Stiffness Parameters Research Articles

The Role of Serum Erythropoietin (EPO) and Vascular Endothelial Growth Factor (VEGF) in Pulse Wave Velocity (PWV) Among Hypertensive Patients: A Cross-Sectional Study.

Background and objective While hypertension (HTN) is a major health-related threat globally, it is often an under-reported clinical condition as most of the stage I hypertensive patients do not present with any symptoms. The relationship between endogenous oxygen-sensing protein [erythropoietin (EPO) andvascular endothelial growth factor(VEGF)] levels and vascular stress in hypertensive patients is not fully understood as the mechanistic pathway by which these oxygen-sensing proteins alter the vascular physiology and cause hypertension is still a matter of debate. In light of this, we explored the role of these two proteins in the development of vascular stress including increased pulse wave velocity (PWV). We aimed to examine the correlation between oxygen-sensing proteins and vascular stress markers including PWV in hypertensive patients. Materials and methods We conducted a cross-sectional study involving age-matched participants classified into three groups (group 1: normotensive persons, n=36; group 2: stage I hypertensive patients, n=36; and group 3, stage II hypertensive patients, n=36). Adiposity-related parameters such as waist circumference (WC), hip circumference (HC), BMI, and waist-hip ratio (WHR) were measured. BPwas recorded manually in resting posture by using a sphygmomanometer. PWV, which predicts the progression of BP and the development of HTN, was recorded using a periscope, which works based on the oscillometric method. Vascular stress-induced oxidative stress parameters [serummalondialdehyde(MDA)and serumnitric oxide(NO)] were also estimated by using a UV spectrophotometer. Quantitative estimations of oxygen-sensing proteins (serum EPO and serum VEGF) were done by using the ELISA kit method. The results were expressed as mean ± standard deviation (SD). The correlation between the variables was done using Spearman's correlation. A p-value <0.05 was considered statistically significant. Results Adiposity indices and vascular stiffness parameters were found to be significantly (p <0.05) increased in group 2 and group 3 compared to group 1. The levels of serum MDA were found to be significantly (p<0.05) increased in group 2 and group 3 than group 1, whereasthe levels of serum NO were significantly (p<0.05) decreased in group 3 and group 2 than group 1. A significant (p<0.05) positive correlation was observed between the PWV and EPO (r=0.492) while a significant (p<0.05) negative correlation was observed between PWV and VEGF(r=-0.406) among thestudy population. Conclusion The results are indicative of the influence of vascular stress in stage I and II hypertensive patients. Furthermore, the relationship between oxygen-sensing proteins and vascular stress in hypertensive patients has also been established.

A Critical Review of Cone Penetration Test-Based Correlations for Estimating Small-Strain Shear Modulus in North Sea Soils

The geotechnical characterisation of offshore wind farm sites requires measurement or estimation of the small-strain shear stiffness Gmax of the subsoil. This parameter can be derived from shear wave velocity Vs measurements if the bulk density of the soil is known. Since direct measurements of Vs are generally not available at all foundation locations in a wind farm, correlations with cone penetration test (CPT) results are often used to determine location-specific stiffness parameters for foundation design. Existing correlations have mostly been calibrated to onshore datasets which may not contain the same soil types and stress conditions found in the North Sea. The distinct geological history of the North Sea necessitates a critical review of these existing CPT-based correlations. They are evaluated against an extensive database of in situ Vs measurements in the southern North Sea. The importance of modelling the stress-dependent nature of Vs is highlighted, and a novel stress-dependent model for Vs from CPT data, which leads to an improved fit, is presented. As the small-strain stiffness is used as an input to foundation response calculations, the model uncertainty of the correlation can introduce significant uncertainty into the resulting foundation response. This transformation uncertainty is quantified for each of the correlations evaluated in this study and shows important variations.

A gazelle optimization expedition for key term separated fractional nonlinear systems with application to electrically stimulated muscle modeling

Various real-time processes are effectively represented with a fractional nonlinear autoregressive exogenous (F-NARX) model where estimation of model parameters is considered as an essential task. In this study, a population-based gazelle optimization algorithm (GOA) inspired by the evolutionary characteristics of gazelle's is exploited for the parameter estimation of the key term-separated F-NARX system. The Grünwald-Letnikov derivative, a fractional order calculus operator is integrated to develop the F-NARX system from a conventional non-linear autoregressive system. The mean square error-based merit function is developed and the effectiveness of the GOA for the F-NARX system is analyzed in terms of speedy convergence, estimation accuracy, complexity and robustness for different noise scenarios. The extendibility of the GOA is assessed through the estimation of stiff parameters of the electrically stimulated muscle model (ESMM) required for rehabilitation of paralyzed muscles. The efficacy of the GOA is endorsed through Wilcoxon signed rank statistical test in comparison with recent counterparts of Runge Kutta optimization algorithm, Whale optimization algorithm, and Harris Hawks optimization algorithm.

