COVER A person recovering materials amid a massive fire at the Bhalswa landfill site in India symbolizes the challenges of solid waste mismanagement. Urgent action is vital as temperatures approach the Paris Agreement limit and jeopardize the Global Methane Pledge goal. Solutions demand a critical shift in technical and behavioral practices to prevent an impending environmental catastrophe and unsustainable use of resources. See pages 762 and 797.

Photo: Sanchit Khanna/Hindustan Times via Getty Images

ONLINE COVER A temperature-dependent 2D switch sitting on a 3D-printed soft metamaterial. Li et al. used multi-material 3D printing and an algorithm to create a soft metamaterial with programmable temperature-switchable mechanical responses. Controlling the material’s behavior relies on distinct glass transition temperatures of different polymers that produce stiffness changes in a predictable manner. These allow the metamaterial to react to its environment. This research may enable environmentally interactive programmable metamaterials for soft robotics, flexible electronics, and biomedical devices.

ONLINE COVER A Shield for Muscle During Exercise. Exercise induces changes in muscle metabolism and structure that support long-term improvements in performance. Langston et al. found that regulatory T cells support the beneficial effects of exercise by protecting muscle mitochondria from excessive exercise-induced inflammation. This month’s cover features a mouse engaging in voluntary wheel running, which was used to model chronic endurance exercise.

ONLINE COVER Robot Trajectory Planning – Framework for Planning Optimized Robot Trajectories Around Obstacles. Marcucci et al. report on a method for collision-free robot motion planning. The planning method relies on finding the shortest paths with graphs of convex sets to generate optimal trajectories in less time than other sampling-based algorithms. The framework was able to achieve collision-free motion planning on a quadrotor flying robot through a building in simulation, as well as the coordinated trajectories of two physical robot arms working jointly to sort objects. This month’s cover is an image of two robot arms using the framework for coordinated motion planning.

ONLINE COVER This week, Morales-Soto et al. show in mice that inflammation-induced changes in glia-to-neuron signaling in the gut underlie the pain associated with colitis. The microscopy image shows a myenteric ganglion from a mouse colon stained for glia (green) and nociceptive nerve terminals (pink).

ONLINE COVER More than Adipose Tissue. Obesity is defined as excess adipose tissue accumulation, but this simple definition belies the downstream effects that excess body fat can have on whole-body health. This special issue looks at the complexity of how other body systems, depicted in the cover, are both involved in and affected by obesity. Three Review articles discuss the chronic, low-grade inflammation that can promote health complications in obesity (Schleh et al.), the tenuous connection between the microbiome and the obesity epidemic (De Wit et al.), and the hormones and neural signals that affect appetite, which have been targeted by the first successful obesity drugs (Tschöp and Friedman). A Viewpoint offers perspective on the relationship between obesity and aging (Diaz-Ruiz et al.), and a Focus article discusses how effective anti-obesity strategies require suitable models of obesity alongside recognition of concurrent social and political factors (Ulijaszek). Research articles accompanying this special issue demonstrate a hormonal basis for antipsychotic drug-induced weight gain and metabolic disease (Zhao et al.) and present a leptin receptor agonist antibody for treating the metabolic consequences and weight gain associated with leptin deficiency (Altarejos et al.).