Neotectonics of Asia: Thin-shell finite-element models with faults

As India pushed into and beneath the south margin of Asia in Cenozoic time, it added a great volume of crust, which may have been (1) emplaced locally beneath Tibet, (2) distributed as regional crustal thickening of Asia, (3) converted to mantle eclogite by high-pressure metamorphism, or (4) extruded eastward to increase the area of Asia. The amount of eastward extrusion is especially controversial: plane-stress computer models of finite strain in a continuum lithosphere show minimal escape, while laboratory and theoretical plane-strain models of finite strain in a faulted lithosphere show escape as the dominant mode. We suggest computing the present (or neo)tectonics by use of the known fault network and available data on fault activity, geodesy, and stress to select the best model. We apply a new thin-shell method which can represent a faulted lithosphere of realistic rheology on a sphere, and provided predictions of present velocities, fault slip rates, and stresses for various trial rheologies and boundary conditions. To minimize artificial boundaries, the models include all of Asia east of 40 deg E and span 100 deg on the globe. The primary unknowns are the friction coefficient of faults within Asia and the amounts of shear traction applied to Asia in the Himalayan and oceanic subduction zones at its margins. Data on Quaternary fault activity prove to be most useful in rating the models. Best results are obtained with a very low fault friction of 0.085. This major heterogeneity shows that unfaulted continum models cannot be expected to give accurate simulations of the orogeny. But, even with such weak faults, only a fraction of the internal deformation is expressed as fault slip; this means that rigid microplate models cannot represent the kinematics either. A universal feature of the better models is that eastern China and southeast Asia flow rapidly eastward with respect to Siberia. The rate of escape is very sensitive to the level of shear traction in the Pacific subduction zones, which is below 6 MPa. Because this flow occurs across a wide range of latitudes, the net eastward escape is greater than the rate of crustal addition in the Himalaya. The crustal budget is balanced by extension and thinning, primarily within the Tibetan plateau and the Baikal rift. The low level of deviation stresses in the best models suggests that topographic stress plays a major role in the orogeny; thus, we have to expect that different topography in the past may have been linked with fundamentally different modes of continental collision

Fano Resonance in High-Permittivity Objects

In this chapter, Fano resonances in simple structures with high permittivity such as spheres or core-shell particles are analyzed by Mie theory. The Mie scattering coefficients can be decomposed into slow varying backgrounds and narrow resonances, which cause the Fano resonances in scattered field. For structures of arbitrary shapes, temporal coupled-mode theory is applied to explain the Fano resonances found in the scattering cross section. At last, we analyze the periodic structures by using band diagram, and it shows that the Fano resonances can be viewed as the superposition of the Bloch wave and the Mie scattering wave

Engineering band structures and topological invariants by transformation optics

By introducing the transformation optics method to periodic systems, we show the tunability of the band structures by comparing the results from original spaces and transformed spaces. Interestingly, we find the topological invariant Chern number will change sign when the orientation of the Brillouin zone flipped. The new platform we provided for engineering the band diagram and topological invariant might lead to the development of both transformation optics and photonic topological states.Comment: 6 pages, 3 figure

Delivery of the Sox9 gene promotes chondrogenic differentiation of human umbilical cord blood-derived mesenchymal stem cells in an in vitro model

SRY-related high-mobility-group box 9 (Sox9) gene is a cartilage-specific transcription factor that plays essential roles in chondrocyte differentiation and cartilage formation. The aim of this study was to investigate the feasibility of genetic delivery of Sox9 to enhance chondrogenic differentiation of human umbilical cord blood-derived mesenchymal stem cells (hUC-MSCs). After they were isolated from human umbilical cord blood within 24 h after delivery of neonates, hUC-MSCs were untreated or transfected with a human Sox9-expressing plasmid or an empty vector. The cells were assessed for morphology and chondrogenic differentiation. The isolated cells with a fibroblast-like morphology in monolayer culture were positive for the MSC markers CD44, CD105, CD73, and CD90, but negative for the differentiation markers CD34, CD45, CD19, CD14, or major histocompatibility complex class II. Sox9 overexpression induced accumulation of sulfated proteoglycans, without altering the cellular morphology. Immunocytochemistry demonstrated that genetic delivery of Sox9 markedly enhanced the expression of aggrecan and type II collagen in hUC-MSCs compared with empty vector-transfected counterparts. Reverse transcription-polymerase chain reaction analysis further confirmed the elevation of aggrecan and type II collagen at the mRNA level in Sox9-transfected cells. Taken together, short-term Sox9 overexpression facilitates chondrogenesis of hUC-MSCs and may thus have potential implications in cartilage tissue engineering.publishedVersio

