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Observation-constrained sensitivities of Arctic methane emissions to warming
The sensitivity of pan-Arctic (60 to 90°N) natural methane emissions to climate warming lacks direct observational constraints. Long-term atmospheric measurements of methane, which reflect integrated Arctic fluxes and atmospheric transport, show that in the pan-Arctic the autumn-to-winter CH 4 build-up (as indicated by the “autumn zero crossing date”) is becoming earlier. This advancing trend in autumn zero crossing date is explained by growing natural Arctic CH 4 emissions in response to climate warming in July, August and September, with a rate of increase of 0.14 ± 0.04 Tg CH 4 y −2 during the period 1998–2020. Atmospheric δ 13 C CH4 observational records allowed us to attribute this increase to 0.08 ± 0.02 Tg CH 4 y −2 from natural biogenic emissions (wetlands, lakes, permafrost soils) and 0.06 ± 0.02 Tg CH 4 y −2 from wildfire emissions. Our results point to a larger warming sensitivity of natural emissions (3.1 ± 0.9 Tg CH 4 y −1 per °C) than previous estimates, and potentially a larger positive feedback on climate warming.
Green–Kubo relation in a mesoscale odd fluid model
Fluids, characterized by broken time-reversal and parity symmetries, exhibit odd transport phenomena where longitudinal drivings can induce transverse fluxes. Recently, a mesoscale model called chiral stochastic rotation dynamics (CSRD) has been developed to simulate odd fluids with high computational efficiency. In this work, we verify the Green–Kubo relations for both normal and odd transport coefficients in this model, confirming that this model correctly captures the underlying statistical relationship between macroscopic transport and microscopic fluctuations in odd fluids. This work solidifies the physical foundation of the CSRD model, paving the way for its application in studying the statistical physics and nonequilibrium behavior of odd fluids.
Correction for Reinhart et al., An open repository of real-time COVID-19 indicators
Polaron-mediated exciton dynamics of P(NDI2OD-T2) unveiled by transient absorption spectroscopy under electrochemical conditions
Granted by the suitable characteristics of its electronic band structure, high electron mobility, and remarkable durability, P(NDI2OD-T2) stands out among conjugated polymers and is regarded as a prominent candidate for electron accepting materials in the third generation of photoelectrochemical and photovoltaic devices. However, a comprehensive understanding of exciton–polaron interactions, which provides the key to optimizing the efficiency of these devices, is lacking. In this study, we fabricated P(NDI2OD-T2) into a film working electrode of an electrochemical cell and changed its surrounding electrochemical environments by exerting different electric biases. Transient absorption (TA) spectroscopy was employed synchronously to interrogate the corresponding exciton dynamics. Careful inspection of the TA spectra of P(NDI2OD-T2) under different electrochemical conditions gives detailed insights into the interactions between excitons and polarons. Our results highlight that polarons have a significant influence on exciton behavior. Merely applying cathodic biases without efficiently doping the polymer yields excited-state dynamics similar to that in the neutral state. However, in the presence of polarons, the lifetime of excitons is significantly reduced by ∼5 times. Through analyzing the TA spectra and kinetics of P(NDI2OD-T2) at −1.0 and −1.2 V (vs Ag/Ag+ reference electrode), an efficient exciton–polaron quenching effect was identified. Furthermore, we report the absorption features of the excited states of polaron, i.e., charged excitons (trions) in P(NDI2OD-T2). We propose that bipolarons and such charged excitons may have similar electronic structures as they manifest resemblance in their absorption features. Our strategy of integrating ultrafast spectroscopy and electrochemistry to investigate the exciton–polaron interactions in polymers provides an effective methodology in research fields of photoelectrochemistry and photovoltaics, more broadly applicable beyond soft materials.
