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Phase amplitude coupling

Eefje S Poppelaars, Anita Harrewijn, P Michiel Westenberg, Melle J W van der Molen
Cross-frequency coupling (CFC) between frontal delta (1-4 Hz) and beta (14-30 Hz) oscillations has been suggested as a candidate neural correlate of social anxiety disorder, a disorder characterized by fear and avoidance of social and performance situations. Prior studies have used amplitude-amplitude correlation (AAC) as a CFC measure and hypothesized it as a candidate neural mechanism of affective control. However, using this metric has yielded inconsistent results regarding the direction of CFC, and the functional significance of coupling strength is uncertain...
May 17, 2018: Cognitive, Affective & Behavioral Neuroscience
Soham Pal, Naveen Nishad, T S Mahesh, G J Sreejith
We experimentally study the response of star-shaped clusters of initially unentangled N=4, 10, and 37 nuclear spin-1/2 moments to an inexact π-pulse sequence and show that an Ising coupling between the center and the satellite spins results in robust period-2 magnetization oscillations. The period is stable against bath effects, but the amplitude decays with a timescale that depends on the inexactness of the pulse. Simulations reveal a semiclassical picture in which the rigidity of the period is due to a randomizing effect of the Larmor precession under the magnetization of surrounding spins...
May 4, 2018: Physical Review Letters
Ziying Yin, Yi Sui, Joshua D Trzasko, Phillip J Rossman, Armando Manduca, Richard L Ehman, John Huston
PURPOSE: To introduce newly developed MR elastography (MRE)-based dual-saturation imaging and dual-sensitivity motion encoding schemes to directly measure in vivo skull-brain motion, and to study the skull-brain coupling in volunteers with these approaches. METHODS: Six volunteers were scanned with a high-performance compact 3T-MRI scanner. The skull-brain MRE images were obtained with a dual-saturation imaging where the skull and brain motion were acquired with fat- and water-suppression scans, respectively...
May 17, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Saeed Khan, Hakan E Türeci
We investigate the dynamics of a microwave-driven Josephson junction capacitively coupled to a lumped-element LC oscillator. In the regime of driving where the Josephson junction can be approximated as a Kerr oscillator, this minimal nonlinear system has been previously shown to exhibit a bistability in phase and amplitude. In the present study, we characterize the full phase diagram and show that besides a parameter regime exhibiting bistability, there is also a regime of self-oscillations characterized by a frequency comb in its spectrum...
April 13, 2018: Physical Review Letters
Daniel Werdehausen, Tomohiro Takayama, Marc Höppner, Gelon Albrecht, Andreas W Rost, Yangfan Lu, Dirk Manske, Hidenori Takagi, Stefan Kaiser
The excitonic insulator is an intriguing electronic phase of condensed excitons. A prominent candidate is the small bandgap semiconductor Ta2 NiSe5 , in which excitons are believed to undergo a Bose-Einstein condensation-like transition. However, direct experimental evidence for the existence of a coherent condensate in this material is still missing. A direct fingerprint of such a state would be the observation of its collective modes, which are equivalent to the Higgs and Goldstone modes in superconductors...
March 2018: Science Advances
Kaitlyn Morgan, Yuan Li, Wenzhe Li, J Keith Miller, Richard J Watkins, Eric G Johnson
Information can be encoded onto transverse spatial light modes, providing a platform that can improve the spectral efficiency of a communications link. Switching speed between these spatial modes and detection methods limit the information capacity of such links. This work demonstrates high speed capabilities of such a link. Transverse modes are created and switched at high rates by coherently coupling twisted light modes using passive optical elements in line with electro-optical modulators. Here we demonstrate the encoding and detection of two coherently coupled modes encoded with 0...
April 30, 2018: Optics Express
Paul A Dirmeyer, Liang Chen, Jiexia Wu, Chul-Su Shin, Bohua Huang, Benjamin A Cash, Michael G Bosilovich, Sarith Mahanama, Randal D Koster, Joseph A Santanello, Michael B Ek, Gianpaolo Balsamo, Emanuel Dutra, D M Lawrence
We confront four model systems in three configurations (LSM, LSM+GCM, and reanalysis) with global flux tower observations to validate states, surface fluxes, and coupling indices between land and atmosphere. Models clearly under-represent the feedback of surface fluxes on boundary layer properties (the atmospheric leg of land-atmosphere coupling), and may over-represent the connection between soil moisture and surface fluxes (the terrestrial leg). Models generally under-represent spatial and temporal variability relative to observations, which is at least partially an artifact of the differences in spatial scale between model grid boxes and flux tower footprints...
