Search Results (73)

Escherichia coli (E. coli) is one of the most common strains that produce Shiga toxin, which can contaminate food and water, causing serious diseases and even endangering life. Therefore, the detection of E. coli is crucial for protecting public health. At present, most traditional methods have disadvantages such as long detection cycles, high cost, and complex operations. This article proposed a novel commercial Rayleigh surface acoustic wave (R-SAW) biosensor for the detection of trace amounts of E. coli, which utilized the coordination reaction between carboxyl (-COOH) groups and aluminum ions (Al³⁺) to form the bio-enhanced probes, enabling the 5-terminal -COOH-modified aptamers to be preferentially enriched and directionally immobilized on the electrode surface. The biosensor could complete the detection within 100 s, with a linear detection range of 10³–10⁸ cells/mL, a limit of detection (LOD) as low as 732 cells/mL, and a selectivity ratio of 3270:1. This article conducted spiked detection on six types of food, indicating that the biosensor had the advantages of rapid speed, high sensitive, wide detection range, low LOD, strong specificity, and low cost, providing an economical and convenient solution for detecting trace amounts of E. coli in food. Full article

The article describes a basic comparison of soldering materials (preforms) from several suppliers, focusing on the main differences in surface structure, internal structure, and contamination on the surface and in the interior of the solder. As a result, we are able to define how different preforms of the surface, preforms related to impurities, or preforms of the structures of the composition parts of the power modules, which are subjected to the soldering process, influence the formation of different void types. Simultaneously an investigation of the impact on the soldering process (heating, cleaning, soldering, cooling), which influences the formation of the solder joint and on the formation intermetallic structure (IMC) and voids, is performed as well. A comparison of the individual results between RTG or X-ray (Radioisotope Thermoelectric Generator) and SAM (Scanning Acoustic Microscopy) are given together with the highlighted differences. This application study was carried out under various settings to investigate the effects of temperature and exposure time on formic acid. The findings confirm that oxide reduction is a time-dependent process. The lowest average void area—0.2%—was observed at the highest tested temperature of 230 °C, and the longest formic acid exposure duration of 300 s. Full article

For non-destructive testing (NDT) of defects in aluminum alloy plates, traditional ultrasonic contact methods face challenges from high temperatures and liquid couplant contamination. Using electromagnetic acoustic transducers (EMATs), a key issue is that longitudinal waves (L-waves) excited by the butterfly-coil EMATs interfere with the desired shear waves (S-waves) reflected by internal defects. To solve this problem, a simulation–experiment approach optimized the butterfly coil parameters. An FE model visualized the electromagnetic acoustic transducer (EMAT) acoustic field and predicted signals. Orthogonal simulations tested three main parameters: excitation frequency, wire diameter, and effective coil width. Tests on aluminum specimens with artificial defects used the optimized EMAT. Simulated and measured signals showed strong correlation, validating optimal parameters. The results confirmed suppressed L-wave interference and improved defect detection sensitivity, enabling detection of a 3 mm diameter flat-bottomed hole buried 37 mm deep. Full article

Two-dimensional (2D) materials have attracted significant attention, owing to their atomically thin thickness; large specific surface area; and excellent mechanical, optical, and electronic properties. Suspended 2D materials, which eliminate substrate effects, exhibit unique potential in a variety of applications, including ultrasensitive sensors, flexible electronic devices, acoustic devices, and optoelectronic devices. However, a central challenge in the fabrication of high-quality suspended structures lies in transfer technology—how to accurately transfer atomically thin layers onto target substrates or form self-suspended structures without introducing contamination or causing mechanical damage. This review summarizes recent advances in the fabrication, characterization, and applications of suspended 2D materials. We focus particularly on transfer methods, offering a comparative analysis of their advantages and limitations, and conclude with insights into future directions and remaining challenges. Full article

As society develops, the aquaculture industry faces challenges such as environmental changes and water contamination. Water quality monitoring and preventive measures have become essential to prevent property losses. Traditional water quality monitoring methods rely on manual sampling and laboratory analysis, which are inefficient and costly. Additionally, the operational lifespan of conventional water quality sensors is limited by battery capacity, making long-term and continuous monitoring difficult to ensure. This review focuses on water quality sensor systems and provides a comprehensive analysis of self-powered schemes utilizing acoustic energy harvesting technology. It comprehensively discusses the overall architecture of self-powered sensors, energy harvesting principles, piezoelectric transducer mechanisms, and wireless transmission technologies. It also covers acoustic energy enhancement devices and the types and development status of piezoelectric materials used for acoustic energy harvesting. Furthermore, the review systematically summarizes and analyses the current applications of these sensors in aquaculture monitoring and evaluates their advantages, disadvantages, and prospects. Full article

