Neural computational modeling reveals a major role of corticospinal gating of central oscillations in the generation of essential tremor

Essential tremor, also referred to as familial tremor, is an autosomal dominant genetic disease and the most common movement disorder. It typically involves a postural and motor tremor of the hands, head or other part of the body. Essential tremor is driven by a central oscillation signal in the brain. However, the corticospinal mechanisms involved in the generation of essential tremor are unclear. Therefore, in this study, we used a neural computational model that includes both monosynaptic and multisynaptic corticospinal pathways interacting with a propriospinal neuronal network. A virtual arm model is driven by the central oscillation signal to simulate tremor activity behavior. Cortical descending commands are classified as alpha or gamma through monosynaptic or multisynaptic corticospinal pathways, which converge respectively on alpha or gamma motoneurons in the spinal cord. Several scenarios are evaluated based on the central oscillation signal passing down to the spinal motoneurons via each descending pathway. The simulated behaviors are compared with clinical essential tremor characteristics to identify the corticospinal pathways responsible for transmitting the central oscillation signal. A propriospinal neuron with strong cortical inhibition performs a gating function in the generation of essential tremor. Our results indicate that the propriospinal neuronal network is essential for relaying the central oscillation signal and the production of essential tremor.

Generating mechanism of pathological beta oscillations in STN-GPe circuit model: A bifurcation study

Parkinson’s disease(PD)is characterized by pathological spontaneous beta oscillations(13 Hz-35 Hz)often observed in basal ganglia(BG)composed of subthalamic nucleus(STN)and globus pallidus(GPe)populations.From the viewpoint of dynamics,the spontaneous oscillations are related to limit cycle oscillations in a nonlinear system;here we employ the bifurcation analysis method to elucidate the generating mechanism of the pathological spontaneous beta oscillations underlined by coupling strengths and intrinsic properties of the STN-GPe circuit model.The results reveal that the increase of inter-coupling strength between STN and GPe populations induces the beta oscillations to be generated spontaneously,and causes the oscillation frequency to decrease.However,the increase of intra-coupling(self-feedback)strength of GPe can prevent the model from generating the oscillations,and dramatically increase the oscillation frequency.We further provide a theoretical explanation for the role played by the inter-coupling strength of GPe population in the generation and regulation of the oscillations.Furthermore,our study reveals that the intra-coupling strength of the GPe population provides a switching mechanism on the generation of the abnormal beta oscillations:for small value of the intra-coupling strength,STN population plays a dominant role in inducing the beta oscillations;while for its large value,the GPe population mainly determines the generation of this oscillation.

Centennial Oscillations in an Ocean-ice Coupled Model

Irregular centennial oscillations, with a spectral peak at 106 years, were obtained from an ocean-ice coupled model for the North Atlantic with realistic coastline and bottom topography. The model's thermohaline circulation is forced by mixed boundary conditions, i.e., a Haney-type relaxation condition for temperature, but an equivalent virtual salt flux condition for salinity. All forcing fields are taken from the observed monthly mean climatological wind stress and buoyancy fluxes. The oscillations appeared in the form of a surface—intensified tripole in both the sea surface temperature and salinity fields located in the vicinity of the Labrador Sea. The oscillations involve a delicate interplay between heat and fresh water advection by meridional overturning circulation, horizontal gyres, vertical convection, and the seasonal cycle. The oscillations are primarily controlled by the salinity component of the circulation; however, sea ice plays a minor role in driving the oscillations observed in the model. On the other hand, a regular seasonal cycle in the forcing fields is an important ingredient for the centennial oscillations.

Mathematical Modeling of Peat Self-ignition at Ambient Temperature Oscillations

In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the oscillation periods, commensurate with the adiabatic induction period of thermal explosion, implement a kind of resonance which corresponding with average ambient temperature. At both high and very low frequencies oscillations at ambient temperature, their influence on the critical condition and on the induction period of thermal explosion is negligible. However, at low-frequencies influence of ambient temperature oscillations, even a relatively low amplitude, on critical condition and especially on induction period of thermal explosion, can be very strong.

A Multi-Model Approach to Design a Robust SVC Damping Controller Using Convex Optimization Technique to Enhance the Damping of Inter-Area Oscillations Considering Time Delay

This paper introduces a multi-model approach to design a robust supplementary damping controller. The designed fixed-order supplementary damping controller adjusts the voltage reference set point of SVC. There are two main objectives of the controller design, damping low frequencies oscillations and enhancing power system stability. This method relies on shaping the closed-loop sensitivity functions in the Nyquist plot under the constraints of these functions. These constraints can be linearized by choosing a desired open-loop transfer function. The robust controller is designed to minimize the error between the open-loop of the original plant model and the desired transfer functions. These outcomes can be achieved by using convex optimization methods. Convexity of the problem formulation ensures global optimality. One of the advantages of the proposed approach is that the approach accounts for multi-model uncertainty. In contrast to the methods available in the literature, the proposed approach deals with full-order model (i.e., model reduction is not required) with lower controller order. The issue of time delay of feedback signals has been addressed in this paper for different values of time delay by applying a multi-model optimization technique. The proposed approach is compared to other existing techniques to design a robust controller which is based on H2 under pole placement. Both techniques are applied to the 68-bus system to evaluate and validate the robust controller performance under different load scenarios and different wind generations.

