Abstract Despite rising global-mean temperatures, large parts of the Southern Ocean and tropical eastern Pacific Ocean have cooled during the satellite era. These regions may be linked by teleconnections, with Southern Ocean cooling contributing to tropical eastern Pacific cooling. We demonstrate that, on average, state-of-the-art Earth system models (ESMs) underestimate the magnitude of interaction between the Southern Ocean and tropical eastern Pacific Ocean. The strength of the teleconnection is shown to be mediated by the magnitude of the positive cloud–sea surface temperature (SST) feedback in the subtropical eastern Pacific Ocean and the strength of the wind–evaporation–SST (WES) feedback. We link excessive precipitation in the tropical Pacific south of the equator to the strength of the Southern Ocean–eastern Pacific teleconnection. This model bias, known as the double intertropical convergence zone (ITCZ), is shown to be related to erroneous convection south of the equator, weakened cross-equatorial trade winds, and unfavorable meteorological conditions for marine boundary layer subtropical clouds. We postulate there is a two-way interaction, in which a double-ITCZ occurs with weaker cloud–SST and WES feedbacks, which in turn impact local SSTs and amplify the double-ITCZ. Models with a stronger Southern Ocean to tropical Pacific teleconnection tend to exhibit more multidecadal variability in the Walker circulation, ITCZ, and west–east equatorial SST gradient, as well as greater delayed warming in the tropical eastern Pacific Ocean resulting from delayed Southern Ocean warming under greenhouse gas forcing. These results provide insight into why ESMs struggle to replicate observed tropical Pacific temperature trend patterns and point to ITCZ location as a key target for improvement in future model development. Significance Statement The key advancement of this study is to demonstrate that, on average, state-of-the-art Earth system models underestimate the magnitude of interaction between the Southern Ocean and tropical east Pacific. As a result, historical cooling in the Southern Ocean may explain a larger fraction of observed east Pacific cooling than previously appreciated. Initial evidence suggests unrealistic precipitation simulated by models in the southeast equatorial Pacific may result in a “blocking” of high latitude influence due to its impact on the magnitude of the cloud–SST feedback and response of easterly trade winds. These results improve our understanding of the processes controlling the Southern Ocean–eastern Pacific teleconnection and provide a guide for future model development and climate trend attribution.

NMR spectroscopy is the most important technique for understanding the structure of peptides and proteins in solution. Contemporary publications in the interpretation of NMR spectra of peptides and proteins generally focus on advanced techniques and complex spectra, with a lack of simple spectra and guides available for beginning students. A data set of 1H NMR spectra was generated from a series of simple peptides that include all canonical amino acids (X) [Ac-X(S/pS)-NH2, Ac-X(T/pT)-NH2, and Ac-XPPGY-NH2; pS = phosphoserine, pT = phosphothreonine]. The characterization of each peptide includes 1-D and TOCSY spectra, with both raw and processed data available. The spectra can be used for instructional applications, including analysis of regions of the spectra (e.g., amide, aromatic, Hα, and aliphatic); identification of spin systems and residue assignment via TOCSY spectra; analysis of conformational features including amide HN chemical shift dispersion and changes due to hydrogen bonding or post-translational modifications; the 3JαN coupling constant that reports on the ϕ torsion angle and on order versus disorder at a residue; conformational preferences at Hα via chemical shift index analysis; understanding of diastereotopic hydrogens; dynamic processes, including hydrogen exchange; and identification of proline cis-trans isomerism. In addition, for a limited number of peptides, NOESY spectra are included to allow sequential resonance assignment and for assignment of trans versus cis proline conformations. Spectra from closely related peptides allow the analysis of the relative effects of single amino acid changes. The paper is written to be directly accessible to students in research laboratories or in the classroom as a tutorial guide.

