Mass Measurements and the Bound--Electron g Factor

The accurate determination of atomic masses and the high-precision measurement of the bound-electron g factor are prerequisites for the determination of the electron mass, which is one of the fundamental constants of nature. In the 2002 CODATA adjustment [P. J. Mohr and B. N. Taylor, Rev. Mod. Phys. 77, 1 (2005)], the values of the electron mass and the electron-proton mass ratio are mainly based on g factor measurements in combination with atomic mass measurements. In this paper, we briefly discuss the prospects for obtaining other fundamental information from bound-electron g factor measurements, we present some details of a recent investigation of two-loop binding corrections to the g factor, and we also investigate the radiative corrections in the limit of highly excited Rydberg S states with a long lifetime, where the g factor might be explored using a double resonance experiment.Comment: 13 pages, LaTeX; dedicated to Prof. H.-J. Kluge on the occasion of his 65th birthday, to appear in Int. J. Mass. Spectrometr

Radio Wavelength Transients: Current and Emerging Prospects

Known classes of radio wavelength transients range from the nearby--stellar flares and radio pulsars--to the distant Universe--\gamma-ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, prompt emission from \gamma-ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely.Comment: to appear in proceedings of Hot-wiring the Transient Universe, 2008 March issue of Astronomische Nachrichte

Techniques in Analytic Lamb Shift Calculations

Quantum electrodynamics has been the first theory to emerge from the ideas of regularization and renormalization, and the coupling of the fermions to the virtual excitations of the electromagnetic field. Today, bound-state quantum electrodynamics provides us with accurate theoretical predictions for the transition energies relevant to simple atomic systems, and steady theoretical progress relies on advances in calculational techniques, as well as numerical algorithms. In this brief review, we discuss one particular aspect connected with the recent progress: the evaluation of relativistic corrections to the one-loop bound-state self-energy in a hydrogenlike ion of low nuclear charge number, for excited non-S states, up to the order of alpha (Zalpha)^6 in units of the electron mass. A few details of calculations formerly reported in the literature are discussed, and results for 6F, 7F, 6G and 7G states are given.Comment: 16 pages, LaTe

Multi-wavelength analysis of high energy electrons in solar flares: a case study of August 20, 2002 flare

A multi-wavelength spatial and temporal analysis of solar high energy electrons is conducted using the August 20, 2002 flare of an unusually flat (gamma=1.8) hard X-ray spectrum. The flare is studied using RHESSI, Halpha, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below 100 keV. The positions of the Halpha emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Halpha emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Halpha intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.Comment: 26 pages, 9 figures, accepted to Solar Physic

Étude stéréoscopique et spectrographique des sursauts radio solaires de type III

Study made using stereo space experiments 1 and 5, which allowed to compare the intensities and the propagation times between 2 different directions (earth and interplanetary probe) and by means of the radio spectrograph of Nançay. The shape of the apparent radiation pattern is obtained for the first time. Study of the dynamic spectrum of groups of type 4 and discovered types N, highlighting the possibility of reflection of the beams on magnetic mirrors. The results are shown to contain important information on the coronal density structure, and a number of extensions are suggested for a more complete understanding of the types III as a heliospheric phenomenon.Étude faites au moyen des expériences spatiales stéréo 1 et 5, qui ont permis de comparer les intensités et les temps de propagation entre 2 directions différentes (terre et sonde interplanétaire) et au moyen du radio spectrographe de Nançay. On obtient pour la première fois la forme du diagramme de rayonnement apparent. Étude du spectre dynamique des groupes de type 4 et découvertes des types N, mettant en évidence la possibilité de réflexion des faisceaux sur miroirs magnétique. On montre que les résultats contiennent une information importante sur la structure de la densité coronale, et on suggère un certain nombre de prolongements en vue d'une appréhension plus complète des types III en tant que phénomène héliosphèrique

Whole genome sequencing for mutation discovery in rare neurodevelopmental disorders

Recent developments in next generation sequencing (NGS) technologies and their accompanying bioinformatic tools have set the stage for an era of unprecedented progress in research on rare genetic disorders. Here, we develop a whole genome sequencing workflow for the analysis of NGS data and apply it to search for pathogenic mutations in four individuals affected by rare neurodevelopmental disorders. A list of high confidence pathogenic variants was finalized for all individuals. Our developed workflow and findings pave the way for further functional analyses of the brain developmental pathogenesis of the novel mutation(s).Les développements récents dans le séquençage nouvelle génération (NGS) du génome ainsi que les outils de bioinformatique qui les accompagnent font que nous entrons une ère de progrès rapide en recherche sur les désordres génétiques rares. Ici, nous développons un workflow pour l'analyse des données NGS et l'appliquons pour chercher les mutations pathogènes dans quatre individus atteints d'une maladie neurodéveloppementale rare. Une liste de variantes probables pathogènes a été développée pour tout individu. Notre workflow et trouvailles permettent d'avancer notre recherche en analyse fonctionnelle des mécanismes pathogénétiques de la mutation

