Journal articles on the topic 'Coherent oscillations'
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Le Van Quyen, Michel, Lyle E. Muller, Bartosz Telenczuk, Eric Halgren, Sydney Cash, Nicholas G. Hatsopoulos, Nima Dehghani, and Alain Destexhe. "High-frequency oscillations in human and monkey neocortex during the wake–sleep cycle." Proceedings of the National Academy of Sciences 113, no. 33 (August 1, 2016): 9363–68. http://dx.doi.org/10.1073/pnas.1523583113.
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Beta (β)- and gamma (γ)-oscillations are present in different cortical areas and are thought to be inhibition-driven, but it is not known if these properties also apply to γ-oscillations in humans. Here, we analyze such oscillations in high-density microelectrode array recordings in human and monkey during the wake–sleep cycle. In these recordings, units were classified as excitatory and inhibitory cells. We find that γ-oscillations in human and β-oscillations in monkey are characterized by a strong implication of inhibitory neurons, both in terms of their firing rate and their phasic firing with the oscillation cycle. The β- and γ-waves systematically propagate across the array, with similar velocities, during both wake and sleep. However, only in slow-wave sleep (SWS) β- and γ-oscillations are associated with highly coherent and functional interactions across several millimeters of the neocortex. This interaction is specifically pronounced between inhibitory cells. These results suggest that inhibitory cells are dominantly involved in the genesis of β- and γ-oscillations, as well as in the organization of their large-scale coherence in the awake and sleeping brain. The highest oscillation coherence found during SWS suggests that fast oscillations implement a highly coherent reactivation of wake patterns that may support memory consolidation during SWS.
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Salzwedel, Robert, Andreas Knorr, Dominik Hoeing, Holger Lange, and Malte Selig. "Theory of radial oscillations in metal nanoparticles driven by optically induced electron density gradients." Journal of Chemical Physics 158, no. 6 (February 14, 2023): 064107. http://dx.doi.org/10.1063/5.0139629.
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We provide a microscopic approach to describe the onset of radial oscillation of a silver nanoparticle. Using the Heisenberg equation of motion framework, we find that the coupled ultrafast dynamics of coherently excited electron occupation and the coherent phonon amplitude initiate periodic size oscillations of the nanoparticle. Compared to the established interpretation of experiments, our results show a more direct coupling mechanism between the field intensity and coherent phonons. This interaction triggers a size oscillation via an optically induced electron density gradient occurring directly with the optical excitation. This source is more efficient than the incoherent heating process currently discussed in the literature and well-describes the early onset of the oscillations in recent experiments.
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Hoseini, Mahmood S., Jeff Pobst, Nathaniel Wright, Wesley Clawson, Woodrow Shew, and Ralf Wessel. "Induced cortical oscillations in turtle cortex are coherent at the mesoscale of population activity, but not at the microscale of the membrane potential of neurons." Journal of Neurophysiology 118, no. 5 (November 1, 2017): 2579–91. http://dx.doi.org/10.1152/jn.00375.2017.
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Bursts of oscillatory neural activity have been hypothesized to be a core mechanism by which remote brain regions can communicate. Such a hypothesis raises the question to what extent oscillations are coherent across spatially distant neural populations. To address this question, we obtained local field potential (LFP) and membrane potential recordings from the visual cortex of turtle in response to visual stimulation of the retina. The time-frequency analysis of these recordings revealed pronounced bursts of oscillatory neural activity and a large trial-to-trial variability in the spectral and temporal properties of the observed oscillations. First, local bursts of oscillations varied from trial to trial in both burst duration and peak frequency. Second, oscillations of a given recording site were not autocoherent; i.e., the phase did not progress linearly in time. Third, LFP oscillations at spatially separate locations within the visual cortex were more phase coherent in the presence of visual stimulation than during ongoing activity. In contrast, the membrane potential oscillations from pairs of simultaneously recorded pyramidal neurons showed smaller phase coherence, which did not change when switching from black screen to visual stimulation. In conclusion, neuronal oscillations at distant locations in visual cortex are coherent at the mesoscale of population activity, but coherence is largely absent at the microscale of the membrane potential of neurons. NEW & NOTEWORTHY Coherent oscillatory neural activity has long been hypothesized as a potential mechanism for communication across locations in the brain. In this study we confirm the existence of coherent oscillations at the mesoscale of integrated cortical population activity. However, at the microscopic level of neurons, we find no evidence for coherence among oscillatory membrane potential fluctuations. These results raise questions about the applicability of the communication through coherence hypothesis to the level of the membrane potential.
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Kay, Leslie M., and Philip Lazzara. "How Global Are Olfactory Bulb Oscillations?" Journal of Neurophysiology 104, no. 3 (September 2010): 1768–73. http://dx.doi.org/10.1152/jn.00478.2010.
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Previous studies in waking animals have shown that the frequency structure of olfactory bulb (OB) local field potential oscillations is very similar across the OB, but large low-impedance surface electrodes may have favored highly coherent events, averaging out local inhomogeneities. We tested the hypothesis that OB oscillations represent spatially homogeneous phenomena at all scales. We used pairs of concentric electrodes (200 μm outer shaft surrounding an inner 2–3 μm recording site) beginning on the dorsal OB at anterior and medial locations in urethane-anesthetized rats and measured local field potential responses at successive 200 μm depths before and during odor stimulation. Within locations (outer vs. inner lead on a single probe), on the time scale of 0.5 s, coherence in all frequency bands was significant, but on larger time scales (10 s), only respiratory (1–4 Hz) and beta (15–30 Hz) oscillations showed prominent peaks. Across locations, coherence in all frequency bands was significantly lower for both sizes of electrodes at all depths but the most superficial 600 μm. Near the pial surface, coherence across outer (larger) electrodes at different sites was equal to coherence across outer and inner (small) electrodes within a single site and larger than coherence across inner electrodes at different sites. Overall, the beta band showed the largest coherence across bulbar sites and electrodes. Therefore larger electrodes at the surface of the OB favor globally coherent events, and at all depths, coherence depends on the type of oscillation (beta or gamma) and duration of the analysis window.
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Sassaroli, Angelo, Kristen Tgavalekos, and Sergio Fantini. "The meaning of “coherent” and its quantification in coherent hemodynamics spectroscopy." Journal of Innovative Optical Health Sciences 11, no. 06 (November 2018): 1850036. http://dx.doi.org/10.1142/s1793545818500360.
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We have recently introduced a new technique, coherent hemodynamics spectroscopy (CHS), which aims at characterizing a specific kind of tissue hemodynamics that feature a high level of covariation with a given physiological quantity. In this study, we carry out a detailed analysis of the significance of coherence and phase synchronization between oscillations of arterial blood pressure (ABP) and total hemoglobin concentration ([Hbt]), measured with near-infrared spectroscopy (NIRS) during a typical protocol for CHS, based on a cyclic thigh cuff occlusion and release. Even though CHS is based on a linear time invariant model between ABP (input) and NIRS measurands (outputs), for practical reasons in a typical CHS protocol, we induce finite “groups” of ABP oscillations, in which each group is characterized by a different frequency. For this reason, ABP (input) and NIRS measurands (output) are not stationary processes, and we have used wavelet coherence and phase synchronization index (PSI), as a metric of coherence and phase synchronization, respectively. PSI was calculated by using both the wavelet cross spectrum and the Hilbert transform. We have also used linear coherence (which requires stationary process) for comparison with wavelet coherence. The method of surrogate data is used to find critical values for the significance of covariation between ABP and [Hbt]. Because we have found similar critical values for wavelet coherence and PSI by using five of the most used methods of surrogate data, we propose to use the data-independent Gaussian random numbers (GRNs), for CHS. By using wavelet coherence and wavelet cross spectrum, and GRNs as surrogate data, we have found the same results for the significance of coherence and phase synchronization between ABP and [Hbt]: on a total set of 20 periods of cuff oscillations, we have found 17 coherent oscillations and 17 phase synchronous oscillations. Phase synchronization assessed with Hilbert transform yielded similar results with 14 phase synchronous oscillations. Linear coherence and wavelet coherence overall yielded similar number of significant values. We discuss possible reasons for this result. Despite the similarity of linear and wavelet coherence, we argue that wavelet coherence is preferable, especially if one wants to use baseline spontaneous oscillations, in which phase locking and coherence between signals might be only temporary.
