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Novel numerical methods for stochastic ordinary and partial differential equations in modelling complex systems : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textMany natural and engineered systems are complex due to inherent uncertainty. Stochastic Differential Equations (SDEs) and Stochastic Partial Differential equations (SPDEs) provide a rigorous mathematical foundation for modelling these systems. Understanding the dynamics of complex systems under stochastic influences is crucial for predicting system behaviour. Numerical techniques often struggle to handle the complexity and stochastic nature of these equations. This research focuses on adapting and enhancing numerical methods to provide efficient and reliable solutions. The numerical accuracy and stability of these methods are assessed through simulations and examples. This study introduces the synthesis of stochastic spectral methods to solve complex systems by representing random variables as a sum of orthogonal polynomials. We applied Polynomial Chaos Expansion (PCE) methods to contaminant transport problem and to differential equations with random forcing term. We compute the Wick exponentials and show that Wick product coincides with the ordinary product for deterministic functions. We use Malliavin calculus to find the derivatives of a stochastic quantity and are visualised through graphs. We discuss numerical challenges associated with the PCE methods and their solution strategies. In all examples, our chosen method does better and allows us to lead the way in developing robust and efficient strategies to deal with randomness, ultimately enhancing the reliability and resilience of complex systems across various scientific and engineering domains
Efficacy of commercial peroxyacetic acid on Vibrio parahaemolyticus planktonic cells and biofilms on stainless steel and Greenshell™ mussel (Perna canaliculus) surfaces
No full textThe potential of using commercial peroxyacetic acid (PAA) for Vibrio parahaemolyticus sanitization was evaluated. Commercial PAA of 0.005 % (v/v, PAA: 2.24 mg/L, hydrogen peroxide: 11.79 mg/L) resulted in a planktonic cell reduction of >7.00 log₁₀ CFU/mL when initial V. parahaemolyticus cells averaged 7.64 log₁₀ CFU/mL. For cells on stainless steel coupons, treatment of 0.02 % PAA (v/v, PAA: 8.96 mg/L, hydrogen peroxide: 47.16 mg/L) achieved >5.00 log₁₀ CFU/cm² reductions in biofilm cells for eight strains but not for the two strongest biofilm formers. PAA of 0.05 % (v/v, PAA: 22.39 mg/L, hydrogen peroxide: 117.91 mg/L) was required to inactivate >5.00 log₁₀ CFU/cm² biofilm cells from mussel shell surfaces. The detection of PAA residues after biofilm treatment demonstrated that higher biofilm production resulted in higher PAA residues (p < 0.05), suggesting biofilm is acting as a barrier interfering with PAA diffusing into the matrices. Based on the comparative analysis of genomes, robust biofilm formation and metabolic heterogeneity within niches might have contributed to the variations in PAA resistance of V. parahaemolyticus biofilms
Soil carbon, erosion, and the stormflow mobilisation of sediment and nutrients in a high-country landscape : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textThis study was carried out at Mt. Grand Station, a high-country pastoral farm in the South Island of New Zealand. The landscape (400 - 1300 m altitude) supports a gradient and mosaic of native and endemic woody shrub and tussock grassland vegetation amongst more productive exotic pasture, the latter established through aerial seed top-dressing and fertilisation. In recent years several areas of the farm at higher altitudes have been converted to conservation management following Tenure Review, placing additional pressure on the remaining farmland to maximise productivity, a situation similarly faced by many other high-country farms. However, further intensification of pasture grassland would compromise existing less productive native vegetation. This research project investigated soil conservation and loss, and freshwater quality, aiming to advance existing knowledge relating to environmental sustainability of the high-country.
