Presence Of Oscillations Research Articles

Precision evaluation of theGa71(νe,e−)solar neutrino capture rate from the(He3,t)charge-exchange reaction

A high-resolution measurement of the ${}^{71}$Ga(${}^{3}$He,$t$)${}^{71}$Ge charge-exchange reaction extracts the Gamow-Teller strength distribution in ${}^{71}$Ge and allows a precision evaluation of the expected solar-neutrino capture rate, assuming a non-oscillation scenario. The new measurements can be used as a benchmark for comparing to neutrino capture rates in the presence of oscillations. With the new results, the dominant statistical uncertainty of the ${}^{71}$Ga capture rate lies now in the solar fluxes from the CNO cycle.

Multiple oscillations detection in control loops by using the DFT and Raleigh distribution

This work introduces an oscillation detection method by analyzing the magnitude of signal after the discrete Fourier transform (DFT). Properties of Raleigh distribution are used to calculate a threshold in order to detect multiple oscillations simultaneously. The proposed algorithm is able to detect oscillations in presence of colored noise based on a statistical test. Two simulation examples are provided to verify the effectiveness of the method.

Differentiation filter‐based technique for robust estimation of single‐phase grid voltage frequency under distorted conditions

This study proposes a robust estimation technique for the single-phase grid voltage fundamental frequency under grid disturbances. The technique relies on a demodulation method and a finite-impulse-response-based differentiation filter (DF). A frequency domain analysis for designing the DF is presented and is used to estimate the time-varying fundamental frequency from the instantaneous phase angle obtained by the demodulation method. The technique can reject the negative effects caused by the presence of DC offset and harmonics. The proposed DF shows less sensitivity to the presence of oscillations caused by the demodulation method when compared to a similar finite-impulse-response-based DF. Simulation and experimental results are provided to verify the performance of the proposed technique.

How delays matter in an oscillatory whole-brain spiking-neuron network model for MEG alpha-rhythms at rest

In recent years the study of the intrinsic brain dynamics in a relaxed awake state in the absence of any specific task has gained increasing attention, as spontaneous neural activity has been found to be highly structured at a large scale. This so called resting-state activity has been found to be comprised by nonrandom spatiotemporal patterns and fluctuations, and several Resting-State Networks (RSN) have been found in BOLD-fMRI as well as in MEG signal power envelope correlations. The underlying anatomical connectivity structure between areas of the brain has been identified as being a key to the observed functional network connectivity, but the mechanisms behind this are still underdetermined. Theoretical large-scale brain models for fMRI data have corroborated the importance of the connectome in shaping network dynamics, while the importance of delays and noise differ between studies and depend on the models' specific dynamics. In the current study, we present a spiking neuron network model that is able to produce noisy, distributed alpha-oscillations, matching the power peak in the spectrum of group resting-state MEG recordings. We studied how well the model captured the inter-node correlation structure of the alpha-band power envelopes for different delays between brain areas, and found that the model performs best for propagation delays inside the physiological range (5–10m/s). Delays also shift the transition from noisy to bursting oscillations to higher global coupling values in the model. Thus, in contrast to the asynchronous fMRI state, delays are important to consider in the presence of oscillation.

Magnetoresistance in domain walls of magnetic nanowires: Possible role of the Rabi oscillations in presence of decoherence

Magnetoresistance in domain walls of magnetic nanowires: Possible role of the Rabi oscillations in presence of decoherence

Posterior singular spectrum analysis

A method is proposed for finding interesting underlying features of a time series, such as trends, maxima, minima, and oscillations. A combination of singular spectrum analysis SSA and Bayesian modeling is used where the credibility of SSA signal components is analyzed via posterior simulation. The potential of the technique is demonstrated using artificial and real data examples. Our analysis of a Bayesian reconstruction of post-Ice Age temperature variation lends support for the presence of oscillations detected in previous studies of the paleoclimate. © 2013 Wiley Periodicals, Inc. Statistical Analysis and Data Mining, 2013

Features of the kinetics of the immersion clarification of biological tissue

A model is proposed that adequately describes how the optical characteristics of biological samples behave when they undergo immersion clarification. It is shown that the presence of oscillations in the kinetics of the immersion clarification of the sample is associated with the fibrillar structure of the tissue. The influence of the geometrical parameters of a sample of biological tissue on the kinetics of the process of immersion clarification of this sample is investigated.

