Browse Articles

Dual-Spin Centers in a Grid-like Covalent Organic Framework Promote Near-Unity CO ₂ Electroreduction

Dietary exposure assessment and risk characterization of aflatoxin $$\hbox {B}_1$$ in cereal grains consumed in Somalia

Abstract Aflatoxin $$\hbox {B}_1$$ (AFB $$_1$$ ) is a genotoxic carcinogen that frequently contaminates cereals in tropical food systems. Somalia lacks nationally representative dietary intake data to support exposure assessment and risk management. To estimate dietary exposure to AFB $$_1$$ from maize and sorghum among Somali adults and children and to characterize risk using internationally endorsed toxicological reference points. A deterministic exposure assessment integrated AFB $$_1$$ occurrence data from Somali market surveys with per-capita daily cereal intake derived from SIHBS 2022. Average Probable Daily Intake (APDI; ng/kg bw/day) was calculated for adults (60 kg) and children (20 kg) across mean, P50, P95, and P97.5 consumption levels combined with minimum, median, and maximum contamination scenarios. Margin of Exposure (MOE) was computed using BMDL $$_{10}$$ = 400 ng/kg bw/day. Maize—especially white maize—dominated exposure. Under median contamination, adult maize APDI ranged 293–1366 ng/kg bw/day (MOE 1.37–0.29), while children’s APDI ranged 878–4101 ng/kg bw/day (MOE 0.46–0.10). Sorghum generally contributed much lower exposure except under maximum contamination for red sorghum. Children had approximately three-fold higher exposure than adults on a body-weight basis. Estimated MOEs were far below 10,000, indicating very high priority for risk management. Strengthened regulation, monitoring, and post-harvest interventions are urgently needed, alongside improved dietary data systems.

Daily briefing: The secrets of the centenarians

Computational design of a ferroelectric framework material based on dipolar rotors

In this work, we present a hierarchical approach to generate ferroelectric covalent frameworks based on rotatable polar groups. By using a multi-step workflow of increasing theoretical sophistication but also increasing computational costs, a unit cell with ferroelectric behavior can be generated for a given organic linker group. Starting with a basic point dipole model to find an appropriate unit cell, followed by a three-dimensional representation of the organic rotor, up to the full framework, each step confirms the desired attributes. This is achieved by using molecular dynamics and Monte Carlo Metropolis sampling in combination with the “Universal Force Field for Metall-Organic-Frameworks” (UFF4MOF) and the van der Waals corrected density functional tight-binding approach (known as GFN1-xTB) for the energy calculations. As a result, we demonstrate a covalent organic framework that is predicted to show a ferroelectric ground state that is stable up to temperatures beyond 100 K.

Electrified Hydrogenation of Aliphatic Ketones in a Palladium Membrane Reactor

A self-evolution cyber attack scheme generation system for cybersecurity evaluation

Abstract With the increasing complexity of network attacks, defense systems face significant challenges in maintaining cybersecurity. To effectively evaluate and optimize defense strategies, this paper proposes a self-evolution attack scenario generation system tailored for assessment purposes. To address the scalability challenges in attack graph generation and improve the efficiency and relevance of security evaluations, the system incorporates a real-time generation method capable of dynamically adapting attack scenarios based on specific goals and constraints. Additionally, a methodology is developed to construct potential attack paths using attack graph techniques enhanced with self-evolving mechanisms. The feasibility and adaptability of the generated attack scenarios are validated through simulation experiments. This paper details the system’s design, highlighting its core technical innovations-including incremental graph updates, scalable goal-driven path generation, and quantitative path ranking–which address key limitations of traditional tools like MulVAL. The system’s effectiveness and superiority in scalability and usability are demonstrated through extensive simulations.

Analytic <i>G</i> 0 <i>W</i> 0 gradients based on a double-similarity transformation equation-of-motion coupled-cluster treatment

The accurate prediction of ionization potentials (IPs) is central to understanding molecular reactivity, redox behavior, and spectroscopic properties. While vertical IPs can be accessed directly from electronic excitations at fixed nuclear geometries, the computation of adiabatic IPs requires nuclear gradients of the ionized states, posing a major theoretical and computational challenge, especially within correlated frameworks. Among the most promising approaches for IP calculations is the many-body Green’s function GW method, which provides a balanced compromise between accuracy and computational efficiency. Furthermore, it is applicable to both finite and extended systems. Recent work has established formal connections between GW and coupled-cluster doubles (CCD) theory, leading to the first derivation of analytic GW nuclear gradients via a unitary CCD framework. In this work, we present an alternative, fully analytic formulation of GW nuclear gradients based on a modified version of the traditional equation-of-motion CCD formalism, enabling the inclusion of missing correlation effects in the traditional CCD methods.

