Browse Articles

Impact of physiological and coronary artery disease risk factors on myocardial perfusion in stress computed tomography myocardial perfusion imaging

Native antisite defects in <i>h</i>-BN

Hexagonal boron nitride (hBN) is an excellent host for solid-state single phonon emitters. Experimental observed emission ranges from infrared to ultraviolet. The emission centers are generally attributed to either intrinsic or extrinsic point defects embedded into hBN. Nevertheless, the microscopic structure of most of these defect emitters is uncertain. Here, through density-functional theory calculations, we studied the native antisite defects in hBN. We find that the neutral boron antisite might be a nonmagnetic single photon source with zero-phonon-line (ZPL) at 1.58 eV and such a line shape is often observed in experiments. Furthermore, the positively charged nitrogen antisite might be associated with a dim color center recently observed as a blue emitter with ZPL at 2.63 eV. These simple single substitution defects indicate the existence of out-of-plane phonon mode, which significantly affects the optical properties. Our results could provide useful information for the identification of quantum emitters in hBN.

Machine learning approaches for resilient modulus modeling of cement-stabilized magnetite and hematite iron ore tailings

Methane sensing via unbalanced nonlinear interferometry using a CMOS camera and undetected mid-infrared light

Here, we present a high-sensitivity, rapid, and low-cost method for methane sensing based on a nonlinear interferometer. This method utilizes signal photons generated by stimulated parametric downconversion (ST-PDC), enabling the use of a silicon detector to capture high-precision methane absorption spectra in the mid-infrared region. By controlling the system loss, we achieve more significant changes in visibility, thereby increasing sensitivity. A low-cost CMOS camera is employed to capture spatial interference fringes, ensuring fast and efficient detection. Thereby, we demonstrate an accurate measurement of methane concentration within a gas cell. In addition, we show that ST-PDC enables long-distance sensing and the capability to measure open-path low ambient methane concentrations in the real world.

Associations of heatwaves and their characteristics with ischaemic stroke hospital admissions

Energy level alignment of confined hole states in InAs1−x−ySbxPy asymmetric double quantum dots for single-photon energy up- and downconversion

We present a combined experimental and theoretical study of uncapped In(As, Sb, P) graded composition laterally coupled asymmetric double quantum dots (DQDs), suited for application in nanodiodes or single-photon nano-optical up- and downconverters in the mid-infrared spectral range. We provide details on the growth process using liquid-phase epitaxy and characterization using atomic-force microscopy and scanning electron microscopy (SEM). We find that most DQDs exhibit asymmetry such that the two quantum dots (QDs) of each pair have different dimensions, giving rise to correspondingly different quantum confinement of hole states localized in each QD. Based on these data, we have performed systematic simulations using an eight-band k·p model to identify the relationship between QD dimensions and the energy difference between corresponding confined hole states in the two QDs. Finally, we have determined the strength of an applied electric field required to energetically align the hole ground states of two QDs of different dimensions in order to facilitate hole tunneling to the next QD for further recombination and single-photon emission with a different wavelength.

An integrated workflow combining machine learning and wavelet transform for automated characterization of heterogeneous groundwater systems

Abstract Groundwater aquifers are complex systems that require accurate lithological and hydrogeological characterization for effective development and management. Traditional methods, such as core analysis and pumping tests provide precise results but are expensive, time-consuming, and impractical for large-scale investigations. Geophysical well logging data offers an efficient and continuous alternative, though manual interpretation of well logs can be challenging and may result in ambiguous outcomes. This research introduces an automated approach using machine learning and signal processing techniques to enhance the aquifer characterization, focusing on the Quaternary system in the Debrecen area, Eastern Hungary. The proposed methodology is initiated with the imputation of missing deep resistivity logs from spontaneous potential, natural gamma ray, and medium resistivity logs utilizing a gated recurrent unit (GRU) neural network. This preprocessing step significantly improved the data quality for subsequent analyses. Self-organizing maps (SOMs) are then applied to the preprocessed well logs to map the distribution of the lithological units across the groundwater system. Considering the mathematical and geological aspects, the SOMs delineated three primary lithological units: shale, shaly sand, and sand and gravel which aligned closely with drilling data. Continuous wavelet transform analysis further refined the mapping of lithological and hydrostratigraphical boundaries. The integrated methods effectively mapped the subsurface aquifer generating a 3D lithological model that simplifies the aquifer into four major hydrostratigraphical zones. The delineated lithology aligned closely with the deterministically estimated shale volume and permeability, revealing higher permeability and lower shale volume in the sandy and gravelly layers. This model provides a robust foundation for groundwater flow and contaminant transport modeling and can be extended to other regions for improved aquifer management and development.