February 2018: Journal of hydrometeorology
Esther Florin, Sylvain Baillet
No abstract text is available yet for this article.
2018: Frontiers in Computational Neuroscience
Olivier Authier, Hind Ouhabaz, Stefano Bedogni
CO2 capture and utilization (CCU) is a process that captures CO2 emissions from sources such as fossil fuel power plants and reuses them so that they will not enter the atmosphere. Among the various ways of recycling CO2 , reduction reactions are extensively studied at lab-scale. However, CO2 reduction by standard methods is difficult. Sonochemistry may be used in CO2 gas mixtures bubbled through water subjected to ultrasound waves. Indeed, the sonochemical reduction of CO2 in water has been already investigated by some authors, showing that fuel species (CO and H2 ) are obtained in the final products...
July 2018: Ultrasonics Sonochemistry
Alex Krasnok, Denis G Baranov, Andrey Generalov, Sergey Li, Andrea Alù
Extraction of electromagnetic energy by an antenna from impinging external radiation is at the basis of wireless communications and wireless power transfer (WPT). The maximum of transferred energy is ensured when the antenna is conjugately matched, i.e., when it is resonant and it has an equal coupling with free space and its load. This condition, however, can be easily affected by changes in the environment, preventing optimal operation of a WPT system. Here, we introduce the concept of coherently enhanced WPT that allows us to bypass this difficulty and achieve dynamic control of power transfer...
April 6, 2018: Physical Review Letters
Yifan Zhu, Jie Hu, Xudong Fan, Jing Yang, Bin Liang, Xuefeng Zhu, Jianchun Cheng
The fine manipulation of sound fields is critical in acoustics yet is restricted by the coupled amplitude and phase modulations in existing wave-steering metamaterials. Commonly, unavoidable losses make it difficult to control coupling, thereby limiting device performance. Here we show the possibility of tailoring the loss in metamaterials to realize fine control of sound in three-dimensional (3D) space. Quantitative studies on the parameter dependence of reflection amplitude and phase identify quasi-decoupled points in the structural parameter space, allowing arbitrary amplitude-phase combinations for reflected sound...
April 24, 2018: Nature Communications
Yen-Chun Chen, Han Yeh, Chien-Ju Lee, Wen-Hao Chang
Two-dimensional (2D) semiconductors, particularly the direct-gap monolayer transition metal dichalcogenides (TMDs), are currently being developed for various atomically-thin optoelectronic devices. However, practical applications are hindered by their low quantum efficiencies in light emissions and absorptions. While photonic cavities and metallic plasmonic structures can significantly enhance the light-matter interactions in TMDs, the narrow spectral resonance and the local hot spots considerably limit the applications when broadband and large area are required...
April 24, 2018: ACS Applied Materials & Interfaces
Michael Christopher Melnychuk, Paul M Dockree, Redmond G O'Connell, Peter R Murphy, Joshua H Balsters, Ian H Robertson
The locus coeruleus (LC) has established functions in both attention and respiration. Good attentional performance requires optimal levels of tonic LC activity, and must be matched to task consistently. LC neurons are chemosensitive, causing respiratory phrenic nerve firing to increase frequency with higher CO2 levels, and as CO2 level varies with the phase of respiration, tonic LC activity should exhibit fluctuations at respiratory frequency. Top-down modulation of tonic LC activity from brain areas involved in attentional regulation, intended to optimize LC firing to suit task requirements, may have respiratory consequences as well, as increases in LC activity influence phrenic nerve firing...
April 22, 2018: Psychophysiology
Honglun Su, Congcong Huo, Bitian Wang, Wenhao Li, Gongcheng Xu, Qianying Liu, Zengyong Li
Cerebral autoregulation (CA) is the complex homeostatic regulatory relationship between blood pressure (BP) and cerebral blood flow (CBF). This study aimed to analyze the frequency-specific coupling function between cerebral oxyhemoglobin concentrations (delta [HbO2]) and mean arterial pressure (MAP) signals based on a model of coupled phase oscillators and dynamical Bayesian inference. Delta [HbO2] was measured by 24-channel near-infrared spectroscopy (NIRS) and arterial BP signals were obtained by simultaneous resting-state measurements in patients with stroke, that is, 9 with left hemiparesis (L-H group), 8 with right hemiparesis (R-H group), and 17 age-matched healthy individuals as control (healthy group)...
