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We present a preliminary study of combined anterior posterior (AP) and medial lateral (ML) sway assuming a classic inverted pendulum with included subtalar movement. Based on a feedback control posture model in the sagittal plane as presented by Maurer and Peterka [1], we have investigated parameters needed to model ML sway components. Center of Pressure (COP) data was collected from a population...
Unobtrusive sleep monitoring allows older adults to have continuous monitoring during the night in their own homes. We propose a method to reliably estimate respiratory rate using a bed-based pressure sensor array. Movements are detected prior to respiratory rate estimation and suppressed. The amount of movement during an estimate and a weighting for the estimate are used to create a reliability metric...
Pulse transit time (PTT) has been reported correlated with heart rate (HR) and blood pressure (BP), however, the results are not consistent in different investigations. Towards a better understanding of the underlying mechanisms of the PTT changes, this study compares the power spectrum density of the variability in PTT with that in HR and BP under rest and post-exercise physiological conditions....
The vestibule ocular reflex (VOR), in which cerebellum is intimately involved to produce compensatory eye movements during head motion to stabilize retinal image. The VOR is under adaptive control whose gain (eye velocity/head velocity) can be modified by visual-vestibular mismatch stimuli. It exhibits frequency selectivity in which largest gain change is observed at the training frequency. Currently,...
The ability to change or adapt is critical in the survival of a species. Research has shown that the dynamics of disparity vergence eye movements, the inward (convergence) or outward (divergence) turning of the eyes, are malleable and depend to some extent on the amplitude of preceding stimuli. Divergence eye movements are dependent on initial stimulus position where responses that occur closer to...
This paper investigates the specific contributions of the pre-ejection period (PEP) and pulse transit time (PTT) for blood pressure estimation based on the pulse wave methodology. We show that in short-term physical stress tests, PEP dominates PTT variations raising the question of a suitable blood pressure calibration. A model using a generalized pulse wave velocity achieves acceptable accuracy for...
Near-infrared spectroscopy (NIRS) is a useful technique for noninvasive measurement of muscle oxygenation. However, analyses of the dynamic changes in muscle metabolism based only on experimental observations of NIRS are difficult. Therefore, we constructed a mathematical model of muscle metabolism, comprising of the ATP synthesizing systems and O2 diffusion system, to identify the mechanisms responsible...
Stroke patients have a decreased ability in performing activity of daily living (ADL) tasks such as in `drinking a glass of water', `turning a key', `picking up a spoon', `lifting a bag', `reaching a bottle' and `lifting and carrying a bottle'. These tasks can be quantified by measuring forces and torques exerted on the objects. However, the resulting force and torque time series represent information...
Theory and previous studies showed that KLT (an application of principal component transform for imaging) can be use for analysis of cardiac function. This paper presents the results of our studies concerning the applications of KLT for images smoothing, quantification of myocardial contraction, and improvement of inter-observer reproducibility in cardiac imaging. The paper also describes the use...
It is estimated that over 200 million people worldwide have osteoporosis. The prevalence of osteoporosis is continuing to escalate with the increasingly elderly population. The major complication of osteoporosis is an increase in fragility fractures leading to morbidity, mortality, and decreased quality of life. This investigation aimed at profiling the incidence and risk of osteoporosis in adult...
The purpose of the current study was to evaluate the clinically used epidural anesthesia needles based on quantitative comparative data. Precise measurement of the tip shape and puncture force analysis were conducted on six different needles. Tip angle (alpha+beta) and tip length (L) were measured by X-ray computed tomography (CT). The one-axial puncture force through a silicone phantom (thickness...
Heart tracking in ultrasound sequences is a difficult task due to speckle noise, low SNR and lack of contrast. Therefore it is usually difficult to obtain robust estimates of the heart cavities since feature detectors produce a large number of outliers. This paper presents an algorithm which combines two main operations: i) a novel denoising algorithm based on the Lyapounov equation and ii) a robust...
Real time left ventricular (LV) pressure-volume (P-V) loops have provided a framework for understanding cardiac mechanics in experimental animals and humans. Conductance measurements have been used for the past 25 years to generate an instantaneous left ventricular (LV) volume signal. The standard conductance method yields a combination of blood and ventricular muscle conductance; however, only the...
The efficiency of heart pump function greatly depends on synchronized contraction of myocardial muscle. In this work, contraction simulation of an excitable ventricular tissue cable was constructed to study the influence of excitation patterns on tissue contraction. The tissue cable is composed of elements which contract when excited by an external stimulus. In each calculation step, contraction force...
Osteoarthritis (OA) of knee is the most commonly occurring non-fatal irreversible disease, mainly in the elderly population and particularly in female. Various invasive and non-invasive methods are reported for the diagnosis of this articular cartilage pathology. Well known techniques such as X-ray, computed tomography, magnetic resonance imaging, arthroscopy and arthrography are having their disadvantages,...
This paper proposes a simplified distributed-parameter model of the brachial-radial arteries segment for the determination of mechanical parameters of these arteries and compares it with a four-element Windkessel model. The comparison is performed using data collected noninvasively of pressure pulse waveforms at two different locations of the arterial segment, under physiological (normotensive) and...
Employing the analysis of a biomarker, an oculomotor angle and a subjective evaluation, we have examined the acute, psychological effect human stress of driving using a motor-vehicle driving simulator. Salivary amylase is used as a biomarker, as it is considered to be one of the indicators of sympathetic nervous activity. 20 healthy female subjects in their early twenties were enrolled in this study...
Compared to cardiac ischemia, relatively little is known about ischemia that develops within the gastrointestinal system. The work presented here is a first step towards developing a detailed anatomically and biophysically based model of the mesenteric arterial system of the human intestine to be used to simulate normal and compromised blood flows. Data from the Visible Human project were used to...
Cardiac mechanics attempts to relate loading (stress), deformation (strain), and material properties (stress-strain relationships) in the normal and diseased heart. Currently, imaging is employed in cardiac mechanics almost exclusively to track myocardial strains; a number of available methods and their relative strengths and weaknesses are discussed. Looking forward, reliable techniques to image...
The following two characteristics have been well demonstrated concerning the features of a point-to-point human arm movement on a plane. (1) The path is a roughly straight line, but is slightly curved. (2) The velocity profile is bell shaped with a single peak. Several models have been proposed to explain these features. Four criteria for trajectory planning based on optimal principles have been proposed...
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