Academic literature on the topic 'Waves-Oscillations-Pulses'

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Journal articles on the topic "Waves-Oscillations-Pulses"

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OTTERSTEDT, R. D., N. I. JAEGER, and P. J. PLATH. "VARIOUS WAVE PHENOMENA DURING THE OSCILLATORY ELECTRODISSOLUTION OF COBALT." International Journal of Bifurcation and Chaos 04, no. 05 (October 1994): 1265–73. http://dx.doi.org/10.1142/s0218127494000952.

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Experimental studies have been carried out with disk-like cobalt sheets in unstirred diluted phosphoric acid under potentiostatic control. Voltages were chosen such that oscillations of the integral current indicating transitions between the active and the passive state of the metal occurred. Spatiotemporal patterns during these transitions, visible due to changes of the reflectivity of the surface, were recorded with a video camera. High-amplitude periodic relaxation oscillations of the integral current are linked to the accelerated propagation of activation waves covering the whole electrode surface. Low-amplitude aperiodic oscillations of the integral current are associated with propagation in a series of pulses, i.e., accelerating and decelerating waves. Often, the stepwise propagating waves emit during acceleration another wave backwards. Annihilation of waves was also observed.
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Gelens, Lendert, Graham A. Anderson, and James E. Ferrell. "Spatial trigger waves: positive feedback gets you a long way." Molecular Biology of the Cell 25, no. 22 (November 5, 2014): 3486–93. http://dx.doi.org/10.1091/mbc.e14-08-1306.

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Trigger waves are a recurring biological phenomenon involved in transmitting information quickly and reliably over large distances. Well-characterized examples include action potentials propagating along the axon of a neuron, calcium waves in various tissues, and mitotic waves in Xenopus eggs. Here we use the FitzHugh-Nagumo model, a simple model inspired by the action potential that is widely used in physics and theoretical biology, to examine different types of trigger waves—spatial switches, pulses, and oscillations—and to show how they arise.
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Kostenko, V., O. Zavialova, S. Pozdieiev, T. Kostenko, and A. Vinyukov. "SUBSTANTIATION OF DESIGN PARAMETERS OF COAL DUST EXPLOSION CONTAINMENT SYSTEM." Series of Geology and Technical Sciences 447, no. 3 (June 15, 2021): 72–79. http://dx.doi.org/10.32014/2021.2518-170x.65.

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The aim of the paper is to identify the qualitative and quantitative parameters of seismic waves and accelerations on the mine working contour after an explosion of the gas-and-dust mixture. Information about the formation of seismic waves in the rock mass accommodating the mine working was received using modelling in order to improve the means of containment of explosion of further developed dust-air mixture. The parameters of seismic waves, such as propagation velocity and acceleration, amplitude, and frequency of oscillations of mine working walls, were established for the conditions of the experimental structure, which allows to scientifically substantiating the design parameters of the systems protecting the miners against explosion. The energy of the explosion propagates in the rock mass in the form of a series of peak-like pulses and oscillations with smaller amplitude. Modulus of acceleration is an informational indicator, which suits the most for registration by seismic sensors responding, specifically, to the most powerful peak pulses formed by seismic waves. By revealing the qualitative and quantitative indicators of seismic wave propagation on the mine working contour and in the rock mass, the parameters of seismic sensors of the systems protecting the miners against explosion can be substantiated.
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Young, Bruce A., Skye Greer, and Michael Cramberg. "Slithering CSF: Cerebrospinal Fluid Dynamics in the Stationary and Moving Viper Boa, Candoia aspera." Biology 10, no. 7 (July 16, 2021): 672. http://dx.doi.org/10.3390/biology10070672.

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In the viper boa (Candoia aspera), the cerebrospinal fluid (CSF) shows two stable overlapping patterns of pulsations: low-frequency (0.08 Hz) pulses with a mean amplitude of 4.1 mmHg that correspond to the ventilatory cycle, and higher-frequency (0.66 Hz) pulses with a mean amplitude of 1.2 mmHg that correspond to the cardiac cycle. Manual oscillations of anesthetized C. aspera induced propagating sinusoidal body waves. These waves resulted in a different pattern of CSF pulsations with frequencies corresponding to the displacement frequency of the body and with amplitudes greater than those of the cardiac or ventilatory cycles. After recovery from anesthesia, the snakes moved independently using lateral undulation and concertina locomotion. The episodes of lateral undulation produced similar influences on the CSF pressure as were observed during the manual oscillations, though the induced CSF pulsations were of lower amplitude during lateral undulation. No impact on the CSF was found while C. aspera was performing concertina locomotion. The relationship between the propagation of the body and the CSF pulsations suggests that the body movements produce an impulse on the spinal CSF.
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Pagano, P., and I. De Moortel. "Contribution of observed multi frequency spectrum of Alfvén waves to coronal heating." Astronomy & Astrophysics 623 (February 27, 2019): A37. http://dx.doi.org/10.1051/0004-6361/201834158.

