![]() ![]() Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. Observations are more consistent with the modeled amplitude perturbations associated with sprite halos than those with elves.Ī direct localization of a fast radio burst and its host.Ĭhatterjee, S Law, C J Wharton, R S Burke-Spolaor, S Hessels, J W T Bower, G C Cordes, J M Tendulkar, S P Bassa, C G Demorest, P Butler, B J Seymour, A Scholz, P Abruzzo, M W Bogdanov, S Kaspi, V M Keimpema, A Lazio, T J W Marcote, B McLaughlin, M A Paragi, Z Ransom, S M Rupen, M Spitler, L G van Langevelde, H Jįast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. ![]() ![]() Results indicate that the observed frequency dependence of VLF scattering during early/ fast events results from the combination of scattering source properties and Earth-ionosphere waveguide propagation effects. Theoretical predictions for VLF scattering from ionization changes associated with elves are compared with those associated with sprite halos, and each are compared with experimental observations. VLF scattering observations, each identified with causative lightning logged by the National Lightning Detection Network (NLDN), are compared with the predictions of the Long-Wave Propagation Capability (LWPC) code, a three-dimensional earth-ionosphere waveguide propagation and scattering model. The spread spectrum analysis technique determines the amplitude and phase of a subionospherically propagating VLF signal as a function of time during the early/ fast event and as a function of frequency across the 200 Hz bandwidth of the VLF transmission. In this paper, we present spread spectrum VLF scattering observations of early/ fast events. It is yet unresolved, however, whether a specific type of TLE is directly related to the ionospheric conductivity changes responsible for the typical early/ fast event. Early/ fast amplitude and phase perturbations have been observed coincidentally with various optical observations of transient luminous events (TLEs), including elves, sprites, and sprite halos, each of which can have temporal characteristics consistent with those of early/ fast VLF events. All rights reserved.Ī New Observation Technique Applied to Early/ Fast VLF Scattering EventsĮarly/ fast very low frequency (VLF, 3-30 kHz) events are understood to result from ionospheric conductivity changes associated with lightning. These results can be explained by direct mapping between visual input and motor output, compatible with a sub-cortical pathway for visual control of the upper limb. When we introduced a condition of altered stimulus-response mapping, RT went up and a cost of choice was observed. Using a target-pointing paradigm we observed very fast reaction times (<150 ms) which were completely unaffected as the number of possible target choices was increased from 1 to 4. Here we asked if the choice-invariance established for the eyes also applies to a special class of fast visuomotor responses of the upper limb. This can be explained by the sub-cortical circuitry underlying eye movements, which involves direct mapping between retinal input and motor output in the superior colliculus. In contrast to conventional reaction time (RT) tasks, saccadic RT's to visual targets are very fast and unaffected by the number of possible targets. The implications for larger structural changes that occur on much longer time scales are discussed.ĭirect visuomotor mapping for fast visually-evoked arm movements. These results demonstrate that interconversion between protein conformational substates can occur on very fast time scales. The exchange between substates changes the frequency of the CO, which is detected by the time dependence of the 2D-IR vibrational echo spectrum. The conformational switching involves motion of the distal histidine/E helix that changes the location of the imidazole side group of the histidine. The conformational dynamics are directly measured through the growth of cross peaks in the 2D-IR spectra of CO bound to the heme active site. By using ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy, conformational switching between two well defined substates of a myoglobin mutant is observed on the approximately 50-ps time scale. Each substate reflects a local minimum on the free-energy landscape with a distinct structure. ![]() Ishikawa, Haruto Kwak, Kyungwon Chung, Jean K Kim, Seongheun Fayer, Michael Dįolded proteins can exist in multiple conformational substates. Direct observation of fast protein conformational switching. ![]()
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