Correction for Liu et al., Occludin acts as a dynein adaptor regulating permeability and collateral angiogenesis
Molecular origins of capillary wave structure and interfacial viscosity at surfactant-laden oil–water interfaces
Capillary wave theory has been employed to study the concentration dependent effects of surfactants upon the spatial structure and temporal dynamics of surfactant laden oil–water interfaces. Surface concentrations up to a monolayer of trioctyl phosphine oxide and tributyl phosphate were examined at the water–hexane interface. We demonstrate that changes to capillary wave modes are consistent with the perturbations to the surface geometry (orientation and curvature) induced by surfactant–surfactant interactions and disruption of interfacial water hydrogen bond networks. The surfactant induced perturbations have the largest effect on the long wavelength capillary modes in terms of the amplitudes; however, curvature changes are due to the coupling of small wavelength modes, resulting in the increase in curvature and inducing long lived structures on the interface. As a result, the impact of the surfactants upon the characteristic relaxation times of the surface is pronounced for the short wavelength modes. Additionally, for each surfactant studied, there is a critical surface coverage value, related to the formation of water-bridged surfactant pairs, at which the interfacial dynamics dramatically slow down, leading to an increase in the interfacial surface viscosity.
Policy snapshots cannot establish journal AI-policy failure
Reward prediction is encoded by orexin neuron activity during motivated behavior
Orexin neurons regulate physiological functions, such as energy homeostasis, wakefulness, and motivated behaviors. However, studies linking orexin neuron activity to behavior via selectively activating/inactivating these inputs in a temporally controlled manner in rats are scarce. Here, we examined the role that orexin neurons play in motivated behavior in transgenic rats using cell type–specific fiber photometry and optogenetic manipulation. Using chemogenetics, we found that motivation for a reward increased when orexin neurons were activated. Furthermore, during motivated behavior, orexin neuron activity changed dynamically: Activity increased during reward prediction and decreased after reward receipt. When an unexpected event occurred (i.e., not obtaining an expected reward), increased orexin activity was sustained. Notably, orexin activity strengthened with increasing effort. Optogenetic inhibition of orexin neuron activation during reward prediction and treatment with an orexin 1-receptor antagonist reduced reward-seeking behavior. Therefore, orexin is crucial for linking predicted expectations with motivated behavior. Moreover, optimization of orexin activity is necessary to overcome difficulties during motivated behaviors.
Neural tissues and chondrostean traits in a Carboniferous actinopterygian
Ray-finned fishes (Actinopterygii) represent over half of extant vertebrate species, but their early evolutionary history is largely unresolved. Current phylogenetic estimates, corroborated by discoveries of preserved neural tissues, place most Palaeozoic actinopterygians outside the crown group and leave the deep roots of major extant divisions depauperate. Moreover, apparent fossil brains in early fishes are minuscule relative to endocranial chamber space, implying that endocasts are poor indicators of neuroanatomical gross morphology. Here, through X-ray micro-computed tomography of the early actinopterygian Trawdenia planti, we show unexpected neurocranial and neural soft tissue morphology indicative of a large brain fitting snugly within the endocranium. We find internal ventricular structures, present a model of neural tissue preservation, identify neuroanatomical characters, and demonstrate that endocasts capture phylogenetically and ecologically informative signal. These data suggest that Trawdenia bridges the gap between early actinopterygians and modern Chondrostei, thereby offering an alternative framework for understanding early actinopterygian neural evolution that departs radically from current phylogenetic hypotheses.
More connections, higher polarization: The role of weak ties and status-driven dynamics
Proteostasis and unfolded protein response dynamics in human neuron/mouse glia co-cultures reveal a cell-specific maturation response
Proteostasis, or protein homeostasis, is a tightly regulated network of cellular pathways essential for maintaining proper protein folding, trafficking, and degradation. Neurons are particularly vulnerable to proteostasis collapse due to their postmitotic and long-lived nature and thus represent a unique cell type to understand the dynamics of proteostasis throughout development and maturation. Here, we utilized a dual-species co-culture model of human excitatory neurons and mouse glia to recapitulate and investigate cell type–specific, maturation-related changes in the proteostasis network using data-independent acquisition LC–MS/MS proteomics. We quantified branch-specific unfolded protein response (UPR) activation by monitoring curated effector proteins downstream of the ATF6, IRE1/XBP1s, and PERK pathways, enabling a comprehensive, unbiased evaluation of UPR dynamics during in vitro neuronal maturation between 30 d and 60 d. Species-specific analysis revealed that mature neurons largely preserved proteostasis, although they showed some signs of collapse, primarily in endoplasmic reticulum (ER)-to-Golgi transport mechanisms. However, these changes were accompanied by upregulation of proteostasis-related machinery and activation of the ATF6 branch, as well as maintenance of the XBP1s and PERK branches of the UPR over time. In contrast, glia exhibited broad downregulation of proteostasis factors and UPR components, independent of neuronal presence. Furthermore, we quantified stimulus-specific modulation of select UPR branches in matured neurons exposed to pharmacologic ER stressors. These findings highlight distinct, cell-type-specific stress adaptations during in vitro maturation and provide a valuable proteomic resource for dissecting proteostasis and UPR regulation in human neurons.
