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Artigos de revistas sobre o assunto "Frequency entrainment"
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Zalalutdinov, M., K. L. Aubin, M. Pandey, A. T. Zehnder, R. H. Rand, H. G. Craighead, J. M. Parpia e B. H. Houston. "Frequency entrainment for micromechanical oscillator". Applied Physics Letters 83, n.º 16 (20 de outubro de 2003): 3281–83. http://dx.doi.org/10.1063/1.1618363.
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Guo, Yifei, Rory John Bufacchi, Giacomo Novembre, Marina Kilintari, Massieh Moayedi, Li Hu e Gian Domenico Iannetti. "Ultralow-frequency neural entrainment to pain". PLOS Biology 18, n.º 4 (13 de abril de 2020): e3000491. http://dx.doi.org/10.1371/journal.pbio.3000491.
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Higgs, Matthew H., e Charles J. Wilson. "Frequency-dependent entrainment of striatal fast-spiking interneurons". Journal of Neurophysiology 122, n.º 3 (1 de setembro de 2019): 1060–72. http://dx.doi.org/10.1152/jn.00369.2019.
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Striatal fast-spiking interneurons (FSIs) fire in variable-length runs of action potentials at 20–200 spikes/s separated by pauses. In vivo, or with fluctuating applied current, both runs and pauses become briefer and more variable. During runs, spikes are entrained specifically to gamma-frequency components of the input fluctuations. We stimulated parvalbumin-expressing striatal FSIs in mouse brain slices with broadband noise currents added to direct current steps and measured spike entrainment across all frequencies. As the constant current level was increased, FSIs produced longer runs and showed sharper frequency tuning, with best entrainment at the stimulus frequency matching their intrarun firing rate. We separated the contributions of previous spikes from that of the fluctuating stimulus, revealing a strong contribution of previous action potentials to gamma-frequency entrainment. In contrast, after subtraction of the effect inherited from the previous spike, the remaining stimulus contribution to spike generation was less sharply tuned, showing a larger contribution of lower frequencies. The frequency specificity of entrainment within a run was reproduced with a phase resetting model based on experimentally measured phase resetting curves of the same FSIs. In the model, broadly tuned phase entrainment for the first spike in a run evolved into sharply tuned gamma entrainment over the next few spikes. The data and modeling results indicate that for FSIs firing in brief runs and pauses firing within runs is entrained by gamma-frequency components of the input, whereas the onset timing of runs may be sensitive to a wider range of stimulus frequency components. NEW & NOTEWORTHY Specific types of neurons entrain their spikes to particular oscillation frequencies in their synaptic input. This entrainment is commonly understood in terms of the subthreshold voltage response, but how this translates to spiking is not clear. We show that in striatal fast-spiking interneurons, entrainment to gamma-frequency input depends on rhythmic spike runs and is explained by the phase resetting curve, whereas run initiation can be triggered by a broad range of input frequencies.
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Dushanova, Juliana, Yordanka Lalova, Antoaneta Kalonkina e Stefan Tsokov. "Speech–Brain Frequency Entrainment of Dyslexia with and without Phonological Deficits". Brain Sciences 10, n.º 12 (28 de novembro de 2020): 920. http://dx.doi.org/10.3390/brainsci10120920.
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Developmental dyslexia is a cognitive disorder characterized by difficulties in linguistic processing. Our purpose is to distinguish subtypes of developmental dyslexia by the level of speech–EEG frequency entrainment (δ: 1–4; β: 12.5–22.5; γ1: 25–35; and γ2: 35–80 Hz) in word/pseudoword auditory discrimination. Depending on the type of disabilities, dyslexics can divide into two subtypes—with less pronounced phonological deficits (NoPhoDys—visual dyslexia) and with more pronounced ones (PhoDys—phonological dyslexia). For correctly recognized stimuli, the δ-entrainment is significantly worse in dyslexic children compared to controls at a level of speech prosody and syllabic analysis. Controls and NoPhoDys show a stronger δ-entrainment in the left-hemispheric auditory cortex (AC), anterior temporal lobe (ATL), frontal, and motor cortices than PhoDys. Dyslexic subgroups concerning normolexics have a deficit of δ-entrainment in the left ATL, inferior frontal gyrus (IFG), and the right AC. PhoDys has higher δ-entrainment in the posterior part of adjacent STS regions than NoPhoDys. Insufficient low-frequency β changes over the IFG, the inferior parietal lobe of PhoDys compared to NoPhoDys correspond to their worse phonological short-term memory. Left-dominant 30 Hz-entrainment for normolexics to phonemic frequencies characterizes the right AC, adjacent regions to superior temporal sulcus of dyslexics. The pronounced 40 Hz-entrainment in PhoDys than the other groups suggest a hearing “reassembly” and a poor phonological working memory. Shifting up to higher-frequency γ-entrainment in the AC of NoPhoDys can lead to verbal memory deficits. Different patterns of cortical reorganization based on the left or right hemisphere lead to differential dyslexic profiles.
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Wiesman, Alex I., e Tony W. Wilson. "Alpha Frequency Entrainment Reduces the Effect of Visual Distractors". Journal of Cognitive Neuroscience 31, n.º 9 (setembro de 2019): 1392–403. http://dx.doi.org/10.1162/jocn_a_01422.
