Tissue Engineering
Giti Torkamaan; Ali Fallah; Mahmoud Mofid; Sedighe Ghiasi; Ghadam Ali Talebi
Volume 1, Issue 3 , June 2007, , Pages 215-225
Abstract
In this study 22 male Guinea Pigs, 4-6 months old, weighting 400-450 g were used. A computer controlled indentor system was used to apply a controlled pressure. The applied pressure was 291 mmHg for 3 hours over the trochanter region of animal hind limb. The animals were divided in three groups; in group ...
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In this study 22 male Guinea Pigs, 4-6 months old, weighting 400-450 g were used. A computer controlled indentor system was used to apply a controlled pressure. The applied pressure was 291 mmHg for 3 hours over the trochanter region of animal hind limb. The animals were divided in three groups; in group 1, pressure was applied 3 hours continuously, in group 2, pressure was applied 90 minutes at two days and in group 3, Pressure was applied in two cycles of 90 minutes with 15 minutes rest between them. To study the biomechanical and histological changes, tissue was removed 7 days after pressure application. Uniaxial tensile test was performed at a deformation rate of 20 mm/min. In this test, the contralateral site on the experimental animal served as intra-animal control. Tissue biopsy was taken and stained with H&E and Trichorome for histological examination. Continuous pressure induced muscle necrosis. Also ultimate stress, stiffness, ultimate strain and area under the load-deformation curve decreased significantly. These results suggest that application of continuous pressure is the major cause of ischemia and necrosis of soft tissue.
Biological Computer Modeling / Biological Computer Simulation
Siamak Haghipour; Seyed Mohammad Reza Hashemi Golpayegani; Seyed Mohammad Firouzabadi; Sirous Momenzadeh
Volume 3, Issue 3 , June 2009, , Pages 227-241
Abstract
The procedure of pain formation embarks on primary sensory neurons and then ends in central nervous system which is the first stage in the dorsal horn of the spinal cord. Nowadays the great challenge of some researchers for pain control has been to elucidate the mechanisms that are able to switch the ...
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The procedure of pain formation embarks on primary sensory neurons and then ends in central nervous system which is the first stage in the dorsal horn of the spinal cord. Nowadays the great challenge of some researchers for pain control has been to elucidate the mechanisms that are able to switch the state of the dorsal horn of the spinal cord from an unwanted state to a favorite one. In order to achieve such an aim, a model of the function of the dorsal horn of the spinal cord is extracted in order to be able to control the created pains with changing the parameters of the aforementioned model. In this study a cybernetic model is presented with the aid of bifurcation methodologies and reconstructing the dynamics linked with the process of pain formation via clinical experiment that can express different states in the dorsal horn of the spinal cord as normal, suppressed, sensitized, the functionality of memory, the effect of other primary afferents and the effect of descending signals. Input signals in this model consist of thermal stimulation degree proportional to action potential firing rate from Ab afferents, inhibitory descending signals from midbrain and inhibitory or excitatory descending signal from thalamus and cortex and the output signal is the action potential firing rate from transmission cells in dorsal horn of the spinal cord proportional to pain level have been sensed. The significant and remarkable characteristic of this model is applying a cybernetical model based on a sequence of input-output data which can obviate the drawbacks of other models in which simplification and reduction of terms reduce the operation of components of a system. On the other hand, unlike previous models which have been modeled based on membrane (slow) potential, this model is based on the action potential firing rate from transmission cells of the dorsal horn of the spinal cord that has the adaptability with cellular recording as well as having a higher accuracy.
Biomedical Image Processing / Medical Image Processing
Ali Taalimi; Emadoddin Fatemizadeh
Volume 4, Issue 3 , June 2010, , Pages 231-248
Abstract
Functional magnetic resonance imaging (fMRI) is widely used for investigation of brain neural activity. This imaging technique obtains signals and images from human brain’s response to prescheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear ...
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Functional magnetic resonance imaging (fMRI) is widely used for investigation of brain neural activity. This imaging technique obtains signals and images from human brain’s response to prescheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear behavior in response to a stimulus. In this paper we investigate nonlinear modeling of BOLD signal activity to model the nonlinear and time variant behaviors of this physiological system. For this purpose two categories of nonlinear methods are considered, first those one with emphasis on physiological parameters which affect BOLD response and methods model the input and output of system without any refer to all the hidden state variables (physiological parameters. Balloon model is analzyed and a new approach for activation detection based on this model is introduced. In addition, the Hammerstein-Wiener, NARMA and Volterra kernels are investigated as nonlinear and nonphysiological methods and their ability in detection of activation detection are compared. The Activation detection methods have been applied on the two data sets (real and synthetic). For synthetic data and threshold equal to 0.45, the Jaccard index for Wiener- Hammerstein, NARMA, and Volterra model was 0.9, 1.0, and 0.91, respectively. In real dataset and for optimal threshold (0.35, 0.4, and 0.45) the same index was 0.85, 0.90, and 0.87, respectively.