Antimicrobial peptoids pass rapidly through bacterial membranes and flocculate ribosomes and DNA: A single-cell fluorescence study
Certain peptoids designed as mimics of host defense peptides such as LL-37 exhibit potent, broad-spectrum antibacterial, antifungal, antiparasitic, and antiviral activity with minimal cytotoxicity. Previous fixed-cell studies have suggested that the peptoids can pass through bacterial membranes and rapidly kill bacteria by aggregating intracellular macroanions, including ribosomes and DNA. However, the dynamic mechanisms of action of these biomimetic peptoids have remained elusive. We employed single-bacterial-cell, time-resolved fluorescence microscopy, and single-particle tracking methods to investigate the effects of the 12mer peptoid TM1, along with shorter alkylated and brominated analogues, on cytoplasmic membrane permeabilization and DNA and ribosome rigidification of Escherichia coli . Our results demonstrate that TM1 and several of its analogues permeabilize the cytoplasmic membrane within five minutes of flowing the peptoid solution over the cells—faster than seen for the important human antimicrobial peptide LL-37—and rigidify DNA and ribosomes as effectively as LL-37. Detailed biophysical structural and dynamical studies show that TM1 binds to both DNA (double-stranded and single-stranded) and single-stranded RNA in a similar manner to LL-37, which is well known to display strong nucleic acid binding. These results support our hypothesis that TM1 and its analogues exert their antimicrobial effects through intracellular aggregation of biomacromolecules such as ribosomes, RNA, and DNA. TM1 displays a higher affinity for RNA compared to DNA, suggesting it will preferentially bind in vivo to bacterial ribosomes. Our study yields insight into the dynamic effects of antimicrobial peptoids, facilitating their future development as biomimetic anti-infectives, with the additional advantage of protease invulnerability.
Wind turbines do not appear to harm health, unlike fossil power plants
Local partisan context and mental health
We find that, relative to Republicans residing in more Republican neighborhoods, Republicans in neighborhoods with a higher concentration of Democratic residents report higher levels of anxiety, depression, and loneliness. While Democrats in general report worse mental health than Republicans, Democrats show no sensitivity to partisan context. Using a large-scale national survey and fine-grained data on residential political context, we establish that these patterns persist even when examining partisans who live in the same Zip Codes, and while controlling for other individual and geographic features. The correlation is strongest for the most strongly partisan individuals, suggesting that politics is a significant factor in the relationship. For Republicans, the size of the relationship between partisan context and mental health is comparable to or larger than the correlation between mental health reports and other contextual features of residential areas, such as neighborhood poverty or the way racial minorities respond to changes in the racial or ethnic composition of local geography.
A Topotactic Leap: 2D Layers to 3D Large-Pore Zeolite
Optimal interventions to curb urban conflagration
Understanding the efficacy of wildfire mitigation policies is a clear first step toward curbing wildfire losses during an urban conflagration. In this study, we used a validated model to quantify the impact of the spatial distribution of the combined management of open-space vegetation and mitigation of the home ignition zone (HIZ) on the resulting fire boundary and damage to the built environment in the Palisades area of Los Angeles, California. Fuel management in open-space involves reducing vegetation density by a specific percentage to emulate vegetation thinning and prescribed burning. HIZ mitigation involves hardening building features and removing defensible space fuel. For each type of intervension, we employed both random and targeted strategies to quantify their effectiveness in reducing the fire boundary and mean relative vulnerability of buildings. When combined vegetation management and HIZ mitigation are applied randomly, we observed a maximum reduction in mean relative vulnerability of 57%, while targeted strategies result in a maximum reduction of 78%. The study demonstrates the effectiveness of combining mitigation strategies in reducing damage caused by urban conflagrations.
