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“Spanish” Casta paintings in nineteenth-century Britain
No full textCasta painting, the distinctive Hispanic genre that depicts bi-racial families, has been well-studied by scholars for what it reveals about colonial Latin America. We study its reception in nineteenth-century Britain, which is where some of the earliest known examples of these paintings first appear in the historical record. As we show, they were consistently ascribed to early-modern Spanish artists such as Velázquez. Taking seriously such misattributions reveals what nineteenth-century Britons understood by Spanish art and helps recover the period eye that made them plausible. Misattributions are not mere mistakes to be corrected, but important subjects in their own right
Where the bee sucks : a dynamic Bayesian network approach to decision support for pollinator abundance strategies
Get PDFFor policymakers wishing to make evidence-based decisions, one of the challenges is how to combine the relevant information and evidence in a coherent and defensible manner in order to formulate and evaluate candidate policies. Policymakers often need to rely on experts with disparate fields of expertise when making policy choices in complex, multi-faceted, dynamic environments such as those dealing with ecosystem services. The pressures affecting the survival and pollination capabilities of honey bees (Apis mellifera), wild bees, and other pollinators is well documented, but incomplete. In order to estimate the potential effectiveness of various candidate policies to support pollination services, there is an urgent need to quantify the effect of various combinations of variables on the pollination ecosystem service, utilising available information, models and expert judgement. In this paper, we present a new application of the integrating decision support system methodology, using dynamic Bayesian networks, for combining inputs from multiple panels of experts to evaluate policies to support an abundant pollinator population
Exact solutions for the Erdos-Rothschild problem
Get PDFLet k:=(k1,…,ks) be a sequence of natural numbers. For a graph G, let F(G;k) denote the number of colourings of the edges of G with colours 1,…,s such that, for every c∈{1,…,s}, the edges of colour c contain no clique of order kc. Write F(n;k) to denote the maximum of F(G;k) over all graphs G on n vertices. There are currently very few known exact (or asymptotic) results for this problem, posed by Erdős and Rothschild in 1974. We prove some new exact results for n→∞:
(i) A sufficient condition on k which guarantees that every extremal graph is a complete multipartite graph, which systematically recovers all existing exact results.
(ii) Addressing the original question of Erdős and Rothschild, in the case k=(3,…,3) of length 7, the unique extremal graph is the complete balanced 8-partite graph, with colourings coming from Hadamard matrices of order 8.
(iii) In the case k=(k+1,k), for which the sufficient condition in (i) does not hold, for 3≤k≤10, the unique extremal graph is complete k-partite with one part of size less than k and the other parts as equal in size as possible
Back to the stone age : Europe's mainstream right and climate change
Get PDFWhile populist radical right parties’ stances on climate change are well‐researched, accounts of Europe's mainstream right parties’ actions in this policy area are less common. This article provides a survey of the approach of four European centre‐right parties—the Christian Democratic Union in Germany, the Moderate Party in Sweden, the People's Party in Spain and the Austrian People's Party—to climate change in recent years. It examines some of the key strategic challenges that mainstream right parties are facing and their implications for climate policy, finding evidence of common approaches among this party family to climate policy
ADP-based optimal control for discrete-time systems with safe constraints and disturbances
No full textIn this paper, a novel adaptive dynamic programming (ADP)-based optimal control method is developed for discrete-time systems subject to constraints and disturbances. Particularly, a safe policy iteration scheme is designed to handle state and input constraints, including both hard and soft constraints, by converting the original policy improvement strategy into a constrained optimization problem with a prescribed state cost function. After that, an actor-critic-disturbance framework is introduced to address the constrained optimal control problem. The robust safety against disturbances is treated as a two-player zero-sum game, where the actor and disturbance neural networks are used to approximate the optimal control input and the disturbance policy, respectively. The convergence property of the proposed algorithm is analyzed, and the multi-step version of the proposed ADP scheme is derived based on this property. Simulation results are demonstrated and discussed to validate the effectiveness and performance of the proposed method. Note to Practitioners —Addressing constraints in optimal control problems is essential for guaranteeing the safe operation of controlled systems. However, conventional ADP algorithms struggle to simultaneously manage state and control input constraints during the search for the optimal solution. In real-world applications, another critical and common issue is the presence of external disturbances, where disturbances that cause the control object to deviate from the safe region must be constrained while seeking an optimal control policy. Bearing these factors in mind, this study presents a novel ADP scheme for solving optimal control problems of discrete-time systems, taking into account state and control constraints as well as the impact of disturbances. Moreover, the convergence analysis of the proposed SADP scheme is provided, offering a powerful theoretical foundation for guaranteeing the safety and feasibility of the controlled syst..
