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An adoption model of cryptocurrencies
Get PDFThe network effect, measured by users’ adoption, is considered an important driver of cryptocurrency market dynamics. This study examines the role of adoption timing in cryptocurrency markets by decomposing total adoption into two components: innovators (early adopters) and imitators (late adopters). We find that the innovators’ component is the primary driver of the association between user adoption and cryptocurrency returns, both in-sample and out-of-sample. Next, we show that innovators’ adoption improves price efficiency, while imitators’ adoption contributes to noisier prices. Furthermore, we demonstrate that the adoption model captures significant cryptocurrency market phenomena, such as herding behaviour, more effectively, making it better suited for forecasting models in cryptocurrency pricing. These results suggest that our methodology for linking early and late adopters to market dynamics can be applied to various domains, offering a framework for future research at the intersection of operational research and financial markets
Invariant Manifolds in a Class-Structured Model From Adaptive Dynamics
No full textWe consider a family of structured population models from adaptive dynamics in which cells transition through a number of growth states, or classes, before division. We prove the existence and global asymptotic stability of invariant (‘resident') manifolds in that family; furthermore, we re-derive conditions under which scarce mutants can invade established resident populations, and we show the existence of corresponding ‘invasion’ manifolds that are obtained as critical manifolds under the additional assumption that resident has attained quasi-steady state, which induces a separation of scales. Our analysis is based on standard phase space techniques for ordinary differential equations, in combination with the geometric singular perturbation theory due to Fenichel
Body composition, vascular health, cardiorespiratory fitness, lung function, muscle architecture, and physical activity in people with young onset dementia:A case-control study
No full textBackground: Body composition, blood pressure, estimated maximal oxygen uptake (VO2max), lung function, physical activity, muscle architecture, and endothelial function had not previously been examined in people with young onset dementia. Therefore, the study measured these variables in a young onset dementia group, compared them to age-matched controls. Methods: Estimated VO2max (via the Astrand-Rhyming test), body composition, blood pressure, lung function (via spirometry), muscle architecture (via ultrasonography), and endothelial function (via flow-mediated dilation) were assessed. Physical activity was measured using ActiGraph accelerometers for 7 days. Results: We recruited 33 participants (16 young onset dementia, 17 controls). The young onset dementia group had shorter fascicle lengths of the vastus lateralis, were sedentary for longer over a 7-day period, and completed less moderate-vigorous physical activity than controls (P = .028, d = 0.81; large effect, P = .029, d = 0.54; moderate effect, and P = .014, d = 0.97; large effect, respectively for pairwise comparisons). Pairwise comparisons suggest no differences at the P < .05 level between young onset dementia and controls for estimated VO2max (despite a moderate effect size [d = 0.66]), height, body mass, BMI, blood pressure, light physical activity, lung function, muscle thickness, pennation angle, or endothelial function. Conclusions: This study highlights differences between people with young onset dementia and controls, underscoring the need for multicomponent exercise interventions. Future interventions should target muscle architecture, increase moderate-vigorous physical activity, and reduce sedentariness, with the goal of improving quality of life and promoting functional independence.</p
Enhanced mechanical performance of 3D printed continuous carbon fibre reinforced polyphenylene sulphide composites through dopamine treatment and post-processing compression
Get PDFThis study investigates the impact of dopamine-treated carbon fibre reinforcement and post-processing techniques in polyphenylene sulphide (PPS) composites, with a focus on improving interfacial and interlayer properties. The synergistic effects of continuous carbon fibre (CCF) treatment with polydopamine/silica nanoparticles (PDA/NPs) and post-processing on the mechanical performance of 3D printed composites are explored. The findings demonstrate that treated composites exhibit significant improvements in interlaminar properties, with increases in flexural strength by 27% and interlaminar shear strength (ILSS) by 172%, compared to untreated specimens. Molecular dynamics (MD) simulations and nano-indentation tests reveal the mechanisms behind the improved fibre/matrix interfacial adhesion attributing to PDA/NPs network on the fibre. Differential scanning calorimetry (DSC) and microscopic analyses are utilised to assess enhancements in crystallinity, void content, and fibre orientation after post-processing. Furthermore, we introduce a novel post-processing method involving a salt bath, which aligns with the unique advantages offered by 3D-printed complex composites. This approach is validated with two complex demonstrative geometries, confirming its effectiveness in maintaining structural integrity while enhancing interlayer properties. The integration of pre-processing with the PDA/NPs network and post-processing techniques with a salt bath offers particular benefits for additively manufactured high-performance materials
On the printability and inter-layer adhesion in 3D printing of continuous carbon fibre reinforced PEEK composite using tape and filament
Get PDFThis study, for the first time, investigates using a 3D printing nozzle instead of a compression roller to print sliced width of continuous carbon fibre-reinforced PEEK composite tape. Pultrusion of sliced tape was performed to further enhance the printability and inter-layer adhesion of curved raster, highlighting the significance of this approach towards 3D printing of complex parts. Peel and shear delamination tests of curved and straight rasters, printed using tape and filament was performed. The delamination tests were conducted at room temperature, 150 °C and 300 °C to elaborate the influence of 3D printing feedstock geometry on the printed part performance. It was found that pultruded filaments can delaminate at up to 40 % higher force as compared to tape for curved paths and vice-versa, as delamination strength corresponds to fibre alignment in the rasters. This study proves the applicability of using ATP graded small tapes (with a width of 1 mm) for 3D printing, and instead of introducing expensive additives to the composites, the feedstock geometry could significantly impact the inter-layer adhesion and facilitate complex part manufacturing
Do foster youth face harsher juvenile justice outcomes? Reinvestigating child welfare bias in juvenile justice processing