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Context. Whilst there are observational indications that transverse magnetohydrodynamic (MHD) waves carry enough energy to maintain the thermal structure of the solar corona, it is not clear whether such energy can be efficiently and effectively converted into heating. Phase-mixing of Alfvén waves is considered a candidate mechanism, as it can develop transverse gradient where magnetic energy can be converted into thermal energy. However, phase-mixing is a process that crucially depends on the amplitude and period of the transverse oscillations, and only recently have we obtained a complete measurement of the power spectrum for transverse oscillations in the corona. Aims. We aim to investigate the heating generated by phase-mixing of transverse oscillations triggered by buffeting of a coronal loop that follows from the observed coronal power spectrum as well as the impact of these persistent oscillations on the structure of coronal loops. Methods. We considered a 3D MHD model of an active region coronal loop and we perturbed its footpoints with a 2D horizontal driver that represents a random buffeting motion of the loop footpoints. Our driver was composed of 1000 pulses superimposed to generate the observed power spectrum. Results. We find that the heating supply from the observed power spectrum in the solar corona through phase-mixing is not sufficient to maintain the million-degree active region solar corona. We also find that the development of Kelvin–Helmholtz instabilities could be a common phenomenon in coronal loops that could affect their apparent life time. Conclusions. This study concludes that is unlikely that phase-mixing of Alfvén waves resulting from an observed power spectrum of transverse coronal loop oscillations can heat the active region solar corona. However, transverse waves could play an important role in the development of small scale structures.
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Macdonald, Kurt D., Eva Fifkova, Michael S. Jones, and Daniel S. Barth. "Focal Stimulation of the Thalamic Reticular Nucleus Induces Focal Gamma Waves in Cortex." Journal of Neurophysiology 79, no. 1 (January 1, 1998): 474–77. http://dx.doi.org/10.1152/jn.1998.79.1.474.

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MacDonald, Kurt D., Eva Fifkova, Michael S. Jones, and Daniel S. Barth. Focal stimulation of the thalamic reticular nucleus induces focal gamma waves in cortex. J. Neurophysiol. 79: 474–477, 1998. Electrical stimulation of the thalamic reticular nucleus (TRN; 0.5-s trains of 500-Hz 0.5-ms pulses at 5–10 μA) evokes focal oscillations of cortical electrical potentials in the gamma frequency band (∼35–55 Hz). These evoked oscillations are specific to either the somatosensory or auditory cortex and to subregions of the cortical receptotopic map, depending on what part of the TRN is stimulated. Focal stimulation of the internal capsule, however, evokes focal slow potentials, without gamma activity. Our results suggest that the TRN's role extends beyond that of general cortical arousal to include specific modality and submodality activation of the forebrain.
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Bastrakova, Marina, Nikolay Klenov, Vsevolod Ruzhickiy, Igor Soloviev, and Arkady Satanin. "Sub-nanosecond operations on superconducting quantum register based on Ramsey patterns." Superconductor Science and Technology 35, no. 5 (March 22, 2022): 055003. http://dx.doi.org/10.1088/1361-6668/ac5505.

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Abstract An ultrafast qubit control concept is proposed and analyzed theoretically to reduce the duration of operations with single and multiple superconducting qubits. It is based on the generation of Ramsey fringes due to unipolar sub-nanosecond control pulses. The interference of waves of qubit states population propagating forward and backward in time play a key role in the concept. The influence of the shape and duration of control pulses on the contrast of the interference pattern is revealed in the frame of Ramsey’s paradigm. Protocols for the observation of Ramsey oscillations and an implementation of various gate operations are developed for flux qubits. We also suggest a notional engineering solution for creating the required sub-nanosecond control pulses with the desired shape and amplitude. It is demonstrated that this makes it possible to control the quantum states of the system with a fidelity of more than 99%.
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Lu, Yao, Wilson Truccolo, Fabien B. Wagner, Carlos E. Vargas-Irwin, Ilker Ozden, Jonas B. Zimmermann, Travis May, Naubahar S. Agha, Jing Wang, and Arto V. Nurmikko. "Optogenetically induced spatiotemporal gamma oscillations and neuronal spiking activity in primate motor cortex." Journal of Neurophysiology 113, no. 10 (June 2015): 3574–87. http://dx.doi.org/10.1152/jn.00792.2014.

