Browse Articles

Thermal equilibrium in coupled trajectory mixed quantum–classical dynamics

Detailed balance, the correct thermalization of electronic state populations, is an essential and elusive property of quantum–classical non-adiabatic dynamics methods. While some methods can reproduce detailed balance through physically well-motivated algorithmic adaptations, or by construction of a conserved Hamiltonian function, the physical mechanism leading to detailed balance is not understood from first principles. Coupled trajectory mixed quantum–classical (CTMQC) dynamics may provide some insight into the question, as it can be derived from first principles in the exact factorization theorem of full quantum mechanics. Although we find that the current conventional flavor of CTMQC, which conserves energy across the ensemble of trajectories (known as CTMQC-E), fails to reproduce detailed balance as in Ehrenfest dynamics, we show that a similar variant, where total energy is conserved on each trajectory independently, provides a major improvement over Ehrenfest with respect to detailed balance. Moreover, we show that the theory achieves convergence of the mean electronic potential energy with the number of energy levels that successively increase in energy. This new variant is shown to, by simulations on the Tully models and double arch model, retain a good description electronic populations and coherence compared to exact quantum dynamics. We explain the thermalization mechanism through the additional terms that distinguish CTMQC from Ehrenfest dynamics. We show that the improvement can be explained via geometric contributions to the nuclear force, resulting from the quantum momentum, which act to oppose motion when electrons decohere upward in energy and act to enhance motion otherwise, somewhat emulating the mechanism of frustrated hops. These results have considerable implications for the applicability of CTMQC to condensed phase simulations.

Evaluating the diagnostic accuracy of 99mTc-labeled somatostatin receptor imaging for suspected pheochromocytomas and paragangliomas

Lattice thermal conductivity of CsSnBr3/Cs2SnBr6 interface from <i>ab initio</i> based neuroevolution potential simulations

Engineering of interface phonons is of vital importance to achieve extremely low thermal conducting candidates, which are crucial for energy conversion devices. Here, we reported an ultralow lattice thermal conductivity (0.173 W m−1 K−1) across the all-inorganic halide perovskite CsSnBr3/Cs2SnBr6 interface based on large-scale atomic molecular dynamics simulations. Accurate neuroevolution potential derived from ab initio density functional theory was employed to reveal the enhanced anharmonicity and phonon scattering/localization that contribute to the low lattice thermal transport capability. A strong mixed phonon liquid character and nonlinear interface density dependent thermal conductivity have been observed for the CsSnBr3/Cs2SnBr6 interface. The insights obtained from our findings might provide an efficient way to design crystalline anisotropic thermoelectric materials.

Fused filament fabrication of thermoplastics in high vacuum without convective heat transfer

Abstract In-space additive manufacturing (AM) offers significant potential to expand human space exploration beyond low Earth orbit and the moon. Although extrusion-based AM has proven feasible in zero gravity, the functionality of such a process in orbit-like vacuum conditions with practically no convective heat loss remains barely explored. To this end, a Fused Filament Fabrication (FFF) system was designed that successfully operated in high vacuum at 10− 4 mbar where convective heat transfer is negligible. Polylactic acid (PLA) tensile specimens were fabricated in three orthogonal print orientations under high vacuum conditions. Tensile testing, scanning electron microscopy, and micro-computed tomography were employed to assess tensile strength, elongation at break, void content, and the effects of vacuum on thermal dissipation. The objective was to evaluate how the vacuum environment influences the anisotropy of mechanical properties in printed parts. The absence of convective losses improved the layer bonding strength of specimens printed in the vertical (z) direction with load applied perpendicular to the filament strand orientation (V90), compared to specimens printed in horizontal (x or y) direction with load applied perpendicular to filament strand orientation (H90). This was attributed to the considerably slower cooling process in the case of V90 specimens. Moreover, thermal insulation provided by the vacuum environment had a beneficial influence on heat break and hot end. In vacuum, the set extrusion temperature was closer to the temperature measured at the tip of the nozzle. This study also identifies a temperature undershoot during decrease in hot end temperature in the printing process, which adversely affected interlayer adhesion. The findings indicate that the current PID-based hot-end control requires optimization to enhance the temperature control rate and minimize thermal deviations. These insights contribute to a deeper understanding of thermoplastic processing under convection-free conditions using fused filament fabrication (FFF).