Get PDFResearch summary: For decades, child welfare scholars and policy makers have been concerned with the strong association between foster care and juvenile justice involvement. Foster care placement may lead to differences in justice system outcomes if youth in foster care face “processing bias”—differentially harsh treatment by agents of the juvenile court. Previous research found that youth in foster care at the time of juvenile justice contact were treated more harshly by the court, resulting in higher rates of punitive case outcomes. We revisit the question of processing bias using detailed administrative data on more than 10,000 adolescents in Pennsylvania in 2015–2019 and a selection-on-observables design. We find no evidence of processing bias against youth in foster care. Compared to observationally equivalent cases, those that involve youth in foster care do not experience more punitive outcomes. If anything, our estimates suggest the opposite—youth in foster care are less likely to have a charge adjudicated, be placed under court-ordered supervision, or enter into juvenile detention. The precision of our estimates and bounding exercises allow us to rule out even modest evidence of punitive processing bias. Policy implications: This paper highlights the importance of revisiting the evidence of processing bias within juvenile justice and child welfare agencies. Given the decentralized and continuously evolving nature of these systems, local jurisdictions should investigate their own case outcomes and contexts before implementing reforms to address bias. Yet, many lack the resources for such research and federal support is essential to enhance local data analysis capabilities, promoting more tailored and effective policy reforms. Initiatives that aim to integrate data from multiple systems can better understand and address the needs of overlapping populations, ultimately improving the quality of services and outcomes.</p
The nature of sports coach development in China:What are we trying to achieve?
Get PDFCoach education and continuing career development have become a significant focus of global discussion within the sport domain. Current mainstream strategies for developing and assessing coaches in most countries, including China, are based on competency-based systems. However, there are many shortcomings of this system, especially when considering the varied practical challenges and needs of coaches and athletes; in short, such an approach does not facilitate enough adaptability. The purpose of this article is to critically review the literature, exploring both competence- and expertise-based coach development systems and their implications for coaching practice in China. Firstly, we introduce and discuss the competency-based approach, including its strengths and weaknesses and how this applies within the Chinese development system. Next, we introduce and evaluate an alternative, expertise-based development system characterised by adaptability and greater inclusiveness within the coaching domain, which is underpinned by a distinct set of cognitive decision making skills from the coach’s perspective. In addition, we expand this discussion by explaining the implications of this approach for coach assessment and offer some future suggestions for research in this area
Polyhedral Properties of RLT Relaxations of Nonconvex Quadratic Programs and Their Implications on Exact Relaxations
Get PDFWe study linear programming relaxations of nonconvex quadratic programs given by the reformulation-linearization technique (RLT), referred to as RLT relaxations. We investigate the relations between the polyhedral properties of the feasible regions of a quadratic program and its RLT relaxation. We establish various connections between recession directions, boundedness, and vertices of the two feasible regions. Using these properties, we present necessary and sufficient exactness conditions for RLT relaxations. We then give a thorough discussion of how our results can be converted into simple algorithmic procedures to construct instances of quadratic programs with exact, inexact, or unbounded RLT relaxations
Parental beliefs towards the inclusion of autistic children in mainstream schools
Get PDFResearch has examined teacher attitudes, knowledge, and stigma towards inclusion of autistic children in mainstream schools. Less focus has been given to these beliefs among parents. This is problematic as parents are important in the implementation of inclusion and fostering a positive school environment. The current study examined differences in autism attitudes, knowledge, stigma, and inclusive education attitudes (core perspective; expected outcomes; classroom practices) among parents with and without an autistic child; The study also investigated whether autism knowledge, attitudes and stigma predicted inclusion attitudes. 185 parents in the UK (52% had an autistic child) completed questionnaires measuring these variables. Parents of an autistic child had significantly higher core perspective inclusive attitudes than parents without an autistic child. However, this group also reported more beliefs that parents of autistic children are stigmatised. For all parents, core perspective inclusive attitudes were predicted by autism attitudes and stigma towards parents of autistic children. Predictors of expected outcomes and classroom practices inclusive attitudes differed between groups. Findings highlight the need for parental attitude research to be disability-specific and consider different aspects of inclusive attitudes. Parent education to enhance inclusive attitudes should be tailored for distinct parent groups and contact interventions should be considered
The problem of disinformation:A critical approach
Get PDFThe term disinformation is generally used to refer to information that is false and harmful, by contrast with misinformation (false but harmless) and malinformation (harmful but true); disinformation is also generally understood to involve coordination and to be intentionally false and/or harmful. However, particular studies rarely apply all these criteria when discussing cases. Doing so would involve applying at least three distinct problem framings: an epistemic framing to detect that a proposition in circulation is false, a behavioural framing to detect the coordinated efforts at communicating that proposition, and a security framing to identify threats or risks of harm attendant on widespread belief in the proposition. As for the question of intentionality, different kinds of clues can be picked up within each framing, although none alone is likely to be conclusive. Yet particular studies tend to centre on or prioritise a single framing. Many today aim to make policy recommendations about combatting disinformation, and they prioritise security concerns over the demands of epistemic diligence. This carries a real risk of disinformation research being ‘weaponised’ against inconvenient truths. Against combative approaches, this article argues for a critical approach which recognizes the importance of epistemic diligence and transparency about normative assumptions.</p
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