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Abnormal activation of the mechanistic target of rapamycin (mTOR) signaling is commonly observed in many cancers and attracts extensive attention as an oncology drug discovery target, which is encouraged by the success of rapamycin and its analogs (rapalogs) in treatment of mTORC1-hyperactive cancers in both pre-clinic models and clinical trials. However, rapamycin and existing rapalogs have typically short-lasting partial responses due to drug resistance, thereby triggering our interest to investigate a potential mTORC1 inhibitor that is mechanistically different from rapamycin. Here, we report that hayatine, a derivative from Cissampelos, can serve as a potential mTORC1 inhibitor selected from a natural compound library. The unique properties owned by hayatine such as downregulation of mTORC1 activities, induction of mTORC1's translocation to lysosomes followed by autophagy, and suppression on cancer cell growth, strongly emphasize its role as a potential mTORC1 inhibitor. Mechanistically, we found that hayatine disrupts the interaction between mTORC1 complex and its lysosomal adaptor RagA/C by binding to the hydrophobic loop of RagC, leading to mTORC1 inhibition that holds great promise to overcome rapamycin resistance. Taken together, our data shed light on an innovative strategy using structural interruption-based mTORC1 inhibitors for cancer treatment.

Several Late Devonian sedimentary successions host pyrite with highly positive sulfur isotope values (δ34Spyrite). These anomalous values have been linked to marine anoxia, low sulfate concentrations in seawater, or aerobic re-oxidation of dissolved sulfide within well-oxygenated bottom waters in a local depositional environment. Implicit to these previous models is the assumption of a biogenic genesis from microbial sulfate reduction (MSR) of these pyrites, which, in turn, can be used to understand the biogeochemical sulfur cycle and reconstruct paleoenvironmental conditions. In South China, the Late-Devonian bulk-rock sulfur isotope excursion occurs in the lower Fammenian Wuzhishan Formation of the Youjiang Basin, in both the sedimentary limestone that corresponds to the Late triangularis conodont zone at the Fuhe section and the sediment-hosted Xialei Mn deposit that lies between the Late triangularis and crepida conodont zones. To further constrain the significance of these 34S-enriched pyrites, we carried out detailed textural and in-situ sulfur isotope examinations of pyrites in the Xialei Mn deposit. We found one type of pyrite in siliceous limestone referred to as the host rocks and three distinct pyrite types in Mn ores: Type I – pyrites with Mn-carbonate inclusion-rich cores; Type II – pyrite overgrowths surrounding an “inclusion-rich” core; and Type III – relatively inclusion-poor and mainly subhedral disseminated pyrite grains. Type I pyrites in Mn ores have negative δ34Spyrite values from −7.8‰ to −2.0‰. Types II and III pyrites, and pyrites in the host rock are characterized by highly positive δ34Spyrite values (+4.2‰ to +37.6‰), with some values being higher than that of contemporaneous seawater sulfate. Type I pyrites with negative δ34S values likely formed via MSR in a closed porewater system, driven by increased sedimentation rates during a sea level lowstand. The other pyrites with highly positive δ34S values appear to have formed during secondary hydrothermal alteration, with their sulfur sourced through thermochemical sulfate reduction (TSR) of sulfate from dissolved barites in the underlying Liujiang Formation. This implies that the positive δ34S values of the Late Devonian pyrites from the Wuzhishan Formation represent a later alteration event caused by post-depositional hydrothermal fluids, and may lack a direct biogeochemical connection to the surface sulfur cycle. These results provide an important perspective on the origin of variability in sulfur isotope records and suggest the need for careful petrographic screening and micrometer-scale analysis of sedimentary units used to reconstruct paleoenvironmental conditions.

