Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Highly chemoselective hydrogenation method using novel finely dispersed palladium catalyst on silk-fibroin: its preparation and activity

A palladium-fibroin complex (Pd/Fib) was prepared by soaking silk-fibroin in MeOH solution of Pd(OAc)₂ for 2 days (under Ar atmosphere)—4 days (under air). Pd(OAc)₂ was gradually absorbed by fibroin and the rapid reduction of fibroin conjugated Pd(OAc)₂ proceeded with MeOH as a reductant at room temperature to be the Pd(0) complex. Pd/Fib catalyzed chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst.     

Selective chemical vapor deposition synthesis of double-wall carbon nanotubes on mesoporous silica

Double-wall carbon nanotubes (DWNTs) have been selectively synthesized over Fe/Co loaded mesoporous silica by catalytic chemical vapor deposition of alcohol. Several silica materials with desired pore diameter and morphology have been investigated for the DWNT growth. The diameter distribution and selectivity of the DWNT are found to depend on the reaction temperature, pore size, and thermal stability of the support material. A high-yield synthesis of DWNTs has been achieved at 900 degrees C over high-temperature stable mesoporous silica. The outer diameter of DWNTs is found to be in the range of 1.5-5.4 nm with a "d" spacing of 0.38 +/- 0.02 nm between inner and outer layers, which is much larger than those of multiwall carbon nanotubes.     

Effect of mono-CDNP substitution of lysine residues on the redox reaction of cytochrome c electrostatically adsorbed on a mercaptoheptanoic acid modified Au(111) surface

The effect of charge-inverting modification of single surface lysine residue on the electron transfer (ET) reaction of horse heart cytochrome c (cyt c) is examined for 12 different types of mono-4-chloro-2,5-dinitrobenzoic acid substituted cyt c (mCDNPc) adsorbed on a Au(111) electrode modified with a self-assembled monolayer (SAM) of 7-mercapto-heptanoic acid (MHA). A negative shift in the redox potential by 10-35 mV as compared to that of native cyt c and a monolayer coverage in the range of 13-17 pmol cm(-2) are observed for electroactive mCDNPc's. The magnitude of the decrease in the ET rate constant (k(et)) of mCDNPc's compared with that of native cyt c depends on the position of the CDNP substitution. For mCDNPc's in which the modified lysine residue is outside of the interaction domain of cyt c with the SAM, the ratio of the k(et) of mCDNPc to that of native cyt c is correlated to the change in the dipole moment vector of cyt c due to the CDNP modification. This correlation suggests that the dipole moment of cyt c determines its orientation of adsorption on the SAM of MHA and significantly affects the rate of the ET. The CDNP modification of lysine residues at the interaction domain significantly decreases the rate, demonstrating the importance of the local charge environment in determining the rate of ET.     

Highly regio- and stereoselective hydrometallation reactions of fluorine-containing internal alkynes: Novel approaches to fluoroalkylated alkenes

Hydroalumination, hydrocupration, and hydroboration reactions of various fluorine-containing alkynes were investigated. The alkyne reacted smoothly with 2.0 equiv. of Red-Al at −78 °C to give the hydroaluminated adduct in a highly regio- and stereoselective manner, which was treated with iodine, the corresponding vinyliodide being produced in moderate yield. Hydrocupration of the alkynes also took place, but the resulting vinylmetal reacted with various electrophiles sluggishly. In sharp contrast, the reaction with dicyclohexylborane proceeded smoothly to afford the cis-addition products preferentially, which were subjected to Suzuki-Miyaura cross-coupling reaction, leading to trisubstituted alkenes in high yields.     

Synthesis of α-hydroxy-γ-butyrolactones from acrylates and 1,3-dioxolanes using N-hydroxyphthalimide (NHPI) as a key catalyst

A new route to α-hydroxy-γ-butyrolactones through three-component radical coupling of 1,3-dioxoranes, acrylates, and molecular oxygen using N-hydroxyphthalimide (NHPI) as a key catalyst has been developed. For example, the addition of 1,3-dioxarane to methyl acrylate under dioxygen by NHPI followed by catalytic hydrogenation of the resulting adduct on Pd/C afforded α-hydroxy-γ-butyrolactone in good yield. This method provides a facile approach to α-hydroxy-γ-butyrolactones, which are difficult to synthesize by conventional methods.     