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Numerous studies have linked alpha frequency (∼10 Hz) visual entrainment to the inhibition of incoming visual information. However, although these studies have provided key evidence for the intrinsic sensitivity of the human brain to incoming alpha frequency signals, they have only examined the negative impact of alpha entrainment on target stimuli. Thus, it remains uncertain whether the perception of distracting or nonimperative stimuli can also be affected by alpha frequency entrainment. In the current study, we address this question using an adapted version of the arrow-based Erikson “flanker” paradigm that incorporates stimuli flickering at two distinct frequencies: 10 Hz (alpha) and 30 Hz. By presenting flickering stimuli in the portions of the visual field where the flanking arrows would soon appear, we aimed to determine whether the frequency of visual entrainment (i.e., 10 Hz vs. 30 Hz) significantly interacted with the congruency of the flanking arrows (representing selective attention processing) using behavioral task performance and neural oscillations as the outcome metrics. Twenty-three healthy adult participants underwent magnetoencephalography during performance of the task. Our results indicated a reduced congruency effect (i.e., a smaller difference between congruent and incongruent trials) in the alpha flicker condition, as compared with the 30-Hz flicker condition, which suggests a robust relationship between alpha entrainment and the active inhibition of distractor stimuli appearing in that portion of the visual field. Supporting this, alpha frequency (but not 30 Hz) entrainment responses in the primary visual cortex also covaried significantly with the behavioral congruency effect.
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Hong, Hyunsuk, e Beom Jun Kim. "Frequency-Entrainment Measures in Coupled-Oscillator Systems". Journal of the Korean Physical Society 52, n.º 2 (15 de fevereiro de 2008): 198–202. http://dx.doi.org/10.3938/jkps.52.198.
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Barnikol, Utako B., Oleksandr V. Popovych, Christian Hauptmann, Volker Sturm, Hans-Joachim Freund e Peter A. Tass. "Tremor entrainment by patterned low-frequency stimulation". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, n.º 1880 (16 de julho de 2008): 3545–73. http://dx.doi.org/10.1098/rsta.2008.0104.
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High-frequency test stimulation for tremor suppression is a standard procedure for functional target localization during deep brain stimulation. This method does not work in cases where tremor vanishes intraoperatively, for example, due to general anaesthesia or due to an insertional effect. To overcome this difficulty, we developed a stimulation technique that effectively evokes tremor in a well-defined and quantifiable manner. For this, we used patterned low-frequency stimulation (PLFS), i.e. brief high-frequency pulse trains administered at pulse rates similar to neurons' preferred burst frequency. Unlike periodic single-pulse stimulation, PLFS enables one to convey effective and considerably greater integral charge densities without violation of safety requirements. In a computational investigation of an oscillatory neuronal network temporarily rendered inactive, we found that PLFS evokes synchronized activity, phase locked to the stimulus. While a stronger increase in the amount of synchrony in the neuronal population requires higher stimulus intensities, the portion of synchronously active neurons nevertheless becomes strongly phase locked to PLFS already at weak stimulus intensities. The phase entrainment effect of PLFS turned out to be robust against variations in the stimulation frequency, whereas enhancement of synchrony required precisely tuned stimulation frequencies. We applied PLFS to a patient with spinocerebellar ataxia type 2 (SCA2) with pronounced tremor that disappeared intraoperatively under general anaesthesia. In accordance with our computational results, PLFS evoked tremor, phase locked to the stimulus. In particular, weak PLFS caused low-amplitude, but strongly phase-locked tremor. PLFS test stimulations provided the only functional information about target localization. Optimal target point selection was confirmed by excellent post-operative tremor suppression.
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Cronin, Jane. "Entrainment of frequency in singularly perturbed systems". Methods and Applications of Analysis 3, n.º 3 (1996): 370–400. http://dx.doi.org/10.4310/maa.1996.v3.n3.a6.
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Mausser, G., e G. Schwarz. "Air entrainment during high-frequency jet ventilation". British Journal of Anaesthesia 100, n.º 3 (março de 2008): 418–19. http://dx.doi.org/10.1093/bja/aen008.
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Varangis, P. M., A. Gavrielides, T. Erneux, V. Kovanis e L. F. Lester. "Frequency Entrainment in Optically Injected Semiconductor Lasers". Physical Review Letters 78, n.º 12 (24 de março de 1997): 2353–56. http://dx.doi.org/10.1103/physrevlett.78.2353.
Texto completo da fonteTeses / dissertações sobre o assunto "Frequency entrainment"
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Iaccarino, Hannah Frances. "Gamma frequency entrainment attenuates amyloid load and modifies microglia". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109020.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, February 2017.Cataloged from PDF version of thesis. "January 2016."
Includes bibliographical references (pages 101-107).