Arterial stiffness in non-alcoholic fatty liver disease

Background. The presence of metabolic-associated pathology, namely obesity, diabetes mellitus, dyslipidemia, and non-alcoholic fatty liver disease (NAFLD), significantly accelerates the development of the cardiovascular continuum. This is associated with an increased risk of major cardiovascular events (myocardial infarction, stroke). An important organ damage in hypertension (HTN) is the remodeling of small arteries and an increase in stiffness of large arteries. The relationship between NAFLD, dyslipidemia, hypertriglyceridemia, obesity (especially abdominal), diabetes, and HTN is well studied, but there is a lack of clinical studies examining changes in arterial stiffness in NAFLD. Aim of the research was to study the parameters of arterial stiffness in patients with NAFLD. Materials and methods. Eighty-two Caucasian patients with NAFLD (mean age (56.8 ± 1.1) years, 59.8 % men) were enrolled. Participants were divided into two groups: group 1 (n = 44) — NAFLD and concomitant HTN, group 2 (n = 38) — HTN without NAFLD. All patients underwent a standard general clinical examination, laboratory and instrumental work-up. In addition, all patients were assessed for the parameters of arterial stiffness via non-invasive arteriography. Results. Patients with NAFLD had significantly higher office systolic and diastolic blood pressure (by 15.2 and 10.4 %, respectively, p &lt; 0.01) despite comparable drug therapy. The same trends were observed in relation to the central aortic pressure, which was 19.3 % higher in patients with NAFLD (p &lt; 0.01), and central pulse pressure that was 35.9 % higher than in patients without NAFLD (p &lt; 0.01). Brachial artery augmentation index in NAFLD turned to be elevated compared to patients without NAFLD (p &lt; 0.01), but aortic augmentation index was comparable between groups. The return time interval in group 1 was 50.3 % higher than in group 2 (p &lt; 0.01). Finally, patients with NAFLD had a significant increase in pulse wave velocity by 52.3 % compared to those without NAFLD with average value exceeding 12 m/sec (p &lt; 0.01). Conclusions. There is an association between NAFLD and worse indices of arterial stiffness in patients with concomitant HTN.

Researching low frequency vibration of automobile-robot

Automobile-robot (self-driving automobile) is being researched and developed vigorously. When the automobile-robot is moving on the road surface, the low frequency vibration excitation not only influences the ride comfort of the automobile-robot but also strongly affects the durability of the vehicle’s structures. To research the automobile-robot’s vibration in the low frequency region, a dynamic model of the vehicle is established to calculate the vibration equations in the time region. Based on the theory of the Laplace transfer function, the automobile-robot’s vibration equations in the time region are transformed and converted to the vibration equations in the frequency region. Then, the effect of the design parameters and operation parameters on the characteristic of the automobile-robot’s acceleration-frequency is simulated and analyzed to evaluate the ride comfort as well as the durability of the automobile-robot’s structures in the frequency region. The research results show that the design parameters of the stiffness, mass, and road wavelength remarkably affect the characteristic of the automobile-robot’s acceleration-frequency. To reduce the resonant amplitude of the acceleration-frequency in the vertical and pitching direction of the automobile-robot, the stiffness parameters of the automobile-robot's and tires should be reduced while the mass of the automobile-robot’s body should be increased. Additionally, the road’s roughness also needs to be decreased or the road’s quality needs to be enhanced to reduce the resonant amplitude of the automobile-robot’s acceleration-frequency.

Stiffness parameter prediction for elastic supports of non-uniform rods

The present research focuses on establishing the stiffness parameter of elastic springs placed at the ends of non-uniform rods. The governing equation for the longitudinal vibrations of the rod was solved using the Haar wavelet integration method. The calculated natural frequency parameters closely aligned with those available in the literature. The normalised values of the first ten natural frequency parameters were used in the feature vector to predict the stiffness parameter of the springs. A feedforward neural network with two hidden layers made accurate predictions when the range of each natural frequency parameterwithin its domain exceeded one. The insights garnered from this study contribute to the design, optimisation and assessment of diverse engineering applications.

