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121.
In the presence of trifluoromethanesulfonic acid (TfOH) or bis(trifluoromethane-sulfonyl)imide (Tf2NH), iodosobenzene (PhI=O) efficiently promoted the reactions of dicarbonyl compounds as well as monocarbonyl compounds with nitriles to give 2,4-disubstituted and 2,4,5-trisubstituted oxazole in a single step under the mild conditions. 相似文献
122.
Spin-orbit interaction of positronium (Ps) with the surrounding atoms, predicted by Mitroy and Novikov [Phys. Rev. Lett. 90, 183202 (2003)], has been detected experimentally. We have found that the lifetime of the magnetically unperturbed ortho-Ps in Xe gas of 1 atm decreases significantly when a magnetic field of 1.0 T is applied. This decrease is attributed to the Ps spin conversion caused by spin-orbit interaction during Ps-Xe collision. The annihilation cross section of ortho-Ps due to this interaction has been determined to be 3 times as large as that expected by Mitroy and Novikov. 相似文献
123.
Yuasa T Maksimenko A Hashimoto E Sugiyama H Hyodo K Akatsuka T Ando M 《Optics letters》2006,31(12):1818-1820
The unique tomographic imaging method based on refractive effects that was recently developed by Maksimenko et al. [Appl. Phys. Lett. 86, 124105 (2005)] exhibits an excellent imaging property in the hard-x-ray region for phase objects such as soft materials and biological samples. However, there seems to have been little consideration of the physical aspects of the underlying imaging principles. Also, as the method is similar to diffraction-enhanced-imaging (DEI)-based computed tomography (CT), the difference between these two methodologies has not been made clear. We theoretically consider the imaging principles starting from the measurement process to the reconstruction procedures from the viewpoint of geometrical optics and then clarify their difference in relationship to the physical quantities to be depicted. The major feature of this novel method is the in-plane two-dimensional vector-field reconstruction of the refractive-index gradient in an object, while DEI CT obtains the out-of-plane scalar-field gradient component. In other words, the novel method and DEI CT present the transverse and the longitudinal components, respectively, of the three-dimensional vector fields of the gradient refractive index. Therefore they can be considered complementary to each other. 相似文献
124.
K. Kirihara H. Hyodo Z. Wang K. Kawaguchi T. Sasaki K. Soga 《Journal of solid state chemistry》2006,179(9):2799-2804
We measured electrical conductance of single crystalline boron nanobelts having α-tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. The pure boron nanobelt is a p-type semiconductor and its electrical conductivity was estimated to be on the order of 10-3 (Ω cm)−1 at room temperature. The carrier mobility of pure boron nanobelt was measured to be on the order of 10−3 (cm2 Vs−1) at room temperature and has an activation energy of ∼0.19 eV. The Mg-doped boron nanobelts have the same α-tetragonal crystalline structure as the pristine nanobelts. After Mg vapor diffusion, the nanobelts were still semiconductor, while the electrical conductance increased by a factor of 100-500. Transition to metal or superconductor by doping was not observed. 相似文献
125.
Yuki Tsujikawa Makoto Shoji Masashi Hamada Tomoya Takeda Izumi Mochizuki Toshio Hyodo Iwao Matsuda Akari Takayama 《Molecules (Basel, Switzerland)》2022,27(13)
We have investigated the structure of χ3-borophene on Ag(111), a monolayer material of boron atoms, via total-reflection high-energy positron diffraction (TRHEPD). By comparing the experimental rocking-curves with ones for several structures calculated by using dynamical diffraction theory, we confirmed that the χ3-borophene layer has a flat structure. The distance from the topmost layer of the metal crystal is 2.4 Å, which is consistent with results reported by X-ray standing wave-excited X-ray photoelectron spectroscopy. We also demonstrated that the in-plane structure of χ3-borophene is compatible with the theoretical predictions. These structural properties indicate that χ3-borophene belongs to a group of epitaxial monolayer sheets, such as graphene, which have weak interactions with the substrates. 相似文献