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Abstract Photoacoustic imaging has emerged as a powerful, non-invasive modality for various biomedical applications. Conventional photoacoustic systems require contact-based ultrasound detection and expensive, bulky high-power lasers for the excitation. The use of contact-based detectors involves the risk of contamination, which is undesirable for most biomedical applications. While other non-contact detection methods can be bulky, in this paper, we demonstrate a proof-of-concept experiment for compact and contactless detection of photoacoustic signals on silicone samples embedded with ink-filled channels. A silicon photonics-based Laser Doppler Vibrometer (LDV) detects the acoustic waves excited by a compact pulsed laser diode. By scanning the LDV beam over the surface of the sample, 2D photoacoustic images were reconstructed of the sample.

Abstract The development of ultrasonic‐guided wave sensors is of great significance for structural health monitoring (SHM). In this work, a shear horizontal (SH) ultrasonic guided wave sensor based on the Ca3TaGa3Si2O14 (CTGS) piezoelectric single crystal is demonstrated. The findings reveal that the CTGS‐based ultrasonic guided wave sensor is proficient in transmitting and receiving pure fundamental SH wave (SH0 wave) along two orthogonal main directions (0° and 90°) over a wide frequency range (100–350 kHz), exhibiting strong response to the SH0 wave. Under the driving voltage of 100 V, the peak‐to‐peak values of the sensor output are 110.8 and 8.0 mV at room temperature and high temperature of 600 °C, respectively. Additionally, the signal‐to‐noise ratio (SNR) of the CTGS‐based SH0 sensor is evaluated to be >18.9 dB even at the elevated temperature of 600 °C. Moreover, the CTGS‐based SH0 sensor showcases its reasonable defect localization ability at temperatures up to 600 °C, demonstrating its great potential for application in the high temperature in‐situ SHM.

Abstract Two-dimensional (2D) XY ferromagnets have drawn pronounced interest in recent years, but the characteristic of easy-plane magnetization restricts their application in spintronics to some extent. Here, we propose a general strategy for constructing multiferroic van der Waals heterostructures, aiming to achieve electrical control over the magnetic anisotropy in 2D XY ferromagnets. The validity of this strategy is verified by the heterostructure composed of ferromagnetic VBi2Te4 and ferroelectric In2Se3 monolayers. By manipulating the polarized states of In2Se3, the VBi2Te4 can be reversibly transformed between 2D XY and Heisenberg ferromagnets, characterized by the switching of easy magnetization axis between in-plane and out-of-plane directions. More interestingly, accompanied by the changes in magnetic anisotropy, the VBi2Te4 also demonstrates a phase transition from a semiconductor to a half-metal state, which can be ascribed to the band alignment and interfacial charge transfer. The switchable magnetic and electronic properties enable the heterostructure to be utilized in nonvolatile memory and logic devices. Additionally, the half-metallicity and magnetocrystalline anisotropy energy of the heterostructure can be effectively tuned by biaxial strain. These findings not only pave the way for electrically nonvolatile control of 2D XY ferromagnet, but also facilitate the development of interfacial magnetoelectric physics and applications.

This study aimed to evaluate the effects of combined replacement of fishmeal (FM) and fish oil (FO) with poultry byproduct meal (PBM) and mixed oil (MO, poultry oil: coconut oil = 1 : 1) on growth performance, body composition and muscle quality of tiger puffer (Takifugu rubripes). Fish with an average initial body weight of 14.29 g were selected for the feeding experiment. FM accounting for 0%, 5%, and 10% of the diet was replaced by PBM. For each grade of FM replacement, 5% FO or MO was used as added oil. The six experimental diets were designated as FO-FM, MO-FM, FO-5PBM, MO-5PBM, FO-10PBM, and MO-10PBM, respectively. Each treatment was performed in triplicate with 30 fish per replicate. The feeding period was 45 days. There was no significant difference in growth performance among the groups. Dietary supplementation of both PBM and MO had marginal effects on whole-fish proximate composition, except that dietary MO supplementation significantly increased the liver moisture content. In serum, there were no significant differences in contents of triglyceride, total cholesterol, total bile acid, and protein carbonyl among groups, but the malondialdehyde content was reduced by MO. The fatty acid composition in fish mirrored those in the diets, but the omega-3 sparing effects of saturated and monounsaturated fatty acid in MO can still be observed. Dietary PBM and MO had marginal effects on free amino acid composition and texture of fish muscle, but exerted complicated effects on the muscle volatile flavor compound composition. In conclusion, combined fishmeal (10% of the diet) and fish oil (5% of the diet) replacement with poultry byproduct and mixed oil (poultry oil + coconut oil) had no adverse effects on the growth performance and body proximate composition of farmed tiger puffer. However, these replacements changed the muscle flavor compound profile.