Spontaneous itch and pain are the most common symptoms in various skin diseases, including allergic contact dermatitis (ACD). The chemokine (C-C motif) ligand 2 (CCL2, also referred to as monocyte chemoattractant protein 1 (MCP-1)) and its receptor CCR2 are involved in the pathophysiology of ACD, but little is known of the role of CCL2/CCR2 for the itch- and pain-behaviors accompanying the murine model of this disorder, termed contact hypersensitivity (CHS). C57BL/6 mice previously sensitized to the hapten, squaric acid dibutyl ester, applied to the abdomen were subsequently challenged twice with the hapten delivered to either the cheek or to the hairy skin of the hind paw resulting in CHS at that site. By 24 h after the 2nd challenge to the hind paw CCL2 and CCR2 mRNA, protein, and signaling activity were upregulated in the dorsal root ganglion (DRG). Calcium imaging and whole-cell current-clamp recordings revealed that CCL2 directly acted on its neuronal receptor, CCR2 to activate a subset of small-diameter, nociceptive-like DRG neurons retrogradely labeled from the CHS site. Intradermal injection of CCL2 into the site of CHS on the cheek evoked site-directed itch- and pain-like behaviors which could be attenuated by prior delivery of an antagonist of CCR2. In contrast, CCL2 failed to elicit either type of behavior in control mice. Results are consistent with the hypothesis that CHS upregulates CCL2/CCR2 signaling in a subpopulation of cutaneous small diameter DRG neurons and that CCL2 can activate these neurons through neuronal CCR2 to elicit itch- and pain-behavior. Targeting the CCL2/CCR2 signaling might be beneficial for the treatment of the itch and pain sensations accompanying ACD in humans.

To date, intermediate hosts of SARS-CoV-2 remain obscure and controversial. Several studies have shown that SARS-CoV-2-related pangolin coronavirus (Pangolin-CoV) has a high sequence similarity to SARS-CoV-2 and might be the initial source of SARS-CoV-2; however, the biological characteristics of Pangolin-CoV are still largely unknown. In this study, we evaluated the pathogenicity and transmissibility of Pangolin-CoV in Syrian golden hamsters

Since December 2019, coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a great challenge to the world's public health system. Nosocomial infections have occurred frequently in medical institutions worldwide during this pandemic. Thus, there is an urgent need to construct an effective surveillance and early warning system for pathogen exposure and infection to prevent nosocomial infections in negative-pressure wards. In this study, visualization and construction of an infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward were performed to describe the distribution regularity and infection risk of SARS-CoV-2, the critical factors of infection, the air changes per hour (ACHs) and the viral variation that affect infection risk. The SARS-CoV-2 distribution data from this model were verified by field test data from the Wuhan Huoshenshan Hospital ICU ward. ACHs have a great impact on the infection risk from airborne exposure, while they have little effect on the infection risk from surface exposure. The variant strains demonstrated significantly increased viral loads and risks of infection. The level of protection for nurses and surgeons should be increased when treating patients infected with variant strains, and new disinfection methods, electrostatic adsorption and other air purification methods should be used in all human environments. The results of this study may provide a theoretical reference and technical support for reducing the occurrence of nosocomial infections.

Lonicera japonica (LJ) is widely used as the local medicine to improve body and prevent ills in China, but mechanisms of its healthy beneficial effects remain largely unclear. Here, we evaluated the anti-aging and healthspan promoting activities of 75% ethanol extract of LJ (LJ-E) in the animal model Caenorhabditis elegans. Our results showed that LJ-E (500 μg/mL) treatment enhanced the mean lifespan of worms by over 21.87% and significantly improved age-associated physiological functions in C. elegans. The 500 μg/mL concentration of LJ-E enhanced the survival rates under oxidative and thermal stresses, and decreased reactive oxygen species (ROS) levels and fat accumulation in the worms. Gene-specific mutant studies showed that LJ-E-mediated lifespan extension was dependent on mev-1, daf-2, daf-16, and hsf-1, but not eat-2 genes. LJ-E could upregulate stress-inducible genes, viz., hsp-16.2, sod-3 and mtl-1. Moreover, we found that the D1086.10 protein interacted with superoxide dismutase (SOD)–3 by functional protein association networks analysis according to RNA-sequencing results. It was confirmed that D1086.10 was needed to promote longevity, and positively regulated expression of sod-3 by using D1086.10 mutants. Furthermore, LJ-E significantly delayed amyloid β-protein induced paralysis in CL4176 strain. Given the important role of autophagy in aging and protein homeostasis, we observed that LJ-E could remarkably increase the mRNA expression of autophagy gene bec-1 in CL4176 strain, and decrease expression of autophagy substrate p62 protein by more than 40.0% in BC12921 strain. Finally, we found that combination composed of three major compounds (54 μg/mL chlorogenic acid, 15 μg/mL 1,5-dicaffeoylquinic acid and 7.5 μg/mL 1,3-dicaffeoylquinic acid) of 500 μg/mL LJ-E could significantly delay paralysis in CL4176 worms caused by Aβ toxicity, comparable to that of LJ-E. Overall, our study may have important implications in using Lonicera japonica to promote healthy aging and have a potency to design therapeutics for age-related diseases.

