsteegt, E. L.; Gemmell, N. J.
    The stunning sexual transformation commonly triggered by age, size or social context in some fishes is one of the best examples of phenotypic plasticity thus far described. To date our understanding of this process is dominated by studies on a handful of subtropical and tropical teleosts, often in wild settings. Here we have established the protogynous New Zealand spotty wrasse, Notolabruscelidotus, as a temperate model for the experimental investigation of sex change. Captive fish were induced to change sex using aromatase inhibition or manipulation of social groups. Complete female-to-male transition occurred over 60 days in both cases and time-series sampling was used to quantify changes in hormone production, gene expression and gonadal cellular anatomy. Early-stage decreases in plasma 17β-estradiol (E2) concentrations or gonadal aromatase (cyp19a1a) expression were not detected in spotty wrasse, despite these being commonly associated with the onset of sex change in subtropical and tropical protogynous (female-to-male) hermaphrodites. In contrast, expression of the masculinising factor amh (anti-Müllerian hormone) increased during early sex change, implying a potential role as a proximate trigger for masculinisation. Collectively, these data provide a foundation for the spotty wrasse as a temperate teleost model to study sex change and cell fate in vertebrates.
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    Human activities shape global patterns of decomposition rates in rivers
    (Journal Article, American Association for the Advancement of Science (AAAS), 2024) Tiegs, SD; Capps, KA; Costello, DM; Schmidt, JP; Patrick, CJ; Follstad Shah, JJ; LeRoy, CJ; Acuña, Vicenç; Albariño, Ricardo; Allen, Daniel C; Alonso, Cecilia; Andino, Patricio; Arango, Clay; Aroviita, Jukka; Barbosa, Marcus VM; Barmuta, Leon A; Baxter, Colden; Bellinger, Brent; Boyero, Luz; Bragina, Lyubov; Brown, Lee E; Bruder, Andreas; Bruesewitz, Denise A; Burdon, Francis J.; Callisto, Marcos; Camacho, Antonio; Canhoto, Cristina; Castillo, María M; Chauvet, Eric; Clapcott, Joanne; Colas, Fanny; Colón-Gaud, Checo; Cornut, Julien; Crespo-Pérez, Verónica; Cross, Wyatt F; Culp, Joseph; Danger, Michael; Dangles, Olivier; de Eyto, Elvira; Derry, Alison M; Villanueva, Veronica Díaz; Douglas, Michael M; Elosegi, Arturo; Encalada, Andrea C; Entrekin, Sally; Espinosa, Rodrigo; Ferreira, Verónica; Ferriol, Carmen; Flanagan, Kyla M; Flecker, Alexander S; Fleituch, Tadeusz; Frainer, André; Friberg, Nikolai; Frost, Paul C; Garcia, Erica A; García-Lago, Liliana; Soto, Pavel Ernesto García; Gessner, Mark O; Ghate, Sudeep; Giling, Darren P; Gilmer, Alan; Gonçalves, José Francisco; Gonzales, Rosario Karina; Graça, Manuel AS; Grace, Mike; Griffiths, Natalie A; Grossart, Hans-Peter; Guérold, François; Gulis, Vlad; Gutiérrez-Fonseca, Pablo E; Hepp, Luiz U; Higgins, Scott; Hishi, Takuo; Huddart, Joseph; Hudson, John; Imberger, Moss; Iñiguez-Armijos, Carlos; Isken, Mark W; Iwata, Tomoya; Janetski, David J; Kirkwood, Andrea E; Koning, Aaron A; Kosten, Sarian; Kuehn, Kevin A; Laudon, Hjalmar; Leavitt, Peter R; Lemes da Silva, Aurea L; Leroux, Shawn; Lisi, Peter J; MacKenzie, Richard; Marcarelli, Amy M; Masese, Frank O; McIntyre, Peter B; McKie, Brendan G; Medeiros, Adriana; Meissner, Kristian; Miliša, Marko; Mishra, Shailendra; Miyake, Yo; Moerke, Ashley; Mombrikotb, Shorok; Mooney, Rob; Moulton, Timothy; Muotka, Timo; Negishi, Junjiro; Neres-Lima, Vinicius; Nieminen, Mika L; Nimptsch, Jorge; Ondruch, Jakub; Paavola, Riku; Pardo, Isabel; Peeters, Edwin THM; Pozo, Jesus; Prussian, Aaron; Quenta, Estefania; Reid, Brian; Richardson, John S; Rigosi, Anna; Rincón, José; Risnoveanu, Geta; Robinson, Christopher T; Rodríguez-Gallego, Lorena; Royer, Todd V; Rusak, James A; Santamans, Anna C; Selmeczy, Géza B; Simiyu, Gelas; Skuja, Agnija; Smykla, Jerzy; Sponseller, Ryan; Sridhar, Kandikere R; Stoler, Aaron; Swan, Christopher M; de Mello, Franco Teixeira; Tonkin, Jonathan D; Uusheimo, Sari; Veach, Allison M; Vilbaste, Sirje; Vought, Lena B-M; Wang, Chiao-Ping; Webster, Jackson R; Wilson, Paul B; Woelfl, Stefan; Woodward, Guy; Xenopoulos, Marguerite A; Yates, Adam G; Yoshimura, Chihiro; Yule, Catherine M; Zhang, Yixin; Zwart, Jacob A
    Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf litter decomposition rates with high accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth and reveals rapid decomposition across continental-scale areas dominated by human activities.