Abstract We introduce and investigate a generalized methodological framework for constraining a class of modified gravity theories characterized by temporal screening mechanisms. These mechanisms implement scale-independent, redshift-dependent coupling evolution, resulting in constant modifications across all cosmological scales at fixed redshift, while evolving sharply across cosmic time. This approach is designed to test the class of theories that employ temporal screening rather than environment-dependent (chameleon, Vainshtein) screening. We demonstrate this methodology using several alternative functional forms, including exponential suppression as a primary worked example. The parameterizations generate distinctive observational signatures including µ(k, z) = µ(z) independent of wavenumber, vanishing gravitational slip Σ ≈ 0, and minimal background expansion modifications ∆H/H ≲ 1%.Fisher forecasts using DESI Year 1 specifications establish a critical detectability threshold (null-boundary) for this entire class of models. We show that a coupling strength of β 0 ≳ 0.2 is required for detection with 2σ -3σ sensitivity using a multi-probe combination. For our fiducial exponential model with β 0 = 0.3 and z tr = 1.5, redshiftspace distortions alone yield σ(β 0 ) = 0.162 (54% uncertainty), while * Independent Researcher, Nice, France. E-mail:

Covering: 2018 to 2025This Highlight article describes a personal selection of recent misassigned structures of natural products and their revision with the aid of DU8ML, a machine learning-augmented DFT computational method for fast and accurate calculations of solution NMR chemical shifts and spin-spin coupling constants.

Abstract RuO 2 is a highly active catalyst for the oxygen evolution reaction (OER). However, very little is known about the kinetics of the elementary steps that support the OER cycle on RuO 2 . The dehydrogenation of surface hydroxyl (OH*) to surface oxo (O*) is one of the elementary steps in the OER on RuO 2 . Here, we investigate the kinetics of this dehydrogenation step, which converts surface hydroxyl to surface oxo by applying scan-rate-dependent cyclic voltammetry to RuO 2 (110) surfaces. Under strongly acidic or alkaline conditions, the apparent rate constant for the OH* dehydrogenation is quicker than 10 3 s –1 . We characterize this rate across different pH values. At a constant cation strength, the O* formation rate shows a reaction order of ~0.5 with respect to [OH – ] in alkaline and to [H + ] in acidic media. This observation suggests a first-order proton-coupled electron transfer (PCET) mechanism. Higher cation concentrations positively affect the rate of OH* dehydrogenation. We attribute this finding to the impact of interfacial environment on the PCET, where charged ions can influence interfacial water molecules and facilitate electron transfer during dehydrogenation.

Employing density functional theory (DFT), we systematically investigate the structural, electronic, and magnetic spin-coupling properties of a series of homogeneous and heterogeneous dimers of reduced uracil radicals (U•-, U6H•, U5H•, U4H•). Different hydrogen-bonding (Watson-Crick, Hoogsteen, and minor-groove) and π-π stacking configurations are examined. DFT and complete active space self-consistent field calculations reveal that the double-electron reduced, hydrogen-bonded base pairs (U6H•U6H•, U5H•U5H•, U6H•U5H•, U4H•U4H•) exhibit diradical character with tunable ferromagnetic (FM) or antiferromagnetic (AFM) coupling. Hydrogen-bonded dimers linked through Watson-Crick sites typically form weakly coupled open-shell singlets, while Hoogsteen or minor-groove connections significantly enhance AFM coupling strength. These magnetic interactions are governed by a balance of hydrogen bonding, electrostatic repulsion, and radical coupling. Notably, the U6H•U•- and U5H•U•- pairs form stable, nonmagnetic closed-shell complexes under strong hydrogen bonding. For the U•-U•- dimer, double-electron reduction induces metastability, leading to a negative yet barrier-hindered dissociation energy, an unusual phenomenon arising from competing hydrogen-bond attraction and electrostatic repulsion. In contrast, π-π stacked systems exhibit significantly stronger magnetic coupling and richer magnetic behavior. This work provides the first theoretical prediction of the electronic properties of potentially doubly reduced uracil-uracil base pairs, offering new insights into their magnetic tunability.

Abstract Recently, the Covarying Coupling Constants and Tired Light (CCC+TL) hybrid model was proposed to explain the unexpectedly small angular diameters of high-redshift galaxies observed by the James Webb Space Telescope (JWST) that are challenging to reconcile with the ΛCDM model. In this work, we test the CCC+TL model against model-independent Hubble parameter [H(z)] measurements obtained from cosmic chronometers. It turns out that the parameter set optimized for the type-Ia supernova (SN Ia) dataset within the CCC+TL model fails to reproduce the H(z) data, but the ΛCDM model works well. Statistical comparison using the Δχ2 strongly favors ΛCDM over CCC+TL for the H(z) data, with Δχ2 = 61.52. Crucially, the CCC+TL framework exhibits a severe internal tension, where the SN Ia-optimized speed-of-light variation index α is rejected by the H(z) dataset with a likelihood ratio of $\mathcal {R} \approx 1.7 \times 10^{-14}$. Our result suggests that the tension posed by JWST observations of compact high-z galaxies may originate from the intrinsic properties and evolution of galaxies in the early universe.

