What happened to the Indian mantle lithosphere (IML) during the Indian–Eurasian collision and what role it has played on the plateau growth are fundamental questions that remain unanswered. Here, we ...show clear images of the IML from high-resolution P and S tomography, which suggest that the subducted IML is torn into at least four pieces with different angles and northern limits, shallower and extending further in the west and east sides while steeper in the middle. Intermediate-depth earthquakes in the lower crust and mantle are located almost exclusively in the high-velocity (and presumably strong) part of the Indian lithosphere. The tearing of the IML provides a unified mechanism for Late Miocene and Quaternary rifting, current crustal deformation, and intermediate-depth earthquakes in the southern and central Tibetan Plateau and suggests that the deformations of the crust and the mantle lithosphere are strongly coupled.
We present a new high-resolution shear-velocity model of the lithosphere (down to about 160 km) beneath China using Rayleigh-wave tomography. We combined ambient noise and earthquake data recorded at ...1316 seismic stations, the largest number used for the region to date. More than 700,000 dispersion curves were measured to generate group and phase velocity maps at periods of 10–140 s. The resolution of our model is significantly improved over previous models with about 1–2° in eastern China and 2–3° in western China. We also derived models of the study region for crustal thickness and averaged S velocities for upper and mid-lower crust and uppermost mantle. These models reveal important lithospheric features beneath China and provide a fundamental data set for understanding continental dynamics and evolution. Different geological units show distinct features in the Moho depth, lithospheric thickness, and shear velocity. In particular, the North China Craton (NCC) lithosphere shows strong east–west structural variations with thin and low-velocity lithosphere in eastern NCC and thick and high-velocity lithosphere beneath western NCC and the lithosphere of the Ordos Block seems to have undergone strong erosion. The results support the progressive destruction of the NCC lithosphere from east to west at least partly caused by the thermal–chemical erosion of the cratonic lithosphere from the asthenosphere. Another pronounced feature of our model is the strong lateral variations of the mantle lithosphere beneath the Tibetan Plateau (TP). The Indian lithosphere beneath the TP shows variable northward advancement with nearly flat subduction in western and eastern TP and steep subduction in central TP with evidence for the tearing of Indian lithosphere beneath central TP, which may be important for the riftings at the surface in Himalayas and southern TP. The low-velocity zone in northern TP shows strong correlation with the region of the mid-Miocene to Quaternary potassic magmatism, suggesting that delamination of lithosphere may have played an important role in the rise of the TP.
•Use unprecedented amount of seismic data from ambient noise and earthquake data.•Construct an S-velocity model for mainland China with much improved resolution.•North China lithosphere shows strong east–west structural variations.•Underthrusting of Indian Plate beneath Tibet shows complex geometry.
The crustal thickness and average Vp/Vs ratio are basic parameters to understand the current state and the tectonic processes in the Tibetan Plateau (TP). We gather receiver functions in the ...central‐southern TP and extract spatial variation of crustal thickness and Vp/Vs ratio using the H‐κ‐c method with careful quality control and stability analysis. Our results highlight the regions with high Vp/Vs ratios in the central‐southern Qiangtang block and two isolated patches around the Yarlung‐Zangbo suture, suggesting crustal partial melting. The disconnected high‐Vp/Vs patches imply a restrained pattern for present‐day crustal flow in the southern TP. Further correlation with mantle observations suggests that the high Vp/Vs region in the north can be attributed to mantle upwelling after lithospheric delamination, and the two isolated patches in the south may be related to the tearing of the Indian mantle lithosphere.
Plain Language Summary
The Tibetan Plateau (TP), as the Third Pole, is known for its unusual characteristics and hot debate on how it uplifts and grows. To better understand this, we collect available receiver function data in the central‐southern part of the TP, and use an improved method to study the crustal thickness and the average Vp/Vs ratio. The crustal Vp/Vs ratio is a good indicator for partial melting in parts of the crust. In our results, the crust in the central‐southern Qiangtang block and two isolated regions near the Yarlung‐Zangbo suture has high Vp/Vs ratio, indicating the crust in these areas may have been partially melted. A partially melted crust is favorable for crustal flow to develop, and the crustal flow is considered to be an important mechanism of plateau growth. However, the high‐Vp/Vs patches in the southern TP are too disconnected to develop large‐scale crustal flow. By comparing with mantle observations, we think the crustal parting melting is related to mantle upwelling and heating, caused by lithosphere detachment in the northern TP and Indian slab tearing in the south, respectively.