The Earth-life system witnessed dramatic changes over the Neoproterozoic (1000–541 Ma). It saw supercontinent reconfigurations from the breakup of Rodinia to the assembly of Gondwana; climatically, the deepest global freeze in Earth history; geochemically, some of the most extreme perturbations on record; and biologically, the prominent rise of complex multicellular eukaryotes. However, the potential mechanisms that lie behind the convergence of such geological and biological revolutions remain elusive. The 27 articles in this special issue represent frontiers in disentangling the potential links between geological and biological changes in the Neoproterozoic and will inspire future interdisciplinary studies toward a better understanding of the Neoproterozoic Earth-life system.

A fiber Fabry-Perot (F-P) temperature sensor sealed with thermosensitive polymer has been proposed and demonstrated. The structure of fully enclosed quartz probe reduces the interference from ambient pressure and refractive index (RI). The automatic fabrication process of microflow injection and discharge welding is simple and improves the controllability and repeatability of the structural parameters. A demodulation method is proposed for expanding the measurement range of temperature. The results show that the sensor has good linear response with a sensitivity of −1.014 nm/°C in the range of 30 ∼ 70 °C. In addition, the interference spectrum doesn’t change with ambient RI. The sensor has a good application prospect in the field of biochemical process on-line monitoring, such as cell culture.

The Ediacaran Period (ca. 635–541 Ma) witnessed the earliest paleontological evidence for macroscopic animals (i.e., Ediacara biota) and geochemical observations of the largest carbon cycle anomaly in Earth history (i.e., Shuram Excursion, SE). Numerous hypotheses have been proposed for the origins of the SE, ranging from primary seawater anomaly to syn- or post-depositional diagenesis. Despite intensive geochemical and theoretical work published in the past decade, empirical evidence that is strictly based on fundamental petrographic results at the micrometer scale is still limited. To evaluate depositional compositions and diagenetic effects on samples from the SE, we investigated the EN3 interval in the Doushantuo Formation of South China via integrated cathodoluminescence (CL), secondary ion mass spectrometry (SIMS), and scanning electron microscope (SEM). Detailed petrographic observations reveal that the EN3 limestone is dominated by calcite microspar, with minor but variable amounts of disseminated zoned dolomite crystals. The former likely formed via neomorphism of depositional micrite, while the latter was the result of progressive post-depositional dolomitization. The mean values of paired SIMS δ13Ccalcite and δ13Cdolomite compositions are indistinguishable in each sample and consistent with published micro-drilled bulk-powder δ13C values, which we interpret to represent depositional “background” signals of seawater dissolved inorganic carbon (DIC). We also observed μm-scale variability of SIMS δ13C data that may reflect a variable diagenetic overprint after deposition. Our integrated petrographic and geochemical results are consistent with a depositional origin of the SE and provide little evidence for the hypothesized isotope alteration by meteoric and mixing-zone diagenesis or late burial diagenesis. In light of this study, we propose that the SE indeed represents a marine carbon cycle anomaly that bears a close temporal link to the Ediacaran surface environment.

