Potential Oscillations Research Articles

The Feynman propagator within three parameters generalized Dunkl derivative: One-dimensional case

In this paper, the Feynman path integral approach within three parameters Dunkl derivative is investigated in the one-dimensional case of nonrelativistic quantum mechanics. We successfully derive the propagator in Cartesian coordinates and give its exact expression for the free particle, inverse square, harmonic oscillator and pure Coulomb potentials. The energy eigenvalues and their corresponding wave functions are determined.

Comparisons of oscillatory potentials and 30 Hz flicker electroretinograms for discriminating eyes with diabetic retinopathy from normal eyes.

To compare the amplitudes and implicit times of the oscillatory (OPs) of the full-field electroretinograms (ERGs) to those of the 30 Hz flicker ERGs in differentiating eyes with diabetic retinopathy (DR) from normal eyes. Single-center observational study. Full-field ERGs were recorded in 55 patients with Type 2 diabetes mellitus (DM) and 20 normal control subjects. The amplitudes and implicit times of the OPs and of the 30 Hz flicker ERGs were measured. Optical coherence tomography angiography (OCTA) was used to record 3×3 mm enface images of the retina from which the vascular density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were obtained. The receiver operating characteristic (ROC) curves were used to determine the ability of each ERG parameter to discriminate diseased eyes from normal eyes. The significance of the correlations between each ERG parameter and the VD of the SCP and DCP was determined. The area under the ROC curves (AUCs) was significantly larger for the implicit times than for the amplitudes of each ERG component (P<0.005). There were no significant differences in the AUCs between the OPs and 30 Hz flicker ERGs in differentiating eyes with DM or DR from normal eyes. The implicit time of the 30 Hz flicker ERG had the highest significant correlation coefficient with the VD of the DCP (r = - 0.31, P <0.001). The OPs and 30 Hz flicker ERGs have equal ability in differentiating eyes with DR from normal eyes but with better ability for the implicit times than the amplitudes. The implicit time of the 30 Hz flicker ERG is the most sensitive parameter that is correlated with the reduction of VD among the full-field ERG components.

Hilbert transform analysis of the mouse scotopic electroretinogram reveals two distinct bursts of oscillatory potentials with progressively dimmer flashes.

Study the scotopic oscillatory potentials (OPs) in mice over a wide range of flash luminance levels using the Hilbert transform (HT) to extract new features of the high frequency components of the electroretinogram (ERG). Scotopic ERGs [Intensity: - 6.3 to 0.9 log cd∙s∙m-2; 12h of dark-adaptation] were obtained from adult mice (C57BL/6; n = 7). The Hilbert transform (HT) was obtained within 3 consecutive frequency bands (65-90Hz, 90-115Hz and 115-140Hz), with OPs being denoised, automatically identified and analyzed. Measurements included: number of OPs, duration of the OP response, surface-under-the-curve (SUC) of the HT envelopes, implicit times, and instantaneous frequency at the HT envelope peak, mean peak time differences (PTD) between the envelopes of each frequency band (measuring their synchrony), correlation coefficient and lag between consecutive HT envelopes, as well as the number of peaks on the HT envelopes. The OP response duration, number of OPs and PTD all peaked for flashesbetween the level corresponding to the RodVmax (maximal b-wave amplitude of the rod ERG; i.e., the first asymptote of the scotopic luminance-response curve) and K (the flash luminance at which the amplitude of the b-wave is half of that of the RodVmax;), i.e., between -3.9 and -2.4 log cd∙s∙m-2. The correlation between consecutive envelopes is close to 1 at flashes > -1.2 log cd∙s∙m-2, with small lags (min. = 1.93 ± 0.45ms at - 1.2 log cd∙s∙m-2), then gradually drops to 0.81 ± 0.02 at the dimmest flash intensity (with a max. lag = 14.76 ± 8.92ms at - 5.1 log cd∙s∙m-2). Finally, we found that the single OP burst (i.e., a single HT envelope peak) seen at flash intensities > - 1.2 log cd∙s∙m-2 progressively divided in two (or more) OP bursts (i.e., multiple HT envelope peaks) with gradually dimmer flashes. Our HT method enabled the analysis of the OP response without the subjective interpretation of the experimenter. Analysis of the scotopic OPs at dim flashes with the HT revealed a novel feature of the OP response not yet reported elsewhere, namely: a split of the OP response into two (or more) distinct bursts. Furthermore, the synchrony peak (measured with the PTD) matched the peak in OP response duration between K and RodVmax, suggesting a disorganization (or dephasing) of the retinal signal in ERGs evoked for weaker flashes. The increased synchronization and correlation of the single burst observed for the strongest flashes could suggest an optimization or saturation of the retinal response. We believe that these novel features of the OP components of the ERG went unnoticed given that previous studies did not use weak enough flashes and failed to recognize the added value that time and frequency domain analysis of the ERG (such as what is achieved with the HT) brings to the interpretation (and our understanding) of the retinal response.

