To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Turbulence accounts for most of the energy losses associated with the pumping of fluids in pipes. Pulsatile drivings can reduce the drag and energy consumption required to supply a desired mass flux, when compared with steady driving. However, not all pulsation waveforms yield reductions. Here, we compute drag- and energy-optimal driving waveforms using direct numerical simulations and a gradient-free black-box optimisation framework. Specifically, we show that Bayesian optimisation is vastly superior to ordinary gradient-based methods in terms of computational efficiency and robustness, due to its ability to deal with noisy objective functions, as they naturally arise from the finite-time averaging of turbulent flows. We identify optimal waveforms for three Reynolds numbers and two Womersley numbers. At a Reynolds number of $8600$ and a Womersley number of 10, optimal waveforms reduce total energy consumption by 22 % and drag by 37 %. These reductions are rooted in the suppression of turbulence prior to the acceleration phase, the resulting delay in turbulence onset, and the radial localisation of turbulent kinetic energy and production towards the pipe centre. Our results pinpoint that the predominant, steady operation mode of pumping fluids through pipes is far from optimal.
Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae) is a significant pest of wheat, Triticum aestivum Linnaeus (Poaceae), in Canada. Monitoring currently relies on labour-intensive counts of ovipositing females. Although traps baited with S. mosellana pheromone are used as decision support tools in the United Kingdom, in Canada, they are considered reliable only to indicate adult activity. Recent findings show that variability in pheromone release from commercial lures affects the number of midges captured and limits the reliability of pheromone monitoring. Here, two lure types and two trap types were compared for their ability to attract and retain S. mosellana males. We then compared the number of males captured in pheromone traps with the information provided by other monitoring tools, including emergence traps, soil cores, and ovipositing female counts. Jackson traps with Trécé rubber septa lures captured the most midges. The number of males captured in pheromone-baited traps was not related to overwintering, ovipositing, or emerging populations, suggesting that pheromone traps may not accurately reflect S. mosellana populations under field conditions. Variability in extracted pheromone amount between lures, regional climate, and Canada’s vast wheat-growing area may limit the development of an effective pheromone-based decision support tool for this region. Nevertheless, refinement of lure formulation, standardisation of trapping protocols, and integration of complementary monitoring approaches may enhance trap reliability and support a stronger monitoring system.
Pelmatozoa is an informal grouping of filter-feeding echinoderms including crinoids, paracrinoids, rhombiferans, and eocrinoids that possess a theca, an erect stalk, and feeding appendages. Although crinoids were major constituents of marine communities with high diversity and abundance throughout the Paleozoic, most other pelmatozoans had relatively low species diversity and/or short temporal durations. It has been proposed that these different diversification trajectories could have resulted from crinoids outcompeting other filter-feeding pelmatozoans during the early Paleozoic, although this hypothesis involving niche overlap has never been formally tested. Here, we tested this hypothesis using the incredibly diverse pelmatozoan fauna of the Late Ordovician (Sandbian) Bromide Formation of Oklahoma, which preserves a rich, ecologically complex fauna that developed as a result of the Great Ordovician Biodiversification Event. We developed a framework to quantitatively characterize pelmatozoan feeding ecology using multivariate analysis of ecomorphological traits and explored niche space occupation and potential competition between crinoids, rhombiferans, paracrinoids, eocrinoids, and diploporans from the Bromide fauna. Results revealed key ecological factors controlling niche differentiation and showed that crinoids, paracrinoids, and rhombiferans occupy nonoverlapping regions of niche space, indicating competition between groups was unlikely. Although the competition hypothesis was not supported, narrow niche space occupation suggests that paracrinoids and rhombiferans were more ecologically limited than crinoids, which might have played a role in their differential diversification dynamics. These results elucidate both the nature of interactions between pelmatozoan taxa and the potential mechanisms driving their evolutionary trajectories, as well as the complexity of ecological communities that arose during the Ordovician radiation.
