Browse Articles

Intramolecular nuclear dynamics in intermolecular Coulombic electron capture

We present an analytical model for intermolecular Coulombic electron capture (ICEC), which includes the internal nuclear dynamics of the molecules involved. In ICEC, an electron attaches to an atom or molecule by transferring excess energy to a neighbor, ionizing said neighbor. While previous theoretical investigations assumed fixed nuclei, recent studies indicate that relative motion between the two ICEC partners significantly influences the process. Here, we incorporate the internal nuclear motion of the molecules involved into an analytical equation of the ICEC cross section. We employ two approaches: (1) utilizing theoretical vibrationally resolved photoionization cross sections and (2) applying the Franck–Condon principle. Our theory yields electron spectra, ICEC cross sections for individual vibronic transitions, and temperature dependent cross sections. Nuclear dynamics lead to a distribution of the electronic cross section over several vibrational states and, in our model system H+ LiH, trigger dissociation of LiH during ICEC.

Decoupling sublattice dynamics in low-dose neutron-irradiated 4H-SiC via two-component density functional theory guided positron annihilation spectroscopy

Silicon carbide (SiC) is a premier candidate for nuclear applications, yet characterizing the nascent damage from low-dose neutron irradiation remains a challenge due to the complex behavior of its two sublattices. A typical example is that the standard S–W parameter analysis method for Positron Annihilation Doppler Broadening Spectroscopy (PADBS) is insensitive to low-density vacancy-type defects in materials. In this study, we investigate 4H-SiC subjected to 14 MeV fusion neutron fluences of 1 × 1013–2 × 1013 n/cm2. We report a distinct inconsistency: while the positron lifetime (τ) obtained from Positron Annihilation Lifetime Spectroscopy indicates a measurable evolution in defect characteristics, standard S and W parameters obtained from PADBS remain seemingly static. By combining experimental data with Two-Component Density Functional Theory calculations, we demonstrate that this stagnation is an artifact caused by the overwhelming positron trapping cross section of silicon vacancies (VSi), which masks the carbon vacancies (VC) signal. By utilizing a chemically resolved P-parameter method, we successfully decouple the sublattice signatures, revealing a ∼4.4% decrease in the carbon-to-silicon vacancy ratio (VC/VSi). This shift provides direct evidence of preferential dynamic annealing on the carbon sublattice and the clustering of vacancies into VSi-like complexes, mechanisms previously invisible to standard S–W analysis. Most importantly, this study extends the application of PADBS, enabling the effective detection of initial damage characteristics at low doses.

A prospective study of TyG index and ePWV in relation to hypertension risk

Phase behavior, self-assembly, and interfacial tension of a dynamically linked polymer blend

Compatibilizing immiscible polymer blends is a challenge and a significant barrier to improving the recycling of polymers. Recent computational and experimental studies have demonstrated that the addition of dynamic cross-links (bonds between chains with a finite lifetime) provides a potentially viable approach to compatibilize blends. We implement a Metropolis-based algorithm for creating reversible dynamic bonds within molecular dynamics simulations, which allows us to systematically investigate the impact of dynamic cross-linking on phase behavior, self-assembly, and surface tension. We find that the presence of dynamic cross-linkers between different polymer types decreases both the critical temperature for phase separation and surface tension, i.e., improved compatibilization. We also show that the assembly of cross-linked chains can be mapped to a coarse-grained model of patchy particle self-assembly, where the effective number of sticky sites increases with chain length. The competing effects of inter-species cross-links vs self-cross-links (between the homopolymer chains of the same chemistry) are also systematically examined. Curiously, we find that when the propensity for cross-links between different polymer types is the same as the propensity for cross-links with the same type, the effect of dynamic bonds on phase behavior and surface tension is essentially neutralized, and thus, the blend behaves nearly the same as a cross-link-free blend. Moreover, when the propensity for self-cross-linking is higher, the blend becomes less miscible, so the type of cross-linking is critically important. In addition, we demonstrate that the surface tension for phase-separated systems with varying propensities to form dynamic bonds collapses to a master curve that is dictated by the interfacial density of distinct dynamic cross-links.

