Browse Articles

Extend the scope of negative thermal expansion in PbTiO3-based perovskites

PbTiO3 is a typical perovskite-type ferroelectric that shows unique negative thermal expansion (NTE) from room temperature to its Curie temperature (α¯V = −1.99 × 10−5 K−1, 300–763 K). It is widely accepted that enhanced NTE can be achieved in PbTiO3-based ferroelectrics by improving the tetragonality of PbTiO3 (c/a = 1.064) through chemical substitutions. Nevertheless, most substituted PbTiO3-based ferroelectrics exhibit reduced tetragonality and weakened NTE, while enhanced NTE has only been achieved in those materials with enhanced tetragonality so far. Herein, we report on (1 − x)PbTiO3-xBiAlO3 solid solutions for which we observe reduced tetragonality accompanied by an unusual enhanced NTE (c/a = 1.057, α¯V = −2.23 × 10−5 K−1, 300–740 K), without much degradation of the NTE temperature range of pristine PbTiO3 upon doping. The present study provides an example of unusual enhanced NTE accompanied by reduced tetragonality in PbTiO3-based perovskites, which will extend the scope of NTE in PbTiO3-based ferroelectrics and shed light on the understanding of enhanced NTE in PbTiO3 family.

Advanced wave dynamics in the STF-mBBM equation using fractional calculus

Study on thermal quenching mechanism and recombination dynamics of Si-bound exciton transition in AlN

Steady-state photoluminescence (PL) and time-resolved photoluminescence spectroscopy are employed to study near-band edge excitonic emission lines in an aluminum nitride (AlN) film over a range of temperatures. The thermal quenching of the neutral silicon-bound exciton (Si0X) emission peak in AlN is observed, which is caused by the thermally activated processes from Si0X to two types of free exciton (Γ1 and Γ5), along with a two-electron satellite (TES) transition as a competing pathway. Among these, the activation process to the higher-energy Γ1 free exciton state is predominant, which may be related to the symmetry of the exciton states. The non-monotonic temperature dependence of the TES emission intensity is observed, which originates from the predominance of the thermally activated TES transition rate at low temperatures, as opposed to the delocalization tendency of Si0X. Due to the rapid reduction in the nonradiative recombination lifetime, the PL lifetime of the Si0X emission peak decreases from 160 ps at 4.5 K to 15 ps at 80 K. Meantime, the radiative recombination lifetime increases with temperature, which further accelerates the thermal quenching of the Si0X emission peak to some extent.

Stress management with HRV following AI, semantic ontology, genetic algorithm and tree explainer

Abstract Heart Rate Variability (HRV) serves as a vital marker of stress levels, with lower HRV indicating higher stress. It measures the variation in the time between heartbeats and offers insights into health. Artificial intelligence (AI) research aims to use HRV data for accurate stress level classification, aiding early detection and well-being approaches. This study’s objective is to create a semantic model of HRV features in a knowledge graph and develop an accurate, reliable, explainable, and ethical AI model for predictive HRV analysis. The SWELL-KW dataset, containing labeled HRV data for stress conditions, is examined. Various techniques like feature selection and dimensionality reduction are explored to improve classification accuracy while minimizing bias. Different machine learning (ML) algorithms, including traditional and ensemble methods, are employed for analyzing both imbalanced and balanced HRV datasets. To address imbalances, various data formats and oversampling techniques such as SMOTE and ADASYN are experimented with. Additionally, a Tree-Explainer, specifically SHAP, is used to interpret and explain the models’ classifications. The combination of genetic algorithm-based feature selection and classification using a Random Forest Classifier yields effective results for both imbalanced and balanced datasets, especially in analyzing non-linear HRV features. These optimized features play a crucial role in developing a stress management system within a Semantic framework. Introducing domain ontology enhances data representation and knowledge acquisition. The consistency and reliability of the Ontology model are assessed using Hermit reasoners, with reasoning time as a performance measure. HRV serves as a significant indicator of stress, offering insights into its correlation with mental well-being. While HRV is non-invasive, its interpretation must integrate other stress assessments for a holistic understanding of an individual’s stress response. Monitoring HRV can help evaluate stress management strategies and interventions, aiding individuals in maintaining well-being.