Asymptotic solution for a class of sea-air oscillator model for El Nio-southern oscillation

The El Nifio-Southern Oscillation （ENSO） is an interannual phenomenon involved in the tropical Pacific Oceanatmosphere interactions. In this paper, an asymptotic method of solving the nonlinear equation for the ENSO model is used. And based on a class of oscillator of ENSO model, the approximate solution of a corresponding problem is studied by employing the perturbation method. Firstly, an ENSO model of nonlinear time delay equation of equatorial Pacific is introduced, Secondly, by using the perturbed method, the zeroth and first order asymptotic perturbed solutions are constructed. Finally, from the comparison of the values for a figure, it is seen that the first asymptotic perturbed solution using the perturbation method has a good accuracy. And it is proved from the results that the perturbation method can be used as an analytic operation for the sea surface temperature anomaly in the equatorial Pacific of the atmosphere-ocean oscillation for the ENSO model.

The North Atlantic Oscillation Simulated by Versions 2 and 4 of IAP/ LASG GOALS Model

The capabilities of two versions of the Global–Ocean–Atmosphere–Land–System model (i.e. GOALS–2 and GOALS–4) developed at State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), are validated in terms of the simulations of the winter North Atlantic Oscillation (NAO), which is currently the subject of considerable scientific interest. The results show that both GOALS–2 and GOALS–4 exhibit a realistic NAO signal associated with relatively reasonable spatial patterns of sea level pressure, surface air temperature, and precipitation. Generally speaking, the associated patterns of precipitation in GOALSs match better with the observation in comparison with the case of surface temperature. For the imprint of NAO on the ocean, or perhaps a coupling between the two fluids, the associated tripole patterns of the North Atlantic SST anomaly are presented distinctly in GOALS–2, for GOALS-4 however, this is not the case. Spatially, the models’ main deficiencies appear to be that the simulated Icelandic lows shift northward apparently, which in turn result in the blemish of GOALSs in reproducing the accompanied surface wind anomalies. For the interannual and even longer time scale variations of DJF sea level pressure (SLP) over the North Atlantic region, GOALSs reproduce the center with the strongest variability rationally, but the intensities are far weaker than the observation. Key words North Atlantic Oscillation (NAO) - Model evaluation - GOALS model This study was jointly supported by the National key Project (Grant No. 96-908-02-03), the Excel-lent National Key Laboratory Research Project (Grant NO. 49823002), Chinese Academy of Sciences (CAS) under grant “ Bai Ren Ji Hua” for “ Validation of Coupled Climate Models”, and IAP innova-tion fund (No.8-1204).The authors gratefully acknowledge Dv. Jin Xuingze, Mr. Liu Xiying in IAP /LASG, and Dr. Gong Daoyi in Geophysical Department of Peking University for providing ardent help.

Perturbed Solving Method for Interdecadal Sea-air Oscillator Model

A coupled system of the interdecadal sea-air oscillator model is studied. The E1 Nifio-southem oscillation （ENSO） atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions. The oscillator model is involved with the variations of both the eastern and western Pacific anomaly pat- terns. This paper proposes an ENSO atmospheric physics model using a method of the perturbation theory. The aim is to create an asymptotic solving method for the ENSO model. Employing the perturbed method, the asymptotic solution of corresponding problem is obtained, and the asymptotic behaviour of the solution is studied. Thus we can obtain the prognoses of the sea surface temperature anomaly and related physical quantities.

The homotopic mapping method for sea-air oscillator model of interdecadal climate fluctuations

The E1 Nifio/La Nifia Southern Oscillation （ENSO） is an interannual phenomenon involved in the tropical Pacific ocean-atmosphere interactions. In this paper, a coupled system of sea-air oscillator model is studied. The aim is to create an asymptotic solving method of nonlinear equation for the ENSO model. And based on a class of oscillators of ENSO model, employing the method of homotopic mapping, the approximate solution of corresponding problem is studied. It is proven from the results that the homotopic method can be used for analysing the sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the atmosphere-ocean oscillation for ENSO model.

