701 research outputs found
Observations of [C II] 158 micron Line and Far-infrared Continuum Emission toward the High-latitude Molecular Clouds in Ursa Major
We report the results of a rocket-borne observation of [C II] 158\micron line
and far-infrared continuum emission at 152.5\micron toward the high latitude
molecular clouds in Ursa Major. We also present the results of a follow-up
observation of the millimeter ^{12}CO J=1-0 line over a selected region
observed by the rocket-borne experiment. We have discovered three small CO
cloudlets from the follow-up ^{12}CO observations. We show that these molecular
cloudlets, as well as the MBM clouds(MBM 27/28/29/30), are not gravitationally
bound. Magnetic pressure and turbulent pressure dominate the dynamic balance of
the clouds. After removing the HI-correlated and background contributions, we
find that the [C II] emission peak is displaced from the 152.5\micron and CO
peaks, while the 152.5\micron continuum emission is spatially correlated with
the CO emission. We interpret this behavior by attributing the origin of [C II]
emission to the photodissociation regions around the molecular clouds
illuminated by the local UV radiation field. We also find that the ratio of the
molecular hydrogen column density to velocity-integrated CO intensity is
1.19+-0.29x10^{20} cm^{-2} (K kms^{-1})^{-1} from the FIR continuum and the CO
data. The average [C II] /FIR intensity ratio over the MBM clouds is 0.0071,
which is close to the all sky average of 0.0082 reported by the FIRAS on the
COBE satellite. The average [C II]/CO ratio over the same regions is 420, which
is significantly lower than that of molecular clouds in the Galactic plane.Comment: 15 pages, LaTeX (aaspp4.sty) + 2 tables(apjpt4.sty) + 6 postscript
figures; accepted for publication in the Astrophysical Journal; Astrophys. J.
in press (Vol. 490, December 1, 1997 issue
High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud
We carried out an unbiased survey for massive dense cores in the giant
molecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,
13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15
cores are associated with IRAS point sources whose luminosities are larger than
10^4 Lo, which indicates that massive star formation is occuring within these
cores. Five cores including the two with IRAS sources are associated with MSX
point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of
which is associated with neither IRAS nor MSX point sources. This core shows
the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that
star formation is also occuring in the core. In total, six C18O cores out of 15
are experienced star formation, and at least 2 of 15 are massive-star forming
cores in the eta Car GMC. We found that massive star formation occurs
preferentially in cores with larger column density, mass, number density, and
smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores
in the eta Car GMC are characterized by large line width and Mvir/M on average
compared to the cores in other GMCs. We investigated the origin of a large
amount of turbulence in the eta Car GMC. We propose the possibility that the
large turbulence was pre-existing when the GMC was formed, and is now
dissipating. Mechanisms such as multiple supernova explosions in the Carina
flare supershell may have contributed to form a GMC with a large amount of
turbulence.Comment: 41 pages, including 11 fugures and 9 tables. Accepted by ApJ. Author
changed. Paper with high resolution figures is available at
http://astrol.cias.osakafu-u.ac.jp/~yonekura/work/paper/etaCar
Modelling of the multi-transition periodic flaring in G9.62+0.20E
We present detailed modeling of periodic flaring events in the 6.7 GHz and
12.2 GHz methanol lines as well as the OH 1665 MHz and 1667 MHz transitions
observed in the G9.62+0.20E star-forming region. Our analysis is performed
within the framework of the one-dimensional Maxwell-Bloch equations, which
intrinsically cover the complementary quasi-steady state maser and transient
superradiance regimes. We find that the variations in flaring time-scales
measured for the different species/transitions, and sometimes even for a single
spectral line, are manifestations of and are best modeled with Dicke's
superradiance, which naturally accounts for a modulation in the duration of
flares through corresponding changes in the inversion pump. In particular, it
can explain the peculiar behaviour observed for some features, such as the
previously published result for the OH 1667 MHz transition at
km s as well as the methanol 6.7 GHz line at
km s, through a partial quenching of the
population inversion during flaring events.Comment: 13 pages, 13 figures, accepted MNRA
Pulmonary Arterial Pressure Management Based on Oral Medicine for Pediatric Living Donor Liver Transplant With Portopulmonary Hypertension
