scholarly journals Synchronization of Independent Neural Ensembles in Human EEG during Choice Tasks

2019 ◽  
Vol 9 (12) ◽  
pp. 132
Author(s):  
Alexander Zaleshin ◽  
Galina Merzhanova
Keyword(s):  
Time Lag ◽  
Individual Characteristics ◽  
Situational Factors ◽  
Time Lags ◽  
Risk Averse ◽  
Behavioral Experiments ◽  
Neural Ensembles ◽  
Long Time ◽  
Beta Rhythms ◽  
Alpha Beta

During behavioral experiments, humans placed in a situation of having to choose between a more valuable but risky reward and a less valuable but guaranteed reward make their decisions in accordance with external situational factors and individual characteristics, such as inclination to risk or caution. In such situations, humans can be divided into “risk-inclined” and “risk-averse” (or “cautious”) subjects. In this work, characteristics of EEG rhythms, such as phase–phase relationships and time lags between rhythms, were studied in pairs of alpha–beta and theta–beta rhythms. Phase difference can also be expressed as a time lag. It has been suggested that statistically significant time lags between rhythms are due to the combined neural activity of anatomically separate, independent (in activation/inhibition processes) ensembles. The extents of synchronicity between rhythms were compared as percentages between risk-inclined and risk-averse subjects. The results showed that synchronicity in response to stimuli was more often observed in pairs of alpha–beta rhythms of risk-averse subjects compared with risk-inclined subjects during the choice of a more valuable but less probable reward. In addition, significant differences in the percentage ratio of alpha and beta rhythms were revealed between (i) cases of synchronization without long time lags and (ii) cases with long time lags between rhythms (from 0.08 to 0.1 s).

Non-Gaussian probability distributions of solar wind fluctuations

1994 ◽  
Vol 12 (12) ◽  
pp. 1127-1138 ◽  
Author(s):  
E. Marsch ◽  
C. Y. Tu
Keyword(s):  
Solar Wind ◽  
Probability Distributions ◽  
Time Lag ◽  
Small Scale ◽  
Time Lags ◽  
Mhd Turbulence ◽  
Theoretical Concepts ◽  
Fluid Turbulence ◽  
Long Time ◽  
Non Gaussian

Abstract. The probability distributions of field differences ∆x(τ)=x(t+τ)-x(t), where the variable x(t) may denote any solar wind scalar field or vector field component at time t, have been calculated from time series of Helios data obtained in 1976 at heliocentric distances near 0.3 AU. It is found that for comparatively long time lag τ, ranging from a few hours to 1 day, the differences are normally distributed according to a Gaussian. For shorter time lags, of less than ten minutes, significant changes in shape are observed. The distributions are often spikier and narrower than the equivalent Gaussian distribution with the same standard deviation, and they are enhanced for large, reduced for intermediate and enhanced for very small values of ∆x. This result is in accordance with fluid observations and numerical simulations. Hence statistical properties are dominated at small scale τ by large fluctuation amplitudes that are sparsely distributed, which is direct evidence for spatial intermittency of the fluctuations. This is in agreement with results from earlier analyses of the structure functions of ∆x. The non-Gaussian features are differently developed for the various types of fluctuations. The relevance of these observations to the interpretation and understanding of the nature of solar wind magnetohydrodynamic (MHD) turbulence is pointed out, and contact is made with existing theoretical concepts of intermittency in fluid turbulence.

scholarly journals The relationship between meteorological variables and sporadic cases of Legionnaires' disease in residents of England and Wales

2014 ◽  
Vol 142 (11) ◽  
pp. 2352-2359 ◽  
Author(s):  
K. D. HALSBY ◽  
C. A. JOSEPH ◽  
J. V. LEE ◽  
P. WILKINSON
Keyword(s):  
Conditional Logistic Regression ◽  
Time Lag ◽  
Time Lags ◽  
England And Wales ◽  
Long Time ◽  
Sporadic Cases ◽  
Risk Of Disease ◽  
Legionnaires Disease ◽  
Short Time ◽  
The Relationship

SUMMARYWe studied the timing of occurrence of 1676 sporadic, community-acquired cases of Legionnaires' disease in England and Wales between 1993 and 2008, in relation to temperature, relative humidity, rainfall, windspeed and ultraviolet light using a fixed-stratum case-crossover approach. The analysis was conducted using conditional logistic regression, with consideration of appropriate lag periods. There was evidence of an association between the risk of Legionnaires' disease and temperature with an apparently long time lag of 1–9 weeks [odds of disease at 95thvs. 75th centiles: 3·91, 95% confidence interval (CI) 2·06–7·40], and with rainfall at short time lags (of 2–10 days) (odds of disease at 75thvs.50th centiles: 1·78, 95% CI 1·50–2·13). There was some evidence that the risk of disease in relation to high temperatures was greater at high relative humidities. A higher risk of Legionnaires' disease may be indicated by preceding periods of warmer wetter weather.

