Fluctuation Lifetimes Research Articles

Behavioral state-dependent associations between EEG temporal correlations and depressive symptoms

Previous studies have shown abnormal long-range temporal correlations in neuronal oscillations among individuals with Major Depressive Disorders, occurring during both resting states and transitions between resting and task states. However, the understanding of this effect in preclinical individuals with depression remains limited. This study investigated the association between temporal correlations of neuronal oscillations and depressive symptoms during resting and task states in preclinical individuals, specifically focusing on male action video gaming experts. Detrended fluctuation analysis (DFA), Lifetimes, and Waitingtimes were employed to explore temporal correlations across long-range and short-range scales. The results indicated widespread changes from the resting state to the task state across all frequency bands and temporal scales. Rest-task DFA changes in the alpha band exhibited a negative correlation with depressive scores at most electrodes. Significant positive correlations between DFA values and depressive scores were observed in the alpha band during the resting state but not in the task state. Similar patterns of results emerged concerning maladaptive negative emotion regulation strategies. Additionally, short-range temporal correlations in the alpha band echoed the DFA results. These findings underscore the state-dependent relationships between temporal correlations of neuronal oscillations and depressive symptoms, as well as maladaptive emotion regulation strategies, in preclinical individuals.

Capillary fluctuations of surface steps: An atomistic simulation study for the model Cu(111) system.

Molecular dynamics (MD) simulations are employed to investigate the capillary fluctuations of steps on the surface of a model metal system. The fluctuation spectrum, characterized by the wave number (k) dependence of the mean squared capillary-wave amplitudes and associated relaxation times, is calculated for 〈110〉 and 〈112〉 steps on the {111} surface of elemental copper near the melting temperature of the classical potential model considered. Step stiffnesses are derived from the MD results, yielding values from the largest system sizes of (37±1)meV/A[over ˚] for the different line orientations, implying that the stiffness is isotropic within the statistical precision of the calculations. The fluctuation lifetimes are found to vary by approximately four orders of magnitude over the range of wave numbers investigated, displaying a k dependence consistent with kinetics governed by step-edge mediated diffusion. The values for step stiffness derived from these simulations are compared to step free energies for the same system and temperature obtained in a recent MD-based thermodynamic-integration (TI) study [Freitas, Frolov, and Asta, Phys. Rev. B 95, 155444 (2017)2469-995010.1103/PhysRevB.95.155444]. Results from the capillary-fluctuation analysis and TI calculations yield statistically significant differences that are discussed within the framework of statistical-mechanical theories for configurational contributions to step free energies.

Observation of two distinct pairs fluctuation lifetimes and supercurrents in the pseudogap regime of cuprate junctions

Pairs fluctuation supercurrents and inverse lifetimes were measured on epitaxial c-axis junctions of the cuprates in the pseudogap regime, with a $PrBa_2Cu_3O_{7-\delta}$ barrier sandwiched in between two $YBa_2Cu_3O_{7-\delta}$ or doped $YBa_2Cu_3O_y$ electrodes, with or without magnetic fields parallel to the a-b planes. All junctions had a $\rm T_c(high)\approx 85-90$ K and a $\rm T_c(low)\approx 50-55$ K electrodes, allowing us to study pairs fluctuation supercurrents and inverse life times in between these two temperatures. In junctions with a pseudogap electrode under zero field, an excesss current due to pair fluctuations was observed which persisted at temperatures above $\rm T_c(low)$, in the pseudogap regime, and up to about $\rm T_c(high)$. No such excess current was observed in junctions without a pseudo-gap in the electrode. The measured conductance spectra at temperatures above $\rm T_c(low)$ were fitted using a modified fluctuations model by Scalapino [Phys. Rev. Lett. \textbf{24}, 1052(1970)] of a junction with a serial resistance. We found that in the pseudo-gap regime, the conductance vs voltage consists of a narrow peak sitting on top of a very broad peak. This yielded two distinct pairs fluctuation lifetimes in the pseudogap electrode which differ by an order of magnitude up to about $\rm T_c(high)$. Under in-plane fields, these two lifetime values remain separated in two distinct groups, which varied with increasing field moderately. We also found that detection of Amperian pairing [Phys. Rev. X \textbf{4}, 031017 (2014)] in our cuprate junctions is not feasible, due to Josephson vortices penetration into the superconducting electrodes which drove the necessary field above the depairing field.

Hybrid lipids increase nanoscale fluctuation lifetimes in mixed membranes

A recently proposed ternary mixture model is used to predict fluctuation domain lifetimes in the one phase region. The membrane is made of saturated, unsaturated, and hybrid lipids that have one saturated and one unsaturated hydrocarbon chain. The hybrid lipid is a natural linactant which can reduce the packing incompatibility between saturated and unsaturated lipids. The fluctuation lifetimes are predicted as a function of the hybrid lipid fraction and the fluctuation domain size. These lifetimes can be increased by up to three orders of magnitude compared to the case of no hybrids. With hybrid, small length scale fluctuations have sizable amplitudes even close to the critical temperature and, hence, benefit from enhanced critical slowing down. The increase in lifetime is particularly important for nanometer scale fluctuation domains where the hybrid orientation and the other lipids composition are highly coupled.

