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Articles 1 - 7 of 7
Full-Text Articles in Physics
Scroll Waves In The Presence Of Slowly Varying Anisotropy With Application To The Heart, S. Setayeshgar, Andrew J. Bernoff
Scroll Waves In The Presence Of Slowly Varying Anisotropy With Application To The Heart, S. Setayeshgar, Andrew J. Bernoff
All HMC Faculty Publications and Research
We consider the dynamics of scroll waves in the presence of rotating anisotropy, a model of the left ventricle of the heart in which the orientation of fibers in successive layers of tissue rotates. By choosing a coordinate system aligned with the fiber rotation and studying the phase dynamics of a straight but twisted scroll wave, we derive a Burgers’ equation with forcing associated with the fiber rotation rate. We present asymptotic solutions for scroll twist, verified by numerics, using a realistic fiber distribution profile. We make connection with earlier numerical and analytical work on scroll dynamics.
Mode Locking In A Periodically Forced Integrate-And-Fire-Or-Burst Neuron Model, S. Coombes, R. Owen, Gregory D. Smith
Mode Locking In A Periodically Forced Integrate-And-Fire-Or-Burst Neuron Model, S. Coombes, R. Owen, Gregory D. Smith
Arts & Sciences Articles
The minimal “integrate-and-fire-or-burst” (IFB) neuron model reproduces the salient features of experimentally observed thalamocortical relay neuron response properties, including the temporal tuning of both tonic spiking (i.e., conventional action potentials) and post-inhibitory rebound bursting mediated by the low-threshold Ca2+ current, IT. In previous work focusing on experimental and IFB model responses to sinusoidal current injection, large regions of stimulus parameter space were observed for which the response was entrained to periodic applied current, resulting in repetitive burst, tonic, or mixed (i.e., burst followed by tonic) responses. Here we present an exact analysis of such mode-locking in the integrate-and-fire-or-burst model under …
On The Effect Of Electron Plasma Waves With Relativistic Phase Velocity On Large-Angle Stimulated Raman Scattering Of Modulated Short Laser Pulse In Plasmas, Nikolai E. Andreev, Serguei Y. Kalmykov
On The Effect Of Electron Plasma Waves With Relativistic Phase Velocity On Large-Angle Stimulated Raman Scattering Of Modulated Short Laser Pulse In Plasmas, Nikolai E. Andreev, Serguei Y. Kalmykov
Serge Youri Kalmykov
Suppression of a large-angle stimulated Raman scattering (LA-SRS) of a short modulated (two-frequency) laser pulse in a transparent plasma in the presence of a linear long-wavelength electron plasma wave (LW EPW) having relativistic phase velocity is considered under the conditions of weak and strong coupling. The laser spectrum includes two components with a frequency shift equal to the frequency of the LW EPW. The mutual influence of different spectral components of a laser on the SRS under a given angle in the presence of the LW EPW is examined.
N-Methyl-D-Aspartate Channel And Consciousness: From Signal Coincidence Detection To Quantum Computing, Armando F. Rocha, Alfredo Pereira Jr
N-Methyl-D-Aspartate Channel And Consciousness: From Signal Coincidence Detection To Quantum Computing, Armando F. Rocha, Alfredo Pereira Jr
Armando F Rocha
Research on Blindsight, Neglect/Extinction and Phantom limb syndromes, as well as electrical measurements of mammalian brain activity, have suggested the dependence of vivid perception on both incoming sensory information at primary sensory cortex and reentrant information from associative cortex. Coherence between incoming and reentrant signals seems to be a necessary condition for (conscious) perception. General reticular activating system and local electrical synchronization are some of the tools used by the brain to establish coarse coherence at the sensory cortex, upon which biochemical processes are coordinated. Besides electrical synchrony and chemical modulation at the synapse, a central mechanism supporting such a …
Eddy Structures Induced Within A Wedge By A Honing Circular Arc, C. P. Hills
Eddy Structures Induced Within A Wedge By A Honing Circular Arc, C. P. Hills
Articles
In this paper we outline an expeditious numerical procedure to calculate the Stokes flow in a corner due to the rotation of a scraping circular boundary. The method is also applicable to other wedge geometries. We employ a collocation technique utilising a basis of eddy (similarity) functions introduced by Moffatt (1964) that allows us to satisfy automatically the governing equations for the streamfunction and all the boundary conditions on the surface of the wedge. The circular honing problem thereby becomes one-dimensional requiring only the satisfaction of conditions on the circular boundary. The advantage of using the Moffatt eddy functions as …
Eddies Induced In Cylindrical Containers By A Rotating End Wall, Christopher Hills
Eddies Induced In Cylindrical Containers By A Rotating End Wall, Christopher Hills
Articles
The flow generated in a viscous liquid contained in a cylindrical geometry by a rotating end wall is considered. Recent numerical and experimental work has established several distinct phases of the motion when fluid inertia plays a significant role. The current paper, however, establishes the nature of the flow in the thus far neglected low Reynolds number regime. Explicitly, by employing biorthogonality relations appropriate to the current geometry, it is shown that a sequence of exponentially decaying eddies extends outward from the rotating end wall. The cellular structure is a manifestation of the dominance of complex eigensolutions to the homogeneous …
A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali
A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
Design and analysis of a new compensating element for improving the electron pulse front and compressing the pulse duration in a femtosecond photoelectron gun are described. The compensating element is a small metallic cylindrical cavity in which an external voltage is applied in such a way that a special electric field forms and interacts with the electron pulse. This electric field reduces the distances between the faster and slower electrons inside the cavity and efficiently compensates for electron pulse broadening caused by the photoelectron energy spread and space charge effects. Poisson's equation and the equation of motion are solved to …