The impulse breakdown voltage and time-lag characteristics of long gaps in air I. The positive discharge

1964 ◽  
Vol 256 (1069) ◽  
pp. 185-212 ◽  
Keyword(s):  
Space Charge ◽  
Wave Front ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Electrical Breakdown ◽  
Time Lag ◽  
Short Wave ◽  
Time Lags ◽  
Long Time ◽  
Statistical Time

The electrical breakdown of rod/rod, rod/sphere and rod/plane gaps in the atmosphere has been examined oscillographically and photographically. Positive polarity impulse potentials of crest value up to 1 MV, of wave-front variable between 0.06 and 2.0 μs and of wave tail 2 ms were used. It has been found that the lack of a sharply defined breakdown potential was due to the existence of long time lags quite distinct from the shorter times to breakdown observed with the conventional short wave-tail impulse. A ‘ dead-time ’ of low probability of breakdown on the wave tail separated the two classes of breakdown. The breakdown voltage of a rod/rod gap has been found to be dependent upon the wave front of the impulse. An accompanying photographic examination of the initial corona phase of breakdown also revealed a variation with the impulse voltage wave front. It is shown that these results were consistent with the electric field distortion arising from space charge. The corona phase of breakdown was responsible for this space charge. The statistical behaviour of long gap breakdown was due to random variations in the corona phase. The effect of the statistical time lag in the production of initiatory electrons upon the corona phase is discussed. A rotating-mirror camera of f/1.0 aperture and a technique for controlled suppression of the breakdown enabled the growth of the discharge with time to be studied in some detail. It was shown that the positive leader either preceded or was coincident with the negative leader, depending upon the gap arrangement. It is concluded that the establishment of the leader at the high-tension electrode is the criterion for breakdown. The role of the earthed cathode in aiding this leader development was dependent upon its size and geometry. For cathodes of small dimensions the occurrence of a negative corona phase increased the anode electric gradient; for large cathodes the surface charge induced by the anode corona discharge became important. The variation of breakdown strength with gap geometry is accountable in these terms.

The impulse breakdown voltage and time-lag characteristics of long gaps in air II. The negative discharge

1964 ◽  
Vol 256 (1069) ◽  
pp. 213-234 ◽  
Keyword(s):  
Wave Front ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Time Lag ◽  
Time Lags ◽  
Impulse Wave ◽  
Time Resolved ◽  
Wide Range ◽  
Negative Impulse ◽  
Long Time

Oscillographic measurement and time-resolved photographic recording have been used to examine the breakdown of rod/rod, rod/sphere and rod/plane gaps with long-duration negative impulse potentials of up to 1 MV crest. As in the positive discharge, the breakdown process is found often to cease for considerable periods on the impulse wave tail. Breakdown then occurs after a long time lag for gaps composed of rod cathodes and rod or small sphere anodes. Where the anode is large, no long time lags are observed. Measurement of the variation of breakdown strength with time during the impulse duration has been made by the superimposition of a second impulse upon the first, following a controllable delay. The results show a minimum probability of breakdown initiation after 15 μs of the applied impulse, and a subsequent slow recovery. It is suggested that this confirms the effect of the initial corona phase in causing space charge fouling of the gap. The breakdown voltage of rod/rod gaps is shown to decrease by up to 30 % when the impulse wave front is reduced from 0.50 to 0.06 μs. The breakdown strength with negative impulses is thus less than with positive impulses for wave fronts faster than 0.20 μs. For the wave form 0.50/2000 μs, the breakdown voltage is found to depend more critically upon the dimensions of the earthed electrode than is the case with positive impulses. The breakdown voltage for a rod/25 cm sphere gap is 73 % greater than for a rod/rod gap, yet also 15 % greater than for a rod/plane gap. For gap lengths between 25 and 65 cm, the breakdown voltage of the rod/plane gap is found to increase with decreasing wave front duration. The variation of the negative impulse corona with rate of potential rise and with crest voltage is examined photographically. Many of the observed variations of breakdown voltage and time-lag characteristics can be accounted for in terms of the impulse corona phase. The time-resolved photography of the negative discharge over a wide range of conditions suggests that in the range of gap lengths investigated the formation of the positive leader rather than the negative leader is the necessary forerunner of sparkover.

