Browse Articles

Early detection of autism spectrum disorder: gait deviations and machine learning

Control of structural phase transition and energy storage behavior through cooling rate in (Bi0.5Na0.5)TiO3–BaTiO3 ceramics

In lead-free (Bi0.5Na0.5)TiO3–BaTiO3 (BNT–BT) ceramics, the BNT-rich side has R3c ferroelectric domains at room temperature, and modulated P4bm tetragonal nanodomains develop within the R3c rhombohedral phase at approximately the depolarization temperature Td. Such structural phase transitions have conventionally been modulated by doping with additives or by controlling the composition. However, it is considered that the coexistence region between the R3c and P4bm phases is important for enhancing the energy storage behavior because the phase reversal between them, caused by the electric field, can cause the BNT-based ceramics to exhibit an antiferroelectric-like pinched hysteresis loop. In this study, the structural phase transition of BNT–BT ceramics is promoted through process control, that is, by adjusting the cooling rate, and then the stabilization of the P4bm phase and the expansion of the coexistence region of the R3c and P4bm phases were examined, which results in enhanced energy storage behavior. Consequently, BNT–BT ceramics prepared at a slower cooling rate (0.01 °C s−1) than that of normal firing (0.05 °C s−1) demonstrate the stabilization of the P4bm phase and expansion of the coexistence region of the R3c and P4bm phases. Therefore, process control modulates the structural phase transition, which can cause enhanced energy storage behavior.

Explainable attention based breast tumor segmentation using a combination of UNet, ResNet, DenseNet, and EfficientNet models

Printing quantum dot color conversion layer in etch pits using EHD technology based on mini-LED

The rapid development of display technologies has boosted the demand for efficient and high-resolution color conversion techniques. However, conventional approaches such as photolithography and inkjet printing are constrained by limitations in pixel size and material compatibility, making it difficult to meet the demands of industrialization. Due to the low luminescence efficiency of the red quantum dot (QD) material, an innovative quantum dot color conversion (QDCC) layer structure was proposed in this study. The red QD film was prepared in pixel pits below the glass surface using electrohydrodynamic inkjet printing, thus integrating the QD film into the glass substrate. This results in a more vivid and accurate full-color display. The results indicate that the fabricated QDCC layer achieves a pixel size of 216 × 116 μm2, with a maximum external quantum efficiency (EQE) of 5.81% and a luminance of 1 315 205 cd/m2. To improve the performance of the device, the transparent photoresist used for leveling between the LEDs was substituted with a black photoresist. Although the EQE changes to 3.93% and the luminance changes to 1 206 038 cd/m2, the color coordinates move closer to the red region, changing from (0.4396, 0.2089) to (0.4786, 0.2258). This innovative method significantly not only reduces the thickness and weight of the display but also improves its color performance. This research lays the foundation for high-performance displays, paving the way for ultra-thin and energy-efficient display technologies.

Ensemble genetic and CNN model-based image classification by enhancing hyperparameter tuning

Millikelvin Nb nanoSQUID-embedded tunable resonator fabricated with a neon focused-ion-beam

SQUID-embedded superconducting resonators are of great interest due to their potential for coupling highly scalable superconducting circuits with quantum memories based on solid-state spin ensembles. Such an application requires a high-Q, frequency-tunable resonator that is both resilient to magnetic field and able to operate at millikelvin temperatures. These requirements motivate the use of a higher Hc metal such as niobium; however, the challenge then becomes to sufficiently reduce the operating temperature. We address this by presenting a monolithic Nb nanoSQUID-embedded resonator, where neon focused-ion-beam fabrication of the nanoSQUID results in a device displaying frequency tunability at T=16 mK. In order to assess the applicability of the device for coupling to small spin clusters, we characterize the flux sensitivity as a function of microwave drive power and externally applied magnetic field and find that the noise is dominated by dielectric noise in the resonator. Finally, we discuss improvements to the device design that can dramatically improve the flux sensitivity, which highlights the promise of Nb SQUID-embedded resonators for hybrid superconductor-spin applications.

