Fabrication of blue-light emission fused-silica substrates by using Si-ion implantation and high-temperature annealing

We fabricated fused-silica substrates which emit blue light by using Si-ion implantation and high-temperature annealing. Photoluminescence peak wavelengths are around 400 nm, and the peak intensities can be remarkable after annealing above 1150 °C.     

Strain-induced ordering of microdomain structures in polystyrene-block-polybutadiene-block-polystyrene triblock copolymers cross-linked in the disordered state

Strain-induced ordering of microdomain structures in cross-linked polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymers was examined by the small-angle X-ray scattering technique. To stretch the SBS samples at elevated temperature above the glass transition temperature of polystyrene, polybutadiene blocks were chemically cross-linked in the disordered state. The initial morphology was disorder-like or bicontinuous due to incompletion of microphase separation in the presence of the chemical cross-links. When the cross-linked SBS samples were mechanically stretched at 130 °C and were further annealed for 24 h under a stretched state, the random domain structures ordered gradually and lamellar-like regularity was finally attained. It was found that the ordering proceeded more for the case of the higher strain.     

Visualizing Intramolecular Dynamics of Membrane Proteins

Membrane proteins play important roles in biological functions, with accompanying allosteric structure changes. Understanding intramolecular dynamics helps elucidate catalytic mechanisms and develop new drugs. In contrast to the various technologies for structural analysis, methods for analyzing intramolecular dynamics are limited. Single-molecule measurements using optical microscopy have been widely used for kinetic analysis. Recently, improvements in detectors and image analysis technology have made it possible to use single-molecule determination methods using X-rays and electron beams, such as diffracted X-ray tracking (DXT), X-ray free electron laser (XFEL) imaging, and cryo-electron microscopy (cryo-EM). High-speed atomic force microscopy (HS-AFM) is a scanning probe microscope that can capture the structural dynamics of biomolecules in real time at the single-molecule level. Time-resolved techniques also facilitate an understanding of real-time intramolecular processes during chemical reactions. In this review, recent advances in membrane protein dynamics visualization techniques were presented.     

Molybdenum‐Catalyzed Stereospecific Deoxygenation of Epoxides to Alkenes

Mild and simple catalytic systems consisting of molybdenum(VI) dichloride dioxide [MoO₂Cl₂] as a catalyst and a phosphine as reductant have been developed for the stereospecific deoxygenation of epoxides to alkenes. The reactions using 1,2‐bis(diphenylphosphino)ethane (dppe) and triphenylphosphine (PPh₃) proceed with retention and inversion of stereochemistry, respectively. The mild reaction tolerates the presence of various functional groups and affords stereodefined substituted olefins in good yields.

     

Production of Carbon Nanotube by Ethylene Decomposition over Silica-Coated Metal Catalysts

Formation of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) through the decomposition of ethylene at 973 K was achieved using various metal catalysts covered with silica layers. CNFs of various diameters were formed by ethylene decomposition over a Co metal catalyst supported on the outer surface of the silica. In contrast, silica-coated Co catalysts formed CNTs with uniform diameters by ethylene decomposition. Silica-coated Ni/SiO₂ and Pt/carbon black also formed CNTs with uniform diameters, while CNFs and CNTs with various diameters were formed over Ni/SiO₂ and Pt/carbon black without a silica coating. These results indicate that silica layers that envelop metal particles prevent sintering of the metal particles during ethylene decomposition. This results in the preferential formation of CNTs with a uniform diameter.     

Template‐Free Fabrication of Mesoporous Alumina Nanospheres Using Post‐Synthesis Water‐Ethanol Treatment of Monodispersed Aluminium Glycerate Nanospheres for Molybdenum Adsorption

