278 research outputs found
Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models
No full textM-dwarf stars are the most numerous stars in the Universe; they span a wide range in mass and are in the focus of ongoing and planned exoplanet surveys. To investigate and understand their physical nature, detailed spectral information and accurate stellar models are needed. We use a new synthetic atmosphere model generation and compare model spectra to observations. To test the model accuracy, we compared the models to four benchmark stars with atmospheric parameters for which independent information from interferometric radius measurements is available. We used χ2-based methods to determine parameters from high-resolution spectroscopic observations. Our synthetic spectra are based on the new PHOENIX grid that uses the ACES description for the equation of state. This is a model generation expected to be especially suitable for the low-temperature atmospheres. We identified suitable spectral tracers of atmospheric parameters and determined the uncertainties in Teff, log g, and [Fe/H] resulting from degeneracies between parameters and from shortcomings of the model atmospheres. The inherent uncertainties we find are σTeff = 35 K, σlog g = 0.14, and σ[Fe/H] = 0.11. The new model spectra achieve a reliable match to our observed data; our results for Teff and log g are consistent with literature values to within 1σ. However, metallicities reported from earlier photometric and spectroscopic calibrations in some cases disagree with our results by more than 3σ. A possible explanation are systematic errors in earlier metallicity determinations that were based on insufficient descriptions of the cool atmospheres. At this point, however, we cannot definitely identify the reason for this discrepancy, but our analysis indicates that there is a large uncertainty in the accuracy of M-dwarf parameter estimates
Literatur-Rundschau
Get PDFLiteratur-RundschauRundfunk-Gremien in Deutschland. Namen, Organe, Institutionen, hg. v. Hans-Joachim Berg (Ansgar Hollah)Werner Faulstich, Geschichte der Medien Bd. 1: Das Medium als Kult. Von den Anfängen bis zur Spätantike (8. Jahrhundert) Bd. 2: Medien und Öffentlichkeiten im Mittelalter 800-1400 Bd. 3: Medien zwischen Herrschaft und Revolte. Die Medienkultur der frühen Neuzeit (1400-1700) (Michael Schmolke)Claudia Mast, Berufsziel Journalismus. Aufgaben, Anforderungen und Ansprechpartner (Lars Rademacher)Bernhard Schneider, Katholiken auf die Barrikaden? Europäische Revolutionen und deutsche katholische Presse 1815-1848 (Hermann-Josef Große Kracht)Gerfried Stocker/Christine Schöpf (Hg.), Ars Electronica 98. Information. Macht. Krieg (Michael Schmolke) Jürgen Wilke (Hg.), Nachrichtenproduktion im Mediensystem. Von den Sport- und Bilderdiensten bis zum Internet (ast
A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
No full textAims. We present a new library of high-resolution synthetic spectra
based on the stellar atmosphere code PHOENIX that can be used for a wide range of
applications of spectral analysis and stellar parameter synthesis.
Methods. The spherical mode of PHOENIX was used to create model
atmospheres and to derive detailed synthetic stellar spectra from them. We present a new
self-consistent way of describing micro-turbulence for our model atmospheres.
Results. The synthetic spectra cover the wavelength range from 500 Å
to 5.5 μm with resolutions of R = 500 000 in the
optical and near IR, R = 100 000 in the IR and
Δλ = 0.1 Å in the UV. The parameter space covers
2300 K ≤ Teff ≤ 12 000 K,
0.0 ≤ log g ≤ +6.0, − 4.0 ≤ [Fe/H] ≤ +1.0, and
− 0.2 ≤ [α/Fe] ≤ +1.2. The library is a work in progress and we
expect to extend it up to Teff = 25 000 K
Is increased intima-media thickness associated with preatherosclerotic changes in intrauterine growth restricted newborns?\u96 Reply
No full textReturn on Investment in Public Relations: A critical assessment of concepts used by practitioners from the perspectives of communication and management sciences
No full textReturn on Investment (ROI) is a term commonly and non-specifically used by public relations practitioners when discussing the value to be created from communication activities. It mimics business language, particularly from business administration and financial management, but does not figure widely in academic discourse (Watson, 2005).
Although the Institute for Public Relations [now CIPR] undertook a review of ROI practice in the United Kingdom (IPR/CDF 2004) and Likely, Rockland & Weiner (2006) proposed variations of ROI as alternatives to the discredited Advertising Value Equivalence (AVEs) measure of value creation, there has been little discussion other than Macnamara (2007) and Gregory and Watson (2008).
This paper gives an overview on the views of ROI in public relations literature and concepts used by agencies and providers of measurement services. It reports on survey research amongst practitioners in several European countries on identifying the economic value of public relations. The findings are compared with the concepts of ROI used in business and accounting literature (Weber and Schäffer, 2006; Drury, 2007).
Applied theory and parameters for the development of measurement and evaluation techniques are proposed. The paper concludes that the use of the term ROI in public relations needs a proper foundation in overriding management theory; otherwise PR theory and practice will discredit themselves
A Resilient 'European Peace Project'. Robert Menasse’s "The European Courier" and "The Capital”
No full textRobert Menasse’s Die Hauptstadt (The Capital), published in 2017, was immediately
awarded with the prestigious Deutscher Buchpreis and considered as an unequivocal
success for the author in the German-speaking and above all European literary field.
The seven members of the jury highlighted that in his novel Menasse digs “with a light
hand into the deeper strata of this world that we call our own” and they praised the
book as “a multilayered text that interweaves existential questions on the private and
political spheres in a masterly fashion, and releases the reader into open-endedness”
(Peschel 2017
A Novel Text Analysis Method: Numerals Reveal the Author
No full textTwo approaches to the statistical analysis of texts are suggested, both based on the study of numerals occurring in literary texts. The first approach is related to the study of the frequency distribution of various leading digits of numerals occurring in the text. This approach is convenient for testing whether a group of texts has common authorship: the latter is dubious if the frequency distributions are sufficiently different. The second approach requires the study of the frequencies of numerals themselves. The approach yields information about the author, stylistic and genre peculiarities of the texts and is suited for advanced study of authorial texts. The hypothesis that I. Ilf and E. Petrov are fake authors of novels "The Twelve Chairs" and "The Little Golden Calf", and they were ghosted by M. Bulgakov, is checked. The frequency distribution of numerals, as well as its cluster analysis, do not confirm this hypothesis
Is increased intima-media thickness associated with preatherosclerotic changes in intrauterine growth restricted newborns? Reply
No full textSemantic Web: Past, Present, and Future
Get PDFEver since the vision was formulated, the Semantic Web has inspired many generations of innovations. Semantic technologies have been used to share vast amounts of information on the Web, enhance them with semantics to give them meaning, and enable inference and reasoning on them. Throughout the years, semantic technologies, and in particular knowledge graphs, have been used in search engines, data integration, enterprise settings, and machine learning.
In this paper, we recap the classical concepts and foundations of the Semantic Web as well as modern and recent concepts and applications, building upon these foundations. The classical topics we cover include knowledge representation, creating and validating knowledge on the Web, reasoning and linking, and distributed querying. We enhance this classical view of the so-called "Semantic Web Layer Cake" with an update of recent concepts that include provenance, security and trust, as well as a discussion of practical impacts from industry-led contributions. We conclude with an outlook on the future directions of the Semantic Web.
This is a living document. If you like to contribute, please contact the first author and visit: https://github.com/ascherp/semantic-web-prime
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