Browse Articles

Immunoproteomic insights into inflammatory diseases of the critically endangered black rhinoceros (Diceros bicornis)

Abstract Black rhinoceros are critically endangered due to poaching in the wild (in situ). Globally, fewer than 200 animals are maintained as an ex situ insurance population. Unfortunately, the ex situ population faces major sustainability challenges from disease syndromes characterized by high inflammatory burdens and diverse manifestations of immunometabolic dysfunction, not known to be present among their wild counterparts. Overlapping ex situ disease phenotypes limit diagnostic specificity and highlight the need to define underlying disease mechanisms. In the present study, using a cohort of presumed clinically healthy and inflammatory black rhinoceros, we generated the first immunoproteomic profile of any endangered mammal species and identified 1,311 immune cell proteins. However, no significant differences were detected among clinical phenotypes. Therefore, we applied unsupervised machine learning approaches to detect molecular features suggestive of healthy versus inflammatory phenotypes. Forty-three proteins associated with inflammatory pathways were differentially expressed in a cohort of samples derived from both presumed healthy and inflammatory phenotypes. Results suggest subclinical disease may be relatively widespread ex situ, and that animals experience temporal fluctuations in inflammatory state over time. Findings implicate neutrophil degranulation and dysregulation of the oral-gut-liver axis as drivers of disease syndromes of ex situ black rhinoceros. The forty-three proteins associated with inflammatory pathways represent candidate inflammatory biomarkers to be assessed for clinical applications in future validation studies. Upon validation, these candidate biomarkers may guide management practices to strengthen long-term population sustainability.

Impact of mode hybridization on spin-wave profiles in bi-component magnonic crystals

Abstract The study investigates mode hybridisation in two-dimensional permalloy–cobalt magnonic crystals. Calculations were performed using the plane-wave method, with particular emphasis on the effects accompanying hybridisation. A distinctive feature revealed in this work is the exchange, between hybridising modes, of the excitation concentration coefficient in the constituent materials (e.g. in cobalt). This coefficient describes the fraction of spin-wave energy concentrated within one of the components of the composite. Its analysis enables the identification of hybridisation even when other manifestations—such as profile swapping or clear branch repulsion—are only weakly pronounced. We demonstrate cases in which the exchange of the concentration coefficient occurs between hybridising modes without the typical swapping of spin-wave profiles, or with only minimal repulsion between their branches in the frequency spectrum.

Standardizing oral microbiome sampling for qPCR: methodological and exploratory insights into nutritional status

Abstract Standardization of oral sample collection methods is essential for accurate and reproducible microbiota quantification. This methodological study aimed to evaluate different oral collection methods to identify the most consistent approach for bacterial quantification by qPCR using samples from adolescent individuals. In addition, to assess the biological applicability of the best method, an exploratory analysis compared bacterial profiles between eutrophic and overweight/obese adolescents and explored associations between bacterial abundance and body composition parameters. Samples of unstimulated saliva, cheek swabs, and biofilm were collected from the same individuals, and qPCR was used to quantify total bacteria (16 S rRNA gene), Bacillota , and Bacteroidota phyla. Unstimulated saliva produced the lowest variability in bacterial quantification compared with other methods ( p  < 0.05). Moderate correlations were observed between saliva and biofilm, whereas saliva and cheek swab showed weak associations. Although bacterial copy numbers tended to be higher in overweight/obese individuals, these differences were not statistically significant. Correlation matrices suggested group-specific associations between bacterial taxa and body composition parameters, demonstrating the potential of saliva for microbiome assessment in studies of nutritional and metabolic health. This study validated unstimulated saliva as a reproducible, non-invasive, and cost-effective biofluid for oral microbiota quantification by qPCR. The method provides consistent results suitable for large-scale, translational, or point-of-care applications.

