Display omitted
•3% Al-addition to Ni-14Cr-9Co (wt.%) suppresses formation of Ni-rich oxides.•Ti-addition to Ni-14Cr-9Co-3Al significantly increases chromia scale growth.•5wt.% Ta added to ...Ni-14Cr-9Co-3Al promotes alumina scale formation.•Exposures in wet air increases growth of Ni-rich oxides compared to dry air.
Ni-14Cr-9Co (wt.%) based alloys with additions of Al, Ti and Ta were exposed in dry and wet (+20 vol.%H2O) air at 950 °C for up to 100 h and characterized with GD-OES and SEM/EDX. Ni-14Cr-9Co-alloy exhibited initially Cr2O3-scale formation followed by breakaway Ni-oxidation. 3%Al addition to Ni-14Cr-9Co stabilized the Cr2O3-scale and largely suppressed Ni-oxide formation. Ni-14Cr-9Co-3Al-5Ti formed a fast growing Cr2O3-scale attributed to p-type Ti-doping, but Ni-oxide formation was completely inhibited. 5%Ta addition to Ni-14Cr-9Co-3Al promoted formation of a thin alumina scale. Addition of H2O to the test gas increased growth of Ni-rich oxides and shortened time to breakaway for the Al-free alloy.
In the present paper the high temperature oxidation behavior of a free standing NiCoCrAlY coating produced by high-velocity atmospheric plasma spraying (HV-APS) is investigated and compared with that ...produced by conventional low pressure plasma spraying (LPPS). Isothermal thermogravimetric experiments at 1000 and 1100°C in synthetic air revealed a lower oxidation rate of the HV-APS than the LPPS coating. Both coatings formed oxide scales based on alpha alumina, however, in the LPPS coating incorporation of coarse mixed Y/Al-oxide pegs into the scale occurred, increasing the oxidation rate by providing short circuit paths for oxygen diffusion probably due to higher diffusivities in the mixed oxide and/or along the interfaces between mixed oxide and alumina. In the HV-APS coatings most of the yttrium was tied-up in sub-μm Y-containing oxide particles and only minor amounts of mixed Y/Al oxide precipitates were found in the alumina surface scale. Cyclic air oxidation tests at 1100°C revealed a lower oxidation rate and better scale adherence for the HV-APS coating.
The results thus show that HV-APS is a promising method for the processing of MCrAlY coatings. The specific yttrium distribution in form of fine oxide precipitates in the HV-APS material prevents the formation of deleterious Y-rich oxide pegs and promotes formation of a slowly growing, protective alumina scale with excellent adherence.
Mass change of free standing LPPS and HV-APS coating during oxidation at 1100°C and cross section images after 72h. Display omitted
•Oxidation behavior of CoNiCrAlY coating manufactured by HV-APS was investigated.•Freestanding HV-APS coating showed better oxidation resistance than LPPS specimens.•Different properties related to differences in yttrium incorporation in the scale•HV-APS is a promising method for depositing coatings on various types of components.
Aims. Most hot Jupiters are expected to spiral in toward their host stars because the angular momentum of the orbital motion is transferred to the stellar spin. Their orbits can also precess as a ...result of planet-star interactions. Calculations show that both effects might be detected for the very-hot exoplanet WASP-12 b using the method of precise transit-timing over a time span of about 10 yr. Methods. We acquired new precise light curves for 29 transits of WASP-12 b, spannning four observing seasons from November 2012 to February 2016. New mid-transit times, together with those from the literature, were used to refine the transit ephemeris and analyze the timing residuals. Results. We find that the transit times of WASP-12 b do not follow a linear ephemeris with a 5σ confidence level. They may be approximated with a quadratic ephemeris that gives a change rate in the orbital period of (−2.56 ± 0.40) × 10-2 s yr-1. The tidal quality parameter of the host star was found to be equal to 2.5 × 105, which is similar to theoretical predictions for Sun-like stars. We also considered a model in which the observed timing residuals are interpreted as a result of the apsidal precession. We find, however, that this model is statistically less probable than the orbital decay.
