249 research outputs found
Dichotomy in the Dynamical Status of Massive Cores in Orion
To study the evolution of high mass cores, we have searched for evidence of
collapse motions in a large sample of starless cores in the Orion molecular
cloud. We used the Caltech Submillimeter Observatory telescope to obtain
spectra of the optically thin (\H13CO+) and optically thick (\HCO+) high
density tracer molecules in 27 cores with masses 1 \Ms. The red- and
blue-asymmetries seen in the line profiles of the optically thick line with
respect to the optically thin line indicate that 2/3 of these cores are not
static. We detect evidence for infall (inward motions) in 9 cores and outward
motions for 10 cores, suggesting a dichotomy in the kinematic state of the
non-static cores in this sample. Our results provide an important observational
constraint on the fraction of collapsing (inward motions) versus non-collapsing
(re-expanding) cores for comparison with model simulations.Comment: 9 pages, 2 Figures. To appear in ApJ(Letters
Massive Quiescent Cores in Orion. -- II. Core Mass Function
We have surveyed submillimeter continuum emission from relatively quiescent
regions in the Orion molecular cloud to determine how the core mass function in
a high mass star forming region compares to the stellar initial mass function.
Such studies are important for understanding the evolution of cores to stars,
and for comparison to formation processes in high and low mass star forming
regions. We used the SHARC II camera on the Caltech Submillimeter Observatory
telescope to obtain 350 \micron data having angular resolution of about 9
arcsec, which corresponds to 0.02 pc at the distance of Orion. Our analysis
combining dust continuum and spectral line data defines a sample of 51 Orion
molecular cores with masses ranging from 0.1 \Ms to 46 \Ms and a mean mass of
9.8 \Ms, which is one order of magnitude higher than the value found in typical
low mass star forming regions, such as Taurus. The majority of these cores
cannot be supported by thermal pressure or turbulence, and are probably
supercritical.They are thus likely precursors of protostars. The core mass
function for the Orion quiescent cores can be fitted by a power law with an
index equal to -0.850.21. This is significantly flatter than the Salpeter
initial mass function and is also flatter than the core mass function found in
low and intermediate star forming regions. Thus, it is likely that
environmental processes play a role in shaping the stellar IMF later in the
evolution of dense cores and the formation of stars in such regions.Comment: 30 pages, 10 figures, accepted by Ap
ROS Promote Epigenetic Remodeling and Cardiac Dysfunction in Offspring Following Maternal Engineered Nanomaterial (ENM) Exposure
Background: Nano-titanium dioxide (nano-TiO2) is amongst the most widely utilized engineered nanomaterials (ENMs). However, little is known regarding the consequences maternal ENM inhalation exposure has on growing progeny during gestation. ENM inhalation exposure has been reported to decrease mitochondrial bioenergetics and cardiac function, though the mechanisms responsible are poorly understood. Reactive oxygen species (ROS) are increased as a result of ENM inhalation exposure, but it is unclear whether they impact fetal reprogramming. The purpose of this study was to determine whether maternal ENM inhalation exposure influences progeny cardiac development and epigenomic remodeling. Results: Pregnant FVB dams were exposed to nano-TiO2 aerosols with a mass concentration of 12.09 ± 0.26 mg/m3 starting at gestational day five (GD 5), for 6 h over 6 non-consecutive days. Aerosol size distribution measurements indicated an aerodynamic count median diameter (CMD) of 156 nm with a geometric standard deviation (GSD) of 1.70. Echocardiographic imaging was used to assess cardiac function in maternal, fetal (GD 15), and young adult (11 weeks) animals. Electron transport chain (ETC) complex activities, mitochondrial size, complexity, and respiration were evaluated, along with 5-methylcytosine, Dnmt1 protein expression, and Hif1α activity. Cardiac functional analyses revealed a 43% increase in left ventricular mass and 25% decrease in cardiac output (fetal), with an 18% decrease in fractional shortening (young adult). In fetal pups, hydrogen peroxide (H2O2) levels were significantly increased (~ 10 fold) with a subsequent decrease in expression of the antioxidant enzyme, phospholipid hydroperoxide glutathione peroxidase (GPx4). ETC complex activity IV was decreased by 68 and 46% in fetal and young adult cardiac mitochondria, respectively. DNA methylation was significantly increased in fetal pups following exposure, along with increased Hif1α activity and Dnmt1 protein expression. Mitochondrial ultrastructure, including increased size, was observed at both fetal and young adult stages following maternal exposure. Conclusions: Maternal inhalation exposure to nano-TiO2 results in adverse effects on cardiac function that are associated with increased H2O2 levels and dysregulation of the Hif1α/Dnmt1 regulatory axis in fetal offspring. Our findings suggest a distinct interplay between ROS and epigenetic remodeling that leads to sustained cardiac contractile dysfunction in growing and young adult offspring following maternal ENM inhalation exposure
Viable Influenza A Virus in Airborne Particles Expelled During Coughs Versus Exhalations
Background To prepare for a possible influenza pandemic, a better understanding of the potential for the airborne transmission of influenza from person to person is needed.
