126 research outputs found
Non-Thermal Continuum toward SGRB2(N-LMH)
An analysis of continuum antenna temperatures observed in the Green Bank
Telescope (GBT) spectrometer bandpasses is presented for observations toward
SgrB2(N-LMH). Since 2004, we have identified four new prebiotic molecules
toward this source by means of rotational transitions between low energy
levels; concurrently, we have observed significant continuum in the GBT
spectrometer bandpasses centered at 85 different frequencies in the range of 1
to 48 GHz. The continuum heavily influences the molecular spectral features
since we have observed far more absorption lines than emission lines for each
of these new molecular species. Hence, it is important to understand the
nature, distribution, and intensity of the underlying continuum in the GBT
bandpasses for the purposes of radiative transfer, i.e. the means by which
reliable molecular abundances are estimated. We find that the GBT spectrometer
bandpass continuum is consistent with optically-thin, non thermal (synchrotron)
emission with a flux density spectral index of -0.7 and a Gaussian source size
of ~143" at 1 GHz that decreases with increasing frequency as nu^(-0.52). Some
support for this model is provided by high frequency Very Large Array (VLA)
observations of SgrB2.Comment: Accepted for Publication in the Astrophysical Journal Letter
The effect of administration order of BU and CY on toxicity in hematopoietic SCT in humans
Universidade Federal de São Paulo, Div Bone Marrow Transplantat, São Paulo, BrazilUniversidade Federal de São Paulo, Div Bone Marrow Transplantat, São Paulo, BrazilWeb of Scienc
Esophageal perforation secondary to malignant gastric outlet obstruction: a case report
Background
Esophageal perforation is a rare presenting sign of gastric cancer. To date, only nine case reports of this phenomenon have been previously published.
Case presentation
Esophageal perforation was diagnosed radiographically during workup for acute chest pain in a 67-year-old man. Emergent endoscopy confirmed esophageal perforation and biopsied a pre-pyloric mass confirmed to be adenocarcinoma. The perforation was managed with endoscopically placed transluminal pleural and mediastinal drains and esophageal stenting. The gastric outlet obstruction was temporized with a transpyloric stent. After the patient recovered from sepsis, distal gastrectomy was performed and he made a full recovery.
Conclusions
Rarely, pre-pyloric gastric cancer can present with Boerhaave syndrome, spontaneous esophageal perforation associated with forceful vomiting. We present the tenth report in the literature of this phenomenon and the first to be initially treated with endoscopic stenting and transluminal thoracoscopic drainage. When endoscopic management is used to treat patients with Boerhaave syndrome, it may be beneficial to examine the entire stomach to evaluate for malignant etiology
The Formaldehyde Masers in NGC 7538 and G29.96-0.02: VLBA, MERLIN, and VLA Observations
The 6 cm formaldehyde (H2CO) maser sources in the compact HII regions NGC
7538-IRS1 and G29.96-0.02 have been imaged at high resolution (beams < 50 mas).
Using the VLBA and MERLIN, we find the angular sizes of the NGC 7538 masers to
be ~10 mas (30 AU) corresponding to brightness temperatures ~10^8 K. The
angular sizes of the G29.96-0.02 masers are ~20 mas (130 AU) corresponding to
brightness temperatures ~10^7 K. Using the VLA, we detect 2 cm formaldehyde
absorption from the maser regions. We detect no emission in the 2 cm line,
indicating the lack of a 2 cm maser and placing limits on the 6 cm excitation
process. We find that both NGC 7538 maser components show an increase in
intensity on 5-10 year timescales while the G29.96-0.02 masers show no
variability over 2 years. A search for polarization provides 3-sigma upper
limits of 1% circularly polarized and 10% linearly polarized emission in NGC
7538 and of 15% circularly polarized emission in G29.96-0.02. A pronounced
velocity gradient of 28 km/s/arcsecond (1900 km/s/pc) is detected in the NGC
7538 maser gas.Comment: accepted to ApJ, 15 figures, 11 table
Low Velocity Ionized Winds from Regions Around Young O Stars
We have observed seven ultracompact HII regions in hydrogen recombination
lines in the millimeter band. Toward four of these regions, there is a high
velocity (full width to half maximum 60-80 km/s) component in the line
profiles. The high velocity gas accounts for 35-70% of the emission measure
within the beam. We compare these objects to an additional seven similar
sources we have found in the literature. The broad recombination line objects
(BRLOs) make up about 30% of all sources in complexes containing ultracompact
HII regions. Comparison of spectral line and continuum data implies that the
BRLOs coincide with sources with rising spectral indices, >=0.4 up to 100 GHz.