A seminal result of Komlós, Sárközy, and Szemerédi states that any $n$-vertex graph $G$ with minimum degree at least $(1/2+\alpha )n$ contains every $n$-vertex tree $T$ of bounded degree. Recently, Pham, Sah, Sawhney, and Simkin extended this result to show that such graphs $G$ in fact support an optimally spread distribution on copies of a given $T$, which implies, using the recent breakthroughs on the Kahn-Kalai conjecture, the robustness result that $T$ is a subgraph of sparse random subgraphs of $G$ as well. Pham, Sah, Sawhney, and Simkin construct their optimally spread distribution by following closely the original proof of the Komlós-Sárközy-Szemerédi theorem which uses the blow-up lemma and the Szemerédi regularity lemma. We give an alternative, regularity-free construction that instead uses the Komlós-Sárközy-Szemerédi theorem (which has a regularity-free proof due to Kathapurkar and Montgomery) as a black box. Our proof is based on the simple and general insight that, if $G$ has linear minimum degree, almost all constant-sized subgraphs of $G$ inherit the same minimum degree condition that $G$ has.
In a retrospective cohort of 6363 neonates admitted to three NICUs, there was no reduction in Staphylococcus aureus acquisition when comparing pre- and post-pandemic incidence rates. While additional infection prevention practices introduced during the pandemic helped prevent SARS-CoV-2 transmission, these practices may not have reduced S. aureus transmission to infants.
We analyze the extent to which the prospects for economic development may relate to the environmental damages associated with economic activities. We consider an economic growth framework in which production activities generate polluting emissions which in turn negatively affect production capabilities, and publicly-funded abatement is pursued to mitigate such effects. Since the time preference is endogenously related to capital, abatement affects the size of the discount factor through its implications on capital accumulation. We show that the elasticity of environmental damages affects the optimal tax rate and thus the abatement level, which in turn determines whether the economy will end up in a stagnation or growth regime. This suggests that the cross-country heterogeneity in environmental damages may explain the different development patterns experienced by industrialized and developing economies. Our results are robust to the presence of productive public spending and two alternative forms of capital (clean and dirty capital).
This paper presents a novel robust control method for a hip-assist exoskeleton robot’s joint module, addressing dynamic performance under variable loads. The proposed approach integrates traditional PID control with robust, model-based strategies, utilizing the system’s dynamic model and a Lyapunov-based robust controller to handle uncertainties. This method not only enhances traditional PID control but also offers practical advantages in implementation. Theoretical analysis confirms the system’s uniform boundedness and ultimate boundedness. A Matlab prototype was developed for simulation, demonstrating the control scheme’s feasibility and effectiveness. Numerical simulations show that the proposed fractional-order hybrid PD (FHPD) controller significantly reduces tracking error by 58.70% compared to the traditional PID controller, 55.41% compared to the MPD controller, and 32.32% compared to ADRC, highlighting its superior tracking performance and stability.
The end of the nineteenth century saw the emergence of nationalism as the primary ideological underpinning of Australian identity, defining the broader Australian people as a culturally British, Protestant community. Such developments drew strength from key events of the early twentieth century, such as Australian federation and the Great War. Although historians have conceded that Irish Australians could adhere to the cultural tenets of Anglo-Australia, they have overlooked the extent to which Irish-Australian Catholics, especially those from the middle class, adopted Britishness as an integral part of their ethno-religious identity. Middle-class Catholic individuals, families and groups negotiated the extent of their Irishness to suit their needs within economic, social and cultural spaces dominated by Australia’s Protestant majority. This article argues that the expression of Britishness was an intrinsic part of Catholics’ middle-class ambitions, as they sought to rectify their implicit ‘otherness’ in an Australia committed to a myth of national unity on non-Irish, and non-Catholic, terms.
We establish a polynomial ergodic theorem for actions of the affine group of a countable field K. As an application, we deduce—via a variant of Furstenberg’s correspondence principle—that for fields of characteristic zero, any ‘large’ set $E\subset K$ contains ‘many’ patterns of the form $\{p(u)+v,uv\}$, for every non-constant polynomial $p(x)\in K[x]$. Our methods are flexible enough that they allow us to recover analogous density results in the setting of finite fields and, with the aid of a finitistic variant of Bergelson’s ‘colouring trick’, show that for $r\in \mathbb N$ fixed, any r-colouring of a large enough finite field will contain monochromatic patterns of the form $\{u,p(u)+v,uv\}$. In a different direction, we obtain a double ergodic theorem for actions of the affine group of a countable field. An adaptation of the argument for affine actions of finite fields leads to a generalization of a theorem of Shkredov. Finally, to highlight the utility of the aforementioned finitistic ‘colouring trick’, we provide a conditional, elementary generalization of Green and Sanders’ $\{u,v,u+v,uv\}$ theorem.
