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Abstract A two-dimensional phononic crystal sensor model with high-quality factor and excellent sensitivity for sensing acetone solutions and operating at 25–45 kHz is proposed. The model for filling solution cavities is based on reference designs of quasi-crystal and gradient cavity structures. The transmission spectrum of sensor is simulated by the finite element method. High-quality factor of 45,793.06 and sensitivity of 80,166.67 Hz are obtained for the acetone concentration with 1–9.1%, and quality factor of 61,438.09 and sensitivity of 24,400.00 Hz are obtained for the acetone concentration range of 10–100%, which indicated the sensor could still achieve high sensitivity and quality factor at operating frequencies from 25 to 45 kHz. To verify the application of the sensor to sensing other solutions, the sensitivity for sound velocity and density is calculated as 24.61 m-1 and 0.7764 m3/(kg × s), respectively. It indicates the sensor is sensitive to acoustic impedance changes of the solution and equally suitable for sensing other solutions. The simulation results reveal the phononic crystal sensor possessed high-performance in composition capture in pharmaceutical production and petrochemical industry, which can provide theoretical reference for the design of new biochemical sensors for reliable detection of solution concentration.

Abstract In view of the influence of variability of low-frequency noise frequency on noise prevention in real life, we present a novel two-dimensional tunable phononic crystal plate which is consisted of lead columns deposited in a silicone rubber plate with periodic holes and calculate its bandgap characteristics by finite element method. The low-frequency bandgap mechanism of the designed model is discussed simultaneously. Accordingly, the influence of geometric parameters of the phononic crystal plate on the bandgap characteristics is analyzed and the bandgap adjustability under prestretch strain is further studied. Results show that the new designed phononic crystal plate has lower bandgap starting frequency and wider bandwidth than the traditional single-sided structure, which is due to the coupling between the resonance mode of the scatterer and the long traveling wave in the matrix with the introduction of periodic holes. Applying prestretch strain to the matrix can realize active realtime control of low-frequency bandgap under slight deformation and broaden the low-frequency bandgap, which can be explained as the multiple bands tend to be flattened due to the localization degree of unit cell vibration increases with the rise of prestrain. The presented structure improves the realtime adjustability of sound isolation and vibration reduction frequency for phononic crystal in complex acoustic vibration environments.

Background: Puberty is a life milestone that marks the transition from childhood to adulthood. An ambispective Chongqing Pubertal Timing (CQPT) cohort was started in 2014 to understand pubertal timing and identify environmental risk factors. Methods: A total of 1429 children and adolescents were recruited and have been followed up once every 6 months for 8 years in a district of Chongqing, China. Data were collected via questionnaires for social and family environment, health conditions, gestational and maternal information, and in-person physical examinations by trained medical school graduate students in follow-ups. Environmental exposures of polycyclic aromatic hydrocarbons (PAHs), neonicotinoids, and heavy metals in urine samples were measured at different time points. Results: The mean ages at pubertal onset were 10.20 for thelarche, 11.62 for pubic hair development, and 11.84 for menarche in girls, and 11.16 for genital development, 11.66 for testicular enlargement, and 12.71 for first spermatorrhea in boys. Four OH-PAHs were associated with delayed timing of menarche, thelarche, pubic hair, and axillary hair development in girls, and thiacloprid was found to potentially impact genital stages in boys and axillary hair development in girls. Conclusions: We built a cohort to provide evidence of regional pubertal timing of boys and girls and the significant environmental factors. Further health outcomes, especially mental health and women's health and its long-term health implications, will be followed. [ABSTRACT FROM AUTHOR]

A growing number of studies indicate that mitochondrial dysfunction serves as a pathological mechanism for periodontitis. Therefore, this two-sample Mendelian randomization (MR) study was carried out to explore the causal associations between mitochondrial biological function and periodontitis, because the specific nature of this causal relationship remains inconclusive in existing MR studies. Inverse variance weighting, Mendelian randomization-Egger, weighted mode, simple mode, and weighted median analyses were performed to assess the causal relationships between the exposure factors and periodontitis. The results of the present study revealed a causal association between periodontitis and medium-chain specific acyl-CoA dehydrogenase (MCAD), malonyl-CoA decarboxylase (MLYCD), glutaredoxin 2 (Grx2), oligoribonuclease (ORN), and pyruvate carboxylase (PC). Notably, MCAD and MLYCD are causally linked to periodontitis, and serve as protective factors. However, Grx2, ORN, and PC function as risk factors for periodontitis. Our study established a causal relationship between mitochondrial biological function and periodontitis, and such insights may provide a promising approach for treating periodontitis via mitochondrial regulation. [ABSTRACT FROM AUTHOR]

