Search

Abstract The development of high-performance noble metal-free electrochemical catalyst for effective water splitting is a key factor to achieve low-cost and sustainable renewable energy production. Herein, for the first time, highly dispersed cobalt nanoparticles decorated uniform nitrogen doped graphene (CoNPs-N-GR) was design synthesized. In the preparation procedure, graphene oxide (GO) was employed as supporting material, polydopamine as nitrogen source, location reagent as well as connecting agent for uploading cobalt metal ion, and then cobalt metal-organic frameworks (ZIF-67) in situ grew on GO. During the calcining process, GO reduction, nitrogen doping and cobalt nanoparticles forming were finished in one step. Scanning electron microscopy (SEM) images, transmission electron microscopy (TEM), energy-dispersive X-ray (EDS), X-ray photoelectron spectrometer (XPS) and X-ray diffraction (XRD) were applied to characterize the as-prepared CoNPs-N-GR. Moreover, owing to the presence of dopamine, high dispersed cobalt nanoparticles were obtained, leading to high electrocatalytic activity of CoNPs-N-GR for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. HER reaches 10 mA cm−2 at the over-potential of 0.453 V with a Tafel slope of 67 mV dec−1. OER reaches 10 mA cm−2 at the over-potential of 1.63 V with a Tafel slope of 65 mV dec−1. And the as-prepared CoNPs-N-GR shows excellent durability in the long-term stability for HER and OER. Graphical abstract Image 1 Highlights • Highly dispersed CoNPs decorated uniform nitrogen doped graphene was prepared. • Polydopamine as nitrogen source, location reagent as well as connecting agent. • In situ grow of cobalt metal-organic frameworks (ZIF-67) as cobalt precursor. • High electrocatalytic performance for both HER and OER in alkaline media. [ABSTRACT FROM AUTHOR]

The phenomenon has raised the concerns about the safety of an extended manned mission into deep space due to the high potential for exposure to high-LET radiation during space missions. Heavy ions such as 56 Fe are main radiation sources in deep space, which could pose a significant hazard to space flight crews during and after missions. Since the testis is a radiosensitive organ, which may be susceptible to space radiation-induced changes. In this study, we investigated the effect and potential mechanisms of 56 Fe irradiation on mouse testis. Pathological characteristics were measured following whole-body irradiation with 0.5 and 1 Gy 56 Fe irradiation. Flow cytometry and terminal dUTP nick end-labeling (TUNEL) were performed to detect apoptotic cells. Western blot was applied to identify potential biomarkers. Immunofluorescence was used to investigate protein localization. We found that pathologic changes and apoptosis cells were significantly higher in 1 Gy group than those in 0 Gy groups. In addition, protein expression and localization studies confirmed Nrf2 was involved in this acute injury. Nrf2 and its target genes HO-1 and NQO1 were up-regulated in the irradiated testis in a dose-dependent manner. Nrf2 may be useful molecular markers in radiation-induced cellular responses and is important for detecting abnormal spermatogenesis following exposure to space radiation. [ABSTRACT FROM AUTHOR]

The loess-palaeosol deposits of the Central Shandong Mountains (CSM) to the east of the Chinese Loess Plateau (CLP) potentially provide valuable archives for the reconstruction of East Asian monsoon patterns. However, compared to the abundant attention given to the loess layer, fewer studies have explored the palaeosols documenting the processes and characteristics of interglacial climate changes. The high-resolution chronologies and provenances of the palaeosol in the CSM area are still unclear. In this work, the luminescence ages and paleoclimate proxies in the Shaozhuang (SZ) and Focun (FC) sections were studied, by combining detrital zircons U–Pb ages from the loess-palaesosol in Jingbian, Licheng, Focun, Pianguan and Dongming Yellow River sediments. Quartz single-aliquot regenerative dose protocol (SAR) and K-feldspar post-infrared IRSL (pIRIR 290) dating results were obtained in the SZ (8.0 ± 1.1 ka −50.8 ± 2.7 ka) and FC (3.8 ± 0.3 ka—144.0 ± 7.8 ka) sections to develop the most detailed CSM region chronologies to date. The analyzed grain sizes and detrital zircon U–Pb ages suggest that the provenance of the CSM loess was dominated by local Yellow River sediments. The palaeosols observed in the field in these two sections were composed of both aggradation soils deposited in the interglacial period and non-aggradation soil formed by the weathering and leaching of the underlying loess. We found evidences for the presence of non-aggradation soils as indicated the relatively high 5–16 μm particle percentages, relatively low chemical index of alteration (CIA) values and the percentages of >63 μm particles compared to those of the overlying palaeosol layers. Nevertheless, the loess-palaeosol deposits in the CSM are still the product of the East Asian monsoon and global climatic variations, as the deposits have recorded the glacial-interglacial cycles. [ABSTRACT FROM AUTHOR]

