Journal of Mechanics in Medicine and Biology

One of the goals of affective computing field is to provide to computers the ability to recognize automatically the affective state of the user in order to have more intuitive human–machine communication. This paper aims to detect automatically the stress user when he is interacting with computer. The developed system is based on instantaneous pulse rate (PR) signal extracted from imaging photoplethysmography (PPG). Seven features from time and frequency domain are extracted from PR signal and processed by learning pattern recognition systems. Two methods based on Support Vector Machine (SVM) and Linear Discriminant Analysis (LDA) are used and compared to classify the user’s emotional state. A computer application based on “Stroop color word Test” is developed to elicit emotional stress in the subject. The proposed method can achieve the overall average classification accuracy of 94.42% and 91.10% with SVM and LDA, respectively. Current results indicate that our approach is effective for stress classification.

Several types of middle ear implants (MEIs) have been invented as an alternative to conventional hearing aids for the rehabilitation of sensorineural hearing loss. Temporal bone and clinical studies have shown that the implantation of MEIs’ transducers influences middle ear transfer function. But there is little comparative data available about these influences. We conducted comparative studies on the influences of three principal types of MEI transducers in respect to their attachment points on the ossicular chain. To aid the investigation, a human middle ear finite element model was constructed. The model was built based on a complete set of micro-computerized tomography section images of a human ear by reverse engineering technology. The validity of the developed model was verified by comparing the motions obtained by this model with published experimental measurements on human temporal bones. The results show that the eardrum driving transducer (EDT) and the floating mass transducer (FMT) decrease stapes displacement prominently at high frequencies. The greater these transducers’ mass, the smaller is the displacement of the stapes footplate. In contrast, the incus body driving transducer (IBDT) decreases stapes displacement severely at low frequencies, and its adverse effect on residual hearing increases with increasing stiffness of the IBDT’s driving rod.

The lever ratio, the vibration mode and the stiffness of the ossicular joints were studied using the finite element (FE) analysis of the response of human ear under the outer ear sound excitation. The three-dimensional FE model was constructed based on serial micro CT images of a temporal bone block, and validated through comparison with the experimental data from previous literatures. The displacements of the umbo and stapes footplate and the vibration mode of the ossicles under different grades of stiffness of middle ear components were derived. It is suggested that the flexible ossicular joint combined with the shift of rotation axis causes the increase of lever ratio at high frequency. In addition, the flexible incudostapedial joint (ISJ) can reduce sound transmission especially at high frequency, meanwhile it also permits more vibration energy transmitted to the piston-like directions.

Coracoclavicular space fixation with suture loops is a well-known surgical technique for the treatment of dislocations. However, out of 100 different surgical treatments no single one has been established as a gold standard. The following research aims to improve the technique and focuses on a development of new fixation technique using composite sutures, which would withstand forces during ligament healing process. Three different fixation techniques (one loop and two separate suture loops and W-system) were tested on a custom built mechanical testing device. Applied load was continuously increased at a loading rate of 30N/min until the failure of the sutures. Ultimate tensile strength and suture elongation at failure were measured. The W-system had statistically significant higher load to failure and higher stiffness compared to one loop and two separate loops techniques. Biomechanical properties of a suture fixation technique can be improved by connecting them into one system to create particular arrangement of the sutures. The measurements can be easily repeated and this testing protocol can serve as a good starting point to standardize procedures of evaluation of different joint fixation techniques and to develop new ones.

Malfunction of the cardiovascular system is a serious disease affecting human life around the world that is caused by several factors. One of the major factors is atherosclerosis that is a disease of the artery. Atherosclerosis is a serious vascular condition, which always occurs in branch vessels such as the abdominal aortic bifurcation and the carotid artery bifurcation. Wall shear stress (WSS) and wall pressure gradient (WPG) pertaining to these vessels will dramatically change when the geometry of these vessels is varied. Computational hemodynamics, as an invasive method, can be employed to understand the blood flow characteristics. In this paper, blood flow through arteries with variable side branches is presented using a computational framework. Numerical models pertaining to the different side-branch bifurcation angles are simulated to verify this. The side-branch bifurcation angle correlates positively to the maximum WSS experienced by the artery and this has an effect on atherogenesis. The low WPG regions are found to decrease with increased values of the angles, while the high WPG regions concentrate in the same region with larger values. Such hemodynamics information can be used to understand the effect of arterial geometrical variation on hemodynamics and the causes of atherosclerosis.

