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6,479 results on '"Phase dynamics"'

101. Phase dynamics and particle production in preheating

Author

Charters, T., Nunes, A., and Mimoso, J. P.

Subjects
High Energy Physics - Phenomenology, Astrophysics
Abstract

We study a simple model of a massive inflaton field $\phi$ coupled to another scalar filed $\chi$ with interaction term $g^2\phi^2\chi^2$. We use the theory developed by Kofman {\em et al.} (Phys. Rev. D {\bf 56} (1997) 3258 [arXiv:hep-ph/9704452])for the first stage of preheating to give a full description of the dynamics of the $\chi$ field modes, including the behaviour of the phase, in terms of the iteration of a simple family of circle maps. The parameters of this family of maps are a function of time when expansion of the universe is taken into account. With this more detailed description, we obtain a systematic study of the efficiency of particle production as a function of the inflaton field and coupling parameters, and we find that for $g \lesssim 3 \times 10^{-4}$ the broad resonance ceases during the first stage of preheating., Comment: 14 pages, 12 figures, accepted for publication in Phys. Rev. D. Correct Figure 9, results unchanged. Added references and corrected misprints/misspellings

Published
2005
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102. Population and phase dynamics of F=1 spinor condensates in an external magnetic field

Author

Romano, Dimas Rodrigues and de Passos, Emerson José Veloso

Subjects
Condensed Matter - Statistical Mechanics
Abstract

We show that the classical dynamics underlying the mean-field description of homogeneous mixtures of spinor F=1 Bose-Einstein condensates in an external magnetic field is integrable as a consequence of number conservation and axial symmetry in spin space. The population dynamics depends only on the quadratic term of the Zeeman energy and on the strength of the spin-dependent term of the atom-atom interaction. We determine the equilibrium populations as function of the ratio of these two quantities and the miscibility of the hyperfine components in the ground state spinors are thoroughly discussed. Outside the equilibrium, the populations are always a periodic function of time where the periodic motion can be a libration or a rotation. Our studies also indicates the absence of metastability., Comment: 8 pages, 5 figures. Accepted for publishing in PRA

Published
2004

103. Do Cosmic Backgrounds Cyclical Renew by Matter and Quanta Emissions? The Origin of Backgrounds, Space Distributions and Cyclical Earth Phenomena by Two Phase Dynamics

Author

Garcia, Eduardo del Pozo

Subjects
Physics - General Physics
Abstract

A numerical coincidence Dp of -0.000489 was found between the ratios of proton emission at 459-keV and cosmic background at 0.25-keV respect to proton and to electron proper energy respectively. Multiplying 459-keV and 0.25-keV by Dp, two more numerical coincidences were found with 0.1-keV background and 0.06-eV of neutrino energy, respectively. Global criticality phenomena plus c and G discontinued decreasing provoke small cyclical reorganization of particles and quanta originating background emissions every 30-Myr are propose. At the beginning of each cycle, gradually emissions from electrons lasting 0.1 Myr originate the 0.25-keV background and, a possible 459-keV background from proton emissions. At following cycle, the 459-keV quanta makes two emissions of 0.1-keV originating a diffuse background, and 0.25-keV quanta makes two of 0.06-eV originating the relic neutrinos. The Dp is a possible physical constant that characterize the threshold, which trigger cyclical phenomena at space and Earth every 30-Myr, Comment: 18 pages, 4 figures

Published
2004

104. Phase Dynamics of Nearly Stationary Patterns in Activator-Inhibitor Systems

Author

Hagberg, Aric, Meron, Ehud, and Passot, Thierry

Subjects
Nonlinear Sciences - Pattern Formation and Solitons
Abstract

The slow dynamics of nearly stationary patterns in a FitzHugh-Nagumo model are studied using a phase dynamics approach. A Cross-Newell phase equation describing slow and weak modulations of periodic stationary solutions is derived. The derivation applies to the bistable, excitable, and the Turing unstable regimes. In the bistable case stability thresholds are obtained for the Eckhaus and the zigzag instabilities and for the transition to traveling waves. Neutral stability curves demonstrate the destabilization of stationary planar patterns at low wavenumbers to zigzag and traveling modes. Numerical solutions of the model system support the theoretical findings.

Published
2000
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105. Phase dynamics of a multimode Bose condensate controlled by decay

Author

Haroutyunyan, H. L. and Nienhuis, G.

Subjects
Quantum Physics
Abstract

The relative phase between two uncoupled BE condensates tends to attain a specific value when the phase is measured. This can be done by observing their decay products in interference. We discuss exactly solvable models for this process in cases where competing observation channels drive the phases to different sets of values. We treat the case of two modes which both emit into the input ports of two beam splitters, and of a linear or circular chain of modes. In these latter cases, the transitivity of relative phase becomes an issue.

Published
2003
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106. Phase turbulence in the Complex Ginzburg--Landau equation via Kuramoto--Sivashinsky phase dynamics

Author

van Baalen, Guillaume

Subjects
Mathematical Physics, Mathematics - Analysis of PDEs, Physics - Fluid Dynamics, 35Q30, 35Q35, 35B05, 35B40
Abstract

