1,338 research outputs found
Gas dynamics in Massive Dense Cores in Cygnus-X
We study the kinematic properties of dense gas surrounding massive protostars
recognized by Bontemps et a. (2010) in a sample of five Massive Dense Cores in
Cygnus-X. We investigate whether turbulent support plays a major role in
stabilizing the core against fragmentation into Jeans-mass objects or
alternatively, the observed kinematics could indicate a high level of dynamics.
We present IRAM 30m single-dish (HCO+ and H13CO+) and IRAM PdBI high
angular-resolution observations of dense gas tracers (H13CO+ and H13CN) to
reveal the kinematics of molecular gas at scales from 0.03 to 0.1 pc. Radiative
transfer modeling shows that H13CO+ is depleted within the envelopes of massive
protostars and traces the bulk of material surrounding the protostars rather
than their inner envelopes. H13CN shows a better correspondence with the peak
of the continuum emission, possibly due to abundance anomalies and specific
chemistry in the close vicinity of massive protostars. Analyzing the
line-widths we show that the observed line-dispersion of H13CO+ at the scale of
MDCs is smaller than expected from the quasi-static, turbulent-core model. At
large-scales, global organized bulk motions are identified for 3 of the MDCs.
At small-scales, several spectral components are identified in all MDCs showing
filamentary structures and intrinsic velocity gradients towards the continuum
peaks. The dynamics of these flows show diversity among the sample and we link
this to the specific fragmentation properties of the MDCs. No clear evidence is
found for a turbulence regulated, equilibrium scenario within the sample of
MDCs. We propose a picture in which MDCs are not in equilibrium and their
dynamics is governed by small-scale converging flows, which may initiate
star-formation via their shears
Long-term X-ray changes in the emission from the anomalous X-ray pulsar 4U 0142+61
We present results obtained from X-ray observations of the anomalous X-ray
pulsar (AXP) 4U 0142+61 taken between 2000-2007 using XMM-Newton, Chandra and
Swift. In observations taken before 2006, the pulse profile is observed to
become more sinusoidal and the pulsed fraction increased with time. These
results confirm those derived using the Rossi X-ray Timing Explorer and expand
the observed evolution to energies below 2 keV. The XMM-Newton total flux in
the 0.5-10 keV band is observed to be nearly constant in observations taken
before 2006, while an increase of ~10% is seen afterwards and coincides with
the burst activity detected from the source in 2006-2007. After these bursts,
the evolution towards more sinusoidal pulse profiles ceased while the pulsed
fraction showed a further increase. No evidence for large-scale, long-term
changes in the emission as a result of the bursts is seen. The data also
suggest a correlation between the flux and hardness of the spectrum, with
brighter observations on average having a harder spectrum. As pointed out by
other authors, we find that the standard blackbody plus power-law model does
not provide the best spectral fit to the emission from 4U 0142+61. We also
report on observations taken with the Gemini telescope after two bursts. These
observations show source magnitudes consistent with previous measurements. Our
results demonstrate the wide range of X-ray variability characteristics seen in
AXPs and we discuss them in light of current emission models for these sources.Comment: 10 pages, 9 figures, in emulateapj style. Submitted to Ap
Vector Meson Exchanges and CP Asymmetry in
Using a current algebra framework, we discuss the contribution of vector
meson exchanges to the CP violating asymmetry in the decay
, resulting from the interference of the
amplitude with the radiative correction
.Comment: 9 pages (plain-TEX), IC/93/186, UTS-DFT-93-18, (two figures not
included
Tratamiento de la artropatÃa crónica hemofÃlica mediante inyecciones intraarticulares de cortisona
Se evaluaron las historias clÃnicas de 34 pacientes hemofÃlicos con artropatÃa crónica
severa (25 grado III y 9 grado IV), todos ellos con deformidades axiales, atrofia muscular y limitación
del movimiento articular (31 rodillas, 2 tobillos y 2 hombros), a quienes se les inyectó intraarticularmcnte
entre 1 y 9 dosis de cortisona de liberación prolongada con intervalos de 3 semanas.
