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Phase amplitude coupling

Lianqing Xue, Boli Zhu, Changbing Yang, Guanghui Wei, Xianyong Meng, Aihua Long, Guang Yang
The simulation abilities of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) models to the arid basin (the Tarim River Basin, TRB) and humid basin (the Yangtze River Basin, YRB) were evaluated, determining the response of precipitation to external changes over typical basins. Our study shows that the future temporal and spatial variation characteristics of precipitation are different in different regions with the CMIP5. The annual and seasonal changes in precipitation were analyzed for the RCP2.6, RCP4...
November 9, 2017: Scientific Reports
Pu Duan, Klaus Schmidt-Rohr
Improved multiple cross polarization (multiCP) pulse sequences for quickly acquiring quantitative (13)C NMR spectra of organic solids are presented. Loss of (13)C magnetization due to imperfect read-out and storage pulses in multiCP has been identified as a significant mechanism limiting polarization enhancement for (13)C sites with weak couplings to (1)H. This problem can be greatly reduced by composite 90° pulses with non-orthogonal phases that flip the magnetization onto the spin-lock field and back to the longitudinal direction for the (1)H repolarization period; the observed loss is <3% for over ±10 kHz resonance offset and up to 20% flip-angle error...
November 6, 2017: Journal of Magnetic Resonance
A L Gaskell, D F Hight, J Winders, G Tran, A Defresne, V Bonhomme, A Raz, J W Sleigh, R D Sanders
Background: The isolated forearm test (IFT) is the gold standard test of connected consciousness (awareness of the environment) during anaesthesia. The frontal alpha-delta EEG pattern (seen in slow wave sleep) is widely held to indicate anaesthetic-induced unconsciousness. A priori we proposed that one responder with the frontal alpha-delta EEG pattern would falsify this concept. Methods: Frontal EEG was recorded in a subset of patients from three centres participating in an international multicentre study of IFT responsiveness following tracheal intubation...
October 1, 2017: British Journal of Anaesthesia
Victor Nadtochenko, Nikolay Denisov, Arseniy Aybush, Fedor Gostev, Ivan Shelaev, Andrey Titov, Stanislav Umanskiy, And Dmitry Cherepanov
The main goal of the present work is to study the coherent phonon in strongly confined CdSe quantum dots (QDs) under varied pump fluences. The main characteristics of coherent phonons (amplitude, frequency, phase, spectrogram) of CdSe QDs under the red-edge pump of the excitonic band [1S(e)-1S3/2(h)] are reported. We demonstrate for the first time that the amplitude of the coherent optical longitudinal-optical (LO) phonon at 6.16 THz excited in CdSe nanoparticles by a femtosecond unchirped pulse shows a non-monotone dependence on the pump fluence...
November 4, 2017: Nanomaterials
Ilija Uzelac, Yanyan C Ji, Daniel Hornung, Johannes Schröder-Scheteling, Stefan Luther, Richard A Gray, Elizabeth M Cherry, Flavio H Fenton
Rationale: Discordant alternans, a phenomenon in which the action potential duration (APDs) and/or intracellular calcium transient durations (CaDs) in different spatial regions of cardiac tissue are out of phase, present a dynamical instability for complex spatial dispersion that can be associated with long-QT syndrome (LQTS) and the initiation of reentrant arrhythmias. Because the use of numerical simulations to investigate arrhythmic effects, such as acquired LQTS by drugs is beginning to be studied by the FDA, it is crucial to validate mathematical models that may be used during this process...
2017: Frontiers in Physiology
Min-Hee Ahn, Sung Kwang Hong, Byoung-Kyong Min
Tinnitus is a psychoacoustic phantom perception of currently unknown neuropathology. Despite a growing number of post-stimulus tinnitus studies, uncertainty still exists regarding the neural signature of tinnitus in the resting-state brain. In the present study, we used high-gamma cross-frequency coupling and a Granger causality analysis to evaluate resting-state electroencephalographic (EEG) data in healthy participants and patients with tinnitus. Patients with tinnitus lacked robust frontal delta-phase/central high-gamma-amplitude coupling that was otherwise clearly observed in healthy participants...