Coronary bypass surgery is a usual therapy for vessel-related diseases as several thousand of this kind of surgery are reported annually. In this surgery, saphenous vein, internal mammary artery or radial artery are grafted to replace coronary vessels. This research aims to evaluate viscoelastic properties of human saphenous vein vessel wall used in bypass surgery using a device designed in our laboratory. The most important feature of this device is its ability to simulate physiological conditions which exist inside humans’ bodies. During experiments, variations in both vessel diameter and exerted pressure are recorded simultaneously. After performing measurements at frequencies near to heart beat frequency and finding loss and storage modulus for each frequency, it is found that, in the scanned frequency range, Kelvin model is the best approach to assess viscoelastic behavior of vessels. Remarkably, the results found in this research are in agreement with literature.

A liquid jet injector is a biomedical device intended for drug delivery. Medication is delivered through a fluid stream that penetrates the skin. This small diameter liquid stream is created by a piston forcing a fluid column through a nozzle. These devices can be powered by springs or compressed gas. In this study, a CFD simulation is carried out to investigate the fluid mechanics and performance of needle free injectors powered specifically by compressed air. The motion of the internal mechanisms of the injector which propels a liquid jet through an orifice is simulated by the moving boundary method and the fluid dynamics is modeled using LES/VOF techniques. In this paper, numerical results are discussed by comparing the fluid stagnation pressures of the liquid jet with previously published experimental measurements obtained using a custom-built prototype of the air-powered needle free liquid injector. Performance plots as a function of various injector parameters are presented and explained.

Using of forceps during labors and vaginal delivery accomplished operative deliveries in some circumstances. Forceps may induce fractures in the neonatal skull if excessive force is applied to it during an operative delivery. Therefore, newborns may be affected by forceps. The aim of this study was to investigate the effects of different curve angles and materials of the blades of forceps on neonates during labor or delivery for gynecologists and obstetricians using a finite element analysis (FEA). Computer models of the forceps, neonate’s scalp, and skull, were generated for the FEA. Moreover, the use of different materials (stainless steel and titanium alloy) and three different angles of the blades of forceps (20${}^{\circ }$, 40${}^{\circ }$, and 60${}^{\circ }$) on a newborn’s head were simulated in a biomechanical analysis. The results indicate that a larger curve angle of the blades of forceps can decrease the stress and pressure on the neck of the newborn but may lead to rotation toward the posterior side. Moreover, forceps made of a lower Young’s modulus material can also reduce the stress and pressure on the neck of the newborn. It is hoped that this research can provide a more reasonable reference for manufacturers to design better medical equipment such as forceps in the future for obstetricians and gynecologists to use to attenuate the stress and pressure on the neck of a newborn.

In this paper, we investigate the effects of heat and mass transfer on peristaltic motion of magnetohydrodynamic (MHD) viscous fluid in a symmetric channel in the presence of Hall and ion-slip currents, viscous and Joule dissipations, and variable temperature-dependent viscosity. The governing field equations are solved using series solution under the normal assumptions of long wavelength and low Reynolds number. The pumping characteristics are obtained using numerical integration. The results are critically analyzed for the physical parameters that characterize the peristaltic motion. These parameters include amplitude ratio, volume flow rate, viscosity parameter, Brinkman number, heat generation parameter, magnetic parameter, Hall parameter and ion-slip parameter. The results are presented graphically to understand the behavior of the field quantities and the physics of peristaltic transport of physiological and industrial fluids. Special emphasis has been given to analyze the effects of heat transfer with viscous and Joule dissipations — essentially the new features added in this study.

Morphological and positional factors that can affect the actual performance of the hearing-support (HS) devices are utilized to support the damaged hearing ability of the sensorineural hearing-impaired persons. However, there have been few studies that demonstrated the effects of variations in such design factors on the frequency response of the device experimentally. In this study, the effect of design variations in the shape of the microphone cover on the housing and the wearing position of the device mounted on the ear on the input frequency response of the device and on the performance of an embedded beamforming algorithm were investigated using a human upper body model, a hearing aid housing model, and an acoustic environment model using computer simulation. Experimental results showed that the implemented simulator could simulate the actual acoustic situations (differences less than 5 dB in audible frequency range) and that both of the response patterns of the device and beamforming algorithm were varied in accordance with the variations in the shape of the microphone cover and the mounting position of the device on the ear. These results demonstrate the necessity of additional design and algorithm fine-tuning of each (HS) device to improve its actual speech enhancement performance.

