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SoxB subfamily is an important branch of Sox family and plays a key role in animal physiological process, but little is known about their function in planarian regeneration. This study aims to evaluate the function of DjSoxB family genes in intact and regenerating planarians Dugesia japonica. Here, we amplify the full-length cDNA of DjSoxB1 and DjSoxB2 in D. japonica by rapid amplification of the cDNA ends (RACE), detect the expression of DjSoxB family genes in planarian. The results show that DjSoxBs are expressed in parenchymal tissue and the hybridization signals partially disappear after irradiation indicates DjSoxB family genes are expressed in neoblasts. After the RNA interference (RNAi) of DjSoxB1, DjSoxB2 and DjSoxB3 separately, the numbers of proliferative cells are all reduced that causes planarians show slower growth of blastema in the early stage of regeneration, and nerves of planarians are affected that the movement speed of planarians decreases in varying degrees. Specially, planarians in the DjSoxB3 RNAi group show shrinkage and twisting. Overall, this study reveals that DjSoxB family genes play a role in cell proliferation during regeneration. They also play an important role in the maintenance of normal nerve function and nerve regeneration. These results provide directions for the functional study of SoxB family genes and provide an important foundation for planarian regeneration. [ABSTRACT FROM AUTHOR]

Catalytic olefin metathesis represents a vital reaction in the chemical industry, as it provides a feasible route for the interconversion of olefins. However, traditional supported catalysts usually suffer from low activity due to sluggish kinetics for the formation of catalytically active metal‐carbene species. This work tackles this issue by taking phosphoric acid as a promoter and constructing a Brønsted acidic site to cooperate with the MoOx sites, thus facilitating the formation of Mo‐carbene. It turns out that the turnover frequency of propene metathesis over the Mo−P/Al2O3 catalyst is 7.1 times higher than that over the unmodified Mo/Al2O3 catalyst. The combined characterization reveals the promotion of phosphorus results from the alignment of olefin toward adjacent MoOx and thus facilitates formation of active Mo‐carbene species. [ABSTRACT FROM AUTHOR]

Abstract This study leveraged milling steel fibers to enhance the flexural capacity of ultra-high-performance concrete (UHPC). We assessed UHPC's flexural performance, measuring compressive strength and flowability, considering three fiber types: milling, straight, and a hybrid. UHPC with milling fibers displayed superior compressive strength and flowability compared to straight fiber. Milling fibers consistently enhanced UHPC’s flexural capacity by over 120%, with a flowability reduction below 15%. Hybrid fiber demonstrated a balanced and commendable performance. Data-driven and theoretical flexural models were developed for UHPC with both fibers. the Gaussian process regression data-driven model outperformed the other 18 models, with an error below 3.5%. [ABSTRACT FROM AUTHOR]

The bottom ash (OIBA) generated from the incineration of hazardous oil sludge is classified as a hazardous waste. In this work, the OIBA was applied as raw material to prepare SiO 2 -Al 2 O 3 -CaO system glass-ceramics by melt-sintering with the addition of waste glass wool (GW). The effects of basicity (CaO/SiO 2 ratio, 0.52-1.05) and sintering temperature (900–1050 °C) on the crystallization kinetics, properties, microstructure, leaching concentrations of heavy metals and potential toxicity of glass-ceramics were investigated. The results showed that the crystallization pattern was two-dimensional crystallization, and with the decrease of basicity, the main crystalline phase evolved from gehlenite to diopside. And the glass-ceramics with basicity of 0.88 and sintering temperature of 950 °C exhibited the best comprehensive properties, including density (2.72 g/cm3), water absorption (0.06%), compressive strength (452.45 MPa) and chemical corrosion resistance. In addition, the reduction of heavy metal leaching concentration indicates that produced glass-ceramics showed excellent solidification effect on heavy metals, the low toxicity of glass-ceramics leaching solution to the wheat seeds and Artemia suggests the environmental protection characteristics of OIBA-based glass-ceramics. These findings proved that the glass-ceramics produced by OIBA and GW could be a promising method to dispose hazardous waste with preparing high value-added construction materials. [ABSTRACT FROM AUTHOR]

To meet the lightweight needs of modern machinery equipment, welded structure is widely used in practical engineering. During the service period, the welded structure is often subjected to multilevel variable amplitude loading, and fatigue failure is easy to occur. Due to the complexity and stochasticity of fatigue process, the traditional life prediction models cannot meet the demand of practical engineering. In this work, a novel prediction model based on the whale optimization algorithm (WOA) together with the support vector regression (SVR), namely, a WOA‐SVR model, is established. It combines the advantages of WOA and SVR for global searching optimization and high prediction accuracy dealing with small sample size. By taking into account the sequence of loadings and the interaction effect between loadings, the proposed WOA‐SVR model could overcome the deficiencies and shortcomings in existing models. Experiment results show that WOR‐SVR has better prediction performance than five models. Highlights: The WOA‐SVR model is established to predict the fatigue life under two‐level loading.The proposed model is verified by 190 experimental results.The proposed model has higher accuracy compared with other five models.The proposed model can be effectively applied to both welded joints and metal materials. [ABSTRACT FROM AUTHOR]

Class imbalance distribution widely exists in real-world engineering. However, the mainstream optimization algorithms that seek to minimize error will trap the deep learning model in sub-optimums when facing extreme class imbalance. It seriously harms the classification precision, especially in the minor classes. The essential reason is that the gradients of the classifier weights are imbalanced among the components from different classes. In this paper, we propose Attraction–Repulsion-Balanced Loss (ARB-Loss) to balance the different components of the gradients. We perform experiments on large-scale classification and segmentation datasets, and our ARB-Loss can achieve state-of-the-art performance via only one-stage training instead of 2-stage learning like nowadays SOTA works. [ABSTRACT FROM AUTHOR]

In the context of internationalization, this longitudinal qualitative study explores the diverse and challenging experiences of Chinese international doctoral students in science, technology, engineering, and mathematics. The endeavor is to identify factors that facilitate or constrain their successful completion of a PhD abroad over time. By incorporating a three-dimensional multi-world conceptual framework that highlights the relationship between an individual's research, personal, and social worlds, this study identified six patterns of congruence or difference across the worlds and the corresponding transitions, illustrated with narratives for each pattern. Evidence shows that congruence of an individual's multi-worlds facilitates, but difference does not necessarily mean constraint when differences are respected, understood, and accommodated. Rather, it is how the transitions are negotiated that is important for the success of transnational and transcultural PhD study. This article contributes a conceptual framework, empirical evidence, and practical implications to the understanding of doctoral study abroad experiences. [ABSTRACT FROM AUTHOR]

With the trend of student mobility, talented individuals have been pursuing doctoral education opportunities abroad. Prior research addressed specific aspects or challenges of doing a PhD in a cross-cultural context, leaving a need to understand the nature of students' experiences from a holistic perspective. To address the need, this study develops a framework that conceptualises an international doctoral student's research, personal, and social worlds as multi-worlds, highlighting transitions across the worlds that make a difference in student experiences. It also structures the continuous, interactive, and situative nature of study abroad as a three-dimensional space to encompass the multi-worlds and transitions across and over time. Illustrated by one international student's in-depth narrative inquiry, this framework offers both theoretical insights and practical approaches to the comprehensive understanding of PhD abroad experiences. [ABSTRACT FROM AUTHOR]