Probing solvent fluctuations in deep eutectic solvents: Influence of probe charge and nano-domain localization

Deep eutectic solvents (DESs) segregate into hydrogen bond acceptor or hydrogen bond donor (HBD) rich nano-domains, leading to molecular heterogeneity. Understanding how this heterogeneity affects the DES structure and dynamics is essential. In this study, we used two-dimensional nuclear magnetic resonance (2D NMR) and two dimensional infrared (2D IR) spectroscopies, combined with molecular dynamics (MD) simulations, to investigate solvation structure and dynamics in two choline chloride-based DESs with different HBDs—levulinic acid and glycolic acid. We introduced two thiocyanate vibrational probes, methyl thiocyanate (CH3SCN, neutral) and ammonium thiocyanate (NH4SCN, anionic), which selectively localize in specific nano-domains. 2D NMR provided insights into solvent structure and probe location, while 2D IR captured solvation dynamics. Our results show that these small probes do not alter the solvent structure, regardless of charge. However, solvation dynamics depend on long-range electrostatic ordering in the DES and the local shielding effects of the nano-domain where the probe resides. MD simulations complement experimental findings, providing a molecular-level understanding of solvation in DESs.

Scenario based land use simulation for climate adaptability in coastal urban agglomerations of Guangdong Hong Kong and Macao Bay area

Ring polymer molecular dynamics with independent-bead approximation

It was recently reported [Zhao et al., Phys. Rev. Lett. 130, 166401 (2023)] that the full quantum dynamics of a correlated electron–nuclear system can be approximated to the dynamics of a classical ring polymer isomorphism with n beads each bearing distinct electronic configurations, namely, ring polymer molecular dynamics with independent-bead approximation. Here, we present a detailed description of the formalism, including the idea of this approximation and how it combines with existing Ehrenfest dynamics. This approach is applied to several model systems and compared with exact full quantum wavepacket dynamics, along with the widely used fewest switch surface hopping and standard Ehrenfest mean-field dynamics. The evolution of real-time electronic population and quantum nuclear trajectories obtained by this approach is in good agreement with the exact quantum solution, even in regions of strong non-adiabatic coupling, where the conventional surface hopping and Ehrenfest approaches fail to yield adequate results.

Exploring latent classes of complete blood count profiles and their association with smoking status in the Bandar Kong cohort study

Anisotropic interlayer force fields for van der Waals interfaces: Development and applications

The anisotropic nature of layered materials is key to many of their unique physical properties. The design and control of novel layered architectures requires a microscopic understanding of their intra- and inter-layer interactions. Ab initio simulations, based on, e.g., density functional theory, often provide valuable insights regarding their structural, mechanical, dynamical, and electronic properties. However, such calculations are often computationally demanding, thus limiting the treatment to relatively small length and time scales. Classical molecular dynamic simulations, based on physically motivated force-fields, may offer a viable computationally efficient alternative, when parameterized appropriately against ab initio reference data for small model systems. The general strategy usually relies on a separate treatment of intra- and inter-layer interactions. When considering the latter, popular isotropic potentials, such as those presented by Lennard-Jones and Morse, often fail to simultaneously capture binding and sliding physics. Therefore, anisotropic interlayer force fields, based on the Kolmogorov-Crespi scheme, have become the tool-of-choice. In this review, we summarize progress in the field of anisotropic interlayer force field, including the fundamental theoretical framework, parameterization, and representative applications to selected physical properties. We also discuss potential directions for further advancement, based on state-of-the-art developments in simulation technologies.

Blockchain-enabled federated learning with edge analytics for secure and efficient electronic health records management

Abstract The rapid adoption of Federated Learning (FL) in privacy-sensitive domains such as healthcare, IoT, and smart cities underscores its potential to enable collaborative machine learning without compromising data ownership. However, conventional FL frameworks face several critical challenges: high computational overhead on edge devices, significant communication latency due to frequent model updates, vulnerability to model and data poisoning attacks, and limited privacy-preserving mechanisms that expose systems to inference risks. These issues hinder the scalability, efficiency, and trustworthiness of FL in real-world, large-scale deployments—particularly in domains like Electronic Health Records (EHR) management, where data sensitivity is paramount. To address these challenges, this paper introduces the Enhanced Privacy-Preserving Blockchain-Enabled Federated Learning (EPP-BCFL) framework, which integrates blockchain with hybrid privacy mechanisms and intelligent aggregation strategies. The architecture comprises three layers: (1) an Edge Nodes Layer for on-device learning; (2) a Federated Aggregation Layer using Secure Multi-Party Computation (SMPC) and Differential Privacy (DP); and (3) a Blockchain Layer with a lightweight PoS + BFT consensus mechanism. Experimental evaluation on CIFAR-10 demonstrates 95.2% accuracy, a 43% reduction in communication latency, a 37% decrease in computational cost, and robust defense against data/model poisoning and adversarial attacks. Attack resilience improved accuracy from 72.5 to 93.2%, while privacy budget tuning achieved 90.3% accuracy at ε = 1.0. Compared to state-of-the-art models, EPP-BCFL exhibits superior performance in terms of security, scalability, and support for edge device heterogeneity, validating its applicability in secure EHR management.