Biomedical Image Processing / Medical Image Processing
Raheleh Kafieh; Alireza Mehri Dehnavi; Saeed Sadri; Seyed Hamid Raji
Volume 2, Issue 3 , June 2008, , Pages 233-246
Abstract
Cephalometry is the scientific measurement of head dimensions to predict craniofacial growth, plan treatment and compare different cases. There have been many attempts to automate cephalometric analysis with the aim of reducing the time required to obtain an analysis, improve the accuracy of landmark ...
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Cephalometry is the scientific measurement of head dimensions to predict craniofacial growth, plan treatment and compare different cases. There have been many attempts to automate cephalometric analysis with the aim of reducing the time required to obtain an analysis, improve the accuracy of landmark identification and reduce the errors due to clinician subjectivity. This paper introduces a method for automatic landmark detection on cephalograms. We introduced a combination of model-based methods and neural networks on cephalograms. For this purpose, first some feature points were extracted using a nonlinear diffusion filter and Susan Edge Detector to model the size, rotation, and translation of skull. A neural network was used to classify the images according to their geometrical specifications. Using learning vector quantization (L VQ) for every new image, the possible coordinates of landmarks were estimated. Then a modified active shape model (ASM) was applied and a local search to find the best match to the intensity profile was used and every point was moved to get the best location. Finally, a sub-image matching procedure was applied to pinpoint the exact location of each landmark. In order to evaluate the results of this method, 20 randomly selected images were used with a drop-one-out method. Each image had a dimension of about 170x200 mm, digitized in 100 dpi (4 pixel == 1mm). On average, 24% of the 16% landmarks were within 1mm of correct coordinates, 61 percent within 2 mm, and 93 percent within 5 mm. the proposed method in this study has had a distinct improvement over the other proposed methods of automatic landmark detection.
Medical Ultrasound / Diagnostic Sonography / Ultrasonography
Hannaneh Keyhanian; Sayed Mahmoud Sakhaei
Volume 12, Issue 3 , November 2018, , Pages 235-248
Abstract
The method of multi-beam beamforming is a low-computational adaptive beamforming method in which, instead of calculating the covariance matrix and inverting it for each point of the image, only one matrix is calculated for all points on the same radial distance. Then, to reduce the complexity of the ...
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The method of multi-beam beamforming is a low-computational adaptive beamforming method in which, instead of calculating the covariance matrix and inverting it for each point of the image, only one matrix is calculated for all points on the same radial distance. Then, to reduce the complexity of the inverse matrix calculation, the problem is solved in the beamspace domain. We introduce a new two-stage method to reduce the complexity of the minimum variance (MV) beamforming method, which outperforms the beamspace method in computational burden aspect in multi-beam method. In the first step, instead of using the signals of all array elements in calculating the covariance matrix, the signals of a decimated one are chosen such that the resulting covariance matrix contains all the correlation information of the signals. In the second stage, the weights of all elements of the array are determined by a proper interpolation method from the weights of the decimated array. According to the simulation results of point targets and cyst phantom, the new method has a performance similar to that of the beamspace multi-beam method in terms of resolution, contrast, and robustness against the errors with at least 3 times lower computational burden.
Neuro-Muscular Engineering
Abed Khorasani; Abbas Erfanian Omidvar
Volume 5, Issue 3 , June 2011, , Pages 245-255
Abstract
During the last decade, functional neuromuscular stimulation (FNS) has been proposed as a potential technique for restoring motor function in paralyzed limbs. A major challenge to restoring a desired functional limb movement through the use of intramuscular stimulation is the development of a robust ...
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During the last decade, functional neuromuscular stimulation (FNS) has been proposed as a potential technique for restoring motor function in paralyzed limbs. A major challenge to restoring a desired functional limb movement through the use of intramuscular stimulation is the development of a robust control strategy for determining the stimulation patterns. A major impediment to stimulating the paralyzed limbs and determining the stimulation pattern has been the highly non-linear, time-varying properties of electrically stimulated muscle, muscle fatigue, large latency and time constant which limit the utility of pre-specified stimulation pattern and open-loop FES control system. In this paper we present a robust strategy for multi-joint control through intramuscular stimulation in which the system parameters are adapted online and the controller requires no offline training phase. The method is based on the combination of sliding mode control with fuzzy logic and neural control. Extensive experiments on three rats are provided to demonstrate the robustness, stability, and tracking accuracy of the proposed method. The results show that the proposed strategy can provide accurate tracking control with fast convergence.