Terrestrial silicate weathering records from the tectonically active Tibetan Plateau are crucial to explore the interactions among climate change, tectonic uplift and chemical weathering during the Cenozoic. However, the complex sedimentary facies changes and frequent occurrence of coarse lithologies related to intense tectonic uplift of the Tibetan Plateau have largely limited the reliability of bulk chemical weathering indexes to reveal the silicate weathering history. Here, we present detailed records of clay minerals and geochemical compositions from clay-sized (< 2 μm) sediments collected from the well-dated Huaitoutala section (ca. 15.3–1.8 Ma) in the NE Qaidam Basin to reconstruct the chemical weathering history of the NE Tibetan Plateau during the late Cenozoic. The relatively high (illite–smectite mixed layers + smectite)/(chlorite + illite) ratio indicates a strong silicate weathering intensity from 15.3 to 12.6. Ma, while a continuous decrease in this ratio since 12.6 Ma reflects a long-term decreasing intensity of silicate weathering. By comparing the clay mineral records with the climatic reconstruction and the tectonic events in the NE Tibetan Plateau, the results reveal that middle Miocene global cooling-related drying exerted a significant influence on the decreasing weathering intensity since ca. 12.6 Ma. Furthermore, the late Cenozoic episodic and persistent uplift of the NE Tibetan Plateau may have exerted an additional influence on the long-term decrease in weathering intensity. Specifically, the dramatic fluctuation in the silicate weathering intensity during ∼11–9.6 Ma is mainly due to uplift-induced provenance changes. Moreover, the fluctuating increase in the silicate weathering intensity during ∼8–5 Ma may have been caused by intensified East Asian summer monsoon precipitation. Our study suggests that both climate change and tectonic deformation controlled the chemical weathering intensity in the NE Tibetan Plateau during the late Cenozoic. • Detailed 15.3–1.8 Ma clay minerals records from the northeastern Qaidam Basin. • Long-term continuous weakening of silicate weathering intensity since 12.6 Ma. • Global cooling-related drying mainly caused weakening of silicate weathering. • Uplift-induced provenance change influenced weathering proxy during 11–9.6 Ma. • Increase in silicate weathering intensity during ∼8–5 Ma caused by monsoon rainfall. [ABSTRACT FROM AUTHOR]

Cenozoic basin sediments on the Tibetan Plateau are commonly characterized by frequent changes in sediment facies and coarse lithologies, which largely limits our understanding of the relationship between the Tibetan Plateau uplift and its environmental impacts. The monomineral index derived from those sediments can effectively eliminate the effects of grain size and sedimentary facies changes. Here, we present detailed mineralogical, spectroscopic, and micromorphological investigations of smectites collected from the Hongliugou section of the Qaidam Basin to explore the relationship between climate change and the Tibetan Plateau uplift in the early–middle Eocene. Multiple methods involving X–ray diffraction, transmission electron microscopy, 27Al nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy collectively show that the smectites in the Hongliugou section are mixtures of montmorillonites and beidellites. The origin of the beidellites was likely the weathering product of illite, as indicated by the presence of illite–beidellite mixed layers (an intermediate product of the alteration of illite to beidellite). The long–term decreasing trend of beidellite/smectite ratios from the highest values (∼1.1–82.0%, averaging 14.8%) in the Early Eocene Climate Optimum (∼52.0–49.5 Ma) to generally <2% at 49.5–43.9 Ma suggested a long–term climatic drying. This climate change history deduced from the variation of beidellite content is consistent with other climate records and supports that global climate change was the driving factor regulating regional climate change. Our study thus suggests that the monomineral index of smectite may serve as an effective method for reconstructing regional climate change, especially within complex sedimentary environments. • Both beidellite and montmorillonite were identified in the Qaidam Basin. • A continuous drying trend is shown by the beidellite content at ∼53–43.9 Ma. • Global climate change mainly regulated regional climate change during ∼53–43.9 Ma. • Smectite monomineral index reveals climate change in complex sedimentary settings. [ABSTRACT FROM AUTHOR]

We present a new type of acquisition function for online decision-making in multi-armed and contextual bandit problems with extreme payoffs. Specifically, we model the payoff function as a Gaussian process and formulate a novel type of upper confidence bound acquisition function that guides exploration towards the bandits that are deemed most relevant according to the variability of the observed rewards. This is achieved by computing a tractable likelihood ratio that quantifies the importance of the output relative to the inputs and essentially acts as an attention mechanism that promotes exploration of extreme rewards. Our formulation is supported by asymptotic zero-regret guarantees, and its performance is demonstrated across several synthetic benchmarks, as well as two realistic examples involving noisy sensor network data. Finally, we provide a JAX library for efficient bandit optimization using Gaussian processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dense seismic array deployed 18 days is used to image a 3D Vs model. • Three LVZs are revealed in the shallow crust beneath the Shiziyang Waterway area. • Three cross-cutting fault zones in the sedimentary basement are identified. • Two-stage differential fault movements dominated the opening of the Shiziyang Waterway. The Shiziyang Waterway, located in the northern continental margin of the South China Sea, has developed a complex fault system owing to the coupling action of the oceanic crust and continental crust. However, the geological structure in the shallow crust beneath the Shiziyang Waterway and the relationship between faults and waterway development are still unclear, resulting in difficulty in assessing the earthquake risk to the surrounding cities. In this study, based on a high-density short-period seismic array that was recently deployed around the Shiziyang Waterway, a high-resolution shear wave velocity model is inverted to as shallow as 4 km by the ambient noise tomography method. The results showed that at depths ranging from 0.2 to 4 km, three sets of low-velocity zones (LVZs), trending east–west, northeast, and northwest, are revealed, which are speculated to be the Shougouling fault (SGLF), Xinhui-Shiqiao fault (XSF), and Shiziyang fault bundle (SZYFb), respectively. The shear-wave velocity anomalies illustrate that the SGLF stopped extending east at the north endpoint of the Wenchong-Zhujiangkou fault (WZF). The two-stage differential vertical movements of the WZF, Nangang-Humen fault (NHF), and Hualong-Haioudao fault (HHF) dominated the opening of the Shiziyang Waterway. This study provides new seismological evidence of the opening process for the Shiziyang Waterway and reveals that internal fault activity dominated the development and evolution of the Pearl River Delta. [ABSTRACT FROM AUTHOR]

Based on the semi-discrete artificial boundary condition introduced by Ji, Yang, and Antoine [Comput. Phys. Commun. 222 (2018), pp. 84–93] for the two-dimensional free Schrödinger equation in a computational rectangular domain, we propose to analyze the stability and convergence rate with respect to time of the resulting full scheme. We prove that the global scheme is L2-stable and that the accuracy is second-order in time, confirming then the numerical results reported by Ji et al. (2018). [ABSTRACT FROM AUTHOR]

The Oligocene-Miocene boundary Asian climatic reorganization linked to the northward migration of the East Asian monsoon into subtropical China is a potentially important but poorly constrained atmospheric CO2 consumption process. Here, we performed a first-order estimate of the CO2 consumption induced by silicate chemical weathering and organic carbon burial in subtropical China related to this climatic reorganization. Our results show that an increase in long-term CO2 consumption by silicate weathering varies from 0.06×1012 to 0.87×1012 mol yr−1 depending on erosion flux reconstructions, with an ~50% contribution of Mg-silicate weathering since the late Oligocene. The organic carbon burial flux is approximately 25% of the contemporary CO2 consumption by silicate weathering. The results highlight the significant role of weathering of the Mg-rich upper continental crust in East China, which would contribute to the rapid decline in atmospheric CO2 during the late Oligocene and the Neogene rise in the seawater Mg content. If this climatic reorganization was mainly induced by the Tibetan Plateau uplift, our study suggests that the growth of the Himalayan-Tibetan Plateau can lead to indirect modification of the global carbon and magnesium cycles by changing the regional hydrological cycle in areas of East Asia that are tectonically less active. [ABSTRACT FROM AUTHOR]

Exceedingly strong aeolian dust activity has occurred in inland Asia. Comparisons of the late Cenozoic sedimentation rates between aeolian and fluvial‐lacustrine sequences around the northern Tibetan Plateau suggest that aeolian process has played an important role in the erosion, weathering and deposition of sediment. However, recognizing dust as an important source in fluvial‐lacustrine sequences is a vital but difficult task. Here, clay‐sized mineral and elemental records of regional silicate weathering histories are revisited during the period of Asian dust expansion at ~9–8 Ma. The aeolian dust input from the Tianshan‐Altay Orogens into the Jiuquan Basin is identified using the Th/Sc ratio while that from the Qilian Shan into the Xining Basin is identified based on inconsistent fine‐grained silicate weathering proxies. Our study suggests that the use of appropriate dust provenance tracers and recognition of wind transport‐induced changes in dust grain size and chemistry can provide useful aeolian dust discrimination approaches. [ABSTRACT FROM AUTHOR]

