title: Laser-induced breakdown spectroscopy applied to pasture, titanium, and bioplastics

authors: Jull, Harrisson Balabat

abstract: Precision agriculture is a farming practice that makes production more efficient. Farmers are able to treat infield variability optimising efficiency, growth, and yield by tailoring the time, rate, and type of fertilizer that is applied. This reduces costs, waste, and environmental side effects such as runoff and leaching caused by overfertilization. Precision agriculture technology measures the nutritional status of crops to inform what, and where, nutrients are needed. The sensors need to be precise, discriminative, and work in real time to ensure that optimal windows for nutrition are not missed. These sensor systems provide aerial imaging, and crop, or soil, colour index maps.

A technology that has proven effective on some agricultural specimens is laserinduced breakdown spectroscopy (LIBS). LIBS is an optical emission technique that utilizes a high-powered pulsed laser to create a plasma on the sample surface. As the plasma cools, photons are emitted at distinct wavelengths corresponding to the elemental composition in the plasma, which should represent the sample. This thesis investigates using LIBS as a sensor for precision agriculture. Multiple chemometric methods have been used on the pasture spectra to build calibration models. There are large deviations between spectra belonging to a single sample. This is due to surface inhomogeneity, particle size, lens-to-sample distance, temperature fluctuations between plasmas, and other causes. Temperature corrections were investigated using Boltzmann plots, Saha-Boltzmann plots, and intensity ratios.

With limited success in mitigating the variations in pasture spectra, LIBS was used to investigate non-aqueous systems. The ability to selectively sinter the surface of injection moulded titanium was examined. Titanium metal injection moulding allows the creation of complex metal parts that are lightweight, biocompatible, and costs less than machining. Multiple LIBS pulses produced sintering in the ablation crater of injection moulded titanium by sufficiently heating the titanium particles so that fusion occurred. The spectra from LIBS can be used to monitor the extent to which the surface is sintered by measuring the reduction in carbon emissions. An autofocus system, based on the triangulation method, was used to minimise variations caused by lens-to-sample distance (LTSD).

With the success of sintering titanium, LIBS was used to investigate non-aqueous organic systems. Employing LIBS to discriminate bioplastics from regular plastics was explored in recycle waste streams. If bioplastics are present in the recovery process of regular plastics the resulting product contains impurities. This study was undertaken to determine the feasibility of incorporating bioplastics in the curbside pickup of recyclables in New Zealand. The common recyclables are plastics, glass, tin cans, and aluminium cans. The setup was designed to emulate a one-shot LIBS detection system in a recycling plant. Models were created using k nearest neighbours and soft independent modelling class analogy from the spectra. 100 % discrimination between bioplastics and regular plastics was achieved. An autofocus system, combining dual lasers, was used to overcome the occlusions produced by sample geometry.

text: Laser-induced breakdown spectroscopy applied to pasture, titanium, and bioplastics Precision agriculture is a farming practice that makes production more efficient. Farmers are able to treat infield variability optimising efficiency, growth, and yield by tailoring the time, rate, and type of fertilizer that is applied. This reduces costs, waste, and environmental side effects such as runoff and leaching caused by overfertilization. Precision agriculture technology measures the nutritional status of crops to inform what, and where, nutrients are needed. The sensors need to be precise, discriminative, and work in real time to ensure that optimal windows for nutrition are not missed. These sensor systems provide aerial imaging, and crop, or soil, colour index maps.

A technology that has proven effective on some agricultural specimens is laserinduced breakdown spectroscopy (LIBS). LIBS is an optical emission technique that utilizes a high-powered pulsed laser to create a plasma on the sample surface. As the plasma cools, photons are emitted at distinct wavelengths corresponding to the elemental composition in the plasma, which should represent the sample. This thesis investigates using LIBS as a sensor for precision agriculture. Multiple chemometric methods have been used on the pasture spectra to build calibration models. There are large deviations between spectra belonging to a single sample. This is due to surface inhomogeneity, particle size, lens-to-sample distance, temperature fluctuations between plasmas, and other causes. Temperature corrections were investigated using Boltzmann plots, Saha-Boltzmann plots, and intensity ratios.

