Direct Observation of Nonlinear Coupling between Pedestal Modes Leading to the Onset of Edge Localized Modes.

Prior to eruptive events such as edge localized modes (ELMs), quasicoherent fluctuations, referred to as pedestal modes, are observed in the edge of fusion devices. We report on the investigations of nonlinear coupling between these modes during quasistationary inter-ELM phases leading to the ELM onset. Three dominant modes, with density and magnetic signatures, are identified as key players in the triggering mechanism of certain classes of ELMs. We demonstrate that one of these modes is amplified by the two others through three wave interactions. The amplified mode is radially shifted relative to the other two modes towards the last-closed flux surface as the ELM event approaches. Our results suggest that nonlinear coupling of pedestal modes, associated with radial distortions pushing out of the pedestal, is a possible mechanism for the triggering of low frequency ELMs relevant for future fusion devices.

[A modification in technology improves the specificity of the Du Pont de Nemours immunoenzyme kit for the detection of anti-HIV antibodies]. / Une modification de technologie améliore la spécificité de la trousse immuno-enzymatique Du Pont De Nemours de dépistage des anticorps anti-HIV.

Du Pont De Nemours perfected a new enzyme immunoassay for the screening of anti-HIV 1 antibodies, characterized by its rapidity: 2 hours of incubation, when the normal procedure needed 3 hours 30 minutes of incubation. We tested with the normal procedure and the shortened one 4,025 randomly selected blood donors. 55 samples of the SNTS panel and 10 sera representing the Western-Blot reference panel of the "Retrovirus" study group of the SNTS. We can say that shortening the incubation time results in certain advantages opposite the previous procedure: time saving (1 hour 30 minutes); improved specificity: the rate of false positive, 0.37% with the normal method, drops to 0.07% with the short one; good sensitivity, since all the individual positive samples were detected but it seems slightly less sensitive than the normal method for the diluted positive samples.

[Wellcozyme: a new kit for the detection of anti-HIV antibodies. Considerations apropos of the initial trials]. / Wellcozyme: une nouvelle trousse de dépistage des anticorps anti-HIV. Reflexions à propos des premiers essais.

We tested the Wellcozyme anti-HTLV III kit on: 600 blood donors fresh sera, simultaneously tested by Elavia (Diagnostics Pasteur) or Vironostika (Organon); 20 plasmas, known to be anti-HIV negative; 22 sera, already labelled, and a panel of 10 specimens from the "Retrovirus" study group of the French National Society of Blood Transfusion, also tested by Elavia, Vironostika, Abbott HTLV III EIA and by two confirmatory tests: Immuno-blot (Diagnostics Pasteur) and Abbott confirmatory test. The Wellcome kit is, at present, the only one to use a competitive Elisa method and not to require any sample predilution. The method is easy to perform, rapid (results in 1 h 30 time) and it tests as well serum as plasma. No interferences have been observed from high lipid concentrations or strong hemolysis on the Elisa reaction. The performances of the Wellcozyme test are satisfactory. We did not find any "false positive" result. But the study shows that this kit is not sensitive enough for the detection of anti-P25 antibodies, which appear on the beginning of seroconversion, unless the "grey range" is extended: the Wellcome Laboratories have just made this recommendation.

[Comparative study of three presentations for research on HBs antigen by the immunoenzyme technique]. / Etude comparative de trois présentations de recherche de l'antigène HBs par technique immunoenzymatique.

The authors present the results of a study comparing the detection of HbSAg by enzyme immunoassay using the following three different commercial kits and their corresponding apparatus: Auszyme II, Quantum II from Abbott; Enzygnost micro Elisa, Elisa Processor from Behring; Hepanostika, washer and reader micro Elisa system from Organon. The purpose of the study is to determine the sensitivity and specificity of the reaction and the extent of automation of this method. The sensitivity and specificity of the 3 kits are compared with those of a reference technique, the radioimmunoassay Ausria II, Abbott. The sensitivity of Auszyme II is equivalent to that of Ausria II and is approximately 0.2 mg/ml. The other two kits are somewhat less sensitive. The proportion of false negative is less than 1%, but with all 3 kits it is necessary to verify a negative result. The results of this study confirm the high level of sensitivity and specificity of the enzyme immunoassay for the detection of HbSAg in the serum or plasma of blood donors. This technique therefore offers an alternate method of HbSAg detection to laboratories which cannot or prefer not to use a radioimmunoassay.

A study on the topological distribution of phospholipids in microsomal membranes of chick brain using phospholipase C and trinitrobenzenesulfonic acid.

The transbilayer distribution of phospholipids in chicken brain microsomal membranes has been investigated using trinitrobenzenesulfonic acid and phospholipase C from Clostridium welchii. The exposure of intact microsomes to trinitrobenzenesulfonic acid showed that the labelling of aminophospholipids followed biphasic kinetics, indicating that these membranes contain a fast- and a slow-reacting pool of aminophospholipids. Use of microsomes radioiodinated on their surface led to the conclusion that the fast-reacting pool may be located on the outer leaflet of the microsomal vesicles. It contains about 35% of the phosphatidylethanolamine, 29% of the ethanolamine plasmalogens and 18% of the phosphatidylserine. The treatment of intact microsomes with the phospholipase C Cl. welchii produced the hydrolysis of 50% of the phospholipids without any loss of their permeability properties, indicating that they are not permeable to the hydrolase. Phospholipids extracted from the microsomes were hydrolyzed rapidly by the phospholipase C with the exception of phosphatidylserine and phosphatidylinositol. In intact microsomes about 90% of phosphatidylcholine, 32% of ethanolamine phospholipids and 60% of sphingomyelin were accessible to the phospholipase. These results suggest that the phospholipids have an asymmetric distribution in chicken brain microsomes, the external leaflet containing about 75% of the choline phospholipids and 25% of the aminophospholipids, whereas an opposite distribution is observed in the inner leaflet.