Adaptation mechanism of interlimb coordination in human split-belt treadmill walking through learning of foot contact timing: a robotics study

Human walking behaviour adaptation strategies have previously been examined using split-belt treadmills, which have two parallel independently controlled belts. In such human split-belt treadmill walking, two types of adaptations have been identified: early and late. Early-type adaptations appear as rapid changes in interlimb and intralimb coordination activities when the belt speeds of the treadmill change between tied (same speed for both belts) and split-belt (different speeds for each belt) configurations. By contrast, late-type adaptations occur after the early-type adaptations as a gradual change and only involve interlimb coordination. Furthermore, interlimb coordination shows after-effects that are related to these adaptations. It has been suggested that these adaptations are governed primarily by the spinal cord and cerebellum, but the underlying mechanism remains unclear. Because various physiological findings suggest that foot contact timing is crucial to adaptive locomotion, this paper reports on the development of a two-layered control model for walking composed of spinal and cerebellar models, and on its use as the focus of our control model. The spinal model generates rhythmic motor commands using an oscillator network based on a central pattern generator and modulates the commands formulated in immediate response to foot contact, while the cerebellar model modifies motor commands through learning based on error information related to differences between the predicted and actual foot contact timings of each leg. We investigated adaptive behaviour and its mechanism by split-belt treadmill walking experiments using both computer simulations and an experimental bipedal robot. Our results showed that the robot exhibited rapid changes in interlimb and intralimb coordination that were similar to the early-type adaptations observed in humans. In addition, despite the lack of direct interlimb coordination control, gradual changes and after-effects in the interlimb coordination appeared in a manner that was similar to the late-type adaptations and after-effects observed in humans. The adaptation results of the robot were then evaluated in comparison with human split-belt treadmill walking, and the adaptation mechanism was clarified from a dynamic viewpoint.     

16S rRNA pyrosequencing-based investigation of the bacterial community in nukadoko, a pickling bed of fermented rice bran

Nukadoko is a naturally fermented rice bran mash traditionally used for pickling vegetables in Japan; its refreshment and fermentation cycles sometimes continue for many years. Here, we investigated the structure and dynamics of the bacterial community in nukadoko by conducting pyrosequencing and quantitative polymerase chain reaction (PCR) analyses of 16S ribosomal RNA genes (rDNA). Of the 16 different samples studied, 13 showed Lactobacillus-dominated microbiota, suggesting that aged nukadoko samples tend to realize a niche, favorable Lactobacillus species. The lactic acid bacterial community of each of the 16 samples was classified into 3 types according to the presence or absence of 2 predominant species, Lactobacillus namurensis and Lactobacillus acetotolerans. The dynamics of the bacterial community during fermentation and the subsequent ripening process were examined using a laboratory model of nukadoko inoculated with an aged nukadoko sample (inoculated model). Lb. namurensis grew rapidly in the first 2 days, accompanied with a rapid decrease in pH and an increase in lactate levels, while Lb. acetotolerans grew with a longer doubling time and slow acidification during the 20 days after inoculation. On the other hand, spontaneous fermentation of the nukadoko model prepared from fresh rice bran without the nukadoko inoculation (inoculant-free model), showed the growth of some non-Lactobacillus species such as staphylococci and bacilli within the first 10 days; thereafter, Lb. namurensis was dominant, while Lb. acetotolerans was not detected during the 20-day experimental period. These results suggest that the naturally established Lactobacillus community in aged nukadoko is effectively involved in the biocontrol of the microbial community of nukadoko during the refreshment and fermentation cycles.     

Evaluation of hydrogen-assisted cracking behavior of low-alloy steel in the range 95 °C to 350 °C

In this report, hydrogen-assisted cracking (HAC) behavior of low-alloy steel was evaluated using a constant elongation rate tensile test, and the temperature and crack tip strain rate effects were observed. It was found that temperature dependence of the threshold condition (C _σm ^c ) of HAC above about 100 °C followed the relation C _σm ^c = Kexp(−41,300/Rr) whereK is a constant andT is absolute temperature. The relationship between HAC growth rate and crack tip strain rate was established as almost linear, irrespective of temperature and hydrogen concentration at the crack tip. Hydrogen heat release tests were also performed. From these tests, formation and growth of microcracks which are trap sites of hydrogen were thought to be the mechanism of HAC in the steel. From this mechanism, HAC behavior of the low-alloy steel could be qualitatively explained.     

A stacked-CMOS cell technology for high-density SRAM's

A stacked-CMOS SRAM cell technology for high-density SRAMs has been developed. It has been found that the increase of the on-current of the thin-film transistor (TFT) load leads not only to the increase of the cell noise margin, but also to the reduction of the cell area. The improvement of the electrical characteristics of the TFT load has been achieved by enlarging the grains of the polysilicon film through the use of a novel solid-phase growth technique. As a result, TFT loads with on/off current ratio of 10⁵ and off-current of 0.07 pA/μm, both promising for high-density SRAMs, have been obtained     

Electron-transfer function of NAD+-immobilized alginic acid

Polymerized NAD+ (Alg-NAD+) was prepared and its electrochemical properties were investigated. NAD+ has been covalently immobilized at the carboxyl group of alginic acid using water soluble carbodiimide (EDC) and then Alg-NAD+s of various NAD+ density were obtainable depending on NAD+ concentration in the reaction mixture. Absorbance of 260 nm of Alg-NAD+s showed that 3.4 to 17.6% of carboxyl groups of alginic acid were coupled with NAD+. The coenzyme activity of immobilized NAD+ has reached 80 to 90% on each Alg-NAD+. A cathodic peak in the cyclic voltammogram of Alg-NAD+ appeared at -1.2 V (vs. SCE) corresponding to the reduction wave of free NAD+. The anodic wave of NAD dimer was not observed in the presence of 2.0 mM methyl viologen and 5 units of diaphorase and NAD+ immobilized on the composite electrode could be reduced to the normal NADH. The ratio of apparent diffusion coefficient (Dapp.) of Alg-NAD+ and free NAD+ was evaluated from the variation of ipc with the square root of sweep rate (v 1/2). Despite the high molecular weight of Alg-NAD+, Dapp. Alg-NAD+/Dapp. free NAD+ are larger than that expected. These results indicate that electron transfer occurred effectively between each NAD+ molecule immobilized onto the polymer chain. It is also confirmed by a conjugated redox enzyme reaction with Alg-NAD+.     

Improvement of diamond X-ray mask membrane: Optical transmittance, surface roughness and irradiation durability

A viable method for the improvement of the polycrystalline diamond X-ray mask membrane is proposed. The use of an ionized cluster beam yields the smoothest surface. Sol-gel planarization film coating with indium tin oxide is the most effective method for obtaining high optical transmittance without sacrificing high synchrotron irradiation durability.