Propulsion contribution from individual filament in a flagellar bundle

Flagellated microorganisms overcome the low-Reynolds-number time reversibility by rotating helical flagella [E. M. Purcell, Am. J. Phys. 45, 3–11 (1977); D. Bray, Cell Movements: From Molecules to Motility, 2nd ed. (Garland Publishing, New York, NY, 2001); Lauga and Powers, Rep. Prog. Phys. 72, 096601 (2009); and E. Lauga, Annu. Rev. Fluid Mech. 48, 105–130 (2016)]. For peritrichous bacteria, the randomly distributed flagellar filaments align in the same direction to form a bundle, facilitating complex locomotive strategies [Berg and Brown, Nature 239, 500–504 (1972); Turner et al., J. Bacteriol. 182, 2793–2801 (2000); and Darnton et al., J. Bacteriol. 189, 1756–1764 (2007)]. To understand the process of flagellar bundling, especially propulsion force generation, we develop a multi-functional macroscopic experimental system and employ advanced numerical simulations for verification. Flagellar arrangements and phase differences between helices are investigated, revealing the variation in propulsion contributions from individual helices. Numerically, we build a time-dependent model to match the bundling process and study the influence of hydrodynamic interactions. Surprisingly, it is found that the total propulsion generated by a bundle of two filaments is constant at various phase differences between the helices. However, the difference between the propulsion from each helix is significantly affected by a phase difference, and only one of the helices is responsible for the total propulsion when the phase difference is equal to π. Building on our experimental and computational results, we develop a theoretical model considering the propulsion contribution of each filament to better understand microbial locomotion mechanisms, especially the wobbling behavior of the cell. Our work also sheds light on the design and control of artificial microswimmers.

Revealing the distribution and change of abandoned cropland in Ukraine based on dual period change detection method

Field-free switching of perpendicular magnetization via out-of-plane spin-polarization induced by Ta with crystalline phase gradient

Contrary to the conventional spin current with the in-plane spin polarization, spin current with the out-of-plane spin polarization can achieve efficient all electrical control of perpendicular magnetization by spin–orbit torques (SOTs) without an external magnetic field. This feature is essential for high-density magnetic memory and logic devices. While such spin current with the out-of-plane spin polarization has been demonstrated in a limited number of high-quality low crystal or magnetic symmetry systems, its generation in conventional heavy metal is challenging but crucial for field-free spintronic devices. Here, we show that overcoming this challenge is possible by fabricating a crystalline phase gradient in heavy metal tantalum, where the out-of-plane spin polarization was induced and triggers an out-of-plane SOT providing the field-free switching for perpendicularly magnetized ferromagnet in Pt/Co/Ta (crystalline phase gradient) heterojunction. Meanwhile, the critical switching current density is lower than that of the Pt/Co/Ta (non-crystalline phase gradient) control case, and the polarity of field-free switching is determined by the sign of the crystalline phase gradient. Our work demonstrates that the crystalline phase gradient is a promising platform to generate the spin current with the out-of-plane spin polarization and achieve efficient field-free magnetization switching based on heavy metal tantalum, thus opening an avenue toward energy-efficient spintronic devices.

Whole genome sequencing of hepatitis B virus using tiled amplicon (HEPTILE) and probe based enrichment on Illumina and Nanopore platforms

Abstract Hepatitis B virus (HBV) whole genome sequencing (WGS) is currently limited as the DNA viral loads (VL) of many clinical samples are below the threshold required to generate full genomes using current sequencing methods. We developed two pan-genotypic viral enrichment methods, using probe-based capture and tiled amplicon PCR (HEP-TILE) for HBV WGS. We demonstrate using mock samples that both enrichment methods are pan-genotypic (genotypes A-J). Using clinical samples, we demonstrate that HEP-TILE amplification successfully amplifies full genomes at the lowest HBV VL tested (30 IU/ml), and the PCR products can be sequenced using both Nanopore and Illumina platforms. Probe-based capture with Illumina sequencing required VL > 300,000 IU/ml to generate full length HBV genomes. The capture-Illumina and HEP-TILE-Nanopore pipelines had consensus sequencing accuracy of 100% in mock samples with known DNA sequences. Together, these protocols will facilitate the generation of HBV sequence data, enabling a more accurate and representative picture of HBV molecular epidemiology, cast light on persistence and pathogenesis, and enhance understanding of the outcomes of infection and its treatment.