Effect of rapid cooling, frozen storage, and thawing on the passive viscoelastic properties and structure of the rat aorta

Biological tissues decay over time after harvesting, which alters their biomechanical properties. This poses logistical challenges for studies investigating passive arterial biomechanics as tissues need to be characterized shortly after excision. Freezing and cryopreservation methods can help alleviate the need for biomechanical testing of fresh tissue in human ex vivo studies. However, these methods tend to eliminate or reduce arterial cell functionality and affect passive biomechanics. Furthermore, their impact on dynamic arterial biomechanics remains unknown despite arterial viscoelastic properties being an integral component contributing to arterial stiffness under in vivo loading conditions. The present study aims to investigate the impact of rapid cooling and subsequent storage at −80 °C on the passive viscoelastic properties of arterial tissue and aid in ascertaining whether this is a suitable method to delay tissue analysis for studies investigating passive arterial biomechanics. Control and frozen abdominal rat aorta segments were quasi-statically and dynamically tested using a biaxial testing set-up. The results were modeled using a constituent-based quasi-linear viscoelastic modeling framework, yielding directional stiffness parameters, individual constituent biomechanical contributions, and a quantification of viscoelastic stiffening under dynamic pressurization conditions. Frozen samples displayed significantly decreased wall thickness, viscoelastic dissipation, viscoelastic stiffening, and significantly decreased circumferential deformation with changes in luminal pressure. Furthermore, frozen samples displayed significantly increased circumferential stiffness, pulse wave velocity, and collagen load bearing. Consequently, these changes should be considered when utilizing this tissue preservation method to delay biomechanical characterization of rat aortic tissue.

Parametric Analysis of “Zollinger Type” Ribbed Timber Shells

The following article presents the study and further development of the roof system developed and patented by Friedrich Zollinger in 1920. The so-called Zollinger construction system is based on short timber components ‐ lamellae, connected by a bolt and a form of decking only for covering purpose. By developing the micro step joint, an increase in joint stiffness can be achieved. In addition, by applying and activating a load-bearing roof covering, a further increase in system stiffness can be achieved and demonstrated. Especially with regard to large spans, the increase of the stiffness and reduction of the deflection becomes inevitable against the background of an economic feasibility. Based on the analysis of the historic Zollinger system, it is possible to evaluate potential for improvements in terms of system stiffness as well as contemporary design, development and manufacturing. Due to the large number of different influencing factors, the system was modeled as a parametric master model. In this, a closed process cycle can be developed from the geometric definition, to the static analysis and to the derivation of the computer-aided manufacturing data. In the present study especially the exact recording, description and modeling of the stiffness and feasibility of the connection details “lamella‐lamella” and “lamella‐planking” was investigated. A parametric finite element model can be used to determine the stiffness parameters as a function of the fasteners used and the spacing of the fasteners. Staple connections are used as the main means of connection between the lamella and the planking. The implementation of the staple connections in the finite element analysis was carried out using spring parameters, which are determined in the course of the development. The analysis and optimization of the connection stiffnesses is presented against the background of an economical structure development. By using digital planning methods and interfaces, a contemporary way of working is presented. In addition, a contribution is made to digitalization in the construction industry.

Evaluating the influence of volumetric properties on back-calculated asphalt layer moduli using falling weight deflectometer data

The back-calculation process performed in pavement systems is the numerical analysis of captured deflections to estimate layer stiffness parameters. Prediction of fatigue performance in terms of back-calculated asphalt layer moduli by using a Falling Weight Deflectometer (FWD) has specific challenges in terms of testing protocol, skillset, and complex back-calculation analysis. The performance of the asphalt layer is primarily governed by extrinsic parameters such as temperature, vehicular transient loading characteristics, moisture content, and intrinsic parameters such as binder properties and aggregate mix properties. The role of volumetric properties of asphalt mixes contributes significantly to the back-calculated asphalt layer moduli in terms of the overall life of the structure. The asphalt layer moduli value is dependent on the traditional volumetric properties of asphalt mixes such as air voids in the mix, voids in mineral aggregate, and the percentage of bitumen mix. In this study, a total of 60 in-service pavement sections are identified from three different categories of roads to perform FWD tests and collection of asphalt layer core samples. A detailed laboratory investigation has been carried out to estimate the volumetric properties of different core samples. This study uses field investigations to determine the degree of interdependency between the volumetric characteristics of asphalt mixtures and temperature on the back-calculated layer moduli. Furthermore, the findings from this study are utilized to establish several correlations at the aggregate level, demonstrating strong relationships with R2 values ranging from 0.84 to 0.875. The developed model is validated and depicted in good agreement with the actual values.