We study the Complex Ginzburg--Landau initial value problem $\partial_t u=(1+i\alpha) \partial_x^2 u + u - (1+i\beta) u |u|^2$, $u(x,0)=u_0(x)$ for a complex field $u\in{\bf C}$, with $\alpha,\beta\in{\bf R}$. We consider the Benjamin--Feir linear instability region $1+\alpha\beta=-\epsilon^2$ with $\epsilon\ll1$ and $\alpha^2<1/2$. We show that for all $\epsilon\leq{\cal O}(\sqrt{1-2\alpha^2} L_0^{-32/37})$, and for all initial data $u_0$ sufficiently close to 1 (up to a global phase factor $\ed^{i \phi_0}, \phi_0\in{\bf R}$) in the appropriate space, there exists a unique (spatially) periodic solution of space period $L_0$. These solutions are small {\em even} perturbations of the traveling wave solution, $u=(1+\alpha^2 s) \ed^{i \phi_0-i\beta t} \ed^{i\alpha \eta}$, and $s,\eta$ have bounded norms in various $\L^p$ and Sobolev spaces. We prove that $s\approx-{1/2} \eta''$ apart from ${\cal O}(\epsilon^2)$ corrections whenever the initial data satisfy this condition, and that in the linear instability range $L_0^{-1}\leq\epsilon\leq{\cal O}(L_0^{-32/37})$, the dynamics is essentially determined by the motion of the phase alone, and so exhibits `phase turbulence'. Indeed, we prove that the phase $\eta$ satisfies the Kuramoto--Sivashinsky equation $\partial_t\eta= -\bigl({\textstyle\frac{1+\alpha^2}{2}}\bigr) \triangle^2\eta -\epsilon^2\triangle\eta -{(1+\alpha^2)} (\eta')^2$ for times $t_0\leq{\cal O}(\epsilon^{-52/5} L_0^{-32/5})$, while the amplitude $1+\alpha^2 s$ is essentially constant.

Published
2003

109. Phase dynamics after connection of two separate Bose-Einstein condensates

Author

Zapata, I., Sols, F., and Leggett, A. J.

Subjects
Condensed Matter
Abstract

We study the dynamics of the relative phase following the connection of two independently formed Bose-Einstein condensates. Dissipation is assumed to be due to the creation of quasiparticles induced by a fluctuating condensate particle number. The coherence between different values of the phase, which is characteristic of the initial Fock state, is quickly lost after the net exchange of a few atoms has taken place. This process effectively measures the phase and marks the onset of a semiclassical regime in which the system undergoes Bloch oscillations around the initial particle number. These fast oscillations excite quasiparticles within each condensate and the system relaxes at a longer time scale until it displays low-energy, damped Josephson plasma oscillations, eventually coming to a halt when the equilibrium configuration is finally reached., Comment: 4 pages, 1 figure, submitted to Physical Review A

Published
2002
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110. The Phase Dynamics of Earthquakes: Implications for Forecasting in Southern California

Author

Tiampo, Kristy F., Rundle, John B., McGinnis, Seth, Gross, Susanna, and Klein, William

Subjects
Condensed Matter - Statistical Mechanics
Abstract

We analyze the space-time patterns of earthquake occurrence in southern California using a new method that treats earthquakes as a phase dynamical system. The system state vector is used to obtain a probability measure for current and future earthquake occurrence. Thousands of statistical tests indicate the method has considerable forecast skill. We emphasize that the method is not a model, and there are no unconstrained or free parameters to be determined by fits to training data sets., Comment: email: kristy@fractal.colorado.edu

Published
2001

111. Phase Dynamics of Bose-Einstein Condensates: Losses versus Revivals

Author

Sinatra, Alice and Castin, Yvan

Subjects
Physics - Atomic Physics, Physics - General Physics
Abstract

In the absence of losses the phase of a Bose-Einstein condensate undergoes collapses and revivals in time due to elastic atomic interactions. As experiments necessarily involve inelastic collisions, we develop a model to describe the phase dynamics of the condensates in presence of collisional losses. We find that a few inelastic processes are sufficient to damp the revivals of the phase. For this reason the observability of phase revivals for present experimental conditions is limited to condensates with a few hundreds of atoms., Comment: 24 pages, 9 figures. submitted to European Journal of Physics D

Published
1998
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113. Phase dynamics in a binary-collisions atom laser scheme

Author

Zobay, O. and Meystre, P.

Subjects
Condensed Matter, Physics - Atomic Physics
Abstract

Various aspects of the phase dynamics of an atom laser scheme based on binary collisions are investigated. Analytical estimates of the influence of elastic atom-atom collisions on the laser linewidth are given, and linewidths achievable in a recently proposed atom laser scheme [Phys. Rev. A 56, 2989 (1997)] are evaluated explicitly. The extent to which a relative phase can be established between two interfering atom lasers, as well as the properties of that phase, are also investigated., Comment: Revtex, 10 pages, 6 figures

Published
1997
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114. Spin picture of the one-dimensional Hubbard model: Two-fluid structure and phase dynamics

Author

Montorsi, Arianna and Penna, Vittorio

Subjects
Condensed Matter - Superconductivity
Abstract

We propose a scheme for investigating the quantum dynamics of interacting electron models by means of time-dependent variational principle and spin coherent states of space lattice operators. We apply such a scheme to the one-dimensional hubbard model, and solve the resulting equations in different regimes. In particular, we find that at low densities the dynamics is mapped into two coupled nonlinear Schroedinger equations, whereas near half-filling the model is described by two coupled Josephson junction arrays. Focusing then to the case in which only the phases of the spin variables are dynamically active, we examine a number of different solutions corresponding to the excitations of few macroscopic modes. Based on fixed point equation of the simpler among them, we show that the standard one-band ground state phase space is found., Comment: 10 pages, 1 figure, to appear on Phys. Rev. B

Published
1999
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115. Binary Mixtures of Bose-Einstein Condensates: Phase dynamics and Spatial Dynamics

Author

Sinatra, Alice and Castin, Yvan

Subjects
Condensed Matter
Abstract

We investigate the relative phase coherence properties and the occurrence of demixing instabilities for two mutually interacting and time evolving Bose-Einstein condensates in traps. Our treatment naturally includes the additional decoherence effect due to fluctuations in the total number of particles. Analytical results are presented for the breathe-together solution, an extension of previously known scaling solution to the case of a binary mixture of condensates. When the three coupling constants describing the elastic interactions among the atoms in the two states are close to each other, a dramatic increase of the phase coherence time is predicted. Numerical results are presented for the parameters of the recent JILA experiments., Comment: 19 pages, 3 figures, final version of the paper

Published
1999
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120. Probing the Gas-Phase Dynamics of Graphene Chemical Vapour Deposition using in-situ UV Absorption Spectroscopy