Both the number of BRLOs and their frequency of occurrence within HII region
complexes, when coupled with their small size and large internal motions, mean
that the apparent contradiction between the dynamical and population lifetimes
for BRLOs is even more severe than for ultracompact HII regions. We evaluate a
number of models for the origin of the broad recombination line emission. The
lifetime, morphology, and rising spectral index of the sources argue for photo-
evaporated disks as the cause for BRLOs. Existing models for such regions,
however, do not account for the large amounts of gas observed at supersonic
velocities.Comment: 36 pages, 8 figure
Synchrotron emission from the T Tauri binary system V773 Tau A
The pre-main sequence binary system V773 Tau A shows remarkable flaring
activity around periastron passage. Here, we present the observation of such a
flare at a wavelength of 3 mm (90 GHz) performed with the Plateau de Bure
Interferometer. We examine different possible causes for the energy losses
responsible for the e-folding time of 2.3 hours of that flare. We exclude
synchrotron, collisional, and inverse Compton losses because they are not
consistent with observational constraints, and we propose that the fading of
the emission is due to the leakage of electrons themselves at each reflection
between the two mirror points of the magnetic structure partially trapping
them. The magnetic structure compatible with both our leakage model and
previous observations is that of a helmet streamer that, as in the solar case,
can occur at the top of the X-ray-emitting, stellar-sized coronal loops of one
of the stars. The streamer may extend up to 20 R and interact with the corona
of the other star at periastron passage, causing recurring flares. The inferred
magnetic field strength at the two mirror points of the helmet streamer is in
the range 0.12 - 125 G, and the corresponding Lorentz factor, gamma, of the
partially trapped electrons is in the range 20 < gamma < 632. We therefore rule
out that the emission could be of gyro-synchrotron nature: the derived high
Lorentz factor proves that the nature of the emission at 90 GHz from this
pre-main binary system is synchrotron radiation.
Based on observations carried out with the IRAM Plateau de Bure
Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN
(Spain).Comment: 8 pages, 5 figures, A&A in pres
Time-dependent Stochastic Modeling of Solar Active Region Energy
A time-dependent model for the energy of a flaring solar active region is
presented based on a stochastic jump-transition model (Wheatland and Glukhov
1998; Wheatland 2008; Wheatland 2009). The magnetic free energy of the model
active region varies in time due to a prescribed (deterministic) rate of energy
input and prescribed (random) flare jumps downwards in energy. The model has
been shown to reproduce observed flare statistics, for specific
time-independent choices for the energy input and flare transition rates.
However, many solar active regions exhibit time variation in flare
productivity, as exemplified by NOAA active region AR 11029 (Wheatland 2010).
In this case a time-dependent model is needed. Time variation is incorporated
for two cases: 1. a step change in the rates of flare jumps; and 2. a step
change in the rate of energy supply to the system. Analytic arguments are
presented describing the qualitative behavior of the system in the two cases.
In each case the system adjusts by shifting to a new stationary state over a
relaxation time which is estimated analytically. The new model retains
flare-like event statistics. In each case the frequency-energy distribution is
a power law for flare energies less than a time-dependent rollover set by the
largest energy the system is likely to attain at a given time. For Case 1, the
model exhibits a double exponential waiting-time distribution, corresponding to
flaring at a constant mean rate during two intervals (before and after the step
change), if the average energy of the system is large. For Case 2 the
waiting-time distribution is a simple exponential, again provided the average
energy of the system is large. Monte Carlo simulations of Case~1 are presented
which confirm the analytic estimates. The simulation results provide a
qualitative model for observed flare statistics in active region AR 11029.Comment: 25 pages, 9 figure
A differentially rotating disc in a high-mass protostellar system
A strong signature of a circumstellar disc around a high-mass protostar has
been inferred from high resolution methanol maser observations in NGC7538-IRS1
N. This interpretation has however been challenged with a bipolar outflow
proposed as an alternative explanation. We compare the two proposed scenarios
for best consistency with the observations. Using a newly developed formalism
we model the optical depth of the maser emission at each observed point in the
map and LOS velocity for the two scenarios. We find that if the emission is
symmetric around a central peak in both space and LOS velocity then it has to
arise from an edge-on disc in sufficiently fast differential rotation. Disc
models successfully fit ~100 independent measurement points in
position-velocity space with 4 free parameters to an overall accuracy of 3-4%.
