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Microplastics (MPs) are pollutants of global concern, and bioaccumulation determines their biological effects. Although microorganisms form a large fraction of our ecosystem's biomass and are important in biogeochemical cycling, their accumulation of MPs has never been confirmed in natural waters because current tools for field biological samples can detect only MPs > 10 µm. Here, we show that stimulated Raman scattering microscopy (SRS) can image and quantify the bioaccumulation of small MPs (<10 µm) in protozoa. Our label-free method, which differentiates MPs by their SRS spectra, detects individual and mixtures of different MPs (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene, and poly(methyl methacrylate)) in protozoa. The ability of SRS to quantify cellular MP accumulation is similar to that of flow cytometry, a fluorescence-based method commonly used to determine cellular MP accumulation. Moreover, we discovered that protozoa in water samples from Yangtze River, Xianlin Wastewater Treatment Plant, Lake Taihu and the Pearl River Estuary accumulated MPs < 10 µm, but the proportion of MP-containing cells was low (â¼2-5%). Our findings suggest that small MPs could potentially enter the food chain and transfer to organisms at higher trophic levels, posing environmental and health risks that deserve closer scrutiny.
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Microplásticos , Poluentes Químicos da Água , Plásticos , Bioacumulação , Ecossistema , Microscopia Óptica não Linear , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodosRESUMO
Knowledge of the molecular composition and electronic structure of electrified solid-liquid interfaces is key to understanding elemental processes in heterogeneous reactions. Using X-ray absorption spectroscopy in the interface-sensitive electron yield mode (EY-XAS), first-principles electronic structure calculations, and multiscale simulations, we determined the chemical composition of the interfacial region of a polycrystalline platinum electrode in contact with aqueous sulfuric acid solution at potentials between the hydrogen and oxygen evolution reactions. We found that between 0.7 and 1.3 V vs Ag/AgCl the electrical double layer (EDL) region comprises adsorbed sulfate ions with hydrated hydronium ions in the next layer. No evidence was found for bisulfate or Pt-O/Pt-OH species, which have very distinctive spectral signatures. In addition to resolving the long-standing issue of the EDL structure, our work establishes interface- and element-sensitive EY-XAS as a powerful spectroscopic tool for studying condensed phase, buried solid-liquid interfaces relevant to various electrochemical processes and devices.
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The electronic structure at the Ni, Mn and O sites and their evolution upon the electrochemical lithiation of Li(1-x)Ni0.5Mn1.5O4 (LNMO) in a lithium ion battery has been explored using comprehensive X-ray absorption near edge structure spectroscopy (XANES) at the Ni and Mn L3,2- and O K-edges, with both surface-sensitive and bulk-sensitive detection. It has confirmed that Ni reduction from Ni(4+) to Ni(2+) plays the leading role in charge compensation when the lithiation voltage is above 4.5 V. Our study also unveils the participation of oxygen in the charge compensation. Furthermore, the enhanced difference in the electronic structures of the surface and bulk in electrochemically cycled samples, and the different surface electronic structures of the fully discharged LNMO and the pristine one, highlight the importance of electrochemical activation. These findings are critical for a better understanding of the electrochemical reaction of LNMO and the influence of structural modifications to the surface region upon its performance, and will assist further efforts to improve this high-voltage cathode material for its application in lithium ion batteries.
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Single-crystalline LiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered as one of the most promising cathode materials. It addresses the pulverization issue present in its polycrystalline counterpart by eliminating intergranular cracks. However, synthesis of high-performance single-crystalline NCM is still a challenge owing to the lower structure stability of NCM811 at high calcination temperatures (≥900 °C), which is often required to grow single crystals. Herein, we report a synthesis process for microsized single-crystalline NCM811 particles with exposed (010) facets on their lateral sides [named as SC-NCM(010)], which includes the preparation of a well-dispersed microblock-like Ni0.8Co0.1Mn0.1(OH)2 precursor through coprecipitation assisted with addition of PVP and Na2SiO3 and subsequent lithiation of the precursor at 800 °C. The SC-NCM(010) cathode exhibits an excellent capacity retention rate (91.6% after 200 cycles at 1 C, 4.3 V) and a high rate capability (152.2 mAh/g at 20 C, 4.4 V), much superior to those of polycrystalline NCM811 cathodes. However, despite the removal of interparticle boundaries, when cycled between 2.8 and 4.5 V, the SC-NCM(010) cathode still suffers from structural changes including lattice gliding and intragranular cracking. These structural changes are correlated with the interior structural inhomogeneity, which is evidenced by the coexistence of H2 and H3 phases in the fully deintercalated state.
