Browse Articles

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.

Unilateral biportal endoscopic decompression combined with percutaneous pedicle screw fixation offers new treatment option for thoracolumbar burst fractures with secondary spinal stenosis

Compact high-precision Jones matrix metasurfaces for producing high-order vector vortex waves at microwave frequencies

Compact, high-precision Jones matrix metasurfaces, employing quasi-two-dimensional metasurfaces composed of a single-layer quasi-H-type patch, are presented for producing high-order vector vortex waves at microwave frequencies. The relationship between the spatial polarization mode of the vector waves described in the higher-order Poincaré (HOP) sphere and the higher-precision Jones matrix metasurface is established based on a derivation of the Jones matrix. The numerical results show that vector waves with spatial polarization mode orders of ±1 and ±2 can be accurately realized using compact, high-precision Jones matrix metasurfaces with orders of ±1 and ±2. In principle, Jones matrix metasurfaces can realize vector vortex waves of arbitrary order described in the HOP sphere. Two prototypes, namely, high-precision Jones matrix metasurfaces with orders of +1 and +2, are fabricated and experimentally investigated with various polarization morphologies. Good agreement is achieved between the simulations and the experimental results. These results will benefit the development of polarization multiplexing and help expand the applications of vector beams in the microwave range.

Using electrical resistivity techniques (ERT and SP) for nondestructive detection of seepage channels at the Leitai heritage site, China

Optimization of fin-slanted angles for enhanced electrical performance in lateral <i>β</i>-Ga2O3 MOSFETs

In this work, the influence of fin-slanted angles (α) on the electrical performance of lateral β-Ga2O3 MOSFETs was investigated through a combination of experiments and Sentaurus TCAD simulations. The fin-slanted devices demonstrated enhancement-mode characteristics with an on/off ratio of around 107. The increment in α resulted in improved drain-to-source current (IDS) and extrinsic transconductance (Gm). The voltage-blocking performance also showed significant enhancement with increasing α due to the mitigation of edge crowding, achieving a 40% increase in the breakdown voltage (VBR) for devices with an α of 15° and gate-to-drain length (LGD) of 10 μm. A detailed simulation analysis of the electric field distribution within the fin at the gate electrode edge identified an optimal α of approximately 25°, which effectively mitigates electric field crowding and has the potential to enhance the DC performance of the MOSFETs. These findings highlight the critical role of fin-slanted angle optimization in advancing the performance of lateral β-Ga2O3 MOSFETs, positioning them as promising candidates for next-generation power electronics.

Antimicrobial properties of Graphene sheets embedded with Titanium Oxide and Calcium Oxide nanoparticles for industrial wastewater treatment

Enhanced red-light photorefractive response speed of LiNbO3 crystals for full color holographic display

As a promising candidate material for holographic displays, lithium niobate (LN) is limited by its slow photorefractive (PR) response. Recently, it was discovered that Bi3+, with its lone-pair electrons, can effectively enhance the PR speed of LN crystals. However, this enhancement is only effective in the short-wavelength range of visible light, and the response time remains inadequate for full-color dynamic displays. In this paper, a theoretical framework is established to guide the shallow energy-level PR doping of LN crystals. We simulate the energy band structure, electron mobility, and other properties of LN crystals doped with Tl, Pb, and Sb ions, which feature lone-pair electrons, using first-principles calculations. The theoretical results indicate that when Sb occupies the Nb site (SbNb0), the defect level position in the bandgap is shallow, and the electron mobility is 79.029 cm2 V–1 s–1 subsequently, we grew a series of LN:Sb and LN:Sb,Mg crystals and characterized their crystalline quality and PR properties. High-resolution x-ray rocking curve results demonstrate that all the as-grown crystals exhibit excellent crystalline quality, with FWHM values ranging from approximately 0.007° to 0.008°. Notably, the LN:Sb1.0,Mg6.0 crystal demonstrates a rapid PR response time of 1.67 s at 671 nm, nearly three times faster than that of the LN:Bi1.0,Mg6.0 crystal.

Possible glendonite mineral pseudomorphs in the aftermath of the end-Permian extinction

AbstractGlendonites (from the precursor of ikaite, CaCO3.6H2O) preferentially precipitate within sediments in cold waters (− 2 to 7°C) via either organotrophic or methanogenic sulphate reduction. Here, we report the first occurrence of possible glendonites associated with the end Permian mass extinction in the earliest Triassic (ca. 252 Million years ago, Ma) subtropical marine carbonates on the Arabian Plateau, Oman. The authigenic carbonate crystals are small (&lt; 2 mm) and precipitated either on bedding planes or reworked within micro cross-laminations, erosional scours, or lags at the base of calcisiltite turbidites, supporting a syn-depositional origin. The observed shape and macrostructure bear resemblance to that of glendonites. SEM and cathodoluminescent imaging reveals unzoned internal structures with three mineral phases: irregular, pseudo-hexagonal and spherical low-Mg calcite crystals (Type 1), low-Mg calcite cement (Type 2), and a later void-filling silica cement (Type 3). The pseudomorphs show δ13C values from − 0.14‰ to − 0.85‰ (mean − 0.43‰; n = 5) that are more positive than the associated micritic matrix, where values range from − 0.92‰ to − 2.39‰ (mean − 1.64‰; n = 7), indicating that oceanic dissolved inorganic carbon (DIC) was the primary carbon source rather than either methane or organic matter. These δ13C values significantly differ from typical δ13C signatures of authentic glendonites, except for Ordovician examples. If these are glendonites, we infer that they could have precipitated due to the unusually elevated alkalinity and pH (&gt; 9) oceanic conditions present in the aftermath of the end-Permian extinction associated with highly disrupted carbon cycle dynamics, possibly accompanied with the upwelling of cold, anoxic oceanic water.

Large piezoelectric response in paraelectric region of PMN-32PT near morphotropic phase boundary

We report an effective piezoelectric coefficient of deff = 40 ± 6 pm/V in the paraelectric phase of (1-x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 single crystals with x = 0.32 (PMN-32PT), which is near the morphotropic phase boundary (x = 0.30). This value for deff in the paraelectric phase is significantly larger than that for other ferroelectrics measured so far. Our detailed investigation of symmetry-disallowed piezoelectricity indicates bias effects due to alternating current (AC) electric fields (100–800 kHz) and AC field cooling. The application of moderate AC fields (100–350 V/cm) gives rise to a nonlinear response of the piezoelectric effect, leading to an irreversible increase in the piezoelectric coefficient in the paraelectric phase. Along with changes in the elastic properties, the observed poling due to AC electric fields is reminiscent of irreversible ferroelectric–ferroelastic domain wall motion in ferroelectric phases. Such behavior is absent in cubic SrTiO3 where precursor effects are commonly observed at much lower temperatures.