1,185,571 research outputs found
PHOENIX model chromospheres of mid- to late-type M dwarfs
We present semi-empirical model chromospheres computed with the atmosphere
code PHOENIX. The models are designed to fit the observed spectra of five mid-
to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used
various metal lines, e. g. from Fe {\sc i}, for the comparison between data and
models. Our computations show that an NLTE treatment of C, N, O impacts on the
hydrogen line formation, while NLTE treatment of less abundant metals such as
nickel influences the lines of the considered species itself. For our coolest
models we investigated also the influence of dust on the chromospheres and
found that dust increases the emission line flux.
Moreover we present an (electronically published) emission line list for the
spectral range of 3100 to 3900 and 4700 to 6800 \AA for a set of 21 M dwarfs
and brown dwarfs. The line list includes the detection of the Na {\sc i} D
lines in emission for a L3 dwarf.Comment: 14 pages, 18 figure
Iron K-alpha Emission from X-ray Reflection: Predictions for Gamma-Ray Burst Models
Recent observations of several gamma-ray burst (GRB) afterglows have shown
evidence for a large amount of X-ray line emitting material, possibly arising
from ionized iron. A significant detection of an X-ray spectral feature, such
as that found in the Chandra observation of GRB 991216, may provide important
constraints on the immediate environment of the burst and hence on progenitor
models. The large Fe K-alpha equivalent widths inferred from the X-ray
observations favor models in which the line is produced when the primary X-ray
emission from the source strikes Thomson-thick material and Compton scatters
into our line of sight. We present such reflection spectra here, computed in a
fully self-consistent manner, and discuss the range of ionization parameters
that may be relevant to different models of GRBs. We argue that the presence of
a strong hydrogen-like K-alpha line is unlikely, because Fe-XXVI photons would
be trapped resonantly and removed from the line core by Compton scattering. In
contrast, a strong narrow emission line from He-like Fe-XXV is prominent in the
model spectra. We briefly discuss how these constraints may affect the line
energy determination in GRB 991216.Comment: 8 pages, 3 figures, Ap.J. Letters accepte
Filtering the Unknown: Speech Activity Detection in Heterogeneous Video Collections
In this paper we discuss the speech activity detection system that we used for detecting speech regions in the Dutch TRECVID video collection. The system is designed to filter non-speech like music or sound effects out of the signal without the use of predefined non-speech models. Because the system trains its models on-line, it is robust for handling out-of-domain data. The speech activity error rate on an out-of-domain test set, recordings of English conference meetings, was 4.4%. The overall error rate on twelve randomly selected five minute TRECVID fragments was 11.5%
557 GHz Observations of Water Vapor Outflows from VY CMa and W Hydrae
We report the first detection of thermal water vapor emission in the 557 GHz,
ground state transition of ortho-HO toward VY Canis
Majoris. In observations obtained with the Submillimeter Wave Astronomy
Satellite (SWAS), we measured a flux of Jy, in a spectrally resolved
line centered on a velocity km s with a full width half
maximum of km s, somewhat dependent on the assumed line shape.
We analyze the line shape in the context of three different radial outflow
models for which we provide analytical expressions. We also detected a weaker
557 GHz emission line from W Hydrae. We find that these and other HO
emission line strengths scale as suggested by Zubko and Elitzur (2000).Comment: Astrophysical Journal Letters, accepte
Improved early detection of ovarian cancer using longitudinal multimarker models
© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.Background: Ovarian cancer has a poor survival rate due to late diagnosis and improved methods are needed for its early detection. Our primary objective was to identify and incorporate additional biomarkers into longitudinal models to improve on the performance of CA125 as a first-line screening test for ovarian cancer. Methods: This case–control study nested within UKCTOCS used 490 serial serum samples from 49 women later diagnosed with ovarian cancer and 31 control women who were cancer-free. Proteomics-based biomarker discovery was carried out using pooled samples and selected candidates, including those from the literature, assayed in all serial samples. Multimarker longitudinal models were derived and tested against CA125 for early detection of ovarian cancer. Results: The best performing models, incorporating CA125, HE4, CHI3L1, PEBP4 and/or AGR2, provided 85.7% sensitivity at 95.4% specificity up to 1 year before diagnosis, significantly improving on CA125 alone. For Type II cases (mostly high-grade serous), models achieved 95.5% sensitivity at 95.4% specificity. Predictive values were elevated earlier than CA125, showing the potential of models to improve lead time. Conclusions: We have identified candidate biomarkers and tested longitudinal multimarker models that significantly improve on CA125 for early detection of ovarian cancer. These models now warrant independent validation.Peer reviewe
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