Topsoil carbon stocks were quantified beneath various vegetation communities at different altitudes of the station to gain a better understanding of soil carbon and its dynamics. Two watershed catchments were targeted for high-frequency sampling during rainfall events, to investigate the likely significance of water flow on the mobilisation of sediment and nutrients, and to help improve the accuracy of existing run-off estimates. In addition, soil erosion was estimated from differences in residual soil 137Cs activity, which was generated from historic Pacific nuclear testing, between two of the dominant types of vegetation cover. The results revealed the potential for native vegetation to enhance soil carbon sequestration. At low - middle altitudes (450 - 850 m) of the farm, topsoil beneath a woody shrub (kānuka) vegetation cover had significantly higher carbon concentrations and carbon stocks than areas of adjacent pasture. At higher elevations (>1000 m) topsoil beneath dominant snow tussocks had significantly higher carbon, nitrogen and phosphorus concentrations, with higher carbon stocks than adjacent inter-tussock spaces. The total loads of suspended solids, nitrogen and phosphorus exported to catchment waterways were significantly larger during high-flow events in comparison to baseflow conditions, and large proportions of the high-flow loads were mobilised on the rising hydrograph following high rainfall. These findings draw attention to the significance of taking account of the early stages of rainfall events to improve accuracy when quantifying high-country catchment loads. Data for 137Cs were variable but these provisional results indicate that soil beneath kānuka is likely to have undergone lower rates of erosion over the previous 65 years in comparison to areas of adjacent pasture.
The combined findings of the three parts of the experimental work in this study are interpreted as being indicative of the present and future potential for South Island high-country farming environments to make a significant contribution towards climate change mitigation through vegetation management, resultant soil building and prevention of soil erosion. It is argued that closer attention to ecological restoration is likely to have mutual benefits for conservation, the farming system and the environment. Maintenance and better-informed management of the mosaic of native and exotic vegetation can play a more important role in longer-term sustainability of this high-country land management system than is currently appreciated
Investigation of the microbiome structure and function in grapevines escaping trunk diseases : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textGrapevine trunk diseases (GTD) represent a substantial challenge to viticulture in New Zealand and other winegrowing regions worldwide. With no approved fungicides for their eradication, alternative methods, such as biological control, are of significant interest. Key international studies have identified plants, called disease escape plants, that remain healthy under a high disease pressure, and this trait has been linked to microbiome function. In some New Zealand vineyards, such disease escape vines have been observed in backgrounds of heavy GTD pressure. This study aimed to investigate a microbiome approach to GTD management by surveying New Zealand vineyards for the occurrence of GTD escape vines and characterising the trunk microbiome of such vines.
Based on preliminary assessments of nine vineyards across Hawke's Bay and Canterbury, New Zealand, a detailed visual survey was conducted in four vineyards, two each in Hawke's Bay and Canterbury. Candidate GTD escape vines were identified based on the absence of GTD symptoms, chlorophyll content of leaves, and high GTD pressure in the vineyard block. Woody trunk tissue samples were collected from these vines and the diseased vines nearby. The fungal and bacterial communities in the samples were characterised using a combination of DNA metabarcoding of the ribosomal internal transcribed spacer 1 (ITS1) and 16S ribosomal RNA gene and microbial isolations.
The results showed that the status of the vine as either GTD escape or diseased was a strong determinant of the structure of the bacterial and fungal microbiomes of the grapevine trunk. For bacteria, the GTD escape vines consistently harboured Pseudomonas and Hymenobacter in higher relative abundance. Aureobasidium, Seimatosporium, Cladosporium, and Rhodotorula were fungal genera differentially associated with GTD escape vines. On the other hand, the GTD pathogen, Eutypa lata, was differentially associated with diseased vines.
Bacterial and fungal isolates matching the key taxa identified by DNA metabarcoding from GTD escape vines were retrieved and tested for inclusion in microbial consortia. Additional selection criteria for inclusion were the microorganism's functional properties, such as not being a known plant pathogen, not causing lesions on grapevine shoots, and exhibiting desirable inhibitory activities against E. lata and Neofusicoccum luteum in dual culture plate assays. Using these criteria, consortium members Aureobasidium pullulans, Seimatosporium vitis, and seven Pseudomonas isolates were selected. Combined and separate fungal and bacterial consortia were tested in plant assays against the GTD pathogens E. lata and N. luteum. Over 3 months, the bacteria successfully established and persisted within the grapevines, significantly altering the grapevines' microbiome structure. Treatment with combined bacterial and fungal consortia resulted in significantly shorter lesions (71% reduction, p = 0.002) than the pathogen controls. The relative abundance of E. lata was reduced by 85% in the presence of the bacteria-only consortium.
