224 research outputs found
Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9
We investigated the response of the solar atmosphere to non-thermal electron
beam heating using the radiative transfer and hydrodynamics modelling code
RADYN. The temporal evolution of the parameters that describe the non-thermal
electron energy distribution were derived from hard X-ray observations of a
particular flare, and we compared the modelled and observed parameters. The
evolution of the non-thermal electron beam parameters during the X1.5 solar
flare on 2011 March 9 were obtained from analysis of RHESSI X-ray spectra. The
RADYN flare model was allowed to evolve for 110 seconds, after which the
electron beam heating was ended, and was then allowed to continue evolving for
a further 300s. The modelled flare parameters were compared to the observed
parameters determined from extreme-ultraviolet spectroscopy. The model produced
a hotter and denser flare loop than that observed and also cooled more rapidly,
suggesting that additional energy input in the decay phase of the flare is
required. In the explosive evaporation phase a region of high-density cool
material propagated upward through the corona. This material underwent a rapid
increase in temperature as it was unable to radiate away all of the energy
deposited across it by the non-thermal electron beam and via thermal
conduction. A narrow and high-density ( cm) region at
the base of the flare transition region was the source of optical line emission
in the model atmosphere. The collision-stopping depth of electrons was
calculated throughout the evolution of the flare, and it was found that the
compression of the lower atmosphere may permit electrons to penetrate farther
into a flaring atmosphere compared to a quiet Sun atmosphere.Comment: 12 pages, 12 figure
An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm
We present a detection of molecular gas emission at using the
technique of line intensity mapping. We make use of a pair of 3 mm
interferometric data sets, the first from the ALMA Spectroscopic Survey in the
Hubble Ultra Deep Field (ASPECS), and the second from a series of Atacama
Compact Array (ACA) observations conducted between 2016 and 2018, targeting the
COSMOS field. At 100 GHz, we measure non-zero power at 97.8% and 99.9%
confidence in the ACA and ALMA data sets, respectively. In the joint result, we
reject the zero-power hypothesis at 99.99% confidence, finding
.
After accounting for sample variance effects, the estimated spectral shot power
is $\tilde{I}^{2}_{s}(\nu)=1010_{-390}^{+550}\ \mu\textrm{K}^2\ \textrm{Hz}\
\textrm{sr}120_{-40}^{+80}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}200^{+120}_{-70}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}90^{+70}_{-40}\ \mu\textrm{K}^2\ h^{-3}\,\textrm{Mpc}^{3}z=1.3z=2.5z=3.6\alpha_{\rm CO}=3.6\ M_{\odot}\ (\textrm{K}\ \textrm{km}\ \textrm{s}^{-1}\
\textrm{pc}^{2})^{-1}\rho_{\textrm{H}_2}(z)\sim 10^{8}\ M_{\odot}\ \textrm{Mpc}^{-3}z=1-3$.Comment: 25 pages, 12 figures, 6 tables, 2 appendices. Accepted for
publication in Ap
The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations
This paper presents measurements of the energy radiated by the lower solar
atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare
(SOL2011-02-15T01:56) in response to an injection of energy assumed to be in
the form of nonthermal electrons. Hard X-ray observations from RHESSI were used
to track the evolution of the parameters of the nonthermal electron
distribution to reveal the total power contained in flare accelerated
electrons. By integrating over the duration of the impulsive phase, the total
energy contained in the nonthermal electrons was found to be
erg. The response of the lower solar atmosphere was measured in the free-bound
EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II
at 304\AA\ and H I (Ly) at 1216\AA\ by SDO/EVE, the UV continua at
1600\AA\ and 1700\AA\ by SDO/AIA, and the WL continuum at 4504\AA, 5550\AA, and
6684\AA, along with the Ca II H line at 3968\AA\ using Hinode/SOT. The summed
energy detected by these instruments amounted to erg;
about 15% of the total nonthermal energy. The Ly line was found to
dominate the measured radiative losses. Parameters of both the driving electron
distribution and the resulting chromospheric response are presented in detail
to encourage the numerical modelling of flare heating for this event, to
determine the depth of the solar atmosphere at which these line and continuum
processes originate, and the mechanism(s) responsible for their generation.Comment: 14 pages, 18 figures. Accepted for publication in Astrophysics
Journa
Ultradeep Ks Imaging in the GOODS-N
We present an ultradeep Ks-band image that covers 0.5*0.5 deg^2 centered on
the Great Observatories Origins Deep Survey-North (GOODS-N). The image reaches
a 5 \sigma depth of Ks(AB) = 24.45 in the GOODS-N region, which is as deep as
the GOODS-N Spitzer Infrared Array Camera (IRAC) 3.6 \mu m image. We present a
new method of constructing IRAC catalogs that uses the higher spatial