Air-coupled ultrasound overcomes the limitations of traditional contact-based ultrasonic methods that rely on liquid couplants. Still, it faces challenges due to the acoustic impedance mismatch between air and wood, causing significant signal scattering and attenuation. This results in weak transmission signals contaminated by clutter and noise, compromising measurement accuracy. This study proposes a coded pulse air-coupled ultrasonic method for detecting defects in wood. The method utilizes Golay code complementary sequences (GCCSs) to generate excitation signals, with its feasibility validated through mathematical analysis and simulations. A-scan imaging was performed to analyze the differences in signal characteristics between defective and non-defective areas, while C-scan imaging facilitated a quantitative assessment of defects. Experimental results demonstrated that GCCS-enhanced signals improved the ultrasonic penetration and axial resolution compared to conventional multi-pulse excitation. The method effectively identified defects such as knots and pits, achieving a coincidence area of 85% and significantly enhancing the detection accuracy. Full article

In induction motor bearings, distributed faults are prevalent, often resulting from factors such as inadequate lubrication and particle contamination. Unlike localized faults, distributed faults produce complex and unpredictable motor signal behaviors. Although existing research predominantly addresses localized faults in mains-fed motors, particularly single-point defects, a comprehensive investigation into particle contamination in bearings of inverter-fed motors is essential for a more accurate understanding of real-world bearing issues. This paper conducts a comparative analysis of vibration, stator current, speed, and acoustic signals to detect particle contamination through signal analysis across three domains: time, frequency, and time-frequency. These domains are analyzed to assess and compare the characteristics of each monitored signal in the context of bearing wear detection. The data were collected from both steady-state and startup transients of an induction motor controlled by a variable frequency drive. The experimental results highlight the most significant characteristics of each monitored signal, evaluated across the different domains of analysis. The primary conclusion indicates that, in inverter-fed motors, sound and vibration signals exhibit abnormal levels when the bearing is damaged but the related-fault signature becomes complicated. Additionally, the findings demonstrate that the analysis of startup stator current and speed signals presents the potential to detect distributed bearing damage in inverter-fed induction motors. Full article

A biosensor was designed for detecting Pseudomonas aeruginosa (P. aeruginosa) bacteria in whole milk samples. The sensing layer involved the antifouling linking molecule 3-(2-mercaptoethanoxy)propanoic acid (HS-MEG-COOH), which was covalently linked to an aptamer for binding P. aeruginosa. The aptasensor uses the thickness shear mode (TSM) system for mass-sensitive acoustic sensing of the bacterium. High concentrations (10⁵ CFU mL⁻¹) of nonspecific bacteria, E. coli, S. aureus, and L. acidophilus, were tested with the aptasensor and caused negligible frequency shifts compared to P. aeruginosa. The aptasensor has high selectivity for P. aeruginosa, with an extrapolated limit of detection (LOD) of 86 CFU mL⁻¹ in phosphate-buffered saline (PBS) and 157 CFU mL⁻¹ in milk. To improve the sensitivity of the sensor, gold nanoparticles (AuNPs) were functionalized with the same aptamer for P. aeruginosa and flowed through the sensor following bacteria, reducing the extrapolated LOD to 68 CFU mL⁻¹ in PBS and 46 CFU mL⁻¹ in milk. The frequency variations in the aptasensor are proportional to various concentrations of P. aeruginosa (10²–10⁵ CFU mL⁻¹) with and without AuNPs, respectively. The low and rapid mass-sensitive detection demonstrates the ability of the aptasensor to quantitatively identify bacterial contamination in buffer and milk. Full article

