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Slow viscous flow around a fixed body generates a shape-dependent drag. We explore the drag-minimising shapes of bodies centred between two parallel plates in two-dimensional viscous flow. The channel width introduces a length scale so that the optimal profile is area-dependent. We solve the shape optimisation problem numerically over a wide range of areas. We also compute the optimal elliptical shapes and this identifies how these shapes should be slightly altered to reduce the drag with reductions of up to $3.8\,\%$ attained at high areas. More broadly, we derive two properties of general optimal shapes within the confined flow: the magnitude of the surface vorticity is approximately (but not exactly) constant and the noses have sharp angles that are independent of area. For relatively small bodies, the optimal shape becomes identical to that in an unconfined geometry, but the drag is qualitatively different owing to the influence of confinement; within a channel, it is proportional to the inverse of the logarithm of the body area. At relatively large areas, the optimal body becomes long and its surface is approximately parallel to the channel boundaries, except in the vicinity of the noses. Using a lubrication approximation, we recast the optimisation problem as an Euler–Lagrange equation that is solved to determine the drag-minimising shape, finding that the drag is proportional to the body area in this regime.
This study investigates the effect of sagging correction errors on image quality and geometric coordinate accuracy.
Methods:
This study utilised the Elekta radiotherapy system, ball bearing (BB), Catphan phantom and MultiMet-WL phantom. Ten distinct flex maps (FMs) were acquired by positioning the BB at the accuracy isocentre and introducing shifts of 0.2, 0.4 and 0.6 mm in the left, table and up directions, respectively. Cone-beam computed tomography images of the Catphan phantom were acquired using 10 FMs. The images were analysed for modulation transfer function (MTF) values and geometric coordinates. Additionally, the Winston–Lutz (W-L) test was conducted under reference couch positions and with a 0.3 mm couch shift.
Results:
For the Catphan phantom analysis, the standard deviations of MTF10% across FMs were 0.19. The centre-of-gravity coordinates of the insert exhibited shifts of approximately 0.2, 0.4 and 0.6 mm when comparing reference images to those acquired with the shifted FMs. The results of the W-L test with a 0.3 mm couch shift showed radiation isocentre deviations exceeding 1 mm compared to the reference couch positions.
Conclusions:
Minor sagging correction calibration errors did not remarkably impact image quality; however, they altered the geometric coordinates of the image isocentre. These calibration errors decreased the accuracy of off-isocentre positioning.
The determinants of nest-site selection and nest success are important for conservation planning for endangered birds. Here we examine factors driving nest-site selection and success for the Mariana Crow Corvus kubaryi, also known as the Åga, across the entire range of the population, by comparing 370 nests that were found during surveys (2014–2021) against random points sampled from all forested areas on the island. Nest-sites were more likely to have high canopy cover than random points, while proximity to human infrastructure (e.g. roads, buildings) did not impact nest-site selection. None of our tested covariates impacted nest success, nor did the land-cover type in which the nests were found. Our results suggest that the Åga is able to nest successfully in close proximity to humans, and that nest success is not negatively affected by current land-use practices. Future research on the low nest success rate (23.9%) would be most fruitfully targeted towards local biotic stressors, such as nest predation or environmental factors, which may exacerbate the unknown inflammatory disease that afflicts many wild nestlings.
Existing research on descriptive representation maintains that political candidates often receive more political support from in-group voters than their out-group competitors. Scholars claim this is due in large part to the assumption that descriptive candidates have a greater inclination to act in ways that benefit their shared identity group. This paper explores the other side of these heightened expectations and asks—How do voters evaluate a descriptive representative whose actions are perceived as being at odds with group expectations? Moreover, how do those evaluations compare to out-group candidates who behave in similarly? Using an experimental test, we examine the costs leveraged against political candidates who meet voters’ expectations and those who do not, and seeing whether the shared identity conditions voters’ evaluations. In doing so, we provide a more holistic view of the ways in which descriptive representation matters to voters.
This article advances a law-and-economics critique of fractional-reserve banking, focusing on the legal taxonomy of bank contracts and the risk externalities of maturity transformation. We argue that the conflation of custody-like deposits with mutuum loans blurs property-rights boundaries and weakens liability discipline. Drawing on Austrian monetary theory, we link fiduciary media and demandable debt to pro-cyclical liquidity, run dynamics and the amplification of systemic risk. We reassess the real-bills doctrine and “demand loans,” showing why they do not neutralise run risk in practice and may obscure solvency–liquidity interactions. We then outline institutional reforms – 100%-reserve custodial deposits and a strict functional separation between custody and intermediation – together with market-based loss allocation. The article concludes with regulatory implications for lender-of-last-resort, deposit insurance, and capital/liquidity regimes consistent with risk reduction and legal coherence.
