74 research outputs found
L-Ascorbate Biosynthesis Involves Carbon Skeleton Rearrangement in the Nematode Caenorhabditis elegans
Ascorbate (AsA) is required as a cofactor and is widely distributed in plants and animals. Recently, it has been suggested that the nematode Caenorhabditis elegans also synthesizes AsA. However, its biosynthetic pathway is still unknown. To further understand AsA biosynthesis in C. elegans, we analyzed the incorporation of the 13C atom into AsA using gas chromatography-mass spectrometry (GC-MS) in worms fed with D-Glc (1-13C)-labeled Escherichia coli. GC-MS analysis revealed that AsA biosynthesis in C. elegans, similarly to that in mammalian systems, involves carbon skeleton rearrangement. The addition of L-gulono-1,4-lactone, an AsA precursor in the mammalian pathway, significantly increased AsA level in C. elegans, whereas the addition of L-galactono-1,4-lactone, an AsA precursor in the plant and Euglena pathway, did not affect AsA level. The suppression of E03H4.3 (an ortholog of gluconolactonase) or the deficiency of F54D5.12 (an ortholog of L-gulono-1,4-lactone oxidase) significantly decreased AsA level in C. elegans. Although N2- and AsA-deficient F54D5.12 knockout mutant worm (tm6671) morphologies and the ratio of collagen to non-collagen protein did not show any significant differences, the mutant worms exhibited increased malondialdehyde levels and reduced lifespan compared with the N2 worms. In conclusion, our findings indicate that the AsA biosynthetic pathway is similar in C. elegans and mammals
Long-term Remission of Hepatitis-associated Aplastic Anemia Possibly due to Immunosuppressive Therapy after Liver Transplantation
Hepatitis-associated aplastic anemia (HAAA) is an acquired bone marrow failure syndrome that develops after seronegative fulminant hepatitis. Abnormal cytotoxic T-cell activation with cytokine release is a possible pathophysiology. We present the case of a 16-month-old Japanese male who developed HAAA following living-donor liver transplantation for fulminant hepatitis. His aplastic anemia was successfully treated with immunosuppressive therapy. He had been administered tacrolimus for prophylaxis against hepatic allograft rejection. Ten years after the HAAA onset, the patientās bone marrow was found to be slightly hypoplastic. Tacrolimus may be effective in controlling abnormal immune reactions that can cause recurrent impaired hematopoiesis
Outburst of LS V+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile
We report on the first observation of an X-ray outburst of a Be/X-ray binary
pulsar LS V +44 17/RX J0440.9+4431, and the discovery of an absorption dip
structure in the pulse profile. An outburst of this source was discovered by
MAXI GSC in 2010 April. It was the first detection of the transient activity of
LS V +44 17 since the source was identified as a Be/X-ray binary in 1997. From
the data of the follow-up RXTE observation near the peak of the outburst, we
found a narrow dip structure in its pulse profile which was clearer in the
lower energy bands. The pulse-phase-averaged energy spectra in the 3100 keV
band can be fitted with a continuum model containing a power-law function with
an exponential cutoff and a blackbody component, which are modified at low
energy by an absorption component. A weak iron K emission line is also
detected in the spectra. From the pulse-phase-resolved spectroscopy we found
that the absorption column density at the dip phase was much higher than those
in the other phases. The dip was not seen in the subsequent RXTE observations
at lower flux levels. These results suggest that the dip in the pulse profile
originates from the eclipse of the radiation from the neutron star by the
accretion column.Comment: 18 pages, 7 figures, accepted for publication in PAS
Bright X-ray flares from the BL Lac object Mrk 421, detected with MAXI in 2010 January and February
Strong X-ray flares from the blazar Mrk 421 were detected in 2010 January and
February through the 7 month monitoring with the MAXI GSC. The maximum 2 -- 10
keV flux in the January and February flares was measured as 120 +- 10 mCrab and
164 +- 17 mCrab respectively; the latter is the highest among those reported
from the object. A comparison of the MAXI and Swift BAT data suggests a convex
X-ray spectrum with an approximated photon index of about 2. This spectrum is
consistent with a picture that MAXI is observing near the synchrotron peak
frequency. The source exhibited a spectral variation during these flares,
slightly different from those in the previous observations, in which the
positive correlation between the flux and hardness was widely reported. By
equating the halving decay timescale in the January flare, s, to the synchrotron cooling time, the magnetic field was
evaluated as B = 0.045 G , where is the jet
beaming factor. Assuming that the light crossing time of the emission region is
shorter than the doubling rise time, s,
the region size was roughly estimated as cm
. These are consistent with the values previously reported. For
the February flare, the rise time, s, gives a
loose upper limit on the size as cm ,
although the longer decay time s, indicates
B = 0.015 G , which is weaker than the previous results.