#1550 Incident hypertension: immune biomarkers and vascular phenotypes

Abstract Background and Aims Blood pressure (BP) regulation is mediated by cardiac, vascular, endocrine, renal, and immune system interactions. Hence, hypertension may exist as different phenotypic variants, with different clinical features and susceptibility to target organ damage. We aimed to analyse the circulating protein biomarker ‘signature’ of: 1) untreated hypertension; 2) hypertensive phenotypes identified by arterial and blood pressure parameters. Method 61 patients with hypertension, and 61 controls were assessed using 24hr ambulatory BP monitoring; endothelial function, arterial stiffness, carotid intima-media thickness (CIMT), and cardiovascular variability [1]. Circulating protein biomarkers analysed using Olink® Inflammation plasma biomarker panel, reported as NPX (Normalized Protein eXpression), in Log2 scale. Results 34 biomarkers dominated by cytokines and chemokines differed between normotensive and hypertensive subjects (Fig. 1), though failed to meet Bonferroni-adjusted threshold. Inflammatory biomarkers correlated with BP and arterial stiffness, BP variability, and CIMT, but not endothelial function. Associations were concordant across systolic and diastolic BP; TPP1, CCL7, CCL11, and CCL21 positively correlating; IL18R1, and KYNU negatively. These relationships were more pronounced in hypertensive subgroup, 85 biomarkers correlating including CD molecules (CD200R1, CD22, CD58, CD6, CD70) and cytokines (IL-5, IL-11, IL-15, IL-18, IL-32, IL-1RL2, IL-22RA1, IL-5RA). HGF, AGE, and CCL21 showed greatest between group differences and correlated with multiple BP or vascular parameters. Systolic nocturnal dipping demonstrated negative correlation with biomarkers relating to immune cell interactions and cellular adhesion (CTRC, EPHA1, LGALS4, SIT1, SMOC, IL-18 and TNFSF11). Machine learning techniques identified three phenotypes of hypertension, ‘arterially stiffened’, ‘vaso-protected’, and ‘non-dipper’ [1]. Sixteen of the 85 correlating biomarkers also differed between these phenotypic groups: Conclusion Hypertension is linked to alterations in circulating immune biomarkers. Multiple biomarkers correlated with both arterial stiffness and BP parameters. Some biomarkers are only correlated in the hypertensive group. Many also relate to nocturnal dipping, and differed across the hypertension endotypes. HGF is a promising biomarker for BP and arterial function; warranting further validation.

#2032 Heart rate-adjusted augmentation index reduces after switching low-flux dialyzers to medium cut-off dialyzers in maintenance hemodialysis patients

Abstract Background and Aims Arterial stiffness affects almost all maintenance hemodialysis (MHD) patients and is one of the most important predictors of cardiovascular morbidity and mortality. Medium cut-off (MCO) membrane technology provides higher clearance of large-middle uraemic toxin and cytokines compared to conventional dialyzers. In this case-control study, we investigated the change in the arterial stiffness parameters after the transition to MCO dialyzers in MHD patients receiving treatment with low-flux dialyzers. Method We conducted a prospective, single-center cross-over study including 19 MHD patients receiving treatment with low-flux dialyzers. Baseline and repeated parameters were measured from the brachial artery on a mid-week HD session at 0th, 120th, and 240th minutes, and the average of the three measurements were analyzed. The repeated parameters were measured two weeks after the switching to MCO dialyzers which were decided by the clinician according to clinical indication. Results The median age was 71 (51, 79) years, and 57.9% of the patients were female. The frequency of diabetes was 36.8%, and hypertension was 73.7%. 21.1% patients were smokers. 31.6% of the patients had a history of cardiovascular disease. Two weeks after switching to MCO dialyzers, the Kt/Vs, urea reduction ratios, laboratory parameters, systolic, diastolic, and mean arterial pressures remained similar to baseline. The mean pulse wave velocity was 10.3 m/s (8.4, 11.0) with low-flux dialyzers and 10.2 m/s (7.0, 11.5) with MCO dialyzers (p = 0.38). The mean heart rate adjusted augmentation index [AIx(75)] was 20.0% (15.0, 30.3) with low-flux dialyzers and 13.0% (11.0, 22.0) with MCO dialyzers (p = 0.04). Conclusion Our study showed that the rapid effect of MCO membranes is the reduction in peripheral wave reflections defined by AIx(75). Additional long-term diseases are required to determine whether MCO dialyzers might improve the cardiovascular prognosis of MHD patients.