Gamma oscillations (20-50 Hz), a common local field potential signature in many brain regions, are generated by a resonant circuit between fast-spiking (FS)-parvalbumin (PV)-interneurons and pyramidal cells. Changes in gamma oscillations have been observed in several neurological disorders. However, the relationship between gamma oscillations and cellular pathologies of these disorders is unclear. Here, we investigated this relationship using the 5XFAD mouse model of Alzheimer's disease (AD) and found reduced behaviorally driven gamma activity before the onset of plaque formation or evidence of cognitive decline. Because of the early onset of gamma deficits, we aimed to determine if exogenous gamma manipulations could influence disease pathology progression. We discovered that optogenetically driving FS-PV-interneurons at gamma frequency (40 Hz) reduced levels of amyloid-[beta] (A[beta])₁-₄₀ and A[beta] ₁-₄₂ isoforms in the hippocampus of 5XFAD mice. Neither driving FS-PV-interneurons at other frequencies, nor driving excitatory neurons, reduced A[beta] levels. Furthermore, driving FS-PV-interneurons at 40 Hz reduced enlarged endosomes and amyloid precursor protein (APP) cleavage intermediates in hippocampus. Gene expression profiling revealed an induction of microglia specific genes associated with morphological transformation of microglia and increased A[beta] phagocytosis by microglia. Inspired by these observations, we designed a non-invasive light-flickering paradigm that induced 40 Hz activity in visual cortex. The light-flickering paradigm profoundly reduced A[beta]₁-₄₀ and A[beta]₁-₄₂ levels in the visual cortex of pre-depositing mice and mitigated plaque load in aged, depositing mice. A GABAA antagonist completely blocked this effect; further evidence that GABAergic signaling is essential for this neuroprotective gamma activity. Finally, we showed that 40 Hz activity reduced tau phosphorylation in the TauP301S mouse model. Overall, our findings uncover a previously unappreciated function of the brain's gamma rhythms in neuroprotection by recruiting both neuronal and glial responses to mitigate AD-associated pathology.
by Hannah Frances Iaccarino.
Ph. D.
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Suk, Ho-Jun. "Automated cell-targeted electrophysiology in vivo and non-invasive gamma frequency entrainment". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122429.
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Thesis: Ph. D., Harvard-MIT Program in Health Sciences and Technology, 2019Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 105-110).
Targeted patch clamp recording is a powerful method for characterizing visually identified cells in intact neural circuits, but it requires skill to perform. We found that a closed-loop real-time imaging strategy, which continuously compensates for cell movement while approaching the cell with a pipette tip, allows for the development of an algorithm amenable to automation. We built a robotic system that can implement this algorithm and validated that our system can automatically patch fluorophore-expressing neurons of multiple types in the living mouse cortex, with yields comparable to skilled human experimenters. By facilitating targeted patch clamp recordings in vivo, our robot may enable scalable characterization of identified cell types in intact neural circuits. Activities of individual neurons in neural circuits give rise to network oscillations, whose frequencies are closely related to specific brain states.
For example, network oscillations in the 30 - 90 Hz range, observed using electroencephalogram (EEG), are called gamma oscillations and increase during attention, memory formation, and recall. In Alzheimer's disease (AD), gamma oscillations are disrupted compared to healthy individuals. Recently, noninvasive visual and auditory stimulations at 40 Hz, called Gamma ENtrainment Using Sensory stimulus ("GENUS"), have been shown to positively impact pathology and improve memory in AD mouse models, with concurrent visual and auditory GENUS leading to a more widespread effect in the AD mouse brain compared to visual or auditory stimulation alone. However, it is unclear what effect such sensory stimulations would have on the human brain. To test for the safety and feasibility of GENUS in humans, we developed a device that can deliver 40 Hz light and sound stimulations at intensity levels tolerable to humans.
We found that our device can safely lead to steady 40 Hz entrainment in cognitively normal young (20 - 33 years old) and older (55 - 75 years old) subjects, with concurrent visual and auditory stimulation leading to stronger and more widespread entrainment than visual or auditory stimulation alone. These findings suggest that GENUS can be a safe and effective method for widespread 40 Hz entrainment, which may have therapeutic effects in people suffering from AD.
by Ho-Jun Suk.
Ph. D.
Ph.D. Harvard-MIT Program in Health Sciences and Technology
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Bouvet, Cécile. "Auditory-motor entrainment : behavioural and cerebral dynamics". Thesis, Montpellier, 2020. http://www.theses.fr/2020MONT4002.