Simulation study of the polymer translocation free energy barrier

Monte Carlo simulations are used investigate the properties of the free energy barrier associated with polymer translocation through a nanopore. We employ a multiple-histogram method to calculate the variation of the free energy with Q, a coordinate used to quantify the degree of translocation. The system is modeled as a flexible hard-sphere chain that translocates through a cylindrical hole in a hard flat wall. Some calculations were carried out for nanopores connected to a spherical cavity at one or both ends. Attractive monomer-nanopore interactions and a linear driving force through the nanopore were also included in some calculations. The properties of the free energy functions for short polymers were studied upon variation in all of the key system parameters, including polymer length, the nanopore dimensions, the strengths of the attractive, and driving force interactions. The results were analyzed using a simple theoretical model, whose only free parameter is the confinement free energy per link for monomers inside the nanopore. Generally, the results are in excellent quantitative agreement with the model. One notable feature of the free energy functions is the presence of oscillations whose amplitude increases with decreasing pore radius. These oscillations are due to the nature of the variation with Q of the orientational entropy of bonds at the two edges of the pore. A simple model was constructed to account for dependence of the oscillation amplitude and period on the system parameters. We propose that the theoretical models developed here can be used to make quantitatively accurate predictions of translocation free energy functions for very long polymers using simulation data acquired for short polymers.

Oscillations in MAPK cascade triggered by two distinct designs of coupled positive and negative feedback loops

BackgroundFeedback loops, both positive and negative are embedded in the Mitogen Activated Protein Kinase (MAPK) cascade. In the three layer MAPK cascade, both feedback loops originate from the terminal layer and their sites of action are either of the two upstream layers. Recent studies have shown that the cascade uses coupled positive and negative feedback loops in generating oscillations. Two plausible designs of coupled positive and negative feedback loops can be elucidated from the literature; in one design the positive feedback precedes the negative feedback in the direction of signal flow and vice-versa in another. But it remains unexplored how the two designs contribute towards triggering oscillations in MAPK cascade. Thus it is also not known how amplitude, frequency, robustness or nature (analogous/digital) of the oscillations would be shaped by these two designs.ResultsWe built two models of MAPK cascade that exhibited oscillations as function of two underlying designs of coupled positive and negative feedback loops. Frequency, amplitude and nature (digital/analogous) of oscillations were found to be differentially determined by each design. It was observed that the positive feedback emerging from an oscillating MAPK cascade and functional in an external signal processing module can trigger oscillations in the target module, provided that the target module satisfy certain parametric requirements. The augmentation of the two models was done to incorporate the nuclear-cytoplasmic shuttling of cascade components followed by induction of a nuclear phosphatase. It revealed that the fate of oscillations in the MAPK cascade is governed by the feedback designs. Oscillations were unaffected due to nuclear compartmentalization owing to one design but were completely abolished in the other case.ConclusionThe MAPK cascade can utilize two distinct designs of coupled positive and negative feedback loops to trigger oscillations. The amplitude, frequency and robustness of the oscillations in presence or absence of nuclear compartmentalization were differentially determined by two designs of coupled positive and negative feedback loops. A positive feedback from an oscillating MAPK cascade was shown to induce oscillations in an external signal processing module, uncovering a novel regulatory aspect of MAPK signal processing.

WMAP7 constraints on oscillations in the primordial power spectrum

We use the WMAP 7 data to place constraints on oscillations supplementing an almost scale-invariant primordial power spectrum. Such oscillations are predicted by a variety of models, some of which amount to assuming there is some non-trivial choice of the vacuum state at the onset of inflation. In this paper we will explore data-driven constraints on two distinct models of initial state modifications. In both models the frequency, phase and amplitude are degrees of freedom of the theory for which the theoretical bounds are rather weak: both the amplitude and frequency have allowed values ranging over several orders of magnitude. This requires many computationally expensive evaluations of the model CMB spectra and their goodness-of-fit, even in a Markov Chain Monte Carlo (MCMC), normally the most efficient fitting method for such a problem. To search more efficiently we first run a densely spaced grid, with only 3 varying parameters; the frequency, the amplitude and the baryon density. We obtain the optimal frequency and run an MCMC at the best fit frequency, randomly varying all other relevant parameters. To reduce the computational time of each power spectrum computation, we adjust both comoving momentum integration and spline interpolation (in l) as a function of frequency and amplitude of the primordial power spectrum. Applying this to the WMAP 7 data allows us to improve existing constraints on the presence of oscillations. We confirm earlier findings that certain frequencies can improve the fitting over a model without oscillations. For those frequencies we compute the posterior probability, allowing us to put some constraints on the primordial parameter space of both models.

