Interfacial fracture strength evaluation of Cu/SiN micro-components: applicability of the linear fracture mechanics criterion under a hydrogen environment

In this study, we have investigated microstructures of the delamination cracks observed from tensile and fracture toughness test specimens using an API X70 pipeline steel. It is found that the delaminations observed from both tensile and toughness specimens are intergranular fractures. At the occurrence, characteristics of brittle fracture were observed, but it was found not to be a brittle fracture as the delaminations were induced by plastic deformation. It is shown that severe plastic deformation produced strain concentration around particles located along grain boundaries and caused decohesion between adjacent grains, resulting in intergranular fracture.     

Sintering and crystallization behaviour of a glass powder and block with a composition of anorthite and the microstructure dependence of its thermal expansion

Two kinds of glass specimens were prepared in the form of powders and blocks with anorthite compositions, and an examination was made of the sintering and crystallization behaviour of the specimens and the microstructure dependence of their thermal expansion. It was found that the addition of a few wt% of Ti0₂ was necessary to obtain a good sintered body by heat treatment at 1050°C. Specimens with low expansion coefficients were obtained when no TiO₂ was added and when the grain size of the starting glass powder was large (ca. less than 180 m). It was estimated that this was mainly due to the presence of orthorhombic and hexagonal anorthite in the central part of each grain. In order to explain the abnormally low expansion coefficient of the sintered specimens, the crystallization behaviour of glass blocks with the same composition was examined. The crystallization proceeded by two mechanisms: the triclinic phase precipitated from the surface, and the orthorhombic and the hexagonal phase precipitated from the central part of the specimens. The orthorhombic phase showed a strong tendency for a preferred orientation, and the thermal-expansion measurements showed strong anisotropy. The addition of TiO₂ to the mother glass suppressed the precipitation of the orthorhombic and hexagonal phases, and the resultant pieces were composed mainly of the triclinic phase; the thermal-expansion coefficient became isotropic.     

Micro-Osteoperforations Induce TNF-α Expression and Accelerate Orthodontic Tooth Movement via TNF-α-Responsive Stromal Cells

Micro-osteoperforations (MOPs) have been reported to accelerate orthodontic tooth movement (OTM), and tumor necrosis factor (TNF)-α has been reported to play a crucial role in OTM. In this report, the influence of MOPs during OTM was analyzed. We evaluated the expression of TNF-α with and without MOPs by RT-PCR analysis. A Ni-Ti closed coil spring was fixed between the maxillary left first molar and the incisors as an OTM mouse model to move the first molar in the mesial direction. MOPs were prepared on the lingual side and mesial side of the upper first molars. Furthermore, to investigate the target cell of TNF-α for osteoclast formation during OTM with MOPs in vivo, we created four types of chimeric mice in which bone marrow of wild-type (WT) or TNF receptor 1- and 2-deficient mice (KO) was transplanted into lethally irradiated WT or KO mice. The results showed that MOPs increased TNF-α expression, the distance of tooth movement and osteoclast formation significantly. Furthermore, mice with TNF-α-responsive stromal cells showed a significant increase in tooth movement and number of osteoclasts by MOPs. We conclude that MOPs increase TNF-α expression, and tooth movement is dependent on TNF-α-responsive stromal cells.     

Scanning Tunneling Microscopy Study of the Anomalous Metallic Phases in θ-(BEDT-TTF)2 MZn(SCN)4 (M= Rb, Cs)

We have studied metallic phases of the title organic conductors by means of STM at room temperature. An image obtained in the salt with M=Rb is very different from a typical one in the salt with M=Cs. We suggest “vertical stripe” charge ordering in the salt with M=Rb at room temperature, which can naturally explain its anomalous metallic behavior.     

Natural convection heat transfer from a horizontal cylinder to mercury under magnetic field

This paper presents the experimental data of natural convection heat transfer from a horizontal cylindrical heater immersed in mercury pool under the two applied magnetic fields of which directions are perpendicular and parallel to the direction of gravity, respectively. The presence of both magnetic fields causes increase in heater surface temperature and liquid temperature surrounding the heater and also increase in thermal boundary layer thickness, at the fixed surface heat flux. From these results, it is expected that the magnetic field affects the inception of boiling. Variation of local heat-transfer coefficient along the periphery of the heater is also discussed.     

Semi-wet peptide/protein array using supramolecular hydrogel

The protein microarray is a crucial biomaterial for the rapid and high-throughput assay of many biological events where proteins are involved. In contrast to the DNA microarray, it has not been sufficiently established because of protein instability under the conventional dry conditions. Here we report a novel semi-wet peptide/protein microarray using a supramolecular hydrogel composed of glycosylated amino acetate. The spontaneous gel-formation and amphiphilic properties of this supramolecular hydrogel have been applied to a new type of peptide/protein gel array that is compatible with enzyme assays. Aqueous cavities created in the gel matrix are a suitable semi-wet reaction medium for enzymes, whereas the hydrophobic domains of the fibre are useful as a unique site for monitoring the reaction. This array system overcomes several drawbacks of conventional protein chips, and thus can have potential applications in pharmaceutical research and diagnosis.     

Effective selection system for experimental evolution of random polypeptides towards DNA-binding protein

An experimental evolution with selection based on binding affinity to DNA was carried out on a library of phage-displayed random polypeptides of about 140 amino acid residues. First, we constructed a system to artificially evolve phage-displayed random polypeptides toward binding to a target DNA containing a restriction enzyme site, in which random polypeptides capable of binding the DNA were recovered as complexes with the target DNA by digestion with the restriction enzyme. The experimental evolution cycle, including the above selection system and random mutagenesis for generating the next mutant library, was repeated until the fourth generation. The ability to bind to the DNA was enhanced per generation. In the fourth generation, convergence of the selected clones to a dominant sequence was observed. These results indicate that the newly constructed selection system is effective for exploring the evolvability of random polypeptides towards DNA-binding proteins.