Extending the exquisite control of molecular beam epitaxy to the other dimensions: Nanostructure engineering

Molecular beam epitaxy (MBE) is a widely used tool for growing nanostructures and thin films, offering precise control and a near defect-free growth environment. While state-of-the-art MBE-grown materials remain primarily limited to small-scale research settings, the transition toward scalable production is critical for enabling real-world device applications. This Perspective highlights recent developments in nanostructures, which include quantum dots, van der Waals materials, and nanoparticle inclusions, and discusses techniques for integrating them into devices such as emitters and waveguides. It further explores emerging approaches for the fabrication of 3D nanostructures in predefined positions, incorporating semi-metals in semiconductors, and their subsequent large-scale integration into quantum devices.

Author Correction: Enteric neurons increase maternal food intake during reproduction

Apparent diffusion coefficient and intravoxel incoherent motion-derived true diffusion serve as early non-contrast longitudinal biomarkers of neoadjuvant chemotherapy response

Abstract Locally advanced breast cancer (LABC) frequently requires neoadjuvant chemotherapy (NAC), and early, non-contrast imaging biomarkers are of increasing clinical interest for monitoring treatment response. Diffusion-weighted imaging (DWI) and intravoxel incoherent motion (IVIM) MRI provide quantitative measures of tumour microstructure without gadolinium administration. To evaluate whether the apparent diffusion coefficient (ADC) and true diffusion (Dt) derived from IVIM can serve as early non-contrast imaging biomarkers of NAC response in patients with LABC. Fourteen women with biopsy-proven LABC underwent MRI at baseline (T0), after the first NAC cycle (T1), and after the third cycle (T2). ADC was calculated from b = 0 and 1000 s/mm², while Dt, Dp, and f were obtained using a full bi-exponential IVIM model incorporating all b-values (0–1000 s/mm²). Only four patients completed all three MRI timepoints. Tumour diameter and diffusion parameters were compared across time. At baseline, ADC and Dt were significantly lower in malignant lesions compared with contralateral fibroglandular tissue ( p  < 0.01). Following NAC, mean tumour ADC increased by 27.2% at T1 and 39.5% at T2, accompanied by progressive tumour size reduction (50.9% at T2). Dt demonstrated a similar upward trend. Perfusion-related IVIM parameters (Dp and f) showed no consistent differences. ROC analysis demonstrated high discriminatory performance of ADC for differentiating invasive ductal carcinoma from normal tissue (AUC = 1.00), although this finding must be interpreted cautiously given the small sample size. ADC and Dt showed early increases following NAC that paralleled reductions in tumour size, supporting their potential as practical, contrast-free imaging biomarkers of treatment-related microstructural changes. However, the limited number of complete longitudinal datasets ( n  = 4) and the pilot nature of the study require cautious interpretation. Larger prospective studies are needed to validate these findings.

Accurate thermophysical properties of water using machine-learned potentials

Simulating water from first principles remains a significant computational challenge due to the slow dynamics of the underlying system. Although machine-learned interatomic potentials (MLPs) can accelerate these simulations, they often fail to achieve the required level of accuracy for reliable uncertainty quantification. In this study, we use MACE—an equivariant graph neural network architecture that has been trained using an extensive RPBE-D3 database—to predict density isobars, diffusion constants, radial distribution functions, and melting points. Although equivariant MACE models are computationally more expensive than simpler architectures, such as kernel-based potentials (KbPs), their significantly lower total energy errors allow for reliable thermodynamic reweighting with minimal bias. Our results are consistent with those of previous studies using KbPs; however, equivariant models can be validated against the ground-truth density functional theory (DFT) ensemble with significantly increased efficiency. These findings establish equivariant MLPs as robust and reliable tools for investigating the thermophysical properties of water with DFT-level accuracy.

