Browse Articles

A comparative study on different machine learning approaches with periodic items for the forecasting of GPS satellites clock bias

Temperature and pressure dependence of the fluorescence spectrum of high-pressure synthetic corundum-type Ga2O3:Cr3+, structural stability, and crystal growth under high pressure

The pressure dependence of the R1 and R2 peaks of the fluorescence spectra of high-pressure-synthesized corundum-type Ga2O3:Cr3+ was measured up to 50 GPa using a diamond anvil cell pressurized at room temperature in an argon medium. The temperature dependence of the R1 and R2 peaks was measured at low temperatures under ambient pressure from 303 to 83 K. From the measurement results, the pressure scale and low-temperature scale were determined using R1 and R2. X-ray diffraction experiments at high pressure, which were performed to confirm the effective range of the pressure scale, showed that the corundum structure undergoes a phase transition to a Rh2O3(II)-type structure at 54–65 GPa; this pressure scale is, thus, valid up to approximately 50 GPa. We also investigated the crystal growth time to optimize the crystal size of Ga2O3:Cr3+ for diamond anvil cell experiments.

Effect of intracameral air injection during Ahmed glaucoma valve implantation on hypertensive phase

Impedance matching assistance based on frequency modulation for capacitively coupled plasmas

The efficiency and repeatability of capacitively coupled plasma (CCP) processes are highly dependent on achieving precise impedance matching between the plasma load and the RF power supply. This paper presents a numerical investigation of the role of frequency modulation in enhancing impedance matching of RF CCPs, a technique that can be critical to maintaining operational efficiency and plasma stability. Through a detailed simulation approach, the research explores how variations in the driving frequency impact plasma characteristics and electrical parameters, particularly focusing on the CCP’s impedance behavior. The simulations demonstrate that when impedance matching is achieved at a fixed fundamental frequency of 13.56 MHz, changes in driving frequency will lead to reduced power coupling efficiency and increased reflection. The study introduces a frequency modulation strategy that allows us to re-establish high-quality impedance matching after changes of the plasma impedance occur, e.g., due to changes of the variable capacitor settings inside the matchbox or gas pressure, thereby improving the CCP’s performance. As the driving frequency can be adjusted electrically, adjusting the impedance matching by frequency modulation is much faster than based on mechanical adjustments of variable capacitors inside the matching and could, thus, allows quicker matching. The findings underscore the impact of frequency modulation on power absorption efficiency and highlight the sensitivity of impedance matching to driving frequency fluctuations. This study provides a foundation for further exploration into the optimization of RF CCP systems with the potential to enhance process control and plasma performance across a range of industrial applications, especially pulsed CCPs.

Design of an integrated model with temporal graph attention and transformer-augmented RNNs for enhanced anomaly detection

The spallation characteristics of polycrystalline aluminum with helium bubbles under a wide range of shock stresses

The spallation behavior of polycrystalline Al with helium (He) bubbles (poly Al–He) under unsupported shock loadings at a wide range of impact velocities was investigated via molecular dynamics simulations. We found that the microstructural features during shock compression and release processes for the poly Al–He are highly analogous to those observed in polycrystalline Al (poly Al), indicating that the bubbles studied here do not have a significant influence on the mechanical deformation before tension. During the tension process, the expansion-merging of He bubbles dominates damage accumulation and leads to the ultimate fracture of the metal, the same as that in a single crystal with He bubbles. The presence of grain boundaries (GBs) does not exhibit an apparent effect on the evolution of He bubbles, resulting in comparable expansion rates for the bubbles in different locations (i.e., near GBs or at grain interiors). Additionally, the nucleation of voids occurs subsequent to bubble expansion due to the much higher critical stress. Voids are preferentially nucleated on GBs when the material is solid and at liquid parts when the material is partially molten, demonstrating that GBs and melting can strongly facilitate void nucleation. However, He bubbles significantly impede void nucleation and growth, resulting in a much smaller quantity and volume of voids formed in the poly Al–He, compared to the poly Al. Furthermore, the critical stress for void nucleation and the spall strength of the metal matrix are reduced by He bubbles.

