22,508 research outputs found
Specific heats of quantum double-well systems
Specific heats of quantum systems with symmetric and asymmetric double-well
potentials have been calculated. In numerical calculations of their specific
heats, we have adopted the combined method which takes into account not only
eigenvalues of for obtained by the
energy-matrix diagonalization but also their extrapolated ones for ( or 30). Calculated specific heats are shown to be rather
different from counterparts of a harmonic oscillator. In particular, specific
heats of symmetric double-well systems at very low temperatures have the
Schottky-type anomaly, which is rooted to a small energy gap in low-lying
two-level eigenstates induced by a tunneling through the potential barrier. The
Schottky-type anomaly is removed when an asymmetry is introduced into the
double-well potential. It has been pointed out that the specific-heat
calculation of a double-well system reported by Feranchuk, Ulyanenkov and
Kuz'min [Chem. Phys. 157, 61 (1991)] is misleading because the zeroth-order
operator method they adopted neglects crucially important off-diagonal
contributions.Comment: 27 pages, 12 figures; Correted figure numbers (accepted in Phys. Rev.
E
Low temperature metallic state induced by electrostatic carrier doping of SrTiO
Transport properties of SrTiO-channel field-effect transistors with
parylene organic gate insulator have been investigated. By applying gate
voltage, the sheet resistance falls below 10 k at low
temperatures, with carrier mobility exceeding 1000 cm/Vs. The temperature
dependence of the sheet resistance taken under constant gate voltage exhibits
metallic behavior (/ 0). Our results demonstrate an insulator to
metal transition in SrTiO driven by electrostatic carrier density control.Comment: 3 pages, 4 figure
Recombination kinetics of a dense electron-hole plasma in strontium titanate
We investigated the nanosecond-scale time decay of the blue-green light
emitted by nominally pure SrTiO following the absorption of an intense
picosecond laser pulse generating a high density of electron-hole pairs. Two
independent components are identified in the fluorescence signal that show a
different dynamics with varying excitation intensity, and which can be
respectively modeled as a bimolecular and unimolecolar process. An
interpretation of the observed recombination kinetics in terms of interacting
electron and hole polarons is proposed
Specific heat and entropy of -body nonextensive systems
We have studied finite -body -dimensional nonextensive ideal gases and
harmonic oscillators, by using the maximum-entropy methods with the - and
normal averages (: the entropic index). The validity range, specific heat
and Tsallis entropy obtained by the two average methods are compared. Validity
ranges of the - and normal averages are ,
respectively, where , and
() for ideal gases (harmonic oscillators). The energy and
specific heat in the - and normal averages coincide with those in the
Boltzmann-Gibbs statistics, % independently of , although this coincidence
does not hold for the fluctuation of energy. The Tsallis entropy for obtained by the -average is quite different from that derived by the
normal average, despite a fairly good agreement of the two results for . It has been pointed out that first-principles approaches previously
proposed in the superstatistics yield -body entropy () which is in contrast with the Tsallis entropy.Comment: 27 pages, 8 figures: augmented the tex
Source mechanism of the magnitude 7.2 Grand Banks earthquake of November 1929: Double couple or submarine landslide?
We have examined P, S, and surface waves derived from seismograms that we collected for the 1929 Grand Banks, Canada, earthquake. This event is noteworthy for the sediment slide and turbidity current that broke the trans-Atlantic cables and for its destructive tsunami. Both the surface-wave magnitude, M_S, and the body-wave magnitude, m_B, calculated from these seismograms are 7.2. Fault mechanisms previously suggested for this event include a NW-SE-striking strike-slip mechanism and an approximately E-W-striking thrust mechanism. In addition, because of the presence of an extensive area of slump and turbidity current, there exists the possibility that sediment slumping could also be a primary causative factor of this event. We tested these fault models and a horizontal single-force (oriented N5°W) model representing a sediment slide against our data. Among these models, only the single-force model is consistent with the P-, S-, and surface-wave data. Our data, however, do not preclude fault models which were not tested. From the spectral data of Love waves at a 50-sec period, we estimated the magnitude of the single force to be about 1.4 × 10^(20) dynes. From this value, we estimated the total volume of sedimentary slumping to be about 5.5 × 10^(11) m^3, which is approximately 5 times larger than a recent estimate of volume from in situ measurements. The difference in estimates of overall volume is likely due to a combination of the inherent difficulty in estimating accurately the displaced sediments from in situ measurements, and of inadequacy of the seismic model; or perhaps because not only the slump but also a tectonic earthquake could have been the cause of this event and contributed significantly to the waveforms studied
VLBI Observations of Water Masers in the Circumstellar Envelope of IRC+60169
Water masers around an AGB star, IRC+60169, were observed at four epochs
using the Japanese VLBI networks. The distribution of the maser features is
limited in a thick-shell region, which has inner and outer expansion velocities
of 7 km/s and 14 km/s at radii of 25 mas and 120 mas, respectively. The
distribution of the red-shifted features exhibits a ring-like structure, the
diameter of which is 30 mas, and corresponds to the inner radius of the maser
shell. This implies that dense gas around the star obscures red-shifted
emission. Although a position--radial velocity diagram for the maser features
is consistent with a spherical shell model, the relative proper motions do not
indicate an expansion motion of the shell. A remarkable property has been found
that is a possible periodic change of the alignment pattern of water maser
spots.Comment: 9 pages including 7 figures, to appear in PASJ, Vol. 54, No.
Cultural background modulates how we look at other persons' gaze
The current study investigated the role of cultural norms on the development of face-scanning. British and Japanese adults’ eye movements were recorded while they observed avatar faces moving their mouth, and then their eyes toward or away from the participants. British participants fixated more on the mouth, which contrasts with Japanese participants fixating mainly on the eyes. Moreover, eye fixations of British participants were less affected by the gaze shift of the avatar than Japanese participants, who shifted their fixation to the corresponding direction of the avatar’s gaze. Results are consistent with the Western cultural norms that value the maintenance of eye contact, and the Eastern cultural norms that require flexible use of eye contact and gaze aversion
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