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To improve the hydrothermal durability of Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, a thin Al2O3 modification layer was coated on the external surface of Cu-SSZ-13 by a chemical liquid deposition (CLD) method. The high-temperature SCR activity of the Al-modified Cu-SSZ-13 can be maintained upon 750-800 °C hydrothermal aging, and over-oxidation of NH3 is largely inhibited. Based on H2-TPR and EPR results, it is revealed that CuAl2O4-like species forms upon Al modification and converts further to CuAlO2-like species during aging. The high affinity of Al-containing species (i.e., Al2O3 and CuAl2O4-like species) with Cu(OH)2 is suggested by DFT calculations, indicating that Cu(OH)2 detached from ion-exchange sites are captured by Al to form CuAlO2-like species instead of CuO-like species. The passivation of aggregated Cu species by coated Al leads to somewhat weakened low-temperature SCR activity, but successfully preserves the high-temperature SCR performance upon aging, which can be applied to high-temperature SCR scenarios.

Stem cells derived from cartilage endplate (CEP) cells (CESCs) repair intervertebral disc (IVD) injury; however, the mechanism remains unclear. Here, we evaluated whether CESCs could transdifferentiate into nucleus pulposus cells (NPCs) via autocrine exosomes and subsequently inhibit IVD degeneration. Exosomes derived from CESCs (CESC-Exos) were extracted and identified by ultra-high-speed centrifugation and transmission electron microscopy. The effects of exosomes on the invasion, migration, and differentiation of CESCs were assessed. The exosome-activating hypoxia-inducible factor (HIF)-1α/Wnt pathway was investigated using lenti-HIF-1α and Wnt agonists/inhibitors in cells and gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis in normal and degenerated human CEP tissue. The effects of GATA binding protein 4 (GATA4) on transforming growth factor (TGF)-β expression and on the invasion, migration, and transdifferentiation of CESCs were investigated using lenti-GATA4, TGF-β agonists, and inhibitors. Additionally, IVD repair was investigated by injecting CESCs overexpressing GATA4 into rats. The results indicated that CESC-Exos promoted the invasion, migration, and differentiation of CESCs by autocrine exosomes via the HIF-1α/Wnt pathway. Additionally, increased HIF-1α enhanced the activation of Wnt signaling and activated GATA4 expression. GATA4 effectively promoted TGF-β secretion and enhanced the invasion, migration, and transdifferentiation of CESCs into NPCs, resulting in promotion of rat IVD repair. CESCs were also converted into NPCs as endplate degeneration progressed in human samples. Overall, we found that CESC-Exos activated HIF-1α/Wnt signaling via autocrine mechanisms to increase the expression of GATA4 and TGF-β1, thereby promoting the migration of CESCs into the IVD and the transformation of CESCs into NPCs and inhibiting IVDD.

There are critical needs for platinum catalysts with high hydrothermal stability and tunable Pt–acid site proximity, which could not be achieved via traditional methods. Here, we describe a simple strategy (SiO2 alumination combined with controlled removal of the capping agent) through which Pt-based core–shell catalysts that tolerant both high-temperature steam and boiling water can be obtained. More importantly, this strategy allows precise control of the distance between acid sites and Pt; thus, the interfacial electronic interaction can be cut off without prohibiting the spillover of adsorbed species. This tunable structure not only helps to unravel the mechanism of C3H8 oxidation over acidic Pt catalyst but also increases the N2 selectivity for NOx selective catalytic reduction. Given that the component of both the “core” and “shell” can be changed easily, this strategy should have wide application in mechanism exploration as well as the development of catalysts for various reactions.

A series of Ag/CeO 2 catalysts was synthesized by the incipient wetness method. Compared with Ag/Al 2 O 3 and CeO 2 catalysts, Ag/CeO 2 catalysts are more promising candidates for naphthalene oxidation, in which Ce x + act as the main active sites and are efficiently promoted by Ag species. By characterizing the solid properties and the redox ability, the mechanism of ceria catalysis by the Ag-modified catalysts was investigated. It was found that Ag species can work as an oxygen pump to enhance the oxygen availability in the ceria bulk. They also promote the oxygen regeneration capacity by the oxygen spillover effect. However, such an effect would also decrease the ability for active oxygen regeneration at higher Ag loading, which arises from the lower surface oxygen vacancy concentration. Because of the balance between these two factors, the Ag/CeO 2 catalyst with 1 wt.% Ag shows the best performance for isothermal catalytic oxidation of naphthalene.

