39 research outputs found

    Using the Rheological Index to Quantitatively Evaluate the Mechanical Performance of High-Elasticity Modified Asphalt

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    High-elasticity modified asphalt is widely used in OGFC and bridge deck paving due to its high viscosity and strong displacement recovery capacity. It can improve the high-temperature deformation resistance and elastic recovery ability of the pavement. Especially in bridge deck pavement, high-elastic modified asphalt can inhibit the formation of reflective cracks and extend the service life. In order to quantitatively evaluate properties of the high-elasticity modified asphalt, rheological properties are studied by using a dynamic shear rheometer (DSR) test. The parameters were fitted with the Burgers model, and the constitutive equation was established. The 3 s elastic recovery rate Er was proposed to quantitatively evaluate the elastic recovery of high-elasticity modified asphalt. The experimental results show that the instantaneous modulus of elasticity G0 and the delayed modulus of elasticity G1 can be used to evaluate the elastic capacity. Er can quantitatively evaluate the elastic resilience of high-elasticity modified asphalt. The correlation coefficient between the test results of high-elasticity modified asphalt and those of impact toughness evaluation reached 0.9966, and the 3 s elastic recovery rate Er could be used to evaluate the elastic recovery ability of high-elasticity modified asphalt

    Towards the circular nitrogen economy - a global meta-analysis of composting technologies reveals much potential for mitigating nitrogen losses

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    Composting is an important technology to treat biowastes and recycle nutrients, but incurs nitrogen (N) losses that lower the value of the final products and cause pollution. Technologies aimed at reducing N losses during composting have inconsistent outcomes. To deepen insight into mitigation options, we conducted a global meta-analysis based on 932 observations from 121 peer-reviewed published studies. Overall, N losses averaged 31.4% total N (TN), 17.2% NH-N, and 1.4% NO-N, with NH-N accounting for 55% of TN losses. The primary drivers affecting N losses were composting method, type of biowaste, and duration of composting. N losses were significantly impacted by the carbon-to-nitrogen (C/N) ratio of the input materials (feedstock of nutrient dense biowastes and C-rich bulking agents), moisture content and pH. Our analysis revealed N-conserving optima with C/N ratios of 25-30, 60-65% moisture content and pH 6.5-7.0. In situ mitigation technologies that control feedstock and processing conditions reduced average N losses by 31.4% (TN), 35.4% (NH-N) and 35.8% (NO-N). Biochar and magnesium-phosphate salts emerged as the most effective N-conserving strategies, curbing losses of TN by 30.2 and 60.6%, NH by 52.6 and 69.4%, and NO by 66.2 and 35.4% respectively. We conclude that existing technologies could preserve ~0.6\ua0Tg of biowaste-N globally, which equates to 16% of the chemical N-fertilizer used in African croplands, or 39% of the annual global increases of 1.58\ua0Tg fertilizer-N. However, the adoption of N-conserving technologies is constrained by a lack of knowledge of best practice, suitable infrastructure, policies and receptive markets. To realize an N-conserving composting industry that supports sustainable practices and the circular nitrogen economy, stakeholders have to act collectively. Benefits will include lowering direct and indirect greenhouse gas emissions associated with agriculture, and facilitating the recarbonization of soils

    Cold Climate during Bud Break and Flowering and Excessive Nutrient Inputs Limit Apple Yields in Hebei Province, China

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    Apples have become a major source of income for smallholder farmers in Bohai Bay. However, the annual productivity of apples in the area is relatively low and the interannual yield gap varies drastically. Identifying the apple yield gap and interannual production constraints can potentially promote the sustainable development of apple production. Based on track monitoring data of 45 smallholder farmers from 2016 to 2018, the yield gap and constraint factors were determined by adopting boundary analysis methodology. The results showed that the yield potential of apples during 2016–2018 was 75, 108, and 87 t ha−1, and actual yields were 36.8, 52.3, and 35.2 t ha−1, respectively. The explainable yield gaps were 40.5, 56.9, and 55.1 t ha−1. Soil, management, and climatic factors limit apple yield improvement. Among these, low temperatures during the bud break and flowering periods can induce yield losses. Soil nutrient content and fertilizer management are also important limiting factors that have polynomial relationships with yield. Too much fertilizer and high levels of nutrients in the soil have already caused yield losses in some fields. Sound scientific guidance to help farmers adopt reasonable management techniques adapted to climate change is necessary to close the yield gap

