This paper focuses on quadratic Hom–Leibniz algebras, defined as (left or right) Hom–Leibniz algebras equipped with symmetric, non-degenerate, and invariant bilinear forms. In particular, we demonstrate that every quadratic regular Hom–Leibniz algebra is symmetric, meaning that it is simultaneously a left and a right Hom–Leibniz algebra. We provide characterizations of symmetric (resp. quadratic) Hom–Leibniz algebras. We also investigate the $\mathrm{T}^*$-extensions of Hom–Leibniz algebras, establishing their compatibility with solvability and nilpotency. We study the equivalence of such extensions and provide the necessary and sufficient conditions for a nilpotent quadratic Hom–Leibniz algebra to be isometric to a $\mathrm{T}^*$-extension. Furthermore, through the procedure of double extension, which is a central extension followed by a generalized semi-direct product, we get an inductive description of all quadratic regular Hom–Leibniz algebras, allowing us to reduce their study to that of quadratic regular Hom–Lie algebras. Finally, we construct several non-trivial examples of symmetric (resp. quadratic) Hom–Leibniz algebras.

We consider a population consisting of two types of individuals, each of which can produce offspring on two different islands (in particular, the islands can be interpreted as active or dormant individuals). We model the evolution of the population of each type using a two-type Feller diffusion with immigration and study the frequency of one type on each island, when the total population size on each island is forced to be constant at a dense set of times. This leads to the solution of a stochastic differential equation, which we call the asymmetric two-island frequency process. We derive properties of this process and obtain a large population limit as the total size of each island tends to infinity. Additionally, we compute the fluctuations of the process around its deterministic limit. We establish conditions under which the asymmetric two-island frequency process has a moment dual. The dual is a continuous-time two-dimensional Markov chain that can be interpreted in terms of mutation, branching, pairwise branching, coalescence, and a novel mixed selection–migration term.

A paradox has emerged in the growing literature on the legacies of the precolonial past: areas home to precolonial centralized polities are associated with beneficial long-run outcomes in some studies, but harmful ones elsewhere. This article introduces an original dataset of precolonial African states in the nineteenth century to explain this seeming contradiction. By developing a typology of precolonial statehood, I show that there is no single legacy of the precolonial past. Rather, statehood only increases civil conflict where political power was highly concentrated in a polity. Where political authority was more diverse, conflict prevalence is lower. A largely inverse pattern holds for development outcomes. These findings, and the associated dataset, suggest promising new pathways for understanding not only the legacies of Africa’s precolonial past, but the study of comparative state-building, which has largely relegated the African experience to a single story.

Anomalous origin of the left main coronary artery from the pulmonary artery (ALCAPA) is a rare congenital cardiovascular defect in young children. It is typically diagnosed through direct visualisation of the left coronary artery arising from the main pulmonary artery or observing retrograde flow from the left coronary artery to the main pulmonary artery at angiography or echocardiography. This case highlights the diagnostic challenges of ALCAPA in young kids, where antegrade left coronary artery flow due to pulmonary hypertension masked the anomalous origin on echocardiography. Despite the absence of congenital shunts, long-term severe mitral regurgitation led to pulmonary hypertension, presenting with atypical imaging features. The boy accepted a successful surgical reimplantation of the left coronary artery to the aorta with concomitant mitral valve repair and had significant resolution of symptoms.

This article explores urban memory politics in Komsomolsk-na-Amure – a military-industrial stronghold erected in Russia’s Far East in the 1930s with the participation of Komsomol volunteers from across the USSR. Known as pervostroiteli or ‘first-builders’, Komsomolsk’s founders became the city’s first chroniclers, who played an enduring role in shaping the city’s heroic popular image. I argue that the Soviet government’s active efforts to glorify Komsomol builders endowed the figures of pervostroiteli with unparalleled moral authority, which participants in the city’s early development used to curate their own memorialization and local historical politics.

This article proposes a novel method for estimating quantile regression models that account for sample selection. Unlike the approach by Arellano and Bonhomme (2017, Econometrica 85(1), 1–28; hereafter referred to as AB17), which employs a parametric selection equation, our method utilizes a standard binary quantile regression model to handle the selection issue, thereby accommodating general heterogeneity in both the selection and outcome equations. We adopt a semiparametric estimation technique for the outcome quantile regression by integrating local moment conditions, resulting in $\sqrt {n}$-consistent estimators for the quantile coefficients and copula parameter. Monte Carlo simulation results demonstrate that our estimator performs well in finite samples. Additionally, we apply our method to examine the wage distribution among women using a randomly simulated sample from the US General Social Survey. Our key finding is the presence of significant positive selection among women in the US, which is notably more pronounced than the estimates produced by the AB17’s model.

Numerous oligochaete cocoons, previously interpreted as cladoceran crustaceans, are described from the upper Permian (Lopingian) freshwater Karaungir Lagerstätte in eastern Kazakhstan. The cocoons appear as small, wrinkled, ovoid capsules, prolonged into a neck at one pole and a long slender stalk at the other; both extensions are covered with minute ridges forming a striated pattern. By their size range and distinct (although limited) morphological features, the cocoons are identical to those of the extant freshwater genus Rhynchelmis Hoffmeister, 1843 (Oligochaeta: Lumbriculidae) and thus represent the oldest undoubted record of the Clitellata. We interpret Archedaphnia Smirnov, 1970 (= Propleuroxus Smirnov, 1970, n. syn.) as a genus for fossil microdrile oligochaete cocoons similar to those of Rhynchelmis, and synonymize all five species described in Archedaphnia and Propleuroxus under Archedaphnia kazakhstanica Smirnov, 1970 sensu lato.

