18 research outputs found
L’improvisation comme forme d’expérience. Généalogie d’une catégorie d’appréciation du jazz
No full textInternational audienceThe term « improvisation » refers both to the act of improvising and to the product of this act. However, in both cases, it refers to a musical activity : it is the musician who improvises, and who is therefore the author of the resulting improvisation. This article aims at questionning that supposedly necessary correlation-in other words, the act of attribution implied by these uses of the term « improvisation ». Tracing a history of these uses – through the example of jazz in France –,the link between the act of improvising, its product and the author appears far from obvious. Understanding improvisation as a appreciation category rather than as a musical activity, as an experience form rather than as just a type of action, enables us to trace the various activity and subject situations which have been performatively invented and implemented throughout the history of jazz in France.Le terme « improvisation » peut désigner autant l'action d'improviser que le produit de cette action. Or dans les deux cas, le terme réfère une activité musicienne : c'est le musicien qui improvise, et qui est donc l'auteur de l'improvisation qui en résulte. Le propos de cet article consiste à interroger ce « donc », ou dit autrement, le geste d'attribution qu'impliquent ces usages du terme « improvisation ». À faire l'histoire de ces usages – en l'occurrence, dans le cas du jazz en France – il apparaît en effet que le lien entre l'action d'improviser, son produit et leur auteur est rien moins qu'évident. Saisir l'improvisation comme une catégorie d'appréciation plutôt que d'activité musicienne, une forme d'expérience plus largement qu'un simple type d'action, permet alors de restituer les différents dispositifs d'activité, et avec, de sujets, qui ont été inventés et mis en pratiques de façon performative tout au long de l'histoire du jazz en France
Laboratory Characterization And Astronomical Detection Of The Nitrosylium Ion, No+
No full textWe report the discovery for the first time in space of the nitrosylium ion, NO. The observations were performed towards the cold dense core Barnard 1-b. The identification of the = 2 1 line is supported by new laboratory measurements of rotational lines of NO in the ground vibrational state up to the = 8 7 transition (953207.189 MHz).
The ion was produced in a magnetically extended negative glow discharge in NO. Vibrational excitation of the ion was high enough to measure rotational lines up to = 2. A few transitions of NO were also measured (). All known rotational and ro-vibrational frequencies of this close-shell ion were included in an isotopically invariant analysis.
In Barnard 1-b, the observed line profile of NO exhibits two velocity components at 6.5 and 7.5 km s, with column densities of 1.510 and 6.510 cm, respectively. New observations of NO and HNO have been performed and allowed to estimate the following abundance ratios: (NO)/(NO) 511, and (HNO)/(NO) 1.
The chemistry of NO has been investigated by means of a time-dependent gas phase model which includes an updated chemical network according to recent experimental studies. The predicted abundance for NO and NO is found to be consistent with the observations. However, that of HNO relative to NO is too high. No satisfactory chemical paths have been found to explain the observed low abundance of HNO.Made available in DSpace on 2014-09-17T16:55:52Z (GMT). No. of bitstreams: 3
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Previous issue date: 2014-06-1
L’improvisation comme forme d’expérience. Généalogie d’une catégorie d’appréciation du jazz
No full textL’article envisage l’improvisation comme une catégorie d’appréciation esthétique plutôt que d’action musicale. Sous cet angle, les formes d’expérience et l’écoute qu’elle engage régulent les activités tout autant auditrices que musiciennes, et leur inscription dans le jeu de langage « improvisation » équivaut à un geste d’attribution d’autorité : c’est l’artiste interprète qui est institué comme auteur des performances, et son intériorité qui est censée « s’exprimer » à travers elles. L’improvisation ne peut alors plus être pensée que comme une énigme à élucider, l’alchimie mystérieuse d’une « composition sur le vif ». La généalogie des usages du terme « improvisation » dans le cas du jazz en France permet ainsi de restituer les différents dispositifs d’activité, et avec, de sujets, qui ont été inventés et mis en pratique au cours du vingtième siècle, du soliste virtuose à l’expérimentateur singulier, en passant par l’artiste racialisé ou l’artiste maudit.Improvisation is considered here as a category of aesthetic appreciation rather than as a category of musical activity. It is seen as determining different forms of experience which regulate listeners’ as well as musicians’ activities, because it implies an act of attribution : the artist is regarded as the author of the performance, through which his internal subjectivity is supposed to « express » itself. Consequently, improvisation can only be thought of as an enigma which needs to be explained, the mysterious alchemy of an « instantaneous composition ». A genealogy of the uses of the word « improvisation » in the history of jazz in France enables us to trace the various situations of activity and subjectivity which have been performatively invented and implemented throughout the 20th Century, from the virtuoso to the racialized artist, the accursed artist, and finally the experimenter