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    Robust stutter bisimulation for abstraction and controller synthesis with disturbance
    (Journal Article, Elsevier, 2023) Krook, Jonas; Malik, Robi; Mohajerani, Sahar; Fabian, Martin
    This paper proposes a method to synthesise controllers for cyber-physical systems subjected to disturbances, such that the controlled system satisfies specifications given as linear temporal logic formulas. To solve this problem, a finite-state abstraction of the original system is first constructed, and then a controller is synthesised for the abstraction. Due to the disturbances and uncertainty in the environment, future states cannot be predicted exactly, and the abstraction must take this into account. For this purpose, the robust stutter bisimulation relation is introduced, which preserves the existence of controllers for any given linear temporal logic formula that excludes the next operator. States are related by the robust stutter bisimulation relation if the same target sets can be guaranteed to be reached or avoided under control of some controller, thus ensuring that disturbances have similar effect on paths that start in related states. It is shown that there exists a controller enforcing a linear temporal logic formula for the original system if and only if a controller exists for the abstracted system. The approach is illustrated by a robot navigation example.
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    Using tertiary building performance to define post-disaster functionality timeframes for community recovery and resilience
    (Poster, 2023-08-29) Mayer, Bethany; Boston, Megan
    Building damage from earthquakes can have significant consequences for communities, leading to direct and indirect losses. These losses include casualties and repair costs, reduced productivity and well-being. Current building codes prioritize life safety by aiming to prevent deaths, but lack provisions for repairability and functionality, resulting in potentially long recovery times. There has been growing interest in enhancing post-earthquake building functionality, which refers to a building's ability to serve its intended purpose. Beyond life safety, additional functionality states have been defined, including re-occupancy (safe shelter), functional recovery (basic service provision), and full functionality (restoration to pre-earthquake conditions). Several frameworks and design methodologies have been developed in the United States to understand the requirements for achieving these higher functionality states. However, these frameworks predominantly focus on structural and non-structural component damage, with limited consideration for external impacts (e.g., neighbouring buildings) and social factors (e.g., pre-event planning and occupancy policies). Furthermore, their applicability outside the United States and on a broader scale remains uncertain. In response to the disruptions caused by the Canterbury earthquake sequence in 2010/2011, New Zealand government organizations have expressed a desire to move beyond existing life safety codes and increase the country's resilience. The requirements for achieving higher functionality states within a New Zealand context remains an active research area. This poster proposes developing a framework for post-earthquake building functionality tailored explicitly to New Zealand. Tertiary education institutions in New Zealand are selected as a case study due to their functional similarities to other community buildings such as libraries, offices, cafes, and auditoriums. The research objectives include learning from institutions affected by the Canterbury earthquake sequence, understanding the needs of institutions nationwide, and investigating the framework's applicability to other types of buildings. The poster presents these objectives and details on required resources, timelines, risks, and ethical considerations.
