This paper presents bifurcation analyses characterising the nonlinear dynamics of fully developed laminar annular jets with respect to the centrebody diameter ${ {d}}$, Reynolds number ${ {Re}}$, and swirl ratio ${ {S}}$. Similar flows appear in numerous applications and feature a vibrant range of topological and dynamical characteristics associated with phenomena including shear layer separation and vortex breakdown. Our results begin by describing the non-monotonic evolution of the axisymmetric jet's steady topology under varying ${ {S}}$. In accord with earlier reports, the jet progresses through a sequence of wake, breakdown and wall jet regimes in a qualitatively similar manner across a wide span of ${ {d}}$ and ${ {Re}}$ values. In the wake regime, the non-swirling jet bifurcates to a plane-symmetric, but not axisymmetric, steady flow pattern beyond a ${ {d}}$-dependent critical ${ {Re}}$ value. With further increase in ${ {Re}}$, the steady non-swirling jet destabilises subsequently via multiple distinct Hopf bifurcations. Introducing ${ {S}}>0$ to the jet also induces unsteadiness by twisting the singly azimuthally periodic ($|m|=1$) asymmetric wake structure and causing it to precess periodically in time about the central axis. Intermediate swirl stabilises this unsteady dynamics and restores the jet's axisymmetry. This stabilising effect is then reversed in the breakdown regime at higher ${ {S}}$, where a variety of different $|m|=1$ and $|m|=2$ instabilities bifurcate from the steady flow as ${ {S}}$ is increased. Several instances of hysteresis and subcritical behaviour are reported and discussed, including one that manifests precessing vortex core oscillations.

Flow data are often decomposed using proper orthogonal decomposition (POD) of the space–time separated form, $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (t\right )\boldsymbol {\phi }_j\left (\boldsymbol {x}\right )$, which targets spatially correlated flow structures in an optimal manner. This paper analyses permuted POD (PPOD), which decomposes data as $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (\boldsymbol {n}\right )\boldsymbol {\phi }_j\left (s,t\right )$, where $\boldsymbol {x}=(s,\boldsymbol {n})$ is a general spatial coordinate system, $s$ is the coordinate along the bulk advection direction and $\boldsymbol {n}=(n_1,n_2)$ are along mutually orthogonal directions normal to the advection characteristic. This separation of variables is associated with a fundamentally different inner product space for which PPOD is optimal and targets correlations in $s,t$ space. This paper presents mathematical features of PPOD, followed by analysis of three experimental datasets from high-Reynolds-number, turbulent shear flows: a wake, a swirling annular jet and a jet in cross-flow. In the wake and swirling jet cases, the leading PPOD and space-only POD modes focus on similar features but differ in convergence rates and fidelity in capturing spatial and temporal information. In contrast, the leading PPOD and space-only POD modes for the jet in cross-flow capture completely different features – advecting shear layer structures and flapping of the jet column, respectively. This example demonstrates how the different inner product spaces, which order the PPOD and space-only POD modes according to different measures of variance, provide unique ‘lenses’ into features of advection-dominated flows, allowing complementary insights.

Do labor unions still motivate their members to participate in politics, or have social and economic changes undermined their political importance? This question is important to revisit, as globalization and economic reform have weakened many popular sector organizations in Latin America, reducing some to mere patronage machines. This article examines the case of the teachers’ union in Bogotá, Colombia to assess whether and how labor unions are able to promote the political activation of their members. Employing a multimethod research design that begins with a quantitative analysis of a survey of Colombian teachers, this study finds that union affiliation is associated with higher levels of motivation to vote. It then uses evidence from interviews to show how union advocacy and internal elections for leadership positions shape political behavior, contributing to civic engagement. This research engages with broader debates about democratic quality and political representation in contemporary Latin America.