Asymptotic normality of wavelet estimators of the memory parameter for linear processes
No full textWe consider linear processes, not necessarily Gaussian, with long, short or negative memory. The memory parameter is estimated semi‐parametrically using wavelets from a sample X1,…, Xn of the process. We treat both the log‐regression wavelet estimator and the wavelet Whittle estimator. We show that these estimators are asymptotically normal as the sample size n → ∞ and we obtain an explicit expression for the limit variance. These results are derived from a general result on the asymptotic normality of the scalogram for linear processes, conveniently centred and normalized. The scalogram is an array of quadratic forms of the observed sample, computed from the wavelet coefficients of this sample. In contrast to quadratic forms computed on the basis of Fourier coefficients such as the periodogram, the scalogram involves correlations which do not vanish as the sample size n → ∞.We thank the referee for his comments. Murad S. Taqqu thanks Telecom ParisTech for their hospitality. This research was partially supported by the NSF Grants DMS-0505747 and DMS-0706786 at Boston University. (DMS-0505747 - NSF; DMS-0706786 - NSF)First author draf
OBSERVING A COLUMN-DEPENDENT IN THE HORSEHEAD PDR
No full textAuthor Institution: Department of Physics, Ohio State University, Columbus, OH 43210; Institute of Astronomy and Astrophysics, Academia Sinica, Tapei 11677, Taiwan; Observatoire de Paris, LUTH and Universite Denis Diderot, Place J. Janssen 92190 Meudon, France; Departments of Astronomy, Physics, and Chemistry, Ohio State University, Columbus, OH 43210The molecules CCH, CH, HCO, and HCN have been observed at the edge of the Horsehead Nebula in abundances far higher than those predicted by Photodissociation Region (PDR) models, 885 (2005)}. Using a column-dependent cosmic ray ionization rate (), 619 (2009)}, we model the edge of the Horsehead Nebula as a one-dimensional nearly-``edge-on'' heterogeneous PDR with temperature ranging from 15-250 K, number density from - cm, and - s. The resulting abundances for the molecules listed above are much closer to the observed abundances. In this talk, we will discuss this method, its results, and the usefulness of incorporating a column-dependent in astrochemical PDR models, especially in the advent of ALMA
THE EMISSION CONTINUUM OF ELECTRON EXCITED MOLECULAR HYDROGEN
No full textAuthor Institution: Jet Propulsion Laboratory; University of Southern California, Jet Propulsion Laboratory; Observatoire de Paris, Section de Meudon, Jet Propulsion LaboratoryPhoto-excitation of hydrogen molecule from the state to the , , , and D states and subsequent emission to the dissociation continuum is the primary destruction mechanism of in interstellar clouds. We have recently calculated continuum emission profiles of , and D transitions of . Synthetic spectra based on the calculated profiles are in excellent agreement with high-resolution electron-impact induced emission spectra obtained at 100eV. An improved intensity calibration standard and dissociation yields of the Lyman and Werner continuua produced by both electron and photon impact excitation will be presented
INTERSTELLAR N IN THE DIFFUSE ISM TOWARD 20 AQUILAE
No full textAuthor Institution: Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208; Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218Molecular nitrogen (N) is the most abundant molecule in the Earth's atmosphere and in the less chemically-processed atmosphere of Titan. N is also of considerable interest for studies of the interstellar medium because both models of steady-state gas-phase chemistry (Viala 1986) and millimeter wave observations of NH (Womack, Ziurys, \& Wyckoff 1992) predict that N should be the dominant nitrogen-bearing molecule in interstellar space. We previously presented the first detection of interstellar N toward HD 124314 with an observed fractional abundance of N/H = x(N) = 3.3 10 (Knauth et al. 2004). Here we report on the second detection of interstellar N based on {\it Far Ultraviolet Spectroscopic Explorer} () observations of the moderately-reddened star 20 Aquilae (Knauth et al. 2005) with (N) 4.7 10. This fractional abundance is surprisingly low given that 20 Aql has a factor-of-4 higher CN abundance than that found toward HD 124314. Is this possible anti-correlation caused by differences in the predictions of diffuse and dark cloud chemistry? Recent work (Herbst 2004, private communication; Roueff 2005) show that a single homogeneous cloud chemical model cannot reproduce the observations. Further observations of interstellar N and other nitrogen-bearing species (e.g., NH) toward lines of sight with different physical conditions are required to understand the implications for interstellar nitrogen chemistry
EXCITATION PROFILES IN DIFFUSE INTERSTELLAR CLOUDS