Association behavior of a nitrilotriacetic-acid-modified dye in a poly(vinyl alcohol) film containing Ni(II)-adsorbed gold nanoparticles.

The association behavior of the dyes 5(6)-carboxyfluorescein and nitrilotriacetic acid (NTA)-modified 5(6)-carboxyfluorescein (F-NTA) in a poly(vinyl alcohol) (PVA) film and in a PVA film containing metal nanoparticles is investigated. Well-dispersed gold nanoparticles (AuNps) and Ni(II)-adsorbed AuNps are formed in the PVA film using in situ photochemical fabrication method. 5(6)-carboxyfluorescein and F-NTA are doped into the films. The F-NTA forms an H-aggregate in the PVA film containing Ni(II)-adsorbed AuNps. It is suggested that the interaction between NTA and Ni(II) adsorbed on the AuNps promotes the formation of the H-aggregate.     

Raman spectroscopic studies on methane + tetrafluoromethane mixed-gas hydrate system

Raman spectra of intramolecular vibration mode for each guest species in the methane + tetrafluoromethane (CF₄) mixed-gas hydrate crystal have been measured at 291.1 K. Both of pure guest species generate the structure-I hydrate in the present pressure ranges. Isothermal phase-equilibrium curve exhibits two discontinuous points around the equilibrium methane compositions (water-free) in the gas phase of 0.3 and 0.8. At the above points, the Raman spectra of both guest molecules have been drastically changed. One of the most important findings is that the crystal of methane + tetrafluoromethane mixed-gas hydrate shows the structural phase-transition (from the structure-I to the structure-II and back to the structure-I) caused by composition changes.     

Oxime-based salen-type tetradentate ligands with high stability against imine metathesis reaction

Although salen and its analogues are versatile chelate ligands in inorganic and organometallic chemistry, synthesis of unsymmetrical salen derivatives consisting of two different salicylideneimine moieties is difficult because of the C=N bond recombination. To develop stable analogues of salen-type ligands, we synthesized a series of new ligands salamo (=1,2-bis(salicylideneaminooxy)ethane) on the basis of O-alkyl oxime instead of the imine moiety. Eight salamo ligands 1a-h were prepared in 64-88% yields as colorless crystals from the corresponding salicylaldehydes 2a-h. The crystal structure of 1a-c suggests that the oxime-OH form is more predominant than the keto-NH form. The reaction of 2a-e with excess 1,2-bis(aminooxy)ethane gave monooximes 3a-e in 59-86%, which further reacted with a different salicylaldehyde to afford unsymmetrical salamo ligands 4-8 as stable crystals in 51-70%. No reaction took place when a mixture of salamo derivatives 1a and 1b was treated at 40 degrees C in H2O/MeCN (5:95). However, the metathesis reaction of salen derivatives 9a and 9b completed in 2 h to give a statistical mixture. Monooxime 3b was much more stable than monoimine 11 which is difficult to be isolated. These results indicate the extremely high stability of the salamo derivatives 1 and precursors 3.     

Preparation of monodisperse SiO2 nanoparticles by membrane emulsification using ideally ordered anodic porous alumina

Monodisperse SiO2 particles of nanometer dimensions were fabricated by membrane emulsification using ideally ordered anodic porous alumina. For the preparation of monodisperse emulsion droplets, the dispersed phase was pressed through a porous alumina membrane into the continuous phase. After solidification treatment of the emulsion droplets, prepared spherical SiO2 nanoparticles with uniform sizes were obtained. From scanning electron microscope observation of the obtained particles, it was confirmed that the size distribution of SiO2 nanoparticles is relatively narrow.