Journal of Mechanics in Medicine and Biology

A mathematical model is developed to study the characteristics of blood flow through flexible inclined arteries under the influence of an inclined magnetic field. The blood is supposed to be couple stress fluid and the geometry of wall surface of inclined arteries is taken as peristaltic wave. The expressions for axial velocity, volume flow rate, pressure gradient and stream function are obtained under the assumptions of long wavelength and low Reynolds number. The effects of different physical parameters reflecting couple stress parameter, Hartmann number, Reynolds number, Froude number, inclination of channel and inclination of magnetic field on velocity profile, pressure and frictional force are discussed. The stream lines are drawn for various values of emerging parameters and the trapping phenomenon is discussed. The significant features of the blood flow characteristics are analyzed by plotting graphs and discussed numerically in detail.

The heel-pad as a biological shock absorber has an important role in the initial contact phase of gait cycle dissipating the impact forces resulted in locomotion. An axisymmetric finite element model of human heel-pad has been generated and the heel-pad experimental data deduced from a published force-deflection graph of the same specimen (Iain R. Spears, Janice E. Miller-Young), Iterative identification task has been used to extract nonlinear material properties describing hyper-elastic behavior of heel-pad. The genetic algorithm was incorporated into estimation process using an interface program. Two parameters of hyper-elastic materials potential energy function represented by Mooney–Rivlin were determined by using the genetic algorithm technique to minimize the displacement error between the experimental data and the corresponding finite element results after a considerable number of iterations. The result can be used for design and construction of synthetic heel-pad and therapeutic foot wear as well as insoles, especially for diabetic patients.

In this article, we considered the peristaltic flow of Newtonian incompressible fluid of chyme in small intestine. The analysis has been performed using an endoscope. The peristaltic flow of chyme is modeled by assuming that the peristaltic wave is formed in non-periodic mode comprising two sinusoidal waves of different wave lengths propagating with same speed along the outer wall of the tube. Heat transfer mechanisms have been taken into account, such that the constant temperature and are assigned to inner and outer tubes, respectively. A complex system of equations has been simplified using long wavelength and low Reynolds number approximation because such assumptions exist in small intestine. Exact solutions have been carried out for velocity temperature and pressure gradient. Graphical results have been discussed for pressure rise, frictional forces, temperature, and velocity profile. Comparison of present results with the results of the existing literature have been presented through figures. Trapping phenomena have been presented at the conclusion of the article.

Electrocardiogram (ECG) is a noninvasive, economic, and convenient detecting tool in myocardial ischemia (MI), and its clinical appearance is mainly exhibited by ST-T complex changes. Recently, QRS complex characters in detecting MI were proposed by an increasing number of researchers. In this paper, various QRS complex characters were extracted in ECG, and their relationship was analyzed systematically. As a result, these characters were divided into two groups, and there was good correlation among them in each group, while the correlation between the groups was poor. Finally, these QRS complex characters were applied to myocardial ischemia, and five characters had significant differences after 59 normal ECG recordings verification, which were: QRS upward and downward slopes, transient heart rate, angle R and angle Q in a triangle QRS. Experimental results showed it was apparent that the trend changes of these five characters when MI events occurred were consistent with their relationship. The conduction velocity of action potentials in ventricular depolarization is slower in MI states than in normal states.

The effect of mechanically heterogenized (MCH) microparticles of tumor cells (TCs) on antimetastatic action of dendritic cells (DCs) is studied in C57BL/6 mice with Lewis' carcinoma. DCs isolated from mice spleens and loaded with MCH-TCs are analyzed with flow cytometry methods. MCH-TCs are analyzed with optical and/or electron microscopy. The paper describes an original high-precision medical microvibromill with high-acceleration linear induction motor that generates magnetic levitation to produce mechanical heterogenization of TCs. MCH-TCs have a more asymmetric morphology, larger surface and higher internal structure heterogeneity, and higher concentration of free radicals with respect to conventionally treated TCs. The rate of DCs maturity, being affected by pre-incubation with MCH-TCs is found to be higher than its counterpart treated with conventional TCs. DCs loaded with MCH-TCs show a significantly higher ability to induce proliferation of allogeneic lymphocytes in mixed leukocyte reaction. The inhibition index of metastases formation increases from 42% (conventional TCs) to 66% when DCs are treated with MCH-TCs. The present results demonstrate the feasibility of increasing antimetastatic activity of DCs-based vaccines when MCH-TCs is used for their loading. Mathematical model is developed in order to simulate the processes of capture, processing and presentation of tumor antigens by DCs when using conventional TCs or MCH-TCs.

