Fatigue Behaviors of Ultra Fine Wires of -Type and -Type Titanium Alloys

Fatigue behaviors of ultra fine wires of -type Ti-14Mo-3Nb-1.5Zr alloy and -type Ti-10Zr alloy and -type CP (commercially pure) titanium with diameters in the range of 35-100 mm were investigated by rotating-bending fatigue testing in 1 mass% lactic acid solution maintained at 310 K. The maximum number of cycles during fatigue testing was 10 7 . The -type Ti-14Mo-3Nb-1.5Zr alloy wires showed a clear fatigue limit. On the other hand, the -type Ti-10Zr alloy wire and -type CP titanium wire did not show a clear fatigue limit, and their fatigue strengths gradually decreased with decreasing maximum bending stress. The fatigue limit of a -type Ti-14Mo-3Nb-1.5Zr alloy wire with a polished surface was greater than 50% of its tensile strength, while the fatigue limits of titanium wires with as-drawn surfaces were less than 50% of their tensile strengths. Surface defects that were introduced during the cold drawing process of the wires might act as crack origins of the fatigue fracture. Therefore, surface polishing is an effective technique for improving fatigue properties of titanium wires. The elution of metallic ions from the wires into the 1 mass% lactic acid solution was suppressed at a very low level during fatigue testing of all the investigated titanium wires

Elucidating the multiple genetic lineages and population genetic structure of the brooding coral Seriatopora (Scleractinia: Pocilloporidae) in the Ryukyu Archipelago

The elucidation of species diversity and connectivity is essential for conserving coral reef communities and for understanding the characteristics of coral populations. To assess the species diversity, intraspecific genetic diversity, and genetic differentiation among populations of the brooding coral Seriatopora spp., we conducted phylogenetic and population genetic analyses using a mitochondrial DNA control region and microsatellites at ten sites in the Ryukyu Archipelago, Japan. At least three genetic lineages of Seriatopora (Seriatopora-A, -B, and -C) were detected in our specimens. We collected colonies morphologically similar to Seriatopora hystrix, but these may have included multiple, genetically distinct species. Although sexual reproduction maintains the populations of all the genetic lineages, Seriatopora-A and Seriatopora-C had lower genetic diversity than Seriatopora-B. We detected significant genetic differentiation in Seriatopora-B among the three populations as follows: pairwise F (ST) = 0.064-0.116 (all P = 0.001), pairwise G\u27\u27(ST) = 0.107-0.209 (all P = 0.001). Additionally, only one migrant from an unsampled population was genetically identified within Seriatopora-B. Because the peak of the settlement of Seriatopora larvae is within 1 d and almost all larvae are settled within 5 d of spawning, our observations may be related to low dispersal ability. Populations of Seriatopora in the Ryukyu Archipelago will probably not recover unless there is substantial new recruitment from distant populations

The potential role of temperate Japanese regions as refugia for the coral Acropora hyacinthus in the face of climate change

As corals in tropical regions are threatened by increasing water temperatures, poleward range expansion of reef-building corals has been observed, and temperate regions are expected to serve as refugia in the face of climate change. To elucidate the important indicators of the sustainability of coral populations, we examined the genetic diversity and connectivity of the common reef-building coral Acropora hyacinthus along the Kuroshio Current, including recently expanded (<50 years) populations. Among the three cryptic lineages found, only one was distributed in temperate regions, which could indicate the presence of Kuroshio-associated larval dispersal barriers between temperate and subtropical regions, as shown by oceanographic simulations as well as differences in environmental factors. The level of genetic diversity gradually decreased towards the edge of the species distribution. This study provides an example of the reduced genetic diversity in recently expanded marginal populations, thus indicating the possible vulnerability of these populations to environmental changes. This finding underpins the importance of assessing the genetic diversity of newly colonized populations associated with climate change for conservation purposes. In addition, this study highlights the importance of pre-existing temperate regions as coral refugia, which has been rather underappreciated in local coastal management

Critical Temperature in Bulk Ultrafine-Grained Superconductors of Nb, V, and Ta Processed by High-Pressure Torsion

This overview describes the progressive results of the superconducting critical temperature in bulk nanostructured metals (niobium, vanadium and tantalum) processed by high-pressure torsion (HPT). Bulk nanostructured superconductors provide a new route to control superconducting property, because ultrafine-grain structures with a high density of grain boundaries, dislocations, and other crystalline defects modify the superconducting order parameter. The critical temperature Tc in Nb increases with the evolution of grain refinement owing to the quantum confinement of electrons in ultrafine grains. In V and Ta, however, Tc decreases at a certain HPT revolution number (i.e. at certain strain levels). The different behaviour of Tc in the three materials is explained by the competition effect between the quantum size effect and disorder effect; these effects are characterized by the parameters of grain size, electron mean free path, and superconducting coherence length