Geophysics Ringing the Earth with a rockslide
Brent Grocholski
A rockslide within a glacial canyon in Greenland generated a massive seismic event and tsunami.
PHOTO: SVENNEVIG ET AL.
A large rockslide occurred in Greenland on 16 September 2023 that generated a local tsunami. The event was energetic enough to generate a global signal that resonated for 9 days. Svennevig et al. used a range of geophysical tools to detail the sequence of events that occurred and then determined the origin of the global signal. The authors found that the signal was generated by standing waves in the Dickson Fjord due to the rockslide. Climate change drives feedback among the cryosphere, hydrosphere, and mass wasting events, and signals such as the one the authors observed may provide a different way of understanding these interactions.
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Electoral Politics Polarization holds steadier than expected
Aaron Shaw
Idealistic accounts of political democracy portray elections as unifying moments of cohesive collective decision-making. The reality is often quite different, as the approximately 4 billion eligible voters in sundry democratic contests happening around the world this year can attest. Much prior political science research suggests that elections make partisanship more salient. Fasching et al. now report new evidence of durable polarization in the US and beyond. The authors focused on a large-scale dataset from the US around the 2022 elections and found that partisan animus constituted a persistent feature of the American political landscape well before and after election day. They report similar results around the 2020 election in the US and for a substantial portion of 86 countries around the world using data from 2000 to 2014. In many contexts, polarization is the status quo, not an exception.
Environmental Policy Waste not
Bianca Lopez
Food waste produces about half of the greenhouse gas emissions from the global food system, including methane emissions from food waste deposited in landfills. To reduce emissions, some governments have banned food waste disposal in landfills. Anglou et al. evaluated the effectiveness of bans that applied to commercial waste producers in five US states. They found that such policies can succeed, but this has not been the norm. The states with bans showed almost no change in organic waste disposal into landfills compared with controls derived from states without bans. The exception to this was the state of Massachusetts. Simplicity of regulation, sufficient infrastructure, low cost of compliance, and/or strong enforcement may have contributed to Massachusetts’ success.
Plant Science A peroxide trigger
Ankit Walia
Systemic acquired resistance (SAR) triggered by the local immune response could prime plants for protection against a wide range of pathogens. Salicylic acid (SA) is known to be required for SAR, but the mobile signal and the mechanism by which SA is produced in distal parts of a plant in response to a local infection have remained elusive. Cao et al. found that the mobile signal is hydrogen peroxide produced by NADPH oxidase. In a concentration-dependent manner, the peroxide is sufficient to oxidize a cysteine residue in the transcription factor CCA1 HIKING EXPEDITION (CHE). Sulfenylation of CHE allows the transcription factor to bind to the promoter of the SA-biosynthesis gene. CHE mutants lacking the cysteine are compromised in SAR.
Structural Biology A protean protein coat
Michael A. Funk
Hepatitis B virus is transmitted in lipid membrane–bound virions coated in the protein surface antigen HBsAg. The structure of this protein and how it assembles into particles of various shapes and sizes have been unknown, and this has been complicated by the heterogeneity and flexibility of the protein coat. Wang et al. isolated two classes of spherical particles containing 40 and 48 copies of the HBsAg dimer with one trimeric and three different tetrameric local assembly patterns as determined by cryo–electron microscopy. HBsAg and some of the subassemblies identified were highly flexible, possibly explaining how a single dimer can generate so many different oligomerization forms. Based on the observed assembly rules, the authors speculate how the spherical structure might be extended into well-known, larger, tube-like structures.
Batteries A deep dive into self-discharge
Marc S. Lavine
A limitation to the efficiency and reliability of lithium ion batteries is their tendency to self-discharge over time. Wan et al. used a series of experimental surface characterization methods and theoretical calculations on representative high-nickel-content cathodes to investigate the mechanism by which nickel at the surface is reduced compared with the bulk. They observed that the self-discharge was caused by the insertion of protons into the charged cathode, which was triggered by the decomposition of the electrolyte. This mechanism, based on a surface hydrogenation reaction, differs from the widely accepted model that is based on lithium diffusion from the electrolyte into the cathode.