Long Short-Term Memory

1997 ◽  
Vol 9 (8) ◽  
pp. 1735-1780 ◽  
Author(s):  
Sepp Hochreiter ◽  
Jürgen Schmidhuber
Keyword(s):  
Short Term Memory ◽  
Constant Error ◽  
Time Lag ◽  
Back Propagation ◽  
Time Lags ◽  
Short Term ◽  
Time Step ◽  
Term Memory ◽  
Long Time ◽  
Long Short Term Memory

Learning to store information over extended time intervals by recurrent backpropagation takes a very long time, mostly because of insufficient, decaying error backflow. We briefly review Hochreiter's (1991) analysis of this problem, then address it by introducing a novel, efficient, gradient based method called long short-term memory (LSTM). Truncating the gradient where this does not do harm, LSTM can learn to bridge minimal time lags in excess of 1000 discrete-time steps by enforcing constant error flow through constant error carousels within special units. Multiplicative gate units learn to open and close access to the constant error flow. LSTM is local in space and time; its computational complexity per time step and weight is O. 1. Our experiments with artificial data involve local, distributed, real-valued, and noisy pattern representations. In comparisons with real-time recurrent learning, back propagation through time, recurrent cascade correlation, Elman nets, and neural sequence chunking, LSTM leads to many more successful runs, and learns much faster. LSTM also solves complex, artificial long-time-lag tasks that have never been solved by previous recurrent network algorithms.

Hopf bifurcation for a discontinuous HTLV-1 model

Filomat ◽  
2017 ◽  
Vol 31 (20) ◽  
pp. 6247-6267 ◽  
Author(s):  
Elham Shamsara ◽  
Zahra Afsharnezhad ◽  
Reihaneh Mostolizadeh
Keyword(s):  
Hopf Bifurcation ◽  
Sliding Mode ◽  
Early Stage ◽  
Time Lag ◽  
Discontinuous System ◽  
Steady State Condition ◽  
Ctl Response ◽  
Optimal Drug ◽  
Long Time ◽  
Immunosuppressive Diseases

Developing accurate mathematical models for host immune response in immunosuppressive diseases such as HIV and HTLV-1 are essential to achieve an optimal drug therapy regime. Since for HTLV-1 specific CTL response typically occurs after a time lag, we consider a discontinuous response function to better describe this lagged response during the early stage of the infectious, thus the system of HTLV-1 model will be a discontinuous system. For analyzing the dynamic of the system we use Filippov theory and find conditions in which the Filippov system undergoes a Hopf bifurcation. The Hopf bifurcation help us to find stable and unstable periodic oscillations and can be used to predict whether the CTL response can return to a steady state condition. Also, Hopf bifurcation in sliding mode is investigated. In this case the solutions will remain in the hyper-surface of discontinuity and as a consequence the disease cannot progress, at least for a long time. Finally we use numerical simulations to demonstrate the results by example.

scholarly journals In Vitro Model of Mycobacterial Growth Arrest Using Nitric Oxide with Limited Air

2008 ◽  
Vol 53 (1) ◽  
pp. 157-161 ◽  
Author(s):  
Syed Hussain ◽  
Muhammad Malik ◽  
Lanbo Shi ◽  
Maria Laura Gennaro ◽  
Karl Drlica
Keyword(s):  
Nitric Oxide ◽  
In Vitro Model ◽  
Transition Period ◽  
Time Lag ◽  
Growth Arrest ◽  
Ring Structure ◽  
Time Lags ◽  
Vitro Model ◽  
Mycobacterial Growth