Biological Computer Modeling / Biological Computer Simulation
Hosein Ghasemi; Mohammad Saeid Saeidi; Bahar Firoozabadi
Volume 7, Issue 3 , June 2013, , Pages 255-264
Abstract
Knowledge regarding particle deposition processes in the pulmonary system is important in aerosol therapy and inhalation toxicology applications. The present work describes a computational model of human lung airway consisting of the three-generation pathway from the trachea down to segmental bronchi. ...
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Knowledge regarding particle deposition processes in the pulmonary system is important in aerosol therapy and inhalation toxicology applications. The present work describes a computational model of human lung airway consisting of the three-generation pathway from the trachea down to segmental bronchi. In order to more appropriately model human air passage, an asymmetric geometry (i.e. three generation airway) is extracted from the 1th to 3th branches of the Hoursfield model and on dealing with the complexities of simulations (e.g. computation time) structured mesh is developed which also leads to more accurate computations. The fully three-dimensional incompressible laminar Navier– Stokes equations and continuity equation have been solved using CFD home code on generated mesh. Computations are carried out in the Reynolds number range of 800–1800, corresponding to mouthair breathing rates ranging from 0.18 to 0.41 l/s, representative. The study leads to establishing relations for overall particle deposition efficiency in the second generation of bronchial tree as a function of two dimensionless groups of Reynolds and Stocks numbers. Furthermore, interpretation of correlations are enlightened the fact of that in the initial generations of bronchial trees, consideration of asymmetric geometry has a significant influence on the particle deposition pattern. The results of the paper are valuable in aerosol therapy and inhalation toxicology.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Marjan Mozaffarilegha; Seyed Mohammad Sadegh Movahed
Volume 11, Issue 3 , September 2017, , Pages 255-264
Abstract
The complexities and the effects of inter-subject variations on the encoding of sounds are features of the brainstem processing. Examining such data based on linear analysis is not reliable, encouraging to take into account non-linear methods which are effective ways of explaining such non-stationary ...
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The complexities and the effects of inter-subject variations on the encoding of sounds are features of the brainstem processing. Examining such data based on linear analysis is not reliable, encouraging to take into account non-linear methods which are effective ways of explaining such non-stationary signals. The purpose of this study is to explore the behavior of the brainstem in response to complex auditory stimuli /da/ using Multifractal Detrended Fluctuation Analysis modified by Singular Value Decomposition (SVD), Adaptive Detrending (AD) and Empirical Mode Decomposition (EMD). Auditory brainstem responses to synthetic /da/ stimuli were recorded for 40 normal subjects with a mean age of 22.7 years. MFDFA is carried out on the s-ABR time series data to evaluate the variation of their complexity and multiscaling. To utilize optimal Detrending of s-ABR time series, AD, SVD and EMD algorithms are applied on time series. By computing the fluctuation function and evaluating scaling behavior, scaling exponents such as generalized Hurst exponent and multifractal spectrum are determined. Given results in this method indicate that underlying signal has non-stationary nature in small scales, but property of system is controlled by trend in large scales. There is a crossover at msec on the behavior of fluctuation function corresponding to dominant sinusoidal trend in all samples. The average of Hurst exponent is at 68% confidence interval in small scales msec. The -dependency of demonstrate that underlying data sets have multifractality nature and are almost due to long-range correlations. The width of singularity spectrum which is a measure of the signal complexity of underlying data in average equates to at confidence interval.
Cell Biomechanics / Cell Mechanics / Mechanobiology
sajad ghazavi; Bahman Vahidi
Volume 10, Issue 3 , October 2016, , Pages 257-266
Abstract
Due to the importance of the brain and neurons, a vast area of research has been conducted in this field. However, due to the complexity of the neural behavior, each study investigated the functionality of neurons from one perspective such as electrophysiological, chemical, or mechanical perspective. ...
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Due to the importance of the brain and neurons, a vast area of research has been conducted in this field. However, due to the complexity of the neural behavior, each study investigated the functionality of neurons from one perspective such as electrophysiological, chemical, or mechanical perspective. In spite of the large number of research conducted on the brain injury topic, there is no study investigating the interaction of the mechanical and electrical characteristics of the neurons and its effect on the cell functionality. Understating the interaction between the mechanical and electrical properties of a neuron will have a substantial effect on treating neurological diseases such as traumatic brain injury and improving treatment methods such as ultrasound. As a result, there is a vital need to simulate the effect of mechanical forces on the electrophysiological behavior of a neuron. This study is one of the few attempts to achieve this goal by taking into account the mechanosensitivity of ion channels which affects the action potentials. Our proposed comprehensive model is based on power law equation (fractional dashpot) for mechanical modeling, Hodgkin Huxley (HH) equation for electrophysiological model and recent experiments for combination of these two equations. Based on the model, the calculated strain from the power law equation affects the activation and inactivation of ion channels. By changing the activation and inactivation variable in the HH equation, we can evaluate the effect of strain and mechanical stimulation on neural function. The results reveal neuron functions’ deficiency during neuron mechanical damage. As a result, action potential signal’s amplitude reduces. This reduction in amplitude of the action potential may be reversible or irreversible based on the amount of damage (plastic deformation).