A novel approach for spectroscopic study of Ωbbc baryon in the hypercentral constituent Quark model

In this paper, we determine the radial and orbital states mass spectra of the triply heavy baryon [Formula: see text] with total spin [Formula: see text] and 3/2 using the hypercentral constituent quark model (hCOM). The mass spectra are obtained by incorporating the color Coulomb plus linear confining term and the harmonic oscillator potential with first-order correction. Additionally, we considered spin–spin, spin-orbit and tensor interactions for hyperfine splitting calculation. Our computed mass spectra of the [Formula: see text] baryon is compared with existing literature. Further, we establish Regge trajectories of this baryon in ([Formula: see text]) and ([Formula: see text]) planes which are helpful in determining the unknown quantum number and [Formula: see text] values.

Background white noise increases neuronal activity by reducing membrane fluctuations and slow-wave oscillations in auditory cortex.

The brain faces the challenging task of preserving a consistent portrayal of the external world in the face of disruptive sensory inputs. What alterations occur in sensory representation amidst noise, and how does brain activity adapt to it? Although it has previously been shown that background white noise (WN) decreases responses to salient sounds, a mechanistic understanding of the brain processes responsible for such changes is lacking. We investigated the effect of background WN on neuronal spiking activity, membrane potential, and network oscillations in the mouse central auditory system. We found that, in addition to increasing background spiking activity in the auditory cortex and thalamus, background WN decreases neural activity fluctuations, as reflected in the membrane potential of single neurons and the local field potential. Blocking acetylcholine signaling in the auditory cortex eliminated the WN-dependent increase in background activity as well as the shift in slow-wave oscillations. Together, our observations show that background WN is not filtered away along the auditory pathway, but rather drives sustained changes in cortical activity that can be reverted by blocking cholinergic inputs.

On Oscillations in the External Electrical Potential of Sea Urchins.

Sea urchins display complex bioelectric activity patterns, even with their decentralized nervous system. Electrophysiological recordings showed distinct spiking patterns. The baseline potential was about 8.80 mV. It had transient spikes with amplitudes up to 21.05 mV. We observed many types of depolarization events. They included burst-like activity and prolonged state fluctuations lasting several seconds. Frequency domain analysis showed a power-law behavior. It had a scaling exponent of 6.21 ± 0.06, indicating critical dynamics. The analysis showed potential variations between 3.69 and 21.05 mV. The oscillation periods ranged from 4 to 3102 s. The varied timing of bioelectric signals suggests that these organisms can process information. This challenges traditional views of neural computation in simpler animals. These findings provide quantitative insights into the complex signaling mechanisms of the sea urchin's distributed nervous system.

Longitudinal assessment of retinal and visual pathway electrophysiology and structure after high altitude exposure.

