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Phase amplitude coupling

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https://www.readbyqxmd.com/read/28914903/experimental-demonstration-of-an-apodized-imaging-chip-fiber-grating-coupler-for-si3n4-waveguides
#1
Yang Chen, Thalia Domínguez Bucio, Ali Z Khokhar, Mehdi Banakar, Katarzyna Grabska, Frederic Y Gardes, Robert Halir, Íñigo Molina-Fernández, Pavel Cheben, Jian-Jun He
A silicon nitride waveguide is a promising platform for integrated photonics, particularly due to its low propagation loss compared to other complementary metal-oxide-semiconductor compatible waveguides, including silicon-on-insulator. Input/output coupling in such thin optical waveguides is a key issue for practical implementations. Fiber-to-chip grating couplers in silicon nitride usually exhibit low coupling efficiency because the moderate index contrast leads to weak radiation strengths and poor directionality...
September 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28901011/persistent-aberrant-cortical-phase-amplitude-coupling-following-seizure-treatment-in-absence-epilepsy-models
#2
Atul Maheshwari, Abraham Akbar, Mai Wang, Rachel Marks, Katherine Yu, Suhyeorn Park, Brett L Foster, Jeffrey L Noebels
In childhood absence epilepsy, cortical seizures are brief and intermittent; however there are extended periods without behavioural or electrographic ictal events. This genetic disorder is associated with variable degrees of cognitive dysfunction, but no consistent functional biomarkers that might provide insight into interictal cortical function have been described. Previous work in monogenic mouse models of absence epilepsy have shown that the interictal EEG displays augmented beta/gamma power in homozygous stargazer (stg/stg) mice bearing a presynaptic AMPA receptor defect, but not homozygous tottering (tg/tg) mice with a P/Q type calcium channel mutation...
September 12, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28890054/home-cage-odors-spatial-cues-elicit-theta-phase-gamma-amplitude-coupling-between-olfactory-bulb-and-dorsal-hippocampus
#3
Roberta Ribas Pena, Daniel de Castro Medeiros, Leonardo de Oliveira Guarnieri, Julio Boriollo Guerra, Vinícius Rezende Carvalho, Eduardo Mazoni Andrade Marçal Mendes, Grace Schenatto Pereira, Márcio Flávio Dutra Moraes
The brain oscillations may play a critical role in synchronizing neuronal assemblies in order to establish appropriate sensory-motor integration. In fact, studies have demonstrated phase-amplitude coupling of distinct oscillatory rhythms during cognitive processes. Here we investigated whether olfacto-hippocampal coupling occurs when mice are detecting familiar odors located in a spatially restricted area of a new context. The spatial olfactory task (SOT) was designed to expose mice to a new environment in which only one quadrant (target) contains odors provided by its own home-cage bedding...
September 7, 2017: Neuroscience
https://www.readbyqxmd.com/read/28886647/signatures-of-vibronic-coupling-in-two-dimensional-electronic-vibrational-and-vibrational-electronic-spectroscopies
#4
James D Gaynor, Munira Khalil
Two-Dimensional Electronic-Vibrational (2D EV) spectroscopy and Two-Dimensional Vibrational-Electronic (2D VE) spectroscopy are new coherent four-wave mixing spectroscopies that utilize both electronically resonant and vibrationally resonant field-matter interactions to elucidate couplings between electronic and vibrational degrees of freedom. A system Hamiltonian is developed here to lay a foundation for interpreting the 2D EV and 2D VE signals that arise from a vibronically coupled molecular system in the condensed phase...
September 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28877456/distinct-circadian-signatures-in-liver-and-gut-clocks-revealed-by-ketogenic-diet
#5
Paola Tognini, Mari Murakami, Yu Liu, Kristin L Eckel-Mahan, John C Newman, Eric Verdin, Pierre Baldi, Paolo Sassone-Corsi
The circadian clock orchestrates rhythms in physiology and behavior, allowing organismal adaptation to daily environmental changes. While food intake profoundly influences diurnal rhythms in the liver, how nutritional challenges are differentially interpreted by distinct tissue-specific clocks remains poorly explored. Ketogenic diet (KD) is considered to have metabolic and therapeutic value, though its impact on circadian homeostasis is virtually unknown. We show that KD has profound and differential effects on liver and intestine clocks...