This research enhanced knowledge of the grapevine trunk microbiome structure within the context of the GTD escape phenotype. In addition, it expanded the understanding of grapevine microbiome manipulation by developing and delivering microbial consortia into grapevines, which resulted in changes in the grapevine microbiome structure. These results highlight the potential of using selected microbial consortia as a promising strategy for controlling GTD pathogens in planta. Given the perennial nature of grapevines and the extended development periods associated with GTD, future research could investigate the potential long-term impact of grapevine microbiome manipulation on the protection of grapevines against GTD pathogens
The effect of unmixed information on consumers’ preference and willingness to pay for animal welfare enhanced eggs in New Zealand
Get PDFPresentation given at AARES 2023, Christchurch, New Zealand
Grapevines escaping trunk diseases in New Zealand vineyards have a distinct microbiome structure
Get PDFGrapevine trunk diseases (GTDs) are a substantial challenge to viticulture, especially with a lack of available control measures. The lack of approved fungicides necessitates the exploration of alternative controls. One promising approach is the investigation of disease escape plants, which remain healthy under high disease pressure, likely due to their microbiome function. This study explored the microbiome of grapevines with the disease escape phenotype. DNA metabarcoding of the ribosomal internal transcribed spacer 1 (ITS1) and 16S ribosomal RNA gene was applied to trunk tissues of GTD escape and adjacent diseased vines. Our findings showed that the GTD escape vines had a significantly different microbiome compared with diseased vines. The GTD escape vines consistently harbored a higher relative abundance of the bacterial taxa Pseudomonas and Hymenobacter. Among fungi, Aureobasidium and Rhodotorula were differentially associated with GTD escape vines, while the GTD pathogen, Eutypa, was associated with the diseased vines. This is the first report of the link between the GTD escape phenotype and the grapevine microbiome
Hypoxic exposure at rest or during light to moderate-intensity exercise improved blood pressure and heart rate variability in cardiovascular risk individuals
Get PDFThis study evaluated the effects of 6 weeks of intermittent hypoxic at rest or plus exercise and long-lasting effects on blood pressure and heart rate variability (HRV) in cardiovascular risk individuals. Thirty combinations of several CVD risks participants: hypertension, hyperlipidemia, and obesity were randomly allocated into 3 groups: (a) the Control Group (CON, n = 11) received no intervention; (b) the intermittent hypoxic exposure during rest (IHR, n = 9), and the intermittent hypoxic training (IHT, n = 10) combined with walking on a motorized treadmill at a light to moderate-intensity. Both IHR and IHT performed 8 sessions of 3 minutes of hypoxic breathing alternated with 3 minutes of normoxic breathing for 6 weeks. All participants blood pressure and HRV were measured at baseline, at week 6 (POST1), and at week 10 (POST2). The IHR and IHT Groups showed significantly lower SBP (P < 0.05) compared to the CON Group, but not DBP and MAP after the IH training program. Compared to CON, the low-frequency band (VLF) and the low-frequency band and the high-frequency band (LF/HF ratio) showed a significant decrease only in IHT (P < 0.05) at POST1 and VLF remained significantly decreased at POST2. VLF in the IHT Group remained significantly lower than in the IHR Group at POST2. After the IH training program, IHT revealed a significant increase in HF (P < 0.05) compared to the CON Group. HF (n.u.) was a significantly stronger negative correlation with changes in SBP (P < 0.05). The IHT Group showed more effectiveness than the IHR Group. The study suggested this IH training program improved SBP and HRV at POST1. An increase in parasympathetic activity may have played an important role in the SBP reduction seen in this study
Den lille blå parlør om havstigning
No full textSamlet viden og dialog:
Ingen kan vide alt, og i tilpasningen af vores kystbyer er der brug for at udveksle viden, samarbejde og gå i dialog. Den Lille Blå Parlør om Havstigning er et bidrag til dialogen om klimatilpasning og løsningsrum i fremtidens by- og landskabsudvikling. Parløren søger at gå på tværs af viden, fagligheder, interesser, aldersgrupper, ansvarsområder og visioner for på den vis at bidrage til at binde samtalen mellem forskellige interessenter sammen.
