24 research outputs found
Radioactive decay simulations for testing of the timing detectors in the Nab experiment
Located at the Spallation Neutron Source in Oak Ridge National Lab, the Nab experiment aims to yield a measurement of the electron-neutrino correlation parameter, a, and the Fierz interference term, b, in neutron beta decay. These parameters are located in the energy and the angular distribution of the particles produced through neutron beta decay. Using silicon detectors, a direct measurement of the phase space distribution of the resultant electron energy and proton momentum can be obtained. The silicon detectors of the Nab experiment will be tested using well-known radioactive isotopes. Simulations of systematic testing use the associated energy levels, decay probabilities, and decay options of radioactive sources such as Ce-139, Ba-133, and Sn-113 to determine the expected results of experimental testing. Presented here is an analysis of the Monte Carlo simulations of the radioactive decay of Ce-139, Ba-133, and Sn-113, and their ability to be useful to the Nab experiment as a whole
Kepler-16: A Transiting Circumbinary Planet
We report the detection of a planet whose orbit surrounds a pair of low-mass
stars. Data from the Kepler spacecraft reveal transits of the planet across
both stars, in addition to the mutual eclipses of the stars, giving precise
constraints on the absolute dimensions of all three bodies. The planet is
comparable to Saturn in mass and size, and is on a nearly circular 229-day
orbit around its two parent stars. The eclipsing stars are 20% and 69% as
massive as the sun, and have an eccentric 41-day orbit. The motions of all
three bodies are confined to within 0.5 degree of a single plane, suggesting
that the planet formed within a circumbinary disk.Comment: Science, in press; for supplemental material see
http://www.sciencemag.org/content/suppl/2011/09/14/333.6049.1602.DC1/1210923.Doyle.SOM.pd
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
The Flat Transmission Spectrum of the Super-Earth GJ1214b from Wide Field Camera 3 on the Hubble Space Telescope
Capitalizing on the observational advantage offered by its tiny M dwarf host,
we present HST/WFC3 grism measurements of the transmission spectrum of the
super-Earth exoplanet GJ1214b. These are the first published WFC3 observations
of a transiting exoplanet atmosphere. After correcting for a ramp-like
instrumental systematic, we achieve nearly photon-limited precision in these
observations, finding the transmission spectrum of GJ1214b to be flat between
1.1 and 1.7 microns. Inconsistent with a cloud-free solar composition
atmosphere at 8.2 sigma, the measured achromatic transit depth most likely
implies a large mean molecular weight for GJ1214b's outer envelope. A dense
atmosphere rules out bulk compositions for GJ1214b that explain its large
radius by the presence of a very low density gas layer surrounding the planet.
High-altitude clouds can alternatively explain the flat transmission spectrum,
but they would need to be optically thick up to 10 mbar or consist of particles
with a range of sizes approaching 1 micron in diameter.Comment: 17 pages, 12 figures, accepted for publication in Ap
Kepler Planet-Detection Mission: Introduction and First Results
The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet’s surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (~0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets
Recommended from our members
Toward implementing autonomous adaptive data acquisition for scanning hyperspectral imaging of biological systems
Autonomous experimentation is an emerging area of research, primarily related to autonomous vehicles, scientific combinatorial discovery approaches in materials science and drug discovery, and iterative research loops of planning, experimentation, and analysis. However, autonomous approaches developed in these contexts are difficult to apply to high-dimensional mapping technologies, such as scanning hyperspectral imaging of biological systems, due to sample complexity and heterogeneity. We briefly cover the history of adaptive sampling algorithms and surrogate modeling in order to define autonomous adaptive data acquisition as an objective-based, flexible building block for future biological imaging experimentation driven by intelligent infrastructure. We subsequently summarize the recent implementations of autonomous adaptive data acquisition (AADA) for scanning hyperspectral imaging, assess how these address the difficulties of autonomous approaches in hyperspectral imaging, and highlight the AADA design variation from a goal-oriented perspective. Finally, we present a modular AADA architecture that embeds AADA-driven flexible building blocks to address the challenge of time resolution for high-dimensional scanning hyperspectral imaging of nonequilibrium dynamical systems. In our example research-driven experimental design case, we propose an AADA infrastructure for time-resolved, noninvasive, and label-free scanning hyperspectral imaging of living biological systems. This AADA infrastructure can accurately target the correct state of the system for experimental workflows that utilize subsequent expensive, high-information-content analytical techniques
ICT in support of science education A practical users guide
Includes bibliographical references. Also available via the InternetAvailable from British Library Document Supply Centre- DSC:m03/29535 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
Preparation of Tc99m-Labeled Pseudomonas Bacteriophage without Adversely Impacting Infectivity or Biodistribution
Bacteriophages
(phages) are ubiquitous viruses which have adapted
to infect and replicate within target bacteria, their only known hosts,
in a strain specific fashion with minimal cross infectivity. The recent
steep rise in antibiotic resistance throughout the world has renewed
interest in adapting phages for the imaging and treatment of bacterial
infection in humans. In this article, we describe the current limitations
surrounding the radiolabeling of phage for the imaging and treatment
of bacterial infection and methods to overcome these difficulties.
Specifically, we examined the effects of hydrazinonicotinamide conjugation
and removal of bacterial DNA on the infectivity, biodistribution,
and radionuclide imaging of a phage lytic for a clinically relevant
strain of Pseudomonas aeruginosa, a
common Gram-negative bacterial pathogen often resistant to multiple
antibiotics. We found that all but the briefest reaction of concentrated
phage with hydrazinonicotinamide (≤3 min) resulted in nearly
complete loss of infectivity. Furthermore, we determined that digestion
and removal of bacterial DNA was needed to avoid high nonspecific
uptake of hydrazinonicotinamide-labeled phage within the liver and
spleen as well as prolonged circulation in the blood. We also demonstrate
the surprisingly wide soft tissue and organ biodistribution and rapid
pharmacokinetics of <sup>99m</sup>Tc-hydrazinonicotinamide-labeled
phage in normal mice as well as its imaging characteristics and efficacy
in wounded mice infected with bioluminescent Pseudomonas
aeruginosa. In conclusion, the preservation of phage
infectivity and removal of all bacterial containments including DNA
are critical methodologic considerations in the labeling of phages
for imaging and therapy
Gut Microbiome in Inflammatory Bowel Disease: Role in Pathogenesis, Dietary Modulation, and Colitis-Associated Colon Cancer
The gut microbiome has increasingly been recognized as a critical and central factor in inflammatory bowel disease (IBD). Here, we review specific microorganisms that have been suggested to play a role in the pathogenesis of IBD and the current state of fecal microbial transplants as a therapeutic strategy in IBD. We discuss specific nutritional and dietary interventions in IBD and their effects on gut microbiota composition. Finally, we examine the role and mechanisms of the gut microbiome in mediating colitis-associated colon cancer