We investigate the angular dynamics of a single spheroidal particle with large particle-to-fluid density ratio in simple shear flows, focusing on the influence of the fluid-inertial torque induced by slip velocity. A linear stability analysis is performed to examine how the fluid-inertial torque, viscous shear torque and particle inertia affect the various stable rotation modes, including logrolling, tumbling and aligning modes. As particle inertia increases, bistable or tristable rotation modes emerge depending on initial conditions. For prolate spheroids, three distinct stable-mode regimes are identified, i.e. logrolling, tumbling and tumbling–logrolling (TL). The presence of these modes depends on particle shape and inertia. For oblate spheroids, when the Stokes number is small, we observe monostable modes (logrolling, tumbling and aligning) and bistable modes (TL, aligning–logrolling) varying with different factors. As Stokes number increases, the tristable mode (aligning–tumbling–logrolling) of oblate spheroids appears. These results of the stability analysis further highlight the intricate and significant effect of fluid-inertial torque compared with the results in the absence of fluid-inertial torque. When we apply fluid-inertial torque to the point-particle model, we reproduce the stable rotation modes observed in particle-resolved simulations, which validates the present stability analysis.
The global use of antimicrobial chemicals drastically increased during and after the COVID-19 pandemic owing to heightened awareness of personal and surface hygiene needs. Disinfectants, especially chlorine-based disinfectants (CBDs), were extensively used for surface and equipment decontamination in the domestic, industrial, veterinary and healthcare sectors during the heights of the pandemic. The increased use of disinfectants has resulted in their increased discharge into municipal wastewater systems and surface waters. Our Perspective article considers the One Health challenges associated with the increased discharge of disinfectants into wastewater. One Health is a collaborative approach that ensures the well-being of people, animals and the environment. Wastewater is a common endpoint to the many interactions between people, animals and their environment. The potential One Health challenges and knowledge gaps associated with the constant discharge of low but sublethal concentrations of CBDs into wastewater are discussed. The data gaps point to the risks associated with the unregulated use of CBDs and need for their judicial use.
Burkholderia cepacia is a rare cause of prosthetic valve endocarditis. We report an 18-year-old male with Tetralogy of Fallot and two sequential transcatheter pulmonary valves (Melody and Myval), presenting with persistent bacteraemia unresponsive to antibiotics. Surgical explantation of both valves with homograft replacement and tricuspid repair achieved complete recovery, emphasising surgery in refractory infections.
Historians continue to debate what form colonial rule took in early modern Ireland. This article explores how the reception and resistance to anglicisation, located in the everyday body language of submission and subordination encoded in gesture, might be understood in the experience of colonial rule. Exploring the gestural code operating in early modern Ireland, this article examines the role of body politics in the reception of and reaction to English rule. English ‘manners and apparel’ were central to the project of anglicisation. The body played a central role in representing and articulating social hierarchies in the early modern world. Body language offered a troubling everyday reminder of the inequalities signalled in the — non-reciprocal or non-reciprocated — gestures expected of ‘subordinates’ towards ‘superiors’. If the enforcement of the gestural order was important to the establishment of English rule, this also made gesture a focus for resistance and opposition. A body politics that exploited a shared understanding of the meaning of particular gestures could be drawn on in both everyday politics and collective protests to subvert, resist and retaliate against the political agenda of anglicisation. Looking forward to the eighteenth century and beyond state action, the article calls for more work on gesture.
We introduce a new family of coalescent mean-field interacting particle systems by producing a pinning property that acts over a chosen sequence of multiple time segments. Throughout their evolution, these stochastic particles converge in time (i.e. get pinned) to their random ensemble average at the termination point of any one of the given time segments, only to burst back into life and repeat the underlying principle of convergence in each of the successive time segments, until they are fully exhausted. Although the architecture is represented by a system of piecewise stochastic differential equations, we prove that the conditions generating the pinning property enable every particle to preserve their continuity over their entire lifetime almost surely. As the number of particles in the system increases asymptotically, the system decouples into mutually independent diffusions, which, albeit displaying progressively uncorrelated behaviour, still close in on, and recouple at, a deterministic value at each termination point. Finally, we provide additional analytics including a universality statement for our framework, a study of what we call adjourned coalescent mean-field interacting particles, a set of results on commutativity of double limits, and a proposal of what we call covariance waves.