Head porterage, popularly known in Ghana as Kayayei, has been an old economic venture for young girls and women who migrate from the northern to the southern part of the country. Even though Head Porters view Kayayei as a source of livelihood, conditions such as the outbreak of the 2019 coronavirus disease (COVID-19) further worsened their sexual vulnerabilities, as well as their autonomy to make decisions on contraceptive use. Head Porters, as a term defined in this study, refers to women aged 15 years or older who carry loads from one point of the town to another for a fee. The study is qualitative and used both purposive and simple random sampling in recruiting 120 Head Porters for focus group discussions. The study was planned and implemented in three zones in Kumasi, the Ashanti Regional capital of Ghana, during the lockdown period (between March and April 2020). Factors such as access to contraceptives, self-reported sexual desire, and partner desire to use condoms, sexual demands, and the impact of the COVID-19 pandemic on contraceptive access were assessed. Sexual demands increased during the COVID-19 period, with most Head Porters indicating they used fewer condoms and contraceptives during the same period. The desire to use a condom was limited among both Head Porters and their partners, and access to contraceptives was hampered by fear of getting infected by COVID-19 from a health worker at family planning clinics. The COVID-19 pandemic significantly increased the sexual and economic vulnerabilities of Head Porters in Ghana and impacted their access to family planning services. Governmental and international organizations need to start developing intervention programs for vulnerable populations such as Head Porters before future disease outbreaks.

We find the optimally time-dependent (OTD) orthogonal modes about a time-varying flow generated by a strong gust vortex impacting a NACA 0012 airfoil. This OTD analysis reveals the amplification characteristics of perturbations about the unsteady base flow and their amplified spatiotemporal structures that evolve over time. We consider four time-varying laminar base flows in which a vortex with a strength corresponding to the gust ratio $G$ of $\{-1,-0.5,0.5,1\}$ impinges on the leading edge of the airfoil at an angle of attack of $12^\circ$. In these cases, the impingement of the strong gust vortex causes massive separation and the generation of large-scale vortices around the airfoil within two convective time units. As these flow structures develop around the airfoil on a short time scale, the airfoil experiences large transient vortical lift variations in the positive and negative directions that are approximately five to ten times larger than the baseline lift. The highly unsteady nature of these vortex–airfoil interactions necessitates an advanced analytical technique capable of capturing the transient perturbation dynamics. For each of the considered gust ratios, the OTD analysis identifies the most amplified region to perturbations, the location of which changes as the wake evolves differently. For interactions between a moderate positive vortex gust ($G=0.5$) and the airfoil, the area where perturbations are amplified transitions from the leading-edge vortex (LEV) sheet to the forming LEV. Later, this most amplified structure becomes supported in the airfoil wake directly behind the trailing edge. In contrast, a strong vortex gust ($G=\pm 1$) encountered by the airfoil shows the most amplified OTD mode to appear around the core of the shed vortices. This study provides an analysis technique and fundamental insights into the broader family of unsteady aerodynamic problems.

When we open a random political science journal, we have a roughly two-to-one chance that the article is written by a man. Beyond this general finding, we know little about the gender gaps within political science knowledge production: Are women more represented in lower- or higher-ranked journals? Do they publish more single-authored or multiauthored papers? Do they publish more content in some fields than in others? This article answers these questions by analyzing an original dataset based on the International Political Science Abstracts (a peer-reviewed academic journal) from 2022 consisting of more than 7,000 articles and more than 13,000 authors in political science from around the world. We find no difference in the percentage of female authors between higher- and lower-ranked journals. We find a slightly higher propensity among women to publish in teams. Regarding subfields of study, women are particularly underrepresented in political theory, in which they publish only 21.6% of all published articles—which is an approximate 12-percentage-point deviation from the overall average.

The current study examines the application of the Pediatric-Buccal-Epigenetic (PedBE) clock, designed for buccal epithelial cells, to endothelia. We evaluate the association of PedBE epigenetic age and age acceleration estimated from human umbilical vein endothelial cells (HUVECs) with length of gestation and birthweight in a racially and ethnically diverse sample (analytic sample n = 333). PedBE age was positively associated with gestational age at birth (r = 0.22, p < .001) and infant birth weight (r = 0.20, p < .001). Multivariate models revealed infants with higher birth weight (adjusted for gestational age) had greater PedBE epigenetic age acceleration (b = 0.0002, se = 0.0007, p = 0.002), though this effect was small; findings were unchanged excluding preterm infants born before 37 weeks’ gestation. In conclusion, the PedBE clock may have application to endothelial cells and provide utility as an anchoring sampling point at birth to examine epigenetic aging in infancy.

We derive leading-order governing equations and boundary conditions for a sheet of viscous fluid retracting freely under surface tension. We show that small thickness perturbations about a flat base state can lead to regions of compression, where one or both of the principal tensions in the sheet becomes negative, and thus drive transient buckling of the sheet centre-surface. The general theory is applied to the simple model problem of a retracting viscous disc with small axisymmetric thickness variations. Transient growth in the centre-surface is found to be possible generically, with the dominant mode selected depending on the imposed initial thickness and centre-surface perturbations. An asymptotic reduction of the boundary conditions at the edge of the disc, valid in the limit of large normalised thickness perturbations, reduces the centre-surface evolution equation to an ordinary differentional equation (ODE) eigenvalue problem. Analysis of this eigenvalue problem leads to insights such as how the degree of transient buckling depends on the imposed thickness perturbation and which thickness perturbation gives rise to the largest transient buckling.

