The lithospheric lager and block velocity structure and motion of Substance for Tibetan plateau

Abstract HKT-ISTP 2013 A

Transition from continental collision to tectonic escape? A geophysical perspective on lateral expansion of the northern Tibetan Plateau

A number of tectonic models have been proposed for the Tibetan Plateau, which origin, however, remains poorly understood. In this study, investigations of the shear wave velocity (Vs) and density (ρ) structures of the crust and upper mantle evidenced three remarkable features: (1) There are variations in Vs and ρ of the metasomatic mantle wedge in the hanging wall of the subduction beneath different tectonic blocks of Tibet, which may be inferred as related to the dehydration of the downgoing slab. (2) Sections depicting gravitational potential energy suggest that the subducted lithosphere is less dense than the ambient rocks, and thus, being buoyant, it cannot be driven by gravitational slab pull. The subduction process can be inferred by the faster SW-ward motion of Eurasia relative to India as indicated by the plate motions relative to the mantle. An opposite NE-ward mantle flow can be inferred beneath the Himalaya system, deviating E and SE-ward toward China along the tectonic equator. (3) The variation in the thickness of the metasomatic mantle wedge suggests that the leading edge of the subducting Indian slab reaches the Bangoin-Nujiang suture (BNS), and the metasomatic mantle wedge overlaps with a region with poor Sn-wave propagation in north Tibet. The metasomatic layer, north of the BNS, deforms in the E-W direction to accommodate lithosphere shortening in south Tibet

Weakly coupled lithospheric extension in southern Tibet

AbstractWest–east extension is a prominent tectonic feature of southern and central Tibet despite ongoing north–south (N–S) convergence between India and Eurasia. Knowledge of deep structure beneath the N–S trending rifts is key to evaluating models proposed for their origin, including gravitational collapse, oblique convergence along the arcuate plate boundary, and mantle upwelling. We model direct S and Moho-reflected SsPmp phases at teleseismic distances to constrain variations in crustal thickness across the major rifts crossed by a ∼900-km long, W–E broadband array in the Lhasa Terrane. Crustal thicknesses are ∼70–80 km. However, Moho depth decreases by ∼10 km within a horizontal distance of 100 km west of the Yadong–Gulu rift (YGR) and Nyainquentanghla mountains (NQTL). This Moho uplift, taken with deep, extensional focal mechanisms and reduced seismic velocity in the upper mantle, suggests that asthenospheric upwelling has significantly contributed to the pattern of extension across the YGR and NQTL. The ∼100-km separation between surface rift and Moho uplift is likely enabled by partial decoupling across a ductile middle crust

Transient Receptor Potential V Channels Are Essential for Glucose Sensing by Aldolase and AMPK

Fructose-1,6-bisphosphate (FBP) aldolase links sensing of declining glucose availability to AMPK activation via the lysosomal pathway. However, how aldolase transmits lack of occupancy by FBP to AMPK activation remains unclear. Here, we show that FBP-unoccupied aldolase interacts with and inhibits endoplasmic reticulum (ER)-localized transient receptor potential channel subfamily V, inhibiting calcium release in low glucose. The decrease of calcium at contact sites between ER and lysosome renders the inhibited TRPV accessible to bind the lysosomal v-ATPase that then recruits AXIN:LKB1 to activate AMPK independently of AMP. Genetic depletion of TRPVs blocks glucose starvation-induced AMPK activation in cells and liver of mice, and in nematodes, indicative of physical requirement of TRPVs. Pharmacological inhibition of TRPVs activates AMPK and elevates NAD(+) levels in aged muscles, rejuvenating the animals' running capacity. Our study elucidates that TRPVs relay the FBP-free status of aldolase to the reconfiguration of v-ATPase, leading to AMPK activation in low glucose