A series of experiments were carried out in linked vessels with two spherical vessels of 600 mm and 350 mm diameter respectively and pipe of 60 mm diameter to investigate the influential factors on H2-air mixtures explosion. This research is focused on the effects of ignition position, initial pressure and pipe length on H2-air mixtures explosion in linked vessels. The experimental results show that the different ignition position has less impact on the maximum hydrogen explosion pressure in big vessel, however, the impact on the maximum hydrogen explosion pressure in small vessel and the maximum hydrogen explosion pressure rising rate in linked vessels is obvious. The initial pressure has a distinct effect on the maximum hydrogen explosion pressure in linked vessels. In big vessel, the maximum hydrogen explosion pressure increases with the increasing of initial pressure nearly linear relationship. In small vessel, the maximum hydrogen explosion pressure also increases with the increasing of initial pressure. Moreover, the maximum hydrogen explosion pressure has a sharp increase from 0.02 MPa to 0.03 MPa. When the ignition in big vessel, the maximum hydrogen explosion pressures are all increased with the pipe length. Meanwhile, the change of the maximum hydrogen explosion pressure in small vessel is more severe than in big vessel. The maximum hydrogen explosion pressure in the big vessel increases with pipe length when the ignition is located in the small vessel. However, the maximum hydrogen explosion pressure in small vessel increases first then decreases. The maximum hydrogen explosion pressure, the maximum rates of pressure rise and the time delay between ignition in the big and small vessel are discussed.

BackgroundThe degenerative disc disease (DDD) is a major cause of low back pain. The physiological low-glucose microenvironment of the cartilage endplate (CEP) is disrupted in DDD. Glucose influences proteinO-GlcNAcylation via the hexosamine biosynthetic pathway (HBP), which is the key to stem cell fate. Thiamet-G is an inhibitor ofO-GlcNAcase for accumulatingO-GlcNAcylated proteins while 6-diazo-5-oxo-l-norleucine (DON) inhibits HBP. Mechanisms of DDD are incompletely understood but include CEP degeneration and calcification. We aimed to identify the molecular mechanisms of glucose in CEP calcification in DDD.MethodsWe assessed normal and degenerated CEP tissues from patients, and the effects of chondrogenesis and osteogenesis of the CEP were determined by western blot and immunohistochemical staining. Cartilage endplate stem cells (CESCs) were induced with low-, normal-, and high-glucose medium for 21 days, and chondrogenic and osteogenic differentiations were measured by Q-PCR, western blot, and immunohistochemical staining. CESCs were induced with low-glucose and high-glucose medium with or without Thiamet-G or DON for 21 days, and chondrogenic and osteogenic differentiations were measured by Q-PCR, western blot, and immunohistochemical staining. Sox9 and Runx2O-GlcNAcylation were measured by immunofluorescence. The effects ofO-GlcNAcylation on the downstream genes of Sox9 and Runx2 were determined by Q-PCR and western blot.ResultsDegenerated CEPs from DDD patients lost chondrogenesis, acquired osteogenesis, and had higher proteinO-GlcNAcylation level compared to normal CEPs from LVF patients. CESC chondrogenic differentiation gradually decreased while osteogenic differentiation gradually increased from low- to high-glucose differentiation medium. Furthermore, Thiamet-G promoted CESC osteogenic differentiation and inhibited chondrogenic differentiation in low-glucose differentiation medium; however, DON acted opposite role in high-glucose differentiation medium. Interestingly, we found that Sox9 and Runx2 wereO-GlcNAcylated in differentiated CESCs. Finally,O-GlcNAcylation of Sox9 and Runx2 decreased chondrogenesis and increased osteogenesis in CESCs.ConclusionsOur findings demonstrate the effect of glucose concentration on regulating the chondrogenic and osteogenic differentiation potential of CESCs and provide insight into the mechanism of how glucose concentration regulates Sox9 and Runx2O-GlcNAcylation to affect the differentiation of CESCs, which may represent a target for CEP degeneration therapy.

Different Ag/CeO2 catalysts with uniform structures and diverse surface oxygen vacancy (VO-s) contents were synthesized via a modified solution combustion method. Based on the results of Raman spectroscopy, H2-TPR and isothermal soot oxidation, it was suggested that even with gaseous O2 participating in the reaction, ceria surface sites around the catalyst–soot contact points can still be reduced by soot gradually. This interfacial reduction led to the generation of extra VO-s without changing the oxygen vacancies in the bulk of CeO2. Notably, this VO-s dynamic change and the insufficient O2− regeneration/delivery further resulted in the activation and deactivation of Ag/CeO2 during reaction with soot. This means that both the existence of ceria VO-s and its dynamic change during reaction may have a crucial influence on catalyst behavior. By further exploring these activity variations, the VO-s content, catalyst–soot contact condition and extra oxygen supplier were proved to be the three most important structural factors behind the soot oxidation activity of all the ceria-based catalysts. In this sense, Ag/CeO2 catalysts with appropriate morphology and moderate initial VO-s content may exhibit good activity for soot oxidation.