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Nous synchronisons nos mouvements avec les rythmes auditifs présents dans notre environnement sans même en avoir l’intention. Cette coordination, qui influence la stabilité du mouvement produit, s’est avéré bénéfique dans des contextes sportifs et thérapeutiques. À ce jour, la recherche a atteint un large consensus sur les mécanismes sous-tendant les processus de coordination sensori-motrice intentionnelle, mais explore toujours les mécanismes d’entraînement audio-moteur spontanés. Cette thèse aborde la dynamique de synchronisation non-intentionnelle pour différentes relations de fréquence entre un mouvement périodique et un rythme auditif. À travers quatre études complémentaires, ce travail questionne le rôle de multiples niveaux de graduation temporelle et de leur accentuation dans l’émergence et la stabilité de formes simples vs. complexes de synchronisation. La 1ère étude confirme quantitativement l’émergence d’une synchronisation audio-motrice spontanée, différente d’une relation de fréquence de 1:1. La 2ème étude introduit le bénéfice de l’addition d’un patron d’accentuation congruent pour l’émergence de synchronisation à différents rapports de fréquence. Elle permet également d’observer qu’un patron d’accentuation ternaire est plus favorable à la synchronisation qu’un patron d’accentuation binaire. La 3ème étude s’intéresse à cette découverte via l’enregistrement Électroencéphalographique des réponses neurales aux différents patrons d’accentuation, confirmant une différence de réponse aux stimulations binaires et ternaires, liée aux performances comportementales. La 4ème étude se concentre sur le bénéfice des patrons d’accentuation sur la production de mouvement plus complexe. Elle considère également les réponses neurales aux différents patrons d’accentuation en prenant en compte la congruence avec la coordination motrice produite, démontrant l’influence des systèmes sensoriels et moteur sur la perception rythmique. En résumé, ces résultats démontrent qu’un entraînement audio-moteur spontané peut émerger à différents ratios de fréquences en conformité avec les prédictions de l’approche des systèmes dynamiques de l’action et de la perception. De plus, l’entraînement audio-moteur spontané est modulé (i.e., promu ou dégradé) par l’addition de patrons d’accentuation, selon leur congruence avec le mode de fréquence audio-moteur et les réponses neurales. D’autre part, des formes plus complexes de coordination répondent de façon similaire à la présence d’accentuation, soutenues par le couplage audio-moteur et les processus de perception rythmique auditive. Ainsi, les conclusions de cette thèse ouvrent de nouvelles pistes de recherche sur la synchronisation audio-motrice spontanée et son application à l’entraînement et la réhabilitation des performances motricesWe often synchronise our movements to auditory rhythms in our environment without the intention to do so. Such coordination influences the stability of movement performance, and, therefore, can be used to our benefit in sport and therapeutic contexts. Research to date has largely reached a consensus about the mechanisms underlying intentional sensory-motor coordination, but spontaneous auditory-motor entrainment is still under exploration. This thesis addresses the dynamics of unintentional synchronisation towards various frequency relationships between periodic movement and auditory rhythm frequencies. It presents four complementary studies questioning the role of multiple metrical levels and their accentuation on the emergence and stability of simple vs. complex synchronisation in healthy adults. The 1st study confirms quantitatively the emergence of spontaneous synchronisation at frequency ratios different from 1:1. The 2nd study introduces the benefit of a congruent accentuation pattern on the emergence of various frequency ratios. It leads to the observation that a ternary accentuation pattern facilitates synchronisation more than a binary accentuation pattern. The 3rd study examines this new finding through the recording of neural responses to various accented patterns using Electroencephalography, confirming a differential response to ternary and binary patterns linked to behavioural performance. The 4th study focuses on the benefit of accentuation patterns for the production of a more complex type of movement coordination. It also measured neural tracking of the accentuation pattern relative to the congruence of the motor coordination performed, showing that both sensory and motor systems influenced rhythm perception. All together, these results demonstrate that spontaneous auditory-motor entrainment can emerge at various frequency ratios in accordance with the predictions of the dynamical systems approach to action and perception. Furthermore, spontaneous auditory-motor entrainment is modulated (i.e., increased or decreased) by the addition of simple accentuation patterns, depending on congruence with the auditory-motor frequency mode and the neural response to the accents. In addition, more complex multi-limb motor coordination performance responds similarly to accentuation, underpinned by auditory-motor coupling and sensory processing of the auditory rhythms. Therefore, the findings of this thesis open new avenues for future research on spontaneous auditory-motor coordination and its application in the training and rehabilitation of motor performance
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Eisenhower, Bryan A. "Identification of Thermoacoustic Dynamics Exhibiting Limit Cycle Behavior". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33095.
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Identification of thermoacoustic dynamics that exhibit limit cycle behavior is needed to gain a better intuitive feel of the system, to design complex control strategies, and to validate modeling efforts. Limit cycle oscillations arise in thermoacoustic systems due to the coupling between a nonlinear heat release process and the acoustic dynamics of the combustor. This response arises in lean premixed gaseous power generating turbines and is a concern due to the detrimental effect of the pressure oscillations on the structural integrity of the combustor. Due to the volatile environment intrinsic in the combustor, multiple sensing apparatuses are not available. Therefore, in the current study, an identification approach is assessed considering only a single output from the thermoacoustic system.
As a means to further investigate the thermoacoustic limit cycle behavior, a scaled version of the industry-based turbine was constructed. By anchoring a flame halfway from end-to-end of a closed-open tube, a similar nonlinear response is achieved. A harmonic balance technique that linearly incorporates the nonlinearity is developed which uses frequency entrainment to offer sufficient information for the identification. Its validity is assessed on a model, which is based on known dynamics of the thermoacoustic system. The structure of the identification algorithm is based on a two-mode acoustic model with both dynamics and nonlinearity in the feedback loop. The limitations of using only a two-mode identification structure for a system with more than two modes is discussed as well as future efforts that may alleviate this problem.
Master of Science
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Cloherty, Shaun Liam Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Cellular interaction in the cardiac pacemaker: a modelling study". Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2005. http://handle.unsw.edu.au/1959.4/22512.
