The southern Qiangtang magmatic belt was formed by the north-dipping subduction of the Bangong–Nujiang Tethyan Ocean during Mesozoic. To better understand the petrogenesis, time–space distribution ...along the length of this belt, 21 samples of several granitoid bodies, from west to east, in the Bangong Co, Gaize, Dongqiao and Amdo areas were selected for in-situ zircon U–Pb dating, Hf isotopic and whole-rock chemical analyses. The results suggest a prolonged period of magmatic activity (185–84Ma) with two major stages during the Jurassic (185–150Ma) and the Early Cretaceous (126–100Ma). Both the Jurassic and Cretaceous granitoids are high-K calc-alkaline I-type rocks, except the Cretaceous two-mica granite from Amdo in the east, which belongs to S-type. The granitoids are generated from different source materials as indicated by zircon Hf isotopic compositions. The Bangong Co and Dongqiao granitoids show high zircon εHf(t) values of −1.3–13.6 with younger TDMC ages of 293–1263Ma, suggesting a relatively juvenile source; whereas the Gaize and Amdo granitoids have low εHf(t) values of −16.1–2.9 with older TDMC ages of 999–2024Ma, indicating an old crustal contribution. These source rocks melt at different P–T conditions as suggested by Sr/Y ratio and TZr. The Sr/Y ratio of both stage granitoids increases with decreasing age. However, the TZr of the Jurassic granitoids decreases, whereas the TZr of the Cretaceous granitoids increases with decreasing age. The contrasting geochemical signatures of these granitoids may be controlled by the varying contribution of slab-derived fluids involved in the generation of the Jurassic and Cretaceous granitic magmas; i.e. increasing amount of fluids in the Jurassic, whereas decreasing amount of fluids in the Cretaceous. Therefore, it is proposed that the Jurassic and Cretaceous magmatism may be related to subduction and closure of the Bangong–Nujiang Tethyan Ocean, respectively. The age pattern of the Jurassic and Cretaceous granitoids suggests an oblique subduction of the Bangong–Nujiang Tethyan Ocean and a diachronous collision between the Lhasa and Qiangtang blocks.
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•Systematic study of grantoids in south Qiangtang•Long period of magmatic activity (185 ~ 80 Ma) with two peaks (185 ~ 150 Ma and 126 ~ 100 Ma)•Jurassic and Cretaceous magmatism may be related to subduction and closure of the BNT, respectively•An oblique BNT subduction and a diachronous Lhasa-Qiangtang collision
Rheumatoid arthritis (RA) is a common, chronic, systemic autoimmune disease, and its clinical features are the proliferation of joint synovial tissue, the formation of pannus and the destruction of ...cartilage. The global incidence of RA is about 1%, and it is more common in women. The basic feature of RA is the body's immune system disorders, in which autoreactive CD4
T cells, pathogenic B cells, M1 macrophages, inflammatory cytokines, chemokines and autoantibodies abnormally increase in the body of RA patients B cell depletion therapy has well proved the important role of B cells in the pathogenesis of RA, and the treatment of RA with B cells as a target has also been paid more and more attention. Although the inflammatory indicators in RA patients receiving B-cell depletion therapy have been significantly improved, the risk of infection and cancer has also increased, which suggests that we need to deplete pathogenic B cells instead of all B cells. However, at present we cannot distinguish between pathogenic B cells and protective B cells in RA patients. In this review, we explore fresh perspectives upon the roles of B cells in the occurrence, development and treatment of RA.
The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In ...this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone（YTSZ） between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.