Malihe Molaie; Reza Aghaeizadeh Zoroofi
Volume 13, Issue 3 , October 2019, , Pages 259-271
Abstract
Quantifying and modeling of the skeletal muscles can lead to an easier investigation of muscle diseases, specific mobility problems, and required simulations for the relevant surgeries. To this end, medical images should be segmented, firstly. In this research, thigh muscles segmentation is performed ...
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Quantifying and modeling of the skeletal muscles can lead to an easier investigation of muscle diseases, specific mobility problems, and required simulations for the relevant surgeries. To this end, medical images should be segmented, firstly. In this research, thigh muscles segmentation is performed in CT images, since these muscles play a critical role in walking and balancing the body. To this aim, a multi-atlas method is used which is an improvement of the hierarchical multi-atlas method in the previous work. In this method, the muscles region is extracted automatically from the other tissues using FRFCM (Fast and Robust Fuzzy C-Means Clustering) method after the preprocessing stage. This muscle binary mask and the improved mask are used in the multi-atlas method for individual muscle segmentation. The proposed method is implemented using 20 CT data sets consisting of 12 female and 8 male subjects. The results show a less consumed computational time than the hierarchical multi-atlas method. The average computational time required for the muscles segmentation using the proposed method is 24 seconds and for the hierarchical multi-atlas method is 71 seconds per one slice of each case. Therefore, the proposed method reduces the implementation time by a rough factor of three. The means of the Dice similarity coefficient for the proposed method with improved muscle mask and for the hierarchical multi-atlas method are 86.58±7.69 and 83.07±8.26, respectively. The means of the precision and sensitivity for our method are 89.78±9.6 and 84.63±9.25, and for the hierarchical multi-atlas method are 88.85±12.04 and 78.04±10.88. Consequently, this method has better results based on the Dice similarity coefficient, precision, and sensitivity metrics.
Biomedical Image Processing / Medical Image Processing
Mahdie Ghasemi; Ali Mahloojifar; Mehdi Omidi
Volume 8, Issue 3 , September 2014, , Pages 261-275
Abstract
Functional changes in the brain motor network are responsible for the major clinical features of Parkinson’s disease (PD). Recent studies on investigation of the brain function show that there are spontaneous fluctuations between regions at rest as resting state network affected in various disorders. ...
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Functional changes in the brain motor network are responsible for the major clinical features of Parkinson’s disease (PD). Recent studies on investigation of the brain function show that there are spontaneous fluctuations between regions at rest as resting state network affected in various disorders. In this paper, we examine changes of functional dependency between brain regions of interest associated with known anatomical pathology in Parkinson Disease (PD) using copula theory on resting state fMRI. Five types of copulas were tested: Gaussian and t (Euclidean), Clayton, Gumbel and Frank (Archimedean). We used an efficient maximum likelihood procedure for estimating copula parameters. Goodness of fits was tested using root mean square error (RMSE) and kulback-leibler divergence between each copula function and joint empirical cumulative distribution. Control vs PD group comparison was also done on dependency parameter using parametric and nonparametric tests. The results show that functional dependency between cerebellum and basal ganglia is much stronger in PD than in control. In this paper, we proposed for the first time that joint distribution characteristics could potentially provide information on discriminative features for functional connectivity analysis between healthy and patients.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Parastoo Sadeghinia; Hamed Danandeh Hesar
Volume 16, Issue 3 , December 2022, , Pages 271-287
Abstract
Phonocardiography (PCG) signals provide valuable information about the heart valves .These auditory signals can be useful in the early diagnosis of heart diseases. Automatic heart sound classification has a promising potential in the field of heart pathology. In this research, a new method based on machine ...
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Phonocardiography (PCG) signals provide valuable information about the heart valves .These auditory signals can be useful in the early diagnosis of heart diseases. Automatic heart sound classification has a promising potential in the field of heart pathology. In this research, a new method based on machine learning techniques is proposed for discriminating normal and abnormal heart sounds. In this method, first, the heart sounds are segmented into 4 main parts: S1, S2, systole and diastole segments. From these segments, statistical and time-frequency features are extracted for classification. Before classification, the distinctive features are selected using two approaches. In the first approach, the feature selection is accomplished using particle swarm optimization algorithm (PSO). In the second approach, we use Sequential Forward Feature Selection (SFFS) method. The proposed method was evaluated on the Physionet 2016 Challenge database using 10-fold cross-validation method. In this database, the number of normal and abnormal PCG signals are not balanced. Therefore, in this paper, the synthetic minority over-sampling technique (SMOTE) is applied to produce balanced data. The evaluation results showed that the proposed method can distinguish the normal heart sounds from abnormal ones with accuracy of 98/03% and sensitivity and specificity of 97.64%, 98.43%respectively.
