Les formations comprises entre les marnes du miocène et la dalle moulouyenne : quelques données d'intérêt morpho-pédologique

in Actes du Colloque "Le Villafranchien méditerranéen" (1982, December 09)

Interprétation des données en chimie clinique. Méthodes classiques et innovatrices.

Conference (1982, December 03)

The variability of RR Tel

in The Messenger (1982), 30

Photometric measurements of RR Tel performed at ESO are discussed. RR Tel is a galactic nova which has been associated with a sole outburst, observed in 1944. The photometric observations were made in the ... [more ▼]

Photometric measurements of RR Tel performed at ESO are discussed. RR Tel is a galactic nova which has been associated with a sole outburst, observed in 1944. The photometric observations were made in the ubvy system in August 1981, when a strong brightening was detected in V. IUE data subjected to a Fourier analysis indicate that the object has a period within 5 days of 395 days. Measurements of brightening of the J component also yield a period of 390 days. The presence of a Mira variable is considered, noting the supporting evidence from H2O and TiO spectral bands, but equally the lack of IR data until after 1960. It is suggested that data from before 1944 indicate that modulated bursts of mass transfer and accompanying accretion events preceeded the outburst of the underlying binary star, which could be a link between dwarf novae, classical novae, and symbiotic stars. [less ▲]

Stages intensifs d'initiation à l'informatique

in Actes du colloque "Enseignement, formation et pratique active de l'informatique par l'enfant" (1982, December)

The far-UV spectrum of the low-excitation planetary nebula HD 138403

in Astronomy and Astrophysics (1982), 116

Two high-resolution far-UV spectra of the low-excitation planetary nebula HD 138403 are analyzed which were obtained with the IUE satellite over the wavelength range from 1170 to 2070 A. It is shown that ... [more ▼]

Two high-resolution far-UV spectra of the low-excitation planetary nebula HD 138403 are analyzed which were obtained with the IUE satellite over the wavelength range from 1170 to 2070 A. It is shown that the nebula's far-UV spectrum comprises a stellar continuum on which are superimposed a few emission lines, numerous interstellar absorption lines, and various types of P Cygni profiles. Evidence is examined for substantial mass loss from the central nucleus, with terminal velocities of the order of 800 km/s. The observed nebular emissions are used to derive the electron density in the main nebula. The results are taken as supporting the hypothesis that a bipolar structure is expanding around HD 138403 via a selective radiation process involving an edge- or line-locking mechanism or both. [less ▲]

Rotation-Invariant Optical Processing

in Journal of the Optical Society of America (1982), 72(12), 1670-1676

Transport of aurorally produced N/2D/ by winds in the high latitude thermosphere

in Planetary and Space Science (1982), 30

A time-dependent, two-dimensional model is developed for describing the meridional circulation of thermospheric odd nitrogen species produced in the auroral zone. The model is based on a previous model by ... [more ▼]

A time-dependent, two-dimensional model is developed for describing the meridional circulation of thermospheric odd nitrogen species produced in the auroral zone. The model is based on a previous model by Roble and Gary (1979) extended to upper altitude transport of the nitrogen species. Assumptions made include the existence of a steady neutral wind flowing from low to high latitudes, and an initial background due to scattered Lyman-beta and nightglow emissions. The aurora is also assumed as steady, along with a constant ion production. Predictions made using the model are compared with observations with the Atmosphere Explorer C spacecraft and rocket sounding measurements of the 5200 A distribution near the day-side polar cusp. The model requires thermospheric winds of 100-200 m/sec, flowing from day to nightside. Convective velocities near 1000 m/sec were detected by the Explorer spacecraft, as well as a day-to-nightside flow at the cusp. [less ▲]

Determination of mass-loss rates from the first order moment W1 of unsaturated Cygni line profiles

in Astrophysics & Space Science (1982), 88

The relationship between the first order moment and the mass loss rate is investigated within the framework of the Sobolev approximation (1947, 1957, 1958) under various physical and geometrical ... [more ▼]

The relationship between the first order moment and the mass loss rate is investigated within the framework of the Sobolev approximation (1947, 1957, 1958) under various physical and geometrical conditions. By assuming that the size of the expanding envelope from which the observed P Cygni profiles arise is large with respect to the central stellar core, a general expression for the n-th order moment is obtained for the case of a point-like source in terms of the usual parameters inherent to Sobolev-type theories. It is then shown how the first result is altered when considering separately the effects due to collisions and rotation, the presence of the underlying photospheric absorption line, the finite size of the central core, and the limb-darkening of the stellar core. It is concluded that the total uncertainty of the mass loss rate determination made with the approach proposed here should be less than 60 percent. [less ▲]

Penicillin target enzyme and the antibiotic binding site

in Science (1982), 218(4571), 479-481

The three-dimensional structure of a penicillin-sensitive D-alanyl-carboxypeptidase-transpeptidase has been determined by x-ray crystallography to a resolution of 2.8 angstroms. The site of binding of the ... [more ▼]

The three-dimensional structure of a penicillin-sensitive D-alanyl-carboxypeptidase-transpeptidase has been determined by x-ray crystallography to a resolution of 2.8 angstroms. The site of binding of the beta-lactam antibiotics penicillin and cephalosporin has been located. These findings constitute direct observation of the interaction of beta-lactams with a transpeptidase enzyme and establish the feasibility of defining the molecular stereochemistry of this interaction for purposes of drug design. [less ▲]

Isolation of the membrane-bound 26 000-Mr penicillin-binding protein of Streptomyces strain K15 in the form of a penicillin-sensitive D-alanyl-D-alanine-cleaving transpeptidase

in Biochemical Journal (1982), 207(1), 109-115

The membrane-bound, 26 000-Mr penicillin-binding protein of Streptomyces K15 has been isolated in the form of an effective, penicillin-sensitive D-alanyl-D-alanine-cleaving peptidase exhibiting high ... [more ▼]

The membrane-bound, 26 000-Mr penicillin-binding protein of Streptomyces K15 has been isolated in the form of an effective, penicillin-sensitive D-alanyl-D-alanine-cleaving peptidase exhibiting high transpeptidase activity (greater than 95%) and very low carboxy-peptidase activity (less than 5%). The penicillin-binding protein/transpeptidase can be extracted directly from the mycelium with N-cetyl-NNN-trimethylammonium bromide (Cetavlon) and subsequently obtained at 90% purity and with an 8000-fold specific enrichment (when compared with the activity of the isolated membranes) by a two-step procedure involving Sephadex filtration and affinity chromatography on ampicillin-linked CH Sepharose 4B in the presence of detergent. At saturating concentrations of the co-substrates diacetyl-L-Lys-D-Ala-D-Ala and Gly-Gly, the catalytic-centre activity is about 0.3 s-1. [less ▲]