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The alignment of elongated fibers and thin disks is known to be significantly influenced by the presence of fluid coherent structures in near-wall turbulence (Cui et al. 2021). However, this earlier study is confined to the spheroids with infinitely large or small aspect ratio, and the shape effect of finite aspect ratio on the alignment is not considered. The current study investigates the shape-dependent alignment of inertialess spheroids in structure-dominated regions of channel flow. With utilizing an ensemble-averaged approach for identifying the structure-dominated regions, we analyze the eigensystem of the linear term matrix in the Jeffery equation, which is governed by both particle shape and local fluid velocity gradients. In contrast to earlier conventional analysis based on local vorticity and strain rate, our findings demonstrate that the eigensystem of the Jeffery equation offers a convenient, effective, and universal framework for predicting the alignment behavior of inertialess spheroids in turbulent flows. By leveraging the eigensystem of the Jeffery equation, we uncover a diverse effect of fluid coherent structures on spheroid alignment with different particle shapes. Furthermore, we provide explanations for both shape-independent alignments observed in vortical-core regions and shape-dependent alignments around near-wall streamwise vortices. [ABSTRACT FROM AUTHOR]

The angular dynamics of tiny spheroidal particles in shear flows have been widely investigated, but most of the studies mainly focus on the effect of strong shear, while the combined effect of both shear and slip velocity at the center of the particle has been less considered. Actually, the fluid inertial torque induced by the slip velocity between particle and fluid plays a significant role in spheroid angular dynamics. However, it is difficult to investigate these dynamics theoretically until the analytical expression of the fluid inertial torque at a small Reynolds number was derived by Dabade et al. [J. Fluid Mech. 778, 133–188 (2015)]. In this study, the effect of the fluid inertial torque on the particle rotations is considered in a linear shear flow with a small streamwise slip velocity at the center of the particle. We find that as the fluid inertial torque dominates, the prolate spheroids tend to logroll while oblate ones have a tendency to tumble or align to a direction with a relative angle to the streamwise direction. These results are opposite to the earlier results in the absence of the fluid inertial torque. Different ultimate rotation modes of spheroids are dependent on the relative importance between the fluid inertial torque and the particle inertia, as well as the initial orientations. This reflects a non-trivial effect of fluid inertial torque on the angular dynamics of inertial spheroidal particles. [ABSTRACT FROM AUTHOR]

Purpose: Infections caused by carbapenem-resistant Klebsiella pneumoniae (CR-KP) are an important public health problem. This study aimed to evaluate the clinical characteristics of patients with CR-KP. Methods: A retrospective cohort study was conducted of all patients with CR-KP infection. A total of 615 patients with CR-KP infection were identified and 135 patients who did not meet the eligibility criteria were excluded. Clinical characteristics, antimicrobial regimens, and patient outcomes were analyzed. Results: The overall mortality rate of CR-KP infections was 37.3% and the mortality rate in patients with bloodstream infections was 66.2%. Survival analysis revealed that there were statistically significant differences between patients with bloodstream infections and those with pulmonary and drainage fluid infections. Logistics regression analysis showed that hemopathy, age >60 years, solid tumors, diabetes, septic shock, acute kidney injury, and stroke were independent predictors of 30-day mortality rate. The chi-square test showed that treatment with a combination of carbapenems, tigecycline, and polymyxin B was superior to treatment with carbapenems with polymyxin B, without tigecycline. Conclusions: CR-KP infections, especially bloodstream infections, have a high mortality rate. The outcome is strongly dependent on patients' clinical conditions. Antimicrobial regimens combining carbapenems, tigecycline, and polymyxin B might be a better choice. [ABSTRACT FROM AUTHOR]

In this work, we carry out direct numerical simulations of particle suspensions in the compressible turbulent vertical channel (TVC) flows with Mach number Ma = 1.5 and particle Stokes number St = 1–100. The compressibility effect is considered in the particle dynamic model for the first time in the study of compressible particle-laden wall turbulence. We find that in both incompressible and compressible flow, gravity weakens the wall-normal and spanwise fluctuations of particle velocities as the Stokes number increases. However, compared to the incompressible flow case, the compressible effect amplifies the mean velocity, fluctuations of velocity, and slip velocity of particle in the streamwise direction. The wall-normal and spanwise fluctuations of particle velocities are augmented by the compressible effect in the channel core region. Moreover, in the core region, the effect of fluid compressibility on the wall-normal and spanwise fluctuations of particle velocities attenuates as the Stokes number increases, indicating a competition between the compressible effect and the particle inertia effect. We, furthermore, conduct the quadrant analysis of the local fluctuation velocities of fluid at particle positions and observe preferential distributions in the second and the fourth quadrants at y+ = 12.5–13.5. For compressible TVC flows, the pattern of probability distributions is more elongated, and the percentage is slightly higher in the second and fourth quadrants than that of incompressible flows. This observation implies that more particles locate in the ejection and sweep events in compressible flows than that in incompressible flows, which is anticipated to influence the particle wall-normal transport. [ABSTRACT FROM AUTHOR]

The alignment between the inertialess spheroids and the directions of the fluid Lagrangian stretching or compression is sensitive to the particles shape near the wall but not near the center of the channel [Cui et al. "Alignment statistics of rods with the Lagrangian stretching direction in a channel flow," J. Fluid Mech. 901, A16 (2020)]. This observation is further investigated in the current study to uncover the mechanism of particle alignment behavior in different regions of channel flows at R e τ ≈ 180 and 1000. Meanwhile, by using the probability distributions of the sign of the discriminant of the linear term in the Jeffery equation, we find that the turbulent channel flow can be distinctly divided into strong and weak shape-dependent regions. In the weak shape-dependent region, the slender (flat) particles have extraordinarily similar alignments with the directions of fluid Lagrangian stretching (compression). However, in the strong shape-dependent region, the alignments of these inertialess particles are sensitive to the particles shape, especially with the particle positions approaching the wall. The ranges of these shape-dependent regions rely on the Reynolds number, but the probability distributions of the sign of the discriminant of the linear term in the Jeffery equation are a useful tool to distinguish these shape-dependent regions in the wall turbulence regardless of the Reynolds number. [ABSTRACT FROM AUTHOR]