Stability and decay of Bloch oscillations in the presence of time-dependent nonlinearity

We consider Bloch oscillations of Bose-Einstein condensates in presence of a time-modulated s-wave scattering length. Generically, interaction leads to dephasing and decay of the wave packet. Based on a cyclic-time argument, we find---additionally to the linear Bloch oscillation and a rigid soliton solution---an infinite family of modulations that lead to a periodic time evolution of the wave packet. In order to quantitatively describe the dynamics of Bloch oscillations in presence of time-modulated interactions, we employ two complementary methods: collective-coordinates and the linear stability analysis of an extended wave packet. We provide instructive examples and address the question of robustness against external perturbations.

Fast Geometric T2-Fuzzy Based Improved Lower Extremities Stimulation Response

This study emphasizes the use of type-2 fuzzy (T2-Fuzzy) to improve the adaptive proportional-integrative-derivative (PID) control in the lower extremities. Several problems were identified from previous studies and those were the slow achievement of the target angle and the presence of oscillation in the achievement of the target blade. The oscillation occurred as the consequence of deploying the early adaptive PID which was not sufficient to overcome the lower extremities nonlinearity. The difference between proposed method of T2-Fuzzy and the others lies in the defuzzification. This research adopts a fast geometric defuzzification that maintains the level of uncertainty T2-Fuzzy in real-time. A functional electrical stimulation (FES) stimulator is proposed to design and to be connected to the computer for processing the T2-Fuzzy. This stimulator stimulates lower extremities of normal subjects each cycle, and the computer record the point of measured achievement of using a goniometer sensors mounted on a knee joint. The results show that the target point of lower extremities is achieved within three initial cycles without oscillations in the achievement of the angle. It is also found that T2-Fuzzy is able to immediately restore the point of achievement when the external parameters of control occur.

Asymptotic analysis of small-angle scattering intensities of plane columnar layers

The asymptotic behaviour, at large scattering vectorq, of the small-angle scattering intensities of isotropic plane samples is similar to that of three-dimensional samples. In fact, its expression, limited to the first two leading terms, isc1γ(1)(0)/q3 + c3γ(3)(0)/q5, wherec1andc3are appropriate numerical constants, and γ(1)(0) and γ(3)(0) the values, at the origin, of the first and third derivatives, respectively, of the two-dimensional correlation function. These values are proportional to the specific length and to the mean square reciprocal curvature radius of the interface curve. The angularity of the latter can also be determined, while the presence of oscillations in the appropriate Porod plot is related to a parallelism condition obeyed by the interface curve. These results are useful for analysing the small-angle scattering intensities collected under grazing incidence and diffused by film samples that are a collection of homogeneous cylinders of arbitrary right sections.

Oscillations in the primordial bispectrum: Mode expansion

We consider the presence of oscillations in the primordial bispectrum, inspired by three different cosmological models; features in the primordial potential, resonant type non-Gaussianities and deviation from the standard Bunch Davies vacuum. In order to put constraints on their bispectra, a logical first step is to put these into factorized form which can be achieved via the recently proposed method of polynomial basis expansion on the tetrahedral domain. We investigate the viability of such an expansion for the oscillatory bispectra and find that one needs an increasing number of orthonormal mode functions to achieve significant correlation between the expansion and the original spectrum as a function of their frequency. To reduce the number of modes required, we propose a basis consisting of Fourier functions orthonormalized on the tetrahedral domain. We show that the use of Fourier mode functions instead of polynomial mode functions can lead to the necessary factorizability with the use of only 1/5 of the total number of modes required to reconstruct the bispectra with polynomial mode functions. Moreover, from an observational perspective, the expansion has unique signatures depending on the orientation of the oscillation due to a resonance effect between the mode functions and the original spectrum. This effect opens the possibility to extract informa- tion about both the frequency of the bispectrum as well as its shape while considering only a limited number of modes. The resonance effect is independent of the phase of the reconstructed bispectrum suggesting Fourier mode extraction could be an efficient way to detect oscillatory bispectra in the data.

