4,182 research outputs found
Temporal extensivity of Tsallis' entropy and the bound on entropy production rate
The Tsallis entropy, which is a generalization of the Boltzmann-Gibbs
entropy, plays a central role in nonextensive statistical mechanics of complex
systems. A lot of efforts have recently been made on establishing a dynamical
foundation for the Tsallis entropy. They are primarily concerned with nonlinear
dynamical systems at the edge of chaos. Here, it is shown by generalizing a
formulation of thermostatistics based on time averages recently proposed by
Carati [A. Carati, Physica A 348, 110 (2005)] that, whenever relevant, the
Tsallis entropy indexed by is temporally extensive: linear growth in time,
i.e., finite entropy production rate. Then, the universal bound on the entropy
production rate is shown to be . The property of the associated
probabilistic process, i.e., the sojourn time distribution, determining
randomness of motion in phase space is also analyzed.Comment: 25 pages, no figure
An AKARI Search for Intracluster Dust of Globular Clusters
We report the observations of 12 globular clusters with the AKARI/FIS. Our
goal is to search for emission from the cold dust within clusters. We detect
diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show
the presence of strong background radiation. They are likely emitted from the
galactic cirrus, while we cannot rule out the possible association of a bump of
emission with the cluster in the case of NGC 6402. We also detect 28 point-like
sources mainly in the WIDE-S images (90 micron). At least several of them are
not associated with the clusters but background galaxies based on some external
catalogs. We present the SEDs by combining the near-and-mid infrared data
obtained with the IRC if possible. The SEDs suggest that most of the point
sources are background galaxies. We find one candidate of the intracluster dust
which has no mid-infrared counterpart unlike the other point-like sources,
although some features such as its point-like appearance should be explained
before we conclude its intracluster origin. For most of the other clusters, we
have confirmed the lack of the intracluster dust. We evaluate upper limits of
the intracluster dust mass to be between 1.0E-05 and 1.0E-03 solar mass
depending on the dust temperature. The lifetime of the intracluster dust
inferred from the upper limits is shorter than 5 Myr (T=70K) or 50 Myr (35K).
Such short lifetime indicates some mechanism(s) are at work to remove the
intracluster dust. We also discuss its impact on the chemical evolution of
globular clusters.Comment: Accepted for publication in PASJ AKARI special issue. 14 pages, 11
figure
SiO Maser Survey of the Large-Amplitude Variables in the Galactic Center
We have surveyed ~400 known large-amplitude variables within 15' of the
galactic center in the SiO J=1--0 v=1 and 2 maser lines at 43 GHz, resulting in
179 detections. SiO lines were also detected from 16 other resulting in 180
detections. SiO lines were also detected from 16 other sources, which are
located within 20" (the telescope half beamwidth) of the program objects. The
detection rate of 48 percent is comparable to that obtained in Bulge IRAS
source surveys. Among the SiO detections, five stars have radial velocities
greater than 200 km/s. The SiO detection rate increases steeply with the period
of light variation, particularly for stars with P>500 d, where it exceeds 80%.
We found that, at a given period, the SiO detection rate is approximately three
times that for OH. These facts suggest that the large-amplitude variables in
the Nuclear Disk region are AGB stars similar in their overall properties to
the inner and outer Bulge IRAS/SiO sources. From the set of radial velocity
data, the mass distribution within 30 pc of the galactic center is derived by a
new method which is based on the collisionless Boltzmann equation integrated
along the line of sight. The mass within 30 pc is about 6.4 [\pm 0.7] \times
10^7 M_{\odot} and the mass of the central black hole is 2.7 [\pm 1.3] \times
10^6 M_{\odot}. Consideration of the line-of-sight velocity of each star and
its potential energy leads to the conclusion that the five high-velocity stars
come from galactocentric distances as high as 300 pc. The high-velocity
subsample of stars with negative radial velocities exhibits a tendency to have
brighter K magnitudes than the subsample of stars with positive velocities. The
origin of these high-velocity stars is discussed.Comment: Hires. figures are available as No.604 of NRO report at
http://www.nro.nao.ac.jp/library/report/list.html . PASJ 56 (april 28 issue)
in pres
SiO Maser Survey of IRAS Sources in the Inner Galactic Disk
We have surveyed 401 color selected IRAS sources in the Galactic disk in the
SiO J=1--0 v= 1 and 2 maser lines at 43 GHz, resulting in 254 (239 new)
detections. The observed sources lie mostly in a strip of the inner Galactic
disk with boundaries -10<l<40 deg and |b|<3 deg. This survey provides radial
velocities of inner-disk stars for which optical measurements cannot be made
due to interstellar extinction. The SiO -- diagram in the area lv$ map does, indicating a slight difference of stellar
type between SiO and OH emitting stars. After identifying all of the SiO
detected sources in the 2MASS near-infrared catalog, we computed their
luminosity distances based on the infrared fluxes. We then mapped these objects
