Ryosuke Tajima

Building Spined Muscle-Tendon Humanoid

Human can perform variety of limber whole-body motions using numerous muscles and huge number of various sensors. The human brain has all the connections to the sensors and muscles, and learn how to manage them for whole-body motions. In this research, we have aimed to build a complex body with physically massive parallel sensor-motor systems to enter the next stage for studying humanoid brain systems. It is designed to have a flexible spined torso and a whole-body with fully muscle-tendon driven systems. In this paper the design and implementation of the first model of the humanoid is described with some experiments.

A new “zero-strain” material for electrochemical lithium insertion

A new “zero-strain” system, spinel Li1+xRh2O4, is found as an insertion material for lithium ions. A very small volume change of ca. 0.5% is observed in the two-phase reaction process. The “zero-strain” behavior is likely induced by itinerant t2g electrons with a suppressed Jahn–Teller effect.

Nitrogen-fixing activity of root nodules in relation to their size in peanut (Arachis hypogaea L.)

Abstract The nitrogen-fixing activity of root nodules was examined with reference to the nodule size in peanut. Root nodules of field-grown peanut were collected at flowering through harvesting stages and classified into five groups of size using a circle template. Then acetylene reduction activity was measured to evaluate nitrogen-fixing activity for respective size groups. In addition, the diameter of the cross-section of each root nodule and rhizobium-infected areas on the cross-section were measured. The results showed that the nitrogen-fixing activity of root nodules is closely related with their size. In the root nodules in the medium size group (1.5− 2.0 mm in diameter), nitrogen-fixing activity per unit fresh weight of nodule was highest at the flowering stage and rapidly decreased thereafter. The nitrogen-fixing activity of root nodules larger than 2.0 mm in diameter did not vary significantly with their size. Colors of rhizobium-infected zones varied with their size: white in small nodules; red in medium-sized nodules; and greenish in larger nodules, which suggests that the concentration of leghemoglobin is highest in the medium-sized nodules. Nitrogen-fixing activities of the medium-sized nodules might determine the amount of nitrogen fixation in the whole root system during pod-filling because medium-sized nodules had high activity and were large in number. Classification of root-nodule size based on the circle template is a simple, rapid, and useful method to evaluate nitrogen-fixing activity of root nodules.

Distribution Pattern of Root Nodules in Relation to Root Architecture in Two Leading Cultivars of Peanut (Arachis hypogaea L.) in Japan

Abstract To effectively utilize symbiotic nitrogen fixation, we examined the formation of root nodules along with root system development in two leading peanut cultivars in Japan, Chibahandachi and Nakateyutaka. Differences in the number, size and distribution pattern of root nodules between the two cultivars are discussed in relation to their root architecture. Many root nodules are formed on the 1st-order lateral roots in the peanut. The difference between the two cultivars in the number of nodules on the 1st–order lateral roots and the diameter of the 1st-order lateral roots at the basal part of the taproot increased during secondary thickening period. Those changes were significantly greater in Chibahandachi than in Nakateyutaka at later growth stages. Chibahandachi had fewer, but larger nodules than those in Nakateyutaka. In Nakateyutaka, a larger number of new nodules were formed on the lateral roots at the middle part of the taproot than in Chibahandachi. This suggests that in Chibahandachi nodules grow for a longer period during plant growth, and in Nakateyutaka new nodules are formed even at late stages of plant growth. In addition, there appears to be an optimal diameter of the 1st-order lateral roots for nodulation at each growth stage.

Root Anatomical Responses to Waterlogging at Seedling Stage of Three Cordage Fiber Crops

Waterlogging tolerance of tropical cordage fiber crops is an important agricultural subject in northeast Thailand, because they are often grown in dry-wet transition period as pre-rice crops. Since root anatomical characteristics are often considered to be important traits determining waterlogging tolerance of plants, we examined root anatomy of three fiber crops that are different in waterlogging tolerance one another. Seedlings of three cordage fiber crops, Hibiscus cannabinus (kenaf, cv. KhonKaen60), Hibiscus sabdariffa (roselle, Thai kenaf, cv. NonSoong2) and Corchorus olitorius (jute, cv. KhonKaen1), were grown in tall beakers of 1000 ml vermiculite with 40% v/v (control) and 80% v/v (waterlogging) water contents. It is known that the H. cannabinus cultivar is tolerant to waterlogging while other two species (C. olitorius, H. sabdariffa) cultivars are sensitive to waterlogging from soil-grown pot experiments in northeast Thailand. Ten days after sowing, freehand cross-sections of taproot (i.e., primary root) were made with 1 cm increments from the root tip along root axis followed by staining by toluidine blue O (0.01%) for light and fluorescence microscopy. Only H. cannabinus formed aerenchyma in cortex of the taproot under waterlogging condition. The aerenchyma of waterlogged H. cannabinus first appeared at 3 cm from the root tip and developed up to the base of taproot. The formation of aerenchyma in H. cannabinus roots may contribute to the waterlogging tolerance. Casparian bands were found in both endodermis and exodermis of taproot in all the three species. However, formation of exodermal Casparian bands was not stable, and they were restricted to the basal part of taproot in H. sabdariffa and C. olitorius. Waterlogging treatment suppressed formation of Casparian bands, particularly in exodermis.