Ultrahigh-performance concrete (UHPC) is susceptible to various forms of abrasion during its service life. This study is an investigation of the abrasion resistance of UHPC, focusing on two primary causes of wear: dynamic traffic loads and hydraulic impacts. To enhance the material's resistance to abrasion, milling steel fibres were utilised. For comparative purposes, straight steel fibres and hybrid milling–straight steel fibres were also employed. The protective function of the steel fibres primarily comes into effect once the concrete cover has experienced wear. When subjected to traffic and hydraulic loads, UHPC containing milling fibres exhibited superior resistance, compared with that containing straight fibres, while maintaining favourable workability. Notably, the UHPC incorporating hybrid steel fibres, which form a composite skeleton, owing to the presence of two fibre types, demonstrated even greater effectiveness in resisting external abrasion. Furthermore, the abrasion resistances observed under both traffic and hydraulic conditions displayed a positive linear correlation, with R2 > 0.8. These findings suggest the feasibility of evaluating the material's abrasion resistance under various wearing causes using a single test method. The outcomes of this study hold promise in advancing the development of UHPC and promoting its utilisation in conditions characterised by severe abrasion. [ABSTRACT FROM AUTHOR]

The influence of the curing methods on the flexural performances of the milling steel fiber reinforced ultra-high-performance concrete (UHPC) with a high fiber content was systematically evaluated in this study, alongside the flowability and compressive strength. The UHPC specimens were subjected to standard curing and steam curing, employing three steel fiber reinforcing schedules: single milling fiber, single straight fiber, and a combination of both. The flowability of the UHPC was found to be less affected by the milling fiber compared to the straight fiber. Steam curing significantly enhanced the compressive strength but had a slight negative effect on the flexural behavior. However, this adverse effect could be mitigated as the fiber content increased. The flexural strength and toughness of the UHPC with milling fiber were minimally influenced by steam curing, suggesting that standard curing was sufficient for the milling fiber-reinforced UHPC. Conversely, steam curing exhibited an improvement in the flexural behavior of the UHPC containing a hybrid combination of milling and straight fibers. In addition to developing an empirical model for compressive and flexural strengths, we proposed a data-driven model called Gaussian process regression (GPR) to predict the flexural behaviors of the UHPC with varying fiber content, types, and curing methods. The data-driven model demonstrated high accuracy, with an R2 value of 1.0 when compared to the experimental data. [ABSTRACT FROM AUTHOR]

Non‐noble Ni−Cu alloys serve as an alternative catalytic material for noble metal‐based catalysts that could be applied in the efficient conversion of levulinic acid (LA) into the high value γ‐valerolactone (GVL). However, maintaining the catalytic stability for Ni−Cu nanoparticles in the LA hydrogenation process remains a substantial challenge, Herein, this problem is solved by constructing carbon‐protected catalytic sites within carbon layer‐coated Ni−Cu nanoalloy composite via pyrolysis of NiCux(OH)/glucose precursor. The optimized NiCu0.68@C catalyst exhibits excellent stability and selectivity to GVL (>99 %) in the hydrogenation of LA reaction. Various characterization indicates that the enhancement in stability originates from the protective effect of the carbon layer, which prevents the metal leaching, oxidation and aggregation of Ni−Cu nanoparticles during the reaction process. This work greatly advances non‐noble metal‐catalyzed conversion of LA to GVL and helps the rational design of bimetallic catalysts. [ABSTRACT FROM AUTHOR]

The arid interior of Asia is the largest source of dust deposited in the North Pacific Ocean, and some dust is even transported to Greenland. Investigating the provenance history of Asian dust can provide strong constraints on the evolution of topography and climate in the Asian interior. Eolian dust Nd isotopic records preserved in North Pacific Ocean sediments since ∼40 Ma provide a spatially integrated first-order constraint on the provenance changes of Asian dust. However, a lack of similarly long dust Nd isotopic records from Asian dust source areas, namely, the northern Tibetan Plateau and the Central Asian Orogenic Belt, has hindered a full understanding of Asian dust provenance changes linked to the Cenozoic evolution of tectonics, climate and topography in inland Asia. Here, we have constructed the first fine-grained and whole-rock Nd isotopic records from sediments deposited on the northern Tibetan Plateau since ∼52 Ma. The results indicate two major changes, a gradual increase in ε Nd (0) values between ∼42 Ma and ∼25 Ma and a general decrease since ∼25 Ma, which were probably caused by the incremental northward growth of the Tibetan Plateau. Further mass balance estimates based on comparisons between the Nd isotopic characteristics of dust from the northern Tibetan Plateau and the North Pacific Ocean indicate that a rapid increase in the contribution of the Central Asian Orogenic Belt to Asian dust at ∼25 Ma can be closely linked to rapid exhumation caused by tectonic uplift and aridification in inland Asia. Our provenance analyses, together with the onset of eolian sediment in central and eastern Asia, suggest that a modern-like regime promoting Asian dust emissions and transport might have been in place since the late Oligocene. [ABSTRACT FROM AUTHOR]

In recent years, convolutional neural networks have achieved great success in streak artifacts reduction. However, there is no special method designed for the artifacts reduction of the prostate. To solve the problem, the artifacts reduction CliqueNet (ARCliqueNet) to reconstruct dense‐view computed tomography images form sparse‐view computed tomography images is proposed. In detail, first, the proposed ARCliqueNet extracts a set of feature maps from the prostate sparse‐view CT image by Clique Block. Second, the feature maps are sent to ASPP with memory to be refined. Thenanother Clique Block is applied to the output of ASPP with memory and reconstruct the dense‐view CT images. Later on, reconstructed dense‐view CT images are used as new input of the original network. This process is repeated recurrently with memory delivering information between these recurrent stages. The final reconstructed dense‐view CT images are the output of the last recurrent stage. Our proposed ARCliqueNet outperforms the SOTA (state‐of‐the‐art) general artifacts reduction methods on the prostate dataset in terms of PSNR (peak signal‐to‐noise ratio) and SSIM (structural similarity). Therefore, we can draw the conclusion that Clique structures, ASPP with memory and recurrent learning are useful for prostate sparse‐view CT Artifacts here. [ABSTRACT FROM AUTHOR]

This study investigates the early performance and potential issues of ultra-high-performance concrete (UHPC) light-weight composite decks (LCBDs) used in municipal highway bridge design. The major objective of this research was to understand the complex evolution of temperature and humidity within immature UHPC thin layers, which can lead to deformation and secondary stress, potentially causing cracks and threatening the long-term applicability and safety of steel-concrete composite bridges. Understanding of the mechanism of this process will be the basis for subsequent work. The early performance of UHPC with ordinary concrete is compared. Besides, discussions are conducted on the basic thermal conductivity theory of three-dimensional porous media and the hydration mechanism of cement-based materials that are appropriate for early-stage UHPC. Subsequently, a refined thermo-mechanical coupling analysis method for steel-UHPC LCBD was proposed, implemented using ABAQUS, and validated through a UHPC composite beam test. This method was applied to calculate the early shrinkage of the UHPC layer in a steel-UHPC LCBD and evaluate the risk of cracking in an actual bridge expansion project, providing a rationality evaluation of a bridge design and its construction procedure. • An approach for early shrinkage and crack assessment of UHPC light-weight composite bridge decks (LCBD) is suggested. • The aforementioned method is validated by an existing experiment and data therein. • Parametric analysis based on varying curing conditions of the composite beam is performed. • The design of the upper deck is evaluated, and construction & maintenance tips for a certain bridge project are proposed. [ABSTRACT FROM AUTHOR]