Comprehensive determination of Burgers vectors of threading dislocations in GaN substrates by combining reflection and transmission synchrotron-radiation x-ray topography

Burgers vectors (b) of threading dislocations (TDs) in an acidic ammonothermal-grown GaN substrate were investigated using synchrotron radiation x-ray topography (SR-XRT) by combining both reflection and transmission modes. Reflection XRT images recorded with six equivalent g vectors of 112¯4 revealed spot-like contrasts corresponding to TDs. Based on the contrast conditions, the possible Burgers vectors were constrained, and the c axis component of b for mixed-type TDs was estimated from the contrast size. Using transmission XRT images recorded under several two-beam diffraction conditions, the (0001) in-plane direction of b was evaluated based on the g·b invisibility criterion. Furthermore, by analyzing the linewidths of dislocation images observed under kinematical diffraction contrast, the magnitude of the a axis component of b was determined. By combining these analyses, the Burgers vectors of individual TDs, including edge- and mixed-type dislocations, were determined. In addition, a pair of screw-type TDs with opposite Burgers vectors, ±1c, was observed in the transmission SR-XRT. These results demonstrate that the combined use of reflection and transmission SR-XRT provides a practical approach for complete determination of Burgers vectors in GaN substrates.

Knowledge, attitudes, and practices among guardians toward inherited retinal diseases: a structural equation modeling analysis

Abstract This study aimed to investigate the knowledge, attitudes, and practices (KAP) among guardians toward inherited retinal diseases (IRDs) in children. This multicenter cross-sectional study, conducted from June 23, 2024, to February 23, 2025, invited guardians of children diagnosed with IRDs at the outpatient or inpatient departments of Tongren City People’s Hospital and its affiliated hospitals to complete a questionnaire. Path analysis was employed to examine the relationships among KAP. This study included 459 participants (51.2% male; mean age 51.44 ± 8.12 years). The KAP scores for KAP were 8.32 ± 1.61 (range: 0–17), 33.25 ± 3.51 (range: 10–50), and 36.93 ± 3.76 (range: 10–50), respectively. Path analysis revealed that knowledge had a significant direct effect on attitudes (β = 0.22, P  = 0.023), and attitudes had a significant direct effect on practices (β = 0.66, P  < 0.001). Although the direct effect of knowledge on practices was not significant, an indirect effect was observed through attitudes (β = 0.15, P  = 0.024). Guardians of children with IRDs have limited knowledge and relatively negative attitudes, yet their practices are comparatively positive. These findings highlight the need for enhanced disease-related education on clinical variability to improve parental knowledge, foster more positive attitudes, and promote proactive health practice.

Anomalous thermodynamic properties of water: What is wrong and/or missing in SAFT equations?

This work is motivated by a simple question: why have none of the Statistical Association Fluid Theory (SAFT)-type equations of state proposed for water so far—perturbation-like models with several adjustable parameters—been able to reproduce water’s thermodynamic properties over a broad range of conditions, even at a qualitative level? We examine two theoretical, analytically treatable water models of different character, i.e., models that provide genuine predictions without being parameterized to experimental thermodynamic data. The first is an extremely simple toy model designed to capture the essential physics of association. The second is a short-range model derived from the realistic TIP4P force field and intended for the same purpose. For both models, we compute the isobaric temperature dependence of the density and three response functions: the isothermal compressibility, the isobaric expansivity, and the isobaric heat capacity over a wide range of thermodynamic conditions. The results are compared with experimental data and with predictions from the best-performing SAFT equation identified in our earlier work. We show that the short-range models correctly capture the characteristic behavior of the density and the isothermal compressibility, as well as the critical compressibility factor and the universal expansivity point (the crossing point) of the isobaric expansivity—features that are generally missing in SAFT-type equations. However, these short-range models fail to reproduce the heat capacity, which is an expected consequence of missing long-range electrostatic contributions. We argue that the shortcomings of existing SAFT equations for water stem from (i) the arbitrariness in defining the reference system, (ii) neglecting the van der Waals interaction in the reference completely, (iii) the ambiguity of the correction terms, and (iv) the subsequent parameter-estimation strategy.