Perovskite light-emitting diodes (PeLEDs) with green and red emissions have made tremendous progress in recent years. However, the realization of efficient and spectra-stable blue-emission PeLEDs remains challenging, which greatly limits their future commercialization. Here, a self-assembling strategy is proposed to achieve efficient blue PeLEDs with stable emission by modulating low-dimensional domains of pure-bromide perovskites to Bohr’s radii. A spacer of butylamine with polyamine is used as a modifier to facilitate the formation of homogeneous perovskite films with precious tailoring of the numbers (N) of metal halide octahedron PbBr64− layers. The cubic-phase quasi-2D perovskite films featuring the improved domain distributions and the enhanced luminance are realized, and their emissions can be modulated from violet (~436 nm) to greenish region (~500 nm), corresponding to the emission from N = 2 to N > 3 layered perovskites. The PeLEDs with deep-blue, pure-blue, and sky-blue emissions are obtained with the colour coordinates of (0.13, 0.06), (0.11, 0.13), and (0.08, 0.25), respectively, yielding the maximum external quantum efficiencies of 1.74%, 2.44%, and 5.71%. The approach demonstrated in this work paves the way for constructing efficient, endurable, spectra-stable perovskite emitters for the next-generation display and lighting technologies.

The Ediacaran Period is characterized by the most profound negative carbon isotope (δ13C) excursion in Earth history, the Shuram Excursion. Various hypotheses – including the massive oxidation of dissolved organic carbon (DOC) in the oceans, the weathering of terrestrial organic carbon, or the release and oxidation of methane hydrates and/or expelled petroleum from the subsurface – have been proposed as sources of the 13C-depleted carbon. More recently, it has been suggested that global-scale precipitation of early authigenic carbonates, driven by anaerobic microbial metabolism in unconsolidated sediments, may have caused the Shuram Excursion, but empirical evidence is lacking. Here we present a comprehensive analysis of a Shuram-associated interval from the uppermost Doushantuo Formation in South China. Our study reveals petrographic evidence of methane-derived authigenic calcite (formed as early diagenetic cements and nodules) that are remarkably depleted in 13C – suggesting a buildup of alkalinity in pore fluids through the anaerobic oxidation of methane (AOM) – and systematically depleted in 18O relative to co-occurring dolomite. Early authigenesis of these minerals is likely to be driven by increased microbial sulfate reduction, triggered by enhanced continental weathering in the context of a marked rise in atmospheric oxygen levels. In light of the finding of methane-derived authigenic carbonates at Zhongling, and based on our basin-scale stratigraphic correlation, we hypothesize that the marked 13C and 18O depletion (including their co-variation noted worldwide) in the Shuram Excursion may reflect an episode of authigenesis occurring within a sulfate–methane transition zone (SMTZ). If true, the Shuram Excursion was then a global biogeochemical response to enhanced seawater sulfate concentration in the Ediacaran ocean driven by the Neoproterozoic oxidation of surface environments. This paleo-oceanographic transition may have therefore paved the way for subsequent evolution and diversification of animals. Our study highlights the significance of an integrated approach that combines petrography, mineralogy, and texture-specific micro-drilling geochemistry in chemostratigraphic studies.

The Ediacaran Period witnessed the first appearance of macroscopic animal life in Earth's history. However, the biogeochemical context for the stratigraphic occurrence of early metazoans is largely uncertain, in part due to the dearth of integrated paleobiological and chemostratigraphic datasets. In this study, a comprehensive geochemical analysis was conducted on the fossiliferous Khatyspyt Formation in Arctic Siberia, in order to gain insights into the Ediacaran paleoenvironments. This study was designed to specifically address the relationship between paleoredox conditions and Ediacaran fossil occurrences in the Khatyspyt Formation. Our data reveal a dramatic shift in pyrite sulfur isotope compositions (δ 34 S pyrite ) from ca. − 20‰ to ca. 55‰, and this shift is intriguingly associated with the first occurrence of Ediacara-type macrofossils at the studied section, suggesting a possible link between seawater redox conditions and distribution of early macroscopic organisms. Based on multiple lines of sedimentological and geochemical evidence, we propose that the development of oceanic euxinia — which may be widespread in the continental margins due to enhanced oxidative weathering in the terminal Ediacaran Period — may have locally prohibited the colonization of Ediacara-type organisms and resulted in low δ 34 S pyrite values in the lower Khatyspyt Formation. In the middle and upper Khatyspyt Formation, progressive secular transition from euxinic to non-euxinic and more habitable conditions may have allowed for the colonization of Ediacara-type and other macro-organisms.

