Showing papers by "Richard B. Miles published in 1983"
TL;DR: It is suggested that each population discharge is followed by a period of relative population refractoriness, and activity elicited in one neurone spreads to other neurones through multisynaptic excitatory pathways and leads eventually to the participation of the whole population in a synchronous burst.
Abstract: The synchronized firing of neuronal populations is frequently observed in the mammalian central nervous system. The generation of motor activities such as locomotion and respiration requires the simultaneous activation of many neurones and synchronous firing also underlies the cortical alpha rhythm and the hippocampal theta rhythm. However the influence that single neurones may have on such neuronal population discharges is not clear. We have examined this question using small isolated segments of the CA3 region of the guinea pig hippocampus. We report here that in the presence of picrotoxin, a gamma-aminobutyric acid (GABA) antagonist, these segments spontaneously generate synchronized rhythmic bursts comparable with the interictal epileptiform discharges observed in the hippocampus and neocortex in the presence of penicillin. The activation of some individual neurones by intracellular current injection can partially entrain and reset the rhythm. The probability that a synchronized burst will follow stimulation of a single cell increases with time after a spontaneous synchronized discharge, suggesting that each population discharge is followed by a period of relative population refractoriness. A delay of 40-200 ms elapses between the activation of a single neurone and the synchronized discharge. We suggest that during this time activity elicited in one neurone spreads to other neurones through multisynaptic excitatory pathways and leads eventually to the participation of the whole population in a synchronous burst.
385 citations
TL;DR: In this paper, laser-induced fluorescence of sodium atoms seeded into a supersonic nitrogen jet is used to determine the velocity, temperature, and pressure of the flow, which is sufficiently intense for spatially resolved flow visualization purposes.
Abstract: Laser‐induced fluorescence of sodium atoms seeded into a supersonic nitrogen jet is used to determine the velocity, temperature, and pressure of the flow. The visible signal is sufficiently intense for spatially resolved flow visualization purposes.
43 citations
TL;DR: An in vitro preparation of the medulla oblongata of the rat was used to examine the responses to reducing pH of neurons in several identified nuclei, and neurons in an area close to the ventral surface did not respond differently from neurons in other medullary nuclei.
36 citations
TL;DR: In this paper, the mean square velocity, temperature, and pressure fluctuations of a supersonic nitrogen jet were determined by varying the frequency of the pumping laser, as well as their correlations.
Abstract: Turbulence is measured by resonant fluorescence of sodium atoms seeded into a supersonic nitrogen jet. By varying the frequency of the pumping laser, the mean square velocity, temperature, and pressure fluctuations (as well as their correlations) may be determined.
23 citations
01 Nov 1983
TL;DR: In this paper, the authors evaluate various nonintrusive techniques for the measurement of the flow field on the windward side of the Space Shuttle orbiter or a similar reentry vehicle.
Abstract: This study evaluates various non-intrusive techniques for the measurement of the flow field on the windward side of the Space Shuttle orbiter or a similar reentry vehicle. Included are linear (Rayleigh, Raman, Mie, Laser Doppler Velocimetry, Resonant Doppler Velocimetry) and nonlinear (Coherent Anti-Stokes Raman, Laser-Induced Fluorescence) light scattering, electron-beam fluorescence, thermal emission, and mass spectroscopy. Flow-field properties were taken from a nonequilibrium flow model by Shinn, Moss, and Simmonds at the NASA Langley Research Center. Conclusions are, when possible, based on quantitative scaling of known laboratory results to the conditions projected. Detailed discussion with researchers in the field contributed further to these conclusions and provided valuable insights regarding the experimental feasibility of each of the techniques.
1 citations
17 May 1983
TL;DR: The resonant Doppler velocimeter (RDV) as mentioned in this paper is a nonintrusive diagnostic tool which takes advantage of laser absorption effects to measure the velocity, temperature, and pressure of a flowing gas.
Abstract: We report the first use of the resonant Doppler velocimeter (RDV) for the separation of time averaged turbulence components. The RDV is a new nonintrusive diagnostic tool which takes advantage of laser absorption effects to measure the velocity, temperature, and pressure of a flowing gas.1,2 in this manner it eliminates particle lag which is characteristic of standard laser Doppler velocimetry. Tracer atoms or molecules are seeded into the flowing gas under investigation and are excited by an intersecting laser beam. Since the gas is moving, the absorption frequency is Doppler shifted. The shift provides the velocity component in the direction of the laser beam. Line broadening mechanisms furnish information regarding the temperature and pressure of the flow. The experiment was conducted in a sodium seeded laminar supersonic jet created in a converging/diverging conical nozzle.
01 Jan 1983