Hemiplegia means paralysis of half of the body. It commonly occurs following "stroke", which is due to impedance of blood supply to the brain, hence also termed as "cerebrovascular accident" (CVA). As a consequence of this, the brain tissues suffer from ischemic damage resulting in several symptoms, such as mere weakness, numbness to complete loss of power (paralysis). In order to restore or improve the lost functional movement of the body of the stroke-affected and hemiplegic subjects, a method called functional electrical stimulation (FES) has often been employed as the measure of rehabilitation. FES makes use of low levels of electrical current to activate the nerves and then the muscles, affected. The response of the body to this electrically triggered nervous stimulation could be recorded through different bio-signals. In our work, we measured the accelerometers of hemiplegic patient in two states; with FES and without FES. The nonlinear and nonstationary walking-function-related accelerometers are analyzed using recurrence plots (RP), which helps to visualize the dynamic behavior of the signals. The RPs of electromyography (EMG) signals with stimulation showed distinct periodicity and rhythm when compared to that without stimulation. In addition, we extracted recurrence quantification analysis (RQA) parameters from RP to quantify the obtained information from the RP. Lower values were observed for most of the RQA parameters with FES than obtained without FES. This also confirmed the fact that FES is very useful in bringing more order, rhythm and better control in the physical activities of hemiplegic people.

Heart rate is a non-stationary signal and provides a powerful interplay between the sympathetic and parasympathetic nervous systems. The heart rate variation signal can reveal disorders associated with how these nervous systems regulate the heart rate, and hence may contain indicators of this disease state, or warnings about impending or future cardiac diseases. These indicators may be present at all times or may occur at random during certain intervals in the time scale. It is difficult and time consuming to pinpoint these abnormalities in a huge cardiac data set. Heart rate variability (HRV) constitutes a tool for assessing the activities of the autonomic nervous system (ANS). In this work, we have proposed a computer based analytical system to determine the HRV, and analyzed it to obtain HRV Power-spectrum for normal, diabetes and diabetes with neuropathy subjects in deep breathing, standing and supine position. We have then designated indices based on the HRV power-spectra power values and frequency shift of these peaks from their normal frequency values. We have shown the efficacy and sensitivity of these indices, to differentiate between normals, diabetics and diabetics with ischemic heart disease. Thus we have demonstrated how effectively these HRV power-spectral indices can enable diagnosis of diabetic autonomic neuropathy. Finally, we have composed an integrated index made up of these power-spectral indices, to facilitate distinguishing and diagnosing diabetic autonomic neuropathy in terms of just one index or number.

It has been found that a pronounced secondary systolic peak appears on the oscillometric wave recorded by a brachial oscillometric cuff as cuff pressure is raised to a suprasystolic level. This finding has accordingly motivated some studies aimed to explore the potential value carried by the cuff wave for assessing arterial stiffness. However, so far, there remain considerable controversies in the literature regarding the cardiovascular properties that dominate the characteristics of the cuff wave. In this context, we developed a simple arterial-tree model and applied it to investigate the respective influence on the cuff wave of various cardiovascular properties and the associated wave interaction phenomena. It was found that (1) neither aortic stiffness nor brachial arterial stiffness can uniquely determine the time lag (Δt) between the first and secondary peaks of the cuff wave, although both of them significantly influence Δt; and (2) the BAIx (an index that characterize the height of the secondary peak relative to the first) is sensitive to most of the investigated cardiovascular properties and physiological conditions, such as arterial stiffness, intensity of wave reflection in the lower body and heart rate, etc. These findings suggest that the reliability of assessing aortic stiffness based solely on the timings and heights of the two peaks is limited. Moreover, we argued that the controversial findings presented in previous model-based studies are likely to be caused by limitations related to the research objectives or computation conditions of the studies.