Author

Abhay Shivayogimath, David Mackenzie, Birong Luo, Ole Hansen, Peter Bøggild, and Timothy J. Booth

Subjects
Medicine, Science
Abstract

Abstract The processes governing multilayer nucleation in the chemical vapour deposition (CVD) of graphene are important for obtaining high-quality monolayer sheets, but remain poorly understood. Here we show that higher-order carbon species in the gas-phase play a major role in multilayer nucleation, through the use of in-situ ultraviolet (UV) absorption spectroscopy. These species are the volatilized products of reactions between hydrogen and carbon contaminants that have backstreamed into the reaction chamber from downstream system components. Consequently, we observe a dramatic suppression of multilayer nucleation when backstreaming is suppressed. These results point to an important and previously undescribed mechanism for multilayer nucleation, wherein higher-order gas-phase carbon species play an integral role. Our work highlights the importance of gas-phase dynamics in understanding the overall mechanism of graphene growth.

Published
2017
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123. Quantitative Phase Dynamics of Cancer Cell Populations Affected by Blue Light

Author

Feith, Marek, Vičar, Tomáš, Gumulec, Jaromír, Raudenská, Martina, Gjörloff Wingren, Anette, Masařík, Michal, Balvan, Jan, Feith, Marek, Vičar, Tomáš, Gumulec, Jaromír, Raudenská, Martina, Gjörloff Wingren, Anette, Masařík, Michal, and Balvan, Jan

Abstract

Increased exposition to blue light may induce many changes in cell behavior and significantly affect the critical characteristics of cells. Here we show that multimodal holographic microscopy (MHM) within advanced image analysis is capable of correctly distinguishing between changes in cell motility, cell dry mass, cell density, and cell death induced by blue light. We focused on the effect of blue light with a wavelength of 485 nm on morphological and dynamical parameters of four cell lines, malignant PC-3, A2780, G361 cell lines, and the benign PNT1A cell line. We used MHM with blue light doses 24 mJ/cm2, 208 mJ/cm2 and two kinds of expositions (500 and 1000 ms) to acquire real-time quantitative phase information about cellular parameters. It has been shown that specific doses of the blue light significantly influence cell motility, cell dry mass and cell density. These changes were often specific for the malignant status of tested cells. Blue light dose 208 mJ/cm2 × 1000 ms affected malignant cell motility but did not change the motility of benign cell line PNT1A. This light dose also significantly decreased proliferation activity in all tested cell lines but was not so deleterious for benign cell line PNT1A as for malignant cells. Light dose 208 mJ/cm2 × 1000 ms oppositely affected cell mass in A2780 and PC-3 cells and induced different types of cell death in A2780 and G361 cell lines. Cells obtained the least damage on lower doses of light with shorter time of exposition.

Published
2020

124. The Quantitative-Phase Dynamics of Apoptosis and Lytic Cell Death

Abstract

Cell viability and cytotoxicity assays are highly important for drug screening and cytotoxicity tests of antineoplastic or other therapeutic drugs. Even though biochemical-based tests are very helpful to obtain preliminary preview, their results should be confirmed by methods based on direct cell death assessment. In this study, time-dependent changes in quantitative phase-based parameters during cell death were determined and methodology useable for rapid and label-free assessment of direct cell death was introduced. The goal of our study was distinction between apoptosis and primary lytic cell death based on morphologic features. We have distinguished the lytic and non-lytic type of cell death according to their end-point features (Dance of Death typical for apoptosis versus swelling and membrane rupture typical for all kinds of necrosis common for necroptosis, pyroptosis, ferroptosis and accidental cell death). Our method utilizes Quantitative Phase Imaging (QPI) which enables the time-lapse observation of subtle changes in cell mass distribution. According to our results, morphological and dynamical features extracted from QPI micrographs are suitable for cell death detection (76% accuracy in comparison with manual annotation). Furthermore, based on QPI data alone and machine learning, we were able to classify typical dynamical changes of cell morphology during both caspase 3,7-dependent and -independent cell death subroutines. The main parameters used for label-free detection of these cell death modalities were cell density (pg/pixel) and average intensity change of cell pixels further designated as Cell Dynamic Score (CDS). To the best of our knowledge, this is the first study introducing CDS and cell density as a parameter typical for individual cell death subroutines with prediction accuracy 75.4% for caspase 3,7-dependent and -independent cell death.

Published
2020

125. Phase switching dynamics for body-powered hand prostheses: Design of a booster to passively switch between phase dynamics

Author

de Jong, Randy (author) and de Jong, Randy (author)

Abstract

Body-powered prosthetic hands used by below-elbow amputees function in two phases. There is the opening and closing motion of the hand (Motion Phase) and the phase when the hand is in contact with an object, and the fingers apply a pinching force (Pinching Phase). Each phase requires a different set of dynamics to properly function. In the Motion Phase, a small amount of applied force must result in a large translation of the fingers, in the Pinching Phase a small amount of force must result in a large pinching force and a small translation. The problem is that body-powered prostheses have fast motion given a low force input during the motion phase but cannot achieve a high pinching force with a low force input during the pinching phase. The goal of the project is to design a mechanism that passively switches between the dynamics of the motion phase and pinching phase for body-powered active closing hook prostheses. In the motion phase a small force input must result in a large output translation and in the pinching phase a small force input must result in a larger force output and a small output translation. In the motion phase a minimum cable force of 10 N is required and in the pinching phase a pinching force of 30 N must be achieved with an input force of 40 N or less The prototype consists of a hydraulic telemanipulation system with a master (shoulder), operated by the shoulder harness, and slave (hand), operates the hand prosthesis, cylinder connected to each other via a booster mechanism. The booster is inactive in the motion phase and active in the pinching phase. The results show that in the motion phase an input force of 5 N can perform the full translation of the prosthesis. If the hand is met with resistance the input 5 N input can increase up to 24 N until the pinching phase activates. The translation in the pinching phase is too small to observe any change. The pinching phase activates at a pinching force of 12 N and an input force of 24 N. In the pinc, Biomedical Engineering

