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The HST treasury programme BUFFALO provides extended wide-field imaging of the six Hubble Frontier Fields galaxy clusters. Here we present the combined strong and weak-lensing analysis of Abell 370, a massive cluster at z = 0.375. From the reconstructed total projected mass distribution in the 6 arcmin × 6 arcmin BUFFALO field-of-view, we obtain the distribution of massive substructures outside the cluster core and report the presence of a total of seven candidates, each with mass ∼5 × 1013 M⊙. Combining the total mass distribution derived from lensing with multiwavelength data, we evaluate the physical significance of each candidate substructure, and conclude that five out of the seven substructure candidates seem reliable, and that the mass distribution in Abell 370 is extended along the north-west and south-east directions. While this finding is in general agreement with previous studies, our detailed spatial reconstruction provides new insights into the complex mass distribution at large cluster-centric radius. We explore the impact of the extended mass reconstruction on the model of the cluster core and in particular, we attempt to physically explain the presence of an important external shear component, necessary to obtain a low root-mean-square separation between the model-predicted and observed positions of the multiple images in the cluster core. The substructures can only account for up to half the amplitude of the external shear, suggesting that more effort is needed to fully replace it by more physically motivated mass components. We provide public access to all the lensing data used as well as the different lens models.

 

We investigate structural properties of massive galaxy populations in the central regions (< 0.7  r 500 ) of five very massive ( M 200  > 4 × 10 14   M ⊙ ), high-redshift (1.4 ≲  z  ≲ 1.7) galaxy clusters from the 2500 deg 2 South Pole Telescope Sunyaev Zel’dovich effect (SPT-SZ) survey. We probe the connection between galaxy structure and broad stellar population properties at stellar masses of log( M / M ⊙ ) > 10.85. We find that quiescent and star-forming cluster galaxy populations are largely dominated by bulge- and disk-dominated sources, respectively, with relative contributions being fully consistent with those of field counterparts. At the same time, the enhanced quiescent galaxy fraction observed in these clusters with respect to the coeval field is reflected in a significant morphology-density relation, with bulge-dominated galaxies already clearly dominating the massive galaxy population in these clusters at z  ∼ 1.5. At face value, these observations show no significant environmental signatures in the correlation between broad structural and stellar population properties. In particular, the Sersic index and axis ratio distribution of massive, quiescent sources are consistent with field counterparts, in spite of the enhanced quiescent galaxy fraction in clusters. This consistency suggests a tight connection between quenching and structural evolution towards a bulge-dominated morphology, at least in the probed cluster regions and galaxy stellar mass range, irrespective of environment-related processes affecting star formation in cluster galaxies. We also probe the stellar mass–size relation of cluster galaxies, and find that star-forming and quiescent sources populate the mass–size plane in a manner largely similar to their field counterparts, with no evidence of a significant size difference for any probed sub-population. In particular, both quiescent and bulge-dominated cluster galaxies have average sizes at fixed stellar mass consistent with their counterparts in the field. 

In recent years, professional organizations in the United States have suggested undergraduate mathematics shift away from pure lecture format. Transitioning to a student-centered class is a complex instructional undertaking especially in the proof-based context. In this paper, we share lessons learned from a design-based research project centering instructional elements as objects of design. We focus on how three high leverage teaching practices (HLTP; established in the K-12 literature) can be adapted to the proof context to promote student engagement in authentic proof activity with attention to issues of access and equity of participation. In general, we found that HLTPs translated well to the proof setting, but required increased attention to navigating between formal and informal mathematics, developing precision around mathematical objects, supporting competencies beyond formal proof construction, and structuring group work. We position this paper as complementary to existing research on instructional innovation by focusing not on task trajectories, but on concrete teaching practices that can support successful adaption of student-centered approaches. 

The COVID-19 pandemic and response has significantly disrupted fishery supply chains, creating shortages of essential foods and constraining livelihoods globally. Small-scale fisheries (SSFs) are responding to the pandemic in a variety of ways. Together, disruptions from and responses to COVID-19 illuminate existing vulnerabilities in the fish distribution paradigm and possible means of reducing system and actor sensitivity and exposure and increasing adaptive capacity. Integrating concepts from literature on supply chain disruptions, social-ecological systems, human wellbeing, vulnerability, and SSFs, we synthesize preliminary lessons from six case studies from Indonesia, the Philippines, Peru, Canada, and the United States. The SSF supply chains examined employ different distribution strategies and operate in different geographic, political, social, economic, and cultural contexts. Specifically, we ask (a) how resilient have different SSF supply chains been to COVID-19 impacts; (b) what do these initial outcomes indicate about the role of distribution strategies in determining the vulnerability of SSF supply chains to macroeconomic shocks; and (c) what key factors have shaped this vulnerability? Based on our findings, systemic changes that may reduce SSF vulnerability to future macroeconomic shocks include: diversification of distribution strategies, livelihoods, and products; development of local and domestic markets and distribution channels; reduced reliance on international markets; establishment of effective communication channels; and preparation for providing aid to directly assist supply chains and support consumer purchasing power.

 

Halogenated organic compounds are pervasive in natural and built environments. Despite restrictions on the production of many of these compounds in most parts of the world through the Stockholm Convention on Persistent Organic Pollutants (POPs), many “legacy” compounds, including polychlorinated biphenyls (PCBs), are routinely detected in human tissues where they continue to pose significant health risks to highly exposed and susceptible populations. A major concern is developmental neurotoxicity, although impacts on neurodegenerative outcomes have also been noted. Here, we review human studies of prenatal and adult exposures to PCBs and describe the state of knowledge regarding outcomes across domains related to cognition (e.g., IQ, language, memory, learning), attention, behavioral regulation and executive function, and social behavior, including traits related to attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD). We also review current understanding of molecular mechanisms underpinning these associations, with a focus on dopaminergic neurotransmission, thyroid hormone disruption, calcium dyshomeostasis, and oxidative stress. Finally, we briefly consider contemporary sources of organohalogens that may pose human health risks via mechanisms of neurotoxicity common to those ascribed to PCBs.