October 30, 2017: Hearing Research
Antonia Karamatskou, Robin Santra, Oriol Vendrell
Strong light fields may be used to control molecular structure, thus providing a route to new, light-induced phases of matter. In this context, we present an ab initio molecular dynamics investigation of nonlinear mode coupling in C60 and show that, under suitable conditions, resonant infrared excitation induces significant structural changes in the system. Surprisingly, exciting the highest-frequency infrared mode at field strengths employed in a recent experiment [Nature 2016, 530, 461-464], we observe no significant structural change...
November 1, 2017: Journal of Physical Chemistry Letters
A Ahnaou, D Moechars, L Raeymaekers, R Biermans, N V Manyakov, A Bottelbergs, C Wintmolders, K Van Kolen, T Van De Casteele, J A Kemp, W H Drinkenburg
Synaptic dysfunction and disconnectivity are core deficits in Alzheimer's disease (AD), preceding clear changes in histopathology and cognitive functioning. Here, the early and late effects of tau pathology induction on functional network connectivity were investigated in P301L mice. Multichannel EEG oscillations were used to compute (1) coherent activity between the prefrontal cortex (PFC) and hippocampus (HPC) CA1-CA3 networks; (2) phase-amplitude cross frequency coupling (PAC) between theta and gamma oscillations, which is instrumental in adequate cognitive functioning; (3) information processing as assessed by auditory evoked potentials and oscillations in the passive oddball mismatch negativity-like (MMN) paradigm...
October 27, 2017: Scientific Reports
Stavros I Dimitriadis, Ioannis Tarnanas, Mark Wiederhold, Brenda Wiederhold, Magda Tsolaki, Elgar Fleisch
INTRODUCTION: We sought to identify whether intensive 10-week mobile health mnemonic strategy training (MST) could shift the resting-state brain network more toward cortical-level integration, which has recently been proven to reflect the reorganization of the brain networks compensating the cognitive decline. METHODS: One hundred fifty-eight patients with mild cognitive impairment (MCI) were selected and participated in 10-week training lasting 90 min/d of memory training...
November 2016: Alzheimer's & Dementia: Translational Research & Clinical Interventions
Sang-Yoon Kim, Woochang Lim
For studying how dynamical responses to external stimuli depend on the synaptic-coupling type, we consider two types of excitatory and inhibitory synchronization (i.e., synchronization via synaptic excitation and inhibition) in complex small-world networks of excitatory regular spiking (RS) pyramidal neurons and inhibitory fast spiking (FS) interneurons. For both cases of excitatory and inhibitory synchronization, effects of synaptic couplings on dynamical responses to external time-periodic stimuli S(t) (applied to a fraction of neurons) are investigated by varying the driving amplitude A of S(t)...
October 2017: Cognitive Neurodynamics
Jesus Poza, Alejandro Bachiller, Carlos Gomez, Maria Garcia, Pablo Nunez, Javier Gomez-Pilar, Miguel A Tola-Arribas, Monica Cano, Roberto Hornero
This study was aimed at exploring phase-amplitude coupling (PAC) patterns of neural activity in dementia due to Alzheimer's disease (AD). For this task, five minutes of spontaneous electroencephalographic (EEG) activity from 22 patients with mild AD and 16 cognitively healthy controls were studied. To assess PAC patterns, phase-locking value was computed between the phase of low frequencies and the power of high frequencies within each sensor. Our results showed that high-frequency gamma power is phase-locked to the alpha peak in EEG signals...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Jingjiang Xu, Shaozhen Song, Yuandong Li, Ruikang K Wang
Optical coherence tomography angiography (OCTA) is increasingly becoming a popular inspection tool for biomedical imaging applications. By exploring amplitude, phase and complex information available in the OCT signals, numerous algorithms are proposed to contrast functional vessel networks with microcirculation tissue beds. However, it is not clear which algorithm delivers optimal imaging performance. Here, we investigate systematically how the amplitude and phase information would have an impact on the OCTA imaging performance, upon which to establish the relationship of amplitude and phase stability with OCT signal-to-noise ratio (SNR), time interval and particle dynamics...
October 19, 2017: Physics in Medicine and Biology
Alejandro Díaz, Araceli Peña-Alvarez
A simple method was developed using ultrasound-assisted extraction (UAE) combined with solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) for the simultaneous determination of eight different pharmaceuticals and personal care products (PPCPs) (ibuprofen, 2-benzyl-4-chlorophenol, naproxen, triclosan, ketoprofen, diclofenac, bisphenol A and estrone) in river sediment. UAE conditions were optimized involving extraction variables such as extraction solvent, extraction time, sample amount, extraction temperature, pH and salt addition...
