Interleukin-37 の lipopolysaccharide による破骨細胞形成及び骨吸収への影響の in vivo での検討

要約のみTohoku University山本照子課

Coupling between time series: a network view

Recently, the visibility graph has been introduced as a novel view for analyzing time series, which maps it to a complex network. In this paper, we introduce new algorithm of visibility, "cross-visibility", which reveals the conjugation of two coupled time series. The correspondence between the two time series is mapped to a network, "the cross-visibility graph", to demonstrate the correlation between them. We applied the algorithm to several correlated and uncorrelated time series, generated by the linear stationary ARFIMA process. The results demonstrate that the cross-visibility graph associated with correlated time series with power-law auto-correlation is scale-free. If the time series are uncorrelated, the degree distribution of their cross-visibility network deviates from power-law. For more clarifying the process, we applied the algorithm to real-world data from the financial trades of two companies, and observed significant small-scale coupling in their dynamics

Marangoni Propulsion of Active Particles

We study the surfing motion of active particles located at a flat liquid-gas interface. The particles create and maintain a surface tension gradient by asymmetrically discharging a surface tension-reducing agent. We employ theory and numerical simulation to investigate the Marangoni propulsion of these active surfers. First, we use the reciprocal theorem to establish a relationship between the propulsion speed and the release of the active chemical. This theoretical relation is utilized to examine the effect of wall confinement and geometry on the Marangoni-driven motion of active particle when the inertial effects are negligible and when the transports of the released agent is dominated by diffusion. Contrary to what might be the usual expectation, we find that the surfers may propel in the lower surface tension direction depending on their geometry and proximity to the bottom of the liquid layer. We then extend our theory beyond the Stokes regime with the aid of the perturbation theory and calculate the leading-order corrections to the propulsion speed due to the advective transport of momentum and mass when (Re, Pe) (denoted by Re and Pe, respectively) are small, but finite. Next, we develop a computational framework that enables us to study the effects of intermediate and large Re and Pe on the propulsion speed. Our numerical approach is validated against theory and available experimental data. Interestingly, our simulations reveal that the normalized propulsion speed initially increases with increasing Re and Pe from zero. It then reaches a maximum and afterward sharply declines when Re or Pe becomes large. That there exist certain intermediate (Re, Pe) at which the Marangoni propulsion reaches a peak is a new discovery that can guide engineering to design Marangoni surfers with superior performance. We also numerically analyze the translational stability of Marangoni surfers of spherical shape. An overset-grid is adopted to carry out the simulations. We demonstrate that a Marangoni surfer can retain its stability at higher Reynolds numbers relative to the same surfer moving at an interface with no Marangoni effect present. Lastly, we computationally investigate the change in the mobility of the surfers as a result of the depth of the liquid layer. We consider the motion of thin cylindrical disks and oblate spheroids for a wide range of release rates and diffusivity of the exuded chemical species, that control the effective (Re, Pe). We show that indeed the surfers can undergo a forward, a backward, or an arrested motion. We also identify the links between these modes of mobility and the forces acting on the surfers as well as the flow structure in their vicinity. Rather unexpectedly, we discover that negative pressure is the primary contributor to the fluid force experienced by the surfer and that this suction force is mainly responsible for the reverse Marangoni propulsion. Overall, our findings substantially improve the current understanding of the Marangoni-driven motion of active particles at liquid-gas interfaces and pave the way for engineering future miniature surfing robots

An Estimation of Tax Evasion in Iran

The aim of this research is to estimate the size of tax evasion between 1971 and 2007 in Iran. Among the present direct and indirect approaches, the indirect approach presented by Tanzi based on currency demand, is used to estimate the size of the underground economy, then taking the effective tax rate into consideration, the amount of the underground economy taxes. Our results show that the size of the underground economy is increasing in a long-term trend and also the ratio of the underground economy to gross domestic product has increased during the period under consideration. Our findings also indicate that tax evasion has markedly increased during the period. Therefore, policies to alleviate the tax evasion in the country should be implemented by policy makers