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Impact of anomalous surface boundary conditions on the planar negative-refractive index lens
Get PDFIt is shown that anomalous boundary conditions at the surface of a negative-refractive-index metamaterial planar lens severely diminishes the resolution of the lens when its relative permittivity and permeability are both −1. Anomalous boundary conditions arise in practical microwave metamaterials that are typically a periodic array of identical unit cells comprising dielectric and conducting elements. For a unit-cell size much smaller than the wavelength, homogenised permittivity and permeability are the constituent parameters of the average fields. Average fields vary on a scale larger than the unit cell size compared to localised fields associated with the constituent elements. Unlike the tangential components of the localised field, tangential components of the average fields are discontinuous across the surface of such materials. This anomalous boundary condition at the lens surface must be described by generalised sheet transition conditions. This study develops expressions for the negative-refractive-index lens optical transfer functions, as a function of spatial frequency, for transverse-electric waves, that account for anomalous surface boundary conditions. Both the simulations and experimental data are used to verify the expressions at a frequency of 3 GHz
The sources of total factor productivity growth, changes in technical efficiency and the threshold effects of herd size on the productivity of New Zealand dairy farms : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textMany studies have been carried out to analyse dairy farms’ production performance but, for New Zealand, only a limited number have gone beyond the technical efficiency (TE) component of farm productivity. The current study aims to: (1) analyse the regional total factor productivity (TFP) growth and the role of different components, i.e. technological progress, technical efficiency change, and scale effect change in increasing TFP; (2) assess the regional differences in technical efficiency (TE) and the technological gap; and (3) investigate the threshold effects of herd size on the productivity of New Zealand dairy farms. The data for the TFP and TE analysis are unbalanced farm-level panel data from the 2004-05 to 2019-20 seasons, for 2,001 farms and 9,943 observations from the DairyNZ surveys. Farms are grouped into three regions: Region 1 (Northland and West Coast-Tasman); Region 2 (Waikato, Bay of Plenty, Taranaki and Lower North Island); and Region 3 (Marlborough-Canterbury, Otago-Southland). Stochastic frontier models are used to estimate the production functions for three different regions and to calculate the TFP growth. The results indicate heterogeneity in the different areas so a state-of-the-art stochastic meta-frontier approach is used to estimate TEs and technological gap ratios (TGRs). For the threshold analysis, the study uses balanced panel data from the 2015-16 season to the 2019-20 season (1,770 observations). The results suggest that there are different effects of herd size on productivity, and the significance of other inputs and farm-specific variables are evaluated. This study provides empirical evidence of the relative importance of the various components of TFP growth and distinct TE scores in different regions, and provides empirical evidence of the threshold effects of herd size on dairy farms’ productivity
The Tokyo Olympics had no Soul: A swimming cap controversy
No full textThe Soul swimming cap that is designed specifically for long hair including afro and dreadlock hair was banned by the swimming body FINA at the 2021 Tokyo Olympics. The ban was due to the possibility that the Soul cap could increase swimming performance. The ban attracted considerable media attention and backlash centred around inclusivity and the low participation of minority groups in swimming. Anecdotally, swimmers suggested a larger cap such as the Soul cap could actually decrease performance, and previous research has found wrinkled swimming caps produced higher drag. There is no research on the drag of the Soul cap, therefore the purpose of this study was to investigate the drag of Soul caps compared to a standard Speedo competition cap. A wind tunnel, set at a speed equivalent to swimming speed, was used to measure the drag on a model head with a long wig (representing a swimmer with long hair) in different swimming cap conditions (Soul swimming caps designed for long hair (small (S-Soul), large (L-Soul), extra-large (XL-Soul)) and a Speedo cap). The Speedo cap produced significantly less (p < 0.0001) drag compared to all Soul caps (mean ± SD - Speedo:141.54 ± 2.92 g vs. 150.53 ± 4.83 g (S-Soul,), 164.54 ± 3.24 g (L-Soul) and 172.87 ± 3.70 (XL-Soul)). Differences in drag were progressively larger with a statistically significant increase with a larger size of Soul swimming caps (8.89 g to 31.33 g, p < 0.0001). It is likely the differences in cap conditions were due to wrinkles, with less wrinkling occurring in Speedo and increased wrinkling in the larger Soul swimming caps. Our findings indicate it is unlikely that a Soul cap would confer a performance advantage relative to a standard Speedo cap. Future research could investigate if our results are substantiated in aquatic conditions.
