Echinoderm skeletons record sea temperatures

Poster (2005, December 31)

Handling Liveness Properties in (ω-)Regular Model Checking

in Electronic Notes in Theoretical Computer Science (2005, December 28), 138(3), 101-115

Since the topic emerged several years ago, work on regular model checking has mostly been devoted to the verification of state reachability and safety properties. Though it was known that liveness ... [more ▼]

Since the topic emerged several years ago, work on regular model checking has mostly been devoted to the verification of state reachability and safety properties. Though it was known that liveness properties could also be checked within this framework, little has been done about working out the corresponding details, and experimentally evaluating the approach. This paper addresses these issues in the context of regular model checking based on the encoding of states by finite or infinite words. It works out the exact constructions to be used in both cases, and solves the problem resulting from the fact that infinite computations of unbounded configurations might never contain the same configuration twice, thus making cycle detection problematic. Several experiments showing the applicability of the approach were successfully conducted. [less ▲]

A mutliwavelength observational study of the non-thermal emission from O-type stars.

Doctoral thesis (2005)

The present work is devoted to an observational multiwavelength study of the non-thermal emission of O-type stars. The non-thermal radio emission is believed to be synchrotron radiation, therefore ... [more ▼]

The present work is devoted to an observational multiwavelength study of the non-thermal emission of O-type stars. The non-thermal radio emission is believed to be synchrotron radiation, therefore requiring the existence of a magnetic field as well as of a population of relativistic electrons. The physical circumstances responsible for the acceleration of electrons up to relativistic velocities are not yet completely elucidated, but such an acceleration most probably occurs through the first order Fermi mechanism in the presence of hydrodynamic shocks, also called the Diffusive Shock Acceleration (DSA) mechanism. In the context of massive stars, the shocks responsible for this acceleration process may be intrinsic to their stellar winds, or arise from the collision between stellar winds in binary systems. In addition, the existence of non-thermal emission processes such as inverse Compton scattering suggests the possibility to detect a high-energy counterpart to the non-thermal emission observed in the radio domain. The objectives of this work are to (1) study the impact of the multiplicity on the non-thermal emission, (2) investigate the issue of the non-thermal emission of massive stars in the high-energy domain, and (3) discuss the possibility to constrain physical quantities such as the magnetic field strength through the study of these non-thermal emission processes. We investigate in detail several non-thermal emitting O-type stars, namely HD168112, HD167971, Cyg OB2 #8A, Cyg OB2 #9, and HD15558. For most of these targets, high quality XMM-Newton data are used in order to study their X-ray properties. In most case, the question of the multiplicity is also addressed through optical studies performed on the basis of data obtained with ground-based telescopes. The most intensive study is carried out on the Cyg OB2 region, for which we also obtained and analysed INTEGRAL data, in order to investigate the possible relation between the massive stars in Cyg OB2 and the unidentified EGRET source 3EG J2033+4118. In addition, high quality XMM-Newton data of the close massive binary HD159176 are also studied. Even though this latter target does not belong to the category of non-thermal radio emitters, its study unexpectedly turns out to be crucial in the context of this campaign as it might be the first O + O system likely to be classified as an n! on-thermal X-ray emitter. Considering our observational results, along with results from radio observations mainly coordinated by colleagues from the Royal Observatory of Belgium, we propose a general qualitative schematic view of the non-thermal emission from massive stars. First, it seems that the multiplicity plays a crucial role in the non-thermal emission processes. Second, we have found that the simultaneous detection of non-thermal radiation in the radio and X-ray (below 10.0 keV) domains is unlikely. Non-thermal radio emitters are indeed most probably binaries with periods longer than a few weeks, whilst only close binaries with periods of at most a few days may be non-thermal emitters in the soft X-ray domain. However, such a simultaneous detection is possible if the very hard X-rays or soft gamma-rays are considered, i.e. in a domain where the thermal emission from the colliding winds does not overwhelm the non-thermal emission. Moreover, it appears that the existence of non-thermal X-ray emitters without a non-thermal radio counterpart should be envisaged. Finally, the simultaneous detection of radio and high-energy non-thermal emissions is likely to lead to an indirect method to estimate the local magnetic field strength in the colliding-wind region of massive binaries. [less ▲]

Uncertainty assessment from robustness testing applied on an LC assay for R-timolol and other related substances in S-timolol maleate

in Analytica Chimica Acta (2005), 531

The robustness testing of a normal-phase liquid chromatographic (LC) method for the Determination of R-timolol and other related substances in S-timolol maleatewas performed applying a two-level ... [more ▼]

The robustness testing of a normal-phase liquid chromatographic (LC) method for the Determination of R-timolol and other related substances in S-timolol maleatewas performed applying a two-level Plackett–Burman design. Two qualitative and five quantitative factors were examined. Two types of responses were considered, qualitative, i.e. chromatographic performance criteria, and quantitative ones. The latter were taken into account to determine if the analytical procedure was robust. The quantitative responses were the contents of R-timolol in two S-timolol maleate samples. Even though some significant factor effects were observed on the qualitative responses, the R-timolol contents were not significantly different from those observed at nominal conditions, which demonstrated the robustness of the procedure. Since the experiments of the Plackett–Burman design can be assimilated to laboratories in an nterlaboratory study, uncertainty can be evaluated using the robustness test data. The robustness test was set-up in such a way that the required variances could be estimated. It was shown that the robustness set-up allows estimating the reproducibility uncertainty without performing an interlaboratory study. [less ▲]

Vibration Testing and System Identification

Scientific conference (2005, December 16)

This presentation is a summary of the recent activity of the Dynamics and Aeroelasticity Research Group of the University of Manchester on the subjects of Vibration Testing and System Identification.

L’employabilité : un impératif de concurrence

Conference (2005, December 16)

Nederlands, de taal van een tweestromenland

Conference given outside the academic context (2005)

Expérience de soi, mémoire collective. Les femmes amérindiennes et le texte témoin.

Conference (2005, December 16)

Excited [70,l(+)] baryons in large N-c QCD

in Physics Letters B (2005), 631(1-2), 7-15

The masses of the positive parity [70, 0(+)] and [70, 2(+)] non-strange baryons are calculated in large N-c QCD by considering the most dominant operators in an 1/N-c expansion. The approach is based on ... [more ▼]

The masses of the positive parity [70, 0(+)] and [70, 2(+)] non-strange baryons are calculated in large N-c QCD by considering the most dominant operators in an 1/N-c expansion. The approach is based on the introduction of an excited core, obtained after the last particle (an excited quark) has been removed. Configuration mixing is neglected, for simplicity. Although being a sub-leading 1/Nc order, we find that the spin-spin interaction plays a dominant role in describing the data. The role of No operators is also pointed out. We show how the contribution of the linear term in Nc, of the spin-spin and of the spin-orbit terms vary with the excitation energy. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

Les Wallons à Versailles : Henri-Joseph Rutxhiel. Sculpteur du pouvoir entre Empire et Restauration

in Carpeaux, Carole (Ed.) Les Wallons à Versailles (2005)

Édité dans le cadre de la journée d'études "Les Wallons à Versailles" organisée par la Commission royale des Monuments, Sites et Fouilles, le 5 décembre 2007, au château de Versailles, cet ouvrage ... [more ▼]

Édité dans le cadre de la journée d'études "Les Wallons à Versailles" organisée par la Commission royale des Monuments, Sites et Fouilles, le 5 décembre 2007, au château de Versailles, cet ouvrage regroupe les communications scientifiques du colloque ainsi que l’histoire de grands acteurs wallons à travers deux siècles d'Histoire commune entre la France et la Wallonie. [less ▲]