A non-symmetric Kesten criterion and ratio limit theorem for random walks on amenable groups
No full textWe consider random walks on countable groups. A celebrated result of Kesten says that the spectral radius of a symmetric walk (whose support generates the group as a semigroup) is equal to one if and only if the group is amenable. We give an analogue of this result for walks which are not symmetric. We also conclude a ratio limit theorem for amenable groups
Elucidating gas evolution of Prussian white cathodes for sodium‐ion battery application : the effect of electrolyte and moisture
Get PDFAs global energy storage demand increases, sodium-ion batteries are often considered as an alternative to lithium-ion batteries. Hexacyanoferrate cathodes, commonly referred to as Prussian blue analogues (PBAs), are of particular interest due their low-cost synthesis and promising electrochemical response. However, because they consist of ~50 wt% cyanide anions, a possible release of highly toxic cyanide gases poses a significant safety risk. Previously, we observed the evolution of (CN)2 during cycling via differential electrochemical mass spectrometry (DEMS), but were unable to determine a root cause or mechanism. In this work, we present a systematical investigation of the gas evolution of Prussian white (PW) with different water content via DEMS. While H2 is the main gas detected, especially in hydrated PW and during overcharge (4.6 V vs. Na+/Na), the evolution of CO2 and (CN)2 depends on the electrolyte conductive salt. The use of oxidative NaClO4 instead of NaPF6 is the leading cause for the formation of (CN)2. Mass spectrometric evidence of trace amounts of HCN is also found, but to a much lower extent than (CN)2, which is the dominant safety risk when using NaClO4-containing electrolyte, which despite being a good model salt, is not a viable option for commercial applications
Del ‘Consenso’ a la complejidad : relaciones interamericanas diversas y en transición
No full textDurante los últimos quince años, la política internacional ha sido alterado por una mayor difusión de recursos económicos y capacidades militares. Para muchos, este hecho constituye una transformación radical—el fin de la hegemonía estadounidense en América Latina. Investigamos esta proposición, comenzando con el concepto de hegemonía. En lugar de verla como una característica estructural, conceptualizamos la hegemonía como una red de relaciones asimétricas y jerárquicas. Observamos no una sola transformación sino la emergencia de un contexto hemisférico definido por la asimetría diferenciada. Estados Unidos aun ocupa una posición central, pero su política exterior está marcada por la fragmentación subregional y la externalización de prioridades electorales. Exploramos los efectos a nivel subregional con un enfoque en las oportunidades y los desafíos para los países latinoamericanos
Rapid diversification of grey mangroves (Avicennia marina) driven by geographic isolation and extreme environmental conditions in the Arabian Peninsula
Get PDFBiological systems occurring in ecologically heterogeneous and spatially discontinuous habitats provide an ideal opportunity to investigate the relative roles of neutral and selective factors in driving lineage diversification. The grey mangroves (Avicennia marina) of Arabia occur at the northern edge of the species' range and are subject to variable, often extreme, environmental conditions, as well as historic large fluctuations in habitat availability and connectivity resulting from Quaternary glacial cycles. Here, we analyse fully sequenced genomes sampled from 19 locations across the Red Sea, the Arabian Sea and the Persian/Arabian Gulf (PAG) to reconstruct the evolutionary history of the species in the region and to identify adaptive mechanisms of lineage diversification. Population structure and phylogenetic analyses revealed marked genetic structure correlating with geographic distance and highly supported clades among and within the seas surrounding the Arabian Peninsula. Demographic modelling showed times of divergence consistent with recent periods of geographic isolation and low marine connectivity during glaciations, suggesting the presence of (cryptic) glacial refugia in the Red Sea and the PAG. Significant migration was detected within the Red Sea and the PAG, and across the Strait of Hormuz to the Arabian Sea, suggesting gene flow upon secondary contact among populations. Genetic-environment association analyses revealed high levels of adaptive divergence and detected signs of multi-loci local adaptation driven by temperature extremes and hypersalinity. These results support a process of rapid diversification resulting from the combined effects of historical factors and ecological selection and reveal mangrove peripheral environments as relevant drivers of lineage diversity