B Cells One of a kind
Hannah M. Isles
Immunoglobulin E (IgE)–mediated allergic diseases can be fatal, yet our understanding of IgE-producing plasma cells (PCs) is limited. Vecchione et al. used a transgenic mouse reporter strain to characterize IgE PCs during chronic house dust mite exposure. IgE PCs were transcriptionally and phenotypically distinct compared with other immunoglobulin isotypes, with higher levels of endoplasmic reticulum stress and increased antibody production. Short-lived IgE PCs appeared early in the lung-draining lymph nodes after allergen exposure, whereas long-lived bone marrow IgE PCs were not detected until much later. IgE bone marrow PCs from humans with allergy also had distinctive transcriptional signatures.
Blood Stem Cells Innate signals define clonal diversity
Sarah H. Ross
During embryonic development, macrophages interact with blood stem cells, removing those exhibiting high levels of cellular stress. The surviving hematopoietic stem and progenitor cells (HSPCs) can proliferate and give rise to blood cell linages in adults. Pessoa Rodrigues et al. used zebrafish models and mammalian systems to investigate signals within HSPCs that could prevent macrophages from engulfing them. Molecules associated with innate immune nucleic acid sensing promoted the expression of Beta-2-microglobulin on the surface of HSPCs to increase their survival when they interacted with macrophages. Impairing this pathway decreased the number of distinct stem cell clones in adult zebrafish.
Immunology T cells splice up their life
Sarah H. Ross
RNA-binding proteins (RBPs) fine-tune gene expression. Some RBPs, such as TRA2b, amplify their own protein abundance by removing, or skipping, ultraconserved poison exon (PE) elements from their gene transcripts. Karginov et al. found that high-affinity ligands for the T cell receptor (TCR) stimulated PE skipping in the TRA2β transcript in CD8 T cells. TRA2β protein bound to mRNAs encoding proteins involved in TCR signaling and was implicated in splicing events that augmented T cell effector function. Enforcing PE skipping in TRA2β promoted the initial activation of naive T cells to form effector cells and enhanced responses to low-affinity antigen. Reinclusion of the PE was correlated with termination of the immune response.
Artificial Intelligence Can a chatbot dispel conspiracy theories?
Ekeoma Uzogara
Beliefs in conspiracies that a US election was stolen incited an attempted insurrection on 6 January 2021. Another conspiracy alleging that Germany’s COVID-19 restrictions were motivated by nefarious intentions sparked violent protests at Berlin’s Reichstag parliament building in August 2020. Amid growing threats to democracy, Costello et al. investigated whether dialogues with a generative artificial intelligence (AI) interface could convince people to abandon their conspiratorial beliefs (see the Perspective by Bago and Bonnefon). Human participants described a conspiracy theory that they subscribed to, and the AI then engaged in persuasive arguments with them that refuted their beliefs with evidence. The AI chatbot’s ability to sustain tailored counterarguments and personalized in-depth conversations reduced their beliefs in conspiracies for months, challenging research suggesting that such beliefs are impervious to change. This intervention illustrates how deploying AI may mitigate conflicts and serve society.
Ultrasound Sounding things out
Yevgeniya Nusinovich
The most widely known application of ultrasound is for diagnosis, such as in prenatal care, but that is far from the only possible use for this versatile technology. An important feature of ultrasound is that it can be focused for precise application of mechanical waves to a small volume of carefully selected tissue. Depending on the specifics of the tissue and how the ultrasound is delivered, such an approach can generate heat and/or mechanical effects at the site. O’Reilly reviewed recent advances in the clinical applications of focused ultrasound for purposes as varied as drug delivery, immune activation, neuromodulation, and others.
Marine Lipids A matter of taste
Caroline Ash
Carbon export into the ocean is vital to understand because of its role in mediating climate change. Much carbon export in this environment is driven by microbial activity, but little is known about how lipids contribute to the carbon pump. Behrendt et al. investigated the biotic degradation of lipids in the oceans by following the degradation of lipid droplets isolated from the marine alga Phaeodactylum tricornutum grown in nitrogen-limited media with a range of combinations of marine bacteria (see the Perspective by Schubotz). The authors found that the occurrence of suites of genes in organisms, rather than any specific bacterial taxon, drove the dynamics of lipid degradation. They were able to observe this process by measuring autofluorescence. Using the experimental data, a mathematical model was developed to explore how microbial consumption controls the attenuation of vertical lipid flux with depth in the ocean.