Unsteady pulsatile flow of blood through a porous-saturated, tapered and overlapping stenotic artery in the presence of magnetic field is examined theoretically and computationally. The power law constitutive model is employed to simulate hameo-rheological characteristics. The governing equation is derived assuming the flow to be unsteady, laminar, uni-directional and one-dimensional (1D). A robust, finite difference method is employed for the solution of the governing equation, subject to appropriate boundary conditions. Based on this solution, an extensive quantitative analysis is performed to analyze the effects of blood rheology, body acceleration, magnetohydrodynamic parameter, permeability parameter and arterial geometrical parameters of stenosis on various quantities of interest such as axial velocity, flow rate, resistance impedance and wall shear stress. The computations demonstrate that velocity, flow rate and shear stress increase while resistance to flow decreases with greater permeability parameter. Additionally, the effects of magnetic field are observed to be converse to those of permeability i.e., flow is decelerated and resistance is increased, demonstrating the powerful utility of exploiting magnetic fields in hemodynamic flow control (e.g., intra-corporeal surgical procedures). Furthermore, the size of trapped bolus of fluid is also found to be reduced for large values of the permeability parameter indicating that progressively more porous media circumvent bolus growth.

One of the complication of cervical laminoplasty is the restenosis of the opened laminae. Weakness of the screws placed on laminae may cause restenosis. Here, we describe a new technic ‘spinolaminoplasty (Turkish Open-door laminoplasty)’ with newly designed titanium mini plate that placed one side to lateral mass, and the other on spinous process to keep the laminae opened. Two different fixation materials were used for axial compression tests. One was Ultra high molecular weight polyethylene block with cervical vertebrae geometry and fresh ovine cervical vertebrae. In the first group, mini plates were fixed on laminae as in the conventional method described by Hirabayashi. In the second group, mini plates were fixed on spinous process to perform spinolaminoplasty with single and double screws. New fixation method with double screw provides 26% higher stiffness than the closest group, namely new fixation on polyethylene block. And new fixation method with double screw was exhibited significantly higher ($P<0.005$) performance between the Ovine groups. As in the spinolaminoplasty technic fixing the mini plates to spinous process with longer screws instead of laminae, strengthens the system compared to the conventional method. This proves that rigidity of new construction model is more stable than the conventional method. Tight fixed laminae may prevent restenosis. Also applying the screw through spinous process instead of laminae may prevent the possible cord injuries.

In the biomedical field, Near-Infrared Spectroscopy (NIRS) is often used to determine the physiological information by the noninvasive detection of the regional tissue oxygen saturation (rSO₂). Because the fatigue degree of body could be obviously demonstrated by the oxygen saturation under different vibration conditions, an effective technology to evaluate the vibration comfortability by rSO₂ is innovatively proposed in this paper. Without losing generality, the vibration comfortability is analyzed by taking the driving position for example. Different from much more factors in previous approaches, only four main body factors, i.e., brain, musculus biceps brachii, erector spinae and biceps femoris, and three main influence factors on vibration comfortability, i.e., acceleration, frequency, and exposure time, are taken into account in our technology. Under different conditions of the three vibration factors, the rSO₂ for the four body factors is detected one by one. Then the relationship among the rSO₂, subjective feeling, and the vibration parameters can be obtained by the least square method, and the quantitative evaluation model on vibration comfortability is established. It is found experimentally that the rSO₂ trends of musculus biceps brachii, erector spinae and biceps femoris are all greatly increased with the acceleration and frequency, but brain is decreasing obviously. Through our experiment it is verified that this technology can be used in objectively and effectively evaluating under different vibration conditions. This novel technology could provide theoretical support for vibration comfortability assessment and have potential applications in other relative fields.

In this paper, we have studied the application of drug delivery in magnetohydrodynamics (MHD) peristaltic blood flow of nanofluid in a non-uniform channel. The governing equation of motion and nanoparticles are modeled under the consideration of creeping flow and long wavelength. The resulting non-linear coupled differential equation is solved with the help of perturbation. Numerical Integration has been used to obtain the results for pressure rise and friction forces. The impact of various pertinent parameters on temperature profile, concentration profile such as density Grashof number, thermal Grashof number, Brownian motion parameter, thermophoresis parameter and MHD is demonstrated mathematically and graphically. The present analysis is also applicable for three-dimensional profile.

