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We study the navigation of a self-propelled inertial particle in two-dimensional Rayleigh–Bénard convection at Prandtl number $\textit{Pr}=0.71$ and cell aspect ratio $\varGamma =4$ for Rayleigh numbers $Ra$ ranging from $10^7$ to $10^{11}$. A reinforcement-learning (RL) controller selects the propulsive acceleration, subject to an upper bound $\mathcal{A}_{\textit{max}}$, to achieve a prescribed horizontal displacement. We find that the success rate increases abruptly with $\mathcal{A}_{\textit{max}}$ at moderate $Ra$, whereas at higher $Ra$ the transition becomes more gradual and shifts to larger $\mathcal{A}_{\textit{max}}$. Moreover, although the completion time increases with $Ra$, the propulsion energy required for successful traversal decreases. Proper orthogonal decomposition indicates that these performance differences are associated with reorganisation of the carrier flow. At moderate $Ra$, the dominant large-scale circulation partitions the domain through persistent transport barriers, requiring a finite thrust surplus to cross them; at higher $Ra$, energy is distributed across many modes, the barriers fragment and transient plume-assisted pathways emerge. Compared with a constant-heading baseline, the learned policy aligns with local currents and consumes significantly less energy. Lagrangian coherent structure analysis further suggests that the RL agent tends to cross repelling barriers and surf along attracting pathways. Finally, by mapping these behaviours onto the local Eulerian flow topology using Voronoi tessellation and the $Q$-criterion, we distil an interpretable, physics-based heuristic strategy that retains robust navigability. These results connect turbulent-flow organisation with autonomous navigation under bounded actuation.
A number of high-profile people seem to have moved from the left to the right quite suddenly, and without appearing to move through intermediate positions. Often, they do not just go right; they go right and bananas: accepting bizarre conspiracy theories and other such beliefs. This paper argues that this phenomenon can be explained by a combination of psychological pressures and genuine reasons, with the person pivoting from left to right on the fulcrum provided by a belief to which they are strongly committed and on which their side initially splits. This account explains how people go bananas while remaining rational and remaining concerned with evidence. The evidence to which they respond is provided by testimony. The pivot belief provides them with reasons to place much heavier weight on the testimony of the right, their former opponents, than on their own former side.
Protein intake and the resulting postprandial aminoacidemia are an important anabolic stimulus. However, considerable individual variation in postprandial amino acid (AA) kinetics can be expected. In this study the aim was to quantify the variability in postprandial AA kinetics within and between individuals after consumption of a moderately digestible plant protein concentrate (Lucerne (Alfalfa), LPC) and an easy digestible animal protein concentrate (Whey, WPC). Eighteen healthy young adults consumed a 20g protein drink on five occasions (3xLPC;2xWPC). Plasma AA kinetics were calculated and a mixed-model was fitted to describe within- and between-individual variability, and to calculate the intra-class correlation coefficient (ICC). AA kinetics showed significant variation between and within individuals, both for WPC and LPC. Between-individuals variation in postprandial response for total or total essential AA (TAA, TEAA) was in general larger than within-individual variation for WPC with the ICCs with or without blood volume correction ranging from 0.45-0.77. For LPC the within-individual variation of the TAA response was higher than the between-individual, for TEAA they were more or less equal; with the ICCs with or without blood volume correction ranging from 0.34-0.58 for LPC. Subjects with a high level of aminoacidemia for one protein source were not necessarily those with a high level for the other protein source. Our results indicate that between- and within-person variation in postprandial AA kinetics are substantial, and should not be neglected.
We show that exponential sums over such sets satisfy inequalities analogous to Weyl’s inequality, and in many circumstances of the same strength as classical versions of Weyl’s bound. We also examine equidistribution of polynomials modulo $1$ in which the summands are restricted to these subconvex $L^p$-sets. In addition, we describe applications to problems involving character sums and averages of arithmetic functions.
