Hiroyuki Matsuda

Effect of zinc on diversity of riverine benthic macroinvertebrates: Estimation of safe concentrations from field data

We conducted field surveys at 25 sites in three Japanese catchments to provide conservative estimates of the safe concentration of zinc (Zn) for the protection of riverine macroinvertebrate diversity. The relationships between the Zn concentration and six macroinvertebrate metrics for taxon richness were determined by using regression analysis; this included a piecewise regression model, where two lines are joined at an unknown point. For each metric the piecewise regression model with a zero slope below a threshold concentration was selected as the best model to explain the influence of Zn. Under the assumption that macroinvertebrate diversity reductions of <10% are acceptable, the safe concentrations of Zn were estimated to be 84, 115, 84, 80, 85, and 70 µg/L for total taxon richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, mayfly richness, caddisfly richness, chironomid richness, and estimated total taxon richness at the riffle scale, respectively. These concentrations are more than twice the water quality standard for Zn in Japan (30 µg/L), suggesting that the standard is likely overprotective for macroinvertebrate diversity. Field studies are useful for evaluating the level of protectiveness of safe concentrations (water quality standards) based on individual-level effects from laboratory toxicity tests, and this evaluation process will have a crucial role in implementing more purpose-driven ecological risk managements that aim to protect natural populations and communities.

Characterizing Edge and Stacking Structures of Exfoliated Graphene by Photoelectron Diffraction

The two-dimensional C 1s photoelectron intensity angular distributions (PIADs) and spectra of exfoliated graphene flakes and crystalline graphite were measured using a focused soft X-ray beam. Suitable graphene samples were selected by thickness characterization using Raman spectromicroscopy after transferring mechanically exfoliated graphene flakes onto a 90-nm-thick SiO2 film. In every PIAD, a Kagome interference pattern was observed, particularly clearly in the monolayer graphene PIAD. Its origin is the overlap of the diffraction rings formed by an in-plane C–C bond honeycomb lattice. Thus, the crystal orientation of each sample can be determined. In the case of bilayer graphene, PIAD was threefold-symmetric, while those of monolayer graphene and crystalline graphite were sixfold-symmetric. This is due to the stacking structure of bilayer graphene. From comparisons with the multiple scattering PIAD simulation results, the way of layer stacking as well as the termination types in the edge regions of bilayer graphene flakes were determined. Furthermore, two different C 1s core levels corresponding to the top and bottom layers of bilayer graphene were identified. A chemical shift to a higher binding energy by 0.25 eV for the bottom layer was attributed to interfacial interactions.

New Display‐type Analyzer for Three‐dimensional Fermi Surface Mapping and Atomic Orbital Analysis

We have developed and installed a new Display‐type ANAlyzer (DIANA) at Ritsumeikan SR center BL‐7. We measured the angle‐integrated energy distribution curve of poly‐crystal gold and the photoelectron intensity angular distribution (PIAD) of HOPG to estimate the total energy resolution and to check the condition of the analyzer. The total energy resolution (ΔE/E) is up to 0.78%, which is much higher than the old type. The PIAD of HOPG we obtained was the ring pattern as expected. Therefore, a detailed three‐dimensional Fermi surface mapping and an analysis of the atomic orbitals constituting the electron energy bands are possible by combining them with a linearly polarized synchrotron radiation.

Elimination of the Background of Electron Microscope Images by Using FPGA

The purpose of our development is to design an FPGA based hardware acceleration system that is able to be used for analyzing photoemission electron microscope (PEEM) images or improving their quality. Even though a usual PEEM has an energy filter unit, which is able to eliminate certain disturbing signals, a post processing computation can also be useful to improve the image quality. Here we propose an FPGA based hardware acceleration system for the computation of a certain image background component. It has uniquely designed hardware modules that perform the computations in parallel, resulting in less calculation time. The system shown here is a prototype which was only used for testing and experimental purposes.