2,039 research outputs found
A multichannel passive microwave atmospheric temperature sounding system
The development of a small, lightweight, low-power, seven channel passive microwave radiometer system for use on the Defense Meteorological Satellite Program (DMSP) was described. The 50-60 GHz sensor system operates in the region of an intense atmospheric oxygen absorption band to provide atmospheric temperature profiles to 30 kilometer altitudes on a global basis
Extinction and dust/gas ratio in LMC molecular clouds
Aims. The goal of this paper is to measure the dust content and distribution in the Large Magellanic Cloud (LMC) by comparing extinction maps produced in the near-infrared wavelengths and the spatial distribution of the neutral and molecular gas, as traced by Hi and CO observations.
Methods. In order to derive an extinction map of the LMC, we have developed a new method to measure the color excess of dark clouds, using the 2MASS all-sky survey. Classical methods to measure the color excess (including the NICE method) tend to underestimate the true color excess if the clouds are significantly contaminated by unreddened foreground stars, as is the case in the LMC. We propose a new method that uses the color of the X percentile reddest stars and which is robust against such contamination. Using this method, it is possible to infer the positions of dark clouds with respect to the star distribution by comparing the observed color excess as a function of the percentile used and that predicted by a model.
Results. On the basis of the resulting extinction map, we perform a correlation analysis for a set of dark molecular clouds. Assuming similar infrared absorption properties for the dust in the neutral and molecular phases, we derive the absorption-to-column density ratio AV/NH and the CO-to-H2 conversion factor X_(CO). We show that AV/NH increases from the outskirts of the LMC towards the 30 Dor star-forming region. This can be explained either by a systematic increase of the dust abundance, or by the presence of an additional gas component not traced by Hi or CO, but strongly correlated to the Hi distribution. If dust abundance is allowed to vary, the derived X_(CO) factors for the selected regions are several times lower than those derived from a virial analysis of the CO data. This could indicate that molecular clouds in the LMC are not gravitationally bound, or that they are bounded by substantial external pressure. However, the X_(CO) values derived from absorption can be reconciled with the virial results assuming a constant value for the dust abundance and the existence of an additional, unseen gas component. These results are in agreement with those derived for the LMC from diffuse far-infrared emission
The molecular complex associated with the Galactic HII region Sh2-90: a possible site of triggered star formation
We investigate the star formation activity in the molecular complex
associated with the Galactic HII region Sh2-90, using radio-continuum maps
obtained at 1280 MHz and 610 MHz, Herschel Hi-GAL observations at 70 -- 500
microns, and deep near-infrared observation at JHK bands, along with Spitzer
observations. Sh2-90 presents a bubble morphology in the mid-IR (size ~ 0.9 pc
x 1.6 pc). Radio observations suggest it is an evolved HII region with an
electron density ~ 144 cm^-3, emission measure ~ 6.7 x 10^4 cm^-6 pc and a
ionized mass ~ 55 Msun. From Hi-GAL observations it is found that the HII
region is part of an elongated extended molecular cloud (size ~ 5.6 pc x 9.7
pc, H_2 column density >= 3 x 10^21 cm^-2 and dust temperature 18 -- 27 K) of
total mass >= 1 x 10^4 Msun. We identify the ionizing cluster of Sh2-90, the
main exciting star being an O8--O9 V star. Five cold dust clumps (mass ~ 8 --
95 Msun), four mid-IR blobs around B stars, and a compact HII region are found
at the edge of the bubble.The velocity information derived from CO (J=3-2) data
cubes suggests that most of them are associated with the Sh2-90 region. 129
YSOs are identified (Class I, Class II, and near-IR excess sources). The
majority of the YSOs are low mass (<= 3 Msun) sources and they are distributed
mostly in the regions of high column density. Four candidate Class 0/I MYSOs
have been found; they will possibly evolve to stars of mass >= 15 Msun. We
suggest multi-generation star formation is present in the complex. From the
evidences of interaction, the time scales involved and the evolutionary status
of stellar/protostellar sources, we argue that the star formation at the
immediate border/edges of Sh2-90 might have been triggered by the expanding HII
region. However, several young sources in this complex are probably formed by
some other processes.Comment: 22 pages, 22 figures, accepted for publication in Astronomy and