Achieving dynamic control of light-matter coupling regimes in plasmonic nanocavities at room temperature is pivotal for quantum technologies but remains challenging due to limitations in polarization-selective excitation efficiency. Here, we demonstrate a polarization-driven reversible switch between weak and strong coupling at the vertical incidence. Leveraging radial vector beam (RVB's) cylindrical symmetry, we generate a confined longitudinal electric field that directly couples to nanoparticle-on-mirror plasmonic modes without sample tilting. This strategy enhances the local electric field by 327-fold (71% higher than linearly polarized beam, LPB) and compresses the mode field volume, amplifying the coupling strength to g = 107 meV, surpassing the strong coupling criterion. Using Rhodamine 800 as a quantum emitter, we demonstrate reversible all-optical switching between a Purcell-enhanced weak coupling regime (under LPB) and a strong coupling regime with 32.8 meV Rabi splitting (under RVB) within the molecule-nanocavity coupling system characterized by highly resolved Rabi splitting in the fluorescence spectra. Further optimization via Au nanoparticle size (R = 40 nm) and collective molecular coupling (N ≥ 5) establishes a ternary synergy for robust quantum control. This noninvasive, polarization-mediated platform enables on-demand manipulation of quantum states for reconfigurable nanophotonic devices.

We provide practical simulation methods for scalar field theories on a quantum computer that yield improved asymptotics as well as concrete gate estimates for the simulation and physical qubit estimates using the surface code. We achieve these improvements through two optimizations. First, we consider a finite volume approach for estimating the elements of the S-matrix. This approach is appropriate in general for 1+1D and for certain low-energy elastic collisions in higher dimensions. Second, we implement our approach using a series of different fault-tolerant simulation algorithms for Hamiltonians formulated both in the field occupation basis and field amplitude basis. Our algorithms are based on either second-order Trotterization or qubitization. The cost of Trotterization in occupation basis scales as O ( λ N 7 | Ω | 3 / ( M 5 / 2 ϵ 3 / 2 ) ) where λ is the coupling strength, N is the occupation cutoff, | Ω | is the volume of the spatial lattice, M is the mass of the particles and ϵ is the uncertainty in the energy calculation used for the S -matrix determination. Qubitization in the field basis scales as O ( | Ω | 2 ( k 2 Λ + k M 2 ) / ϵ ) , where k is the cutoff in the field and Λ is a scaled coupling constant. We find in both cases that the bounds suggest physically meaningful simulations can be performed using on the order of 4 × 10 6 physical qubits and 10 12 T -gates which corresponds to roughly one day on a superconducting quantum computer with surface code and a cycle time of 100 ns. This places the simulation of scalar field theory within striking distance of the gate counts for the best available chemistry simulation results.

Abstract Electron localization is one of the focal topics in condensed matter physics. Particularly in materials where electrons couple with lattice/spin degrees of freedom, an accurate characterization of electron localization would not only advance our understanding of correlated electron systems but also hold potential as a key to unraveling the long-standing puzzle of high-temperature superconductivity. Here, utilizing angle-resolved photoemission spectroscopy (ARPES), we unveiled an electron localization that occurs on the surface of a two-dimensional antiferromagnetic metal PdCrO 2 . Various characteristics of electron localization were observed including quasiparticle mass renormalization, the "waterfall" feature, high-energy incoherent states, and pseudogap. We found that the energy scale of band renormalization is highly correlated with the mode coupling energy observed in the metallic state, suggesting that the localization behavior can be explained by a polaron localization driven by an enhancement of coupling between electrons and lattice/spin excitations. Our data highlight the phenomena that emerges universally in complex correlated systems where electrons couple with lattice/spin excitations. This provides experimental validations for various theoretical models of delocalized correlated systems. Our results also demonstrate that the coupling strength can be tuned continuously on the surface of PdCrO 2 , making it a model system for investigating the exotic phenomena in complex correlated materials.

