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A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.

Understanding the rich social lives of animals benefits international conservation efforts Animal culture, defined as “information or behavior—shared within a community—which is acquired from conspecifics through some form of social learning” ( 1 ), can have important consequences for the survival and reproduction of individuals, social groups, and potentially, entire populations ( 1 , 2 ). Yet, until recently, conservation strategies and policies have focused primarily on broad demographic responses and the preservation of genetically defined, evolutionarily significant units. A burgeoning body of evidence on cultural transmission and other aspects of sociality ( 3 ) is now affording critical insights into what should be conserved (going beyond the protection of genetic diversity, to consider adaptive aspects of phenotypic variation), and why specific conservation programs succeed (e.g., through facilitating the resilience of cultural diversity) while others fail (e.g., by neglecting key repositories of socially transmitted knowledge). Here, we highlight how international legal instruments, such as the Convention on the Conservation of Migratory Species of Wild Animals (CMS), can facilitate smart, targeted conservation of a wide range of taxa, by explicitly considering aspects of their sociality and cultures.

To evaluate the association of a validated chest computed tomography (Chest-CT) severity score in COVID-19 patients with their respiratory outcome in the Intensive Care Unit. A single-center, prospective study evaluated patients with positive RT-PCR for COVID-19, who underwent Chest-CT and had a final COVID-19 clinical diagnosis needing invasive mechanical ventilation in the ICU. The admission chest-CT was evaluated according to a validated Chest-CT Severity Score in COVID-19 (Chest-CTSS) divided into low ≤50% (<14 points) and >50% high (≥14 points) lung parenchyma involvement. The association between the initial score and their pulmonary clinical outcomes was evaluated. 121 patients were clustered into the > 50% lung involvement group and 105 patients into the ≤ 50% lung involvement group. Patients ≤ 50% lung involvement (<14 points) group presented lower PEEP levels and FiO2 values, respectively GEE P = 0.09 and P = 0.04. The adjusted COX model found higher hazard to stay longer on invasive mechanical ventilation HR: 1.69, 95% CI, 1.02-2.80, P = 0.042 and the adjusted logistic regression model showed increased risk ventilator-associated pneumonia OR = 1.85 95% CI 1.01-3.39 for COVID-19 patients with > 50% lung involvement (≥14 points) on Chest-CT at ICU admission. COVID-19 patients with >50% lung involvement on Chest-CT admission presented higher chances to stay longer on invasive mechanical ventilation and more chances to developed ventilator-associated pneumonia.

There is enduring debate over the question of which early-life effects are adaptive and which ones are not. Mathematical modelling shows that early-life effects can be adaptive in environments that have particular statistical properties, such as reliable cues to current conditions and high autocorrelation of environmental states. However, few empirical studies have measured these properties, leading to an impasse. Progress, therefore, depends on research that quantifies cue reliability and autocorrelation of environmental parameters in real environments. These statistics may be different for social and non-social aspects of the environment. In this paper, we summarize evolutionary models of early-life effects. Then, we discuss empirical data on environmental statistics from a range of disciplines. We highlight cases where data on environmental statistics have been used to test competing explanations of early-life effects. We conclude by providing guidelines for new data collection and reflections on future directions. This article is part of the theme issue ‘Developing differences: early-life effects and evolutionary medicine'.

