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Bubbles and Crashes : A Tale of Quantiles
Get PDFPeriodically collapsing bubbles, if they exist, induce asymmetric dynamics in asset prices. In this paper, I show that unit root quantile autoregressive models can approximate such dynamics by allowing the largest autoregressive root to take values below unity at low quantiles, which correspond to price crashes, and above unity at upper quantiles, that correspond to bubble expansions. On this basis, I employ two unit root tests based on quantile autoregressions to detect bubbles. Monte Carlo simulations suggest that the two tests have good size and power properties, and can outperform recursive least-squares based tests. The merits of the two tests are further illustrated in three empirical applications that examine Bitcoin, U.S. equity and U.S. housing markets. In the empirical applications, special attention is given to the issue of controlling for economic fundamentals. The estimation results indicate the presence of asymmetric dynamics that closely match those of the simulated bubble processes
Critical Race Theory for Historical Criminology in Britain
No full textThis chapter posits that the contemporary moral panics about Critical Race Theory (CRT) in schools, characteristic of American politics, have relevance to Britain. British Conservative Member of Parliament (MP) Kemi Badenoch’s recent declaration that CRT is political and should be treated as such is one way to understand, (a) CRT’s relevance in Britain, and (b) how this relevance can be adduced in terms of the intersections with historical criminology. We outline what critical race theory is, criminological examples of applying critical race theory, and its relationship with intersectionality. CRT was developed by American legal scholars, including Derrick Bell, Kimberlé Williams Crenshaw, Patricia J. Williams, and Patricia Hill Collins. American criminologists thus originated intersectional and Black criminologies, incorporating the analysis of race and racism. However, race is not only an American phenomenon and racism is not only an American problem. Focusing on the United Kingdom, the chapter argues that CRT has application for historical criminology beyond the United States and presents illustrative examples from the authors’ historical criminological research. It examines the significance of gender and the need for intersectionality in historical criminological research about, and with, racialised women in Britain
Experimental investigation of the behavior of UHPCFST under repeated eccentric compression
Get PDFThis paper investigates the mechanical behavior of ultra-high-performance concrete-filled steel tubes (UHPCFST) under repeated eccentric compression. A total of 30 UHPCFST specimens are designed, fabricated, and tested. The design variables include steel tube thickness, UHPC type, loading eccentricity and load pattern. Failure modes, force-axial shortening curves, section strain distributions, lateral deflection distributions, bearing capacity and stiffness are studied. Three failure modes, i.e., steel tube bulge, compressive crush and tensile crack of the UHPC infill are observed. Specimens with larger loading eccentricity and thinner steel tube are more likely to exhibit all the three modes. Subjected to eccentric loading, the compressive strength and stiffness of the UHPCFST increase significantly with the increase of steel tube thickness and UHPC strength. In the case of repeated loading, stiffness degradation is observed. Existing formulas for the N-M curve and the eccentric compressive capacity are evaluated against the test results. A formula for eccentric compressive stiffness is derived based on the parabolic function assumption. Additionally, an empirical model is introduced to describe the force-axial shortening relationship of the UHPCFST under repeated eccentric compression, which may be applied in practical design and analysis
Migration patterns, habitat use and genetic origins of sea trout ( Salmo trutta ) in Norfolk chalk streams : implications for management of a mixed stock fishery
No full textSea trout, the anadromous ecotype of the species Salmo trutta, are subject to multiple threats, including exploitation and aquaculture impacts in the marine environment, habitat fragmentation and pollution in freshwaters, loss of genetic resilience due to interbreeding with hatchery strains and environmental change. Small streams contribute relatively little biomass to European sea trout stocks but are thought to be important in maintaining genetic diversity and therefore wider population resilience. The current study combined data from acoustic telemetry, stable isotopes, genetics and scalimetry to assess the current status of sea trout in the rivers Stiffkey and Glaven, two locally important chalkstreams in East Anglia, UK, to provide an evidence base for future management. The incidence of anadromy was low, and most sea trout were near migrants, residing in the lower reaches of rivers and close to the tidal outfalls. A small number migrated to the North Sea where they were vulnerable to exploitation in the coastal fishery, which comprises a mixed stock. Straying between the two rivers was recorded among 10% of sea trout, leading to apparent high gene flow. Nonetheless, genetic data also demonstrated structuring of River Glaven trout into two distinct groups. Quantification of patterns of freshwater and estuarine habitat use, and of passage at cross-channel obstructions, was used to identify where remedial measures such as habitat restoration would be most effectively targeted. Findings are discussed in the context of local supplementary stocking and the potential impact of the nearshore fishery on limited and vulnerable small stream anadromous trout populations
The role of networks in shaping entrepreneurial leadership : A longitudinal case study
Get PDFThis paper explores the relationship between leadership and networks in entrepreneurial firms. A longitudinal perspective is adopted to consider how leadership evolves and develops over time in an entrepreneurial setting, based on how leaders draw on networks in which they are embedded. Findings from a qualitative study of an organisation operating for over 70 years and including over 50 business-owning families are presented. These show that networks not only shape and define the leadership of the entrepreneurial firm, but also that the firm’s evolution, growth and development are the result of how networks entwine with leadership. These findings are theorized in the form of an entrepreneurial life-cycle model that is driven by the form and reach of embedded network connections and draws on Leader-Member Exchange (LMX) theory. The paper concludes with some thoughts on the benefits of networks for practicing leaders
Classifying early apple scab infections in multispectral imagery using convolutional neural networks