Sedimentary deposits in the foreland basin of the northeastern Qilian Mountains are crucial documents recording tectonic activity and climate changes on the Tibetan Plateau. In this study, luminescence dating was used to date alluvial conglomerates and fluvial terrace sediments collected from the Beida River in the Jiuquan Basin, a foreland basin in the Hexi Corridor, northeastern Qilian Mountains. Detailed sedimentology and luminescence ages reveal that alluvial conglomerates accumulated from before 620 ka to 12 ka and that sediment accumulation rates increased at ∼330 ka and ∼35 ka, coinciding with the dates of two tectonic events (∼350 and ∼50 ka) and followed by climate cooling (from marine isotope stage (MIS) 9 to MIS 8 and from MIS 3 to MIS 2). This reveals that variations in the sediment accumulation rates are controlled by the coupling of tectonic uplift and climate cooling. The highest terrace (T7) that developed on the alluvial conglomerate base formed at ∼ 12 ka. The incision rate in the early Holocene was ∼2.1 mm/yr and increased to ∼14.6 mm/yr during the middle and late Holocene. The variations in the river incision rate provide geomorphic evidence for Holocene climate patterns in arid and semiarid areas. Luminescence dating offers a credible temporal framework for the deposits and reveals climate and tectonic effects on the evolution of the foreland basin, northeastern Qilian Mountains. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the effect of water temperature on phytoplankton–zooplankton dynamics with Holling type III functional response. Remarkably, growth rate, capture rate, handling time, death rate and Holling parameter are considered to be temperature dependent, which makes the model different from those in the existing related literatures. First, the relationships between model parameters and water temperature are presented. Then we give the positivity and boundedness of the solutions. And parameters dependent equilibrium analysis and stability analysis are obtained, respectively. It shows that when the water temperature is lower or higher than the optimal temperature, the equilibrium density of phytoplankton increases with decreasing capture rate and increasing handling time. Meanwhile, we show that the decrease of capture rate and increase of handing time cause the density of zooplankton also increases without the optimal temperature, while the population of zooplankton tends to decrease with decrease of growth rate. In addition, sensitivity of coexisting equilibrium to the parameters of the phytoplankton–zooplankton model is analyzed. Finally, one parameter bifurcation analysis is done. [ABSTRACT FROM AUTHOR]

Several attempts at reconstructing geological settings and palaeoclimatic changes of the siliciclastic deposits of the Dahomey Basin, SW Nigeria, using relative age dating and correlation methods, have resulted in serious discrepancies on the ages. Therefore, a chronology framework established by an absolute age dating method is requisite to constrain the geological interpretation. This research focuses on quartz optically stimulated luminescence (OSL) dating of the upper siliciclastic sediments to help bridge the lacuna that arose from previous relative geologic dating. Ten sub-surface sediment samples were collected from the eastern part of the basin, and quartz OSL dating using single-aliquot regenerative-dose protocol was conducted for all the samples. The OSL signals appear well bleached prior to deposition and the OSL ages are reliable and robust. Through the application of OSL, the age framework of the uppermost part of sediments in the study area was established. The OSL dating results revealed that these depositional periods fall within the Holocene and are concentrated during two groups: 3.52 ka–1.55 ka, and 0.64 ka–0.05 ka. The samples with ages of 3.52 ka–1.55 ka distribute in the belt-like inland zone approximately parallel to the coastline. This deposition episode appears to be caused by the decrease in relative sea level during late Holocene. Thus, this study sheds light on the understanding past coast dynamics in the region. [ABSTRACT FROM AUTHOR]

