Potential Oscillations Research Articles

Critical adsorption and charge reversal in polyelectrolyte solutions: Analytical mean-field theory.

An analytical linearized mean-field theory is presented to describe the adsorption behavior of polyelectrolytes near charged colloidal surfaces with additional short-ranged non-electrostatic interactions. The coupling between the polyelectrolyte segment density and electrostatic potential is explicitly accounted for in a self-consistent manner. This coupling gives rise to highly non-linear behavior, such as oscillations of the electrostatic potential. We derive analytical expressions for the critical surface charge density σc, after which adsorption takes place, and recover the well-known σc∼ns3/2 scaling regime, where ns is the salt concentration. In addition, the theory yields a new ns1 scaling regime if the surface is hard and a unified ns1 scaling regime if the surface also possesses some short-ranged attraction with the polyelectrolyte. Furthermore, we derive an analytical expression to describe the critical polyelectrolyte concentration φc to achieve complete charge reversal, which is found to scale as φc ∼ σ2/(f2c2), where c is related to the magnitude of short-ranged interactions and f is the average charge per monomer of the polyelectrolyte. It is observed that within our theory, complete charge reversal can only take place if the short-ranged interactions are sufficiently strong to completely compensate for the entropy loss of adsorption.

Human Electroretinography Shows Little Polarity Specificity Following Full-Field Ramp Adaptation.

The ramp aftereffect, a visual phenomenon in which perception of light changes dynamically after exposure to sawtooth-modulated light, was first described in 1967. Despite decades of psychophysical research, location and mechanisms of its generation remain unknown. In this study, we investigated a potential retinal contribution to effect formation with specific emphasis on on-/off-pathway involvement. A 100ms flash electroretinogram (ERG) was employed to probe the adaptive state of retinal neurons after presentation of stimuli that were homogenous in space but modulated in time following a sawtooth pattern (upward or downward ramps at 2Hz). Additionally, a psychophysical nulling experiment was performed. Psychophysics data confirmed previous findings that the ramp aftereffect opposes the adapting stimuli in ramp direction and is stronger after upward ramps. The ERG study revealed significant changes of activity in every response component in the low-frequency range (a-wave, b-wave, on-PhNR, d-wave and off-PhNR) and high-frequency range (oscillatory potentials) in amplitudes, peak times, or both. The changes are neither specific to the on- or off-response nor antagonistic between ramp directions. With downward ramp adaptation, effects were stronger. Neither amplitudes nor peak times were correlated with perception strength. Amplitudes and peak times were uncorrelated, and the effect diminished over time, ceasing almost completely with three seconds. Despite abundant effects on retinal responses, the pattern of adaptational effects was not specific to the sawtooth nature of adaptation. Although not ruling out retinal contributions the present findings favor post-retinal mechanisms as the primary locus of the ramp aftereffect.

Oscillatory potential findings in patients with acute ischaemic central retinal vein occlusion

AimsTo explore the sensitive components of full-field electroretinography (ERG) as indicators of retina function at the onset of acute ischaemic central retinal vein occlusion (CRVO).Methods11 patients (11 eyes) with ischaemic...

Constraining the general oscillatory inflaton potential with freeze-indark matter and gravitational waves

The reheating phase after inflation is one of the least observationally constrained epochs in the evolution of the Universe. The forthcoming gravitational wave observatories will enable us to constrain at least some of the non-standard scenarios. For example, models where the radiation bath is produced by the perturbative inflaton decay that oscillates around a minimum of the potential of the form V ∝ ϕ 2n, with n > 2. In such scenarios a part of the inflationary gravitational wave spectrum becomes blue tilted, making it observable, depending on the inflation energy scale and the reheating temperature. The degeneracy between the latter two parameters can be broken if dark matter in the Universe is produced via the freeze-in mechanism. The combination of the independent measurement of dark matter mass with gravitational wave observations makes it possible to constrain the reheating temperature and the energy scale at the end of inflation, at least within some parameter ranges.

Neural coding of space by time.

The intertwining of space and time poses a significant scientific challenge, transcending disciplines from philosophy and physics to neuroscience. Deciphering neural coding, marked by its inherent spatial and temporal dimensions, has proven to be a complex task. In this paper, we present insights into temporal and spatial modes of neural coding and their intricate interplay, drawn from neuroscientific findings. We illustrate the conversion of a purely spatial input into the temporal form of a singular spike train, demonstrating storage, transmission to remote locations, and recall through spike bursts corresponding to Sharp Wave Ripples. Moreover, the converted temporal representation can be transformed back into a spatiotemporal pattern. The principles of the transformation process are illustrated using a simple feed-forward spiking neural network. The frequencies and phases of Subthreshold Membrane potential Oscillations play a pivotal role in this framework. The model offers insights into information multiplexing and phenomena such as stretching or compressing time of spike patterns.

