Nobuyasu Naruse

Discrimination of areas infected with coffee leaf rust using a vegetation index

ABSTRACT Coffee leaf rust is for the coffee industry potentially one of the causes of a sustainability crisis. Currently, on-site disease detection is the only effective method to fell coffee trees for prevention of the infection. However, accurate infection detection over wide areas is difficult when conducted by ground surveys. Here, we examine the application of a remote sensing method. The Normalized Difference Vegetation Index (NDVI) values of coffee farms were computed using satellite images and compared with the results of the ground truth. We found that the standard deviation of the NDVI value (σNDVI) in damaged farms increases as the average NDVI value decreases. This fact implies that the disease progresses in-homogeneously inside a damaged area. In the present analysis, up to 94.1% of the damaged farms were discriminated by combining the NDVI and σNDVI thresholds when 75.0% of the damaged farms had NDVI values under 0.732 and σNDVI over 0.044. Our monitoring method enabled us to take early-stage countermeasures against the infection, and it could be applied to other vegetation diseases.

Resistive switching at the high quality metal/insulator interface in Fe3O4/SiO2/α-FeSi2/Si stacking structure

Fe3O4-based films composed of ubiquitous elements are promising for resistive switching. In general, the disadvantage of this film is the low Off/On resistance ratio. We achieved the highest resistance ratio in a Fe3O4-based stacking structure including a thin SiO2 layer with a high quality interface. For fabrication of the stacking structure, Fe oxide films were epitaxially grown on the intentionally formed α-FeSi2 layers on Si substrates, where the high quality epitaxial interfaces were formed owing to the α-FeSi2 layer role: blocking of Si atom diffusion from the substrate through the interface. The high quality Fe3O4/α-FeSi2 interfaces were oxidized by the low O2 pressure annealing process to succeed in inserting thin SiO2 layers at the interfaces. The resulting stacking structure of the Fe3O4 film/SiO2 layer/α-FeSi2 layer showed the resistive switching behavior with the resistance ratio of ∼140 which is the highest value of Fe3O4 materials. This high value comes from much higher resistance in the high resistive state because the stacking structure has a thin SiO2 insulator layer with high quality interfaces without defects working as leakage sites. This means overcoming the disadvantage of conventional Fe3O4-based films, low resistance ratio, and demonstrates the possibility of realization for rare-metal-free resistance random access memory.Fe3O4-based films composed of ubiquitous elements are promising for resistive switching. In general, the disadvantage of this film is the low Off/On resistance ratio. We achieved the highest resistance ratio in a Fe3O4-based stacking structure including a thin SiO2 layer with a high quality interface. For fabrication of the stacking structure, Fe oxide films were epitaxially grown on the intentionally formed α-FeSi2 layers on Si substrates, where the high quality epitaxial interfaces were formed owing to the α-FeSi2 layer role: blocking of Si atom diffusion from the substrate through the interface. The high quality Fe3O4/α-FeSi2 interfaces were oxidized by the low O2 pressure annealing process to succeed in inserting thin SiO2 layers at the interfaces. The resulting stacking structure of the Fe3O4 film/SiO2 layer/α-FeSi2 layer showed the resistive switching behavior with the resistance ratio of ∼140 which is the highest value of Fe3O4 materials. This high value comes from much higher resistance in the hig...

Multidisciplinary field research in Kabwe, Zambia, towards better understanding of lead contamination of the city - A short report from a field survey

Heavy metal contamination is a serious issue in many post-mining area around the world. Kabwe city, Zambia, is known as one of the most polluted cities in the world and high lead (Pb) levels that have been reported in soils, plants, animals and human bloods. Multidisciplinary approaches are critically needed to understand the current situation and to remediate the polluted area. In the current research, we performed a large scale preliminary field survey to understand the current situation in Kabwe and to plan future mitigation approaches. Mainly, three aspects were observed; 1) plant communities during the dry season in Kabwe city, 2) spectral images of the land surfaces in various locations in Kabwe and 3) lead concentrations in soils and water. Overall, >15 different plant species were observed and many of them maintained their green color even during the dry season. Some tree species, for example, Caesalpiniaceae and Fabaceae families may be utilized as phytostabilization approaches although their impacts on the soil lead mobility have to be further studied. For the spectral images, we used a handmade portable spectrometer and our obtained spectral images showed typical curves observed from soils. These data may be used to understand the distribution of different soil types in this area, using aboveground images such as satellite images. For Pb concentrations in soils, extremely high total Pb levels (>1,000 ppm) was observed only within 2 km from the mining site. There was a weak but a positive correlation between the total and soluble lead thus further study should also focus on the mobility of Pb from soils to plant ecosystems.