521 research outputs found
Interactive Restless Multi-armed Bandit Game and Swarm Intelligence Effect
We obtain the conditions for the emergence of the swarm intelligence effect
in an interactive game of restless multi-armed bandit (rMAB). A player competes
with multiple agents. Each bandit has a payoff that changes with a probability
per round. The agents and player choose one of three options: (1)
Exploit (a good bandit), (2) Innovate (asocial learning for a good bandit among
randomly chosen bandits), and (3) Observe (social learning for a good
bandit). Each agent has two parameters to specify the decision:
(i) , the threshold value for Exploit, and (ii) , the probability
for Observe in learning. The parameters are uniformly
distributed. We determine the optimal strategies for the player using complete
knowledge about the rMAB. We show whether or not social or asocial learning is
more optimal in the space and define the swarm intelligence
effect. We conduct a laboratory experiment (67 subjects) and observe the swarm
intelligence effect only if are chosen so that social learning
is far more optimal than asocial learning.Comment: 18 pages, 4 figure
Technical Efficiency, Regulation, and Heterogeneity in Japanese Airports
In this paper, the random stochastic frontier model is used to estimate the technical efficiency of Japanese airports taking into regulation and heterogeneity in the variables. The airports are ranked according to their productivity for the period 1987 to 2005 and homogenous and heterogeneous variables in the cost function are disentangled. Policy implication is derived.Japan; airports; efficiency; random frontier models; policy implications
Universal Scaling Bounds on a Quantum Heat Current
We derive new bounds on a heat current flowing into a quantum -particle
system coupled with a Markovian environment. By assuming that a system
Hamiltonian and a system-environment interaction Hamiltonian are extensive in
, we show that the absolute value of the heat current scales at most as
in a limit of large . Also, we present an example that
saturates this bound in terms of scaling: non-interacting particles globally
coupled with a thermal bath. However, the construction of such system requires
many-body interactions induced by the environment, which may be difficult to
realize with the current technology. To consider more feasible cases, we focus
on a class of system where any non-diagonal elements of the noise operator
(derived from the system-environment interaction Hamiltonian) become zero in
the system energy basis, if the energy difference is beyond a certain value
. Then, for , we derive another scaling
bound on the absolute value of the heat current, and the
so-called superradiance belongs to a class to saturate this bound. Our results
are useful to evaluate the best achievable performance of quantum-enhanced
thermodynamic devices, which contain far-reaching applications for such as
quantum heat engines, quantum refrigerators and quantum batteries.Comment: 6+18 pages, 2+2 figure
Anti-invasive activity of α-tocopherol against hepatoma cells in culture via protein kinase C inhibition
Effects of α-, β-, γ- and δ-tocopherols on the proliferation and invasion of AH109A hepatoma cells and their modes of action were investigated. Four tocopherols inhibited the invasion as well as the proliferation of AH109A cells. Their inhibitory effects were more prominent on the invasion than on the proliferation. At 1 µM, α-tocopherol showed most potent anti-invasive activity without any influence on the proliferation. We have previously demonstrated that reactive oxygen species increase the invasion of AH109A cells. α-Tocopherol suppressed the reactive oxygen species-induced invasion but failed to suppress the reactive oxygen species-induced rises in intracellular peroxide level. GF 109203X, a protein kinase C inhibitor, decreased the invasive activity of AH109A cells. In contrast, phorbol-12-myristate-13-acetate, a protein kinase C activator, increased the invasive capacity of AH109A cells. α-Tocopherol suppressed the phorbol-12-myristate-13-acetate-induced increase in the invasion, and canceled the phorbol-12-myristate-13-acetate-induced rises in protein kinase C activity and phosphorylation of extracellular signal-regulated kinase. These results suggest that tocopherols, especially α-tocopherol, possess inhibitory effect more strongly on the invasion of AH109A cells than on the proliferation. They also suggest that the anti-invasive activity of α-tocopherol is raised through suppression of PKC/ERK signaling
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