An Improved Theory for Designing and Numerically Calibrating Circular Touch Mode Capacitive Pressure Sensors.

The design, especially the numerical calibration, of a circular touch mode capacitive pressure sensor is highly dependent on the accuracy of the analytical solution of the contact problem between the circular conductive membrane and the rigid plate of the sensor. In this paper, the plate/membrane contact problem is reformulated using a more accurate in-plane equilibrium equation, and a new and more accurate analytical solution is presented. On this basis, the design and numerical calibration theory for circular touch mode capacitive pressure sensors has been greatly improved and perfected. The analytical relationships of pressure and capacitance are numerically calculated using the new and previous analytical solutions, and the gradually increasing difference between the two numerical calculation results with the gradual increase in the applied pressure is graphically shown. How to use analytical solutions and analytical relationships to design and numerically calibrate a circular touch mode capacitive pressure sensor with a specified pressure detecting range is illustrated in detail. The effect of changing design parameters on capacitance-pressure analytical relationships is comprehensively investigated; thus, the direction of changing design parameters to meet the required or desired range of pressure or capacitance is clarified.

Prediction of an impaired myocardial work using infarct size in acute myocardial infarction.

BACKGROUND: The relationship between myocardial infarct size (MIS) on late gadolinium-enhanced cardiac MRI (LGE MRI) and myocardial work (MW) indices assessed with MW echocardiography (MWE) has not been well characterized. This study aimed to determine an impaired MW using MIS in patients with acute myocardial infarction. METHODS: Left ventricular (LV) two-dimensional speckle-tracking echocardiography, MWE, and LGE MRI were performed in 33 patients with ST-segment elevation myocardial infarction and in 30 age- and sex-comparable controls. LV global longitudinal strain (GLS), global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) and MIS were acquired, respectively. RESULTS: MIS was negatively correlated with GWI (r = -0.60, P  = 0.005), GCW (r =- 0.66, P  = 0.002) and GWE (r = -0.71, P  = 0.0004), but positively correlated with GLS (r = 0.68, P  = 0.001). With the receiver operating characteristic curve, the cutoff value of MIS for the prediction of an impaired GLS was 16.5% [area under the curve (AUC) = 0.867)], an impaired GWI was 19.2% (AUC = 0.727), an impaired GCW was 19.2% (AUC = 0.725), an increased GWW was 15.8% (AUC = 0.656), an impaired GWE was 15.8% (AUC = 0.880). CONCLUSION: MIS is a strong predictor of impaired MW. Timely reduction of infarct size is essential to improve myocardial function.

Analysis of patency rates and factors associated with arteriovenous fistula in maintenance hemodialysis patients followed for 10 years.

OBJECTIVE: This study analyzed the long-term arteriovenous fistula (AVF) patency rate and its determinants in patients undergoing maintenance hemodialysis. METHODS: General data and laboratory examinations of hemodialysis patients were collected retrospectively. The primary patency time, primary functional patency time, cumulative patency time, cumulative functional patency time, and temporary central venous catheterization (CVC) time were counted. Cox regression was used to analyze the relationships between different factors and AVF survival time. Kaplan-Meier survival analysis was used to analyze the primary patency, primary functional patency, cumulative patency, and cumulative functional patency rates between different groups. RESULTS: A total of 174 patients were included (mean age 58.38 ± 15.35 years), 57 women (32.76%) and 68 diabetics (39.08%). Univariate and multivariate Cox regression showed a correlation between UCR and AVF primary patency time, primary functional patency time, cumulative patency time, and cumulative functional patency time (HR 1.127, 1.116, 1.127, 1.115, 1.088, 1.075, 1.087, 1.013; 95%CI 1.055-1.204, 1.043-1.194, 1.055-1.204, 1.042-1.194, 1.022-1.158, 1.006-1.149, 1.021-1.157, 1.004-1.147; p < 0.001, 0.001, <0.001, 0.002, 0.008, 0.033, 0.009, 0.039, respectively). Duration of temporary CVC was also correlated (HR 1.013, 1.013, 1.013, 1.014, 1.008, 1.008, 1.008, 1.008; 95%CI 1.007-1.018, 1.008-1.019, 1.008-1.019, 1.009-1.020, 1.004-1.012, 1.004-1.012, 1.004-1.012, 1.004-1.012; p < 0.001, <0.001, <0.001, <0.001, <0.001, <0.001, <0.001, <0.001, respectively). Female sex was correlated with the primary patency time and the primary functional patency time (HR 1.755, 1.765, 1.767; 95%CI 1.028-2.997, 1.034-3.014, 1.021-3.057; p = 0.039, 0.037, 0.042, respectively), but not with the cumulative patency time and the cumulative functional patency time, the primary patency rate and primary functional patency rate of AVF were higher in male than in female patients (χ2 = 4.439, 4.531; p = 0.035, 0.033, respectively). The primary patency rate, primary functional patency rate, cumulative patency rate, and cumulative functional patency rate of AVF with UCR > 10.11 group are lower than those with UCR ≤ 10.11 (χ2 = 10.745, 10.712, 4.605, 4.472; p = 0.001, 0.001, 0.032, 0.034, respectively). The group of DTCP ≤ 42 days is better than DTCP > 42 days (χ2 = 6.014, 6.055, 8.572, 8.461; p = 0.014, 0.014, 0.003, 0.004, respectively). CONCLUSION: Women with high UCR values at the beginning of dialysis and a long duration of temporary CVC have a poor long-term survival rate of AVF. Therefore, UCR can be used as an indicator to predict the long-term survival rate of AVF. Simultaneously, clinicians should remove the temporary catheter as early as possible if conditions permit it.

