Physiological and visible injury responses in different growth stages of winter wheat to ozone stress and the protection of spermidine

AbstractThe open top chamber (OTC) method was used in a farmland to study the influence of different levels of O3 concentrations (40 ppb, 80 ppb and 120 ppb) on the enzymatic activity and metabolite contents of the antioxidation system of the winter wheat leaves during the jointing, heading and milk stage. The protective effect of exogenous spermidine (Spd) against the antioxidation of winter wheat under the O3 stress was investigated. With the increasing O3 concentrations and fumigation time, the injuries of the winter wheat leaves were observed to be more serious. For instance, when the O3 concentration reached 120 ppb, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and nitrate reductase (NR) in the jointing stage decreased by 50.3%, 64.9%, 75.5% and 92.9%, respectively; peroxidase (POD) and glutathione reductase (GR) increased by 45.1% and 80.5%, respectively; the contents of malondialdehyde (MDA), ascorbic acid (AsA) and reduced glutathione (GSH) increased by 314.3%, 8.4% and 31.7%, respectively; and the soluble protein (SP) content decreased by 47.5%. The O3 stress also had significant impact on the contents of proline (Pro), NO3––N and NH4+–N of the winter wheat leaves. During the heading stage, when the O3 concentration was 40 ppb and 80 ppb, the content of Pro was 163.9% and 173.2% higher than that in the control group, respectively. But under 120 ppb, it was decreased by 42.4%. Exogenous application of Spd increased the activities of SOD, POD, CAT, APX and GR, as well as the contents of GSH and SP, but decreased the contents of MDA and AsA. This indicates that Spd is an effective antioxidant to relieve the O3 stress on winter wheat leaves, thereby might be applicable to protect winter wheat from the harm of O3

Constructing ecological security pattern based on spatio-temporal evaluation of ecosystem services and ecological health in Chengdu, Southwest China

IntroductionWith the acceleration of urbanization, human population and built surface in urban areas have increased rapidly, triggering numerous environmental problems. Identification of ecological security pattern (ESP) can be helpful to optimize the interaction and relationship between ecological conservation and socioeconomic development in a given region. In this study, taking Chengdu City as an example, a methodology was used to analyze the city’s ESP.MethodologyEcological sources were identified based on their ecological security values, which were derived from the spatio-temporal evaluation of ecosystem services and ecological health. The ecological resistance surface was revised with nighttime light index. Linkage Mapper combined with circuit theory was used to extracted ecological corridors and key ecological nodes.Results:The results showed that the mean values of ecological security in Chengdu City presented a downward and then upward trend from 2000 to 2018. In 2018, the ESP in Chengdu City was formed by 140 ecological sources with the total area of 8,819.78 km2, 302 ecological corridors with the area of 456.91 km2, as well as 61 pinch-points and 17 barrier points. The ecological sources in Chengdu City were mainly distributed in or nearby Longmen Mountain and Longquan Mountain, two flanks of the Chengdu Plain, and connected each other with hundreds of ecological corridors. Most of ecological sources and corridors were composited of forests in mountainous areas and linpan units (wooded lots) in rural plain areas. On the contrary, pinch-points and barrier points were mainly distributed in the districts nearby the metropolitan urban center.ConclusionFinally, this study proposed that constructing ESP must adopt a dynamic and holistic approach in considering the change of restoring ecosystems, shift of urban demands for ecosystem services and transformation of urban-rural land use/cover. Restoring and managing corridors sustainably are important for improving the ecological connectivity of all over ecological sources in a city, all of which together, if functioning well, could further support the realization of sustainable urbanization

Meteorological impacts on surface ozone: A case study based on Kolmogorov–Zurbenko filtering and multiple linear regression