ABSTRACT An in vitro model of mycobacterial growth arrest was developed using Mycobacterium bovis BCG. When an exponentially growing culture was transferred to an evacuated tube, growth continued; treatment with a source of nitric oxide (diethylenetriamine-nitric oxide adduct [DETA-NO] at 50 μM) halted growth immediately, and aeration restored growth. When the period of growth arrest exceeded 4 h, a time lag occurred before aeration could restore growth. The lag time was maximal (24 h) after 16 h of growth arrest. These time lags indicated that one transition period was required for cells to achieve full arrest of growth and another for them to recover fully from growth arrest. DETA-NO-induced growth arrest failed to protect from the lethal effects of anaerobic shock, which caused rapid lysis of both growing and growth-arrested cells. While growth arrest had little effect on the lethal action of rifampin, it eliminated isoniazid lethality. Growth arrest reduced but did not eliminate fluoroquinolone lethality. Two fluoroquinolones, moxifloxacin and gatifloxacin, were equally lethal to exponentially growing cells, but moxifloxacin was more active during growth arrest. This difference is attributed to the fluoroquinolone C-7 ring structure, the only difference between the compounds. Collectively these data characterize a new system for halting mycobacterial growth that may be useful for evaluating new antituberculosis agents.

IRREVERSIBLE INVESTMENT, OPERATING FLEXIBILITY, AND TIME LAGS

2010 ◽  
Vol 27 (02) ◽  
pp. 271-286 ◽  
Author(s):  
RYUTA TAKASHIMA ◽  
MAKOTO GOTO ◽  
MOTOH TSUJIMURA
Keyword(s):  
Time Lag ◽  
Peak Load ◽  
Price Volatility ◽  
Optimal Investment ◽  
Capacity Expansion ◽  
Fixed Cost ◽  
Time Lags ◽  
Investment Timing ◽  
Power Company ◽  
Optimal Investment Problem

We consider an optimal investment problem when a firm such as an electric power company has the operational flexibility to expand and contract capacity with fixed cost. This problem is formulated as an impulse control problem combined with optimal stopping. Consequently, we obtain optimal investment timing, optimal capacity expansion and contraction timing, and the investment value. We also show investment, capacity expansion and contraction rule are influenced by the price volatility and the initial capacity is also influenced by the ratio between base-load plant and peak-load plant. In addition, we investigate how time lag between investment and operation influences the investment rule.

scholarly journals Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates

2019 ◽  
Vol 49 (6) ◽  
pp. 1521-1539
Author(s):  
Yu-Kun Qian ◽  
Shiqiu Peng ◽  
Chang-Xia Liang
Keyword(s):  
Time Lag ◽  
Effective Diffusivity ◽  
Delta Function ◽  
Spreading Rate ◽  
Particle Dispersion ◽  
Small Scale ◽  
Time Lags ◽  
Conservative Tracer ◽  
Stirring Effect ◽  
Short Time

AbstractThe present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion, is naturally isolated from diabatic cross-contour motions. Therefore, Lagrangian particle motions in the transformed coordinate obey a transformed zeroth-order stochastic (i.e., random walk) model with the diffusivity replaced by the effective diffusivity. Such a stochastic model becomes the theoretical foundation on which both diffusivities are exactly unified. In the absence of small-scale diffusion, particles do not disperse at all in the transformed contour coordinate. Besides, the corresponding Lagrangian autocorrelation becomes a delta function and is thus free from pronounced overshoot and negative lobe at short time lags that may be induced by either Rossby waves or mesoscale eddies; that is, particles decorrelate immediately and Lagrangian diffusivity is already asymptotic no matter how small the time lag is. The resulting instantaneous Lagrangian spreading rate is thus conceptually identical to the effective diffusivity that only measures the instantaneous irreversible mixing. In these regards, the present study provides a new look at particle dispersion in contour-based coordinates.

A “Natural” Proposal for Addressing Climate Change

2014 ◽  
Vol 28 (3) ◽  
pp. 359-363 ◽  
Author(s):  
Thomas E. Lovejoy
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Ethical Issues ◽  
Time Lag ◽  
Radiant Heat ◽  
Time Frame ◽  
Future Generations ◽  
Considerable Time ◽  
Long Time

One of the fundamental challenges of climate change is that we contribute to it increment by increment, and experience it increment by increment after a considerable time lag. As a consequence, it is very difficult to see what we are doing to ourselves, to future generations, and to the living planet as a whole. There are monumental ethical issues involved, but they are obscured by the incremental nature of the process and the long time frame before reaching the concentration of greenhouse gases and the ensuing accumulation of radiant heat—and consequent climate change—that ensues.

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