64 research outputs found

    139^{139}La-NMR study of spin-dynamics coupled with hole mobility in TT*-type La0.86_{0.86}Eu0.86_{0.86}Sr0.28_{0.28}CuO4δ_{4-\delta}

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    In TT*-type cuprate oxides with five oxygen coordination, little is known about the relationship between the spin correlations and dope carriers. We performed 139^{139}La-nuclear magnetic resonance (NMR) and electrical resistivity measurements on an as-sintered (AS) and oxidation annealed (OA) polycrystalline TT*-type La0.86_{0.86}Eu0.86_{0.86}S0.28_{0.28}CuO4_4 (LESCO) to investigate its magnetic and superconducting (SC) properties. Upon cooling, the NMR spectrum of AS LESCO broadened below 3 K, at which the nuclear spin-lattice relaxation rate 1/T11/T_1 against the temperature exhibited a maximum, thereby indicating the appearance of static magnetism. The temperature dependence of 1/T11/T_1 between 3 K and 20 K was similar to that of the resistivity displaying the semiconducting behavior. Furthermore, the energy scale of the transport gap and spin-dynamics estimated was found to be comparable. These results suggest a close connection between the mobility of the doped carriers and low-energy spin-dynamics, as reported for lightly doped TT-type La2x_{2-x}Srx_xCuO4_4. In the OA SC sample, we confirmed the absence of a magnetic order and the Korringa relation above 10 K. Therefore, in the TT*-type LESCO with xx = 0.28, the magnetic state coupled with holes drastically turns to the weakly correlated metallic state by oxidation annealing.Comment: 6 pages, 6 figure

    On invariant 2x2 \beta-ensembles of random matrices

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    We introduce and solve exactly a family of invariant 2x2 random matrices, depending on one parameter \eta, and we show that rotational invariance and real Dyson index \beta are not incompatible properties. The probability density for the entries contains a weight function and a multiple trace-trace interaction term, which corresponds to the representation of the Vandermonde-squared coupling on the basis of power sums. As a result, the effective Dyson index \beta_{eff} of the ensemble can take any real value in an interval. Two weight functions (Gaussian and non-Gaussian) are explored in detail and the connections with \beta-ensembles of Dumitriu-Edelman and the so-called Poisson-Wigner crossover for the level spacing are respectively highlighted. A curious spectral twinning between ensembles of different symmetry classes is unveiled. The proposed technical tool more generically allows for designing actual matrix models which i) are rotationally invariant; ii) have a real Dyson index \beta_{eff}; iii) have a pre-assigned confining potential or alternatively level-spacing profile. The analytical results have been checked through numerical simulations with an excellent agreement. Eventually, we discuss possible generalizations and further directions of research.Comment: Minor modifications. Published versio

    Asymmetric Adaptability to Temporal Constraints Among Coordination Patterns Differentiated at Early Stages of Learning in Juggling

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    In this study, we examined the degree of adaptability to new constraints after learning of a fundamental skill in juggling. Adaptation of sensorimotor synchronization with the various constraints is important for expertise. However, this adaptability may not be equivalent between coordination patterns which learners acquired in the previous learning process. In other words, there may be “asymmetric” adaptability among intrinsic patterns. Then, we examined the influence of intrinsic patterns on the adaptation of sensorimotor synchronization according to various temporal constraints. To set the adaptation task, experiment 1 was designed to examine the relationship between tempo and coordination pattern for expert jugglers. Based on experiment 1, juggling in accordance with the tempo change was performed as adaption task in experiment 2, and we compared the performances of the jugglers from the viewpoint of the intrinsic pattern. In experiment 1, participants performed juggling by adjusting catch timing to beep timing in ten conditions with the interval from 260 to 620 ms in steps of 40 ms. Results of experiment 1 presented that when the juggling tempo is fast, the coordination pattern with “rhythmic” frequency characteristics appeared. By contrast, when the tempo is slow, the coordination pattern with “discrete” frequency characteristics appeared. That is, jugglers should switch their coordination patterns when performing under various tempo conditions. In experiment 2, we compared the adaptability to perform juggling under temporal constraints among intermediate jugglers who have different intrinsic coordination patterns acquired through a previous learning process. The adaptation task required participants to adjust their catch timing to a gradually changing tempo. Participants performed juggling under two conditions: gradually ascending and descending tempo ranging from 300 to 600 ms. The results of experiment. 2 showed that participants who had a discrete pattern showed a significantly better adaptation than participants who had a rhythmic pattern. Furthermore, this result of adaptation was not related to juggling experience. This suggests that an intrinsic pattern characterized by different frequency characteristics has the different adaptability to sensorimotor synchronization tasks. Collectively, the degree of adaptability was dependent on the pattern acquired in the early stages of learning

    Numerical and experimental studies on circulation of working fluid in liquid droplet radiator

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    A model of the circulation of the working fluid in a liquid droplet radiator has been developed. The model is based on Bernoulli's law and the loss of the hydraulic head. The behavior of the circulation of the working fluid calculated from the model is compared with that obtained from experiments in the case that the flow rate of the circulating working fluid is changed. In radiators, the flow rate of the circulating working fluid is changed in order to match the change of the waste heat generated in large-space structures. The flow rates of the circulating working fluid calculated from the model correspond to those obtained from the experiments well. The circulation mechanism of the working fluid in the liquid droplet radiator has been clarified. The model developed in the present work will allow us to control the flow rate of the working fluid in the liquid droplet radiator automatically.Space for Inspiration of Humankind, Selected Proceedings of the 56th International Astronautical Federation Congress, Fukuoka, Japan, 17-21 October 200
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