At present, there is no quantitative test to definitely diagnose Parkinson's disease (PD). For this purpose, we computed the power spectra of stride and swing signals of normal persons and patients. The evaluation of power spectra in stride on normal group shows that the main peak of the frequency range is in the range of 0.018 to 0.02 Hz. In contrast, the main peak frequency is different in different PD patients. Our studies on swing signal and its power spectra show that there is a significant difference between the amplitude of frequency components between normal and PD groups. Patients show power spectra amplitude even more than 10 times that of normal patients. The clinical data were obtained from http://www.physionet.org. For measuring time intervals, force sensors were used in the plantar portion of the foot. Power spectra of left stride, right stride, and left swing were computed. Frequency domain of power spectra was divided into 10 parts and then the surface area under each part was calculated. We used artificial neural network for classification of these groups. The clinical data was divided into two parts, training and test sets. An accuracy of 93.75% was obtained during training. The test data was used for validation of the classifier and an accuracy of 92.86% was obtained. The proposed classifier may be used as a tool for helping the clinicians to diagnose PD. Surely the final diagnosis should be obtained by an expert neurologist.

Aseptic loosening of cemented hip implants frequently indicates failure by shear or tension of the cement–bone interface. An element-failure algorithm is proposed for the simulation of the mechanical behavior of the cement–bone interface until failure, under tensile and shear loading. To validate the model proposed, analysis on the cement–bone interface properties (elastic modulus, strength and thickness) and failure criteria, as well as mesh convergence analysis, were performed. Numerical results showed that the proposed element-failure method is able to determine the initiation and progression of interface failure in cemented hip replacements.

The incidence of amputation varies between 2.8 and 43.9 per 100,000 of population. Nearly 43% of the lower limb amputations are below knee amputee. One of the prosthesis which has being used for transtibial is patellar-tendon-bearing prosthesis (PTB) developed in the Biomechanics laboratory of California University. It is made of socket, foot and suspension system. The main role of the suspension system is to minimize the motion occurring between residual limb and prosthesis. Any failures in the function of the suspension system increase the interface motion between stump and socket and lead to troubling issues for the prosthesis users. It is not clearly defined which types of suspension systems of this prosthesis have better performance to decrease the pistoning motions. Therefore, the aim of this research was to evaluate the effects of using different kinds of suspension systems on the magnitude of pistoning motion and also on the functional performance of the below knee prosthesis.

Method: A group of 51 below knee amputee participated in this study. The main criteria for selecting the patients were having no contraindications for standing and walking with prosthesis and using the current prosthesis for at least one year. In order to evaluate the efficiency of suspension system on pistoning movement, the distance between some fixed markers on the prosthesis was measured under various weight bearing conditions.

Results: The correlation between the amount of pistoning movement and the type of suspension system was not significant. However, the function of the supracondylar strap and PTB total contact was better than other systems. The amount of pistoning movement differed between left and right sides.

Conclusion: The magnitude of pistoning motion of the stump is not influenced by the type of selected suspension system and the stump length.

This paper develops a model of axonal transport drug delivery that includes three populations (kinetic states) of pharmaceutical agent complexes (PACs), namely PACs transported by dynein motors, PACs freely suspended in the cytosol, and PACs accumulated at the Nodes of Ranvier. The number of model parameters is minimized by recasting governing equations into the dimensionless form. The obtained equations are solved numerically. The dependencies of the three PAC concentrations as well as the diffusion-driven, motor-driven, and total PAC fluxes on the PAC diffusivity and the length of the axon are investigated. Two situations are analyzed: when all kinetic constantans are the same (in this case the dynein-driven PAC flux exceeds the diffusion flux by a large amount) and when kinetic constants describing PAC transition from the freely suspended state are small (in the this case the diffusion-driven flux is the major component of the total flux, but since the diffusion transport mechanism is highly inefficient compared to the motor-driven one for large particles, the total PAC flux is much smaller in this case).

