Petrographic carbon in ancient sediments constrains Proterozoic Era atmospheric oxygen levels.

Oxygen concentration defines the chemical structure of Earth's ecosystems while it also fuels the metabolism of aerobic organisms. As different aerobes have different oxygen requirements, the evolution of oxygen levels through time has likely impacted both environmental chemistry and the history of life. Understanding the relationship between atmospheric oxygen levels, the chemical environment, and life, however, is hampered by uncertainties in the history of oxygen levels. We report over 5,700 Raman analyses of organic matter from nine geological formations spanning in time from 742 to 1,729 Ma. We find that organic matter was effectively oxidized during weathering and little was recycled into marine sediments. Indeed, during this time interval, organic matter was as efficiently oxidized during weathering as it is now. From these observations, we constrain minimum atmospheric oxygen levels to between 2 to 24% of present levels from the late Paleoproterozoic Era into the Neoproterozoic Era. Indeed, our results reveal that eukaryote evolution, including early animal evolution, was not likely hindered by oxygen through this time interval. Our results also show that due to efficient organic recycling during weathering, carbon cycle dynamics can be assessed directly from the sediment carbon record.

A Mesoproterozoic iron formation.

We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500-1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

Sufficient oxygen for animal respiration 1,400 million years ago.

The Mesoproterozoic Eon [1,600-1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0.1% of present levels, sufficiently low to have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon-oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels >4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.

Orbital forcing of climate 1.4 billion years ago.

Fluctuating climate is a hallmark of Earth. As one transcends deep into Earth time, however, both the evidence for and the causes of climate change become difficult to establish. We report geochemical and sedimentological evidence for repeated, short-term climate fluctuations from the exceptionally well-preserved ∼1.4-billion-year-old Xiamaling Formation of the North China Craton. We observe two patterns of climate fluctuations: On long time scales, over what amounts to tens of millions of years, sediments of the Xiamaling Formation record changes in geochemistry consistent with long-term changes in the location of the Xiamaling relative to the position of the Intertropical Convergence Zone. On shorter time scales, and within a precisely calibrated stratigraphic framework, cyclicity in sediment geochemical dynamics is consistent with orbital control. In particular, sediment geochemical fluctuations reflect what appear to be orbitally forced changes in wind patterns and ocean circulation as they influenced rates of organic carbon flux, trace metal accumulation, and the source of detrital particles to the sediment.

Lacustrine carbon sink: A hidden driver of the Late Cretaceous Cooling Event.

Lacustrine systems since the Mesozoic have sequestered large quantities of organic carbon, which may have important value for global climate cooling, but there is still a lack of geological evidence of this sequestration. Taking the Songliao Basin in China as a case study, we elucidate the important function of lacustrine basins as sinks of a large amount of organic carbon, particularly when the contemporaneous marine sediments were poor sinks of organic carbon. Volcanic activities and orbital forcing were likely key factors influencing the water transportation between the land and oceans, as well as the alternating burial of organic carbon in the oceans and land. Microorganisms related to methane metabolism may have been highly involved in the mineralization and sequestration of lacustrine organic carbon. This study provides new insights into the coupled carbon-water cycle between the land and oceans and the influence of this process on global climate evolution.

Subaerial volcanism broke mid-Proterozoic environmental stasis.

The mid-Proterozoic, spanning 1.8 to 0.8 billion years ago, is recognized as a phase of marine anoxia, low marine primary productivity (MPP), and constrained eukaryotic biodiversity. However, emerging evidence suggesting intermittent environmental disturbances and concurrent eukaryotic evolution challenges the notion of a stagnant Earth during this era. We present a study detailing volcanic activity and its consequential impact on terrestrial weathering and MPP, elucidated through the examination of 1.4-billion-year-old tropical offshore sediments. Our investigation, leveraging precise mercury (Hg) and lithium (Li) isotopic analyses, reveals the introduction of fresh rock substrates by local volcanism. This geological event initiated a transformative process, shifting the initial regolith-dominated condition in tropical lowland to a regime of enhanced chemical weathering and denudation efficiency. Notably, the heightened influx of nutrient-rich volcanic derivatives, especially phosphorus, spurred MPP rates and heightened organic carbon burial. These factors emerge as potential drivers in breaking the long-term static state of the mid-Proterozoic.

Postweaning sodium citrate exposure induces long-lasting and sex-dependent effects on social behaviours in mice.