This could be reconciled by invoking a scenario that this flare is a
superposition of unresolved events with a shorter timescale.Comment: 14 pages, 4 figures, accepted for PASJ (Vol. 62 No. 6
MAXI GSC observations of a spectral state transition in the black hole candidate XTE J1752-223
We present the first results on the black hole candidate XTE J1752-223 from
the Gas Slit Camera (GSC) on-board the Monitor of All-sky X-ray Image (MAXI) on
the International Space Station. Including the onset of the outburst reported
by the Proportional Counter Array on-board the Rossi X-ray Timing Explorer on
2009 October 23, the MAXI/GSC has been monitoring this source approximately 10
times per day with a high sensitivity in the 2-20 keV band. XTE J1752-223 was
initially in the low/hard state during the first 3 months. An anti-correlated
behavior between the 2-4 keV and 4-20 keV bands were observed around January
20, 2010, indicating that the source exhibited the spectral transition to the
high/soft state. A transient radio jet may have been ejected when the source
was in the intermediate state where the spectrum was roughly explained by a
power-law with a photon index of 2.5-3.0. The unusually long period in the
initial low/hard state implies a slow variation in the mass accretion rate, and
the dramatic soft X-ray increase may be explained by a sudden appearance of the
accretion disk component with a relatively low innermost temperature (0.4-0.7
keV). Such a low temperature might suggest that the maximum accretion rate was
just above the critical gas evaporation rate required for the state transition.Comment: Publication of Astronomical Society of Japan Vol.62, No.5 (2010) [in
print
Long-term Monitoring of the Black Hole Binary GX 339-4 in the High/Soft State during the 2010 Outburst with MAXI/GSC
We present the results of monitoring the Galactic black hole candidate GX
339-4 with the Monitor of All-sky X-ray Image (MAXI) / Gas Slit Camera (GSC) in
the high/soft state during the outburst in 2010. All the spectra throughout the
8-month period are well reproduced with a model consisting of multi-color disk
(MCD) emission and its Comptonization component, whose fraction is <= 25% in
the total flux. In spite of the flux variability over a factor of 3, the
innermost disk radius is constant at R_in = 61 +/- 2 km for the inclination
angle of i = 46 deg and the distance of d=8 kpc. This R_in value is consistent
with those of the past measurements with Tenma in the high/soft state. Assuming
that the disk extends to the innermost stable circular orbit of a non-spinning
black hole, we estimate the black hole mass to be M = 6.8 +/- 0.2 M_sun for i =
46 deg and d = 8 kpc, which is consistent with that estimated from the Suzaku
observation of the previous low/hard state. Further combined with the mass
function, we obtain the mass constraint of 4.3 M_sun < M < 13.3 M_sun for the
allowed range of d = 6-15 kpc and i < 60 deg. We also discuss the spin
parameter of the black hole in GX 339-4 by applying relativistic accretion disk
models to the Swift/XRT data.Comment: 9 pages, 8 figures, accepted for publication in PASJ (Suzaku+MAXI
special issue
Burnout among kindergarten teachers and associated factors
Burnout among kindergarten teachers is a subject of great concern. Although burnout is reported to be significantly associated with turnover intention and work engagement, few studies have examined factors associated with burnout among these teachers. Therefore, in the present study, we performed a cross-sectional survey of burnout and associated factors among kindergarten teachers. We distributed 3363 questionnaires to all 205 authorized kindergartens and childcare institutions in Nagasaki Prefecture and received 1086 responses (response rate: 32.3%). The participants were limited to full-time female class teachers. After excluding survey forms with incomplete content, we ultimately examined valid responses from 442 participants. The survey examined burnout (Maslach Burnout Inventory, MBI), teacher stress (Nursery Teacherās Stress Scale, NTSS), coping behaviors (Brief Scales for Coping Profile, BSCP), and social support (Social Support Scale, SSS). A multiple regression analysis revealed that all 3 MBI subscales were positively associated with āunderstanding of how to handle childrenā on the NTSS and negatively associated with āsuperiorsā on the SSS. āEmotional exhaustionā was significantly associated with āinterpersonal relations at workā and ālack of timeā on the NTSS, and āavoidance and suppressionā on the BSCP. āDepersonalizationā was significantly associated with age, ādisconnect in working conditionsā on the NTSS, and āproactive problem solvingā and āventing emotions to othersā on the BSCP. āDiminished professional accomplishmentā was significantly associated with age, ālack of timeā on the NTSS, and āproactive problem solvingā and āchange in perspectiveā on the BSCP. These results suggest that support from superiors that enables teachers to better understand children and handle them appropriately is necessary to prevent burnout
A Spectral Study of the Black Hole Candidate XTE J1752-223 in the High/Soft State with MAXI, Suzaku and Swift
We report on the X-ray spectral analysis of the black hole candidate XTE\
J1752--223 in the 2009--2010 outburst, utilizing data obtained with the
MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work
complementarily. As already reported by Nakahira et al. (2010) MAXI monitored
the source continuously throughout the entire outburst for about eight months.
All the MAXI/GSC energy spectra in the high/soft state lasting for 2 months are
well represented by a multi-color disk plus power-law model. The innermost disk
temperature changed from 0.7 keV to 0.4 keV and the disk flux
decreased by an order of magnitude. Nevertheless, the innermost radius is
constant at 41 km, where is the
source distance in units of 3.5 kpc and the inclination. The multi-color
disk parameters obtained with the MAXI/GSC are consistent with those with the
Swift/XRT and Suzaku. The Suzaku data also suggests a possibility that the disk
emission is slightly Comptonized, which could account for broad iron-K features
reported previously. Assuming that the obtained innermost radius represents the
innermost stable circular orbit for a non-rotating black hole, we estimate the
mass of the black hole to be 5.510.28 , where the correction for the stress-free inner boundary condition
and color hardening factor of 1.7 are taken into account. If the inclination is
less than 49 as suggested from the radio monitoring of transient jets
and the soft-to-hard transition in 2010 April occurred at 1--4% of Eddignton
luminosity, the fitting of the Suzaku spectra with a relativistic
accretion-disk model derives constraints on the mass and the distance to be
3.1--55 and 2.3--22 {\rm kpc}, respectively. This confirms that the
compact object in XTE J1752--223 is a black hole.Comment: 12 pages including 7 figures and 4 tables, accepted for publication
in PAS
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