Natural silk fibroin fiber is slowly degraded, which makes it difficult to be replaced quickly by regenerating tissues of tissue engineering. We used poly(lactic-co-glycolic acid) (PLGA, lactic acid:glycolic acid $=$ 10:90) fibers to adjust the overall degradation rate of the scaffolds. This study fabricated a three-strand helical composite rope-like scaffold from silk fibroin and PLGA fibers (silk fibroin:PLGA $=$ 36:64) using a twisting method. In vitro and in vivo degradation experiments were performed over 16 weeks. Results suggest that the in vitro and in vivo degradation tendencies of the scaffold were similar, with mass loss lagging behind mechanical property loss. The speed of degradation in vivo was faster than that in vitro. Mechanical property loss of the scaffold was fast during the first three weeks, when mass loss was slow. Mass loss rate accelerated from weeks 3 to 8. The mass and mechanical properties were relatively stable from 8 to 16 weeks. After 16 weeks of degradation, the scaffold still had considerably strong mechanical properties. The scaffold showed a reasonable and suitable degradation speed with good histocompatibility for ligament tissue engineering.

The growth plate is a cartilaginous structure located in the metaphysis of long bones, characterized histologically by its stratification and columnar arrangement. It is responsible for assuring longitudinal growth. Evaluation of growth plate histological characteristics has been traditionally performed using qualitative observation; however, some quantitative approaches have been reported using complex techniques. Here, we propose a simple quantitative images based analysis in order to evaluate objectively columnar arrangement within growth plate. For this, we defined six descriptors that were condensated in a geometric tensor. This tensor could be used as a single parameter to evaluate the growth plate organization. Validation of the tensor was performed with growth plate microphotographs of three healthy species (rat, pig and rabbit) and an abnormal one (Csf1^tl/Csf1^tl rat) found in specialized literature. According to our results, the descriptors and the tensor give a complete picture of the organization of the growth plate, reflecting the expected stratification and columnar arrangement of the cells within the tissue. This methodology could be a reliable tool for evaluation of growth plate structure for research and diagnostic purposes, taking into account that it can be easily implemented.

Most of the anatomical changes related to the body of pregnant women occur between the second and third trimesters of pregnancy. The purposes of the study were to quantify the lower limb kinetics of gait and draw a comparison between women in the second and third trimesters of pregnancy, and a nonpregnant group. Subjects and methods: A three-dimensional (3D) kinetic analysis of gait was performed in 24 pregnant and 12 nonpregnant women. Results: Between trimesters of pregnancy, a decrease in the third peak of vertical ground reaction force (GRF) in the third trimester was observed. Most of the changes found between pregnant and nonpregnant women were in the sagittal plane for hip, knee and ankle moments, which report a decrease in mechanical load of the lower limb. In frontal plane a significant decrease in ankle joint moment was found, and in the transverse plane a significant increase in hip moment was found. Joints power decreases for hip and ankle power in sagittal and frontal plane, and increases for hip power in transverse plane. The function of propulsion and mobilization appears to be related to the different changes that occur between the right leg and left. Conclusion: These results suggest that adaptations regarding muscle participation occur first (second trimester), followed by adaptations in muscle power (third trimester). Understanding the biomechanical adaptations during pregnancy may provide more information about mechanical loads, which subsequently will be helpful for prescribing exercise and rehabilitation programs, as well as for the prevention of musculoskeletal injuries.

In this research, intestinal anastomosis was compared in hand and automatic suturing. This work is based on two different experiments: The first one is the tensile test with the aim of finding the maximum breaking strength with the elongation rate of 5mm/min; and the second one is the fatigue test with a frequency of 0.2Hz and the amplitude of 16, 24 and 32mm of stretch in each phase to discover the total number of cycles to failure. For this purpose, 42 fresh bovine intestines were used; 21 specimens for the tensile and 21 for the fatigue test. These two tests were compared by two hand sewing techniques: simple continuous and ford interlocking stitches, and one automatic technique, i.e., the lock stitches. Seven samples were examined for each particular technique. The results of the tensile test indicated that the breaking strength of automatic sutured specimens is significantly greater than those of hand sutured specimens ($p=1.31\mathrm{\text{e}}-5$). That might be due to the regularity, as the suturing lines by machines are more regular than suturing by hand. In addition, results showed that automatic sutured specimens failed in greater number of cycles than hand sutured specimens in the fatigue test ($p=2.86\mathrm{\text{e}}-6$).