resolution Ks image and catalog as priors and iteratively subtracts fluxes from
the IRAC images to estimate the IRAC fluxes. Our iterative method is different
from the \chi^2 approach adopted by other groups. We verified our results using
data taken in two different epochs of observations, as well as by comparing our
colors with the colors of stars and with the colors derived from model spectral
energy distributions (SEDs) of galaxies at various redshifts. We make available
to the community our WIRCam Ks-band image and catalog (94951 objects in 0.25
deg^2), the Interactive Data Language (IDL) pipeline used for reducing the
WIRCam images, and our IRAC 3.6 to 8.0 \mu m catalog (16950 objects in 0.06
deg^2 at 3.6 \mu m). With this improved Ks and IRAC catalog and a large
spectroscopic sample from our previous work, we study the color-magnitude and
color-color diagrams of galaxies. We compare the effectiveness of using Ks and
IRAC colors to select active galactic nuclei (AGNs) and galaxies at various
redshifts. We also study a color selection of z = 0.65--1.2 galaxies using the
Ks, 3.6 \mu m, and 4.5 \mu m bands.Comment: Accepted for publication on ApJS. Online data are availabl
VLA 1.4 GHz Catalogs of the Abell 370 and Abell 2390 Cluster Fields
We present 1.4 GHz catalogs for the cluster fields Abell 370 and Abell 2390
observed with the Very Large Array. These are two of the deepest radio images
of cluster fields ever taken. The Abell 370 image covers an area of 40'x40'
with a synthesized beam of ~1.7" and a noise level of ~5.7 uJy near field
center. The Abell 2390 image covers an area of 34'x34' with a synthesized beam
of ~1.4" and a noise level of ~5.6 uJy near field center. We catalog 200
redshifts for the Abell 370 field. We construct differential number counts for
the central regions (radius < 16') of both clusters. We find that the faint
(S_1.4GHz < 3 mJy) counts of Abell 370 are roughly consistent with the highest
blank field number counts, while the faint number counts of Abell 2390 are
roughly consistent with the lowest blank field number counts. Our analyses
indicate that the number counts are primarily from field radio galaxies. We
suggest that the disagreement of our counts can be largely attributed to cosmic
variance.Comment: 13 pages, accepted for publication in ApJ
Clinical classification of symptomatic heterotopic pancreas of the stomach and duodenum: A case series and systematic literature review
BACKGROUND: Heterotopic pancreas (HP) is an aberrant anatomic malformation that occurs most commonly in the upper gastrointestinal tract. While the majority of heterotopic pancreatic lesions are asymptomatic, many manifest severe clinical symptoms which require surgical or endoscopic intervention. Understanding of the clinical manifestations and symptoms of HP is limited due to the lack of large volume studies in the literature. The purpose of this study is to review symptomatic cases at a single center and compare these to a systematic review of the literature in order to characterize common clinical manifestations and treatment of this disease. AIM: To classify the common clinical manifestations of heterotopic pancreas. METHODS: A retrospective review was conducted of pathologic samples containing heterotopic pancreas from 2000-2018. Review was limited to HP of the upper gastrointestinal tract due to the frequency of presentation in this location. Symptomatic patients were identified from review of the medical records and clinical symptoms were tabulated. These were compared to a systematic review of the literature utilizing PubMed and Embase searches for papers pertaining to heterotopic pancreas. Publications describing symptomatic presentation of HP were selected for review. Information including demographics, symptoms, presentation and treatment were compiled and analyzed. RESULTS: Twenty-nine patient were identified with HP at a single center, with six of these identified has having clinical symptoms. Clinical manifestations included, gastrointestinal bleeding, gastric ulceration with/without perforation, pancreatitis, and gastric outlet obstruction. Systemic review of the literature yielded 232 publications detailing symptomatic cases with only 20 studies describing ten or more patients. Single and multi-patient studies were combined to form a cohort of 934 symptomatic patients. The majority of patients presented with abdominal pain (67%) combined with one of the following clinical categories: (1) Dyspepsia, (n = 445, 48%); (2) Pancreatitis (n = 260, 28%); (3) Gastrointestinal bleeding (n = 80, 9%); and (4) Gastric outlet obstruction (n = 80, 9%). The majority of cases (n = 832, 90%) underwent surgical or endoscopic resection with 85% reporting resolution or improvement in their symptoms. CONCLUSION: Heterotopic pancreas can cause significant clinical symptoms in the upper gastrointestinal tract. Better understanding and classification of this disease may result in more accurate identification and treatment of this malformation
Observations of enhanced extreme ultraviolet continua during an X-class solar flare using <i>SDO</i>/EVE.