Abstract High‐temperature vibration sensors are of great importance for accurate monitoring of dynamic mechanical conditions in automotive, aerospace and energy‐generation‐related systems. Currently, piezoelectric crystals with ultrahigh operational temperature and good piezoelectric performance for high‐temperature sensing applications are attracting considerable attention. Herein, a novel piezoelectric crystal YbBa3(PO4)3 with cubic symmetry and a high melting point of ≈1850 °C is explored, and grown by using the Czochralski method. The temperature‐dependent behaviors of electro‐elastic constants and electrical resistivity are investigated ranging from 25 to 800 °C, where the dielectric loss of the YbBa3(PO4)3 crystal is found to be ≈15% at 800 °C. In addition, an optimal crystal cut with a pure thickness shear vibration mode is designed. The optimal crystal cut presents a good piezoelectric activity (d26∗ = 12.6 pC N−1) as well as good temperature stability. Furthermore, a high‐temperature accelerometer with shear piezoelectric mode is designed and fabricated using the YbBa3(PO4)3 crystal, and the sensing performance at elevated temperature are evaluated. The average sensitivity is found to be 1.16 pC g−1, with a small temperature deviation (≈7.7%), exhibiting a good temperature stability. All these results indicate that YbBa3(PO4)3 piezoelectric crystal is a promising candidate for high‐temperature piezoelectric sensing applications.

Abstract Electrically controlled half-metallicity in antiferromagnets is of great significance for both fundamental research and practical application. Here, by constructing van der Waals heterostructures composed of two-dimensional (2D) A-type antiferromagnetic NiI2 bilayer (bi-NiI2) and ferroelectric In2Se3 with different thickness, we propose that the half-metallicity is realizable and switchable in the bi-NiI2 proximate to In2Se3 bilayer (bi-In2Se3). The polarization flipping of the bi-In2Se3 successfully drives transition between half-metal and semiconductor for the bi-NiI2. This intriguing phenomenon is attributed to the joint effect of polarization field-induced energy band shift and interfacial charge transfer. Besides, the easy magnetization axis of the bi-NiI2 is also dependent on the polarization direction of the bi-In2Se3. The half-metallicity and magnetic anisotropy energy of the bi-NiI2 in heterostructure can be effectively manipulated by strain. These findings provide not only a feasible strategy to achieve and control half-metallicity in 2D antiferromagnets, but also a promising candidate to design advanced nanodevices.

A feeding trial was conducted to evaluate the biological activities of Enteromorpha prolifera bio-products in the diets of Pacific white shrimp (Litopenaeus vannamei). Bio-products of E. prolifera included E. prolifera meal, E. prolifera hydrolysate and E. prolifera polysaccharide, which was supplied using different processing procedures. The control diet was supplemented without any E. prolifera bio-products or dietary attractants. Experimental diets were formulated to contain 0.2% and 0.4% of E. prolifera hydrolysate (EPH0.2% and EPH0.4%), 0.03% of E. prolifera polysaccharide (EPP0.03%), 3% of E. prolifera meal (EPM3%), 0.1% of dimethyl-β-propiothetn (DMPT0.1%) and 1% of squid paste (SP1%). Shrimp (~8 g) were randomly distributed in 21 tanks and fed for 44 days. Feed intake showed that 3% of E. prolifera meal and 0.4% of E. prolifera hydrolysate in diets exhibited similar attractant effects as 0.1% of DMPT. Gross qualitative observation showed that the abundance of lipid droplets decreased in hepatopancreas of the EPH0.4% and EPM3% groups, which were supported by hepatopancreas triacylglycerol (TG), where significantly lower concentrations were observed in the EPH0.4% and EPM3% groups compared with the control group. Similarly, TG and low-density lipoprotein cholesterol in serum significantly decreased in the EPH0.4%, EPP0.03% and EPM3% groups compared to the control group. Supplemental E. prolifera bio-products resulted in significantly higher serum glutathione level of EPP0.03% or superoxide dismutase activities of EPH0.4% and EPM3%, but significantly lower serum malondialdehyde level of EPM3%. In addition, tnf-α expression in hepatopancreas was significantly down-regulated in shrimp fed the EPH0.2%, EPH0.4% and EPM3% diets. Based on survival analysis, E. prolifera bio-products improved the resistance of shrimp to hypoxic stresses. Thus, this study confirmed that bio-products of E. prolifera supplied using different processing procedures could be used to reduce the amount of E. prolifera in feed of shrimp without compromising their biological functions.