Developmental defects in ectodermal appendages caused by missense mutation in edaradd gene in the nfr mangrove killifish kryptolebias marmoratus

Abstract The mangrove killifish, Kryptolebias marmoratus, can reproduce with self-fertilisation, offering a unique and useful genetic tool for generation of genetic mutants and quick identification of mutated genes. From an ENU-mutated mangrove killifish line R228, we have isolated a novel mutant line, no-fin-ray/nfr in which homozygous mutant of adult fish fin ray development is largely reduced. Illumina RNAseq with 3 embryos each from mutants, siblings and the parental WT strain Hon9 (only 9 embryos as total) identified a mutation in the edaradd in a highly conserved C-terminal death domain. Edaradd is known as a cytoplasmic accessory protein for the Ectodysplasin A (EDA) signalling pathway. To confirm the crucial role of edaradd during fin development, CRISPR RNAs were designed to suppress the gene in another killifish species, Arabian killifish. Indeed, Arabian killifish edaradd crispants showed a potent reduction of the fin development with 100% frequency. Furthermore, EDA crispants also showed identical phenotypes to that of edaradd crispants, confirming the fin defect in the mutants/crispants is caused by the signalling pathway of the EDA in the killifish species. These data demonstrate a powerful genetic approach using isogenic self-fertilising mangrove killifish as a tool for identifying mutants and their mutations, and revealed the crucial role of edaradd for the first time in the fish fin development.

Enhanced flexoelectric properties in sodium bismuth titanate-based lead-free relaxor ferroelectrics by inducing polar nanoregions

The presence of polar nanoregions (PNRs) is widely recognized as playing a crucial role in the functionalities of numerous solid dielectrics. However, the contribution of PNRs to the specific coupling between strain gradient and electric polarization (flexoelectricity) has not yet been thoroughly understood. Herein, we investigated the impact of varying PNR concentrations on the dielectric and flexoelectric properties of lead-free relaxor ferroelectric (Bi0.5Na0.5)TiO3 ceramics, achieved through stoichiometric BaTiO3 doping. The temperature-dependent dielectric properties indicated the presence of PNRs in doubly doped ceramics as compared to pure BNT. Complex impedance analysis and piezoresponse force microscopy measurements demonstrated significant differences in PNR concentrations among the different components. The reorientation of PNRs notably enhanced the flexoelectric response of the doubly doped BNT-xBT ceramics, with this enhancement being positively correlated with the concentration of PNR. Specifically, the flexoelectric coefficient was found to be approximately 10 times higher in the morphotropic phase boundary (MPB) region (x = 0.08) compared to pure BNT. These findings illustrate that adjusting the concentration of PNRs in lead-free relaxation ferroelectrics is an effective strategy for improving flexoelectric properties.

Author Correction: The role of mineralogical and textural complexity in the damage evolution of brittle rocks

Impact of thermal crosstalk on dependent failure rates of multilayer ceramic capacitors undergoing lifetime testing

Several research studies have investigated the degradation of BaTiO3-based dielectric capacitor materials, focusing on the impact of composition, defect chemistry, and microstructural design to limit the electromigration of oxygen vacancies under electric fields at finite temperatures. Electromigration can be a dominant mechanism that controls failure rates in the individual multilayer ceramic capacitor (MLCC) components in testing the reliability of failures with highly accelerated lifetime testing (HALT) to determine the mean time to failure of MLCCs surface mounted onto printed circuit boards (PCBs). Conventional assumptions often consider these failures as independent, with no interaction between components on the PCB. However, this study employs a Physics of Failure (PoF) approach to closely examine transient degradation and its impact on MLCC reliability, emphasizing thermal crosstalk and its influence on dependent and independent failure rates. Finite element analysis thermal modeling and infrared thermography were used to assess the impact of circuit layout and component spacing on heat dissipation and thermal crosstalk under various electrical stress conditions. The study distinguishes between dependent and independent failures under a HALT, quantified through a β′ factor reflecting common cause failures due to thermal crosstalk. Through a series of experimental and statistical analyses, the β′ factor is evaluated with respect to temperature, voltage, and component spacing. These insights highlight the importance of understanding the nature of the data in reliability testing of MLCCs and optimizing the layout design of high-density circuits to mitigate dependent failures, improving overall reliability and informing better design and packaging strategies.

CT-based scoring system for diagnosing eosinophilic solid and cystic renal cell carcinoma versus clear cell renal cell carcinoma

Creation, annihilation and transport of nonmagnetic antiskyrmions within Ginzburg–Landau–Devonshire model

Atomistic model calculations recently revealed that the polarization pattern at the cross section through nanoscale ferroelectric nanodomains in rhombohedral barium titanate shows a clear antiskyrmion attributes such as the net invariant topological charge of minus two. The present work confirms that these topological defects also exist as local minima in the discretized Ginzburg–Landau–Devonshire model, which is widely used in phase-field modeling studies. We explore by phase-field simulations how an electric field can be used to create or move antiskyrmions within a monodomain ferroelectric matrix. The process of field-induced antiskyrmion annihilation reveals the existence of a discrete ladder of intermediate antiskyrmion states with distinct radii but common symmetry, topology, and geometrical properties.

