The upper crust in the SE Tibetan Plateau is rotating around the eastern Himalayan syntax clockwise, and the western margin of the Yangtze Craton has been involved in the active tectonics. However, ...it is still unclear whether and how the deep crust and upper mantle respond to the plateau expansion. In this study we present a high‐resolution three‐dimensional model of P wave velocity tomography and azimuthal anisotropy in the crust and uppermost mantle beneath the SE Tibetan Plateau determined using traveltime data recorded by a dense seismic network. Widespread low‐velocity zones are revealed around a high‐velocity body in the deep crust and uppermost mantle beneath the southwest Yangtze Craton, where fast‐velocity directions of the azimuthal anisotropy are mostly parallel to the contour lines of the surface topography and the Moho depth along the plateau margin. These results indicate that gravitational potential plays an important role in the crustal and uppermost‐mantle deformations in the SE Tibetan Plateau. Meanwhile, the shallow crust may drop down to the deep crust and drive the ductile deep‐crustal material to intrude into the adjacent regions. The extruded crust is trapped in a deep‐crustal corner and obstructed by the surrounding strong blocks. The trapped crustal material may rise up, causing significant uplift and high heat flow at the surface.
Key Points
We present a high‐resolution P wave anisotropic tomography of the SE Tibetan Plateau
Widespread low‐velocity zones with margin‐parallel anisotropy exist in the deep crust and uppermost mantle
A shallow‐crustal block drops down, causing deep‐crustal and uppermost‐mantle materials to extrude into adjacent regions
Abstract
Single-atom catalysts are widely investigated heterogeneous catalysts; however, the identification of the local environment of single atoms under experimental conditions, as well as operando ...characterization of their structural changes during catalytic reactions are still challenging. Here, the preferred local coordination of Rh single atoms is investigated on TiO
2
during calcination in O
2
, reduction in H
2
, CO adsorption, and reverse water gas shift (RWGS) reaction conditions. Theoretical and experimental studies clearly demonstrate that Rh single atoms adapt their local coordination and reactivity in response to various redox conditions. Single-atom catalysts hence do not have static local coordinations, but can switch from inactive to active structure under reaction conditions, hence explaining some conflicting literature accounts. The combination of approaches also elucidates the structure of the catalytic active site during reverse water gas shift. This insight on the real nature of the active site is key for the design of high-performance catalysts.
Competing geodynamic models, such as rigid-block extrusion, continuous deformation, and the mid-lower crustal flow, have been proposed to describe the growth and expansion of eastern Tibet. However, ...the dynamic processes responsible for plateau evolution and deformation remain poorly understood partly due to resolution limitations of previous models of lithospheric structure. On the basis of joint inversion of Rayleigh wave dispersion and receiver functions using data from a newly deployed seismic array, we have obtained a high-resolution 3D image that reveals the distribution of low-velocity zones (LVZs) with unprecedented clarity. The prominent feature of our model is two low-velocity channels that bound major strike-slip faults in SE Tibet and wrap around the Eastern Himalaya Syntaxis, consistent with the clockwise movement of crustal material in this region. Most large earthquakes in this region occurred in the boundaries of the LVZs. We propose that ductile flow within these channels, in addition to shear motion along strike-slip faults, played a significant role in accommodating intensive lithospheric deformation during the eastward expansion of Tibet in the Cenozoic.
•Image two channels of low-velocity zones with unprecedented resolution.•The two channels bound main strike-slip faults of SE Tibet.•The two channels wrap around the Eastern Himalaya Syntaxis.•Large earthquakes occurred at the edge of the two channels.•Deformation of SE Tibet is accommodated by both ductile flow and shearing.
The structure and dynamics in SE Tibet are the key to understand the tectonic evolution of the Tibetan Plateau. In this study we determined high-resolution P-wave seismic images in the upper mantle ...and transition zone in SE Tibet by jointly inverting the travel-time residuals of local events and the relative travel-time residuals of teleseismic events recorded by very dense seismic stations. We revealed a high-velocity body in the upper mantle beneath South China that represents the root of the Yangtze Craton. The high-velocity body extends in the entire Yangtze Craton at 300–450 km depths, but it is constrained just beneath the Sichuan Basin and surrounded by extensive low-velocity zones to the southwest at 65–250 km depths. We propose that the Yangtze Craton is destructed laterally by the mantle flow extruded from the Tibetan Plateau. We obtain a low-velocity column in the upper mantle under the Tengchong volcano as well as the visible high-velocity bodies in the upper mantle and transition zone below the low-velocity column. The images suggest that the Tengchong volcano is closely related to the subduction of the Burma plate and caused by the dehydration of the subducted slab. The present study reveals unprecedented details of the mantle structures beneath SE Tibet and provides new insights into the geodynamics of the Tibetan Plateau and its interaction with the stable Yangtze Craton.