Musculoskeletal Systems Modeling
Sharareh Kian-Bostanabad; Mahmoud Reza Azghani; Leila Rahnama
Volume 9, Issue 3 , December 2015, , Pages 283-291
Abstract
Cervical multifidus muscle is one of the neck extensor muscles that plays an important role in the neck stability. By observing the different behaviors for this muscle during the six shoulder activities in previous study, it was modeled within the software and the effect of its action on the different ...
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Cervical multifidus muscle is one of the neck extensor muscles that plays an important role in the neck stability. By observing the different behaviors for this muscle during the six shoulder activities in previous study, it was modeled within the software and the effect of its action on the different shoulder activities evaluated as a parametric study. For this end, a biomechanical model of the human locomotion system, which includes muscles of the shoulder, forearm and hand and 3 joints, was considered. After finding the maximum strength in six movement directions of the shoulder joint including flexion, extension, internal rotation, external rotation, abduction and adduction, the strength of 0, 25, 50, 75 and 100 percent of the maximum strength applied to model for each activities separately and the percentage of cervical multifidus and shoulder muscles activities have been saved. Moreover, applied torques by these muscles during different activities have been measured by calculating their effective torque arm. Assesing the relationship between the strength of cervical multifidus muscle with contraction level using the regression models showed a high correlation between these two factors during abduction, external rotation and extension activities (R2= 0.96-0.997). The produced torque by this muscle is more than the main muscles during the abduction and external rotation activities. This study showed that cervical multifidus muscle disfunction in addition to effect on the range of motion of neck, can be effective on the shoulder joint activities that it should be considerd in NIOSH lifting equation for individuals with neck pain.
Yaser Rezaei Moghaddam; Seyed Mehdi Rezaei; Mahnaz Shamshirsaz; Mohammad Zareinejad; Mohammad Reza Dehghan
Volume 6, Issue 4 , June 2012, , Pages 299-305
Abstract
In vitro fertilization (IVF) is a solution to overcome the problem of infertility of couples .Lately with the development of technology and using robotic systems, telesurgery systems are used in order to increase the accuracy, better control of needle movement and preventing injury to the ovum cell while ...
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In vitro fertilization (IVF) is a solution to overcome the problem of infertility of couples .Lately with the development of technology and using robotic systems, telesurgery systems are used in order to increase the accuracy, better control of needle movement and preventing injury to the ovum cell while injection in IVF. To provide better control of injection, haptic systems are used. In this study, a haptic system is designed with virtual reality environment in order to perform In vitro fertilization. For modeling of injection force, point-load model is utilized. A mass-spring model is used to simulate cell deformation during insertion. Simulation results have a good conformity with related researches.
Tissue Engineering
Mohsen Rabbani; Mohammad Tafazzoli Shadpour; Zahra Goli Malekabadi; Mohsen Janmaleki; Mohammad Taghi Khorasani; Mohammad Ali Shokrgozar
Volume 3, Issue 4 , June 2009, , Pages 307-314
Abstract
Vital function of the cell is correlated with the mechanical loads that the cell experiences. The cell shape and morphology are also related to its mechanical environments. Different methods have been proposed to obtain cell groups with the same morphology and alignment which considered desirable features ...
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Vital function of the cell is correlated with the mechanical loads that the cell experiences. The cell shape and morphology are also related to its mechanical environments. Different methods have been proposed to obtain cell groups with the same morphology and alignment which considered desirable features in tissue engineering applications. For instance, applying cyclic loading makes cells elongated and aligned as bundles in a specific direction to the tension axis. Applying static stretches also affect the cells morphology, extra-cellular matrix, enzymes secretion and genes expression. The effect of applying in vivo static stretch on cellular alignment was evaluated in this study. Human mesenchymal stem cells (hMSCs) were cultured on the elastic membrane, and then subjected to static stretch. The results demonstrated that applying a 10% static stretch for 24 hours aligns intra-structure actin filaments and applying a 20% static stretch had a significant effect on the arrangement of the oriented fibers.
Biomedical Image Processing / Medical Image Processing
Hadi Jafariani; Hamid Abrishami Moghaddam; Mohammad Shahram Moein
Volume 1, Issue 4 , June 2007, , Pages 311-318
Abstract
One of the most accurate techniques for human identification is based on the uniqueness of the retinal blood vessels pattern. In this paper, we present a new approach for human identification using retina image. This approach is insensitive to rotation, scaling and translation. The Fourier-Mellin transform ...
