Crystal chemistry and compressibility of Fe0.5Mg0.5Al0.5Si0.5O3 and FeMg0.5Si0.5O3 silicate perovskites at pressures up to 95 GPa

Silicate perovskite, with the mineral name bridgmanite, is the most abundant mineral in the Earth’s lower mantle. We investigated crystal structures and equations of state of two perovskite-type Fe3+-rich phases, FeMg0.5Si0.5O3 and Fe0.5Mg0.5Al0.5Si0.5O3, at high pressures, employing single-crystal X-ray diffraction and synchrotron Mössbauer spectroscopy. We solved their crystal structures at high pressures and found that the FeMg0.5Si0.5O3 phase adopts a novel monoclinic double-perovskite structure with the space group of P21/n at pressures above 12 GPa, whereas the Fe0.5Mg0.5Al0.5Si0.5O3 phase adopts an orthorhombic perovskite structure with the space group of Pnma at pressures above 8 GPa. The pressure induces an iron spin transition for Fe3+ in a (Fe0.7,Mg0.3)O6 octahedral site of the FeMg0.5Si0.5O3 phase at pressures higher than 40 GPa. No iron spin transition was observed for the Fe0.5Mg0.5Al0.5Si0.5O3 phase as all Fe3+ ions are located in bicapped prism sites, which have larger volumes than an octahedral site of (Al0.5,Si0.5)O6

Determination of phase relations of the olivine-ahrensite transition in the Mg2SiO4−Fe2SiO4Mg_{2}SiO_{4}-Fe_{2}SiO_{4} system at 1740 K using modern multi-anvil techniques

The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments; however, the transition pressures contained significant uncertainties. Here we determined the binary loop of the olivine–ahrensite transition in the (Mg,Fe)$_2$SiO$_4$ system at 1740 K in the pressure range of 7.5–11.2 GPa using a multi-anvil apparatus with the pressure determined using in situ X-ray diffraction, compositional analysis of quenched run products, and thermochemical calculation. Based on the determined binary loop, a user-friendly software was developed to calculate pressure from the coexisting olivine and ahrensite compositions. The software is used to estimate the shock conditions of several L6-type chondrites. The obtained olivine–ahrensite phase relations can also be applied for precise in-house multi-anvil pressure calibration at high temperatures

Typing of the Gut Microbiota Community in Japanese Subjects

Gut microbiota are involved in both host health and disease and can be stratified based on bacteriological composition. However, gut microbiota clustering data are limited for Asians. In this study, fecal microbiota of 1803 Japanese subjects, including 283 healthy individuals, were analyzed by 16S rRNA sequencing and clustered using two models. The association of various diseases with each community type was also assessed. Five and fifteen communities were identified using partitioning around medoids (PAM) and the Dirichlet multinominal mixtures model, respectively. Bacteria exhibiting characteristically high abundance among the PAM-identified types were of the family Ruminococcaceae (Type A) and genera Bacteroides, Blautia, and Faecalibacterium (Type B); Bacteroides, Fusobacterium, and Proteus (Type C); and Bifidobacterium (Type D), and Prevotella (Type E). The most noteworthy community found in the Japanese subjects was the Bifidobacterium-rich community. The odds ratio based on type E, which had the largest population of healthy subjects, revealed that other types (especially types A, C, and D) were highly associated with various diseases, including inflammatory bowel disease, functional gastrointestinal disorder, and lifestyle-related diseases. Gut microbiota community typing reproducibly identified organisms that may represent enterotypes peculiar to Japanese individuals and that are partly different from those of indivuals from Western countries

Extreme Conditions Research Using the Large Volume Press at the P61B End Station, PETRA III.