Solutions for Keplerian rotation require a central mass of at least 4 solar
masses. Close to best-fitting models are obtained if Keplerian motion is
assumed around a central mass equaling ~30 solar masses as inferred from other
observations. In contrast we find that classical bipolar outflow models cannot
fit the data, although could be applicable in other sources. Our results
strongly favour the differentially rotating disc hypothesis to describe the
main feature of the 12.2 (and 6.7) GHz methanol maser emission in NGC7538 IRS1
N. Furthermore, for Keplerian rotation around a ~30 solar masses protostar we
predict the position and velocity at which tangentially amplified masers should
be detected in high dynamic range observations. [abridged]Comment: 13 pages, 11 figures, accepted for publication in A&
A near-infrared study of the NGC 7538 star forming region
We present sub-arcsecond (FWHM ~ 0".7), NIR JHKs-band images and a high
sensitivity radio continuum image at 1280 MHz, using SIRIUS on UH 88-inch
telescope and GMRT. The NIR survey covers an area of ~ 24 arcmin^2 with
10-sigma limiting mags of ~ 19.5, 18.4, and 17.3 in J, H, and Ks-band,
respectively. Our NIR images are deeper than any JHK surveys to date for the
larger area of NGC 7538 star forming region. We construct JHK CC and J-H/J and
H-K/K CM diagrams to identify YSOs and to estimate their masses. Based on these
CC and CM diagrams, we identified a rich population of YSOs (Class I and Class
II), associated with the NGC 7538 region. A large number of red sources (H-K >
2) have also been detected around NGC 7538. We argue that these red stars are
most probably PMS stars with intrinsic color excesses. Most of YSOs in NGC 7538
are arranged from the N-W toward S-E regions, forming a sequence in age: the
diffuse H II region (N-W, oldest: where most of the Class II and Class I
sources are detected); the compact IR core (center); and the regions with the
extensive IR reflection nebula and a cluster of red young stars (S-E and S). We
find that the slope of the KLF of NGC 7538 is lower than the typical values
reported for the young embedded clusters, although equally low values have also
been reported in the W3 Main star forming region. From the slope of the KLF and
the analysis by Megeath et al. (1996), we infer that the embedded stellar
population is comprised of YSOs with an age of ~ 1 Myr. Based on the comparison
between models of PMS stars with the observed CM diagram we find that the
stellar population in NGC 7538 is primarily composed of low mass PMS stars
similar to those observed in the W3 Main star forming region.Comment: 36 pages, 13 figures in JPEG format. Accepted for the publication in
ApJ. Report is also available at : http://www.tifr.res.in/~ojha/NGC7538.htm
Intersubject and intrasubject variability of potential plasma and urine metabolite and protein biomarkers in healthy human volunteers
A limited understanding of intersubject and intrasubject variability hampers effective biomarker translation from in vitro/in vivo studies to clinical trials and clinical decision support. Specifically, variability of biomolecule concentration can play an important role in interpretation, power analysis, and sampling time designation. In the present study, a wide range of 749 plasma metabolites, 62 urine biogenic amines, and 1,263 plasma proteins were analyzed in 10 healthy male volunteers measured repeatedly during 12 hours under tightly controlled conditions. Three variability components in relative concentration data are determined using linear mixed models: between (intersubject), time (intrasubject), and noise (intrasubject). Biomolecules such as 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, platelet-derived growth factor C, and cathepsin D with low noise potentially detect changing conditions within a person. If also the between component is low, biomolecules can easier differentiate conditions between persons, for example cathepsin D, CD27 antigen, and prolylglycine. Variability over time does not necessarily inhibit translatability, but requires choosing sampling times carefully.Analytical BioScience
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