Policy approaches for enhanced dairy sector innovation – A review of future pathways and policies for effective implementation of digital agriculture
Get PDFInnovation and technology are a feature of New Zealand’s dairy sector. To overcome current challenges, dairy farmers require agile and multi-dimensional innovation, supported by forward-looking and integrated policy from both the sector and government. In this paper, we outline some of the current dairy sector challenges, and potential technologies to address these challenges. We focus on the future for digital agriculture innovation and discuss policy approaches to enable the sector to leverage digitalisation. These approaches include co-innovation, responsible innovation, multi-scale approaches, micro-innovation and poly-innovation and mission-oriented innovation. Digital agriculture and policy may interact in two ways: (1) policy may be used to enhance digital agriculture innovation and, (2) digitalisation itself may act to enhance agricultural policy design and delivery. Overall, innovation policy requires greater directionality, use of policy bundles and a focus on technology as a mediator of new dairy farming practices and institutional configurations
Newly-claimed seascapes: Options for repurposing inundated areas
Get PDFSea-level rise is unstoppable. Communities worldwide are facing difficult choices in responding to changing coastlines and estuaries. Understandably, there is little attention on the potential for repurposing inundated areas because retreat and adaptation take precedence. Repurposing may be infeasible for newly-claimed seascapes in exposed and high energy coasts. Nevertheless, for sheltered coastal areas, shallow estuaries and harbours, there may be potential for repurposing some areas for aquaculture, fisheries, wetlands, and/or blue carbon. For example, abandoned and decontaminated structures may provide fish nursery habitat as artificial reefs. Here, we present the results of a systematic literature review of potential options, along with identified benefits and implementation barriers. Our purpose is not to examine the feasibility of such options because these will be place- and context-specific; rather, we explore whether the solution space can be extended beyond the point of impact. We suggest that repurposing could be added to the PARA management framework
Impact of water management on methane emission dynamics in Sri Lankan paddy ecosystems
Get PDFPaddy ecosystems constitute a dominant source of greenhouse gases, particularly of methane (CH₄), due to the continuous flooding (CF) practiced under conventional paddy cultivation. A new management method, namely alternative wetting and draining (AWD) (i.e., flooding whenever surface water levels decline to 15 cm below the soil surface), is an emerging practice developed to mitigate CH₄ emissions while providing an optimal solution for freshwater scarcity. Despite extensive paddy cultivation in Sri Lanka, no systematic research study has been conducted to investigate CH₄ emissions under different water management practices. Thus, field experiments were conducted in Sri Lanka to investigate the feedback of controlled water management on seasonal and diel variation of CH₄ emission, water consumption, and crop productivity. Adopting the same rice variety, two water management methods, continuous flooding (CF) and alternative wetting and draining (AWD), were compared with plants (W/P) and without plants (N/P) present. The emission of CH₄ was measured using the static closed chamber method. The results show a 32% reduction in cumulative CH₄ emission, on average, under AWD when compared to CF. The yield under the AWD was slightly higher than that of CF. Although it was not statistically significant (p > 0.05) there was not any reduction in yield in AWD than in CF. The total water saving under AWD ranged between 27–35% when compared to CF. Thus, the results support (without considering the effect of nitrous oxide) AWD as a promising method for mitigating CH₄ emissions while preserving freshwater and maintaining grain yield in paddy systems
Modification of soil biogeochemistry by plants during a restoration trajectory (Punakaiki, New Zealand) : A thesis submitted in partial fulfilment of the requirements for the Master of International Nature Conservation at Lincoln University
Get PDFThe Punakaiki Coastal Restoration Project (PCRP) was carried out to restore native vegetation in a farmed pasture, aiming to establish a functioning sandplain. More than 30 species and >150,000 individual plants were transplanted from containers-grown specimens across the 70 ha site on a pragmatic and adhoc basis over several years. A restoration trajectory is also an ecological succession with temporal changes in species composition of plant communities. The present study focuses soil biogeochemistry in areas of the site where different plant species have been planted.
Plants and soils were sampled from different locations at PCRP, and chemical properties of these samples were analysed using ICP-OES to determine macronutrient and trace elements. Olsen-P, mineral nitrogen, soil pH, and organic matter were also analysed. Olsen- P was determined using colorimetrically, while mineral nitrogen was determined using a triple-channel CHN analyser.
The results showed that soil chemistry varied beneath different plant species, indicating that plants have different potentials to influence soil nutrient concentrations. Nutrient concentrations also varied with soil depth. Soil concentrations of NO3-N, Fe, Mn, Mo, Na, P, and S differed significantly under different species. Patterns of similarity and differences
within the data were investigated. The study also found that a major factor causing the element difference under different plants was site variation. Soil samples were taken from the transects with different soil ages. Younger soil was more likely to contain more abundant trace and major elements and more biological activity, and soil pH was also impacted by soil age. Nutrient concentrations in soil and foliage were often either positively or negatively correlated.
Whist primary minerals usually determine major nutrients and trace elements in the soil, differences can be due to passive or active absorptive channels in the soil and by physiological differences between plants. Rhizosphere processes can also alter soil chemistry. Coprosma robusta showed a passive response to salinity, suggesting it might be unable to regulate Na uptake, with a positive correlation between soil Na and foliage Na. By contrast, Coprosma propinqua appeared to actively control uptake of Al, Mg, Na, and Ni; it was the only species that showed a potential mechanism for exclusion of some elements, with a negative correlation of these elements between foliage and soil.