Social learning of emotion and its implication for memory: an ERP study

Abstract Social learning of emotional salience from surrounding social cues is particularly advantageous under conditions of uncertainty. Yet, the neural mechanisms underlying this process and its consolidation into long-term memory remain poorly understood. In this two-day EEG study, we examined whether emotional salience from social cues (facial expressions) transfers to perceptually uncertain target images, and whether such learned salience is preserved in memory even after the social cues are removed. On Day 1 (learning session), preregistered analyses provided no evidence for an automatic emotional salience transfer across trials under the task’s uniform perceptual uncertainty. Instead, exploratory ERP analyses indicated that the use of social cues depended on subjective perceptual uncertainty, indexed by participants’ classification accuracy of the target image. P1 amplitudes in the learning session reflected this modulation. On Day 2 (test session), recognition performance and ERPs revealed evidence for additive emotional salience effects. EPN amplitudes were enhanced for accurately classified positive target images previously paired with social cues. In contrast, LPC amplitudes were reduced for negative target images in the social cue condition, independent of classification accuracy. Together, these findings suggest that the influence of social cues is contingent on subjective uncertainty. When internal valence judgments were strong (positive images), social cues added to emotional salience; when internal valence judgments were weaker (negative images), participants relied more heavily on the social cue, resulting in weaker memory encoding. Protocol registration The stage 1 protocol for this Registered Report was accepted in principle on 08/11/2023. The protocol, as accepted by the journal, can be found at: https://doi.org/10.17605/OSF.IO/TYQ84 .

Tailoring electronic structure and magnetic anisotropy in spray-pyrolyzed NiFe2O4 thin films for spintronic applications

Improvement of wide-bandgap Cu(In,Ga)Se2 solar cells by Cd-free ZnSnO buffer layers deposited via atomic layer deposition

Wide-bandgap chalcopyrite Cu(In,Ga)Se2 (CIGS) thin-film solar cells are promising candidates for tandem photovoltaic applications due to their high optical absorption and tunable bandgap. However, achieving both a high open-circuit voltage (VOC) and high fill factor (FF) in wide-gap devices remains a significant challenge, primarily due to substantial VOC losses originating from the bulk absorber quality relative to the bandgap, while interface properties with conventional CdS buffer layers also play an important role. In this study, a Cd-free Zn1−xSnxO (ZTO) buffer layer is applied to wide-gap CIGS solar cells, and its interfacial and device properties are systematically investigated. Temperature-dependent J–V analysis suggested a near-flat to spike-type conduction-band alignment at the ZTO/CIGS interface, which effectively suppressed interface recombination and enabled a high VOC. However, a conduction-band well-like structure within the CIGS-absorber layer initially limited short-circuit current density (JSC) and FF. Both JSC and FF were significantly improved using compositional tuning of the absorber to optimize this well-like structure. A maximum conversion efficiency of 13.5% was achieved (VOC: 806 mV, JSC: 24.9 mA cm−2, and FF: 67.3%), surpassing the performance of the simultaneously fabricated CdS reference cell. These results demonstrate the potential of ZTO as a Cd-free buffer layer for high-efficiency wide-gap CIGS solar cells.

Special topic on phonon–magnon interactions: From fundamentals to device physics

Phonons and magnons are collective excitations in solids that provide charge-free platforms for information transport. Phonons are distinguished by their robustness and long coherence times, while magnons offer wide frequency tunability, enabling energy-efficient and high-speed operation. Growing interest has, therefore, focused on materials, metamaterials, and devices that enable the observation and control of magnon–phonon interactions, as their coupling allows complementary properties to be combined and gives rise to novel physical effects. These developments hold strong potential for analog, digital, and quantum information technologies at microwave frequencies. This Special Topic aims to gather recent advances spanning experimental techniques, materials and engineered systems, theoretical concepts, and modeling approaches that advance the understanding and exploitation of coupled magnonic and phononic phenomena.