Computational fluid dynamics (CFD) simulations of the flow in an axial blood pump with different blade heights (BH150, BH200 and BH250) were performed in the present study. The flow in the pump was assumed as steady and turbulent, and blood was treated as incompressible and Newtonian fluid. The flow rate increased with the rise in blade heights. At the impeller rotating speed of 20,000 rpm and a pressure of 100 mm Hg, the pump produces a flow rate up to 5 L/min in BH200 and BH250 models. The reverse flow and vortices have been identified in the BH150 and BH200 models in the outlet regions, but not for BH250 model. The high shear stress of the flow in the pump mainly occurred at the blade tips. The BH200 model achieved an expected flow rate up to 5 L/min with 90% of the shear stresses less than 500 Pa and the exposure time less than 22 ms, which has the acceptable shear stress level in the literature.

The reliable knowledge that model-based three-dimensional (3D) fluoroscopy can provide about in vivo joints kinematics is essential to diagnose orthopedic pathologies, develop new prosthesis, and evaluate clinical procedures. To exploit 3D fluoroscopy for the analysis of elbow kinematics, its use was evaluated considering a single model for the forearm or two different models for the ulna and radius. Active elbow flexion-extension and prono-supination motor tasks of a healthy male subject were acquired by means of fluoroscopy. The 3D bone models were automatically aligned to the relevant projections. The pose estimation algorithm sought the tangency condition of the projection rays with the model surface, minimizing a cost function and exploiting an adaptive distance map. Five iterative guided alignments were performed to avoid the final convergence to a local minimum. The results highlighted the critical alignment of the ulna/radius model, particularly when prono-supination is performed. From the physiological motion patterns and given the values of the cost function, 3D fluoroscopy was proven to be applicable to the analysis of the elbow kinematics when single bone models for the ulna and radius are used.

This study focuses on the transmissibility of whole body vibration stimuli through human body in different standing postures to explore the mechanism in which vibration stimuli could be better used as a regimen for bone loss. Five volunteers were guided to stay at three standing postures and imposed of frequency-adjustable vibration stimuli on the plantar surfaces side-alternately. Motion capture system was used to acquire the vibration signals at head, pelvis, knee up, knee down and ankle, from which the transmissibility of vibration stimuli can be obtained. The results showed that transmissibility of vibration stimuli was closely correlated with frequency and skeletal sites. Transmissibility of vibration stimuli in head was much smaller than any other skeletal sites. Transmissibility in the ankle was always in the vicinity of unit one in all the three postures for the vibration stimuli applied side-alternately on the plantar surfaces of both feet. There was an obvious peak around 9 to 11 Hz in the transmissibility curves for knee joint and pelvis. In the resonant peak, transmissibility of vibration stimuli in knee joint and pelvis both exceeded unit one and reached 150%. As the frequency increased after 11 Hz, transmissibility of vibration stimuli decayed rapidly as a function of frequency and dropped to 25% at 30 Hz. This study may help to gain insight into the interaction mechanism between mechanical vibration stimuli and the responses of human musculoskeletal system.

The paper deals with a theoretical investigation of the peristaltic transport of a couple stress fluid in a porous channel. The study is motivated toward investigating the physiological flow of blood in the micro-circulatory system, by taking account of the particle size effect. The velocity, pressure gradient, stream function, and frictional force of blood are investigated, when the Reynolds number is small and the wavelength is large, by using appropriate analytical and numerical methods. Effects of different physical parameters reflecting porosity, Darcy number, couple stress parameter, as well as amplitude ratio on velocity profiles, pumping action and frictional force, streamlines pattern, and trapping of blood are studied with particular emphasis. The computational results are presented in graphical form. The results are found to be in good agreement with those reported by Shapiro et al.⁵² that was carried out for a non-porous channel without consideration of couple stress effect. The present study puts forward an important observation that for peristaltic transport of a couple stress fluid during free pumping, flow reversal can be considerably controlled by suitably adjusting the couple stress effect of the fluid/Darcy permeability of the channel. It is also possible to avoid the occurrence of trapping, by reducing the permeability.