The aim of this study was to investigate the effects of imbalanced dietary BCAAs, especially Leu, on the growth and BCAA metabolism in turbot. A control diet was formulated by keeping optimum levels of Leu, Ile and Val. Four experimental diets were prepared by removing supplemental crystalline Leu (deficiency) or supplementing double the amount of Leu, Ile or Val (excess) in the control diet. The growth was not significantly decreased by an excess of Leu, Ile or Val. Fish fed an excess of any particular BCAA significantly increased its postprandial (2 and 6 h) concentration in the plasma, muscles, and liver, but did not decrease the other two BCAA concentrations. The expression of intestinal b0at1 was down-regulated by excessive dietary Leu, Ile or Val. For BCAA catabolism, the mRNA levels of bcat2 in the muscles as well as bckdha and bckdhb in the livers of the Leu-deficient group were the lowest among all the groups, but were up-regulated by excess dietary Leu, Ile or Val. In conclusion, in terms of growth, turbot had high plasticity to an excess of any particular BCAA. Meanwhile, the antagonistic effect caused by an excess of one BCAA were reflected in intestinal amino acid absorption and BCAA catabolism.

Optical coherent detection is widely used for highly sensitive sensing applications, but nonlinearity issues pose challenges in accurately interpreting the system outputs. Most existing compensation methods require access to raw measurement data, making them not useful when only demodulated data are available. In this study, we propose a compensation method designed for direct application to demodulated data, effectively addressing the 1st and 2nd-order nonlinearities in both homodyne and heterodyne systems. The approach involves segmenting the distorted signal, fitting and removing baselines in each section, and averaging the resulting distortions to obtain precise distortion shapes. These shapes are then used to retrieve compensation parameters. Simulation shows that the proposed method can effectively reduce the deviation caused by the nonlinearities without using the raw data. Experimental results from a silicon-photonics-based homodyne laser Doppler vibrometry prove that this method has a similar performance as the conventional Heydemann correction method.

Cholesterol has been used as additive in fish feeds due to the reduced use of fish meal and fish oil. In order to evaluate the effects of dietary cholesterol supplementation (D-CHO-S) on fish physiology, a liver transcriptome analysis was performed following a feeding experiment on turbot and tiger puffer with different levels of dietary cholesterol. The control diet contained 30% fish meal (0% fish oil) without cholesterol supplementation, while the treatment diet was supplemented with 1.0% cholesterol (CHO-1.0). A total of 722 and 581 differentially expressed genes (DEG) between the dietary groups were observed in turbot and tiger puffer, respectively. These DEG were primarily enriched in signaling pathways related to steroid synthesis and lipid metabolism. In general, D-CHO-S downregulated the steroid synthesis in both turbot and tiger puffer. Msmo1, lss, dhcr24, and nsdhl might play key roles in the steroid synthesis in these two fish species. Gene expressions related to cholesterol transport (npc1l1, abca1, abcg1, abcg2, abcg5, abcg8, abcb11a, and abcb11b) in the liver and intestine were also extensively investigated by qRT-PCR. However, the results suggest that D-CHO-S rarely affected the cholesterol transport in both species. The protein-protein interaction (PPI) network constructed on steroid biosynthesis-related DEG showed that in turbot, Msmo1, Lss, Nsdhl, Ebp, Hsd17b7, Fdft1, and Dhcr7 had high intermediary centrality in the dietary regulation of steroid synthesis. In conclusion, in both turbot and tiger puffer, the supplementation of dietary cholesterol inhibits the steroid metabolism but does not affect the cholesterol transport.