Manipulating high-throughput microparticle aggregation in capillary via elastic-acoustics orbital angular momentum transfer

Vortex acoustic fields are an emerging particle manipulation technique that gathers particles at a central zero-pressure point. Acoustic fields carrying orbital angular momentum (OAM) are reflected by hard boundaries, limiting their application within capillaries for aggregation of bioparticles in the cell analysis and biomolecule purification. We report a design for generating standing wave vortex acoustic fields within a capillary and investigate its effects on particle aggregation. The design uses a spiral phase helical tube placed outside the capillary to transfer elastic OAM to the fluid inside. Simulation results show that the first-order acoustic field is identical to the first-order Bessel beam and exhibits single vortex second-order acoustic streaming. In a background flow of 1×10−5 L/s, polystyrene particles with a diameter of 2 μm aggregated along a radial trajectory under the combined action of radial acoustic radiation force and tangential Stokes drag force. This method offers an efficient solution for the manipulation and detection of biological particles.

Optimizing blast design and bench geometry for stability and productivity in open pit limestone mines using experimental and numerical approaches

Probing the band structure and phonon dynamics in Fe mediated Cu2SnS3 for thermoelectric applications

Ternary Cu2SnS3 (CTS) is a less toxic, earth abundant, and low-cost p-type semiconductor material, suitable for thermoelectric applications, which can work at mid-temperature. This work aims to investigate the effect of substituting Fe on the thermoelectric properties of the CTS system. It is found that the electrical conductivity enhanced after Fe substitution due to the simultaneous enhancement of carrier concentration, as well as a reduced bandgap from 0.88 to 0.5 eV. The high power factor of ∼514 μW/mK2 was obtained for the Cu2Sn0.7Fe0.3S3 sample. The Fe substitution generated different types of phonon scatterings, such as mass fluctuation scattering arising from the difference in atomic mass of Sn and Fe and strain field scattering as a result of size and interatomic coupling force difference between Sn and Fe. Accordingly, the Fe-substituted CTS samples obtained the thermal conductivity of 0.45 W/mK at 753 K. In addition, the density functional theory calculations reveal that the substitution of Fe in Cu2SnS3 significantly alters the electronic structure and reduces the bandgap, resulting in enhanced electrical conductivity and power factor, thereby a high zT of ∼0.5 is obtained in Cu2Sn0.7Fe0.3S3.

Author Correction: Changes in the potato rhizosphere microbiota richness and diversity occur in a growth stage-dependent manner

Compliance for enhanced electroadhesion: Designing kirigami patterns for local conformation on rough surfaces

We aim to improve the adhesion capabilities of electroadhesive pads on rough surfaces by using geometry-driven compliance to increase effective contact area. We present a kirigami-based approach for enhancing compliance through an exploration of geometric features cut into an adhesive disk. We experimentally test a range of geometries, comparing shear adhesion strength to understand structure–function relationships in our chosen parameter space. Our findings indicate that introducing cuts to form serpentine paths in a disk results in longer effective lengths and enhanced compliance, thus requiring less energy to deform into a rough surface. Leveraging this insight and associated scaling analysis, we conclude that serpentine-like features arranged in a radially symmetric wedge configuration achieve high levels of adhesion, even on rough surfaces, enabling robust adhesion relative to featureless electroadhesive disks.

Baseline choroidal microvasculature dropout as a predictor of rapid global structural loss in open-angle glaucoma

Acoustic non-Hermitian higher-order topological bound states in the continuum

Recently, the concept of bound states in the continuum (BICs) has been extended to topological physics, inspiring investigations into higher-order topological BICs (TBICs) and related ultra-strong wave localization, which not only enriches the realm of topological physics but also bestows the BICs with inherent topological protection. However, previous explorations toward higher-order TBICs have been limited to the Hermitian assumption, omitting the nonconservative characteristics present in many artificial materials. In this work, we propose and experimentally demonstrate an acoustic lattice model supporting higher-order TBICs that solely rely on non-Hermiticity, in which the non-Hermiticity is implemented by strategically applying additional loss to specific sites in the lattice. Importantly, these in-band corner states are protected by chiral symmetry and can be spectrally switched by introducing perturbations to the corner sites or couplings. Our findings highlight the distinctive role of non-Hermiticity in constructing higher-order TBICs, which may inspire sophisticated and externally tunable approaches for designing high-Q devices in wave-based technologies.