Information-theoretic measures and Compton profile of H atom under finite oscillator potential

Information-theoretic measures for nl (2L) states of a H atom (with n=1−10 and l=0−2 , where n and l denote principal and angular momentum quantum numbers) have been investigated within a quantum dot by utilizing the Ritz variational principle, with the help of a Slater-type basis set. A well-established two-parameter (depth and width) model of finite oscillator potential is used to simulate the dot environment. The variationally optimized position (r)-space wave function is utilized to determine the momentum (p)-space wave function, leading to the generation of p-space radial density distribution. We explore the impact of cavity parameters on quantum information theoretic measures, such as Shannon (S) and Fisher information (I) entropy, in the ground as well as the excited state. The results of S were also used to test the Bialynicki–Birula–Mycielski inequality, related to the entropic uncertainty principle for the confined H atom. Some simple new fitting laws pertaining to S and I have been proposed. Furthermore, the p-space radial density is employed to derive the Compton profile of the confined H atom. Possible tunability of S,I and Compton profiles with respect to the parameters is noted.

Fluorescent Nanocable as a Biomedical Tool: Intracellular Self-Assembly Formed by a Natural Product Interconnects and Synchronizes Mitochondria.

Self-assembly processes commonly occur in various biological contexts to form functional biological structures. However, the self-assembly of nanofibers within cells by heterologous molecules showing a biological function is rare. In this work, we reported the intracellular formation of fluorescent nanofibers by a natural small molecule, lycobetaine (LBT), which facilitated the direct physical connection between mitochondria and synchronized their membrane potential oscillations. The luminescent properties of LBT enabled the real-time observation of nanofiber formation, while the semiconductive nature of the LBT nanofiber facilitated electrical signal transduction among the connected mitochondria. This study introduces an approach to modulate mitochondrial connectivity within cells using "nano-cables" which facilitate studies on synchronized mitochondrial operations and the underlying mechanisms of drug action.

Supersymmetric Expansion Algorithm and Complete Analytical Solution for the Hulthén and Anharmonic Potentials

Abstract An algorithm for providing analytical solutions to Schrödinger’s equation with non-exactly solvable potentials is elaborated. It represents a symbiosis between the logarithmic expansion method and the techniques of the supersymmetric quantum mechanics as extended toward non shape invariant potentials. The complete solution to a given Hamiltonian H0 is obtained from the nodeless states of the Hamiltonian H0 and of a set of supersymmetric partners H1, H2, …, Hr. The nodeless states (dubbed “edge” states) are unique and in general can be ground or excited states. They are solved using the logarithmic expansion which yields an infinite system of coupled first order hierarchical differential equations, converted later into algebraic equations with recurrence relations which can be solved order by order. We formulate the aforementioned scheme, termed to as “Supersymmetric Expansion Algorithm” step by step and apply it to obtain for the first time the complete analytical solutions of the three dimensional Hulthén–, and the one-dimensional anharmonic oscillator potentials.

Potential oscillation enhanced lithium ion pump membrane for lithium ion extraction

In this work, a novel electrochemically switched ion permselective membrane (ESIPM) has been applied to the recovery of lithium from brine in the electrochemically switched ion permselective (ESIP) membrane separation system. This ESIPM was prepared by multi-layer assembly, with polyacrylonitrile ultrafiltration membrane (PAN) as the base membrane, and CNTs/CS membranes pressed and filtered on the base membrane as the current collector, crosslinking a lithium manganate/carbon black/polyvinyl alcohol/polyacrylic acid (LiMn2O4/C/PVA/PAA) composite material, which coated on a polyacrylonitrile ultrafiltration membrane/carbon nanotubes (PAN/CNTs) composite membrane as the electroactive lithium ion exchange layer. In the ESIP system, by alternately applying oscillation potentials between the ESIPM membrane and counter-electrodes to regulate the placement and release of the target ions on the membrane, Meanwhile the target ions are driven by the electric field to be enriched in the ESIPM and directionally transported through the ESIPM. As a result, it was found that compared with the electrodialysis (ED) system, the flux of Li+ in ESIPM in the ESIP system increased by 12 times and the selectivity factor for Li+/Mg2+ increased by 1.4 times for the brine with Mg2+/Li+=1. Besides, the selectivity factor for Li+/Mg2+ reaches 4.4 for the brine with Mg2+/Li+=20 in ESIPM in the ESIP system, which was 2.2 times higher than that of the commercial ion exchange membrane CIMS in the ED system.