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Choi, Jeong-Ryeol. "Characterizing Quantum Effects in Optically Induced Nanowire Self-Oscillations: Coherent Properties." Photonics 8, no. 7 (June 25, 2021): 237. http://dx.doi.org/10.3390/photonics8070237.
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Mechanical properties of metallic-nanowire self-oscillations are investigated through a coherent-state analysis. We focus on elucidating the time behavior of quantum energy in such oscillations, in addition to the analysis of fluctuations, evolution of eigenstates, and oscillatory trajectories. The quantum energy varies somewhat randomly at first, but, at a later time, it undergoes a stable periodical oscillation; the mean energy in the stabilized motion is large when the frequency of the driving force is resonated with that of the intrinsic oscillation of the nanowire. We confirmed that when the oscillatory amplitude is sufficiently low, the quantum energy is quite different from the classical one due to zero-point energy, which appears in the quantum regime. Because the power in such an oscillation is typically ultra low, quantum effects in the nanowire oscillations are non-negligible. Detailed analysis for the evolution of the probability densities and their relation with the oscillation trajectories of the nanowire are also carried out. Characterizing quantum effects in the actual oscillatory motions and clarifying their difference from the classical ones are important in understanding nanowire self-oscillations.
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Gelperin, A., L. D. Rhines, J. Flores, and D. W. Tank. "Coherent network oscillations by olfactory interneurons: modulation by endogenous amines." Journal of Neurophysiology 69, no. 6 (June 1, 1993): 1930–39. http://dx.doi.org/10.1152/jn.1993.69.6.1930.
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1. The procerebral (PC) lobe of the terrestrial mollusk Limax maximus contains a highly interconnected network of local olfactory interneurons that receives direct axonal projections from the two pairs of noses. This olfactory processing network generates a 0.7-Hz oscillation in its local field potential (LFP) that is coherent throughout the network. The oscillating LFP is modulated by natural odorants applied to the neuroepithelium of the superior nose. 2. Two amines known to be present in the PC lobe, dopamine and serotonin, increase the frequency of the PC lobe oscillation and alter its waveform. 3. Glutamate, another putative neurotransmitter known to be present in the lobe, suppresses the PC lobe oscillation by a quisqualate-type receptor and appears to be used by one of the two classes of neurons in the PC lobe to generate the basic LFP oscillation. 4. The known activation of second messengers in Limax PC lobe by dopamine and serotonin together with their effects on the oscillatory rhythm suggest the hypothesis that these amines augment mechanisms mediating synaptic plasticity in the olfactory network, similar to hypothesized effects of amines in vertebrate olfactory systems. 5. The use of a distributed network of interneurons showing coherent oscillations may relate to the highly developed odor recognition and odor learning ability of Limax.
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van Loosdrecht, P. H. M., B. Beschoten, I. Dotsenko, and S. van Smaalen. "Optically induced coherent voltage oscillations in K0.3MoO3." Journal de Physique IV 12, no. 9 (November 2002): 303–6. http://dx.doi.org/10.1051/jp4:20020420.
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Optical induced transient changes of the electrical conductivity are investigated in the non-linear transport regime of the blue bronze K0.3MoO3 below its Peierls transition using the impulsive infrared excitation of a free-electron laser a t energies above the Peierls gap. The transients of the sample voltage have typical relaxation times of 0.5-2 ms superimposed by coherent voltage oscillations, which exhibit lifetimes of up 100 ms. The frequency of those voltage oscillation is found to be time dependent. This, in comparison with voltage oscillations purely driven by static electrical fields, enables the study of quasiparticle dynamics in the charge density condensate of the blue bronze.
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Akeju, Oluwaseun, M. Brandon Westover, Kara J. Pavone, Aaron L. Sampson, Katharine E. Hartnack, Emery N. Brown, and Patrick L. Purdon. "Effects of Sevoflurane and Propofol on Frontal Electroencephalogram Power and Coherence." Anesthesiology 121, no. 5 (November 1, 2014): 990–98. http://dx.doi.org/10.1097/aln.0000000000000436.
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Abstract Background: The neural mechanisms of anesthetic vapors have not been studied in depth. However, modeling and experimental studies on the intravenous anesthetic propofol indicate that potentiation of γ-aminobutyric acid receptors leads to a state of thalamocortical synchrony, observed as coherent frontal alpha oscillations, associated with unconsciousness. Sevoflurane, an ether derivative, also potentiates γ-aminobutyric acid receptors. However, in humans, sevoflurane-induced coherent frontal alpha oscillations have not been well detailed. Methods: To study the electroencephalogram dynamics induced by sevoflurane, the authors identified age- and sex-matched patients in which sevoflurane (n = 30) or propofol (n = 30) was used as the sole agent for maintenance of general anesthesia during routine surgery. The authors compared the electroencephalogram signatures of sevoflurane with that of propofol using time-varying spectral and coherence methods. Results: Sevoflurane general anesthesia is characterized by alpha oscillations with maximum power and coherence at approximately 10 Hz, (mean ± SD; peak power, 4.3 ± 3.5 dB; peak coherence, 0.73 ± 0.1). These alpha oscillations are similar to those observed during propofol general anesthesia, which also has maximum power and coherence at approximately 10 Hz (peak power, 2.1 ± 4.3 dB; peak coherence, 0.71 ± 0.1). However, sevoflurane also exhibited a distinct theta coherence signature (peak frequency, 4.9 ± 0.6 Hz; peak coherence, 0.58 ± 0.1). Slow oscillations were observed in both cases, with no significant difference in power or coherence. Conclusions: The study results indicate that sevoflurane, like propofol, induces coherent frontal alpha oscillations and slow oscillations in humans to sustain the anesthesia-induced unconscious state. These results suggest a shared molecular and systems-level mechanism for the unconscious state induced by these drugs.
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Vos, L. "Damping of coherent oscillations." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 391, no. 1 (May 1997): 56–63. http://dx.doi.org/10.1016/s0168-9002(97)00025-9.
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Cogliati, Chiara, Renata Magatelli, Nicola Montano, Krzysztof Narkiewicz, and Virend K. Somers. "Detection of low- and high-frequency rhythms in the variability of skin sympathetic nerve activity." American Journal of Physiology-Heart and Circulatory Physiology 278, no. 4 (April 1, 2000): H1256—H1260. http://dx.doi.org/10.1152/ajpheart.2000.278.4.h1256.
