Burst synchronization in two pulse-coupled resonate-and-fire neuron circuits

The present paper addresses burst synchronization in out of phase observed in two pulse-coupled resonate-and-fire neuron (RFN) circuits. The RFN circuit is a silicon spiking neuron that has second-order membrane dynamics and exhibits fast subthreshold oscillation of membrane potential. Due to such dynamics, the behavior of the RFN circuit is sensitive to the timing of stimuli. We investigated the effects of the sensitivity and the mutual interaction on the dynamic behavior of two pulse-coupled RFN circuits, and will demonstrate out of phase burst synchronization and bifurcation phenomena through circuit simulations.Applications in Artificial Intelligence - ApplicationsRed de Universidades con Carreras en Informática (RedUNCI

達成可能及び残り一つを除いて達成可能な線量体積・平均線量制約に基づく計画のための強度変調放射線治療の最適化

We give a novel approach for obtaining an intensity-modulated radiation therapy (IMRT) optimization solution based on the idea of continuous dynamical methods. The proposed method, which is an iterative algorithm derived from the discretization of a continuous-time dynamical system, can handle not only dose-volume but also mean-dose constraints directly in IMRT treatment planning. A theoretical proof for the convergence to an equilibrium corresponding to the desired IMRT planning is given by using the Lyapunov stability theorem. By introducing the concept of “acceptable,” which means the existence of a nonempty set of beam weights satisfying the given dose-volume and mean-dose constraints, and by using the proposed method for an acceptable IMRT planning, one can resolve the issue that the objective and evaluation are different in the conventional planning process. Moreover, in the case where the target planning is totally unacceptable and partly acceptable except for one group of dose constraints, we give a procedure that enables us to obtain a nearly optimal solution close to the desired solution for unacceptable planning. The performance of the proposed approach for an acceptable or unacceptable planning is confirmed through numerical experiments simulating a clinical setup

Burst synchronization in two pulse-coupled resonate-and-fire neuron circuits

The present paper addresses burst synchronization in out of phase observed in two pulse-coupled resonate-and-fire neuron (RFN) circuits. The RFN circuit is a silicon spiking neuron that has second-order membrane dynamics and exhibits fast subthreshold oscillation of membrane potential. Due to such dynamics, the behavior of the RFN circuit is sensitive to the timing of stimuli. We investigated the effects of the sensitivity and the mutual interaction on the dynamic behavior of two pulse-coupled RFN circuits, and will demonstrate out of phase burst synchronization and bifurcation phenomena through circuit simulations.Applications in Artificial Intelligence - ApplicationsRed de Universidades con Carreras en Informática (RedUNCI

A Novel Analog CMOS Cellular Neural Network for Biologically-Inspired Walking Robot

Abstract-We propose a novel analog CMOS circuit that implements a class of cellular neural networks (CNNs) for biologically-inspired walking robots. Recently, a class of autonomous CNNs, so-called a reaction-diffusion (RD) CNN, has applied to locomotion control in robotics. We have introduced a novel RD-CNN, and implemented it as an analog CMOS circuit by using multiple-input floating-gate (MIFG) MOS FETs. As a result, the circuit can operate in voltage-mode. From the results on computer simulations, we have shown that the circuit has capability to generate stable rhythmic patterns for locomotion control in a quadruped walking robot

Variable Stars in the Magellanic Clouds: Results from OGLE and SIRIUS

We have performed a cross-identification between OGLE-II data and single-epoch SIRIUS JHK survey data in the LMC and SMC. After eliminating obvious spurious variables, we determined the pulsation periods for 9,681 and 2,927 variables in the LMC and SMC, respectively. Based on these homogeneous data, we studied the pulsation properties and metallicity effects on period-K magnitude (PK) relations by comparing the variable stars in the LMC and SMC. The sample analyzed here is much larger, and we found the following new features: (1) variable red giants in the SMC form parallel sequences on the PK plane, just like those found by Wood (2000) in the LMC; (2) both of the sequences A and B of Wood (2000) have discontinuities, and they occur at the K-band luminosity of the TRGB; (3) the sequence B of Wood (2000) separates into three independent sequences B+- and C'; (4) comparison between the theoretical pulsation models (Wood et al. 1996) and observational data suggests that the variable red giants on sequences C and newly discovered C' are pulsating in the fundamental and first overtone mode, respectively; (5) the theory can not explain the pulsation mode of sequences A+- and B+-, and they are unlikely to be the sequences for the first and second overtone pulsators, as was previously suggested; (6) the zero points of PK relations of Cepheids in the metal deficient SMC are fainter than those of LMC ones by ~0.1 mag but those of SMC Miras are brighter than those of LMC ones by ~0.13 mag, which are probably due to metallicity effects.Comment: 9 pages, 10 figures, accepted for publication in MNRAS. High resolution version is available at: http://www.ioa.s.u-tokyo.ac.jp/~yita/scr/astro/papers/RefereedPaper/yitaMD250 .pd

The Effects of Low-Dose-Rate γ-irradiation on Forced Swim Test-Induced Immobility and Oxidative Stress in Mice

The forced swim test (FST) induces immobility in mice. Low-dose (high-dose-rate) X-irradiation inhibits FSTinduced immobility in mice due to its antioxidative function. We evaluated the effects of low-dose γ-irradiation at a low-dose-rate on the FST-induced depletion of antioxidants in mouse organs. Mice received whole-body low-dose-rate (0.6 or 3.0 mGy/h) of low-dose γ-irradiation for 1 week, followed by daily FSTs (5 days). The immobility rate on day 2 compared to day 1 was significantly lower in the 3.0 mGy/h irradiated mice than in sham irradiated mice. The FST significantly decreased the catalase (CAT) activity and total glutathione (t-GSH) content in the brain and kidney, respectively. The superoxide dismutase (SOD) activity and t-GSH content in the liver of the 3.0 mGy/h irradiated mice were significantly lower than those of the non-FST-treated mice. The CAT activity in the lungs of mice exposed to 3.0 mGy/h γ-irradiation was higher than that of non-FST treated mice and mice treated with FST. However, no significant differences were observed in the levels of these antioxidant markers between the sham and irradiated groups except for the CAT activity in lungs. These findings suggest that the effects of low-dose-rate and low-dose γ-irradiation on FST are highly organ-dependent

X-Irradiation at 0.5 Gy after the forced swim test reduces forced swimming-induced immobility in mice

The forced swim test (FST) is a screening model for antidepressant activity; it causes immobility and induces oxidative stress. We previously reported that radon inhalation has antidepressant-like effects in mice potentially through the activation of antioxidative functions upon radon inhalation. This study aimed to investigate the effect of prior and post low-dose X-irradiation (0.1, 0.5, 1.0 and 2.0 Gy) on FST-induced immobility and oxidative stress in the mouse brain, and the differences, if any, between the two. Mice received X-irradiation before or after the FST repeatedly for 5 days. In the post-FST-irradiated group, an additional FST was conducted 4h after the last irradiation. Consequently, animals receiving prior X-irradiation (0.1 Gy) had better mobility outcomes than sham-irradiated mice; however, their levels of lipid peroxide (LPO), an oxidative stress marker, remained unchanged. However, animals that received post-FST X-irradiation (0.5 Gy) had better mobility outcomes and their LPO levels were significantly lower than those of the sham-irradiated mice. The present results indicate that 0.5 Gy X-irradiation after FST inhibits FST-induced immobility and oxidative stress in mice