In the 1940's, several destructive earthquakes occurred in western Japan. Seismograms in this period were usually recorded on smoked paper and the quality was poor compared to modern digital data. But the recent development of image processing technology enabled us to reconstruct feasible waveform data, whereby we investigated source rupture processes of two devastating earthquakes: the Tonankai earthquake (M7.9) of December 7, 1944, and the Mikawa earthquake (M6.8) of January 13, 1945. The results for the Tonankai earthquake show that the source roughly consists of a single asperity with a length scale of 100 km, having no segment structure with a smaller length-scale. Such a feature seems to be reflected to the sea bottom topography above the source region. The main source parameters are as follows: the seismic moment = 1.0 × 10 21 Nm (Mw=7.9); the fault area = 140 km × 80 km; (strike, dip, rake) = (225• , 15• , 79 • ); the maximum and averaged dislocations = 4.4 m and 3.0 m, respectively. The analysis of the seismograms for the Mikawa earthquake shows that the source is a reverse fault with a slight left-lateral component. The pressure axis is directed to ENE-WSW, which is a little rotated from the EW compression axis prevailing in western Japan. This fault can be regarded as the southern extension of the Nobi earthquake fault system. The main source parameters are as follows: the seismic moment = 1.0 × 10 19 Nm (Mw=6.6); the fault area = 20 km × 15 km; (strike, dip, rake) = (135• , 30• , 65 • ); the maximum and averaged dislocations are 2.1 m and 1.1 m, respectively. The slip distribution mainly consists of two asperities: the one near the hypocenter and the other 10-15 km northwest from it. The heavily damaged area is well correlated with the northwestern asperity.
Repeated stressful events are known to be associated with onset of depression. Further, stress activates the hypothalamic–pituitary–adrenocortical (HPA) system by elevating plasma cortisol levels. However, little is known about the related downstream molecular pathway. In this study, by using repeated water-immersion and restraint stress (WIRS) as a stressor for mice, we attempted to elucidate the molecular pathway induced by elevated plasma corticosterone levels. We observed the following effects both, in vivo and in vitro: (1) repeated exposure to WIRS activates the 3-phosphoinositide-dependent protein kinase (PDK1)–serum glucocorticoid regulated kinase (SGK1)–N-myc downstream-regulated gene 1 (NDRG1)–adhesion molecule (i.e., N-cadherin, α-catenin, and β-catenin) stabilization pathway via an increase in plasma corticosterone levels; (2) the activation of this signaling pathway induces morphological changes in oligodendrocytes; and (3) after recovery from chronic stress, the abnormal arborization of oligodendrocytes and depression-like symptoms return to the control levels. Our data strongly suggest that these abnornalities of oligodendrocytes are possibly related to depression-like symptoms.
We studied the temperature and chirality dependence of the photoluminescence ͑PL͒ linewidth of single carbon nanotubes to clarify the mechanism of exciton dephasing. The PL linewidth of a single carbon nanotube broadened linearly with increasing temperature, indicating that the linewidth and exciton dephasing are determined through exciton-phonon interactions. From the chirality dependence of the PL linewidth, we concluded that exciton dephasing is caused by both the longitudinal acoustic and twisting phonon modes.The dynamics of electrons and excitons are strongly influenced by phonons. In bulk materials, the loss of coherence ͑i.e., dephasing͒ of electrons and excitons occurs by phonon scattering on subpicosecond time scales. 1 The dephasing time and mechanism depend strongly on the dimensionality and size of the electronic states in low-dimensional semiconductors, such as one-dimensional ͑1D͒ quantum wires and zero-dimensional quantum dots. 2,3 A single-walled carbon nanotube ͑SWNT͒ is a prototypical 1D electronic system. The optical properties of SWNTs have attracted a great deal of attention, both from the perspective of their fundamental physics, and for their optoelectronic device applications. Potential applications include electroluminescence, 4 saturable absorbers for ultrafast lasers, 5 and fluorescent biolabeling. 6 These optical properties are due to the creation of stable excitons by enhanced Coulomb interactions. [7][8][9] The exciton dynamics are dominated by the exciton dephasing and energy relaxation processes, in which the exciton-phonon interactions play an important role. 10 However, the exciton dephasing mechanism in SWNTs is still poorly understood.Single carbon nanotube photoluminescence ͑PL͒ provides inherent properties of SWNT beyond the ensembleaveraged PL measurements. [11][12][13][14][15][16][17][18] As the exciton dephasing induced by phonon scattering broadens the linewidths of optical transitions, information on the exciton dephasing mechanism can be obtained directly from the intrinsic spectral linewidth of a single carbon nanotube, free from the inhomogeneous broadening. In this paper, we studied the exciton dephasing using single carbon nanotube PL spectroscopy. The PL linewidth of a single carbon nanotube broadened linearly with temperature, indicating that the linewidth and exciton dephasing were determined by exciton-phonon interactions. From the diameter and chirality dependence of the linewidth, we also investigated the mechanism of the exciton dephasing in detail.Isolated and suspended SWNTs between the grooves were used as samples. The SWNTs were synthesized on patterned SiO 2 and Si substrates by the alcohol catalytic chemical vapor deposition method. 19 The substrates were patterned with parallel grooves of typical width and depth of 0.5-5 and 0.5-5 m, respectively. Several SWNT samples were prepared with different growth temperatures and times, and single nanotube PL spectroscopy was performed on samples grown at 650-800°C for 10 min. The average density of luminescent...
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