Conventional enhanced permeation and retention (EPR) mediates the effects of many drugs, including the accumulation of nanocarriers at tumor sites, but its efficiency remains low. In this study, this limitation was overcome by developing a dual-targeting delivery system based on hyaluronan (HA, a major ligand of CD44) and tetraiodothyroacetic acid (tetrac, a specific ligand of αvβ3), which was exploited to carry docetaxel (DTX) for the synergistic active targeting to tumors. First, a tetrac-HA (TeHA) conjugate was synthesized and grafted onto the surfaces of solid lipid nanoparticles (SLNs) (TeHA-SLNs/DTX), with a high encapsulation efficiency of >91.6%. The resulting SLNs exhibited an approximately toroid morphology revealed using TEM. The cellular uptake and cytotoxicity of various formulations on CD44/αvβ3-enriched B16F10 cells were then assessed, and both results confirmed the selective uptake and high cytotoxicity of the TeHA-SLNs/DTX in a TeHA-dependent manner. In vivo imaging and vessel distribution tests revealed the efficiency of synergistic active targeting was higher than that of EPR-mediated passive targeting by the TeHA-SLNs to αvβ3-expressing tumor blood vessels and CD44-expressing tumor cells via selective targeting. Finally, in both xenograft tumor mice and in situ lung metastasis tumor mice, tumor growth was significantly inhibited by TeHA-SLNs/DTX. Therefore, TeHA-SLNs are an efficient system for the dual-targeted delivery of drugs to treat cancer in vivo.

The Ediacaran Period witnessed one of the largest phosphogenic events in Earth's history. Coincidently, some phosphorite deposits in South China are associated with the largest-known carbon isotope negative excursion (i.e., Shuram Excursion), suggesting an intimate coupling of the biogeochemical carbon and phosphorous cycles. However, the geomicrobiological linkage between these anomalies remain poorly understood. In this study, we investigated the phosphorite samples from the uppermost Doushantuo Formation in South China. Carbon isotope compositions of authigenic calcite cements and nodules in the phosphorites are as low as –34‰ (VPDB). Petrographic and geochemical investigations indicate that the 13 C-depleted carbonates likely formed as the result of microbial sulfate and iron reduction that released phosphorous from iron oxyhydroxide, concentrating phosphorous in pore waters, and thereby promoting phosphate mineralization. The timing of this event appears to coincide with enhanced sulfate delivery to seawater through continental weathering. The basin-scale distribution of Doushantuo phosphorites suggests a redox control on the availability of iron oxyhydroxide and the recycling of pore water phosphorous. Both inner and outer shelf regions were likely characterized by an oxic water column, and were the main loci for phosphogenesis; on the contrary, intra-shelf and slope regions, which are lean in phosphorite, were subjected to euxinic or ferruginous water column conditions. The intimate coupling between Ediacaran phosphogenesis and the Shuram Excursion suggests strong links among seawater redox conditions, C-S-P-Fe cycling, and fossil phosphatization. Increased microbial sulfate reduction driven by enhanced sulfate reservoir in the Ediacaran ocean may have played an essential role on these biogeochemical events.

Organic-rich Cretaceous source rocks of the petroliferous Songliao Basin in northeast China are considered to be lacustrine in origin, but paleontological and organic geochemical evidence suggest episodic marine incursions. As a test of this hypothesis, we applied time-series measurements of elemental and isotopic abundances on core and cutting samples to evaluate fluctuations in the sulfur and carbon cycles across the Santonian–Campanian transition preserved in the upper Yaojia and lower Nenjiang formations. The data reveal a spike in pyrite sulfur abundance and a marked negative excursion in δ34S at the base of the Nenjiang Formation when the basin expanded to its maximal extent. The elemental and isotopic data suggest that flooding was associated with rapid marine transgression that enhanced sulfate concentrations, which promoted microbial sulfate reduction in anoxic bottom waters that were episodically euxinic. Subsequent restriction of the basin and a decline in marine influence is supported by progressive upsection 34S enrichment (up to 30‰) in Nenjiang Member I, which are interpreted to reflect the distillation of sulfate through enhanced pyrite burial, followed by a gradual return to lacustrine conditions that prevailed in overlying strata.