The effect of rhizosphere processes on soil organic matter depends on plant species and soil properties, and microorganism activity and community play fundamental roles in driving organic carbon accumulation and decomposition. This study found that Olsen-P and soil organic matter tended to be higher in rhizosphere soil than in bulk soil, although the difference was not statistically significant. This may have been due to microbial activity differing between rhizospheric and bulk soil, probably associated with root morphology and exudates.
An incubation experiment of litter of different plant species mixed with soil showed that plant litter could significantly change soil chemistry, and this varied between plant species. Plant litter reduced soil acidity and increased soil Olsen-P, but this differed in magnitude between plant species. Soil concentrations of NO3-N and NH4-N decreased after incubation; it is argued this might result from microorganism consumption of soil organic carbon.
This research also aimed to evaluate finding of an earlier study on the role of seabird guano on soil nutrient concentrations and the accumulation of nutrients in New Zealand flax (Phormium tenax). The present study indicated that there was no significant difference in soil P levels under flax compared to other plants, contradicting the earlier findings of Zhong (2016). It was suggested that the variation in P levels were more likely to be due to soil age and location differences. Furthermore, P. tenax was found to have a significantly higher concentration of sodium than other plants, suggesting its ability to absorb substantial amounts of sodium from the soil. The findings also raise the question of whether P. tenax captures sodium in cuticular wax from marine spray due to its morphological features, which could be explored in further research.
Overall, this study has shown that soil and plant nutrients differ between plant species and that plants have significant effects on soil chemistry. Plant and soil nutrients interact with litter quality and other environmental factors. It is concluded that understanding soil biogeochemistry has a role to play in ecological restoration, although this is currently poorly understood
Gender, careers, and kids: A qualitative study of the partners of international employees
Get PDFThis paper examines the relocation experiences of sixteen women and men who moved with their children to Aotearoa New Zealand when their partners took up career positions in that country. It analyses the relative weight they gave to their careers and their relationships with their partners as they responded to the challenges posed by these transitions. Attention to the interests of children is also identified as significant in their career decisions. Interviews with similar numbers of women and men whose partners were globally mobile employees enables analysis of the diverse ways in which gender shapes career pathways during a period of transition. The findings contribute to a complex analysis of the situation of those previously referred as a ‘trailing’ or ‘accompanying’ spouse when a dual career couple engages in international relocation
Dynamic connectedness between crude oil and equity markets: What about the effects of firm's solvency and profitability positions?
No full textThe paper aims to explore the presence of connectedness between oil price changes and stock returns of oil & gas sector. The analysis, adopting the connectedness approach developed by and the frequency connectedness developed by demonstrates a high level of connectedness, especially during the extreme economic meltdown. The short-term (1–5 days) level of total connectedness is substantially higher than the medium-term (5–30 days) and long-term levels (30–262 days). In addition, when examining the impact of the sectors' financial characteristics on the extent of the connectedness, we found that sectors with greater solvency position (lower debt to asset ratio and higher interest coverage) are less connected with the oil price changes. The impact of sector's solvency position on connectedness (between stock return and oil prices) is even more obvious for financially more open markets. Also, change in oil prices have a less impact on the returns of sectors with higher profitability ratios. The paper, therefore, brings several implications to both policy makers and investors
Beyond the genomes of Fulvia fulva (syn. Cladosporium fulvum) and Dothistroma septosporum: New insights into how these fungal pathogens interact with their host plants
No full textFulvia fulva and Dothistroma septosporum are closely related apoplastic pathogens with similar lifestyles but different hosts: F. fulva is a pathogen of tomato, whilst D. septosporum is a pathogen of pine trees. In 2012, the first genome sequences of these pathogens were published, with F. fulva and D. septosporum having highly fragmented and near-complete assemblies, respectively. Since then, significant advances have been made in unravelling their genome architectures. For instance, the genome of F. fulva has now been assembled into 14 chromosomes, 13 of which have synteny with the 14 chromosomes of D. septosporum, suggesting these pathogens are even more closely related than originally thought. Considerable advances have also been made in the identification and functional characterization of virulence factors (e.g., effector proteins and secondary metabolites) from these pathogens, thereby providing new insights into how they promote host colonization or activate plant defence responses. For example, it has now been established that effector proteins from both F. fulva and D. septosporum interact with cell-surface immune receptors and co-receptors to activate the plant immune system. Progress has also been made in understanding how F. fulva and D. septosporum have evolved with their host plants, whilst intensive research into pandemics of Dothistroma needle blight in the Northern Hemisphere has shed light on the origins, migration, and genetic diversity of the global D. septosporum population. In this review, we specifically summarize advances made in our understanding of the F. fulva–tomato and D. septosporum–pine pathosystems over the last 10 year