Peer-Reviewed Publication

Researchers at the Johns Hopkins Bloomberg School of Public Health contributed to a new Centers for Disease Control and Prevention report examining autism among children who turned 4 and 8 years old in 2022. The CDC report, which includes data from 16 study sites across the U.S. including Maryland, found an overall prevalence of autism of 1 in 31 (3.2%) among 8-year-olds in 2022.

Based on data from over 1000 regional studies combined with machine learning, researchers estimate that as many as 1.4 billion people live in areas with soil dangerously polluted by heavy metals like arsenic, cadmium, cobalt, chromium, copper, nickel, and lead. The study reveals a global risk, but also a previously unrecognized high-risk, metal-enriched zone in low-latitude Eurasia, in particular. The growth in demand for critical metals means toxic heavy metal pollution in soils is only likely to worsen. “We hope that the global soil pollution data presented in this report will serve as a scientific alert for policymakers and farmers to take immediate and necessary measures to better protect the world’s precious soil resources,” say the authors. Toxic heavy metal pollution in soil, originating from both natural sources and human activities, poses significant risks to ecosystems and human health. Once introduced into soils, such metals can persist over decades. These pollutants reduce crop yields, affect biodiversity, and jeopardize water quality as well as food safety through bioaccumulation in farm animals. However, while previous studies have shown that toxic metal pollution is ubiquitous in soils, its worldwide distribution remains poorly understood. To address this knowledge gap, Deyi Hou compiled data from 1,493 regional studies encompassing 796,084 soil samples to assess the global distribution of toxic metals in agricultural soils and to identify where concentrations exceed safety thresholds. Using machine learning and modeling approaches, Hou et al. estimate that 14–17% of cropland globally – roughly 242 million hectares – is contaminated by at least one toxic metal, with cadmium being the most widespread, especially in South and East Asia, parts of the Middle East, and Africa. Nickel, chromium, arsenic, and cobalt also exceeded thresholds in various regions, largely due to a mix of natural geological sources and human activities such as mining and industrialization. Moreover, findings revealed a transcontinental “metal-enriched corridor” stretching across low-latitude Eurasia, which likely reflects the cumulative effects of ancient mining, weathering of metal-rich bedrock, and limited leaching over time. By superimposing these data with global population distribution, Hou et al. estimate that 0.9 to 1.4 billion people live in high-risk areas.

NASA’s Curiosity rover has uncovered a hidden chemical archive of ancient Mars’ atmosphere, which suggests that large amounts of carbon dioxide have been locked into the planet’s crust, according to a new study. The findings provide in situ evidence that a carbon cycle once operated on ancient Mars and offer new insights into the planet’s past climate. The Martian landscape shows clear signs that liquid water once flowed across its surface, which would have required a much warmer climate than the planet has today. It is therefore thought that Mars’ CO₂ atmosphere must have been thicker in the past, to maintain warmer conditions. A climate containing abundant liquid water and atmospheric CO₂ is expected to have reacted with Martian rocks, triggering geochemical processes that produce carbonate minerals. However, while previous analyses of Martian rock have detected the presence of carbonates, the quantities found were lower than expected from geochemical models.

 

Using data from the Curiosity rover, Benjamin Tutolo and colleagues investigated carbonate minerals in part of Gale crater – which once contained an ancient lake. In 2022 and 2023, Curiosity drilled four rock samples from different stratigraphic units representing transitions from lakebed to wind-blown environments and analyzed their mineralogy using the rover’s onboard X-ray diffractometer. Tutolo et al. identified siderite (iron carbonate) in high concentrations – ranging from approximately 5% to over 10% by weight – within magnesium sulfate-rich layers. This was unexpected, because orbital measurements had not detected carbonates in these strata. Given its provenance and chemistry, the authors infer that the siderite formed by water-rock reactions and evaporation, indicating that CO₂ was chemically sequestered from the Martian atmosphere into the sedimentary rocks. If the mineral composition of these sulfate layers is representative of sulfate-rich regions globally, those deposits contain a large, previously unrecognized carbon reservoir. The carbonates have been partially destroyed by later processes, indicating that some of the carbon dioxide was later returned to the atmosphere, forming a carbon cycle. “As details of Mars’ geochemistry are discovered through orbital and rover investigations around the planet, additional clues are revealed about the diversity of potentially habitable environments,” write Janice Bishop and Melissa Lane in a related Perspective.