BACKGROUND: Postweaning is a pivotal period for brain development and individual growth. As an important chemical used in medicines, foods and beverages, sodium citrate (SC) is commonly available. Although some effects of SC exposure on individual physiology have been demonstrated, the potential long-lasting effects of postweaning dietary SC exposure on social behaviours are still elusive. METHODS: Both postweaning male and female C57BL/6 mice were exposed to SC through drinking water for a total of 3 weeks. A series of behavioural tests, including social dominance test (SDT), social interaction test (SIT), bedding preference test (BPT) and sexual preference test (SPT), were performed in adolescence and adulthood. After these tests, serum oxytocin (OT) levels and gut microbiota were detected. RESULTS: The behavioural results revealed that postweaning SC exposure decreased the social dominance of male mice in adulthood and female mice in both adolescence and adulthood. SC exposure also reduced the sexual preference rates of both males and females, while it had no effect on social interaction behaviour. ELISA results indicated that SC exposure decreased the serum OT levels of females but not males. 16S rRNA sequencing analysis revealed a significant difference in ß-diversity after SC exposure in both males and females. The correlation coefficient indicated the correlation between social behaviours, OT levels and dominant genera of gut microbiota. CONCLUSION: Our findings suggest that postweaning SC exposure may have enduring and sex-dependent effects on social behaviours, which may be correlated with altered serum OT levels and gut microbiota composition.

Organic carbon cycling and black shale deposition: an Earth System Science perspective.

Earth has a prolonged history characterized by substantial cycling of matter and energy between multiple spheres. The production of organic carbon can be traced back to as early as ∼4.0 Ga, but the frequency and scale of organic-rich shales have varied markedly over geological time. In this paper, we discuss the organic carbon cycle and the development of black shale from the perspective of Earth System Science. We propose that black shale depositions are the results of interactions among lithospheric evolution, orbital forcing, weathering, photosynthesis and degradation. Black shales can record Earth's oxygenation process, provide petroleum and metallic mineral resources and reveal information about the driver, direction and magnitude of climate change. Future research on black shales should be expanded to encompass a more extensive and more multidimensional perspective.

Dynamic redox and nutrient cycling response to climate forcing in the Mesoproterozoic ocean.

Controls on Mesoproterozoic ocean redox heterogeneity, and links to nutrient cycling and oxygenation feedbacks, remain poorly resolved. Here, we report ocean redox and phosphorus cycling across two high-resolution sections from the ~1.4 Ga Xiamaling Formation, North China Craton. In the lower section, fluctuations in trade wind intensity regulated the spatial extent of a ferruginous oxygen minimum zone, promoting phosphorus drawdown and persistent oligotrophic conditions. In the upper section, high but variable continental chemical weathering rates led to periodic fluctuations between highly and weakly euxinic conditions, promoting phosphorus recycling and persistent eutrophication. Biogeochemical modeling demonstrates how changes in geographical location relative to global atmospheric circulation cells could have driven these temporal changes in regional ocean biogeochemistry. Our approach suggests that much of the ocean redox heterogeneity apparent in the Mesoproterozoic record can be explained by climate forcing at individual locations, rather than specific events or step-changes in global oceanic redox conditions.

Spontaneous Hyperventilation Is Common in Patients with Spontaneous Cerebellar Hemorrhage, and Its Severity Is Associated with Outcome.

BACKGROUND: The spontaneous hyperventilation (SHV) accompanying spontaneous cerebellar hemorrhage has yet to attract a sufficient amount of attention. This study aimed to analyze the incidence of SHV in spontaneous cerebellar hemorrhage patients and its risk factors as well as its association with the outcome. METHODS: We retrospectively reviewed the medical records of all spontaneous cerebellar hemorrhage patients who underwent surgical treatment at Tongji Hospital from July 2018 to December 2020. Arterial blood gas (ABG) test results and clinical characteristics, including demographics, comorbidities, imaging features, laboratory tests, and therapy choices, were collected. The Glasgow Outcome Scale was used to assess the outcome at two weeks and six months after admission. RESULTS: A total of 147 patients were included, and of these patients 44.9% had spontaneous hyperventilation. Hypertension (OR, 3.175; CI, 1.332-7.569), usage of sedation drugs (OR, 3.693; CI, 1.0563-8.724), and hypernatremia (OR, 2.803; CI, 1.070-7.340) seemed to positively correlate to SHV occurrence. Hematoma removal had an inverse association with SHV (OR, 0.176; CI, 0.068-0.460). Patients with poor and good outcomes had significant differences in pH, PaCO2, and HCO3- values, and the severity of SHV was associated with the PaCO2 level. CONCLUSIONS: Spontaneous hyperventilation is common in patients with spontaneous cerebellar hemorrhage, and its severity is associated with the outcome.

In vitro cytotoxicity of transparent yellow iron oxide nanoparticles on human glioma cells.

