Osteosarcoma is the most common primary bone malignancy. Recently, studies showed chemokine receptor 4 (CXCR4) played a critical role in osteosarcoma. However, the regulation of CXCR4 is not fully ...understood. microRNAs are short, non‐coding RNAs that play an important roles in post‐transcriptional regulation of gene expression in a variety of diseases including osteosarcoma. miR‐613 is a newly discovered miRNA and has been reported to function as a tumor suppressor in many cancers. In this study, we confirmed that both Stromal Cell‐Derived Factor (SDF‐1) and CXCR4 could be prognostic markers for osteosarcoma. Meanwhile this study found that SDF‐1/CXCR4 pathway regulated osteosarcoma cells proliferation, migration and reduced apoptosis. Besides, we demonstrated that miR‐613 was significantly downregulated in osteosarcoma patients. Elevated expression of miR‐613 directly suppressed CXCR4 expression and then decreased the proliferation, migration and induced apoptosis of osteosarcoma cells. Moreover, our study found that CXCR4 promoted the development of lung metastases and inhibition of CXCR4 by miR‐613 reduced lung metastases. These data indicated that CXCR4 mediated osteosarcoma cell growth and lung metastases and this effect can be suppressed by miR‐613 through directly downregulating CXCR4.
SDF‐1/CXCR4 pathway promoted osteosarcoma cells proliferation, migration, and reduced apoptosis. Elevated expression of miR‐613 directly suppressed CXCR4 expression and then decreased the proliferation, migration and induced apoptosis of osteosarcoma cells. CXCR4 promoted the development of lung metastases and inhibition of CXCR4 by miR‐613 reduced lung metastases.
The catalytic activity of natural vanadium–titanium magnetite was investigated in the decolorization of Acid Orange II by non-homogeneous Fenton process. The natural catalysts purified by magnetic ...separation were characterized using X-ray diffraction (XRD), polarizing microscope, X-ray absorption fine structure (XAFS) analysis and Mössbauer spectroscopy. The obtained results show that the natural samples after magnetic separation mainly contain titanomagnetite, with a small amount of ilmenite and chlorite. Titanomagnetite is doped with vanadium, whose the valency is mainly +3 and occupies the octahedral site. Batch decolorization studies were performed to evaluate the influences of various experimental parameters like initial pH, the amount of catalyst and initial concentration of hydrogen peroxide on the decolorization efficiency of Acid Orange II. The decolorization of the dye mainly relied on degradation. The degradation efficiency was strongly dependent on pH of the medium where it increased as the pH decreased in acid range. The increase of catalyst and hydrogen peroxide could accelerate the degradation. The catalytic property of natural vanadium–titanium magnetite in the degradation of Acid Orange II was stronger than that of synthetic magnetite (Fe
3O
4). The catalytic activity of the natural samples was greatly related to the titanomagnetite content. The degradation process was dominated by heterogeneous Fenton reaction, complying with pseudo-first-order rate law. The natural catalyst has a good catalytic stability.
Abstract Advances in crystal nucleation and growth over the past three decades have led to the understanding that crystallization proceeds through a variety of pathways, ranging from the conventional ...atom-by-atom model to the particle aggregation- or amorphous transformation-based non-classical modes. Here, we present a novel mineralization mechanism exemplified by a lunar chromite formed via solid-liquid interface reactions, through investigations towards a lunar breccia returned by the Chang'e 5 mission. The chromite occurs in the middle of a whisker-shaped intergrowth structure made by olivine at the bottom and nanospheres of troilite and metallic iron at the top. Morphological observation and size statistics of the nanospheres, including those within the whisker structure and the others dispersed in glass, suggest the nanophases attached to olivine with coherent crystallographic orientations, possibly through an oriented aggregation process. The chromium deficiency in the olivine near the interface between olivine and chromite suggests that Cr in chromite originated from olivine, but the significantly reduced ferrous concentration in the glass surrounding chromite indicates the iron was derived from surrounding impact-induced glass. Based on laboratory observations and simulated calculations of energy and lattice mismatch, we propose that chromite crystallized at the interface between troilite and olivine in the impact melts, during which the nanospheres were lifted up and transported away from olivine surface and form a mushroom-shaped structure. This finding suggests that oriented attachment growth, chiefly confined to homogeneous systems thus far, can also take place in heterogeneous systems far from equilibrium, such as that produced by the impacts. It is conceivable that the studied crystallization pathway occurring on the heterogeneous interfaces may have been a common mineralization mode at highly-nonequilibrium conditions.