Development of a Biotinylated Nanobody-Based Gold Nanoparticle Immunochromatographic Assay for the Detection of Procymidone in Crops.

A heavy-chain antibody (VHH) library against procymidone (PRM) was constructed via immunizing Bactrian camels. Through careful biopanning, seven nanobodies (Nbs) with different sequences were obtained. The variability in their performance was primarily attributed to the amino acid differences in complementarity-determining region 3 (CDR3), as analyzed by molecular docking. The Nb exhibiting the highest sensitivity, named NbFM5, was biotinylated and conjugated to streptavidin-labeled gold nanoparticles to preserve the epitope's activity and prevent a decrease in sensitivity due to traditional random electrostatic adsorption. Subsequently, a simple and sensitive immunochromatographic assay (ICA) was developed for rapid detection of PRM based on biotinylated Nb (btNb). The developed btNb-ICA showed a cut-off value of 200 ng/mL for visual judgment and a half-inhibitory concentration (IC50) of 6.04 ng/mL for quantitative detection. The limit of detection (LOD) was as low as 0.88 ng/mL. The recoveries in actual samples of crops ranged from 82.2 to 117.3%, aligning well with the results obtained from GC-MS/MS (R2 = 0.995). In summary, the developed btNb-ICA demonstrated high specificity and good accuracy for the rapid detection of PRM residues in vegetables. The total analysis time from preparing the sample to obtaining the result was less than 25 min.

The Thermal Stress Problem of Bimodular Curved Beams under the Action of End-Side Concentrated Shear Force.

A bimodular material is a kind of material that presents two elastic moduli in tension and compression. In classical thermoelasticity, however, the bimodular material is rarely considered due to its complexity in analysis. In fact, almost all materials will present, more or less, bimodular characteristics, and in some cases, the mechanical properties of materials cannot be fully utilized simply by ignoring the bimodular characteristics. In this study, the thermal stress problem of bimodular curved beams under the action of end-side concentrated shear force is analytically and numerically investigated, in which the temperature rise modes in a thermal environment are considered arbitrary. Using the stress function method based on compatibility conditions, a two-dimensional solution of thermoelasticity of the bimodular curved beam subjected to end-side concentrated shear force was obtained. The results show that the solution for a bimodular curved beam with a thermal effect can be reduced to that of a bimodular curved beam without a thermal effect. At the same time, the numerical simulation for the problem verifies the correctness of the theoretical solution. The results may serve as a theoretical reference for the refined analysis and optimization of curved beams in a thermal environment.

16,17-dinor-abietane diterpenoids from Casearia kurzii.