In the present paper, we have studied the effects of endoscope and heat transfer on the peristaltic flow of second grade fluid through an inclined tube. The endoscope is a solid circular cylinder which is inserted in a peristaltic tube, and the flow takes place through the gap between endoscope and the peristaltic tube. The endoscope is maintained at a temperature $T_1$, while the outer tube has a sinusoidal wave traveling down its wall and is exposed to temperature $T_0$. The flow is investigated in a wave frame of reference moving with the velocity of the wave. The equations governing the flow of second grade fluid are modeled in cylindrical coordinates. Using perturbation method, the solutions are obtained for the stream function, pressure gradient and temperature fields. The pressure difference and frictional force at both the walls are calculated using numerical integration. The graphical results are presented to interpret the effect of various physical parameters of interest. It is found that, velocity increases with an increase in inclination angle and the best pumping rate appear in the vertical tube as compared to the horizontal tube. It is also found that, the heat generation parameter has an increasing effect on the velocity of the fluid.

Pressure ulcers, involving sub-dermal tissue damage and originating in deep tissue injury (DTI), have attracted much attention of physicians and researchers for three decades. Finite element (FE) model is a very efficient tool to investigate internal stresses and strains in human body that induce pressure ulcers. However, there was scarce report available to explore stresses distribution in human buttocks during manual wheelchair propulsion. A three-dimensional (3D) comprehensive FE model, incorporating ischial tuberosities (ITs), muscle, fat, and custom-contoured cushion (CCC), was developed to investigate internal stress distribution in soft tissue of the buttocks. Based on the FE model, pressure distribution under ITs in static sitting and during different wheelchair propulsions is studied. Internal stresses in fat and muscle were about three times and five times higher than that on cushion surface in terms of static sitting and wheelchair propulsion. All peak pressures under wheelchair propulsion were higher than those of static sitting, and peak pressures went on increasing with increase of wheelchair movement speed. This method based on the comprehensive FE model allowed for the optimization of wheelchair seat cushion design.

The effects of wear mechanisms on the long-term survivorship of artificial hip implants emphasized the importance of determining the 3D volumetric wear in retrieved hip replacements. Traditional methods for determining the volumetric wear on acetabular cups require reference surface from a pre-worn model, which is not feasible for clinical retrieved implants. In this study, a methodology based on co-ordinate measuring machine (CMM) measurement is proposed to reconstruct the reference surface by applying a mathematical model on those selected unworn regions of the acetabular liners. For validation purposes, three polyethylene liners from 5-million-cycle hip simulator testing were employed, whose wear volume at different measurement points was determined by applying the developed method and the results were compared to those determined via traditional approaches. Volumetric loss estimated by the developed method was found to correlate well with the results estimated by the traditional methods ($R^2=0.9949$). Moreover, two surgically retrieved inserts were analyzed using the developed methodology. The wear volume estimated from the two retrieved liners was also found to agree well with the observation from X-ray photograph. Results demonstrated that the proposed method is effective in determining the volumetric wear for retrieved components providing viable unworn regions on the liner.

Purpose: Construct a finite element model of the human eye to quantitatively analyze the mechanical characteristics of the human eye, especially the glaucoma damage process of the optic nerve head (ONH). Method: First, the geometry model of the human eye with nonuniform thickness was established based on a reasonable hypothesis and assumptions. Because the ONH is an important factor for glaucoma, we refine the structure of the ONH with lamina cribrosa. Then, mesh division was applied for finite element analysis. To simplify the complexity of the analysis, the materials of the model were assumed to be isotropic linear elastic materials, and physical properties such as Young’s modulus and Poisson’s ratio were set according to published literature. Next, proper constraints and loads were applied to the model and solved with a finite element method. Result: A finite element model of the human eye was created to simulate the mechanical characteristics of the eye structures under high intraocular pressure (IOP). The ONH depressed 1.057mm under 0.009MPa pressure to simulate high IOP. Conclusion: The constructed model is able to quantitatively simulate excavation of the optic disc and damage of the optic nerve. The result proved Houcheng Liang’s hypothesis about the ONH damage mechanism in glaucoma.