Molecular diffusion is a fundamental mass transport phenomenon crucial to many scientific and industrial fields. Its accurate description relies on diffusion coefficients that can be either experimentally measured or theoretically estimated. The constant volume diffusion (CVD) method is a widely used approach to measure liquid-phase diffusion coefficients at high pressures. However, it requires analytical or numerical solutions to interpret the measured data. In this study, we described in detail a legacy CVD simulation code developed by Michael L. Michelsen and showed how his algorithm can determine constant or composition-dependent diffusion coefficients from the CVD data using the orthogonal collocation method. We further coupled the code with five diffusion coefficient correlations, including the Wilke-Chang (WC), Hayduk–Minhas (HM), extended Sigmund (ES), Riazi–Whitson (RW), and Leahy-Dios-Firoozabadi (LDF), to investigate their performance in terms of predicting and regressing the CVD data for methane-n-alkane and nitrogen-n-alkane systems. We found that the CVD results are insensitive to the gas-phase diffusion coefficients. The simple WC and HM give the closest predictions despite their empirical nature and inherent inconsistency. In contrast, the predictions by LDF under the rigorous Maxwell-Stefan framework are not satisfactory. The regression results using different correlations and a constant liquid-phase diffusion coefficient are almost the same. Different correlations result in different ranges of the regressed coefficients, and those determined using the assumption of constant diffusion coefficients are always within these ranges. We also compared and illustrated the differences in the profiles of diffusion coefficients between these correlations. The study demonstrates that Michelsen's algorithm is an effective tool for processing CVD data, and it also highlights how the interpretation of CVD data depends on the assumed composition-dependence. [ABSTRACT FROM AUTHOR]

This paper presents a machine learning framework for Bayesian systems identification from noisy, sparse and irregular observations of nonlinear dynamical systems. The proposed method takes advantage of recent developments in differentiable programming to propagate gradient information through ordinary differential equation solvers and perform Bayesian inference with respect to unknown model parameters using Hamiltonian Monte Carlo sampling. This allows an efficient inference of the posterior distributions over plausible models with quantified uncertainty, while the use of sparsity-promoting priors enables the discovery of interpretable and parsimonious representations for the underlying latent dynamics. A series of numerical studies is presented to demonstrate the effectiveness of the proposed methods, including nonlinear oscillators, predator–prey systems and examples from systems biology. Taken together, our findings put forth a flexible and robust workflow for data-driven model discovery under uncertainty. All codes and data accompanying this article are available at https://bit.ly/34FOJMj. [ABSTRACT FROM AUTHOR]

We present a deep learning framework for quantifying and propagating uncertainty in systems governed by non-linear differential equations using physics-informed neural networks. Specifically, we employ latent variable models to construct probabilistic representations for the system states, and put forth an adversarial inference procedure for training them on data, while constraining their predictions to satisfy given physical laws expressed by partial differential equations. Such physics-informed constraints provide a regularization mechanism for effectively training deep generative models as surrogates of physical systems in which the cost of data acquisition is high, and training data-sets are typically small. This provides a flexible framework for characterizing uncertainty in the outputs of physical systems due to randomness in their inputs or noise in their observations that entirely bypasses the need for repeatedly sampling expensive experiments or numerical simulators. We demonstrate the effectiveness of our approach through a series of examples involving uncertainty propagation in non-linear conservation laws, and the discovery of constitutive laws for flow through porous media directly from noisy data. • We developed self-supervised deep learning methods for modeling stochastic systems. • Regularized adversarial inference enables learning generative models from small data. • This yields a flexible workflow for characterizing uncertainty in physical systems. • This method bypasses the need for sampling costly simulators for tackling UQ tasks. [ABSTRACT FROM AUTHOR]

We present a probabilistic deep learning methodology that enables the construction of predictive data-driven surrogates for stochastic systems. Leveraging recent advances in variational inference with implicit distributions, we put forth a statistical inference framework that enables the end-to-end training of surrogate models on paired input–output observations that may be stochastic in nature, originate from different information sources of variable fidelity, or be corrupted by complex noise processes. The resulting surrogates can accommodate high-dimensional inputs and outputs and are able to return predictions with quantified uncertainty. The effectiveness our approach is demonstrated through a series of canonical studies, including the regression of noisy data, multi-fidelity modeling of stochastic processes, and uncertainty propagation in high-dimensional dynamical systems. [ABSTRACT FROM AUTHOR]

In this paper, we focus on exploring effective methods for faster and accurate semantic segmentation. A common practice to improve the performance is to attain high-resolution feature maps with strong semantic representation. Two strategies are widely used: atrous convolutions and feature pyramid fusion, while both are either computationally intensive or ineffective. Inspired by the Optical Flow for motion alignment between adjacent video frames, we propose a Flow Alignment Module (FAM) to learn Semantic Flow between feature maps of adjacent levels and broadcast high-level features to high-resolution features effectively and efficiently. Furthermore, integrating our FAM to a standard feature pyramid structure exhibits superior performance over other real-time methods, even on lightweight backbone networks, such as ResNet-18 and DFNet. Then to further speed up the inference procedure, we also present a novel Gated Dual Flow Alignment Module to directly align high-resolution feature maps and low-resolution feature maps where we term the improved version network as SFNet-Lite. Extensive experiments are conducted on several challenging datasets, where results show the effectiveness of both SFNet and SFNet-Lite. In particular, when using Cityscapes test set, the SFNet-Lite series achieve 80.1 mIoU while running at 60 FPS using ResNet-18 backbone and 78.8 mIoU while running at 120 FPS using STDC backbone on RTX-3090. Moreover, we unify four challenging driving datasets (i.e., Cityscapes, Mapillary, IDD, and BDD) into one large dataset, which we named Unified Driving Segmentation (UDS) dataset. It contains diverse domain and style information. We benchmark several representative works on UDS. Both SFNet and SFNet-Lite still achieve the best speed and accuracy trade-off on UDS, which serves as a strong baseline in such a challenging setting. The code and models are publicly available at https://github.com/lxtGH/SFSegNets. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to achieve beam angle control in vertical cavity surface emitting lasers (VCSELs) using microstructures. The proposed microstructured VCSEL (MVCSEL) models are designed and optimized to simulate the effect of various microstructure parameters on beam diffraction. And the MVCSELs with different microstructure period lengths are modeled and their emission angles are characterized. By varying the microstructure period length from 18 μ m to 1 μ m , the emission angle of the MVCSELs is found to vary from ± 3° to ± 70°, resulting in a large scanning range of 134°. Additionally, the vertical divergence angle of these MVCSELs is controlled to be in the range of 0.67° to 0.23°. Integration of these MVCSELs in an array provides a promising option for miniaturization and integration of LiDAR and can be directly used as a transmitter chip for LiDAR applications. These results suggest that the proposed MVCSELs array chip could have significant potential in the development of high-performance and low-cost LiDAR systems. [ABSTRACT FROM AUTHOR]