September 5, 2017: Cell Metabolism
https://www.readbyqxmd.com/read/28876005/the-mechanism-of-excimer-formation-an-experimental-and-theoretical-study-on-the-pyrene-dimer
#6
Joscha Hoche, Hans-Christian Schmitt, Alexander Humeniuk, Ingo Fischer, Roland Mitrić, Merle I S Röhr
The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer...
September 6, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28863491/experimental-phase-synchronization-detection-in-non-phase-coherent-chaotic-systems-by-using-the-discrete-complex-wavelet-approach
#7
Maria Teodora Ferreira, Rosangela Follmann, Margarete O Domingues, Elbert E N Macau, István Z Kiss
Phase synchronization may emerge from mutually interacting non-linear oscillators, even under weak coupling, when phase differences are bounded, while amplitudes remain uncorrelated. However, the detection of this phenomenon can be a challenging problem to tackle. In this work, we apply the Discrete Complex Wavelet Approach (DCWA) for phase assignment, considering signals from coupled chaotic systems and experimental data. The DCWA is based on the Dual-Tree Complex Wavelet Transform (DT-CWT), which is a discrete transformation...
August 2017: Chaos
https://www.readbyqxmd.com/read/28862611/phase-merging-enhanced-harmonic-generation-free-electron-laser-with-a-normal-modulator
#8
Zhouyu Zhao, Heting Li, Qika Jia
A phase-merging enhanced harmonic generation free-electron laser (FEL) was proposed to increase the harmonic conversion efficiency of seeded FELs and promote the radiation wavelength towards the X-ray spectral region. However, this requires a specially designed transverse gradient undulator (TGU) as the modulator to couple the transverse and longitudinal phase space of the electron beam. In this paper, the generation of the phase-merging effect is explored using the natural field gradient of a normal planar undulator...
September 1, 2017: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/28859916/the-effect-of-type-of-afferent-feedback-timed-with-motor-imagery-on-the-induction-of-cortical-plasticity
#9
N Mrachacz-Kersting, M Voigt, Ajt Stevenson, S Aliakbaryhosseinabadi, N Jiang, K Dremstrup, D Farina
A peripherally generated afferent volley that arrives at the peak negative (PN) phase during the movement related cortical potential (MRCP) induces significant plasticity at the cortical level in healthy individuals and chronic stroke patients. Transferring this type of associative brain-computer interface (BCI) intervention into the clinical setting requires that the proprioceptive input is comparable to the techniques implemented during the rehabilitation process. These consist mainly of functional electrical stimulation (FES) and passive movement induced by an actuated orthosis...
August 28, 2017: Brain Research
https://www.readbyqxmd.com/read/28852139/giant-thz-surface-plasmon-polariton-induced-by-high-index-dielectric-metasurface
#10
Shuai Lin, Khagendra Bhattarai, Jiangfeng Zhou, Diyar Talbayev
We use computational approaches to explore the role of a high-refractive-index dielectric TiO2 grating with deep subwavelength thickness on InSb as a tunable coupler for THz surface plasmons. We find a series of resonances as the grating couples a normally-incident THz wave to standing surface plasmon waves on both thin and thick InSb layers. In a marked contrast with previously-explored metallic gratings, we observe the emergence of a much stronger additional resonance. The mechanism of this giant plasmonic resonance is well interpreted by the dispersion of surface plasmon excited in the air\TiO2\InSb trilayer system...
