165 research outputs found
Spectroscopic Survey of {\gamma} Doradus Stars I. Comprehensive atmospheric parameters and abundance analysis of {\gamma} Doradus stars
We present a spectroscopic survey of known and candidate \,Doradus
stars. The high-resolution, high signal-to-noise spectra of 52 objects were
collected by five different spectrographs. The spectral classification,
atmospheric parameters (\teff, , ), and chemical
composition of the stars were derived. The stellar spectral and luminosity
classes were found between G0-A7 and IV-V, respectively. The initial values for
\teff\ and \logg\ were determined from the photometric indices and spectral
energy distribution. Those parameters were improved by the analysis of hydrogen
lines. The final values of \teff, \logg\ and were derived from the iron
lines analysis. The \teff\ values were found between 6000\,K and 7900\,K, while
\logg\,values range from 3.8 to 4.5\,dex. Chemical abundances and
values were derived by the spectrum synthesis method. The values were
found between 5 and 240\,km\,s. The chemical abundance pattern of
\,Doradus stars were compared with the pattern of non-pulsating stars.
It turned out that there is no significant difference in abundance patterns
between these two groups. Additionally, the relations between the atmospheric
parameters and the pulsation quantities were checked. A strong correlation
between the and the pulsation periods of \,Doradus variables
was obtained. The accurate positions of the analysed stars in the H-R diagram
have been shown. Most of our objects are located inside or close to the blue
edge of the theoretical instability strip of \,Doradus.Comment: 18 pages, 13 figure
The ToxCast pipeline: updates to curve-fitting approaches and database structure
Introduction: The US Environmental Protection Agency Toxicity Forecaster (ToxCast) program makes in vitro medium- and high-throughput screening assay data publicly available for prioritization and hazard characterization of thousands of chemicals. The assays employ a variety of technologies to evaluate the effects of chemical exposure on diverse biological targets, from distinct proteins to more complex cellular processes like mitochondrial toxicity, nuclear receptor signaling, immune responses, and developmental toxicity. The ToxCast data pipeline (tcpl) is an open-source R package that stores, manages, curve-fits, and visualizes ToxCast data and populates the linked MySQL Database, invitrodb.Methods: Herein we describe major updates to tcpl and invitrodb to accommodate a new curve-fitting approach. The original tcpl curve-fitting models (constant, Hill, and gain-loss models) have been expanded to include Polynomial 1 (Linear), Polynomial 2 (Quadratic), Power, Exponential 2, Exponential 3, Exponential 4, and Exponential 5 based on BMDExpress and encoded by the R package dependency, tcplfit2. Inclusion of these models impacted invitrodb (beta version v4.0) and tcpl v3 in several ways: (1) long-format storage of generic modeling parameters to permit additional curve-fitting models; (2) updated logic for winning model selection; (3) continuous hit calling logic; and (4) removal of redundant endpoints as a result of bidirectional fitting.Results and discussion: Overall, the hit call and potency estimates were largely consistent between invitrodb v3.5 and 4.0. Tcpl and invitrodb provide a standard for consistent and reproducible curve-fitting and data management for diverse, targeted in vitro assay data with readily available documentation, thus enabling sharing and use of these data in myriad toxicology applications. The software and database updates described herein promote comparability across multiple tiers of data within the US Environmental Protection Agency CompTox Blueprint
Patient-Powered Research Networks of the Autoimmune Research Collaborative: Rationale, Capacity, and Future Directions
Patient-Powered Research Networks (PPRNs) are US-based registry infrastructures co-created by advocacy groups, patient research partners, academic investigators, and other healthcare stakeholders. Patient-Powered Research Networks collect information directly from patients to conduct and disseminate the results of patient-centered/powered research that helps patients make more informed decisions about their healthcare. Patient-Powered Research Networks gather and utilize real-world data and patient-reported outcomes to conduct comparative effectiveness, safety, and other research, and leverage the Internet to accomplish this effectively and efficiently. Four PPRNs focused on autoimmune and immune-mediated conditions formed the Autoimmune Research Collaborative: ArthritisPower (rheumatoid arthritis, spondyloarthritis, and other rheumatic and musculoskeletal diseases), IBD Partners (inflammatory bowel disease), iConquerMS (multiple sclerosis), and the Vasculitis PPRN (vasculitis). The Autoimmune Research Collaborative aims to inform the healthcare decision making of patients, care partners, and other stakeholders, such as clinicians, regulators, and payers. Illustrated by practical applications from the Autoimmune Research Collaborative and its constituent PPRNs, this article discusses the shared capacities and challenges of the PPRN model, and the opportunities presented by collaborating across autoimmune conditions to design, conduct, and disseminate patient-centered outcomes research
UVSat: a concept of an ultraviolet/optical photometric satellite
Time-series photometry from space in the ultraviolet can be presently done
with only a few platforms, none of which is able to provide wide-field
long-term high-cadence photometry. We present a concept of UVSat, a twin space
telescope which will be capable to perform this kind of photometry, filling an
