Plasticity initiation and subsequent deformation behavior in the vicinity of single grain boundary investigated through nanoindentation technique

The initiation of plasticity and the subsequent state in the vicinity of a single grain boundary during indentation-induced deformation were investigated to understand an elementary step of a stress-strain behavior of polycrystalline materials. Nanoindentation measurements on several points on a single grain boundary and the grain interior of an interstitial-free steel and an analysis on the pop-in behavior and the plastic nanohardness were carried out. The pop-in load P ^c that was obtained on the loading curve is different for each measurement. However, the loading curves overlap one another and the unloading curves coincide as well after the pop-in event. The nanohardness Hn has no dependence on the P ^c in the range of 150–550 μN. The relation between P ^c and Δh can be expressed as a simple cubic polynomial function based on a geometrically necessary dislocation loop model. The fitted function differed for various grains with different crystallographic orientations.     

Development of a novel hydrate-based refrigeration system: A preliminary overview

This paper gives a preliminary overview of our attempt at developing a hydrate-based refrigeration system based on a novel conceptual design. The system forms a closed cycle, which is more or less analogous to the conventional vapor-compression refrigeration cycle. The cycle of present interest is performed by a multiphase refrigerant, which is typically a mixture of one or two hydrate-forming substances and water. The refrigerant is required to form a hydrate at a temperature as high as 30 °C or above, desirably under a modest pressure, such that the heat released by the exothermic hydrate formation can be efficiently removed by an environmental fluid such as the atmospheric air, groundwater or river water. The hydrate slurry thus formed is depressurized to dissociate at a lower temperature, typically 5–9 °C, thereby absorbing heat from a space to be refrigerated. To confirm the feasibility of the above conceptual design of the hydrate-based refrigeration system, a thermodynamic analysis of the system and a simulation of its operation have been performed. Also a laboratory-scale refrigerator based on the above design was constructed and tested. The paper summarizes the results of these efforts to show the potential advantages of the hydrate-based refrigeration system over conventional ones and to give the prospects of our refrigeration-system development.     

Phase Equilibrium for Structure-H Hydrates Formed with Methane and Methyl-Substituted Cyclic Ether

Clathrate hydrate formation in a (methane + either 3-methyltetrahydropyran or 2-methyltetrahydrofuran + water) system is demonstrated. The first data of the quadruple (water + structure-H hydrate + either 3-methyltetrahydropyran or 2-methyltetrahydrofuran + methane) equilibrium pressure–temperature conditions are measured over temperatures from 273 to 286 K. In the 3-methyltetrahydropyran system, the equilibrium pressures are lower by 1.6–2 MPa than those of the structure-I methane hydrate formed in the methane + water system at given temperatures. In the 2-methyltetrahydrofuran system, equilibrium pressures at temperatures below 278 K are lower than those for the structure-I methane hydrate, and at temperatures above 278 K, they are higher. These phase equilibria suggest the formation of hydrates other than structure-I methane hydrates in the two systems. The crystallographic structures of the hydrates are determined to be structure H by means of X-ray diffraction as expected from considerations of sizes and shapes of the 3-methyltetrahydropyran and 2-methyltetrahydrofuran molecules     

Advanced Dicing Technology for Semiconductor Wafer—Stealth Dicing

ldquoStealth dicing (SD)rdquo was developed to solve inherent problems of a dicing process such as debris contaminants and unnecessary thermal damages on a work wafer. A completely dry process is another big advantage over other dicing methods. In SD, the laser beam power of transmissible wavelength is absorbed only around focal point in the wafer by utilizing the temperature dependence of the absorption coefficient of the wafer. The absorbed power forms a modified layer in the wafer, which functions as the origin of separation in the separation process. In this paper, we applied this method for an ultra-thin wafer. The reliability of devices that is diced by SD was confirmed.     

Subzero Nonfreezing Hypothermia with Insect Antifreeze Protein Dramatically Improves Survival Rate of Mammalian Cells

Cells for therapeutic use are often preserved at +4 °C, and the storage period is generally limited to 2–3 days. Here, we report that the survival rate (%) of mammalian cells is improved to 10–20 days when they are preserved with a subzero supercooled solution containing the antifreeze protein (AFP), for which an ability to stabilize both supercooled water and cell membrane integrity has been postulated. We chose adherent rat insulinoma (RIN-5F) cells as the preservation target, which were immersed into −5 °C-, −2 °C-, or +4 °C-chilled “unfrozen” solution of Euro-Collins or University of Washington (UW) containing the AFP sample obtained from insect or fish. Our results show that the survival rate of the cells preserved with the solution containing insect AFP was always higher than that of the fish AFP solution. A combination of the −5 °C-supercooling and insect AFP gave the best preservation result, namely, UW solution containing insect AFP kept 53% of the cells alive, even after 20 days of preservation at −5 °C. The insect AFP locates highly organized ice-like waters on its molecular surface. Such waters may bind to semiclathrate waters constructing both embryonic ice crystals and a membrane–water interface in the supercooled solution, thereby protecting the cells from damage due to chilling.     