A bstract We present a comprehensive analysis of generic 5-dimensional Einstein-Maxwell-Dilaton-Axion (EMDA) holographic theories with exponential couplings. We find and classify exact, analytic, anisotropic solutions, both zero-temperature vacua and finite-temperature black brane backgrounds, with anisotropy sourced by scalar axions, magnetic fields, and charge densities, that can be interpreted as IR fixed points of renormalisation-group flows from UV-conformal fixed points. The resulting backgrounds feature a hyperscaling violation exponent and up to three independent Lifshitz-like exponents, generated by an equal number of independent coupling constants in the EMDA action. We derive the holographic stress-energy tensor and the corresponding equation of state, and discuss the behavior of the anisotropic speed of sound and butterfly velocity. We show that these theories can be consistently constrained by imposing several natural requirements, including energy conditions, thermodynamic stability, and causality. Additionally, we analyse hard probes in this class of theories, including Brownian motion, momentum broadening and jet quenching, and we demonstrate that a fully analytic treatment is possible, making their dependence on the underlying anisotropy explicit. We highlight the relevance of these models as benchmarks for strongly coupled anisotropic matter in nature, from the quark-gluon plasma created in heavy-ion collisions to dense QCD phases in neutron-star mergers and the cores of compact objects.

Electronic-structure calculations using complex absorbing potentials (CAPs) to stabilize temporary anion states are very sensitive to the CAP configuration, including the coupling strength (η) and boundary geometry. We present high-resolution surveys of several two-dimensional parameter spaces (CAP spaces for short) for the CO- (2Π) and N2- (2Πg) resonances and propose an efficient optimization strategy for box-CAPs that relies on Gyamfi and Jagau's ξ error function [J. Chem. Theory Comput. 2024, 20, 1096-1107]. In all CAP spaces probed, only narrow parameter ranges yield the highest-quality results (ξ ∼ 10-4-10-5) that minimize wave function reflections and perturbations. Such optimal conditions are unlikely to be found by ad hoc methods, necessitating a systematic optimization protocol. Ours begins with (η, ro)L optimization trajectories, where ro is a geometric variable controlling the CAP boundary and L is a distinct parameter such as the box elongation. Unlike extensively studied η- and ro-trajectories, the (η, ro)L trajectories are optimum-seeking paths in two-dimensional CAP spaces searching for ξ minima. After optimizing CAPs across multiple (η, ro)L spaces with varying L, CAP strength minimization along the L-trajectory defines the overall optimal configuration in the higher-dimensional (η, ro, L) space. This hierarchical optimization, min ξ ≻ min η (where "≻" denotes lexicographic precedence), produces a low-error description of the resonance (min ξ) stabilized by the weakest (but sufficient) CAP possible, i.e., min η subject to the min ξ constraint.

An adaptive decoupling learning system informed by the brain functional structure for EEG decoding.

We perform a comparative Bayesian analysis of fermionic and bosonic dark matter admixed neutron stars (DMANS) by incorporating a comprehensive set of theoretical, experimental, and astrophysical constraints. The hadronic matter equation of state (EoS) is modeled using a relativistic mean-field approach, constrained by chiral effective field theory (χEFT) calculations at low densities, finite nuclei and heavy-ion collision data at intermediate densities, and neutron star (NS) observations at high densities. For the dark sector, we consider fermionic dark matter (FDM) interacting via a dark vector meson, and two bosonic dark matter models (BDM1 and BDM2) characterized by self-interacting scalar fields. Bayesian inference is employed to constrain the model parameters, including the dark matter mass, coupling strength, and dark matter fraction within NSs. Our analysis finds that all models yield consistent nuclear matter parameters, allowing a small dark matter fraction under 10%. The presence of dark matter slightly softens the EoS, leading to a modest reduction in NS mass, radius, and tidal deformability, though all models remain compatible with NICER and GW170817 observations. The log-evidence and likelihood analyses reveal no statistical preference among the FDM and BDM models, indicating that current astrophysical data cannot decisively distinguish between fermionic and bosonic dark matter scenarios. This study provides a unified statistical framework to constrain dark matter properties using NS observables.