Rotational envelope simulations in photodetachment spectroscopy: Precise measurement of electron affinity of NO and O2

The slow-electron velocity-map imaging (SEVI) technique can achieve accuracy better than 0.1 meV for atomic electron affinity (EA) determinations. However, molecular photoelectron energy spectra frequently exhibit complex rotational fine structures that induce substantial spectral congestions, thereby compromising the precision of molecular EA measurements. To obtain precise EA values of molecular species, we implement rotational envelope simulations of photoelectron energy spectra of molecular anions. Benchmark simulations for the well-characterized OH− successfully reproduce our cryogenic SEVI experimental spectra. Through application of this methodology to NO− and O2−, we establish EA(NO) = 0.029 24(46) eV and EA(O2) = 0.4477(10) eV, markedly enhancing the precision of these fundamental parameters compared to previous determinations.

Consistent vehicle trajectory extraction from aerial recordings using oriented object detection

Abstract Vehicle trajectories offer valuable insights for a wide range of road transportation applications. Due to the rise of drone technology, a growing branch of literature explores optical vehicle trajectory extraction from aerial videos, where object detection using neural networks is an important component. Horizontal bounding box object detection struggles to differentiate well between rotated vehicles, especially when dealing with complex backgrounds or densely packed vehicles. This work proposes a generalizable computation pipeline that leverages angular information to extract high-quality trajectories starting from video recordings and ending in trajectories in Cartesian and lane coordinates. A trajectory reconstruction algorithm is designed to be vehicle- and driver-informed and to maximize the physical consistency of the reconstructed trajectories both on the individual vehicles’ and platoon levels. A comprehensive benchmark of 18 object detection models on a real-world video dataset demonstrates how oriented object detection and the use of angular information can be used to significantly improve the consistency of extracted trajectories (15% better internal, and 20% better platoon consistency), and that orientation-informed trajectories can be reconstructed to lane coordinates of higher quality. The reconstructed vehicle trajectories better capture car-following and traffic dynamics, thereby improving their usability for traffic flow studies.

On the rank-reduced relativistic coupled cluster method

The efficiency of the Tucker decomposition of amplitude tensors within the single-reference relativistic coupled cluster method with single and double excitations was studied in a series of benchmark calculations for (AuCl)n chains, Aun clusters, and the cluster model of solid YbCl2. The 1 kJ/mol level of accuracy for correlation energy estimates of moderate-size systems and typical reaction energies can be achieved with relatively high compression rates of amplitude tensors via rejecting singular values smaller than ∼10−4. For the most extensive system studied (the YbCl7 cluster used for modeling of the ytterbium center in the ytterbium dichloride crystal), only ∼3% of compressed double amplitudes were shown to be significant. Thus, the rank reduction for the relativistic coupled cluster method with single and double theory, improving its computational scaling, is feasible. The advantage (if not necessity) of using the Goldstone diagrammatic technique rather than the “antisymmetrized” Brandow one is underlined. The proposed approach is promising for high-precision modeling of relatively large systems with heavy atoms.

Mindfulness and academic performance among nursing students in Saudi Arabia: a cross-sectional study

Self-assembly and time-dependent control of active and passive triblock Janus colloids

We perform Brownian dynamics simulations to explore the self-assembly of a two-dimensional model system of triblock Janus colloids as an example of “patchy” colloids forming complex structures. Previous experiments and simulation studies have shown that such systems are capable of forming a two-dimensional kagome lattice at room temperature. However, it is well established that the crystallization is strongly hampered by the formation of long-lived metastable aggregates. For this reason, recent studies have investigated activity, i.e., self-propulsion of the Janus particles, as a mechanism to accelerate the formation of stable kagome structures [S. A. Mallory and A. Cacciuto, J. Am. Chem. Soc. 141, 2500–2507 (2019)] at selected state points. Here, we extend, first, the investigations of active Janus colloids for a broader range of densities and temperatures. We also characterize in detail the associated nucleation of kagome clusters, as well as their structure in the steady state. Second, to make contact with the equilibrium case, we propose a simple activity time protocol where an initially chosen activity is switched off after a finite time. With this protocol, we not only find kagome structures in a much broader range of densities than in the purely passive case but also obtain a kagome crystallization boundary very close to that proposed in earlier Monte Carlo simulations.

