Sensory regulation of stance-to-swing transition in generation of adaptive human walking: A simulation study

In this paper, we investigated sensory mechanisms to regulate the transition from the stance to swing phases in the generation of adaptive human bipedal walking based on a neuromusculoskeletal model. We examined the contributions of the sensory information from the force-sensitive afferents in the ankle extensor muscle and from the position-sensitive afferents from the hip, inspired by a neuro-mechanical simulation for the stepping of the hind legs of cats. Our simulation results showed that the sensory signals related to the force in the ankle extensor muscle make a larger contribution than sensory signals related to the joint angle at the hip to produce robust walking against disturbances, as observed in the simulation results of cat locomotion. This suggests that such a sensorimotor mechanism is a general property and is also embedded in the neuro-control system of human bipedal walking.     

Adaptive behavior in turning of an oscillator-driven biped robot

This paper concentrates on a biped robot’s turning behavior that consists of straight and curved walking and the transition between these two patterns. We investigate how a robot achieves adaptive walking during such turning by focusing on rhythm control and propose a locomotion control system that generates robot motions by rhythmic signals from internal oscillators and modulates signal generation based on touch sensor signals. First, we verify that the robot attains limit cycles of straight and curved walking by numerical simulations and hardware experiments. Second, we examine the transition between these walking patterns based on the basin of attraction of the limit cycles in numerical simulations. Finally, we verify whether the robot actually accomplishes transition and turning by hardware experiments. This paper clarifies that the robot establishes such turning motions by adequate modulation of walking rhythm and phase through interactions between the dynamics of its mechanical system, oscillators, and environment.

Synthesis of 0.4Pb(Mg1/3Nb2/3)O3–0.3Pb(Mg1/2W1/2)O3–0.3PbTiO3 Ceramics by Metal Alkoxide Method, and Its Dielectric Properties

0.4Pb(Mg_1/3Nb_2/3)O₃–0.3Pb(Mg_1/2W_1/2)O₃–0.3PbTiO₃+ x MgO ( x = 0 to 0.04) were prepared by a metal alkoxide method. The percent of perovskite phase of the calcined powders increased with increased calcination temperatures. About 89% of perovskite phase was obtained at 1050°C. The dielectric constant of the pellets fired at 1100°C was increased by the addition of 10 wt% excess Mg(OC₂H₅)₂ and had a maximum value of 7532 at 1 kHz.     

High-potential magnetic anisotropy of CoPtCr-SiO/sub 2/ perpendicular recording media

The magnetic anisotropy of CoPtCr-SiO/sub 2/ perpendicular recording media, including higher energy terms, was studied as a function of film composition and seed layer materials. All series of CoPtCr films with various Cr content, deposited on Ru seed layers, show maximum values of total anisotropy K/sub u/ at 25-30 at%Pt. The maximum value for CoPt(Cr=0) films reaches /spl sim/15/spl times/10/sup 6/ erg/cm/sup 3/. The addition of SiO/sub 2/ to the CoPtCr films reduces the grain K/sub u/, however the grain K/sub u/ maintains a large value of 8/spl times/10/sup 6/ erg/cm/sup 3/ even when 10at%SiO/sub 2/ is added to (Co/sub 90/Cr/sub 10/)/sub 80/Pt/sub 20/, for instance, which indicates the high-potential thermal stability. Theoretical calculations for media designs of 400 Gbits/in/sup 2/ revealed that the ratio of the high-energy anisotropy term K/sub u2/ to K/sub u1/(K/sub u/=K/sub u1/+K/sub u2/) is required to be 0.2-0.35 to enhance the energy barrier for the remanent state, without a notable change in switching field. The films deposited on Ru seed layers were found to show negligibly small K/sub u2/ values, however, the values of K/sub u1/ and K/sub u2/ vary significantly with the seed layer material used. K/sub u1/ decreases almost linearly as the K/sub u2/ value increases. It is concluded that CoPtCr films have a sufficient potential in the values of K/sub u1/ and K/sub u2/ for high-density perpendicular media.     

Experimental and simulation analysis of community structure of nitrifying bacteria in a membrane-aerated biofilm.

Until now, only few attempts have been made to assess biofilm models simulating microenvironments in a biofilm. As a first step, we compare the microenvironment observed in a membrane aerated biofilm (MAB) to that derived from a two-dimensional computational model with individual ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) embedded in a continuum EPS matrix. Gradients of oxygen were determined by means of microelectrodes. The change in nitrifying bacterial populations with the biofilm depth was quantified using fluorescence in situ hybridization (FISH) in combination with a confocal laser scanning microscopy (CLSM). Microelectrode measurements revealed that oxic and anoxic or anaerobic regions exist within the MAB. The oxygen profile predicted by the model showed good agreement with that obtained by microelectrode measurements. The oxic part of the biofilm was dominated by NSO190 probe-hybridized AOB, which formed relatively large clusters of cells directly on the membrane surface, and by the NOB belonging to genus Nitrobacter sp. On the other hand, NOB belonging to genus Nitrospira sp. were abundant at the oxic-anoxic interface. The model prediction regarding AOB and Nitrobacter sp. distribution was consistent with the experimental counterpart. Measurements of AOB cluster size distribution showed that colonies are slightly larger adjacent to the membrane than at the inner part of the biofilm. The sizes predicted by the current model are larger than those obtained in the experiment, leading to the arguments that some factors not contained in the model would affect the cluster size.     

GDNF administration induces recovery of the nigrostriatal dopaminergic system both in young and aged parkinsonian mice

Glial cell line-derived neurotrophic factor (GDNF) is a member of the transforming growth factor beta superfamily and acts as a neurotrophic factor for the nigrostriatal dopaminergic system. GDNF was injected stereotaxically into the striatum of young (2 months old) and aged (12 months old) C57BL/6 mice that were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) 1 week earlier. Immunocytochemical and neurochemical analyses showed significant recovery of the nigrostriatal dopaminergic system both in young and in aged mice. Since Parkinson's disease is a neurodegenerative disorder mainly affecting elderly people, this result demonstrates the potential usefulness of GDNF in treating Parkinson's disease.