Existing end-member models sparked debates concerning plateau formation in the southeast Tibetan Plateau through early-middle Cenozoic transpressional and shortening deformation or late Cenozoic ...regional lower crustal flow with limited crustal shortening. Therefore, the spatiotemporal pattern of deformation and exhumation is essential for distinguishing these models. Here, we present a compilation of new and previously published structural and geo-thermochronological data to explore the Cenozoic deformation history and the underpinning mechanism of the southeast Tibetan Plateau. The synthesis shows two main phases of deformation during the Cenozoic: (1) spaced late Eocene-early Miocene crustal shortening and thickening along major fault zones, including the Ailaoshan-Red River, the Xianshuihe-Xiaojiang and Yalong-Yulong faults, and (2) late Miocene deformation and exhumation that is widely distributed within and away from the major faults. Our new structural analysis in the Yuanmou area, bounded by the major fault zones, reveals an open ~N-trending antiform, named here as Yuanmou antiform, outcropping Precambrian basement in core, mantled by Mesozoic-Cenozoic strata. The youngest strata (upper Cretaceous-Paleogene) involved in the folding are unconformably overlain by undeformed late Miocene deposits, suggesting that the antiform accommodated a phase of early-middle Cenozoic ~E-W contraction, whose shortening rate is estimated as ~9%. The timing of the Cenozoic folding is quantified as ~40–28 Ma by low temperature thermochronological data. Our study shows that late Eocene-early Miocene crustal shortening and surface uplift mainly occurs along major fault zones, with limited shortening in the intervening regions. Such a shortening pattern and history suggests the formation of the regional crustal thickening and surface uplift should have occurred in the late Miocene time. Here we proposed a new progressive deformation model to explain the deformation history and the regional crustal thickening. The model infers that the spaced late Eocene-early Miocene shortening thickened the crust beneath major fault zones and progressively led to the late Miocene lateral diffusive expansion of the mid-lower crust after sufficient thermal weakening at a timescale of ~30–20 Myr. The expansion of the weakened mid-lower crust resulted in regional crustal thickening and surface uplift in the southeast Tibetan Plateau.
•Structural and thermochronological data reveal limited late Eocene-early Oligocene shortening in areas between major faults.•The SE Tibetan Plateau experienced late Eocene-early Miocene spaced shortening and late Miocene distributed deformation.•Prior shortening weakened the crust and led to late Miocene mid-lower crustal expansion and regional surface uplift.
Exosome therapy is a promising therapeutic approach for intervertebral disc degeneration (IVDD) and achieves its therapeutic effects by regulating metabolic disorders, the microenvironment and cell ...homeostasis with the sustained release of microRNAs, proteins, and transcription factors. However, the rapid clearance and disruption of exosomes are the two major challenges for the application of exosome therapy in IVDD. Herein, a thermosensitive acellular extracellular matrix (ECM) hydrogel coupled with adipose-derived mesenchymal stem cell (ADSC) exosomes (dECM@exo) that inherits the superior properties of nucleus pulposus tissue and ADSCs was fabricated to ameliorate IVDD. This thermosensitive dECM@exo hydrogel system can provide not only in situ gelation to replenish ECM leakage in nucleus pulposus cells (NPCs) but also an environment for the growth of NPCs. In addition, sustained release of ADSC-derived exosomes from this system regulates matrix synthesis and degradation by regulating matrix metalloproteinases (MMPs) and inhibits pyroptosis by mitigating the inflammatory response in vitro. Animal results demonstrated that the dECM@exo hydrogel system maintained early IVD microenvironment homeostasis and ameliorated IVDD. This functional system can serve as a powerful platform for IVD drug delivery and biotherapy and an alternative therapy for IVDD.
