Browse Articles

An innovative complex-valued encoding black-winged kite algorithm for global optimization

Sliding ferroelectricity-induced triple barrier modulation in van der Waals boron arsenide tunnel junctions

To develop low-power, miniature, nonvolatile memory resistor integrated devices for in-memory computing technologies, the exploration of atomic-scale ferroelectric channel semiconductor devices is necessary. We theoretically designed tunnel junction devices based on two-dimensional ferroelectric semiconductors, with two-dimensional metal TaSe2 used as the top electrode and van der Waals bilayer boron arsenide (BAs) as the ferroelectric semiconductor channel, aiming to achieve high-performance, low-power, two-dimensional ferroelectric memory resistors. Our findings demonstrate that the bilayer BAs, upon contact with metal electrodes, can achieve two stable and switchable ferroelectric states. Interlayer relative sliding enables stable and alternating two-dimensional ferroelectric domains, altering the types of triple potential barriers at interfaces from Schottky contacts to Ohmic contacts. Thus, under the modulation of the “triple barrier” mechanism, control over channel carrier switching is achieved, resulting in a tunneling electroresistance of 104%. Additionally, non-equilibrium Green's function results indicate nonlinear changes in the I–V curve when switching between the two stable ferroelectric states, highlighting the multi-resistive state nature of channel resistance. Our research underscores the potential of sliding ferroelectric tunnel junctions in integrating nonvolatile storage and computing units, emphasizing their innovative applications in in-memory computing technologies.

A latent diffusion approach to visual attribution in medical imaging

Abstract Visual attribution in medical imaging seeks to make evident the diagnostically-relevant components of a medical image, in contrast to the more common detection of diseased tissue deployed in standard machine vision pipelines (which are less straightforwardly interpretable/explainable to clinicians). We here present a novel generative visual attribution technique, one that leverages latent diffusion models in combination with domain-specific large language models, in order to generate normal counterparts of abnormal images. The discrepancy between the two hence gives rise to a mapping indicating the diagnostically-relevant image components. To achieve this, we deploy image priors in conjunction with appropriate conditioning mechanisms in order to control the image generative process, including natural language text prompts acquired from medical science and applied radiology. We perform experiments and quantitatively evaluate our results on the COVID-19 Radiography Database containing labelled chest X-rays with differing pathologies via the Frechet Inception Distance (FID), Structural Similarity (SSIM) and Multi Scale Structural Similarity Metric (MS-SSIM) metrics obtained between real and generated images. The resulting system also exhibits a range of latent capabilities including zero-shot localized disease induction, which are evaluated with real examples from the cheXpert dataset.

Study of carrier diffusion in InGaN/GaN quantum wells: Impact of quantum well thickness and substrate type

In InGaN/GaN micro-light-emitting diodes (μLEDs), the size-dependent efficiency loss is commonly attributed to carrier diffusion within quantum wells (QWs). When the μLED size is sufficiently small, carriers can diffuse laterally to reach defective sidewalls, leading to non-radiative recombination. This challenges earlier assumptions of short-range carrier diffusion in InGaN/GaN QWs. However, recent studies have demonstrated the potential for long-range diffusion, prompting further investigation into how QW design and growth conditions influence carrier diffusion length and μLED efficiency. This paper contributes to this investigation by examining carrier diffusion in c-plane InGaN/GaN single QW samples using photoluminescence experiments. By varying the QW thickness, we observe an increase in diffusion length with thicker QWs, consistent with the increased radiative recombination lifetime due to the quantum confined Stark effect. This suggests that reducing QW thickness could mitigate the size-dependent efficiency loss in μLEDs. As the substrate type plays a crucial role in advancing the industrialization of μLEDs, we compare carrier diffusion in QWs grown on a substrate of different nature: sapphire, freestanding GaN, and Si (111). Our results demonstrate that the three types of substrates enable long-range diffusion. Finally, analyzing the evolution of carrier diffusion length with carrier density reveals two opposite regimes. In the high-excitation regime, carrier diffusion length decreases by increasing the excitation power, which is in agreement with previous studies and supported by a diffusion–recombination model. However, in the low-excitation regime, carrier diffusion length unexpectedly increases by increasing the excitation power.

