Daisuke Yamaguchi

Properties and physiological functions of UDP-sugar pyrophosphorylase in Arabidopsis.

UDP-sugar pyrophosphorylase catalyzes the conversion of various monosaccharide 1-phosphates to the respective UDP-sugars in the salvage pathway. Using the genomic database, we cloned a putative gene for UDP-sugar pyrophosphorylase from Arabidopsis. Although relatively stronger expression was detected in the vascular tissue of leaves and the pollen, AtUSP is expressed in most cell types of Arabidopsis, indicating a housekeeping function in nucleotide sugar metabolism. Recombinant AtUSP expressed in Escherichia coli exhibited broad specificity toward monosaccharide 1-phosphates, resulting in the formation of various UDP-sugars such as UDP-glucose, -galactose, -glucuronic acid, -xylose and -L-arabinose. A loss-of-function mutation in the AtUSP gene caused by T-DNA insertion completely abolished male fertility. These results indicate that AtUSP functions as a UDP-sugar pyrophosphorylase in the salvage pathway, and that the generation of UDP-sugars from monosaccharide 1-phosphates catalyzed by AtUSP is essential for pollen development in Arabidopsis.

Bifunctional cytosolic UDP-glucose 4-epimerases catalyse the interconversion between UDP-D-xylose and UDP-L-arabinose in plants

UDP-sugars serve as substrates in the synthesis of cell wall polysaccharides and are themselves generated through sequential interconversion reactions from UDP-Glc (UDP-glucose) as the starting substrate in the cytosol and the Golgi apparatus. For the present study, a soluble enzyme with UDP-Xyl (UDP-xylose) 4-epimerase activity was purified approx. 300-fold from pea (Pisum sativum L.) sprouts by conventional chromatography. The N-terminal amino acid sequence of the enzyme revealed that it is encoded by a predicted UDP-Glc 4-epimerase gene, PsUGE1, and is distinct from the UDP-Xyl 4-epimerase localized in the Golgi apparatus. rPsUGE1 (recombinant P. sativum UGE1) expressed in Escherichia coli exhibited both UDP-Xyl 4-epimerase and UDP-Glc 4-epimerase activities with apparent Km values of 0.31, 0.29, 0.16 and 0.15 mM for UDP-Glc, UDP-Gal (UDP-galactose), UDP-Ara (UDP-L-arabinose) and UDP-Xyl respectively. The apparent equilibrium constant for UDP-Ara formation from UDP-Xyl was 0.89, whereas that for UDP-Gal formation from UDP-Glc was 0.24. Phylogenetic analysis revealed that PsUGE1 forms a group with Arabidopsis UDP-Glc 4-epimerases, AtUGE1 and AtUGE3, apart from a group including AtUGE2, AtUGE4 and AtUGE5. Similar to rPsUGE1, recombinant AtUGE1 and AtUGE3 expressed in E. coli showed high UDP-Xyl 4-epimerase activity in addition to their UDP-Glc 4-epimerase activity. Our results suggest that PsUGE1 and its close homologues catalyse the interconversion between UDP-Xyl and UDP-Ara as the last step in the cytosolic de novo pathway for UDP-Ara generation. Alternatively, the net flux of metabolites may be from UDP-Ara to UDP-Xyl as part of the salvage pathway for Ara.

A study on temperature dependence of an ultrasonic motor for cryogenic environment

In this study, we have examined the temperature dependence of an ultrasonic motor for a cryogenic environment. When we use an ultrasonic motor at low temperatures, thermal stress is induced at the ultrasonic transducer owing to the difference in temperature. Thus, the preload for the transducer needs to be regulated for a cryogenic environment. By finite element method (FEM) analysis, we have simulated the thermal stress at piezoelectric elements of the transducer. We have designed the transducer consisting of a body and a nut made of SUS304, and a bolt made of titanium. We have fabricated and evaluated the transducer at temperatures from 4.5 to 293 K. To evaluate the temperature dependence of the relationship between the preload and the thermal stress, we have measured the clamping torque and admittance. The optimal clamping torque shows a low-temperature dependence from 4.5 to 293 K. We have also evaluated the performance of an ultrasonic motor of the transducer. The ultrasonic motor can be driven at temperatures from 4.5 to 293 K without the regulation of the preload of the transducer.

Proposal of lateral vibration control based on force detection in magnetic suspension system

A method of suppressing vibration in lateral directions is investigated based on varying stiffness strategy. A vertically controlled magnetic suspension system is often subjected to vibration in lightly damped lateral directions. In this paper, a novel approach is proposed to detect the lateral displacement of such magnetic suspension system, and how this displacement can be used to reduce vibration by varying stiffness control is presented. The principle of edge effect is applied to detect the lateral displacement in a magnetic suspension system operated in differential mode. A switching stiffness control and a modified control strategies are used to vary the stiffness of the system in order to reduce lateral vibration. Several experiments are carried out to validate the efficiency of the proposed method.