Spinal cord injury (SCI) is a severe neurological disease; however, few drugs have been proved to treat SCI effectively. Neuroinflammation is the major pathogenesis of SCI secondary injury and ...considered to be the therapeutic target of SCI. Salidroside (Sal) has been reported to exert anti‐inflammatory effects in airway, adipose and myocardial tissue; however, the role of Sal in SCI therapeutics has not been clarified. In this study, we showed that Sal could improve the functional recovery of spinal cord in rats as revealed by increased BBB locomotor rating scale, angle of incline, and decreased cavity of spinal cord injury and apoptosis of neurons in vivo. Immunofluorescence double staining of microglia marker and M1/M2 marker demonstrated that Sal could suppress M1 microglia polarization and activate M2 microglia polarization in vivo. To verify how Sal exerts its effects on microglia polarization and neuron protection, we performed the mechanism study in vitro in microglia cell line BV‐2 and neuron cell line PC12. The results showed that Sal prevents apoptosis of PC12 cells in coculture with LPS‐induced M1 BV‐2 microglia, also the inflammatory secretion phenotype of M1 BV‐2 microglia was suppressed by Sal, and further studies demonstrated that autophagic flux regulation through AMPK/mTOR pathway was involved in Sal regulated microglia polarization after SCI. Overall, our study illustrated that Sal could promote spinal cord injury functional recovery in rats, and the mechanism may relate to its microglia polarization modulation through AMPK‐/mTOR‐mediated autophagic flux stimulation.
The Pearl River is one of the largest rivers entering the South China Sea, yet its initiation time remains debated, a topic we address using Pb isotopes in detrital K‐feldspar. Based on these Pb ...data, Eocene and Early Oligocene sandstones from the northern South China Sea are interpreted to have been supplied with sediment by proximal rivers draining the Cathaysia Block. In contrast, the Late Oligocene and Miocene sandstones are mainly derived from the western Pearl tributaries (e.g., Hongshui River), suggesting that the Pearl River had formed by the Late Oligocene. Detrital zircon data from the Beibuwan Basin previously suggested that the western tributaries flowed into this basin before being captured by the paleo‐Pearl River. These lines of evidence suggest that progressive headward erosion of the eastern Pearl River and late Oligocene integration of this large fluvial system can be linked to contemporaneous sea‐floor spreading of the South China Sea.
Plain Language Summary
The Pearl River is one of the largest rivers flowing into the South China Sea. However, when this river achieved its present drainage character remains debated. Here we report a comprehensive investigation of sand/sandstone provenance of the Pearl River as well as the Pearl River Mouth Basin (PRMB) using Pb isotopes measured in detrital K‐feldspar. Our results suggest that Eocene and Early Oligocene sandstones were mainly fed by proximal rivers within the Cathaysia Block, while the Late Oligocene samples are enriched in K‐feldspar grains from the Hongshui River, suggesting that the Pearl River had achieved its present character by the Late Oligocene. Early Oligocene deposits in the Beibuwan Basin share an indistinguishable detrital zircon provenance signal to that of the western tributaries of the Pearl River, indicating that the western tributaries likely flowed into the Beibuwan Basin before being captured by the paleo‐Pearl River. Taken together, this evidence suggest that progressive headward erosion of the eastern Pearl River triggered by the subsidence of PRMB and sea‐floor spreading of the South China Sea played an important role in the late Oligocene integration of this large fluvial system.
