We investigate experimentally the effects of micro-grooves on the development of a zero pressure gradient turbulent boundary layer at two different values of the friction Reynolds number. We consider both the well-known streamwise aligned riblets as well as wavy riblets, characterized by a sinusoidal pattern in the mean flow direction. Previous investigations by the authors showed that sinusoidal riblets yield larger values of drag reduction with respect to the streamwise aligned ones. We perform new particle image velocimetry experiments on wall-parallel planes to get insights into the effect of the sinusoidal shape on the near-wall organisation of the boundary layer and the structures responsible for the friction drag reduction and the turbulence generation. Conditional averages, aimed at identifying the topology of the low-speed streaks in the turbulent boundary layer, reveal that the flow is highly susceptible to wall manipulation. This is particularly evident in the cases that are associated with greater values of drag reduction. The results suggest a fragmentation and/or weakening of the streaks in the sinusoidal cases, that is triggered by the larger values of the wall-normal vorticity found at the streaks’ edges. The results are also confirmed by applying the variable interval spatial averaging events eduction technique. The turbulent kinetic energy budget also shows that the sinusoidal geometry significantly attenuates the turbulence production, hence supporting the idea of the manipulation of the turbulence regeneration cycle.

Acanthocephalans are a group of obligate endoparasites that alternate between vertebrates and invertebrates to complete their life cycles. Occasionally, the same individual host acts as a definitive or paratenic host for different acanthocephalan species. In this study, acanthocephalans were sampled in marine fish in three localities of the Yucatán Peninsula; adults and cystacanths were recovered from the intestine and body cavity, respectively, of Haemulon plumierii from off the coast of Sisal, Yucatán. Ribosomal DNA sequences (small and large subunits) were used to test the phylogenetic position of the species of the genus Dollfusentis, whereas the mtDNA gene cox 1 was used for assessing species delimitation. The cox 1 analysis revealed an independent genetic lineage, which is recognized herein as a new species, Dollfusentis mayae n. sp. The new species is morphologically distinguished from the other six congeners by having a cylindrical proboscis armed with 22–25 longitudinal rows bearing 12 hooks each. The cystacanths were morphologically identified as Gorgorhynchus medius by having a cylindrical trunk covered with tiny irregular spines on the anterior region, and a cylindrical proboscis armed with 17–18 longitudinal rows of 21 hooks each; small and large subunit phylogenetic analyses yielded G. medius within the family Isthomosacanthidae, suggesting that Gorgorhynchus should be transferred to this family from Rhadinorhynchidae where it is currently allocated.

From music recommendation to assessment of asylum applications, machine-learning algorithms play a fundamental role in our lives. Naturally, the rise of AI implementation strategies has brought to public attention the ethical risks involved. However, the dominant anti-discrimination discourse, too often preoccupied with identifying particular instances of harmful AIs, has yet to bring clearly into focus the more structural roots of AI-based injustice. This paper addresses the problem of AI-based injustice from a distinctively epistemic angle. More precisely, I argue that the injustice generated by the implementation of AI machines in our societies is, in some paradigmatic cases, also a form of epistemic injustice. With a particular focus on AIs employed as gatekeepers of our epistemic resources, this paper shows how their epistemically conformist behaviour is responsible for the marginalisation and the ostracism of minoritarian perspectives. Because it clarifies key structural flaws and weaknesses of current AI design, this paper helps make headway in critical discussion of current AI technologies. And because it forges new theoretical tools to understand forms of epistemic oppression, this paper also contributes to the advancement of feminist theorisation.

In addition to the loss of life, Russian aggression against Ukraine, which began in February 2022, also brings interpersonal losses resulting from the need to emigrate. Parallel to the fighting men, women bear most of the burden of caring for the family. Using in-depth interviews supplemented by questions about adverse childhood experiences and administration of The Centrality of Events Scale and the PTSD Checklist – PCL-5 with 43 Ukrainian women (18–60 years old), we analyzed adaptation to the situation of emigration and the association of their war and earlier experiences with the level of traumatization. Women were interviewed shortly after emigration to the Czech Republic (3–42 week afterward). High levels of adverse childhood experiences and post-traumatic stress symptoms were found. The war was perceived as a currently negative central event associated with traumatic stress symptoms, and 79% of the sample expressed the opinion that the war had changed them. The results of this study suggest an intertwining of previous life experiences with the current need and ability to adapt.