Eleven undescribed 16,17-dinor-abietane diterpenoids, caseazins A-K (1-11), and ten known diterpenoids (12-21) were isolated from the twigs and leaves of Casearia kurzii (Flacourtiaceae). Caseazins A-K were the first abietane -type dinorditerpenoids to have been isolated from the plant of Casearia kurzii. Their chemical structures were elucidated using a combination of 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configurations of 5 and 10 were established by electronic circular dichroism calculations. Moreover, compounds 2, 3, 13, 14, and 18 exhibited anti-inflammatory activity with IC50 values of 0.17, 0.36, 6.55, 1.30, and 4.53 µM, respectively. IL-1ß and caspase-1 analyses suggested that compound 14 inhibited NLRP3 inflammasome activation and blocked macrophage pyroptosis.

Application of the Variational Method to the Large Deformation Problem of Thin Cylindrical Shells with Different Moduli in Tension and Compression.

In this study, the variational method concerning displacement components is applied to solve the large deformation problem of a thin cylindrical shell with its four sides fully fixed and under uniformly distributed loads, in which the material that constitutes the shell has a bimodular effect, in comparison to traditional materials, that is, the material will present different moduli of elasticity when it is in tension and compression. For the purpose of the use of the displacement variational method, the physical equations on the bimodular material model and the geometrical equation under large deformation are derived first. Thereafter, the total strain potential energy is expressed in terms of the displacement component, thus bringing the possibilities for the classical Ritz method. Finally, the relationship between load and central deflection is obtained, which is validated with the numerical simulation, and the jumping phenomenon of thin cylindrical shell with a bimodular effect is analyzed. The results indicate that the bimodular effect will change the stiffness of the shell, thus resulting in the corresponding change in the deformation magnitude. When the shell is relatively thin, the bimodular effect will influence the occurrence of the jumping phenomenon of the cylindrical shell.

Polymer Conductive Membrane-Based Circular Capacitive Pressure Sensors from Non-Touch Mode of Operation to Touch Mode of Operation: An Analytical Solution-Based Method for Design and Numerical Calibration.

Polymer-based conductive membranes play an important role in the development of elastic deflection-based pressure sensors. In this paper, an analytical solution-based method is presented for the design and numerical calibration of polymer conductive membrane-based circular capacitive pressure sensors from non-touch mode of operation to touch mode of operation. The contact problem of a circular membrane in frictionless contact with a rigid flat plate under pressure is analytically solved, and its analytical solution is used for the design of touch mode circular capacitive pressure sensors for the first time. The analytical relationship with input pressure as independent variable and output capacitance as dependent variable is precisely derived and is used for the numerical calibrations of the analytical relationships with input capacitance as the independent variable and output pressure as the dependent variable in order to meet the capacitive pressure sensor mechanism of detecting pressure by measuring capacitance. For the first time, an example showing the design and numerical calibration of a given (given design parameters) polymer conductive membrane-based circular capacitive pressure sensor from non-touch mode of operation to touch mode of operation is provided. Then, the influence of changing several important design parameters on input capacitance-output pressure relationships is comprehensively investigated in order to clarify the desired input-output relationships when changing design parameters.

Polymer Conductive Membrane-Based Non-Touch Mode Circular Capacitive Pressure Sensors: An Analytical Solution-Based Method for Design and Numerical Calibration.

In this paper, an analytical solution-based method for the design and numerical calibration of polymer conductive membrane-based non-touch mode circular capacitive pressure sensors is presented. The accurate analytical relationship between the capacitance and applied pressure of the sensors is derived by using the analytical solution for the elastic behavior of the circular polymer conductive membranes under pressure. Based on numerical calculations using the accurate analytical relationship and the analytical solution, the analytical relationship between the pressure as output and the capacitance as input, which is necessary to achieve the capacitive pressure sensor mechanism of detecting pressure by measuring capacitance, is accurately established by least-squares data fitting. An example of how to arrive at the design and numerical calibration of a non-touch mode circular capacitive pressure sensor is first given. Then, the influence of changing design parameters such as membrane thickness and Young's modulus of elasticity on input-output relationships is investigated, thus clarifying the direction of approaching the desired input-output relationships by changing design parameters.

A Further Theoretical Study of Capacitive Pressure Sensors Based on Thin Film Elastic Deflection and Parallel Plate Capacitor: Refined Closed-Form Solution and Numerical Calibration.