Key Points
H‐κ‐c results reveal two isolated patches with high crustal Vp/Vs in the southern Tibetan Plateau (TP), suggesting crustal partial melting
The disconnection between the two patches does not support present‐day eastward crustal flow in the southern TP
Correlation with mantle observations indicates the two patches may be related to tearing of the Indian mantle lithosphere
Classic nucleophilic substitution reactions (S
1 and S
2) are not generally amenable to the enantioselective variants that use simple and racemic alkyl halide electrophiles. The merging of transition ...metal catalysis and radical chemistry with organometallic nucleophiles is a versatile method for addressing this limitation. Here, we report that visible light-driven catalytic asymmetric photoredox radical coupling can act as a complementary and generic strategy for the enantioconvergent formal substitution of alkyl haldies with readily available and bench-stable organic molecules. Single-electron reductive debrominations of racemic α-bromoketones generate achiral alkyl radicals that can participate in asymmetric C
-C
bonds forming cross-coupling reactions with α-amino radicals derived from N-aryl amino acids. A wide range of valuable enantiomerically pure β
- and β
-amino ketones were obtained in satisfactory yields with good-to-excellent enantioselectivities by using chiral phosphoric acid catalysts to control the stereochemistry and chemoselectivity. Fluoro-hetero-quaternary and full-carbon quaternary stereocenters that are challenging to prepare were successfully constructed.
Ce substitution level in Nd-Fe-B magnets has been significantly increased via the binary main phase (BMP) approach, i.e. sintering the mixture of Ce-free and Ce-containing RE2Fe14B (RE, rare earth) ...powders. REFe2 phase that forms in the high Ce-containing Nd-Ce-Fe-B magnets has been considered to be harmful to magnetic performance due to its soft magnetism. In this work, we found that REFe2 phase with lower melting point than the 2:14:1 phase plays positive role on optimizing the microstructure and retaining magnetic performance of the Nd-Ce-Fe-B BMP magnets. The wettability of 2:14:1 phase can be improved by sintering above the melting point of REFe2 phase, which promotes densification of the magnet and the formation of continuous and smooth grain boundary (GB) phases. This contributes to the weakened short-range exchange coupling between adjacent grains, hence ensures superior magnetic performance of BMP magnets to the single main phase (SMP) ones with the same average composition. As a result, magnetic properties of Br = 12.4 kG, Hcj = 9.0 kOe and (BH)max = 36.7 MGOe can be obtained even when 45 wt % Ce substitutes for Nd in the BMP magnets.
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Repetitively pulsed gas volume and dielectric surface discharges have gained growing attention because of peculiar and exciting physics phenomena, high efficiency, high reactivity, and potential to ...obtain conventionally unachievable plasma properties. Nevertheless, incomplete understanding of fundamental mechanisms renders the repetitively pulsed discharge far less predictable and controllable, where the inherent memory effect and the discharge mode transition are universal challenges. In this topical review, the authors will explore the macroscopic characteristics of the gas gap breakdown and the surface flashover, state-of-the-art mechanisms and dominant agents of discharge memory effects, operation regimes and transitions of the discharge mode, and how waveform parameters affect the pulsed discharge properties. Challenges and potential approaches for further understanding the memory effect and the discharge mode transition in the repetitively pulsed discharge are discussed.
The central midcontinent of the USA's cratonic platform is a region of low elevation and relief underlain by tectonic basins, domes, faults, and monoclines. To investigate potential correlations ...among shallow crustal structure and crustal thickness, we produced a high‐resolution Moho‐depth map of the region by applying the recently developed H‐κ‐c receiver‐function method to data from EarthScope Transportable‐Array and Flexible‐Array stations. Results indicate that Moho depth varies from 38 to 57 km. Changes of Moho depth and of Vp/Vs ratios do not correlate with Precambrian tectonic boundaries, suggesting that they reflect post‐accretion tectonics. Deeper Moho underlies sedimentary basins, implying a relationship between crustal thickness and lithospheric subsidence. Thicker crust may be due to rift‐related underplating, and thinner crust may have undergone delamination. Some depth changes underlie known faults and fold zones. Since short‐wavelength undulations were detected only under high‐density seismic arrays, they may occur more widely but have yet to be resolved.
Plain Language Summary
Studies of the central midcontinent region of the USA, a portion of North America's relatively stable craton, reveal that both the Moho (the crust/mantle boundary) and the surface of the Great Unconformity (the boundary between crystalline basement and overlying Phanerozoic sedimentary cover) have kilometers of relief, even though land‐surface relief in the region is, at most, 0.5 km. To clarify the nature of variations in Moho depth, so as to make it possible to correlate these variations with other geologic features of the shallow continental crust, we applied a new, more robust, method in estimating Moho depth to data from all available EarthScope seismic stations in the region. This effort yielded a new, high‐resolution map of Moho depth. Significantly, we found large undulations (ups and downs) of the Moho both at the regional scale and at the local scale. Some of these undulations correlate with the boundaries of regional basins and domes, as defined by the depth to the Great Unconformity, and others correlate with known faults. The development of thickness variations may reflect geologic events, such as addition of new rock to the base of the crust, or removal of lower crust, which happened after the crust first formed.