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Spectral analysis of skin blood flow has demonstrated low-frequency (LF, 0.03–0.15 Hz) and high-frequency (HF, 0.15–0.40 Hz) oscillations, similar to oscillations in R-R interval, systolic pressure, and muscle sympathetic nerve activity (MSNA). It is not known whether the oscillatory profile of skin blood flow is secondary to oscillations in arterial pressure or to oscillations in skin sympathetic nerve activity (SSNA). MSNA and SSNA differ markedly with regard to control mechanisms and morphology. MSNA contains vasoconstrictor fibers directed to muscle vasculature, closely regulated by baroreceptors. SSNA contains both vasomotor and sudomotor fibers, differentially responding to arousals and thermal stimuli. Nevertheless, MSNA and SSNA share certain common characteristics. We tested the hypothesis that LF and HF oscillatory components are evident in SSNA, similar to the oscillatory components present in MSNA. We studied 18 healthy normal subjects and obtained sequential measurements of MSNA and SSNA from the peroneal nerve during supine rest. Measurements were also obtained of the electrocardiogram, beat-by-beat blood pressure (Finapres), and respiration. Spectral analysis showed LF and HF oscillations in MSNA, coherent with similar oscillations in both R-R interval and systolic pressure. The HF oscillation of MSNA was coherent with respiration. Similarly, LF and HF spectral components were evident in SSNA variability, coherent with corresponding variability components of R-R interval and systolic pressure. HF oscillations of SSNA were coherent with respiration. Thus our data suggest that these oscillations may be fundamental characteristics shared by MSNA and SSNA, possibly reflecting common central mechanisms regulating sympathetic outflows subserving different regions and functions.
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Neupane, Sujaya, Daniel Guitton, and Christopher C. Pack. "Coherent alpha oscillations link current and future receptive fields during saccades." Proceedings of the National Academy of Sciences 114, no. 29 (July 3, 2017): E5979—E5985. http://dx.doi.org/10.1073/pnas.1701672114.
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Oscillations are ubiquitous in the brain, and they can powerfully influence neural coding. In particular, when oscillations at distinct sites are coherent, they provide a means of gating the flow of neural signals between different cortical regions. Coherent oscillations also occur within individual brain regions, although the purpose of this coherence is not well understood. Here, we report that within a single brain region, coherent alpha oscillations link stimulus representations as they change in space and time. Specifically, in primate cortical area V4, alpha coherence links sites that encode the retinal location of a visual stimulus before and after a saccade. These coherence changes exhibit properties similar to those of receptive field remapping, a phenomenon in which individual neurons change their receptive fields according to the metrics of each saccade. In particular, alpha coherence, like remapping, is highly dependent on the saccade vector and the spatial arrangement of current and future receptive fields. Moreover, although visual stimulation plays a modulatory role, it is neither necessary nor sufficient to elicit alpha coherence. Indeed, a similar pattern of coherence is observed even when saccades are made in darkness. Together, these results show that the pattern of alpha coherence across the retinotopic map in V4 matches many of the properties of receptive field remapping. Thus, oscillatory coherence might play a role in constructing the stable representation of visual space that is an essential aspect of conscious perception.
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Lee, Johanna M., Oluwaseun Akeju, Kristina Terzakis, Kara J. Pavone, Hao Deng, Timothy T. Houle, Paul G. Firth, Erik S. Shank, Emery N. Brown, and Patrick L. Purdon. "A Prospective Study of Age-dependent Changes in Propofol-induced Electroencephalogram Oscillations in Children." Anesthesiology 127, no. 2 (August 1, 2017): 293–306. http://dx.doi.org/10.1097/aln.0000000000001717.
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Abstract Background In adults, frontal electroencephalogram patterns observed during propofol-induced unconsciousness consist of slow oscillations (0.1 to 1 Hz) and coherent alpha oscillations (8 to 13 Hz). Given that the nervous system undergoes significant changes during development, anesthesia-induced electroencephalogram oscillations in children may differ from those observed in adults. Therefore, we investigated age-related changes in frontal electroencephalogram power spectra and coherence during propofol-induced unconsciousness. Methods We analyzed electroencephalogram data recorded during propofol-induced unconsciousness in patients between 0 and 21 yr of age (n = 97), using multitaper spectral and coherence methods. We characterized power and coherence as a function of age using multiple linear regression analysis and within four age groups: 4 months to 1 yr old (n = 4), greater than 1 to 7 yr old (n = 16), greater than 7 to 14 yr old (n = 30), and greater than 14 to 21 yr old (n = 47). Results Total electroencephalogram power (0.1 to 40 Hz) peaked at approximately 8 yr old and subsequently declined with increasing age. For patients greater than 1 yr old, the propofol-induced electroencephalogram structure was qualitatively similar regardless of age, featuring slow and coherent alpha oscillations. For patients under 1 yr of age, frontal alpha oscillations were not coherent. Conclusions Neurodevelopmental processes that occur throughout childhood, including thalamocortical development, may underlie age-dependent changes in electroencephalogram power and coherence during anesthesia. These age-dependent anesthesia-induced electroencephalogram oscillations suggest a more principled approach to monitoring brain states in pediatric patients.
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Inokuma, Yasuko, Tsuyoshi Inoue, Satoshi Watanabe, and Yutaka Kirino. "Two Types of Network Oscillations and Their Odor Responses in the Primary Olfactory Center of a Terrestrial Mollusk." Journal of Neurophysiology 87, no. 6 (June 1, 2002): 3160–64. http://dx.doi.org/10.1152/jn.2002.87.6.3160.
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We identified two classes of network oscillations with different frequency ranges in the tentacle ganglion (TG), the primary olfactory center of the terrestrial mollusk Limax marginatus, and investigated the responses of these oscillations to odor inputs. A recent study indicated that there are serotonergic terminals in the TG. We found that when serotonin was applied to the TG, the spontaneous network oscillation of about 1.5 Hz in the TG changed its oscillatory frequency to 0.5 Hz. These two oscillations are distinct, because 1) in most cases, the application of serotonin to the TG initially inhibited the 1.5-Hz oscillation and subsequently generated the slow 0.5-Hz oscillation; and 2) occasionally, the application of serotonin did not inhibit the spontaneous 1.5-Hz oscillation, resulting in the coexistence of two network oscillations. Thus the TG has two different oscillatory dynamics. We named the spontaneous 1.5-Hz oscillation the fast oscillation (FO), and the serotonin-induced 0.5-Hz oscillation the slow oscillation (SO). By calculating the spatial coherence of the TG oscillations, we found that the FO is a noncoherent oscillatory mode and the SO is a coherent oscillatory mode. Finally, odor presentation to the olfactory receptors selectively modulated the SO by decreasing the oscillatory amplitude, but the FO was not modulated by the odor input. These results indicate that 1) the TG has two oscillatory states (FO and SO) and these states are changed by the extracellular level of serotonin, and 2) these two oscillatory states have different responses to odors.
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Warner, Brian, and Patrick A. Woudt. "Quasi-Periodic Oscillations in Accretion Discs." International Astronomical Union Colloquium 185 (2002): 584–85. http://dx.doi.org/10.1017/s0252921100017164.
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Quasi-Periodic Oscillations (QPOs) in Cataclysmic Variable stars (CVs) with periods in the range 100 – 2000 s have been known for 25 years (see Chapter 8 of Warner, 1995a). We distinguish here between QPOs and Dwarf Nova Oscillations (DNOs) – the latter being of shorter period (5 – 50 s) and greater coherence. QPOs appear as brightness modulations and typically have quite short coherence lengths (a few cycles).QPOs are largely associated with discs transferring mass at a high rate – i.e., dwarf novae during outburst or nova-like variables; but the QPOs are not always present and many systems have not shown QPOs at all.Generally it is thought that QPOs result from non-radial oscillations of the accretion discs surrounding the white dwarf component in CVs (Carroll et al., 1985; Collins et al., 2000). They could, e.g., be quite coherent oscillations of individual annuli in a disc, each with a different period. Alternatively, a particular oscillation mode may be excited for only a few cycles and then be re-excited at an arbitrary phase. Most theoretical proposals have sought to make the QPOs self-luminous pulsations of the disc, in analogy with the kappa or epsilon processes of stellar pulsation.