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Transient gamma-band (40–80 Hz) spatiotemporal patterns are hypothesized to play important roles in cortical function. Here we report the direct observation of gamma oscillations as spatiotemporal waves induced by targeted optogenetic stimulation, recorded by intracortical multichannel extracellular techniques in macaque monkeys during their awake resting states. Microelectrode arrays integrating an optical fiber at their center were chronically implanted in primary motor (M1) and ventral premotor (PMv) cortices of two subjects. Targeted brain tissue was transduced with the red-shifted opsin C1V1(T/T). Constant (1-s square pulses) and ramp stimulation induced narrowband gamma oscillations during awake resting states. Recordings across 95 microelectrodes (4 × 4-mm array) enabled us to track the transient gamma spatiotemporal patterns manifested, e.g., as concentric expanding and spiral waves. Gamma oscillations were induced well beyond the light stimulation volume, via network interactions at distal electrode sites, depending on optical power. Despite stimulation-related modulation in spiking rates, neuronal spiking remained highly asynchronous during induced gamma oscillations. In one subject we examined stimulation effects during preparation and execution of a motor task and observed that movement execution largely attenuated optically induced gamma oscillations. Our findings demonstrate that, beyond previously reported induced gamma activity under periodic drive, a prolonged constant stimulus above a certain threshold may carry primate motor cortex network dynamics into gamma oscillations, likely via a Hopf bifurcation. More broadly, the experimental capability in combining microelectrode array recordings and optogenetic stimulation provides an important approach for probing spatiotemporal dynamics in primate cortical networks during various physiological and behavioral conditions.
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Annenkov, Vladimir, Evgeny Berendeev, Evgeniia Volchok, and Igor Timofeev. "Particle-in-Cell Simulations of High-Power THz Generator Based on the Collision of Strongly Focused Relativistic Electron Beams in Plasma." Photonics 8, no. 6 (May 21, 2021): 172. http://dx.doi.org/10.3390/photonics8060172.

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Based on particle-in-cell simulations, we propose to generate sub-nanosecond pulses of narrowband terahertz radiation with tens of MW power using unique properties of kiloampere relativistic (2 MeV) electron beams produced by linear induction accelerators. Due to small emittance of such beams, they can be focused into millimeter and sub-millimeter spots comparable in sizes with the wavelength of THz radiation. If such a beam is injected into a plasma, it becomes unstable against the two-stream instability and excites plasma oscillations that can be converted to electromagnetic waves at the plasma frequency and its harmonics. It is shown that several radiation mechanisms with high efficiency of power conversion (∼1%) come into play when the radial size of the beam–plasma system becomes comparable with the wavelength of the emitted waves.
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Charloux, Anne, Claude Gronfier, Evelyne Lonsdorfer-Wolf, François Piquard, and Gabrielle Brandenberger. "Aldosterone release during the sleep-wake cycle in humans." American Journal of Physiology-Endocrinology and Metabolism 276, no. 1 (January 1, 1999): E43—E49. http://dx.doi.org/10.1152/ajpendo.1999.276.1.e43.

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The aim of this study was to assess the relative influence on the 24-h aldosterone profile of the adrenocorticotropic system, primarily modulated by a circadian rhythmicity, and the renin-angiotensin system, which is influenced by sleep. Cortisol, plasma renin activity (PRA), and aldosterone were measured for 24 h in healthy subjects under basal conditions, once with nocturnal sleep and once with a night of sleep deprivation followed by 8 h of daytime sleep. The sleep period displayed high mean aldosterone levels, pulse amplitude, and frequency that were reduced during waking periods. During sleep, aldosterone pulses were mainly related to PRA oscillations, whereas they were mainly associated with cortisol pulses during waking periods. Cross-correlation analysis between sleep electroencephalographic activity in the delta band and aldosterone levels yielded significant results, aldosterone following delta waves by ∼30 min. This study demonstrates that the 24-h aldosterone profile is strongly influenced by sleep processes. A dual influence, by the renin-angiotensin system during sleep and by the adrenocorticotropic system during wakefulness, is exerted on aldosterone pulses throughout the 24-h period.
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Book chapters on the topic "Waves-Oscillations-Pulses"

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"Wave Pulses." In Oscillations and Waves, 157–74. CRC Press, 2013. http://dx.doi.org/10.1201/b14579-10.