We investigate three-dimensional Kolmogorov flow as a model flow featuring turbulent superstructures, i.e. large-scale coherent structures within a turbulent flow. Previous works have shown that turbulent Kolmogorov flow features the emergence of various configurations of large-scale vortex pairs and dynamic switching between these flow states. Here, we devise a low-dimensional model and characterise the meandering of these large scales between different numbers of vortex pairs through two complex amplitudes. We identify these different large-scale states as remnants of instabilities far from the onset of turbulence. We obtain the statistics of the two complex amplitudes from direct numerical simulations. We then construct a set of stochastic amplitude equations whose statistical properties reproduce the ones observed in the three-dimensional Kolmogorov flow up to a fair agreement. Based on these results, we discuss how fast-evolving terms in the form of noise can be introduced into the averaged equations to capture the complex dynamics of the large scales. We thereby shed light on the interplay between the large scales and the small-scale fluctuations.
This article discusses the development of the German-speaking anti-vaccination movement from the second half of the nineteenth century to the early twentieth century as an actor-centred history of knowledge. Although the German anti-vaccination movement was a heterogeneous milieu, recurring shared narratives can be identified within the argumentation of its actors: The movement is characterised by a high affinity to conspiracy theories and an anti-science attitude. Antisemitism and völkish ideologies are also a recurring element of this radical rejection of vaccination in the German-speaking region from the second half of the nineteenth century onwards. These narratives are used to construct a knowledge system of smallpox vaccination that was an alternative to medical science and the political decisions based on it.
European fascist regimes have attached great importance to nationalistic families and designed policies to perpetuate them. Most offered policy packages with interest-free loans repayable through childbirth, along with allowances and tax deductions for large families. Using a difference-in-difference approach and Nazi Germany as a case study, we show that these policies may have counterproductive effects due to negative selection mechanisms in the marriage market. The excessive pressure to marry exerted on singles results in lower quality, ultimately less fertile, and more fragile unions. This finding is important as the main European far-right parties today propose reinstating these policy packages.
During the Second World War and the Cold War, the U.S. military developed a hydrophone array system called SOSUS (Sound Surveillance System) to listen underwater in the ocean. This arose in response to the threat posed by enemy submarines. But this technology was also fundamental for listening to oceanic living beings. This paper explores the history of the invention of SOSUS as fundamental to redefining a subaquatic Caribbean by tracing the history of research that led to its deployment. Through the interrelationship between military and environmental sonic history, the author seek to problematize the notion of encounter and explore the following questions: What does the encounter between animal and machine biopower tell us about the history of acoustic Atlantic crossings? Moreover, why was SOSUS deployed in the Caribbean initially and what sort of understandings of the submarine ocean and the history of the Anthropocene does this give rise to?
This article examines how operational-level grievance mechanisms (OGMs) implemented by transnational mining companies in Africa entrench corporate control over victims’ access to remedy. Although OGMs are central to the United Nations Guiding Principles on Business and Human Rights, their deployment in weak governance contexts often transforms them from early-warning tools into the sole avenue for redress. Through a comparative analysis of four different mines that reveal converging mining and business and human rights dynamics unique to Africa, this article considers how OGMs reproduce power asymmetries through opaque procedures, limited consultation, information imbalances, and unpredictable remedies. These dynamics undermine the UNGPs’ effectiveness criteria and reveal structural gaps within Pillar Three’s design. The article argues for alternatives, such as independent grievance mechanisms and additional guidance on implementing the UNGPs that guarantee legal representation, prohibit restrictive waivers, and introduce sector-specific recommendations. Without such changes, OGMs risk legitimising corporate abuses rather than remedying harm.
Several mechanisms have been identified by which turbulence may either enhance or reduce the settling velocity of heavy particles. However, the conditions under which some of them may dominate over others are not well known, thwarting our ability to predict the net outcome. We investigate this issue experimentally, focusing on spherical particles of size comparable to the Kolmogorov scale in homogeneous turbulence. We combine results obtained in two zero-mean-flow chambers working with water and air and various particle densities, leveraging high-resolution imaging of both phases and spanning a substantially wider range of parameters compared with previous studies. The change in settling velocity is found to be dictated by a single parameter: the ratio between the still-fluid fall speed and the characteristic velocity of the turbulent fluctuations, with settling enhancement and reduction occurring when this is smaller and larger than unity, respectively. This marks the transition from particles being preferentially swept by downward fluctuations to them loitering in upward ones. Counterintuitively, nonlinear drag effects are most significant in the regime of settling enhancement, while their contribution to settling reduction is modest.
