University of Tsukuba

About: University of Tsukuba is a education organization based out in Tsukuba, Ibaraki, Japan. It is known for research contribution in the topics: Population & Gene. The organization has 36352 authors who have published 79483 publications receiving 1934752 citations. The organization is also known as: Tsukuba daigaku & Tsukuba University.

Control method of robot suit HAL working as operator's muscle using biological and dynamical information

Abstract: For assisting human motion, assistive devices working as muscles would be useful. A robot suit HAL (hybrid assistive limb) has been developed as an assistive device for lower limbs. Human can appropriately produce muscle contraction torque and control joint viscoelasticity by muscle effort such as co-contraction. Thus, to implement functions equivalent to human muscles using HAL, it is necessary to control viscoelasticity of HAL as well as to produce torque in accordance with operator's intention. Therefore the purpose of this study is to propose a control method of HAL using biological and motion information. In this method, HAL produces torque corresponding to muscle contraction torque by referring to the myoelectricity that is biological information to control operator's muscles. In addition, the viscoelasticities of HAL are adjusted in proportion to operator's viscoelasticity that is estimated from motion information by using an on-line parameter identification method. To evaluate the effectiveness of the proposed method, the method was applied to a swinging motion of a lower leg. When this method was applied, HAL could work like operator's muscles in the swinging motion, and as a consequence, the muscle activities of the operator were reduced. As a result of this experiment, we confirmed the effectiveness of the proposed method.

Behavioral State Instability in Orexin Knock-Out Mice

Abstract: Narcolepsy is caused by a lack of orexin (hypocretin), but the physiologic process that underlies the sleepiness of narcolepsy is unknown. Using orexin knock-out (KO) mice as a model of narcolepsy, we critically tested the three leading hypotheses: poor circadian control of sleep and wakefulness, inadequate activation of arousal regions, or abnormal sleep homeostasis. Compared with wild-type (WT) littermates, orexin KO mice had essentially normal amounts of sleep and wake, but wake and non-rapid eye movement (NREM) bouts were very brief, with many more transitions between all behavioral states. In constant darkness, orexin KO mice had normal amplitude and timing of sleep-wake rhythms, providing no evidence for disordered circadian control. When placed in a new, clean cage, both groups of mice remained awake for approximately 45 min, demonstrating that, even in the absence of orexin, fundamental arousal regions can be engaged to produce sustained wakefulness. After depriving mice of sleep for 2-8 hr, orexin KO mice recovered their NREM and rapid eye movement sleep deficits at comparable rates and to the same extent as WT mice, with similar increases in EEG delta power, suggesting that their homeostatic control of sleep is normal. These experiments demonstrate that the fragmented wakefulness of orexin deficiency is not a consequence of abnormal sleep homeostasis, poor circadian control, or defective fundamental arousal systems. Instead, the fragmented behavior of orexin KO mice may be best described as behavioral state instability, with apparently low thresholds to transition between states.

Observation of the DsJ(2317) and DsJ(2457) in B Decays

Abstract: We report the first observation of the B-->(D) over barD(sJ)(2317) and B-->(D) over barD(sJ)(2457) decays based on 123.8x10(6) B (B) over bar events collected with the Belle detector at KEKB. We observe the D-sJ(2317) decay to D(s)pi(0) and the D-sJ(2457) decay to the D(s)(*)pi(0) and D(s)gamma final states. We also set 90% C.L. upper limits for the decays D-sJ(2317)-->D-s*gamma, D-sJ(2457)-->D-s*gamma, D-sJ(2457)-->D(s)pi(0), and D-sJ(2457)-->D(s)pi(+)pi(-).

Martensitic transformation and shape memory behavior in sputter-deposited TiNi-base thin films

Abstract: Since 1990, TiNi and TiNiX (X=Cu, Pd, Hf) thin films have been made by sputtering The motivation for fabricating sputter-deposited TiNi-base shape memory alloy thin films originates from the great demand for the development of powerful microactuators which can drive micromachines, because actuation force and displacement are greatest in shape memory alloys amongst many actuator materials Stable shape memory effect and superelasticity, which are equivalent to those of bulk alloys, have been achieved in the sputter-deposited TiNi thin films Narrow transformation temperature hysteresis and high transformation temperatures were also achieved in TiNiCu and TiNi(Pd or Hf) thin films, respectively In the meantime, unique microstructures consisting of nonequilibrium nanoscale precipitates and nonequilibrium compositions in the matrix have been found in Ti-rich TiNi thin films which were fabricated from amorphous condition by annealing at a considerably low temperature Several micromachining processes have been proposed to fabricate some prototypes of microactuators utilizing TiNi thin films The present paper will review the recent development of the above mentioned topics relating to sputter-deposited TiNi-base shape memory alloy thin films

Extremely high stability of glutathionate-protected Au25 clusters against core etching.

Abstract: It is well known that so-called magic-numbered clusters can be preferentially populated by dissociative excitation of larger precursors, because the energy required for removal of a single atom from a magic-numbered cluster is higher than from a neighbor. Thus, if the Au atoms can be removed sequentially from preformed thiolated-protected gold (Au:SR) clusters, one can anticipate a population growth of certain stable Aun:SR clusters. Chemical etching by free thiols is one feasible method for core size reduction of the Au:SR clusters. The etching rate of Aun:SR clusters must be determined as a function of core size, in order to provide a synthesis for welldefined Aun(SR)m clusters in large quantity, as well as to provide information regarding the stability of Aun(SR)m. In the present paper, we studied etching reactions of Aun(SG)m clusters with (n,m) = (10,10), (15,13), (18,14), (22,16), (25,18), (29,20), (33,22), (39,24) by free glutathione (GSH). It was found that Au25:SG clusters show higher stability against etching than the others and as a result two different reaction modes are operative depending on the core size. The Aun(SG)m (n < 25) clusters are completely oxidized to Au(I):SG complexes while Aun(SG)m (n ≥ 25) clusters are etched into Au25: SG by free GSH molecules. On the basis of this observation, a model is proposed to explain our recent finding that Au25 (SG)18 clusters are selectively formed during the reaction of triphenylphosphine-stabilized Au11 clusters and an excess amount of GSH.