<i>In situ</i> characterization of microstrip line using near-field scanning microwave microscopy

With the continuous scaling and increasing operating frequencies of microwave integrated circuits, accurate characterization of on-chip microwave signal propagation and field distributions has become increasingly important for ensuring circuit reliability and performance stability. To address this challenge, we have developed a beat-frequency-enhanced near-field scanning microwave microscopy, which enables in situ, non-destructive characterization of the microwave field distributions on microstrip line surfaces under operating conditions. When the probe–sample distance and the surrounding dielectric environment are kept constant, the oscillation amplitude of the transmission coefficient S21, ΔS21can serve as a relative indicator of the surface microwave field strength of the microstrip line. The experimental results demonstrate that ΔS21 exhibits a positive correlation with the input signal power applied to the sample. Furthermore, as the input signal frequency of the sample approaches the resonant frequency of the probe–sample coupling, the detection sensitivity of ΔS21 to the input signal power is significantly enhanced, with a minimum detectable power as low as −40 dBm. Surface scanning results reveal clear visualization of microwave field strength distributions for both standard and defective microstrip lines, in good agreement with simulation data. The proposed technique offers a promising pathway for real-time diagnostics of high-frequency integrated circuits, combining high sensitivity, non-destructive evaluation, and compatibility with practical operating environments.

Experimental investigation of ZnO nanoparticle–enhanced pongamia biodiesel for performance, combustion, emission, and sustainability assessment in a CI engine

Geometric thermodynamics in open quantum systems: Coherence, curvature, and work

We formulate a geometric framework for quasistatic thermodynamics in open quantum systems by parameterizing the dynamics on a control manifold. In the quasistatic limit, the system follows a manifold of stationary states, and the work performed over a cycle is given by the flux of a curvature two-form, W ∼∫Ω, defined by the parametric response of the stationary state, establishing an open-system analog of classical thermodynamic area laws. For thermal stationary states at a fixed temperature, the curvature vanishes, reflecting the integrability of the work one-form. Beyond this limit, nonequilibrium stationary states can retain coherence in the energy representation; using a fixed-basis Lindblad model, we show that this coherence reshapes the curvature, making it anisotropic and sign-changing, so that work depends sensitively on the placement and orientation of the cycle. Quantum coherence, therefore, partitions the control manifold into regions of opposite curvature, producing geometric cancellation of work and allowing the net work over a cycle to be reduced or reversed despite dissipative dynamics. Thermodynamic work thus emerges as a curvature flux whose structure is set by thermodynamic response in classical systems and by basis misalignment between the Hamiltonian eigenbasis and the environment-selected pointer basis in open quantum systems.

Surface height modulation in strain relaxation and its smoothing using solid state crystallization in InAs quantum-well growth on GaAs

Relaxation of lattice-mismatch strain in the epitaxial growth of InAs quantum-well structures on GaAs substrates produces height modulations on the surface. The surface meandering is known as the cross-hatch pattern that appears generally in the highly lattice-mismatched growth of (001)-oriented cubic crystals. We show that the magnitude of the height modulation in molecular beam epitaxy is reduced by incorporating a layer prepared using solid state crystallization. The surface morphology is also shown to become irregular or even checker-board-like when the relaxation is caused immediately by an abrupt composition change. We demonstrate a method for localizing threading dislocations in the buffer layer in such a circumstance. Electron mobility increases for the quantum wells prepared on the abruptly-relaxed buffer layer.