Ozone variation, excluding meteorological effects, is very important to assess the effects of air pollution control policies. In this study, the Kolmogorov-Zurbenko (KZ) filter method and multiple linear stepwise regression are combined to study the impact of meteorological parameters on ozone concentration over the past 5 years (2016–2020) in a petrochemical industrial city in northern China. Monte Carlo simulations were used to evaluate the reliability for the potential quasi quantitative prediction of the baseline component. The average level of the city and the details of five stations in the city were studied. The results show that the short-term, seasonal, and long-term component variances of maximum daily running average 8 h (MDA8) ozone in Zibo city (City) decomposed by the KZ filter account for 32.06%, 61.67% and 1.15% of the total variance, for a specific station, the values were 32.37%–34.90%, 56.64%–62.00%, and .35%–3.14%, respectively. The average long-term component increase rate is 3.19 μg m−3 yr−1 on average for the city, while it is 1.52–5.95 μg m−3 yr−1 for a specific station. The overall meteorological impact was not stable and fluctuated between −2.60 μg m−3 and +3.77 μg m−3. This difference in trends between the city and specific stations implied that the O3 precursor’s mitigation strategy should be more precise to improve its practical effects

The oxidative potential of PM10 from coal, briquettes and wood charcoal burnt in an experimental domestic stove

Coal contains many potentially harmful trace elements. Coal combustion in unvented stoves, which is common in most parts of rural China, can release harmful emissions into the air that when inhaled cause health issues. However, few studies have dealt specifically with the toxicological mechanisms of the particulate matter (PM) released by coal and other solid fuel combustion. In this paper, PM10 particles that were generated during laboratory stove combustion of raw powdered coal, clay-mixed honeycomb briquettes, and wood charcoal were analysed for morphology, trace element compositions, and toxicity as represented by oxidative DNA damage. The analyses included Field Emission Scanning Electron Microscopy (FESEM), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Plasmid Scission Assay (PSA). Gravimetric analysis indicated that the equivalent mass concentration of PM10 emitted by burning raw powdered coal was higher than that derived by burning honeycomb briquette. FESEM observation revealed that the coal burning-derived PM10 particles were mainly soot aggregates. The PSA results showed that the PM10 emitted by burning honeycomb briquettes had a higher oxidative capacity than that from burning raw powdered coal and wood charcoal. It is also demonstrated that the oxidative capacity of the whole particle suspensions were similar to those of the water soluble fractions; indicating that the DNA damage induced by coal burning-derived PM10 were mainly a result of the water-soluble fraction. An ICP-MS analysis revealed that the amount of total analysed water-soluble elements in the PM10 emitted by burning honeycomb briquettes was higher than that in PM produced by burning raw powdered coal, and both were higher than PM from burning wood charcoal. The total analysed water-soluble elements in these coal burning-derived PM10 samples had a significantly positive correlation with the level of DNA damage; indicating that the oxidative capacity of the coal burning-derived PM10 was mainly sourced from the water soluble elements. The water-soluble As, Cd, Ge, Mn, Ni, Pb, Sb, Se, Tl, and Zn showed the highest correlation with the oxidative potential, implying that these elements in their water soluble states were the primary responsible factor for the plasmid DNA damage. The exposure risk was further assessed using the particle mass concentrations multiplied by the percent of DNA damage under the dose of 500 μg ml−1. The results revealed that the exposure risk of burning raw powdered coal was much higher than that of burning honeycomb briquette

A comprehensive survey of the analytical, numerical and experimental methodologies for dynamics of multibody mechanical systems with clearance or imperfect joints

"Available online 19 December 2017"A comprehensive survey of the literature of the most relevant analytical, numerical, and experimental approaches for the kinematic and dynamic analyses of multibody mechanical systems with clearance joints is presented in this review. Both dry and lubricated clearance joints are addressed here, and an effort is made to include a large number of research works in this particular field, which have been published since the 1960′s. First, the most frequently utilized methods for modeling planar and spatial multibody mechanical systems with clearance joints are analyzed, and compared. Other important phenomena commonly associated with clearance joint models, such as wear, non-smooth behavior, optimization and control, chaos, and uncertainty and links’ flexibility, are then discussed. The main assumptions procedures and conclusions for the different methodologies are also examined and compared. Finally, future developments and new applications of clearance joint modeling and analysis are highlighted.This research was supported in part by the China 111 Project (B16003) and the National Natural Science Foundation of China under Grants 11290151, 11472042 and 11221202. The work was also supported by the Portuguese Foundation for Science and Technology with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio