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In mammalian hearts, initiation of the heartbeat occurs in a region of specialised pacemaker cells known as the sinoatrial node (SAN). The SAN is a highly complex spatially distributed structure which displays considerable cellular heterogeneity and is subject to complex electrotonic interactions with the surrounding atrial tissue. In this study, biophysically detailed ionic models of central and peripheral SAN pacemaker cells are described. These models are able to accurately reproduce experimental recordings of the membrane potential from central and peripheral SAN tissue. These models are used to investigate frequency synchronisation of electrically coupled cardiac pacemaker cells. Based on simulation results presented, it is proposed that cellular heterogeneity in the SAN plays an important role in achieving rhythm coordination and possibly contributes to the efficient activation of the surrounding atrial myocardium. This represents an important, previously unexplored, mechanism underlying pacemaker synchronisation and cardiac activation in vivo. A spatial-gradient model of action potential heterogeneity within the SAN is then formulated using a large-scale least squares optimisation technique. This model accurately reproduces the smooth spatial variation in action potential characteristics observed in the SAN. One and two dimensional models of the intact SAN are then formulated and three proposed models of SAN heterogeneity are investigated: 1) the discrete-region model, in which the SAN consists of a compact central region surrounded by a region of transitional pacemaker cells, 2) the gradient model, in which cells of the SAN exhibit a smooth variation in properties from the centre to the periphery of the SAN, and 3) the mosaic model, in which SAN and atrial cells are scattered throughout the SAN region with the proportion of atrial cells increasing towards the periphery. Simulation results suggest that the gradient model achieves frequency entrainment more easily than the other models of SAN heterogeneity. The gradient model also reproduces action potential waveshapes and a site of earliest activation consistent with experimental observations in the intact SAN. It is therefore proposed that the gradient model of SAN heterogeneity represents the most plausible model of SAN organisation.
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Demir, Semahat Siddika. "Mechanisms of frequency-entrainment in neuromodulated, synaptically driven pacing and bursting cells". Thesis, 1995. http://hdl.handle.net/1911/16810.
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The development of quantitative models that describe how neural inputs control the electrophysiological behavior of two cellular oscillators is presented. These cellular oscillators are a spontaneously beating mammalian cardiac cell (the sinoatrial node (SAN) cell of the rabbit heart) and a well-known endogenously bursting neuron (neuron R15 cell from the abdominal ganglion in Aplysia). The models representing the SAN cell and the R15 cell have two major components: a Hodgkin-Huxley type membrane model and a fluid compartment model. Each membrane model consists of the ionic membrane currents, membrane pumps and the exchanger. The fluid compartment model describes the changes for the ions inside and outside the cell. The neuromodulatory effects of the neurotransmitters used in the SAN cell and the R15 cell are modeled in the membrane and fluid compartments in detail consistent with available experimental data. These neuromodulatory effects resulting from single neural inputs are investigated by transient phase sensitivity analysis and are presented in terms of phase response curves (PRCs). Moreover, the effects due to the periodic neural stimulation are analyzed by steady-state entrainment curves. Even though, there are differences in the two biological oscillators studied (SAN and R15 cells), our simulations show that they share many qualitative and quantitative features in their phase sensitivity to input stimuli.
This dissertation provides a better understanding of the requirements for the control of a biological oscillator since the study deals with quantitative cell models that permit the investigation of basic mechanisms (currents, concentrations, etc.) underlying the phenomena of phase sensitivity and entrainment in two cells that are representative of the range of complexity in biological oscillators.
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Wargsjö, Ebba, e Damberg Albin Hedehag. "Experimental Investigation Of The Air-Water Flow Properties In The Cavity Zone Downstream A Chute Aerator". Thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328438.
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Chute aerators are widely used in spillways to avoid cavitation damage. When the water flow passes the aerator, two jets form – upper and lower jet. The purpose of this thesis has been to study the effects from the aerator by conducting experiments in a model with a flow depth large enough to ensure that the upper and lower jet remain separated. This means that the effects from the self-aeration at the upper surface has no effect on the process in the lower jet, thus making it possible to quantify the effects from the aerator. This thesis has also provided information of the bubble formation in the lower jet to aid in the ongoing research at Sichuan University. The following questions were set up for this thesis: • What is cavitation and how is it harmful? • What is the working principle of an aerator? • How is air concentration and bubble frequency distributed in the flow? • How well do the experimental results coincide with theoretical calculations? • How are air bubbles formed and transported within the flow? The effects from the aerator have been quantified by measuring the air concentration and bubble frequency throughout the cavity zone. The model was modified and the velocity was varied between the experiments to study how different parameters effected the aeration. The results indicate that much air is being entrapped in the lower surface, but only a small amount of the entrapped air is being entrained into the flow and that the bubble frequency increases with both distance from the aerator and with an increased flow velocity. No difference in behaviour was noticed between the different modifications of the model. The bubble formation was studied by recording the flow with a high-speed camera. These recordings were used to obtain data about important parameters for the ongoing research at Sichuan University.
Capítulos de livros sobre o assunto "Frequency entrainment"
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Sharpe, Ryan, e Mufti Mahmud. "Effect of the Gamma Entrainment Frequency in Pertinence to Mood, Memory and Cognition". In Brain Informatics, 50–61. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-59277-6_5.