The circadian clock gene period regulates the composition and daily bacterial load of the gut microbiome in Drosophila melanogaster

Effect of doping in small-size hybrid nanostructures for plasmonic catalysis

The effect of doping on the lowest quantum state of hot electron trapped in the semiconductor shell of small size hybrid nanoparticles is investigated. Assuming a spherical Ag-AgBr hybrid nanoparticle with a metal core and a semiconductor shell, we study the changes in the spatial profile of the contact electric potential in the Schottky barrier as a function of the doping density under the Sze approximation of a completely depleted layer. The energy of the lowest quantum state of an electron in the semiconductor shell is estimated along with the tunneling time into the metal core. It is found that when the characteristic size of the depletion layer of the Schottky barrier exceeds the size of the semiconductor shell, this energy varies throughout the Schottky barrier height by changing the shell thickness and the doping density, with the tunneling lifetime varying from subpicoseconds to submicroseconds. This possibility can be exploited to improve the efficiency of plasmonic photocatalysis with small-sized hybrid nanoparticles: By adjusting the energy of the discrete electron state to the given lowest unoccupied molecular orbit level of the chemical adsorbed on the surface of the hybrid nanoparticle, one should expect the resonance transfer of an electron, thus a dramatic increase in the rate of photocatalysis. The proposed method introduces Quantum-Size Resonance-Enhanced Photocatalysis in the hybrid structure.

Investigating Seidel energies and thermodynamic properties of benzenoid hydrocarbons through regression models

Ultrafast manipulation of Néel-type merons using electric field pulses

A nanoscale meron, as a type of topological magnetic soliton with half topological charge, can function as a quantum mechanical object whose core spin (polarity) represents the qubit states |0⟩ and |1⟩. Here, we demonstrate ultrafast steering of Néel-type merons through a simple sequence of picosecond electric field pulses via magnetoelectric interactions. All four distinct meron states exhibit well-defined switching behavior. Both volatile and nonvolatile control of the meron polarity are achieved using step and half-cycle pulses, respectively. Our approach offers an energy-efficient and localized method for controlling high density storage and fast logic computations based on nanoscale merons.

Cell free supernatants of Bifidobacterium adolescentis and Bifidobacterium longum suppress the tumor growth in colorectal cancer organoid model

Tunneling effect in quantum-dot light-emitting diodes

Charge carrier transportation in semiconductor films is a fundamental but crucial process for the light-emitting diodes. Although there have been many studies on charge transport properties of devices based on traditional inorganic crystals and organic amorphous films, such charge behavior within emerging quantum-dot light-emitting diodes (QLEDs)—which are composed of amorphous nanocrystal films with strong quantum confinement effects—has rarely been discussed. Here, we demonstrate that the tunneling effect really occurs in the hybrid QLEDs with ZnO as the electron-transport layer. By suppressing the thermal effect, a negative differential resistance (NDR) phenomenon is observed by decreasing the working temperature of the QLED low to 150 K. Two types of quantum dots (QDs) with different shell structures (i.e., different tunneling barrier) are used to comparatively examine the tunneling effect. The current density–voltage properties of the QLEDs reveal that the device based on QDs with the sharp core-shell structure (i.e., larger tunneling barrier) exhibits more obvious NDR behavior, which is attributed to the stronger tunneling effect. Our results offer significant insight into the charge dynamics and working mechanism in the QLEDs.

Interpretable machine learning for predicting sepsis risk in emergency triage patients

Theoretical analysis of thermal conductivities of water and heavy water based on thermal resistance network model

Thermal conductivity of liquid water is distinct from that of ordinary liquids due to its complex hydrogen bonding network. In this study, we develop the thermal resistance network model, supplemented by molecular dynamics simulations, to calculate the thermal conductivities of water and heavy water over a temperature range of 275–375 and 300–375 K, respectively. The thermal conductivities of both water and heavy water are computed at various temperatures and pressures, and the results provide agreement with experimental data. Furthermore, it is pointed out that our model offers an interpretation of thermal conductivity based on heat paths among water clusters rather than the traditional vibrational modes.

Integrated singlecell and bulk RNA-seq analysis identifies a prognostic signature related to inflammation in colorectal cancer

The characteristics of line-shaped defects and their impact mechanism on device performance in <i>β</i>-Ga2O3 Schottky barrier diodes

Beta-phase gallium oxide (β-Ga2O3) has attracted increasing attention in the field of power electronic devices due to its ultra-wide bandgap and high Baliga figure-of-merit. However, the premature breakdown deteriorated with the increase in device area, hindering the scale-up of the current rating. In this work, we unveil the formation and characteristics of killer defects responsible for the premature breakdown in an Si-doped (001) β-Ga2O3 epitaxial layer grown by halide vapor phase epitaxy. The killer defects feature a line-shaped morphology along the [010] orientation. Specifically, the high-resolution transmission electron microscopy characterization links the line-shaped defects to underlying voids. These voids are surrounded by amorphous phase regions, and the transition from amorphous phase to crystalline phase results in twins extending along the [010] orientation, which eventually become line-shaped defects on the wafer. Additionally, the defect area exhibits smaller capacitance and lower surface potential compared to the defect-free region. This is attributed to the absence of local ionized donors in the defect area, leading to electric field concentration in this region. This study systematically investigates a killer defect in β-Ga2O3, which contributes to the scale-up process of β-Ga2O3 power devices and advances their application.