This article explores nuclear cultural heritage-making as a spatial activity in the context of nuclear secrecy and restricted access. It focuses on the closed city Sarov, formerly Arzamas-16, the birthplace of Soviet nuclear weapons. Since the end of the Cold War, Sarov has cultivated its image as a heritage site, opening a Museum of Nuclear Weapons, pioneering nuclear scientists and local history, as well as reconstructing religious sites. Based on interviews and fieldwork in Russia, this article maps the hitherto unstudied development of cultural heritage infrastructure in a closed city and its diverse and conflicting political uses and assesses the ambivalence of nuclear material culture as it is selectively preserved and deployed to achieve these conflicting goals.

This article uses amphora quantification and regression analysis to trace economic changes in the Mediterranean between the Principate (27 bc to ad 284) and Late Antiquity. It indicates that, during the Principate, there was a clear pattern of amphora distribution across the Mediterranean, which can be explained by the predominance of market forces among the factors governing trade. In contrast, the weak correlation between exports and prices observed in Late Antiquity suggests a significant shift in the underlying principles of trade during this period.

One of the objectives of the Trump administration’s economic policy is to revitalize the American industrial fabric and create a large number of high-paying blue-collar jobs. However, the main instrument used to achieve this goal – tariff protection – is a point of contention. We discuss the relevance of the recently introduced policy for an emblematic sector: the automotive industry. The latter operates highly integrated production chains where intermediate products frequently cross borders to circulate within a ‘Big Factory’ encompassing production sites located mainly in Mexico, Canada, and the USA, but also in other countries. The imposition of a 25% tariff on finished cars and their parts could lead to significant disruptions for consumers and producers alike. The lessons learned from the automotive sector retain much of their relevance for other areas of the US economy.

In the absence of a nationwide adequate solution, the lot of displaced workers could be improved through place-based workforce transition programmes limited to disadvantaged areas. Industrial policy measures targeting disadvantaged communities and regions could also be envisaged. In this case, however, it would be necessary to deploy a variety of instruments adapted to the circumstances and to take into account, as far as possible, the interests of trading partners in order to avoid conflicts.

The challenge of addressing contentious and repressive histories in authoritarian regimes that have undergone post-totalitarian transitions presents precious opportunities for historical justice, as the representation of history and the production of historiography are decentralized from the central state. Using the production of Chinese local gazetteers in post-Mao China as a case and drawing upon a combination of historiographical, archival, and field methods, we investigate three critical negotiation fields where gazetteer compilers, who also held government ranks, interacted with central leaders and other local bureaucracies to exert discretionary control over local historical production within their jurisdictions. This decentralized negotiation over historiography illuminates the intricate interplay between ideology, agency, and tradition in the production process of the Chinese county gazetteers, offering nuanced insights into modern Chinese history and the complexities of historiographical writing under authoritarian governance. Overall, our article shows that knowledge production under authoritarian rule is more interactive and horizontal than thought, and that historiographical writing can adapt to and challenge authority in pursuit of historical justice.

This study investigated intestinal retraction and regeneration in the Japanese sea cucumber (Apostichopus japonicus) during high water temperature periods and compared these morphological changes with those during low water temperature conditions in the subarctic. We examined the intestinal morphology of A. japonicus during the aestivation and winter low-activity periods under natural-like environmental conditions, including the water temperature, photoperiod, and seawater quality. Water temperatures ranged from −1.1°C to 29.2°C. Aestivating individuals were observed from July to September when water temperatures were high. During this period, intestinal length, weight, and thickness decreased, with signs of recovery by November. The mucosal layer height also decreased, with partial loss or disappearance. In contrast, no intestinal retraction occurred from January to March at low temperatures. Additionally, under high temperatures, the muscle layer thinned significantly, and lipofuscin-like granules, thought to be residual material from intracellular digestion by lysosomes, appeared in the submucosal layer. A common feature in both temperature periods was the presence of haemolymph-like cells in the submucosal layer near the mucosa. These findings suggest that intestinal retraction and degeneration in A. japonicus under high temperatures may result from energy conservation mechanisms, fasting, or reduced food intake during aestivation and winter dormancy.

When evaluating competing hypotheses in archaeology, researchers frequently invoke the principle of parsimony, which states that simpler hypotheses should be preferred. However, the criteria for measuring simplicity and the rationale for labeling a hypothesis as most parsimonious often remain unclear. More broadly, the epistemic merit of parsimony and its relevance to archaeological reasoning are generally assumed but rarely clarified. This article explores how archaeologists use parsimony in ethnographic analogy and formal model selection. In the first context, it is usually uncertain how simplicity should be measured or why increased simplicity raises the plausibility of an ethnographic analogy. We contend that discussions of ethnographic analogy are better characterized under inference to the best explanation, where parsimony is only one heuristic among others. In the second context, simplicity is assessed by the relative complexity, rather than the quantity, of postulates in a model. This approach to parsimony, which does track plausibility under certain conditions, helps prevent false positives in archaeological interpretation. However, it also heightens the risk of rejecting alternative, complex causes. We argue that parsimony can aid in evaluating the relative likelihood of competing models and, more importantly, serve as a guide to clarify the complex histories of archaeological phenomena.