Heat transfer of settling particles in homogeneous isotropic turbulence is investigated in one-way coupled Eulerian–Lagrangian direct numerical simulations. In the absence of gravity, our observations highlight that there was a correlation between particles concentration and temperature fronts, which are characterized by high-temperature gradients. The particle clustering is mainly influenced by the preferential concentration and the non-local effect, the latter being the memory of their interaction with the flow along their trajectories. Nevertheless, gravity significantly affects the clustering of particles, which further influence the heat transfer of particles with the fluid. We find that the heat transfer of particles is intricately related to particle dynamic inertia and thermal inertia, which can be quantified by the particle Stokes number S t and particle thermal Stokes number S t θ , respectively. In this study, we observe that the variance of particle temperature rate of change is independent of S t θ at small thermal inertia but inversely proportional to S t θ 2 for large thermal inertia. In the presence of gravity, the variance converges to S t θ − 1 for particles with negligible thermal inertia. Our findings reveal that the second-order structure function of the particle temperature, indicating the enhancement of Lagrangian scalar intermittency, adheres to a power-law behavior with limited thermal inertial particles in the dissipation region, denoted as r 2. However, as S t θ increases, the power law of the structure function of the particle temperature is disrupted leading to 'thermal caustics'. The present findings of the heat transfer behavior of settling particles advance the understanding of gravity effect, and are valuable for the modeling of heat transfer in particle-laden turbulent flows. • Particle clustering and temperature fronts are correlated. • Particle-induced thermal dissipation varies with thermal Stokes number. • The particle temperature structure function follows a power law. [ABSTRACT FROM AUTHOR]

Finite-time Lyapunov exponents (FTLEs) and Lyapunov vectors (LVs) are powerful tools to illustrate Lagrangian coherent structures (LCSs) in experiments and numerical simulations of fluid flows. To obtain the FTLEs and LVs with the flow simulation simultaneously, we computed the eigenvectors and eigenvalues of the left Cauchy–Green tensor along the trajectories of fluid particles separately instead of computing deformation gradient tensor directly. The method proposed in the present study not only avoids solving the eigenvalue problem of the singular matrix at each time step but also guarantees a stable simulation for a long time. The method is applied in the computation of FTLEs and LVs in two-/three-dimensional (2D/3D) compressible/incompressible cases. In 2D cases, we found that LCSs are folded as fine filaments induced by vortices, while LCSs are sheet-like structures among the vortices for 3D cases. Meanwhile, the directions of stretching and compression of LVs are tangent and normal to the FTLE ridges (2D)/iso-surfaces (3D), respectively. [ABSTRACT FROM AUTHOR]

The phenomenon of acoustic waves inducing electric fields in porous media is called the seismoelectric effect. Earlier investigators proposed the usage of seismoelectric effect for well logging. Soil texture has a strong influence on the coupled wave fields during shallow surface explorations. In this article, we study the borehole pure shear‐horizontal wave and the coupling transverse‐electric field (acoustic–electrical coupling wave fields) in the partially saturated soil. Combined with related theories, we expand the formation parameters to partially saturated forms and discuss the influence of soil texture conditions on the seismoelectric wave fields. The results show that the elastic and electrical properties of porous media are sensitive to water saturation. The compositions of the acoustic and electric fields for different soil textures do not change, but the waveforms differ. We also use the secant integral method to simulate the interface‐converted electromagnetic waves. The results show that interface response strength is greatly influenced by soil texture. In addition, considering the sensitivity of the inducing electric field to fluid salinity, we also simulate the time‐domain waveforms of electric field for different pore fluid salinity levels. The results show that as the salinity increases, the electric field amplitude decreases monotonically. The above conclusions have certain significance for the application of borehole shear wave and its coupled electric fields for resource exploration, saturation assessment and groundwater pollution monitoring. [ABSTRACT FROM AUTHOR]

The rotation of anisotropic particles in fluid flow is essential for particle transport and collisions of nearby particles. The earlier studies indicate that both axis-symmetric spheroids and tri-axial ellipsoids in a simple shear flow tend to rotate about their shortest axes in the absence of fluid inertia. However, tri-axial ellipsoids display more complicated behavior with variations of the Stokes number and aspect ratio. In this paper, we theoretically studied the rotation stability of both axis-symmetric spheroids and tri-axial ellipsoids in a simple shear flow with negligible fluid inertia by the Floquet analysis. In the case of axis-symmetric spheroids, we find that tumbling motion of a prolate spheroid is neutrally stable, but logrolling motion is unstable, while logrolling of an oblate spheroid is stable, but tumbling is unstable. A tri-axial ellipsoid rotating about the shortest axis is found to be stable at large Stokes numbers (St > St0.5, where St0.5 is denoted as a critical Stokes number) but becoming unstable with small particle inertia (St < St0.5) for a tri-axial elongated particle. Moreover, stable intermediate-axial rotation is observed for the ellipsoids with small inertia. Meanwhile, small shape variations of slightly tri-axial ellipsoids could result in different stability states. The slightly tri-axial elongated ellipsoids easily reach a chaotic rotation state, while the rotation of slightly tri-axial flat ellipsoids is relatively more stable. [ABSTRACT FROM AUTHOR]