Baggrund, formål og struktur:
Parløren er struktureret som en ABC med en række nøgleord på tværs af tematiske sammenhænge. Her beskrives termer og begreber alfabetisk og flere steder fulgt af illustrationer. Nogle steder udbygges teksten med en note, hvor primære kilder angives eller der gives link til yderligere viden. Mange af termerne knytter sig nært til, eller overlapper med, andre ord og begreber. Tingene hænger sammen, og jo mere helhedsorienteret der arbejdes med klimatilpasning, des mere hænger forskellige begreber og tilgange sammen. Af samme årsag er parløren - ligesom andre parlører – ikke tiltænkt kronologisk læsning men kan ses som et lille opslagsværk med en række kernebegreber, hvorefter yderligere viden kan søges.
Målgruppe og hvordan bogen kan bruges:
Den Lille Blå Parlør er udarbejdet som formidling til en bred gruppe af både lægfolk og fagfolk, elever og studerende, borgere og politikere,
praktikere og forskere. Det er en introduktion til en række kernebegreber og termer, der ofte er vigtige i forbindelse med udvikling af løsninger for havstigning og kraftigere stormfloder i de danske kystbyer. Formålet er at give en overordnet, introducerende viden, som den enkelte kan bruge som enkeltopslag, eksempelvis Bidragsmodel, Kote eller Omkostningseffektivitet, eller som tematiske opslag som f.eks. Løsningstypologier, der spænder bredt med korte beskrivelser
af forskellige tilgange. Parløren kan også ses som en overordnet bred introduktion, hvorefter man selv kan søge mere viden. Parløren har fokus på kystbyer i Danmark og det danske klima med referencer til udlandet
Response of nitrate leaching to no-tillage is dependent on soil, climate, and management factors: A global meta-analysis
Get PDFNo tillage (NT) has been proposed as a practice to reduce the adverse effects of tillage on contaminant (e.g., sediment and nutrient) losses to waterways. Nonetheless, previous reports on impacts of NT on nitrate (NO¯₃) leaching are inconsistent. A global meta-analysis was conducted to test the hypothesis that the response of (NO¯₃) leaching under NT, relative to tillage, is associated with tillage type (inversion vs non-inversion tillage), soil properties (e.g., soil organic carbon [SOC]), climate factors (i.e., water input), and management practices (e.g., NT duration and nitrogen fertilizer inputs). Overall, compared with all forms of tillage combined, NT had 4% and 14% greater area-scaled and yield-scaled NO¯₃ leaching losses, respectively. The NO¯₃ leaching under NT tended to be 7% greater than that of inversion tillage but comparable to non-inversion tillage. Greater NO¯₃ leaching under NT, compared with inversion tillage, was most evident under short-duration NT (200 kg ha¯¹) and lower (0–100 kg ha¯¹) rates of nitrogen addition. Of these, SOC was the most important factor affecting the risk of NO₃‾ leaching under NT compared with inversion tillage. Globally, on average, the greater amount of NO₃‾ leached under NT, compared with inversion tillage, was mainly attributed to corresponding increases in drainage. The percentage of global cropping land with lower risk of NO₃‾ leaching under NT, relative to inversion tillage, increased with NT duration from 3 years (31%) to 15 years (54%). This study highlighted that the benefits of NT adoption for mitigating NO¯₃ leaching are most likely in long-term NT cropping systems on high-SOC soils
Developing a new resetting tool for controlling rats
Get PDFA resetting toxin device (the “Spitfire”) has been designed that delivers a toxic paste to a rat’s ventral surface when it passes through a tunnel. The rat grooms off the paste and ingests the toxin. The system was assessed in cage trials and one field trial. The purpose of the cage trials was to investigate whether a range of toxins can be delivered by the Spitfire to rats (Rattus rattus and R. norvegicus), namely 0.55% sodium fluoroacetate (1080), 0.2% brodifacoum, 15% cholecalciferol, and 12.5% zinc phosphide. The trials with 1080, brodifacoum, and zinc phosphide were successful with > 85% of rats ingesting lethal doses. The trials with cholecalciferol were less successful with only 58% of rats dying. A one-month pilot field trial was undertaken using 1080 in the Spitfires. There was a knockdown in rat (and stoat Mustela erminea) abundance, establishing proof of concept for the Spitfire delivery system with this toxin. The long-term, effective control of introduced rats will require a range of toxins with different modes of action. The Spitfire could be a useful additional control tool for rats and is currently being re-engineered to be made more reliable