•Southeastward mantle flow exists in the upper mantle under SE Tibet.•Yangtze Craton is destructed laterally by the upper-mantle extrusion.•Tengchong volcano is related to the subduction of the Burman plate.
Fecal microbiota transplantation is an effective treatment for many gastrointestinal diseases, such as Clostridium difficile infection and inflammatory bowel disease, especially ulcerative colitis. ...Changes in colonic microflora may play an important role in the pathogenesis of ulcerative colitis, and improvements in the intestinal microflora may relieve the disease. Fecal bacterial transplants and oral probiotics are becoming important ways to relieve active ulcerative colitis.
This systematic review with meta-analysis compared the efficacy and safety of basic treatment combined with fecal microbiota transplantation or mixed probiotics therapy in relieving mild to moderate ulcerative colitis.
The PubMed, Embase, and Cochrane libraries (updated September 2019) were searched to identify randomized, placebo-controlled, or head-to-head trials assessing fecal microbiota transplantation or probiotic VSL#3 as induction therapy in active ulcerative colitis. We analyze data using the R program to obtain evidence of direct comparison and to generate intermediate variables for indirect treatment comparisons.
Seven randomized, double-blind, placebo-controlled trials were used as the sources of the induction data. All treatments were superior to placebo. In terms of clinical remission and clinical response to active ulcerative colitis, direct comparisons showed fecal microbiota transplantation (OR = 3.47, 95% CI = 1.93-6.25) (OR = 2.48, 95% CI = 1.18-5.21) and mixed probiotics VSL#3 (OR = 2.40, 95% CI = 1.49-3.88) (OR = 3.09, 95% CI = 1.53-6.25) to have better effects than the placebo. Indirect comparison showed fecal microbiota transplantation and probiotic VSL#3 did not reach statistical significance either in clinical remission (RR = 1.20, 95% CI = 0.70-2.06) or clinical response (RR = 0.95, 95% CI = 0.62-1.45). In terms of safety, fecal microbiota transplantation (OR = 1.15, 95% CI = 0.51-2.61) and VSL #3 (OR = 0.90, 95% CI = 0.33-2.49) showed no statistically significant increase in adverse events compared with the control group. In terms of serious adverse events, there was no statistical difference between the fecal microbiota transplantation group and the control group (OR = 1.29, 95% CI = 0.46-3.57). The probiotics VSL#3 seems more safer than fecal microbiota transplantation, because serious adverse events were not reported in the VSL#3 articles.
Fecal microbiota transplantation or mixed probiotics VSL#3 achieved good results in clinical remission and clinical response in active ulcerative colitis, and there was no increased risk of adverse reactions. There was no statistical difference between the therapeutic effect of fecal microbiota transplantation and that of mixed probiotics VSL#3. However, the use of fecal microbiota transplantation and probiotics still has many unresolved problems in clinical applications, and more randomized controlled trials are required to confirm its efficacy.
Abstract
Background
N6-methyladenosine (m
6
A) is the most abundant modification in mRNA of humans. Emerging evidence has supported the fact that m
6
A is comprehensively involved in various diseases ...especially cancers. As a crucial reader, YTHDF2 usually mediates the degradation of m
6
A-modified mRNAs in m
6
A-dependent way. However, the function and mechanisms of m
6
A especially YTHDF2 in prostate cancer (PCa) still remain elusive.
Methods
To investigate the functions and mechanisms of YTHDF2 in PCa, in vitro
,
in vivo biofunctional assays and epigenetics experiments were performed. Endogenous expression silencing of YTHDF2 and METTL3 was established with lentivirus-based shRNA technique. Colony formation, flow cytometry and trans-well assays were performed for cell function identifications. Subcutaneous xenografts and metastatic mice models were combined with in vivo imaging system to investigate the phenotypes when knocking down YTHDF2 and METTL3. m
6
A RNA immunoprecipitation (MeRIP) sequencing, mRNA sequencing, RIP-RT-qPCR and bioinformatics analysis were mainly used to screen and validate the direct common targets of YTHDF2 and METTL3. In addition, TCGA database was also used to analyze the expression pattern of YTHDF2, METTL3 and the common target LHPP in PCa, and their correlation with clinical prognosis.