Optical pulling of chiral Rayleigh particle due to coupling effect

The presence of strong near-field coupling interactions is shown in significant alterations to the electromagnetic field distribution of the nearby nanoparticles (NPs) in recent research studies, resulting in the formation of unique optical force behavior. Through interactions with plasmonic, glass, and anisotropic metamaterial substrates, chiral Rayleigh particles show not only unique optical force behaviors in this article but also a strong capacity to change the surrounding electromagnetic environment, which can be a novel approach. To date, as far as we know, no report has identified numerical and analytic solutions of the chiral NP pulling force behavior due to coupling with another NP on plasmonic and anisotropic metamaterial substrates. Counterintuitive force direction reversal is observed on chiral Rayleigh particle when plane-wave illumination is applied to not only an isolated chiral Rayleigh particle but also when chiral with nearby dielectric and plasmonic NPs, resulting in an individual chiral experiencing a pushing force, the introduction of nearby other NPs induces an optical pulling force on variation in wavelength, incidence angle, and radius. It is unfortunate that this pulling behavior does not work on a glass substrate. The intrinsic chiral nature influences the configuration of the surrounding electromagnetic fields, thereby increasing the system’s susceptibility to environmental variations. To interpret these phenomena, the coupled electric and magnetic dipole approximation method was employed in this paper, and this study establishes the crucial role in achieving precision manipulation of chiral NP that offers new pathways for control in nanophotonics, optical trapping, and optimizing metamaterials.

Diffusion of oxygen in aluminum nitride

In this study, we investigate the thermal diffusion behavior of oxygen in bulk aluminum nitride (AlN) using an aluminum oxide (Al2O3) coating layer as an oxygen source. We used dynamic secondary ion mass spectrometry (D-SIMS) and time-of-flight SIMS (ToF-SIMS) for accurate profiling of the oxygen concentration across the Al2O3/AlN interface of as-grown and annealed samples. Initial tailing and limited dynamic range of ToF-SIMS measurements due to oxygen redeposition was addressed by employing an optimized dual-beam sputtering strategy with staged crater resizing. This eliminates all adverse effects and allows achieving detection sensitivity and depth resolution comparable to D-SIMS. Additional artifacts in the chemical profiling arise from surface roughening and localized phase transitions from amorphous Al2O3 to partially crystalline AlxOy induced by the high-temperature annealing, which are supported by correlative AFM (atomic force microscopy) and TEM (transmission electron microscopy) analyses. Eliminating all these factors reveals that, upon high-temperature annealing, a limited thermal diffusion of oxygen into AlN occurs after 12 h at 1600°C, or after 4 and 1 h at 1700°C, respectively, indicating an oxygen diffusion coefficient below 1.8×10−16cm2s−1 under these conditions.

Out-of-plane angle resolved second harmonic Hall analysis in perpendicular magnetic anisotropy systems

Spin–orbit torques (SOTs) are used to manipulate magnetization of ferromagnets in heavy metal/ferromagnetic bilayers and, thus, are technologically relevant from magnetization switching perspective. This necessitates development of methods which give an insight into SOT behavior and enable SOT efficiency estimation. In this article, we demonstrate an experimental approach of out-of-plane angle resolved Second Harmonic Hall (SHH) measurement, in Pt/Co and Ta/CoFeB perpendicular magnetic anisotropy (PMA) systems, for damping-like and field-like SOT efficiency estimation. This method reveals an angle dependent field-like term which depends on the magnetization direction in the Ta/CoFeB system. The damping-like and field-like SOT efficiencies are extracted by solving Landau–Lifshitz–Gilbert–Slonczewski equation in the low frequency limit of magnetic susceptibility. Along with SHH measurements, we also experimentally demonstrate anomalous Hall effect based spin-torque ferromagnetic resonance technique for SOT efficiency quantification in PMA systems.