Astrophysic
Modeling and predicting the shape of the far-infrared to submillimeter emission in ultra-compact HII regions and cold clumps
Dust properties are very likely affected by the environment in which dust
grains evolve. For instance, some analyses of cold clumps (7 K- 17 K) indicate
that the aggregation process is favored in dense environments. However,
studying warm (30 K-40 K) dust emission at long wavelength (300
m) has been limited because it is difficult to combine far
infared-to-millimeter (FIR-to-mm) spectral coverage and high angular resolution
for observations of warm dust grains. Using Herschel data from 70 to 500
m, which are part of the Herschel infrared Galactic (Hi-GAL) survey
combined with 1.1 mm data from the Bolocam Galactic Plane Survey (BGPS), we
compared emission in two types of environments: ultra-compact HII (UCHII)
regions, and cold molecular clumps (denoted as cold clumps). With this
comparison we tested dust emission models in the FIR-to-mm domain that
reproduce emission in the diffuse medium, in these two environments (UCHII
regions and cold clumps). We also investigated their ability to predict the
dust emission in our Galaxy. We determined the emission spectra in twelve UCHII
regions and twelve cold clumps, and derived the dust temperature (T) using the
recent two-level system (TLS) model with three sets of parameters and the
so-called T- (temperature-dust emissvity index) phenomenological models,
with set to 1.5, 2 and 2.5. We tested the applicability of the TLS
model in warm regions for the first time. This analysis indicates distinct
trends in the dust emission between cold and warm environments that are visible
through changes in the dust emissivity index. However, with the use of standard
parameters, the TLS model is able to reproduce the spectral behavior observed
in cold and warm regions, from the change of the dust temperature alone,
whereas a T- model requires to be known.Comment: Accepted for publication in A&A. 19 pages, 8 figures, 7 table
Toward a better understanding of the mid-infrared emission in the LMC
In this paper we aim to constrain for the first time the dust emission in the
mid-to-far infrared domain, in the LMC, with the use of the Spitzer IRS and
MIPS SED data, combined with Herschel data. We also consider UV extinction
predictions derived from modeling. We selected 10 regions observed as part of
the SAGE-Spec program, to probe dust properties in various environments
(diffuse, molecular and ionized regions). All data were smoothed to the
40arcsec angular resolution. The SEDs were modeled with DustEM models, using
the standard Mathis RF, as well as three additional RFs, with stellar clusters
ages ranging from 4 Myr to 600 Myr. Standard dust models used to reproduce the
Galactic diffuse medium are clearly not able to reproduce the dust emission in
the MIR wavelength domain. This analysis evidences the need of adjusting
parameters describing the dust size distribution and shows a clear distinct
behavior according to the type of environments. In addition, whereas the small
grain emission always seems to be negligible at long wavelengths in our Galaxy,
the contribution of this small dust component could be more important than
expected, in the submm-mm range, in the LMC averaged SED. Properties of the
small dust component of the LMC are clearly different from those of our Galaxy.
Its abundance, significantly enhanced, could be the result of large grains
shattering due to strong shocks or turbulence. In addition, this grain
component in the LMC systematically shows smaller grain size in the ionized
regions compared to the diffuse medium. Predictions of extinction curves show
significantly distinct behaviors depending on the dust models but also from one
region to another. Comparison of model predictions with the LMC mean extinction
curve shows that no model gives satisfactory agreement using the Mathis
radiation field while using a harder radiation field tends to improve the
agreementComment: Accepted for publication in A&
Language control and parallel recovery of language in individuals with aphasia
Background: The causal basis of the different patterns of language recovery following stroke in bilingual speakers is not well understood. Our approach distinguishes the representation of language from the mechanisms involved in its control. Previous studies have suggested that difficulties in language control can explain selective aphasia in one language as well as pathological switching between languages. Here we test the hypothesis that difficulties in managing and resolving competition will also be observed in those who are equally impaired in both their languages even in the absence of pathological switching.
