2,873 research outputs found
Data Science for all : a stroll in the foothills.
Data science presents both opportunities and threats to conventional statistics courses.
Opportunities include being at the bleeding edge of data analysis, and learning new ways to model
phenomena; threats include the challenge of learning new skills and reviewing fundamental
assumptions about explanation, prediction and modeling. Powerful data visualisations makes it
easier to introduce students to fundamental statistical ideas associated with multivariate data.
Data science provides methods to tackle problems that are intractable using analytic methods.
Students need to learn how to model complex problems, and to understand the problematic nature
of modeling – and they need to consider the practical and ethical implications of their (and others’)
work. Here, we offer a stroll into the foothills, along with aphorisms and heuristics for data
analysts
DarkHistory: A code package for calculating modified cosmic ionization and thermal histories with dark matter and other exotic energy injections
We present a new public Python package, DarkHistory, for computing the
effects of dark matter annihilation and decay on the temperature and ionization
history of the early universe. DarkHistory simultaneously solves for the
evolution of the free electron fraction and gas temperature, and for the
cooling of annihilation/decay products and the secondary particles produced in
the process. Consequently, we can self-consistently include the effects of both
astrophysical and exotic sources of heating and ionization, and automatically
take into account backreaction, where modifications to the
ionization/temperature history in turn modify the energy-loss processes for
injected particles. We present a number of worked examples, demonstrating how
to use the code in a range of different configurations, in particular for
arbitrary dark matter masses and annihilation/decay final states. Possible
applications of DarkHistory include mapping out the effects of dark matter
annihilation/decay on the global 21cm signal and the epoch of reionization, as
well as the effects of exotic energy injections other than dark matter
annihilation/decay. The code is available at
https://github.com/hongwanliu/DarkHistory with documentation at
https://darkhistory.readthedocs.io . Data files required to run the code can be
downloaded at https://doi.org/10.7910/DVN/DUOUWA .Comment: 40 pages, 17 figure
A comparison of Voxel compression mapping & longitudinal Voxel-Based morphometry
Clinical motivation: Serial brain imaging can reveal patterns of change over time with important clinical implications for
neurodegenerative disease [1]. We investigate the
performance of four analysis methods, in terms of
a comparison of 20 patients with probable AD to
20 age- and sex-matched controls, characterising
differences in change from baseline to later scans
Processing of DMSP magnetic data: Handbook of programs, tapes, and datasets
The DMSP F-7 satellite was an operational Air Force meteorological satellite which carried a magnetometer for geophysical measurements. The magnetometer was located within the body of the spacecraft in the presence of large spacecraft fields. In addition to stray magnetic fields, the data have inherent position and time inaccuracies. Algorithms were developed to identify and remove time varying magnetic field noise from the data. These algorithms are embodied in an automated procedure which fits a smooth curve through the data and then identifies outliers and which filters the predominant Fourier component of noise from the data. Techniques developed for Magsat were then modified and used to attempt determination of the spacecraft fields, of any rotation between the magnetometer axes and the spacecraft axes, and of any scale changes within the magnetometer itself. Software setup and usage are documented and program listings are included in the Appendix. The initial and resulting data are archived on magnetic cartridge and the formats are documented
Deep Spectroscopy in the Field of 3C 212
We present the results of longslit and multiaperture spectroscopy of faint
galaxies in the field of the z=1.049 quasar 3C212. We show that an apparently
aligned optical feature beyond the NW radio lobe has a redshift z=0.928, and a
similarly aligned feature just beyond the SE radio lobe has a redshift z=1.053,
quite close to that of the quasar. While the NW optical component is extremely
well aligned with the radio jet and has a morphology that is very similar to
that of the radio lobe lying 3" interior to it, the fact that we find three
other field galaxies with closely similar redshifts indicates that it is most
likely a member of an intervening group rather than an unusual example of true
alignment with the radio structure. In addition, we have found two galaxies
(besides the one near the SE radio lobe) having redshifts close to that of
3C212. We have firm or probable redshifts for 66 out of 82 galaxies we have
observed in this field. Comparison with the redshift distribution of faint
field galaxies indicates that a large fraction of the remaining 16 galaxies are
likely to be at redshifts >1.4. There are at least two low-redshift dwarf
starburst galaxies showing low metal abundance and high ionization in our
sample; such galaxies are likely to be relatively common in very faint samples,
and, under certain conditions, they could be confused with high-redshift
objects.Comment: 15 pages, 4 figures, one of which is a separate JPEG plate. To be
published in the April 1998 issue of The Astronomical Journa
Review of \u3ci\u3ePolyklet\u3c/i\u3e, by Thuri Lorenz; \u3ci\u3eDer Kanon des Polyklet: Doryphoros und Amazone\u3c/i\u3e, by Hans von Steuben
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