Linear RAG scanning mediates editing of Igκ variable region repertoires

Abstract V(D)J recombination-mediated Igκ light chain variable region exon assembly in precursor (pre)-B cells involves recombination activating gene (RAG) endonuclease-orchestrated cleavage between and joining of paired Vκ and Jκ gene segments and flanking RAG-targeting recombination signal sequences (RSSs) 1–3 . The 3.1-megabase Igk contains 4 Jκs (Jκ1, 2, 4, 5) and 100-plus Vκs in clusters oriented for deletional or inversional joining 2 . Vκ-to-Jκ joining is ordered, with primary Vκ-to-Jκ1 rearrangements occurring first, followed by secondary rearrangements of upstream Vκs that replace primary VκJκ1s by joining to Jκ2-5 (refs. 4,5 ). Loop extrusion moves deletional-oriented and inversional-oriented, locus-wide Vκs past the Cer/Sis CTCF-binding element-based diffusion platform for short-range diffusional presentation to Jκ1-bound RAG in the primary recombination centre (RC). To achieve diffusion-mediated Vκ-to-Jκ1 joining, Igk evolved powerful Vκ-associated and Jκ-associated RSSs 3 . Secondary Igk rearrangements replace non-functional or autoreactive primary VκJκ1 rearrangements, expanding the Igκ repertoire and mediating central tolerance by means of receptor editing 4,6–11 . Here we describe studies that elucidate the physiologically critical secondary Igk recombination mechanism. Primary deletional and inversional VκJκ1 joins, respectively, delete or displace Cer/Sis, creating a pre-B cell population that harbours secondary VκJκ1-based RCs across the Vκ locus and leaves most unrearranged Vκs immediately upstream of secondary RCs in deletional orientation. High-throughput assays demonstrated that RAG scanning from secondary VκJκ1-based RCs, collectively, extends linearly across the Vκ locus in primary pre-B cell populations. Correspondingly, studies of induced pluripotent stem (iPS) cell-generated mouse models or cell lines with physiological VκJκ-rearrangements further revealed that deletional and, originally, inversional Vκs are mostly captured by Jκ2-5-based secondary RCs in deletional orientation by means of linear RAG scanning. Strong Vκ - RSSs contribute to restricting secondary rearrangements, including potential editing rearrangements, to Vκs immediately upstream of a given secondary RC and support, at a lower level, linear scanning-based inversional Vκ-to-Jκ rearrangements. Our findings implicate Cer/Sis deletion and/or displacement as a developmental switch that converts the two-loop-based diffusional primary Igk rearrangement mechanism into a one-loop-based linear scanning secondary rearrangement mechanism.

Impact of music intervention on endoscopic retrograde cholangiopancreatography patients’ pain, anxiety, and vital signs: a randomized controlled trial

Ghost-mode filtered fluctuating lattice Boltzmann method

Fluctuating lattice Boltzmann solvers are widely employed to model mesoscopic fluid behavior in soft-matter systems, including colloidal suspensions and dilute polymer solutions. Despite their utility, these methods can lose accuracy and stability when non-hydrodynamic modes interfere with the dynamics, especially in single-relaxation-time schemes. Here, we introduce a ghost-mode filtered fluctuating lattice Boltzmann method (GMF-FLBM) for the D3Q27 lattice, obtained by selectively eliminating the propagation of the ghost deterministic content while preserving the necessary stochastic forcing. We show, over a broad range of relaxation times, that GMF-FLBM recovers the amplitudes of equilibrium fluctuations with a comparable accuracy to a fully regularized high-order formulation, while requiring only minor adjustments to the conventional BGK collision framework.

A brief pedagogic review of frequency-dependent Johnson Nyquist noise

We present a pedagogical and self-contained derivation of Johnson–Nyquist formula that relates the voltage fluctuations due to the thermal noise to the impedance in linear electrical circuits using linear response theory. Spectral densities and measurement bandwidth are carefully defined following Nyquist’s original formulation. Explicit expressions are derived for voltage fluctuations across a resistor in R, RC (series and parallel), and LCR circuits. Reactive elements are shown to shape but not generate noise, producing frequency-dependent Johnson–Nyquist relations governed by circuit susceptibility. We demonstrate that while pure resistors exhibit frequency-independent (white) Johnson–Nyquist noise, circuits containing reactive elements can display frequency-dependent colored noise spectra. Specifically, we analyze pure resistors, series RC circuits, parallel RC circuits, and series LCR resonators, showing how circuit topology determines whether the noise spectrum is white or colored. We explain the physical origin of frequency dependence through the concept of effective resistance and current redistribution at different frequencies. Analogies with the generalized Langevin equation are explained.

Associations between body mass index and body composition among Pacific adolescents in Aotearoa New Zealand