A key challenge in multiphase flow through porous media is to understand and predict the conditions under which trapped fluid clusters become mobilised. Here, we investigate the stability of such clusters in two-phase flow and present a simple, quasistatic model that accurately determines the critical Bond number (that is, the critical ratio between the average pressure gradient of the flow and the surface tension) for the onset of cluster mobilisation. The model is derived by combining elementary geometrical considerations with mass conservation and a mechanical equilibrium condition, resulting in a system of coupled differential equations. Our derivation sheds new light on the mechanisms that govern cluster stability. In addition, since the number of equations equals the number of cluster openings, our model is significantly faster than direct numerical simulations of the same problem and enables efficient exploration of the system’s parameter space. Using this approach, we highlight a discrepancy with the prediction of current mean-field theories, which predict that the largest stable cluster size scales in proportion to $r/{\textit{Bo}}^\alpha$, where $r$ is a typical pore size, ${\textit{Bo}}$ is the Bond number and $\alpha$ is a fixed exponent. We discuss the mechanisms that explain the breakdown of the mean field theories and we show that a scaling law of this form can only exist if $\alpha$ is allowed to depend on a broad set of flow and geometric parameters.
Historians of science have demonstrated the many ways in which science and politics are interrelated. The production of scientific knowledge, the organization of research and the application of science and technology are deeply intertwined with structures of power and governance. Climate science is a prime example to demonstrate the political qualities of science and the diversity of entanglements of science and politics. We argue that these entanglements have a wide range of meanings, such as scientists’ political agendas and manoeuvres, the policies of scientific and funding institutions, the uses of science by corporate or state actors, and the political agency of science and technology, as well as public debates about them. To better capture the diversity of these entanglements, we suggest developing more fine-grained conceptual taxonomies or categories. As a possible starting point for further differentiation, we introduce the concepts politics of science, science for policy and politics in science. Next, we illustrate this conceptual differentiation using the history of weather and climate science as an example. Finally, we provide a short summary of the contributions to this special issue and their addition to the state of knowledge regarding the epistemology and politics of climate science.
Maya glyphic texts from the Classic period (250–900 CE) typically chronicle the exploits of historical or divine characters; everyday or functional records are rare. Here, the authors offer a reconstruction and transcription of a ‘microtext’ painted on an interior wall of Structure 10K-2 at the site of Xultun, Guatemala. The text records a unique astronomical formula that concludes with a name, attributing the work to an individual named Sak Tahn Waax (‘White-chested Fox’). To date, this is the only known example of a Classic Maya mathematician directly credited for their work, attesting to the value of its intellectual authorship.
In recent years, global context has resulted in a growing number of forcibly displaced migrants (FDM) in Europe, including Ireland. Several factors can impact determinants of health, including traumatic experiences, resilience, and cultural background, along with local frameworks and accessibility to services. Interpreter availability, level of knowledge, and utilisation are of relevance to quality service provision, as is training and supervision. FDM are a vulnerable group; studies suggest higher rates of mental illness, but understanding this is complex. While community structures have been suggested to respond to specific needs, pathways to access secondary mental health services in Ireland can cause challenges and inequity. This review brings together relevant literature to conceptualise the topic and make recommendations for health professionals engaged in mental healthcare of FDM. Understanding professionals’ perspectives, inclusion of people with lived experience, strong inter-agency collaboration, supervision, and training are some of the recommendations proposed.
A new species of dissorophoid temnospondyl, Melanerpeton kuselense new species, is reported from the Remigiusberg Formation (Carboniferous-Permian boundary) of southwestern Germany. The type and only known specimen is a skull belonging to a moderately advanced larva with distinctive features: (1) a very slender postorbital skull table, (2) large nasal, (3) short squamosal giving a short gape, and (4) a gracile and extremely small pterygoid. Phylogenetic analysis finds it to fall well within the branchiosaurids, above the Pennsylvanian Branchiosaurinae, and sister taxon to Melanerpeton pusillum Fritsch, 1878 from lower Permian deposits of the Czech Republic. It is not closely related to any of the branchiosaurids from the Saar-Nahe Basin, adding to the distinctive Remigiusberg tetrapod faunal assemblage.