High altitude (HA) exposure induces impairments in visual function. This study was designed to dynamically observe visual function after returning to lowland and elucidate the underlying mechanism by examining the structure and function of retina and visual pathway. Twenty-three subjects were recruited before (Test 1), and one week (Test 2) and three months (Test 3) after their return from HA (4300m) where they resided for 30 days. The clock task was used to assess visual cognition; and pattern-reversal visual evoked potential (p-VEP) and full-field electroretinogram (ff-ERG) were employed to record electrophysiological responses of retinal cells; optical coherence tomography (OCT), color doppler imaging (CDI) and magnetic resonance imaging(MRI) were used to measure structures of retina and visual pathway. In Test 2 vs. Test 1, there was increased reaction time during angle task; the amplitudes of scotopic 3.0cd·s/m2 and scotopic 10.0cd·s/m2 ERG a-wave and scotopic 3.0cd·s/m2 oscillatory potential in the right eye were significantly decreased, all of which were negatively correlated with the increased reaction time during the angle task. In Test 3 vs. Test 1, there were decreased amplitude of scotopic 10.0cd·s/m2 a-wave in the right eye and increased velocity of ophthalmic artery and ocular perfusion pressure in bilateral eyes. The VEP and visual pathway structures remained normal throughout the entire test. HA exposure caused damage to rod and cone responses in both outer and inner retina. After returning to sea level, the damaged visual cell functions gradually recovered over time, coinciding with an increase in the ocular perfusion.

Quantum pseudo-harmonic oscillator potential in non-Euclidean space: application to diatomic molecules

Abstract The present work analyzes a physical system with a quantum pseudo-harmonic oscillator in three-dimensional constant curvature spaces within the framework of non-relativistic theory. We present expressions for the energy equation and radial wavefunctions that depend on the curvature parameter k, using the functional analysis approach and the asymptotic iteration method. Additionally, we calculate the energy eigenvalues for diatomic molecules N2, H2, and ScH as a function of the constant curvature k. Using the Hellmann-Feynmann theorem, we derive expressions for the curvature-dependent expectation values of r-2 and p2, which we detail for the diatomic molecule system in this work. Furthermore, we perform a comparative analysis of the results for non-Euclidean space (spherical and hyperbolic spaces with constant curvature) and Euclidean space.

Common neocortical and hippocampal correlates of Performance errors in a timing task.

We aimed to identify the neuronal correlates of performance errors in a difficult timing task. Male rats were trained to seek rewards and avoid shocks depending on the position of photic conditioned stimuli (CS-R and CS-S, respectively). Then, they were exposed to conflict trials where they had to time the interval between the CS-R and CS-S to obtain rewards while avoiding footshocks. There were pronounced individual differences in behavioral strategies on conflict trials. When presented with a CS-S, some rats quickly left the shock sector, forsaking the option of earning a reward, and rarely got shocked. Others earned rewards by delaying avoidance based on the interval between the CS-R and CS-S but were shocked more often. The probability rats would fail a given trial was not stable across trials as rats engaged in incorrect trial runs that were longer than expected by chance. Since this finding suggested that rats shift between two quasi-stable processing modes, we next examined the neuronal correlates of errors. Incorrect trials coincided with reduced firing rates in CA1 and sensory cortical neurons. Moreover, trial-to-trial variations in the firing rates of simultaneously recorded neurons were more strongly correlated on error than correct trials. Last, the power of low frequency local field potential oscillations was higher during incorrect trials. The finding that the neuronal correlates of correct and error trials are similar in the hippocampus and neocortex lead us to hypothesize that they depend on changes in the activity of common afferents, such as neuromodulatory inputs.Significance statement We studied the neuronal correlates of performance errors in a task where rats had to time the interval between reward- and shock-predicting stimuli to obtain rewards while avoiding footshocks. Rats engaged incorrect trial runs that were longer than expected by chance, suggesting that they shift between two quasi-stable modes of processing. Error trials coincided with a drop in the firing rates of CA1 and sensory cortical neurons. Trial-to-trial variations in the firing rates of simultaneously recorded CA1 and cortical neurons were more strongly correlated on error than correct trials. The finding that the correlates of correct and error trials are similar in the hippocampus and neocortex suggest that they depend on common changes in neuromodulator levels.

Enhancing Micro-Droplet Mixing in Microfluidic Systems Via Electrowetting-Induced Parametric Oscillations

In the context of space exploration, electrowetting-on-dielectric (EWOD) microfluidic systems hold substantial promise for enhancing in-situ analysis and experimentation, particularly given its potential for precise control of fluid dynamics in the microgravity environment. This study investigates the effects of electrowetting-induced parametric oscillations on mixing efficiency within coalesced micro-droplets in EWOD microfluidic devices using numerical simulations. The mechanism by which parametric oscillation affects the mixing process of micro-droplets in EWOD devices is unraveled, which is previously uninverstigated in the literature to the best of our knowledge. The simulations reveal that parametric oscillations significantly increase vorticity magnitude and shear rate around the droplet interface, leading to improved mixing compared to free oscillation. Notably, the study identifies fluctuations in the mixing index associated with the oscillation-induced shape changes of the droplets. These findings underscore the potential of parametric oscillation as a strategy for optimizing mixing in EWOD systems, with implications for the design of more efficient microfluidic devices.