Associations between the conicity index and kidney stone disease prevalence and mortality in American adults

Ferromagnetic permalloy/<i>p</i>-type boron-doped diamond Schottky barrier diodes

Ferromagnetic permalloy/p-type boron (B)-doped diamond Schottky barrier diodes (SBDs) were demonstrated. The SBDs showed a clear rectifying behavior with a high on/off ratio of over 109 and an ideality factor close to unity at 300 K. The Schottky barrier height was 2.07 eV at the permalloy/B-doped diamond interface. The permalloy Schottky electrodes did not intermix with B-doped diamond and had almost the same magnetic properties as bulk permalloy.

Investigations on the synthesis and characterization of silver-doped MoO3 thin films for photocatalytic applications

AbstractIn this study, we aimed to enhance the photocatalytic performance of molybdenum oxide (MoO3) thin films by doping with silver (Ag) via a spray pyrolysis technique. The primary objective for silver incorporation was intended to introduce additional energy levels into the band structure of MoO3, improving its efficiency. Structural, optical, and photocatalytic properties were analyzed using X-ray diffraction (XRD) and optical spectroscopy. XRD results confirmed an orthorhombic phase with a (040) preferential orientation for all samples. Optimal crystallinity was observed with 2% Ag doping, yielding an 84 nm crystallite size, while higher doping levels reduced crystallite size. Band gap energy narrowed from 3.07 eV (undoped) to 2.94 eV (2% Ag-doped), indicating electronic structure changes. Impedance spectroscopy revealed superior electrical properties at 4% Ag doping, enhancing charge transport. Photocatalytic performance, assessed via dye degradation, showed significant improvement with silver doping, the degradation rate peaking at 4% Ag. These results demonstrate that silver doping optimizes structural and electronic properties of MoO3 thin films, leading to enhanced photocatalytic activity.

Topological sonic whispering gallery protected by the synthetic Weyl points

The synthetic dimension provides us with a powerful platform to explore the topological properties of matter. In this paper, we choose two physical dimensions (kx and ky) and one geometric structure parameter (the height of the air cavity δ) to construct a synthetic space. The simulation results display that the three couples of Weyl points and Fermi arcs appear in the synthetic space. We find that changing the position of the boundary truncation of a sonic crystal can flexibly regulate the frequency range of valley chiral edge states. Both theoretically and experimentally, we demonstrate the sonic topological valley-locked whispering gallery, in which the valley states propagate along the interfaces between a sonic crystal and a hard wall. In the valley-locked whispering gallery, the sonic waves propagate unidirectionally along the closed channel, with high scattering efficiency and small diffraction.

Surrounding rock control for the roadway driven under the goafs of small collieries and heading for adjacent advancing face

Nitrogen-induced filament confinement strategy for implementing reliable resistive switching performance in a-HfOx memristors

Hafnium oxide (HfOx) films are highly valued as functional layers in nonvolatile resistive switching (RS) memristors due to their scalability, compatibility with CMOS technology, and high dielectric constant. However, the low reliability of HfOx-based memristors is the key factor hindering their widespread practical applications. Herein, amorphous HfOx (a-HfOx) films are used as the switching layers to construct memristors, and the nitrogen treatment strategy is employed to enhance the switching characteristics. All the fabricated Al/a-HfOx/ITO memristors demonstrate bipolar digital RS behaviors, and specifically, the 500 °C-treated a-HfOx device exhibits highly reliable RS performance, including low cycle-to-cycle variability, concentrated distributions and low operating voltages, long-term retention capacity (&amp;gt;104 s), and good cycle endurance (&amp;gt;200 cycles). The mechanisms and physical models for enhanced switching performance are thoroughly elucidated, revealing that the formation of stable oxygen vacancy–dinitrogen complexes confines the conductive filament path and significantly reduces filament randomness during formation and rupture. This work renders an effective material engineering strategy for widening a path toward designing highly reliable nonvolatile data storage devices with striking switching performances.