85 research outputs found
Gravitational Redshift Detection from the Magnetic White Dwarf Harbored in RX J1712.6-2414
Gravitational redshift is a fundamental parameter that allows us to determine
the mass-to-radius ratio of compact stellar objects, such as black holes,
neutron stars, and white dwarfs (WDs). In the X-ray spectra of the close binary
system, RX J1712.62414, obtained from the Chandra High-Energy Transmission
Grating observation, we detected significant redshifts for characteristic
X-rays emitted from hydrogen-like magnesium, silicon (), and sulfur () ions, which are over the instrumental absolute energy accuracy
(). Considering some possible
factors, such as Doppler shifts associated with the plasma flow, systemic
velocity, and optical depth, we concluded that the major contributor to the
observed redshift is the gravitational redshift of the WD harbored in the
binary system, which is the first gravitational redshift detection from a
magnetic WD. Moreover, the gravitational redshift provides us with a new method
of the WD mass measurement by invoking the plasma-flow theory with strong
magnetic fields in close binaries. Regardless of large uncertainty, our new
method estimated the WD mass to be .Comment: 13 pages, 5 figures. Accepted for publication in Ap
3-O-Acyl-epicatechins Increase Glucose Uptake Activity and GLUT4 Translocation through Activation of PI3K Signaling in Skeletal Muscle Cells
Tea catechins promote glucose uptake in skeletal muscle cells. In this study, we investigated whether the addition of an acyl group to the C-3 position of catechins to generate 3-O-acyl-catechins promoted glucose uptake in L6 myotubes. 3-O-Myristoyl-(-)-epicatechin (EC-C14) and 3-O-palmitoyl-(-)-epicatechin (EC-C16) promoted glucose uptake and translocation of glucose transporter (GLUT) 4 in the cells. The effect of 3-O-acyl-(-)-epicatechins was stronger than that of (-)-epicatechin (EC), whereas neither 3-O-myristoyl-(+)-catechin (C-C14) nor 3-O-palmitoyl-(+)catechin (C-C16) promoted glucose uptake or GLUT4 translocation as well as (+)-catechin (C). We further investigated an affinity of catechins and 3-O-acyl-catechins to the lipid bilayer membrane by using surface plasma resonance analysis. Maximum binding amounts of EC-C16 and C-C16 to the lipid bilayer clearly increased compared with that of (-)-EC and (+)-C, respectively. We also examined the mechanism of GLUT4 translocation and found EC-C14 and EC-C16 induced the phosphorylation of PI3K, but did not affect phosphorylation of Akt or IR. In conclusion, the addition of an acyl group to the C-3 position of (-)-EC increases its affinity for the lipid bilayer membrane and promotes GLUT4 translocation through PI3K-dependent pathways in L6 myotubes
Near-Infrared and X-Ray Observations of XSS J12270-4859
XSS J12270-4859 (J12270) is an enigmatic source of unknown nature. Previous
studies revealed that the source has unusual X-ray temporal characteristics,
including repetitive short-term flares followed by spectral hardening,
non-periodic dips, and dichotomy in activity; i.e. intervals filled with flares
and those without. Together with a power-law X-ray spectrum, it is suggested to
be a low-mass X-ray binary (LMXB). In order to better understand the object, we
present the results of our near-infrared (NIR) photometry and linear
polarimetry observations as well as X-ray spectroscopy observations, which
overlap with each other partially in time, taken respectively with the InfraRed
Survey Facility (IRSF) and the Rossi X-ray Timing Explorer (RXTE). We detected
several simultaneous NIR and X-ray flares for the first time. No significant
NIR polarization was obtained. We assembled data taken with IRSF, RXTE, Suzaku,
Swift, and other missions in the literature and compared the flare profile and
the spectral energy distribution (SED) with some representative high-energy
sources. Based on some similarities of the repetitive NIR and X-ray flaring
characteristics and the broad SED, we argue that J12270 is reminiscent of
microquasars with a synchrotron jet, which is at a very low luminosity state of
~1e-4 Eddington luminosity for a stellar mass black hole or neutron star at a
reference distance of 1 kpc.Comment: 12 pages, 9 figures, accepted for publication in PAS
The early X-ray emission from V382 Velorum (=Nova Vel 1999): An internal shock model
We present the results of ASCA and RXTE observations of the early X-ray
emission from the classical nova V382 Velorum. Its ASCA spectrum was hard
(kT~10 keV) with a strong (10**23 cm**-2) intrinsic absorption. In the
subsequent RXTE data, the spectra became softer both due to a declining
temperature and a diminishing column. We argue that this places the X-ray
emission interior to the outermost ejecta produced by V382 Vel in 1999, and
therefore must have been the result of a shock internal to the nova ejecta. The
weakness of the Fe K alpha lines probably indicates that the X-ray emitting
plasmas are not in ionization equilibrium.Comment: 16 pages (including 4 figures), accepted for publication in Ap
Suzaku Discovery of Hard X-ray Pulsations from the Rotating Magnetized White Dwarf, AE Aquarii
The fast rotating magnetized white dwarf, AE Aquarii, was observed with
Suzaku, in October 2005 and October 2006 with exposures of 53.1 and 42.4 ks,
respectively. In addition to clear spin modulation in the 0.5--10 keV band of
the XIS data at the barycentric period of 33.0769 \pm 0.0001 s, the 10--30 keV
HXD data in the second half of the 2005 observation also showed statistically
significant periodic signals at a consistent period. On that occasion, the
spin-folded HXD light curve exhibited two sharp spikes separated by about 0.2
cycles in phase, in contrast to approximately sinusoidal profiles observed in
energies below about 4 keV. The folded 4--10 keV XIS light curves are
understood as a superposition of those two types of pulse profiles. The phase
averaged 1.5--10 keV spectra can be reproduced by two thermal components with
temperatures of keV and keV, but
the 12-25 keV HXD data show a significant excess above the extrapolated model.