Biphasic adaptation of gBOLD-CSF coupling during sleep deprivation reflects compensatory enhancement and temporal disruption in glymphatic function.

Observed declining strength of vegetation-atmosphere coupling

Abstract We present a spherically symmetric stellar model within the framework of seven dimensional third order Lovelock gravity for a neutral perfect fluid distribution. The third order Lovelock field equations are generated for such a fluid configuration by imposing pressure isotropy. This condition yields a first order nonlinear differential equation which is an extension of the Abel differential equation. This is due to the additional higher order curvature effects arising in third order Lovelock gravity. We demonstrate new exact solutions that can model a static spherically symmetric star. The energy density and pressure are both variable. We also show that a special case arises, which is a constant density model with a cosmological interpretation. Furthermore, we illustrate the matching conditions to generate a spherically symmetric stellar model in third order Lovelock gravity when the EGB and third order Lovelock coupling constants are related.

The Higgs sector of the Two-Measure Theory (TMT) extension of the electroweak SM (TMSM) is studied in the context of cosmology, where the only non-zero component φ of the cosmologically averaged Higgs field plays the role of the inflaton.The self-consistency of the system of equations obtained from the original action has the form of an algebraic constraint defining the scalar ζ, which is the ratio of two volume measures, as a function of the field φ and its first derivatives.The scalar ζ is present in all equations of motion and has a significant effect on the dynamics of the fields. After the transition in the equations of motion to the Einstein frame with the spatially flat Friedmann metric, it is convenient to describe the resulting system of equations using the action S eff and the Lagrangian L eff, which we call the TMT-effective action and the TMT-effective Lagrangian and from which these equations can be obtained. Due to the constraint, the original model parameters are converted in L eff into φ-dependent classical effective parameters. In particular, the effective potential U eff(φ) in L eff has the form U eff = λ/4ξ 2 MP 4· F(φ)·tanh4(√(ξ)φ/MP ), where F(φ) is a smooth function equal to F(φ) ≈ 1/2 for φ > 6MP .It is fundamentally important that the constant ξ of non-minimal coupling to the scalar curvature can be chosen small. If ξ = 1/6, then to ensure agreement with CMB observational data, the Higgs field self-coupling parameter λ in the original action must be of the order of ∼ 10-11. During cosmological evolution after the end of inflation, the decrease of φ leads to a change in the sign of the effective Higgs mass term in L eff. This TMSM effect provides an answer to the mystery of the Higgs potential structure and leads to spontaneous symmetry breaking. As φ approaches VEV, the scalar function ζ(φ) changes in such a way that the classical TMT-effective self-coupling parameterλ(ζ(φ)) increases by 10 orders of magnitude compared to λ, which is necessary for the implementation of the GWS theory. Applying the model to the very beginning of the classical evolution of the Universe shows that under certain initial conditions, cosmological dynamics can begin with a “pathological” and even phantom regime preceding inflation.However, if evolution begins with normal dynamics, then it proceeds only as inflation, and the problem of initial conditions for the onset of inflation does not arise. The fermion preheating model is described as a preliminary study of preheatig after inflation. Mathematical and physical arguments in favor of using the TMT are presented.

Neutron stars (NS), with their extreme gravitational and magnetic fields, provide an exceptional astrophysical laboratory for studying axion dark matter (DM). Through the Primakoff effect, axions can convert into photons within the magnetospheres of NS, a process that may produce observable radio and X-ray signals. In this work, we investigate axion-photon conversion using a novel, time-dependent state evolution formalism, moving beyond the commonly used stationary-path approximations. We derive a generic analytical expression for the conversion probability and calculate the associated radiated power. Our analysis demonstrates that this approach allows NS to strongly constrain the axion-photon coupling constant, reaching sensitivities of gaγγ ≃ 10−14 −10−15 GeV−1 for axion masses of ma ≃ 10−3 −10−10 eV. These results establish a new pathway to constrain gaγ via NS observations. Future campaigns using powerful observatories like the James Webb Space Telescope (JWST), Green Bank Telescope (GBT), and More Karoo Array Telescope (MeerKAT) array will be ideally suited to probe the distinct spectral signatures predicted by our model across multiple frequency domains.

Clinical study on glymphatic system dysfunction in patients with temporal lobe epilepsy.