Published
2020

126. The Quantitative-Phase Dynamics of Apoptosis and Lytic Cell Death

Abstract

Cell viability and cytotoxicity assays are highly important for drug screening and cytotoxicity tests of antineoplastic or other therapeutic drugs. Even though biochemical-based tests are very helpful to obtain preliminary preview, their results should be confirmed by methods based on direct cell death assessment. In this study, time-dependent changes in quantitative phase-based parameters during cell death were determined and methodology useable for rapid and label-free assessment of direct cell death was introduced. The goal of our study was distinction between apoptosis and primary lytic cell death based on morphologic features. We have distinguished the lytic and non-lytic type of cell death according to their end-point features (Dance of Death typical for apoptosis versus swelling and membrane rupture typical for all kinds of necrosis common for necroptosis, pyroptosis, ferroptosis and accidental cell death). Our method utilizes Quantitative Phase Imaging (QPI) which enables the time-lapse observation of subtle changes in cell mass distribution. According to our results, morphological and dynamical features extracted from QPI micrographs are suitable for cell death detection (76% accuracy in comparison with manual annotation). Furthermore, based on QPI data alone and machine learning, we were able to classify typical dynamical changes of cell morphology during both caspase 3,7-dependent and -independent cell death subroutines. The main parameters used for label-free detection of these cell death modalities were cell density (pg/pixel) and average intensity change of cell pixels further designated as Cell Dynamic Score (CDS). To the best of our knowledge, this is the first study introducing CDS and cell density as a parameter typical for individual cell death subroutines with prediction accuracy 75.4% for caspase 3,7-dependent and -independent cell death.

Published
2020

127. The Quantitative-Phase Dynamics of Apoptosis and Lytic Cell Death

Abstract

Cell viability and cytotoxicity assays are highly important for drug screening and cytotoxicity tests of antineoplastic or other therapeutic drugs. Even though biochemical-based tests are very helpful to obtain preliminary preview, their results should be confirmed by methods based on direct cell death assessment. In this study, time-dependent changes in quantitative phase-based parameters during cell death were determined and methodology useable for rapid and label-free assessment of direct cell death was introduced. The goal of our study was distinction between apoptosis and primary lytic cell death based on morphologic features. We have distinguished the lytic and non-lytic type of cell death according to their end-point features (Dance of Death typical for apoptosis versus swelling and membrane rupture typical for all kinds of necrosis common for necroptosis, pyroptosis, ferroptosis and accidental cell death). Our method utilizes Quantitative Phase Imaging (QPI) which enables the time-lapse observation of subtle changes in cell mass distribution. According to our results, morphological and dynamical features extracted from QPI micrographs are suitable for cell death detection (76% accuracy in comparison with manual annotation). Furthermore, based on QPI data alone and machine learning, we were able to classify typical dynamical changes of cell morphology during both caspase 3,7-dependent and -independent cell death subroutines. The main parameters used for label-free detection of these cell death modalities were cell density (pg/pixel) and average intensity change of cell pixels further designated as Cell Dynamic Score (CDS). To the best of our knowledge, this is the first study introducing CDS and cell density as a parameter typical for individual cell death subroutines with prediction accuracy 75.4% for caspase 3,7-dependent and -independent cell death.

Published
2020

128. Quantitative Phase Dynamics of Cancer Cell Populations Affected by Blue Light

Abstract

Increased exposition to blue light may induce many changes in cell behavior and significantly affect the critical characteristics of cells. Here we show that multimodal holographic microscopy (MHM) within advanced image analysis is capable of correctly distinguishing between changes in cell motility, cell dry mass, cell density, and cell death induced by blue light. We focused on the effect of blue light with a wavelength of 485 nm on morphological and dynamical parameters of four cell lines, malignant PC-3, A2780, G361 cell lines, and the benign PNT1A cell line. We used MHM with blue light doses 24 mJ/cm2, 208 mJ/cm2 and two kinds of expositions (500 and 1000 ms) to acquire real-time quantitative phase information about cellular parameters. It has been shown that specific doses of the blue light significantly influence cell motility, cell dry mass and cell density. These changes were often specific for the malignant status of tested cells. Blue light dose 208 mJ/cm2 × 1000 ms affected malignant cell motility but did not change the motility of benign cell line PNT1A. This light dose also significantly decreased proliferation activity in all tested cell lines but was not so deleterious for benign cell line PNT1A as for malignant cells. Light dose 208 mJ/cm2 × 1000 ms oppositely affected cell mass in A2780 and PC-3 cells and induced different types of cell death in A2780 and G361 cell lines. Cells obtained the least damage on lower doses of light with shorter time of exposition.

Published
2020

129. Quantitative Phase Dynamics of Cancer Cell Populations Affected by Blue Light

Abstract

Increased exposition to blue light may induce many changes in cell behavior and significantly affect the critical characteristics of cells. Here we show that multimodal holographic microscopy (MHM) within advanced image analysis is capable of correctly distinguishing between changes in cell motility, cell dry mass, cell density, and cell death induced by blue light. We focused on the effect of blue light with a wavelength of 485 nm on morphological and dynamical parameters of four cell lines, malignant PC-3, A2780, G361 cell lines, and the benign PNT1A cell line. We used MHM with blue light doses 24 mJ/cm2, 208 mJ/cm2 and two kinds of expositions (500 and 1000 ms) to acquire real-time quantitative phase information about cellular parameters. It has been shown that specific doses of the blue light significantly influence cell motility, cell dry mass and cell density. These changes were often specific for the malignant status of tested cells. Blue light dose 208 mJ/cm2 × 1000 ms affected malignant cell motility but did not change the motility of benign cell line PNT1A. This light dose also significantly decreased proliferation activity in all tested cell lines but was not so deleterious for benign cell line PNT1A as for malignant cells. Light dose 208 mJ/cm2 × 1000 ms oppositely affected cell mass in A2780 and PC-3 cells and induced different types of cell death in A2780 and G361 cell lines. Cells obtained the least damage on lower doses of light with shorter time of exposition.