Made available in DSpace on 2020-12-12T01:35:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The Ediacaran-Cambrian Bambuí Group in Brazil records an anomalously positive excursion in carbonate carbon isotopes (δ13Ccarb) with a sustained plateau of ca. +15‰ (aka the Middle Bambuí Excursion–MIBE). Considering that the δ13Ccarb signals in Ediacaran-Cambrian seawaters do not typically exceed +6‰, the MIBE therefore represents a profound carbon cycle anomaly in Earth's history. Although intensive studies have been done on the Bambuí Group, origins of the MIBE remain enigmatic. In order to better constrain the biogeochemical carbon and sulfur cycles during the MIBE, high-resolution chemostratigraphic analysis was conducted for both the plateau (i.e., Lagoa do Jacaré Formation) and the recovery part (i.e., lower Serra da Saudade Formation) of the MIBE. Chemostratigraphic profiles reveal remarkably different values in δ13Ccarb, δ13Corg, δ18Ocarb, and δ34Spyrite between these two studied MIBE intervals. The new data show that the plateau of the MIBE is characterized by coupled higher δ13Ccarb, higher δ13Corg, and higher δ34Spyrite signals compared with the recovery part of the MIBE. Based on multiple lines of sedimentological, geochemical, and model evidence, we propose that the possibilities of enhanced organic carbon burial and porewater methanogenesis are insufficient to explain the MIBE. Instead, local or regional controlling factors, including water-column methanogenesis, low-sulfate conditions, and enhanced carbonate recycling in a restricted basin may have played a role, independently or in unison, in generating this profound positive δ13Ccarb excursion. Therefore, the MIBE may reflect a regional event, instead of a global carbon cycle anomaly. We caution against the use of the MIBE in chemostratigraphic correlations on a global scale or any other attempt to infer global carbon cycling at that time. The biogeochemical landscape of the late Ediacaran-Cambrian basins and ocean margins may be more heterogeneous than previously thought. Analytical Environmental and Geo- Chemistry Group Vrije Universiteit Brussel ET-HOME (Evolution and Tracers of the Habitability of Mars and Earth) Astrobiology Research Consortium Department of Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp) Centro de Pesquisas Manoel Teixeira da Costa Instituto de Geociências Universidade Federal de Minas Gerais, Pampulha Department of Geological Sciences University of North Carolina Hydrology and Remote Sensing Laboratory Beltsville Agricultural Research Center US Department of Agriculture Department of Geology Faculty of Engineering University of Mons State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation School of Geoscience and Technology Southwest Petroleum University Department of Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp) CNPq: CNPq-486416/2006-2

As a classical electron transport layer, the high crystallinity TiO2 has been widely used in perovskite solar cells (PSCs), however, its high-temperature preparation process elevates the fabrication cost and limits its application. Here, we report an ultraviolet-ozone assisted strategy to modify low-temperature TiO2 interface for PSCs. In addition to the more appropriate work function and reinforced built-in potential, the lattice strain of perovskite films crystallized on modified TiO2 has also been released in some degree. Ultrafast transient absorption technique is employed to provide a deep insight into the carrier dynamics, revealing that less non-radiative recombination exists in the modified device. Interestingly, transient surface photovoltage results demonstrate that ultraviolet-ozone modification can efficiently suppress the decomposition of perovskite films under light illumination. Taking advantage of these facts, this device exhibits better efficiency and remarkable stability. This demonstrated low-temperature strategy is a promising way for fabricating low-cost, efficient and stable perovskite device.

