1,054 research outputs found
Jadeite originating from plagioclase in L6 and H6 chondrites
第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日(金) 国立国語研究所 2階講
High-Energy Neutrino Astronomy
Kilometer-scale neutrino detectors such as IceCube are discovery instruments
covering nuclear and particle physics, cosmology and astronomy. Examples of
their multidisciplinary missions include the search for the particle nature of
dark matter and for additional small dimensions of space. In the end, their
conceptual design is very much anchored to the observational fact that Nature
accelerates protons and photons to energies in excess of and
eV, respectively. The cosmic ray connection sets the scale of cosmic
neutrino fluxes. In this context, we discuss the first results of the completed
AMANDA detector and the reach of its extension, IceCube. Similar experiments
are under construction in the Mediterranean. Neutrino astronomy is also
expanding in new directions with efforts to detect air showers, acoustic and
radio signals initiated by super-EeV neutrinos.Comment: 9 pages, Latex2e, uses ws-procs975x65standard.sty (included), 4
postscript figures. To appear in Proceedings of Thinking, Observing, and
Mining the Universe, Sorrento, Italy, September 200
Nonthermal X-radiation of SNR RX J1713.7-3946: The Relations to a Nearby Molecular Cloud
The recent X-ray and CO observations of RX J1713.7-3946 show that a
significant fraction of the nonthermal X-ray emission of this unique supernova
remnant associates, in one way or another, with a molecular cloud interacting
with the west part of the shell. This adds a new puzzle in the origin of X-ray
emission which cannot be easily explained within the standard model in
accordance of which X-rays are result of synchrotron radiation of multi-TeV
electrons accelerated by supernova shock waves. We explore an alternative
origin of the X-ray emission assuming that it is produced by secondary
electrons resulting from high energy hadronic interactions in the molecular
gas. Such a scenario could explain in a quite natural way the apparent
correlation between the X-ray and CO morphologies. However, the TeV gamma-ray
emission recently reported by H.E.S.S. significantly constrains the parameter
space of this model. Namely, this mechanism cannot reproduce the bulk of the
observed X-ray flux unless one postulates existence of a PeV cosmic-ray
component penetrating with an unusually hard spectrum into the dense cloud.Comment: 6 pages, 3 figures, to appear in Proc. of Int. Symp. on High Energy
Gamma-ray Astronomy, Heidelberg (July 2004
Enhanced bone-forming activity of side population cells in the periodontal ligament.
Regeneration of alveolar bone is critical for the successful treatment of periodontal diseases. The periodontal ligament (PDL) has been widely investigated as a source of cells for the regeneration of periodontal tissues. In the present study where we attempted to develop an effective strategy for alveolar bone regeneration, we examined the osteogenic potential of side population (SP) cells, a stem cell-containing population that has been shown to be highly abundant in several kinds of tissues, in PDL cells. Isolated SP cells from the rat PDL exhibited a superior ability to differentiate into osteoblastic cells compared with non-SP (NSP) and unsorted PDL cells in vitro. The mRNA expressions of osteoblast markers and bone morphogenetic protein (BMP) 2 were significantly upregulated in SP cells and were further increased by osteogenic induction. To examine the boneforming activity of SP cells in vivo, PDL SP cells isolated from green fluorescent protein (GFP)-transgenic rats were transplanted with hydroxyapatite (HA) disks into wild-type animals. SP cells exhibited a high ability to induce the mineralized matrix compared with NSP and unsorted PDL cells. At 12 weeks after the implantation, some of the pores in the HA disks with SP cells were filled with mineralized matrices, which were positive for bone matrix proteins, such as osteopontin, bone sialoprotein, and osteocalcin. Furthermore, osteoblast- and osteocyte-like cells on and in the bone-like mineralized matrices were GFP positive, suggesting that the matrices were directly formed by the transplanted cells. These results suggest that PDL SP cells possess enhanced osteogenic potential and could be a potential source for cell-based regenerative therapy for alveolar bone
Computationally designed libraries of fluorescent proteins evaluated by preservation and diversity of function
To determine which of seven library design algorithms best introduces new protein function without destroying it altogether, seven combinatorial libraries of green fluorescent protein variants were designed and synthesized. Each was evaluated by distributions of emission intensity and color compiled from measurements made in vivo. Additional comparisons were made with a library constructed by error-prone PCR. Among the designed libraries, fluorescent function was preserved for the greatest fraction of samples in a library designed by using a structure-based computational method developed and described here. A trend was observed toward greater diversity of color in designed libraries that better preserved fluorescence. Contrary to trends observed among libraries constructed by error-prone PCR, preservation of function was observed to increase with a library's average mutation level among the four libraries designed with structure-based computational methods
Suzaku X-Ray Imaging and Spectroscopy of Cassiopeia A
Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were
carried out. K-shell transition lines from highly ionized ions of various
elements were detected, including Chromium (Cr-Kalpha at 5.61 keV). The X-ray
continuum spectra were modeled in the 3.4--40 keV band, summed over the entire
remnant, and were fitted with a simplest combination of the thermal
bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits
with this assumption indicate that the continuum emission is likely to be
dominated by the non-thermal emission with a cut-off energy at > 1 keV. The
thermal-to-nonthermal fraction of the continuum flux in the 4-10 keV band is
best estimated as ~0.1. Non-thermal-dominated continuum images in the 4--14 keV
band were made. The peak of the non-thermal X-rays appears at the western part.
The peak position of the TeV gamma-rays measured with HEGRA and MAGIC is also
shifted at the western part with the 1-sigma confidence. Since the location of
the X-ray continuum emission was known to be presumably identified with the
reverse shock region, the possible keV-TeV correlations give a hint that the
accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements
in the reverse shock region.Comment: Publ. Astron. Soc. Japan 61, pp.1217-1228 (2009
Search for Sc-K line emission from RX J0852.0--4622 Supernova remnant with Suzaku
We searched for evidence of line emission around 4keV from the northwestern
rim of the supernova remnant RX J0852.0-4622 using Suzaku XIS data. Several
papers have reported the detection of an emission line around 4.1keV from this
region of the sky. This line would arise from K-band fluorescence by Sc, the
immediate decay product of 44Ti. We performed spectral analysis for the entire
portion of the NW rim of the remnant within the XIS field of view, as well as
various regions corresponding to regions of published claims of line emission.
We found no line emission around 4.1keV anywhere, and are able to set a
restrictive upper limit to the X-ray flux: 1.1x10^-6 s^-1 cm^-2 for the entire
field. For every region, our flux upper limit falls below that of the
previously claimed detection. Therefore, we conclude that, to date, no definite
X-ray line feature from Sc-K emission has been detected in the NW rim of RX
J0852.0-4622. Our negative-detection supports the recent claim that RX
J0852-4622 is neither young (1700--4000 yr) nor nearby(~750 pc).Comment: Published in PAS
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