Natural history on canvas: Brueghel knew about bird-eating noctule bats
A recent study has provided the first direct evidence that the greater noctule bat ( Nyctalus lasiopterus ) preys on and consume nocturnally migrating passerines in flight, using a combination of biologging, acoustic and movement monitoring, and molecular analyses. This result builds upon evidence accumulated over the past two decades. The research began with the first study reporting passerine feathers in the feces of this bat species. Subsequent fecal pellet analyses revealed peaks in the consumption of migratory avian prey, which coincided with migration periods. This body of evidence culminated in the recent publication demonstrating that greater noctules capture and consume migratory birds in flight at high altitudes. Here, we show that this interaction was depicted more than four centuries ago. In the canvas Air (1611), a painting by Jan Brueghel the Elder that contains detailed representations of more than 60 bird species, the artist also included three bat species. One of them, unmistakably identified as noctule bat, is represented in flight with a small passerine in its mouth. Although the behavior portrayed does not fully match contemporary descriptions of prey handling, the specificity of this predation scene suggests some familiarity of the artist with this behavior in the greater noctule. As the digitization of art collections accelerates and analytical tools continue to advance, the value of these sources to provide valuable data—previously difficult to extract and often overlooked—and complement modern research approaches will notably increase.
Charting light harvesting in purple bacteria in vivo
Understanding the remarkable quantum efficiency of solar energy collection in phototrophic bacteria requires a clear description of the functional connectivity between the individual complexes comprising the photosynthetic apparatus. While significant progress has been made since the 1980s in understanding energy transfer dynamics within isolated complexes, information about intercomplex processes in intact cells is still sparse. One reason is the great complexity of intact systems that leads to highly congested spectra, especially at room temperature. Two-dimensional electronic spectroscopy (2DES) is a method that is well suited to discriminating between different subsystems and disentangling their responses, since the excitation energy is resolved along the “second dimension” of the spectra. However, 2DES on intact photosynthetic systems such as whole bacterial cells is challenging due to the high scattering properties of such samples. With a 2DES setup designed to reduce scattering, we were able to overcome these limitations. Here, we present physiological temperature measurements on intact cells of the purple photosynthetic bacterium Rhodobacter sphaeroides , which enabled us to fully map the energy transfer processes in an intact photosynthetic unit with femtosecond resolution, from the initial light-harvesting steps in the antenna complexes LH2 and LH1 through to arrival of the excitation to the reaction center. In particular, we observe the appearance of a clear signature of charge separation in the reaction center as a strong electrochromic band-shift signal. Through a global analysis approach, we extract the effective time constants for all these processes and expand the existing picture of how bacterial light harvesting works in vivo.
Assessing the foundations of forensic identification evidence: A critical examination of proficiency test design and results
Proficiency testing is widely used to assess expertise in medicine, engineering, and other high-stakes fields. In forensic science, such tests are often cited in court as evidence that pattern-comparison methods are accurate and reliable. Yet, the scientific value of proficiency testing depends on test design, scoring rules, and the extent to which results support valid inferences about real-world performance. A recent proficiency test of forensic firearm identification—the comparison of bullets and cartridge cases to determine whether they were fired from a particular gun—reported a false-positive error rate of nearly 20%. The broader significance of that result extends beyond the reported figure. We identify several limitations that can arise in forensic proficiency testing: use of items that may not reflect casework difficulty, reliance on consensus scoring rather than independently verified ground truth, inconsistent treatment of inconclusive responses, variation in test materials across examinees, and procedures vulnerable to contextual bias, including nonblind verification. These features make it difficult to distinguish examiner performance from properties of the test itself and weaken claims that reported scores estimate operational error rates. Properly constructed tests could measure individual differences in performance, identify sources of error, evaluate decision thresholds, and provide courts with more meaningful evidence about reliability. Although our focus is on firearms, these challenges extend to other pattern-comparison disciplines, including fingerprints and handwriting. We conclude that comprehensive, evidence-based reform of forensic proficiency testing is warranted.