#1943 The association of uncarboxylated, non-phosphorylated Matrix Gla protein with arterial stiffness in hemodialysis and peritoneal dialysis patients

Abstract Background and Aims Vitamin K deficiency has been identified as a marker of vascular calcification AND STIFNESS and an independent cardiovascular risk factor in hemodialysis (HD) and peritoneal dialysis (PD) patients, as the most powerful inhibitor of vascular calcification, Matrix Gla Protein requires vitamin K to become activated. However, until to date, it has not yet been clarified whether hepatic or extrahepatic markers of vitamin K status reflect the arterial status of dialysis patients. In this study we aimed to investigate the association of vitamin K deficiency with arterial stiffness in End-Stage Kidney Disease (ESKD) patients. Method In 42 ESKD patients undergoing either HD or PD, we measured plasma levels of the inactive vitamin-K dependent Matrix Gla Protein (dp-ucMGP) and serum levels of prothrombin (PIVKA-II) as markers of extrahepatic and hepatic insufficiency of vitamin K (CARIM Institute, Maastricht, Netherlands). In these patients we determined arterial stiffness parameters (pulse wave velocity-PWV) by the Mobil-O-Graph device (IEM, Stolberg, Germany). Results Serum PIVKA-II was associated with T2D duration (r = −0.38, p = 0.013), phosphorus levels (r = −0.41, p = 0.009) serum albumin (r = −0.33, p = 0.036) Spearman's rho test, and the type of transporter in PD patients (p = 0.039), Kruskal-Wallis test. Plasma dp-ucMGP was associated with PWV (r = 0.51, p = 0.001), peripheral (r = −0.37, p = 0.016) and central diastolic blood pressure (BP) (r = −0.34, p = 0.026) and age (r = 0.41, p = 0.007), Spearman's rho. Patients with T2DM, history of acute myocardial infarction and those receiving warfarin had significantly increased levels of circulating dp-ucMGP (p = 0.036, p = 0.039 and p &amp;lt; 0.0001, respectively, Kruskal-Wallis). Warfarin was associated with a 2.5-fold and a 23-fold increase in dp-ucMGP and PIVKA-II levels, respectively. Stepwise multiple regression analysis showed that PWV (p = 0.001, B = 494, 95% CI: 242-746) was an independent predictor of dp-ucMGP, independent of age, T2T2, history of myocardial infraction and diastolic BP. Conclusion Elevated plasma dp-ucMGP levels (suggesting extrahepatic vitamin K deficiency) were associated with increased arterial stiffness in dialysis patients.

Estimating mechanical properties of natural siliceous offshore sands

Large area civil engineering projects, such as offshore wind farms, require extensive soil investigations for detailed soil characterisations. Site-wide geotechnical soil units are commonly defined for simplification due to budgetary constraints. Consequently, practitioners rely on a limited number of costly laboratory tests and a set of semi-empirical CPT correlations, predominantly established based on research sands, for deriving sand parameters. A recent publication by the authors highlights some valid concerns about currently often applied idealisation when deriving strength parameters of natural sands and presents some possible pathways to address the limitations with a grading curve parameter (d10 +d30 ). In the current paper, the size of the original laboratory test database is increased to improve the robustness of the methods. In addition, the database is used to also explore the potential of the d10 +d30 -parameter to improve estimations of drained stiffness parameters. However, since the current database mainly consists of relatively fine sands with varying fines content, a previously published database of much coarser clean sands is applied to investigate the limitations of the presented methods. Finally, a new independent trial database is collected to demonstrate the performance of the new methods for estimating drained strength and stiffness parameters compared with commonly applied industry-acknowledged methods. Even though limitations of the presented methods are identified for coarser clean sands, significantly improved reliability is demonstrated when deriving drained strength and stiffness parameters of relatively fine and slightly silty to very silty siliceous offshore sands.

Small pouches, but high nicotine doses-nicotine delivery and acute effects after use of tobacco-free nicotine pouches.

