19366 research outputs found
Sort by
Formulation of numerical solutions for Wick Type Stochastic Differential Equations (WSDEs)
No full textIn this chapter, we develop a simple finite difference scheme to approximate the WSDEs using a linear WSDE with constant coefficients. We also compute the solutions and introduce noise ratio as a measure to gauge the influence of noise on the system
Wick algebra, diffusions, and computations
No full textWe summarize pertinent mathematical results in Chap. 2,= and in this chapter, we focus on more useful derivations based on the Wick products with the aim of developing a consistent mathematical machinery for computations. Central to these developments are the Hermite polynomials, and they are used in the Wick products related to the Itô diffusions. The idea of using the Itô diffusions to model the stochastic variables that participate in the Wick type equations is inspired by the fact that many physical variables have drift and diffusive components to them. The forces and flows governed by the physical laws drive the average behaviors in noisy environments and the fluctuations in intrinsic and extrinsic forces and flows give rise to the “noise” in the system. Therefore, it is reasonable to assume that the drift term represents the average behavior, and the diffusion term is a result of the fluctuations. Another important assumption is that the effects of average behaviors and the fluctuations are additive, not multiplicative, and to simplify the analysis, we assume the coefficients associated with these terms are constant
Disabled people, arts festivals and emotional timescapes: An exploratory case study
No full textThis exploratory study contributes to the leisure studies literature in three main ways: through foregrounding the emotionality of intellectually disabled people, an under-represented group within the context of events; through focusing on an arts festival, a form of event overlooked in comparison to other commonly studied types of events; and finally, through the testing of a new methodological framework – Brown’s emotional timescapes for events, itself adapted from Maguire and Geiger’s work on servicescapes. In this New Zealand-based study, we explore the emotions experienced by attendees, performers, volunteers, support workers and event organisers. Data from 20 interviews, participant observation and autoethnography was deductively analysed with a focus on expressions of emotion. We crafted a narrative for each individual, allowing us to identify the influence of the eventscape and map temporal patterns of emotional responses across the festival timescape. Findings show that participants experienced strong positive emotions. This was influenced by elements of the eventscape. In particular, interaction with others (including audience reaction) played a significant role in emotional timescapes. While the emotional timescape model was useful for broadly representing intensity of emotion over the duration of an event, we also identified limitations and propose a way to expand Brown’s theory
Behavioural and neural correlates of social hierarchy formation in a sex-changing fish
No full textSocial hierarchies in sex-changing fish determine which fish will change sex, yet the complexities of hierarchy formation at the neurobehavioural level are still being unravelled. Here, we investigate the formation of social hierarchies within groups of New Zealand spotty wrasse, integrating behavioural observations with neural activation patterns upon social disruption. We find that dominance hierarchies form linearly based on size, with larger fish displaying more dominant behaviours and smaller fish displaying more submissive behaviours. Disruption of the social hierarchy induced rapid behavioural changes, particularly in second-ranked fish, highlighting that second-ranked fish will opportunistically adopt a dominant position. Analysis of neural activation patterns reveals that the social decision-making network is deeply involved in the establishment of dominance, with the fish attaining dominance showing significant differences to all other ranked fish. Overall, this study underscores the complexity of social relationships and their neural underpinnings in the spotty wrasse, providing a foundation for further research into the cellular and molecular mechanisms of socially controlled sex change, and demonstrates that disruption of the social hierarchy triggers rapid changes in both behaviour and the social decision-making regions of the brain
Mapping the voices: Spanish boat owners and marina operators on non-indigenous marine species—knowledge and key informants
Full text linkThe public need to be aware of nonindigenous species (NIS) and how they spread to effectively manage this marine biosecurity risk. In most countries, the management of biosecurity risks associated with recreational boating relies exclusively on vessel owners and marina managers engaging in pro-environmental behaviours. To understand if this management approach is feasible, stakeholders’ perceptions first need to be identified. Surveys assessed people’s knowledge, awareness about NIS and channels involved in risk communication in three countries with different management scenarios and marine biosecurity histories: Spain, Australia and New Zealand. There was a mismatch between perceived and actual knowledge of NIS among respondents, with clear significant differences in perceptions between countries and socio-demographic profiles. Spanish stakeholders are significantly unaware of this biosecurity risk, and inaccurate knowledge was associated with specific media channels of the risk communication network. We provide recommendations to assist policymakers and science communicators when implementing an early risk communication strategy for Spanish influencing stakeholder groups
Interactions between insect pests, grasses and their endophytes under resource limitation : A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Lincoln University
Full text linkEnvironmental resource limitations, such as drought and reduced availability of phosphorus (P) pose significant challenges to pasture systems, impacting plant health and productivity. Despite advances in developing resilient pasture species and systems, little is known about how such environmental changes influence the complex relationship between Epichloë endophytes, host cool-season grasses, and pasture insect pests. This study focuses on how environmental resource constraints, specifically drought and P availability, affect pasture grasses, with attention to the modulating role of fungal Epichloë endophytes under these conditions.