Published
2020

130. Modeling of gain and phase dynamics in quantum dot amplifiers

Author

Moreno, Pablo, Rossetti, Marco, Deveaud-Plédran, Benoît, Fiore, Andrea, Moreno, Pablo, Rossetti, Marco, Deveaud-Plédran, Benoît, and Fiore, Andrea

Abstract

By means of an electron hole rate equation model we explain the phase dynamics of a quantum dot semiconductor optical amplifier and the appearance of different decay times observed in pump and probe experiments. The ultrafast hole relaxation leads to a first ultrafast recovery of the gain, followed by electron relaxation and, in the nanosecond timescale, radiative and non-radiative recombinations. The phase dynamics is slower and is affected by thermal redistribution of carriers within the dot. We explain the ultrafast response of quantum dot amplifiers as an effect of hole escape and recombination without the need to assume Auger processes

Published
2018

132. Slow-paced inspiration regularizes alpha phase dynamics in the human brain

Author

Shen-Mou Hsu, Chih-Hsin Tseng, Chang-Wei Hsieh, and Chao-Hsien Hsieh

Subjects
Adult, Cerebral Cortex, Male, Physiology, Computer science, General Neuroscience, Emotional functions, Magnetoencephalography, Alpha (ethology), Cognition, Human brain, Alpha Rhythm, Young Adult, medicine.anatomical_structure, Respiratory Rate, Phase dynamics, Breathing, medicine, Humans, Female, Neuroscience
Abstract

The phase of low-frequency, rhythmic cortical activity is essential for organizing brain processes because it provides a recurrent temporal frame for information coding. However, the low-frequency cortical phase exhibits great flexibility in response to external influences. Given that brain rhythms have been found to track respiratory inputs, we hypothesized that slow breathing, commonly associated with mental regulation, could reorganize the relationship between these two rhythmic systems through the adjustment of the cortical phase to such a slow train of inputs. Based on simultaneous magnetoencephalography and respiratory measurements, we report that while participants performed paced breathing, slow relative to normal breathing modulated cortical phase activity in the alpha range across widespread brain areas. Such modulation effects were specifically locked to the middle of the inspiration stage and exhibited a well-structured pattern. At the single-subject level, the phase angles underlying the effects became more likely to be diametrically opposed across breaths, indicating unique and consistent phase adjustment to slow inspiratory inputs. Neither cardiac fluctuations nor breathing-unrelated task effects could account for the findings. We suggest that slow-paced inspiration could organize the cortical phase in a regularized phase pattern, revealing a rhythmic but dynamic neural network integrated with different neurophysiological systems through volitional control. NEW & NOTEWORTHY Breathing is more complicated than a simple gas exchange, as it is integrated with numerous cognitive and emotional functions. Controlled slow breathing has often been used to regulate mental processes. This magnetoencephalography study demonstrates that slow-paced relative to normal-paced inspiration could organize the timing of alpha rhythmic activities across breathing cycles in a structured manner over widespread brain areas. Our results reveal how a volitionally controlled change in respiratory behavior could systematically modulate cortical activity.

Published
2020
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133. Measurements of Phase Dynamics in Planar Josephson Junctions and SQUIDs

Author

D. Z. Haxell, E. Cheah, F. Křížek, R. Schott, M. F. Ritter, M. Hinderling, W. Belzig, C. Bruder, W. Wegscheider, H. Riel, and F. Nichele

Subjects
Critical current, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, superconductivity, FOS: Physical sciences, General Physics and Astronomy, Superconductivity (cond-mat.supr-con), quantum, Phase slips, Andreev reflection, Condensed Matter::Superconductivity, Josephson junction, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), ddc:530, Two-dimensional electron system
Abstract

We experimentally investigate the stochastic phase dynamics of planar Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs) defined in epitaxial InAs/Al heterostructures, and characterized by a large ratio of Josephson energy to charging energy. We observe a crossover from a regime of macroscopic quantum tunneling to one of phase diffusion as a function of temperature, where the transition temperature T∗ is gate-tunable. The switching probability distributions are shown to be consistent with a small shunt capacitance and moderate damping, resulting in a switching current which is a small fraction of the critical current. Phase locking between two JJs leads to a difference in switching current between that of a JJ measured in isolation and that of the same JJ measured in an asymmetric SQUID loop. In the case of the loop, T∗ is also tuned by a magnetic flux., Physical Review Letters, 130 (8), ISSN:0031-9007, ISSN:1079-7114

Published
2023
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135. Characterization of Bitumen Micro-Mechanical Behaviors Using AFM, Phase Dynamics Theory and MD Simulation

Author

Civil and Environmental Engineering, Hou, Yue, Wang, Linbing, Wang, Dawei, Guo, Meng, Liu, Pengfei, Yu, Jianxin, Civil and Environmental Engineering, Hou, Yue, Wang, Linbing, Wang, Dawei, Guo, Meng, Liu, Pengfei, and Yu, Jianxin

Abstract

Fundamental understanding of micro-mechanical behaviors in bitumen, including phase separation, micro-friction, micro-abrasion, etc., can help the pavement engineers better understand the bitumen mechanical performances at macroscale. Recent researches show that the microstructure evolution in bitumen will directly affect its surface structure and micro-mechanical performance. In this study, the bitumen microstructure and micro-mechanical behaviors are studied using Atomic Force Microscopy (AFM) experiments, Phase Dynamics Theory and Molecular Dynamics (MD) Simulation. The AFM experiment results show that different phase-structure will occur at the surface of the bitumen samples under certain thermodynamic conditions at microscale. The phenomenon can be explained using the phase dynamics theory, where the effects of stability parameter and temperature on bitumen microstructure and micro-mechanical behavior are studied combined with MD Simulation. Simulation results show that the saturates phase, in contrast to the naphthene aromatics phase, plays a major role in bitumen micro-mechanical behavior. A high stress zone occurs at the interface between the saturates phase and the naphthene aromatics phase, which may form discontinuities that further affect the bitumen frictional performance.