Tobacco-free nicotine pouches are new nicotine products for oral consumption. They can contain very high nicotine amounts that have not been addressed with clinical studies yet. Thus, nicotine delivery, effects on craving, and side effects were assessed using pouches with up to 30mg nicotine. In this single-center, five-arm, crossover study, 15 regular cigarette smokers consumed tobacco-free nicotine pouches from different brands with 6, 20, and 30mg for 20min. Comparators were nicotine-free pouches and tobacco cigarettes. At baseline and predefined time points over a study period of 240min, plasma nicotine concentrations, effects on cigarette craving, and side effects were assessed. Cardiovascular parameters including arterial stiffness were measured using a MobilOGraph. Consumption of 30mg nicotine pouches has led to a higher nicotine uptake compared with the cigarette (Cmax: 29.4 vs 15.2ng/mL; AUC: 45.7 vs 22.1ng/mL × h). Nicotine uptake in the acute phase was rapid during use of the 30mg pouch and cigarette. Extraction rate of nicotine differed between pouches. Use of all products has reduced acute cigarette craving, even the nicotine-free pouch. During consumption of the cigarette and the pouches with 20 and 30mg, heart rate increased about 27, 12, and 25 bpm, respectively. Parameters for arterial stiffness were elevated and all pouches have induced mouth irritations. The pouches with 30mg nicotine had overall the strongest side effects and may induce addiction. As craving was also reduced by products with less nicotine, it is questionable whether such high nicotine contents should be allowed on the market. A limit of nicotine content is warranted. The nicotine release rate varies across products and needs to be known to estimate the nicotine delivery.

Two-Dimensional Shear-Wave Elastography of the Thyroid in Clinically Healthy Dogs in Different Age Groups.

The thyroid of dogs has not been extensively studied in 2D shear-wave elastography, making it challenging to apply this technique in the diagnosis of thyroid diseases in a non-invasive manner. The aim of this study is to evaluate the thyroid glands of healthy dogs using 2D shear-wave elastography in order to establish qualitative and quantitative parameters of tissue stiffness in dogs in different age groups. A total of 31 dogs of various breeds, sexes, and sizes were evaluated. Animals with clinical signs or ultrasound findings indicative of endocrine disease or thyroid lesions were excluded from the study. The shear-wave velocity data in meters per second (m/s) and color elastograms were evaluated and calculated using QelaXto™ 2D software. A healthy thyroid exhibits a blue-color elastogram, indicative of low stiffness. The reference range for the shear-wave velocity of thyroid tissue assessed by 2D shear-wave elastography can be between 1.6 and 2.0 m/s, with a variation of ±0.889 in adult and senior dogs.

Research on the stability prediction for multi-posture robotic side milling based on FRF measurements

In robotic side milling, frequent chatter extremely restricts the acquisition of high surface quality due to weak stiffness, and cutting parameters optimization guided by stability boundary is regarded as an effective solution to solve the chatter problem. In this research, the influence mechanisms of stability were analyzed by evaluating the structural static stiffness and dynamic parameters, and the main factor was characterized as regenerative chatter by means of stability measurements and the theoretical prediction model. The distance-driven multi-posture frequency response function (FRF) prediction model was improved in terms of the dominant modal. Grey correlation analysis was carried out to investigate the influence law of robotic joints to modal parameters, and the difference between far-distance posture and near-distance posture was re-characterized by cross-validation of FRF measurements. Finally, the third-order Hermite–Newton approximation was employed to solve the dynamic model by considering process damping effect, and the results showed the prediction accuracy of the constructed stability boundary was over 85%.

Nonlinear Wave Interaction of Nanorods Embedded in a Viscoelastic Medium

Abstract Purpose Nonlinear interactions between two acoustic waves in nanorods traveling at various wave numbers, group velocities, and frequencies are examined in this study. Methods The nonlinear equation of the nanorod in a viscoelastic medium is obtained using the theory of nonlocal elasticity. Furthermore, the multiple-scale expansion method is applied to study strongly dispersive, weakly nonlinear waves in a nonlocal viscoelastic medium. Using this expansion technique, we can derive the coupled nonlinear Schrödinger equations as the governing equations, which we solve as differential equations of some parameters by expanding the field quantities into an asymptotic series of the smallness parameter. Results We give the nonlinear plane wave solutions to these equations in several special cases. The plane wave solutions show how the wave amplitude affects the frequencies of nonlinear plane waves. Additionally, we show numerically how the real and imaginary parts of the group velocities and natural frequency of the system for a carbon nanotube in a viscoelastic medium are affected by the nonlocal, damping, and stiffness parameters.

