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The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian-Lower Triassic deepsea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ S anomaly with the extinction horizon in western Canada suggests that shoaling of H 2 S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem.end-Permian mass extinction | Panthalassic Ocean | multiple sulfur isotopes | sulfidic waters T he end-Permian mass extinction was the largest biotic catastrophe of the last 540 million years, resulting in the disappearance of >80% of marine species, and a full biotic recovery did not occur until 4-8 million years after the extinction event (1-6). Several lines of evidence from the low paleolatitude Paleotethys and high paleolatitude Boreal oceans, which accounted for ∼10-15% of the contemporaneous global ocean area, suggest that sulfidic (H 2 S-rich) conditions may have developed widely during the end-Permian extinction (7-13). However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain controversial, with competing hypotheses proposing extensive deepwater anoxia ("superanoxic ocean") or suboxic deep waters in combination with spatially constrained thermocline anoxia (14-18). Evidently, redox chemistry changes in the Panthalassic Ocean are central to an examination of the links between global-ocean conditions and the end-Permian extinction event as well as the subsequent delayed biotic recovery.The preservation of Permian-Triassic boundary deep-sea sediments is limited because most oceanic crust of that age has been subducted, and the only surviving Panthalassic seafloor sediments are within accretionary terranes or marginal uplifts

The Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ13C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus, corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ13C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus. We also used a box model to quantitatively explore the genesis of the negative δ13C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ13C excursions observed in the Stage 10 at Wa'ergang in South China.

The late Ming Dynasty Megadrought (LMDMD) (1637–1643) occurred at the end of Ming Dynasty and is the severest drought event in China in the last millennium. This unprecedented drought contributed significantly to the collapse of the Ming Dynasty in 1644, casting profound impacts on Chinese history. Here, the physical mechanism for the LMDMD is studied. Based on paleoclimate reconstructions, we hypothesize that this drought was initially triggered by a natural drought event starting in 1637 and was then intensified and extended by the tropical volcanic eruption at Mount Parker in 1641. This hypothesis is supported by the case study of the Community Earth System Model‐Last Millennium Experiment archive as well as sensitivity experiments with volcanic forcing superimposed on natural drought events. The volcano‐intensified drought was associated with a decreased land‐ocean thermal contrast, a negative soil moisture response, and a weakening and eastward retreating West Pacific Subtropical High.

The variability and mechanisms of multi-decadal megadroughts over eastern China during the last millennium were investigated using a control, full-forcing, and four sensitivity experiments from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) archive. The model simulated megadroughts have comparable magnitudes and durations with those derived from reconstructed proxy data, although the megadroughts are not temporally synchronous. In all experiments, the megadroughts exhibit similar spatial structures, corresponding to a weakening of the East Asia summer monsoon (EASM) and a strengthening of the East Asia winter monsoon (EAWM). The results show that internal climate variability within the coupled climate system plays an essential role in triggering megadroughts, while different external forcings may contribute to persistence and modify the anomaly patterns of megadroughts. A pattern of meridional tripolar (warm-cold-warm) sea surface temperature (SST) anomalies in the western Pacific stretching from the equator to high latitude is responsible for the EASM weakening and EAWM strengthening. The weakening of the EASM and strengthening of the EAWM are essentially caused by negative SST anomalies over the northwestern Pacific and positive SST anomalies over the equatorial western Pacific, which are associated with a La Niña-like SST gradient across the tropical Pacific. The external forcings prolong the megadroughts through maintenance of the meridional tripolar SST anomalies and enlarge the megadrought spatial extent by magnifying the meridional tripolar SST anomalies.

With rapid progress in the use of colloidal quantum dots (QDs) as light emitters, the next challenge for this field is to achieve high brightness. Unfortunately, Auger recombination militates against high emission efficiency at multiexciton excitation levels. Here, we suppress the Auger-recombinationinduced photoluminescence (PL) quantum yield (QY) loss in CdSe/CdS core− shell QDs by reducing the absorption cross section at excitation wavelengths via a thin-shell design. Studies of PL vs shell thickness reveal that thin-shell QDs better retain their QY at high excitation intensities, in stark contrast to thickershell QDs. Ultrafast transient absorption spectroscopy confirms increased Auger recombination in thicker-shell QDs under equivalent external excitation intensities. We then further grow a thin ZnS layer on thin-shell QDs to serve as a higher conduction band barrier; this allows for better passivation and exciton confinement, while providing transparency at the excitation wavelength. Finally, we develop an isolating silica matrix that acts as a spacer between dots, greatly reducing interdot energy transfer that is otherwise responsible for PL reduction in QD films. This results in the increase of film PL QY from 20% to 65% at low excitation intensity. The combination of Auger reduction and elimination of energy transfer leads to QD film PL QY in excess of 50% and absolute power conversion efficiency of 28% at excitation powers of 1 kW/cm 2 , the highest ever reported for QDs under intense illumination.

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rechargeable batteries, the key to realizing high performance lies in electrode materials. [7][8][9][10][11][12] However, traditional electrode materials, such as graphite, conductive polymers (CPs), and transition metal oxides, have the drawbacks of low capacitance, high cost, and poor stability, which are far from enough to satisfy the requirements of high energy density, high capacity rate, and long cycle life. In comparison with rechargeable batteries, SCs have the advantages of long cycle life, fast chargeÀdischarging capability, and high-power density, but their wide adhibition is impeded by the low-rate capability and inferior energy density. For fuel cells, their overall efficiency is severely hampered via the sluggish oxygen reduction reaction (ORR). Similarly, in the electrochemical energy conversion system of water splitting, the two half reactions (at the anode: oxygen evolution reaction (OER), at the cathode: hydrogen evolution reaction (HER)) require an excess of driving force to overcome resistance such as activation energy barriers from the electrode/electrolyte and solution contact interfaces. Therefore, efficient electrocatalysts are urgently needed to optimize the efficiency of specific applications. To date, the commercial electrocatalysts for ORR, HER, and OER are mainly precious metal-based materials (e.g., Pt-based materials for HER and ORR and Ru-/Ir-based materials for OER). Nonetheless, their expensive cost and inferior durability greatly restrict the widespread practical applications in renewable energy technologies. [13] In view of these limitations, it is urgently needed to develop costeffective electroactive materials with high activity and long-term durability, being challenges.MetalÀorganic frameworks (MOFs), which are known as porous coordination polymers (PCPs), are a class of crystalline porous materials assembled by inorganic nodes (clusters/metal ions) and organic ligands through coordination bonds. [14][15][16][17][18][19][20] Up to now, MOFs, as functional materials, have received extensive attention in multiple advanced technology adhibition, such as separation, [21,22] drug delivery, [23][24][25] sensing, [26,27] gas adsorption, [28,29] catalysis, [30,31] and energy storage. [32][33][34][35][36][37][38][39] As MOFs are constructed by two main components, the structure can be easily adjusted to realize the desired properties for target applications by properly selecting the organic ligands and inorganic nodes. [40][41][42][43][44][45][46][47][48][49] Recently, MOF-based materials have been proved to be more competitive than other porous materials as electroactive materials in electrochemical energy storage and conversion due to their high specific surface areas, huge and clear void structures, and uniform