As one of the largest dust sources on the Earth's surface, dryland in Central Asia gives rise to thick eolian deposits over East Asia (e.g., the Chinese Loess Plateau, CLP) and significantly influences the regional hydrochemistry in the downwind drainage areas. However, the formation of thick eolian dust deposits requires not only climatic prerequisites for dust emission and transport but also climatic and topographic conditions favourable for deposition and accumulation. The scarcity of widespread eolian deposition around the CLP before 7-8 Ma hinders a full understanding of the processes and mechanisms of Central Asian aridification. The deposition of eolian dust also impacts the hydrogeochemistry of fluvial systems and the precipitation of authigenic phases in continental sedimentary systems could be an archive for studying eolian dust dynamics when pure eolian deposits are scarce. Here, we present the Ca-Mg-Sr concentrations and 87Sr/86Sr isotope compositions of bulk carbonates in a new fluvial sequence (12.7-4.8 Ma) of the Xining Basin. The Mg/Ca and Sr/Ca ratios of the carbonate describe a power law relationship with a power coefficient of ∼0.8, lower than the coefficient characteristic of prior calcite precipitation (PCP). An input of eolian dust with the dissolution of Mg-rich carbonate is likely responsible for the deviation from a pure PCP process. The bulk carbonates also show a general decrease of 87Sr/86Sr ratios from 12.7 to 4.8 Ma, with a transition around 8.6 Ma revealed by lower Sr/Mg ratios. The comparison of these proxies to a previously reported fluvial section (12.2-5.1 Ma) in the Linxia Basin, ∼200 km to the southeast, shows that the 87Sr/86Sr ratios of the bulk carbonates and water-soluble salts in the Linxia Basin are around 0.7098, which is 0.0018 lower than those in the Xining Basin before 8.6 Ma, but shows a significant rise between 8.6 and 7.0 Ma. The two basins share the same range of carbonate 87Sr/86Sr ratios when sediments are younger than 7 Ma. For the last 7 Myrs, the evolution of the 87Sr/86Sr ratios in bulk carbonates of fluvial sediments and Pliocene-Quaternary eolian deposits found in the Xining Basin are similar to those in typical eolian red clays/loess-palaeosol sequences on the CLP. These results suggest a transition of the hydrochemical regime at 8.6 Ma in the Linxia Basin from a catchment only influenced by the weathering of its bedrock to one significantly impacted by eolian dust input. In the Xining Basin, the carbonate elemental and 87Sr/86Sr ratios are consistent with a hydrochemistry more impacted by the presence of the eolian dust. There, the dust input occurred earlier, at ≥12.7 Ma, though it has strengthened since 8.6 Ma. The eolian dust impact on fluvial systems in the Xining Basin was much earlier than in the Linxia Basin and also preceded the initial accumulation of widespread eolian red clays on the CLP (7-8 Ma), suggesting a temporally propagating and spatially stepwise expansion of eolian dust delivery across the Asian inland during the late Cenozoic. • Fluvial carbonate elemental and Sr isotopic geochemistry reveals eolian dust input. • Eolian dust affected the river chemistry of the Xining Basin at least since 12.7 Ma. • The impact of eolian dust in the Xining Basin has strengthened at ∼8 Ma. • Eolian dust affected the river chemistry of the Linxia Basin but only since ∼8 Ma. • A south-eastward expansion of the dust impact on river water occurred in NE Tibet. [ABSTRACT FROM AUTHOR]

Abstract The Eocene-Oligocene climate transition (EOCT) at ~34 Ma is a pronounced environmental reorganization that occurred in the Cenozoic era and has been extensively studied via marine archives. However, to date, there is still a less well-dated continental record across the EOCT, which can mostly be attributed to a lack of suitable proxies used in the varied continental settings in terms of sedimentary facies, provenance and climate, thus resulting in a poor understanding of the continental response to this transition. Located on the northeastern Tibetan Plateau, the Qaidam Basin is filled with continuous and well-exposed Cenozoic fluvio-lacustrine sediments. Cenozoic lacustrine sediment has been proven to be an ideal archive to study the continental climatic response to the EOCT. Here, we present the detailed mineralogical and elemental composition of chlorite, a widespread clay mineral in continental sediments formed by rock weathering, collected from a lacustrine sequence in the northern Qaidam Basin to constrain the onset of the EOCT and the related climatic response. The results show that chlorite abundance, crystallinity indices, intensity ratios of chlorite diagnostic peaks and chemical composition collectively exhibit remarkable changes at ~34.3 Ma. To be more specific, the well-crystallized Fe-Mg-rich chlorites were characterized by a high Fe content before the EOCT and turned into high-Mg-content Mg-chlorites with poor crystallinity. The chlorite chemical composition change is assumed to have been related to regional drying after the EOCT, thus providing new insights into the continental paleoenvironmental change based on this novel proxy. Highlights • The first chlorite-derived record of Eocene-Oligocene (EOCT) climate transition • Chlorite abundance, crystallinity and Fe/Mg ratio change together after the EOCT. • Well-crystallized Fe-Mg chlorites turned into Mg-chlorites with poor crystallinity. • Chlorite chemical composition changes linked with regional drying after the EOCT • Chlorite chemical composition can be used as a novel paleoclimatic proxy. [ABSTRACT FROM AUTHOR]

The runt family genes play important roles in physiological processes in eukaryotic organisms by regulation of protein transcription, such as hematopoietic system, proliferation of gastric epithelial cells and neural development. However, it remains unclear about the specific functions of these genes. In this study, the full-length cDNA sequences of two runt genes are first cloned from Dugesia japonica , and their roles are investigated by WISH and RNAi. The results show that: (1) the Djrunts are conserved during evolution; (2) the Djrunts mRNA are widely expressed in intact and regenerative worms, and their expression levels are up-regulated significantly on day 1 after amputation; (3) loss of Djrunts function lead to lysis or regeneration failure in the intact and regenerating worms. Overall, the data suggests that Djrunts play important roles in regeneration and homeostatic maintenance in planarians. [ABSTRACT FROM AUTHOR]

Cellulose aerogels have been widely studied as promising environmentally friendly materials due to their low density, biocompatibility and degradability. However, their applications are limited due to their highly combustible nature. In this study, polyaniline (PANI) decorated bacterial cellulose (BC) composite aerogel has been synthesized with in situ polymerization of aniline monomer on the surface of BC scaffold. The PANI decorated BC composite aerogel has a very high specific area of 124.0 m 2 /g and well-preserved nanoporous structure, while its conductivity drastically increased to 10.44 S/m. Interestingly, phosphate groups were incorporated onto PANI backbones due to its unique doping/dedoping structure. The resultant composite aerogel presented excellent flame retardancy, which can be self-extinguished within 1 s. Moreover, PANI@BC composite hydrogel exhibited self-motion behavior under low voltage electric field, illustrating potential electromechanical actuator application. This simple and sustainable in situ doping method opens up new opportunities for cost-efficient fabrication of multifunctional cellulose-based electronics. [ABSTRACT FROM AUTHOR]

Opportunistic Mobile Social Networks (OMSNs), formed by mobile users with social relationships and characteristics, enhance spontaneous communication among users that opportunistically encounter each other. Such networks can be exploited to improve the performance of data forwarding. Discovering optimal relay nodes is one of the important issues for efficient data propagation in OMSNs. Although traditional centrality definitions to identify the nodes features in network, they cannot identify effectively the influential nodes for data dissemination in OMSNs. Existing protocols take advantage of spatial contact frequency and social characteristics to enhance transmission performance. However, existing protocols have not fully exploited the benefits of the relations and the effects between geographical information, social features and user interests. In this paper, we first evaluate these three characteristics of users and design a routing protocol called Geo-Social-Interest (GSI) protocol to select optimal relay nodes. We compare the performance of GSI using real INFOCOM06 data sets. The experiment results demonstrate that GSI overperforms the other protocols with highest data delivery ratio and low communication overhead. [ABSTRACT FROM AUTHOR]

Traffic is one of the most fundamental dynamical processes in networked systems. With the traditional shortest path routing (SPR) protocol, traffic congestion is likely to occur on the hub nodes on scale-free networks. In this paper, we propose an improved optimal routing (IOR) strategy which is based on the betweenness centrality and the degree centrality of nodes in the scale-free networks. With the proposed strategy, the routing paths can accurately bypass hub nodes in the network to enhance the transport efficiency. Simulation results show that the traffic capacity as well as some other indexes reflecting transportation efficiency are further improved with the IOR strategy. Owing to the significantly improved traffic performance, this study is helpful to design more efficient routing strategies in communication or transportation systems. [ABSTRACT FROM AUTHOR]

Exploring the interplay between the mid-latitude Westerlies and East Asian monsoon systems is crucial for revealing the mechanisms and processes behind the aridification of the central Asian interior. In this study, a high-resolution acid-dissolved Mn record of lacustrine sediments from a drilling core (SG-1) in the arid western Qaidam Basin on the northeastern Tibetan Plateau (TP) largely reveals the evolution of lake levels and climate change over the last 600 kyr. The climate in the western Qaidam Basin shows distinct glacial and interglacial changes in accordance with changes in the global climate, and in North Atlantic sea surface temperatures (SSTs), indicating the teleconnection between the basin's climate and the North Atlantic in the form of the Westerlies. However, the basin's climate also correlates closely with East Asian Winter Monsoon (EAWM) activity as recorded by the grain size variations in loess-paleosol sequences on the Chinese Loess Plateau (CLP) over a glacial-interglacial timescale. Even during glacial periods, some relatively warm/humid stages accompanied by high paleolake levels in the western Qaidam Basin are generally conformable with relatively weak EAWM, whereas these warm/humid stages show a weak relation with the East Asian Summer Monsoon (EASM) and North Atlantic SSTs. These results collectively provide evidence that climate change in the western Qaidam Basin is, and was, not only controlled by the Westerlies, but also strongly influenced by the Siberian High, at least during glacial periods. The exact driving mechanism, however, needs to be explored further in future studies. [ABSTRACT FROM AUTHOR]