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Wang, Chi-Yuen, e Michael Manga. "Liquefaction". In Lecture Notes in Earth System Sciences, 301–21. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64308-9_11.
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AbstractLiquefaction of the ground during earthquakes has long been documented and has drawn much attention from earthquake engineers because of its devastation to engineered structures. In this chapter we review a few of the best studied field cases and summarize insights from extensive experimental data critical for understanding the interaction between earthquakes and liquefaction. Despite the progress made in the last few decades, several outstanding problems remain unanswered. One is the mechanism for liquefaction beyond the near field, which has been abundantly documented in the field. This is not well understood because, according to laboratory data, liquefaction should occur only in the near field where the seismic energy density is great enough to cause undrained consolidation leading up to liquefaction. Another outstanding question is the dependence of liquefaction on the frequency of the seismic waves, where the current results from the field and laboratory studies are in conflict. Finally, while in most cases the liquefied sediments are sand or silty sand, well-graded gravel has increasingly been witnessed to liquefy during earthquakes and is not simply the result of entrainment by liquified sand. It is challenging to explain how pore pressure could build up in gravely soils and be maintained at a level high enough to cause liquefaction.
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"Chapter 12. Entrainment of Frequency". In Nonlinear Oscillations in Physical Systems, 285–308. Princeton University Press, 1986. http://dx.doi.org/10.1515/9781400852871.285.
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Riess Jones, Mari. "Tuning in to Very Fast Events". In Time Will Tell, 107–34. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190618216.003.0006.
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This chapter demonstrates that entrainment applies to very fast events, namely sounds with high frequencies. To illustrate this, prominent approaches to pitch perception are sketched along with basic pitch perception phenomena (e.g., virtual pitch perception). In this chapter, multiple frequency components comprise a single complex sound, and people must judge the pitch of this collection of frequencies. Both a successful psychoacoustic theory of pitch perception and a dynamic attending approach offer valid explanations of various phenomena surrounding the pitch of such sounds. This suggests the potential of entrainment in describing pitch perception (i.e., entrainments at fast time scales). The perception of consonance and dissonance is also considered, where dissonance is linked to complex synchronicities termed attractors. Finally, this chapter introduces oscillator clusters, a group of endogenously entrained oscillations.
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"Length-Frequency (Mixed Beta) Model". In Defining and Assessing Adverse Environmental Impact from Power Plant Impingement and Entrainment of Aquatic Organisms, 71–76. CRC Press, 2003. http://dx.doi.org/10.1201/b16996-11.
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Shibasaki, Hiroshi, Mark Hallett, Kailash P. Bhatia, Stephen G. Reich e Bettina Balint. "Functional (Psychogenic) Movement Disorders". In Involuntary Movements, 155–62. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780190865047.003.0007.
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Functional movement disorders are any type of movement disorder due to a brain network disorder where normal function is possible. The terminology of functional movement disorders has changed; in the recent past, these disorders were most frequently called psychogenic. Characteristics of functional movements include incongruity with a known type of involuntary movement; inconsistency in the pattern, degree, and distribution during the clinical course; improvement with distraction; and possible psychogenic background. While the movements are said to be fully involuntary, there is often some suggestibility. In the case of unilaterally predominant tremor, if the patient is requested to repeat voluntary movements with the intact or less affected hand at a certain pace, the tremor frequency might be replaced by the frequency of the voluntary movement, the phenomenon called entrainment.
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Nolte, David D. "Coupled Oscillators and Synchronization". In Introduction to Modern Dynamics, 177–204. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198844624.003.0006.
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Coupled linear oscillators provide a central paradigm for the combined behavior of coupled systems and the emergence of normal modes. Nonlinear coupling of two autonomous oscillators provides an equally important paradigm for the emergence of collective behavior through synchronization. Simple asymmetric coupling of integrate and fire oscillators captures the essence of frequency locking. Quasiperiodicity on the torus (action-angle oscillators) with nonlinear coupling demonstrates phase locking, while the sine-circle map is a discrete map that displays multiple Arnold tongues at frequency-locking resonances. External synchronization of a phase oscillator is analyzed in terms of the “slow” phase difference, resulting in a beat frequency and frequency entrainment that are functions of the coupling strength.
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Riess Jones, Mari. "Musical Melodies". In Time Will Tell, 228–51. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190618216.003.0011.
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This chapter has three major sections. The first section introduces musical scales together with psychological implications. The second section focuses on theory and research surrounding musical tonality. The third section presents issues surrounding the perception of melodic contours. A number of theories are explored, some including Gestalt concepts, as well as concepts based on dynamic attending theory (DAT). The latter theory is shown to address attending to both musical tonality and contour. In general, percepts of tonal melodies lend themselves to DAT interpretations based on attractor profiles, whereas melodic contour perceptions can be explained in terms of exogenous entrainment to a changing frequency.
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Riess Jones, Mari. "Melodies of Speech". In Time Will Tell, 279–300. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190618216.003.0013.