Revisiting the dead time effects of Insight-HXMT/ME on timing analysis

ABSTRACT Dead time is a common instrumental effect of X-ray detectors, which would alter the behaviour of timing properties of astronomical signals, such as distorting the shape of power density spectra (PDS), affecting the root-mean-square of potential quasi-periodic oscillation signals, etc. We revisit the effects of the dead time of Medium Energy X-ray telescope (ME) onboard Insight-HXMT based on the simulation of electronic read-out mechanism that causes the dead time and the real data. We investigate dead time effects on the pulse profile as well as the quasi–periodic oscillation (QPO) signals. The dead time coefficient suggests a linear correlation with the observed count rate in each phase bin of the pulse profile according to the simulation of periodic signal as well as the real data observed on Swift J0243.6+6124. The Fourier-amplitude-difference (FAD) method could well recover the intrinsic shape of the observed PDS in the case that the PDS is from two identical detectors. We apply this technique on ME, by splitting the nine FPGA modules into two groups. The results indicate that the FAD technique suits the case when two groups of detectors are not largely different; and the recovered PDS of Sco X-1 observed by ME slightly enhances the significance of the previously known QPO signal, meanwhile the root-mean-square of QPO is significantly improved. We provide the FAD correction tool implemented in HXMTDAS for users in the future to better analyse QPO signals.

Attentional resource consumption of verbal-humor processing: An ERP study

As a high-demanding mental activity with both cognitive and emotional factors, verbal-humor processing consumes more attentional resources than non-humor processing, which has been demonstrated by behavioral studies, but little has been examined at a real-time scale. Based on the three-stage model (incongruity detection, incongruity resolution, and mirth), the current study used event-related potential (ERP) and event-related oscillation (ERO) to explore the attentional resource consumption of verbal-humor processing by employing a dual-task paradigm in which sentence comprehension (humorous, positive, neutral) was the primary task and arithmetical calculation (simple, difficult) was the secondary task.Participants’ (N=38) behavioral performance and ERP/ERO measures in two tasks were analyzed. ERP results of verbal-humor processing revealed significantly larger LAN, LLAN, and LPP activation, which indexed three stages. ERO results showed significant beta power changes in the detection stage and theta changes in the resolution and mirth stages. The behavioral data indicated that the Reaction Times (RTs) of the arithmetical task following verbal-humor processing were longer than those following non-humorous positive and neutral ones. The ERP results of arithmetical calculation found that the calculations following verbal-humor processing elicited significantly greater P2, P3b, and positive slow wave amplitudes than those following the other two processings, which reflected more resource allocation in the calculation to compensate for the resource preemption of verbal-humor processing. In addition, the calculation following positive sentence exhibited a greater ERP amplitude in the relatively early P2 time intervals than that following the neutral sentences. Collectively, the behavioral, ERP, and ERO results concurrently confirmed that verbal-humor processing consumed more attentional resources compared with non-humorous counterparts, and moreover, the comparison of ERP following humorous and positive sentences suggested that the processing of the cognitive factor consumes more attentional resources than the emotional factor although both factors play a role in the process.

Complete critical bound region of the generalized exponential cosine screened Coulomb potential

The complete critical bound region of the generalized exponential cosine screened Coulomb potential (ECSCP) V(r)=−r−1e−(βcos⁡θ)rcos⁡[(βsin⁡θ)r] is investigated by employing the generalized pseudospectral method. Highly accurate critical screening parameters are determined over the entire parameter space, spanning from the exponential screened Coulomb potential (θ = 0), via the oscillatory ECSCP ( θ=π/4 ), to the strongest oscillatory cosine Coulomb potential (CCP) ( θ=π/2 ). With an efficient extrapolation technique, the critical screening parameter for the CCP is estimated at about βc=2.34 . By analyzing the variation of the ground state energy in the critical bound region, we separate the parameter space into two regions, i.e. the exponential region at small and moderate values of θ where the exponential screening term dominates the critical behavior of system, and the cosine region for θ close to π/4 where the oscillatory cosine term dominates.