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Tahara, Hirokazu, and Yoshihiko Kanemitsu. "(Invited, Digital Presentation) Photocurrent Detection of Cooperative Exciton Quantum Interference in Nanocrystal Thin Films." ECS Meeting Abstracts MA2022-02, no. 20 (October 9, 2022): 922. http://dx.doi.org/10.1149/ma2022-0220922mtgabs.
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Colloidal semiconductor quantum dots (QDs) are excellent materials for studying the photophysics of exciton complexes such as biexcitons, triexcitons, and charged excitons (trions). Dynamics of exciton complexes usually determines the performance of optoelectronic devices [1]. For example, trions reduce the optical gain threshold in QD lasers and multiexcitons increase photon-to-current conversion efficiencies via carrier multiplication processes in QD solar cells. In addition, unconventional properties of multiexcitons emerge in coherent processes in QD systems. We recently discovered the high-frequency coherent oscillations with integer multiples of the exciton resonance frequency, which is called multiexciton harmonic quantum coherence [2,3]. The multiexciton coherent properties have been investigated using optical methods. However, to clarify their roles in optoelectronic devices, it is necessary to conduct the electrical detection of multiexciton coherence. Here, we performed photocurrent detection of exciton quantum interference signals in QD thin films. The samples used in this study were closely packed PbS QD thin films. The QD films were sandwiched between the electron and hole transport layers to extract photogenerated carriers. Multiexcitons were generated by phase-locked femtosecond laser pulses, and then their photocurrent quantum interference signals were measured by using a quantum interference technique [4]. The photocurrent interference signal in the weak excitation shows a single sinusoidal oscillation originating from single excitons, while the interference signal changes to the profile involving multiple sinusoidal oscillations with increasing excitation intensity. This means that the multiexciton quantum coherence exhibiting harmonic oscillations is successfully detected in a photocurrent technique [5]. Furthermore, the amplitudes of harmonic quantum coherent signals in coupled QDs are significantly larger than those in isolated QDs. We clarified that the enhancement of the amplitudes is caused by cooperative processes in coupled QDs, where excitons in adjacent QDs interact with each other through their inter-QD coherent coupling. This cooperative effect can provide a new way to use inter-QD coherent coupling in advanced optoelectronic applications, e.g., amplifiers of coherent signals. Part of this work was supported by JSPS KAKENHI (JP19H05465 and JP22H01990) and JST CREST (JPMJCR21B4). References [1] Kanemitsu, Y. Trion dynamics in lead halide perovskite nanocrystals. J. Chem. Phys. 151, 170902 (2019). [2] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Harmonic Quantum Coherence of Multiple Excitons in PbS/CdS Core-Shell Nanocrystals. Phys. Rev. Lett. 119, 247401 (2017). [3] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Quantum coherence of multiple excitons governs absorption cross-sections of PbS/CdS core/shell nanocrystals. Nat. Commun. 9, 3179 (2018). [4] Tahara, H.; Kanemitsu, Y. Quantum Interference Measurements and Their Application to Analysis of Ultrafast Photocarrier Dynamics in Semiconductor Solar Cell Materials. Adv. Quantum Technol. 3, 1900098 (2020). [5] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Collective enhancement of quantum coherence in coupled quantum dot films. Phys. Rev. B 104, L241405 (2021).
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Hoseini, Mahmood S., and Ralf Wessel. "Coherent and intermittent ensemble oscillations emerge from networks of irregular spiking neurons." Journal of Neurophysiology 115, no. 1 (January 1, 2016): 457–69. http://dx.doi.org/10.1152/jn.00578.2015.
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Local field potential (LFP) recordings from spatially distant cortical circuits reveal episodes of coherent gamma oscillations that are intermittent, and of variable peak frequency and duration. Concurrently, single neuron spiking remains largely irregular and of low rate. The underlying potential mechanisms of this emergent network activity have long been debated. Here we reproduce such intermittent ensemble oscillations in a model network, consisting of excitatory and inhibitory model neurons with the characteristics of regular-spiking (RS) pyramidal neurons, and fast-spiking (FS) and low-threshold spiking (LTS) interneurons. We find that fluctuations in the external inputs trigger reciprocally connected and irregularly spiking RS and FS neurons in episodes of ensemble oscillations, which are terminated by the recruitment of the LTS population with concurrent accumulation of inhibitory conductance in both RS and FS neurons. The model qualitatively reproduces experimentally observed phase drift, oscillation episode duration distributions, variation in the peak frequency, and the concurrent irregular single-neuron spiking at low rate. Furthermore, consistent with previous experimental studies using optogenetic manipulation, periodic activation of FS, but not RS, model neurons causes enhancement of gamma oscillations. In addition, increasing the coupling between two model networks from low to high reveals a transition from independent intermittent oscillations to coherent intermittent oscillations. In conclusion, the model network suggests biologically plausible mechanisms for the generation of episodes of coherent intermittent ensemble oscillations with irregular spiking neurons in cortical circuits.
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Qin, Xiao-Ke. "How to control the coherent oscillations in Landau–Zener–Stueckelberg dynamics of three-level system." Modern Physics Letters B 30, no. 09 (April 10, 2016): 1650149. http://dx.doi.org/10.1142/s0217984916501499.
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Coherent pulse is used to control and measure the quantum state of three-level system in double quantum dots. We analyze the coherent oscillations in Landau–Zener–Stueckelberg (LZS) dynamics by the adiabatic-impulse model, which simplifies the applied pulse as an optical interference device. Under the designed “hat-shape” pulse, the sweeping speed through each avoid crossing can be tuned independently. The coherent oscillations in LZS dynamics of three-level system are optimized by the control pulse. Moreover, we can filter out the coherent oscillations with the unexpected frequency and only keep the coherent oscillations with the frequency we are interested in.
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Formisano, F., R. M. Dubrovin, R. V. Pisarev, A. M. Kalashnikova, and A. V. Kimel. "Laser-induced THz magnetism of antiferromagnetic CoF2." Journal of Physics: Condensed Matter 34, no. 22 (March 30, 2022): 225801. http://dx.doi.org/10.1088/1361-648x/ac5c20.
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Abstract Excitation, detection, and control of coherent THz magnetic excitation in antiferromagnets are challenging problems that can be addressed using ever shorter laser pulses. We study experimentally excitation of magnetic dynamics at THz frequencies in an antiferromagnetic insulator CoF2 by sub-10 fs laser pulses. Time-resolved pump-probe polarimetric measurements at different temperatures and probe polarizations reveal laser-induced transient circular birefringence oscillating at the frequency of 7.45 THz and present below the Néel temperature. The THz oscillations of circular birefringence are ascribed to oscillations of the magnetic moments of Co2+ ions induced by the laser-driven coherent E g phonon mode via the THz analogue of the transverse piezomagnetic effect. It is also shown that the same pulse launches coherent oscillations of the magnetic linear birefringence at the frequency of 3.4 THz corresponding to the two-magnon mode. Analysis of the probe polarization dependence of the transient magnetic linear birefringence at the frequency of the two-magnon mode enables identifying its symmetry.
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Wang, Hailin, Jagdeep Shah, T. C. Damen, W. Y. Jan, J. E. Cunningham, M. Hong, and J. P. Mannaerts. "Coherent oscillations in semiconductor microcavities." Physical Review B 51, no. 20 (May 15, 1995): 14713–16. http://dx.doi.org/10.1103/physrevb.51.14713.
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Kuznetsov, A. V., and C. J. Stanton. "Coherent phonon oscillations in GaAs." Physical Review B 51, no. 12 (March 15, 1995): 7555–65. http://dx.doi.org/10.1103/physrevb.51.7555.
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Börgers, Christoph, and Nancy J. Kopell. "Gamma Oscillations and Stimulus Selection." Neural Computation 20, no. 2 (February 2008): 383–414. http://dx.doi.org/10.1162/neco.2007.07-06-289.