Ventricular arrhythmia, especially ventricular fibrillation, is a type of arrhythmia that can cause sudden death. The aim of this paper is to characterize ventricular arrhythmias using semantic mining by extracting their significant characteristics (frequency, damping coefficient and input signal) from electrocardiogram (ECG) signals that represent the biological behavior of the cardiovascular system. Real data from an arrhythmia database are used after noise filtering and were statistically classified into two groups; normal sinus rhythm (N) and ventricular arrhythmia (V). The proposed method achieved high sensitivity and specificity (98.1% and 97.7%, respectively) and was capable of describing the differences between the N and V types in the ECG signal.

A mathematical study is conducted of the oscillatory hydromagnetic flow of a viscous, incompressible, electrically conducting, non-Newtonian bio-fluid in an inclined, rotating channel with nonconducting walls, incorporating couple stress effects. The constitutive equations for a couple-stress fluid and the Maxwell electromagnetic field equations are presented and then reduced to a set of coupled partial differential equations for the primary and secondary flow. The model is then nondimensionalized with appropriate variables and shown to be controlled by the inverse Ekman number (K² = 1/Ek), the hydromagnetic body force parameter (M), channel inclination (α), Grashof number (Gr), Prandtl number (Pr), oscillation frequency (ω), and time variable (ωT). Analytical solutions are derived using complex variables. The influence of the governing parameters on the primary velocity (u), secondary velocity (w), temperature (θ), primary and secondary flow discharges per unit depth in the channel (Q_x, Q_z), and frictional shear stresses due to primary and secondary flow (τ_x, τ_z), are studied graphically and using tables. Applications of the study arise in the simulation of the manufacture of electrically conducting bio-polymeric liquids and magneto-physiological flow devices.

The transient squeezing flow of a magneto-micropolar biofluid in a noncompressible porous medium intercalated between two parallel plates in the presence of a uniform strength transverse magnetic field is investigated. The partial differential equations describing the two-dimensional flow regime are transformed into nondimensional, nonlinear coupled ordinary differential equations for linear and angular momentum (micro-inertia). These equations are solved using the robust Homotopy Analysis Method (HAM) and also numerical shooting quadrature. Excellent correlation is achieved. The influence of magnetic field parameter (Ha), micropolar spin gradient viscosity parameter (Γ) and unsteadiness parameter (S) on linear and angular velocity (micro-rotation) are presented graphically, for specified values of the micropolar vortex viscosity parameter (R), Darcy number (Da i.e. permeability parameter) and medium porosity parameter (ε). Increasing magnetic field (Ha) serves to decelerate both the linear and angular velocity i.e. enhances lubrication. The excellent potential of HAM in bio-lubrication flows is highlighted.

An improved one-dimensional mathematical model based on the Pulsed Flow Equations (PFE) is derived by integrating the axial component of the momentum equation over the transient Womersley velocity profile, providing a dynamic momentum equation whose coefficients are smoothly varying functions of the spatial variable. The resulting momentum equation along with the continuity equation and pressure-area relation form our reduced-order model for physiological fluid flows in one dimension and are aimed at providing accurate and fast-to-compute global models for physiological systems represented as networks of quasi one-dimensional fluid flows. The consequent nonlinear coupled system of equations is solved by the Lax-Wendroff scheme and is then applied to an open model arterial network of the human vascular system containing the largest 55 arteries. The proposed model with functional coefficients is compared with current classical one-dimensional theories which assume steady state Hagen-Poiseuille velocity profiles, either parabolic or plug-like, throughout the whole arterial tree. The effects of the nonlinear term in the momentum equation and different strategies for bifurcation points in the network, as well as the various lumped parameter outflow boundary conditions for distal terminal points are also analyzed. The results show that the proposed model can be used as an efficient tool for investigating the dynamics of reduced-order models of flows in physiological systems and would, in particular, be a good candidate for the one-dimensional, system-level component of geometric multiscale models of physiological systems.