Magnetic properties of different phases iron oxide nanoparticles prepared by micro emulsion-hydrothermal method

Photon number-resolving aluminum kinetic inductance detectors

We study the multi-photon energy resolution and demonstrate photon counting up to about 30 photons at near-infrared wavelengths in a kinetic inductance detector made from aluminum (Al) film. The detector has a lumped-element design comprising a large interdigitated capacitor in parallel with a narrow inductive strip. A fiber-coupled lens is used to focus the light onto the inductive absorber to minimize photon scattering. Detectors with different designs and film thicknesses are studied. From the histogram of the optimally filtered multi-photon response pulse height, we find that the square of the energy resolution of the n-photon peak ΔEn2 increases linearly with the absorbed photon energy nhν. The detector made from a thicker Al film has a smaller slope of ΔEn2 with nhν, suggesting lower phonon loss in a thicker absorber. We also discuss other factors that limit the energy resolution and maximum resolvable photon number, including the dark noise and position-dependent response.

A survey of Australian dairy farmers’ attitudes to their business, its challenges and transitioning to alternative enterprises

Observation of flexoelectric effect in PECVD silicon nitride

Flexoelectricity, a universal electromechanical coupling effect present in all dielectric materials, has garnered significant theoretical and experimental interest in recent years, particularly in ferroelectric perovskite oxides. However, nitride-based materials have received considerably less attention. In this Letter, we report the observation of direct flexoelectric effect in plasma-enhanced chemical vapor deposition silicon nitride thin film with a thickness of 200 nm. From three-point bending tests, we determined the effective flexoelectric coefficient of Si3N4 to be 1.64±0.22  nC/m. Additionally, the measured flexoelectric-induced voltages are consistent with finite element computational models. This observation of the flexoelectric coupling effect could contribute to the development of silicon nitride-based micro-scale devices.

Structural reliability assessment using quartic normal transformation

Observation of topological edge states in photonic bilayer SSH lattice

We present experimental observations of topological edge states in photonic bilayer Su–Schrieffer–Heeger (SSH) lattices. Using the femtosecond laser direct writing technology, we establish two distinct types of nontrivial bilayer SSH lattices with varying interlayer couplings, allowing us to observe two different types of topological edge states. Interestingly, we find that these topological edge states can either remain within the bandgap or transition into gapless bound states in the continuum without hybridization under different interlayer couplings. Our work illustrates a scheme to investigate topology and bound states in the continuum physics in artificial systems, potentially opening up many possibilities in topology-driven photonic devices.

The effects and predictive values of novel anthropometric parameters on uric acid levels and hyperuricemia in adults

Three-channel terahertz beam steering based on polarization multiplexed metasurfaces

Terahertz (THz) beam steering is of great significance for realizing high-speed communication, radar scanning, and information processing, but it is limited by the number of channels and strong crosstalk between different channels. In this work, we demonstrate a three-channel polarization multiplexed metasurface, enabling polarization-dependent and frequency-dependent multi-beam steering. The independent phase gradients are superimposed on a single-layer structure for three non-orthogonal polarization states, and we solved the supercell structure of the metasurface by Least Squares Approximation and Gradient Descent Algorithm to effectively suppress the crosstalk between non-orthogonal modes. The experimental results show that the deflection angles on different linear polarization states and frequencies can cover the angle range of 15°–50° in the broadband range of 0.3–0.5 THz, and the maximum crosstalk between channels is −27.84 dB at the center frequency of 0.4 THz. The proportion of beam energy correctly multiplexed by each channel reaches >80%. This non-orthogonal polarization multiplexing mechanism is of great value for THz metasurface multi-channel wavefront manipulation.

A multi-level analysis of motor and behavioural dynamics in 9-month-old preterm and term-born infants during changing emotional and interactive contexts

AbstractComputational analysis of infant movement has significant potential to reveal markers of developmental health. We report two studies employing dynamic analyses of motor kinematics and motor behaviours, which characterise movement at two levels, in 9-month-old infants. We investigate the effect of preterm birth (< 33 weeks of gestation) and the effect of changing emotional and social-interactive contexts in the still-face paradigm. First, multiscale permutation entropy was employed to analyse acceleration kinematic timeseries data collected from Inertial Measurement Unit (IMU) sensors on infants’ torso, wrists, and ankles (N = 32: 10 term; 22 preterm). Second, Recurrence Quantification Analysis was used to characterise patterns of second-to-second behavioural changes, from observationally coded behavioural timeseries on infants’ emotional self-regulation (N = 111: 61 term; 50 preterm). We found frequency-specific effects of context on permutation entropy. Relative to infants born at term (> 37 weeks of gestation), infants born preterm showed greater permutation entropy in their left ankle and torso movements, but not in right ankle or wrist movements. We did not find effects of preterm birth or emotional context on micro-level behavioural dynamics. Our methodology and findings inform future work using multiscale entropy to study infant development. Dynamic analysis of behaviour is a relatively young field, and applications to emotional self-regulation requires further methodological development.