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The focus in this chapter is on fast speech events. Specifically, it centers upon the melodies of speech created by vocal modulations of micro-driving rhythms associated with a speaker’s fundamental frequency. Briefly, it is about vocal intonation patterns in speech. Theoretically, it concentrates on a listener’s ability to engage pitch tracking (i.e., frequency following) to follow a speaker’s changing vocal pitch. To describe pitch tracking, pitch contrasts arising from vocal modulations are formalized using the important entrainment construct of a detuning curve. This methodology is described in detail. A derivative of this curve is the isolation of pitch accents as extreme pitch contrasts. The remainder of this chapter focuses on the role of pitch accents in outlining slower macro-rhythms of intonation that invite either traditional mode-locking (hence global attractors) or transient mode-locking (hence attractor profiles).
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Haldar, Chandana, e Jayita Pal Chowdhury. "Chronodisruption and Loss of Female Reproductive Potential Due to Shift Work". In Climate Change and Its Impact on Fertility, 70–98. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4480-8.ch004.
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Entrainment of 24 hrs light/dark cycle is nowadays getting altered in corporate sector and even at home due to over exposure to artificial light at night (ALAN) and is commonly denoted as chronodisruption. Chronodisruption interferes with the daily physiology that is regulated by SCN/pineal-melatonin/Hypothalamo-Pituitary axis. In females, reduction in sleep due to shift work desynchronizes HPG-HPA axis induces a stress like condition, accompanied by increased free radical generation in ovary leading to polycystic ovaries, depletion of ovarian reserve, luteal phase defects, endometriosis, implantation failure, etc. Evidence suggest that there is remedial rescue by management of circulatory melatonin due to its chronobiotic/antioxidant/anti-inflamatory/antiapoptotic potentials and its role in ovarian folliculogenesis and steroidogenesis. Advancement in melatonin research suggests that it could be beneficial for commercial use, that is, (1) as an endogenous synchronizer, (2) to improve the quality of oocyte, and (3) for promoting success in the frequency of IVF.
Trabalhos de conferências sobre o assunto "Frequency entrainment"
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Nenkova, Ani, Agustín Gravano e Julia Hirschberg. "High frequency word entrainment in spoken dialogue". In the 46th Annual Meeting of the Association for Computational Linguistics. Morristown, NJ, USA: Association for Computational Linguistics, 2008. http://dx.doi.org/10.3115/1557690.1557737.
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Akhmediev, Nail, Jose-Maria Soto-Crespo e Adrian Ankiewicz. "Entrainment of Pulse Modulation Frequency in Fiber Lasers". In Nonlinear Guided Waves and Their Applications. Washington, D.C.: OSA, 2005. http://dx.doi.org/10.1364/nlgw.2005.wc2.
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Han, Sam. "Effects of the Primary Flow Frequency on the Secondary Flow Entrainment". In 32nd AIAA Fluid Dynamics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-2857.
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Zlotnik, Anatoly, e Jr-Shin Li. "Optimal Asymptotic Entrainment of Phase-Reduced Oscillators". In ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-5923.
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We derive optimal periodic controls for entrainment of a self-driven oscillator to a desired frequency. The alternative objectives of minimizing power and maximizing frequency range of entrainment are considered. A state space representation of the oscillator is reduced to a linearized phase model, and the optimal periodic control is computed from the phase response curve using formal averaging and the calculus of variations. Computational methods are used to calculate the periodic orbit and the phase response curve, and a numerical method for approximating the optimal controls is introduced. Our method is applied to asymptotically control the period of spiking neural oscillators modeled using the Hodgkin-Huxley equations. This example illustrates the optimality of entrainment controls derived using phase models when applied to the original state space system.
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Li, Bangming, Qi Xiao, Yong Li, Xu Hu e Wei Wang. "Numerical Study on Streamwise Vorticity and Entrainment Enhancement of a Round Jet". In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81794.
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The jet pump has many outstanding advantages such as simple structure, high reliability, and low operation and maintenance costs and so on. Therefore, it has been widely used in nuclear industry fields. The entrainment ability of the jet pump is the core performance. It is generally recognized that, although the vorticity value of streamwise vortex is smaller than that of spanwise, it plays an important role in the entrainment process. Thus, a numerical simulation of streamwise vortex influence on the entrainment ability of a round jet is carried out. To enhance the entrainment of the round jet, tabs (streamwise vortex generator) and vibrator (perturbation) are set at the exit of nozzle. Tabs are set of number as 0, 2, 4 and 6, and the frequency of vibrator is set as natural frequency and its half. Based on the above configuration, numerical simulations of different nozzle types were carried out. Based on above results, firstly the influence of tabs on the entrainment ability was analyzed. The vortex intensity of the jet flow is obviously enhanced under introducing tabs. Similarly, the intensity of streamwise vortex downstream also increase significantly, thus enhance the entrainment ability. From the figure of local entrainment flow rate, the jet of nozzle with 6 tabs has the strongest entrainment ability; its local entrainment flow rate is 1.5 times of the round jet. Then, the influence of perturbation on the entrainment ability is analyzed. After introducing velocity perturbation, the evolution of the mixing layer evidently accelerated. Under natural frequency perturbation, mixing layer evolution is the most rapid. The mixing layer roll into a vortex ring in less than one diameter distance downstream allowing to 1.75 times the amount of fluid entrained in comparison with the round jet. Finally, integrating the influence of tabs and perturbation, the variation of the jet entrainment ability is analyzed. Due to the combined effect of tabs enhancing vortex intensity and natural frequency accelerating the evolution process, local entrainment ability of the jet is further improved which is more than three times that of the round jet. Taking the nozzle with 6 tabs and perturbation of natural frequency as an example, the streamwise vorticity increases rapidly to a maximum. Local entrainment flow rate also has a corresponding maximum value, which is one-to-one correspondence with the intensity distribution of streamwise vortex, indicating that streamwise vortex plays a predominant role in the entrainment ability of the jet.