Eolian dust is one of the most important factors controlling fluvial hydrological evolution in modern arid and semi-arid central Asia. Here, we present the bulk carbonate Ca–Mg–Sr concentrations and Sr isotopic compositions recorded in water soluble salts, carbonate and silicate fractions, as well as the Nd isotopic compositions in the silicate fraction of a Late Miocene (12.2–5.1 Ma) fluvial sequence exhibiting paleosol development, in the Linxia Basin on the northeastern Tibetan Plateau (TP). Bulk carbonate Mg–Sr systematics show a distinct pattern in log–log plots of Mg/Ca versus log Sr/Ca ratios, and clearly higher 87 Sr/ 86 Sr ratios since ∼8 Ma. These findings cannot be adequately explained by the mechanism of prior calcite precipitation (PCP) – this latter process results in a positive correlation between the Mg/Ca and Sr/Ca ratios in authigenic calcite, evident in the fixed gradient in their log–log plots and has been isolated as being the major factor controlling carbonate Mg–Sr systematics before 8 Ma. Nor can these findings be explained by other mechanisms related to the catchment's provenance/sedimentation. The dramatic changes in carbonate Sr contents, Sr isotopes, and Sr/Mg ratios since ∼8 Ma may therefore be inferred to have been triggered by significant inputs of eolian dust via the dissolution of dust carbonates and evaporites in the paleowaters where fluvial and paleosol carbonates precipitated. This process of eolian dust input can be reliably illustrated using a binary mixing model corresponding to a series of varying PCP fluxes (identical to processes affecting the area before 8 Ma) combined with a constant eolian influx calculated from the co-variations between Mg/Ca, Sr/Ca and Sr isotopic ratios. Eolian dust also leaves a fingerprint in the carbonate and silicate minerals of bulk sediments, as revealed respectively by their Sr and Nd isotopic compositions. Eolian dust compositions for the ∼8–5 Ma on the northeastern TP can thus be taken to be characterized by a ε Nd value ≤−10.5 for the silicate fraction, and by a 87 Sr/ 86 Sr value ≥0.7115 for the labile faction (carbonates and evaporites). Eolian dust is now recognized to have made a significant impact on the hydrological evolution of arid and semi-arid northern China as far back as ∼8 Ma, suggesting an enhanced regime of dust activity and regional aridification in central Asia at that time. [ABSTRACT FROM AUTHOR]

The Qaidam Basin, located on the northeastern Tibetan Plateau and containing Cenozoic sediments with a maximum thickness of ~ 12,000 m, is an ideal place to study the phased uplift of the NE Tibetan Plateau and regional climate change. The estimation of the paleosalinity of sedimentary environments not only helps to evaluate the evolution of lakes in this region but offers insights into contemporaneous climate change. We present detailed geochemical and mineralogical investigations from the lacustrine interval of the Hongliugou section in the northern Qaidam Basin to reconstruct salinity fluctuations in the paleolake during the late Eocene era (~ 42.0–35.5 Ma). The clay mineral assemblages mainly contain smectite, illite, chlorite, kaolinite and irregular illite/smectite mixed layers. Clay boron-derived paleosalinity estimates (equivalent boron content, Couch's paleosalimeter and B/Ga ratios) along with other proxies sensitive to salinity changes (e.g., Rb/K ratios and ostracod assemblages) collectively indicate an overall brackish sedimentary environment with a higher-salinity period at approximately 40.0–39.2 Ma. This higher-salinity period indicates a more arid environment and is probably related to global cooling. However, the global cooling in late Eocene cannot explain the overall stable long-term salinity pattern, implying that other factors exist. We propose that the migration of the Yiliping depression depocenter in the northern Qaidam and increased orographic rainfall induced by late Eocene tectonic activity at the northern margin of the basin might have partly offset the increase in salinity driven by global cooling. [ABSTRACT FROM AUTHOR]

The uplift of the northern Tibetan Plateau (TP) has long been regarded as one of major factors accounting for both the enhanced process of aridification recorded in central Asia and the shifts in the Asian monsoonal circulations that are known to have occurred at approximately 8 Ma. Until now, there have been few sedimentary records reported on which can directly, and in an integrated fashion, shed light on the region's tectonic and climate regimes. This can be largely attributed to the fact that the influence exerted by the presence of source materials and subsequent sedimentary sorting in this tectonically active region would be likely to bias significantly any paleoclimatic interpretation of silicate-derived proxies. Based on detailed investigations of strontium (Sr) distributions revealed by multi-step leaching in a fluvial sequence from the Linxia Basin which includes paleosols, we reconstructed the long-term late Miocene regional climatic and environmental changes likely to have occurred on the northeastern TP from 12.1 to 5.2 Ma. We investigated Sr-related proxies in two typical paleosol profiles to constrain Sr mobility in paleosol weathering, and, thus, to further prompt the interpretation of Sr-related proxies along the whole section. We would suggest that carbonate-derived Sr concentrations and Sr/Ca ratios are suitable proxies for tracing regional climate change associated with weathering and pedogenesis; together, they exhibit weakened chemical weathering intensity and pedogenesis at ~ 8.6 Ma. The concomitant appearance of immature sediments through poor sedimentary sorting revealed by silicate-derived Rb/Sr, 87 Sr/ 86 Sr and Eu anomaly (Eu/Eu*) alongside a sharp increase in sedimentation rates noted at this time suggests that it was indeed tectonic uplift that principally controlled the dramatic climatic and environmental changes. This multi-proxy record of concomitant tectonic uplift and climate change in the Linxia Basin provides direct geological evidence for uplift driven climate change in the northeastern TP region. [ABSTRACT FROM AUTHOR]

The relative contribution of the westerlies and the Asian monsoon has played a critical role in regulating the evolution of the Cenozoic Asian interior environment in response to regional tectonic uplift and global climate change. Here, we reconstruct a long-term record of atmospheric moisture oxygen isotopes in the Asian interior using the oxygen isotopic composition of authigenic carbonates in terrestrial sediments from the Xining Basin on the northeastern Tibetan Plateau spanning the last 52 Myrs. On the VPDB scale, the average carbonate δ18O is characterised by a long-term decrease from −1.5‰ at ca. 43 Ma to −7.5‰ at 33 Ma and smaller variations from −7‰ to −8.5‰ after 33 Ma, with the exception of one period that contains samples with higher δ18O values at −6‰ at 17–14 Ma. At the same time, there is a corresponding long-term rise in average carbon isotope δ13C values from −9.5‰ at ca. 43 Ma to −3.5‰ at 33 Ma, followed by a less variable but similar variation in δ18O values after 33 Ma. The oxygen and carbonate isotopic compositions are negatively correlated before 33 Ma and positively after, suggesting a transition at ∼33 Ma in the context of atmospheric circulation coupled with regional aridity. The δ18O record can be explained by a simple binary mixing model of the atmospheric moisture between the recycling moisture with a positive δ18O value in the westerlies-dominated region and the monsoon rainfall or related moisture with a negative δ18O value from the Indo-Pacific Ocean. In that case, the first-order carbonate δ18O decrease from ca. 43 Ma to 33 Ma was primarily controlled by the retreat of the Para-Tethys Sea, which induced a remarkable decline in westerly rainfall relative to the monsoon. After ∼33 Ma, the contribution from the westerlies could be constant and the lower limits of the carbonate δ18O values are modelled by episodic increases in monsoon rainfall corresponding to enhanced Asian monsoon periods at 26–24 Ma, 17–14 Ma, and 9–8 Ma induced by the tectonic uplift of the Tibetan Plateau and the global climate. Our study, also, suggests that the Oligocene was a transitional stage of moisture sources from the dominance of Eocene westerlies to the Miocene-Quaternary monsoon in continental Asian environments. • Carbonate stable oxygen and carbon isotopic records since 52 Ma in the Xining Basin. • Correlation between carbonate oxygen and carbon isotopes has changed since 33 Ma. • Change in westerly and monsoon moisture amount regulates moisture oxygen isotope. • Decrease in carbonate δ18O before 33 Ma is induced by a decline in westerly rainfall. • Episodic increases in monsoon rainfall occur at 26–24 Ma, 17–14 Ma, and 9–8 Ma. [ABSTRACT FROM AUTHOR]