Solid-state lithium batteries fail for the same reason over-bent paperclips snap – metal fatigue in the anode itself, according to a new study. The findings, which show that this fatigue follows well-documented mechanical behavior, provide a quantitative framework for predicting the cycle life of solid-state batteries, enabling new pathways for designing longer-lasting and safer energy storage systems. Solid-state lithium metal batteries (SSBs) promise both high energy and improved safety by combining a lithium metal anode with a solid, nonflammable electrolyte and a high-voltage cathode. However, their widespread use is hindered by early failure due to the growth of lithium dendrites—tiny, needle-like structures that can cause short circuits. Recent evidence suggests that mechanical factors play a more important role in failures than previously appreciated. The solid electrolyte, unlike liquid counterparts, struggles to absorb the stresses caused by lithium expansion and contraction during battery cycling. These stresses can lead to material fatigue, resulting in cracking, dendrite formation, and eventual failure, even when electrochemical conditions appear stable. However, lithium fatigue from the repeated stresses of battery cycling has been largely overlooked, leaving a gap in our understanding of long-term SSB reliability. Using scanning electron miscopy, phase-field simulations, and electrochemical analysis, Tengrui Wang and colleagues discovered that the failure of SSBs is closely linked to the cycle fatigue of the lithium metal anode, which leads to microcracks at the anode-electrolyte interface, driving degradation and dendrite growth – even at low current densities. Moreover, Wang et al. found that this fatigue follows well-established mechanical laws, namely the Coffin-Manson law, confirming it as an intrinsic and predictable property of the system. “The work of Wang et al. recognizes the importance of fatigue in the performance of lithium metal anodes in solid-state batteries,” write Jagjit Nanda and Sergiy Kalnaus in a related Perspective. “Further investigations should follow to describe the complex stress-strain state of lithium, including cycle rate, length scale, and temperature.”

Shedding light on how the brain fine-tunes its wiring during learning, a new study finds that different dendritic segments of a single neuron follow distinct rules. The findings challenge the idea that neurons follow a single learning strategy and offer a new perspective on how the brain learns and adapts behavior. The brain's remarkable ability to learn and adapt is rooted in its capacity to modify the connections within its neural circuits – a phenomenon known as synaptic plasticity, in which specific synapses are altered to reshape neural activity and support behavioral change. Neurons, unlike most other cell types, are characterized by their intricate, tree-like dendritic arbors, which extend from the cell body and serve as the primary site for receiving signals from other neurons via synaptic inputs. These dendrites are not uniform; instead, they are organized into distinct compartments with specialized anatomical and biophysical properties which likely influence how various patterns of neural activity trigger the biochemical processes that underlie synaptic plasticity. However, how the brain determines which synapses should be modified during learning and whether individual neurons apply the same plasticity rules uniformly across their structurally and functionally distinct dendritic compartments remains unknown.

 

To explore how synapses function and adapt during learning, William Wright and colleagues used advanced imaging to observe single synapses in the motor cortex of mice as the animals learned new motor skills. Wright et al. trained mice on a motor task known to drive synaptic plasticity in layer 2/3 motor cortex neurons, observing clear behavioral signs of learning over two weeks. Then, to investigate how individual synapses adapt during this process, Wright et al. used in vivo two-photon imaging with molecular sensors that simultaneously tracked synaptic input (via glutamate release) and neuronal output (via calcium activity). The authors discovered that learning-related patterns of neural activity drive synaptic plasticity differently across dendritic compartments. In apical dendrites, synapses were strengthened when they were coactive with nearby neighbors, suggesting that plasticity here is governed by local interactions between adjacent inputs. In contrast, plasticity in basal dendrites was linked to the neuron's overall output—strengthening or weakening depending on how synapse activity aligned with global action potential firing. Suppressing a neuron's activity selectively impaired plasticity in basal, but not apical, dendrites. In a related Perspective, Ayelén Groisman and Johannes Letzkus discuss the study and its findings in greater detail.

In plants, the space between cells is a key battleground during infection. To avoid recognition in this space, a strain of the bacterial tomato disease Pseudomonas syringae manipulates plants by producing a substance called glycosyrin. This substance suppresses the immune response and allows the bacteria to remain unnoticed.

A new study led by the University of Oxford has revealed that glycosyrin does this by mimicking galactose, a simple sugar found in many living things – acting like a wolf in sheep’s clothing.