Effect of Zr on the Oxidation Properties of Fe3Al Intermetallic Compound

This review is concerned with the effect of the addition of zirconium as a third element on the heat-resisting properties of Fe_3Al intermetallic compounds and explains their high-temperature oxidation mechanism.The Fe_3Al and Fe_3Al-0.05Zr specimens were isothermally oxidized in the temperature range of 1173～1473 K in synthetic air for 100 h.The formation of the alumina layer approximately obeyed the parabolic rate law,with the exception of short initial stage.The parabolic rate constant values for the Zr-doped Fe_3Al decreased at all tested temperatures.Fe_3Al revealed massive spallation,whereas Fe_3AlZr produced a flat,adherent oxide layer.The microstructure investigations of the alumina scales grown thermally on the Fe_3Al-Zr alloy by means of SEM-EDS showed that they were 1.5～2μm thick and consisted of a small inner columnar layer and an equiaxed outer grain layer.Additionally,very fine(50～150 nm) oxide particles rich in Zr were found across the alumina scales.The addition of Zr significantly affected the oxidation behavior of Fe_3Al by improving the adherence of theα-Al_2O_3 scale.TEM-SAD investigations of the alumina scales on samples prepared using the FIB(Focused Ion Beam) method confirmed the presence of small tetragonal zirconia grains near the scale/gas and alloy/scale interfaces,most of which were formed along alumina grain boundaries(gbs).Zr gb-segregation was found using HRTEM.The role of preferential formation of zirconium oxide along the alumina scale grain boundaries and the effect of Zr gb-segregation on oxidation and scale growth mechanisms were analyzed by means of two-stage oxidation experiments using ^(16)O_2/^(18)O_2.The SIMS oxygen isotope profiles for the Fe_3Al-Zr alloy oxidized at 1373 K, after two-stage oxidation experiments,revealed that oxygen anion diffusion is predominant compared to that of aluminum cation diffusion.

^(57)Fe Mössbauer spectrometry: A powerful technique to analyze the magnetic and phase characteristics in RE–Fe–B permanent magnets

This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.

Deciphering the Role of Klf10 in the Cerebellum

Recent studies have demonstrated a new role for Klf10, a Krüppel-like transcription factor, in skeletal muscle, specifically relating to mitochondrial function. Thus, it was of interest to analyze additional tissues that are highly reliant on optimal mitochondrial function such as the cerebellum and to decipher the role of Klf10 in the functional and structural properties of this brain region. In vivo (magnetic resonance imaging and localized spectroscopy, behavior analysis) and in vitro (histology, spectroscopy analysis, enzymatic activity) techniques were applied to comprehensively assess the cerebellum of wild type (WT) and Klf10 knockout (KO) mice. Histology analysis and assessment of locomotion revealed no significant difference in Klf10 KO mice. Diffusion and texture results obtained using MRI revealed structural changes in KO mice characterized as defects in the organization of axons. These modifications may be explained by differences in the levels of specific metabolites (myo-inositol, lactate) within the KO cerebellum. Loss of Klf10 expression also led to changes in mitochondrial activity as reflected by a significant increase in the activity of citrate synthase, complexes I and IV. In summary, this study has provided evidence that Klf10 plays an important role in energy production and mitochondrial function in the cerebellum.

Diabetes and pulmonary infection:how hyperglycaemia shapes the immune system

In a recent study published in Nature,Nobs and colleagues aimed to identify novel mechanisms that may explain why diabetes is associated with an increased susceptibility to viral respiratory infections.Their analyses revealed a central role of lung dendritic cells(DC)which exhibited several functional defects induced by hyperglycaemia and consequently result in impaired antiviral immune responses.