BackgroundAmbient temperature change is a risk factor for urolithiasis that cannot be ignored. The association between temperature and urolithiasis varies from region to region. Our study aimed to analyze the impact of extremely high and low temperatures on the number of inpatients for urolithiasis and their lag effect in Ganzhou City, China.MethodsWe collected the daily number of inpatients with urolithiasis in Ganzhou from 2018 to 2019 and the meteorological data for the same period. The exposure-response relationship between the daily mean temperature and the number of inpatients with urolithiasis was studied by the distributed lag non-linear model (DLNM). The effect of extreme temperatures was also analyzed. A stratification analysis was performed for different gender and age groups.ResultsThere were 38,184 hospitalizations for urolithiasis from 2018 to 2019 in Ganzhou. The exposure-response curve between the daily mean temperature and the number of inpatients with urolithiasis in Ganzhou was non-linear and had an observed lag effect. The warm effects (30.4°C) were presented at lag 2 and lag 5–lag 9 days, and the cold effects (2.9°C) were presented at lag 8 and lag 3–lag 4 days. The maximum cumulative warm effects were at lag 0–10 days (cumulative relative risk, CRR = 2.379, 95% CI: 1.771, 3.196), and the maximum cumulative cold effects were at lag 0–5 (CRR = 1.182, 95% CI: 1.054, 1.326). Men and people between the ages of 21 and 40 were more susceptible to the extreme temperatures that cause urolithiasis.ConclusionExtreme temperature was correlated with a high risk of urolithiasis hospitalizations, and the warm effects had a longer duration than the cold effects. Preventing urolithiasis and protecting vulnerable people is critical in extreme temperature environments.

Exogenous cholesterol has been supplemented into aqua-feeds due to the reduced proportions of fishmeal and fish oil. This study aimed to investigate the effects of dietary cholesterol supplementation on the muscle lipidomics of two marine fish species, turbot and tiger puffer. A 70-day feeding trial was conducted, where two low-fishmeal diets supplemented with 0 or 1% cholesterol were used. The lipidomic analysis with targeted tandem mass spectrometry showed that, in turbot, a total of 49 individual lipids exhibited significant differences in their abundance in response to dietary cholesterol, whereas the number was 30 for tiger puffer. Dietary cholesterol up-regulated the abundance of cholesterol and cholesterol ester in both species. In turbot, the dietary cholesterol also increased the abundance of triacylglycerol and acylcarnitine, whereas in tiger puffer, it primarily regulated the abundance of phospholipids and BMP. This was the first time the responses of marine fish muscle lipidomics to dietary cholesterol supplementation have been investigated.

Studies have reported that Mo-doped LiNbO3 exhibits excellent photorefractive performance, which may be attributed to the Mo abnormally occupation in Nb sites (MoNb) and the MoNb photorefractive centres. Therefore, we investigate the basic characteristics of Mo-doped LiNbO3, including the preferable substitutional sites, doping stability, lattice relaxation, and electronic structures using the spin-polarised density functional theory within semi-local and hybrid functionals. Particularly, the type and properties of the polarons in Mo-doped LiNbO3 are studied intensively, and the advantages of MoNb polarons with respect to the MoLi polarons are highlighted. The calculation results of both transfer energies and defect formation energies show that MoNb are preferable to be formed in both stoichiometric and congruent LiNbO3, while Mo substitutional Li (MoLi) is consumed in small amounts. MoNb could act as small bound polarons that exhibit fast response to light with respect to the MoLi bound bipolarons. The introduced double-centre by Mo doping is partly responsible for the excellent photorefractive properties of Mo-doped LiNbO3. Keywords: Density functional theory, Electronic property, Polaron, Mo-doped LiNbO3

Background: Laser-Doppler Vibrometry (LDV) is a laser-based technique that allows measuring the motion of moving targets with high spatial and temporal resolution. To demonstrate its use for the measurement of carotid-femoral pulse wave velocity, a prototype system was employed in a clinical feasibility study. Data were acquired for analysis without prior quality control. Real-time application, however, will require a real-time assessment of signal quality. In this study, we (1) use template matching and matrix profile for assessing the quality of these previously acquired signals; (2) analyze the nature and achievable quality of acquired signals at the carotid and femoral measuring site; (3) explore models for automated classification of signal quality.Methods: Laser-Doppler Vibrometry data were acquired in 100 subjects (50M/50F) and consisted of 4–5 sequences of 20-s recordings of skin displacement, differentiated two times to yield acceleration. Each recording consisted of data from 12 laser beams, yielding 410 carotid-femoral and 407 carotid-carotid recordings. Data quality was visually assessed on a 1–5 scale, and a subset of best quality data was used to construct an acceleration template for both measuring sites. The time-varying cross-correlation of the acceleration signals with the template was computed. A quality metric constructed on several features of this template matching was derived. Next, the matrix-profile technique was applied to identify recurring features in the measured time series and derived a similar quality metric. The statistical distribution of the metrics, and their correlates with basic clinical data were assessed. Finally, logistic-regression-based classifiers were developed and their ability to automatically classify LDV-signal quality was assessed.Results: Automated quality metrics correlated well with visual scores. Signal quality was negatively correlated with BMI for femoral recordings but not for carotid recordings. Logistic regression models based on both methods yielded an accuracy of minimally 80% for our carotid and femoral recording data, reaching 87% for the femoral data.Conclusion: Both template matching and matrix profile were found suitable methods for automated grading of LDV signal quality and were able to generate a quality metric that was on par with the signal quality assessment of the expert. The classifiers, developed with both quality metrics, showed their potential for future real-time implementation.

