The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Farshid Jafarpour - One of the best experts on this subject based on the ideXlab platform.
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cell size regulation induces sustained oscillations in the population growth rate
Physical Review Letters, 2019Co-Authors: Farshid JafarpourAbstract:We study the effect of Correlations in generation times on the dynamics of population growth of microorganisms. We show that any Nonzero Correlation that is due to cell-size regulation, no matter how small, induces long-term oscillations in the population growth rate. The population only reaches its steady state when we include the often-neglected variability in the growth rates of individual cells. We discover that the relaxation timescale of the population to its steady state is determined by the distribution of single-cell growth rates and is surprisingly independent of details of the division process such as the noise in the timing of division and the mechanism of cell-size regulation. We validate the predictions of our model using existing experimental data and propose an experimental method to measure single-cell growth variability by observing how long it takes for the population to reach its steady state or balanced growth.
Jesper Jensen - One of the best experts on this subject based on the ideXlab platform.
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novel acoustic feedback cancellation approaches in hearing aid applications using probe noise and probe noise enhancement
IEEE Transactions on Audio Speech and Language Processing, 2012Co-Authors: Soren Holdt Jensen, Jesper JensenAbstract:Adaptive filters are widely used in acoustic feedback cancellation systems and have evolved to be state-of-the-art. One major challenge remaining is that the adaptive filter estimates are biased due to the Nonzero Correlation between the loudspeaker signals and the signals entering the audio system. In many cases, this bias problem causes the cancellation system to fail. The traditional probe noise approach, where a noise signal is added to the loudspeaker signal can, in theory, prevent the bias. However, in practice, the probe noise level must often be so high that the noise is clearly audible and annoying; this makes the traditional probe noise approach less useful in practical applications. In this work, we explain theoretically the decreased convergence rate when using low-level probe noise in the traditional approach, before we propose and study analytically two new probe noise approaches utilizing a combination of specifically designed probe noise signals and probe noise enhancement. Despite using low-level and inaudible probe noise signals, both approaches significantly improve the convergence behavior of the cancellation system compared to the traditional probe noise approach. This makes the proposed approaches much more attractive in practical applications. We demonstrate this through a simulation experiment with audio signals in a hearing aid acoustic feedback cancellation system, where the convergence rate is improved by as much as a factor of 10.
Chong-wei Xie - One of the best experts on this subject based on the ideXlab platform.
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the stationary properties and the state transition of the tumor cell growth mode
European Physical Journal B, 2004Co-Authors: D. C. Mei, Chong-wei Xie, Lei ZhangAbstract:We study the stationary properties and the state transition of the tumor cell growth model (the logistic model) in presence of correlated noises for the case of Nonzero Correlation time. We derived an approximative Fokker-Planck equation and the stationary probability distribution (SPD) of the model. Based the SPD, we investigated the effects of both Correlation strength ( $\lambda$ ) and Correlation time ( $\tau$ ) of cross-correlated noises on the SPD, the mean of the tumor cell population and the normalized variance ( $\lambda_2$ ) of the system, and calculated the state transition rate of the system between two stable states. Our results indicate that: (i) $\lambda$ and $\tau$ play opposite roles in the stationary properties and the state transition of the system, i.e. increase of $\lambda$ can produce a smaller mean value of the cell population and slow down the state transition, but increase of $\tau$ can produce a larger mean value of the cell population and enhance state transition; (ii) For large $\lambda$ , there a peak structure on both $\lambda_2$ - $\lambda$ plot and $\lambda_2$ - $\tau$ plot. For the small $\lambda$ , $\lambda_2$ increases with increasing $\lambda$ , but $\lambda_2$ increases with decreasing $\tau$ . Copyright Springer-Verlag Berlin/Heidelberg 2004
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Intensity Correlation Function and Relaxation Time of a Single-Mode Laser Driven by Cross-Correlated Noises for the Case of Nonzero Correlation Time
Physica Scripta, 2004Co-Authors: Chong-wei Xie, D. C. Mei, Li CaoAbstract:We consider a single-mode laser model driven by correlated quantum and pump noise and study the effects of the cross Correlation time τ between noises on the steady-state intensity Correlation function and the associated relaxation time. Based on an approximated Fokker–Planck description of the laser model and the Stratonovich-like ansatz, we find the steady-state probability distribution function Pst(I), the steady-state intensity Correlation function K(s) and the associated relaxation time T. From numerical computations we found the following: (1) τ suppresses the fluctuation of the laser intensity for the case of positively correlated noises (i.e. the Correlation strength between noises λ > 0) and increases the intensity fluctuation for the case of negatively correlated noises (λ > 0); (2) τ slows down the decay of the intensity Correlation for the case of λ > 0 but speeds up the decay for the case of λ 0.
Ariel Amir - One of the best experts on this subject based on the ideXlab platform.
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evolution of microbial growth traits under serial dilution
Genetics, 2020Co-Authors: Jie Lin, Michael Manhart, Ariel AmirAbstract:Selection of mutants in a microbial population depends on multiple cellular traits. In serial-dilution evolution experiments, three key traits are the lag time when transitioning from starvation to growth, the exponential growth rate, and the yield (number of cells per unit resource). Here, we investigate how these traits evolve in laboratory evolution experiments using a minimal model of population dynamics, where the only interaction between cells is competition for a single limiting resource. We find that the fixation probability of a beneficial mutation depends on a linear combination of its growth rate and lag time relative to its immediate ancestor, even under clonal interference. The relative selective pressure on growth rate and lag time is set by the dilution factor; a larger dilution factor favors the adaptation of growth rate over the adaptation of lag time. The model shows that yield, however, is under no direct selection. We also show how the adaptation speeds of growth and lag depend on experimental parameters and the underlying supply of mutations. Finally, we investigate the evolution of covariation between these traits across populations, which reveals that the population growth rate and lag time can evolve a Nonzero Correlation even if mutations have uncorrelated effects on the two traits. Altogether these results provide useful guidance to future experiments on microbial evolution.
Li Cao - One of the best experts on this subject based on the ideXlab platform.
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Intensity Correlation Function and Relaxation Time of a Single-Mode Laser Driven by Cross-Correlated Noises for the Case of Nonzero Correlation Time
Physica Scripta, 2004Co-Authors: Chong-wei Xie, D. C. Mei, Li CaoAbstract:We consider a single-mode laser model driven by correlated quantum and pump noise and study the effects of the cross Correlation time τ between noises on the steady-state intensity Correlation function and the associated relaxation time. Based on an approximated Fokker–Planck description of the laser model and the Stratonovich-like ansatz, we find the steady-state probability distribution function Pst(I), the steady-state intensity Correlation function K(s) and the associated relaxation time T. From numerical computations we found the following: (1) τ suppresses the fluctuation of the laser intensity for the case of positively correlated noises (i.e. the Correlation strength between noises λ > 0) and increases the intensity fluctuation for the case of negatively correlated noises (λ > 0); (2) τ slows down the decay of the intensity Correlation for the case of λ > 0 but speeds up the decay for the case of λ 0.