    Study of Pavement Performance and Temperature Regulation Capacity of Asphalt Binders Modified with Dual-Phase-Change Materials

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    Due to the temperature changes caused by seasonal changes and extreme weather, asphalt pavement suffers from rutting, cracking, and other damage. With commonly used pavement additives, the high-temperature performance and the low-temperature performance of asphalt pavement show opposite trends, with related research endeavoring to find a balance between the two. In this study, a dual-phase-change material (DPCM) with both high- and low-temperature effects was prepared. The chemical stability and rheological properties of modified asphalt binders were characterized using Fourier transform infrared spectroscopy (FTIR) and a dynamic shear rheometer (DSR). Temperature control tests of the DPCM-modified asphalt binders were carried out with an indoor simulation device. The results show that the DPCMs could improve the rutting resistance of the asphalt binders at a high temperature, but the fatigue performance of the modified asphalt binder with different DPCM contents was reduced. The FTIR results showed that no chemical reaction occurred in the mixing of the asphalt binder and the DPCM. In the indoor simulation temperature control test, the 40% DPCM-content-modified asphalt binder reduced the high-temperature extreme value by 4.2 °C and increased the low-temperature extreme value by 2.5 °C, showing a good temperature control effect and practical application value

    Cold Climate during Bud Break and Flowering and Excessive Nutrient Inputs Limit Apple Yields in Hebei Province, China

    No full text
    Apples have become a major source of income for smallholder farmers in Bohai Bay. However, the annual productivity of apples in the area is relatively low and the interannual yield gap varies drastically. Identifying the apple yield gap and interannual production constraints can potentially promote the sustainable development of apple production. Based on track monitoring data of 45 smallholder farmers from 2016 to 2018, the yield gap and constraint factors were determined by adopting boundary analysis methodology. The results showed that the yield potential of apples during 2016–2018 was 75, 108, and 87 t ha−1, and actual yields were 36.8, 52.3, and 35.2 t ha−1, respectively. The explainable yield gaps were 40.5, 56.9, and 55.1 t ha−1. Soil, management, and climatic factors limit apple yield improvement. Among these, low temperatures during the bud break and flowering periods can induce yield losses. Soil nutrient content and fertilizer management are also important limiting factors that have polynomial relationships with yield. Too much fertilizer and high levels of nutrients in the soil have already caused yield losses in some fields. Sound scientific guidance to help farmers adopt reasonable management techniques adapted to climate change is necessary to close the yield gap

    Tetrandrine sensitizes nasopharyngeal carcinoma cells to irradiation by inducing autophagy and inhibiting MEK/ERK pathway

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    Abstract Radioresistance was the main reason for local recurrence and metastasis of nasopharyngeal carcinoma. Tetrandrine is reported as an antitumor drug via inducing cell cycle arrest and apoptosis. In this study, the radiosensitization effects of maximum noncytotoxic doses of tetrandrine in nasopharyngeal carcinoma were analyzed both in vitro and in vivo, using MTT assay, western blot, TUNEL, and HE staining. It was found that the maximum dose of tetrandrine inhibited the phosphorylation of ERK and MEK induced by irradiation, and significantly enhanced irradiation‐induced cell growth inhibition in nasopharyngeal carcinoma cells CNE1, CNE2, and C666‐1. The ERK activator and overexpression of ERK reversed the radiosensitization effect of tetrandrine. About 50 mg/kg of tetrandrine which was used as the maximum noncytotoxic dose of tetrandrine in vivo, enhanced the radiosensitivity of the xenograft tumor and increased the apoptosis rate of the xenograft tumor cells caused by irradiation, while did not raise the side effect of the treatment. Moreover, tetrandrine increased autophagy in nasopharyngeal carcinoma cells. These results suggested that the maximum noncytotoxic dose of tetrandrine sensitized nasopharyngeal carcinoma to irradiation by inhibiting MEK/ERK pathway and inducing autophagy

    IL‐19 induced by IL‐13/IL‐17A in the nasal epithelium of patients with chronic rhinosinusitis upregulates MMP‐9 expression via ERK/NF‐κB signaling pathway