The intrinsic n-type of epitaxial graphene on SiC substrate limits its applications in microelectronic devices, and it is thus vital to modulate and achieve p-type and charge-neutral graphene. The main groups of metal intercalations, such as Ge and Sn, are found to be excellent candidates to achieve this goal based on the first-principle calculation results. They can modulate the conduction type of graphene via intercalation coverages and bring out interesting magnetic properties to the entire intercalation structures without inducing magnetism to graphene, which is superior to the transition metal intercalations, such as Fe and Mn. It is found that the Ge intercalation leads to ambipolar doping of graphene, and the p-type graphene can only be obtained when forming the Ge adatom between Ge layer and graphene. Charge-neutral graphene can be achieved under high Sn intercalation coverage (7/8 bilayer) owing to the significantly increased distance between graphene and deformed Sn intercalation. These findings would open up an avenue for developing novel graphene-based spintronic and electric devices on SiC substrate.

Surface defects are usually associated with the formation of other forms of expansion defects in crystals, which have an impact on the crystals’ growth quality and optical properties. Thereby, the structure, stability, and electronic structure of the hydrogen and oxygen vacancy defects (VH and VO) on the (100) and (101) growth surfaces of KDP crystals were studied by using density functional theory. The effects of acidic and alkaline environments on the structure and properties of surface defects were also discussed. It has been found that the considered vacancy defects have different properties on the (100) and (101) surfaces, especially those that have been reported in the bulk KDP crystals. The (100) surface has a strong tolerance for surface VH and VO defects, while the VO defect causes a large lattice relaxation on the (101) surface and introduces a deep defect level in the band gap, which damages the optical properties of KDP crystals. In addition, the results show that the acidic environment is conducive to the repair of the VH defects on the surface and can eliminate the defect states introduced by the surface VO defects, which is conducive to improving the quality of the crystal surface and reducing the defect density. Our study opens up a new way to understand the structure and properties of surface defects in KDP crystals, which are different from the bulk phase, and also provides a theoretical basis for experimentally regulating the surface defects in KDP crystals through an acidic environment.

The yttrium calcium oxyborate crystal (YCa4O(BO3)3, YCOB) has been actively studied for high-temperature piezoelectric sensing applications. In this work, the stability of electric properties of YCOB crystal annealed in critical conditions (high-temperatures of 900–1100 °C with a low oxygen partial pressure of 4 × 10−6 atm for 24 h) was investigated and the recovery mechanism for the electrical resisitivity, dielectric permittivity and dielectric loss were studied, taking advantage of the X-ray photoelectron spectra and the first principle calculations. The electrical resistivity of the annealed YCOB crystal was slightly decreased when compared to the pristine counterpart, being (2–5) × 107 Ω·cm at 850 °C. The dielectric permittivity and dielectric loss were found to increase after annealing, showing recoverable behaviours after thermal treatment above 650 °C in air. The calculated vacancy formation energy indicates that the oxygen vacancy is the dominant defects in YCOB. The formation of oxygen vacancy weakens the chemical bonding strength between B (Ca or Y) and O atoms, introduces extra donor levels in the band gap, which excites the electrons to conduction band more easily thus enhances the electrical conductivity and dielectric loss. The recovered electrical properties are believed to be associated with the reduced vacancy defects at elevated temperatures in air. Keywords: YCOB crystal, Recoverable dielectric properties, First principle calculations

Laser Doppler vibrometry (LDV) is a non-contact vibration measurement technique based on the Doppler effect of the reflected laser beam. Thanks to its feature of high resolution and flexibility, LDV has been used in many different fields today. The miniaturization of the LDV systems is one important development direction for the current LDV systems that can enable many new applications. In this paper, we will review the state-of-the-art method on LDV miniaturization. Systems based on three miniaturization techniques will be discussed: photonic integrated circuit (PIC), self-mixing, and micro-electrochemical systems (MEMS). We will explain the basics of these techniques and summarize the reported miniaturized LDV systems. The advantages and disadvantages of these techniques will also be compared and discussed.