Ueno T., Hiwatashi S., Saka R., et al. Pulmonary Arterial Pressure Management Based on Oral Medicine for Pediatric Living Donor Liver Transplant With Portopulmonary Hypertension. Transplantation Proceedings 50, 2614 (2018); https://doi.org/10.1016/J.TRANSPROCEED.2018.03.068.Pediatric living donor liver transplantation (LDLT) in patients with advanced portopulmonary hypertension (PoPH) is associated with poor prognoses. Recently, novel oral medications, including endothelin receptor antagonists (ERAs), phosphodiesterase 5 (PDE5) inhibitors, and oral prostacyclin (PGI2) have been used to treat PoPH. Pediatric patients with PoPH who underwent LDLT from 2006 to 2016 were enrolled. Oral pulmonary hypertension (PH) medication was administered to control pulmonary arterial pressure (PAP). Four patients had PoPH. Their ages ranged from 6 to 16 years, and their original diseases were biliary atresia (n = 2), portal vein obstruction (n = 1), and intrahepatic portal systemic shunt (n = 1). For preoperative management, 2 patients received continuous intravenous PGI2 and 2 oral medications (an ERA alone or an ERA and a PDE5 inhibitor), and 2 received only oral drugs (an ERA and a PDE5 inhibitor). One patient managed only with intravenous PGI2 died. In the remaining 3 cases, intravenous PGI2 or NO was discontinued before the end of the first postoperative week. Postoperative medications were oral PGI2 alone (n = 1), an ERA alone (n = 1), or the combination of an ERA and a PDE5 inhibitor (n = 1). An ERA was the first-line therapy, and a PDE5 inhibitor was added if there was no effect. New oral PH medications were effective and safe for use in pediatric patients following LDLT. In particular, these new oral drugs prevent the need for central catheter access to infuse PGI2
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The cryo-EM structure of the bacterial flagellum cap complex suggests a molecular mechanism for filament elongation
The bacterial flagellum is a remarkable molecular motor, whose primary function in bacteria is to facilitate motility through the rotation of a filament protruding from the bacterial cell. A cap complex, consisting of an oligomer of the protein FliD, is localized at the tip of the flagellum, and is essential for filament assembly, as well as adherence to surfaces in some bacteria. However, the structure of the intact cap complex, and the molecular basis for its interaction with the filament, remains elusive. Here we report the cryo-EM structure of the Campylobacter jejuni cap complex, which reveals that FliD is pentameric, with the N-terminal region of the protomer forming an extensive set of contacts across several subunits, that contribute to FliD oligomerization. We also demonstrate that the native C. jejuni flagellum filament is 11-stranded, contrary to a previously published cryo-EM structure, and propose a molecular model for the filament-cap interaction
Photon Dominated Regions in NGC 3603
Aims: We aim at deriving the excitation conditions of the interstellar gas as
well as the local FUV intensities in the molecular cloud surrounding NGC 3603
to get a coherent picture of how the gas is energized by the central stars.
Methods: The NANTEN2-4m submillimeter antenna is used to map the [CI] 1-0, 2-1
and CO 4-3, 7-6 lines in a 2' x 2' region around the young OB cluster NGC 3603
YC. These data are combined with C18O 2-1 data, HIRES-processed IRAS 60 and 100
micron maps of the FIR continuum, and Spitzer/IRAC maps. Results: The NANTEN2
observations show the presence of two molecular clumps located south-east and
south-west of the cluster and confirm the overall structure already found by
previous CS and C18O observations. We find a slight position offset of the peak
intensity of CO and [CI], and the atomic carbon appears to be further extended
compared to the molecular material. We used the HIRES far-infrared dust data to
derive a map of the FUV field heating the dust. We constrain the FUV field to
values of \chi = 3 - 6 \times 10^3 in units of the Draine field across the
clouds. Approximately 0.2 to 0.3 % of the total FUV energy is re-emitted in the
[CII] 158 {\mu}m cooling line observed by ISO. Applying LTE and escape
probability calculations, we derive temperatures (TMM1 = 43 K, TMM2 = 47 K),
column densities (N(MM1) = 0.9 \times 10^22 cm^-2, N(MM2) = 2.5 \times 10^22
cm^-2) and densities (n(MM1) = 3 \times 10^3 cm^-3, n(MM2) = 10^3 -10^4 cm^-3)
for the two observed molecular clumps MM1 and MM2. Conclusions: The cluster is
strongly interacting with the ambient molecular cloud, governing its structure
and physical conditions. A stability analysis shows the existence of
gravitationally collapsing gas clumps which should lead to star formation.