Non-equilibrium fluctuations on earth and in micro-gravity. The GRADFLEX experiment

We present the results of measurements of giant nonequilibrium fluctuations in a single component fluid (density fluctuations) and a mixture (concentration fluctuations) driven by applied temperature gradients, both on Earth and in space. Flight data were obtained during the September 2007 FOTON M3 mission. Spatial power spectra obtained using the shadowgraph method, during flight, confirm that the asymptotic behaviour extends to such low wave vector q, as to be limited by the sample thickness. Quantitative comparison with theory is provided, and is generally quite good. Temporal sequences of shadowgraph images for the mixture, both on Earth and during flight will be presented to emphasize the dramatic differences. Fluctuation lifetimes of thousands of seconds were observed during flight. The rugged but sensitive shadowgraph scattering method (phase fluctuations below 10 milliradians measured to within a few percent absolute accuracy) will be described briefly.

Demagnetization of Pr ion in (R 1-xPr x)Ba 2Cu 3O 7-y systems (R  Yb, Er, Y, Dy, Gd, Eu, Sm and Nd)

Detailed measurements of the superconducting transition temperature in (R 1-xPr x)Ba 2Cu 3O 7-y systems at low Pr concentration have revealed that when the Pr concentration is sufficiently low, the local state of the Pr ion is short-lived compared to thermal fluctuation lifetimes. The resulting magnetic moment averages over time to zero demagnetizing the Pr ions, thus superconductivity is no longer suppressed by the pair-breaking mechanism.

Nonmagnetic-magnetic transition of Pr ion in (R 1− xPr x)Ba 2Cu 3O 7− y systems (R  Er, Y, Dy, Gd, Eu)

Detailed measurements of the superconducting transition temperature T c in (R 1− x Pr x )Ba 2Cu 3O 7− y (R  Er, Y, Dy, Gd, Eu) systems in the low Pr concentration regime ( x⩽0.1 have revealed that when the Pr-doping concentration is sufficiently low, the local state of Pr ion is short-lived compared to thermal fluctuation lifetimes. The resulting magnetic moment averages over time to zero demagnetizing the Pr ions, thus superconductivity is no longer suppressed by the pair-breaking mechanism. We observed an interesting nonmagnetic-magnetic transition of the Pr ions in the (R 1− x Pr x )Ba 2Cu 3O 7− y systems induced either by increasing the Pr concentration in one of these systems or by changing the R ion in the host matrix RBa 2Cu 3O 7− y (R  Er, Y, Dy, Gd, Eu) in a fixed low Pr concentration.

Theory of electric fields in the auroral acceleration region

Electric field fluctuations identified as electrostatic ion cyclotron waves, double layers, and near solitary wave potential structures have been observed in the auroral particle acceleration region by the S3‐3 and Viking satellites. Here these electric fields are explained in terms of a three‐dimensional model of nonlinear ion hole/clump instability. A novel feature of the instability is its occurrence in plasma that is linearly stable to ion acoustic and electrostatic ion cyclotron waves, the inferred state of the plasma in the auroral acceleration region. A growing ion hole has a double layer potential structure which, in the latter phase of the instability, decays to a near solitary wave potential structure. In addition, the holes can coexist with and be a source for electrostatic ion cyclotron waves. Instability thresholds, amplitudes for potentials, electric fields, and density depletions, as well as fluctuation velocities, lifetimes, scale sizes, and relative probablities for occurrence are calculated and compared with the satellite data.

Anomalous behavior of discrete resistance fluctuation lifetimes in novel metal insulator-metal tunnel junctions

Measurements are reported of the switching lifetimes of the discrete resistance fluctuations in AuAl 20 3Au tunnel junctions which have small Al particles randomly embedded within the insulating barrier. The tunnel junctions are 50×50 Pin 2 and the Al particles are nominally disk-shaped with thickness about 30Å and radius 500Å. Tunnel M-I-M junctions which do not contain embedded metal particles typically have switching lifetimes that decrease exponentially with applied d.c. bias voltage. However, we have found that the presence of embedded particles leads to anomalous behavior, in which the switching lifetimes increase with applied bias voltage. We ascribe this behavior to the interaction of defects with the charge state of the embedded Al particles.

Anomalous behavior of discrete resistance fluctuation lifetimes in novel metal insulator-metal tunnel junctions

Anomalous behavior of discrete resistance fluctuation lifetimes in novel metal insulator-metal tunnel junctions

Polaronic effects on interconfigurational fluctuation lifetimes in intermediate valence systems

Abstract It is shown that in systems exhibiting intermediate valence polaronic effects can lead to significant reductions in interconfiguration fluctuation frequency and to a shift in the electronic excitation spectrum. Numerical estimates for SmS give a shift in good accord with recent experiments and indicate a non-negligible lifetime enhancement factor.

Analysis of composition fluctuation lifetimes in a critical oxide mixture by volume relaxation spectroscopy

The distribution of volume relaxation times in a critical oxide mixture is calculated from longitudinal and shear modulus measurements. Ultrasonic relaxation allows the investigation of two distinct effects in the distribution of relaxation times as the temperature is lowered toward the critical point. At high temperatures, a coupling between the compressional component of the ultrasonic wave and supercritical fluctuations in composition leads to an anomalous broadening of the distribution of volume relaxation times. This interaction allows a measure of the average composition fluctuation lifetime, τ D, as a function of temperature. At lower temperatures, as τ D becomes longer than the volume relaxation times, the behavior of the distribution follows closely the predictions of an environmental relaxation model proposed by these authors for the analysis of shear relaxation processes in the same material.