Guilu erxian glue improves sperm quality in oligasthenospermia mice by promoting TDRP methylation and regulating the cAMP/PKA pathway

Pressure-enhanced and quantum-dot-activated photoluminescence in zero-dimensional organic metal halide hybrids family: Dual-channel modulation

Lead-free zero-dimensional (0D) organic metal halide hybrids (OMHHs) offer exceptional structural and property flexibility for applications in electronics and optoelectronics. Here, a comprehensive investigation into the modulation effects of pressure and laser on a 0D OMHHs family was conducted. For TPP2MnCl4 ([(C6H5)4P]2MnCl4), high-pressure studies up to 10 GPa reveal competition between lp–π interactions and π–π stacking, accompanied by an 18-fold photoluminescence (PL) enhancement. In TPP2CuCl4 ([(C6H5)4P]2CuCl4), we first observe laser-activated orange PL with self-trapped exciton characteristics, originating from quantum dots (2–4 nm) generated by irradiation. Further investigation of thermal stability of TPP2CuCl4 PL showed its exceptional emission and structural thermal stability and potential application as a thermochromic material. This work provides new perspectives into the physical characteristics and advanced utilization of low-dimensional OMHHs.

Neprilysin 2 catalyses the degradation of natriuretic peptides despite sacubitrilat Inhibition

Two-photon photodissociation dynamics study of CS2: The S(1S) atom channel

Two-photon photodissociation dynamics of carbon disulfide (CS2) were studied by means of the sliced velocity map ion imaging technique. The S(1S) + CS(X1Σ+) channel was directly observed from the measured images of S(1S) products in the wavelength range of 290.10–336.88 nm. The translational energy distributions and angular distributions of fragments have been derived. Rovibrational states of the CS(X1Σ+) co-products were partially resolved in the translational energy spectra and can be populated up to the energy limit of the available energy. Experimental results also show that the product anisotropy parameters are β2 &amp;gt; 0 and β4 ∼ 0. The latter indicates that the intermediate state reached by the first one photon excitation has a quite long lifetime, while the former suggests the molecules undergo a parallel transition from the intermediate state to the final state upon the second photon excitation and then experience a fast dissociation process. Combined with previous studies, we propose a possible dissociation mechanism: after absorbing two photons in the range of 290.10–336.88 nm, the CS2 molecule may undergo a sequential transition 1A1(1Σg+) ← 11B2(1Δu)/1A2(1Δu) ← X1Σg+, then directly dissociate or couple to other electronic states and dissociate.

Molecular characterization of human respiratory syncytial virus in Mexico (season 2023–2024) through whole-genome sequencing

Abstract Human respiratory syncytial virus (hRSV) is a one of major cause of severe acute respiratory infection (SARI) in young children and the elderly. Because genomic surveillance of hRSV is essential to understand viral evolution and the genetic variation that may affect transmissibility and pathogenicity, we sequenced complete genomes of hRSV-A and B from season 2023–2024, isolated from pediatric and adult patients with SARI. One hundred pediatrics and 43 hospitalized adult and 14 non-hospitalized adult patients testing positive for hRSV were enrolled. Libraries of whole hRSV genomes were generated and sequenced on a MiSeq platform. Phylogenetic analysis and maximum likelihood trees were constructed with the 64 hRSV-A and 29 hRSV-B sequences obtained in our study. Additionally, we analyzed the list of non-synonymous substitutions and their frequencies for each of the eleven viral proteins. hRSV-A was prevalent (68%) and principally affected children under five years old. The hRSV-A isolates belonged to the A.D lineage with sub-lineages A.D.1.5, A.D.1.8, A.D.3, and A.D.5.2 observed. The hRSV-B subgroup was less diverse since the dominant sub-lineage was B.D.E.1. Amino acid substitutions per viral isolate for each of the eleven viral proteins indicated higher variability in hRSV-A compared to hRSV-B. As expected, we observed a high diversity of substitutions in proteins G, F and L. Multiple lineages and a high mutation rate were identified in hRSV-A during winter season 2023–2024 in Mexico. The increasing availability of whole hRSV genome sequences will enhance the surveillance of specific genetic substitutions, contributing to a better understanding of viral evolution and the effectiveness of prophylactic and diagnostic strategies.