The capacitive pressure sensor based on thin film elastic deflection and a parallel plate capacitor uses a non-conductive elastic annular thin film centrally connected to a conductive, rigid, flat, concentric-circular thin plate as a pressure sensing unit. On application of pressure, the non-conductive thin film deflects elastically, which in turn moves the conductive thin plate (as a movable upper electrode plate of the parallel plate capacitor) towards the lower electrode plate, resulting in a change in the capacitance of the capacitor. Therefore, the applied pressure can be determined by measuring the capacitance change, based on the closed-form solution for the elastic behavior of the annular thin film under pressure. Such capacitive pressure sensors are more suitable for large-sized sensors such as those used for building-facade wind pressure measurements, etc. In this paper, a further theoretical study of such capacitive pressure sensors is presented. The newly presented, more refined closed-form solution can greatly reduce the output pressure error under the same input capacitance, in comparison with the previously presented closed-form solution. A numerical example of how to use the resulting closed-form solution to numerically calibrate input-output characteristics is given for the first time. The variation trend of pressure operation ranges and input-output characteristics with important parametric variations, which can be used for guiding the design of such capacitive pressure sensors, is investigated.

Large Deflection Analysis of Peripherally Fixed Circular Membranes Subjected to Liquid Weight Loading: A Refined Design Theory of Membrane Deflection-Based Rain Gauges.

The anticipated use of elastic membranes for deflection-based rain gauges has provided an impetus for this paper to revisit the large deflection problem of a peripherally fixed circular membrane subjected to liquid weight loading, a statics problem when the fluid-structure interaction of membrane and liquid reaches static equilibrium. The closed-form solution of this statics problem of fluid-structure interaction is necessary for the design of such membrane deflection-based rain gauges, while the existing closed-form solution, due to the use of the small rotation angle assumption of the membrane, cannot meet the design requirements for computational accuracy. In this paper, the problem under consideration is reformulated by giving up the small rotation angle assumption, which gives rise to a new and somewhat intractable nonlinear integro-differential equation of the governing out-of-plane equilibrium. The power series method has played an irreplaceable role in analytically solving membrane equations involving both integral and differential operations, and a new and more refined closed-form solution without the small rotation angle assumption is finally presented. Numerical examples conducted show that the new and more refined closed-form solution presented has satisfactory convergence, and the effect of giving up the small rotation angle assumption is also investigated numerically. The application of the closed-form solution presented in designing such membrane deflection-based rain gauges is illustrated, and the reliability of the new and more refined closed-form solution presented was confirmed by conducting a confirmatory experiment.

Application of Variational Method to Stability Analysis of Cantilever Vertical Plates with Bimodular Effect.

In the design of cantilevered balconies of buildings, many stability problems exist concerning vertical plates, in which reaching a critical load plays an important role during the stability analysis of the plate. At the same time, the concrete forming vertical plate, as a typical brittle material, has larger compressive strength but lower tensile strength, which means the tensile and compression properties of concrete are different. However, due to the complexities of such analyses, this difference has not been considered. In this study, the variational method is used to analyze stability problems of cantilever vertical plates with bimodular effect, in which different loading conditions and plate shapes are also taken into account. For the effective implementation of a variational method, the bending strain energy based on bimodular theory is established first, and critical loads of four stability problems are obtained. The results indicate that the bimodular effect, as well as different loading types and plate shapes, have influences on the final critical loads, resulting in varying degrees of buckling. In particular, if the average value of the tensile modulus and compressive modulus remain unchanged, the introduction of the bimodular effect will weaken, to some extent, the bending stiffness of the plate. Among the four stability problems, a rectangular plate with its top and bottom loaded is most likely to buckle; next is a rectangular plate with its top loaded, followed by a triangular plate with its bottom loaded. A rectangular plate with its bottom loaded is least likely to buckle. This work may serve as a theoretical reference for the refined analysis of vertical plates. Plates are made of concrete or similar material whose bimodular effect is relatively obvious and cannot be ignored arbitrarily; otherwise the greater inaccuracies will be encountered in building designs.

A Theoretical Study on an Elastic Polymer Thin Film-Based Capacitive Wind-Pressure Sensor.