A new sensor cluster orientation is proposed to localize an acoustic source in a plate from the time difference of arrival (TDOA) with the help of only four to eight sensors. This technique requires neither a priori knowledge of the plate material properties nor a dense array of sensors to localize the acoustic source in isotropic as well as anisotropic plates. It is achieved by placing four sensors in a cluster in the shape of letter “Z” over a small region of the plate and a second Z-shaped cluster at another location of the plate. Experimental results show that it is possible to accurately localize the acoustic source with this new configuration. It reduces the number of sensors required for acoustic source localization in an anisotropic plate. Although one cluster in principle is capable of localizing the acoustic source in absence of any experimental error for accurate source localization in presence of experimental error two such Z-shaped clusters are needed. In the currently available technique three L-shaped clusters having a total of 9 sensors are needed to achieve the same level of confidence in the acoustic source localization. Thus, the proposed new technique reduces the number of sensors by 1 (from 9 to 8) for confidently and accurately predicting the acoustic source. [ABSTRACT FROM AUTHOR]

The relationship between the maximum shear stress in a substrate solid and the elastic wave reflection coefficient from the interface between the substrate solid and an overlying solid half-space is investigated. Both substrate and overlying solid media are assumed to be initially isotropic and stress-free. Then as the substrate is subjected to horizontal confined stresses it becomes anisotropic. It is shown that longitudinal and shear wave reflection coefficients are related to the degree of stress induced anisotropy in the substrate medium. From this relation the confined stress level and the maximum shear stress generated on the vertical planes of the substrate are estimated. Authors in their previous investigation computed plane wave reflection coefficient in a biaxially compressed solid substrate immersed in a fluid. This paper reports for the first time how the maximum shear stress in a biaxially compressed substrate medium can be measured from the plane wave reflection coefficients when the overlying medium is also a solid half-space. [ABSTRACT FROM AUTHOR]

• The numbers of adaptive and innate immune cells decreased upon sepsis onset. • Sepsis downregulated adaptive immunity and innate immune. • Sepsis patients transitioned into a later state of immune suppression. • Proportion of Treg cells increased gradually with the progression of disease. • Humoral and innate immunity recovered later than cellular immunity. Sepsis, characterized by cytokine-mediated hyper-inflammation and a consistent decline in immune responsiveness, is associated with a high risk of death in the intensive care unit (ICU). Here, we for the first time investigated the changes in immune and inflammatory responses to understand the interactions between immune and inflammatory biomarkers and their association with patient outcomes. The cytokine and lymphocyte subset levels were analyzed in healthy donors (HD) and patients with sepsis upon admission to the ICU (D0), D3, D7, D14, and D28 using flow cytometry. The primary endpoint was mortality on day 90. The trends in lymphocyte subsets and cytokine levels in all patients (n = 47), HD (n = 27), and patient subgroups (surviving, n = 30; dead, n = 17) were analyzed using an independent sample t -test and principal component analysis. Age, steroids (steroids used > 48 h), secondary infection, acute heart failure, acute kidney injury, coagulopathy, hypohepatia, organ transplant and septic shock (when transferred to the ICU) were associated with mortality. Absolute lymphocyte counts and lymphocyte subsets levels were reduced in most patients with sepsis. The proportion of Tregs in the patients increased with disease progression and was associated with immunosuppression. In conclusion, sepsis downregulated adaptive immunity, and induced the transition of the patients to prolonged immune suppression. The study suggests that while cellular immunity recovered within 2 weeks of admission, humoral and innate immunity recovery takes longer. These findings may assist in developing appropriate therapeutic approaches to improve the immune responses in patients with sepsis. [ABSTRACT FROM AUTHOR]

• A new technique for rapid damage localization on composite laminates with different ply orientations is proposed. • The extraction of TDOA from edge reflected signals is investigated. • This investigation verifies that the proposed method can localize delamination without a priori knowledge of the group velocity and other material properties. Composite materials are prone to impact damage, which affects structural stability and causes safety concerns. Due to the complexity and diversity of them, the damage localization in composite materials is very challenging and is getting more attention in the research community. This paper presents a rapid technique for composite damage localization without any prior knowledge of direction-dependent velocity profile. The proposed solution technique uses the time difference of arrival (TDOA) of Lamb waves. The TDOA is obtained by the cross-correlation technique applied to the received signals at different sensor pairs in two "L" shaped sensor clusters (LSSCs). With the help of the LSSC, only seven sensors are required to quickly predict the delamination damage location for quasi-isotropic and anisotropic composite materials (QACM). A simulation model was established to study the influence of damage location and different layup directions on the localization results. The experimental verification was carried out on a T300 carbon fiber board. The localization results of simulation and experiment showed good matching, which proves that the technique is suitable for QACM. [ABSTRACT FROM AUTHOR]

• Six sensors for locating the acoustic source in 3-D structure unknown wave speed. • Sensor clusters is flexibly placed, has a compact structure, a small footprint. • The influence of random error is reduced, the error fluctuation range is smaller. Structural health monitoring can predict defects at the early stage of their formation and avoid safety hazards or catastrophic accidents caused by structural degradation. However, the cost and the need for additional operating space restricted their wide application for monitoring building materials. The main purpose of this paper is to propose a simple and fast defect localization technique, which can locate the acoustic source using fewer sensors when the operating space outside the structure is limited. With the help of the 'L'-shaped coupled sensor cluster, only six sensers are required to quickly predict the damage location for both isotropic and anisotropic materials. Experiments were carried out on several building material samples, and the finite element simulation was used to explore the localization relationship of different relative positions of acoustic sources and the cluster. The experimental and simulation results verify the feasibility of the technique. [ABSTRACT FROM AUTHOR]

Abstract: Based on Pride theory, we studied the propagation of seismoelectric waves in a fluid-filled poroelastic hollow cylinder. We presented the expressions of seismoelectric waves in the poroelastic hollow cylinder, acoustic and electromagnetic field in inner and outer of the hollow cylinder, and we used the boundary condition to determine acoustic and electromagnetic field. Also this problem is accomplished by using the quasi-static method. The numerical simulation is operated on acoustic field and electromagnetic field in inner fluid of hollow poroelastic cylinder, and the transient waveform is obtained. It shows that there is no difference on the graph between the electric field obtained from Pride equations and that obtained from quasi-static method. The influence of hollow cylinder thickness, molarity and permeability on wave amplitude are discussed. The results show that for the acoustic field the amplitude of longitudinal mode and Stoneley wave will increase with hollow cylinder thickness increasing, and for the converted axial electric field the amplitude of Stoneley wave increases with hollow cylinder thickness increasing, while the amplitude of longitudinal mode will decrease. The amplitude of electric field in inner fluid will decrease with the molarity of fluid increasing. The amplitude of the fluid acoustic and electric field will decrease with the permeability increasing. The influence of impermeable outer surface on the amplitude of longitudinal wave is obviously much larger than that of Stoneley wave in the electric field. [Copyright &y& Elsevier]

