134,512 research outputs found
ELSA: An Integrated, Semi-Automated Nebular Abundance Package
We present ELSA, a new modular software package, written in C, to analyze and
manage spectroscopic data from emission-line objects. In addition to
calculating plasma diagnostics and abundances from nebular emission lines, the
software provides a number of convenient features including the ability to
ingest logs produced by IRAF's splot task, to semi-automatically merge spectra
in different wavelength ranges, and to automatically generate various data
tables in machine-readable or LaTeX format. ELSA features a highly
sophisticated interstellar reddening correction scheme that takes into account
temperature and density effects as well as He II contamination of the hydrogen
Balmer lines. Abundance calculations are performed using a 5-level atom
approximation with recent atomic data, based on R. Henry's ABUN program.
Improvements planned in the near future include use of a three-region
ionization model, similar to IRAF's nebular package, error propagation, and the
addition of ultraviolet and infrared line analysis capability. Detailed
documentation for all aspects of ELSA are available at
http://www.williams.edu/Astronomy/research/PN .Comment: 2 pages, contributed paper, IAU Symp. 234, Planetary Nebulae in Our
Galaxy and Beyon
Search for transient ultralight dark matter signatures with networks of precision measurement devices using a Bayesian statistics method
We analyze the prospects of employing a distributed global network of
precision measurement devices as a dark matter and exotic physics observatory.
In particular, we consider the atomic clocks of the Global Positioning System
(GPS), consisting of a constellation of 32 medium-Earth orbit satellites
equipped with either Cs or Rb microwave clocks and a number of Earth-based
receiver stations, some of which employ highly-stable H-maser atomic clocks.
High-accuracy timing data is available for almost two decades. By analyzing the
satellite and terrestrial atomic clock data, it is possible to search for
transient signatures of exotic physics, such as "clumpy" dark matter and dark
energy, effectively transforming the GPS constellation into a 50,000km aperture
sensor array. Here we characterize the noise of the GPS satellite atomic
clocks, describe the search method based on Bayesian statistics, and test the
method using simulated clock data. We present the projected discovery reach
using our method, and demonstrate that it can surpass the existing constrains
by several order of magnitude for certain models. Our method is not limited in
scope to GPS or atomic clock networks, and can also be applied to other
networks of precision measurement devices.Comment: See also Supplementary Information located in ancillary file
Rumble: Data Independence for Large Messy Data Sets
This paper introduces Rumble, an engine that executes JSONiq queries on
large, heterogeneous and nested collections of JSON objects, leveraging the
parallel capabilities of Spark so as to provide a high degree of data
independence. The design is based on two key insights: (i) how to map JSONiq
expressions to Spark transformations on RDDs and (ii) how to map JSONiq FLWOR
clauses to Spark SQL on DataFrames. We have developed a working implementation
of these mappings showing that JSONiq can efficiently run on Spark to query
billions of objects into, at least, the TB range. The JSONiq code is concise in
comparison to Spark's host languages while seamlessly supporting the nested,
heterogeneous data sets that Spark SQL does not. The ability to process this
kind of input, commonly found, is paramount for data cleaning and curation. The
experimental analysis indicates that there is no excessive performance loss,
occasionally even a gain, over Spark SQL for structured data, and a performance
gain over PySpark. This demonstrates that a language such as JSONiq is a simple
and viable approach to large-scale querying of denormalized, heterogeneous,
arborescent data sets, in the same way as SQL can be leveraged for structured
data sets. The results also illustrate that Codd's concept of data independence
makes as much sense for heterogeneous, nested data sets as it does on highly
structured tables.Comment: Preprint, 9 page
Method of producing a storage bulb for an atomic hydrogen maser
A storage bulb for an atomic hydrogen maser is produced by coating its internal surface with an emulsion containing both TFE and FEP particles. The emulsion is produced by mixing a first quantity of TFE in an aqueous dispersion with a second quantity of FEP in an aqueous dispersion, with a third quantity of distilled water. The emulsion is poured into the bulb to coat it uniformly so as to form a thin film of emulsion on the bulb's internal surface. After excess emulsion is drained out of the bulb the emulsion in the bulb is dried to remove the water and most of the aqueous matter therefrom. The remaining emulsion is then cured by heating the bulb to a temperature of at least 380 C
Perspectives on Astrophysics Based on Atomic, Molecular, and Optical (AMO) Techniques
About two generations ago, a large part of AMO science was dominated by
experimental high energy collision studies and perturbative theoretical
methods. Since then, AMO science has undergone a transition and is now
dominated by quantum, ultracold, and ultrafast studies. But in the process, the
field has passed over the complexity that lies between these two extremes. Most
of the Universe resides in this intermediate region. We put forward that the
next frontier for AMO science is to explore the AMO complexity that describes
most of the Cosmos.Comment: White paper submission to the Decadal Assessment and Outlook Report
on Atomic, Molecular, and Optical (AMO) Science (AMO 2020
Holography and Coherent Diffraction with Low-Energy Electrons: A Route towards Structural Biology at the Single Molecule Level
The current state of the art in structural biology is led by NMR, X-ray
crystallography and TEM investigations. These powerful tools however all rely
on averaging over a large ensemble of molecules. Here, we present an
alternative concept aiming at structural analysis at the single molecule level.
We show that by combining electron holography and coherent diffraction imaging
estimations concerning the phase of the scattered wave become needless as the
phase information is extracted from the data directly and unambiguously.
Performed with low-energy electrons the resolution of this lens-less microscope
is just limited by the De Broglie wavelength of the electron wave and the
numerical aperture, given by detector geometry. In imaging freestanding
graphene, a resolution of 2 Angstrom has been achieved revealing the 660.000
unit cells of the graphene sheet from one data set at once. Applied to
individual biomolecules the method allows for non-destructive imaging and
imports the potential to distinguish between different conformations of
proteins with atomic resolution.Comment: 17 pages, 10 figures; Ultramicroscopy 201
Petascale computations for Large-scale Atomic and Molecular collisions
Petaflop architectures are currently being utilized efficiently to perform
large scale computations in Atomic, Molecular and Optical Collisions. We solve
the Schroedinger or Dirac equation for the appropriate collision problem using
the R-matrix or R-matrix with pseudo-states approach. We briefly outline the
parallel methodology used and implemented for the current suite of Breit-Pauli
and DARC codes. Various examples are shown of our theoretical results compared
with those obtained from Synchrotron Radiation facilities and from Satellite
observations. We also indicate future directions and implementation of the
R-matrix codes on emerging GPU architectures.Comment: 14 pages, 5 figures, 3 tables, Chapter in: Workshop on Sustained
Simulated Performance 2013, Published by Springer, 2014, edited by Michael
Resch, Yevgeniya Kovalenko, Eric Focht, Wolfgang Bez and Hiroaki Kobaysah
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