Study on the nonlinear optical properties of Ag/CdS nanocomposite films

Using physical vapor deposition, cadmium sulfide (CdS) films, Ag nanoparticle films, and Ag/CdS composite films were successfully fabricated on substrates. The surface morphology, crystal structure, and optical bandgap of the samples were systematically characterized using scanning electron microscopy, x-ray diffraction, and ultraviolet–visible spectrophotometry, respectively. Using femtosecond Z-scanning technology, the nonlinear optical properties of composite materials were investigated at a wavelength of 800 nm. By adjusting the laser energy, the evolution of their nonlinear optical response with excitation intensity was systematically examined. The results indicate that, in comparison to single-component thin films, the Ag/CdS composite demonstrates significant characteristics of nonlinear absorption and nonlinear refraction. These characteristics are specifically manifested as saturated absorption behavior and self-defocusing effects. Notably, the incorporation of Ag nanoparticles effectively enhances the nonlinear optical response of the composite system, with this enhancement becoming increasingly pronounced as the Ag deposition power rises. Furthermore, the saturation absorption effect of the composite material gradually intensifies with rising laser energy. These outstanding nonlinear properties indicate that Ag/CdS composites hold significant application potential for integrated optoelectronic functional devices.

Theoretical study of orbital torque: Dependence on ferromagnet species and nonmagnetic layer thickness

The manipulation of magnetization in ferromagnetic metals (FMs) through orbital torque (OT) has emerged as a promising route for energy-efficient magnetic devices without relying on heavy metals. While Ti and Cu are among the most extensively studied light nonmagnetic metals (NMs) for OT devices, theoretical calculations of the resulting torque have remained limited. Here, we present a systematic and quantitative theoretical study of current-induced torques in Ti/FM and Cu/FM (FM = Co, Ni) bilayers using realistic tight-binding models derived from ab initio electronic structures. We find that the torque in Ti/FM is larger for Ni than for Co, but this trend does not necessarily hold in Cu/FM, revealing that the FM dependence of OT is not universal but varies with the orbital current source. Moreover, the dependence of OT on NM thickness clearly indicates its NM bulk origin in both Ti- and Cu-based systems. Notwithstanding, the quantitative characteristics of OT cannot be explained by a simplified picture based on the individual bulk properties of the NM or FM layers. These results provide microscopic insight and practical guidance for designing light-metal-based orbitronic devices.

Heterostructured B-C particles: Bridging solid and mesoporous domains

Microparticles comprising two macroscopically distinct domains with different compositions, structures, and porosity are attractive as multifunctional materials. B–C microparticles with dual-domain structures were synthesized via single-pulse laser heating of graphite–boron mixtures on chemical vapor deposition diamond. Vapor condensation forms Cassie–Baxter droplets featuring two distinct regions: a near-contact, mesoporous rapidly quenched (RQ) boron-doped onion-like carbon (OLC) network (∼4.7 at. % B) and a dense, quasi-equilibrium (QE) hypereutectic C–B4.5C mixture. Molecular dynamics simulations support the RQ structure. The results demonstrate that local supercooling suppresses boron diffusion, enabling the coexistence of mesoporous and dense domains within a single heterostructured microparticle.

Examination of doping limits in GaN:Mg layers for superjunction devices

With the promise of lower specific on resistances and higher breakdown voltages, superjunction devices can be employed to improve power efficiency. GaN superjunction devices, however, have mostly been achieved through heterojunction structures. One reason for this is the traditionally accepted need for higher doping in GaN:Mg layers to maintain reasonable conduction. In this work, we examine the lower doping limits of GaN:Mg layers to facilitate charge balancing in superjunction structures. Circular transmission line measurements, temperature-dependent Hall effect, capacitance–voltage, and SIMS analysis show that layers grown from NH3-MBE of targeted [Mg] between 5 × 1017 and 1 × 1019 cm−3 are capable of being employed in superjunction device architectures. When the layer doping is reduced to 2 × 1017 cm−3, the layer is compensated and unable to function as a p-type layer for charge balancing. This provides a reasonable parameter space for GaN:Mg layers in future GaN superjunction devices.