Texture analysis of optical coherence tomography retinal images: Its potential use for the early diagnosis of diabetic retinopathy

Aims/Purpose: Diabetic retinopathy (DR) is usually diagnosed many years after diabetes onset. The early diagnosis of DR remains challenging, and identifying novel biomarkers is crucial. We aim to identify novel early biomarkers for DR, based on texture analysis of optical coherence tomography (OCT) retinal images.Methods: A type 1 diabetes (T1D) rat (Wistar) model (streptozotocin‐induced) was used. Volume OCT scans (N = 40‐44) and electroretinograms (N = 25) were acquired before and after 1, 2 and 4 weeks of diabetes. Automated OCT image segmentation was performed, followed by retinal thickness and texture analysis. Changes in blood‐retinal barrier (tight junctions and permeability), glial reactivity and nitrosative stress were assessed.Results: Early T1D induced significant changes in retinal texture. Several texture metrics, autocorrelation, correlation, homogeneity, information measure of correlation II (IMCII), inverse difference moment normalized (IDMN), inverse difference normalized (IDN), and sum average, decreased in all retinal layers at week 4. Correlation, homogeneity, IMCII, IDMN, and IDN decreased at week 2. T1D induced a progressive weekly reduction in the texture metrics. T1D also induced significant thinning of the inner plexiform and inner nuclear layers, inner/outer photoreceptor segments, and total retina, at weeks 1, 2 and 4. Impaired retinal function was also observed (increased latencies in a‐wave and oscillatory potentials at weeks 1, 2 and 4), as well as decreased tight junction proteins immunoreactivity and increased microglial cell number and nitrosative stress, but vascular permeability was unchanged.Conclusions: Early T1D impacts retinal texture, concomitant with molecular, cellular and physiological retinal changes, thus unlocking the potential of texture analysis for DR early diagnosis, but this needs further proof in clinical studies.Support: FCT, Portugal: 2020.07432.BD, PEst UIDB/04539/Base/2020 and UIDP/04539/Programatico/2020, and PEst UIDB/04950/Base/2020 and UIDP/04950/Programatico/2020.

Kinetics and dynamics of atomic-layer dissolution on low-defect Ag.

Electrochemical metal dissolution reaction is a fundamental process in various critical technologies, including metal anode batteries and nanofabrication. However, experimentally revealing the kinetics and dynamics of active sites of metal dissolution reactions is challenging. Herein, we investigate metal dissolution on near-perfect single-crystal surfaces of Ag within regions of a few hundred nanometers isolated by scanning electrochemical cell microscopy (SECCM). Potential oscillation is observed under constant current conditions for dissolution. The one-to-one correspondence between the dissolution charge and the geometry of the dissolution pit from colocalized imaging allows ambiguous correlation, which suggests that each oscillation cycle corresponds to the dissolution of one atomic layer. The oscillation behavior is further explained in a kinetic model, which reveals that the oscillation comes from the dynamic evolution of the number of different active sites as the dissolution progresses on each atomic layer. In addition to the fundamental interest, the ability to observe layer-by-layer dissolution in electrochemical measurements suggests a potential pathway for developing electrochemical atomic layer etching for fabricating structures and devices with atomic precision.

Modelling pacemaker oscillations in lymphatic muscle cells: lengthened action potentials by two distinct system effects.