Key Points
Sedimentary provenance of the Pearl River and Pearl River Mouth Basin constrained using detrital K‐feldspar Pb isotopes
Pb isotopic data indicate that the Pearl River achieved its present character by the Late Oligocene
The opening of the South China Sea played an important role in the drainage reorganization of the Pearl River
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Wound therapy with a rapid healing performance remains a critical clinical challenge. Cellular delivery is considered to be a promising approach to improve the efficiency of healing, ...yet problems such as compromised cell viability and functionality arise due to the inefficient delivery. Here, we report the efficient delivery of endothelial progenitor cells (EPCs) with a bioactive nanofibrous scaffold (composed of collagen and polycaprolactone and bioactive glass nanoparticles, CPB) for enhancing wound healing. Under the stimulation of CPB nanofibrous system, the viability and angiogenic ability of EPCs were significantly enhanced through the activation of Hif-1α/VEGF/SDF-1α signaling. In vivo, CPB/EPC constructs significantly enhanced the formation of high-density blood vessels by greatly upregulating the expressions of Hif-1α, VEGF, and SDF-1α. Moreover, owing to the increased local delivery of cells and fast neovascularization within the wound site, cell proliferative activity, granulation tissue formation, and collagen synthesis and deposition were greatly promoted by CPB/EPC constructs resulting in rapid re-epithelialization and regeneration of skin appendages. As a result, the synergistic enhancement of wound healing was observed from CPB/EPC constructs, which suggests the highly efficient delivery of EPCs. CPB/EPC constructs may become highly competitive cell-based therapeutic products for efficient impaired wound healing application. This study may also provide a novel strategy to develop bioactive cell therapy constructs for angiogenesis-related regenerative medicine.
This paper reported a highly efficient local delivery of EPCs using bioactive glass-based CPB nanofibrous scaffold for enhancing angiogenesis and wound regeneration. In vitro study showed that CPB can promote the proliferation, migration, and tube formation of EPCs through upregulation of the Hif-1α/VEGF/SDF-1α signaling pathway, indicating that the bioactivity and angiogenic ability of EPCs can be highly maintained and promoted by the CPB scaffold. Moreover, CPB/EPC constructs effectively stimulated the regeneration of diabetic wounds with satisfactory vascularization and better healing outcomes in a full-thickness wound model, suggesting that the highly efficient delivery of EPCs to wound site facilitates angiogenesis and further leads to wound healing. The high angiogenic capacity and excellent healing ability make CPB/EPC constructs highly competitive in cell-based therapeutic products for efficient wound repair application.
This article is dedicated to developing an online collision detection and identification (CDI) scheme for human-collaborative robots. The scheme is composed of a signal classifier and an online ...diagnosor, which monitors the sensory signals of the robot system, detects the occurrence of a physical human-robot interaction, and identifies its type within a short period. In the beginning, we conduct an experiment to construct a data set that contains the segmented physical interaction signals with ground truth. Then, we develop the signal classifier on the data set with the paradigm of supervised learning. To adapt the classifier to the online application with requirements on response time, an auxiliary online diagnosor is designed using the Bayesian decision theory. The diagnosor provides not only a collision identification result but also a confidence index which represents the reliability of the result. Compared to the previous works, the proposed scheme ensures rapid and accurate CDI even in the early stage of a physical interaction. As a result, safety mechanisms can be triggered before further injuries are caused, which is quite valuable and important toward a safe human-robot collaboration. In the end, the proposed scheme is validated on a robot manipulator and applied to a demonstration task with collision reaction strategies. The experimental results reveal that the collisions are detected and classified within 20 ms with an overall accuracy of 99.6%, which confirms the applicability of the scheme to collaborative robots in practice. Note to Practitioners -This article is intended to provide a novel online collision event handling scheme for robots in industrial environments. This scheme is designed to quickly and accurately detect an accidental collision and distinguish it from the intentional human-robot interaction. The method takes the raw signals from external torque sensors and provides a collision diagnosis result with a reliability index. The simple structure makes it easy to be implemented as a regular fault monitoring routine for collaborative robots. Different from the conventional methods, the proposed collision identification scheme in this article especially focuses on overcoming the following two challenges in practice: first, to timely and accurately report a collision within its early stage, and second, to ensure a high identification accuracy in a complicated environment, where ubiquitous disturbance and noise are unneglectable. The experimental validation at the end of this article confirms its promising application value in human-robot collaboration.