Natural Killer T Cells Are Involved in Atherosclerotic Plaque Instability in Apolipoprotein-E Knockout Mice

The infiltration and activation of macrophages as well as lymphocytes within atherosclerotic lesion contribute to the pathogenesis of plaque rupture. We have demonstrated that invariant natural killer T (iNKT) cells, a unique subset of T lymphocytes that recognize glycolipid antigens, play a crucial role in atherogenesis. However, it remained unclear whether iNKT cells are also involved in plaque instability. Apolipoprotein E (apoE) knockout mice were fed a standard diet (SD) or a high-fat diet (HFD) for 8 weeks. Moreover, the SD- and the HFD-fed mice were divided into two groups according to the intraperitoneal injection of α-galactosylceramide (αGC) that specifically activates iNKT cells or phosphate-buffered saline alone (PBS). ApoE/Jα18 double knockout mice, which lack iNKT cells, were also fed an SD or HFD. Plaque instability was assessed at the brachiocephalic artery by the histological analysis. In the HFD group, αGC significantly enhanced iNKT cell infiltration and exacerbated atherosclerotic plaque instability, whereas the depletion of iNKT cells attenuated plaque instability compared to PBS-treated mice. Real-time PCR analyses in the aortic tissues showed that αGC administration significantly increased expressional levels of inflammatory genes such as IFN-γ and MMP-2, while the depletion of iNKT cells attenuated these expression levels compared to those in the PBS-treated mice. Our findings suggested that iNKT cells are involved in the exacerbation of plaque instability via the activation of inflammatory cells and upregulation of MMP-2 in the vascular tissues.     

First 3-D calculation of core disruptive accident in a large-scale sodium-cooled fast reactor

The SIMMER-IV computer code is a three-dimensional fluid-dynamics code coupled with a fuel-pin model and a space- and energy-dependent neutron transport kinetics model. The present study has attempted the first application of SIMMER-IV to a core disruptive accident in a large-scale sodium-cooled fast reactor. A principal point of this study was to investigate reactivity effects with fuel relocation under three-dimensional core representation including control rods. The calculation has indicated that the fuel discharge from the core was disturbed by a significant flow resistance at the entrance nozzle in the current design. Additional static neutronic calculations have been performed to compare basic neutronic characteristics between different scale cores. The static neutronic calculations have clarified that the outward fuel compaction within the inner core increased the reactivity in the large-scale core unlike the small-scale core.     

Combinational use of antibody affinities in an immunoassay for extension of dynamic range and detection of multiple analytes

Here, we describe the coordinated use of two antibodies with different affinities in a single immunoassay to extend the dynamic range and to enable detection of multiple analytes. The combination of dual antibodies was permitted with a flow-based assay at the antibody concentration below the dissociation constant, enabling affinity to govern the antibody-antigen binding. Both high and low affinity antibodies to estriol were used in combination to extend the range. The binding of each antibody was mutually independent and individually occurred over concentration ranges of 10 pM(-1) nM and 100 pM(-1) microM. The wide dynamic range of 10 pM(-1) microM was thus achieved as summation of the proportional signals to the total binding. When a combination of antibodies toward different antigens was used, it effectively detected multiple analytes within a mixture. In simultaneous analysis of a mixture of estradiol and estriol, the total signal was the sum of the binding signals from anti-estradiol and anti-estriol antibodies. In a further refinement, the individual antibodies were flowed through the flow cell sequentially, allowing the quantification of each binding signal within the combination. With this sequential format, measurement of the individual hormones in the range of 1.6 pM(-1) nM was shown. Furthermore, the same flow format was successfully applied to assay estriol and estradiol hormones in mixtures of six related compounds.     

High temperature fatigue crack growth in a cobalt base superalloy

The rates of fatigue crack propagation of a cobalt base superalloy (HS 188) were measured at 75, 1112, 1400 and 1600°F as a function of the range of the stress intensity factor ΔK. Test frequencies were 0.01, 0.1, 1 and 10 Hz. At each elevated temperature there is a critical frequency below which the crack growth rate is oxidation and creep dependent, increasing with decreasing frequency. The mode of fracture changes from transgranular at high frequencies to intergranular at low frequencies.