Performance Test of Gamma-ray Burst Polarimeter for Small Satellite (12H308)

We have been developing Gamma-Ray Burst (GRB) polarimeter for small tellite. The polarimeter consists of plastic scintillator and inorganic scintillator such as CsI(Tl), GSO(Ce), GYSO(Ce), or GAGG(Ce). To investigate the optimum rganic scintillator, we have compared the characteristics of the spallation for four kinds of scintillator, using 150 MeV proton beam in HIMAC. After irradiation of about 10 krad, we measured the background pulse height spectrum of each scintillator in the cave of lead for three months. As the results, we confirmed that the unting rate of the background for the GAGG scintillator is the lowest of the four afterone month of the irradiation. Then we decided to adopt the GAGG as the sorber of the GRB polarimete

Inverse Bayesian inference in swarming behaviour of soldier crabs

Animals making a group sometimes approach and sometimes avoid a dense area of group mates, and that reveals the ambiguity of density preference. Although the ambiguity is not expressed by a simple deterministic local rule, it seems to be implemented by probabilistic inference that is based on Bayesian and inverse Bayesian inference. In particular, the inverse Bayesian process refers to perpetual changing of hypotheses. We here analyse a time series of swarming soldier crabs and show that they are employed to Bayesian and inverse Bayesian inference. Comparing simulation results with data of the real swarm, we show that the interpretation of the movement of soldier crabs which can be based on the inference can lead to the identification of a drastic phase shift-like transition of gathering and dispersing. This article is part of the theme issue ‘Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)’.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Supporting data for "Interaction between path integration and visual orientation during the homing run of fiddler crabs"

This file contains the raw data (x-y coordinates of true burrows, fake entrances and crabs)

Emergent runaway into an avoidance area in a swarm of soldier crabs.

Emergent behavior that arises from a mass effect is one of the most striking aspects of collective animal groups. Investigating such behavior would be important in order to understand how individuals interact with their neighbors. Although there are many experiments that have used collective animals to investigate social learning or conflict between individuals and society such as that between a fish and a school, reports on mass effects are rare. In this study, we show that a swarm of soldier crabs could spontaneously enter a water pool, which are usually avoided, by forming densely populated part of a swarm at the edge of the water pool. Moreover, we show that the observed behavior can be explained by the model of collective behavior based on inherent noise that is individuals' different velocities in a directed group. Our results suggest that inherent noise, which is widely seen in collective animals, can contribute to formation and/or maintenance of a swarm and that the dense swarm can enter the pool by means of enhanced inherent noise

Estimating the radiative activation characteristics of a Gd3Al2Ga3O12:Ce scintillator in low earth orbit

Gd3Al2Ga3O12:Ce (GAGG:Ce) is a recently developed inorganic scintillator. With excellent characteristics of high density and high light yield, GAGG:Ce could be potentially applied as a gamma-ray detector for astrophysical experiments on satellite missions. We report the characteristics of GAGG:Ce for radiation dose by irradiating 150 MeV protons up to 100 Gy, as compared with GSO:Ce, CsI:Tl and GYSO:Ce scintillators. We investigated the radio-activated intrinsic background count rates due to spallation within an energy range of 30–400 keV for each scintillator, and then estimated the background count rates for a satellite experiment conducted in low earth orbit. The results showed that the background count rate of GAGG:Ce was the lowest per day or in a longer timescale than the other scintillators