Browsing by Author "Cleland, Josiah David"

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    ATR-FTIR chemometrics for biological samples : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2018) Cleland, Josiah David
    This project has used the analytical infrared reflectance technique of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, for the prediction of chemical components in a range of biological samples. Data collection was carried out on 40 hyperaccumulator samples, 56 chicken feed samples, 54 lamb faecal samples and 188 forage feed samples. Predictions were made using several different regression methods including: Ridge, Least Absolute Shrinkage and Selection Operator (LASSO), Elastic Net, Principal Components (PCR) and Partial Least Squares (PLS). The best methods were identified as LASSO, Elastic Net and PLS. Several spectral data pre-treatments were explored, the best of which combined Standard Normal Variant scaling (SNV) with a first-order Savitzky – Golay (SG) spectral derivative and smoothing filter. Several of the resulting models illustrated high quality predictions (R2 > 0.8, Relative Performance Deviation (RPD) ≥ 2). The SNV and SG pre-treatment almost completely reduces the contribution of strong water-based signals to the regression model, allowing the possibility of in situ prediction of forage feed composition with minimal sample preparation. ATR-FTIR spectrometers are available in a hand-held form, and the results of this research suggest that in situ forage quality analysis could be performed using mid – infrared (MIR) reflectance spectroscopy.
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    Generalised diffusion equations for anomalous diffusion in polymer networks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics, School of Natural Sciences, Massey University, Manawatu, New Zealand
    (Massey University, 2022) Cleland, Josiah David
    Fractional and generalised derivative equations have proven to be a powerful tool in the modelling of anomalous diffusion within complex fluids. The suitability of these equations arises from to their capacity to include memory effects prevalent in the fluid, as well as allowing for the inclusion of external forces and relevant boundary values. Fractional derivative equations may be derived from underlying continuous-time random-walk models, however, the fractional derivative equations (and their generalisations) are simpler to deal with. This thesis investigated the ability of fractional derivative equations (and their generalisations) to model long timescale anomalous diffusion phenomena observed in some visco-elastic polymer networks. Recent work has suggested that within certain physical polymer networks there is a tendency for internal stresses to continuously build and dissipate. This phenomenon manifests itself within recordings of probe-particle mean squared displacements at long time scales. The dynamic behaviour of these networks parallels behaviour observed in earthquakes, earning the phenomena the name gel or cyto quakes. This link suggests that statistical features involved in other stress driven events may provide insight into the modeling of gel quakes. Both temporal and spatial considerations relevant to these quaking systems will be outlined and modelled within this work.