Se les realizó una evaluación subjetiva y objetiva en base a los siguientes parámetros: bueno: no dolor,
incremento en los rangos de movimiento y total integración a las actividades de la vida diaria;
regular: disminución del dolor, igual rango de movilidad y actividades de la vida diaria limitadas, y
malo: persistencia del dolor, disminución de los rangos articulares y gran limitación para las actividades
de la vida diaria. En la evaluación subjetiva obtuvimos 19 pacientes con buenos resultados,
12 regulares y 4 malos; en la evaluación objetiva obtuvimos 22 pacientes con buenos resultados, 9 regulares
y 4 malos. Según los resultados obtenidos, la cortisona intraarticular parece ser un excelente
tratamiento paliativo en la artropatÃa crónica hemofÃlica.Thirty four patients with chronic haemophilic arthropathy (25 grade III and 9 grade
IV), having all axial deformities, muscular atrophy, and limitation of range of motion in the joint
(31 knees, 2 ankles and 2 shoulders) were injected intrarticulary at 3 weeks interval with a long
standing cortisone from 1 to 9 injections. Subjective and objective evaluation parameters were
assessed considering as good no pain, increase range of motion and normal activity of daily life;
fair with less pain, same range of motion and slight diminution of activity of daily life; and bad with
persistence of pain, less range of motion and greater diminution of activity. We obtained in subjective
evaluation 19 good results, 12 fair, and 4 bad; in objective evaluation we obtained 22 good
results, 9 fair, and 4 bad. In conclusion, intrarticular cortisone seems to be a reliable treatment of
chronic haemophilic arthropathy
Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts
We present results from observations of the magnetar 1E 1547.0-5408 (SGR
J1550-5418) taken with the Chandra X-ray Observatory and the Rossi X-ray Timing
Explorer (RXTE) following the source's outbursts in 2008 October and 2009
January. During the time span of the Chandra observations, which covers days 4
through 23 and days 2 through 16 after the 2008 and 2009 events, respectively,
the source spectral shape remained stable, while the pulsar's spin-down rate in
the same span in 2008 increased by a factor of 2.2 as measured by RXTE. The
lack of spectral variation suggests decoupling between magnetar spin-down and
radiative changes, hence between the spin-down-inferred magnetic field strength
and that inferred spectrally. We also found a strong anti-correlation between
the phase-averaged flux and the pulsed fraction in the 2008 and 2009 Chandra
data, but not in the pre-2008 measurements. We discuss these results in the
context of the magnetar model.Comment: 4 figures, accepted for publication in Ap
On the Extended Emission Around the Anomalous X-ray Pulsar 1E 1547.0-5408
We present an analysis of the extended emission around the anomalous X-ray
pulsar 1E 1547.0-5408 using four XMM-Newton observations taken with the source
in varying states of outburst as well as in quiescence. We find that the
extended emission flux is highly variable and strongly correlated with the flux
of the magnetar. Based on this result, as well as on spectral and energetic
considerations, we conclude that the extended emission is dominated by a
dust-scattering halo and not a pulsar wind nebula (PWN), as has been previously
argued. We obtain an upper limit on the 2-10 keV flux of a possible PWN of
4.7e-14 erg/s/cm^2, three times less than the previously claimed value,
implying an efficiency for conversion of spin-down energy into nebular
luminosity of <9e-4 (assuming a distance of 4 kpc). We do, however, find strong
evidence for X-ray emission from the supernova remnant shell surrounding the
pulsar, as previously reported.Comment: 16 pages, 3 tables, 4 figures, published in the Astrophysical Journa
Strategies and approaches in plasmidome studies—uncovering plasmid diversity disregarding of linear elements?
The term plasmid was originally coined for circular, extrachromosomal genetic elements. Today, plasmids are widely recognized not only as important factors facilitating genome restructuring but also as vehicles for the dissemination of beneficial characters within bacterial communities. Plasmid diversity has been uncovered by means of culture-dependent or -independent approaches, such as endogenous or exogenous plasmid isolation as well as PCR-based detection or transposon-aided capture, respectively. High-throughput-sequencing made possible to cover total plasmid populations in a given environment, i.e., the plasmidome, and allowed to address the quality and significance of self-replicating genetic elements. Since such efforts were and still are rather restricted to circular molecules, here we put equal emphasis on the linear plasmids which—despite their frequent occurrence in a large number of bacteria—are largely neglected in prevalent plasmidome conceptions
Years of RXTE Monitoring of Anomalous X-ray Pulsar 4U 0142+61: Long-Term Variability
We report on 10 years of monitoring of the 8.7-s Anomalous X-ray Pulsar 4U
0142+61 using the Rossi X-Ray Timing Explorer (RXTE). This pulsar exhibited
stable rotation from 2000 March until 2006 February: the RMS phase residual for
a spin-down model which includes nu, nudot, and nuddot is 2.3%. We report a
possible phase-coherent timing solution valid over a 10-yr span extending back
to March 1996. A glitch may have occured between 1998 and 2000, but is not
required by the existing timing data. The pulse profile has been evolving since
2000. In particular, the dip of emission between its two peaks got shallower
between 2002 and 2006, as if the profile were evolving back to its pre-2000
morphology, following an earlier event, which possibly also included the glitch
suggested by the timing data. These profile variations are seen in the 2-4 keV
band but not in 6-8 keV. We also detect a slow increase in the pulsed flux
between 2002 May and 2004 December, such that it has risen by 36+/-3% over 2.6
years in the 2-10 keV band. The pulsed flux variability and the narrow-band
pulse profile changes present interesting challenges to aspects of the magnetar
model.Comment: 28 pages, 8 figures, accepted by Ap
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