No full textMultispectral imaging systems combined with deep learning classification models can be cost-effective tools for the early detection of apple scab (Venturia inaequalis) disease in commercial orchards. Near-infrared (NIR) imagery can display apple scab symptoms earlier and at a greater severity than visible-spectrum (RGB) imagery. Early apple scab diagnosis based on NIR imagery may be automated using deep learning convolutional neural networks (CNNs). CNN models have previously been used to classify a range of apple diseases accurately but have primarily focused on identifying late-stage rather than early-stage detection. This study fine-tunes CNN models to classify apple scab symptoms as they progress from the early to late stages of infection using a novel multispectral (RGB-NIR) time series created especially for this purpose. This novel multispectral dataset was used in conjunction with a large Apple Disease Identification (ADID) dataset created from publicly available, pre-existing disease datasets. This ADID dataset contained 29,000 images of infection symptoms across six disease classes. Two CNN models, the lightweight MobileNetV2 and heavyweight EfficientNetV2L, were fine-tuned and used to classify each disease class in a testing dataset, with performance assessed through metrics derived from confusion matrices. The models achieved scab-prediction accuracies of 97.13 % and 97.57 % for MobileNetV2 and EfficientNetV2L, respectively, on the secondary data but only achieved accuracies of 74.12 % and 78.91 % when applied to the multispectral dataset in isolation. These lower performance scores were attributed to a higher proportion of false-positive scab predictions in the multispectral dataset. Time series analyses revealed that both models could classify apple scab infections earlier than the manual classification techniques, leading to more false-positive assessments, and could accurately distinguish between healthy and infected samples up to 7 days post-inoculation in NIR imagery
Growing practices and the use of potentially harmful chemical additives from a web survey of mainly small-scale cannabis growers in 18 countries
Get PDFBackground: There is emerging recognition of the risks of harmful chemical pesticides, fertilizers and ‘nutrients’ by cannabis growers. One group of chemicals, Plant Growth Regulators (PGRs), many of which have been banned from food crops for decades, have been found unlisted in a number of fertilizers and supplements marketed at cannabis growers. Methods: This paper predominately uses data from a 2020-21 convenience web survey of mainly small-scale, recent (last 5yrs) cannabis growers from 18 countries (n=11,479). We describe their growing practices and use of chemicals and employ logistic regression to explore predictors of chemical use. We also compare chemical use in our 2020-21 sample with that from our 2012-13 data in the 3 countries (Australia, Denmark, UK) where respondents were asked about their use of growing chemicals in both surveys. Results: In 2020-21, 26% of recent cannabis growers reported use of chemicals. Growers who were at highest odds of using chemicals were male, older, living in urban/cities, not growing for environmental reasons, growing in order to sell, growing where they believed cannabis was legal, and growing under artificial light in soil or nonsoil media. We found significant reductions in the proportions of our samples who reported using chemical fertilizers in the 3 countries where we collected data in both waves. Conclusion: Growers using soil and artificial light comprised over half of all the chemical users in the sample. Efforts at informing and educating growers about the problems of chemical fertilizer, nutrient and pesticide use should include all growers including those who grow in soil under artificial light. Possible explanations for the apparent decrease in chemical use from our 2012-13 to 2020-21 samples are discussed. Stricter regulation of the legal cannabis fertilizer market is required to empower growers to reduce the toxicity of cannabis they grow, distribute and consume
Integrated policymaking is needed to deliver climate and ecological benefits from solar farms
No full textMulti‐purpose land use is of great importance for sustainable development, particularly in the context of increasing pressures on land to provide ecosystem services (e.g. food, energy) and support biodiversity. The recent global increase in land‐take for utility‐scale ground‐mounted solar farms (hereafter referred to as solar farms) to meet Net Zero targets presents an opportunity for enhanced delivery of ecosystem services, especially in temperate ecosystems where solar farm development often results in land use change away from comparatively intensive agricultural land management. Solar farms have long operational lifespans, experience low levels of disturbance during operation and can be managed for ecosystem services beyond low‐carbon electricity generation, including food production and biodiversity conservation. Here, we briefly synthesise the mechanisms by which solar farm development and operation may impact natural capital and ecosystem services, and provide policy recommendations for policymakers and the solar farm sector. Solar farms can deliver environmental benefits for hosting ecosystems while minimising negative impacts, with outcomes depending on location, construction techniques, and land management practices. However, the historical misalignment between climate, nature, and land use policies has hindered efforts to simultaneously address the climate and biodiversity crises through land use change for solar farms. For instance, existing public financial incentives in the UK that encourage landowners and developers to manage land for biodiversity largely exclude land with solar farms. Policy implications: We call for public policymakers to identify appropriate opportunities to amend existing national laws that address climate and biodiversity separately to improve integration of multiple aspects of the climate‐nature‐land use nexus into policymaking by: (1) formulating ecological and socio‐economic indicators and metrics that are appropriate to underpin the development, implementation, and assessment of public policies; (2) adopting a cross‐sectoral and cross‐government approach to form public policies; (3) ensuring solar farms can access public financial incentives that encourage sustainable land use; (4) implementing land use policies that incentivise funding from non‐government sources (e.g. private sector) into nascent nature markets; (5) embedding solar farms in biodiversity‐inclusive spatial planning policies and decision‐making; and (6) building equity and clarity into responsibilities and benefits for all actors involved
CEO risk taking equity incentives and workplace misconduct
Get PDFWe examine the relation between CEO risk taking equity incentives, as captured by CEO vega, and workplace misconduct. Workplace misconduct includes health and safety violations, non-compliance with labor laws, and other violations broadly related to labor exploitation, and it results in significant economic costs. Using regression analysis, matched sample tests, and a quasi-natural experiment, we find a positive relation between CEO vega and workplace misconduct. We identify a reduction in discretionary expenses and increased employee workload as channels through which CEO vega affects workplace misconduct