Ostéologie et relations phylogénétiques des Protobramidae (Teleostei, Tselfatiiformes) du Cénomanien (Crétacé supérieur) du Liban

The osteology of Protobrama avus, of a new species of this genus, P. woodwardi, and of two new monospecific genera of protobramid fishes, Eusebichthys byblosi and Abisaadichthys libanicus, is studied. Protobramidae are small deep-bodied marine teleosts from the Lower Cenomanian of Lebanon. They are characterised by the gomphosis of the neural and haemal arches on the centra all along the axial skeleton, the loss of segmentation on the dorsal and anal fin rays, the small cycloid scales covering the basis of the unpaired fins, the ribs fused with the haemapophyses, the loss of epicentrals and epipleurals, the loss of epurals, the reduced number (4 or 5) of hypurals and the fusion of hypurals 3 and 4 into a dorsal hypural plate. The skull is medio-parietal. The temporal fossa is dorsally bordered by the parietal. The jaws are feebly toothed or toothless. The maxillary, which is bordering the mouth, is always toothless. The supramaxillaries are lost. The possible synonymy of the Protobramidae and Plethodidae (or Tselfatiidae) as well as the integration of the Protobramidae, the Araripichthyidae and the Ferrifronsidae into a suborder of the Protobramoidei are discussed and rejected. The analysis of the protobramid characters leads to range them as a valid family in the clupeocephalan order Tselfatiiformes near the Plethodidae

Nouvelle description d’<i>Halecopsis insignis</i> de l’Éocène marin de l’Europe et les relations de ce taxon avec les Gonorynchiformes (Teleostei, Ostariophysi)

New description of dagger Halecopsis insignis from marine Eocene of Europe and relationships of this taxa with the Gonorynchiformes (Teleostei, Ostariophysi).The osteology of dagger Halecopsis insignis from the marine Eocene of Europe is briefly revised. The frontals are elongated and narrow at the preorbital level. The skull is latero-parietal. The mesethmoid is small and longer than broad. The lateral ethmoids are reduced. The pleurosphenoids are small and there is no orbitosphenoid. The lower jaw is short and the quadrate and the ventral branch of the preopercle very long. There are only four infraorbitals, all possessing a well developed membranodermic component. The supratemporal is strongly reduced. The extrascapular sensory commissure is enclosed in the parietals and passes also in a thin groove on the supraoccipital. The osteological characters allow to confirm that H. insignis belongs to the suborder Gonorynchoidei and to propose that it is phylogenetically lying between the family dagger Apulichthyidae, where the lateral ethmoid remains large, and the other families of this suborder, in which the membranodermic component of the infraorbitals is already lost

Helium Cryoplant Off-line Commissioning and Operator Training: Two Applications of the PROCOS Simulation System at CERN

The off-line commissioning step, through reliable simulation of physical models, aims to correct and validate control systems before their implementation into real equipments. It prepares and minimizes plant commissioning phase and at the same time validates the efficiency of the new process control logic. This paper describes how different CERN/UNICOS cryogenic control systems have been pre-commissioned off-line, using the CERN cryogenic simulation environment PROCOS. Some examples are reported. Additionally the presented simulation environment will be used for operator training. The second part of the paper will presents the simulation platform and the first feedback from the operation crew

Coulomb-Volkov approach of ionization by extreme ultraviolet laser pulses in the subfemtosecond regime

In conditions where the interaction betweeen an atom and a short high-frequency extreme ultraviolet laser pulse is a perturbation, we show that a simple theoretical approach, based on Coulomb-Volkov-type states, can make reliable predictions for ionization. To avoid any additional approximation, we consider here a standard case : the ionization of hydrogen atoms initially in their ground state. For any field parameter, we show that the method provides accurate energy spectra of ejected electrons, including many above threshold ionization peaks, as long as the two following conditions are simultaneously fulfilled : (i) the photon energy is greater than or equal to the ionization potential ; (ii) the ionization process is not saturated. Thus, ionization of atoms or molecules by the high order harmonic laser pulses which are generated at present may be addressed through this Coulomb-Volkov treatment.Comment: 19 pages including 5 figures and figure caption

Beam related thermal losses on the cryogenic and vacuum systems of LEP

The LEP Collider was operated in 1997 with 60 superconducting four-cavity accelerating modules (about 2600 MV available) installed at the four interaction points. During operation for physics it was o bserved that the dissipated heat in the superconducting cavities is not only a function of the acceleration gradient but it also depends on beam characteristics: number of bunches, bunch length and cu rrent per bunch. These beam effects were not foreseen in the original heat budget of the LEP refrigerators. Three days of LEP Machine Development were dedicated in August 97 to clarifying the correlat ion of the losses with the beam characteristics. The beam dependent heat load of the cryogenic system for the superconducting cavities is described. The dependence on various beam parameters is presen ted and scaling laws are given. A possible explanation will be presented and the consequence for LEP operation will be discussed