In-site mineral geochemistry and whole-rock Fe isotopes of the quartz-magnetite-pyroxene rocks in the Wuyang area, North China Craton: Constraints on the genesis of the pyroxene-rich BIF

Quartz-magnetite-pyroxene (QMP) rocks with high Fe contents are of greatly economic and petrological importance and generally occur within the oldest and largest exposures of supracrustal rocks preserved on Earth. However, the chemical composition and genesis of QMP rocks remain unclear. To constrain the protolith and genesis, we present new whole-rock geochemistry and Fe isotopic data, mineral EPMA and LA-ICP-MS analysis and X-ray mapping for the QMP rocks in the Wuyang area, North China Craton. The Wuyang QMP rocks have undergone high-temperature metamorphism and have special mineral assemblages with coexisting magnetite, quartz, clinopyroxene and variable orthopyroxene. Pyroxenes of the Wuyang QMP rocks show very distinct major, trace and rare earth element (REE) compositions from those of the nearby pyroxene-marbles and pyroxenite intrusions. Such difference excludes a contact metamorphic origin for pyroxenes of the QMP rocks. X-ray elemental mapping suggests that Fe-poor carbonate minerals (dolomite and calcite) and quartz inclusions are well preserved in these pyroxene grains and no reaction phenomenon can be observed between them, indicating that these pyroxenes are not the product of metamorphic decarbonation reactions of pre-existing sedimentary silica and Fe-rich carbonate phase. Shale-normalized REE + Y patterns of the whole-rock samples and pyroxenes display geochemical features consistent with classic banded iron formations (BIFs), which show light REE depletion, positive La-SN, Eu-SN and Y-SN anomalies. This indicates that the geochemical features are compositionally inherited from their original pure chemical sediments. The Wuyang QMP rocks are therefore considered as pyroxene-rich BIF. Neotocite and hisingerite inclusions in pyroxene grains from the QMP rocks could be metamorphic products of some early Fe- and Mn-rich silicates before pyroxene. Moreover, the Wuyang QMP rocks are enriched in light iron isotopes similar to other Fe- and Ca-rich minerals in Archean BIFs. Therefore, we inferred that pyroxene from the QMP rocks could result from dehydration of initial sedimentary hydrous Ca-, Mg- and Mn-containing Fe(II)-silicate gel during diagenesis and re-crystallization in later metamorphism, providing a new interpretation for the origin of pyroxene-rich BIF

Spatial Dynamics of a Leslie–Gower Type Predator-Prey Model with Interval Parameters

Due to various imprecisions in nature, imprecise parameters in biological modeling should be taken into account. This paper studies the spatial dynamics of an imprecise prey-predator model of the Leslie–Gower type by presenting imprecise parameters as interval parameters. First, conditions of Turing instability are obtained via bifurcation analysis and interval-valued functions. Then, the effects of interval parameters on pattern selection are discussed via multiple-scale analysis. We discover that when all the parameters of the model are interval parameters, the value of the controlled parameter increases, and the range of the pattern selection domain expands as the value of the interval variable increases, i.e., both the controlled parameter and boundary of the pattern selection domain are interval numbers. Finally, under the effects of the interval parameters of diffusion and the prey’s conversion rate into biomass for the predator, the density of the prey decreases or increases, respectively, and the structure or the microstructure of the pattern of the model changes with the growing value of the interval variable. This paper provides a new perspective on the study of the spatial predator-prey model

Geochemistry, U-Pb zircon geochronology and Sm-Nd isotopes of the Xincai banded iron formation in the southern margin of the North China Craton: Implications on Neoarchean seawater compositions and solute sources