Soot oxidation was conducted over Ag/Al2O3 and Ag/SO42−/Al2O3 catalysts. Spent catalysts were found to exhibit higher activities than fresh ones for soot oxidation in oxygen. Environmental transmission electron microscopy (ETEM) was performed for the catalytic oxidation of soot over fresh and spent catalysts. Aggregation of silver nanoparticles occurred significantly on the alumina support under very low oxygen pressure. On increasing the oxygen pressure, redispersion of large Ag particles was observed on both supports, which explains the superior activities of the spent catalysts. Sulphated alumina was found to anchor the silver species effectively and deter the migration of silver to soot particles. Hence, the aggregation of silver was alleviated over Ag/SO42−/Al2O3, leading to higher activity than the Ag/Al2O3 catalyst.

Transplantation of mesenchymal stem cells (MSCs) into the degenerated intervertebral disc (IVD) has shown promise for decelerating or arresting IVD degeneration. Cellular mechanical properties play crucial roles in regulating cell-matrix interactions, potentially reflecting specific changes that occur based on cellular phenotype and behavior. However, the effect of co-culturing of MSCs with nucleus pulposus cells (NPCs) on the mechanical properties of NPCs remains unknown. In our study, we demonstrated that co-culture of degenerated NPCs with MSCs resulted in significantly decreased mechanical moduli (elastic modulus, relaxed modulus, and instantaneous modulus) and increased biological activity (proliferation and expression of matrix genes) in degenerated NPCs, but not normal NPCs. SDF-1, CXCR4 ligand, was highly expressed in MSCs when co-cultured with degenerated NPCs. Inhibition of SDF-1 using CXCR4 antagonist AMD3100 or knocking-down CXCR4 in degenerated NPCs abolished the MSCs-induced decrease in the mechanical moduli and increased biological activity of degenerated NPCs, suggesting a crucial role for SDF-1/CXCR4 signaling. AKT and FAK inhibition attenuated the MSCs- or SDF-1-induced decrease in the mechanical moduli of degenerated NPCs. In conclusion, it was demonstrated in vitro that MSCs regulate the mechanical properties of degenerated NPCs through SDF-1/CXCR4/AKT signaling. These findings highlight a possible mechanical mechanism for MSCs-induced modulation with degenerated NPCs, which may be applicable to MSCs-based therapy for disc degeneration.

Background Radiotherapy to cancer patients is inevitably accompanied by normal tissue injury, and the bone is one of the most commonly damaged tissues. Damage to bone marrow mesenchymal stem cells (BM-MSCs) induced by radiation is thought to be a major cause of radiation-induced bone loss. Exosomes exhibit great therapeutic potential in the treatment of osteoporosis, but whether exosomes are involved in radiation-induced bone loss has not been thoroughly elucidated to date. The main purpose of this study is to investigate the role of exosomes derived from BM-MSCs in restoring recipient BM-MSC function and alleviating radiation-induced bone loss. Methods BM-MSC-derived exosomes were intravenously injected to rats immediately after irradiation. After 28 days, the left tibiae were harvested for micro-CT and histomorphometric analysis. The effects of exosomes on antioxidant capacity, DNA damage repair, proliferation, and cell senescence of recipient BM-MSCs were determined. Osteogenic and adipogenic differentiation assays were used to detect the effects of exosomes on the differentiation potential of recipient BM-MSCs, and related genes were measured by qRT-PCR and Western blot analysis. β-Catenin expression was detected at histological and cytological levels. Results BM-MSC-derived exosomes can attenuate radiation-induced bone loss in a rat model that is similar to mesenchymal stem cell transplantation. Exosome-treated BM-MSCs exhibit reduced oxidative stress, accelerated DNA damage repair, and reduced proliferation inhibition and cell senescence-associate protein expression compared with BM-MSCs that exclusively received irradiation. Following irradiation, exosomes promote β-catenin expression in BM-MSCs and restore the balance between adipogenic and osteogenic differentiation. Conclusions Our findings indicate that BM-MSC-derived exosomes take effects by restoring the function of recipient BM-MSCs. Therefore, exosomes may represent a promising cell-free therapeutic approach for the treatment of radiation-induced bone loss. Electronic supplementary material The online version of this article (10.1186/s13287-018-1121-9) contains supplementary material, which is available to authorized users.