Asymptotic solution for the El Nio time delay sea-air oscillator model

A sea-air oscillator model is studied using the time delay theory. The aim is to find an asymptotic solving method for the El Nino-southern oscillation （ENSO） model. Employing the perturbed method, an asymptotic solution of the corresponding problem is obtained. Thus we can obtain the prognoses of the sea surface temperature （SST） anomaly and the related physical quantities.

Nucleation of Kinetic Ising Model Under Oscillating Field

We have studied the nucleation process of a two-dimensional kinetic Ising model subject to a bias oscillating external field, focusing on how the nucleation time depends on the oscillation frequency. It is found that the nucleation time shows a clear-cut minimum with the variation of oscillation frequency, wherein the average size of the critical nuclei is the smallest, indicating that an oscillating external field with an optimal frequency can be much more favorable to the nucleation process than a constant field. We have also investigated the effect of the initial phase of the external field, which helps to illustrate the occurrence of such an interesting finding.

The El Ni?o-Southern Oscillation cycle simulated by the climate system model of Chinese Academy of Sciences

On the basis of more than 200-year control run, the performance of the climate system model of Chinese Academy of Sciences （CAS-ESM-C） in simulating the E1 Nifio-Southern Oscillation （ENSO） cycle is evalu- ated, including the onset, development and decay of the ENSO. It is shown that, the model can reasonably simulate the annual cycle and interannual variability of sea surface temperature （SST） in the tropical Pacif- ic, as well as the seasonal phase-locking of the ENSO. The model also captures two prerequisites for the E1 Nino onset, i.e., a westerly anomaly and a warm SST anomaly in the equatorial western Pacific. Owing to too strong forcing from an extratropical meridional wind, however, the westerly anomaly in this region is largely overestimated. Moreover, the simulated thermocline is much shallower with a weaker slope. As a result, the warm SST anomaly from the western Pacific propagates eastward more quickly, leading to a faster develop- ment of an E1 Nino. During the decay stage, owing to a stronger E1Nino in the model, the secondary Gill-type response of the tropical atmosphere to the eastern Pacific warming is much stronger, thereby resulting in a persistent easterly anomaly in the western Pacific. Meanwhile, a cold anomaly in the warm pool appears as a result of a lifted thermocline via Ekman pumping. Finally, an E1 Nino decays into a La Nina through their interactions. In addition, the shorter period and larger amplitude of the ENSO in the model can be attribut- ed to a shallower thermocline in the equatorial Pacific, which speeds up the zonal redistribution of a heat content in the upper ocean.

Perturbation method of studying the EI Nifio oscillation with two parameters by using the delay sea-air oscillator model

The EI Nino-southern oscillation （ENSO） is an interannual phenomenon involved in tropical Pacific ocean- atmosphere interactions. In this paper, we develop an asymptotic method of solving the nonlinear equation using the ENSO model. Based on a class of the oscillator of the ENSO model, a approximate solution of the corresponding problem is studied employing the perturbation method.

A mathematical model of a P53 oscillation network triggered by DNA damage

Taking the interaction between a DNA damage repair module, an ATM module, and a P53--MDM2 oscillation module into account, this paper presents a mathematical model of a P53 oscillation network triggered by a DNA damage signal in individual cells. The effects of the DNA damage signal and the delay time of P53-induced MDM2 expression on the behaviours of the P53 oscillation network are studied. In the oscillatory state of the P53--MDM2 oscillator, it is found that the pulse number of P53--P oscillation increases with the increase of the initial DNA damage signal, whereas the amplitude and the period of P53--P oscillation are fixed for different initial DNA damage signals, and the period numbers of P53--P oscillations decrease with the increase of time delay of MDM2 expression induced by P53. These theoretical predictions are consistent with previous experimental results. The combined negative feedback of P53--MDM2 with the time delay of P53-induced MDM2 expression causes oscillation behaviour in the P53 network.

A Novel Wake Oscillator Model for Vortex-Induced Vibrations Prediction of A Cylinder Considering the Influence of Reynolds Number

It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV) of cylinders. In this paper, a novel in-line(IL) and cross-flow(CF) coupling VIV prediction model for circular cylinders has been proposed, in which the influence of the Reynolds number was comprehensively considered. The Strouhal number linked with the vortex shedding frequency was calculated through a function of the Reynolds number. The coefficient of the mean drag force was fitted as a new piecewise function of the Reynolds number, and its amplification resulted from the CF VIV was also taken into account. The oscillating drag and lift forces were modelled with classical van der Pol wake oscillators and their empirical parameters were determined based on the lock-in boundaries and the peak-amplitude formulas. A new peak-amplitude formula for the IL VIV was developed under the resonance condition with respect to the mass-damping ratio and the Reynolds number. When compared with the results from the experiments and some other prediction models, the present model could give good estimations on the vibration amplitudes and frequencies of the VIV both for elastically-mounted rigid and long flexible cylinders. The present model considering the influence of the Reynolds number could generally provide better results than that neglecting the effect of the Reynolds number.