Retraction Note: Sustainable pretreatment and adsorption of chemical oxygen demand from car wash wastewater using Noug sawdust activated carbon

Reduced density matrices and phase-space distributions in thermofield dynamics

Thermofield dynamics (TFD) is a powerful framework for accounting for thermal effects in a wave function setting and has been extensively used in physics and quantum optics. TFD relies on a duplicated state space and creates a correlated two-mode thermal state via a Bogoliubov transformation acting on the vacuum state. However, a very useful variant of TFD uses the vacuum state as the initial condition and transfers the Bogoliubov transformation into the propagator. This variant, referred to here as the inverse Bogoliubov transformation (iBT) variant, has recently been applied to vibronic coupling problems and coupled-oscillator Hamiltonians in a chemistry context, where the method is combined with efficient tensor network methods for high-dimensional quantum propagation. In the iBT-TFD representation, the mode expectation values are clearly defined and easy to calculate, but the thermalized reduced particle distributions, such as the reduced 1-particle densities or Wigner distributions, are highly non-trivial due to the Bogoliubov back-transformation of the original thermal TFD wave function. Here, we derive formal expressions for the reduced 1-particle density matrix (1-RDM) that use the correlations between the real and tilde modes encoded in the associated reduced 2-particle density matrix. We apply this formalism to define the 1-RDM and the Wigner distributions in the special case of a thermal harmonic oscillator. Moreover, we discuss several approximate schemes that can be extended to higher-dimensional distributions. These methods are demonstrated for the thermal reduced 1-particle density of an anharmonic oscillator.

Helical Complex Ladder Polymer with Amplification of Asymmetry

Genome-wide analysis reveals differential admixture dynamics and historical demographic contractions in African cattle

Rotational spectrum and theoretical calculations of pyrazole⋯CO2 complex: Tetrel and hydrogen bond interactions

The complex between pyrazole and carbon dioxide has been generated in a supersonic jet and characterized using Fourier transform microwave spectroscopy and state of the art CCSD(T) theoretical calculations. The complex presents a planar configuration showing a simultaneous N⋯C=O n → π* tetrel bond and a NH⋯O hydrogen bond. The TS internal rotation barrier that interconverts the oxygen atoms of CO2 has been calculated to be 10 kJ mol−1 at the CCSD(T) level. The electronic characteristics of the minimum and TS have been analyzed. Machine learning methods have been applied to predict the potential energy surface of the pyrazole⋯carbon dioxide complex.

Efficacy of electronic travel aids for the blind and visually impaired during wayfinding

Abstract Independent traveling remains challenging for blind and visually impaired (BVI) individuals. While the white cane is effective at detecting ground-level obstacles, it provides no information about elevated obstacles or object characteristics. Recent technologies have been designed to support navigation as well as object detection. In our study, we compared the performance of 13 BVI participants who separately used two secondary electronic travel aids (ETAs) versus cane use alone. One ETA was a camera-based mobility vest (NOA), and the other was an ultrasonic sensor-based wearable (BuzzClip). Participants completed an obstacle avoidance task with both ETAs and an object detection task using two versions of NOA’s object-finding functionality. Quantitative performance measures and semi-structured interviews were collected. NOA resulted in enhanced obstacle avoidance. Participants used their canes less and collided less with obstacles when using NOA than the BuzzClip or the white cane alone. NOA resulted in lower frustration and higher perceived performance, as well as greater perceived safety and obstacle detection than the BuzzClip. Object-finding performance outcomes were similar across both versions, suggesting potential benefit from a dynamic combination of approaches tailored for each user. Collectively, these data underscore how ETAs may be integrated into use by the BVI community.

Nudged elastic band method in the CRYSTAL code: Theory and Applications

The nudged elastic band (NEB) method is a widely used algorithm for determining minimum energy paths and transition states in chemical reactions and phase transitions. In this work, we present the implementation of different NEB algorithm schemes in the CRYSTAL code, a quantum mechanical ab initio program for the calculation of electronic properties of condensed matter systems, based on Hartree–Fock and density functional theory. The use of a set of localized Gaussian-type functions to expand the wavefunction permits a very efficient evaluation of the exact exchange series for the hybrid exchange–correlation functionals. Therefore, our implementation allows an accurate characterization of transition states in both molecular and condensed phase systems, at the hybrid functional level of theory. The theoretical framework, including the force projection scheme, tangent estimation, optimization strategies, as well as the extensions of the method with climbing image and variable spring constants variants, is recalled. Then, the NEB algorithm is validated through a series of benchmark tests: two molecular reactions (a collinear proton transfer process and the keto-enol tautomerization in formamide) and a proton exchange process in a periodic chabazite zeolite. Our results are in excellent agreement with experimental and previous theoretical data, confirming the accuracy and applicability of the implementation. This work opens the possibility for future studies of complex reactive processes on extended periodic systems, using hybrid functionals.