Embedded IR sources have already been observed in the outskirts of the
molecular cloud and seem to support our conclusions.Comment: 13 pages, 10 figures, accepted for publication by A&
Pre-main sequence stars in the Cepheus flare region
We present results of optical spectroscopic and BVR_CI_C photometric
observations of 77 pre-main sequence (PMS) stars in the Cepheus flare region. A
total of 64 of these are newly confirmed PMS stars, originally selected from
various published candidate lists. We estimate effective temperatures and
luminosities for the PMS stars, and comparing the results with pre-main
sequence evolutionary models we estimate stellar masses of 0.2-2.4M_sun and
stellar ages of 0.1-15 Myr. Among the PMS stars, we identify 15 visual binaries
with separations of 2-10 arcsec. From archival IRAS, 2MASS, and Spitzer data,
we construct their spectral energy distributions and classify 5% of the stars
as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar
objects (YSOs). We identify 12 CTTS and 2 WTTS as members of NGC 7023, with
mean age of 1.6 Myr. The 13 PMS stars associated with L1228 belong to three
small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17
PMS stars associated with L1251 suggests that star formation has propagated
with the expansion of the Cepheus flare shell. We detect sparse aggregates of
6-7 Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of
400 pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV
Cep at a distance of 600 pc. Our results confirm that the molecular complex in
the Cepheus flare region contains clouds of various distances and star forming
histories.Comment: 61 pages, 27 figures, 8 tables; accepted for publication by ApJ
Multifractal Scaling, Geometrical Diversity, and Hierarchical Structure in the Cool Interstellar Medium
Multifractal scaling (MFS) refers to structures that can be described as a
collection of interwoven fractal subsets which exhibit power-law spatial
scaling behavior with a range of scaling exponents (concentration, or
singularity, strengths) and dimensions. The existence of MFS implies an
underlying multiplicative (or hierarchical, or cascade) process. Panoramic
column density images of several nearby star- forming cloud complexes,
constructed from IRAS data and justified in an appendix, are shown to exhibit
such multifractal scaling, which we interpret as indirect but quantitative
evidence for nested hierarchical structure. The relation between the dimensions
of the subsets and their concentration strengths (the "multifractal spectrum'')
appears to satisfactorily order the observed regions in terms of the mixture of
geometries present: strong point-like concentrations, line- like filaments or
fronts, and space-filling diffuse structures. This multifractal spectrum is a
global property of the regions studied, and does not rely on any operational
definition of "clouds.'' The range of forms of the multifractal spectrum among
the regions studied implies that the column density structures do not form a
universality class, in contrast to indications for velocity and passive scalar
fields in incompressible turbulence, providing another indication that the
physics of highly compressible interstellar gas dynamics differs fundamentally
from incompressible turbulence. (Abstract truncated)Comment: 27 pages, (LaTeX), 13 figures, 1 table, submitted to Astrophysical
Journa
New young planetary nebulae in IPHAS
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory. DOI: 10.1051/0004-6361/200811575Aims. We search for very small-diameter galactic planetary nebulae (PNe) representing the earliest phases of PN evolution. The IPHAS catalogue of H-emitting stars provides a useful basis for this study since all sources present in this catalogue must be of small angular diameter. Methods. The PN candidates are selected based on their location in two colour-colour diagrams: IPHAS (r' - H) vs. (r' - i'), and 2MASS (J - H) vs. (H - ). Spectroscopic follow-up was carried out on a sample of candidates to confirm their nature. Results. We present a total of 83 PN candidates. We were able to obtain spectra or find the classification from the literature for 35 candidates. Five of these objects are likely to be new PNe, including one large bipolar PN discovered serendipitously close to an emission-line star. PN distances deduced from extinction-distance relations based on IPHAS field-star photometry are presented for the first time. These yield distance estimates for our objects in the range 2 kpc and 6 kpc. From the data in hand, we conclude that four of the discovered objects are probably young PNe.Peer reviewe
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