Summary Background The 2014 Zaire Ebola virus outbreak highlighted the need for a safe, effective vaccine with a rapid onset of protection. We report the safety and immunogenicity of the recombinant ...vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein vaccine (rVSV∆G-ZEBOV-GP) across a 6 log10 dose range in two sequential cohorts. Methods In this phase 1b double-blind, placebo-controlled, dose-response study we enrolled and randomly assigned healthy adults (aged 18–61 years) at eight study sites in the USA to receive a single injection of vaccine or placebo, administered by intramuscular injection. In cohort 1, participants were assigned to receive 3 × 103 , 3 × 104 , 3 × 105 , or 3 × 106 PFU doses of rVSV∆G-ZEBOV-GP or placebo. In cohort 2, participants were assigned to receive 3 × 106 , 9 × 106 , 2 × 107 , or 1 × 108 PFU doses of rVSV∆G-ZEBOV-GP or placebo. Participants were centrally allocated by the study statistician to vaccine groups or placebo through computer-generated randomisation lists. The primary safety outcome was incidence of adverse events within 14 days in the modified intention-to-treat population (all randomly assigned participants who received vaccine or placebo), and the primary outcome for immunogenicity was IgG ELISA antibody titres at day 28 in the per-protocol population. Surveillance was enhanced for arthritis and dermatitis through to day 56. This study is registered with ClinicalTrials.gov , number NCT02314923. Findings Between Dec 26, 2014, and June 8, 2015, 513 participants were enrolled and randomly assigned; one was not immunised because of unsuccessful phlebotomy. In cohort 1, 256 participants received vaccine (3 × 103 n=64, 3 × 104 n=64, 3 × 105 n=64, or 3 × 106 PFU n=64) and 74 received placebo. In cohort 2, 162 participants received vaccine (3 × 106 n=20, 9 × 106 n=47, 2 × 107 n=47, or 1 × 108 PFU n=48) and 20 received placebo. Most adverse events occurred in the first day after vaccination, and were mild to moderate in intensity, of a short duration, and more frequent at high vaccine doses (9 × 106 PFU and greater). At the 2 × 107 PFU dose (used in phase 3 trials), the most common local adverse events versus placebo within the first 14 days were arm pain (57·4% 27 of 47 vs 7·4% seven of 94) and local tenderness (59·6% 28 of 47 vs 8·5% eight of 94). The most common systemic adverse events at the 2 × 107 PFU dose versus placebo, occurring in the first 14 days, were headache (46·8% 22 of 47 vs 27·7% 26 of 94), fatigue (38·3% 18 of 47 vs 19·1% 18 of 94), myalgia (34·0% 16 of 47 vs 10·6% 10 of 94), subjective fever (29·8% 14 of 47 vs 2·1% two of 94), shivering or chills (27·7% 13 of 47 vs 7·4% seven of 94), sweats (23·4% 11 of 47 vs 3·2% three of 94), joint aches and pain (19·1% nine of 47 vs 7·4% seven of 94), objective fever (14·9% seven of 47 vs 1·1% one of 94), and joint tenderness or swelling (14·9% seven of 47 vs 2·1% two of 94). Self-limited, post-vaccination arthritis occurred in 4·5% (19 of 418) of vaccinees (median onset 12·0 days IQR 10–14; median duration 8·0 days 6–15) versus 3·2% (three of 94) of controls (median onset 15·0 days 6–20; median duration 47·0 days 37–339), with no apparent dose relationship. Post-vaccination dermatitis occurred in 5·7% (24 of 418) of vaccinees (median onset 9·0 days IQR 2–12; median duration 7·0 days 4–9) versus 3·2% (three of 94) of controls (median onset 5·0 days 3–53; median duration 33·0 days 5–370). A low-level, transient, dose-dependent viraemia occurred in concert with early reactogenicity. Antibody responses were observed in most participants by day 14. IgG and neutralising antibody titres were dose-related (p=0·0003 for IgG ELISA and p<0·0001 for the 60% plaque-reduction neutralisation test PRNT60 by linear trend). On day 28 at the 2 × 107 PFU dose, the geometric mean IgG ELISA endpoint titre was 1624 (95% CI 1146–2302) and seroconversion was 95·7% (95% CI 85·5–98·8); the geometric mean neutralising antibody titre by PRNT60 was 250 (176–355) and seroconversion was 95·7% (85·5–98·8). These robust immunological responses were sustained for 1 year. Interpretation rVSV∆G-ZEBOV-GP was well tolerated and stimulated a rapid onset of binding and neutralising antibodies, which were maintained through to day 360. The immunogenicity results support selection of the 2 × 107 PFU dose. Funding Biomedical Advanced Research and Development Authority, US Department of Health and Human Services.
Atmospheric CO2 enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, ...or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO2 enrichment, with an emphasis on water relations. Increasing CO2 led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO2 enrichment were relatively greater in dry years. In contrast, CO2-induced aboveground biomass increases in the Texas C3/C4 grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO2 in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO2-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO2 were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO2 on plant and soil water relations may contribute substantially to experimentally induced CO2-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO2 effects on photosynthesis and those indirect CO2 effects via soil moisture as documented here.
To validate and clinically evaluate autocontouring using atlas-based autosegmentation (ABAS) of computed tomography images.