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    Optimization of friction stir spot welding process using bonding criterion and artificial neural network
    (Journal Article, MDPI, 2023-05-01) Jo, DS; Kahhal, Parviz; Kim, JH
    The objectives of this study were to analyze the bonding criteria for friction stir spot welding (FSSW) using a finite element analysis (FEA) and to determine the optimal process parameters using artificial neural networks. Pressure-time and pressure-time-flow criteria are the bonding criteria used to confirm the degree of bonding in solid-state bonding processes such as porthole die extrusion and roll bonding. The FEA of the FSSW process was performed with ABAQUS-3D Explicit, with the results applied to the bonding criteria. Additionally, the coupled Eulerian–Lagrangian method used for large deformations was applied to deal with severe mesh distortions. Of the two criteria, the pressure-time-flow criterion was found to be more suitable for the FSSW process. Using artificial neural networks with the bonding criteria results, process parameters were optimized for weld zone hardness and bonding strength. Among the three process parameters used, tool rotational speed was found to have the largest effect on bonding strength and hardness. Experimental results were obtained using the process parameters, and these results were compared to the predicted results and verified. The experimental value for bonding strength was 4.0 kN and the predicted value of 4.147 kN, resulting in an error of 3.675%. For hardness, the experimental value was 62 Hv, the predicted value was 60.018 Hv, and the error was 3.197%.
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    eDNA is a useful environmental monitoring tool for assessing stream ecological health
    (Journal Article, Wiley, 2024-07) Suren, Alastair; Burdon, Francis J.; Wilkinson, Shaun P.
    Environmental DNA (eDNA) is increasingly used in biodiversity assessments, but there remain uncertainties regarding its congruence with data based on traditional approaches involving habitat sampling and morphological‐based taxonomy. Using eDNA for biomonitoring has several advantages, including improved processing efficiencies and precision of taxonomic identification. In contrast, traditional biomonitoring is time‐consuming and expensive, often limiting the number of sites monitored. Establishing that eDNA‐derived metrics are congruent with their traditional equivalents on a national scale would support its wider use in biomonitoring. Our study compared ecosystem health assessments made by traditional biomonitoring techniques to those using eDNA from 53 sites throughout Aotearoa New Zealand. Because eDNA sampling was not done concurrently with benthic sampling at most sites, we used the average community composition at each site based on previous sampling occasions. We also allocated species identified by eDNA to the traditional level of identification to allow comparisons with eDNA data identified to broader taxonomic groups. We assessed similarities between the three datasets and found a high degree of correlation and convergence between biotic indices calculated from the different methods. eDNA did, however, appear to under‐represent some taxa, reflecting challenges in matching barcodes with an often‐incomplete sequence library. eDNA data did not always perform better in terms of showing the effects of land use on invertebrate community composition, but all datasets produced similar patterns. Multivariate analyses (redundancy analysis and variation partitioning) identified congruent relationships between environmental and spatial variables with the invertebrate community structure described by the three methods. eDNA data replicated the environmental responses and showed the same overall patterns in community composition as the traditionally collected data. We suggest that eDNA biomonitoring can complement traditional methods, and will perform at least as well as traditional data at detecting patterns in invertebrate community composition and ecosystem health at a national scale.
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    Introducing the global work-integrated learning modules: Global connectivity for practitioners
    (Conference Contribution, WACE Inc, 2022-09) Ferns, Sonia J.; Kay, Judie; Hoskyn, Katharine; Zegwaard, Karsten; Johansson, Kristina; McRae, Norah
    As the focus on strengthening graduate employability intensifies for institutions, work-integrated learning (WIL) has become a strategic priority for higher education globally (Rowe & Zegwaard, 2017). The need for a highly skilled workforce to sustain the economy is driving mounting pressure to equip graduates with capabilities to navigate the volatile workplace and contribute to the social and commercial aspects of humanity (Dacre Pool et al., 2019). To achieve this imperative, staff with the capacity to design, deliver, and assess quality WIL learning experiences are essential. The concept of the Global WIL modules was driven by a pressing need for professional development globally as the profile of WIL grows and is increasingly a strategic priority for institutions worldwide (Zegwaard et al., 2019).
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    The changing professional development needs of the international work-integrated learning community
    (Conference Contribution, WACE Inc, 2022-09) Zegwaard, Karsten E.; Ferns, Sonia; Johansson, Kristina; Hoskyn, Katharine; McRae, Norah; Kay, Judie
    The practice of work-integrated learning (WIL) continues to expand across the higher education sector, with many universities introducing or expanding their WIL offerings to align curriculum more closely to employability outcomes (Rowe & Zegwaard, 2017). Universities in Australia have rapidly developed WIL, with all universities offering WIL in almost all the disciplines (Universities Australia, 2019). In New Zealand, WIL has been given increasing attention with the Universities NZ, the peak body for NZ universities, DVCA’s Committee creating a WIL sub-committee to develop national strategy, and with the University of Waikato introducing compulsory WIL for all undergraduates degrees (Muller et al., 2021). The Canadian government recognised WIL as crucial to economic advancement and provided CAD$150 million to support work placement opportunities (Beaulne-Stuebing, 2019).
