373 research outputs found
Filamentary Star Formation: Observing the Evolution toward Flattened Envelopes
Filamentary structures are ubiquitous from large-scale molecular clouds (few
parsecs) to small-scale circumstellar envelopes around Class 0 sources (~1000
AU to ~0.1 pc). In particular, recent observations with the Herschel Space
Observatory emphasize the importance of large-scale filaments (few parsecs) and
star formation. The small-scale flattened envelopes around Class 0 sources are
reminiscent of the large-scale filaments. We propose an observationally derived
scenario for filamentary star formation that describes the evolution of
filaments as part of the process for formation of cores and circumstellar
envelopes. If such a scenario is correct, small-scale filamentary structures
(0.1 pc in length) with higher densities embedded in starless cores should
exist, although to date almost all the interferometers have failed to observe
such structures. We perform synthetic observations of filaments at the
prestellar stage by modeling the known Class 0 flattened envelope in L1157
using both the Combined Array for Research in Millimeter-wave Astronomy (CARMA)
and the Atacama Large Millimeter/Submillimeter Array (ALMA). We show that with
reasonable estimates for the column density through the flattened envelope, the
CARMA D-array at 3mm wavelengths is not able to detect such filamentary
structure, so previous studies would not have detected them. However, the
substructures may be detected with CARMA D+E array at 3 mm and CARMA E array at
1 mm as a result of more appropriate resolution and sensitivity. ALMA is also
capable of detecting the substructures and showing the structures in detail
compared to the CARMA results with its unprecedented sensitivity. Such
detection will confirm the new proposed paradigm of non-spherical star
formation.Comment: 9 pages, 10 figures. Accepted by Ap
A Flattened Protostellar Envelope in Absorption around L1157
Deep Spitzer IRAC images of L1157 reveal many of the details of the outflow
and the circumstellar environment of this Class 0 protostar. In IRAC band 4, 8
microns, there is a flattened structure seen in absorption against the
background emission. The structure is perpendicular to the outflow and is
extended to a diameter of 2 arcminutes. This structure is the first clear
detection of a flattened circumstellar envelope or pseudo-disk around a Class 0
protostar. Such a flattened morphology is an expected outcome for many collapse
theories that include magnetic fields or rotation. We construct an extinction
model for a power-law density profile, but we do not constrain the density
power-law index.Comment: ApJL accepte
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TCR Convergence in Individuals Treated With Immune Checkpoint Inhibition for Cancer.
Tumor antigen-driven selection may expand T cells having T cell receptors (TCRs) of shared antigen specificity but different amino acid or nucleotide sequence in a process known as TCR convergence. Substitution sequencing errors introduced by TCRβ (TCRB) repertoire sequencing may create artifacts resembling TCR convergence. Given the anticipated differences in substitution error rates across different next-generation sequencing platforms, the choice of platform could be consequential. To test this, we performed TCRB sequencing on the same peripheral blood mononuclear cells (PBMC) from individuals with cancer receiving anti-CTLA-4 or anti-PD-1 using an Illumina-based approach (Sequenta) and an Ion Torrent-based approach (Oncomine TCRB-LR). While both approaches found similar TCR diversity, clonality, and clonal overlap, we found that Illumina-based sequencing resulted in higher TCR convergence than with the Ion Torrent approach. To build upon this initial observation we conducted a systematic comparison of Illumina-based TCRB sequencing assays, including those employing molecular barcodes, with the Oncomine assay, revealing differences in the frequency of convergent events, purportedly artifactual rearrangements, and sensitivity of detection. Finally, we applied the Ion Torrent-based approach to evaluate clonality and convergence in a cohort of individuals receiving anti-CTLA-4 blockade for cancer. We found that clonality and convergence independently predicted response and could be combined to improve the accuracy of a logistic regression classifier. These results demonstrate the importance of the sequencing platform in assessing TCRB convergence
Probing the Protostellar Envelope around L1157: the Dust and Gas Connection
We present observations of the Class 0 protostar L1157-mm using the Combined
Array for Research in Millimeter-wave Astronomy (CARMA) in 3 mm dust continuum
and N2H+ line emission. In the N2H+ line, we detect a large-scale envelope
extended over a linear size of ~20,000AU flattened in the direction
perpendicular to the outflow. This N2H+ feature coincides with the outer
envelope seen in the 8 micron extinction by Looney et al. Meanwhile, the dust
continuum traces the compact, nearly spherical structure of the inner envelope,
where N2H+ becomes depleted. This highly flattened N2H+ envelope also shows
dynamical signatures consistent with gravitational infall in the inner region,
but a slow, solid-body rotation at large scales. This flattened structure is
not a rotationally supported circumstellar disk; instead, it resembles a
prestellar core both morphologically and kinematically, representing the early
phase of a Class 0 system. In this paper, we construct a simple model to
interpret both the dust continuum and N2H+ emission and suggest a possible
dynamical scenario for the overall properties of the envelope.Comment: Accepted for publication by the ApJ, 34 pages, 10 figures and 2
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Comparative Cost Analysis of Alternative Animal Tracing Strategies Directed Toward Foot and Mouth Disease Outbreaks in the Texas High Plains
The primary objective of this study is to evaluate the industry impact of a
hypothetical Foot and Mouth Disease (FMD) outbreak in the Texas High Plains using
alternative animal tracing levels. To accomplish this objective, an epidemiological
disease spread model, AUSSPREAD, is used to simulate the FMD outbreak and an
economic model is used to examine the impacts of different animal identification levels
in cattle. The different levels of animal identification relate to the model?s ability to
trace back the subsequent infected and/or dangerous contacts with which the initial
outbreak herd has been in contact. The study examines direct disease management costs
(slaughter, euthanasia, disposal, surveillance, and cleaning disinfection), forgone
income, and other indirect costs (indemnity payments and welfare slaughter) for
outbreaks originating from a large beef operation, a feedlot, and a saleyard across
subsequent tracing periods from 1 to 10 days. Welfare slaughter and quarantine costs
were estimated for the best and worst outbreaks from the feedlot operation. It is
noteworthy that total direct costs of a FMD outbreak would be more extensive than the
current study's calculations, which only analyzed the direct disease management costs.
The increased days to trace dangerous contacts presented overall increases in
outbreak losses over each outbreak scenario. Although outcome averages appear
insensitive at times under the assumptions applied, the epidemiological model presented
the possibility that traceability could reduce the risk of extreme outcomes in respect to
the overall distribution of losses. For each cattle operation, the outbreaks stayed
consistent or marginally increased with their respective average costs, but their
maximum losses rose steadily, across the trace periods examined. The impact of
increased traceability and decreased outbreak length can be justified in affecting FMD
outbreak costs in a positive manner. The results provide the industry with estimations of
different outbreak scenarios which can be used to inform the decision on the NAIS
system. Longer tracing periods, larger simulations (by iteration), and further study of the
model is necessary in order to more accurately imitate FMD outbreaks within the Texas
High Plains and its detrimental effects
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