Association between life’s essential 8 and bone mineral density among adults aged 20–59 years

Numerical investigation of an anti-symmetric nanophotonic structure for accelerating sub-relativistic electron beams

This study investigates an anti-symmetrically positioned nanophotonic dual-pillar structure, in which the dielectric and vacuum components are evenly distributed along the direction of electron propagation, with each dielectric pillar facing a vacuum region. Our numerical simulation results show that the previously proposed symmetric dielectric grating structure, where dielectric pillars facing each other are alternated with vacuum gaps, is accompanied by a deceleration region, preventing the achievement of high gradients during the acceleration process. By contrast, the anti-symmetric grating structure eliminates the deceleration field and generates a uniformly distributed acceleration field. This requires that the two oppositely directed laser beams crossing the structure in the transverse region must have a phase shift of π in the anti-symmetric case. This structure has significant potential for accelerating sub-relativistic electron beams. In this numerical simulation, the initial energy of the sub-relativistic electron beams is selected as 79 keV. The acceleration gradient provided by the symmetric design for sub-relativistic electrons is approximately 70 MeV/m; however, the anti-symmetric structure can provide a maximum acceleration gradient of up to ∼430 MeV/m.

Genome assembly and population analysis of tetraploid marama bean reveal two distinct genome types

Structural and optical properties of cubic GaN films on high-thermal conductivity substrates

A thin cubic-GaN epitaxial layer was grown by plasma-assisted molecular-beam epitaxy directly on a (100) cubic-boron-nitride nucleation layer that was previously deposited on a (100)-oriented, type IIA, single-crystal chemical-vapor deposition diamond substrate. X-ray diffraction measurements verified that (100)-plane zincblende is the dominant crystal structure of the GaN layer, with a small contribution from the wurtzite phase in some sample regions. Detailed atomic force microscopy and Raman scattering measurements confirmed the XRD findings. Low temperature photoluminescence spectra show a dominant emission line near 3.12 eV and a weaker emission line near 3.21 eV. The former is assigned to a recombination process involving electrons bound to shallow donors with holes bound to shallow acceptors (donor–acceptor pair recombination process). The latter, which becomes dominant at temperatures above 50 K, is assigned to a recombination process involving the annihilation of excitons bound to shallow impurities. Room temperature transmission measurements yielded a direct bandgap of 3.23 eV, which is close to the reported values for c-GaN. These results confirm that cubic-GaN was successfully deposited on a high thermal-conductivity diamond substrate. This opens the door to exploring the potential of cubic-GaN devices for high-power applications, given that large area diamond substrates are becoming available.

Using roof borehole electrical resistivity tomography to monitor roof water infiltration in a mine work face

A metal-only transmission metasurface with dual-layer configuration for generation of orbital angular momentum wave

In this paper, we present a metal-only transmission metasurface adopting dual-layer elements with I-shaped grooves etched on each layer, which is designed for orbital angular momentum (OAM) generation. The special arrangement of the grooves on the elements results in a wider phase compensation range, and by varying the length of the grooves, a full 360° phase coverage with a transmission amplitude of more than −2 dB can be achieved at 10 GHz. As a proof of concept, a metal-only transmission metasurface composed of 400 elements is designed, fabricated, and measured. The simulated and measured results suggest that the OAM transmitted waves with the mode l = −1 can be efficiently generated by a double-layer metal-only metasurface at around 10 GHz. Compared with conventional configurations of OAM transmitted beam generation, this configuration has great potential for high power microwave and space environment applications.

Publisher's note: “Unveiling the impact of biaxial strain on phonon transport in Janus <i>γ</i> -Ge2SSe monolayer for thermoelectric applications” [J. Appl. Phys. 136, 234301 (2024)]

Doping with FeSe greatly enhances mobility in topological insulator Bi2Se3 single crystals

In this paper, we demonstrate a novel strategy to introduce Fe into a Bi2Se3 system through growth of crystals with nominal composition (FeSe)xBi2Se3. For x&amp;lt;0.04, Fe is shown to act mostly as a non-magnetic impurity; it uniformly enters the lattice and monotonically increases the c-lattice parameter, electronic doping level, and Shubnikov–de Haas mobility. The most striking observation is the record high Hall mobility of 8600 cm2/V s at 4.2 K for the smallest FeSe content (x=0.002) that further decreases with x. Elevated mobility is accompanied by a high residual resistance ratio and a rather moderate shift of Shubnikov–de Haas oscillations to a smaller field. These findings indicate that Fe admixture cures the point defects in Bi2Se3 and, thus, opens an effective way to suppress the defect subsystem in Bi2Se3-based topological insulator materials.