This excess can be explained by either a power-law model with photon index of
or a third thermal component with a temperature of
keV. At a distance of 102 pc, the 4--30 keV luminosities of
the thermal and the additional components become and
erg s, respectively. The latter
corresponds to 0.09% of the spin down energy of the object. Possible emission
mechanisms of the hard pulsations are discussed, including in particular
non-thermal ones.Comment: Accepted for publication on PASJ Vol.60, No.2, 2008 see Press Release
page(http://www.heal.phy.saitama-u.ac.jp/~terada/01work/press_release2008/index_e.html
Delivery advantage to the unilateral kidney by direct drug application to the kidney surface in rats and pharmacokinetic verification based on a physiological model
The objective of this study was to evaluate the drug delivery advantage to the unilateral kidney by direct drug application to the rat kidney surface based on a physiological pharmacokinetic model. Under anesthesia, a cylindrical diffusion cell (i.d. 6 mm, area 0.28 cm(2)) was attached to the right kidney surface in rats. Phenolsulfonphthalein (PSP), an organic anion chosen as a model compound, was added into the diffusion cell. The free PSP concentration in the right (applied) kidney after application to the right kidney surface at a dose of 1 mg was significantly higher than that of the left (non-applied) kidney until 60 min after application. Similarly, the urinary excretion rate of free PSP from the applied kidney was much faster than that from the non-applied kidney, with a 2.6 times larger excreted amount in 240 min. These results imply the possibility that a considerable drug delivery advantage to the unilateral kidney could be obtained after direct absorption from the kidney surface. This tendency was also observed at the other application doses of 0.3 and 1.5 mg. On the other hand, fluorescein isothiocyanate dextran (Mw 4400, FD-4) was equally excreted into the urine from each kidney and the renal concentrations in the applied and non-applied kidneys were almost the same, possibly due to the involvement of passive transport for the absorbed FD-4, i.e. glomerular filtration. The computer simulations of free PSP concentrations in the plasma and each kidney based on a physiological model after kidney surface application were consistent with the respective experimental data. Moreover, the delivery advantage of kidney surface application of PSP was verified by its comparison with other routes such as i.v. and i.a. administrations
Narrow-band imaging with magnifying endoscopy for Peyer's patches is useful in predicting the recurrence of remissive patients with ulcerative colitis
Background/AimsPeyer's patches (PPs) are aggregates of lymphoid follicles that are mainly located in the distal ileum; they play a major role in mucosal immunity. We recently reported that patients with ulcerative colitis (UC) have alterations in PPs that can be detected using narrow-band imaging with magnifying endoscopy (NBI-ME). However, the usefulness of NBI-ME in UC treatment as a whole is still unknown.MethodsWe collected NBI-ME images of PPs from 67 UC patients who had undergone ileocolonoscopy. We evaluated changes in the villi using the "villi index," which is based on three categories: irregular formation, hyperemia, and altered vascular network pattern. The patients were divided into two groups on the basis of villi index: low (L)- and high (H)-types. We then determined the correlation between morphological alteration of the PPs and various clinical characteristics. In 52 patients who were in clinical remission, we also analyzed the correlation between NBI-ME findings of PPs and clinical recurrence.ResultsThe time to clinical recurrence was significantly shorter in remissive UC patients with H-type PPs than in those with L-type PPs (P<0.01). Moreover, PP alterations were not correlated with age, sex, disease duration, clinical activity, endoscopic score, or extent of disease involvement. Multivariate analysis revealed that the existence of H-type PPs was an independent risk factor for clinical recurrence (hazard ratio, 3.3; P<0.01).ConclusionsUC patients with morphological alterations in PPs were at high risk of clinical relapse. Therefore, to predict the clinical course of UC, it may be useful to evaluate NBI-ME images of PPs
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