This paper describes the study of the acoustic field of a fluid-filled pipe subjected to axial stress based on the acoustoelastic theory. The pipe with applied axial stresses can be approximated as a transversely isotropic pipe, and hence, its acoustic fields can be expressed using potential functions. The velocity changes of longitudinal wave modes with applied stresses are analyzed for the pipe filled with oil by an analytical method. It was found that the longitudinal mode velocity changes almost uniformly with the applied stresses. The high speed and low frequency plateaus of longitudinal wave modes are sensitive to stress. The relationship between stress and the velocity change of the guided wave is given. The results indicate that non-destructive testing techniques using longitudinal wave modes have strong potential to identify and monitor the stress levels in pipe structures. [ABSTRACT FROM AUTHOR]

Acoustic and electromagnetic fields are coupled in a fluid saturated porous medium due to seismoelectric effect. Seismoelectric well logging method has been proposed to detect deep target formation utilizing such effect. Because of uncoupling of SH waves with P-SV waves, a simple and forthright way to get shear waves information is possible, especially for soft or slow formation whose shear wave velocity is lower than the velocity of borehole fluid. We consider the wave fields excited by a vertical magnetic dipole (VMD) source. Two methods are used to simulate, one is the coupled method based on Pride model and the other is the uncoupled method. For two methods, the frequency wavenumber domain representations of the acoustic field and associated seismoelectric field are formulated. The full waveforms of acoustic waves and electromagnetic wave induced SH waves excited by VMD source in the time domain propagation in borehole are simulated and analyzed. [ABSTRACT FROM AUTHOR]

The angular dynamics of small rigid fibers and disks in turbulent channel flow has been investigated numerically, focusing on interactions between particles and near-wall coherent vortices. Three distinctly different alignment patterns of fibers and disks around ensemble-averaged vortices were identified. From the wall to the channel center we observed a shear-dominant, a structure-dominant, and an isotropic region, each with its unique alignment pattern. These regions are different from those based on the conventional Reynolds-averaging view. The structure-dominant region, for instance, extends from about 3 to 60 wall units from the channel wall. Unlike the prevailing view that preferential alignment of fibers and disks are more common in the viscous sublayer than in the buffer layer, where the turbulence intensity reaches its maximum, the conditional ensemble-averaged approach revealed that fibers and disks align preferentially in the structure-dominant region. The particles moreover align differently in sweep and ejection events. The physical alignment mechanism we proposed may also be carried over to polymer- and fiber-induced drag reduction in wall-turbulence. • Alignment of fibers and disks around ensemble-averaged vortices in near-wall turbulence is investigated. • Preferentially alignment is observed around the ensemble-averaged structures. • The alignment mechanism in near-wall turbulence is discussed. [ABSTRACT FROM AUTHOR]

• We propose measuring temperature with a dual-head 1D-CNN using two thermocouples. • Two thermocouples of the same material and different diameters are used together. • The dual-head 1D-CNN is applied to simulation and experimental datasets. • The dynamic temperature error of the model reconstruction is analyzed. Dynamic temperature measurement is important in industry. The traditional method with a dual-thermocouple is easily disturbed by noise, so it is only suitable for a high signal-to-noise ratio (SNR). To obtain more accurate dynamic temperature, a dual-thermocouple method based on a one-dimensional convolutional neural network is proposed. This method extracts and fuses the temperature signals of two thermocouples with the same material and but different diameters, thereby weakening noise. The method was simulated with a numerical simulation dataset. Evaluations under different SNRs reveal that the method has a higher fit percentage (FIT), lower root mean square error (RMSE), and lower dynamic error. The algorithm was also applied to an experimental dataset. The experimental results also confirm that this measurement method is better than the traditional methods, with a FIT of 96.49% and RMSE of 0.0149. The average dynamic error is 0.0078 and the standard deviation is 0.0127. [ABSTRACT FROM AUTHOR]

• A damage localization method based on wave front shape for composite laminates is proposed. • The a priori knowledge of the direction-dependent acoustic velocity profile is not needed. • The localization stability of the two wave front shape models is discussed. • The feasibility of the proposed method is verified by numerical simulations and experiments. Composite laminates are widely used in various fields, but their structures are prone to cracks and damage. Due to the difference in angles of the instantaneous direction of the wave front propagation and the direction of the energy flow in an anisotropic material, the use of Lamb waves for damage localization in composite laminates is a challenging task. Establishing the wave front shape equation can overcome the difficulty of damage localization caused by anisotropy, but this usually requires a priori knowledge of the acoustic velocity distribution of the laminates, which is not convenient for efficient damage localization. In this paper, a damage localization method based on wave front shapes for composite laminates without any knowledge of the velocity profile is presented. Numerical simulation and experimental results show that the proposed method works. This method shows good damage localization accuracy and has broad application prospects in non-destructive testing for plate structures with strong anisotropy. [ABSTRACT FROM AUTHOR]

