Effects of additives and impurity on the adhesive behavior of the NiAl(110)/Al2O3 (0001) interface: An Ab Initio study

Using ab initio density functional theory (DFT), the adhesive behavior of NiAl(110)/Al2O3(0001) interface in thermal barrier coatings was systematically studied with an emphasis on the effects of alloying additives and impurity elements. To reveal possible atomic-scale mechanisms, the separations between certain atoms at the interface, the electron localization function (ELF), and the electron density of states (DOS) are thoroughly investigated. First, effects of individual elements such as S, Pt, and Cr, and reactive elements (REs) Hf, Zr, and Y, on the work of separation, W sep, of the interface were examined. As expected, the segregation of S to the interface significantly degrades the adhesion, while the substitution of Pt for Ni adjacent to the interface does not enhance the W sep. Cr and RE addition to the interface individually result in a considerable increase of W sep. Second, the addition of Pt, Hf, and Cr to the S containing interface is shown to mitigate the detrimental effect of sulfur to some extent. Co doping the interface with a selected combination of (Pt, Hf), (Pt, Cr), (Cr, Hf), (Cr, Y), (Hf, Y), and (Y, Zr) was implemented to probe possible synergistic interactions between elements on W sep. Synergistic effects are detected on increasing W sep for (Hf, Y), (Hf, Zr) combinations. Co doping the interface with (Cr, Y) and (Cr, Hf), however, is found to weaken the adhesion. Through a detailed analysis of electronic structures in terms of ELF and DOS, four dominant bonds across the interface, RE-O, RE-Ni, Aloxide-Ni, and AlNiAl-O, are identified to play a decisive role in governing the adhesive strength of the interface. \ua9 2011 The Minerals, Metals & Materials Society and ASM International.Peer reviewed: YesNRC publication: Ye

Different antioxidant defense responses to salt stress during germination and vegetative stages of endemic halophyte Gypsophila oblanceolata Bark

Salinity is a major limiting factor to agricultural productivity. To ensure future productivity of the agricultural regions and achieve a selection of genetically transformed salt-tolerant plants, there is a need to select and characterize salt-tolerant plants. Gypsophila oblanceolata Bark. is a Turkish endemic and endangered halophyte occurring in salt marshes/hydromorphic soils. The aim of this experiment was to determine the responses of G. oblanceolata to salt stress during germination and vegetative growth. Therefore, effects of salinity (0, 50, 100, 150, 300mM NaCl) on germination and changes in the activities of antioxidant enzymes/isoenzymes (SOD, CAT and POX) during germination under stress and recovery after stress were determined. Moreover, during vegetative growth (60d old plants), changes in physiological parameters, ion concentrations, proline (Pro) content, lipid peroxidation (MDA), H 2O 2 content, NADPH oxidase activity and, antioxidant enzyme/isoenzyme system (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR)) were also investigated. Salt stress decreased both the germination percentage and rate. Few seeds germinated at 100mM NaCl. Exposure to high concentrations of NaCl did not permanently inhibit germination. Salinity (50mM NaCl) caused a decrease in activities of SOD, CAT and POX during germination. However, after stress, the activities of all enzymes were increased in recovered-plants. During vegetative growth, increased activities of SOD, CAT and APX in 50 and 100mM NaCl treated-plants may help to avoid oxidative damage in G. oblanceolata. However, at higher doses, induced stimulation of the CAT, POX and GR was not sufficient to cope with the enhanced ROS production and MDA level. From the results obtained in present study, it can be suggested that G. oblanceolata is a moderately salt-tolerant species. Differential responses of antioxidant enzymes to salt stress during germination and vegetative growth suggested different antioxidant metabolism in G. oblanceolata. © 2011 Elsevier B.V.2010-FEN-067This work was supported by Ege University Research Foundation [ 2010-FEN-067 ]. The authors wish to thank Dr. Evren Yıldıztugay for providing G. oblanceolata seeds and his technical assistance on ICP-AES analyses. -

Naringenin induces tolerance to salt/osmotic stress through the regulation of nitrogen metabolism, cellular redox and ROS scavenging capacity in bean plants

The present study was conducted to uncover underlying possible effect mechanisms of flavonoid naringenin (Nar, 0.1–0.4 mM) in nitrogen assimilation, antioxidant response, redox status and the expression of NLP7 and DREB2A, on salt (100 mM NaCl) and osmotic-stressed (10% Polyethylene glycol, ?0.54 MPa) Phaseolus vulgaris cv. Yunus 90). Nar ameliorated salt/osmotic stresses-induced growth inhibition and improved the accumulation of proline, glycine betaine and choline. In response to stress, Nar increased endogenous content of nitrate (NO3?) and nitrite (NO2?) by regulating of nitrate reductase and nitrite reductase. Stress-triggered NH4+ was eliminated with Nar through increases in glutamine synthetase and glutamate synthase. After NaCl or NaCl + PEG exposure, Nar utilized the aminating activity of glutamate dehydrogenase in the conversion of NH4+. The stress-inducible expression levels of DREB2A were increased further by Nar, which might have affected stress tolerance of bean. Nar induced effectively the relative expression of NLP7 in the presence of the combination or alone of stress. Also, the impaired redox state by stress was modulated by Nar and hydrogen peroxide (H2O2) and TBARS decreased. Nar regulated the different pathways for scavenging of H2O2 under NaCl and/or PEG treatments. When Nar + NaCl exposure, the damage was removed by superoxide dismutase (SOD), catalase (CAT), POX (only at 0.1 mM Nar + NaCl) and AsA-GSH cycle. Under osmotic stress plus Nar, the protection was manifested by activated CAT and, glutathione S-transferase and the regeneration of ascorbate. 0.1 mM Nar could protect bean plant against salt/osmotic stresses, likely by regulating nitrogen assimilation pathways, improving expression levels of genes associated with tolerance mechanisms and modulating the antioxidant capacity and AsA-GSH redox-based systems. © 2020 Elsevier Masson SASAuthors were grateful to Bahri Dagdas International Agricultural Research Institute for providing the seeds of bean. We thank to Selcuk University Scientific Research Projects Coordinating Office (project number: 20401044) for financial support