Sustainable Development Goal 6.1 seeks universal access to safe drinking water for all by 2030, yet persistent disparities remain even in high-income countries. Indigenous, remote and small communities are disproportionately affected by poor drinking water quality, but comparable evidence to evaluate performance across communities is very limited due to inconsistent monitoring and reporting. To this end, we constructed a community-level meta-panel dataset of 839 communities (4,137 observations) across 4 Australian jurisdictions (Northern Territory, South Australia, Victoria and Western Australia) and Ontario, Canada, over the period 2018–2022. Drinking water quality was assessed using the Australian Drinking Water Guidelines and Canadian Boil Water Advisories. Logistic regression was employed to estimate the probability of accessing good-quality drinking water, with Indigenous status, remoteness, population size and socio-economic condition as key explanatory variables. Results reveal systematic disparities: Indigenous and very remote communities are statistically significantly less likely to have good-quality drinking water than non-Indigenous and regional communities after controlling for other factors. Our findings indicate that structural inequities – rather than geographic or demographic variation alone – are critical determinants of poor drinking water outcomes in small, Indigenous communities in both Australia and Canada.
The consensus on the need to regulate artificial intelligence is clear, but the how remains elusive. Private regulation, as proposed by the tech industry itself, and state regulation, as embodied in the recent EU Artificial Intelligence Act, are two common forms of governance. We advance a third option that has received very little attention to date: professional regulation. Professional regulation is modeled after hybrid public-private regulatory structures found in medicine, such as those put forth by the American Medical Association. Such governance schemes develop both technical and ethical standards, shaping professional training, continuing knowledge, and conduct. We contend that it is the most practical means of ensuring the development of human-centered AI in an era of rapid technological change and intensely opposing views of what regulation ought to do. This article places the responsibility of acting ethically on the group that knows the technology best and can anticipate its effects: AI developers. But unlike other voluntary standards, professional regulation articulates and enforces standards to certify individuals. Professional licensing is an alternative that provides public protections based on privately developed standards that ensure the safety of AI prior to their release.
A high serum total cholesterol (TC) concentration is a major risk factor for CVD, and lifestyle modifications including a healthy diet are among the first-line strategies for lowering cholesterol concentration and reducing CVD risk. Several studies in rodents have demonstrated a lower circulating TC concentration after intake of cetoleic acid (CA, C22:1n-11). The primary aim was to investigate the effect of consuming herring oil (HERO) containing CA or a CA concentrate (CECO) on the circulating TC concentration in obese hypercholesterolaemic rats. Secondary aims included investigating effects of CA on a selection of hepatic enzymes and receptors involved in cholesterol metabolism, lipogenesis and VLDL assembly. Thirty male obese Zucker fa/fa rats were fed a diet containing either HERO or CECO, containing 0·70 or 1·40 wt% CA, respectively, or a Control diet with soyabean oil for 5 weeks. Data were analysed using one-way ANOVA. The serum TC concentration was lower in the HERO and CECO groups compared with the Control group (17 and 20 percent, respectively). Both the HERO and the CECO diets down-regulated de novo lipogenesis, cholesterol esterification and lipidation of VLDL in the liver compared with the Control diet, but did not affect the hepatic cholesterol synthesis, the LDL receptor or the faecal excretion of cholesterol and bile acids. To conclude, rats fed the HERO or CECO diets had a lower serum concentration of TC, probably as a result of down-regulated VLDL secretion in response to lower lipogenesis. This may have relevance for lowering TC in hypercholesterolaemic humans.
Positioning Indian and Iranian elite tourists to the Tokugawa pilgrimage town of Nikko in relation to their European and American counterparts, this article shows how Meiji-era modern hotels served as mechanisms for an informal and amateur mode of learning about Japanese culture. What enabled Nawwab Hamid Ali Khan, Maharajah Jagatjit Singh, Mehdi Qoli Hedayat, and Ali Asghar Khan to visit the inland shrine town was its integration into the modern tourist infrastructure of the Meiji period by way of the rail connection to Tokyo; the construction of the Kanaya Hotel; and the availability of guides and guidebooks. Consequently, Nikko—and the Kanaya Hotel in particular—functioned as venues for pioneering Indian and Middle Eastern encounters with ‘authentic’ Japanese culture, subsequently published in Urdu and Persian. Japan’s ties to a global tourist system of hotels, restaurants, guides, guidebooks, postcards, photographs, and souvenirs thus contributed not only to Euro-American Japonisme, but also to nascent Indian and Middle Eastern appreciations of Japanese culture.