Objectives: To develop an objective method based on texture analysis on MRI for diagnosis of congenital muscular torticollis (CMT). Material and methods: The T1- and T2-weighted imaging, Q-dixon, and T1-mapping MRI data of 38 children with CMT were retrospectively analyzed. The region of interest (ROI) was manually drawn at the level of the largest cross-sectional area of the SCM on the affected side. MaZda software was used to obtain the texture features of the T2WI sequences of the ROI in healthy and affected SCM. A radiomics diagnostic model based on muscle texture features was constructed using logistic regression analysis. Fatty infiltration grade was calculated by hematoxylin and eosin staining, and fibrosis ratio by Masson staining. Correlation between the MRI parameters and pathological indicators was analyzed. Results: There was positive correlation between fatty infiltration grade and mean value, standard deviation, and maximum value of the Q-dixon sequence of the affected SCM (correlation coefficients, 0.65, 0.59, and 0.58, respectively, P < 0.05).Three muscle texture features—S(2,2)SumAverg, S(3,3)SumVarnc, and T2WI extreme difference—were selected to construct the diagnostic model. The model showed significant diagnostic value for CMT (P < 0.05). The area under the curve of the multivariate conditional logistic regression model was 0.828 (95% confidence interval 0.735–0.922); the sensitivity was 0.684 and the specificity 0.868. Conclusion: The radiomics diagnostic model constructed using T2WI muscle texture features and MRI signal values appears to have good diagnostic efficiency. Q-dixon sequence can reflect the fatty infiltration grade of CMT. [ABSTRACT FROM AUTHOR]

• Acoustic source localization technique in heterogeneous structure is presented. • The new technique does not require a priori knowledge of any material property. • The proposed technique has been verified numerically and experimentally. Acoustic source localization (ASL) or predicting the location of the acoustic source in a structure by analyzing the recorded signals at the receivers is of considerable interest for various applications. Recent research advances on this topic have been limited to homogeneous media. This paper presents a solution for acoustic source localization in a heterogeneous medium without knowing the properties of different materials constituting the heterogeneous structure. In this paper new developments for acoustic source localization in an anisotropic plate is first reviewed briefly. Then an ASL technique is presented for localizing acoustic source in heterogeneous layered structures when the layer properties are not known. The proposed technique is verified experimentally and numerically. The experimental results were generated with a specimen having one interface while numerical results were generated for both two-layered medium with one interface and three-layered medium with two interfaces. [ABSTRACT FROM AUTHOR]

The purpose of this Letter to the Editor is to demonstrate the effects of the nonlinear parameter of fluid-solid coupling on the acoustic field in porous media. The nonlinear acoustic field excited by a one-dimensional finite-amplitude shear wave propagating in the uniform and infinite saturated porous media is studied. Researchers use the complete strain energy formula with third-order terms of strain in saturated porous media. The formula for calculating the fluid-solid coupling nonlinear parameter γ from the dynamic compatibility condition is given. To illustrate the effect of the fluid-solid coupling nonlinear term on the nonlinear acoustic field excited by the longitudinal and transverse waves, this study compares nonlinear acoustic fields excited by a finite amplitude wave with and without nonlinear parameter γ. The results show that the nonlinear parameter γ has an influence on the nonlinear acoustic field excited by the one-dimensional shear wave, but it has no influence on the nonlinear acoustic field excited by the one-dimensional longitudinal wave. [ABSTRACT FROM AUTHOR]

A borehole multipole acoustic field in a pre-stressed formation is investigated. The pre-stressed formation is modeled as a transversely isotropic medium induced by uniaxial stress. The formation is assumed to be isotropic in absence of any static stress and then becomes anisotropic due to the applied stress parallel to the borehole axis. The approximate equivalent elastic constants of the stress-induced anisotropic medium are derived from the theory of acoustoelasticity. The nonlinear static stress-strain relation is used for both small and large static deformations. This problem can be solved analytically because of uniformity of deformation induced by static stress applied parallel to the borehole axis. The stress effects on the velocity of guided waves and amplitude of waveforms excited by monopole, dipole, and quadrupole sources are investigated. Numerical results show that the velocities of guided waves increase with uniaxial stress. The uniaxial stress affects both amplitude and arrival time of the acoustic waves in the borehole. The integral amplitude of full waveforms varies almost in a parabolic manner with the increasing stress level and thus shows sensitivity to the uniaxial stress. This result may be helpful for remote stress measurements in boreholes. [ABSTRACT FROM AUTHOR]

• A rapid localization technique for multiple damages in plate-like structures is proposed. • The prior knowledge of direction-dependent velocity profile is not needed. • The method to remove the artifacts is given. • Multi-damage localizations at different locations are validated by simulation and experiment. When using Lamb wave for damage detection in plate-like structures, factors such as unknown material properties, anisotropy and iterative operation for solving nonlinear equations make it difficult to accurately localize damages. This problem becomes even more difficult when multiple damages exist in the plate. To overcome these difficulties, a rapid technique for localizing multiple damages in plate-like structures without any prior knowledge of direction-dependent velocity profile is proposed in this paper. The time difference of arrival is obtained by performing cross-correlation processing on the damage features extracted from the received signal. Damage artifacts are removed using relative location determination and relative probability density analysis. Multi-damage localization at different locations were simulated. The proposed technique is validated experimentally for steel plates. Simulation and experimental results show that the proposed technique can realize multiple damage localization in plate-like structures with unknown material properties. With the help of L-shaped sensor clusters, damage locations for isotropic and anisotropic materials can be quickly predicted without solving nonlinear equations and without taking into account the dispersion effects. The results suggest that a suitable threshold range is set to 0.5–0.7 to remove damage artifacts. [ABSTRACT FROM AUTHOR]

