Industrie minérale et environnement : Aspects géochimiques, hydrogéochimiques, biogéochimiques

National audienc

Vacuum ultraviolet emission of a permanent magnet undulator on the ACO storage ring in Orsay

We present VUV emission spectra taken on the ACO storage ring from the permanent magnet undulator NOEL (1), currently dedicated to free electron laser experiments, along with an overview at the properties of undulator radiation. The analysis of the spectra includes corrections for the emittance of the electron beam and a small mismatch between the direction of the measurement and the undulator axis. We conclude that this undulator represents a powerful source of VUV radiation in the spectral range 100-1 300 A.Les principales caractéristiques du rayonnement émis par des électrons de haute énergie traversant un onduleur sont résumées. Nous présentons des spectres VUV obtenus sur l'anneau de stockage ACO avec l'onduleur à aimants permanents NOEL (1), utilisé jusqu'à présent pour des études sur le laser à électrons libres. Ces spectres sont interprétés en introduisant les corrections dues à l'émittance du faisceau d'électrons ainsi que celles dues à un petit écart entre la direction d'observation et l'axe de l'onduleur. Nous en concluons que cet onduleur représente une source puissante de rayonnement VUV dans le domaine spectral 100-1 300 Å

Contribution to the transient analysis of the self-controlled synchronous machine

The association of a synchronous motor and a load-commutated invertor can be considered as a drive system which is well adapted to high power levels, since a conventional thyristor bridge is triggered synchronously with the revolution of the rotor. Generally the detailed analysis of an association of that type is possible only by numerical simulation. The analysis of the behaviour of the drive in a more complex system necessitates simplified global models; such a dynamical model is developed in this communication.Anglai

A simplified analysis of the rectifier bridge fed by a polyphase synchronous machine

Presents a simplified global model considering the rectifier-loaded synchronous generator as a DC machine with shifted brushes. The model can be used for synchronous machines having more than three phases or more than one armature circuit. For steady-state and transient conditions, the proposed method gives a good approximation of the average and instantaneous values of currents and voltages of the system.Anglai

Ultrastructural nucleolar alterations induced by an ametantrone - Poly r(A-U) complex

The current study has documented changes in the ultrastructure as well as in the intranucleolar distribution of rDNA and rRNA in RT4 (human transitional cell bladder carcinoma) cell nucleoli following a 3-h exposure to toxic doses of 50 μM ametantrone (AMT), 200 μM poly (adenylate-uridylate) (poly r(A-U)) or an AMT/poly r(A-U) combination with an AMT/polyribonucleotide ratio of 1:4 and a poly r(A-U) concentration of 200 μM. While the main nucleolar components (fibrillar center (F), dense fibrillar component (D), granular component (G) and interstices (I)) can be discerned following all treatments, the nucleoli exhibit: compaction, segregation, a decrease in the number of F, an increase in the size of remaining F, margination of intranucleolar chromatin and retention of intranucleolar pre-rRNA and rRNA. The relative abilities of the test agents to induce nucleolar compaction are AMT/poly r(A-U) > poly r(A-U) > AMT > sham-treated, while the abilities of the test agents to induce the remaining nucleolar changes are AMT/poly r(A-U) ≥ AMT > poly r(A-U) > sham-treated cells. Poly r(A-U) and the induced interferon induce nucleolar compaction, while AMT produces nucleolar segregation. These results are consistent with a model in which the poly r(A-U) and/or the AMT inhibit DNA transcription and rRNA processing as well as the release of nascent preribosomes from the nucleolus. © 1998 Harcourt Brace & Co. Ltd.SCOPUS: ar.jinfo:eu-repo/semantics/publishe