Simulation of Gaussian wave packets used to illustrate elementary quantum mechanics scenarios

In this paper we numerically solve the time dependent Schrödinger equation for scenarios using wave packets. These examples include the free wave packet, which we use to show the difference between group and phase velocities, the packet in a harmonic oscillator potential with non-trivial initial conditions in one and two dimensions, which is compared with their classical analogs to show how Ehrenfest theorem holds. We also include simulations of the diffraction through the single and double slit potentials, the refraction with a step potential and the dispersion by a central potential. The aim of this paper is to illustrate with simulations, nowadays easy to implement, scenarios that can help explaining the basics of the wave-particle duality.

Probing ultralight scalar, vector and tensor dark matter with pulsar timing arrays

Pulsar timing arrays (PTAs) are sensitive to oscillations in the gravitational potential along the line-of-sight due to ultralight particle pressure. We calculate the probing power of PTAs for ultralight bosons across all frequencies, from those larger than the inverse observation time to those smaller than the inverse distance to the pulsar. We show that since the signal amplitude grows comparably to the degradation in PTA sensitivity at frequencies smaller than inverse observation time, the discovery potential can be extended towards lower masses by over three decades, maintaining high precision. We demonstrate that, in the mass range 10−26−10−23 eV, existing 15-year PTA data can robustly detect or rule out an ultralight component down to O(1−10)% of the total dark matter. Non-detection, together with other bounds in different mass ranges, will imply that ultralight scalar/axion can comprise at most 1−10% of dark matter in the 10−30−10−17 eV range. With 30 years of observation, current PTAs can extend the reach down to 0.1−1%, while next-generation PTAs such as SKA can attain the 0.01−0.1% precision. We generalize and derive predictions for ultralight spin-1 vector (i.e. dark photon) and spin-2 tensor dark components.

S-cone contribution to oscillatory potentials in patients with blue cone monochromacy

PurposeThe aim of this exploratory study is to investigate the role of S-cones in oscillatory potentials (OPs) generation by individuals with blue-cone monochromacy (BCM), retaining S-cones, and achromatopsia (ACHM), lacking cone functions.MethodsThis retrospective study analyzed data from 39 ACHM patients, 20 BCM patients, and 26 controls. Central foveal thickness was obtained using spectral-domain optical coherence tomography, while amplitude and implicit time (IT) of a- and b-waves were extracted from the ISCEV Standard dark-adapted 3 cd.s.m−2 full-field ERG (ffERG). Time–frequency analysis of the same measurement enabled the extraction of OPs, providing insights into the dynamic characteristics of the recorded signal.ResultsBoth ACHM and BCM groups showed a significant reduction (p < .00001) of a- and b-wave amplitudes and ITs as well as the power of the OPs compared to the control groups. The comparison between ACHM and BCM didn’t show any statistically significant differences in the electrophysiological parameters. The analysis of covariance revealed significantly reduced central foveal thickness in the BCM group compared to ACHM and controls (p < .00001), and in ACHM compared to controls (p < .00001), after age correction and Tukey post-hoc analysis.ConclusionsS-cones do not significantly influence OPs, and the decline in OPs' power is not solely due to a reduced a-wave. This suggests a complex non-linear network influenced by photoreceptor inputs. Morphological changes don’t correlate directly with functional alterations, prompting further exploration of OPs’ function and physiological role.

Water structural effects on DNA–DNA interactions and homologous recognition

Comprehending the principles underlying the interaction between DNA molecules in electrolyte solution is of crucial importance for understanding the phenomena of DNA condensation, recognition of homologous genes, and properties of DNA liquid crystals. Although DNA was considered in all its helical complexity over the last two decades, only a primitive, local, electrostatic model of the aqueous solution was considered. The forces acting between DNA molecules however must be influenced by the structure of the liquid separating them. In this paper we make a step towards unravelling earlier neglected effects of water structure on DNA–DNA interactions. We develop a model of DNA interaction accounting for the nonlocal dielectric response of water and of the electrolyte plasma dissolved in it. We focus particularly on the study of the dipolar overscreening effect, which leads to decaying oscillations of the electrostatic potential about DNA, and how it will affect electrostatic energy surfaces as a function of interaxial separation and mutual azimuthal orientation of the parallelly aligned interacting DNAs. We found that going beyond the classical electrostatic description of water (the so-called primitive model) reveals a complex oscillatory interaction surface in space, with many possible metastable configurations. These however vanish rapidly with smearing of the DNA charge distribution, due to dephasing of the oscillatory components of the interaction. This dephasing results in the suppression of oscillation amplitudes and leads to the dominance of non-oscillatory components in spatial dipolar correlations and the Debye screening. These dominant correlation patterns are shown to lead to a substantial enhancement of the difference between the interaction of homologous and nonhomologous DNA sequences, deepening and sharpening the homology recognition well.