Background: Congenital muscular torticollis (CMT) is a common musculoskeletal disease affecting infants and young children. If CMT is not treated correctly and timely, it can lead to limited head and neck movements, head and neck deviation, and abnormal posture. In order to improve patients' symptoms and alleviate the negative impact of the disease on their lives, we are committed to exploring the treatment of CMT. Methods: The general clinical and ultrasonographic data of 2599 children with CMT who received standardized treatment at Shenzhen Children's Hospital from 2004 to 2020 were retrospectively reviewed. According to given treatment, children with CMT were divided into the physiotherapy group, physiotherapy combined with glucocorticoid treatment group, and surgical treatment group. We divided children with CMT into local mass, uniform thickening, and atrophy according to ultrasound features. General clinical information, treatment, and ultrasound examination data in each group were compared. Additionally, electronic medical records of 2344 patients admitted due to CMT in 17 tertiary children's hospitals of China's Futang Research Center of Pediatric Development (FRCPD) from 2015 to 2019 were retrospectively analyzed. Data on sex, age, year of admission and discharge, and treatment costs during hospitalization were extracted from the first medical record pages according to the ICD codes. The data were assessed for normality using the Kolmogorov–Smirnov test. Depending on the data distribution, they were analyzed using parametric tests, such as the t-test, or non-parametric tests. Qualitative data are expressed as percentages (%) and analyzed using the chi-square or Fisher's exact probability test, with α = 0.05 as the test level. P < 0.05 was considered to be indicative of a statistically significant difference. Results: Three types of CMT were defined based on sternocleidomastoid muscle ultrasound examination characteristics: local mass, uniform thickening, and atrophy. Age at first diagnosis was 69.21 ± 108.41 days in local mass type group, 216.85 ± 324.09 days in uniform thickening group, and 417.88 ± 739.05 days in atrophy- type group; while age at first physiotherapy use was 94.06 ± 206.49 days, 255.00 ± 430.62 days, 540.92 ± 1059.29 respectively. The children included in local mass type group have shown a high success rate of conservative treatment, with a rate of 7.5% of children underwent surgery. Age at first diagnosis was 112.44 ± 224.12 days in the physiotherapy group, 115.87 ± 144.86 days in the physiotherapy combined with glucocorticoid treatment subgroup, whereas the age at first physiotherapy use was 137.38 ± 312.11 and 196.91 ± 344.26 days respectively. In the observation period (2015–2019) the mean age at surgery for CMT in 17 tertiary children's hospitals of the FRCPD was 50 months. Overall, 663 children with CMT were 1–2 years of age, accounting for the largest proportion (28.3%). Followed by 417 individuals (17.8%) were 7–14 years of age, indicating that there are still more children with CMT receiving surgical treatment later. Conclusions: Early diagnosis and treatment are essential to improve the conservative treatment success rate and achieve good prognosis in children with CMT. Our team's concept for treating CMT is as follows: after diagnosing the children, we will adopt the standardized protocol of treatment, with physiotherapy combined with the injection of glucocorticoid drugs and SCM release surgery, when needed. This program has a high conservative treatment success rate and may facilitate the achievement of better prognosis and reduced teratogenicity rate. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the factors influencing and long-term effects of manual myotomy (MM) occurring during physiotherapy for congenital muscular torticollis (CMT).Methods: We retrospectively collected the clinical data of children with CMT receiving physiotherapy between 2008 and 2018. The children were divided into manual myotomy (MM) and non-manual myotomy (NMM) groups according to whether MM occurred during treatment. We assessed physiotherapy outcomes in children with CMT using craniofacial asymmetry parameters and the Cheng-Tang rating score. By measuring the ear-eye distance, ear-nose distance, eye-mouth distance, ear-mouth distance, half-head circumference, and half-head top at two sides to evaluate craniofacial asymmetry. Based on the Cheng-Tang assessment criteria, we recorded the range of rotation, range of lateral flexion, the status of the contracted muscle, the hardness of the mass, the extent of head tilting during activities and sleeping, the status of daily activities, face size, type of head shape, cranial changes, and subjective head tilting to assess the effectiveness of treatment. Clinical data and outcome indicators (craniofacial asymmetry parameters and Cheng-Tang rating score) were compared.Results: The MM group had a significantly higher total Cheng-Tang rating score than the NMM group (P < 0.05). Age at initial physiotherapy session was the risk factor for MM during physiotherapy.Conclusion: Children with CMT developing MM during physiotherapy generally have a good outcome, although we do not recommend MM as a goal of treatment. Physiotherapists should understand this phenomenon, assess relevant factors to predict risk, and carefully observe treatment to prevent possible complications. [ABSTRACT FROM AUTHOR]

In this paper, we construct a borehole model with an impermeable/permeable wall and study the seismoelectric responses. First, we define the boundary conditions at the borehole wall, then the acoustic field and electric field are simulated by the real axis integral method. In order to have a comprehensive analysis of the body wave components, we use the secant integral method to simulate the body waves and give the excitation intensity spectrum in the frequency domain. The results show that the impermeability of the borehole wall significantly increases the amplitude of the acoustic field generated by Stoneley waves. This is because the closed pores at the boundary make Stoneley waves energy leak more slowly and hence attenuating less. The impermeable borehole wall weakens the electromagnetic interface response. Besides, both P wave and S wave and their accompanying electric field properties are affected by boundary connectivity. This investigation provides a theoretical basis for qualitatively judging borehole wall permeability by the seismoelectric signals. [ABSTRACT FROM AUTHOR]