Biotransformation of 6-deoxypseudoanisatin by Synechocystis sp. PCC6803

Objective: To explore the ability of Synechocystis sp. PCC6803 in transforming 6-deoxypseudoanisatin. Methods: The experiment was performed by incubating 6-deoxypseudoanisatin with the freshwater cyanobacterium Synechocystis sp. PCC6803 under continuous white light at 30°C for 5 days. The crude converted product was detected using thin-layer chromatography (TLC) and further analyzed using high-performance liquid chromatography (HPLC) as well as HPLC with electron spray ionization mass spectrometry (HPLC-ESI-MS). Results: TLC results showed that 6-deoxypseudoanisatin was converted into a less polar product. HPLC and MS data indicated that the retention time of the converted product increased in comparison with the standard of 6-deoxypseudoanisatin. Conclusion: Thus, the study appears to demonstrate that Synechocystis sp. PCC6803 can transform 6-deoxypseudoanisatin. The polarity of the converted product is less than that of 6-deoxypseudoanisatin

Anti-tumor activities of macromolecular fractions of fresh gecko in vivo and their induction of Bel-7402 cell differentiation

Objective: To investigate the anti-tumor effect of macromolecular fractions of fresh gecko (M-AG) in vivo and their differentiation-inducing activity in Bel-7402 cells in vitro. Methods: An H22 hepatocarcinoma-bearing mouse model was used to evaluate the anti-tumor activity of M-AG samples. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was applied to analyze cell viability. Cell morphology was observed by phase contrast microscopy. The quantity of the alpha-fetoprotein was detected by a radioimmunoassay. Chromatometry was used to assay the albumin quantity. Activities of alkaline phosphatase and γ-glutamyl trans-peptidase were measured by biochemical methods. Finally, western blotting was applied to assess proteins in the mitogen-activated protein kinase (MAPK) signaling pathway. Results: Macromolecular fractions of fresh gecko exerted a significant anti-tumor effect in mice. The inhibition rate of tumor growth was 63% in the moderate M-AG dose group. Cells treated with M-AG displayed a differentiated state. The treatment lowered alpha-fetoprotein secretion and significantly decreased the activities of γ-glutamyl trans-peptidase and alkaline phosphatase in Bel-7402 cells. In contrast, M-AG increased the amount of albumin in the cell culture medium. All biochemical indices demonstrated that M-AG induced Bel-7402 cell differentiation. Western blotting showed no changes in the quantities of extracellular signal-regulated kinase (ERK) 1/2, p38 MAPK, or c-Jun N-terminal protein kinase 1/2. However, M-AG significantly activated the phosphorylation of ERK1/2 in a dose-dependent manner. In addition, M-AG had no significant influence on the expression of nuclear factor-kappa B. Conclusion: Macromolecular fractions of fresh gecko has an anti-tumor activity in H22 hepatocarcinoma-bearing mice in vivo and inhibits Bel-7402 cell proliferation in vitro by inducing cell differentiation related to activation of ERK1/2

A Graph Neural Networks-Based Learning Framework With Hyperbolic Embedding for Personalized Tag Recommendation

Learning high-quality representations of users, items, and tags from historical interactive data is crucial for personalized tag recommendation (PTR) systems. Currently, most PTR models are committed to learning representations from first-order interactions without considering the exploitation of high-order interactive relations, which can be beneficial for avoiding sub-optimal learning. Although several PTR models equipped with graph neural networks (GNN) have been proposed to capture higher-order semantic relevance from raw data, they all carry out representation learning in Euclidean space, which can still easily result in sub-optimal learning due to embedding distortion. In order to further improve the quality of representation learning for PTR, the paper proposes a novel PTR model based on a lightweight GNN framework with hyperbolic embedding, namely GHPTR. GHPTR explicitly injects higher-order relevance into entity representation through the message propagation and aggregation mechanism of GNN and leverages hyperbolic embedding to alleviate the embedding distortion problem. Experimental results on real-world datasets have demonstrated the superiority of our model over its Euclidean counterparts and state-of-the-art baselines