The composition and microstructure of phyllosilicates are prone to transformation due to their great sensitivity to surrounding physicochemical changes. Berthierine (R
,R
,□)
(Si,Al)
(OH)8 (□ ...represents octahedral vacancy) is a typical ferromagnesian phyllosilicate that commonly occurs in ferruginous rocks of shallow-marine habitats and has been used as an indicator of local depositional and/or hydrothermal activity in marine environments. However, little is known about the formation and mineralogy of non-marine berthierine, particularly in volcanic systems. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), we have identified a berthierine twin structure within weakly altered biotite in a rhyolite from Long Valley, California, U.S.A. The presence of nanoscale Fe-rich layers in the host biotite is revealed by energy-dispersive spectroscopy and electron energy loss spectroscopy (EELS). The HAADF-STEM pictures with atomic resolution demonstrate that the Fe-rich layers are composed of twinning berthierine layers rather than a single chlorite layer. The transformation of biotite to berthierine requires the dissolution of a tetrahedral (T) layer and the introduction of a new TO (O represents octahedral sheet) structure into the biotite stacking sequence, resulting in substituting one biotite layer (i.e., TOT) with two twinning berthierine layers (i.e., TO-OT). Observations based on morphology indicate that the transformation began at biotite defect locations (such as screw dislocation, edge dislocation, and microcleavage fracture), concurrent with the rearrangement of metal cations. During the fluid alteration of biotite, berthierine was produced via an interface-coupled dissolution-reprecipitation process. The EELS analyses further demonstrate that the Fe-rich biotite promotes the production of berthierine as the principal alteration product in low-temperature environments. Additionally, this study suggests that the combination of HAADF-STEM and EELS is effective for identifying nanominerals and elucidating their formation and alteration mechanisms.
Sedimentary phosphorites enriched in rare earth elements (i.e., REE) are an important reservoir of these critical metals and may have the potential to resolve the global REE supply risk in the ...future, which is widely distributed around world. However, the occurrence and utilizability of REE in phosphorites remain contentious. In this study, multiple-scale analysis techniques were used to investigate the mineralogical and geochemical characteristics of typical REE-enriched phosphorites from Zhijin, SW China. The mineralization was divided into two stages: early fluorapatite (Fap1) that formed during the sedimentary–diagenetic stage, and late fluorapatite (Fap2) that formed during the hydrothermal alteration stage. The in situ REE geochemical data (i.e., quantitative data and mapping analysis) and scanning electron microscopy images show that Fap1 is the main REE host phase, because it is abundant and high REE concentration. Data obtained by both laser-ablation–inductively coupled plasma–mass spectrometry and high-resolution transmission electron microscopy reveal that most REE are resident in the lattice of nano-scale fluorapatite, which could be remobilized by hydrothermal fluids during the process of dissolution of nano-scale Fap1 and reprecipitation of micro-scale Fap2. In addition, the formation of synchysite-(Y) in the altered phosphorites involved reprecipitation of the mobilized REE. We suggest that F− and SO42− in fluids play a major role in the mobilization of REE in fluorapatite and that CO32− sourced from dolomite alteration contributes to the precipitation of REE. Our results indicate that REE in fluorapatite can be remobilized and further enriched by hydrothermal alteration to REE fluorocarbonates (the current predominant economic source of REE minerals). Overall, our results reveal that REE occur mainly in the lattices of fluorapatite and synchysite-(Y) in phosphorites, and provide new insights into the mineralization mechanism and industrial availability of REE-enriched phosphorites.
•REY were mainly enriched in sedimentary–diagenetic stage.•Z-contrast image confirm most REE are resident in the lattice of fluorapatite.•REY in fluorapatite can be re-distributed to form synchysite-(Y) by hydrothermal alteration.
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► Cr substitution improved Fenton degradation of methylene blue and acid orange II. ► The extent of improvement by Cr substitution varied with the substitution level. ► The ...degradation of two dyes followed different mechanism and kinetics equations. ► This study is a benefit for the application of magnetite in treating wastewater.