This paper characterises the steady and time-periodic behaviour of swirling jets using numerical bifurcation analysis. Its objective is to elucidate the dynamics of fully developed, unconfined, laminar swirling jets under variations in the Reynolds number $\textit {Re}$ and swirl ratio $S$. Within the $(0,0)\leq (\textit {Re},S)\leq (300,3)$ range, the steady, axisymmetric flow exhibits several distinct patterns ranging from a quasi-columnar jet along the central axis at low $S$ to a radial jet attached to the containing wall at high $S$ with various forms of vortex breakdown in between. A cusp bifurcation appears in the steady solution manifold which triggers bistable behaviour due to a competition between inner and outer low pressure regions associated with vortex breakdown and entrainment of the ambient fluid, respectively. Instability of the steady flow is linked to eigenmodes which are singly ($|m|=1$) or doubly ($|m|=2$) azimuthally periodic, although additional instabilities with other azimuthal wavenumbers occur at $(\textit {Re},S)$-values beyond the leading neutral curves. The various branches of limit cycle solutions stemming from these neutral curves are associated with both super- and sub-critical Hopf bifurcations. The resulting unsteady flow fields exhibit a wide array of rotating, three-dimensional flow structures, and comparisons between the time-averaged and steady flow patterns highlight the role of these unsteady nonlinear interactions on the overall behaviour of swirling jets. Similarities and differences between this laterally unconfined jet and broader classes of swirling flows, including confined swirling jets and unconfined vortex models, are also discussed.

Deposits linked to abandonment have been widely recorded across the Maya lowlands, associated with the final activities occurring in ceremonial areas of Classic Maya centers. Various models have been applied to explain the activities that lie behind the formation of these contexts, including those linked to rapid abandonment (e.g., warfare) and others focused on more protracted events (termination rituals, and/or pilgrimages). Here, we assess Bayesian models for three chronological scenarios of varying tempo to explain the formation of peri-abandonment deposits at Baking Pot, Belize. Using stratigraphic information from these deposits, hieroglyphic dates recovered on artifacts, and direct dates on human skeletal remains and faunal remains from distinct layers in three deposits in Group B at Baking Pot, we identify multiple depositional events that spanned the eighth to ninth centuries AD. These results suggest that the processes associated with the breakdown of institutionalized rulership and its command of labor to construct and maintain ceremonial spaces were protracted at Baking Pot, with evidence for the final depositional activity dated to the mid-to-late ninth century. This interval of deposition was temporally distinct from the earlier deposition(s) in the eighth century. Together, these data offer a detailed view of the end of the Classic period at Baking Pot, in which the ceremonial spaces of the site slowly fell into disuse over a period of more than a century.

This article emerged as the human species collectively have been experiencing the worst global pandemic in a century. With a long view of the ecological, economic, social, and political factors that promote the emergence and spread of infectious disease, archaeologists are well positioned to examine the antecedents of the present crisis. In this article, we bring together a variety of perspectives on the issues surrounding the emergence, spread, and effects of disease in both the Americas and Afro-Eurasian contexts. Recognizing that human populations most severely impacted by COVID-19 are typically descendants of marginalized groups, we investigate pre- and postcontact disease vectors among Indigenous and Black communities in North America, outlining the systemic impacts of diseases and the conditions that exacerbate their spread. We look at how material culture both reflects and changes as a result of social transformations brought about by disease, the insights that paleopathology provides about the ancient human condition, and the impacts of ancient globalization on the spread of disease worldwide. By understanding the differential effects of past epidemics on diverse communities and contributing to more equitable sociopolitical agendas, archaeology can play a key role in helping to pursue a more just future.

Investigations at Xunantunich indicate that this major Belize River Valley site rose rapidly to regional prominence during the Late Classic Hats' Chaak phase (a.d. 670–780). While the social, political, and economic reasons for Xunantunich's relatively late and rapid rise are still not fully understood, it has been suggested that this ascent was a direct result of either a patron-client relationship with, or owing to direct control by, the larger primary center of Naranjo in neighboring Guatemala. In this paper, we evaluate previous arguments for this proposed dynamic relationship between the two sites, and we discuss the political implications of more recently acquired data in our assessment of this relationship.

