2,615 research outputs found

    Determination of Boundary Scattering, Intermagnon Scattering, and the Haldane Gap in Heisenberg Chains

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    Low-lying magnon dispersion in a S=1 Heisenberg antiferromagnetic (AF) chain is analyzed using the non-Abelian DMRG method. The scattering length aba_{\rm b} of the boundary coupling and the inter-magnon scattering length aa are determined. The scattering length aba_{\rm b} is found to exhibit a characteristic diverging behavior at the crossover point. In contrast, the Haldane gap Δ\Delta, the magnon velocity vv, and aa remain constant at the crossover. Our method allowed estimation of the gap of the S=2 AF chain to be Δ=0.0891623(9)\Delta = 0.0891623(9) using a chain length longer than the correlation length ξ\xi.Comment: 6 pages, 3 figures, 1 table, accepted in Phys. Rev.

    Recent biotelemetry research on lacustrine salmon homing migration

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    One of the most interesting aspects of the salmon\u27s life history and the most challenging to study is the homing migration during which the fish return from their oceanic feeding grounds to the natal river to spawn. However, because of the difficulties encountered in studying the movements of fish, particularly in the sea, there is still very little information regarding this phase in the life cycle of the salmon. Lake Toya in Hokkaido, Japan supports populations of both lacustrine sockeye salmon (Onchorynchus nerka) and masu salmon (O. masou). The lake provides an ideal model for an "oceanic system" where the physiological and behavioral basis of the homing migrations of salmon can be studied. Previously a number of studies have been undertaken in Lake Toya using biotelemetry techniques to investigate and describe the homing migratory behavior of mature and sockeye salmon. The three principal biotelemetry techniques that have been utilized include ultrasonic telemetry, electromyographic telemetry and micro data logging telemetry. Each of these techniques has been shown to have advantages and disadvantages in describing the movements of adult salmon. Therefore, it was decided to combine all three techniques in a single system and develop a robotic tracking platform (robot boat) that encompassed three interrelated telemetry systems, acoustic telemetry, a signal processing system and a telecommunication system for transmission of data between the boat and a land based station. This review describes the new technology that has provided the opportunity to investigate the physiological and behavioral basis of salmon homing migration using the unique Lake Toya lacustrine salmon model

    Current Issues in Dementia and Dementia Care in Japan

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    Current issues in dementia and dementia care in East Asi