We present a simple and effective approach for posterior uncertainty quantification in deep operator networks (DeepONets); an emerging paradigm for supervised learning in function spaces. We adopt a frequentist approach based on randomized prior ensembles, and put forth an efficient vectorized implementation for fast parallel inference on accelerated hardware. Through a collection of representative examples in computational mechanics and climate modeling, we show that the merits of the proposed approach are fourfold. (1) It can provide more robust and accurate predictions when compared against deterministic DeepONets. (2) It shows great capability in providing reliable uncertainty estimates on scarce data sets with multi-scale function pairs. (3) It can effectively detect out-of-distribution and adversarial examples. (4) It can seamlessly quantify uncertainty due to model bias, as well as noise corruption in the data. Finally, we provide an optimized JAX library called UQDeepONet that can accommodate large model architectures, large ensemble sizes, as well as large data sets with excellent parallel performance on accelerated hardware, thereby enabling uncertainty quantification for DeepONets in realistic large-scale applications. All code and data accompanying this manuscript will be made available at https://github.com/PredictiveIntelligenceLab/UQDeepONet. [ABSTRACT FROM AUTHOR]

This study focuses on the concentration of major and trace elements in the diluted acetic acid-soluble fraction of SG-1 core lacustrine sediments from the western Qaidam Basin (Tibetan Plateau) in order to explore the potential of applying bulk carbonate analysis to tracing paleolake evolution and climate change. The SG-1 core sediments are considered highly suited to the exploration of the paleoenvironmental significance of bulk carbonate geochemistry, because most carbonates in the core are authigenic in origin. Based on a principal component analysis of the elemental composition of diluted acetic acid leachate, four major components with distinct characteristics have been extracted, accounting for ~ 80% of the total variance. The first and most important component is associated with a high positive loading of Mn, P, Y, Sc and rare earth elements (REE); the second component is characterized by a high positive loading of Ca, Sr, and U; the third component displays a high negative loading of Mg, Li, and B; and the fourth component is associated with a relatively high positive loading of Fe, V and Cr. After considering the geochemical behavior of these element assemblies during acid leaching, we have concluded that these four components contain information indicative of watershed climate conditions, carbonate precipitation, lake water salinity and iron oxide content, respectively. Reconstructions of watershed climate change and paleolake evolution using the component scores are comparable to those reconstructed from other independent proxy records, indicating a long-term trend of lake shrinkage and climatic drying since ~ 2.7 Ma with abrupt drying events at ~ 2.5 Ma, ~ 1.8 Ma, ~ 1.2 Ma and ~ 0.6 Ma. Our results suggest that lake carbonates bear more information about watershed climate and lake evolution than expected, and that occurrences of some elements, in particular trace elements, in the diluted acetic acid leachate are not solely and necessarily linked to carbonate minerals. [ABSTRACT FROM AUTHOR]

Using co-variations of Sr/Ca and Mg/Ca, we examined the carbonate compositions of various bedrocks (silicate and carbonate rocks) and sediments (eolian and fluvial sediments, sand, and topsoil) found in the NE Tibetan Plateau (TP) region. A combined carbonate composition dataset based on our results and other reported data shows that bedrock carbonate composition on the NE TP displays a much broader range of Sr/Ca and Mg/Ca ratios than restricted source carbonate endmembers reported upon in previous studies. This has clear implications for modern weathering studies in addition to paleo-reconstructions in this tectonically active and climatically variable area during the Late Cenozoic. Bedrock carbonate compositions are characterized by disseminated carbonates with higher Sr/Ca and Mg/Ca ratios, and sedimentary carbonates (mostly marine) with lower Sr/Ca, but variable Mg/Ca, ratios. The mostly authigenic carbonates found in sediments show similar trends, with a gradient ~ 0.97–1.00 in a plot of log (Sr/Ca) versus log (Mg/Ca), suggesting that ‘calcite precipitation’ processes – i.e. the sources of the dissolved cations in the water – control their chemistry. Based on observations and modeling, we conclude that the mixing of authigenic and bedrock carbonate endmembers, plus the incongruent dissolution of bedrock carbonates, accounts for the bulk carbonate composition of sediments ( e.g. loess, sand and topsoil). A comparison of bedrock and sedimentary carbonate composition with reported fluvial water data in the NE TP suggests that weathering of carbonates in terrigenous sediments, rather than in bedrock, is mostly responsible for the changes in fluvial Sr, Mg and Ca compositions. Our study suggests that interactions between carbonates and water occur widely during the exposure, transport and deposition of sediments, significantly modifying regional carbonate compositions and fluvial geochemistry. [ABSTRACT FROM AUTHOR]

The carbon pool stored in soil carbonate is comparable to the soil organic carbon. Therefore, secondary calcite precipitation in supersaturated catchment could be an important, yet poorly constrained, carbon sink within the modern global carbon cycle. The chemical analysis of some dissolved species transported by rivers, such as elevated Sr/Ca and Mg/Ca ratios but also heavy stable Ca isotopic compositions, witness the formation of secondary calcite in rivers draining arid regions. However, in areas affected by active tectonics and rapid physical erosion, co-variations in the fluvial Sr/Ca and Mg/Ca ratios could also be related to incongruent carbonate weathering processes. Here, we present a model to assess the roles played by incongruent carbonate dissolution and secondary calcite precipitation in modern weathering processes. We tested and applied the model to rivers draining the Himalayan-Tibetan region. The results suggest that regional aridity in the drainage basin promotes carbon sequestration as secondary carbonate but that for a given runoff, incongruent dissolution of carbonate possibly related to rapid physical erosion amplifies such sequestration. The isotopic compositions (C/C and O/O) of detrital carbonate transported by the main rivers in South and South-East Tibet imply that around 1% of the suspended material transported by those rivers corresponds to secondary carbonate and can represent between 5% and 15% of the alkalinity flux. Most of these alkalinity transported as particulate material is, nevertheless related to the weathering of carbonate lithologies and is also subjected to dissolution prior its final storage in sedimentary basins. However, on glacial-interglacial timescale this will amplify the significant role of mountain weathering on climatic variations. [ABSTRACT FROM AUTHOR]

• Clay-sized geochemistry reveals the Qaidam Basin (QB) Paleogene weathering history. • QB Paleogene silicate weathering intensity presents a continuously decreasing trend. • Global cooling was the main regulator of Paleogene chemical weathering processes. • Clay-sized geochemical indices aptly reveal weathering histories in coarse sediment. An integrated multiproxy dataset involving both mineralogical and geochemical investigations of the northern Tibetan Plateau helps in assessing regional weathering processes linked to topographic evolution and environmental change. However, changes in landscape and drainage reorganizations caused by active tectonics and remarkable climate change during the Cenozoic characterize the basins in and around the Tibetan Plateau by frequent facies changes and coarse lithologies, which largely limit the reliability of bulk geochemical indicators for revealing the regional weathering history. Here, we present detailed geochemical investigations of clay-sized sediments collected from the Hongliugou section (54–26 Ma) in the northern Qaidam Basin to reconstruct high-resolution chemical weathering records of the northern Tibetan Plateau. To prevent chlorite bias when calculating the chemical index of alteration (CIA) in the clay-sized sediments, we propose a modified CIA formula (CIA Mg+), in which Mg is added as a soluble cation that can be removed during weathering, similar to Na, K and Ca; thus, CIA Mg+ = Al 2 O 3 /(Al 2 O 3 + Na 2 O + K 2 O + CaO* + MgO) × 100. The CIA Mg+ and illite chemistry indices are generally the highest values in the early Eocene Climate Optimum (∼52–49.5 Ma) and a long-term decreasing trend is present from ∼ 49.5–26 Ma; the Mg/Al ratios of the clay-sized sediments and hydrochloric acid leachates are the lowest during the EECO and present a long-term increasing trend in the following 49.5–26 Ma, thus collectively indicating a continuous decrease in the regional chemical weathering intensity. The weakening weathering process during the Paleogene is mainly attributed to the decreasing global temperature and decline in precipitation caused by global cooling. Our study suggests that the proposed geochemical index based on clay-sized sediments can serve as an efficient proxy for regional chemical weathering reconstruction, even in thick sedimentary sequences with frequently changing facies and lithology. [ABSTRACT FROM AUTHOR]

