Preparation of a platinum electrocatalyst by coaxial pulse arc plasma deposition

We have developed a new method of preparing Pt electrocatalysts through a dry process. By coaxial pulse arc plasma deposition (CAPD), highly ionized metal plasma can be generated from a target rod without any discharged gases, and Pt nanoparticles can be deposited on a carbon support. The small-sized Pt nanoparticles are distributed over the entire carbon surface. From transmission electron microscopy (TEM), the average size of the deposited Pt nanoparticles is estimated to be 2.5 nm, and their size distribution is narrow. Our electrocatalyst shows considerably improved catalytic activity and stability toward methanol oxidation reaction (MOR) compared with commercially available Pt catalysts such as Pt black and Pt/carbon (PtC). Inspired by its very high efficiency toward MOR, we also measured the catalytic performance for oxygen reduction reaction (ORR). Our PtC catalyst shows a better performance with half-wave potential of 0.87 V, which is higher than those of commercially available Pt catalysts. The higher performance is also supported by a right-shifted onset potential. Our preparation is simple and could be applied to other metallic nanocrystals as a novel platform in catalysis, fuel cells and biosensors.     

Adult headform impact tests of three Japanese child bicycle helmets into a vehicle

The head is the body region that most frequently incurs fatal and serious injuries of cyclists in collisions against vehicles. Many research studies investigated helmet effectiveness in preventing head injuries using accident data. In this study, the impact attenuation characteristics of three Japanese child bicycle helmets were examined experimentally in impact tests into a concrete surface and a vehicle. A pedestrian adult headform with and without a Japanese child bicycle helmet was dropped onto a concrete surface and then propelled into a vehicle at 35 km/h in various locations such as the bonnet, roof header, windshield and A-pillar. Accelerations were measured and head injury criterion (HIC) calculated. In the drop tests using the adult headform onto a concrete surface from the height of 1.5 m, the HIC for a headform without a child helmet was 6325, and was reduced by around 80% when a child helmet was fitted to the headform. In the impact tests, where the headform was fired into the vehicle at 35 km/h at various locations on a car, the computed acceleration based HIC varied depending on the vehicle impact locations. The HIC was reduced by 10–38% for impacts headforms with a child helmet when the impact was onto a bonnet-top and roof header although the HIC was already less than 1000 in impacts with the headform without a child helmet. Similarly, for impacts into the windshield (where a cyclist’s head is most frequently impacted), the HIC using the adult headform without a child helmet was 122; whereas when the adult headform was used with a child helmet, a higher HIC value of more than 850 was recorded. But again, the HIC values are below 1000. In impacts into the A-pillar, the HIC was 4816 for a headform without a child helmet and was reduced by 18–38% for a headform with a child helmet depending on the type of Japanese child helmet used. The tests demonstrated that Japanese child helmets are effective in reducing accelerations and HIC in a drop test using an adult headform onto a relatively rigid hard surface, i.e., simulating a road surface or concrete path. However, when the impact tests are into softer surfaces, the child helmet’s capacity to decrease accelerations is accordingly reduced. Impacts into the windshield, while below the critical HIC value of 1000, indicated higher HIC values for a headform with a child helmet compared to an adult headform without a child helmet. The unpredictable nature of the results indicates further research work is required to assess how representative the stiffness of an adult headform is when compared to an actual head.     

Global network structure of dominance hierarchy of ant workers

Dominance hierarchy among animals is widespread in various species and believed to serve to regulate resource allocation within an animal group. Unlike small groups, however, detection and quantification of linear hierarchy in large groups of animals are a difficult task. Here, we analyse aggression-based dominance hierarchies formed by worker ants in Diacamma sp. as large directed networks. We show that the observed dominance networks are perfect or approximate directed acyclic graphs, which are consistent with perfect linear hierarchy. The observed networks are also sparse and random but significantly different from networks generated through thinning of the perfect linear tournament (i.e. all individuals are linearly ranked and dominance relationship exists between every pair of individuals). These results pertain to global structure of the networks, which contrasts with the previous studies inspecting frequencies of different types of triads. In addition, the distribution of the out-degree (i.e. number of workers that the focal worker attacks), not in-degree (i.e. number of workers that attack the focal worker), of each observed network is right-skewed. Those having excessively large out-degrees are located near the top, but not the top, of the hierarchy. We also discuss evolutionary implications of the discovered properties of dominance networks.     