Purpose: There is a need for new tools to screen large populations for cardiovascular disease risk. The CARDIS consortium (European Union H2020 funding) developed an easy-to-use, non-contact device for measuring carotid to femoral pulse wave velocity (cfPWV). It consists in a laser doppler vibrometer (LDV), which measures skin vibrations induced by large artery pulses. Pulse waveforms can be tracked and transit time (TT) can be calculated. This study aimed at comparing LDV-cfPWV with the reference cfPWV measured by applanation tonometry (Sphygmocor). Methods: We included 100 patients with mild to stage 3 hypertension, controlled or not. Reflective tapes were applied on the carotid and femoral arteries to measure LDV-cfPWV 4 times. TT was measured by the foot-to-foot method from the maximum of 2nd derivative using in-house algorithms not requiring ECG, and compared to Sphygmocor (3 acquisitions). Results: LDV-cfPWV was obtained in 100% of patients. Mean age was 47 ± 19 (range 19–85). Hypertensives were well controlled (119/65 mmHg). Mean value of LDV-cfPWV was 6.9 ± 1.7 m/s, compared to 7.5 ± 1.7 m/s with Sphygmocor, bias 0.65 ± 1.27, R value 0.72 (Figure 1), which qualifies agreement as acceptable according to the guidelines from the ARTERY Society [1]. Reproducibility was good with a median coefficient of variation of 5.6%. LDV-cfPWV showed similar associations with age and blood pressure than tonometry (r = 0.68, p < 0.001 and r = 0.44, p < 0.001, respectively). Figure 1 Conclusion: Non-contact measurement of pulse wave velocity by laser doppler vibrometry is feasible, fast and easy to perform, and provides acceptable agreement with reference technique.

Epitaxial graphene on SiC without substrate interaction is viewed as one of the most promising two-dimensional (2D) materials in the microelectronics field. In this study, quasi-free-standing bilayer epitaxial graphene (QFSBEG) on SiC was fabricated by H2 intercalation under different time periods, and the temperature-dependent Raman spectra were recorded to evaluate the intrinsic structural difference generated by H2 time duration. The G peak thermal lineshift rates dω/dT showed that the H2 intercalation significantly weakened the pinning effect in epitaxial graphene. Furthermore, the G peak dω/dT value showed a perspicuous pinning effect disparity of QFSBEG samples. Additionally, the anharmonic phonon effect was investigated from the Raman lineshift of peaks. The physical mechanism responsible for dominating the G-mode temperature-dependent behavior among samples with different substrate coupling effects was elucidated. The phonon decay process of different samples was compared as the temperature increased. The evolution from in situ grown graphene to QFSBEG was determined. This study will expand the understanding of QFSBEG and pave a new way for its fabrication.

Early detection of asymptomatic carotid stenosis may help identifying individuals at risk of stroke. We explore a new method based on laser Doppler vibrometry (LDV) which could allow the non-contact detection of stenosis from neck skin vibrations due to stenosis-induced flow disturbances. Experimental fluid dynamical tests were performed with water on a severely stenosed patient-specific carotid bifurcation model. Measurements were taken under various physiological flow regimes both in a compliant and stiff-walled version of the model, at 1 to 4 diameters downstream from the stenosis. An inter-arterial pressure catheter was positioned as reference. Increasing flow led to corresponding increase in power spectral density (PSD) of pressure and LDV recordings in the 0-500 Hz range. The stiff model lead to higher PSD. PSD of the LDV signal was less dependent on the downstream measurement location than pressure. The strength of the association between PSD and flow level, model material and measuring location was highest in the 0-50 Hz range, however useful information was found up to 200 Hz. This proof-of-concept suggests that LDV has the potential to detect stenosis-induced disturbed flow. Further computational and clinical validation studies are ongoing to assess the sensitivity and specificity of the technique for clinical screening.