Banded iron formations (BIFs) that are distal from submarine volcanic activity and generally lack direct relationships with volcanic rocks have been extensively used as proxies to infer the chemical composition of ancient seawater and trace the effects of continental weathering at the time of their deposition. Here, we discuss the major and trace elements and Sm-Nd isotopic geochemistry of the poorly-studied Xincai BIF, located west of the Superior-type Huoqiu BIF along a NW-SE trending supracrustal belt in the southern margin of the North China Craton, to understand the compositions and solute sources of seawater during the Xincai BIF precipitation. U-Pb zircon dating of granitic intrusive rock and biotite schist interlayer of the BIF constrains the depositional age of the Xincai BIF to 2.5-2.7 Ga for the first time, indicating that the Xincai BIF could be part of the Huoqiu BIF or consist of contemporaneous sediments formed in a similar tectonic-depositional environment. Shale normalized rare earth element and yttrium (REY) patterns of the bulk and individual band samples display features that are characteristic of other Archean BIFs with light REE depletion relative to heavy REE, positive La-SN, Gd-SN and Y-SN anomalies, indicative of pure chemical sedimentation. The marine origin of these samples is further supported by their super-chondritic Y/Ho ratios (average Y/Ho = 47). The very low Al, Ti and high field strength element contents of the Xincai BIF indicate an essentially detritus-free component. The bulk BIF samples show a narrow range of epsilon(Nd)(t) values from -1.5 to + 1.0, and most of the samples have negative epsilon(Nd)(t) values, - 0.3 on average, which is different from Archean BIFs with mantle-derived depleted Nd isotopes. Deviations toward negative epsilon(Nd)(t) values of the iron bands (-0.5 to -0.1) and the silica bands (- 4.7 to - 0.5) further indicate a continental Nd contribution. In addition, positive Eu-SN anomalies that were found in all of the bulk and individual band samples indicate that a high-T hydrothermal input also contributed to their REY signatures. It is considered that both high-T hydrothermal fluids and ambient seawater with solutes from erosion and weathering of a nearby landmass can provide their REY signatures

Trace elemental modification in magnetite from high-grade metamorphosed BIFs in the southern North China Craton

Magnetite, as a common oxide mineral in banded iron formations (BIFs) and ore deposits, is an ideal provenance indicator for mineral exploration, and its composition has long been used for genetic studies of ore deposits. However, many ore deposits, particularly the BIFs worldwide, have undergone various grades of secondary metamorphism or hydrothermal alteration. It is still unclear whether the original magnetite composition was modified during the secondary processes and, if so, to what extent the compositions were modified. In this study, we conduct mineralogical and LA-ICP-MS trace elemental investigations on magnetite from the amphibolite- to granulite-facies metamorphosed BIFs in the southern North China Craton. The new results were compared with those of unmetamorphosed and greenschist-facies metamorphosed BIFs worldwide to understand how the original composition of magnetite was modified during different grades of metamorphism. Magnetite grains from the amphibolite- to granulite-facies BIFs have low Cr, Co, Ni and Ga (less than 10 ppm) and slightly variable V and Zn. These elements do not show remarkable changes during high-grade metamorphism when compared with the unmetamorphosed and greenschist-facies metamorphosed magnetite, indicating that these elements in magnetite are immobile during metamorphism. A very narrow range of Fe2+/Fe3+ mole ratios of the high-grade metamorphosed magnetite roughly suggest limited changes of oxygen fugacity during metamorphism, which is also supported by the limited change of Cr and V contents. High Mn contents in these magnetite grains are associated with low Mg contents possibly due to the fact that these elements occupy the same site in magnetite structure. Compared with unmetamorphosed magnetite, the high-grade metamorphic magnetite in the BIFs of the southern North China Craton has elevated Al, Ti and Mn. Such a change of magnetite compositions is mainly controlled by coexisting Fe-Mg silicates that formed during high-grade metamorphism. For example, our new results of trace elemental mapping on magnetite show that the edge of magnetite grains that are in contact with Fe-Mg silicates (e.g., hornblende, grunerite and pyroxene) are remarkably enriched in Mg, Mn, Al, Si, and Na compared to the cores (some elements up to 10 times more). All these features indicate that elemental diffusion and exchange between magnetite and coexisting silicate minerals during high-grade metamorphism have extensively modified original compositions of magnetite from BIFs

Identification of Extracellular Actin As a Ligand for Triggering Receptor Expressed on Myeloid Cells-1 Signaling