Interactions of Airflow Oscillation, Tracheal Inclination, and Mucus Elasticity Significantly Improve Simulated Cough Clearance

Viscoelastic properties of simulated mucus, angle of tracheal inclination (theta), and high-frequency airflow oscillations on median displacement of simulated mucus during simulated cough were investigated in this study. Mucus simulants with viscoelastic properties similar to healthy individuals and patients with COPD were prepared using locust bean gum (LBG)-water solution (0.38 g LBG in 100 mL water) cross-linked with 3-mL and 12-mL borax-water solution (0.02 M), respectively. Aliquots of 0.3 mL of simulants were placed on a dry Plexiglas insert inside a D-shaped clear Plexiglas tracheal model. Movement of aliquots of mucus simulants was measured during cough of 0.3 s duration. Cough velocities studied (5-30 m/s) are typical of patients with weak expiratory muscles and airway obstruction. Studies were conducted with tracheal model placed horizontally (0 degrees) and at increasing theta (15 degrees, 30 degrees, and 45 degrees), with and without superimposed airflow oscillations during coughs. Effects of different parameters and their interactions on displacements of aliquots were compared using analysis of covariance (n = 849). Significant positive nonlinear associations existed between displacement and cough velocity for both 3-mL and 12-mL simulants (P < .0001). Displacement was greatest for the cohesive 12-mL simulant at all cough velocities. Displacement increased significantly (P < .0001) as theta was increased for both types of simulants. Largest displacements at low cough velocities occurred with 12-mL simulant in the presence of oscillations at 45 degrees angle. Results support the use of airflow oscillations and sitting upright to facilitate mucus displacement during cough, particularly with thick, elastic mucus found in patients with COPD (P < .0001).

The Role of Ongoing Dendritic Oscillations in Single-Neuron Dynamics

The dendritic tree contributes significantly to the elementary computations a neuron performs while converting its synaptic inputs into action potential output. Traditionally, these computations have been characterized as both temporally and spatially localized. Under this localist account, neurons compute near-instantaneous mappings from their current input to their current output, brought about by somatic summation of dendritic contributions that are generated in functionally segregated compartments. However, recent evidence about the presence of oscillations in dendrites suggests a qualitatively different mode of operation: the instantaneous phase of such oscillations can depend on a long history of inputs, and under appropriate conditions, even dendritic oscillators that are remote may interact through synchronization. Here, we develop a mathematical framework to analyze the interactions of local dendritic oscillations and the way these interactions influence single cell computations. Combining weakly coupled oscillator methods with cable theoretic arguments, we derive phase-locking states for multiple oscillating dendritic compartments. We characterize how the phase-locking properties depend on key parameters of the oscillating dendrite: the electrotonic properties of the (active) dendritic segment, and the intrinsic properties of the dendritic oscillators. As a direct consequence, we show how input to the dendrites can modulate phase-locking behavior and hence global dendritic coherence. In turn, dendritic coherence is able to gate the integration and propagation of synaptic signals to the soma, ultimately leading to an effective control of somatic spike generation. Our results suggest that dendritic oscillations enable the dendritic tree to operate on more global temporal and spatial scales than previously thought; notably that local dendritic activity may be a mechanism for generating on-going whole-cell voltage oscillations.

Nonlinear analysis of nuclear coupled density wave instability in time domain for a boiling water reactor core undergoing core-wide and regional modes of oscillations

The objective of the paper is to develop a nuclear coupled thermal-hydraulic model in order to simulate core-wide (in-phase) and regional (out-of-phase) stability analysis in time domain within the limitation of desktop research facility for a boiling water reactor subjected to operational transients. The integrated numerical tool, which is a combination of thermal-hydraulic, neutronic and fuel heat conduction models, is used to analyze a complete boiling water reactor core taking into account the strong nonlinear coupling between the core neutron dynamics and primary circuit thermal-hydraulics via the void-temperature reactivity feedback effects. The integrated model is validated against standard benchmark and published results. Finally, the model is used for various parametric studies and a number of numerical simulations are carried out to investigate core-wide and regional instabilities of the boiling water reactor core with and without the neutronic feedback effects. Results show that the inclusion of neutronic feedback effects has an adverse effect on boiling water reactor core by augmenting the instability at lower power for same inlet subcooling during core-wide mode of oscillations, whereas the instability is being suppressed during regional mode of oscillations in presence of the neutronic feedback. Dominance of core-wide instability over regional mode of oscillations is established for the present case of simulations which indicates that the preclusion of the former will automatically prevent the latter at the existing working condition.

