Evolution of long-period stacking ordered structures on annealing as-cast Mg85Y9Zn6 alloy ingot observed by synchrotron radiation small-angle scattering

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Colored Fluorescent Silk Made by Transgenic Silkworms

Silk is a protein fiber used to weave fabrics and as a biomaterial in medical applications. Recently, genetically modified silks have been produced from transgenic silkworms. In the present study, transgenic silkworms for the mass production of three colors of fluorescent silks, (green, red, and orange) are generated using a vector originating from the fibroin H chain gene and a classical breeding method. The suitability of the recombinant silks for making fabrics is investigated by harvesting large amounts of the cocoons, obtained from rearing over 20 thousand silkworms. The application of low temperature and a weakly alkaline solution for cooking and reeling enables the production of silk fiber without loss of color. The maximum strain tolerated and Young's modulus of the fluorescent silks are similar to those of ordinary silk, although the maximum stress value of the recombinant silk is slightly lower than that of the control. Fabrics with fluorescent color are demonstrated using the recombinant silk, with the color persisting for over two years. The results indicate that large amounts of genetically modified silk can be made by transgenic silkworms, and the silk is applicable as functional silk fiber for making fabrics and for use in medical applications.     

New type of pressurized cultivation method providing oxygen for piezotolerant yeast

For efficient oxygen supply to pressurized culture, we developed a method using a highly pressurized membrane reactor with an air-saturated medium circulation system. The new method increased the cell growth of aerobic yeast approximately 20 folds larger than that in the case of using a conventional method.     

Synthesis of stable and soluble one-handed helical poly(substituted acetylene)s without chiral pendant groups via polymer reaction in membrane state

A soluble and stable one-handed helical conjugated polymer without the coexistence of any other chiral moieties was successfully synthesized by asymmetric-induced polymerization of a chiral monomer having two hydroxyl groups followed by desubstitution of the chiral groups in a solid membrane state. The reason for the success was the polymer reaction was carried out in the membrane state. This is an alternative method to obtain such a unique chiral polymer which was obtained only by the helix-sense-selective polymerization (HSSP) we reported before. In addition the efficiency of the chiral induction was higher than that of the HSSP. It is interesting that the “Membrane state” acted like as if a protecting group.     

Experimental analysis of flow structure in contra-rotating axial flow pump designed with different rotational speed concept

As a high specific speed pump, the contra-rotating axial flow pump distinguishes itself in a rear rotor rotating in the opposite direction of the front rotor, which remarkably contributes to the energy conversion, the reduction of the pump size, better hydraulic and cavitation performances. However, with two rotors rotating reversely, the significant interaction between blade rows was observed in our prototype contra-rotating rotors, which highly affected the pump performance compared with the conventional axial flow pumps. Consequently, a new type of rear rotor was designed by the rotational speed optimization methodology with some additional considerations, aiming at better cavitation performance, the reduction of blade rows interaction and the secondary flow suppression. The new rear rotor showed a satisfactory performance at the design flow rate but an unfavorable positive slope of the head-flow rate curve in the partial flow rate range less than 40% of the design flow rate, which should be avoided for the reliability of pump-pipe systems. In the present research, to understand the internal flow field of new rear rotor and its relation to the performances at the partial flow rates, the velocity distributions at the inlets and outlets of the rotors are firstly investigated. Then, the boundary layer flows on rotor surfaces, which clearly reflect the secondary flow inside the rotors, are analyzed through the limiting streamline observations using the multi-color oil-film method. Finally, the unsteady numerical simulations are carried out to understand the complicated internal flow structures in the rotors.     

Apatite mineralization abilities and mechanical properties of covalently cross-linked pectin hydrogels

Natural bone has features such as high fracture toughness and bone-bonding bioactivity, and is organic–inorganic hybrid composed of collagen and apatite crystals. Therefore, apatite-polymer hybrids designed to mimic the structure of bone represent candidates for high-performance bone substitutes. In this study, we prepared pectin hydrogels through covalent cross-linking using divinylsulfone (DVS) and investigated their apatite-forming abilities of the gels in simulated body fluid (SBF) and mechanical properties by tensile test. The obtained results were interpreted in terms of surface charge of the gels and chemical reaction with SBF. The apple- and citrus-derived gels formed the apatite on their surfaces in SBF within 3 days. These gels showed tensile strength around 30 MPa.     