This study is devoted to the design of an elastic polymer thin film-based capacitive wind-pressure sensor to meet the anticipated use for real-time monitoring of structural wind pressure in civil engineering. This sensor is composed of four basic units: lateral elastic deflection unit of a wind-driven circular polymer thin film, parallel plate capacitor with a movable circular electrode plate, spring-driven return unit of the movable electrode plate, and dielectric materials between electrode plates. The capacitance of the capacitor varies with the parallel move of the movable electrode plate which is first driven by the lateral elastic deflection of the wind-driven film and then is, after the wind pressure is reduced or eliminated, returned quickly by the drive springs. The closed-form solution for the contact problem between the wind-driven thin film and the spring-driven movable electrode plate is presented, and its reliability is proved by the experiment conducted. The numerical examples conducted show that it is workable that by using the numerical calibration based on the presented closed-form solution the proposed sensor is designed into a nonlinear sensor with larger pressure-monitoring range and faster response speed than the linear sensor usually based on experimental calibration.

Closed-Form Solution and Experimental Verification for the Axisymmetric Deformation Problem of Blistering Circular Thin Polymer Films under Uniformly Distributed Gas Pressure.

The existing studies indicate that the measurement formulas used in blister test techniques, which are used to measure the mechanical properties of thin-film/substrate systems, are usually given based on an approximation-that is, the applied direction of the uniformly distributed transverse load is always vertical, while the applied direction of the uniformly distributed gas pressure is always perpendicular to the surface of the thin film. This approximation will lead to a large measurement error. In this study, we obtained the analytical solution to the problem of axisymmetric deformation of blistering circular thin polymer films under the action of uniformly distributed gas pressure via the power series method. An example is given to illustrate the error caused by the approximation mentioned above, and the validity of the solution presented here is verified. The result shows that the chance of error caused by the approximation increases with the increase in the applied load, and it far exceeds the allowable error of measurement when the applied load is relatively large. In addition, the related experiments of the blistering circular thin polymer film under uniformly distributed gas pressure are carried out, and the experimental results are compared with the theoretical results. The comparison results show that the analytical solution given in this paper is correct. The solution presented here is of great significance to improve the measurement accuracy of the blister test technique.

A Multi-Parameter Perturbation Solution and Experimental Verification for Bending Problem of Piezoelectric Cantilever Beams.

The existing studies indicate that the application of piezoelectric polymers is becoming more and more extensive, especially in the analysis and design of sensors or actuators, but the problems of piezoelectric structure are usually difficult to solve analytically due to the force-electric coupling characteristics. In this study, the bending problem of a piezoelectric cantilever beam was investigated via theoretical and experimental methods. First, the governing equations of the problem were established and non-dimensionalized. Three piezoelectric parameters were selected as perturbation parameters and the perturbation solution of the equations was finally obtained using a multi-parameter perturbation method. In addition, the relevant experiments of the piezoelectric cantilever beam were carried out, and the experimental results were in good agreement with the theoretical solutions. Based on the experimental results, the effect of piezoelectric properties on the bending deformation of piezoelectric cantilever beams was analyzed and discussed. The results indicated that the multi-parameter perturbation solution obtained in this study is effective and it may serve as a theoretical reference for the design of sensors or actuators made of piezoelectric polymers.

An Electroelastic Solution for Functionally Graded Piezoelectric Circular Plates under the Action of Combined Mechanical Loads.

In this study, we obtained an electroelastic solution for functionally graded piezoelectric circular plates under the action of combined mechanical loads which include the uniformly distributed loads on the upper surface of the plate and the radial force and bending moment at the periphery of the plate. All electroelastic materials parameters are assumed to vary according to the same gradient function along the thickness direction. The influence of different functionally graded parameters on the elastic displacement and elastic stress, as well as the electric displacement and electric potential, was discussed by a numerical example. The solution presented in this study is not only applicable to the case of combined loads, but also to the case of a single mechanical load. In addition, this solution reflects the influence of the function gradient on the pure piezoelectric plate, which is helpful to the refined analysis and optimization design of similar structures.

One-Dimensional and Two-Dimensional Analytical Solutions for Functionally Graded Beams with Different Moduli in Tension and Compression.

