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This study examines the dynamics of vortical interactions and their implications for mitigating thermoacoustic instability in a turbulent combustor. The regions of intense vortical interactions are identified as vortical communities in the network space of weighted directed vortical networks constructed from two-dimensional experimental velocity data. One can expect vortical interactions in the combustor to be strongest near the moment of vortex shedding, as the shed vortices gradually weaken due to dissipation while convecting downstream. However, we show that, during the state of thermoacoustic instability, there is a non-trivial consistent phase lag of approximately $52^\circ$ between the shedding of the coherent structures from the backward-facing step and the time instant when the vortical interactions attain their local maximum value. We explain this phase lag by investigating the correlation between acoustic pressure fluctuations, spatio-temporal dynamics of coherent structures and vortical interactions in the reaction field of the combustor. We also show the aperiodic variation of vortical interactions during the states of combustion noise and aperiodic epochs of intermittency. Furthermore, the spatio-temporal evolution of pairs of vortical communities with the maximum inter-community interactions provides insight into explaining the critical regions detected in the reaction field during the states of intermittency and thermoacoustic instability, also identified in previous studies. We further show that the most efficient suppression of thermoacoustic instability via air microjet injection is achieved when steady air jets are introduced to disrupt the maximum inter-community interactions present during the state of thermoacoustic instability.
This essay discusses the contours of what I call a new instrumental turn in Nigerian historical scholarship. It argues that the historical discipline in Nigeria is experiencing a new instrumental turn, which finds expression in several new features of academic history writing, teaching, and programming. Some aspects of this trend hearken back to the original instrumental history of the pioneers of Nigerian and African nationalist history; others represent something new, being responses to novel twenty-first-century anxieties and imperatives of nation-building, development, and the place of humanities knowledge in those aspirations. Unlike old conceptions of instrumentality, this new turn signals a more explicit agenda of problem-solving through historical research. It also entails a rather formulaic embrace of proposals for solutions to problems identified in or through historical research.
Kant’s description of the moral politician in ‘Perpetual Peace’ is the most detailed statement of his template for legislative reform. I argue that the moral politician responds to criticisms of Kant’s earlier ‘Theory and Practice’ essay by Friedrich Gentz and August Wilhelm Rehberg. Gentz and Rehberg objected to: Kant’s treatment of the relationship between theory and practice in politics, his conception of popular sovereignty, and his account of political transformation. By showing that Kant used the moral politician to rebut Gentz and Rehberg, I highlight an underappreciated dimension of ‘Perpetual Peace’ while situating Kant’s political stance in its historical context.
This study experimentally investigates wake recovery mechanisms behind a floating wind turbine subjected to imposed fore-aft (surge) and side-to-side (sway) motions. Wind tunnel experiments with varying free-stream turbulence intensities ($\textit{TI}_{\infty } \in [1.1, 5.8]\,\%$) are presented. Rotor motion induces large-scale coherent structures – pulsating for surge and meandering for sway – whose development critically depends on the energy ratio between the incoming turbulence and the platform motion. The results provide direct evidence supporting the role of these structures in enhancing wake recovery, as previously speculated by Messmer, Peinke & Hölling (J. Fluid Mech., vol. 984, 2024, A66). These periodic structures significantly increase Reynolds shear stress gradients, particularly in the streamwise–lateral direction, which are key drivers of wake recovery. However, their influence diminishes with increasing $\textit{TI}_{\infty }$: higher background turbulence weakens the coherent flow patterns, reducing their contribution to recovery. Beyond a threshold turbulence level – determined by the energy, frequency and direction of motion – rotor-induced structures no longer contribute meaningfully to recovery, which becomes primarily driven by the free-stream turbulence. Finally, we show that the meandering structures generated by sway motion are more resilient in turbulent backgrounds than the pulsating modes from surge, making sway more effective for promoting enhanced wake recovery.
The rapid advancement of satellite-based monitoring technologies and niche modelling present unprecedented opportunities to enhance conservation efforts, especially over large areas, yet their practical application in guiding conservation strategies remains limited. This study examines how land-use changes affect ant diversity in the Acre River basin, south-western Brazilian Amazon. Using niche modelling with climatic, environmental and land-use data, we examined species distributions for three ant guilds – forest specialists, generalists and open-habitat specialists – across 1985, 2019 and 2050. The results show that forest specialists are concentrated in the eastern regions but are projected to decline, while open-habitat specialists – dominant in the south-west – are expected to increase in distribution. Generalists displayed broader, stable distributions. These patterns highlight the critical role of forest conservation in preserving the diversity of forest-specialist species and the threat posed by Amazon forest conversion, and they point to the need for strategic landscape planning to mitigate deforestation impacts.
This article argues against the cliché (posited most famously by Alexis de Tocqueville and Carl Schmitt), that there were inherent correspondences between religious and political concepts. Such connections were historically contingent, and had to be forged by polemicists and apologists who eclectically drew upon a variety of sources. This is evident from an examination of differing Presbyterian reactions to the French Revolution. John Brown in Scotland combined an aristocratic Presbyterian ecclesiology with a Burkean view of authority to argue for an anti-democratic conception of “representative government.” By contrast, the Scottish-American Alexander McLeod synthesized radical Presbyterian political theology with Painite ideas of “representative democracy.” Thus representation emerged as the key concept in both authors, yet its compatibility with democracy was an open question. The examples of Brown and McLeod also show that religion, as much as “secular” politics, had to grapple with and re-imagine “democracy.”