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Rolling element bearings typically operate with fluctuating speed, leading to nonstationary vibrations. Moreover, bearings vibration signals are frequently hidden by strong distributions, making it difficult to detect clear bearing fault characteristics for diagnosis. Under this circumstance, the key issue is effectively extracting the transient features from the background interference and highlighting the time-varying fault characteristics. To address this issue, a sparse and low-rank decomposition approach is proposed. In this study, the sparsity of the variable defective characteristics and low-rank of background interference is revealed and exploited for bearing fault detection. Firstly, the time-frequency representation (TFR) of the envelope of measured signal is generated by the time-frequency transform. Then, a sparse and low-rank decomposition model is established based on robust principal component analysis (RPCA) to denoise the measured time-frequency representation and gain the sparse component. Finally, a time-frequency reassignment strategy is utilized to further enhance the capability of detecting the faulty characteristics in the decomposed sparse TFR. The synthetic and actual signals are evaluated to illustrate the reliability and efficacy of the proposed technique. The superiority is also validated by comparisons with STFT, synchrosqueezing transform (SST), ridge extraction method, and scaling-basis chirplet transform (SBCT).
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Discharging lithium-ion batteries to zero-charge state is one of the most reliable ways to avoid the thermal runaway during their transportation and storage. However, the zero-charge state causes the degradation or even complete failure of lithium-ion batteries. Specialized solutions are required to endow lithium-ion batteries with improved zero-charge storage performance, namely, the ability to tolerate zero-charge state for a long time without unacceptable capacity loss. Here, we report that a Li5FeO4 cathode additive can improve the zero-charge storage performance of LiCoO2/mesocarbon microbead (MCMB) batteries. The irreversible charge capacity of the Li5FeO4 additive results in the downregulation of anode and cathode potentials when the battery is at zero-charge state. More importantly, the Li5FeO4 additive offers a small discharge plateau below 2.9 V versus Li/Li+, which can hold the anode potential at zero-charge battery state (APZBS) in a potential range of 2.4â¼2.5 V versus Li/Li+ during storage for 10 days. Such a precise control on APZBS not only suppresses the decomposition of the solid electrolyte interface film on the MCMB anode and inhibits the dissolution of the copper current collector occurring at high potentials but also avoids the excessive decrease of the cathode potential at the zero-charge battery state and consequently protects the LiCoO2 cathode from overlithiation occurring at low potentials. As a result, the Li5FeO4 additive with a charge capacity percentage of 23% in the cathode increases the capacity recovery ratio of the LiCoO2/MCMB battery from 37.6 to 95.5% after being stored at the zero-charge state for 10 days.
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The energy supply of food available at stopover sites plays an important role in the life cycle of migratory birds. The Yellow River National Wetland in Baotou, China, is an essential migration station and a source of energy for migratory birds as it is located at an important intersection between East Asian/Australian and Central Asian flyways. From February to may 2020, we measured diet composition and energy content of whooper swans (Cygnus cygnus) by fecal micro-tissue analysis to understand their use of the stopover site and inform conservation. The following results were obtained: (1) whooper swans mainly fed on nine species of plants belonging to four families, including corn (Zea mays), reeds (Phragmites australis), and Suaeda (Suaeda glauca), which is related to the availability of local crops and abundance of plants. (2) The energy provided by crops to whooper swans was significantly higher than that of the most abundant plants in wetlands. Zea mays was the most consumed crop, and other abundant wetland plants played complementary roles. (3) The daily energy intake of whooper swans was 1393.11 kJ, which was considerably higher than their daily energy consumption. This suggested that the wetlands and the surrounding farmlands provide energy for the whooper swans to continue their migration. In order to protect migratory whooper swans, protection of important refuelling areas such as our study site should be implemented to provide sufficient energy supplies for continuing migration.
