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261.
Yamazaki S Hosomura Y Matsuda I Hobara R Eguchi T Hasegawa Y Hasegawa S 《Physical review letters》2011,106(11):116802
We have succeeded in detecting metallic transport in a monatomic layer of In on an Si(111) surface, Si(111)-sqrt[7]×sqrt[3]-In surface reconstruction, using the micro-four-point probe method. The In layer exhibited conductivity higher than the minimum metallic conductivity (the Ioffe-Regel criterion) and kept the metallic temperature dependence of resistivity down to 10?K. This is the first example of a monatomic layer, with the exception of graphene, showing metallic transport without carrier localization at cryogenic temperatures. By introducing defects on this surface, a metal-insulator transition occurred due to Anderson localization, showing hopping conduction. 相似文献
262.
Haruaki Kurasaki Iwao Okamoto Dr. Nobuyoshi Morita Dr. Osamu Tamura Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12754-12763
This article describes in detail the first total synthesis of grandisine alkaloids, grandisines B, D, and F, which show affinity for the human δ‐opioid receptor. The key steps in this synthesis are construction of the isoquinuclidinone moiety of 2 by intramolecular imine formation and the tetracyclic ring system of 4 by stereoselective ring closure of the enolate of amine 8 generated by 1,4‐addition of ammonia to 9 . Synthesis of key intermediate 9 featured a highly stereoselective Brønsted acid mediated Morita–Baylis–Hillman (MBH) reaction via the N‐acyl iminium ion. 相似文献
263.
Hiroshi Murata Iwao Satake Katumitu Hayakawa Masaru Tanokura 《Colloid and polymer science》2006,284(7):725-732
The conformation of poly(l-lysine) (PLL) was investigated in sodium alkanesulfonate CnSO3Na (n=8, 7) at various temperatures by circular dichroism spectrum measurements. C8SO3Na induced a double-step conformational change from a coil, to a β-sheet, and then to an α-helix, in which C7SO3Na induced a single-step coil-to-helix conformational change. Binding isotherms of C8SO3Na by PLL were constructed from the potentiometry of equilibrium concentration of the surfactant using a surfactant ion-selective electrode. The curves indicated the cooperative binding characteristic and were analyzed by a linear lattice model using the Bethe approximation. The thermodynamic parameters obtained from the model revealed that the binding of C8SO3Na by PLL was an entropy-driven process. The conformational change was observed at nearly full binding, presumably due to the surfactant clustering of the ordered conformation. 相似文献
264.
Using angle-resolved photoemission spectroscopy, we investigate changes in the band dispersion of a free-electron-like surface state of [FORMULA: SEE TEXT], induced by adsorption of submonolayer Au adatoms. At room temperature, where the adatoms are in a two-dimensional adatom-gas phase, electrons are transferred from the Au adatoms to the substrate, shifting the surface band downwards and causing it to deviate from a parabolic dispersion. At 135 K where the Au adatoms are frozen at specific sites of the substrate, the band splits into two. This band splitting can be explained in terms of hybridization between the unperturbed surface band and the localized virtual bound states induced by the Au adatoms. 相似文献
265.
We have demonstrated the operation of a frontside-illuminated GaAs/AlGaAs quantum-well photodetector based on intersubband absorption in a quantum well (QW) with a targeted peak frequency of 3 THz. A multiple-quantum-well structure consists of 20 periods of 18 nm QWs interleaved by 80 nm barriers with an Al alloy content of 2%. We measured the following performance characteristics: dark current, responsivity, and spectral response. A responsivity of 13 mA/W at an electric bias of 40 mV and an operating temperature of 3 K was obtained with a peak response close to the designed detection frequency. The dark current density was a few microA/cm2 and was limited by thermally assisted tunneling through the barriers. We looked also at possible designs to optimize the device's performance. 相似文献
266.
Ikufumi Katayama Hiroshi Shimosato Masaaki Ashida Iwao Kawayama Masayoshi Tonouchi Tadashi Itoh 《Journal of luminescence》2008,128(5-6):998-1000
We have measured the complex dielectric constants of SrTiO3 thin films deposited on MgO substrate, by using the broadband terahertz time-domain spectroscopy. The dielectric dispersion of SrTiO3 thin films with thickness of 1046, 460 and 55 nm has been observed in the frequency range from 0.1 to 8 THz. The dispersion mainly consists of the TO1 ferroelectric soft mode with a slight absorption of the TO2 phonon mode. From the analysis of the obtained dispersion, we found that the soft mode frequency hardens as the thickness of the film becomes thinner, and is extremely large compared with the bulk crystals. The damping of the soft mode is also larger than that of bulk SrTiO3, which suggests the extrinsic nature of the broadening of the soft mode dispersion. In the thinnest film of 55 nm, even the shape of the dielectric dispersion changes, which may be related to integrated defects near the interface. 相似文献
267.
A formulation ofentropy production is given with the aid of relative entropy in the nonlinear response theory of a quantum dynamical system. It allows a natural interpretation of the quantity in terms of familiar thermodynamic notions, such as force and response current conjugate to it, without sacrificing the full nonlinearity in the perturbing force. For the understanding ofdissipativity aspositive entropy production, the stationarity of states and coarse graining of time scale turn out to be essential, which are implemented by some time averaging procedures involvingalmost periodic external forces. Finally, it is shown that the obtained result reduces, in the linear response regime, to the power dissipation appearing in the well-known fluctuation-dissipation relation. 相似文献
268.
269.
Successful synergetic combination of the electron-transfer catalyst, TPPMn, and the phase-transfer catalyst, TOMA, in the oxidation of alcohols or hydrocarbons were reported. 相似文献
270.