Fructose-1,6-bisphosphate and aldolase mediate glucose sensing by AMPK

葡萄糖是生物中最基本、最主要的营养物质，它不仅是机体能量的主要来源，也是生物质合成的主要原料。因此，葡萄糖的水平对于生物体是极其重要的。然而，在生活中，体内葡萄糖水平的波动是十分常见的，这是因为我们不可能每时每刻都在摄入葡萄糖：睡一大觉、剧烈运动几个小时或者太忙了没时间吃饭，都会引起葡萄糖水平的显著下降。这时，机体能够触发一套有效的过程应对这类“不利情况”，其中最为关键的就是激活“代谢的核心调节”——AMPK。在葡萄糖水平下降时，被激活的AMPK能够迅速启动脂肪、蛋白质的分解代谢，关闭它们的合成代谢，从而起到维持机体的能量和物质代谢的平衡，弥补机体因葡萄糖不足引起的胁迫压力。那么，机体如何感受葡萄糖水平下降，并“传递”给AMPK使其激活呢？林圣彩教授课题组的这项研究正是发现了生理状态下机体感受葡萄糖水平的机制。通过研究他们发现，无论在不含葡萄糖的细胞培养条件下，还是在饥饿的低血糖的动物体内，都不能观测到AMP水平的上升，这充分说明了机体有一套尚不为人知的、独立于AMP的感应葡萄糖水平的机制。在进一步的研究中他们揭示了这一完整过程：葡萄糖水平下降将引起的葡萄糖代谢中间物——果糖1,6-二磷酸（fructose-1,6-bisphosphate）水平的下降，该过程进一步地被糖酵解通路上的代谢酶——醛缩酶（aldolase）感应，因为醛缩酶正是将含有6个碳原子的果糖1,6-二磷酸裂解成三碳糖的酶，一旦醛缩酶“吃不到”由葡萄糖衍生的果糖1,6-二磷酸，它便“翻脸”，传递给也正是林圣彩教授课题组先前发现的溶酶体途径进而激活AMPK。该过程完全不涉及AMP水平，即能量水平的变化，是一条全新的、完全建立在实际的生理情况上的通路。林圣彩教授进一步地把葡萄糖水平总结为一种“状态信号”，以区别于传统的“能量信号”。据悉，该葡萄糖感知通路的发现对开发用于治疗肥胖症，乃至延长寿命的药物具有深远的意义。【Abstract】The major energy source for most cells is glucose, from which ATP is generated via glycolysis and/or oxidative metabolism. Glucose deprivation activates AMP-activated protein kinase (AMPK)1, but it is unclear whether this activation occurs solely via changes in AMP or ADP, the classical activators of AMPK2, 3, 4, 5. Here, we describe an AMP/ADP-independent mechanism that triggers AMPK activation by sensing the absence of fructose-1,6-bisphosphate (FBP), with AMPK being progressively activated as extracellular glucose and intracellular FBP decrease. When unoccupied by FBP, aldolases promote the formation of a lysosomal complex containing at least v-ATPase, ragulator, axin, liver kinase B1 (LKB1) and AMPK, which has previously been shown to be required for AMPK activation6, 7. Knockdown of aldolases activates AMPK even in cells with abundant glucose, whereas the catalysis-defective D34S aldolase mutant, which still binds FBP, blocks AMPK activation. Cell-free reconstitution assays show that addition of FBP disrupts the association of axin and LKB1 with v-ATPase and ragulator. Importantly, in some cell types AMP/ATP and ADP/ATP ratios remain unchanged during acute glucose starvation, and intact AMP-binding sites on AMPK are not required for AMPK activation. These results establish that aldolase, as well as being a glycolytic enzyme, is a sensor of glucose availability that regulates AMPK.D.G.H. was supported by an Investigator Award from the Wellcome Trust (097726) and a Programme Grant from Cancer Research UK (C37030/A15101). S.-C.L. was supported by grants from the National Key Research and Development Project of China (2016YFA0502001) and the National Natural Science Foundation of China (#31430094, #31690101, #31571214, #31601152 and #J1310027)

A group velocity of seismic love surface wave and lithosphere structure in Antarctic Peninsula

This paper is based on the surface wave seismogram of South Sandwich Island earthquake (Ms = 6.4) recorded by Antarctic General Bernardo O'Higgins Station. We computed a group velocity dispersion of Love surface wave and obtained lithosphere structure by using the method of the matched-filter frequency-time analysis and grid dispersion inversion. Our result shows that crust structure below Antarctic Peninsula may be divided into three layers and their thickness are respectively 5km, 8km and 10km. Upper mantle velocity is 5.32 km/s and gradually changes into 5.11 - 4.9 km/s below 53 km. The minimum velocity is 4.8 km/s. It can be referred that Antarctic mantle is also of layered structure

Structural model of the lithosphere-asthenosphere system beneath the Qinghai-Tibet Plateau and its adjacent areas

The deep structure of the lithosphere\u2013asthenosphere system, as imaged from geophysical data, of the Qinghai\u2013 Tibet Plateau, the highest on the Earth, provides important clues in understanding its orogenic processes. Here we reconstruct the main features of the structure of the crust and upper mantle from surface wave tomography in the Qinghai\u2013Tibet Plateau and its adjacent areas, in order to understand the modality of the convergence and collision process between the Indian and Eurasian plates. Based on Rayleigh waves dispersion theory, we collect- ed long period and broad-band seismic data from the global and regional seismic networks surrounding the study area (20\ub0N\u201350\ub0N, 70\ub0E\u2013110\ub0E). After applying instrument response calibration and filtering, group veloc- ities of the fundamental mode of Rayleigh waves are measured using the frequency\u2013time analysis (FTAN). Com- bining the published dispersion data, a 2-D surface-wave tomography method is applied to calculate the lateral variations of group velocity distribution at different periods, in the range from 8 s to 150 s. The Hedgehog non- linear inversion method is performed to obtain shear wave velocity (Vs) versus depth models of the crust and upper mantle for 181 cells, with size 2\ub0 7 2\ub0. In order to identify the cellular representative models, we applied the local smoothness optimization method (LSO). Fairly detailed structural models of the lithosphere\u2013astheno- sphere system have been defined. The Vs models demonstrate the lateral variation of the thickness of the meta- somatic lid between the south and north of the Bangong\u2013Nujiang Suture (BNS) and the west and east of Tibet. The variation in thickness of the metasomatic lid may suggest that the leading edge of the subducting Indian slab reaches up to BNS