Published
2017

136. Functional optoretinography: concurrent OCT monitoring of intrinsic signal amplitude and phase dynamics in human photoreceptors

Author

Guangying Ma, Tae-Hoon Kim, Taeyoon Son, and Xincheng Yao

Subjects
Physics, 0303 health sciences, Retinal pigment epithelium, genetic structures, medicine.diagnostic_test, Stimulus (physiology), 01 natural sciences, Signal, Photoreceptor outer segment, eye diseases, Atomic and Molecular Physics, and Optics, 010309 optics, 03 medical and health sciences, Amplitude, medicine.anatomical_structure, Phase dynamics, Optical coherence tomography, 0103 physical sciences, medicine, sense organs, Neuroscience, 030304 developmental biology, Biotechnology, Visual phototransduction
Abstract

Intrinsic optical signal (IOS) imaging promises a noninvasive method for objective assessment of retinal function. This study demonstrates concurrent optical coherence tomography (OCT) of amplitude-IOS and phase-IOS changes in human photoreceptors. A new procedure for differential-phase-mapping (DPM) is validated to enable depth-resolved phase-IOS imaging. Dynamic OCT revealed rapid amplitude-IOS and phase-IOS changes, which occur almost right away after the stimulus onset. These IOS changes were predominantly observed within the photoreceptor outer segment (OS), particularly two boundaries connecting to the inner segment and retinal pigment epithelium. The comparative analysis supports that both amplitude-IOS and phase-IOS attribute to transient OS morphological change associated with phototransduction activation in retinal photoreceptors. A simulation modeling is proposed to discuss the relationship between the photoreceptor OS length and phase-IOS changes.

Published
2021

138. Reconstruction of Phase Dynamics from Macroscopic Observations Based on Linear and Nonlinear Response Theories

Author

Yamaguchi, Yoshiyuki Y. and Terada, Yu

Subjects
FOS: Physical sciences, Chaotic Dynamics (nlin.CD), Nonlinear Sciences - Chaotic Dynamics, Adaptation and Self-Organizing Systems (nlin.AO), Nonlinear Sciences - Adaptation and Self-Organizing Systems
Abstract

We propose a novel method to reconstruct phase dynamics equations from responses in macroscopic variables to weak inputs. Developing linear and nonlinear response theories in coupled phase-oscillators, we derive formulae which connect the responses with the system parameters including the time delay in interactions. We examine our method by applying it to two phase models, one of which describes a mean-field network of the Hodgkin--Huxley type neurons with a nonzero time delay. The method does not require much invasiveness nor microscopic observations, and these advantages highlight its broad applicability in various fields., Comment: 12 pages, 5 figures

Published
2023
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139. Phase dynamics of delay-coupled quasi-cycles with application to brain rhythms

Author

Arthur S. Powanwe and André Longtin

Subjects
Physics, QC1-999
Abstract

We consider the phase locking of two delay-coupled quasi-cycles. A coupled envelope-phase system obtained via stochastic averaging enables a stability analysis. While for deterministic limit-cycle oscillators the coupling can produce in-phase, antiphase, and the intermediate “out-of-phase” locking (OPL) behavior via spontaneous symmetry breaking, such outcomes for the quasi-cycle case are shown to require instead both noise and coupling delay. The theory, which applies the stochastic averaging method to delayed dynamics, generates stochastic stability functions that predict the numerically observed OPL behavior as a function of all the system parameters. OPL for coupled quasi-cycles occurs for additive or multiplicative noise, and for coupled networks of excitatory and inhibitory neurons as well as networks of inhibitory neurons coupled to one another. Our theory also predicts that the bifurcation at which the in-phase state becomes unstable lies at smaller delays for stronger noise. The noise produces the realistic quasi-cycle rhythms and out-of-phase behavior, all the while causing random reversals of the phase leader. Asymmetry in the coupling between networks, as well as heterogeneity within each network, also allows for quasi-cycle OPL, although it produces asymmetric bifurcations that bias the leadership towards one of the networks. These results are relevant to communication between brain areas and other networks that rely on noise-induced rather than noise-perturbed rhythms.

Published
2020
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140. Quantitative Phase Dynamics of Cancer Cell Populations Affected by Blue Light

Author

Marek Feith, Tomáš Vičar, Jaromír Gumulec, Martina Raudenská, Anette Gjörloff Wingren, Michal Masařík, and Jan Balvan

Subjects
holographic microscopy, quantitative phase imaging, blue light, cell mass, cell motility, cell death, Technology, Engineering (General). Civil engineering (General), TA1-2040, Biology (General), QH301-705.5, Physics, QC1-999, Chemistry, QD1-999
Abstract

Increased exposition to blue light may induce many changes in cell behavior and significantly affect the critical characteristics of cells. Here we show that multimodal holographic microscopy (MHM) within advanced image analysis is capable of correctly distinguishing between changes in cell motility, cell dry mass, cell density, and cell death induced by blue light. We focused on the effect of blue light with a wavelength of 485 nm on morphological and dynamical parameters of four cell lines, malignant PC-3, A2780, G361 cell lines, and the benign PNT1A cell line. We used MHM with blue light doses 24 mJ/cm2, 208 mJ/cm2 and two kinds of expositions (500 and 1000 ms) to acquire real-time quantitative phase information about cellular parameters. It has been shown that specific doses of the blue light significantly influence cell motility, cell dry mass and cell density. These changes were often specific for the malignant status of tested cells. Blue light dose 208 mJ/cm2 × 1000 ms affected malignant cell motility but did not change the motility of benign cell line PNT1A. This light dose also significantly decreased proliferation activity in all tested cell lines but was not so deleterious for benign cell line PNT1A as for malignant cells. Light dose 208 mJ/cm2 × 1000 ms oppositely affected cell mass in A2780 and PC-3 cells and induced different types of cell death in A2780 and G361 cell lines. Cells obtained the least damage on lower doses of light with shorter time of exposition.