Background: Fractures are the most common type of unintentional injury in children, with traumatic upper limb fractures accounting for approximately 80% of all childhood fractures. Many epidemiological investigations of upper limb fractures in children have been conducted, but with the development of society, the patterns of childhood fractures may have changed. This study aimed to analyze the epidemiology and economic cost factors of upper limb fractures in Chinese children. Methods: We retrospectively reviewed children with upper limb fractures or old upper limb fractures hospitalized between December 1, 2015, and December 31, 2019, in 22 tertiary children's hospitals, under China's Futang Research Center of Pediatric Development. We used the ICD10 codes on the front sheet of their medical records to identify cases and extracted data on age, sex, injury cause, fracture site, treatment, the year of admission and discharge, visiting time, and various costs during hospitalization from the medical record. Results: A total of 32,439 children (21,478 boys and 10,961 girls) were identified, of whom 32,080 had fresh fractures and 359 had old fractures. The peak age was 3–6 years in both sexes. A total of 4788 were infants, 14,320 were preschoolers, 10,499 were in of primary school age, and 2832 were adolescent. Fractures were most frequent in autumn (August to October). Admissions peaked at 0 o'clock. Among the 32,080 children with fresh upper limb fractures, the most common fracture site was the distal humerus, with a total of 20,090 fracture events including 13,134 humeral supracondylar fractures and 4914 lateral humeral condyle fractures. The most common cause of injuries was falling over. The most common joint dislocation accompanying upper limb fractures occurred in the elbow, involving 254 cases. Surgery was performed in 31,274 children, and 806 did not receive surgery. Among those with clear operative records, 10,962 children were treated with open reduction and 18,066 with closed reduction. The number of cases was largest in the East China region (Anhui Province, Shandong Province, Jiangsu Province, Zhejiang Province, and Fujian Province), with 12,065 cases overall. Among the 359 children with old fractures, 118 were admitted with a diagnosis of "old humerus fracture," accounting for the highest proportion; 244 underwent surgical open reduction, 16.16% of whom had osteotomy. For the children with fresh fractures, the average total hospital cost was 10,994 yuan, and the highest average total hospital cost was 14,053 yuan, for humeral shaft fractures. For the children with old fractures, the average total hospital cost was 15,151 yuan, and the highest average total hospital cost was 20,698 yuan, for old ulna fractures. Cost of materials was the principle factor affecting total hospital cost, followed by surgery and anesthesia costs, both in children with fresh fractures and those with old fractures. Significant differences were observed in all hospital costs (P < 0.001) except treatment costs (P = 0.702), between children with fresh fractures and those with old fractures. Among the 32,439 children, full self-payment accounted for the highest proportion of all payment methods, involving 17,088 cases, with an average cost of 11,111 yuan. Conclusion: Information on the epidemiological characteristics of childhood fractures suggests that health and safety education and protective measures should be strengthened to prevent upper limb fractures in children. For both fresh and old fractures, the cost of materials was the principal factor affecting total hospital cost, followed by surgery and anesthesia costs. The overall average total hospital cost is higher in children with old fractures than in children with fresh fractures. Among all children, full self-payment, at 53% of children, accounted for the highest proportion of all payment methods. Hospital costs are a headache for those families who will pay on their own. It can lead to a delayed treatment and unhealed fractures or malunion in some children. Therefore, the child trauma care system and training on fractures need to be improved, to reduce the late presentation of fractures. These combined measures will improve children's quality of life, reduce the expenditure of families, and decrease the public health burden. To provide better medical services for children, authorities must improve the allocation of health resources, establish a comprehensive medical security system for children, and set up more child trauma centers. [ABSTRACT FROM AUTHOR]

• An acoustic source localization technique for composite laminates based on an improved signal energy-based approach is proposed. • The prior knowledge of the orientation of the symmetry axes of the composite laminate is not needed. • Experiments of the proposed technique for a composite laminate are verified. • Discussion of the reasons for errors and suggestions for improving the feasibility are given. Composite laminates are widely used in various fields, but their structural properties make them prone to impact damage. Thus, the real-time localization of the impact source in composite laminates is of great importance. The signal energy-based approach for acoustic source localization, as a new technique proposed in recent years, has advantages in that it can be applied in the case of low signal-to-noise ratio and does not need to have a priori knowledge of material properties. In this paper, an acoustic source localization technique for composite laminates based on an improved signal energy-based approach is proposed. The prior knowledge of the orientation of the symmetry axes of the composite laminate is not needed. The proposed approach is verified by numerical simulation and experiment. The results show that proposed approach has good stability and accuracy. The error analysis and suggestions for improving the feasibility of this technique are also given. [ABSTRACT FROM AUTHOR]

Cellular fibronectin (cFN) is one of the main components of tissue extracellular matrices and is involved in multiple physiologic and pathologic processes such as embryogenesis, wound healing, inflammation and tumor progression. The function of fibronectin in regulating normal cell adhesion and migration is well documented, but its function in cancer progression is only partially unraveled. We have reported previously that fibronectin stimulates the proliferation and survival of non-small lung carcinoma cells through upregulation of pro-oncogenic signals related to cyclooxygenase-2/phosphatidylinositol-3-kinase/protein kinase B (COX-2/PI3-K/AKT)/mammalian target of rapamycin triggered by activation of the integrin α5β1. Here, we extend these studies by showing that fibronectin promotes epithelial–mesenchymal transition (EMT) in lung cancer cells. We found that cFN, but not plasma fibronectin or type 1 collagen, induces lung carcinoma cell scattering in vitro, promotes cell migration and invasion of Matrigel and stimulates the expression of the mesenchymal marker α-smooth muscle actin while decreasing the expression of the epithelial marker E-cadherin through PI3-K and Erk pathways. Interestingly, the extra domain A (EDA) within cFN was found to be crucial for this process, as confirmed by testing cells overexpressing EDA or cells exposed to EDA-containing matrices. We found that the integrin α9, but not α5, mediated cFN-induced EMT as silencing integrin α9 neutralized cFN-induced EMT. Overall, our findings show that the EDA domain within cFN induces EMT in lung carcinoma cells through integrin α9-mediated activation of PI3-K and Erk. [ABSTRACT FROM AUTHOR]