Secular variation of 87Sr/86Sr in carbonate strata has been widely used in regional and global chemostratigraphic correlations. Typically, diagenesis results in higher 87Sr/86Sr signals relative to their primary composition due to the alteration by Rb-rich fluids and radiogenic decay of 87Rb to 87Sr. Surprisingly, 87Sr/86Sr values in the Ediacaran limestones from Saudi Arabia (from 0.7029 to 0.7059) are significantly lower than typical Ediacaran seawater values (mostly from 0.7080 to 0.7090) based on a global compilation. Understanding the origin of these anomalies is important insofar as early macrofossils are preserved in these strata. Two hypotheses have been independently evaluated in this study. The first hypothesis shows a low temperature scenario with isolated oceans or lakes in proximity to a mafic source. The second hypothesis is characterized by a high temperature scenario with profound overprints by juvenile hydrothermal fluids. Integrated Sr and Nd isotope data reveal that the 87Sr/86Sr anomalies are closely coupled with positive eNd(t = 560 Ma) values (up to +4.1). Clear covariations between 87Sr/86Sr, eNd, TOC, δ13Ccarb, δ13Corg, and δ18Ocarb were found. Based on multiple lines of petrographic, field, and geochemical evidence, the second hypothesis (i.e., hydrothermal alteration by juvenile fluids) is preferred in this study. Thermogenic breakdown of organic matter in host sediments may have caused the increasingly low TOC abundance and high δ13Corg signals of the residual organic matter. We argue that the concept that the Ediacaran biotic radiation took place in an isolated lake environment should be treated with caution. These remarkably low 87Sr/86Sr signals have neither temporal nor biogeochemical significance. Sr isotope chemostratigraphy in this particular region may not be a reliable tool for stratigraphic correlations.

Major radiations of microscopic and macroscopic eukaryotes occurred respectively in the early and middle Ediacaran Period. Various hypotheses have been proposed to attribute these evolutionary events to changes in ocean redox conditions. To date, published models of the Ediacaran ocean in South China have largely been focused on the Upper and Middle Yangtze blocks, as opposed to the slope and basin sections of the Lower Yangtze Block, where the oldest complex macrofossils of the Ediacaran (i.e. the ~600 Ma Lantian Biota) are preserved. To achieve a holistic understanding of the record of ocean chemistry in the entire Yangtze Block, we carried out carbon (δ13Ccarb and δ13Corg) and sulfur (δ34SCAS and δ34Spyr) isotopic investigations of four new sections (i.e., Wujialing, Meishuxia, Wangfu and Zhushuwu) in the Lower Yangtze Block, in addition to one previously reported drill core at Lantian. The Doushantuo and Lantian formations at these sections represent shelf margin, upper slope, lower slope, and deep basin environments. In conjunction with previous work on sections of the Upper and Middle Yangtze blocks, our study reconstructs the redox structure of the entire Ediacaran ocean in South China. The new results show profound δ13Ccarb negative excursions in the slope and deep basinal sections, which can be correlated to the EN3 and Shuram excursions at a global scale. Notably, the δ13Ccarb and δ34Spyr profiles from shelf to basinal sections show distinct spatial and temporal patterns, which can be explained by model of a redox stratified ocean during the early and middle Ediacaran Period. The finding of isotopically light (34S-depleted) pyrite from this time suggests that the oceanic chemocline extended to intermediate depth. Integrating this study with existing ecological and taphonomic data, it is likely that marine redox stratification in the early Ediacaran limited the spatial distribution of early metazoans in the Lower Yangtze Block.

We consider the classical problem of searching for a heavier coin in a set of n coins, n-1 of which have the same weight. The weighing device is b-balance which is the generalization of two-arms balance. The minimum numbers of weighings are determined exactly for worst-case sequential algorithm, average-case sequential algorithm, worst-case predetermined algorithm, average-case predetermined algorithm.We also investigate the above search model with additional constraint: each weighing is only allowed to use the coins that are still in doubt. We present a worst-case optimal sequential algorithm and an average-case optimal sequential algorithm requiring the minimum numbers of weighings.