Surface Structure Stabilizing an aluminum oxide surface
Phil Szuromi
Noncontact atomic force microscopy and density functional theory were used to determine the origin of the massive surface rearrangement of the (0001) surface of aluminum oxide. Previous studies had suggested that the surface loses oxygen atoms and has a metallic character, but Hutner et al. show that the complex (√31 × √31)R±° reconstruction is nearly stoichiometric (see the Perspective by Giessibl and Weymouth). Imaging determined the lateral atomic positions, and theory shows that aluminum rehybridization allows bonding to subsurface oxygen atoms, which greatly stabilizes the reconstruction.
Organic Chemistry Competing bond motifs
Jake S. Yeston
As reaction partners form a chemical bond, they often engage in a short-lived, weak interaction before forging the stronger linkage. Liu and Gabbai report an unusual compound in which steric and electronic constraints stabilize both the weak and strong bonding motifs in equilibrium (see the Perspective by Jupp). The bonds in question bridge carbon and phosphorus centers with an oxygen. Two distinct isomers could be crystallized, bearing, respectively, C···O=P and C–O–P geometries, the former with a stronger O–P interaction at the expense of the C–O bond.
EMI Shielding More efficient and flexible shielding
Marc S. Lavine
Although stacking electronic components makes it possible to shrink devices, two problems that arise are the heat accumulation and the need to prevent electromagnetic cross talk. Typically, materials that show better electromagnetic interference shielding have worse thermal properties and vice versa. Zhou et al. developed a composite using liquid metal particles embedded in a silicone polymer matrix. The advantage of using the liquid metal is that it forms larger, phase-separated particles but without forming a percolating network that would reduce the shielding efficiency. The composite material can be used as a direct potting compound and can thus be placed in tight spaces and crevices, unlike typically used rigid shielding materials.
Coronavirus Predicting COVID-19 outcomes
Courtney Malo
A major challenge early during the COVID-19 pandemic was the inability to determine when a patient was going to recover from or succumb to disease. Although vaccines, antivirals, and other therapeutics have now limited the fatalities caused by COVID-19, the ability to predict disease progression remains important because it could help to determine the best therapeutic approach for each patient. Da Silva Filho et al. integrated antemortem peripheral blood analysis and clinical data with postmortem analysis of lung tissues to define signatures of recovery, early death, and late death from COVID-19. They then used these integrated signatures to identify peripheral blood and clinical parameters that could predict a patient’s trajectory. These data could be useful for anticipating a patient’s clinical course and for identifying personalized therapeutic approaches.
Plant-Plant Signaling An inherited call to arms
Bianca Lopez
Plants release volatiles in response to herbivory, and these chemicals can act as cues for nearby plants to initiate chemical defenses to herbivores. However, volatiles can quickly oxidize into secondary organic aerosols (SOAs). Yu et al. found that SOAs, which can persist longer than the original volatiles, also serve as signals for neighboring plants. Volatiles produced by pine seedlings in response to underground feeding by weevils and their resulting SOAs induced responses in neighboring seedlings, including heightened defenses, less herbivore damage, and higher photosynthesis. The relevance of SOAs for plant-plant interactions has thus been underestimated.
Mass Extinctions The heat was on
Jesse Smith
Only a few of the many volcanism-driven hyperthermals during the Phanerozoic caused mass extinctions, and none of them approached the level of global species loss seen at the end of the Permian. Why was the end-Permian so different? Sun et al. found that a combination of extreme El Niño events and mean state warming led to deforestation, reef demise, and a plankton crisis, all of which resulted in a positive feedback cycle that led to an even warmer mean climate and still stronger El Niño events.
Neuroscience Learning to be afraid with ROCK
Wei Wong
Learning and memory require activation of the NMDAR family of receptors, which stimulates the growth of protrusions on neurons called dendritic spines that strengthen synaptic transmission. Funahashi et al. delineated the signaling pathway downstream of NMDARs that mediates aversive learning. Biochemical and behavioral analyses in mice showed that dendritic spine growth and aversive learning were attenuated when the cytoskeleton-regulating kinase ROCK was inhibited or deleted or when the ROCK-mediated phosphorylation of a specific substrate, the scaffolding protein SHANK3, was blocked.
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