Unsteadiness lies at the heart of turbulent fluid dynamics, eddy formation and instabilities in flows, thus making it central to both understanding and controlling fluid systems. In this work, we present an objective measure for the unsteadiness of a time-dependent velocity field, the deformation unsteadiness, derived from a spatio-temporal variational principle, allowing for a frame-independent assessment of the unsteadiness of a given flow field. Additionally, as an application of our main result, we define an objective analogue of the classical $Q$-criterion based on extremisers of unsteadiness minimisation. We apply our results to several examples of analytical flows as well as simulated flow data sets in two and three dimensions. In particular, we apply our newly derived vortex criterion to several explicit, time-dependent solutions of the Navier–Stokes equation and compare the results with existing vortex criteria. We give a physical interpretation of the deformation unsteadiness and discuss future research directions.
The WEAR project is developing integrative methods to analyse and predict use-related shape transformation of Neolithic stone tools from Central Europe through experimental archaeology and computational modelling.
Political parties play important roles in contemporary and historical contexts. With the digital turn in the humanities, historians and, increasingly, political scientists are turning to party archives for doing comparative analysis. Party archives provide unique insights on the role of party structures, actors, motivations, and discourses in real time. Yet despite their institutional and scholarly importance, comparative analysis is difficult given the heterogeneous landscape of party archives. This article aims to facilitate comparative analysis. We show that the establishment of different types of party archives follows distinct motivations before we link common obstacles (location, content, searchability, and usage) arising in comparative archival work to them. These obstacles’ severity is often connected to the type of archive, where personal and scholarly archives mark the extremes. The findings can help scholars gain deeper, broader, and, above all, comparable insights about political parties.
Why would a strong authoritarian state choose not to enforce its own policy? We extend the theory of forbearance to autocracies, highlighting its distinct incentives and characteristics. Using China’s social insurance policies as a case study, we argue that promotion-driven local officials under intense interjurisdictional competition allow firms to evade payroll taxes to boost economic performance and advance their careers. This effect is most significant among domestic private firms and foreign firms. We conduct one of the first systematic analyses of firm-level social insurance contributions in an authoritarian context, supplemented by individual-level survey data. Our findings show that bureaucratic forbearance of China’s social insurance policies has a pro-business bias, undermining the policies originally designed to address inequalities during market reforms.
In this paper, I explore the poetic virtue of filmmaking. In the first part, I look at the virtue of art more generally, drawing on Catholic philosopher Jacques Maritain’s Aquinas-inspired conception of poetic virtue. In the rest of the paper, I then map Maritain’s poetic virtue onto the artform of the moving image, its processes of production and reception. Here, I show how poetic intuition is conceived by filmmakers such as David Lynch and translated into the realities of filmmaking in the Sci-Fi mystery thriller, The Silent Messenger, in which I was involved in as producer and performer. Enlisting the help of film philosopher Alain Badiou and film phenomenologist Vivian Sobchack, I claim that for the poetic virtue of film to come into full presence, both filmmaker and viewer need to take responsibility for their moral capacity for gaze. It is only when the viewer loses themselves (their self) in the shared sight of the filmmaker, and the artist respects the audience’s own intellectual creativity, that film can teach us that seeing is always a relational enterprise, one that brings our human relationships – in all its tragedy and beauty – into shared vision.
We develop generalized Petersson/Bruggeman-Kuznetsov (PBK) formulas for specified local components at non-archimedean places. In fact, we introduce two hypotheses on non-archimedean test function pairs $f \leftrightarrow \pi (f)$, called geometric and spectral hypotheses, under which one obtains “nice” PBK formulas by the adelic relative trace function approach. Then, given a supercuspidal representation $\sigma $ of $\operatorname {\mathrm {PGL}}_2(\mathbb Q_p)$, we study extensively the case that $\pi (f)$ is a projection onto the line of the newform if $\pi $ is isomorphic to $\sigma $ or its unramified quadratic twist, and $\pi (f) = 0$ otherwise. As a first application, we prove an optimal large sieve inequality for families of automorphic representations that arise in our framework.