RIKEN

Gold nanoparticles (AuNPs) have been utilised as colorimetric biosensors because of their optical properties. Single-stranded DNA (ssDNA)-immobilised AuNPs (ssDNA-AuNPs) are widely used for nucleic acid detection. AuNPs strongly scatter light, allowing individual particles to be observed using dark-field microscope (DFM). In this study, we performed target ssDNA detection using the cross-linked aggregation of ssDNA-AuNPs via DFM. The limit of detection (LOD) was determined by evaluating the aggregation ratio of the ssDNA-AuNPs estimated at the single-cluster level using DFM images. The LOD for the target ssDNA detection based on the intensity of each spot in the DFM image was 15pM. To the best of our knowledge, this study is the first to perform a single-cluster analysis based on the red/gree/blue (RGB) values of individual spots in DFM images, and the LOD was determined to be 13pM. These LOD values are approximately 50 times lower than those obtained using the colorimetric method. Our results indicate that single-cluster analysis based on the intensity or colour of each spot in DFM images enables sensitive detection of target molecules.

The gut microbiome is a highly dynamic ecosystem, yet its temporal organization remains poorly understood because microbiome sampling is typically limited to sparse time points. To overcome this challenge, we developed an automated device to enable continuous fecal sampling from individual mice at minute- to hour-scale resolution. Combining full-length 16S rRNA amplicon sequencing with a limited set of long-read metagenomic references, we economically reconstructed genome- and function-level trajectories at high temporal resolution. Automated hourly sampling over 14 consecutive days enabled phase analysis, revealing collective synchronization of taxa partitioned by carbohydrate utilization strategies between day and night, with microbial taxa and functional genes showing reproducible temporal succession across mice. Perturbations such as cage transfer or antibiotic treatment transiently disrupted this functional synchronization, followed by recovery toward a coherent dynamical state. This system and analytic frameworks will enable us to explore rapid microbiome dynamics in health and disease.

Both long-tailed and noisily labeled data frequently appear in real-world applications and impose significant challenges for learning. Most prior works treat either problem in an isolated way and do not explicitly consider the coupling effects of the two. Our empirical observation reveals that such solutions fail to consistently improve the learning when the dataset is long-tailed with label noise. Moreover, with the presence of label noise, existing methods do not observe universal improvements across different sub-populations; in other words, some sub-populations enjoyed the benefits of improved accuracy at the cost of hurting others. Based on these observations, we introduce the Fairness Regularizer (FR), inspired by regularizing the performance gap between any two sub-populations. We show that the introduced fairness regularizer improves the performances of sub-populations on the tail and the overall learning performance. Extensive experiments demonstrate the effectiveness of the proposed solution when complemented with certain existing popular robust or class-balanced methods.

Abstract We report the detection of methanol (CH 3 OH) toward interstellar comet 3I/ATLAS using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1 and of hydrogen cyanide (HCN) on September 12 and 15. These observations spanned pre-perihelion heliocentric distances ( r H ) of 2.6–1.7 au. The molecules showed outgassing patterns distinct from one another, with HCN production being depleted in the sunward hemisphere of the coma, whereas CH 3 OH was enhanced in that direction. Statistical analysis of molecular scale lengths in 3I/ATLAS indicated that CH 3 OH included production from coma sources at L p &gt; 258 km at 99% confidence. However, low signal-to-noise ratio (S/N) on long baselines, which sample emission on small spatial scales closest to the nucleus, prevented definitively ruling out CH 3 OH as purely a parent species. In contrast, HCN production was indistinguishable from direct nucleus sublimation. The CH 3 OH production rate increased sharply from August through October, including an uptick near the inner edge of the H 2 O sublimation zone at r H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH 3 OH/HCN ratios in 3I/ATLAS of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>34</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>30</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (Pan-STARRS).

Precise control over multiple coordination sites is critical for directing molecular assembly on surfaces, a challenge well suited to N-heterocyclic carbenes (NHCs) owing to their strong σ-donation and tunable steric properties. In previously reported bisNHC systems, on-surface carbene generation from salt precursors requires elevated temperatures, driving adsorption into thermodynamically favored flat-lying configurations that obscure intrinsic binding behavior. Here, we employ isolable bisNHC derivatives bearing isopropyl and tert-butyl substituents, enabling their direct deposition as unprotected molecular precursors. Scanning tunneling microscopy and near-edge X-ray absorption fine structure measurements reveal that both derivatives adopt flat-lying geometries; however, their lateral assembly behavior differs markedly. The isopropyl substituted derivative forms mutually repulsive chains, whereas the more sterically hindered tert-butyl derivative (bisNHCtBu) unexpectedly assembles into a close-packed, dipole-driven molecular lattice. The bisNHCtBu lattice is stable at room temperature but thermally fragile, underscoring the difficulty of accessing this architecture via protected-precursor approaches. The bisNHCtBu lattice exhibits a wide spectroscopic bandgap and contains aligned metal-binding cavities that enable observation of spin-flip excitations of deposited dysprosium atoms. This molecular lattice provides a versatile platform for probing emergent electronic and magnetic properties and the single molecule reactivity of surface-confined, low-coordinate metal complexes.