The tensor notation used in several areas of mathematics is a useful one, but it is not widely available to the functional programming community. In a practical sense, the (embedded) domain-specific languages (dsls) that are currently in use for tensor algebra are either 1. array-oriented languages that do not enforce or take advantage of tensor properties and algebraic structure or 2. follow the categorical structure of tensors but require the programmer to manipulate tensors in an unwieldy point-free notation. A deeper issue is that for tensor calculus, the dominant pedagogical paradigm assumes an audience which is either comfortable with notational liberties which programmers cannot afford, or focus on the applied mathematics of tensors, largely leaving their linguistic aspects (behaviour of variable binding, syntax and semantics, etc.) for the reader to figure out by themselves. This state of affairs is hardly surprising, because, as we highlight, several properties of standard tensor notation are somewhat exotic from the perspective of lambda calculi. We bridge the gap by defining a dsl, embedded in Haskell, whose syntax closely captures the index notation for tensors in wide use in the literature. The semantics of this edsl is defined in terms of the algebraic structures which define tensors in their full generality. This way, we believe that our edsl can be used both as a tool for scientific computing, but also as a vehicle to express and present the theory and applications of tensors.

Electro-osmotic flow (EOF) in nanochannels exhibits a puzzling non-monotonic dependence on salt concentration, which contrasts with observations in microchannels and remains not fully understood. In this work, we address this phenomenon through a theoretical investigation of EOF in $\mathrm{pH}$-regulated channels. New analytical approximations for electrostatic potential, EOF profile and electro-osmotic mobility beyond the Debye–Hückel limit are derived through asymptotic analysis. Our findings reveal that the surface electrostatic potential is independent of the channel size only when the half-channel size exceeds the Gouy–Chapman length. In contrast, surface ionization and net charge distribution play more crucial roles in EOF at the nanoscale, as they govern both the magnitude and the spatial distribution of the Coulomb driving force. As salt concentration increases, EOF velocity initially rises due to enhanced surface ionization, followed by a decline attributed to increased wall shear stress. This work provides key insights for EOF applications in nanofluidics and biomedical devices, and deepens the understanding of electrokinetic phenomena influenced by $\mathrm{pH}$-regulation effects.

In 1974, the International Species Information System (ISIS) was launched as a computerised database for zoo animals. Developed by a small group in Minneapolis, ISIS is now used by over 1,300 zoos on five continents and recognised as a crucial tool for ex situ conservation. The founders aimed to transform long-standing global patterns of zoo animal management. Rather than places where wild-caught animals went to die, they envisioned zoos as interconnected hubs supporting the global breeding and survival of endangered species. This article examines how the ‘infrastructural globalism’ of ISIS took shape. At first sight, the system appears to be a universal instrument for collecting neutral data. Yet, using the lens of ‘infrastructural inversion’ and examining the legal, socio-political, and scientific contexts in which it was developed, the article highlights how locally rooted ambitions and global competitions shaped its design and operation. Despite its aura of global reach, the effectiveness of ISIS relied on continuous local human effort, which explains its limitations. On a broader level, the history of ISIS reminds us that the influence of infrastructural globalism extends to non-human animals, and the ways they move around the world.

The muscular restructuring and loss of function that occurs during a transfemoral amputation surgery has a great impact on the gait and mobility of the individual. The hip of the residual limb adopts a number of functional roles that would previously be controlled by lower joints. In the absence of active plantar flexors, swing initiation must be achieved through an increased hip flexion moment. The high activity of the residual limb is a major contributor to the discomfort and fatigue experienced by individuals with transfemoral amputations during walking. In other patient populations, both passive and active hip exosuits have been shown to positively affect gait mechanics. We believe an exosuit configured to aid with hip flexion could be well applied to individuals with transfemoral amputation. In this article, we model the effects of such a device during whole-body, subject-specific kinematic simulations of level ground walking. The device is simulated for 18 individuals of K2 and K3 Medicare functional classification levels. A user-specific device profile is generated via a three-axis moment-matching optimization using an interior-point algorithm. We employ two related cost functions that reflect an active and passive form of the device. We hypothesized that the optimal device configuration would be highly variable across subjects but that variance within mobility groups would be lower. From the results, we partially accept this hypothesis, as some parameters had high variance across subjects. However, variance did not consistently trend down when dividing into mobility groups, highlighting the need for user-specific design.

What does it mean to be a brave woman? In 2020, we saw Belarusian women take to the streets dressed in white to oppose the violent dictatorship that had been in power for twenty-six years. In 2021, our television screens showed the Fall of Kabul, and the takeover by Taliban fighters, who overnight began to reverse decades of women’s empowerment. In response, and despite the risks, women demonstrators took to the streets in Kabul to demand their rights to work, education, and political participation. And in late 2022, we saw Iranian women fight for freedom, cutting their hair and burning their headscarves as they called for women’s rights in the context of brutal repression. These are but a handful of the myriad examples of women transgressing what is societally expected of them. They go out into the streets, they post on social media, they protest governments and make demands for change. Around the world, we see women being brave. They do so at great personal risk, and often when the potential benefits of being brave are infinitesimally small.