The sedimentary archive of the Jianchuan Basin provides a critical constraint on the formation of the “First Bend”, a major geomorphological feature of the Yangtze River, involving an abrupt 150° ...change in flow direction. Despite extensive detrital zircon provenance studies, no consensus has been reached on the timing of this event. Prior to the formation of the First Bend, the Yangtze is thought to have flowed southwards through the Jinchuan Basin, entering the South China Sea via the Red River. In this study, we constrain the timing of the First Bend using detrital K-feldspar Pb isotopic and detrital zircon U-Pb age datasets from Jianchuan Basin sandstones. Provenance data from late Eocene detrital zircon and K-feldspar populations concur in suggesting that they were fed by the southward flowing paleo-upper Yangtze River. Distinct K-Feldspar Pb isotopic data indicate that the overlying later Eocene and Pliocene deposits were fed by local Eocene syenites, granites and tuffs. Stratigraphic constraints on this change in provenance indicate that the southward flowing paleo-Yangtze River was cut off in the late Eocene at or before ∼37 Ma, thereby dating the formation of the First Bend. In contrast, detrital zircon U-Pb geochronology from the youngest units within the Jianchuan Basin is similar to those of the older sandstones and upper Yangtze River sands. This evidence indicates that the majority of zircons deposited in the upper part of the Jianchuan Basin were recycled from older sedimentary rocks. In our view, much of the disagreement relating to the formation time of the First Bend can be attributed to the failure to recognize sedimentary recycling. This study highlights the need to consider the possible presence of recycled detrital zircons when investigating paleo-drainage systems.
The timing of formation of the Three Gorges, a critical capture point on the Yangtze River, has been debated for more than a century. In this paper, we review the existing evidence and apply two ...sedimentary provenance proxies (Pb isotopic compositions of detrital K-feldspar and detrital zircon UPb ages) to date its incision based on samples from the early Cretaceous to Quaternary western Jianghan Basin and from the Neogene Yangtze Gravel, both located downstream of the Three Gorges. We show that from the early Cretaceous to the late Eocene, the western Jianghan Basin was mainly fed by the proximal sources, including the Qinling orogen and the Huangling dome. Similarly, from the latest Oligocene to the Miocene, local paleo-rivers supplied the Yangtze Gravel, mainly from the nearby Tongbai-Dabieshan. By the late Pliocene, the Jianghan Basin was fed by a river delivering sands with a Pb isotopic character indistinguishable from that of the modern Yangtze River. These provenance indicators suggest that the Three Gorges was cut through after the late Miocene (~10 Ma) but prior to the late Pliocene (~3.4 Ma). Cretaceous-Cenozoic deposits from the Jianghan Basin and the Yangtze Gravel have a detrital zircon UPb geochronology signature indistinguishable from that of the modern Yangtze River. It is inferred from this that the detrital zircon provenance signal has effectively been homogenized by complex transportation/recycling processes in the Yangtze Craton.
Cenozoic passive margin sediments in Taiwan provide an important natural archive to reconstruct drainage reorganization in eastern China. In this study, we used Pb isotope compositions of detrital ...K-feldspar to investigate the sedimentary provenance of Cenozoic strata in Taiwan and to constrain fluvial system evolution in eastern China. Eocene to lower Oligocene sandstones in Taiwan are characterized by radiogenic K-feldspar grains (206Pb/204Pb>18.4), indicating that the eastern Cathaysia Block served as the dominant sediment contributor. In contrast, a late Oligocene sample has a Pb isotopic character indistinguishable from that of the Gan River, a major tributary of the Yangtze River. This provenance change is interpreted as the result of headward (westward) migration of the paleo-Min River to the Wuyishan (Wuyi Mountains) during the late Oligocene. Miocene deposits are enriched in relatively unradiogenic K-feldspar (206Pb/204Pb<17.0) which can be reliably traced back to the Dabie and Sulu orogenic belts. Since the early Miocene, the paleo-Yangtze River, mainly draining the Yangtze Craton and the Dabie orogenic belt, delivered a large volume of detritus to the East China Sea Shelf Basin and also to the proto-Taiwan region.
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