Published
2020
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141. Probing the Gas-Phase Dynamics of Graphene Chemical Vapour Deposition using in-situ UV Absorption Spectroscopy

Author

Shivayogimath, Abhay, Mackenzie, David, Luo, Birong, Hansen, Ole, Bøggild, Peter, Booth, Tim, Shivayogimath, Abhay, Mackenzie, David, Luo, Birong, Hansen, Ole, Bøggild, Peter, and Booth, Tim

Abstract

The processes governing multilayer nucleation in the chemical vapour deposition (CVD) of graphene are important for obtaining high-quality monolayer sheets, but remain poorly understood. Here we show that higher-order carbon species in the gas-phase play a major role in multilayer nucleation, through the use of in-situ ultraviolet (UV) absorption spectroscopy. These species are the volatilized products of reactions between hydrogen and carbon contaminants that have backstreamed into the reaction chamber from downstream system components. Consequently, we observe a dramatic suppression of multilayer nucleation when backstreaming is suppressed. These results point to an important and previously undescribed mechanism for multilayer nucleation, wherein higher-order gas-phase carbon species play an integral role. Our work highlights the importance of gas-phase dynamics in understanding the overall mechanism of graphene growth.

Published
2017

142. Phase dynamics of delay-coupled quasi-cycles with application to brain rhythms

Author

André Longtin and Arthur S. Powanwe

Subjects
Physics, Coupling (electronics), 0303 health sciences, 03 medical and health sciences, 0302 clinical medicine, Rhythm, Quantitative Biology::Neurons and Cognition, Artificial neural network, Phase dynamics, Noise intensity, Topology, 030217 neurology & neurosurgery, 030304 developmental biology
Abstract

The authors show that neural networks exhibiting noise-induced rhythms, also known as quasi-cycle oscillations, can synchronize through out-of-phase locking depending on the noise intensity and the size of the coupling delay

Published
2020
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143. The Role of the Solvent in the Condensed-Phase Dynamics and Identity of Chemical Bonds: The Case of the Sodium Dimer Cation in THF

Author

Benjamin J. Schwartz and Devon. R. Widmer

Subjects
010304 chemical physics, Sodium, media_common.quotation_subject, Dimer, chemistry.chemical_element, Electronic structure, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Solvent, Crystallography, chemistry.chemical_compound, chemistry, Phase dynamics, Chemical bond, Identity (philosophy), 0103 physical sciences, Materials Chemistry, Molecule, Physical and Theoretical Chemistry, media_common
Abstract

When a solute molecule is placed in solution, is it acceptable to presume that its electronic structure is essentially the same as that in the gas phase? In this paper, we address this question from a simulation perspective for the case of the sodium dimer cation (Na

Published
2020

144. Infrared action spectroscopy as tool for probing gas-phase dynamics: protonated dimethyl ether, (CH3)2OH+, formed by the reaction of CH3OH2+ with CH3OH

Author

Richardson, V., Rap, D. B., Brünken, S., and Ascenzi, D.

Abstract

Methanol is one of the most abundant interstellar Complex Organic Molecules (iCOMs) and represents a major building block for the synthesis of increasingly complex oxygen-containing molecules. The reaction between protonated methanol and its neutral counterpart, giving protonated dimethyl ether, (CH3)2OH+, along with the ejection of a water molecule, has been proposed as a key reaction in the synthesis of dimethyl ether in space. Here, gas phase vibrational spectra of the (CH3)2OH+ reaction product and the [C2H9O2]+ intermediate complex(es), formed under different pressure and temperature conditions, are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to record these vibrational fingerprint spectra using different types of infrared action spectroscopy in the 600-1700 cm−1 frequency range, complemented with measurements using an OPO/OPA system to cover the O−H stretching region 3400−3700cm−1. The formation of protonated dimethyl ether as a product of the reaction is spectroscopically confirmed, providing the first gas-phase vibrational spectrum of this potentially relevant astrochemical ion.

Published
2023
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146. Estimation of Delay Times in Coupling Between Autonomic Regulatory Loops of Human Heart Rate and Blood Flow Using Phase Dynamics Analysis

Author

Tatyana A. Galushko, Mikhail D. Prokhorov, Vladimir S. Khorev, Anatoly S. Karavaev, Elena E. Lapsheva, and Anton R. Kiselev

Subjects
0301 basic medicine, Physics, Human heart, Blood flow, Autonomic regulation, Coupling (electronics), 03 medical and health sciences, 030104 developmental biology, 0302 clinical medicine, Phase dynamics, Control theory, Cardiology and Cardiovascular Medicine, 030217 neurology & neurosurgery, Delay time
Abstract

Objective:We assessed the delay times in the interaction between the autonomic regulatory loop of Heart Rate Variability (HRV) and autonomic regulatory loop of photoplethysmographic waveform variability (PPGV), showing low-frequency oscillations.Material and Methods:In eight healthy subjects aged 25–30 years (3 male, 5 female), we studied at rest (in a supine position) the simultaneously recorded two-hour signals of RR intervals (RRIs) chain and finger photoplethysmogram (PPG). To extract the low-frequency components of RRIs and PPG signal, associated with the low-frequency oscillations in HRV and PPGV with a frequency of about 0.1 Hz, we filtered RRIs and PPG with a bandpass 0.05-0.15 Hz filter. We used a method for the detection of coupling between oscillatory systems, based on the construction of predictive models of instantaneous phase dynamics, for the estimation of delay times in the interaction between the studied regulatory loops.Results:Averaged value of delay time in coupling from the regulatory loop of HRV to the loop of PPGV was 0.9±0.4 seconds (mean ± standard error of the means) and averaged value of delay time in coupling from PPGV to HRV was 4.1±1.1 seconds.Conclusion:Analysis of two-hour experimental time series of healthy subjects revealed the presence of delay times in the interaction between regulatory loops of HRV and PPGV. Estimated delay time in coupling regulatory loops from HRV to PPGV was about one second or even less, while the delay time in coupling from PPGV to HRV was about several seconds. The difference in delay times is explained by the fact that PPGV to HRV response is mediated through the autonomic nervous system (baroreflex), while the HRV to PPGV response is mediated mechanically via cardiac output.