Despite myths of its dematerialization, capitalism continues to deepen its reliance on resource extraction. Performances by Otobong Nkanga and Seba Calfuqueo confront this trend, mapping it onto longer histories of expropriation in Namibia and Chile, respectively. By activating sculptural objects composed of mined raw materials, both artists make visible the colonial and ongoing forms of extractive violence that underpin automation and the socalled green energy transition.
This article examines the factors that enabled French merchants to enter the Spanish Indies markets during the 1620s, particularly in the period betwen the Peace of Monzón (1627) and the outbreak of the Franco-Spanish War (1635). It highlights how the French nation of Seville received unprecedented support from the Crown to develop their marginal enterprises in the Carrera de Indias. Royal patronage played a significant role in integrating—or exluding—wealthy merchant communities from the Spanish Atlantic trading system, therby expanding their networks for direct exchanges with the Americas. The study reconstructs French commercial connections within the Spanish Atlantic trade, contextualized alongside Flemish and Italian networks already operating in New Spain. These three nations dominated much of the cargo legally shipped to and from the viceroyalty in the 1620s and 1630s. The analysis details French business interactions with “native” and “foreign” merchants, their resilience following the economic reprisal of 1635, and observations on the reconfiguration of foreign trading networks alongthe New Spain axis during the Spanish Empire’s economic and political crises of the 1640s.
This article examines the fear of death in fourteenth-century Italy by analysing miracle testimonies through the methodological frameworks of terror management theory (TMT) and lived religion. It argues that devotion to saints served as a key coping mechanism for existential anxiety. Examples from the canonisation processes of Clare of Montefalco and Nicholas of Tolentino reveal how individuals turned to saints for protection, seeking to prolong life rather than accept death. This study provides both empirical and methodological insights into the medieval fear of death, illustrating its parallels with contemporary experiences of death anxiety.
It is a truism that legitimacy is relational inasmuch as an international institution’s legitimacy hinges on how it is perceived by relevant audiences. What is less discussed is that legitimation practices may have another strong relational dimension as well, in which institutions portray themselves as being related to respected others. While the idea that international institutions associate themselves with others to borrow their legitimacy is not new, it has not as yet been thoroughly theorised. This article therefore brings together insights from research on the legitimation of international institutions and relational sociology, as well as from related fields, to theorise the notion of ‘relational legitimation’. It also presents a case study on the Special Procedures of the United Nations Human Rights Council. Based on qualitative content analysis of annual thematic reports, the paper suggests that relational legitimation is a common practice among the Special Procedures, and possibly also among other international institutions. It shows that relational legitimation relies on a number of different frames – alignment being the most important one – and that association is sought primarily with epistemic authorities, especially those from the West, and other ‘family members’.
Specialization is a core concept in the study of flowering plants and their relationships with floral visitors. In recent decades, researchers have increasingly used bipartite floral interaction networks to study these relationships. Networks are typically built from simple observations of floral visitation and ignore which resources visitors acquire during visits. However, flowers can provide nectar, pollen, or both, and floral visitor species may only forage for one or the other on a given plant. Here, using data we collected which differentiates nectar from pollen foraging for floral visitors to 15 Bornean rainforest tree species, we investigate whether estimates of specialization change when multiple floral resources are accounted for. We find that the same visitors have different estimated values of specialization when calculated using the overall visitation data (the standard approach), versus only nectar or pollen foraging. Differences in specialization estimates for flower-visiting taxa scale up to affect estimates of specialization for the whole community of floral visitors, with greater specialization found in nectar than pollen foraging. Our findings highlight some important considerations when using resource-agnostic visitation data in network-based studies of plant-pollinator relationships. In addition, this study represents one of the first network analyses of plant-pollinator interactions in a tropical rainforest canopy.
This study aimed to provide an in-depth analysis of women’s experiences following a major forest fire.
Methods
In qualitative research, sample size is not statistically determined, as generalization is not the primary goal. A small number of participants can yield rich data. The interview form included 3 demographic questions and 10 open-ended items aligned with the study’s objectives. Data analysis was conducted using MAXQDA version 24.1.0.
Results
Thematic analysis identified 3 main themes: Emotional Response, Fire Intervention, and Gender, comprising 8 categories. Participants commonly reported intense fear and anxiety, accompanied by physical symptoms such as tension and elevated blood pressure. Primary concerns involved the loss of pets, resources, security, and shelter. Women were found to be deeply affected emotionally and psychologically by the fire experience.
Conclusions
The study revealed that women were equally engaged in firefighting efforts as men and also played a crucial caregiving role, offering support to affected individuals. These dual roles reflect both their resilience and the emotional burden they carried. The findings underscore the significant psychological impact of wildfires on women and highlight the necessity of integrating gender-sensitive approaches in disaster response and recovery efforts.