Synthesis of novel amino(alkylamino)deoxychitins and the adsorption behavior of acid dye onto the resulting polymers

Novel chitin‐based materials were synthesized and the adsorption behavior of typical acid dyes to the resulting polymers has been evaluated. The successful synthetic reaction was confirmed by the infrared spectroscopic measurements. By the reaction of alkalichitin with tosyl chloride, the corresponding tosylchitin was synthesized as a soluble and reactive precursor. Next, aminodeoxychitin was synthesized by the reaction of the tosylchitin with ammonia. Similarly, 2′‐aminoethylamino‐ and 6′‐aminohexylaminodeoxychitins were synthesized by reacting the tosylchitin with ethylenediamine and hexamethylenediamine, respectively. It has been confirmed that the adsorption abilities of these polymers for acid dyes were significantly high, and also that one of the aminodeoxychitins showed a high adsorption ability for Cu²⁺ ion. On the basis of the adsorption data of acid dye on the aminodeoxychitin, the tosylchitin and the original chitin, the amino group contents at C₆ and C₂ positions were estimated. The aminodeoxychitin and aminoalkylaminodeoxychitins could be applicable to the adsorbent for anionic dyes and Cu²⁺ ion along with a precursor for further novel derivatives. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphology control of ZnO crystalline particles in aqueous solution

We developed an aqueous solution process to synthesize crystalline ZnO particles and control their morphology. ZnO crystals were prepared in an aqueous solution containing zinc acetate and ammonia at 50 °C with no additional phase. ZnO particles having long hexagonal cylinder, short hexagonal cylinder, rounded hexagonal cylinder, rounded ellipse, pointed ellipse or multi-needle shapes were homogeneously nucleated and precipitated in solution. Crystal growth and preferential growth faces were controlled by solution conditions. Morphological control techniques in this system will contribute to the development of solution chemistry for inorganic materials and future oxide devices.     

Interactive mesh deformation using equality-constrained least squares

Mesh deformation techniques that preserve the differential properties have been intensively studied. In this paper, we propose an equality-constrained least squares approach for stably deforming mesh models while approximately preserving mean curvature normals and strictly satisfying other constraints such as positional constraints. We solve the combination of hard and soft constraints by constructing a typical least squares system using QR decomposition. A well-known problem of hard constraints is over-constraints. We show that the equality-constrained least squares approach is useful for resolving such over-constrained situations. In our framework, the rotations of mean curvature normals are treated using the logarithms of unit quaternions in . During deformation, mean curvature normals can be rotated while preserving their magnitudes. In addition, we introduce a new modeling constraints called rigidity constraints and show that rigidity constraints can effectively preserve the shapes of feature regions during deformation. Our framework achieves good performance for interactive deformation of mesh models.     

关于屋顶绿化

重点介绍了屋顶绿化工法中的关键构造层次——防水层和耐根层，并对佛甲草屋顶绿化工法、日本各地推动屋顶绿化的相关政策等作了概述。     

Dynamic equilibrium of self-assembled cyclic trimer and tetramer of 1-methyl-5-imidazolylcobalt(III)porphyrin

Dynamic equilibrium of self-assembled multi-porphyrin systems is of interest in obtaining switchable photoresponsive material, but rarely reported. 1-methyl-5-imidazolylcobalt(III)porphyrin ( 1Co ) synthesized here assembled automatically into cyclic trimer and tetramer by intermolecular imidazolyl-cobalt(III) coordination. The trimer-tetramer equilibrium was dependent on concentration and solvent, as examined by NMR spectrometry. In CDCl₃, the tetramer formation was favored at high concentrations, as the ratio of the trimer to the tetramer was 1:2 at 14.8 mM 1Co , and shifted to 1:8 at 74 mM. Further, when the sample was concentrated from a CHCl₃ solution to dryness, the ratio increased to 1:24 on dissolution. In CD₃OD, on the other hand, only the trimer was observed in the wide concentration range. Accordingly, both the trimeric and the tetrameric structures could be prepared selectively by the choice of concentration and solvent.