Cyclic oxidation of coated and uncoated single-crystal nickel-based superalloy MC2 analyzed by continuous thermogravimetry analysis

The previously developed cyclic thermogravimetry analysis (CTGA) [Monceau D, Poquillon D. Oxid Met 2004;61:143–163] method is applied to the cyclic oxidation at 1150 C of a NiCoCrAlYTa-coated and an uncoated single-crystal nickel-based superalloy MC2. A new procedure to correct the buoyancy effect is proposed in order to evaluate the amount of oxide formed during the heating periods, which can be important for alloys forming fast-growing transient oxides or during cycling with slow heating rates. It is shown that cyclic thermogravimetry is an useful technique for uantifying the oxidation resistance of an industrial alloy. Moreover, the behaviour of the alloy is better described with CTGA than with a classic cyclic gravimetric test, because both isothermal oxidation kinetics and spalling behaviour are assessed independently. In the present case, it is shown clearly that the NiCoCrAlYTa coating greatly improves the cyclic oxidation resistance without decreasing the isothermal oxidation kinetics. Finally, the use of CTGA for performance and time-of-life evaluations is demonstrated

Etude par chromatografie d'affinite' de la variation chez l'homme pendant une surcharge sodee de l'inhibiteur endogene de la Na-K-ATPase [Affinity chromatographic study of the changes in the endogenous Na+-K+-ATPase inhibitor during sodium loading in man]

Semi-purified dog kidney Na+-K+-ATPase was cross-linked with ovalbumin. This immobilized enzyme was able to hydrolyse ATP and this hydrolysis was ouabain-sensitive. It was then used in batch wise affinity chromatography for the detection of endogenous Na+-K+-ATPase inhibitor in human plasma and urine. Ammonium acetate 1 mM washed off the endogenous Na+-K+-ATPase inhibitor from the immobilized enzyme. The inhibitory activity of the eluate from hypertensive plasma was significantly higher (p less than 0.0025, n = 6) than that of normotensive plasma. Similar results were obtained (n = 3) from human urine eluates during salt loading as compared to control urine

Oxydation et protection des matériaux pour sous-couches (NiAlPd, NiAlPt, NiCoCrAlYTa, CoNiCrAlY) de barrières thermiques

Le comportement en oxydation isotherme des divers matériaux utilisés pour la fabrication des sous-couches pour barrières thermiques (systèmes superalliage base-nickel/sous-couche/zircone partiellement stabilisée) a été caractérisé en fonction de la température (900 à 1 100°C), de la vitesse de montée en température (12,20 ou 60 K/min) et de l'atmosphére (pressions partielles d'oxygène de 10-5, 1 ou 105 Pa). Cela nous a permis de définir les conditions de pré-oxydation permettant de contrôler l'oxyde formé sur la sous-couche avant le dépôt de la zircone. Pour les aluminiures de nickel modifiés palladium ou platine comme pour les sous-couches MCrAlY, une transition cinétique est observée lors d'oxydations courtes (6h) en dessous de 1000°C (entre 1000 et 1100°C pour (Ni,Pt)Al). L'analyse thermogravimétrique combinée aux analyses chimiques (XPS, SIMS, MEB-EDS) et structurales (DRX) montrent que cet accroissement des cinétiques d'oxydation à 900°C est dû à la formation d'alumine de transition ( θ ou δ). La transition peut être supprimée en combinant un état de surface sablé (aluminiures) ou rectifié (MCrAlY) et une oxydation sous vide primaire d'air (10 Pa)

Evolution of sex chromosomes prior to speciation in the dioecious Phoenix species

International audienceUnderstanding the driving forces and molecular processes underlying dioecy and sex chromosome evolution, leading from hermaphroditism to the occurrence of male and female individuals, is of considerable interest in fundamental and applied research. The genus Phoenix, belonging to the Arecaceae family, consists uniquely of dioecious species. Phylogenetic data suggest that the genus Phoenix has diverged from a hermaphroditic ancestor which is also shared with its closest relatives. We have investigated the cessation of recombination in the sex-determination region within the genus Phoenix as a whole by extending the analysis of P. dactylifera SSR sex-related loci to eight other species within the genus. Phylogenetic analysis of a date palm sex-linked PdMYB1 gene in these species has revealed that sex-linked alleles have not clustered in a species-dependent way but rather in X and Y-allele clusters. Our data show that sex chromosomes evolved from a common autosomal origin before the diversification of the extant dioecious species

Investigation of the endogenous Na+-pump inhibitor in essential hypertension and blood volume expansion

The digitalis-like activities of plasma extracts from 108 patients and normal subjects were measured by their ability to compete with ouabain for binding to the digitalis sites of the Na+-pump. High levels were found in 18 of 54 untreated patients with moderate hypertension, 10 of 14 patients with end-stage renal failure and six patients with active acromegaly. These levels returned to control values after dialysis in the patients with renal insufficiency and high levels of the inhibitor, and after successful surgery and cobalt therapy in seven acromegalic patients. An increase in circulating Na+, K+-ATPase inhibitor was also found in rats after chronic sodium loading. These results indicate that levels of the circulating compound with digitalis-like properties do not result from high blood pressure but, rather, are related to blood volume and Na+ balance

The Casuarina NIN gene is transcriptionally activated throughout Frankia root infection as well as in response to bacterial diffusible signals

Root nodule symbioses (RNS) allow plants to acquire atmospheric nitrogen by establishing an intimate relationship with either rhizobia, the symbionts of legumes or Frankia in the case of actinorhizal plants. In legumes, NIN (Nodule INception) genes encode key transcription factors involved in nodulation. Here we report the characterization of CgNIN, a NIN gene from the actinorhizal tree Casuarina glauca using both phylogenetic analysis and transgenic plants expressing either ProCgNIN::reporter gene fusions or CgNIN RNAi constructs. We have found that CgNIN belongs to the same phylogenetic group as other symbiotic NIN genes and CgNIN is able to complement a legume nin mutant for the early steps of nodule development. CgNIN expression is correlated with infection by Frankia, including preinfection stages in developing root hairs, and is induced by culture supernatants. Knockdown mutants were impaired for nodulation and early root hair deformation responses were severely affected. However, no mycorrhizal phenotype was observed and no induction of CgNIN expression was detected in mycorrhizas. Our results indicate that elements specifically required for nodulation include NIN and possibly related gene networks derived from the nitrate signalling pathways