It is of prime importance to harness the transfer and flow of photogenerated electrons and holes to elongate the lifetimes of charge carriers and enhance the activity of semiconductor photocatalyst, ...which can be achieved by hybridizing the photocatalyst with appropriate cocatalysts with right electronic properties and placement. Herein, MXenes, a young family of two-dimensional transition metal carbides, are exploited as a hole mediator to enhance the photocatalytic activity of TiO2. We grow TiO2 sheets exposing (001) surfaces on layered Ti3C2Tx, and then photodeposited Cu2O nanodots on TiO2. We experimentally prove that the Ti3C2Tx MXene from the wet HF etching method behaves as a low work function material (ϕ = 3.4 eV). Thanks to this unique electronic property, the photogenerated electrons on TiO2 hybridized with Ti3C2Tx accumulate and tunnel to Cu2O to reduce it to elemental Cu as a reduction cocatalyst. The resulting Cu/TiO2@Ti3C2Tx photocatalyst efficiently split water to produce hydrogen at 860 μmol g−1 h−1. The results presented here demonstrate the promise of MXene materials in photocatalytic solar energy utilization. The insight into the electronic property of MXene sheds light on the new approach to the rational design of high-efficiency photocatalysts composed of MXenes.
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•Cu2O nanoparticles are photodeposited on TiO2 nanosheets hybridized with 2D Ti3C2.•The work function of –OH terminated 2D Ti3C2 is determined as 3.4 eV.•2D Ti3C2 as hole mediator enables the in-situ reduction of Cu2O to Cu as reduction cocatalyst.•The Cu/TiO2@Ti3C2 photocatalyst is highly active for water splitting to produce hydrogen at 860 μmol g−1 h−1.
•Carbonate clumped isotopes validate the preservation of primary carbonate of the Gonjo Basin in the early and middle Eocene.•The Gonjo Basin was low (0.7 km) in the early Eocene and rose to 3.8 km ...in the middle Eocene.•Rapid uplift was induced by intracontinental subduction between the Lhasa and Qiangtang terrains.
Views differ on the uplift history of the SE Tibetan Plateau and causal geodynamic mechanisms, yet reliable age-constrained paleoaltimetry in this region could test growth models of the entire plateau. Here we apply carbonate clumped isotope thermometry to well-dated carbonate paleosols and marls in the Gonjo Basin, SE Tibet, to reveal the topographic evolution of the basin. The sedimentary ages of carbonates of the lower and upper Ranmugou Formation are constrained to 54-50 Ma and 44-40 Ma, respectively. The temperature derived from carbonate clumped isotope thermometry indicates the mean annual air temperature (MAAT) of the Gonjo Basin in the early Eocene was ∼24°C, which is consistent with the warm climate indicated by palm fossils. The MAAT of the basin in the middle Eocene was ∼7°C, 17°C cooler than in the early Eocene. Carbonate clumped oxygen isotope thermometry-based paleoaltimetry shows the Gonjo Basin experienced a rapid uplift of 3.1 km, from ∼0.7 km in the early Eocene to ∼3.8 km in the middle Eocene. This rise explains the marked cooling. As a cause of this rapid rise, and the associated regional climate change transforming the landscape from desert to forest, we invoke crustal deformation and thickening induced by intracontinental subduction between the Lhasa and Qiangtang terranes that comprise the core of the Tibet.
Abstract
To investigate the micro-scale mechanism of strength deterioration under different times of dry–wet cycles, laboratory tests of physical properties, triaxial compression, X-ray diffraction ...(XRD) and scanning electron microscopy (SEM) were conducted on red sandstone on reservoir bank slopes. The research results showed that when the 5th dry–wet cycle ended, the dry mass and peak strength started to rapidly decline, while the porosity and saturated mass increased rapidly. In general, all of these behaviours become relatively stable when the number of cycles increased. Similarly, cohesion and internal friction angle changed most significantly from 0 to 10 cycles and then became stable. In addition, the physical expansion of the adsorbed water film and the dissolution and expansion of mineral particles increased the number of internal microcracks and pores and the porosity and saturated mass of the sample. In addition, the pore fluid effect and fracture flow effect made the microcracks in the red sandstone grow and connect; thus, the peak strength of the sample decreased. Moreover, during the dry–wet cycles, the change in the relative content of mineral particles and the pore fluid effect weakened the clay cementation, and then the dry mass and cohesion of the samples decreased. The research reported in this paper will play a very significant role in the scientific analysis of slope stability in the Three Gorges Reservoir area.