No full textDepartment of Astronomy, University of California, Berkeley, CA 94720.Author Institution: Department of Chemistry, University of California; Division of Geological and Planetary Sciences 150-21, California Institute of Technology; Department of Chemistry, University of CaliforniaThe very high-resolution , very high signal-to-noise , optical (4051 {\AA}) spectrum of the carbon-chain molecule is reported for 10 diffuse interstellar clouds, demonstrating the possibility for detailed study of polyatomic molecules in the diffuse interstellar medium (ISM). Thus far, is the largest identified molecular species to be observed in absorption in the diffuse ISM. The first detection of toward three stars (Maier et al., 2001) contained a single spectrum of sufficient quality to show a non-thermal equilibrium rotational excitation profile. This data was adequately modeled with a two-temperature thermal distribution. Rotationally resolved was then measured in one additional source, and a detailed radiative balance model was used to analyze the data (Roueff et al., 2002). A low resolution survey (Oka et al., 2002) has measured the column densities of in roughly 30 targets, laying the groundwork for high resolution observations. We present rotationally resolved and very high signal-to-noise spectra taken with the HIRES spectrometer on the 10-m Keck telescope and with the Hamilton echelle spectrometer on the Shane 3-m Lick Observatory telescope. The measurements allow for a detailed analysis of the molecular excitation in a variety of diffuse interstellar environments. The observed excitation profiles are modeled using 1) thermal distributions incorporating either one or two kinetic temperatures and 2) a new technique involving a least squares fit of the entire spectrum using the population in each rotational level as a fit parameter. We discuss how these observations constrain our understanding of the various environments in these sightlines, correlation between and , and the prospects for the study of larger polyatomic molecules in the diffuse ISM
LASER EXCITATION OF SHAPE RESONANCES IN
No full textH. Abgrall, A. Giusti-Suzor, and E. Roueff, Astrophys. J. 207, L69 (1976). P. C. Cosby, H. Helm, and J. T. Moseley, Astrophys. J. 235, 52 (1980).Author Institution:Radiative association of is Che principal formation mechanism of in diffuse interstellar clouds. Current description of this process relies on model calculations using theoretical potential energy curves for the and ; states of , but cannot account for the observed abundance of this We are attempting to determine experimentally the potential curves for these states in the regions relevant to radiative association by observing the reverse process: predissociation of through shape resonances In the state. A mass selected beam of ions is merged with a laser beam over a distance of 60 cm. The appearance of fragment ions from the photodissociation of is studied as a function of both wavelength and production kinetic energy. The wavelength dependence is studied either by employing a tunable dye laser or by Doppler tuning a fixed ion laser frequency by variation of the ion beam velocity. Our Initial measurements of the predissociation of using ion laser lines in the region of 3500 {\AA} are described in Ref. 2. We have extended these measurements to 6471 {\AA} using both ion laser lines and a tunable dye laser. Predissociations of rotationally quasi-bound levels of the state are observed throughout this wavelength range. Assignment of the transitions has been made on the basis of the observed transition frequencies, Photofragment kinetic energies, and predissociation lifetimes. Several significant discrepancies are found between the photodissociation measurements and the predictions of theory, demonstrating that the potential energy curve of the ; state is less attractive at large internuclear distances and somewhat shallower than predicted
FIRST DETECTION OF GROUND STATE ROTATIONAL LINES OF DOUBLY DEUTERATED AMMONIA
No full textAuthor Institution: California Institute of Technology, Downs Laboratory; of Physics 320-47, Pasadena, CA 91125; LERMA, UMR 8112 du CNRS, Observatoire de Paris and; Ecole Normale Superieure, 24 Rue Lhomond, 75231 Paris cedex 05,; France; LUTH and UMR 8102 du CNRS, Observatoire de Paris,; Section de Meudon, Place J. Janssen, 92195 Meudon, France; California Institute of Technology, Downs Laboratory; of Physics 320-47, Pasadena, CA 91125We report the first detection of the and ground state rotational lines of o-NDH at 335.5 and 388.7 GHz, obtained in the Lynds 1689N and Barnard 1 molecular clouds using the Caltech Submillimeter Observatory (CSO). The hyperfine splitting is detected in both lines allowing direct determination of the line opacity and the excitation temperature. The line of p-NDH at 335.4 GHz is also detected in both sources and the derived ortho-to-para ratio is consistent with the expected LTE value of 2:1. The two ground state o-NDH transitions have different spontaneous emission rate coefficients and therefore critical densities. With the help of modeling tools, they can thus provide good constraints on the excitation conditions and gas kinematics in dense, cold pre-stellar and protostellar cores. These places are sites of strong molecular depletion and heavy deuteration. Non-accreting molecules, H and its isotopologues, are difficult to study, but in several cases it appears that ammonia and its isotopologues are not completely frozen out. On good sites, such as Mauna Kea or Chajnantor, the submillimeter NDH lines are easier to detect than the 3 mm lines previously used to study the distribution and abundance of this molecule in the interstellar medium. Interferometric observations of these submillimeter NDH lines with the Submillimeter Array (SMA), and subsequently the Atacama Large Millimeter Array (ALMA), will provide new opportunities to image the inner structure of cold, dense cores, where most molecules are depleted onto dust grains