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    Comparison of resilience rating systems:‎ Assessing post earthquake hospital functionality
    (Conference Contribution, 2018-06) Boston, Megan; Mitrani-Reiser, Judith
    A community’s ability to recover from an earthquake is heavily tied to the overall resilience of that community. Damage to critical infrastructure can dictate how the community as a whole recovers. Efforts have been made to quantify the resilience of important infrastructure components of a community, i.e., individual buildings. These resilience frameworks aim to predict damage, life safety concerns, and recovery times and cost. Several rating systems have been developed to help stakeholders assess vulnerabilities in their buildings and address specific areas for improvement. Each rating system has a different way of quantifying resilience, however, they have a common goal of reducing the adverse effects of a disaster and keep critical facilities running. Hospitals are critical to a community’s well being, and contribute to their resilience and ability to recover following an earthquake. Physical damage to structural and nonstructural components in a hospital can severely limit the ability of the hospital to provide critical life saving services to the community. Predicting post-earthquake hospital functionality is critical for planning and preparing for future earthquakes. Rating systems provide valuable information on the predicted performance of these critical facilities. The results of three different rating systems are compared for a single hospital building.
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    Using the framework for design alternatives and variants
    (Journal Article, International Federation for Information Processing (IFIP), 2019-02) Bowen, Judy; Dittmar, Anke
    This paper presents a framework for considering multi-team, multi‐disciplinary design of interactive systems in a structured manner. IT practitioners can read the paper to gain a deeper understanding and new perspectives of interaction design processes.
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    Generating accurate rule sets without global optimization
    (Conference Contribution, Morgan Kaufmann Publishers Inc., 1998-07-24) Frank, Eibe; Witten, Ian H.
    The two dominant schemes for rule-learning, C4.5 and RIPPER, both operate in two stages. First, they induce an initial ruleset and then they refine it using a rather complex optimization stage that discards (C4.5) or adjusts (RIPPER) individual rules to make them work better together. In contrast, this paper shows how good rule sets can be learned one rule at a time, without any need for global optimization. We present an algorithm for inferring rules by repeatedly generating partial decision trees, thus combining the two major paradigms for rule generation—creating rules from decision trees and the separate-and-conquer rule-learning technique. The algorithm is straightforward and elegant: despite this, experiments on standard datasets show that it produces rulesets that are as accurate as and of similar size to those generated by C4.5, and more accurate than RIPPER’s. Moreover, it operates efficiently, and because it avoids postprocessing, does not suffer the extremely slow performance on pathological example sets for which the C4.5 method has been criticized.
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    Mechanenzymatic production of natural fibre from harakeke (New Zealand flax) and its characterization for potential use in composites for building and construction applications
    (Journal Article, Elsevier B.V., 2024) Akindoyo, John O.; Pickering, Kim L.; Mucalo, Michael R.; Beg, Mohammad Dalour Hossen; Hicks, Joanna
    Mechanical processing of natural fibres can be used to produce large quantities of clean and refined fibres. However, this often results in fibre damage when used alone, thereby affecting the quality of fibres produced, and it generally makes them of insufficient quality for high-performance composite applications. In contrast, the use of biological agents such as enzymes have become a rapidly expanding area of research for producing high quality fibres, but this is still limited to pilot scales. This paper reports the effect of synergizing the salient features of mechanical processing (using a super masscolloider) and enzymatic treatment, on the structure and properties of harakeke (indigenous New Zealand flax) fibre. The cellulose fibres produced are characterized for their potential use as reinforcement in composites. Results show that the combination of mechanical processing with enzymatic treatment could help to overcome the limitations of both processes.
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    Gelatin and collagen from sheepskin
    (Journal Article, MDPI AG, 2024-05-31) Matinong, Andrea Marie E.; Pickering, Kim L.; Waterland, Mark R.; Chisti, Yusuf; Haverkamp, Richard G
    Abattoirs dispose of sheepskins as solid waste due to low price and poor demand for sheepskin leather. In principle, as an alternative to being disposed of in landfill, sheepskins can serve as a source of the protein collagen or the hydrolysis product, gelatin. In this research, sheepskins collected from abattoirs were used as a source of collagen. Three extraction methods were compared: acid extraction, acid with enzymes, and alkali extraction. The extracted material was characterized using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The collagen and gelatin extraction yield ranged from 3.1% to 4.8% with the product purity determined by hydroxyproline, ranging from 7.8% for the alkali process to 59% and 68% for the acid and acid-enzyme processes. SDS PAGE showed that the acid process produced fragments with molecular weights in the range 100 to >250 kDa, while acid–enzyme resulted in smaller fragments, below 30 kDa. The FTIR region of the amide I band at 1800–1550 cm−1, which was used as an indicator of the collagen and gelatin content, showed that the gelatin dominated in the acid extracts, and the alkaline extract contained a large portion of keratin. SAXS was found to be a sensitive method for showing the presence of intact collagen fibrils in materials from all of the extraction methods, albeit at low concentrations. Herein, sheepskin is shown to be a useful source for collagen–gelatin material of varying molecular weights.