In non-Hermitian systems, spectral degeneracies can arise that can cause unusual, counter-intuitive effects; here exciton-polaritons—hybrid light–matter particles—within a semiconductor microcavity are found to display non-trivial topological modal structure exclusive to such systems. Non-Hermitian dynamics in a quantum chaotic exciton-polariton system In non-Hermitian systems, which are open and subject to gain and loss, exceptional points can arise, spectral degeneracies that can cause unusual, counter-intuitive effects. Recent efforts to observe non-Hermitian physics have concentrated on various optical systems, but not yet on exciton-polaritons. These are hybrid light–matter particles, formed by strongly interacting photons and excitons (electron–hole pairs) in semiconductor microcavities. Such systems require constant pumping of energy and continuously decays releasing coherent radiation, so are a profoundly open quantum system. In a striking experiment involving a chaotic exciton-polariton billiard —a two-dimensional area enclosed by a curved potential barrier — these authors demonstrate this non-Hermitian nature for the first time. The experiment reveals the non-trivial topological modal structure exclusive to non-Hermitian systems. These findings open the way for novel types of operating principles for polariton-based optoelectronic devices. Exciton-polaritons are hybrid light–matter quasiparticles formed by strongly interacting photons and excitons (electron–hole pairs) in semiconductor microcavities 1 , 2 , 3 . They have emerged as a robust solid-state platform for next-generation optoelectronic applications as well as for fundamental studies of quantum many-body physics. Importantly, exciton-polaritons are a profoundly open (that is, non-Hermitian 4 , 5 ) quantum system, which requires constant pumping of energy and continuously decays, releasing coherent radiation 6 . Thus, the exciton-polaritons always exist in a balanced potential landscape of gain and loss. However, the inherent non-Hermitian nature of this potential has so far been largely ignored in exciton-polariton physics. Here we demonstrate that non-Hermiticity dramatically modifies the structure of modes and spectral degeneracies in exciton-polariton systems, and, therefore, will affect their quantum transport, localization and dynamical properties 7 , 8 , 9 . Using a spatially structured optical pump 10 , 11 , 12 , we create a chaotic exciton-polariton billiard—a two-dimensional area enclosed by a curved potential barrier. Eigenmodes of this billiard exhibit multiple non-Hermitian spectral degeneracies, known as exceptional points 13 , 14 . Such points can cause remarkable wave phenomena, such as unidirectional transport 15 , anomalous lasing/absorption 16 , 17 and chiral modes 18 . By varying parameters of the billiard, we observe crossing and anti-crossing of energy levels and reveal the non-trivial topological modal structure exclusive to non-Hermitian systems 9 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 . We also observe mode switching and a topological Berry phase for a parameter loop encircling the exceptional point 23 , 24 . Our findings pave the way to studies of non-Hermitian quantum dynamics of exciton-polaritons, which may uncover novel operating principles for polariton-based devices.

People often react to low probability, high damage events in which many die with strong avoidance behaviour. Indeed, analyses of behaviour following the September 11 terror attacks on New York City suggest that this caused a substantial number of additional, ‘indirect’ deaths as many people avoided flying for 12 months afterwards and took to the relatively risky highways of the US instead. We argue that such responses may have arisen as an adaptation to risks that wipe out a significant proportion of all carriers of an allele if they strike, e.g. storms. These are environmental fluctuations known as environmental or aggregate risks. At the opposite extreme, demographic risks affect individuals independently. We show that evolution by natural selection in fluctuating environments means it is adaptive to inflate environmental (aggregate) risks relative to demographic risks, where the inflation factor depends on the proportion of carriers of the allele that die if the risk strikes.

Bruce E DallWestern Michigan University School of Medicine, Kamamazoo, MI, USACorrespondence: Bruce E Dall, Email [email protected]View the original paper by Dr Sayed and colleaguesA Response to Letter has been published for this article.

Ghost imaging is demonstrated using beams of correlated pairs of ultracold helium atoms, rather than photons, yielding a reconstructed image with submillimetre resolution. Ghost imaging with massive particles Ghost imaging achieves a feat that sounds impossible: the reconstruction of an image of an object using a beam of light that has never interacted with the object. The trick that makes it possible involves the use of two beams of correlated photons. One beam passes through the object to a bucket (single-pixel) detector, while the spatial profile of the second beam is measured by a high-resolution (multi-pixel) detector; but, this second beam never interacts with the object. Until now ghost imaging has been achieved only with photons, but here Andrew Truscott and colleagues report a technique for producing ghost images with massive particles—specifically, with ultracold helium atoms. Substituting photons in quantum mechanical experiments for massive particles could shed light on fundamental questions such as the quantum-to-classical transition. In addition, this methodology may facilitate applications such as real-time control of atom lithography while imaging the deposition remotely via the ghost imaging technique. Ghost imaging is a counter-intuitive phenomenon—first realized in quantum optics 1 , 2 —that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a ‘ghost’ image. Here we report the realization of ghost imaging using massive particles instead of photons. In our experiment, the two beams are formed by correlated pairs of ultracold, metastable helium atoms 3 , which originate from s -wave scattering of two colliding Bose–Einstein condensates 4 , 5 . We use higher-order Kapitza–Dirac scattering 6 , 7 , 8 to generate a large number of correlated atom pairs, enabling the creation of a clear ghost image with submillimetre resolution. Future extensions of our technique could lead to the realization of ghost interference 9 , and enable tests of Einstein–Podolsky–Rosen entanglement 9 and Bell’s inequalities 10 with atoms.