In a glasshouse pot trial, the effect of drought on root aphid populations and plant performance was measured using endophyte-infected perennial ryegrass (AR37, NZCT) (Chapter 3). Endophyte infection reduced root aphid numbers. In general, aphid populations were higher in drought-stressed than in well-watered plants. Under drought conditions, compared to endophyte-free plants, root aphid populations increased 4-fold and 8-fold for NZCT andAR37, respectively. In endophyte-free plants root aphids reduced shoot dry weight by 16% in drought-exposed and 26% in well-watered plants while reducing root biomass by 49%. These results suggest that root aphids are likely able to exploit the higher availability of amino acids in the plant sap of drought-exposed plants. This study provides evidence that climate change-mediated impacts of root aphids could reduce production in perennial ryegrass-dominant pastures.
In a no-choice bioassay, African black beetle (ABB) were fed semi-synthetic diets containing freeze-dried foliage material from drought-exposed and well-watered perennial ryegrass containing no endophyte (Nil) or with endophyte strains AR37 or NZCT (Chapter 4). Diet consumption, beetle weight change, fungal alkaloid concentrations, and phytohormones were measured. Except for AR37, ABB consumed more diets containing drought-exposed rather than well-watered material, with a 61% increase in Nil and a 50% increase in diets containing NZCT. This study discusses the implications of these results on ABB damage in New Zealand pastures in the context of increasing drought. Areas that do not currently have high populations of ABB such as Manawatū-Whanganui, Wairarapa and Marlborough are predicted to become increasingly vulnerable to damage.
This research also investigated the interplay between P, plant growth, and grass grub (Costelytra giveni) fitness in Epichloë endophyte-infected perennial ryegrass (Epichloë sp. LpTG-3 strain AR37) and meadow fescue
infected with E. uncinata (strain MaxR) (Chapter 5). In a glasshouse trial, plants were grown in P-enriched soil with varying Olsen P levels (9, 18, 28, and 78 mg L-1), and grass grubs were introduced. Their survival, weight gain, and plant performance were measured. Results highlighted a decrease in the survival of grass grub on plants infected with MaxR endophyte, but not with AR37. Increasing Olsen P levels correlated with diminished grass grub performance, revealing a nuanced relationship between soil fertility and pest dynamics. The study underscores the pivotal role of selected Epichloë endophyte-grass associations in mitigating grass grub damage across varying phosphorus levels. This study highlights the potential to integrate P applications for sustainable pest control against grass grub.
This study examined the indirect impact of various P fertiliser regimes on cool-season grasses, which serve as food sources for porina larvae (Wiseana copularis). Endophyte-infected (Epichloë sp. LpTG-3 strain AR37) perennial ryegrass and meadow fescue infected with E. uncinata (MaxR), were grown in P-enriched soil with varying Olsen P levels (9, 18, 28, and 78 mg L-1) (Chapter 6). Freeze-dried foliage was added to semi-synthetic diets and fed to porina larvae in a no-choice assay. Measurements included porina survival, weight gain, fungal alkaloid concentration, fungal mass, and plant nutrient levels. Endophyte infection of AR37 and MaxR and AR37 significantly reduced porina diet consumption, larval weight gain and survival irrespective of soil Olsen P levels. The concentration of loline alkaloids in herbage infected with MaxR increased with rising soil Olsen P levels, whereas the concentration of epoxyjanthitrem in AR37 remained unchanged despite variations in Olsen P levels. The fungal mass remained unchanged in response to variations in Olsen P levels. These results suggest that the improved performance of porina feeding on endophyte-free plants is largely driven by P-induced changes in food quality. This study discusses the implications of porina damage in New Zealand pastures in the context of decreasing P availability.
This study also assessed the effects of repeated P-fertilizer applications on pasture invertebrate pest fauna over three years in two long-term trials in New Zealand: Ballantrae (0 and 375 kg P ha-1 annually) in the hill country in the lower North Island and Winchmore (0, 175, 188, 250, and 375 kg P ha-1 annually) in the flat land of the Canterbury Plains of the South Island (Chapter 7). The aim was to determine how P applications influenced the abundance and order richness of pasture insect pests and their relationship with pasture production and botanical composition. While order richness did not change significantly, this study observed increased total invertebrate pest abundance in flat land pastures. Notably, grass grub abundance decreased with higher P input, whereas clover root weevil (Sitona obsoletus) increased, positively correlating with clover content. This study highlights the complex interactions between P-fertiliser application and pasture invertebrates and plant communities, suggesting that strategic P management can enhance productivity while naturally reducing pest populations like grass grub.