Satellite remotely sensed aerosol optical depth (AOD) provides an effective way to fill the spatial and temporal gaps left by ground PM 2.5 monitoring network. Previous studies have established robust advanced statistical models to estimate PM 2.5 using AOD data in China. However, their coarse resolutions (∼10 km or greater) of PM 2.5 estimations are not enough to support the health effect studies at urban scales. In this study, 3 km AOD data from Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 products were used to estimate the high resolution PM 2.5 concentrations in Yangtze Delta Region of China. We proposed a nested linear mixed effects (LME) model including nested month-, week-, and day-specific random effects of PM 2.5 -AOD relationships. Validation results show that the LME model only with day-specific random effects (non-nested model) used in previous studies has poor performance in the days without PM 2.5 -AOD matchups (the R 2 of day-of-year-based cross validation (DOY-based CV) is 0.148). The results also show that our nested model cannot improve the performance of non-nested model in the days with PM 2.5 -AOD matchups (sample-based CV R 2 = 0.671 for nested model vs. 0.661 for non-nested model), but can greatly improve the model performance beyond those days (DOY-based CV R 2 = 0.339 for nested model vs. 0.148 for non-nested model). To further improve the model performance, we applied the “buffer models” (i.e., models fitted from datasets which ground PM 2.5 were matched with the average AOD values within certain radius buffer zones of gridded PM 2.5 data) on the 3 km AOD data since the “buffer models” has more days with PM 2.5 -AOD matchups and can provide more day-specific relationships. The results of this study show that 3 km MODIS C6 AOD data can be used to estimate PM 2.5 concentrations and can provide more detailed spatial information for urban scale studies. The application of our nested LME model can greatly improve the accuracy of 3 km PM 2.5 predictions. [ABSTRACT FROM AUTHOR]

Red mud and coal fly ash (CFA) are bulk aluminum-containing solid waste in the industrial production process, posing a great threat to the environment and ecological security. The present paper proposes a novel method for one-step producing potassium-containing fertilizer synergistically extracting Al 2 O 3 by KOH hydrothermally treating red mud or CFA. In this paper, the dissolving ratio of Al 2 O 3 in the K 2 O-Al 2 O 3 -H 2 O ternary system and the extraction of Al 2 O 3 from red mud or CFA after hydrothermal treatment with KOH were investigated. The phase structure transformation of leaching residue obtained under various conditions was analyzed by X-ray diffraction and scanning electron microscopy, and the fertilization efficiency of the products was verified by potting experiments. The results show that the dissolving ratio of Al 2 O 3 can reach the highest value of 85.04% at 120 °C with the K 2 O mass fraction of 24.90% in the ternary system. When red mud or CFA was hydrothermally leached with 240 g/L K 2 O at 240 ℃, the Al 2 O 3 extraction rates of 25.50% and 31.42% could be separately obtained, and the leachate could be reused. The main phases of the leaching residue were kaliophilite, illite, and megakalsilite, and the content of K 2 O was 7.83% and 26.89%, which can be applied as potassium-containing fertilizer to improve soil fertility and effectively promote the growth of pakchoi. The process improves the comprehensive utilization of red mud and CFA without secondary pollution, reduces the negative impact on the environment, and opens up a new way to apply bulk solid waste in the agricultural field. [ABSTRACT FROM AUTHOR]