This work reports the template‐free fabrication of mesoporous Al₂O₃ nanospheres with greatly enhanced textural characteristics through a newly developed post‐synthesis “water‐ethanol” treatment of aluminium glycerate nanospheres followed by high temperature calcination. The proposed “water‐ethanol” treatment is highly advantageous as the resulting mesoporous Al₂O₃ nanospheres exhibit 2–4 times higher surface area (up to 251 m² g^?1), narrower pore size distribution, and significantly lower crystallization temperature than those obtained without any post‐synthesis treatment. To demonstrate the generality of the proposed strategy, a nearly identical post‐synthesis “water treatment” method is successfully used to prepare mesoporous monometallic (e.g., manganese oxide (MnO₂)) and bimetallic oxide (e.g., CuCo₂O₄ and MnCo₂O₄) nanospheres assembled of nanosheets or nanoplates with highly enhanced textural characteristics from the corresponding monometallic and bimetallic glycerate nanospheres, respectively. When evaluated as molybdenum (Mo) adsorbents for potential use in molybdenum‐99/technetium‐99m (⁹⁹Mo/^99mTc) generators, the treated mesoporous Al₂O₃ nanospheres display higher molybdenum adsorption performance than non‐treated Al₂O₃ nanospheres and commercial Al₂O₃, thereby suggesting the effectiveness of the proposed strategy for improving the functional performance of oxide materials. It is expected that the proposed method can be utilized to prepare other mesoporous metal oxides with enhanced textural characteristics and functional performance.     

Formation of high performance ice slurry by W/O emulsion in ice storage (effective method to propagate supercooling dissolution)

This study focused ice slurry formation in an ice storage system using W/O emulsions with 70 and 80% water contents. Emulsions consisted of a silicone oil–water mixture with a small amount of amino-group-modified silicone oil additive. Ice slurry was formed by cooling the emulsion without ice adhesion to the cooling wall, as water in the emulsion did not directly contact the cooling wall. As the structure of W/O emulsion slowed the propagation rate of supercooling dissolution, voltage and ultrasonic wave were applied to the W/O emulsion to propagate dissolution more quickly and decrease maximum supercooling degree, respectively. Thus, the effects of voltage and ultrasonic wave applications on propagation rate were clarified.     

High-intensity multi-bunch beam generation by a photo-cathode RF gun

A multi-bunch photo-cathode RF gun system has been developed as an electron source for the production of intense quasi-monochromatic X-rays based on inverse Compton scattering. The desired multi-bunch beam is 100 bunches/pulse with a total charge of 500 nC and a bunch spacing of 2.8 ns. We modified the gun cavity of a ‘BNL-type IV’ RF gun to allow a CsTe cathode plug in the end plate. The system uses a four-dipole chicane beam line to allow the injection of laser light normal to the cathode surface. We compensate the gun cavity beam loading caused by the high-intensity multi-bunch electron beam by injecting the laser pulse before RF power has filled the cavity. We have achieved a total intensity of 220 nC in 100 bunches with a bunch-to-bunch energy spread under 1.3% (peak-to-peak). This paper concentrates on experiments to generate the high-intensity multi-bunch beam with compensation of the bunch-to-bunch energy spread due to heavy beam loading.     

Reinitiation of spermatogonial mitotic differentiation in inactive old BDF1 mouse seminiferous tubules transplanted to W/Wv mouse testis

The seminiferous epithelia of old mice (33 mo of age) are composed of spermatogonia and Sertoli cells. Histochemical examination using the anti-c-kit monoclonal antibody demonstrated that the number of differentiating type A spermatogonia decreases with age. To elucidate the differential activity of old mouse spermatogonia, we transplanted extremely thin seminiferous epithelia of old BDF, mice into W/Wv mouse testes and examined whether or not they could reinitiate differentiation. Artificially cryptorchid mice were used as the control. At 2 wk after transplantation, spermatocytes and round spermatids were detected in transplanted seminiferous tubules of the control, whereas the most advanced spermatogenic cells in those of old mice were spermatocytes. At 4 wk after transplantation, although elongated spermatids were detected in transplanted tubules of the control, haploid cells (spermatids) were still undetectable in those derived from old mice. Thus, meiosis was never restored, although spermatogonia of old mice can reinitiate differentiation into spermatocytes under suitable testicular conditions. Since it has been reported in several mammalian species that age-related changes in the testicular microenvironment lead to the gerontal cessation of spermatogenesis, the present results suggest that both a defective extratubular environment and a defective intratubular environment may cause the cessation of spermatogenesis in old BDF, mice.