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    Options to reduce New Zealand's process heat emissions
    (Report, 2019-03-01) Atkins, Martin John
    The New Zealand Energy Efficiency and Conservation Strategy (NZEECS) 2017-2022 committed MBIE and EECA to prepare an action plan for mitigating the greenhouse gas emissions impact of process heat in New Zealand. To meet this commitment the Process Heat in New Zealand (PHiNZ) project was initiated and this work will contribute to PHiNZ. The purpose of this work was to identify, quantify and cost mitigation options to reduce the GHG emissions associated with the use of process heat in New Zealand. The information supplied by the work will inform: - analysis and policy development, both by MBIE and EECA as part of PHiNZ but also by the Ministry for the Environment (MfE) as part of its wider climate change work; - priority areas for action by government; - process heat users about their emissions profile; - process heat users of possible options to mitigate their emissions.
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    Combined digestion and bleaching of New Zealand flax /harakeke fibre and its effects on the mechanical, thermal, and dynamic mechanical properties of poly(lactic) acid matrix composites
    (Journal Article, Elsevier BV, 2023-01) Akindoyo, John O.; Pickering, Kim; Beg, Dalour; Mucalo, Michael
    In this study, New Zealand flax (harakeke) fibre was initially modified through digestion in an alkali solution followed by bleaching with hydrogen peroxide and sodium silicate with the aim of improving thermal and mechanical performance of its composites, through increased interfacial bonding. X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy and lignin analysis showed that the combination of bleaching and alkali treatment resulted in a higher cellulose content than digestion alone. Fibre inclusion was found to increase the crystallinity of PLA, likely due to heterogeneous nucleation on the treated fibres, which in turn helped to improve the composite strength. The highest tensile strength, tensile modulus and thermal stability were achieved with the bleached fibre which is believed to be due to better fibre distribution and stronger interfacial interaction. This was supported by the adhesion factor and effectiveness coefficient calculated using the data obtained from dynamic mechanical analysis.
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    Influence of pumice and fines contents on the extent of particle crushing in pumiceous sand-silt mixtures during undrained cyclic triaxial loading
    (Journal Article, The Japanese Geotechnical Society, 2024-06-17) Chaneva, Jordanka; O Kluger, Max; Moon, Vicki G.; J Lowe, David J.; Orense, Rolando P.
    Pumiceous particles have a distinct vesicular nature as well as a complex surface texture that makes them potentially vulnerable to crushing under cyclic loading. Pumiceous sand mixtures have received more scientific attention than pumiceous silts in this regard. Researchers have found the undrained cyclic behaviour of pumiceous sands to be significantly different from that of hard-grained sands because of the particle crushing that occurs during cyclic testing and/or sample reconstitution. The liquefaction resistance of pumiceous sands is also considered to be higher because of the pore-water pressure distribution in the sample that occurs during particle crushing. The undrained behaviour of pumiceous silt has only been studied once previously: such material did not crush during sample reconstitution and undrained cyclic testing, which was attributed to a cushioning effect taking place between silty, non-crushable particles and coarse sandy pumice particles. Whether there are thresholds of fines content and/or pumice content at which pumiceous soil mixtures start to behave more similarly to hard-grained soils are yet to be unravelled and remain relevant for engineers and scientists. This paper analyses particle crushing after sample reconstitution and undrained cyclic triaxial testing of three pumiceous natural soil mixtures (lacustrine tephra deposits) from northern New Zealand having fines (< 0.075mm) and pumice contents ranging between 20% and 70% and 30% and 51%, respectively. The results examine potential changes in (1) fines content, (2) pumice content, and (3) undrained cyclic behaviour by comparing both pore-water pressure and axial strain development of the pumiceous soils with other crushable and non-crushable soils.
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