In this study, the heterogeneous Fenton degradation of cationic and anionic dyes catalyzed by a series of Cr-containing magnetites (Fe3−xCrxO4, x=0.00, 0.18, 0.33, 0.47 and 0.67) has been investigated under neutral pH conditions. Methylene blue (MB) and acid orange II (AOII) were chosen as models of cationic and anionic contaminants. Emphases were laid on the comparison of degradation characteristic between MB and AOII and the effect of Cr substitution on the degradation efficiency of both dyes. The octahedral occupancy of Cr3+ increased the BET surface area and superficial hydroxyl amount of magnetite, resulting in an improvement of adsorption ability of MB. However, these Cr-containing magnetites showed no adsorption to AOII. The MB degradation, following the Langmuir–Hinshelwood model, was well fitted by zero-order equation while AOII degradation following the Eley–Rideal model, was well fitted with two-stage pseudo-first-order kinetics. The Cr incorporation significantly improved the catalytic activity of magnetite in heterogeneous Fenton reaction, but the extent of improvement varied with the substitution level. These new insights are of high importance for the environmental application of metal substituted magnetites in the purification of textile wastewater.
Abstract Ion-adsorption-type rare earth element (REE) deposits are the source of more than 90% of global heavy REEs (HREEs). Thus, understanding the ore genesis of REEs, particularly the distribution ...characteristics and enrichment mechanisms of HREEs, is vital for efficient exploration and mining of ion-adsorption-type REE deposits worldwide. The characteristics and petrogenesis of bedrock, and the aqueous mobility of REEs, are known to be important factors controlling REE accumulation and fractionation in the weathering crust of REE deposits. However, the effect of REE adsorption on secondary minerals, which is a crucial step in deposit formation, remains poorly understood. This problem was addressed by the study described herein, which involved a systematic analysis of the complete weathering profile (78 m) of the Renju ion-adsorption-type REE deposit in South China and a simulated adsorption experiment. Clay minerals and iron (Fe) (hydr)oxides are the dominant REE adsorbents in the weathering crust and most are micro-to-nanosized particles. Thus, the fine particle fraction (< 2 μm) was separated from field samples, to better disclose their effects on the concentration and redistribution of REEs. Phase compositions and morphologies were characterized by X-ray diffraction, Mössbauer spectrometry, and scanning/transmission electron microscopy (SEM/TEM), which revealed that various clay minerals and Fe (hydr)oxides form composites along the profile of the deposit. Composites of ferrihydrite–kaolinite, goethite–kaolinite/halloysite, and hematite–kaolinite/halloysite were found to be distributed in the semi-weathered, completely weathered, and topsoil layers, respectively, with different sizes and shapes. The concentrations and partition patterns of REEs in different occurrence states were distinguished after sequential extraction. Ion-exchangeable-REEs were the major state and enriched in the upper completely weathered layer. These species were found to be adsorbed onto kaolinite and halloysite via electrostatic attraction, without obvious fractionation. Fe (hydr)oxides were determined to comprise ca. 20% of REEs at most depths and over 50% of REEs in the topsoil and semi-weathered layer. It was found that Fe (hydr)oxides scavenge REEs through complexation and oxidation, resulting in HREE enrichment and a positive cerium (Ce) anomaly, respectively. In addition, compared with crystalline Fe (hydr)oxides, amorphous Fe (hydr)oxides immobilize more REEs but exhibit weaker preferential adsorption of HREEs. The above-described findings are consistent with the results of simulated experiments for REE adsorption onto a clay mineral–Fe (hydr)oxide composite (Bt-60), which was obtained from hydrothermal processing of biotite. Furthermore, the distributions and stabilities of LREEs and HREEs were distinguished by TEM–energy–dispersive spectroscopy (EDS) of Bt-60 before and after REE extraction by ammonium sulfate. The phase transformation pathways of clay minerals and Fe (hydr)oxides, and their different enrichment and fractionation characteristics in REEs, were also discussed in terms of the structure and surface properties of minerals, adsorption mechanisms, and variations in chemical properties across the REE group. The results shed new light on how clay minerals and Fe (hydr)oxides affect the enrichment and fractionation of REEs in ion-adsorption-type deposits.
