Motoaki Sano

The Successive Magnetic Phase Transition of Hexagonal Antiferromagnet CsMnI3 Observed by Optical Birefringence

Birefringence measurement was made on a triangular lattice antiferromagnet CsMnI 3 at temperatures around the Neel point of 11.42 K. The birefringence for light propagating along the hexagonal c -axis shows that CsMnI 3 has an intermediate ordered phase in the temperature region between 8.20±0.03 K and 11.42 K. Below 8.20 K CsMnI 3 takes the orthorhombic spin structure of the triangular spin arrangement with the spin moments restricted in a plane perpendicular to the basal plane.

Study on Water Distribution Imaging in the Sand Using Propagation Velocity of Sound with Scanning Laser Doppler Vibrometer

We propose a method for the monitoring and imaging of the water distribution in the rooting zone of plants using sound vibration. In this study, the water distribution measurement in the horizontal and vertical directions in the soil layer was examined to confirm whether a temporal change in the volume water content of the soil could be estimated from a temporal changes in propagation velocity. A scanning laser Doppler vibrometer (SLDV) is used for measurement of the vibration velocity of the soil surface, because the highly precise vibration velocity measurement of several many points can be carried out automatically. Sand with a uniform particle size distribution is used for the soil, as it has high plasticity; that is, the sand can return to a dry state easily even if it is soaked with water. A giant magnetostriction vibrator or a flat speaker is used as a sound source. Also, a soil moisture sensor, which measures the water content of the soil using the electric permittivity, is installed in the sand. From the experimental results of the vibration measurement and soil moisture sensors, we can confirm that the temporal changes of the water distribution in sand using the negative pressure irrigation system in both the horizontal and vertical directions can be estimated using the propagation velocity of sound. Therefore, in the future, we plan to develop an insertion-type sound source and receiver using the acceleration sensors, and we intend to examine whether our method can be applied even in commercial soil with growing plants.

Generation of disk-like domains with nanometer scale thickness in merocyanine dye LB film induced by hydrothermal treatment

We have characterized the binary LB films of merocyanine dye (MS) and arachidic acid (C20) before and after hydrothermal treatment (HTT), which is defined as a heat treatment under relative humidity of 100%, focusing on the morphology studied by bright field (BF) microscopy and fluorescence (FL) microscopy. BF microscopy observation has revealed that the as-deposited MS-C20 binary LB film is found to emit intense red fluorescence over the whole film area by 540-nm excitation. Since the surface image is almost featureless, it is considered that the crystallite sizes of J-aggregate are less than 10 μm. Interestingly, after HTT, round-shaped domains are observed in the LB systems, and the sizes are reaching 100 μm in diameter. Crystallites of J-aggregate, which are bluish in color and emit intense red fluorescence, tend to be in the round domains. We have observed two different types of domains, i.e., blue-rimmed domains and white-rimmed domains, which are postulated to be confined in the inner layers and located at the outermost layer, respectively. The thickness of the domains is equal to or less than that of the double layer of the MS-C20 mixed LB film, which is ca. 5.52 nm. The molecular order of MS in the J-aggregate is improved by the HTT process leading to the significant sharpening of the band shape together with the further red shift of the band (from 590 to 594 nm up to 597 to 599 nm). The reorganized J-band is considered to be ‘apparently’ isotropic owing to the random growth of the J-aggregate in the film plane. We consider that the lubrication effect by the presence of water molecules predominates in the HTT process.

Water distribution measurement in soil using sound vibration

Now in agriculture, it tends to save the agricultural water as much as possible. Therefore, the irrigation method using the minus pressure difference of soil water attracts attention. This method has the nature keeping the water content inside the ground. In other words, when there are crops, it is the mechanism which supplies the water content which is same quantity with the water content that it absorbed. However, effective saving water is not able to be performed, because the water distribution in soil is difficult to grasp. Therefore, we propose a method of monitoring and imaging of the water content in the rooting zone using a sound vibration and the scanning laser Doppler vibrometer (SLDV). The plastic container (40×50×30 cm) which is made from acrylic in the laboratory that had been filled with sand of uniform particle size (200 to 300 μm) was used for this experiment. In this experiment, it measures the status of the water distribution by the change of the vibration propagation. The making method ...

Symmetry breaking birefringence of a hexagonal antiferromagnet CsMnI3

Magnetic symmetry in the basal-plane of a hexagonal antiferromagnet CsMnI 3 was investigated by measuring the birefringence (Δ n x y ) for light propagating along the c -axis as a function of the strength and the direction of a magnetic field H . The results showed that Δ n x y ( H ) saturates for H >1 kOe applied perpendicular to the c -axis in the low temperature phase ( T < T N2 =8.20 K) and the saturation value of Δ n x y was almost constant irrespective of the direction of the field. A feature was that Δ n x y ( H ) returned to initial value without hysteresis even after the saturation. These behaviors were discussed in terms of a modified spin-flop theory taking account of the volume variations of the three equivalent domains.

Basic Study on Estimating Water Stress of a Plant Using Vibration Measurement of Leaf

A new noninvasive method for estimating the water stress of a plant was proposed. In order to investigate this method, we first examined the characteristic frequency of an individual leaf picked from the plant, and obtained the result that its characteristic frequency decreased in proportion to the reduction in the water content of the leaf. Next, we applied this method to a leaf on a branch and confirmed the same tendency when the water stress was increased by stopping the water supply of a plant cultured in water. From these results, it was suggested that the water stress of the plant could be estimated from the vibration measurement of the leaf. Lastly, the relationship between the water potential of the leaf and its elastic constant was discussed with the soil-plant-atmosphere-continuum model (SPAC model), and Youngs modulus of a tomato leaf was roughly estimated.

Basic study of water distribution measurement in soil using SLDV

We propose a method of monitoring and imaging of the water content in the rooting zone using a sound vibration and the scanning laser Doppler vibrometer (SLDV). Also, we study about stable calculation method of propagation velocity in soil. There is an advantage that is possible to measure a wide area by using a sound vibration. From the experimental results, we can confirm that the speed of sound value becomes fast in the place which is near the position of the water distribution. Also, we can see that the difference of the propagation velocity distribution reflected the difference of the water distribution. We plan to measure when changing the depth of the water distribution position and the implication water ratio in the future.

A method of determining the sense and magnitude of optical rotation in uniaxial crystals, together with a study of the gyrotropic phase transition of CsCuCl3

A method of determining the sense and magnitude of the optical rotatory power of unixial crystals has been developed, and has been used to measure the optical activity of CsCuCl3, a gyrotropic crystal. Virgin crystals grown from aqueous solution were found to be predominantly dextrorotatory, though a crystal with a single gyrotropic domain was rarely found. The racemization effect was produced when the temperature was reduced through the gyrotropic phase transition point at about 420 K.