observational niche. The satellite will host two telescopes, one for
observations in the ultraviolet, the other for observations in the optical
band. We also briefly show what science can be done with UVSat.Comment: 6 pages, 2 figures, accepted for publication in the Proceedings of
the PAS (Proc. of the 2nd BRITE Science conference, Innsbruck
Removal of CO2 from a submersible atmosphere by scrubbing with water:Experiments in a single column
In order to explore methods of removing CO2 from submersible habitats with sea water, gas scrubbing experiments (using tap water, and tap water with 3.5 wt% sea salt) were performed in a 108 mm i.d. pilot-scale column, investigating the removal efficiency of CO2 (e.g. at 2 vol%) from a gaseous stream. The performance of this column fitted with 5 spray nozzles was compared with a column packed with 1/8th in. Dixon rings (packing depth = 1480 mm). More detailed experiments were then performed in the column packed with Dixon rings at: liquid flows from 4 to 8 dm3 min−1; gas flows 18 and 36 N dm3 min−1, column pressures = 1 and 4 bar(g); column temperatures approximately 5 and 17 °C. In general, CO2 removal increased as column operating pressure was increased, or fluid temperature was decreased. When approaching low gas outlet CO2 levels at the top of the column (e.g. 0.1 vol%), the concentration of carbonate species in the tap water (fed into the column) restricted further improvements in the performance of the column.In experiments in a short column with Dixon rings (packing depth = 180 mm), using fresh water in each column, the performance of a multi-column eight chamber compact scrubber was simulated, and shown to be significantly better than a single tall column.<br/
The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star
A multisite photometric campaign for the Beta Cephei and eclipsing variable
16 Lacertae is reported. 749 h of high-quality differential photoelectric
Stromgren, Johnson and Geneva time-series photometry were obtained with ten
telescopes during 185 nights. After removing the pulsation contribution, an
attempt was made to solve the resulting eclipse light curve by means of the
computer program EBOP. Although a unique solution was not obtained, the range
of solutions could be constrained by comparing computed positions of the
secondary component in the Hertzsprung-Russell diagram with evolutionary
tracks.
For three high-amplitude pulsation modes, the uvy and the Geneva UBG
amplitude ratios are derived and compared with the theoretical ones for
spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be
incompatible with the observations. One mode is found to be radial, one is l =
1, while in the remaining case l = 2 or 3.
The present multisite observations are combined with the archival photometry
in order to investigate the long-term variation of the amplitudes and phases of
the three high-amplitude pulsation modes. The radial mode shows a
non-sinusoidal variation on a time-scale of 73 yr. The l = 1 mode is a triplet
with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and
29.1 yr. The amplitude and phase of the l = 2 or 3 mode vary on time-scales of
380.5 d and 43 yr.
The light variation of 2 And, one of the comparison stars, is discussed in
the Appendix.Comment: 18 pages, 19 figures, accepted for publication in MNRA
Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910
As a result of the variability survey in Chi Persei and NGC6910, the number
of Beta Cep stars that are members of these two open clusters is increased to
twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational
properties, in particular the frequency spectra, of Beta Cep stars in both
clusters and explain the differences in terms of the global parameters of the
clusters. We also indicate that the more complicated pattern of the variability
among B type stars in Chi Persei is very likely caused by higher rotational
velocities of stars in this cluster. We conclude that the sample of pulsating
stars in the two open clusters constitutes a very good starting point for the
ensemble asteroseismology of Beta Cep-type stars and maybe also for other
B-type pulsators.Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife,
Lanzarote, Feb 2010, submitte
Catalog of Galactic Beta Cephei Stars
We present an extensive and up-to-date catalog of Galactic Beta Cephei stars.
This catalog is intended to give a comprehensive overview of observational
characteristics of all known Beta Cephei stars. 93 stars could be confirmed to
be Beta Cephei stars. For some stars we re-analyzed published data or conducted
our own analyses. 61 stars were rejected from the final Beta Cephei list, and
77 stars are suspected to be Beta Cephei stars. A list of critically selected
pulsation frequencies for confirmed Beta Cephei stars is also presented. We
analyze the Beta Cephei stars as a group, such as the distributions of their
spectral types, projected rotational velocities, radial velocities, pulsation
periods, and Galactic coordinates. We confirm that the majority of these stars
are multiperiodic pulsators. We show that, besides two exceptions, the Beta
Cephei stars with high pulsation amplitudes are slow rotators. We construct a
theoretical HR diagram that suggests that almost all 93 Beta Cephei stars are
MS objects. We discuss the observational boundaries of Beta Cephei pulsation
and their physical parameters. We corroborate that the excited pulsation modes
are near to the radial fundamental mode in frequency and we show that the mass
distribution of the stars peaks at 12 solar masses. We point out that the
theoretical instability strip of the Beta Cephei stars is filled neither at the
cool nor at the hot end and attempt to explain this observation
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