Coal fly ash (CFA) is the main solid waste discharged from coal-fired power plants, a new method for preparing silicon-potassium mineral fertilizer using KOH hydrothermal treatment CFA was proposed to improve its comprehensive utilization rate and reduce its threat to ecological environment security. In this paper, the characteristics of CFA raw material and transformation residue were studied, the agricultural applicability of the process was verified by pakchoi planting experiments, and the effects of the silicon-potassium mineral fertilizer on soil physical-chemical characteristics were investigated. The results show that increasing the leaching temperature and time can improve the extraction rate of alumina from CFA, and the reaction rate is controlled by the mixing of interfacial chemical reaction and solid product layer diffusion. The CFA raw material was hydrothermally leached at 280 g/L K 2 O 200 °C for 1 h, in which the Al 2 O 3 extraction rate was 27.46%. The main component of the transformation residue was potassium aluminum silicate hydrate, which is the main component of the silicon-potassium mineral fertilizer, and the effective K 2 O and SiO 2 content is 25.07% and 34.56%. The application of CFA residue can effectively improve the fertility and productivity of the soil, providing nutrients for the growth of pakchoi and improving the soil quality. This research provides theoretical guidance for the preparation of silicon-potassium mineral fertilizer using CFA and has the potential for practical production, which is important for the resourceful use of CFA and its application in agriculture. [Display omitted] • A novel process of Al separation in coal fly ash to prepare silicon-potassium mineral fertilizer was proposed. • The feasibility of the process was determined by thermodynamic calculations. • The mechanism of the new technology was studied by batch hydrothermal leaching experiments. • The products can be used as silicon-potassium mineral fertilizer to promote pakchoi growth. • KOH hydrothermal treatment of CFA has broad application prospects. [ABSTRACT FROM AUTHOR]

Palaeoflood deposits record extreme climatic and environmental events. While historic data show that floods occurred frequently in the Yongding River in China and have caused many natural disasters. The sedimentologic records of palaeoflood in the Yongding River have not been well studied. This study investigates the palaeoflood deposits at the Tanmugou site in the middle reach of the Yongding River. Six episodes of palaeoflood were identified in the sediment profile. Optically stimulated luminescence (OSL) dating method was applied to establish the chronology of the palaeoflood deposits. Both the improved single-aliquot regenerative-dose (SAR) protocol and standard growth curve (SGC) method were employed for equivalent dose (D e ) determinations. The minimum age model (MAM), central age model (CAM) and arithmetic mean were applied to calculate the D e values. The OSL dating results show that these palaeoflood events occurred in the Holocene and concentrated during three stages, including 8.5–7.3 ka, 2.8–2.4 ka and 1–0.5 ka. The timings of these palaeoflood events in the Yongding River coincide with the timings of palaeoflood events in other river systems in China. Compared with the continuously high-resolution climate record in China, these palaeoflood events occurred during climate transition periods. [ABSTRACT FROM AUTHOR]

The toxicological mechanism of low sperm motility induced by iron ion radiation (IIR) was investigated in mice. Reproductive organ indices were measured following whole-body irradiation with a 2 Gy iron ion beam. Two-dimensional gel electrophoresis, immunoblotting and immunofluorescence were used to analyze protein expression, and real-time polymerase chain reaction was performed to confirm altered gene expression. Reproductive organ indices and sperm motility were lowest 2 weeks after IIR. Sperm function changes via testis and cauda epididymis function were also determined at this time point. Sixteen differentially expressed proteins were identified in sperm 2 weeks after IIR. Bioinformatics analysis indicated that alpha-enolase (Eno1) may be important in the regulation of glycolysis in sperm, and Eno1 expression was correlated with sperm motility. Eno1 may be a potential marker for low sperm motility induced by IIR, and these results may provide a useful reference for changes in astronaut fertility during long space missions. [ABSTRACT FROM AUTHOR]

Two new rhamnosides, 18-O- α - l -rhamnopyranosylabietic acid (1) and (E) -3,5-dimethoxystilben-4′-O- α - l -rhamnopyranoside (2), five known glucosides (3 – 7) along with three others were isolated from Cynanchum atratum roots. The structures of new compounds were elucidated by physical data analyses such as NMR, UV, IR, HR-ESI-MS, as well as acid hydrolysis. All of them were assessed for their antioxidant activities through 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical ion (ABTS•+), 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH•) and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) assay, with l -ascorbic acid used as the positive control. As a result, compounds 3 – 5 exhibited obvious antioxidant activities. These bioactive components could be promising antioxidants. [Display omitted] • Two new rhamnosides (1 – 2) and eight known compounds (3 – 10) were isolated from Cynanchum atratum roots. • The structures of new compounds (1 – 2) were elucidated by HR-ESI-MS, NMR, acid hydrolysis, and comparisons with literatures. • Compounds 3 – 5 exhibited obvious antioxidant activities. [ABSTRACT FROM AUTHOR]

