Takafumi Takahashi

Learn More
Deep observation (∼ 113 hrs) of the Cygnus region at TeV energies using the HEGRA stereoscopic system of air Čerenkov telescopes has serendipitously revealed a signal positionally inside the core of the OB association Cygnus OB2, at the edge of the 95% error circle of the EGRET source 3EG J2033+4118, and ∼ 0.5 north of Cyg X-3. The source centre of gravity(More)
An experimental comparison of sensitivity and resolution of satellite transition (ST) MAS and multiple quantum (MQ) MAS was performed for (27)Al (I=5/2) using several pulse sequences with a z-filter and SPAM, and two inorganic samples of kaolin (Al(2)Si(2)O(5)(OH)(4)) and glass (43.1CaO-12.5Al(2)O(3)-44.4SiO(2)). Six pulse sequences of STMAS (double-quantum(More)
Atomic scale chemical environments of boron in coal has been studied by solid state NMR spectroscopy including magic angle spinning (MAS), satellite transition magic angle spinning (STMAS), and cross-polarization magic angle spinning (CPMAS). The (11)B NMR spectra can be briefly classified according to the degree of coalification. On the (11)B NMR spectra(More)
The chemical states of boron in coal fly ash, which may control its leaching into the environment, were investigated by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) and satellite-transition magic angle spinning nuclear magnetic resonance (STMAS NMR) spectroscopy. The distribution of boron on the surface and in the interior(More)
The atomic structure of a molten 0.3Li2O-0.7B2O3 glass at 1250 K was investigated using ab initio molecular dynamics (AIMD) simulations. The gauge including projector augmented wave (GIPAW) method was then employed for computing the chemical shift and quadrupolar coupling constant of (11)B, (17)O, and (7)Li from 764 AIMD derived structures. The chemical(More)
Complex formation of the uranyl ion (UO(2)(2+)) with triphenylphosphine oxide (OPPh(3)) in 1-butyl-3-methylimidazolium nonafluorobutanesulfonate ([BMI][NfO]) ionic liquid was investigated by means of (31)P NMR spectroscopy. In [BMI][NfO], coordination of OPPh(3) to UO(2)(2+) was found, and its coordination number was 4.1 +/- 0.2, indicating(More)
Diffusion coefficients of water in Na-montmorillonite (Na-mon) suspensions have been determined by pulsed-field gradient spin-echo (PGSE) NMR spectroscopy for three directions (x, y, and z), where x and y mean the directions perpendicular to the static magnetic field, and z the direction parallel to it. Diffusion anisotropy was observed in the suspensions(More)
  • 1