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Anseriformes , AnimaisRESUMO
In nature, live fish has various deformable fins which are capable to promote the swimming speed, efficiency, stability, and thrust generation. However, this feature is rarely possessed by current man-made biomimetic robotic fishes. In this paper, a novel deformable caudal fin platform is proposed to improve thrust generation of biomimetic robotic fish. First, the design of the deformable caudal fin is given, which includes a servo motor, a gear-based transmission mechanism, fin bones, and silica membrane. Second, an improved Central Pattern Generator (CPG) model was developed to coordinately control the flapping of the tail and the deformation of the caudal fin. More specifically, three deformation patterns, i.e., conventional nondeformable mode, sinusoidal-based mode, instant mode, of the caudal fin are investigated. Third, extensive experiments are conducted to explore the effects of deformation of the caudal fin on the thrust generation of the biomimetic robotic fish. It was found that the instant mode of the caudal fin has the largest thrust, which sees a 27.5% improvement compared to the conventional nondeformable mode, followed by the sinusoidal-based mode, which also sees an 18.2% improvement. This work provides a novel way to design and control the deformation of the caudal fin, which sheds light on the development of high-performance biomimetic robotic fish.
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Tin disulfide (SnS2) has been extensively researched as a promising sensing material due to its large electronegativity, suitable band gap, earth abundance, and nontoxicity. However, the poor conductivity and slow response/recovery speed at room temperature greatly hinder its application in high-performance practical gas sensors. Herein, to promote the study of SnS2-based gas sensors, a hierarchical SnS2/TiO2 heterostructure was synthesized and used as a sensing material to detect NO2 with the help of light illumination. Through the synergistic effect of the SnS2/TiO2 heterostructure and 525 nm light activation, the NO2 sensor based on the SnS2/TiO2 heterostructure exhibited a high response factor of 526% toward 1 ppm NO2 and a short response/recovery time of 43/102 s at room temperature due to the enhanced charge transfer and increased adsorption sites, which was superior to the vast majority of other NO2 sensors. An obvious decrease in the surface-adsorbed oxygen content based on the X-ray photoelectron spectroscopy measurement further confirmed that light illumination was helpful to clear the surface of SnS2/TiO2 and thus increased active sites for NO2 sensing. In addition, a flexible SnS2/TiO2 sensor was also fabricated to confirm its potential application in portable and wearable devices.
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Nanostructured amorphous and anatase TiO2 are both considered as high rate Li-insertion/extraction electrode materials. To clarify which phase is more desirable for lithium ion batteries with both high power and high density, we compare the electrochemical properties of anatase and amorphous TiO2 by using anodic TiO2 nanotube arrays (ATNTAs) as electrodes. With the same morphological features, the rate capacity of nanostructured amorphous TiO2 is higher than that of nanostructured anatase TiO2 due to the higher Li-diffusion coefficient of amorphous TiO2 as proved by the electrochemical impedance spectra of an amorphous and an anatase ATNTA electrode. The electrochemical impedance spectra also prove that the electronic conductivity of amorphous TiO2 is lower than that of anatase TiO2. These results are helpful in the structural and componential design of all TiO2 mesoporous structures as anode material in lithium ion batteries. Moreover, all the advantages of the amorphous ATNTA electrode including high rate capacity, desirable cycling performance and the simplicity of its fabrication process indicate that amorphous ATNTA is potentially useful as the anode for lithium ion batteries with both high power and high energy density.