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One of the most accurate techniques for human identification is based on the uniqueness of the retinal blood vessels pattern. In this paper, we present a new approach for human identification using retina image. This approach is insensitive to rotation, scaling and translation. The Fourier-Mellin transform coefficients and moments of the retinal image were used to extract the suitable features. To compensate the rotational effects caused by different relative positions of the retina scanner with respect to the eye, a rotation compensator was designed. For retinal image interpretation, the optic disc location was considered as a fixed and reference point. For its localization, the Haar wavelet and the Snakes model were used. The experimental results demonstrated an error rate close to zero for the proposed method.
Mohammad Ali Ardakani; Vahid Reza Nafisi
Volume 2, Issue 4 , June 2008, , Pages 325-333
Abstract
Hot-wire anemometry (HWA) is a suitable method for pulmonary research and routine tests. This anemometry method has high frequency response, calibration stability, low pressure drop and desired precision over whole clinical range of human respiration. Nevertheless, flow direction detection in inspiratory ...
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Hot-wire anemometry (HWA) is a suitable method for pulmonary research and routine tests. This anemometry method has high frequency response, calibration stability, low pressure drop and desired precision over whole clinical range of human respiration. Nevertheless, flow direction detection in inspiratory and expiratory phases is one of the main problems in this method. We apply the obstacle-wake probe as a solution. In this probe, an obstacle is inserted between 2 bot-wire sensors; and the effects of the shape and relative position of the obstacle and hot-wire sensors are discussed. Finally the results are used in manufacturing a clinical spirometer. It satisfies common clinical/research demands along with inspiratory/expiratory flow direction detection.
Rehabilitation Engineering
Vahab Nekoukar; Abbas Erfanian Omidvar
Volume 4, Issue 4 , June 2010, , Pages 327-336
Abstract
One major limitation of walker-supported walking using functional electrical stimulation (FES) in paraplegic subjects is the high energy expenditure and the high upper body effort. Paraplegics should exert high amount of hand force to stabilize the body posture and to compensate lack of the sufficient ...
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One major limitation of walker-supported walking using functional electrical stimulation (FES) in paraplegic subjects is the high energy expenditure and the high upper body effort. Paraplegics should exert high amount of hand force to stabilize the body posture and to compensate lack of the sufficient torques at the lower extremity joints. In this paper, we introduce a 2-D musculoskeletal model of walker-assisted FES-supported walking of paraplegics. Using the developed model and an optimal controller, the stimulation patterns are determined such that the tracking errors of lower joint reference trajectories are minimized and the muscle activations and the handle reaction force (HRF) are reduced. Outputs of the optimal controller are stimulation patterns of the lower body muscles and torque acting on the upper body joints. The results show that the HRF and ground reaction force (GRF) generated by simulation are in agreement with the measured HRF and GRF. Moreover, the results indicate that the simulation-generated stimulation patterns of lower body muscles are in consist with the stimulation patterns reported in the literatures.
Biomechanics / Biomechanical Engineering
Maedeh Najafi Ashtiani; Mohammad Reza Asghari Oskoei; Mohammed Najafi Ashtiani
Volume 12, Issue 4 , January 2019, , Pages 331-340
Abstract
Balance is essential for human daily activities. Standing on an unstable platform requires continuous effort of the neuro-musculoskeletal system. Cognitive interference and support surface perturbation may cause loss of balance. The aim of this study is to evaluate the ability of stability provision ...
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Balance is essential for human daily activities. Standing on an unstable platform requires continuous effort of the neuro-musculoskeletal system. Cognitive interference and support surface perturbation may cause loss of balance. The aim of this study is to evaluate the ability of stability provision of individuals while standing in different levels of postural and cognitive difficulty. To this end, twelve healthy young women were participated in six levels (three levels of support surface × two levels of cognitive intereference). Three levels support surface were standing on a firm surface, unstable platform surface with and without spring support. Two levels of attentional cognitive involvements were considered with or without questions by presenting on a curtain and asking to response by a yes/no joystick. Motion analysis was used to measure joint angles by capturing body movements in the sagittal plane by a high-speed camera and active markers. To quantitatively investigate the stability, two linear (pathlength, root mean square) and two nonlinear (approximate entropy, fractal dimension) metrtics were calculated. Results showed that the ankle mechanism plays a more prominent role in keeping balance than the knee and hip joint mechanisms. Merely the approximate entropy indicated significant differences between the postural difficulty levels. Also, the mediocre level of support surface perturbation (spring-supported unstable platform) revealed multi-joint collaboration between the mechanisms. The inconsistence between postural and cognitive difficulty levels might vanish the role of cognitive questions in the present study. Therefore, considering consistent postural and cognitive tasks may highlight the effects of cognitive involvements on standing.
