Freeman and Baird [5; Freeman WJ, Baird B. Behav Neurosci 1987;101:393-408] recorded from the surface of the brain in waking rabbits and found spatial patterns of voltage that covaried with sensory experience. We simulate mathematically the electric fields produced by radial dipoles in cortical gyri and show that patterns with the spatial frequencies observed by Freeman and Baird could be produced by cortical dipoles spaced 3 mm apart. We further calculate that to resolve the patterns produced by such dipole arrays, it is necessary to record less than 2.5 mm above the surface of the cortex. High-pass spatial filters increase this distance to 4.5 mm. Since the human scalp is 15-16 mm above the brain, we conclude that spatial patterns of voltage covarying with sensation are unlikely to be detectable in scalp records. If such patterns do exist in humans, dural or sub-dural electrode arrays, with an inter-electrode spacing of 1 mm or less, will be necessary to record them.
Inhalation administration requests the microparticles with appropriate average diameters and narrow diameter distribution. In this paper, the tetracycline microparticles suitable for inhalation administration were prepared successfully by Supercritical anti-solvent (SAS) process developed in recent years. A continuous SAS process had been adopted to prepare the micro-particles of tetracycline using ethanol as solvent and supercritical CO2 as anti-solvent. The effects of pressure, temperature, solution concentration and nozzle diameter on the morphology, size and size distribution of the particles were investigated. The results showed that tetracycline micro-particles with diameters range of 20nm to 40nm could be obtained by SAS continuous process when ethanol was used as organic solvent at the experimental operation parameters of the pressure of 15MPa, the temperature of 35°C, the solution concentration of 5mg/ml and the nozzle diameter of 75µm. The nano-particles of tetracycline prepared by the above continuous SAS process can be used for alveolus targeting drug delivery and the preparation of sustained-releases micro-spheres
The mathematical tangential and radial dipole models were constructed. Dipoles can be use to answer if any special electrical and magnetic patterns exist in human head, and also use them to reveal many other magic phenomena of head nero-system. Construct of a mathematical models of the electric potentials. Use validation of the mathematical model and interrogation of the validated model to determine what sort of dipole separation would produce patterns. Our models were simulated by using MATLAB. Simulation clearly show that those tangential and radial dipole models reflected real dipoles physical and electrical characteristic of them. Those models show that even with spatial filtering, the electrode array can not be more than 4.5 mm above the surface of the cortex for the sorts of patterns we are looking for to be resolved.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.