Fiber-tip photothermal transducer with gold-coated multi-beam interferometric cavity for high sensitivity gas detection

The power-boosted laser transmitted via a fiber tip sinusoidally excites the target trace molecules, generating a photothermal (PT) effect. The Gaussian-distributed plane wave heats the medium adjacent to the Fresnel reflection surface. Meanwhile, a continuous probe light traverses the heating field, and the periodic temperature change then modulates the phase of the probe light. A multi-beam interferometer formed by aligning the Fresnel reflection surface to a gold-coated high-reflection surface possesses high resolution and sensitivity, significantly enhancing the detection performance. A well-established theoretical model of instantaneous PT transduction and optical phase modulation is employed to obtain the optimized interferometric configuration. To validate the effective interferometric phase transformation within the cavity, a comparison is made between the simple silicon cavity and the gold-coated cavity. The limitation of detection of such extrinsic fiber-tip PT sensors indicates one magnitude lower as compared to the conventional PT interferometric gas sensor with such robust and compact sensing designs. This work lays a solid foundation for future research on gas laser phase modulators and nonlinear laser–matter interactions.

Identification and validation of diagnostic biomarkers for temporal lobe epilepsy related to ferroptosis and potential therapeutic targets

Anticathode effect on multimodal azimuthal oscillations in electron beam generated E×B plasma

Electron beam (e-beam) generated plasmas with applied crossed electric and magnetic (E×B) fields are promising for low-damage (gentle) material processing. However, these plasmas can be subject to the formation of plasma non-uniformities propagating in the E×B direction. These rotating plasma structures (or “spokes”) enhance the transport of charged species across the magnetic field, which can harm the gentle processing capability of the plasma. In this work, we investigate the role of electrostatically active boundaries on the spoke formation by incorporating a variable bias conducting boundary (known as an anticathode) placed on the axially opposite side of the cathode. Our findings indicate azimuthal mode suppression occurs when the anticathode is electron collecting. Furthermore, we show selective azimuthal mode suppression by biasing the anticathode to an intermediate potential between the cathode and anode potentials. These findings suggest a link between the axial electron confinement in the e-beam generated plasma and azimuthally propagating plasma structure formation.

Male reproductive phenotype alterations in heterozygous β-globin gene knockout thalassemia (BKO) mice as a model for β-thalassemia patients

High-power GeSn photodetector for 2-<i>μ</i>m RoF system

A radio-over-fiber (RoF) link simplifies the base station and network structure, adapting to the trends of high capacity and rapid development in modern communication. The development of 2-μm-band links improves the capacity of communication systems, which can solve future optical fiber capacity crises. In this work, a relaxed high-Sn-content GeSn absorption layer was grown on a Si substrate, and high-power GeSn photodetectors were fabricated. The photodetectors achieved a low dark current with a cutoff wavelength of about 2930 nm. The GeSn photodetectors had a saturated photocurrent of up to 70 mA operating in the 2-μm-wavelength range and a 3-dB bandwidth of approximately 1.6 GHz. The results provide a technical reference for the application of GeSn 2-μm detectors in RoF links.

Distinct water and phosphorus extraction patterns are key to maintaining the productivity of sorghum under drought and limited soil resources

Abstract Nutrient and water limitations contribute to yield losses in semi-arid regions. Therefore, crop rotations incorporating nitrogen-fixing legumes and drought-tolerant sorghum varieties offer a strategy to improve the utilization of scarce soil resources. Under semi-arid, field-like conditions, sorghum crop rotations with either cowpea pre-crop or fallow, including two early and three late maturing genotypes, were tested to identify stress adaptation traits of sorghum to water and phosphorus limitations. Morphological and physiological parameters were evaluated on a single-plant basis. Lower soil P content significantly delayed flowering compared to higher P levels. However, improved P availability arising from pre-crop residues reduced this effect. Mycorrhizal infection rates and root-to-shoot ratios were positively correlated with panicle N and P content at anthesis under low P conditions. Although drought significantly impacted yield, early maturing genotypes with the highest reduction in shoot biomass and reduced water use before flowering, could sustain yield production. Early-maturing genotypes characterized by high root-to-shoot ratios, rapid AMF establishment, and reduced water use before flowering exhibit a strong potential for maintaining yield and biomass production on nutrient-poor soils in semi-arid regions. Such genotypes conserve water before flowering and thus can alleviate post-flowering water stress, ensuring adequate P uptake despite low soil P availability.