With rapid development of nanotechnology, concerns about the possible adverse health effects on human beings by using nanomaterials have been raised. Transparent yellow iron oxide (alpha-FeOOH) nanoparticles have been widely used in paints, plastic, rubber, building materials, papermaking, food products and pharmaceutical industry, thus the potential health implications by the exposure should be considered. The purpose of this study is to assess the cytotoxicity of transparent yellow iron oxide nanoparticles on U251 human glioma cells. The alpha-FeOOH nanoparticles are in clubbed shapes with 9 nm in diameter and 43 nm long. The specific surface area is 115.3 m2/g. After physicochemical characterization of the nanoparticles, U251 cells were exposed to a-FeOOH at the doses of 0, 3.75, 15, 60 and 120 microg/mL. The results showed that the alpha-FeOOH nanoparticles reduced the cell viability and induced necrosis and apoptosis in U251 cells. In addition, nanoparticle exposure significantly increased the levels of superoxide anion and nitric oxide in a dose-dependent fashion in the cells. Our results suggest that exposure to alpha-FeOOH nanoparticles induce significant free radical formation and cytotoxic effects. The large surface area that induced high surface reactivity may play an important role in the cytotoxic effect of alpha-FeOOH nanoparticles.

Paleoenvironmental proxies and what the Xiamaling Formation tells us about the mid-Proterozoic ocean.

The Mesoproterozoic Era (1,600-1,000 million years ago, Ma) geochemical record is sparse, but, nevertheless, critical in untangling relationships between the evolution of eukaryotic ecosystems and the evolution of Earth-surface chemistry. The ca. 1,400 Ma Xiamaling Formation has experienced only very low-grade thermal maturity and has emerged as a promising geochemical archive informing on the interplay between climate, ecosystem organization, and the chemistry of the atmosphere and oceans. Indeed, the geochemical record of portions of the Xiamaling Formation has been used to place minimum constraints on concentrations of atmospheric oxygen as well as possible influences of climate and climate change on water chemistry and sedimentation dynamics. A recent study has argued, however, that some portions of the Xiamaling Formation deposited in a highly restricted environment with only limited value as a geochemical archive. In this contribution, we fully explore these arguments as well as the underlying assumptions surrounding the use of many proxies used for paleo-environmental reconstructions. In doing so, we pay particular attention to deep-water oxygen-minimum zone environments and show that these generate unique geochemical signals that have been underappreciated. These signals, however, are compatible with the geochemical record of those parts of the Xiamaling Formation interpreted as most restricted. Overall, we conclude that the Xiamaling Formation was most likely open to the global ocean throughout its depositional history. More broadly, we show that proper paleo-environmental reconstructions require an understanding of the biogeochemical signals generated in all relevant modern analogue depositional environments. We also evaluate new data on the δ98 Mo of Xiamaling Formation shales, revealing possible unknown pathways of molybdenum sequestration into sediments and concluding, finally, that seawater at that time likely had a δ98 Mo value of about 1.1‰.

The aerobic diagenesis of Mesoproterozoic organic matter.

The Xiamaling Formation in the North China Block contains a well-preserved 1400 Ma sedimentary sequence with a low degree of thermal maturity. Previous studies have confirmed the dynamic and complex nature of this evolving marine setting, including the existence of an oxygen-minimum zone, using multi-proxy approaches, including iron speciation, trace metal dynamics, and organic geochemistry. Here, we investigate the prevailing redox conditions during diagenesis via the biomarkers of rearranged hopanes from the finely laminated sediments of the organic-rich black shales in Units 2 and 3 of the Xiamaling Formation. We find that rearranged hopanes are prominent in the biomarker composition of the oxygen-minimum zone sediment, which is completely different from that of the sediment in the overlying anoxic strata. Since the transition process from hopanes to rearranged hopanes requires oxygen via oxidation at the C-l6 alkyl position of 17α(H)-hopanes, we infer that dissolved oxygen led to the transformation of hopane precursors into rearranged hopanes during the early stages of diagenesis. The use of hopanoid hydrocarbons as biomarkers of marine redox conditions has rarely been previously reported, and the hydrocarbon signatures point towards oxic bottom waters during the deposition of Unit 3 of the Xiamaling Formation, which is consistent with the earlier oxygen-minimum zone environmental interpretation of this Unit.

Highly fractionated chromium isotopes in Mesoproterozoic-aged shales and atmospheric oxygen.

The history of atmospheric oxygen through the Mesoproterozoic Era is uncertain, but may have played a role in the timing of major evolutionary developments among eukaryotes. Previous work using chromium isotopes in sedimentary rocks has suggested that Mesoproterozoic Era atmospheric oxygen levels were too  low in concentration (<0.1% of present-day levels (PAL)) for the expansion of eukaryotic algae and for the evolution of crown-group animals that occurred later in the Neoproterozoic Era. In contrast, our new results on chromium isotopes from Mesoproterozoic-aged sedimentary rocks from the Shennongjia Group from South China is consistent with atmospheric oxygen concentrations of >1% PAL and thus the possibility that a permissive environment existed long before the expansion of various eukaryotic clades.

Catalytic reforming of toluene as tar model compound: effect of Ce and Ce-Mg promoter using Ni/olivine catalyst.

Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni-Ce-Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10ppm H2S poison at 100mLmin(-1) for up to 400min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio=5, T=790°C, space velocity=782h(-1) and t=2h, the Ni-Ce-Mg/olivine system yielded 89% toluene conversion, 5.6Lh(-1) product gas rate, 62.6mol% H2 content and 10% (mol useful gas mol(-1) toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning.

Reducing Poisson noise and baseline drift in X-ray spectral images with bootstrap Poisson regression and robust nonparametric regression.

X-ray spectral imaging provides quantitative imaging of trace elements in a biological sample with high sensitivity. We propose a novel algorithm to promote the signal-to-noise ratio (SNR) of x-ray spectral images that have low photon counts. Firstly, we estimate the image data area that belongs to the homogeneous parts through confidence interval testing. Then, we apply the Poisson regression through its maximum likelihood estimation on this area to estimate the true photon counts from the Poisson noise corrupted data. Unlike other denoising methods based on regression analysis, we use the bootstrap resampling method to ensure the accuracy of regression estimation. Finally, we use a robust local nonparametric regression method to estimate the baseline and subsequently subtract it from the x-ray spectral data to further improve the SNR of the data. Experiments on several real samples show that the proposed method performs better than some state-of-the-art approaches to ensure accuracy and precision for quantitative analysis of the different trace elements in a standard reference biological sample.

The distribution profile and oxidation states of biometals in APP transgenic mouse brain: dyshomeostasis with age and as a function of the development of Alzheimer's disease.

The enrichment of transition metals in the brain and the dyshomeostasis of metals are thought to be important etiological factors for elderly people in a number of neurodegenerative diseases, including Alzheimer's disease (AD). However, the understanding of how biometals dynamically dysregulate in the stages of AD development, such as the exact time-dependent and site-dependent accumulation in the brain with AD progression, is still limited. Herein, by using the APP/V717I transgenic mouse model and age-matched mice as control, we offer distinctive in situ and quantitative images of metals (Cu, Fe, Zn and Ca) in brain sections by synchrotron radiation micro beam X-ray fluorescence (SR-µXRF). The images show that Fe and Ca increased with brain aging in both AD and control (CNT) mice, and Cu, Fe, Zn and Ca appeared significantly elevated in AD mice and showed an obvious age-dependent rise. Fe, Cu and Zn were obviously specifically enriched in the cortex and hippocampus, which were also the plaque-formation sensitive brain regions. Our results demonstrate that the enrichment of transition metals with age and metals' dyshomeostasis in specific regions may contribute together to the etiology and development of AD in elderly people. The XANES measurements of Cu and Fe show evidence that Cu may have redox properties in the AD brain.

Immunogold labeling and X-ray fluorescence microscopy reveal enrichment ratios of Cu and Zn, metabolism of APP and amyloid-ß plaque formation in a mouse model of Alzheimer's disease.

The mechanism that triggers amyloid-ß (Aß) fibrillation and aggregation is still elusive. Evidence suggests that the extensional interactions of the amyloid precursor protein (APP) and Aß with transition biometals, copper (Cu) and zinc (Zn), may be key occurrences in the processes of Aß aggregation and toxicity. By using an immunogold labeling technique combined with synchrotron radiation X-ray fluorescence microprobe (SR-µXRF) scanning analysis, the profiles of APP, Aß42 and Cu, Zn in the brain of APP transgenic mouse with the development of the disease were characterized. This investigation provides visual, kinetic and spatial evidence of the correlation of APP and Aß-metals in AD brain sections. The visual evidence demonstrates the association of metals Cu and Zn with Aß42 during plaque formation, which helps implicate the role of metal ion homeostasis in human AD pathology.

Microglial activation, recruitment and phagocytosis as linked phenomena in ferric oxide nanoparticle exposure.

Microglia as the resident macrophage-like cells in the central nervous system (CNS) play a pivotal role in the innate immune responses of CNS. Understanding the reactions of microglia cells to nanoparticle exposure is important in the exploration of neurobiology of nanoparticles. Here we provide a systemic mapping of microglia and the corresponding pathological changes in olfactory-transport related brain areas of mice with Fe(2)O(3)-nanoparticle intranasal treatment. We showed that intranasal exposure of Fe(2)O(3) nanoparticle could lead to pathological alteration in olfactory bulb, hippocampus and striatum, and caused microglial proliferation, activation and recruitment in these areas, especially in olfactory bulb. Further experiments with BV2 microglial cells showed the exposure to Fe(2)O(3) nanoparticles could induce cells proliferation, phagocytosis and generation of ROS and NO, but did not cause significant release of inflammatory factors, including IL-1ß, IL-6 and TNF-α. Our results indicate that microglial activation may act as an alarm and defense system in the processes of the exogenous nanoparticles invading and storage in brain.