766 research outputs found
Suzaku Observations of M82 X-1 : Detection of a Curved Hard X-ray Spectrum
A report is presented on Suzaku observations of the ultra-luminous X-ray
source X-1 in the starburst galaxy M82, made three time in 2005 October for an
exposure of ~ 30 ks each. The XIS signals from a region of radius 3 around the
nucleus defined a 2-10 keV flux of 2.1 x 10^-11 erg s-1 cm-2 attributable to
point sources. The 3.2-10 keV spectrum was slightly more convex than a
power-law with a photon index of 1.7. In all observations, the HXD also
detected signals from M82 up to ~ 20 keV, at a 12-20 keV flux of 4.4 x 10^-12
erg s-1 cm-2 . The HXD spectrum was steeper than that of the XIS. The XIS and
HXD spectra can be jointly reproduced by a cutoff power-law model, or similar
curved models. Of the detected wide-band signals, 1/3 to 2/3 are attributable
to X-1, while the remainder to other discrete sources in M82. Regardless of the
modeling of these contaminants, the spectrum attributable to X-1 is more curved
than a power-law, with a bolometric luminosity of (1.5 -3) x 10 ^40 erg s-1.
These results are interpreted as Comptonized emission from a black hole of
100-200 solar masses, radiating roughly at the Eddington luminosity.Comment: 19 pages, 9 figures, accepted in Publications of the Astronomical
Society of Japa
Discovery of a bright transient ultraluminous X-ray source Suzaku J1305-4931 in NGC 4945
This paper reports the discovery of a bright X-ray transient source, Suzaku
J1305-4913, in the south-west arm of the nearby Seyfert II galaxy NGC 4945. It
was detected at a 0.5 -- 10 keV flux of erg cm
s during the Suzaku observation conducted on 2006 January 15 -- 17, but
was undetectable in a shorter observation on 2005 August 22 --23, with an upper
limit of erg cm s (90% confidence level).
At a distance of 3.7 Mpc, the bolometric luminosity of the source becomes
erg s, where and is the disk inclination. Therefore, the source is
classified into so-called ultraluminous X-ray sources (ULXs). The time-averaged
X-ray spectrum of the source is described by a multi-color disk model, with the
innermost accretion disk temperature of
keV. During the 2006 January observation, it varied by a factor of 2 in
intensity, following a clear correlation of .
It is inferred that the innermost disk radius stayed constant at
km, suggesting the presence of a
standard accretion disk. Relating with the last stable orbit
around a non-rotating black hole yields a rather low black hole mass, solar masses, which would imply that the source is shining at a
luminosity of times the Eddington limit. These results
can be better interpreted by invoking sub-Eddington emission from a rapidly
spinning black hole with a mass of 20 -- 130 solar masses.Comment: 21 pages, 10 figures, Accepted for PASJ 2nd Suzaku special issu
Large Magnetic-Field-Induced Strains in Sintered Chromium Tellurides
Sintered samples of Cr3Te4 and Cr2Te3 are found to show large strains
accompanied by large volume changes under a magnetic field. In Cr3Te4, volume
increases of deltaV/V = 500-1170 ppm by applying a magnetic field of 9 T are
observed over the entire temperature range below 350 K. At room temperature,
the deltaV/V value exceeds 1000 ppm, which is considerably larger than the
maximum values reported for Cr-based magnets thus far and is comparable to the
room-temperature value of forced-volume magnetostriction in invar alloys.
Cr2Te3 show a large deltaV/V of 680 ppm when applying a magnetic field of 9 T
at 200 K. Both samples display particularly large volume increases around the
Curie temperature, where they also show negative thermal expansion due to
microstructural effects, suggesting that the cooperation between anisotropic
lattice deformation associated with the magnetic ordering and microstructural
effects is essential for the manifestation of the large magnetic-field-induced
volume changes.Comment: 6 pages, 6 figure
Sets of RNA Repeated Tags and Hybridization-Sensitive Fluorescent Probes for Distinct Images of RNA in a Living Cell
BACKGROUND: Imaging the behavior of RNA in a living cell is a powerful means for understanding RNA functions and acquiring spatiotemporal information in a single cell. For more distinct RNA imaging in a living cell, a more effective chemical method to fluorescently label RNA is now required. In addition, development of the technology labeling with different colors for different RNA would make it easier to analyze plural RNA strands expressing in a cell. METHODOLOGY/PRINCIPAL FINDINGS: Tag technology for RNA imaging in a living cell has been developed based on the unique chemical functions of exciton-controlled hybridization-sensitive oligonucleotide (ECHO) probes. Repetitions of selected 18-nucleotide RNA tags were incorporated into the mRNA 3'-UTR. Pairs with complementary ECHO probes exhibited hybridization-sensitive fluorescence emission for the mRNA expressed in a living cell. The mRNA in a nucleus was detected clearly as fluorescent puncta, and the images of the expression of two mRNAs were obtained independently and simultaneously with two orthogonal tag-probe pairs. CONCLUSIONS/SIGNIFICANCE: A compact and repeated label has been developed for RNA imaging in a living cell, based on the photochemistry of ECHO probes. The pairs of an 18-nt RNA tag and the complementary ECHO probes are highly thermostable, sequence-specifically emissive, and orthogonal to each other. The nucleotide length necessary for one tag sequence is much shorter compared with conventional tag technologies, resulting in easy preparation of the tag sequences with a larger number of repeats for more distinct RNA imaging
Insulin regulates Presenilin 1 localization via PI3K/Akt signaling.
Recently, insulin signaling has been highlighted in the pathology of Alzheimer's disease (AD). Although the association between insulin signaling and Tau pathology has been investigated in several studies, the interaction between insulin signaling and Presenilin 1 (PS1), a key molecule of amyloid beta (Abeta) pathology, has not been elucidated so far. In this study, we demonstrated that insulin inhibited PS1 phosphorylation at serine residues (serine 353, 357) via phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway and strengthened the trimeric complex of PS1/N-cadherin/beta-catenin, consequently relocalizing PS1 to the cell surface. Since our recent report suggests that PS1/N-cadherin/beta-catenin complex regulates Abeta production, it is likely that insulin signaling affects Abeta pathology by regulating PS1 localization
Low fat intake is associated with pathological manifestations and poor recovery in patients with hepatocellular carcinoma
BACKGROUND: This study aimed to clarify whether dietary deviation is associated with pathological manifestations in hepatocellular carcinoma (HCC) patients. METHODS: Dietary intake was estimated in 35 HCC cases before and after hospitalization by referencing digital camera images of each meal. Pathological conditions were evaluated in nitrogen balance, non-protein respiratory quotient (npRQ), neuropsychiatric testing and recovery speed from HCC treatment. RESULTS: On admission, nitrogen balance and npRQ were negative and less than 0.85, respectively. Five patients were judged to have suffered from minimal hepatic encephalopathy that tended to be associated with a lowered value of npRQ (pβ=β0.082). The energy from fat intake showed a tendency of positive correlation with npRQ (pβ=β0.11), and the patients with minimal hepatic encephalopathy took significantly fewer energy from fat (pβ=β0.024). The energy difference from fat between diets at home versus those in the hospital showed a significant positive correlation with npRQ change after admission (pβ=β0.014). The recovery speed from invasive treatments for HCC showed a significant negative correlation with npRQ alteration after admission (pβ=β0.0002, rβ=ββ0.73). CONCLUSIONS: These results suggest the lower fat intake leads to deterioration of energy state in HCC patients, which associates with poor recovery from invasive treatments and various pathological manifestations
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