Objective: PWV measurement devices are technically demanding, expensive and prone to artefacts, thus limiting the measurement of arterial stiffness in primary care. The CARDIS consortium developed a non-contact device based on the detection of skin movements induced by arterial pulses through a laser Doppler vibrometer (CARDIS-LDV). Our objective is to validate CARDIS-LDV against reference techniques. Methods: This study sponsored by INSERM will include 100 essential hypertensives, males and females, grade I–III, aged 18–80. The CARDIS-LDV comprises two rows of 6 laser beams spaced 5 mm (2.5 cm wide). These rows are either situated 2.5 cm apart for local PWV measurement or can be split in two for carotid to femoral measurement. To calculate PWV, the time delay between the two rows is assessed by analyzing the corresponding skin displacement signals. Aortic stiffness is measured by the Sphygmocor® technique and carotid stiffness by echotracking ArtLab® Results: Measurements by CARDIS-LDV are easy and fast to perform. A simple palpation of pulse is enough to position the device and obtain good signals thanks to the 6-beam array. Figure 1 shows an example of a carotid-femoral recording on a healthy volunteer (age 28). PWV is 5.88 ± 0.30 m/s using the maximum of 1st derivative method, compared with 5.96 ± 0.40 m/s with tonometry. Data on larger sample size will be presented at the meeting. Conclusion: CARDIS-LDV is a promising technique to assess arterial stiffness; we expect to demonstrate its good agreement with reference techniques and that it improves the screening of cardiovascular risk in large populations.

Background: An innovative device using Laser Doppler Vibrometry (LDV) has been designed [1] to measure the transit time of the pulse wave between two locations along the course of the carotid artery (CA) from skin surface vibrations for assessment of local pulse wave velocity (PWV) [2]. Aim: Tests were conducted on in-vitro models to assess the feasibility of the LDV to estimate the local PWV; preliminary in-vivo measurements were also performed. Methods: Two CA geometries embedded within a soft-tissue-mimicking hydrogel were considered: i) a straight latex tube and ii) a patient-specific CA silicone-rubber model including the bifurcation. Models were pressurised in a water-filled loop and pulsatile flow was generated with a pump and/or high frequency impulses induced externally. For all measurements, two sets of six beams were used to measure surface displacement perpendicular to the external surface. PWV was calculated from the distance between selected beams and the delay between corresponding signals, using the time of the maximum of first and second derivatives of pressure (P-PWV) and displacement (LDV-PWV) as fiducial points [3]. A windowed cross correlation method [4] was also used for the in-vivo data analysis. Results: PWV values for the in-vitro models are summarized in Table 1, while preliminary in-vivo LDV-PWV results are shown in Fig 1. Table 1P-PWV and LDV-PWV mean values under pulsatile flow and induced impulse conditions. Conclusions: Good agreement between P-PWV and LDV-PWV in the tubular model was found under impulse loading, while complex waveforms measured under pulsatile flow and in-vivo conditions lead to more disparate effects when using different analysis methods. Further signal analysis is warranted.

Background: Within the H2020 CARDIS project, we explore the use of a Laser Doppler Vibrometer (LDV) [1] to detect asymptomatic carotid stenosis from measurement of skin vibrations on the neck of affected patients. We hypothesise that flow instabilities induced by the stenosis will propagate as mechanical waves through soft tissues of the neck. We here report measurements on an experimental model to assess the ability of LDV to detect stenosis-induced vibrations. Methods: A compliant carotid bifurcation with Internal Carotid Artery (ICA) 76% area-stenosis model was surrounded by hydrogel and a skin-like layer to mimic neck’s skin and soft tissues. Measurements were acquired (20 KHz) at physiological flows (water) through the artery [2, 3], at several distances downstream from the stenosis. Intra-arterial pressure measurements were performed at the same location for reference (Fig. 1A). To assess in which frequency range the Fast Fourier Transform spectra of the signals are most sensitive to changes in flow rate, we constructed a univariate linear model in SPSS for the integral of the normalized spectra (8K, Hann, 50%-overlap, LabChart), where inflow was used as covariate and the frequency range as fixed factor. Results: The spectrograms (Fig 1B) showed that the LDV was able to detect flow-induced instabilities in the 0–500 Hz range. The sensitivity was highest between 50–150 Hz for both LDV and pressure. Conclusion: The LDV was able to detect stenosis-related flow features with a sensitivity comparable to the intra-arterial manometer, proving the potential of the technique for stenosis diagnosis by detecting neck skin vibrations. In-vivo validation is in progress.

The bismuth layer-structured ferroelectrics (BLSFs) materials have potential for high-temperature piezoelectric applications. Among these piezoelectric materials, the CaBi4Ti4O15 (CBT) piezoelectric ceramic with a high decomposition temperature of about 1250 °C attracts a lot of attention. Achieving a CBT single crystal is a significant way to improve its piezoelectric properties. For this purpose, the flux system for growing CBT crystal was explored in this study. The optimum flux composition ratio was found to be PbO:B2O3:CBT = 3:3:1 in mol%, where the PbO–B2O3 mixtures were used as a flux system. Millimeter size flake-shaped CBT crystals were obtained using the spontaneous growth process for the first time. The relationship between the crystal structure and flake growth habit was analyzed. In addition, the bandgap was evaluated by the combination of transmittance spectrum and first-principle calculations. Besides, the piezoelectric property was predicted from the perspective of polyhedral distortion, which indicated the potential of CBT crystal for piezoelectric applications.