This study aims to investigate the influence of cadmium (Cd) speciation transformation on P-wave velocity under different soil moisture conditions, providing critical insights into the subsurface characteristics of contaminated soils. Taking Cd-contaminated soil as the research subject, P-wave velocity and the speciation distribution of Cd in soils with different moisture contents and Cd adsorption levels were measured. The results reveal that when the soil is contaminated by Cd, the porosity is altered and it eventually lead to change P-wave velocity. By increasing the moisture content of soils, the redox potential (Eh) rises and the pH decreases, which lead to the speciation transformation of Cd from carbonate-bound state (CAB), Fe-Mn oxide-bound state (FMO), and organic and sulfide-bound state (ORB) to the exchangeable state (EX). These transformations of Cd to EX result in the increase in soil porosity, which lead to the decrease in P-wave velocity. In addition, linear regression analysis was conducted the P-wave velocity (∆V) and the EX (∆EX) at various Cd adsorption levels. The analysis shows that there is a strong linear relationship between exchangeable Cd content and P-wave velocity, and the determination coefficient is about 0.9, which provides a reliable basis for monitoring soil Cd contamination by using P-wave velocity. This study provides valuable insights into the relationship between the speciation distribution of heavy metals in soil and the properties of acoustic wave. Full article

Global Navigation Satellite System/Acoustic (GNSS/A) underwater positioning technology is attracting more and more attention as an important technology for building the marine Positioning, Navigation, and Timing (PNT) system. The random error of the tracking point coordinate is also an important error source that affects the accuracy of GNSS/A underwater positioning. When considering its effect on the mathematical model of GNSS/A underwater positioning, the Total Least-Squares (TLS) estimator can be used to obtain the optimal position estimate of the seafloor transponder, with weak consistency and asymptotic unbiasedness. However, the tracking point coordinates and acoustic ranging observations are inevitably contaminated by outliers because of human mistakes, failure of malfunctioning instruments, and unfavorable environmental conditions. A robust alternative needs to be introduced to suppress the adverse effect of outliers. The conventional Robust TLS (RTLS) strategy is to adopt the selection weight iteration method based on each single prediction residual. Please note that the validity of robust estimation depends on a good agreement between residuals and true errors. Unlike the Least-Squares (LS) estimation, the TLS estimation is unsuitable for residual prediction. In this contribution, we propose an effective RTLS_Eqn estimator based on “total residuals” or “equation residuals” for GNSS/A underwater positioning. This proposed robust alternative holds its robustness in both observation and structure spaces. To evaluate the statistical performance of the proposed RTLS estimator for GNSS/A underwater positioning, Monte Carlo simulation experiments are performed with different depth and error configurations under the emulational marine environment. Several statistical indicators and the average iteration time are calculated for data analysis. The experimental results show that the Root Mean Square Error (RMSE) values of the RTLS_Eqn estimator are averagely improved by 12.22% and 10.27%, compared to the existing RTLS estimation method in a shallow sea of 150 m and a deep sea of 3000 m for abnormal error situations, respectively. The proposed RTLS estimator is superior to the existing RTLS estimation method for GNSS/A underwater positioning. Full article

During long-term operation in complex environments, the pressure pipeline systems are prone to damage and faults, and serious safety accidents may occur without real-time condition monitoring. Moreover, in traditional non-contact monitoring approaches, acoustic signals are widely employed for condition monitoring for pressure pipelines, which are easily contaminated by background noise and provide unsatisfactory accuracy. As a tool for quantifying uncertainty and complexity, signal entropy is applied to detect abnormal conditions. Based on the characteristics of entropy and acoustic signals, an improved entropy-based condition monitoring method is proposed for pressure pipelines through acoustic denoising. Specifically, this improved entropy-based noise reduction model is proposed to reduce the noise of monitoring acoustic signals through adversarial training. Based on the denoising of acoustic signals, an abnormal sound detection method is proposed to realize condition monitoring for pressure pipelines. In addition, the experimental platform is built to test the effectiveness and reliability of the proposed method. The results indicate that the quality of signal denoising can reach over 3 dB, while the accuracy of condition monitoring is about 92% for different conditions. Finally, the superiority of the proposed method is verified by comparing it with other methods. Full article

