3,417 research outputs found
Participation of Cbfa1 in regulation of chondrocyte maturation
AbstractObjective Cbfa1 is a transcription factor, which is classified into the runt family. The mice lacking this gene display complete loss of bone formation, indicating that Cbfa1 is an essential factor for osteoblast differentiation. The Cbfa1-deficient mice also show an abnormality in cartilage development. Although cartilage anlagens are well formed in these mice, endochondral ossification is blocked, and most of chondrocytes fail to differentiate into their maturation form as characterized by the absence of type X collagen and low levels of alkaline phosphatase activity. It is suggested that Cbfa1 may participate in chondrocyte differentiation. In this study, we have investigated the role of Cbfa1 in chondrocytes during their cytodifferentiation in vitro.Design To investigate the role of Cbfa1 in regulation of chondrocyte differentiation, we over-expressed Cbfa1 or its dominant negative form in cultured chick chondrocytes using a retrovirus (RCAS)system and examined changes in chondrocyte behaviour induced by the introduced genes.Results Mature chondrocytes isolated form the cephalic portion of sterna seemed to express Cbfa1 more prominently than immature chondrocytes isolated from the one-third caudal portion of sterna. Over-expression of Cbfa1 in immature chondrocytes strongly stimulated alkaline phosphatase activity and matrix calcification. In contrast, expression of a dominant negative form of Cbfa1, which lacks the C-terminal PST domain, severely inhibited alkaline phosphatase activity and matrix calcification in mature chondrocytes.Conclusion Taken together with the observation that Cbfa1 transcripts dominantly localized in hypertrophic chondrocytes as well as in osteoblasts, it is suggested that Cbfa1 plays an important role in the progression of chondrocyte maturation
The monitoring system for the aerogel Cherenkov counter of the BELLE detector
We report on a design and performances of a monitoring system developed for
the aerogel Cherenkov counters (ACC) of the BELLE detector. The system consists
of blue LEDs, a diffuser box, and optical distributors which distribute the LED
light to the ACC modules. The employed LED (NSPB series) has been observed to
have high reliability on the long term stability and the temprature dependence.
The diffuser box is employed to reduce the intrinsic non-uniformity of the LED
light intensity. The overall performances of the present monitoring system on
uniformity and intensity of the light output have been found to satisfy all the
requirements for the monitoring.Comment: 24 pages, LaTeX, 13 eps figures, to be published in Nucl. Instrum.
and Meth. A. Postscript file (4.5 MB) is available at
http://www-hep.phys.saga-u.ac.jp/~murakami/paper/xxx_accmon.p
Constraints on Cold Dark Matter in the Gamma-ray Halo of NGC 253
A gamma-ray halo in a nearby starburst galaxy NGC 253 was found by the
CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). By fitting the
energy spectrum with expected curves from Cold Dark Matter (CDM) annihilations,
we constrain the CDM-annihilation rate in the halo of NGC 253. Upper limits for
the CDM density were obtained in the wide mass range between 0.5 and 50 TeV.
Although these limits are higher than the expected values, it is complementary
important to the other experimental techniques, especially considering the
energy coverage. We also investigate the next astronomical targets to improve
these limits.Comment: 13 pages, 5 figures, aastex.cls, natbib.sty, To appear in ApJ v596n1,
Oct. 10, 200
Study of a Threshold Cherenkov Counter Based on Silica Aerogels with Low Refractive Indices
To identify and in the region of GeV/c, a
threshold Cherenkov counter equipped with silica aerogels has been
investigated. Silica aerogels with a low refractive index of 1.013 have been
successfully produced using a new technique. By making use of these aerogels as
radiators, we have constructed a Cherenkov counter and have checked its
properties in a test beam. The obtained results have demonstrated that our
aerogel was transparent enough to make up for loss of the Cherenkov photon
yield due to a low refractive index. Various configurations for the photon
collection system and some types of photomultipliers, such as the fine-mesh
type, for a read out were also tested. From these studies, our design of a
Cherenkov counter dedicated to separation up to a few GeV/c %in the
momentum range of GeV/c with an efficiency greater than \%
was considered.Comment: 21 pages, latex format (article), figures included, to be published
in Nucl. Instrm. Meth.
Radiogenic power and geoneutrino luminosity of the Earth and other terrestrial bodies through time
We report the Earth's rate of radiogenic heat production and (anti)neutrino
luminosity from geologically relevant short-lived radionuclides (SLR) and
long-lived radionuclides (LLR) using decay constants from the geological
community, updated nuclear physics parameters, and calculations of the
spectra. We track the time evolution of the radiogenic power and luminosity of
the Earth over the last 4.57 billion years, assuming an absolute abundance for
the refractory elements in the silicate Earth and key volatile/refractory
element ratios (e.g., Fe/Al, K/U, and Rb/Sr) to set the abundance levels for
the moderately volatile elements. The relevant decays for the present-day heat
production in the Earth ( TW) are from K, Rb,
Sm, Th, U, and U. Given element concentrations
in kg-element/kg-rock and density in kg/m, a simplified equation to
calculate the present day heat production in a rock is: The
radiogenic heating rate of Earth-like material at Solar System formation was
some 10 to 10 times greater than present-day values, largely due to
decay of Al in the silicate fraction, which was the dominant radiogenic
heat source for the first Ma. Assuming instantaneous Earth formation,
the upper bound on radiogenic energy supplied by the most powerful short-lived
radionuclide Al ( = 0.7 Ma) is 5.510 J,
which is comparable (within a factor of a few) to the planet's gravitational
binding energy.Comment: 28 pages, 6 figures, 5 table
CANGAROO-III Observation of TeV Gamma Rays from the vicinity of PSR B1 706-44
Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov
Telescope has detected extended emission of TeV gamma rays in the vicinity of
the pulsar PSR B170644. The strength of the signal observed as
gamma-ray-like events varies when we apply different ways of emulating
background events. The reason for such uncertainties is argued in relevance to
gamma-rays embedded in the "off-source data", that is, unknown sources and
diffuse emission in the Galactic plane, namely, the existence of a complex
structure of TeV gamma-ray emission around PSR B170644.Comment: 10 pages, 13 figures, to be published in Ap
Equilibrium magnetisation structures in ferromagnetic nanorings
The ground state of the ring-shape magnetic nanoparticle is studied.
Depending on the geometrical and magnetic parameters of the nanoring, there
exist different magnetisation configurations (magnetic phases): two phases with
homogeneous magnetisation (easy-axis and easy-plane phases) and two
inhomogeneous (planar vortex phase and out-of-plane one). The existence of a
new intermediate out-of-plane vortex phase, where the inner magnetisation is
not strongly parallel to the easy axis, is predicted. Possible transitions
between different phases are analysed using the combination of analytical
calculations and micromagnetic simulations.Comment: LaTeX, 19 pages, 11 figure
- …