A simple action of right index finger induces rubber hand illusion to static left hand

The rubber hand illusion (RHI) is a bodily illusion that a fake rubber hand is felt as if it was ones own hand when both the hands are synchronously stimulated. Also, it is well-known that people can experience the RHI when the movements of the visible fake and invisible real hands are synchronized. However, underlying mechanism of the RHI and relationship between action and body ownership are still open questions. Based on the RHI paradigm, the present paper discusses how the agency of a body part affects the sense of body ownership at the other body part. In this study, we examined if a simple up-and-down action of right index finger induces the RHI to left hand which was kept still by using virtual reality and robotics technologies. Our experimental results indicated that the action of the right index finger allowed the embodiment of the virtual hands at both the right and left hands. This implies that only a simple action of a body part increases the sense of body ownership at the other body part.

A cryogenic ultrasonic actuator using a torsional transducer

In this study, a torsional transducer type ultrasonic motor which realizes the continuous rotation and the positioning of the angle in cryogenic temperature has been fabricated and evaluated. In the cryogenic temperature environment, the performance of the transducer falls. In order to drive the motor at cryogenic temperature, the torsional transducer is designed to generate the resonant stick-slip drive. The transducer can perform the resonant stick-slip drive by combining the first and the second vibration modes. The ultrasonic motor using the transducer was evaluated. The rotation speed and the starting torque are 111 rpm and 0.75 mNm at 4.5 K.

Characteristics of Minute Hole Dewatering Using Focused Ultrasonic Wave

Using the focused ultrasound wave for the purpose of removing the residual water in minute hole has been proposed. There are some advantages in dewatering. For example, this method can discharge water as liquid droplet from minute and non-through hole easily. For radiation of ultrasonic wave with strong intensity, an ultrasonic focusing device is applied, then the focus can be arranged at three dimensions. It has been observed that success rate of dewatering depends on the size of the hole. To discuss the success rate, we proposed a dimensionless number which is ratio of surface tension and pressure by ultrasonic wave. The relationship between the surface tension and dewatering behavior at minute holes was observed by using working water with different concentration of ethanol. Then, relationship between the number and success rate of dewatering was plotted on a graph.

Precise positioning characteristics of multi-mode ultrasonic motor

Previously developed multi-mode ultrasonic motor has three driving modes, which are fast driving mode with figure-of-eight locus resonant vibration, impact driving with saw tooth wave form and DC voltage driving mode. The impact driving mode can be divided into two categories. One utilized resonant vibration (fast) and the other uses individual off resonance vibration (slow). For precise positioning, characteristics of stable driving of the slow impact driving mode and stroke of the DC mode are important. This paper reports the characteristics obtained through experiments.

Development of non-contact carrier system using solar magnetic suspension (3ed report: Continuous 5-day and installation of sloping propulsion mechanism)

A solar-powered magnetic suspension carrier system is developed in which the carrier is powered without contact. There are two conventional methods of powering the coils of the magnetic suspension carrier: (i) through wire, (ii) onboard battery (wireless) power supply. The contactless is lost in the former while stations for charging the battery are necessary in the latter. These problems are overcome by the proposed carrier system using solar magnetic suspension that can attain continuous levitation. The magnetic suspension carrier is assumed to operate inside rooms like inside a factory building. Because the generation power by solar cells is small, power saving us acritical requirement. Therefore, the zero power control is applied for suspension. In addition, low-power peripheral devices are fabricated. The developed carrier system achieved a five-day levitation without external power supply in a bright environment. In addition, a sloping propulsion mechanism was introduced. The mechanism consists of a track rail and two pillars with actuators to move up and down the track rail. The carrier slides and moves to the lower direction due to gravity below a sloped rail.

Comparison of zero-power controllers in double parallel magnetic suspension system with parallel connected coils

A basic single-degree-of-freedom magnetic suspension system consists of one floator, one electromagnet and one amplifier. For multi-degrees-of-freedom control, multiple electromagnets and multiple amplifiers are necessary, which increases the cost of total system. As a means of overcoming this problem, parallel magnetic suspension has been proposed where multiple floators are controlled with a single power amplifier. Parallel magnetic suspension systems are classified into two types according to the output of the power amplifier: current-controlled and voltage-controlled. Voltage-controlled parallel magnetic suspension systems are classified into two types: series connected and parallel connected. The feasibilities of these systems have been already demonstrated in the previous work. This paper focuses on the voltage-controlled parallel magnetic suspension system with parallel-connected coils. Three approaches to zero-power control are applicable in such a system. This paper compares these approaches in a viewpoint of pole assignment. In addition, a relationship in the feedback gains between the three approaches are presented numerically.