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In order to alleviate the inferior cycle stability of the sulfur cathode, a self-assembled SnO2-doped manganese silicate nanobubble (SMN) is designed as a sulfur/polysulfide host to immobilize the intermediate Li2S x, and nitrogen-doped carbon (N-C) is coated on SMN (SMN@C). The exquisite N-C conductive network not only provides sufficient free space for the volume expansion during the phase transition of solid sulfur into lithium sulfide but also reduces Rct of SMN. During cycling, the soluble polysulfide could be fastened by the silicate with an oxygen-rich functional group and heteronitrogen atoms through chemical bonding, enabling a confined shuttle effect. The synergistic effect between N-C and SMN could also effectively facilitate the interconversion between lithium polysulfides and Li2S, reducing the potential barrier and accelerating the redox kinetics. With an areal sulfur loading of 2 mg/cm2, the S-SMN@C cathodes demonstrate a high initial capacity of 1204 mA·h/g at 0.1 C, and an outstanding cycle stability with a capacity fading rate of 0.0277%, ranging from the 2nd cycle to the 1000th cycle at 2 C.
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Spinel LiNi0.5Mn1.5O4 (LNMO) has been considered as one of the most promising candidate cathode materials for power lithium-ion batteries. However, its cycle performance suffers from the increasing impedance of the LNMO-cathode/electrolyte interface (LNMO-CEI) layer caused by parasitic reactions on the electrode surface at high operating potentials. To address the capacity degradation upon cycling, we present a feasible way to realize electrode modification by electrophoretically deposited graphene ultrathin films on the exterior surface of the LNMO cathodes without decreasing the electrode density. A p-phenylene diamine reduced graphene oxide (pPD-rGO) film with an area density of 20 µg/cm2 not only increases the capacity retention rate of the 1000th cycle at 4.2-5.2 V from 71.7 to 81.7% but also boosts the specific capacity from 110.6 to 122.4 mAh/g. X-ray photoelectron spectroscopy (XPS) spectra reveal that the pPD-rGO film with Lewis-base nature increases the content of LiF and reduces the number of RCFx groups in the cycled electrode, indicating the consumption of high-potential-generated F radicals by the pPD-rGO film. Such consumption favors the formation of a robust interphase between the pPD-rGO film and the electrolyte, which could hinder the sustained production of F radicals, consequently stabilize the LNMO-CEI layer, and improve the cycle performance. An electrophoretically deposited Lewis-acid GO film of 20 µg/cm2 reduces the specific capacity and fails to work as the pPD-rGO film. The chemical process for the formation of interphase on the GO film is similar to that on the bare LNMO electrode.
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The unique features of SnS2 make it a sensitive material ideal for preparing high-performance nitrogen dioxide (NO2) gas sensors. However, sensors based on pristine tin disulfide (SnS2) fail to work at room temperature (RT) owing to their poor intrinsic conductivity and weak adsorptivity toward the target gas, thereby impeding their wide application. Herein, an ultrasensitive and fully recoverable room-temperature NO2 gas sensor based on SnS2/SnS p-n heterojunctions with an accumulation layer was fabricated. The amounts of SnS2/SnS heterojunctions can be effectively controlled by tuning the ratios of tin and sulfur precursors in the easy one-step solvothermal synthesis. Compared with pristine SnS2, the conductivity of SnS2/SnS heterostructures improved considerably. Such improvement was caused by the electron transfer from p-type SnS to n-type SnS2 because the Fermi level of SnS was higher than that of SnS2. The sensing response of optimized SnS2/SnS toward 4 ppm NO2 was 660% at room temperature, which was higher than most reported sensitivity values of other two-dimensional (2D) materials at room temperature. The superior sensing response of SnS2/SnS heterostructures was attributed to the enhanced electron transport and the increased adsorption sites caused by the SnS2/SnS p-n heterojunctions. Moreover, the SnS2/SnS sensor showed good selectivity and long-term stability. These achievements of SnS2/SnS heterostructured sensors make them highly desirable for practical applications.
