112 research outputs found
X-Ray Spectrum of a Peculiar Supernova Remnant G359.1-0.5
We present the Suzaku results of a supernova remnant (SNR), G359.1-0.5 in the
direction of the Galactic center region. From the SNR, we find prominent
K-shell lines of highly ionized Si and S ions, together with unusual structures
at 2.5-3.0 and 3.1-3.6 keV. No canonical SNR plasma model, in either ionization
equilibrium or under-ionization, can explain the structures. The energies and
shapes of the structures are similar to those of the radiative transitions of
free electrons to the K-shell of He-like Si and S ions (radiative recombination
continuum: RRC). The presence of the strong RRC structures indicates that the
plasma is in over-ionization. In fact, the observed spectrum is well fitted
with an over-ionized plasma model. The best-fit electron temperature of 0.29
keV is far smaller than the ionization temperature of 0.77 keV, which means
that G359.1-0.5 is in extreme condition of over-ionization. We report some
cautions on the physical parameters, and comment possible origins for the
over-ionized plasma.Comment: 7 pages, 5 figures, accepted for publication in PAS
New Insights into SNR Evolution Revealed by the Discovery of Recombining Plasmas
We report the discovery of recombining plasmas in three supernova remnants
(SNRs) with the Suzaku X-ray astronomy satellite. During SNR's evolution, the
expanding supernova ejecta and the ambient matter are compressed and heated by
the reverse and forward shocks to form an X-ray emitting hot plasma. Since
ionization proceeds slowly compared to shock heating, most young or middle-aged
SNRs have ionizing (underionized) plasmas. Owing to high sensitivity of Suzaku,
however, we have detected radiative recombination continua (RRCs) from the SNRs
IC 443, W49B, and G359.1-0.5. The presence of the strong RRC is the definitive
evidence that the plasma is recombining (overionized). As a possible origin of
the overionization, an interaction between the ejecta and dense circumstellar
matter is proposed; the highly ionized gas was made at the initial phase of the
SNR evolution in dense regions, and subsequent rapid adiabatic expansion caused
sudden cooling of the electrons. The analysis on the full X-ray band spectrum
of IC 443, which is newly presented in this paper, provides a consistent
picture with this scenario. We also comment on the implications from the fact
that all the SNRs having recombining plasmas are correlated with the
mixed-morphology class.Comment: Published by Advances in Space Researc
Expansion Velocity of Ejecta in Tycho's Supernova Remnant Measured by Doppler Broadened X-ray Line Emission
We show that the expansion of ejecta in Tycho's supernova remnant (SNR) is
consistent with a spherically symmetric shell, based on Suzaku measurements of
the Doppler broadened X-ray emission lines. All the strong K_alpha line
emission show broader widths at the center than at the rim, while the centroid
energies are constant across the remnant (except for Ca). This is the pattern
expected for Doppler broadening due to expansion of the SNR ejecta in a
spherical shell. To determine the expansion velocities of the ejecta, we
applied a model for each emission line feature having two Gaussian components
separately representing red- and blue-shifted gas, and inferred the Doppler
velocity difference between these two components directly from the fitted
centroid energy difference. Taking into account the effect of projecting a
three-dimensional shell to the plane of the detector, we derived average
spherical expansion velocities independently for the K_alpha emission of Si, S,
Ar, and Fe, and K_beta of Si. We found that the expansion velocities of Si, S,
and Ar ejecta of 4700+/-100 km/s are distinctly higher than that obtained from
Fe K_alpha emission, 4000+/-300 km/s, which is consistent with segregation of
the Fe in the inner ejecta. Combining the observed ejecta velocities with the
ejecta proper-motion measurements by Chandra, we derived a distance to the
Tycho's SNR of 4+/-1 kpc.Comment: Accepted to Apj, 25 pages, 7 figures, 5 table
Comprehensive Dipeptide Analysis Revealed Cancer-Specific Profile in the Liver of Patients with Hepatocellular Carcinoma and Hepatitis
As the physical properties and functionality of dipeptides differ from those of amino acids, they have attracted attention in metabolomics; however, their functions in vivo have not been clarified in detail. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, and its major cause is chronic hepatitis. This study was conducted to explore tumor-specific dipeptide characteristics by performing comprehensive dipeptide analysis in the tumor and surrounding nontumor tissue of patients with HCC. Dipeptides were analyzed by liquid chromatography tandem mass spectrometry and capillary electrophoresis tandem mass spectrometry. Principal component analysis using 236 detected dipeptides showed differences in the dipeptide profiles between nontumor and tumor tissues; however, no clear difference was observed in etiological comparison. In addition, the N- and C-terminal amino acid compositions of the detected dipeptides significantly differed, suggesting the substrate specificity of enzyme proteins, such as peptidase. Furthermore, hepatitis-derived HCC may show a characteristic dipeptide profile even before tumor formation. These results provide insight into HCC pathogenesis and may help identify novel biomarkers for diagnosis
Principles of the magnetic resonance imaging movie method for articulatory movement : a review