User experience questionnaire in sign language for native users of Slovenian sign language

Evaluation of bias-dependent band structure changes in metal–oxide–semiconductor structures with varying doping concentrations using laboratory hard x-ray photoelectron spectroscopy

Direct observation of the band structure variation of electrical devices, such as MOSFETs, during device operation is the most important for understanding MOSFET device operation. However, there are a few reports on the direct measurement of variation in the metal–oxide–semiconductor (MOS) interface band structure during operation, and further investigation is required. This paper focuses on elucidating the changes in the band structure at buried interfaces under applied bias using a nondestructive approach. We conducted measurements using bias-applied laboratory hard x-ray photoelectron spectroscopy (Lab. HAXPES) with liquid gallium (Ga) x-ray source on MOS structures, which are widely recognized as fundamental and commonly used devices. We utilize HAXPES with Ga x-ray, providing high-energy/intensity x-rays, to achieve sufficient detection depth and enable observation of the deeper regions of the silicon substrate buried under gold and silicon dioxide layers. As a result, this approach allowed us to observe bias-dependent peak shifts resulting from changes in the band structure in detail. We observe HAXPES peak shift caused by the different substrate concentrations. Additionally, we obtained detailed information on band bending by applying a wider range of bias compared to previous bias applied HAXPES.

Job satisfaction, life satisfaction, and associated factors among hospital nurses: a cross-sectional study in Türkiye

Abstract Job satisfaction strongly affects nurses’ life satisfaction and is directly affected by life satisfaction. Our study aimed to determine nurses’ life and job satisfaction, show their relationship, and evaluate the factors affecting them. This cross-sectional study was conducted in 2022 at a university hospital in Türkiye. The study population included all nurses working at the hospital for at least one month, and 920 nurses participated. Data were collected using a structured questionnaire, which consisted of sections on sociodemographic characteristics, job and life satisfaction, and factors related to the nursing profession. Job satisfaction was measured using the Index of Job Satisfaction, while life satisfaction was assessed with the Life Satisfaction Scale, both validated tools. Data collection occurred during periodic health examinations through face-to-face interviews. Most participants chose the nursing profession willingly and found it suitable for themselves. However, many reported dissatisfaction with their earnings. Higher job satisfaction was associated with older age, having children, good perceived health, shorter weekly working hours, willingly choosing the nursing profession and unit, and favorable working conditions and income. Similarly, life satisfaction was higher among those with good perceived health, fewer weekly working hours, willingly chosen profession and unit, and no smoking or chronic diseases. Supportive working conditions and adequate income strongly influenced both job and life satisfaction. A significant, positive, and moderate correlation was found between job and life satisfaction, highlighting their interconnectedness. These findings suggest that improving nurses’ working conditions, ensuring adequate income, and supporting healthier lifestyles could enhance job and life satisfaction. Enhancing working conditions is essential to improving nurses’ job satisfaction, which, in turn, positively impacts their overall life satisfaction. Policymakers should prioritize initiatives that address workplace challenges and foster a supportive environment for nurses.

Room-temperature ferromagnetism and photoluminescence in layer-conjugated 2D Cu-BDC

Magnetic metal-organic frameworks (MOFs) hold immense promise as multifunctional materials for next-generation spintronic and optoelectronic devices. Here, we introduce a layered conjugated MOF 2D Cu-BDC, i.e., Cu(BDC)(DMF), synthesized via a simple solution co-deposition method at ambient conditions. Cu-BDC exhibits robust room-temperature ferromagnetism arising from strong coupling between Cu2+ ions and delocalized π-electrons in the ligand, as revealed by magnetic measurements and density functional theory calculations. Ferromagnetic resonance studies further demonstrate a low Gilbert damping factor of 8.4 × 10−3, highlighting its potential for efficient spin transport. In parallel, Cu-BDC MOFs show a high conductivity (σ) of 115.7 S cm−1 at room temperature and efficient photoluminescence (λex = 462 nm) induced by π*-π electron transitions in the temperature range of 100–300 K. This unique integration of magnetic, electronic, and optical properties positions Cu-BDC as a compelling candidate for multifunctional applications in advanced opto-spintronics.

Hollow cathode electron properties are consistent with marginally stable turbulence

The scaling of the electron Mach number in a 20 A class hollow cathode plume is characterized experimentally as a function of the local plasma properties. These local properties are inferred from measurements with an incoherent Thomson scattering diagnostic, configured to measure the axial projection of the electron velocity distribution on the cathode centerline. The time-averaged electron temperatures are found to be 1–2 eV for xenon flow rates between 1.35 and 2.25 mg/s and increase above 5 eV at a lower flow rate of 0.45 mg/s. This transition in temperature corresponds to the cathode's transition from the so-called spot mode to the plume mode. The electron Mach number is found to be between 0.2 and 0.8 for all flow rates. The scaling of the Mach number with the ratio of electron temperature to ion temperature is examined, which reveals a non-monotonic relationship that can be approximately described by the assumption of marginally stable wave growth. The possibility of leveraging this assumption as a zero-equation closure for the electron fluid equations is discussed in the context of past experiments.