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After the construction of the Xiangjiaba Dam, the hydrodynamic conditions, nutrient distributions, and transport conditions of the Jinsha River were changed. Here, the nutrient distribution characteristics and retention effects of Xiangjiaba Reservoir were investigated according to the results of water quality monitoring from 2015 to 2016. Spatial and temporal variations in TN, TP, SiO32-Si, and other nutrients, and retention flux and retention rate were analyzed. The results showed that the nutrient mass concentration of TN, TP, and SiO32--Si was 0.905 mg·L-1, 0.034 mg·L-1, and 7.98 mg·L-1, respectively. The distribution of TN was affected by point sources and the concentration of TN was large in urban areas. This distribution of TP was mainly granular and the mass concentrations decreased along the river path. The mass concentration of SiO32--Si did not significantly vary over time and space. Furthermore, Xiangjiaba Reservoir had a persistent effect on nutrient salts; the average annual retention of TN, TP, and SiO32--Si was 2.30×104 t·a-1, 0.146×104 t·a-1, and -2.4×104 t·a-1, respectively. During different seasons, the retention of TN and SiO32--Si varied between positive or negative; however, TP appeared to be consistent. The average monthly retention efficiency of TN, TP, and SiO32--Si was 17.5%, 32.8%, and -2.14%, respectively. Overall, retention efficiencies were higher during the dry season than that wet season, and phosphorus retention was most pronounced. The retention of TN in the reservoir may be related to denitrification and the input of external load; the flux of SiO32--Si was mainly affected by runoff; and the particle morphology of phosphorus, as well as reservoir period, were the main factors affecting TP retention. There were no clear correlations between nutrient retention and the mass concentrations of TN and SiO32--Si, but the nutrient retention effect of Xiangjiaba Reservoir reduced TP concentrations along the river path and increased TP concentration with vertical depth.
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Without the hypothesis of atmospheric parameters and auxiliary equipment, it is proven the slope method is capable of deriving extinction coefficients profiles and atmosphere optical depth through the analysis of the atmospheric environment detecting airborne lidar (AEDAL) data collected during November 7 to 11, 2005. The spatial and temporal variations of the planet boundary layer (PBL), aerosol optical depth (AOD) of the PBL and aerosol distribution along flight lines are exhibited from the AEDAL inversion results. Firstly, the sinking of aerosol was found in Yellow Sea area, moreover, the PBL altitude also dropped while the multi-layer aerosol presented after a cold front passage; secondly, the AOD of the PBL is the highest over Qingdao city, the lowest over foothill area and in between them over sea area, Meanwhile, it is relatively stable over sea area but slightly increases nearby upslope. The AOD values of the PBL were determined to be 0.15-0.35 in clear day and 0.3-0.45 in foggy day over the area from Qingdao to Bohai, but they are higher and reach around 0.55 in Yellow Sea area. It is evidenced that the aerosol in the PBL mainly comes from city and also is contributed by salt sea over Qingdao area, and ridge and surface wind play an important role in the aerosol transport while the monsoon affects the aerosol distribution.
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Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Aerossóis/química , Calibragem , China , Oceanos e MaresRESUMO
OBJECTIVE: To develop an HPLC method for the determination of eleutheroside B in As1 (the extract fraction from Acanthopanax senticosus, which has a good effect of antifatigue). METHOD: The antifatigue effect of Asl was evaluated by mice burden swimming testing. One compound was isolated by silica gel, Sephadex LH-20 column chromatography and preparative high performance liquid chromatography. The structure was identified by physicochemical properties and spectral evidences. Eleutheroside B in Asl was determined by HPLC. Chromatographic conditions included Diamonsil C18 column (4.6 mm x 250 mm, 5 microm) and the mobile phase consisting of a mixture of acetonitrile-water-ethanoic acid (10: 90: 0.01). The UV detection wavelength was set at 344 nm. RESULT: As1 showed an excellent antifatigue activity; One compound was isolated from As1 and its structure was identified as Eleutheroside B; The calibration cure was linear in the range of 0.104-20.8 microg (r = 0.9999), the average recovery was 97.68%, RSD 1.4% (n=6). CONCLUSION: This HPLC method is simple,accurate and reliable.