Abstract We propose that a hierarchical shock model—including supernova remnant shocks, galactic wind termination shocks, and accretion shocks around cosmic filaments and galaxy clusters—can naturally explain the cosmic-ray spectrum from ∼1 GeV up to ∼ 200 EeV. While this framework applies to the entire cosmic-ray spectrum, in this work we focus on its implications for ultra-high-energy cosmic rays (UHECRs). We perform a hydrodynamic cosmological simulation to investigate the power processed at shocks around clusters and filaments. The downstream flux from nearby shocks around the local filament accounts for the softer, lower-energy extragalactic component around the ankle, and the upstream escaping flux from nearby clusters accounts for the transition to a hard spectral component at the highest energies. This interpretation is in agreement with UHECR observations. We suggest that a combination of early Universe galactic outflows, cosmic-ray streaming instabilities, and a small-scale turbulent dynamo can increase magnetic fields enough to attain the required rigidities. Our simulation suggests that the available volume-averaged power density of accretion shocks exceeds the required UHECR luminosity density by 3 orders of magnitude. We show that microgauss magnetic fields at these shocks could explain both the origin of UHECRs and potentially contribute to the diffuse radio synchrotron background below 10 GHz. The shock-accelerated electrons produce a hard radio background without overproducing diffuse inverse Compton emission. These results motivate further observational tests with upcoming facilities to help distinguish accretion shocks from other UHECR sources.

Skin impedance reflects both the barrier function and psychophysiological state of the human body, but long-term monitoring remains challenging due to the lack of electrodes that simultaneously offer water resistance, stretchability, and breathability. In this study, we developed poly(vinyl alcohol)/waterborne polyurethane (PVA/WBPU) blend nanomesh electrodes with controlled polymer composition to address these requirements. Electrospinning produced nanofibers with an island–sea morphology, where partial dissolution of PVA enabled temporary skin adhesion while residual WBPU maintained structural integrity. The optimized PVA/WBPU = 5/5 electrodes showed minimal resistance increase (1.02-fold) after 24 h of continuous water flow and retained conductivity under 80% strain and after 1000 stretch cycles. When applied to the palm, they maintained stable resistance ( < 50 Ω) for at least 4 h, whereas PVA-only electrodes frequently exhibited resistance increases above 1 kΩ or electrical disconnection. These results indicate that controlling the PVA/WBPU blending ratio ensures mechanical and electrical stability while preserving breathability, establishing a materials design strategy for long-term, skin-conformable, and breathable bioelectronic interfaces.

ABSTRACT In natural environments, plants are exposed to several abiotic stresses. Although plant responses to individual stressors have been well characterized, our knowledge of their responses to combined stressors is limited. In this study, we have analyzed the transcriptional responses of Arabidopsis to a combination of high light and cold stresses, because these conditions are considered major stressors that impact the same target, photosynthesis. Transcriptome analysis revealed that cold-activated genes can be divided into the following two groups: (1) genes whose expression is enhanced by high light and (2) genes whose expression is not enhanced by high light. The first group includes photoprotection-related genes, such as ELIP2 and CHS, and the second group includes DREB1A/CBF3-activated frost tolerance genes, which are associated with their physiological roles. Our findings help to elucidate the molecular machinery involved in plant acclimation during the winter season.

Abstract We investigate the chemical evolution of a forming molecular cloud behind an interstellar shock wave. We conduct three-dimensional magnetohydrodynamics simulations of the converging flow of atomic gas, including a simple chemical network and tracer particles that move along the local velocity field. Then we perform detailed chemical network calculations along the trajectory of each tracer particle. The diffuse part of forming molecular clouds is CO-poor; i.e., H2 and CO abundances do not correlate. In diffuse regions of nH ≲ 103 cm−3, we find that the abundances of hydrocarbons and oxygen-bearing molecules are determined by steady-state chemistry reflecting the local H2 abundance, which is determined by the gas density along the trajectory. In denser regions, the abundances are affected by water ice formation, which changes the elemental abundance of carbon and oxygen (i.e., C/O ratio) in the gas phase. Assuming quasi-steady-state chemistry given the abundances of major molecules (e.g., H2) from the simple network, we derive analytic solutions for molecular abundances, which reproduce the calculation results. We also calculate the molecular column densities based on the spatial distribution of tracer particles and their molecular abundances, and compare them with observations of diffuse molecular clouds. We find that the column densities of CH, CCH, and OH are linearly correlated with those of H2, which supports the empirical relation used in the observations. On the other hand, the column density of HCO+ shows non-linear dependence on the H2 column density, reflecting the difference in HCO+ formation paths in CO-poor and CO-rich regions.

In lines 2, 3, 7, and 11 of Algorithm 2, our 27 half-box patterns are mathematically defined.In lines 11-14 of Algorithm 2, hi for i [21, 26] is computed by subtracting the color sum of 9 voxels from h27 rather than taking the color sum of 18 voxels for efficiency.