Cristal trapézoïdal en spectroscopie X d'implosion par laser

Elastically bent, trapezoidal crystals for Bragg diffraction of X-rays allow designing broadband spectrometers with flat field, normal incidence and high resolution. This is applied to study microballoon implosions driven by six laser beams.En courbant élastiquement un cristal trapézoïdal pour la diffraction de Bragg des rayons X, on réalise un spectrographe à champ plan, large bande et haute résolution, sous incidence normale. Grâce à lui, on étudie des implosions de microballons par un laser à six faisceaux

Mindfulness as an Intervention Targeted to Core Cognitive Theories of Autism

Purpose: An important complement to molecular treatments, psychological interventions for autism spectrum disorder (ASD) are efficient and sustainable. The Western-influenced mindfulness concept is one such particularly powerful psychological construct with widespread benefits spanning health, education and business spheres. By alleviating the difficulties inherent to certain rigid patterns of cognition and behavior, cognitively fluidifying mindfulness-based interventions anchored in training one’s attention to variability have emerged as promising for improving the well-being of individuals with ASD. The purpose of this paper is to review the evidence supporting these benefits and suggest their potential underlying mechanisms. Approach: In this conceptual paper, we first review the broad evidence of the benefits of a range of Western-influenced mindfulness interventions for individuals with ASD, after which we deconstruct their underlying intra-individual processes and effects, and, finally, frame these psychological mechanisms in light of current core cognitive theories of ASD. Findings: This paper highlights the established importance and continued promise of Western-influenced mindfulness training in understanding and improving the psychological health and overall well-being of individuals with ASD. Our hope through this work is to lay the foundation for avenues of future research on mindfulness-inspired interventions aimed at non-invasively improving the lives of individuals and families affected by ASD. Originality: To the best of our knowledge, this work is the first to provide a synoptic perspective bringing forth an under-explored area of focus, bridging Western-influenced mindfulness and cognitive theories of ASD. In so doing, it sheds light on this ripe intersection highly amenable to therapeutic intervention

ÉTUDE EXPÉRIMENTALE DU CHAUFFAGE D'UN PLASMA AU MOYEN D'UN LASER DE PUISSANCE

La production et le chauffage par laser de plasmas de fusion nécessitent une bonne connaissance de l'interaction d'un faisceau laser de puissance avec un plasma dense. La densité électronique doit être proche de la densité critique pour laquelle la fréquence de l'onde est voisine de la fréquence plasma électronique. Nous décrivons quelques résultats obtenus dans ces conditions lorsque l'on focalise sur un plasma dense le faisceau d'un laser CO2. Le plasma cible a une densité de 8 à 9 × 1018 e/cm-3 et une température initiale de 10 eV. On étudie l'absorption et les variations de température du plasma en fonction du flux lumineux. Dans le régime des faibles flux (inférieurs à 1010 W/cm2), les résultats sont en accord avec le mécanisme classique de Bremsstrahlung inverse. Pour des flux plus élevés, les calculs montrent que, dans l'expérience proposée, l'absorption aura essentiellement pour origine les mécanismes anormaux dus aux instabilités paramétriques et que les conditions expérimentales se prêtent à l'observation des processus de rétrodiffusion prévus par Rosenbluth. La mise en évidence expérimentale se poursuit et nécessite le développement de lasers plus puissants qui sont actuellement en cours de réalisation.The realisation of laser produced and heated fusion plasma requires a good knowledge of the interaction of high power laser beam with plasmas near critical density where the plasma frequency is equal to the frequency of the laser. We present some results obtained under these conditions where a CO2 laser is focussed in a high, density plasma. The target plasma has an electronic number density of 8-9 × 1018 e/cm-3 and an initial temperature of 10 eV. We study absorption and temperature variation as a function of laser flux in the plasma. In the low flux regime (< 1010 W/cm2) the experimental results are in agreement with absorption due to Inverse Bremsstrahlung. For higher flux calculations show that in the proposed experiment absorption will be significant only in the case of an anomalous mecanism due to the onset of parametric instabilities induced by the laser. Experimental conditions will permit also the observation of back scattering as predicted by Rosenbluth when sufficiently high laser flux will be reached

INTERACTION AVEC UN CHAMP MAGNETIQUE D'UN PLASMA CREE PAR IRRADIATION LASER DE SOLIDE

Nous présentons les résultats de l'étude expérimentale de l'interaction avec un champ magnétique d'un plasma de laser. L'accord est assez bon avec les prévisions théoriques pour l'arrêt de l'expansion d'un plasma de conductivité électrique élevée.We present some results of the experimental investigation of the interaction with a magnetic field of a laser produced plasma. A reasonably good agreement is found with the theoretical prediction for a high conductivity expanding plasma