Realistic Shell Model Interpretation for the Nuclear Structure of Some 1f-2p Shell Nuclei

The charge density distributions (CDD), charge form factors, occupation numbers of states, and root mean square charge (rmsch) radii, have been calculated for several 1f-2p shell-model nuclei, such as 48Ti, 50Ti, 50Cr, 52Cr, 58Ni, and 60Ni nuclei using the wave functions for a single particle in a harmonic oscillator (HO) potential. The size parameter b of the HO potential is considered as a free parameter chosen to reproduce the rmsch radii. The nuclear real states occupation numbers have been assumed to differ from the simple shell model predictions. Introducing extra parameters such as and to characterize the disparity between the occupation numbers of real states and those anticipated by the simple shell model, leads to achieving a high level of agreement between the calculations and experimental data. Obtained results lead to the conclusion that the proposed parameters and , bring the calculated CDD and form factors closer to the experimental data along with all values of radius r and momentum transfer q, respectively.

Superfluid excitations in rotating two-dimensional ring traps

We studied a rotating Bose–Einstein condensate confined in ring trap configurations that can be produced starting with a bubble trap confinement, approximated by a Mexican hat and shift harmonic oscillator potentials. Using a variational technique and perturbation theory, we determined the vortex configurations in this system by varying the interparticle interaction and the angular velocity of the atomic cloud. We found that the phase diagram of the system has macrovortex structures for small positive values of the interaction parameter, and the charge of the central vortex increases with rotation. Strengthening the atomic interaction makes the macrovortex unstable, and it decays into multiple singly charged vortices that arrange themselves in a lattice configuration. We also look for experimentally realizable methods to determine the vortex configuration without relying upon absorption imaging since the structures are not always visible in the latter. More specifically, we study how the vortex distribution affects the collective modes of the condensate by solving the Gross–Pitaevskii equation numerically and by analytical predictions using the sum-rule approach for the frequencies of the modes. These results reveal important signatures to characterize the macrovortices and vortex lattice transitions in the experiments.

Effects of power on ion behaviors in radio-frequency magnetron sputtering of indium tin oxide (ITO)

This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide (ITO) target. The positive ion energies exhibit an upward trajectory with increasing RF power, attributed to heightened plasma potential and initial emergent energy. Simultaneously, the positive ion flux escalates owing to amplified sputtering rates and electron density. Conversely, negative ions exhibit broad ion energy distribution functions (IEDFs) characterized by multiple peaks. These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential, alongside ion transport time. This elucidation finds validation in a one-dimensional model encompassing the initial ion energy. At higher RF power, negative ions surpassing 100 eV escalate in both flux and energy, posing a potential risk of sputtering damages to ITO layers.

Anoctamin-like protein 1 regulates repolarization in Paramecium behavioral responses.

Paramecium exhibits responsive behavior to environmental changes, moving either closer to or further away from stimuli. Electrophysiological experiments have revealed that these behavioral responses are controlled by membrane potentials. Anoctamin, a Ca2+-activated Cl- channel, is involved in the regulation of membrane potential in mammals. However, it remains uncertain whether Cl- channels like anoctamin regulate Paramecium behavior. Herein, replacement of external Cl- ions with acetate ion and application of Cl- channel blocker niflumic acid (NFA, 0.1 μM) increased spontaneous avoiding reactions (sARs). Hence, we hypothesized that anoctamin is involved in the stabilization of membrane potential fluctuation. Paramecium cells in which the anoctamin-like protein 1 gene was knocked down displayed frequent sARs in the culture medium without external stimulation. Treatment of anoctamin-like protein 1-knockdown cells with the Ca2+ chelator BAPTA or Ca-channel blocker nicardipine reversed the increase in sARs. Electrophysiological experiments revealed extension of membrane depolarization when positive currents were applied to anoctamin-like protein 1-knockdown cells. We concluded that anoctamin-like protein 1 works as a Cl-channel and stabilizes the membrane potential oscillation, reducing sARs.