Synthesis of Bi2223 by Low

Silver-sheathed Bi(Pb)2223 tapes have been developed as the first-generation high-Tc superconducting material. Generally, a long-time sintering condition exceeding 100 h at 830 ~ 845 °C in PO2 ~ 0.08 atm has been fixed for more than 20 years to prepare Bi(Pb)2223. In addition, there are few studies on the optimization of PO2 during sintering. In the present study, a low PO2(= 0.02 ~ 0.03 atm) synthesis was applied for fabrication of the Bi(Pb)2223 bulks and tapes. The silver-sheathed Bi(Pb)2223 tapes were prepared by sintering under various conditions including hot isostatic pressing treatment. Fine Bi(Pb)2223 grains were observed in the samples when the first sintering was performed in PO2 ~ 0.02 atm. This led to densification of oxide core by second sintering using hot isostatic pressing treatment (Ptotal = 100 atm), resulting in improvements of sharpness of superconducting transition and Ic at 77 K.

P_{{\rm O}2}

ABSTRACT Poor response of rice to phosphorus (P) fertilization and low phytoavailability of soil P have been reported in sandy rainfed fields in northeast Thailand. In order to evaluate the effects of mild soil drying on the uptake of P by rainfed lowland rice, we carried out nutrient omission trials for nitrogen (N) and P at Ubon Ratchathani Rice Research Center under rainfed and flooded conditions. The surface soil was classified as sandy loam. To avoid severe soil drying and drought stress in the rainfed field, soil water potential at a depth of 20 cm was maintained at the field capacity (> −20 kPa) by flush irrigation. The effects of flooding and drying on the soil properties were also evaluated in the laboratory using soils with diverse textures in and around the center. In the field experiments, the above-ground biomass of rice plants (RD6) did not respond significantly to P fertilization in the rainfed field, although it responded positively to N fertilization. Root length in the surface 10 cm under the rainfed condition was significantly smaller than that under the flooded condition due partly to the increased soil hardness upon drying, but this could not quantitatively explain the large discrepancy of P uptake observed between the rainfed and flooded conditions. Under the rainfed condition, the P uptake did not increase significantly, even when the concentration of soil Bray P was tripled by transferring the surface soil from the flooded to the rainfed field. From the laboratory experiments, it was further suggested that soil P was supplied mainly by diffusion and that the effective diffusion coefficient for P can become less than one-tenth of the value in the flooded field when the sandy soil with clay at around 10% dried to −100 kPa. Our results suggest that the uptake of P by the rainfed lowland rice grown in sandy soil can be limited physically by mild soil drying that reduces the supply of P to roots by diffusion rather than the chemical extractability of soil P.

Sintering

Abstract Digital images for determining root traits have been analyzed using WinRHIZO, commercial software. A freeware ImageJ has been developed for the analysis but whether root lengths assigned to root diameter classes obtained by this method correspond to those estimated by WinRHIZO has not been confirmed. In this study, root lengths estimated using ImageJ were compared with those estimated using WinRHIZO. In ImageJ, the root lengths were estimated using a triangle thresholding algorithm that was valid for total root length in our previous study. For the small-diameter classes (<0.5 mm), the estimates obtained using ImageJ and the conversion factor 2/3, corresponded closely to the estimates obtained using WinRHIZO. For large-diameter classes (>0.5 mm), root lengths estimated using ImageJ were similar to those obtained using WinRHIZO without using the conversion factor. These results were valid for rice roots. In this report, we propose completely automated estimation of root lengths for roots in each diameter class by using ImageJ.

Mild drying of sandy soil can physically limit the uptake of phosphorus by rainfed lowland rice in northeast Thailand

This video demonstrates a one-legged robot which moves by repeating jumps. The motions having flight phases such as jumping or running are expected to expand the speed and stability of legged robots. A novel method of determining the Center of Mass (COM) and foot locations is proposed that is independent of the target robot actuators or assignments of joints, and suitable for building an on-line control system. Using the toe joint of the robot, the proposed method can reduce the angular velocities of the joints remarkably. This video includes an experiment to control of the direction, velocity and turning of the robot. In addition, the maximum vertical jumps which have 180[ms] flight phases are shown.