Lymphatic system failures contribute to cardiovascular and various other diseases. A critical function of the lymphatic vascular system is the active pumping of fluid from the interstitium back into the blood circulation by periodic contractions of lymphatic muscle cells (LMCs) in the vessel walls. As in cardiac pacemaking, these periodic contractions can be interpreted as occurring due to linked pacemaker oscillations in the LMC membrane potential (M-clock) and calcium concentration (C-clock). We previously reported a minimal model of synchronized dual-clock-driven oscillations. While this qualitatively replicated the period of oscillations under different conditions, it did not replicate the action potential shape as it varied under those conditions, particularly as regards the extent or lack of a systolic plateau. Here, we modify the model to replicate the plateau behaviour. Using phase-plane analysis we show two qualitatively different dynamical mechanisms that could account for plateau formation, one largely M-clock-driven, the other largely C-clock-driven. The second case occurs with the introduction of a ryanodine receptor; in both cases, we find improved predictions for calcium levels. With enhanced fidelity to the experimental data, the improved model has the potential to help determine opportunities for pharmacological treatment of lymphatic system pumping defects.

Analysis of broadband oscillation mechanisms in grid‐forming and grid‐following converters based on virtual synchronous generator

AbstractAiming at the problem of increased complexity in broadband oscillations caused by the introduction of virtual synchronous generator (VSG) control to grid‐forming and grid‐following grid‐connected converters interacting with inductive weak grids, positive and negative sequence impedance of such converters is established under small perturbations in phase angle and voltage using harmonic linearization. The impact of various control links on the broadband impedance characteristics associated with different control strategies is then analysed. It is observed that the grid‐forming converter equipped with VSG demonstrates lower impedance magnitude and inductive behaviour in the medium‐to‐high frequency range, thus emulating the external behaviour of a synchronous generator more accurately. Furthermore, the analysis based on the maximum peak Nyquist stability criterion reveals that voltage control and current‐type VSG lack phase margin, leading to potential oscillation risks within their respective dominant frequency bands. Finally, the validity of the broadband oscillation mechanism analysis is confirmed through hardware‐in‐loop experiments and impedance sweep analyses.

The effect of atomic vibration on thermal transport in diatomic semiconductors investigated via ab initio molecular dynamics.

Based on the ab initio molecular dynamics (AIMD), the temperature and velocity statistics of diatomic semiconductors were proposed to be classified by atomic species. The phase differences resulting from lattice vibrations of different atoms indicated the presence of anharmonicity at finite atomic temperatures. To further explore the electronic properties, the effect of temperature on electrostatic potential field vibrations in semiconductors was studied, and the concept of electrostatic potential oscillation (EPO) at finite atomic temperature was introduced. It was confirmed that EPO in semiconductors was driven by lattice vibrations at finite temperatures. As the temperature increased, both the intensity of EPO and the rate of EPO change in heavy and light atoms increased, influencing electron thermal transport. To characterize the uncertainties in atomic lattice vibrations and EPO, the entropies of atomic EPO, atomic velocity of EPO (VEPO), atomic temperature, and atomic velocity were defined, with results consistent with the principle of entropy increase. This study not only aids in understanding the fundamental physical picture of electronic properties in semiconductors at finite temperatures but also provides a method for describing their uncertainties. The new theoretical concepts and statistical methods presented here can advance the understanding of electron thermal transport issues in semiconductor devices.

Variation in (Hyper)Polarizability of H2 Molecule in Bond Dissociation Processes Under Spatial Confinement.

We report the results of calculations of the linear polarizability and second hyperpolarizability of the H2 molecule in the bond dissociation process. These calculations were performed for isolated molecules, as well as molecules under spatial confinement. The spatial confinement was modeled using the external two-dimensional (cylindrical) harmonic oscillator potential. In contrast to the recently investigated polar LiH molecule, it was shown that the spatial confinement significantly diminishes the linear and nonlinear response of H2 for each interatomic (H-H) distance.