Uranium (U) provides especially useful information for reconstructing paleoredox conditions due to its unique geochemical properties and behavior in supergene environments. Its proxy potential under suboxic –oxic conditions associated with salinization of surface water in closed hydrologic systems, however, has not been adequately explored. This study examined the abundance and distribution of U in a sedimentary sequence of calcareous lacustrine clastics and salt layers from a high quality (938.5 m-long) core drilled in the western Qaidam Basin, NE Tibetan Plateau. This study examined U concentrations in calcareous clastic sediments (including carbonates, acid insoluble fractions, as well as the amounts of iron and manganese oxides/oxyhydroxides) and salt layers. In the calcareous clastic sediments, variations in U concentrations within the acid insoluble fraction follow the fluctuations of reconstructed lake levels based on lithologic investigations, providing a tool for tracing redox conditions in paleolake bottom water. Correlations between the variations in carbonate content with U and Sr concentrations in the carbonate fractions demonstrate that the types and abundance of carbonate minerals control the U distribution in carbonates. In the salt layers, U and Al concentrations correlate closely, implying that both derived mainly from the detrital fraction in the salt layers. However, enrichments of U and Mg are systematically higher in salt minerals formed in more concentrated brine and lower in those formed in less concentrated brine. These results indicate that during the process of carbonate precipitation, carbonate might effectively remove U from lake water. During the subsequent stage of salt mineral precipitation, U behavior is conservative, and U resides for a long period in dissolved forms within the saline water, giving rise to enhanced U enrichment in the more concentrated brines and the associated precipitated salt minerals. Our study suggests, however, that U-related redox proxies should be interpreted with caution in suboxic–oxic environments during the long-term paleolake evolution. [ABSTRACT FROM AUTHOR]

Hydrothermal systems, including hot springs and hydrothermal calcite, are common features of orogenic belts. The hot springs and hydrothermal calcite in the Himalayas are characterized by radiogenic Sr related to metamorphic processes. Such metamorphism-driven processes have contributed significant amounts of radiogenic Sr to rivers and groundwater, which has affected the evolution of global seawater 87Sr/86Sr during the Cenozoic. However, whether such hydrothermal systems with highly radiogenic Sr occur in other continental collisional belts with intense metamorphism remains unknown, which hinders a better understanding of regional and global Sr cycles. Compiled 87Sr/86Sr ratios in surface water around the Tibetan Plateau show that the Qilian-North Qaidam region displays a higher 87Sr/86Sr ratio than other regions, except for the Himalayas. Here, we report 87Sr/86Sr ratios of a hydrothermal system on the northern margin of the early Paleozoic North Qaidam ultrahigh-pressure metamorphic belt, NE Tibetan Plateau. The high 87Sr/86Sr ratios (0.757–0.734) of the hot spring water and the acetic acid leachates of the surrounding rocks (gneiss and schist) with other isotopic tracers (e.g., oxygen, hydrogen, lithium, and boron isotopes) indicate that 1) Sr was exchanged during metamorphism between carbonate and silicate phases in crustal rocks and the high 87Sr/86Sr ratio of the hot spring water was acquired from a deep water-rock reaction process; and 2) hydrothermal systems around the Qilian-North Qaidam region operate like those in the Himalayas. Mass balance calculations indicate that the metamorphism-forced hydrothermal system plays a key role in delivering radiogenic Sr to rivers and lakes and yielding higher 87Sr/86Sr ratios in surface water around the Qilian Shan region than in the surrounding areas. The reactivated early Paleozoic Qilian orogenic belts with ultrahigh-pressure metamorphism caused by the India-Asia collision have significantly impacted the regional water 87Sr/86Sr ratio, suggesting that the reactivated old orogenic belts with intense metamorphic processes formed by continental subduction/collision can play a pivotal role in regulating past seawater 87Sr/86Sr evolution. [Display omitted] • Hot spring with a high 87Sr/86Sr of 0.757 was found in North Qaidam metamorphic belt. • Spring radiogenic Sr was formed during intense metamorphism and fluid-rock interaction. • Metamorphism-forced processes caused radiogenic Sr in surface water in Qilian Shan. • Hydrothermal systems in Qilian-North Qaidam region operate like those in Himalayas. • Reactivated orogen with intense metamorphism could affect regional or global Sr cycle. [ABSTRACT FROM AUTHOR]

Abstract: Phosphorus (P) provides an important biologically limiting nutrient in lake ecosystems, and its concentrations furnish significant information on lake nutrient status, climatic change, and landscape development within a drainage area. This study explores the potential of calcium-bound P and iron-bound P in calcareous lacustrine sediments to reveal variations of the paleolake nutrient status and its related climatic changes. Data come from the nearly 1000-m long core (SG-1) from the western Qaidam Basin (NE Tibetan Plateau), which has been well-dated by paleomagnetism to between 2.77 and 0.1 Ma. Calcium-bound P and iron-bound P make up the two most frequent phases of inorganic phosphorus pools in the calcareous sediment. This study compares the variations of calcium-bound P and iron-bound P with the independent proxy for biologic production proxy Total Organic Carbon (TOC) as well as a climatic proxy for lake level fluctuation from the borehole. Those results indicate that calcium-bound P responds sensitively to paleolake nutrients and climatic changes, while the iron-bound P responds to more complex factors, more specific, to the content of iron oxides. Variations of the calcium-bound P in the core SG-1 show a long-term, stepwise decrease, with shifts at ∼2.5 Ma, 1.8 Ma, 1.2 Ma, and 0.6 Ma, indicating a long-term stepwise decrease of the paleolake nutrient supply in the drainage. This suggests that the ecologic systems experienced a long-term deterioration, and the climate in central Asia became increasingly arid since after the late Pliocene. [Copyright &y& Elsevier]

Abstract: Manganese (Mn) in lake sediments reacts strongly to changes of redox conditions. This study analyzed Mn concentrations in oxides, carbonates, and bulk phases of the calcareous lacustrine sediments of a 938.5-m-long core (SG-1) taken from the western Qaidam Basin, well dated from 2.77Ma to 0.1Ma. Comparisons of extractions from diluted hydrochloric acid, acetic acid and citrate–bicarbonate–dithionite demonstrate that variations of Mn concentrations from acetic acid leaching (MnHOAc) are mostly responsible for Mn (II) fluctuations in the carbonate phase. Taking into account the relevant processes during weathering, transportation, deposition and post-deposition of Mn-bearing rocks, we conclude that Mn input from catchment weathering and paleolake redox condition provide the primary controls on variations in the Mn records of carbonate and oxide phases. We propose MnHOAc as a new sensitive indicator of paleolake redox evolution and catchment-scale climate change. The MnHOAc variations show a long-term upward decreasing trend, indicating a long-term decrease of Mn input from catchment weathering associated with increasing oxygen content in the paleolake bottom water. The great similarities of the MnHOAc record with other regional and global records suggest that paleolake redox changes and climatic drying in the Qaidam Basin may be largely related to global cooling. [Copyright &y& Elsevier]