Search results for "CEF"
showing 10 items of 318 documents
Recombination processes in unintentionally doped GaTe single crystals
2002
Emission spectra of GaTe single crystals in the range of 1.90–1.38 eV have been analyzed at different temperatures and excitation intensities by photoluminescence, photoluminescence excitation, and selective photoluminescence. A decrease in band gap energy with an increase in temperature was obtained from the redshift of the free exciton recombination peak. The energy of longitudinal optical phonons was found to be 14±1 meV. A value of 1.796±0.001 eV for the band gap at 10 K was determined, and the bound exciton energy was found to be 18±0.3 meV. The activation energy of the thermal quenching of the main recombination peaks and of the ones relating to the ionization energy of impurities and…
Coronal mass ejections in the heliosphere
2010
With the advent of the NASA STEREO mission, we are in a position to perform unique investigations of the evolution of coronal mass ejections (CMEs) as they propagate through the heliosphere, and thus can investigate the relationship between CMEs and their interplanetary counterparts, so-called interplanetary CMEs (ICMEs). ICME studies have been principally limited to single-point, in-situ observations; interpretation of the in-situ characteristics of ICMEs has been used to derive a range of ICME properties which we can now confirm or refute using the STEREO imaging data. This paper is a review of early STEREO CME observations and how they relate to our currently understanding of ICMEs based…
Super Heavy Dark Matter Anisotropies from D-particles in the Early Universe
2004
We discuss a way of producing anisotropies in the spectrum of superheavy Dark matter, which are due to the distortion of the inflationary space time induced by the recoil of D-particles upon their scattering with ordinary string matter in the Early Universe. We calculate such distortions by world-sheet Liouville string theory (perturbative) methods. The resulting anisotropies are found to be proportional to the average recoil velocity and density of the D-particles. In our analysis we employ a regulated version of de Sitter space, allowing for graceful exit from inflation. This guarantees the asymptotic flatness of the space time, as required for a consistent interpretation, within an effec…
The Spanish Fireball Network: Popularizing Interplanetary Matter
2005
In order to increase in Spain the social interest in the study of interplanetary matter (asteroids, comets and meteoroids) we created the Spanish Photographic Meteor Network (SPMN) in 1997. This network has been dedicated to studying interplanetary matter with participation of researchers from three universities (Universitat Jaume I, Universitat de Barcelona and Universitat de Valencia), the Institut d'Estudis Espacials de Catalunya (IEEC) and the Instituto de Astrofisica de Andalucia and it is also supported by the Atmospheric Sounding Station at El Arenosillo (INTA-CEDEA) and by the Experimental Station La Mayora (EELM-CSIC). In order to promote the participation of amateurs, our homepage…
First Direct Observation of the Interaction between a Comet and a Coronal Mass Ejection Leading to a Complete Plasma Tail Disconnection
2007
This a discovery report of the first direct imaging of the interaction a comet with a coronal mass ejection (CME) in the inner heliosphere with high temporal and spatial resolution. The observations were obtained by the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) Heliospheric Imager-1 (HI-1) aboard the STEREO mission. They reveal the extent of the plasma tail of comet 2P/Encke to unprecedented lengths and allow us to examine the mechanism behind a spectacular tail disconnection event. Our preliminary analysis suggests that the disconnection is driven by magnetic reconnection between the magnetic field entrained in the CME and the interplanetary field draped around t…
Remarks on quadratic Hamiltonians in spaceflight mechanics
2006
A particular family of Hamiltonian functions is considered. Such functions are quadratic in the moment variables and arise in spaceflight mechanics when the averaged system of energy minimizing trajectories of the Kepler equation is computed. An important issue of perturbation theory and averaging is to provide integrable approximations of nonlinear systems. It turns out that such integrability properties hold here.
Un programme doctoral hors-les-murs : le cas du CEFAG
2023
National audience
Evidence for Impaired Hepatic Vitamin K1 Metabolism in Patients Treated with N-Methyl-Thiotetrazole Cephalosporins
1984
SummaryIn 8 patients on no oral intake and with parenteral alimentation, administration of cephalosporins with N-methyl-thiotetrazole side chain (moxalactam, cefamandole), was associated with prolongation of prothrombin time, appearance in the circulation of descarboxy-prothrombin (counter immunoelectrophoresis and echis carinatus assay) and diminution of protein C. Acute administration of 10 mg vitamin Ki was followed by the transient appearance of vitamin K1 2,3-epoxide, indicating an impaired hepatocellular regeneration of vitamin K1 from the epoxide. Impaired hepatic vitamin K1 metabolism, tentatively ascribed to the N-methyl-thiotetrazole group, is one (but possibly not the only) cause…
Particulate Matter Contamination of Intravenous Antibiotics Aggravates Loss of Functional Capillary Density in Postischemic Striated Muscle
2002
Through the increased use of less expensive and counterfeit medicines, the contamination of parenteral fluids and drugs by particulate matter poses an increasing health hazard worldwide. However, the mechanism of action of such contamination has never been conclusively demonstrated. We have systemically injected the particles contained in three different 1-g preparations of the antibiotic cefotaxime into hamsters and visualized the functional capillary density in striated skin muscle, using intravital fluorescence microscopy. Injection of particles from either of the three preparations did not affect capillary perfusion in normal muscle (n = 3 hamsters, each). However, injection of particle…
Roberto Pane e la ricostruzione postbellica. Un approfondimento su alcuni temi siciliani
2010
Nella relazione che Roberto Pane scrive per gli Atti del IV Congresso Nazionale di Storia dell’Architettura del 1950, con il termine «pseudo restauri», lo studioso si riferisce a quegli interventi gestiti dalle Curie che si improvvisano con propri uffici tecnici, promuovendo restauri in perenne contrasto con i pareri delle Soprintendenze. È in questo passaggio appassionato, della sua militante relazione al congresso, che Pane cita chiaramente il caso da lui conosciuto del Duomo di Cefalù con il suo chiostro. Inoltre è chiaro come Roberto Pane avesse avuto modo di conoscere direttamente il monumento, dato che nell’archivio fotografico che lo studioso dedicava alle lezioni universitarie, si t…