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Mitsuhashi, Kento, Masatsugu Nishihara e Fumihiko Asano. "Experimental Verification of Vibratory Conveyor System Based on Frequency Entrainment of Limit Cycle Walker". In 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). IEEE, 2020. http://dx.doi.org/10.1109/iros45743.2020.9341553.
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Abdel-Rahim, A., F. Sisto e S. Thangam. "Computational Study of Stall Flutter in Linear Cascades". In ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-005.
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Aeroelastic interaction in turbomachinery is of prime interest to operators, designers and aeroelasticians. Operation at off-design conditions may promote blade stall; eventually the stall pattern will propagate around the blade annulus. The unsteady periodic nature of propagating stall will force blade vibration and blade flutter may occur if the stall propagation frequency is entrained by the blade natural frequency. In this work a computational scheme based on the vortex method is used to simulate the flow over a linear cascade of airfoils. The viscous effect is confined to a thin layer which determines the separation points on the airfoil surfaces. The preliminary structural model is a two-dimensional characteristic section with a single degree of freedom in either bending or torsion. A study of the relationship between the stall propagation frequency and the blade natural frequency has been conducted. The study shows that entrainment, or frequency synchronization, occurs resulting in pure torsional flutter over a certain interval of reduced frequency. A severe blade torsional amplitude (of order 20°) has been computed in the entrainment region reaching its largest value in the center of the interval. However, in practice, compressor blades will not sustain this vibration and blade failure may occur before reaching such a large amplitude. Outside the entrainment interval the stall propagation is shown to be independent of the blade natural frequency. In addition, computational results show that there is no entrainment in the pure bending mode. Rather “de-entrainment” occurs with similar flow conditions and similar stall frequencies, resulting in blade buffeting in pure bending.
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Alessi, Alessio, Dino Accoto e Eugenio Guglielmelli. "Self-entrainment to optimal gaits of an underactuated biomimetic swimming robot using adaptive frequency oscillators". In 2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). IEEE, 2015. http://dx.doi.org/10.1109/embc.2015.7319178.
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Ahn, Jooeun, e Neville Hogan. "The Basin of Entrainment of Human Gait Under Mechanical Perturbation". In ASME 2008 Dynamic Systems and Control Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/dscc2008-2168.
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Using Anklebot, a therapeutic robot module, we perturbed human gait by applying external torque to the human ankle at various frequencies. We observed that with a properly designed perturbation, 8 subjects out of 10 exhibited entrained gaits: their gait frequencies were adapted to the frequency of mechanical perturbation, and they synchronized their ankle actuation with the external torque supplied by the robot. This preliminary result suggests that a limit-cycle oscillator, a plausible element of the coupled system of central nervous system and musculo-skeletal periphery, plays a significant role in the neuro-motor execution of human locomotion. The entrainment of human gait by periodic torque from a robotic aid may provide a novel approach to walking therapy that is uniquely supportive of normal biological function.
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Mantilla, I., L. Gomez, R. Mohan, O. Shoham, G. Kouba e R. Roberts. "Modeling of Liquid Entrainment in Gas in Horizontal Pipes". In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78459.
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The purpose of the present study is to improve the current prediction capabilities of the entrainment fraction in horizontal gas-liquid flow. Since it is recognized that waves at the gas-liquid interface are the main source of entrainment, an experimental and theoretical work has been carried out to characterize the waves at the gas-liquid interface and to develop a model for entrainment calculations based on such characteristics. The model consists of three sub-models, namely, onset of entrainment, maximum entrainment and entrainment values in between. The onset of entrainment model determines the conditions at which the gas starts shearing the wave crests through a force balance between drag and surface tension forces. The maximum entrainment model provides the maximum fraction of liquid that can be entrained at high gas velocities by integration of the turbulent velocity profile to a determined dimensionless film thickness within the buffer sub layer. The entrainment fraction in between onset and maximum boundaries is calculated from an equilibrium between atomization and deposition rates. The atomization rate is calculated by first determining the wave mass flux in the liquid film and second by calculating the fraction of a single wave that is sheared by the gas through a force balance. The deposition rate is calculated as a linear function of the droplet concentration in the gas. Closure relationships have been developed from data for wave celerity, frequency, amplitude and width which are used in the entrainment model. A review of the most used correlations for calculating the entrainment fraction is presented and their performance evaluated. The present model shows better prediction than available models when compared to the acquired experimental data and the available experimental data in the literature.