Effects of temperature on surface plasmon resonance in organic thin-film transistor

Pentacene organic thin-film transistors (OTFTs) adopting n-Si gate electrodes with a wide range of doping concentrations (1015–1020 cm−3) are fabricated to study the effects of the quantum-mechanical interaction between gate electrode and gate dielectric on the carrier mobility in the pentacene channel. At room temperature, significant carrier-mobility reduction is observed for the OTFTs with gate doping concentrations of 1.75 × 1018 and 4.19 × 1018 cm−3 due to enhanced remote phonon scattering resulting from the resonance between the surface plasmons of the gate electrode and the phonons of the HfLaON gate dielectric (from Hf-O and La-O bonds) and the silicate interlayer (from Si-O bond), respectively, namely the anti-screening effect (ASE). This ASE can be further supported by increasing the measurement temperature from room temperature to 40, 60, and 80 °C, under which the frequency of gate-electrode plasmon increases (due to higher electron thermal energy and also higher electron concentration produced by stronger ionization of dopants in the gate electrode) to enhance, weaken, or create the resonance, resulting in stronger ASE, reduced ASE, or ASE with another phonon mode in the gate dielectric, respectively, in the OTFT. These results can help address the issue of the temperature-dependent reliability of OTFTs operating under heating or at low temperatures.

Rapid climate action is needed: comparing heat vs. COVID-19-related mortality

AbstractThe impacts of climate change on human health are often underestimated or perceived to be in a distant future. Here, we present the projected impacts of climate change in the context of COVID-19, a recent human health catastrophe. We compared projected heat mortality with COVID-19 deaths in 38 cities worldwide and found that in half of these cities, heat-related deaths could exceed annual COVID-19 deaths in less than ten years (at + 3.0 °C increase in global warming relative to preindustrial). In seven of these cities, heat mortality could exceed COVID-19 deaths in less than five years. Our results underscore the crucial need for climate action and for the integration of climate change into public health discourse and policy.

Multi-field coupling challenges the stability test of silicon solar cells

UV-induced degradation is an important factor affecting the stability of silicon heterojunction (SHJ) solar cells. Many works investigated the root cause of this degradation previously, but its coupling with other external stress, such as temperature, has rarely been reported. Here, we examine the decrease in SHJ solar cells induced by UV irradiation at different temperatures (−30 and 80 °C) using ultraviolet lamps at 200 W/m2 for 300 h. The results showed that the UV-induced degradation is more severe at low temperature (−30 °C), leading to a significant power decrease (13.5% on average) compared with the power attenuation of the solar cell at 80 °C (1.59% on average). At a low temperature (−30 °C), the VOC and FF evidently decrease much faster. Light soaking can repair the damage to some extent, but the power conversion efficiency cannot restore to the initial value. A 3D microscope confirmed this is because the silver metal electrodes are permanently degraded. These findings challenge the standard International Electrotechnical Commission (IEC) stability test for solar cells, in other words, we have to take into account multi-field coupling to evaluate the long-term reliability of solar cells in real environments.

A mouse model of deep vein thrombosis by inferior vena cava hypoperfusion using ameroid constrictors

Synthetic frequency dimension in a spatiotemporally driven phononic ring resonator

The concept of synthetic dimensions offers a unique approach to exploring higher-dimensional physics within lower-dimensional systems. Since its initial demonstration in atomic systems, synthetic dimensions have been implemented in various optical platforms, often by forming a lattice through the coupling of photonic states. In this work, we propose a similar method for realizing synthetic frequency dimensions on a phononic platform. Specifically, we design a parametrically driven phononic ring resonator composed of cantilever beams and conduct numerical investigations into the modal dynamics along this synthetic frequency dimension. Our approach employs detuned spatiotemporal stiffness modulation, which generates synthetic electric fields for the phononic modes. This modulation induces both harmonic and anharmonic Bloch oscillations along the synthetic frequency dimension. To elucidate these modal dynamics, we numerically construct and visualize a dynamic band structure within the Brillouin zone in the presence of synthetic electric fields.