In this study, the mathematical model of oscillating flow in an annular straight pipe due to an imposed oscillating pressure gradient and with harmonic boundary motion is established. So far, no literature is devoted to investigate the effect of harmonic boundary motion on the velocity profile and shear stress. The Navier–Stokes Equation in the cylindrical coordinate is the governing equation of fluid motion. The exact solution of this system in terms of real function only is presented. This method is more understood and helpful for deeply investigating the internal oscillating flow than the conventional complex method presented by Womersley. It is found that the effects of the boundary motion, the wave frequency, the Womersley number, and the radius ratio on the velocity profile and shear stress distribution are significant.

Intracranial saccular aneurysms tend to be thin walled and stiffer compared with a normal artery. The current work describes computational structural dynamics (CSD) in an anatomically realistic model of a cerebral aneurysm located in the ophthalmic region, using different wall thickness, model data for the artery and aneurysm, and geometry size. The model was obtained from three-dimensional rotational angiography image data. The wall was assumed three-dimensional hyperelastic solid with different thickness in the artery and in the aneurysm regions. The effects of carotid siphon length are reported. The CSD was solved with the finite elements package ADINA. The predictions of stress and strain on the aneurysm wall were compared.

The purpose of this research was to evaluate the standing stability with plantar pressure distribution (PPD), and to assess the effects of limb laterality, ankle inversion and stabilizer on PPD during unipedal standing. Nineteen young healthy adults were requested to stand on different inclined surfaces (level 0° and inclined 10° and 20°) with each foot. Three ankle stabilizer conditions were designed as barefoot control, elastic ankle tape and semi-rigid brace. Statistically analyzed with multivariate analysis of variance, the anterior/posterior (A/P) and medial/lateral (M/L) force ratios and total contact area (TPCA) were the main parameters to evaluate the stability. Compared with non-dominant side, the dominant foot was safer during unipedal standing with significantly greater TPCA, and especially when standing with ankle inversion due to additional significantly greater A/P force ratio. Ankle inversion harmed the stability while standing with the non-dominant foot due to significantly decreased A/P force ratio and local contact areas. Ankle brace improved the standing stability with significantly increased TPCA.

Quantizing the relationship between finger force and multitendoned extrinsic hand muscles could be useful for understanding the control strategies that underlie the coordination of finger movements and forces. The objective of this study is to explore the relationship of fingertip force production and total power of surface electromyography (sEMG) recorded on extrinsic hand muscles under isometric voluntary contraction. Thirteen healthy volunteers were recruited to participate in this study. In the designed force-tracking tasks, all volunteers were required to produce a certain force with either index finger or middle finger to match the target force for 5 s. Meanwhile, the sEMG signals were acquired from two extrinsic hand muscles: extensor digitorum (ED) and flexor digitorum superficialis (FDS). For each trial, sEMG of the effective force segment was extracted; then, the power spectrum was estimated based on autoregressive (AR) model and from which the corresponding total power of sEMG was computed. The experimental results reveal that the total power of sEMG linearly increases with force level regardless of the task finger and extrinsic hand muscle. It is also found that the total power obtained from index finger is significantly less than that of middle finger for FDS at the same force level (p < 0.05), while this kind of statistical significance cannot be found for ED. However, with respect to the measurement of total power, the type of extrinsic hand muscle has not exhibited significantly different contribution to the task finger under a certain fingertip force level. The findings of this study indicate that the total power of the extrinsic hand muscle's sEMG can be used to characterize finger's activities.

The purpose of this study is to discuss the influence of induced magnetic field on the peristaltic flow of an incompressible third-grade fluid in a curved channel. The problem formulation is presented in a wave frame of reference. The continuity, linear momentum, and induction equations lead to the mathematical development. The relations of stream function, pressure gradient, magnetic force function, induced magnetic field, and current density are developed. The effects of embedded parameters are explained by plots.