Background: Unintentional injury is one of the top three causes of death for infants. However, the epidemiological studies of skeletal trauma and skull fractures in infants younger than 1 year were poorly understood in China. Therefore, our study aimed to examine accidental and emergency attendance in infants under 1 year. It also tried to determine the prevalence and severity of accident types in infants.Methods: A retrospective analysis was performed on the demographic characteristics of infants younger than 1 year with skeletal trauma and skull fractures who visited the Shenzhen Children's Hospital from January 1, 2016 to December 31, 2019. Age, gender, fracture site and type, mechanism of injury, length of visit, length of hospital stay, hospitalization cost, and treatment methods were analyzed.Results: A total number of 675 fractures in 664 infants were included, the median age was 187days (IQR,90-273days), including 394 males and 270 females. The top three fracture sites were the skull (430 sites, 63.70 %), long bones of the limbs (168 sites, 24.89 %), and clavicle (53 sites, 7.85 %). The top three causes of injury were locomotion injuries (256 cases, 38.55 %), falls or trips from low height (from beds, tables, chairs, etc.) (130 cases, 19.58 %), and birth injuries (97 cases, 14.61 %). The greatest amount of fractures occurred in children 1-28 days of life (d) reached a top of 101 cases, followed by 331-365 days, accounting for 15.21 and 10.24 %, respectively. The number of fractures reached a trough of 29 cases in the 29-60d group (4.37 %). And increased again to 65 cases in the 151-180d group (9.79 %). The proportion remained relatively constant at 9 % in the 181-210d group (9.19 %) and 211-240d group (9.64 %). The interval between injury and visiting our hospital was ≤ 72 h in 554 cases.Conclusions: Special attention should be given to the demographic characteristics of fractures in infants under 1 year of age, and appropriate outreach should be implemented. For example, health education should be provided to aid in the prevention especially for frequently occurring locomotion injuries, and prompt access to specialist medical care should be recommended for skull fractures, which are prone to delayed treatment. In addition, multidisciplinary collaboration should be implemented in trauma care, while also promoting the establishment of trauma centers in specialist children's hospitals with a stronger capacity to treat pediatric trauma, and a regional system for pediatric trauma treatment. [ABSTRACT FROM AUTHOR]

Acoustic source localization in a large pressure vessel or a storage tank-type cylindrical structure is important in preventing structural failure. However, this can be challenging, especially for cylindrical pressure vessels and tanks that are made of anisotropic materials. The large area of the cylindrical structure often requires a substantial number of sensors to locate the acoustic source. This paper first applies conventional acoustic source localization techniques developed for the isotropic, flat plate-type structures to cylindrical structures. The experimental results show that the conventional acoustic source localization technique is not very accurate for source localization on cylindrical container surfaces. Then, the L-shaped sensor cluster technique is applied to the cylindrical surface of the pressure vessel, and the experimental results prove the applicability of using this technique. Finally, the arbitrary triangle-shaped sensor clusters are attached to the surface of the cylindrical structure to locate the acoustic source. The experimental results show that the two acoustic source localization techniques using sensor clusters can be used to monitor the location of acoustic sources on the surface of anisotropic cylindrical vessels, using a small number of sensors. The arbitrarily triangle-shaped sensors can be arbitrarily placed in a cluster on the surface of the cylindrical vessel. The results presented in this paper provide a theoretical and experimental basis for the surface acoustic source localization method for a cylindrical pressure vessel and lay a theoretical foundation for its application. [ABSTRACT FROM AUTHOR]

The problems with elastic wave reflection at the interface between the water/patchy saturated porous media and the underlying solid matrix are considered. When porous media is saturated by biphasic fluids, the patchy saturation theory can explain the wave dispersion and attenuation better than the classical Biot theory at mesoscopic scales. Based on patchy saturation theory, this paper focuses on the reflection of elastic waves by patchy saturated porous media inclusion in layered media. Using numerical calculation, the reflection coefficients with different excitation frequencies, water saturations, and porous media depths are discussed. The results show that the differences between two kinds of patchy saturated porous media cases in the oil-water model are lower than those between the same two cases in the gas-water model. Low water saturation and high water saturation have significant effects on the reflection coefficient. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Alternating DO levels in PTBR achieved 95% TN removal of domestic sewage by KSND. • Anaerote adversely affected nitrification of KSND, but conducive to denitrification. • Transcription analysis revealed correlation between DO level and genes expression. • With two-stage DO control, KSND removed 88% TN from low-C/N domestic sewage in 180-d. Abstract Nitrogen removal performance of a simultaneous heterotrophic nitrifying-aerobic denitrifying (SND) bacterium (KSND) in a purification tank bioreactor (PTBR) amended with two-stage dissolved oxygen (DO) control was investigated. NH 4 +–N and total nitrogen (TN) removal efficiencies under aerobic conditions for domestic wastewater treatment were 97.12% and 52.64%, respectively. Under serial aerobic (DO > 4.0 mg/L) and anaerobic (DO < 0.5 mg/L) phases, average TN removal efficiency from effluent was 95.45%, without nitrate and nitrite accumulation. DO control assay demonstrated that anaerobic condition adversely affected nitrification (46.13%), but was conducive to denitrification (93.52%). Transcriptional analysis revealed 2.72-fold increase in hydroxylamine reductase expression under aerobic condition as compared to anaerobic condition. Nitrate reductase and nitric oxide reductase homologs had the additional activity of supporting anaerobic or aerobic denitrification in SND bacteria. Under two-stage DO control, KSND maintained high abundance in oligotrophic PTBR, removing 87.88% TN from low-carbon to nitrogen domestic sewage in 180-days. [ABSTRACT FROM AUTHOR]

• LSSC's contribution in developing different techniques and its future potentials are discussed. • The LSSC-based time difference of arrival and the wave front shape-based localization techniques are reviewed. • It will give readers a more comprehensive and clear understanding of LSSC based techniques. • The current limitations and future development prospects of ASL and damage detection techniques based on LSSC are also discussed. Acoustic source localization (ASL) plays an important role in structural health monitoring (SHM). The L-shaped sensor cluster (LSSC) is very convenient for ASL, and hence SHM. Various techniques based on LSSC have been developed rapidly in the past decade. LSSC can be conveniently used for damage detection and localization, a necessary step for monitoring structures through non-destructive testing (NDT). After ten years of development, LSSC still has a wide development space. In this paper, the fundamental roles of LSSC in developing different techniques within last ten years and its future potentials are discussed. The LSSC-based time difference of arrival localization techniques and the wave front shape-based localization techniques are reviewed in detail in this paper. This paper aims to give readers a more comprehensive and clear understanding of these techniques. The discussion on the advantages and disadvantages of these techniques and various sources of the errors will give the readers the current limitations and future development prospects of ASL and damage detection techniques using LSSC. [ABSTRACT FROM AUTHOR]