August 29, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28836641/magnetoelastoelectric-coupling-in-core-shell-nanoparticles-enabling-directional-and-mode-selective-magnetic-control-of-thz-beam-propagation
#11
Moumita Dutta, Kamaraju Natarajan, Soutik Betal, Rohit P Prasankumar, Amar S Bhalla, Ruyan Guo
Magnetoelastoelectric coupling in an engineered biphasic multiferroic nanocomposite enables a novel magnetic field direction-defined propagation control of terahertz (THz) waves. These core-shell nanoparticles are comprised of a ferromagnetic cobalt ferrite core and a ferroelectric barium titanate shell. An assembly of these nanoparticles, when operated in external magnetic fields, exhibits a controllable amplitude modulation when the magnetic field is applied antiparallel to the THz wave propagation direction; yet the same assembly displays an additional phase modulation when the magnetic field is applied along the propagation direction...
September 14, 2017: Nanoscale
https://www.readbyqxmd.com/read/28835526/parkinsonism-and-vigilance-alteration-in-neural-oscillatory-activity-and-phase-amplitude-coupling-in-the-basal-ganglia-and-motor-cortex
#12
David Escobar, Luke A Johnson, Shane D Nebeck, Jianyu Zhang, Matthew D Johnson, Kenneth B Baker, Gregory F Molnar, Jerrold L Vitek
Oscillatory neural activity in different frequency bands as well as phase-amplitude coupling (PAC) are hypothesized to be biomarkers of Parkinson's disease (PD) that could explain dysfunction in the motor circuit and be used for closed-loop deep brain stimulation (DBS). How these putative biomarkers change from the normal to the parkinsonian state, across nodes in the motor circuit, and within the same subject, however, remains unknown. In this study, we characterized how parkinsonism and vigilance altered oscillatory activity and PAC within the primary motor cortex (M1), subthalamic nucleus (STN), and globus pallidus (GP) in two nonhuman primates...
August 23, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28833629/olfactory-bulb-drives-respiration-coupled-beta-oscillations-in-the-rat-hippocampus
#13
André Lv Lockmann, Diego A Laplagne, Adriano Bl Tort
The synchronization of neuronal oscillations has been suggested as a mechanism to coordinate information flow between distant brain regions. In particular, the olfactory bulb (OB) and the hippocampus (HPC) have been shown to exhibit oscillations in the beta frequency range (10-20 Hz) that are likely to support communication between these structures. Here we further characterize features of beta oscillations in OB and HPC of rats anesthetized with urethane. We find that beta oscillations simultaneously appear in HPC and OB and phase-lock across structures...
August 22, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28828401/abnormalities-in-dynamic-brain-activity-caused-by-mild-traumatic-brain-injury-are-partially-rescued-by-the-cannabinoid-type-2-receptor-inverse-agonist-smm-189
#14
Yu Liu, Samuel S McAfee, Natalie M Guley, Nobel Del Mar, Wei Bu, Scott A Heldt, Marcia G Honig, Bob M Moore, Anton Reiner, Detlef H Heck
Mild traumatic brain injury (mTBI) can cause severe long-term cognitive and emotional deficits, including impaired memory, depression, and persevering fear, but the neuropathological basis of these deficits is uncertain. As medial prefrontal cortex (mPFC) and hippocampus play important roles in memory and emotion, we used multi-site, multi-electrode recordings of oscillatory neuronal activity in local field potentials (LFPs) in awake, head-fixed mice to determine if the functioning of these regions was abnormal after mTBI, using a closed-skull focal cranial blast model...
July 2017: ENeuro
https://www.readbyqxmd.com/read/28827337/dynamic-connectivity-modulates-local-activity-in-the-core-regions-of-the-default-mode-network
#15
Wei Tang, Hesheng Liu, Linda Douw, Mark A Kramer, Uri T Eden, Matti S Hämäläinen, Steven M Stufflebeam
Segregation and integration are distinctive features of large-scale brain activity. Although neuroimaging studies have been unraveling their neural correlates, how integration takes place over segregated modules remains elusive. Central to this problem is the mechanism by which a brain region adjusts its activity according to the influence it receives from other regions. In this study, we explore how dynamic connectivity between two regions affects the neural activity within a participating region. Combining functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in the same group of subjects, we analyzed resting-state data from the core of the default-mode network...
