Nobuhide Takahashi

Reaction model of dense Sm0.5Sr0.5CoO3 as SOFC cathode

Overpotential and AC impedance spectra were measured to study the reaction model of dense Sm0.5Sr0.5CoO3 (SSC) as SOFC cathode. From the PO2 dependence of interfacial conductivity, the rate determining step of dense SSC electrode was adsorption and desorption processes at the surface of the electrode. Rate constants of adsorption and desorption were calculated from the interfacial conductivity of the dense electrode to be 3×10−5 mol cm−2 s−1 atm−1 and 2×10−8 mol cm−2 s−1, respectively. These were approximately one order of magnitude larger than the corresponding values calculated for La0.6Sr0.4CoO3. These rate constants can elucidate the overpotentials of porous electrodes.

Estimation of water requirement per unit carbon fixed byEucalyptus camaldulensis in semi-arid land of Western Australia

Afforestation in arid land is a promising method for carbon fixation, but the effective utilization of water is highly important and required. Thus, the evaluation of the amount of water per unit carbon fixed with the tree growth is required to minimize the amount of water supplied to the plants. In this research, a tree is regarded as a carbon fixation reactor with inflows of water and nutrients from roots, and CO2 as the carbon source from leaves with outflow of water vapor from leaves and accumulation in the tree itself. In the process of photosynthesis and respiration nutritional elements are dissolved in water flow in trees. They do not flow out by these reactions, but are accumulated in trees. Thus, we have treated the behaviour of nutrients as a marker to evaluate the water/carbon ratio.Assuming that nutrient concentration is constant in sap, and the differences in the ratios of nutrient to carbon in living trees and dead (i.e. litter fall, etc.) are neglected, the ratio of the used water to fixed carbon is given as the ratio of nutrient to carbon in the tree body divided by the ratio of nutrient to water in sap. However, some nutrients are translocated and concentrated within the tree and some may be discarded through litter fall. Thus it is important to examine which nutrient element is the most suitable as the tracer.In this paper, the results of the above method applied toEucalyptus camaldulensis in semiarid land of Western Australia are shown. The value of water requirement per unit carbon fixation determined from potassium balance is between 421 kg-H2O/kg-C for mature trees and 285 kg-H2O/kg-C for young trees, while the values from calcium balance are much larger than these. The cause of the discrepancy between these values is discussed based on the measured element concentrations in sap and trees and the plant physiology. Finally, the actual average value through the life of a tree is suggested to fall between the two values.

Effect of acidity on the physicochemical properties of α- and β-chitin nanofibers

We have investigated whether acidity can be used to control the physicochemical properties of chitin nanofibers (ChNFs). In this study, we define acidity as the molar ratio of dissociated protons from the acid to the amino groups in the raw chitin powder. The effect of acidity on the physicochemical properties of α- and β-ChNFs was compared. The transmittance and viscosity of the β-ChNFs drastically and continuously increased with increasing acidity, while those of the α-ChNFs were not affected by acidity. These differences are because of the higher ability for cationization based on the more flexible crystal structure of β-chitin than α-chitin. In addition, the effect of the acid species on the transmittance of β-ChNFs was investigated. The transmittance of β-ChNFs can be expressed by the acidity regardless of the acid species, such as hydrochloric acid, phosphoric acid, and acetic acid. These results indicate that the acidity defined in this work is an effective parameter to define and control the physicochemical properties of ChNFs.

Vector locus of an equivalent radius of the root in growing plants

Tree planting on arid land is taken up as one of the measures against global warming prevention. It is important for the tree planting to grasp growth state of the root after planting. To monitor the root advancement, a method measuring electric ground impedance of the root has been presented. By this method, we can know the growth state without digging the soil. To estimate the value of impedance, we introduce a concept of an equivalent radius. In this method, the value of ground impedance is converted to a radius of the disk electrode that has the same value as the object. Moreover, ground impedance of the root is indicated as complex number, which consists of resistance and capacity components of the root. The equivalent radius is also expressed by complex number. We propose the method indicating the change of equivalent radius as growing of the root by means of vector locus. It is demonstrated by the experiments on sunflower and kenaf during one summer that the present method is useful for estimating the growth state of the plant root.

An estimation method of ground resistance of trees growing in different lands

It is important to monitor the growing state of tree roots without digging the soil away from the bottom of the tree. Electrical ground resistance of tree roots indicates the grade of the growing state. The better roots advanced in the ground, the smaller the value of ground resistance becomes. However, ground resistance of the tree is modified by resistivity of the soil. If the growing state of roots is the same in trees growing in different lands, the value of ground resistance of each tree shows different values according to soil resistivity where trees are growing. This disables the comparison of the growth level between different lands, and complicates the estimation of results. In order to make comparison possible between the two without the effect of soil resistivity, the value of ground resistance of the tree is converted to that of a metal disk electrode. Here, if we know the soil resistivity, a radius of the disk becomes to be known. This disk radius is called equivalent radius that can indicate the growth level according to its value regardless of soil resistivity. Using the equivalent radius, we can estimate the growth level of plants growing in different lands evenly. Measured equivalent radii and the ratios to their butt radius of objective trees in West Australia, Hawaii Island, and Japan are summarized in figures.

Possibility of CO2 Fixation on Arid Land in Western Australia

Publisher Summary CO 2 fixation by afforestation is expected to be a sustainable, economical, and also low environmental burden method. Carbon fixation by afforestation is one of the few effective countermeasures against the carbon dioxide problem. In particular, afforestation of arid land is promising, because the arid land exists in large quantities in the world. The main research area was set up in the interior of Western Australia where mean annual rainfall is about 200 mm. The growth tendency of trees at the site C, where the breakage of the impermeable layer was conducted, is reported. At this site, 12 water ponding banks were developed surrounding a planting area (50 m x 50 m) to collect runoff and retain rainfall. Then, around 50 trees were planted in each planting area. Tree height, crown diameter and trunk diameter at 0.3 m and 1.3 m from ground level for several species such as Eucalyptus camaldulensis, Acacia aneura, and Casuarina obesa were measured every few months after planting. The results from other site have also been reported. Finally, an integrated simulator of plant growth, photosynthesis, transpiration, and soil water transport was developed as a platform for the competition of arid land afforestation technologies for CO 2 Fixation.