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System miniaturization and steady progress towards a totally implantable prosthetic system is the current trend in cochlear implant technology. To achieve this objective, the external microphone of present implants needs to be implantable. This goal can be accomplished by placing a miniature accelerometer on the ossicular chain in the middle ear to detect and convert bone vibrations into an electrical...
Rhinomanometry includes a set of methodologies to diagnose pathological alterations of the nostrils and nasal cavities. Some anatomic variations could cause partial or subtotal obstruction of one or both nostrils, leading to insufficient nasal respiration. Rhinomanometry measures the airflow through one nostril at time, while a pad occludes the other. This method has some drawbacks, such as the alteration...
This paper investigates a two-channel Doppler radar sensor that can provide information on the direction of movement. The radar sensor has the advantage of non-invasive, contactless measurements, compared to ultrasound. From theoretical considerations and a working model, we deduce a criterion for extracting points of no movement in a heart cycle. We propose to use this criterion to characterize the...
Gastro-esophageal reflux disease (GERD) is a common cause of chronic cough. However, a low-cost diagnostic tool for linking GERD and cough in a cause and effect relationship is still lacking. In the present study, an intra-esophageal cough detection probe that comprises a miniature white-light interferometric fiber optic pressure sensor is proposed. This innovative catheter provides a custom encapsulation...
Placement accuracy of different types of surgical needles in soft biological tissues depends on a variety of factors. The needles used for prostate brachytherapy procedures are typically about 200mm in length and 1.27-1.47mm in diameter. These needles are prone to deflection and thereby depositing the seeds at a location other than the planned one. Thus tumorous tissues may not receive the planned...
Recent research has exploited the inherent bending of a bevel-tipped needle during insertion, accomplishing steering of the needle by rotating the needle shaft. Combining this technique with the observation that a straight trajectory can be accomplished by spinning the needle at a constant rate during insertion, this paper presents a novel technique for proportional control of the curvature of the...
During the prostate brachytherapy procedure, multiple needles are inserted into the prostate and radioactive seeds are deposited. Stabilizing needles are first inserted to provide some rigidity and support to the prostate, ideally this will provide better seed placement and an overall improved treatment. However, there is much speculation regarding the effectiveness of using regular brachytherapy...
Teleoperated robot-assisted surgical systems provide surgeons with improved precision, dexterity, and visualization over traditional minimally invasive surgery. The addition of haptic (force and/or tactile) feedback has been proposed as a way to further enhance the performance of these systems. However, due to limitations in sensing and control technologies, implementing direct haptic feedback to...
Adult-derived stem cells have recently been found to respond in vivo to inductive signals from the microenvironment and to differentiate into a phenotype that is characteristic of cells in that microenvironment. We examined the differentiation potential of an adult liver stem cell line (WBF344) in a cardiac microenvironment in vitro. WBF344 cells were established from a single cloned non-parenchymal...
"Unequal anisotropy ratios" is an important property of cardiac tissue. Many of the fundamental mechanisms governing how the heart responds to an electrical shock require unequal anisotropy ratios. In this paper, I explain the role of unequal anisotropy ratios using pictures rather than mathematics. My goal is to help you develop physical insight, so you can better understand qualitatively...
Accurate cardiac tissue-based modeling using the bidomain equations requires the incorporation of fine-scale structures observed at the 50-100 micron level. By including such features we can more easily observe how defibrillation shocks lead to total depolarization of the heart. Several modeling studies that have investigated the effect of fine scale structures on defibrillation success have been...
Vagally-induced action potential duration (APD) heterogeneity can lead to the breakdown of atrial flutter into fibrillation. The exact distribution of vagal mediated effects in the atria is unknown, however. This study analyzed canine electrograms in order to determine changes in APD. Electrograms were recorded under control, and left and right vagal nerve stimulation. Simulations in a computer model...
Assessment of brain connectivity among different brain areas during cognitive or motor tasks is a crucial problem in neuroscience today. Aim of this work is to use a neural mass model to assess the effect of various connectivity patterns in the power spectral density (PSD) of cortical EEG, and investigate the possibility to derive connectivity circuits from real EEG data. To this end, a model of an...
Incoming sensory information is first processed in the thalamocortical network. Previous studies showed that the responses generated in the nuclei of this network are behaviorally modulated, suggesting that the processing of the somatosensory information could be state dependent. Most theories, proposed to describe this response modulation have postulated that the thalamic reticular nucleus (TRN)...
We apply an adaptive approach to optimal experimental design in the context of estimating the unknown parameters of a model of a neuron's response. We present an algorithm to choose the optimal (most informative) stimulus on each trial; this algorithm can be implemented efficiently even for high-dimensional stimulus and parameter spaces (in particular, no high-dimensional numerical optimizations or...
A new transient finite element model of extracellular action potentials recording with a microelectrode in a tissue slice is presented. The neuron model is based on the Hodgkin-Huxley equations implemented with a thin film approximation of the neuron membrane. The computations of the membrane potential and currents, as well as that of the intra and extracellular potential fields, are performed at...
This modeling study investigates the functional role of pacemaker neurons in generating stable rhythms in the pre-Botzinger complex, a subcircuit of the respiratory pattern-generating circuitry in mammals. While the presence of pacemakers within the network is without doubt, the percentage and significance of such pacemakers is still unresolved. Here we revisited earlier network simulations by varying...
Motoneurons are known to possess the latent ability to amplify their inputs in a voltage-dependent manner. Additionally, this synaptic amplification is known to be under neuromodulatory control. This paper presents results from a computer modeling study for one possible mechanism, termed electrotonic compression, which could underlie this behavior.
To realize precise simulation of the left ventricular motion, it is important to utilize an accurate myocardial tissue model which can reproduce various characteristics of myocardial tissue contraction. In this study, we show that the nonlinear characteristics of the passive myocardial tissue property is the essential nature of the nonlinear force-velocity relation and present a formulation for hyperelastic...
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