The key novel contributions of this research are that drought and P availability significantly influence the dynamics between cool-season grasses, fungal Epichloë endophytes and pasture insect pests; drought imposes stress on grasses, altering their chemical composition and attracting herbivorous pests such as root aphids and ABB, while P fertilisation enhances plant quality by improving palatability and nutrient availability for some insects, although its availability can also negatively affect others such as grass grub. These findings highlight the importance of understanding the adaptive mechanisms of endophytes in maintaining pasture health under environmental resource limitations. As climate change increases the frequency and intensity of droughts, there is an escalating need for precision nutrient management. Ultimately, recognising and harnessing these complex interactions, especially regarding integrating endophytes into these systems, will be essential for developing effective pest management strategies that promote the long-term resilience and sustainability of agricultural systems in an increasingly variable environment
Harnessing energy transition to power rural development and female empowerment
Full text linkMore than 2 billion people around the world still rely on traditional, inefficient energy sources for cooking, such as wood, crop residues, and animal dung. The household energy transition refers to the shift toward modern, cleaner, and more efficient energy sources, including electricity, natural gas, solar power, and other renewable technologies. While facilitating this transition is essential to achieving Sustainable Development Goal 7: Affordable and Clean Energy, many countries continue to face significant challenges in moving away from polluting fuels
Vineyard management systems influence on mycorrhizal fungi
No full textArbuscular mycorrhizal fungi (AMF) play a vital role in sustainable viticulture by enhancing nutrient uptake, stress tolerance, and soil health. This research explored both the effects of vineyard management on AMF diversity and the functional impact of AMF communities on grapevine rootstocks. Vineyard surveys revealed that rootstock was the main driver of AMF followed by specific soil parameters. The study showed distinct differences in AMF communities between organic and conventional systems, with interactions between rootstock and management suggesting certain rootstocks may be better suited to organic conditions. To investigate the functional significance of these communities, a glasshouse experiment using a 'home' and 'away' design was conducted. Grapevines paired with AMF communities from their native soil ('home') showed greater biomass, chlorophyll content, and nutrient uptake than those grown with 'away' AMF. These findings highlight the specificity of AMF-rootstock relationships and suggest that targeted use of AMF communities could enhance grapevine performance and resilience, supporting more sustainable and biodiverse vineyard management practices
Effects of anthropogenic activities on soil microbial community structure and methane anaerobic oxidation rate in coastal wetlands of Yellow River Delta, China
No full textAnaerobic oxidation of methane (AOM) is widely recognized in wetland soils as an important sink for methane (CH₄), a potent greenhouse gas, and an important pathway for CH4 reduction. However, the process of AOM in coastal wetland soil in the context of various anthropogenic impacts and the impacts on microorganisms are not clear due to the intricate interplay among numerous factors in nature and the impacts of anthropogenic activities. Therefore, in this study, laboratory culture methods integrated with molecular biology techniques were used to investigate the rate of AOM in soils of different depths under the influence of several typical anthropogenic activities in the Yellow River Delta, as well as the mechanisms of influence on environmental and microbiological factors. The findings of the study indicated that AOM rates decrease with depth; the effects of various forms of nitrogen (N) on the anaerobic oxidation of soil methane in different soil horizons were inconsistent; and inorganic nitrogen (NH₄⁺, NO₂¯) was found to affect AOM processes by influencing some of the functional communities (ANME-2d, ANME, and Geobacter), as well as some microorganisms (Euryarchaeota, Methanosarcinales) that indirectly affect the AOM process. Moreover, Geobacter, ANME, and ANME-2d were the key functional microorganisms influencing the AOM process in the anthropogenic samples and served as crucial factors in the AOM process. Therefore, this study could provide data support and a theoretical basis for mitigating global warming
Performance of sustainable investments: do green-labeled bonds outperform green-unlabeled bonds?
No full textPurpose ̶ The increase in demand for sustainable investments globally raises the question of benefits of investing in green bonds. A green label attracts investors because it represents less information asymmetry on green bonds with lower potential environmental risks. However, not all bonds with green features are easily recognized and labeled, creating limited options for bond investors. This paper helps investors to identify green-unlabeled bonds, offering them more sustainable investment options in the market. Next, we investigate the performance of green-labeled and green-unlabeled bonds to identify which bond can serve as a safe-haven asset in different economic conditions.
Design/methodology/approach ̶ To identify green-unlabeled bonds, we screen three bond categories: climate, sustainability, and ESG (Environmental, Social, and Corporate Governance). Using the generalized least squares regression models and daily data of 7250 bonds in 83 countries and entities from 2012 to 2021, we compare the performance of green-labeled and green-unlabeled bonds between corporate and government bonds, high-income and lower-income economies, and short-term and long-term periods.
Findings ̶ The results show that green-labeled bonds underperform green-unlabeled counterparts in terms of bond liquidity and yield. For both green-labeled and green-unlabeled bonds, corporate bonds are less liquid than government bonds in the short term; but offer higher yield in the long term. Green-labeled and green-unlabeled bonds have short-term hedging potential in volatile market conditions. Regarding green-unlabeled bonds, financing climate-related activities via climate bonds is unattractive and risky during uncertain periods; but sustainability bonds are a safe-haven asset in the economic downturns.
Originality/value – This study timely contributes to the scarcity of studies on green-unlabeled bonds in the literature. We expand the screening categories to identify green-unlabeled bonds, including climate, sustainability, and ESG bond categories, to form the Sustainable Bond group. Our findings show the existence of greenium effect between green-labeled and green-unlabeled bonds; provide valuable insights to investors, bond issuers, and governments; and suggest that investors may add green-labeled bonds and green-unlabeled bonds in their portfolios to hedge downside risk, especially during extreme market conditions.