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The onset of second heart sound is triggered by the closure of aortic valve due to the interaction of left ventricle and arterial system. Noninvasive experiments found that RS2 defined by the time delay from the peak of ECG R wave to the onset of the second heart sound had a close inverse correlation with arterial systolic blood pressure. However, no theoretical study has been carried out to investigate...
The onset of second heart sound is triggered by the closure of aortic valve due to the interaction of left ventricle and arterial system. Noninvasive experiments found that RS2 defined by the time delay from the peak of ECG R wave to the onset of the second heart sound had a close inverse correlation with arterial systolic blood pressure. However, no theoretical study has been carried out to investigate...
Computational modeling and simulation can provide important insights into the electrical and electrophysiological properties of cells, tissues, and organs. Commonly, the modeling is based on Maxwell's and Poisson's equations for electromagnetic and electric fields, respectively, and numerical techniques are applied for field calculation such as the finite element and finite differences methods. Focus...
Computational modeling and simulation can provide important insights into the electrical and electrophysiological properties of cells, tissues, and organs. Commonly, the modeling is based on Maxwell's and Poisson's equations for electromagnetic and electric fields, respectively, and numerical techniques are applied for field calculation such as the finite element and finite differences methods. Focus...
One requirement of a chronically implantable, wireless neural interface device is the integration of electronic circuitry with the microelectrode array. Since the electronic IC dissipates a certain amount of power, it will affect the temperature in the tissues surrounding the implant site. In this paper, the thermal influence of an integrated, 3-dimensional Utah electrode array, to be implanted in...
One requirement of a chronically implantable, wireless neural interface device is the integration of electronic circuitry with the microelectrode array. Since the electronic IC dissipates a certain amount of power, it will affect the temperature in the tissues surrounding the implant site. In this paper, the thermal influence of an integrated, 3-dimensional Utah electrode array, to be implanted in...
There is a growing interest in the use of chronic deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. Fundamental questions remain about the physiologic effects and safety of DBS. Previous basic research studies have focused on the direct polarization of neuronal membranes by electrical stimulation. The goal of...
There is a growing interest in the use of chronic deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. Fundamental questions remain about the physiologic effects and safety of DBS. Previous basic research studies have focused on the direct polarization of neuronal membranes by electrical stimulation. The goal of...
When a brief current pulse is incident on excitable cells in cardiac and other nervous tissue, a change in phase of the cell's response is usually observed. In cardiac tissue, the cells are bared to external stimulation of generally positive currents, which depolarize the cells. In this paper an overview of the application of the phase resetting technique (PRT) in several cardiac models is presented...
When a brief current pulse is incident on excitable cells in cardiac and other nervous tissue, a change in phase of the cell's response is usually observed. In cardiac tissue, the cells are bared to external stimulation of generally positive currents, which depolarize the cells. In this paper an overview of the application of the phase resetting technique (PRT) in several cardiac models is presented...
The skull is a tissue with a widely controversial range of conductivity values. This article correlates live skull conductivity measurements with post mortem conductivity measurements with a scaling factor ranging between 2.5 and 4. The scaling factor is validated by a mathematical model that determines the skull conductivity using saline and cerebrospinal fluid (CSF) conductivities and correlated...
The skull is a tissue with a widely controversial range of conductivity values. This article correlates live skull conductivity measurements with post mortem conductivity measurements with a scaling factor ranging between 2.5 and 4. The scaling factor is validated by a mathematical model that determines the skull conductivity using saline and cerebrospinal fluid (CSF) conductivities and correlated...
A framework for modeling the activation of skeletal muscle is presented for studying functional electrical stimulation. A mathematical model of the cellular responses of skeletal muscle, created at AgResearch (Ruakura, New Zealand www.agresearch.co.nz), has been integrated with an anatomical, finite element model of the semitendinosus muscle, which was constructed from CT scans of the hind limb of...
A framework for modeling the activation of skeletal muscle is presented for studying functional electrical stimulation. A mathematical model of the cellular responses of skeletal muscle, created at AgResearch (Ruakura, New Zealand www.agresearch.co.nz), has been integrated with an anatomical, finite element model of the semitendinosus muscle, which was constructed from CT scans of the hind limb of...
The long-term goal of our research is to restore standing function via selective activation of target fascicles in the femoral nerve by a flat interface nerve electrode (FINE). The optimal number and location of contacts within a FINE had not been determined previously. A realistic three-dimensional finite element model based on a cross section of human femoral nerve and FINE is presented. Simulated...
The long-term goal of our research is to restore standing function via selective activation of target fascicles in the femoral nerve by a flat interface nerve electrode (FINE). The optimal number and location of contacts within a FINE had not been determined previously. A realistic three-dimensional finite element model based on a cross section of human femoral nerve and FINE is presented. Simulated...
High frequency alternating current (HFAC) sinusoidal waveforms can block conduction in mammalian peripheral nerves. A nerve simulation software package was used to simulate HFAC conduction block in a mammalian axon model. Eight axon diameters from 7.3 mum to 16 mum were tested using sinusoidal waveforms between 1 kHz to 40 kHz. Block was obtained between 3 kHz to 40 kHz and the current threshold for...
High frequency alternating current (HFAC) sinusoidal waveforms can block conduction in mammalian peripheral nerves. A nerve simulation software package was used to simulate HFAC conduction block in a mammalian axon model. Eight axon diameters from 7.3 mum to 16 mum were tested using sinusoidal waveforms between 1 kHz to 40 kHz. Block was obtained between 3 kHz to 40 kHz and the current threshold for...
Driven by the need for a more anatomically realistic ventricular model and with access to greater computational power the Auckland porcine ventricular model has been re-engineered based on the original anatomical recordings. The model retains an accurate representation of the ventricular geometry including the apex and valve rings and also the underlying tissue microstructure. A computational modeling...
Driven by the need for a more anatomically realistic ventricular model and with access to greater computational power the Auckland porcine ventricular model has been re-engineered based on the original anatomical recordings. The model retains an accurate representation of the ventricular geometry including the apex and valve rings and also the underlying tissue microstructure. A computational modeling...
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