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More coherent excitatory stimuli are known to have a competitive advantage over less coherent ones. We show here that this advantage is amplified greatly when the target includes inhibitory interneurons acting via GABAA-receptor-mediated synapses and the coherent input oscillates at gamma frequency. We hypothesize that therein lies, at least in part, the functional significance of the experimentally observed link between attentional biasing of stimulus competition and gamma frequency rhythmicity.
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Morales-Molina, L., and E. Arévalo. "One-BEC-species coherent oscillations with frequency controlled by a second species atom number." New Journal of Physics 24, no. 1 (January 1, 2022): 013023. http://dx.doi.org/10.1088/1367-2630/ac40ce.
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Abstract Controlling the tunneling of atoms of one species using a different atom species is a fundamental step in the development of a new class of atom quantum devices, where detection, motion control, and other functions over the atoms, can be achieved by exploiting the interaction between two different atomic species. Here, we theoretically study coherent oscillations of a non-self-interacting Bose–Einstein condensate (BEC) species in a triple-well potential controlled by a self-interacting species self-trapped in the central well of the potential. In this system, a blockade, due to the interspecies interaction, prevents atoms of the non-self-interacting species from populating the central well. Thus, for an initial population imbalance between the left- and right-hand wells of the non-self-interacting species, coherent BEC oscillations are induced between these two wells, resembling those of Rabi-like BEC oscillations in a double-well potential. The oscillation period is found to scale linearly with the number of self-trapped atoms as well as with the interspecies interaction strength. This behavior is corroborated by the quantum many-particle and the mean-field models of the system. We show that BEC oscillations can be described by using an effective bosonic Josephson junction with a tunneling amplitude that depends on the number of the self-trapped atoms in the central well. We also consider the effect of the self-trapped atom losses on the coherent oscillations. We show, by using quantum trajectories, that this type of losses leads to a dynamical change in the oscillation period of the non-self-interacting species, which in turn allows the number of self-trapped atoms lost from the system to be estimated.
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Gerstner, Wulfram, J. Leo van Hemmen, and Jack D. Cowan. "What Matters in Neuronal Locking?" Neural Computation 8, no. 8 (November 1996): 1653–76. http://dx.doi.org/10.1162/neco.1996.8.8.1653.
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Exploiting local stability, we show what neuronal characteristics are essential to ensure that coherent oscillations are asymptotically stable in a spatially homogeneous network of spiking neurons. Under standard conditions, a necessary and, in the limit of a large number of interacting neighbors, also sufficient condition is that the postsynaptic potential is increasing in time as the neurons fire. If the postsynaptic potential is decreasing, oscillations are bound to be unstable. This is a kind of locking theorem and boils down to a subtle interplay of axonal delays, postsynaptic potentials, and refractory behavior. The theorem also allows for mixtures of excitatory and inhibitory interactions. On the basis of the locking theorem, we present a simple geometric method to verify the existence and local stability of a coherent oscillation.
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Classen, Joseph, Christian Gerloff, Manabu Honda, and Mark Hallett. "Integrative Visuomotor Behavior Is Associated With Interregionally Coherent Oscillations in the Human Brain." Journal of Neurophysiology 79, no. 3 (March 1, 1998): 1567–73. http://dx.doi.org/10.1152/jn.1998.79.3.1567.
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Classen, Joseph, Christian Gerloff, Manabu Honda, and Mark Hallett. Integrative visuomotor behavior is associated with interregionally coherent oscillations in the human brain. J. Neurophysiol. 79: 1567–1573, 1998. Coherent electrical brain activity has been demonstrated to be associated with perceptual events in mammals. It is unclear whether or not it is also a mechanism instrumental in the performance of sensorimotor tasks requiring the continuous processing of information between primarily executive and receptive brain areas. In particular it is unknown whether or not interregional coherent activity detectable in electroencephalographic (EEG) recordings on the scalp reflects interareal functional cooperativity in humans. We studied patterns of changes in EEG-coherence associated with a visuomotor force-tracking task in seven subjects. Interregional coherence of EEG signals recorded from scalp regions overlying the visual and the motor cortex increased in comparison to a resting condition when subjects tracked a visual target by producing an isometric force with their right index finger. Coherence between visual and motor cortex decreased when the subjects produced a similar motor output in the presence of a visual distractor and was unchanged in a purely visual and purely motor task. Increases and decreases of coherence were best differentiated in the low beta frequency range (13–21 Hz). This observation suggests a special functional significance of low frequency oscillations in information processing in large-scale networks. These findings substantiate the view that coherent brain activity underlies integrative sensorimotor behavior.
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Chaouachi, Nizar, and Sihem Jaziri. "Possibility of observation quantum beat coherent exciton states with time-resolved photoemission." Journal of Applied Physics 131, no. 15 (April 21, 2022): 155704. http://dx.doi.org/10.1063/5.0086440.
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We develop a theoretical study to evaluate the dynamic of the time-resolved photoemission spectrum arising from the dissociation of exciton steady-states 1s, 2s in a monolayer transition metal dichlacogenides. We discuss the dielectric environment effect on the exciton binding energies. Quantum beat signatures in photoemission intensity demonstrate coherent coupling between 1s and 2s excitons. The beating contribution due to excitonic coherence is also discussed. The periodic oscillations arising from coherent superposition states and quantum beats enable exploration of novel coherent phenomena.
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Stacey, William C., Maciej T. Lazarewicz, and Brian Litt. "Synaptic Noise and Physiological Coupling Generate High-Frequency Oscillations in a Hippocampal Computational Model." Journal of Neurophysiology 102, no. 4 (October 2009): 2342–57. http://dx.doi.org/10.1152/jn.00397.2009.
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There is great interest in the role of coherent oscillations in the brain. In some cases, high-frequency oscillations (HFOs) are integral to normal brain function, whereas at other times they are implicated as markers of epileptic tissue. Mechanisms underlying HFO generation, especially in abnormal tissue, are not well understood. Using a physiological computer model of hippocampus, we investigate random synaptic activity (noise) as a potential initiator of HFOs. We explore parameters necessary to produce these oscillations and quantify the response using the tools of stochastic resonance (SR) and coherence resonance (CR). As predicted by SR, when noise was added to the network the model was able to detect a subthreshold periodic signal. Addition of basket cell interneurons produced two novel SR effects: 1) improved signal detection at low noise levels and 2) formation of coherent oscillations at high noise that were entrained to harmonics of the signal frequency. The periodic signal was then removed to study oscillations generated only by noise. The combined effects of network coupling and synaptic noise produced coherent, periodic oscillations within the network, an example of CR. Our results show that, under normal coupling conditions, synaptic noise was able to produce gamma (30–100 Hz) frequency oscillations. Synaptic noise generated HFOs in the ripple range (100–200 Hz) when the network had parameters similar to pathological findings in epilepsy: increased gap junctions or recurrent synaptic connections, loss of inhibitory interneurons such as basket cells, and increased synaptic noise. The model parameters that generated these effects are comparable with published experimental data. We propose that increased synaptic noise and physiological coupling mechanisms are sufficient to generate gamma oscillations and that pathologic changes in noise and coupling similar to those in epilepsy can produce abnormal ripples.
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Putzke, Carsten, Maja D. Bachmann, Philippa McGuinness, Elina Zhakina, Veronika Sunko, Marcin Konczykowski, Takashi Oka, et al. "h/e oscillations in interlayer transport of delafossites." Science 368, no. 6496 (June 11, 2020): 1234–38. http://dx.doi.org/10.1126/science.aay8413.
