Spectral Diagnostics of Active Prominences

Active prominences exhibit plasma motions, resulting in difficulties with the interpretation of spectroscopic observations. These solar features being strongly influenced by the radiation coming from the solar disk, Doppler dimming or brightening effects may arise, depending on which lines are observed and on the velocity of the plasma. Interlocking between the different atomic energy levels and non local thermodynamic equilibrium lead to non-trivial spectral line profiles, and this calls for complex numerical modelling of the radiative transfer in order to understand the observations. We present such a tool, which solves the radiative transfer and statistical equilibrium for H, He I, He II, and Ca II, in moving prominences where radial plasma motions are taking place. It is found that for isothermal, isobaric prominence models, the He II resonance lines are very sensitive to the Doppler effect and show a strong Doppler dimming. The Ca II lines are not very sensitive to the Doppler effect for the prominence models considered here. We illustrate how the code makes it possible to retrieve the plasma thermodynamic parameters by comparing computed and observed line profiles of hydrogen and helium resonance lines in a quiescent prominence.Comment: 6 pages, 5 figures. In press,"Physics of Chromospheric Plasmas" (Coimbra), ASP 368, 337 (2007). Revised version matches published version

The Helium spectrum in erupting solar prominences

Even quiescent solar prominences may become active and sometimes erupt. These events are occasionally linked to coronal mass ejections. However we know very little about the plasma properties during the activation and eruption processes. We present new computations of the helium line profiles emitted by an eruptive prominence. The prominence is modelled as a plane-parallel slab standing vertically above the solar surface and moving upward as a solid body. The helium spectrum is computed with a non local thermodynamic equilibrium radiative transfer code. The effect of Doppler dimming / brightening is investigated in the resonance lines of He I and He II formed in the EUV, as well as on the He I 10830 A and 5876 A lines. We focus on the line profile properties and the resulting integrated intensities. It is shown that the helium lines are very sensitive to Doppler dimming effects. We also study the effect of frequency redistribution in the formation mechanisms of the resonance lines and find that it is necessary to use partial redistribution in frequency for the resonance lines.Comment: 5 pages, 4 figures. Proceedings of IAU GA 2006, JD03: Solar Active Regions and 3D Magnetic Structure. See also a more detailed paper at astro-ph/060822

Prominence observations with ALMA

This review comes at the time when ALMA successfully obtained the first regular observations of both a prominence and a filament. These observations have a spatial resolution of 1-2 arcsec, far better than previous prominence observations in the mm/sub-mm radio domain. The achieved resolution is compatible with the cotemporal ground-based coronagraphic observations in the hydrogen Hα line that accompany the ALMA Band 3 prominence observations. A core part of this review is the description and analysis of these pioneering ALMA observations of a quiescent prominence, focusing on various physical and geometrical properties of the observed prominence fine structures. We also summarize the basic physical processes behind the formation of mm/sub-mm continua under prominence conditions and describe the plasma diagnostics potential of ALMA solar observations. Finally, we discuss future prospects of ALMA prominence observations and the value of coordinated optical and UV spectra and images

European communication networks in the Early Modern Age

Recent contributions to knowledge about early journalism developed in different parts of Europe*Italy, France, England, Germany, the Netherlands, Portugal, Spain . . . *have made it possible to trace a fairly precise map for the historical origin of this phenomenon. However, the scope of work carried out with a view to developing frameworks of interpretation to explain the reasons for this appearance is not as far-reaching. This paper reviews the recurring theoretical models found to date in the specific bibliography and proposes a new framework of interpretation, capable of encompassing the complexity and pan-European nature of early journalism in history

Impact of the HIV-1 env Genetic Context outside HR1–HR2 on Resistance to the Fusion Inhibitor Enfuvirtide and Viral Infectivity in Clinical Isolates

Resistance mutations to the HIV-1 fusion inhibitor enfuvirtide emerge mainly within the drug's target region, HR1, and compensatory mutations have been described within HR2. The surrounding envelope (env) genetic context might also contribute to resistance, although to what extent and through which determinants remains elusive. To quantify the direct role of the env context in resistance to enfuvirtide and in viral infectivity, we compared enfuvirtide susceptibility and infectivity of recombinant viral pairs harboring the HR1–HR2 region or the full Env ectodomain of longitudinal env clones from 5 heavily treated patients failing enfuvirtide therapy. Prior to enfuvirtide treatment onset, no env carried known resistance mutations and full Env viruses were on average less susceptible than HR1–HR2 recombinants. All escape clones carried at least one of G36D, V38A, N42D and/or N43D/S in HR1, and accordingly, resistance increased 11- to 2800-fold relative to baseline. Resistance of full Env recombinant viruses was similar to resistance of their HR1–HR2 counterpart, indicating that HR1 and HR2 are the main contributors to resistance. Strictly X4 viruses were more resistant than strictly R5 viruses, while dual-tropic Envs featured similar resistance levels irrespective of the coreceptor expressed by the cell line used. Full Env recombinants from all patients gained infectivity under prolonged drug pressure; for HR1–HR2 viruses, infectivity remained steady for 3/5 patients, while for 2/5 patients, gains in infectivity paralleled those of the corresponding full Env recombinants, indicating that the env genetic context accounts mainly for infectivity adjustments. Phylogenetic analyses revealed that quasispecies selection is a step-wise process where selection of enfuvirtide resistance is a dominant factor early during therapy, while increased infectivity is the prominent driver under prolonged therapy

Stratégie et discours

Parmi les diverses méthodes et les nouvelles approches que se donne l’étude ou la science du périodique, l’une consiste à étudier les stratégies du discours (narratives, argumentatives, discursives). En effet, rares sont les phénomènes culturels et les supports qui, autant que les périodiques, permettent un examen adapté des rapports entre langage et stratégie. On peut distinguer dans ce mode d’étude, trois niveaux correspondant à trois modes d’articulation du discours. Envisager, pour un sec..

L'Instrument périodique

Cet ouvrage rassemble deux études sur le périodique littéraire du XVIIIe siècle : « Fonctions culturelles du périodique littéraire » de Claude Labrosse et « Forme et discours d’un journal révolutionnaire : les Révolutions de Paris en 1789 » de Pierre Rétat

Chapitre VIII. Les estampes

La fiction et le livre de la Julie sont faits à la fois d’images, de récit et de discours. Le roman donne à voir, il raconte, il argumente. Ce procès complexe est distribué dans l’ensemble du texte, il est coextensif à la totalité des mots. La lecture tend à fixer des images, à marquer des péripéties, à souligner certains moments du discours. Elle extrait et découpe mais elle peut en même temps affilier, superposer et feuilleter ce qu’elle découpe dans les images, le récit ou le discours. Ell..

La figure de Julie dans la Nouvelle Héloïse

Lorsque le lecteur ouvre ce livre, le premier signe qui l’interpelle, c’est aussi le premier mot du titre : Julie. Le nom du personnage appelle l’image d’un visage, il peut s’entendre comme la promesse d’un portrait. Or si, dans ce roman, la « figure » de Julie est obsédante et omniprésente, il semble que l’auteur n’ait pas pu ou n’ait pas voulu en faire réellement le portrait. Pour comprendre ce phénomène, on peut analyser les états successifs de la figure au cours de la genèse de l’œuvre et..