Targeted Drug Delivery / Smart Drug Delivery / Drug Targeting
Mohammad Koohimoghadam; Adel Torkamaan Rahmani
Volume 5, Issue 4 , June 2011, , Pages 333-351
Abstract
Discovery of new drugs and study of their side effects has been an important research field in recent years. Because of direct effect of the pharmaceutical products on human health usually the drug design projects are challenging and technically demanding. The incorporation of computer simulations into ...
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Discovery of new drugs and study of their side effects has been an important research field in recent years. Because of direct effect of the pharmaceutical products on human health usually the drug design projects are challenging and technically demanding. The incorporation of computer simulations into drug design projects is one of the best ways to optimize drugs' potency. In this approach, researchers try to find the best interaction between protein structure and drug in a virtual environment; this procedure is called "molecular docking". The molecular docking problem can be considered as a search problem. The search space in this problem is defined with all possible protein-ligand interactions and the best interaction is the solution of problem. In this paper, a new approach for finding the best interaction is proposed. The proposed method is based on opposition based differential evolution algorithm. Also the proposed method is enhanced by a local search algorithm and a pseudo-elitism operator. Like other metaheuristic algorithms, our method uses a population of possible solution and AutoDock scoring function is used to evaluate each vector in the population. Six different protein-ligand complexes are used to verify the efficiency of the proposed algorithm. The experimental results show that the proposed algorithm is more robust and reliable than other algorithms such as simulated annealing and Lamarckian genetic algorithm.
Computational Neuroscience
Maryam Sadeghi Talarposhti; Mohammad Ali Ahmadi-Pajouh; Frazad Towhidkhah
Volume 14, Issue 4 , February 2021, , Pages 333-344
Abstract
Human being is capable of performing more than one task simultaneously. This ability has been investigated in many researches. Performing more than one task at the same time has always been a challenging topic in psychology and human perception fields. The output and the effect of two tasks have been ...
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Human being is capable of performing more than one task simultaneously. This ability has been investigated in many researches. Performing more than one task at the same time has always been a challenging topic in psychology and human perception fields. The output and the effect of two tasks have been studied in previous researches for understanding the brain’s performance and also the disease origin and the symptoms. The influence of different difficulty levels has been explored via discrete-continuous motor-cognitive dual-task (DT). To this aim, a manual tracking task combined with discrete auditory stimuli to establish DT procedure. Twenty-five participants in this paradigm were asked to track the target on screen while reacting to the auditory task at the same time. Two levels of difficulty in manual tracking plus a single auditory task (ST) were considered for the experiment. The variability of output via different difficulties was investigated by analyzing factors of error rate and the response time (RT). For this analysis, a Drift Diffusion Model (DDM) method was used. In this 4-parameter model, the drift parameter is assumed to show the difficulty levels. The results show that by applying different drift rates (the average of 0.5, 0.3, and 0.2), the model is consistent with experimental output RT and the drift factor has the potential to be considered as the difficulty factor in the DT procedure.
Biomimetics
Hiwa Sufikarimi; Karim Mohammadi
Volume 11, Issue 4 , February 2018, , Pages 337-349
Abstract
In this paper, we tried to present a robust and reliable approach to object recognition by inspiring human visual system. A famous model, inspiring mammalian visual system, is HMAX (Hierarchical Model and X). It shows significant accuracy rates on object recognition tasks. However, there are some differences ...
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In this paper, we tried to present a robust and reliable approach to object recognition by inspiring human visual system. A famous model, inspiring mammalian visual system, is HMAX (Hierarchical Model and X). It shows significant accuracy rates on object recognition tasks. However, there are some differences between this model and human visual system. Indeed cortex's functions are not properly modeled. Unrepeatability under fixed conditions, redundancy, high computing load and being slow are some drawbacks of HMAX. By modeling the secondary visual cortex and adding to the HMAX, we tried to introduce a more accurate model of the human visual system and cover the drawbacks of the previous models. The proposed approach functionally mimics the secondary visual cortex. Attending to high-level features, selecting discriminative and repeatable features, it has higher performance than standard HMAX. The added parts have negligible computation load. Therefore, it does not slow down this model. On the contrary, by selecting brief and useful features, the speed of the model is increased. The proposed approach is compared to the standard HMAX in terms of speed and accuracy rate. The results showed the advantage of proposed approach rather than the standard HMAX. In addition, the effect of the number of features and training images on their performance was shown. It is shown that the proposed approach has a better performance than the standard HMAX especially when the number of feature and training images is small.
