Search

In this study, the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) gravitational gradients in the North China Craton (NCC) are processed. The normal gravitational gradient correction, the downward continuation from the mean orbit altitude to the geoid, and the gravitational gradient corrections for the topography, sediment, Moho undulations and the deep-source field are taken into account. After processing, the residual gravitational gradient anomalies corresponding to density heterogeneities are acquired. The preconditioned conjugate gradient method is introduced to invert the density structures using the roughness matrix to constrain the density distribution and the depth-weighting function to prevent the density distribution from migrating to the top of the model due to the decay of the gravitational gradient kernel with depth. The density structure derived from the seismic tomography is used as the initial model, and the GOCE gravitational gradient anomalies are used to invert the density structures in the NCC using the preconditioned conjugate gradient method. The results show that the density structures of the NCC lithosphere reflect obvious lateral and vertical heterogeneities. The density structure in the eastern part of the NCC is different from that in the western part of the NCC. The distribution of the density anomalies corresponds to the tectonic characteristics. The density structures in Taihang Mountain exhibit segmentation features. The thinning of the lithosphere observed in the NCC may extend into the northern part of Taihang Mountain. The density changes significantly within the area between the Ordos Block and the Qilian Block, which corresponds with the different lithospheric features in these two blocks.

To solve the non-uniqueness problem of gravity gradient inversion, we proposed a folding calculation method based on preconditioned conjugate gradient inversion. Compared with the original algorithm in which the entire study area is taken as the research subject and all grids are used simultaneously in the inversion, the proposed folding method divides the research area into several sub-areas. A prism unit from any of the four corner grids is selected for the first iteration, whose density anomaly result is taken as the initial density anomaly for the next iteration of the same sub-area. The folding in the left–right and up–down directions takes turns during the calculation until the inversion calculation has covered the entire research area. This folding algorithm demonstrates strong regularity. The inversion results of multiple synthetic models show that the folding calculation method performs multiple parameter corrections in the initial model. Meanwhile, on the basis that the relative fitting of standard errors of the observed values satisfies the convergence condition, the model errors are constrained, and thus, the model errors of the inversion results are consequently reduced. The 3-D density anomaly pattern over the Craton area in North China was obtained via a joint inversion of the four components ( $$\varvec{T}_{\text{xx}} ,$$ $$\varvec{T}_{\text{xz}} ,$$ $$\varvec{T}_{\text{yy}} ,$$ and $$\varvec{T}_{\text{zz}}$$ ) of the Gravity field and steady-state Ocean Circulation Explorer L2 gravity gradient after preprocessing. We compared the inversion results from the folding calculation method and the original method, and performed detailed analysis and discussion on the inversion results with existing geological and geophysical data. Our analysis shows that the improved calculation method is effectively applicable to the inversion of measured gravity gradient data, and the inversion results provide more detailed and reliable pattern information for the density anomaly.

Keloids are skin fibroproliferative tumors characterized by locally invasive growth of fibroblasts and excessive collagen deposition. The objective of this study is to investigate the molecular basis of the keloid scar by studying the mutation of related genes. We performed gene screening of mechanoreceptors by quantitative polymerase chain reaction (qPCR), Sanger sequencing to detect the CXCR1gene mutation, and immuno-histochemistry to determine CXCR1 protein expression. Among the genes encoding mechanoreceptors, the expression of CXCR1 mRNA was significantly higher in keloid scar tissues than in the surrounding tissues of normal controls (P A (p.Gly192Glu). Immunohistochemistry showed heightened protein expression of CXCR1 in keloid scars as compared to controls. Our findings indicate that CXCR1 gene mutation and altered protein expression are associated with keloid scar development. Identification of the CXCR1 gene mutation might provide insights into the molecular mechanism underlying keloid scar and underscores the potential importance of mechanoreceptors in keloid scar pathogenesis. Electronic supplementary material The online version of this article (10.1007/s00403-018-1847-3) contains supplementary material, which is available to authorized users.

The satellite-derived gravity gives us an opportunity to investigate the basement structures of the East and South China Seas since the satellite gravimetry could provide large scale gravity data with high resolution of 1 arc-min by 1 arc-min. We isolate the residual gravity anomaly corresponding to the basement by subtracting the gravity anomalies of sediments and Moho undulations from satellite-derived free-air gravity anomalies. Two methods, namely gravity inversion method and convolution method based on flexure isostasy model, are used to calculate the Moho undulations in order to guarantee the accuracy of the Moho undulations since it occupies large percentages of the gravity anomalies. We invert the isolated gravity anomaly for the basement depths of East and South China Seas and adjacent areas with resolution of 1 arc-min by 1 arc-min. The basement depths of East and South China Seas range from 0.5 km to 12 km and the Moho depths vary between 6 km and 32 km. The basement topography reveals many tectonic depressions and two spreading axes concealed by the sediments, which are unseen in the bathymetry. The two spreading axes correspond to the spreading ridges derived from magnetic anomaly and the SW–NE oriented spreading axis extends SW much farther than that identified from magnetic anomaly, almost reaching to the Nam Con Son Basin. We also find that the faults constrain the distributions of basement depressions since the faults usually lie along the places where large changes of basement depth take place. Reversely, the basement map could be used to identify the unknown faults. Besides, according to the four profiles in the East and South China Seas, the mirror–image relation was found between the basement topography and the underlying Moho undulations that when the basement depth increases or decreases, the corresponding Moho depth decreases or increases.

The crustal structure of Xiachayu-Gonghe geophysical profile in eastern Tibetan plateau is simulated with Bouguer anomaly corrected for sediments and lithosphere. The forward simulation shows that the thickness of upper crust in eastern Tibetan plateau is about 20 km, and the density is 2.78×103kg/m3. The bottom interface of middle crust changes from 30 km to 40 km, the density of middle crust is 2.89×103kg/m3. The materials with low density of 2.78 ×103kg/m3 exist in middle crust, and those with high density of 3.33 ×103kg/m3 exist at the bottom of middle crust between Wenquan and Tanggemu. The density is 3.10 ×103kg/m3 in lower crust. The shallowest depth of Moho interface is about 56 km, and the deepest one is about 74 km, the undulation of interface is large, the deep Moho is located in Xiachayu, Chayu, Nujiang, and Wenquan. The crustal density of eastern Tibetan plateau is larger than that of central section; the low velocity layers are located in middle crust and bottom in eastern Tibetan plateau and at the bottom of the upper crust in the central plateau.