Revisiting the anisotropic complex refractive indices of sodium nitrate for interpretation of the reflectance spectra of pressed pellets

Reflectance spectroscopy is notoriously confounding in that the spectral response is highly dependent upon morphology. Fortunately, all such perturbations are neatly encoded by the complex refractive index. Herein, we quantitatively model the infrared reflectance spectrum of a specularly flat pressed pellet sample of the birefringent compound, sodium nitrate. Single crystals of sodium nitrate were synthesized and spectroscopically analyzed using polarization-dependent single-angle reflectance spectroscopy. Once measured and validated, the optical constants were applied to model the pressed pellet reflectance spectrum. It was evident that an average of the anisotropic refractive indices was insufficient to account for the measured pellet reflectance. The Python package pyElli was used to calculate a basis set of orientation-dependent reflection spectra spanning the distinct φ and θ Euler rotations of the uniaxial crystal. When the population of orientations was allowed to vary freely in a spectral fit analysis, the fit-deduced orientations were tightly clustered along φ = 45°, hinting at residual anisotropy in the pressed pellet sample. Conversely, an equally valid spectral fit (with marginally worse fit metric) was obtained when the population was constrained to an isotropic distribution of orientations. Subsequent non-zero cross-polarization reflectance measurements likewise suggested anisotropy in the pellet. However, both grazing-incidence wide-angle x-ray scattering and scanning electron microscopy measurements revealed that the microcrystal orientations at the surface of the pressed pellet sample were isotropically distributed. Application of the measured complex refractive indices for modeling the reflectance spectrum of the pressed pellet, and rectification of these seemingly contradictory observations will be discussed.

A time-resolved thermodynamic model for shock-induced chemical reactions in energetic structural materials

Energetic structural materials (ESMs) have garnered considerable interest owing to their combination of structural strength and ability to release chemical energy. The energy release of ESMs under shock loading is primarily attributed to shock-induced chemical reactions (SICRs), which can cause significant deviations in the shock compression data from the Hugoniot curves predicted for inert counterparts. In this study, a time-resolved thermodynamic model was established to characterize the SICRs in ESMs. By decoupling the chemical reaction zone from the shock-wave front, the model resolves the transient thermomechanical states of the shock front and reaction zone. A reaction rate equation incorporating Arrhenius kinetics quantifies the energy release process, while a novel termination criterion based on the energy dissipation balance replaces the empirical thresholds. Validated against experimental Hugoniot data for porous Al/Ni and dense Al/CuO, the model successfully predicted reaction-induced shock-wave velocity enhancements and volume expansions. Based on the proposed model, the analysis revealed the following key findings: (1) elevated porosity lowers the reaction-onset pressure but attenuates detectable shock-wave velocity differences between reactive and inert responses, (2) for Johnson–Mehl–Avrami kinetics, activation energy Ea and mechanism exponent n are both governing factors, leading to different responses of reaction extent to shock temperature, (3) reaction zone width exhibits non-monotonic pressure dependence. The initial increase in the reaction zone width is followed by a decline beyond a critical pressure, with the dominant factors transitioning from the reaction extent to temperature. This theoretical framework enables modeling based on time-dependent physical quantities, further establishing a viable approach for determining reaction kinetic parameters using Hugoniot data, thereby creating opportunities for advancing research on ESMs and SICRs.

Hydrogen gas sensing using platinum nanoparticles with nanogaps

In this study, we fabricated Pt nanoparticles with nanogaps on glass substrates and evaluated their electrical response to H2 gas. Pt nanoparticles with various gap sizes were exposed to H2 gas at 100 ppm, and we observed that a resistance change of 51.4% is achieved by optimizing the gap size. In conventional Pt nanostructure-based sensors, the H2 gas was detected through the resistance changes caused by electron scattering from H atoms adsorbed on the Pt surface or those diffused into grain boundaries and defects. The resistance change observed in this study was significantly larger than those observed in conventional sensors, and the above mechanism cannot fully explain the substantial resistance change. Consequently, our findings suggest that structural changes at the contact interfaces between nanoparticles contribute to the resistance change in Pt nanoparticles with nanogaps.