Key Points
We applied an improved receiver‐function method in central midcontinent of the U.S. to construct a refined Moho‐depth map
Our results indicate Moho depth variations of different wavelengths, some of which correspond with known geological structures
Moho depth variations cross Precambrian boundaries, suggesting a likely post‐accretion tectonic modification of the lithosphere
Edge computing provides higher computational power and lower transmission latency by offloading tasks to nearby edge nodes with available computational resources to meet the requirements of ...time-sensitive tasks and computationally complex tasks. Resource allocation schemes are essential to this process. To allocate resources effectively, it is necessary to attach metadata to a task to indicate what kind of resources are needed and how many computation resources are required. However, these metadata are sensitive and can be exposed to eavesdroppers, which can lead to privacy breaches. In addition, edge nodes are vulnerable to corruption because of their limited cybersecurity defenses. Attackers can easily obtain end-device privacy through unprotected metadata or corrupted edge nodes. To address this problem, we propose a metadata privacy resource allocation scheme that uses searchable encryption to protect metadata privacy and zero-knowledge proofs to resist semi-malicious edge nodes. We have formally proven that our proposed scheme satisfies the required security concepts and experimentally demonstrated the effectiveness of the scheme.
To study how to display the scientific and technological information of enterprise products through interactive dissemination and make a pre-marketing, the Internet of Things is integrated and how to ...attract people's attention and interact more with the support of the Internet of Things technology is discussed. With the rapid development of science and technology, there are more and more platforms to display enterprise products. Because of its extensive application needs, it opens a new direction for the development of various fields in China and provides new innovative ideas. In terms of product exhibition, the Internet of Things may connect various scenarios of product use, satisfy the practical needs of consumers, truly realize customer experience, gain the trust of consumers, and ultimately facilitate transactions. Therefore, referring to relevant literature and through the perception layer of the Internet of Things, obtain the information of visitors, guide them to exhibition visits, and give feedback in the process of experience. The results show that the identification and sensing technology in the Internet of Things can be applied to the interactive display, which can interact with the visitors well, not only let them have a better experience, but also achieve efficient marketing in the exhibition. It lays a certain foundation for expanding the audience of related technologies and products after that but also provides new ideas for the application of the Internet of Things technology in the direction of cultural communication.
This study explored the ability of microRNA-135a (miR-135a) to influence cell proliferation, migration, invasion, apoptosis and tumor angiogenesis through the IGF-1/PI3K/Akt signaling pathway in ...non-small cell lung cancer (NSCLC).
NSCLC tissues and adjacent normal tissues were collected from 138 NSCLC patients. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression levels of miR-135a and IGF-1, PI3K, Akt, VEGF, bFGF and IL-8 mRNA; western blotting was used to determine the expression levels of IGF-1, PI3K and Akt protein; and enzyme-linked immunosorbent assay (ELISA) was used to analyze the expression levels of VEGF, bFGF and IL-8 protein. Human NSCLC cell lines (A549, H460, and H1299) and the human bronchial epithelial cell line (HBE) were selected. A549 cells were assigned to blank, negative control (NC), miR-135a mimics, miR-135a inhibitors, IGF-1 siRNA and miR-135a inhibitors + IGF-1 siRNA groups. The following were performed: an MTT assay to assess cell proliferation, a scratch test to detect cell migration, a Transwell assay to measure cell invasion, and a flow cytometry to analyze cell apoptosis.
The expression level of miR-135a was lower while those of IGF-1, PI3K and Akt mRNA were higher in NSCLC tissues than in the adjacent normal tissues. Dual-luciferase reporter assay indicated IGF-1 as a target of miR-135a. The in vitro results showed that compared with the blank group, cell proliferation, migration and invasion were suppressed, mRNA and protein levels of IGF-1, PI3K, Akt, VEGF, bFGF and IL-8 were reduced, and cell apoptosis was enhanced in the miR-135a mimics and IGF-1 siRNA groups. Compared with the IGF-1 siRNA group, cells in the miR-135a inhibitors + IGF-1 siRNA group demonstrated increased cell proliferation, migration and invasion, elevated mRNA and protein levels of IGF-1, PI3K, Akt, VEGF, bFGF and IL-8 and reduced cell apoptosis.
These findings indicated that miR-135a promotes cell apoptosis and inhibits cell proliferation, migration, invasion and tumor angiogenesis by targeting IGF-1 gene through the IGF-1/PI3K/Akt signaling pathway in NSCLC.
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