With limited success in mitigating the variations in pasture spectra, LIBS was used to investigate non-aqueous systems. The ability to selectively sinter the surface of injection moulded titanium was examined. Titanium metal injection moulding allows the creation of complex metal parts that are lightweight, biocompatible, and costs less than machining. Multiple LIBS pulses produced sintering in the ablation crater of injection moulded titanium by sufficiently heating the titanium particles so that fusion occurred. The spectra from LIBS can be used to monitor the extent to which the surface is sintered by measuring the reduction in carbon emissions. An autofocus system, based on the triangulation method, was used to minimise variations caused by lens-to-sample distance (LTSD).

With the success of sintering titanium, LIBS was used to investigate non-aqueous organic systems. Employing LIBS to discriminate bioplastics from regular plastics was explored in recycle waste streams. If bioplastics are present in the recovery process of regular plastics the resulting product contains impurities. This study was undertaken to determine the feasibility of incorporating bioplastics in the curbside pickup of recyclables in New Zealand. The common recyclables are plastics, glass, tin cans, and aluminium cans. The setup was designed to emulate a one-shot LIBS detection system in a recycling plant. Models were created using k nearest neighbours and soft independent modelling class analogy from the spectra. 100 % discrimination between bioplastics and regular plastics was achieved. An autofocus system, combining dual lasers, was used to overcome the occlusions produced by sample geometry.

year: 2018

title: Finding the good vibes of life, man: Identifying catalytic vibrations in enzyme catalysis

authors: Schipper, Daniel-Albert

subjects: MMRT

abstract: Enzyme catalysis is one of the most vital components of life. As such the elucidation of the exact mechanics of this kind of catalysis is important. The aim of this work is to look into enzyme catalysis though the lens of macromolecular rate theory (MMRT). MMRT is an idea focused around the heat capacity of an enzyme changing over the course of a reaction. Our hypothesis is that this change in heat capacity is strongly tied to the nature of enzyme catalysis. As such, the focus of this thesis is to determine what a large change in heat capacity at the transition state on the reaction pathway means and why it happens.     
			
From previous work I know that there is a difference in heat capacity when an enzyme is bound to a reaction state compared to a transition state analog. One of the components of this project is to investigate the causes of this difference using all-atom molecular dynamics (MD) and calculations based on the MD trajectories.
			
In the harmonic case, it was found that there was no significant difference between our chosen enzyme in the reaction state and it in a transition state analog; which was possibly either due to insufficient simulation time or higher order anharmonic behavior driving the change in heat capacity. I computed the vibrational frequencies used to test this from the trajectories of a molecular dynamics simulation. 
			
			
In addition, the patterns of how the change in heat capacity evolves with temperature acts similarly to how changes in heat capacity act during phase transitions. These transitions are characterized by long range fluctuations, which I aimed to detect; however, no change in the distance of fluctuations was detected in the harmonic case in the simulations. 
			
Finally, I looked into computing heat capacities for a large system using the variance in energies. Previous attempts at doing this found reasonable values for the change in heat capacity when looking at an enzyme bound to a transition state analog vs bound to the reactant state. However, the absolute values of the heat capacities were an order of magnitude too high for each state. I investigated why this was the case and concluded that it was almost entirely due to not including quantum effects and the fact that interaction energies between the system and the solvent are dynamic.

text: Finding the good vibes of life, man: Identifying catalytic vibrations in enzyme catalysis Enzyme catalysis is one of the most vital components of life. As such the elucidation of the exact mechanics of this kind of catalysis is important. The aim of this work is to look into enzyme catalysis though the lens of macromolecular rate theory (MMRT). MMRT is an idea focused around the heat capacity of an enzyme changing over the course of a reaction. Our hypothesis is that this change in heat capacity is strongly tied to the nature of enzyme catalysis. As such, the focus of this thesis is to determine what a large change in heat capacity at the transition state on the reaction pathway means and why it happens.     
			
From previous work I know that there is a difference in heat capacity when an enzyme is bound to a reaction state compared to a transition state analog. One of the components of this project is to investigate the causes of this difference using all-atom molecular dynamics (MD) and calculations based on the MD trajectories.
			
In the harmonic case, it was found that there was no significant difference between our chosen enzyme in the reaction state and it in a transition state analog; which was possibly either due to insufficient simulation time or higher order anharmonic behavior driving the change in heat capacity. I computed the vibrational frequencies used to test this from the trajectories of a molecular dynamics simulation. 
			