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Microstructures can be carefully designed to reveal the quantum phase of the wave-like nature of electrons in a metal. Here, we report phase-coherent oscillations of out-of-plane magnetoresistance in the layered delafossites PdCoO2 and PtCoO2. The oscillation period is equivalent to that determined by the magnetic flux quantum, h/e, threading an area defined by the atomic interlayer separation and the sample width, where h is Planck’s constant and e is the charge of an electron. The phase of the electron wave function appears robust over length scales exceeding 10 micrometers and persisting up to temperatures of T > 50 kelvin. We show that the experimental signal stems from a periodic field modulation of the out-of-plane hopping. These results demonstrate extraordinary single-particle quantum coherence lengths in delafossites.
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Gokhale, M. H., J. Javaraiah, and K. M. Hiremath. "Study of Sun's ‘Hydromagnetic’ Oscillations Using Sunspot Data." Symposium - International Astronomical Union 138 (1990): 375–78. http://dx.doi.org/10.1017/s0074180900044351.
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Spherical-harmonic-fourier (SHF) analysis of sun's ‘nominal toroidal magnetic field’, computed using sunspot data during 1874-1976, shows that sunspot activity can be considered as possibly originating in interference of sun's axi-symmetric ‘hydromagnetic’ oscillations of odd degrees up to ℓ ≈ 21 and periods ≈ 22y. The relative amplitudes and relative phases of these oscillations remain fairly constant, leading to butterfly diagrams with stable latitude-time correlations on all latitude scales ≳9°. The amplitudes and phases do however undergo slow coherent variations. The main modes (η<11) represent an approximately standing oscillation.
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Zvyagin, A. A. "Fluctuators and qubits: coherent quantum oscillations." Journal of Physics: Condensed Matter 17, no. 36 (August 25, 2005): L385—L391. http://dx.doi.org/10.1088/0953-8984/17/36/l02.
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Guinea, F., and G. Schön. "Coherent Charge Oscillations in Tunnel Junctions." Europhysics Letters (EPL) 1, no. 11 (June 1, 1986): 585–93. http://dx.doi.org/10.1209/0295-5075/1/11/007.
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Mukherjee, Rupak, Rajaraman Ganesh, and Abhijit Sen. "Coherent nonlinear oscillations in magnetohydrodynamic plasma." Physics of Plasmas 26, no. 4 (April 2019): 042121. http://dx.doi.org/10.1063/1.5083001.
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Lipkin, Harry J. "What is coherent in neutrino oscillations." Physics Letters B 579, no. 3-4 (January 2004): 355–60. http://dx.doi.org/10.1016/j.physletb.2003.11.013.
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Yee, K. J., Y. S. Lim, X. Liu, W. L. Lim, D. S. Kim, M. Dobrowolska, and J. K. Furdyna. "Coherent Optical Phonon Oscillations in GaMnAs." Journal of Superconductivity 18, no. 1 (February 2005): 115–19. http://dx.doi.org/10.1007/s10948-005-2161-9.
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Sha, W., Arthur L. Smirl, and W. F. Tseng. "Coherent Plasma Oscillations in Bulk Semiconductors." Physical Review Letters 74, no. 21 (May 22, 1995): 4273–76. http://dx.doi.org/10.1103/physrevlett.74.4273.
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Němec, P., K. Nitsch, M. Nikl, and P. Malý. "Coherent phonon oscillations in CsPbCl3 nanocrystals." physica status solidi (c) 1, no. 11 (November 2004): 2670–73. http://dx.doi.org/10.1002/pssc.200405370.
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Zhu, Ruidan, Meixia Ruan, Hao Li, Xuan Leng, Jiading Zou, Jiayu Wang, Hailong Chen, Zhuan Wang, and Yuxiang Weng. "Vibrational and vibronic coherences in the energy transfer process of light-harvesting complex II revealed by two-dimensional electronic spectroscopy." Journal of Chemical Physics 156, no. 12 (March 28, 2022): 125101. http://dx.doi.org/10.1063/5.0082280.
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The presence of quantum coherence in light-harvesting complex II (LHCII) as a mechanism to understand the efficiency of the light-harvesting function in natural photosynthetic systems is still debated due to its structural complexity and weak-amplitude coherent oscillations. Here, we revisit the coherent dynamics and clarify different types of coherences in the energy transfer processes of LHCII using a joint method of the high-S/N transient grating and two-dimensional electronic spectroscopy. We find that the electronic coherence decays completely within 50 fs at room temperature. The vibrational coherences of chlorophyll a dominate over oscillations within 1 ps, whereas a low-frequency mode of 340 cm−1 with a vibronic mixing character may participate in vibrationally assisted energy transfer between chlorophylls a. Our results may suggest that vibronic mixing is relevant for rapid energy transfer processes among chlorophylls in LHCII.
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Pinna, G. D., R. Maestri, A. Mortara, and M. T. La Rovere. "Cardiorespiratory interactions during periodic breathing in awake chronic heart failure patients." American Journal of Physiology-Heart and Circulatory Physiology 278, no. 3 (March 1, 2000): H932—H941. http://dx.doi.org/10.1152/ajpheart.2000.278.3.h932.
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We applied spectral techniques to the analysis of cardiorespiratory signals [instantaneous lung volume (ILV), instantaneous tidal volume (ITV), arterial O2 saturation ([Formula: see text]) at the ear, heart rate (HR), systolic (SAP), and diastolic (DAP) arterial pressure] during nonapneic periodic breathing (PB) in 29 awake chronic heart failure (CHF) patients and estimated the timing relationships between respiratory and slow cardiovascular (<0.04 Hz) oscillations. Our aim was 1) to elucidate major mechanisms involved in cardiorespiratory interactions during PB and 2) to test the hypothesis of a central vasomotor origin of PB. All cardiovascular signals were characterized by a dominant (≥84% of total power) oscillation at the frequency of PB (mean ± SE: 0.022 ± 0.0008 Hz), highly coherent (≥0.89), and delayed with respect to ITV (ITV-HR, 2.4 ± 0.72 s; ITV-SAP, 6.7 ± 0.65 s; ITV-DAP, 3.2 ± 0.61 s; P < 0.01). [Formula: see text] was highly coherent with (coherence function = 0.96 ± 0.009) and almost opposite in phase to ITV. These findings demonstrate the existence of a generalized cardiorespiratory rhythm led by the ventilatory oscillation and suggest that 1) the cyclic increase in inspiratory drive and cardiopulmonary reflexes and 2) mechanical effects of PB-induced changes in intrathoracic pressure are the more likely sources of the HR and blood pressure oscillations, respectively. The timing relationship between ITV and blood pressure signals excludes the possibility that PB represents the effect of a central vasomotor rhythm.
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KANO, HIDEAKI, TAKASHI SAITO, AKIKATSU UEKI, and TAKAYOSHI KOBAYASHI. "FIRST OBSERVATION OF DYNAMIC INTENSITY BORROWING INDUCED BY COHERENT MOLECULAR VIBRATIONS IN J-AGGREGATES REVEALED BY SUB-5-FS SPECTROSCOPY." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3817–20. http://dx.doi.org/10.1142/s0217979201008743.
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Sub-5-fs spectroscopy of porphyrin J-aggregates reveals for the first time coherent molecular vibration coupled to the Frenkel exciton. The oscillations with the frequency of 244cm-1 are described by a plus-cosine function for bleaching and a minus-cosine function for induced absorption. The coherent oscillation is explained by a modulated transition dipole moment, which is due to the transfer of an oscillator strength from the intense B-band to the weak Q-band through the ruffling mode with 244cm-1-frequency.
