Proposal of Evaluation Method for Crack Propagation Behaviors of Second-Generation Acrylic Adhesives under Mode I Static Loading.

Second-generation acrylic (SGA) adhesives, possessing high strength and toughness, are applicable in automotive body structures. Few studies have considered the fracture toughness of the SGA adhesives. This study entailed a comparative analysis of the critical separation energy for all three SGA adhesives and an examination of the mechanical properties of the bond. Loading-unloading test was performed to evaluate crack propagation behaviors. In the loading-unloading test of the SGA adhesive with high ductility, plastic deformation was observed in the steel adherends; the arrest load dominated the propagation and non-propagation of crack for adhesive. The critical separation energy of this adhesive was assessed by the arrest load. In contrast, for the SGA adhesives with high tensile strength and modulus, the load suddenly decreased during loading, and the steel adherend was not plastically deformed. The critical separation energies of these adhesives were assessed using the inelastic load. The critical separation energies for all the adhesives were higher for thicker adhesive. Particularly, the critical separation energies of the highly ductile adhesives were more affected by the adhesive thickness than highly strength adhesives. The critical separation energy from the analysis using the cohesive zone model agreed with the experimental results.

Camera-trapping estimates of the relative population density of Sympetrum dragonflies: application to multihabitat users in agricultural landscapes.

Although camera trapping has been effectively used for wildlife monitoring, its application to multihabitat insects (i.e., insects requiring terrestrial and aquatic ecosystems) is limited. Among such insects, perching dragonflies of the genus Sympetrum (darter dragonflies) are agroenvironmental indicators that substantially contribute to agricultural biodiversity. To examine whether custom-developed camera traps for perching dragonflies can be used to assess the relative population density of darter dragonflies, camera trapping, a line-transect survey of mature adult dragonflies, and a line-transect survey of exuviae were conducted for three years in rice paddy fields in Japan. The detection frequency of camera traps in autumn was significantly correlated with the density index of mature adults recorded during the transect surveys in the same season for both Sympetrum infuscatum and other darter species. In analyses of camera-detection frequency in autumn and exuviae in early summer, a significant correlation was observed between the camera-detection frequency of mature adults and the exuviae-density index in the following year for S. infuscatum; however, a similar correlation was not observed for other darter species. These results suggest that terrestrial camera trapping has the potential to be effective for monitoring the relative density of multihabitat users such as S. infuscatum, which shows frequent perching behavior and relatively short-distance dispersal.

Temporal and interspecific dietary variation in wintering ducks in agricultural landscapes.

Farmlands are becoming more important as waterfowl foraging habitats, while natural wetlands are being lost globally. However, it is unclear how waterfowl coexist in agricultural landscapes by resource partitioning. We evaluated the diets of seven sympatric dabbling ducks foraging in rice paddy and lotus fields around Lake Kasumigaura, the second largest lake in Japan, during two wintering seasons (from November to February) by faecal DNA metabarcoding using chloroplast trnL and mitochondrial CO1 region sequences. We examined 420 faecal samples and found different patterns of dietary diversity and composition among the duck species. The pattern also differed between plant and invertebrate food. Dietary niche partitioning was clear in plant food. Large-bodied ducks intensively use crop plants, and other ducks might mediate competition by using terrestrial and aquatic plants that are suitable for their foraging behaviours or microhabitats. Dietary segregation among species was the most apparent in February, when the abundance of foraging ducks was the largest. This study illustrated the complex pattern of dietary niche partitioning of dabbling ducks in agricultural landscapes, which might be difficult to evaluate by conventional approaches. The availability of crop plants, as well as other plant food resources in flooted areas and farmland dikes, may enable ducks to coexist by spatial or behavioural resource partitioning.

Projections of surface air temperature required to sustain permafrost and importance of adaptation to climate change in the Daisetsu Mountains, Japan.