The role of ongoing dendritic oscillations in single-neuron dynamics

AbstractThe dendritic tree contributes significantly to the elementary computations a neuron performs while converting its synaptic inputs into action potential output. Traditionally, these computations have been characterized as temporally local, near-instantaneous mappings from the current input of the cell to its current output, brought about by somatic summation of dendritic contributions that are generated in spatially localized functional compartments. However, recent evidence about the presence of oscillations in dendrites suggests a qualitatively different mode of operation: the instantaneous phase of such oscillations can depend on a long history of inputs, and under appropriate conditions, even dendritic oscillators that are remote may interact through synchronization. Here, we develop a mathematical framework to analyze the interactions of local dendritic oscillations, and the way these interactions influence single cell computations. Combining weakly coupled oscillator methods with cable theoretic arguments, we derive phase-locking states for multiple oscillating dendritic compartments. We characterize how the phase-locking properties depend on key parameters of the oscillating dendrite: the electrotonic properties of the (active) dendritic segment, and the intrinsic properties of the dendritic oscillators. As a direct consequence, we show how input to the dendrites can modulate phase-locking behavior and hence global dendritic coherence. In turn, dendritic coherence is able to gate the integration and propagation of synaptic signals to the soma, ultimately leading to an effective control of somatic spike generation. Our results suggest that dendritic oscillations enable the dendritic tree to operate on more global temporal and spatial scales than previously thought.

Crystallographic plane dependent Fe and Si dopant incorporation and activation in InP

AbstractVarious crystallographic planes are exposed when growing along mesa sidewalls during metalorganic vapor phase epitaxy. Dopant incorporation and activation on these higher index surfaces can be quite different from that observed on (001) surfaces. Incorporation and activation of Si and Fe in MOVPE grown InP on (001), (110), and (311)A and B surfaces are reported. The Si donor concentration is higher on the P‐terminated B surface than the A surface while the opposite behavior is observed for Fe incorporation. In the fabrication of optoelectronic devices, it must be remembered that it is the carrier concentration, that is, activated atomic species, that is relevant for device performance and not the incorporation of atomic species alone. Activation of Si is &gt;1 on all surfaces; however, Fe is shown to be an effective compensating species only on the (001) and (311)A crystallographic surfaces. Data for the presence of oscillations in the iron concentration on (001) surfaces are also reported. The active Fe concentration is shown to be related to the Fe atomic concentration relative to the donor density on the different crystallographic surfaces, suggesting that Fermi level position sets a limit to the fraction of Fe centers which are electrically active as a deep trap. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

FOUR-FLUID MODEL AND NUMERICAL SIMULATIONS OF MAGNETIC STRUCTURES IN THE HELIOSHEATH

The first part of this paper extends the three-fluid model of Avinash & Zank for magnetic structures in the heliosheath to a four-fluid model consisting of electrons, pick-up ions (PUIs), solar wind ions (SWIs), and neutral hydrogen. The PUIs are generated by neutrals via charge exchange with SWI. Since the kinetic pressure of PUI is nearly three to four times the pressure of SWI, these are more suited to mediate small-scale structures in the heliosheath such as magnetic holes (MH)/humps etc. The constant energy exchange between these two fluids drives them nonadiabatic. The PUIs are isothermal (γ = 1) while SWIs are nonadiabatic with an index γ ≈ 1.25. The four-fluid model captures these effects via a modified equation of state for PUI and SWI. The phase space of time-independent solutions in terms of the Mach numbers of PUI and SWI is constructed to delineate the parameter space which allows structure formation in the heliosheath. The second part of the paper examines the stability of the time-independent solutions computed in the first part by evolving them via a full system of Hall-MHD equations. The simulation results show that these solutions are not quite stable. As the structure propagates it develops growing oscillations in the wings. Concomitantly, there are changes in the amplitude and width of the structure. This instability could be due to local changes in the velocity of the structure and reflects an exchange between the kinetic and magnetic parts of the total energy. Our results about the presence of growing oscillations in the wings of solitary wave solutions are consistent with the recent analysis of MHs in the heliosheth by Burlaga et al. Their analysis also shows evidence for the presence of oscillations and instabilities in the wings of MHs in the heliosheath.