2,077 research outputs found
Calibrating and Stabilizing Spectropolarimeters with Charge Shuffling and Daytime Sky Measurements
Well-calibrated spectropolarimetry studies at resolutions of 10,000 with
signal-to-noise ratios (SNRs) better than 0.01\% across individual line
profiles, are becoming common with larger aperture telescopes.
Spectropolarimetric studies require high SNR observations and are often limited
by instrument systematic errors. As an example, fiber-fed spectropolarimeters
combined with advanced line-combination algorithms can reach statistical error
limits of 0.001\% in measurements of spectral line profiles referenced to the
continuum. Calibration of such observations is often required both for
cross-talk and for continuum polarization. This is not straightforward since
telescope cross-talk errors are rarely less than 1\%. In solar
instruments like the Daniel K. Inouye Solar Telescope (DKIST), much more
stringent calibration is required and the telescope optical design contains
substantial intrinsic polarization artifacts. This paper describes some
generally useful techniques we have applied to the HiVIS spectropolarimeter at
the 3.7m AEOS telescope on Haleakala. HiVIS now yields accurate polarized
spectral line profiles that are shot-noise limited to 0.01\% SNR levels at our
full spectral resolution of 10,000 at spectral sampling of 100,000. We
show line profiles with absolute spectropolarimetric calibration for cross-talk
and continuum polarization in a system with polarization cross-talk levels of
essentially 100\%. In these data the continuum polarization can be recovered to
one percent accuracy because of synchronized charge-shuffling model now working
with our CCD detector. These techniques can be applied to other
spectropolarimeters on other telescopes for both night and day-time
applications such as DKIST, TMT and ELT which have folded non-axially symmetric
foci.Comment: Accepted to A&
Thermonuclear .Ia Supernovae from Helium Shell Detonations: Explosion Models and Observables
During the early evolution of an AM CVn system, helium is accreted onto the
surface of a white dwarf under conditions suitable for unstable thermonuclear
ignition. The turbulent motions induced by the convective burning phase in the
He envelope become strong enough to influence the propagation of burning fronts
and may result in the onset of a detonation. Such an outcome would yield
radioactive isotopes and a faint rapidly rising thermonuclear ".Ia" supernova.
In this paper, we present hydrodynamic explosion models and observable outcomes
of these He shell detonations for a range of initial core and envelope masses.
The peak UVOIR bolometric luminosities range by a factor of 10 (from 5e41 -
5e42 erg/s), and the R-band peak varies from M_R,peak = -15 to -18. The rise
times in all bands are very rapid (<10 d), but the decline rate is slower in
the red than the blue due to a secondary near-IR brightening. The
nucleosynthesis primarily yields heavy alpha-chain elements (40Ca through 56Ni)
and unburnt He. Thus, the spectra around peak light lack signs of intermediate
mass elements and are dominated by CaII and TiII features, with the caveat that
our radiative transfer code does not include the non-thermal effects necessary
to produce He features.Comment: Accepted for publication in The Astrophysical Journal; 9 pages, 9
figures; v2: Minor changes to correct typos and clarify conten
Research into the use of pyrolytic oxides and polymers for the fabrication of thin film high energy capacitors
Construction, capacitance and dissipation factor, and electrode materials for single layer capacitors are discussed. Basic construction, phosphosilicate glass, ten layer capacitors, twenty layer capacitors, stress measurements, buffered oxide layers, and 30 layer capacitors are also discussed. Spin-on phosphosilicate glass is addressed. Polymers as dielectric materials are also considered
Post-settlement land uses and their effects on the Cedarburg Bog
During a study of the plant species of a lowland hardwood stand at the western edge of the Cedarburg Bog (Farley, 1973), it was noted that significant environmental changes had occurred here and throughout the bog which resulted in the present-day vegatation patterns. Many of these changes can be attributed to the various post-settlement land-use practices which were employed in the Town of Saukville (TllN, R21E), Ozaukee County, Wisconsin, where this bog is located. To document this information a literature survey was made of the various studies which ha ve been carried out in this area (Cutler, 1936; Grittinger, 1969; Krauskopf, 1972; Farley, 1973; Meyer, 1973), land records were checked and several long-time residents of the area were interviewed to corroborate these land practices and their effects on the bog. It is hoped the data compiled in this report may be of value in future studies of the biota of this area
An Ecological Study of the Lagoons Surrounding the John F. Kennedy Space Center, Brevard County, Florida
The studies reported here are the result of a three year effort to define the major biological, microbiological, chemical and geological characteristics of the water of the Indian River lagoon around the Kennedy Space Center and to determine the movements of those waters within and between the various basins. This work was the result of a jointly funded agreement between the Florida Institute of Technology and John F. Kennedy Space Center, NASA under NASA Grant NGR 10-015-008, dated April 11, 1972. This cost sharing grant was renewed for each of two successive years. Sampling operations were terminated August 31, 1975
Unpacking Relational Dignity: In Pursuit of an Ethic of Care for Outdoor Therapies
Dignity is a universal principle that requires us to treat every person as having worth
beyond who a particular person is or what they do. Dignity is a complex and sometimes
contested idea, that at times can be compromised in health care and allegedly
also within the practice of outdoor therapy. Outdoor therapies comprise a range of
therapeutic approaches including nature-based therapy, adventure therapy, animalassisted therapy, forest therapy, wilderness therapy, surf therapy, and more. Within
the literature of outdoor therapies there has been limited research on ethics related
to common understandings of care concepts such as relational dignity and human
rights. The aim of this paper is therefore to unravel briefly whether dignity in general,
and relational qualities of dignified care more particularly, might be a useful concept to
apply in order to support an ethical practice in outdoor therapies.publishedVersio
An approach for analysing the impact of data integration on complex network diffusion models
Complex networks are a powerful way to reason about systems with non-trivial patterns of interaction. The increased attention in this research area is accelerated by the increasing availability of complex network data sets, with data often being reused as secondary data sources. Typically, multiple data sources are combined to create a larger, fuller picture of these complex networks and in doing so scientists have to make sometimes subjective decisions about how these sources should be integrated. These seemingly trivial decisions can sometimes have significant impact on both the resultant integrated networks and any downstream network models executed on them. We highlight the importance of this impact in online social networks and dark networks, two use-cases where data are regularly combined from multiple sources due to challenges in measurement or overlap of networks. We present a method for systematically testing how different, realistic data integration approaches can alter both the networks themselves and network models run on them, as well as an associated Python package (NIDMod) that implements this method. A number of experiments show the effectiveness of our method in identifying the impact of different data integration setups on network diffusion models
Studies On The Lagoons Of East Centeral Florida
Detailed examination of the water quality parameters of the lagoons of East Central Florida were begun in 1969. This investigation was subsequently expanded to include other aspects of these waters. General trends and a statistical model are beginning to emerge for the water quality parameters. Man-made and natural effects have resulted in substantial alteration of water parameters since the study was initiated
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