Cosmogenic beryllium-10 and beryllium-7, and the ratio of the two (10Be/7Be), are powerful atmospheric tracers of stratosphere–troposphere exchange (STE) processes; however, measurements are sparse for altitudes well above the tropopause. We present a novel high-altitude balloon campaign aimed to measure these isotopes in the mid-stratosphere called Beryllium Isotopes for Resolving Dynamics in the Stratosphere (BIRDIES). BIRDIES targeted gravity waves produced by tropopause-overshooting convection to study their propagation and impact on STE dynamics, including the production of turbulence in the stratosphere. Two custom-designed payloads called FiSH and GASP were flown at altitudes approaching 30 km to measure in situ turbulence and beryllium isotopes (on aerosols), respectively. These were flown on nine high-altitude balloon flights over Kansas, USA, in summer 2022. The atmospheric samples were augmented with a ground-based rainfall collection targeting isotopic signatures of deep convection overshooting. Our GASP samples yielded mostly negligible amounts of both 10Be and 7Be collected in the mid-stratosphere but led to design improvements to increase aerosol capture in low-pressure environments. Observations from FiSH and the precipitation collection were more fruitful. FiSH showed the presence of turbulent velocity, temperature, and acoustic fluctuations in the stratosphere, including length scales in the infra-sonic range and inertial subrange that indicated times of elevated turbulence. The precipitation collection, and subsequent statistical analysis, showed that large spatial datasets of 10Be/7Be can be measured in individual rainfall events with minimum terrestrial contamination. While the spatial patterns in rainfall suggested some evidence for overshooting convection, inter-event temporal variability was clearly observed and predicted with good agreement using the 3D chemical transport model GEOS-CHEM. Full article

Micro- and nanoplastics have become increasingly relevant as contaminants to be monitored due to their potential health effects and environmental impact. Nanoplastics, in particular, have been shown to be difficult to detect in drinking water, requiring new capture technologies. In this work, we applied the acoustofluidic seed particle method to capture nanoplastics in an optimized, tilted grid of silica clusters even at the high flow rate of 5 mL/min. Moreover, we achieved, using this technique, the enrichment of nanoparticles ranging from 500 nm to 25 nm as a first in the field. We employed fluorescence to observe the enrichment profiles according to size, using a washing buffer flow at 0.5 mL/min, highlighting the size-dependent nature of the silica seed particle release of various sizes of nanoparticles. These results highlight the versatility of acoustic trapping for a wide range of nanoplastic particles and allow further study into the complex dynamics of the seed particle method at these size ranges. Moreover, with reproducible size-dependent washing curves, we provide a new window into the rate of nanoplastic escape in high-capacity acoustic traps, relevant to both environmental and biomedical applications. Full article

Thyroid hormones (THs) require iodine for biosynthesis and play critical roles in brain development. Perchlorate is an environmental contaminant that reduces serum THs by blocking the uptake of iodine from the blood to the thyroid gland. Using a pregnant rodent model, we examined the impact of maternal exposure to perchlorate under conditions of dietary iodine deficiency (ID) on the brain and behavior of offspring. We observed modest reductions in thyroxine (T4) in the serum of dams and no effect on T4 in pup serum in response to maternal exposure to 300 ppm of perchlorate in the drinking water. Likewise, serum T4 was reduced in ID dams, but, as with perchlorate, no effects were evident in the pup. However, when ID was coupled with perchlorate, reductions in pup serum THs and transcriptional alterations in the thyroid gland and pup brain were detected. These observations were accompanied by reductions in the number of cortical inhibitory interneurons containing the calcium-binding protein parvalbumin (Pvalb). Alterations in Pvalb expression in the neonatal brain were associated with deficits in the prepulse inhibition of acoustic startle in adult male offspring and enhanced fear conditioning in females. These findings support and extend structural defects in the brain previously reported in this model. Further, they underscore the critical need to consider additional non-chemical stressors in the determination of hazards and risks posed by environmental contaminants that affect the thyroid system. Full article

Since the Industrial Revolution, underwater soundscapes have become more complex and contaminated due to increased cumulative human activities. Anthropogenic underwater sources have been growing in number, and shipping noise has become the primary source of chronic acoustic exposure. However, global data on current and historic noise levels is lacking. Here, using the Listening to the Deep-Ocean Environment network, we investigated the baseline shipping noise levels in thirteen observatories (eight stations from ONC Canada, four from the JAMSTEC network, and OBSEA in the Mediterranean Sea) and, in five of them, animal presence. Our main results show yearly noise variability in the studied locations that is not dominated by marine traffic but by natural and biological patterns. The halt in transportation due to COVID was insignificant when the data were recorded far from shipping routes. In order to better design a legislative framework for mitigating noise impacts, we highlight the importance of using tools that allow for long-term acoustic monitoring, automated detection of sounds, and big data handling and management. Full article