Results
The upregulated YTHDF2 and METTL3 in PCa predicted a worse overall survival rate. Knocking down YTHDF2 or METTL3 markedly inhibited the proliferation and migration of PCa in vivo and in vitro. LHPP and NKX3–1 were identified as the direct targets of both YTHDF2 and METTL3. YTHDF2 directly bound to the m
6
A modification sites of LHPP and NKX3–1 to mediate the mRNA degradation. Knock-down of YTHDF2 or METTL3 significantly induced the expression of LHPP and NKX3–1 at both mRNA and protein level with inhibited phosphorylated AKT. Overexpression of LHPP and NKX3–1 presented the consistent phenotypes and AKT phosphorylation inhibition with knock-down of YTHDF2 or METTL3. Phosphorylated AKT was consequently confirmed as the downstream of METTL3/YTHDF2/LHPP/NKX3–1 to induce tumor proliferation and migration.
Conclusion
We propose a novel regulatory mechanism in which YTHDF2 mediates the mRNA degradation of the tumor suppressors LHPP and NKX3–1 in m
6
A-dependent way to regulate AKT phosphorylation-induced tumor progression in prostate cancer. We hope our findings may provide new concepts of PCa biology.
Understanding the Mesozoic–Cenozoic tectonic evolution of the North China Craton (NCC) and the NE Tibetan Plateau (TP) requires detailed knowledge of the lithospheric structure. Using dense regional ...networks and temporary deployments as well as updated reference models, we obtain the crust and upper mantle structure to 120km depth. Our tomographic results show several major features, which have particular implications for the Weihe–Shanxi rift system (WSRS), deformation of the NE TP, and lithospheric evolution of the NCC. Beneath the WSRS, the crust gradually thickens from south to north, the lithospheric mantle gradually becomes slower, and the mid-lower crustal velocities are lower in the Weihe Rift, where rifting of the WSRS initiated. We suggest that along-strike variations of the lithospheric structures of the WSRS have played an important role in its multistage evolution. A low-velocity zone (LVZ) in the mid-crust beneath the Qilian Orogen is characterized by relatively higher velocities compared to LVZs in other parts of the TP. Thus, coherent lithospheric deformation may occur due to the high viscosity of the LVZ during early plateau growth, causing strong anisotropy to develop. The western NCC (including the Ordos Block and part of the Alashan Block) shows a high-velocity cratonic root extending to the base of our model. In contrast, the lithosphere of the eastern NCC appears to have been completely modified during the Mesozoic through Cenozoic and presents a thin lithosphere of relatively low velocities underlain by hot asthenosphere. We observed significant upper-mantle heterogeneities in the NCC, which may reflect its diachronous lithospheric modification.
•Use of unprecedented amount of seismic data, including dense regional networks.•Combine ambient noise and earthquake data from recent national models.•The initiation of the Weihe–Shanxi Rift is controlled by the deformation of the Tibetan Plateau.•Isolated mid-crust low velocity zone in Qilian Shan may reconcile vertically coherent deformation model.•Significant upper-mantle heterogeneities are revealed in North China.
The exceptional characteristics of magnesium alloys make them appropriate materials in various applications, although their low corrosion resistance critically limits their use. Sol–gel coating is ...among the most efficient ways to avoid corrosion, and silanes/siloxane polymers play a very essential role in the formation of sol–gel coating materials. These materials form very stable chemical bonds on surfaces of metals because of their siloxane (−Si–O−) network along with their thermal and chemical stability. In this work, the current progress of silane-based coatings on magnesium alloys is reviewed. First, we have focused on hybrid organic–inorganic sol–gel coatings using silanes and then a critical examination of protection effects of these coatings on a magnesium alloy. Modification methods of these coatings to achieve improved barrier properties have also been emphasized along with the role of silanes in the making of superhydrophobic surfaces. The recent development of silanes as outstanding precursors was also highlighted.
Understanding the structures of catalysts under realistic conditions with atomic precision is crucial to design better materials for challenging transformations. Under reducing conditions, certain ...reducible supports migrate onto supported metallic particles and create strong metal–support states that drastically change the reactivity of the systems. The details of this process are still unclear and preclude its thorough exploitation. Here, we report an atomic description of a palladium/titania (Pd/TiO2) system by combining state-of-the-art in situ transmission electron microscopy and density functional theory (DFT) calculations with structurally defined materials, in which we visualize the formation of the overlayers at the atomic scale under atmospheric pressure and high temperature. We show that an amorphous reduced titania layer is formed at low temperatures, and that crystallization of the layer into either mono- or bilayer structures is dictated by the reaction environment and predicted by theory. Furthermore, it occurs in combination with a dramatic reshaping of the metallic surface facets.
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