The data from 10 head-and-neck patients were selected as input for ABAS, ...and neck levels I-V and 20 organs at risk were manually contoured according to published guidelines. The total contouring times were recorded. Two different ABAS strategies, multiple and single subject, were evaluated, and the similarity of the autocontours with the atlas contours was assessed using Dice coefficients and the mean distances, using the leave-one-out method. For 12 clinically treated patients, 5 experienced observers edited the autosegmented contours. The editing times were recorded. The Dice coefficients and mean distances were calculated among the clinically used contours, autocontours, and edited autocontours. Finally, an expert panel scored all autocontours and the edited autocontours regarding their adequacy relative to the published atlas.
The time to autosegment all the structures using ABAS was 7 min/patient. No significant differences were observed in the autosegmentation accuracy for stage N0 and N+ patients. The multisubject atlas performed best, with a Dice coefficient and mean distance of 0.74 and 2 mm, 0.67 and 3 mm, 0.71 and 2 mm, 0.50 and 2 mm, and 0.78 and 2 mm for the salivary glands, neck levels, chewing muscles, swallowing muscles, and spinal cord-brainstem, respectively. The mean Dice coefficient and mean distance of the autocontours vs. the clinical contours was 0.8 and 2.4 mm for the neck levels and salivary glands, respectively. For the autocontours vs. the edited autocontours, the mean Dice coefficient and mean distance was 0.9 and 1.6 mm, respectively. The expert panel scored 100% of the autocontours as a "minor deviation, editable" or better. The expert panel scored 88% of the edited contours as good compared with 83% of the clinical contours. The total editing time was 66 min.
Multiple-subject ABAS of computed tomography images proved to be a useful novel tool in the rapid delineation of target and normal tissues. Although editing of the autocontours is inevitable, a substantial time reduction was achieved using editing, instead of manual contouring (180 vs. 66 min).
In the present work it is shown that the lifetime of air plasma sprayed thermal barrier coatings systems with high velocity oxyfuel bondcoats can be substantially extended by application of a thin ...air plasma sprayed “flashcoat” layer onto the base, high velocity oxyfuel bondcoat. This approach allows improvement of the bondcoat roughness profile to the extent typically obtained by optimized vacuum plasma spraying. The oxidation resistance of the flashcoat strongly depends on the spray parameters used. Deviation from the set of the optimized spray parameters was found to result in early catastrophic oxidation of the flashcoat and corresponding very rapid thermal barrier coating-failure. In order to explain the thermal barrier coating lifetime variations between the various bondcoat morphologies, the roughness profiles of high velocity oxyfuel, vacuum plasma sprayed and air plasma sprayed bondcoats were evaluated using fractal analysis. It is suggested that such an approach provides better correlation between the bondcoat morphology and thermal barrier coating-lifetime than the calculation of the arithmetic mean roughness (Ra) of the bondcoat frequently used in industrial practice.
•The effect of bondcoat roughness profile on APS–TBC-life studied•Optimized APS-flashcoat over HVOF-bondcoat extends TBC-life by factor of 3.•Similar TBC life with optimized APS-flashcoat and LPPS bondcoat•Oxidation resistance of APS-flashcoat sensitive to spraying parameters
•IHTC between Ni-based alloys and ceramic mold was calculated by inverse method.•IHTC decreases from 7962Wm−2K−1 to of 1425Wm−2K−1 during solidification.•Increase of IHTC was observed at final stage ...of solidification of casting.•Effect of thermophysical parameters of mold on cooling rate of casting was determined.•Formation mechanism of interface thermal resistance taking into account oxide scale was proposed.
The study of thermal resistance (TR) at the casting-mold interface has been performed to describe the solidification process aimed at the improvement of technology and the reduction of defect quantity of investment castings. The analysis of thermal resistance at casting–mold interface between the solidifying IN 713C nickel superalloy plate casting and ceramic shell mold has been presented. The temperature measurements in the plate casting of IN 713C nickel superalloy and the ceramic shell mold were carried out to determine the casting–mold interface heat transfer coefficient (IHTC) with the use of inverse heat conduction method. The calculations were performed using a ProCAST software. It was found that the casting–mold IHTC (7962Wm−2K−1) was the highest for the alloy in the liquid state and then it intensively decreased during solidification and cooling followed by its increase close to the end of the solidification process forming another peak on the obtained curve. The formation mechanism of gap between the ceramic mold and Ni based superalloy casting as well as another peak were proposed taking into account the occurrence of mixed oxide scale at the interface. On the basis of numerical simulation, it was found that the IHTC had less influence on cooling rate of casting than the thickness, thermal conductivity and emissivity of the mold for the applied technological parameters of the process.
PDF