October 1, 2017: Journal of Chromatographic Science
Bhargab Das, Nandan S Bisht, R V Vinu, Rakesh Kumar Singh
We propose and experimentally demonstrate lensless complex amplitude image retrieval through a visually opaque scattering medium from spatially fluctuating fields using intensity measurement and a phase-retrieval algorithm. The complex amplitude information of the hidden object is encoded in the form of a real and nonnegative amplitude function represented as an interference pattern. A single charge coupled device (CCD) image of the scattered light collected through a visually opaque optical diffuser contains enough information to digitally regenerate the interference pattern...
June 1, 2017: Applied Optics
Jacob C Dean, Gregory D Scholes
The role of coherences, or coherently excited superposition states, in complex condensed-phase systems has been the topic of intense interest and debate for a number of years. In many cases, coherences have been utilized as spectators of ultrafast dynamics or for identifying couplings between electronic states. In rare cases, they have been found to drive excited state dynamics directly. Interestingly though, the utilization of coherences as a tool for high-detail vibronic spectroscopy has largely been overlooked until recently, despite their encoding of key information regarding molecular structure, electronically sensitive vibrational modes, and intermolecular interactions...
October 18, 2017: Accounts of Chemical Research
H Cheng, Y Zhou, A E Mironov, W Wang, T Qiao, W Lin, Q Qian, S Xu, Z Yang, J G Eden
Multiplication of the pulse repetition frequency (PRF) of a compact, mode-locked fiber laser by a factor as large as 25 has been achieved with two coupled Fabry-Perot (FP) resonators of low finesse (F = 2). Reducing the FP finesse by at least two orders of magnitude, relative to previous pulse frequency multiplication architectures, has the effect of stabilizing the oscillator with respect to pulse-to-pulse amplitude, dropped pulses, and other effects of cavity detuning. Coupling two Fabry-Perot cavities, each encompassing a 3...
October 2, 2017: Optics Express
Nicolás Márquez Peraca, D Taner Bilir, Behrang H Hamadani
The frequency dependence of the external quantum efficiency (EQE) of high-quality multijunction solar cells was examined by the modulated photocurrent spectroscopy method via an optical setup comprised of a light-pipe-coupled compact LED array. The optical excitation was achieved through sinusoidal electrical modulation of an appropriate LED by a custom-designed, high bandwidth amplifier. We observed unique features in the amplitude and phase data of the EQE frequency sweeps that are very sensitive to various subcell parameters and light bias conditions...
August 7, 2017: Optics Express
Reza Sameni, Esmaeil Seraj
The instantaneous phase (IP) and instantaneous frequency (IF) of the electroencephalogram (EEG) are considered as notable complements for the EEG spectrum. The calculation of these parameters commonly includes narrow-band filtering, followed by the calculation of the signal's analytical form. The calculation of the IP and IF is highly susceptible to the filter parameters and background noise level, especially in low analytical signal amplitudes. The objective of this study is to propose a robust statistical framework for EEG IP/IF estimation and analysis...
October 16, 2017: Physiological Measurement
Allan R Willms, Petko M Kitanov, William F Langford
In 1665, Huygens observed that two identical pendulum clocks, weakly coupled through a heavy beam, soon synchronized with the same period and amplitude but with the two pendula swinging in opposite directions. This behaviour is now called anti-phase synchronization. This paper presents an analysis of the behaviour of a large class of coupled identical oscillators, including Huygens' clocks, using methods of equivariant bifurcation theory. The equivariant normal form for such systems is developed and the possible solutions are characterized...
September 2017: Royal Society Open Science
Ning Cheng, Qun Li, Sitong Wang, Rubin Wang, Tao Zhang
Cross-frequency phase-amplitude coupling (PAC) in neuronal oscillations network plays an important functional role in large scale neuronal communication and neuronal encoding. In the present study, a novel approach named permutation mutual information (PMI) was applied in measuring PAC. It is derived from the permutation entropy based on the mutual information theory, by which the mutual information of permutations of two time series can be evaluated. In order to verify the ability of PMI, a numerical test was performed by using both simulation data and experimental data...
October 5, 2017: Brain Topography
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