2018: PloS One
Pauline Maurice, Neville Hogan, Dagmar Sternad
Manipulation of complex objects as in tool use is ubiquitous and has given humans an evolutionary advantage. This study examined the strategies humans choose when manipulating an object with underactuated internal dynamics, such as a cup of coffee. The object's dynamics renders the temporal evolution complex, possibly even chaotic, and difficult to predict. A cart-and-pendulum model, loosely mimicking coffee sloshing in a cup, was implemented in a virtual environment with a haptic interface. Participants rhythmically manipulated the virtual cup containing a rolling ball; they could choose the oscillation frequency, while the amplitude was prescribed...
April 18, 2018: Journal of Neurophysiology
Lynn Ferres, Khai-Nghi Truong, Wolfgang Stahl, Ha Vinh Lam Nguyen
To determine the structural properties of 2,3-dimethyl-anisole, a multidisciplinary approach was carried out where gas phase rotational spectroscopy recorded from 2 to 26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer was combined with solid state X-ray diffraction. Both methods revealed that only one conformer with a heavy-atom planar structure exists. In the solid state, the packing in the monoclinic space group is P21/n with Z = 4. In the gas phase spectrum, torsional splittings due to the internal rotations of two methyl groups attached on the phenyl ring were resolved and analyzed, providing an estimate of the barriers to methyl internal rotation of V3 = 26...
April 17, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Adam T Brockett, Gary A Kane, Patrick K Monari, Brandy A Briones, Pierre-Antoine Vigneron, Gabriela A Barber, Andres Bermudez, Uma Dieffenbach, Alexander D Kloth, Timothy J Buschman, Elizabeth Gould
The medial prefrontal cortex (mPFC) is important for cognitive flexibility, the ability to switch between two task-relevant dimensions. Changes in neuronal oscillations and alterations in the coupling across frequency ranges have been correlated with attention and cognitive flexibility. Here we show that astrocytes in the mPFC of adult male Sprague Dawley rats, participate in cognitive flexibility through the astrocyte-specific Ca2+ binding protein S100β, which improves cognitive flexibility and increases phase amplitude coupling between theta and gamma oscillations...
2018: PloS One
Chenyi Fei, Yuansheng Cao, Qi Ouyang, Yuhai Tu
Biological systems need to function accurately in the presence of strong noise and at the same time respond sensitively to subtle external cues. Here we study design principles in biochemical oscillatory circuits to achieve these two seemingly incompatible goals. We show that energy dissipation can enhance phase sensitivity linearly by driving the phase-amplitude coupling and increase timing accuracy by suppressing phase diffusion. Two general design principles in the key underlying reaction loop formed by two antiparallel pathways are found to optimize oscillation performance with a given energy budget: balancing the forward-to-backward flux ratio between the two pathways to reduce phase diffusion and maximizing the net flux of the phase-advancing pathway relative to that of the phase-retreating pathway to enhance phase sensitivity...
April 12, 2018: Nature Communications
Chunxiu Yu, Yuhui Li, Iain M Stitt, Zhe Charles Zhou, Kristin K Sellers, Flavio Frohlich
Higher-order visual thalamus plays a fundamental but poorly understood role in attention-demanding tasks. To investigate how neuronal dynamics in higher-order visual thalamus are modulated by sustained attention, we performed multichannel electrophysiological recordings in the lateral posterior-pulvinar complex (LP/pulvinar) in the ferret ( Mustela putorius furo ). We recorded single unit activity and local field potential (LFP) during the performance of the five-choice serial reaction time task (5-CSRTT), which is used in both humans and animals as an assay of sustained attention...
January 2018: ENeuro
Timothy D Matchen, Jeff Moehlis
Deep brain stimulation (DBS) is a common method of combating pathological conditions associated with Parkinson's disease, Tourette syndrome, essential tremor, and other disorders, but whose mechanisms are not fully understood. One hypothesis, supported experimentally, is that some symptoms of these disorders are associated with pathological synchronization of neurons in the basal ganglia and thalamus. For this reason, there has been interest in recent years in finding efficient ways to desynchronize neurons that are both fast-acting and low-power...
April 3, 2018: Journal of Computational Neuroscience
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