Biomechanics of Bone / Bone Biomechanics
Mahmoud Reza Azghani; Sharareh Kian-Bostanabad; Tara Ahmadi; Hamid Khabiri
Volume 10, Issue 4 , January 2017, , Pages 339-346
Abstract
Long bone fracture is the most prevalent traumatic fractures that accures due to the strike and attacted load exertions, which one of them is the butterfly fracture. This type of fracture may happen with sudden and combined forces. Since in this type of fracture, the number of fracture lines is more ...
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Long bone fracture is the most prevalent traumatic fractures that accures due to the strike and attacted load exertions, which one of them is the butterfly fracture. This type of fracture may happen with sudden and combined forces. Since in this type of fracture, the number of fracture lines is more than other types of fractures, developing a prohibitive method may be usfull. The present paper is aimed to investigate the effects of strain rate and use of fastener on butterfly fracture in bone samples. To this end, invivo sheep metacarpal bone samples were examined in four groups: distinguished based on different strain rates, loading conditions and boundry conditions. The first one underwent pure bending at rate of 20 mm/s. The second group and third group experience combined bending and axial compression at rate of 5 mm/s and 20 mm/s, respectively. Bone samples in the fourth group, however, sustained combined loading of bending and axial compression while their ends had been fixed. Comparison between the first and third groups significantly stated that exerting axial compression increases the number of butterfly fractured samples. Results show that at the higher strain rates, the number of butterfly fracture increases. Constraining the ends of the bone samples, on the other hand, led to dissipate the effects of combined loading and also high strain rate. Furthermore, a considerable accordance was observed based on Pearson Correlation test by amount of 0.947.
Orthotics & Prosthesis
Mostafa Lashgari; Farzan Ghalichi; Behnam Mirzakouchaki
Volume 7, Issue 4 , June 2013, , Pages 341-349
Abstract
Orthodontic specialists interest in study of tooth movement mechanic, such as the relationship between applied force and the rate of tooth movement in orthodontic treatment. It is because of the complexity and variety of factors that can affect orthodontic treatment. The friction force at the contact ...
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Orthodontic specialists interest in study of tooth movement mechanic, such as the relationship between applied force and the rate of tooth movement in orthodontic treatment. It is because of the complexity and variety of factors that can affect orthodontic treatment. The friction force at the contact surfaces with an undetermined magnitude, makes the orthodontic treatment unpredictable. In this study, friction coefficient and forces were investigated in new designed bracket that had beveled edge which has been modeled based on standard bracket. Torque, tip and angulations angles of the brackets slot are designed. Arch wires were modeled by two rectangular and circular cross-sections and the effect of geometry on the stress distribution and the friction force was investigated using Finite Element Method (FEM). The results have showed that the stress concentration generated in the bracket which has been the most curvature, decreased compared to the standard bracket at the contact wire and bracket braces. In addition, results have showed that friction in the beveled edge bracket was significantly decline compared to the standard bracket and also are less than the type with minor curvature. Results of investigation of friction between the two types of round and square wire, have revealed that the round wire has lower friction and confirmed previous studies. Finally, due to the reduced friction in the brackets which have been the most curvature, this type of design is appropriate to decrease friction force.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Tahereh Taleei; Ali Motie Nasrabadi
Volume 15, Issue 4 , March 2022, , Pages 341-353
Abstract
To interact with such an ever-changing environment in which we live, our brain requires to continuously generate and update expectations about relevant upcoming events and their estimation for the corresponding sensory and motor responses. The goal of this study is to investigate the connectivity in ...
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To interact with such an ever-changing environment in which we live, our brain requires to continuously generate and update expectations about relevant upcoming events and their estimation for the corresponding sensory and motor responses. The goal of this study is to investigate the connectivity in time perception in the two predictable and unpredictable conditions. The data needed for the study from EEG signals recorded from the existing database that included an experiment was conducted on 29 healthy subjects in the two predictable and unpredictable conditions and in 4 delays of 83, 150, 400, 800 ms for each person was done. To estimate the functional connectivity between brain regions, we used the phase lag index method. This method is used to detect time perception in two conditions, predictable and unpredictable events. Initially, by comparing the two conditions in 4 delays was shown that more of the differences were in the gamma, beta, and theta bands. Also, the significant difference between the delays in the predictable condition was greater than the unpredictable condition. Then, the difference between the two conditions in each delay was discussed. The results showed a significant difference in all delays. The alpha band in the unpredictable condition in 400-ms delay, the number of connectivity between occipital and temporal regions was increased and stronger, and also the mean of the unpredictable connectivity was higher than predictable condition. In the delta band for 150, 400 and 800-ms delays, there was connectivity between the central and frontal regions, whereas in 83-ms-delay there was stronger connectivity between the central and prefrontal regions. The right hemisphere of the prefrontal is important in time perception. At the longest delay (800 ms), in three bands, delta, theta, and beta, connectivity decreased in both conditions compared to the other delays.