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    Abstract Background Tissue remodeling is a crucial characteristic of chronic rhinosinusitis (CRS). Imbalance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) is crucial for the pathologic tissue remodeling in CRS. Elevation of interleukin (IL)‐19 or MMP‐9 levels in patients with CRS had been proven in previous studies. Here, we aimed to investigate the role of IL‐19 in mediating MMP‐9 expression in CRS. Methods Nasal tissue samples were collected from 45 individuals having chronic rhinosinusitis with nasal polyps (CRSwNP), 24 CRS without nasal polyps (CRSsNP), and 17 controls. Expression of IL‐19, its receptors (IL‐20R1/IL‐20R2), and MMP‐9 were investigated using RT‐qPCR and Immunofluorescence (IF). Human nasal epithelial cells (HNECs) were stimulated by IL‐19; ERK phosphorylation, nuclear factor‐κB (NF‐κB) pathway activation, and MMP‐9 level were detected by RT‐qPCR, enzyme‐linked immunosorbent assay, western blot, and IF. We also explored the effect of type1/2/3 cytokines on IL‐19 production by RT‐qPCR, and western blot. Results Expression levels of IL‐19, its receptors (IL‐20R1/IL‐20R2), and MMP‐9 were increased in nasal tissues from individuals with CRSwNP compared to those with CRSsNP as well as the controls. IL‐19 significantly elevated the production of MMP‐9 in HNECs. Furthermore, IL‐19 could activate the ERK and NF‐κB pathways, accompanied by increased MMP‐9 production in HNECs. Conversely, both ERK and NF‐κB inhibitors significantly attenuated the role of IL‐19 in MMP‐9 production. siRNA knockdown of IL‐20R1 suppressed ERK and NF‐κB pathway activation, thereby decreasing MMP‐9 expression. IL‐13 and IL‐17A were found to stimulate IL‐19 production in HNECs. Conclusion IL‐19, promoted by IL‐13 and IL‐17A, contributes to the upregulation of secretion of the tissue remodeling factor MMP‐9 in patients with CRS

    Processing 2‑Methyl‑l‑Tryptophan through Tandem Transamination and Selective Oxygenation Initiates Indole Ring Expansion in the Biosynthesis of Thiostrepton

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    Thiostrepton (TSR), an archetypal member of the family of ribosomally synthesized and post-translationally modified thiopeptide antibiotics, possesses a biologically important quinaldic acid (QA) moiety within the side-ring system of its characteristic thiopeptide framework. QA is derived from an independent l-Trp residue; however, its associated transformation process remains poorly understood. We here report that during the formation of QA, the key expansion of an indole to a quinoline relies on the activities of the pyridoxal-5′-phosphate-dependent protein TsrA and the flavoprotein TsrE. These proteins act in tandem to process the precursor 2-methyl- l-Trp through reversible transamination and selective oxygenation, thereby initiating a highly reactive rearrangement in which selective C2–N1 bond cleavage via hydrolysis for indole ring-opening is closely coupled with C2′–N1 bond formation via condensation for recyclization and ring expansion in the production of a quinoline ketone intermediate. This indole ring-expansion mechanism is unusual, and represents a new strategy found in nature for l-Trp-based functionalization

    An enzymatic [4+2] cyclization cascade creates the pentacyclic core of pyrroindomycins

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    The [4+2] cycloaddition remains one of the most intriguing transformations in synthetic and natural products chemistry. In nature, however, there are remarkably few enzymes known to have this activity. We herein report an unprecedented enzymatic [4+2] cyclization cascade that has a central role in the biosynthesis of pyrroindomycins, which are pentacyclic spirotetramate natural products. Beginning with a linear intermediate that contains two pairs of 1,3-diene and alkene groups, the dedicated cyclases ​PyrE3 and ​PyrI4 act in tandem to catalyze the formation of two ​cyclohexene rings in the dialkyldecalin system and the tetramate spiro-conjugate of the molecules. The two cyclizations are completely enzyme dependent and proceed in a regio- and stereoselective manner to establish the enantiomerically pure pentacyclic core. Analysis of a related spirotetronate pathway confirms that homologs are functionally exchangeable, establishing the generality of these findings and explaining how nature creates diverse active molecules with similar rigid scaffolds
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