Most previously reported Dirac valley degeneracies in continuous phononic crystal plates originate from Bragg scattering of the structures and generally have only single-band elastic-wave topological edge states. In the present work, a pair of triangular prisms is used in the construction of hexagonal-lattice phononic crystal plates to mimic the dual-band elastic valley Hall effect. Based on the spatial inversion symmetry conditions, which are related to the intrinsic frequencies of the resonators, the valley degeneracies, topological nontrivial bandgaps, and energy band inversion characteristics of multiple resonance modes are investigated by using the finite element method. Edge passbands combining distinct topology phases exist in each of the two nontrivial bandgaps of the ribbon configuration. The full-field simulations for flexural waves in the waveguide structure are demonstrated to support topologically valley-protected edge transmission in both bands, which immunizes the transport against backscattering from large corners and defects in the route. This work provides a reference for valley edge protection in subwavelength continuous elastic plate media and for the manipulation of the elastic waves at multiple frequencies. [ABSTRACT FROM AUTHOR]

In recent years, wireless energy transmission technology has developed rapidly and has received increasing attention in the industry. For microwave wireless energy transfer system applications, Ge Schottky diodes as the core components of the rectifier circuit are commonly used. Compared with Ge semiconductor, strained Ge semiconductor on Si substrate has the advantages of compatibility with Si process, low cost, and high electron mobility. It is an ideal replacement material for Ge semiconductor applications. In view of this, based on the model of the relationship between the performance of strained Ge semiconductor on Si substrate Schottky diodes and the geometric parameters of the device and the physical parameters of the material, Silvaco TCAD and ADS simulation software are jointly used to propose a novel strained Ge semiconductor on Si substrate Schottky diode for microwave rectification circuit. Simulation results show that the strained Ge semiconductor on Si substrate Schottky diode has a rectification efficiency of 70.1% when the input of the rectifier circuit is 20 dBm, the load resistance is R = 1000 Ω, and the load capacitance is C = 100 pF. Compared with traditional Ge Schottky diodes, this optimal operating point is closer to a low energy density, which is beneficial to a wide range of energy absorption. Studies have shown the feasibility of replacing Ge Schottky diodes. The research in this paper can provide valuable reference for the design and development of the core components of the rectifier circuit of the microwave infinite energy transmission system.

A high-sensitivity liquid concentration-sensing structure based on a phoxonic crystal slot nanobeam with gradient cavities is presented and its sensing properties are investigated using the finite element method. The proposed sensing structure, which can be made from either isotropic or anisotropic materials, can have excellent sensing properties that are designed via geometric optimization. We investigate the influences of various solution concentrations on electromagnetic and elastic wave transmission spectra. The results demonstrate that the introduction of gradient cavities can enable the system to avoid lattice mutation and reduce energy loss, thereby concentrating light and sound energy in the slot and holes, enhancing interactions between the electromagnetic and elastic waves, and improving sensitivity. It is worth noting that the sensing characteristics are related to the electric field distribution in the light sensor. That is, the sensitivity is better when more electric energy is distributed in the liquid-filled slot and holes. The sensitivity can reach 238.1 nm/RIU. The acoustic sensing properties are related to the solid–liquid interaction. This is especially true for the modal sensing characteristics, where the acoustic energy is concentrated on the solid–liquid interface. Therefore, greater interaction strength implies better sensitivity. The acoustic sensitivity can reach 3167 kHz/ms−1. The proposed structure provides acoustic and optical cross-checks for different types of solutions. This helps us to improve sensing accuracy and reduce sensing uncertainty. [ABSTRACT FROM AUTHOR]

The boundary control problem of fractional ordinary differential equations coupled with a time fractional reaction–advection–diffusion equation with delay is studied in this paper. To ensure the asymptotic stability of the system we studied, a state feedback boundary controller is proposed. By backstepping method, we transform the fractional coupled system into a chosen target system under a controller. Furthermore, we obtain the existence and uniqueness of the state solution of the considered system. A Lyapunov functional is constructed to show the asymptotic stability of the fractional coupled system by the special fractional Halanay inequality. The asymptotic stability criterion of the fractional coupled system is described by Linear Matrix Inequalities (LIMs). Which can be easily solved and verified. Finally, the applicability of our theoretical results is showed by a numerical simulation. [ABSTRACT FROM AUTHOR]