The abiotic oxidation of pyrite (FeS2) is a geochemically crucial reaction involved in acid mine drainage, the release of toxic trace elements and the generation of hydroxyl radicals (•OH) that can ...oxidize environmental substances. Studies on •OH generation from the abiotic oxidation of pyrite have drawn wide interest, but the effects of the common substitution of transition metal ions on •OH generation are still largely unknown, and worthy of comprehensive comparison. We therefore synthesized and comprehensively characterized micron-sized pyrites containing low concentrations of cobalt (Co), nickel (Ni), or manganese (Mn) ions, and tested the relative ability of these transition metal ion-substituted pyrites to generate •OH under abiotic oxidation. We found that transition metal ion substitutions inhibited the growth of pyrite crystals to various extents and increased Fe–S bond distances, leading to distinct alterations in surface chemical composition, conductivity, and the exposure of active faces. These differences resulted in an increase in •OH generation by the oxidation of transition metal ion-substituted pyrites, relative to pure pyrite, with the order of increase being Mn2+-substituted < Ni2+-substituted < Co2+-substituted pyrites. These substituent-dependent differences were explored by linking the crystal properties and physical chemistry of these pyrites to various reaction pathways that were possible in such contexts. For pure pyrite, the heterogeneous Fenton reaction was the chief generator of •OH. The substitution of pyrite with Co2+, which was redox-active, increased the conductivity of pyrite and accelerated the reduction of surface Fe3+ to Fe2+, resulting in a significant increase in H2O2 and •OH production. The substitution of pyrite with Mn2+, which was also redox-active, likewise increased the conductivity; however, the high oxidizing ability of surface Mn4+ inhibited the reduction of Fe3+ and thus decreased •OH generation. By contrast, the substitution of pyrite with Ni2+ did not affect electron transfer but led to absolute exposure of the (111) face of pyrite, which increased its activity toward O2 and H2O, slightly increasing H2O2 and •OH generation. These results highlight the vital role of transition metal ion-substituted pyrite in various geochemical processes.
The thermal characteristics of montmorillonite (Mt) play significant roles in the application of Mt In this work, a systematic and comparative study regarding the influence of interlayer species on ...thermal characteristics of Mt was conducted. The raw Mt (Ca-Mt) was first saturated with small inorganic cation (Li+), polyhydroxy-metal cation (polyhydroxy-aluminum, Al13), and organic cation (methylene blue, MB), respectively. The obtained Mt samples (i.e., Li-Mt, Al13-Mt, and MB-Mt) and Ca-Mt were heated from room temperature to 1100°C under Ar atmosphere. X-ray diffraction results indicated that the layers of Ca-Mt and Li-Mt collapsed at 500 and 300°C, respectively; while those of Al13-Mt and MB-Mt would not collapse in this temperature range, owing to the protection of the aluminum oxide pillars and graphene-like carbon sheets within the interlayer spaces, respectively. As the temperature further increased, the layers of Al13-Mt was directly destroyed at 900°C, while those of MB-Mt could be somewhat preserved even at 1100°C. Thermogravimetry analysis showed the DSC exothermic peaks related to the breakdown of the layered structures and the formation of new phases increased in the order Li-Mt<Ca-Mt<Al13-Mt; while no evident DSC exothermic peak was observed for MB-Mt in this high temperature range. Fourier transform infrared spectroscopy further confirmed that the formation of high-temperature mineral phases greatly depended on the interlayer species of Mt. This work would contribute to better understanding the physico-chemical properties of Mt, and developing novel Mt-based materials.
•The effect of interlayer species on thermal characteristics of Mt was conducted.•The thermal characteristics of Mt were greatly influenced by interlayer species.•This work contributes to better understanding the physico-chemical properties of Mt.•This work contributes to developing novel Mt-based materials.
On mineral dust aerosol hygroscopicity Chen, Lanxiadi; Peng, Chao; Gu, Wenjun ...
Atmospheric chemistry and physics,
11/2020, Letnik:
20, Številka:
21
Journal Article
Recenzirano
Odprti dostop
Despite its importance, hygroscopicity of mineral dust aerosol remains
highly uncertain. In this work, we investigated water adsorption and
hygroscopicity of different mineral dust samples at 25 ∘C, ...via
measurement of sample mass at different relative humidity (RH, up to 90 %)
using a vapor sorption analyzer. Mineral dust samples examined (21 in total)
included seven authentic mineral dust samples from different regions in the
world and 14 major minerals contained in mineral dust aerosol. At
90 % RH, the mass ratios of adsorbed water to the dry mineral ranged from
0.0011 to 0.3080, largely depending on the BET surface areas of mineral dust
samples. The fractional surface coverages of adsorbed water were determined
to vary between 1.26 and 8.63 at 90 % RH, and it was found that the
Frenkel–Halsey–Hill (FHH) adsorption isotherm could describe surface
coverages of adsorbed water as a function of RH well, with AFHH and
BFHH parameters in the range of 0.15–4.39 and 1.10–1.91, respectively.
The comprehensive and robust data obtained would largely improve our
knowledge of hygroscopicity of mineral dust aerosol.
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