Objectives The objective of this study was to directly compare the generation of aerosol particles containing viable influenza virus during coughs and exhalations.
Methods Sixty-one adult volunteer outpatients with influenza-like symptoms were asked to cough and exhale three times into a spirometer. Aerosol particles produced during coughing and exhalation were collected into liquid media using aerosol samplers.The samples were tested for the presence of viable influenza virus using a viral replication assay (VRA).
Results Fifty-three test subjects tested positive for influenza A virus. Of these, 28 (53%) produced aerosol particles containing viable influenza A virus during coughing, and 22 (42%) produced aerosols with viable virus during exhalation. Thirteen subjects had both cough aerosol and exhalation aerosol samples that contained viable virus, 15 had positive cough aerosol samples but negative exhalation samples, and 9 had positive exhalation samples but negative cough samples.
Conclusions Viable influenza A virus was detected more often in cough aerosol particles than in exhalation aerosol particles, but the difference was not large. Because individuals breathe much more often than they cough, these results suggest that breathing may generate more airborne infectious material than coughing over time. However, both respiratory activities could be important in airborne influenza transmission. Our results are also consistent with the theory that much of the aerosol containing viable influenza originates deep in the lung
Can We Trust the Dust? Evidence of Dust Segregation in Molecular Clouds
Maps of estimated dust column density in molecular clouds are usually assumed
to reliably trace the total gas column density structure. In this work we
present results showing a clear discrepancy between the dust and the gas
distribution in the Taurus molecular cloud complex. We compute the power
spectrum of a 2MASS extinction map of the Taurus region and find it is much
shallower than the power spectrum of a 13CO map of the same region previously
analyzed. This discrepancy may be explained as the effect of grain growth on
the grain extinction efficiency. However, this would require a wide range of
maximum grain sizes, which is ruled out based on constraints from the
extinction curve and the available grain models. We show that major effects due
to CO formation and depletion are also ruled out. Our result may therefore
suggest the existence of intrinsic spatial fluctuations of the dust to gas
ratio, with amplitude increasing toward smaller scales. Preliminary results of
numerical simulations of trajectories of inertial particles in turbulent flows
illustrate how the process of clustering of dust grains by the cloud turbulence
may lead to observable effects. However, these results cannot be directly
applied to large scale supersonic and magnetized turbulence at present.Comment: 10 pages, 8 figures included, ApJ, in pres
Deep Learning for Detection and Localization of B-Lines in Lung Ultrasound
Lung ultrasound (LUS) is an important imaging modality used by emergency
physicians to assess pulmonary congestion at the patient bedside. B-line
artifacts in LUS videos are key findings associated with pulmonary congestion.
Not only can the interpretation of LUS be challenging for novice operators, but
visual quantification of B-lines remains subject to observer variability. In
this work, we investigate the strengths and weaknesses of multiple deep
learning approaches for automated B-line detection and localization in LUS
videos. We curate and publish, BEDLUS, a new ultrasound dataset comprising
1,419 videos from 113 patients with a total of 15,755 expert-annotated B-lines.
Based on this dataset, we present a benchmark of established deep learning
methods applied to the task of B-line detection. To pave the way for
interpretable quantification of B-lines, we propose a novel "single-point"
approach to B-line localization using only the point of origin. Our results
show that (a) the area under the receiver operating characteristic curve ranges
from 0.864 to 0.955 for the benchmarked detection methods, (b) within this
range, the best performance is achieved by models that leverage multiple
successive frames as input, and (c) the proposed single-point approach for
B-line localization reaches an F1-score of 0.65, performing on par with the
inter-observer agreement. The dataset and developed methods can facilitate
further biomedical research on automated interpretation of lung ultrasound with
the potential to expand the clinical utility.Comment: 10 pages, 4 figure
Egg Formation in Lepidoptera
Reproductive biology in the Twentieth Century produced comprehensive descriptions of the mechanisms of egg formation in most of the major orders of insects. While many general principles of ovarian development and physiology emerged, every order turned out to have a set of its own special motifs. Discovery of the lepidopteran motifs is summarized in this essay. The emphasis is on developmental mechanisms, beginning with the early growth and differentiation of female germ cells and ending, after many turns in morphogenesis, physiology and biosynthesis, with eggs that are filled with yolk and encased in chorions. Examples of uniquely lepidopteran traits include the cellular composition of ovarian follicles, the number of tubular ovarioles in which they mature, the functions of cell-to-cell junctional complexes in their maturation, their use of glycosaminoglycans to maintain intercellular patency during vitellogenesis, the role of proton and calcium pumps in their ion physiology, a separate postvitellogenic period of water and inorganic ion uptake, and the fine structure and protein composition of their chorions. Discovery of this combination of idiosyncracies was based on advances in the general concepts and techniques of cell and molecular biology and on insights borrowed from studies on other insects. The lepidopteran ovary in turn has contributed much to the understanding of egg formation in insects generally
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