Foreign Direct Investment and the Environment Cole, Matthew A; Elliott, Robert J.R; Zhang, Liyun
Annual review of environment and resources,
10/2017, Letnik:
42, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We review the literature that investigates the relationship between foreign direct investment (FDI) and the environment. After reviewing the theoretical literature, we discuss two broad strands of ...research. First, the impact of environmental regulations on the choice of plant location and second, the impact of FDI on the emissions of various pollutants and the related question of whether we can observe environmental spillovers from foreign to domestic firms. Finally, we review the more recent literature on environmental outsourcing as an alternative to FDI and conclude with suggestions for future research.
Changes of histone modification status at critical lineage-specifying gene loci in multipotent precursors can influence cell fate commitment. The contribution of these epigenetic mechanisms to ...natural killer (NK) cell lineage determination from common lymphoid precursors is not understood. Here we investigate the impact of histone methylation repressive marks (H3 Lys27 trimethylation; H3K27me3) on early NK cell differentiation. We demonstrate that selective loss of the histone-lysineN-methyltransferase Ezh2 (enhancer of zeste homolog 2) or inhibition of its enzymatic activity with smallmolecules unexpectedly increased generation of the IL-15 receptor (IL-15R) CD122⁺ NK precursors and mature NK progeny from both mouse and human hematopoietic stem and progenitor cells. Mechanistic studies revealed that enhanced NK cell expansion and cytotoxicity against tumor cells were associated with up-regulation of CD122 and the C-type lectin receptor NKG2D. Moreover, NKG2D deficiency diminished the positive effects of Ezh2 inhibitors on NK cell commitment. Identification of the contribution of Ezh2 to NK lineage specification and function reveals an epigenetic-based mechanism that regulates NK cell development and provides insight into the clinical application of Ezh2 inhibitors in NK-based cancer immunotherapies.
We present two robust and well‐dated paleomagnetic poles from upper Eocene and Oligocene volcanics in the Urumieh‐Dokhtar magmatic arc, Central Iran. These two poles place Iran ∼3.7°–3° of latitude ...south of its present position between ca. 40 and 23 Ma. Our new paleomagnetic declination data indicate that the Central Iran block may have experienced a ∼11.6° clockwise rotation since the Late Eocene. We integrated our new data with the retrodeformed margins of the Zagros collision zone and contemporaneous Arabia positions to better constrain the age and configuration of the Arabia and Eurasia assembly process. In our model, the Arabia‐Eurasia collision occurred first in the western Main Zagros suture between ca. 35 and 30 Ma and then diachronously spread eastwards. Our paleogeographic reconstruction and initial continental collision timing supports the Arabia‐Eurasia collision as a first‐order driver of global cooling, Red Sea rifting, and Mediterranean extension.
Plain Language Summary
The demise of the Neo‐Tethyan ocean and accompanied continent‐continent collisions created the thick crust and the low relief surfaces of the Iran Plateau and Tibetan Plateau. The onset timing and configuration in the Zagros collisional belt are critical for understanding the uplift of the Iran Plateau, tectonic evolution of the Mediterranean and Zagros regions, as well as the associated Cenozoic climate change. However, the age and configuration of the Arabia‐Eurasia continental collision are hotly debated. Previous works generated competing collision timing estimates ranging from Late Cretaceous to Pliocene, with most estimates from Eocene to Miocene. By conducting geochronology and paleomagnetism on the Eocene‐Oligocene volcanic rocks in Central Iran, we show that the Arabia‐Eurasia collision occurred first in the western Main Zagros suture at the Eocene/Oligocene boundary, and then diachronously spread eastwards. We suggest the Arabia‐Eurasia collision facilitates the slowing of Africa, the opening of the Red Sea, the extension in the Mediterranean, and the Eocene/Oligocene global cooling.
Key Points
Our paleomagnetic results indicate a ∼3.7°–3° of latitude south of the present position of Central Iran during ca. 40–23 Ma
Central Iran has experienced ∼11.6° clockwise rotation since ca. 40 Ma
Arabia‐Eurasia collision began at the Eocene/Oligocene boundary in the western Main Zagros suture and diachronously spread eastwards
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