Vibration analysis of graphene-reinforced porous aluminum-based variable-walled thickness sandwich joined conical-conical panel with elastic boundary conditions using differential quadrature method

In this paper, a unified solution is proposed to investigate the vibration characteristics of the variable-walled thickness graphene-reinforced porous aluminum-based (GRPA) sandwich joined conical-conical panel (JCCP) with the arbitrary elastic support boundary conditions by using the differential quadrature method (DQM). The two surfaces of the sandwich JCCP are made of metallic aluminum and the central core layer is the GRPA. The core thickness of each conical plate varies linearly with its generatrix. Three types of the graphene distributions and two types of porosity distributions are considered along the core thickness direction. Based on the first-order shear deformation theory (FSDT), von-Karman strain displacement relationship, constitutive relationship and Hamiltonian principle, the partial differential governing equations of motion are obtained for the variable wall thickness GRPA sandwich JCCP. Using the DQM, the dynamic equation is discretized into the ordinary differential equation. The matrix of the characteristic equation is analyzed to solve the frequencies and mode shapes of the variable wall thickness GRPA sandwich JCCP. The effects of the spring stiffness, boundary conditions, graphene distributions, porosity distributions and geometric parameters on the vibration properties are studied for the variable wall thickness GRPA sandwich JCCP with two interesting elastic supported boundary conditions. At the same time, this article provides a useful approach for studying the arbitrary boundary coupled plate and shell structures with the variable wall thickness.

Should aortic stiffness parameters be used in MIS-C patient follow-up?

We evaluated the short- and long-term effects of multisystem inflammatory syndrome in children (MIS-C) on their cardiovascular system. The study population consisted of 38 MIS-C patients and 55 control patients. Standard echocardiographic measurements and aortic stiffness parameters were compared between the two groups at different time points. During the standard echocardiographic examination at the time of diagnosis, mitral valve insufficiency was detected in 42% of the cases, left ventricular systolic dysfunction in 36%, aortic valve insufficiency in 3%, tricuspid valve insufficiency in 13%, and coronary artery dilatation in 31%. The ejection fraction, pulse pressure of the experimental group were significantly lower than the control group (p < 0.01, p = 0.045, respectively). When aortic stiffness parameters were compared, it was seen that the parameters increased in the experimental group and the difference was significant for aortic distensibility. (p = 0.105, p = 0.029 respectively). When comparing the experimental group's results at diagnosis and at the sixth month, there was a decrease in aortic stiffness parameters at the sixth month compared to the time of diagnosis, but the difference wasn't significant (p = 0.514, p = 0.334). However, no statistically significant difference was detected when comparing the aortic distensibility results of the experimental group with the control group at the sixth month (p = 0.667). Our results showed that many pathological echocardiographic findings detected at diagnosis in MIS-C patients returned to normal within six months. Therefore, we believe that the cardiovascular follow-up period of MIS-C cases should be at least six months.

Home exercise is considered essential, but patient compliance remains a mystery

BackgroundRegular exercise is essential in the treatment of Ankylosing Spondylitis (AS), as the main goals of the treatment are to reduce pain, restore function, avoid disability and structural deterioration, and improve quality of life (QoL). The purpose of this study is to ascertain whether patients adhere to exercise recommendations and to evaluate the effects of consistent exercise on patients' pain, function, disease activity, mood, and quality of life. Many studies emphasize the need for exercise in treatment of AS, but none reveal whether patients follow prescribed practices and the results of doing so.ResultsExercising group had significantly decreased pain, erythrocyte sedimentation rate and Bath ankylosing spondylitis functional index and Bath ankylosing spondylitis disease activity index (BASDAI) scores (p < 0.05). There was no significant difference between the two groups in morning stiffness, mood, spinal mobility, and QoL parameters (p > 0.05). Regular exercise was positively correlated with physiotherapy history. Regression analysis revealed that with an increase of 1 unit in visual analog scale and BASDAI, regular exercise decreased by 0.087 and 0.116 units, respectively.ConclusionOur study revealed how much the patients considers and follows the recommended exercises and concluded that regular exercise habits should be developed since they offer promising effects in treatment of AS, hence, patients should be educated in this area, and particular exercise routines should be developed to encourage them to exercise.