Immersion Freezing at Topographic Active Sites: Dual-Barrier Prediction of Ice Nucleation Temperatures

Environmental and energetic exergetic sustainability of stevia leaf drying in a PVT indirect solar dryer with variable airflow and tray levels

Abstract During the current study, Stevia rebaudiana leaves were dried using a photovoltaic thermal–indirect solar dryer (PVT-ISD), and the influence of tray position inside the drying chamber was assessed using six trays under two airflow rates (0.08 and 0.13 m 3 /s) with a uniform layer thickness of 3 cm. The fastest drying occurred on the lowest tray, closest to the hot air inlet, particularly at the higher airflow rate, achieving a final moisture content of 5.7%. Energy analysis showed that thermal efficiency of the solar collector reached up to 55.7% at the higher airflow. Exergy analysis supported this improvement, with maximum exergy efficiency of the solar collector increasing to 14.68%. Conversely, the drying room performed better at the lower airflow, reaching a maximum exergy efficiency of 37.89%. Sustainability indicators revealed slight improvements in the solar collector but declines in the drying room at higher airflow. Environmental indicators further demonstrated enhanced performance of the solar collector at higher airflow, with maximum reductions observed in the environmental destruction coefficient (19.6%), environmental impact factor (20.6%), and environmental effect factor (20.4%).

Chemical repair of oxidized aromatic amino acids by monohydroxylated 2-pyridones

The oxidative modification of tryptophan and tyrosine residues in proteins has been strongly associated with the onset and progression of neurodegenerative disorders, such as Alzheimer’s disease and amyotrophic lateral sclerosis. Consequently, the identification of small molecules capable of repairing these oxidized residues is of considerable medicinal interest. In this study, the antioxidant activity of four hydroxy-2-pyridones against tyrosyl and tryptophanyl radicals was investigated in silico using density functional theory, with the aim of elucidating their structure–activity relationships at the molecular level. Thermochemical analyses were conducted to evaluate the most favorable repair pathways, focusing on formal hydrogen transfer (FHT) and single electron transfer (SET) processes. For exergonic reactions, kinetic parameters were determined within the quantum mechanics-based overall free radical scavenging activity (QM-ORSA) protocol, providing predictive data on radical-scavenging efficiency. The results indicate that three of the tested pyridones can repair the tyrosyl radical and that two of them react at rates comparable with the dityrosine formation, thereby competing with this deleterious pathway. In contrast, all four pyridones are able to reduce the tryptophanyl radical, although the calculated kinetics suggest that they may not efficiently suppress the Trp–Trp cross-linking in small peptides. Mechanistic analysis further revealed that FHT proceeds through proton-coupled electron transfer for tyrosyl radical repair, whereas tryptophanyl radical repair involves a proton–electron sequential transfer mechanism. These findings establish hydroxy-2-pyridones as promising scaffolds for the rational design of neuroprotective antioxidants and provide molecular insights that may guide the development of new therapeutic agents targeting oxidative stress.

Optimized Photoemission from Organic Molecules in 2D Layered Halide Perovskites

Minimizing frictional irreversibility in a rough-walled tapered bearing with a nanoparticle-enhanced Sutterby lubricant

Spin–charge transport in chirally induced spin selectivity

Chiral Induced Spin Selectivity (CISS) is an intriguing phenomenon in chiral molecules, in which spin polarization emerges at room temperature in two-terminal junctions without requiring ferromagnetic contacts or strong intrinsic spin–orbit coupling. This work develops a unified tight-binding framework that reproduces charge and spin transport in single- and double-helical molecules, including ordered oligopeptides and DNA. We first reproduce the spin-independent conductance–distance behavior observed by Giese, Curr. Opin. Chem. Biol. 6, 612 (2002), and Lindsay, Life 10, 72 (2020), by including electron–phonon interactions through Einstein phonon reservoirs at temperature T. Upon introducing spin–orbit coupling under the tunneling barrier for single-stranded DNA, we obtain a clear spin-conductance asymmetry, leading to strong spin polarization (20%–40%) that increases with molecular length and reverses sign with molecular chirality. The temperature dependence of the polarization exhibits a linear increase near room temperature, consistent with experimental trends. Double-stranded configurations yield similar spin-selective behavior within the experimental setup. We argue that this class of models provides the closest microscopic correspondence to current CISS measurements and that further refinements can be achieved by identifying specific decoherence processes and barrier parameters associated with each molecular system.