Temperature affects carbon and nitrogen stable isotopic signatures of aquatic plants

Aquatic plants are vital components of shallow aquatic ecosystems, and they can substantially contribute to food webs. However, the large spatial and temporal variations of δ13C and δ15N signatures of aquatic plants have hindered the interpretation of their trophic interactions with organisms at higher trophic levels, and the effects of temperature on plant isotopic signatures remain to be fully elucidated. Herein, we cultured three common submerged macrophytes [Elodea nuttallii (Planch.) St. John, Vallisneria spiralis L., and Potamogeton lucens L.] at four temperatures (10, 15, 20 and 25 °C) for 16 weeks and analyzed their δ13C and δ15N signatures. Results showed that temperature altered the isotopic signatures of all three plant species. δ13C and δ15N varied by 16.06‰ and 11.68‰ in P. lucens at different temperatures, respectively. Plant δ15N significantly decreased with rising temperature in all three plant species and was correlated with plant growth, N content, and pore water dissolved inorganic N (DIN) concentrations. Conversely, δ13C responded non-linearly with temperature: a hump-shaped response of δ13C with temperature was observed for P. lucens. Plant δ13C was not correlated with any of the measured parameters. Temperature can alter plant metabolism and photosynthesis and the compositions and concentrations of C and N sources, thereby influencing plant δ13C and δ15N signatures, respectively. Temperature plays a key role in altering plant C and N isotopic signatures. Therefore, we recommend future studies to carefully consider the effects of temperature on plant stable isotopic signatures when interpreting the food contribution of aquatic plants in food webs and long-term environmental changes via historical isotopic signatures of plants exposed to different temperatures, particularly in light of changing climate conditions

Super-reflector enabled by non-interleaved spin-momentum-multiplexed metasurface

Electromagnetic wave multiplexing, especially for that occurring at different incidences (spatial-frequency multiplexing), is pivotal for ultrathin multifunctional interfaces and high-capacity information processing and communication. It is yet extremely challenging based on passive and compact wave elements, since the wave excitation and scattering channels are exclusively coupled through gradient phases and hence momentum matching condition at the interface. Here, we propose a spin-momentum multiplexed paradigm called a super-reflector enabling on-demand control of both retroreflections and anomalous reflections using a non-interleaved single-celled metasurface. By multiplexing four channels connecting two spin states excited onto each input of three spatial frequencies, a total of twelve channels are engineered, among which three are retroreflected channels and the residual are anomalous reflection ones. Our compound multiplexed super-reflector allows five degrees of freedom in circular polarization Jones' matrix, approaching the intrinsic upper limit of such planar metasurface. The concept has been experimentally verified by a proof-of-concept super-reflector at microwave frequency, showcasing twelve reflected beams and a high efficiency exceeding 90.6% defined as the ratio of reflected power to incidence for each channel beam. Our strategy opens a new avenue for angle multiplexing and angle-resolved metadevices toward the capacity limit of 2D planar Jones' matrix.Published versionThis work is supported by the National Natural Science Foundation of China under Grant No. 62171459, the National Defense Foundation of China under Grant No. 2019-JCJQ-JJ-081, Key Program of Natural Science Foundation of Shaanxi Province under Grant No. 2020JZ-33, and also the Special Talents Support Program of Shaanxi Province for Young Top Talents