A general class of Cohen-Grossberg neural networks with time-varying delays, distributed delays, and discontinuous activation functions is investigated. By partitioning the state space, employing analysis approach and Cauchy convergence principle, sufficient conditions are established for the existence and locally exponential stability of multiple equilibrium points and periodic orbits, which ensure that n-dimensional Cohen-Grossberg neural networks with k-level discontinuous activation functions can have kn equilibrium points or kn periodic orbits. Finally, several examples are given to illustrate the feasibility of the obtained results.

This paper is concerned with the stability of impulsive stochastic reaction-diffusion differential systems with mixed time delays. First, an equivalent relation between the solution of a stochastic reaction-diffusion differential system with time delays and impulsive effects and that of corresponding system without impulses is established. Then, some stability criteria for the stochastic reaction-diffusion differential system with time delays and impulsive effects are derived. Finally, the stability criteria are applied to impulsive stochastic reaction-diffusion Cohen-Grossberg neural networks with mixed time delays, and sufficient conditions are obtained for the exponential p-stability of the zero solution to the neural networks. An example is given to illustrate the effectiveness of our theoretical results. The systems we studied in this paper are more general, and some existing results are improved and extended.

BACKGROUND: Carotid-femoral pulse wave velocity (cfPWV) is the gold standard for noninvasive arterial stiffness assessment, an independent predictor of cardiovascular disease, and a potential parameter to guide therapy. However, cfPWV is not routinely measured in clinical practice due to the unavailability of a low-cost, operator-friendly, and independent device. The current study validated a novel laser Doppler vibrometry (LDV)-based measurement of cfPWV against the reference technique. METHODS: In 100 (50 men) hypertensive patients, cfPWV was measured using applanation tonometry (Sphygmocor) and the novel LDV device. This device has 2 handpieces with 6 laser beams each that simultaneously measure vibrations from the skin surface at carotid and femoral sites. Pulse wave velocity is calculated using ECG for the identification of cardiac cycles. An ECG-independent method was also devised. Cardiovascular risk score was calculated for patients between 40 and 75 years old using the WHO risk scoring chart. RESULTS: LDV-based cfPWV correlated significantly with tonometry (r=0.86, P<0.0001 ECG-dependent [cfPWVLDV_ECG] and r=0.80, P<0.001 ECG-independent [cfPWVLDV_w/oECG] methods). Bland-Altman analysis showed nonsignificant bias (0.65 m/s) and acceptable SD (1.27 m/s) between methods. Intraobserver coefficient of variance for LDV was 4.7% (95% CI, 3.0%-5.5%), and interobserver coefficient of variance was 5.87%. CfPWV correlated significantly with CVD risk (r=0.64, P<0.001; r=0.41, P=0.003; and r=0.37, P=0.006 for tonometry, LDV-with, and LDV-without ECG, respectively). CONCLUSIONS: The study demonstrates clinical validity of the LDV device. The LDV provides a simple, noninvasive, operatorindependent method to measure cfPWV for assessing arterial stiffness, comparable to the standard existing techniques. [ABSTRACT FROM AUTHOR]

The integration of 6G networks with emerging key technologies such as blockchain, artificial intelligence, and digital twins continues to improve. However, it carries many issues with security threats and challenges of 6G networks. In this article, we analyzed the security issues of 6G networks and presented some possible solutions. First, we discussed the developments of mobile communication technology, the research motivation of 6G networks, the comparison of Key Performance Indicators (KPIs) between 5G/6G networks, and the key technologies of 6G networks. Next, security threats in the 6G network were analyzed concerning architecture, major visions and related applications. This was followed by solutions to security issues in applying key technologies for 6G networks. We also presented the application of AI in solving 6G network security problems. Firstly, we illustrated the impact of AI on 6G networks from two aspects: AI promotes the construction of 6G networks, and AI brings security threats to 6G networks. Then, we demonstrated that AI can assist 6G networks in solving security problems in many ways. Lastly, the is summarized, and the future directions in this area are proposed. [ABSTRACT FROM AUTHOR]