Penetrating, high-energy synchrotron X-rays are strongly in demand, particularly for high-pressure research in physics, chemistry, and geosciences and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the end-station P61B. In detail, particular attention is given to the unprecedented high-energy photon flux delivered by the 10 wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world’s first 6-ram, Hall-type LVP called ‘Aster-15’ at a synchrotron facility is described for research with synchrotron X-rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy-dispersive X-ray diffraction and radiography techniques are presented

DataSheet1_Crystal chemistry and compressibility of Fe0.5Mg0.5Al0.5Si0.5O3 and FeMg0.5Si0.5O3 silicate perovskites at pressures up to 95 GPa.pdf

Silicate perovskite, with the mineral name bridgmanite, is the most abundant mineral in the Earth’s lower mantle. We investigated crystal structures and equations of state of two perovskite-type Fe3+-rich phases, FeMg0.5Si0.5O3 and Fe0.5Mg0.5Al0.5Si0.5O3, at high pressures, employing single-crystal X-ray diffraction and synchrotron Mössbauer spectroscopy. We solved their crystal structures at high pressures and found that the FeMg0.5Si0.5O3 phase adopts a novel monoclinic double-perovskite structure with the space group of P21/n at pressures above 12 GPa, whereas the Fe0.5Mg0.5Al0.5Si0.5O3 phase adopts an orthorhombic perovskite structure with the space group of Pnma at pressures above 8 GPa. The pressure induces an iron spin transition for Fe3+ in a (Fe0.7,Mg0.3)O6 octahedral site of the FeMg0.5Si0.5O3 phase at pressures higher than 40 GPa. No iron spin transition was observed for the Fe0.5Mg0.5Al0.5Si0.5O3 phase as all Fe3+ ions are located in bicapped prism sites, which have larger volumes than an octahedral site of (Al0.5,Si0.5)O6.</p

Depressed 660-km discontinuity caused by akimotoite-bridgmanite transition

The 660-km seismic discontinuity is the boundary between the Earth’s lower mantle and transition zone and is commonly interpreted as the dissociation of ringwoodite to bridgmanite plus ferropericlase (post-spinel transition)1-3. A distinct feature of the 660-km discontinuity is its depression to 750 km beneath subduction zones4-10. However, in situ X-ray diffraction studies using multianvil techniques have demonstrated negative but gentle Clapeyron slopes of the post-spinel transition that do not allow a significant depression11-13. On the other hand, conventional high-pressure experiments face difficulties in accurate phase identification due to inevitable pressure changes during heating and the persistent presence of metastable phases1,3. Here, we determined the post-spinel and akimotoite-bridgmanite transition boundaries by multi-anvil experiments using in situ X-ray diffraction strictly based on the definition of phase equilibrium. The post-spinel boundary has almost no temperature dependence, whereas the akimotoite–bridgmanite transition has a very steep negative boundary at temperatures lower than ambient mantle geotherms. The large depressions of the 660-km discontinuity in cold subduction zones are thus interpreted as the akimotoite–bridgmanite transition. The steep negative boundary of the akimotoite-bridgmanite transition will cause slab stagnation due to significant upward buoyancy14,15

Macrophage hypoxia signaling regulates cardiac fibrosis via Oncostatin M

The fibrogenic response in tissue-resident fibroblasts is determined by the balance between activation and repression signals from the tissue microenvironment. While the molecular pathways by which transforming growth factor-1 (TGF-β1) activates pro-fibrogenic mechanisms have been extensively studied and are recognized critical during fibrosis development, the factors regulating TGF-β1 signaling are poorly understood. Here we show that macrophage hypoxia signaling suppresses excessive fibrosis in a heart via oncostatin-m (OSM) secretion. During cardiac remodeling, Ly6Chi monocytes/macrophages accumulate in hypoxic areas through a hypoxia-inducible factor (HIF)-1α dependent manner and suppresses cardiac fibroblast activation. As an underlying molecular mechanism, we identify OSM, part of the interleukin 6 cytokine family, as a HIF-1α target gene, which directly inhibits the TGF-β1 mediated activation of cardiac fibroblasts through extracellular signal-regulated kinase 1/2-dependent phosphorylation of the SMAD linker region. These results demonstrate that macrophage hypoxia signaling regulates fibroblast activation through OSM secretion in vivo