459 research outputs found
The spatiokinematical structure of H_2O and OH masers in the "water fountain" source IRAS 18460-0151
Using the Very Long Baseline Array and the European VLBI Network, we have
observed 22.2 GHz H_2O and 1612 MHz OH masers in the "water fountain" source
IRAS 18460-0151. The H_2O maser spectrum has a very wide line-of-sight velocity
range (~310 km/s) and consists of three groups of emission features at the
blue-shifted (-68 km/s <~ V_LSR <~ -17 km/s) and red-shifted (V_LSR ~= 240
km/s) edges as well as around the systemic velocity (112 km/s <~ V_LSR <~ 133
km/s). The first two H_2O spectral components exhibit a highly-collimated
high-velocity bipolar jet on the sky, with an angular separation of ~120
milliarcseconds (mas) (240 AU in linear length) and a three-dimensional flow
velocity of ~160 km/s. The flow dynamical age is estimated to be only ~6 yr (at
the time of the observation epochs of 2006--2007). Interestingly, the systemic
velocity component clearly exhibits a spherically-expanding outflow with a
radius of ~36 AU and a flow velocity of ~9 km/s. On the other hand, the OH
maser spectrum shows double peaks with a velocity separation of ~25 km/s
(V_LSR=$111--116 and 138--141 km/s), as typically seen in circumstellar
envelopes of OH/IR stars. The angular offset between the velocity-integrated
brightness peaks of the two high-velocity H_2O components is ~25 mas (50 AU).
The offset direction and the alignment of the red-shifted maser spots are
roughly perpendicular to the axis of the H_2O maser flow. High-accuracy
astrometry for the H_2O and OH masers demonstrates that the collimated fast jet
and the slowly expanding outflow originate from a single or multiple sources
which are located within 15 mas (30 AU). On the other hand, the estimated
systemic velocity of the collimated jet (V_sys ~87--113 km/s) has a large
uncertainty. This makes it difficult to provide strong constraints on models of
the central stellar system of IRAS 18460-0151.Comment: 25 pages, 5 figures, 8 tables, accepted for publication in Ap
The S₄ and Few-Group Diffusion Calculations of Fast Reactors
To economize a large amount of numerical work in the calculation of fast breeders, the present work has been done in the hope that few-group diffusion theory might give acceptable results in some cases. A hypothetic 233TJ-232Th system with large core size (~670/) as well as a hypothetic 239Pu-238U fast reactor with small core size (~50l) are adopted. These systems are assumed to be of spherically symmetric geometry. One dimensional calculations are applied to obtain the static characteristics of the systems. The results from few-group S4 and diffusion method are investigated. These results seem to indicate that fouror three-group diffusion calculation might at least be used in place of three-group S4 computation for both large and small fast reactors. A new convergence criterion imposed upon the static parameters is proposed. The leakage rate of neutrons from the blanket is selected as the sensitive measure of convergence. This rate is estimated in two ways, i.e. with the aid of neutron current and by neutron inventory. The sufficiently converged state can be reached when these two values coincide with each other. One is also able to infer the necessary number of spatial mesh points by comparing these two values
High Velocity Precessing Jets from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations
We report the results of multi-epoch VLBA observations of the 22.2GHz water
maser emission associated with the "water fountain" IRAS 18286-0959. We suggest
that this object is the second example of a highly collimated bipolar
precessing outflow traced by water maser emission, the other is W43A. The
detected water emission peaks are distributed over a velocity range from
-50km/s to 150km/s. The spatial distribution of over 70% of the identified
maser features is found to be highly collimated along a spiral jet (jet 1)
extended southeast to northwest, the remaining features appear to trace another
spiral jet (jet 2) with a different orientation. The two jets form a
"double-helix" pattern which lies across ~200 milliarcseconds. The maser
distribution is reasonably fit by a model consisting of two bipolar precessing
jets. The 3D velocities of jet 1 and jet 2 are derived to be 138km/s and
99km/s, respectively. The precession period of jet 1 is about 56 years. For jet
2, three possible models are tested and they give different values for the
kinematic parameters. We propose that the appearance of two jets is the result
of a single driving source with significant proper motion.Comment: 84 pages, 16 figures, accepted for publication in Ap
CO J=3-2 Emission from the "Water Fountain" Sources IRAS 16342-3814 and IRAS 18286-0959
We observed CO J=3-2 emission from the "water fountain" sources, which
exhibit high-velocity collimated stellar jets traced by water maser emission,
with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope. We
detected the CO emission from two sources, IRAS 16342-3814 and IRAS 18286-0959.