Published
2017
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147. Kinesin and Myosin Motors Compete to Drive Rich Multi-Phase Dynamics in Programmable Cytoskeletal Composites

Author

Robertson-Anderson, Rae

Abstract

Raw video files associated with the paper described as follows: The cellular cytoskeleton relies on diverse populations of motors, filaments, and binding proteins acting in concert to enable non-equilibrium processes ranging from mitosis to chemotaxis. The cytoskeleton’s versatile reconfigurability, programmed by interactions between its constituents, make it a foundational active matter platform. However, current active matter endeavors are limited largely to single force-generating components acting on a single substrate–far from the composite cytoskeleton in cells. Here, we engineer actin-microtubule composites, driven by kinesin and myosin motors and tuned by crosslinkers, to ballistically restructure and flow with speeds that span three orders of magnitude depending on the composite formulation and time relative to the onset of motor activity. Differential dynamic microscopy analyses reveal that kinesin and myosin compete to delay the onset of acceleration and suppress discrete restructuring events, while passive crosslinking of either actin or microtubules has an opposite effect. Our minimal advection-diffusion model and spatial correlation analyses correlate these dynamics to structure, with motor antagonism suppressing reconfiguration and de-mixing, while crosslinking enhances clustering. Despite the rich formulation space and emergent formulation-dependent structures, the non-equilibrium dynamics across all composites and timescales can be organized into three classes–slow isotropic reorientation, fast directional flow, and multimode restructuring. Moreover, our mathematical model demonstrates that diverse structural motifs can arise simply from the interplay between motor-driven advection and frictional drag. These general features of our platform facilitate applicability to other active matter systems, and shed light on diverse ways that cytoskeletal components can cooperate or compete to enable wide-ranging cellular processes.

Published
2022
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148. Phase dynamics in an AC driven multiterminal Josephson junction analogue

Author

François Amet, Sara Idris, Aeron McConnell, Brian Opatosky, and Ethan Arnault

Subjects
Superconductivity (cond-mat.supr-con), Condensed Matter - Superconductivity, FOS: Physical sciences
Abstract

In the presence of an AC drive, multiterminal Josephson junctions exhibit the inverse AC Josephson effect, where the oscillations of the superconducting phase of each junction can lock onto one another or onto the external drive. The competition between these different phase locked states results in a complex array of quantized voltage plateaus whose stability strongly depend on the circuit parameters of the shunted junctions. This phase diagram cannot be explored with low temperature transport experiments alone, given the breadth of the parameter space, so we present an easily tunable analog circuit whose dynamical properties emulate those of a three terminal junction. We focus on the observation of the multiterminal inverse AC Josephson effect, and we discuss how to identify Shapiro steps associated with each of the three junctions as well as their quartet states. We only observe integer phase locked states in strongly overdamped networks, but fractional Shapiro steps appear as well when the quality factor of the junctions increases. Finally, we discuss the role of transverse coupling in the synchronization of the junctions., 11 pages, 7 figures

Published
2022

149. The Foot in Walking - Towards Developing a Constrained Model of Stance Phase Dynamics

Author

Daniel Renjewski, Susanne Lipfert, Michael Günther, and Lehrstuhl f. Angewandte Mechanik

Subjects
ddc
Abstract

Bipedal walking is the most prevalent form of human locomotion — versatile, robust, and efficient. However, it is a form of motion few other animals share, and plantigrade bipedalism is fairly unique to our species. Plantigrade feet play an important role in shaping the fundamental gait dynamics, and understanding their role unlocks a huge potential for biomechanical insights for locomotion research, gait rehabilitation, and humanoid robotics. Still, a comprehensive functional model of the foot, which ties the fundamental dynamics of walking to the interaction of foot and ground, does not yet exist due to the inherent mechanical complexity. In this paper, we present a set of assumptions in detail to simplify the development of a mathematical description of the foot’s motion during stance phase in human walking. These assumptions are validated using experimental data. We can show that the complex motion of the foot can be ultimately reduced to a simple rotation, which allows the formulation of a single degree of freedom equation of motion that ties proximal dynamics and constraints into a planar foot model of dynamic interactions.

Published
2022
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150. Anomalous Phase Dynamics of Driven Graphene Josephson Junctions

Author

Sandesh S. Kalantre, Fan Yu, Francois Amet, Ming-Tso Wei, Kenji Watanabe, Takashi Taniguchi, James R. Williams, and M. Hernandez-Rivera

Subjects
Josephson effect, Physics, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Graphene, Chaotic, FOS: Physical sciences, Nonlinear Sciences - Chaotic Dynamics, Bridge (interpersonal), law.invention, Nonlinear system, Phase dynamics, law, Condensed Matter::Superconductivity, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Chaotic Dynamics (nlin.CD), Quantum
Abstract

Josephson junctions with weak-links of exotic materials allow the elucidation of the Josephson effect in previously unexplored regimes. Further, such devices offer a direct probe of novel material properties, for example in the search for Majorana fermions. In this work, we report on DC and AC Josephson effect of high-mobility, hexagonal boron nitride (h-BN) encapsulated graphene Josephson junctions. On the application of RF radiation, we measure phase-locked Shapiro steps. An unexpected bistability between $\pm 1$ steps is observed with switching times on the order of seconds. A critical scaling of a bistable state is measured directly from the switching time, allowing for direct comparison to numerical simulations. We show such intermittent chaotic behavior is a consequence of the nonlinear dynamics of the junction and has a sensitive dependence on the current-phase relation. This work draws connections between nonlinear phenomena in dynamical systems and their implications for ongoing condensed matter experiments exploring topology and exotic physics.

Published
2019

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