2,971 research outputs found
The Influence of Reaction Rates on the Final p-Abundances
The astrophysical p-process is responsible for the origin of the proton rich
nuclei,which are heavier than iron. A huge network involving thousands of
reaction rates is necessary to calculate the final p-abundances. But not all
rates included in the network have a strong influence on the p-nuclei
abundances. The p-process was investigated using a full nuclear reaction
network for a type II supernovae explosion when the shock front passes through
the O/Ne layer. Calculations were done with a multi-layer model adopting the
seed of a pre-explosion evolution of a 25 mass star. In extensive simulations
we investigated the impact of single reaction rates on the final p-abundances.
The results are important for the strategy of future experiments in this field.Comment: 4 page
Peer Evaluation of Video Lab Reports in a Blended Introductory Physics Course
The Georgia Tech blended introductory calculus-based mechanics course
emphasizes scientific communication as one of its learning goals, and to that
end, we gave our students a series of four peer-evaluation assignments intended
to develop their abilities to present and evaluate scientific arguments. Within
these assignments, we also assessed students' evaluation abilities by comparing
their evaluations to a set of expert evaluations. We summarize our development
efforts and describe the changes we observed in student evaluation behavior.Comment: 4 pages, 1 table, 2 figures, submitted to Summer 2014 PERC
Proceeding
The Initial State of Students Taking an Introductory Physics MOOC
As part of a larger research project into massively open online courses
(MOOCs), we have investigated student background, as well as student
participation in a physics MOOC with a laboratory component. Students completed
a demographic survey and the Force and Motion Conceptual Evaluation at the
beginning of the course. While the course is still actively running, we have
tracked student participation over the first five weeks of the eleven-week
course.Comment: Accepted to PERC Proceedings 201
Understanding Student Computational Thinking with Computational Modeling
Recently, the National Research Council's framework for next generation
science standards highlighted "computational thinking" as one of its
"fundamental practices". 9th Grade students taking a physics course that
employed the Modeling Instruction curriculum were taught to construct
computational models of physical systems. Student computational thinking was
assessed using a proctored programming assignment, written essay, and a series
of think-aloud interviews, where the students produced and discussed a
computational model of a baseball in motion via a high-level programming
environment (VPython). Roughly a third of the students in the study were
successful in completing the programming assignment. Student success on this
assessment was tied to how students synthesized their knowledge of physics and
computation. On the essay and interview assessments, students displayed unique
views of the relationship between force and motion; those who spoke of this
relationship in causal (rather than observational) terms tended to have more
success in the programming exercise.Comment: preprint to submit to PERC proceedings 201
The reactions and ashes of thermonuclear explosions on neutron stars
This paper reports on the detailed rp-process reaction flow on an accreting
neutron star and the resulting ashes of a type I X-ray burst. It is obtained by
coupling a 298 isotope reaction network to a self-consistent one-dimensional
model calculation with a constant accretion rate of dM/dt=1.0e17g/s (0.09
Eddington).Comment: 4 pages, 2 figures, submitted to the INPC2004 proceeding
Calculating Nonlocal Optical Properties of Structures with Arbitrary Shape
In a recent Letter [Phys. Rev. Lett. 103, 097403 (2009)], we outlined a
computational method to calculate the optical properties of structures with a
spatially nonlocal dielectric function. In this Article, we detail the full
method, and verify it against analytical results for cylindrical nanowires.
Then, as examples of our method, we calculate the optical properties of Au
nanostructures in one, two, and three dimensions. We first calculate the
transmission, reflection, and absorption spectra of thin films. Because of
their simplicity, these systems demonstrate clearly the longitudinal (or
volume) plasmons characteristic of nonlocal effects, which result in anomalous
absorption and plasmon blueshifting. We then study the optical properties of
spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we
compare the maximum and average electric field enhancements around nanowires of
various shapes to local theory predictions. We demonstrate that when nonlocal
effects are included, significant decreases in such properties can occur.Comment: 30 pages, 12 figures, 1 tabl
Extracting the rp-process from X-ray burst light curves
The light curves of type I X-ray bursts (XRBs) result from energy released
from the atmosphere of a neutron star when accreted hydrogen and helium ignite
and burn explosively via the rp-process. Since charged particle reaction rates
are both density and very temperature dependent, a simulation model must
provide accurate values of these variables to predict the reaction flow. This
paper uses a self-consistent one-dimensional model calculation with a constant
accretion rate of dM/dt=5e16g/s (0.045 Eddington) and reports on the detailed
rp-process reaction flow of a given burst.Comment: 4 pages, submitted to Nucl. Phys. A as part of the Nuclei in Cosmos 8
proceeding
Teaser: Individualized benchmarking and optimization of read mapping results for NGS data
Mapping reads to a genome remains challenging, especially for non-model organisms with lower quality assemblies, or for organisms with higher mutation rates. While most research has focused on speeding up the mapping process, little attention has been paid to optimize the choice of mapper and parameters for a user's dataset. Here, we present Teaser, a software that assists in these choices through rapid automated benchmarking of different mappers and parameter settings for individualized data. Within minutes, Teaser completes a quantitative evaluation of an ensemble of mapping algorithms and parameters. We use Teaser to demonstrate how Bowtie2 can be optimized for different data
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