Aims: To examine difficulties in language control in bilingual individuals with parallel recovery in aphasia and to compare their performance on different types of conflict task.
Methods & procedures: Two right-handed, non-native English-speaking participants who showed parallel recovery of two languages after stroke and a group of non-native English-speaking, bilingual controls described a scene in English and in their first language and completed three explicit conflict tasks. Two of these were verbal conflict tasks: a lexical decision task in English, in which individuals distinguished English words from non-words, and a Stroop task, in English and in their first language. The third conflict task was a non-verbal flanker task.
Outcomes & Results: Both participants with aphasia were impaired in the picture description task in English and in their first language but showed different patterns of impairment on the conflict tasks. For the participant with left subcortical damage, conflict was abnormally high during the verbal tasks (lexical decision and Stroop) but not during the non-verbal flanker task. In contrast, for the participant with extensive left parietal damage, conflict was less abnormal during the Stroop task than the flanker or lexical decision task.
Conclusions: Our data reveal two distinct control impairments associated with parallel recovery. We stress the need to explore the precise nature of control problems and how control is implemented in order to develop fuller causal accounts of language recovery patterns in bilingual aphasia
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Biomarkers and overall survival in patients with advanced hepatocellular carcinoma treated with TGF-βRI inhibitor galunisertib.
BackgroundTransforming growth factor beta (TGF-β) signalling is involved in the development of hepatocellular carcinoma (HCC). We followed changes in biomarkers during treatment of patients with HCC with the TGF-βRI/ALK5 inhibitor galunisertib.MethodsThis phase 2 study (NCT01246986) enrolled second-line patients with advanced HCC into one of two cohorts of baseline serum alpha-fetoprotein (AFP): Part A (AFP ≥1.5x ULN) or Part B (AFP <1.5x ULN). Baseline and postbaseline levels of AFP, TGF-β1, E-cadherin, selected miRNAs, and other plasma proteins were monitored.ResultsThe study enrolled 149 patients (Part A, 109; Part B, 40). Median OS was 7.3 months in Part A and 16.8 months in Part B. Baseline AFP, TGF-β1, E-cadherin, and an additional 16 plasma proteins (such as M-CSF, IL-6, ErbB3, ANG-2, neuropilin-1, MIP-3 alpha, KIM-1, uPA, IL-8, TIMP-1, ICAM-1, Apo A-1, CA-125, osteopontin, tetranectin, and IGFBP-1) were found to correlate with OS. In addition, a range of miRs were found to be associated with OS. In AFP responders (21% of patients in Part A with decrease of >20% from baseline) versus non-responders, median OS was 21.5 months versus 6.8 months (p = 0.0015). In TGF-β1 responders (51% of all patients) versus non-responders, median OS was 11.2 months versus 5.3 months (p = 0.0036).ConclusionsConsistent with previous findings, both baseline levels and changes from baseline of circulating AFP and TGF-β1 function as prognostic indicators of survival. Future trials are needed to confirm and extend these results
Advancement of a Conceptual Framework for Positional Competition in Sport: Development and Validation of the Positional Competition in Team Sports Questionnaire
Dust Emission from Evolved and Unevolved HII Regions in the Large Magellanic Cloud
We present a study of the dust properties of 12 classical and superbubble HII
regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer
(8, 24, 70, and 160 \mum bands), obtained as part of the Surveying the Agents
of a Galaxy's Evolution (SAGE) program, along with archival spectroscopic
classifications of the ionizing stars to examine the role of stellar sources on
dust heating and processing. Our infrared observations show surprisingly little
correlation between the emission properties of the dust and the effective
temperatures or bolometric magnitudes of stars in the HII regions, suggesting
that the HII region evolutionary timescale is not on the order of the dust
processing timescale. We find that the infrared emission of superbubbles and
classical HII regions shows little differentiation between the two classes,
despite the significant differences in age and morphology. We do detect a
correlation of the 24 \mum emission from hot dust with the ratio of 70 to 160
\mum flux. This correlation can be modeled as a trend in the temperature of a
minority hot dust component, while a majority of the dust remains significantly
cooler.Comment: 15 pages, 5 figures. Accepted to Ap
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