Observations of extreme-ultraviolet (EUV) emission from an X-class solar
flare that occurred on 2011 February 15 at 01:44 UT are presented, obtained
using the EUV Variability Experiment (EVE) onboard the Solar Dynamics
Observatory. The complete EVE spectral range covers the free-bound continua of
H I (Lyman continuum), He I, and He II, with recombination edges at 91.2, 50.4,
and 22.8 nm, respectively. By fitting the wavelength ranges blue-ward of each
recombination edge with an exponential function, lightcurves of each of the
integrated continua were generated over the course of the flare, as well as
emission from the free-free continuum (6.5-37 nm). The He II 30.4 nm and
Lyman-alpha 121.6 nm lines, and soft X-ray (0.1-0.8 nm) emission from GOES are
also included for comparison. Each free-bound continuum was found to have a
rapid rise phase at the flare onset similar to that seen in the 25-50 keV
lightcurves from RHESSI, suggesting that they were formed by recombination with
free electrons in the chromosphere. However, the free-free emission exhibited a
slower rise phase seen also in the soft X-ray emission from GOES, implying a
predominantly coronal origin. By integrating over the entire flare the total
energy emitted via each process was determined. We find that the flare energy
in the EVE spectral range amounts to at most a few per cent of the total flare
energy, but EVE gives us a first comprehensive look at these diagnostically
important continuum components.Comment: 6 pages, 3 figures, 1 table. Accepted to ApJ Letter
Autologous humanized PDX modeling for immuno-oncology recapitulates features of the human tumor microenvironment
BACKGROUND: Interactions between immune and tumor cells are critical to determining cancer progression and response. In addition, preclinical prediction of immune-related drug efficacy is limited by interspecies differences between human and mouse, as well as inter-person germline and somatic variation. To address these gaps, we developed an autologous system that models the tumor microenvironment (TME) from individual patients with solid tumors.
METHOD: With patient-derived bone marrow hematopoietic stem and progenitor cells (HSPCs), we engrafted a patient\u27s hematopoietic system in MISTRG6 mice, followed by transfer of patient-derived xenograft (PDX) tissue, providing a fully genetically matched model to recapitulate the individual\u27s TME. We used this system to prospectively study tumor-immune interactions in patients with solid tumor.
RESULTS: Autologous PDX mice generated innate and adaptive immune populations; these cells populated the TME; and tumors from autologously engrafted mice grew larger than tumors from non-engrafted littermate controls. Single-cell transcriptomics revealed a prominent vascular endothelial growth factor A (VEGFA) signature in TME myeloid cells, and inhibition of human VEGF-A abrogated enhanced growth.
CONCLUSIONS: Humanization of the interleukin 6 locus in MISTRG6 mice enhances HSPC engraftment, making it feasible to model tumor-immune interactions in an autologous manner from a bedside bone marrow aspirate. The TME from these autologous tumors display hallmarks of the human TME including innate and adaptive immune activation and provide a platform for preclinical drug testing
Anthropometric indices of Gambian children after one or three annual rounds of mass drug administration with azithromycin for trachoma control.
BACKGROUND: Mass drug administration (MDA) with azithromycin, carried out for the control of blinding trachoma, has been linked to reduced mortality in children. While the mechanism behind this reduction is unclear, it may be due, in part, to improved nutritional status via a potential reduction in the community burden of infectious disease. To determine whether MDA with azithromycin improves anthropometric indices at the community level, we measured the heights and weights of children aged 1 to 4 years in communities where one (single MDA arm) or three annual rounds (annual MDA arm) of azithromycin had been distributed. METHODS: Data collection took place three years after treatment in the single MDA arm and one year after the final round of treatment in the annual MDA arm. Mean height-for-age, weight-for-age and weight-for-height z scores were compared between treatment arms. RESULTS: No significant differences in mean height-for-age, weight-for-age or weight-for-height z scores were found between the annual MDA and single MDA arms, nor was there a significant reduction in prevalence of stunting, wasting or underweight between arms. CONCLUSIONS: Our data do not provide evidence that community MDA with azithromycin improved anthropometric outcomes of children in The Gambia. This may suggest reductions in mortality associated with azithromycin MDA are due to a mechanism other than improved nutritional status
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