August 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28821753/dynamic-reconfiguration-of-cortical-functional-connectivity-across-brain-states
#16
Iain Stitt, Karl J Hollensteiner, Edgar Galindo-Leon, Florian Pieper, Eva Fiedler, Thomas Stieglitz, Gerhard Engler, Guido Nolte, Andreas K Engel
Throughout each day, the brain displays transient changes in state, as evidenced by shifts in behavior and vigilance. While the electrophysiological correlates of brain states have been studied for some time, it remains unclear how large-scale cortico-cortical functional connectivity systematically reconfigures across states. Here, we investigate state-dependent shifts in cortical functional connectivity by recording local field potentials (LFPs) during spontaneous behavioral transitions in the ferret using chronically implanted micro-electrocorticographic (µECoG) arrays positioned over occipital, parietal, and temporal cortical regions...
August 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28816086/inducible-knockout-of-mouse-zfhx3-emphasizes-its-key-role-in-setting-the-pace-and-amplitude-of-the-adult-circadian-clock
#17
Ashleigh G Wilcox, Lucie Vizor, Michael J Parsons, Gareth Banks, Patrick M Nolan
The transcription factor zinc finger homeobox 3 (ZFHX3) plays a key role in coupling intracellular transcriptional-translational oscillations with intercellular synchrony in mouse suprachiasmatic nucleus (SCN). However, like many key players in central nervous system function, ZFHX3 serves an important role in neurulation and neuronal terminal differentiation while retaining discrete additional functions in the adult SCN. Recently, using a dominant missense mutation in mouse Zfhx3, we established that this gene can modify circadian period and sleep in adult animals...
August 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28801622/decoupling-frequencies-amplitudes-and-phases-in-nonlinear-optics
#18
Bruno E Schmidt, Philippe Lassonde, Guilmot Ernotte, Matteo Clerici, Roberto Morandotti, Heide Ibrahim, François Légaré
In linear optics, light fields do not mutually interact in a medium. However, they do mix when their field strength becomes comparable to electron binding energies in the so-called nonlinear optical regime. Such high fields are typically achieved with ultra-short laser pulses containing very broad frequency spectra where their amplitudes and phases are mutually coupled in a convolution process. Here, we describe a regime of nonlinear interactions without mixing of different frequencies. We demonstrate both in theory and experiment how frequency domain nonlinear optics overcomes the shortcomings arising from the convolution in conventional time domain interactions...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28801562/explosive-death-induced-by-mean-field-diffusion-in-identical-oscillators
#19
Umesh Kumar Verma, Amit Sharma, Neeraj Kumar Kamal, Jürgen Kurths, Manish Dev Shrimali
We report the occurrence of an explosive death transition for the first time in an ensemble of identical limit cycle and chaotic oscillators coupled via mean-field diffusion. In both systems, the variation of the normalized amplitude with the coupling strength exhibits an abrupt and irreversible transition to death state from an oscillatory state and this first order phase transition to death state is independent of the size of the system. This transition is quite general and has been found in all the coupled systems where in-phase oscillations co-exist with a coupling dependent homogeneous steady state...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28794978/localization-of-beta-and-high-frequency-oscillations-within-the-subthalamic-nucleus-region
#20
B C M van Wijk, A Pogosyan, M I Hariz, H Akram, T Foltynie, P Limousin, A Horn, S Ewert, P Brown, V Litvak
Parkinsonian bradykinesia and rigidity are typically associated with excessive beta band oscillations in the subthalamic nucleus. Recently another spectral peak has been identified that might be implicated in the pathophysiology of the disease: high-frequency oscillations (HFO) within the 150-400 Hz range. Beta-HFO phase-amplitude coupling (PAC) has been found to correlate with severity of motor impairment. However, the neuronal origin of HFO and its usefulness as a potential target for deep brain stimulation remain to be established...
2017: NeuroImage: Clinical
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