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Gene expression involves bursts of production of both mRNA and protein, and the fluctuations in their number are increased due to such bursts. The Langevin equation is an efficient and versatile means to simulate such number fluctuation. However, how to include these mRNA and protein bursts in the Langevin equation is not intuitively clear. In this work, we estimated the variance in burst production from a general gene expression model and introduced such variation in the Langevin equation. Our approach offers different Langevin expressions for either or both transcriptional and translational bursts considered and saves computer time by including many production events at once in a short burst time. The errors can be controlled to be rather precise (<2%) for the mean and <10% for the standard deviation of the steady-state distribution. Our scheme allows for high-quality stochastic simulations with the Langevin equation for gene expression, which is useful in analysis of biological networks.
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http://dx.doi.org/10.1038/s41598-017-16835-y | DOI Listing |
J Chem Phys
September 2025
Department of Physics and Astronomy, Tokyo University of Science, Noda, Chiba 278-8510, Japan.
We investigate the relaxation dynamics of the generalized Langevin equation (GLE) with an exponential memory kernel. Our analysis reveals that the relaxation time to equilibrium scales inversely with the square of the memory decay rate λ, i.e.
View Article and Find Full Text PDFInt J Pharm
August 2025
Phenikaa Institute for Advanced Study, Phenikaa University, Yen Nghia, Ha Dong, Hanoi 12116, Viet Nam; Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha Dong, Hanoi 12116, Viet Nam.
Indomethacin has grabbed considerable attention since the 1960s due to its special analgesic, antipyretic, and anti-inflammatory abilities. However, the glassy dynamics of this nonselective cyclooxygenase inhibitor remains poorly understood, particularly at low temperatures and high pressures. Here, we develop a theory based on the elastically collective nonlinear Langevin equation to shed light on the relaxation and diffusion behaviors of indomethacin in supercooled, vitrified, and compressed states.
View Article and Find Full Text PDFPhys Rev E
July 2025
Indian Institute of Science, Freie Universität Berlin, Fachbereich Physik, 144195 Berlin, Germany and Centre for Condensed Matter Theory, Department of Physics, Bangalore 560012, India.
When analyzing experimental or simulation time-series data, the question arises whether it is possible to tell from the mere observation of the time-dependent trajectory of a one-dimensional observable whether the system is in equilibrium or not. We here consider the nonequilibrium version of the generalized Langevin equation for a Gaussian non-Markovian observable and show that (i) the multipoint joint distribution solely depends on the two-point correlation function and that (ii) for any nonequilibrium process an equilibrium process with uniquely determined parameters can be found that produces the same two-point correlation function. Since the multipoint joint distribution completely characterizes the dynamics of an observable, we conclude that the nonequilibrium character of a system, in contrast to its non-Markovianity, cannot be read off from the one-dimensional trajectory of a Gaussian observable.
View Article and Find Full Text PDFPhys Rev E
July 2025
University of Potsdam, Institute of Physics & Astronomy, 14476 Potsdam, Germany.
The effects of "diffusing diffusivity" (DD), a stochastically time-varying diffusion coefficient, are explored within the frameworks of three different forms of fractional Brownian motion (FBM): (i) the Langevin equation driven by fractional Gaussian noise (LE-FBM), (ii) the Weyl integral representation introduced by Mandelbrot and van Ness (MN-FBM), and (iii) the Riemann-Liouville fractional integral representation (RL-FBM) introduced by Lévy. The statistical properties of the three FBM-generalized DD models are examined, including the mean-squared displacement (MSD), mean-squared increment (MSI), autocovariance function (ACVF) of increments, and the probability density function (PDF). Despite the long-believed equivalence of MN-FBM and LE-FBM, their corresponding FBM-DD models exhibit distinct behavior in terms of MSD and MSI.
View Article and Find Full Text PDFPhys Rev E
July 2025
Université Hassan II. Casablanca, Ecole Normale Supérieure, LBGIM, Morocco.
This paper investigates the simulation and analysis of collective self-propelled motion in the presence of a leader, a phenomenon commonly observed in natural and artificial systems, such as bird flocks or robotic swarms. Using a dynamic approach based on the Langevin equation, the study models interactions between particles and a leader through elastic restoring forces and incorporates stochastic noise to simulate random fluctuations. These forces ensure group cohesion, avoid collisions, and mimic real-world conditions where unpredictability plays a significant role.
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