The material considered in this study not only has a functionally graded characteristic but also exhibits different tensile and compressive moduli of elasticity. One-dimensional and two-dimensional mechanical models for a functionally graded beam with a bimodular effect were established first. By taking the grade function as an exponential expression, the analytical solutions of a bimodular functionally graded beam under pure bending and lateral-force bending were obtained. The regression from a two-dimensional solution to a one-dimensional solution is verified. The physical quantities in a bimodular functionally graded beam are compared with their counterparts in a classical problem and a functionally graded beam without a bimodular effect. The validity of the plane section assumption under pure bending and lateral-force bending is analyzed. Three typical cases that the tensile modulus is greater than, equal to, or less than the compressive modulus are discussed. The result indicates that due to the introduction of the bimodular functionally graded effect of the materials, the maximum tensile and compressive bending stresses may not take place at the bottom and top of the beam. The real location at which the maximum bending stress takes place is determined via the extreme condition for the analytical solution.

Theoretical Study on Synchronous Characterization of Surface and Interfacial Mechanical Properties of Thin-Film/Substrate Systems with Residual Stress Based on Pressure Blister Test Technique.

In this study, based on the pressure blister test technique, a theoretical study on the synchronous characterization of surface and interfacial mechanical properties of thin-film/substrate systems with residual stress was presented, where the problem of axisymmetric deformation of a blistering film with initial stress was analytically solved and its closed-form solution was presented. The expressions to determine Poisson's ratios, Young's modulus, and residual stress of surface thin films were derived; the work done by the applied external load and the elastic energy stored in the blistering thin film were analyzed in detail and their expressions were derived; and the interfacial adhesion energy released per unit delamination area of thin-film/substrate (i.e., energy release rate) was finally presented. The synchronous characterization technique presented here has theoretically made a big step forward, due to the consideration for the residual stress in surface thin films.

The expression of α2A-adrenoceptors in the calcium-binding protein immunoreactive interneurons in rat prefrontal cortex.

The α2A adrenoceptors (α2A-ARs) are the most common adrenergic receptor subtype found in the prefrontal cortex (PFC). It is generally accepted that stimulation of postsynaptic α2A-ARs on pyramidal neurons are key to PFC functions, such as working memory. However, the expression of α2A-ARs in interneurons is largely unknown. In the present study using double-labeling immunofluorencence technique, we investigated the expression of α2A-ARs in major types of rat PFC interneurons expressing calcium-binding proteins parvalbumin (PV), calretinin (CR), and calbindin (CB). Our data demonstrated that α2A-ARs are highly expressed in calcium-binding protein immunoreactive interneurons of rat PFC, suggesting that stimulation of α2A-ARs may alter neural networks comprising pyramidal neurons and interneurons, thereby exerting a beneficial effect on PFC cognitive functions. The present study provides the morphological basis for a potential mechanism by which stimulation of α2A-ARs induces cognitive improvement.

Activation of ß2-adrenoceptor enhances synaptic potentiation and behavioral memory via cAMP-PKA signaling in the medial prefrontal cortex of rats.

The prefrontal cortex (PFC) plays a critical role in cognitive functions, including working memory, attention regulation, behavioral inhibition, as well as memory storage. The functions of PFC are very sensitive to norepinephrine (NE), and even low levels of endogenously released NE exert a dramatic influence on the functioning of the PFC. Activation of ß-adrenoceptors (ß-ARs) facilitates synaptic potentiation and enhances memory in the hippocampus. However, little is known regarding these processes in the PFC. In the present study, we investigate the role of ß2-AR in synaptic plasticity and behavioral memory. Our results show that ß2-AR selective agonist clenbuterol facilitates spike-timing-dependent long-term potentiation (tLTP) under the physiological conditions with intact GABAergic inhibition, and such facilitation is prevented by co-application with the cAMP inhibitor Rp-cAMPS. Loading postsynaptic pyramidal cells with Rp-cAMPS, the PKA inhibitor PKI(5-24), or the G protein inhibitor GDP-ß-S significantly decreases, but does not eliminate, the effect of clenbuterol. Clenbuterol suppresses the GABAergic transmission, while blocking GABAergic transmission by the GABA(A) receptor blocker partially mimics the effect of clenbuterol. In behavioral tests, a post-training infusion of clenbuterol into mPFC enhances 24-h trace fear memory. In summary, we observed that prefrontal cortical ß2-AR activation by clenbuterol facilitates tLTP and enhances trace fear memory. The mechanism underlying tLTP facilitation involves stimulating postsynaptic cAMP-PKA signaling cascades and suppressing GABAergic circuit activities.