IK Channel Confers Fine-tuning of Rod Bipolar Cell Excitation and Synaptic Transmission in the Retina

Abstract During retinal visual processing, rod bipolar cells (RBC) transfer scotopic signals from rods to AII amacrine cells as second-order neurons. Elucidation of the RBC's excitation/inhibition is essential for understanding the visual signal transmission. Excitation mechanisms via mGluR6 and voltage-gated Ca2+ channels in the RBCs and GABAergic inhibitory synaptic inputs have been studied in previous studies. However, its intrinsic inhibitory mechanisms like K+ and Cl− channels remain unclear. We focused on RBC's prominent K+ current, which exhibits voltage and Ca2+ dependence. We isolated and confirmed the expression of intermediate-conductance Ca2+-activated K+ channels (IK) in RBCs using the patch-clamp method with IK inhibitors (clotrimazole and TRAM34) and immunohistochemistry. The regulation of the IK channel primarily relies on Ca2+ influx via low-threshold Ca2+ channels during RBC's excitation. Additionally, IK mediates late repolarization and suppresses excessive oscillation of the membrane potential in the RBCs, enabling fast and transient synaptic transmission to AII amacrine cells. Our findings highlight the unique role of the IK channel in RBCs, suggesting that it plays a critical role in the scotopic pathway by fine-tuning RBC activity.

An Agent-Based Model of Metabolic Signaling Oscillations in Bacillus subtilis Biofilms.

Microbes of nearly every species can form biofilms, communities of cells bound together by a self-produced matrix. It is not understood how variation at the cellular level impacts putatively beneficial, colony-level behaviors, such as cell-to-cell signaling. Here we investigate this problem with an agent-based computational model of metabolically driven electrochemical signaling in Bacillus subtilis biofilms. In this process, glutamate-starved interior cells release potassium, triggering a depolarizing wave that spreads to exterior cells and limits their glutamate uptake. More nutrients diffuse to the interior, temporarily reducing glutamate stress and leading to oscillations. In our model, each cell has a membrane potential coupled to metabolism. As a simulated biofilm grows, collective membrane potential oscillations arise spontaneously as cells deplete nutrients and trigger potassium release, reproducing experimental observations. We further validate our model by comparing spatial signaling patterns and cellular signaling rates with those observed experimentally. By oscillating external glutamate and potassium, we find that biofilms synchronize to external potassium more strongly than to glutamate, providing a potential mechanism for previously observed biofilm synchronization. By tracking cellular glutamate concentrations, we find that oscillations evenly distribute nutrients in space: non-oscillating biofilms have an external layer of well-fed cells surrounding a starved core, whereas oscillating biofilms exhibit a relatively uniform distribution of glutamate. Our work shows the potential of agent-based models to connect cellular properties to collective phenomena and facilitates studies of how inheritance of cellular traits can affect the evolution of group behaviors.

Morphological and functional observations of a novel model of retinal ischemia injury induced by bilateral carotid artery stenosis in mice.

To investigate the features of retinal ischemic injuries in a novel mouse model with bilateral carotid artery stenosis (BCAS). BCAS was induced with microcoil implantation in 6-8-week-old C57BL6 mice. Cerebral blood flow was monitored at 2, 7, and 28d postoperatively. Retinal morphological changes were evaluated by fundus photography and hematoxylin-eosin staining. Fluorescein fundus angiography (FFA) was performed to detect retinal vascular changes and circulation. The levels of apoptosis, activation of neurogliosis, and expression of hypoxia-inducible factor (HIF)-1α in the retina were assessed by Western blotting and immunofluorescence staining, followed by retinal ganglion cell (RGC) density detection. Additionally, electrophysiological examinations including photopic negative response (PhNR) was also performed. The mice demonstrated an initial rapid decrease in cerebral blood flow, followed by a 4-week recovery period after BCAS. The ratio of retinal artery and vein was decreased under fundus photography and FFA. Compared with the sham mice, BCAS mice showed thinner retinal thickness on day 28. Additionally, apoptosis was increased and RGC density was decreased mainly in peripheral retinal region. Neurogliosis was mainly located in the inner retinal layers, with a stable increase in HIF-1α expression. The dark-adapted electroretinogram showed a notable reduction in the a-, b-, and oscillatory potential (OP) wave amplitudes between days 2 and 7; this gradually recovered over the following 4wk. However, the b- and OP-wave amplitudes were still significantly decreased on PhNR examination on day 28. BCAS can result in relatively mild retinal ischemia injuries in mice, mainly in the inner layer and peripheral region. Our study provides a novel animal model for investigating retinal ischemic diseases.

Shape phase transition in the Xe and Ba isotope chains with the sextic oscillator potential

Shape phase transition in the Xe and Ba isotope chains with the sextic oscillator potential