Shifting from shellfish collecting to fishing as a primary coastal foraging strategy can allow hunter-gatherers to obtain more food and settle in larger populations. On California's northern Channel Islands (NCI), after the development of the single-piece shell fishhook around 2500 cal BP, diet expanded from primarily shellfish to include nearshore fishes in greater numbers. During the Medieval Climatic Anomaly (1150–600 cal BP), settlement on the islands condensed to a small number of large coastal villages with high population densities supported largely by nearshore fish species including rockfishes, surfperches, and señoritas. Faunal data from five sites on western Santa Rosa Island (CA-SRI-15, -31, -97, -313, and -333) demonstrate an increase in nearshore fishing through time. We argue that demographic changes that occurred on the northern Channel Islands were accompanied by changes in subsistence strategies that were related in part to risk of failure when attempting to acquire different resources. As population density increased, the low-risk strategy of shellfish harvesting declined in relative importance as a higher-risk strategy of nearshore fishing increased. While multiple simultaneous subsistence strategies are frequently noted among individual hunter-gatherer communities in the ethnographic record, this study provides a framework to observe similar patterns in the archaeological record.

Archaeological investigations by the Belize Valley Archaeological Reconnaissance Project at Cahal Pech uncovered several Terminal Classic (a.d. 750–900) peri-abandonment deposits and activity areas at this Belize River Valley center. The deposits contained a diverse assemblage of cultural remains located above and between collapsed architecture, associated with evidence for burning activities. In the past, archaeologists have generally interpreted similar assemblages as “problematic deposits”—“de facto” refuse (garbage)—as associated with building termination and desecration, or as evidence for rapid abandonment during the violent destruction of these ancient cities. It is argued here that the microstratigraphic excavation and contextual analysis of these features provide limited support for these explanations. Alternatively, we suggest that the deposits are more likely associated with peri-abandonment rituals that were conducted by a reduced remnant population at Cahal Pech, or by small groups who continued to reside in the site's periphery during the last stages of the Terminal Classic period.

Organizations all over the world, both national and international, gather demographic data so that the progress of nations and peoples can be tracked. This data is often made available to the public in the form of aggregated national level data or individual responses (microdata). Product designers likewise conduct surveys to better understand their customer and create personas. Personas are archetypes of the individuals who will use, maintain, sell or otherwise be affected by the products created by designers. Personas help designers better understand the person the product is designed for. Unfortunately, the process of collecting customer information and creating personas is often a slow and expensive process. In this paper, we introduce a new method of creating personas, leveraging publicly available databanks of both aggregated national level and information on individuals in the population. A computational persona generator is introduced that creates a population of personas that mirrors a real population in terms of size and statistics. Realistic individual personas are filtered from this population for use in product development.

Recent observations of globular clusters encourage to revise some aspects of the traditional paradigm, in which they were considered to be isotropic in velocity space and non-rotating. However, the theory of collisionless spheroids with some kinematic richness has seldom been studied. We present here a further step in this direction, owing to new results regarding the linear stability of rotating Plummer spheres, with varying anisotropy in velocity space and total amount of angular momentum. We extend the well-known radial orbit instability to rotating systems, and discover a new regime of instability in fast rotating, tangentially anisotropic systems.

Recent observations of globular clusters imposed major revisions to the previous paradigm, in which they were considered to be isotropic in velocity space and non-rotating. However, the theory of collisionless spheroids with some kinematic richness has seldom been studied. We present here a first step in this direction, owing to new results regarding the linear stability of rotating Plummer spheres, with varying anisotropy in velocity space and total amount of angular momentum. We extend the well-known radial orbit instability to rotating systems, and discover a new regime of instability in fast rotating, tangentially anisotropic systems.

Contemporary dictionary-based approaches to sentiment analysis exhibit serious validity problems when applied to specialized vocabularies, but human-coded dictionaries for such applications are often labor-intensive and inefficient to develop. We demonstrate the validity of “minimally-supervised” approaches for the creation of a sentiment dictionary from a corpus of text drawn from a specialized vocabulary. We demonstrate the validity of this approach in estimating sentiment from texts in a large-scale benchmarking dataset recently introduced in computational linguistics, and demonstrate the improvements in accuracy of our approach over well-known standard (nonspecialized) sentiment dictionaries. Finally, we show the usefulness of our approach in an application to the specialized language used in US federal appellate court decisions.