The phenomenon of the ‘coil-stretch’ (C-S) transition, wherein a long-chain polymer initially in a coiled state undergoes a sudden configuration change to become fully stretched under steady elongational flows, has been widely recognized. This transition can display intricate hysteresis behaviours under specific critical conditions, giving rise to unique rheological characteristics in dilute polymer solutions. Historically, microscopic stochastic models and Brownian dynamics simulations have shed light on the underlying mechanisms of the transition by uncovering bistable configurations of polymer chains. Following the initial work by Cerf (J. Chem. Phys., vol. 20, 1952, pp. 395–402), we introduce a continuum model in this study to investigate the C-S transition in a constant uniaxial elongational flow. Our approach involves approximating the unfolding process of the polymer chain as an axisymmetric deformation of an elastic particle. We make the assumption that the particle possesses uniform material properties, which can be represented by a nonlinear, strain-hardening constitutive equation to replicate the finite extensibility of the polymer chain. Subsequently, we analytically solve for the steady-state deformation using a polarization method. By employing this reduced model, we effectively capture the C-S transition and establish its specific correlations with material and geometric properties. The hysteresis phenomena can be comprehended through a force-balance analysis, which involves comparing the externally applied viscous forces with the intrinsic elastic responsive forces. We demonstrate that our model, while simple, unveils rich elastohydrodynamics of the C-S transition.

This paper presents an audiovisual perceptual analysis of the wh-question and wh-exclamation intonation in Brazilian Portuguese using auditory–visual congruent and incongruent stimuli, to investigate the relative importance of each modality in signaling pragmatic meanings. Ten Brazilian Portuguese speakers (five female) were filmed while producing both speech acts 10 times. Next, artificial stimuli were created: audio and visual cues were either matched (audio and video from the same speech act) or mismatched (audio and video from the different speech acts), resulting in 10 congruent and 10 incongruent stimuli of the wh-questions and the wh-exclamations. The perceptual experiment was taken by 36 Brazilians who identified the stimulus as a question or an exclamation. Results from the logistic regression showed that the factor ‘congruence’ was significant and had a significant interaction with ‘speakers’, which means that the congruent stimuli increased the comprehension of the Brazilian Portuguese wh-questions and wh-exclamations. In contrast, the incongruent stimuli tended to lower listeners’ identification, but to a degree depending on individual speakers’ strategies. Although variation in the accuracy of expressing both speech acts was also found across speakers, this study corroborates that the visual channel impacts the perceptual identification of the pragmatic intonation function of distinguishing sentence mode.

Soft intertwined channel systems are frequently found in fluid flow networks in nature. The passage geometry of these systems can deform due to fluid flow, which can cause the relationship between flow rate and pressure drop to deviate from the Hagen–Poiseuille linear law. Although fluid–structure interactions in single deformable channels have been extensively studied, such as in Starling's resistor and its variations, the flow transport capacity of an intertwined channel with multiple self-intersections (a ‘hydraulic knot’), is still an open question. We present experiments and theory on soft hydraulic knots formed by interlinked microfluidic devices comprising two intersecting channels separated by a thin elastomeric membrane. Our experiments show flow–pressure relationships similar to flow limitation, where the limiting flow rate depends on the knot configuration. To explain our observations, we develop a mathematical model based on lubrication theory coupled with tension-dominated membrane deflections that compares favourably with our experimental data. Finally, we present two potential hydraulic knot applications for microfluidic flow rectification and attenuation.

Six species of freshwater turtles dominate the Chaco-Pampa Plain in southern South America and their parasites have been relatively understudied, with most records concentrated in Brazil. Particularly in Argentina, there are only scattered records of parasites for most of the turtles that inhabit the region, leaving a large knowledge gap. The purpose of the present contribution is to increase the knowledge of the internal parasites of six species of freshwater turtles from Argentina, after 15 years of fieldwork, by providing new hosts and additional geographic records for many host-parasite relationships. Some molecular sequences of the studied parasites were provided as a tool for better species identification. We processed 433 stomach and fecal samples from live individuals and visceral and soft tissue samples from 54 dissected turtles collected from a wide range and different ecoregions. We found 6230 helminths belonging to 18 taxa (one cestode, 11 digeneans and six nematodes). Fourteen new parasite-host associations are reported here, and for the first time parasites are recorded for Phrynops williamsi. This work contributes significantly to the knowledge of the parasitofauna in freshwater turtles in Argentina, providing a detailed list of parasites present in each turtle species and reporting molecular characters for future studies.

In this note, we study the Li coefficients $\lambda _{n,a}$ for the quadrilateral zeta function. Furthermore, we give an arithmetic and asymptotic formula for these coefficients. Especially, we show that for any fixed $n \in {\mathbb {N}}$, there exists $a>0$ such that $\lambda _{2n-1,a}> 0$ and $\lambda _{2n,a} < 0$.

This article explores the politics which lay behind the Presbyterian petitioning campaigns in Lancashire and Cheshire during 1646. Focusing particularly upon clerical activists, this article traces the linkages back to the petitioning campaigns of 1641-2 and highlights the continuities in both personnel and an impulse for accommodation. The article unravels the networks which stretched between London and north-western England, and investigates how Presbyterian politics in London in 1646 might have influenced the Lancashire and Cheshire campaigns for a Presbyterian settlement of the Church. Finally, the article comments upon why the Lancashire campaign succeeded when the Cheshire campaign did not.