Atmospheric new particle formation (NPF) and growth significantly influences climate by supplying new seeds for cloud condensation and brightness. Currently, there is a lack of understanding of whether and how marine biota emissions affect aerosol-cloud-climate interactions in the Arctic. Here, the aerosol population was categorised via cluster analysis of aerosol size distributions taken at Mt Zeppelin (Svalbard) during a 11 year record. The daily temporal occurrence of NPF events likely caused by nucleation in the polar marine boundary layer was quantified annually as 18%, with a peak of 51% during summer months. Air mass trajectory analysis and atmospheric nitrogen and sulphur tracers link these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. The occurrence of such events across a full decade was anti-correlated with sea ice extent. New particles originating from open water and open pack ice increased the cloud condensation nuclei concentration background by at least ca. 20%, supporting a marine biosphere-climate link through sea ice melt and low altitude clouds that may have contributed to accelerate Arctic warming. Our results prompt a better representation of biogenic aerosol sources in Arctic climate models.

Background Regular physical activity is the prime modality for the prevention of numerous non-communicable diseases and has also been advocated for resilience against COVID-19 and other infectious diseases. However, there is currently no systematic and quantitative evidence synthesis of the association between physical activity and the strength of the immune system. Objective To examine the association between habitual physical activity and (1) the risk of community-acquired infectious disease, (2) laboratory‐assessed immune parameters, and (3) immune response to vaccination. Methods We conducted a systemic review and meta-analysis according to PRISMA guidelines. We searched seven databases (MEDLINE, Embase, Cochrane CENTRAL, Web of Science, CINAHL, PsycINFO, and SportDiscus) up to April 2020 for randomised controlled trials and prospective observational studies were included if they compared groups of adults with different levels of physical activity and reported immune system cell count, the concentration of antibody, risk of clinically diagnosed infections, risk of hospitalisation and mortality due to infectious disease. Studies involving elite athletes were excluded. The quality of the selected studies was critically examined following the Cochrane guidelines using ROB2 and ROBINS_E. Data were pooled using an inverse variance random-effects model. Results Higher level of habitual physical activity is associated with a 31% risk reduction (hazard ratio 0.69, 95% CI 0.61–0.78, 6 studies, N  = 557,487 individuals) of community-acquired infectious disease and 37% risk reduction (hazard ratio 0.64, 95% CI 0.59–0.70, 4 studies, N  = 422,813 individuals) of infectious disease mortality. Physical activity interventions resulted in increased CD4 cell counts (32 cells/µL, 95% CI 7–56 cells/µL, 24 studies, N  = 1112 individuals) and salivary immunoglobulin IgA concentration (standardised mean difference 0.756, 95% CI 0.146–1.365, 7 studies, N  = 435 individuals) and decreased neutrophil counts (704 cells/µL, 95% CI 68–1340, 6 studies, N  = 704 individuals) compared to controls. Antibody concentration after vaccination is higher with an adjunct physical activity programme (standardised mean difference 0.142, 95% CI 0.021–0.262, 6 studies, N  = 497 individuals). Conclusion Regular, moderate to vigorous physical activity is associated with reduced risk of community-acquired infectious diseases and infectious disease mortality, enhances the first line of defence of the immune system, and increases the potency of vaccination. Protocol registration The original protocol was prospectively registered with PROSPERO (CRD42020178825).