The IRAS 16342-3814 CO emission exhibits a spectrum that is well fit to a
Gaussian profile, rather than to a parabolic profile, with a velocity width
(FWHM) of 158+/-6 km/s and an intensity peak at VLSR = 50+/-2 km/s. The mass
loss rate of the star is estimated to be ~2.9x10^-5 M_sun/yr. Our
morpho-kinematic models suggest that the CO emission is optically thin and
associated with a bipolar outflow rather than with a (cold and relatively
small) torus. The IRAS 18286-0959 CO emission has a velocity width (FWHM) of
3.0+/-0.2 km/s, smaller than typically seen in AGB envelopes. The narrow
velocity width of the CO emission suggests that it originates from either an
interstellar molecular cloud or a slowly-rotating circumstellar envelope that
harbors the water maser source.Comment: 10 pages, 4 figure, accepted for publication in the Publications of
the Astronomical Society of Japan, Vol. 61, No.6, 2009 December issu
On the Dominance of Trivial Knots among SAPs on a Cubic Lattice
The knotting probability is defined by the probability with which an -step
self-avoiding polygon (SAP) with a fixed type of knot appears in the
configuration space. We evaluate these probabilities for some knot types on a
simple cubic lattice. For the trivial knot, we find that the knotting
probability decays much slower for the SAP on the cubic lattice than for
continuum models of the SAP as a function of . In particular the
characteristic length of the trivial knot that corresponds to a `half-life' of
the knotting probability is estimated to be on the cubic
lattice.Comment: LaTeX2e, 21 pages, 8 figur
Extremely Strong ^{13}CO J=3-2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning
We observed four "water fountain" sources in the CO J=3-2 line emission with
the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope in
2010-2011. The water fountain sources are evolved stars that form high-velocity
collimated jets traced by water maser emission. The CO line was detected only
from IRAS 16342-3814. The present work confirmed that the ^{12}CO to ^{13}CO
line intensity ratio is ~1.5 at the systemic velocity. We discuss the origins
of the very low ^{12}CO to ^{13}CO intensity ratio, as possible evidence for
the "hot-bottom burning" in an oxygen-rich star, and the CO intensity variation
in IRAS 16342-3814.Comment: 10 pages, 3 figures, accepted for publication to the Publications of
the Astronomical Society of Japan, Vol. 64, No.
SPR METHOD : REHABILITATION TECHNOLOGIES TO REVIVE DECREPIT PIPELINES
Abstract In the SPR (Sewage Pipe Renewal) method, a rigid PVC liner is formed inside an existing pipe by using a specially designed winding machine that is placed inside the existing pipe. A rigid PVC profile strip is fed through a manhole entrance above ground, and the winding machine is used to wind and interlock the profiles together to form a liner. Rehabilitation technologies are needed that can cope with various existing installation site conditions; i.e. long or curved pipelines, with round, square or horseshoe shaped crossections. Under such circumstances, we have developed a new technology to form the PVC liner in which self running winding machenes travel around a frame that is set inside the existing pipeline, and which is made to conform to the interior cross sectional shape of the pipe
Major role of organic anion transporter 3 in the transport of indoxyl sulfate in the kidney
Major role of organic anion transporter 3 in the transport of indoxyl sulfate in the kidney.BackgroundIndoxyl sulfate is a uremic toxin that accumulates in the body because of the patient's inability to excrete it and it induces a number of uremic symptoms and leads to chronic renal failure. The functional failure of the excretion system for indoxyl sulfate causes its accumulation in blood. The purpose of the present study was to characterize the transport mechanism responsible for the renal excretion of indoxyl sulfate.MethodsThe [3H]indoxyl sulfate transport mechanism was investigated using an in vivo tissue-sampling single-injection technique, the kidney uptake index (KUI) method. Rat organic anion transporter 3 (rOAT3)-expressing Xenopus laevis oocyte system was used for measuring [3H]indoxyl sulfate uptake activity.ResultsProbenecid showed a concentration-dependent inhibitory effect on the uptake of [3H]indoxyl sulfate using the KUI method, and uptake was inhibited by organic anions such as para-aminohippuric acid (PAH) and benzylpenicillin, by weak base such as cimetidine, and by uremic toxins, such as 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) and hippuric acid (HA). However, salicylic acid, indomethacin, 3,5,3′-triiodo-L-thyronine and indole acetic acid (IA) had no effect on the uptake. rOAT3-expressing oocytes exhibited uptake of [3H]indoxyl sulfate by rOAT3 (Km = 158 μmol/L). Moreover, a number of uremic toxins inhibited the uptake of [3H]indoxyl sulfate by rOAT3.ConclusionsThese results suggest that rOAT3 is responsible for the renal uptake of indoxyl sulfate, and uremic toxins share the transport mechanism for indoxyl sulfate. Mutual inhibition of these uremic toxins via OAT3 may accelerate their accumulation in the body and, thereby, the progression of nephrotoxicity in uremia
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