Oxygen control in lead-bismuth eutectic: First validation of electrochemical oxygen sensors in static conditions

The control of the impurities, and of oxygen in particular, is of major interest for ensuring adequate and safe operation of lead alloys facilities from the viewpoint of the corrosion phenomenon : spallation targets or coolants for hybrid or fast reactors, currently under studies within the transmutation topic of the 1991 law on nuclear waste disposal. In addition, because of the very low oxygen solubility in lead alloys, it is compulsory to avoid saturation in any part of a defined system and in any operating condition so as to avoid any plugging by lead oxide built-up (fuel assembly feet, ...). For the oxygen control, the on-line monitoring of the dissolved oxygen content is required. Electrochemical sensors built with yttria stabilized zirconia were developed and tested in various static facilities : BIP, JACOMEX glove box, COLIMESTA. The experimental results were compared to the theoretical formulation, and a calibration method was applied (search for the singular point defining the saturation temperature). The operating range is as follows: 280°C-550°C, $10^{-10}$ - 10 ppm (1 ppm = l0$^{-4}$ weight%), for a 40% estimated accuracy. Service life is more than 1000 hours up to now. Reproducibility, time drift, time to response, and mechanical resistance are satisfactory. Based upon these results a first validation of these oxygen sensors is obtained in static conditions

The angiotensin system elements in invertebrates

In this review, the different components of the renin-angiotensin system (RAS) in invertebrates are discussed. This system is implicated in osmoregulation, reproduction, memory processes and immune system regulation. As the elements of this hormone-enzymatic system also exist in invertebrates, it appears that the RAS originated very early in evolution. (C) 2001 Elsevier Science B V All rights reserved.status: publishe

Angiotensin-converting enzyme inhibition studies by natural leech inhibitors by capillary electrophoresis and competition assay

A protocol to follow the processing of angiotensin I into angiotensin II by rabbit angiotensin-converting enzyme (ACE) and its inhibition by a novel natural antagonist, the leech osmoregulator factor (LORF) using capillary zonal electrophoresis is described. The experiment was carried out using the Beckman PACE system and steps were taken to determine (a) the migration profiles of angiotensin and its yielded peptides, (b) the minimal amount of angiotensin II detected, (c) the use of different electrolytes and (d) the concentration of inhibitor. We demonstrated that LORF (IPEPYVWD), a neuropeptide previously found in leech brain, is able to inhibit rabbit ACE with an IC50 of 19.8 mum. Interestingly, its cleavage product, IPEP exhibits an IC50 of 11.5 mum. A competition assay using p-benzoylglycylglycylglycine and insect ACE established that LORF and IPEP fragments are natural inhibitors for invertebrate ACE. Fifty-four percent of insect ACE activity is inhibited with 50 mum IPEP and 35% inhibition with LORF (25 mM). Extending the peptide at both N- and C-terminus (GWEIPEPYVWDES) and the cleavage of IPEP in IP abolished the inhibitory activity of both peptides. Immunocytochemical data obtained with antisera raised against LORF and leech ACE showed a colocalization between the enzyme and its inhibitor in the same neurons. These results showed that capillary zonal electrophoresis is a useful technique for following enzymatic processes with small amounts of products and constitutes the first evidence of a natural ACE inhibitor in invertebrates.status: publishe

Angiotensin-converting enzyme inhibition studies by natural leech inhibitors by capillary electrophoresis and competition assay.

A protocol to follow the processing of angiotensin I into angiotensin II by rabbit angiotensin-converting enzyme (ACE) and its inhibition by a novel natural antagonist, the leech osmoregulator factor (LORF) using capillary zonal electrophoresis is described. The experiment was carried out using the Beckman PACE system and steps were taken to determine (a) the migration profiles of angiotensin and its yielded peptides, (b) the minimal amount of angiotensin II detected, (c) the use of different electrolytes and (d) the concentration of inhibitor. We demonstrated that LORF (IPEPYVWD), a neuropeptide previously found in leech brain, is able to inhibit rabbit ACE with an IC(50) of 19.8 micro m. Interestingly, its cleavage product, IPEP exhibits an IC(50) of 11.5 micro m. A competition assay using p-benzoylglycylglycylglycine and insect ACE established that LORF and IPEP fragments are natural inhibitors for invertebrate ACE. Fifty-four percent of insect ACE activity is inhibited with 50 micro m IPEP and 35% inhibition with LORF (25 mm). Extending the peptide at both N- and C-terminus (GWEIPEPYVWDES) and the cleavage of IPEP in IP abolished the inhibitory activity of both peptides. Immunocytochemical data obtained with antisera raised against LORF and leech ACE showed a colocalization between the enzyme and its inhibitor in the same neurons. These results showed that capillary zonal electrophoresis is a useful technique for following enzymatic processes with small amounts of products and constitutes the first evidence of a natural ACE inhibitor in invertebrates

Rhythmites preservation in macrotidal estuarine environments : from upstream to downstream estuary

Estuaries are interface environments between continental and marine domains. The estuarine system classifications allow estuarine zonation based on the longitudinal distribution of hydrodynamic forcing relative energies (flow, tide and swell) which contribute to the hydrodynamics and sediment dynamics. The respective influence of hydrodynamic processes was represented by Dalrymple et al., 1992 (Fig. 1). The resulting hydrodynamics is highly variable and nonlinear in space but also in time: from seconds (swell) to multi-year (interannual variability of hydrological flows)

Impurities and oxygen control in lead alloys

International audienceThe control of the impurities is of major interest for ensuring adequate and safe operation of lead alloys facilities from the viewpoint of the corrosion phenomenon. Specific methods have to be implemented for effective control of the liquid lead–bismuth eutectic quality to the required specifications, as for instance: dissolved oxygen monitoring, dip sampling system, analytical techniques for impurities measurement. Even though the oxygen control in the static facility BIP proved difficult, a better knowledge of kinetics behaviour of the oxygen is acquired. Oxygen sensors gave results in agreement with the theory during the tests achieved on the BIP and on the COLIMESTA facilities. The dip sampler was validated on static device: it allows an effective sampling of the liquid metal melt and an easy separation of the melt from the sampling device when cold. The set of analytical techniques for the measurements of metallic impurities is efficient as well, except for the nickel element, for which the method of analysis with atomic absorption spectroscopy coupled with spiking method should allow the lower detection limit to be decreased below the 5 $\mu$g/g as for the iron impurity