			
In addition, the patterns of how the change in heat capacity evolves with temperature acts similarly to how changes in heat capacity act during phase transitions. These transitions are characterized by long range fluctuations, which I aimed to detect; however, no change in the distance of fluctuations was detected in the harmonic case in the simulations. 
			
Finally, I looked into computing heat capacities for a large system using the variance in energies. Previous attempts at doing this found reasonable values for the change in heat capacity when looking at an enzyme bound to a transition state analog vs bound to the reactant state. However, the absolute values of the heat capacities were an order of magnitude too high for each state. I investigated why this was the case and concluded that it was almost entirely due to not including quantum effects and the fact that interaction energies between the system and the solvent are dynamic.

year: 2020

title: An exploration of wellbeing in Hapū Wānanga through a Te Wheke framework analysis

authors: Hawaikirangi, Lena

subjects: Antenatal education

abstract: Before colonisation, Māori had comprehensive knowledge and practices around pregnancy and childbirth. With colonisation, traditional maternity knowledge and practices were replaced by western medical practices. In more recent times, antenatal education classes have played an essential role in providing information on pregnancy, birth and caring for newborns. Research reports that Māori are less likely to attend antenatal programmes and  have suggested that culturally responsive programmes may encourage better engagement by Māori. Hapū Wānanga is a kaupapa Māori antenatal education programme. No previous research has explored how whānau experience wellbeing through Hapū Wānanga. This research explores how participants experience wellbeing within the Kia Wana  Lakes Baby Service Hapū Wānanga. Three participants, including one couple, and three facilitators were interviewed. Transcripts were analysed through a framework analysis using the Te Wheke model (Pere, 1997), a comprehensive Māori model of health. Findings showed that Hapū Wānanga caters to Māori holistic views of wellbeing, as demonstrated through the Te Wheke Model (Pere, 1997). All participants reported negative experiences with mainstream antenatal services; however, whānau enjoyed their experience at Hapū Wānanga. The two dimensions that influenced participants most were whānaungatanga (kinship ties) and hā ā koro mā ā kuia mā (cultural heritage). Although whānau were empowered by their experience at Hapū Wānanga, they wanted to learn more about parenting and postpartum, mental health. Overall, my findings highlighted that culturally adapted programmes that cater to  holistic models of wellbeing could engage Māori service users in an enjoyable and empowering way. If healthcare providers are to be successful in improving indigenous peoples' wellbeing, they need to prioritise culturally adapted programmes based on holistic models of wellbeing.

text: An exploration of wellbeing in Hapū Wānanga through a Te Wheke framework analysis Before colonisation, Māori had comprehensive knowledge and practices around pregnancy and childbirth. With colonisation, traditional maternity knowledge and practices were replaced by western medical practices. In more recent times, antenatal education classes have played an essential role in providing information on pregnancy, birth and caring for newborns. Research reports that Māori are less likely to attend antenatal programmes and  have suggested that culturally responsive programmes may encourage better engagement by Māori. Hapū Wānanga is a kaupapa Māori antenatal education programme. No previous research has explored how whānau experience wellbeing through Hapū Wānanga. This research explores how participants experience wellbeing within the Kia Wana  Lakes Baby Service Hapū Wānanga. Three participants, including one couple, and three facilitators were interviewed. Transcripts were analysed through a framework analysis using the Te Wheke model (Pere, 1997), a comprehensive Māori model of health. Findings showed that Hapū Wānanga caters to Māori holistic views of wellbeing, as demonstrated through the Te Wheke Model (Pere, 1997). All participants reported negative experiences with mainstream antenatal services; however, whānau enjoyed their experience at Hapū Wānanga. The two dimensions that influenced participants most were whānaungatanga (kinship ties) and hā ā koro mā ā kuia mā (cultural heritage). Although whānau were empowered by their experience at Hapū Wānanga, they wanted to learn more about parenting and postpartum, mental health. Overall, my findings highlighted that culturally adapted programmes that cater to  holistic models of wellbeing could engage Māori service users in an enjoyable and empowering way. If healthcare providers are to be successful in improving indigenous peoples' wellbeing, they need to prioritise culturally adapted programmes based on holistic models of wellbeing.

year: 2021