Permafrost is known to occur in high mountainous areas such as the Daisetsu Mountains in Japan, which are located at the southernmost limit of the permafrost distribution in the world. In this study, areas with climatic conditions suitable for sustaining permafrost in the Daisetsu Mountains are projected using bias-corrected and downscaled climate model outputs and statistical relationships between surface air temperatures and permafrost areas. Using freezing and thawing indices, the size of the area in the Daisetsu Mountains where climatic conditions were suitable for permafrost were estimated to be approximately 150 km2 in 2010. Under the RCP8.5 scenario, this area is projected to decrease to about 30 km2 by 2050 and it is projected to disappear by around 2070. Under the RCP2.6 scenario, the area is projected to decrease to approximately 20 km2 by 2100. The degradation of mountain permafrost could potentially affect the stability of trekking trails due to slope displacement, and it may also have deleterious effects on current alpine ecosystems. It is therefore important to accurately monitor changes in the mountain ecosystem environment and to implement measures to adapt to an environment that is projected to change significantly in the future.

Development of a camera trap for perching dragonflies: a new tool for freshwater environmental assessment.

Although dragonflies are excellent environmental indicators for monitoring terrestrial water ecosystems, automatic monitoring techniques using digital tools are limited. We designed a novel camera trapping system with an original dragonfly detector based on the hypothesis that perching dragonflies can be automatically detected using inexpensive and energy-saving photosensors built in a perch-like structure. A trial version of the camera trap was developed and evaluated in a case study targeting red dragonflies (Sympetrum spp.) in Japan. During an approximately 2-month period, the detector successfully detected Sympetrum dragonflies while using extremely low power consumption (less than 5 mW). Furthermore, a short-term field experiment using time-lapse cameras for validation at three locations indicated that the detection accuracy was sufficient for practical applications. The frequency of false positive detection ranged from 17 to 51 over an approximately 2-day period. The detection sensitivities were 0.67 and 1.0 at two locations, where a time-lapse camera confirmed that Sympetrum dragonflies perched on the trap more than once. However, the correspondence between the detection frequency by the camera trap and the abundance of Sympetrum dragonflies determined by field observations conducted in parallel was low when the dragonfly density was relatively high. Despite the potential for improvements in our camera trap and its application to the quantitative monitoring of dragonflies, the low cost and low power consumption of the detector make it a promising tool.

Mountaintop observation of CO2 absorption spectra using a short wavelength infrared Fourier transform spectrometer.

The absorption spectra of surface-scattered solar radiation were measured from the top of Mount Tsukuba (altitude 833 m) in the short wavelength infrared region using a Fourier transform spectrometer (FTS). The FTS used in this experiment was the breadboard model of the FTS on the Greenhouse Gases Observing Satellite, which was launched on 23 January 2009. In situ measurement of carbon dioxide (CO(2)) from a Cessna airplane was performed simultaneously with the FTS observation. The CO(2) column abundances were retrieved from the observed spectra under the assumption of the absence of aerosol. The retrieved CO(2) column abundances over a few minutes dispersed within 1%. The remaining bias was considered to be caused by the no-aerosol assumption.

Spatial assessment of the alder tree in Kushiro Mire, Japan using remotely sensed imagery--effects of the surrounding land use on Kushiro Mire.

The relationship between alder (Alnus japonica) distribution and surrounding land use in Kushiro Mire was spatially assessed using remotely sensed imagery. From the result, it was found out that the expanding area of alder trees in Kushiro Mire was affected by the agricultural land area in the upper course of the river basin and flooding in the lower course of the river. The soil sediments flowing into the Kushiro Mire from the agricultural land resulted in heavy sedimentation that favors the growth of alder trees. Consequently, the number and density of alder trees has increased. The future distribution of alder trees was predicted based on the mechanism of expansion of the alder-tree area in Kushiro Mire, and it was found that large vegetation areas in Kushiro Mire will be changed to areas with alder trees.