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a potent amplifier of pro-inflammatory innate immune reactions, and it is an essential mediator of death in sepsis. However, the ligand for TREM-1 has not been fully identified. Previous research identified a natural ligand of TREM-1 distributed on platelets that contributed to the development of sepsis. However, the exact signal for TREM-1 recognition remains to be identified. Here, we identified actin as a TREM-1-interacting protein on platelets and found that recombinant actin could interact with recombinant TREM-1 extracellular domain directly. Furthermore, actin co-localized with TREM-1 on the surface of activated mouse macrophage RAW264.7 cells interacting with platelets. In addition, recombinant actin could enhance the inflammatory response of macrophages from wt mice but not from trem1−/− mice, and the enhancement could be inhibited by LP17 (a TREM-1 inhibitor) in a dose-dependent manner. Importantly, extracellular actin showed co-localization with TREM-1 in lung tissue sections from septic mice, which suggested that TREM-1 recognized actin during activation in sepsis. Therefore, the present study identified actin as a new ligand for TREM-1 signaling, and it also provided a link between both essential regulators of death in sepsis

Controllable Synthesis of N₂-Intercalated WO₃ Nanorod Photoanode Harvesting a Wide Range of Visible Light for Photoelectrochemical Water Oxidation

A highly efficient visible-light-driven photoanode, N2-intercalated tungsten trioxide (WO3) nanorod, has been controllably synthesized by using the dual role of hydrazine (N2H4), which functioned simultaneously as a structure directing agent and as a nitrogen source for N2 intercalation. The SEM results indicated that the controllable formation of WO3 nanorod by changing the amount of N2H4. The β values of lattice parameters of the monoclinic phase and the lattice volume changed significantly with the nW: nN2H4 ratio. This is consistent with the addition of N2H4 dependence of the N content, clarifying the intercalation of N2 in the WO3 lattice. The UV-visible diffuse reflectance spectra (DRS) of N2-intercalated exhibited a significant redshift in the absorption edge with new shoulders appearing at 470–600 nm, which became more intense as the nW:nN2H4 ratio increased from 1:1.2 and then decreased up to 1:5 through the maximum at 1:2.5. This addition of N2H4 dependence is consistent with the case of the N contents. This suggests that N2 intercalating into the WO3 lattice is responsible for the considerable red shift in the absorption edge, with a new shoulder appearing at 470−600 nm owing to formation of an intra-bandgap above the VB edges and a dopant energy level below the CB of WO3. The N2 intercalated WO3 photoanode generated a photoanodic current under visible light irradiation below 530 nm due to the photoelectrochemical (PEC) water oxidation, compared with pure WO3 doing so below 470 nm. The high incident photon-to-current conversion efficiency (IPCE) of the WO3-2.5 photoanode is due to efficient electron transport through the WO3 nanorod film

Survivin Improves Reprogramming Efficiency of Human Neural Progenitors by Single Molecule OCT4

Induced pluripotent stem (iPS) cells have been generated from human somatic cells by ectopic expression of four Yamanaka factors. Here, we report that Survivin, an apoptosis inhibitor, can enhance iPS cells generation from human neural progenitor cells (NPCs) together with one factor OCT4 (1F-OCT4-Survivin). Compared with 1F-OCT4, Survivin accelerates the process of reprogramming from human NPCs. The neurocyte-originated induced pluripotent stem (NiPS) cells generated from 1F-OCT4-Survivin resemble human embryonic stem (hES) cells in morphology, surface markers, global gene expression profiling, and epigenetic status. Survivin keeps high expression in both iPS and ES cells. During the process of NiPS cell to neural cell differentiation, the expression of Survivin is rapidly decreased in protein level. The mechanism of Survivin promotion of reprogramming efficiency from NPCs may be associated with stabilization of β-catenin in WNT signaling pathway. This hypothesis is supported by experiments of RT-PCR, chromatin immune-precipitation, and Western blot in human ES cells. Our results showed overexpression of Survivin could improve the efficiency of reprogramming from NPCs to iPS cells by one factor OCT4 through stabilization of the key molecule, β-catenin