Magnetic resonance imaging (MRI) has become a critical tool for dental examination. MRI has many advantages over radiographic examination methods, including the lack of a requirement for patient exposure and the ability to capture high-contrast images of various tissue and organ types. However, MRI also has several limitations, including long examination times and the existence of metallic or motion artifacts. A cardiac imaging method using cine sequences was developed in the 1990s. This technique allows for analysis of heart movement and functional blood flow. Moreover, this method has been applied in dentistry. Recent research involving 3T MRI has led to the achievement of a temporal resolution of <10 ms, surpassing the frame rate of typical video recording. The current review introduces the history and principles of the cine sequence method and its application to the oral and maxillofacial regions
X-ray Spectral Study of the extended emission,'the Cap', located 11.6 kpc above the disk of M82
The extended X-ray emission from 'the Cap' region located 11' (11.6 kpc)
above the disk of the starburst galaxy M82 has been observed with Suzaku and
XMM-Newton. Owing to the good energy resolution and the large collecting area
of the XIS on Suzaku, combined with similar properties of the EPIC instrument
on XMM-Newton, we have clearly detected K-shell emission lines from O VII, O
VIII, Ne X, Mg XI, Mg XII and the Fe-L complex. Two optically-thin thermal
plasma components are required to fit the observed X-ray spectra. We have
determined the metal abundances of O, Ne, Mg, Si and Fe in this region for the
first time. Their metal abundance ratios agree well with those of metal-poor
stars and the model prediction of metals synthesized by type-II supernovae, but
they are not consistent with the metallicities of type-Ia supernovae. This
result is support for the idea that the origin of the metals in the Cap is
type-II supernovae explosions occurring in the starburst regions in the M82
galaxy. We discuss the possible contribution from sputtered dust grains to the
metals in the Cap. An emission line consistent with the C VI transition of n=4
to 1 at 0.459 keV is marginally detected, although it is not statistically
significant at the 99% confidence level; the presence of this line would
suggest charge-exchange processes in the Cap.Comment: 16 pages, 10 figuer
New CTI Correction Method for the Spaced-Row Charge Injection of the Suzaku X-Ray Imaging Spectrometer
The charge transfer inefficiency (CTI) of the X-ray CCDs on board the Suzaku
satellite (X-ray Imaging Spectrometers; XIS) has increased since the launch due
to radiation damage, and the energy resolution has been degraded. To improve
the CTI, we have applied a spaced-row charge injection (SCI) technique to the
XIS in orbit; by injecting charges into CCD rows periodically, the CTI is
actively decreased. The CTI in the SCI mode depends on the distance between a
signal charge and a preceding injected row, and the pulse height shows periodic
positional variations. Using in-flight data of onboard calibration sources and
of the strong iron line from the Perseus cluster of galaxies, we studied the
variation in detail. We developed a new method to correct the variation. By
applying the new method, the energy resolution (FWHM) at 5.9 keV at March 2008
is ~155 eV for the front-illuminated CCDs and ~175 eV for the back-illuminated
CCD.Comment: 7 pages, 14 figure
Single electron yields from semileptonic charm and bottom hadron decays in AuAu collisions at GeV
The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured
open heavy-flavor production in minimum bias AuAu collisions at
GeV via the yields of electrons from semileptonic decays
of charm and bottom hadrons. Previous heavy-flavor electron measurements
indicated substantial modification in the momentum distribution of the parent
heavy quarks due to the quark-gluon plasma created in these collisions. For the
first time, using the PHENIX silicon vertex detector to measure precision
displaced tracking, the relative contributions from charm and bottom hadrons to
these electrons as a function of transverse momentum are measured in AuAu
collisions. We compare the fraction of electrons from bottom hadrons to
previously published results extracted from electron-hadron correlations in
collisions at GeV and find the fractions to be
similar within the large uncertainties on both measurements for
GeV/. We use the bottom electron fractions in AuAu and along
with the previously measured heavy flavor electron to calculate the
for electrons from charm and bottom hadron decays separately. We find
that electrons from bottom hadron decays are less suppressed than those from
charm for the region GeV/.Comment: 432 authors, 33 pages, 23 figures, 2 tables, 2011 data. v2 is version
accepted for publication by Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Measurement of higher cumulants of net-charge multiplicity distributions in AuAu collisions at GeV
We report the measurement of cumulants () of the net-charge
distributions measured within pseudorapidity () in AuAu
collisions at GeV with the PHENIX experiment at the
Relativistic Heavy Ion Collider. The ratios of cumulants (e.g. ,
) of the net-charge distributions, which can be related to volume
independent susceptibility ratios, are studied as a function of centrality and
energy. These quantities are important to understand the quantum-chromodynamics
phase diagram and possible existence of a critical end point. The measured
values are very well described by expectation from negative binomial
distributions. We do not observe any nonmonotonic behavior in the ratios of the
cumulants as a function of collision energy. The measured values of and can be directly compared to lattice
quantum-chromodynamics calculations and thus allow extraction of both the
chemical freeze-out temperature and the baryon chemical potential at each
center-of-mass energy.Comment: 512 authors, 8 pages, 4 figures, 1 table. v2 is version accepted for
publication in Phys. Rev. C as a Rapid Communication. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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