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POKORNÝ, JIŘÍ, JAN POKORNÝ, JITKA KOBILKOVÁ, ANNA JANDOVÁ, JAN VRBA, and JAN VRBA. "CANCER — PATHOLOGICAL BREAKDOWN OF COHERENT ENERGY STATES." Biophysical Reviews and Letters 09, no. 01 (March 2014): 115–33. http://dx.doi.org/10.1142/s1793048013300077.
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The fundamental property of biological systems is a coherent state far from thermodynamic equilibrium excited and sustained by energy supply. Mitochondria in eukaryotic cells produce energy and form conditions for excitation of oscillations in microtubules. Microtubule polar oscillations generate a coherent state far from thermodynamic equilibrium which makes possible cooperation of cells in the tissue. Mitochondrial dysfunction (the Warburg effect) in cancer development breaks down energy of the coherent state far from thermodynamic equilibrium and excludes the afflicted cell from the ordered multicellular tissue system. Cancer lowering of energy and coherence of the state far from thermodynamic equilibrium is the biggest difference from the healthy cells. Cancer treatment should target mitochondrial dysfunction to restore the coherent state far from thermodynamic equilibrium, apoptotic pathway, and subordination of the cell in the tissue. A vast variety of genetic changes and other disturbances in different cancers can result in several triggers of mitochondrial dysfunction. In cancers with the Warburg effect, mitochondrial dysfunction can be treated by inhibition of four isoforms of pyruvate dehydrogenase kinases. Treatment of the reverse Warburg effect cancers would be more complicated. Disturbances of cellular electromagnetic activity by conducting and asbestos fibers present a special problem of treatment.
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Miller, Jeremy A., and Garrett T. Kenyon. "Extracting Number-Selective Responses from Coherent Oscillations in a Computer Model." Neural Computation 19, no. 7 (July 2007): 1766–97. http://dx.doi.org/10.1162/neco.2007.19.7.1766.
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Cortical neurons selective for numerosity may underlie an innate number sense in both animals and humans. We hypothesize that the number- selective responses of cortical neurons may in part be extracted from coherent, object-specific oscillations . Here, indirect evidence for this hypothesis is obtained by analyzing the numerosity information encoded by coherent oscillations in artificially generated spikes trains. Several experiments report that gamma-band oscillations evoked by the same object remain coherent, whereas oscillations evoked by separate objects are uncorrelated. Because the oscillations arising from separate objects would add in random phase to the total power summed across all stimulated neurons, we postulated that the total gamma activity, normalized by the number of spikes, should fall roughly as the square root of the number of objects in the scene, thereby implicitly encoding numerosity. To test the hypothesis, we examined the normalized gamma activity in multiunit spike trains, 50 to 1000 msec in duration, produced by a model feedback circuit previously shown to generate realistic coherent oscillations. In response to images containing different numbers of objects, regardless of their shape, size, or shading, the normalized gamma activity followed a square-root-of-n rule as long as the separation between objects was sufficiently large and their relative size and contrast differences were not too great. Arrays of winner-take-all numerosity detectors, each responding to normalized gamma activity within a particular band, exhibited tuning curves consistent with behavioral data. We conclude that coherent oscillations in principle could contribute to the number-selective responses of cortical neurons, although many critical issues await experimental resolution.
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AlAhmadi, Ameenah N. "Förster Blockade and Excitation Transfer Behaviors of Two-Photon Rabi Oscillations of Exciton–Biexciton Levels in Coupled Quantum Dots." Journal of Nanomaterials 2023 (February 12, 2023): 1–8. http://dx.doi.org/10.1155/2023/4662648.
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We provide a theoretical study for the dynamical behavior of two-photon Rabi oscillations in two coupled quantum dots. Each dot is a three-level quantum system (ground, one-exciton, and biexciton states). We describe the optical dynamics within the density matrix formalism framework. The two-photon Rabi oscillations are found to be significantly affected by the strength of the interdot dipolar interaction. Using a detuned laser pulse with an exciton state of the driven quantum dot in our numerical simulations, a direct coherent excitation between the biexciton states can be established, but whether Rabi oscillations can be observed depend mainly on the strength of the dipolar interaction and bandwidth of the excitation laser. When the strength of the dipolar coupling is less than the excitation laser bandwidth, the time-dependent populations of the various two biexciton states of the system exhibit coherent oscillations with several frequencies. However, as we increase the dipolar coupling strength, the population transfer between the quantum dots levels amazingly becomes forbidden, and the excitation gets trapped at the initial state. The reduction of the influence of the dipolar interaction leads to a manipulation of two-photon Rabi oscillation in an ultrashort timescale (∼ps), opening possibilities to achieve ultrafast quantum state control and quantum logic gate generation.
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Zhao, Binbin, Yibo Peng, Xingguang Wang, and Cheng Wang. "Modulation Characteristics of Period-One Oscillations in Quantum Cascade Lasers." Applied Sciences 11, no. 24 (December 10, 2021): 11730. http://dx.doi.org/10.3390/app112411730.
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Quantum cascade lasers subject to tilted optical feedback produce periodic oscillations, quasi-periodic oscillations, and low-frequency oscillations. This work presents the modulation characteristics of period-one (P1) oscillations in a quantum cascade laser with tilted optical feedback. The electrical signal at the oscillation frequency is more than 50 dB higher than the noise level, and the electrical linewidth is less than 2.0 kHz. This electrical linewidth is about four orders of magnitude narrower than the optical linewidth (around 16 MHz) of the free-running laser, which suggests that the optical sidebands induced by the P1 oscillations are highly coherent with the main optical mode. In addition, the modulation depth of the optical signal is found to be in the range of 1% to 3.5%. In addition, it is verified in the simulations that the P1 oscillations induce not only amplitude modulation but also frequency modulation due to the phase-amplitude coupling effect.
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Deineka, Kateryna, Yurii Naumenko, and Anatolii Zmiievskyi. "THE DRUM ROTATION VELOCITY VALUE WHEN AUTO-OSCILLATION SELF-EXCITATION WITH MAXIMUM SWING OF A POLYGRANULAR INTRACHAMBER FILL." Vibrations in engineering and technology, no. 1(96) (August 27, 2020): 61–69. http://dx.doi.org/10.37128/2306-8744-2020-1-7.
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The influences of the structure of two-fractional polygranular intrachamber fill on the drum rotation velocity value when auto-oscillation self-excitation with maximum swing is considered. The pulsating mode of flow of such intrachamber fill is used in the self-oscillating grinding process in a tumbling mill. Spherical particles of non-coherent granular material of 2.2 mm size were used as a large fraction modeling the grinding bodies. Cement was used as the small fraction modeling the particles of the crushed material. The factors of experimental studies were accepted: the gaps between particles of large fraction degree of filling at rest dispersed particles of small fraction 0, 25, 50 and 100%, the relative size of particles of large fraction in the drum chamber 0.519, 0.733, 1.04, 1.47, 2.08, 2.93, 4.15 and 5.87% (drum chamber radius 212, 150, 106, 75, 53, 37.5, 26.5 and 18.75 mm), the chamber degree of filling at rest 25, 35 and 45%. The method of visual analysis of transient processes of self-oscillating fill flow modes in the cross section of a rotating chamber was applied. Measurements of the drum rotation velocity during fill self-excited self-oscillations were performed. The magnitude of the self-oscillation swing was estimated by the increase in the difference of the maximum and minimum values of the fill dilatation over one period of pulsating. The magnitude of the relative drum rotation velocity at the maximum range of fill self-oscillation swing varied within 0.777-1.4. The effect of a decrease in the relative drum rotation velocity value, when the maximum polygranular intrachamber fill self-oscillations swing, with enhanced fill coherent properties has been registered. A decrease in the relative rotational velocity was established with a decrease in the relative particle size of large fill fraction and an increase in the content of small fill fraction and an increase in the chamber degree of filling. A sharp intensification of the decrease in the relative rotation velocity at a value of the relative size of large particles of less than 0.015 is revealed.
