arXiv subjects

Fumito Mori

Publications and source records attributed to Fumito Mori.

4 recordsLinked to original sources

arXiv2024

Pb Substitution Effects on Lattice and Electronic System of the BiS2-based Superconductors La(O F)BiS2

We examined the effect of Pb substitution in the layered superconductor LaO0.5F0.5Bi1-xPbxS2 (x=0~0.15) through the measurements of the resistivity, thermal expansion, specific heat, and Seebeck coefficient. These transport and thermal properties show anomalies at certain temperatures (T*) for x${\geq}$0.08. The large thermal expansion anomalies, specific heat anomalies, and the existence of hystereses in the above measurements indicate a first-order structural phase transition at T*. Additionally, the Seebeck coefficient indicates that the anomalies at T* are related not only to the lattice system, but also to the electronic system. Superconductivity is not observed above 2 K at x=0.08, which is around the phase boundary where T* vanishes. The suppression of superconductivity around the structural phase boundary suggests a close relationship between the lattice and superconductivity.

cond-mat.supr-con↗

arXiv2022

Enhanced precision of circadian rhythm by output system

Circadian rhythms are biological rhythms of approximately 24 h that persist even under constant conditions without environmental daily cues. The molecular circadian clock machinery generates the physiological rhythms, which can be transmitted into the downstream output system. Owing to the stochastic nature of the biochemical reactions, the oscillation period of circadian rhythms exhibited by individual organisms or cells is not constant on a daily basis with variations as high as 10 % in terms of the coefficient of variation. Although the fluctuations in circadian rhythm is measured through a reporter such as bioluminescence or fluorescence, experimentally confirming whether the fluctuations found in the reporter system are the same as those in the clock itself is challenging. This study numerically and analytically investigated a coupled system of a circadian clock and its output system, and then compared the fluctuations in the oscillation period of the two systems. We found that the amount of fluctuation in the output system is smaller than that in the circadian clock when the degradation rate of the molecules responsible for the output system was at typical values. The results obtained imply that the output system improves the accuracy of the circadian rhythm without the need for any special denoising processes.

q-bio.MN↗

arXiv2021

Inference Methods for Interaction and Noise Intensities Using Only Spike-time Data on Coupled Oscillators

We propose theoretical methods to infer coupling strength and noise intensity simultaneously through an observation of spike timing in two well-synchronized noisy oscillators. A phase oscillator model is applied to derive formulae relating each of the parameters to some statistics from spike-time data. Using these formulae, each parameter is inferred from a specific set of statistics. We demonstrate the methods with the FitzHugh-Nagumo model as well as the phase model. Our methods do not require any external perturbation and thus are ready for application to various experimental systems.

physics.bio-ph↗

arXiv2013

Period Variability of Coupled Noisy Oscillators

Period variability, quantified by the standard deviation (SD) of the cycle-to-cycle period, is investigated for noisy phase oscillators. We define the checkpoint phase as the beginning/end point of one oscillation cycle and derive an expression for the SD as a function of this phase. We find that the SD is dependent on the checkpoint phase only when oscillators are coupled. The applicability of our theory is verified using a realistic model. Our work clarifies the relationship between period variability and synchronization from which valuable information regarding coupling can be inferred.

physics.bio-ph↗