Fabrication and characteristics of polyfluorene based organic photodetectors using fullerene derivatives

The characteristics of organic photodetectors (OPDs) by solution process using one of the polyfluorene derivatives poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) and two fullerene derivatives [6-6]phenyl-C61-butyric acid methyl ester (PCBM) or N-Ts aziridinofullerene (TsAF) are investigated. F8T2:PCBM devices showed good rectifying characteristics in a dark state and photosensitive characteristics, and fast frequency responses. Weight ratio of 1:1 device showed larger photocurrent than 1:4 device and obtained over 50 MHz of cutoff frequency under reverse bias voltage of 10 V. This result suggests that F8T2:PCBM device can be applied to a photodetector for detecting several tens of megahertz optical signals under blue light irradiation. The polarity of J–V characteristics of F8T2:fullerene derivative device is strongly affected by charge injection and extraction between fullerene derivative and electrodes.     

Unstable sinking of spheres at higher air velocity in a gas-solid fluidized bed

Float-sink of large objects (on order of cm) in a gas-solid fluidized bed of powder (on order of 100 s of microns) based on density difference has been utilized for dry density separation in industry. The air velocity u₀/u_mf is one of the important factors operating the fluidized bed, where u₀ and u_mf are the superficial air velocity and the minimum fluidization air velocity, respectively. It is empirically known that the sinking of heavy objects is “occasionally” unstable in the fluidized bed combustor, for which the higher air velocity u₀/u_mf > 4 is used. Unstable sinking means heavy objects that are expected to sink but sometimes do not. However, the precise conditions at which the unstable sinking occurs are not clear. In this study, we investigated the float-sink characteristics at a given air velocity u₀/u_mf = 2–7 using glass beads of size D_gb = 425–600 μm and 600–850 μm as the fluidized powder bed media. The float-sink experiments were carried out at the bed height h_gb = 150 mm and 75 mm using density adjusted spheres (diameter = 30 mm). We found that the spheres stably float or sink based on density difference at D_gb = 425–600 μm & h_gb = 150 mm and at D_gb = 600–850 μm & h_gb = 75 mm. However, the unstable sinking does occur at u₀/u_mf > 4 at D_gb = 600–850 μm & h_gb = 150 mm. These results indicate that the powder size and the bed height are key factors to induce the unstable sinking at the higher air velocity.     

Thermal conductivity and electrical resistivity of liquid Ag–In alloy

To understand and predict the progression of core meltdown accidents in nuclear power plants, it is important to understand the behavior of molten core materials. We focused on the melting behavior of Ag–In–Cd alloys used in the control rods of pressurized water reactors that are known to melt first when a severe accident occurs. To obtain fundamental knowledge about these alloys, we studied the thermal conductivity of Ag–In binary alloys in this study. We evaluated thermal conductivity using two approaches: evaluating from thermal diffusivity up to 873 K measured by the laser-flash method, and calculating based on the Wiedemann–Franz law using the electrical resistivity up to 1273 K measured by the four-probe method. The values of thermal conductivity of liquid Ag–In alloys obtained by these two methods agreed well except for pure indium. Although Ag is known as a material that has one of the highest thermal conductivities, the thermal conductivity of liquid Ag–In alloys is much lower than that of pure liquid Ag (177 W/mK at 1273 K), but almost the same or less than that of liquid In (59.2 W/mK at 1273 K) in all Ag_1?xIn_x (x = 0.2–0.8) alloys at all temperatures in this measurement.     

Synthesis and in vitro biodegradation of pure octacalcium phosphate spheres

Octacalcium phosphate (OCP) is a key precursor of biological apatite in hard tissues with excellent osteoconductive and biodegradable properties for bone regeneration. OCP spherical granules are expected to be useful as drug delivery carriers, since OCP has high specific surface area. Although there have been some reports of OCP sphere preparation, methods for preparing pure OCP spheres are limited. The objective of this study is the preparation of spherical granules of pure OCP and assessment of their in vitro biodegradation in physiological conditions. We successfully prepared spherical pure OCP granules with a size of ~500 µm without any organic additives by simple immersion of α-tricalcium phosphate spherical granules in pH 5.0 acetate buffered solutions at 60°C. The granules had core-shell structure composed of OCP crystals different particle size. The spherical granules showed 20%-40% in vitro degradation in physiological conditions; however, the phase transition of OCP was not significantly observed.