onto the first quadrant of the Galactic plane. Combining the distances with the
SiO radial-velocities, we obtained a pattern speed for SiO maser sources,
Omega_P=21 (+- 13) km s^{-1} kpc^{-1}, between the distances 1 and 5.5 kpc,
without the use of any dynamical models. The increase of the pattern speed
toward the Galactic center (up to 60 km s^{-1} kpc^{-1} between the distances,
5.5 and 7 kpc) suggests the presence of two pattern speeds in the Galaxy.Comment: 38 page 9 figures, high res. eps files are available as NRO report
No. 608 (http://www.nro.nao.ac.jp/library/report/list.html). PASJ 56 No. 4 in
pres
Detections of SiO Masers from the Large-Amplitude Variables in the Galactic Nuclear Disk
We have surveyed known large-amplitude variables within 15' of the Galactic
center in the SiO J=1-0 v=1 and 2 maser lines at 43 GHz, resulting in 79
detections and 58 non-detections. The detection rate of 58 percent is
comparable to that obtained in Bulge IRAS source surveys. SiO lines were also
detected from four other sources near the program objects. The SiO detection
rate increases steeply with the period, particularly for stars with P>500 d,
where it exceeds 80%. We found at a given period that the SiO detection rate is
approximately double that for OH. These facts suggest that the large-amplitude
variables in the Nuclear Disk region are AGB stars similar in their overall
properties to the inner and outer bulge IRAS/SiO sources.Comment: 5 pages, 2 figures, 1 Table. PASJ 54, No 2 April 25 issue in pres
AKARI Near- to Mid-Infrared Imaging and Spectroscopic Observations of the Small Magellanic Cloud. I. Bright Point Source List
We carried out a near- to mid-infrared imaging and spectroscopic observations
of the patchy areas in the Small Magellanic Cloud using the Infrared Camera on
board AKARI. Two 100 arcmin2 areas were imaged in 3.2, 4.1, 7, 11, 15, and 24
um and also spectroscopically observed in the wavelength range continuously
from 2.5 to 13.4 um. The spectral resolving power (lambda/Delta lambda) is
about 20, 50, and 50 at 3.5, 6.6 and 10.6 um, respectively. Other than the two
100 arcmin2 areas, some patchy areas were imaged and/or spectroscopically
observed as well. In this paper, we overview the observations and present a
list of near- to mid-infrared photometric results, which lists ~ 12,000
near-infrared and ~ 1,800 mid-infrared bright point sources detected in the
observed areas. The 10 sigma limits are 16.50, 16.12, 13.28, 11.26, 9.62, and
8.76 in Vega magnitudes at 3.2, 4.1, 7, 11, 15, and 24 um bands, respectively.Comment: 16 pages, 7 figures, accepted for publication in PASJ. Full
resolution version is available at
http://www-irc.mtk.nao.ac.jp/%7Eyita/smc20100112.pd
Parity Dependence of Nuclear Level Densities
A simple formula for the ratio of the number of odd- and even-parity states
as a function of temperature is derived. This formula is used to calculate the
ratio of level densities of opposite parities as a function of excitation
energy. We test the formula with quantum Monte Carlo shell model calculations
in the -shell. The formula describes well the transition from low
excitation energies where a single parity dominates to high excitations where
the two densities are equal.Comment: 14 pages, 4 eps figures included, RevTe
PP4 is a γH2AX phosphatase required for recovery from the DNA damage checkpoint
Phosphorylation of histone H2AX on Ser 139 (γH2AX) is one of the earliest events in the response to DNA double-strand breaks; however, the subsequent removal of γH2AX from chromatin is less understood, despite being a process tightly coordinated with DNA repair. Previous studies in yeast have identified the Pph3 phosphatase (the PP4C orthologue) as important for the dephosphorylation of γH2AX. By contrast, work in human cells attributed this activity to PP2A. Here, we report that PP4 contributes to the dephosphorylation of γH2AX, both at the sites of DNA damage and in undamaged chromatin in human cells, independently of a role in DNA repair. Furthermore, depletion of PP4C results in a prolonged checkpoint arrest, most likely owing to the persistence of mediator of DNA damage checkpoint 1 (MDC1) at the sites of DNA lesions. Taken together, these results indicate that PP4 is an evolutionarily conserved γH2AX phosphatase
Diacylglycerol kinase zeta inhibits G alpha q-induced atrial remodeling in transgenic mice
ArticleHEART RHYTHM. 6(1):78-84 (2009)journal articl
Theory of superconductivity of carbon nanotubes and graphene
We present a new mechanism of carbon nanotube superconductivity that
originates from edge states which are specific to graphene. Using on-site and
boundary deformation potentials which do not cause bulk superconductivity, we
obtain an appreciable transition temperature for the edge state. As a
consequence, a metallic zigzag carbon nanotube having open boundaries can be
regarded as a natural superconductor/normal metal/superconductor junction
system, in which superconducting states are developed locally at both ends of
the nanotube and a normal metal exists in the middle. In this case, a signal of
the edge state superconductivity appears as the Josephson current which is
sensitive to the length of a nanotube and the position of the Fermi energy.
Such a dependence distinguishs edge state superconductivity from bulk
superconductivity.Comment: 5 pages, 2 figure
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