Grain boundary construction and properties enhancement for hot deformed(Ce,La,Y)-Fe-B magnet by a two-step diffusion process

The rare earth-iron-boron magnets based on high abundance rare earths(REs)show potential for costeffective permanent magnets but their hard magnetic properties have to be greatly improved.The grain boundary diffusion process(GBDP)is known as an effective way to improve the coercivity of Nd-Fe-B magnets,however,the conventional diffusion method faces a challenge for Ce-based magnets since there is no enough continuous GB layer as the diffusion channel.Here,a two-step(Nd-Cu doping followed by Nd-Cu diffusion)GBDP was introduced for hot deformed(Ce,La,Y)-Fe-B magnet,and the excellent magnetic properties ofμ0Hc=0.63 T,μ0Mr=0.68 T,and(BH)max=72.4 kJ/m^(3)were achieved.The Nd-Cu doping helps the formation of RE-rich GB layer,and then it acts as the diffusion channel for increasing the ef-ficiency of the subsequent Nd-Cu diffusion and results in the increased volume fraction of continuously distributed GB phase,whose paramagnetism was verified by 57Fe Mössbauer spectrometry.Those paramagnetic GB phases help to form the discontinuous domain walls,as observed by Lorentz transmission electron microscopy,and break the magnetic exchange coupling of RE2Fe14B grains.It thus contributes to the coercivity enhancement of the hot deformed magnet with two-step diffusion,which is further proved by micromagnetic simulation.This study proposes a potential technique to prepare anisotropic hot deformed(Ce,La,Y)-Fe-B magnet with high cost-performance.

Effects of meteorological conditions and topography on the bioaccumulation of PAHs and metal elements by native lichen(Xanthoria parietina)

The bioaccumulation of PAHs and metal elements in the indigenous lichens Xanthoria parietina was monitored during two years at a quarterly frequency,in 3 sites of contrasted anthropic influence.The impact of the meteorological factors(temperature,relative humidity,rainfall,wind speed)was first estimated through principal component analysis,and then by stepwise multilinear regressions to include wind directions.The pollutants levels reflected the proximity of atmospheric emissions,in particular from a large industrial harbor.High humidity and mild temperatures,and in a lower extent low wind speed and rainfall,also favored higher concentration levels.The contributions of these meteorological aspects became minor when including wind direction,especially when approaching major emission sources.The bioaccumulation integration time towards meteorological variations was on a seasonal basis(1–2 months)but the wind direction and thus local emissions also relied on a longer time scale(12 months).This showed that the contribution of meteorological conditions may be prevalent in remote places,while secondary in polluted areas,and should be definitely taken into account regarding long-term lichen biomonitoring and inter-annual comparisons.In the same time,a quadruple sampling in each site revealed a high homogeneity among supporting tree species and topography.The resulting uncertainty,including sampling,preparation and analysis was below 30%when comfortable analytical conditions were achieved.Finally,the occurrence of unexpected events such as a major forest fire,permitted to evaluate that this type of short,although intense,events did not have a strong influence on PAH and metals bioaccumulation by lichen.

A common metabolomic signature is observed upon inoculation of rice roots with various rhizobacteria

Plant growth-promoting rhizobacteria(PGPR),whose growth is stimulated by root exudates,are able to improve plant growth and health.Among those,bacteria of the genus Azospirillum were shown to affect root secondary metabolite content in rice and maize,sometimes without visible effects on root architecture.Transcriptomic studies also revealed that expression of several genes involved in stress and plant defense was affected,albeit with fewer genes when a strain was inoculated onto its original host cultivar.Here,we investigated,via a metabolic profiling approach,whether rice roots responded differently and with gradual intensity to various PGPR,isolated from rice or not.A common metabolomic signature of nine compounds was highlighted,with the reduced accumulation of three alkylresorcinols and increased accumulation of two hydroxycinnamic acid amides(HCAA),identified as N-p-coumaroylputrescine and N-feruloylputrescine.This was accompanied by the increased transcription of two genes involved in the N-feruloylputrescine biosynthetic pathway.Interestingly,exposure to a rice bacterial pathogen triggered a reduced accumulation of these HCAA in roots,a result contrasting with previous reports of increased HCAA content in leaves upon pathogen infection.Accumulation of HCAA,that are potential antimicrobial compounds,might be considered as a primary reaction of plant to bacterial perception.