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Conference papers on the topic "Waves-Oscillations-Pulses"

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Rothenberg, Joshua E. "Buildup of modulational instability from wave breaking in birefringent fiber propagation." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.thee1.

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Optical modulational instability (MI), the spontaneous generation of intensity modulation on a continuous wave, has received much recent attention as a novel nonlinear process and as a source of terahertz repetition-rate subpicosecond pulses. The MI phenomenon was first observed for anomalous group-velocity dispersion,1 and it has recently been observed with coupled nonlinearly visible waves in a birefringent fiber.2 For use of generated terahertz pulse trains it is desirable to have oscillations with stable relative delay. However, MI, being a parametric process, typically builds up from noise. As a result, the oscillations are not coherently generated, and their timing relative to the input is not controlled. In this paper it is observed that when coupled, visible picosecond pulses propagate in a birefringent fiber, the pulses first form "wave-breaking" oscillations, which then, owing to MI gain, grow exponentially. When cross-correlation with a 100 fs probe pulse was employed, terahertz oscillations were observed to form on orthogonally polarized pulses copropagating in the fiber. The correlations were measured by averaging over many pulses, and they demonstrate the stability and relative coherence of the oscillations. Numerical simulations confirm this description, showing the formation and amplification of wave-breaking oscillations, and they also indicate the formation of dark soliton trains.
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Siders, C. W., S. P. Le Blanc, D. Fisher, T. Tajima, M. C. Downer, A. Babine, A. Stepanov, and A. Sergeev. "Measurement of Laser Wakefield Oscillations by Femtosecond Longitudinal Interferometry." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.saa.3.

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Because the electrostatic fields present in plasma waves can exceed those achievable in conventional accelerators and approach atomic scale values (E a ~ 500 GV/m), plasma based accelerators have received considerable attention as compact sources of high-energy electron pulses [1]. Although stimulated Raman scattering [2] and terahertz radiation at the plasma frequency ω p [3] provide spatially averaged optical signatures of the plasma wave, new diagnostic techniques are required to map the the temporal and spatial structure of the plasma wave directly since such information is vital for addressing fundamental issues of wakefield generation and propagation. In this paper, we report femtosecond time resolved measurements of the longitudinal and radial structure of laser wakefield oscillations using an all optical technique known as ’photon acceleration’ [4].
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Trosztel, István, Iván Tóth, and György Ézsöl. "Validation of ATHLET Code by LOCA-Induced Pressure Wave Propagation Tests." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30706.

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Propagation of pressure waves inside the reactor vessel after a large break LOCA is an issue since it affects pressure drop across core internals and, as a result, induces stresses in different components, like core barrel, core structures and even fuel. For reactor safety analysis pressure wave propagation is traditionally performed by systems codes. However, strong dispersion among the calculated results calls for test results to validate the calculations. The pressure wave propagation following a larger LOCA is being systematically addressed by experiments in the PMK-2 integral-type test facility. In order to capture the high speed propagation of pressure waves special pressure transducers (capable to resolve the pressure variation with a frequency of 4 kHz) have been installed. The first four tests were conducted with rupture disks for opening the break, but a special quick opening valve will be installed for future tests, allowing the adjustment of the opening time between 12 and 50 ms. The paper presents results of validation of the ATHLET code by the test results. The low-frequency oscillation of the measured system pressure was shown to be caused by flow rate coming from the pressuriser that compensates mass lost via the break: the frequency of the oscillation was slightly under-predicted. The propagation of the first rarefaction wave from the top of the downcomer to the upper plenum is very well calculated by ATHLET: in spite of the first order discretisation no numerical diffusion can be observed. The calculated pressure differences between two different locations in the system are of primary interest, since they define the loads on primary system internals. ATHLET somewhat overestimates the amplitude of the pressure difference pulses, while it fairly well describes the frequency of oscillations. First analyses indicate an effect of the calculated break flow rate. ATHLET calculates a slower attenuation of the pressure oscillations as compared to test results. This can be the consequence of rigid walls assumed in the analysis. The tendency of increasing first pressure peak with increasing system pressure is well predicted by the code. In summary, it can be stated that ATHLET calculations produce slightly conservative results based on comparison with measured data.
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Vorontsova, Irina, Maksim Melnik, Anton Tcypkin, and Sergei Kozlov. "The limits of applicability of the z-scan method for THz pulses from a small number of oscillations." In 2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz). IEEE, 2021. http://dx.doi.org/10.1109/irmmw-thz50926.2021.9566930.

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