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Raghavachari, S., J. E. Lisman, M. Tully, J. R. Madsen, E. B. Bromfield, and M. J. Kahana. "Theta Oscillations in Human Cortex During a Working-Memory Task: Evidence for Local Generators." Journal of Neurophysiology 95, no. 3 (March 2006): 1630–38. http://dx.doi.org/10.1152/jn.00409.2005.
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Cortical theta appears important in sensory processing and memory. Intracanial electrode recordings provide a high spatial resolution method for studying such oscillations during cognitive tasks. Recent work revealed sites at which oscillations in the theta range (4–12 Hz) could be gated by a working-memory task: theta power was increased at task onset and continued until task offset. Using a large data set that has now been collected (10 participants/619 recording sites), we have sufficient sampling to determine how these gated sites are distributed in the cortex and how they are synchronized. A substantial fraction of sites in occipital/parietal (45/157) and temporal (23/280) cortices were gated by the task. Surprisingly, this aspect of working-memory function was virtually absent in frontal cortex (2/182). Coherence measures were used to analyze the synchronization of oscillations. We suspected that because of their coordinate regulation by the working-memory task, gated sites would have synchronized theta oscillations. We found that, whereas nearby gated sites (<20 mm) were often but not always coherent, distant gated sites were almost never coherent. Our results imply that there are local mechanisms for the generation of cortical theta.
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Lee, Chang Young, Wonjoon Choi, Jae-Hee Han, and Michael S. Strano. "Coherence Resonance in a Single-Walled Carbon Nanotube Ion Channel." Science 329, no. 5997 (September 9, 2010): 1320–24. http://dx.doi.org/10.1126/science.1193383.
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Biological ion channels are able to generate coherent and oscillatory signals from intrinsically noisy and stochastic components for ultrasensitive discrimination with the use of stochastic resonance, a concept not yet demonstrated in human-made analogs. We show that a single-walled carbon nanotube demonstrates oscillations in electroosmotic current through its interior at specific ranges of electric field that are the signatures of coherence resonance. Stochastic pore blocking is observed when individual cations partition into the nanotube obstructing an otherwise stable proton current. The observed oscillations occur because of coupling between pore blocking and a proton-diffusion limitation at the pore mouth. The result illustrates how simple ionic transport can generate coherent waveforms within an inherently noisy environment and points to new types of nanoreactors, sensors, and nanofluidic channels based on this platform.
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Castelhano, João, Inês Bernardino, José Rebola, Eugenio Rodriguez, and Miguel Castelo-Branco. "Oscillations or Synchrony? Disruption of Neural Synchrony despite Enhanced Gamma Oscillations in a Model of Disrupted Perceptual Coherence." Journal of Cognitive Neuroscience 27, no. 12 (December 2015): 2416–26. http://dx.doi.org/10.1162/jocn_a_00863.
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It has been hypothesized that neural synchrony underlies perceptual coherence. The hypothesis of loss of central perceptual coherence has been proposed to be at the origin of abnormal cognition in autism spectrum disorders and Williams syndrome, a neurodevelopmental disorder linked with autism, and a clearcut model for impaired central coherence. We took advantage of this model of impaired holistic processing to test the hypothesis that loss of neural synchrony plays a separable role in visual integration using EEG and a set of experimental tasks requiring coherent integration of local elements leading to 3-D face perception. A profound reorganization of brain activity was identified. Neural synchrony was reduced across stimulus conditions, and this was associated with increased amplitude modulation at 25–45 Hz. This combination of a dramatic loss of synchrony despite increased oscillatory activity is strong evidence that synchrony underlies central coherence. This is the first time, to our knowledge, that dissociation between amplitude and synchrony is reported in a human model of impaired perceptual coherence, suggesting that loss of phase coherence is more directly related to disruption of holistic perception.
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Aebischer, H. A., and Yu S. Sayasov. "Drift waves and magnetic field oscillations in cylindrical plasmas." Journal of Plasma Physics 40, no. 2 (October 1988): 319–36. http://dx.doi.org/10.1017/s0022377800013301.
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A general investigation of linear drift-wave phenomena in cylindrically bounded plasmas, immersed in a magnetic field without shear and curvature, is performed within the two-fluid hydrodynamical approximation, taking into account electron-temperature oscillations and inhomogeneous radial distributions of the undisturbed electron density and temperature. For plasmas in which the electron temperature strongly exceeds the ion temperature the problem is reduced to an ordinary complex second-order differential equation describing the radial distribution of the oscillating electric potential. It is shown that the presence of electron-temperature oscillations (which must always exist in order to satisfy electron-energy conservation) and of radial gradients in the undisturbed electron temperature (which must always exist owing to cooling of the plasma at the boundary) leads to an important modification of the theory of drift waves in cylindrical plasmas (with regard to their stability and the radial distribution of the oscillating quantities) compared with previous papers in which these phenomena were disregarded. A numerical program for solving the corresponding complex-eigenvalue problem has been derived that allows a realistic calculation of all the quantities pertaining to drift-wave phenomena. It has been applied, in particular, to the calculation of the radial distribution of the oscillating coherent magnetic fields accompanying the coherent drift waves. The numerical results prove to be in good agreement with experiments performed with a helium plasma.
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Fu Wang, Fu Wang, Zhi Wang Zhi Wang, Chongqing Wu Chongqing Wu, and Zhenchao Sun Zhenchao Sun. "Superluminal and slow light propagation in SOA based on coherent population oscillations." Chinese Optics Letters 13, s1 (2015): S11902–311906. http://dx.doi.org/10.3788/col201513.s11902.
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Durkin, Jaclyn, Aneesha K. Suresh, Julie Colbath, Christopher Broussard, Jiaxing Wu, Michal Zochowski, and Sara J. Aton. "Cortically coordinated NREM thalamocortical oscillations play an essential, instructive role in visual system plasticity." Proceedings of the National Academy of Sciences 114, no. 39 (September 11, 2017): 10485–90. http://dx.doi.org/10.1073/pnas.1710613114.
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Two long-standing questions in neuroscience are how sleep promotes brain plasticity and why some forms of plasticity occur preferentially during sleep vs. wake. Establishing causal relationships between specific features of sleep (e.g., network oscillations) and sleep-dependent plasticity has been difficult. Here we demonstrate that presentation of a novel visual stimulus (a single oriented grating) causes immediate, instructive changes in the firing of mouse lateral geniculate nucleus (LGN) neurons, leading to increased firing-rate responses to the presented stimulus orientation (relative to other orientations). However, stimulus presentation alone does not affect primary visual cortex (V1) neurons, which show response changes only after a period of subsequent sleep. During poststimulus nonrapid eye movement (NREM) sleep, LGN neuron overall spike-field coherence (SFC) with V1 delta (0.5–4 Hz) and spindle (7–15 Hz) oscillations increased, with neurons most responsive to the presented stimulus showing greater SFC. To test whether coherent communication between LGN and V1 was essential for cortical plasticity, we first tested the role of layer 6 corticothalamic (CT) V1 neurons in coherent firing within the LGN-V1 network. We found that rhythmic optogenetic activation of CT V1 neurons dramatically induced coherent firing in LGN neurons and, to a lesser extent, in V1 neurons in the other cortical layers. Optogenetic interference with CT feedback to LGN during poststimulus NREM sleep (but not REM or wake) disrupts coherence between LGN and V1 and also blocks sleep-dependent response changes in V1. We conclude that NREM oscillations relay information regarding prior sensory experience between the thalamus and cortex to promote cortical plasticity.