1,324 research outputs found
Photo-ionization modelling of planetary nebulae -- II. Galactic bulge nebulae, a comparison with literature results
We have constructed photo-ionization models of five galactic bulge planetary
nebulae using our automatic method which enables a fully self-consistent
determination of the physical parameters of a planetary nebula. The models are
constrained using the spectrum, the IRAS and radio fluxes and the angular
diameter of the nebula. We also conducted a literature search for physical
parameters determined with classical methods for these nebulae. Comparison of
the distance independent physical parameters with published data shows that the
stellar temperatures generally are in good agreement and can be considered
reliable. The literature data for the electron temperature, electron density
and also for the abundances show a large spread, indicating that the use of
line diagnostics is not reliable and that the accuracy of these methods needs
to be improved. Comparison of the various abundance determinations indicates
that the uncertainty in the electron temperature is the main source of
uncertainty in the abundance determination. The stellar magnitudes predicted by
the photo-ionization models are in good agreement with observed values.Comment: Accepted for publication in MNRA
Radio Observations of New Galactic Bulge Planetary Nebulae
We observed 64 newly identified galactic bulge planetary nebulae in the radio
continuum at 3 and 6 cm with the Australia Telescope Compact Array. We present
their radio images, positions, flux densities, and angular sizes. The survey
appears to have detected a larger ratio of more extended planetary nebulae with
low surface brightness than in previous surveys. We calculated their distances
according to Van de Steene & Zijlstra (1995). We find that most of the new
sample is located on the near side around the galactic center and closer in
than the previously known bulge PNe. Based on H-alpha images and spectroscopic
data, we calculated the total H-alpha flux. We compare this flux value with the
radio flux density and derive the extinction. We confirm that the distribution
of the extinction values around the galactic center rises toward the center, as
expected.Comment: accepted for publication in A&
Comment on “providing value to new health technology: the early contribution of entrepreneurs, investors, and regulatory agencies”
Lehoux et al provide a highly valid contribution in conceptualizing value in value propositions for new health technologies and developing an analytic framework that illustrates the interplay between health innovation supply-side logic (the logic of emergence) and demand-side logic (embedding in the healthcare system). This commentary brings forth several considerations on this article. First, a detailed stakeholder analysis provides the necessary premonition of potential hurdles in the development, implementation and dissemination of a new technology. This can be achieved by categorizing potential stakeholder groups on the basis of the potential impact of future technology. Secondly, the conceptualization of value in value propositions of new technologies should not only embrace business/economic and clinical values but also ethical, professional and cultural values, as well as factoring in the notion of usability and acceptance of new technology. As a final note, the commentary emphasises the point that technology should facilitate delivery of care without negatively affecting doctorpatient communications, physical examination skills, and development of clinical knowledge.peer-reviewe
Synthesis of analogues of (E)-1-hydroxy-2-methylbut-2-enyl 4-diphosphate, an isoprenoid precursor and human γδ T cell activator
(E)-1-Hydroxy-2-methyl-but-2-enyl 4-diphosphate (HMBPP) is an intermediate in the non-mevalonate pathway for the biosynthesis of isoprenoids and also serves as a very strong activator of human gamma delta T cells expressing V gamma 9V delta 2 receptors. This paper describes the synthesis of analogues of HMBPP, in which the diphosphate group is replaced by potential isosteric moieties, i.e., carbamate, N-acyl-N'-oxy sulfamate, or aminosulfonyl carbamate functionalities. The potential of the synthesized analogues to stimulate V gamma 9/V delta 2 T cell response or to inhibit GcpE and LytB, the last enzymes in the non-mevalonate pathway, was assessed
A Herschel study of Planetary Nebulae
We present Herschel PACS and SPIRE images of the dust shells around the
planetary nebulae NGC 650, NGC 6853, and NGC 6720, as well as images showing
the dust temperature in their shells. The latter shows a rich structure, which
indicates that internal extinction in the UV is important despite the highly
evolved status of the nebulae.Comment: 2 pages, 1 figure, 2012, proceedings IAU Symposium 283 Planetary
Nebulae: An Eye to the Futur
Logic-based AI for Interpretable Board Game Winner Prediction with Tsetlin Machine
Hex is a turn-based two-player connection game with a high branching factor,
making the game arbitrarily complex with increasing board sizes. As such,
top-performing algorithms for playing Hex rely on accurate evaluation of board
positions using neural networks. However, the limited interpretability of
neural networks is problematic when the user wants to understand the reasoning
behind the predictions made. In this paper, we propose to use propositional
logic expressions to describe winning and losing board game positions,
facilitating precise visual interpretation. We employ a Tsetlin Machine (TM) to
learn these expressions from previously played games, describing where pieces
must be located or not located for a board position to be strong. Extensive
experiments on boards compare our TM-based solution with popular
machine learning algorithms like XGBoost, InterpretML, decision trees, and
neural networks, considering various board configurations with to
moves played. On average, the TM testing accuracy is , outperforming
all the other evaluated algorithms. We further demonstrate the global
interpretation of the logical expressions and map them down to particular board
game configurations to investigate local interpretability. We believe the
resulting interpretability establishes building blocks for accurate assistive
AI and human-AI collaboration, also for more complex prediction tasks
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