Twentieth-century Pacific Decadal Oscillation simulated by CMIP5 coupled models

The authors examine the spatial and temporal characteristics of the simulated Pacific Decadal Oscillation （PDO） in 109 historical （i.e. all forcings） simulations derived from 25 coupled models within CMIPS. Compared with observations, most simulations successfully simulate the observed PDO pattern and its teleconnections to the SSTs in the tropical and southern Pacific. BNU-ESM, CanESM2, CCSM4, CESM 1 -FASTCHEM, FGOALS-g2, GFDL CM3, MIROCS, and NorESM 1 -M show better performance. Compared with the temporal phases of the observed PDO in the twentieth century, only five simulations -- from CNRM^CMS, CSIRO Mk3o6.0, HadCM3, and IPSL-CMSA-LR -- simulate an evolution of the PDO similar to that derived from observation, which suggests that current coupled models can barely reproduce the observed phase shifting of the PDO. To capture characteristics of the observed PDO in the twentieth century, a requirement is that all the relevant external forcings are included in the models. How to add realistic oceanic initial states into the model may be another key point.

Representation of the Arctic Oscillation in the CMIP5 Models

The temporal variability and spatial pattern of the Arctic Oscillation(AO)simulated in the historical experiment of26 coupled climate models participating in the Coupled Model Intercomparison Project Phase 5(CMIP5)are evaluated.Spectral analysis of the monthly AO index indicates that 23 out of the 26 CMIP5 models exhibit no statistically significant spectral peak in the historical experiment,as seen in the observations.These models are able to reproduce the AO pattern in the sea level pressure anomaly field during boreal winter,but the intensity of the AO pattern tends to be overestimated in all the models.The zonal-mean zonal wind anomalies associated with the AO is dominated by a meridional dipole in the mid-high latitudes of the Northern Hemisphere during boreal winter,which is well reproduced by only a few models.Most models show significant biases in both strength and location of the dipole compared to the observation.In considering the temporal variability as well as spatial structures in both horizontal and vertical directions,the MPI-ESM-P model reproduces an AO pattern that resembles the observation the best.

Asymptotic solving method for a sea air oscillator model of atmospheric physics

In this paper, a class of coupled system for the E1 Nifio/La Nifia southern oscillation （ENSO） atmospheric physics oscillation model is considered. We propose an ENSO atmospheric physics model using a method from the asymptotic theory. It is indicated from the results that the asymptotic method can be used for analyzing the sea surface temperature anomaly and the thermocline depth anomaly of the atmosphere-ocean oscillation for the ENSO model in the equatorial Pacific.

VARIATIONAL ITERATION SOLVING METHOD FOR SEA-AIR OSCILLATOR MODEL OF INTERDECADAL CLIMATE FLUCTUATIONS

Atmospheric physics is a very complicated natural phenomenon and needs to simplify its basic models for the sea-air oscillator. And it is solved by using the approximate method. The variational iteration method is a simple and valid method. In this paper the coupled system for a sea-air oscillator model of interdecadal climate fluctuations is considered. Firstly, through introducing a set of functions, and computing the variations, the Lagrange multipliers are obtained. And then, the generalized expressions of variational iteration are constructed. Finally, through selecting appropriate initial iteration from the iteration expressions, the approximations of solution for the sea-air oscillator model are solved successively.

Response of Growing Season Gross Primary Production to El Nino in Different Phases of the Pacific Decadal Oscillation over Eastern China Based on Bayesian Model Averaging

Gross primary production(GPP) plays a crucial part in the carbon cycle of terrestrial ecosystems.A set of validated monthly GPP data from 1957 to 2010 in 0.5°× 0.5° grids of China was weighted from the Multi-scale Terrestrial Model Intercomparison Project using Bayesian model averaging(BMA).The spatial anomalies of detrended BMA GPP during the growing seasons of typical El Nino years indicated that GPP response to El Nino varies with Pacific Decadal Oscillation(PDO) phases: when the PDO was in the cool phase,it was likely that GPP was greater in northern China(32°–38°N,111°–122°E) and less in the Yangtze River valley(28°–32°N,111°–122°E);in contrast,when PDO was in the warm phase,the GPP anomalies were usually reversed in these two regions.The consistent spatiotemporal pattern and high partial correlation revealed that rainfall dominated this phenomenon.The previously published findings on how El Nino during different phases of PDO affecting rainfall in eastern China make the statistical relationship between GPP and El Nino in this study theoretically credible.This paper not only introduces an effective way to use BMA in grids that have mixed plant function types,but also makes it possible to evaluate the carbon cycle in eastern China based on the prediction of El Nino and PDO.