Hash-matching-based local density matrix reuse method for efficient <i>ab initio</i> electronic structure construction in large-scale complex systems

First-principles electronic structure calculations for large-scale material systems with defects or dopants remain a major computational bottleneck in atomistic simulations. Here, we propose a target-driven, non-learning-based method termed HaMLR (Hash-Matching-based Local density-matrix Reuse) to efficiently construct the density matrix of periodic atomic structures containing local defects or dopants. Leveraging the nearsightedness principle of electronic matter, the method systematically scans all atoms in the target system to extract local substructures within a defined nearsightedness radius, thereby covering the full sample space of local environments. Each substructure is encoded based on its geometric and chemical features, hashed, and deduplicated. Distinct substructures are then evaluated using self-consistent density functional theory (DFT) calculations to obtain the density-matrix blocks between the central atom and its neighbors within the cutoff radius. During reconstruction, the full-system density matrix is assembled by matching local environments via hash values and reusing the precomputed local density blocks—thereby avoiding full-scale DFT calculations. Unlike machine learning-based approaches, HaMLR does not require model training, offering improved physical consistency and computational efficiency. Validation on defective graphene, MoS2, and doped silicon demonstrates that HaMLR achieves high accuracy while significantly accelerating density-matrix construction, providing an efficient and robust alternative for large-scale electronic structure modeling.

Formation process and composition-dependent properties in non-centrosymmetric Ta2O5 phase with Zr substitution

(ZrxTa1−x)2O5−x was prepared by a solid-state reaction of ZrO2 and Ta2O5, and the L′-Ta2O5 phase was obtained by cooling the H-Ta2O5 phase. High-temperature x-ray diffraction measurements showed that the starting materials, ZrO2 and low-temperature L-Ta2O5, formed the high-temperature H-Ta2O5 phase when heated above 1360 °C. Upon cooling, this phase sequentially transformed into L″-Ta2O5, the high-temperature L′-Ta2O5 phase, and L′-Ta2O5 phases. As the Zr content, x, decreased, the transition from the H-Ta2O5 phase to the L″-Ta2O5 phase slowed. The temperature dependence of the dielectric constant revealed a maximum value, which is attributed to the phase transition from L′-Ta2O5 to L″-Ta2O5. This transition temperature decreases by approximately 50 °C for every 0.01 increase in the x value. The L′-Ta2O5 phase exhibited negative volumetric thermal expansion (NTE) behavior near the phase transition temperature. As x decreased, the NTE coefficient increased from −1.09 × 10−6/K (77–127 °C) for x = 0.10 to −2.06 × 10−5/K (327–427 °C) for x = 0.05. The substitution of Zr into Ta2O5 stabilized the non-centrosymmetric L′-Ta2O5 phase and controlled the phase transition temperature and thermal expansion behavior.

Crystallinity regulated flexoelectricity in cellulose membranes

Compared to ferroelectric ceramics, polymers exhibit lower flexoelectric coefficients but offer superior processability and flexibility, making them attractive for deformable electromechanical systems. Cellulose, a biodegradable and biocompatible polymer, is a promising candidate for materials with controllable flexoelectricity. Nevertheless, the intrinsic flexoelectric properties of cellulose remain unexplored, with key influencing mechanisms barely understood either. It is notable that cellulose exhibits a typical crystalline–amorphous dual-phase configuration, making polarization behavior in cellulose strongly depends on the proportion and microstructure of crystalline regions. Therefore, this work located crystallinity as a vital structural parameter in cellulose membrane and unraveled the regulation law of crystallinity on flexoelectric properties. As crystallinity in cellulose membranes increases, which is determined by three independent methods (Segal peak height method: 79.46%–91.37%; peak fitting method: 60.35%–73.09%; FTIR method: 23.21%–44.03%), the flexoelectric coefficient correspondingly rises from 7.33 ± 2.01 to 22.25 ± 1.35 nC/m, revealing a clear linear positive correlation. This trend is found to be independent of the dielectric and piezoelectric properties, suggesting a mechanism related to crystallinity-regulated variations in dipole reorientation. The cellulose membranes also display high mechanical properties, optical transparency, and shapeability. These findings elucidate the essential role of crystallinity in cellulose flexoelectricity and provide crucial insights for the design of high-performance sustainable flexible electronic devices.