Universal scaling of electrostatic effects of a curved counter-electrode on the emitter field enhancement

Experiments on field electron emission from single-tip nanoemitters have typically been carried out using a counter-electrode with a finite curvature radius R, positioned at a distance dgap from the emitter's apex. The effects of the counter-electrode's curvature on the apex field enhancement factor (γCa) of the emitter are still not understood. In this Letter, we theoretically explore how the apex field enhancement factor of an emitter, represented by a hemisphere on a cylindrical post (HCP) with apex radius ra=50 nm, is influenced by the curvature of a sphere-shaped counter-electrode. Importantly, our results show that for HCPs with sharpness aspect ratios typically between 102 and 103, there is a universal scaling such that γCa=γPaΨ(R/dgap), where γPa represents the apex field enhancement factor for the emitter assuming a planar counter-electrode, and Ψ(R/dgap) is a universal scaling function such that Ψ∼1 for R/dgap≫1 and Ψ∼(R/dgap)α, with α close to unity, for R/dgap≪1. These findings help partially explain discrepancies observed in orthodox field electron emission experiments, where it was reported that the effective γCa values extracted from the current–voltage characteristics of single-tip carbon nanotubes typically underestimate the theoretical γPa values when R∼dgap≫ra, a trend that is predicted by our results.

Genetic characterization and phylogenetic analysis of common house crows (Corvus splendens)

Enhanced piezoelectricity in TiSXY monolayers based on electronegative polar moments effect

It is a challenge to find the relationship between the microscopic property of atoms in monolayers and the macroscopic piezoelectricity of monolayer. By first-principles calculation, we find not only the super-dipole moment (SDM) effect but also the electronegative polar moments (EPMs) effect, which can lead to the remarkable piezoelectricity in TiSXY monolayers. The SDM and EPM effects can deepen the understanding of the piezoelectric physical mechanism and provide the design strategy for ultrathin nano-devices.

Identifying invasiveness to aid lung adenocarcinoma diagnosis using deep learning and pathomics

Light-induced enhancement of alternating current poling quality and mechanical quality factor in ferroelectric single crystals

Alternating current poling (ACP) and light fields have been studied as domain engineering methods for regulating the domain structures and improving the physical properties of ferroelectric crystals because of their convenience, effectiveness, and economic advantages. In this study, we propose a LACP method (ACP under above-bandgap light illumination), by which the transparency and electro-optic properties of Mn- and Fe-doped KTa1−xNbxO3 single crystals were improved compared with only ACP. Furthermore, the mechanical quality factor (Qm = 538) of the sample poled using the LACP method increased significantly by 206% in contrast to that of the sample poled by the conventional high-temperature direct current poling method. The results reveal that the light-induced reorientation of defect dipoles is responsible for the enhancement of the ACP quality and Qm. This study provides an efficient and fast poling approach to the material design for multifunctional devices.

The effects of experimental conditions on extraction of polyphenols from African Nutmeg peels using NADESs-UAE: a multifactorial modelling technique

Strong interface coupling for enhanced photoresponse in 1D BiInSe/2D WSe2 phototransistor

With the improvement of heterostructure preparation technology, research on the physical properties and device performance of mixed-dimensional heterostructures has been greatly developed. Numerous studies have focused on 2D/2D heterostructures, but research on 1D/2D heterostructures is comparatively limited, and the interface electron transfer mechanism needs to be further explored. In this study, we leverage the inherent band structure alignment characteristics of 1D Bi1.3In0.7Se3 and 2D WSe2 to create Bi1.3In0.7Se3/WSe2 heterostructure with Type-I band alignment. The results of PL, Raman, and KPFM prove the existence of a strong coupling effect at the heterostructure interface. The Bi1.3In0.7Se3 nanowire enhances the PL intensity and red-shifts the PL peaks of WSe2. This strong local electric field at the heterojunction interface improves the photoresponse performance of the Bi1.3In0.7Se3/WSe2 heterostructures devices. They achieve excellent photoresponce properties in a wide spectral range from solar-blind ultraviolet C (254 nm) to near-infrared (980 nm) region, with a large responsivity of 98 A/W, a high detectivity of 1.16 × 1013 Jones, and a fast photoresponse time of 500 μs. In addition, the optoelectronic performance of the device is controlled by modulating the Fermi level of the heterostructure by the applied gate electric field. Our work paves the way for the development of 1D/2D heterostructures for multifunctional optoelectronic applications.