Exploring the Energy Landscape of the Charge Transport Levels in Organic Semiconductors at the Molecular Scale

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Biochemical Diagnosis of a Fatal Case of Günther’s Disease in a Newborn with Hydrops Foetalis

Peer Reviewe

Electron Impact Excitation Cross Sections for Hydrogen-Like Ions

We present cross sections for electron-impact-induced transitions n --> n' in hydrogen-like ions C 5+, Ne 9+, Al 12+, and Ar 17+. The cross sections are computed by Coulomb-Born with exchange and normalization (CBE) method for all transitions with n < n' < 7 and by convergent close-coupling (CCC) method for transitions with n 2s and 1s --> 2p are presented as well. The CCC and CBE cross sections agree to better than 10% with each other and with earlier close-coupling results (available for transition 1 --> 2 only). Analytical expression for n --> n' cross sections and semiempirical formulae are discussed.Comment: RevTeX, 5 pages, 13 PostScript figures, submitted to Phys. Rev.

On inelastic hydrogen atom collisions in stellar atmospheres

The influence of inelastic hydrogen atom collisions on non-LTE spectral line formation has been, and remains to be, a significant source of uncertainty for stellar abundance analyses, due to the difficulty in obtaining accurate data for low-energy atomic collisions either experimentally or theoretically. For lack of a better alternative, the classical "Drawin formula" is often used. Over recent decades, our understanding of these collisions has improved markedly, predominantly through a number of detailed quantum mechanical calculations. In this paper, the Drawin formula is compared with the quantum mechanical calculations both in terms of the underlying physics and the resulting rate coefficients. It is shown that the Drawin formula does not contain the essential physics behind direct excitation by H atom collisions, the important physical mechanism being quantum mechanical in character. Quantitatively, the Drawin formula compares poorly with the results of the available quantum mechanical calculations, usually significantly overestimating the collision rates by amounts that vary markedly between transitions.Comment: 9 pages, 6 figures, accepted for A&

Non-LTE Model Atom Construction

Model atoms are an integral part in the solution of non-LTE problems. They comprise the atomic input data that are used to specify the statistical equilibrium equations and the opacities and emissivities of radiative transfer. A realistic implementation of the structure and the processes governing the quantum-mechanical system of an atom is decisive for the successful modelling of observed spectra. We provide guidelines and suggestions for the construction of robust and comprehensive model atoms as required in non-LTE line-formation computations for stellar atmospheres. Emphasis is given on the use of standard stars for testing model atoms under a wide range of plasma conditions.Comment: 19 pages, 8 figure

Dynamics and Radiation of Young Type-Ia Supernova Remnants: Important Physical Processes

We examine and analyze the physical processes that should be taken into account when modeling young type-Ia SNRs, with ages of several hundred years. It is shown, that energy losses in the metal-rich ejecta can be essential for remnants already at this stage of evolution. The influence of electron thermal conduction and the rate of the energy exchange between electrons and ions on the temperature distribution and the X-radiation from such remnants is studied. The data for Tycho SNR from the XMM-Newton X-ray telescope have been employed for the comparison of calculations with observations.Comment: 19 pages, 8 figure

Carbon abundances of early B-type stars in the solar vicinity. Non-LTE line-formation for C II/III/IV and self-consistent atmospheric parameters

Precise determinations of the chemical composition in early B-type stars consitute fundamental observational constraints on stellar and galactochemical evolution. Carbon is one of the most abundant metals in the Universe but analyses in early-type stars show inconclusive results, like large discrepancies between analyses of different lines in C II, a failure to establish the C II/III ionization balance and the derivation of systematically lower abundances than from other objects. We present a comprehensive and robust C II/III/IV model for non-LTE line-formation calculations based on carefully selected atomic data. The model is calibrated with high-S/N spectra of six apparently slow-rotating early B-type dwarfs and giants, which cover a wide parameter range and are randomly distributed in the solar neighbourhood. A self-consistent quantitative spectrum analysis is performed using an extensive iteration scheme to determine stellar atmospheric parameters and to select the appropriate atomic data used for the derivation of chemical abundances. We establish the carbon ionization balance for all sample stars based on a unique set of input atomic data, achieving consistency for all modelled lines. Highly accurate atmospheric parameters and a homogeneous carbon abundance with reduced systematic errors are derived. This results in a present-day stellar carbon abundance in the solar neighbourhood, which is in good agreement with recent determinations of the solar value and with the gas-phase abundance of the Orion H II region. The homogeneous present-day carbon abundance also conforms with predictions of chemical-evolution models for the Galaxy. The present approach allows us to constrain the effects of systematic errors on fundamental parameters and abundances. (abridged)Comment: 25 pages, 22 figures. Accepted for publication in A&

Contributions à la prévention des malformations congénitales

Doctorat en sciences médicalesinfo:eu-repo/semantics/nonPublishe