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Eleutherococcus/química , Fadiga/tratamento farmacológico , Glucosídeos/análise , Fenilpropionatos/análise , Animais , Cromatografia Líquida de Alta Pressão , Medicamentos de Ervas Chinesas/química , Medicamentos de Ervas Chinesas/isolamento & purificação , Fadiga/fisiopatologia , Humanos , Masculino , Camundongos , NataçãoRESUMO
The Ni oxidation state in Li1-xNi0.5Mn1.5O4 (LNMO) within a composite electrode mapped by soft X-ray scanning transmission X-ray microscopy (STXM) has shown unexpected distinct variations in phase separation among and within individual battery particles, which has been experimentally correlated to both their morphology and interface structure for the first time. The obtained new insights will assist the further development of long-life high voltage LNMO batteries.
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We investigated the X-ray absorption spectroscopy (XAS) fingerprint of EMImTFSI ionic liquid (IL) and its fragmentation products created by X-ray irradiation. To accomplish this, we used an open geometry where an IL droplet is directly exposed in the vacuum chamber and an enclosed geometry where the IL is confined in a cell covered by an X-ray transparent membrane. In the open geometry, the XAS signature was stable and consistent with experimental and theoretical spectra reported in the literature. In contrast, when the IL is enclosed, its XAS evolves continuously under X-ray illumination due to the accumulation of volatile fragmentation products inside the closed cell, while they evaporate in the open geometry. The changes in the XAS from the core levels of relevant elements (C, N, S, F) together with density functional theory calculations allowed us to identify the chemical nature of the fragment products and the chemical bonds most vulnerable to rupture under soft X-ray irradiation.
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Ordered mesoporous materials show great importance in energy, environmental, and chemical engineering. The diffusion of guest species in mesoporous networks plays an important role in these applications, especially for energy storage, such as supercapacitors based on ordered mesoporous carbons (OMCs). The ion diffusion behavior in two different 2-D hexagonal OMCs was investigated by using cyclic voltametry and electrochemical impedance spectroscopy. In addition, transmission electron microscopy, small-angle X-ray diffraction, and nitrogen cryosorption methods were used to study the pore structure variations of these two OMCs. It was found that, for the OMC with defective pore channels (termed as pore packing defects), the gravimetric capacitance was greatly decayed when the voltage scan rate was increased. The experimental results suggest that, for the ion diffusion in 2-D hexagonal OMCs with similar mesopore size distribution, the pore packing defect is a dominant dynamic factor.
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Molybdenum disulfide with a layered structure and high theoretical capacity is attracting extensive attention for high-performance lithium-ion batteries. In this study, a simple and scalable method by freeze-drying of (NH4)2MoS4 and dopamine mixed solutions along with subsequent calcination is developed to realize the self-assembly of hierarchical MoS2/carbon composite nanosheets via the effect of dopamine-induced morphology transformation, in which ultrasmall few-layer MoS2 nanosheets were homogeneously embedded into a N-doped carbon framework (denoted as MoS2@N-CF). The embedded ultrasmall MoS2 nanosheets (â¼5 nm in length) in the composites consist of less than five layers with an expanded interlayer spacing of the (002) plane. When tested as anode materials for rechargeable Li-ion batteries, the obtained MoS2@N-CF nanosheets exhibit outstanding electrochemical performance in terms of high specific capacity (839.2 mAh g-1 at 1 A g-1), high initial Coulombic efficiency (85.2%), and superior rate performance (702.1 mAh g-1 at 4 A g-1). Such intriguing electrochemical performance was attributed to the synergistic effect of uniform dispersion of few-layer MoS2 into the carbon framework, expanded interlayer spacing, and enhanced electronic conductivity in the unique hierarchical architecture. This work provides a simple and effective strategy for the uniform integration of MoS2 with carbonaceous materials to significantly boost their electrochemical performance.