We investigated potential mechanisms of acute injury in pubertal mice testes after exposure to carbon ion radiation (CIR). Serum testosterone was measured following whole-body irradiation with a 2 Gy carbon ion beam. Comparative proteomic profiling and Western blotting were applied to identify potential biomarkers and measure protein expression, and terminal dUTP nick end-labeling (TUNEL) was performed to detect apoptotic cells. Immunohistochemistry and immunofluorescence were used to investigate protein localization. Serum testosterone was lowest at 24 h after CIR, and 10 differentially expressed proteins were identified at this time point that included eIF4E, an important regulator of initiation that combines with mTOR and 4EBP1 to control protein synthesis via the mTOR signaling pathway during proliferation and apoptosis. Protein expression and localization studies confirmed their association with acute injury following exposure to CIR. These three proteins may be useful molecular markers for detecting abnormal spermatogenesis following exposure to environmental and therapeutic radiation. [ABSTRACT FROM AUTHOR]

The Yangtze River Delta (YRD) is one of the regions with the most dynamic economy and severe atmospheric pollution in China. In order to characterize the particle features, especially the carbonaceous component in the YRD, particulate matter smaller than 2.5 μm (PM 2.5 ) and 10 μm (PM 10 ) samples in each season were collected in urban Nanjing, a typical city that locates in the west part of the YRD. The organic carbon (OC) and elemental carbon (EC) was differentiated using the thermal optical reflectance method. The average concentrations of PM 2.5 , OC and EC during the study periods were observed to be 117.6, 13.8, and 5.3 μg/m 3 respectively, with all the highest levels in winter. The mass fraction of the Total carbonaceous aerosol (TCA) in PM 2.5 was estimated at 23% on average, lower than those reported for other cities in the YRD. The OC and EC correlated well in all the seasons, especially in spring and winter, implying that OC and EC were attributed to common emission sources. Good correlation was observed between OC and estimated K + from biomass burning in the harvest season in autumn and summer, indicating biomass burning a significant source of carbonaceous aerosols. This could also be confirmed by the lower fraction of OC3 + OC4 in OC during autumn and summer. The secondary organic carbon (SOC) estimated by EC-tracer method was the highest in winter (7.3 μg/m 3 ) followed by autumn (6.7 μg/m 3 ), summer (3.7 μg/m 3 ) and spring (2.0 μg/m 3 ). However, the SOC/OC in winter was not as high as that in summer and autumn, implying the high concentration of OC in winter was probably due to the stable weather but not mainly caused by SOC formation. The high SOC/OC ratio in summer was attributed to stronger oxidation, which could be suggested by higher sulfur oxidation ratio (SOR). [ABSTRACT FROM AUTHOR]

Ambient particulate matter was collected in a megacity, Nanjing in western YRD during the spring and summer periods. Chemical compositions of fine PM including organic carbon, elemental carbon, elements and water soluble ions were analyzed. The light extinction coefficients were reconstructed following the IMPROVE formula. Organic matter was the most abundant composition in PM2.5 (20–25% of total mass), followed by the inorganic ions. During the spring time, geological materials contributed 25% of the total PM2.5. Estimated light extinction coefficient ranged from 133 to 560 Mm−1 with the deciview haze index value of 26–40 dv, indicating strong light extinction by PM and subsequently low visibility in the city. Reconstructed ammonium sulfate, ammonium nitrate, organic matter and light absorption carbon in fine PM contributed significantly (37 ± 10, 16 ± 6, 15 ± 4 and 10 ± 3%, respectively) to the total light extinction of PM, while soil (5–7%) and sea salt fractions (2–4%) in fine PM and coarse PM (6–11%) had relatively minor influences. The results of backward air trajectory showed that the site was strongly influenced by the air from the eastern (39%) and southeastern (29%) areas during the sampling period. Air plumes from the Southeastern had both high PM mass pollution and large light extinction, while the air mass originating from the Northwestern resulted in high PM mass loading but relatively lower light extinction. [ABSTRACT FROM AUTHOR]